摘要:

1291 On-line Dilution System for Extending the Calibration Range of Flame Atomic Absorption Spectrometry-lgnacio Lopez Garcia Jeslis Arroyo Cortez Manuel Hernandez Cordoba 1295 Coupling of a Continuous Liquid-Liquid Extractor t o a Flame Atomic Absorption Spectrometer for the Determination of Alkaloids-Marcelina Eisman Mercedes Gallego Miguel Valcarcel COMMUNICATION 1299 Long-term Stability of a Mixed Palladium-Iridium Trapping Reagent for In Situ Hydride Trapping Within a Graphite Electrothermal Atomizer-Ian L Shuttler Michaela Feuerstein Gerhard Schlemmer 1303 ERRATA 1305 CUMULATIVE AUTHOR INDEX ATOMIC SPECTROMETRY 349R Industrial Analysis Metals Chemicals and Advanced Materials-John Marshall UPDATE John Carroll James S Cnghton Charles L R . Barnard 389R References I FACSS Announcement and Call for PapersThe XXVIII Colloquium Spectroscopicurn Internationale will be held in The University of York United Kingdom June 29-July 4,1993 "his traditional biennial conference in analytical spectroscopy will once again provide a forum for atomic nuclear and molecular spectroscopists worldwide to encourage personal contact and the exchange of experience. Participants are invited to submit papers for presentation at the XXVm CSI dealing with the following topics Basic Theory Techniques and Instrumentation of- Applications of Spectroscopy in the Analysis of- Computer Applications and Chemometrics Laser Spectroscopy Environmental Samples Atomic Spectroscopy (Emission Absorption Fluorescence) Electron Spectroscopy Geological Materials Gamma Spectroscopy Industrial Products Mass Spectrometry (Inorganic and Organic) Methods of Surface Analysis and Depth Profiling Molecular Spectroscopy (UV VIS IR) Mossbauer Spectroscopy Nuclear Magnetic Resonance Spectrometry Photoacoustic Spectrometry Raman Spectroscopy X-ray Spectroscopy Biological Samples Food and Agricultural Products Metals Alloys PLENARY AND INVITED SPEAKERS The scientific programme will consist of Plenary and Invited Speakers.To date the following scientists have accepted invitations to present keynote lectures Plenary- Invited- M L Gross Lincoln NE R E Hester York C L Wilkins Riverside CA J D Winefordner Gainemille FL F C Adams Antwerp F V Bright Bufldo NY J A Caruso Ciwimri OH B T Chait New York NY R Donovan Edinburgh D E Games Swansea D L Glish Oak Ridge TN P Hendra Southampton F Hillenkamp Munster J A Holcombe Austin TX J Reffner Stagord CT B L Sharp Loughborough M Sigrist Zurich M Thompson London J C Vickerman Manchester PRE- and POST-SYMPOSIA In connection with the XXVIII CSI a number of symposia and workshops will be organized.EXHIBITION The conference will feature an exhibition of the latest instrumentation. ACCOMMODATION Accommodation has been reserved on campus and in the halls of residence although hotel accomodation in York will be available if desired. SOCIAL PROGRAMME The scientific programme will be punctuated with memorable social events and excursions of scientific cultural and tourist interest. The social programme is open to all participants and accompanying persons. For further information contact- THE SECRETARIAT XXVIII CSI Department of Chemistry Loughborough University of Technology Loughborough Leicestershire LE113TU UK.Telephone +44 (0) 509 222575; Fax +44 (0) 0509 233163; Telex 34319.The XXVIII Colloquium Spectroscopicurn Internationale will be held in The University of York United Kingdom June 29-July 4,1993 "his traditional biennial conference in analytical spectroscopy will once again provide a forum for atomic nuclear and molecular spectroscopists worldwide to encourage personal contact and the exchange of experience. Participants are invited to submit papers for presentation at the XXVm CSI dealing with the following topics Basic Theory Techniques and Instrumentation of- Applications of Spectroscopy in the Analysis of- Computer Applications and Chemometrics Laser Spectroscopy Environmental Samples Atomic Spectroscopy (Emission Absorption Fluorescence) Electron Spectroscopy Geological Materials Gamma Spectroscopy Industrial Products Mass Spectrometry (Inorganic and Organic) Methods of Surface Analysis and Depth Profiling Molecular Spectroscopy (UV VIS IR) Mossbauer Spectroscopy Nuclear Magnetic Resonance Spectrometry Photoacoustic Spectrometry Raman Spectroscopy X-ray Spectroscopy Biological Samples Food and Agricultural Products Metals Alloys PLENARY AND INVITED SPEAKERS The scientific programme will consist of Plenary and Invited Speakers.To date the following scientists have accepted invitations to present keynote lectures Plenary- Invited- M L Gross Lincoln NE R E Hester York C L Wilkins Riverside CA J D Winefordner Gainemille FL F C Adams Antwerp F V Bright Bufldo NY J A Caruso Ciwimri OH B T Chait New York NY R Donovan Edinburgh D E Games Swansea D L Glish Oak Ridge TN P Hendra Southampton F Hillenkamp Munster J A Holcombe Austin TX J Reffner Stagord CT B L Sharp Loughborough M Sigrist Zurich M Thompson London J C Vickerman Manchester PRE- and POST-SYMPOSIA In connection with the XXVIII CSI a number of symposia and workshops will be organized.EXHIBITION The conference will feature an exhibition of the latest instrumentation. ACCOMMODATION Accommodation has been reserved on campus and in the halls of residence although hotel accomodation in York will be available if desired. SOCIAL PROGRAMME The scientific programme will be punctuated with memorable social events and excursions of scientific cultural and tourist interest.The social programme is open to all participants and accompanying persons. For further information contact- THE SECRETARIAT XXVIII CSI Department of Chemistry Loughborough University of Technology Loughborough Leicestershire LE113TU UK. Telephone +44 (0) 509 222575; Fax +44 (0) 0509 233163; Telex 34319.The XXVIII Colloquium Spectroscopicurn Internationale will be held in The University of York United Kingdom June 29-July 4,1993 "his traditional biennial conference in analytical spectroscopy will once again provide a forum for atomic nuclear and molecular spectroscopists worldwide to encourage personal contact and the exchange of experience. Participants are invited to submit papers for presentation at the XXVm CSI dealing with the following topics Basic Theory Techniques and Instrumentation of- Applications of Spectroscopy in the Analysis of- Computer Applications and Chemometrics Laser Spectroscopy Environmental Samples Atomic Spectroscopy (Emission Absorption Fluorescence) Electron Spectroscopy Geological Materials Gamma Spectroscopy Industrial Products Mass Spectrometry (Inorganic and Organic) Methods of Surface Analysis and Depth Profiling Molecular Spectroscopy (UV VIS IR) Mossbauer Spectroscopy Nuclear Magnetic Resonance Spectrometry Photoacoustic Spectrometry Raman Spectroscopy X-ray Spectroscopy Biological Samples Food and Agricultural Products Metals Alloys PLENARY AND INVITED SPEAKERS The scientific programme will consist of Plenary and Invited Speakers.To date the following scientists have accepted invitations to present keynote lectures Plenary- Invited- M L Gross Lincoln NE R E Hester York C L Wilkins Riverside CA J D Winefordner Gainemille FL F C Adams Antwerp F V Bright Bufldo NY J A Caruso Ciwimri OH B T Chait New York NY R Donovan Edinburgh D E Games Swansea D L Glish Oak Ridge TN P Hendra Southampton F Hillenkamp Munster J A Holcombe Austin TX J Reffner Stagord CT B L Sharp Loughborough M Sigrist Zurich M Thompson London J C Vickerman Manchester PRE- and POST-SYMPOSIA In connection with the XXVIII CSI a number of symposia and workshops will be organized. EXHIBITION The conference will feature an exhibition of the latest instrumentation. ACCOMMODATION Accommodation has been reserved on campus and in the halls of residence although hotel accomodation in York will be available if desired. SOCIAL PROGRAMME The scientific programme will be punctuated with memorable social events and excursions of scientific cultural and tourist interest. The social programme is open to all participants and accompanying persons. For further information contact- THE SECRETARIAT XXVIII CSI Department of Chemistry Loughborough University of Technology Loughborough Leicestershire LE113TU UK. Telephone +44 (0) 509 222575; Fax +44 (0) 0509 233163; Telex 34319.

ISSN:0267-9477    

DOI:10.1039/JA99207FP004

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

The XXVIII Colloquium Spectroscopicurn Internationale will be held in The University of York United Kingdom June 29-July 4,1993 "his traditional biennial conference in analytical spectroscopy will once again provide a forum for atomic nuclear and molecular spectroscopists worldwide to encourage personal contact and the exchange of experience. Participants are invited to submit papers for presentation at the XXVm CSI dealing with the following topics Basic Theory Techniques and Instrumentation of- Applications of Spectroscopy in the Analysis of- Computer Applications and Chemometrics Laser Spectroscopy Environmental Samples Atomic Spectroscopy (Emission Absorption Fluorescence) Electron Spectroscopy Geological Materials Gamma Spectroscopy Industrial Products Mass Spectrometry (Inorganic and Organic) Methods of Surface Analysis and Depth Profiling Molecular Spectroscopy (UV VIS IR) Mossbauer Spectroscopy Nuclear Magnetic Resonance Spectrometry Photoacoustic Spectrometry Raman Spectroscopy X-ray Spectroscopy Biological Samples Food and Agricultural Products Metals Alloys PLENARY AND INVITED SPEAKERS The scientific programme will consist of Plenary and Invited Speakers.To date the following scientists have accepted invitations to present keynote lectures Plenary- Invited- M L Gross Lincoln NE R E Hester York C L Wilkins Riverside CA J D Winefordner Gainemille FL F C Adams Antwerp F V Bright Bufldo NY J A Caruso Ciwimri OH B T Chait New York NY R Donovan Edinburgh D E Games Swansea D L Glish Oak Ridge TN P Hendra Southampton F Hillenkamp Munster J A Holcombe Austin TX J Reffner Stagord CT B L Sharp Loughborough M Sigrist Zurich M Thompson London J C Vickerman Manchester PRE- and POST-SYMPOSIA In connection with the XXVIII CSI a number of symposia and workshops will be organized.EXHIBITION The conference will feature an exhibition of the latest instrumentation. ACCOMMODATION Accommodation has been reserved on campus and in the halls of residence although hotel accomodation in York will be available if desired. SOCIAL PROGRAMME The scientific programme will be punctuated with memorable social events and excursions of scientific cultural and tourist interest. The social programme is open to all participants and accompanying persons. For further information contact- THE SECRETARIAT XXVIII CSI Department of Chemistry Loughborough University of Technology Loughborough Leicestershire LE113TU UK.Telephone +44 (0) 509 222575; Fax +44 (0) 0509 233163; Telex 34319.The XXVIII Colloquium Spectroscopicurn Internationale will be held in The University of York United Kingdom June 29-July 4,1993 "his traditional biennial conference in analytical spectroscopy will once again provide a forum for atomic nuclear and molecular spectroscopists worldwide to encourage personal contact and the exchange of experience. Participants are invited to submit papers for presentation at the XXVm CSI dealing with the following topics Basic Theory Techniques and Instrumentation of- Applications of Spectroscopy in the Analysis of- Computer Applications and Chemometrics Laser Spectroscopy Environmental Samples Atomic Spectroscopy (Emission Absorption Fluorescence) Electron Spectroscopy Geological Materials Gamma Spectroscopy Industrial Products Mass Spectrometry (Inorganic and Organic) Methods of Surface Analysis and Depth Profiling Molecular Spectroscopy (UV VIS IR) Mossbauer Spectroscopy Nuclear Magnetic Resonance Spectrometry Photoacoustic Spectrometry Raman Spectroscopy X-ray Spectroscopy Biological Samples Food and Agricultural Products Metals Alloys PLENARY AND INVITED SPEAKERS The scientific programme will consist of Plenary and Invited Speakers.To date the following scientists have accepted invitations to present keynote lectures Plenary- Invited- M L Gross Lincoln NE R E Hester York C L Wilkins Riverside CA J D Winefordner Gainemille FL F C Adams Antwerp F V Bright Bufldo NY J A Caruso Ciwimri OH B T Chait New York NY R Donovan Edinburgh D E Games Swansea D L Glish Oak Ridge TN P Hendra Southampton F Hillenkamp Munster J A Holcombe Austin TX J Reffner Stagord CT B L Sharp Loughborough M Sigrist Zurich M Thompson London J C Vickerman Manchester PRE- and POST-SYMPOSIA In connection with the XXVIII CSI a number of symposia and workshops will be organized.EXHIBITION The conference will feature an exhibition of the latest instrumentation. ACCOMMODATION Accommodation has been reserved on campus and in the halls of residence although hotel accomodation in York will be available if desired. SOCIAL PROGRAMME The scientific programme will be punctuated with memorable social events and excursions of scientific cultural and tourist interest. The social programme is open to all participants and accompanying persons. For further information contact- THE SECRETARIAT XXVIII CSI Department of Chemistry Loughborough University of Technology Loughborough Leicestershire LE113TU UK. Telephone +44 (0) 509 222575; Fax +44 (0) 0509 233163; Telex 34319.

ISSN:0267-9477    

DOI:10.1039/JA99207FX005

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JASPE2 7 ( 2 ) 9N-l8N 69-480 March 1992 Journal of Analytical Atomic Spectrometry I nc I u d i n g Atom ic S p ec t rorne t ry U pda tes CONTENTS CONFERENCE REPORTS 9N XXVll CSI-Finn J Langrnyhr and Yngvar Thomassen 1 ON CSI-Award for Major Scientific Contributions to Analytical Spectroscopy 1ON A Personal Tribute to Sir Alan Walsh-L R P Butler 1 1 N Sir Alan Walsh-The Scientist and the Man-P L Larkins 1 3N Atomic Absorption Spectroscopy-Present and Fusure Aspects-Ralph E Sturgeon 1 7 N Reflections and Cornmerits from Sir Alan Walsh FRS PAPERS XXVll CSI BERGEN NORWAY JUNE 9-14 1991 PLENARY LECTURES 69 New Developments and Final Frontiers in Inductively Coupled Plasma Spectrometry-Gary M Hieftje P J Galley M Glick D S Hanselman 75 Glow Discharge Considerations as a Versatile Analytical Source-W W Harrison 81 Microanalysis of Individual Environmental Particles-Rene Van Grieken Chris Xhoffer 89 99 105 109 115 121 127 131 135 141 147 Photon Detection Based on Pulsed Laser-enhanced Ionization and Photoionization of Magnesium Vapour Quantum Efficiency Versus Ion Yield.Invited Lecture-Nicolo Omenetto Benjamin W Smith Paul B Farnsworth James D Winefordner Detection of Trace Amounts of Toxic Metals in Environmental Samples by Laser- excited Atomic Fluorescence Spectrometry. Invited Lecture-Mikhail A Bolshov Vsevolod G Koloshnikov Sergei N Rudnev Claude F Boutron Ursula Gorlach Clair C Patterson Determination of Lead in Natural and Waste Waters Using a Non-dispersive Atomic Fluorescence Spectrometer With a Tungsten Spiral Atomizer-Svetlana S Grazhulene Vladimir A Khvostikov Nina N Vykhristenko Mikhatl V Sorokin Precise Determination of Iron Isotope Ratios in Whole Blood Using Inductively Coupled Mass Spectrometry.Invited Lecture-Paul G Whittaker. Jon F R Barrett John G Williams Application of Isotope Dilution Analysis-Inductively Coupled Plasma Mass Spectrometry t o the Precise Determination of Silver and Antimony in Pure Copper-Koichi Chiba lsamu Inamoto Masao Saekt Analysis of Conducting Solids by Inductively Coupled Plasma Mass Spectrometry With Spark Ablation-Norbert Jakubowski lngo Feldmann Brigitte Sack Dietmar Stuewer Rapid and Accurate Element Determination in Lubricating Oils Using Inductively Coupled Plasma Optical Emission Spectrometry-Elisabeth B M Jansen Joop H Knipscheer Mario Nagtegsal Matrix Effects of Easily Ionized Elements on the Spatial Distribution of Electron Number Densities in an Inductively Coupled Plasma Using an Optical Fibre Probe and a Photodiode Array Spectrometer-Xiao Jian Li Qingyan Li Wenchong Qian Haowen Tan Jingyuan Zhang Zhanxia Monte Carlo Study of Analyte Desorption Adsorption and Spatial Distribution in Electrothermal Atomizers.Invited Lecture-Oscar A Guell James A Holcombe Effects of Modifier Mass and Temperature Gradients on Analyte Sensitivity in Electrothermal Atomic Absorption Spectrometry. Invited Lecture-Wolfgang Frech Ke Li Michael Berglund Douglas C Baxter Chemical Modification in Electrothermal Atomic Absorption Spectrometry. Organization and Classification of Data by Multivariate Methods. Invited Lecture-Dimiter L Tsalev Vera I Slaveykova continued inside back cover Typeset by Burgess & Son (Abmgdon) Ltd 0 2 6 7 - 9 4 7 7 1 1992.12-2 (-1 Printed in Great Britain by BRos Page Bros NorwichJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 155 165 171 175 179 183 187 191 197 201 21 1 21 9 225 229 235 239 247 251 255 261 265 273 281 287 293 Application of Radiotracers to Methodological Studies in Atomic Absorption Spectrometry.Invited Lecture-ViIiam Krivan Determination of Selenium in Staple Foods and Total Diets by Electrothermal Atomic Absorption Spectrometry Without Solvent Extraction-Jorma Kumpulainen Kjell-Erik Saarela Determination of Lead by Hydride Generation and Atomization Under Low Pressure Using Atomic Absorption Spectrometry-Baougi Zhang Keyi Tao Jianxing Feng Sensitivity Enhancement Effects of Organic Reagents on Ytterbium Aluminium and Chromium in Atomic Absorption Spectrometry-Jizhong Wei Hulling Mu Xinsheng Wang Huiming Shi Fan Lin Determination of Vanadium in Vegetable Matter by Flame Atomic Absorption Spectrometry-Seref Gucer Mehmet Yaman Column Preconcentration of Iron(iii) With an Ion Pair of 1,2-Dihydroxybenzene-3,5- disulfonate and Benzyldimethyltetradecylammonium Ion Supported on Naphthalene Using Flame Atomic Absorption Spectrometry-Masatada Satake Tohru Nagahiro Bal Krishan Purl Determination of Some Trace Elements in Sea-water by Atomic Absorption Spectrometry After Concentration With Modified Silicas-Suleyman Akman Hurrem Ince Unel Koklu Selective Determination of Toxicologically Important Arsenic Species in Urine by High-performance Liquid Chromatography-Hydride Generation Atomic Absorption Spectrometry-Erkki Hakala Lauri Pyy Nitrogen-selective Detection for Gas Chromatography With a Helium Radiofrequency Plasma Detector.Invited Lecture-Mingin Wu Milton L Lee Paul B Farnsworth Microwave-induced Plasma as an Element-specific Detector for Speciation Studies at the Trace Level. Invited Lecture-Ewa Bulska Analyte Volatilization Procedure for Continuous-flow Determination of Bromine by Atmospheric Pressure Helium Microwave-induced Plasma Atomic Emission Spectrometry-Taketoshi Nakahara Satoru Morimoto Tamotsu Wasa Considerations in the Gas Flow Design of a Graphite Furnace Vaporization Interface Effects of a Halocarbon Atmosphere and Sample Matrix.Invited Lecture-Ti bor Ka n tor Direct Analysis of Liquid and Solid Samples Without Sample Preparation Using Laser-enhanced Ionization-Nikolai V Chekalin lgor I Vlasov Evaluation of a Gas Jet-enhanced Sputtering Device for Atomic Absorption Spectrometry-Samantha J O’Gram John R Dean William R Tomlinson John Marshall Boron Calcium and Silicon in an Arc Plasma in Air With Chlorine Calculation of the Plasma Composition-Jelena RadiC-Pen6 Quantitative Depth Profiling of Oxide Scales on High-temperature Alloys by Means of Glow Discharge Optical Emission Spectrometry-Hubertus Nickel Werner Fischer Daru Guntur Aristidis Naoumidis Analytical System for the Analysis of Ferrovanadium Using Spark Ablation Coupled With Inductively Coupled Plasma Atomic Emission Spectrometry-Aurora Gomez Coedo M Teresa Dorado L6pez.Isabel Gutierrez Cobo Esther Escudero Baquero Quantitative Analysis of Glass Using Inductively Coupled Plasma Atomic Emission and Mass Spectrometry Laser Micro-analysis Inductively Coupled Plasma Atomic Emission Spectrometry and Laser Ablation Inductively Coupled Plasma Mass Spectrometry-Lieselotte Moenke-Blankenburg Thomas Schumann Detlef Gunther Heinz-Martin Kuss Michael Paul Methods for the Detection of Single Atoms Using Optical and Mass Spectrometry. Invited Lecture- Heinz Fa1 k Quantitative Analysis of Steel Samples With Laser Ionization Mass Spectrometry-Mats Andersson Arne Rosh Atomic Line Profiles-Their Measurement and Importance in Analytical Atomic Spectroscopy. Invited Lecture-Peter L Larkins Total Reflection X-ray Fluorescence-An Efficient Method for Micro- Trace and Surface Layer Analysis.Invited Lecture-Reinhold Klockenkamper Alex von Bohlen Principles and Applications of Energy-dispersive X-ray Fluorescence Analysis With Polarized Radiation-Joachim Heckel Michael Haschke Mathias Brumme Rolf Schindler Flow Injection-Electrochemical Hydride Generation Technique for Atomic Absorption Spectrometry. Invited Lecture-Yuehe Lin Xiaoru Wang Dongxing Yuan Pengyuan Yang Benli Huang Zhixia Zhuang Critical Evaluation of the Efficiency and Synergistic Effects of Flow Injection480 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 301 307 31 5 323 329 335 Techniques for Sensitivity Enhancement in Flame Atomic Absorption Spectrometry-Zhaolun Fang Liping Dong Shukun Xu Flow Injection Systems for Directly Coupling On-line Digestions With Analytical Atomic Spectrometry.Part 1. Dissolution of Cocoa Under Stopped-flow High- pressure Conditions-Thomas J Gluodenis Jr Julian F Tyson Quartz Tube Atomizers for Hydride Generation Atomic Absorption Spectrometry Mechanism for Atomization of Arsine. Invited Lecture-JiPi DBdina Bernhard Welz Determination of Arsenic in a Nickel-based Alloy by Flow Injection Hydride Generation Atomic Absorption Spectrometry Incorporating Continuous-flow Matrix Isolation and Stopped-flow Pre-reduction Procedures-Julian F Tyson Stephen G Offley. Nichola J Seare Helen A B Kibble Craig Fellows Flow Injection Flame Atomic Absorption Spectrometric Determination of Copper With Preconcentration on Ligand Loaded Amberlite XAD-2-Abdulmagid M Naghmush Marek Trojanowicz Ewa Olbrych-Sleszynska Protocol for the Design and Interpretation of Method Evaluation in Atomic Absorption Spectrometric Analysis.Application to the Determination of Lead and Manganese in Blood-Jyttle Molin Christensen Otto Melchior Poulsen Thomas Anglov On-line Gradient Calibration for Atomic Absorption Spectrometry-Timothy K Starn Gary M Hieftje 339 343 347 353 357 365 371 383 389 397 405 409 41 7 421 425 ~~ XXVll CSl PRE-SYMPOSIUM ON GRAPHITE ATOMIZER TECHNIQUES IN ANALYTICAL SPECTROSCOPY LOFTHUS NORWAY JUNE 6-8,1991 Excitation and Detection of Molecular Species With Furnace Atomization Plasma Emission Spectrometry-Ralph E Sturgeon Scott N Willie Thermal Disequilibrium Effects in a Molecular Glow Discharge-G Lupke G Marowsky F Sieverdes N Wenzel T Kishimoto H Grosse-Wilde Atomization Mechanisms of Silicon in a Graphite Furnace Atomizer-C J Rademeyer I Vermaak Investigations of Gas-flow Patterns Within a Cylindrical Glass Tube Having Dimensions Identical With Those of a Graphite Furnace Atomizer Under the Influence of Forced Convective Flow-Nian Wu Carmen W Huie Aluminium Atom Formation in Electrothermal Graphite Atomizer Atomic Absorption Spectrometry by In Siru Spectroscopic Measurements of Aluminium and Aluminium Hydride-K E Anders Ohlsson Simplified Kinetic Model Describing the Analyte Losses During Pre-atomization Thermal Treatment in Electrothermal Atomic Absorption Spectrometry-Vera I Slaveykova Dimiter L Tsalev Mechanisms of Chloride Interferences in Atomic Absorption Spectrometry Using a Graphite Furnace Atomizer Investigated by Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry. Part 1.Effect of Magnesium Chloride Matrix and Ascorbic Acid Chemical1 Modifier on Manganese-J P Byrne C L Chakrabarti D C Gregoire M Lamoureux T Ly Direct Determination of Cadmium in Sea-water Using Electrothermal Atomization Atomic Absorption spectrometry With Zeeman-effect Background Correction and Oxalic Acid as a Chemical Modifier-J Y Cabon A Le Bihan Application of Palladium iPS a Chemical Modifier in Electrothermal Atomic Absorption Spectrometry With a Tungsten Tube Atomizer-Shan Xiao-quan Bernard Radziuk Berhard Welz Vaclav Sychra Chemical Modification and Spectral Interferences in Selenium Determination Using Zeeman-effect Electrothermal Atomic Absorption Spectrometry-Bernard Radziuk Yngvar Thomassen Determination of Total Mercury in Human Whole Blood by Electrothermal Atomic Absorption Spectrometry Following Extraction-H5kan Emteborg Ewa Bulska Wolfgang Frech Douglas C.Baxter Vapour-phase Behaviour aB Slurries in hectrothermal Atomic Absorption Spectrometry-Paolo Tittarelli Claudio Biffi Determination of Beryllium in Coal Fly Ash by Electrothermal Atomic Absorption Spectrometry-Shuvendu S E3hattacharyya Arabinda K Das Determination of Tin by Electrothermal Atomic Absorption Spectrometry With a Tungsten-coated Tube- Etsuro I wamoto H iromic hi S h imazu Kayoko Yokota Taka hiro Kumamaru Determination of Cadmium in Environmental Samples by Electrothermal AtomicJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL.7 479 433 439 447 451 457 461 471 478 Absorption Spectrometry Using a Tantalum-foil Platform With the Possibility of Standardless Analysis-Ma Yizai Bai Jian Wang Jiazhen LI Zhikun Zhu Lei Li Yongquan Zheng Hui Li Bingwei Combination of Flow Injection Hydride Generation and Sequestration on a Graphite Tube for the Automated Determination of Antimony in Potable and Surface Waters-Hans-Werner Sinemus Joachim Kleiner Hans-Henning Stabel Bernard Radzruk Flow Injection On-line Coprecipitation Preconcentration for Electrothermal Atomic Absorption Spectrometry-Zhaolun Fang Liping Dong Determination of Alkylselenides by Gas Chromatography-Electrothermal Atomic Absorption Spectrometry-Jiang Gui-bin Ni Zhe-ming Zhang Li Li Ang Han Heng-bin Shan Xiao-quan Detection of Technetium in Electrothermal Atomic Absorption Spectrometry Using Coincident Emission Lines of Other Elements-Hermann 0 Haug Radiation-enhanced Field-forced Deposition of a Laser-produced Aerosol in a Graphite Furnace and Continuum-source Coherent Forward Scattering Multi- element Determination-Geed M. Hermann George F Lasnitschka Ralph Moder Thomas W. Szardening Computer Program (CHMASS) for Calculating Theoretical Characteristic Mass Values in Electrotherma I Atomic Absorption Spectrometry- M ich ael Berg lu nd Douglas C. Baxter WE KNOW? CUMULATIVE AUTHOR INDEX DISCUSSION-MODELLING OF GRAPHITE FURNACE PROCESSES WHAT DO

ISSN:0267-9477    

DOI:10.1039/JA99207BX007

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

9N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 XXVll Colloquium Spectroscopicum Internationale June 9-14 1991 Bergen Norway Finn J. Langmyhr (Chairman of the XXVll CSI) Department of Chemistry University of Oslo P.O. Box 1033 Blindern N-0315 Oslo 3 Norway Yngvat Thomassen (Vice-chairman and Programme Chairman of the XXVll CSI) National Institute of Occupational Health P.O. Box 8149 DEP N-0033 Oslo I Norway This traditional biennal conference in analytical spectroscopy was organized for the first time in a Nordic country by the Norwegian Chemical Society. The long and distinguished history of the CSI meetings obligated the Organizing Committee ofeight members to provide participants with a similarly satisfying scientific and personal experience. The XXVII CSI attracted 580 registrants and 59 accompanying persons repre- senting 4 1 countries and all continents.The scope of the conference covered research in basic theory and instrumen- tation ofatomic nuclear and molecular spectroscopy and the application of spectroscopy to the analysis of a broad variety of matrices. In continuance of the scientific tradi- tion of this conference 49 invited plenary and keynote speakers reviewed and discussed recent advances. Over the four days of the meeting a total of 134 contributions were presented or- ally in parallel sessions and 254 posters were shown and thoroughly discussed. The broad scope is reflected in the papers that constitute the special issues of JAAS and The Analyst. The CSI conference conforms to the rules and regulations of the Interna- tional Council of Scientific Unions thus ensuring sponsorship by the Inter- national Union of Pure and Applied Chemistry (IUPAC).At the 35th IUPAC General Assembly in 1989 it was decided to concentrate a significant part of future efforts on projects related to Chemistry and the Environment. To promote this effort the XXVII CSI programme highlighted the key role of spectroscopy in overcoming environ- mental problems and in protecting our environment in a special plenary ses- sion on the Role of Spectroscopy in Environmental Studies. Two special satellite meetings dealing with this topic were also organized the pre- symposium ‘Measurement of Radio- Nuclides after the Chernobyl Accident’ and the post-symposium ‘Speciation of Elements in Environmental and Bio- logical Sciences’.The third pre-symposium ‘Graphite Atomizer Techniques in Analytical Spectroscopy’ emphasized the unique importance of electrothermal atomiza- tion in trace element measurements. Increasing concerns about the conse- quences of both harmful and beneficial constituents in environment matrices encouraged a great number of analyti- cal spectroscopists to meet with other scientists at these satellite meetings for an interchange of knowledge and ideas. Further information and selected pre- sentations from these meetings are available either in JAAS or The Analyst. To enhance the scientific stature of the CSI further the present organizing committee awarded Sir Alan Walsh the Award of the XXVII CSI for his outstanding contribution to spectro- scopy. Sir Alan’s work covers many fields of spectroscopy ‘and in all his work he has contributed original and applied knowledge.In particular his investigations into and thefinal develop- ment of the field of atomic absorption spectroscopy stands out in the field of scientiJic endeavour and his work has found applications in virtually all areas of man> scientijc achievement. In making this award the XXVII CSI is paying tribute to a great but humble man for his inspiration his leadership his ability to apply his talent to many fields and his promotion of knowledge’ as is stated in the award scroll. The organizers and the participants were extremely pleased that Sir Alan and Lady Walsh were both able to travel to Norway. They participated as special guests in the pre-symposium on graph- ite atomizers and the post-symposium on speciation and indeed they charmed us all! Acknowledgement of credit for the success of the award session must also go to four contribu- tors L.R. P. Butler (Republic of South Africa) A. Hulanicki (Poland) P. Lar- kins (Australia) and R. Sturgeon (Canada). Special acknowledgement is owed to Perkin-Elmer and Varian for their generous economic contributions to the XXVII CSI-Award. At the Meeting of the National Delegates in Bergen a proposal to amend the Constitution of the CSI was passed unanimously. The new sub- chapter 6 in Chapter 3 reads as follows ‘On the occasion of each Colloquium a CSI-Award for major contributions to analytical spectroscopy may be pre- sented. The Continuation Committee is responsible for the selection of the recipient.The names of Candidates for the Award should be submitted to the Continuation Committee by the Na- tional Delegates not later than 6 months before thd coming Colloquium. The selection is made by a simple majority vote by the Continuation Committee. The name(s) should be accompanied by a brief summary of the candidate(s) qualijica t ions’. Owing to the recent dramatic changes in Eastern European countries the XXVII CSI in Bergen became for the first time a meeting-place for the entire spectroscopy family. The re- sponse from these countries to the 20 000 first circulars distributed world- wide was overwhelming and many interesting abstracts were received from outstanding scientists. The scar- city of foreign currency made it how- ever extremely difficult for most of them to participate.The Organizing Committee was pleased to be able to provide funds for the support of 30 participants. Certainly any meeting of this type depends on the support and sponsor- ship of a number of organizations and sources. The main source of income was the exhibition of scientific equip- ment and products. Special acknow- ledgements must be given to the 28 exhibiting companies for their support and their effort in preparing the well attended exposition. Most participants took the opportunity to view the latest instrumentation. We would also like to express our appreciation to all speakers poster contributors and chairmen for their excellent cooperation. Finally we also thank the editorial staff of the Royal Society of Chemistry for their inestim- able support in publishing the great number of contributions presented in Bergen.A conference is not only a scientific meeting but also a social event. The venue of the XXVII CSI was we feel a delightful location which all partici- pants enjoyed. During a cheese and wine tasting party a conference excur- sion and a farewell party on the fjord after a week of scientific activities the spectroscopic family demonstrated once again that life is not lived only in the ground state.1 ON JOURNAL OF ANAL,YTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 CSI-Award for Major Scienti ic Contributions to Analytical Spectroscopy On June 10 1991 in Bergen Norway in a session chaired by Dr. J.-M. Mermet (Villeurbanne France) the Award of the XXVII CSI was pre- sented to Sir Alan Walsh FRS by Professor A. Hulanicki (Warsaw Po- land) who was representing IUPAC. Presentations by Dr. L. R. P. Butler Dr. P. Larkins and Dr. R. Sturgeon were then given as tributes to Sir Alan and his work.

ISSN:0267-9477    

DOI:10.1039/JA992070009N

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

1 ON JOURNAL OF ANAL,YTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 A Personal Tribute to Sir Alan Walsh L. R. P. Butler Spectro Analytical Instruments S.A. (Pty) Ltd. P.O. Box 17063 0027 Groenkloof Republic of South Africa It is not everyday that we can be present when a great person is honoured by a presentation from his peers. I believe we should all be very happy that Alan Walsh-a very special person and scientist (in that order) is here today in that position. I first knew about Alan’s work long before I heard about atomic absorp- tion. For indeed Alan’s earliest work in other fields of spectroscopy i.e. ( i ) the invention of the double beam modu- lated light infrared spectrometer and (ii) the Walsh Spark Source also known as the BNF source the forerun- ner of todays ignited uni-directional spark source made significant contri- butions to analytical spectroscopy be- fore AAS.But it was really his work in AAS that has made such a great contribu- tion to science and drew attention to him. I can recall reading his first paper in Spectrochimica Acta as an undergraduate in 1955 and not under- standing it. When his applied paper appeared in 1957 this really excited me but we still did not really appreci- ate how to measure atomic absorption. When we wrote to Alan in his true style of understanding and coopera- tion he wrote back to give us as much information as he could and we were able to build our own ,4A unit. In 196 1 he very kindly visited us. I blush today to think how naive and ignorant we must have appeared to Alan. But with his usual patience and care Alan dis- cussed his experience and carefully criticised us but most of all he moti- vated us with his enthusiasm.He did this with several people all over the world and we saw AAS de- velop almost into a club of people often in keen competition but always in friendship. At the centre of this was Alan who managed to travel a good deal and injected his jokes and goodwill at times when they were most needed. There is nothing more reward- ing or inspiring to a young scientist than to have a person with status such as Alan look over an experiment linked to you look you in the eye and say ‘I like this-I like what you are doing. It is good.’ Talking about Alan’s jokes I cannot resist the temptation to recall one of them. During the war a group of engineers were frantically trying to fathom the secrets of the V-1 and V-2 rockets. A sample of brass was brought to the laboratory of BNF for urgent analysis. When a senior officer came into the lab sometime later to enquire how it was progressing he found the senior analyst with his feet up on the desk reading a magazine.With anger the engineer officer asked the senior chemist what the H . . . ! was happen- ing to the analysis. The analyst put down his magazine and said ‘Well Mr. Jones is doing the copper Mr. Kicks is doing the iron and Mr. Cooper is doing the magnesium.’ ‘And what are you doing?’ asked the officer.‘Oh I am doing the zinc-by difference’ the analyst replied. When one of Alan’s former colleagues at BNF heard it he said to me ‘Yes but it is true you see the senior analyst was Alan!’ Whether this is true or not I do not know but I know that Alan never allowed himself nor any of his team to take it easy.Alan always worked! If not physically then mentally his mind was always active. His great enthusiasm rubbed off. When he spoke about the beautiful colours which could be seen in the focal plane of a spectrograph and the remarkable ability of atoms to absorb one could not help becoming excited.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 11N Talking about atomic absorption I feel I must caution you about his Australian accent (tainted with North Country English). It is rumoured that Alan visited a small university town in the midwest of the USA and was interviewed by a local newspaper re- porter.Some time later while Alan was talking to a well known professor a telephone call came through from the president of the local ladies society. This lady in a very excited voice asked Alan if he would be prepared to ad- dress the ladies the next day on his field of expertise. Alan never a person to say no to a lady was rather intri- gued by the request and after agreeing as an afterthought asked the lady what the topic was to be. ‘Oh Dr. Walsh we have read in the paper .about your special’ field and our ladies are so excited.’ ‘What is that?’ asked Alan. ‘Why atomic abortions’ she said! Friends I could tell you much more but most of you already know about Alan’s work. He introduced AAS. He enthusiasti- cally promoted it supported it devel- oped it and sold it to such an extent that it is today one of the most important methods of elemental ana- lysis that exists. Atomic absorption spectrometers are virtually as common as chemical balances in analytical lab- oratories. We have seen its application and use in every sphere where ma- terials must be characterized from metals to medicine from blood to food from moonrocks to motor cars. We know that these analyses have advanced mans’ knowledge and have excited him to improve and advance. It is indeed fitting that we should acknowledge the work of this great but humble man who always has a twinkle in his eye and a wordofencouragement. Let me ask you to acknowledge him in a way in which he would especially appreciate i.e. as if it were a game of football. Let us give him three cheers!

ISSN:0267-9477    

DOI:10.1039/JA992070010N

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 11N Sir Alan Walsh-The Scientist and the Man P. L. Larkins CSIRO Division of Materials Science and Technology Locked Bag 33 Clayton Victoria 31 68 Australia I would like to start by saying that I am delighted to have been given the opportunity to participate in this pre- sentation of the inaugural CSI-Award to Sir Alan Walsh. I believe that it would be difficult to find a more fitting recipient of this award and I congratu- late those who were responsible for this decision. I would like to present to you briefly my view of Alan's work and its importance and also to give some personal views of Alan derived from working with him for nearly 10 years prior to his retirement in 1976 and in a less formal association since then.Various details of Alan's early years have been recorded in the literat~rel-~ so I will give only a very brief sum- mary. Alan was born in Lancashire in England in 1916 and was one of a family of four children; one sister and two brothers. He was educated in England at the Danven Grammar School and then at Manchester University where he studied physics specializing in X-ray crystallography. He commenced his scientific career in 1939 with the British Non-Ferrous Metals Association working on spec- trochemical methods of analysis and in the short period up to the end of the war he had become a recognized ex- pert in this field particularly in rela- tion to source units for arc and spark spectrograph y . In 1946 Alan joined the CSIR (later CSIRO) in Australia as the first mem- ber of the Spectroscopy Group which was being formed in the Chemical Physics Section of the division of Industrial Chemistry.He was appointed to carry out research in optical spectroscopy especially infra- red (IR) and he arrived in Australia in April 1947 to commence work in this area. By 195 1 he had made a substan- tial contribution to instrumentation in this field by inventing and patenting a double-pass (multiple) mono- chromatol"' which gave increased reso- lution and decreased stray light. A commercial version of this instrument was produced soon after by Perkin- Elmer under licence to CSIRO and production continued for many years. Thus even prior to his work on atomic absorption spectroscopy Alan had established himself as gin ex- tremely capable and inventive spec- troscopist.Although Alan continued his work and interest in IR spectroscopy until about 1958 the invention of atomic absorption spectroscopy began with a thought which occurred to him one Sunday in March 1952 while he was working in his garden. In this regard he is in company with one of the previous great physicists Sir Isaac Newton of whom it is reported that he came to a realization of the laws of gravitation while watching apples falling from trees. Perhaps there is a moral in this; that those among us who aspire to greater things should spend more time gardening. In Alan's case the realiza- tion that the measurement of atomic absorption constituted a possible new method of analysis must have made him quite excited as he then went to the telephone to discuss his new in- sight with one of hiss colleagues.His initial attempt at measuring the absorption by atoms in a flame was successful but the more difficult task of convincing the rest of the world of the value of the technique was only just beginning. In fact when he then de- monstrated his results to some of his colleagues their response was 'Well so hat?'.^ Alan's initial papers on this topic are quite remarkable not only because the details of the instrumenta- tion which he proposed are essentially those which are still in use today but also because in those early papers he proposed many of the other variations and developments of the technique which have since been investigated either at CSIRO or by others. Some examples of these techniques are ca- thodic sputtering for sample atomiza- tion resonance detectors and selective modulation. It is interesting to note that in his first papee Alan even referred to the possible use of a (vacuum) furnace for sample atomiza- tion however no work on furnaces was carried out at CSIRO.In regard to the basic technique Alan has written' that he 'had the great good fortune to select flames for atom- ization and hollow cathode lamps for light sources'. In addition he had used an a.c. detection system to avoid prob- lems from flame emission. I believe that all these choices were not the result of good luck but arose from a thorough understanding of the various possible light sources and atomization and detection systems. This under- standing had been gained during his earlier work on arc and spark emission and on IR and Raman spectroscopy.Perhaps the only piece of good fortune was the fact that he had the opportu- nity to carry out extensive work in both these fields and had a keen12N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 interest in and understanding of the instrumentation associated with these techniques. Closing the gap between the initial thought and the final product of com- mercial standard required extensive work on the part of Alan and the group that he gathered to work on the pro- ject. Development of each of the main components of the atomic absorption instrument required almost a separate research project for each component and the work involved could be dis- cussed at length but I will indicate the size of the project by reference to the work on light sources.The truly crea- tive part of this work was the initial realization that the problem of the narrow width of flame absorption lines could be overcome by the use of a light source with an even narrower emission line. This represented a substantial departure from existing absorption techniques which used continuum light sources combined with a mono- chromator to provide the required spectral bandwidth. In his Raman spectroscopy work Alan had worked with microwave lamps and his initial experiments with atomic absorption had involved lab- oratory discharge lamps. While either of these types of lamps could have been chosen for further development he realized that neither would be capable of providing for the elemental coverage inherent in the technique itself.Instead he chose to base further work on the hollow cathode lamp. This was not a trivial decision since at that time hollow cathode lamps were generally made by the scientists using them and had only short lifetimes. The aim of the work at CSIRO was to develop these lamps in a sealed form with a reasonable lifetime and to be able to make them for all the elements accessible to the atomic absorption technique. This aim was eventually achieved and the wisdom of the initial choice of the hollow cathode is demon- strated by the fact that they are still the main type of light source used in atomic absorption spectroscopy. Having developed the sealed hollow cathode lamp work in this area was not abandoned.In association with Jack Sullivan,’ Alan proceeded to de- velop a modified form of this lamp which they called a high-intensity (or boosted-output) hollow cathode lamp. This modified lamp had the advan- tages of higher intensity combined with narrow linewidths but in this work they were too far ahead of their time. Some of these lamps were pro- duced commercially for a few years in the late 1970s but then interest waned. However developments in atomic fluorescence and the introduction of the carbon furnace revived the need for more intense light sources and a more highly developed version of this lamp is now in production by the Australian firm Photron Pty. Ltd. and is meeting with rapidly growing commercial success. I first became aware of AAS in the early 1960s and I was very impressed.This technique did far inorganic ana- lysis what chromatographic methods and gas chromatography in particular had done for organic analysis. Here was a technique which could be used for an enormous range of sample types with little or no pre-treatment other than that required to bring the sample into solution. This provided an enor- mous increase in productivity as some analyses which required a day or more using previous techniques could now be carried out in less than a minute. Apart from the benefit to analytical chemists worldwide which came from the development and promotion of AAS there were and continue to be real and substantial benefits to Australia which result from this work having been carried out within CSIRO.A cost benefit analysis carried out in 1 9698 conservatively estimated the value to the country to that date to be $20-$23 million. An on-going be- nefit is the fact that this work resulted in the establishment within Australia of two firms which now rank second and third in the world in production of atomic absorption spectrometers. Al- though there were some small instru- ment firms operating previously the manufacture of AAS instruments represented the real birth of the scien- tific instrument industry in Australia. The benefits from AAS however are not all counted in economic terms. Very early in the development of atomic absorption a 7 year old boy had been undergoing treatment in a Syd- ney (Australia) hospital for extensive bums. During the course of his treat- ment he developed convulsions and seemed likely to die.An early atomic absorption unit was used to measure magnesium in his blood and this was found to be very low. Treatment with magnesium salts stopped the convul- sions and he recovered ~ompletely.~ Prior to the introduction of atomic absorption the determination of mag- nesium in blood was very difficult. Moving now to ,41an himself I believe that perhaps the most impor- tant personal characteristic which he brought to his work was enthusiqsm. As those working in (science will know the best scientists inre not detached observers but rather they have a keen almost passionate involvement in their work and the development of their ideas and promote them enthusi- astically to their colleagues. In addition to enthusiasm of course one has to have something to be enthusiastic about. In Alan’s case this was not a problem as he often came into the laboratory with new ideas to discuss or new suggestions to over- come problems in current work.In fact there was one memorable occasion when some work was being carried out on a sputtering-fluorescence tech- nique. Alan made a suggestion which it was estimated would improve the re- sults by a factor of about two. He returned to his office but came back a while later with another suggestion to give another factor of two improve- ment. By lunchtime it was estimated that he had been back 15 times and simple mathematics indicated that the total improvement resulting from his suggestions should be 2 to the power of 15 i.e.about 32000. Actually many of the ideas were useful but the im- provements never reached the esti- mated figure. Not all of Alan’s ideas fell on receptive ears however. Alan has occasionally related a story con- cerning a laboratory assistant who worked for him early in the AAS project. Some time after this person had left CSIRO Alan was looking through her note book and on one page found the cryptic comment ‘Boss sug- gests try. . . ’ followed by some results. On the next page was the equally cryptic comment ‘Didn’t work‘. Some pages on was another note ‘Boss sug- gests try.. . ’ more results and then ‘Didn’t work either’. Of Alan’s various ideas for improve- ment or modification of atomic ab- sorption or related methods none have met with the success of the original idea but this is not surprising.The basic simplicity and broad range of application of AAS more than satisfied most analytical requirements for many years. Although some of his ideas were aimed at problems which are now either much reduced in im- portance or no longer exist others such as sputtering-atomization and boosted hollow cathode lamps (as mentioned earlier) are now having a renaissance and may well see further development in the future. Another characteristic which stood out in Alan’s approach to his work was the desire to keep it simple. This simplicity was obvious in most of the equipment depicted in the early papers on the subject and also in develop- ments in areas such as selective modu- lation. This latter technique effectively put the functions of both the light source and monochromator within the lamp envelope.Unfortunately simpli- city and versatility do not often go together and generally users have opted for versatility with its related complexity. Other characteristics which made itJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 13N a pleasure to work with Alan were his tolerance and his sense of humour. In my early days at CSIRO as a relatively young scientist there were times when I made suggestions or offered opinions which were based on inadequate knowledge. I was never ridiculed but mostly had my ideas discussed and from this I learnt much and with little pain. Alan has many humorous stories to tell of the early days of AAS and some of these have appeared in his written accounts of those times.s During his career Alan has received many honours and awards.I will not try to list them all but among the more prestigious are being made a Knight Bachelor in 1977 and election to Fellowship of the Royal Society and Foreign membership of the Royal Aca- demy of Sciences Stockholm. Among his many medals are the Royal Medal of the Royal Society the Analytical Division of The Royal Society of Chemistry Robert Boyle Medal in An- alytical Chemistry the Talanta Gold Medal and the Maurice Hastler Award of the Society for Applied Spectro- scopy (USA). All the honours and awards which he has received over the years have not altered his generous and friendly nature. In fact he recently agreed to be the subject of a young boy’s school project and readily made the time available to be interviewed. As the young lad noted in the introduc- tion to his report despite ‘his achieve- ments.. . he still doesn’t get big headed’. In finishing I would like to add a final thought. We are of course here to honour Sir Alan Walsh but it is often said that beliind every great man is a great woman and I believe that this is true also for Alan. It would be difficult to find a warmer friendlier lady than Lady Walsh Audrey to all her many friends and I have no doubt that she has been an enormous help to Alan throughout his career. Perhaps this is the area of his life in which he had great good fortune. References Walsh A. Chzmica 1980 34 427. Willis J. B. Hist. Rec. Aust. Sc. 1988 7 153. Annual Report CSIRO Division of Chemical Physics 1976177. Walsh A. Aust. Phys. 1990 27 164. Walsh A. Anal. Chem. 1974 46 698A. Walsh A. Spectrochim. Acta 1955 7 108. Sullivan J. V. and Walsh A. Spectro- chim. Acta 1965 21 721. Brown A. W. CSIRO Industrial Re- search News No. 76 July 1969. Willis J. B. Spectrochim. Acta Part B 1980 35 653.

ISSN:0267-9477    

DOI:10.1039/JA992070011N

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 13N Atomic Absorption Spectroscopy-Present and Future Aspects Ralph E. Sturgeon Institute for Environmental Chemistry National Research Council of Canada Ottawa Ontario KIA OR9 Canada This XXVII Colloquium Spectroscop- icum Internationale has chosen to honour Sir Alan Walsh with its first CSI-Award for major scientific contri- butions to analytical spectroscopy. It is equally an honour and a great privilege to participate in this event and I extend my congratulations to Sir Alan the recognized ‘Father of AAS’. Although Sir Alan has published widely in areas of atomic infrared and Raman spectroscopy he is universally noted for his pioneering contributions in atomic absorption spectrometry (AAS). Since the initial inception of the concept as revealed in his land- mark paper of 1955,’ Walsh perceived the significance of this technique which would revolutionize analytical atomic spectroscopy and pursued it with the conviction necessary to estab- lish it as an acceptable methodology.2 As an instrumental method it has had until recently few equals in popu- larity as of 1986 AAS was ranked the most significant advance to occur in analytical chemistry in the past 50 years.3 Recent market projections4 suggest a 3.8% sales increase for AAS spectrometers in 199 1 to be surpassed for the first time by ICP-AES pur- chases.What does the future hold for AAS? This question has been ad- dressed numerous times in the p a ~ t * . ~ - ~ ~ and I will attempt to examine this perspective once again. This exer- cise is most often indulged in with techniques which have been deemed to have evolved through at least several of the latter ‘seven stages of instru- ment development’1° and may be pre- sently residing in the age of senes- cence.Having already celebrated its ‘silver jubilee’ more than a decade ago,” it certainly merits broad accep- tance. The major challenge facing the fu- ture of AAS stems from increased competition from newly emerging or ‘rediscovered’ (e.g. glow discharge) spectroscopic techniques. Its con- tinued viability will only be assured through successful evolution and ad- aptation of more productive instru- mentation. In comparison with other popular state-of-the-art spectrochemical tech- niques AAS proffers a number of attractive and unique features for rou- tine analyses as well as fundamental investigation,*J2 not the least of which are its competitive cost per analysis high detection power [for electrother- mal AAS (ETAAS)] and simplistic instrumentation.It is well recognized however that the major shortcoming is sample throughput AAS is by de- sign a ‘single-element at a time’ tech- nique. This can be attributed primarily to the source-detector arrangement and to some extent to the atomizer. If this problem is to be addressed major changes/modifications will have to be implemented to have any impact on these areas. Current international re- search efforts have identified and ex- plored a number of options and these will be the target of discussion of this text. Flame AAS (FAAS) suffers most acutely from competition with induc- tively coupled plasma atomic emission spectrometry (ICP-AES).The latters’ multi-element capability (fast sequen- tial and simultaneous) and detection power that rivals or surpasses FAAS especially for the refractory elements have placed FAAS in a vulnerable position. Instrumentation for FAAS has altered little since Walsh’s first description of the method.’ Since the introduction of the dinitrogen oxide- acetylene flame by Willis in 1965 there has been no subsequent major advance in flame methods ‘which appear to have reached a plateau of de~elopment’.’~ Although this state- ment was made by Walsh more than a decade ago it remains valid today. A limited amount of research continues to be invested in the design of more efficient burner heads14 but the major-14N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL.7 ity of interest in the fabrication and characterization of new nebulizers and spray chambers appears to lie with ICP users. Automation of commercial FAAS instruments is currently well devel- oped permitting some 500 determina- tions per hour. However as has been noted,I5 such instruments can be de- scribed as multi-sample rather than multi-element in that they repetitively determine the same element in all samples prior to quantifying the next element. An instrumental approach to multi-element capability has been de- scribedI5 using conventional hollow cathode line sources having the capa- city for an estimated 1200 determina- tions per hour-very competitive with sequential ICP based instrumentation. Although automation of instrumenta- tion via onboard microprocessor con- trol has revolutionized performance and (unattended) sample throughput of FAAS as well as other atomic spectrometric techniques it is hoped that the intelligent instrument of the future will go beyond these narrow confines and actively participate in the implementation of quality assurance/ quality control of the data.16 Although unfortunately still consi- dered within the realm of a laboratory research tool the wavelength modu- lated continuum source based instru- ment conceived by O'Haver and col- leagues provides an attractive and viable approach to true multi-element AAS when coupled to a high-resolu- tion polychr~mator.~~*~~ When inter- faced to photodiode array detectors the optics are simplified by omission of the wavelength m o d ~ l a t i o n ~ ~ (as well as the need for multiple PMTs).Currently this approach is limited in scope to those elements having reso- nance lines lying above 280 nm be- cause of the poor source intensity at shorter wavelengths. This of course precludes application to the measure- ment of many elements of current environmental interest. This limita- tion may be lifted as a result of promising recent studies aimed at pulsing the continuum source to high intensity levels thereby boosting the UV output. Moulton et aLto reported a signal-to-noise ratio (S/N) increase of 1.4-fold at 24 1 nm by using a pulsed continuum source in conjunction with linear photodiode array detection.An improvement factor of 6.7-fold was noted over the case of PMT detection with a non-pulsed lamp. It is expected that significantly greater benefits in S/N will be reaped with larger pulse currents. An alternative approach to achiev- ing the resolution needed for con- tinuum source AAS is by application of interferometry. Although a Fourier transform AA spectrometer provides all of the advantages of other con- tinuum source dispe:rsive systems it can be subject to a multiplex disadvan- tage when a practical free spectral range is desired and. at high resolu- tion suffers from long scan times.21 How will such research impact on the practising analyst and the market for FAAS? The answer of course is. little unless a commercial instrument becomes available. Despite the ac- knowledged benefits of multi-element capability faster throughput compar- able detection power and greater dy- namic range the increased complexity of utilizing a high-resolution polychro- mator offsets the current cost advan- tage cited for FAAS over its ICP-AES competitor. This is not the whole picture however because such an in- strument would also find application with the graphite furnace and this is the area that could revolutionize the use of AAS.A cursory examination of current analytical spectroscopic litera- ture reveals that it is the graphite furnace atomizer that is of prime interest for further development (not only for AAS but as an atomizer for use in a variety of ,atomic and mass spectroscopic instrumentation). The introduction of the graphite furnace by L'vov in 195922 was even- tually to elevate AAS to a foremost position amongst preferred techniques for ultratrace analysis.The reason was clear all of the inherent advantages of AAS were coupled to a highly efficient atomization device.23 Significant im- provements in signal processing fur- nace design and operation have oc- curred in the last decade and many of these are now embodied in the concept of the stabilized temperature platform furnace (STPF) pioneered by Slavin and c o - w o ~ k e r s . ~ ~ ~ ~ ~ The remarkable success of this relatively interference free technique has permitted extension of the procedure to the analysis of solids and and has advanced to the point where the concept of absolute (standardless) analyses may be realistically e n t e ~ t a i n e d .~ ~ . ~ ~ With the recent release of a commercial graphite furnace atomizer (Perkin- Elmer) based on the design of the spatially isothermal cuvette of Frech et al.,29 analysts are expected to have even greater freedomi from matrix in- terferences as well as reduced spectral background and memory effects. Of course matrix effects cannot be com- pletely eliminated even for constant temperature atomize~rs.~~ Unfortunately graphite furnace (GF) techniques are aho characterized by the single-element-at-a-time AAS syndrome which was further com- pounded by the need to establish indi- vidual atomization programmes op- timized for each element or a few broad classes of elements-a situation which turned out to be more inflexible than that encountered by the choice of two different flames in FAAS.Conven- tional single-channel GF instruments usually cannot achieve more than 20-30 determinations per hour in a multi-sample approach. This rate may be increased up to 100 per hour if the furnace cycle time is reduced to a minimum using such measures as hot injections elimination of the drying and/or char stage and reducing the delay between injections by the auto- sampler.31 Bank et ~ 1 . ~ ~ 9 ~ ~ recently de- monstrated the feasibility of flow in- jection thermospray deposition for ETAAS which boosted potential throughput into the 150-200 per hour range while retaining sensitivity preci- sion and the use of pl volumes. The excellent scope for the correction of high non-specific background absorp- tion offered by Zeeman-effect systems serves to more easily implement such modifications to the thermal pre-treat- ment of the sample.Although commercially available 2 and 4 channel instruments (Hitachi and Thermo Jarrell Ash) could serve to increase the multi-sample efficiency of the technique further increased com- petition from the now well established field of ICP mass spectrometry (ICP- MS) will eventually require that ETAAS adopts a true multi-element approach to survive. In this respect the shortcomings of AAS highlighted by Hieftje,7 i.e. those resident in the hollow cathode light (HCL) source and the atomizer need to be addressed and promising alternatives pursued. Multi-element AAS necessitates a multi-wavelength source and com- patible detector. Systems based on multiple HCLs rapidly become im- practical with more than only a few elements and with ETAAS any at- tempt at rapid sequential measure- ment will fail.Only continuum sources and cheap tunable lasers inherently meet the necessary requirements. Dis- persive rather than interferometric means should be considered as a consequence of the cost and practical limitations associated with the lat- Continuum source based ap- proaches are presently the most attrac- tive. Those employing high-resolution polychromators with PMT detectors and wavelength modulation have been shown to provide exceptional perfor- mance for elements having resonance lines above 280 nm. Here detection limits are generally within a factor of 2-3 of those obtained with line sources background correction is rapid and accurate and dynamic range can be extended to cover 4-6 dec- a d e ~ .~ ~ As noted earlier useful access ter.7,1221JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 15N to resonance lines lying below 250 nm now appears promising using pulsed continuum source^*^^^^ but extensive work will be required to evaluate this comprehensively. Schmidt et ~ 1 . ~ ~ re- cently described such an approach based on an Cchelle spectrometer and a charge coupled linear array device as detector. Electrothermal AAS detec- tion limits achieved for Cd and Pb at 228.8 and 283.3 nm respectively were within a factor of two of their line source counterparts. The coupling of pulsed continuum sources and diode array detectors should also find application in the domain of coherent forward scattering wherein more intense sources should improve performance. This technique has already demonstrated useful multi-element results with commercial atomizers and 4-6 decades of linear range.36 Hergenroder and NiemaxJ7 recently demonstrated the feasibility of multi- element ETAAS using temperature and diode current controlled semicon- ductor diode lasers as sources. With modulated diode laser power (using electro-optic KDP crystals) the signal measured with a photodiode in a non- dispersive system can be subjected to Fourier analysis to separate multiple channels.Rapid square wave diode current modulation permits absorp- tion measurements to be made on/off line for simultaneous background cor- rection or in the wings of the profile for extended linear range.Compact multi channel capability may be realistically achieved using optical fibre techno- logy. The availability of diode lasers covering a wider wavelength range is anticipated. Successful solutions to the optical aspects of the multichannel AAS chal- lenge highlight the remaining deficien- cies resident in the atomizer. Pre- sently separate optimization of ther- mal parameters is generally required for each element due to either pre- atomization losses or incomplete atomization. Three solutions merit consideration the quest for and appli- cation of a ‘universal’ chemical modi- fier; the elimination of the thermal pre- treatment stage and the application of new atomizers. Multi-element analyses may be heavily dependent upon the use of chemical modification techniques in that compromise thermal conditions will be utilized.Reduced palladium appears to be emerging as a potentially universal modifier that will be useful for this purpose.38 It should be noted that the need for chemical modifica- tion techniques should be verified be- fore use on a sample. Manning and S l a ~ i n ~ ’ ” ~ have presented examples of systems in which adequate perform- ance can be achieved by eliminating the char stage and modifier com- pletely. The larger background which normally occurs is then easily handled with a Zeeman-based system. It is easier to conceive of universal com- promise conditions in such circum- stances. ‘If atomic absorption methods are to be substantially improved it seems inescapable that the advances can only result from improved methods of atomization’.This statement was penned by Walsh in 1980.13 With the conventional GF this has included implementation of ideas fostered by L‘vov,~~ i.e. vaporization of samples from a platform placed within the furnace (on which STPF techniques are now based) from a probe subse- quently inserted into an isothermal furnace41 and by rapid heating achieved through capacitive dis- charge.42 The last has proved to be too difficult to utilize routinely because of materials requirements whereas the performance of the probe technique can generally be matched through ap- plication of the simpler STPF con- ~ e p t . ~ ~ Similarly the spatially and tem- porally isothermal two-step atomizer described by Frech and J o n s ~ o n ~ ~ while deemed too complex to justify routine applicati~n,~~ may provide an excellent vehicle for implementation as an atomizer for multi-element M S .This configuration is amenable to automation and lends itself more eas- ily to the establishment of compromise conditions. It has been suggested that use could be made of non-thermal atomizers in particular the rare gas sputter systems which are advantageous in producing a low background and high yield of atomic vapour. A version of the popu- lar glow discharge lamp (Atomsource) has been introduced into the market- place and configured so as to optimize production of ground-state atoms in the analytical volume.*5 In such sys- tems there is a greater conformity between the composition of the sample and the vapour being analysed such that matrix effects may be greatly reduced and samples having a range of compositions can be analysed with the same working curve.‘To date all sput- tering work has been concerned with steady-state systems. Would it not be worthwhile considering the use of ca- thodic sputtering in association with the “total vaporization” method evolved by L‘vov?’. This remark by WalshI3 follows from his early work on sputtering at CSIRO (Australia) and recognizes the significance of L’vov’s approach which has been so successful with the GF. Recent studies by Chak- rabarti et al.46 confirmed the benefits of transient sputter atomization of discrete samples for which absolute detection limits rival those of conven- tional ETAAS. Although an evaluation of the effect of the matrix is awaited it is tempting to speculate that such an approach might present an attractive source for multi-element AAS.Non- conductive samples may likely be sputtered via r.f. discharge^.^' A hurdle to be surmounted in the quest for multi-element AAS is the limited linear range (currently 2-4 decades) which makes it necessary to undertake multiple dilutions in order to cover the variation of elemental concentrations present in a typical sample. Several means have been sug- gested to extend this figure of merit the most promising working concept for commercial instrumentation being use of three-field ax. Zeeman modula- t i ~ n ~ ~ which readily achieves a 5- 10 fold wider dynamic range. Alterna- tively instrumentation based on the ‘Smith-Hieftje’ pulsed HCL back- ground correction approach may take advantage of a corresponding multi- level current pulse to elicit different source profiles and thereby extend linear range.With continuum source based instruments the dynamic range can cover 4-6 decades by making use of information in the line wings. Thus it appears that this obstacle can be easily circumvented with existing tech- nology. The demand for reliable analytical data at ever decreasing concentration levels has outstripped current detec- tion capabilities of ETAAS for many elements. It is for this reason that methodology for enhancing detection power is evolving at a rapid pace. Such approaches include conventional off- line matrix separation and preconcen- tration schemes as well as in situ trapping of volatile forms of elements [e.g.hydrides Ni(C0)4 Pb(CzH!)4J.49 The latter are ultratrace techniques which make specific and profitable use of the GF and are ripe for automation. Throughput even in the single- element mode can be considerably enhanced utilizing flow injection tech- niques to speed both calibration proce- dures and sample analyses. On-line sample preparation systems for matrix management and analyte preconcen- t r a t i ~ n ~ ~ ? ~ ~ will have substantial im- pact on all areas of analytical atomic spectroscopy in the coming years. More difficult samples will be amen- able to quantitation at lower analyte concentrations with greater speed pre- cision and accuracy. As these develop- ments are likely to influence all instru- mentation without prejudice no rela- tive gains can be claimed by AAS proponents.However it is evident from the foregoing that greater atten- tion must be paid to enhancing the16N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 versatility of GF autosamplers. Soft- ware control should permit the user to program the timing and mechanical events associated with this process. It is clear that it should be possible to provide AAS users with multi- element capability using present tech- nology In this regard current research directions suggest the suitability of an image detector approach in combina- tion with a pulsed continuum source and a GF or sputtering cell. Means will be devised for coping with the volumi- nous amount of data generated by the necessary two-dimensional detectors if a significant wavelength range is de- sired.52 However in the final analysis ‘it is unlikely that AAS would in its over-all capability surpass those tech- niques with which it is now competi- tive’17 (ie.ICP-AES and -MS). Of course it is not necessary perform- ance wise for future AAS instruments to surpass that of other spectrometric techniques in order to remain viable. Quite apart from its sustained contri- butions to fundamental and diagnostic studies of atomic systems AAS will continue to be used in a routine analyt- ical capacity. When methods are com- pared for ultratrace capability the power of detection and accuracy or reliability become the most important criteria.53 Inductively coupled plasma AES is gradually replacing FAAS and this trend will accelerate as the cost of ICP equipment continues to decline and the demand for multi-element capability rises in the face of environ- mental challenge and legislation.Elec- trothermal AAS however is currently ‘holding its own’ and will continue to act in a complimentary rather than redundant manner to enhance the capability of alternative spectrometric techniques. It is the acknowledged ‘benchmark’ against which all other commercial- and laboratory research- based atomic spectrometric tech- niques (including ICP-MS LEAFS LEI CFS FANES and FAPES) are currently and will continue to be gauged. The decline noted in the total number of AAS publications in the last 5 years7 in no way construes the demise of this technique-it only serves to reflect its broad and unchal- lenged acceptance.The remarkable fact that publications continue in this already mature discipline reflects the substantial interest of researchers and users alike. Of course one of the principal ad- vantages of absorption measurements is that they are amenable to undertak- ing absolute analyses. This subject has been raised earlier by RannS4 for the flame and by L‘vovz7 for the furnace. It would be no great surprise to find analysts using this approach in future at least for semiquantitative work. We are indebted to !Sir Alan Walsh for his many contributilons to the birth and growth of this fascinating and ubiquitous analytical tool. The ques- tion posed by him2 some 17 years ago ‘AAS-Stagnant or Pregnant?’ can still be answered with the same re- tort... ‘the subject has not really been stagnant but merely pregnant and has now given birth to new offsprings’. References 1 Walsh A. Spectrochim. Acta 1955 7 108. 2 Walsh A. Anal. Chem. 1974 46 698A. 3 Braun T. Fresenius’ Z. Anal. Chem. 1986,323 105. 4 Howard B. Am. Lab. 1991 Jan. 66. 5 Koirtyohann S. R. Anal. Chem. 1980 52 736A. 6 Slavin W. Trends Anal. Chem. 1987 6 194. 7 Hieftje G. M. J. And. At. Spectrom. 1989 4 11 7. 8 Sturgeon R. E. Fresenius’ 2. Anal. Chem. 1990,337 538. 9 Slavin W. Anal. C‘hem. 1982 54 685A. 10 Koirtyohann S. R. and Kaiser M. L. Anal. Chem. 1982 54 15 1 5A. 11 Boumans P. W. J. M. Spectrochim. Acta Part B 1980 35 637. 12 Hieftje G. M. Fresenius’ 2. Anal. # Chem. 1990,337 5289. 13 Walsh A. Spectrochim. Acta Part B 1980 35 639.14 I Willis J. B. Sturman. B. T. and Frary B. D. J. Anal. At. Spectrom. 1990 5 399. 15 Bernhard A. E. and Kahn H. L. Am. Lab. 1988 June 1261. 16 Hieftje G. M. Spectrochim. Acta 1990 44 (Spec. Suppl.) 11 3. 17 Zander A. T. O’Haver T. C. and Keliher P. N. Anal. Chem. 1976 48 1166. ’ ’18 Harnly J. M. Kane J. S. and Miller- Ihli N. J. Appl. Spelctrosc. 1982 36 637. 19 Jones B. T. Mignardi M. A. Smith B. W. and Winefordner J. D. J. Anal. At. Spectrom. 1989 4 647. 20 Moulton G. P. O’Haver T. C. and Harnly J. M. J. A n d . At. Spectrom. 1989 4 673. 21 Glick M. R. Jones B. T. Smith B. W. and Winefordner J. D. Anal. Chem. 1989,61 1694. 22 L‘vov B. V. Spectrochim. Acta 1961 17 761. 23 Falk H. and Tilch J. J. Anal. At. Spectrom. 1987 2 5.27. 24 Slavin W. Manning D.C. and Carn- rick G. R. At. Spectrosc. 1981 2 137. 25 Slavin W. and Carririck G. R. Am. Lab. 1988 Oct. 88. I 26 Epstein M. S. Carnrick G. R. Slavin W. and Miller-Ihli N. J. Anal. Chem. 1989,61 1414. 27 L‘vov B. V. Spectrochim. Acta Part B 1990 45 633. 28 Slavin W. and Carnrick G. R. Spec- trochim. Acta Part B 1984 39 27 1. 29 Frech W. Baxter D. and Hutsch B. Anal. Chem. 1986 58 1973. 30 Frech W. Cedergren A. Lundberg E. and Siemer D. D. Spectrochim. Acta Part B 1983 38 1435. 31 Slavin W. Manning D. C. and Carn- rick G. R. Spectrochim. Acta Part B 1989,44 1237. 32 Bank P. C. de Loos-Vollebregt M. T. C. and de Galan L. Spectrochim. Acta Part B 1988 43 983. 33 Bank P. C. de Loos-Vollebregt M. T. C. and de Galan L. Spectrochim. Acta Part B 1989 44 571. 34 Harnly J.M. Fresenius’ 2. Anal. Chem. 1986,323 759. 35 Schmidt K. P. Becker-Ross H. and Florek S. Spectrochim. Acta Part B 1990,45 1203. 36 Hermann G. Jung M. Lasnitschka G. Moder R. Scharmann A. and Zhou X . Spectrochim. Acta Part B 1990,45 763. 37 Hergenroder R. and Niemax K. Spectrochim. Acta Part B 1988 43 1443. 38 Schlemmer G. and Welz B. Spectro- chim. Acta Part B 1986 41 1 157. 39 Manning D. C. and Slavin W. Spec- trochim. Acta Part B 1988 43 11 57. 40 L‘vov B. V. Spectrochim. Acta Part B 1978 36 153. 41 Littlejohn D. Cook S. Durie D. and Ottaway J. M. Spectrochim. Acta Part B 1984 39 295. 42 Chang S. B. and Chakrabarti C. L. Prog. Anal. At Spectrosc. 1985 8 83. 43 Wu S. Chakrabarti C. L. and Rogers J. T. Prog. Anal. Spectrosc. 1987 10 111. 44 Frech W. and Jonsson S. Spectro- chim. Acta Part B 1982 37 1021. 45 Lundberg E. Frech W. Baxter D. and Cedergren A. Spectrochim. Acta Part B 1988 43 45 1. 46 Chakrabarti C. L. Headrick K. L. Hutton J. C. and Bertels P. C. Spec- trochim. Acta Part B 1991 46 183. 47 Duckworth D. C. and Marcus R. K. Anal. Chem. 1989 61 1879. 48 de Loos-Vollebregt M. T. C. Koot J. P. and Padmos J. J. Anal. At. Spec- trom. 1989 4 387. 49 Sturgeon R. E. Spectrochim. Acta Part B 1989,44 1209. 50 Karakaya A. and Taylor A. J. Anal. At. Spectrom. 1989 4 261. 51 Fang Z. Sperling M. and Welz B. J. Anal. At. Spectrom. 1990 5 639. 52 Kolczynski J. D. Radspinner D. A. Pomeroy R. S. Baker M. E. Norris J. A and Denton M. B. Am. Lab. 1991 May 48. 53 Tolg G. Analyst 1987 112 365. 54 Rann C. S. Spectrochim. Acta Part B 1968 23 827.

ISSN:0267-9477    

DOI:10.1039/JA992070013N

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 17N Reflections and Comments from Sir Alan Walsh FRS In a brief speech following the presen- tation of the inaugural CSI-Award Sir Alan spoke of his delight and surprise on learning that he was to be the first recipient. The surprise was complete since he had been totally unaware that such an Award had been proposed. He thanked Pat Butler Peter Larkins and Ralph Sturgeon for their generous re- marks which were in sharp contrast to the apathy and suspicion which greeted the first papers on atomic absorption spectroscopy in the 1950s. He wondered if the delayed impact of these early papers was partly due to them having originated from small and/or remote countries such as Hol- land Australia New Zealand and South Africa.The production in Australia in the late 1950s of ‘do-it-yourself kits’ which permitted the construction of the ‘working-man’s atomic absorption spectrometer’ led to rapid acceptance of atomic absorption methods. Sir Alan paid high tribute to all those who took part in the design construction marketing and operation of these cost- effective instruments. He felt quite sure that these many contributions had been influential in the decision to present the first CSI-Award to Australia! After the conference Sir Alan reflected that it had been outstandin- gly successful. He considered that he had little expertise in most of the subjects being presented (a typically humble comment) but the standard of lecturing had been remarkably high and the discussions lively. The enthu- siasm was sustained throughout the proceedings. The social events had Sir Alan and Lady Walsh been most enjoyable and all partici- pants had appreciated the meetings held in remote but beautiful surround- ings which contributed to the confer- ence being such a happy one. For he and his wife the conference had been a very special occasion. They had been overwhelmed by kindness and the conference organizers had spared no effort to make their visit to Norway a particularly happy one. It had been especially good to see many old friends who they had not met for a long time. Sir Alan and Lady Walsh brought a great deal of pleasure to everyone at the conference and for this we thank them and wish them good health and happiness for many years to come. We also hope it will not be too long before we meet them both again.

ISSN:0267-9477    

DOI:10.1039/JA992070017N

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 69 New Developments and Final Frontiers in Inductively Coupled Plasma Spectrometry* Plenary Lecture Gary M. Hieftje P. J. Galley M. Glick and D. S. Hanselman Indiana University Department of Chemistry Bioomington IN 4 7405 USA A number of areas of study are indicated which are important in furthering the application and capability of the inductively coupled plasma. Featured especially are the importance of overcoming matrix and inter-element interferences the development of diagnostics to monitor instrument operation the use of adaptive computer- based feedback control to optimize instruments and the introduction of intelligent sample processing. Examples are taken from the author’s laboratory of ways in which new developments in instrumentation and understanding are permitting these frontiers to be conquered.Keywords inductively coupled plasma; matrix and inter-element interference; instrument operation; intelligent sample processing It has been just about 20 years since I first became aware of the inductively coupled plasma (ICP) and its potential power in analytical atomic spectrometry.’ Since that time the ICP has become perhaps the world’s most powerful tool for routine multi-element analysis. Applied mostly as a source for atomic emission spectrometry the ICP is used to analyse samples of interest in geology biomedicine petro- leum engineering the chemical industry forensic science environmental monitoring and others. Such an emission system is capable of providing literally thousands of elemental determinations each working hour most at the part per billion level.Somewhat more recently the ICP has also been used effectively as an ion source for elemental mass spectro- metry. In this role the source retains its high-throughput capability but offers also part per trillion detection limits excellent semi-quantitative determinations isotope analy- sis and isotope dilution capability and virtually complete elemental coverage across the Periodic Table. Considering these capabilities the widespread applica- tion of the ICP and the power of modern computer- controlled commercial ICP instrumentation it is appropri- ate to ask at the present time what important developments might take place that could appreciably enhance the power of this versatile source.Are there developments that could make the source even more beneficial? Are there important unsolved questions to which workers in ICP spectrometry should devote their attention? An examination of recent journal articles and a perusal of lectures and posters being presented at the conference at which the present paper was given2 dictates that these questions all be answered in the affirmative. In the following sections of this paper a number of new developments and remaining frontiers in ICP spectrometry will be described. Some of the challenges are to overcome remaining shortcomings of the source and of the instrumentation that utilizes it; others involve improving the utility convenience and reliability of the systems; and still others will emphasize taking greater advantage of the flood of data that the ICP is capable of producing. These ‘final frontiers* can in some instances be explored with current knowledge and technology.In other situations new developments will be needed. Of course in a document of reasonable length it is impossible to detail or even describe the many investiga- *Presented at the XXVII Colloquium Spectroscopicum Interna- tionale (CSI) Bergen Norway June 9- 14 I99 l . tions and improvements which might profitably be pursued in ICP spectrometry. To narrow the scope somewhat attention will be focused on ICP atomic emission spectro- metry. Firstly a brief overview of a number of the remaining frontiers in ICP emission spectrometry will be offered. Next only a few of those frontiers will be selected for amplification.It can be hoped that future manuscripts or other workers will cover the remaining topics in greater detail. The Final Frontiers A few of the ‘final frontiers* that remain in ICP emission spectrometry are compiled in Table 1. Although many readers will feel that other topics should have been included in the list few would dispute the importance of those that are cited. Interestingly many of the topics are related; efforts made to attack one of the ‘frontiers* will be likely to have an impact on others also. For example adding diagnostics to current instrumentation might help reduce the severity or incidence of matrix interferences especially if the operating characteristics of such instruments are adaptively controlled by an on-line computer.In an ideal embodiment of such a system the ICP itself might be monitored by for example a low-cost video camera equipped with spectral-selection capability. The spatial pattern of emission so monitored could then be used by an appropriately programmed control computer to adjust operating conditions of the plasma in a manner to alleviate inter-element interferences. More details will be provided on this topic later. Similarly an instrument that can adapt its operating conditions to different incoming samples would benefit from and also could be employed in schemes to automate sample preparation. Again more will be offered on this topic later. One of the challenges ,in Table 1 that is now being addressed but for which an optimum solution seems still Table 1 Final frontiers in atomic spectrometry Overcoming matrix interferences Automating and minimizing sample preparation Adding diagnostics to instrumentation Developing self-adaptive instrumentation Achieving total-spectrum simultaneous read-out Enhancing information extraction and display Improving precision70 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL.7 Atom Source .) detection * Sample processing * not to be available is the rapid electronic and error-free recording of a complete emission spectrum from the ICP. The immediate availability of a full high-resolution spec- trum such as that recorded and processed much more slowly on a photographic film would permit far more reliable background correction the use of multiple or alternative elemental emission lines and would provide a diagnostic tool in itself useful for adaptive control of the instrument by an associated computer.Furthermore if the wavelength registration of such a full spectrum were sufficiently accurate it would enable new signal-processing options to be explored. Such options would include but would not be limited to spectral stripping the use of multilinear regression for calibration application of neural networks for sample recognition and characterization and noteworthy enhancements in information extraction and display. This last topic is a worthy one for examination in itself. New statistical algorithms of increased power are continu- ously being introduced that could enhance data treatment from an ICP spectrometer in important ways.New visual- display approaches in particular could enable a scientist or technician more rapidly to grasp the meaning of subtleties in a data set. Human beings are capable of perceiving amazingly subtle nuances in projected images. Consider for example our ability to recognize the mood even of a stranger and how difficult it would be to describe what minutiae of facial expression led us to the conclusion. In the same way large datasets involving elemental concentrations or even emission spectra themselves could perhaps be displayed to permit visual recognition of errors in plasma performance the presence of unexpected species the class to which a sample belongs or even the answer to an underlying question that the elemental analysis was intended to answer.For example the answer which an elemental analysis is expected to provide is ultimately not really ‘What are the elemental concentrations?’ but rather ‘Is the patient healthy?’ ‘Is the engine lubricant still useful? or ‘Is the site from which this geological sample was taken an attractive target for further prospecting? It should be possible to devise data-display approaches that would enable a human operator to answer such questions directly and immediately. As a further indication of how the goals listed in Table 1 are inter-related consider the functional block diagram of an atomic spectrometric instrument displayed in Fig. 1. In this diagram the sample processing unit includes all of those devices which might be required to extract dissolve dilute or introduce samples into the spectrometric source (here an ICP).It might involve or require the use of electronic balances microwave-digestion systems auto- matic dilutors chromatographic columns possibly a laser- ablation device nebulizers spray chambers or others. The processed sample generated by this first block is then introduced into the source (the ICP). The ICP has the function of converting the introduced sample into the form of free atoms or ions and for the present discussion of exciting those atoms or ions in a reliable reproducible fashion. Only if these operations are carried out appropri- ately can the resulting emission spectrum be related unambiguously to elemental concentrations in the original sample. The atom detection module might be a direct-reader a slew-scan monochromator a linear or two-dimensional 1 Signal processing Fig.1 Functional block diagram of an atomic spectrometric instrument. See text for discussion detector-array spectrometer a Fourier-transform spectro- meter or another interferometric device. Whatever its character its purpose is to process the emitted radiation from the ICP so that the resulting display can again be related clearly to the elemental composition of the sample. Although perhaps the least developed of all the compo- nents in Fig. 1 the signal processing unit is in many ways the most important. At present signal processing is ordinar- ily limited to such mundane functions as spectral-line identification background subtraction the preparation of working curves and the calculation of concentrations.As indicated briefly above future signal-processing schemes will be far more powerful and complex. To improve this conventional instrument dramatically will require feedback from the signal-processing block to all the earlier components (see Fig. 2). For instance raw sample processing could be improved to insure that a sample is completely dissolved or maintained properly in suspension. The signal-processing module could also moni- tor the aerosol character or laser-ablation rate if the sample processor is equipped with suitable monitors or diagnostic devices. With additional diagnostic tools such as the special-purpose television camera cited earlier excitation or ionization conditions in the ICP could also be gauged so that they are either kept constant or adjusted for special- purpose applications or to accommodate specific sample types.The atom detection unit could also be optimized. For example spectral alignment could be continuously ad- justed the strength of internal-standard lines could be monitored and used for feedback purposes or the internal- standard lines themselves could be changed. Many other possibilities exist of course. For this type of future capability to be achieved will require modifications in current instrumentation and in part in the ways we think about such instruments. For example even though most modem ICP emission spectro- meters are equipped with computers the instruments in many instances are not optimized for computer monitoring or control. Many of the control inputs are fashioned after knobs or levers that were meant originally for human control. Also data outputs from such systems are often analogue and ordinarily limited to the response time of a human operator (typically 0.1 s) rather than tailored to the millisecond time scale on which a computer can respond.Moreover as stated before for this scheme to be effective will require the introduction and use of novel diagnostic approaches among which will be a full spectral display. In this spectral display the fidelity of both the horizontal and vertical axes will be critical. Fidelity on the horizontal (wavelength) axis of a spectrum permits more reliable spectral subtraction spectral stripping and the identifica- tion of lines and bands. Fidelity on the vertical axis of a spectrum means that precision will be enhanced and once more that spectral subtraction will not introduce unaccep- table levels of error.An adaptive-feedback computer-control approach such as in Fig. 2 will also require that a great deal more be known about all the blocks in Fig. 1 than is currently the situation. ~~ Control feedback paths Fig. 2 Future atomic spectrometric instruments will be improved by adaptive feedback from an on-board signal-processing unit to the various components that control the performance of the instrumentJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992. VOL. 7 71 For example unless samples are restricted to a particular type (i.e. unless matrices are matched) more will have to be understood about how matrix interferences originate if computer control is to be used to overcome them.In turn the means by which atoms and ions are generated and excited in the ICP will have to be better characterized and more must be learned about how the sampling process takes place. Indeed characterization of the ICP and how it acts on a sample remains one of the most fruitful areas for continuing research in ICP emission spectrometry. Finally new means will have to be developed for intelligent sample processing. Instrumentation will have to be devised that is amenable to control and in which aerosol character solvent load and sample-introduction rate can be monitored and adjusted independently of other instrumen- tal characteristics. Processing units will have to be created that can handle a variety of sample types forms and phases or that can be quickly modified to accept a different sort of sample.From this discussion it is clear that many of the 'final frontiers' are tied together. Let us therefore examine briefly two pairs of the 'frontiers'. We will devote the greatest attention to matrix interferences and the possible use of diagnostic techniques to overcome them. Less attention will be given to the automation of sample preparation and its use in self-adaptive experimentation since those topics are covered in a companion paper in this issue.3 Overcoming Matrix Interferences Inter-element (matrix) interferences in ICP emission spec- trometry arise from several sources and are still only partially characterized. For example it is now well known that the introduction of alkali metals or other easily ionized elements (EIE) causes a spatial shift and/or a change in emission intensity from both neutral atoms and atomic ions in the ICP. Depending on the observation location such changes can result in either positive or negative errors during an analysis.Other elements less easily ionized (non- EIEs) can also cause errors. Most recently it has been shown that intact droplets or the vapour clouds that result from them survive to points high in the ICP and no doubt affect sample atomization ionization and excitati~n.~*~ It would be surprising if droplet-related events were not linked in some way to matrix interferences. It is not yet clear how a concomitant species (EIE or non- EIE) influences the emission strength or pattern of an analyte element. For example an added element or the electrons it releases upon ionization might alter any of several things (i) the manner by which energy is coupled into the plasma; (ii) the rate of propagation of such energy throughout the plasma and therefore the plasma structure itself; and (iii) the coupling of the plasma energy with a sample aerosol to atomize it with sample atoms to ionize or excite them or with sample ions to excite them.Importantly no matter which of these events is affected by a concomitant element it would be tied in some way to one or more of three fundamental parameters in the plasma the electron number density the electron distribu- tion and the gas temperature. Consequently much can be learned about the ICP and how it interacts with a sample by characterizing these three parameters.Of course because the ICP is highly heterogeneous the three variables must be mapped spatially. Also although the ICP is certainly a steady-state source,6 additional information could be gleaned by its response to a transient pert~rbation.~-l~ Thus it would be desirable if the three parameters could be monitored temporally as well. Laser-light scattering has been found to be among the most powerful of possible methods for providing the necessary information. One such technique Thomson A Pulsed Electron - motion (e7- Thomson Fig. 3 Schematic diagram of the Thomson-scattering process. Radiation from a pulsed Nd:YAG laser (532 nm) is scattered from a rapidly moving electron (e) in a plasma causing a substantial Doppler shift in the scattered light.As a result the velocity (energy) distribution of a collection of electrons can be deduced from the spectrum of the scattering and the local number density of the electrons can be calculated by integrating the intensity of the scattered light over the entire spectrum scattering yields temporally and spatially resolved knowl- edge about electron energy distributions and number densities. Another method Rayleigh scattering can be performed at the same time and with the same apparatus as Thomson scattering and offers temporal and spatial values for gas-kinetic temperatures. Thomson scattering has been described in detail else- ~ h e r e l ~ - ~ ~ but its nature can be appreciated from the simple drawing of Fig.3. Simplified Thomson scattering is the quasi-elastic scattering of light from free electrons in a discharge. Because there is an unambiguous intersection between the incident laser beam and the observation direction the measurement of Thomson scattering provides point-by-point spatial information. Furthermore because a pulsed laser is utilized temporal resolution is also possible. Naturally electrons in a high-temperature plasma such as the ICP move at extremely high velocities (approaching 1 x lo6 m s-l); consequently the light they scatter is greatly Doppler shifted Indeed the Doppler shift is so significant that it can be measured with a conventional optical spectrometer. Because the electrons in an ICP travel at different speeds and in different directions with respect to both the incident laser and observation system a distribu- tion of Doppler shifts is registered.With the proper instrumental configuration and for an electron-velocity distribution that is Maxwellian (behaviour that has recently been confirmed20) the Doppler shifted scattered light assumes a Gaussian pattern. From the width ofthe Gaussian peak an electron temperature can be ascertained.22 Furthermore the wavelength-integrated intensity of the Doppler shifted scattered light indicates the total number of electrons that are present in the viewing volume. Therefore from the shape and integrated amplitude of the Thomson- scattering spectra both the electron energy distribution (temperature) and localized electron concentration can be found. At the same time the Doppler shifted Thomson spectrum is determined the Rayleigh-scattering intensity can be measured.Because Rayleigh scattering occurs from large particles principally argon atoms in the ICP it is not noticeably Doppler shifted and thus appears as an ex- tremely large peak centred at the laser wavelength on top of the Thomson-scattering spectrum. Because the contribu- tion of Thomson scattering at the laser wavelength is small compared with that of Rayleigh scattering the two can bc gauged separately.72 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 Of course the intensity of Rayleigh scattering is propor- tional to the number of scattering species (argon atoms) in the viewing volume. In turn the number of argon atoms in the viewing volume is inversely proportional to the gas- kinetic temperature in accordance with the gas law,19*22*23 that is as the gas temperature goes up the gas number density decreases proportionally and the Rayleigh scatter- ing drops.With a calibrated spectrometer the Rayleigh scattering can therefore be used to ascertain gas-kinetic temperature. Rayleigh- and Thomson-scattering maps have now been developed for the ICP under a wide variety of operating conditions solvent loads and with different combinations of elements added. Unfortunately the resulting maps have led to a data ‘flood’. At first attempts were made directly to compare values for electron temperature gas temperature and argon-ionization temperatures which would be derived from localized number density data.I3-I9 Similarly values from different plasmas or different operating conditions were correlated.The impossibility of managing the result- ing torrent of data led to the use of contour maps.22 However meaningful conclusions were difficult to derive because of the complexity of the resulting patterns and the unsurprising difficulty of detecting subtle shifts in them. Very recently more sophisticated image-development software has been used (Spyglass Dicer Transform View Format Spyglass Champaign IL USA) and it has been found that the resulting displays are far more easy to manipulate appreciate and interpret. For example Fig. 4 shows a side-by-side comparison of spatial maps taken at a variety of applied radiofrequency (r.f.) power levels of an ICP in the presence and absence of introduced solvent (water) vapour.The images in Fig. 4 show a wealth of information; five dimensions are displayed in ways that can be manipulated rapidly and easily. In this instance the five dimensions are radial position in the discharge height above the load coil (ALC) r.f. power level electron concentration (by the colour) and the influence of added solvent. Importantly each of the false-colour images in Fig. 4 resides in the computer as a four-dimensional array. As a result variables can be displayed in different ways ‘cuts’ can be shown through volume elements as desired and outer levels in a displayed volume can be rendered transparent so the underlying structure can be examined. False-colour images similar to those in Fig.4 for electron number density are displayed in Figs. 5 and 6 for electron temperature and gas temperature respectively. A striking example of the degree to which the ICP departs from local thermal equilibrium (LTE) is apparent by comparing Figs. 5 and 6. No matter whether a solvent is present or not the gas temperature in an ICP is in most locations and at every r.f. power level considerably lower than the electron temperature. Immediately obvious also in the images is the startling and somewhat surprising effect that water vapour has on the discharge. For example in Fig. 4 the introduction of water vapour appears to reduce electron number density in most plasma zones when the r.f. power level is low. In contrast the presence of water vapour has the effect of elevating electron concentrations when the r.f.power is high. Of course many other observations concerning the images in Figs. 4-6 could be made. However they represent only a small fraction of the data which have now been collected and which are better left for interpretation in a later paper. Therefore the mapping of other plasma features will now be considered. Although electron temperatures electron number densi- ties and gas temperatures are undeniably important in unravelling matrix interferences in the ICP of significance also are excited-state and ground-state maps of analyte and concomitant species and those intrinsic to the ICP itself. To obtain such maps a device termed a ‘monochromatic imaging spectrometer’ (MIS)24 and computed tomography have been ~ t i l i z e d .~ ~ ~ ~ The MIS employs a two-dimensional charge-coupled device (CCD) detector and is capable of recording electronically a full two-dimensional spatial image of the ICP at a selected wavelength. If the ICP is assumed to be cylindrically symmetrical each horizontal row in the CCD image could be Abel inverted to yield a radially resolved map. However it was found that the ICP is more often than not asymmetrical and computed tomo- graphy was used instead to unravel the true three- dimensional structure of the discharge. Considered simply computed tomography requires view- ing the plasma from a number of angles much as a human observer would do in order to discern the shape of a solid object. To perform this task the apparatus has the ICP placed on a rotational stage so that the MIS can view the plasma from 100 angles over a 180” range.The resulting array of images can then be reconfigured using computed tomography into the radially resolved equivalent. Further details about the tomographic set-up are provided else- here.^^-^^ In the tomographic investigations as in the application of Thornson and Rayleigh scattering it was found that the use of image-display software was indispensable. For example Fig. 7 contains a false-colour slice of an ICP and reveals immediately its lack of cylindrical symmetry. This particu- lar image is for the argon emission line at 430 nm in a dry argon plasma and not surprisingly shows a strong off-axis rnaximum low in the discharge in the toroidal region. Multiple slices through the ICP disclose additional details.Fig. 8 shows both the horizontal slice of Fig. 7 and a superimposed vertical cross-section. This mode of display reveals that argon emission is weakest in the centre of the plasma throughout its entire vertical length. Multiple horizontal slices (Fig. 9) or vertical cross-sections (Fig. 10) are also possible. Regrettably a detailed discussion of these images is beyond the scope of the present coverage as with the Thornson- and Rayleigh-scattering data. Importantly however the images of Figs. 7-10 demon- strate immediately the diagnostic value of visual informa- tion. In most situations where only the diagnostic power of an image is desired it would not be necessary to perform a full tomographic reconstruction or even an Abel inversion of the collected laterally resolved data.Instead the lateral images could be used directly to indicate the status of the discharge. Useful lateral presentations would include back- ground emission maps the intensity of plasma gas (argon) emission excitation temperatures throughout the plasma t?fc. Such displays would be of immense diagnostic value iind a great benefit to computer-control schemes. Intelligent Sample Processing and Adaptive Control In a fully adaptive instrument incoming data from a sample would be combined with diagnostic input about instrumental components and used to generate feedback- control signals which could alter conditions in the plasma the sample-processing unit or the spectrometric system. In .that way each sample would be analysed under conditions that were optimum for it under which interferences would be minimized and figures of merit maximized.However the liability of such an arrangement is that each sample would be analysed under different conditions so that an earlier calibration would probably not be valid. For this scheme to be attractive it will therefore be necessary either to perform emission measurements on an absolute (stan- dardless) basis or to provide a means for rapid recalibration of the instrument. Importantly rapid recalibration using a single standard isFig. 4 False colour maps ofclectron density in an ICP opcrated at Fig. 5 False colour maps of electron tcmpcraturc in an 1('P different r.C powcr lcvcls and in the presence and absence of opcrated at dil'ferent r.f.powcr levels arid in the prrscnc-e mid introduced water vapour. Data were obtaincd b> means of absence of introduced water vapour. Data wrc obtaincd by mcans Thomson scattering. Thc K'P was opcrated with an outer-gas of Thornson scattering and under the samc operating wilditions its flow of 14.0 I min-I. an intcrmediatc-gas flow of 0.8 I min-' and used for Fig. 4 an inner-gas flow of 0.5 I min-I. Solvcnt vapour was added using a bubble (gas-dispersion) nebulizer at a total solvent load of 17 mg min-' Fig. 6 False colour maps of kinetic temperature of the gas in an ICP operated at different r.f. power levels and in the presence and absence of introduced water vapour. Data were obtained by means of Rayleigh scattering at the same time and under the samc operating conditions as used for Fig.4 [to face page 721Fig. 7 False colour map of Ar I emission at 430 nm obtained by means of computed tomography. The 40.68 MHz ICP contained no solvent or solvent vapour and was operated at an r.f. power of 1.25 kW an outer-gas flow of 14.0 I min-I an intermediate-gas flow of 1.0 1 min-' and an inner-gas flow of 0.8 1 min-' Fig. 8 As for Fig. 7 but with an added vertical segment of the Ar 430 nm emission. The lack of cylindrical symmetry is apparent Fig. 9 Multiple horizontal slices taken along the vertical axis of an ICP indicating not only the conical shape of the discharge but also how the plasma becomes radially more homogeneous in its upper zones taken under the same conditions as in Fig. 7 Fig. 10 Multiple vertical cross-sectional cuts of the Ar 430 nm emission providing a useful and intuitively satisfying view of the spatial features of the ICP taken under the same conditions as in Fig.7 (to facepage 731JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 73 now possible using a modem high-performance liquid chromatography (HPLC) pumps3 Such pumps are readily available and are intended to produce pulse-free concentra- tion gradients useful for gradient-elution HPLC. Ordinar- ily the pumps are equipped with computer-controlled valves and have at least two pumping systems. As a result it is a simple matter to change standard solutions for use with different elements and to generate concentration gradients at any desired sample flow rate. Such pumps have many potential uses some of which are documented in a companion paper in this issue.3 For example a range of standard concentrations from a single stock solution can be generated by the pump in rapid sequence to produce a calibration curve under newly optimized instrumental conditions.Also it should be possible to use a pseudo-null-point approach2* for calibra- tion in situations where the dynamic range of an instrument is limited. In a null-point scheme the signal from a sample solution would be measured and the HPLC pump pro- grammed to vary the concentration of the introduced standard solution until the resulting signal matched that from the original sample. The sample concentration would therefore be directly determined and in a way that did not depend on instrumental linearity.Calibration based on standard additions is also simplified with the HPLC gradient-calibration m e t h ~ d . ~ Here the sample solution itself serves as a carrier and different flows of a standard solution are introduced into it; the combined flow is programmed to be held constant. In this way a standard additions calibration curve could be constructed quickly and a number of potential matrix interferences overcome. Because the gradient-calibration scheme enables any desired sample flow rate over a wide range to be chosen it permits a nebulizer to be starved or over-fed a capability that in turn permits the resulting aerosol character to be modified in an on-line fashion. Finally because the HPLC pump is capable of delivering sample or standard solutions at extremely high pressure it facilitates the use of unusual nebulizer types such as the jet- impact nebulizer (JIN) developed in this laboratory a number of years In the JIN the sample or standard solution is forced from a small capillary to produce a fine jet of liquid.Ordinarily such a jet would break up into random-sized droplets because of natural stochastic distur- bances within the jet. However the jet can be forced to break up into far smaller droplets simply by placing a solid impact surface just before the point where the jet begins to disintegrate by itself. The result is an extremely fine aerosol which is generated in a fashion independent of any auxiliary gas flows enabling both aerosol characteristics and sample-carrier flows to be optimized independently.Clearly the JIN would benefit greatly from the gradient- calibration scheme and is now being utilized in our laboratories. Conclusion It should be clear from the foregoing discussion that many exciting frontiers remain in ICP emission spectrometry. Of course even more challenging and unexplored frontiers exist in the combination of ICP and mass spectrometry as well. Perhaps the most important and intriguing develop- ments will arise from an enhanced understanding of the ICP itself from improvements in instrumentation that incorporate it and in our ability to control through computer-based adaptive feedback the characteristics of components in such instrumentation. Despite its maturity the ICP remains an important object of study development and characterization.This work was supported by the National Science Founda- tion through grant CHE 90-20631 and by the Leco Corporation. 1. 2 3 4 5 6 7 .8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 References Fassel V. A Electrical ‘Flame’ Spectroscopy Colloquium Spectroscopicum Internationale XVI Plenary Lectures and Reports Heidelberg Germany October 4-9 197 1 Adam Hilger London 1972 p. 63. Hieftje G. M. Recent Developments and Final Frontiers in ICP Spectrometry Colloquium Spectroscopicum Internationale X X VII Bergen Norway June 9- 14 paper C-PL2. Starn T. and Hieftje G. M. J. Anal. At. Spectrom. 1992 7 335. Olesik J. W. and Fister J. C. 111 Spectrochim. Acta Part B 1991,46 851. Fister J. C. 111 and Olesik J. W. Spectrochim Acta Part B 199 1,46,869.Rayson G. D. and Hieftje G. M. Spectrochim. Acta Part B 1986 41 683. Ensman R. E. Carr J. W. and Hieftje G. M. Appl. Spectrosc. 1983 37 57 1. Cam J. W. and Hieftje G. M. Determination of Energy Transport Rates in the Inductively Coupled Plasma Collo- quium Spectroscopicum Internationale XXIII Amsterdam The Netherlands June 26-July 1 1983 paper 143. Farnsworth P. B. Appl. Spectrosc. 1985 39 1078. Parisi A. F. and Hieftje G. M. Appl. Spectrosc. 1986 40 181. Farnsworth P. B. Rodham D. A. and Ririe D. W. Spectrochim. Acta Part B 1987 42 393. Fey F. H. A. G. Stoffels W. W. van der Mullen J. A. M. van der Sijde B. and Schram D. C. Spectrochim. Acta. Part B 1991,46 885. Marshall K. A. Huang M. and Hieftje G. M. Spectrochim. Acta Part B 1985 40 121 1. Huang M. and Hieftje G. M. Spectrochim. Acta Part B 1985,40 1387. Huang M. Marshall K. A. and Hieftje G. M. Anal. Chem. 1986 58 207. Marshall K. A. and Hieftje G. M. Specrochim. Acta Part B 1988 43 841. Marshall K. A. and Hieftje G. M. Spectrochim. Acta Part B 1988 43 85 1. Huang M. and Hieftje G. M. Spectrochim. Acta Part B 1989,44 291. Huang M. and Hieftje G. M. Spectrochim. Acta Part B 1989,44 773. Huang M. Yang P. Hanselman D. S. Monnig C. A. and Hieftje G. M. Spectrochim. Acta Part B 1990 45 51 1. Huang M. Hanselman D. S. Jin,’ Q. and Hieftje G. M. Spectrochim. Acta Part B 1990 45 1339. Huang M. Hanselman D. S. Yang P. and Hieftje G. M. Spectrochim. Acta Part B in the press. Marshall K. A. and Hieftje G. M. J. Anal. At. Spectrom. 1987 2 567. Olesik J. W. and Hieftje G. M. Anal. Chem. 1985,57,2049. Monnig C. A. Marshall K. A. Rayson G. D. and Hieftje G. M. Spectrochim. Acta Part B 1988 43 1217. Monnig C. A. Gebhart B. D. Marshall K. A. and Hieftje G. M. Spectrochim. Acta Part B 1990 45 261. Hieftje G. M. Spectrochim. Acta Part B 1992 47 3. Bastiaans G. J. and Hieftje G. M. Anal. Chem. 1973 45 1994. Doherty M. P. and Hieftje G. M. Appl. Spectrosc. 1984 38 405. Paper 1/03645I Received July 17 1991 Accepted September 2 1991

ISSN:0267-9477    

DOI:10.1039/JA9920700069

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL. 7 75 Glow Discharge Considerations as a Versatile Analytical Source* Plenary Lecture W. W. Harrison Department of Chemistry University of Florida Gainesville FL 3261 I USA This paper reviews the advantages and limitations of the glow discharge as an analytical source for atomic spectroscopy. Salient features of the glow discharge are linked to specific analytical techniques that benefit from these characteristics. The direct analysis of samples in the solid state is of particular importance for ultratrace elemental methods for which dissolution of the sample can introduce unacceptable impurities. Keywords Glow discharge; sputter; excitation; ionization; negative glow In the past decade the inductively coupled plasma (ICP) has become a popular analytical spectroscopic source for elemental analysis both for atomic emission'*2 and for mass spectr~metry.~*~ The ICP certainly deserves the recognition it has received particularly for solution samples or those materials easily transformed into the solution state.Increas- ingly ICP techniques are being used for solid samples including those that might more conveniently be analysed directly in the solid state. Solid sampling accessories for the ICP,5 including lasers sparks filaments and furnaces have been used with some success but create a complex sampling train. A simpler integrated souce for the direct analysis of solids would offer some obvious advantages. This report examines the analytical characteristics of the glow discharge that make it increasingly useful as an analysis source for solids in a variety of spectroscopic techniques including atomic absorption (AA) atomic emission (AE) atomic fluorescence (AF) and mass spectrometry (MS).Glow Discharge Characteristics The glow discharge has many strengths that should make it the source of choice for elemental analysis of solids. Many of its advantages arise from the fundamental steps compris- ing its operation.6 As shown in Fig. 1 the voltage applied to the low pressure environment causes breakdown of the discharge gas normally argon whose ions are then acceler- ated across the dark space and impact on the cathode (sample) surface thereby ejecting primarily neutral atoms and electrons although some ions and polyatomic species are also released. In addition to the ions striking the cathode the charge-exchange processes in the dark space create fast atoms that also can cause sputter ablation.Through these sputtering steps the solid sample yields an atom population that diffuses across a thin dark space into the adjacent negative glow where collisions with electrons metastable atoms and other energetic species cause excita- tion and ionization of a fraction of the sample atoms creating species that are analytically useful. More detailed descriptions of these deceptively 'simple' processes are available.'J An intrinsic phenomenon of the glow discharge that distinguishes it from most other spectroscopic sources is a natural separation of the initial sampling step (atomization) from the subsequent analytical processes (e.g.excitation and ionization). Analysts often go to great lengths to create useful separations such as the tandem use of laser atomiza- tion and ICP ex~itation,~ or even ablation by one laser *Presented at the XXVIl Colloquium Spectroscopicurn Interna- tionale (CSI) Bergen Norway June 9-14 1991. I I I e-/q L Negative glow I Fig. 1 Representation of sputtering excitation and ionization processes in the glow discharge. Mo=neutral sample atom; * =excited state followed in space and time by a second laser for ioniza- tion.Io Fig. 2 shows a representation of this principle as manifested in the glow discharge and from which arise many inherent glow discharge applications and advantages. Step I represents sputter ablation as an atom generator that produces a steady-state sample atom population with a density gradient extending from the sample to the source walls.Atoms sputtered from complex sample matrices lose any chemical memory of that environment after their release and in effect undergo matrix conversion into a dilute argon solution where the analytical signals are produced as represented by Step 11. In this way the glow discharge has produced an advantageous transformation of a solid sample into a totally different matrix (low-pressure argon) that normalizes sample-to-sample inconsistencies. Clearly the space-time separation of atomization from emission and ionization zones is not as complete as indicated but the analytical effect as demonstrated in diverse sample matrices is a good virtual approximation.76 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL.7 Fig. 2 Separation of atomization and analytical zones in the glow discharge. Mo= neutral sample atom Analytical Advantages To appreciate fully the growing popularity of glow dis- charges for atomic spectroscopy a brief review of the inherent advantages might be worthwhile. Direct solids analysis The feature that engenders the greatest interest in the glow discharge is its ability to accept an analytical sample directly in a solid form. Little or no sample preparation is required for bulk solids and even powders require only pressing into an appropriate electrode. Conducting ma- terials may be run by a d.c. discharge; non-conductors will require an r.f. dischargeLLIL2 to avoid the addition of a conducting matrix thus taking full advantage of the solid sampling benefits.Time-consuming sample dissolutions particularly of difficult sample matrices are avoided. Unlike solution techniques in which a solid sample normally undergoes at least a 100-fold dilution during sample preparation no dilution need occur with the glow discharge and the contamination problem associated with dissolution steps is avoided. Minimal matrix efects Solution-based techniques minimize the effects of the original chemical matrix by dissolving a sample in a solution matrix. The glow discharge is able to obtain similar effects while still sampling directly in the solid state primarily owing to the previously described zone separation (Fig. 2). When comparing many different sample matrices differential elemental response is fortunately slight.Rela- tive sensitivity factors determined in steel for example do not differ greatly from those found in aluminium or copper. l 3 Discharge options While a d.c. powered glow discharge is the normal choice and is the only type found in commercial instrumentation other formats have proved useful or are being developed. An r.f. discharge has the considerable advantage of running non-conducting samples such as glasses geological ma- terials or ceramics,** whereas a d.c. discharge requires alteration of the matrix for these samples to be electrically conducting. The d.c. or r.f. discharge also can be run in a pulsed mode with promising time-resolved advantages.15J6 A dual discharge configurationL7 offers an in situ standardi- zation against a known standard. Low power A small inexpensive power supply suffices for the glow discharge. While discharge conditions do vary with applica- tion power levels are often of a low wattage (e.g.1000 V at ? mA). This is in sharp contrast to the ICP which requires kilowatts of power with associated larger costs. Pulsed operation of a glow discharge necessitates a power supply that can accept an external driving pulse. Discharge stability With proper control of the discharge parameters analytical signals have good long term stability without the need for complex discharge monitoring. Perhaps only the glow discharge can produce a steady-state atomic population directly from a solid and continue to sustain that equilib- rium over sample lifetime.Given that actual sample consumption is small these equilibria conditions can be maintained essentially indefinitely (e.g. for hours). Low gas utilization Flow rates of the discharge gas normally argon are very small (e.g. 2-4 cm3 min-I). Laboratory costs from gas tank demurrage charges are often greater than the argon cost ilself. This may be contrasted to flow rates of other discharge methods such as the ICP where the flow is measured in litres per minute with all the attendant gas costs particularly in those countries in which argon is an expensive reagent. Llischarge gas flexibility While argon is the gas used most often for glow discharges many other gases are also suitable and there might be advantages to selecting the best gas for a given application.The normal alternatives are other rare gases. For example the use of neon might eliminate a particular spectral interference caused by an argon product. Different excita- tion and ionization efficiencies are also created by changing the gas. The heavier xenon can be useful for its greater sputter yield for certain elements or helium might be useful when the need is primarily for a high energy negative glow rogion but with little sputtering. Reactive gases such as oxygen nitrogen or even water vapour will easily support a glow discharge although the complexity of the spectra makes such use more specialized. There is also the possibility that a combination of gases (e.g. argon and hydrogen) might give some particular advantage such as a more reducing plasma.Sample adaptability Solids are of course the primary consideration. Bulk conducting samples can be fashioned into sample cathodes; powdered materials are pressed into discs or pins. Non- conducting samples can be mixed with a conducting powder matrix (aluminium copper graphite) or run di- rectly in the pure pressed form using an r.f. discharge. Solution samples can be run by either direct injection of desolvated aliquots or by drying a sample on an electrode for subsequent sputter release of the thin film residue into the plasma. Solutions also can be electroplated onto a conducting cathode.'* Gaseous samples have been analysed b:y bleeding the sample into the negative glow discharge.19 Sdfcleaning of samples A critical process in many trace element procedures is the removal of surface contamination from samples withoutJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL.7 71 the concomitant introduction of other impurities from the cleaning itself. The glow discharge features the unique capability of permitting a final atomic polish by use of the discharge itself to bombard the sample with a high-purity gas thereby stripping away surface layers and exposing the bulk sample for subsequent analysis. This simplifies sample preparation and reduces contamination which is particu- larly important in glow discharge mass spectrometry appli- cations in which sub-ppb concentrations are measured. Matrix bond breaking To those accustomed to high-energy sources the efficiency with which the glow discharge is able to break molecular bonds even tenacious oxides,*O to produce an atomic population directly from a solid sample is often a surprise.The average energy of the argon ions striking the surface is reduced by charge exchange argon collisions in the dark space but sufficient momentum remains to exceed the sputter threshold energy of sample atoms. High-current arcs high-voltage sparks and high-power discharges use thermal means to tear bonded atoms asunder. Instead the glow discharge uses the atom-by-atom momentum transfer of each accelerated ion impacting on the sample to produce a form of 'three-dimensional billiards' whereby a surface atom is cleanly ejected from its matrix. This process can remove one or two sample atoms for every incoming ion. The fact that ion sputtering can remove atoms from metals and alloys might be more easily understood than the corresponding task of freeing atoms from complex tightly bound matrices.For example geological materials often feature silicate chains that encompass elemental inclusions all in a sample that is a non-conductor. Fig. 3 attempts to illustrate the added difficulty presented by a compacted sample consisting of 10% sample and 90% conducting matrix. The great majority of the bombarding species will strike the matrix particles and not the sample. In addition the non-conducting sample particle is continuously being covered by atoms sputtered from the matrix. Sensitive analyses of such materials by glow discharge techniques have been repeatedly demonstrated even so.z' Much is yet to be learned about the analytical processes that are central to the glow discharge in its interaction with these chemi- cally resistant samples.Uniform sputter response Essentially all elements exhibit sputter yields (the number of atoms released per impacting argon ion) that are relatively uniform within a factor of 3-5 of each other.z2 By comparison many analytical spectrochemical techniques produce sensitivities that vary by many orders of magni- tude among the range of elements examined. Thus the initial sputter step supplies subsequent analytical processes (AA AE AF MS) with a reservoir of sample atoms that will promote uniformity of response. Techniques that are affected by widely ranging transition probabilities exhibit considerable variation in elemental detection limits.On the other hand for techniques such as MS wherein the electron impact or metastable ionization steps are relatively uni- form detection limits are confined within a range generally construed as narrow. Sampling integrity After the discharge reaches stability normally within a few minutes the sputtered atoms presented to the glow dis- charge are representative of the bulk composition of the sample. The initial sputter yields will differ somewhat among elements causing surface enrichment of some elements and depletion of others. However as the sputter Compacted sample 90+ 10 Fig. 3 Considerations of a non-conducting compacted sample ( looh) mixed with a conducting matrix (90%) for glow discharge atomization. M =metal conducting matrix process continues to ablate its way through the sample those elements with lower sputter yields will be compen- sated for by larger surface concentrations shifting the plasma equilibrium towards a population more representa- tive of the sample atom concentrations.Trace element methods place great demands on the glow discharge sampling mode (i) representative atomic populations should be created from elemental concentrations that range over many orders of magnitude and (ii) the plasma populations should remain stable with respect to each other throughout the measurement process. The glow discharge performs well with respect to both aspects. Ease of accessibility Because the glow discharge requires little in the way of optical or other radiation shields or high voltage/current protection the source can be situated conveniently in a multi-windowed chamber (such as a standard six-way cross) that permits easy interaction with external probes or injection devices.While this is not a common feature with commercial instrumentation analysts designing their own sources for potential research applications find this an attractive feature. Atomic absorption or laser fluorescence is easily effected by the introduction of appropriate spectral beams through quartz window ports.' The discharge might be investigated by the insertion of measurement probes (e.g. Langmuir) without the danger of their melting. The ports also permit convenient sample injection or the introduction of special reagents. In such an open configura- tion the glow discharge is a very user-friendly source.Fundamental studies In this paper the glow discharge is being considered as a working analytical source for elemental analysis but analyt- ical chemists are also interested in the fundamental pro- cesses that take place in the discharge. Because many different analytical techniques can be easily interfaced to the glow discharge basic properties can be explored by monitoring sequentially or even simultaneously critical parameters such as atom densities excited state popula- tions and the number of ionic species. Even though local thermal equilibrium does not exist in glow discharges useful estimations can still be made of critical discharge parameters. In this manner the effect of variation in78 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL.7 experimental parameters can be advantageously followed by monitoring a range of species that might be involved in a given reaction ionization mechanism etc. Spectral simplicity The sputter process in glow discharge sources yields primarily atomic species,’ with relatively low abundances of molecules and assorted polyatomic species. The negative glow reactions excite resonance lines and other high probability transitions leading to optical spectra that are essentially line dominant with little band structure and exhibiting very low background continua. Mass spectra are atomic in nature and thus relatively simple. The low energy nature of the glow discharge prevents the analyst from being overwhelmed by excessive data. Interpretation of both optical and mass spectra is thus simplified compared with corresponding ICP results.Non-elemen tal applications While the glow discharge is primarily an atomic source it plays an increasing role in alternative applications includ- ing organic samples.23 The sputter process generates some polyatomic and small cluster species that are of interest to physical chemists. Discharge conditions can be adjusted to enhance the formation of such species. In addition the plasma can serve as a simple and convenient detector for chromatographic effluents,24 using either optical or mass spectrometric read-out. The latter approach is used in several commercial instruments for the detection of organic compounds which are injected into the negative glow region and ionized.Glow discharge as a chemical reaction cell The glow discharge can be thought of as a low pressure reaction chamber in which countless chemical reactions are taking place or might be caused to occur by analyst intervention. In its normal rare-gas mode the source is hardly inert. As can be determined particularly by MS myriad reactions occur in an argon discharge that can be useful analytically or that can help in understanding reaction mechanisms. Optimization or alteration of critical reactions can greatly benefit the analyst. In addition the glow discharge can serve as a reaction cell for the injection of beneficial analytical reagents. Reagents may be added as a vapour to an incoming gas stream or by direct sputter injection from a cathodic sample. In some cases a secon- dary reagent electrode may be used for pulsed reagent addition by means of an auxiliary discharge.Glow dis- charges are fascinating in terms of the opportunities they present for chemical modification of plasma chemistry. For example reactive atoms can be added as reagents in a very controlled manner by pulsed sputter addition permitting a pseudo-titration of the host species. Analytical Limitations Primarily applicable to solids Just as the application of the glow discharge to solids is one of its great advantages the fact that solutions require special sample handling is a real limitation given the large number of materials that are either solutions by nature or are conveniently handled in solution form. It would be just as inefficient to use a solid-based technique for solutions as the reverse which is actually now much more prevalent. Spectral interferences The predominantly atomic nature of the glow discharge and the occasional overstatements regarding spectral purity can mislead the inexperienced analyst into failing to take proper precautions for spectral interferences.More spectral inter- ferences are seen at levels that cause problems as greater demands are placed on analyses at extremely low concen- trations. The discharge plasma will support the presence of unusual (and therefore often unanticipated) polyatomic species that can contribute to optical and mass spectra (i.e. molecular band species in optical emission and cluster ions in MS). Plasma susceptibility to contaminants The presence in the discharge gas of even trace amounts of certain contaminants greatly affects the operation of the source.2s The most notorious of these is water vapour which may enter through the discharge gas system leaks or more commonly by simple desorption from the surface of the source housing sample probe and inlet lines.Water affects discharge efficiency in two major ways. Firstly it quenches argon metastable species that are important in excitation and ionization mechanisms. Secondly and per- haps more importantly it yields discharge products such as H+ and H3+ that contribute disproportionately to the ion current striking the sample and yet because of their small mass produce little sputtering of the sample. Vacuum system requirements Glow discharges operate at reduced pressure requiring vacuum technology that is modest by today’s standards but because of the contaminant problem discussed above must be of high quality.In addition the water problem makes a cryogenic attachment to the source highly desirable parti- cularly for those elements at the low mass end of the spectrum. Low energy While the glow discharge sputter step is quite fairly efficient in breaking even tenacious bonds the energetics of the plasma itself are relatively low. Unlike the ICP which features high thermal energies throughout the analytical region of the torch the glow discharge is a low-energy source so that polyatomic species formed within the negative glow may not be completely dissociated. In fairness it should be noted that even the ICP does not fully dissociate all polyatomic species.Standards problem Solid-sampling techniques suffer a particular problem of difficulty in switching frequently between sample and standard something that can easily be done in solution methods. The low-pressure environment of a glow dis- charge exacerbates this problem because of the required passage of samples and standards in and out through vacuum interlocks and the attendant re-equilibration of the system each time. The net result is that internal standards are often used for glow discharge methods particularly in MS and since it is somewhat difficult to add a standard to a metal or alloy sample in the solid state an element intrinsic to the sample is selected often the matrix itself. An added discomfort to analysts in solids analysis is the lack of a real ‘blank for consideration of detection limits.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY MARCH 1992 VOL.7 79 Mass spectrometry + Atomic emission fluoresc Atomic absorption :ence -A ...,.,.lP- Laser RIMS Sample Fig. 4 Analytical techniques that have been demonstrated using a glow discharge RIMS resonance-ionization mass spectrometry; Po unattenuated radiant power; and P attenuated radiant power Analytical Versatility of the Glow Discharge These strengths and limitations of the glow discharge have led analysts and commercial instrument manufacturers to focus on the opportunities presented in today’s competitive analytical market-place. It is not a source that will necessa- rily replace highly active existing sources but there exist sufficient advantages to make it a complementary valuable approach.For example a recently introduced instrumentz6 has combined a glow discharge and an ICP in a single mass spectrometer permitting selection of the best source for the application at hand a possible harbinger of future develop- ments. Other have explored the instrumenta- tion and applications of broad glow discharge use in a variety of spectroscopic Settings. These are based on the generation of species that permit the analyst to select an ultimate measurement approach. The basic discharge processes in the glow discharge permit a variety of techniques to be employed. The initial sputter step primarily creates atoms so the analyst can take advantage of this process to conduct AA analysis. As the atoms diffuse into the glow discharge they are subjected to excitation interactions the relaxation from which serves as the basis for AE.Those atoms that encounter sufficiently energetic species suffer complete loss of an electron yielding ions representative of the sample easily employed for MS. Fig. 4 represents some of the analytical processes that can result. The ‘intrinsic’ selfcontained analytical phenomena should be distinguished from those that require external stimulation. The glow discharge is a complete source for AE and MS in that the negative glow produces photons and ions than can be sampled directly to provide analytical information. On the other hand AA requires a line source probe (normally from a hollow cathode lamp) to measure atomic populations.Similarly AF requires a laser probe to stimulate emission for the analytical measure- ment. The laser alsopermits resonant ionization techniques for high specificity. To varying degrees each of these processes finds increasing use in trace element analysis. Those techniques that have benefitted from commercially developed instrumentation are not surprisingly finding the greatest use. Glow discharge techniques came through a considerable gestation period long awaited withe interest by instrument manufacturers and are now in the midst of a maturing process. How long they remain a competitive player among the numerous elemental techniques depends on the per- ceived advantages and the development of some new source(s) that diverts attention and resources. Presently however the glow discharge exhibits advantages for solids analysis that offer promise of a substantial analytical lifetime.The author expresses appreciation to the Department of Energy Basic Energy Sciences for support. References 1 humans P. W. J. M. Inductively Coupled Plasma Emission Spectrometry Part I Wiley New York 1987. 2 Mayer G. A. Anal. Chem. 1987 59 1345A. 3 Houk R. 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Mass Spectrom. 1990 1 138. 16 Klingler J. A. Ph.D. Dissertation University of Florida Gainesville FL USA 199 1. 17 Klingler J. A. and Harrison W. W. Anal. Chem. 1991 63 2982. 18 Ahearn A. J. J. Appl. Phys. 1961 32 1197. 19 Strange C. M. and Marcus R. K. Spectrochim. Acta Part B 1991,46 517. 20 Coburn J. W. Taglauer E. and Kay E. Jpn. J. Appl. Phys. Suppl. 1974 2 501. 21 Brenner 1. B. Laqua K. and Dvorachek M . J. Anal. At. Spectrom. 1987 2 623. 22 Laegreid N. and Wehner G. K. J. Appl. Phys. 1961,32,365. 23 McLuckey S. A. Glish G. L. and Asano K. G. Anal. Chim. Acta 1989 225 25. 24 Pfasma Discharge LC-MS Technical Bulletin Kratos Analyti- cal Manchester UK. 25 Mei Y. and Hamson W. W. Spectrochim. Acta Part B 199 1 46 175. 26 TS SOLA Technical Bulletin Turner Scientific Wamngton UK. 27 Harrison W. W. Barshick C. M. Klinger J. A. Ratliff P. H. and Mei Y. Anal. Chem. 1990 62 943A. 28 King F. L. and Hamson W. W. Mass Spectrom. Rev. 1990 9 285. Paper 1 /04520B Received August 29 I991 Accepted November 11 I991

ISSN:0267-9477    

DOI:10.1039/JA9920700075

出版商:RSC    

年代:1992

数据来源: RSC