摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 37N Conference Report ~~ Pittsburg Conference McCormick Place Chicago IL USA February 27 to March 4 1994 PittCon ’94 celebrated its 45th anniver- sary in Chicago IL with the billing ‘From a Handful of Scientists to the Greatest Science Show Ever’. PittCon’s juggernaut of exhibitors symposia speakers and conferees; (a total of over 30 000 people their booths equipment and at least their luggage) rolled into Chicago during the last week of February despite calf-deep snow uncomfortably howling winds off the Great Lakes and a closed O’Hare airport on the Friday before the show started. This was all too reminiscent of last year’s PittCon in Atlanta GA where so many people were stranded in the blizzard after the show. What a relief that PittCon ’95 will be held in the deep South of New Orleans! However excellent restaurants and good Blues Bars make the prospect of returning to Chicago in 1996 (instead of Atlanta which will be busy hosting the Olympics) a happier one.And of course Chicago was happy to host PittCon. Me1 Patla Interim President of the Chicago Board of Tourism thanked PittCon and its attendees for the many benefits their presence brought to Chicago’s con- vention hospitality and service indus- tries. When those benefits to the city total $51m in one week; that’s a big thank you! Moreover PittCon ploughs back all of its profits from the show to the host city by sponsoring ‘Science Week‘ events in the city. This year 1,800 high school students accompanied by their teachers were invited to tour PittCon attend special lectures and the special exhibit on Science Vans (one of which was donated to the city this year by PittCon). The point of all this is at the core of the PittCon Committee’s goal; to encourage young people to take an interest in science if not foster their ideals for a career in science and sow the seeds of the future.Only a handful of cities can now shoe- horn PittCon into their environment. Other than the usual rotation (CHATNO as it is known) of Chicago Atlanta and New Orleans there is Las Vegas but I suspect that it is too far ‘West’ for what has historically always been an ‘East Coast Show’ and Las Vegas is always booked decades in advance. Geographical note in the US there is of course the North and South and the forever pxesent Mason-Dixon Line but there is also another dimension the East and the West which is held in a similar vein to North and South.Like the Mason-Dixon line it does not exist in reality but is a divider of people nonthe- less. Happy news for PittConees though the rotation will be broken in 1999 by the inclusion of Orlando FL which has three big advantages over the CHATNO locations it is located in the ‘Sunshine State’ is the home of Mickey Mouse and other friends and will have completed an over 1 million ft2 facility suitable for housing PittCon in 1998. In 1994 though PittCon once again was able to boast over 1000 exhibitors filling up over 5 miles of exhibits and over 1800 technical presentations. The entirely volunteer committee is staunchly proud of PittCon’s growth evolution and its roots in the industrial steel town of Pittsburg Pennsylvania. From its inception in 1950 as the sober-sounding Pittsburg Conference on Analytical Chemistry and Applied Spectroscopy which was held in one small room of the William Penn Hotel in downtown Pittsburg PittCon has matured into ‘the premier conference and exposition for laboratory equipment and chemical analyses’.Despite the global recession PittCon continues to grow attracting more exhibitors from a wider scientific base than ever before. This year both the technical pro- gramme and the exhibition had an air of reflection on good times past when chem- ists were pioneers of new analytical tech- niques which were invented seemingly for the hell of it without thought to applications. The analytical instrumen- tation industry is now so applications driven that it is difficult to imagine what it must have been like to be on the threshold of a new method of jiggling atoms and molecules into repeatable pat- terns and not have a firm idea of what possible benefits it could have to the scientific community.That era was clearly expressed by David Nelson whose company Nelson Analytical became Perkin-Elmer Nelson in 1988 during Tuesday’s Plenary ses- sion entitled ‘A History of the Pittsburg Conference’. This session also included lectures by Foil A. Miller University of Pittsburg on how a venue such as PittCon influences the development of new technology and also James Waters founder of Waters Associates who pre- sented another although similar view- point from an industrial manufacturer.Nelson recalled that the 1950s were the formative years when ‘lots of com- panies would bring their products (to PittCon) and hope that someone would come along and find an application for them’. Companies were not applications driven at that time and therefore not business and commercially oriented. The 1960s heralded the end of the ‘golden age of grants and research for research‘s sake’ but saw the coming of the age of chromatography. By the 1970s the world was in recession grants were a fleeting memory and analytical chemistry was more apt to be pigeon-holed into this or that application. The mini-computer became truly accessible and the environ- mental and pharmaceutical markets began to take off.The 1980s were the growth years attendance at PittCon38N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 soared with the growth of the analytical instrument manufacturers who had by then learnt the commercial lessons of focused targeted applications market- ing. PittCon became less regional and more an East coast show eventually leading to the circuitous route of CHATNO. Nelson described what is happening in the analytical instrument industry now. There is still a ‘wait and see’ atti- tude evident by the constant acquisition of smaller growth companies by the industry leaders in an effort to cover all their bases and be prepared for an upswing in market indicators for any application area. To complement this historical view of PittCon there was a special exhibit throughout the week of early instrumen- tation and PittCon memorabilia.Over 90 instruments were on display including a typical laboratory set-up from the 1950s. Some of the instruments dated back to the just-post World War I1 era a time when many of the analytical methods that we use today gained their impetus. However the Antiquities Museum was carefully put together and many of the instruments on display were those from companies who were pioneers of that particular analytical technique or were the mass producers and thus com- mercial leaders in that application. These simple but sometimes huge instruments including a 21 ft spectrograph from Jarrell Ash encased in a beautiful mahogany raised-panel cabinet caused those who had spent so much time working with these instruments to revel in nostalgia and the new kids on the block to gasp in horror at the big ugly boxes and the lack of automation! So what new offerings in atomic spec- troscopy have the major manufacturers come up with this year? The cost- conscious consumer was high on the manufacturer’s list.Enhancements and add-ons to already successful instrument leaders were more evident than in pre- Jarrell Ash 21ft Wadsworth Stigmatic Grating Spectrograph. Built in 1943 there were about 60 instruments in use worldwide. It was the largest and most expensive spectrograph avail- able and became the preferred instrument for locating and measuring uranium and other important minerals. It was also used for the determination of trace alloying elements in high- temperature super alloys for aircraft engines.vious years Manufacturers are very aware that their customers do not cur- rently have the money available to spend on an entirely new replacement for what already sits in the laboratory and that instruments with add-ons and upgrades which improve the end result of the instrument’s performance are very much in demand. One of the most simply impressive offerings was from ATI whose range of SOLAAR AA instrunients is now avail- able with graphite furnace television (GFTV). Users can now watch the sample injection process the drying and the ashing by pressing a button on the SOLAAR toolbar. The video window on the PC monitor opens and presents live video of the graphite tube. The software package offers additional features such as video capture for later playback arid editing.Making its entry into the inorganics market Hewlett-Packard created much interest with the first benchtop ICP-MS. Certainly not portable but definitely benchtop the HP 4500 is a full function scaled-down instrument which offers the ruggedness and ease-of-use required to bring ICP-MS into the routine labora- tory environment. Although not avail- able in Europe until next year the HP 4500 combines a revolutionary interface which is claimed to virtually eliminate many polyatomic interferences ion- optics technology and a hyperbolic quadropole for maximum detection power. The axial plasma viewing position €or ICP torches certainly made an impact at PittCon. Most of the leading manufac- turers have turned the ICP torches on their sides and thus are able to claim much better detection limits for their ICP instruments.Thermo-Jarrell Ash introduced its IRISIAP spectrometer which combines a CID detector and axial-viewing technology. The IRIS/AP utilizes a CID in an eclielle optical design which gives the instrument the capability of continuous and simultaneous wave- length coverage from 175 to 900nm. Background correction measurements are simultaneous resulting in more accu- rate measurements than before. The axial-view provides detection limits at least one order of magnitude below those previously reported for any conventional ICP emission instrument. Thermo-Jarrell Ash has extended its axial-viewing technology to the low- priced end of the ICP marketplace with a new sequential ICF’ instrument with detection limits 10-20 times lower than those achieved on an instrument with a conventional design.The Tracescan will meet most furnace application needs without graphite cuvettes hollow cath- ode lamps and chemical modifiers. In comparison with an electrothermal AA spectrometer the TraceScan provides freedom from chemical interferences multi-element analysis increased pro- ductivity and reduced cost per sample analysis. Also from Thermo-Jarrell Ash is its high capacity electrothermal AA spec- trometer designed as ‘the workhorse for routine ETAA applications’. It is com- pact and comparatively low-priced but incorporates an automated 40 position discrete autosampler capable of pl volume depositions a 0.33 m Ebert monochromator with high resolution grating a 190-600 nm spectral range and an integral water recirculating system.The Perkin-Elmer Optima 3000 XL ICP-OES also has an axial viewing pos- ition which enables the analysis of 22 of the 23 elements in the US Environmental Protection Agency’s Contract Lab Program. This instrument is based on the successful Optima 3000 and it com- prises an Cchelle-based polychromator with a segmented-array charge-coupled detector and temperature-controlled plasma pneumatics. It also includes more than 5000 emission lines providing the flexibility to select alternate interference- free lines for superior results. Perkin-Elmer also launched a flow injection mercury system (FIMS) which is a fully-automated and easy-to-use AA spectrometer dedicated to mercury analysis. Exceptional detection limits of (0.01 pg 1-’ and fast analysis times coupled with much lower sample and reagent use make this a cost-effective instrument .The Fisons Group launched 12 new products at PittCon. The Accuris ‘E (environmental) is a standard system offering the 24 key environmental elements with the option to expand to a total range of 45 elements. Additional elements are available through the use of Multiscan. The Accuris ‘C’ (custom) is a more versatile instrument which is designed to be configured to provide the best possible performance for all ICP applications. Up to 60 elements can be selected with additional prominent lines provided by Multiscan. Maxim also from Fisons is claimed to be the world’s first super-simultaneous ICP spectrometer which is equipped with 195 simultaneous wavelengths has com- plete coverage of the useful ICP spectrum providing all of the wavelengths required for complete ICP analysis of any element in any matrix.Every Maxim analysis provides the highest sensitivity with the lowest resolution (0.0055 nm at 200 nm) using standard analysis times. Use of a photomultiplier tube (PMT) multiplies the analytical signal and for further flexibility if needed Multiscan is incor- porated. The Fisons ‘Super Torch’ is also in an axial viewing position. The Kevex Omicron from Fisons is the world’s only X-ray microfluorescence analyser which combines the elementalJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 39N sensitivity of XRF with spatial resolution in the range of SEM microanalysis. A colour remote monitor provides real- time imaging of samples during analysis. Of historical note for this reflective PittCon Fisons celebrated Applied Research Laboratories’ (ARL) 60th anni- versary.ARL was one of the founding companies of PittCon and the first company to introduce a commercial ICP-AES in 1974. At the Royal Society of Chemistry booth which was well-positioned in the main hall many attendees stopped by to browse through the latest book titles pick up copies of the various journals and magazines and be given demon- strations of the Society’s databases. The staff reported that generally they seemed to be busier than usual; an excellent sign of the growing recognition of and interest in the RSC’s publications. However it was not until Tuesday evening during the RSC reception that this interest was confirmed.Despite quite a few alternative receptions that evening the one hosted by the RSC was undoubt- edly the best attended to date with more than 350 guests many of them well recognized key symposia lecturers PittCon committee members authors and referees. That the Society should do so well in the USA and at a premiere conference and exhibition is a true feather in its cap. PittCon’s technical programme did have a sense of maturity this year. The Committee had taken great pains to exclude the sales pitches from most of the symposia; not an easy task. It stands to reason that the most skilled presenters and spokespeople from the manufactur- ing industry find it difficult to differen- tiate between a ‘sales pitch’ and an interesting and informative talk on the applications or developments of their products.At the other end of the spec- trum there are always the most knowl- edgeable of speakers who find it difficult to convey what they know with any enthusiasm or presentation skills. However this year’s programme struck a pleasing balance being informative entertaining and covering a broad base of interest. Overall the only irritating obscurity was that some of the lectures were not assigned to obvious session titles hence it was easy to miss talks of interest. The broad base of interest was helped greatly by this year’s Plenary sessions which were sorely missed last year. These sessions are always sandwiched (forgive the pun) between morning and afternoon lectures at lunchtime and are always well attended.The first session concerned the Pittsburg Conference-45 years and beyond and has already been described. The second was given by James Trefil author and physicist George Mason University entitled ‘Scientific Literacy What It Is Why We Don’t Have It and How Can We Get It’. During Trefil’s lecture the audience appeared to let out a collective sigh of relief that they were not alone in trying to retain all the information that is thrown at them or gathered during a normal working day. According to Trefil one cannot retain information of any kind unless the basic matrix for that information has already been installed in one’s brain. Once the matrix is installed one should find it easier to slot information into its relevant pigeon-hole or series of linked pigeon- holes across various disciplines of science rather than keeping to the traditional boundaries of chemistry biology physics and their numerous sub-disciplines.Trefil suggested a new more open- minded approach to science and as he said ‘What better way to start than to have a physicist address an audience of chemists? Continuing the program’s nostalgic theme was the symposium ‘The Direct Reading Polychromator-45 years later’ arranged by Gary Horlick University of Alberta. In his talk entitled ‘The Evolution of Direct Reading Poly- chromator Design’ Horlick described how the classic direct reading poly- chromator was the result of combining a grating spectrometer with electronic light sensors (PMTs) and electronic readout sub-systems.The original designs developed in the mid- to late-1940s were marketed by ARL and Baird. The dramatic evolution of the direct reader design owes much to the improvement in electronic data acqui- sition and computing technologies. Whereas the basic optical design has evolved at a much slower pace recently there has been a flurry of activity spurred on primarily by the development of elec- tronic image sensors (PDAs CCDs CIDs) coupled with Cchelle spec- trometers. Forty-five years later Horlick brought to our attention a keynote paper presented at the first PittCon ‘Progress in Spectrographic Instrumentation’ by Professor George R. Harrison of MIT which dealt specifically with the benefits of using an Cchelle grating spectrometer.Back to the present again the choice of electronic image sensors is still very much open to discussion as the following speakers described the benefits of the various detectors coupled with Cchelle spectrometers currently available from the major manufacturers. Bob Fry of Fisons Instruments described the development of the Maxim 195 channel PMT-Cchelle spectrometer in his talk ‘The PMT-Cchelle Direct Reader All The Lines You Need’. The 195 exit slits are cut by a robotically controlled laser and breakthroughs in fibre-optic technology allow the coupling of exit slits >190nm to remote PMT detectors. Benefits of real exit slits for multichannel analysis include excellent channel isolation stray light reduction and enhanced wavelength stability. In Jean-Michel Mermet’s (Universite Claude Bernard) lecture ‘A Segmented- Array CCD Echelle Grating Direct Reader The Solid State Solution’ he described the benefits of the SCD Cchelle- based system developed by Perkin- Elmer.Use of the multichannel detector rather than the PMT allows the ICP user to have simultaneous multi- element multi-wavelength acquisition of the entire line profile. Furthermore the coupling of an SCD sensor with a custom designed Cchelle system provides simul- taneous coverage of four or five of the ‘best’ ICP lines for all the elements. Gary Hieftje Indiana University touted the benefits of the CID-Cchelle spectrometer such as the one developed by Thermo-Jarre!l Ash in his talk ‘The Array Detector/Echelle Direct Reader The Whole Spectrum’. With full spectral coverage nearly at hand Hieftje illus- trated how the modern array detector designs could possibly allow such spec- trometers to be used not only in the conventional passive mode but in an active computer-controlled fashion.Looking to the future Hieftje suggested that spatially resolved diagnostic features of the plasma could be gathered routinely and used by the instrument itself to control the plasma the wavelengths that are measured and the sample introduc- tion method to achieve results that required less calibration and less oper- ator attention. Another symposium devoted to the ‘battle of the array detectors’ entitled ‘Array Detectors and Spectrometer Improvements for ICP-AES’ covered much of the same ground with some interesting additions made by Gary Fulton University of Alberta in his talk ‘Utilization of an Acousto-Optic Tuneable Filter to Combat Dynamic Range Limitation in UV-VIS Fourier Transform Spectroscopy’ and Brian Peltz Northern Illinois University on ‘Development of an Acoustic-Optic Spectral Manipulator for Background Correction’.The pioneering slant of PittCon continued with Monday’s symposium entitled ‘Pioneers of Analytical Chem- istry’ arranged by IS. J. McKaveney of Hewlett-Packard. Five stories of triumph and trouble were told ‘Reflecting on the Past Creating for the Future’ by H. V. Malmstadt University of Nations Kailua-Kona HI ‘Tales of a Reluctant Instrument Maker’ by J. Lovelock ‘The First Fifty Years of Commercial Infrared and Beyond’ by P. Wilks of General Analysis Corp. ‘Laser-Based Chemical Analysis’ by R.N. Zare Stamford University and lastly ‘Highways and Byways in Mass Spectrometry’ by K. Biemann of MZT. Of particular inter-40N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 est was Malmstadt’s story which outlined his philosophy that there is a powerful incentive to get things done when it is a matter of life and death. A good example of this is of course the motivational aspects of World War I1 and also research in the medical field. According to Malmstadt the catalyst is often a simple question or statement ‘Why wouldn’t this work? ‘There must be a better way!’ ‘This takes too much time!’ Comments such as these lead Malmstadt on a search for answers and subsequently resulted in improved analytical methods and instrumentation.Malmstadt is also concerned with the present and how important it is to understand what hap- pens behind the technology of today’s push-button instruments that seem to do everything for us. It is clear from this way of thinking why Malmstadt is such a wonderful teacher and why former pupils now run leading research groups of their own. Another pioneer acknowledged as the father of analytical chemistry Izaak Maurits Kolthoff was honoured in a Memorial Symposium. Kolthoff died last year at the age of 99 but will always be remembered for the profound and con- tinuing influence he had on his students postdoctoral research associates and col- leagues with whom he worked during his years at the University of Minnesota. His genius inspired new fields of research and technology. Back to the future and a symposium entitled ‘Emerging Scientists’ was arranged by K. J. McKaveney of Hewlett-Packard. Of particular interest were the comments of Ken Marcus of Clemson University who described some enlightening work on ‘Radio Frequency Powered Glow Discharges for Atomic and Molecular Spectroscopy; Operating Characteristics Figures of Merit and Future Prospects’ and the need for the development of direct solids analysis methods yielding far greater powers of detection and versatility. To that end he discussed the operating characteristics and figures of merit for the r.f. glow discharge analysis of metals glasses and thin film samples by atomic emission and mass spectrometries. Most attendees left PittCon 1994 inspired by the pioneering stories they had heard throughout the week enlight- ened by the new ideas spawned by the research of others and clutching bro- chures on the latest available techniques perhaps for inclusion in next year’s budget? They were also clutching their PittCon souvenir - a green umbrella. Let’s hope that the umbrella was inspired by the spiteful weather of past PittCon’s; I’d be quite happy to use mine in New Orleans next year but only as a parasol! Andrea Bedson Ka ymich Po whatan VA USA

ISSN:0267-9477    

DOI:10.1039/JA994090037N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

40N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 Book Reviews Applications of Plasma Source Mass Spectrometry I1 Edited by Grenville Holland and Andrew N. Eaton. Pp. x+245. Royal Society of Chemistry. 1993. Price E45. ISBN 0 85186 465 1. Applications of Plasma Source Mass Spectrometry comprises the Proceedings of the 3rd International Conference on Plasma Source Mass Spectrometry held at Durham UK in September 1992. Papers relating to Inductively Coupled Plasma (ICP) and Glow Discharge (GD) sources are presented in this book including both fundamental research and applications development. Having said that reports of ICP-mass spectrometry (MS) applications studies predominate. Fundamental studies are represented by papers on ion kinetic energy measure- ments in ICP-MS and GD source characterization research.The only other paper on GDMS describes depth profi- ling for a selection of low mass elements in scale formed on steel. The applications papers in this book demonstrate the diversity of fields in which ICP-MS is now employed. Industrial applications include trace element determination in electronic chemicals and analysis of metals includ- ing steels and copper. Within the nuclear industry applications of ICP-MS for isotopic analysis and impurity determi- nations are presented. Environmental applications are well represented cover- ing analysis of natural waters and geo- logical samples through to measurement of platinum in car exhaust fumes. Two papers describe certification of new stan- dard reference materials (SRM’s) one relating to plant materials and the other to toxic metals on membrane filters used for industrial workplace air monitoring.Biological and archaeological appli- cations of ICP-MS are both represented by papers describing lead isotopic ratio measurements the first relating to lead uptake through the skin using an isotopic tracer technique and the second to analysis of metallurgical samples for provenance studies. In addition to new applications of ‘standard’ ICP-MS technology the papers in this book describe new sample preparation and introduction techniques. The advantages of ultrasonic nebuliz- ation and laser ablation for the analysis of waters and radioactive solids respect- ively are described. On-line chromato- graphic separation of analytes for fission product determinations is also reported.The use of flow injection sample presen- tation to reduce matrix effects in samples with high total dissolved solids and to allow on-line sample manipulations is described in several papers. Two new sample preparation methods for the determination of the platinum group elements in rocks testify to the continued challenge posed by this analysis. The presentation of papers in the varying styles offered by different authors emphasises the discontinuity in the book but perhaps that is the aim. The indexing although not comprehensive is certainly better than that encountered in many conference proceedings. This book provides a snapshot of the status of plasma source MS in 1992. It is likely to be of most value to libraries to laboratories where up-to-date infor- mation on a wide range of plasma source MS applications is collected and to workers interested in the specific subject matter of one or more included paper(s).Ros Cox AEA Technology Didcot Oxfordshire UK OX11 ORA Laser Ionization Mass Analysis Edited by A. Vertes R. Gijbels and F. Adams. Pp. xxi + 560. John Wiley Sons Ltd. 1993. Price E79. ISBN 0 471 53673 3. This volume describes the development and diverse applications of laser ioniz- ation mass spectrometry (LIMS). The book opens with a brief overview of the subject and an outline of the way the material is structured. Chapter 2 reviews the history of laser ionization from the 1960s to the present day and discusses the instrumentation used for both atomic and molecular ion generation describing instruments based on sector quadrupole time-of-flight and ion-trap mass spec- trometers.The use of lasers for ion fragmentation outside the ion source is also addressed. Following this generalJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 41N introduction the theory and applications of each of the methods are discussed. This large subject area has been subdivided into low medium and high laser-irradiance regimes each of which has its own set of analytical applications. The low and medium irradiance regimes lead to the generation of polyatomic ions which provide structural as well as molecular weight information for appli- cations such as polymer characterization and the study of a range of biochemicals. Laser desorption matrix-assisted laser desorption and multi-photon ionization techniques and their applications are discussed in some detail.The methods enable the characterization of non- volatile and fragile biomolecules of high molecular weight. A systematic descrip- tion of the fragmentation of ions derived from various classes of biomolecules is presented. The high irradiance regime generates atomic ions and can allow the determi- nation of elemental compositions. The application of laser ionization to atomic mass spectrometry is the subject of the last two chapters. This section is likely to be of most interest to readers of JAAS but unfortunately comprises only a minor fraction of the text. The first of these chapters begins with a section by Phipps and Dreyfus who provide a clear outline of the physics of laser-plasma formation at solid surfaces.Their theor- etical discussions are supported by a selection of corroborative experimental findings providing a most profitable read. Their discussion includes outlines of diagnostic techniques applicable to these small transient plasmas. The next part of the same chapter seems a little out of place as it describes laser sampling for subsequent ionization in an inductively coupled plasma (ICP) rather than direct laser ionization. The important theme of separating vaporiz- ation atomization and ionization pro- cesses is mentioned however it would be valuable to have a more detailed inter-comparison of direct laser ioniz- ation under vacuum conditions and laser ablation sampling at atmospheric press- ure.This section is brief but does provide a useful summary of applications with a table showing limits of detection and reproducibility reported for a variety of measurements and will be of interest to practitioners of ICP-MS. The chapter concludes with a section by Dietze and Becker who discuss atomic LIMS resonance ionization mass spectrometry (RIMS) and again very briefly laser ablation sampling for ICP-MS. The discussion of LIMS includes useful tables of applications of the method to a variety of different matrix types. The capabilities and limi- tations of the commercially available LAMMA@ LIMA@ and LASERMAT@ instruments are assessed. The authors discuss how sample dissolution and homogenization the incorporation of internal standards and even isotope dilution can be used to improve the accuracy and precision of LIMS.However I would question the value of LIMS if spatial resolution is lost and if significant sample preparation is required. The authors’ discussion of mass spectral interferences due to cluster for- mation and the variation in accuracy precision and relative sensitivity coefficients as a function of laser power is particularly valuable. Resonance ioniz- ation mass spectrometry is in my view one of the more exciting methods of atomic mass spectrometry due to its potential for high sensitivity and selec- tivity. However the coverage of the subject is disappointing providing only a brief introduction to this powerful technique. Perhaps this reflects the fact that this expensive and complex method is not in widespread use.The concluding chapter by Managadze and Shutyaev describes the development of a laser ionization time- of-flight mass spectrometer designed to sample the surface of Phobos from a space vehicle flying past this satellite of Mars at a distance of up to 80 m. Despite the loss of the spacecraft prior to the experiment an interesting account is provided of the development of this rather esoteric mass spectrometer. In summary I feel that the book has attempted to cover a very large subject and that the coverage is uneven with a small amount of repetition. Most atten- tion has been paid to the low and medium irradiance regimes and their molecular applications with correspond- ingly less emphasis on atomic methods. This is an inevitable outcome of a multi- authored approach to what is a very large subject area. The book provides a useful introduction to the variety of analytical methods based on laser ioniz- ation and their many applications and is likely to be of value to the advanced undergraduate or postgraduate entering the field. Adam McMahon Department of Chemistry Munchester Metropolitan University Munchester UK M1 5GD

ISSN:0267-9477    

DOI:10.1039/JA994090040N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

1995 European Winter Conference on Plasma Spectrochemistry 8-13 January 1995 CAMBRIDGE UK Short Courses A series of short courses of one half day duration will take place on Sunday 8th January. Notes and tuition material will be distributed with each course. Courses 1 and 2 Short Courses on ICP-MS Professor R.S. Houk Ames Laboratory Iowa State University USA Course 1 (AM) Instrumentation and Theory The course will cover fundamental aspects of ICP-MS including:- a) Molecular beam sampling b) Quadrupole and high resolution c) Vacuum technology d) Ion sources e) Detection systems and data hand1 ing f) Sample introduction technologies analys ers Course 2 (PM) Advanced Topics The course will cover more advanced topics on ICP-MS particularly relevant to problem solving. Each topic will be illustrated with relevant applications examples.a) Interferences (spectroscopic and non-spectroscopic and methods of alleviation b) Isotopic analysis c) Chromatographic methods d) Overview of commercial instrumentation Course 3 (PM) Sample Preparation for ICPs Dr S.J. Haswell Hull University UK The course will focus on important aspects of sampling and sample preparation with particular emphasis on ICP measurements. a) Batch methods f o r wet oxidation b) Recent trends in microwave preparation for ICP-MS atomic spectrometry general analytical techniques c) On-line sample preparation d) Extraction methods e) On-line chemical processing f) Miniaturization Course 4 (PM) Speciation Professor O.X. Donard University of Bordeaux France The course will focus on practical aspects of speciation analysis with particular emphasis on ICP and other plasma sampling systems.Sample collection and handling preservation and preparation prior to injection into hyphenated systems using atomic spectrometry and ICP-AES or ICP-MS as detectors will be illustrated with applications from current topical fields . a) Sampling and sample pretreatment b) Separative techniques Differential chemistry Gas liquid ion and SCF c ) Interfacing chromatography techniques to ICPs and other plasma sources and detectors chromatographies Course 5 (AM) Quality Systems in the Laboratory Professor L. Ebdon Dr E.H. Evans University of Plymouth UK The course will discuss how high quality analytical data can be produced in the laboratory that are accurate reliable and adequate f o r the intended purpose.a) Quality assurance principles b) Sampling and sample preparation c) Personnel aspects d) Statistics for quality control e Use of reference materials and f) Equipment and records maintenance g) Audits and accreditation. traceability Course 6 (AM) Sample Presentation for ICPS Dr C McLeod Sheffield Hallam University UK The course is intended as a problem solving workshop and will attempt to rationalise the choice of sampling system for ICP spectrometries by use of practical examples. a) Nebulisation techniques Traditional and high efficiency The role of desolvation Hydride Other vapour techniques e . g . b) Vapour generation Hg oso c) Microsampling systems d) Flow injection e) Laser ablation1995 European Winter Conference on Plasma Spectrochemistry 8-13 January 1995 CAMBRIDGE UK Short Courses A series of short courses of one half day duration will take place on Sunday 8th January. Notes and tuition material will be distributed with each course.Courses 1 and 2 Short Courses on ICP-MS Professor R.S. Houk Ames Laboratory Iowa State University USA Course 1 (AM) Instrumentation and Theory The course will cover fundamental aspects of ICP-MS including:- a) Molecular beam sampling b) Quadrupole and high resolution c) Vacuum technology d) Ion sources e) Detection systems and data hand1 ing f) Sample introduction technologies analys ers Course 2 (PM) Advanced Topics The course will cover more advanced topics on ICP-MS particularly relevant to problem solving. Each topic will be illustrated with relevant applications examples.a) Interferences (spectroscopic and non-spectroscopic and methods of alleviation b) Isotopic analysis c) Chromatographic methods d) Overview of commercial instrumentation Course 3 (PM) Sample Preparation for ICPs Dr S.J. Haswell Hull University UK The course will focus on important aspects of sampling and sample preparation with particular emphasis on ICP measurements. a) Batch methods f o r wet oxidation b) Recent trends in microwave preparation for ICP-MS atomic spectrometry general analytical techniques c) On-line sample preparation d) Extraction methods e) On-line chemical processing f) Miniaturization Course 4 (PM) Speciation Professor O.X. Donard University of Bordeaux France The course will focus on practical aspects of speciation analysis with particular emphasis on ICP and other plasma sampling systems.Sample collection and handling preservation and preparation prior to injection into hyphenated systems using atomic spectrometry and ICP-AES or ICP-MS as detectors will be illustrated with applications from current topical fields . a) Sampling and sample pretreatment b) Separative techniques Differential chemistry Gas liquid ion and SCF c ) Interfacing chromatography techniques to ICPs and other plasma sources and detectors chromatographies Course 5 (AM) Quality Systems in the Laboratory Professor L. Ebdon Dr E.H. Evans University of Plymouth UK The course will discuss how high quality analytical data can be produced in the laboratory that are accurate reliable and adequate f o r the intended purpose. a) Quality assurance principles b) Sampling and sample preparation c) Personnel aspects d) Statistics for quality control e Use of reference materials and f) Equipment and records maintenance g) Audits and accreditation. traceability Course 6 (AM) Sample Presentation for ICPS Dr C McLeod Sheffield Hallam University UK The course is intended as a problem solving workshop and will attempt to rationalise the choice of sampling system for ICP spectrometries by use of practical examples. a) Nebulisation techniques Traditional and high efficiency The role of desolvation Hydride Other vapour techniques e . g . b) Vapour generation Hg oso c) Microsampling systems d) Flow injection e) Laser ablation

ISSN:0267-9477    

DOI:10.1039/JA99409FX041

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

42N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 Future Issues Will lnclude- Thermospray Nobulization as Sample Introduction for Inductively Coupled Plasma Mass Spectrometry-Hans Vanhoe Luc Moens Richard Dams On-line Flow Injection Cobalt- Ammonium Pyrrolidin-1-yldithioformate Coprecipitation for Preconcentration of Trace Amounts of Metals in Waters With Simultaneous Determination by Inductively Coupled Plasma Atomic Emission Spectrometry-Z.-x. Zhuang X.-r. Wang P.-y. Yang C.4 Yang B.4. Huang Interferences in the Determination of Lithium by Flame Atomic Emission Spectrometry With Platinum-loop Ato- mizer-Yuksel Ozdemir A. Ersin Kara- gozler Seref Gucer Evaluation and Validation of Instrumen- tal Procedures for the Determination of Nickel and Vanadium in Fuel Oils- M.Bettinelli Paolo Tittarelli Analysis of Aluminium Alloys Using Inductively Coupled F’lasma and Glow Discharge Mass Spectrometry-Gary Horlick X.-b. Feng Evaluation of Axially and Radially Viewed Inductively Coupled Plasma Using Echelle Spectrometer With Wavelength Modulation and Second Derivative Detection--Yoshisuke Naka- mura Cameron W. McLeod Katsuyuki Takahashi Osamu Kujirai Haruno Okochi Halocarbon-assisted Slurry Vaporization in Inductively Coupled Plasma Atomic Emission Spectrometry for the Analysis of Silicon Nitride Powder-Guyla Zaray Imre Varga Tibor Kantor Study of Analytical Performance of Low- powered Microwave Plasma Torch Atomic Emission Spectrometry-Q.-h. Jin H.-q. Zhang Y. Wang X . 4 Yuan W.-j. Yang Determination of Barium in Waters by Tungsten Coil Electrothermal Atomic Absorption Spectrometry-Marcia M.Silva Francisco J. Krug Joaquim A. Nobrega R.B. Silva H. Berndt Electrothermal Vaporization Inductively Coupled Plasma Atomic Emission Spec- trometric Technique Using a Tungsten- coil Furnace and Slurry Sampling- V. Krivan Peter BarthJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 Direct Solid Sample Analysis in a Mod- erate-power Argon Microwave Induced Plasma With the Spark Generation- Yong-Nam Pak S.R. Koirtyohann Flow Injection Preconcentration of Gol- d@) on Cellex T for Determination by Flame Atomic Absorption Spec- trometry-Krystyna Pyrzynska Triethanolamine as a Releasing Agent for Controlling Interferences in the Atomic Absorption Spectrometric Deter- mination of Gold and Its Use as a Collector for the Flotation of Gold- S.E.Ghazy M.A. Kabil M.A. Mostafa High-sensitivity Microwave-induced Plasma Mass Spectrometry for Trace Element Analysis-Yukio Okamoto Preconcentration of Beryllium on the Outer Membrane of Escherichia Coli and Pseudornonas Putida Prior to Deter- mination by Electrothermal Atomic Absorption Spectrometry-L.C. Robles A.J. Aller 43N Analysis of Trace Impurities in Organometallic Semiconductor-grade Reagents by Electrothermal Vaporiz- ation-Inductively Coupled Plasma Atomic Emission Spectrometry-Mark D. Argentine Antoaneta Krushevska Ramon M. Barnes Carbon-enhanced Inductively Coupled Plasma Mass Spectrometric Detection of Arsenic Selenium and Antimony and Its Application to Arsenic Speciation- Erik H. Larsen Stefan SturupJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL.9 Direct Solid Sample Analysis in a Mod- erate-power Argon Microwave Induced Plasma With the Spark Generation- Yong-Nam Pak S.R. Koirtyohann Flow Injection Preconcentration of Gol- d@) on Cellex T for Determination by Flame Atomic Absorption Spec- trometry-Krystyna Pyrzynska Triethanolamine as a Releasing Agent for Controlling Interferences in the Atomic Absorption Spectrometric Deter- mination of Gold and Its Use as a Collector for the Flotation of Gold- S.E. Ghazy M.A. Kabil M.A. Mostafa High-sensitivity Microwave-induced Plasma Mass Spectrometry for Trace Element Analysis-Yukio Okamoto Preconcentration of Beryllium on the Outer Membrane of Escherichia Coli and Pseudornonas Putida Prior to Deter- mination by Electrothermal Atomic Absorption Spectrometry-L.C. Robles A.J. Aller 43N Analysis of Trace Impurities in Organometallic Semiconductor-grade Reagents by Electrothermal Vaporiz- ation-Inductively Coupled Plasma Atomic Emission Spectrometry-Mark D. Argentine Antoaneta Krushevska Ramon M. Barnes Carbon-enhanced Inductively Coupled Plasma Mass Spectrometric Detection of Arsenic Selenium and Antimony and Its Application to Arsenic Speciation- Erik H. Larsen Stefan Sturup

ISSN:0267-9477    

DOI:10.1039/JA994090042N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

1995 European Winter Conference on Plasma Spectrochemistry 8-13 January 1995 CAMBRIDGE UK Short Courses A series of short courses of one half day duration will take place on Sunday 8th January. Notes and tuition material will be distributed with each course. Courses 1 and 2 Short Courses on ICP-MS Professor R.S. Houk Ames Laboratory Iowa State University USA Course 1 (AM) Instrumentation and Theory The course will cover fundamental aspects of ICP-MS including:- a) Molecular beam sampling b) Quadrupole and high resolution c) Vacuum technology d) Ion sources e) Detection systems and data hand1 ing f) Sample introduction technologies analys ers Course 2 (PM) Advanced Topics The course will cover more advanced topics on ICP-MS particularly relevant to problem solving. Each topic will be illustrated with relevant applications examples.a) Interferences (spectroscopic and non-spectroscopic and methods of alleviation b) Isotopic analysis c) Chromatographic methods d) Overview of commercial instrumentation Course 3 (PM) Sample Preparation for ICPs Dr S.J. Haswell Hull University UK The course will focus on important aspects of sampling and sample preparation with particular emphasis on ICP measurements. a) Batch methods f o r wet oxidation b) Recent trends in microwave preparation for ICP-MS atomic spectrometry general analytical techniques c) On-line sample preparation d) Extraction methods e) On-line chemical processing f) Miniaturization Course 4 (PM) Speciation Professor O.X. Donard University of Bordeaux France The course will focus on practical aspects of speciation analysis with particular emphasis on ICP and other plasma sampling systems.Sample collection and handling preservation and preparation prior to injection into hyphenated systems using atomic spectrometry and ICP-AES or ICP-MS as detectors will be illustrated with applications from current topical fields . a) Sampling and sample pretreatment b) Separative techniques Differential chemistry Gas liquid ion and SCF c ) Interfacing chromatography techniques to ICPs and other plasma sources and detectors chromatographies Course 5 (AM) Quality Systems in the Laboratory Professor L. Ebdon Dr E.H. Evans University of Plymouth UK The course will discuss how high quality analytical data can be produced in the laboratory that are accurate reliable and adequate f o r the intended purpose.a) Quality assurance principles b) Sampling and sample preparation c) Personnel aspects d) Statistics for quality control e Use of reference materials and f) Equipment and records maintenance g) Audits and accreditation. traceability Course 6 (AM) Sample Presentation for ICPS Dr C McLeod Sheffield Hallam University UK The course is intended as a problem solving workshop and will attempt to rationalise the choice of sampling system for ICP spectrometries by use of practical examples. a) Nebulisation techniques Traditional and high efficiency The role of desolvation Hydride Other vapour techniques e . g . b) Vapour generation Hg oso c) Microsampling systems d) Flow injection e) Laser ablation1995 European Winter Conference on Plasma Spectrochemistry 8-13 January 1995 CAMBRIDGE UK Short Courses A series of short courses of one half day duration will take place on Sunday 8th January. Notes and tuition material will be distributed with each course.Courses 1 and 2 Short Courses on ICP-MS Professor R.S. Houk Ames Laboratory Iowa State University USA Course 1 (AM) Instrumentation and Theory The course will cover fundamental aspects of ICP-MS including:- a) Molecular beam sampling b) Quadrupole and high resolution c) Vacuum technology d) Ion sources e) Detection systems and data hand1 ing f) Sample introduction technologies analys ers Course 2 (PM) Advanced Topics The course will cover more advanced topics on ICP-MS particularly relevant to problem solving. Each topic will be illustrated with relevant applications examples.a) Interferences (spectroscopic and non-spectroscopic and methods of alleviation b) Isotopic analysis c) Chromatographic methods d) Overview of commercial instrumentation Course 3 (PM) Sample Preparation for ICPs Dr S.J. Haswell Hull University UK The course will focus on important aspects of sampling and sample preparation with particular emphasis on ICP measurements. a) Batch methods f o r wet oxidation b) Recent trends in microwave preparation for ICP-MS atomic spectrometry general analytical techniques c) On-line sample preparation d) Extraction methods e) On-line chemical processing f) Miniaturization Course 4 (PM) Speciation Professor O.X. Donard University of Bordeaux France The course will focus on practical aspects of speciation analysis with particular emphasis on ICP and other plasma sampling systems.Sample collection and handling preservation and preparation prior to injection into hyphenated systems using atomic spectrometry and ICP-AES or ICP-MS as detectors will be illustrated with applications from current topical fields . a) Sampling and sample pretreatment b) Separative techniques Differential chemistry Gas liquid ion and SCF c ) Interfacing chromatography techniques to ICPs and other plasma sources and detectors chromatographies Course 5 (AM) Quality Systems in the Laboratory Professor L. Ebdon Dr E.H. Evans University of Plymouth UK The course will discuss how high quality analytical data can be produced in the laboratory that are accurate reliable and adequate f o r the intended purpose. a) Quality assurance principles b) Sampling and sample preparation c) Personnel aspects d) Statistics for quality control e Use of reference materials and f) Equipment and records maintenance g) Audits and accreditation. traceability Course 6 (AM) Sample Presentation for ICPS Dr C McLeod Sheffield Hallam University UK The course is intended as a problem solving workshop and will attempt to rationalise the choice of sampling system for ICP spectrometries by use of practical examples. a) Nebulisation techniques Traditional and high efficiency The role of desolvation Hydride Other vapour techniques e . g . b) Vapour generation Hg oso c) Microsampling systems d) Flow injection e) Laser ablation

ISSN:0267-9477    

DOI:10.1039/JA99409BX043

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 171R ATOMIC SPECTROMETRY UPDATE-ATOMIC EMISSION SPECTROMETRY Barry L. Sharp* Chemistry Department L ough boro ugh University o f Technology Lo ugh bo ro ugh L eices tershire UK LE77 3TU Simon Chenery Analytical Geochemistry Group British Geological Survey Keyworth Nottingham UK NE 12 5GG Raymond Jowitt British Steel Technical Teesside Laboratories P. 0. Box 7 7 Grangetown Middlesbrough Cleveland UK TS6 6UB Simon T. Sparkes and Andrew Fisher Department of Environmental Sciences University of Plymouth Drake Circus Plymouth Devon UK PL4 8AA Summary of Contents 1 Arcs Sparks Low-pressure Discharges and Lasers 1.1 Arcs 1.2. Sparks 1.3. Low-pressure Discharges 1.3.1. Glow discharge lamps 1.3.2. Hollow cathode discharges 1.3.3.Other sources 1.4. Lasers 2 Inductively Coupled Plasmas 2.1 Fundamental Studies 2.2. Sample Introduction 2.2.1. Nebulizers 2.2.2. Flow injection 2.2.3. Chromatography 2.2.4. Electrothermal vaporization 2.2.5. Solid sampling procedures 2.2.6. Chemical vapour generation 2.3.1. Torch and generator design 2.3.2. Spectrometers 2.3.3. Instrument control and chemometrics 2.3. Instrumentation 3 Microwave-induced Plasmas 3.1 Fundamental Studies 3.2. Instrumentation 3.3. Sample Introduction 3.3.1. Direct nebulization 3.3.2. Electrothermal vaporization 3.3.3. Chemical vapour generation 3.3.4. Direct analysis of solids 3.4.1. Instrumentation 3.4.2. Gas chromatography-microwave-induced plasma applications 3.4.3. Supercritical fluid chromatography 3.4. Chromatography 4 Direct Current Plasmas This review describes developments in all aspects of atomic emission spectrometry including fundamental processes and instrumentation reported in the Atomic Spectrometry Updates References in JAAS Volume 7 (93/1012-93/862) and Volume 8 (94/1-94/960).The full references names and addresses of authors can be readily found from the Atomic Spectrometry Update References in the relevant issues of JAAS. However as an additional service to readers an abbreviated form of each reference quoted (except those to Conference Proceedings) is given at the end of the review. The trend towards the use of array detectors for emission spectrometry both CCD and CID types noted last year has accelerated with the availability of commercial instrumentation. These have undoubtedly encouraged developments in chemometric techniques for spectral reduction and offer convenient means for spatial mapping of plasma character- istics. There is also evidence that axial viewing of plasmas is gaining in popularity perhaps as a response to the requirement to optimize light throughput for the echelle spectrometers that are usually used in conjunction with array detectors.172R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL.9 Laser ablation sample introduction is an active area of research with more use being made of UV lasers particularly excimer lasers with outputs down to 193 nm (ArF). Improvements in laser design have led to the introduction of field- based instrumentation for geochemical applications. Analyses based on the emission from individual particles produced by laser ablation have been described which complements the continuing work on the fate of individual aerosol droplets in plasmas.In contrast it appears that laser enhanced ionization spectrometry is likely to remain an area for research rather than routine application. Sample introduction always provides a large number of reports and it is interesting to note that the ultrasonic nebulizer is now accepted as a reliable means of improving detection limits at least for low matrix samples The thermospray which potentially offers similar performance has yet to make the transition to general acceptance. The coupling of chromatographic techniques to atomic spectrometric detectors is now well established and although attention has inevitably moved towards mass spectrometric detection the stubbornly mono-isotopic element As retains its attraction for optical spectrometry.1. ARCS SPARKS LOW PRESSURE DISCHARGES AND LASERS Two atomic emission reviews have been produced the first (93/1165) giving 127 refs. related to the use of plasmas as spectroscopic sources and the second (94/670) covering the development of AES in China from 1990 to 1992 citing 412 refs. 1.1. Arcs Fundamental aspects of plasmas have been reported in three papers diagnostics based on line profile measurements of self- reversed lines (93/4046); non-linear interference effects and the role of ion dynamics in the kinetic theory of Stark broadening (94/958); and aspects of signal treatment (93/4041). Chemical reactions in d.c.arc discharges have been reviewed by Hu et al. (93/2136) and the application of the sulfidation reaction to the direct determination of Bi Mo Pb Sn and W in geological samples reported by Liu (93/3 132). Halogen buffer (93/2170) was mixed with powdered rocks and minerals prior to introduction into an arc discharge and ZnCl (94/669) was added prior to ashing foamed plastic used for extraction of Au. Caesium chloride together with PdCl was used (94/850) to achieve 0.01 ppm detection limits for Co Cr Fe Mn and Ni in trimetallic anhydride. Palladium chloride was also used in the determination of impurities in high-temperature super- conducting materials (93/800). Graphite containing 10% NaCl has been used by Li and Zhou (93/616) in the determination of REE impurities in high-purity holmium oxide.Trace element determination in human hair after ashing (94/836) in zinc tungstate after mixing with C-BaO-CaCO at a ratio of 18 1 1 (93/619) and in sodium chloride (93/703) by ETV into an arc have been reported. Preconcentration by distilling off the matrix in the case of red phosphorus (93/736) and oil (93/475) and by sublimation onto a cold finger in the case of iodine (94/343) was used to obtain ppb level LODs for trace elements. The determination of trace levels of toxic elements in environmental samples (93/C1577) has illustrated the potential of a charge injection device (CID) as an alternative to photographic emulsion for the simultaneous measurement of spectral line and background intensities. Direct specimen excitation has been used by Severin et al. (93/2642) for the determination of Ce in low-alloy steel whereas Strasheim and Bohmer (93/1951) have studied the changes that occurred on the surface of ferrous samples prior to quasi- stationary conditions being established.1.2. Sparks Analytical implications of plasma dynamics in the high voltage spark discharge have been reported by Bye and Scheeline (93/C1394). The spatial and temporal dependence of analyte excitation in several analytical matrices were investigated and compared with earlier large bandpass echelle measurements. Pomeroy et al. (92/2055) used an Cchelle spectrometer with a CID array detector in conjunction with an expert system for the qualitative and quantitative analysis of steel and alu- minium.Water analysis has been carried out by Lucht and Salje (93/2689) using an HPLC system to inject sample at 20pl min-' into a spark plasma operating between copper electrodes the upper electrode being a heated copper plate to which a stainless-steel tube was soldered. The well established rotating disc electrode technique for wear metals in oils has been modified by Kauffman (93/2686) to enable the detection of particles > 45 pm. The sample was placed on the flat surface of the rotating-platform electrode ashed in a furnace at 400 "C for 30s and then inserted into the analysis chamber of the emission spectrometer. 1.3. Low Pressure Discharges 1.3.1. Glow discharge lamps The advantages and disadvantages of the use of GD as an analytical source for spectrometry have been reviewed by Harrison (92/4598) whilst a more specific review of 61 refs.discussing layer-by-layer analysis has been prepared by Drobysher (93/792). Fundamental mechanisms of excitation and ionization have been reported by Hess et al. (93/C1500) for both d.c. and pulsed GDs. Wagatsuma and Hirokawa (94/622) made obser- vations of singly ionized Cu emission lines in the visible wavelength region produced by an argon-helium GD plasma and Weston et al. (93/C1594) gave details of data acquisition and evaluation by a computer controlled Langmuir probe system. Spatial measurements were made by Kuraica et al. (93/1646) who reported radial distribution measurements of electron density and temperatures in the plane cathode GD whilst Rusnak and Vicek (94/874) studied the distributions of excited states of hydrogen and nitrogen in the cathode region of a G D used for the formation of nitride on the surface of steel.Temporal signal profiles of analytical species in modu- lated GD plasmas have been investigated by King and Pan (93/C1433 93/3433) using AES AAS and MS measurements which for argon atoms maximized within 2 ms following termination of the discharge power. Various aspects of gas compositions used in GDs have been reported. De la Cal et al. (93/3601) characterized a He-CH d.c. GD plasma and proposed a simplified kinetic model which accounted for all their observations. Chambers et al. (93/3437) investigated the role of gas dynamics in negative ion formation in a GD ionization source sampling from the atmosphere. The source was used in conjunction with MS.Mixtures of Ne Xe and halogens were used by Galaritskii (93/4093) to study excitation efficiency a mixture of 4.8 Torr (1 Torr = 133.322 Pa) Xe with 0.8 Torr C1 was found to produce the maximum UV radiation yield. Hieftje et al. (93/C1475) reported on a gas sampling GD for the quantification of element ratios among C C1 F and S in organic compounds quoting high excitation energy and low background as the features of GD which made it useful for this application. Ulgen et al. (93/3370) were not content with the levels of argon line background and obtained a 6- to 9-fold improvement in detection limits for sputtered species by using a pulsed supply of square wave form at 400JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL.9 173R and 700 V together with a lock-in amplifier. As Ar emissions predominate at the low voltage these intensities were factorized and used in background subtraction to obtain net analyte signals at the higher voltage. Four presentations relating to the r.$ GD source have been made by Marcus et al. (93/C1358 93/C1360 93/C1496 93/C3026). These dealt with the conflicts involved in the development of the source (93/C3026) figures of merit for r.f. GD-AES (93/C1496) plasma parameter effects on crater shapes in the r.f. GD (93/C1358) and sputtering characteristics of glasses and ceramics using the same source (93/C1350). The effects of parameters such as r.f. power gas pressure and sample thickness on the AE and mass spectra of sintered ceramics have been investigated (93/591 93/C1389) and alternative gases were evaluated by Caruso et al.(93/C1498). Heintz and Hieftje (93/C1499) reported on their recently started work on a magnetically enhanced rJ GD in which they compared the performance of two designs in relation to the basic source without a magnetic field. Reference was made to the prolific work of Sacks et al. who have produced two further papers (93/1945 93/3421) in which the effect of the addition of CF4 at a ratio of 1 1 with Ar on the sputtering behaviour of Ag Al As Cu and Zn was reported. It was also shown that the CF4 addition resulted in significant quenching of numerous spectral features at both high and low pressures. Harrison et al. (93/C1380 94/604) have also considered the GD as a reactive cell using AES and MS to study the presence of metal argides and the effects of reactive contaminants such as air and water vapour.Microwave boosted GDs have been used to provide improved sensitivity to compensate for the dilution effects of mixing non- conductors with a conductive matrix (93/C1480) and by Tomellini (93/3993) in the direct determination of trace elements in surface layers and bulk materials. Steers and Thorne (94/40) have used UV/VIS FT spectrometry to study the excitation of Cr and Fe spectra in a microwave-boosted GD source and their results emphasized that excitation tem- peratures deduced from data on a limited number of lines are meaningless. Gas-jet assisted GD-AAS has been used by Dean et al. (92/4624) and in Korea (93/3263) as a technique for the analysis of conducting samples by AAS.Subsequent work on plastics and ceramics (93/C1600 93/C1626) has also been reported by Dean’s group. Banks and Blades (93/1648) have investigated directed support gas flows for improved sampling efficiency but point out the disadvantage of reduced depth projiling resolution. Practical applications of quantitative depth profiling analysis by GD-AES have been described by Mitchell and Shirley (93/C1481) and a study of the influence of anode geometry on electric field distribution and crater profile using a GD has been made by Demeny et al. (93/1019). Glick and Hieftje (93/723) have embarked on a futuristic analytical scheme using an artificial neural network and multi- variate calibration of a GD for the classification of alloys.Atomic spectra for seven elements in 37 nickel-based and 15 iron- based alloys were acquired with a pho to-diode array spectrometer. A more traditional approach was used by Lundholm and Baltzer (93/3994) in the determination of N in steel by GD-AES. 1.3.2. Hollow cathode discharges The Memphis State University group have been most active with two papers (93/2211,94/634) and four conference presen- tations (93/C1359 93/C1363 93/C1364 93/C1447). Improved analytical precision was achieved by introduction of a current controlled switch (93/C1447) 93/2211) together with a mech- anically stable photometer (93/C1363) and optimization of sputtering prior to sample introduction (93/C1359). Temporal profiles of emission signals for pulse widths from 15 to 500 s for Al C Mo Nb Ti and stainless-steel microcavity HCs were also presented (93/C1364).Studies of the axial evolution of the negative glow in a HC discharge (94/634) using a vidicon video camera confirmed that the optimum pulse width for analytical AES was 7-11 p. A study of matrix eflects on REEs in HC discharges has been made by Mierzwa and Zyrnicki (93/2088) who used solutions of halides of the studied elements in association with calcium barium and strontium matrices. It was concluded that calcium should be removed from a sample prior to the determination of REE traces. You and Marcus (93/C1477) have developed a thermal concentric nebulizer for the intro- duction of volume-limited solutions and Papp (93/3660) reported on an electrothermal and/or HC combined spectro- scopic atomizer and/or radiation source for qualitative and quantitative elemental microanalysis.The excitation mechanism of metal vapour spectra in an HC has been studied by Chera et al. (93/3330). Klemp et al. (93/4036) have characterized a low-pressure HC device for element-selective GC detection and Jin et al. (93/3122) have used an HCL for the trace determination of sulfide and SO by vapour molecular absorption spectrometry. Wilson (94/673) has reported the merits of a boosted HC lamp as a source for AAS and Sansonetti et al. (93/4050) have produced an atlas of the spectrum of a Pt-Ne HC reference lamp. 1.3.3. Other sources Flame characteristics have been investigated by Pupysher et al. (93/3202) using a thermodynamic simulation of element atom- ization in air-C,H N20-C2H2 N,O-propane and air- methylacetylene flames.Temperatures and compositions were calculated for a wide range of fuel-oxidant ratios and equilib- rium concentrations of different forms of 58 elements were established. The ionization behaviour of the alkaline-earth metals in air-C2H and N,O-C,H2 flames was considered by Luecke (93/3967) and the spatial distribution of flame emission intensities reviewed by Sohma (93/4055). Flame emission has been proposed for the determination of Na in cement presented as a slurry (93/2123) and for La in REE concentrates by measurement of the La0 band at 441.8 nm (93/2728). Real-time production control information has been obtained by Wendt and Persson (94/835) from spectroscopic measurements of off-gas flame emissions enabling the desired Cu content of white metal to be achieved with an accuracy of +0.2% in the range 74-78%.In situ measurements were also made by Sorenson et al. (93/1937) in scattered light for the measurement of soot-cluster monomer particle radius and to count the number of monomers per cluster in a methane-oxygen flame. Charalampopoulos et al. (93/2711) further investigated light scattering from flame par- ticles with particular attention to the role of iron pentacarbonyl vapour additions. Calloway and Jones (93/C1450) have reported on the use of a flame as an emission source for AAS and Karanssias et al. (93/3391) used an oxygen-hydrogen flame to introduce slurries of marine sediment into an ICP. Systems for sample introduction into James were reported (93/C1621 93/1952,93/3659) as were flame photometric detec- tors for chromatography (94/858 94/860).Sturgeon et al. (92/2750 92/4642 93/C1473) have further characterized the FAPES technique dealing with the d.c. self- bias potential which develops in the asymmetric r.f. system (93/C1473) the influence of generator frequency (92/2750) and the excitation and detection of molecular species (92/4642). Two different geometries of a capacitively coupled r.J plasma source for use with furnace atomization have been charac- terized by Blades et al. (92/2753,93/542 93/C1356,93/C1553) Helium plasmas could be sustained over a much wider power range 5-150 W than argon plasmas. Gilchrist et al. (94/595) also used argon and helium plasmas in a capacitively coupled version of FAPES and found better sensitivity and S/N for Ag Au Cd Pb Sb Sn TI and Zn with argon.Riby and Harnly174R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 (93/C1474) characterized a helium plasma in hollow-anode FANES sustaining a plasma at pressures up to 900Torr although analytical results were only obtained at pressures up to 600Torr. The FANES technique was compared with ICP-MS for the analysis of laser-ablated biological material by Hoffmann et al. (93/C3034). Plasma characteristics involving a range of gases have been reported. Mehdi et al. (94/620) used optical emission to study an r.f. magnetron sputtering discharge at an argon pressure of 7-150 mTorr as did Ropcke et al. (94/594) to measure relative concentration distributions and energies of species in low- pressure argon discharges.Jones and Carnahan (93/1650) produced an explanation for non-metal ion emission behaviour in argon and helium discharges whilst Alekseer et al. (94/956) determined trace levels of Ne in helium. A neon plasma was investigated by Gavrilov (93/3656 93/4084) and a spectro- scopic study of the plasma produced through bombardment of Mg with Kr+ ions was carried out by Belyaer et al. (94/882). Plasmas involving common gases have also been examined. The temperature distribution in carbon dioxide plasma arc welding (94/809) IR spectroscopic detection of ions and free radicals in a hydrogen discharge plasma (94/916) and optical emission spectra excited by an r.f. oxygen plasma used to evaporate yttrium barium copper oxide have all been studied.Optical emission characteristics and measurements related to the study and control of processing by plasma deposition have been reviewed by Barney et al. (93/3471) and reported by Ishii et al. (93/3319) for titanium nitride films Pan et al. (93/3574) for sodium deposition Peignon et al. (93/3608) for ion etching of tungsten and Durrant et al. (93/3766) for fluorinated poly- mer films. A plasma gun source for the direct atomization of the most refractory materials has been characterized by Goldberg et al. (92/2393) and used in conjunction with pulsed and steady state microwave plasmas (93/C1391) and capacitively coupled r.f. plasmas (93/C1393). A microwave discharge was also used to produce the active nitrogen afterglow used by Yu et al.(93/3281 94/839 94/848) for the determination of Hg and Zn in water by metastable energy transfer emission Spectrometry. Sheeline et al. (92/2607 93/C1392) have again reported on their study of a theta-pinch discharge emission source covering various aspects of quantification. Spatial and temporal tem- perature studies of electrothermal chemical plasmas using atomic spectroscopy have been reported by the Army Ballistics Research Laboratory of the USA (94/921). Typical events involved the deposition of about 300 J of energy yielding temperatures from 10000 to 50000 K the latter being the result of shock wave heating of the supersonic exit flow from a polyethylene capillary. Emission spectra from a high-current line plasma have been reported for the first time (94/789).The formed-ferrite plasma source was driven by a 4.6 pF capacitor bank charged to 25 kV and spectra in the region 120-290 mm were measured. What applications could such a source be useful for? 1.4. Lasers The most significant review of the year was by Darke and Tyson (94/280). They have culled a wide spectrum of infor- mation from the literature on laser-solid interaction and its significance to analytical spectrometry. This review will provide a valuable source of information for several years to come. Thiem et al. (93/478 93/3779) have twice reviewed the use of lasers in atomic spectrometry during this update period once in detail (208 refs. in 93/478) and again with reference to recent advances (19 refs. in 93/3779). Majidi and Joseph (93/3514) reviewed the use of laser induced plasmas for spectroscopy (93 refs.) for a wide variety of applications both industrial and environmental concluding that the major advantage of the technique is its ability to readily sample solids.Sjoestroem and Mauchien (94/687) focused on trace element determination using spectroscopic techniques dependent on resonant absorp- tion of laser radiation by atoms. The 74 refs. provided a very useful bibliography for this specialized field. Other reviews were 9312666 and 94/825. The ready availability of excimer laser systems operating in the UV and array-based solid state detector systems is revol- utionizing direct LA-AES. The excimer laser seems to provide an excellent excitation source and the array detector systems allow simultaneous collection of background signals.Workers at the University of Massachusetts Lowell have continued their investigations into the potential of the ArF excimer laser for LA-AES. They demonstrated (93/3189) that when an ArF laser operated at 193nm was focused onto selected metal targets higher excitation temperatures and ion populations resulted compared with conventional plasmas. Quantitative emission measurements with respect to both space and time were reported (93/3297 93/3257). These studies suggested a confined plasma production with a peak emission after approximately 20 s and a lifetime of less than <lOOs. Simeonsson and Miziolek (93/2882) have also looked at the fundamental properties of the micro-plasma produced by an ArF laser in various carbon-based atmospheres (CO COz methanol and chloroform) and measured similar ionization/ excitation temperatures ( 15000-20000 K) and electron densi- ties ( 1017-1018 ~ m - ~ ) but different breakdown thresholds. The aim of the study was to provide a firm basis for laser microplasma-gas chromatography.Mauchien et al. (93/C 1564) used a 400 mJ XeCl laser with a time-gated multichannel spectrometer and a precise positioning device to produce an experimental apparatus that would maximize reproducibility . It was demonstrated with different aluminium alloys that there were no matrix effects a reproducibility of 1.3% at the 1OOOOpgg-' was possible and this is normally limited by sample heterogeneity. Excimer lasers are not just being used to sample solids. Ng et al. (93/3254) used an ArF excimer laser (193 nm wavelength) with LA-AES to analyse liquid aerosols produced by a conventional concentric nebulizer and spray chamber with an argon carrier gas flow rate of 0.51 min-'.Emission signals lasted for 35-50 ps after each laser pulse. The excitation temperature decreased from 3994 K at 1 ps to only 3607 K at 35 ps after the laser pulse. Detection limits for the nine elements determined varied between 0.3 g 8-l for Li and 20g 8-l for Sr. Nyga and Neu (94/906) developed a double- pulse LA-AES technique with an excimer laser for sampling liquids. They observed that ablated liquids normally produce broad and quenched spectral lines. However with the double pulse system the first pulse generated a cavitation bubble on the surface of the liquid providing a gaseous environment for the micro-plasma produced by the second pulse.The result was sharp atomic and ionic line atomic emission spectra. Uebbing et al. (93/2120) have also demonstrated a double pulse LA-AES system using a 1064 nm Nd:YAG to overcome some deficiencies of a single pulse system. The first pulse was fired at a solid producing a micro-plasma. A second more energetic laser was then fired into the microplasma parallel to and 1.5mm above the surface of the test material. Linear calibration graphs were then obtained for A1 and Mn in glass and steel and for Mg and Mn in glass copper and aluminium using internal standardization. The effect of the atmosphere on the spectroscopic conditions of an LA microplasma is also known to be important. Sdorra and Niemax (93/3125) as part of their continuing basic investigations into LA-AES studied the effects of pressure and composition of bufSer gases (air Ar He N and Ne) as well as laser energy on ablation crater diameter depth and mass loss.The variation in plasma tem- perature and relative electron densities with time were also measured for each gas at a fixed pressure and laser energy. It was demonstrated that Ar was the best buffer gas for elemental analysis of solid samples by LA-ICP-AES although Ne might have advantages in certain instances. Further to their work on buffer gases Sdorra et al. (93/3115) compared the determi-175R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 nation of A1 and Mn in steel and borax glass by LA-AES using a Nd YAG laser at both its fundamental IR frequency ( 1064 nm) and its frequency quadrupled into the UV (266 nm).Unexpectedly when using UV irradiation results were inferior to IR irradiation and the authors considered that the use of internal standards was not possible. They concluded that an additional atomization step was required before the UV system would be analytically useful. Vaskovskii et al. (94/881) investi- gated the effect of air pressure on the dynamic and optical characteristics of a micro-plasma produced by a CO laser. They also studied the morphology of the test material after ablation. Majidi and Joseph (93/C1556) evaluated the effect of various concentrations and pressures of a helium atmosphere on the emission spectra of a laser induced micro-plasma. The laser plasma excitation of electrothermally atomized species was compared for helium argon and nitrogen atmospheres.Lee et al. (93/3267 93/C1565) used air argon and helium atmospheres in the pressure range 10-760 Torr when observing the micro-plasma produced from a Cu target by their ArF excimer laser. Observations on reducing the atmospheric press- ure included a decrease in plasma size; an increase in atom line intensity; decrease in plasma temperature; and a movement of the maximum away from the test material surface for air and argon. In contrast Owens and Majidi (92/2752) investi- gated the effect of high pressure (up to 2300 Torr) Ar He and N2 on the A1 I1 emission at 281.6 nm. Ablation of A1 embedded in resin was performed with a Nd:YAG laser. Calibration graphs were not linear but the results were reproducible.An LOD of 17 pg g-' was obtained. A theoretical and experimen- tal investigation into the effect of atmosphere (He Ar and N,) and gas pressure (severalTorr to atmospheric) on micro- plasma initiation when using an IR laser at 10.6 pm was performed by Hermann et al. (93/3602). The plasma was studied by both space- and time-resolved AES. Theoretical predictions agreed reasonably well with experimental data if the vaporization-initiated plasma breakdown mechanism was used. An explanation of the influence of the atmospheric gas on the laser light to metal surface energy transfer was given. Keefer (94/920) used a modern digital signal image processing system to acquire spectral images of a micro-plasma produced by a 1.5 kW CW C02 laser in an Ar atmosphere.Using the measured temperature field the laser power absorption and thermal plasma emission could be calculated at any point in the plasma to provide a detailed understanding of the energy conversion process. Ultra-fast LA has been reviewed (27 refs.) by Von Linde (93/411 l) and Mehlman et al. (94/922) reported experimental results from the 'Table Top Terawatt' laser. Emission in the far UV range from laser irradiation of targets was recorded. Test materials were silicon wafers coated with A1 layers of variable thickness (10-500 nm). The laser energy penetration depths obtained for 1064 nm irradiation were 30-70 nm but only 25-40 nm at 532 nm. It is likely to be some time before systems of this kind are available generally. The use of LA to mobilize material for vapour deposition is of increasing interest particularly with reference to ceramic superconductors.Jiao et al. (94/843) used plasma emission spectra and time-of-flight (TOF) mass spectrometry to study laser evaporation and deposition of the YBa2Cu,0 - supercon- ductor. Fan et al. (93/3285) investigated laser-induced plasma emission spectra of YBa2Cu30 and observed component atoms singly and doubly charged ions as well as monoxide molecules. Mueller et al. (94/917) compared ablation of diamond-like carbon silicon and copper test materials using a pulse length of 30ns and 500 fs for a 248nm wavelength laser. Optical emission spectra indicated a higher contribution of C + ions rather than C2 and larger molecules for the shorter wavelength laser.Using the 30ns ablation cluster formation was quite obvious using TOF-MS and this coincided with the deposition of micrometre-sized particulates. There was no evidence for cluster formation using the shorter wavelength laser. Vega et al. (94/791) used an excimer laser to ablate a germanium target in an oxygen atmosphere at various pressures. The oxygen content of the deposited film increased to the full stoichiometric value (GeO,) at pressures higher than 5 x lop3 mbar (1 bar= lo5 Pa). Observation of the spectral emission showed no evidence of oxidized species even at high oxygen pressures and the authors concluded that the oxidizing reactions mainly take place at the substrate site. The applications of LA-AES have been very varied.Wisbrun et al. (94/915) investigated laser-induced breakdown spec- troscopy for the detection of heavy metals in environmental samples. Detection limits were usually below those needed for regulatory levels. This particular application required optimiz- ation of the experimental set-up to overcome matrix effects resulting from water and organic fibres as well as problems resulting from the mechanical properties of the test material and the particular distribution of the contaminants in the sample. Aguilera and Campos (93/3153) determined carbon in steel using time-resolved spectroscopy of a plasma produced by a focused Nd:YAG laser in a nitrogen atmosphere. They achieved good agreement with conventional techniques a precision of 1.6% and a detection limit of 65 pg g-I.Carlhoff and Kirchhoff (93/3990) reported on the use of LA-AES for the direct analysis of molten steel inside a converter with a fibre optic to take the light from the plasma to an optical multichannel analyser. The authors claimed the application of this method reduced consumable costs and improved steel quality. The more general application of this particular system to the detection of trace elements down to 10-100 pg g-' in matrices as diverse as steel rubber and rocks was described by Lorenzen et al. (93/2075). With the reduction in size of laser systems there is now a welcome move of LA-AES away from the laboratory and out into the field where speed of results outweighs the limitation of the technique in terms of absolute accuracy and precision.Hardjoutomo et al. (93/3320) designed and constructed a transversely excited atmospheric pressure (TEA) CO laser with a 180 mJ output energy and 50 ns pulse duration especially for jield-based laser microprobe spectrochemical analysis of geological test materials. The use of helium as an atmospheric gas improved the S/N ratio by reduction of the continuous spectrum of the plasma and minimum detectable concen- trations of 50 pg g-' for a Zn I line and 500 pg g-' for an F I1 line were demonstrated. Another field-based system has been devised by Cremers and Kane (93/C1558) for the determi- nation of lead in paint. Various Pb lines were investigated for possible spectral interferences and the 220.35 nm line chosen as optimal. This yielded a detection limit of 1% of Pb in paint corresponding to a surface density of 0.06 mg cmP2.Calibration was performed for between 1 and 11% Pb as normally found in Pb based paints. Sequential laser sampling allowed depth profiles of lead/no-lead layers to be built up. An unusual application of laser-induced breakdown was particle detection in liquids. Fujimori et al. (93/4054) applied this technique to polystyrene particles in water and were able to detect particles as small as 0.02 pm. They observed a change in laser breakdown threshold and plasma emission delay time with particle size and concluded that it should be possible to measure both the concentration and size of particles in fluids by the proposed method. Coupled techniques can sometimes be used to overcome specific difficulties in LA-AES.Majidi et al. (92/2384,93/C1563) coupled an electrothermal vaporization step with excitation from laser ablation and trace element detection by AES. Test solution (5 1) was deposited in the graphite furnace then dried ashed and atomized. At the start of the atomization cycle a pulsed Nd YAG laser was focused and fired along the axis of the furnace into the gas phase. The atomic emission spectra were collected through the dosing hole orthogonal to the laser light. Further work (93/3620) extended this to using a frequency doubled Nd YAG laser (532 nm) for excitation. Similar work176R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 has been carried out by Ridge and Crouch (93/C1562) but using a carbon rod atomizer rather than a graphite furnace.Goldberg et al. (93/C1561) built on their previous work using a theta pinch magnetic field to re-excite a laser-produced plasma for atomic emission studies. This time they used a higher frequency (120kHz) but a lower intensity (20 kG peak) magnetic field. The higher frequency induced current allowed the separation of emission due to the decaying laser plasma from emission due to the interaction of the pulsed magnetic field with the atom/ion cloud. This also allowed the probing of the ionic environment in the decaying plasma. Results on the effect of the atmosphere as well as temporal and spatial emission were presented. Laser enhanced ionization spectrometry remains a topic of research but has never achieved widespread acceptance. Turk (93/2209) compared single and double resonance LEI of phosphorus monoxide in an air-C2H2 flame for the determi- nation of phosphorus.Detection limits of 200 and 30 ng g-' of P were obtained by single and double resonance LEI. The sensitivity of the double resonance was four times that of the single. Axner and Rubinsztein-Dunlop (93/2878) evaluated two step LEI in flames and laser-induced fluorescence (LIF) in a graphite furnace for the determination of Cr in water. They achieved LODs of 1.4 and 0.3 ngml-'. The effect of large amounts of Na on the LEI was investigated. They concluded that detection limits were limited by contamination of the burner and graphite furnace. Yan et al. (93/676) discussed the interference of the OH radical on LEI spectrometry for some trace element determinations in an air-C2H2 flame.The deter- mination of Pb at 288.305 nm was given as an example proving to be a particular problem at low analyte concentration and when a fuel rich flame was operated. Axner et al. (93/2879) used LEI to investigate the lifetimes of atomic metastable states of Au in an air-C,H flame. From this they were able to map the local stoichiometric conditions of the flame. Lee et al. (94/9 19) have investigated resonant multi-photon ioniz- ation (REMPI) both theoretically and practically for the Hg atom. Ayala et al. (93/C1536) evaluated resonance line lasers (RLLs) as excitation sources for analytical spectrometry. Three metal halide RLLs were constructed and characterized GaT In1 and TII. The potential advantages of these sources included narrow line widths natural locking to an atomic transition and the irradiance and coherence of a laser.They investigated the fundamental figures of merit for such sources including spectral output and source lifetime. The application of RLLs was demonstrated for LEI and LIF with ngml-' LODs for both techniques being obtained. It might seem attractive to try LEI type experiments with the ICP. However Turk et al. (93/1954) have previously reported problems with background signals but have now attempted laser-induced ionization in a power-modulated ICP. Detection limits were improved but were still less than adequate. Resonance ionization either with detection by atomic or mass spectrometry has great potential by virtue of the selec- tivity of the excitation processes.But much fundamental data is needed to make this a practical analytical tool. The National Institute of Standards and Technology (NIST) USA has established a data service to provide fundamental information for resonance ionization spectrometry (RIS) and resonance ionization mass spectrometry (RIMS). This service includes atomic data appropriate resonance ionization schemes and operating details. Saloman (94/633) has published NIST's fourth data sheet for Ag Be In Li K Rb Ti and V which includes an update on Ni. Ray et al. (93/3310) scanned the spectral region 6150-670 nm using a dye-laser pumped by a Nd:YAG laser 176 resonances were observed for U. Most were assigned to three photon resonant-ionization processes but some resonances suggested that four photon processes were occuring. Sampling of a solid test material can be achieved directly by resonant laser ablation as used by Borthwick et al.(93/2590) to measure ppm levels of A1 in steel. This procedure was used to measure ion to neutral atom yields at low laser fluences. This group have also developed a novel ablation chamber (93/Ct614) where the laser light is transmitted directly onto the sample using short lengths of optical fibre. Devyatykh et al. (93/2601) determined Fe in high-purity aluminium fluor- ide by electrothermal vaporization in a graphite cell and three- step resonance ionization mass spectrometry. Theoretical absol- ute LODs of 4 x lo-'' pg were calculated. Katsuragawa et al. (93/3686) have developed a simple low cost pulsed atomizer for RIS of Mo enabling them to measure isotope shifts with a 200 g sample.Ma et al. (93/3788) used resonance ionization TOF-MS to determine Ru with a detection limit of 50 ppt 20 times better than using non-resonant schemes. Perhaps one of the most exotic concepts recently has been demonstrated by Matsuo et al. (93/2944). See also Gill et al. Spectrochem. Acta. Part B 1991,46,1227-1235. Sampling and ionization of a test material was performed using laser ablation behind a ring electrode. The singly charged ions produced are then confined using either hyperbolic and cylindrical electrodes for up to 20 min in a He buffer gas. Doubly charged ions were confined for several seconds while some ions like Nd+ and Ta' were highly reactive with background gaseous molecules. Once trapped the ions were studied using either a quadrupole mass spectrometry or laser-induced fluorescence spectrometry. 2.INDUCTIVELY COUPLED PLASMAS 2.1. Fundamental Studies Boumans as an early pioneer of ICP-AES was in an ideal position to view the developments and trends in plasma spectrometry over the last 40 years (94/590). This paper provides the reader with an ideal opportunity to put ICP-AES into past present and future context. More specifically Boumans (93/C1403) reviewed multi-element line selection from first principles discussing true LODs in spectral inter- ference situations and means for improving these and line selection. Also discussed were spectral simulations and auto- matic line selection by expert systems. The future was seen as real-time line selection using multiple lines measurements and the implementation of chemometric approaches.De Loos- Vollebregt and van Veen (93/C1402) have already gone some way to implementing Boumans' view of the future using Kalman filter based software for the determination of different elements in uranium tungsten and environmental test mate- rials. They concluded that this approach led to easier line selection and an improvement in LODs when spectral inter- ference caused problems. Simulation studies demonstrated that the Kalman filter could also have benefits for the new gener- ation of Cchelle spectrometers with charge coupled device (CCD) or photodiode array detectors. Miller-Ihli (93/2988) compared ICP-AES with ICP-MS ( 13 refs.) highlighting fea- tures and identifying their limitations.Scholze et al. (93/C3031) also compared the two techniques specifically for the determi- nation of certain elements in soils. They were particularly interested in the possibilities of solid sample introduction by slurry nebulization or laser ablation as alternatives to digestion and aqueous nebulization. In this period Miyazaki has twice reviewed (92/4404 30 refs. and 93/4060 8 ref.) the principles and characteristics of ICP-AES and its application to the determination of trace elements in water. The fundamental properties of the ICP continue to provide a rich area of investigation. Galley and Hieftje (94/581) pro- pounded the use of a new spatial reference point for analytical atomic and ionic emission measurements. Conventionally this has been the height above the top of the r.f.load coil always a dubious reference with the differences in torch box design,JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 177R however readily found in any system. They suggest that an ideal spatial reference point should have the following charac- teristics tracking of positional trends in the number density of atomic and ionic species or their emission; no influence on the spatial distribution of analyte emission; require no additional sample preparation or adulteration; and be simple to establish measure and track. The suggested reference point was the ‘bullet’ shaped emission pattern from the OH bandhead at 306nm. It has the advantage over the addition of other elements in that it is always present it moves position with changes in power but tracks both ionic and atomic emission.The addition of an EIE enhances its intensity again following atomic and ionic trends. It should be possible to follow the ‘bullet’ in one dimension with some commercial equipment although it is suggested that a simple video camera combined with a narrow band emission filter should allow two- dimensional tracking. Marawi et al. (93/2057) directly com- pared plasma temperature measurements made from the N2+ rotational temperature method and the optical pyrometry method. The use of molecular gas ions such as N2+ or the OH radical as temperature probes has been common practice in the past. These workers followed the method of Strother et al. (Appl. Spectrosc. 1991 45 1031) making use of Planck’s radiation law with two-colour IR optical pyrometry to measure plasma temperature.The pyrolytic probe was placed 15 mm above the load coil and recorded temperatures of 1700-2200 K for r.f. powers ranging from 0.75-2.00 kW. The ICP tempera- ture was found to be linearly dependent on the forward power of the generator. Ogilvie et al. (93/3248 and 93/C1591) used a novel method to identify the mechanism by which ionic lines are excited. They noted that perturbations in atomic resonance line emission are caused by incompletely atomized droplets of solution and associated with these droplets are regions of elevated neutral atom density and depressed temperature. Therefore they were able to observe that (i) charge transfer excitation of ionic lines was only weakly dependent on tempera- ture and therefore positively correlated with atomic resonance line emission and (ii) electron impact excitation was strongly temperature dependent and showed a negative correlation.Rayson (93/C3002) investigated Penning ionization and charge transfer as possible mechanisms for the production of excess populations of excited analyte ions. Pulsed-laser excitation experiments demonstrated that Penning ionization is relatively unimportant whereas droplet-induced fluctuations as used above provided correlations between ground-state atom and excited-state ion populations. Travis et al. (93/C1388) have made preliminary studies on the precision and accuracy of the determination of spectral line wavelengths by ICP-FT spec- trometry. The aim of the work is to establish a suite of wavelengths in the ICP which are known to sufficient accuracy to be used for periodic re-calibration of the FT spectrometer and for calibration transfer to dispersive ICP atomic emission spectrometers. The effect of an introduced matrix on plasma properties has led to several detailed studies.Tripkovic et al. have investigated the influence of matrix elements easily ionizable (Li) and non- easily ionizable (Zn and Ba) on atomic emission both exper- imentally (94/297) and theoretically (94/298). Apparent exci- tation and ionization temperatures electron number density and LTE were measured and calculated. Results with and without the presence of the matrix were compared and it was found that the Li changed the ionization temperature. A theoreti- cal calculation procedure based on the minimization of free energy in the ICP was applied in the temperature range 1000-9000 K assuming chemical equilibrium and the influence of matrix elements (Li Ba and Zn) on the emission intensities of Ca and Cd was investigated.Karyakin and Simonova (93/3972) also investigated the influence of matrix elements on trace element emission both theoretically and experimentally. They concluded that the matrix affects not only plasma tempera- ture and electron density but also allows the collision of major element atoms with analyte atoms resulting in a lowering of analyte emission. Chomet (93/2630) studied the easily ionizable element matrix effect on both ICP-AES and ICP-MS using a wide range of matrix concentrations.The observable effect at low concentrations depended on plasma-generator impedance matching. Phenomena observed with both AES and MS detec- tion systems showed that the alkali element effect occurs during the uolatilization/atomization phase and resulted from a change in the plasmas thermal condition. Wu and Hieftje (93/C1590) tried to separate the influence of solvent and EIEs on matrix effects. Two dimensional CCD imaging spectrometry was employed to measure analyte emission intensity and excitation temperature with and without desolvation and EIE addition. These measurements have demonstrated the efficacy of desolv- ation in reducing the EIE interference. Sesi et al. (93/C1593) reported the effects of EIEs on the fundamental parameters of the ICP.Gas temperatures electron temperatures and electron number densities were measured by laser-light Thompson and Rayleigh scattering. Other work has included the simulation of ionization and excitation processes using the Monte Carlo method (93/C3050). Attempts to improve on conventional argon ICP-AES have taken many forms the simplest has been the use of mixed-gas plasmas. Wagatsuma and Kichinsuke (93/3357) observed an increase in the intensity of Zn emission lines in an Ar-He plasma. They concluded that this was the result of an increase in plasma temperature in the central channel only and that this resulted from the higher heat conductivity of helium. This mixed-gas pair has also been evaluated by Sheppard (93/3276). Du et al. (93/3163 and 93/4007) have used an air-Ar ICP to support the introduction of petroleum distillation residues dis- solved in xylene.It showed several advantages over an all Ar plasma including no carbon deposition a reduction in spectral interferences by molecular bands and better LODs. Heavy metals were detected in the samples using AES. Gomes et al. (93/2085) calculated the temperature of an air ICP by measur- ing the widths of a rotationally non-resolved band of the NO system at different plasma heights. In contrast Morgan et al. (93/3221) used an ICP with a Fourier transform infrared (FTIR) spectrometer to observe the near infrared (NIR) emission spectra of carbon and oxygen on the introduction of lower alcohols. A 4% addition of nitrogen to the plasma was found to enhance the resultant signals.Other approaches to improve performance have included that of Thompson et al. (93/2084) who investigated the use of a specialized time-resolued ICP atomic emission spectrometer. A fast multichannel analogue-to-digital converter allowed tran- sient signals (<1 ms) from several elements to be acquired simultaneously. This was used to study the signals arising from the injection of 1-5 pm solid particles produced either by LA or slurry nebulization. Work at the University of Massachusetts has continued on sealed ICP sources for AES (93/2045,93/2046 93/2047,93/3247). Experimental variables for the sealed system were optimized for As and P. Important parameters included plasma power gas mixture discharge container geometry and operating pressure (93/2045). Analysis of silane (93/2046) identified traces of Fe Ge Mg Sn Ti and Zr while arsine (93/2047) was analysed for C Fe Ge Mg Mo Ni Sn and V impurities.Both static and flowing modes were compared with a conventional 40.68 MHz ICP discharge (93/3247). In the sealed system the white noise level was lower and the noise arising from the formation of vortices in a conventional plasma was absent. Borer and Hieftje (94/295 and 94/296) have evaluated a pressure-differential tandem plasma source for AES. The first stage was an ICP an effective atomizer because it has a high thermal mass and gas kinetic temperature while allowing rapid and versatile sample introduction. The second stage was a reduced pressure MIP. A reduced pressure dis- charge might be expected to be more homogeneous and less noisy.Unfortunately the system exhibited no improvement in178R JOURNAL O F ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 LODs over conventional ICP-AES but the authors were positive about future possibilities. 2.2. Sample Introduction 2.2.1. Nebulizers A considerable amount of work has been reported in this area during this review period. Chen (93/3336) has conducted a review (73 refs.) on the advances in sample introduction tech- niques for ICP-AES. The techniques included those for gas liquid solid and suspended samples. A discussion of some of the problems associated with each technique was also pre- sented. Jin et al. (93/614) reviewed liquid sampling into AES AAS and AFS (170 references). This paper included gas propelled nebulizers spray chambers desolvation arrange- ments micro-sample nebulization organic solvent sampling and liquid sample non-nebulization methodology. Recently the use of ultrasonic nebulizers (USNs) has increased considerably. This is presumably because of the availability of stable convenient commercial equipment that gives high- efficiency nebulization and thus improved LODs and sensi- tivity.This increase in sensitivity has been demonstrated by several workers (93/3794 93/2208 93/C1580 and 93/2042). Typical improvements in LODs and sensitivity were by 1 and 2 orders of magnitude respectively. Conflicting reports of the response times were made. For example in one paper it was reported to be 2-3 times longer than when using a cross-flow nebulizer (93/3794) but in another (93/2042) it was reported as being comparable to a pneumatic nebulizer. Long term stability has also been investigated by Shkolnik et al.(93/C1448). The factors governing the performance of a nebul- izer e.g. carrier gas flow rate or sample uptake rate have been optimized (93/862). Eleven analytes were determined in urine and LODs were 28 times better than those obtained using a Meinhard nebulizer. A paper that contradicts those that claim increased sensitivity for ultrasonic nebulization has been pro- duced by Brenner and Ehrlich (93/C1371). This lack of improvement was attributed to the detrimental effects of high concentrations of salts and major cations entering the plasma source. It was also suggested that interferences by EIEs resulted in inaccurate results.In another paper Brenner et al. (93/2044) found that a USN used with a 40.67 MHz plasma generator gave 10-fold enhancements in LODs (down to the pg I-' level). The use of a Trassy-Mermet sheath gas assembly and a 0.3 mm injector tube allowed the analysis of saline waters. Memory effects were described as minimal and the analysis of CRMs gave accurate results. In a similar paper (94/599) geological materials were analysed for REEs. Various sample decomposition methods were attempted and it was found that the content of some of the analytes varied significantly in the final analysis solution depending on the method used. Aerosol transport eflects have been studied by Tarr et al. (93/721) who used laser-scattering particle size and vapour and aerosol mass transport measurements to characterize the performance of a USN.It was found that the aerosol generated had a broader droplet size distribution but also yielded a greater mass transport of solvent and analyte when compared with a pneumatic nebulizer. The same group has compared the transport effects in dribble and jet USNs (93/2043). Desolvation using a heated spray chamber followed by a condenser reduced solvent loading of the plasma but signifi- cant analyte losses in these regions were observed. The jet USN was found to show greater repeatability and better peak shape for FI measurements. The sensitivity of dry and wet aerosols has been studied by Weber et al. (93/808). Dry aerosols of Ag were produced by a spark discharge and transported by argon at 1.41 min-' to the plasma. Alternatively the dry aerosol was passed through a USN for mixing with dilute HNOJ to give a wet aerosol.The USN was also used to nebulize standard solutions of Ag. This meant that the effects of the nebulizer and the plasma on the signal could be separated. It was found that larger water droplets decreased the signal by 43%. Clifford et al. (93/1641) used dual-beam light scattering interferometry to measure particle size particle velocity distributions size-velocity corre- lation particle number density and volume flux of desolvated aerosols. Several acids and salts were passed through the USN and it was found that the mean diameter and volume flux increased as the acid or salt level rose. A comparison of a commercial and an inexpensive humidifier based USN was also made.Botto (93/3406) used a USN with a plasma formed from Ar and 02. Working conditions for water and for organic solvents were tabulated. The system was applied to the determination of tetraethyllead in aviation fuel. Limits of detection and enhancement factors were also given. A novel micro-flow USN that delivered solvent at rates of pl min-' has been described in a continuation of the work by Tarr et al. (94/693). The Sauter mean diameter of the aerosol generated was very low (2 pm) and the analyte transportation efficiency was close to 100%. Acceptable stability precision and reproducibility were observed and LODs with a flow rate of 10 pl min-l were comparable with those from a pneumatic nebulizer operating at 1 ml min-'. The device was considered to be readily transferable to ICP-MS and microwave instru- ments and would allow coupling with chromatographic techniques such as capillary electrophoresis.Thermospray nebulizers have again been studied by several groups of workers. This is because of their improved analyte transport S/N ratios and LODs. Veber et al. (93/3154) com- pared the matrix effects produced by a fused silica aperture thermospray with other nebulizer types. A calcium matrix provided a comparable amount of interference between the thermospray and the USN which in turn was more than for a pneumatic nebulizer. Conver et al. (93/C1379) used this nebulizer and found it to be highly stable and to have low background contamination. A simple therrnopneurnatic sample introduction system for ICP-AES has been developed by Krasil'shchik and Voropaev (94/763).The LODs obtained were 5-10 times lower in pure water and 2-5 times lower in natural waters when compared with conventional pneumatic nebulization. Precision was between 3 and 5%. Concentric nebulizers have again been studied extensively. The noise characteristics of a Meinhard nebulizer have been investigated by Pang et al. (93/2041). It was found that the primary source of the noise arose from the pump. The use of a pulse free pump (e.g. a double head reciprocating HPLC pump) allowed the discrete frequency noise to be eliminated. The use of an appropriate spray chamber also decreased the amount of noise. A Meinhard nebulizer has also been studied by Tan et al. (93/C1413). Parameters such as the flow rates sample uptake rates and geometry of the nebulizer were all studied.Decreasing the sample flow rate from 2.3 to 0.2ml min-' has been found to result in a 4-fold increase in sensitivity if a Meinhard nebulizer was used (92/2560). It was also found that precision was improved 5-fold if natural aspiration uia a capillary was used rather than a peristaltic pump. Several other types of nebulizer have been investigated. A semi-demountable recirculating nebulizer that allowed 0.5 ml of solution to be nebulized continuously over a period of 4 minutes has been evaluated by Qin et al. (93/3289). The system was tested for parameters such as LODs precision and memory effects. A high efficiency high solids nebulizer has been reported by Meyer (93/C1418). It has been used to determine metals in a variety of matrices including organic solvents pharmaceutical preparations and urine. A comparison of performance with a conventional concentric nebulizer demonstrated that it gave improved LODs.Ilic et al. (93/834) used a cross-flow nebulizer to determine U in different organic solvents. The LODs for the U at the 385.958 nm line were 0.3 1.2 and 1.1 pgrn1-l in water xylene and kerosene respectively. Wear metals in lub- ricating oils have been determined by on-line dilution withJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 179R kerosene (92/4606). Using a V-groove nebulizer particle sizes of up to 10 pm could be tolerated. A V-groove nebulizer and a heated spray chamber have been used to determine metals in molten waxes (94/572).Standard additions was used as the method of calibration. The dynamic range was 0-1Opg g-l. Detection limits were 0.31 0.56 0.47 and 0.87 pg g-' for Cd Cu Fe and V respectively. Direct injection nebulizers (DINS) are still receiving attention. A DIN has been used by Wiederin and Pinkson to determine trace metals in H F samples (93/C1420). A volume of 20 p1 was necessary to provide a steady signal. The aerosol particle size distribution from a DIN has been measured by Wiederin and Houk (93/2119). Photographs and laser scattering data have shown that the DIN produced a finer aerosol with a narrower drop-size distribution than a conventional concentric nebulizer operating with the same flow rates. However the drops were larger than those emanating from a concentric nebulizer coupled with a Scott-type double-pass spray chamber.Shepherd et al. (93/C1453) have used a DIN to introduce volatile hydrocarbon samples into the plasma. It was found that this overcame the problem of excess solvent loading of the plasma giving different results compared with those involving calibration against non-volatile solutions. The effect of surfactants on the analytical performance of an ICP has been evaluated by Bertagnolli et al. (93/3193). Triton X-100 UltraWet 60L and BRIJ-35 were selected to be studied and the analytes of interest were Cu Fe and Mn. The three surfactants had similar effects on analyte transport (k it was improved) but it was found that the use of Triton X-100 led to plugging of the cross-flow nebulizer.Various acids (nitric hydrochloric and sulfuric) and 1 1 mixtures of them caused signal depression (93/3469). This was attributed to a difference in nebulization efficiency caused by a different viscosity surface tension and droplet size distribution. Pulse nebulization has been used to introduce micro-volume samples (93/C1620). Nebulization times of 0.02-10 s and volumes of 2-1000 pl were tested. The precision of the analytical measurements was claimed to be 0.02-0.05% and increased as volume decreased. Several papers comparing nebulizers have also been pro- duced. Droplet size measurements of various nebulizers have been made by Zarrin et al. (93/2411). Electrospray thermospray and pneumatic nebulizers were all studied to determine whether the liquid composition and flow rate had any effect on the droplet size.Browner et al. (93/3962) have used laser scattering on several different nebulizers to study the effect of analyte and solvent transport efficiencies on signal intensity. For most of the nebulizers tested there was a linear relationship between the analyte mass transport and the net intensity of the signal. Several theoretical papers on nebulizers have also been produced although most of them have been conference presen- tations. Monte Carlo techniques have been applied to the simulation of the generation the losses and size distribution of aerosols (93/C3048). These parameters have then been used to calculate the mass transfer rate which in turn allows optimization of the working conditions. Another model has been produced which described the effects of aerosol particle size on discrete sample introduction (93/C1528).The effects of organic solvents on signal intensity in ICP-AES have been discussed by Xin (93/C3071). It was found that increased nebulization efficiency led to increased signal and that this increased efficiency was a function of viscosity density and surface tension of the solvent. Bochert and Dannecker (94/854) have used ICP-AES to analyse single aerosol particles in monodisperse test aerosols. High precision (geometric standard deviation 1.02) LODs in the femtogram range and linear calibrations for particles in the 1-10pm range were all obtained. Spray chambers and desolvation devices have been studied more in this review period than they have for some time.Wu and Hieftje (93/3424) have developed a new spray chamber for ICP spectrometry that produced a 30 YO increase in sample utilization efficiency and 2-3 times less sample clean-out time at half the cost of a conventional Scott type double-pass spray chamber. In addition it also improved S/B ratios LODs and precision. Another spray chamber has been developed by Gregoire et a!. (93/1067). This was a modified Scott type that allowed change from simple liquid nebulization to electro- thermal vaporization or LA without the need for plasma shut-down. Losses due to condensation on curved or irregular surfaces were minimized because of the straight-line gas flow geometry. 2.2.2. Flow injection As ever there have been a number of reviews of this popular method of sample introduction. A literature survey of on-line preconcentration techniques containing 82 refs.has been made by Carbonell et al. (93/771). Liquid-liquid extraction column methods and precipitation were discussed. Tyson continues to produce reviews in this area (93/861 379 refs.) and in another paper he discussed recent and future developments for improving precision and accuracy (93/273 1). The use of micro-columns of ion-exchange or chelation media is still proving popular as a means of preconcentrating analytes prior to their determination. Schramel et al. (93/3114) used a commercial preconcentration system with EDTA-cellulose as a packing to preconcentrate Cr Cu Fe Mn Ni V and Zn in biological and environmental materials. Detection limits were improved by at least 7-fold compared with continuous nebuliz- ation.Precision was typically 0.5-1.5% RSD. Caroli et al. (92/2515) used iminodiacetic acid-ethylcellulose micro- columns to preconcentrate Cd Co Cu and Pb from waters and urine. An acetate buffer (pH 5.5; 2 mol 1-') was used to retain the analytes on the column and nitric acid (2 mol 1-l) was used to elute them. Detection limits were improved by at least an order of magnitude for Cd and Pb. Throughput was 10-12 samples h -I. 8-Hydroxyquinoline (oxine) or its deriva- tives has also been used. Schramel et al. (94/736) used oxine- cellulose to preconcentrate 11 analytes (Al Cd Co Cr Cu Fe Mn Ni Pb V and Zn). Parameters such as the pH of the mobile phase and the concentration of acid eluent were optim- ized. The effects of potential interferences were examined and CRMs analysed.The majority of results were satisfactory and possible reasons for the exceptions (Cr and Fe) were given. Peng et al. (93/C3074) used oxine loaded on a mixture of activated carbon and silica gel to preconcentrate Al Cd Cu Fe and Mn and separate them from potentially interfering matrix ions. A desolvation system was also used to further increase the sensitivity. The LODs were at the ngml-' level and precision (n=6) was in the range 2.6-4.3% RSD for a 120 p1 injection. Anion exchange micro-columns have also been used. Israel et al. (94/569) used an automated ion-exchange device to separate trace constituents from matrix alkali metal salts. Arsenic Cr Mo S and Se have been preconcentrated on 'resin DZ96) by Liu et al.(94/721). The paper described an FI system and optimized the working parameters. Sample throughput was 14 h-' and LODs were 13.0 3.64 2.04 6.19 and 25.2 ng ml-' for As Cr Mo S and Se respectively. Basic alumina has been used by Yamada et a!. (93/1012) to enrich S (as sulfate) from iron samples and separate it from the matrix. Interferences were evaluated and CRMs analysed. The LOD was 0.3 pg of sulfur per gram of iron. Gomez and McLeod (94/568) enriched Au on columns of sulfydryl cotton with KCN as eluent and on Amberlyst A26 resin with NH as eluent. For a sample volume of 10 ml and an eluent volume of 250 pl preconcentration factors of 50 and 40 were obtained on the sulfydryl cotton and Amberlyst respectively. The LOD was 1 pg 1-' for both columns and the precision at the 50 pg I-' level was 1.2-3.5%.As an application Au in waste water was determined. Gold has also been preconcentrated by Guo and Tang (93/C3060). These authors used 'Levextrel' resin180R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 and an eluent of 2.5% thiourea. A 20-fold enhancement factor was achieved with a sampling frequency of 60 h-'. Preconcentration of mercury using complexation of the metal ion with 1,5 bis (di-2-pyridy1)methylene thiocarbonohydrazide followed by on-line extraction into IBMK has been reported by Canada-Rudner et al. (94/579). Vapour generation of the preconcentrated mercury was achieved by mixing with SnC1 in DMF. Potential interferences were evaluated and optimum conditions described.The LOD was 2 ng ml-' the calibration was linear between 10 ng ml-' and 5 pg ml-' and the precision was 3.3% RSD. One of the more novel methods of analyte preconcentration prior to atomic spectrometric determination has been devel- oped by Pretty and Caruso (93/3222). These workers used on- line anodic stripping voltammetry to preconcentrate Pb and T1 by factors of over 60. The technique was reported as being rapid and gave acceptable precision. Electrochemical preconcen- tration has been described by Deng et al. (93/C3055). Analytes were deposited on a mercury plated glassy carbon electrode in a flow-through cell and then released for detection by electro- lytic dissolution. Electrolytic dissolution has also been used by the same group of workers for the multi-element analysis of aluminium alloys (92/2762).The electrolyte used was 1 moll-' HN03 and the electrolysis was at 1150 mA cm- for 20s. Chromium Cu Fe Mg Mn Si and Zn were the analytes determined. Results for the analysis of CRMs agreed well with the certified values. Donnan dialysis has continued to be used by some workers (93/3438 and 93/C1421). This technique has provided precon- centration factors of over 200 for an 8 min dialysis period allowing p1 I-' levels to be determined. Detection limits may be improved further if the dialysis time the final solution temperature and the length of the cation-exchange tubing are increased. Dilution by dialysis has been used to determine Ca K Mg and Na in wines (92/2645). The linear ranges for the method (in pg ml-') were 7-120 for Ca 9-1500 for K 3-180 for Mg and 5-300 for Na.Sampling rates were 120-150 h-' and precision was less than 4% RSD. On-line digestion has again been studied by some workers (94/578). In a continuation of previous work slurried samples were transported to a microwave oven nitric acid added and the system sealed prior to exposure to microwave radiation for 5 min. The sample was then diluted to volume and analysed. Analysis of CRMs yielded good recoveries for all samples except coal. This was attributed to incomplete dissolution. On-line dilutions have been made using computer-controlled hardware to analyse minor constituents of nitric acid-per- chloric acid digestions of plant materials (93/2051). In addition standard additions analyses were also achieved by merging the sample zone with an aliquot delivered from a trapped standard zone.Analysis of plant RMs gave results in agreement with the certificate values. Hill's group determined impurities in organometallic com- pounds such as trimethylgallium and methyllithium by FI-ICP-MS and AES (93/2056). The sample (10-25 pl) was injected into 2% HNO desolvated using a membrane drier tube and admitted to the plasma. Recoveries for Al Cu In Pb and Zn ranged from 92.6 to 107.6%. The effect of matrix acid on the determination of transition metals by FI-ICP- AES was evaluated by Chen et al. (93/3555). Emission sensi- tivity was reduced by the presence of some of the acids (HCl HNO and H2S04) and by some metals (Ca Fe Na and Zn) but electron number density and excitation temperature were unaffected.A micro-computer controlled refractor plate has been used to improve background correction FI transient signals (93/1961). 2.2.3. Chromatography The coupling of chromatographic techniques with ICP-AES has been discussed in general reviews by Chan (92/4590) (68 refs.) and by Hill et al. (93/3219) (127 refs.). Jinno (93/3406) has reviewed the coupling of SFC to ICP-AES (35 refs.). Compared with previous years there have been fewer publi- cations possibly because for speciation work the development effort is concentrating upon ICP-MS. Reports concerning element speciation for this review period focus upon As and were typically based upon the HPLC separation of the species followed by HG (94/483 94/596). Detection limits for As"' AsV monomethylarsonic acid and dimethylarsinic acid were quoted at the sub ng ml-' level.Unfortunately conventional HG is not appropriate for import- ant arsenic species such as arsenobetaine which do not reduce to a volatile form. Rubis et al. (93/C3035) have described the preliminary development of a UV photolysis method for the degradation of arsenobetaine and arsenocholine which may provide a relatively straightforward adaptation of these methods for these compounds. Ion chromatography has been used to separate impurities from molybdenum and tungsten matrices (94/733) impurities in uranium oxide (93/3337) and for preconcentration of analyte elements in samples from biological matrices (93/2591) prior to determination by ICP-AES. 2.2.4. Electrothermal vaporization A review (131 refs.) of ETV into ICPs has been presented by Carey and Caruso (94/827).The advantages of the technique viz ( i ) separating the analytes from the matrix and (ii) removing the solvent which allows the plasma to use more energy for atomization ionization and excitation and (iii) the current state of the technology and possible future directions were all discussed. The use of chemical modifiers to assist in the volatilization of analytes is still proving to be a popular technique. The most popular of the modifiers still appears to be fluorinating agents such as polytetrafluoroethylene. A slurry of this modifier has continued to be used by Bin et al. (93/C3073) to assist in the vaporization of refractory analytes such as Nb Ta U and Zr. Calibrations covered 3 orders of magnitude no memory effects were observed and absolute LODs were 50 90 150 and 16 pg for Nb Ta U and Zr respectively.The same workers have presented a paper that employed a similar technique for determining Ti and V in coal (93/3533). The LODs were 0.8 and 1.5 ngml-' and precision was 1.9 and 2.8% RSD for Ti and V respectively. The procedure was validated by the analysis of certified coal (NIST 1635). Jiang (93/C3068) has again used this technique to improve LODs reduce matrix effects and determine B Cr Mo Ti and V in environmental samples. Huang et al. (93/2240) used the same method to determine 16 REEs. Detection limits were 0.1 ng-1 pg. A number of different modifiers have been evaluated by Nickel et al. (93/3367) for the analysis of ceramic powders.The modifiers included different combinations of KF (C2F4)" Na2B407 BaCO Ba(NO& BaO AgC1 CoF and Pb(B03)2. Techniques such as electron microscopy and X-ray analysis were used to evaluate the efficiency of the modifiers. The mixed modifier BaO and CoF (1 1) helped to volatilize all the impurities. Tungsten vaporizers continue to be used. Okamoto et al. (93/3359) determined Cd and Pb in biological and environmen- tal samples using a modified commercial atomizer and diam- monium hydrogen phosphate as a chemical modifier. Detection limits were quoted as 0.28 and 2.8 ngml-' for Cd and Pb respectively. The calibrations for both elements were linear up to 10 pg ml-' and precision was <8% RSD. Mei et al. (93/3138) have used a tungsten coil atomizer to analyse rice digests for Co Cr Cu Fe Mg Mn and Ni.In another paper (93/3242) the authors use this technique to analyse rice for the same elements plus eight REEs. Detection limits for the REEs were 10-9-10-11 g which exceed those obtained byJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 181 R simple ETAAS and conventional ICP-AES. Precision was typically <6% RSD. Several papers have been published on the more theoretical or mechanistic aspects of ETV-ICP-AES. Verrept et al. (94/753) used Cd Cu and Pb to investigate several of the parameters that may potentially affect the results. Observation height was independent of the sample matrix but the matrix affected the optimal carrier gas flow rate greatly. The forward power did not influence the signal but the higher the power the more matrix loading was permissible.Transport efficiencies for pneu- matic nebulization liquid ETV and solid sampling ETV were also compared. Efficiency was found to be increased for the ETV techniques in comparison with nebulization but there was no difference between the two types of ETV. Byrne et al. (93/3231) have investigated the mechanism of sodium chloride interference on Mn determinations by ETV-ICP-MS. It was concluded that it was a vapour phase interference caused by the formation of MnC1 during atomization. The addition of ascorbic acid increased the volatility of the chloride and thus facilitated interference free determination of the Mn. The interest in ETV as a method of sample introduction means that modifications of old or the manufacture of new instrumentation is fairly common.Golloch et al. (93/3504) developed a vaporizer that had a maximum of 100 heating stages and could reach temperatures of up to 2800 K. Verrept et al. (93/C1367) have modified a commercial atomizer to transport the analytes to the ICP. They also optimized the operating parameters and analysed CRMs for Cd Cu and Pb. Ren and Salin (93/3407) have also modified a commercial vaporizer. By adding a sheath gas between the analyte flow and the wall of the tube analyte condensation decreased transport efficiency increased and matrix effects were reduced. With 10 pl sample injections LODs for Cd Cu Mn Pb and Zn were 1-6 ppb; precision was 3 to 6% RSD. The same workers have also discussed the relative merits of ETV-ICP- AES and described the determination of Pb in soils (93/C1406).The standard additions method of calibration for solid sampling ETV-ICP-AES has been described by Boonen et al. (94/580). Analysis of biological and environmental CRMs for Cd Cu and Pb yielded results in good agreement with the certified values. 2.2.5. Solid sampling procedures Interest in laser ablation solid sampling for ICP-AES continues to wane despite its increasing use as a sampling tool for ICP-MS. However reports have concentrated on using the advantages of laser ablation namely rapid analysis spatial resolution and the ability to sample materials that are difficult to dissolve. Moenke-Blankenburg (93/3713) provided a com- prehensive review (122 references) of laser ablation as a solid sampling mechanism for ICP-AES and ICP-MS.The same group (92/4628) also conducted a detailed comparison of the analysis of jiuorophosphate glasses by laser ablation-ICP- AES/MS conventional dissolution followed by ICP-AES and classical methods. They concluded that the accuracy and precision of the methods were comparable. Xu and Tian (93/C3065) studied the ablation of Zr in reference materials using three different laser systems. (i) A conventional pulsed Nd YAG using either free running or Q-switched mode. Problems were found with mineral zircon (ZrSiO,) which gave lower values for zirconium than chemically produced ZrO in a standard. Q-switched mode was observed to be more accurate and precise. (ii) A dual laser system with a CO laser fusing the sample with a flux followed by a pulsed Nd YAG laser for ablative sampling.Good results were obtained but some problems with deposits on the ICP torch were found. (iii) A Nd YAG laser with acousto-optic Q-switching. Compared with a conventional Q-switched laser the acousto-optic method produces a higher repetition rate (1-5 kHz to 1-20 Hz) lower pulse power (104-106 W) and a longer duration of pulse ( 10-4-10-7 to lo-' ns). The authors were confident that this system fulfilled all their requirements. Koskelo and Cremers (93/C1566) suggested that the major advantage of LA-ICP- AES analysis of metal particles on air-filters was one of speed and efficiency. The analysis of a complete 37 mm diameter filter in less than thirty seconds rather than over an hour for a conventional digestion and analysis could be very important for worker health and safety. Optimization of instrumentation detection limits precision and the use of carbon from the ablated filter medium as an internal standard were discussed. Thompson et al.(94/940) performed a geochemical reconnais- sance suruey of a mineralized area in NE Wales using a multi- elemental data set produced by the LA-ICP-AES analysis of stream-sediment pebble coatings. These manganese and iron oxide coatings are known to provide a natural preconcentration mechanism for both base metals and pathfinder elements. The survey revealed anomalous concentrations of As Cd Co Cu Mo Pb and Zn delineating the copper mineralized Coed-y- Brenin diorite and Dolgellau gold belt. Problems associated with LA include finding suitable solid standards and matrix effects associated with the LA process.Mochizuki et al. (93/706) used a novelfour tube ICP torch so as to introduce both laser-ablated solids and nebulized solu- tions for calibration purposes into the same bulk plasma environment. Water was aspirated while the laser-ablated material was introduced. Differences in transport efficiency were compensated for by internal standardization to a matrix element. Selective vaporization was minimized by using a Q-switched laser with a high peak power. The method was applied to low-alloy steel reference materials and also aluminium- and titanium-based alloys. Chan et al. (93/1948) observed matrix effects when laser ablating high temperature superconductors such as Bi-Sr-Ca-Cu-0.Both KrF excimer picosecond and Nd-YAG nanosecond lasers with ICP-AES photodiode array detection were used. There was an enrichment of volatile Bi,03 and CuO in the vapour phase but melted droplets and the ablation crater showed enrichment of Ca and Sr. Thompson et al. (93/C1602) commented on the particles produced by LA and the matrix effects possibly arising from production of particles with a different composi- tion to that of the bulk or with more than one composition. Observations were made using time resolved-ICP-AES and electron microscopy. Fewer reports on slurry nebulization have been noted with work concentrating on improving performance and overcom- ing problems. Sample preparation of solids is vitally important to quantitative elemental determinations by slurry nebuliz- ation-ICP-AES.Halicz et al. (94/570) addressed this problem by employing a 3-dimensional turbulent mixer mill with the popular zirconia bead and bottle method to produce micron and sub-micron particles of geological test materials. Using a V-groove type nebulizer and a Trassy-Mermet type torch system major and trace elements were determined using aqueous standards. In some cases incomplete recoveries were observed and factors were calculated to correct for this. Alternatively matrix-matched geological RMs were used to overcome this. There has been much interest recently for all forms of argon ICP in the addition of molecular gases to improve performance. Ebdon and Goodall (93/2086) used hydrogen to aid volatilization of solid particles introduced by slurry nebulization and they observed an improvement in accuracy which corresponded to an elimination of interferences when analysing highly refractory particles.The increase in temperature from 2200 to 3900K was attributed to an increased energy transfer from the toroidaI to the annular region of the plasma. This was considered to be a consequence of the higher thermal conductivity of hydrogen. Lobinski et al. (93/773) demonstrated the analysis of refractory ZrO,. Calibration was performed by standard additions with detection limits between 0.03 to 10 pg g-' obtained for 11 elements. Results were shown182R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 to be comparable with those produced by digestion if the particle size was kept below 10 pm.Coedo et al. (94/598) continuing from work reported last year compared the determination of boron in reference steels by spark ablation sampling with microwave digestion followed by pneumatic nebulization. Both methods were optimized for the analyte and matrix accuracy. was satisfactory for both methods but spark ablation proved superior in terms of precision (0.5-1% RSD compared with 1-3.5% RSD) and detection limit (0.65 pg 8-l compared with 2.6 pg g-I). Uchida (94/700) used r.f. sputtering to solid sample doped lead zircon- ate titanates. The material was sputtered onto a quartz plate then dissolved off using mineral acids. Analytical results agreed well with original target composition and the precision was better than 8% for trace elements. Blain and Salin (93/540) using a simpler approach directly introduced pellets of sediment reference material mixed with graphite in a 1 5 ratio into an ICP-AES instrument.This technique gave sharp intense peaks for many environmentally sensitive elements including As Cd Hg Pb Se and Sn. Vaporization of refractory elements was facilitated by addition of a AgCl matrix modifier. The authors further explored the use of this matrix modifier (93/3249) with standard additions being used for calibration. Metal oxide powders were found to be suitable for spiking for Co Cr Ni and V. Accuracy and reproducibility were adequate for trace element analysis but less suitable for high concentrations. Fujimoto et al. (93/3197) investigated the use of a directly inserted thin stemmed graphite cup.The system was designed with a low thermal capacity and a high thermal conductivity for the analysis of trace elements in organic and aluminium nitride matrices. Calibration curves were obtained using aqueous solutions. To improve the sensitivity of refractory or carbide-forming elements the halogenating agents freon or hydrochloric acid were added to the carrier gas. Suganuma et al. (94/908) used a similar system to analyse micro amounts of a glass for Na. Developments in other solid sampling techniques have included a high-energy plasma gun that operates in a low- volume chamber and allows rapid transport of ablated material to an ICP-AES instrument. The transport properties of this system were investigated by McKinstry and Goldberg (93/C1417) and some initial quantitative determinations on refractory reference materials made.Wang and Jia (92/2965) devised a thermo-chemical distillation method for treating solid pulverized river sediment with a flux/reactant and transporting the resulting vapours to an ICP-AES intstrument. Detec- tion limits at the ppt level were claimed for environmentally sensitive elements such as As Cd and T1. 2.2.6. Chemical vapour generation A critical review of hydride generation (134 references) focus- ing upon As and Se has been published (93/641). Sahayam et al. (94/621) have described a modified sample introduction system for hydride generation using a co-axial jet that gave a modest improvement in signal intensities for Bi. A generally accepted convention for hydride generation is that because of the differing chemistries for production of the volatile species it is normally a single element technique.The development of simultaneous techniques for the determination of hydride forming elements has been described by various workers (92/2644 93/686 93/689 93/C3067 94/300). In all of these studies attention was paid to interferences. The most active group in this field that of Sanz-Medel at Oviedo have published some interesting work using a didodecyldimethyl ammonium bromide medium. Methods were developed for As (94/325) where tolerance to interferences was improved and for Cd (94/602) using a sodium tetrahydroborate reduction. Using this approach the authors demonstrated a modest improvement in the LOD to 1 ngml-l. Other work published by this group has included the determination of Pb using a continuous-flow potassium dichromate-lactic acid system (94/597) that gave an LOD of 2 ng m1-l.Other reports concerning vapour generation included the determination of As in hair (93/3262) the determination of Ge in groundwater (93/3128) and the determination of Se ( 94/8 1 ). 2.3. Instrumentation 2.3.1. Torch and generator design There has been a slight increase in the number of papers being published in this area. A review ( 5 refs.) on ICP-AES instrumen- tation has been presented by Steiner (93/3216). Topics included were user objectives instrumentation design criteria echelle spectrometers noise studies instrument performance and sample introduction. A linear flow torch (UFT) has been evaluated by Sesi et al.(94/279). The operating conditions were simplex optimized and the torch was then compared with a conventional tangen- tial flow torch. The data obtained from the LiFT were found to be more precise have better long term stability and the torch consumed less gas and gave rise to less noise and background molecular band emission than the conventional torch. Detection limits for the two torches were comparable. Another LiFT has been described by Rayson and Shen (93/1957). The torch operated at reduced power levels and again used less argon than conventional torches. Additionally the new LiFT gave improved S/N ratios better detection limits and had a similar dynamic range but was slightly more susceptible to interferences due to calcium emission signals. Many of the torches seem to have been developed to cope more easily with the introduction of organic matrices.Lim et al. (93/3261) extended the torch and modified the injector. A cooling system enabled an improvement in S/B of 20-30% to be achieved. Detection limits in xylene were reported to be comparable to those obtained in aqueous solution although memory effects were problematic. A low-power air-argon plasma (50 50) was used with a 40.67 MHz generator by Tang et al. (93/3163). Molecular emissions arising from hydro- carbons (e.g. C2 and CN) were eliminated in such a plasma. Detection limits for some analytes in IBMK were measured and were found to be better for most atomic and some ionic lines when compared with those obtained from a pure argon ICP. The role of the auxiliary gas flow in organic sample introduction was found by Pan et al.(93/3390) to be far more significant than in aqueous nebulization. Changing the flow rate altered the distribution of the solvent loading which in turn changed the plasma excitation temperatures. A new demountable torch has been developed by Eames et al. (93/3191). It consisted of a PTFE base into which the outer and intermediate fused-silica tubes were shrink-fitted. The inner tube was co-axially aligned by means of a PTFE bush which had a three start helical U-shaped groove machined in its outer surface to increase gas swirl velocities. This had the effect of stabilizing the plasma. The silica inner tubes may readily be changed and there was an option to use alumina inserts to provide a torch that is resistant to HF.Ross et al. (92/1262) evaluated a 13 mrn torch using an ICP- mass spectrometer. The torch consumed substantially less argon than a conventional torch (9.35 1 min-’) and was found to produce sensitivities ionization temperatures oxide-ion ratios and doubly charged ratios similar to a conventional torch. Better precision was obtainable with the smaller plasma. Rayson and Shen (93/2114) have modified an ICP torch so that atomic absorption measurements could be made. A power- modulated source generated a plasma in a ‘see-through’ torch. An HCL was focused through the base of the discharge and a time-gated Boxcar averager was used for data aquisition. An end-on viewed ICP with a modified torch and optical system has been described by Yang and Nygaard (93/C3070).The i.d. of the central channel was increased to 3mm thus183R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 decreasing the sample gas velocity and increasing the analyte residence time in the observation zone. Ten-fold improvements in LODs were observed and substantially decreased chemical interferences by the alkali metals were observed. A torch that operated at very high temperature using a mixture of Ar and He has been developed by Romanosky et al. (94/913) to analyse fossil fuel process streams. The torch runs with a conventional annular flow coolant gas no auxiliary gas and the inner tube has been modified so that the nebulizer gas may be admitted at a temperature of 650°C. Multi-element detection was achieved by using several monochromators simultaneously.2.3.2. Spectrometers This has been a relatively quiet area in this review period with only 14 papers being produced. Computerized multichannel AES has been reviewed (36 refs) by Bilhorn et al. (93/4001). The characteristics of a commercial spectrometer with a charge injection device has been described in 2 papers (93/C1392 and 93/C3006). The detector was described as having similar detection limits sensitivities and linear ranges to a photomul- tiplier tube whilst having the capability of observing the background and analytical signals simultaneously. In addition the spectrum between 170 and 800 nm may be stored for later access. This will provide an invaluable aid to practising ana- lysts. In another paper (93/C1382) a CID was used as a detector for the comparison of argon and helium plasmas.The system was used in conjunction with Abel inversion to spatially map the plasmas at various forward powers gas flow rates and sample uptake rates. High quality images were produced because of the solid state stability and anti-blooming capability of the CID. A charge-coupled device (CCD) was used to facilitate real- time internal standardisation (94/593). Precision values of <0.1% RSD were obtained when a signal generated from a linear combination of signals coming from a multi-element line set was used as the reference signal for internal standardiz- ation. This spectrometer has recently become commercially available and it is likely that numerous papers will be produced in the near future.A laboratory produced photodiode array (PDA) spec- trometer has been characterized by Li et a!. (93/507) for a number of elements (Al Ba Co Cu Ga K Mn Na Pr Y and Zn). Limits of detection and some applications were assessed. In addition the PDA was used with an optical fibre probe to measure the spatial distribution of temperature in the ICP. A PDA in conjunction with an FT interferometer has been used by Clarke and Adams (93/3354) for simultaneous multi-element AES. The system was used to determine K Li and Na simultaneously at 13158 14925 and 16978 cm-I respectively in a propane-air flame. Calibrations were linear to 100ppm for each of the analytes and limits of detection were 0.2 1.0 and 1.6 ppm for K Li and Na respectively. An kchelle-based ICP spectrometer that employed twin nebulizers and spray chambers with a single torch has been described in two papers (93/3205 and 93/3460).This patented multiplexed tandem sample introduction system reduces 'dead time' and allowed the analysis of 42 samples h-l compared with 33 samples h-' for a conventional simultaneous spec- trometer. The system was reportedly extremely stable accurate and precise. Another Cchelle spectrometer has been described by Steiner (93/3216). The instrument performance noise characteristics various sample introduction methods and a sample desolvation system were all discussed. Combined ICP-MS and ICP-AES spectrometers have been described by Denton (93/C1398) and by Ayala et al. (93/C3011). In the latter paper the dynamic range of detection was extended and atom-ion equilibria were explored. The importance of wavelength positioning accuracy for multi-component analyses by ICP-AES has been described by Yang et al.(94/748). Serious errors in the estimated analyte concentration may occur if the monochromator does not position itself precisely. A theoretical approach to solving this problem was compared against experimental results. Verrept et al. (93/438) modified a commercial spectrometer by using a quartz refractor plate to measure background corrected transient signals. The computer controlled refractor plate performed scans over a small wavelength interval. The software then allowed background corrected peak areas to be calculated for electrothermal atomization and other methods that produce transient signals.The stability and the resolving power of the instrument were not impaired and the precision for Sr at 10 to 100 pg ml-' in waters was 1.2-0.3%. 2.3.3. Instrument control and chemometrics Chemometric methods for improving the resolution of spec- trometers has proved to be a popular topic in this review period with several papers being produced by Chinese workers. Zhang et al. (93/699 and 93/3286) have used a polynomial smoothing method to correct for interferences arising from severe overlapping of lines. The same authors have also used factor analysis to correct for spectral overlap (94/743). A data matrix was composed from a pure spectrum and a spectrum of the mixture. This data matrix was decomposed by target transformation factor analysis to a spectra matrix and a concentration matrix.The concentration of the component of interest in the mixture may then be obtained from the concen- tration matrix and the interference from the other component is eliminated. As an application the spectral interference exerted by Y on the determination of Cu and A1 was eliminated. Yang et al. (94/849) used Kalrnan Jiltering to resolve closely spaced lines. They found that the resolving power of the filter could be strengthened by decreasing the step size in the scans. Difference in the line profiles of the analyte ion and the interfering ions allowed the filter to resolve coincident lines more easily. The effects of wavelength positioning errors on the results obtained by Kalman filtering ICP-AES have been determined by Yang et al.(93/3422). It was found that a positioning accuracy of 0.1 pm was necessary to obtain accurate and precise measures of analyte concentration. In a related paper (93/3 166) the reliability of Kalman filtering results was evaluated using two methods the NAC criterion (which is based on auto-correlation analysis of the innovation sequence) and the innovation number. Both methods compensate for wavelength positioning errors but the NAC gives information on each individual result whereas the innovation number must have other data to perform the same task. Kalman filtering has also been used for several applications based papers. Brindle and Zheng (94/291) found an improvement in accuracy for the determination of transient signals produced by a computer-controlled hydride generator.The filter was used to remove the white noise and thus determine the signal under the noise even at a ratio of 1 :4. Thirty trace elements in uranium were determined without matrix separation because of Kalman filtering (93/3921). This would not have been possible in conventional ICP-AES. Ytterbium has been deter- mined in vanadium by Ma et al. (93/C3046). This was made possible by separating the V" 328.94 from the Yb" 328.94 line. Detection was by a photodiode array detector made in-house. Relative errors were found to be 1-3%. Errors in apparent analyte concentrations caused by wavelength positioning errors have also been investigated by the use of multi-component analysis (MCA) techniques (94/741). By assuming Gaussian line profiles a model was constructed and the results tested experimentally.In general good agreement between theoretical and experimental measurements was made. It was concluded that MCA techniques have no advantage over conventional correction methods unless they can bring about a reducion in the positioning error. Multivariate methods have also been reported by a few184R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 workers. For example Principal Components Analysis (PCA) has been used by Yates and Aries (93/C1425) to interpret multi-element analytical data. It was found that although standardization within the PCA was not required the use of standards in the data set checked the validity of the procedure. Ivaldi et al. (93/3165 and 93/C1400) used multivariate methods (the method of least squares) to enhance the information obtained from a CCD. The method of least squares smoothing has also been applied by Zhang et al. (93/431) to correct for the V 328.939 nm and Y 308.203 nm line interferences on the determination of Yb at 328.937nm and A1 at 308.215nm respectively.A comparison of Multiple Linear Regression (MLR) with a neural network has been made by Schierle and Otto (94/31). The network was trained from emission spectra from As and Cd and the concentration of both analytes were determined successfully in mixed spectra. It was concluded that close relations exist between the MLR procedure and the operation of the perceptron of the network. Otto et al. have also used a neural network in conjunction with the method of least squares to obtain qualitative determination of sixty-eight analytes (93/3112).The method yielded acceptable results although problems did occur when samples rich in tungsten were analysed. Nikdel (93/C 1374) applied a neural network named ANN (artificial neural network) to the analysis of orange juice. This network mimics the brain's problem solving process and builds a system that makes new decisions classifications and forecasts using pattern recognition and fuzzy logic. Neubock et al. (94/683) have also used fuzzy logic to achieve automated qualitative analysis. Background equivalent concentrations were used to calculate a Bayes' probability that measured the usefulness of a peak for identifying a certain element. Evaluation of the performance of the system showed it to function satisfactorily.Optimization procedures have again proved popular. A review with 4 references describing strategies for multi- parameter optimization has been presented by Noelte (93/3 104). A simplex-optimized program for the determination of temperatures in reduced pressure ICPs has been described by Turner and Fannin (93/3425). The results for several Ar-He reduced-pressure plasmas were tabulated. The optimization of analytical techniques for eliminating matrix effects has been studied by two groups of workers. Spectral interferences arising from Eu have been eliminated by Lu and Zou (93/C3072); while Sun and Zhang (93/C3051) have removed interferences caused by Al Ca Mg K Na and Zn. A program designed to facilitate optimization has been described by Borer et al.(93/1643). The algorithm enabled the net signal background S/B ratio S/B noise ratio precision of the background and precision of the signal to be calculated. Processing time was reduced and the optimization studies were easier and more informative. Several pieces of software have been developed that are designed to maximize analyte sensitivity improve precision and enhance the reliability of the determination in general. Lorber (93/C1399) achieved precision better than 5% RSD and eliminated spectral interferences using a chemometrics approach. Meanwhile Yan et a!. (93/C3054) developed some software that specialized in the detection and processing of multichannel transient signals arising from FI peaks. Huang et al. (94/668) analysed high-purity nitrogen trioxide by ICP- AES removing spectral interferences by an interference coefficient correction method.Recoveries of REEs were 85-115%. Ma et al. have also analysed a mixture of REEs using a computer spectrum stripping method (93/C3049). The method was described as simple rapid and capable of cor- recting for several types of background interference. A program designed to assist in the collection reduction and analysis of echelle spectra from a CCD has been developed by Miller and Scheeline (94/624). Wavelength calibration was better than 41 pixel across a 576x384 pixel array. A user friendly spectroscopic data system covering several techniques (e.g. IR NMR MS) has been described by Hearmon (94/638). It was based on a hierarchical network with high speed local networks and designed to accept data from a wide range of instruments.Webb and Salin (94/42) have developed a computer-assisted method for line selection. The system may be taught the composition of a sample and from this data decisions of which lines to use were made in less than one second. Instrument control procedures have been developed by several workers. A computer supported ICP-AES spectrometer was described by Bortlisz (93/3203). This instrument was capable of determining 33 analytes simultaneously. As an application the analysis of water waste water and water treatment sludges was undertaken. Drift diagnostics have been described by Carre et al. (93/2040). The behaviour of Ba" 455.403 Zn" 206.200 and Ar' 404.442 nm lines as a function of parameters such as power sample uptake rate and gas flow rate was measured.The most probable causes of drift were changes in energy transfer efficiency of sample introduction and surprisingly too long a warm up period. Recent improvements in the factors governing basic ICP stability have been discussed by Dahlquist et al. (93/C3010). These workers state that precision in older instru- ments (which was often at the 0.8% level) had different contribu- tory factors than modern instruments whose precision is 0.2% or better. The errors associated with calibration detection limits accuracy and sensitivity (quality control or quality assur- ance) have been investigated by several authors. The effect of parameters such as power observation height carrier gas flow rate and sample uptake rate on RSD was measured by Krasil'shchik et a!.(92/2561). In addition the dependence of calibration curve linearity and range and the errors of determi- nation were also investigated. The linearity of calibration curves has also been discussed by Miller (93/2705). He discussed the method of using the product moment correlation coefficient (r) the coefficient of determination (r2) and the coefficient of non- determination (1 -r2) for measuring linearity. The quality con- trol procedures used by the US Geological Survey National Water Quality Laboratory were described by Zayhowski and Bushly (93/C1427). As should be the norm calibration check standards blanks and standard reference water samples were run periodically. In addition blind quality control samples were also run.A collaborative study of ICP analysis has been reported by Ambrose and Jowitt (93/3997). In this paper the instrumental performance criteria were quoted and the compre- hensive evaluation system was described. The main source of error was the interlaboratory bias. Errors and detection limits have also been discussed from a theoretical and practical viewpoint by Prudnikov et al. (93/C1619). They investigated instrumental non-instrumental and systematic errors and esti- mated the instrumental and non-instrumental detection limits. The alloy was digested in HC1-H202 and an internal standard (La Sc or Y) added. The best internal standard was La. Analytes such as Dy Fe Mn and Tb were determined giving recoveries of 2 99.7% and precisions of between 0.04 and 0.35% for 5 replicates.The accuracy of wavelength tables has been commented on by Doidge and Nham (93/1958). In this paper several incon- sistencies in the wavelength value between different tables is highlighted. An informative 'tutorial review' on background and back- ground correction in emission spectrometry has been presented by Dawson et al. (93/3220). It includes the general principles of background correction source-generated background and its correction and instrument-generated background and its correction.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 3. MICROWAVE-INDUCED PLASMAS 185 R 3.1. Fundamental Studies Probably the most interesting paper published during this review period was that of Besner et al.(94/617) who have described the spatial distribution of excited species in an Ar surface wave plasma. These workers used tomographic recon- struction to create three dimensional distributions of the excited species in Ar Ar-0 Ar-H and Ar-N plasmas at frequencies of 27-2450 MHz and at pressures of 10-600 Torr. The work demonstrated that the radial distribution of excited atoms related to the radial distribution of the electric field the operating frequency and on the radial distribution of the electron number density. The relative influence of the electric field on excited atoms was found to be greater with increasing frequency whereas the influence upon the electron number density was less significant. It was indicated that future work would include studies of rotational temperatures excitation temperatures and electron number densities in order to model the plasma over this pressure range.Such measurements for a 2450 MHz Ar surface wave plasma at atmospheric pressure have been described by Cotrino et al. (93/2111). Spatially resolved studies of a low pressure He plasma have been described by Lei et al. (93/3284) and similar work is also being performed by Goode and Emily (93/C1555). Masamba and Winefordner (94/746) have determined excitation and rotational temperatures in a He/H CCP as a function of the concentration of H in the plasma. These authors also studied potential matrix effects caused by Na and PO,3- upon Ca emission. Boss and co-workers (93/C1387,93/C14417 93/C1551 93/C2998) have outlined their investigations of atomization and excitation mechanisms in MIPs used as chromatographic detectors. This work is particularly directed to the dissociation of hydrocarbon molecules in such devices and indicated that the typical power used to sustain a plasma is close to that required to decompose the components of a typical GC peak. Other reports included the effect of water on an He MIP (93/C1554) and the investigation of the 100-200 nm spectral region of an He MIP (93/C1552).3.2. Instrumentation Barnes et al. have evaluated a stripline source MIP and compared it against a Beenakker cavity MIP (93/2073). The stripline source was tolerant of aerosol sample introduction stable over a wide range of operating conditions and inter- ferences were less severe. Matusiewicz has described a novel combined generator/cavity (93/1649).The device was operated at 2450MHz and could use Ar He N 0 and air at atmospheric pressure. Notably this source was tolerant of up to 10 ml min-' of liquid sample in a flow of 1 1 min-' plasma support gas. The same author has also described a liquid cooled torch where erosion of the silica by the plasma was eliminated (94/745). Borer et al. (93/1953) have described a novel method for stabilizing an MIP power supply that resulted in a substantial reduction in the noise. Stabilization was achieved by adjusting the line voltage via a controllable inductance placed in series with the variable transformer at the generator input. 3.3. Sample Introduction 3.3.1. Direct nebulization Ultrasonic nebulizers have been used by several groups to introduce liquid samples into various MIP devices.Carnahan's group have studied the determination of C P and S in aqueous solution using their 1.6 kW He MIP (93/3392). Detection limits of 0.4 1.4 and 9.7 pg g-' respectively were reported. The group at Jilin University have reported the determination of P with an LOD of 0.03 pg g-' using an 80 W MIP in Ar or an LOD of 0.0045 pg g-' using He as the plasma gas (93/3279). The same group using a heating/condensing/desic- cating desolvation apparatus (94/724) achieved LODs of 0.23 pg g-' Br 0.12 pg g-' C1 and 0.06 pg g-' I (94/886). Not content with this work they have also investigated a pulsed ultrasonic nebulizer (93/3622). The nebulizer was turned off before the sample was introduced and then pulsed on.This reduced the sample volume and improved stability for samples containing high levels of dissolved solids. An evaluation of FI sample introduction for a 200 W Ar MIP has been prepared by Yolanda et al. (94/704). Ultrasonic nebulization was compared with pneumatic nebulization for a range of sample loop sizes. Using an ODS microcolumn pure ethanol as eluent and a 1 min preconcentration at 1 ml per minute the LOD for Cu in synthetic sea-water was 0.16 ng rn1-I. 3.3.2. Electrothermal vaporization In a continuation of work described above ETV has been compared with direct nebulization for sample introduction into a high power MIP (93/3393). Using emission lines in the near IR rather than the visible spectrum gave an LOD for S of 3 to 5 pg g-'. Matrix interferences from Na and K could be removed by temperature programming of the ETV device.Ali and Winefordner have described a tungsten filament vaporizer for sample introduction into a CCP (93/3146). Detection limits were 1-104 pg for a range of elements. Other reports concerned the determination of Cu Zn and Cd (94/107) and of Zn (93/3950). 3.3.3. Chemical vapour generation Bulska et al. have compared hydride generation for As Sb and Se using Ar and He plasmas operating in either a TMOlo resonator or a surfatron (94/702). Both systems were optimized using elemental Hg vapour and LODs were found to be lower using the surfatron device. The determination of mercury has been reported by Fukushi et al. (93/3465) with an LOD of 11 pg ml-' for inorganic Hg. Taketoshi and Wasa (93/3492) used a tin@) chloride reduction and an atmospheric pressure Ar plasma to achieve a 0.04 ng ml-' LOD for Hg in waste water.The continuousflow generation of halogens has been described by Camufia et al. (94/631). In a study of instrument design operating conditions and vapour generation chemistries methods for the determination of Br C1 and I were developed and the use of FIA investigated. The determination of Br in pharmaceutical materials has been described by Caldaza et al. (93/3083) using an atmospheric pressure Ar MIP surfatron and an LOD of 2pg g-' was achieved. Nakahara et al. (93/2122) have described the determination of I in sea-water with reduction to I- by ascorbic acid prior to oxidation to I using 1 mmol 1-' NaNO in 5 mmol 1-' H2S04.3.3.4. Direct analysis of solids In the percentage increase in publications for this review period this represents the most rapidly growing area of research using MIPs. Masamba et al. (93/3 190) have described an intriguing approach to the analysis of steel samples by direct insertion of a cylindrical sample into the inner tube of a two tube tangential torch installed in a CCP. Calibration was performed using NIST CRMs and LODs for Pb and Zn were 0.08 pg g-' and 5 pg g-' respectively. Ciocan et al. (93/3959 94/289) have described a laser ablation-MIP system using a low pressure Ar MIP. Applications described included the analysis of pure metals alloys glass and ceramics. Time resolved data were recovered and calibration was performed using reference materials.186R JOURNAL OF ANAL,YTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL.9 3.4. Chromatography 3.4.1. Instrumentation Riva et al. (93/3630) have compared GC-MIP with more conventional GC detectors and concluded that MIP detection could be more effective and economical for the determination of S-containing compounds in crude oil. Similar conclusions were reached by Eckert-Tilota et al. (93/817). Torch design has been studied by Alvarez-Bolainez et al. (93/2213). A water cooled capillary torch gave greater sensitivity than a tangential flow torch when using a 2450 MHz Ar plasma. Park and Yo0 (93/3468) have described a cylindrical MIP cavity that gave LODs of 0.46 pg s-' for Br and 0.51 pg s-' for S at plasma gas flow rates between 10 and 20 ml min-'. A semi-automated FI system for the on-line preparation of water samples for the determination of organotin compounds has been described by Szpunar-Lobinska et al.(94/707). The ionic organotin compounds were adsorbed onto an ODS column derivatized on-column using sodium tetraethylborate and eluted with methanol. The procedure gave an LOD of 0.1 ngml-'. Factorial design and response surface methodology have been used to optimize a surfatron GC-MIP system for the determi- nation of Br and C1 (93/2072). Detection limits of 32 pg s-' Br and 25 pg s-' C1 were obtained and were similar to those obtained with a univariate search optimization. 3.4.2. Gas chromatography-microwave induced plasma applications An extensive review of GC-MIP applications ( 140 references) was given by Bulska (92/4620).Recent developments in the technique have been discussed (28 references) by Lobinski and Adams (94/941) and the application to the analysis of pet- roleum described briefly (4 references) by Kosman (93/3975). Kovac and Ramus (93/2071) have investigated the potential for using a single calibration substance to calibrate response for a wide range of compounds. Variation in element response between the calibrant and determinand compounds was 3 to 6% depending on the analyte and the workers concluded that for some applications such errors were acceptable (see also section 3.1. above). The use of GC-MIP systems has been receiving increasing attention for the determination of metal containing compounds. Examples from Uden's group included the measurement of Al B Cr Ga Mn Re Pa Pt Ti and V in a range of synthetic compounds (93/3610 93/3503) and for Cu and Ni in metal chelates (94/859).Other work from this group concerning natural samples included a study of insoluble fractions of sediments and coals for As N 0 P S and Se using pyrolysis GC (93/2068). The application of GC-MIP in trace element speciation studies has been reported by several workers. Dirx et al. (94/775) and Gremm et al. (93/4121) have reported the determi- nation of organotin compounds in environmental samples. Liu et a!. (94/867) also described the determination of organotin species but in this study SFE was used in the sample prep- aration. Lobinski and Adams (93/3117) have described the determination of organolead compounds with a detection limit of 0.1 ng 1-' for water samples.Other work published in this review period included the determination of S in coal following SFE (93/3547) and the determination of pesticides (93/3264). 3.4.3. Supercriticul fluid chromatography Ducatte and Long have described an Bchelle-based SFC-MZP system for a range of metal and non-metal analytes (93/C1488). The advantages of a SFC-MIP-MS system for the determi- nation of halogenated compounds has been described by Olson and Caruso (93/2070). The LODs obtained using this system were 0.75 pg for Br and 15 pg for C1; reproducibility was 5%. 4. DIRECT CURRENT PLASMAS Publications citing the use of the DCP are fewer in this review echelle grating spectrometer that is normally coupled with this period. Work published included that of Brindle (93/2716) emission source has been exploited for the determination of concerning the determination of Sb by vapour generation and REEs in ores (92/2230 93/3559).Finally the DCP has been the improvement of accuracy for data from transient signals used to determine Se in snails with an LOD of using Kalman filtering (94/291). The high resolution of the 0.07 pg g-' (94/684). LOCATION OF REFERENCES The full list of references cited in this Update have been published as follows 93/998-93/C1354 J. Anal. At. Spectrom. 1993 8(3) 137R-149R. 93/C1355-93/2093 J. Anal. At. Spwtrom. 1993 8(4) 169R-194R. 9312094-9312710 J. Anal. At. Spectrom. 1993 8( 5) 239R-262R. 931271 1-93/3353 J. Anal. At. Spectrom. 1993 8(7) 313R-336R. 9313354-9314131 J. Anal. At. Spectrom.1993 8( 8 ) 377R-404R. 94/1-941614 J. Anal. At. Spectrom. 1994,9( l) 1R-23R. 94/615-941960 J. Anal. At. Spectrom. 1994 9( 2) 73R-85R. 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.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 Abbreviated List of References Cited in Update 187R 9211262 Appl. Spectrosc. 1991 45 190. 9212055 Appl. Spectrosc. 1991 45 1120. 9212230 Chem. Listy 1991 85 654. 9212384 Anal. Chem. 1991 63 1600. 9212393 Anal. Chem. 1991 63 2357. 9212515 Anal. Chim.Acta 1991 248 241. 9212560 Vysokochist. Veshchestva 1991 3 219. 9212561 Vysokochist. Veshchestva 1991 3 226. 9212607 J. Anal. At. Spectrom. 1991 6 553. 9212644 At. Spectrosc. 1991 12 199. 9212645 At. Spectrosc. 1991 12 204. 9212750 Appl. Spectrosc. 1991 45 1413. 9212752 Appl. Spectrosc. 1991 45 1463. 9212753 Appl. Spectrosc. 1991 45 1468. 9212762 Anal. Chim. Acta 1991 251 187.9212965 Guangpuxue Yu Guangpu Fenxi 1991 11 36. 9214404 Kogyo Yosui 1991 395 65. 9214590 Analyst 1992 117 571. 9214598 J. Anal. At. Spectrom. 1992 7 75. 9214606 J. Anal. At. Spectrom. 1992 7 127. 9214620 J. Anal. At. Spectrom. 1992 7 201. 9214624 J. Anal. At. Spectrom. 1992 7 229. 9214628 J. Anal. At. Spectrom. 1992 7 251. 9214642 J. Anal. At. Spectrom. 1992 7 339. 931431 Spectrosc. Lett.1992 25 375. 931438 Anal. Chim. Acta 1992 257 223. 931475 Zavod. Lab. 1991 57(12) 25. 931478 Microchem. J. 1992 45 1. 931507 Guangpuxue Yu Guangpu Fenxi 1991 11 22. 931540 Spectrochim. Acta Part B 1992 47,399.931542 Spectrochim. Acta Part B 1992,47,493.93/591 Anal. Sci. 1991 7 537. 931614 Fenxi Shiyanshi 1991 10 42. 931616 Fenxi Shiyanshi 1991 10 35. 931619 Fenxi Shiyanshi 1991 10 65. 931641 Pure Appl. 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ISSN:0267-9477    

DOI:10.1039/JA994090171R

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

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Univ. Houston Houston TX 94/C1958. Brown P. Clark J. Tye C. T. Hutton R. C. Tailoring ICP-MS to the application. (Fisons Instruments Elemental Analysis Ion Path Road Three Winsford Cheshire UK CW7 3BX). 94/C1959. Anthony L. J. Applications of GC-AED in electronics R&D and manufacturing. (AT&T Bell Labs. Phys. Sci. and Eng. 600 Mountain Ave. Murray Hill NJ 07974 USA). 94/C1960. Reiner G. A. Higgins D. A. Wehman R. W. Comparison of performance characteristics between the atomic emission detector and various element-specific detectors for single element-specific detection in gas chromatography. (Exxon Research & Engineering Clinton Twsp Route 22 E P.O.Box 998 Annandale NJ 08801 USA). 06859-0219 USA). 77204-2709 USA). 94/C 196 1. 94/C 1962. 94/C 1963 94/C 1964 94/C 1965. 94/C 1966. 94/C1967. 94/C1968. 94/C 1969. 94/C 1970. 94/C 197 1. 94/C1972. 94/C 1 973. 94/C 1974. Ramus T. L. Quantitation techniques and standards characterization for chromatography. (Dow Chemical P.O. Box 1398 Pittsburg CA 94565 USA). Sullivan J. J. Quimby B. D. Stable isotope labelling a new AED tool for analytical problems. (Hewlett- Packard 2850 Centerville Rd. Wilmington DE 19808 USA). Albro T. G. Determination of Lewisite and its breakdown products in soil and water by gas chroma- tography with atomic emission detection. (EAI Corp. 1308 Continental Dr.Suite J Abingdon MD 21009 USA). Liu Y. Lopez-Avila V. Alcaraz M. Beckert W. F. Determination of organotin and organolead compounds in environmental solid samples by off-line supercritical fluid extraction and capillary gas chromatography with atomic emission detection. (Midwest Res. Inst. California Operations 625-B Clyde Ave. Mountain View CA 94043 USA). Behlke M. K. Uden P. C. Wise S. A. Schantz M. M. Organomercury speciation in marine reference materials by gas chromatography-atomic emission detection. (Dept. Chem. GRC Towers Univ. Massachusetts Amherst MA 01003 USA). Thomas C. L. Goode S. R. Determination of oxygen- containing additives in gasoline by GC-AED. (Dept. Chem. and Biochem. Univ. South Carolina Columbia SC 29208 USA). Uden P. C. Milestones in atomic emission detection for chromatography. (Dept.Chem. Lederle Grad Res. Tower A Univ. Massachusetts Box 34510 Amherst Nygaard D. D. Almeida M. Bulman F. Maintaining ICP spectrometer compliance with EPA regulations. (Baird Corp. 125 Middlesex Turnpike Bedford MA 01730 USA). Le Blanc E. M. Heilveil A. L. Alloy sorting with X-ray fluorescence using a pattern recognition method. (ASOMA Instruments 11675 Jollyville Rd Austin TX 78759 USA). Smith T. Towards a universal metals identifier-a compact CCD array spectrometer. (Arun Technology Southwater Horsham West Sussex UK RH13 7UD). Pelz B. A. Carnahan J. W. Development of an acousto-optic spectral manipulator for background correction. (Dept. Chem. Northern Illinois Univ. DeKalb Illinois 601 15 USA). Fulton G. 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Critical evaluation of the performance of echelle CTD systems for routine ICP spectrochemical analysis. (Dept. Chem. Indiana Univ. Bloomington IN 47405 USA).194R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 94/C1977. Pilon M. J. Moran P. M. Schleicher R. G. Carbone J. Hutton J. Charge injection device array detectors for atomic emission spectroscopy. (Thermo Jarrell Ash Corp. 8E Forge Pky. Franklin MA 02038 USA). 94/C1978. Karanassios V. Bateman K. Spiers G. Correlation- based signal processing in ICP-AES with photodiode array detection and pneumatic nebulization sample introduction.(Dept. Chem. Univ. Waterloo Waterloo Ontario Canada N2L 3G1). 94/C1979. Thomas C. L. Goode S. R. Factors influencing the determination of oxygen in the GC-MIP. (Dept. Chem. and Biochem. Univ. South Carolina Columbia SC 29208 USA). 94/C1980. Coker W. L. 111 Boss C. B. Direct solid sampling by microwave plasmas. (North Carolina State Univ. Dept. Chem. 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ISSN:0267-9477    

DOI:10.1039/JA994090189R

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 201 R Glossary of Abbreviations Whenever suitable elements may be referred to by their chemical symbols and compounds by their formulae. The following abbreviations are used extensively in the Atomic Spectrometry Updates. a.c. AA AAS AE AES AF AFS AOAC APDC ASV BCR CCP CMP CRM cv cw d.c. DCP DDC DMF DNA ECD EDL EDTA EDXRF EIE EPMA ETA ETAAS ETV EXAFS FAAS FAB FAES FAFS FANES FAPES FI FPD FT FTMS GC GD GDL GDMS Ge( Li) HCL h.f. HG HPGe HPLC IAEA IBMK ICP ICP-MS alternating current atomic absorption atomic absorption spectrometry atomic emission atomic emission spectrometry atomic fluorescence atomic fluorescence spectrometry Association of Official Analytical Chemists ammonium pyrrolidinedithiocarbamate anodic-stripping voltammetry Community Bureau of Reference capacitively coupled plasma capacitively coupled microwave plasma certified reference material cold vapour continuous wave direct current d.c.plasma diet hy ldithiocarbama te N N-dimethylformamide deoxyribonucleic acid electron capture detection electrodeless discharge lamp ethylenediaminetetraacetic acid energy dispersive X-ray fluorescence easily ionizable element electron probe microanalysis electrothermal atomization electrothermal atomic absorption spectrometry electrothermal vaporization extended X-ray absorption fine structure flame AAS fast atom bombardment flame AES flame AFS furnace atomic non-thermal excitation furnace atomization plasma excitation 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-one) inductively coupled plasma inductively coupled plasma mass spectrometry (ammonium pyrrolidin-1-yl dithioformate) spectroscopy spectrometry spectrometry ID IR IUPAC LA LC LEAFS LEI LMMS LOD LTE MECA MIP MS NAA NaDDC NIES NIST NTA OES PIGE PIXE PMT PPb PPm PTFE QC r.f.REE(s) RIMS RM RSD SEC SEM SFC Si ( Li ) SIMAAC SIMS SR SRM SSMS STPF TCA TIMS TLC TMAH TOP0 TXRF u.h.f. uv VDU vuv WDXRF XRF SIB SIN isotope dilution infrared International Union of Pure and Applied Chemistry laser ablation liquid chromatography laser-excited atomic fluorescence spectrometry 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 Studies National Institute of Standards and nitrilotriacetic acid optical emission spectrometry particle-induced gamma-ray emission particle-induced X-ray emission photomultiplier tube parts per billion parts per million polytetrafluoroethylene quality control 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 tetramethylammonium hydroxide trioctylphosphine oxide total reflection X-ray fluorescence ultra-high frequency ultraviolet visual display unit vacuum ultraviolet wavelength dispersive X-ray fluorescence X-ray fluorescence TechnologyJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL.9 201 R Glossary of Abbreviations Whenever suitable elements may be referred to by their chemical symbols and compounds by their formulae. The following abbreviations are used extensively in the Atomic Spectrometry Updates. a.c. AA AAS AE AES AF AFS AOAC APDC ASV BCR CCP CMP CRM cv cw d.c. DCP DDC DMF DNA ECD EDL EDTA EDXRF EIE EPMA ETA ETAAS ETV EXAFS FAAS FAB FAES FAFS FANES FAPES FI FPD FT FTMS GC GD GDL GDMS Ge( Li) HCL h.f. HG HPGe HPLC IAEA IBMK ICP ICP-MS alternating current atomic absorption atomic absorption spectrometry atomic emission atomic emission spectrometry atomic fluorescence atomic fluorescence spectrometry Association of Official Analytical Chemists ammonium pyrrolidinedithiocarbamate anodic-stripping voltammetry Community Bureau of Reference capacitively coupled plasma capacitively coupled microwave plasma certified reference material cold vapour continuous wave direct current d.c.plasma diet hy ldithiocarbama te N N-dimethylformamide deoxyribonucleic acid electron capture detection electrodeless discharge lamp ethylenediaminetetraacetic acid energy dispersive X-ray fluorescence easily ionizable element electron probe microanalysis electrothermal atomization electrothermal atomic absorption spectrometry electrothermal vaporization extended X-ray absorption fine structure flame AAS fast atom bombardment flame AES flame AFS furnace atomic non-thermal excitation furnace atomization plasma excitation 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-one) inductively coupled plasma inductively coupled plasma mass spectrometry (ammonium pyrrolidin-1-yl dithioformate) spectroscopy spectrometry spectrometry ID IR IUPAC LA LC LEAFS LEI LMMS LOD LTE MECA MIP MS NAA NaDDC NIES NIST NTA OES PIGE PIXE PMT PPb PPm PTFE QC r.f.REE(s) RIMS RM RSD SEC SEM SFC Si ( Li ) SIMAAC SIMS SR SRM SSMS STPF TCA TIMS TLC TMAH TOP0 TXRF u.h.f. uv VDU vuv WDXRF XRF SIB SIN isotope dilution infrared International Union of Pure and Applied Chemistry laser ablation liquid chromatography laser-excited atomic fluorescence spectrometry 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 Studies National Institute of Standards and nitrilotriacetic acid optical emission spectrometry particle-induced gamma-ray emission particle-induced X-ray emission photomultiplier tube parts per billion parts per million polytetrafluoroethylene quality control 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 tetramethylammonium hydroxide trioctylphosphine oxide total reflection X-ray fluorescence ultra-high frequency ultraviolet visual display unit vacuum ultraviolet wavelength dispersive X-ray fluorescence X-ray fluorescence Technology

ISSN:0267-9477    

DOI:10.1039/JA994090201R

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 669 General Computer Program (AAS-TOOLS) for Theoretical Studies in Electrothermal Atomic Absorption Spectrometry Liang Yan Zhong and Ni Zhe-ming* Research Centre for Eco-environmental Sciences Academia Sinica P. 0. Box 2877 Beijing China 700085 A general computer program (AAS-TOOLS) is described which can act as a tool-box for theoretical studies in electrothermal atomic absorption spectrometry. This tool-box consists of general data processing tools an on-line data collection system and attendant database. Application of the tool-box is demonstrated by several practical and theoretical examples ( i ) fitting and filtering of analytical data; (ii) on-line data collection for the atomization of Be; (iii) use of Smets' method to determine the kinetic parameters of Mn; and (iv) theoretical simulation of an atomic absorbance signal based on an exponentially modified Gaussian function.Pull-down menus are adopted in the program with on-line help information. The results of data acquisition or processing and graphs (lines or curves) are saved on a diskette as files which can be retrieved directly by Lotus-123 and Wordperfect (V 5.1 or 5.0). Some algorithms for data processing are given in the Appendix. Keywords Computer program; electrothermal atomic absorption spectrometry; data processing The widespread availability of the microcomputer has greatly enhanced its application in analytical chemistry.'-' At present in atomic absorption spectrometry (AAS) the personal com- puter is principally utilized in the following three areas firstly controlling the instrument for data collection;&' secondly for computer ~imulation;~*'*~ and thirdly for signal (or data) proces~ing.'*~*~ With the advance in theoretical studies in electrothermal atomic absorption spectrometry (ETAAS) a large amount of data needs to be processed in order to obtain kinetic parameters such as atomization energy and order of release in atom desorption.However different research have generally employed their own programs and algorithms (e.g. differentiation integration fitting smoothing and regression) for final calculations which is not only time consuming but also makes resultant data difficult to compare with one another due to the variations in the data processing techniques used.In order to attenuate these drawbacks it would be useful if algorithms and a general data processing program could be recommended for theoretical studies in ETAAS. Despite the fact that some efforts have been made to achieve ~niformity,j-~ an integrated software for on-line data collection and data processing is not yet available. The aims of this paper are (i) to present an integrated software (AAS-TOOLS) that has been developed to permit researchers to expedite on-line data collection and data- processing in an integrated environment; and (ii) to provide algorithms for data-processing that are as concise and valid as possible. Experimental Apparatus A Perkin-Elmer 4000 atomic absorption spectrometer with deuterium-lamp background correction and an HGA 400 electrothermal atomizer were used throughout this work.Manganese Zn and Be hollow cathode lamps were utilized with wavelengths of 279.5 307.6 and 234.9 nm respectively. The spectral bandpass was 0.7 nm and the lamp currents were set according to the recommendation of the manufacturer (Beijing Vaccum Instrument Factory China). High-purity argon was employed as the internal gas. Experiments were performed with Perkin-Elmer standard graphite tubes in the mode of inner gas flow on for Mn and Zn and off for Be. The Ge photo-transistor (B 1918-01 Hamamatsu) utilized to obtain the graphite tube wall temperature was calibrated by focusing * Author to whom correspondence should be addressed. an optical pyrometer (Ircon UX-10 USA) through the sample injection hole in the graphite tube. Temperature and atomic absorbance signals were recorded simultaneously by a personal microcomputer (AP-A2OT) during each atomization cycle at 20 ms intervals via a fast 12-bit analogue-to-digital conversion circuit.All programs were tested on an IBM compatible 80386 personal computer. Reagents Analytical-reagent grade Mn( NO3) ZnNO and Be (Specpure Beijing China) were used to prepare stock solutions that contained lOOOpgml-' of Mn Zn and Be respectively. The working solutions were prepared daily by serial dilution of the stock solutions containing lo00 pg ml-' of the analytes as their nitrates with 0.01 mol 1-' nitric acid. Manganese (0.3 ng) Zn (0.5 pg) and Be (0.016 pg) were used for data collection experiments. A solid pyrolytic L'vov platform was employed when studying the atomization of Be.Program Description The software for AAS-TOOLS is written in C using Borland International's Turbo C (version 2.0) compiler and can be run under DOS operating systems. Hardware requirements include a monochrome or colour display monitor CGA EGA VGA or Hercules graphics cards and an IBM XT/AT or compatible 80286 80386 or 80486 personal computer. The output of general data-processing by AAS-TOOLS is stored on a diskette as an ACSIJ file in the format of a Lotus file. The graphics file is stored in the format of a Wordperfect (5.0-5.1) file. Lay-out The program is driven by pull-down menus with on-line help information which reduces the need for the user to interpret input and output filenames or variables.The main menu of AAS-TOOLS is composed of eight sub-menus. Each sub-menu contains about five subroutines which can be run indepen- dently. The initial layout is shown in Fig. 1. The footnote gives explanatory information about each function. All operation orders are displayed in a pop-up window. Functions General services such as file operation OS-shell print clock exit etc. are given in the first sub-menu.670 File Fic/l.'iller Sma*ing JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 Integration Tapflma~ Differentation k2 Sturgeon mclhod Fuller - Kabkov method I 1 FOOTNOTE k=(I/b)NjP Ad1 Fl=Help ESUCUI-X = h i 1 Fig. 1 Initial lay-out map of AAS-TOOLS The second sub-menu consists of three parts smoothing fitting and filtering. Five point cubic smoothing and seven point four order smoothing can be used to slide data points.An improved Gaussian function and a general order (2-20) orthogonal polynomial can be chosen for fitting equally spaced data points. The rx-,4-y filter can be employed to eliminate white noise. Examples of fitting and filter are given in the next section. Differentiation and integration at each of the uniform data points are achieved by the use of the functions listed in the third sub-menu. For differentiation both polynomial and spline methods" are offered. With the integration subroutine one can calculate the integration value at any interval based on a numerical method." The functions for finding the appearance temperature or appearance time peak temperature or peak time ending temperature or time and rate constant of atom removal k based on the method proposed in ref.11 are presented in the fourth sub-menu. The rate constant k can be calculated at any interval using the decay portion of the absorbance pulse. Six models for calculating the activation energy of atom formation are given in the fifth sub-menu namely Smets model,' the improved Smets' method proposed by Yan et ul.,13 Chung's model,14 Akman method,15 Fuller16 and Kaskov" methods for constant temperature atomization and the method of Yan et ~ 1 . ~ Except for Yan et a!. the resultant data for the Arrhenius plot of the corresponding model is stored on a diskette in Lotus file format. This program also gives the slope (activation energy) and intercept (the logorithm of the fre- quency factor) of the Arrhenius plot in a window.One can draw an Arrhenius plot via Lotus 123 by retrieving the data file stored or by calling the graphics functions offered in sub- menu 6 which comprises drawing lines or curves and a dual y-axis plot. The maximum number of lines or curves can be up to 15 which is very convenient for concentration study in AAS,9 as exemplified in the next section. The AAS-TOOLS program contains four kinds of random data generators (in sub-menu 7). The principle of the generator is derived from the multiplicative congruence meth~d.'~*''*'~ These generators can yield infinite random data with uniform or Gaussian distribution between 0 and 1 or at any interval of data without repetition of the cycle. The eighth sub-menu contains several practical programs.The first one is developed for constant temperature atomiz- ation such as probe atomization based on the method cited in ref. 20. A large number of the functions introduced above are involved in this program. The second is the signal simu- lation program based on an exponentially modified Gaussian function ( EMG),21*22 which can yield an absorbance peak with any given height and width. The synthetic signal is a combi- nation of theoretically computed data and random white noise generated by AAS-TOOLS. The simulated absorbance data and corresponding temperature ("C) data are stored together in the file. The linear temperature data are generated by inputing the beginning temperature and heating rate. The third program is a data collection system.With the appropriate hardware interface this program can be used to collect on-line a transient absorbance signal and temperature synchronously. After the acquisition cycle any functions cited above can be called to process the data by returning to the main menu. An IBM/AT and compatible 80286 or more advanced personal computer can finish all the data processing tasks including smoothing fitting filtering regression and plotting within 2 min. Therefore during pre-atomization data processing can be finished without waiting for the next data collection cycle. This sub-menu also contains a database which stores references on the atomization mechanism of a range of elements. Results and Discussion Use of AAS-TOOLS is best illustrated by several practical examples to show how the tool-box can be employed in theoretical studies and how the data collection system should be utilized.General Data Processing Fitting of unalytical duta The fitting of the absorbance signal is an important procedure in the theoretical study of ETAAS7-9*'3 The results of the fitting of a sixth order polynomial to experimental data is shown in Fig. 2 and the corresponding fitting deviation which is the sum of the squares of the deviations between the fitting value and the experimental value is 0.00529. In the fitting pro- cess the coefficients of the polynomial and the fitting deviation are listed in a pop-up window the fitting curve and the experimental curve are also drawn together in a graphical window. Orthogonal polynomial algorithms are given in the Appendix.Filtering of analyticul dutu The absorbance-time curve of Zn and the corresponding filtering curve are shown in Fig. 3. As can be seen the white noise of the experimental data has essentially been filtered. Details of the filter principle are presented in the Appendix. p21 - $ 0.1 f $ 0 1 2 3 4 t m Time/s < Fig. 2 Manganese absorbance profile and corresponding fitting curve of sixth order orthogonal polynomial A experimental; B fitted Y 0.20 r 1 2000 - .- C 3 2 0.15 h 4- .- f - 0.10 Q) C 4 0.05 4 1500 y E . 1000 E al P E 500 P) I- L I I 1 1 I 10 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Time/s 2 Fig. 3 Filtering of Zn absorbance signal A original; and B filtered. C Temperature uersus time curveJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL.9 67 File On-line Data Collection The following is an example of an application of the data collection system on the Perkin-Elmer 4000 atomic absorption spectrometer. The transient absorbance signal of Be the back- ground absorbance and the temperature data (“C) collected synchronously are demonstrated in Fig. 4 and Fig. 3 presents an example of data-collection for Zn absorbance without background absorbance. This performance can be achieved by highlighting the data-collection item in the eighth sub-menu. The data collection system can also be employed for other atomic absorption spectrometers as long as there is a proper interface between the spectrometer and the computer. In brief this data collection system is independent of the hardware such as the computer and the model of atomic absorption spectrometer used.FiVFilter Integration Tapp/Tmaa Graph Randomdata practical generators programs Smoothing Differentation k2 Determination of Activation Energy and Release Order of Mn via AAS-TOOLS Experimental data for the atomization of Mn are obtained by the data collection system introduced above. As an example of the operation of AAS-TOOLS the determination of the activation energy of Mn using Smets’ method12 and deduction of the release order based on a concentration study,’ are given below. Fig. 5 demonstrates procedures for the calculation of acti- vation energy and sequential outputs in a window with high- lighting of Smets’ item from sub-menu 5 where under-lined inputs are filled in by the operator. To deduce the release order the graphical functions listed in sub-menu 6 can be conveniently called to draw concentration curves as shown in Fig.6 which indicate that the release order of Mn is unity. The Arrhenius plot shown in Fig. 7 is drawn uia Lotus 123 by retrieving the data file stored in the process of computing the activation energy. Simulation of Absorbance Signal Based on the Exponentially Modified Gaussian Function (EMG)” Theoretical absorbance signals with and without the addition of random white noise as shown in Fig. 8(a) and (b) can be produced by calIing the EMG applied program in sub-menu 8 where the values of parameters rs z S and t are 0.5 0.5 0.7 and 2.7 respectively where CT is the standard deviation of the Gaussian constituent z is the time constant of the exponential modifier S is the peak area and tg is the difference between peak time and appearance time.Simulated absorbance signals with different shape height and width are shown in Fig. 9 where the values of parameters (r z S and t are 0.5 0.5 I 1 2700 C .z 0.4 2270 3 0 1 2 3 4 5 Time/s Fig. 4 Beryllium absorbance profile as a function of atomization temperature A absorbance profile of 0.016ng of Be; and B background absorbance of 1.4 pg of CaC1,. C Temperature versus time curve I Input dam filename I C:\AGS\1 coeff. oTpolynomid a0:0.175al:-0.299 a0.716 a3:2.251 a40.7982 a5:-4.498 Deviation of Fimng D1:0.005 D20.423 d3:O.m Ln&=16.2 FI=He$ ESC/Ctrl-X =Exit QOTNOTE k=(I/p)A/j,“ Adt Fig.5 Flow-chart of the determination of activation energy of Mn using Smets’ method 10 I 0 1 2 3 4 Time/s 3 Fig.6 Absorbance versus time profiles for various initial masses of Mn.Initial masses are A 0.05; B 0.10; C 0.20; D 0.30; E 0.40; F 0.50 G 0.80; and H 1.00 ng 1.5 I I 1.0 0.5 c 5 0 -I - 0.5 1 .o I I I 60 62 64 66 68 ’/ T x 1 0 - 5 o c Fig. 7 Arrhenius plot of Mn based on Smets’ model 0.7,0.5 and 2.0 respectively. The principle of the EMG function and the definitions of the terms used are given in the Appendix. Conclusion This program is specially developed for the theoretical research of fundamental processes in ETAAS. It integrates on-line data672 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 0.7 0.6 0.5 0.4 0.3 v) 0.2 3 0.1 *.’ .- C L- 2 0 c z -0.1 1 I I I I I s o 1 2 3 4 5 a C m e 2 a 0.8 0.6 0.4 0.2 0 1 2 3 4 5 6 Time/s Fig.8 Simulation of absorbance signals (a) with and (b) without white noise respectively; u = 0.5 7 = 0.5 S =0.7 and t = 2.7 0.6 0.5 - 0.4 0.3 0.2 0.1 0 a 5 0.6 0.5 0.4 0.3 0.2 0.1 1 0 1 2 3 4 5 Time/s Fig.9 white noise respectively; u = 0.5 t =0.7 S = 0.5 and t = 2.0 Simulation of absorbance signals (a) with and (b) without collection data processing and a database with user-friendly and software-friendly interfaces. All subroutines can be called from an integrated menu and used independently. The program developed can be run on IBM-AT or compatible personal computers. This work was supported by the Chinese Academy of Sciences under contract No. KM 85-47.Appendix Fitting The algorithm based on the orthogonal p o l y n ~ m i a l ’ ~ * ~ ~ .~ ~ is given below. Assuming there are n evenly spaced data points (xi yi,) (i = 1,2 . . . n) based on the properties of orthogonal poly- nomials10.22 a general order fitting polynomial (Pm) can be expressed as follows Pm(x)=a +a,x+u,x2+ ... +amxn-’ where m < n m < 20. The fitting polynomial may be defined as Pm(x)= CI QI(x) + C2Q2(x) + * a * + CmQm(X) where C,(j= 1,2 ... rn) are coefficients be constructed from the following sequences Qj(x)(j= 1,2 ... m) are orthogonal polynomials which can Qi(x)= 1 Q2(x) = (X - 4 Qj+l(X)=(X-j+,)Qj(X)-jQj-l(X) (j=2 3 m-1) postulating n dj= C Q?(X~) (j=1,2 ... m) i = l aj + 1 = Pj=dj/dj- xi Q:(xi )/dj ( j = 1,2 ... m- 1) Application of the least-squares criterion gives i = 1 n C,= y,Qj(xi)/dj (j= 1 2 ... m) i = 1 finally the fitting polymial is Pm(x) = a + u2x + a3x2 + .. . + umxm-’ where ai (i= 1,2 ... m) are the coefficients of the polynomial. a-py Filter This filter can eliminate the white noise of evenly spaced data points.” The principle of the filter can be expressed as x*(t)=x(t)+q(t) x*(t) is the measured data x(t) is the accurate value of a useful signal and h ( t ) are white noises the mean of which equals 0 namely E Cm3 = 0 Prediction of the one step value of the next time is based on the formulae given below Xn + l / n = Xn + X’n T + XI’ ( T2/2) X‘ + l/n = X’ + X”,T X ” + 11 = X ” The following equations are used to assess the filter value at this time Xn+ 1 =Xn+ l / n + a(X*n + 1 - x n + l / n ) X’n+l=X’n+l/n+P/T(X*n+l-Xn+1/n) Xt’n+l =X”n+,/n+2y/T2(X*n+ -Xn+l/n) where X*n+l is the measured value at this time and Xn+l,n is the one step prediction assessment of the location at this time compared with the previous time. X’n+l/n is the one step prediction assessment of the rate at this time as compared with the previous time.X ” + l/n is the one step prediction assessment of acceleration at this time as compared with the previous time.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 673 Xn+l is the filtering assessment of the location at this time; X’ + is the filtering assessment of the rate at this time; X” + is the filtering assessment of acceleration at this time; T is the interval of data collection; and a p and y are the structural parameters of the filter. Differentiation via the Spline Function In some kinetic m o d e l ~ ~ ’ ~ ~ the differentiation term dA/dt is calculated.There is an apparent variation in values obtained from different algorithms. In this program two algorithms are offered one is based on the derivation of a fitting polynomial the other is via the spline function. Here only the latter is given.” First assuming that function y=f(x) has n evenly spaced data points (nodes) xl x2 ... x and yl y2 ... y are the corresponding functional values and setting y’(xl) and y‘(x,) to be derivatives of boundary nodes then the values of the other n-2 nodes can be calculated from the following sequences a1=0 b1= Y’(X1) h j = x j + l - ~ j aj=hj_,/(hj-,+hj) forj=2 3 ... n-1 for j = 1,2 ... n - 1 P j = 3 C( 1 - aj>( yj - y j - 1 ) / h j - 1 + aj( ~j + 1 - yj)/hj 1 forj=2 3 ...n-1 aj= -~!~/[2+(1-a~)a~-~] forj=2 3 ... n-1 bj= [ P j - ( 1 - M j ) b j - I]/[ 2 + ( 1 - aj)aj- 11 forj=2 3 ... n-1 y ’ ( x j ) = u j y ’ ( x j + ) + b j j=n-1 n-2 ... 2 where a b CI P and h are all intermediate parameters. Simulation of Absorbance Signal The EMG function h( t ) is a regular Gaussian function G( t S G(t)= ___ e ~ p [ - o& convoluted by an exponential decay term H ( t ) of unit area H(t)=-exp - - tdO ( 3 H(t)=O t<O The expression of the EMG function h ( t ) is or deviation of the Gaussian constituent t the difference between peak time and appearance time and t’ a dummy variable of integration. The above equation contains an integral form that is difficult to estimate numerically the error function erf(t) which has the form j exp [t2] dt’ erf(t)= J;r 0 has often been used to calculate h(t) by using the relation- ship22,24 with but inputing different z S t and CT values one can obtain different absorbance profiles with various peak heights widths and positions.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 References Pawson J. B. Duffield R. J. King P. R. Hajizadeh-Saffar M. and Fisher G. W. Spectrochim. Acta Part B 43 1133. Voigtmall E. Anal. Chim. Acta 1991 246 9. Hsiech C. and Pardue H. L. Anal. Chem. 1993 65 1809. Berglund M. and Baxter D. C. J. Anal. At. Spectrorn. 1992 7 461. Vandecasteele C. Windels G. Desmet B. de Ruck A. D. and Dams R. Analyst 1988 113 1691. Rojas D. and Olivares W. Spectrochim. Acta Part B 1992 47 387. Yan X.-p. Ni Z.-m. Yang X.-t. and Hong G.-q.Spectrochim. Acta Part B 1993 48 460. Cathum S. J. Chakarabarti C. L. and Hutton J. C. Spectrochim. Acta Part B 1991 46 35. Holcombe J. A. Spectrochim. Acta Part B 1989 44 975. Xu S.-l. Fortran 77 Algorithm Tsing Hwa University Press 1st edn. 1992. Chakarabarti C. L. Wan C. C. Teskey R. J. and Chang S. B. Spectrochim. Acta Part B 1981 36 427. Smets B. Spectrochim. Acta Part B 1980 35 33. Yan X.-p. Lin T.-z. and Liu Z.-j. Talanta 1990 37 167. Chung C.-h. Anal. Chem. 1984 56 2714. Akman S. Genc 0. Ozdural A. R. and Balkis T. Spectrochim. Acta Part B 1980 35 373. Fuller C. W. Analyst 1975 100 229. Katskov D. A. Zh. Prikl Spektrosk. 1979 30 612. Guell 0. A. and Holcombe J. A. Anal. Chem. 1990 62 529A. Box G. E. P. and Muller M. E. Ann. Math. Stat. 1958 29 610. Yan X.-p. and Lin T.-z. Acta. Chim. Sin. 1989 47 1139. Berthod A. Anal. Chem. 1991 63 1879. Hanggl D. and Carr P. W. Anal. Chem. 1985 57 2394. Peter A. G. Anal. Chem. 1991 63 534. Gladney H. M. Dowden B. F. and Swalen J. D. Anal. Chem. 1969 41 883. Paper 3/06450F Received October 28 1993 Accepted February 7 1994 where h ( t ) is the EMG peak height at time t S the peak area z the time constant of the exponential modifier Q the standard

ISSN:0267-9477    

DOI:10.1039/JA9940900669

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 675 Reduction of Magnet Size in Direct Zeeman Atomic Absorption Spectrometry Roger Stephens Department of Chemistry Dalhousie University Halifax Nova Scotia Canada B3H 4J3 A field-on-source design is described which gives Zeeman background correction while allowing a significant reduction of magnet size to be achieved. The design is inherently suited to observation of the longitudinal Zeeman effect. The system was tested with copper using polarization modulation to selectively detect the difference in absorption between the c+ and c- components of the longitudinal multiplet emitted by the source. Effective background correction is achieved including tolerance towards anisotropy at the optical boundary of the atomizer. In contrast to the transverse field-on-source configuration the present system did not produce an interfering off-set signal as a result of self-absorption. Keywords Zeeman correction; atomic absorption spectrometry; permanent magnet The use of Zeeman background correction has become com- monplace for measurements in atomic absorption spectrometry (AAS).The theory of the technique and the various types of instrumental design that are used for its implementation have been described in Current information on the practice and development of the method can be found for instance in the series of on-going reviews (Atomic Spectrometry Updates) which appear in the Journal of Analytical Atomic Spectrometry. Zeeman corrected spectrometers are generally designed around an atomization device usually a furnace which is contained within the magnetic field. The emission line from a conventional hollow cathode lamp then interacts with the Zeeman absorption multiplet at the atomizer to generate total and background absorption signals for subsequent electronic processing.A disadvantage which is inherent to this arrange- ment is that the magnet must be large enough to produce a suitably strong field over a gap of sufficient size to contain the atomizer. The need for such a magnet raises the cost of an instrument and reduces its flexibility in terms of the ease of exchange or modification of the atomizer. The present work was carried out in order to investigate the possibility of reducing the demand on magnet size. Theory The size of the magnet needed for Zeeman correction depends upon the volume over which the field must act.In the present apparatus this volume was reduced by use of the field-on- source configuration shown in Fig. 1. In the arrangement shown the planar cathode geometry supports a disc-shaped glow discharge the disc being parallel and immediately adjac- ent to the pole face of the magnet. The depth of the discharge which controls the maximum distance of emitting atoms from the magnet is governed by fill pressure. Visual observation through the lamp wall indicated that the depth never exceeded about 1 mm under the conditions used in this work. The width of the discharge which is set by the internal diameter of the glass envelope was about 2mm across. This degree of con- finement proved sufficient to give adequate Zeeman splitting using only a small bar magnet to generate the field.The geometry shown in Fig. 1 produces approximately paral- lel electric and magnetic fields within the source a condition which allows a stable d.c. discharge to be obtained. The fields are also essentially parallel to the optical axis over the discharge region so that a longitudinal Zeeman effect (no n component; circularly polarized 0 components) is observed. In order to use this configuration in conjunction with the steady field of a bar magnet the optical system shown in Fig. 2 was adopted. In this system an oscillating retarder the photoelastic modulator (PEM) is used to give selective modulation of the intensity difference between the o+ and 6- components emitted by the Vacuum A H 1 cm A r M Fig.1 Schematic diagram of the lamp A anode; C cathode; GD glow discharge; M magnet; and W window PE M L L L Fig.2 Schematic diagram of the optical system F flame-burner assembly; L lens; M monochromator; P polarizer; PEM photoelastic modulator; and S source source. Such an intensity difference is produced as a result of atomic absorption within the atomizer (see Fig. 3) but not by a wide-band background absorption. It should be noted that a structured interference i.e. any background absorption that changes significantly over the wavelength interval between o+ and 0- will be detected similarly and will lead to an error signal which is proportional to the difference in absorption between o+ and 6-. The optical train in Fig.2 is described quantitatively by the Jones calculus.6 The Jones matrix J of the system is written as J= P x R - I ( 0)PEM R( O)FT (1) where P PEM P are the Jones matrices of polarizer P of the PEM and of the flame atomizer 0 is the angle between the transmission axis of P and the stress axis of the PEM,676 2 700 0 0 c - 3 600 500 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 - - - h Emission Fig.3 Schematic diagram of line profiles showing a pressure shift between emission and absorption maxima and the resulting increase in absorption for one Zeeman component and decrease for the other as the magnetic field is applied. (The emission profiles shown here are equivalent to the o+ 0- envelopes in the case of an anomalous mu1 tiplet) and R ( 0 ) is the corresponding rotation matrix T is the transformation matrix between circular and linear basis vectors and connects the circularly polarized emission lines to the linear coordinate system of the other optical components.Separate Jones vectors must be written for o+ and o- because of the frequency shift between them. Hence eqn. (1) can be simplified to J=P,R-'(@)PEM TF (2) Further details on the form and use of the Jones matrices have been given el~ewhere.~ Let the retardance 6 of the PEM be written as 6 = 6 sin(ot) where 6 is the peak retardance of the device and 4 2 7 ~ is its modulation frequency. Let the atom density and path length in the atomizer be N and 1 respectively and the Beer's law absorption coefficients for o+ 6- be K + K -. Evaluation of eqn.(2) then gives the intensity I transmitted by the optical system as I / I = [exp( - K + N l ) + exp( - K - N1)]/2 -sin( 2 0 ) x J1( 26,)[ exp(- K +NI) -exp(- K -NI)] sin@) (3) where J1( ) is the Bessel function of order 1 and ZO=source intensity for o -. Eqn. (3) shows that the optical train selectively modulates the absorption difference between the o+ and 0- components. The frequency shift between the source and atomizer lines caused by pressure broadening ensures that atomic absorption in the atomizer will cause such a difference to occur as seen in Fig. 3. The figure also shows that use of this optical system causes some loss of sensitivity since the absorption difference between o+ and o- is always less than the value of the zero field absorbance for a given N .At the same time however the system is well adapted for use with a low field strength since it is only necessary to produce a CT displacement up to the maximum of the atomizer absorption profile. The field strength required to produce such a displacement depends upon the particular element and type of transition being considered. Experimental Copper was used to test the system. A copper foil cathode (2 x 8 x 0.04 cm thick) was sealed to a glass case with epoxy as in Fig. 1. The anodes were of 14 gauge chrome1 wire. Argon was used as the fill gas. The bar magnet from a magnetic stirrer was 2.8 cm in length x 0.9 cm in diameter weighed 15 g and produced a field of 2.2 kG at the pole faces. Aqueous test solutions from 1 to 100 pg ml-' of copper as copper sulfate were atomized in an air-acetylene flame using a standard Varian-Techtron burner assembly and a 10cm head.The copper line at 624.8 nm was isolated by a McKee-Pederson MP-1018A monochromator with a linear dispersion of 3 nm mm-' at a slit-width of 1 mm. Polarizer P was a 1 x 1 cm calcite prism (Melles-Griot). The modulator was a PEM 80 (Hinds International Portland OR USA) with a fused silica head and oscillating at 0=50 kHz. All other electronics were built in the laboratory. Results Lamp Performance The lamp ran at 5 mA 3 mm of Hg pressure for 24 h before use to condition the cathode. Figs. 4-6 show current versus voltage intensity versus current and emission spectra respectively for the lamp with the magnet in place. Behaviour appears normal with a low pressure current limit and a fairly broad pressure range over which satisfactory performance can be obtained.The optimum output intensity is comparable to that of a commercial source (Varian); however the line-to-background ratio is worse. Stability plots (Fig. 7) show that good magnetic stability is obtained and confirm that the presence of the magnet does not cause any great perturbation of the lamp output. The optimum 1% absorption sensitivity for the source was 800 gOOO 400 ' 1 I I I I 0 1 2 3 4 5 Current/mA Fig. 4 Lamp current versus voltage for fill pressures 0 0.25; 9 1; 0 3 ; and U 6 mm Hg I 0 100 80 - (0 C 0 a z 60 .- c - 40 20 0 Current/mA Fig. 5 Relative intensity versus lamp current for fill pressures a 0.25; 0 1; 0 3 ; and U 6 mm HgJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL.9 677 333 3,” 3 (b) 324.8 327.4 ~ 3 318 5% NaCl Start End -Time Fig. 7 Stability plots over 30 min lamp current 3 mA; fill pressure 3 mm Hg. Upper curve field on; lower curve magnet removed 0.4 pg m1-I; about 10% better when the source was replaced by the Varian lamp. System Performance Absorption signals are shown in Fig. 8. The direction (phase) of the 50 kHz Zeeman signals reversed when the orientation of the magnet was reversed to bring the opposite pole up against the cathode of the lamp an observation confirming that the signals indeed represent a difference in absorption between CT and u- as required by eqn. (3). Calibration curves (Fig. 9) showed little sensitivity to the operating conditions of the lamp. However the signal-to-noise ratio varied markedly with current and pressure.Variations were consistent with the results shown in Fig. 5 for a shot- noise limited response. The roll-over observed in Fig. 9 is probably exacerbated by the low magnetic field strength which was used. Fig. 10 shows the dependence of the signal on the separation between the cathode and the pole face of the magnet. The sharp fall-off illustrates the need to hold the plasma as near to the magnet as possible (however looking at Fig. 3 it can be seen that this would not be the case if the magnet were Fig. 8 Absorption signals observed after successive aspiration of NaCl (5%) and of increasing concentration of Cu2+ Wavelengthhm Fig. 6 Spectra from 318 to 333 nm. Lamp current = 5 mA for both (a) a Varian lamp; and (b) the present source 10 0 20 40 60 80 100 Concentration/pg ml-’ Fig. 9 Calibration curves for fill pressures of 0 0.25; 0 3; and 0 5 mm Hg and lamp currents of 0.8 2 and 5 mA respectively.Fourier series used for curve fitting 100 [i 0 5 10 15 Cathode-pole face distance/mm Fig. 10 Dependence of signal on magnet position stronger allowing both u+ and c- components to be displaced beyond the absorption profile). Background correction for wide-band absorption within the optical path appeared to be satisfactory. No spurious signals were seen under a knife-edge test or as a result of absorption by smoke particles or upon aspiration of a 5% solution of678 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1994 VOL. 9 NaCI. No change in baseline was observed when the modulator was switched on indicating that no background signal occurred as a result of self-absorption within the lamp.This observation contrasts with the behaviour of the transverse field configuration.* The lack of a background signal here due to self-absorption is the result of the symmetry between the emission and self-absorption line frequencies; i.e. because there is no longer any pressure difference between the emitting and absorbing species no frequency shift exists between the zero- field emission and absorption lines in Fig. 3. Hence the differential absorbance between K + and K - remains zero even after the magnetic field is applied. In contrast again to the transverse field arrangement no spectral interference at the edge of the flame was seen.The reasons for this finding are discussed further in the Appendix. Conclusions A Zeeman-corrected spectrometer built around a small bar magnet was found to be functional. The longitudinal-field configuration reduces the spurious signals due to self- absorption and scatter from thermal boundaries which occur with the analogous transverse-field arrangement. No error signals were detected as a result of wide-band absorption. However the occurrence of spectral interferences due to line background absorption must be anticipated. The severity or otherwise of such interferences relative to their effect on a conventional instrument is expected to depend on the nature of the Zeeman splitting shown by the particular interferent. The need to use a specially designed source which is essential to the operation of the present system is a significant disadvan- tage. However it should be noted that fabrication of the source is not complex and that the whole assembly including the magnet is small enough to fit quite easily inside the envelope of a conventional hollow cathode lamp.Appendix Signal Harmonic Generation Through Atomizer Boundary Effects When a Zeeman corrected instrument uses a transverse field applied to the source then the atomizer itself can produce a spectroscopic interference. The effect arises because the thermal gradients around the atomizer cause anisotropic scattering to occur. As a result the n and CJ components of the transverse multiplet are not scattered equally. The consequent imbalance between n and (T intensities creates a spurious signal unless a suitable modulation procedure is adopted.This situation does not occur with the present configuration for the following reason. The Jones matrix X of the thermal boundary can be written in the general form where x1-x4 are complex. Using the same symbols as in the main text the Jones matrix J of the optical train shown in Fig. 2 becomes J = P xR - (n/4)MR( n/4)XT 0 exp(-i6) A cos(6) - iB sin(6) iA* cos(6) + B* sin(c’i) =2a( 0 where a = ( 1 +i),’2J2 A =xl + i x and B=x3+ix4. The output intensity is given by I = { A A * [ l + c o s ( ~ ~ ) ] + B B * [ ~ - c o s ( ~ ~ ) ] } (la+ +Z,-)/2 +(AB*- A*B) sin(26)(1,+ -Z0-)/2 Thus the output contains the even harmonics at 0 2w 4 0 ... However the first harmonic which carries the atomic absorp- tion signal is reduced by the term (la -la-). This term is zero in the absence of any wavelength-dependent absorption over the multiplet or if any absorption which does occur is symmetrical about the zero field line. References 1 Hadeishi T. and McLaughlin R. D. Science 1971 174 404. 2 Grassman E. Dawson J. B. and Ellis D. J. Analyst 1977 102 804. 3 de Loos-Vollebregt M. T. C. and de Galan L. Prog. Anal. Specrrosc. 1985 8 47. 4 Slavin W. and Carnrick G. R. At. Spectrosc. 1985 6 157. 5 de Loos-Vollebregt M. T. C. de Galan L. and van Uffelen J . W . M . Spectrochim. Acta Part B 1988 43 1147. 6 Kliger D. S. Lewis J. W. and Randall C. E. Polarized Light in Optics and Spectroscopy Academic Press 1990 ch. 4. 7 Kankare J. J. and Stephens R. Spectrochim. Acta Part B 1980 35 849. 8 Stephens R. Talunta 1978 25 435. Puper 3106236H Receiued October 19 1993 Accepted Junuary 26 1994

ISSN:0267-9477    

DOI:10.1039/JA9940900675

出版商:RSC    

年代:1994

数据来源: RSC