摘要:

Journal of Analytical Atomic Spectrometry {Including Atomic Spectrometry Updates) JAAS Editorial Board* Chairman B L Sharp (Loughborough UK) J. Egan (Cambridge UK) J M Mermet (Villeurbanne France) S J. Haswell (Hull UK) D A Hickman (London UK) J Marshall (Middlesbrough UK) D L Miles (Keyworth UK) R D Snook (Manchester UK) "The JAAS Editorial Board reports t o the Analytical Editorial Board Chairman A G Fogg (Loughborough UK) JAAS Advisory Board F C Adams (Antwerp Belgium) R M Barnes (Amherst MA USA) L Bezur (Budapest Hungary) R F Browner (Atlanta GA USA) S Caroli (Rome Italy) A J Curtius (Rio de Janeiro Brazin J B Dawson (Leeds UK) M T C de Loos-Vollebregt (Delft The K Dittrich (Leipzig Germany) L Ebdon (Plymouth UK) M S Epstein (Gaithersburg MD USA) Fang Zhao-lun (Shenyang China) W Frech (Umea Sweden) A L Gray(€gham UK) S Greenfield (Loughborough UK) G M Hieftje (Bloomington IN USA) G Horlick (Edmonton Canada) D Littlejohn (Glasgow UK) B V L'vov (Sf Petersburg Russia) T Nakahara (Osaka Japan) Ni Zhe-ming (€?eying China) N Omenetto (lspra Italy) R E Sturgeon (Ottawa Canada) V Sychra (Prague Czechoslovakia) R Van Grieken (Antwerp Belgium) A Walsh K B (Victoria Australia) B Welz (Uberlingen Germany) T S West (Aberdeen UK) Netherlands) A Sanz-Medel (Oviedo Spain) Atomic Spectrometry Updates Editorial Board Chairmarl "D.L. Miles (Keyworth UK) J. Armstrong (Dumfries UK) J. R. Bacon (Aberdeen UK) C. Barnard (Glasgow UIO R. M. Barn-es (Amherst MA USA) S. Branch (High Wycombe UK) R Bye (Oslo Norway) J. Carroll (Middlesbrough UK) M. R.Cave (Keyworth UK) "J. M. Cook (Keyworth UK) "M. S. Cresser (Aberdeen UK) H. M. Crews (Norwich UK) J. S . Crighton (Sunbury-on-Thames UK) J. R. Dean (Newcastle upon Tyne UK) A. W. McMahon (Harwell UK) J M. Mermet ( Villeurbanne France) R. G. Michel (Srorrs CT USA) T. Nakahara (Osaka Japan) Ni Zhe-ming (Belling China) P. R. Poole (Hamilton New Zealand P. J. Potts (Milton Keynes UIO W. J . Price (Ashburton UK) C. J. Rademeyer (Pretoria South Africa) "M. H. Ramsey (London UK) A. Sanz-Medel (Oviedo Spain) "B. L. Sharp (Loughborough UK) I. L. Shuttler (Uberlingen Germany) S. T. Sparkes (Plymouth UK) R.Stephens (Halifax Canada) J.Stupar (Llub/pna Slovenia) R . E. Sturgeon (Ottawa Canada) A. P. Thorne (London UK) G. C. Turk (Gaithersburg MD USA) J. F Tyson (Amherst MA USA) S .J. Walton (Crawley UK) P Watkins (London UN B. Welz ( Uberlingen Germany) J. Williams (Egham UKI J. B. Willis (Victoria Australia) *J. B. Dawson (Leeds UK) "J. Egan (Cambridge UK) *A. T. Ellis (Oxford UIO J. Fazakas (Bucharest Romania) D. J. Halls (Glasgow UK) "A. Taylor (Guildford UK) "D. A. Hickman (London UK) "S. J. Hill (Plymouth UK) K. W. Jackson (Albany NY USA) R. Jowitt (Middlesbrough UK) K. Kitagawa (Nagoya Japan) J. Kubova f Bratislava Czechoslovakd "J. Marshall (Middlesbrough UK) H. Matusiewicz (Poznan Poland) *Members of the ASU Executive Committee Editor JAAS Judith Egan The Royal Society of Chemistry Dr J M Harnly Thomas Graham House Science Park Milton Road Cambridge CB4 4WF UK Telex No 818293 Fax 0223 423623 Beltsville M D 20705 USA E-mail RSCI@UK AC RL GB (JANET) Assistant Editors Brenda Holliday and Ed/tonal Secretary Monique Warner US Associate Editor JAAS US Department of Agriculture Beltsville Human Nutrition Research Center Telephone 0223 420066 BLDG 161 BARC-EAST Telephone 301 -504-8569 Paula O'Riordan Advertisements.Advertisement Department The Royal Society of Chemistry Burlington house Piccadilly London W I V OBN UK Telephone 071-437 8656 Fax 071-494 1134 Information for Authors Full details of how to submit materials for publica tion in JAAS are given in the Instructions to Authors in Issue 1 Separate copies arc available on request The Journal of Analytical Atomic Spectrometry (JAASi is an international journal for the publica- tion of original research papers communications and letters concerned with the development and analytical application of atomic spectrometric techniques The journal is published eight times a year including comprehensive reviews of specific topics of interest to practising atomic spectrosco- pists and incorporates the literature reviews which were previously published in Annual Reports on Analytical Atomic Spectroscopy (ARAAS) Manuscripts inteqded for publication must de- scribe original work related to atomic spectromet- ric anaiysis Papers on all aspects of the subject will be accepted including fundamental studies novel instrument developments and practical ana- lytical applications As well as AAS. AES and AFS papers will be welcomed on atomic mass spec trometry and X-ray fluorescence/emission spec trometry Papers describing the measurement of molecular species where these relate to the char- acterization of sources normally used for the pro duction of atoms or are concerned for example with indirect methods of anaiysis will also be ac- ceptable for publication Papers describing the de velopment and applications of hybrid techniques ( e g GC-coupled AAS and HPLC-ICP) will be par ticularly welcome Manuscripts on other subjects of direct interest to atomic spectroscopists.in- cluding sample preparation aqd dissolution and analyte pre-concentration procedures as wet' as the statistica irterpretation and use of atomic spectrometric data will also be acceptable for pcib- lication There is no page charge The following types of papers will be consid- ered Full papers describing original work Commun/cations which must be on an urgent matter and be of obvious scientific irnportance Communications receive priority and are usually published within 2-3 months of receipt They are Intended for brief descriptions of work that has progressed to a stage at which it is likely to be valuable to workers faced with similar problems Reviews which must be a critical evaluation of the existing state of knowledge on a particular facet of analytical atomic spectrometry Every paper (except Communications) will be submitted to at least two referees by whose advice the Editorial Board of JAAS will be guided as to its acceptance or rejection Papers that are accepted must not be published elsewhere except by permission Submission ot d manu- script will be regarded as an undertaking that the sahe material is not being considered for publica- tion by another journal Manuscripts (three copies typed In double spacing) should be sent to Judith Egan Editor JAAS or Dr J M Harnly US Associate Editor JAAS All queries relating to the presentation and sub- mission of papers and any correspondence re- garding accepted papers and proofs should be directed to the Editor or US Editor (addresses as above) Members of the JAAS Editorial Board (who may be contacted directly or v/a the Editorial Office) would welcome comments suggestions and advice on general policy matters concerning JAAS - Fifty reprints are supplied free of charge Journal of Analytical Atomic Spectrometry (JAAS) (ISSN 0267-9477) is published eight times a year by The Royal Society of Chemistry Thomas Graham House Science Park Milton Road Cambridge CB4 4WF UK All orders accompanied with payment should be sent directly t o The Royal Society of Chemistry Turpin Distribution Services Ltd Blackhorse Road Letchworth Herts SG6 1 HN UK Tel +44 (0) 462 672555 Telex 825372 Turpin G Fax +44 (0) 462 480947 Turpin Distribution Services Ltd is wholly owned by The Royal Society of Chemistry 1992 Annual subscription rate EC €347 00 USA $740 00 Canada €408 (excl GST) Rest of World €389 00 Customers should make payments by cheque in sterling payable on a UK clearing bank or in US dollars payable on a US clearing bank Air freight and mailing in the USA by Publications Expediting Inc 200 Meacham Avenue Elmont NY 11003 USA Postmaster send address changes t o Journal of Analytical Atomic Spectmmetry (JAASI Publications Expediting Inc 200 Meacham Avenue Elmont NY 11003 Second class postage paid at Jamaica NY 11431 All other despatches outside the UK by Bulk Airmail within Europe Accelerated Surface Post outside Europe PRINTED IN THE UK Q The Royal Society of Chemistry 1992 All rights reserved No part of this publication may be reproduced stored in a retrieval system or transmitted in any form or by any means electronic mechanical photographic recording or otherwise without the prior permission of the publishersJournal of Analytical Atomic Spectrometry {Including Atomic Spectrometry Updates) JAAS Editorial Board* Chairman B L Sharp (Loughborough UK) J.Egan (Cambridge UK) J M Mermet (Villeurbanne France) S J.Haswell (Hull UK) D A Hickman (London UK) J Marshall (Middlesbrough UK) D L Miles (Keyworth UK) R D Snook (Manchester UK) "The JAAS Editorial Board reports t o the Analytical Editorial Board Chairman A G Fogg (Loughborough UK) JAAS Advisory Board F C Adams (Antwerp Belgium) R M Barnes (Amherst MA USA) L Bezur (Budapest Hungary) R F Browner (Atlanta GA USA) S Caroli (Rome Italy) A J Curtius (Rio de Janeiro Brazin J B Dawson (Leeds UK) M T C de Loos-Vollebregt (Delft The K Dittrich (Leipzig Germany) L Ebdon (Plymouth UK) M S Epstein (Gaithersburg MD USA) Fang Zhao-lun (Shenyang China) W Frech (Umea Sweden) A L Gray(€gham UK) S Greenfield (Loughborough UK) G M Hieftje (Bloomington IN USA) G Horlick (Edmonton Canada) D Littlejohn (Glasgow UK) B V L'vov (Sf Petersburg Russia) T Nakahara (Osaka Japan) Ni Zhe-ming (€?eying China) N Omenetto (lspra Italy) R E Sturgeon (Ottawa Canada) V Sychra (Prague Czechoslovakia) R Van Grieken (Antwerp Belgium) A Walsh K B (Victoria Australia) B Welz (Uberlingen Germany) T S West (Aberdeen UK) Netherlands) A Sanz-Medel (Oviedo Spain) Atomic Spectrometry Updates Editorial Board Chairmarl "D.L. Miles (Keyworth UK) J. Armstrong (Dumfries UK) J. R. Bacon (Aberdeen UK) C. Barnard (Glasgow UIO R. M. Barn-es (Amherst MA USA) S. Branch (High Wycombe UK) R Bye (Oslo Norway) J. Carroll (Middlesbrough UK) M. R. Cave (Keyworth UK) "J. M. Cook (Keyworth UK) "M. S. Cresser (Aberdeen UK) H. M. Crews (Norwich UK) J. S . Crighton (Sunbury-on-Thames UK) J. R. Dean (Newcastle upon Tyne UK) A. W. McMahon (Harwell UK) J M.Mermet ( Villeurbanne France) R. G. Michel (Srorrs CT USA) T. Nakahara (Osaka Japan) Ni Zhe-ming (Belling China) P. R. Poole (Hamilton New Zealand P. J. Potts (Milton Keynes UIO W. J . Price (Ashburton UK) C. J. Rademeyer (Pretoria South Africa) "M. H. Ramsey (London UK) A. Sanz-Medel (Oviedo Spain) "B. L. Sharp (Loughborough UK) I. L. Shuttler (Uberlingen Germany) S. T. Sparkes (Plymouth UK) R.Stephens (Halifax Canada) J.Stupar (Llub/pna Slovenia) R . E. Sturgeon (Ottawa Canada) A. P. Thorne (London UK) G. C. Turk (Gaithersburg MD USA) J. F Tyson (Amherst MA USA) S . J. Walton (Crawley UK) P Watkins (London UN B. Welz ( Uberlingen Germany) J. Williams (Egham UKI J. B. Willis (Victoria Australia) *J. B. Dawson (Leeds UK) "J. Egan (Cambridge UK) *A.T. Ellis (Oxford UIO J. Fazakas (Bucharest Romania) D. J. Halls (Glasgow UK) "A. Taylor (Guildford UK) "D. A. Hickman (London UK) "S. J. Hill (Plymouth UK) K. W. Jackson (Albany NY USA) R. Jowitt (Middlesbrough UK) K. Kitagawa (Nagoya Japan) J. Kubova f Bratislava Czechoslovakd "J. Marshall (Middlesbrough UK) H. Matusiewicz (Poznan Poland) *Members of the ASU Executive Committee Editor JAAS Judith Egan The Royal Society of Chemistry Dr J M Harnly Thomas Graham House Science Park Milton Road Cambridge CB4 4WF UK Telex No 818293 Fax 0223 423623 Beltsville M D 20705 USA E-mail RSCI@UK AC RL GB (JANET) Assistant Editors Brenda Holliday and Ed/tonal Secretary Monique Warner US Associate Editor JAAS US Department of Agriculture Beltsville Human Nutrition Research Center Telephone 0223 420066 BLDG 161 BARC-EAST Telephone 301 -504-8569 Paula O'Riordan Advertisements. Advertisement Department The Royal Society of Chemistry Burlington house Piccadilly London W I V OBN UK Telephone 071-437 8656 Fax 071-494 1134 Information for Authors Full details of how to submit materials for publica tion in JAAS are given in the Instructions to Authors in Issue 1 Separate copies arc available on request The Journal of Analytical Atomic Spectrometry (JAASi is an international journal for the publica- tion of original research papers communications and letters concerned with the development and analytical application of atomic spectrometric techniques The journal is published eight times a year including comprehensive reviews of specific topics of interest to practising atomic spectrosco- pists and incorporates the literature reviews which were previously published in Annual Reports on Analytical Atomic Spectroscopy (ARAAS) Manuscripts inteqded for publication must de- scribe original work related to atomic spectromet- ric anaiysis Papers on all aspects of the subject will be accepted including fundamental studies novel instrument developments and practical ana- lytical applications As well as AAS.AES and AFS papers will be welcomed on atomic mass spec trometry and X-ray fluorescence/emission spec trometry Papers describing the measurement of molecular species where these relate to the char- acterization of sources normally used for the pro duction of atoms or are concerned for example with indirect methods of anaiysis will also be ac- ceptable for publication Papers describing the de velopment and applications of hybrid techniques ( e g GC-coupled AAS and HPLC-ICP) will be par ticularly welcome Manuscripts on other subjects of direct interest to atomic spectroscopists. in- cluding sample preparation aqd dissolution and analyte pre-concentration procedures as wet' as the statistica irterpretation and use of atomic spectrometric data will also be acceptable for pcib- lication There is no page charge The following types of papers will be consid- ered Full papers describing original work Commun/cations which must be on an urgent matter and be of obvious scientific irnportance Communications receive priority and are usually published within 2-3 months of receipt They are Intended for brief descriptions of work that has progressed to a stage at which it is likely to be valuable to workers faced with similar problems Reviews which must be a critical evaluation of the existing state of knowledge on a particular facet of analytical atomic spectrometry Every paper (except Communications) will be submitted to at least two referees by whose advice the Editorial Board of JAAS will be guided as to its acceptance or rejection Papers that are accepted must not be published elsewhere except by permission Submission ot d manu- script will be regarded as an undertaking that the sahe material is not being considered for publica- tion by another journal Manuscripts (three copies typed In double spacing) should be sent to Judith Egan Editor JAAS or Dr J M Harnly US Associate Editor JAAS All queries relating to the presentation and sub- mission of papers and any correspondence re- garding accepted papers and proofs should be directed to the Editor or US Editor (addresses as above) Members of the JAAS Editorial Board (who may be contacted directly or v/a the Editorial Office) would welcome comments suggestions and advice on general policy matters concerning JAAS - Fifty reprints are supplied free of charge Journal of Analytical Atomic Spectrometry (JAAS) (ISSN 0267-9477) is published eight times a year by The Royal Society of Chemistry Thomas Graham House Science Park Milton Road Cambridge CB4 4WF UK All orders accompanied with payment should be sent directly t o The Royal Society of Chemistry Turpin Distribution Services Ltd Blackhorse Road Letchworth Herts SG6 1 HN UK Tel +44 (0) 462 672555 Telex 825372 Turpin G Fax +44 (0) 462 480947 Turpin Distribution Services Ltd is wholly owned by The Royal Society of Chemistry 1992 Annual subscription rate EC €347 00 USA $740 00 Canada €408 (excl GST) Rest of World €389 00 Customers should make payments by cheque in sterling payable on a UK clearing bank or in US dollars payable on a US clearing bank Air freight and mailing in the USA by Publications Expediting Inc 200 Meacham Avenue Elmont NY 11003 USA Postmaster send address changes t o Journal of Analytical Atomic Spectmmetry (JAASI Publications Expediting Inc 200 Meacham Avenue Elmont NY 11003 Second class postage paid at Jamaica NY 11431 All other despatches outside the UK by Bulk Airmail within Europe Accelerated Surface Post outside Europe PRINTED IN THE UK Q The Royal Society of Chemistry 1992 All rights reserved No part of this publication may be reproduced stored in a retrieval system or transmitted in any form or by any means electronic mechanical photographic recording or otherwise without the prior permission of the publishers

ISSN:0267-9477    

DOI:10.1039/JA99207FX019

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JASPE2 7(5) 41 N-46N 71 9-780 21 5R-278R ( 1 992) August 1992 Ill Journal of Analytical Atomic Spectrometry I n c I ud I n g Atom I c Spectrometry U pd ates Typeset by Burgess Thames View Abingdon Oxfordshire I I I CONTENTS NEWS AND VIEWS 41 N Conference Reports-W Fischer Janet A Armstrong 43N The Benedetti-Pichler Memorial Award of the American Microchemical Society 1992 43N Conferences and Meetings 44N Papers in Future Issues PAPERS 71 9 727 735 743 749 753 761 765 769 775 779 Simplex Optimization of Nitrogen-Argon Plasmas in Inductively Coupled Plasma Mass Spectrometry for the Removal of Chloride-based Interferences-Steve J Hill Michael J Ford and Les Ebdon Studies on the Application of Platform Atomization to Furnace Atomic Non-thermal Excitation Spectrometry for the Simultaneous Multi-element Analysis of Environmental Materials-Douglas C Baxter Robbin Nichol David Littleiohn Christian Ludke Jochen Skole Erwin Hoffmann Electrothermal Atomic Absorption Spectrometric Determination of Antimony in Metal Chloride Matrices Using Probe and Tube-wall Atomization-Paavo Peramaki Lauri H J Lajunen Platform Wall and Probe Electrothermal Atomization for the Determination of Aluminium in Clinical Fluids-Juan M Marchante Gayon Juan Perez Parajon Alfred0 Sanz-Medel Craig S Fellows Determination of Aluminium in Human Brain Tissue by Electrothermal Atomic Absorption Spectrometry-Ning Xu Vahid Majidi William D Ehmann William R Mar kes bery Spectral Interferences on the Determination of Selenium by Electrothermal Atomic Absorption Spectrometry-A Javier Aller Conception Garcia-Olalla Determination of Gallium in Coal and Coal Fly Ash by Electrothermal Atomic Absorption Spectrometry Using Slurry Sampling and Nickel Chemical Modification-Shan Xiao-quan Wang Wen Wen Bei Systematic Investigation of Aluminium Interferences on the Alkaline Earth Elements in Flame Atomic Absorption Spectrometry.Part I. Behaviour of Beryl1 ium-Wern e r Luec ke Sample Introduction and Atomization of Volatile Alkyllead Compounds in Flame Atomic Absorption Spectrometry-Gyula Bagdi Janos Lakatos Istvan Lakatos Determination of Ultratrace Arnounts of Gold in Geological Materials by Arc Emission Spectrometry Using Gas Chamber Profile Electrodes-Xu Peiqing CUMULATIVE AUTHOR INDEX ATOMIC SPECTROMETRY 21 5R 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 247 R ReferencesJASPE2 7(5) 41 N-46N 71 9-780 21 5R-278R ( 1 992) August 1992 Ill Journal of Analytical Atomic Spectrometry I n c I ud I n g Atom I c Spectrometry U pd ates Typeset by Burgess Thames View Abingdon Oxfordshire I I I CONTENTS NEWS AND VIEWS 41 N Conference Reports-W Fischer Janet A Armstrong 43N The Benedetti-Pichler Memorial Award of the American Microchemical Society 1992 43N Conferences and Meetings 44N Papers in Future Issues PAPERS 71 9 727 735 743 749 753 761 765 769 775 779 Simplex Optimization of Nitrogen-Argon Plasmas in Inductively Coupled Plasma Mass Spectrometry for the Removal of Chloride-based Interferences-Steve J Hill Michael J Ford and Les Ebdon Studies on the Application of Platform Atomization to Furnace Atomic Non-thermal Excitation Spectrometry for the Simultaneous Multi-element Analysis of Environmental Materials-Douglas C Baxter Robbin Nichol David Littleiohn Christian Ludke Jochen Skole Erwin Hoffmann Electrothermal Atomic Absorption Spectrometric Determination of Antimony in Metal Chloride Matrices Using Probe and Tube-wall Atomization-Paavo Peramaki Lauri H J Lajunen Platform Wall and Probe Electrothermal Atomization for the Determination of Aluminium in Clinical Fluids-Juan M Marchante Gayon Juan Perez Parajon Alfred0 Sanz-Medel Craig S Fellows Determination of Aluminium in Human Brain Tissue by Electrothermal Atomic Absorption Spectrometry-Ning Xu Vahid Majidi William D Ehmann William R Mar kes bery Spectral Interferences on the Determination of Selenium by Electrothermal Atomic Absorption Spectrometry-A Javier Aller Conception Garcia-Olalla Determination of Gallium in Coal and Coal Fly Ash by Electrothermal Atomic Absorption Spectrometry Using Slurry Sampling and Nickel Chemical Modification-Shan Xiao-quan Wang Wen Wen Bei Systematic Investigation of Aluminium Interferences on the Alkaline Earth Elements in Flame Atomic Absorption Spectrometry.Part I. Behaviour of Beryl1 ium-Wern e r Luec ke Sample Introduction and Atomization of Volatile Alkyllead Compounds in Flame Atomic Absorption Spectrometry-Gyula Bagdi Janos Lakatos Istvan Lakatos Determination of Ultratrace Arnounts of Gold in Geological Materials by Arc Emission Spectrometry Using Gas Chamber Profile Electrodes-Xu Peiqing CUMULATIVE AUTHOR INDEX ATOMIC SPECTROMETRY 21 5R 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 247 R References

ISSN:0267-9477    

DOI:10.1039/JA99207BX021

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 41 N Conference Reports ~ ~ First European Workshop on Surface Analysis by Means of Glow Discharge Optical Spectrometry March 4-6 1992 Paris France On the initiative of the working group ‘Surface Analysis in Giow Discharge Optical Spectrometry’ part of the ‘Groupe Pour L‘Avancement des Sci- ences AnaEytiques’ (GAMS Paris) the first European Workshop on Surface Analysis by Means of Glow Discharge Optical Spectrometry took place in Paris from March 4 to 6 1992. This event sponsored by the LECO Com- pany brought approximately 80 users of glow discharge optical spectrometry from nine European countries together to discuss the stage of development and use of this method for the charac- terization of material surfaces in the participants’ countries show new de- velopment trends expand and co- ordinate the working groups in ques- tion and encourage the propagation of the method in accordance with its productivity.Nineteen lectures were given during five plenary meetings covering the following crucial areas the use of the method in research/development and production; instruments and software; quantification of layer analysis in d.c. discharges; high-frequency (h.f.) glow discharge for non-conductive layers and layer systems; and alternative sur- face analysis methods with ions and electrons. The development of a method for the quantification of GD-OES layer profiies by Bengtson (Sweden) and the implementation of this method in the evaluation-software of commercial glow discharge spectrometers (LECO Instrumente GmbH Munich Ger- many and Jobin Yvon Longjumeau France) represents decisive progress for the method and its use.By Jobin Yvon’s adaptation of the h.f. discharge to the glow discharge as suggested by Grimm for the qualitative depth pro- file analysis of non-conductive layers (ceramics organic layers) the disad- vantage of the limitation of direct current discharge to electrical conduct- ing materials was overcome. Initial method tests (Hunault France) and use of corrosion-protec- tive layers in the car industry (Bau- doin France) show that the referenc- ing and depth resolution of the h.f.- layer analysis are not inferior to those of the direct current dischar‘ge. The workshop made it clear that the exchange of information between European teams working on GD-OES layer analysis has to be intensified in order to elimivate parallel efforts and to ensure the similarity of the results.A connection has to be made between GD-OES and the established surface analysis methods with ions and elec- trons such as SIMS SNMS and AES. By realizing its specific producti- vity/efficiency the GD-OES layer ana- lysis method can be included in the wider field of solid-state physical char- acterizing methods for surface and surface-type materials. In order to promote this and other method-specific concerns a European working team was formed consisting of one represen- tative from each of the participating countries of this first workshop. The European Working Team will gladly welcome further participating coun- tries.Dr. Arne Bengtson of the Swedish Institute for Material Research (S- 1 14 28 Stockholm Sweden) was elected as President. Information about the activ- ities of the working group and the possibilities of active cooperation can be obtained by applying to Dr. Bengtson. A second European Workshop for GD-OES Layer Analysis is planned at the end of 1993/beginning of 1994 in Dusseldorf W. Fischer Institut f i r Reaktorwerkstoge Forschungszen trum Jiilich Gm bH W-5 I70 Jiilich Germany New Approaches to Sample Preparation and Introduction March 25-26 1992 University of Newcastle Newcastle-upon-Tyne UK This year’s joint Atomic Spectrometry Updates (ASU) and Atomic Spectros- copy Group (ASG) meeting took place in the splendid setting of Henderson Hall at the University of Newcastle.On the first day an Executive Com- mittee Meeting followed by an Edi- torial Board Meeting of ASU was held. In the evening a Sherry Reception and Board Dinner took place in the histori- cal surroundings of Langley Castle. After an excellent meal presentations were made by Doug Miles the Chair- man of the ASU Board to the two invited overseas speakers,.. Bernhard Welz from Perkin-Elmer Uberlingen and Ken Jackson from the State University of New York. The scientific meeting on the second day was entitled ‘New Approaches to Sample Preparation and Introduc- tion.’ A diverse range of topics was discussed in the course of the day. Bernhard Welz should have been the first speaker but gremlins in the slide projector delayed the start of his pre- sentation.Instead the first presenta- tion was given by Mike Ramsey (Im- perial College London) who trusted in overhead-projection technology. Mike presented a very challenging lecture on the estimation of errors and in parti- cular errors arising from sampling and sample preparation procedures. He also reminded us of the futility of seeking to improve analytical variance without also assessing these errors which can contribute significantly to the total error. The gremlins having been van- quished Bernhard Welz who was the first of two overseas ASU board mem- bers to present a paper proceeded to discuss his work on on-line pre- concentration using microcolumns prior to determination by electro- thermal atomic absorption spectro- metry (ETAAS). By using CI8 sorbent with sodium diethyldithiocarbamate as complexing agent and ethanol as eluent he had achieved a 20-fold enrichment after a sampling time of only 1 min.This method was able to preconcentrate transition metals from42N Doug Miles (R) presenting a book to Bern- hard Welz sea-water thus offering a clean-up procedure and preconcentration prior to determination by ETAAS. By vary- ing the conditions speciation of Astrt and AsV and of Crttt and CrV1 was also possible. Later in the day Ken Jackson the second overseas board member also discussed preconcentration of transi- tion metals from sea-water prior to determination by ETAAS. Ken how- ever used activated carbon to precon- centrate the analytes after they had been complexed with ammonium pyr- rolidine dithiocarbamate (ammonium pyrolidin- 1 -yldithioformate). A slurry of the carbon was then prepared and injected directly into the furnace. This system offered a 400-fold preconcen- tration of the transition metals. Ken also discussed the use and possible mechanisms of Pd as a modifier when performing slurry ETAAS.He sug- gested that during the determination of Pb crystals of Pd3Pb2/Pd3Pb might be formed which inhibit the vaporiza- tion of Pb thus allowing all the Pb from the slurry to be vaporized at once. This overcame the problem of double peaks that had been experi- enced previously. JOURNAL OF ANALYTICAL ATOMIC Two different aspects of flow injec- tion (FI) were considered by Helen Crews (MAAF Norwich) and Julian Tyson (University of Massachusetts). Helen presented some initial findings for an on-line FI system for microwave digestion of slurried samples prior to analysis by ICP-MS.She used bio- logical reference materials which were prepared to give a 0.02% slurry in 5% HN03. The slurries were passed through a 20 m loop' inside a micro- wave oven and into the ICP spectro- meter. She found that the 0.02% slurry was too dilute for determining most analytes. However where the analyte was present in sufficient amount the results were good. Helen mentioned the need to compromise the optimum flow rate through the microwave oven to allow the optimum flow rate in the ICP spectrometer to be maintained. It was this aspect of the kinetics of FI that Julian Tyson discussed. He suggested putting a sample introduction valve after the FI manifold so that the optimum flow rates for the sample Doug Miles (L) thanking Ken Jackson with a presentation SPECTROMETRY AUGUST 1992 VOL. 7 reaction and flame systqm could be maintained.The valve would then allow the introduction of the reacted sample into the carrier gas flow at the right speed for the flame. The use of a recirculating loop was also proposed. This would allow discrete and repeated analyses of the reacted sample. The winner of the 1991 Hilger Spec- troscopy prize Simon Chenery (Brit- ish Geological Survey) presented a talk on solid sample introduction us- ing laser ablation for plasma spectro- metry. Simon discussed the absolute detection limits of ICP-OES and ICP- MS which then limit the size of sample that can be ablated. Examples of problems requiring small discrete samples were given such as the chal- lenge of determining whether a Rem- brandt is really a Rembrandt.Laser ablation of a flake of paint is an acceptable means of analysis under these circumstances. The final speaker of the day was John Williams (Royal Holloway and Bedford New College Surrey). He highlighted some of the advantages of using electrothermal vaporization as a means of sample introduction in in- ductively coupled plasma mass spec- trometry (ICP-MS). The example of a clinical trial on the uptake of iron by pregnant women was used. It was shown that only small amounts of sample were required sample pre- treatment could be performed in the furnace any water that interfered with the determination of Fe by ICP-MS was driven off and solid or liquid samples could be introduced. Iron enriched with natural isotopes was used in the trial and the isotope ratios were determined by ICP-MS. A wide range of subjects was cov- ered throughout the day and it proved to be a very interesting and stimulating meeting. Janet A. Armstrong Durnfries UK Board members relaxing after an excellent meal are clockwise Julian Obviously enjoying themselves are some members of the ASU Board Tyson Andrew Taylor David Halls Colin Woodward (Editor of clmkwise Bernhard Welz Barry Sharp Doug Miles Ken Jackson ARAAS 1973) John Price John Dawson and Helen Crews Jenny Cook Mike Ramsey Dave Hickman and Judith Egan

ISSN:0267-9477    

DOI:10.1039/JA992070041N

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 43N Conferences and Meetings 1993 European Winter Conference on Plasma Spectrochemistry January 10- 15 1993 Granada Spain The 1993 European Winter Confer- ence on Plasma Spectrochemistry organized by the Grupo Espectroqui- mico and Grupo Espaiiol de Espec- troscopia of the Spanish Royal Socie- ties of Chemistry and Physics will be held in the Congress and Exhibition Center Granada Spain. Scien tijic program me The programme will include six ple- nary lectures ten invited keynote lec- tures daily sessions of original oral presentations and poster presenta- tions. Three Special Discussion Ses- sions on today’s ‘hot’ topics will be held. A prize for the best poster will be awarded. JAAS will publish any submitted contributions after the usual peer review procedure in a Special Confer- ence Issue.Invited speakers include Paul Boumans (Philips Research The Netherlands) Gary Horlick (Univer- sity of Edmonton Canada) Les Ebdon (University of Plymouth UK) Sergio Caroli (Superior di Sanita Institute Italy) Gary Hieftje (Indiana State University USA) Miguel Valchrcel (University of Cordoba Spain) Daniel Batistoni (University of Buenos Aires Argentina) Ramon Barnes (University of Massachusetts USA) Joe Caruso (University of Cin- cinnati USA) Ignacio Garcia Alonso (Karlsruhe Germany) Sam Houk (Iowa State University USA) Fran- cisco Krug (Universidade de Silo Paulo Brazil) Ken Marcus (Clemson University USA) Akbar Montaser (George Washington University USA) Nicolo Omenetto (Ispra Italy) Carlo Vandecasteele (Institute for Nu- clear Sciences Belgium).Short course programme Introductory and advanced four-hour short courses are planned for the after- noon of Wednesday January 13 de- pendant upon the number of delegates who sign up. The topics covered will44N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992. VOL. 7 be sample preparation ICP-MS and ICP-AES ETAAS trace element spe- ciation laser sampling and nebulizer characteristics. The registration fee is 8.000 ptas refunded if the course is cancelled. Instrument exhibition Instrument and reagent manufacturers for analytical atomic spectrometry will exhibit throughout the duration of the conference- Social programme Granada is a university city steeped in history reflecting the cultural achieve- ments of the Moorish settlers.Located only an hour’s drive from the Mediter- ranean coast and 30 km from the Sierra Nevada Mountains Granada offers a host of sights sounds and tastes for the visitor. Excursions and tours of Granada Sevilla Alpujarra are planned as well as an evening concert of traditional Spanish music and the Congress Din- ner in the Gardens of Neptune. A list of approved hotels and hostels can be obtained from Mega-Viajes Granada the last date for booking being October 30 1992. Registrat ion The Conference registration fee in- cludes a copy of Conference abstracts for all oral and poster presentations. The registration fee before November 1 is 35.000 ptas and 10.000 ptas for students and accompanying persons. After November 1 the respective fees are 40.000 and 15.000 ptas.Cali for papers Abstracts are to be submitted by Sep- tember 14 1992 to Professor A. Sanz- Medel Department of Physical and Analytical Chemistry Faculty of Chemistry University of Oviedo C/Julian Claveria 8 33006 Oviedo Spain. Notification of acceptance will be given by November 30 1992 and the final programme will be distri- buted in December. 44th Pittsburgh Conference and Expo- sition on Analytical Chemistry and Applied Spectroscopy March 8-12 1993 Atlanta GA USA The 1993 Pittsburgh Conference and Exposition will be held at the Georgia World Congress Center Atlanta. The schedule of events is as follows deadline for receipt of abstracts on all aspects of methodology and applica- tion of analytical chemistry spectros- copy and related areas August 5 1992; mailing of information on regis- tration and housing October 1992; deadline for receipt of final abstracts December 7 1992; and mailing of preliminary programme December 1992.The Award Symposia currently planned for 1993 are Spectroscopy Award; Maurice F. Hasler Award; Charles N. Reilley Award; Dal Nogare Award; Bomen-Michelson Award; Pittsburgh Analytical Chemistry Award; Keene P. Dimick Award; James L. Waters Symposium; and The Williams- W right Indust rial Spect ros- copist Award. For further information contact Pittsburgh Conference Department CFP 300 Penn Center Boulevard Suite 332 Pittsburgh PA 15235-5503 USA. A comprehensive exhibition of modern laboratory equipment instru- mentation supplies and services will be presented. For further information or to reserve exhibition space contact Joanne H. Smith Exposition Chair- man Pittsburgh Conference 300 Penn Center Boulevard Suite 332 Pittsburgh PA 15235-5503 USA.

ISSN:0267-9477    

DOI:10.1039/JA99207043Nb

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

44N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992. VOL. 7 Future Issues will Include- The September issue of JAAS will feature a selection of papers presented at the 1992 Winter Conference on Plasma Spectrochemistry San Diego CA USA Multipurpose Flow Injection System. Part 1. Programmable Dilutions and Standard Additions for the Analysis of Plant Digests by Inductively Coupled Plasma Atomic Emission Spectrome- try-B. Freire dos Reis Maria Fernanda Gine Francisco Jose Krug and Henrique Bergamin Filho Recycling Nebulization System With a Disposable Spray Chamber for Analy- sis of Sub-milligram Samples of Geo- logical Materials Using Inductively Coupled Plasma Mass Spectrome- try-Zhongxing Chen Henry P. Longerich and Brian J. Fryer Comparison of Strip-line Source and Enhanced Beenakker Microwave Cav- ity Designs for Atomic Emission Spec- trometry-Mark D.Argentine and Ramon M. Barnes Pyrolysis-Gas Chromatography-Ato- mic Emission Spectrometric Detection of Sediments Coals and Other Petro- chemical Precursors-Jeffrey A. See- ley Y. Zeng T. I. Eglinton I. Ericsson and Peter C. Uden Dry-chlorination-Inductively Coup- led Plasma Mass Spectrometfic Method for Platinum Group Elements in Rocks-Bruce J. Perry and Jon C. van Loon Factorial Analysis and Response Sur- face of a Gas Chromatography- Microwave-induced Plasma System for the Determination of Halogenated Compounds-Manuel Caetano Rafael E. Golding and A. Edgar Key Determination of Iron and Ten Other Trace Elements in the Open Ocean Sea-water Reference Material NASS-3 by Inductively Coupled Plasma Mass Spectrometry-Kunihiko Akatsuka J.W. McLaren Joseph W. Lam and Shier S. Berman Analysis of Halogenated Compounds With Supercritical Fluid Chromato- graphy-Microwave-induced Plasma Mass Spectrometry-Lisa K. Olson and Joseph A. Caruso Performance Characteristics of an U1- trasonic Nebulizer Coupled to a 40.68 MHz Inductively Coupled Plasma Mass Spectrometer-I. B. Brenner P. Bremier and A. Lemarchand Application of Glow Discharge Mass Spectrometry With Low Mass Resolu- tion for In-depth Analysis of Technical Surface Layers-Norbert Jakubowski and Dietmar Stuewer Towards the Next Generation of Plasma Source Mass Spectrometers- Gary M. Hieftje Industrial Applications of Laser-in- duced Emission Spectral Analysis for Industrial Process and Quality Con-JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 45N t rol-Claw J. Lorenzen Chris top h Carlhoff Ulrich Hahn and Martin Jogwich Quantification of Copper and Cad- mium Using an On-line Anodic Stripping Voltammetry Flow Cell With Detection by Inductively Coup- led Plasma Mass Spectrometry-Jack R. Pretty Elmo A. Blubaugh E. Hywel Evans Joseph A. Caruso and Timothy M. Davidson Ultratrace Speciation Analysis of Or- ganolead in Water by Gas Chromato- graphy-Atomic Emission Spectrome- try After In-line Preconcentration- Ryszard Lobinski and Freddy C. Adams Temperature Measurements of Induc- tively Coupled Plasma a Comparison of N2+ Rotational Temperatures With Optical Pyrometry-Isam Marawi Bradley A. Bielski Joseph A. Caruso and Frank R. Meeks Determination of Tri- and Tetra-orga- notin Compounds by Supercritical Fluid Chromatography With Induc- tively Coupled Plasma Mass Spectro- metric Detection-Nohora P.Vela and Joseph A. Caruso Sample Preparation of High-purity Titanium for Glow Discharge Mass Spectrometric Analysis-Duencheng Fang and Purnesh Seegopaul Application of a Microwave-induced Plasma Atomic Emission Detector for Gas Chromatographic Quantification of Halogenated Compounds-Nada Kovacic and Terry L. Ramus Drift Diagnostics in Inductively Coup- led Plasma Atomic Emission Spectro- metry-Martine Carre Emmanuelle Poussel and Jean-Michel Mermet Determination of Impurities in Orga- nometallic Compounds Dissolved in Diethyl Ether by Flow Injection Induc- tively Coupled Plasma Mass Spectro- metry-Steve J.Hill James Hartley and Les Ebdon Addition of Molecular Gases to Argon Gas Flows for the Reduction of Polya- tomic-ion Interferences in Inductively Coupled Plasma Mass Spectrome- try-Jiansheng Wang E. Hywel Evans and Joseph A. Caruso Laser-excited Fluorescence Spectro- metry of Phosphorus Monoxide and Phosphorus in an Electrothermal Atomizer for Determination of Phos- phorus in Plant and Biological Refer- ence Materials and in Nickel Alloys-Zhongwen Liang Robert Lonardo Junichi Takahashi Robert G. Michel and Francis R. Preli Jr. Determination of Residual Carbon Content by Inductively Coupled Plasma Atomic Emission Spectrome- try After Decomposition of Biological Samples-Antoaneta Krushevska Ramon M. Barnes Chitra Amarasiri- waradena Henry Foner and Laura Martines.Inductively Coupled Plasma Mass Spectrometric Determination of 70Zn:68Zn Isotope Ratio in Biological Samples (Blood Urine Faeces and Food) From Pre-term Human Babies -Chitra Amarasiriwaradena Antoan- eta Krushevska Henry Foner Mark D. Argentine and Ramon M. Barnes 1992 Alan Date Memorial Award Submissions are invited for the 1992 Alan Date Memorial Award from young scientists active in the area of Atmospheric Plasma Source Mass Spectrometry The closing date for submission is November 30 1992 Further details can be obtained from Dr. R.C. Hutton VG Elemental Ion Path Road Three Winsford Cheshire CW7 3BX UK46N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 1993 EuroDean Winter Conference on Plaima Spectrochemistry Palacio de Congresos Granada Spain 10-15 January 1993 The Grupo Espectroquimico and Grupo Espailol de Espectroscopia of the Spanish Royal Societies of Chemistry and Physics cordially invite your participation in the 1993 European Winter Conference on Plasma Spectrochem- istry SCIENTIFIC PROGRAMME The scientific programme will include six plenary ten invited keynote lectures and oral and poster sessions.Three Special Discussion Sessions on today’s ‘hot’ topics a varied Short Course Programme and an Instrument Exhibition are also planned. Plenary- Paul Boumans Eindhuven Gary Horlick Alberta Les Ebdon Plymouth Sergio Caroli Rome Miguel Valcikcel Cbrdoba Gary Hieftje Indiana Key note- Daniel Batistoni Buenos Aires Ramon Barnes Massachusetts Joe Caruso Cincinnati Ignacio Garcia Alonso Karlsruhe Sam Houk Iowa Francisco Krug Srio Paulo Ken Marcus Clemson Akbar Montaser Washington Niccolo Omenetto Ispra Carlo Vandecasteele Leuven Plasma Spectrochemistry in Search of Innovation or Confirmation ICP-MS Perspectives Hybrid Techniques with Plasma Detection Low Pressure Discharges as Atom and Ion Sources FIA and Plasma Spectroscopy New Perspectives in Atomic/Ionic Sources Plasma Spectrometry in Latin America Isotopic Analysis in Biomedical Research With Analytical Plasma Source MS Potential of LC-ICP-MS for Trace Metal Speciation ICP-MS for the Analysis of Nuclear Materials Latest Developments in ICP-MS Instrumentation FIA On-line Treatments for ICP-AES Glow Discharge Mass Spectrometry Plasmas Other Than Ar-ICP for Atomic Spectroscopy Laser Atomic Spectroscopy ICP-MS for Biological Materials CALL FOR PAPERS Participants are requested to submit their contributions together with the abstracts before September 14 1992 indi.cating the preferred form of presentation oral or poster. A prize for the best poster will be awarded. Notification of acceptance will take place before the end of November 1992. For further information contact- Professor Alfredo Sanz-Medel Department of Physical and Analytical Chemistry Faculty of Chemistry University of Oviedo CIJulian Claveria 8 33006 Oviedo Spain Telephone 3485 10 3480/3474 Telefax 348523 7850

ISSN:0267-9477    

DOI:10.1039/JA992070044N

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 215R 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 PL4 8AA UK John B. Dawson Department of Instrumentation and Analytical Science UMIST P.O. Box 88 Manchester M60 1 QD UK W. John Price 15 Amberley Close Holne Cross Ashburton Devon UK Ian L. Shuttler Bodenseewerk Perkin-Elmer GmbH Postfach 101 164 W-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. 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 1.3.1. Hydride generation 1.3.2. Preparation and speciation of volatile organometallic compounds 1.3.3. Mercury by cold vapour generation 1.4.1. Light sources 1.4.2. Optics 1.4.3. Detectors 1.4.4. Background correction 1.4.5. Continuum source and simultaneous multi-element AAS 1.5.1. Instrument control 1.5.2. Data processing 1.5.3. Chemometrics 1.3.1 .l. Fundamental studies general developments in instrumentation and technique 1.3.1.2.Determination of individual elements by HG-AAS' 1.4. Spectrometers 1.5. Instrument Control and Data Processing 2 Atomic Fluorescence Spectrometry 2.1. Discharge Lamp-excited Atomic Fluorescence 2.2. Laser-excited Atomic Fluorescence Spectrometry 2.2.1. Electrothermal atomization 2.2.2. Low pressure atomization systems 2.3. Studies of Flames and Plasmas Using Laser-induced Fluorescence 2.4. Coherent Forward Scattering (Atomic Magneto-optical Rotation Spectrometry) 3 Laser-enhanced Ionization * Review Co-ordinator to whom correspondence should be addressed.216R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 This is the second 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. Spectrom. 1991 6 187R) and includes fundamental processes and instrumentation in the areas of atomic absorption and atomic fluorescence spectrometry together with 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 7 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 1.1. Flame Atomizers A survey of the atomic spectrometry literature published during this review period reveals that there is relatively little work appearing in the original literature in which flames as compared with other atomizers are used as the atom cell. Of the various sample materials surveyed by the Atomic Spectrometry Updates it is only in the area of the determination of impurities in organic solvents that flame atomization is used extensively (see J. Anal. At. Spectrom. 1991 6 323R).There is also a certain amount of work concerned with development of analytical method- ology involving FAAS that has appeared in the literature. In general these papers describe sample preparation and pre- treatment procedures for a particular analytical problem and therefore they are considered outside the scope of this review. Perusal of the relevant sample-based Updates will locate such papers. Often the methodology involves liquid-liquid extraction with nebulization of the organic phase (9 1/3405 9 1/34 12). Procedures for the determina- tion of various non-metallic elements by both direct and indirect methods and by molecular absorption spectro- metry have been reviewed (9 1/2997). The fact that there are relatively few contributions to the orginal literature does not necessarily indicate that the technique is no longer used as was pointed out by Hieftje (91/3798) in a reply to comments by L’vov and Slavin (J.Anal. At. Spectrom. 1991 6 191). In their response to Hieftje’s original provocative (but light-hearted) comments (J. Anal. At. Spectrom. 1989 4 117) they sought to rebut the notion that AA instrumentation would not be available in the market-place by the year 2000. Although the status of ETAAS may be secure it would seem that both parties agreed that ‘ICP-AES is gradually replacing FAAS for automated inorganic analysis’. Other elder statesmen of the atomic spectrometry world Sir Alan Walsh (91/C3693 Anal. Chem. 1991 63 933A) and J. B. Willis (Hist. Rec. Aust. Sci. 1991 8 151) have been providing insight into the early days of FAAS.It is interesting to note the crucial role played by early applica- tions papers in providing impetus for the continued development of instrumentation. Two papers in The Ana- lyst were thus cited as of historic importance (Allen J. E. Analyst 1958 83 466 and David D. J. Analyst 1958,83 655). They described the determination of Mg in plant material soil extracts blood serum and milk and the determination of Zn in plant digests respectively. 1.1.1. Fundamental studies There would appear to be relatively few publications relating specifically to fundamental studies of flame atomi- zation during this review period. Most of these describe the use of AFS and are therefore discussed later in section 2.3. The basic performance characteristics of flame techniques have been discussed in relation to atomic spectrometric methods based on other atomizer devices (9 1/3 196 921 1469).A theory relating absorbance to concentration that did not assume a limited number of absorbing atoms has been proposed (921C632). The theory took int6 account (i) features of the atomic spectral line such as broadening wavelength shift and hyperfine structure (ii) features of the spectrometer such as slit-width and stray light and (iii) spatial inhomogeneities in atomic and molecular partial pressures. In a study of the standardless determination of A1 (91/2978) it wgs shown that the most important para- meters were the fraction atomized and the factor by which the analyte was diluted by transport from solution to atomizer. The variations of these parameters with observa- tion height and fue1:oxidant ratio were studied 1.1.2.Interference studies As was noted for the previous review period there is a sustained interest in the study of interference effects in flames though there would appear to be a certain amount of repetition and duplication of such studies. The use of caesium as an ionization suppressant and of lanthanum as a releasing agent has been reviewed by Schinkel (9211849). It was concluded that by using these two elements in combination Ca Cr Fe Mg Mn Na and Sr could be accurately determined in almost all inorganic matrices. However Maqueda and Morillo (9 1/3 157) ob- tained low results in the determination of Ca in silicate materials because most of the added lanthanum precipi- tated immediately on addition.The precipitate was identi- fied as lanthanum fluoride and it was proposed that the fluoride was formed by the hydrolysis of the BF4- anion formed as part of the mechanism by which the boric acid added at the end of the digestion complexes with the excess hydrofluoric acid. ,It was found that hydrochloric acid suppressed the hydrolysis and that accurate analyses could be obtained with an air-CzHz flame. In the determination of Ba (9 1/3936) in strontium nitrate at concentrations between 600 and 700 mg kg-* by atomization in an N20-CzHz flame potassium was found to be effective as an ionization suppressant. For the determination of Ba in offshore oil-well waters (9 1/2775) magnesium (5 mg CM-~) was found to be effective in reducing the interference from other alkaline earth ele- ments in both the presence and absence of sodium.The introduction to this paper provides a useful overview of the various types of interference effect that could occur. The interjerence of aluminium on the determination of Ca and Mg in the air-CzHz flame (9 113503) has been found to be dependent on the nature of the anion present. In the presence of sulfate or nitrate a continuous depression of the signal with increasing concentration of aluminium was observed whereas in the presence of chloride the extent of the depression passed through a minimum. It was postu-JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 217R lated that two competing processes were responsible for this behaviour namely the formation of aluminates and the formation of chloro-complexes.Chinese workers adopted a somewhat different approach (9 1/3003) to the removal of this interference. A simplex optimization procedure pro- duced a mixed releasing agent cocktail consisting of lanthanum (1000 mg dm-3) strontium (500 mg dm-3) hexamine ( 10 g dm-3) and hydrochloric acid (diluted 1 + 9). The interference of up to 1000 mg dm-3 of aluminium on 10 mg dm-3 of Ca was removed. A study of the effect of sodium and butanol on the determination of K (921C528) by FAAS and FAES pro- duced results indicating that the K excitation was in excess of that expected on the basis of thermal equilibrium. It was suggested that collisions with electrons were responsible. Taiwanese workers have confirmed (92/287) that of the three acids hydrochloric nitric and sulfuric interferences are worst with sulfuric and least with nitric.Chinese workers have extended the list to include perchioric and phosphoric acids (921 1856) and found their behaviours to be somewhat similar to those of nitric and of sulfuric acids respectively. A variety of enhancement effects arising from the addi- tion of various solvents organic complexing agents and surfactants have again been reported. Chinese workers reported on the determination of Yb (91/3001). The combination of sulfosalicylic acid (0.05 mol dm-3) and sodium chloride (0.024 mol dm-3) in 0.1 mol dm-3 hydrochloric acid solution produced an enhancement factor of 23.6. In addition the depressive effects of sulfuric and phosphoric acids were substantially reduced.These workers have also reported (92/C458) on the effects of 8-hydroxy- quinoline triethanolamine glycine ethanol Chrome Azurol S calcein and some surfactants. Enhancement factors of between 4 and 50 were obtained. The enhance- ments were also obtained when FI presentation was used (9 1 /39 17). The signal for Cr was increased by a factor of 7.6 on injection of an ethanolic analyte solution into a carrier containing 10% sodium dodecyl sulfate (SDS). Russian workers have studied the various interferences by the principal components of non-ferrous alloys on the determination of Fe (9113054). It was found that the addition of triethanolamine could alleviate the effects of chromium lead nickel and tin and that an enhancement could be produced by the addition of methanol or ethanol.An air-C3H8-C4HI0 flame was used and the solutions nebulized were either based in nitric acid or a nitric- boric-hydrofluoric acid mixture. Increased signals in the determination of Cd and Zn were obtained on the addition of butylamine prior to an APDC/IBMK extraction (91/343 1). The procedure was relatively insensitive to pH the effects being observed over the ranges 7-12 for Cd and 2-12 for Zn. There has been further input to the debate concerning the effects of surfactants. Zhang et al. have reiterated in the Chinese literature (9 1/3922) their model of reverse micelle formation (see J. Anal. At. Spectrom. 1991 6 187R) to explain the enhancement effects observed. Mora et al. contributed measurements of drop-size distribution and transport efficiencies (91/3204).However for Mn as the test element no significant change in drop-size distribution was found in the presence of either a cationic surfactant [hexadecyltrimethylammonium bromide (CTAB)] or an anionic surfactant (SDS). Nor were any changes in trans- port efficiency observed and absorbance values remained constant in the presence of up to 1.5 x 1 0-3 mol dm-3 CTAB and 8.5 x mol dm-3 SDS. The solutions contained 2 mg kg-l of Mn and 1% (v/v) hydrochloric acid. The workers proposed that the absence of any measurable effects was due to the slow migration of the surfactant molecules from bulk solution to new surfaces formed in the nebulization processes. They suggested that this process is too slow to allow equilibration on the time-scales of droplet formation prevalent in the pneumatic nebulization pro- cesses and postulated that short chain surfactants might have a possible effect.A preliminary result concerning the enhancement caused by pentanoic acid was cited in support of this. By far the most comprehensive of the recent studies of the efiects of various dodecyl suyates has been made by Pharr et al. (9113598). Fifteen analyte elements were studied (Al Ca Cd Co Cr Cu Fe Mn Ni Pb Rb Sb Sn Sr and Zn) in the presence of four different surfactants (ammonium lithium sodium and potassium dodecyl sul- fates). The effect of 19 possible interfering cations (at concentrations of ten times that of the analyte element) were studied in the presence and absence of SDS. In addition the effects of other surfactants (CTAB and Triton- X 100) were investigated for Cu Cr and Pb and the effect of pH for Cd and Cu in the presence of each dodecyl sulfate was also studied.Four different patterns were observed for the relationship between absorbance and concentration of SDS though each group of elements showed an enhance- ment (including Mn). These workers concluded that the use of SDS produces an enhancement in signal and the masking of interferences for many of the metals studied. Although they discussed the possible role for aerosol ionic redistribu- tion (see J. Anal. At. Spectrom. 1991 6 187R) in some detail they did not comment on the reverse micelle formation model. Neither of these two recent studies (91/3204 91/3598) discussed the possible role for micelle formation and it would seem sensible that any future studies of these effects should address the question of whether in the particular cocktails of analyte surfactant acid and salt prepared the surfactant concentration is above the critical micelle con- centration (CMC). It is well known that the CMC for a surfactant depends on a number of factors including the ionic strength and the charge size and concentration of the counter ions.It is also worth pointing out that a possible confusion exists between SDS and sodium dodecyl sulfon- ate. At least one of the references cited above uses ‘SDS’ as an abbreviation for the latter. Koscielniak has described (9 ~ 3 9 3 5 ) a simple apparatus for the preparation of solutions for interference studies. The device which may also be used for the preparation of calibration standards and for standard additions consists of a small single well-stirred tank into which solutions can be introduced by a two channel automatic microburette. 1.1.3.Sample introduction At least two brief overviews (92/1458 92/1460) and one major overview have appeared during the review period. This latter contribution (Sample Introduction in Atomic Spectroscopy ed. Sneddon J. Elsevier Amsterdam 1 990) consists of a compilation of chapters by well-known investigators in the various areas of sample introduction. Of particular relevance to this Update are the chapters dealing with pneumatic nebulization (Cresser) slurry nebu- lization (McCurdy Weber Hughes and Fry) direct inser- tion of solids and powders (Ng) hydride generation (Nakahara) and flow injection analysis (Valcarcel).There is also a useful brief introductory chapter by the editor (Sneddon). Although there is a chapter on chromatographic techniques (Uden) it is confined to systems that use plasma emission spectrometry. Other techniques (laser ablation ETV and other nebulization techniques) are also covered but of course are more relevant to plasma spectrometry than FAAS. As was mentioned in the introduction there have been several reports of the introduction of organic solvents218R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 directly into flames. Although these were mainly orientated towards particular applications it is worth noting that some involved attempts to optimize the composition of the liquid phase.For example the effects of various organic solvents and hydrochloric acid on the determination of Zn in pharmaceutical preparations have been described (9 ~ 3 3 9 2 ) . The procedure devised involved dissolving the sample in a mixture of ethanol butan-2-one hydrochloric acid and water. It has also been shown to be possible to determine heavy metals in organic solvents by the intro- duction of emulsions (92/ 1 704). Kerosene solutions of bis-2-ethylhexylphosphoric acid were analysed for Mn and Zn following emulsion formation by the addition of Triton X- 100 and water. Workers at Jilin University have described an ultrasonic nebulization device (9 1/2998 9 113009). The system has been used for the determination of Cu in a pig liver reference material (9 1/2998) and for the evaluation of some detection limits (9113009).When used in conjunction with a slotted tube atom retarder (STAR) detection limits for Ag Cd Cu and Pb of 1.4 0.54 2.0 and 8.0 ng ~ m - ~ respectively were obtained. There is still some interest in the introduction of volatile metal derivatives. Bysouth et al. (9 l/C37 12) described a high pressure FI system in which acetylacetonate derivates were injected into a carrier stream of either liquid or super- critical carbon dioxide. The nebulizer was replaced by a simple heated restrictor which operated as a thermospray device. Hungarian workers (9 113475) have determined tetramethyllead and tetraethyllead in various organic solvents and shown that most of the analyte reaches the flame as a vapour.The difference in volatilities of the two lead compounds was exploited as the basis of a method for the determination in gasoline of total lead and the ratio of the two species (see also J. Anal. At. Spectrom. 199 1,6 187R and Mauri et al. J. Anal. At. Spectrom. 1989 4 553). Rigin has described a procedure for the determination of Co Fe and Ni by conversion into the volatile carbonyls (9 113328). The derivatives were generated by the simulta- neous addition of tetrahydroborate solution to and the passage of high purity carbon monoxide through the analyte solution. The procedure was applied to the determi- nation of wear metals in lubricating oils. 1.1.3.1. Discrete procedures. Beinrohr has published further considerations (92/240) on the relative merits of integrated absorbance and peak height for the quantification of transient signals (see J.Anal At. Spectrom. 1991 6 187R). It is concluded that peak area is directly propor- tional to the amount of analyte entering the flame and independent of the concentration profile (see also Tyson J. F. Anal. Chim. Acta 1988 214 57). Liu and Zhang have established an empirical relationship between atomization efficiency uptake rate and volume (92/C505). The possible benefits of decreasing the interferences from aluminium and iron on Ca Cr and Mg with decreasing sample volume were examined. Japanese workers have described a method for the determination of Ge in health beverages (9 1/34 10). Total Ge was determined by discrete nebulization (0.2 cm3) of a tetrachloromethane extract of the nitric acid digest follow- ing the addition of concentrated hydrochloric acid.Heating to 170 "C ensured that all organogermanium compounds were converted into inorganic species. To determine just the inorganic fraction in the original sample a portion was extracted with tetrachloromethane or butylacetate follow- ing hydrochloric acid addition. Calibration was linear from 0.00025 to 0.020 mg and recoveries of spikes between 25 and 250 mg kg-* were greater than 92%. A method for the simultaneous determination of Ag and Cu in silver brazing filler metals has been described (9 1/2708). After dissolution in nitric acid a 0.1 cm3 sample was introduced via a miniature PTFE funnel connected to the nebulizer capillary (the 'discrete nebulization' method).The monochromator bandpass was set so that the resonance lines of both elements (328.07 and 327.40 nm for Ag and Cu respectively) would reach the detector. The silver lamp was mounted as usual and the copper lamp was installed in the deuterium lamp mount. The instrument was modified so that the signals from the lamps could be captured by a personal computer. The dosage-injection system devised by Futekov et al. (see J. Anal. At. Spectrom. 199 1 6 187R) has been applied to the determination of Cu Fe Mn and Pb in concentrated nitric acid (91/3793). The sample was neutralized by gaseous ammonia producing a concentrated solution of ammonium nitrate and 0.25 cm3 portions were introduced between discrete slugs of water at 75 "C. 1.1.3.2. Atom-trapping techniques.As with recent review periods most of the limited activity in this area is by Chinese researchers. Wei et al. (9 11383 1) investigated the mechanism of the trapping of Pb on a water-cooled atom trap (WCAT) and noted that the Pb was collected as lead silicate and that the best enhancement was obtained from collection in a fuel-lean flame. To aid in the rapid release of Pb a solution of ammonium hydrogen difluoride was sprayed. An increase in sensitivity by a factor of 148 was obtained. Liu and Huo (9113341) developed a method for the determination of Ni at pg C M - ~ concentrations in tap water. After preconcentration by ion exchange the eluate was sprayed onto a WCAT coated with alumina. Calcium magnesium potassium and sodium did not interfere. The WCAT increased the sensitivity by a factor of 320. Li and Xiang (9113313) reported on a method for the determina- tion of Ga in aluminium.With trapping for 2 min the sensitivity was increased by a factor of 70 and for 15 min trapping the sensitivity was increased by a factor of 300. The use of the WCAT has been reviewed by Mi (9113013). Matusiewicz et al. have compared the use of a WCAT and a STAR for the determination of several trace elements in river and estuarine waters (92/1634). For the WCAT with 2 min collection detection limits of 0.9 I .5 and 0.3 ng cmF3 were obtained for Cu Mn and Zn respectively. With the STAR values of 4.0 12.1 2.0 and 1.2 ng C M - ~ were obtained for Cu Fe Mn and Zn respectively. Accurate determinations of these elements in two reference waters were reported.In the preliminary report of an As specialion study by HPLC directly coupled to an FAA spectrometer Hansen and Larsen (92/C8 18) increased the sensitivity for As in the air-C2H2 flame by the use of a STAR in a manner similar to that described by other workers (see J. Anal. At. Spectrom. 1990 5 179R). A STAR was also used in conjunction with an ultrasonic nebulizer device (9 113009) to increase the sensitivity over that of conventional nebuli- zation by more than an order of magnitude. 1.1.3.3. Sample introduction by flow injection. There is continued interest in the direct coupling of flow-based sample handling procedures and FAAS. As was apparent in the previous review period (see J. Anal. At. Spectrom. 199 1 6 187R) a majority of contributions to the original literature and conference presentations in which applica- tions of FAAS are described feature in this section of the Update.In addition to Valcarcel's chapter contribution alluded to earlier (see section 1.1.3.) Tyson has reviewed the entire field of flow injection atomic spectrometry (FIAS) (Tyson J. F. Spectrochim. Acta Rev. 1991 14 169) and Fang has provided a detailed survey of on-line column preconcentration (Fang Z. Spectrochim. Acta. Rev. 199 1 14 235) an area in which there is considerable activity at present. Tyson's review contains an update of the table on the analysis of real samples by FIAS following on from tables in earlier reviews (see Tyson J . F. Analyst 1985,JOURNAL OF ANALYTICAL ATOMlC SPECTROMETRY AUGUST 1992 VOL. 7 219R 110 419 and Anal.Chim. Acta 1988 214 57). This table contains a further 78 entries of which 32 feature FAAS as the instrumental finish to the method. Schrader has provided a more modest overview for German readers (92/327) who will also find several papers of interest in the Proceedings of the 6th Colloquium Atomspektrimetrische Spurenanalytik (Welz B. ed. Perkin-Elmer Uberlingen 199 1). There have been several re-evaluations of the basic characteristics of the FI-FAAS combination. Fang et al. (9113212) showed that with a modern spectrometer the contribution of the nebulizer and spray chamber to the over-all dispersion was much reduced in comparison with an earlier generation of instruments. It was shown that with a knotted tube reactor connection between the valve and the nebulizer a signal corresponding to 98% of the steady state could be obtained for an injection volume of 0.065 cm3.Tolerance to high dissolved solids was once again convincingly demonstrated by the introduction of 10 mg dm-3 Pb solutions in saturated lithium borate solution and 30% (m/v) sodium chloride solution at rates of 360 and 180 samples h-l with precisions of 0.9 and 2% RSD respectively. Sperling et a/. devised an FI version of the method of successive dilutions (9 113078). This paper beauti- fully illustrates the power of the controlled disperson chracteristics of FI and is highly recommended reading. These workers exploited the reproducible concentration profile of the FI peak to calculate a ratio between the signal for an analyte peak and a reference peak at a sequence of times across the transient signal.This ratio was plotted and an appropriate function fitted to allow extrapolation to zero concentration (i.e. infinite dilution). At infinite dilution all interference effects have ceased to operate and a linear absorbance-concentration relationship was obtained. The signal ratio can be taken therefore to be the concentration ratio. The method was illustrated by the determination of Ca in the presence of phosphate. In describing the FIAS combination it was stated that ‘Flow injection not only offers AAS a means for automatic sample introduction but also techniques for fully automated sample management including dilution addition of reagents preconcentration separation and calibration hence improving performance in most aspects of the analytical method’.At least three other research groups have described procedures for on-line dilution. Carbonell et al. (9 1/3592) have described a number of manifolds incorporating either a single well-stirred tank or two such tanks in parallel for the on-line dilution of solutions of ceramic samples pre- pared by fusion with alkali carbonates. The maximum dilution factor was such that up to 140 mg C M - ~ of K could be determined. Other analytes included Al Ca Fe Mg and Na. An empirical relationship between concentration and time was adopted (see J. Anal. At. Spectrum. 199 1,6 187R) rather than use the exponential functions which character- ize the theoretical behaviour of a well-stirred tank reactor. A merging-zone configuration was used for the addition of lanthanum.Beinrohr et al. (9 1/3780 92/C508) described the use of a variable volume dilution chamber made from a disposable plastic syringe. The chamber volume could be varied from 0.1 to 10 cm3 which in conjunction with an injection volume variable over the range 0.015-1 cm3 increased the working range of an FAA spectrometer by 2-3 orders of magnitude. In addition good agreement was achieved between the measured peak shape and that predicted on the basis of a simple two-tanks model. Tyson et af. (91/C365) described a manifold for the serial dilution of standards or off-range samples. The system contained a closed recirculating loop. Initially the loop was filled with the most concentrated standard and a sub-sample was injected into a single line for transport to the spectrometer.On return of this valve to the initial position an equal volume of carrier (diluent) was introduced into the loop the contents of which then circulated until the now diluted concentration became uniform. Activation of the valve a second time injected a second standard into the spectro- meter carrier line. The entire process could be repeated as desired. Kimber et af. (92/C 1943) presented results for the coupling of a system for programmed dijjferentiafflow (DF) with an atomic spectrometer for calibration and dilution purposes. It is not clear from the abstract how the system was configured as the DF system normally employs a flow- through detector mounted between two reagent delivering syringe pumps working in opposition (see Arnold et al.Anal. Chem.,’ 1989,61 2 109). If the flow into the aspirating pump is higher than that of the delivery pump sample is aspirated at a confluence point. Further disclosure of the details of this combination is awaited with interest. There is still an interest in using FI techniques for handling solutions with high dissolved solids (9 l/C3652 92/1651). The determination of Fe in beer has been demonstrated (Hergenreder R. L. At. Spectrosc. 1 99 1 12 74). Hinds and collaborators (92/C72 1) showed that solu- tions containing up to 150 g dm-3 of silver nitrate could be introduced into a single-line manifold without excessive build-up of silver acteylide. It was also shown to be possible to remove the interference by on-linejltration of a silver chloride precipitate formed on-line.This work represented a development from manifolds designed to precuncentrate the analyte by precipitation (91/2705) and retention on a disposable membrane filter. Preconcentration has also been achieved by Sperling and co-workers (9 113779 92/C500) by precipitation without filtration. It was shown that Pb could be co-precipitated with iron( 11) hexa h ydroazepinium hexamet hylenedi t hiocar- bamate and retained on the walls of a knotted tube reactor. The precipitate was dissolved in IBMK and transported directly to the flame. An enrichment factor of 20 and an enhancement of 66 were obtained for a precipitation time of 30s. The detection limit (3s) was 2 ng cm-3 and the throughput was 90 h-I. The method was demonstrated initially for the determination of Pb in blood and bovine liver but was later extended (92/C500) to the determination of Cd Co Ni and Pb in these matrices and orchard leaves (see also Welz et al.Appl. Spectrosc. 1991 45 1433). The direct determination of Cu and Fe in edible oils has been described (Carbonell et af. J. Anal. At. Spectrum. 1991 6 581). Tyson’s method of standard additions was used in which the standards (as APDC complexes or as organometallic complexes in oil) were injected into the oil sample stream pumped continuously into the spectrometer. Good agreement between the FI procedure and a dry ashing procedure was obtained. The analysis of iron oxide by FI slurry nebulization with two methods of standardization has been reported (Lopez Garcia et al.Analyst 1991,116 5 17,92/424). In the first of these methods the nebulizer was operated under starvation conditions with air compensation. After drying and grind- ing to pass a 325 mesh sieve the material was suspended in a 1 O/o (m/m) sodium hexametaphosphate solution (also giving a slurry composition of 1%) and a 0.135 cm3 sample volume injected into the carrier flowing at 2 cm3 m1n-l. Calibration was by the introduction of previously analysed ore materials as identical slurries. In the later publication (92/424) a variation of Tyson’s method proposed by Israel and Barnes was adopted in which the sample and a matrix matched standard were injected sequentially into an aque- ous standard carrier stream. For the determination of Cr Cu Mn and Zn there was no significant difference between the results for the proposed method and those obtained by a procedure involving acid dissolution. There are indications of efforts to extend FI methodology220R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 to include solid sample preparation. A procedure for the determination of Cu in aluminium alloys by on-line electrolytic dissolution has been described by Yuan et al. (92/50 92/C639). The method was shown to be suitable for Cu concentrations in the range 0.5- 10% (m/m). The partial digestion of sewage sludge in a recirculating manifold incorporating a microwave-heated zone was described (9 ~ 3 2 5 5 ) by collaborators from Valencia (Spain) and Merida (Venezuela). After emerging from the microwave oven the sample passed through an ice-bath a gas-liquid separator and the loop of an injection valve.Accurate determinations of Pb in two reference materials were made. Tyson et al. (92/C642) have presented some preliminary results for a flow manifold incorporating a stoppedjlow high pressure dissolution step. The slurried sample was injected into a merging stream manifold to add concentrated nitric acid and the flow stopped in a laboratory-constructed miniature thermal oven. After dissolution and depressuri- zation a sub-sample was injected into a carrier stream for delivery to the spectrometer. Agreement between the FI method and other digestion procedures for the determina- tion of Cu in cocoa was reported. This paper also reported on the use of a closed loop manifold to leach Ca from charcoal and the use of supercritical or liquid carbon dioxide as a carrier stream for the introduction of metal complexes into a flame.A high-pressure system was also used by Martinez Calatayud and Garcia Mateo (91/3181) in an indirect procedure for the determination of glycine. The sample was injected into a carbonate-hydrogen carbonate buffer and pumped through a packed bed reactor (0.5 cmx0.9 mm id.) of copper(I1) carbonate. The method was evaluated for the determination of glycine in a pharmaceuticeutical formulation and found to be free from systematic error associated with the presence of other components. At 50 mg dm-3 glycine the RSD was 1.9% and the throughput 40 h-l. The use of flow based indirect atomic spectrometric procedures for the determination of pharmaceuticals has been reviewed by the Cordoba group (9 1 /40 1 1 ).Procedures involving precipitation liquid-solid extraction and liquid-liquid extraction were surveyed. This group has also developed a liquid-liquid extraction procedure for the indirect determination of bromazepam (Santelli et al. Talanta 199 1 38 124 1) based on the extraction of the ion pair between the copper complex and perchlorate into IBMK. Following phase separation a 0.1 cm3 sub-sample was injected into an aqueous carrier stream for transport to the spectrometer. Several pharmaceutical preparations were accurately assayed. A similar procedure was used by Jiminez de Blas et al. (9 1/27 15) for the indirect determina- tion of the dithiocarbamate content of a fungicide. Again the copper complex was extracted into IBMK.A thin-layer cell style phase separator was employed containing a hydrophobic membrane sandwiched between PTFE mem- branes. A detection limit of 30 nmol of diethyldithiocar- bamate was obtained. In both of these procedures the FI valve acts as an interface between the continuous liquid-liquid extraction system whose optimum flow rate is approximately 1 cm3 min-l and the FAA spectrometer operating at an introduction rate of 2.25 cm3 min-I. Indirect precipitation methods for inorganic anions were described by Esmadi et al. (91/3185,91/3310). Acontinuous stream of sample solution was merged with a precipitant stream and the flow stopped for 2 min with the reacting zone in a Tygon tube (7 cm x 2.8 mm id.) containing 1.9 mm diameter glass beads mounted in the loop of the injection valve.Chloride and iodide were determined (91131 85) by precipitation as the silver salts followed by washing with dilute nitric acid and sequential selective dissolution of the choride in ammonia solution and the iodide in cyanide solution. Chloride and carbonate (9 1 /33 10) were separately determined by precipitation as the silver and calcium salts respectively followed by dissolution in ammonia thio- sulfate or cyanide solution for the determination of chloride and hydrochloric acid solution for the determination of carbonate. For this latter method detection limits of 1 x lW7 mol dm-3 were obtained. As was noted for the previous review period (J. Anal. At. Spectrom. 199 1 6 187R) there is considerable activity in the development of solid-phase extraction (SPE) procedures for sample preconcentration.An overview of these has been given (91/C2899) and at the same conference (see Tyson J. F. J. Anal. At. Spectrom. 1991 6 345) a criticism of the manifold design commonly adopted for SPE was made by Lancaster et al. (91K2902A). It was argued that perform- ance was limited by the legacy of chromatography namely tightly packed columns and uni-directional uniform flow. The benefits of the alternatives provided by sequential injection and sinusoidal bi-directionalflow (see Gubeli et a/. Anal. Chem. 1991 63 2407) were demonstrated for preconcentration by sorbent extraction. In this procedure a loosely packed C- 18 solid phase extractant was first loaded with chelating agent and then the sample solution was passed over the ‘derivatized’ surface and the analyte element removed.The chelate complex was dissolved in an organic solvent (ethanol or methanol) and transported directly to the spectrometer. The same C-18 SPE has been used for the determination of Cd Cu and Pb in water samples (92/1720) although in this case the metals were first derivatized by merging with a stream of diethylam- monium diethyldithiocarbamate. The sample loading time was 20 s at a flow rate of 3.3 cm3 min-’ with elution by ethanol at 2.5 cm3 min -l. Enrichment factors of between 19 and 25 were obtained at sampling frequencies of 120 h-l. Detection limits of 0.3 0.2 and 3 ng were obtained for Cd Cu and Pb respectively. Accurate analyses of a standard reference water were reported together with recoveries of Cd and Pb from sea-water samples of 95 and 102% respectively.Xu et al. (92/53) described a method for the determina- tion of Au in ores. Following retention of from a hydrochloric acid medium on an Amberlite XAD-8 column (0.22 cm3 in volume) the preconcentrated Au was eluted with ethanol. An enrichment factor of 35 was achieved at a sampling frequency of 60 h-’ with a detection limit of 2 ng ~ m - ~ . Olbrych-Sleszynska et al. first loaded a chelating ligand onto Amerlite XAD-2 for the determination of Cu and Ni (921C501). A different reagent was used for each with Eriochrome Black R exhibiting good selectivity for Ni in the presence of high concentrations of alkali and alkaline earth metals and Pyrocatechol Violet trapping Cu.Mea- surements at sub-ng concentrations were possible. Beinrohr et al. (92/C508) have developed procedures using chelating ion-exchange resins. This conference presentation also indicated some work involving electrodeposition on powdered glassy carbon as a preconcentration procedure for Cd Cu Mn and Pb was being carried out. Electrodeposi- tion was complete at flow rates of 3-4 cm3 min-I and after short circuiting the electrodes the metals were eluted in dilute acids. A procedure for the determination of Co in glasses involving Chelex- I00 preconcentration has been developed (Valdes-Hevia y Temprano et al. Analyst 199 1,116 1 14 1 ). A detection limit (3s) of 20 ng ~ m - ~ was obtained for a 1 cm3 sample volume. The manifold consisted of a two stage pH adjustment over a total length of 8 m of tubing to load the sample at pH 7.Elution was effected with 0.2 cm3 of 5 mol dm-3 nitric acid. Problems with the dimensional instability of the resin were encountered and it was found important that all traces of silicon from the glass samples were removed in the pre-treatment with hydrofluoric acid.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 221R Citrate was used to mask the interference from iron. The benefits of 8-hydroxyquinoline immobilized on a dimension- ally stable substrate have again been shown Graf-Harsanyi (92/C5 19) used 8-hydroxyquinoline on silica for the pre- concentration of Cd Cu and Pb from a variety of water samples. Chinese workers used several SPE materials including 8-hydroxyquinoline immobilized on controlled pore glass for the determination of Co in natural waters (91K3129).A detection limit of 0.2 ng cm-3 was obtained with a sampling frequency of 60 h-' in a system which employed two columns in parallel. The extraction (pH 7-8) could be performed at 9 cm3 min-' with elution (2 mol dm-3 hydrochloric acid) at 5 cm3 min-I. A series of tercopolymeric resins incorporating 8-hydroxyquinoline re- sorcinol and hydroquinone have been synthesized and characterized for use in FI preconcentration procedures (92/1423) for the determination of Cd Co Cu and Zn. Detection limits (3s) of 1 ng C M - ~ were achieved and it was shown to be possible to elute metals sequentially (in binary mixtures) from the columns by switching the eluent from acetic to hydrochloric acid.Shah and Devi (91/3083) have evaluated the performance of a poly(hydroxamic acid) resin for the preconcentration of CrlI1 from sea-water samples. The material was also evaluated as an LC stationary phase for the separation of CrlI1 from mixtures also containing copper iron uranium and zinc. Various possibilities for FI enhancement of FAAS per- formance have been surveyed by Fang (92/C640). It was shown that by a combination of SPE with nebulization of a suitable organic solvent eluent into a flame containing an atom retarder sensitivities could be enhanced by factors of between 100 and 200 at sampling frequencies of up to 100 h-l. Other Chinese workers have shown (91x39 17 92/C458) that there are additional possibilities if the carrier stream contains a surfactant (see section 1.1.2.). A number of papers have appeared during the period covered by this Update concerned with the use of FI techniques for the implementation of chemical vapour generation procedures especially the generation of volatile hydrides and of cold vapour mercury.Clearly the latter procedure does not involve a flame atomizer but for the former procedure there were some contributions to the literature in which a tube-in-flame atomizer (or even a flame-in-tube atomizer) was used in addition to the more satisfactory electrically heated quartz tube atomizer. As the main interest in these papers was in the chemical vapour generation process these papers are not considered in detail in this section but are described further in section 1.3.However it is of interest to note some of the pre- treatment procedures used in conjunction with HG. For example OMey et al. (91/C3203) devised a method for the determination of Se in copper in which the matrix interfer- ence was eliminated by retention of the copper on a strong cation-exchange resin. The continuous flow matrix removal manifold was linked to the HG manifold via the FI valve. The cation-exchange resin was also linked to a continuous flow regeneration acid stream via a second rotary valve. Workers at various Perkin-Elmer laboratories have investi- gated some of the fundamental performance characteristics of FI-based HG procedures (9 lK2900 92/1652) and demonstrated the improved tolerance to transition metal interferences inherent in the FI method when compared with the batch method (Welz and Schubert-Jacobs At.Spectrosc. 1991 12 91). Lin et al. have provided preliminary results for the electrochemical generation of hydrides (92K639). The determination of mercury (9 1 /C290 1) sometimes provides an example of an FI procedure with a gas-solid phase extraction preconcentration as procedures in which the separated mercury vapour is trapped on a gold (or other noble metal) substrate provide increased sensitivity and potential freedom from gas-phase interferences (92/90 92/C527). The resulting peak shape is governed only by the kinetics of the release of the mercury from the amalgam. This procedure was used as the final stage in a method that distinguished between ionizable and stable forms of mer- cury in animal tissue (9 1/3 180).1.1.3.4. Solid sample introduction. The use of FI proce- dures for the introduction of slurries of iron ores (92/424 Lopez Garcia Analyst 199 I 116 5 17) has already been described in the previous section. A study of the relative sensitivities of some slurries of calcium salts introduced into the air-C2H2 flame the N20-C2H2 flame and an ICP source has been made by Salvador et al. (92K525). It was repoted that particle size (between 4 x and 5 . 0 ~ mm) was not a critical parameter but that the nature of the salt was. For all three atom sources tricalcium phosphate exhibited the lowest sensitivity relative to that of an aqueous solution. Details of the combustion device devised by Campos and collaborators (see J. Anal. At. Spectrom. 1990 5 179R) have now been published (91/2710).The sample material (0.1-2.0 mg) was placed on a graphite platform and inserted into a quartz tube. Radiation from three 150 W IR lamps was focused onto the sample which burned in a stream of air. The resulting smoke was transported into a tube-in- flame atomizer. The system was used for the determination of Cd Cu Hg Pb and Zn in a range of plant materials animal tissues sludge and milk powder. Calibration against a solid standard of similar matrix was necessary. As there is considerably reduced sample dilution compared with a dissolu t ion-based procedure sensitivity improvements of about two orders of magnitude were obtained. 1.1.4. Chromatographic detection As interest in providing information about the speciation of elements grows it is likely that there will be a parallel growth in interest in the combination of chromatographic separation coupled with atomic spectrometric detection.Although it might be argued that this combination ought more properly to be classified under FI atomic spectro- metry a separate category which emphasizes the separation of different forms of the same element is included here. However it is likely that as the greatest interest will be in speciation at trace concentrations flame atomizers will not feature particularly prominently in this area. The separation of seven As species of biological interest by HPLC directly coupled to the nebulizer of a flame atomizer has been demonstrated (92K818). A method for the measurement of four As species in urine had been devised by Py and Hakala (92K452).Ebdon et al. (92/1719) have described a procedure for the determination of Sn species in coastal waters by HPLC with post-column UV photolysis and HG. The atomizer was an entrained air-H flame. It was shown that tributyltin was converted into inorganic tin which could be detected down to a limit of 2 ng. Van Beek and Baars (9 1 /3 102) determined various metalloproteins containing Cu Cd and Zn by directly coupling the eluent from the UV HPLC detector to the nebulizer of the AA instrument. Bovine and rat livers and horse kidney were examined. German workers have described an indirect flame AAS detection procedure for ion chromatography (921 1442). The eluent contained 9.7 x mol dm-3 chromium(~~r) to which the detector responded.The separation of K+ NH4+ and Na+ were detected as negative peaks in a steady absorbance signal. High-pressure nebulization gave better performance than pneumatic nebulization. On an even more exotic note the carbonyls of Co Ni and Fe have been separated on a 1220 mm GC column packed with glass wool coated with OV- 10 1 silicone and Emulphor222R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 ON-870 prior to detection by a variety of atomic spectro- metric techniques (9 113328) including FAAS. 1.2. Electrothermal Atomizers During the period of this review the field of electrothermal atomization appears to be still a fruitful area of research for many. The volume of material produced each year espe- cially with respect to conference abstracts continues to grow.This requires a degree of critical selection to be applied to the material available and in the main applica- tion papers are not considered in this section as these are covered fully in the application reviews. The major area of ETAAS research to have undergone a revival is that of atomization processes and chemical modifier mechanisms and the array of alternative analytical techniques employed to investigate these is certainly impressive. The historical background to the pioneering work in ETAAS and the subsequent commercial development of the technique was discussed by L’vov (Anal. Chem. 199 1 63 924A.). This paper can be recommended as it gives excellent background information on the early days of ETAAS and subsequent developments.1.2.1. Atomizer design and surface modijcation Ortner et al. (921C724) have reviewed the materials used for the construction of a tube furnace. Scanning electron microscopy was shown to be a valuable tool for the study of the structural details of these materials and of changes in the surface morphology upon prolonged use. The major development with respect to atomizer design during the period of this review was the commercial introduction of a transverse-heated graphite atomizer in conjunction with longitudinal Zeeman-effect background correction (9 113546 92/C37 15 921C526 92/C741 921C756). The transverse-heated graphite tube with inte- grated contacts contains a curved platform machined within the tube and supported at only one point (9114049). This design produces a more homogeneous temperature profile with respect to time and space and also allows atomization of refractory elements from the platform (9 11C37 15 921C756).Lower atomization temperatures reduced interferences improved detection limits and a reduction in memory effects are advantages claimed for this design (921C526 921C741 921C756). The atomizer design is based on the work of Frech et al. and the background correction system on that of de Loos Vollebregt et al. which has been discussed in previous reviews. Two new designs of commercial atomizers were reviewed this year. A new version of the transverse-heated tungsten tube WETA design the WETA-90 was discussed by Ortner et al. (91/4050) and Sychra et al. (J. Anal. At. Spectrom. 1991 6 521).The advantages claimed include a homoge- neous surface temperature distribution along and over the surface of the tube spatial and temporal isothermal temperature distribution within the tube almost total absence of memory effects for carbide-forming elements and considerable freedom from interferences. Shan et al. (921C759) examined the use of this device and found lower characteristic masses (3- to 10-fold) for volatile elements using integrated absorbance measurements compared with those obtained with a heated graphite atomizer (HGA-600). The WETA-90 had definite advantages over the longitudi- nally-heated graphite atomizer for the determination of rare earths and other carbide-forming elements. Detection lim- its for Sc and Yb were 5 and 0.4 pg respectively.Other workers (911C2746 911C2754) used the older tungsten atomizer design WETA-82 to examine matrix effects on the determination of Cd (91/C2746) and rare earth ele- ments (9 1 /C2754 92/ 1836). The characteristic values ob- tained were comparable to or better than those obtained with a graphite tube atomizer lined with tantalum foil but worse than those obtained with a tantalum platform in a graphite tube atomizer lined with tantalum foil. Komarek and Ganoczy (9211840) compared a WETA-tungsten atom- izer and a tungsten probe in conjunction with a graphite tube atomizer lined with tantalum for the determination of Eu. The life of the tungsten probe was extended by using an Ar-H2 flame. The sensitivity for Eu in the tungsten atomizer was increased by using lanthanum as a chemical modifier.Ohta et al. (921 13 1) used a tungsten tube atomizer to determine Li by atomic emission in biological samples. Lanthanum nitrate was used as a chemical modifier to eliminate interferences. The same group (9 11325 1) exam- ined the Ca atomization process in a molybdenum tube atomizer using sulfur as a chemical modifier. Russian workers (92/ 149) employed a graphite double tube atomizer coated with sodium tungstate for the determination of Sn in refined gold. An automatic graphite probe system was applied by Lin and Hao (92/122) to the determination of In in geological materials. The probe atomization mechanism was investi- gated and the activation energy for the atomization of In calculated and found to be in good agreement with the bond energy for In-In.The atomization mechanism of tin(I1) chloride from a graphite probe surface was examined by Deng and Wang (92/C675) further details are discussed under section 1.2.3. Chinese workers (92/C698) applied a tungsten probe coated with trioctylphosphine oxide for the determination of Bi in copper alloys and lead. The coated tungsten probe was dipped into the test solution for a set time washed and then inserted into the pre-heated graphite atomizer. With few exceptions the use of metal or metal carbide coated graphite surfaces seems to be the sole preserve of Chinese and Japanese workers. As discussed in last year’s review (J. Anal. At. Spectrom. 1991 6 187R) tantalum continues to be the most popular choice. Wu et al. (9 11336 1) continued their work on tantalum foil-lined graphite tubes for the determination of Sn in canned tomato mushroom and river sediments using copper as a chemical modifier.A 6-fold increase in sensitivity com- pared with that of a pyrolytic graphite coated electrogra- phite tube was found. Addition of H2 to the Ar purge gas maintained the analytical reproducibility of the tantalum foil-lined tube and enabled lifetimes of approximately 650 cycles to be achieved. Liang et al. (91/3268) used STPF conditions with a tantalum boat to determine Gd in biological samples following extraction of the Gd into IBMK and back extraction into hydrochloric acid. The use of the tantalum boat improved sensitivity compared with the use of pyrolytic graphite coated electrographite tubes; approximately 1 50 measurements could be performed with one boat and memory effects were overcome by the use of the tantalum boat.A characteristic mass of 1000 pg and a detection limit (2s) of 2060 pg were found. The vaporiza- tion and atomization characteristics of Cu samples from graphite and tantalum-lined tubes using tantalum and graphite platforms were studied by Fonseca et al. (9 112985). Ma (921C782) used a tantalum foil platform pyrolytic graphite platform and wall atomization in pyrolytic graph- ite coated electrographite tubes in an examination of standardless analysis of Cd in sea-water and various environmental RMs. The combination of a tantalum foil platform with a pyrolytic graphite coated elect rograp h i te tube and a chemical modifier of 0.5 mg cm-3 palladium was preferred.In addition Ma and Sun (921C564) studied the use of pyrolytic graphite coated electrographite tubes lined with tungsten and tantalum for the determination of Er and Yb by standardless (absolute) analysis. No details wereJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 223R given in the abstract of the exact composition of the tungsten-tantalum foil used. Atomization processes for rare earth elements from graphite and tantalum surfaces were studied by Wie et al. (921C766). In combination with a study of cerium(1v) and cerium(1v)-palladium(I1) mixtures as chemical modifiers the effects of electrographite pyro- lytic graphite and a coating of tantalum carbide as the atomization surface were examined (9 1 /3287). Radziuk and Welz (92/1649) examined the influence of graphite and tantalum platforms and tantalum-lined graph- ite tubes on the atomization of alkaline and rare earth elements.Comparison of theoretically predicted and exper- imental values for the characteristic masses showed that atomization efficiencies for such elements in graphite tubes were less than unity and that the use of a tantalum platform makes it possible to perform such determinations under STPF conditions. The shapes of the atomization pulses obtained using metal-foil lined tubes were compared with those for conventional graphite atomizers and interpreted on the basis of model calculations. Chen et al. (9 113 133) found that the sensitivities of Al B Ba Cr Fe and Sn using graphite tubes coated with tantalum and tungsten were improved.No improvement was seen for Pd and T1. The surface characteristics of the coatings were studied using XRD and SEM. A tungstate-coated pyrolytic graphite coated electrographite tube was found by Iwamoto et al. (92/C792) to give improved sensitivity elimination of double peak formation and improved results for the determination of Sn in biological and sea-water samples. The tube was coated by injecting 100 mm3 of 0.01 mol dm-3 sodium tungstate and heating with an atomizer programme of 150 "C ramp 15 s hold I0 s; 900 "C ramp 20 s hold 10 s; 2700 "C ramp 0 s hold 3 s; 2700 "C ramp 1 s hold 1 s. This procedure was repeated five times and the coated surface was stable for at least 100 firings. Ceccarelli et al. (92/C788) compared the performance of new and previously used Perkin-Elmer and Varian pyro- lytic graphite platforms with and without tungsten coatings applied by a pressure vapour deposition (PVD) method.Scanning electron microscopy showed that uniform 5 pm thick coatings could be achieved with this technique. The platform performance was assessed for the elements Cd Cu Ge Mo Pb and V with respect to linear range precision and characteristic mass. In general similar results were obtained from the Perkin-Elmer and Varian systems. Lead showed a 50% increase in signal from a tungsten- coated Perkin-Elmer platform but no change was observed for a tungsten-coated Varian platform however for Ge the tungsten-coated Varian platform enabled the signal to be doubled with only a slight increase for the tungsten-coated Perkin-Elmer platform.It is not clear what the objectives of this work were although it would appear that the sole advantage is an increase in the lifetime of new and used platforms. The same group (92/C783) examined in greater detail the influence of various metal coatings on pyrolytic graphite platforms on the atomization of Cd. The Cd recovery for a platform coated with tungsten by the PVQ method was doubled in comparison with a platform coated with an aqueous tungsten solution. Yang (92/59) treated an arc-shaped platform with molyb- dates to determine A1 in silicon steel and pure iron. The coating reduced the matrix effect on the absorbance signal and improved the precision. Kitagawa et al. (91/3351) have continued their work discussed last year (J. Anal.At. Spectrom. 199 1 6 187R) on the atomization behaviour of Co Fe and Ni from metal strip atomizers. The atomizers of molybdenum tantalum and tungsten are now in the form of an 'M' with solutions pipetted into the well of the 'M'. There appears to be a general consensus among those investigating metal- or metal-coated atomizers that the addition of H2 to the Ar purge gas helps prolong the lifetime of the atomizer (91/3361 J. Anal. At. Spectrom. 1991 6 521) and improves the signal shape (9 1/335 1). Ulsamer and Miiller (92/C446) reviewed in detail the properties of graphite and discussed its manufacture and coating with pyrolytic graphite for the purposes of ETAAS. Zheng and Xiang (91/3425) examined the atomization behaviour of Ag Pb and V from electrographite pyrolytic graphite coated electrographite and total pyrolytic graphite tubes.Not surprisingly they found that broad peaks were obtained for Ag and V in electrographite tubes due to the formation of carbides. With the total pyrolytic graphite tube sharp signals were observed for all three elements and the sensitivity for V was enhanced. Yang (92/C723) discussed the use of electron microscopy techniques to study the kinetics and mechanisms of gas-carbon reactions on a single layer of the single-crystal graphite. The catalytic mechanism of the gasification reactions of graphite by hydrogen oxygen water vapour and carbon dioxide with Group VIII metals for carbon hydrogenation to form methane appeared to be due to the metal particles catalys- ing the gasification reactions by cutting deep (multi-layer) channels on the basal plane of the graphite.Monolayer reactions were also observed. 1.2.2. Sample introduction The topic of sample introduction continues to generate a large volume of publications and conference abstracts. The general trend from this year's review is that the field can be viewed in two halves those considering solid or slurry sample introduction and secondly those using coupled techniques such as FI to link automated hydride or preconqentration techniques with an electrothermal atom- izer. General acceptance and maturity of a technique can be judged when the first review articles start to appear. Bendicho and de Loos-Vollebregt (92/4 10) reviewed the introduction of solid samples in commercial atomizers. This comprehensive review covering 252 papers can be recommended to workers interested in this field.Aspects discussed include atomizer design factors influencing accuracy and precision chemical modification direct solid sampling and preparation of slurries. Detailed tables are presented listing applications of solid and slurry sampling. The authors concluded that slurry sampling offers a number of advantages over direct solid sampling such as automa- tion ease of applying chemical modification which appears to be more effective than direct solid sampling and calibration against aqueous standards is possible. The benefits of automated ultrasonic agitation for slurry preparation were discussed by Miller-Ihli and co-workers (9 1/3508 9 l/C3653 92/C773). Fast atomizer programmes and slurry sampling were combined (9 1/3508) and accurate results found when the samples were homogeneous.In a subsequent conference report (9 1 /C773) ultrasonic agita- tion and the procedure of Ar bubbling through the mixture containing hydrofluoric acid described by Bendicho and de Loos-Vollebregt and discussed last year (J. Anal. At. Spectrom. 199 1 6 187R) were compared for the prepara- tion of coal slurries. The ultrasonic agitation procedure with the slurry prepared in 5% nitric acid and 0.005% Triton X-100 gave results in agreement with the certified values whereas the Ar bubbling and ultrasonic procedure without using Triton X-100 gave only 69-74% of the certified value. It would appear that the hydrofluoric acid and Ar bubbling technique is only suitable for silicate materials.Further results from this work (92/C773) indi- cated that for the successful preparation of slurries by ultrasonic agitation the density of the material has to be considered and that the maximum mass of sample that can be taken is I00 mg suspended in 1 cm3 of solvent. Reference materials were found to be homogeneous when samples224R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 sizes of 10-25 mg were taken. Sedykh et al. (9113815 921C752) used a commercial ultrasonic agitation system to examine the direct introduction of slurries of polymer sorbents for the determination of As Cd Co Cu Ni Pb Sb Se Te and platinum groups metals in mineral waters rocks and ores. Carbon and carbon-containing residues were the main products of polymer sorbent destruction.The carbon remaining on the surface acted as a platform for elements such as Cd Co Cu Ni and Pb. The influence of particle size and density on the analytical signal were studied. The reproducibility of the measurements was improved by the use of ultrasonic agitation. Mo and Holcombe (92117 18) preconcentrated Co and Ni from river- and sea-water samples on unicellular green algae and after centrifugation determined Co and Ni by slurry sampling ETAAS of the algal pellet suspended in 1 cm3 of 0.08 mol dm-3 nitric acid. Rinsing the algae with 0.12 mol dm-3 hydrochloric acid improved the adsorption of Co and Ni. Preconcentration was achieved by mixing 6 mg of algae with 50-100 cm3 of sample and subsequently isolating the algae by centrifugation. The maximum extrac- tion efficiencies were 73 and 84% for Co and Ni respec- tively at pg dm-3 levels.The sea-water matrix and relatively small amounts of many impurities reduced the adsorption efficicency for both Co and Ni. Values found for Co and Ni in river- and sea-water RMs were within the certified values. Tittarelli and Biffi (921C774) used a diode array spectro- meter to examine the vapour phase spectra obtained from slurries of fly ash soil sludge sediment and milk powders during atomization under STPF conditions. Sharp molecu- lar bands due to SiO species were observed in the 200-255 nm region during the atomization of soil and silicate slurries at 1800 "C. The use of a palladium-magnesium modifier decreased the intensity of these structured bands but added a broad background over the entire UV range which appeared at the start of the atomization and remained for 2.5 s and sharp bands due to decomposition of the modifier were observed between 255 and 275 nm.With increased atomization temperatures other molecular bands due to aluminium compounds were observed. The non- specific absorption is strongly dependent on the com- position of the material analysed and the workers recommended that for measurements below 250 nm Zeeman-effect background correction is essential but above 250 nm continuum source background correction can be used provided the spectrometer is equipped with fast electronics. The determination of A1 in natural waters by ETAAS was improved (9 1/3497) by the application of ultrasonic agita- tion as a form of sample pre-treatment.The problems of determining A1 as the major analyte in suspended matter from natural water samples by slurry sampling ETAS were discussed by Hoenig et al. (91/3774). The combination of an alternative analytical wavelength (394.4 nm) a gas flow during atomization and interference from a mixed chemical modifier containing palladium silicon calcium potassium magnesium iron sodium and phosphorus reduced the sensitivity of the determination. Up to 10% m/m of A1 in the original sample could be determined and three sediment RMs were examined to confirm the validity of the proce- dure. For the determination of As in beer (92/C491 92/950) slurries of the ash remaining after thermal pre-treatment with magnesium nitrate and magnesium oxide at 450°C were atomized using STPF conditions with Zeeman-effect background correction and the use of a nickel-ascorbic acid modifier.This procedure was equivalent to a 2.5-fold preconcentration. Recovery of As was 102+2% with an RSD of 4.5% (n=6) for samples containing 8.5 ngg-l ofAs and results for this procedure compared well with those found by HG-AAS and the analysis of a CRM. Hinds et af. (921949) continued their work on the slurry sampling E T A S determination of Pb in soils by examining the use of fast atomizer programmes by optimizing the drying temper- ature and eliminating the pyrolysis step. The use of palladium-magnesium and phosphate chemical modifiers with these procedures was considered. These workers concluded that the addition of a modifier did not appear to assist in the determination of Pb in soil by slurry ETAAS with a fast atomizer programme. The risks of higher blanks temporal differences between standard and sample peaks and reduced sensitivity (for palladium-magnesium) were not sufficiently offset by any substantial benefit.The approach of electric spark colloidal dispersion dis- cussed last year (J. Anal. At. Spectrom. 199 1,6 1 87R) was continued by workers from the same group (921C775). The technique has been applied to the determination of a wide concentration range of 1 x 10-'-1 x lo3 ppm of different elements in a variety of steels copper- cobalt- and nickel- based alloys and pure metals. Sample preparation time is 10-30 min and a colloidal suspension with particle sizes of approximately 1 pm is produced.The technique is claimed to be free of matrix interferences and non-specific absorp- tion. Chinese workers (921 127) produced slurries of flours for the determination of Se by heating a mixture of flour water and triethanolamine on a water-bath for 3 min before introduction into the graphite atomizer. A palladium chemical modifier was used. Luecker et al. (92183) used solid sampling to determine Cd and Pb in calf liver and kidney using both Zeeman-effect and continuum source background correction. Results were compared with those obtained by a decomposition procedure for the determina- tion of Pb in liver; neither method gave significantly different results for concentrations of 5-12 ng mg-* but solid sampling generally gave higher values for concentra- tions of (0.1 ng mg-l.For Cd both methods gave equivalent results. Chinese workers (9211 53) used a labora- tory-made graphite boat to allow solid sampling of biologi- cal samples for the determination of Pb with a chemical modifier of ammonium dihydrogen phosphate. A detection limit of 0.036 mg kg-I of Pb in a sample of 200 pg was claimed. Solid sampling (92184) was used to determine Cd and Pb in food samples with a CRA-type graphite atomizer palladium-magnesium nitrate chemical modifier con- tinuum source background correction and calibration with aqueous standards. Relative SDs were generally < 10% for flour products powdered milk cocoa and chocolate al- though the analysis of meat and oilseed products was not possible owing to severe sample inhomogeneity.Chinese workers (921180 1) determined CrV1 in natural waters by quantitative adsorption of the ion onto several anion-exchange beads which were then diectly injected into a graphite atomizer. The detection limits for Crw and total Cr were 0.01 and 0.2 pg dm-3 respectively. Chaudhry et al. (9 112930) investigated the in situ concen- tration of hydride forming elements in a graphite atomizer. In most studies manual procedures are used whereby the hydride is transferred into the atomizer tube via a glass capillary which is positioned in the injection hole. These workers attempted to automate this procedure with a commercial probe atomizer. The hydrides of As and Ge were adsorbed onto a reduced palladium surface within the tube. Three modes of injecting the palladium solution and hydride vapour into the tube were examined.Method ( a ) involved manual injection of the palladium solution through the injection hole followed by vertical injection of the hydride vapour through the glass capillary placed in the same hole. Method ( b ) used a two-hole tube. The palladium solution was injected by the autosampler through the normal injection hole at approximately 45" to the vertical and the hydride vapour introduced manually through aJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. AUGUST 1992 VOL. 7 225R second hole vertically into the tube. Method (c) also involved a two-hole tube and used the commercial graphite probe unit to support the glass capillary and automatically inject the hydride vapour into the tube.The palladium solution was injected via the autosampler in method (b). In methods (a) and (b) the hydride vapours were injected directly on top of the reduced palladium coating. In method (c) the vapour and palladium coating were separated by 90". In all cases the palladium was reduced to metal by heating at 800 "C and the hydride trapping efficiency was constant over the temperature range 200-900 "C. It was found that the collection efficiency and precision were improved if the hydride vapours impinged directly onto the palladium surface. Method (6) gave reduced sensitivities owing to the increased diffusional losses due to the second hole in the tube. The direct manual procedure method (a) was applied to the determination of As and Ge in sea-water and As in urine and ultrapure hydrochloric acid.The determination of Sn by hydride generation and in situ trapping in a graphite atomizer was discussed by Li et a/. (91/C3630 92/C737). A commercial flow injection unit operating in a continuous mode was used to generate the hydride and simultaneously separate the element from potential interferences. The tin hydride was transferred to the graphite tube manually and trapped on a pyrolytic graphite platform at 300 "C. With this procedure Sn was determined in steel river sediment orchard leaves and bovine liver RMs with good agreement with the certified values. A detection limit of 66 pg was found with a relative detection limit of 7 ng dm-3 in a 10 cm3 sample aliquot. For 1 ng of Sn precision was of the order of 3-5% RSD.Concentrations of 200 pg dm-3 of other hydride-forming elements did not interfere. For the trapping of Ge at 600 "C these workers found that a palladium-coated pyrolytic graphite platform was more effective than an uncoated pyrol yt ic graphite platform. Ni et al. (92/413) applied in situ trapping of tin hydrides on a zirconium coated pyrolytic graphite coated e!ectrogra- phite tube at 500 "C for 100 s at an argon flow rate of 0.3 dm-3 min-l to determine tributyltin and inorganic tin in sea-waters. The insertion of the quartz autosampler cap+ lary and its removal were performed automatically. For speciation studies tributyltin was extracted into dichloro- methane and determined directly in the zirconium coated graphite tube. Peak height characteristic mass values of 20 and 14 pg were obtained for tributyltin and inorganic tin respectively with precisions of the order of 3.4% for inorganic and 5.6% RSD for organic tin.From the same group Yan and Ni (J. Anal. At. Spectrom. 1991 6 483) applied the same procedure for the trapping of lead hydride on a zirconium coated pyrolytic graphite coated electrogra- phite tube at a trapping temperature of 300°C. A 6-fold enhancement of sensitivity with respect to sorption on a pyrolytic graphite coated electrographite tube was found. The peak height characteristic mass was 52.8 pg with an RSD of 2% for 3 ng of Pb. A detection limit (3s) of 242 pg which is equivalent to 0.44 ng C M - ~ for a sample solution flow rate of 3.7 cm3 min-l pumped for 9 s was obtained and the method applied to the determination of Pb in various Chinese biological and environmental RMs and tap water.In a similar approach to that used by Baxter and Frech (J. Anal. At. Spectrom. 199 1 6 187R) Hladky et al. (9 1/27 14) applied the amalgam forming properties of Hg with gold directly in a graphite atomizer to determine Hg in concen- trated mineral acids. The Hg vapour generated with either sodium tetrahydroborate or tin@) chloride was swept by argon into the gold coated graphite atomizer tube and trapped at ambient temperature for 10 min prior to atomization at 900 "C. The inner surface of the graphite tube atomizer was coated with 1 mg of gold by thermal reduction of a solution of gold(rI1) chloride. Both peak and integrated absorbance signals were proportional to Hg concentrations between 5 and 100 ppb with RSDs of up to 15% and recoveries of 0.25-2.5 ng of Hg from a solution containing 80 mg of phosphoric acid were greater than 98%.Welz and co-workers (91/3778 91/3789 92/C735 92/C8 14) have continued their development work on coupling FI on-line sorbent preconcentration with eiectro- thermal atomization. An integrated fully automated sys- tem was used to determine Cd Cu Pb and Ni in sea-water. The application of this system reduced time-consuming manual work and enhanced the reproducibility and preci- sion. In addition on-line reagent purification is another advantage of FI which helps to reduce blank values. Using a time-based technique requiring only 3 cm3 of sample the sensitivity of the graphite electrothermal atomizer tech- nique was enhanced approximately 20-fold compared with direct determination from a 40 mm3 injection volume.Detection limits (3s) were 0.8 6.5 17 and 36 ng dm-3 for Cd Pb Cu and Ni respectively. This work was also discussed by Stelzer (92/158). The use of this technique has been extended (92/C8 14) to allow differential determina- tion of inorganic trace element species such as Asr1' CrV1 and SeIV in natural waters. On-line species selective precon- centration in combination with reduction/oxidation makes possible the highly selective determination of trace ele- ments in particular oxidation states. The short processing times allow the use of reagents under conditions at which they are not normally considered to be stable and conse- quently the equilibrium among the analyte species of interest is not affected measurably by the removal of one component.Hence a problem which can become very dominant when long reduction times are involved is avoided. Fang and Dong (92/C736) applied FI on-line preconcen- tration coupled with graphite electrothermal atomization to the determination of Cd Co Ni and Pb in blood and serum. Following sample digestion the analytes were copre- cipitated on-line with iron hexahydroazepine- 1 -dithiocar- boxylate and collected in a knotted reactor of 0.5 mm i.d. PTFE tubing and eluted with about 50 mm3 of IBMK which was stored in a length of PTFE tubing before introduction into the graphite atomizer by a flow of precipitant solution. The technique is characterized by an approximately 20-fold sensitivity enhancement with almost complete removal of the interfering matrix while sample digest consumption is approximately 1 cm3.Detection limits were of the order of 0.01-0.02 pg dm-3 and up to 20 sample digests could be processed per hour. In what appears to be a similar procedure to that originally proposed by Beinrohr et al. (J. Anal. At. Spec- trom. 1990 5 179R) Porta et al. (91/3200 92/C677) incorporated a miniature silica C18 column into the tip of the graphite electrothermal atomizer autosampler delivery tube. A modification to the tubing line of the autosampler allowed either the flow of the sample through the column or operation of the autosampler in the normal mode. The retention of the metal ions in the form of complexes on the micro-column was achieved by using pyrrolidin- 1 -yldithio- formate as the complexing agent; acetonitrite was used for elution.Preconcentration factors of 20-225-fold were found which allowed the determination of Cd Cu Co Fe Ni and Pb in Antarctic sea-water with detection limits ranging from 0.4 ng dm-3 (Cd) to 25 ng dm-3 (Fe). This system has been further modified and the use of a silica column with functionalized 8-hydroxyquinoline examined (92/C677) though no results were presented in the abstract. The hydraulic high-pressure nebulizer sample introduc- tion system described previously for FAAS (J. Anal. At. Spectrom. 1991 6 187R) has been adapted for on-line sample introduction for ETAAS (92K763). The system allows coupling of HPLChon chromatography with ETAAS226R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 for matrix separation1preconcentration. This system is claimed to deposit a 6-fold greater sample mass than that deposited by conventional pneumatic nebulization for ETAAS. Delude et al. (911C3660) discussed interfacing an ion chromatograph with a multi-element ETAAS system. Sample introduction was via a nebulizer using aerosol deposition and required very little modification to the standard sample introduction system. Improvements in detection limits over direct solution sample introduction ETAAS were found owing to the removal of major interfering matrix constituents and concentration of the analytes due to the sampling procedure though no perform- ance figures are given in the abstract. The ultrasonic nebulizer interface for direct coupling of HPLC with ETAAS discussed previously (J Anal.At. Spectrom. 1990 5 179R) has now been published (921220). An alternative approach to coupling HPLC with ETAAS was discussed by de Loos-Vollebregt and Bendicho (921C739) using an automated thermospray interface. Ar- senate arsenite and dimethylarsinate compounds were separated by reversed-phase isochratic separation on a Delta Pak C-18 100 A column. The thermospray interface operated at a flow rate of 0.6 cm3 min-' allowing periodic deposition in real time of the eluent from the chromato- graph directly into the graphite tube onto a special curved graphite L'vov platform placed opposite the injection hole and pre-heated to 150 "C. This procedure required separate measurements to be made at different times to create a chromatogram of the As species.Detection limits (3s) of 5 8 and 15 pg dm-3 were found for arsenite arsenate and dimethylarsinate respectively with an RSD of 6% for 1 ng of As on the platform based on integrated absorbance. While there was no pyrolysis step in the atomizer pro- gramme the total time required could be reduced if atomizer cooling was more efficient. Workers from Ni's group (921C738) coupled GC with ETAAS to separate and determine alkylselenides. The Se compounds dimethylselenide diethylselenide and dime- thyldiselenide were separated by GC on a column of 1.5% OV- 1 coated on Shimalite W. The GC eluate was led into the graphite atomizer and adsorbed on a palladium-coated graphite tube at 500-600 "C followed by atomization at 2400 "C.The peaks were eluted sequentially and with retention times of about 1 3 and 5 min for (CH3)2Se (Et),Se and (CH3)2Se2 respectively were well resolved hence there was sufficient time between each peak for the atomizer operation and no special GC-ETAAS interface was re- quired. Detection limits of 5 5 and 20 pg for (CH3),Se (Et),Se and (CH3)2Se2 respectively were obtained with RSDs of the order of 2-3.7% though no indication is given to indicate at what concentration these RSDs were estimated. Butyltin and cyclohexyltin compounds were determined by Cullen et al. (921230) with an HPLC-ETAAS procedure using C,* columns in sea-water and oyster tissue though no details of the interface are given in the abstract. Dittrich et al. (911C777) discussed the use of laser ablation coupled with ETAAS and furnace atomic non- thermal excitation spectrometry (FANES).Absolute detec- tion limits were in the picogram range and the technique was applied to the determination of trace elements in sintered metallic materials and alloys. For a copper alloy relative detection limits of 8 4 7 and 2 ppm were found for Ag Mn Pb and Zn respectively with laser ablation ETAAS and 0.3 2.5 4 and 6 ppm with laser ablation FANES. Laser ablation with a Nd:YAG laser was described by Hermann et al. (921C776). The aerosol produced was pumped into the atomizer using the Ar internal gas flow of the atomizer and deposited within the graphite tube by application of a negative voltage to the tube against a positive electrode inside the atomizer.For the determina- tion of dopant elements in layers from single crystals of semi-conductor materials Wend1 et al. (921C778) de- scribed a novel procedure of sputtering the solid material with argon ions onto a graphite L'vov platform. Following the sputtering process the platform is inserted into the atomizer and the sputtered layer atomized without any pre- treatment steps. Initially the sputtered material was found to have different pyrolysis characteristics compared with those of acidified solutions pipetted into the atomizer however addition of 20 mm3 of diluted nitric acid to the sputtered material converted the material into a solution with the same characteristics as normal solutions enabling calibration with aqueous standards. As only microgram amounts of material were sputtered (albeit with sputtering times of up to 1 h) compared with 500 mg required for conventional dissolution analysis of the semi-conductor material virtually non-destructive analysis is allowed.Panichev (9 11407) considered the possibility of using an atomizer as a sample accumulator prior to its use as an atomizer for collecting elements as volatile P-diketonates. This would lower the limits of detection and reduce many interferences. Sneddon (9 113277) has continued work on collecting aerosols describing an electrostatic precipitation system for the collection of metals on a tungsten electrode followed by insertion of this electrode into an electrothermal atomizer for AA measurements. The system parameters were exam- ined for an Mn aerosol and a negative corona of 15 kV with a low aerosol velocity were found to be optimum.The system was used to determine Cu in a laboratory atmos- phere on a near real-time basis. Shiowatana and Matousek (921 1 33) applied electrocode- position with mercury on 6-14 mg pyrolytic graphite platforms followed by atomization of the deposit for the determination of labile Pb in sea-water. Optimization of the experimental parameters such as applied voltage pH and sodium chloride concentration with respect to the deposi- tion efficiency yielded a detection limit of 0.15 pg dm-3 for 120 s deposition with a single platform. Background correction was not required as the technique eliminates spectral interferences due to molecular absorption from the matrix. Along similar lines Matousek and Grey (92K565) developed an automated electrodeposition system.A plati- num wire replaced the normal sampling capillary of the autosampler arm connected to a regulated d.c. voltage1cur- rent supply and connected between the negative platinum terminal and the graphite atomizer housing. The auto- sampler was re-programmed to allow sample loading by electrolysis of a 50 mm3 sample for 60-240 s followed by solution removal washing and chemical pre-treatment steps. Presumably the platinum wire was then inserted into the graphite electrothermal atomizer for further pyrolysis and atomization though the exact procedural details are not clear from the abstract. This technique reduced the background absorption from alkali halide matrices to 1% of the original value consequently the spectral and chemical interferences were considerably reduced and the technique could be applied to the determination of labile forms of Ag Au Bi Cd Co Cr Cu Hg In Mn Ni Pb Pd Pt Sb Sn and Zn.Pasullean et al. (9 113932) examined the electrodeposition of Pb onto a graphite probe electrode for preconcentration purposes prior to ETAAS with the graphite probe. Total pyrolytic graphite was found to be better for electrodeposi- tion than microporous glassy carbon or pyrolytic graphite coated electrographite. Lead could be deposited by anodic and cathodic processes as Pb02 and Pb respectively. With a deposition time of 120 s sensitivity gains of 9- and 3.5- fold were achieved for anodic and cathodic deposition respectively in contrast to the results obtained by direct injection of a 20 mm3 sample volume.A flow-through electrochemical micro-cell prior to injection into a graphiteJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 227R atomizer was applied by Beinrohr et al. (921C832) to separate and speciate trace metals on-line. The sample solution was injected and flowed through the cell and into the graphite tube. This step provided information about the concentration of the metal not deposited at a given potential. During successive steps the electrodeposited metals were dissolved by altering the applied potential of the working electrode and eluting with a small volume of diluted acid. The procedure was applied to the speciation of Mn in waters. The stabilities of trace elements in various organic solvents for ETAAS were studied by Sella et al.(921C567) as a basis for the determination of metal impurities in kerosene. Problems were encountered with adsorption on the walls of the various autosampler vessels and the recoveries depended upon the composition of the organic solution mixtures and organic complexes. 1.2.3. Fundamental processes The reduction of oxides by carbides (ROC) mechanism proposed by L‘vov and co-workers and discussed in depth previously (J. Anal. At. Spectrom. 199 1,6 187R and 1990 5 179R) has been the most prominent general atomization model in which the free atom formation from the oxides of many elements is controlled by the reduction of these oxides by carbides within the graphite atomizer However during the period of this review this mechanism was subjected to examination by a number of other groups who believe that their results do not support the mechanism proposed by L’vov.Both in the literature and at a number of meetings discussion about the conflicting ideas of the various groups has been intense. These discussions claims and counter claims are liable to rage for some time and just as the investigation of fundamental processes occurring within graphite electrothermal atomizers was becoming somewhat repetitive the whole field has been thrown into turmoil. This can only be to the good of increasing our knowledge of the processes taking place within graphite electrothermal atomizers and will no doubt stimulate numerous groups to further investigations. However a word of caution throughout the papers abstracts and discussions reported in this review the one underlying theme that re-occurs is that there is no firm protocol on how to investigate atomization mechanisms.Until some consen- sus or experimental protocols are developed to ensure that different investigators are examining similar effects a considerable degree of confusion will remain. This fact is virtually the only area of agreement between all the conflicting groups! Most of the supporting evidence for the ROC process in ETA comes from the molecular absorption experiments performed by L‘vov and co-workers (see L‘vov and Slavin Zh. Anal Khim. 1983,38 1925 and L‘vov and Ryabchuk Zh. Prikl. Spektrosk. 1980 33 1013) during the atomiza- tion of alumina. Molecular signals coincident with the atomic signals were observed and considered to be due to the presence of A12C2.Further evidence in support of the model came from the observations that molecular absorp- tion was not observed in a tantalum-lined graphite atomizer during atomization of milligram amounts of Group IIIA elements (see L’vov et al. Zh. Prikl. Spektrosk. 1987 47 7 1 1). Holcombe Styris and co-workers (92110 921C727) investigated the ROC model using MS techniques. They examined the atomization of alumina using aqueous slurry and solitary Al-sphere samples under ultra-high vacuum to minimize the formation of gas-phase interferences that might interfere with the observation of species involved in the heterogeneous reactions associated with the model. Conventional heating rates in addition to the low heating rates used to evaluate the ‘formation of spikes’ pheno- menon showed relatively little A12Cz produced during free atom formation. The more abundant and consistently observed species were Al A12 and (unless Al-sphere samples were used) A120.These were also the more abundant species in the ‘spike’ profiles. The ‘spike’ phenomenon was observed even for the metal samples. These workers consider that the MS data does not support the ROC model and that the assignment of A12C2 to the molecular absorp- tion is questionable and that it is more likely to be due to A120. Similarly these workers considered that the absence of a molecular band in a tantalum-lined atomizer may be due to the different abilities of tantalum and carbon to reduce AI20 rather than the difference between their abilities to affect the formation of A12C2. Gilmutdinov et al.(921C728) discussed the dynamics of formation of atomic and molecular layers in graphite ETAAS by employing shadow spectral Jilming (SSF). Sha- dow spectral filming consists of obtaining the image of the atomizer volume by back-lighting with the analytical line of interest and recording by use of a cine-camera the shadow produced by the absorbing layer. With this technique it is possible to visualize the dynamics of the atomic vapour filling the atomizer and simultaneously to obtain informa- tion on the temperature change of the walls and platform of the atomizer. Results showed that the atomic absorption layers were found to be strongly non-uniform both along and across the atomizer the layer structure being depen- dent on the element and varying considerably during atomization.The presence of a platform influenced the non-uniform nature with vapour condensation occurring on the cooler platform with subsequent secondary atomiza- tion. Molecular layers were also found to be strongly non- uniform. For elements such as Al In Ga Ge and others during the atomization cycle the molecular layers had a minimum concentration near the graphite walls. Some of this work has been published (see J. Anal. At. Spectrom. 1991 6 505). Styris et a!. (921C727) considered that the results from the work of Gilmutdinov et al. (921C728 and J. Anal. At. Spectrom. 199 1 6 505) supported their conclusions regarding the ROC mechanism.The SSF results for A1 show the molecular species absorbing in the centre of the tube (i.e. far removed from the graphite wall). This fact coupled with the MS results suggest that the dicarbide may be a relatively unimportant player in the Al-release mechanism and that the initial band assignment may be incorrect. Further work by Styris and Harris (921C726) considered the atomization mechanisms of Al Ga and In using ETA and real-time MS. Vaporization in vacuo allows examination of the surface and condensed-phase effects while atomization at atmospheric pressure shows surface condensed- and gas- phase effects. Comparing the results from in vacuo and atmospheric atomization allows the gas-phase effects to be considered. Vaporizing in vacuo produced free A1 and free In from the condensed oxides; free Ga was however not observed.The gas-phase dimer of each of these elements formed congruently with the gaseous monocarbide (M2C). Any dicarbide gas-phase species of the form M2C2 was only weakly discernable but strong monoxide signals were observed for all of these elements. When vaporizing at atmospheric pressure the dimeric elemental species and the carbides were absent but hydroxides and monoxides appeared during the atomization phase. The atomization mechanism suggested by this study is that of thermal decomposition. L’vov (921C725) reviewed the evidence for the ROC mechanism and discussed the data presented by Holcombe Styris and co-workers (92110 921C727). The ROC process involves on one hand the autocatalytic development of the reduction process with the participation of gaseous car- bides and on the other the formation of a carbon film on228R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 oxide particles as a result of the decomposition of the over- equilibrium excess of gaseous carbides. The formation of carbon blisters and shells of a few micrometres in size shown by Welz et al. (see Spectrochim. Acta Part B 1986 41 1175) is claimed by L‘vov as confirmation of the hypothesis of a carbon film formation as is work by his group on the delay in vaporization of Pd and Au introduced separately into an atomizer with A1203 and MnO (discussed last year J. Anal. At. Spectrom. 1991 6 187R). The formation of a carbon film can also account for the differences in the vaporization of a large group of metals (alkaline earth and rare earth metals copper manganese etc.) from graphite and tantalum platforms under analyti- cal conditions.Another consequence of the decomposition of an over-equilibrium excess of gaseous carbides could be the formation of carbon particles in the gas phase (soot). Evidence for the formation of this carbon/soot cloud was presented in a lecture (92K725) and has been published (L’vov et al. Spectrochim. Acta Part B 1991 46 1001). During the atomization of alumina two methods were used to detect the presence of carbon particles in the gaseous phase measurement of the light intensity attenuation due to scattering from the particles and measurement of the emission of these particles at various wavelengths.The heating rate and final temperature of the atomizer were chosen to ensure reduction of A1203 by carbides and not thermal dissociation of A1203. It was argued that the results interpreted according to Rayleigh’s classical theory of light scattering and Planck’s theory of black-body radiation confirm the presence of a soot cloud during the vaporiza- tion of A1203 in a graphite atomizer. Subsequent work (92/C725) has shown that this soot cloud is produced in the course of atomization of Al Au Cu Mn Pd and Yb. This phenomenon is claimed to be the most convincing arg,u- ment in favour of the gaseous carbide mechanism of spike formation and of the gaseous carbide concept as a whole. L’vov (921C725) interprets the MS studies of Holcombe and co-workers (921 10 92/C727) differently and believes that the MS studies are showing different spikes compared with those observed by his group and that there are different atomization mechanisms involved depending upon whether atomization takes place under atmospheric or vacuum conditions.The A120 species has a higher appearance temperature (2650 K) compared with that of the carbide species 1930 2000 and 2 1 10 K for Al2C3 A12C and Al2CZ respectively consequently the A120 species will only be observed at higher temperatures. L‘vov and Romanova (92/C1789) examined the effect of reduction of aluminium and manganese by carbides on the production of spikes in the AA signals from Ba Be Cr Ga Li and Si. Positive spikes were caused by direct reduction of the oxides by gaseous aluminium and manganese carbides and were observed for the oxides that have a lower thermal stability compared with those of aluminium and manganese oxides.Negative spikes were observed for Ga and Si which are characteristic of the elements that form stable gaseous carbides under the conditions for reduction of aluminium and manganese oxides by carbides. The investigation of the effects of reduction by carbides of aluminium and man- ganese oxides on the shape of absorption signals of other elements enables identification of the sample state during its vaporization and estimation of the stability of the gaseous carbide. The conference reports concerning the atomization mechanisms of Group IIA elements discussed previously (J. Anal. At. Spectrom. 1990 5 179R) have been published (91/3188). Atomic absorption spectrometry and MS were used simultaneously to elucidate the atomization mecha- nisms of Ba Be Ca Mg and Sr in pyrolytic graphite coated electrographite tubes.Gaseous species of these elements deposited as nitrates and vaporized in 1 atm of nitrogen and in vacuo were monitored in real-time by MS sampling. The principal gas-phase analyte species observed were carbides oxides and hydroxides. Excluding Be the data suggested that Group IIA element atomization and carbide formation begins with the dissociative adsorption of the oxides and a perturbation of the surface state associated with the resulting adsorbed elements. Gas-phase oxides were formed as a result of associative adsorption and the hydroxides produced by homogeneous gas-phase reactions of the carbides and oxides with water vapour.The same group examined the mechanism of the atomization of Y by MS (92/ 162 1). Gaseous yttrium oxide was found to either dissociatively adsorb or to be directly reduced on the graphite surface. Subsequent desorption of the resulting Y at higher temperatures yielded the free atom. Absence of free Y and presence of YC2(g) when vaporizing in vacuo was interpreted as indicating that carbides are not involved in the free atom formation process. No low-temperature precursors to atomization were observed but high-tempera- ture losses occurred in the form of oxides the carbide and hydroxide at temperatures above 2400 K. L’vov (9 1/3337) has proposed a mechanism to account for the thermal decomposition of solids and to account for the appearance of gaseous molecules of COO CuO Cu20 NiO PbO and Mg(OH)2 during the thermal decomposition of their anhy- drous and hydrated nitrates.The mechanism consists of two stages simultaneous gasification of all reaction pro- ducts irrespective of their saturated vapour pressure and subsequent condensation of low-volatility species (oxides or hydroxides). The partial pressures of these species at the appearance temperatures calculated from this theory for the first stage of the process (1-50 mPa) agreed with the detection limits obtained by the MS instrumentation used. The proposed mechanism is also supported by literature data obtained by thermal analysis. The material discussed above indicates both the com- plexity of the subject and confusion that exists within the scientific community investigating atomization mecha- nisms within graphite electrothermal atomizers.No doubt the differences in ideas and theories will lead to further investigations by many other groups and the hope that eventually an agreed theory will emerge that accounts for many of the experimental observations within graphite electrothermal atomizers. However it should not be over- looked that there is as yet no agreement on the general principles of how atomization mechanisms should be investigated and the literature abounds with cautionary conclusions regarding some of the assumptions that are often made. If any assumption can be made concerning this topic it is that no assumptions should be made! While the last decade has seen a considerable advance in our knowledge of the processes taking place within graphite atomizers this reviewer feels (from the literature available) that an underlying theory is still some way off.The fact that many studies are carried out under conditions far removed from those used during normal analytical measurements such as mass of analyte taken etc. makes the extrapolation of results extremely difficult. Without any doubt this is an area where further intensive studies are warranted. Ohlsson and Frech (92/6) along with Baxter et al. (92K732) made quantitative in situ spectroscopic measure- ments of C and CN species in graphite atomizers under varying conditions with respect to temperature gas compo- sition and types of samples. These species are key variables in modelling processes within a graphite atomizer.The C2 and CN species were quantified using a high-resolution spectrograph at the bandheads 516 and 383.3 nm respec- tively. The experimental results were compared with those calculated from a thermodynamic equilibrium model. In an empty atomizer at 3000 K the partial pressure of C2 was found to be at heterogeneous equilibrium. For CN theJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 229R partial pressure increased with temperature from 5 to 25% of the model value at 2300 and 2600 K respectively. The CN level was shown both by experiment and modelling to be sensitive to the presence of oxygen. The partial pressure of CN exhibited a gradient between the tube wall and the centre of the tube.It was shown that the amount of CN inside the graphite atomizer could be used as an indicator of air ingress. A side-heated integrated contact atomizer was compared with a Massmann-type atomizer. The work- ers examined the effect of various common chemical modifiers on the levels of C and CN and found that these modifiers reduced the partial pressure of CN during the atomization step which may be of importance for the atomization efficiencies of elements susceptible to cyanide formation. The problem of non-linear activation energy plots drawn from Arrhenius-type equations for atomization reactions in graphite atomizers was discussed by Chakrabarti and Cathum (91/3897). These plots do not give reliable kinetic information about the atomization mechanism of the analyte beyond a few data points located near the very beginning of the absorbance signal profile and if data points near the maximum of the absorbance signal profile are used the plots are non-linear.Two Arrhenius-type equations have been developed that give linear plots over a wide range of data plots and hence reliable' values for the activation energy. In addition a simple method is proposed for calculating the activation energy from the data points anywhere from the initial appearance of the absorbance signal to its maximum. Activation energies given by the two equations and the method of calculation were compared along with those given by other commonly used methods. These methods were used to investigate the order of Cu atomization (921 1620) from a pyrolytic graphite coated electrographite tube.The order of the atom formation of Cu was found to be 0.95 k0.04 by the graphical method and 1 .O 1 ? 0.04 by the method of calculation indicating that the atomization of Cu does appear to follow first order kinetics under the experimental conditions used. L'vov (92lC447) considered a more general approach to the theoretical calculation of kinetics based upon the fundamental conclusions of Hertz that every substance has a maximum rate of evaporation which is dependent only upon the surface temperature and properties of the sub- stance. This approach that the partial vapour pressure cannot exceed the equilibrium vapour pressure was applied to a theoretical consideration of the thermal dissociation reduction of oxides by carbides and thermal decomposition of salts.In the calculations of the equilibrium vapour pressure pe it was proposed that all reaction products irrespective of their saturated vapour pressure were ini- tially transferred into the gas phase. In cases of poyder decomposition account was taken of the partial (45-55%) return of the heat generated in the course of condensation of low-volatility species upon the reactant surface. The kinetic parameters (evaporation rates appearance tempera- tures and activation energies) calculated by this method were in good agreement with experimental results. A kinetic method to evaluate the apparent activation energy of the analyte loss process [Ea(,oss,] during the pyrolysis thermal pre-treatment step in electrothermal atomization has been developed and investigated by Slavei- kova and Tsalev (91/390 92K770).The method is based on extracting information from the declining portion of thermal pre-treatment curves (absorbance versus pyrolysis time at various fixed temperatures) and has been applied to the Josses of .As Pb Sb Se and Sn in the presence of a tungsten chemical modifier. These Eacloss values were compared with existing thermochemical data on bond energies and enthalpies of chemical reactions and possible mechanisms of analyte losses and atomization were dis- cussed. This method seems to be a more detailed version of that discussed previously (J. Anal. At. Spectrom. 1990 5 I 79R) which has been published (Appl. Spectrosc. I99 I 45 1305). The study of atomization mechanisms continues to be one that fascinates workers in this field and a large number of abstracts were received this year.Many of them are conference abstracts and it is to be hoped that these will appear as full papers in the future. The atomization of Cd from a graphite L'vov platform was examined by Carrion et a/. (92/C783) in the presence of silver lanthanum magnesium molybdenum and tungsten salts as chemical modifiers. With these metal salts Cd was stabilized up to pyrolysis temperatures of 800 "C and the appearance times of the atomization signals delayed. A correlation was found between the dissociation energies of the monoxides of these metals and Cd recoveries; the higher the dissocia- tion energy the greater the Cd recovery. Improved sensitiv- ity was observed in the presence of lanthanum molyb- denum and tungsten.These workers postulated that the thermal stability and sensitivity enhancement could be related to the ability of the selected metal salts to block the active sites on the surface of the platform. Ohta et a[. (91/3251) studied the atomization process for Cd in a molybdenum tube atomizer using sulfur as a chemical modifier. Based on XRD patterns of Cd in the presence of sulfur and the calculation of activation energies both in the presence and absence of sulfur the atomization mechanism in the presence of interferents and sulfur was claimed as CdS(g)-Cd(g). Chinese workers (9 1 /34 14) examined the atomization qf A1 and Cd from a graphite probe surface. No details of the experimental procedures were given although it was claimed that the results showed that the atomization of A1 and Cd from the graphite probe surface originated from the thermal decomposition I of their mo- noxides. Zemberyova et al.(9 l/C2774) compared the results from graphite and tungsten-tube atomizers for the atomization of organometallic compounds of Cd Cu and Pb in organic solvents with thermal analysis results from thermogravimetry and differential thermal analysis. The influence of the metal-ligand bond the stability constant of the chelate compound and the nature of the solvent and atomization surface confirmed different atomization mechanisms with respect to the different atomization environments. While good agreement was claimed between the proposed atomization mechanisms and the experimen- tal results sadly no details of the proposed atomization mechanisms were provided.The mechanisms of Co atomization from electrographite pyrolytic graphite coated electrographite and glassy carbon surfaces were investigated by Chakrabarti and Cathum (9 ~3308). The activation energy could be correlated with the dissociation energy of CoO(g) or with the heat of sublimation of Co(s) formed by the carbon reduction of CoO(s) the latter being the product of the thermal decomposition of Co(NO,),. The Co atomization mecha- nism appeared to be the same for electrographite and pyrolytic graphite coated electrographite surfaces but different for glassy carbon. The suggested atomization mechanisms seem to be consistent with the chemical reactivity of the three atomizer surfaces and the physical and thermodynamic properties of Co and its compounds in the temperature range involved in the pyrolysis and atomization cycle of the graphite atomizer.Hou et al. (92/ 1 7 14) compared the atomization character- istics for Cd Co Cr Cu Mn and Pb from the graphite tube wall platform and probe. The shape of the atomization signal was controlled by the properties of the analyte the sample vaporization rate and gas diffusion rate. Under the same instrumental conditions the peak shape was depen- dent mainly on the sample vaporization rate which was230R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 related to the heating rate of the atomization surface. These workers found that the probe had the fastest heating rate and gave better signal shapes than the platform although no indication was given as to whether the probe and platform were manufactured from identical structural forms of graphite.Fonesca et al. (91/2985) studied the vaporization and atomization characteristics of Cu samples at atmospheric pressure from graphite- and tantalum-lined tubes contain- ing either a tantalum or a graphite platform. First-order release of Cu from both tantalum and graphite surfaces was found. The desorption rate of Cu from tantalum was faster although the activation energy of desorption for the Cu- tantalum system is larger than that for Cu-graphite. Neither activation energy corresponds to the enthalpy of vaporiza- tion for Cu and it would appear that Cu is re-adsorbed onto the graphite and tantalum surfaces upon secondary colli- sion. However with vaporization from the platform the wall temperature is higher such that the Cu desorption rate from the wall is sufficiently rapid for the Cu collisions with the wall to appear elastic.These workers made the impor- tant point that while the use of a platform may be advantageous from an analytical point of view however the interpretation of results with a platform are more complicated when fundamental studies on the basic interac- tions occurring in an atomizer are being investigated. The atomization mechanisms of Cu Ir Mn and Pt were investigated by Akman et al. (92K767) by taking into account several parameters affecting the number of gaseous atoms present in the atomizer. The contribution of thermal expansion and diffusion to the dissipation process were investigated and it was found that thermal expansion substantially contributed to the removal of atoms from the furnace.From the calculation of activation energies these workers concluded that the last step leading to gaseous atoms for Cu Ir and Pt is the thermal dissociation of gas- phase dimers and for Mn the dissociation of its monoxide in the gas phase. For those trying to relate fundamental studies to practical reality Hinds (92K768) made the important statement that in most cases atom formation studies use the elements of interest in an acidified aqueous solution whereas typical analyses involve more complex matrices often with a chemical modifier included. The orders of reaction for the release of atoms for Cu Fe Pb and Pt from aqueous solutions were compared with those for solutions with silver nitrate and those for the elements occluded within solid silver.The order of release of Cu changed from first- order for Cu alone to less than 1 with a silver nitrate matrix. The absorbance signals with respect to those produced from aqueous solutions of Cu were delayed in the presence of silver nitrate and further delayed for Cu occluded within solid silver. To aid in the investigation of the atom formation of A1 in a graphite atomizer Ohlsson (92K764) studied the distribution of Al-containing species in the gas phase and their dependency on analytical parameters. With micromole amounts of Al sufficient amounts of A10 and AlH molecules were formed to allow photographic measure- ment of the spectral bandheads within a graphite atomizer operated under analytical conditions.A factorial design was used to find the analytical parameters that gave the maximum absorption for Al A10 and AlH respectively. Deng and Liu (92/C765) and Deng and Wang (92/C675) studied the atomization mechanism of Bi(N03)3 and SnCl respectively from a graphite probe surface with the aid of XRD XPS AES and SEM. For the atomization of Bi (92/C765) all the techniques showed the transformation of Bi(NO,) into Bi,O at temperatures lower than 840 K in agreement with the pyrolysis ETAAS study and some formation of solid Bi on the graphite surface. It was pro- posed that the hydrated Bi(N03)3 decomposes to Bi203(s) and at temperatures greater than 450 K is reduced by carbon to Bi(s) followed by vaporization into the gas phase possibly via a gas-phase dimer.The Sn studies indicated that the hydrated tin@) chloride species can decompose during pyrolysis to form either SnCl,(g) or SnO(l/s) depending upon the temperature. It would appear that the principle cause of volatilization losses of Sn is due to the formation of SnO and not SnC12. Tin@) oxide was found on the graphite probe at temperatures above 670 K. Kantor et al. (92K769) investigated the volatilization of Ca and Ga with conventional ETAAS techniques molecu- lar absorption spectroscopy and electrothermal atomization linked with FAAS. Coupling ETA with FAAS allows an element specific detection of the evolved vapour irrespec- tive of the original chemical form of the release.When Ga was present at the 10 ng level the Ga was evaporated in the 900- 1 100 "C temperature range which most probably corresponded to the evolution of Ga20 species as shown by MS studies (92K726). When Ga was the matrix element at the 10 pg level a major fraction vaporized as metal in the I 120-2300 "C range producing atomic vapour. The Ca (1 ng level) vaporized intensely above 1520 "C and this process overlapped in part with the vaporization of the gallium matrix. However pre-volatilization of the gallium when present at a concentration of not more than 0.3% m/v in nitric acid medium could be achieved to eliminate the interference on Ca. A detection limit of 0.057 p g g-' of Ca in gallium was found. The atomization of refactory elements such as Rh Pt and V from refractory solid surfaces of silica and alumina within a graphite electrothermal atomizer was studied by Greenway et al.(92K688). Decomposition of the matrix at the same temperature as the atomization of the analyte caused interferences and to avoid this problem the use of a linear temperature ramp and the appearance temperature to quantify and identify different species of the metals was investigated. A chemometric approach was adopted by Benzo et a/. (92lC693) to find the optimum ETA conditions for Mo. The most significant parameters affecting the atomization signal were the pyrolysis ramp and its interac- tions with the injection volume pyrolysis temperature and time and acid concentration. Unfortunately no rec- ommended conditions for these parameters were presented in the abstract.Rademeyer and Vermaak (92/C729) have continued their studies on the atomization mechanisms of Si in a graphite atomizer discussed last year (J. Anal. At. Spectrom. 199 1,6 187R). In an attempt to identify the gaseous molecular species formed during atomization the thermodynamic and kinetic parameters were determined for reactions that possibly lead to the formation of oxides and carbides. Factors influencing these reactions such as the presence of O C02 and CO were also investigated by adding various amounts of these gases to the Ar purge gas and examining their effects on the 230 and 500 nm broad bands in the molecular spectrum of Si. From the data shown during the presentation it would appear that there are two species present after pyrolysis namely SiO and Sic,.Based on these conclusions a number of atomization mechanisms were proposed. Investigations into the role of oxygen within a graphite atomizer were continued by Wend1 et al. (92/C730 see J. Anal. At. Spectrom. 1990 5 179R). Oxygen was either added to the Ar purge gas or the graphite surface was pp. treated with oxygen at room temperature prior to heatlng at 2300 K in Ar for 5 S followed after cooling by additinn of the analyte element of interest. This oxygen treatment shifted pyrolysis losses of the elements to higher tempera- tures and slowed down the losses in comparison with those from graphite tubes untreated with oxygen. These results indicated that oxygen has more of a surface effect on theJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 231R graphite rather than directly influencing reactions within a graphite atomizer. Huie et al. (92/C731) presented further work on their studies of gas dynamics within a graphite atomizer. While the effects of analyte expulsion occurring within a graphite atomizer due to rapid gas evolution by the matrix have been theoretically modelled and discussed by Holcombe’s group there have been few studies concerned with measur- ing the gas flows and the distributions of molecules within an atomizer. Spatially and temporally resolved absorbance profiles were measured with an imaging system consisting of a laser light source and a vidicon camera. For the atomization of Na with either cadmium or lead as the matrix species an Na concentration gradient was observed near the dosing hole during the initial atomization period possibly indicating that some Na atoms were being ex- pelled.For samples containing a zinc matrix a different distribution was observed in which the number density of atoms was greater at the bottom of the tube where the sample was deposited. Some interesting experiments were performed using a transparent quartz tube with identical dimensions to a graphite tube in order to provide some initial data on the gas dynamics within an atomizer at different gas flow rates. While it is clear that quartz has different surface characteristics to those of graphite and that these experiments were performed at room tempera- ture they do provide important initial information on gas flows in ETA a topic about which little is known. It is to be hoped that this work is continued in more detail as it could have a major impact on our understanding of some of the physical processes occurring during drying and pyrolysis in graphite electrothermal atomizers.The temperature dependence of dijfusion coeficients was evaluated by Ogun et al. (92/C5 12) who used a mathemati- cal model generated by superposition of the temperature- time profiles on the absorbance-time profiles. Frech et al. (92/C550) posed the question ‘How long is a graphite tube?’ in conjunction with a discussion of the eflects of dijferent rnodijiers and temperature gradients in Massmann-type graphite atomizers. To account for the unusual observation of decreasing analyte sensitivity with increasing mass of palladium chemical modifier for elements such as Pb and Se even though the vapour temperatures increase it was postulated that as the modifier mass increases the effective tube length is reduced.The modifier condenses on the cooler parts of the tube and traps analyte atoms. This also accounts for why this effect is observed for Se in the presence of increasing amounts of copper nickel and palladium nitrates but not when increasing amounts of magnesium nitrate are employed. The sequestering of As and Se hydrides by palladium on the surface of graphite is in line with this hypothesis. In two conference reports Yasuda et af. (92/C451 92/C733) reported on the increasing vapour-phase tempera- tures (calculated using the two-line method) found when platform atomization and a chemical modifier of palladium is used in a Massmann-type atomizer.It would appear that these workers are now able to measure Pb in whole blood without the need for the method of analyte additions. Marowsky et al. (92/C734) reviewed the analysis of temper- ature distributions in ETA with high spatial resolution by the use of coherent anti-Stokes Raman scattering (CARS) and the alternative of degenerate four wave mixing (DFWM) which as it is a resonant process has a higher detection sensitivity than that of non-resonant CARS through proper selection of the input frequency. This high sensitivity together with the relaxed phase matching condi- tions of DFWM should permit two-dimensional imaging of temperature distributions. The use of radiotracers to discover the behaviour of elements in graphite atomizers during the individual steps of the time-temperature programme and with different chemical modifiers was discussed by Krivan (92/C563).The advantages of radiotracers are that the amounts normally taken for routine analysis can be used and they are simple to employ and have higher sensitivity. Only one report was received concerning Monte Carlo modelling with respect to ETAAS. Barkauskas and Weg- scheider (9211 650) reformulated the Monte Carlo approach to allow execution of the calculations on a laboratory-type minicomputer for simulation of the processes in a graphite atomizer. The atomizer was partitioned into single cubes of 1 mm3. For elements with intermediate volatility a spatial non-isothermal temperature distribution in the atomizer was shown to have little influence on peak shapes.However it was claimed that owing to uncertainty in a number of the parameters used such as energy of activation and knowl- edge of the order of the release mechanism etc. only a few elements are currently accessible to Monte Carlo modelling. The importance of fundamental reference data concern- ing atomic fine profiles is well known though little informa- tion for absorption fine profiles in graphite electrothermal atomizers is available. Chang and O’Haver (9 1/2709) measured the collisional linewidth in a graphite atomizer of the resonance absorption lines of Ca Cu and In by using a wavelength modulated echelle spectrometer and transmis- sion profile fitting. A measurement precision of kO.1 pm was observed for Cu (324.754 nm) based on peak area or peak height growth curve shapes.The time-resolved linewidths within a single atomization were measured for Ca (422.673 nm) and In (410.176 nm) with a time resolution of 0.3 s and a precision of k0.5 pm. This measurement precision was sufficient to show clearly the effect of increased gas pressure on the linewidths and the line shift. Collisional cross-sections for Ca and In were estimated from the effect of pressure on the linewidths and compared with previously published theoretically calcu- lated values. Gilmutdinov et al. (92/ 142) calculated and analysed calibration graphs for elements with different spectral characteristics. New data were calculated for the hyperfine structures of the analytical lines and absorption line shifts were taken into account.Hu (92/C694) found that the analytical range for the ETAAS determination of Mg could be extended to 100 ppm by using spectral overlap from a vanadium hollow cathode lamp at 285.2 nm. Satisfactory agreement for Mg at the ppm level in a variety of Chinese geological RMs were achieved. Russian workers (92/ 143) described an ETAAS technique for recording molecular spectra. Only the atomic absorp- tion lines of In and T1 were observed during the evaporation of these elements and their nitrates in graphite and tantalum foil-coated atomizers. Molecular bands of Ga,O at 250 and 260 nm were observed during the evaporation of Ga and Ga203. The presence of Ga,O and very small amounts of GaO were confirmed by MS.1.2.4. Interferences The control reduction and elimination of interferences with chemical modijication ETAAS continues to be an area of considerable interest. While a number of review articles have been published over the last few years none of them encompass the range and detail of that by Tsalev et af. (91/3569). This is an outstanding review of the field of chemical modification in ETAAS containing 528 references and the authors are to be congratulated on producing such an excellent work. Without a doubt any researcher consi- dering ( i ) a ‘new’ chemical modifier or (ii) a new analytical problem should check within the Tsalev et al. paper first. The classification procedures developed by Tsalev et af. (J. Anal. At. Spectrom. 1990 5 179R) to try to bring some order to the mass of empirical information in the literature232R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 have been further discussed (921C562). Carnrick et al. (9211816) discussed the role and history of chemical modifiers in ETAAS. There are still a large number of papers concerning palladium and consideration is now being given to some fundamental studies concerning the action of this chemical modifier. Styris et al. (9 1/3950,9 1/395 1) combined MS and ETAAS to elucidate the mechanisms of stabilization of As (91/3950) and Se (91/3951) by palladium. In the absence of palladium As as As203 was found to decompose thermally forming AsO higher As oxides and condensed-phase As which first polymerizes and then sublimates as As2.The presence of PdO stabilizes the atomization of As by reacting with the condensed phase As preventing evolution of As2 by forming a [Pd,As,,O,] compound or mixed solution. Ele- mental palladium reacts directly with the As203 probably forming the same compound and As2 and oxide losses are completely inhibited. In the case of Se investigations were performed without modifier with thermally reduced palla- dium modifier and with non-reduced palladium modifier. Selenium oxides carbides hydroxides dimer free atom and palladium were all observed during atomization. The reduced palladium modifier eliminated the formation of molecular Se species except SeO. Both SeO and Se02 were observed when the non-reduced palladium modifier was involved. In both cases the palladium forms a stoichiome- tric compound with Se that retains the element until higher temperatures are reached. Volynsky et al.(9 112776) applied Fourier transform infrared spectrometry to examine the gaseous products of the reactions between PbO Ga203 graphite powder and palladium and nickel chlorides in an attempt to elucidate the mechanism of action of palladium and nickel chemical modifiers in ETAAS. It was found by monitoring the evolution of carbon monoxide and dioxide produced during heating that palladium decreased the temperature of the reduction of both PbO and Ga203 with graphite whereas nickel only catalysed the reduction of Ga203. Their hypothesis based on these results although performed on a macro-scale with respect to the masses normally sampled in an atomizer is in broad agreement with those suggested by Styris et al.(9 113950 9 1/395 1) discussed above. Jackson and Qiao (921C747) continued their work on the physical and chemical mechanisms of palladium chemical modifiers in slurry ETAAS (J. Anal. At. Spectrom. 199 1 6 187R). These workers believe that their results indicate a physical as opposed to a chemical effect for palladium. The palladium modifier alone was found to migrate to the left and right hand edges of the pyrolytic graphite platform during pyrolysis at 900 “C but when mixed with magnesium nitrate no migration took place and the modifier mixture formed an even layer over the platform. Generally atomiza- tion peaks of Pb are broad in the sole presence of palladium but sharper peaks are produced from a palladium-magne- sium nitrate mixture which tends to indicate a less diffuse palladium layer in the latter situation. No advantage has been found by Jackson and Qiao (92K747) when using a reducing agent with palladium as they believe that this causes the palladium to agglomerate on the graphite surface hence producing a thicker palladium ‘layer’ and reducing the rate of diffusion of lead atoms into the vapour phase during atomization.Rutherford backscattering was employed (9 l/C3676) to investigate the interaction of palladium and selenium with the graphite surface. Although no conclusions were avail- able when the abstract was written further details will be of considerable interest. Ma (92/C782) used palladium in the absolute determination of Cd in a variety of environmental samples with the exception of sea-water for which an ascorbic acid modifier was preferred.Czechoslovakian workers (911C2736) confirmed that a mixture of palladium and magnesium nitrates was the optimum chemical modi- fier for the determination of Se in clinical samples such as blood serum and urine while Romero et al. (921C682) found that a mixture of palladium citric acid and nitric acid was the optimum chemical modifier for the determina- tion of Pb and V in biological materials. These last workers proposed the term ‘analyte isoformer’ rather than chemical modifier as they believe that this suggests the process that is actually accomplished by the modifier. However the generic term ‘chemical modifier’ is recommended by IUPAC to describe any reagent added to the atomizer to influence the processes taking place.As this term encompasses ‘analyte isoformation’ the term ‘chemical modifier’ should be retained. Authors should consider using more widely the terms recommended by IUPAC as this will alleviate the confusion and ambiguity that is present in some of the literature. For the determination of Cd in selective liquid anion- exchange extractions of marine sediments (9211 lo) only a palladium nitrate chemical modifier in conjunction with STPF conditions appeared to give reliable results. Garcia- Olalla et al. (921C684 921C785) found not surprisingly that a mixture of palladium nitrate and ascorbic acid precipitated palladium. Also addition of the ascorbic acid to highly acidic Se solutions produced a colloidal suspen- sion which gave no signal for se.To overcome these problems they proposed the use of a 1 + 1 mixture of HgCl and PdC12 to take advantage of the strong affinity between Se and mercury. This mercury-palladium mixture was applied to the determination of Se in coal fly ash (92/C684) and to investigate the chloride interferences on Se (921C785). A mixed chemical modifier of palladium and citric acid was found to be more effective by Zhang et al. (9113604) for the determination of Cd and Zn than either palladium or citric acid alone. These workers believe that the addition of citric acid enables the palla- dium salt to be reduced at a temperature below 600 “C the palladium metal providing a ‘solid solution pool’ for the analyte. At the same time the addition of citric acid also reduces Cd and Zn salts to the respective metals which dissolve in the ‘solid solution pool’ to form intermediate species.With this mixed chemical modifier pyrolysis temperatures for Cd and Zn of 900 and 1000 “C respec- tively were achieved. For elements such as As Cd Se and Te Terui et al. (92/1806) confirmed that nickel palladium or platinum are effective chemical modifiers. They considered the phase diagrams of the elements mixed with the chemical modi- fiers to aid in selecting the optimum pyrolysis and atomiza- tion conditions. Chinese workers (9211 932) found that palladium nitrate nickel nitrate and palladium nitrate mixed with magnesium nitrate were the best chemical modifiers for determining As Pb and Se in biological samples by ETAAS.While it is well known that there are spectral interferences when using a continuum source for background correction in the determination of Se in biological materials Radziuk and Thomassen (921C786) reported what they believe to be a spectral interference when Zeeman-effect background correction is used for the determination of Se in blood and urine. They attribute this interference to a Zeeman effect displayed by absorption bands of small molecules contain- ing phosphorus. The errors were minimized for those conditions under which the atomization efficiency for phosphorus was enhanced or the volatilization of phospho- rus-containing species significantly delayed. In contrast to the many papers showing spectral interferences when continuum source background correction is used to deter- mine Se in whole blood Van Cauwenbergh et al.(921211) appear not to have experienced any problems when using a mixed chemical modifier of palladium and magnesiumJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. AUGUST 1992 VOL. 7 233R nitrates. Hoenig (92/1722) found that the best method for determining Se in whole blood was with Zeeman-effect background corrected ETAAS using a chemical modifier of iridium and magnesium pre-injected onto the platform. Problems with the formation of carbonaceous residues on the platform were eliminated by the use of an oxygen ashing step. Maage et al. (91/3775) found that by using an electrographite tube equipped with a L'vov platform a chemical modifier of 50-100 pg of nickel and continuum source background correction Se could be accurately determined in acid digested marine samples. Peak height measurements were used with the method of analyte additions for calibration.The continued interest in and conflicting ideas concern- ing the use of palladium especially the use of reducing agents with palladium shows no signs of decreasing. A consensus seems to be appearing regarding the formation of a solid solution of the analyte in the palladium metal on the graphite surface. However the exact nature of these 'compounds' is as yet unknown. Of importance in gaining further information concerning all these reactions is an in- depth study of the action of reducing agents and/or the graphite surface during the pyrolysis step. The literature is still confusing with some workers recommending and others not the use of reducing agents even when examining the same types of matrix with similar instrumentation.This is a pressing issue that requires clarification. During the period of this review several reports concern- ing the use of organic acids as chemical modifiers have appeared. Cabon and Bihan (92/C784) found that oxalic acid was the best chemical modifier for the determination of Cd in sea-water enabling temporal separation of the analyte and background peaks. It would appear that this work was performed using low wall atomization tempera- tures (700"C) slow heating rates and with continuum source background correction. Nevertheless these workers claimed a surprisingly low detection limit of 3 ng dm-3 for a 99 mm3 injection volume.The effects of ascorbic acid on the atomization signals for Pb from electrographite and pyrolytic graphite surfaces were discussed by Imai and Hayashi (91/3954). Double peaks were observed in the presence of ascorbic acid from both surfaces and it was considered that the peaks were produced by different atomization sites including pyrolytic graphite sites pro- duced by the pyrolysis of ascorbic acid on the electro- graphite surface. Tong et al. (92/C790) examined the effect of ascorbic acid on the atomization of Pb and the reduction of interferences from sodium chloride. These workers found that ascorbic acid reduced the maximum pyrolysis temperature for Pb from 700 to 500 "C which they ascribed as being due to the decomposition of ascorbic acid to carbon and carbide which react with PbO to form Pb metal.Despite this it was claimed that the use of ascorbic acid improves the atomization efficiency for Pb and allows the temporal separation of the atomic and background peaks. Several chemical modifiers based on tungsten were evaluated by Slaveikova and Tsalev (91/3137) and the thermal stabilization of 18 elements of high to moderate volatility demonstrated. From the same group (9 1/3287) cerium(rv) and a cerium(rv)-palladium(n) mixture were also examined as possible chemical modifiers for 24 elements of varying volatilities. The mixed chemical modi- fier gave slightly higher maximum pyrolysis temperatures than cerium alone and the effect of the atomization surface (electrographite pyrolytic graphite or a tantalum carbide coating) was also discussed. It would appear that comments made in last year's review (J.Anal. At. Spectrom. 1991 6 187R) have had an immediate effect as research in phosphate chemical modi- fiers has severely declined. Only one report on this subject was received during the period of this review. The work of Hassell et al. (9 1/3 197) on the effects of phosphate chemical modifiers with temperature programmed static SIMS dis- cussed previously (J. Anal. At. Spectrom. 1990 5 179R) has now been published. With this technique the surface reactions between phosphate chemical modifiers and Ag and Cd were investigated. It was found that Cd-oxyphos- phorus reactions were initiated on the surface during the drying stage with further stabilizing reactions occurring on the surface in the pyrolysis temperature range leading to a delay in the atomization of Cd and a higher appearance temperature.However no Ag-oxyphosphorus reaction products were observed and the addition of phosphate resulted in a reduction in the AAS signal intensity with no increase in appearance temperature. Byrne et af. (92K740) examined the mechanisms of chloride interferences on the atomization of Mn with ETV- ICP-MS. The use of ETV-ICP-MS allows direct observation of analyte losses during pyrolysis and allows a distinction to be made between such losses and vapour-phase interfer- ences caused by the formation of molecular species during atomization. The results of the study suggested that in the case of interference due to MgCl the loss of Mn during pyrolysis was due to hydrolysis of MgClz to produce HC1 and that the Mn is lost by co-volatilization with HCl.Ascorbic acid was found to retard this hydrolysis eliminat- ing the loss of Mn during pyrolysis. In the presence of NaCl ascorbic acid eliminated the interference by removing the chloride. Chloride interferences on the determination of In were removed with the use of a mixed chemical modifier of EDTA nickel and aluminium nitrates by Matsusaki (91/3860). The use of EDTA increased the tolerance to co- existing metallic chlorides by up to 400-1000-fold and increased the sensitivity by a factor of 20 compared with that for atomization in the absence of the mixed chemical modifier. This mixed chemical modifier was also applied to the determination of Ga by the same group (9113947) to eliminate chloride interferences Bektas and Akman (91/3104) studied the effects of alkali and alkaline earth metal chlorides on the atomization of Cr and Pb.Imai et al. (91/3941 92/279) compared the use of chromium(rIr) nitrate as a chemical modifier for the determi- nation of Pb in serum with NH4H2P04 and palladium nitrate. No advantages for the use of chromium(iI1) nitrate were given. These workers also examined (91/3302) the effect of a wide range of sulfates on the atomization of Pb. The interferences were found to decrease as the lattice energy of the sulfates increased and the interferences due to sodium and potassium sulfate were suppressed by the addition of chromium(nr) nitrate. In the determination of Cs in mineral waters Bozsai and Karpati (92/C787) found that by the addition of a large excess of sulfuric acid the severe interferences due to sodium chloride up to 50 pg could be overcome.Interestingly the calibration graphs were concave. It was postulated that this was owing to an ionization effect at low analyte concentrations. He (9211 24) found that the addition of 1% H3B03 overcame many of the interferences due to sulfate and chloride observed during the atomization of Sn. Interferences in the determination of A1 in serum were considered by Kilroe-Smith and Rollin (9 ~ 3 2 8 8 ) and interpreted according to L'vov's theory of reduction of A1203 by gaseous carbon atoms or molecules at high temberatures. These workers considered that current methods do not allow for the presence of these carbon species considering the organic nature of the matrix. They claimed to show how removal of these gaseous carbon species before atomization affects the sensitivity of the analytical method and that ionization interferences can be reduced by adjusting the pyrolysis temperature so as not to remove easily ionizable salts from the matrix.234R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 A group of Chinese workers all apparently from the same institute have examined the background absorption of a range of elements under different conditions (9 1 /3000 9 1/30 12 9 1/3014 9 1 /3834). The characteristics of the background absorption of rare earth compounds of Ce Nd and Pr (91/3000) and Dy Ho and Tb (91/3014) were studied.Double background peaks were attributed to the molecular vapours of the chlorides and oxides. Not surpris- ingly conversion of the rare earth compounds into nitrates prior to atomization considerably reduced the background interferences. The background peaks produced by nickel chloride and nitrate were considered in more detail (9 1/3834) and some assignment of the peaks to species such as NiC12 NiO and NO was attempted. An Ar-H2 (5%) mixture was found to reduce the background absorption of calcium compounds but had no effect on that for sodium potassium and magnesium compounds (9 1 /30 12). Jackson and Alloway (9113540) found that the concentration of chemical modifier used for the determination of Cd in microwave-digested plant tissues is critical. Too high a concentration was found to cause over-correction with the Smith-Hieftje background correction system used and in addition reduced tube lifetimes.Molecular background absorption produced by calcium potassium and sodium compounds was reduced by Wu et al. (92/1803) using a tantalum-foil lined graphite tube compared with a pyrolytic graphite coated electrographite tube. Tserovsky and Arpadjan (921952) considered the factors affecting the determination of Cd Co Cu Fe Ni and Pb in organic solvents. The influence of the nature of the solvent complexing agent atomizer type chemical form and amount of modifier used were evaluated and optimum conditions established. 1.2.5. Developments in technique Few reports of multi-element analysis with ETAAS were received during the period of this review. However Berglund et al.(921C757) discussed the feasibility of using a single set of atomizer conditions with the transverse-heated atomizer with integrated platform and longitudinal Zee- man-effect background correction discussed in section 1.2.1 for a range of elements of differing volatilities. Their results showed that involatile elements such as Mo and V could be effectively vaporized from the platform at a vapour-phase temperature of only 2656 K. Elements such as Cd and V having diverse physical properties were found to be efficiently atomized in the transverse-heated atomizer using a palladium chemical modifier and with the same atomization conditions. It was concluded that the transverse-heated atomizer equipped with an integrated platform presents much better prospects than Massmann- type atomizers for multi-element AAS instruments.This work has recently been published (Spectrochim. Acta Part B 1991 46 1767). Harnly (92K744) considered some of the recent develop- ments that have been applied to electrothermal atomization continuum source AAS such as an improved optical configuration photodiode array detection in conjunction with a larger spectral bandpass and pulsing of the xenon arc continuum source. These all contributed to an increase in S/N ratios and enabled detection limits comparable to those of conventional ETAAS in the far UV range to be obtained. Those workers who were previously active in the field of multi-element AAS appear at least during the period covered by this review to have switched to using emission either with furnace atomization plasma excitation (FAPES) or hollow anode furnace atomic non-thermal excitation (HA-FANES) sources.The FAPES system described previ- ously by Liang and Blades (J. Anal. At. Spectrom. 1990 5 171R) has now been introduced as a commercial product (9 l/C3647). Blades (92/C742) discussed the potential of the FAPES source for simultaneous multi-element analyses in the sub-picogram range for many elements. The system described allows a comparison of atomic emission and absorption signals (with and without a plasma in the graphite tube) and results showed that the shape of the temporal emission profile is a function of analyte concen- tration r.f. input power and the analyte species being studied. In addition the FAPES source can be used to observe signals from both the plasma induced dissociation of vaporized molecular species and from directly vaporized atomic species.This latter benefit of the FAPES source was applied by Sturgeon et al. (92/C743) to study analyte atomization processes in the graphite atomizers. Transient molecular and atomic analyte species as well as gaseous analyte decomposition reaction products can be detected by emis- sion at atmospheric pressure. The effects of phosphate and palladium modifiers on molecular species for elements such as Cd Pb T1 and Zn were examined. In a study of the reasons for the Zeeman-effect background correction prob- lems in the presence of large amounts of phosphate the emission signals for P and PO were examined.When phosphate was present as the matrix low-temperature losses at approximately 700 K were seen for PO but in the presence of palladium there was no signal for PO only for P. Figures of merit (limit of detection sensitivity and precision) for Ag As Cd Mn Pb Se Sn and T1 were obtained by Sturegon et al. (91/3187) for FAPES in combination with atomization from a L 'vov platform and use of a palladium chemical modifier. Utilizing a 50 W helium plasma the estimated limits of detection and sensitivities for integrated intensities improved 3- 10- and 6-1 7-fold respectively for volatile elements (Ag Cd and Pb) compared with those for atomization from the tube wall. Riby et al. (92lC761) applied HA-FANES to the determi- nation of As B Cd Cr and Cu. The emission intensity was investigated with respect to plasma pressure and current.The emission intensities increased with increasing pressure because of increased residence times although background noise was higher at both low and high currents. Detection limits for Cd Cr and Cu were comparable to those of ETAAS improved 500-fold for B but approximately a factor of 2 worse for As. The determination of chloride and bromide by FANES using both atomic and ionic spectral lines was examined by Dittrich et al. (921948). The most sensitive determinations could be made at the ionic lines C1 I1 479.545 and Br I1 470.486 nm. The addition of an ionization buffer potas- sium bromide for chloride and potassium chloride for bromide provided constant plasma conditions resulting in improved linearity of the calibration function.Under optimum conditions and the presence of the appropriate buffers detection limits of 0.6 and 0.2 ng for chloride and bromide respectively were obtained. The possibilities and limitations of FANES were discussed by Hoffmann et al. (921C547). Falk (92K745) outlined the potential of directly coupling electrothermal atomizers to mass spectrometers a combina- tion that has many advantages over nebulizer-type sample introduction systems. Electrothermal atomizers are capable of achieving high efficiencies of evaporation and transpor- tation of the sample into the mass spectrometer and the influence of solvent vapour interferences can be avoided. Chakrabarti et al. (9 113806) described the improvements made to a commercial cathodic-sputtering atomizer which was discussed last year (J.Anal. At. Spectrom. 1991 6 187R). The changes allow independent control of the argon flow rate and pressure which increases the rate at whichJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 235R analyte atoms enter the absorption volume and decreases the rate at which the atoms are removed. This results in an increase in peak height sensitivity by a factor of 5 and an increase in peak area sensitivity by 1-2 orders of magnitude for the new atomizer in relation to the commercial version. The sputtering and transport processes in this sputtering atomizer were investigated (92/ 1624) for atomic emission of Cu atomic absorption of Cr and Cu in steel and Ni in brass. The ground state population within the analysis volume was found to be dependent on the sputtering efficiency and the transport efficiency.An excitation mechanism for Cu of inelastic collision of fast electrons with ground state neutral copper atoms was postulated the number of fast electrons being the limiting species in the excitation mechanism. Larkins (92/ 1630) examined the effect of up to 140 ppm water vapour in argon on the production of free atoms by glow discharge sputtering. The water vapour was found to reduce the number of free atoms the extent of the reduction depending upon the sample being sputtered and the sputtering current. A review by Fishman et al. (9113488) with 1 1 1 references considered the use of electric arc atomization in AAS. Ma (92/C564 92/C782) considered the absolute analysis of Cd in biological materials (92K782) and Er and Yb in water sediments and geological materials after acid diges- tion.For the determination of Cd the use of a tantalum foil platform and a chemical modifier of palladium was pre- ferred whereas for Er and Yb a pyrolytic graphite coated electrographite tube lined with tungsten and tantalum was employed. Although no results were presented in the conference abstracts good agreement with reference ma- terials was claimed. The interlaboratory study of the stability of ET’S Characteristic mass data presented by Shuttler et al. and discussed last year (J. Anal. At. Spectrom. 1991 6 187R) has now been published (92/7). Three platform designs were compared using STPF conditions with Zeeman-effect back- ground correction and NIST SRM 1643b Trace Elements in Water as the test sample in 16 laboratories. The ‘fork’ platform design was shown to provide improved perform- ance with respect to the stability of the characteristic mass.For Cr and Pb the ‘fork’ platform yielded characteristic mass values very close to the +20% limits round the expected values. In a few laboratories the Ag characteristic mass was outside this limit and the most discrepant results were obtained for Cu. The ffork’ L’vov platform design features a pyrolytically coated electrographite tube with two ‘notched’ partition rings inside. One end of the platform is in the form of a two pronged ‘fork’. The platform sits loosely in the notched partition rings which prevent rotation and is secured from lateral movement by the ‘fork’ extensions which clip into a third raised ring on the inner surface at one end of the tube.This design minimizes electrical and conductive heating such that the platform is heated primarily by radiation hence yielding a more reproducible performance especially for the volatile ele- ments. A number of other workers have examined the use of ‘fork’ platforms (91/C3627 91X3655 91/C3669 92/C748) in particular for the analysis of environmental samples (91/3655) and the determination of Mn in urine (9 1/C3627 92K748). Carnrick et al. (9 1/C37 13) discussed the application of the transverse-heated graphite atomizer with longitudinal Zeeman-effect background correction (see section 1.2.1) to reducing the time of graphite atomizer analyses.The reduction in background absorption carry-over and inter- ferences enabled the elimination of the pyrolysis step and use of chemical modifiers. In a detailed study Larsen (92/4 1 I 92/C8 16) compared conventional and fast graphite atomizer programmes with and without a palladium-mag- nesium nitrate chemical modifier for the determination of As in inorganic and organic As species. With a Conventional time-temperature programme the characteristic mass for all the species tested was approximately 16 pg. The fast programme with a chemical modifier led to a slightly poorer characteristic mass though when using the fast furnace programme without chemical modification substantial pre- atomization losses of the quaternary arsonium compounds were seen at 200 “C. 1.3. Chemical Vapour Generation This section will present developments in the understand- ing instrumentation and techniques of chemical vapour generation as used in conjunction with AAS detection. Applications to specific analyses of which there are many particularly of environmental and biological samples and to systems employing AFS and AES detection will be reported in other ASU reviews.There have been no outstanding developments since the last ASU review on chemical vapour generation (J. Anal. At. Spectrom. I99 1,6 205R) and the publications currently reviewed reflect repetition consolidation and modest development. How- ever the inclusion of this material in the current review taken in conjunction with its predecessors will give the reader a comprehensive view of the extent of theoretical understanding and practical application of chemical vapour techniques in analytical atomic spectrometry.1.3.1. Hydride generation 1.3.1.1. Fupdamental studies general developments in instrumentation and technique. Interferences occur princi- pally in the liquid phase during formation and release of the hydride. Radiotracers have been advocated as a tool for investigating such effects in a conference presentation by Krivan (92K563). Unfortunately information on the out- come of the studies was not given in the abstract. The simultaneous determination of As Sb and Se as hydrides is difficult because no reductant can reduce all three from their highest to next lowest stable oxidation state without reducing Se to the elemental state (9 1/3 163).The problem was avoided by ensuring that As and Sb were in the pentavalent state stabilized with 2 mol dm-3 H2S04 before formation of the hydride. The processes associated with the generation of the hydrides of As Sb and Se were studied for each element by Narsito and Santosa (91/3084) with particular reference to the decomposition rate of sodium tetrahydroborate in alkali and acid media the stripping of the hydrides from solution and the role of temperature hydrogen and oxygen during atomization. Evidence for an intermediate in the decomposition of sodium tetrahydrobo- rate in the hydride generator and for the formation of dimers in the atomizer was presented. Flow injection techniques continue to be developed for sample introduction in HG systems. A previously devel- oped batch method (Boampong et al.J. Anal. At. Spec- trom. 1987 2 197) has been transferred to a flow system (92/C6 1 1) and improved by the incorporation of L-cysteine for the reduction of AsV to A P . A detailed description of an FI-HG system and of procedures for minimizing interfer- ences has been given by Marshall and co-workers (9 1 /2 7 1 1 9 1/27 12). Diffuse flame atomization was employed and gave the following detection limits As 8; Sb 10; Se 6; and Te 3 ng ~ m - ~ . It has been suggested by Dedina and Welz (9217 15) that the present systems used for hydride atomiza- tion are far from optimum and significant improvement in atomizer performance is possible. Quartz tubes and graph- ite furnaces were said to be superior to diffuse flames in most respects.In quartz tubes hydrides are atomized in a cloud of hydrogen radicals the generation of that cloud is a key requirement of the atomizer function. When the236R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 atomizer is a graphite furnace the hydride can be trapped on the surface of a platform or the furnace and released by raising the temperature of the furnace (92/C737). This procedure significantly increases the analytical sensitivity by instantaneously releasing into the absorption path all the analyte element collected over a period of time from a relatively large sample. Coating the graphite surface with palladium enhances the efficiency of trapping (9 1/2930). A simple non-dispersive HG-ETMS instrument has been reported (92/C520).It was claimed that the separation of the analyte from its matrix by HG combined with a spectral line source and a detector with appropriate spectral response gave adequate analytical selectivity. 1.3.1.2. Determination of individual elements by HG- M S . General principles for these determinations are well established however the particular combination of analyte element matrix instrumentation and methodology re- quired for a given analysis usually necessitates evaluation of analytical accuracy. Antimony has been determined in metallurgical samples (91/3770 91/3916) natural waters (92/242) and marine sediments (921940). Some interferences by transition metal ions in Sb determination have been attributed to direct interaction between the interferent and sodium tretrahy- droborate (92/47).The effects of cobalt and nickel in a micro-hydride generation system were eliminated using cyclohexylenediaminetetraacetic acid (cobalt) and a combi- nation of oxine and oxalic acid (nickel) (9 1/39 16). Use of a slotted tube atom trap in the analysis of copper-based alloys using HG-FAAS increased sensitivity by a factor of 1.8 but significant signal suppression (> 10%) was produced by large excesses (>250 times) of copper(@ lead(@ iron(III) nickel(II) aluminium(IIr) cobalt(I1) and bismuth(n1) (91/3770). The effect of iron(m) was eliminated by the addition of sodium sulfite and of the remaining elements by the addition of 1,lO-phenanthroline and thiourea. No interferences were observed when total Sb in marine sediments was determined by acidification using HCl of a slurry of the sediment followed by HG-FAAS (92/940).Complexation of Sb with citrate in the analysis of natural waters was used to differentiate between SbIV and SbV (92/242). Interference by iron(nI) iron(Ir) copper(I1) and nickel(@ was noted; the detection limit was 1 ng ~ r n - ~ . Arsenic is most commonly determined in biological and environmental samples including foods (9 1/329 1 92/C490) plants (92/82) urine (9 1/3998 92/80 92/C89 1) and water (9 1/3892 9211637). Mineralization of meat with HN03-H2S04 or H20z in a humid microwave digester set at 50-70% full power for 5- 10 min was found to be faster and more accurate than dry ashing (91/3291). Other workers found dry ashing with Mg(N03)2+Mg0 at 450 "C followed by dissolution in HCl to be satisfactory in the analysis of sea foods.Following solubilization of solids or when liquid samples are used FI-HG is frequently employed to tran- sport the sample to the AA spectrometer. Such systems facilitate sample pre-treatment and increase the speed of analysis. The latter characteristic of FI when combined with suitable automation renders frequent calibration practicable even when standard additions is employed (92/C8 19). Sample pre-treatment has been used to provide a means for speciation of organo-arsenic compounds by photooxidation (92/ 129) and to improve sensitivity by preconcentration (92182). Speciation has also been achieved by using pH sensitive conversion of arsenical compounds to arsine using reaction with sodium tetrahy- droborate (91/3892,92/1637) or by direct HPLC separation of those compounds (92/80 92/C8 17).A thermochemical /rydr-ide generator- was developed by Blais et a/. (92/C8 1 7 ) as the interface between the HPLC and AAS systems. It was constructed in quartz and effected sequentially the follow- ing processes ( i ) thermospray vaporization of the metha- nolic eluent; (ii) pyrolysis and atomization of the analyte in a methanol-oxygen flame; (iii) thermochemical hydride generation by hydrogen radicals; and ( i v ) diffusion flame atomization of the hydride in a quartz cell in the AAS optical beam. The system was applied to the determination of biogenic As and Se compounds in shrimp and urine samples. The reactions and atomization of arsine in a heated quartz tube have been studied by Welz et al.(9 1/2984). They found evidence for the following reactions AsH~+H=AsH~+H~ (600 "C) 2As+3H2=2AsH3 (900 "C) In the absence of monatomic hydrogen (H) AsH3 was thermally decomposed but not atomized and elemental As was retained in the tube. In the presence of H As atoms were formed at temperatures above 650 "C. Molecular and cluster forms of As were relatively stable and were retained in the tube only to a small extent. Methods for the determination of Bi have been described in two papers. One system (9113 144) consisted of a hydride generator under reduced pressure. The generated bismu- thine was swept in an air stream into a heated quartz tube for atomization; the detection limit was 50 pg. The other system (921 1826) was operated at atmospheric pressure and the bismuthine was collected in a cool graphite tube furnace prior to atomization. The detection limit of the latter system was 2 pg demonstrating the benefits of sample collection and transient atomization.Lead hydride is one of the more difficult volatile covalent hydrides to generate efficiently by reaction with sodium tetrahydroborate. The addition of oxidants in acidic solu- tion is a long established means of improving sensitivity (Smith R. At. Spectrosc. 1981 2 229). Madrid et al. (92/41) found that lactic acid was the most satisfactory acid for the generation of plumbane from a potassium dichro- mate medium. The detection limit of 5 ng ~ m - ~ however does not represent any improvement over earlier work. When the low-pressure system reported above for the determination of Bi was applied to the determination of Pb (92/C461) a detection limit of 0.10 ng was obtained.In situ collection of lead hydride on a zirconium-coated graphite furnace tube (92/95 1) at atmospheric pressure enhanced sensitivity 6-fold compared with that of a pyrolytic coating and produced a detection limit of 0.4 ng for a 0.5 cm3 sample with a collection time of 9 s. In contrast to the situation with Bi the furnace system was less sensitive than the reduced pressure system. This may arise from the small sample size '(0.5 cm3) employed in the former. The determination of Se by HG-AAS is well known for its susceptibility to serious inteflerence b-v copper and nickel. Three approaches to overcoming the problem have been reported.In one method potassium hexacyanoferrate(u1) was used (91/3539) to mask the effect of 10 p g of copper on 5 ng of Se. The other methods relied upon removing the interfering copper either by cation exchange (9 1 /2720 9 l/C3632 92/C7 16) or precipitation (92/4 14). Flow injection instrumentation was used in both methods. An ion-exchange column was incorporated into the former system while in the latter precipitation and filtration of copper hydroxide was effected prior to sample injection. The detection limits of the two systems were comparable (2 and 1 pg g-' respectively). Successful determinations of total Se in geological (9 1/3062) and biological (9 1/4019) samples have been reported. Speciation of Se in water extracts of sediments has been effected (9113902) by controlled heating of cold-trapped Se compounds.The trapped compounds were obtained by purging Me2Se from the sample solution and by reaction of sodium tetrahydro- borate with oxidized methylated Se compounds and SeIV.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 237R Molecular absorption of radiation at 200 nm from a deuterium lamp by H2S has been used for the automatic determination of sulfide in solution (921 1665). Sulfide ions reacted with 3 mol dm-3 HCl and the released H2S was swept by an air stream via a gas-liquid separator into the optical path of an atomic absorption spectrometer. The detection limit was 0.06 p g CM-~. Tellurium has been determined in environmental samples with a detection limit of 2-4 pg by trapping hydrogen telluride in a modified graphite furnace followed by atomization (9 1 /3 106).Speciation was achieved by selective reduction of TeV1 to TetV by boiling with HCl prior to reaction with sodium tetrahydroborate. Hydride generation AAS is used in approximately 25% of reports relating to the determination of Sn in environmental and biological samples. For a continuous flow system Beach and Shrader (91/C3536) found that the addition of L-cysteine not only eliminated metal interferences but also reduced pH dependence and improved sensitivity preci- sion and stability. Naturally occurring levels of Sn are very low hence incorporation of a concentration stage into the analytical method might be necessary. Adsorption on sulf- hydryl cotton was used to extract and concentrate SnIV from acid-digested food samples (9 1/3565). The adsorbed Sn was eluted with 1 mol dm-3 HCl and determined by HG-FAAS.Recoveries were ~ 1 0 0 % and the detection limit ~ 0 . 1 pg g-'. When electrothermal atomization is employed trap- ping tin hydride in a warm furnace is a simple means of increasing sensitivity. By this means when a 10 cm3 sample was analysed a detection limit of 0.7 ng was achieved (91K3630). Other workers (92/4 13) used a zirconium- coated furnace and a trapping temperature of 500 "C. They reported a detection limit of the order of 6 pg C M - ~ though the reagent blank was found to contain =30 pg ~ m - ~ . 1.3.2. Preparation and speciation of volatile organometallic compounds Only one report of the synthesis of volatile organometallic compounds for analytical atomic spectroscopic use has been received for incorporation into this review.This report (92/C578) described an on-line volatile chelate gen- erating system. The chelate may be continuously collected on a sintered glass filter which is periodically heated to above the volatilization temperature of the chelate for discontinuous feeding of the chelate to the atomizing flame. Alternatively the chelate is fed continuously to the flame via a thermospray system consisting of a 2 pm bore 25 cm long quartz capillary tube heated to 10 "C above the vaporization temperature of the chelate. The system was used to determine Co following the synthesis of the pyrro- lidin- 1 -yldithioformate; the detection limit was 0.08 pg. In a review of developments in the speciation of organo- metallic compounds Chau and Wong (92/ 1 16) reported an increasing use of HPLC and that the refinement of tandem techniques was leading to improved specificity and sensitiv- ity.Organotin compounds extracted into IBMK were determined by warming the solution with an external heater at 136 or 200 "C and sweeping the vapour into a quartz absorption cell heated by an air-C2H2 flame (9113165). Some differentiation between compounds was achieved by varying the temperature but reproducibility was poor. The detection limit was 15 ng of Sn. Gas chromatography has been investigated as a means for speciation of alkylselenium (92/C738) and alkyltellurium ( 9 2 ~ 4 5 ) compounds. In the former study the eluate was fed into a graphite furnace and collected by adsorption on a palladium coating.As the elution peaks of the Se compounds were well separated in time it was possible to operate the furnace programme between each peak. For the latter study eluted Te com- pounds were continuously atomized in an H2 atmosphere in an electrically heated quartz tube furnace at I 170 K; the detection limit was =5 ng of alkyltellurium. The direct adsorption of volatile Se compounds in a palladium-coated graphite furnace has been used as a means of determining evaporation of Se from soil (92/ 1829). By controlling the furnace temperature during the adsorption stage discrimi- nation between selenium hydride and dimethyl- and di- ethylselenium was possible. 1.3.3. Mercury by cold vapour generation A variety of reagents have been used to generate Hg vapour from aqueous samples.Inorganic Hg can be liberated by means of the well established reducing agents such as potassium tetrahydroborate (9 1/3925) or tin@) chloride (9 1/2987 9211 2 1 92/ 144) assisted on occasion by the use of catalytic agents e.g. copper(I1) or cadmium(I1) (92/46). Detection limits are of the order of 0.1 ppb. Hydrazine borane has also been used as a more powerful reducing agent (921 144). Organo-mercury requires prior breakdown by for example mixtures of potassium dichromate-HC1 (9 1/39(25) or potassium bromate/bromide (92/144) or po- tassium iodide (92/121). Sonication has been used to speed the oxidation of organic-bound Hg in waters prior to reduction (92187). Improved analytical performance was achieved when Hg vapour was transported from the reduction vessel to the absorption cell by suction rather than pressurized gas flow (91/3122).Detection limits were of the order of 0.1 ng. When a considerable increase in sensitivity is sought collection of Hg as a gold amalgam followed by thermal release into the absorption cell has proved to be the most successful approach. The gold may be in the form of either a coating on the surface of a graphite platform or furnace (91/2714) or as wire (91/3978) or gauze (91/3593) in a heated quartz tube. The application of a multi-parameter optimization strategy to the direct cold vapour determina- tion of Hg using a commercial instrument system led to a detection limit of 3.3 ng but when amalgamation was incorporated into the same optimized system the detection limit was lowered to 0.3 ng of Hg ( ~ 0 .0 0 6 pg dm-3) (9 1/3593). It has been suggested (91/C3635,92/C1947) that reagent contamination is frequently of the order of 0.05 pg dm-3 and clearly is a factor to be borne in mind when attempting to reach the ultimate in the determination of Hg. Examples of the successful application of cold vapour Hg generation combined with concentration by amalgama- tion include the analysis of concentrated mineral acids (91/2714) and coal fly ash (91/3886). Successful cold vapour determinations of Hg have been carried out using a conventional double beam spectrometer with an Hg lamp as light source (91/3978). Inorganic and organic Hg were reduced with SnC12 and the Hg vapour was trapped on gold wire.The wire was heated in a quartz tube furnace and the Hg vapour fed to an absorption cell mounted in the sample chamber of the spectrometer. Dedicated instrumentation for the determination of Hg by AAS has been described in a series of patents (92/1667 92/ 1668 92/1669). The AA spectrometer (92/1667) was a non-dispersive instrument using Zeeman-effect wavelength modulation of the resonance line. A trapping chamber containing gold gauze was used to trap the Hg produced by chemical reduction (92/1668) or by direct heating of the sample (92/1669). The chamber was heated to release the Hg rapidly into the measurement cell. 1.4. Spectrometers There have been no major developments in AAS instru- mentation during the period covered by this Update. As far as light sources are concerned the poor frequency stability of diode lasers is again acknowledged but minor238R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 improvements of traditional HCLs have been attained with different fill gas mixtures. There have been some funda- mental studies in optics detectors and background correc- tion methods. Most advances of practical interest again seem to be in the continuum source and multi-element AA area but even here the momentum of recent years seems to be much reduced. It is interesting that the only commercial multi-element AA instrument described uses not a contin- uum source but a 16-lamp turret with very rapid inter- change. One ‘new system’ has been described (9211682 92/1683 921 1684) for measuring partial densities of mixed metal vapours in a high-vacuum environment.Here the measur- ing light beam ‘crosses’ the vapour generated in an electrically heated cylindrical vaporizing probe in what appears to be a physicist’s specialized application of the principle of conventional analytical AAS. 1.4.1. Light sources Research into the traditional source for AAS the HCL is represented by two papers. Russian workers have studied the effect of a helium-nitrogen mixture as Jill gas for a number of elements (921 176). For elements with excitation energies of up to 6 eV the line intensity was increased and in particular the detection limits for Bi Pb and Sn were improved thereby. The temporal absorption behaviour of neutral uranium atoms in a pulsed hollow cathode dis- charge has also been investigated and three dominant mechanisms of decay in the post-discharge period were studied (921 19).A non-tradit ional source a reference-locked diode laser has also been investigated (9 11C3648). The poor frequency stability of a diode laser was overcome by generating a lock- in reference signal in a separate atomic reservoir which contained the same element as that being measured in this case Rb. 1.4.2. Optics The effect of source/absorber width ratio on S/N ratio in dispersive AAS was investigated by O’Haver (9 1/3079). While narrow band sources were assumed to be optimum for a single element AAS measurement it was shown that in some cases improved detection limits were found when the spectral width of the light source is comparable to the absorption linewidth.Larkins (921C63 1) constructed a scanning echelle mono- chromator especially for measuring the width and shape of lines emitted from HCLs and other sources. It was also used to measure absorption linewidths and shifts in flames. The image quality given by holographic optical elements has been investigated and discussed (9 1 /36 14). Suggestions were made for the reduction of aberrations. A new automated spectrometer linearity tester has been designed and built at the National Research Council of Canada (921 17). Piezoelectric motors were used to attain precisely the apertures required in the double aperture method of light addition. A useful application of a wide bandpass monochromator in AAS has been suggested in Japan (9 1/2708). Silver at 328.07 and Cu at 327.40 nm can be measured simultaneously using two HCLs which irradi- ate alternately.The absorption measurements were then synchronized using computer techniques. The discrete nebulization method was used to minimize sample volume uptake. I .4.3. Detectors It is already known that a photon incident on a cathode can be converted into more than one electron. The effect has been studied for a PMT using a high-gain medium for the first dynode and a multi-alkali photocathode (9 1 /36 16). Two-electron emission per incident photon shows a steep onset at 2700 8 towards lower wavelengths yhich increases to 14% of total quantum efficiency at 2000 A. A housing for vacuum operation of side-on IP28 PMTs has been described to enable this detector to be used at wavelengths below 2000 8 (9 1/2932).1.4.4. Background correction An AA spectrometer with a computer controlled deuterium lamp background corrector was developed (92x697) in order to investigate the effect of different chopping wave- Jorms in ETAAS Deuterium 1amp:HCL:furnace emission cycles of 50:25:25 and 33:33:33 were tried and in the differential mode 50:50:0 the furnace contribution being filtered out. Comparative results were obtained but not quoted in this conference abstract. Chinese workers have successfully measured Sr as a major component in geological materials using a-compo- nent Zeeman splitting in FAAS (9 113356). 1.4.5. Continuum source and multi-element AAS Harnly has now claimed that detection limits in continuum source AAS can be comparable to those in conventional line-source AAS over the lower UV wavelength range (92/C633).Very high intensity pulsed xenon arc lamps use of linear photodiode arrays (LPDA) and even the use of low- resolution monochromators (to improve source transmis- sion and reduce LPDA readout noise) all contribute to this improved performance. A similar approach was described by Schmidt et al. from Berlin (9 1/298 1 92/C5 17) although they found that the very high source intensity gave rise to appreciable stray light components within the Pchelle spec- trometer and these required appropriate correction. A practical solution to the problem of using a deuterium lamp continuum source for continuum source AAS with a commercially available instrument has been put forward by Chinese workers (9113901).This is a method of correcting for the increased curvature of the calibration graphs. Linear calibrations were arrived at for Ca Cr and Cu with relative differences from the conventional source results of less than 6 O/o. Two conference papers (9 1/C3654 9 l/C3697) describe an instrument for automatic rapid sequential AAS. The 16- lamp turret and grating drive select any element within 1s. The instrument can be used with a graphite atomizer and with an evacuated GD device for the measurement of C P and S in the far UV. 1.5. Instrument Control and Data Processing I .5.1. Instrument control The preparation of samples for analysis by AAS often requires dilution the addition of chemical modifiers and the preparation of appropriate calibration standards.A number of automatic sample preparation systems (prep. stations) have been described to reduce the time required for these activities. In one report (911C3701) the analytical performance of one such station was evaluated by deter- mining the volumetric accuracy the error associated with dilution and the accuracy in preparing calibration stan- dards. It was found that although the instrument gave satisfactory performance for sample preparation providing the dilution factor of sample or chemical modifier was not greater than 20 (i.e. uptake=0.3 cm3 final volume=6.0 cm3) the calibration standards were poor with up to 36% error.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 239R Other reports in this area detail automatic on-stream analysis by AAS.One such system (91/C3736) describes the determination of Fe in zinc sulfate solution. The instrument had provision for user-written software for instrument control via a GPIO communications utility which handles up to 12 digital outputs and 14 digital inputs 2 RS 232C ports and an HP-GPIB port. A solid state I 1 0 interface was used to activate the flame and stream-selector system during each analysis. In a second report (9113474) a data acquisition system based on an 8085-A single board microcomputer was developed for sampling and storage of data coming from the signal generated by a flow injection gradient profile. The profile was used to perform standard additions in various analyti- cal procedures. The system was capable of serial communi- cation with a host computer.The difficulties in automated background-correction routines and their relation to peak detection have been discussed (92/C69 1). The accurate relation of spectral information (peak position widths and intensities) to concentrations of analytes in a sample requires signals that only originate from the analytes under study. An algorithm has been presented that detects the intense peaks that would influence the background calculations if included as reference channels and groups them into multiplets. Rules based on the convolution signal are then applied for the selection of the reference channel. An F-test is used to select the order of the polynomial to be used (up to the third degree) before the actual background is calculated. The resulting spectra are convoluted again and the lines detected using information from both the convoluted signal and the background corrected spectra.Fraudulent peaks and missing weak signals are reported to be mini- mized resulting in more reliable data. A procedure to calculate the AA coeficient of the Se 196 nm line for conditions corresponding to various atomizers has been described (921 16 18). The procedure employs an exact evaluation of the overlap integral of the emission and absorption line. Computed values of the atomic absorption coefficient of the line for the flame-in-tube atomizer and for the graphite furnace were obtained using a PC with MATHCAD software which employs the Simpson’s rule algorithm for numerical integrations. These values were compared with experimental data from the literature and showed good agreement for the flame-in-tube atomizers where the Lorentz broadening was predicted to dominate the absorption line.However for the Massmann-type graphite furnace sensitivities reported by most workers are lower than those predicted. A computer program for the calculation of the theoretical characteristic mass in ETAAS has also been presented (921C772) and a comparison made with the manufacturer’s data for various atomizer designs used in AAS. The results confirmed the importance of integrated absorbance signal evaluation and the advantages of spatial isothermality for efficient ETAAS performance. Finally a computer program has been devloped for calculation of the light collection eficiency of an arbitrary combination of lenses and stops as a function of position in Cartesian space (9112979).The program was based on a rigorous ray-tracing algorithm and thus accounts for the effects of lens aberrations. It was used to model three three- lens combinations configured to collect atomic fluorescence from a graphite furnace. Calculated single point collection efficiencies were found to differ significantly from those expected from the solid angle subtended by the lenses. They ranged from < 15% of the ideal value for biconvex lenses to nearly 1 00% for achromats. Differences in performance were reduced when the collection efficiency was integrated to account for the 2 mm diameter of the exciting laser beam and the length of the graphite furnace. 1.5.2. Data processing The majority of publications dealing with advances in this area have dealt with calibration.A method for the con- struction of rectilinear calibration graphs from experimen- tal data containing outliers has been described and applied to results of the determination of Cr at 357.9 nm in an air-C2H2 flame by AAS (9112610). The method was based on the least-mean-squares procedure of Carr and Rutan (Anal. Chim. Acta 1988 215 131) although it was reported to perform better than least-squares techniques. The use of the total information contained in the transient signals caused by dispersion in FI procedures (instead of only peak height or integrated absorbance) has been used to expand the dynamic range in AAS (9113078). The algorithm used named CLAIR (calibration graph lineari- zation and interfered signal reconstruction) was based on gradient ratio evaluation and was capable of using the additional information in the transient signal for calibra- tion and interference correction.It was claimed that with this algorithm the entire working range of the instrument could be calibrated by use of a single reference solution and problems due to calibration graph curvature or drift could thus be avoided. A method has been proposed for the correction of matrix effects by successive dilution of the test solution with measurements of the analyte at each stage (9112717). The raw results were extrapolated to zero concentration (or infinite dilution) at which point the hypothetical matrix is a pure solvent. This provided an unbiased estimate of concentration without the need for a matrix matched calibration set.The method was shown to work well for AAS and strategies for implementing the method as an automatic adjunct to modern instruments were discussed. A review of 23 references has also been published (9113533) which discusses statistical tests on calibration lines using the determination of Pb by ETAAS as an example. It was evident from this study that statistical tests can lead to erroneous interpretations according to the level of signifi- cance chosen and that even though a calibration line meets the criteria of the test it might not always be totally reliable. An approach to reduce the relative error in the standard additions method has been proposed (9 1 12706). The paper described a method which reduces the coefficient of variation by a factor of 2 over more common methods but with the same expenditure of effort.The theoretical background to the study which involves weighted linear regression using signals of different reliability such as probit analysis is described in detail. A recommended procedure is also presented for ease of reference. Several microcomputer controlled graphics and data processing systems have also been described. These range from the use of an Apple 11 a 12-bit ADC and DAC a temperature measuring device and two precise amplifiers to acquire absorbance and temperature data simultaneously from an ETAAS instrument in order to produce graphs and Arrhenius’ plots (91/3930) through to the use of data processing techniques for photodiode array spectrometers (91/3090 92/3).In the latter case the accuracy and precision of spectral peak height and position measure- ments were improved by zero-filling or Fourier domain interpolation and spectral line-diode registry effects were eliminated (9 113090). Cross-correlation also allowed auto- matic recalibration of spectral windows and programmable integration times allowed the extension of dynamic range. The use of real-time computer graphics to optimize ETAAS has also been discussed in conjunction with quality assur- ance and quality control programmes (91/3960). In this case a standard additions tree was used as a guide to whether the use of standard additions was necessary i.e. if the post-digestion recovery was found to fall between 85240R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 and 115% standard additions were not used. In a second report on the same subject (911C3711) the possibility of using microcomputers and sophisticated autosamplers with AA instruments was discussed in order to perform intelli- gent operations based on the result of calculations based on spike recovery measurements. Finally two reports have described specific applications of computer data acquisition. The first of these described the computer-assisted measurement of gas temperatures in electrothermal atomizers (921C449). In this study the workers attempted to refine the two-line technique by using computer data acquisition signal averaging and statistical evaluation. Data were acquired by using an Apple IIe microcomputer with a 13-bit A/D card and transferred to an IBM1AT for processing using Lotus 1-2-3 Statgraphics and custom-written software.The use of the computers was found to facilitate the evaluation and helped to reduce errors connected with manual data processing used in earlier work so that the technique could be used routinely. In the second example (92/C843) a program was described written for IBM PC computers which presents chemical speciation results either graphically or in conventional tabular form. The program was menu driven and as such reduced the need for the user to interpret an input file that often resembles a sequence of seemingly meaningless numbers. 1.5.3. Chemometrics A number of specific applications for regression methods have appeared and Miller (9112707) has produced a very useful review of calibration and regression methods. The review covers linear calibration; method of standard additions; residuals in regression analysis; regression tech- niques in the comparison of analytical methods; robust and non-parametric regression methods; analysis of variance in linear regression; weighted linear regression methods; partly straight partly curved calibration plots; the treat- ment of non-linear data by transformations; curvilinear regression; spline functions; and other robust non-linear regression methods.The use of partial least squares modelling to compensate for spectral interferences in ETAAS with continuum source background correction has been reported (9 113 198). The study was based on the determination of As in marine sediments and involved using the absorbance signals obtained from a calibration set of A1 and As standard solutions and mixtures of the two to construct a partial least squares model.The model was then used to derive the concentrations of As (and Al) in dissolved sediment samples from their absorbance signal patterns. In a further report (92/ 1834) two chemometric approaches were used for the rapid screening of samples. Although not strictly in the area of this review the models could be adapted for AAS. In the first method partial least squares was used to quantify both Pu and HN03 by using the information contained in the absorption spectra. The evaluation of the calibration models using test samples that spanned the range of calibration concentrations gave predictions con- sistent with the standard error of the calibration model.In the second method pattern recognition methods (nearest neighbour classification and principal components analysis) were used to investigate the effects of various amounts of nitric acid fluoride or oxalate on visible spectra of PuIV solutions. A short review describing the working principles of standard additions-parallel translating regression curve methods in AAS has also been presented (9113466). The number of papers reporting the use of simplex methods have declined this year however the optimization of cold vapour AAS determination of Hg with and without amalgamation by use of complete and fractional factorial designs with both univariate and modified simplex methods has been reported (9113593). Both peak height and inte- grated absorbance were measured.The effect of the vari- ables was tested by the analysis of variance (ANOVA) at a 99% confidence level. The interaction of air flow rate sample volume and use of a desiccant were optimized according to a complete Z3 factorial design and univariate method. The flow rate of N2 mass of the amalgamator trapping time releasing time and interactions between them were statistically evaluated according to a fractional factorial design (half-replicate of a complete 24 factorial design) and subsequent use of a modified simplex method. This approach for partial optimization of a complete system was rapid and reported to have many advantages over simple univariate methods.A large series of replicate analyses have been carried out by Kurfurst (92/C780) on pulverized materials using ETAAS. This enabled characteristic values for the sample material to be obtained (sampling constant homogeneity factor) from which the minimum amount of sample required for normal distribution of the results or for a demanded RSD could be calculated. The results showed an asymmetric distribution sometimes with several maxima as a consequence of a small mass fraction of higher analyte content within the sample leading to a ‘nuggets-effect’. The distribution of sub-samples with a different number of nuggets was described using the Poisson probability func- tion. Holcombe et al. (911C3656 921C448) have used Monte Carlo techniques to model the atomization processes occurring inside a graphite atomizer.In the first of these papers (9 11C3656) numerical simulations of heat transfer were used to study the effects of non-uniform heating in Massman-type furnaces with different sizes and shapes which heated more isothermally than conventional tubes. In the second paper (92/C448) the Monte Carlo simula- tions were used to produce signals from elements with generally agreed surface and gas reaction kinetics. The resulting profiles were used in an attempt to extract mechanistic information from Arrhenius plots peak alignment spatial distribution peak shape etc. with the aim of optimizing furnace design. Finally the use of expert systems has been reported for method development and validation in AAS (9 lK3737).Two types of system were presented. In the first of these problems with calibration graphs were first identified i.e. blank problems outliers departures from linearity at high concentration curvature insufficient precision and effects of matrix interference. If a problem was diagnosed a remedy was proposed. The system contained several non-standard statistical routines such as the least median of squares. The second system utilized the ‘first guess’ approach where the problem is to select a good initial procedure that is then optimized. The example described involved the selection of a dissolution step prior to the analysis. 2. ATOMIC FLUORESCENCE SPECTROMETRY T ~ C attraction of AFS for the analyst lies in the low element determination or to simultaneous multi-element detection limits and wide linear range that can be achieved analysis. Atomic fluorescence spectrometry is at its most and the possibility of non-dispersive highly selective useful when conventional light sources are used and when instruments.These instruments may be dedicated to single- there is either very little sample matrix or the analyteJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 241R element can be separated from it. As atomic fluorescence is used along with molecular fluorescence as a diagnostic aid in studies of combustion and of plasmas this use of fluorescence will be presented in this review. In addition coherent forward scattering (CFS) [atomic magneto-optical rotation AMORS] will be reviewed under the general heading of AFS as there has been insufficient activity in that area during the past year to justify a separate major heading.2.1. Discharge Lamp-excited Atomic Fluorescence The most commonly determined elements using discharge lamp excitation are those that can be separated from the sample matrix by chemical generation of volatile com- pounds. The analytical methods employed are similar to those used for chemical vapour generation in AAS. Most of the papers to be quoted in this section are devoted to modest developments in methodology. Fuller information on those methods will be found in the applications review of ASU devoted to the particular sample matrix. For the determination of Hg using an FI system photooxidation of organomercury compounds was followed by reduction with tin(I1) chloride extraction of Hg via a PTFE membrane and its determination by non-dispersive AFS with an Hg lamp and solar blind photomultiplier (9 1/3352).The detection limit was 0.18 pg dm-3. Lower detection limits have been achieved by means of special instrumentation (92/49) incorporating a newly developed gas-liquid separator. The detection limit was 0.9 ng dm-3. Amalgamation with gold coated on quartz was used to collect Hg from air prior to its determination by AFS (9 1/308 1); the detection limit was ~ 2 . 0 pg of Hg. Inevitably in chemical vapour generating systems interferences in that process by other components of the sample can occur. In the determination of trace amounts of Hg in sulfide minerals interference from antimony was eliminated by the addition of tartaric acid and those from lead and copper were masked by the addition of EDTA (92/ 180).Several groups have reported on the determination of As by HG-AFS. The application of boosted hollow cathode lamps as high intensity excitation sources for this analysis using dispersive and non-dispersive systems has been investigated by Stockwell et al. (9 1/C3629). Hydride gener- ation-AFS has been successfully applied to the determina- tion of As in electrolytic copper (9211799) and in water (9113179). Arsenic in air was measured by collection on chemically treated filter-paper eluted with 40% of HCl and determined by non-dispersive HG-AFS (9 1 /3940). Tellu- rium in geochemical samples was determined at concentra- tions of around 0.005 ppm by HG-non-dispersive AFS without separation or preconcentration (9 1/385 1).Interfer- ences were minimized by using an iron(rr1) salt as a buffer. The interference of copper in the determination of Se by HG has been investigated by means of the signal shape generated in HG-AFS (92/C5 10). It was concluded that the interfering ion did not affect the SIV-Se1I reduction step and that a mathematical model could be used to minimize interferences. The suitability of the ICP as an atomizer of real samples for AFS using hollow cathode lamp excitation continues to be investigated as for example in the determination of trace metals in hydrocracker feed (9 l/C2767). Its potential for the simultaneous determination of a wide range of elements at low concentrations in granitic waters has been demonstrated by Sansoni and Panday (9 l/C2796).Interfer- ence effects by low concentrations of mineral acids and 100- fold excess of various ions on the determination of Ca Cd Cu Fe K Li Mg Mn and Pb were investigated by the same workers (9 1 /C2865). Mineral acids led to signal enhance- ment while high amounts of sodium produced quenching. A 1 0-fold excess of aluminium completely suppressed the Ca signal and lanthanum reduced the effect. Flow injection on- line preconcentration of Mo and W was used with ICP-AFS to achieve detection limits of 9 and 31 pg dm-3 respec- tively (92/1681). An electrically heated spiral atomizer with non-dispersive AFS has been examined for the determination of Pb in environmental samples (92/C502). The design of the optical and electronic systems minimized the signal from the emission of the hot spiral.The detection limit was xO. 1 pg of Pb. 2.2. Laser-excited Atomic Fluorescence Spectrometry Excitation of atomic fluorescence by laser radiation has the potential to achieve very low detection limits by virtue of the high intensity available. Its practical application is limited by the restricted range of laser wavelengths avail- able and the generation of a background signal by light scattering in the atom cell. The excitation process can be either wholly photo-induced by a single or multi-stage process or a combination of thermal- and photo-induction. When the wavelengths of the excitation and fluorescent radiations differ the problem of scattered light is reduced considerably. The high sensitivity of LEAFS has been illustrated by its being the preferred method for the determination of Cd and Pb in ice cores and snow (92/C444); the values were in the 0.05-40 pg g-l range.Another example of its use for difficult analyses has been in the determination of impurities in high-purity gases. Stepwise (plasma plus laser) excitation was necessary to achieve an adequate signal (911C2843). The limit of detection for Ne in helium was 0.3 ppb and for Nz in helium was 10 ppb (91K2844). In a fundamental study of the two-step excita- tion of Ag in an ICP an increase in the stepwise non- resonance fluorescence signal was predicted theoretically and observed experimentally (92/ 1685). The effect was attributed to an increased population of the fluorescent level caused by cascade de-excitation both radiational and collisional from the upper levels reached with the second excitation step. Collisional depopulation of the 53P1 state of Cd by ground state Cd and noble gas atoms has been studied by Czajkowski et al.(92/1619). Cad- mium vapour and the noble gases were contained in a temperature controlled (403-540 K) quartz cell and irra- diated by pulsed dye laser radiation at 326.1 nm. Fluores- cence decay times at several temperatures and pressure were measured. The total depopulation cross-sections de- duced were 1.67 1.1 x 3 x 6.1 x 1.3 x and 3.3 x nm2 for collisions with ground state cadmium helium neon argon krypton and xenon atoms respectively. The cross-section for the Cd-Cd interaction is notably larger (1 x 1 05-fold) than those for Cd-noble gas interactions.At the present time the most frequently reported atomizers in LAFS are electrothermal and sputtering systems. However from time to time reports of lasers both as atomizer and exciter appear. Laser ablation has the potential whether they are conductors or solids for direct analysis of solids and of microstructures. The processes of ablation and atomization by one laser with excitation of fluorescence by a second laser have been studied from the analytical viewpoint by Niemax and Sdorra (9 1/2940). The sample was ablated under reduced pressure in a noble gas atmosphere. For low alloyed steel samples detection limits ranged from 0.1 5 pg g-l for Mg to 2 1 ,ug g-' for Sn. Ablation atomization avoids the problems of contamination associ- ated with dissolution techniques.242R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 2.2.1. Electrothermal atomization Graphite furnace LEAFS is an extremely sensitive selective technique with a wide dynamic range. The dynamics of the atom vapour in the furnace have been studied by irradiating it with two lasers and varying the time interval between their firings. The first laser ‘pumps’ the system to be studied and the second ‘probes’ it (92/C746). The ‘pump and probe’ approach can also be used analytically to reduce the effects of chemical vapour-phase interferences by careful timing of the firing of the second laser. Computer ray tracing has been used to optimize the collection of laser-excited fluorescence from a graphite furnace (9 1/2979).An instrumental system derived from the model was applied to the determination of T1 and a detection limit of 0.1 fg resulted (9 1/337 1). Other attempts to improve analytical performance have involved the examination of factors affecting signal to noise ratios (S/N) of transient signals and background correction procedures. It was predicted (91/C3650) that in a shot noise limited situation the S/N will increase as the square root of the integration time. When flicker noise is dominant the S/N is independent of repetition rate and inversely proportional to the integration time. Thus in both cases reduction in the signal peak width should lead to improvement in S/N and detection limits. Three approaches to background correction have been reported. Wavelength modulation was employed in two forms in one the wavelength of the exciting radiation was modulated by oscillating the tuning mirror of a grazing incidence dye laser with a piezoelectric device (91K3649); and in the other the energy levels of the absorbing atom were modified by an oscillating magnetic field (91K3698).The feasibility of these systems has been demonstrated but their utility requires further evaluation. The latter system achieved detection limits of 4 fg for Pb and 500 fg for Co. An alternative approach whose practicality has been demonstrated was a dual monochro- mator system designed to monitor background fluorescence from high concentrations of molecular species (9 ~ 3 2 8 0 92/C523). Gold was determined in river water at the 300 fg level with a precision of 15%.The detection limit for Au was 10 fg and for Co was 4 fg. A comparison of ETA-LEAFS with ETAAS for the determination of T1 in food and agricultural reference materials with slurry sampling found that the detection limit of LEAFS was 1-2 orders of magnitude lower than AAS (91/3275). Further the background signal was rela- tively smaller in LEAFS while precision and accuracy were comparable. Palladium can be determined with great sensitivity and little background by ETA-LEAFS. This approach has been applied to the determination of Pd in photographic material (9 1 /C2869). In aqueous solution the detection limit was 0.4 pg for a sample of 10 mm3. Laser-induced molecular fluorescence in a graphite fur- nace has been used as a means for determining F (9 1/3 186) and C1 (921939).Fluorine was observed as magnesium fluoride (excited at 268.94 nm detected at 358.22 nm) and gave a detection limit of 0.3 pg of F as fluoride. Significant interference from other ions (Na+ H+ C1+ and Br-) was found. However the sensitivity for the detection of F was such that a 100-fold dilution of urine and tap water was possible and this eliminated the interferences. Chlorine was determined by adding excess of indium to the sample in the graphite furnace excitation of indium chloride was at 267.18 nm and detection at 359.54 nm the detection limit was 17 pg of C1 as chloride. The similarity of the wavelengths used for both fluoride and chloride excitation and detection and the width of the spectral peaks of the molecular species could render the methods vulnerable to interferences if concentrated samples of complex compo- sition were to be analysed.2.2.2. Low pressure atomization systems Hollow cathode sputtering is the most common of the low- pressure systems used in generating an atomic vapour for LAFS. For the analysis of solutions a disposable graphite cup served as a demountable cathode (91/3809). The discharge system was pulsed in synchronism with the laser. Though detection limits as low as 15 fg of Pb were reported it was stated that improvements in understanding of the discharge process and in the design of the cathode could lead to better limits of detection. A heated graphite hollow cathode has been used for the determination of Co and Ni (9 l/C2853) in powder and dried residues.The cathode was heated to 1600 “C. The plasma background was decreased significantly (1 00-fold) by cutting off the discharge and exciting fluorescence in the afterglow (for up to 1OOps). The detection limit for Co was 15 ng dm-3. For the determination of trace elements in metals by cathodic sputtering-LAFS the cathode is made from the metal sample. The approach is particularly suitable for the analysis of pure metals as it is free from the interferences that can occur at a hot graphite surface and in the gas phase (9 1/3607). The flux of sputtered ions was calculated from the geometry of the atomizer and used to predict the analytical sensitivity of the system The experimental value of the latter was five times less than predicted. The detection limit of Pb in pure copper was 40 ng g-l.Optimization of the parameters of the GD improved the detection limit by a factor of 60. When a planar magnetron was used as atomizer the detection limits were 3 ng g-I for Pb in copper and Si in germanium. Travis et al. (9 1/3773) undertook a comprehensive experimental and theoretical evaluation of cathodic sputtering-AFS. They also found sensitivities to be far less than predicted for the determination of Fe in brass (detection limit 150 ng g-I). Noise studies indicated that laser-induced background fluorescence was the principle limiting noise source. Catho- dic sputtering-LAFS has been applied to depth projfing studies (9 113606). The anode was the atomizer case and the difference in size between the cathode and anode facilitated the r.f.sputtering of metals semiconductors and dielectrics. Under optimum analytical conditions a detection limit of 24 pg g-’ of Na in molybdenum corresponding to a mean layer thickness of 1 nm was obtained. 2.3. Studies of Flames and Plasmas Using Laser-induced Fluorescence The quantitative application of laser-induced fluoresence (LIF) techniques to studies of fundamental processes in flames requires that the laser should not perturb the sample. The occurrence of photochemical efects in laser-based combustion studies of the N20-H2 flame has been reported (91/2935). It was suggested that the perturbation was characterized by single photon creation of radicals in regions of the flame that contain both N20 and H20 a mechanism that has also been used to create OH radicals for kinetic studies.A knowledge of the concentration of OH radicals in flames is important when modelling flame chemistry. This information has been obtained by simulta- neously recording the LIF signals from two focal volumes of different shape (9 1/36 15). The ratio of the signals was a measure of the saturation parameter a function of laser intensity and quenching and from which the species number density was deduced. Multiphoton excited fluores- cence techniques provide powerful tools for the study of processes in flames. Using frequency doubled and fre- quency tripled beams from a single dye laser both OH and H have been excited simultaneously (9 112934). Two- dimensional and picosecond LIF along with absorption spectrometry have been used for the determination of absolute concentrations temperature and collisional life- times of OH radicals in a laminar air-CH flame (9 1/2933).JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 243R The NH2 radical and CO molecule concentrations were also determined. Coherent anti-Stokes Raman scattering (CARS) is widely used in combustion diagnostics for measurement of temper- ature and the concentration of major species. Simultaneous determinations of temperature and CO concentration in mixtures of C02 H2 and N2 in a furnace by multiplex CARS spectra were made to test a theoretical model of the system (92/20).Simultaneous C02 and H2 multiplexed CARS spectra from an 02-CH4 diffusion flame were also recorded. Temperature determinations from the C02 CARS spectra agreed with thermocouple measurements but estimates of the CO concentration were inaccurate.The discrepancy was attributed to failure of the model to include a cross coherent effect factor and to account accurately for back- ground. A single shot CARS measurement using a modeless laser had a precision of 1% in the measurement of temperature in N2 at 1200 K (9 1/36 17) by virtue of reduced noise on the CARS spectrum. Radiation absorption by species in high-temperature gases is also used as a means of studying fundamental processes in such systems. Ouyang and Varghese (91/2937) demon- strated that the accuracy of the absorption measurement in a given experiment is largely determined by the spectral line used for the measurement. A set of criteria for selecting spectral transitions was proposed and incorporated into a PASCAL program.The capabilities of the program which could be extended to LIF measurements were demon- strated by the selection of absorption transitions of CO for simultaneous measurement of temperature and species concentration under several experimental conditions. The LIF technique combined with Raman scattering from the same laser beam has been evaluated as a means for obtain- ing point measurements at the low temperatures and densities encountered in hypersonic wind tunnel flow (9 1/2936). Molecular oxygen was the probed gas and a measurement precision of 2% was predicted for temperatures above 60 K and densities greater than 0.01 amagat at Mach number 10. 2.4. Coherent Forward Scattering (Atomic Magneto-optical Rotation Spectrometry) There has been very little activity in CFS during the past year and all publications to be reviewed here have been prepared by Hermann and colleagues from the Justus-Liebig Univer- sity Giessen Germany.The noise characteristic of aflame CFS spectrometer incorporating a continuum source and a multi-pass optical system have been studied (9 1/2983). The noise power spectra of the xenon short-arc lamp the background intensity and the CFS signal were measured. There were occasional high peaks in the spectra but no minima that could be exploited to improve the SIN ratio. At low intensities shot noise dominated while at high intensi- ties flicker and interference noise was dominant. Multi-pass optics were also incorporated into a furnace system (92/C762).This development led to greater sensitivity and less interference from the furnace emission background and to lower detection limits. Laser ablation was used to generate aerosols from solid samples that were difficult to vaporize by other means (92K776). The aerosol was transported in an Ar gas stream to a graphite furnace where it was collected and then atomized into the CFS optical system. Simultaneous multi-element analysis of drinking waterwas carried out using flame or furnace atomization and a continuum radiation source (a xenon short-arc lamp) (9211648). The elements determined included Ag Ca Cd K Mg Mn Na and Pb. 3. LASER-ENHANCED IONIZATION Lasers may be used to promote ionization in atomic vapours by providing all the energy required to produce ionization (photoionization) or to excite an atom into an energy state from which it can be ionized by collision.These processes are used as sensitive means for determining analyte atoms in an atomic vapour. Omenetto (92/C443) has however proposed that the atomic vapour could alternatively be used as a detector of photons. Using magnesium atoms in an air-C,H flame excited by dye or excimer lasers several weak forbidden transitions and Raman and fluorescence photons were detected with a calculated quantum efficiency of 0.73. Despite its potential for high sensitivity analytical interest in LEI would appear to be waning in that this year's review is based on barely half the number of papers reviewed last year (J. Anal. At. Spectrom.1991 6 216R). At the present time the flame is the most popular atomizer. Axner and Sjostrom (9 1/3869) reported that two- step LEI in which atoms are excited to a higher energy state by a second photon prior to collisional ionization is much more sensitive than photoionization in atmospheric pressure atomizers due to high transition probabilities. One- and two-step excitation processes have been studied for Na in an air-C2H2 flame (91/3342). The technique was applied to the determination of Na in semiconductor silicon. The results were in good agreement with those obtained by AAS. Single and two-photon resonance LEI when. applied to the determination of Eu gave a detection limit of 10 pg dm-3 (91/3993). Several attempts have been made to apply flame LEI to the analysis of real samples. The problems of identifying and suppressing noise gener- ated by the matrix have been addressed in the determina- tion of trace elements in high-purity liquids (91/3903) and solids (92lC586).In the latter analysis a microsample was pulse evaporated from an electrically heated graphite rod into the flame. For In in solutions of cadmium-mercury-t- ellurium alloys the detection limit was 1 x lo- pg g-I; when a solid sample was used the detection limit was Matrix interference by easily ionizable elements (calcium magnesium sodium and potassium) in the determination of Mn at trace concentrations in waters by flame LEI was overcome by extraction in diisobutylketone of the Mn- chelate with sodium diethyldithiocarbamate (9 1/32 1 1). The detection limit in the original sample was 0.09 pg dm-3.No preconcentration of rock digests was required to achieve detection limits of 0.002,O.OOl and 0.5 pgg-' for Cs Li and Rb respectively in the solid samples (9215). The effect of sample matrix on the analytical signal arose principally from an additive multiphoton ionization background due to CaOH+ polyatomic ions in the flame. Multiphoton ionization is often the most sensitive method available for detecting radical species in flames. This technique has been applied to a study of CO and H in a laminar air-CH diffusion flame (9 1/2938). The results show significant variation of electron detection efficiency between the lean stoichiometric and rich flame regions with the greatest sensitivity observed in the high temperature primary reaction zone (i.e. near stoichiometric conditions. A single publication has reported the use of graphite probe atomization for LEI in a graphite tube furnace (9113799); the probe was also used as an electrode. The mechanisms of ionization and interferences were studied. Concentration detection limits were up to two orders of magnitude worse than those achievable by flame atomiza- tion owing to noise generated by thermionic emission of the furnace and noise transferred from the furnace heating current to the detection system. 1 x pg g-1.244R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL 7 LOCATION OF REFERENCES The full list of references cited in this Update have been published as follows 9 112703-9 1lC2928 J. Anal. At. Spectrom.199 1 6(5) 22 1 R-227R. 9 112929-9 113584 J. Anal. At. Spectrom. 199 1 6(7) 257R-280R. 9113585-9114050 J. Anal. At. Spectrom. 1991 6(8) 323R-340R. 9211-921425 J. Anal. At. Spectrom. 1992 7( I) 53R-66R. 921426-9211447 J. Anal. ilt. Spectrom. 1992 7(3) 1 19R-154R. 921 1448-9212589 J. Anal. At. Spectrom. 1992 7(4) 173R-2 13R. 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 9112610. 2. Chem. 1990 30 222. 9112705. Analyst 1990 115 1543. 9112706.Analyst 1990 115 1589. 9112707. Analyst 1991 116 3. 9112708. Analyst 1991 116 31. 9112709. J. Anal. At. Spectrom. 1990 5 663. 9112710. J. Anal. At. Spectrom. 1990 5 669. 9112711. J. Anal. At. Spectrom. 1990 5 675. 9112712. J. Anal. At. Spectrom. 1990 5 68 1. 9112714. J. Anal. At. Spectrom. 1990 5 691. 9112715. J. Anal. At. Spectrom. 1990 5 693. 9112717. J. Anal. At. Spectrom. 1990 5 701. 9112720. Anal. Proc. 1991 28 18. 9112775. Analyst 1991 116 141. 9112776. Analyst 1991 116 145. 9112930. Anal. Proc. 1991,28 44. 9112932. Rev. Sci. Instrum. 1990,61 1558. 9112933. Appl. Opt. 1990 29 4860. 9112934. Appl. Opt. 1990 29 4841. 9112935. Appl. Opt. 1990 29 4852. 9112936. Appl. Opt. 1990 29 4873. 9112937. Appl. 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Chem. 199 1,63 15 1. 9113079. Anal. Chem. 199 1,63 164. 9113081. Anal. Chim. Acta 1990 236 37 1. 9113083. Anal. Chim. Acta 1990,236 469. 9113084. Anal. Chim. Acta 1990 237 189. 9113090. Appl. Spectrosc. 1990 44 1259. 9113102. At. Spectrosc. 1990 11 70. 9113104. Anal. Sci. 1990 6 547. 9113106. Anal. Sci. 1990 6 561. 9113122. Quim. Anal. (Barcelona) 1990 9 115. 9113129. Fenxi Huaxue 1990 18 468. 9113133. Fenxi Huaxue 1990,18,645.91/3137. Anal. Lett. 1990 23 192 1 ~ 91/3144. Fenxi Ceshi Tongbao 1990,9(2) 63. 9113157. Fresenius J. Anal. Chem. 1990 338 253. 9113163. Talanta 1990 37 1029. 9113165. Analusis 1990 18 440.9113179. Huanjing Huaxue 1990 9(1) 58. 9113180. Analyst 199 1 116 26 1. 9113181. Analyst 199 1 116 327. 9113185. Analyst 1991 116 353. 9113186. J. Anal At. Spectrom. 1991 6 9. 9113187. J. Anal. At. Spectrom. 1991 6 19. 9113188. J. Anal. At. Spectrom. 1991 6 25. 9113196. J. Anal. At. Spectrom. 1991 6 93. 9113197. J. Anal. At. Spectrom. 1991 6 105. 9113198. J. Anal. At. 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Guangpuxue Yu Guangpu Fenxi 1990 10(4) 50. 9113371. Spectrochim. Acta Part B 1990 45 1369. 9113392. J. Chem. SOC. Pak 1990 12 157. 9113405. Chem. Express 1990 5 705. 9113410. Eisei Kagaku 1990 36 219.9113412. Fujian Shifan Daxue Xuebao Ziran Kexueban 1989 5(4) 61. 9113414. Gaodeng Xuexiao Huaxue Xuebao 1990,11 780. 9113425. Jilin Daxue Ziran Kexue Xuebao 1990 (2) 107. 9113431. Pertanika 1990 13 95. 9113466. Huaxue Shijie 1990 31 2 16. 9113474. Lab. Microcomput. 1990,9(2) 44. 9113475. Magy. Kem. Foly. 1990 96 268. 9113488. Prog. Anal. Spectrosc. 1989 12 507. 9113497. Tech. Sci. Methodes Genie Urbain Genie Rural 1990 (2) 81. 9113503. Acta Chim. Hung. 1990 127 407. 9113508. Am. Lab. (FairJield Conn.) 1990 22(15) 80. 9113533. GIT Fachz. Lab. 1990 34 1087. 9113539. Huaxi Yike Daxue Xuebao 1990 21 205. 9113540. Int. J. Environ. Anal. Chem. 1990,41 119.9113546. LaborPraxis 1990,14,822. 91/3565. Shipin Yu Fajiao Gongye 1990 (3) 58. 9113569. Spectrochim.Acta Rev. 1990 13 225. 9113592. J. Anal. At. Spectrom. 1991 6 233. 9113593. J. Anal. At. Spectrom. 1991 6 239. 9113598. Analyst 1991 116 51 1. 9113604.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 24513 Can. J. Appl. Spectrosc. 199 1 36 9. 9113606. Spectrochim. Acta Part B 199 1 46 459. 9113607. Spectrochim. Acta Part B 1991 46 467. 9113614. Appl. Opt. 1990 29 5198. 9113615. Appl. Opt. 199 1,30; 95.9113616. Appl. Opt. 199 1 30 387. 9113617. Appl. Opt. 199 1,30 1008.9113770. Anal. Proc. 1991 28 193. 9113773. J. Anal. At. Spectrorn. 1991 6 261. 9113774. J. Anal. At. Spectrorn. 1991 6 273. 9113775. J. Anal. At. Spectrom. 1991 6 277. 9113778. J. Anal. At. Spectrom. 1991 6 295. 9113779. J. Anal. At. Spectrom. 1991 6 301. 9113780. J. Anal. At.Spectrom. 199 1,6 307. 9113789. Fresenius J. Anal. Chem. 1990,337 135. 9113793. Fresenius J. Anal. Chem. 1990 338 895. 9113798. J. Anal. At. Spectrom. 1991 6 191. 9113799. Spectrochim. Acta Part B 1991 46 9. 9113806. Spectro- chim. Acta Part B 1991 46 183. 9113809. Spectrochim. Acta Part B 199 1,46 30 1.9113815. Zh. Anal. Khirn. 1990 45 1895. 9113831. Guangpuxue Yu Guangpu Fenxi 1990 10(4) 59. 9113834. Guangpuxue Yu Guangpu Fenxi 1990 10(5) 41. 9113851. Yejin Fenxi 1990 10(4) 20. 9113860. Bunseki Kagaku 1990 39 823 9113869. Appl. Spectrosc. 1990 44 144. 9113886. Anal. Chim. Acta 1991 243 71. 9113892. J. Environ. Qual. 199 1 20 96. 9113897. Talanta 1991 38 157. 9113900. Spectrosc. Lett. 1991 24 139. 9113901. Spectrosc. Lett. 199 1 24 267.9113902. Spectrosc. Lett. 1 99 1 24 307. 9113903. Vysokochist. Veshchestva 1990 6 121. 9113916. Fenxi Huaxue 1990 18 941. 9113917. Fenxi Huaxue 1990 18 955. 9113922. Fenxi Huaxue 199 1 19( I) 47. 9113925. Fenxi Shiyanshi 1990 9(3) 72.9113930. Fenxi Shiyanshi 1990 9(5) 54.9113932. Mikrochim. Acta 1990 3 213. 9113935. Chem. Anal. (Warsaw) 1989 34 343. 9113936. Chem. Anal. (Warsaw) 1989 34 453. 9113940. Lihua Jianyan Huaxue Fence 1990 26(6) 346. 9113941. Anal. Sci. 1990,6 913.9113947. Anal. Sci. 1991 7 159. 9113950. Anal. 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ISSN:0267-9477    

DOI:10.1039/JA992070215R

出版商:RSC    

年代:1992

数据来源: RSC

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JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 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. 246R a.c. AA AAS AE AES AF AFS AOAC APDC ASV CCP CMP CRM cw d.c. DCP DDDC DMF DNA 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 IR alternating current atomic absorption atomic absorption spectrometry atomic emission atomic emission spectrometry atomic fluorescence atomic fluorescence spectrometry Association of Official Analytical Chemists ammonium pyrrolidinedithiocarbamate (ammonium pyrrolidin-1-yl dithioformate) anodic-stripping voltammetry capacitive1 y coupled plasma capacitively coupled microwave plasma certified reference material continuous wave direct current d.c.plasma diammonium diethyldithiocarbamate N,N-dimethy lformamide deoxyribonucleic acid 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-methylpentan-2- inductively coupled plasma inductively coupled plasma mass spectrome- try infrared spectrometry spectroscopy one) IUPAC LC LEAFS LEI LMMS LOD LTE MECA MIP MS NAA NaDDC NIES NIST NTA OES PIGE PTXE PMT PPb PPm PTFE QC r.f.REE( s) RIMS RM RSD S/B SEC SEM SFC Si(Li) SIMAAC SIMS SIN SR SRM SSMS STPF TCA TIMS TLC TOP0 TXRF u.h.f. uv VDU vuv WDXRF XRF International Union of Pure and Applied liquid chromatography laser-excited atomic fluorescence spectro- 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 pol ytetrafluoroethylene quality control radio frequency 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 trioctylphosphine oxide total reflection X-ray fluorescence ultra-high-frequenc y ultraviolet visual display unit vacuum ultraviolet wavelength dispersive X-ray fluorescence X-ray fluorescence Chemistry metry Studies Technology

ISSN:0267-9477    

DOI:10.1039/JA992070246R

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

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(Bereich Isotopenanwendung Zentral- inst.Isot Strahlenforsch. Germany). 9213276. Zhang Z. Fang X. Yuan Y. Chen J. Laser-enhanced ionization spectrometry and determination of trace samarium Zhongguo Jiguang 1991 18 5 5 8 544. (1st Dept. China Inst. Metrol. Hangzhou China). 9213277. Zhang Q. Yu C. X-ray fluorescence spectroscopic analysis of foundry clay Zhuzao 199 1 5,40. (Shenyang Cast. Inst. Shenyang China). Paper 921C3278-921C3494 were presented at the 1992 Winter Conference on Plasma Spectrochemistry. San Diego CA USA January 6- 1 I 1992. 921C3278. Ruzicka J. Enhancement of atomic spectroscopies by flow injection techniques (Dept. Chem. BG-10 Univ. Washington Seattle WA 98 195 USA). 92lC3279. dos Reis F. Cine M. F. Krug F. J. Bergamin B. H. Jr. Multipurpose flow injection system. 1. Program- mable dilutions and standard additions for ICP-AES (Cent.Energ. Nucl. Agric. Av. Centenario 303 C.P.96 Cep. 13400 Piracicaba Silo Paolo Brazil). 92K3280. Caughlin B. Blok H. Off-peak background correction of transient signals (Chemex Labs. 2 12 Brooksbank Av. North Vancouver British Columbia V7J 2C1 Canada). 921C3281. Salin E. D. Moss P. Hybrid FIA-direct sample insertion system for one hundred-fold improvement of detection limits for ICP-AES (Dept. Chem. McGill Univ. 801 Sherbrooke St. W. Montreal Quebec H3A 2K6 Canada). 921C3282. Emteryd O. Influence of mass flow controller and argon gas quality on the detection limit for organic carbon (Swedish Univ. Agric. Sci. Dept. Forest Ecol. Environ. Res. Lab. 901 83 UmeA Sweden). 921C3283. Browner R. F. Zhu G. Nwogu V.Msimanga N. Sample introduction for ICP-AES and ICP-MS fact versus fiction (Sch. Chem. Biochem. Georgia Inst. Technol. Atlanta GA 30332-0400 USA). 92lC3284. Broekaert J. A. C. Tailoring microwave induced plasma discharges to various types of sampling (Univ. Dortmund Dept. Chem. P.O.B. 500500 W-4600 Dortmund 50 Germany). 921C3285. Lebas K. Marichy M. Mermet M. Poussel E. Mermet J.-M. Effects of acid concentration in induc- tively coupled plasma atomic emission spectrometry using Mg as a test element (Lab. Sci. Anal. Univ. Lyon I 69622 Villeurbanne Cedex France). 921C3286. Luan S. Pang H. Houk R. S. Noise characteristics of aerosols produced by ICP nebulizers (Ames Lab. US Dept. Energy Dept. Chem. Iowa State Univ. Ames IA 5001 1 USA). 92lC3287. Chan S. Geil S. L.Development of high-solid- sample torches for USN-ICP-AES (Cetac Technolo- gies 5600 S 42nd St. Omaha NE 68107 USA). 921C3288. Widerin D. R. New microconcentric direct nebulizer for ICP-AES (Cetac Technologies 5600 S 42nd St. Omaha NE 68 107 USA). 921C3289. Castillano T. M. Story W. C. Carey J. M. Caruso J. A. Evaluation of an ultrasonic nebulizer for sample introduction in inductively coupled plasma atomic emission and mass spectrometry (ICP-AES ICP-MS) (Univ. Cincinnati Dept. Chem. Cincinnati OH 921C3290. Tam M. A. Browner R. F. Liquid jet ultrasonic nebulizer a novel sample introduction device for ICP- AES and ICP-MS (Sch. Chem. Biochem. Georgia Inst. Technol. Atlanta GA 30332-0400 USA). 4522 1-0 172 USA). 921C3291. Salin E. D. Ren J. M. Blain L. Hunt for a solid sample introduction method (McGill Univ.Dept. Chem. 801 Sherbrooke St. W. Montreal Quebec H3A 2K6. Canada). 921C3292. Ohls K. D. Flock J. Leopp H. Determination of traces absorbed on activated carbon by an ICP slurry technique (Hoesch Stahl AG W-4600 Dortmund I Germany). 921C3293. Soman R. S. Gilbert T. R. Salt-induced matrix effects in electrothermal vaporization plasma emission spec- troscopy (Dept. Chem. Barnett Inst. Chem. Anal. Mater. Sci. Northeastern Univ. Boston MA 02 1 15 USA). 921C3294. Sanz-Medel A. Sanchez E. Menendez A. Camuiia F. Quintero C. Cotrino J. Continuous halogen generation for enhancing halide determinations by MIP-AES (Dept. Phys. Anal. Chem. Fac. Chem. 33006 Oviedo Spain). 921C3295. Mermet J.-M. Drift in inductively coupled plasma spectrochemistry origins diagnostics and correction methods (Lab.Sci. Anal. Univ. Lyon I 69622 Villeurbanne Cedex France). 921C3296. Borsier M. Automated plasma spectrochemistry (BRGM B.P. 6009 45060 Orleans France). 921C3297. Agnes G. Horlick G. Automated system for analysis and research in inductively coupled plasma atomic emission spectrometry (Dept. Chem. Univ. Alberta Edmonton Alberta T6G 2G2 Canada). 921C3298. Hull D. R. Wiggenhauser G. W. Hoch R. L. Wojcik J. L. Foster R. Automatic sample dilution with data merging-a new solution to the problem of high concentration sample analysis by ICP (Chem. Waste Management 150 West 137th St. Riverdale IL 60627 USA). 921C3299. D’Silva A. P. Zamzow D. Mobile inductively coupled plasma atomic emission spectrometer system for the analysis of hazardous wastes (Ames Lab.US Dept. Energy Iowa State Univ. Ames IA 500 1 1 USA). 921C3300. Hettipathirana T. Blades M. W. FAPES-a new plasma source for simultaneous multi-element analy- sis (Dept. Chem. Univ. British Columbia Vancouver British Columbia Canada V6T I Z 1 ). 921C330 1. Bir D. J. Rybarczyk J. P. Analytical characterization of a furnace atomization plasma emission source incorporating a novel power supply (Dept. Chem. Ball State Univ. Muncie IN 47306 USA). 921C3302. Furuta N. Koga M. Atomic emission spectrometry with use of a doughnut-shaped and high-power mi- crowave induced plasma source (Natl. Inst. Environ. Stud. 16-2 Onogawa Tsukuba Ibaraki 305 Japan). 921C3303. Lamoureux B. R. Denton M. B. Charge injection device array detection for atomic spectroscopy with applications in gas chromatography (Union Carbide P.O.Box 670 Bound Brook NJ 08805 USA). 92K3304. Salin E. D. Hamier J. Webb D. P. Expert system for autonomous instrument operation the view from the top (McGill Univ. Dept. Chem. 801 Sherbrooke St. W. Montreal Quebec Canada H3A 2K6). 92/C3305. Yates D. Aries R. Analysis of potable water through principle component analysis (Perkin-Elmer 76 I Main Ave. Norwalk CT 06859-02 15 USA). 921C3306. Neubkk R. Wegscheider W. Schierle C. Otto M. Artificial intelligence for automated qualitative ICP- OES fuzzy theory and neural nets (Inst. Anal. Chem. Micro- Radio-chem. Graz Univ. Technol. A-80 10 Graz Austria). 921C3307. Nikdel S. Micro-nutrient analysis by ICP-AES with artificial neural networks for identification of the orange growing regions (Florida Dept.Citrus 700 Experiment Station Rd. Lake Alfred FL 33850-2299 USA).272R 921C3308. 92iC3309. 92x33 10. 92lC33 1 1. 921C33 12. 92lC33 13. 92lC33 14. 92x33 15. 921C33 16. 921C33 17. 92lC33 18. 92JC33 19. 92/C3 320. 921C332 1. 9 2 x 3 322. 9 2 x 3 3 2 3. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 Hutton R. C. Platzer J. Lange J. Optimization of acquisition parameters for ETV-ICP-MS (VG Elemen- tal Ion Path Rd. Three Winsford Cheshire CW7 3BX UK). Long S. E. Martin T. D. Optimization and evalua- tion of an ultrasonic nebulizer for use with ICP-MS (Technol. Appl. USEPA 26 West Martin Luther King Dr. Cincinnati OH 452 19 USA). Voellkopf U. Brueckner P. Barger W . Performance evaluation of ICP-MS with sample introduction by ultrasonic nebulization jBodenseewerk Perkin-Elmer Postfach 101 164 7770 Uberlingen Germany).Tyler G. Shkolnik G. Johnson D. Characterization and performance of an ultrasonic nebulizer in ICP (Varian OSI 679 Sprinvale Rd. Mulgrave Victoria 3 170 Australia). Gell S. L. Chan S. Determination of metals in biological samples using USN-ICP-AES (Cetac Tech- nologies 5600 S 42nd Street Omaha NE 68107 USA). Brenner I. B. Bremier P. Le Marchand A. Perform- ance characteristics of ultrasonic nebulization coupled to 40.68 MHZ ICP (Geol. Surv. Israel 30 Malkhe Israel St. Jerusalem 95501 Israel). Nixon D. E. Meinhard J. E. Performance character- istics of two Meinhard nebulizers operating at identical gas flow rates (Q,) but different pressures (Po) (Dept.Lab. Med. Pathol. Mayo Clinic Rochester MN 55905 USA). Aubin L. Soman R. S. Sandoval J. E. Gilbert T. R. Direct analysis of lubricating oils for wear metals by electrothermal vaporization plasma emission spectros- copy (Dept. Chem. Barnett Inst. Chem. Anal. Mater. Sci. Northeastern Univ. Boston MA 021 15 USA). Botto R. I. Applications of ultrasonic nebulization in the analysis of petroleum and petrochemicals by ICP- AES (Baytown Specialty Products Exxon Res. Eng. Comp. P.O. Box 4255 Baytown Texas 77522-4255 USA,). Beres S. A. Ediger R. D. Factors affecting analytical performance of electrothermal vaporization sample introduction devices used in ICP mass spectrometry (Perkin-Elmer 761 Main Av. Norwalk CT Min Ren J. M. Salin E. D. Modified ETV-ICP-AES system for liquid and solid samples (McGill Univ.Dept. Chem. Montreal Quebec Canada H3A 2K6). Ozaki E. A. de Oliveira E. Simultaneous determina- tion of As Bi and Sb in steel and nickel alloys by inductively coupled argon plasma emission spectrome- try with hydride generation (ICP-HG) (A~os Villares S.A. Av. Dr. Ramos de Azevedo 133 Siio Caetano do Sul CEP 09500 Brazil). Spiers G. A. McGeorge S. W. Moak H. Simulta- neous determination for hydride elements utilizing a photodiode array equipped ICP-AE spectrometer (Dept. Land Resource Sci. Univ. Guelph Guelph Ontario Canada N1G 2WI). De Silva N. Guevremont R. Direct powder introduc- tion inductively coupled plasma emission spectrome- try with a photodiode array spectrometer (Min. Res. Div. Geol.Surv. Canada 601 Booth Street Ottawa Ontario Canada K 1 A OE8). Zhu G. Browner R. F. Characteristics of aqueous sample introduction for atmospheric and reduced- pressure microwave induced plasmas (Sch. Chem. Biochem. Georgia Inst. Technol. Atlanta GA 30332- 0400 USA). Mierwa J. Investigations of wet aerosols introduced to low power microwave-induced helium plasma-an- alytical aspects (Central Lab. Univ. M. Curie-Sklo- 06859-02 15 USA). 921C3324. 'Pilger C. Leis F. Broekaert J. A. C. Study of different forms of MIP discharges obtained in a surfatron (Inst. Spektrochem. angew. Spektrosk. Post- fach 10 1352 W-4600 Dortmund 1 Germany). 921C3325. Argentine M. D. Barnes R. M. Critical evaluation and comparison of enhanced Beenakker and strip line source microwave-induced plasma cavity designs (Dept.Chem. Lederle Grad. Center Univ. Massachus- etts Amherst MA 01003-0035 USA). 92lC3326. Jahl M. J. Barnes R. M. Silane analysis with a sealed non-flowing inductively coupled plasma (Dept. Chem. GRC Towers Univ. Massachusetts Amherst MA 921C3327. Jacksier T. Barnes R. M. Arsine analysis with a sealed inductively coupled plasma (Dept. Chem. LGRC Towers Univ. Massachusetts Amherst MA 921C3328. Nygaard D. D. Bulman F. D. Demers D. End-on viewing of a low-flow 40 MHZ ICP (Baird Corp. 125 Middlesex Turnpike Bedford MA 0 1730 USA). 921C3329. Dahlquist R. L. Fry R. C. Grower G. H. How ICP- AES can routinely meet XRF at precisions of 0.1% or better (IFW Inc. 21901 Burbank Blvd. No. 197 Woodrand Hills CA 9 1367 USA). 921C3330. Marty P. Minier J. Guiberteau Ph.Bergety C. Lang Y. Zegre E. Arniaud D. New enclosed ICP atomic emission spectrometer for radioactive and toxic materials. The design and performances (C.E.A. F- 2 1 120 Is Sur Tille France). 92lC3331. Wiesman H. Garcia Alonso J. I. Koch L. ICP-MS with glove box. Experience in operation service and repair after three years of radioactive sample analysis (Spectrotec GmbH Weidenstrasse 18 D-6097 Trebur Germany). 0 1003-0035 USA,). 01003-0035 USA,). 92K3332. 921C3333. 921C3334. 921C3335. 92lC3 3 36. 92lC3 3 3 7. 921C3338. 921C3339. Anderau C. J. Thomas R. J. Automated approach to ensure the integrity of the results generated by JCP mass spectrometry (Perkin-Elmer 76 1 Main Ave. Norwalk CT 06859-02 15 USA). Cheatham M. M. Sangrey W. F. White W. M. Improved ICP-MS analytical precision using non- linear response drift corrections (Dept.Geol. Sci. Shee Hall Cornell Univ. Ithaca NY 14850-1 504 USA). Caetano M. S. Golding R. M. Key A. E. Factorial analysis and response surface of a GC-MIP system for the determination of halogenated compounds (Univ. Central Venezuela Fac. Cienc. Escuela Quim. P.O. Box 47 102 Caracas Venezuela). Carre M. Mermet J.-M. Proper use of calibration graphs in inductively coupled plasma atomic emission spectrometry (Lab. Sci. Anal. Univ. Lyon I 69622 Villeurbanne Cedex France). Tyler G. Shkolnik G. True optimization of an ICP spectrometer (Varian OSI 679 Springvale Rd. Mul- grave Victoria 3 l 70 Australia). Krushevska A. Barnes R. M. Martines L. Myers- Tracy signal compensation in ICP-AES for minimizing drift and matrix effects (Univ.Massachusetts Dept. Chem. Lederle Grad. Res. Center Amherst Brenner 1. B. Le Marchand A. Samuel O. Lagrave X. Rapid analysis of complex materials by ICP- AES-application of elemental tracers for rapid analy- sis of high solid and viscous materials (Geol. Surv. Israel 30 Malkhe Israel St. Jerusalem 9550 1 Israel). Brenner I. B. Le Marchand A. Optimization of intensity measurement and acquisition in multi-ele- ment sequential analysis by ICP-AES-an evaluation of variable resolution and mathematical modes of mea- surement for the analysis of complex materials (Geol. Sum. Israel 30 Malkhe Israel St. Jerusalem 95501 MA 01003-0035 USA). dowska 20-03 1 Lublin Poland). Israel).JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 273R 921C3340. Burgener J. A Plasma upgrading (Tech. Solutions Limited 944 Meadowwood Rd. Mississauga Ontario Canada L5J 2S6). 921C3341. Meyer G. A. Automated plasma instrumentation approaches (Battelle 505 King Ave. Columbus 921C3342. Boumans P. W. J. M. Spectrochemical analysis seen as an integral of physics chemistry and information science (Philips Res. Lab. 5600 JA Eindhoven The Netherlands). 921C3343. Jassie L. B. Hasty E. Revesz R. Kingston H. M. Microwave sample preparation for spectrochemical analysis (CEM Corp. 3100 Smith Farm Road Mat- thews NC 28 105 USA). 921C3344. Knapp G. Panholzer F. Kettisch P. High-petform- ance digestion systems (Graz Univ. Technol. Dept. Anal. Chem. Micro Radiochem. A-80 10 Graz Tech- nikerstraoe 4 Austria).921C3345. KUSS H.-M. Bossmann D. Miiller M. Rapid mi- crowave digestion procedure for determining boron concentrations in steels (Univ. Duisburg Dept. Anal. Chem. Lotharstr. I W-4 100 Duisburg Germany). 921C3346. Karanassios V. Skinner C. Salin E. D. Microwave interrupted flow digestion system for ICP-AES (McGill Univ. Dept. Chem. 801 Sherbrooke St. W. Montreal Quebec Canada H3A 2K6). 921C3347. Del Monte Tamba M. G. Falciani R. Dissolution of non-metallic powders by microwave oven in iron and steel analysis (Centro Sviluppo Matriali Via Castel Romano 100 00 129 Rome Italy). 921C3348. Sheppard B. S. Gaston C. M. Barnes B. S. Wolnik K. A. Comparison of digestion methods for plasma spectrometry (Natl. Forensic Chem. Center US Food Drug Admin. 1 I4 1 Central Pkwy Cincinnati OH 45202 USA).921C3349. Michel R. G. Liang Z. Su G. Laser excited atomic and molecular spectroscopy in graphite furnaces- measurements of metals and non-metals at the femto- gram level (Dept. Chem. Univ. Connecticut 2 15 Glenbrook Rd. Storrs CT 06269-3060 USA). 921C3350. Dittrich K. Wennrich R. Heiner J. Developmentswith laser furnace techniques (Univ. Leipzig Inst. Anal. Chem. Linnestr. 3 Leipzeig W-0-70 10 Germany). 92lC335 I. Lorenzen C.-J. Carlhoff C. Industrial applications of laser-induced emission spectral analysis (LIESA) for process and quality control (Krupp Forschungsinst. GmbH Postfach 10 22 52 W-4300 Essen 1 Germany). 92K3352. Petit A. Briand A. LaCour J. L. Mauchien P. Optical emission spectroscopy on laser produced plasma for analytical determination in solid samples (DPEISPEAISPS CEN Saclay 91 191 Gif Sur Yvette Cedex France).921C3353. Moenke-Blankenburg L. Gunther D. Kammel J. Description and use of transient signals in laser ablation ICP spectrometry (Martin-Luther-Univ. Halle-Wittenberg Dept. Chem. Weinberweg 16 0- 4050 Halle Germany). 921C3354. Abell I. McCurdy E. Improvement in spatial analysis by LA-ICP-MS (VG Elemental Ion Path Rd. Three Winsford Cheshire CW7 3BX UK). 92K3355. Burns D. W. Microwave digestion of rigid-rod poly- mer films for phosphorus analysis by inductively coupled plasma atomic emission spectrometry (Dow Chemical Co. Anal. Res. Labs. Western R&D Pittsburg CA 94565 USA). 921C3356. Engelhart W. G. Littau S. E. Hasty E. T. Optimiza- tion of microwave acid digestion procedures for or- ganic sample matrices using a microwave immune fibre optic temperature control system (CEM Corp.3 100 Smith Farm Rd. Matthews NC 28105 USA). OH 43201-2693 USA). 9 2lC3 3 5 7. 92lC335 8. 92x335 9. 921C3360. 921C336 1. 921C3362. 921C3363. 921C3364. 92lC3 36 5. 921C3366. 921C3367. 92lC3368. 92lC3369. 92lC3370. Krushevska A. Barnes R. M. Amarasiriwaradena C. Foner H. Martines L. Comparison of sample decom- position procedures for the ICP-AES determination of zinc in biological samples (Univ. Massachusetts Dept. Chem. Lederle Grad. Res. Center Amherst Borsier M. Brenner I. B. Survey of decomposition techniques for multi-element ICP analysis using multi- variable statistics (Bureau Recher. Geolog. Min. (BRGM) Orleans France). Chan. S. Geil S. L. Preparation of oil samples prior to analysis by USN-ICP-AES (Cetac Technol.5600 S 42nd Street Omaha NE 68107 USA). Meyer G. A Direct multi-element analysis of ad- vanced materials using a mini-spray dryer interfaced to a simultaneous ICP-AES (Battelle Columbus Labs. 505 King Ave. Columbus OH 43201 USA). Faires L. M. Patton C. J. Application of induc- tively coupled plasma mass spectrometry to an acid mine drainage contamination study using on-line chelation concentration chromatography (US Geol. Surv. Natl. Water Qual. Lab. Methods Res. Dev. Prog. Mail Stop 41 1 5293 Ward Rd. Arvada CO 80002 USA). Manabe R. M. Riviello J. M. Siriraks A. Determi- nation of arsenic and selenium in drinking water using on-line exchange preconcentration with ICAP-AES (Thermo Jarrell Ash 175 Jefferson Drive Menlo Park CA 94025 USA).Denoyer E. R. Lu Q. Opportunities for chemical sample pre-treatment using flow injection with ICP mass spectrometry (Perkin-Elmer 76 1 Main Ave. Norwalk CT 06859-02 15 USA). Shabani M. B. Masuda A. Elimination of matrix and oxide interferences in determination of platinum group elements by inductively coupled plasma mass spectro- metry using on-line preconcentration (Dept. Chem. Fac. Sci. Univ. Tokyo Hongo Tokyo 113 Japan). Shabani M. B. Masuda A. Off-line and on-line preconcentration techniques for determination of bis- muth in sea-water by inductively coupled plasma mass spectrometry (Dept. Chem. Fac. Sci. Univ. Tokyo Hongo Tokyo 113 Japan). Heitkemper D. T. Sheppard B. S. Gaston C. Wolnik K. A. Chang L. Deutsch E.A. Caruso J. A. Determination of technetium-99 by ICP-MS with on- line sample preconcentration (Natl. Forensic Chem. Center US Food Drug Admin. 1141 Central Pkwy. Cincinnati OH 45202 USA). Michaelis M. Knapp G. Design of molecular off-line sample preparation system for elemental trace analysis using the TraceCon preconcentration system (Knapp Logistik Automation A-8042 Graz). Michaelis M. Maichin B. Knapp G. Automated on- line chelation separation technique for determination of transition elements in sea-water and salinary samples with ICP-OES. (Knapp Logistik Automation GmbH A-8042 Graz Austria). Perng J. Chen S. Sea-water analysis by ICP-AES GFAAS and ICP-MS (China Steel Corp. Steel Alu- minium R & D Dept. Lin Hai Industrial District P.O. 47-29 Hsiao Kang Kaohsiung 8 1233 Taiwan Chin a).Eljuri E. A. Murillo M. A. Fernandez A. J. C. Determination of phosphorous in copper alloys using ICP-AES using electrically dispersed samples (Cent. Quim. Anal. Esc. Quim. Fac. Cienc. Univ. Cent. Venezuela P.O. Box 47 102 Caracas I04 1 -A Vene- zuela). MA 01003-0035 USA).274R 92lC337 I. 92lC3 3 72. 92lC3373. 9 2lC3 3 74. 92lC3 3 7 5. 92lC3376. 92lC3377. 92lC3 3 78. 92x33 79. 92lC3380. 92lC338 I 92lC3382. 92lC3383. 92lC3384. 92lC338 5. 92K3386. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 Alexi H. Broekaert J. A. C. Ohls K. Studies on spark elutriation for the dissolution of metallic samples (Univ. Dortmund Dept. Chem. P.0.B 500500 D-4600 Dortmund 50 Germany). Perry B. J. Speller D. V. Van Loon J. C. Determina- tion of ultra-trace PGE concentrations in rock pulps by high temperature dry chlorination followed by ICP-MS analysis a potential alternative to NiS fire assay (Dept. Geol.Univ. Toronto Toronto Ontario Canada M5T 2x3). Liu X. R. Horlick G. New approaches to laser ablation sample introduction systems for inductively coupled plasma spectrometry (Dept. Chem. Univ. Alberta Edmonton Alberta Canada T6G 2G2). Giinther D. Moenke-Blankenburg L. Paul M. Sys- kakis E. Nickel H. Fischer W. Analysis of Perovs- kite-type ceramic materials by means of ICP-AES and LA-ICP-MS (Martin-Luther-Univ. Halle-Wittenberg Inst. Anal. Chem. Weinbergweg 16 0-4050 Halle Germany). De Carlo E. H. Pruszkowski E. Application of laser ablation ICP-MS to the determination of rare earth elements in marine ferromanganese deposits (Dept.Oceanogr. 1000 Pope Rd. Univ. Hawaii Honolulu HI 96822 USA). Fomenkov I. V. Timofeev P. V. Impurity analysis of crystal LiF by LA-ICP-OES (Gen. Phys. Inst. Acad. Sci. Russia 38 Vavilov St. Moscow 117949 Russia). Zinko H.-P. Wegscheider W. Heifer G. Windholz L. LIF of non-metals in a He plasma (Tech. Univ. Graz Inst. Anal. Chem. Micro- Radiochem. Technik- erstr. 4 A-80 10 Graz Austria). Conti R. A. Bizaio L. R. Determination of metallic trace impurities in special steels by inductively coupled plasma atomic emission spectrometry (ICP-AES) (Fund. Tecnol. Indust. Centro Mater. Refrat. Caixa Postal 16 CEP 12600 Lorena Sio Paulo Brazil). Conti R. A. Bizaio L. R. Determination of compo- sition and metallic trace impurities in niobium-based alloys by inductively coupled plasma atomic emission spectrometry (ICP-AES) (Fund.Tecnol. Ind. Centro Mater. Refrat. Caixa Postal 16 12600 Lorena Sio Paulo Brazil). Tobias M. I. Kobayashi S. Optimized wavelengths for analysis of neodymium-iron alloys by ICP (Neo- met Route 168 P.O. Box 325 West Pittsburg PA 16160 USA). Batistoni D. A Farias de Funes S. S. Inductively coupled plasma atomic emission spectrometric analy- sis of alloys employed in nuclear technology (Dept. Quim. Anal. Com. Nac. Energ. Atbm. Ave. Liberta- dor 8250 ( 1 429) Buenos Aires Agentina). Schwartz R. S. Determination of trace levels of boron in steel fasteners by ICP-AES using methyl borate distillation (US Customs Serv. 1301 Constitution Ave. Washington DC 20229 USA). Kumpulainen J.Plaami S. Indirect determination of phytic acid in cereals by ICP-AES (Cent. Lab. Agric. Res. Center Finland 3 1600 Jokioinen Finland). Yaman M. Yaman S. Determination of heavy metals in animal tissues by ICP-AES after preconcentration on activated carbon (Firat Univ. Sci. Fac. Dept. Chem. 23 I69 Elazig Turkey). Fariiias J. C. Barba M. F. Determination of macro- constituents in advanced ceramic materials by ICP- AES (Lab. Anhl. Quim. Inst. Cerhm. Vidrio (C.S.I.C.) 28500 Arganda del Rey Madrid Spain). Fariiias J. C. Barba M. F. Determination of impuri- ties in lead zirconate-titanate electroceramics by ICP- AES (Lab. Anal. Quim. Inst. Cerhm. Vidrio (C.S.I.C.) 28500 Arganda del Rev. Madrid. SDain). 92lC3387. Amarasiriwardena D. Barnes R. M. Optimization and evaluation of poly(dithi0carbamate) resin precon- centration for determination of platinum group metals in geological samples by ICP-AES and ICP-MS (Sch.Nat. Sci. Hampshire College Amherst MA 0 1002 USA) 92lC3388. Port0 da Silveira C. L. de L. P. Bastos M. Determina- tion of platinum group elements (PGE) in geological samples by ICP-AES (Dept. Chem. Pontifical Catho- lic Univ. (PUC-Rio) R. Marques Sio Vicente 225 22453 Rio de Janeiro Brazil). 92lC3389. Bridenne M. Carre M. Coffre E. Marot Y. Simon- det F. Determination of trace metallic impurities in hydrogen chloride by ICP-AES and GFAAS (L‘Air Liquide CRCD Les-Loges-en-Josas BP 126 78350 Jouy-en-Josas France). 92lC3390. Yates D. Salin E. Blades M. Wegscheider W. (panel) Signal processing in atomic spectroscopy (Top- ical Discussion) (Perkin-Elmer 76 1 Main Ave.Nor- walk CT 06859-021 5 USA). 92lC339 1. Tatro M. E. (Chairman) Novel sample preparation approaches (Panel Discussion) (SPECTRA Spectrosc. Chromatogr. Specialists P.O. Box 352 Pompton Lakes NJ 07442 USA). 92lC3392. Blades M. W. Fundamental studies of the inductively coupled plasma-progress and problems (Dept. Chem. Univ. British Columbia Vancouver British Columbia Canada V6T 1Zl). 92/C3393. Hubert J. Fundamental studies of surface wave induced plasmas (Univ. Montreal Dept. Chim. P.O. Box 6128 Station A. Montreal Quebec Canada H3C 357). 92lC3394. Horlick G. Zhao Y. Wang T. B. Fulton G. Schroeder S. G. Application of a Fourier transform spectrometer system to the fundamental characteriza- tion of analytical emission sources (Dept.Chem. Univ. Alberta Edmonton Alberta Canada T6G 2G2). 92lC3395. Olesik J. W. Hobbs S. E. Influence of individual droplets and vaporizing analyte particles on plasma excitation and ionization processes (Lab. Plasma Spectrochem. Laser Spectrosc. Mass Spectrom. Dept. Cieolog. Sci. 275A Scott Hall Ohio State Univ. Columbus OH 43210 USA). 92lC3396. Weir D. Blades M. W. Parametric study of organic solvent sample introduction on ICP fundamental properties (Dept. Chem. Univ. British Columbia Vancouver British Columbia Canada V6T I Z I). 92lC3397. Farnsworth P. B. Omenetto N. Kinetics of charge transfer between magnesium and argon in the induc- tively coupled plasma (Dept. Chem. Brigham Young Univ. Provo UT 84602 USA). 92lC3398. Galley P. J. Hieftje G. M. Is the ICP ‘bullet’ a useful spatial reference? (Indiana Univ.Dept. Chem. Bloomington IN 47405 USA). 92lC3399. Marawi I. Bielski B. A. Caruso J. A. Meeks F. R. Temperature measurements of inductively coupled plasma a comparison of N2+ rotational spectra and optical pyrometry (Dept. Chem. Univ. Cincinnati Cincinnati OH 45221-0 172 USA). 92lC3400. Galley P. J. Hanselman D. S. Sesi N. Wu M. Hieftje G. M. Recent investigations into the ‘EIE interference’ (Indiana Univ. Dept. Chem. Blooming- ton IN 47405 USA). 92lC340 1. Matousek J. P. Mermet J.-M. Signal enhancement with added hydrogen in electrothermal vaporization inductively coupled plasma atomic emission spectro- metry (Lab. Sci. Anal. Bat. 308 Univ. Claude Bernard-Lyon I 69622 Villeurbanne Cedex France). 92lC3402.Ediger R. D. Vaporization processes of carbide- forming elements in electrothermal vaporization ICP mass spectrometry (Perkin-Elmer 76 I Main Ave Norwalk. CT 06859-02 15. USA).JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 275R 92lC3403. 92x3404. 92lC3405. 9 2/C 3406. 92lC3407. 92lC3408. 92lC3409. 92lC34 10. 92x34 I 1. 92x3412. 92lC34 12. 92lC34 14. 92x34 15. 92lC3416. 92lC34 17. Caroli S. Alimonti A. Delle Femmine P. Menditto A. Morisi G. Petrucci F. Senofonte O. Violante N. Role of ICP-AES in the assessment of reference values for trace elements in biological matrices (1st. Super. Sanita Viale Regina Elena 299 00161 Rome Italy). Ortner H. M. Ultratrace characterization of bulk refractory metals (Sect. Anal. Chem. Fac. Mater. Sci. Tech. Univ.Darmstadt Petersenstr. 20 D-6 100 Darmstradt Germany). Miller W. V. Blacher P. Purification of high-purity materials for the preparation of plasma emission standards (M.V. Labs. P.O. Box 370 Three Bridges NJ 08887 USA). Hettipathirana T. Blades M. W. Analyte atomization and excitation in FAPES studied using temporal and spatial behaviour (Dept. Chem. Univ. British Colum- bia Vancouver British Columbia Canada V6T 1 Zl). Riby P. G. Harnly J. M. Hollow anode-furnace atomization non-thermal atomization spectrometry (USDA ARS BHNRC NCL Bldg. 16 I BARC-east Beltsville MD 20705 USA). Glavin G. G. Mazo G. N. Estimation of atomization efficiency in HCL-ICP-AFS (Moscow State Univ. Chem. Dept. Leninskie Gory I19899 Moscow V-234 Russia). Ohls K. D. Linn H. New pressure microwave digestion system with high security against explosion (Hoesch Stahl AG D-4600 Dortmund 1 Germany).Amarasiriwardena C. J. Krushevska A. Foner H. Argentine M. D. Barnes R. M. Inductively coupled plasma mass spectrometric determination of ’OZn to 68Zn isotope ratio in biolgoical samples (blood urine faeces and food) from pre-term human babies (Dept. Chem. GRC Towers Univ. Massachusetts Amherst Goldfarb V. M. Dresvin S. V. Mikhalkov S. M. Heating of oxide powder particles and metal spheres in plasma jets generated by r.f. discharge (Textron Defense Systems 2385 Revere Beach Parkway Ever- ett MA 02149 USA). Chen Z. Longerich H. P. Fryer B. J. ICP-MS analysis of sub-milligram samples of geological ma- terials using a recycling nebulization system with a disposable spray chamber (Dept.Earth Sci. Centre Earth Resourc. Res. Memorial Univ. Newfoundland St. John’s Newfoundland Canada A1 B 3x5). Agnes G. Horlick G. Electrospray mass spectrometry (ES-MS) as a technique for elemental analysis prelimi- nary results (Dept. Chem. Univ. Alberta Edmonton Alberta Canada T6G 2G2). Peters G. R. Beauchemin D. Design of a versatile interface for gaseous or aerosol sample introduction into ICP-MS (Queen’s Univ. Dept. Chem. Kingston Ontario Canada K7L 3N6). HuldCn S.-G. Ek P. G. Johansson E. Liljefors T. External additions of internal standard for improving precision in multi-element determination of volatile hydrides by ICP-MS (Lab. Anal. Chem. Abo Akademi Univ. Biskopsg. 8 SF-20500 Abo Finland). Ek P. G. Hulden S.-G. Johansson E. Liljefors T.Simultaneous multi-element survey scan analysis of hydride- and non-hydride forming elements with ICP- MS using experimentally determined Saha correction factors for estimation of the analyte concentration (Lab. Anal. Chem. Abo Akadami Univ. Biskopsg. 8 SF-20500 Abo Finland). Koppenaal D. W. Barinaga C. J. Smith M. R. ICP- MS back to the future with ion trap mass spectrometry (Pacific Northwest Laboratory P.O. Box 999 MS P8- 08 Richland WA 99352 USA). MA 01003-0035 USA). 92lC34 18. 92lC34 19. 92lC3420. 92lC342 1. 92E3422. 92lC3423. 92x3424. 92lC3425. 92lC3426. 92lC3427. 92JC3428. 92lC3429. 92IC3430. 92lC343 1. 92lC34 3 2. 92IC3433. Ihnat M. Gamble D. S. Gilchrist G. F. R. Applica- tion of inductively coupled plasma mass spectrometry to agricultural research (Land Resource Res.Centre Agric. Canada Ottawa Ontario Canada K l A OC6). Riglet,’ C. Revy D. Dautheribes J. L. Marque S. Provitina O. Determination of traces of 237Np in enriched uranium solutions using inductively coupled plasma mass spectrometry (Commiss. 1’Energ. Atom. DSDESEPISAED Centre Cadarache Box 152 F- 13 108 Saint Paul lez Durance France). Stewart J. H. Jr. Gouge P. S. Hulmston P. Determination of uranium and transuranium elements in bioassay fluids soilds and air filters by ICP-MS (Oak Ridge Natl. Lab. P.O. Box 2008 Oak Ridge Wang J. Evans E. H. Caruso J. A. Use of a nitrogen-argon plasma for the reduction of poly- atomic-ion interferences in inductively coupled plasma mass spectrometry (Dept. Chem. M.L. 172 Univ. Cincinnati Cincinnati OH 4522 1 USA).Craig J. M. Beauchemin D. Reduction of the effects of concomitant elements in ICP-MS by adding nitro- gen to the plasma gas (Queen’s Univ. Dept. Chem. Kingston Ontario Canada K7L 3N6). Weston J. M. Williams R. R. Marcus R. K. Data acquisition and evaluation by a computer-controlled Langmuir probe system (Dept. Chem. Howard L. Hunter Chem. Labs. Clemson Univ. Clemson Lazik C. Hammond C. N. Marcus R. K. Effects of support gas flow on the emission characteristics of an r.f. glow discharge atomic emission source (Howard L. Hunter Labs. Ckmson Univ. Clemson SC 29634- 1905 USA). Cable P. R. Marcus R. K. Role of anode geometry in r.f. glow discharge mass spectrometry (Dept. Chem. Howard L. Hunter Chem. Labs. Clemson Univ. Clemson SC 29634- 1905 USA). van Straaton M.Vertes A. Gijbels R. Two-dimen- sional diffusion in a glow discharge cell the effect of cell geometry on analytical performance (Dept. Chem. Univ. 1 B-26 10 Wilrijk Belgium). Woo J. C. Lim H. B. Moon D. W. Lee K. W. Kim H. J. Optimization of acquisition and intensity mea- surement for ion source of GD-MS (Inorg. Anal. Chem. Lab. Korea Standard Res. Inst. Taojon 305 606 Korea). Horlick G. Burton L. L. Feng X. Spectral and analytical characteristics of quadrupole glow discharge mass spectrometry (Dept. Chem. Univ. Alberta Edmonton Alberta Canada T6G 2G2). Vieth W. Raith A. Huneke J.C.,QuadropleGDQ-MS versus magnetic sector GD-MS comparison ofquantita- tive analytical capabilities (Charles Evans Assoc. 30 1 Chesapeake Dr. Redwood City CA 94063 USA). Luo F. C. H.Huneke J.C. Evaluation ofglow discharge mass spectrometry for coal fly ash elemental analysis (Charles Evans Assoc. 30 1 Chesapeake Drive Redwood City California 94603 USA). Fang D. Seegopaul P. Analysis of high-purity titanium by glow discharge mass spectrometry (Mater. Res. Corp. Route 303 Orangeburg NY 10962 USA). Kovacic N. Ramus T. L. Application of a microwave induced plasma atomic emission detector for GC to quantitation of halogenated compounds (Dow Chemi- cal P.O. Box 1398 Pittsburg CA 94656 USA). Faust M. Winter F. Cammann K. Determination of volatile halogenated hydrocarbons in public indoor swimming pool air with GC-AED detection (Inst. Chemo- Biosensorics Dept. Gas chromatography c/o Chair Anal. Chem. Wilhelm-Klemm Strasse 8 W-4400 Munster Germany).TN 37831-6128 USA). SC 29634- 1905 USA).276R 92fC3434. 92fC3435. 92lC 3436. 92fC3437. 92lC3438. 921 C34 39. 92lC3440. 92fC344 1. 92fC3442. 92fC3443. 92fC3444. 921 C3445. 921 C3446. 92x3447. 92fC3448. 92X3449. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 Goode S. R. Thomas C. L. Determination of oxygen- containing additives in gasoline by gas chromato- graphy with microwave induced plasma emission detector (Dept. Chem. Univ. South Carolina Colum- bia SC 29208 USA). Bi C. Evans E. H. Caruso J. A. Inductivelycoupled plasma mass spectrometry as detector for chromato- graphy (Univ. Cincinnati Dept. Chem. Cincinnanti Horlick G. Comparison of inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry for elemental ana- lysis (Dept.Chem. Univ. Alberta Edmonton Al- berta Canada T6G 2G2). Houk R. S. Hu K. Clemons P. S. What’s really new in plasma source mass spectrometry? (Ames Lab. US Dept. Energy Dept. Chem. Iowa State Univ. Ames IA 5001 1 USA). Kawaguchi H. Convertible ICP and GD mass spectro- meter (Fac. Eng. Nagoya Univ. Chikusa-ku Furo- cho Nagoya 464 Japan). Tanner S. D. Space charge modification of measured ion kinetic energies in ICP-MS (Sciex 55 Glencam- eron Rd. Thornhill Ontario Canada L3T 1P2). Hobbs S. E. Olesik J . W. Signal fluctuations in inductively coupled plasma mass spectrometry (Lab. Plasma Spectrochem. Laser Spectrosc. Mass Spec- trom. Dept. Geolog. Sci. 275A Scott Hall Ohio State Univ. Columbus OH 432 10 USA). Longerich H. P. Jackson S. E.Fryer B. J. More ICP-MS polyatomic-ion interferences and progress in understanding of concomitant ion matrix suppression and enhancement effects (Dept. Earth Sci. Centre Earth Resourc. Res. Memorial Univ. Newfoundland St. John’s New Foundland Canada Al B 3x5). Boudreau D. Hubert J. Studies of surface wave plasmas as ion sources in mass spectrometry (Univ. Montreal Dept. Chem. P.O. Box 6128 Station A Montreal Quebec Canada H3C 357). Tye C. T. Hitchen P. Seeley C. Design parameters of a new ICP-MS instrument (VG Elemental Ion Path Road Three Winsford Cheshire CW7 3BX UK). Mchren J. W. Akatsuka K. Lam J. W. Berman S. S. Application of ICP-MS to the analysis of natural waters (Inst. Environ. Chem. Natl. Res. Council of Canada Ottawa Canada K1A OR6). Taylor H. E. Garbarino J.R. Beckett R. Utilization of inductively coupled plasma mass spectrometry as a detector for sedimentation field-flow fractionation (US Geolog. Surv. Box 25046 MS 408 Denver Fed. Center Denver CO 80225-0046). Plantz M. R. Holmgren J. A. Multi-elemental analy- sis of environmental samples with a low-cost induc- tively coupled plasma spectrometer (WMI Environ. Monitor. Labs. 2 100 Cleanwater Dr. Geneva IL 601 34 USA). Roehl R. Alforque M. M. Riviello J. Arsenic speciation in biological and environmental samples by liquid chromatography combined with on-line hydride generation and inductively coupled plasma mass spec- trometry (Californian Pub. Health Found. California Dept. Health Sen. Hazardous Mater. Lab. 2151 Berkeley Way Berkeley CA 94704 USA). Johnson G.W. Miller R. O. Brown P. H. ICP-MS for plant analysis (DANR Anal. Lab. Dept. Pomol. Univ. California Davis California 9561 6 USA). Vanderpool R. A. Johnson P. E. Intrinsicfextrinsic boron- 10 in male Long-Evans rats (USDA-ARS Grand Forks Human Nutr. Res. Center Grand Forks ND 58202 USA). OH 45221-0172 USA). 921 C3450. 92lC345 I 92lC3452. 92lC34 5 3. 921 C3454. 92fC345 5. 92lC34 56. 92lC3457. 92lC3458. 92fC3459. 92lC3460. 92fC346 1. 92fC3462. 92fC3463. 92IC3464. 9 21 C346 5. Carey J. M. Vela N. P. Caruso J. A Determination of organometallic compounds by supercritical fluid chromatography-inductively coupled plasma mass spectrometry (SFC-ICP-MS) (Univ. Cincinnati Dept. Chem. Cincinnati OH 4522 1-01 72 USA). Hartley J. Goodall P. Ebdon L. Hill S. J. Novel desolvation system for the analysis of organic solvents by flow injection inductively coupled plasma mass spectrometry (Plymouth Anal.Chem. Res. Unit Dept. Environ. Sci. Polytech. South West Drakes Circus Plymouth PL4 SAA UK). Jackson S. E. Longerich H. P. Fryer B. J. Laser ablation microprobe inductively coupled plasma mass spectrometry (LAM-ICP-MS) (Dept. Earth Sci. Centre Earth Resrouc. Res. Memorial Univ. Newfoundland St. John’s New Foundland Canada A 1 B 3x5). Wolf R. E. Analysis of USGS rock standards by laser ablation inductively coupled plasma mass spectrome- try (Idaho Natl. Eng. Lab. EG&G Idaho P.O. Box 1625 Idaho Falls ID 8341 5-41 07 USA). Lord C. J. 111 Nelson E. W. Determination of trace elements in polymers by laser ablation inductively coupled plasma mass spectrometry (Phillips Petro- leum Res.Dev. Bartlesville OK 74004 USA). Montaser A. Critical needs for plasma source mass spectrometry (Dept. Chem. George Washington Univ. Washington DC 20052 USA). Hieftje G. M. Toward the next generation of plasma source mass spectrometers (Indiana Univ. Dept. Chem. Bloomington IN 47405 USA). Harrison W. W. Glow discharges for plasma spectro- chemistry (Dept. Chem. Univ. Florida Gainesville FL 326 1 1 USA). Bengtson A. Some aspects on line selection for quantitative depth profile analysis with GD-OES (Swedish Inst. Metals Res. Drottning Kristinas vag 48 S-I1428 Stockholm Sweden). Harville T. Marcus R. K. Line selection and analyti- cal figures of merit in radiofrequency glow discharge emission spectrometry (Dept. Chem. Howard L.Hunter Chem. Labs. Clemson Univ. Clemson Marcus R. K. Duckworth D. C. Glish G. L. McLuckey S. A. Buchanan M. Wise M. Pochkow- ski J. M. Weller R. R. Sampling radiofrequency glow discharge sources with ion trap and Fourier transfor- m/ion cyclotron resonance mass spectrometers (Dept. Chem. Howard L. Hunter Chem. Labs. Clemson Univ. Clemson SC 29634- 1905 USA). Giglio J. J. Evans E. H. Caruso J. A. Radiofre- quency glow discharge source for mass spectrometry (Univ. Cincinnati Dept. Chem. Cincinnati Jakubowski N. Stuewer D. Application of glow discharge mass spectrometry for in-depth analysis of technical surface layers (Inst. Spektrochem. angew. Spektrosk. Postfach 10 13 52 W-W-4600 Dortmund 1 Germany). Milton D. Hutton R. Jackson M. Gilmour D. Depth profiling glow discharge MS (VG Elemental Ion Path Road Three Winsford Cheshire CW7 3BX UK).van Straaten M. Gijbels R. Depth of cylindrical and planar layered samples with GD-MS (Univ. Antwerp Univ. I B-26 10 Wilrijk Belgium). Jinno K. Inductively coupled plasma detection in microcolumn chromatography (Sch. Mater. Sci. Toy- ohashi Univ. Technol. Toyohashi 44 1 Japan). SC 29634-1 905 USA). OH 4522 1-0 172 USA).JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 277R 921C3466. 921C3467. 92lC3468. 92lC3469. 92lC3470. 92lC347 1. 92lC3472. 92lC3473. 92lC3474. 92lC3475. 92lC3476. 921C3477. 92lC 347 8. 921C3479. 921C3480. 92lC348 1. Knapp G. Gross R. Leitner E. Platzer B. Schalk A. Application of GC-ESD in environmental analysis (Graz Univ. Technol. Dept. Anal.Chem. Micro Radiochem. A-80 10 Graz Tehnikerstr. 4 Austria). Lobinski R. Dirkx W. M. R. Ceulemans M. Adams F. C. Ultratrace speciation of organometallic com- pounds by capillary gas chromatography atomic emis- sion spectrometry (Univ. Antwerp Dept. Chem. Univ. I B-26 10 Wilrijk Belgium). Sing R. L. A. Lauzon C. Tran K. C. Hubert J. Element specific detection in GC by microwave in- duced plasma atomic emission spectrometry using a surfatron and an NIR FT spectrometer summary of developments and performance (Univ. Montreal Dept. Chim. P.O. Box 6128 Station A Montreal Quebec Canada H3C 357). Uden P. C. Seeley J. A Zeng Y. Eglinton T. I. Pyrolysis-GC-AED of sediments coals and other petro- chemical precursors (Dept. Chem. Lederle Res. Tower A Univ. Massachusetts Amherst MA 01003 USA).Wiederin D. R. Gjerde D. T. Microconcentric direct injection nebulizer for microcolumn ion-exchange chromatography ICP-AES (Cetac Technol. 5600 S 42nd Street Omaha NE 68 107 USA). Shum S. C. K. Neddersen R. Houk R. S. Elemental speciation by liquid chromatography-ICP mass spec- trometry with direct injection nebulization (Ames Lab. US Dept. Energy Dept. Chem. Iowa State Univ. Ames IA 5001 1 USA). Lukasiewicz R. J. Webb B. D. Thermospray-mem- brane separator interface for porphyrin speciation studies in crude oils by HPLC-ICP-MS (Unocal Sci. Technol. Div. 376 South Valencia Ave. Brea CA 9262 1 USA). Kumar U. T. Evans E. H. Dorsey J. G. Caruso J. A. Separation of metalloporphyrins by liquid chromato- graphy and detection by inductively coupled plasma Univ.Cincinnati Dept. Chem. Cincinnati Vela N. P. Evans E. H. Caruso J. A. Effects of temperature pressure programming and mobile phase composition in supercritical fluid chromatography (SFC) for the separation of organotin compounds using ICP-MS detection (Dept. Chem. Univ. Cincin- nati Cincinnati OH 45221-01 72 USA). Olson L. K. Caruso J. A Analysis of pesticide mix- tures by supercritical fluid chromatography-microwave induced plasma mass spectrometry (Univ. Cincinnati Dept. Chem. Cincinnati OH 4522 1-01 72 USA). Caruso J. A. Elemental speciation (Dept. Chem. Univ. Cincinnati Cincinnati OH 4522 1-0 172 USA). Voigtman E. Plasma spectrochemical simulation with a graphical user interface program (Univ. Massachus- etts Amherst Dept. Chem. Lederle Grad. Res.Center Amherst MA 0 1003-0035 USA). Hansen S. H. Larsen E. H. Pritzi G. Cornett C. ICP-MS as a chromatographic detector for arsenic species separated by ion-exchange HPLC (Natl. Food Agency Denmark Morkhoj Bygade 19 DK-2860 So- borg Denmark). Mohr J. NotLold C.-J. Weniger K. Atomic emission spectroanalysis with the Fanoquant 100 (Carl Zeiss Jena GmbH Tatzendpromenade I A 0-6900 Jena Germany). Denton M. B. New tools and directions in spectroche- mica1 analysis-] 992 (Univ. Arizona Dept. Chem. Tucson Arizona 8572 1 USA). Quillfeldt W. NBtzold C.-J. Plasmaquant 1 10-a new type of ICP spectrometer (Carl Zeiss Jena GmbH Tatzendpromenade 1 A 0-6900 Jena Germany). OH 45221-0172 USA). 92lC3482. 921C3483. 92lC3484. 921C3485. 92lC3486. 921C3487. 921C3488. 921C3489. 921C3490.92lC349 1. 921C3492. 921C3493. 92lC3494. Kingston A. Hutton R. C. Analysis of solid samples by laser ablation high resolution ICP-MS (VG Elemen- tal Ion Path Road Three Winsford Cheshire CW7 3BX UK). Ebdon L. (Chairman) Sample introduction ap- proaches (Panel Discussion) (Plymouth Anal. Chem. Res. Unit Polytech. South West Drake Circus Plym- outh PL4 8AA UK). Gomez M. Holmes C. Cox A. G. McLeod C. W. From field sampling to flow injection an integrated approach to trace element analysis and speciation (Chem. Anal. Res. Centre Sheffield City Polytech. Sheffield Sl I WB UK). Klinkenberg H. Beeren T. Van Borm W. Multi- element analysis using FI-ICP-MS analytical aspects of a transient signal calibration (DSM Research Dept. FA-AE P.O. Box 18 NL-6160 MD Geleen The Net herlands).Klinkenberg H. Peng Z. Beeren T. Flach K. Modifications of the roughing pump system of a Perkin-Elmer Sciex Elan 500 ICP-MS (DSM Res. Dept. FA-AE P.O. Box 28 NL-6 160 MD Geleen The Netherlands). Ascanelli M. Poluzzi V. Trentini P. Galliani G. Baldi M. Bucci G. Metals in air particulates using ICP-MS (Presidio Multizonale Prevenzione U.S.L. 3 1 Corso Giovecca 169 1-44 100 Ferrara Italy). Mevissen B. van Dongen C. Klinkenberg H. Beeren T. Van Borm W. Instrumental improvement of the XYZ-translation system for a Perkin-Elmer Sciex Elan 1500 ICP-MS (DSM Res. Dept. Serv. P.O. Box 18 NL-6 160 MD Geleen The Netherlands). Beeren T. Klinkenberg H. Van Borm W. Pyrolysis- ICP-MS as a method for the determination of organo- mercury compounds at ng g-* levels in light hydro- carbon matrixes first results (DSM Res.Dept. FA-AE P.O. Box 18 NL-6160 MD Geleen The Netherlands). KUSS H.-M. Hemstege E. Spectrometry and charac- terization of organic compounds by means of low- pressure low-power microwave induced plasma (MIP). (Dept. Anal. Chem. Univ. Duisburg Lotharstr. 1 W- 4 1 OO Duisburg Germany). KUSS H.-M. Miiller M. Bossmann D. Interferences of matrix elements on trace element determination in steels by ICP-MS (Dept. Anal. Chem. Univ. Duis- burg Lotharstr. 1 W-4 100 Duisburg Germany). Klinkenberg H. Beeren T. Van Borm W. van der Linden F. Raets M. On the use of an enriched isotope as an on-line internal standard for the determi- nation of tellurium in industrial waste water (DSM Res. Dept. FA-AE P.O. Box 18 NL-6 160 MB Geleen The Netherlands).Tielrooij J. A. Stofberg E. M. Dejonghe K. J. Speciation of mercury compounds in chemical wastes (TNO-Inst. Environ. Sci. P.O. Box 601 1 2600 JA Delft The Netherlands). Stuer-Lauriden F. Organic kit ICP-MS operating conditions for analysis of water-immiscible organic solvents usable for in situ extractions of hydrophobic organometallic compounds (Natl. Environ. Res. Inst. Dept. Environ. Chem. Frederiksborgvej 399 Box 358 DK-4000 Roskilde Denmark).278R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 Ramon M. Barnes Editor Department of Chemistry LGRC Towers University of Massachusetts Am hetst MA 01 003-0035 Telephone (41 3) 545-2294 fax 545-4490 0 bjective 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 during the 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- MATlON NEWSLETTER in 1975. Other poputar plasma sources i.e.microwave induced plasmas direct current plasmas and glow discharges also are included in the scope of the ICP IN- FORMATlON NEWSLETTER. Scope As the only authoritative monthly journal of its type the ICP INFORMATlON NEWSLETTER is read in more than 40 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 lNFORMATlON NEWSLETTER provides a concise and systematic source of information and background material needed for the selection of instrumentation or the development of methodology. 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ISSN:0267-9477    

DOI:10.1039/JA992070247R

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 719 Simplex Optimization of Nitrogen-Argon Plasmas in Inductively Coupled Plasma Mass Spectrometry for the Removal of Chloride-based Interferences Steve J. Hill Michael J. Ford and Les Ebdon Plymouth Analytical Chemistry Research Unit Department of Environmental Sciences Polytechnic South West Drake Circus Plymouth Devon PL4 8AA UK In order to establish the effects of nitrogen addition to the coolant auxiliary and nebulizer gas flows of an Ar plasma polyatomic ions in a range of spiked and unspiked chloride reference materials (Rice Flour Citrus Leaves Dogfish Liver and Sea-water) and standard solution have been used. The response of a wide range of polyatomic ions was studied with particular emphasis on the chlorine-based interferences ArCI+ and CIO+.Simplex optimization was used to optimize the operating parameters of the spectrometer in order to facilitate the maximum possible removal of the ArCI+ when using nitrogen addition. The ArCI+ interference is shown to be successfully removed with the addition of nitrogen to the coolant and nebulizer gas flows in the presence of 1% chloride. Best results were obtained when 4.5% nitrogen was added to the nebulizer gas. These conditions have also greatly improved the determination of selenium and vanadium in the presence of chloride. In addition it has been found that nitrogen addition has some benefit in the reduction of MO+ and ArO+ interferences as well as the background response. The addition of nitrogen to the auxiliary gas offered little advantage for the removal of interference.Keywords Inductively coupled plasma mass spectrometry; mixed gases; nitrogen addition; chloride interfer- ence; simplex optimization An important limitation of inductively coupled plasma mass spectrometry (ICP-MS) is the formation of polya- tomic species particularly below mlz= 80 which interfere in the determination of elements in this mass These polyatomic ions typically come from precursors in the Ar support gas entrained atmospheric gases (N and 0) or from the sample matrix (0 OH C1 S and P) and can be reduced though not removed by careful setting of the instrumental parameters of the ICP mass ~pectrometer,~.~~~ of which the nebulizer gas flow and the forward power are most i m p ~ r t a n t . ~ Other methods of reducing the polya- tomic ions include cooling the spray chambefl to reduce the solvent loading and hence the O+ and OH+ levels hydride generation,' electrothermal vaporization,8 laser ablation9 and mathematical c~rrection.~ Also available though more expensive is high-resolution ICP-MS which uses a mag- netic sector mass spectrometer capable of separating the analytes and polyatomics with the same nominal mass.Io More recently attention has been turned towards the use of molecular and inert gases bled into or replacing one of the three gas flows of the ICP.Such mixed gas plasmas in ICP-MS have been utilized in three main areas attenuation of polyatomic interferences enhancement of analyte signal and the analysis of organic samples. The last two have been discussed elsewhere11J2 but have not been studied here.The investigations include coolant additions of air and oxygeni3 and nebulizer addition of 0~ygen.l~ Allain et af." studied the addition of methane to the nebulizer gas to enhance analyte responses. Smith et al.15 investigated the addition of xenon to the nebulizer gas flow and showed that it attenuated polyatomic interferences. In addition several workers have reported the use of nitrogen for the removal of polyatomic interferences. Houk et al. l6 studied the addition of nitrogen to the coolant gas investigating the formation and movement of background species such as N2+ and Ar+ within the plasma. Lam and Horlick13 reported work on the addition of nitrogen to the coolant and some limited studies on the addition of nitrogen to the nebulizer.They found nitrogen addition to the coolant to be useful in attenuating polyatomic interferences and also enhancing analyte sig- nals. Lam and McLareni7 investigated the use of nitrogen addition at 8% to the coolant gas for reduction of UO+ and ArO+. Evans and Ebdon14 examined the introduction of low flows of nitrogen into the nebulizer flow of an ICP mass spectrometer and were successful in reducing many poly- atomic interferences. More recently Beauchemin and Craig18 have investigated nitrogen addition to the coolant to improve the determination of iron and selenium and also reduce the effects of concomitant matrix elements such as sodium. This paper gives details of investigations into the addi- tion of nitrogen to each of the three gas flows of the ICP.Experiments employing the addition of nitrogen to the nebulizer have involved the analysis of chloride-spiked reference materials one naturally high in chloride and standard solutions to define the limits of applicability of nitrogen addition. The effects of increased nitrogen in the nebulizer gas on response curves and for various interfering ions (MO+ M2+ and ArO+) are reported together with the effect of adding nitrogen to the intermediate and coolant gas flows. Simplex optimization aimed at removing the ArC1+ interference was undertaken for nitrogen addition in all of the gas flows and is compared with a simplex with no nitrogen. Experimental Instrumentation A standard ICP mass spectrometer (PQ2 VG Elemental Winsford Cheshire UK) was used although the sample introduction system was modified by the inclusion of a high solids nebulizer (Ebdon type PSA Sevenoaks Kent UK).Nitrogen was added to the nebulizer gas using either the standard mass flow controller of the instrument or a gas blender (Series 850 Signal Camberley Surrey UK). The gas blender was also used in the addition of nitrogen to the auxiliary gas flow. The addition of nitrogen to the coolant flow was achieved by using a T-piece before the torch the flow being regulated using a 1 dm3 air rotameter. Materials and Chemicals Four certified reference materials (CRMs) were analysed Rice Flour unpolished high level Cd [National Institute of720 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 Environmental Standards (NIES) No.1 Oc Onogawa 16-2 Tsukaba Ibaraki Japan] Citrus Leaves [National Bureau of Standards (NBS) Standard Reference Material (SRM) No. 1 5 12 National Institute of Standards and Technology Gaithersburg MD USA] Dogfish Liver (DOLT- 1 Na- tional Research Council of Canada Division of Chemistry Marine Analytical Chemistry Standards Programme Ot- tawa Canada) and Sea-water (NASS-2 National Research Council of Canada). Standard solutions were prepared from 1000 pg stock solutions of Sb As Co Mg Pb and Se [Merck (formerly BDH) Poole Dorset UK] Be and In (Aldrich Chemical Milwaukee WI USA) and Ce Ho La Tb U and V [prepared from compounds Ce2O3 Ho2O3 La203 Tb203 U02(N03)2-6H20 and NH,V03 respective- ly]. Internal standardization employing either Sb Co or In at lOOng was used in all experiments.Chloride spikes were prepared using either sodium chloride (Aristar BDH) or concentrated hydrochloric acid (Aristar BDH) and for sodium spikes sodium acetate (Aristar BDH). All standard solutions were made up in 2% nitric acid (Aristar BDH). Hydrogen peroxide (30% Aristar BDH) was used in the Dogfish Liver digestion. Sample Preparation The Rice Flour Citrus Leaves and Dogfish Liver were all digested using microwave bomb digestion. The procedure has been reported elsewhere,I9 although in this case 5 cm3 of nitric acid were used for the digestion of the Rice Flour and Citrus Leaves and nitric acid-hydrogen peroxide (3 + 2) was used to digest the Dogfish Liver. After digestion the solutions were quantitatively transferred in to calibrat.ed flasks (25 cm3 for Rice Flour and Citrus Leaves and 100 cm3 for Dogfish Liver) and made up to volume with distilled de-ionized water.Samples were spiked with increasing levels of chloride (0 100 1000 and 10000pgcm-3) as NaCI with indium added to a final concentration of 100 ng as an internal standard. Five replicates of each sample were prepared. Duplicate digestions of the Dogfish Liver were carried out and spiked with increasing levels of sodium (0,65,648 and 6480pg ~ m - ~ ) again using indium as an internal standard. The Sea-water was diluted (two- five- and ten-fold) and spiked with indium as above. Standard solutions and calibration solutions were pre- pared fresh from the stock solutions as required. Procedure Addition of nitrogen to the nebulizer gas flow Initial experiments of adding nitrogen to the nebulizer gas were aimed at assessing the limits of its applicability for the removal of chloride-based polyatomic interferences.The chloride spiked reference materials were all analysed with and without nitrogen addition (e0.035 cm3 min-I). Analy- sis of the 10 OOOpg cm -3 chloride-spiked samples employed higher nitrogen flows (0.045 and 0.06 cm3 min-*) and a ten- fold dilution of the samples. Dogfish Liver digests spiked with sodium were also analysed (0.035 dm3 min-l nitrogen) to assess the effect of sodium without chloride. Further experiments continued on the above theme using standard solutions. Solutions of arsenic selenium ( 100 n g ~ m - ~ ) and vanadium ( 1 10 and 100 n g ~ m - ~ ) were prepared and spiked with increasing levels of chloride (0 10 100 1000 and 10000pgcm-3). Sodium chloride was used for the selenium and vanadium and HCl for the arsenic (the spiking agent was changed because at high NaCl levels cone blockage became a problem).All the solutions were spiked with indium as internal standard to a final concentration of 100 ngcmA3 and the solutions were ana- lysed at varying nitrogen levels (O-8%). Finally the instrumental conditions were optimized for the removal of ArCl+ using a variable step size simplex optimization procedure with the ratio of Sb+ to ArCP (Sb+/ArCl+) as the criterion of merit. Antimony was selected in order to try and match the characteristics of arsenic i.e. a metalloid with a high first ionization energy. Although germanium would perhaps seem a better choice in terms of mass it has many isotopes and could potentially suffer from spectral interference from C12+.Solutions of 100 ng cm-3 of antimony and 10 OOOpg of chloride were used. Univariate searches were also performed at around the optimum parameters defined by the simplex and the optimum conditions were used to determine the detection limits for arsenic selenium and vanadium at increasing levels of chloride (0 100 1000 10000 and 33 000pg~m-~) as HCl. Investigations adding nitrogen to the nebulizer gas were concluded with experiments investigating the complete mass range. The mass response curves MO+ MN+ M2+ and ArO+ formation were examined together with random background with increasing nitrogen. This was performed using a solution of Be Ce Co Ho In La Pb Mg Tb and U ( 100 ng ~ m - ~ ) which was analysed at 0-8% nitrogen using 1% increments whilst all of the other instrumental para- meters were kept constant.Addition of nitrogen to the auxiliary gas flow Univariate searches were performed to assess the effect of nebulizer gas flow (from 0.6-1.2 dm3 min-I) and auxiliary gas flow (from 0.6 to 2.0dm3min-I) with 2% nitrogen in the auxiliary gas at 1600 W. The species examined were Be Ce Co La Pb and U; CeO La0 and UO; ClO+/NCl+ (m/z=51) ArN+ ArO+ ArCl+ and Ar2+. Searches were also performed to assess the effect of nebulizer gas at 1200 1400 and 1800 W on Be La and U; UO+; ClO+/NCl+ A m + and ArCl+. Analogous searches without any nitrogen addition were performed for comparison. Simplex optimization of the instrumental parameters was undertaken as above for addition to the nebulizer gas.The associated univariate searches were performed and detec- tion limits were determined. Addition of nitrogen to the coolant gas flow Univariate searches were performed to assess the effect of nebulizer (0.6-1.2 dm3 min-I) auxiliary (0.6-2.0 dm3 min-I) and coolant gas flow (13-15 dm3min-l) with 200 cm3 min-l nitrogen flow in the coolant gas at 1600 W on Be Ce Co and U; CeO; random background at m/z= 150 and 220; ClO+/NCl+ (m/z=5 I) ArO+ ArCl+ and Ar2+. Searches were also performed to assess the effect of nebulizer gas flow at 1400 and 1800 W on Be Co and U; CeO; and ClO+/NCl+ ArO+ and ArCl+. Again searches were repeated without any nitrogen the conditions optim- ized by simplex and the associated experiments performed.Finally for comparison one further simplex optimiza- tion was performed without any nitrogen in order to compare the best argon conditions with the best nitrogen- argon conditions for the removal of ArCl+. Results and Discussion Nitrogen Addition to the Nebulizer Gas Flow Analysis of chloride-spiked CRMs The apparent arsenic concentration with and without nitrogen addition in the three chloride-spiked CRMs is shown in Figs. 1-3. It can be seen that in all of the reference materials the ArCl+ interference is removed at up toJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 72 1 cn i E 8 2 20 60 5 0 - 40 5 30 E .- U Q1 0 I- C 1000 pg cm-3 of chloride but becomes significant at higher levels (1000O,~gcm-~) where a positive error is found in the apparent arsenic value.The data with no nitrogen addition for the three reference materials show that even without a chloride spike there is a positive bias in the apparent arsenic value thus demonstrating the value of nitrogen addition. The apparent arsenic values at the 10 000,~gcm'~ chloride spike are about 6 times too high for the Dogfish Liver,=20 times too high for the Citrus Leaves and ~ 4 0 times too high for the Rice Flour. Further investigation of the 10 0 0 0 p g ~ m - ~ chloride-spiked samples showed that increasing the percentage of nitrogen in the nebulizer gas to 5.03% or higher removed the ArCl+ interference on the Citrus Leaves but not on the other two reference materials. This might be because the digest level of arsenic in the Citrus Leaves was higher than the other two (=65 n g ~ m - ~ compared with ~ 2 2 n g ~ m - ~ for the Dogfish Liver and =3 n g ~ m - ~ for the Rice Flour) and that the residual ArC1+ was not significant.Analysis of 10-fold dilutions of the Dogfish Liver and Citrus Leaves digests resulted in values coincident with the certificate values. This indicated that it was an ArCl+ interference or suppression of the indium internal standard that was causing the positive bias in the apparent arsenic values rather than contamination from the NaCl. Analysis of Dogfish Liver digests spiked with sodium indicated that the sodium was having no effect on the determination of arsenic in the CRMs. It was also noted that when nitrogen was added to the nebulizer gas flow - - - - c 1 0 10 100 1000 10000 Chloride concentration/pg ~ r n - ~ Fig.1 Apparent arsenic concentration in chloride-spiked NIES CRM 1 Oc Rice Flour A with; and B without nitrogen addition to the nebulizer gas c 0 10 100 1000 10000 Chloride concentration/pg ~ r n - ~ Fig. 2 Apparent arsenic concentration in chloride-spiked NIST CRM 1572 Citrus Leaves A with; and B without nitrogen addition to the nebulizer gas there was a much less drastic decrease in the indium response than that found without the nitrogen for samples high in sodium. These observations are in agreement with the work of Beauchemin and Craig1* who added nitrogen to the coolant gas flow and found it beneficial in reducing the matrix effects of sodium. Analysis of standard arsenic selenium and vanadium solutions The apparent arsenic concentration for 100 n g ~ m - ~ arsenic solutions at increasing nitrogen and chloride levels is shown in Fig.4. As might be expected at higher levels of chloride the ArCl+ interference became worse and hence the apparent arsenic concentration increased but at higher nitrogen levels this interference is less severe. This would support the notion that nitrogen suppresses the interference through a competitive mechanism with the argon. The analysis of selenium solutions ( 100 ng cme3) was not totally successful; the values obtained can only be taken as indicative of the true values. The data whilst being poor still indicated a considerable improvement over the analy- sis without nitrogen where at 10000pg~m-~ chloride the apparent selenium value was =6000 n g ~ m - ~ .The poor quality of the data was attributed to the fact that selenium is poorly ionized and that both "Se and 78Se are low abundance isotopes typically yielding just 1-200 area counts per second (ACPS) for a 100 ngcmq3 selenium solution. Chloride concentration/pg ~ r n - ~ Fig. 3 Apparent arsenic concentration in chloride-spiked NRCC CRM DOLT-1 Dogfish Liver A with; and B without nitrogen addition to the nebulizer gas *) 10000 I cn \ 0 .- 5 1000 8 s U 0 .- = 100 3 L nr B 1 I I 1 0 10 100 1000 10000 Chloride concentration/pg ~ r n - ~ Fig. 4 Apparent arsenic concentration with increasing chloride levels (100 ng cm-j As) for increasing percentage nitrogen in the nebulizer gas A 0; B 0.5; C 1.0; D 3.0; E 5.0; and F 7.0%722 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 I $ 0 10 100 1000 10000 Chloride concentration/pg ~ r n - ~ Fig. 5 Apparent vanadium concentration with increasing chloride levels (100 n g ~ m - ~ ) for increasing percentage of nitrogen in the nebulizer gas A 0; and B 3.4 1-8.1 I O/o For vanadium the 100 n g ~ m - ~ solutions gave values within 10% of that expected for all nitrogen ratios and levels of chloride (Fig. 5). These results are a little surprising as it was anticipated that the interference from l4N3’Cl + would become significant at higher nitrogen and chloride levels as had been seen in the CRMs and reported previou~ly.~~ Again the all argon plasma analysis showed the importance of nitrogen in removing poly- atomic ion interference.The data obtained by a similar analysis of 10 n g ~ m - ~ vanadium solutions are shown in Fig. 6 and demonstrate the NCl+ interference which adds to the residual C10+ at higher nitrogen and chloride levels. The 1 n g ~ m - ~ solutions showed similar trends to the 10 ng cm-3 solution. Simplex optimization of operating conditions for the re- moval of Arc/+ with nitrogen addition to the nebulizer gas The optimum parameters obtained from the simplex optimization to remove ArCl+ when using nitrogen addition to the nebulizer gas are shown in column one of Table 1. At these optimum conditions the plasma was seen to be dimmer than normal probably owing to the lower power. The central channel also appeared much wider than normal and consequently the coolant region of the plasma was smaller.The reflected power was about 40W. The large central channel is in practice very useful since the position of the torch is no longer critical. The diffuse central channel probably accounted for the loss of sensitivity for antimony (from about 80000 to about 10000 ACPS) however the effect was far less severe than the reduction in the ArCl+ response which fell to almost background levels (from about 50000 to about 100 ACPS). Univariate searches of the optimum parameters showed the power nebulizer and nitrogen values to lie at the conditions defined by the simplex whilst the coolant and auxiliary settings were seen to have little effect on the Sb+/ArCl+ ratio. This is in agreement with Gray and WilliamsS who when discussing optimization of all argon plasmas found power and nebulizer flow rate to be the most important parameters (if spray chamber temperature and sampling depth are con- stant) when trying to remove polyatomic ion interferences.They found that low power (1 100 W) and higher nebulizer flows (0.85 dm3 min-l for ArO+ and ClO+ and in excess of 1 dm3min-l for Ar2+) generally gave the best ratio of interference to cobalt and this compares well with the conditions shown in column one of Table 1. These conditions however also include the addition of nitrogen flow - I I I I 10 100 1000 10000 ii 1 ; 8 Chloride concentration/pg ~ r n - ~ Fig. 6 Apparent vanadium concentration with increasing chloride levels ( 10 ng ~ m - ~ vanadium) for increasing percentage of nitrogen in the nebulizer gas A 0; B 7; C 1 ; D 2; E and F 3 and 5; and G 4% to the nebulizer gas which further improves the ratio of Sb+/ArCl+ (from 10-20 without nitrogen to about 300 with nitrogen).Column one of Table 2 shows the detection limits determined at these conditions for arsenic selenium and vanadium at various chloride levels. The most important point of note is that the detection limit for arsenic (2.1 n g ~ m - ~ ) in the presence of 33 OOOpg cm-3 of chloride (1 0% HCl) was only a factor of four poorer than that normally obtained on our instrument even in the absence of chloride. The contribution of ArCl+ was equivalent to a background concentration of 5.7 n g ~ m - ~ . These conditions will allow the determination of arsenic in matrices that are extremely high in chloride.The analysis of the NASS-2 Sea-water was undertaken using both the unoptimized and the optimized conditions and both sets of data are presented in Table 3. Under unoptimized conditions values ranging from 5 to 30 times higher than the certificate value were found although these are considerably better than those obtained without nitro- gen which are 3000-4000 times too high. The data obtained with the simplex conditions are even better with a positive error of only 3-6 fold. The use of flow injection techniques could overcome the need to dilute the samples and hence facilitate accurate arsenic determination. Effects of increasing the percentage of nitrogen in the nebulizer gas flow It was found that the incremental increase of nitrogen to the nebulizer gas flow had no visible effect on the shape of the response curves.Metal oxide formation was found to be improved by the addition of nitrogen up to 2% but no further benefit was found above this level. The degree of oxide reduction ranged from a factor of 2.1 for uranium to 12.5 for holmium. These data indicate that even without any form of solvent reduction nitrogen addition could reduce the metal oxide levels. Lam and Horlick13 found that 20% nitrogen in the nebulizer removed almost all of the La0 signal which compares well with these findings. No metal nitrides were found even at the highest levels of nitrogen addition and the doubly charged species such as Ce2+ Ho2+ and U2+ were not detected. Random background and ArO+ were found to be reduced by the addition of nitrogen at 1-2% but once again further addition of nitrogen had no effect.Addition of Nitrogen to the Auxiliary Gas Flow Effects of nitrogen addition to the auxiliary gas flow It was found that the instrument could tolerate a maximum of just 3% v/v nitrogen added to the auxiliary gas since723 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 Table 1 Simplex optimized conditions for the removal of ArCl+ with nitrogen addition Parameter Gas flow/dm3 min-' Coolant Auxiliary Nebulizer Nitrogen addition Forward power/W *Value given as %. tValue given in cm3 min-I. Added to the Added to the Added to the nebulizer gas auxiliary gas coolant gas 13 13 15 1 .o 0.5 0.5 0.9 1.2 1.2 4.50* 2.50* 300t 1300 1350 1300 Table 2 Detection limits determined for arsenic selenium and vanadium at increasing chloride concentrations using simplex optimized conditions for nitrogen addition Detection limitshg ~ m - ~ Addition to the nebulizer gas Chloride level/ p g ~ m - ~ V As 17Se ?%e 0 0.21 0.78 4.9 6.2 100 0.12 0.48 6.5 6.5 1000 0.48 0.69 3.9 42* 1 0 000 1.5 1.1 23 31t 33 000 13 2.1 25 200t *Either two-point or poor three-point calibration.tone-point calibration. Addition to the auxiliary gas V As 17Se ?*Se 0.06 1.5 23 8.5 0.06 1.5 ll*. 40t 0.51 1.5 8* 80t 2.9 3. I 15 19 16 4.9* 33t - Addition to the coolant gas V As 17Se 18Se 0.09 1.1 4* 4* 0.12 0.24 20t 10* 0.24 1.1 11 6.7 3.9 0.96 13 8.4 - 26 - 201- Table 3 Apparent arsenic concentration (average 5 error of duplicates) in NASS-2 CRM Sea-water at different dilutions and nitrogen ratios for unoptimized conditions and different dilutions for simplex optimized conditions Arsenic concentration*/pg ~ r n - ~ Dilution Unoptimized conditions- 0% Nitrogen? 3.4 1% Nitrogen 5.03% Nitrogen 6.59% Nitrogen l o x 7.42 -I- 0.43 0.008 rf 0.004 0.01 1 f 0.002 0.01 2 +- 0.00 1 5x 7.95 k 0.32 0.0 1 1 5 0.00 1 0.01 1 LO.001 0.01 4 5 0.001 2 x 5.56 s+_ 0.3 1 0.053 f 0.00 1 0.022 k 0.001 0.026 +- 0.001 Optimized condilions- Replicate 1 Replicate 2 10 x <0.005$ < 0.00 5$ 5 x 0.006 -I- 0.002 0.010~0.002 2 x 0.0 12 5 0.00 1 0.0 13 -t 0.00 1 *Expected value 0.001 65 pgcm-j.to% Nitrogen values are extrapolated. $Based on 30 of the blank. even at this low level the reflected power was prohibitively high (50 W at an auxiliary flow of 1 dm3min-l).The nitrogen was found to cause the plasma to shrink away from both the sampler cone and the torch. This thermal pinch effect was possibly due to the proximity of the nitrogen to the induction region. Effect of nebulizer and auxiliary gas flow adjustment on argon and nitrogen-argon plasmas A 2% addition of nitrogen to the auxiliary gas had very little effect on analyte response metal oxide formation and polyatomic ion interferences (ArCl+ ClO+ ArO+ and AT2+) compared with an all argon plasma. The optimum nebulizer gas flow was unaltered by the addition of nitrogen to the auxiliary gas unlike the optimum nebulizer gas flow when nitrogen is added to the coolant gas which in- c ~ e a s e s . ~ ~ J ~ Considering the physical similarity of the two types of plasma it might have been expected that the optimum nebulizer gas flow would be similar.A 50% loss in sensitivity was noted when the nitrogen was added to the auxiliary gas flow. Variation in the nebulizer gas flow was compared at four power levels (1200 1400 1600 and 1800 W) for the two plasma types; the data being similar in each case. In agreement with Gray and Williamss the polyatomic ions were least intense at the lower power levels and nitrogen addition offered no improvement. Simplex optimization of the operating parameters for the removal of ArCl+ with nitrogen addition to the auxiliary gas This study was carried out as described above and the optimum conditions are shown in column 2 of Table 1. The plasma was seen to be smaller than usual and most importantly had a wide central channel similar to that observed when the nitrogen was added to the nebulizer gas.The simplex optimized conditions for auxiliary gas nitrogen addition whilst showing effective removal of the ArCl+ (absolute response of about 100 ACPS) were in terms of the Sb+/ArCl+ ratio at least five times poorer than those found previously. As with the previous simplex a series of univariate searches were carried out on these conditions in each case flow724 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 seem that the other parameters particularly the power and the nebulizer gas flow result in most of the ArCl+ loss and that the nitrogen is merely removing a few additional ArCl+ ions. This is discussed below but the data indicated that the addition of nitrogen to the auxiliary gas is of little practical value. Once again the optimum conditions were tested for their analytical performance by determining the detection limits for arsenic selenium and vanadium with increasing levels of chloride.The results obtained are shown in column 2 of Table 2 and are similar to those found at the optimum conditions for the addition of nitrogen to the nebulizer gas. Sampling Almost invisible Torch Intense region cone region I \ I I I I I f r Addition of Nitrogen to the Coolant Gas Effects of nitrogen addition to the coolant gas flow The introduction of even the smallest amount of nitrogen into the coolant gas again caused the plasma to shrink away from both the torch and the sampling cone as discussed above.The addition of nitrogen resulted in a large increase in the reflected power 50 W at ( 5 0 cm3 min-l of nitrogen. The maximum nitrogen addition that the instrument could tolerate in this intance was 300~m~min-l of nitrogen in 15 dm3 min-' of argon (i.e. approximately 2%). It may be noted that the level of nitrogen able to be employed in this work was far less than reported by other workers. Lam and Horlick13 for example added nitrogen at 5-20% Lam and McLaren17 at 8% and Beauchemin and Craig18 at 0-10%. None of these workers reported a problem with the reflected power although all used instruments manufactured by a different company which might have different tuning characteristics. Eflect of nebulizer auxiliary and coolant gas flow adjust- ment on all argon and nitrogen-drgon plasmas When the analyte (beryllium cobalt cerium and uranium) responses are compared for an all argon and a nitrogen- argon plasma two points are of immediate interest.Firstly the maximum response increases from 0.9 dm3 min-' to the maximum flow of 1.2 dm3 min-I and secondly the maxi- mum response is about 50% higher in the nitrogen plasma. These two points are consistent with the findings of other workers.13-17 The increase in the nebulizer gas flow probably corrects for the shrinkage of the plasma which results in moving the sampling zone away from the cones. Oxide formation was found to be similar in both of the plasmas with the nitrogen-argon plasma giving better ratios (MO+/M+) only at the highest nebulizer gas flows. The interference (ArCl+ NCl+/C10+ ArO+ and AT2+) re- sponses were similar to those obtained for the analytes.The plots for the auxiliary and coolant searches for all of the analytes CeO+ and the interference ions are essentially flat with no noticeable difference between the two types of plasma. When the effect of the nebulizer gas flow at three powers was assessed for the two plasmas the results were again found to be very similar. Simplex optimization of the operating parameters for the removal of ArCP with nitrogen addition to the coolant gas flow This procedure was carried out as described above. The optimized conditions which are very similar to those found already are given in column 3 of Table 1. These conditions change the plasma considerably as represented in the schematic diagram in Fig.7. The effect of thermal pinch and also the separation of the plasma into three distinct regions may be noted. Once again the plasma had a dim and wide central channel as found in all of the simy;!ex optimizations. Outer reg& smaller Central chanAel wider than than normal normal and also fainter Fig. 7 Sch,ematic representation of the plasma with nitrogen addition to the coolant gas under the simplex optimized conditions As before univariate searches were undertaken to con- firm the optimum. The optimum nebulizer gas flow power and nitrogen addition were all shown to have correct optima and the coolant and auxiliary were shown not to be influencing the Sb+/ArCl+ ratio. The removal of ArCl+ was effectively complete under these conditions the absolute counts recorded being of the order of 50 ACPS.The detection limits (column 3 Table 2) were found to be similar to those given above. Simplex optimization of the operating parameters for the removal of A r W with an all argon plasma This experiment was undertaken to see how well the instrument could remove the ArCl+ interference without the presence of nitrogen. The optimum conditions are given in Table 4. In this case the plasma once optimized looked similar to that using the nitrogen addition conditions although the central channel was not as wide and the absence of nitrogen meant that the reflected power was less than 10 W. Table 4 Simplex optimized conditions for the removal of ArCI+ with an all argon plasma Parameter Value Gas flow/dm3 min-1 Coolant I8 Auxiliary 0.8 Nebulizer 1.2 Forward power/W 1300 Table 5 Detection limits determined for arsenic selenium and vanadium at increasing chloride concentrations using simplex optimized conditions for minimum interference for an all argon plasma Detection limit/~gcm-~ V As 17Se 78Se 100 0.78 - 21* - Chloride level/ ~ g c m - ~ 0 0.96 3.45 15* 14* 1000 1.14 10.5 30* 1 oot 20$ 303 90$ 60$ 1 ot 3.5* 221 26* 10 000 33 000 *Either two-point or poor three-point calibration.tone-poi n t Cali brat ion. $Doubtful data due to elevated blank level.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 725 Table 6 Antimony to ArCl+ ratios (Sb+/ArCl+) for the four simplex optimizations Maximum ratio Ratios at optimum Simplex in simplex during searches* Nitrogen addition to Nitrogen addition to Nitrogen addition to the nebulizer gas 492 300 (200-350) the auxiliary gas 50 40 (30-35) the coolant gas 105 200 (100-250)’ All argon 46 20 (15-25) *Approximate values from the search graphs.Univariate searches were performed and showed that the auxiliary gas did not affect the conditions. The optimum nebulizer gas coolant gas and power defined by the simplex were confirmed. The actual performance under these conditions was found to be poorer than in the nitrogen work with Sb+/ArCl+ ratios in the region of 20-40. Once again the detection limits were determined and are given in Table 5. The determination of detection limits did however indicate one limitation of the optimized conditions in that they produced a very large 76Ar2+ peak that interfered with the 7sA~+.At the higher chloride levels the calibration graphs were very poor as a result of this. The four simplex optimizations can be compared for their analytical capabilities by either considering the detec- tion limits or the ratios for Sb+ to ArCl+. The use of detection limits does not clearly show any one set to be better than any other. In Table 6 data on the various ratios obtained with each set of conditions are presented. It is apparent that the all argon conditions give the poorest ratios although interestingly the auxiliary gas conditions do not show much improvement. The nebulizer gas and coolant gas optimizatons however are considerably better. It can therefore be concluded that in the case of nitrogen addition to the auxiliary gas the removal of the vast majority of the ArC1+ is as a result of other parameters particularly the power and the nebulizer flow and that the nitrogen has only a marginal effect.Conclusions The initial work showed that the addition of nitrogen to a plasma under normal operating conditions could remove the polyatomic interference on arsenic and vanadium at up to 1000,ug cmw3 of chloride. Subsequent optimization ex- periments enabled the level of chloride to be increased to at least 3.3% without producing any significant interference on arsenic. Work is now continuing using other molecular gases such as the addition to methane to the ICP mass spectrometer with the aim of reducing a wider range of polyatomic interferences. The authors gratefully acknowledge the financial support of M.J.F. by the Science and Engineering Research Council and VG Elemental which has made this work possible. 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17 18 19 References Tan S. H. and Horlick G. Appl. Spectrosc. 1986 40 445. Vaughan M. A. and Horlick G. Appl. Spectrosc. 1986 40 434. Munro S. Ebdon L. and McWeeny D. J. J. Anal. At. Spectrom. 1986 1 21 1. Gray A. L. Spectrochim. Acta Part B 1986 41 15 1. Gray A. L. and Williams J. G. J. Anal. At. Spectrom. 1987 2 599. Hutton R. C. and Eaton A. N. J. Anal. At. Spectrom. 1987 2 595. Branch S. Corns W. T. Ebdon L. Hill S. J. and O’Neill P. J. Anal. At. Spectrom. 1991 6 155. Whittaker P. G. Lind T. Williams J. G. and Gray A. L. Analyst 1989 114 675. Gray A. L. Analyst 1985 110 551. Bradshaw N. Hall E. F. H. and Sanderson N. E. J. Anal. At. Spectrom. 1989 4 801. Allain P. Jaunault L. Mauras Y. Mermet J. M. and Delaporte T. Anal. Chern. 1991 63 1497. Hutton R. C. J. Anal. At. Spectrom. 1986 1 259. Lam J. W. H. and Horlick G. Spectrochim. Acta Part B 1990,45 1313. Evans E. H. and Ebdon L. J. Anal. At. Spectrom. 1990 5 425. Smith F. G. Wiederin D. R. and Houk R. S. Anal. Chem. 1991,63 1458. Houk R. S. Montaser A. and Fassel V. A. Appl. Spectrosc. 1983 37 425. Lam J. W. H. and McLaren J. W. J. Anal. At. Spectrom. 1990 5 419. Beauchemin D. and Craig J. M. Spectrochim. Acta Part B 1991 46 603. Branch S. Ebdon L. Ford M. J. Foulkes M. E. and O’Neill P. J. Anal. At. Spectrom. 1991 6 151. Paper 2/00349J Received January 22 1992 Accepted April 6 I992

ISSN:0267-9477    

DOI:10.1039/JA9920700719

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 727 Studies on the Application of Platform Atomization to Furnace Atomic Non-thermal Excitation Spectrometry for the Simultaneous Multi-element Analysis of Environmental Materials' Douglas C. Baxter,* Robbin Nichol and David Littlejohn Department of Pure and Applied Chemistry Universty of Strafhclyde Cathedral Street Glasgow G 7 IXL UK Christian Ludke Jochen Skole and Erwin Hoffmann lnstitut fur Spektrochemie und Ange wandte Spektroskopie (ISAS) Laboratorium fur Spektroskopische Methoden der Urn weltanalytik (LSME) Rudo wer Chaussee 5 W- I 7 99 Berlin Germany Response surface methodology was used to optimize the discharge current and pressure with respect to detection limits for the simultaneous multi-element determination of Al Cd Cr Cu Fe Ni and Pb by furnace atomic non-thermal excitation spectrometry (FANES).Comparison of wall and platform atomization showed improved detection limits for most elements with the latter. Despite the use of automatic background correction by wavelength modulation residual background signals were observed at all lines those on the Cd Cu Fe and Pb channels being rectified by including an 'autozero' procedure in the data processing software. For the remaining elements spectral interferences disrupted the baseline during the atomization step although blank subtraction provided satisfactory correction. Nevertheless the presence of structured background emission poses a potentially serious source of error in FANES measurements. In the multi-element analysis of microwave-assisted digests of three environmental reference materials [National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1572 Citrus Leaves SRM 1575 Pine Needles and SRM 1645 River Sediment] by platform-equipped FANES non-spectral interferences arose for all analytes except Cd and Pb.The use of the standard additions method was thus necessary for calibration purposes. Keywords Furnace atomic non-thermal excitation spectrometry; platform atomization; multi-element analysis; interference; environmental sample Increasing concern about pollution has resulted in a growing need to monitor the fate and concentrations of trace metals in various environments. Owing to the large number of elements and samples typically involved in such monitoring pr~grarnmes,l-~ there is a requirement for multi-element techniques with high sample throughput rates.While inductively coupled plasma optical emission spectrometry (ICP-OES) meets these two requirements it may be inapplicable in some situations because of insuffici- ent detection power.4 Much improved detection limits are possible using inductively coupled plasma mass spectrome- try,5 but such instrumentation is not readily available owing to the high cost. For trace metal determinations in environmental samples the most widely applied technique is probably electrothermal atomic absorption spectrometry (ETAAS) despite shortcomings in terms of being slow and generally limited to one element at a time.6 This latter limitation has been overcome by the development of a simultaneous multi-element atomic absorption continuum source (SI- MAAC) ~pectrometer~-~O equipped with an electrothermal atomizer.The SIMAAC instrument is capable of determin- ing up to 16 pre-selected elements simultaneously and providing detection limits comparable with conventional ETAAS at analytical wavelengths above 280 nm. An alternative approach to providing high detection power and multi-element capability has been introduced by Falk et al." and is known as furnace atomic non-thermal excitation spectrometry (FANES). This involves the use of an electrothermal atomizer to vaporize and contain the sample combined with a low-pressure hollow cathode discharge to excite the analyte atoms. As yet relatively few analytical applications of FANES have been reported,12-15 *On leave from the Department of Analytical Chemistry University of Umei S-901 87 Umei Sweden.and despite the operational similarities to ETAAS,I3 little use has been made of modern developments in electrother- mal atomizer technology I6 such as platforms and modifiers. In this work this situation is partially redressed and a fork platform-equipped FANES source is evaluated by compar- ing integrated emission intensity detection limits for seven elements (Al Cd Cr Cu Fe Ni and Pb) determined simultaneously both with and without the platform. The fork platform design was selected as this is now commer- cially available and provides better analytical performance than most other platform types." Optimum discharge conditions were established using response-surface metho- dology18J9 and the multi-element detection limits with and without the platform were compared in order to check for any disturbance of the hollow cathode discharge.Compari- son was also made with SIMAAC,*O previous FANES13920 and ETAASZ1 detection limits. Finally application of the platform-equipped FANES source to the simultaneous multi-element analysis of three environmental reference materials following microwave- assisted digestion is described and an assessment of the procedure made. Experimental Instrumentation The FANES source (constructed in the Institut fur Spektro- chemie und Angewandte Spektroskopie ISAS Berlin Germany) consisted of a sealed electrothermal atomizer chamber and power supply unit (Carl Zeiss Jena Ger- many).Some modifications were incorporated in this FANES source. Firstly the graphite tube (length 28 mm i.d. 5.9 mm) was held between two graphite contacts with tubular quartz inserts to prevent the discharge extending outside the tube volume. Secondly a connection to the mechanical vacuum pump was provided outside the injec-728 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 Table 1 Operating programme for the fork platform-equipped FANES source Ramp Hold Total step Argon Discharge Step Temperature/"C rate/"C s-I timeis time*/s pressure/hPa current/mA 90 180 500 35 35 2400 500 2600 35 50 5 20 NPt 0 FPt NP FP NP 0.0 20.0 20.0 0.0 52.2 3.0 8.0 3.0 2.0 1.5 38.0 36.0 7.4 52.2 4.2 12.8 4.0 14.2 10 130 10 130 10 130 10 130 67- 149$ 67- 149 67- 149 67- 149 10 130 0 0 0 0 40-80§ 40-80 40-80fi 0 0 *Sum of hold time and calculated ramp time for a linear heating rate assuming ambient temperature of 15 "C.tNP implies no power; FP is full power,=200O0C s-'. $Injection port lid closed. Evacuated first to 10 hPA then back-filled with Ar to desired pressure after 42 s. §Discharge initiated after 48 s data acquisition triggered after 46 s. IDischarge current switched off 4 s into step. Table 2 Spectrometer and data acquisition parameters slit dimensions (height x width) entrance 200 x 200 pm and exit 200 x 150 pm; and spectral resolving power >lo4 Element Al Cd Cr c u Fe Ni Pb W avelengt h*/nm 396.153 228.802 357.868 324.7 54 248.327 352.454 283.307 *All wavelengths are for atomic lines. Spectral bandwidthhm 0.035 0.020 0.030 0.029 0.02 1 0.030 0.024 Integration time PMT voltage/V t,/s 900 2.47 900 1.97 5 50 2.33 7 50 3.77 950 2.62 750 3.68 750 2.09 tion hole of the tube in addition to the main evacuation port situated in the anode chamber.The entire atomizer assembly was water cooled and connected to an Ar gas supply system for purging of the tube and formation of the low-pressure A t discharge. All operational parameters of the FANES source were controlled by appropriate software installed in an IBM PC ATE except for the discharge pressure (67-149 hPa) and current (40-80 mA) which were set manually. Temperature programmes consisting of up to ten stages could be compiled and saved. In each stage a number of additional functions could be selected open or close lid on injection port; internal (through the tube from the ends to the centre) and externaI purge gas flows; evacuation via the anode chamber and/or injection port; open discharge gas inlets; trigger data acquisition; and ignition of the hollow cathode discharge.The programme used in this work is shown in Table 1. In this study the FANES source was operated in conjunc- tion with an Cchelle PM polychromator developed at ISAS. The polychromator was of a compact (f=SO cm) design featuring a tetrahedral mounting22 arrangement of the optical components. About 120 fibre optic cables (diameter 0.4 mm) were fixed in a two-dimensional array at the 50 x50 mm focal plane corresponding to the analytically interesting wavelengths of over 70 elements. For this work the seven elements listed in Table 2 were monitored simultaneously by connecting the appropriate (quartz) fibre optic cables to Hamamatsu R269 photomultiplier tubes (PMTs).A 3 mm thick quartz refractor plate was affixed to a galvanometer mounted behind the entrance slit of the polychromator to permit background correction by wavelength modulation. 23 The polychromator was constructed to allow the most sensitive analytical wavelengths observed using FANES ETAAS and ICP-OES to be monitored via the fibre optic cables. For the work described here lines were generally selected OR the basis of providing the best detection limits as indicated by previous FANES However in some instances (see under Interferences) the severity of spectral interferences and the limited availability of alterna- tive lines dictated the choice of wavelength.Data acquisition and processing spectrometer control and wavelength modulation were all facilitated using software written in Turbo Pascal version 4.0 for an IBM compatible PCZ4 (Tandon PCA 20+). In this study a three- step square wave modulation waveform was e m p l ~ y e d ~ ~ . ~ ~ and the modulation frequency was 34 Hz. Despite oper- ation of the FANES source at reduced pressures the half- widths of recorded signals were always greater than 0.5 s so that the detection frequency was sufficient for the present application. Operation of the FANES Source A sample aliquot of 20 mm3 was injected manually into the graphite tube or onto the platform using a micropipette and dried and ashed at atmospheric pressure with the injection port lid open (refer to Table 1).After cooling to near ambient temperature (step 3) the lid was closed the Ar purge gas flow stopped and the atomizer chamber was evacuated to about 10 hPa (step 4). Next the valve on the main evacuation line (at the anode chamber) was closed and the Ar discharge gas inlets were opened (42 s into step 4). These inlets were situated at the graphite contact cones and so Ar gas flowed symmetrically from the tube ends towards the centre and out through the injection hole under the influence of the vacuum pump. After 40 s the power supply sent a trigger signal to the second PC to begin data acquisition and 2 s later the discharge current was initiated. The discharge was allowed to stabilize for the remainder of step 4 (4.2 s) before the atomization step commenced.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL.7 729 During the subsequent cool-down step the discharge was switched off followed by a clean-out step at low-pressure to aid in removing residual sample components from the atomizer. Finally another cool-down step was incorporated during which the valves to the vacuum pump were closed the Ar purge gas flow resumed and the lid opened to take the atomizer back to atmospheric pressure prior to the next sample injection. Temperatures stated in the text are those set on the FANES control unit; no attempt was made to verify the accuracy of the settings. Reagents and Materials Multi-element reference solutions were prepared from SpectrosoL standards [Merck (formerly BDH) Poole UK] in 0.5% HN03 (Aristar grade Merck).Neither the distilled water nor the HN03 used contained significant concentra- tions of the elements of interest here. The multi-element optimization standard contained the following analyte concentrations (in pg dm-3) Al Cd and Cu 25; Cr Fe and Ni 5; and Pb 50. Standard pyrolytic graphite coated graphite tubes (Perkin-Elmer Beaconsfield UK) and totally pyrolytic graphite fork platforms in pyrolytic graphite coated graph- ite tubes17 (Ringsdorff-Werke Bonn Germany) were used. Standard Reference Materials (SRMs) were obtained from the National Institute of Standards and Technology (NIST). The following materials SRM 1572 Citrus Leaves SRM 1575 Pine Needles and SRM 1645 River Sediment were prepared for analysis by microwave-assisted digestion.Digestion Procedure For the digestion procedure,25 about 100 mg of powdered SRM were accurately weighed into a screw-topped 25 cm3 poly(tetrafluoroethy1ene) (PTFE) digestion vessel (Valtech Industries Thirsk UK) 2 cm3 of concentrated HN03 were added and the lid was screwed on to finger tightness. The vessel was then placed inside a PTFE beaker with a press-fit top. Five such units (three containing SRMs plus HN03 and two blanks with acid only) were placed in a domestic microwave oven (Samsung RE-606 TC) on the rotating 'sample' tray. In the centre of the tray a polyethylene flask containing 10 cm3 of water was placed in a 100 cm3 glass beaker and the oven thermometer was dipped into the water. The microwave oven was programmed to heat to 75 "C (as measured in the water) at full power (800 W) and maintain this temperature for 3 min.After cooling for 15 min the PTFE beakers were taken to a fume cupboard and the digestion vessels were removed and opened slowly to allow venting of corrosive fumes. The vessel contents were Table 3 Levels of the factors the corresponding variables and the experimental design XI K2 Coded level P,ihPa i,,/mA + 1 (upper) 149 80 0 (centre) 100 60 - 1 (lower) 67 40 + 1 - 1 + l -1 + I - 1 0 0 0 + 1 + 1 - 1 - 1 0 0 + 1 - 1 0 quantitatively transferred into acid-washed Sterilin con- tainers (Sterilin Teddington Middlesex UK) and diluted with distilled water. Final dilution factors (on a mass basis) were 1 + 1 1 1 for SRM 1572 Citrus Leaves 1 + 1 19 for SRM 1575 Pine Needles and 1+194 for SRM 1645 River Sediment.It should be pointed out that the microwave-assisted digestion procedure employed was originally developed as a simple and rapid method for the preparation of biological samples for analysis by ETAAS. Previous work had shown that satisfactory results could also be obtained for a variety of plant and food materials.25 However the use of HN03 alone is certainly insufficient to digest geological materials such as SRM 1645 River Sediment completely. Thus the results for this material represent the microwave-assisted acid-extractable fraction of the total elemental concentra- tions2'j Optimization by Response Surface Methodology To optimize the discharge parameters (current iHK and Ar pressure PAr) for simultaneous multi-element analyses by FANES the use of a multivariate strategy such as response surface methodology is considered necessary.l9 Such a strategy involves the planning of the experiments to conform to an orthogonal statistical design. Furthermore the design should permit non-linearities in response and interactions between the variables to be detected. For a simple two-variable system as considered here the central composite design given in Table 3 provides the maximum amount of information using only nine distinct pairs of discharge conditions.'* Both variables were assigned three experimental levels as shown in Table 3. The series of experiments was carried out (in random order) according to the design. At each design point triplicate injections and measurements were made first of the multi-element opti- mization standard (for concentrations see under Reagents and Materials) and then the blank.The first response function considered was simply the logarithm of the blank- corrected integrated emission intensity or peak area (log PA) either for each individual element or the sum C(1og PA) over all seven analytes where the peak area values used were the means of three replicate standards or blanks. The second response function was based on the logarithm of the signal-to-noise ratio (log SIN) defined here as the mean blank corrected peak area divided by the standard deviation of the three blanks as determined for each individual element or the sum C(1og SIN) of the seven individual values. A third response function log(S/Nc,,,) was initially considered also with the S/N ratio being calculated as the mean corrected peak area divided by the baseline standard deviation of the peak area given byI9v2' where Si is the standard deviation of the individual intensities measured during the pre-atomization period equivalent to the integration time t set for each element (see Table 2) and tc is the time constant (0.02944 s for a 34 Hz modulation frequency).An appropriate routine was written into the data processing software to enable calcula- tion of Sarea for each atomization. The mean intensity value was also used to provide the zero level for peak data processing. The use of eqn. (1) assumes that the limiting noise is statistical in nature depending only on fluctuations in the hollow cathode discharge (initiated 4.2 s before the start of the atomization step see Table 1).It is further assumed that the noise level is independent of the tempera- ture and the atomization process (z.e. black-body line and molecular emissions were negligible),27 which as will be7 30 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 discussed below is not correct for several of the lines monitored. Logarithmic transformation of the response functions was required to permit adequate modelling by a polynomial of the general form18 where R is the response function B is the intercept Bi Bij and Bii are linear quadratic and interaction terms respec- tively and K~ represents the ith of k experimental factors. With k=2 variables (discharge current and pressure in Table 3) the full second order model involves a total of six parameters.Estimation of the parameters in eqn. (2) was realized by a least-squares procedure using appropriate computer subroutines in the SIMCA 3B package,28 as was the plotting of isoresponse curves. It should be noted that the discharge pressure PAr values 67 100 149 67 100 149 P,jhPa Fig. 1 Contour plots of fitted response surfaces for log PA (a) Al (6) Cd (c) Cr (d) Cu (e) Fe (f) Ni (g) Pb and (h) C(1og PA) for platform-equipped FANES source. Crosses indicate maxima on response surfaces; PA is integrated emission intensity or peak area 67 100 149 67 100 149 P,jhPa Fig. 2 Contour plots of fitted response surfaces for log SIN (a) Al (b) Cd (c) Cr (6) Cu (4) Fe u> Ni (g) Pb and ( h ) C(log for platform-equipped FANES source.Crosses indicate maxima on response surfaces given in Table 3 were linearized by logarithmic interpola- tion before coding. Also the log SIN data were normalized to an analyte mass of 500 pg for each element to avoid weighting the C(1og SIN) response function. Results and Discussion Optimization of the Discharge Parameters Naumann et al. l9 used the multivariate response surface approach to FANES optimization and following initial screening experiments selected the atomization tempera- ture and discharge parameters (PAr and iHK) as the most critical three variables affecting the SIN ratio for wall atomization. In most respects the FANES instrument investigated was identical to that used here with the notable exception that no background correction system was installed.It was found that the atomization tempera- ture had comparatively little importance for the SIN ratios relative to the discharge parameters and for that reason it was decided to consider only PAr and iHK in the optimization ex.periments described here. As the objectives of this studyJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 73 1 were to evaluate the use of the fork platform in the FANES source and its application to the multi-element analysis of environmental materials an atomization temperature of 2400 "C was used throughout. This temperature proved sufficient to avoid excessive peak tailingz9 for any of the elements studied even when using the platform and a fairly refractory matrix represented by the SRM 1645 River Sediment digest.Response surfaces fitted to the experimentally deter- mined log PA and log SIN data are shown in Figs. 1 and 2 respectively for the seven elements investigated plus the sum over all the analytes. The boundary conditions em- ployed in the experimental design were limited by the ability to maintain a stable hollow cathode discharge in the FANES source. At 67 hPa higher currents than 80 mA could not be reached and the discharge did not always initiate at pressures higher than 150 hPa. Regarding the log PA contour plots (Fig. I) it is predicted that all analytes except Cd give the greatest net integrated emission intensities at or very close to the highest discharge current (80 mA) in the experimental domain. This apparently anomalous observation for Cd is not an artefact caused by a poor fit to the experimental data since the derived model was significant and for any given pressure the Cd net integrated emission intensity generally decreased with increasing current. For all other elements the peak areas increased with discharge current in agree- ment with previous observations.In a study on the determination of Cd in blood by FANES Falk et also reported the use of a fairly low discharge current 30 mA in the usable range of 15-60 mA. It is also worth mentioning that the slope of the log-log calibration curve for Cd was 1.08 k 0.09 over the mass range from 50 pg to 2 ng (500 pg were used in the optimization experiments) which indi- cates that self-absorption was negligible under the condi- tions prevailing in the FANES source and so the apparently discrepant behaviour of Cd cannot be satisfactorily ex- plained at present.For analytical applications the detection limit rather than the sensitivity is usually the limiting factor. Contour plots of log SIN are given in Fig. 2 the best detection limits being obtained at the highest point on each surface. Comparing Figs. 1 and 2 it is seen that the current for which the SIN ratio is optimum is typically less than that required for maximizing the peak area. Once again however the optimum current for Cd determinations is at the lowest level in the experimental domain. The response surface for Pb is also interesting in that it represents a saddle point18 with two maxima located towards the upper left and lower right hand regions of the plot.Thus the two most volatile elements behave somewhat differently from the other analytes as might be expected. Of the three analytes considered in both this work and that reported by Naumann et d . 1 9 (Cr Cu and Ni) only Cu exhibits similar response surfaces for log SIN in both cases. The differences observed for Cr and Ni are most probably due to the use of wavelength modulation background correction in this study and the presence of structured background emission within the modulation interval as discussed below (under Interferences). With respect to the optimization of the discharge para- meters for simultaneous multi-element analysis by plat- form-equipped FANES the best average detection limit will be realized close to the centre of the experimental domain where the C(1og SIN) surface is at a maximum.Obviously there is some compromise involved in this optimization procedure. However once the response sur- face has been constructed it would be easy to modify the discharge conditions to improve the detection limit of a specific element. Thus the multiple response surfaces may be used as a map to locate the optimum instrumental settings for a given analytical problem. In some cases the maximum response is seen to lie at the extremities of the experimental domain (see Figs. 1 and 2). For Cu [Fig. 2(d)] an improved SIN would be expected by increasing the discharge current and thus extending the experimental domain to a more favorable response region. Unfortunately a stable discharge could not be obtained for parameter settings outside the boundary conditions defined in Table 3.Comparison of Wall and Platform Atomization The same experimental design (Table 3) was also used to study the effects of the discharge parameters on log PA C(1og PA) log SIN and C(1og SIN) for wall atomization and the optimum conditions are reported in Table 4 together with those for the platform-equipped FANES source. For comparison optimum discharge settings are included for Cr Cu and Ni from the study by Naumann et Apart from the use of wavelength modulation background correc- tion here different definitions of the SIN have been considered. Naumann et al. I9 calculated the integrated emission intensity noise on the basis of eqn. (l) whereas the standard deviation of the three blank measurements are used here.This obviously will contribute to differences in the optimum conditions determined by response surface methodology. Although the software used here permitted calculation of the noise according to eqn. ( l ) it was found that detection limits computed using the resultant SIN ratios (S/Nca,c) were far too optimistic about two orders of magnitude better than those reported for this work in Table 5. Also shown are simultaneous multi-element detection limit data for FANESzo and the SIMAAC instrument using probe atornization,l0 and single-element data for FANES13q29 and ETAAS.21 The data included in Table 5 Table 4 Optimum values of the discharge parameters for the response function log SIN using platform and wall atomization and comparison with results from the literature (wall atomization) P,,/hPa i,,ImA Element Platform Wall Ref.19 Platform Wall Ref. 19 A1 98 119 - 59 40* - Cd 104 70 - 40 40* - Cr 149* 67* 188 65 58 90* c u 95 67* 53 80* 80* 90* Fe 83 115 - 55 65 Ni 100 67 155 66 76 90* Pb 70 84 - 80* 58 - z 103 67* 1617 57 61 70t - *Optimum values at the borders of the experimental domain. tlncludes data for a fourth analyte element (Co).732 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 Table 5 Detection limits for various electrothermal atomizer based techniques. Data are calculated on a 30 basis for integrated emission intensity or integrated absorbance measurements with background correction unless otherwise noted Extrapolated detection limit/pg Simultaneous multi-element Single element Element Platform* Wall* FANES? SIMAACS Platform* Wall* FANES$ ETAASf A1 21 28 80 4.8 4.7 22 (15) 4 Cd 3.4 47 - 32 3.4 14 3.4 0.3 Cr 3.0 8.5 40 5.5 3.0 4.1 9.2 1 c u 16 8.1 30 3.0 7.3 8.1 ( 1 .C) 1 Fe 16 16 30 39 6.7 3.4 (4.5) 2 Ni 2.7 4.9 10 93 2.7 4.0 (1.5) 10 Pb 64 36 - 56 20 27 20 5 *This work.?From ref. 20 no background correction. $From ref. 10 probe atomization. §From ref. 29 integrated emission intensity data. Values in parentheses from ref. 13 integrated emission intensity data no background IFrom ref. 21. correction. were selected on the criteria that they were based on integrated emission intensity measurements and were ob- tained with a background correction facility. However the single element FANES data available in the literature generally could not fulfil these criteria.It is difficult to explain the dependencies of the SIN ratio for each element on the discharge parameters (Fig. 2) and differences in the optimum conditions for tube wall and platform atomization. This is because many factors are likely to be involved such as atomization and excitation efficiencies degree of ionization and the effects of the discharge and vaporization conditions on the nature of the FANES background at each analytical wavelength. Of greatest significance is the observation that the platform-equipped FANES system gives comparable simul- taneous multi-element detection limits to SIMAAC. At the same time the introduction of a platform does not appear to have had any disruptive effect on the operation of the hollow cathode discharge as the detection limits are typically better than those for wall atomization.With the exception of Ni (for which no satisfactory explanation can be given at present) the sensitivities for both platform and wall atomization were within a factor of two at the optimum discharge conditions (see Table 6). Thus the improved detection limits (Table 5 ) for the platform- equipped FANES source appear to be mostly due to greater discharge stability although better sensitivity is also of importance for A1 and Cd. This probably reflects more efficient thermal dissociation of the analyte species follow- ing platform vapori~ation.~~ No practical problems were encountered in using the fork platform with FANES and the analytical performance certainly did not appear to suffer at least not judging from the detection limit data in Table 5.Interferences To date only a few reports on the use of automatic background correction with FANES have appeared in the l i t e r a t ~ r e ~ ~ J ~ ~ ~ ~ - ~ ~ and only two of these include analytical appli~ations.~*9~~ In one detection limits using wavelength modulation were poorer than those obtained with intensity mod~lation.~~ This was related to the nature of the background signal generated in the FANES source includ- ing molecular bands of impurities in the He plasma gas. These bands displayed both continuous and line character- istics and the possibility of spectral interferences arising from background structure within the modulation interval Table 6 Relative integrated emission intensities for platform versus wall atomization under optimum discharge conditions for each single element and at the compromise multi-element conditions given in Table 4 Relative sensitivity* Element Single element Multi-element A1 1.50 1.18 Cd 1.86 3.63 Cr 0.93 1.21 c u 0.95 0.70 Fe 0.97 1.15 Ni 0.22 0.15 Pb 1.03 1.1 1 *Defined as peak area (PA) for platform atomization divided by PA for wall atomization.was discussed.29 It was also observed that even with wavelength modulation small residual background signals were generated at all analyte lines studied. In certain wavelength regions the temperature of the atomizer tube has also been shown to have an influence on the character- istics of the FANES background spectrum.31 Problems with residual background signals were also encountered here (see Fig.3) and so the data processing software automatically set the baseline to zero during the pre-atomization period when the noise was calculated according to eqn. (1). Despite this spectral interferences were still observed on three channels A1 (396.2 nm) Cr (357.9 nm) and Ni (352.5 nm) decreasing in severity in that order. In preliminary work attempts were made to use the Cr 425.4 and Pb 405.7 nm lines but the magnitude of the spectral interferences was too great to allow meaningful data to be obtained. The spectral interferences at the Cr (357.9 nm) and Ni (352.5 nm) lines can be attributed to CN bands within the modulation Such bands were located on one side of the spectral region scanned by the refractor plate and so the background measured at these points was greater than that at the line centre resulting in overcorrection.The effect was more severe at the Cr wavelength and depended on the discharge conditions used. Nevertheless the peak areas were fairly constant for sample blanks (0.5% HN03) and so a blank correction of the data proved satisfactory. Previously Riby et al.34 noted that the Cr 359.3 nm line provided the best signal-to-background ratios using a hollow anode FANES system. This line is not included inJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 733 A C 1 c 4 0 '-' -5 0 Time/s 5 Fig. 3 Time resolved emission intensity profiles at the A1 396.2 nm line for a FANES cycle with no sample injected (broken line) and with 20 mm3 of 0.5% HNOJ (solid line). A Discharge on; B peak area standard deviation calculated according to eqn. (1) during this time interval (equivalent to peak integration time) and baseline intensity level zeroed; C start of atomization step; D peak area calculated over these integration limits; and E end of atomization step the register of the echelle PM polychromator so the choice was limited to 357.9 and 425.4 nm.It would appear that at least two distinct sources of molecular species were responsible for the spectral interfer- ence at the A1 396.2 nm line as seen in Fig. 3. One species was observed both with and without a sample and increased in intensity as the platform heated. A second spectrally interfering component appeared only when a sample was deposited and appeared earlier in time than the aforementioned species during the interval where the A1 signal was observed. At present the species responsible for these spectral interferences cannot be identified.As for Cr and Ni blank correction of the A1 integrated emission intensity values was required. However the fact that the hollow cathode discharge can produce such molecular emission interferences suggests that a characterization of the FANES source background spectrum both with and without samples should be undertaken. This would be of considerable importance in the selection of suitable lines for instruments with background correction. Non-spectral interferences were also observed during the simultaneous multi-element analysis of the environmental samples.The magnitude of these interferences are reported in Table 7 as relative slopes obtained by diluting standard solutions (1 + 1) with either the SRM digest or 0.5% HN03. Recoveries of the two most volatile analytes Cd and Pb are almost quantitative and only the River Sediment matrix Table 7 Interferences in the multi-element analysis of microwave digests of environmental samples by FANES Relative slope* SRM 1572 SRM 1575 SRM 1645 Element Citrus Leaves Pine Needles River Sediment A1 0.10 0.25 - Cd 0.99 0.90 1 .oo Cr 0.69 0.64 - c u 0.45 0.42 0.54 Fe 0.1 1 0.12 - Ni 1.06 1.00 0.52 Pb 0.95 0.95 1.01 *Slope of standard additions plot divided by slope of calibration graph. severely affects the response for Ni. It should be noted that the ashing temperature used was only 5OO0C to avoid losses of Cd so considerable amounts of matrix would be left on the platform at the start of the atomization step. Further work with FANES should be performed to deter- mine whether interferences could be reduced by applying chemical modification techniques (see ref. 25) and studying the effects of the discharge parameters on interferences.Simultaneous Multi-element Analysis of Environmental Reference Materials Three SRMs supplied by NIST were analysed by FANES using both the standard additions method and calibration against aqueous reference solutions to test the accuracy of the technique and also to assess the efficacy of the rapid microwave digestion procedure. As shown in Table 7 moderate to severe interferences were observed in deter- mining Al Cr Cu Fe and Ni.However the use of the standard additions method provided results in acceptable agreement with the certified concentrations (see Table 8). It should be noted that the microwave digestion procedure used might not be suitable for the complete destruction of the botanical samples since Nadkarr~i~~ also found slightly low results for A1 (495 pg g-l) Cr (1.8 pg g-') and Fe (152 pg g-l) in SRM 1575 Pine Needles using ICP-OES following similar sample preparation. No attempt was made to determine Al Cr and Fe in SRM 1646 River Sediment as these elements are present at the O/o level and previous studies have shown that they are not completely dissolved even after prolonged periods in the Table 8 Results of simultaneous multi-element analysis of microwave digests of environmental reference materials by platform-equipped FANES Concentration*/pg g- * SRM 1572 Citrus Leaves Element A1 Cd Cr cu Fe Ni Pb Found 75+ 13 N.D.$ N.D.13.2 k 0.9 71 + 8 N.D. 14.1 f 1.3 Certified 92+ 15 0.03+0.01 0.8 k 0.2 16.5+ 1.0 90k 10 0.6 k 0.3 13.3 + 2.4 SRM 1575 Pine Needles SRM 1645 River Sediment? Found Certified Found Certified - - 519+54 545 k 30 0.54 2 0.29 (t0.519 1.820.6 2.6 k 0.2 2.7 + 0.3 3.0 k 0.3 82+ 17 109+ 19 165+20 200k 10 - - 2.8 + 0.5 (3.5% 42.4 + 6.0 45.8 rf 2.9 11.5k1.2 10.8 k 0.5 674 + 80 714k28 9.7 + 1.6 10.2+ 1.5 - - *Mean rf one standard deviation (n= 3). PAl Cr and Fe not determined (see text). $Not detected. ginformation value.7 34 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1992 VOL. 7 microwave oven.26 Complete dissolution of a refractory material such as SRM 1645 River Sediment is only effected using much more aggressive acid mixtures or high-pressure digestion.As substantial amounts of solid residue remained after the digestion it would hardly be surprising to observe incomplete recoveries. Nevertheless the results shown in Table 8 show almost quantitative extraction ofCd Ni and Pb. Conclusions As suggested by Naumann et aLL9 and supported by this work optimization of the FANES discharge parameters using response surface methodology is beneficial for simul- taneous multi-element analysis. This method generates all the information required to identify optimum conditions for a particular analyte or the parameter settings giving the best detection limits for a suite of elements.With such information available the most suitable conditions for a given analytical problem can be selected. The application of platform atomization in the FANES source caused no disturbance of the hollow cathode discharge; in fact the detection limits for all elements except Fe were improved at the optimum conditions for each individual analyte. Nevertheless interferences were ob- tained during the multi-element analysis of environmental materials and so further studies should be performed to attempt to rectify this problem for instance by using modifiers which have been successfully applied in ETAAS.17-21’25 Preliminary results25 using a palladium modifier in FANES with tube wall atomization have also been promising. Perhaps a more serious problem was that of spectral interferences which fortunately could be re- dressed by blank correction in the cases that arose here.However there remains a potential risk of spectral interfer- ences to go undetected and further studies on the character- istics of background emission in FANES are warranted particularly for instruments equipped with automatic back- ground correction systems. This work was supported by the Centre for Environmental Research in UmeA the Swedish Environmental Protection Board and the Swedish Natural Science Research Council. We wish to thank W. Frech (University of UmeA Sweden) for critical comments and B. Hutsch (Ringsdorff-Werke Bonn Germany) for supplying the fork platform and tube used in this study. References Favretto L.Gabrielli Favretto L. and Felician L. Z. Lebensm. Unters. Forsch. 1987 184 101. Tomas X. Rius J. Obiold J. and Sol A. J. Chemom. 1988 3 139. Piepponen S. and Lindstrom R. Chemom. Intell. Lab. Syst. 1989 7 163. Millward C. G. and Kluckner P. D. J. Anal. At. Spectrom. 1989 4 709. Applications of Inductively Coupled Plasma Mass Spectrometry eds. Date A. R. and Gray A. L. Blackie Glasgow 1989. 6 7 8 9 10 1 1 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Cresser M. S. Armstrong J. Dean J. Ramsey M. H. and Cave M. J. Anal. At. Spectrom. 1991 6 1R. Harnly J. M. O’Haver T. C. Golden B. M. and Wolf W. R. Anal. Chem. 1979 51 2007. Harnly J. M. Miller-Ihli N. J. and O’Haver T. C. Spectro- chim. Acta Part B 1984 39 305. O’Haver T. C. Analyst 1984 109 21 1.Carroll J. Miller-Ihli N. J. Harnly J. M. Littlejohn D. Ottaway J. M. and O’Haver T. C. Analyst 1985 110 1153. Falk H. Hoffmann E. and Ludke Ch. Spectrochim. Acta Part B 1981 36 767. Falk H. Hoffmann E. and Ludke Ch. Fresenius’ Z. Anal. Chem. I98 1 308 362. Falk H. Hoffmann E. and Ludke Ch. Spectrochim. Acta Part B 1984 39 283. Falk H. Hoffmann E. Ludke Ch. Ottaway J. M. and Littlejohn D. Analyst 1986 111 285. Falk H. Hoffmann E. Ludke Ch. and Schmidt K. P. Spectrochim. Acta Part B 1986 41 853. Slavin W. Carnrick G. R. Manning D. C. and Pruszkowska At. Spectrosc. 1983 4 69. Frech W. Arshadi M. Baxter D. C. and Hutsch B. J. Anal. At. Spectrom. 1989 4 625. Box G. E. P. Hunter W. G. and Hunter J. S. Statistics for Experimenters Wiley New York 1978. Naumann B. Knull B. Kerstan F. and Opfermann J. J. Anal. At. Spectrom. 1988 3 1121. Falk H. Hoffmann E. and Ludke Ch. Prog. Anal. Spectrom. 1988 11 417. Slavin W. Graphite Furnace AAS-A Source Book Perkin- Elmer Norwalk CT 1984. Schmidt K. P. Becker-Ross H. and Florek S. 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Littlejohn D. Anal. Proc. 1988 25 217. Ballou N. E. Styris D. L. and Harnly J. M. J. Anal. At. Spectrom. 1988 3 1141. Riby P. G. Harnly J. M. Styris D. L. and Ballou N. E. Spectrochim. Acta Part B 199 1 46 203. Nadkarni R. A. Anal.’Chem. 1984 56 2233. Paper 2/01 I93J Received March 3 1992 Accepted April 22 I992

ISSN:0267-9477    

DOI:10.1039/JA9920700727

出版商:RSC    

年代:1992

数据来源: RSC