摘要:

JASPE2 8(8j 61 N-66N 1053-1 122 337R-405R 9 9 ) Typeset by Burgess Thames View Abingdon Oxfordshire December 1993 Printed in Great Britain by Journal of Analytical Atomic Spectrometry Including Atomic Spectrometry Updates CONTENTS NEWS AND VIEWS 61 N Obituary-David A Hickman 61 N Reconstruction of Boris L'vov's Electrothermal Atomizer-Judith Egan-Shuttler 61 N Gordon Kirkbright Bursary 62N Book Review-Adam McMahon 63N Diary of Conferences and Courses 65N Future Issues PAPERS 1053 1059 1067 1075 1085 1091 1097 1103 1109 1113 1117 1121 Determination of Ultratrace Levels of Heavy Metals in Arctic Snow by Electro- thermal Vaporization Inductively Coupled Plasma Mass Spectrometry-Ralph E Sturgeon Scott N Willie James Zheng Akira Kudo D Conrad Gregoire Determination of Palladium and Platinum in Fresh Waters by Inductively Coupled Plasma Mass Spectrometry and Activated Charcoal Preconcentration-Gwendy E M Hall J C.Pelchat Determination of Selenium in Marine Certified Reference Materials by Hydride Generation Inductively Coupled Plasma Mass Spectrometry-Hiroaki Tao Joseph W H Lam James W McLaren Arsenic Speciation in Seafood Samples With Emphasis on Minor Constituents an tnvestigation Using High-performance Liquid Chromatography With Detection by Inductively Coupled Plasma Mass Spectrometry-Erik H Larsen Gunnar Pritzl Steen Honore Hansen Speciation of Arsenic by Ion Chromatography and Off -line Hydride Generation Electrothermal Atomic Absorption Spectrometry-Han Heng-bin Liu Yan-bing Mou Shi-fen Ni Zhe-mmg Electrothermal Vaporization for Sample Introduction in Microwave-induced Plasma Atomic Absorption Spectrometry-Ytxiang Duan Xingyou Li Qinhan Jin Improvement in Mercury Cold Vapour Atomic Techniques by Resorting to Organized Assemblies and On-line Membrane Drying of Vapour-B Aizpun Fernandez M R Fernandez de la Campa Alfred0 Sanz-Medel Improvement in Detection Limits in Graphite Furnace Diode Laser Atomic Absorption Spectrometry by Wavelength Modulation Technique.Plenary Lecture-Christoph Schnurer-Patschan Aleksandr Zybin Henning Groll Kay Niemax Preliminary Study on the Use of Palladium as a Chemical Modifier for the Determination of Silicon by Electrothermal Atomic Absorption Spectrometry-Zhixra Zhuang Pengyuan Yang Xiaoru Wang Zhiwei Deng Benli Huang Effect of Aqueous Organic Solvents on the Determination of Trace Elements by Flame Atomic Absorption Spectrometry and Inductively Coupled Plasma Atomic Emission Spectrometry-M Todorovic S Vidovic.Z IIIC Indirect Flame Atomic Absorption Spectrometric Determination of Papaverine Strychnine and Cocaine by Continuous Precipitation With Dragendorff's Reagent-Marceltna Eisman Mercedes Gallego Miguel Valcarcel CUMULATIVE AUTVOR INDEX ATOMIC SPECTROMETRY 337R Industrial Analysis Metals Chemicals and Advanced Materials-John Marshall UPDATE John Carroll James S. Crighton Charles L. R. Barnard 377R References continued on inside back cover 0267-9477C199318:l-YJASPE2 8(8j 61 N-66N 1053-1 122 337R-405R 9 9 ) Typeset by Burgess Thames View Abingdon Oxfordshire December 1993 Printed in Great Britain by Journal of Analytical Atomic Spectrometry Including Atomic Spectrometry Updates CONTENTS NEWS AND VIEWS 61 N Obituary-David A Hickman 61 N Reconstruction of Boris L'vov's Electrothermal Atomizer-Judith Egan-Shuttler 61 N Gordon Kirkbright Bursary 62N Book Review-Adam McMahon 63N Diary of Conferences and Courses 65N Future Issues PAPERS 1053 1059 1067 1075 1085 1091 1097 1103 1109 1113 1117 1121 Determination of Ultratrace Levels of Heavy Metals in Arctic Snow by Electro- thermal Vaporization Inductively Coupled Plasma Mass Spectrometry-Ralph E Sturgeon Scott N Willie James Zheng Akira Kudo D Conrad Gregoire Determination of Palladium and Platinum in Fresh Waters by Inductively Coupled Plasma Mass Spectrometry and Activated Charcoal Preconcentration-Gwendy E M Hall J C.Pelchat Determination of Selenium in Marine Certified Reference Materials by Hydride Generation Inductively Coupled Plasma Mass Spectrometry-Hiroaki Tao Joseph W H Lam James W McLaren Arsenic Speciation in Seafood Samples With Emphasis on Minor Constituents an tnvestigation Using High-performance Liquid Chromatography With Detection by Inductively Coupled Plasma Mass Spectrometry-Erik H Larsen Gunnar Pritzl Steen Honore Hansen Speciation of Arsenic by Ion Chromatography and Off -line Hydride Generation Electrothermal Atomic Absorption Spectrometry-Han Heng-bin Liu Yan-bing Mou Shi-fen Ni Zhe-mmg Electrothermal Vaporization for Sample Introduction in Microwave-induced Plasma Atomic Absorption Spectrometry-Ytxiang Duan Xingyou Li Qinhan Jin Improvement in Mercury Cold Vapour Atomic Techniques by Resorting to Organized Assemblies and On-line Membrane Drying of Vapour-B Aizpun Fernandez M R Fernandez de la Campa Alfred0 Sanz-Medel Improvement in Detection Limits in Graphite Furnace Diode Laser Atomic Absorption Spectrometry by Wavelength Modulation Technique.Plenary Lecture-Christoph Schnurer-Patschan Aleksandr Zybin Henning Groll Kay Niemax Preliminary Study on the Use of Palladium as a Chemical Modifier for the Determination of Silicon by Electrothermal Atomic Absorption Spectrometry-Zhixra Zhuang Pengyuan Yang Xiaoru Wang Zhiwei Deng Benli Huang Effect of Aqueous Organic Solvents on the Determination of Trace Elements by Flame Atomic Absorption Spectrometry and Inductively Coupled Plasma Atomic Emission Spectrometry-M Todorovic S Vidovic. Z IIIC Indirect Flame Atomic Absorption Spectrometric Determination of Papaverine Strychnine and Cocaine by Continuous Precipitation With Dragendorff's Reagent-Marceltna Eisman Mercedes Gallego Miguel Valcarcel CUMULATIVE AUTVOR INDEX ATOMIC SPECTROMETRY 337R Industrial Analysis Metals Chemicals and Advanced Materials-John Marshall UPDATE John Carroll James S. Crighton Charles L. R. Barnard 377R References continued on inside back cover 0267-9477C199318:l-Y

ISSN:0267-9477    

DOI:10.1039/JA99308FX019

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

The XXVIII Colloquium Spectroscopicum Internationale will be held in The University of York United Kingdom June 29-July 4,1993 rhis traditional biennial conference in analytical spectroscopy will once again provide a forum for atomic nuclear and nolecular spectroscopists worldwide to encourage personal contact and the exchange of experience SCIENTIFIC PROGRAMME Plenary Lecturers M.L. Gross (Nebraska) R.E. Hester (York) D. King (Cambridge) C.L. Wilkins (California) ind J.D. Winefordner (Florida) Four Parallel Streams Atomic Spectroscopy (with ICP-MS) Molecular Spectroscopy Mass Spectrometry and rJMR and Surface Science. Each session will begin with an invited lecture from a prominent scientist in the relevant ‘ield. SOCIAL PROGRAMME 4 full programme has been organised including a choir concert in York Minster choice of excursions and a social :vent in the National Railway Museum.n connection with the XXVm CSI a number of symposia and short courses will be organized. PRE-SYMPOSIUM 3rd Kingston Conference Analytical Spectroscopy in the Earth Sciences June 28-29,1993 Kingston University Surrey SHORT COURSES Introductory Chemometrics June 29,1993 University of York Vapour Generation Techniques Theory and Practice June 29,1993 University of York Spectroscopic Data Handling July 4 4 1 9 9 3 University of York POST-SYMPOSIA 5th Surrey Conference on Plasma Source Mass Spectrometry July 4 6 1 9 9 3 Applications of Glow Discharges in Optical and Mass Spectrometry July 4-7,1993 University of York Graphite Atomizer Techniques in Analytical Spectroscopy July 4-7,1993 University of Durham Trace Elements in Clinical Biochemistry July 7,1993 University of Durham Lumley Castle Hotel Co.Durham For further information contact- XXVIII COLLOQUIUM SPECTROSCOPICUM INTERNATIONALE Department of Chemistry (CSI Secretariat) Loughborough University of Technology Loughborough Leicestershire UK LEll3TUThe XXVIII Colloquium Spectroscopicum Internationale will be held in The University of York United Kingdom June 29-July 4,1993 rhis traditional biennial conference in analytical spectroscopy will once again provide a forum for atomic nuclear and nolecular spectroscopists worldwide to encourage personal contact and the exchange of experience SCIENTIFIC PROGRAMME Plenary Lecturers M.L. Gross (Nebraska) R.E. Hester (York) D.King (Cambridge) C.L. Wilkins (California) ind J.D. Winefordner (Florida) Four Parallel Streams Atomic Spectroscopy (with ICP-MS) Molecular Spectroscopy Mass Spectrometry and rJMR and Surface Science. Each session will begin with an invited lecture from a prominent scientist in the relevant ‘ield. SOCIAL PROGRAMME 4 full programme has been organised including a choir concert in York Minster choice of excursions and a social :vent in the National Railway Museum. n connection with the XXVm CSI a number of symposia and short courses will be organized. PRE-SYMPOSIUM 3rd Kingston Conference Analytical Spectroscopy in the Earth Sciences June 28-29,1993 Kingston University Surrey SHORT COURSES Introductory Chemometrics June 29,1993 University of York Vapour Generation Techniques Theory and Practice June 29,1993 University of York Spectroscopic Data Handling July 4 4 1 9 9 3 University of York POST-SYMPOSIA 5th Surrey Conference on Plasma Source Mass Spectrometry July 4 6 1 9 9 3 Applications of Glow Discharges in Optical and Mass Spectrometry July 4-7,1993 University of York Graphite Atomizer Techniques in Analytical Spectroscopy July 4-7,1993 University of Durham Trace Elements in Clinical Biochemistry July 7,1993 University of Durham Lumley Castle Hotel Co. Durham For further information contact- XXVIII COLLOQUIUM SPECTROSCOPICUM INTERNATIONALE Department of Chemistry (CSI Secretariat) Loughborough University of Technology Loughborough Leicestershire UK LEll3TU

ISSN:0267-9477    

DOI:10.1039/JA993080X021

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JASPE2 8(5) 35N-44N 673-766 197R-260R August 1993 Journal of Analytical Atomic Spectrometry Including Atomic Spectrometry Updates CONTENTS PAPERS 673 681 687 691 697 705 71 1 71 5 723 731 737 745 749 755 759 763 Performance Characteristics of a Glove Box Inductively Coupled Plasma Mass Spectrometer for the Analysis of Nuclear Materials-Jose lgnacio Garcia Alonso Dominique Thoby-Schultzendorff Bruno Giovanonne Lothar Koch Speciation of Mercury by Reversed-phase Liquid Chromatography With Inductively Coupled Plasma Mass Spectrometric Detection-Chung-Wen Huang Shiuh-Jen Jiang Determination of Trace Impurity Rare Earth Elements in High-purity Rare Earth Element Samples Using High-resolution Inductively Coupled Plasma Mass Spectrometry-Yuichi Takaku Kimih i ko Masuda Taka ko Ta kahashi Tadas h t Shimam ura On-line Removal of Interferences in the Analysis of Biological Materials by Flow Injection Inductively Coupled Plasma Mass Spectrometry-Les Ebdon Andrew S Fisher Paul J Worsfold Helen Crews Malcolm Baxter Flow Injection Systems for Directly Coupling On-line Digestions With Analytical Atomic Spectrometry.Part 2. Reactions in a Microwave Field-Thomas J Gluodenis Jr Julian F Tyson On-line Preconcentration and Determination of Mercury by Flow Injection Inductively Coupled Plasma Atomic Emission Spectrometry-P Cafiada Rudner A Garcia de Torres J M Can0 Pavon Use of the Simplified Generalized Standard Additions Method for Calibration in Solid Sampling Electrothermal Vaporization Inductively Coupled Plasma Atomic Emission Spectrometry-Sylvie Boonen.Peter Verrept Luc J Moens Richard F J Dams The OH 'Bullet'-a Promising Spatial Reference for the Inductively Coupled Plasma-Paul J Galley Gary M Hieftje Ultra-trace Determination of Cadmium by Vapour Generation Atomic Fluorescence Spectrometry-Les Ebdon Phillip Goodall Steve J Hill Peter B Stockwell K Clive Thompson Determination of Lead in Human Urine Using Electrothermal Atomic Absorption Spectrometry With Probe Atomization and Deuterium Background Correction-Juan M Varchante Gayon J Enrique Sanchez Uria Alfred0 Sanz-Medel Effect of Nickel and Palladium as Chemical Modifiers and Influence of Urine Matrix on Different Chemical Species of Selenium in Electrothermal Atomic Absorption Spectrometry-Francisco Laborda Jorge Vifiuales Jose M Mir Juan R Castillo Fructose-6-phosphate Kinase Immobilized on Controlled-pore Glass as a Substrate for Selective Separation of Antimony(ii1)-Maria Beatriz de la Calle-Guntifias Yolanda Madrid Carmen Camara Determination of Lead and Copper in Kerosene by Electrothermal Atomic Absorption Spectrometry Stabilization of Metals in Organic Media by a Three- component Solution-lvana A Silva Reinaldo C Campos Adilson J Curtius Silvia M Sella Determination of Tin in Indium Phosphide by Electrothermal Atomic Absorption Spectrometry and Inductively Coupled Plasma Mass Spectrometry-Marco Taddia Michele Bosi Vanes Poluzzi Elimination of the Interfering Effect of Transition Metals in the Determination of Tin by Hydride Generation Atomic Absorption Spectrometry-Amin M Abdallah Mohamed M El-Defrawy Nagwa Nawar Manal M El-Shamy INTER-LABORATORY NOTE Simple Stirring Device for a Slurry Sampling Technique in Electrothermal Atomic Absorption Spectrometry-Boh u mil DoCe kal ATOMIC SPECTROMETRY 197R Advances in Atomic Absorption and Fluorescence Spectrometry and Related UPDATE Techniques-Steve J Hill.John B Dawson W John Price Ian L Shuttler Julian F Tyson 239R References Typeset by Burgess Thames View Abingdon Oxfordshire - -7 Printed in Great Britain by \ - _ _ BRosJ Page Bros Norwich 0267-9477t199315.1-0I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ! I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 I I I 1 I I I I I I I I I I I I I I I I I I I I 1 I I I I I 1 ! I II i m I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I - JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY READER ENQUIRY SERVICE AUGUST '93 8 YOUR JOB TITLE POSITION 9 TELEPHONE NO - OFFICE USE ONLY t i t ( U PHOt I) FOLD HERE I I I I I I I I I I Postage will be paid by Licensee Do not affix Postage Stamps if posted in Gt. Britain Channel Islands N. Ireland or the Isle of Man I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I BUS1 N ESS REPLY SE RV IC E Licence No. WD 106 Reader Enquiry Service Journal of Analytical Atomic Spectrometry The Royal Society of Chemistry Burlington House Piccadilly LONDON W1E 6WF England 2

ISSN:0267-9477    

DOI:10.1039/JA99308BX023

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 35N Conference Report Chemistry and Applied PittCon ’93 44th Pittsburgh Conference and Exposition on Analytical Spectroscopy March 8-1 2 Atlanta GA USA At the opening ceremony of this year’s PittCon as it is fondly known by all who attend Georgia’s Governor Zell Miller declared Georgia ‘an up and coming place to be for science’ and he predicted that Georgia would be a world class scientific research centre in the future. He also invited exhibitors and visitors to take some time out and enjoy Atlanta and ‘spend money-we need it!’. He was possibly thinking of the Olympic Games which Atlanta is hosting in 1996 when he extended those hospitable words. He could not have known that seven days later he would be adding Georgia to the list of 11 US states requesting federal aid after being hit by a Winter storm that stranded many of PittCon’s visitors for days and left them no choice but to stay and spend! PittCon had just wound down when the ‘Blizzard of ’93’ as it was dubbed in the US headlines struck the East coast with up to 12 feet of snow and hurricane-force winds closing most airports from Atlanta to Boston and turning most interstate highways into parking lots.PittCon is the largest exhibition and technical programme of its kind in the world and this year it attracted over 1000 exhibitors displaying over 5 miles of exhibits over 1800 oral pre- sentations in the form of symposia poster-sessions mini-meetings award addresses and short courses and 30000 visitors. In short a blizzard of activity shoe-horned into five days leaving every visitor exhausted and with the feeling that never was so much ground covered on the tip of the iceberg. The sheer size of the exhibition and technical programme limits the num- ber of US cities in which it can be housed and for the immediate future Chicago New Orleans and Atlanta are the only three slated.This year’s facili- ties at the Georgia World Congress Center were excellent and accommo- dated the exhibition in three halls and the technical programme in meeting rooms above. Considering the number of visitors the halls were not uncom- fortably overcrowded and the meeting rooms were spacious. The technical programme this year lacked lustre in its scope. PittCon usually presents a programme that strikes a balance between leading edge research and commercially viable wis- dom which attempts to cover many subjects ranging from the nitty gritty of precise analytical measurements through to the more topical concerns of all chemists with conscience. Con- spicuous by their absence were the plenary lectures-always the most popular and best attended-but one is promised for next year.However there was content aplenty for those willing to sift through the symposia carefully and there was en- tertainment. Some of this year’s speak- ers made courageous efforts to leave the stiff and starchy presentation be- hind them and portray their work with an element of fun and humour. One of those speakers was Professor Robert Samuel Houk senior chemist at the Ames Laboratory US Depart- ment of Energy who was presented with this year’s Maurice F.Hasler award for his work in the fundamental studies and applications of plasma ion sources for mass spectrometry. His research paid particular attention to ICPs time-of-flight and ion-trap mass spectrometry. His award address en- titled ‘Now for Something Completely Different The Scientific Impact of ICP-MS’ was particularly humorous as he likened his career to that of Napo- leon Bonaparte during the Napoleonic wars! For example with the aid of slides Houk was able to show that he like Napoleon started his career with long hair! Environmental science geo- chemistry and the nuclear and semi- conductor materials industries now make widespread use of the high sensi- tivity and selectivity of ICP-MS but Houk feels that there are several areas in which ICP-MS is underutilized; for example stable isotope tracing of min- erals in nutrition particularly zinc and elemental speciation by ICP-MS using a nebulizer.The symposium entitled ‘Promising Analytical Techniques on the Horizon’ was dedicated to the memory of Professor R. Sam Houk recipient of the I993 Maurice Hasler A ward36N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 Professor L. B. (Buck) Rogers who pioneered developments in a wide range of analytical techniques includ- ing electrochemistry separations tech- niques and spectroscopy. Of particular interest was Gary Hieftje’s (Indiana University) talk on ‘Spectrometric Measurements and Instrumentation on the Horizon’ in which he sug- gested future paths that spectrometric measurements and inst rumen t at ion might follow.Particularly that they will be more biologically oriented use a greater range of dimensions make better use of spatial resolution have increased signal processing capa- bilities and use diode lasers. The importance of data visualization and imaging technology will progress for example with ICP imaging to show three spatial dimensions for true 3-D imaging using two spatial axes. The impact of nanotechnology will mean greater development of molecular- level instrumentation and advances now being made in semiconductor lasers suggest that in the not too distant future techniques like these may become routine and practical. Furthermore Hieftje deduced that spectrometric developments coupled with the advancement of new techno- logies would mean that such instru- ments will be capable of examining a sample as it is being analysed of tuning their own operating character- istics in order to optimize the sample characterization and therefore pro- duce accurate analytical results during the initial sample examination.Again H ieftj e’s present at ion was both humorous and enlightening. For example he showed a slide of a natural polarizing spectrometer-a goldfish! The Special Symposium celebrating the ‘10th Anniversary of the First Commercial ICP-MS Instrumenta- tion’ again featured entertaining pre- sentations from Sam Houk (Strategy and Tactics for ICP-MS for the Third Millenia A.D.) and Gary Hieftje (Atomic Mass Spectrometry-Current Status and Future Prospects).The opening remarks to the Symposium were given by Professor Velmer Fassel another early pioneer of ICP-MS and of course Sam’s supervisor. The ses- sion included presentations from other leading exponents of the subject Dr Don Douglas (SCIEX) ‘ICP-MS in 1993 Looking Back Looking Forward’; Professor Joe Caruso (University of Cincinnati) ‘Sample Introduction for ICP-MS’; Dr Jim McLaren (NRC Canada) ‘From Lith- ium to Uranium Picograms to Per Cent’. As can be seen simply from the titles of these presentations this excellent symposium was a fitting cele- bration of the last 10 years work on ICP-MS. It covered the history of the development of ICP-MS practical ex- periences and applications through the exciting future of the technique. A full report of this symposium can be found on page 37N. Meanwhile back down in the exhi- bition halls a technological showcase of the newest fastest best and bright- est that instrument manufacturers have to offer was on display.The continuing impact of developments in electronics and computer technology was evident in terms of faster analysis times improved sensitivity greater flexibility in technique usage and improved data handling and inter- pretation. Commercial viability of all analytical techniques is also greatly influenced by instrument component developments especially when those components have been around long enough to produce significant data. However it would appear that the battle of the arrays is on and diode array detection systems were the talk of spectroscopists at PittCon.Particu- larly Perkin-Elmer with its segmented- array charge coupled device (SCD) which permits operation in the UV region between 160 and 200 nm Baird Corporation with its megapixel charge coupled device (CCD) and Thermo Jarrell Ash which is marketing a charge injection device (CID) spectrometer. The Optima 3000 ICP-OES spectro- meter from Perkin-Elmer consists of an Cchelle based polychromator with an SCD a 40 MHz free running r.f. generator with true power control and temperature-controlled plasma pneu- matics. The user can measure the spectral background and each analyte simultaneously allowing 60 elements to be measured in less than 1 min. The optical system and SCD provide access to over 5000 atomic emission lines including over 200 prominent ICP lines.Inductively coupled plasma mass spectrometry would appear to be to- day’s technique for elemental determi- nations and if the new instruments (and lecture sessions) are anything to go by has a very promising commercial future. Wherever there is an increase in demand an increase in supply is not far behind and so it is not surprising that more companies are now market- ing ICP-MS instruments and new play- ers in the field include Varian Spectro Analytical Thermo ,Jarre1 Ash and Finnigan who are now marketing the previous Turner instrument. Spectro has introduced its Spectro- flame ICP-MS which it is claimed allows the determination of nearly all elements in the ultra-trace range with exceptional precision in approximately 20 s. Leeman Labs and Thermo Jarrell Ash have both introduced dedicated multi-element AA systems.Leeman Labs launched its simultaneous diffi- cult element analyser for the determi- nation of As Se Sb Pb and T1. The PS5000 is a graphite furnace AA sys- tem which is able to measure these elemental wavelengths at very high efficiency and is designed to increase productivity and analytical quality for contract laboratories. The AA-Scan series of AA spectrophotometers from Thermo Jarrell Ash has Smith-Hieftje background correction is run by an external PC and can be configured with either single-beam or double-beam op- tics. Furnace flame or automated flame atomizers are optional. The AA- Scan 4 includes a four lamp arrange- ment and a galvanometer controlled section mirror which provides for the simultaneous determination of up to four elements.The AA-Scan 8 is also a multi-element system which includes a motorized elevator to switch between two four lamp arrays. It is capable of measuring by flame or furnace AA up to four elements at a time and up to eight elements in an unattended run. Also from Thermo Jarrell Ash is the QS-1 mercury analyser which incor- porates a continuous flow mercury cold vapour module detection and readout system and a random access autosampler. The system has im- proved detection limits high sensitiv- ity and an automatic detection system which prevents contamination from high mercury samples. Away from the hustle and bustle of the exhibition halls The Royal Society of Chemistry hosted an evening recep- tion as it has done in past years as part of its role at PittCon.Almost 300 guests including some of PittCon’s organizers and some of the technical programme’s keynote speakers relaxed with friends and colleagues. The recep- tion is hosted each year at PittCon to provide an opportunity to meet all the US chemists who contribute to referee for and purchase the RSC‘s publica- The RSC standJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 37N tions. The RSC’s role at PittCon is vital for the continuing promotion of Infor- mation Services abroad. To that end the RSC’s staff manned an exhibition booth displaying the Society’s books journals and databases while some of the editorial and advertising staff scouted around for new ideas authors articles and book titles and new con- tacts for advertising.Next year PittCon will be held in Chicago Illinois in February-a Northern US city much more likely to Andrea Bedson be snowbound at that time of year KA YMICH INC. than this year’s Southern host city. 3387 Anderson Highway However Atlanta will be remembered Powhatan VA 23139 USA for a long time to come by all PittCon participants as the blizzard city! PittCon Symposium. ICP-MS The 10th Anniversary of the First Commercial Instrumentation (1983-1993) When attending a conference there is usually at least one symposium which one feels simply cannot be missed. For those conferees at the 1993 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy interested in inductively coupled plasma mass spectrometry that session was ‘ICP- MS The 10th Anniversary of the First Commercial Instrumentation (1983-1993)’.The symposium was arranged and presided over by V. B. Conrad (Consol Inc.) Several of the current leaders in the field expressed their views on a number of topics. The symposium began with a few opening remarks by the presider and then the surprise introduction of Vel- mer A. Fassel who gave some delight- ful memories of one of his former students and a co-inventor of ICP-MS Professor Sam Houk who was this year’s recipient of the Maurice F. Hasler Award. Professor Fassel stated there was little research activity on ICP-MS in other laboratories at the time the first paper was published in 1980 by Houk Fassel Gerald D. Flesch Harry J. Svec Alan L. Gray and Charles E. Taylor.This changed of course after the first commercial instrument was introduced in 1983 by SCIEX. In closing Professor Fassel quoted David W. Koppenaal as saying that ‘the technique appears poised for destiny and longevity in the trace analysis field’. These introductory remarks pro- vided an excellent lead into the first speaker’s talk. Donald Douglas of SCIEX discussed ‘ICP-MS in 1993 Looking Back Looking Forward‘. He spoke of the technical developments leading up to the first commercial instrument and the early challenges met by ICP-MS users including clogg- ing of the sampling orifice and very high continuum backgrounds. Rapid progress however ensued and today there are several ICP-MS instrumental manufacturers and roughly 800 ICP- MS systems installed in the world.The technique certainly seems poised for the future which will likely include developments in ion spray MS com- monly used in organic MS. Professor Joseph A. Caruso of the University of Cincinnati presented the second talk of the symposium enti- tled ‘Sample Introduction for ICP- MS’. Professor Caruso discussed work in his research laboratory utilizing novel sample introduction techniques such as electrothermal vaporization hydride generation liquid chromato- graphy (LC) gas chromatography (GC) and supercritical fluid chromato- grapy (SFC). These techniques provide alternatives to solution nebulization which is the most common method of sample introduction for plasma MS. Additionally coupling such chromato- graphic techniques as LC GC and SFC to ICP-MS allows one to obtain speciation information at the ultra- trace level.Finally a few slides in yellow and black were dedicated to Professor Houk who is a big fan of Pittsburgh athletic teams! After a brief recess Professor Gary M. Hieftje from Indiana University spoke on the current status and future prospects of atomic mass spectrome- try. A review of the strengths and weaknesses of modern plasma source (PS)-MS instruments was given. He stated that no other atmospheric pres- sure source is likely to be more effici- ent than the ICP. The most significant shortcomings however include ma- trix and spectral interferences. In addi- tion Professor Hieftje discussed ‘tan- dem’ atomic MS as a means to obtain greater flexibility and the advantages and disadvantages of time-of-flight mass spectrometry.His idea of the next generation of PS-MS instruments includes the simultaneous determina- tion of all isotopes. ‘From Lithium to Uranium Pico- grams to Per Cent’ was the title of the fourth presentation of the symposium. The overall theme of Dr Jim McLar- en’s talk (National Research Council of Canada) was the versatility of ICP- MS. There are numerous trace elemen- tal and environmental applications of the technique to a variety of samples such as sea-water freshwater and marine sediments. In particular Dr McLaren presented his work on the analysis of natural waters; HPLC-ICP- MS techniques were also addressed. The last (but certainly not least) speaker of the symposium was Professor Sam Houk of Iowa State University. Professor Houk discussed ‘Strategy and Tactics for ICP-MS’ for the future and in particular ‘the Third Millenium A.D.’ As with any analysis technique there are areas in ICP-MS which require future im- provements.These areas include the reduction of matrix interferences at- tenuation of polyatomic ion inter- ferences and LC-ICP-MS or capillary electrophoresis ICP-MS for speciation analyses. The future of ICP-MS may include according to Professor Houk ion deposition or ion implantation as well as floating interfaces. Much to the disappointment of his fans Professor Houk did not regale the crowd with detailed excerpts of the adventures of Napoleon and Columbus! For all who attended the ICP-MS symposium honoring the tenth anni- versary of the introduction of the first commercial instrument was an en- lightening and educational experience.It is always exciting to listen to experts in one’s field discuss the events lead- ing up to significant findings review their present work in the area and address directions for the future. In conclusion as David W. Koppenaal humorously put it in his review of atomic mass spectrometry in the 1992 fundamental reviews issue of Analytical Chemistry ICP-MS ‘has truly become a technique for the masses’. Francine A. Byrdy Department of Chemistry University of Cincinnati Cincinnati OH USA38N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 Instrumental Technique Development March 24-25 1993 Fitzwilliam College Cambridge UK Each year the Atomic Spectrometry Updates (ASU) Editorial Board of the Journal of Analytical Atomic Spectro- metry hold a one day Editorial Meet- ing followed by an open one day Scientific Meeting.To all intents and purposes the Scientific Meeting is a celebration of recent developments in the field of Atomic Spectrometry. This years meeting was held in Fitzwilliam College Cambridge and was co-spon- sored by the Atomic Spectroscopy Group of the Analytical Division of the RSC. As has become customary two Editorial Board Members from overseas were invited to the meeting to present a lecture on the general theme of ‘Instrumental Technique Development’. In the evening prior to the meeting a Sherry Reception was held at the Salt- marsh Room of Kings College Cam- bridge. During the Board Dinner on the following evening presentations were made to the visiting overseas speakers Professor Bob Michel (University of Connecticut USA) and Dr Henryk Matusiewicz (University of Poznan Poland).The scientific meeting was opened by Doug Miles chairman of the ASU Editorial Board who introduced the first of the guest speakers Professor Robert Michel (Connecticut USA) who gave an excellent overview on Laser Excited Atomic Fluorescence Spectrometry (LEAFS) in a Graphite Furnace. With such a subject many presenters could easily be bogged down in the theoretical aspects how- ever Robert kept the subject alive with his wit his basic ‘down to earth’ philosophy (i.e. practical) his honesty and openness and simply his enthusi- asm for Atomic Spectrometry. With respect to honesty and openness Robert explained that lasers to say the least are awkward to work with re- quiring at present a few days to change dyes in the tuneable laser in order to change analytical wave- lengths. Once the system is up and running detection limits obtained are at the femtogram level and the concept of ‘single atom detection’ becomes more than a theoretical discussion.Further the graphite furnace LEAFS technique has a dynamic range of 5-7 orders of magnitude. Here lies the root of yet another ‘practical’ problem -the method is so sensitive that the single most likely reason for poor analytical results is solution con- tamination. In order to increase the Doug Miles (L) making a presentation to Bob Michel dynamic range to a more ‘practical’ range of concentration an idea first proposed by L’vov for electrothermal AAS is being investigated.This idea involves the measurement of stray light in the spectrometer and the point of calibration curve ‘rollover’ and then extension of the dynamic range by applying a mathematical correc- tion. This work is on-going as is the development of a more practical laser system based upon solid state lasers with a hydrogen Raman cell to enable final wavelength tuneability. The second guest speaker was Dr Henryk Matusiewicz (Poznan Poland) who presented a lecture on ‘Novel Approaches to Microwave Sample Preparation and Sample Introduction to Microwave Plasma Atomic Emis- sion Spectrometry’. This lecture re- viewed some of the older methods of sample preparatiori and then con- tinued into the area of microwave Doug Miles (L) thanking Henryk Matusiewicz digestion procedures.Henryk showed a high pressure digestion bomb which used a microwave wave-generator in- stead of a magnetron to focus the microwaves inside a water-cooled stainless-steel jacket containing a sealed ceramic sample container. This enabled the complete digestion of organic samples with the main advan- tage of zero cool-time which is the time often ignored by workers report- ing the advantage of speed in micro- wave digestion procedures. The disad- vantages of the method were stated as the ‘batch’ nature of the procedure and that it was labour intensive. Of more current interest was the discussion of ‘on-line’ microwave digestion proce- dures involving ‘stopped-flow’ flow injection (FI) apparatus. It was con- cluded that this procedure is still at the preliminary stages of development and that no high pressure FI microwave digestion systems have as yet been described.Surely this is an idea worthy of commercial investment and development! The morning session was concluded with a lecture by Dr A. McMahon (AEA Technology UK) on ‘Recent Develop- ments in Resonance Ionization Mass Spectrometry (RIMS)’ and a lecture by Dr J. Bacon (Macaulay Land Use Research Institute) on ‘Thermal Ioniza- tion Mass Spectrometry (TIMS) for Measurement of Stable Isotopes in Environmental Studies’. On a lighter note it seems that Adam McMahon had to travel the world just to get a bit of research done on his chosen research interest. Adam suggested that after 20 years of development RIMS is just beginning to find its niche amongst an array of other instrumental techniques in analytical science.The applications discussed included the imaging of trace elements in biological samples and the measurement of Sr isotope ratios. The lecture by Jeffrey Bacon on TIMS in- cluded some excellent precision studies on isotope ratio measurements for Nd Pb and Sr. For Nd and Sr precision figures of one part in 1 O6 were presented for isotope ratio measurements. From the practical point ofview the technique involved extensive sample clean-up/ preparation and the sample throughput is low. However it is probably the most precise method for measuring isotope ratios and when combined with iso- tope dilution analysis the technique can also offer the highest quality accu- racy. One application discussed was the measurement of Sr isotope ratiosJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 39N ASU Board Members at the Board Dinner. From leji Jim Crighton Adam McMahon Simon Sparkes and John Dawson in surface waters. The Sr isotope ratio in surface waters reflects the minimum age of the rocks over which the water flows and is of importance to isotope geologists. Further applications were presented including Cu:Zn isotope ratios in human nutrition studies and Pb isotope ratios in field experiments. The afternoon session included lec- tures by Dr Simon Sparkes (University of Plymouth) on ‘Measurement of Radionuclides by ICP-MS’ Dr Ian Shuttler (Perkin-Elmer Germany) on ‘The Development of AAS Instrument Control Software’ and Alan Batho (Thermo-Electron) on ‘Every Picture Tells a Story-ICP Signals Captured’.The lecture by Simon Sparkes outlined the use of ICP-MS to determine low levels of long-lived radionuclides e.g. 238U 235U 232Th 237Np 99Tc and 1291. One of the interesting points raised by Simon was that the ion-extraction ca- pability of the ICP-MS interface used was only 1 part in lo5 and that a small increase in this efficiency could lead to a large sensitivity increase of the tech- nique. The advantages of the tech- nique for these elements were isotope specificity simplicity speed few inter- ferences and high sensitivity. The presentation by Ian Shuttler changed the emphasis of the day’s proceedings from instrument hard- ware to software. This was a well presented lecture that took the audi- ence back to the days when atomic absorption instruments were com- pletely manual and comprised of knobs switches things that occasion- ally went bang and the requirement of a ‘Buck Rogers’ look-alike to give the results credibility.This reviewer is of course too young to remember such instruments. Ian then proceeded through the years reviewing the intro- duction of automation in analytical instruments and explained the ad- vances in software development up to the present day. The future develop- ment in software was forecast to be focussed upon one computer to con- trol many different instruments; more interactive screen software; intelli- gent/knowledge based systems; im- proved Windows based software; and advanced quality control and self- testing software.This lecture differed from the usual ‘instrument manufac- turer’ type lecture in that it addressed the philosophy of the type of software required by analytical chemists and that can only be praised. It seems that Perkin-Elmer now have an analytical chemist specifying software and that might explain why the newer instru- ments are becoming more user friendly (compare the PE-4100 to the The final lecture of the day from Alan Batho Thermo Electron also started by taking the audience back to the beginnings of optical emission spectroscopy namely with arc and spark sources when the emission spec- tra were recorded on photographic plates. In the intervening years the photographic plate has been super- ceded by the photomultiplier tube (PMT) as detector and while the PMT has many advantages its adoption meant that the complete elemental picture of a sample i.e. all the ele- ments was lost. Alan discussed how with the use of a solid-state detector such as the charge-injection device (CID) array as employed in the IRIS emission spectrometer that this situa- tion has been recovered. Thankfully Alan provided a useful and slow step- by-step approach to how CID arrays work. The CID array provides a com- plete picture of every emission line of every element in the sample which brings us back to the same situation as in the early days with photographic plates. Naturally in the 1990s the information is presented on a com- puter screen and the views of the software images produced and the use of the MS Windows package illus- trated some of the points raised by the previous lecturer. Overall an excellent day was had by all and thanks must go to all the speakers and the organizing commit- tee. My ‘lecturer of the day’ award must go to Professor Robert Michel who told stories of being covered in red dye whilst trying to change analytical wave- lengths in his laser system. My guess is there aren’t many Professors of analyti- cal chemistry worldwide who still get their hands dirty. My thanks must also go to the ASU Editorial Board who asked me to review this meeting. P E-30 30). Alistair A. Brown [Jniversity of Plymouth Drake Circus Plymouth UK PL4 8AA

ISSN:0267-9477    

DOI:10.1039/JA993080035N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 39N Diary of Conferences and Courses 1993 University of Edinburgh UK P. E. Hutchinson Conference Orga- nizer Analytical Division The Royal Euroanalysis v1119 The Eighth Euro- Details can be found in J. Anal. At. Society of Chemistry Burlington House Piccadilly London UK pean Conference on Analytical Chemis- WlV OBN. Telephone 071 437 8656; try September 5-1 1 fax 071 734 1227. Spectrom. 992 7 49N. For further information contact Miss40N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 International Conference on Micro- wave Enhanced Chemistry September 29-30 Birmingham UK The use of Microwave energy to con- trol and aid chemical reactions has made a significant impact on the capa- bilities and demands of todays scien- tists.Current technology speeds up many tedious reactions and gives improved analytical data. Microwave application has revolutionized many procedures in organic and inorganic chemistry by greatly enhancing num- erous analytical chemistry techniques. This symposium brings together many leading authorities in microwave tech- nology who during the symposium will review and discuss past and cur- rent applications highlighting future trends. Exhibition and Workshop A workshop exhibition is planned alongside the Conference for delegates and those who wish to view the latest technology . Venue and Timing The technical sessions of the confer- ence will be held at the Birmingham International Convention Centre Broad Street Birmingham. Registra- tion will take place on Wednesday September 29 1993 from 08.00 am.The Conference will open on the morning of Wednesday September 29 and the technical sessions will conclude late afternoon on Thursday September 30. For those travelling by car there is ample parking. The Convention Centre is also within easy reach of New Street Railway Station. Conference Fee The Conference fee for registration is E235+VAT which includes par- ticipation in all technical sessions conference proceedings; lunch and refreshments; conference dinner; and accommodation. Day delegate rate &95+VAT includes lunch and re- freshments; and conference proceed- ings. Technical Programme Approximately 12 papers will be pre- sented in a series of technical sessions with time allowed for questions and discussion. All papers have been care- fully selected to ensure a high technical standard.Speakers will include Dr H. M. Kingston (Kingston Duquesne Uni- versity PA USA); Dr E. Neas (Rubbright Corporation); Dr D. E. Barclay (CEM Corporation); Dr P. Riby (University of Greenwich); K. E. Williams (University of Hull); Dr L. Jessie (CEM Corporation); Dr M. Collins (CEM Corporation); Dr M. Mingos (Imperial College London); G. Engelhart; (CEM Cor- poration); David Charlesworth (University of Greenwich); Dr G. Bond (University of Hull); Dr R. B. Moyes (University of Hull); and Dr S. Haswell (University of Hull). For further information contact David J. Lofty Conference Organiser MEC Conference c/o CEM Micro- wave Technology Ltd. Buckingham UK MK18 IWA. Telephone 0280 822873; fax 0280 822342.5th Beijing Conference and Exhibition on Instrumental Analysis October 11-16 Beijing China Details can be found in J. Anal At. Spectrom. 1992 7 39N. For further information contact The Secretariat of BCEIA Room 5412 Building 4 Xi Yuan Hotel 10046 Beijing P. R. China. Telephone 86 1 83 13388/54 12; telex 20056 BCEIA CN; fax 86 1 8320908. 2nd National Conference on Inductively Coupled Plasma Mass Spectrometry October 16-17 Detroit MI USA For further information contact F. W. Kunz Ford Research Laboratory M/D 5-3061/SRL Room 1341 P.O. Box 2053 Dearborne MI 48121 USA. Telephone (3 13) 845-8536 fax (31 3) 323-7397. Society for Applied Spectroscopy Short Courses October 16- 17 Detroit MI USA Fourier Transform Infrared Spectro- metry Plasma Spectrochemical Analysis Applied Near-infrared Spectroscopy Modern Analytical Spectroscopy Biological Infrared and Raman Spec- troscopy Modern Furnace Atomic Absorption For further information contact So- ciety for Applied Spectroscopy 198 Thomas Johnson Drive S-2 Fred- erick MD 21702-4317 USA.Tele- phone (3 10) 694-8 122. 20th Annual Meeting of the Federation of Analytical Chemistry and Spectro- scopy Societies (FACSS) October 17-22 Detroit MI USA For further information contact FACSS P.O. Box 78 Manhattan KS 66502-0003. Telephone 30 1 846 4797. Environmental Analysis and Assess- ment. A Series of Nine Short Courses Modules October 1993-March 1994 Course Aims and Content The latest legislation the Environ- mental Protection Act seeks to identify and regulate all forms of con- taminants.The courses are designed for anyone with an interest in environ- mental problems and are suitable for a wide range of participants including managers analysts consultants and researchers from industry regulatory authorities research centres and edu- cation institutions. Each module com- prises lectures discussions practicals and where relevant an external visit. Module 1 Preparing for Analysis October 18-21 CARE Dr K. E. Jarvis Dr R. C. 0. Gill and J. G. Williams Sample preparation methods for ana- lytical techniques. Methods for drying ashing digesting fusing and pre- concentrating samples. Sources of contamination reagent quality and handling hazardous substances. Module 2 Inductively Coupled Plasma Atomic Emission Spectrometry October 25-28 RHUL Dr J.N. Walsh and Dr 1. Jarvis Use of the technique for analysis of a wide range of materials from the natural environment including soils waters dust sediments and sewage sludges. An overview of attainments and limitations. Module 3 Analysis of organic pollu- tants November 1-4 CARE Dr R. Large and Dr G. le Patourel Determination of pesticide residues dioxins dibenzofuran PCBs and petroleum hydrocarbons. Analysis of contaminated soils groundwater qual-JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 41N ity the ‘priority pollutant’ approach to environmental analysis. Module 4 Inductively Coupled Plasma Mass Spectrometry November 8-1 1 RHUL Dr K. E. Jarvis and Dr J. G. Williams Environmental applications of this powerful new multi-elemental anal- ytical technique.Fundamentals in- terferences data collection isotopic measurements stable tracers and lasers for solid sample introduction. Module 5 Radioanalytical Methods November 29-December 2 CARE Dr S. J. Parry Measurement of alpha- beta- and gamma-radiation in the environment. Principles and applications of neutron activation and gamma-ray spectro- metry for multi-elemental analysis of stable trace elements. Module 6 Appropriate Sampling and Analysis of the Environment February 7-10 CARE Dr M. H. Ramsey and Dr P. J. Potts Theory methodology and practice of sampling media such as air water vegetation and soil. Error estimation for sampling and analysis. Selection of the most appropriate methods. Practi- cal field sampling exercises. Module 7 Legal Aspects February 14-17 RHUL Professor J. Mather Environmental impact assessment leg- islation the Control of Pollution and Environmental Protection Acts.Inte- grated pollution control and Duty of Care. The role of HSE HMIP NRA and NII. Module 8a and 8b Environmental Pathways (double module) February 21-24 and February 28-March 3 CARE Dr G. Shaw and Professor J. Mather The analysis and tracing of pathways by which contaminants move through the environment and affect man. Illustrative examples will be used including. Atmospheric to terrestrial transfer. Toxic chemical (PCB) incin- eration heavy metal (cadmium) con- tamination Chernobyl fallout and acid rain. Terrestrial to aquatic trans- fer. Water pollution from pesticides and fertilizers disposal of domestic waste to landfill radioactive waste disposal and mine water pollution.Aquatic to terrestrial transfer. Marine/ land transfer of radionuclides coastal and estuarine pollution. Terrestrial to atmospheric transfer. Methane from landfill sites radon in Cornwall. Soil speciation aerosol deposition and dis- persion field loss and resuspension; uptake of contaminants by plants animals and man. Module 9 Risk assessment March 7-10 CARE M. J. Minski Definition of risk modelling of path- ways discussion of models compari- son and verification. Deterministic and probabilistic risk assessment. Hu- man error identification. CIMAH and the environment. Venue Modules marked CARE will be held at the Centre for Analytical Research in the Environment at Imperial College Silwood Park Campus near Ascot Berkshire.Modules marked RHUL will be held at the Geology Depart- ment Royal Holloway College University of London near Egham Surrey. Accommodation All courses are residential and partici- pants will be accommodated in the same local hotel. Transport can be provided to and from the hotel please indicate on the booking form if it is required. Participants can make their own accommodation arrangements with a reduced course fee. Basic self-catering hostel accommo- dation is available at Silwood Park for students and academic staff wishing to attend the modules at a reduced rate. Transport will not be provided from Silwood to RHUL (5 miles). Fees The full fee (VAT exempt) covers tuition course material and where available a copy of the up-to-date book on the topic written by the presenter.All food and residential accommodation costs are included. The full fee for each module will be €750 but a discount of f50 per mo- dule is available for early payment at least one month before it starts. For participants making their own accom- modation arrangements the module fee is €525 with a ESO discount for early payment. Details of the reduced rate for academics and students who require hostel accommodation will be supplied on request. For further information contact Im- perial College Continuing Education Centre Room 558 Sherfield Building South Kensington London UK SW72AZ. Telephone 071 225 8667; fax 071 225 8668. 3rd International Conference LASER M2P December 8-10 1993 Lyon France Details can be found in J.Anal. At. Spectrom. 1993 8 12N. For further information contact Centre Jacques Cartier Conference Laser M2P 86 rue Pasteur 69365 Lyon Cedex 07 France. Telephone (33) 78 69 72 21; fax (33) 78 61 07 71. 1994 1994 Winter Conference on Plasma Spectrochemistry January 10-15 1994 San Diego CA USA Details can be found in J. Anal. At. Spectrom. 1992 7 49N. For further information contact Dr R. M. Barnes 1994 Winter Conference on Plasma Spectrochemistry c/o ICP In formation Newsletter Department of Chemistry GRC Towers Univer- sity of Massachusetts Amherst MA 01003-0035 USA. Telephone 41 3 545 2294; fax 41 3 545 4490. 45th Pittsburgh Conference and Expo- sition on Analytical Chemistry and Applied Spectroscopy February 28-March 4 Chicago IL USA For further information contact Pittsburgh Conference 300 Penn Cen- ter Boulevard Suite 332 Pittsburgh PA 15235-9962 USA.24th Annual Symposium on Environ- mental Analytical Chemistry May 16-19 1994 Ottawa Canada For further information contact M. Malaiyandi CAEC Chemistry De- partment Carleton University 125542N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 Colonel By Drive Ottawa Ontario Canada. International Symposium on Microche- mica1 Techniques (ISM ’94) May 16-20 Montreux Switzerland The International Symposium on Microchemical Techniques (ISM ’94) will have its next meeting in a joint organization with the Deanville Con- ference 1994-Symposium on Analyt- ical Sciences (SAS ’94) in Montreux Switzerland from May 16-20 1994. For further information contact Nicko & C.R.I. Associes 7 Rue d’Argout F-75002 Paris France.Telephone + 33- 1-42 334766; fax +33-1-40 41 92 41. Biosensors ’94 The Third World Con- gress on Biosensors June 1-3 New Orleans LA USA Following two previous highly success- ful conferences Biosensors ’94 will take place from June 1-3 1994 in New Orleans LA USA. The World Con- gress on Biosensors is the largest and most well represented conference dedicated to this field. Meeting every two years in different continents it serves those interested in research development application and com- mercialization of biosensors. It brings together the prime movers and opin- ion leaders from around the world in a critical appraisal of the latest original research and industrial innovation. Biosensors clearly make money in niche markets but still the fascination of integrating biology and electronics together in novel analytical devices fires the imagination towards a new generation of more widely applicable products.This possibility is fuelled by the increased understanding gleaned in recent years which provides a sound foundation for both novel science and product development. Format of the Congress Biosensors ’94 is a three day event consisting of plenary sessions on the following commercial development and application of biosensors high- lighting the issues and elucidating recent successes in this inherently ap- plied subject; enzyme-based sensors; and affinity sensors including recep- tor-based systems. Plenary sessions will be followed by selected original papers presented in three parallel oral sessions and a poster display.Previously unpublished contribu- tions are invited either within the scope of the plenary topics or under the title ‘Whole Cell-based Sensors and General Aspects of Biosensors’. As a new addition to the Congress there will be a display of commercial equipment. Applications are invited from organizations wishing to exhibit their products. For further information contact Kay Russell Conference Department Elsevier Advanced Technology May- field House 256 Banbury Road Oxford UK OX2 7DH. Telephone +44 (0) 865 512242; fax +44 (0) 865 3 1098 1. 6th International Conference on Flow Analysis June 8-11 Toledo Spain After the successful previous meetings in Amsterdam (1979) Lund (1982) Birmingham (1 985) Las Vegas (1 988) and Kumamoto (1 99 l) the Sixth Flow Analysis conference will be held in Toledo in June 1994.Venue Toledo is a historic city located 90 km from Madrid where the three most relevant cultures of Spanish history (Arabian Jewish and Christian) meet. Its historic and artistic monuments make it especially appealing to visi- tors. The Conference shall be held at the Hotel Beatriz which boasts superb facilities for accommodation of the participants and development of the scientific sessions. Participants and accompanying persons shall be offered an interesting social programme. Topics The Conference will basically be con- cerned with the following flow analysis topics general aspects; FI chemo- metrics; detection systems; separation techniques (on-line sample treatment); sensors and continuous flow tech- niques; applications (environmental food clinical and industrial analysis); and process control (biotechnology).Two special sessions devoted to ‘Flow Analysis Nomenclature’ and ‘Foundation of an International Society for Flow Analysis’ will be arranged. Scientific Programme The scientific programme will consist of invited lectures and oral and poster presentations There will also be an exhibition of commercially available instrumentation for flow analysis. For further information contact M. Valcarcel/M. D. Luque de Castro Flow Analysis VI Departamento de Quimica Analitica Facultad de Cien- cias E- 14004 Cordoba Spain. Tele- phone 34 57 218616; fax 34 57 2 18606. Seventh Biennial National Atomic Spectroscopy Sympsosium July 20-22 1994 University of Hull Hull UK Details can be found in J. Anal. At. Spectrom. 1992 7 49N. For further informtion contact Dr Steve Hill Department of Environ- mental Sciences University of Plymouth Drake Circus Plymouth Devon UK PL4 8AA. 13th International Mass Spectrometry Conference August 29-September 2 Budapest Hungary For further information contact Hun- garian Chemical Society; FO u. 68 H- 1027 Budapest Hungary. Telephone 361 201 6883; fax 316 15 61215. 7th International Symposium on Envi- ronmental Radiochemical Analysis September 2 1-23 Bournemouth UK The purpose of the Symposium is to examine radionuclides in environmen- tal and biological materials; nuclear counting techniques applicable to the above; the application of radio- chemical methods for environmental studies; and quality assurance. Dates to Note Synopses of papers; January 28 1994. Final date for registration July 15 1994. For further details contact Dr P. Warwick Department of Chemistry Loughborough University of Techno- logy Loughborough Leicestershire UK LEll 3TU. Telephone 0509 222585 or 0509 222545; fax 0509 233 163.

ISSN:0267-9477    

DOI:10.1039/JA993080039N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 43N Future Issues will Include- The September issue of JAAS will feature a selection of papers presented at the 1993 European Winter Conference on Plasma Spectrochemistry Granada Spain. Profile of Serum Silicon in Aluminium Overloaded Patients on Regular Hae- modialysis Treatment-Ibrahim H. Fahal Mohammed Yaqoob Peter McClelland Peter S. Williams Rash- eed Ahmad James D. Birchall and Norman B. Roberts Sensitive Method for Determination of Lead by Potassium Dichromate- Lactic Acid Hydride Generation In- ductively Coupled Plasma Atomic Emission Spectrometry-M. C. Valdes-Hevia y Temprano M. R. Fer- nandez De La Campa and A. Sanz- Medel Boron Determination in Steels by In- ductively Coupled Plasma Atomic Emission Spectrometry.Comparative Study of Spark Ablation and Pneuma- tic Nebulization Sampling Systems -Aurora G. Coedo Teresa Dorado Ester Escudero and Isabel G. Cob0 Consideration of the Chemical Reacti- vity of Trace Impurities Present in a Glow Discharge-S. K. Ohorodnik S. Degendt S. L. Tong and W. W. Harrison Analysis of Aluminium Oxide Powder by Glow Discharge Mass Spectrometry With Low Mass Resolution-Norbert Jakubowski Dietmar Stuewer and Jin Chun Woo Comparison of Optical Emission Spec- trometric Measurements of the Con- centration and Energy of Species in Low-pressure Microwave and Radio- frequency Plasma Sources-Jurgen Riipcke Andreas Oh1 and Martin Schmidt Detection Limits versus Matrix Ef- fects Analysis of Solutions With High Amounts of Dissolved Solids by Flow Injection Inductively Coupled Plasma Mass Spectrometry-Peter Richner Determination of Nickel in Biological Samples by Inductively Coupled Plasma Atomic Emission Spectro- metry After Extraction with 1,SBis- [ phenyl-(2-pyridyl)methylene] thiocarb- onohydrazide-E.Vereda Alonso A. Garcia De Torres and J. M. Can0 Pavon Vesicle-mediated High-performance Liquid Chromatography Coupled to Hydride Generation Inductively Coupled Plasma Atomic Emission Spectrometry for Arsenic Speciation -Yi Ming Lui M. L. Fernandez San- chez Elisa Blanco Gonzalez and A. Sanz-Medel Plasma Temperature from Ion Kinetic Energies and Implications for the Source of Diatomic Oxide Ions in Inductively Coupled Plasma Mass Spectrometry-Scott D. Tanner Analysis of Glasses From the V,05- As20,-Ba0 System Using Inductively Coupled Plasma Atomic Emission Spectrometry-S.Del Barrio R. Benito and F. J. Valle Simultaneous Multi-element Determi- nation Using Helium or Argon Plasma for Graphite Furnace Capacitively Coupled Plasma Atomic Emission Spectrometry-Glen F. R. Gilchrist Peter Celliers Huacheng Yang Changbin Yu and Dong C. Liang Analysis of Soils by Glow Discharge Mass Spectrometry-Douglas C. Duckworth Chris top her M. Barshick and David H. Smith Determination of Aluminium by In- ductively Coupled Plasma Mass Spec- trometry in Serum of Patients Treated by Haemodialysis Dialysis Solutions and Tap Water and a Comparison with Atomic Absorption Spectro- metry-Francesco Fagioli Pier Luigi Trentini Monica Ascanelli Bernadette Zanforlini and Franco Venturini Developments and Trends in Plasma Spectrochemistry-A View-P.W. J. M. Boumans Versatility of Microwave Digestion for the Determination of Some Elements in Biological Samples-M. D. Mingo- rance M. L. Perez-Vazquez and M. Lachica Anion Exchange for the Determina- tion of Arsenic and Selenium by In- ductively Coupled Plasma Mass Spec- trometry-Jan Goosens Luc Moens and Richard Dams Generation of Volatile Cadmium Spe- cies with Sodium Tetrahydroborate from Organized Media Application to Cadmium Determination by Induc- tively Coupled Plasma Atomic Emis- sion Spectrometry-Valdes-Hevia y Temprano M. C. M. R. Fernandez De La Campa and A. Sanz-Medel Application of Ultrasonic Nebuliza- tion for the Determination of Rare Earth Elements in Phosphates and Related Sedimentary Rocks Using In- ductively Coupled Plasma Atomic Emission Spectrometry with Com- ments on Dissolution Procedures-I. B.Brenner and E. Dorfman Concentration and Distribution of Sil- icon in Uremic Serum and its Relation to Aluminium Levels-Katarzyna Wrhbel Elisa Blanco Gonzalez and A. Sam-Medel Real-time Internal Standardization for Inductively Coupled Plasma Atomic Emission Spectrometry Using a Cus- tom Segmented-array Charge Coupled Device Detector-Jean-Michel Mer- met and Juan C. Ivaldi Optimization of Quantitative Depth Profiling With Glow Discharge Mass Spectrometry. Part 1. Optimization Studies on Crater Shape and Time- Depth Conversion-Angelika Raith R. C. Hutton and John C. Huneke Noise in Inductively Coupled Plasma Mass Spectrometry Some Preliminary Measurements-A.T. Ince J. G. Williams and A. L. Gray Inductively Coupled Plasma Mass Spectrometry of Biological Samples- Carlo Vendecasteele H. Vanhoe and Richard Dams Potential of Liquid Chromatography- Inductively Coupled Plasma Mass Spectrometry for Trace Metal Specia- tion-Nohara P. Vela and Joseph A. CarusoRamon M. Barnes,,Editor Department of Chemistry LGRC Towers University of Massachusetts Am herst MA 01 003-0035 Telephone (413) 545-2294 fax 545-4490 Objective The ICP INFORMATION NEWSLETTER is a monthly journal published by the Plasma Research Group at the University of Massachusetts and is devoted exclusively to the rapid and impartial dissemination of news and literature information re- lated to the development and applications of plasma sources for spectrochemical analysis.Background ICP stands for inductively coupled plasma discharge which duringthe past decade has become the leading spectrochemi- cal excitation source for atomic emission spectroscopy. ICP discharges also are applied commercially as an ion source for mass spectrometry and as an atom and ion cell in atomic fluo- rescence spectrometry. The popularity of this source and the need to collect in a single literature reference all of the pertinent data on ICP stimulated the publication of the ICP INFOR- MATION NEWSLETTER in 1975. Other popular plasma sources i.e. microwave induced plasmas direct current plasmas and glow discharges also are included in the scope of the ICP IN- FOR MA TlON N€ WSL E TTER. Scope As the only authoritative monthly journal of its type the ICP INFORMATION NEWSLETTER is read in more than $0 coun- tries by scientists actively applying or planning to use the ICP or other types of plasma spectroscopy.For the novice in the field the ICP INFORMATION NEWSLETTER provides a amuse and systematic source of information and background material needed for the selection of instrumentation or the development of methodology. For the experienced scientist it offers a sin- gle-source reference to current developments and literature. Editorial The ICP INFORMATION NEWSLETTER is edited by Dr. Ramon M. Barnes Professor of Chemistry University of Mas- sachusetts at Amherst with the assistance of a 20-member Board of National Correspondents composed of leading plasma spectroscopists. The Board members from around the world report news viewpoints and developments. Dr.Barnes has been conducting plasma research on ICP and other dis- charges since 1968. He also serves as chairman of the Winter Conference on Plasma Spectrochemistry sponsored by the IC P INFOR MA TI0 N NEWS LETTER. 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ISSN:0267-9477    

DOI:10.1039/JA993080043N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 197R ATOMIC SPECTROMETRY UPDATE-ADVANCES IN ATOMIC ABSORPTION AND FLUORESCENCE SPECTROMETRY AND RELATED TECHNIQUES Steve J. Hill* Department of Environmental Sciences University of Plymouth Plymouth Devon UK PL4 8AA John B. Dawson Department of Instrumentation and Analytical Science UMIST P.O. Box 88 Manchester UK M60 7QD W. John Price 15 Amberley Close Holne Cross Ashburton Devon UK Ian L. Shuttler Bodenseewerk Perkin-Elmer GmbH Postfach 707 164 0-7770 Uberlingen Germany Julian F. Tyson Department of Chemistry University of Massachusetts Amherst MA 01 003-0035 USA Summary of Contents 1. Atomic Absorption Spectrometry 1 .l. Flame Atomizers 1.1 .l. Fundamental studies 1.1.2. Interference studies 1.1.3. Sample introduction 1.1.3.1.Discrete procedures 1.1.3.2. Atom-trapping techniques 1.1.3.3. Sample introduction by flow injection 1.1 -3.4. Solid sample introduction 1.1.4. Sample pre-treatment 1.1 5. Chromatographic detection 1.2. Electrothermal Atomizers 1.2.1. Atomizer design and surface modification 1.2.2. Sample introduction 1.2.3. Fundamental processes 1.2.4. Interferences 1.2.5. Developments in technique 1.3. Chemical Vapour Generation 1.4 1.5 1.3.1. Hydride generation 1.3.1.1. Fundamental studies 1 -3.1.2. General developments in instrumentation and technique 1.3.1.3. Determination of individual elements 1.3.2. Preparation and separation of volatile organometallic compounds 1.3.3. Mercury by cold vapour generation Spectrometers 1.4.1. Light sources 1.4.2. Optics 1.4.3. Detectors 1.4.4.Continuum source and simultaneous multi-element AAS Instrument Control and Data Processing 1.5.1. Instrument control 1.5.2. Data processing 1.5.3. Chemometrics 2. Atomic Fluorescence Spectrometry 2.1. Discharge Lamp-excited Atomic Fluorescence 2.2. Laser-excited Atomic Fluorescence Spectrometry 2.3. Studies of Flames Plasmas and Atomic Vapours using Laser-induced Fluorescence 2.4. Coherent Forward Scattering (Atomic Magneto-optical Rotation Spectrometry) 3. Laser Enhanced Ionization This is the third review describing developments in atomic absorption and atomic fluorescence spectrometry since the restructuring of the earlier third and fourth ASU reviews on ‘Atomization and Excitation’ and ‘Instrumentation’ in 1990. Thus it follows on from the review published last year (J.Anal. At. Spectrorn. 1992 7 215R) and includes fundamental processes and instrumentation in the areas of atomic absorption and atomic fluorescence spectrometry together with *Review Co-ordinator to whom correspondence should be addressed.198R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 advances in related techniques such as atomic magneto-optical rotation spectrometry and laser-enhanced ionization. The review of ‘Atomic Emission Spectrometry’ may be found in JAAS Volume 8 Issue 4. The full references names and addresses of authors can be readily found from the Atomic Spectrometry Updates References in the relevant issue of JAAS. However as an additional service to readers an abbreviated form of each literature reference quoted (except for those of Conference Abstracts) is given at the end of the review. Comments as to possible improvements in future reviews are always welcome. 1.ATOMIC ABSORPTION SPECTROMETRY 1 .l. Flame Atomizers The original literature contains fewer abstracts relating to atomic spectrometry with flame atom sources than with other atomizers and this is reflected in the amount of material covered in this section of this Update. There have been a considerable number of publications in which the development of a successful analytical method for the determination of trace minor elements in a particular matrix has been the aim of the study reported. The relevant applications literature has been reviewed in other ASUs and most of these publications are considered outside the scope of this review.As always there are difficulties in classification of material and therefore some material will be covered in more than one ASU. This is particularly true of papers in which novel sample pre-treatments are described where the aim has been to develop a new method of preconcentra- tion or analyte-matrix separation. When such procedures are directly coupled with the spectrometer either by FI or continuous flow techniques they have been included in this ASU. As FI methodology is increasingly being used and can be readily implemented with commercial apparatus infor- mation about selected novel sample pre-treatment pro- cedures which could be implemented in such a format has been included in this Update. The relevant material is presented in a new section entitled Sample pre-treatment (see section 1.1.4.).Much of the revised version of a 1982 text (Atomic Absorption Spectrometry ed. Cantle J. E. Elsevier Amster- dam 1982) deals with applications of frame AAS to the analysis of real samples for which some considerable amount of preparation is needed (see Atomic Absorption Spectrometry Theory Design and Applications ed. Haswell S. J. Elsevier Amsterdam 199 1). Sample materials include waters sewage and effluents sea-water and marine organ- isms airborne particulates in the workplace foods ferrous and non-ferrous metal geochemicals petrochemicals glasses ceramics clinical specimens fine and industrial chemicals and polluted soils. Introductory chapters deal with basic theory and principles of instrument design and operation. Flame techniques have been surveyed (Jackson K.W. and Qiao H. Anal. Chem. 1992 64 50R) as part of the biennial Fundamental Review series published in the June issue of Anal. Chem. As the scope of this review is broader than the present Update and the period covered longer the detail available is limited though as usual with these reviews the coverage is comprehensive. The review period covered by this Update includes publications arising from the Colloquium Spectroscopicum Internationale (CSI) conference in Bergen Norway in June 1991 and associated pre- and post-CSI symposia. The March 1992 issues of the Analyst and of J. Anal. At. Spectrom. contain about 90 and 70 articles respectively relating to presentations at these meetings.Although the majority of the Analyst articles concern molecular spectro- metry a number of papers relate to atomic spectrometry. The review period has also seen the publication of the special issue of Anal. Chim. Acta (1992 261) containing papers presented at the Flow Analysis V conference held in Kumamoto City Japan in August 1991 several of which relate to the FI atomic spectrometry. 1 . 1 . 1 . Fundamental studies There is a sustained if limited interest in the study of the distribution of species within combustion flames. Some of these are concerned with the characterization of flame combustion species. Optical double-resonance pump probe techniques were used to study the ground state saturated population distribution of OH in an air-C2H2 flame (92/3863).Information (92/386 1 ) concerning this species was also obtained for an air-CH flame by the use of resonant degenerate four-wave mixing (DFWM). Measure- ments of this type allow accurate mapping of temperature distributions within flames. The technique can be consi- dered complementary to Raman spectrometry. The use of a tunable KrF excimer laser source for the stimulation of the Raman signals from a variety of species in an air-H flame has been reported (93142 1 ). Interference from fluorescence of OH and 0 was avoided by tuning the narrow band laser to an appropriate UV wavelength. By working with UV radiation the Raman signal being a scattering signal is increased by a factor related to the inverse fourth power of the wavelength. Two-photon stimulated emission was used to monitor the spatial distribution of N in one dimensional 02-NH3 flames (92/4014).The Na number density in 02-C2H,-N2 flames was measured by the pump probe method of asynchronous optical sampling (93/425). This paper provides a useful tutorial introduction on the use of laser-induced fluorescence techniques for the study of flames. A novel four-wave difference signal has been observed from Na in air-CH flames (93/ 1073). The process was attributed to a near two photon resonant difference FWM process involving 532 nm photons from a frequency doubled Nd:YAG laser with a photon from a dye laser at or near the Na D line wavelength. At least three groups of workers have reported on the spatial distribution of atoms in flames. Implications for the accurate determination of the elements concerned were discussed and deductions concerning atomization mecha- nisms were made.Hu (921C4168) studied the effect of acetylene frow rate and observation height and mapped the distribution of atoms and ions of Ba Ca Mg and Sr as well as some hydroxide species in an air-C,H flame. It was concluded that the atomization of Mg from a chloride solution was achieved predominantly by thermal dissocia- tion of a chloride molecular precursor while for the other elements atomization occurred by a mechanism in which the hydroxide was first formed and then reduced. Lakatos (921C4220 9311 186) used Hg vapour to track atom distri- bution in an air-C,H flame as a result of diffusion and flame gas flow and expansion effects. When results were compared with aerosol introduction of Ca and Cu solutions (93/1186) it was concluded that a change in gas flow would affect both aerosol distribution and residence time of particles in the flame.Hence whether an increase or a ,decrease in absorbance would be observed was dependent on the ratio of these two processes. In an extreme case the introduction of a slurry it was found that increasing the gas flow resulted in a decrease in absorbance which wasJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 199R attributed to a reduction in the residence time of the slurry particles and in the consequent decreased vaporization efficiency. Batistoni (93/C92) has commented on the role of matrix components on the analyte distribution. A number of relevant parameters were identified including polydisper- sity of the injected aerosol and resultant population of desolvated particles vaporization rates heterogeneous chemical reactions with flame components dissociation vapour diffusion and recombination reaction rates.It was deduced that specific effects would be observed for refrac- tory elements for which the atom distribution would be a function of these various kinetically controlled processes. Results concerning the distribution of Ti in a N20-C2H2 flame have been published (92/4266). The various processes leading to the formation of A/ atoms in the N20-C2Hz flame have been briefly reviewed (9212979) and the degree of atomization and dilution as functions of observation height and fuel to oxidant ratio measured. Russian workers (92/3934) have developed a model to calculate the equilibrium composition of an N20-C2H2 flame between 2860 and 3200 K.The atomiza- tion efficiency as a function of fuel to oxidant ratio was also calculated. Good agreement between the experimentally determined absorbance change with this ratio and the calculated change was obtained for a number of elements including Al B Be Cr Ge Hf Mg Mo Si Sn Ta Ti V W and Zr. Another Russian group has examined the behaviour of Ge in a fuel rich N20-C2H2 flame (9214535). The effect of temperature on the vapour-phase composition was modelled thermodynamically. Reference should also be made to later sections concern- ing interference effects (section 1.1.2.) and sample introduc- tion (section 1.1.3.) for reports on studies in which amounts of organic material sufficient to cause changes in flame properties are introduced.1.1.2. Interference studies In contrast to the previous review period (see J. Anal. At. Spectrom. 1992,7 2 15R) most of the studies reported this year are concerned not with the effects of surfactants but with interelement effects. This year’s favourite analyte element is Cr! One of the most comprehensive evaluations of organic reagent effects appears in a paper that is difficult to follow (92/46 14). Workers at Nankai University have made measurements of the atomic absorption of Al Cr and Yb in an air-CzH2 flame. For Yb the effect of 38 organic reagents at concentrations ranging from 4 x 1 0-4-t~ 0.1 moll-’ was investigated. The enhancement factors with respect to water ranged from 0.035 for urea to 26.5 for Chrome Azurol S.The results for only nine compounds were given for Al. Triethanolamine and quinolin-8-01 both gave factors of 10. The beneficial effects were interpreted as due to the coordination of the ligands through N atoms thereby preventing the formation of refractory oxides on decompo- sition in the flame. The effect of four surfactants (sodium lauryl sulfate sodium dodecyl sulfate sodium dodecyl benzenesulfonate and Triton X-100) on the Yb signal were investigated. The enhancements obtained were explained as being due to a surface energy decrease leading to beneficial changes in drop size distribution and uptake rate. It was also reported that a significant increase in signal was obtained when solutions containing sodium docdecyl sul- fate (SDS) and sulfosalicylic acid were nebulized.This cocktail appeared to give rise to an aerosol ionic redistribu- tion effect Mass spectrometric and X-ray diffraction studies were performed to confirm the formation of a ternary complex. The effects of various acids (enhance- ments were diminished in acid solutions) and the releasing effect of SDS were investigated. For a solution containing 1 mg I-l of Cr and 100 mg 1-1 of iron the presence of 10% m/v SDS caused the signal depression to be only 6%. Other Chinese workers (93/ 1276) have investigated the effect of octylpyridinium (OP) bromide and sodium dodecyl ben- zenesulfonate on the determination of Cr in an air-C,H flame. Recoveries of between 97 and 103% were obtained for the analysis of steels and electroplating waste water.Yet a third group of Chinese workers has reported on the effects of surfactants (93/790). Chinese investigators (931665) have eliminated the inter- ference of tungsten on the determination of Mo in the air- CzH2 flame by the addition of a cocktail of OP emulsifying agent (4% v/v) calcium (2 g 1-I) and phosphoric acid (4% v/v). Russian workers (92/4535) studied the effects of 1 1 elements on the determination of Ge in a multi-component alloy in an N20-C2H2 flame. For the determination of Ti in ferrous metals it was reported (92/4730) that the addition of 500 mg 1-l of aluminium produced a useful signal enhancement in the N20-C2H2 flame. The spatial distribu- tion of this element in this flame was studied by Batistoni (9214266) as a function of various matrix components.The roles of the elements were reversed in a study by Yugosla- vian workers (92/4425) of the interference of aluminium and titanium on the determination of V. In a comparative study of the determination of Cd and Pb in calcium-rich matrices by different atomic spectrometry techniques (92/2602) and ASV discrepancies between the results obtained by FAAS and the other techniques were noted. There was no detailed study made of these only a brief discussion in terms of ‘anion interferences’. The inhibition release titration method (see J. Anal. At. Spectrom. 1986 1 137R) was used to study a variety of interferences in the determination of Cr (93/452) many of which were removed by the addition of 5 x mol 1 - I aminosalicylic acid.It was shown (93/449) that the addition of cyanide was also effective in removing interferences not only on Cr but also on Au Fe and Pd in the air-C2H2 flame. It was postulated that the formation of cyano complexes in both standards and samples produces identical spatial distributions in the flame and also that the excess cyanide scavenges oxidizing species in the flame giving rise to a reducing atmosphere. The utility of reducing conditions for the determination of Cr in the air-C2H2 flame was re- confirmed (93/1098) as was the ability of chloride to remove the interference of iron in this determination (92/2448 93/C 1240). In the former study the interference of cobalt was also shown to be removed by chloride (added as ammonium chloride) and the effects of iron and cobalt were removed by the addition of potassium hydrogensul- fate.Argentinian workers (93/ 1 1 13) have studied the effectiveness of a number of nitrogenous compounds as releasing agents in the determination of Cr in ferrous alloys. Hydroxylamine formamide guanidine ethylenediamine and ethanolamine investigated in an earlier study of Mo (92/1112) were found to inhibit the interference from a number of alloying elements as well as the matrix element iron. The study has been extended to the determination of both Cr and Mo (93/1114 93/1115) with particular reference to the use of ethylenediamine ethanolamine or formamide. A method for the determination of Be in the air-C2H2 flame which uses the enhancing effect of up to 500 mg 1-1 magnesium has been developed by Chinese investigators (92/2969).The effects of 18 cations including aluminium were studied. The aluminium interference on the determi- nation of Be has been extensively studied (93/1029). It was shown that lanthanum EDTA and quinolin-8-01 were effective in removing the interference but that fluoride was not. A protocol for dealing with various Be to aluminium mass ratios was devised. A method for the detection of chemical and incomplete200R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 volatilization interferences based on observation at two heights in theflame was devised (92/2455). The burner was moved vertically by a stepper motor under the control of a computer which also acquired and processed the absor- bance signals.Two calibrations were stored and if the calculated concentrations at each height were more than 10% different an error message was displayed. The proce- dure was tested for the effect of phosphate silicate and aluminum on Ca and of phosphate silicate aluminium and titanium on Mg. It has also been reiterated (93/C94 93/C96) that FI procedures can be used to detect and study interference effects. In the latter conference presentation some further developments of the procedure implemented by the CLAIR (calibration graph linearization and inter- fered signal reconstruction) algorithm of Sperling et al. (Anal. Chem. 199 1 63 15 1) were described to enable the effects of large excesses of interferents to be corrected. Publication is awaited with some interest.A somewhat similar procedure has been implemented in an off-line mode by Bosch Reig et al. (92/3826) who devised a version of the successive dilutions method (see Gilbert P. T. Anal. Chem. 1959 31 1 10). Although the method was shown to be effective in correction of the interference of phosphate and sulfate on Ca and silicate and aluminium on Mg over somewhat limited mass ratios it would appear cumbersome to use in practice as the procedure would appear to require the preparation of nine solutions with dilution factors ranging from 0.9 to 0. I . The possible interferences due to the europium matrix on the determination of Co Cr Cu Fe Mn Ni Pb and Zn by both FAAS and ETAAS were evaluated (92/2624). No interferences were observed in the presence of 1% m/v of europium except in the case of Cu for which a spectral interference at the 324.754 nm line due to the 324.753 nm europium line.It was found that the Cu line at 327.4 nm was unaffected and could be used. Some further studies on the mutual interference eflects between Sr and Na and Sr and K in air-C2H2 flames (931C1628) have been presented. Both absorbance and emission measurements were made. The effects were accounted for by ion-electron collisional excitation (see Zaranyika et al. Fresenius' J. Anal. Chem. 1991 341 577) and ion-electron collisional excitation coupled with charge transfer between the alkali metal ion and the Sr atom. The spatial distribution of these alkali metal mutual interfer- ences in the air-C2H2 flame has been studied by Chinese workers (92/43 16).The reduction in interference possible through the im- proved aerosol characteristics obtained with the hydraulic high pressure nebulizer has been demonstrated by Berndt and Muller (Fresenius' J. Anal. Chem. 1993,345 18). The depressive effects of aluminium (30 g l-l) iron (150 g 1-l) and copper (330 g 1-l) on trace concentrations of Ag Cd Co Cr Mg Mn Ni Pb and Zn (Cu and Fe were included as appropriate) were discussed. Introduction via the high pressure system resulted in significantly reduced interfer- ences and increases in sensitivity by factors of 2-8 depending on the matrix and analyte. 1.1.3. Sample introduction An overview of sample introduction for atomic spectrometry has been provided (Sneddon J. in Advances in Atomic Spectroscopy ed.Sneddon J. JAI Press Greenwich 1992 vol. 1 pp. 8 1-124) which covers all types of atomizers and spectrometries. It has been suggested (93/C 1405) that given the considerable effort that has been devoted to their development the performance limit of sample solution aerosol introduction techniques has been reached and that more effort should be devoted to the development of other bond breaking procedures such as ETV LA sputtering and adspark ablation. It was also pointed out that there was (considerable potential for the implementation of matrix removal and preconcentration procedures through the ,judicious use of some chemistry. Some comments concern- ing the type of material used for spray chamber construc- tion were made by Mullins (93lC68). As was discussed in section 1.1.2.there is still interest in investigating the effect of the addition of surfactants to aqueous sample solutions on the absorbance signal of a spectrometer with a conventional concentric nebulizer and spray chamber. Although these studies have been concerned with the removal of interferences part of the mechanism by which surfactants change signal intensity in the absence of interferent involves changes in the sample introduction processes. Mora and co-workers (92/2409) studied the role of solvent properties on drop size distribution and mass transport for Mn as the analyte. It was concluded that for the solvents water benzaldehyde formic acid acetic acid propan-1-01 and methanol the mean drop size was primarily a function of the surface tension.However the size distribution could not be accounted for by any simple relation and was found to be largest for water and smallest for propan-1-01. When considering the role of solvent volatility it was found that possible absorbance increases due to increases in mass transport were partially offset by dilution in the flame due to the increased solvent load. Willis and Sturman (9311 956) showed that it was possible to control the nebulizer uptake rate when spraying organic solvents by control of the impact bead position. The solvent studied included IBMK xylene and Pegasol (a non- aromatic hydrocarbon solvent of b.p. 179-194 "C). The range of aerosol delivery could be changed by as much as a factor of 6 allowing the determination of high concentra- tions of Cu and Fe in lubricating oils without the need to dilute the sample.It was pointed out that for some elements changes in the flame stoichiometry caused by the organic solvent would affect atomization efficiency and that changes in flame structure would affect the distribution of analyte atoms and hence the absorbance at any given viewing height Work on the introduction of emulsions originally pub- lished in Hungarian and discussed two years ago (see J. Anal. At. Spectrom. 1991 6 190R) is now available in English (92/2227). With the aid of a dual nebulizer device it was shown that for easily atomized elements the presence of an organic solvent did not affect the distribution of atoms in the flame and thus the beneficial effect of emulsion formation was due to the interaction between the surfactant and the metal chelate dissolved in the organic phase.The use of emulsions in atomic spectrometry and FI relevant to both flame and plasma atomizers has been reviewed (92/2533). It has been shown that there are some benefits to the introduction of volatile metal compounds by nebulization. Work previously published in Hungarian and discussed last year (see J. Anal. At. Spectrom. 1992 7 218R) on the determination of volatile lead compounds is now available in English (93/1030). The solvents investigated for the introduction of tetramethyllead and tetraethyllead included isobutyl acetate acetone and gasoline. A procedure was developed for the determination of each compound in gasoline. One of the problems to be overcome in the development of procedures for introducing metals as volatile compounds is that the solvents used are more volatile than the analyte derivatives and thus large volumes of solvent vapour are introduced into the atomizer. Prelimi- nary results on the use of a relatively innocuous solvent supercritical or liquid carbon dioxide were reported by Bysouth and Tyson (93/439).The test anaiyte was Cu introduced by an FI system as the pyrrolidin-l-yldithiofor-JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. AUGUST 1993 VOL. 8 201R mate complex in IBMK into the carbon dioxide carrier. The nebulizer was replaced by a simple heated restrictor which acted as a thermospray. Improved atomization efficiency with respect to that of aqueous solution nebuliza- tion was achieved. Spanish workers reported (93/C89) on the use of a thermospray device for the introduction of various acetylacetonate derivatives of Al Co Cr and Zn.However the nature of the solvent was not disclosed in the conference abstract. A second Spanish group has also reported the use of a thermospray device (93/C67) presum- ably for the introduction of aqueous sample solutions. Berndt and his various collaborators around the world have described further studies with the so-called hydraulic high pressure nebulization system (93/754 93/1082). The work reported concerns applications to real samples show- ing the improved sensitivity (and detection limit) and tolerance to high levels of dissolved solids. Flow injection sample introduction was used and procedures involving on- line chemistry were also described.These will be considered further under section 1.1.3.3. Applications included the determination of 1 1 trace elements in saturated sodium tungstate solution containing about 63% m/v dissolved solids (93/754) the determination of Cu in saturated sodium chloride lithium borate and potassium dihydrogen- phosphate solutions (93/ 1082). More recent examples described in conference presentations include the determi- nation of Cd in 20% ammonium sulfate solutions (92/C3745) the determination of Sn in 16% m/v zinc nitrate solutions (921C3650) and of up to 20 elements in 20% m/v antimony chloride in 24% hydrochloric acid solution 50% m/v magnesium sulfate solution and 60% cobalt nitrate solution (92/C42 16). 1.1.3.1. Discrete procedures. The general decline in the number of papers describing the use of discrete or pulse nebulization procedures appears to have continued through the present review period.Beinrohr has discussed (93/1132) the relative merits of peak height and peak area measure- ment from a theoretical viewpoint (see J. Anal. At. Spectrum. 1992 7 2 18R). Russian workers have reported (93/C983) on the use of a system in which the volume of solution aspirated was controlled by the length of time the nebulizer capillary was dipped into the solution. The capillary movement was electronically controlled and by changing the time from 0.02 to 10 s volumes ranging from 2 to 1000 pl were aspirated. The procedure was applied to the analysis of geochemical materials. Japanese workers (9214435) used pulse nebulization of 80 pl samples of hair digests for the determination of Zn.The analysis was performed on 5 mg of fresh beard hair samples daily and the results used to estimate the Zn concentration in the body. Spanish workers determined Pb in blood by direct nebulization of the nitric acid digest of a 130 p1 sample from a specially designed PTFE microbomb (92/3 15 1). The detection limit aided by a slotted tube atom retarder (STAR) was improved to 70 ppb. Koropchak has extended the description of aerosol inter- facing eflects on discrete sample introduction (931C1528) with particular attention paid to the regions of laminar flow. The dispersion processes were described by a convec- tive model (see Koropchak et al. Appl. Spectrosc. 1992,46 682). 1.1.3.2. Atom-trapping techniques.Improvements in sen- sitivity for easily atomized elements such as Cd Cu and Pb by the use of a quartz STAR have once again been confirmed (92K3666). As for previous review periods most of the published work originates from Chinese research groups who devised a method for the determina- tion of Au (92/24 15) and of Cu in urine and Pb in sediment (9214391). In this latter study a stainless-steel cover was placed on the STAR to increase further the sensitivity to factors of up to 9 in comparison with conventional nebulization. Some preliminary results for the performance of a graphite STAR have been presented (92/C4165). In comparison with a quartz STAR the device was shown to increase further the sensitivity by factors ranging from 1.1 to 1.6 for a range of ten elements.It appeared from the abstract that the device had only one slot 1.2 mm wide and 28 mm long in a graphite tube 140 mm long and 8 mm internal diameter. The commercially available quartz STARS have two slots. No information was given concern- ing the lifetime of the tube. As was mentioned in the previous section a quartz STAR was used in a procedure for the determination of Pb in blood microsamples (92/3 15 1). It was shown that a quartz STAR could further enhance the sensitivity when used in conjunction with high pressure nebulization (921C3745). Additional factors of between 2 and 3 were found over and above the factors of 2-7 owing to the improved nebulization process. A quartz STAR was also used in a speciation study (Hansen et al.J. Anal. At. Spectrom. 1992 7 629) in which As species separated by HPLC were atomized in an Ar-H diffusion flame. Various designs of STAR were evaluated and the best S/N was obtained with a tube 140 mm long mounted 20 mm above the burner. The tube contained lower and upper slots of lengths 100 and 60 mm respectively. The diameter of the tube was not given. One of the disadvantages of the quartz devices is their limited lifetime particularly when solutions containing alkali metals are nebulized. Flow injection introduction (see J. Anal. At. Spectrom. 1991 6 191R) clearly has the potential to extend tube lifetime and this possibility has been extensively investigated by workers in Zhaolun Fang's laboratory (Xu et al. Talanta 1992 39 581). Three different tube designs were evaluated and it was found that lifetimes were extended by factors of 5-6.Sensitivity enhancements for Au Cd Cu and Pb by factors of 4.0 5.3 3.1 and 5.5 were obtained respectively with precisions (at the minimum of the Ringbom plot) of 1-2%. Recoveries of Cd Cu and Pb spiked into undiluted urine at concentra- tions of 10 100 and 100 ppb respectively ranged between 100- 102%. Slotted tube atom retarders have also been used as part of an overall procedure to enhance sensitivity using FI proce- dures (92/2111 92/4635). The second paper is another comprehensive study from Fang's group in which a mathe- matical model for the combined effect of a chemical preconcentration procedure (precipitation ion-exchange sorbent extraction) is combined with the additional enhancement effects of organic solvent introduction and the STAR.For the determination of Pb a total multi- plicative enhancement of 135-fold was achieved for co-precipitation with iron(r1) ammonium hexahydroaze- pine-1-dithiocarboxylate followed by dissolution in IBMK and nebulization into an air-C2H2 flame equipped with a STAR. The quartz tube was 140 x 15 mm i.d. with a 1 10 x 3 mm slot mounted 10 mm above the primary combustion zone and had six 3 mm holes 9 mm apart at 180" to the entrance slot. The sample throughput was 72 h-l and 2.7 ml of sample solution were required. 1.1.3.3. Sample introduction by flow injection. The com- ments made by way of introduction to the last review (see J. Anal. At. Spectrum. 1992 7 2 18R) are also relevant to this review period namely that there is a sustained interest in the development of FI procedures for atomic spectrometry and that a substantial amount of the published work involves FAAS.There is probably a discernable increase in the number of publications relating to ETAAS and to202R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 chemical vapour generation (considered in more detail in section 1.3.). A number of overviews and reviews have appeared (93/77 1 93/860 93/86 1 see also Microchem. J. 1992 45 143 Anal. Chim. Acta 1992 261 75 Spectro- scopy 1992 7 14). The volume of Anal. Chim. Acta cited contains papers presented at the Flow Analysis V confer- ence held in Kumamoto City Japan in August 199 1 several of which relate to the FI atomic spectrometry (FI-AS) combination including an overview of the first decade of FI analysis in China (Fang et al.Anal. Chim. Acta 1992,261 557). In this article Fang briefly described Chinese contri- butions to FI-AS but provided a total of 347 references to FI work much of which is in the Chinese literature (titles are provided in English). Sixty-two papers relating to atomic spectrometry were identified. Relatively little work of a fundamental nature has appeared during the review period. Most of the published work concerns the use of FI procedures for implementing some kind of sample pre-treatment. However Koropchak has presented (931C1528) some further developments in a theory of aerosol dispersion relevant to discrete sample introduction procedures such as FI and chromatography.Sperling et al. described (Anal. Chim. Acta 1992 261 1 15) a procedure for the improvement of the detection limit obtainable in an FI-FAAS procedure. By dividing the sample solution into a number of aliquots and employing an ensemble summation procedure and using gated integra- tion following Savitsky-Golay smoothing detection limits comparable to those for conventional aspiration could be obtained for Ca Cu and Zn. An HPLC pump was used for liquid delivery (to ensure high precision) and dispersion in the connecting line was minimized by using a knotted tubular reactor. The sample volume was 130 p1 chosen so that the same sample volume was used in five injections as was needed for 5 s of conventional nebulization at 8 ml min-l. The usefulness of FI introduction for a sample that would be difficult to nebulize continuously is nicely illustrated by the determination of Fe in beer (92/2437) at concentrations of around 6 ppb.Interestingly enough the method detec- tion limit based on three standard deviations of the blank signal was quoted as 12 ppb. Recoveries of 50 ppb spikes ranged from 87-1 12%. Although some drift due to burner clogging was observed when 500 pl samples were injected this was removed when the sample size was reduced to 200 pl. Burguera et a!. determined Ca K Mg and Na in tropical fruits by an FI slurry nebulization procedure (931483). Samples were dried ground and mixed with 25 ml of 0.1% Triton X-100 solution (only particles smaller than 200 pm were taken). Results in agreement with a wet digestion procedure were obtained.Accurate determinations of the elements in NIST SRM 1575 (Pine Needles) and SRM 1572 (Citrus Leaves) were also performed (certificate values for Mg and Na for SRM 1575 are not provided). Although the method was described as a 'direct' procedure the manifold diagram showed a closed-loop system into which the sample was introduced and out of which a sub-sample was taken by the FI valve. As dilution in the closed loop was not discussed it is concluded that the entire recirculating loop contained undiluted sample slurry. It is possible that this method of presentation keeps the prepared slurry homo- geneous but must make for difficulties in changing from one sample to another. How this was done was not stated although a sample throughput of 60 h-* was quoted.An earlier paper in which the manifold was described (see Becerra et al. Quim Anal. 1987 6 52) might be informa- tive in this regard. By using a reversed FI procedure Carbonell et al. determined Cu and Fe in edible oils (9212609). Tyson's method of standard additions was used with either commercially available organometallic com- pounds or APDC complexes dissolved in the minimum amount of IBMK and diluted to volume with olive oil. Values for the concentrations of Cu and Fe of around 1 and 30 mg l-' respectively were found in agreement with the results of a dry ashing procedure. A comparison of three propulsion systems has been made (Fang et al. Anal. Chim. Acta 1992,269,9). The evaluation was based on both short- and long-term precision of (a) the zone penetration (or sequential injection) dilution proce- dure and (b) an on-line preconcentration procedure in which the sample volume loaded onto the solid-phase extraction column was controlled by the run time of the pumps.The three systems were the peristaltic pumps of the Perkin-Elmer FIAS 200 unit a dual piston reciprocating pump (Sanuki model DMX-2000) and a dual syringe sinusoidal flow pump (Alitea model SV-2). For the on-line dilution studies the peristaltic pump and the reciprocating pump performed similarly and significantly better than the sinusoidal pump. It was suggested that this was due to the need to refill the syringes (by reversing the piston direction) prior to each injection. During the fill time the nebulizer still provided suction and it was thought that the normal flow pattern was disturbed.Evidence in support of this hypothesis in the form of improved precision when the nebulizer suction was set to zero and degraded precision when the stop time was increased was cited. For the preconcentration studies the short-term precisions of all three pumps were similar but the peristaltic pump pro- duced significantly poorer precision over an extended 3 d period. The surprisingly good short-term precision of the peristaltic pump was attributed to the pulse damping effect of the relatively long knotted tubular reactors used. Further evidence in support of this was found in the equally good precision of the dilution studies obtained with a wider bore pump tube and a considerably reduced pump head rotation speed.The valley between the two peaks gave a dilution factor of 20 with an RSD of 2% (for the peristaltic and reciprocating pumps). Some further developments by Sperling et al. in the implementation of their FI version of the successive dilution method for interference correction (see Anal Chem. 199 1 63 15 1 and J. Anal At. Spectrom. 1992,7,2 19R) have been described in a conference presentation (931C96). It would appear that improved accuracy and correction for larger excess of interferent may be obtained by the combination of the information in the concentration gradients of the peak and chemical modification. It is hoped that further details will appear shortly in the open literature. This review period has seen an increase in efforts to link sample preparation procedures involving digestion leaching and dissolution with FAA spectrometers using flow and FI procedures.It could well be that several papers that will eventually be regarded as significant have appeared. Gluo- denis and Tyson devised a procedure for the dissolution of a model sample whose predominantly organic matrix is resistant to wet oxidation (cocoa powder) in a high pressure stopped flow procedure (921C3362 9214636). The sample was slurried in nitric acid and a 170 pl sub-sample injected into a double line FI manifold merged with concentrated nitric acid and sealed by PTFE stop valves in an oven at 210 "C. After 3 min during which complete dissolution occurred the contents of the reactor in the oven were vented into a two-stage depressurization system and a further sub- sample injected into a single line carrier for transport to the spectrometer.Results for Cu and Fe in agreement with the results of other wet digestion procedures were obtained. Low results obtained for Fe when aqueous standards were used were taken as evidence that although complete dissolution had occurred complete destruction of the matrix had not. Further studies of this approach are in hand (931C1586) in which a microwave oven was used to heat the sample under stopped flow conditions.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 203R Further information concerning the manifold for the microwave assisted sample pre-treatment used by collabo- rating workers in Venezuela (Burguera) and Spain (de la Guardia) has been published (9312082).Samples [arti- choke diet chocolate sewage sludge (real and BCR CRMs 144 and 146 domestic and industrial respectively) To- mato Leaves (NIST SRM 173)] were slurried in a 1 + 1 mixture of concentrated nitric acid and hydrogen peroxide (30% v/v) at concentrations of 0.25-2%. The slurry was continuously pumped around an open recirculating system part of which (120 cm of PTFE tubing i.d. not given) was located inside a domestic microwave oven. The tubing was passed through the existing vent holes and no modifications to the oven were made. The slurry sample reservoir which formed part of the recirculating loop external to the oven was cooled to de-gas the sample. After the appropriate time had elapsed a sub-sample was injected into a single line manifold for delivery to the spectrometer.A double valve configuration was used to allow the injection of standards during the sample preparation period (see Carbonell et al. Anal. Chim. Acta 1990 238 4 17). Although no statistical procedures were used (by either the authors or this reviewer) inspection (by this reviewer) of the tabulated results (means and standard deviations for the Cu and Mn content) suggests that accurate determinations were ob- tained for 19 out of the 30 results reported. The workers reported that after circulation through the oven for the desired period ‘a small portion of the matrix of the dispersed solids remains undissolved and so the samples are introduced into the flame as acid slurries’. As the authors claim to have verified that neither analyte was associated with the remaining solid it is tempting to conclude that stirring the powdered sample in the nitric acid-hydrogen peroxide solution in a beaker on a hot-plate followed after settling by the aspiration of the supernatant would be equally effective sample preparation and analysis proce- dures.The use of beakers on hot-plates is a remarkably effective method of sample preparation with consequent benefits in sample throughput. This paper also raises some interesting questions of terminology. The title of the paper (93/2082) contains the word ‘digestions’ the abstract refers to ‘extraction’ and ‘digestion’ and in the introductory material the process is referred to as ‘decomposition’. For readers of what may become a considerable body of literature there are clearly possibilities for confusion. Haswell and Barclay described (9213838) a continuous jlow microwave digestion procedure directly coupled to an FAA spectrometer.Some organic based reference materials (Chlorella Mussel Sargasso Pepperbush and Bovine Liver with particle size less than 180 pm) were slurried in dilute nitric acid (5% v/v) at concentrations of between 0.005 and 0.5% m/v. A 1 ml sub-sample was injected into the water carrier of a single line FI system and pumped through 20 m of 0.8 mm i.d. PTFE tubing wound round the carousel in a laboratory microwave oven. The emerging solution was cooled by passage through 5 m of tubing immersed in a Peltier cooled bath of antifreeze passed through a filter (mounted in the loop of a six-port rotary valve to allow cleaning by back-flushing) and back pressure regulator and introduced directly into the spectrometer nebulizer.Results were presented for the determination of Ca Fe Mg and Zn but as with the previous work discussed no statistical evaluation of these was made although enough information was presented to allow a calculation of the 95% confidence interval about the experimentally determined mean values. Not all of these confidence intervals would include the certificate value. However no information on the uncer- tainty in the certificate value was given and thus the significance of such discrepancies cannot be evaluated. The authors calculated that recoveries ranged from 94- 107% for the 17 results quoted. Although particles were always present in the emerging solution the amount of undissolved material was minimized when the applied power pro- gramme was sufficient to cause bubble formation. Provided that the bubbles were not too large they could be re- dissolved in the cooling stage and thus had little effect on the sample introduction.The pressure in they system was somewhat in excess of the rating of the 520 kPa (75 psi) regulator which would facilitate the re-dissolution of evolved gases. Also the PTFE tubing used in the study is known to be porous to gases. Good recoveries appeared to be a function of nitric acid concentration and for the chlorella material the plot of percent recovery against percent nitric acid exhibited a rather sharp maximum around 5%. The through-put was 30-60 h;f. On-going FI work in Welz’s group in Uberlingen con- cerning on-line microwave digestion for chemical vapour generation (CVG) AAS has been described in a series of three papers (Welz et al.Anal. Chim. Acta 1992 261 91,Tsalev et al. Analyst 1992 117 1729 and 1735). Although these papers are not concerned with FAAS they are considered here because of the use of microwave digestion procedures. The first of the papers describes the manifold and apparatus and results are presented for the determination of Hg in some reference urine materials and some natural water. A commercially available ‘open vessel’ microwave apparatus is used with microwave energy focused into a small cavity. The reaction coil was 10.2 m of 1.07 mm i.d. PTFE tubing. It is apparent from the second paper that the appearance of bubbles in the reactor was considered undesirable and the manifold was designed to avoid this by arranging the reactor tubing so that it passed repeatedly in and out of the microwave cavity by winding it in vertical coils on a PTFE former of which only a fraction was situated in the cavity.All the samples analysed were liquids. The role of the pre-treatment was to convert all analyte species to inorganic forms so that total elemental concentrations could be obtained from the CVG procedure. Appropriate volumes of sample solution and an oxidizing agent were mixed in the autosampler cups. For the determination of Hg the reagent used was a mixture of bromate and bromide. However the results showed that the role of the microwaves was simply to warm the solution and improve the gas-liquid separation efficiency rather than aid in the sample decomposition reaction as the recoveries of Hg for a number of organomercury compounds were independent of microwave power which was varied from 0 to 120 W.Accurate determinations of Hg in the reference urines at concentrations between 12 and 114 pg 1-* were made. For the water samples agreement with the results of another laboratory was obtained for concentrations in excess of 50 ng l-l but at concentrations below this the microwave results were low possibly owing to absorption losses in the intervening time period. The second and third papers described the use of the manifold for the determination of hydride forming elements with emphasis on As Bi Pb and Sn.Although the evidence presented was not as clear as for the Hg work it would appear that the role of the microwave energy was to heat the solution thereby improving ( a ) the dowstream HG reaction kinetics and (b) the efficiency of gas-liquid separation. Again all the samples were solutions (urine and environmental waters) and stong oxidizing agents were added to the samples in the autosampler cups. Attempts to convert monomethylarsonate and dimethylarsinate to inorganic As failed As has been mentioned in an earlier section the FI format has been used with high pressure nebulization. For the introduction of volatile chelate complexes Bysouth and Tyson (Anal. Chim. Acta 1992,258 5 5 ) injected the sample into a carrier of supercritical COz. Introduction into the flame atomizer was via a thermospray device consisting of a204R JOURNAL OF ANAL,YTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 heated restrictor. It was also shown that it was possible to atomize copper pyrrolidin-1-yldithioformate in a heated quartz tube atomizer after dissolution of the precipitated solid in the C02 carrier. Most of the work with the hydraulic high pressure nebulizer (HHPN) now appears with FI sample introduction. This prevents the sample components coming into contact with the pump. The basic features of micro-sampling and ability to handle solutions containing high concentrations of dissolved solids incom- patible with conventional continuous nebulization have been described (921C3747 92/42 16 931 1082) and dis- cussed in section 1.1.3. The improved tolerance to inter- ferents that is obtained in comparison with conventional pneumatic nebulization (Berndt H.and Muller A. Fresenius' J. Anal. Chem. 1993,345 18) was also discussed earlier (see section 1.1.2.). The system has also been used with on-line matrix separation and preconcentration (921C3650 931754). A number of trace elements in tungsten were determined by retention of the analytes on a strong cation exchange resin from 1 to 3 mol 1-I HF solution. Tungsten is not retained and the effluent from loading is diverted away from the nebulizer to waste. After washing with water the retained cations were eluted with a slug of 5 mol 1-I nitric acid. Detection limits of between 0.1 and 1 pg g-' were obtained. Indirect FI procedures for the determination of anions have been surveyed (9212 108). Esmadi et al.have described (9212524) a further development in the application of their precipitation procedure (see J. Anal. At. Spectrom. 1992,7 220R) this time for the determination of bromide or iodide. After precipitation as the silver salts and collection in the loop of the injection valve the precipitates were dissolved in an appropriate reagent (thiosulfate and cyanide for the bromide and cyanide for the iodide). The manifold was also used for the determination of Ag. The detection limit for the determination of each of the two halide ions was 1 pmol l-l. The precipitation of AgCl has been used as a means of reducing the amount of silver introduced into the nebulizer (with the subsequent deposition of silver acetylide) in a procedure for the determination of some minor elements in silver electrolysis solutions (921C3688 931C1529 Debrah et al.Talanta 1992 39 1525). The manifold made use of a closed loop recirculating reactor in which the precipitate formed on injection and circulation of the sample solution into a chloride-containing carrier was collected in a column of nylon fibres. After circulation for an appropriate time a sub-sample was injected into a single line manifold for transport to the flame. Recoveries of between 95 and llOo/o were obtained for solutions containing up to 100 g 1 - I silver. The filter was cleaned by flushing the loop with ammonia solution. The recirculating loop reactor has also been used for the acid leaching of calcium from charcoal in a study concerned with the determination of the relative amounts of calcium oxide and calcium carbonate in this material (921C3688).A collabora- tion between workers in Brazil and in Spain (931C122) has produced an FI precipitation method for the determination of Ni in rocks by a procedure very similar to that for Co already published (see J. Anal. At. Spectrom. 1991 6 193R) by the Spanish group. This same group that of Valcarcel at Cordoba has also described (931433) a procedure for the indirect determina- tion of amphetamines which involves liquid-liquid extrac- tion (LLE). The FI valve acted as the interface between the continuous extraction manifold and the spectrometer. The method was based on the reaction of methamphetamine or amphetamine with carbon disulfide to form a dithiocar- bamic acid which in turn formed a complex extractable into IBMK with either copper nickel or zinc.After phase separation (a previously described device was used see Gallego et al. Anal. Chem. 1986 58 2265) a 130 pl sub- sample of the IBMK extract was injected into a water carrier for transport to the spectrometer. The method was used successfully for the analysis of some pharmaceutical preparations and of spiked urine. Another group of Spanish workers (at Salamanca) have extended the work already described on indirect liquid-liquid extraction procedures (see J. Anal. At. Spectrom. 1992 7 220R) for fungicides to the determination of dimethoxydithiophosphate (9212678). This was a double extraction procedure based on the formation of a copper complex which was extracted off-line into chloroform.The chloroform extract was pumped continuously into the back extraction manifold (Isoversinic fluorinated-plastic tubing was used) and merged with a pH 10 buffer solution. The aqueous phase was transferred across a hydrophilic membrane (Millipore HA 0.45 pm pore size) and a sub-sample injected into an aqueous carrier. The nebulizer was run under starvation conditions and air compensation was used. The method was success- fully applied to the determination of malathion in an agricultural formulation. Japanese workers have described (9214400) a rapid FI-LLE method for measuring Cu after extraction with potassium ethylxanthate. A 1 0-fold increase in speed over a manual LLE procedure was obtained. Flow injection LLE procedures have been reviewed (Trojanow- icz M.and Szpunar-Lobinska J. Chem. Anal. (Warsaw) 1992 37 5 17). The 63 references cover fundamentals and applications with various molecular spectrometries as well as AAS. As with the last two review Yeriods there is continued interest in the development of on-line directly coupled solid-phase extraction (SPE) procedures. The relevant litera- ture has been reviewed by Fang (931860) who covers the material of 82 references. This is the same number of references cited by Carbonell et al. (93171 1) in a literature survey of on-line preconcentration procedures which covers LLE and precipitation as well as SPE but excludes chemical vapour generation. Both reviews cover other atomic spectrometries in addition to FAAS.At least one overview conference presentation was made (921463 5). A critical evaluation of the performance characteristics of FI preconcentration procedures including two SPE methods has been made by Fang et al. (9214635). Equations were derived for ( a ) the enrichment factor EF being the ratio of the slope of the calibration after the preconcentration procedure to that obtained without preconcentration (b) the enhancement factor N being the product of the various sensitivity enhancement factors and EF (c) the concentra- tion efficiency CE being the product of the number of samples per minute and the EF and (6) the consumptive index CI being the sample volume in ml consumed to achieve a unit EF. Four procedures for the preconcentra- tion of Pb were compared on the basis of these parameters and theoretical values were compared with the experimen- tally determined values.The SPE procedures involved retention on quinolin-8-01 immobilized on controlled pore glass or retention on C silica. The other procedures involved coprecipitation with iron@) hexahydroazepinium hexahydroazepin-1-ylformate collection in a knotted tubu- lar reactor and dissolution in IBMK followed by nebuliza- tion into a flame atomizer both with (see section 1.1.3.2.) and without a STAR. Reasonable agreement between calculated and experimental values of the CE EF and CI values were obtained. It was shown that various enhance- ment eflects were multiplicative in that the value of N for the procedures involving precipitation and atomization with the aid of the STAR was 135.Other Chinese workers (931C 136) have reported on the preconcentration of Cd Cr Cu Fe and Mn on ion-exchange material. A weak cation exchanger was used for all the elements except Cr for which an anion exchanger was used. Values of N ranging from 16JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 205R to 24 were obtained. Yet a third Chinese group has presented results for preconcentration using an unspecified chelate resin (92/C4 162). The results of a number of studies in which a mini- column of chelating ion-exchange material has been used for preconcentration have been published during this review period. In a special issue of the Microchem. J. devoted to FI techniques Townshend and Habib (Microchemical J. 1992 45 2 10) described procedures for the preconcentra- tion of Co Cu Hgl Hg*I and Rh1I1 on a column consisting of dialkyldithiocarbamate immobilized on controlled pore glass.The metal ions from an appropriate volume of sample solution were loaded onto the column by continuous pumping of the sample solution for the required time. After washing with water elution was effected with a 100 pl injection of acid (either nitric or hydrochloric). To remove Hg' and Hg" it was found necessary to add a competing complexing agent to the eluent namely thiourea. The uptake of Rh*I1 was found to be slow and a recovery of only 46% was obtained. Enhancement factors ranged from 6 to 12 with the corresponding concentration efficiencies rang- ing from 1.8 to 5.4. The interference from a variety of metal ions at concentrations of up to 50 mg 1-1 was shown to be negligible and some measurements of the capacity of the column material were made.Values ranged from 0.9 mmol g-' for Rh to 4 mmol g-' for Co Cu and Hg. The columns had lifetimes of up to 1 month. Purohit and Devi (9212677) have published further studies on the synthesis and use of resin material synthesized from quinolin-8- 01-formaldehyde-resorcinol and from quinolin-8-01-form- aldehyde-hydroquinone (see J. Anal. At Spectrom. 1992,7 221R). The material was used in both batch and FI preconcentration procedures for the determination of Cu. Some studies of the fundamental thermodynamic and kinetic properties of the reaction between Cu and the resin materials were made and it was demonstrated that separa- tions of binary mixtures of Cu with lead or nickel were possible by suitable step changes in eluent composition. Calibrations after preconcentration from 10 ml of sample solution from 20 to 100 ng ml-I were performed.The Cu was eluted into 50 pl of 0.5 moll-' HCl. For a 15 ml sample volume the detection limit based on three standard deviations of the blank signal was 5 ng ml-l. This work has been extended (93/446) to an evaluation of a further four resins produced by the scheme described previously (92/2677) but with two different cross-linking agents replac- ing the formaldehyde namely furfuraldehyde or benzal- dehyde. The protocols adopted were identical to those of the previous publication except that Pb was used as the test element. It was found that the FI preconcentration proce- dure was more pH dependent than the batch procedure and for a 5 ml sample volume the detection limit was calculated to be 10 ng ml-I.Littlejohn and co-workers (931C265 93/1017) have evaluated the performance of an FI precon- centration system for A1 in which a column of quinolin-8-01 immobilized on controlled pore glass was used. The intro- duction to this paper provides a useful tutorial discussion of the thermodynamics of the reactions of A1 in solution and with the chelating ligand in which the role of the buffer solution is critically assessed. It was concluded that it was necessary to use an anionic alkaline buffer which would form a complex strong enough to prevent precipitation of aluminium hydroxide but weak enough to allow complexa- tion with the immobilized ligand.The final choice of buffer was 0.1 moll-' malonate adjusted to pH 10 by the addition of ammonia. For a preconcentration time of 3 min at a flow rate of 6 ml rnin-l and enhancement factor N of 76 and a detection limit of 3 ng ml-1 were obtained. The method was evaluated by a comparison of the results of the analysis of some river water samples with results obtained by two collaborating laboratories in which ETAAS and ICP-OES were used. The results were in agreement. An accurate analysis of National Research Council of Canada CRM SLRS-1 River Water in which the A1 content is 23.5 k 1.2 ng ml-I was made. For the determination of Co in glass Valdes-Hevia y Temprano et al. (9212589) used a column of Chelex- 100 for preconcentration and separation from the major matrix elements calcium magnesium and sodium remaining after removal of the silicon with HF.Despite the dimensional instability of Chelex- 100 as a function of pH which reduced the lifetime of the column to about 50 injections this material was used because of its low affinity for alkali and alkaline earth elements. Interference from iron was prevented by the addition of citrate and from aluminium by adjustment of the solution to pH 7. Silicon interference was also severe and it was found necessary to ensure that the HF treatment reduced the silicon concentra- tion to within a factor of 2-3 of the cobalt concentration. The detection limit was improved by a factor of 4 over that obtained with direct aspiration to 20 ng ml-1 in the injected solution corresponding to 1 mg kg-l in the solid sample. Results in agreement with those of direct nebuliza- tion ICP-OES were obtained for two real samples.The work of Olbrych-Sleszynska on 'designer' SPE chemistries re- ported last year in a conference presentation (see J. Anal. At. Spectrom. 1992 7 220R) has now in part been published (92/4639). In this procedure a chelating agent [ Pyrocatechol Violet 4-( 2-pyridy1azo)resorcinol or Erio- chrome Blue Black R] was first sorbed onto a non-polar sorbent Amberlite XAD-2 (a styrene-divinylbenzene type resin). The procedure was successfully applied to the determination of Cu at concentrations of around 1 pg 1-' in some natural waters. Pyrocatechol Violet was used as the chelating ligand and a preconcentration time of 20 min was needed at a flow rate of 6.8 ml m1n-I.Elution was effected with 1 ml of 1 moll-' nitric acid at 2.8 ml min-'. Calcium was found to interfere at concentrations above 50 mg 1-I. The iron interference could be eliminated by the addition of fluoride. The literature relating to FI on-line sorbent extraction procedures based on the retention of neutral metal complexes on C,,.material has been reviewed by Welz (93/482). The work discussed concerns both FAAS and ETAAS. It was concluded that such procedures have developed into a very promising and widely applicable technique for the determination of elements in water samples including sea-water. When applied to FAAS N values of 20 or more can be achieved with only 20 s loading time and thus the sensitivity gap between flame and furnace AAS is bridged while maintaining sampling frequencies of around 120 h-l comparable to those of conventional FAAS procedures. The on-going collaboration between Welz's group and various Chinese visiting scientists continues to be fruitful in this area.Xu and co-workers (Fresenius' J. Anal. Chem. 1992 344 535) have described a procedure for the determination of Cd and Cu in various biological materials using on-line sorbent extraction of the diethylam- monium-N-N-diethyldithiocarbamate (DDTC) complex onto CIS. Methanol was used to elute the retained com- plexes and dispersion in the connecting lines between column and nebulizer was reduced by the insertion of small air segments. The sampling frequency was 85 h-' and the overall enhancement factors (N values) were 126 and 114 for Cd and Cu respectively.The corresponding detection limits were 0.15 and 0.2 pg 1-I. Accurate analyses of up to seven SRMs (tissue flour leaves pine needles bovine liver and muscle lobster and urine) were obtained except for the cases in which Cd was determined in samples which contained high concentrations of copper or iron. In these instances low Cd values were obtained. One of the useful features of the DDTC complexes of these metals is that they are formed in conditions of high acidity (up to 1 mol l-I) and thus after a wet oxidation dissolution procedure it is206R JOURNAL OF ANAILYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 not necessary to adjust the pH by the addition of large amounts of buffer components. However the maximum sensitivity for Cd was not achieved until the acidity was reduced to pH 3 a value at which severe iron interference would be observed.In the determination of Cd therefore an acidity of 0.5 mol 1-l was used. The same authors have also published a method for the determination of CrlI1 and CrVI in waters using a procedure in which the selected species were preconcentrated on activated alumina (see Sperling et al. Anal. Chem. 1992 64 3101) by suitable control of the pH. At pH 7 CrlI1 is present predominantly as uncharged Cr(OH) and can therefore be retained by sorption on the surface of the alumina which is also unchanged at this pH. Chromium(vI) is anionic at this pH and is not retained. The retained CrlI1 was eluted with 0.1 mol 1-1 nitric acid solution. At pH 2 the column material is positively charged and thus will retain anionic CrV1 species but not cationic CrlI1 species (a mixture of Cr3+ and CrOH2+). The retained CrV1 was eluted with 0.5 mol I-' ammonia solution.The retention efficiencies were better than 80 and 90% for Cr1I1 and Crvl respectively which gave N values of 25 for a 3 ml sample. The interference effects of several possible anionic and cationic concomitants were investigated and recoveries from various natural water samples of between 91 and 102% were obtained for concentrations between 20 and 100 pg I-'. The detection limits obtained were 1.0 and 0.8 pg 1-1 for CrlI1 and Crvl respectively. The introduction to this paper provides a useful overview of the previously reported work for the determination of these two species by procedures involving on-line separation.Finally in this section on SPE it is of interest to note the use of immobilized algal biomass as a preconcentration medium for a variety of trace metals (92/26 19). A fast growing and easily cultivated species Selenestrum capricornutum was selected grown harvested heat treated freeze dried ground and solubilized in a mixture of dilute hydrochloric acid and ethanol and finally immobilized on controlled pore glass by a procedure adapted from that used to immobilize enzymes. The relevant operating parameters were investigated and some univariate optimization studies performed. Although algae are not as resistant to acid eluent solutions as some other immobilized agents which poses a problem for the elution of some metals suitable procedures for the elements under investigation were developed.As reported above (Town- shend A. and Habib K. A. J. Microchem. J. 1992 45 210) by other workers from the same laboratory the addition of thiourea was necessary to remove Hg. For a 5 ml sample volume detection limits for Cd Co Cu Hg Pb and Zn of 2.0 8.0 0.05 30 2.5 and 0.2 ng ml-l respectively were obtained. The sampling rate was 20 h-l. The columns retained their activity if stored below 4 "C when not in use for periods of about 3 months. There has also during this review period been a sustained level of activity in the use of FI procedures for the implementation of the appropriate chemistry of chemical vapour generation procedures.A group of papers has already been discussed earlier in this section in relation to the use of microwave sample pre-treatment and a further group will be discussed later in section 1.3. The atomizers in general use are usually electrically heated quartz tubes and therefore these papers are strictly outside the scope of sections relating to flame atomization. It should be borne in mind that the use of a graphite furnace to trap hydrides prior to atomization appears to be a significant develop- ment and therefore future FI-HG could well be classified with electrothermal atomization. As was pointed out last year (see J. Anal. At. Spectrom. 1992,7,22 1 R) some of the sample pretreatment procedures employed prior to the chemical vapour generation reaction are of interest.For example Tyson et al. (J. Anal. At. Spectrom. 1992,7 3 15) devised a procedure for the determination of As in nickel in which the nickel matrix was removed by passage through a cation-exchange resin and an on-line stopped flow reduc- tion of the AsV to As111 was implemented. 1.1.3.4. Solid sample introduction. Few papers concerning the direct introduction of slurries into flame atomizers have appeared during this review period. Slurries have been handled in flowing systems as part of a coupled sample digestion procedure (9212082 9213838 92/4636) although in these studies the sample was eventually introduced into the spectrometer as a solution. These were considered in the previous section as was the determination of Ca K Na and Mg in various tropical fruits (931483) by FI slurry sampling.Batistoni (9311 186) used the introduction of slurries as part of a study of atom distribution in the air-C2H2 flame to demonstrate that increased mass transport into the flame resulted in reduced sensitivity because of the decrease in atomization resulting from the decreased residence time (see also section 1 . 1 . 1 ) . For the determination of several metals in atmospheric particulates (92/2638) slurries were prepared from the material collected on cellulose acetate membranes by ultrasonication in 2.5 ml of nitric acid for 30 min. After dilution with water to a slurry concentration of 1 O/o Fe Mn and Pb were determined by FAAS (and Cu Cd Ni and V by ETAAS). Accurate analyses of NIST SRM 1648 Urban Particulate Matter were obtained.The lower sensitivity obtained for the slurry nebulization of calcium phosphate compared with the same concentra- tion of Ca in solution has been exploited (92/3082) as a method for the determination of these two forms of Ca in the same sample. The use of air-C2H2 and N20-C2H2 flames was investigated. Workers at Aberdeen University (9312087) have followed up their suggestion (see Jerrow et al. Anal. Proc. 1992 29 45) that the success of the standard additions method in the analysis of soils and sediments by slurry nebulization DCP- AES was due to the binding of the added analyte to ion- exchange sites created by the slurry preparation procedure thereby producing accurately matched slurry standards. The hypothesis was effectively proved for the determina- tion of Ba in barytes and soils by FAAS or ionic absorption spectrometry (at 455.4 nm) with a N20-C2H2 flame.Competition for the solid binding sites between Ba and potassium was clearly observed. It was concluded that the deliberate addition of high concentrations of cations for spectroscopic buffering purposes could have a deleterious effect on the accuracy of the analysis as the analyte elements could be displaced into solution from surface binding sites. 1.1.4. Sample pre-treatment A number of papers have appeared in this review period for which the reason for publication has been some novel sample pre-treatment procedure. Although these have been implemented off-line (otherwise the work would have been included in the previous section) it is considered that such procedures may be of interest to readers of this particular Update.Most of the procedures included in this section are liquid-liquid or solid-phase extractions of one sort or another. A procedure for the determination of Mo based on the extraction of the complex with 5,5'-methylenesalicylo- hydroxamic acid into IBMK has been developed (92/2487) which suffers only from interference from TiIV and Wvl. These interferences were minimized by the addition of fluoride. The same solvent also featured in a procedure for the determination of Au Cd Cu Ni Pb and Zn after extraction of the complexes with 4-amino-3,5-di-2-pyridyl-JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 207R 4-H-1,2,4-triazole (93/ 12 10). The Mn content of some botanical material was determined (9212004) by a proce- dure which involved extraction of the complex with Amberlite LA-2 (N-lauryltrialkylmethylamine) in chloro- form.A procedure that has the characteristics of both liquid and solid extraction procedures has been described (92/46 1 6) for the determination of Fell1. A solid extractant phase was produced from disodium 1,2-dihydroxybenzene-3,5-disul- fonate (Tiron) and benzyldimethyltetradecylammonium chloride supported on naphthalene held on polypropylene fibres in the stem of a small filter funnel. On passage of an aqueous sample solution (pH 6-9) through the filter funnel Fell1 was retained. The entire column was dissolved in 5 ml of dimethylformamide and introduced directly into an air- C2H2 flame. Interference effects were evaluated and accu- rate analyses of two biological reference materials (chlorella and mussel) were performed.The same principal author has also devised a method for the determination of Cu (931458). This time the metal was retained by complexation with 2- nitroso-1-naphthol-4-sulfonic acid and retained as an ion pair with the same ion-pairing reagent (benzyldimethyl- tetradecylammonium chloride). A detection limit of 3 pg 1-1 was obtained and the method was applied to the analysis of some magnesium alloys and vehicle exhaust samples. Amino and thiol modified silicas were synthesized by Akman et al. (J. Anal. At. Spectrom. 1992 7 187) and applied for the preconcentration of Cd and Cu from sea- water samples. It was found that the metals were quantita- tively retained in slightly acidic media and released into 2 mol 1-I HCl solution.Chinese workers reported (93/ 1 147) on the preconcentration of Cd from urine samples by retention on sulfhydryl cotton followed by desorption into hydrochloric acid solution. The detection limit was 0.22 Fg 1 - I and recoveries between 99.8 and 101.4% were reported. Other Chinese workers (92124 19) developed a procedure for the determination of Crlll and Crvl in water samples by the use of ion-exchange resins. After adjustment of the pH a cation-exchange resin was added and after filtration CrV1 was determined in the filtrate. A similar procedure was used for the determination of CrlI1 after removal of the CrV1 with an anion-exchange resin. Some preliminary results (93/C902) for the determination of Pb in soil extracts and surface waters after preconcentration on a column of dithizone immobilized on polyurethane foam have been presented.Chinese workers (92/4672) have demonstrated the quantitative retention of Au on this support material from diluted aqua regia. Elution was with a boiling solution containing 0.02% thiourea 0.1 Yo hydro- gen peroxide and 0.1 O/o hydrochloric acid. As an alternative to the retention of ion-association complexes on naphthalene described above it has been shown possible to separate and preconcentrate a number of metals by a flotation process (92/24 13). The metals were complexed with either bromide iodide or thiocyanate and then floated in toluene as the ion-association complex with Methylene Blue. The froth was then dissolved in dimethyl- formamide and nebulized directly to give sensitivity enhancement factors of over 100.In addition a procedure for the determination of Cu and Fe in sea-water based on the thiocyanate-cetylpyridinium chloride system was developed. 1.1.5. Chromatographic detection In a review article in the CSI issue of the Analyst alluded to earlier Van Loon and Barefoot have provided an overview of analytical methods for elemental speciation (92/4099). Procedures involving FAAS are included as part of this 64 reference review which contains brief sections on the 14 most frequently studied elements namely Al Au Cd Cr Cu Fe Hg Mn Pt Se Sn Te and Zn. Various methods of interfacing a chromatographic separation with an atomic spectrometer and some electrochemical methods were discussed.In another article in the same issue Chau (Analyst 1992 117 57 1) provided a brief survey of the use of LC and GC procedures in conjunction with atomic spectrometry for metal speciation again FAAS procedures were included. A more restricted overview in terms of elemental coverage and sample type has been provided by Donard and Martin (93/ 126 1). Particular attention was given to the determination of the various species of As Hg Pb Sb Se and Sn in environmental samples. Some attention was focused on Hg-cryogenic trapping-GC as the basis of the separation of the various species. The separation of seven arsenic compounds by HPLC coupled with FAAS has been reported (Hansen et al. J. Anal. At. Spectrom. 1992 7 629). The interface was a vented PTFE tube connected to the nebulizer and the atomizer was an Ar-H flame.A STAR (see section 1.1.3.2.) was used to enhance the sensitivity by a factor of 2-3. The detection limits for 100 pl injections for arsenic(n1) arsenic(v) monomethylarsonate dimethylarsinate arseno- betaine arsenocholine and the tetramethylarsonium ion were 1.1 1.4 1.4,0.7,. 0.3,0.5 and 0.4 mg l-l respectively. These values were considered suitable for use in a study of contaminated soils. For the lower concentrations expected in fish tissue a preliminary evaluation of the use of ICP-MS was also reported. Marshall and co-workers (9212726 92/3 1 14 92/43 17) have reported further studies using the post-column deriva- tization system in which a thermochemical HG process is used in conjunction with FAAS with atomization in a cool 02-H2 flame (see J.Anal. At. Spectrom. 1991 6 195R). The first of these studies (92/2726) concerned the determi- nation of arsenobetaine arsenocholine and tetramethylar- sonium cations in seafoods and human urine in which the species were separated by HPLC. As part of the sample pre- treatment procedure the extracts were passed through an anion-exchange resin in order to remove anionic forms of arsenic. Recoveries of spikes at concentrations of 0.1-3.4 mg kg-l fresh mass were greater or equal to 83%. The second of these reports (9213114) is an overview of HPLC-AAS interfaces for the determination of ionic alkyllead alkyltin arsonium and selenonium compounds. The third study concentrated (92/43 17) on the optimization of the chromatography mainly in terms of mobile-phase composition.The separation and detection of organolead compounds by GC-AAS has been reviewed (9213 1 15). A procedure for the determination of alkyllead compounds in gasoline by GC-AAS has been described (93/1933) in which atomiza- tion in a heated silica tube was aided by the addition of hydrogen to the GC eMuent before entering a quartz cell mounted in an air-C2H2 flame. Detection limits of between 0.1 and 0.25 mg 1 - I were obtained. A study of methods for the extraction of alkyltin species from sewage and sludge has been made (9311035). The GC-AAS procedure used was as reported previously (Chau et al. Anal. Chem. 1982,54 246) with some modifications to the procedure originally designed for methylbutyl compounds to allow the separation of ethylbutyl com- pounds.The atomizer was a flame-in-tube device. The method developed involved extraction of the various butyltin species into cycloheptatrienone (tropolone) fol- lowed by ethylation with ethylmagnesium bromide. It was found that the non-pesticide octlytin species and acid leachable SnIV species could also be determined. A similar methodology was described by Forsyth and Cleroux (92/2492) for the determination of various alkyltin species in marine food products. The detection limits for tetra- methyltin and tetraethyltin were 0.8 and 0.7 pg kg-l (as Sn),208R JOURNAL OF ANA.LYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 respectively. It is of interest to note that GC-AES has also been used for the determination of organotin species extracted from fish and sediment samples (921427 1).Organomercury compounds in biological samples were determined (931 1236) by a combined capillary GC-AAS method in which the eluted compounds were converted to elemental Hg on passage through a stainless-steel pyrolyser. Detection limits in various biological samples of between 0.1 and 20 pg kg-’ were obtained. An HPLC method for Hg speciation has also been described (9212553) in which inorganic Hg ethyl and methylmercury were converted in a post-column reactor into elemental Hg by a two-stage process in which the mercury compounds were first oxidized with acidified dichromate solution and the resulting inorganic Hg reduced with sodium tetrahydro- borate solution. The detection limits of around 100 ppb were improved by as much as three orders of mgnitude by the use of an on-line preconcentration unit.The combination of ion chromatography and FAAS (9214670) was used for the determination of CrlI1 and CrV1 in electroplating waste solution. The precision reported was not particularly impressive being 9.6 and 3.5% RSD for 10 mg 1-l of CrlI1 and CrV1 respectively. A combination of elec- trochemical detection and FAAS was used in the speciation of Fe in some alcoholic beverages (9212008). The Fell was detected electrochemically and total iron by FAAS. This would appear to render the need for separation redundant. Chinese workers have reported (9214371) on the use of gel permeation chromatography and AAS for the indirect quantification of metallothioneins to which Cd or Zn was bound.It is not clear whether the chromatography and the atomic spectrometry were directly coupled. The use of the hydraulic high pressure nebulizer as a means of coupling HPLC and FAAS has again been described (921C3650) with particular reference to separa- tions and enrichment of traces. 1.2. Electrothermal Atomizers Electrothermal atomizers continue to be a rich area of both applied and fundamental research. It is a source of constant amazement that a technique which although it is nearly 30 years old and has been written off by some workers finds more roles to play in the field of analytical chemistry. The increasing use of coupling techniques i.e. graphite tubes as vaporizers as opposed to atomizers linked with a variety of atomic spectrometric techniques as discussed by Dittrich et al.(93/C158) and the linking of FI with electrothermal atomizers shows that the field continues to prosper and it will be some time before this reviewer has to ask to be transferred to another topic group! As in previous years the emphasis within this review is on fundamental papers rather than applications. Naturally it is hard in many cases to draw a distinct line between the two but in the main only those papers and conference reports which offer some investigation of a fundamental nature though possibly linked with an application will be included here. Those more concerned purely with the employment of ETAAS as the means of performing the final measurement will find the information they require in the relevant sample-application based reviews.Some reviews have appeared during this period. Comple- mentary to this Update is the review by Jackson and Qia (Anal. Chem. 1992 64 50R) who also share the optimism of this reviewer about the state of ETAAS research. Littlejohn et al. (931432) posed an interesting question ‘graphite furnace analysis-getting easier and achieving more?’ and discussed the influence of microwave digestion for sample preparation improved performance of platform and probe atomizers injection into a pre-heated tube application of palladium modifiers and how all these allow the use of similar atomizer programmes which then enables simultaneous multi-element determinations with contin- uum source ETAAS. A Japanese review (9212046) appeared concerning ETAAS and simultaneous multi-element analy- sis with 93 references.In the last Update (see J. Anal. At. Spectrorn.,l992 7 2 15R) a considerable number of the conference abstracts presented at the CSI conference in Bergen Norway in June 199 1 and the associated Pre-Symposium on Graphite Atomizer Techniques in Analytical Spectroscopy were discussed. During this review period many of these have been published in the special conference issues of J. Anal. At. Spectrom. and The Analyst in March 1992. In an effort to avoid the coverage in this review becoming repetetive mention is made of those papers which have been pub- lished but extensive discussion is only devoted to those papers which offer new information that was not contained within the original conference abstract. Of particular interest and required reading for all those concerned with publishing in the field of ETAAS is the publication of the IUPAC recommendations (931642) on ‘Nomenclature Symbols Units and their Usage in Spectro- chemical Analysis-XII.Terms related to electrothermal atomization.’ Here the terminology related to electrothermal atomization in particular with respect to AAS is discussed and recommendations made. The adoption of many of the terms proposed in this report would help considerably in avoiding a great deal of the ambiguity that can arise from authors using identical terms to describe different things. While one may not agree with all the recommendations the effort to produce some uniformity in the field is to be applauded. Another area which requires attention discussed by Welz (9311086) is the symbols and units for integrated absorbance.Over the years a large number of different symbols and units have crept into the literature but what is clear is that the commonly used term for integrated absorbance ‘Ass’ applied together with the numerical integrated absorbance value as if it were a unit is not in keeping with the recommendations of IUPAC regarding Quantities Units and Symbols and their Use in Physical Chemistry. In terms of SI base units the only appropriate ‘unit’ for integrated absorbance is seconds s because A is a dimensionless quantity. Welz proposed that as a symbol for integrated absorbance Ain or A be used analagous to Apeak and wondered whether it would be worthwhile considering the introduction of a separate unit for integrated absorb- ance similar to Hertz for frequency (Hz=vibrations per second) and suggested the use of L’vov (Lv) as the symbol for that unit.No doubt this discussion will continue for some time presumably at many scientific meetings but it is one which we should all consider seriously as defined units and terminology enable us to communicate in the same scientific language and avoid confusion. 1.2.1. Atomizer design and surface modijication During the last year a trend has been the increased attention paid to the development and application of the low-cost tungsten coil atomizer originally proposed by Berndt and Schaldach (see J. Anal. At. Spectrom. 1988 3 709). This work mainly originates from South America and is to be welcomed as until now very little further work has appeared in the literature. It is to be hoped that this information which is at present in the form of conference abstracts will appear in due course in the literature and enable an objective assessment of the tungsten coil atomizer with respect to the established graphite tube atomizers to be made.Berndt and Schaldach (9212093) discussed three closed-type and one open-type different configurations of the tungsten coil atomizer. Gine eta!. (921C3570) examined the configuration of a tungsten coil mounted in a 10 cm longJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. AUGUST 1993 VOL. 8 209R T-shaped cell with quartz windows. The tungsten coil power supply was equipped with a voltage-feedback circuit to improve voltage stability and temperature control.The simultaneous measurement of current and voltage during solvent evaporation pyrolysis and atomization enabled the optimum conditions for Cd to be established. Cadmium was determined in biological digests containing either 1.4 mol 1-I nitric acid or 0.25 mol 1 - I perchloric acid using a mixture of 90% argon and 10% hydrogen as the purge- reducing gas. They found in contrast to graphite atomizers that the lifetime of the tungsten coil was not significantly affected by perchloric acid-digested samples. The effect of various heating rates and signal resolution for the tungsten coil atomizer were examined by Nobrega et al. (931C162) using Pb in 2% m/v sodium chloride solu- tions. By choice of a suitable atomization heating rate it was possible to separate the analyte and background signals temporally and improve analyte precision.These same workers (93/C161) examined the effect of varying the argon-hydrogen purge gas composition on the atomization conditions for Cd and Pb. Silva et al. (93/C163) compared the atomization of Ba from tungsten coil and graphite tube atomizers and claimed that concentrations as low as 1.0 ,ug 1-l in a 10 p1 sample volume could be determined. The interferences due to 500 mg 1-l of aluminium calcium iron magnesium manganese strontium and titanium nitrates and up to 2% m/v sodium chloride on Ba were evaluated. Bruhn et al. (93/C 165) compared the analytical perform- ance of the tungsten coil atomizer with a graphite tube atomizer (HGA-400) with respect to linear working range characteristic mass repeatability reproducibility accuracy and detection limits for measurements quantified in peak height absorbance.They found that the tungsten atomizer yielded significantly better sensitivity and absolute detec- tion limits (3s) of 0.6 12 and 23 pg for Cd Ni and Pb respectively though in comparison with the manufac- turer's published detection limits based on integrated absorbance measurements these represent no real improve- ment. However it was concluded that the tungsten coil atomizer represents an inexpensive alternative to conven- tional graphite atomizers. The direct determination of Cr in waters using a tungsten coil atomizer was examined by Silva et al. (93/C 164). Matrix interferences were found for aluminium calcium cobalt iron magnesium manganese nickel potassium sodium and titanium.As elements such as calcium and magnesium are typically encountered in water samples severe depression of the Cr signal could be caused. Chinese workers (92/C3653) determined Cd in PVC samples digested with an HN03-H2S04-H202 mix- ture with a tungsten coil atomizer and claimed that this eliminated the disadvantages of a conventional graphite tube such as short tube lifetime and high cost. However the signals given show a background overcompensation problem and quantification required the method of analyte additions. A tungsten-rhenium wire-loop atomizer was used by Chauvin et al. (93/802) to investigate the interference effects caused by various compounds on the determination of Be Cd Cu and Mg. The major mode of suppression appeared to be the formation of analyte compounds such as oxides and chlorides in the vapour phase.A tungsten tube atomizer (34 mm long 1.8 mm i.d. and 0.05 mm wall thickness) was applied by Ohta et a!. (92/C3586 93/584) to the determination of Ti in geological samples. A mixed purge gas of argon (200 mi 1-l) and hydrogen (300 ml 1-l) provided narrower and larger peaks than those obtained in pure argon. The characteristic mass presumably using peak-height measurements was found to be 7.5 pg with a detection limit of 0.73 ,ug 1-1 for a 10 pl sample volume. Interference effects were overcome by the use of a high pyrolysis temperature. The same workers (9212490 931804) examined the use of a platinum tube atomizer (33 mm long 2.0 mm i.d. and 0.03 mm wall thickness). The advantage of this atomizer appears to be its stability apparently no inert purge gas is required and the tubes have lifetimes greater than 1000 firings in air.Detection limits and characteristic masses for seven ele- ments with the platinum tube atomizer have been pub- lished (93/804) and its use described for the determination of Cd in biological CRMs (92/2490). For 2.5 pg of Cd 1 04- 1 Os-foid amounts of aluminium calcium copper iron lead magnesium potassium sodium and zinc did not interfere with the absorption signal. A detection limit of 0.09 pg (9 ng 1 - I for a 10 pl sample volume) was found though tailing peaks were obtained which prevented the use of integrated absorbance measurements. Japanese workers (92/3048) examined a metal atomizer for the determination of Yb in geological materials.Sadly the abstract failed to identify the metal used to construct the atomizer. Nitric sulfuric phosphoric and perchloric acids interfered with Yb but hydrochloric acid (up to 2 mol 1-I) did not. The introduction of the WETA-90 transverse heated tungsten tube atomizer (92/2403) was discussed last year (see J. Anal. At. Spectrom.,l992 7 215R). Shan et al. (92/4650) examined the use of palladium as a chemical modifier in the WETA tungsten atomizer. They rightly pointed out that there have been very few reports on the application of chemical modifiers in metal atomizers. They investigated the performance of palladium as a chemical modifier with respect to sensitivity stabilizing power and increasing the range for the interference-free determination of volatile elements such as Ag Au Bi Ga In Pb Se and Sn.The characteristic masses (integrated absorbance) were found to be higher by a factor of 3-10 compared with a graphite electrothermal atomizer. Palladium increased the sensitivity for most elements studied by 20-200% except for Ag. The use of up to 15% hydrogen in the argon purge gas had no influence on the sensitivity but increased the tube lifetime; higher concentrations of hydrogen in the purge gas resulted in a decrease in sensitivity for most of the elements examined. Chinese and Japanese workers continue to dominate the investigation of metal or metal carbide coated graphite surfaces though in contrast to previous years when tanta- lum has been the dominant element this review year has seen an increase in the use of tungsten.In general these materials appear to be used for those more refractory elements which have severe atomization or carbide forma- tion problems in conventional graphite atomizers. Chinese workers (92/24 18) found that a tantalum foil lined graphite tube furnace improved the sensitivity 6-fold for Ga. Combined with a mixed chemical modifier of vanadium and copper the atomization temperature could be reduced pyrolysis temperature increased and interferences elimi- nated. These same workers (92/2425) found that the sensitivity for Li was doubled when a pyrolytic graphite coated electrographite tube atomizer was lined with tanta- lum foil. The atomization temperature could be reduced from 2200 to 1900 "C and the method was applied to the determination of Li in biological and geological materials.Chruscinska (92/25 10) examined the impregnation of graphite tubes with aqueous solutions of 8- 10% tantalum and containing various amounts of HF H3B03 oxalic acid and H202. The tubes were then dried and ignited at temperatures up to 2550 "C under controlled heating rates to complete the coating process. The use of a tantalum foil platform combined with different chemical modifiers (pal- ladium sodium dihydrogenphosphate and ascorbic acid) for the determination of Cd in environmental samples and discussed in last years review (see J. Anal. At. Spectrom. 1992 7 2 1 SR) has now been published (92/4656).210R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 The work of Iwamoto et al. (9214655) concerning the determination of Sn with tungsten coated graphite tubes was discussed last year (see J. Anal. At. Spectrorn. 1992 7 2 15R). Further information is provided in the paper and it would appear that a tunsten coating on electrographite tubes (i.e. no pyrolytic graphite coating) produced the highest and most stable signals for Sn in a sea bass sample. Shen and Shi (9213842) applied a pyrolytic graphite coated electrographite tube lined with tungsten foil to the determi- nation of La in food and water samples. The tungsten foil eliminated the memory effect found with non-lined graph- ite tubes. Water samples were concentrated 10-fold by evaporation and food samples (5-10 g) by dry ashing followed by dissolution of the residue in HCl and dilution to 5.0 ml.The use of a tungsten wire probe coated with trioctylphos- phine oxide for the determination of Bi in copper alloys and lead and discussed last year (see J. Anal. At. Spectrom. 1992 7 215R) has now been published (9212681). This technique has also been applied by Lu et al. (9212684) for the determination of Au in waste waters. With the coated probe inserted into the sample solution for 2 min a detection limit of 0.2 pg 1-l was achieved. Komarek et al. (9212229) studied the atomization effici- ency of Eu Pr and Y from uncoated and pyrolytic graphite coated electrographite tubes with molybdenum tantalum and tungsten carbide coatings or lined with tantalum or tungsten foils. The two metal foils gave a decrease in the memory effect and signal tailing with respect to uncoated and pyrolytic graphite coated electrographite tubes and the carbide coatings.However though these workers state that a limited lifetime was found for the tantalum and tungsten linings no indication is given of the actual lifetime. Luguera et al. (9212623) examined the use of tantalum vanadium and zirconium carbide coatings on uncoated and pyrolytic graphite coated electrographite tubes (prepared by soaking under vacuum) with nickel palladium and ascorbic acid chemical modifiers for the determination of B in waste and river waters. The best results were obtained with zirconium coated tubes in conjunction with nickel as the chemical modifier. This gave a higher sensitivity a reduced memory effect and an increased tube lifetime (200 atomiza- tion cycles at 2650 "C for 3 s).Bermejo-Barrera et al. (931C 1599) compared the performance of zirconium- coated graphite tubes or the use of a palladium-magnesium nitrate chemical modifier and concluded that sensitivity was better in the zirconium-coated tubes. Japanese workers (9212062) applied a molybdenum coated pyrolytic graphite coated electrographite tube for the determination of Ga in environmental RMs. Sulfuric hydrochloric and perchloric acids showed suppressive effects on the Ga signal but nitric acid did not show a significant depressive effect up to a concentration of 3 mol 1-l. The molybdenum coated graphite tubes showed a 30-fold increase in sensitivity compared with a normal pyrolytic graphite coated electro- graphite tube.For the determination of Ge in ginseng Chinese workers (93150 1) used an ammonium molybdate impregnated pyrolytic graphite coated electrographite tube with a nickel nitrate chemical modifier. Kubota et al. (931707) found an increase in sensitivity for P with a zirconium treated graphite surface. X-ray diffraction FT- IR SIMS phosphine generation and XPS were used to investigate the nature of the P and zirconium interaction. An ammonium molybdate coated L'vov platform was claimed by D'Haese et al. (92/3865) to overcome matrix and spectral interferences in the determination of Cd and Pb in urine and blood with continuum source background correction ETAAS. A number of abstracts reported on further investigations into the use of probe atomizer systems though they present little new information that is not already in the literature.In a conference presentation Alvarado (931C 160) reviewed the use of a probe atomizer. The interference-free vapour- phase probe atomization determination of Cd and Pb in samples with high salt concentrations was discussed by Marchante Gay6n and Sanz-Mendel(931C74). They exarn- ined the use of a commercial system for the determination of Cd in urine (which has been published see 931208 1) and Pb in urine and sea-water. From the same group (9311029 platform wall and probe atomization were compared for the determination of A1 in clinical fluids. Platform atomiza- tion was the preferred method and while the probe system was convenient for reducing interference effects there were some practical disadvantages for serum analysis.Workers at the University of Strathclyde (9311016) evaluated the probe atomization system for the determination of Cd Co Cry Mn Ni and Pb in clinical RMs. Accurate analyses were achieved on diluted samples with calibration against aque- ous solutions. High atomization temperatures were used to minimize chemical interferences. Their conclusions were that the probe system could be useful for the determination of elevated concentrations caused by industrial exposure but that further work is required to assess the suitability for lower concentrations. Not surprisingly Chinese workers (9212223) found that probe atomization reduced the inter- ference effects compared with wall atomization for the determination of Ga in geological samples.From the same laboratory (92/2733) a laboratory-made autoprobe system has been described with slurry sampling for the determina- tion of Sb in geological samples. Chinese workers (9212962) also discussed the use of a new angle-type graphite platform and showed that it was suitable for use in total pyrolytic graphite electrographite and pyrolytic graphite coated electrographite tubes. Sadly no detailed information was given as to how this platform differs in design from those currently available. Similarly Barzev (93/C944) described a geometrically modified pyro- lytic graphite tube for use in an HGA-600. This it was claimed achieves better atomization efficiencies due to its lower thermal mass smaller internal diameter and different temperature gradient along the tube length.However no details of the tube design were given. 1.2.2. Sample introduction As in previous years the topic of sample introduction continues to generate a large volume of work. While solid and slurry sampling techniques have in the past been the preserve of a few workers the techniques are becoming more widely accepted and other groups are starting to publish in this area. A short review by Miller-Ihli (931 1944) of solid and slurry analysis by ETAAS contained 50 references and another by Hoenig (931460) contained 18. However it is clear that there are a number of areas where gross errors can be introduced in slurry sampling proce- dures and several groups (921C3649 931C111 931C1365 931C1395 931C1396) have drawn attention to the impor- tance of sample particle size ensuring that a homogeneous slurry mixture is prepared optimized slurry preparation taking into account the distribution of the analyte in the sample (93/C1395) the density of the material and the extraction of the analyte into the liquid phase of the slurry (931C1396).Several workers discussed the benefits of slurry sampling (92121 15 921C3546 931C115 931C277) and in most instances used automated ultrasonic agitation for prepara- tion of a homogeneous slurry mixture prior to injection into the atomizer. Refractory materials were examined by Bradshaw and Slavin (931C115 931C277) using both transverse and longitudinally heated graphite atomizer systems. Both Jackson et al. (921C4079 931C312) and Japanese workers (9212064) introduced a subtle variationJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY.AUGUST 1993. VOL. 8 21 1R on slurry sampling by preconcentrating trace elements from water samples with the use of a suitable chelating agent followed by a small amount (10-40 mg) of powdered activated carbon. After shaking the carbon was removed by filtration and then made into a slurry with a small volume of water and introduced directly into the atomizer. This procedure results in quantitative recoveries of metals and preconcentration factors of up to 400. Naganuma and Okutani (92/2064) determined T1 in sediments with this procedure. To 100 ml of the digested sample solution were added a complexing agent of potassium ethyldithiocarb- amate and activated carbon as the adsorbent. After filtration the activated carbon was dispersed in 5 ml of water by ultrasonic agitation and 10 pl aliquots taken into the atomizer.Both palladium and ascorbic acid were used as chemical modifiers and good agreement was found for RMs. There are several ways to prepare slurries for introduction into an atomizer such as the use of thixotropic agents ultrasonic mixing magnetic stirring and bubbling gases through the mixture to name but a few. These various sampling strategies have been a rich ground for the investigation of errors associated with the measurements. Hinds and Jackson (92/2637) discovered that results for the determination of Pb in samples of an iron-rich soil could be biased low due to adherence of particles to the magnetic stirrer bar. Vortex mixing enabled the slurries to be prepared and the results obtained for the soil samples agreed with the certified values.de Loos-Vollebregt and van Oosten (93/C1396) found that the degree of extraction from slurries prepared in 3% hydrofluoric acid by agitation with a stream of argon severely affected the results. Experimental data indicated that atomization was not complete from particles larger than 10 pm. The analyte atoms arise from smaller particles and the extracted part of the larger particles only. It was shown that accuracy and precision improved with a greater degree of extraction. For the environmental monitoring of Pb in dust soil paint and water Miller-Ihli (93/C 1 1 1) applied ultrasonic slurry ETAAS. Average accuracies were of the order of k 5-1 0% based on the analysis of SRMs.Fernandez et al. (92/2638) determined Cd Cu Ni and V in airborne particulates directly by slurry sample introduction ETAAS. The filter samples were destroyed by ultrasonic agitation in nitric acid and the final sample solution adjusted to a slurry concentration of 0.1-0.4 mg ml-l before injection into the atomizer. No differences were found in the results obtained between calibrations established in aqueous solu- tions or suspensions of NIST Urban Particulate Matter SRM 1648. For the determination of Ag Cu Fe Mn Pb and Zn in NIST food and agricultural SRMs Byrd and Butcher (92/C3649) found that the success of slurry sampling was dependent upon the analyte and particle size. With particle sizes of up to 500 pm Ag Fe Mn Pb and Zn could be determined accurately but a particle size of less than 200 pm was required for the accurate determination of Cu.This difference was attributed to the greater proportion of Cu in heavier particles which are more difficult to suspend in solution. These results are not surprising as most workers in this field recommend a particle size of at least less than 100 pm and typically of the order of 50 pm. Cordoba and Garcia (9212682) found a considerable particle size effect when determining Pb in slurry samples prepared from the ash residues of paprika samples remaining after dry ashing at 350 "C. They found satisfactory results in terms of accuracy and acceptable precision by a comparison of slurry sampling and dry ashing and acid dissolution methods only when the slurry particle size was less than 30 pm.A similar procedure was used by these same workers (92/4569) for the determination of Ti in plant materials. With a procedure involving ashing 10 g of sample and suspending 0.25-2.5 g of the ground and sieved residue in 25 ml of 0.03°/o m/v hexametaphosphate solution a detection limit of 0.03 pg 1 - I was achieved for 5% suspensions. Chinese workers (92/3939) prepared slurries of tea soil or liver samples by sonication in a water-magne- sium nitrate-glycerol mixture. The slurries were stable for 50 min. Barnett et al. (92/3052) determined B in plant materials with slurry sampling ETAAS. The memory effects associ- ated with this element in a graphite atomizer were over- come by employing a cleaning mixture of methanol-sul- furic acid (4+ 1 v/v) and sodium fluoride (1% m/v) in combination with a totally pyrolytic graphite tube. The use of slurry sampling ETAAS was applied by Docekal and Krivan (92/4568) to the direct determination of impurities in powdered silicon carbide without the need for any further sample pre-treatment.The methods were optimized with respect to sample preparation dispensing thermal pre-treatment and atomization parameters. For slurry suspensions of 0.5-2.5% m/v detection limits (3s) were found to be in the sub-microgram per gram level. The accuracies of the developed procedures were checked by comparison with ICP-AES and NAA. Hinds (93K114) discussed the problems of determining trace elements in metallurgical samples. In those instances where high dissolved solids or the possibility of forming explosive acetylide compounds from the matrix prevents the use of FAAS or the analyte is not soluble in the acids required to dissolve the matrix for example in the case of determining Au Pd and Pt in silver where these elements are only partially soluble in nitric acid then solid or slurry sampling can be employed. Direct sample introduction avoids tedious sample pre-treatment and in many cases the matrix element i.e.silver can act as a modifier for the volatile elements. DolinSek et al. (92/262 1) evaluated a laboratory-assem- bled graphite-cup atomizer for the direct analysis of geologi- cal and botanical reference materials for Cd and Pb. The samples were introduced either directly (0.02-5 mg) or with a slurry technique (5-200 mg). Integrated absorbance measurements and calibrations established with aqueous solutions were employed.A chemical modifier of diammon- ium hydrogenphosphate was necessary for the analysis of the botanical samples. These workers found that for direct solid sampling the samples must be finely ground ( 1 pm) whereas the slurry sampling technique was more tolerant to particle size effects. Atsuya (93/3089) discussed the use of simultaneous multi-element determinations with cup solid sampling for the direct analysis of biological samples. Hou (93/491) employed a probe atomizer and slurry sampling to determine Sn in geological samples. Calibration with aqueous solutions was possible. The direct solid introduction for the determination of Ag and Cd in fly ash samples (93/C374 93/C920) and Pb in copper (93/C920 93/C1416) was described by Wang and Holcombe.An integrated contact cuvette atomizer design was employed. By regulating the nitrogen purge gas pressure during atomization the analytical sensitivity could be controlled and a large dynamic range obtained. Solid samples of up to 3 mg could be used. Results showed good agreement with those obtained on samples digested using mixtures of nitric-hydrochloric acids or hydrofluoric acid and hydrogen peroxide. The atomization signals obtained were used to study the form and location of the trace elements in the fly ash. The results indicated that Ag and Cd are located on the surface of the fly ash and not incorpor- ated into the aluminium silicate matrix. For the copper sample (93/C920 93/C 14 16) when atomizing at atmos- pheric pressure a single Pb peak was observed and at a pressure of 0.1 Torr (13.33 Pa) three distinct Pb signals were observed.These were tentatively assigned to surface212R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 Pb Pb grains within the solid and Pb which is in solid solution with the copper. Atsuya et al. (92/2551) preconcentrated Pb and Se from water samples by coprecipitation using a combination of APDC and nickel as a carrier element. The precipitates were sampled directly into the atomizer using a miniature cup. Detection limits for 100 ml samples were claimed to be 30 and 70 ng 1-I for Pb and Se respectively with RSDs (n=10) of the order of 6.9 and 4.5% for 0.05 pg 1-' concentrations of Pb and Se.A similar procedure was employed by Hiraide et al. (93/548) for the determination of Cd in water by coprecipitation with In(OH),. The precipitate was collected on a membrane filter and the sample slurry prepared by ultrasonic agitation of the filter in nitric acid. A sulfonated dithiazone loaded onto an anion-exchange resin was employed by Japanese workers (93/561) to preconcentrate heavy metals from water samples. The solid resin was sampled directly into the electrothermal atomizer. Cup-in-tube ETAAS was applied to the determination of Cu in human liver biopsy specimens by Aadland et al. (92/2857). A chemical modifier of mixed palladium and magnesium nitrates was found to delay the volatilization of Cu from both aqueous standards and a powdered NIST Bovine Liver SRM to an appearance time comparable to the solid biopsy specimens; however calibration against the solid liver SRM was preferred to that against aqueous standards.A wide range of sensitivities were achieved by employing a variety of Cu absorption lines. The less sensitive line of 222.6 nm was optimal for the determina- tion of Cu concentrations in the range 20-200 mg kg-' in liver biopsy specimens. The use of slurry sampling for the determination of trace elements in difficult samples such as coal and fly ash continues to generate several reports a year (92/4653 93/C985 93/1028 93/C1366) and it is doubtful if any one would argue that this appears to be the recommended technique for such samples. Schlemmer and Erler (93/C1366) discussed the ease with which slurry sampling deals with samples such as coal coke ashes and sludges giving results in agreement with thoses obtained from decomposed samples analysed by conventional ETAAS.In contrast Tittarelli et al. (93/C985) considered the general application of slurry sampling for coal samples to suffer from various limitations such as uneven element atomiza- tion and spectral interferences due to the presence of molecular species in the vapour phase. These workers do however point out that some of these problems can be overcome by the use of a suitable chemical modifier. The paper presented by Tittarelli and Biffi on the vapour phase behaviour of slurries and discussed last year (see J. Anal. At. Spectrom.,1992 7 215R) has now been published (92/4653). Shan et al. (93/1028) determined Ga in coal and coal fly ash by slurry sampling and applying a nickel nitrate chemical modifier which overcame matrix interferences. The RSDs (n=19) were in the range 2-5.7% for Ga concentrations in coal and 1.05-59.7 pg g-l in fly ash.The use of CRMs for calibration in solid sampling ETAAS was discussed by Pauwels et al. (92/2548). They concluded that for routine purposes CRMs can be used for calibration purposes however they felt that the usefulness of solid sampling has not been fully exploited for CRM production control purposes and can provide more information on the micro-composition of candidate CRMs. Herber (92/2250) suggested classifying the various biological RMs based on the inorganic matrix content in order to aid in selecting the correct RM for solid sampling calibration purposes.An important issue in the whole field of solid/slurry sampling was discussed by Kurfurst (92/2549 93x1 395) namely the statistical treatment of the solid sampling data from heterogeneous samples. If pulverized samples contain rare particles of high analyte content 'nuggets' skewed distribu- tions of analytical results could be found. The 'nugget' effect has been documented and discussed for a bovine muscle sample (BCR CRM 184). For the solid sampling ETAAS technique skewed distributions must be accepted to obtain accurate results. However if only a few replicates are performed extreme values caused by several 'nuggets' in a sub-sample must be rejected and then the mean result is often too low. The conclusions are that compared with the errors of other methods the accuracy of the solid sampling technique is sufficient even for samples which show micro- heterogeneity.Belarra et al. (93/C138) determined Pb in solid PVC samples by the direct introduction of 2-5 mg samples into a pyrolytic graphite tube though further experimental details were not given. The use of laser ablation as a means of direct solid sampling by producing a plasma that is then introduced into an electrothermal atomizer was discussed by Dittrich et af. (93/C112) using either laser-ETAAS a single-element technique or laser-furnace atomization non-thermal excita- tion spectrometry (FANES) a multi-element technique. The sputtering of solid material onto a L'vov platform for the determination of dopants in single cadmium telluride crystals and discussed last year (see J.Anal. At. Spec- trum. 1992 7 2 15R) was presented again (93/C113) and has now been published (93/1640). The procedure of laser ablation with a Nd:YAG laser followed by deposition of the aerosol within a graphite atomizer also commented upon last year (92/4661) appears to have been modified (93/C139) and the aerosol is now irradiated with an additional a-source before flowing into the atomizer. Multi- element detection was by coherent forward scattering spec- trometry in combination with a xenon continuum source. The application of FI techniques to ETAAS shows no signs of abatement and is increasingly being used to enable even lower detection limits to be attained. Schlemmer and co-workers (92/C3664 93/C16 93/C1527) and Welz et al.(921C4075) have reviewed the advantages of this technique both for its ability to perform analyte preconcentration automatically on-line as demonstrated by Sperling et al. (92/26 14) for the determination of Co in sea-water but also for the trapping of hydride forming elements to enable baseline levels of Bi Sb and Se to be determined in drinking waters (931C1527). The advantages of coupling FI with ETAAS lies not only in lower limits of detection but also in the ability to perform speciation measurements as dis- cussed by Welz and Sperling (93/C237). The differential determination of CrlI1 and CrV1 (92/4 102) and As"' and total As (93/521) was described by Sperling et al. In both cases FI on-line sorbent extraction preconcentration coupled with ETAAS using sodium diethyldithiocarbamate as the complexing agent and C18 bonded silica reversed-phase sorbent as the column material was used.Chromium(v1) was determined directly using the FI system and total Cr after oxidation of CrlI1 to CrV1 by potassium peroxydisulfate hence Crlll could be calculated by difference. A 12-fold enhancement in sensitivity compared with the direct introduction of 40 p1 samples was achieved after preconcen- tration for 60 s giving detection limits (based on 3s) of 16 ng 1-' for Crvl and 18 ng 1-l for total Cr. The results obtained for sea- and river-water RMs were all within the certified range for total Cr with a precision of better than 10% RSD in the range 100-200 ng I-'. The selectivity of the determination for Crvl was demonstrated by the quantita- tive recovery of CrV1 in spiked RMs in the presence of CP1.For As the sorbent extraction is carried out with and without the on-line reduction of AsV to As111 using a mixture of sodium sulfite hydrochloric acid sodium thiosulfate and potassium iodide. Consequently the As111 and total As can be determined sequentially with detection limits (3s) ofJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 213R 0.32 ng for As"' and 0.43 ng for total As. A 7.6-fold enhancement in integrated absorbance compared with direct injection of 40 pl samples was obtained after a 60 s preconcentration. Results for synthetic mixtures of triva- lent and pentavalent As agreed well with expected values. Rather than the procedure of direct elution into the graphite tube used by the workers from Perkin-Elmer to couple FI with ETAAS LaRue and Tyson (93/C1469) described a recirculating loop injection system.This over- comes the timing problem whereby it is essential that the eluate arrives at the autosampler tip at the same time as the tip is positioned inside the graphite tube. Following preconcentration on either ion-exchange or CIS columns the analyte is released into a recirculating loop and sampled by the normal ETAAS autosampler after complete dispersion has occurred and the concentration of the analyte is the same throughout the loop. Azeredo and Sturgeon (93/C 107 93/C147 1) described a discontinuous micro-scale preparation system based on the chelation of trace metals with a 20 pl column of silica- immobilized 8-hydroxyquinoline interfaced to an ETAAS instrument.With 835 pl sample loop injections and elution of the trace metals directly into the atomizer in 48 p1 volumes of acid quantitative recovery of Cd Cu Fe Pb Mn Ni and Zn with detection limits (3s) of 0.3 15 4 9 20 13 and 11 ng l-l respectively could be achieved with a frequency of 10-20 samples per hour. Atallah et al. (92/2525) applied microcolumns (1 mm i.d. 5 cm long) to differentiate between neutral and cationic metal species. Silica gel columns quantitatively adsorb free Cull and Pb*I ions at pH>8 and these are eluted with 0.1 mol 1-1 nitric acid but not with methanol while neutral APDC chelates are partially adsorbed on silica columns but are quantitatively adsorbed on C18 bonded columns and are eluted with methanol.Using a mixed column or sequential columns of silica gel and C18 bonded silica cationic and neutral metal species could be adsorbed followed by sequential elution and measurement using methanol fol- lowed by 0.1 moll-' nitric acid. The on-line coprecipitation system described by Fang and Dong for the determination of heavy metals in whole blood digests and discussed last year (see J. Anal. At. Spectrom. 1992 7 2 15R) has been published (92/465 8). Based on the Fleitmann reaction Burguera and Burguera (93/C134) determined As11* and AsV species with the direct coupling of Fl hydride generation and in situ trapping of the hydrides in a graphite atomizer. They found that the sequestration of the arsine was more efficient at 200 "C when the graphite tubes had been treated with either cerium palladium or ruthenium.Based on 100 pl sample injections into the FI system the detection limit (3s) was found to be 0.1 pg 1-I with a precision of 3.5% ( n = 10) for a solution containing 15 pg 1-I of As111 and AsV. The procedure was applied to the direct determination of As in various river water samples. These same workers (93/C 135) coupled an in-line micro- wave digestion system with a FI unit to an ETAAS system for the determination of Pb in biological materials. It would appear that an acid-Triton X- 100-sample slurry mixture was prepared by means of ultrasonic mixing before injec- tion into the flow-through microwave digestion unit con- taining a Teflon coil. This was followed by a degassification device a modified time-based variable volume injector a peristaltic pump and a quartz capillary.The digested samples were collected in the capillary and pushed into the atomizer by means of air displacement through the injector. The atomizer autosampler was used to add the chemical modifier. Results in agreement with CRMs were claimed. Haug and Ju (92/2099) used hydride generation and in situ trapping in a graphite atomizer to determine low levels of Ge. The hydride was generated from an acetate buffered solution with sodium tetrahydroborate and introduced directly into the atomizer at 700-800 "C. A chemical modifier of palladium or palladium and magnesium was employed to reduce Ge losses during the thermal decompo- sition of the hydrides. An improvement in signal magnitude was seen when a pyrolytic graphite platform or foil was used.Kan et al. (92K3648) trapped the organic complex of Ge with phenylfluorone on a membrane filter of cellulose nitrate or PTFE. The cellulose filters and trapped complex were dissolved in N,N-dimethylformamide and the Ge determined in the resultant solution. Palladium was used as the chemical modifier and added as the bis(acety1ace- tonato)palladium(xx) complex dissolved in DMF which was found to enhance the Ge signal by a factor of approximately five. In situ hydride trapping was applied by Matusiewicz and Kurzawa (92/2228) for the determination of As and Se in sulfur samples after microwave digestion with nitric acid in a closed Teflon bomb. Based on a 10 ml sample solution detection limits (3s) of 15 and 20 pg ml-1 were found for As and Se respectively with precisions in the range 5-8%.The coupling of GC with ETAAS to determine alkylselen- ides and discussed last year (see J. Anal. At. Spec- trorn. 1992 7 2 15R) has been published (92/4659). Other Chinese workers (92124 1 1 ) developed a laboratory-made interface to link the GC with ETAAS instrumentation and determined dimethylselenium and diethylselenium species. The problems of coupling HPLC with ETAAS were dis- cussed by Laborda et al. (93/C137) for the determination of Se species and they concluded that the discontinuous approach whereby each fraction was collected and then analysed by ETAAS was the simplest. In this approach the volume injected into the atomizer should be as large as possible and the collected fraction volume as small as possible.Fraction volumes of 0.5 ml were collected and 60 pl ETAAS sample volumes taken and dried using a pre-heated tube at 120 "C with a sample injection rate of 3.3 pl s-I. Similarly using a discontinuous approach Xin et al. (92/C3561) separated and concentrated the chloride anion complexes of Au Pd and Pt at ppb levels with an HPLC-ETAAS system. A programmable sequence controller was used to sample the peak top eMuents and to control the sampling and analytical procedure of the ETAAS instrument. The procedure was used to determine Au Pd and Pt in rocks and minerals and the detection limits (2s) were found to be 0.38 0.53 and 0.34 ppb for these elements respectively. Electrodeposition onto various types of supports for preconcentration and/or matrix separation prior to intro- duction into an atomizer continues to generate a few reports but the difficulties of automating such a procedure and the time required for each electrodeposition appears to mitigate against this approach apart from in certain special applications.Zhang et al. (92/27 12) developed an approach whereby a tungsten wire electrode was placed in a 20 ml digested sample and Cd electrodeposited for 2 min. After this the electrode was placed in a graphite tube and Cd determined at 228.8 nm by ETAAS. It was claimed that this approach had been used for the determination of Cd in urine and sea-water with recoveries of between 95 and 102%. In a similar approach Xu et al. (92/2737) deter- mined Cu and Ni in pure barium nitrate by electrodeposi- tion of the Cu and Ni onto a tungsten electrode followed by introduction of the electrode into a graphite atomizer.The difficulties of calibrating an atomizer system for the determination of airborne particle bound Pb via an electo- static deposition system was considered by Magyar et al. (9212104). A standard Pb solution was atomized and the resulting aerosol freeze dried. The dried particles were electrostatically deposited on the graphite tube which acted as the grounded positive electrode. To enable calibration the transport yield was determined. This system was used to214R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 determine Pb in air (9212424). Air was passed at 1.3-5.5 1 min-’ through a graphite atomizer in which the graphite tube acted as a positive electrode and a vitreous carbon wire fixed in the tube acted as the negative electrode and airborne particles were collected at 400 V.The detection limit was 0.6 ng of Pb (95% confidence limit) and the collection time for the determination of 1 pg m-3 of Pb was 5 min. The device was also applied to the determination of Pb in water with a detection limit of 1.4 ng g-’ using a 2 min collection time. An extremely interesting paper regarding sample intro- duction was published by Howell and Koirtyohann (9311947). These workers compared the effect of direct injection of a microdroplet or injection of an aerosol spray into a graphite tube on the formation ofthe residue deposits corrosive effects on the graphite and analytical results for the determination of Se with nickel as a chemical modifier.Examination of the deposits by SEM revealed for aerosol introduction a ring of solids with a relatively large crystal structure but direct pipetting produced much smaller crystals in the valleys of the pryrolytic graphite coated surface. More severe corrosive effects on the graphite surface were seen with aerosol introduction though in- creased integrated absorbance signals were seen for Se with aerosol introduction. This was suggested as being due to the large crystal structure of nickel making it more effective as a modifier to stabilize Se during the pyrolysis step. 1.2.3. Fundamental processes The consideration of what is actually happening in a graphite electrothermal atomizer during atomization con- tinues to generate a considerable number of abstracts each year.Sadly not all of these eventually appear in the primary literature and this can make the review writers job somewhat difficult as one attempts to interpret conference abstracts which very rarely contain all the necessary information. As in previous years the reduction of oxides by carbides (ROC) mechanism has been a dominant topic though in contrast this year most papers are concerned with trying to disprove the theory. Consequently it would appear that most workers have spent the last year trying to produce A1 ‘spikes’ and then having to explain them! The evidence being collected seems to point to the fact that the assignment of the molecular band at 255 nm to A12C2 is erroneous and is more likely due to A120.However the results are still not unambiguous and possible theories for the atomization of A1 are still forthcoming. L‘vov et al. (92/2440) discussed the atomization of Tm from Tm203 in terms of the ROC theory but in recent work it would appear that even L‘vov is questioning this theory. L‘vov and Frech (93/C175) considered the interferences due to the condensation of matrix vapour in a graphite atomizer and one coated with boron nitride. For A1 as well as for other elements the same effects were observed in both tubes at different temperatures which they admitted effectively disproved the ROC theory. In work continuing into the investigation of spike formation with Al Frech et al. (931C 167) have examined the transport and redistribution of A1 compounds within the atomizer after or at the moment of spike formation by employing a platform probe technique and changing the conditions for diffusional mass transport.A spatially isothermal atomizer was used to avoid condensation and re-evaporation processes. From the same group Ohlsson (9214646) discussed the formation of A1 atoms in a graphite electrothermal atomizer by in situ spectroscopic measurements of A1 and aluminium hydride. With 500 ng of A1 in an aqueous solution the partial pressures of A1 and AIH were estimated to be of the same order of magnitude i.e. 10 Pa both species appearing at 2200 K. Aluminium oxide was not observed either in a spatially isothermal (integrated contact tube) or non- isothermal (Massmann-type) atomizer.On investigating the effects of several analytical variables on the A1 and AlH signals using a fractional factorial design it was found that for decreasing masses of Al the ratio of A1H to A1 decreased and the A1 signal became sensitive to a new set of variables. The conclusion was that an atomization model based on measurements performed using microgram amounts of A1 is probably not valid at the nanogram or picogram level. Working with Frech’s group Iwamoto et al. (9312078) performed direct spatially resolved spectroscopic measure- ments of C2 in spatially isothermal and non-isothermal atomizers and showed that the partial pressure of gaseous carbon is in thermodynamic heterogeneous equilibrium for temperatures above 2970 K. No evidence for an over equilibrium excess of C2 was found.Spatially resolved measurements of A1 also indicated the importance of O2 ingress and the sheath gas flow rate on the A1 atomic absorption signals indicating that the p 0 2 largely deter- mines the degree of A1 atom formation and not the presence of gaseous carbon-containing species. Katskov et al. investi- gated the atomization of A1 (9311085) and other elements (931C1409) to try and verify some of the assumptions and conclusions made for the reduction of oxides by the carbide theory. Theoretical calculations were made by applying the Langmuir model of vaporization from an open surface at normal pressure and calculations of the equilibrium compo- sition of vapours over A1203 taking into account the concentration of oxygen impurity in the purge gas.Experi- mental measurements were made using a dual channel scanning spectrometer an atomizer with independent temperature control of the atomizer and vaporizer; and a vaporizer in which the temperature could be controlled by feedback of the analytical signal. Atomizer tubes manufac- tured from tantalum tungsten molybdenum and graphite were employed. The results from Katskov et al. showed that the basic vapour components during the atomization of A1203 are Al A120 and A10. The relative amounts of these components are determined by the content of oxygen in the purge gas. A reduction in the PO via reactions in the graphite atomizer is accompanied by an increase in the fraction of A120 molecules. From these investigations it was concluded that it is possible to reject the assumption of a ‘super-equilibrium’ concentration of gaseous carbon and the presence of significant amounts of volatile carbides in the atmosphere of a graphite atomizer.There are the two assumptions which form the basis of the theory of the reduction of oxides by carbides. The molecular band with a maximum at 255 nm previously assigned by L’vov and co- workers to the presence of A12C2 was observed by Katskov et al. (931 1085) in a non-graphite atomizer consequently they assign this band to A120 which is in agreement with the conclusions of Holcombe Styris and co-workers and dis- cussed last year (see J. Anal. At. Spectrom.,1992 7 215R). Further mass spectrometric work has been performed on the atomization of A1 by Redfield et al. (931C22 1).During the atomization of A1 in a Massmann-type atomizer the molecule A12C was found to be a major species whether atomization occurred at atmospheric pressure or at high vacuum. A two-step atomizer was employed to enable the molecular species which precede the ‘free atoms’ formed during normal atomization at 2100 K but which occur concurrently in the Massman atomizer to be detected by MS. Two distinct A1 atomization signals were observed the first arising from the decomposition of A12C molecules vaporized from the cup at a temperature (1500 K a temperature below which the mass spectrometer detected A1,C but at which neither AA nor MS detected free A1 in the Massmann atomizer. These molecules decompose to ‘free’ A1 atoms in the hot tube atomizer and represent 10% of the total A1 signal.The second signal approximates the forma-JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 215R tion of free atoms arising during a normal atomization profile. Chinese workers (921C4 1 52) have also turned their attention to the atomization of A1 and in particular the formation of A1 Spikes’. Zeng et al. (921C4 152) found spikes during the slow heating of 0.2 pg amounts of A1 added as AlC13 which they assigned to A12C2 from measurements at 255 nm. They investigated the action of adding platinum as H2PtC16 and found that this eliminated the formation of spikes and from XRD measurements concluded that this was due to the formation of an alloy of A1,Pt. Both shadow spectral Jilming and ETV-ICP-MS were employed by Chakrabarti et al.(931C1408) to investigate the mechanisms associated with the atomization of Al. The results showed that A1 atoms have a greater concentration near the surface of the graphite tube while the A1 molecules are located in the central part of the tube. With a modified graphite atomizer coupled to an ICP-MS instrument the temporal distributions of A1 atoms and Al-containing species were studied. This configuration allowed the simul- taneous recording of the AA or molecular absorption and ICP-MS signals due to these species. The experimental results showed that A120 appears simultaneously with A1 during each spike. However the temporal distribution of A1 carbides was found not to correlate with the observed A1 spikes. The shadow spectral imaging work using a CCD camera described in this conference abstract has recently been published (Chakrabarti C.L.Gilmutdinov A. Kh. and Hutton J.C. Anal Chem. 1993 65 716). The measured distributions of A1 atoms and Al-containing species were consistent with a proposed atomization mechanism that consisted of three reactions ( i ) thermal dissociation of solid A1203 that yields both gaseous A1 atoms and gaseous A1 sub-oxides (ii) homogeneous oxida- tion of A1 atoms by gaseous oxygen molecules that yields gaseous A1 sub-oxides and (iii) heterogeneous reduction of gaseous A1 sub-oxides at the graphite surface that yields gaseous A1 atoms. Gilmutdinov (931C222) elegantly summed up the nature and difficulty in understanding electrothermal atomization processes with the following sentence ‘Electrothermal atomization in a graphite atomizer is a complicated variety of high-temperature physico-chemical processes ocurring simultaneously in the gaseous phase on the surface and in the atomizer body.’ A theory describing the non-stationary structure of atomic and molecular layers within a graphite atomizer has been developed by this group.Part of this has been published (92/2445) and considered the absorbance as a function of the number of analyte element atoms in the atomizer volume allowed for the spatial heterogeneity in the distribution of analyte atoms and in addition the spectral characteristics of the analytical lines. The effect of longitudinal and cross-sectional heterogeneities were also discussed. The first publications (9212402 9311014) and presenta- tions concerned with shadow spectraljlrning were discussed last year (see J.Anal. At. Spectrom.,1992 7 215R). This technique has been further developed (931C 1 7 1) by the use of a digital charge coupled device (CCD) which allows the two-dimensional dynamics of the distribution of atomic and molecular species within the graphite atomizer to be monitored over a much wider range of analyte concentra- tions. A mathematical model describing the three-dimen- sional dynamics of analyte vapour within tube atomizers was developed. The model takes into account ( i ) three- dimensional diffusion of the analyte inside a non-isother- ma1 tube atomizer; (ii) analyte loss through the tube ends and through the sample dosing hole; (iii) the initial coverage of the graphite surface by the sample before atomization; and ( i v ) heterogeneous interactions of the analyte with the atomizer walls. It was claimed that this model allowed the simulation of the dynamics and formation of atomic and molecular species in a graphite atomizer.A direct compari- son of the computer images produced by this model and the quantitative results obtained using the SSF-CCD technique allowed the physico-chemical processes in an atomizer to be visualised and investigated. Using this computer model Gilmutdinov et al. (931C170 9312077) modelled the three-dimensional distributions of oxygen and nitrogen inside both graphite and metal tube atomizers. The model allowed for the ingress of oxygen and nitrogen through the sample dosing hole and through the tube ends (from impurities in the purge gas); the kinetics of the heterogeneous reactions of the molecules with the atomizer walls; and the fact that the tube atomizer is non- isothermal.The results obtained for a pyrolytic graphite coated electrographite atomizer showed that the oxygen concentration is much higher and the distribution of the concentration much more uniform than was generally accepted. In contrast the calculated distributions of oxygen in metal tubes were found to be strongly non-uniform and when the ingress of oxygen through both the sample dosing hole and through the tube ends was accounted for the molecular cloud consisted of three independent regions. These regions were confined to the ends and centre of the tube. It would appear that Majidi and Ratliff (93/C219) have taken a similar approach to that employed by Gilmutdinov and co-workers but simultaneously have monitored both the molecular and atomic species generated in an atomizer.The transient molecular species were detected by back lighting the atomizer with a laser-induced plasma while atomic absorption was monitored by passing the emission from a hollow cathode lamp through the atomizer. Further work has been presented by Styris et al. (931C223) on the atomization mechanisms ofAl Ga and In and by Brown and Styris (931C172) on the atomization of Sn as the oxide and chloride. In the latter case results from the vaporization and atomization at atmospheric pressure and under vacuum conditions were compared to establish whether they were related to homogeneous gas-phase interactions or condensed gas-phase interactions. The monoxide was observed for both types of sample and gaseous carbides were not indicated in the spectra.Gaseous precursors to free Sn were not evident in either sample. The presence of free Sn during vacuum atomization of the oxide sample indicated that atomization of the oxide occurs from the condensed phase. However gas-phase Sn was not present indicating that the metal itself was probably not involved. Vacuum vaporization of fresh chloride samples yielded gaseous molecular species only; free Sn was observed to form in vacuo for these samples only if the samples were allowed to age in air and hence form the oxide. Since atmospheric pressure enhances the proba- bility of homogeneous or heterogeneous interactions involving molecular species that evolve from the condensed phase these interactions are likely to control the atomiza- tion process. The atomization mechanism of Sn was considered by two groups of Chinese workers (93/713 9311159) using a variety of surface analytical techniques.In one study (93/1159) it was suggested that from a graphite surface Sn atoms are formed mainly through the thermal dissociation of SnO whereas with a zirconium-coated graphite tube the zirconium carbide reduces SnO or SnO to Sn which is then atomized through vaporization. The atomization mechanisms of Pb and Sn from a pyrolytic graphite probe system were investigated by Gilchrist et al. (931809). For Pb and Sn vaporization and atomization were found to be separate processes and both elements were vaporized as molecular species.The rate constants and activation energies for the vaporization of216R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 the molecular species were determined and the latter were found to be 90 +- 6 kJ mol-1 and 130 k 10 kJ mol-I for Pb and Sn respectively. It was suggested that these represented the energy for the desorption of PbO and SnO from the graphite surface. The effects of gas phase chemical modi- fiers hydrogen and oxygen on the AA signals for Pb and Sn were considered. Deng and Liu (92x4 1 56 92/C4 167 93/ 1 164) have continued their studies on investigating the atomization mechanisms of elements from a probe atom- izer. Antimony as the chloride (92/4 167) Sr as the nitrate (92/C4156) and Cr (9311 164) were considered.Akman et al. (93/522) studied the atomization mecha- nisms of Cu Ir Mn and Pt taking into account certain parameters that affect the number of gaseous atoms in an atomizer. The contributions of thermal expansion and diffusion to the dissipation rate of atoms was investigated and they observed that the dissipation process cannot be described by diffusion alone. Thermal expansion contri- buted substantially to the removal of atoms from the atomizer and should not be ignored. From the E values obtained they concluded that the last step leading to gaseous atoms for Cu Ir and Pt was the thermal dissocia- tion of dimers and for Mn the dissociation of its monoxide in the gas phase. The analyte loss by molecular and atomic diffusion through bulk pyrolytic graphite coated electrogra- phite was investigated by Styris et al.(93X1431) who used MS to monitor in vacuo vaporized Ga species that had diffused through a 0.3 mm thick graphite barrier. An inverted capillary tube-like graphite cup was used as the barrier to ensure that the monitored species were involved in diffusion and not simply vaporized from the tube wall. By comparing the signal amplitudes obtained from an open (non-inverted) and inverted cup it was estimated that 3-5% of the analyte was lost through bulk diffusion. However the implications of these findings were not considered in the conference abstract. Wend1 et al. (92/2100) studied the chemical reactions of Ga in a graphite atomizer in the presence or absence of sodium chloride or palladium nitrate to obtain information on the reaction temperature pressure and oxygen and ion effects on the rate of reduction of Ga compounds.An interesting study was performed by Chaudhry et al. (9213823) using radiotracers to investigate the vaporization of Dy and Mn in a graphite atomizer using pyrolytic graphite coated electrographite tubes (PGC) and wall platform and probe atomization in total pyrolytic graphite tubes (TPG). Manganese was chosen as an example of a relatively volatile element whereby differences in the mode of atomization should not greatly affect the vaporization and Dy as being representative of a more difficult element hence the activity of the graphite surface and mode of atomization were more likely to have significant effects on the efficiency of desorption.For Mn almost complete vaporization (95- 100%) was found for all atomization modes and Mn was redeposited at the ends of PGC tubes the amount of redeposition increasing with tube age. For TPG tubes redeposition was reduced and found to be mainly on the outside of the tube. As to be expected Dy was almost totally retained in both PGC and TPG tubes. Vaporized Dy was redeposited very rapidly mainly at the centre of the tube and caused a memory effect on subsequent atomization cycles. An interesting result was that about 60% of Dy was vaporized from a probe at 2750 "C but only 7% from a platform. Wall atomization gave the best sensitivities for Dy but was only 1.5-fold better than probe atomization. The study of the mechanisms of vaporization provides useful information on the type of interactions of metals and graphite.Fonseca and Holcombe (93K220) investigated the atomization of Ag and Au. These elements are consi- dered to exhibit weak interactions which lead to the formation of microdroplets on the graphite surface. The atomization of Ag and Au was studied at atmospheric pressure and the influence of the drying temperature the heating rate and analyte concentration on the shape of the atomization profiles and activation energies for the ele- ments examined. The presence of adsorbed oxygen on the graphite surface as well as sanding the surface decreased the activation energies of release. Slow heating rates resulted in higher activation energies probably because the particles or atoms had more time to move around the surface and recombine thereby increasing the number of microdroplets.The activation energies were found to vary over a wide range of values. The maximum values ap- proached those of the heat of vaporization and the minimum values were thought to correspond to the interac- tion of the atoms on the surface. Surface alterations seemed to play a major role and affect the number of active sites on the graphite surface and consequently the ratio of adsorbed atoms to microdroplets. On further work using a tube-in- tube electrothermal atomizer (93/C14 12) this group investi- gated the desorption processes for Ag Au Cd and Cu using inner tubes of graphite tantalum and non-conductive materials such as alumina. The alignment of the peak maxima at increasing concentrations were observed to approximate the order of release.The advantage of this procedure was that the measurements were performed at atmospheric pressure which is a difficult task for most common surface analytical techniques. A temperature programmed static secondary ion mass spectrometer (93/C1415) was applied to study the metal-surface reac- tions using parameters and analyte concentrations typical of ETAAS. L'vov et al. (931536) considered the two different approaches currently proposed to account for the theory of the kinetics and mechanism of atomization in ETAAS. The first assumes that the dominant role is the adsorption- desorption process and the second that the condensation- evaporation is dominant. These workers believe that the first approach is not properly substantiated and that the second approach appears to be preferred for explaining the many experimental facts and the quantitative evalua- tion of the kinetics.The atomization of and interferences on Cd were investi- gated by Wang and Holcombe (93/C270) using a pressure regulated atomizer. Cadmium species were found to desorb via a first-order release process either of dispersed CdO or Cd bound to active sites of the graphite surface. With increasing sample amounts the atomization process ap- proaches a zero-order release. Cadmium chloride species formed on the graphite surface not in the gas phase and desorbed from the graphite surface before the evolution of free atomic Cd when either NaCl or CuC12 (in 0.5% hydrochloric acid) solutions were employed as the sample matrix.These molecular species then decomposed to elemental species in a furnace operated at atmospheric pressure. Sodium and copper species also affected the atomization behaviour of Cd by either blocking or creating the active sites on the graphite surface. Increasingly those workers investigating ETAAS funda- mentals are trying to assess these processes in the actual sample matrices and/or with chemical modifiers an ap- proach which is to be welcomed. Granadillo et al. (93/C116) assessed the behaviour of Pb in clinical samples with respect to different chemical modifiers (ammonium dihydrogenphosphate and palladium) and the use of an oxygen ashing step. Uniform signals and results were obtained when palladium was used and it was speculated that this was due to the formation of a graphite surface- Pd-PbO chemisorbed species.Nobrega et al. (93/C 16 1) investigated the atomization mechanisms for Cd and Pb using a tungsten coil atomizerJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 21 7R by varying the purge gas composition and suggested that for both elements the processes are metal oxide thermal decomposition. In the case of lead oxide hydrogen reduc- tion from the argon-hydrogen purge gas appeared to be significant. The kinetic model proposed by Slaveykova and Tsalev to evaluate the apparent activation energy of the analyte loss process [EacloSs,] and discussed last year (see J. Anal. At. Spectrom.,1992 7 215R) has now been published (92/4647) as has the model proposed by Rayson and Johnson (92/263 1).Rojas and Olivares (93/C272 931539) proposed a proce- dure for the determination of kinetic parameters for the atom formation process in electrothermal atomizers. From the kinetic equations of a mechanism where the rate of atom formation is assumed to have an arbitrary order m the rate constant for the non-isothermal generation of the atomic vapour k,(,) is given. An Arrhenius-type plot constructed with the experimental absorbance data as a function of the reciprocal of the time dependent atomiza- tion temperature gave a linear curve for the appropriate order and allowed the determination of the atomization energy E,. Results for Cu Li Ni and Ru were presented. In another study Rojas (93x1 69) investigated the effect of the heating rate of an electrothermal atomizer on the kinetic order the atomization energy and the calibration curves for Co Cu and Ni.Kinetic orders equal to 1 were determined for masses in the linear range of the calibration graph and greater than 1 for masses in the non-linear range of the calibration graph. It was considered that the non-linearity of calibration graphs could be due to changes in the atomization mechanisms as the concentrations increase. Chinese workers (921C3520) investigated the removal process of the atomic vapour in a graphite probe furnace. They found atom removal not to be a pure diffusion process and that the temperature gradient along the tube length caused adsorption-desorption processes after atomization of the sample and atom removal deviated from a pure gas diffusion process.As the atomization temperature increased the adsorption-desorption action decreased and the atom removal process approached a more ideal gas diffusion process. Experimental and theoretical results were com- pared for Ag Cu Mo and Pb. The theoretical magnitude of the diffusion coefficients and the rate constants for atom removal indicated the following order Mo>Cu>Ag> Pb however the experimental results showed Ag> Pb>Cu> Mo. For Ag and Pb the theoretical and experimental values agreed as in these cases there is little interaction with the graphite surface. However for Cu and Mo especially for Mo with the production of stable carbides this decreased the rate of atom removal and caused a deviation between the theoretical and experimental results.Further work on Monte Carlo modelling was reported from Holcombe’s group. Guell and Holcombe (931C27 1) carried out the numerical simulation of heat transfer combined with a Monte Carlo simulation of atomization to study the impact of atomization from a platform on the signals obtained. The effects of non-isothermality during platform and wall atomization were compared in the presence of interferences along with the effect of readsorp- tion on the platform and wall. Readsorption on the hotter wall was found to be negligible however this was found to be an effect of non-isothermal conditions since wall atomization was still significant for elements which show strong interactions with the graphite. The analytical advan- tages of the platform were observed but as was mentioned last year (see J.Anal. At. Spectrum. 1992,7 2 15R) and was reiterated in this report it would appear that the increased non-isothermal temperature distribution of an atomizer with a platform increases the complexity of the system for mechanistic studies. In a further study (92/2056) the deviations previously observed between Monte Carlo simulated and experimental Cu atomization signals were investigated by considering that the difference could be due to the simplifying assump- tions made that the absorbance signal is proportional to the gas density throughout the transient signal profile and no account is taken of the spectral line shape. As the gas phase temperature varies by several hundred degrees during the course of an atomization signal the relative absorbance may be altered by line broadening.Spectral line shape considerations (i.e. Voigt profile and hyperfine structure) were introduced into the Monte Carlo model. At low Cu concentrations there was no significant difference between this study and theory but it was found that spectral line shape considerations became increasingly important as the analyte density increased. An isothermal (9 mm long CRA- 90-type) and a non-isothermal (28 mm long HGA-type) tube both gave signal profiles that agreed with the previous theory i.e. no effect of non-isothermality was seen with the longer tube. This was attributed to most of the analyte being near the tube centre where there is less spatial temperature variation.Guell et al. (931C224) compared Monte Carlo simulations for defined elements with known (i.e. ‘fixed’) complex mechanisms for surface-gas kinetics with results obtained from experiments with elements exhibiting similar atomi- zation characteristics. By this means it was hoped to be able to study the interaction of any analyte with a surface by fixing an adequate model to the experimetal data. The use of the phase angle from the Fourier transformations of atomization signals was applied by Wegscheider et al. (92/3061) to characterize the peak form and position in electrothermal atomization. Lead was employed as an example and interferences as well as tube ageing were found to produce variations in the signal forms. Using complete neglect of dgferential overlap (CNDO) calculations Sierraalta et al.(93/1257) studied the atomiza- tion of Mo from a pyrolytic graphite surface modelled using a polycyclic aromatic system (coronene) for the surface. Three different types of adsorption were considered 6-fold bridge and on-top adsorptions taking into account both the edges and central sites. Diffusion of Mo was very difficult because of the high stability of the six-fold adsorption site with respect to the bridge and top sites. The co-adsorption of hydrogen ions however decreased the Mo adsorption energy and allowed Mo atoms to diffuse along the surface. This finding was considered to explain the experimentally observed effects of mineral acids on the ETAAS signals for Mo. The study on the atomization mechanisms of Si in a graphite atomizer discussed last year (see J.Anal. At. Spectrom. 1992 7 2 15R) has now been published (92/4644). From the results presented the initial reaction is the production of Si atoms from silicon dioxide. Depending on whether the partial pressure of oxygen in the atomizer is lower than a certain critical value then the Si atoms appear to react with the carbon surface to form gaseous silicon carbide which decomposes by reaction with silicon di- or monoxide to Si atoms and carbon monoxide. If the partial pressure of oxygen is greater than this value then the Si atoms react with the oxygen to form silicon monoxide which decomposes on the graphite surface to Si atoms and carbon monoxide. The eflect of oxygen in a graphite atomizer was discussed last year (see J.Anal. At. Spectrom.,1992 7 215R) and modification of the graphite surface by oxygen and its effect on the determination of oxide forming elements was considered again by Muller-Vogt et al. (93/C168) and Hahn et al. (9212101). Fazakas and Zugravescu in a series of papers (92/2552 92/4042 93/ 1229) considered the fundamental and applied218R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 aspects of pressurised atomization. Using As as an example (92/2552) the volatile and non-volatile forms of the element were shown to be influenced differently by pressure and that the pre-treatment temperature also influences the behaviour of the analytes in relation to the atomization pressure. These workers considered that furnace designs which avoid high pressures within the atomizer during atomization could produce an enhancement in sensitivity.On the other hand in another paper (92/4042) they discussed that a pressure higher than atmospheric in a graphite atomizer results in a longer residence time of atoms in the analytical zone therefore enhanced sensitivity is to be expected. However this is offset by the increased Lorentzian line broadening and wavelength shift but can be overcome by the use of a continuum light source. The use of low-pressure atomization was discussed by Wang and Holcombe (93/C173) and the expected drop in sensitivity due to the increased rate of atom removal at low pressures was used to increase the dynamic range. In addition the increased removal rate at low pressure could well serve to increase the isolation of the generation function and perhaps provide some additional information with respect to atomization mechanisms.For the determination of Pb in high-purity copper samples three distinct Pb atomic peaks were observed at reduced pressure and these were tenta- tively assigned to ( i ) surface Pb (ii) Pb in the bulk and (iii) a peak that may be indicative of the Pb grain size in the copper. Welz and co-workers (93/C156 93/C217 93K1414) have assessed the influence of operating conditions the dosing hole and the presence of a platform on the gas-phase temperatures in a graphite electrothermal atomizer using coherent anti-Stokes Raman scattering (CARS) thermo- metry. Using this technique subtle details of the tempera- ture evolution at various locations in the tube atomizer can be identified with high temporal and spatial resolution. The effect of the sample dosing hole was found to be very pronounced (93/C2 17).An increase in gas temperature at the tube ends due to enhanced gas expansion in these directions was measured when the sample dosing hole was blocked. A L'vov platform inserted into a graphite tube delayed the increase in gas-phase temperature (93/C 14 14) and reduced the heating rate but not the maximum temperature. The lower the starting temperature the more pronounced was the 'platform' effect i.e. the delay in heating. However the effect was restricted to the central part of the tube in which the platform was situated. It would appear that the conference reports concerning vapour-phase temperature measurements calculated by the two-line method and discussed last year have now been published and presented at other meetings (92/248 1 92/2482 92/C3590 93/C4150). Exactly how the temperature correc- tion factors obtained using two-line measurements in a dinitrogen oxide-acetylene flame are applied to the mea- surement of vapour-phase temperatures in a graphite atomizer is still not clear even after reading some of the papers.Using these vapour-phase temperature measure- ments the effect of a palladium chemical modifier upon the atomization of In Pb Se and Sn was investigated (93/545) and it was concluded that atomization occurs from specific phases of the analyte-palladium alloy. The temperature distribution in a platform atomizer was discussed by Chakrabarti et al. (9212495).Chinese workers (92/224 1) determined the heating rate of a graphite probe atomizer and found heating rates of 8700 and 4500 "C s-* after 0.25 and 0.5 s of heating. How these heating rates were achieved was not disclosed. The investigations into gas dynamics within a graphite atomizer discussed last year (see J. Anal. At. Spectrom. 1992,7,2 15R) have now been published (92/4645). The gas flow patterns under the influence of forced convective flow were studied using a cylindrical glass tube having dimen- sions identical with those of a graphite electrothermal atomizer. A light-scattering medium of argon seeded with titanium dioxide was introduced into the open ends of the tube and the scattering profiles observed. In addition samples of iodine were placed near the centre or ends of the tube to gain further insight into the spatial distributions of the iodine vapour under the influence of the convective flow.The titanium dioxide particle and iodine spatial profiles appeared to suggest that at room temperature the argon streams follow a laminar flow pattern in the bulk-flow region between the ends of the cylindrical tube and the sample introduction hole. However at the junction region where the two argon streams converge and discharge from the dosing hole local turbulences or eddies may be generated owing to abrupt changes in gas-flow velocity and direction in the vicinity of an area (boundary layer) directly beneath the dosing hole. An interesting insight (92/4663) into how discusssions can range far and wide over any subject including philoso- phy when scientists with an enthusiasm for electrothermal atomizers gather together appeared in the literature when the transcript of an evening discussion at the CSI Pre- Symposium on graphite atomizer techniques in analytical spectrometry held in Norway in 199 1 was published.1.2.4. Interferences In any Update there are many papers that do not fall easily into any one category. It is often difficult to decide where to discuss papers concerning the fundamental investigations into modifier processes. The author of this section of the review believes that it is easier to discuss the fundamental work concerned with atomization processes in section 1.2.3. Fundamental processes and work concerned with modifiers and interference mechanisms in this section. Chemical modiJication is a subject area which continues to dominate electrothermal atomization research both pure and applied.Some of the classification procedures for chemical modifiers explored by Tsalev et al. and discussed previously (see J. Anal. At. Spectrorn.,1990 5 179R) have now been published (92/2098,92/2505,92/46 10). In the last of these papers Tsalev et al. considered the use of a range of multivariate methods such as cluster correlation discrimi- nant and factor analysis based on a consideration of fundamental parameters e.g. electronic configuration of analyte elements and also experimental data such as the maximum thermal pre-treatment temperatures in the pres- ence of a series of chemical modifiers in organizing and classifying the experimental and theoretical information on chemical modification and analytes in ETAAS.They concluded that classifying chemical modifiers on the basis of fundamental parameters resulted in a general and rather abstract classification with limited practical application and prognostic power. This was most probably due to an over- estimation of the electronic configuration of the elements and an under-estimation of the role of modifier oxides species and their reaction with graphite. Classification of the analytes by employing fundamental or experimental data parameters produced chemically meaningful groups of analytes which agreed with previous expert classification based on the combined use of qualitative and quantitative parameters.A further bibliography of chemical modification (9212643) was published and complements the review published and discussed last year (see J. Anal. At. Spectrom. 1992 7 2 15R). Over 560 references are listed considering 1 58 different modifiers and a number of indexes are included under the following categories analyte element sample matrix modifier and other keywords. In terms of the number of references palladium is the most popular chemical modifier followed closely by nickel.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 219R L'vov and Frech (93K 175) discussed the interference effects arising from the condensation of matrix vapours. They observed a distribution of particles across a cross- section of the tube and considered that these results gave support to the condensation of matrix particles in the tube centre.With a platform the effects were reduced presum- ably owing to a hotter gas-phase temperature. Scattering of Au lines by condensed silver in the gas phase in an HGA- type atomizer was observed and also with 5 pg of palladium in a transverse heated graphite atomizer (THGA). They compared the effect of using a 'mini-flow' of gas (30 ml mine' of argon) during atomization to prevent diffusion of the matrix and to try and eliminate any condensation effects with respect to gas-stop conditions; a reduction in the scattering effects was found. Their interpretation of these results was that at the cooler ends of the tube gas- phase condensation is highly likely especially with large matrix masses and this causes scattering.In the presence of 20 pg of silver matrix and various analyte elements using gas-stop conditions the recoveries were less compared with those obtained with a mini-flow. From this study L'vov and Frech came to the conclusion that a mini-flow should be used with STPF conditions instead of gas stop although they pointed out that this did cause a decrease in sensitivity. This suggestion seems to go against the collected electro- thermal atomization experiences of the last ten years and it is to be hoped that others will repeat this study as the conclusions and/or interpretations of the data are impor- tant for our perceived understanding of what is happening within a graphite electrothermal atomizer. During this Update period a number of papers have been published considering the effects of chloride inter- ferences in electrothermal atomization.While it is well known that chloride is a major interferent and that in many cases this interference can be overcome by the use of chemical modification what is poorly understood is the actual mechanism of both the interference and chemical modification. Some of these published papers address these questions and described some novel investigative procedures. Workers at Strathclyde investigated sodium and magne- sium chloride intet$erences (92/4570) on the simultaneous determination of Cd Co Cr Cu Mo Ni Pb and V with continuum source AAS using wall platform and probe atomization. No pyrolysis step was used and in all cases the atomization temperature was 2700 "C.No great differences were seen in the analyte signal recovery values obtained with the three different atomization modes when sodium chloride was the interferent however with magnesium chloride greater interferences were observed with wall atomization. In general probe atomization was considered to be as good as if not better than platform atomization for the elements examined. Carrying on from this work Chaudhry et al. (93/ 10 18) applied ion chromatography radioactive tracers FAAS and ICP-MS to analyse the residues remaining on the platform and determine the effects of the pyrolysis temperature on the analytes (Cd Ga and Pb) and matrices of sodium magnesium and nickel chlorides. Magnesium chloride and nickel chloride exhi- bited partial hydrolysis and also underwent significant vaporization.The results from these investigations showed conclusively that in the presence of high masses (50-200 pg) of chloride salts pre-atomization loss of analyte elements occurs and can only be prevented by the correct selection of the pyrolysis temperature and use of chemical modi- fication. Finnish workers (93/1024) examined the use of probe and tube wall atomization for the determination of Sb in metal chloride matrices. Probe atomization was useful to overcome interferences from alkali and alkaline earth chlorides but severe background correction interferences were present in matrices containing iron and cobalt. With the use of magnesium as a chemical modifier and a reduced slit-width the over-compensation interference could be avoided.Japanese workers (92/4294) investigated the effect of chloride on Pb signals in an iron-containing matrix. The conference report discussed last year (see J. Anal. At. Spectrum 1992 7 2 15R) concerning the mechanisms of chloride interferences on the atomization of Mn has now been published (92/4648). Normally the efficiency of a chemical modifier is deter- mined by the reduction of the previously observed interfer- ence. However two groups have turned their attention to examining the effects and reactions of chemical modifiers in a more direct way. In a novel study Chaudry and Littlejohn (92/4580) applied ion chromatography to examine the effectiveness of ammonium nitrate as a chemical modijier for removing a sodium chloride matrix from in a graphite atomizer.The residues remaining on the pyrolytic graphite platform after different pyrolysis temperatures and times were analysed for ammonium chloride nitrate nitrite and sodium which allowed losses of the various ions to be monitored. In the absence of ammonium nitrate losses of sodium and chloride began at about 700 "C and were complete by 1 100 "C. The addition of 300 pg of ammonium nitrate to 100 pg of sodium chloride caused an 85-90% loss of chloride from the platform at 200 "C although complete removal of chloride was not achieved until a temperature of 1000 "C was attained. Removal of chloride was accompanied by almost total loss of ammonium and partial loss of nitrate at 200 "C. From 200 to 600 "C a more gradual loss of the remaining nitrate occurred and production of nitrite was observed in the range 300-700 "C.Sodium loss commenced at 800 "C and was complete by 1100 "C. These results confirmed what most workers in this field have felt to be happening from a consideration of the basic chemistry. The advantage of this approach is that the use of ion chromato- graphy allows chemical modifier and matrix masses to be used that are equivalent to those present in routine samples. There is sufficient information in the literature to indicate that milligram amounts of material do not react in exactly the same way as microgram amounts in a graphite atomizer. It is to be hoped that these workers continue with this approach and examine some of the other commonly used chemical modifiers. Japanese workers (93/547) applied ion chromatography to investigate the effects of the use of a chromium(n1) nitrate as chemical modifier in the presence of a magnesium chloride matrix on the atomization of Pb.These workers also found that chloride was lost at a very low pyrolysis temperature 620 K. Using a different approach Welz et al. (931C154) investigated the eflciency of different chemical modifiers by directly determining the amount of chloride that was volatilized in the atomization step at 2000 "C. The volatilized components from the matrix were introduced into a capacitively coupled helium plasma which was connected to a graphite electrothermal atomizer and the chlorine emission measured at the 837.6 nm line. They found that nitric acid and ammonium nitrate were very effective at removing chloride at low temperatures (for the latter chemical modifier a finding that agrees with the conclusions of Chaudrey and Littlejohn discussed above) but did not stabilize sufficiently volatile analytes such as Cd.Palladium as expected did not allow vaporization of chloride at temperatures below 1000 "C but it did stabilize many analyte elements at temperatures well above 1000 "C when the chloride could be removed even when present as sodium chloride. A mixture of palladium and ammonium nitrate appeared to be a good compromise as chemical modifier for some applications. Majidi et al. (93/C166 93X1430) applied Rutherford backscattering to examine the effects of phosphate chemical modifiers and their interactions with analyte elements on220R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 the heated graphite surface. Using this approach the surface chemistry can be examined and their results indicated that the analyte-chemical modifier interactions on the graphite surface are important. For Cd in the absence of phosphate the Cd remained mostly on the surface. When phosphate was added the Cd was found to penetrate into the graphite substrate. These are important results and raise interesting questions as to some of the more accepted ideas about the analyte-modifier-graphite interactions and their influence on atomization. The influ- ence of an oxygenated surface on the interactions of Ag Cd and Pb with graphite at two different temperatures was also evaluated (931C1430). It is to be hoped that these presentations are published soon and that this group continues with their investigations into an important area of electrothermal atomization chemistry.Palladium continues to be the chemical modifier of major interest though it appears that the point is now approach- ing which phosphate modifiers reached some years ago where some investigators are repeating older work and finding the same conclusions. However if palladium is the most popular chemical modifier then its effect on Se as the analyte element must also be the most investigated area of application. From this years abstracts and reports one could be forgiven for thinking that every laboratory with one or two exceptions appears to be busily investigating the reactions of palladium and Se however it makes a change from Pb and phosphate! Yang et al.(92/4567) investigated the mechanisms of stabilization of As Pb and Zn by a palladium modifier in the graphite electrothermal atomizer with a variety of surface analytical techniques such as SEM X-ray diffrac- tion spectrometry and X-ray photoelectron spectrometry. All three elements were found to form an intermetallic solid solution with an excess of palladium and the concentration ratio of palladium to analyte varied with the surface depth of the palladium analyte species. However it has to be pointed out that the masses taken were of the order 1 000-1 0 000 times greater than those normal in routine electrothermal atomization measurements. These workers believed that it is the intermetallic bond between palladium and the analyte which is the major force in retarding the analyte vaporization until a relatively high pyrolysis tem- perature is reached and that the analyte atoms are released when the temperature is high enough to break down the palladium lattice.In contrast Jackson and Qiao (93K110 931C218 931C1428 931523) proposed that the stabilization by palladium occurs via a physical diffusion process and considered that the term 'chemical modifier' assumes that the stabilizing effect is due to a chemical reaction. The effects of palladium on the absorbance characteristics of Cd Co Mn Pb Se and T1 and SEM measurements of the distribution of palladium on the graphite surface were interpreted as indicating that palladium has a physical mechanism of analyte modification.During atomizer heat- ing the analyte dissolves in molten palladium and may combine with it chemically however the rate-limiting step leading to atomization appears to be the diffusion of the analyte from palladium. The addition of magnesium molybdenum or powdered carbon increases the speed of diffusion by causing palladium to form smaller droplets which accounts for the sharper absorbance peaks. Palla- dium becomes less effective as the atomization temperature increases because the rate of diffusion is higher and this accounts for its smaller stabilizing effect on less volatile elements such as Co and Mn. Results from kinetic studies on the atomization of Au were consistent with analyte diffusion out of palladium as the rate-limiting step and the addition of ascorbic acid was found to have no significant effect on the stabilizing properties of palladium in a dilute nitric acid matrix.These workers (931C1 10 931C218) also examined the use of cobalt copper magnesium nickel and palladium as modifiers for Se. Pyrolysis curves and kinetic measurements were performed in an attempt to deduce whether chemical or physical processes predominated. This physical mechanism of stabilization by palladium was also proposed to explain the effect of palladium in reducing the severe interference of chloride on T1 (93K1428). The use of a mercury-palladium chloride mixture as a chemical modifier was investigated further by Garcia-Olalla et al. (9212484). From the mixture of metals studied silver cadmium copper magnesium mercury nickel and palla- dium as both chloride sulfate and nitrate salts the best enhancement of the Se signal was obtained with the mercury-palladium chloride mixture.In a subsequent paper (931759 the effects of the counter ion and mass of mercury were examined. Negative shifts in the appearance temperature were noted for low levels of mercury while higher levels caused only a slight increase in the appearance temperature. The integrated absorbance for Se increased with mercury mass but a plateau was reached above a certain mercury chloride concentration. However interpre- tation of these findings is difficult as it would appear that wall atomization was used for these investigations. Not surprisingly Creed et al. (9213178) found that the use of a palladium-magnesium nitrate chemical modifier and 5% hydrogen in the purge gas reduced the signal suppression from chloride interferences for Cd Pb and T1 in a mixed acid digestion to less than 5'10 and palladium alone with 5% hydrogen to less than 5% for Sn.These workers found that if the 5% hydrogen was not adequately purged from the atomizer prior to atomization the Se response was reduced by 18%. Docekalova et al. (9212622) examined the effects of various chemical modifiers including the nitrates of alumi- nium calcium europium lanthanum magnesium nickel and palladium on various Se compounds such as selenite selenate selenomethionine and trimethylselenium iodide. They found that the shape of the atomization signal appeared to be strongly influenced by vaporization effects connected with the physical character of the charred residue.Successful chemical modification involved the application of at least a 1000-fold excess of the metal nitrate to produce refractory oxides no thermally stable carbides and at the same time quantitative conversion of the analyte into a single form. These workers also consi- dered that an integral part of the modifier action is the trapping of the resulting compound by the modifier residue. The effect of using nickel and palladium nitrates on different chemical species of Se was examined by Laborda et al. (931C75). With nickel nitrate similar responses were found for both selenite and trimethylselenium but with palladium nitrate a negative interference (approximately 50%) was observed for trimethylselenium with respect to selenite.This interference was also observed in the presence of reducing agents or thermally pre-reducing the modifier in the atomizer prior to introduction of the analyte. Nixon et al. (9212914) compared the use of nickel and palladium chemical modifiers with and without the addition of potassium persulfate for the determination of total As in urine. Complete recovery of As1'' AsV dimethylarsinic acid monomethylarsinic acid and o-arsenilic acid was found with both nickel and palladium chemical modifiers. Com- bined arsenobetaine and arsenocholine extracted from a Dogfish Muscle RM (DORM- 1) were only completely recovered with a palladium-persulfate chemical modifier. Using a matrix-matched calibration prepared in urine and the combined palladium-persulfate chemical modifier good agreement was found with external quality assurance samples which contained As from a variety of sources. Bermejo-Barrera et al.(931C 1599) applied a palladium andJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 221R magnesium nitrate modifier to the determination of A1 in water. Welz and co-workers (92/4565 93/4 12) have continued their series of publications on the use of a mixed palladium nitrate-magnesium nitrate chemical modifier. This chemi- cal modifier was applied to the determination of Hg (931412) in environmental SRMs and Se (92/4565) in sulfate-rich mineral waters. Mercury is not the easiest of elements to determine by ETAAS and in the procedure developed here a low atomization temperature 1000 "C and a clean-out step with a temperature no higher than 1500 "C were employed to prevent loss of the palladium.With these conditions a single application of 15 pg of palladium was sufficient for 40-60 determinations. Good agreement was found for the determination of Hg in Aquatic Plant Albacore Tuna River Sediment and Coal Fly Ash RMs and interferences caused by high sodium chloride concentrations could be eliminated using a mix- ture of 95% argon and 5% hydrogen as the purge gas. Welz and co-workers (92/2 102 92/4565) also investi- gated the application of the mixed palladium nitrate-mag- nesium nitrate chemical modifier with the addition of barium nitrate on the interference of sulfate on the determination of Se. From molecular spectra measure- ments CS was observed when sodium sulfate was volatil- ized and the interference caused by this salt was considered to be due to the expulsion of Se with the violently volatilized matrix early in the atomization stage.Sulfuric acid and magnesium sulfate decomposed at elevated tem- peratures with the formation of SO3 which was partially reduced to SO2 in the graphite tube. The most probable interference mechanism considered in this instance was the formation of SeO in the presence of excess SO3 and its volatilization during the pyrolysis stage. Addition of bar- ium nitrate to the palladium nitrate-magnesium nitrate modifier reduced the background absorption and also the sulfate interferences. This additional reagent was consi- dered to act by binding some of the sulfate as barium sulfate which decomposes during the atomization stage.Conse- quently SeO if formed is not lost through expulsion of the matrix but volatilized at temperatures which are high enough for its atomization. This mixed chemical modifier was applied to the determination of low levels of Se (about 3 pg 1-*) in mineral waters and overcame interferences from high sulfate concentrations as was shown by recovery measurements which improved from approximately 84% to 94- 100%. While not within the abstracting period for this Update yet of relevance to any discussion regarding the use of chemical modz$ers the final paper in the series by Welz et al. (see J. Anal. At. Spectrom. 1992 7 1257) has been published. The performance of the mixed palladium nitrate-magnesium nitrate chemical modifier was consi- dered for 21 elements and a brief overview was given for each element.For most elements the use of such a modifier enabled higher pyrolysis temperatures to be applied than found with the previously recommended chemical modifi- ers. A 10 pg amount of sodium chloride had no influence on the determination of the elements investigated and most of the analyte elements were not affected by a 10-fold greater mass. However the amounts of sodium chloride and potassium sulfate which could be tolerated increased when the pyrolysis temperature was lowered by 200-300 "C and the pyrolysis times increased. The characteristic masses obtained for these elements were compared with those found previously in the literature and in most instances the values were comparable to those published.For some volatile elements such as Bi Pb and Te the characteristic masses were significantly higher. This was attributed to the increased stabilizing power of the palladium-magnesium nitrate mixture requiring higher optimized atomization temperatures but also with an increase in the diffusional losses. These workers concluded that the palladium-magne- sium nitrate mixture can be rightly considered as the most universally applicable chemical modifier in that it can be used for a large number of elements and in a wide variety of matrices. However it does have some limitations the most serious of which is the requirement for higher atomization temperatures which produces a slightly greater character- istic mass. Interestingly some South American workers (93/C 133 931562) feel that there has been a plague of chemical modifiers ('isoformers') inundating the literature acting as some form of environmental pollution! They examined the use of nitric acid magnesium nitrate citric acid and palladium as chemical modifiers for the determination of V in biological and clinical materials (93/562).A pyrolytic graphite platform was employed and a mixture of palla- dium and citric acid was found to be optimum with an oxygen ashing step at 800 "C and two additional pyrolysis steps at 1 100 and 1700 "C followed by atomization at 2700 "C. This modifier mixture did not show spectral or non- spectral interferences as did the others. This was thought to be due to the reductive effect of citric acid on the palladium at 1100 "C and its contribution to creating a reducing atmosphere within the graphite tube which was thought to decrease the atomization temperature of the V.It was claimed that no memory effects were detected. In contrast to palladium and graphite decreasing the refractory nature of V Dabeka (93/1941) believes that this combination results in the formation of refractory species of Pb when maximum power heating (0 s ramp) and atomization temperatures above 2300-2400 "C are used. This refractory behaviour was found to be so great that the absorbance peak for the second Pb refractory signal occurred after those due to Cr and Mo under the same conditions. Hydrogen was found to enhance this peak and the refractory signal was enhanced if an uncoated or impregnated graphite platform was used compared with the signal from pyrolytic graphite.The hypothesis was proposed that a refractory species of Pb is produced by the high temperature interaction of Pb carbon and palladium. However even though this worker believes that this may cause analytical errors when palla- dium is used as a chemical modifier for Pb at elevated atomization temperatures the data presented in the paper show the absence of this effect at atomization temperatures less than 2400 "C a range which countless other workers have found to be optimum for Pb. Yang and Smeyers-Verbeke (93/414) investigated the effectiveness of palladium combined either with ammon- ium nitrate or with magnesium nitrate for the determina- tion of TI in blood and urine. They found that the palladium modifier was less effective for TI than for Cd or Pb.The best results were obtained with a mixture of palladium and ammonium nitrate 6 and 100 pg respec- tively. This combination allowed the direct determination of T1 in blood diluted 10-fold against a calibration curve produced in aqueous solutions. However the detection limit (3s) was rather high 25 pg 1-'. For urine analysis the use of the standard additions technique was recommended because complete recovery of TI from all urines was not possible. Several groups have studied the spectral interferences on Se with either Smith-Hieftje (931 1027) or Zeeman-effect (92/465 1 ) background correction systems. The work of Aller and Garcia-Olalla (93/ 1027) appears to be publication of part of the work discussed earlier in this section.The spectral interferences caused by aluminium calcium and magnesium chlorides and nitrates on Se were compared as were the influence of palladium mercury cadmium cadmium-palladium and mercury-palladium chemical modifiers. These workers found similar spectral interfer-222R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 ences for both wall and platform atomization but by a proper combination of chemical modification and pyrolysis temperature some of the spectral interferences could be overcome. The work by Radziuk and Thomassen concern- ing apparent spectral interferences found under certain conditions when determining Se in whole blood and urine using Zeeman-effect background correction and either nickel or palladium as the chemical modifier and discussed last year (see J.Anal. At. Spectrom. 1992,7,2 15R) has now been published (92/4651). The masses of palladium or nickel employed were found to be critical to the reduction or elemination of these interferences. Doidge (93/520) described Zeeman-effect background corrected baseline shifts for several hollow cathode lamp lines of up to an absorbance of 0.1 with firings of an empty graphite atomizer and clear differences in the sizes of the shifts depending upon whether the atomizer was purged with N or Ar. The baseline shifts were seen for hollow cathode lines close to listed rotation lines of the (0,O) and higher bands of the CN violet system. These shifts were accounted for by the possibility of overlap by the hollow cathode lines with Zeeman-shifted CN lines and support for this suggestion was the known behaviour of CN lines in magnetic fields. Evidence was presented for the existence of interfering lines near the main resonance line of Cr (357.9 nm) as a spectral interference occurs in both Zeeman-effect with lamps containing iron and continuum source background correc- tion systems.The work of Frech et al. on the effects of chemical modifier mass and temperature gradients in Massmann-type atomizers on integrated absorbance sensi- tivity under STPF conditions for palladium copper nickel and palladium plus magnesium nitrate and discussed last year (see J. Anal. At. Spectrom. 1992,7,2 15R) has also now been published (9214609). Chinese workers (92/C3521) examined the use of basic lithium chloroplatinic acid as a chemical modiJier for As Sb Se and Te and a nickel amino compound (no further details are available) for Ge.They claimed that these gave a better performance than the more commonly used chemical modifiers. The use of s-electrondonor reagents as chemical modifiers for Hg was investigated by Brazilian workers (93/C 132). Thioacetals derived from cetones with thiogly- collic acid and prepared from propanone cyclohexanone and pentanone were found to have the highest chemical modification effect though no quantitative data are pre- sented in the conference abstract. Organophosphous vapours were employed by Ebdon et al. (9214566) as chemical modifiers for the determination of Cd. The vapour pro- duced from triethyl phosphite was found to be optimum and had the same stabilizing effect as a more traditional solution based phosphate chemical modifier.The advantage of using a vapour produced by passing argon gas through a Dreschel bottle in the alternative gas line of the atomizer is the reduced risk of contamination. A Japanese group (92/C3529) examined the effects of organo-palladium com- pounds as chemical modifiers for the determination of alkyltin compounds in organic solvents. Dissolving PdC12(CH3CN)2 in ethylacetate-hexane solution and add- ing to the sample solution (1 + I ) appeared to give the best performance as assessed by the 'enhancement ratio' on tetrabutyltin chloride dissolved in ethylacetate-hexane (3+2 v/v) solution. The procedure was applied to the determination of tetrabutyltin chloride in artificial sea- water samples and ship paints (93/582). These same workers (92/C3524 93/554) investigated the sensitivity enhancement of adding albumin to palladium as a chemical modifier for the determination of As Ga In Sb Se Sn and Te but found that the addition of albumin did not show any appreciable enhancement effect.The behaviour of dithiocarbamate complexes of As Bi Cd Pb Se Sb Sn and Te in IBMK was investigated by Tserovsky et al. (93/1079) comparing atomization from the wall of pyrolytic graphite coated electrographite tubes tungsten tubes and from a pyrolytic graphite platform. Utilizing palladium or platinum as ion associate complexes soluble in IBMK as chemical modifiers higher pyrolysis temperatures could be used for As Se Sn and Te.Japanese workers (921C3567 931583) examined the use of rhodium nitrate as a chemical modifier for Ga In Te and T1. Tsalev and Slaveikova (93/430) compared the efficiency of ruthenium rhodium and palladium as chemical modifiers for 18 elements. The addition of ascorbic acid allowed higher pyrolysis temperatures by + 50 to + 250 "C for As Ge P Pb Se Sn and T1. Vanadyl chloride was found to be effective as a chemical modifier for the determination of Au in ores (92/2766). For the determination of Mo in serum (92/2015 93/C1636) and water (93/C1635) magnesium nitrate barium difluoride nitric acid palladium-mag- nesium nitrate and palladium-hydroxylamine mixtures were examined. However no recommendations as to the optimum chemical modifier were provided. Matsusaki (92/25 16) applied a mixture of nickel and copper nitrates and (NHJ2H2EDTA as a chemical modifier for the determi- nation of Bi in aluminium.The same worker (92/2065) applied a mixture of nickel nitrate and (NH4)4EDTA as a chemical modifier for TI. According to this paper the EDTA suppressed chloride interferences and the nickel nitrate overcame the sensitivity loss caused by the presence of EDTA. Two other groups have investigated the determina- tion of Bi in clinical samples and even though using similar instrumentation Zeeman-effect background corrected sys- tems seem to have arrived at very different conclusions. Slikkerveer et al. (92/3 169) found it neccessary to overcome spectral and vapourphase interferences from sodium on Bi by means of a solvent extraction procedure (APDC-IBMK).The IBMK solution was evaporated to dryness under nitrogen and the residue dissolved in the platinum chemical modifier solution. Detection limits of 0.7 and 1.0 pg 1-I in serum and blood respectively were found with between- batch OhRSDs of 44.5% at a concentration of 40pg I-'. On the other hand Dean et al. (93/848) claim that simple protein precipitation and the use of a palladium chloride- ammonium nitrate chemical modifier was all that was required to achieve a robust and reproducible procedure for the determination of Bi in serum and urine with calibration against aqueous solutions and using peak height measure- ments. A detection limit of 0.2 pg 1-' was claimed in this paper which appears rather good when compared with that obtained by Slikkerveer et al.(92/3 169) with a method which includes a 2-fold preconcentration step. Another conflict of opinion regarding the presence or otherwise of interferences can be seen in the two papers from D'Haese et al. (92/3865) and Marchante Gayon et al. (93/2081) concerning the determination of Cd and Pb in urine and blood and Cd in urine respectively. D'Haese et al. (92/3865) claimed that the severe matrix and spectral interference effects found with continuum source ETAAS could be overcome by coating the L'vov platform with ammonium molybdate and using an ammonium dihydro- genphosphate chemical modifier. In this study electrogra- phite tubes with coated platforms were used and it would appear that the peak-height measurements were obtained from a chart recorder though it is surprising that a paper published in 1992 using peak height was accepted.How- ever matrix-matched standards were neccessary indicating that interference effects were still present though results obtained with a Zeeman-effect background correction instrument (where no coating of the platform was required) compared well. For this procedure a detection limit (3s) of 0.4 pg 1-I was found. Marchante Gayon et al. (93/2081) simply diluted the samples 1 + 3 with water and using probe atomization with continuum source background correctionJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 223R found no need for chemical modification and were able to calibrate with aqueous solutions. Both atomization from the probe and platform with a pyrolysis temperature of 600 "C allowed the temporal separation of the atomic and background signals but a better signal-to-background ratio was found with probe atomization.Even though the atomic signal was reduced 1.5-fold compared with that obtained from the platform the background was reduced 3-fold with the probe and this was considered important with respect to the continuum source background correction system. These workers found a detection limit (3s) of 0.3 pg 1-1 and recoveries of 100 -t 5%. Chemical modifiers of calcium and magnesium for B and calcium for Si were employed by Littlejohn et al. (93/C7) for the determination of B and Si in clinical samples. Chinese workers (931720) examined the use of calcium strontium calcium-magnesium calcium-lanthanum and strontium-magnesium mixtures as chemical modifiers for B.The binary mixtures were found to be more efficient than the single element chemical modifiers. This same group (92/2967,92/C3522) examined the use of calcium nitrate as a chemical modifier for the determination of Al B Be Cd Dy Ge P Se Sm and Sn. The chemical modifier was found to enhance the sensitivity for Al B Be Dy Ge and Sn and increase the maximum pyrolysis temperature and decrease the atomization temperature for all the elements examined. It was postulated that the mechanism of the enhancement effect was due to the gas-phase reduction of analyte oxides by calcium. Elci and Dogan (92/2523) investigated the interference of various concentrations of aluminium nitrate on Cd Ni and Pb. The interferences were found to be different.Chinese workers (92/4392) found that perchloric acid suppressed the absorption signal of Cr and V. This suppression could be overcome by pyrolysis at 1500 or 1900 "C for Cr and V respectively or by the addition of The conference report discussed last year (see J. Anal. At. Spectrom. 1992 7 2 15R) concerning the use of oxalic acid as a modijier for the determination of Cd in sea-water has now been published (92/4649). Chinese workers (9317 15) used organic acid chemical modijiers such as citric tartaric and ascorbic acids for the determination of As Cd Co Cr Cu Mn Ni Pb Se and V in sea-water. Volynsky et al. (92/2488) applied ascorbic acid as a chemical modifier to the determination of Sn in 0.05-0.30 mol 1 - I boric acid solutions.While the use of a palladium chloride modifier reduced the interferences in 0.2 mol 1-1 boric acid by a factor of 1.3 the interferences were reduced more effec- tively when ascorbic acid was used. These workers pro- posed that the observed reduction in interferences is due to the bonding of boron with the amorphous carbon produced as a result of the thermal destruction of ascorbic acid to form B4C which is thermally stable at the atomization temperature for Sn (2200 "C). Imai and Hayashi (93/1117) found that changes in the concentration of ascorbic acid shifted the AA signals for Au and also calculated the activation energies for the desoption of Au with and without the addition of ascorbic acid and a pre-pyrolysis treatment of the ascorbic acid. Norberg and Sjoestroem (92/2 127) were able to reduce the chemical vapour interferences due to the matrix in a graphite atomizer by laser-induced photodissociation of the analyte-containing molecules.The laser-induced fluore- sence signal from In was reduced 40-fold when 3% NaCl was present. This signal suppression was due to InCl and by photodissociation of InC1 the interference was reduced by 50%. Finally another group of workers (93/1136) have discovered the benefits of oxygen ashing in the pyrolysis step for the determination of Cd and Pb in biological samples. Not surprisingly they found that this procedure reduced the background absorption on atomization. (NH4)ZHzEDTA. 1.2.5. Developments in technique While not seeming to be of direct relevance to electro- thermal atomization the paper by Kantor (92/4622) on the considerations for the gas flow design of a graphite electrothermal vaporization interface is worth studying.Working with a conventional end-heated graphite electro- thermal atomizer (HGA-400) coupled to an air-acetylene flame the efficiency of transport for the vaporized sample either through the normal graphite tube sample hole described as 'upward streaming' or passed through the ends of the graphite tube described as 'end-on streaming' was compared. Using Cd as the test element and in the presence of various sample matrices and with and without carbon tetrachloride vapour it was found that 'end-on streaming' produced a significantly higher transport efficiency than 'upward streaming' though the difference in performance of the two different interfaces decreased in the presence of sample matrix and carbon tetrachloride vapour.Of major importance to the efficiency of an ETV sample introduction system is the supply of carrier aerosol particles. These particles can be produced from the main constituents (i.e. sample matrix) that covolatilize with the analyte and also from the introduction of halocarbon vapours into the vaporizer. Falk (92126 17) discussed the analytical capabilities and the limitations of glow discharge tandem sources using electrothermal atomizers. In theory tandem sources should allow a relatively complete separation of the processes of volatilization and atomization from the excitiation step such that during atomization the excitation conditions can be kept constant.While this can be achieved by spatial separation of the atomizer and plasma it is not very efficient owing to transport losses. However those tandem systems which overcome this problem whereby atomiza- tion and excitation take place in the same volume such as furnace atomization non-thermal excitation spectrometry (FANES) and furnace atomization plasma excitation spec- trometry (FAPES) suffer from an interaction between these two processes. In considering the matrix effects on emission sources based on tandem systems Falk concluded that while tandem sources are very efficient the analyte and matrix concentrations in the excitation souces are relatively high. In addition it is not possible to separate the volatilization and atomization processes completely when these are taking place in the same volume.As glow discharges are more prone to matrix interferences than excitation sources when used at atmospheric pressure this requires that the electrothermal atomizer time-temperature programmes employed must ensure that the levels of matrix are kept at an acceptable level. This need for elaborate procedures with tandem sources may well limit their multi- element capability for samples containing high matrix concentrations. In contrast to the previous Update (see J. Anal. At. Spectrum. 1992 7 2 1 SR) during the period covered by this one hardly any material has been received on the use of furnace atomization plasma excitation spectrometry (FAPES). In several conference presentations Blades and co-workers (93/C2 93x1 404) discussed FAPES and drew attention to the fact that as analyte vaporization excitation and emission are taking place in the same volume it is important to understand the role of condensed and gas- phase species on the analytical signal.Liang et al. (93/C182) described the commercially available system. However an interesting development is that proposed by Majidi et al. (93/C33 1 93/CI 563) whereby a laser-induced plasma is formed in the middle of a graphite electrothermal atomizer. As the analytes are vaporized and introduced into the plasma the emission from the plasma is collected perpendi- cular to the direction of the original laser beam through the224R JOURNAL OF ANAL,YTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 atomizer dosing hole. It would appear that this system can be used for simultaneous multi-element analysis and the lowest masses determined were 50 and 5 pg of Cd and Co respectively with RSDs of 5%.As laser-induced plasmas provide the highest temperatures reported for laboratory plasmas this should minimize or eliminate matrix interfer- ences and has the added advantage of operating at atmo- spheric pressure. There continues to be a steady trickle of papers on simultaneous multi-element ETAAS determinations either performed on those commercially available instruments which allow this or on research instruments using contin- uum sources. Japanese workers (93/ 1 134) have applied the Hitachi system to the determination of Cd and Pb in whole blood and urine using ammonium dihydrogenphosphate as chemical modifier and found detection limits of 0.026 and 0.36 pg I-' for Cd and Pb respectively.Another group (93/563) used the same system for the determination of Cd Cr Ni and Pb in urine after a l + l dilution with palladium chloride as chemical modifier but using the method of analyte additions for quantification. Delude et al. (93/C 1434) applied the system from Thermo Jarrell Ash to determine Cd and Pb simultaneously in vegetable oils after dilution in tetrahydrofuran and to the determination of Cu Pb Sb and T1 in drinking water. One of the major problems concerning simultaneous multi-element ETAAS determinations is the need for compromise atomizer conditions. Berglund et al. (93/5 19) addressed this issue by considering the ability of a platform equipped integrated- contact atomizer and palladium chemical modification to achieve efficient multi-element atomization conditions.Results indicated that with an integrated contact atomizer non-volatile elements such as Mo and V can be vaporized from the platform at a vapour-phase temperature of only 2660 K. Atomization efficiencies were calculated by com- paring experimental characteristic masses with those ob- tained using a theoretical model at this temperature. Elements having diverse physical properties such as Cd and V were found to be effectively atomized using the same conditions with a palladium chemical modifier in the integrated contact atomizer. Berglund et al. concluded that such an atomizer system has much better prospects for multi-element AAS instruments than the Massmann atomizer design.Nichol et al. (93/C19) assessed the use of a linear photodiode array detector (LPDA) for continuum source ETAAS. In a continuum source AAS system the repetetive scanning of a quartz refractor plate is used to allow measurement of the lamp intensity on either side of the absorption line and at the line centre. When using an LPDA the refractor plate is no longer required and intensity measurements can be made by scanning the array of either 128 or 256 pixels. By integrating the line profile an extension of the linear range of the calibration curves compared with those obtained with refractor plate modula- tion and detection was achieved. However detection limits were no better than those achieved with a PMT. Another group based at Wake Forest University NC USA (93/C1467) have built a continuum source ETAAS instru- ment with a xenon source and a photodiode array detector though no indication is given as to the type and character- istics of the polychromator employed.The detection limits for this system are claimed to be one order of magnitude lower than those reported for previous continuum source ETAAS instruments. This system was applied to the simultaneous determination of Ca using a very weak absorption line (227.5 nm) and Cd using the 228.8 nm line in urine. This allowed the two elements to be determined without the need for multiple dilutions since they are present at very different concentrations; Bi (227.7 nm) was used as an internal standard to correct for variations in the atomization procedure.The application of a continuum source with electrothermal atomization and coherent for- ward scattering (atomic magneto-optical rotation) spectro- metry was described by Hermann et a/. (921466 1,93/C159). A continuum source allowed the use of weak atomic lines and enabled the simultaneous measurement of elements present at high concentrations. Baxter et al. (93/ 1023) studied the application of platfarm atomization to FANES for the simultaneous multi-element analysis of environmental samples. Response surface methodology was used to optimize the discharge current and pressure with respect to the detection limits for Al Cd Cr Cu Fe Ni and Pb. Platform atomization gave im- proved detection limits compared with wall atomization and despite the use of automated background correction by wavelength modulation residual background signals were observed at all lines.This presence of structured back- ground emission poses a potentially serious source of error in FANES measurements. For the analysis of environmen- tal SRMs non-spectral interferences arose for all analytes except Cd and Pb consequently the method of analyte additions was necessary for calibration purposes. Fortunately not everyone is faced with the problem of having to measure elements such as Tc for which there is a serious problem in the lack of a commercial source of hollow cathode lamps containing radioactive 99Tc. Haug (92/4660) used the coincident emission lines of other elements. Analytically useful sensitivity was found for a variety of lines which partially overlap with non-resonant lines of the low energy levels of Tc.Using the Pd I line at 371.9 nm a Tc characteristic mass of 0.8 ng (integrated absorbance) and a detection limit (3s n= 10) of 2 ng was obtained with wall atomization. Botha and Fazakas (92/404 1) used non-resonance lines to determine In Pb and T1. They found that the sensitivities of the non-resonance lines improved with platform atomiza- tion temperatures up to 2200 "C and that the linearity of the non-resonance line absorption versus concentration rela- tionship was better than for resonance lines and this effect was independent of the vaporization temperature. While the comment is made that vapour-phase dissociation should give less interference at non-resonance lines in the absence of any quantitative information it is difficult to see why this approach was used given the severe loss in sensitivity found with non-resonance lines.A number of workers have attempted to address the problem of the limited dynamic range in atomic absorption measurements (93/C1 93/C 17 93/C 102 93/C 103 93/C919 9311647 L'vov et al. Spectrochim. Acta Part B 1992 47 889 and L'vov et al. Spectrochim. Acta Part B 1992 47 141 l) in particular with respect to electrother- mal atomization and approached the problem from two different angles. L'vov and co-workers (93/C1 93/C102 93/C919 93/1647 L'vov et al. Spectrochim. Acta Part B 1992 47 889 and L'vov et al. Spectrochim. Acta Part B 1992 47 14 1 I) proposed a number of theoretical models for calibration curves (Spectrochim. Acta Part B 1992 47 889) taking into account the non-absorbed fraction of the light source radiation.Of the three models that based on one involving only a single parameter the roll-over absor- bance A was found to provide linearization of calibration curves over a range extending from the characteristic mass m up to analyte masses exceeding the m values by two or three orders of magnitude. Subsequent work (93/ 1647 L'vov et al. Spectrochim. Acta Part B 1992 47 141 I) extended this model to restore the dip formed in the region of the absorption pulse maximum and resulting from the roll-over of the calibration curve. Applying two parameters A and the Zeeman sensitivity ratio R in the model it was claimed that it is possible to linearize the calibration graph over the entire range of absorption variation and extend theJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 225R range of Zeeman-effect ETAAS measurements to 3-4 orders of magnitude higher than the m,. The method was applied to Be Bi and Cd elements having different A and R parameters. In contrast de Loos-Vollebregt et a/. (93K 103) and Shuttler and de Loos-Vollebregt (93/C 1 7) investigated extending the dynamic range of ETAAS measurements through the use of three-field Zeeman- eflect measurements. A modified commercially available transverse-heated electrothermal atomizer equipped with a longitudinal Zeeman-effect background correction system was employed. Results for elements such as Ag Cr and TI showed that the calibration curves obtained with the conventional Zeeman AAS signal could be extended with the intermediate Zeeman AAS measurements by up to 5-to 10-fold.While the precision of the absorbance signals at high analyte masses remained good consideration of the analytical precision obtained in terms of concentration showed that while calibration curves could be extended the useful range was limited by the acceptable precision for results in concentration. Although both approaches to extending the dynamic range of ETAAS measurements are of interest and no doubt further work will be appearing from these groups the approach of de Loos-Vollebregt et a/. in interpreting the value of the extension in terms of the useful analytical precision obtained illustrates how these different approaches can be assessed.The topic of absolute analysis and the ways and means by which some of the problems in achieving this can be overcome continues to provide a rich research area for many workers. With the benefit of hindsight it is clear that a great deal of information concerning the physico-chemical processes in a graphite electrothermal atomizer and also the influence spectral line profiles have on AAS measurements have been found as a result of investigations in this area. In recent years Chinese workers appear to have been prolific though it is difficult to interpret their findings as in the main little has appeared in English. Some recent studies by Ma and co-workers (92/2249,92/3824,92/4656,92/C4 149) have appeared in the English language literature and have described investigations into the absolute analysis of Cd (92/4656) Er (92/3824) and Yb (92/2249 93/541) using a pyrolytic graphite coated electrographite tube a pyrolytic graphite coated electrographite tube lined with tantalum foil held in place with a tungsten spiral and a tantalum-foil platform.The characteristic masses were close to those theoretically calculated and in these investigations it was considered that standardless methods could have an accu- racy of 10-1 5% for the determination of Cd Er and Yb in complex matrices. In a variety of different atomizers Ma (92/C4149) showed that for Cr the experimental character- istic mass values over an atomization temperature range of 2600-2900 K are very stable and that integrated absor- bance is preferred for absolute analysis studies.Other Chinese workers (92/266) described a model to calculate characteristic masses based on L’vov’s model but taking into account Doppler broadening Lorentzian broadening and hyperfine splitting of the Zeeman splitting on the absorption line. Calculated and experimental values were compared for Cd Co Cr Cu Pb V and Zn. Except for Cd Pb and Zn good agreement was found. Hou et a/. (92/C4 1 54) calculated theoretical characteristic masses using L’vov’s model for a probe atomizer and found for ten elements a value of 1.07 -t 0.25 for mDcal/mOexp. Torsi et a/. (92K3788) constructed a special atomizer which they claimed enabled all atoms to be present in the optical beam simultaneously. This was used in an attempt to avoid having to measure 7(+ the average time spent by an atom in the optical beam and eliminate this term from the equation used by this group for absolute analysis.No specific details about the atomizer were given in the conference abstract. From the same group (92/205 1 ) the absolute analysis of Pb was considered in the presence of a palladium chemical modifier. Reducing the over-all length of electrothermal atomizer time-temperature cycles continues to be a general theme often in the form of conference presentations though it appears that little of this information or advice is finding its way into the primary literature. Carnrick et al. (92/C3701 93/C273) and Taylor (93/C 1440) discussed the recent developments in electrothermal atomization instrumenta- tion and how these have aided the application of yast furnace’ programmes. Coutinho et a/.(93/C108) tried to apply fast furnace programmes to the determination of Cd Pb and Se in food samples. They found that even for samples that one would consider ‘simple’ i.e. wine only reliable results could be obtained when conventional programmes with the use of chemical modifiers and carefully optimized drying and pyrolysis conditions were employed. However calibration could then be achieved with aqueous calibration solutions. For the determination of base metals in silver Hinds (931 10 1 5) was able to employ short atomizer programmes (less than 60 s) drying was accomplished with a fast heating to 600 “C and no pyrolysis step was required prior to atomization. The silver matrix acted as a physical modifier for the volatile elements by delaying atomization and no matrix interferences were observed.Analyte concentrations determined with this procedure overlapped with the 95% confidence intervals for an ‘in-house’ reference standard. 1.3. Chemical Vapour Generation Developments in the understanding instrumentation and techniques of chemical vapour generation as used in conjunction with AAS detection are presented in this section. In addition when significant information relating to chemical vapour generation is contained in reports of specific analytical applications or of systems using detection other than AAS such material is also included in this review. References to chemical vapour generation can also be found in section 1.1.3 Sample introduction. There have been no outstanding developments in chemical vapour generation since the last ASU review (J.Anal. .4t. Spec- trom. 1992 7 215R) and the publications currently reviewed once again reflect repetition consolidation and modest developments in technique and understanding. 1.3.1. Hydride generation Hydride generation is widely used in association with AFS and AES detection as well as AAS and has been the subject of several reviews e.g. 93/64 1 93/708,93/C 16 18. Termino- logy relating to chemical vapour generation has been proposed by an IUPAC Commission in No. XI11 of its series of publications on ‘Nomenclature symbols units and their usage in spectrochemical analysis’ (93/643). 1.3.1.1. Fundamental studies. Chemical interferences can be a serious problem in the HG technique.They have been studied in depth for 20 years and been the subject of frequent reviews e.g. 92/2257. One of the most promising of recent studies has been undertaken by Krivan (92/4611) and was based on the use of radiotracers. Examples of interferences in the determination of As Sb Se and Sn were given. Three sources of interference were discussed pre- hydride generation sample handling cross-interference of hydride forming elements and the effect of hydrofluoric acid. Step-by-step addition of reagent to a solution of mixed hydride forming elements (As Bi Sb and Sn) was used to determine the sequence of hydride evolution (92/C4 13 1). Detection was by simultaneous multi-element ICP-AES.226R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 Antimony and Bi hydrides were rapidly released and generated sharp emission peaks. Arsenic appeared later and was followed by Sn. Peak width increased as the delay in element appearance increased. Interpretation of these observations is complicated by the simultaneous variation of two parameters viz time and reagent concentration. The authors concluded that 'the classic nascent hydrogen mechanism cannot give a convincing explanation of the HG sequence of these elements'. The interference of cobalt copper and nickel on the determination of As Sb Se and Te was overcome by coprecipitation of the latter with lanthanum hydroxide (92K4159). The precipitate was dissolved in HC1 and the hydrides generated with KBH,-KOH. The effect of nickel was studied and it was concluded that the interference occurs in the liquid phase where black sponge nickel and NiBI2 were produced leading to adsorption of ASH on the surface of the precipitate.Hydride generation using NaBH suffers from a number of disadvantages e.g. the reagent can introduce contamina- tion it is expensive and being unstable solutions have to be freshly prepared each day further the hydride generat- ing reaction is susceptible to interferences. For these reasons an FI-electrochemical (EC) HG system was devel- oped (92/4634). Interference effects in the determination of Se using the EC system were comparable to those found when NaBH was employed except for the effect of Hg when interference in the EC system was much greater. Detection limits for As Sb and Se were 0.45 0.62 and 0.92 ng ml-l respectively.1.3.1.2. General developments in instrumentation and tech- nique. As an aid to batchwise HG a simple mixing vessel has been developed (92/4395). The system consisted of a PTFE vial with a magnet sealed in its base to contain the NaBH solution. The vial was placed in a reaction bottle containing acid sample solution. An external magnet was used to control the position of the vial. Mixing and HG were easily effected under gas-tight conditions. The detec- tion limits achieved were As 0.3; Bi 1.2; Ge 6 1 ; Pb 16; Sb 1.6; Se 1.3; Sn 0.1 and Te 1.1 ng ml-I. A simultaneous multi-element AA continuous frow HG system based on commercial instrumentation has been optimized by Dulude et al. (931C1574) for the determina- tion of As and Sb.L-cysteine and L-cystine are used to increase the reaction rate and sensitivity of HG reduce interferences and for the pre-reduction of AsV to Asi1'. To exploit these advantages in a continuous flow a new hydride generatorheparator has been developed for use in DCP-AES (9214094 931807). The application of the system to the determination of As in water was investigated thoroughly. When a sample introduction rate of 15 ml min-l and strippingkarrier gas flow rate of 2.4 ml min-l were employed the detection limits for As Ge and Se were 4 0.3 and 8 ng rnl-l respectively. The generator was also used in connection with the determination of As Sb and Sn by FAAS (93/444). Cysteine (1% in the sample solution) minimized interferences by Ni2+ Ca2+ and Cu2+ and enhanced sensitivities.Hydride generation efficiency was greater than 95%. Flow injection-HG-AAS continues to be an actively developing technique whose advantages have been re- viewed by Welz (92/2106). The author has also reported (9212635) the results of an optimization and evaluation study for the determination of As Bi Sb Se Sn and Te in a variety of biologicallenvironmental samples. Compared with a batch HG-AAS system the characteristic masses of the FI system were improved by factors ranging from 16 to 57 whereas the characteristic concentrations were close to those of the batch system owing to the 100 times smaller volumes used in FI. Less pronounced interferences found in the FI system were attributed to lower tetrahydroborate concentration and better kinetic discrimination.In the analysis of real samples F1 was found to be superior by virtue of its lower sample and reagent consumption easy automation and higher sampling frequency. This work was extended to the determination of Sb As Bi Hg Se and Te by FI-HG dual channel non-dispersive AFS (93/ 10 13). The most important factors affecting performance were concen- tration of NaBH carrier gas flow rate observation height and temperature of the electrically heated quartz furnace. The same advantages of FI over batch processing were found in this work as previously in the AAS study. The sensitivity of FI-HG-AAS can be increased by trap- ping the generated hydride on the pre-heated interior surface of a graphite furnace prior to atomization. The efficiency of trapping and atomization using uncoated or pyrolytic graphite coated tubes was almost identical for small sample volumes (93lC152).With large (several ml) sample volumes trapping efficiency on the different sur- faces was found to depend strongly on sample volume but not on analyte concentration. When the surface was coated with Pd (93/C153) Ge in water biological and geological samples was determined at the 0.1 ng ml-I level with an RSD of 0.025 and in good agreement with certified values. The detection limit was 0.004 ng ml-1 Ge. The detection limit as reported by Chinese workers (931695) was much higher (40 ng ml-l Ge) when a T-type electrically heated closed-ended slotted quartz tube was used without trapping. 1.3.1.3. Determination of individual elements. Hydride generation AAS is used for the determination of Sb in a variety of samples.Flow injection and continuous flow systems were applied to the determination of Sb in sea- water (92/2767); the detection limit was 7 pg of Sb. Antimony in potable and surface water was determined by FI-HG with trapping on a graphite tube at 200 "C followed by atomization and determination by AAS (9214657). The detection limit was 15 pg of Sb (3 rig 1-1). Two discrete sample processing procedures have been described for the determination of Sb in waters. Improved sensitivity and elimination of interferences were achieved (921274 1) by extraction of the analyte from water into tributyl phosphate or with APDC into IBMK. The hydride was generated by NaBH in DMF solution and anhydrous acetic acid; detection was by non-dispersive AFS.In the other study (92/4430) the hydride was generated in a laboratory-made device. Stibine was generated with NaBH and AAS measurements made in a flame heated quartz tube. The error caused by the different oxidation states of Sb was overcome by the addition of KI-ascorbic acid to reduce all states to SbiI1. The detection limit was 0.35 ng ml-* of Sb. Hydride generation is well established as a method for the determination of As however some problems of interference remain to be solved. The interference eflects of antimony bismuth selenium tellurium and tin on As determination have been studied and a procedure for their elimination proposed (931C65 9311 645). The most impor- tant interferents were antimony and tin. The effect of these elements was eliminated by the addition of a mixture of lactic acid and KI to the hydride generating reaction mixture.For the determination of As in yellow phosphorus by HG-AFS ascorbic acid-thiourea was recommended as the masking-reducing agent prior to hydride generation with KBH and 20% HC1-4% H2S04 (9213974). The detection limit was 0.3 ng of As. Solvent extraction was used to separate As from an interfering matrix (92/24 16). Ethyl alcohol was used to dissolve NaBH in place of the usual DMF in the APDC-IBMK hydride generation system. TheJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 227R method was claimed to be safer and cheaper and to generate less background in the AFS detection system. A detailed study of the mechanisms of the atomization of ASH has been carried out by Dedina and Welz (9214637). The effect of atomizer design and temperature purge gas type and flow rate and oxygen supply on sensitivity and curvature of the calibration graph were investigated. It was found that the H radical density derived from the reactions between oxygen and hydrogen was a decisive factor determining the decomposition of ASH,.Two procedures for the determina- tion of As in nickel based alloys have been described by Tyson and co-workers. Both use FI systems. In one (92lC3663 931 1638) miniaturization of the gas-liquid separator allowed for dilution of the interfering nickel to a tolerable concentration while leaving the As at a measur- able concentration the other (92/4638) incorporated a microcolumn of strongly acidic cation-exchange resin (Dowex SOW) to remove the nickel. In the former system the detection limit was 0.5 ppb and accurate analysis of BCS-CRM 346 nickel-based alloy was achieved (certified 50.2+3.2 pg g-'; found 49.6+3.3 pg g-l).The second procedure incorported a stopped-flow iodide pre-reduction procedure within the matrix isolation unit to convert the arsenic present into As111 prior to determination by AAS with a tube-in-flame atomizer. A sample throughput of 54 h-l was obtained and a detection limit of 3.9 ng ml-1 of As. Arsenic can be separated from a matrix by precipitation with tetraphenylphosphonium chloride of the Asv-molyb- date complex (9212765). The procedure can be used as a means for As speciation by its selective removal of AsV.Competition of phosphate with AsV for complexation with molybdate limits the use of the procedure to samples containing less than 6 pg ml-L of phosphate. Hafnium''' hydroxide quantitatively co-precipitates As111 and AsV from solutions at pH 6.0-10.5 (93/1912). Arsenic111 can then be determined by HG-AAS AsV requires pre-reduction to AsL1' prior to determination. Interference by hafnium(v) in the determination of Asi1' is overcome by the addition of perchloric acid; in the case of AsV the addition of KI is effective. Comprehensive speciation of As in urine has been carried out using ion-pair chromatographic separation (92/46 18). The species separated were As111 AsV monome- thylarsonic acid (MMA) and dimethylarsinic acid (DMA). The separation was completed within 4 min using tetrabu- tylammonium ion in a phosphate buffer as the ion pairing agent and a CI8 reversed-phase column; detection was by HG-AAS giving detection limits for As of 1.0 1.6 1.2 and 4.7 pg dm- as As111 AsV MMA and DMA respectively.Arenas and Victor (93/1141) have described an optimized procedure for speciation of As in marine samples by HPLC- automated HG-AAS following extraction of As compounds. Japanese workers (931 1 195) have suggested that control of pH can be used as a means of discriminating between inorganic Asiii and AsV. Total As including dimethylarsinic acid was determined in dilute HCl; above pH 9 only As111 was detected. In ground and river water only AsV at the 2.6-8.0 ppb level was detected. Discrimination between As11* and AsV (93/435) and their 'simultaneous' determina- tion has been achieved based on the different absorbance at I90 nm-time profiles of the gas-phase molecular absorption curves of arsine which result from the different rates of reaction of As111 and AsV.The widespread medical use of bismuth salts has necessi- tated the development of methods for the determination of Bi in biological materials. One such method for the analysis of blood and urine based on HG-AAS and incorporating wet digestion has been described (92/2438). It is claimed that the method is sensitive reproducible and economical. Bismuth and Sb have been determined in soils by an automated hydride system with an electrically heated quartz tube atomizer and AA detection (93/485). Detection limits in dry soil were 0.7 and 7.0 ng g-' for Bi and Sb respectively.The determination of Pb by HG techniques is limited by the small yield of the volatile hydride and its low thermal stability. The former problem is reduced when oxidants are present in the solution (92146 13). Trace amounts of Pb in lithium and its salts have been determined by HG-AAS. Lead was co-precipitated with lanthanum hydroxide (92/2736) followed by dissolution of the precipitate and the addition of K,Fe(CN),. This solution and a solution of KBH4 were automatically introduced into the hydride generator. The detection limit was -9 ng m1-I. Low pressure electrothermal AAS used in conjunction with HG of plumbane gave a considerable improvement in sensitiv- ity and detection limit (92/46 13). Plumbane was generated from an HN03-(NH4)2S20s solution with NaBH and rapidly drawn into an evacuated electrically heated quartz tube. The detection limit was 0.1 ng ml-1 Pb compared with 1.1 ng ml-' Pb when operated at normal atmospheric pressure.In-situ concentration of plumbane on a zirconium- coated graphite tube prior to ETAAS gave a 6-fold enhancement in sensitivity compared with that obtained with adsorption on a pyrolytic graphite coated graphite tube (92/C4 142). The peak height sensitivity was 52.8 pg and the detection limit was 242 pg of Pb. The most severe interferences in the determination ofSe by HG-AAS with a heated quartz tube atomizer are caused by other hydride forming elements (93/C895,93/C 1433). Tube surface and temperature and oxygen/hydrogen concentra- tion were significant factors in determining the extent of interferences.Interferences were less pronounced in FI systems than in batch systems. The determination of total Se in biological samples requires the breakdown of a number of organoselenium compounds. The decomposition of tri- methyl selenonium selenomethionine selenopurine and selenocystyne by an HBr-Br2 reagent has been investigated (92/C3635). Differential pulse polarographic measurements demonstrated that the organoselenium compounds were converted into inorganic SeIv. Inorganic Selv and Sevl were quantitatively recovered by the digestion procedure. The detection limit for Se in serum and urine using HG-non- dispersive AFS determination was 0.5 ng ml-I. Analysis of NIST SRM-2670 (Freeze Dried Urine) agreed with the certified value.Collection on sulfiydryl cotton has been used to separate Se and Te from an ore digest matrix (92/2674). The analytes were stripped from the cotton by boiling in HNO and determined by HG-non-dispersive AFS. Liquid- phase interferences in the generation of volatile hydrides is a long established problem of HG systems. An attempt has been made to elucidate the mechanisms of liquid-phase interference caused by copper(Ir) gold(II1) and silver(1) on the evolution of hydrogen selenide (92/2408). A physical model of the interferences based on the trapping of hydrogen selenide at the surface of interferent particles grown in the solution and possessing a highly folded surface led to an equation which accurately describes the experimentally derived interference plots.Non-dispersive AFS was used to detect Se. Interference and sample variability problems in the determination of Sn in food digests were reduced and some preconcentration achieved by converting the Sn into its chlorostannate complex (93/429). The complex was then separated and preconcentrated on-line on a microcolumn packed with a strongly basic anion-exchanger and eluted with dilute HN03. Analysis was by FI-HG-AAS and yielded a detection limit of 80 ng I-'. A gas-liquid separator with integrated manifold as the interface of an HPLC-HG-AAS system for the determination of organotin compounds has been described (931763). The length of the reaction line was very short (4 mm) thereby minimizing additional broadening of the HPLC peak.228R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 1.3.2. Preparation and separation of volatile organometallic compounds Very few reports on the generation of volatile organometal- lic compounds have been received. Preliminary studies of sodiurn tetraethylborate as an aqueous alkylating reagent for the generation of volatile compounds of Cd have been reported (931C33). A continuous flow organocadmium generating system with flame AFS detection achieved detection limits in the parts per trillion (ppt) range. Derivatization and cryogenic trapping of analytes followed by chromatographic separation and ETAAS determination yield both good separation and high sensitivity. The possibilities and limitations of this technique have been discussed with respect to the compounds of Hg Pb Se and Sn and possible extensions suggested (9212 109 9214584).I .3.3. Mercury by cold vapour generation The CV determination of Hg continues to be a topic for research even though some 30 years have passed since the technique was first described. Its principal applications have been in the field of environmental studies where current analytical developments are directed at improving accuracy lowering detection limits and quantification of the Hg species; AFS is being used increasingly as the atomic detection technique. Specific instrumental systems have been developed for the determination of Hg by CVAAS (92/3055) and by CVAFS (931C12). The latter is a commercial system capable of detecting a few ppt of Hg while the former was a laboratory-made absorption tube placed in a commercial AA instrument and gave a detection limit of xO.1 ng ml-I. A low power MIP torch has been evaluated as an atomizer of Hg for determination by AFS (92/3221 9213818 9311124). The plasma exhibited a large dynamic range (several orders of magnitude of concentration) and was relatively free from background interference. The detection limit for Hg (3 ppb) was comparable to or better than that for an ICP with the same excitation source. Normal CV methods are not always sufficiently sensitive to satisfy the needs of environmental legislation. Considerable improve- ment in sensitivity can be achieved by Hg collection by amalgamation with gold followed by thermal release. Methods have been described based on this technique using AA detection (9214008 931C 195 93/ 12O3) AF detection (92/4525) and AE detection using preconcentration on Pt (9311644).Detection limits were typically in the picogram range. When Hg in waters was concentrated on xanthate cotton ion-exchange Jibres followed by desorbtion with a HC1-NaCl solution reduction with NaBH and detection by AF a detection limit of 5 pg 1 - I was achieved (93/1239). The performances of AAS AFS and AES as detection systems for Hg have been compared by Sturgeon and co- workers (921C3604 93/C197). Publication of this study is awaited with interest. Flow injection procedures for the analysis of urine and whole blood (921C3530) and waters and urine (93K64 93K99) by CV generation of Hg and AAS detection have been described. Pre-treatment of the sample was required in all cases.Waters were treated on-line with concentrated sulfuric acid to release organically bound Hg. Off-line procedures were used for the pre-treatment of whole blood and urine. The former was diluted with an anti-foaming agent and water while the latter required vigorous oxidation with KMnO and either H2S04 (931C64) or HNO with H202 (92K3530). The detection limit was 0.1 pg 1-1 and the RSD over the range 5.0 to 10 pg 1 - I was 0.01 5. When AFS was used as the detecting technique with continuous flow CV generation detection limits in the region of 10 ng 1-1 and a linear response up to 100 ,ug 1 - I were achieved (9318 12). The linear range was extended to 10 ng 1-1 when FI was used. The need for off-line sample pre-treatment can be a limitation in continuous flow systems.Two on-line procedures have been proposed to overcome this difficulty both approaches used detection of Hg by AAS. In one (92/2483) a microflow system (tube bore 0.5 mm i.d.) achieved sample digestion reduction and extraction with flow rates of several pl min-l of reagents. The detection limit was 0.15 pg 1-1 and the RSD at 4 pg 1 - I was 0.01. The other procedure (931C90) incorporated on-line microwave diges- tion and was evaluated for its accuracy and precision in the analysis of a range of environmental water based samples. Moisture carry-over originating in the gas-liquid separa- tion process can lead to baseline drift and loss of sensitivity in the determination of Hg by continuous-flow CV. Three papers have described procedures designed to overcome the problem.Chemical desiccants and physical moisture traps can be used for short periods but can give rise to contamination and analyte loss. The simplest approach (92/2107) which evolved from trials of a number of gas-liquid separators with and without membranes was the use of a membrane-free separator with a wide (1 2 mm i d . ) waste channel; under optimal conditions the detection limit by AAS was 0.5 pg 1 - I ( 0.6 ng of Hg). The other two papers employed semi-permeable membrane separators. In one (92/458 I) a hygroscopic Nafion membrane was used to remove water vapour from the analytical gas stream while the other (92/C3743) used a hydrophobic membranewhereby Hg diffused from the liquid phase through the membrane into an air stream on the opposite side.In the former case using AFS detection an RSD of 0.02 was achieved for 90 runs of a 1 pg 1 - I standard over a period of 3 h. The determination of total Hg in a variety of matrices has led to a corresponding variety of digestion procedures. For Hg in water by CVAAS reaction with HC1 or HNO in the presence of bromate and bromide at room temperature for 20 min gave recoveries >92% with an RSD x 0.01 and a detection limit of I0 ng I-'. The method was claimed to be superior to H2S0,-KMn0 digestion (9212968). Blood was mineralized with HN0,-H2S04 at 60 "C for 10-15 min without loss of Hg (9213081). The detection limit by CVAAS in blood was 14 ng ml-I. In the analysis of air particles were trapped on a quartz membrane-filter and extracted into aqua regia by heating for 1 h at $5 "C (921242 1).After dilution with 5% HCI Hg was liberated with 8% KBH and determined by AAS. When 360 m3 of air was sampled the detection limit was 20 pg m-,. The oxidation of organomercury compounds has been effected on-line by two methods. In one (93/553) was generated continuously in an electro[ytic ceN by the oxida- tion of ColI and was used as the oxidant in the determina- tion of total Hg in waters by AFS. The other method (931760) decomposed organomercury compounds with K2S20S with the addition of FeCl as catalyst. The response of organomercury in this system was then similar to that of HgCl and the method was used for the determination of total Hg in waste waters by AAS. Slurry procedures avoid the problems of time consuming digestion procedures and the accompanying risks of contamination or analyte loss.This technique has been applied successfully to the determi- nation of Hg by CVAAS in iron oxide-titanium oxide pigments (92126 16). The samples were suspended in water containing 0.02% m1v sodium hexametaphosphate and Hg generated from an HCl medium with NaBH,. Calibration was with aqueous solutions of Hg and there was excellent agreement between results from slurry and acid digestion procedures. The detection limit for Hg was 5 ng g-I. For the speciation of Hg ion chromatographic separation has been combined with on-line CVAAS for the determina- tion of methyl- ethyl- and inorganic Hg (92K3637). The detection limits using 100 ml samples were Hg 2; CH,Hg 10 and C2HSHg 4 ng.In the original analytical procedure,JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 229R spectrophotometric detection was employed however the concentration of cysteine required to optimize the chroma- tographic performance generated a high background hence an on-line CVAAS detection system was developed. An investigation into the forms of Hg in natural waters has been reported (921C35 13). It was found that at pH 6-9 Hg combined with fulvates humates and hydroxocomplexes was not reduced by tin(1r) chloride. Acidification of water samples with 3 mol I-* HN03 and heating for 5-6 h decomposed those compounds but not methylmercury chloride added to the sample. These observations were used as a basis for determining the different forms of Hg in natural waters.The determination of methylmercury in biological samples has been reported in two papers. Fish homogenate was mixed with H2SO4 and NaBr and methyl- mercury extracted with CHC13 (931C 105). Mercury was determined by CVAAS after reduction with NaBH in DMF and HN03. Inorganic Hg was determined in the aqueous phase after liquid-liquid extraction. When applied to CRMs the procedure gave results in agreement with the certified values. An alternative procedure (921C3605) was based on generation of the volatile methylmercury iodide with iodoacetic acids in H2S04. The liberated methyl- mercury iodide was headspace injected into a gas chromato- graph. The MIP of the system was replaced with a pyrolytic decomposition cell and AFS detection which improved the sensitivity of the system 20-fold and gave a detection limit of 50 pg.Derivatization of Hgl* and methylmercury has been used as a means of separating the two forms of Hg by the differing volatilities of their derivatives (931C 1 544). The detection limits (as Hg) of the method using AFS detection were 0.6 0.6 and 1.3 pg for (CH,)*Hg CH3Hg+ and Hg2+ respectively. 1.4. Spectrometers An article by Walsh (9212387) briefly mentioned in last year’s updates (JAAS 1992 7 216R) reviewed the early fortunes (and misfortunes) of AA methods between the years 1952 and 1962. The historical view of those events seen from about 30 years later makes an interesting commentary on the way they appeared at the time and it may be that a less involved scientific historian would present still different emphases within the general picture.Two conclusions drawn by Sir Alan must however always be valid in this particular kind of development the subject needs to be first studied fully at a basic level without research being directed at a specific target; and the performance of new instrumentation in its intended role is far more important to the eventual user than the cleverness of all the technical arguments in its favour. In 1992 the proceedings of the XXVII CSI in Bergen (held in June of the previous year) (J. Anal. At. Spectrom. 1992 7,69-480) were published. This was the occasion of special tributes to Sir Alan Walsh from the scientific community and was marked by papers from Butler (a personal tribute 92/4085) Larkins (a short biography and appreciation 9214086,9214595) and Sturgeon (present and future aspects of AAS 9214087 9214596).The last of these gives an excellent overview of the state of the art instrumentation and looks forward realistically to its continuing develop- ment. Yet more honours and tributes were showered upon Walsh and L‘vov and others at the 1991 Pittsburgh Conference. The relevant papers appeared later that year. Koirtyohann (92/2397) from an academic perspective gives a nicely balanced history of AAS from its inception to the present day noting with much justification that while in the early days a young scientist could have been taught the operation of an AA instrument within about thirty minutes today it takes much longer just to read the software manual without knowledge of which you cannot even turn the instrument on! Koirtyohann is always readable but in a conference review (921C37 16) he insisted presumably in spite of the above that AAS just keeps getting better.He likens the technique to a work-horse spurned by some modern academic cowboys as merely a hack which in reality is a steady mount that can carry you safely through the analytical back country. As one of AA’s most experienced cowboys (in the very best sense of that term of course) Koirtyohann’s words carry much weight. Another report on the same theme the success of AA comes from Slavin (9212398). But in addition to the back- slapping and crystal-ball gazing there is an amount of good solid material of general coverage that deserves notice. Volume 5 in the Elsevier Analytical Spectroscopy Library has appeared.This is a treatise on theory design and applications of AAS edited by S. J. Haswell. There is also a general review in Spanish (9213 100) running to nearly forty pages but with only 22 references. After discovering that a particular design of AAS furnace gives results which are almost free of matrix effects Carnrick et al. (931C155) go on to investigate the measure- ment of characteristic mass independently of instrument characteristics. If the relevant data were established then absolute AAS would be a real possibility. 1.4.1. Light sources The effects of higher lamp currents on HCL lampproJles and their resultant modification of calibration graph shapes have been investigated for a number of typical elements in AAS (921463 1).A scanning echelle monochromator was used for this work as it provides resolution comparable to room temperature Doppler widths and gives ready access to the UV region. In order to obtain direct comparison of the performances of ostensibly similar HCLs four Se HCLs were mounted in a four-channel Hitachi 2-9000 Spectrometer (92/2053). The same series of samples were measured with each lamp one a boosted lamp and three typical lamps from different makers. The boosted lamp gave the best figure of merit and the other three through varying from each other provided satisfactory analytical performance. Chinese workers (92/2412) operating with time resolved emission of a Ca HCL show that with pulses of 1-4 p s duration major emission energy is transferred to the excitation of ionic levels rather than atomic levels as in conventional operation.Diode laser sources for AAS have again been investigated (9211986) (see also ASU J. Anal. At. Spectrom. Aug 1992 7 238R). A new method has been devised to overcome the frequency instability of the laser. A diode laser has also been utilized as the source in high resolution spectroscopy to measure the hyperfine splittings and isotope ratios in rare earth metal vapours (931C1537). The problem of laser frequency instability was again acknowledged. Resonance line lasers RLLs constructed using metal halide salts as the active media lock in to an atomic transition and radiate the corresponding wavelength (931C1536). Three RLLs employing Gal3 In1 and TlI have been critically investigated (though not specifically for AAS) and clearly merit further examination.A demountable d.c. HC discharge cell was used as a trace concentration atomizer in providing Doppler-free condi- tions for laser polarization spectroscopy (9213869). Isotope ratio and hyperfine structure analysis was carried out on samples as small as 10 ng.230R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 1.4.2. Optics There has been virtually no development in optics for AA spectrometers other than for continuum source AA. How- ever Indian workers (9212692) have investigated the aberration properties of plane holographic gratings in a Czerny-Turner spectrometer mounting by actual ray trac- ing methods while a ruling engine with piezoelectric control for high groove density gratings is reported from Hitachi (931420).1.4.3. Detectors Work on the improvement of performance of photodiodes i.e. increases in sensitivity to low light levels and better signal to noise ratios continues. This work is generally more relevant to AES and AFS instrumentation than to AAS although photodiodes are being exploited in the specialized area of continuum source AA (see next section). Fundamental work on the improvement of Ag-Ti-nGaAs grating photodiodes (9212686) and large area silicon photo- diodes (9212688) may however be of interest to those responsible for instrument development. 1.4.4. Continuum source and simultaneous multi-element AAS The main practical developments in continuum source (CS) AAS to be reported this year again originate from the US Department of Agriculture.Two conference papers deal with instrumentation. The pulsed xenon arc is the preferred source (931C 18) and a linear photodiode array (LPDA) covers a wavelength interval of less than 1 nm centred about each analytical line of interest in this case Cd Co Fe Ni and Zn. Wavelength absorbance is obtained by summing the computed absor- bance for each pixel across the absorption profile. As claimed last year (see J. Anal. At. Spectrom. l992,7,238R) detection limits for these elements are comparable to those achieved with the conventional methods of AAS. The LPDA used in conjunction with a CS is shown to eliminate lamp flicker noise and background absorption provided that the source is blocked during the readout process (931C405).Although all pixels experience the same intensity variations simultaneously they do not begin integration at the same point in time. An electronic shutter is therefore opened so that each pixel integrates over precisely the same period and flicker events occurring between the readings of the first and last pixels remain undetected. Further work on detection limits and character- istic mass as obtained with pulsed high-intensity continuum sources is reported in two more conference papers (931C1464 931C1466). Wall platform and probe atomization techniques have also been used with an instrument developed by Harnly (9214570). Interferences by NaCl and MgClz on a number of common elements were investigated. With both probe and platform procedures freedom from interference was achieved with chloride sa1t:analyte ratios of up to A critical investigation into the design of instruments for CSAAS including light sources spectrometers and detec- tors has been undertaken by Smith et al. (Anal.Proc. 1992 29 262). Bandpass values similar to those of atomic absorption linewidths can be achieved with an echelle spectrometer but at 214 nm the best CS lamp available provides only about 11500 of the useful photon flux of a Zn HCL. Developments in multi-element and multi-channel AAS using conventional light sources have been reviewed in three papers (9212095 9212096 931C1573) and Jarrel-Ash 1 x 103-1 x 105. (described their Smith-Hieftje 8000 four channel (32 ele- ments) computer controlled instrument (92K3754). Another conference paper describes the inclusion of an on-line microwave sample digestion procedure in automatic multi-element AAS (931C36).Soils and sludges in slurry concentrations of up to 2% m/v have been treated using a method previously applied to biological RMs. 1.5. Instrument Control and Data Processing 1.5.1. Instrument Control. Automation is a common theme in modern instrumentation and the use of customized computerized routines to automate instrumentation continue to be reported. Details of a program written in OBEY (Perkin-Elmer) have been re- ported for automated ETAAS analysis following Environ- mental Protection Agency quality control protocols (9212430). The program was configured to determine Ag As Cd Cr Pb Sb Se and Th in both aqueous extracts and solid samples. To achieve defined detection limits the program indicated spike concentrations and required the identifica- tion of calibration and control standards.The program also featured automaticflagging to reduce the need to review the data to validate the results during periods of unattended use. Computer aided measurements and data interpretation in ETAAS has also been reported (92147 13). The program in this study was prepared in Turbo Pascal on an IBM PC1XT compatible computer coupled to an operational amplifier and analogue-to-digital converter (ADC). The results from investigations on the mechanisms of atomization in the furnace were discussed the output from the system being obtained via either a recorder printer VDU or floppy disk. An interface card for the Apple IIe computer has been reported for the control of instruments generating transient signals such as ETAAS instruments (931859).The interface card consists of a multiplexed ADC a DAC and a timer1counter chip with 16 built in registers that can be independently programmed to provide a time base for real- time measurements. The system was applied to deuterium- lamp background correction for ETAAS employing a mechanical chopper driven by a stepper motor and electroni- cally modulated HCL. The data acquisition program was written in machine language and synchronization between light sources and computer was provided by chopper position signals using the interrupts. A sampling rate of 16 points per cycle at a chopping frequency of 50 Hz was found to be optimum. The use of machine code enabled the large number of data points collected during atomization to be compressed facilitating a saving on both storage space and analysis time.A computer controlled AAS scanning method to study flame atomization processes has been reported (9212986). By slightly changing the optical and burner configuration of the system the method was reported to give information on the absorbance distribution over the entire cross section of the flame quickly reproducibly and with high resolution. Interference effects and flame chemistry processes for Co and Mg salts were discussed with reference to the different distribution functions obtained using the technique. A novel system for wavelength modulation has been described (931C1603) in which the frequency limits imposed upon previous designs by torque problems are overcome.The system was applied to flame AFS and characterized in terms of instrumental noise and the importance of careful selection of modulation frequency for effective noise reduction. A microprocessor controlled automated on-line method for generating calibration standards for AAS has been described by Starn and Hieftje (92/464 1). Mathematical gradients programmed with a HPLC pump module were used to mix and dilute solutions to form the desiredJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 231R concentrations. The calibration lines produced were shown to be comparable to those obtained with individual stan- dard solutions and offered a saving in terms of both time and reagents. The only drawback reported was a slight but noticeable time lag between successive gradient steps.1.5.2. Data processing. Various reports in the literature continue to emphasize how easily data can be transferred from the spectrometer to wordprocessors spreadsheets and data bases to allow the efficient production of reports further processing of the data and the creation of data archives. Several specific systems have been discussed. The first of these described the ADISS Program (Analytical Data Interchange and Storage Standards) which aims to set up a framework for standardizing analytical data in a way that is independent of any operating system application hardware or vendor (92lC3660). The organization CAALS (Consortium on Automated Analytical Laboratory Systems) has been formed to create automated chemical analysis systems that will improve the quality of data facilitate the entire analytical process and promote the standardization and transfer of analytical methods whilst providing industry with competitive advantages in chemical measurement technology (92K3659).However both of these ambitious projects are still in the development stage and although the work is progressing the reports reflect the fact that much still needs to be done to make either system viable on a wide scale. However a more established program for collecting baseline blank background and signal waveforms from an optical detection system associated with a d.c. source has also been reported (93/1643). From the data the net signal background SIB S/B noise RSD of the background and RSD of the signal are calculated.A diskette containing this program is available from the authors. The development of LIMS continues to be reported. In a recent paper (9214476) the features necessary for improving efficiency and quality by coupling quality assurance/quality control testing and process control systems to such a system in a production environment have been discussed. A computer programme (CHMASS) has been described which calculates characteristic mass values for ETAAS following user-specific input of atomizer type or dimensions and atomization temperature (92/4662). All the necessary spectroscopic and physical parameters for calculating the values for 40 elements and 44 analytical wavelengths were included in the database.Applications of the program were illustrated by theoretical and practical examples including a study of the effect of atomization temperature on absorp- tion and diffusion coefficients for Ag; an investigation of how the sample injection hole limits the maximum attain- able ETAAS sensitivity for Cu as the tube length is increased; optimization of the atomization temperature for the determination of Cd in an SRM; and a comparison of several commercial atomizer designs as regards the calcu- lated atomization efficiencies using data from the manufac- turers literature. This last comparison has also claimed to provide evidence for the superiority of platform atomiza- tion and integrated absorbance measurements over wall atomization combined with peak height evaluation.A computer simulation study to determine the kinetic para- meters for the formation of gaseous analyte atoms from the absorbance signal in ETAAS has also been reported (92K4143). Here the curvature of Arrhenius plots often reported using other methods was suggested to be due to the assumption of first order kinetics for atom formation i.e. the steady state approximation. In addition this paper proposed a method for obtaining the diffusion coefficient and its temperature dependence from the decay part of the absorbance signal. The Jitting of calibration curves in AAS has received considerable attention. A detailed analysis of the correla- tion between the number of absorbing atoms and the absorbance has been presented by Gilmutdinov et al. (93K1639).The study considered the optical thickness of the absorbing layer and accounted for the Doppler broadening and pressure broadening of the emission and absorption lines hyperfine structure and collisional shift as well as spatial temperature distribution and analyte distri- bution non-uniformities of the absorbing layer. The results obtained showed that all the spatial features lead to curvature and a decrease of the slope of the initial portion of the concentration curve. It was also shown that the spatial non-uniformities acted in two different ways longi- tudinal temperature and concentration gradients resulted in a decrease in the slope of the concentration curve while the cross-sectional non-uniformities led to curvature of the concentration curve. The authors also concluded that the lateral non-homogeneity of the analyte distribution is the main cause for curvature of the analytical working curves in ETAAS.Correction for non-linear calibration curves in ETAAS has also been the subject of several reports. A computer algorithm has been developed by Boss (93K1456) to linearize such curves. Two assumptions are made in this work that some fraction of the light has a lower absorption probability than the centre of the atomic line; and that the total integrated linearized absorbance should be directly proportional to the mass of analyte placed in the furnace. This idea has been adopted by Hamilton (93K1457) who has reported a menu driven interfacehoftware package. A slope ranking method which is based on the sequence of the individual slopes of the calibration data has also been presented as a useful method for checking the linearity of calibration lines (93/459).Two short reviews have also considered calibration methods. In the first of these (92/2253) the calibration methods employed in AAS with FI techniques were discussed (17 references) and in the second a statistical comparison was made between calibra- tion line and standard additions methods (1 5 references) (93/856). The use of the unweighted least-squares method for the construction of calibration curves has also been discussed (92/473 1). Although not strictly falling into the subject area of this section of the review a number of papers have discussed the role of RMs in quality control which might be relevant for some aspects of data processing.An overview of this area by Byrne (92/4088) considered both the viability and suitability of reference materials for atomic spectroscopy and the problems that might result in their use such as incomplete dissolution and lack of homogene- ity. Solid sampling ETAAS has been proposed for the production of animal tissue RMs for quality control (92/2013). Statistical tests were used to compare the results obtained using this method with other sample preparation procedures and analytical techniques the results of which are described as adequate by the authors. More general papers by Rasberry (92/3989) and Walker (92/3988 93K1609) have looked at the availability of reference materials from NIST and the Laboratory of the Government Chemist respectively. In Rasberry’s paper the increasing attention being paid to standards for atomic spectrometry was highlighted i.e.the availability of 65 single and multi-element solutions specifically for this purpose. A general overview of new RMs in a range of matrices has also been presented (92/4702). Two re- ports from ASTM Standards have been published. These cover the practice for preparation of calibration solutions for spectroscopic atomic analysis (9213968) and the prac- tice for verification and the use of control charts in spectrochemical analysis (9 2/ 3967).232R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 1.5.3. Chemometrics Although most workers will pay lip service to the need to evaluate their methods fully all too often this critical aspect of any study is given little attention when it comes to the publication of results. Several authors have recently addressed this problem.In one such report (92/4640) the protocol and the general principal of method evaluation design in AAS using ordinary statistical calculations was applied to the determination of Pb and Mn in blood. The method evaluation design provides information on whether or not the method is in statistical control i.e. whether the values observed belong to a normal distribution around the mean values. Thus the estimated uncertainty is truly representative of the methods and includes both within-run and between-run variations. Further the method evalua- tion design produces estimates of the magnitude of the systematic error the LOD and the limit of quantification.The application of the mean square error and the square root of the relative mean square error combines the systematic error with the total uncertainly and hence the square root of the relative mean square error depicts the total analytical error. The paper describes the effect of using this approach on the above examples although clearly it could be applied to quality assurance and the characteriza- tion of analytical methods in general. The use of principal component analysis continues to receive attention (92/4338). In this report nine variables were reduced to four principal components accounting for 75% of the total variance in the differentiation of raw and commercial milk using trace element markers. Using a two- dimensional plot of the principal component scores it was possible to distinguish between 42 milk samples.Other workers have used a similar approach for the classification of chemical modifiers used in ETAAS (92/46 10). However the abuse of multivariate calibration has also been discussed with respect to the limitations of current techniques (92lC3709). Pitfalls to watch for include the identification of outliers the problems of using replicates and identifying truly independent samples. The use of robust statistics designed to deal with large isolated errors without the need for controversial outlier tests has also been reported (93K1606). Several other approaches have also been discussed. These include the chemometrics of fuzzy systems (93/1264) a comparison of simple factor variation Box- Wilson and simplex optimization methods (93/1189) and the use of Bayesian deconvolution (92/C38 12).This latter technique is based on recovering the most probable para- meters of a model function for a given set of data. Besides recovering the parameters another advantage of this method is that for a Lorentzian model function the amplitudes can be eliminated as a fitting parameter and back calculated thereby decreasing computational time. Monte Carlo simulation models have been employed by Guell and Holcombe (92/2056 92/4608) to investigate analyte desorption adsorption and spatial distribution in electrothermal atomizers. This work attempted to evalu- ate the general assumption that the ETAAS signal is proportional to the gas-phase distribution throughout the transient profile. Spectral line shape considerations (i.e.Voigt profile and hyperfine structure) were introduced into the Monte Carlo model to exploit the time and spatial distribution and temperature information avail- able from the simulation. In general it was found that non-isothermality did not produce spectral results notice- ably different from those observed with isothermally heated tubes and that the temperature dependent spectral changes for a non-isothermally heated furnace could be closely approximated in many cases by considering only the temperature at the centre of the tube. The use of adaptivefilters to quantify a target signal with good accuracy and precision in the presence of an interfer- ent has been discussed (93/C1385).Here the adaptive filter based on the re-calculation of the measurement variance using the observed fit residuals was used and its perform- ance characterized for a wide range of peak ratios and overlapping peaks. The study showed that information theory could be used to provide an estimate for the precision of the analysis as well as for the area under the peak corresponding to the interference signal. The use of Kalman filters which are basically recursive algorithms used to fit model parameters to measurements have also been discussed (93lC1383 931C1384). These presentations discussed the use of such filters in multi-element analysis and the role of second order adaptive Kalman filters for estimating noise processes even in the presence of an incomplete or incorrect calibration model (93K 1 384).Finally the use of knowledge-based and expert systems have been reported for a number of applications. Intel- ligent data management systems have been applied to water quality studies (93/C 1424) inorganic environmental studies (93/C 1423) method selection for AAS analysis of drugs 993/C1607) and the determination of a range of elements in waste waters by AAS (92K3700). In each case details of the database programming language file transfer and reporting facilities were discussed together with the specific requirements of each application. With respect to expert systems the use of commercial expert system shells such as Crystal KES and Leonard0 have been discussed (92/3832). This paper also discusses systems i.e. the knowledge base the inference engine and the user inter- face. The design and implementation of an expert system used to diagnose problems in AAS has also been described (931806).2. ATOMIC FLUORESCENCE SPECTROMETRY Developments in AFS are occurring chiefly in the field of laser excitation. Most analytical applications of AFS utilize hydride or cold vapour generation to separate the analyte from its matrix followed by discharge lamp excitation of fluorescence. As the AF detection process is often a minor part of those applications such reports have been reviewed laser-induced fluorescence (CW-LIF). It was shown that in these circumstances the simplistic assumption of infinite detection capability whereby every atom can be detected is untrue because the probability of false positive errors increases as the number of laser pulses increases. under the heading of Chemical Vapour Generation or in the Applications Reviews of Atomic Spectrometry Updates.2.1. Discharge Lamp-excited Atomic Fluorescence -~ The development and application of AFS has been the subject of several reviews (9213977 9311214 93/1249). Theoretical aspects of single atom detection (SAD) have been further explored by Stevenson and Winefordner (93/1960). The analysis was applied to monitoring a flow of atoms passing through a laser beam by continuous wave In the determination of Hg by CV-AFS several inteflerences in the AF process have been detected (92/3979). These effects included quenching by gases in air and gases produced by chemical reactions and scattering by dust and water vapour.Discrimination against emission by and scattering from a tungsten spiral atomizer was maximizedJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. AUGUST 1993 VOL. 8 233R by the use of light traps a special optical system for collection of fluorescence radiation a modulated light source and electronics optimized to detect the 20-50 ms atomization signal (92/4602). The instrument was evalu- ated for the determination of Pb in waste waters by non- dispersive AFS; the detection limit was 350 ng 1 - I . A modifed MIP torch similar in appearance to an ICP torch has been evaluated as an atomizer for AFS (92/C4140). High current pulse operation of an HCL was used to excite fluorescence. The detection limits reported were 2 19,0.33 0.68 10 1.1 42.6 and 6.7 ng ml-l for Ag Au Cd Cu Fe Mg Pb and Zn respectively and were similar to those of an HCL-ICP-AFS system.It was claimed that the modified MIP torch had the advantages of low cost high efficiency and improved tolerance of sample composition; aqueous samples were introduced without desolvation. The use of the ICP in conjunction with AFS has not led to many publications during the past year. The subject has been reviewed (92/2047 93/C1373) while other papers have examined the influence of organic reagents on the determination of Ca K Mg and Na (92/2422) and Ca Cd Cu Fe Mg Mn Sr and Zn (931689). As may be expected the effect of organic reagents varied with the reagent and its molecular structure. Organic solvents of moderate viscosity and volatility increased the AF signal.Two reports of studies of the application of ICP-AFS have been received. Zinc was determined in organic materials and waste water with a detection limit of 0.2 1 ng ml-l (93/6 13) and Bi Ca Cu and Si in high temperature superconductors (93/ 125 1). 2.2. Laser-excited Atomic Fluorescence Spectrometry The first applications of lasers to the excitation of atomic fluorescence were made over 20 years ago. General develop- ments in LIF over that period have been reviewed by Pfab (92/2596) while current usage of lasers in atomic spectro- scopy has been discussed by Sneddon and co-workers (92K3667 93/478) and Andrews (92/4039). Despite the established advantages of LEAFS for sensitivity specificity long linear range discrimination of signal from thermal background and the possibility of saturating the excitation transition of the analyte atom no commercial instrument has yet been offered.This absence of commercial instru- mention has been attributed to the technical demands of operating the laser system and limited wavelength range available. It has been proposed (92/C361 I ) that an inte- grated computer controlled pulsed dye-laser system could make possible the application of LEAFS to general routine analysis. An instrument incorporating laser ablation/ atomization with LEAFS has been developed (93/ 1 168). The analysis of standard samples containing traces ( 10-1-10-4 Yo) of Al Cr and Ga in silicon and Ga in indium gave results within 2 10% of the values determined by calculation and NAA. The optical characteristics of lasers for spectroscopy have been reviewed by Laserna (92/4056).One of the most tantalizing areas of development is that of solid state lasers. If such devices could be made to cover a wide spectral range while emitting a narrow spectral band and be stable and tunable then AAS and AFS would be revolutionized. Winefordner et al. have investigated the possible applica- tions of existing laser diodes (92K3665). As the laser diode can be rapidly wavelength modulated background correc- tion in both AAS and AFS can be greatly simplified. In the LEAFS determination of Rb the output wavelength of the laser was modulated to scan the analytical line (92/1987). This was achieved by modulating the current through the laser with a triangular or sinusoidal waveform.A detection limit of 0.2 ng ml-l and a linear response of up to 2.5 pg ml-l were obtained. To accommodate the wide range of intensities possible in LEAFS the range of linear response of a side-on photomultiplier was increased by approximately two orders of magnitude when it was operated in gated rather than d.c. mode (92/2756). The gating was achieved by switching dynodes 1 and 5 and produced cut-off ratios greater than 7 x lo5 with gating times of 6 ns. The gates were normally ‘off. The gating aperture was variable from 40 ns to 1.3 pus at rates of up to 10 kHz. Ng et al. (931668) have reviewed the combination of ICP atomization with laser excited fluorescence for the determi- nation of Ag Au Cu In Pb Pd Pt and Ru by atomic fluorescence and Ce Cp Dy Eu Gd Sc Sm and W by ionic fluorescence.Detection limits ranging from 0.2 ng ml-l for Sc to 364 ng ml-1 for W were reported. In another publication the same workers reported studies of the ICP-LEAF determination of Ag Au Co Cu Ni Pb Pd and Sc (9212751); the single resonance approach gave detection limits of 0.8 4.2 15 2.7 5.0,0.7 3.9 3.3 and 0.2 ng ml-l respectively and for the double resonance the limits were 1.7 6.9 530 6.9 170 30 45 29 and 13 ng ml-l respectively. Uranium isotopic abundances have been determined by ICP-LEAFS (93/518). The line pair 286.57/288.96 nm was used for excitation and fluorescence respectively and the detection limit was =2 pg ml-l. The non-resonance fluorescence determination of U in a com- plex matrix was free from spectral line interference.Electrothermal atomization for AFS continues to be the subject of active research. The topic has been reviewed by Sjoestroem (92/2545) while Omenetto (92/3069) has dis- cussed the possibility of absolute analysis. In particular it is argued that at the low levels of analytes measurable by ETA-LEAFS (ferntograms) there is a lack of CRMs and difficulty in preparing standard solutions hence absolute analysis derived from known parameters of the experimen- tal system would be advantageous. Bolshov and co-workers have published a number of papers on the application of ETA-LEAFS to the determination of toxic metals in environmental samples (93/C388). Their work has been particularly directed at measurements on snow and ice. The levels of Cd ranged from 0.1 to 3 pg ml-l and for Pb from 0.3 to 30 pg ml-’ (92/2760 92/4333 92/4601).In support of these studies Bolshov et a1 (92/3817) carried out a thorough investigation of the LEAFS determination of Cd by means of its ‘strong’ (228.802 nm) and ‘weak’ (326.106 nm) lines. The limiting process for the ‘strong’ line was scattering of the laser exciting radiation and for the ‘weak’ line it was electronic noise. Detection limits of 0.07 pg ml-l and 0.31 mg ml-l for the ‘strong’ and ‘weak’ lines respectively were achieved. Preconcentration of Cd Co Cu and Pb was necessary for the determination of those elements in sea-water by ETA- LEAFS (93/C 1470). The metals were complexed with DDC and extracted on a microcolumn packed with C18-bonded silica reversed-phase sorbent. Thallium has been deter- mined directly in solid samples of bovine liver and tomato leaves by ETA-LEAFS (92/2555).The detection limit of TI was 100 fg and the T1 content of bovine liver was 0.059 pg g-l and of tomato leaves 0.055 pg g-l. Solid sampling has also been used for the determination of P Sb Sn and Te in nickel-based alloys by ETA-LEAFS (93K1370). The results for Te were in agreement with the certified value but those for P Sb and Sn were lower than certified which was attributed to an inability to completely vaporize those elements from the matrix. Using the vacuum UV region Se in standard aqueous solutions and human blood has been determined with a 7% accuracy and a detection limit of 80 fg for a 10 pl sample (92/2085). It was found that the matrix did not interfere when Ru was determined in copper and lead alloys by vacuum ETA-LEAFS (92/2827).The system was calibrated with aqueous standards as the matrix did not interfere; the detection limit for Ru in the solid sample was 1 ng g-’.234R JOURNAL OF ANAL,YTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 Michel and co-workers have examined the feasibility of determining a range of metals and non-metals by ETA- LEAFS (931C389). By optimization of atomization temper- atures laser energy repetition rate and integration time the following detection limits were achieved for Bi Co Fe Sb and Te 30 30 25 15 and 10 fg respectively (92K3669). The determination of Cf by ETA laser-excited molecular fluorescence of indium monochloride was also studied and analysis of real samples attempted (931C34 931C 1459).High resolution excitation and fluorescence spectra were obtained and vibrational transitions associated with elec- tronic transitions assigned. The same workers have re- ported the determination of F by the fluorescence of the MgF molecule (931C 153 1). They also compared atomic and molecular fluorescence of P and PO respectively for the determination of P (93/2074). Both methods gave good agreement with certified values for P in NIST plant and biological SRMs. For PO however significant interference could be generated by cations such as Ni2+ and Ca2+. The detection limit for P by ETA-LEAFS was 8.0 pg and by ETV-laser excited molecular fluorescence was 80 pg. 2.3. Studies of Flames Plasmas and Atomic Vapours Using Laser-induced Fluorescence A technique for the detection of nitrogen atoms inflames has been described (92/2687).As the resonance lines of atomic nitrogen are in the VUV spectral region where there is strong molecular absorption in flames it was necessary to use a 2-photon excitation scheme with near-IR detection. The interpretation of results was complicated by photodis- sociation of nitrogen-containing molecules photochemical effects molecular absorption stimulated emission and gas mixing. It was concluded that these complications required further investigation before the technique could be used to promote the understanding of the chemistry of nitrogen in flames. The OH number density in high pressureflames (up to 12.3 atm) (1 atm= 101.325 kPa) has been measured by Carter et al. (931422) using laser saturated fluorescence.Results agreed with those obtained by absorption up to 3.1 atm. At higher pressures correction for quenching was required. The collisional quenching rate of H atoms in a low pressure flame has been measured by time resolved two- photon-excited fluorescence (9214050). Excitation was at 205 nm with 50 ps pulses generated by the frequency doubling in a dye laser system of pulses from a Nd:YAG laser. An interference filter was used to select the fluores- cence radiation at 656 nm. Fluorescence dip-spectroscopy has been used to study collisional rate exchanges between excited levels in both an air-C2H2 flame and in an ICP (931C1535). Though a model of fluorescence dip based on steady-state considerations has been shown to be in good agreement with experimental results for both Cu and Ag it is now being replaced by theories using a density matrix approach for estimation of collisional coupling constants. Processes in the ICP have been studied by LIF.A power modulated ICP was investigated as an atom source for the LEAFS determination of Fe (9311955). It was found that modulation of the plasma led to decreased background signal with the Fe fluorescence signal remaining constant for 1.4 ms after the complete interruption of power to the ICP indicating that there was a stable population of free atoms in a chemically inert environment during the plasma- off cycle. The detection limit was 5 pg 1-’ of Fe. Matrix egects found in ICP-MS have been investigated using laser- induced strontium ion-fluorescence measurements (9212749).The effects of nebulizer gas flow rate and applied power in the presence and absence of the interfering matrix were examined. Significant matrix effects appeared to originate in the plasma but were not mass dependent. Analyte ICP-MS signals increased near vaporizing particles and were depressed near incompletely desolvated droplets. Together these effects led to fluctuations in the output signal of the instrument. Laser induced ion-to-atom fluores- cence intensity ratios have been used together with the Burton-Blades model to estimate electron number densities and temperatures in the neighbourhood of vaporizing droplets and particles (93K1378). The presence of either a droplet or particle produced similar falls in temperature (from 8500 to 6200 K) and in electron number density (from 3 x 1015 to 5 x 1013 ~ m - ~ ) .The signal enhancement was attributed to a large local analyte-ion concentration near particles and the depression to reduced efficiency of ion transfer from near a droplet to the MS detector. The mechanisms of formation of magnesium mono- fluoride molecules from NaF and Mg(N03)2 solutions in the gas phase of ETA-AAS has been investigated by laser excited molecular fluorescence (931C 1520). It was shown that the formation of magnesium monofluoride in the gas phase was a result of interaction of free Mg atoms from MgO with F from MgF2. The addition of a barium modifier increased the magnesium monofluoride signal by synchronizing the vaporization of fluoride and magnesium.Two step laser- inducedfluorescence of Hg in both a graphite furnace and an Hg vapour filled cell has been studied by Resto et al. (931C 1455). A strong amplified stimulated emission (ASE) (A= 546.1 nm) was found in the zone of intersection of the two exciting lasers (Al =253.7 nm,A2=435. 1 nm). The ASE signal showed a highly non-linear dependence on Hg number density and ‘pumping’ laser energy. The signal was not detectable below 1013 Hg atoms cm-3 in the vapour cell or 2 ng of Hg in the graphite furnace. Laser generated plumes have been studied using excita- tion of fluorescence as the means of determining the analyte distribution in the plume (931C1557). Laser-induced fluo- rescence was used to examine populations of neutral atoms of Zr released by a zirconium filament and of U vaporized from a tungsten filament (9311069).Particular care was taken to minimize the background signal. No neutral atoms were detected by fluorescence though mass spectroscopic data indicated that it should have been possible. 2.4. Coherent Forward Scattering (CFS) (Atomic Magneto- optical Rotation Spectrometry) The advantages and limitations of CFS have been reviewed by Hirokawa (9212501) and Herman (931C104). When light sources of low brightness are used e.g. hollow cathode lamps there is no advantage in the S/N of CFS compared with Zeeman-effect AAS. Sources of noise in a Faraday configuration air-C,H flame atomization CFS instrument have been examined (9213836). The dominant source of noise was found to be fluctuation noise arising in the atomic vapour.Photon noise proportional to the square root of the signal intensity from the HCL was also detected. A continuum light source combined with high quality polariz- ers (rejection ratio 107:l) was found to be suitable for simultaneous multi-element analysis and for the determina- tion of highly concentrated elements using weak atomic lines. When a laser is used as the light source highly selective isotope analysis is possible (931C104). The CFS effect may also be used as aselectiveJilter for transmitting the resonance spectrum of elements excited in an atomic vapour (9212501). Laser produced aerosols were used in the determination of Pb in brass by ET-CFS (9214661). The aerosol was electrically charged by a-irradiation followed by electrostatic collection on the interior of the graphite tube furnace.With negative polarity (1000 V) on the tube the aerosol deposi- tion efficiency was lo3-fold greater than that when no field was applied. By appropriate choice of the number of laser ablation pulses and analytical spectral line a wide range of concentrations and elements could be accommodated.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 3. LASER ENHANCED IONIZATION 235R Several groups world-wide continue to investigate the potential of LEI for the analysis of real samples and as a tool in other spectroscopic studies. The level of activity is modest and comparable with that reported in last year’s review. Laser-enhanced ionization is a very sensitive technique for trace element analysis but this is greatly reduced when measuring samples containing large amounts of easily ionized elements.The practical scope of LEI and means for overcoming its limitations have been studied by Axner et al. (9212139). The interference of the OH radical on the LEI determination of trace elements in the air-C,H using the UV spectral region has been examined (93/676). The OH band at 283 nm interferes seriously with the LEI determina- tion of Pb using the 283.305 nm line. The detection limits by LEI of Ce Lu and Sm in pure solutions were determined by Zhang and co-workers. Using a tunable dye (Rhodamine 6G) laser pumped with a YAG laser they achieved detection limits of 4 ng ml-I of Ce and 8 mg ml-l of Lu (92/2243) and 2 ng ml-I of Sm (92/3276). Laser-enhanced radiation has been applied to the analysis of high purity materials by Chekalin and Vlasor (92/2 135 92/4623).The sample in either liquid or powder form was pulse evaporated from an electrically heated graphite rod into a flame. Calibration was by aqueous standards or standard additions. The detection limit for In in Cd-Hg-Te alloys was 1 x ppm by solution methods and 1 x ppm when the solid was used; for Cu in germanium the detection limits were higher. Electrothermal vaporization into a fuel-lean air-C2H2 flame was used for the determina- tion of T1 in water by LEI (93/559). To eliminate interfer- ence by EIE T1 was extracted into 2,6-dimethyl-4-hepta- none giving a 200-fold concentration factor and a detection limit of 43 ng I-’. Laser induced ionization of atoms has been detected in a power modulated ICP (93/1954).The measurement was made 1.4 ms after the complete interrup- tion of the 40 MHz power to a 400 w plasma. Detection limits of 80 pg 1 - I of Fe and 20 pg 1-1 of Ga were achieved. Compared with the flame however the detection limits were up to three orders of magnitude worse. Laser-enhanced ionization can also be used as a sensitive detector ofphotons and as a means for measuring flame temperature. The former application has been developed as a resonance ionization detector based on the two-step LEI of Mg in a miniature air-CzHz flame (=2 mm diameter) and applied to the detection of weak Raman scatter of carbon tetrachloride chloroform and dimethyl sulfoxide (9214563). The quantum eficiency of Mg vapour in the air-CzH flame as a photon detector was examined theoreti- cally and experimentally by Omenetto et al.(92/4600). It was concluded that ( i ) in the case of collisional ionization theoretically the quantum efficiency should not be less than 0.7 but experimental evidence is lacking; (ii) for photoioni- zation quantum efficiency can be deduced from fluores- cence measurements and an efficiency close to unity should be possible with a sufficiently high ionization rate; and ( i i i ) a conventional flame is not an ideal detector owing to quenching a thermal argon reservoir would be better. Gallium was used as the ionizable element in experiments to determine the temperature of an air-C2H2 frame by means of LEI (92/2632). A three-level model of rate equations was developed based upon the Boltzmann popu- lation of the ground fine structure of Ga.A temperature of 2512-t 50 K was deduced and compared well with the mean value (2483 _+ 12 K) of a number of published AA AE and AF methods. LOCATION OF REFERENCES The full list of references cited in this Update have been published as follows 9211973-9212589 J. Anal. At. Spectroin. 1992 7(4) 173R-213R. 9212590-92lC3494 J. Anal. At. Spectrom. 1992 7(5) 247R-277R. 92lC3495-9214073 J. Anal. At. Spectrom. 1992 7(6) 329R-348R. 9214074-9214734 J. Anal. At. Spectrom. 1992 7( 8) 389R-4 1 1 R. 93ICl-93lC997 J. Anal. At. Spectrom. 1993 8( l) 45R-78R. 931998-93lCl354 J. Anal. At. Spectrom. 1993 8(3) 137R-149R. 93lC1355-9312093 J. Anal. At. Spectrom. 1993 8(4) 169R-194R. Abbreviated forms of the literature references quoted (excluding those to Conference Proceedings) are given on the following pages for the convenience of the readers.The full references names and addresses of the authors and details of the Conference presentations can be found in the appropriate issues of JAAS cited above. Abbreviated List of References Cited in Update 9211112. Nucl. Instrum. Methods Phys. Res. Sect. B 1990 B52 357. 9211986. Spectrochim. 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ISSN:0267-9477    

DOI:10.1039/JA993080197R

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

238R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 Glossary of Abbreviations Whenever suitable elements may be referred to by their chemical symbols and compounds by their formulae. The following abbreviations are used extensively in the Atomic Spectrometry Updates. a.c. AA AAS AE AES AF AFS AOAC APDC ASV BCR CCP CMP CRM cv cw d.c. DCP DDC DMF DNA ECD EDL EDTA EDXRF EIE EPMA ETA ETAAS ETV EXAFS FAAS FAB FAES FAFS FI FPD FT FTMS GC GD GDL GDMS Ge( Li) HCL h.f. HG HPGe HPLC IAEA IBMK ICP ICP-MS ID alternating current atomic absorption atomic absorption spectrometry atomic emission atomic emission spectrometry atomic fluorescence atomic fluorescence spectrometry Association of Official Analytical Chemists ammonium pyrrolidinedithiocarbamate anodic-stripping voltammetry Community Bureau of Reference capacitively coupled plasma capacitively coupled microwave plasma certified reference material cold vapour continuous wave direct current d.c.plasma diet h yldi thiocarbamate N,N-dimethylformamide deoxyribonucleic acid electron capture detection electrodeless discharge lamp ethylenediaminetetraacetic acid energy dispersive X-ray fluorescence easily ionizable element electron probe microanalysis electrothermal atomization electrothermal atomic absorption electrothermal vaporization extended X-ray absorption fine structure flame AAS fast atom bombardment flame AES flame AFS flow injection flame photometric detector Fourier transform Fourier transform mass spectrometry gas chromatography glow discharge glow discharge lamp glow discharge mass spectrometry lithium-drifted germanium hollow cathode lamp high frequency hydride generation high-purity germanium high-performance liquid chromatography International Atomic Energy Agency isobutyl methyl ketone (4-methylopentan-2- inductively coupled plasma inductively coupled plasma mass spectrometry isotope dilution (ammonium pyrrolidin-1-yl dithioformate) spectrometry spectroscopy one) IR IUPAC LA LC LEAFS LEI LMMS LOD LTE MECA MIP MS NAA NaDDC NIES NIST NTA OES PIGE PIXE PMT PPb PPm PTFE QC r.f.REE(s) RIMS RM RSD SIB SEC SEM SFC Si(Li) SIMAAC SIMS SIN SR SRM SSMS STPF TCA TIMS TLC TMAH TOP0 TXRF u.h.f. uv VDU vuv WDXRF XRF infrared International Union of Pure and Applied Chemistry Laser ablation liquid chromatography laser-excited atomic fluorescence laser-enhanced ionization laser-microprobe mass spectrometry limit of detection local thermal equilibrium molecular emission cavity analysis microwave-induced plasma mass spectrometry neutron activation analysis sodium diethyldithiocarbamate National Institute for Environmental National Institute of Standards and nitrilotriacetic acid optical emission spectrometry particle-induced gamma-ray emission particle-induced X-ray emission photomultiplier tube parts per billion parts per million polytetrafluoroethylene quality control radiofrequency rare earth element(s) resonance ionization mass spectrometry reference material relative standard deviation signal to background ratio size-exclusion chromatography scanning electron microscopy supercritical fluid chromatography lithium-drifted silicon simultaneous multi-element analysis with a continuum source secondary ion mass spectrometry signal to noise ratio synchrotron radiation Standard Reference Material spark source mass spectrometry stabilized temperature platform furnace trichloroacetic acid thermal ionization mass spectrometry thin-layer chromatography tetra methlammonium hydroxide trioctylphosphine oxide total reflection X-ray fluorescence ultra-high frequency ultraviolet visual display unit vacuum ultraviolet wavelength dispersive X-ray fluorescence X-ray fluorescence spectrometry Studies Technology

ISSN:0267-9477    

DOI:10.1039/JA993080238R

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

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ISSN:0267-9477    

DOI:10.1039/JA993080239R

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

673 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 Performance Characteristics of a Glove Box Inductively Coupled Plasma Mass Spectrometer for the Analysis of Nuclear Materials Jose lgnacio Garcia Alonso Dominique Thoby-Schultrendorff Bruno Giovanonne and Lothar Koch Commission of the European Communities Joint Research Centre Institute for Transuranium Elements Postfach 2340 76125 Karlsruhe Germany Helmut Wiesmann Spectrotec GmbH Mainzerstrasse 46 64572 Buttelborn Germany A commercial inductively coupled plasma mass spectrometer (Elan 250) was modified in order to analyse nuclear materials in a glove box. The nebulizer plasma torch and sliding interface are situated inside the glove box while the mass spectrometer and associated electronics are outside. The sensitivity of the modified instrument is slightly reduced compared with the original owing to a flange that separates the mass spectrometer from the vacuum interface.This has modified the original distance between the skimmer cone and the ion lens system. The plasma torch is mounted in a fixed position and the load coil is now separated 25 mm from the tip of the sampling cone. Optimum plasma operating conditions stability of the signal and isotopic ratios levels of oxide and hydroxide polyatomic ions were evaluated in the modified instrument for selected fission products and actinides. The effect of the ion lens settings on sensitivity and mass discrimination were studied in detail. Interference effects due to heavy matrix elements (U and Pu) were also studied.Keywords Inductively coupled plasma mass spectrometry; glove box; nuclear material; performance characteris tics The inductively coupled plasma mass spectrometer is an analytical tool which a priori would be ideally suited for the analysis of materials of nuclear origin. The elemental and isotopic capabilities of inductively coupled plasma mass spectrometry (ICP-MS) could be fully applied to those materials having non-natural isotopes and/or non-natural isotopic abundances. The low detection limits provided by the technique allow the use of very dilute samples with reduced radiation risks for the operator compared with other atomic spectrometric techniques (e.g. ICP atomic emission spectrometry and atomic absorption spectrome- try) used currently in the nuclear field.' The ICP-MS technique can be used to determine both stable and radioactive nuclides simultaneously and can discriminate between natural and artificial sources by the use of isotopic abundances which is an added advantage over other optical spectroscopic techniques.Also the method of isotope dilution can be applied and in many cases natural elements can be used as spikes (e.g. for the analysis of fission products) because of the different isotope abun- dances in the sample. In spite of all these potential advantages very few reports have been published on the use of ICP-MS in the nuclear field.2-13 Only the analysis of natural impurities in non-irradiated uranium 0xide~9~ and zirconium alloy^^-^ by ICP-MS have been reported. Non-natural isotopes have been analysed by ICP-MS in environmental ~amples,~-~O which shows the suitability of the technique for the analysis of long-lived radionuclides compared with radioanalytical techniquesg The use of an ICP mass spectrometer installed in a glove box has also recently been described by Crain and GallimorelI for the analysis of Tc in nuclear materials.Smith et a1.12 compared the intrinsic sensitivity of ICP-MS and radiochemical methods for the determination of radionuclides. It was demonstrated that for half-lives longer than a few hun- dred years ICP-MS can provide lower detection limits than the corresponding counting technique. The ICP-MS technique has been applied recently for the determination of traces of Np in enriched U solutions.13 The tailing of the 238U peak at the low mass side requires separation of U and Np for the determination of ppb levels of Np in U solutions. Nuclear materials to be analysed for trace elements and isotopes include mainly spent nuclear fuel (fission products and actinides) fresh fuels (natural element impurities) input and output solutions from reprocessing plants (minor actinides) high level waste from reprocessing and leachates of spent fuel and high level waste glasses.The presence of a heavy actinide matrix element (U Pu) has to be taken into account for the development of analytical methodologies for ICP-MS because of possible matrix interferences (space- charge effects). For the analysis of these materials other practical difficulties which arise from the radioactive nature of the sample have to be overcome.Firstly the operator has to be protected from the material which means that the use of glove boxes (alpha beta protection) and/or hot cells (alpha beta gamma protection) with master-slave manipulators is a necessity. Secondly in order to avoid contamination of the working area the analytical instruments have to be modified in order that containment is assured and no radioactive material is leaked either to the laboratory or to the environment. Whole instruments cannot be introduced into a glove box because electronics are very sensitive to radiation. In practice electronics and parts that might need special maintenance are kept outside of the glove box and only the samples and the corresponding sampling stage are contained in the box. For atomic spectrometry instruments only the atomization source (plasma graphite furnace etc.) is installed inside the glove box and the rest of the instrument remains outside.For optical instruments con- tainment is easily achieved by the use of optical lenses or fibres built into the walls of the glove box. However when MS measurements are made an opening has to be provided for the ions and absolute containment is no longer achieved. For ICP-MS measurements modification of the commercial instruments is necessary to minimize contami- nation risks. In this paper a modified ICP-MS instrument working since 1988 in a glove box and its performance characteristics for the analysis of radioactive materials of nuclear origin is described.674 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 Experimental Instrumentation The ICP-MS instrument used is an Elan 250 from SCIEX (Canada). Fig. 1 shows a schematic diagram of the glove box in which the instrument is installed. The glove box is provided with an extraction system cooling water and filters for all argon streams. Absolute filters (>99.99% efficiency) are situated both inside and outside of the glove box which is kept at a lower pressure than the exterior (20 mm water column). The peristaltic pump nebulizer assembly plasma torch and sliding interface are situated inside the glove box. The interface with the sampling and skimmer cones is mounted on the stainless- steel left wall of the glove box. The interface is evacuated by an additional rotary pump of the same type as the original one of the instrument which is now used only for pumping down and cryo-cleaning.Absolute filters are installed in the vacuum line inside the glove box to prevent any radioactive material from the plasma con- taminating the primary pump. Owing to security require- ments in the box the load coil had to be mounted in a fixed position at a distance of 25 mm from the sampling cone which is suitable for long ICP torches (the usual distance for the Elan 250 is 15 mm). The plasma off-gases (exiting the plasma) are cooled in a radiator-type water cooling system above the plasma torch before being evacuated through filters to the ventilation system of the laboratory. All vacuum pump outlets are also connected to the ventilation system. Pressure water and tempera- ture detectors are installed in the box.The ICP torch is protected by a moving stainless-steel cover. In order to facilitate maintenance the nebulizer and spray chamber are separated from the torch by a 20 cm long glass tube (1 0 mm i.d.) provided with an additional tangential argon flow (about 0.1 1 min-l) in order to minimize deposition of spray droplets on the wall (Fig. 1). Fig. 2 shows a detail of the connection of the glove box to the quadrupole mass spectrometer. The interface had to be separated from the mass spectrometer by a flange which connects the glove box to the MS housing with a V-type retainer coupling. In case of maintenance the mass spectro- meter could be easily separated from the glove box which with the interface closed remains gas tight.The use of this flange increased by 15 mm the original distance between the skimmer cone and the ion lens assembly in the mass A nn n n n Fig. 1 Schematic diagram of the ICP-MS installed in the glove box A channel electron multiplier; B ion deflector; C quadrupole; D cryoshells; E ion lens; F sliding interface; G r.f. induction coil; H plasma torch; I off-gas cooler; J absolute filters off-gas; K absolute filters sliding interface; L cooling water in-out; M glove box manometer; N nebulizer and spray chamber; 0 peristaltic pump; P liquid sample; Q absolute filters inlet; and R glove box frame A Fig. 2 Detail of the connection between the mass spectrometer and the glove box (scale not accurate) A mass spcctrometer housing; B two-piece flange; C V-retainer coupling; D stainless- steel wall of glove box; € photon stop; F original connection piece to mass spectrometer housing showing O-rings; G sliding interface (horizontal movement); H skimmer cone; and I sampling cone spectrometer. The analytical effect of this flange is a reduction of the ion transmission compared with the original instrument.In the interior of the glove box the interface housing is installed as in the original instrument but in a horizontal configuration and is moved by pneuma- tic activation. The series of O-rings installed in the interface and flange assure that no radioactive contamination can leak outside of the instrument. Maintenance An opening for the ion beam must exist during the analysis by ICP-MS. This means that the ions that enter the interface and mass spectrometer do cause radioactive contamination.Most of the contamination is confined to the interface itself which is situated inside the glove box but some reaches the mass spectrometer. Catastrophic failure of the channel electron multiplier (CEM) in December 1990 required the MS housing to be opened in order to check for contamination in the vacuum chamber. Firstly argon was connected to the spectrometer in order to bleed the chamber and passed through a filter in the outlet of the vacuum chamber. The filter was measured for alpha and beta contamination and no measurable contamination was found. With the sliding interface closed the V-retainer coupling was removed from the flange (Fig. 2) the glove box was separated from the mass spectrometer and the housing could be removed.Plastic surgical gloves and gas masks were used during all the maintenance work. Critical sections like the interface outlet cryo-shells quadrupole and CEM housing were checked for contamination by wiping tests. Light contam- ination was only found at the interface outlet where the photon stop is located (Fig. 2). Finally the CEM was replaced satisfactorily. In March 1992 contamination on the helium line was observed which created malfunctioning in the cold head. The cold head was decontaminated the adsorber changedJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 675 and new high purity helium introduced into the system. No radioactive contamination was found in any part of the cryo-pump which shows the good performance of this type of pump for radioactive applications.No contam- ination was found in the vacuum oil for the primary pumps. Operating Conditions The plasma and quadrupole operating conditions used are summarized in Table 1. Different radiofrequency (r.f.) power and nebulizer flow settings were used to test M+ MO+ and MOH+ signals. The optimum plasma com- promise conditions are those listed in Table I and are similar to those proposed by the manufacturer. Different ion lens settings were studied as shown in Table 1. The optimization procedure proposed by the manufacturer (optimum signal for lo3Rh and similar signals for 'Li and *OSPb) (a) was compared with single element optimizations for lo3Rh (b) and *W (c). Sensitivity curves and mass discrimination errors were evaluated for various ion lens settings.The measurements were made in scanning mode low resolution 1 point per peak and 1 s integration time. Generally five scans were run for each experiment and the data transferred to a PC for evaluation using an electronic spreadsheet. Reagents and Materials Used Stock solutions of natural elements were obtained from Spex (Grasbrunn Germany) as 1000 ppm standards and diluted as necessary with 1% nitric acid. Neptunium-237 and 239Pu standards were obtained from Los Alamos National Laboratory (NM USA) as the metal or oxide and dissolved in nitric acid to prepare stock solutions. These solutions were standardized by titrationI4 and handled in glove boxes. Pure Am and Cm oxides were obtained from the Lenin Research Institute for Atomic Reactors (St Petersburg Russia) and dissolved also in nitric acid.Nitric acid was Merck Suprapur (Darmstadt Germany) and Milli- Q water (Millipore Eschborn Germany) was used through- out this work. Inactive standards were prepared by simple dilution in acid-washed calibrated flasks. Radioactive samples and standards were diluted by mass in the glove box or in the Table I Operating conditions R.f. power/W Reflected power/W Argon outer gas flow ratell min-' Argon intermediate gas flow Argon nebulizer gas flow ratell m h - ' Sample uptake rate/ml min-I Nebulizer type Spray chamber Load coil/sampler cone distancelmm Interface pressure/Pa Quadrupole working pressure/Pa Sampler and skimmer cones rate/l min-I 1200 t 5 12 1.4 0.86 (30 psi) 1 Meinhard Scott type double pass 25 (fixed) 266.64 266.64~ Nickel Settings (O/o range) Lens Range/V (a) (b) (4 Bessel box B 0 +10 39 70 72 Bessel box P 0 -60 14 15 15 Einzel lens E l 0 -20 62 25 14 Photon stop S2 0 -20 36 10 25 hot cell facility.Polyethylene bottles (10 or 20 ml) were used for all radioactive material. Results and Discussion In order to study the performance of the modified instru- ment for the analysis of nuclear samples a series of tests were carried out including sensitivity stability of signals and isotopic ratios suitable internal standards optimum plasma operating conditions oxide and hydroxide ion levels mass discrimination errors and matrix interferences due to heavy elements. Sensitivity and Stability For the sensitivity and stability studies a solution contain- ing 100 ng ml-' of Li Cu Rh Cd Pb and U was nebulized for 2 h and the intensity values for each isotope measured every 5-10 min approximately (n= 19).The results ob- tained for the raw intensities can be compared with similar unmodified Elan 250 instruments using the same rec- ommended plasma operating conditions and similarly optimized ion lenses [settings (a) in Table 13. The results obtained which appear in Table 2 show that the intensity counts are lower by a factor of 2-10 compared with other Elan 250 instruments installed in Germany during 1986- 1988 depending on the particular element and instrument considered. This reduction in sensitivity must be due to the change in the original distance between the skimmer cone and the ion lens assembly by the use of the flange depicted in Fig. 2.However the background counts were not affected so an increase in the detection limits is observed in the modified instrument. The relative standard deviations (RSDs) using each element in solution as internal standard (IS) for the other elements were between 2 and 3%. As expected lower values were found when the mass of the IS was close to that of the other element. Rhodium-103 as IS seemed to give better results than the other elements as far as RSD is concerned. The RSD of the Cu (65:63) Cd (1 12 1 14) and Pb (206:208) isotopic ratios ranged between 1.7 and 1.9% for the 100 ppb standard after 2 h of measurement owing to the poor counting statistics. Significant differences between the expected and observed isotopic ratios were also found which demonstrates the existence of mass discrimination errors.Plasma Operating Conditions Plasma operating conditions were studied for the elements discussed earlier also using configuration (a) (Table 1) of the Table 2 Comparison of sensitivity for different Elan 250 instru- ments Raw intensity*/ions s-' Other instrument* Isotope This instrument? 'Li 2 5 32( 5.3) 12500 8500 15380 63CU 472 5(4.3) 9500 17000 31890 Io3Rh 1258 l(4.8) - - 125400 '14Cd 2193(4.9) 7000 9000 - 208Pb 39 15(4.5) 12000 12000 18820 238U - - - 8 2 7 5( 4.7) * Obtained for 100 ppb solutions of the corresponding elements. 7 Values in parentheses are RSD(%) for 2 h of measurement. $ Elan 250 installed in Germany during 1986-1988 by H. Wiesmann. The data are from performance tests after installation.676 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 3000 I 1 2500 2000 1500 1000 500 0 A 12000 fn fn 0 3 8000 c .- fn C c 4000 0 4000 3000 2000 1000 18 22 26 30 34 6000 5000 4000 3000 2000 1000 0 3000 2500 2000 1500 1000 500 0 8000 6000 4000 2000 0 I (4 I I ~ B A 18 22 26 30 34 Nebulizer pressure/psi Fig. 3 Influence of plasma operating conditions on the response for (a) 'Li; (6) 63Cu; (c) lo3Rh; (d) lI4Cd; (e) zOsPb; and cf) 238U. A nebulizer pressure of 30 psi ( 1 psi=6895 Pa) corresponds to 0.86 1 min-' Ar. R.f. power A 900; B 1000; C 1100; D 1200; E 1300; and F 1400 W ion lenses. The results obtained for the influence of r.f. power on the optimum nebulizer pressure are shown in Fig. 3. These results are comparable to previously published data15J6 showing the interdependence of applied power and nebulizer flow rate.However there is a clear mass depen- dent difference going from Li to U. In the case of Li [Fig. 3(a)] the maximum intensity in the nebulizer pressure curve for each r.f. power setting increased drastically with increasing r.f. power so no optimum conditions for Li could be found. In the case of U [Fig. 3 0 1 the maximum intensity is independent of the r.f. power setting above 1 100 W. For the other elements intermediate values were found betwen these two extremes. Similar results have been obtained p r e v i o u ~ l y ~ ~ ~ ~ ~ for the Elan 250 using both the old and improved ion lens system. Two effects seem to play a role in the optimization of the plasma parameters.Firstly the r.f. applied power has to be balanced with the nebulizer flow in order to obtain maximum ionization at the tip of the sampler cone (interdependent effect) and secondly the change in the plasma applied power could modify the kinetic energy of the ions as they enter the interface. Fulford and DouglasI7 reported that the kinetic energy of the ions depends on their mass on plasma space potential and possibly on ion beam space charge. They suggested a value of 2 eV for the plasma potential which should be added to the kinetic energies as determined by the supersonic expansion. This kinetic energy appeared to be unaffected by changes in plasma operating ~0nditions.l~ Based on the results obtained in the present study for the instrument used here the kinetic energy of the ions seems to be affected by increasing applied power but only to a limited extent.However the relative change in kinetic energy would be greater for lighter than for heavier elements and that would affect ion transmission of lighter elements preferentially; increasing the kinetic energy of lighter ions will increase their transmission through the ion lens system which is optimized for heavier ions (higher kinetic energy). This effect will be less noticeable for heavier ions as their kinetic energy is governed mainly by supersonic expansion. Fur- ther experiments on ion kinetic energy measurements such as those of Chambers and Hieftje,l8 for different plasma applied powers are needed to prove this assumption. The influence of operating conditions on the levels of oxide hydroxide and doubly charged ions was studied using Zr La Nd Th U Np Pu Am and Cm as test elements.The first three elements were selected because of their high fission yield which can produce isobaric inter- ferences on other MO+ or MOH+ lower yield isotopes. The levels of oxide and hydroxide ions for transuranium elements are reported here for the first time. Peaks for hydrides (MH+) were not detected for the actinides. The ion lenses used were those of configuration (b) (fission products) and (c) (actinides) in Table 1. Fig. 4 shows the results obtained for La Nd and Zr at 1200 W forwardJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 677 ( b ) 0.05 1 0*04 t 0.03 2 0 E 0.02 0.01 Nd 0 ' I 1 I I I I I 0.05 ( C) 0- - I I - A 20 22 24 26 28 30 32 34 36 Nebulizer pressu re/psi Fig.4 Levels of M+ MO+ and MOH+ for Zr La and Nd for different nebulizer pressures at 1200 W forward power. (a) M+ raw intensities for the ions shown at the 2 ppm levels. (6) Intensity ratios MO+:M+ 106:90 155 139 and 158 142 for Zr La and Nd respectively. (c) Intensity ratios MOH+:M+ 109:92 156 139 and 163 146 for Zr La and Nd respectively power and different nebulizer pressures. As can be ob- served levels of oxides and hydroxides are below 1 O/o under the standard operating conditions (Table l) which for La and Nd are much lower than previously published results for the Elan 250.19320 The results obtained for the actinides are summarized in Table 3. As can be seen the levels of oxide are reduced drastically from Th to Cm.The levels of hydroxides are lower than 0.05% in all cases. The use of a 25 mm distance between the load coil and the sampler might be responsible for the low oxide levels observed. The determination of 239Pu in the presence of high amounts of 238U can be hindered by the presence of UH+ isobaric interferences. In the instrument used here the 238UH+ peak is less than 0.005°/6 of the 238U+ peak. Effect of Ion Lens Settings on Mass Discrimination The determination of the isotopic abundances of the elements produced by fission in nuclear samples is of great importance in nuclear research in monitoring reactor performance. Traditionally this is carried out by thermal ionization mass spectrometry (TIMS) after chemical separ- ation of the elements.The ability of ICP-MS to provide Table 3 Levels of oxides and hydroxides for actinides under standard operating conditions Element MO+:M+ MOH+:M+ Th 0.026 - U 0.016 - NP 0.0 12 t 0.000 5 Pu 0.005 t0.0005 Am 0.00 1 t0.0005 Cm 0.002 <0.0005 quick and reliable isotopic information for most of the fission products and actinides could provide a new method for this type of study. In order to investigate the precision and accuracy achievable by ICP-MS in the determination of isotope abundances a solution containing natural Li B Mg Ti Cu Rb Mo Sn Ba Nd Eu Gd Yb W Pt Ir T1 and Pb (all 1250 ng ml-l in order to improve counting statistics) along with solutions of certified U isotopic abundances [National Bureau of Standards (NBS) (now National Institute of Standards and Technology (NIST) U350 U500 and U9001 and Pu (in-house standard ana- lysed by TIMS) were tested for mass discrimination errors.Three different ion lens settings were used in the measure- ments [configurations (a)-(c) in Table I] under the standard plasma operating conditions. A series of five scans with 1 point per peak and 1 s integration time per point were measured. Systematic differences between the experimental and theoretical isotope ratios that depended on the ion lens settings were observed. Longerich et alto showed that mass discrimination errors were proportional to the mass differ- ence between the two isotopes used to calculate the ratio. The same results were observed by us for polyisotopic elements but the slope of the error curve was different for different mass ranges and seemed to be independent of the element considered for elements having similar mass. The relative error of the isotopic ratios could be expressed as where IRexg and IRthm are the observed and theoreticalt1 isotope ratios between the isotope of mass M and the isotope of mass M + M respectively and K is the mass discrimination factor.If the expression is transformed to and the K value is calculated for all elements and isotopes present in the solution tested the variation in K for the entire mass range is obtained. The mass discrimination factor K indicates the relative error produced in the measurement of isotopic ratios per mass unit of difference between the isotopes considered. For our calculations the isotopic ratios were always referred to the main isotope for each element and the K values plotted versus the mass of the less abundant isotope.The results obtained for the three ion lens configuration studied are illustrated in Fig. 5. As can be observed in all cases there is a trend of negative mass discrimination errors for the light elements and positive errors for the heavy elements depending on the ion lens configuration used. When the ion lens optimization recommended by the manufacturer (maximum signal for Rh and similar signals for 'Li and 208Pb) is followed mass discrimination errors are important for the actinides [Fig. 5(a)]. When optimizing only for Rh optimum settings for the Besel box B lens and the Einzel lens El change dramatically as can be seen in Table 1. Under those conditions mass discrimination errors increase for elements below mass 100 but decrease for those above that mass.678 4 - JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL.8 (a) 0.08 -0.08 1 I 1 - ( a ) rn 0.04 1 3 140 100 - e 0 0 60- 20 0 . I - .rr. .. La Nd E~ -. -'+-= *.- Sr Mo Rh Pd - I I I I I I 1 0.08 1 0 50 100 150 200 250 m/z Fig. 5 Variation of the mass discrimination factor K between B and Pu for the different ion lens settings (a) (b) and (c) from Table 1 Finally when optimizing only for U mass discrimination errors are eliminated for the actinides but aggravated for the middle of the Periodic Table. The determination of correct isotopic abundances for fission products and actin- ides is strongly influenced by the ion lens settings employed.In order to clarify the role of the ion lenses in mass discrimination the raw intensity data have been converted into ions s-' per pmol of each isotope taking into account the elemental concentration in the solution the atomic mass of the considered isotope and its known isotopic abundance. The so-called molar sensitivity curve for the different ion lens configurations can be seen in Fig. 6. Note that no ionization corrections were taken into account and that affects the response for W Ir and Pt principally. As can be observed there is not a uniform response for all isotopes and elements. Light elements (Li B Mg etc.) show in all cases a much lower response than heavier elements. The maximum sensitivity and its location on the response curve depends on the ion lens used.Also for isotopes of the same element increasing or decreasing response can be obtained which explains the sign and extent of the mass discrimination factors observed. In Fig. 6(a) the slope of the sensitivity curve is lower than in Fig. 6(b) and (c) and hence mass discrimination errors are smaller. For Pu a decrease in sensitivity is observed in Fig. 6(a) and (b) while constant values are obtained in Fig. 6(c) where the slope of the sensitivity curve is steep for the middle of the Periodic Table. The molar sensitivity curves of Fig. 6 show that ion transmission and/or detection for the modified Elan 250 is strongly mass dependent which is also a characteristic of most ICP-MS instruments where the ion kinetic energy is obtained only by supersonic expansion of the plasma gases (i.e. no accelerating electrodes are present). For the analysis of fission products in spent fuel the ion Yb Pu Sn M~ # Eu Ir 5 t Ti Cu I 0 50 100 150 200 250 mlz Fig. 6 Molar sensitivity curves for the different ion lens settings (a) (b) and (c) from Table 1 180 t Fig. 7 Influence of 500 ppm of U on the response for selected fission products. All isotopes of the elements were considered lenses used were those of configuration (b) (Table I) which gave adequate sensitivity [Fig. 6(b)] and constant mass discrimination errors [Fig. 5(b)] for the range to be explored [note that the sensitivity curve in Fig. 6(b) can be assumed linear between 80 and 160 u]. Actinides at low concentra- tions were analysed using the lens optimized for U which gave best sensitivity and minimum mass discrimination.Future reports will show examples of application to various nuclear samples. Matrix Interferences Interferences from heavy elements (U and Pu) were evaluated for the analysis of natural element impurities fission products and other actinides. The effect of levels of U up to 500 ppm on the signal was studied for selected fission products covering the mass range 80- 160 u. Higher concentrations of U were not evaluated as the radiation679 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1993 VOL. 8 I 180.00 140.00 1' % 2 20.00 B ~ 0 40 80 120 160 200 240 mlz Fig. 8 Recovery for 18 natural elements spiked into Pu solutions 1 1700 ppm of Pu; and 2,2000 ppm of Pu Several isotopes of the elements were considered for the analysis using aqueous calibra- tion solutions (1% nitric acid) 600 I A 0 0 100 200 300 400 500 600 Certified concentration/pg g-'of U Fig.9 Comparison between certified and found concentrations for U30s reference materials (NBL 95.1 and 95.2). Final U concentration 2000 ppm. Line of slope 1 is shown. A calibration with aqueous standards (slopex0.7); and B calibration using Rh as internal standard dose of the corresponding spent fuel solution would be too high for glove box analysis. As can be observed in Fig. 7 no effect of the presence of 500 ppm of U can be observed on the signal for 1 ppm of the corresponding fission products between Sr and Eu. In the analysis of natural element impurities in fresh nuclear fuel higher concentrations of U or Pu can be tested.Fig. 8 shows the recovery for natural elements which can be present as traces in actinides in the presence of (1) 1700 or (2) 2000 ppm of Pu. The recovery increases as the mass of the test element increases and quantitative recoveries were observed for the elements above Gd regardless of the concentration of Pu. Fig. 9 shows the results for the analysis of two U30s reference materials [New Brunswick Laboratory (NBL) NJ USA samples 95-1 and 95-21 containing different levels of impurities and prepared to contain 2000 ppm of U. As can be observed the recovery is about 70% for most elements using aqueous calibration solutions (based on the slope of the line A). However when Rh was used as IS satisfactory results were obtained. In the case of the actinides no matrix effect of U on Pu or Np was observed up to 2000 ppm of U in the sample.However low concentrations of 237Np in the presence of a high U matrix required manual adjustment of the mass resolution due to the tailing of the 238U peak at the low mass side. For the determination of ultratrace levels of Np in U chemical separation of the elements would be necessary.I3 Conclusions The performance characteristics of a glove box ICP mass spectrometer have been found to be similar in most respects to standard instruments. The reduction in sensitivity due to the glove box installation is perhaps the most striking effect but other parameters like the low oxide levels and the low interferences observed make up for this loss. For the samples to be measured the sensitivity can be considered adequate. Mass discrimination errors were studied in detail as the isotopic abundances of fission products and actinides have to be measured.Correct isotopic abundances can be obtained by the use of the mass discrimination factor K when the instrument is calibrated for the appropriate mass range. The interference effect arising from high concentration of heavy elements in the sample is perhaps the main drawback when applying ICP-MS to the analysis of real samples. In the present case owing to the lower sensitivity space- charge effects in the mass spectrometer seemed to be drastically reduced and no serious interference effects were observed in the presence of high concentrations of U and Pu which a priori would show the most pronounced effects.The limited interference effects would facilitate the use of semiquantitative approaches when high precision and accuracy is not necessary. 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 20 21 References Nickel H. Spectrochim. Acta Part B 1992 47 27. Cantle J. E. in Analytical Chemistry Instrumentation ed. Laing W. R. Lewis Publishers Chelsea MI 1986 p. 139. Allenby P. Clarkson A. S. and Makinson P. in Analytical Chemistry Instrumentation ed. Laing W. R. Lewis Publish- ers Chelsea MI 1986. Long S. E. and Brown R. M. in Analytical Chemistry Instrumentation ed. Laing W. R. Lewis Publishers Chelsea MI 1986. Luo S. K. and Chang F. C. Spectrochim. Acta Part B 1990 45 527. Beck G. L. and Farmer 0. T. 111 J. Anal. At. Spectrom. 1988 3 771. Kim C. Takaku A. Yamamoto M.Kawamura K. Shi- raishi K. Igarashi Y. Igarashi S. Takayama H. and Ikeda N. J. Radioanal. Nucl. Chem. Art. 1989 132 131. Scott R. D. Baxter M. S. Hursthouse A. S. MacKay K. Sampson K. and Toole J. Anal. Proc. 1991 28 382. Kim C. K. Morita S. Seki R. Takaku Y. Ikeda N. and Assinder D. J. J. Radioanal. Nucl. Chem. Art. 1992,156,201. Hursthouse A. S. Baxter M. S. McKay K. and Livens F. R. J. Radioanal. Nucl. Chem. Art. 1992 157 281. Crain J. S. and Gallimore D. L. Appl. Spectrosc. 1992 46 547. Smith M. R. Wyse E. J. and Koppenaal D. W. J Radioanal. Nucl. Chem. Art. 1992 160 341. Riglet C. Provitinia O. Dautheribes J.-L. and Revy D. J. Anal. At. Spectrom. 1992 7 923. Cromboom O. Garcia Alonso J. I. Koch L. Goerten J. Roesgen E. Wagner H. G. Ottmar H. and Eberle H. Proceedings of the 4th International Conference on Facility Operations-Safeguards Interface ed. American Nuclear Society Illinois 1992 p. 431. Horlick G. Tan S. H. Vaughan M. A. and Rose C. A. Spectrochim. Acta Part B 1985 40 1555. Vaughan M. A. Horlick G. and Tan S. H. J. Anal. At. Spectrom. 1987 2 765. Fulford J. E. and Douglas D. J. Appl. Spectrosc. 1986 40 971. Chambers D. M. and Hieftje G. M. Spectrochim. Acta Part B 1991 46 761. Longerich H. P. Fryer B. J. Strong D. F. and Kantipuly C. J. Spectrochim. Acta Part B 1987 42 75. Longerich H. P. Strong D. F. and Kantipuly C. J. Can. J. Spectrosc. 1986 31 1 1 1. White F. A. and Wood G. M. Mass Spectrometry Applica- tions in Science and Engineering Wiley New York 1986 pp. Paper 3/0 I0 I OD Received February 19 1993 Accepted April 19 1993 759-762.

ISSN:0267-9477    

DOI:10.1039/JA9930800673

出版商:RSC    

年代:1993

数据来源: RSC