摘要:

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

ISSN:0267-9477    

DOI:10.1039/JA99409BP017

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

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

ISSN:0267-9477    

DOI:10.1039/JA99409BP019

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

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

ISSN:0267-9477    

DOI:10.1039/JA99409FX061

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

62N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 Future Issues Will lnclude- Elemental Speciation with Liquid Chromatography-Inductively Coupled Plasma Isotope Dilution Mass Spectrometry -Klaus G. Heumann L. Rottmann J. Vogl Determination of Trace Silicon in Ultra- high-purity Water by Inductively Coupled Plasma Mass Spectrometry- Yuichi Takaku Kimihiko Masuda Takako Takahashi Tadashi Shirnarnura Characteristics of an Inductively Coupled Argon Plasma Operating with Organic Aerosols. Part 2. Axial Spatial Profiles of Solvent and Analyte Species in a Chloroform-loaded Plasma-D. G. Weir Michael W. Blades Sample Preparation Approaches for Isotope Dilution Inductively Coupled Plasma Mass Spectrometry Certification of Reference Materials-E. S. Beary Paul J. Paulsen J.D. Fassett Characteristics of an Inductively Coupled Argon Plasma Operating with Organic Aerosols. Part 1. Spectral and Spatial Observations-D. G. Weir Michael W. Blades Determination of Lead in Wine Other Beverages and Fruit Slurries by Flow Injection Hydride Generation Atomic Absorption Spectrometry with On- line Microwave Digestion-Carmen Carnara Carmen Cabrera Yolanda Madrid Approach to the Determination of Lead by Vapour Generation Atomic Absorp- tion Spectrometry-Steve J. Hill Les Ebdon Phillip Goodall Peter B. Stockwell K. Clive Thompson Evaluation of a Low Pressure Induc- tively Coupled Plasma Mass Spec- trometer for the Analysis of Gaseous Samples-Theresa M. Castillano Jeffrey J. Giglio Hywel E. Evans Joseph A. Caruso Hydride Interference On the Deter- mination of Minor Actinide Isotopes by Inductively Coupled Plasma Mass Spectrometry- Jeffrey S.Crain Jorge AlvaradoJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY7 NOVEMBER 1994 VOL. 9 63N High Efficiency Nebulizer for Argon flow Injection for Inductively Coupled Optimization of a Hydride Generation Inductively Coupled Plasma-Sang-Ho Plasma Mass Spectrometry- Jane Quartz Furnace Atomic Absorption Nam Jong-Soo Lim Akbar Montaser M. Craig Diane Beauchemin Spectrometry Method for Selenium Determination-G. Lespes F. Seby Univariate Optimization of Segmented- Application of Experimental Designs in P. M. Sarradin M. Potin-Gautier COPIES OF CITED ARTICLES The Royal Society of Chemistry Library can usually supply copies of cited articles. For further details contact The Library Royal Society of Chemistry Burlington House Piccadilly London W1V OBN UK. Tel +44 (0) 71-437 8565; fax +44 (0) 71-287 9798; Telecom Gold 84; BUR2 10; Electronic Mailbox (Internet) LIBRARY@RSC.ORG.If the material is not available from the Society’s Library the staff will be pleased to advise on its availability from other sources. Please note that copies are not available from the RSC at Thomas Graham House Cambridge.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY7 NOVEMBER 1994 VOL. 9 63N High Efficiency Nebulizer for Argon flow Injection for Inductively Coupled Optimization of a Hydride Generation Inductively Coupled Plasma-Sang-Ho Plasma Mass Spectrometry- Jane Quartz Furnace Atomic Absorption Nam Jong-Soo Lim Akbar Montaser M. Craig Diane Beauchemin Spectrometry Method for Selenium Determination-G. Lespes F. Seby Univariate Optimization of Segmented- Application of Experimental Designs in P. M. Sarradin M. Potin-Gautier COPIES OF CITED ARTICLES The Royal Society of Chemistry Library can usually supply copies of cited articles. For further details contact The Library Royal Society of Chemistry Burlington House Piccadilly London W1V OBN UK. Tel +44 (0) 71-437 8565; fax +44 (0) 71-287 9798; Telecom Gold 84; BUR2 10; Electronic Mailbox (Internet) LIBRARY@RSC.ORG. If the material is not available from the Society’s Library the staff will be pleased to advise on its availability from other sources. Please note that copies are not available from the RSC at Thomas Graham House Cambridge.

ISSN:0267-9477    

DOI:10.1039/JA994090062N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Federation of Analytical Chemistry and Spectroscopy Socieities Nominations for the Tomas Hirschfeld Student Awards 1994 FACSS Conference October 2-7,1994 Cervantes Convention Center St. Louis A40 Nominations are requested for the Tomas Hnschfeld Student Awards which will be presented at the Twenty-First FACSS Conference. Awards are given for the most outstandmg papers submitted by graduate students in the field of analytical chemistry. The student nominees will present 20 minute papers at the 1994 FACSS Conference. To be considered for these awards students must submit a Call For Paper - Title Submission Fom two letters of nominations including one from their graduate advisor any reprints/preprints and a 250 word abstract to Diane Landoll FACSS National Office P.O. Box 278 Manhattan KS 66502.The deadline for submission of all materials is March 21,1994. Awardees will have their travel arranged and paid for by FACSS. Papers that are not selected for the award will still be scheduled for presentation. If you are unable to attend unless you are an award winner please notify us so we can remove your paper from the Program. For further information concerning the Tomas Huschfeld Student Awards contact the Student Award Chairman Professor S. Roy Koutyohann Univ. of Mssouri-Columbia Dept. of Chemistry 123 Chemistry Bldg. Columbia MO 6521 1 (314) 882-8374Federation of Analytical Chemistry and Spectroscopy Socieities Nominations for the Tomas Hirschfeld Student Awards 1994 FACSS Conference October 2-7,1994 Cervantes Convention Center St. Louis A40 Nominations are requested for the Tomas Hnschfeld Student Awards which will be presented at the Twenty-First FACSS Conference.Awards are given for the most outstandmg papers submitted by graduate students in the field of analytical chemistry. The student nominees will present 20 minute papers at the 1994 FACSS Conference. To be considered for these awards students must submit a Call For Paper - Title Submission Fom two letters of nominations including one from their graduate advisor any reprints/preprints and a 250 word abstract to Diane Landoll FACSS National Office P.O. Box 278 Manhattan KS 66502. The deadline for submission of all materials is March 21,1994. Awardees will have their travel arranged and paid for by FACSS. Papers that are not selected for the award will still be scheduled for presentation.If you are unable to attend unless you are an award winner please notify us so we can remove your paper from the Program. For further information concerning the Tomas Huschfeld Student Awards contact the Student Award Chairman Professor S. Roy Koutyohann Univ. of Mssouri-Columbia Dept. of Chemistry 123 Chemistry Bldg. Columbia MO 6521 1 (314) 882-8374Federation of Analytical Chemistry and Spectroscopy Socieities Nominations for the Tomas Hirschfeld Student Awards 1994 FACSS Conference October 2-7,1994 Cervantes Convention Center St. Louis A40 Nominations are requested for the Tomas Hnschfeld Student Awards which will be presented at the Twenty-First FACSS Conference. Awards are given for the most outstandmg papers submitted by graduate students in the field of analytical chemistry.The student nominees will present 20 minute papers at the 1994 FACSS Conference. To be considered for these awards students must submit a Call For Paper - Title Submission Fom two letters of nominations including one from their graduate advisor any reprints/preprints and a 250 word abstract to Diane Landoll FACSS National Office P.O. Box 278 Manhattan KS 66502. The deadline for submission of all materials is March 21,1994. Awardees will have their travel arranged and paid for by FACSS. Papers that are not selected for the award will still be scheduled for presentation. If you are unable to attend unless you are an award winner please notify us so we can remove your paper from the Program.For further information concerning the Tomas Huschfeld Student Awards contact the Student Award Chairman Professor S. Roy Koutyohann Univ. of Mssouri-Columbia Dept. of Chemistry 123 Chemistry Bldg. Columbia MO 6521 1 (314) 882-8374Federation of Analytical Chemistry and Spectroscopy Socieities Nominations for the Tomas Hirschfeld Student Awards 1994 FACSS Conference October 2-7,1994 Cervantes Convention Center St. Louis A40 Nominations are requested for the Tomas Hnschfeld Student Awards which will be presented at the Twenty-First FACSS Conference. Awards are given for the most outstandmg papers submitted by graduate students in the field of analytical chemistry. The student nominees will present 20 minute papers at the 1994 FACSS Conference.To be considered for these awards students must submit a Call For Paper - Title Submission Fom two letters of nominations including one from their graduate advisor any reprints/preprints and a 250 word abstract to Diane Landoll FACSS National Office P.O. Box 278 Manhattan KS 66502. The deadline for submission of all materials is March 21,1994. Awardees will have their travel arranged and paid for by FACSS. Papers that are not selected for the award will still be scheduled for presentation. If you are unable to attend unless you are an award winner please notify us so we can remove your paper from the Program. For further information concerning the Tomas Huschfeld Student Awards contact the Student Award Chairman Professor S. Roy Koutyohann Univ. of Mssouri-Columbia Dept.of Chemistry 123 Chemistry Bldg. Columbia MO 6521 1 (314) 882-8374Federation of Analytical Chemistry and Spectroscopy Socieities Nominations for the Tomas Hirschfeld Student Awards 1994 FACSS Conference October 2-7,1994 Cervantes Convention Center St. Louis A40 Nominations are requested for the Tomas Hnschfeld Student Awards which will be presented at the Twenty-First FACSS Conference. Awards are given for the most outstandmg papers submitted by graduate students in the field of analytical chemistry. The student nominees will present 20 minute papers at the 1994 FACSS Conference. To be considered for these awards students must submit a Call For Paper - Title Submission Fom two letters of nominations including one from their graduate advisor any reprints/preprints and a 250 word abstract to Diane Landoll FACSS National Office P.O.Box 278 Manhattan KS 66502. The deadline for submission of all materials is March 21,1994. Awardees will have their travel arranged and paid for by FACSS. Papers that are not selected for the award will still be scheduled for presentation. If you are unable to attend unless you are an award winner please notify us so we can remove your paper from the Program. For further information concerning the Tomas Huschfeld Student Awards contact the Student Award Chairman Professor S. Roy Koutyohann Univ. of Mssouri-Columbia Dept. of Chemistry 123 Chemistry Bldg. Columbia MO 6521 1 (314) 882-8374Federation of Analytical Chemistry and Spectroscopy Socieities Nominations for the Tomas Hirschfeld Student Awards 1994 FACSS Conference October 2-7,1994 Cervantes Convention Center St.Louis A40 Nominations are requested for the Tomas Hnschfeld Student Awards which will be presented at the Twenty-First FACSS Conference. Awards are given for the most outstandmg papers submitted by graduate students in the field of analytical chemistry. The student nominees will present 20 minute papers at the 1994 FACSS Conference. To be considered for these awards students must submit a Call For Paper - Title Submission Fom two letters of nominations including one from their graduate advisor any reprints/preprints and a 250 word abstract to Diane Landoll FACSS National Office P.O. Box 278 Manhattan KS 66502. The deadline for submission of all materials is March 21,1994. Awardees will have their travel arranged and paid for by FACSS. Papers that are not selected for the award will still be scheduled for presentation. If you are unable to attend unless you are an award winner please notify us so we can remove your paper from the Program. For further information concerning the Tomas Huschfeld Student Awards contact the Student Award Chairman Professor S. Roy Koutyohann Univ. of Mssouri-Columbia Dept. of Chemistry 123 Chemistry Bldg. Columbia MO 6521 1 (314) 882-8374

ISSN:0267-9477    

DOI:10.1039/JA994090X063

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

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

ISSN:0267-9477    

DOI:10.1039/JA99409BX069

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

307 R JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 ATOMIC SPECTROMETRY UPDATED REFERENCES The address given in a reference is that of the first named author and is not necessarily the same for any co-author. 9412995. 9412996. 9412997. 941299 8. 9412999. 94/3000. 94/3001. 94/3002. 9413003. 9413004. 9413005. Wang Y.-b. Carnahan J. W. Binary mobile phases for supercritical fluid chromatography with helium microwave-induced plasma detection Anal. Chem. 1993 65 3290. (Dept. of Chem. Northern Illinois Univ. DeKalb IL 60115 USA). Alvarado J. S. Carnahan J. W. Reductive pyrolysis for the determination of aqueous sulfur compounds with a helium microwave-induced plasma Anal. Chem. 1993 65 3295. (Dept. Chem. North. Illinois Univ. DeKalb IL 60115 USA). Harville T. R.Marcus R. K. Line selection and evaluation of radiofrequency glow discharge atomic emission spectrometry for the analysis of copper and aluminium alloys Anal. Chem. 1993 65 3636. (Dept. Chem. Clemson Univ. Clemson SC 29634-1905 USA). Birch M. E. Solvent venting technique for gas chromatography with microwave-induced plasma atomic emission spectroscopy Anal. Chim. Acta 1993 282,45 1. (US Dept. Health and Human Services Public Health Service Centers for Disease Control and Prevention National Inst. Occup. Safety and Health Div. Phys. Sci. and Eng. 4676 Columbia Parkway Cincinnati OH 45226 USA). Hiddemann L. Uebbing J. Ciocan A. Dessenne O. Niemax K. Simultaneous multielement analysis of solid samples by laser ablation-microwave-induced plasma optical emission spectrometry Anal.Chim. Acta 1993 283 152. (Inst. Spektrochem. Angewandte Spektrosk. (ISAS) Bunsen-Kirchhoff-Str. 11 P.O. Box 101352 W-4600 1 Dortmund Germany). Kosbino Y. Narukawa A. Investigation and elimin- ation of sodium nitrate-borate interference of manga- nese in electrothermal atomic absorption spectrometry Analyst 1993 118 1027. (Mater. Anal. Lab. NGK Insul. Ltd. Nagoya Japan 467). Alexandrova A. Arpadjan S. Determination of trace elements in analytical-reagent grade sodium salts by atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry after pre- concentration by column solid-phase extraction Analyst 1993 118 1309. (Fac. Chem. Univ. Sofia 1126 Sofia Bulgaria). Welz B. Sucmanova M. L-Cysteine as a reducing agent for the determination of antimony and arsenic using flow injection hydride generation atomic absorp- tion spectrometry.Part 1. Optimization of the analytical parameters Analyst 1993 118 1417. (Dept. Appl. Res. Bodenseewerk Perkin-Elmer GmbH D-88647 Uberlingen Germany). Welz B. Sucmanova M. L-Cysteine as a reducing and releasing agent for the determination of antimony and arsenic using flow injection hydride generation atomic absorption spectrometry. Part 2. Interference studies and the analysis of copper and steel Analyst 1993 118 1425. (Dept. Appl. Res. Bodenseewerk Perkin-Elmer GmbH D-88647 Uberlingen Germany). Kakade S. M. Shinde V. M. Extraction and spectro- photometric determination of gallium(rrr) indium(rr1) and thallium(II1) in aluminum and aluminum alloys Analyst 1993 118 1449. (Dept.Chem. Inst. Sci. Bombay 400 032 India). Shick R. A. Koenig J. L. Ishida H. Theoretical development for depth profiling of stratified layers using variable-angle ATR Appl. Spectrosc. 1993 47 1237. (Dept. Macromol. Sci. Case West Reserve Univ. Cleveland OH 44106 USA). 9413006. 9413 007. 9413008. 9413009. 9413010. 9413011. 9413012. 94/3013. 9413014. 9413015. 941301 6. 9413017. 9413018. Kuzuya M. Matsumoto H. Takechi H. Mikami O. Effect of laser energy and atmosphere on the emission characteristics of laser-induced plasmas Appl. Spectrosc. 1993 47 1659. (Coll. Eng. Chubu Univ. Kasugai 487 Japan). Starn T. K. Pereiro R. Hieftje G. M. Gas-sampling glow discharge for optical emission spectrometry. Part I Design and operating characteristics Appl.Spectrosc. 1993 47 1555. (Dept. Chem. Indiana Univ. Bloomington IN 47405 USA). Lipschultz F. Diode-array spectrometer for nitrogen isotopic analysis Appl. Spectrosc. 1993 47 2093. (Bermuda Biol. Stn. Res. Inc. Ferry Reach Bermuda). Pan C.-k. King F. L. Atomic emission spectrometry employing a pulsed radiofrequency-powered glow dis- charge Appl. Spectrosc. 1993 47 2096. (Dept. Chem. West Virginia Univ. Morgantown WV 26506-6045 USA). Hu B. Jiang Z.-c. Zeng Y.-n. Matrix effect on fluorination assisted electrothermal vaporization induc- tively coupled plasma atomic emission spectrometry Fenxi Huaxue 1993 21 1139. (Dept. Chem. Wuhan Univ. Wuhan 430072 China). Liu J.-s. Qiu HA. Li L.-x. Determination of impurity elements in highly pure gold by inductively coupled plasma atomic emission spectrometry Fenxi Huaxue 1993,21 1188.(Kunming Precious Met. Inst. Kunming 650221 China). Hu Q.4 Luo S.-rn. Continuous determination of trace calcium and zinc in high-purity europium oxide by extraction and flame atomic absorption spec- trometry Fenxi Huaxue 1993 21 1240. (Changchun Inst. Appl. Chem. Acad. Sin. Changchun 130022 China). Luo S.-m. Dong W. Geng L.-w. Determination of trace aluminium in highly pure lanthanum oxide and yttrium oxide by extraction-graphite furnace atomic absorption spectrometry Fenxi Huaxue 1993 21 1359. (Changchun Inst. Appl. Chem. Acad. Sin. Changchun 130022 China). Padberg S. Burow M. Stoeppler M. Methylmercury determination in environmental and biological reference and other materials by quality control with certified reference materials (CRMs) Fresenius’ J.Anal. Chem. 1993,346(6-9) 686. (Inst. Appl. Phys. Chem. Research Cent. (KFA) Julich W-5170 Juelich Germany). Grudpan K. Taylor C. Sitter H. Keller C. Flow injection analysis using an aquarium air pump Fresenius’ J. Anal. Chem. 1993 346( 10-11) 882. (Fac. Sci. Univ. Chiang Mai Chiang Mai Thailand 50002). Chakraborti D. Burguera M. Burguera J. L. Analysis of standard reference materials after microwave-oven digestion in open vessels using electrothermal atomic absorption spectrophotometry and Zeeman-effect back- ground correction Fresenius’ J. And. Chern. 1993 346( 6-7) 233. (Sch. Environ. Stud. Jadavpur Univ. Calcutta 700032 India). Stab J. A. Cofino W. P. van Hattum B. Brinkman U. A. T. Comparison of GC-MS and CC-AES for the determination of organotin compounds in the environ- ment Fresenius’ J.Anal. Chew. 1993 346(6-7) 247. (Inst. Environ. Stud. Free Univ. 1081 HV Amsterdam Netherlands). Sahayam A. C. Tyagi A. K. Gangadharan S. Chemical modification of tin in electrothermal atomic308 R 9413019. 94/3020. 94/3021. 9413022. 9413023. 9413024. 9413025. 9413026. 9413027. 9413028. 9413029. 9413030. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 absorption spectrometry (ETAAS) Fresenius’ J. Anal. Chem. 1993 346(10-ll) 461. (Anal. Chem. Div. Bhabha At. Res. Cent. Bombay 400 085 India). Okamoto Y. High-sensitivity microwave-induced plasma mass spectrometry for trace element analysis J. Anal. At. Spectrom. 1994 9 745. (Dept. Electrical and Electronic Eng.Fac. Eng. Tokyo Univ. Kawagoe Saitama 350 Japan). Nakarnura Y. Takahashi K. Kujirai O. Okochi H. Evaluation of an axially and radially viewed inductively coupled plasma using an tchelle spectrometer with wavelength modulation and second-derivative detec- tion J. Anal. At. Spectrom. 1994 9 751. (Natl. Res. Inst. Metals 2-3-12 Nakameguro Meguro-ku Tokyo 153 Japan). Imai S. Sturgeon R. E. Willie S. N. Furnace atomization plasma emission spectrometry at controlled pressures J . Anal. At. Spectrom. 1994 9 759. (Dept. Chem. Joetsu Univ. Educ. Joetsu Niigata 943 Japan). Imai S. Sturgeon R. E. Easily ionized element interference effects in furnace atomization plasma emission spectrometry J. Anal. At. Spectrom. 1994 9 765. (Dept. Chem. Joetsu Univ. Educ. Joetsu Niigata 943 Japan).Barth P. Krivan V. Electrothermal vaporization inductively coupled plasma atomic emission spectro- metric technique using a tungsten coil furnace and slurry sampling J Anal. At. Spectrom. 1994 9 773. (Sekt. Anal. Hochstreinigung Univ. Ulm D-89069 Ulm Germany). Zhuang Z.-x. Wang X.-r. Yang P.-y. Yang CJ. Huang B.4 On-line flow injection cobalt-ammonium pyrrolidin-1 -yldithioformate coprecipitation for precon- centration of trace amounts of metals in waters with simultaneous determination by inductively coupled plasma atomic emission spectrometry J. Anal. At. Spectrom. 1994 9 779. (Dept. Chem. Xiamen Univ. Xiamen China). Steffan I. Vujicic G. Analysis of zirconium alloys by inductively coupled plasma atomic emission spec- trometry J. Anal. At. Spectrom. 1994 9 785.(Inst. Anal. Chem. Univ. Vienna Wahringerstr. 38 A-1090 Vienna Austria). Papaspyrou M. Feinendegen L. E. Mohl C. Schwuger M. J. Determination of boron in cell suspensions using electrothermal atomic absorption spectrometry J. Anal. At. Spectrom. 1994 9 791. (Inst. Med. Res. Centre Julich 52425 Julich Germany). Gutierrez J. M. Madrid Y. Camara C. Sensitized determination of mercury by cold vapour generation from micellar media and atomic absorption spec- trometry Spectrochim. Acta Part B 1993 48 1551. (Fac. Quim. Univ. Complutence Madrid 28040 Spain). Lim H. B. Carney K. P. Edelson M. C. Houk R. S. Brenner I. B. Extraction discharge source for induc- tively coupled plasma atomic emission spectrometry spectral linewidths and interference effects Spectrochim. Acta Part B 1993 48(13) 1617.(Dept. Chem. Iowa State Univ. Ames IA 50011 USA). L’vov B. V. Polzik L. K. Novichikhin A. V. Fedorov P. N. Borodin A. V. Automatic correction of absorp- tion pulses in Zeeman graphite furnace atomic absorp- tion spectrometry Spectrochim. Acta Part B 1993 48( 13) 1625. (Dept. Anal. Chem. St. Petersburg Tech. Univ. St. Petersburg 195251 Russia). Chen H.-w. Tang FA Gu C. Brindle I. D. Influence of chelating reagents on plumbane generation determi- nation of lead in the presence of PAN-S Talanta 1993 40 1147. (Dept. Chem. Hangzhou Univ. Hangzhou 3 10028 China). 941303 1. 9413032. 94/3033. 94/3034. 9413035. 9413036. 9413037. 941303 8. 9413039. 9413040. 94/304 1. 9413042. 9413043. Wynn D. A. Complete dissolution procedures for tin-lead solders using nitric and hydrochloric acids with simultaneous determination of major and trace elements by ICP-OES Talanta 1993 40(8) 1207.(Johnson Controls Inc. Milwaukee WI 53209 USA). Ilk Z. Georgijevic J. Georgijevic V. Matrix effect of barium on spectra1 line intensities and detection limits in inductively coupled plasma atomic emission spec- troscopy Talanta 1993 40( 8 ) 1295. (Inst. Nucl. Sci. VINCA 11001 Belgrade Yugoslavia). Gandhi M. N. Deorkar N. V. Khophar S. M. Solvent extraction separation of cobalt(I1) from nickel and other metals with Cyanex 272 Tulunta 1993 40(10) 1535. (Dept. Chem. Indian Inst. Technol. Bombay 400 076 India). de la Guardia M. Carbonell V. Morales-Rubio A. Salvador A. Online microwave-assisted digestion of solid samples for their flame atomic spectrometric analysis Talanta 1993 40( ll) 1609.(Dept. Anal. Chem. Univ. Valencia Burjassot 46100 Spain). Lopez Garcia I. Arroyo Cortez J. Hernandez Cordoba M. Flow injection flame atomic absorption spectrometry for slurry atomization. Determination of iron calcium and magnesium in samples with high silica content Tulanta 1993 40( l l ) 1677. (Dept. Fac. Chem. Univ. Murcia Murcia 30071 Spain). Sanz-Medel A. Fernandez de la Campa M. R. Valdes- Hevia y Temprano M. C. Aizpun Fernandez B. Liu Y. M. Surfactant-based ordered media in analytical atomic spectrometry Talanta 1993 40( 1 l) 1759. (Fac. Chem. Univ. Oviedo Oviedo 33007 Spain). Matousek J. P. Powell H. Kipton J. Analyte pre- concentration and separation from small volumes by electrodeposition for electrothermal atomic absorption spectroscopy Tulanta 1993,40( 12) 1829.(Dept. Chem. Univ. Canterbury Christchurch New Zealand). Morosanova E. I. Selivestrova L. S. Zolotov Yu. A. Sorption recovery of metal ions on silica gel modified with an aza analogue of dibenzo-18-crown-6 Zh. Anal. Khim. 1993 48(4) 617. (Moscow State Univ. Moscow Russia). Dashin S. A. Bol’shov M. A. Maiorov I. A. Analysis of pure substances by laser atomic fluorescence spec- trometry with sample atomization in planar magnetron discharge Zh. Anal. Khim. 1993,48(4) 715. (State Sci.- Res. Des. Inst. Rare Met. Ind. Moscow Russia). Gilmutdinov A. Kh. Zakharov Yu. A. Ivanov V. P. Voloshin A. V. Transient structure of atomic and molecular layers in electrothermal atomic absorption spectrometry.Dynamics of formation of atomic absorb- ing layers of zinc cadmium and mercury Zh. Anal. Khim. 1993 48(5) 813. (Kazan State Univ. Kazan Russia). Tanaka H. Morita H. Shimomura S. Okamoto K. Effect of iodide addition on the mercury determination by flow injection-atomic fluorescence spectrometry using chromium(I1) reduction system Anal. Sci. 1993 9(6) 859. (Fac. Pharm. Sci. Univ. Tokushima Tokushima 770 Japan). Hwang Y. O. Sim S. K. Sung H. J. Yang M. K. Studies on analysis for gallium and indium in zinc ores by inductively coupled plasma atomic emission spec- trometry Anal. Sci. Technol. 1993 6( l) 131. (Instrum. Anal. Group Korea Inst. Geol. Min. Mater. Taejeon 305-350 S. Korea). Lee. G. H. Development of new high temperature plasma sources for spectrochemical analysis multivari- ate optimization by the modified sequential simplex method Bull.Korean Chem. SOC. 1993 14(2) 275. (Dept. Chem. Chungnam Natl. Univ. Taejon 305-764 S. Korea).JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 309 R 9413044. 9413045. 9413046. 9413 047. 9413048. 9413 049. 9413050. 9413051. 9413052. 9413053. 9413054. 9413055. 9413056. 94/3057. Li Y.-m. Duan Y.-x. Liu J. Jin Q.-h. Evaluation of microwave plasma torch for atomic fluorescence spec- trometry with an ultrasonic nebulization sample intro- duction system Chin. Chem. Lett. 1993 4(7) 615. (Dept. Chem. Jilin Univ. Changchun 130023 China). Hammann M. Fichtner W. Pohl B. Separation of chromium(u1) and chromium(v1) with subsequent detection of chromium(v1) in the lower ppb-range CLB Chem.Labor Biotech. 1993 44( l l ) 560. (Fachbereich Chem. Tech. Fachhochsch. Darmstadt Darmstadt Germany). Zamzow D. S. Baldwin D. P. Weeks S. J. Bajic S. J. D’Silva A. P. In situ determination of uranium in soil by laser ablation-inductively coupled plasma atomic emission spectrometry Enuiron. Sci. Technol. 1994,28(2) 352. (Ames Lab. U.S. Dept. Energy Ames IA 50011 USA). Sha W.-n. Huang Z.-r. Wang C.-h. Chen X.-k. Quantitative analysis of europium oxide samples with- out matrix matching standard by ICP-AES Fenxi Shiyanshi 1993 12(5) 16. (Dept. Chem. Nankai Univ. Tianjin 300071 China). Lin Z.-x. Song J.-y. Mo S.-j. Studies on the background absorption of samarium matrix in ETAAS Fenxi Shiyanshi 1993 12(5) 47. (Dept. Chem. South China Norm. Univ. Guangzhou 510631 China).Zheng Y.-s. Su X.-g. Quan Z. Factors influencing characteristic mass in electrothermal atomic absorption spectrometry Gaodeng Xuexiao Huaxue Xuebao 1993 14(7) 937. (Dept. Chem. Jilin Univ. Changchun 130023 China). Nugteren H. W. Morgan R. K. Gold determination by bottle-rolling cyanidation solvent extraction-AAS a first test on operational procedures Gou. Rep. Announce Index (U.S.) 1992 92(20) Abstr. No. 257,108. (Cent. Int. Coop. Appropriate Technol. Tech. Univ. Delft Delft The Netherlands). Li C.-l. Tanaka T. Kawaguchi H. Spectral inter- ferences of matrix elements on rare earth elements Guangdong Gongxueyuan Xuebao Ziran Kexueban 1991,8( 2) 49. (Guangdong Inst. Technol. Guangzhou 510090 China). Li CA. Vertical atomization system Guangdong Gongxueyuan Xuebao Ziran Kexueban 1991 8(4) 27.(Expt. Res. Cent. Guangdong Inst. Technol. Canton 510090 China). Chen HA. Du J.-x. Wang E.-k. Determination of cobalt by differential thermal lens spectrometry Guangpuxue Yu Guangpu Fenxi 1992 12(6) 117. (Changchun Inst. Appl. Chem. Acad.Sin. Changchun 130022 China). Lin Y. P. Su S. L. Chao C. N. Juang I. J. Chang H. Y. Wu. Determination of sodium and potassium in high-purity acetone by an electrothermal atomic absorption spectrometer Huaxue 1992 50( 3) 193. (Union Chem. Lab. Ind. Technol. Res. Inst. Hsinchu 30042 Taiwan). Zhang H.-q. Zhou X.-h. Wang Y. Jin Q.-h. Study on a pneumatic nebulization sample introduction system for MIP-AES Huaxue Xuebao 1993 51 ( 1 l) 1112. (Dept. Chem. Kilin Univ. Changchun 130023 China).Kasik M. Sedivy C. Umanec L. Determination of rare earth elements yttrium and scandium in solutions with aluminium iron and uranium matrixes Hutn. Listy 1993 48(2) 40. (ITC VUK Panenske Brezany Czech Rep.). Lauranto H. M. Kajava T. T. Santala M. I. K. Salomaa R. R. E. Evidence on mode structure effects in the resonance ionization signal of strontium Inst. Phys. Con$ Ser. 1992 128 (Resonance Ionization 9413058. 9413059. 9413060 9413061. 9413062. 9413063. 9413064. 9413065. 94/3066. 9413067. 9413068. 9413069. 9413070. Spectroscopy 1992) 131. (Dept. Tech. Phys. Helsinki Univ. Technol. SF-021 50 Espoo Finland). Monz L. Hohmann R. Kluge H. J. Kunze S. Lantzsch J. Otten E. W. Passler G. Senne P. Stenner J. Collinear resonance ionization spectroscopy for the determination of strontium-90 and strontium-89 in environmental samples Inst. Phys.Conf Ser. 1992 1218( Resonance Ionization Spectroscopy 1992) 225. (Inst. Phys. Johannes Gutenberg-Univ. D-6500 Mainz Germany). Chang C. M. Huang H. J. Indirect determination of sulfate by atomic absorption spectrometry J. Chin. Chem. SOC. (Taipei) 1993 40(5) 425. (Dept. Chem. Natl. Sun Yat-sen Univ. Kaohsiung 80424 Taiwan). Gjerde D. T. Wiederin D. R. Smith F. G. Mattson B. M. Metal speciation by means of microbore columns with direct-injection nebulization by inductively coupled plasma atomic emission spectroscopy J. Chromatogr. 1993 640(1-2) 73. (Sarasep Inc. Santa Clara CA 95054 USA). Gelencser A. Szepvoelgyi J. Hlavay J. Characterization of an element-specific detector for combined gas chromatography atomic emission detec- tion J.Chromatogr. 1993 654(2) 269. (Dept. Anal. Chem. Univ. Veszprem P.O. Box 158 8201 Veszprem Hungary). Liu Y. Lopez-Avila V. Alcaraz M. Beckert W. F. Heithmar E. M. Determination of metals in solid samples by complexation supercritical fluid extraction and gas chromatography atomic emission detection J. Chromatogr. Sci. 1993 31 (S) 310. (California Oper. Midwest Res. Inst. Mountain View CA 94043 USA). Esmadi F. T. Kharoaf M. Attiyat A. S. Determination of cyanide and thiocyanate anions by flame atomic absorption spectrometry in a flow system using an on-line preconcentration technique J. Flow Injection Anal. 1993 10( l) 33. (Chem. Dept. Yarmouk Univ. Irbid Jordan). Sanchez Rojas F. Cristofol Alcaraz E. Can0 Pavon J. M. Resolution of binary mixtures of metal ions by flow injection analysis J.Flow Injection Anal. 1993 10(1) 56. (Fac. Sci. Polytech. Sci. Univ. Malaga Malaga Spain). Vapirev E. I. Grozev P. A. Botsova L. I. Hristova A. V. Beta-spectroscopic separation of strontium-90 yttrium-90 and strontium-89 with a scintillation detec- tor J Radioanal. Nucl. Chem. 1993 173(2) 293. (Fac. Phys. Sofia Univ. 1126 Sofia Bulgaria). Ma L.4 Hua J.-r. Progress in the determination of bismuth in metals and alloys by instrumental analysis Lihua Jianyan Huaxue Fence 1993 29(4) 246. (Shanghai No. 2 Metall. Coll. Shanghai 200940 China). Zhao G.-w. Yang L.-y. Indirect determination of total rare earth content using air-liquefied petroleum gas flame Lihua Jianyan Huaxue Fence 1992 28( 6) 348. (Nanjing Inst. Geogr.Lakes Acad. Sin. Nanjing 210008 China). Qin J.-y. Cui H.-r. ICP-AES simultaneous determi- nation of trace elements in magnesium metal Lihua Jianyan Huaxue Fence 1993 29(4) 217. (Hubei Import-Export Inspect. Bur. 430022 China). Brill M. High-precision measurements of precious metals in jewellry by inductively coupled plasma optical emission spectroscopy (ICP-OES)/ISO standard methods for an international harmonized market Metall (Berlin) 1993 47(7) 630. (W. C. Heraeus G.m.b.H. Hanua Germany). Su E. G. Yuzefovsky A. I. Michel R. G. McCaffrey J. T. Slavin W. Effect of stray light on characteristic mass in Zeeman graphite furnace atomic absorption spectrometry Microchem. J. 1993 48( 3) 278. (Dept.310R 941307 1. 94/3072. 9413073. 94/3074. 9413075.9413076. 9413077. 9413078. 94/3079. 94/3080. 94/308 1. 9413082. 94/308 3. 9413084. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 Chem. Univ. Connecticut Storrs CT 06269-3060 USA). Butcher D. J. Determination of fluorine chlorine and bromine by molecular absorption spectrometry Microchem. J. 1993 48(3) 303. (Dept. Chem. Phys. West. Carolina Univ. Cullowhee NC 28723 USA). Sneddon J. Farah B. D. Farah K. S. Multielement atomic absorption spectrometry a historical perspec- tive Microchem. J. 1993 48(3) 318. (Dept. Chem. McNeese State Univ. Lake Charles LA 70609 USA). Wang M A Yuzefovsky A. I. Michel R. G. Determination of ultratrace amounts of copper and cadmium in seawater by graphite furnace atomic absorption spectrometry with flow-injection semi online preconcentration Microchem.J. 1993 48( 3) 326. (Dept. Chem. Univ. Connecticut Storrs CT Ng K. C. Chen S.-m. Dual microwave-induced plasma system with direct solution introduction for atomic emission spectrometry Microchem. J. 1993 48( 3) 383. (Dept. Chem. California State Univ. Fresno CA Gandhi M. N. Khopkar S. M. Liquid-liquid extraction of copper(I1) with cryptand 222 with erythrosine B as the counter-ion Mikrochirn Acta 1993 111( 1-3) 93. (Cent. Environ. Sci. Eng. Indian Inst. Technol. Bombay 400 076 India). Hara H. Determination of silver in copper by inductively coupled plasma emission spectroscopy Jpn. Kokai Tokkyo Koho J P 05,157,696 [93,157,696] (Cl. GOlN21/73) 25 Jun 1993 Appl. 91/319,551 04 Dec 1991; 12 pp. (Meidensha Electric Mfg. Co. Ltd). Suzuki F.Determination of zirconium in alloys by inductively coupled plasma emission spectrochemical analysis Jpn. Kokai Tokkyo Koho JP 05,157,697 [93,157,697] (Cl. GOlN21/73) 25 Jun 1993 Appl. 91/322,218 06 Dec 1991; 21 pp. (Meidensha Electric Mfg. Co. Ltd). Suzuki F. Determination of nickel in steel by induc- tively coupled plasma emission spectroscopy Jpn. Kokai Tokkyo Koho JP 05,157,698 [93,157,698] (Cl. GOlN21/73) 25 Jun 1993 Appl. 911322,219 06 Dec 1991; 20 pp. (Meidensha Electric Mfg. Co. Ltd). Watanabe K. Determination of impurities on semicon- ductor substrates and thin films on semiconductor substrates Jpn. Kokai Tokkyo Koho JP 05,90,378 [93 90,3781 (Cl. HOlL21/66) 09 Apr 1993 Appl. 91/249,602 27 Sep 1991; 5 pp. (Nippon Electric Co). Orlov N. A. Rodyushkin I.V. Burner for flame spectrometers U.S.S.R. SU 1,749,792 (Cl. G01N21/72) 23 Jul 1992 Appl. 4,769,494 19 Dec 1989. (Geologicheskij i kolskogo nauchnogo tsentra an sssr). Kudryashov V. V. Baranov S. V. Zemskova I. A. Tsygankova T. S. Spectral gas discharge lamp for atomic absorption U.S.S.R. SU 1,737,561 (Cl. HOlJ61/02) 30 May 1992 Appl. 4,813,072 12 Apr 1990. (Otraslevoj nt kompleks ‘soyuztsvetme- tavtornatika’). Khuzmiev M. A. Shashenok V. V. Khuzmieva B. Kh. Electrode-free high-frequency discharge lamp in atomic- absorption analysis and method for its prepara- tion U.S.S.R. SU 1,737,565 (Cl. HOlJ65/04) 30 May 1992 Appl. 4,814,974 17 Apr 1990. (Osoboe k byuro pri ordzhonikidzevskom zavode gazorazryadnykh priborov). Matousek J. P. Powell H. K. J. Electrothermal atomic absorption and preconcentration device PCT Int.Appl. WO 93 17,321 (Cl. G01N1/34) 02 Sep 1993 AU Appl. 92/1,069,25 Feb 1992; 31 pp. (Unisearch Ltd.). Andrassy L. Kozma L. Lendvay P. Lupkovics G. Nernet B. Real time in situ application of the laser 06269-3060 USA). 93740-0070 USA). 9413085. 94/3086. 94/3087. 9413088. 9413089. 94/3090. 94/309 1. 9413092. 9413093. 9413094. 94/3095. 9413096. 9413097. 9413098. induced plasma spectrometry the field mode laser spectrometer LIPS-1-60 Proc. SPIE-Int. SOC. Opt. Eng. 1993 1983(0ptics as a Key to High Technology Pt. 2) 1005-7. (Eotvos Lorand Geophys. Inst. Hungary Budapest Hungary). Collett W. L. Mahajan S. M. Ventrice C. A. Novel hollow cathode device for the detection of trace elements in coal ash Rev. Sci. Instrum.1993 64(9) 2696. (Dept. Electr. Eng. Tennessee Technol. Univ. Cookeville TN 38505 USA). Anghel S. D. Mini-torch for inductively coupled plasma used in atomic emission spectroscopy Stud. Univ. Babes-Bolyai Phys. 1990 35(2) 67. (IAUC Univ. Cluj 3400 Cluj-Napoca Romania). Goto T. Radical measurements in processing plasmas using infrared diode laser spectroscopy Trends Chem. Phys. 1991 1 69. (Dept. Electron. Nagoya Univ. Nagoya 464 Japan). Juvonen R. Vaananen P. J. Determination of gold in geological materials by atomic absorption after lead fire assay separation Tutkimusrup.-Geol. Tutkimuskeskus 1993 114 13. (Geo. Surv. Finland SF-02150 Espoo Finland). Noras P. Determination of gold by aqua regia-potas- sium bromate disgestion methyl isobutyl ketone extrac- tion and flame atomic absorption Tutkimusrap.-Geol.Tutkimuskeskus 1993 114 17. (Geol. Surv. Finland SF-02150 Espoo Finland). Ojaniemi E. Determination of gold palladium and platinum by aqua regia digestion dibutylsulfide-diiso- butyl ketone extraction and flameless atomic absorp- tion Tutkimusrap.-Geol. Tutkimuskeskus 1993 114 25. (Res. Cent. Rautaruukki Co. SF-92170 Raahe Finland). Kontas E. Determination of gold and palladium by aqua regia digestion stannous chloride-mercury co- precipitation and flameless atomic absorption Tutkimusrap.-Geol. Tutkimuskeskus 1993 114 29. (Geol. Surv. Finland SF-96101 Rovaniemi Finland). Gornushkin I. B. Zil’bershtein Kh. I. Rossomakhina M. V. Multielement laser-induced atomic-fluorescence analysis Vysokochist Veshchestva 1993 (6) 114.(Inst. Khim. Silik. St.-Petersburg Russia). Xie G.-x. Lin T.-m. Li W.-j. Guo W A Yan C.-m. Determination of trace elements in organic matters by introducing powdered sample into the ICP arc Xiumen Dame Xuebao Ziran Kexueban 1992 31(5) 569. (Dept. Chem. Xiamen Univ. Xiamen China). Yuan Y.-a. Determination of trace gold by electrother- mal atomic absorption spectrometry with a rapid graphite furnace programme Yunkuang Ceshi 1993 12( 3) 194. (Northwest Geol. Res. Inst. CNNC Xian 710054 China). Ge L.-m. Xiao H.-x. Recent advances in the determi- nation of iodide Yankuang Ceshi 1993 12(3) 217. (Inst. Geol. Miner. Resourc. Zhejiang Province Hangzhou 310007 China). Gong C.-s. Guo X.-w. Zhang Z.-j. Zhang L.-y. Xu H.-w. New magnetic auto-stirrer set and its application in analysis of solid samples with slurry technique by electrothermal atomic absorption spec- troscopy Yejin Fenxi 1993 13( 4) 33.(Northwest Res. Inst. Geol. Xian 710054 China). Teng S.-g. Determination of impurity elements in antimony ingot by ICP-AES Yejin Fenxi 1993 13 50. (Jiangxi Import-Export Inspection Bureau Nanchang 330002 China). Guo J. Atomic absorption spectrometric determination of barium in the presence of large amounts of calcium Yejin Fenxi 1993 13(3) 53 38. (Southwest Geol.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 311R 9413099. 94/3 100. 94/3 101. 94/3 102. 94/3103. 9413 104. 9413 105. 94/3 106. 9413 107. 9413 108. 94/3109. 94/3110. 94/3 11 1. Explorat. Bur. Minist. Metall. Chengdu 610051 China). Ying W.-h. Li D.-q. Determination of zinc in zinc concentrates Yejin Fenxi 1993 13(4) 25.(Tianjin Miner. Resour. Test. Cent. Minist. Metall. Ind. Tianjin 300181 China). Xu H.-c. Manufacture and application of a simple hydride generation device Yejin Fenxi 1993 13(4) 55. (Iron Steel Inst. Wuyang Iron Steel Co. Wuyang 462500 China). Chen J.-g. Jiang Z.-c. Kong L.-y. Determination of trace amounts of rare earth impurities in high-purity lanthanum oxide by using ICP-AES after extraction with TBP Zhongguo Xitu Xuebao 1992 10(1) 89. (Dept. Chem. Wuhan Univ. Wuhan 430072 China). Liang Y. Z. Ni Z.-m. General computer program (AAS-TOOLS) for theoretical studies in electrothermal atomic absorption spectrometry J. Anal. At. Spectrom. 1994 9 669. (Res. Centre Eco-environ. Sci. Acad. Sin. P.O. Box 2871 Beijing 100085 China).Stephens R. Reduction of magnet size in direct Zeeman atomic absorption spectrometry J. Anal. At. Spectrom. 1994 9 675. (Dept. Chem. Dalhousie Univ. Halifax Nova Scotia Canada B3H 453). Ma Y.-z. Li Z.-k. Wang X.-h. Wang J.-z Li Y.-q. Determination of cadmium by electrothermal atomic absorption spectrometry using palladium and tartaric acid as a mixed chemical modifier and a tungsten-foil platform with the possibility of standardless analysis J. Anal. At. Spectrom. 1994 9 679. (Inst. Anal. Meas. Chinese Res. Acad. Environ. Sci. Beijing 100012 China). Liidke C. Hoffmann E. Skole J. Studies on the determination of the metal content of airborne particu- lates by furnace atomization non-thermal excitation spectrometry J. Anal. At. Spectrom.1994 9 685. (Inst. Spektrochem. Angewandte Spektrosk. (ISAS) Lab. Spektrosk. Meth. Ulmweltan. (LSMU) Geb. 11.1 Rudower Chaussee 5 12489 Berlin Germany). Petit de Peiia Y. Gallego M. Valcarcel M. Flame atomic absorption spectrometric determination of cad- mium in biological samples using a preconcentration flow system with an activated carbon column and dithizone as a chelating agent J. Anal. At. Spectrom. 1994 9 691. (Dept. Anal. Chem. Fac. Sci. Univ. Cbrdoba 14004 Cbrdoba Spain). Mixon P. D. Griffin S. T. Williams J. C. Jr. Cai X.-j. J. Williams J. C. Pulse optimization criteria for the microcavity hollow cathode discharge emission source J. Anal. At. Spectrom. 1994 9 697. (Dept. Electr. Eng. Memphis State Univ. Memphis TN 38152 USA). Hu Y.-p. Zhang Z.-x. Zhen J.-g.Simulation of nebulization process in inductively coupled plasma atomic emission spectrometry with a modified model using the Monte Carlo technique J. Anal. At. Spectrom. 1994 9 701. (Dept. Chem. Zhongshan Univ. Guangzhou 510275 China). ZBray G. Varga I. Khntor T. Halocarbon-assisted slurry vaporization in inductively coupled plasma atomic emission spectrometry for the analysis of silicon nitride powder J. Anal. At. Spectrom. 1994 9 707. (Inst. Inorg. and Anal. Chem. L. Eotvos Univ. P.O. Box 32 H-1518 Budapest 112 Hungary). Rosenberg R. J. Zilliacus R. Manninen P. Determination of transition metals in the primary water of pressurized water reactors by inductively coupled plasma mass spectrometry J. Anal. At. Spectrom. 1994 9,713. (Tech. Res. Centre Finland VTT Chem.Technol. P.O. Box 1404 FIN-02044 VTT Finland). Platzner I. Sala J. V. Mousty F. Trincherini P. R. Polettini A. Signal enhancement and reduction of 9413 1 12. 94/3113. 94/3 1 14. interferences in inductively coupled plasma mass spec- trometry with an argon-trifluoromethane mixed aerosol carrier gas J . Anal. At. Spectrorn. 1994,9,719. (Environ. Inst. Joint Res. Centre 1-21020 Ispra (VA) Italy). Laborda F. Baxter M. J. Crews H. M. Dennis J. Reduction of polyatomic interferences in inductively coupled plasma mass spectrometry by selection of instrumental parameters and using an argon-nitrogen plasma effect on multi-element analyses J. Anal. At. Spectrorn. 1994 9 727. (Minis. Agric. Fisheries and Food CSL Food Sci. Lab. Norwich Res. Park Colney Norwich Norfolk UK NR4 7UQ).Segal I. Kloner A. Brenner I. B. Multi-element analysis of archaeological bronze objects using induc- tively coupled plasma atomic emission spectrometry aspects of sample preparation and spectral line selection J. Anal. At. Spectrom. 1994 9 737. (Israel Antiquities Authority P.O. Box 586 Jerusalem 91004 Israel). Sharp B. L. Chenery S. Jowitt R. Sparkes S. T. Fisher A. Atomic spectrometry update-atomic emis- sion spectrometry J. Anal. At. Spectrom. 1994,9 171R. (Chem. Dept. Loughborough Univ. Technol. Loughborough Leicestershire UK LE113TU). Papers 94/C3 115-94/C3121 were presented at the Association of Clinical Biochemists National Meeting Brighton UK May 94/C3 11 5. Dickson D. P. E. Physical techniques for measuring iron Proc. ACB Natl. Meeting Brighton UK 9-13 May 1994 B14.(Dept. Phys. Univ. Liverpool Liverpool UK L69 3BX). 94/C3 1 16. Reynolds A. P. Meadows N. Richman K. Manganese in long term paediatric total parenteral nutrition Proc. ACB Natl. Meeting Brighton UK 9-13 May 1994 B15. (Dept. Chem. Pathol. Hospital Sick Children Great Ormond St. London UK WClN 3JH). 94/C3 117. Bayly G. R. Braithwaite R. Sheehan T. M. T. Ferner R. E. Lead poisoning from traditional ethnic remedies Proc. ACB Natl. Meeting Brighton UK 9-13 May 1994 B16. (Natl. Poisons Information Service (Birmingham Centre) and Regional Lab. Toxicol. Dudley Road Hospital Birmingham UK B18 7QH). 94/C3118. Holding J. D. Lawton R. Yaqoob M. Roberts N. E. Whole blood lead and cadmium concentrations in patients with end-stage renal failure and the effect of haemodialysis Proc.ACB Natl. Meeting Brighton U K 9-13 May 1994 B23. (Dept. Clin. Chem. Royal Liverpool Univ. Hospital Prescot Street Liverpool UK L7 8XP). 94/C3119. Taylor A. Palheta D. Mercury in environmental and biological samples from a gold mining area in the Amazon region of Brazil Proc. ACB Natl. Meeting Brighton UK 9-13 May 1994 C61. (Dept. Clin. Biochem. St Luke’s Hospital Guildford Surrey UK GU13NT). 94/C3120. Taylor A. Pezonaga I. Effects of platinum chemo- therapy on the metabolism of trace elements Proc. ACB Natl. Meeting Brighton UK 9-13 May 1994 C62. (Dept. Clin. Biochem. St Luke’s Hospital Guildford Surrey UK GU13NT). 94/C3121. Peaston. R. T. Measurement of liver iron in needle- 9-13 1994. 94/3 122. biopsy specimens by rapid microwave acid digestion and atomic absorption Proc.ACB Nutl. Meeting Brighton UK 9-13 May 1994 C59. (Dept. Clin. Biochem. Freeman Hospital High Heaton Newcastle- upon-Tyne UK NE7 7DN). Ozdemir Y. Karagozler A. E. Giiger S. Interferences in the determination of lithium by flame atomic emission spectrometry with platinum-loop atomizer J. Anal. At. Spectrom. 1994 9 797. (Inonu Univ. Dept. Chem. 44069 Malatya Turkey).312R 9413 123. 9413124. 94/3 125. 9413126. 9413 127. 9413 128. 94/3129. 94/3 130. 9413131. 9413 132. 94/3 133. 9413 134. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 Pyrzynska K. Flow injection preconcentration of gold(1Ir) on Cellex T for determination by flame atomic absorption spectrometry J. Anal. At. Spectrom. 1994 9 801. (Dept.Chem. Univ. Warsaw Pasteura 1,02-093 Warsaw Poland). Bettinelli M. Tittarelli P. Evaluation and validation of instrumental procedures for the determination of nickel and vanadium in fuel oils J. Anal. At. Spectrom. 1994 9 805. (ENEL SPA DCO-Lab. Centrale via Nino Bixio 39 29100 Piacenza Italy). BorszCki J. Halmos P. KOV~CS K. Tilky P. Method for the determination of ‘active’ sulfur in the graphite packing of a nuclear power station-a proposal for standardization Can. J. Appl. Spectrosc. 1994 39( 1 ) 14 (Univ. Veszprtm Dept. Anal. Chem. Veszprem P.O. Box 158 H-8201 Hungary). Ford M. J. Ebdon L. Hutton R. C. Hill S. J. Simplex optimization of the plasma parameters and ion optics of an inductively coupled mass spectrometer with pure argon and doped argon plasmas using a multi-element figure of merit Anal.Chim. Acta 1994 285 23. (Plymouth Anal. Chem. Res. Unit Dept. Environ. Sci. Univ. Plymouth Drake Circus Plymouth Devon UK PL48AA). Kauppinen M. Smolander K. Determination of rho- dium in organic solutions by flame atomic absorption spectrometry with methyl isobutyl ketone and ethanol as solvents Anal. Chim. Acta 1994 285 45. (Dept. Chem. Univ. Joensuu P.O. Box 11 1 SF-80101 Joensuu Finland). Ohta K. Inui S.-y. Yokoyama M. Mizuno T. Determination of zinc in aluminium metal by sequential metal vapour elution analysis Anal. Chim. Acta 1994 285 53. (Dept. Chem. Mat. Fac. Eng. Mie Univ. Tsu Mie 514 Japan). Atanasov S. K. Stoyanova G. G. Bratinova S. P. Popova S. P. Inductively coupled plasma atomic emission spectrometric determination of trace amounts of metals in palladium compounds Anal.Chim. Acta 1994 285 57. (Univ. Mining and Geol. Central Res. Lab. 1 156 Sofia Bulgaria). Adeloju S. B. Dhindsa H. S. Tandon R. K. Evaluation of some wet decomposition methods for mercury determination in biological and environmental materials by cold vapour atomic absorption spectroscopy Anal. Chim. Acta 1994 285 359. (Centre Electrochem. Res. and Anal. Technol. Dept. Chem. Univ. Western Sydney Nepean P.O. Box 10 Kingswood NSW 2747 Australia). Hori A. Matsumoto T. Nimura Y. Ikedo M. Okada H. Tsuda T. Electro-concentration by using counter-current due to pressurized flow and electropho- retic mobility Anal. Chem. 1993 65(20) 2882. (Dept. Appl. Chem. Nagoya Inst. Technol. Nagoya 466 Japan). Pretty J. R.Blubaugh E. A. Caruso J. A. Determination of arsenic(1n) and selenium(1v) using an online anodic-stripping voltammetry flow cell with detection by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry Anal. Chem. 1993 65(23) 3396. (Natl. Inst. Occupational Safety and Health Cincinnati OH 45226 USA). Uchida T. Isoyama H. Oda H. Wada H. Uenoyama H. Determination of ultra-trace metals in biological standards by inductively coupled plasm2 atomic emission spectrometry with ultrasonic nebuliz- ation Anal. Chim. Acta 1993 283(2) 881. (Dept. Applied Chem. Nagoya Inst. Technol. Nagoya 466 Japan). Rigin V. Simultaneous atomic fluorescence spectro- metric determination of traces of iron cobalt and nickel 94 f 3 135. 94 f3 136. 94/3137.9413 13 8. 94/3 139. 9413 140. 9413 141. 9413 9413 42. 43. 9413 144. 94/3 145. 9413 146. after conversion to their carbonyls and gas-phase atomization by microwave-induced plasma Anal. Chim. Acta 1993,283( 2) 895. (Res. and Design Inst. Problems Dev. Kansk-Achinsk Coal Basin 660041 Krasnoyarsk Russia). Krushevska A Barnes R. M. Inductively coupled plasma atomic emission spectrometric determination of aluminium barium silicon strontium and titanium in food after sample fusion Analyst 1994 119(1) 131. (Dept. Chem. Lederle Graduate Res. Centre Tower Univ. Massachusetts Amherst MA 01003-0035 USA). Alvarado J. Carnahan J. W. Direct detection of vacuum-ultra-violet radiation for non-metal determi- nations with a hellium microwave-induced plasma Appl. Spectrosc.1993 47( 12) 2036. (Dept. Chem. Northern Illinois Univ. DeKalb IL 601 15 USA). Yap C. T. Hua Y. N. Theoretical studies in EDXRF on a new linear relation In(fluorescent intensity ratio of analyte to pure analyte/concentration of analyte) versus In(fluorescent energy) Appl. Spectrosc. 1993 47( 12) 2052. (Dept. Phys. Natl. Univ. Singapore Singapore 051 1 Singapore). Reus U. Markert B. Hoffmeister C. Spott D. Guhr H. Determination of trace metals in river water and suspended solids by TXRF spectrometry. A methodical study on analytical performance and sample homogeneity Fresenius’ J. Anal. Chem. 1993 347( 10-1 l) 430. (Inst. Gewaesserforschung GKSS Forschungszentrum 39 104 Magdeburg Germany). Docekal B. Krivan V. Improved electrothermal atomic absorption spectroscopy method for the determi- nation of lithium in molybdenum oxide using slurry sampling and a tungsten atomizer Spectrochim.Acta Part B 1993 48(13) 1645. (Sektion Anal. u. Hoechstreinigung Univ. Ulm 89069 Ulm Germany). Farnsworth P. B. News on fundamental reference data Spectrochim. Acta Part B 1993 48(13) 1651. (Dept. Chem. Brigham Young Univ. Provo UT 84602-4672 USA). Carneiro M. C. Campos R. C. Curtius A. J. Determination of antimony nickel and vanadium in slurry from airborne particulate material collected on filter by graphite furnace atomic absorption spec- trometry Talanta 1993 40( 12) 1815. (Dept. Quim. Pontificia Univ. Catolica Rio de Janeiro 22453-900 Rio de Janeiro RJ Brazil). Guo T. Baasner J. Online microwave sample pre- treatment for the determination of mercury in blood by flow injection cold vapour atomic absorption spectrometry Talanta 1993 40( 12) 1927.(Atomic Absorption Product Dept. Bodenseewerk Perkin-Elmer GmbH 7770 Ueberlingen Germany). Choi K.-k. Lam L. Luk S.-f. Analysis of cement by atomic absorption spectrophotometry and volumetric method Talanta 1994 41(1) 1. (Lab. China Cement Co. (HK) Ltd. Tuen Mun Hong Kong). Shayachmetova N. M. Stefanov A. V. Tikhomirova T. I. Lobanov F. I. Makarov N. V. Extraction of molybdoarsenic acid with trioctylamine into molten stearic acid Zh. Anal. Khim. 1993,48( ll) 55. (Moscow Inst. Applied Biotechnol. Moscow Russia). Shcherbakov K. G. Gimel’farb F. A. XRF analysis of forensic samples using sample encapsulation in a fusible organic matrix Zh. Anal. Khim.1993 48(11) 137. (M. V. Lomonsov Moscow State Univ. Moscow Russia). Gil’mutdinov A. Kh. Zakharov Yu. A. Ivanov V. P. Voloshin A. V. Non-stationary structure of atomic and molecular layers in electrothermal atomic absorption spectrophotometry. Dynamics of formation of copper manganese and iron atomic absorbing layers Zh. Anal. Khim. 1993 48( 12) 1906. (Kazan State Univ. Kazan Russia).JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 313R 9413 147. 9413148. 9413149. 9413 1 50. 9413 151. 9413 152. 9413153. 9413 154. 9413155. 9413 156. 9413 157. 94/3 158. 9413 159. 94/3 160. Bel’skii N. K. Ochertyanova L. I. Direct determination of trace impurities in high-purity tantalum pentoxide by electrothermal atomic absorption spectrophotom- etry Zh. Anal.Khim. 1993 48(12) 2012. (N. S. Kurnakov Inst. General and Inorg. Chem. Russian Acad. Sci. Moscow Russia). Al-Swaidan H. M. Simultaneous multi-element analysis of Saudi Arabian petroleum by micro-emulsion induc- tively coupled plasma mass spectrometry (ICP-MS) Anal. Lett. 1994 27( l) 145. (Dept. Chem. Coll. Sci. King Saud Univ. Riyadh 11451 Saudi Arabia). Buemi A. Pompilio M. Turchio F. Effect of grinding during sample preparation on the XRF analysis of a basaltic rock Ann. Chim. (Rome) 1993 83(7-8) 285. (1st. Int. Vulcanol. 95123 Catania Italy). Berg T. Royset O. Steinnes E. Blank values of trace elements in aerosol filters determined by ICP-MS Atmos. Environ. Part A Oct. 1993 27(15) 2435. (Norwegian Inst. Air. Res. 2001 Lillestrom Norway). British Standards Institution Water quality.Part 2. Physical chemical and biochemical methods. Section 2.45. Determination of selenium by atomic absorption spectrometry British Standard BS 6068 Section 2.45 1993 [IS0 9965 19931 15 Nov 1993. Pp. 10. (Linford Wood Milton Keynes MK14 6LE UK). British Standards Institution Hard metals-determi- nation of contents of metallic elements by X-ray fluorescence-fusion method British Standard BS EN 24503 1993 [IS0 4503 19781 15 Jun 1993. Pp. 12. (Linford Wood Milton Keynes MK14 6LE UK). British Standards Institution Hard metals-determi- nation of contents of metallic elements by X-ray fluorescence-solution method British Standard BS EN 24883 1993 [IS0 4883 19781 15 Jun 1993. Pp. 12. (Linford Wood Milton Keynes MK14 6LE UK). Kolesov G. M. Anikiev V.Prasad S. K. Sedykh E. M. Determination of trace elements in samples of bottom sediments suspended matter and aerosols Chem. Anal. (Warsaw) 1993 38(5) 625. (V. I. Vernadsky Inst. Geochem. & Anal. Chem. Russian Acad. Sci. Moscow Russia). Pszonicki L. Essed A. M. Palladium and magnesium nitrate as modifiers for the determination of lead by graphite-furnace atomic-absorption spectrometry Chem. Anal. (Warsaw) 1993 38(6) 771. (Inst. Nucl. Chem. and Technol. 03-195 Warsaw Poland). Dong L.-p. Fang Z.4 Flow-injection online ion- exchange preconcentration flame atomic absorption spectrometry Fenxi Shiyanshi 1993 12( 6) 55. (Flow- Injection Anal. Res. Center Inst. Appl. Ecol. Acad. Sinica Shenyang 110015 China). Shi Y. Chen J. H. Chi X. Z. Determination of trace germanium and strontium in patient serum by graphite furnace atomic absorption spectrometry Fenxi Shiyanshi 1993,12( 6) 58.(Dept. Chem. Beijing Normal Univ. Beijing 100875 China). Zhang X. Z. Wu Q. M. Determination of antimony and bismuth in food by hydride generation atomic absorption spectrometry with electrothermal atomiz- ation Fenxi Shiyanshi 1993 12( 6) 63. (Environ. Protection Res. Inst. Ministry Light Ind. Beijing 100037 China). Guan P. L. Rapid analysis of intermediate sample in rare earth extraction by X-ray fluorescence spec- trometry Fenxi Shiyanshi 1993 12( 6) 75. (Chinese). Schnug E. Murray F. Haneklaus S. Preparation techniques of small sample sizes for sulfur and indirect total glucosinolate [mustard oil glycoside] analysis in Brassica seeds by X-ray fluorescence spectroscopy Fett Wiss.Technol. 1993 95 334. (Inst. Plant Nutrition and 9413 16 1. 9413 162. 9413 163. 94 13 164. 9413165. 9413 166. 9413 167. 94/3 168. 9413169. 9413 170. 9413 17 1. 9413 172. 9413173. 94/3 174. Soil Sci. Fed. Agric. Res. Centre (FAL) 38116 Braunschweig-Volkenrode Germany). Sager M. Determination of arsenic cadmium mercury antimony thallium and zinc in coal and coal fly ash Fuel 1993 72( 9) 1327. (Landwirtschaftlich-Chem. Bundesanstalt 1020 Vienna Austria). Fink T. Chang C.-T. Janssen A. Improvement of the sample preparation of iron ore and sinter for X-ray fluorescence analysis by lithium tetraborate fusion GZT Fachz. Lab. 1993 37( 6) 492. (FB Chemieingenieur- wesen FH Muenster/Abteilung Steinfurt 4430 Steinfurt Germany). Sumitani H.Suekane S. Nakatani A. Tatsuka K. Inductively coupled plasma atomic emission spectro- metric determination of tin in canned food J. AOAC Int. 1993 76(6) 1374. (Toyo Inst. Food Technol. Hyogo 666 Japan). Lai J.-J. Jamieson G. C. Determination of dys- prosium in monkey serum by inductively coupled plasma atomic emission spectrometry (ICP-AES) after the administration of Sprodiamide Injection a new contrast medium for magnetic resonance imaging J. Pharm. Biomed. Anal. 1993 ll(l1-12) 1129. (Nycomed Salutar Inc. Sunnyvale CA 94086 USA).’ Sumiya S. Morita S. Tobita K. Kurabayashi M. Determination of technetium-99 and neptunium-237 in environmental samples by inductively coupled plasma mass spectrometry J. Radioanal. Nucl. Chem. 1994 177( l) 149. (Environ. Protection Section Health and Safety Div.Power Reactor and Nuclear Fuel Development Corp. Ibaraki 319-1 1 Japan). Civici N. Determination of trace metals in sea-waters of the Albanian coast by energy-dispersive X-ray fluorescence J. Radioanal. Nucl. Chem. 1994 186( 4) 303. (Inst. Nucl. Phys. Tirana Albania). Meyer A Schwedt G. Coupling of microwave diges- tion and hydride AAS Labor Praxis 1993 117(4) 44. (Clausthaler Umwelttechnik-Inst. GmbH 3392 Clausthal-Zellerfeld Germany). Braun T. Zsindely S. Comparative standing of individual instrumental analytical techniques Magy. Kem. Foly. 1993,99(7-8) 297. (Dept. Inorg. and Anal. Chem. L. Eotvos Univ. 1443 Budapest Hungary). Braun T. Glanzel W. Maczelka H. Zsindely S. Image of analytical chemistry as reflected in the Analytical Abstracts database journal coverage concen- tration and dispersion of the analytical literature Magy.Kem. Foly. 1993,99(7-8) 301. (Dept. Inorg. and Anal. Chem. L. Eotvos Univ. 1443 Budapest Hungary). Cervera M. L. Lopez J. C. Montoro R. Determination of arsenic in orange juice by dry ashing hydride generation atomic absorption spectrometry Microchem. J. 1994 49( l) 20. (Inst. Agrochem. and Food Technol. (CSIC) 46010 Valencia Spain). Webb D. P. Hamier J. Salin E. D. Autonomous instrument a design TrAC Trends Anal. Chem. (Pers. Ed.) 1994 13(2) 44. (Dept. Chem. McGill Univ. Montreal PQ Canada H3A 2K6). Fox R. W. Weimer C. S. Hollberg L. Turk G. C. Diode laser as a spectroscopic tool Spectrochim. Acta Rev. 1993 15(5) 291. (Natl. Inst. Standards and Technol. Boulder CO 80303 USA). Niemax K.Groll H. Schnuerer-Patschan C. Element analysis by diode-laser spectroscopy Spectrochim. Acta Rev. 1993 15(5) 349. (Inst. Spektrochem. und Angewandte Spektroskopie (ISAS) 44139 Dortmund Germany). Lin Y.-b. Zhu Y . 4 Separation and preconcentration of trace selenium and tellurium in rock by MI resin Yankuang Ceshi 1993 12(2) 81. (Inst. Rock and314R 9413175. 9413 176. 9413 177. 9413 178. 9413 179. 9413 180. 9413181. 9413 182. 9413 183. 9413 184. 9413 185. 9413 186. 94/3 187. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 Mineral Anal. Ministry Geol. and Mineral Resources Beijing 100037 China). Chen J.-w. Zeng F.-g. Shen H.-j. Determination of trace gold silver thallium and cadmium by AAS after concentration with isobutyl methyl ketone loaded polyurethane foam Yankuang Ceshi 1993 12( 2) 85.(Inst. Rock and Mineral Anal. Ministry Geol. and Mineral Resources Beijing 100037 China). Zhang X. Gao W.-m. Li B.-x. Absorbance correction in graphite-furnace AAS for aged graphite tubes Yankuang Ceshi 1993 (2) 96. (Dept. Earth and Space Sci. Univ. Sci. and Technol. ina Hefei 230026 China). Murray K. K. Lewis T. M. Beeson M. D. Russell D. H. Aerosol matrix-assisted laser desorption ioniz- ation for liquid chromatography-time-of-flight mass spectrometry Anal. Chem. 1994 66 1610. (Dept. Chem. Texas A&M Univ. College Station TX Popenoe D. D. Morris S. J. 111 Horn P. S. Norwood K. T. Determination of alkyl sulfates and alkyl ethoxysulfates in wastewater treatment plant influents and effluents and in river water using liquid chromatography/ion spray mass spectrometry Anal.Chem. 1994 66 1620. (The Procter and Gamble Company Ivorydale Tech. Center 5299 Spring Grove Avenue Cincinnati OH 45217 USA). Hagen J. J. Monnig C. A. Method for estimating molecular mass from electrospray spectra Anal. Chem. 1994 66 1877. (Dept. Chem. Univ. California Riverside CA 92521-0403 USA). Deng R.-C. Williams P. Suppression of cluster ion interferences in glow discharge mass spectrometry by sampling high-energy ions from a reversed hollow cathode ion source Anal. Chem. 1994,66 1890. (Dept. Chem. and Biochem. Arizona State Univ. Tempe AZ Cisper M. E. Earl W. L. Nogar N. S. Hemberger P. H. Silica-fibre microextraction for laser desorption ion trap mass spectrometry Anal.Chem. 1994 66 1897. (Chem. Sci. and Technol. Div. Los Alamos Natl. Lab. MS G740 Los Alamos NM 87545 USA). Baldwin D. P. Zamzow D. S. D’Silva A. P. Aerosol mass measurement and solution standard additions for quantitation in laser ablation inductively coupled plasma atomic emission spectrometry Anal. Chem. 1994 66 1911. (Ames Lab. U.S. Dept Energy Ames IA 50011 USA). Wang B. H. Blemann K. Matrix-assisted laser desorption/ionization time-of-flight mass spectrom- etry of chemically modified oligonucleotides Anal. Chem. 1994 66 1918. (Dept. Chem. Massachusetts Inst. Technol. Cambridge MA 02139-4307 USA). Veillon C. Patterson K. Y. Rubin M. A. Moser- Veillon P. B. Determination of natural and isotopically enriched chromium in urine by isotope dilution gas chromatography/mass spectrometry Anal.Chem. 1994 66(6) 856. (Vitamin and Miner. Nutr. Lab. Beltsville Human Nutr. Res. Center Beltsville MD 20705 USA) Pickett D. A. Murrell M. T. Williams R. W. Determination of femtogram quantities of proactinium in geologic samples by thermal ionization mass spec- trometry Anal. Chem. 1994 66(7) 1044. (Los Alamos Natl. Lab. Los Alamos NM 87545 USA). Berry J. A. Bishop H. E. Cowper M. M. Fozard P. R. McMillan J. W. Mountfort S. A. Measurement of the sorption of actinides on minerals using microana- lytical techniques Analyst 1993 118( lo) 1241. (AEA Technol. Harwell Lab. Didcot/Oxfordshire UK OX1 1 ORA). Bersier P. M. Howell J. Bruntlett C. Advanced electroanalytical techniques versus atomic absorption 77843-3255 USA). 85287-1604 USA).9413 18 8. 9413 189. 9413 190. 94/3 191. 9413 192. 9413 193. 9413 194. 9413195. 9413 196. 9413 197. 9413198. 9413199. 9413200. spectrometry inductively coupled plasma atomic emis- sion spectrometry and inductively coupled plasma mass spectrometry in environmental analysis Analyst 1994 119(2) 219. (4125 Riehen Switzerland). Shirasaki T. Hiraki K. Determination of trace elements in a photoresist solution by microwave- induced plasma mass spectrometry Bunseki Kagaku 1994 43( l) 25. (Technol. Res. Lab. Hitachi Instrum. Eng. Co Ltd. Katsuta Japan 312). Akatsuka K. Hoshi S. McLaren J. W. Berman S. S. Ion-exchange separation of nanogram platinum in environmental dust samples for isotope dilution ICP-MS Bunseki Kagaku 1994 43( l) 61. (Kitami Inst. Technol. Kitami Japan 090).Wang Z.-s. Dong Z.-q. Sui X.-y. Jiang Z.4 Determination of trace impurity elements in high-purity scandium oxide by chemical separation-spark source mass spectrometry Fenxi Huaxue 1993 21 ( 1 1 ) 1323. (Changchun Inst. Appl. Chem. Chin. Acad. Sci. Changchun 130022 China). Hess C. Trace metal analysis in biological matrix (urine)-methods evaluation and comparison of AAS- ICP-MS Akute Chronische Toxiz. Spurenelem Jahrestag. Ges. Mineralstofle Spurenelem. 8th 1992 (Pub. 1993) 43-7. (Bremen Germany). Soltani-Neshan M. A. Garbe-Schoenberg D. Dorner K. Schaub J. Absorption and retention of molybdenum by adults studied with ICP-mass spec- trometry after dosing with stable ImMo Akute Chronische Toxiz. Spurenelem. Jahrestag. Ges. Mineralstofle Spurenelem. 8th 1992 (Pub.1993) 61-4. (Kiel Germany). Tissue B. M. Olivares J. A. Loge G. W. Fearey B. L. Effect of laser characteristics on thorium isotopic ratios measured by resonance ionization mass spec- trometry Anal. Instrum. ( N . Y.) 1993,21( 1-2) 11. (Isot. Sci. Group Los Alamos Natl. Lab. Los Alamos NM 87545 USA). Zilliacus R. Likonen J. Ronkainen H. Hirvonen J.-P. Characterization of interfaces between TiN or hard carbon coating and substrate by SIMS Appl. Surf. Sci. 1994 75(1-4) 175. (Reactor Laboratory Tech. Res. Centre Finland P.O. Box 200 FIN-021 51 Espoo Finland). Mueller F. U. Hunneman D. H. Kahles R. Hellige G. Investigation of cardiac metabolism using stable isotopes and mass spectrometry Basic Res. Cardiol. 1993,88( 3) 272. (Zent. Anaesthesiol. Rettungs Intensivmed. Univ.Goettingen Germany). Lee G. H. Yang S. R. Park C. J. Lee K. W. Determination of trace impurities in gold by isotope dilution inductively coupled plasma mass spectrometry Bull. Korean Chem. Soc. 1993,14( 6) 696. (Dept. Chem. Chung Nam Natl. Univ. Taejeon 305-764 S. Korea). Moenke-Blankenburg L. High laser irradiance regime. B. Solid sampling or analysis by laser ablation Chem. Anal. (N.Y.) 1993 124 (Laser Ionization Mass Analysis) 433. (Dept. Chem. Martin-Luther-Univ. Halle Germany). Deitze H. J. Becker J. S. High laser irradiance regime. C. Inorganic trace analysis by laser-induced mass spectrometry Chem. Anal. (N.Y.) 1993 124 (Laser Ionization Mass Analysis) 453. (Cent. Dept. Chem. Anal. Res. Centre Julich GmbH Julich Germany). Hirata T. Precise determination of isotopic composi- tions of trace elements with ICP multiple-collection mass spectrometer Chishitsu Nyusu 1993 469 7.(Tokyo Inst. Technol. Sci. Coll. Tokyo Japan). Veillon C. Patterson K. Y. Nagey D. A. Tehan A. M. Measurement of blood volume with an enrichedJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 315R 941320 1. 94/3 202. 9413203. 9413204. 9413205. 9413206 94/3207. 9413208. 9413209. 94/3210. 94/32 1 1. 94/3212. 94/32 13. stable isotope of chromium (53Cr) and isotope dilution by combined gas chromatography-mass spectrometry Clin. Chem. (Washington D.C.) 1994 40(1) 71. (Beltsville Hum. Nutr. Res. Cent. US Dep. Agric. Beltsville MD 20705 USA). Wee A. T. S. Huan C. H. A. Thong P. S. P. Tan K. L. Comparative study of the initial oxygen and water reactions of germanium and silicon using SIMS Corros.Sci. 1994 36(1) 9. (Dept. Phys. Natl. Univ. Singapore Singapore Singapore 05 11 ). Schulze R. K. Ion yield variations in SIMS and ESD of covalently modified surfaces upon surface work function alterations by alkali metal adsorption. Diss Abstr. Znt. B 1992 53(2) 818. (Univ. Minnesota Minneapolis MN USA). Chernyshev I. V. Karpenko M. I. Troitskii V. A. Shcherbinina N. K. Laser microanalysis technique to study galena crystals for lead isotope investigation Geokhimiya 1993 10 1487. (Inst. Geol. Rudn. Mestorozhd. Petrogr. Mineral Geokhim. Moscow Russia). Bi S.-l. Meng X.-h. Determination of trace Dy in U308 by isotope dilution mass spectrometry He Huaxue Yu Fangshe Huaxue 1993 15( 2) 123. (Beijing Res.Inst. Chem. Eng. Metall. Beijing 101149 China). Tomizuka H. Hoshi T. Tanaka A. Ayame A. Graphical analysis of transient behaviour in SIMS depth profiling using I6O2+ Hyomen Kagaku 1993 14(8) 493. (ULVAC-PHI Inc. Chigasaki Japan 253). Kluge H. J. Bollen G. ISOLTRAP A tandem Penning trap mass spectrometer for radioactive isotopes Hyperjne Interact. 1993,81( 1-4) 15. (Inst. Phys. Univ. Mainz D-55099 Mainz Germany). Crawford J. E. Buchinger F. Davey L. Ji Y. Lee J. K. P. Pinard J. Vialle J. L. Zhao W. Z. Laser desorption sources and time-of-flight injection for RFQ traps Hyperfine Interact. 1993 81( 1-4) 143. (Foster Radiat. Lab. McGill Univ. Montreal PQ Canada). Sharma K. S. Barber R. C. Crawford J. E. Lee J. K. P. Moore R. B. Buchioger F. Hagberg E. Hardy J. C.Koslowsky V. T. Savard G. Proposed Penning trap mass spectrometer facility at TASCC Hyperfine Interact. 1993 81( 1-4) 217. (Dept. Phys. Univ. Manitoba Winnipeg MB Canada R3T 2N2). Walczyk T. Hebeda E. H. Heumann K. G. Low blank rhenium isotope ratio determinations by V,O coated nickel filaments using negative thermal ioniz- ation mass spectrometry lnt. J. Mass Spectrom. lon Processes 1994 130( 3) 237. (Inst. Anorg. Chem. Univ. Regensburg D-93040 Regensburg Germany). RUSSOW R. Foerstel H. Use of GC-QMS for stable isotope analysis of environmentally relevant main and trace gases in the air Isotopenpraxis 1993 29( 4) 327. (Sekt. Bodenforsch. Umweltforschungszent. Leipzig- Halle G.m.b.H. D-04318 Leipzig Germany). Wu C. L. Hsu W. C. Shieh H. M. Secondary-ion mass spectrometry analysis in pseudomorphic GaAs/ InGaAsIGaAs heterostructures utilizing &doping superlattice J .Appl. Phys. 1994 75( l) 608. (Dept. Electr. Eng. Natl. Cheng Kung Univ. Tainan 70101 Taiwan). Roland P. A. Wynne J. J. Photoionization and photofragmentation of B,N clusters produced by laser vaporization of boron nitride J . Chem. Phys. 1993 99(11) 8599. (Thomas J. Watson Res. Cent. IBM Yorktown Heights NY 10598-0218 USA). Rosin C. Morlot M. Ganne N. Hartemann P. Boeglin J. C. ICP-MS for the determination of mineral elements in water J Fr. Hydrol. 1992 23( I) 7. (Lab. Hyg. Rech. Sante Publique 54500 Vandoeuvre France). 94/3 2 14. 941321 5. 94/32 1 6. 94/3217. 941321 8. 9413 2 19. 9413220. 9413221. 9413222. 94/3223. 9413224. 9413225. 9413226. Hall G. E. M.Capabilities of production-oriented laboratories in water analysis using ICP-ES and ICP-MS J. Geochem. Explor. 1993,49( 1-2) 89. (Miner. Resour. Div. Geol. Surv. Canada Ottawa Ontario Canada). Lausch J. Berg R. Koch L. Coquerelle M. Glatz J. P. Walker C. T. Mayer K. Dissolution residues of highly burnt nuclear fuels J. Nucl. Muter. 1994 208( 1-2) 73. (Betriebsgesellschaft mbH Wiederaufar- beitungsanlage D-76339 Eggenstein-Leopoldshafen Germany). Balland B. Bureau J. C. PIossu C. Botton R. FT-IR SIMS and electrical characterization of silicon nitride thin films obtained from CVD assisted by in-situ electrical discharge Muter. Res. SOC. Symp. Proc. 1993 284(Amorphous Insulating Thin Films) 39. (L.P.M. 1.N.S.A.-Lyon F-69621 Villeurbanne France). Stesmans A. Vanheusden K.Depth profiling of oxygen vacancy defect generation in buried silicon dioxide Muter. Res. SOC. Symp. Proc. 1993 284(Amorphous Insulating Thin Films) 299. (Dept. Phys. Kathol. Univ. Leuven 3001 Lourain Belgium). Ebdon L. Ford M J. Goodall P. Hill S. J. Hydrogen addition to the nebulizer gas for the removal of polyatomic ion interferences in inductively coupled plasma mass spectrometry Microchem. J. 1993 48( 3) 246. (Dept. Environ. Sci. Univ. Plymouth Plymouth Devon UK PL4 8AA). Mi J. Bouvet D. Letourneau P. Xanthopoulos N. Mathieu H. J. Dutoit M. Dubois C. Dupuy J. C. High-resolution SIMS profiling of nitrogen in ultra- thin silicon dioxide films nitrided by RTP in ammonia and nitrous oxide Microelectron. Eng. 1993 22( 1 -4) 81. (Inst. Micro- Optoelectron.Swiss Fed. Inst. Technol. 101 5 Lausanne Switzerland). Takasuki M. Mukai T. Method for adjusting sensi- tivity of inductively coupled plasma mass spectrometer Jpn. Kokai Tokkyo Koho JP 05,190,135 [93,190,135] (CI. HOlJ49/26) 30 Jul 1993 Appl. 92/21,982 09 Jan 1992; 4 pp. (Sharp Kk). Volkov V. V. Luyten W. Van Landuyt J. Ferauge C. Oksenoid K. G. Gijbels R. Vasilev M. G. Shelyakin A. A. Lazarev V. B. Electron microscopy and mass- spectrometry study of indium gallium arsenide phos- phide/indium phosphide heterostructures (p-i-n diodes) grown by liquid phase epitaxy Phys. Status Solidi A 1993 140( l) 73. (EMAT Univ. Antwerp Belgium). Hocking W. H. Verrall R. A. Lucuta P. G. Matzke H. Depth-profiling studies of ion-implanted casium and rubidium in SIMFUEL and uranium dioxide Radiat.Efl. Defects Solids 1993 125(4) 299. (Whiteshell Lab. At. Energy Canada Ltd. Pinawa MB Canada ROE 1LO). Trautman N. Ultratrace analysis for technetium Radiochim. Acta 1993 63 37. (Inst. Kernchem. Univ. Mainz D-55099 Mainz Germany). Momoshima N. Sayad M. Takashima Y. Analytical procedure for technetium-99 in seawater by ICP-MS Radiochim. Acta 1993 63 73. (Fac. Sci. Kyushu Univ. Fukuoka 812 Japan). Barinaga C. J. Koppenaal D. W. Ion-trap mass spectrometry with an inductively coupled plasma source Rapid Commun. Mass Spectrom. 1994 8( l) 71. (Pac. Northwest Lab. Richland WA 99352 USA). Lu Q. Hultquist G. Aakermark T. In situ SIMS analysis of the initial oxidation of a commercial iron-chromium-aluminum alloy in water vapor/oxygen gas at 600-850K Scand.Corros. Congr. EUROCORR '92 12th 1992 1 581. (Dept. Appl. Electrochem. Corros. R. Inst. Technol. S-100 44 Stockholm Sweden).316R 9413227. 9413228. 9413229. 9413230. 9413231. 9413232. 9413 2 3 3. 9413234. 941323 5. 9413236. 9413237. 9413238. 9413239. 94/3240. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 Bradley J. W. Kato S. Development of an electron- beam-excited plasma SNMS SNART (2) Shinku 1993 36(3) 266. (Inst. Phys. Chem. Res. Wako 351-01 Japan). Godfrey J. McCurdy E. Investigation into the feasibility of ICP-MS as an alternative to fire assay measurements for gold and the platinum group elements Spec. Pub1.- R. SOC. Chem. 1993 124 (Applications of Plasma Source Mass Spectrometry 11) 64. (VG Elemental Ltd. Winsford UK CW74BX). Anderson S.T. G. Taylor M. J. C. Williams S. J. S. Application of flow injection analysis to ICP-MS Spec. Pub[.-R. SOC. Chem. 1993 124 (Applications of Plasma Source Mass Spectrometry II) 72. (Anal. Sci. Div. Mintek Randburg 2125 S. Africa). Perry B. J. Barefoot R. R. Van Loon J. C. Naldrett A. J. Speller D. V. Dry chlorination/microwave digestion/ICP-MS analytical method for the determi- nation of the platinum group elements and gold in metallic and nonmetallic fractions of rocks Spec. Pub1.-R. SOC. Chem. 1993 124 (Applications of Plasma Source Mass Spectrometry 11) 91-101. (Dept. Geol. Univ. Toronto Toronto Ontario Canada M5S 3BI). Turner P. J. Measurement of isotope ratios using ICP-MS Spec. Pub1.-R. SOC. Chem. 1993 124 (Applications of Plasma Source Mass Spectrometry 11) 175.(Unit 7 Finnigan Mat Ltd. Appleton Warrington Cheshire UK WA4 4ST). Pischow K. A. Ristolainen E. O. Korhonen A. S. Elevated temperature wear surfaces of some mould materials studied by STM and SIMS Spec. Pub1.- R. SOC. Chem. 1993 128 (Surface Engineering Vol. 111 Process Technology and Surface Analysis) 229. (Lab. Process. Heat Treatment Mater. Helsinki Univ. Technol. 021 50 Espoo Finland). Naka H. Kurayasu H. Endo J. Hayashi T. Trace analysis for impurities in high-purity quartz Sumitomo Kinzoku 1993 45( 6) 77. (Sumitomo Kinzoku Kogyo K. K. Japan). van der Heide P. A. W. McIntyre N. S. SIMS imaging of insulator surfaces SurJ Interface Anal. 1993 20( 12) 1000. (Univ. West. Ontario London Ontario Canada N6A 5B7). Yoshihara K. Moon D. W. Fujita D. Kim K.J. Kajiwara K. Gallium arsenide-aluminum arsenide superlattice as a proposed new reference material for sputter depth profiling Surf Interface Anal. 1993 20(13) 1061. (Natl. Res. Inst. Met. Tsukuba Japan 305). Benninghoven A. Surface analysis by secondary ion mass spectrometry (SIMS) Surf. Sci. 1994 299-300( 1-3) 246. (Physik. Inst. Univ. Munster Wilhelm-Klemm-Strasse 10,48149 Munster Germany). Peng G.-y. Zhang X. Huang Q.-w. Lin L.-z. New method of determination of nitrogen content and nitrogen-15 abundance with stable isotope tracer Tongweisu 1993 6(4) 208. (Coll. Biol. Beijing Agric. Univ. 100094 China). Wang X.-y. Liu F.-x. Separation of calcium for the isotope determination of strontium Yankuang Ceshi 1992 11(3) 240. (Inst. Geol. Minist. Geol. Miner. Resour.Beijing 100037 China). Vanhoe H. Moens L. Dams R. Thermospray nebuliz- ation as sample introduction for inductively coupled plasma mass spectrometry J. Anal. At. Spectrom. 1994 9 815. (Lab. Anal. Chem. Univ. Ghent Inst. Nucl. Sci. Proeftuinstraat 86 B-9000 Ghent Belgium). Feng X.-b. Horlick G. Analysis of aluminium alloys using inductively coupled plasma and glow discharge mass spectrometry J. Anal. At. Spectrom. 1994 9 823. 9413241. 9413242. 9413243. 9413244. 9413245. 9413246. 9413247. 9413248. 9413249. 9413250. 9413251. (Dept. Chem. Univ. Alberta Edmonton Alberta Canada T6G 2G2). Liu X. R. Horlick G. Direct analysis of materials using direct sample insertion devices and mixed gas inductively coupled plasma atomic emission spec- trometry J. Anal. At. Spectrom.1994 9 833. (Dept. Chem. Univ. Alberta Edmonton Alberta Canada T6G 2G2). Fariiias J. C. Moreno R. Effect of colloidal stability of ceramic suspensions on nebulization of slurries for inductively coupled plasma atomic emission spec- trometry J. Anal. At. Spectrom. 1994 9 841. (Inst. Ceram. y Vidrio (C.S.I.C.) 28500 Arganda del Rey Madrid Spain). Jin Q.-h. Zhang H.-q. Wang Y. Yuan X.-l. Yang W.-j. Study of analytical performance of a low- powered microwave plasma torch in atomic emission spectrometry J. Anal. At. Spectrom. 1994,9,851. (Dept. Chem. Jilin Univ. Changchun 130023 China). Ghazy S. E. Kabil M. A. Mostafa M. A. Triethanolamine as a releasing agent for controlling interferences in the atomic absorption spectrometric determination of gold and its use as a collector for the flotation of gold J.Anal. At. Spectrom. 1994 9 857. (Chem. Dept. Fac. Sci. Mansoura Univ. Mansoura Silva M. M. Silva R. B. Krug F. J. Nobrega J. A. Berndt H. Determination of barium in waters by tungsten coil electrothermal atomic absorption spec- trometry J. Anal. At. Spectrom. 1994 9 861. (Inst. Fis. e Quim. de SZio Carlos USP Caixa Postal 369 CEP 13560-970 Siio Carlos SP Brazil). Baaske B. Golloch A. Telgheder U. Application of a modified atomic absorption spectrometer for the determination of iron traces in gaseous hydrogen chloride J. Anal. At. Spectrom. 1994 9 867. (Dept. Instrum. Anal. Chem. Univ. Duisburg Lotharstr. 1 47057 Duisburg Germany). Robles L. C. Aller A. J. Preconcentration of beryllium on the outer membrane of Escherichia CoEi and Pseudomonas Putidu prior to determination by electro- thermal atomic absorption spectrometry J.Anal. At. Spectrom. 1994,9,871. (Dept. Biochem. and Mol. Biol. Univ. Leon E-24071 Leon Spain). Reed N. M. Cairns R. O. Hutton R. C. Characterization of polyatomic ion interferences in inductively coupled plasma mass spectrometry using a high resolution mass spectrometer J. Anal. At. Spectrom. 1994 9 881. (Fisons Instruments Elemental Ion Path Road Three Winsford Cheshire UK CW7 3BX). Koropchak J. A. Conver T. S. Development of a high liquid flow thermospray sample introduction system for inductively coupled plasma atomic emission spec- trometry-invited lecture J. Anal. At. Spectrom. 1994 9 899. (Dept. Chem. and Biochem. Southern Illinois Univ. Carbondale IL 62901-4409 USA).Botto R. I. Zhu J. J. Use of an ultrasonic nebulizer with membrane desolvation for analysis of volatile solvents by inductively coupled plasma atomic emission spectrometry J. Anal. At. Spectrorn. 1994 9 905. (Baytown Specialty Products Exxon Research and Engineering Company Baytown TX 77522-4255 USA). Byrne J. P. Hughes D. M. Chakrabarti C. L. GrCgoire D. C. Mechanism of volatilization of tungsten in the graphite furnace investigated by electrothermal vaporization inductively coupled plasma mass spec- trometry J. Anal. At. Spectrom. 1994 9 913. (Dept. Chem. Univ. Technol. Sydney P.O. Box 213 Broadway New South Wales 2007 Australia). EgY Pt ).JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 317R 9413252. 9413 2 5 3. 9413254. 9413 25 5.94/3256. 9413257 9413258. 9413259. 9413 260. 9413261. 9413262. 9413263. GrCgoire D. C. Goltz D. M. Lamoureux M. M. Cbakrabarti C. L. Vaporization of acids and their effect on analyte signal in electrothermal vaporization inductively coupled plasma mass spectrometry J. Anal. At. Spectrom. 1994 9 919. (Geol. Survey Canada Dept. Natural Resources Ottawa Ontario Canada K1A OE8). Hollenbacb M. Grohs J. Mamich S. Kroft M. Denoyer E. R. Determination of technetium-99 thorium-230 and uranium-234 in soils by inductively coupled plasma mass spectrometry using flow injection preconcentration J. Anal. At. Spectrom. 1994 9 927. (RUST Geotech Inc. U.S. Dept. Energy Grand Junction Projects Office P.O. Box 14000 Grand Junction Colorado 81502 USA). Bloxham M. J. Hill S. J.Worsfold P. J. Determination of trace metals in sea-water and the on-line removal of matrix interferences by flow injection with inductively coupled plasma mass spectrometric detection J. Anal. At. Spectrom. 1994 9 935. (Dept. Environ. Sci. Univ. Plymouth Drake Circus Plymouth Devon UK PL48AA). Ebdon L. Evans E. H. Pretorius W. G. Rowland S. J. Analysis of geoporphyrins by high-temperature gas chromatography inductively coupled plasma mass spectrometry and high-performance liquid chromatog- raphy inductively coupled plasma mass spectrometry- plenary lecture J. Anal. At. Spectrom. 1994 9 939. (Plymouth Anal. Chem. Res. Unit Dept. Environ. Sci. Drake Circus Plymouth UK PL4 8AA). Cornellis R. De Kimpe J. Elemental speciation in biological fluids-invited lecture J. Anal.At. Spectrom. 1994 9 945. (Lab. Anal. Chem. Univ. Ghent Proeftuinstr. 86 B-9000 Ghent Belgium). Slowick J. J. Uden P. C. Gas chromatography with atomic emission spectrometric detection for the determi- nation of fluoroethers J. Anal. At. Spectrom. 1994 9 951. (Dept. Chem. Lederle Graduate Res. Tower A Univ. Massachusetts Box 34510 Amherst MA Tomlinson M. J. Wang J.-s. Caruso J. A. Speciation of toxicologically important transition metals using ion chromatography with inductively coupled plasma mass spectrometric detection J. Anal. At. Spectrorn. 1994 9 957. (Univ. Cincinnati Dept. Chem. Cincinnati OH Goode S. R. Thomas C. L. Characterizing the factors that influence oxygen selectivity in gas chromatogra- phy-microwave-induced plasma atomic emission spec- trometry J.Anal. At. Spectrom. 1994 9 965. (Dept. Chem. and Biochem. Univ. of South Carolina Columbia SC 29208 USA). Kirschner S. Golloch A. Telgheder U. First investi- gations for the development of a microwave-induced plasma atomic emission spectrometry system to deter- mine trace metals in gases J. Anal. At. Spectrom. 1994 9 971. (Dept. Instrum. Anal. Chem. Univ. Duisburg Lotharstr. 1 47057 Duisburg Germany). Cleland S. L. Olson L. K. Caruso J. A. Carey J. M. Optimization of arsenic supercritical fluid extraction with detection by inductively coupled plasma mass spectrometry J Anal. At. Spectrom. 1994,9,975. (Univ. Cincinnati Dept. Chem. Cincinnati OH 45221-0172 USA). Krushevska A. P. Barnes R. M. Determination of low silicon concentrations in food and coral soil by inductively coupled plasma atomic emission spec- trometry J.Anal. At. Spectrom. 1994 9 981. (Univ. Massachusetts Dept. Chem. Lederle Graduate Res. Center Tower Box 34510 Amherst MA 01003-4510 USA). Evans R. D. Outridge P. M. Richner P. Applications of laser ablation inductively coupled plasma mass 01003-4510 USA). 45221-01 72 USA). 94/3264. 9413265. 9413266. 9413267. 9413268. 9413269. 94/3270. 9413271 9413272. 9413 273. 9413274. 9413275. spectrometry to the determination of environmental contaminants in calcified biological structures J. Anal. At. Spectrom. 1994 9 985. (Environ. Sci. Centre Trent Univ. Peterborough Ontario Canada K9J 7B8). Ohorodnik S. K. Harrison W. W. Plasma diagnostic measurements in the cryogenically cooled glow dis- charge J. Anal. At. Spectrom. 1994 9 991.(Univ. Florida Dept. Chem. P.O. Box 117200 Gainesville F1 Yu L.-j. Koirtyohann S. R. Turk G. C. Salit M. L. Selective laser-induced ionization in inductively coupled plasma mass spectrometry J. Anal. At. Spectrom. 1994 9 997. (Dept. Chem. Univ. Missouri-Columbia Columbia MO 65211 USA). Uchida H. Ito T. Comparative study of 27.12 and 40.68 MHz inductively coupled argon plasmas for mass spectrometry on the basis of analytical characteristic distributions J. Anal. At. Spectrom. 1994 9 1001. (Ind. Res. Inst. Kanagawa Prefecture 3 173 Showa-machi Kanazawa-ku Yokohama 236 Japan). Feldmann I. Tittes W. Jakubowski N. Stuewer D. Glessmann U. Performance characteristics of induc- tively coupled plasma mass spectrometry with high mass resolution J. Anal.At. Spectrom. 1994 9 1007. (Inst. Spektrochem. Angewandte Spektrosk. Postfach 10 13 52 D-44013 Dortmund Germany). Tittes W. Jakubowski N. Stuewer D. Tolg G. Broekaert J. A. C. Reduction of some selected spectral interferences in inductively coupled plasma mass spec- trometry J. Anal. At. Spectrom. 1994 9 1015. (Inst. Spektrochem. Angewandte Spektrosk Postfach 10 13 52 D-44013 Dortmund Germany). Fecber P. A. Nagengast A. Trace analysis in high matrix aqueous solutions using helium microwave induced plasma mass spectrometry J. Anal. At. Spectrom. 1994 9 1021. (Landesuntersuchungsamt f.d. Gesundheitswesen Nordbayern Henkestrasse 9-1 1 D-91054 Erlangen Germany). Marcus R. K. Radiofrequency powered glow discharges for emission and mass spectrometry operating charac- teristics figures of merit and future prospects-invited lecture J.Anal. At. Spectrom. 1994 9 1029. (Dept. Chem. Howard L. Hunter Chem. Lab. Clemson Univ. Clemson SC 29634-1905 USA). Walden W. O. Harrison W. W. Smith B. W. Winefordner J. D. Multi-element glow discharge atomic fluorescence using continuum sources J. Anal. At. Spectrom. 1994 9 1039. (Dept. Chem. Univ. Florida Gainesville F1 326 1 1 USA). Shick C. R. Jr. Raith A. Marcus R. K. Optimization of discharge parameters of a pin-type radio frequency glow discharge source for a quadrupole mass spec- trometer system J. Anal. At. Spectrorn. 1994 9 1045. (Dept. Chem. Howard L. Hunter Chem. Lab. Clemson Univ. Clemson SC 29634-1905 USA). Koppenaal D. W. Barinaga C. J. Smith M. R. Performance of an inductively coupled plasma source ion trap mass spectrometer J.Anal. At. Spectrom. 1994,9 1053. (Pacific Northwest Laboratory P.O. Box 999 MS P8-08 Richland WA 99352 USA). Moenke-Blankenburg L. Schumann T. Nolte J. Direct solid soil analysis by laser ablation inductively coupled plasma atomic emission spectrometry J. Anal. At. Spectrom. 1994 9 1059. (Martin-Luther-Univ. Halle- Wittenberg Dept. Chem. Inst. Anal. and Environ. Chem. Weinbergweg 16 D-06120 HalleISaale Germany). Broekaert J. A. C. Brandt R. Leis F. Pilger C. Pollmann D. Tschopel P. Tiilg G. Analysis of aluminium oxide and silicon carbide ceramic materials by inductively coupled plasma mass spectrometry- 3261 1-7200 USA).318R 9413276. 9413277. JOURNAL OF ANALYT1CA:L ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 invited lecture J. Anal.At. Spectrom. 1994 9 1063. (Univ. Dortmund Fachber. Chem. D-4422 1 Dortmund Germany). Pepelnik R. Prange A. NiedergesaD Comparative study of multi-element determination using inductively coupled plasma mass spectrometry total reflection X-ray fluorescence spectrometry and neutron activation analysis J. Anal. At. Spectrom. 1994 9 1071. (Inst. Phys. GKSS Res. Centre Geesthacht GmbH P.O.B. 1160 D-21494 Geesthacht Germany). 9413279. Moens L. Verrept P. Dams R. Greb U. Jung G. Laser B. New High-resolution inductively coupled plasma mass spectrometry technology applied for the determination of V Fe Cu Zn and Ag in human 9413278. serum J. Anal. At. Spectrom. 1994 9 1075. (Ghent Univ. Lab. Anal. Chem. Proeftuinstr. 86 B-9000 Ghent Belgium). Sutton R. L. Analysis of liquid-phase tungsten hexa- fluoride residue by inductively coupled plasma mass spectrometry with ultrasonic nebulization J.Anal. At. Spectrom. 1994 9 1079. (Airco Electronic Gases P.O. Box 12338 Research Triangle Park NC 27709 USA). Kelrnan J. B. Masri A. R. Quantitative imaging of temperature and OH in turbulent diffusion flames by using a single laser source Appl. Opt. 1994 33 18 3992. (Dept. Mechanical and Mechatronic Engineering Univ. of Sydney Sydney New South Wales 2006 Australia).

ISSN:0267-9477    

DOI:10.1039/JA994090307T

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1185 Modelling the Transmission of X-rays Through Glass Capillary Waveguides Implications for the Design of a Laboratory X-ray Microprobe Norman R. Charnley Department of Earth Sciences University of Oxford Parks Road Oxford OX1 3PR UK Philip J. Potts* Department of Earth Sciences The Open University Walton Hall Milton Keynes MK7 6AA UK James V. P. Long Department of Earth Sciences Bullard Laboratories University of Cambridge Madingley Rise Madingley Road Cambridge CB3 OEZ New results from a ray-tracing program are presented to demonstrate the transmission of X-rays by total external reflection through glass capillaries designed for use as waveguides in laboratory X-ray microprobe instrumentation. The transmission properties of both parallel and tapered-bore capillaries have been con- sidered.In the case of parallel-bore capillaries results have been used to demonstrate the optimization of various experimental parameters required to maximize the intensity of the transmitted beam. In the case of tapered-bore capillaries results have been used to understand the relatively complex transmission pattern observed at the capillary exit. For capillaries with a relatively large taper angle an annular band structure is observed in the transmitted beam with individual components corresponding to directly transmitted rays and rays transmitted after 1 2 3 . . reflections. These bands merge into a single profile for small observation distances from the capillary exit or for capillaries with smaller taper angles.These observations derived by computer modelling have been validated by the agreement with published experimental data for a dihedral waveguide. Keywords Transmission properties; glass capillary; waveguides; X-ray; microprobe; ray-tracing In recent years there has been growing interest in the develop- ment of X-ray microprobe in~trumentationl-~ in which the sample is excited by a beam of X-ray photons to induce X-ray fluorescence. In comparison with other microprobe techniques X-ray excitation offers several advantages including (i) a favourable signal-to-background ratio in comparison with electron microprobe excitation for example such that detec- tion limits around the pg 8-l level can be achieved; (ii) efficient excitation characteristics for the determination of the heavier trace elements (depending on the energy spectrum of the X-ray excitation source); and (iii) much lower energy transfer to the sample during the excitation process in comparison with competitive techniques. Microanalysis may thus be extended to biological dust and other beam sensitive samples.Some of the most successful X-ray microprobe developments have exploited the analytical potential of the synchrotron as an X-ray excitation s o ~ r c e . ~ - ~ The synchrotron offers several analytical advantages in particular X-ray source beams are of very high intensity and low divergence and are plane polarized. For microprobe applications the X-ray beam can be collimated down to microprobe size using appropriate slits.Alternatively it can be focused either by total external reflec- tion from two curved mirrors aligned precisely at right angles to one another or by diffraction from a doubly curved silicon wafer.*-'' However synchrotron facilities are not widely available and access is normally restricted by competition with other research groups. There has therefore also been contemporary interest in the development of alternate laboratory-based X-ray micro- probe instrumentation using a conventional X-ray tube as excitation source. To form a beam for microprobe analysis the X-ray output can either be collimated using slits/apertures of the appropriate size,l2-I4 or constrained to a suitable size using glass capillary waveguide^.'^-^^ These latter devices operate on the principle that when a divergent beam of X-ray * Author to whom correspondence should be addressed.photons interacts with the inner surface of the glass capillary total reflection will occur for those photons that strike the glass wall at an angle of incidence of less than the critical angle (6,) for an air-glass interface. For borosilicate glass the critical angle has the value of a few milliradians the precise value depending on the composition of the glass and the energy of the incident X-ray photon. The glass capillary constrains the beam of X-rays so that part of it (of maximum solid angle 28,) is transmitted down the capillary by multiple reflection the emergent beam then being used to excite the sample. Developments of this form of instrumentation have been undertaken by Rindby and colleagues using a conven- tional X-ray diffraction line focus X-ray tube viewed at an oblique angle by glass capillaries of internal diameter 20-200 pm.Applications described by this group include the analysis of hair and other biological tissue.15-" Similar work has been undertaken independently by Carpenter and co-workers.18-21 using a demountable tube designed so that a glass capillary of internal diameter 10-100 pm can be inserted through the exit window. This instrument was used to obtain scanned X-ray micrograph images of grains in selected alloys. The beneficial properties of glass capillary waveguides have also been recognised in synchrotron X-ray microprobe appli- cations with some advantage claimed for capillaries that have a tapered bore.23-25 A n ovel technique for fabricating sub- micrometre tapered capillary waveguides has been described by Thiel et ~ 1 .~ ~ Denisov et have reported theoretical expressions concerning the propogation of X-rays through tapered waveguides and presented data demonstrating the angular dispersion of X-rays emerging from these devices. Yamamoto and Hosokawa28 have shown that a parabolic inner surface to a capillary offers improved performance and described a 5 pm focused beam X-ray spectrometer incorporat- ing this feature. Lindgren and Selin29 have reported some results from a model used to optimize the dimensions and configuration of tapered glass capillaries designed for use in X-ray microprobe applications.1186 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL.9 Experimental Although several papers have described selected properties of capillary waveguides none to date have offered a comprehen- sive model that may be used to evaluate design criteria of value in optimizing the construction of instrumentation for use as a laboratory X-ray microprobe. The purpose of this paper is therefore to present new results from a ray-tracing program developed by the authors to describe the propogation of X-rays through both parallel-bore and tapered-bore glass capillary waveguides to provide information of value in optim- izing the analytical performance of instrumentation based on an X-ray tube excitation source. The overall configuration of the instrumentation to which the model is appropriate is shown in Fig.1. To simplify calculations it has been assumed that (i) the excitation source can be considered to be a point source (as an approximation to a micro-focus X-ray tube or a line source viewed obliquely) (ii) the angular distribution of photons emitted from the source within the solid angle transmitted by the capillary is uniform and (iii) most interest would be in applications requiring an X-ray probe of diameter 10-200 pm. Verification of results obtained from the ray-tracing computer program has been undertaken by comparison with instrumental measurements reported in the literature. These results are designed to show how the analytical performance of this type of laboratory X-ray microprobe instrumentation can be optimized. Ray-tracing Computer Model The computer model used in this work assumes that an X-ray will be reflected from an air-glass boundary providing its angle of incidence is less than or equal to the critical angle 8 which for borosilicate glass can be computed from 8,=3.8 x 10-2/E where E is the photon energy in keV and 8 is in radians (rad)." For X-ray photons in the range 5-20keV 8 has a value between 1.9 and 7.6mrad with respect to borosilicate glass and 5 mrad (corresponding to X-ray photons of energy 7.6 keV in the middle of the range in which many analytical measurements are made) has been taken as a representative value for calculations in this paper.At angles of incidence greater than the critical angle the model assumes that the X-ray is scattered or absorbed but not reflected and will not then contribute to the transmitted beam.In reality the cut-off at the critical angle is not instantaneous but has a more rounded profile.30 The model allows full flexibility in defining capillary entrance bore diameter capillary exit bore diameter length of capillary distance from source to capillary entrance and distance from capillary exit to the sample plane (for calculating beam profiles). For a parallel-bore capillary and a point X-ray source the model uses Cartesian geometry to calculate the trajectories of a statistically representative number of rays emitted from the source (1000 rays mrad-I). Rays are traced from the source at varying angles of divergence (a) with respect to the axis of the capillary where a is assigned values which satisfy conditions Fig. I Schematic configuration comprising X-ray tube capillary ? \ Energy dispersive X-ray detector of a laboratory X-ray microprobe waveguide sample and detector for total reflection in the range 0 to f 8,.The number of rays calculated to pass directly through the capillary are summed (Zpinhole). The number that are transmitted after one or more reflections off the walls of the capillary are also summed (Creflection). The sum of these two parameters (Ztotal) is the total number of rays transmitted through the capillary. By comput- ing the angle of divergence of rays emerging from the capillary the intensity profile across the beam at any specified distance from the capillary can be calculated. For a tapered-bore capillary the same model is used but a further refinement is necessary.It is well known from previous ~ o r k ~ ~ * ~ ~ that for any ray propagated at an angle a with respect to the capillary axis (where a<8,) the angle of trans- mission after one reflection is increased to a+2# where # is the taper angle of the capillary. If the model indicates that this ray will interact with the capillary walls a second time before emerging from the capillary the program will test to see if a + 24 < 8 (second reflection will occur) or a + 24 > 8 (no further reflection possible). Similar calculations are made for all other multiple order reflections. Two further factors must be taken into account. The first is that transmission losses occur during the total external reflec- tion process resulting from the attenuation of a small pro- portion of X-ray photons caused by the surface roughness of the capillary bore and photoelectric absorption.For borosilic- ate glass transmission losses have been reported in a range up to about 20%.24,31,32 Following the considerations of Stern et a1.,24 transmission losses have been computed here as 6% per reflection. Secondly although calculations are made for a point source the program can be adapted to model an extended source by computing rays propagated from a series of point sources the effects of which are summed at user defined intervals normally selected as between 2 and 10 pm depending on source dimensions. Results and Discussion Application of the Model to Parallel-bore Capillaries Optimizing source-to-capillary distance As a glass capillary is only capable of transmitting a finite cone of X-rays of solid angle (28,) by total external reflection it can be seen schematically from Fig.2 that there is an optimum distance between a point X-ray source and the capillary which represents the configuration in which this cone of X-rays just impinges on the entrance to the capillary [Fig. 2(b)]. Simple trigonometric considerations indicate that the optimum distance of point source to capillary (s) is given by s=d/2 tan(8,) where d is the diameter of the capillary. Representative values of s are listed in Table 1. These values indicate that optimum transmission through a 10 pm diameter capillary occurs when the capillary is placed 1 mm from a point source and for a 100 pm diameter capillary the optimum distance is 10 mm.If the source is placed further away from the capillary than this optimum distance [Fig. 2(a)] part of the X-ray beam that could be transmitted down the capillary is lost because the solid angle of X-rays entering the capillary (24) is less than the critical angle (28,). If the source is closer than the optimum distance [Fig. 2(c)] that part of the capillary closest to the source serves no useful purpose in contributing to the trans- mitted beam (since photons striking this region do so at an angle exceeding the critical angle). The transmission behaviour of the capillary will then be the same as a capillary of shorter length positioned at a larger distance from the source [i.e. corresponding to a capillary with the front portion shown in Fig. 2(c) missing].An illustration of the variation in transmitted intensity calculated by the computer model as a function of source-to- (1)JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1187 Fig. 2 Schematic diagram showing optimization of the distance between a point source and a parallel-bore capillary waveguide for the transmission of a cone of X-rays having a solid angle of 2 8, (a) source too far from capillary full cone of X-rays that could be transmitted by the capillary does not impinge on the entrance; (b) distance optimized; and (c) source too close front end of capillary does not contribute to transmission. (Relative dimensions have been exaggerated for clarity.) Table 1 capillary as a function of capillary diameter Optimum distance of point source from a parallel-bore Optimum source-capillary Diameter of capillary/pm distance/mm 1 2 5 10 20 50 100 200 500 0.1 0.2 0.5 1 2 5 10 20 50 capillary distance is shown in Fig.3 for a capillary of diameter 100pm and 100mm long and follows the same form as measurements reported by Carpenter” and the gain factor data presented by Rindby et al.” The discontinuity corre- sponds to the ‘optimized’ source-to-capillary distance. Data in Fig. 3 are plotted separately for the proportion of rays trans- mitted directly (broken line) and that transmitted after 1 or more reflections (dotted line). These data show that for a capillary of these dimensions the component transmitted by multiple reflection at an optimized source-to-capillary distance contributes one to two orders more than the fraction that is transmitted directly but that at large source-to-capillary dis- tances the difference between these contributions is consider- ably smaller.Spatial resolution at capillary exit X-rays emerge from the capillary after direct transmission ( i e . no interaction with the capillary walls) and reflection following interaction with the walls of the capillary one or more times. The component that is directly transmitted is equivalent in intensity to that which would be observed through a pinhole of the same diameter and placed in the same position as the exit orifice of the capillary This X-ray beam is augmented by 10-7 1 I I 1 I I 20 40 60 80 100 Source-to-capillary distance/mm Fig. 3 Computer calculation of the intensity of X-rays transmitted through a parallel-bore capillary (length 100 mm internal diameter 100 pm) as a function of source-to-capillary distance (0- 100 mm) ignoring reflection losses.A represents the contribution from direct transmission; €3 represents the contribution after one or more reflec- tions; and C represents the total transmission. The point of inflection corresponds to the optimized distance presented in Fig. 2(b). The overall form of this diagram is similar to experimental results of Carpenter” and Rindby et al.” more divergent X-rays transmitted after multiple reflection from the walls of the capillary. From a consideration of simple geometric relationships (see Fig. 2) it is apparent that the most divergent rays that can be transmitted through the capillary by reflection are those with an angle of divergence equal to the critical angle 0 (or 4 if the source is further from the capillary than the optimum distance) irrespective of the length of the capillary.The diameter of the beam available to excite the sample will therefore depend on the distance between the capillary exit and sample but not on the length of the capillary. The spread ( y ) of this transmitted beam may be calculated from y = d + 22 tan(8,) (2) where d is the capillary diameter z the capillary-to-sample distance and assuming Q = 0,. Representative data for the diameter of the exciting beam as a function of capillary-to- sample distance are listed in Table 2. These data show that for small capillary diameters the relative contribution from the divergence factor predominates such that for a sample placed 5 mm from a 1 pm diameter capillary the beam diameter is no less than 51 pm.Conversely for a larger 100 pm diameter capillary the beam spread at 5 mm will have increased to 150 pm a smaller relative proportion. The implication of these data in the design of a high resolution laboratory X-ray microprobe is that the capillary- sample distance must be minimized if the probe is to retain acceptable spatial resolution. The beam spread data cited in Table 2 apply only to capillaries that are linear and have a perfect parallel bore. In practice slight undulations and ripples along the bore of the capillary will cause the device to take on some of the characteristics of a tapered-bore capillary (see below) so increasing the maximum angular divergence in the transmitted beam and possibly causing haloes in the beam profile transmitted through the capillary.These considerations may explain the haloes observed for parallel-bore capillaries by Carpenter.l8*’’ Transmitted intensities An important conclusion derived from the present model is that provided source-to-capillary distance is optimized so that1188 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 Table 2 Maximum spread of transmitted beam calculated as a function of capillary diameter (1-500 pm) and capillary-sample distance (0.5-20 mm) Diameter of capillar y/pm 1 5 10 20 50 100 200 500 Distance from capillary exit to sample/mm 20 20 1 205 210 220 250 300 400 700 0.5 6 10 15 25 55 105 205 505 1 5 10 Diameter of transmitted beam (pm) 11 51 101 15 55 105 20 60 110 30 70 120 60 100 150 110 150 200 210 250 300 510 550 600 Maximum number of reflections for capillaries of given length 100 500 100 50 25 10 5 2 1 200 1000 200 100 50 20 10 4 2 500 mm 2500 500 250 125 50 25 10 5 a cone of X-rays of twice the critical angle (20,) is intercepted by the entrance orifice the transmitted intensity does not depend on the diameter of the capillary only the brightness of the source.This condition is illustrated in Fig. 4 which shows schematically a cone of rays of solid angle 20 intercepted by both small and larger diameter capillaries. As an illustration of this point a 1 pm capillary placed 0.1 mm from a point source is capable in theory of transmitting the same intensity of rays as a 200 pm capillary placed 20 mm from the source.Furthermore the transmitted intensity does not depend pri- marily on the length of the capillary since the entire solid angle of photons accepted for reflection at the capillary entrance by a perfect parallel-bore capillary can in principle be transmitted by multiple reflection to the exit. However 100% transmission will not occur owing to losses during reflection (estimated to be 6% per refle~tion~~) a factor which will increase progressively as the length of the capillary is increased. Simple geometric considerations indicate that for a ray incident at an angle of 4 at the capillary walls the length of capillary traversed before the ray strikes the opposite wall is given by d/ tan 4. The maximum number of reflections that can be accommodated by a capillary of length x with the capillary-source distance optimized (i.e.4 = 0,) is limited by the condition that nd/ tan 0,)<x from which the maximum value of y1 can be estimated from n<x tan0Jd (3) Calculations show that the maximum number of reflections from a 100 mm long capillary of diameter 200 and 10 prn are 2 and 50 respectively (with source-to-capillary distance optim- ized in each case). Data for the maximum number of reflections that can be transmitted through various capillaries of length 100 200 and 500 mm of diameter 1-500 pm are also listed in Table 2. These data indicate that as might be expected smaller diameter (and longer) capillaries support a larger number of reflections. Assuming that transmission losses account for 6% of reflection^,^^ the intensity after n reflections will be [( 100- 6)/100]".From this equation it can be shown that the beam intensity will have been reduced to about 50% of its initial value after 11 reflections to 10% of its value after 37 reflections and to 1% of its initial value after 74 reflections. In Large capillary capillary sma'i - i Fig. 4 Schematic diagram showing that provided source-to-capillary distance in optimized individually both large bore and small bore capillaries are capable of intercepting a cone of X-rays of solid angle 2 8 from a point source relation to the reflection data listed in Table 2 maximum transmitted intensities will be obtained from shorter rather than longer capillaries and from the largest capillary bore appropriate to the application (both factors minimizing the number of reflections and so transmission losses).Indeed data listed in Table 2 for very small diameter capillaries indicate that contributions to the total transmitted intensity from multiple order reflections significantly greater than about 50 are likely to be small. Gain factors as afigure-of-merit One figure-of-merit that has been widely used in evaluating the performance of capillary waveguides is the gain factor normally calculated as the ratio of the total flux of X-rays transmitted through the capillary to the flux that would be transmitted through a pinhole placed at the position of the capillary exit i.e. Ctotal/Cpinhole. However as described above intensities transmitted through a capillary do not depend primarily on capillary diameter or length (assuming source-to- capillary distances are optimized and ignoring reflection loss factors) and yet calculated gain factors are strongly dependent on both these parameters.It is suggested therefore that although used extensively in some earlier publications in this field gain factors calculated in this way are of limited use and indeed may be misleading since they do not allow direct comparison between different capillary configurations. In the case of parallel-bore capillaries calculated gain factors can be made to have very high values (which are essentially illusory) simply by extending the length of the capillary. However whereas the magnitude of the total X-ray flux transmitted through the capillary will diminish slightly owing to reflection losses the flux transmitted through an equivalent pinhole will decrease rapidly in accordance with the inverse square law so increasing the apparent gain factor ratio.For these reasons gain factors have not been used in this work as a figure-of-merit. Overall performance From the observations summarized above it is concluded that the overall benefit resulting from the use of parallel-bore capillary optics is in extending the coupling geometry between source and sample so that a more practical arrangement is possible. Spatial resolution of the transmitted beam is indepen- dent of length of the capillary (since the divergence of the transmitted beam is controlled by the critical angle) but is very dependent on the distance between the exit of the capillary and the sample; the smaller this dimension the better.The intensity of the transmitted beam is controlled largely by the brightness of the X-ray source and for an ideal point source is independent of capillary bore (provided the source-to- capillary distance is optimized) and capillary length (excepting for reflection losses). In practice maximum intensity will beJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1189 obtained from the shortest capillary of largest bore appropriate to the application (so minimizing the reflection loss factor). Application of the Model to Tapered-bore Capillaries In contrast to parallel-bore tubes it is well known from previous publication^^^.^^ that the overall Performance of a tapered-bore capillary is largely controlled by the fact that after each reflection the angular divergence of the reflected ray relative to the axis of the capillary is increased by the value 2a where a is the taper angle of the capillary relative to the capillary axis (Fig.5). Thus after one reflection the angle of divergence of the ray will be ($1 + 2a) where #1 is the initial angle of divergence of the ray (relative to the axis of the capillary) before reflection (see below); after two reflections ($2 + 4a) and so on giving a general expression angular divergence after n reflections = bn + 2na (4) where # is the initial angle of divergence of a ray that can be transmitted through the capillary after n reflections. There are several consequences to this observation.(i) The angle of divergence of the beam emerging from the capillary will be greater than that accepted for reflection at the entrance to the capillary. (ii) Depending on the length of the capillary and other geometric factors considered below the transmitted beam will comprise discrete components of rays that have angles of divergence of ($1 + 2a) (i.e. one reflection) (#2 + 4a) (ie. two reflections) (& + 6%) (ie. three reflections) etc. These components will be shown by the ray-tracing model to form in some circumstances haloes in the transmitted beam. (iii) If the capillary has a sufficiently large taper angle or is sufficiently long the angle of divergence of rays after a finite number of reflections will eventually exceed the critical angle and so be effectively extinguished.This consideration places a finite limit on the maximum number of reflections that can be transmitted by a capillary of given taper angle. Rejection model The inter-relationship between the various geometric factors related to tapered-bore capillaries is not simple. Whereas it is possible to evaluate the performance of a parallel-bore capillary based on the application of simple trigonometry to a model of X-ray reflections the ray-tracing program is essential to under- stand the transmission properties of tapered capillaries. As an example the transmission phenomenon are illustrated here by considering a tapered capillary of entrance diameter 200 pm Fig.5 Model for the transmission of rays by reflection within a tapered-bore capillary.The angular divergence of rays with respect to the axis of the capillary (of taper angle a) after the specified number of reflections are as follows 0 4 1 4 + 2a 2 4 f 4 4 3 4 + 6a 4 4 + 8a (4 is the initial angle of divergence) exit diameter 10 pm and length 100 mm. These dimensions have been selected to give a relatively large taper angle which restricts the number of permitted reflections so that the general transmission characteristics of tapered capillaries can be dem- onstrated. The taper angle (a) of this capillary is given by tan - [( 0.200/2 - 0.010/2)/100] = 0.95 mrad. For a ray to be transmitted through this capillary after one reflection the angle subtended at the capillary wall must be less than 0,. Simple geometric relationships indicate that the limiting angle of divergence of this ray from the source #=(6c-a) where a is the taper angle of the capillary as above.At greater angles of divergence the ray would exceed the critical angle on striking the capillary wall and not be transmitted. The limiting angles of divergence that could be transmitted by the capillary after two or more reflections can be calculated in a similar way and these data are listed in Table 3 for a critical angle of 5 mrad. As might be expected these data indicate that the angle of divergence accepted for multiple reflection is reduced progress- ively with the order of reflection and is in all cases less than the critical angle. Furthermore for the capillary dimensions in question multiple reflections of four or more are not possible for the divergent beam emanating from a point source.Additional reflections are only possible for rays emanating from ‘off-axis’ regions of an extended source or possibly from a point source placed ‘off axis’ since such rays would enter the capillary at a convergent angle with respect to its axis. These conditions have not been modelled here. To extend these considerations to capillaries of a different taper angle the general condition for the nth multiple reflection to occur is given by ( 5 ) By setting 4 to zero an estimate of the maximum number of reflections permitted for a given capillary taper angle a (assuming the capillary is sufficiently long) is given by $ + (2n - 1)a < Bc n < (ec/a + 1 )/2 (6) One consequence of the variation in the limiting angles of acceptance for specific orders of reflection is that only limited sections of the capillary are active in reflecting a given order.This phenomenon may be illustrated using the ray-tracing program applied to the same capillary (200 pm entrance diam- eter 10 pm exit diameter 100 mm long) with the source placed 40 mm from the capillary. Calculations have been undertaken to determine the range of distances along the bore of the tube from which multiple reflections of a given order will occur so that the reflected ray can emerge from the capillary exit. The results of these calculations are listed in Table 4. Taking second order reflections as an example (Fig. 6 ) the model shows that these reflections can only occur for rays that first strike the walls of the capillary at distances of between 82.3 and 90.5 mm from the capillary entrance the corresponding second reflection occurring at distances of 96.7 and 100 mm (k skimming the end of the capillary) respectively.Rays that strike the capillary walls at distances closer to the source than 82.3 mm cannot emerge from the capillary without a third reflection. Rays that strike the walls at distances further from the source end than 90.5mm do not have the opportunity to undergo a second reflection before emerging from the capillary. Similar consider- ations apply to first and third order reflections (Table 5). The model indicates that the first 75 mm of a capillary of the stated Table 3 Limiting angles of divergence that can be accepted for transmission by multiple reflection through a 100 mm capillary which tapers in diameter from 200 to 10 pm; taper angle (a) taken as 0.95 mrad and the critical angle (0,) as 5 mrad No.of reflections Condition for reflection Limiting divergence (d)/mrad Optimum source-capillary distance/mm 1 2 3 4+ct must be less than 8 4 + 3a must be less than 8 4+5a must be less than 0 4 4 + 7a must be less than 0 - 4.05 2.15 0.25 1.65 24.7 46.5 400 -1190 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 Table4 Range of distances along the bore of capillary from which a given order of multiple reflections will occur; 4th order reflections are extinguished with this configuration Limiting values of distance from entrance end of capillary/mm Order of reflection 1st reflection 2nd reflection 3rd reflection Boundary between 1 from 90.5 - lst/2nd order reflections 1st order reflection and direct transmission.2nd/3rd order reflections to 82.3 96.7 3 from 82.3 96.7 (100) 2nd/3rd order reflections to 75.0 93.6 98.0 3rd/4th order reflections - - - to (100) 2 from 90.5 (100) - lst/2nd order reflections - 75.0 82.3 90.5 100 ' I none 3rd 2nd 1st Fig. 6 Segments of a tapered-bore capillary of entrance diameter 200 pm exit diameter 10 pm and length 100 mm with a source-to- capillary distance of 40 mm that contribute to the reflection of rays transmitted after 1 2 and 3 reflections. The first reflection of the ray traced on this diagram intercepts the wall of the capillary at the boundary between a third order reflection (ray just strikes exit lip of capillary for a third reflection) and a second order reflection (ray just skims lip of capillary exit without further reflection).The block diagram below shows the segments with distances inmm from the source end of the capillary from which a ray is first reflected off the wall of the capillary to contribute to a first second or third order reflection dimensions closest to the source end does not contribute at all to the transmission properties (Table 5). Optimizing source-to-capillary distance Optimizing this parameter is not as straight forward as for parallel-bore capillaries the problem being that optimum source-to-capillary distance varies according to the number of reflections under consideration. Calculations for the optimum source-to-capillary distance for the tapered capillary considered above (200 pm entrance 10 pm exit 100 mm long) are listed in Table 3.Data in this Table give the limiting angle of divergence above which rays cannot be transmitted through the capillary after the specified number of reflections and the optimum source-to-capillary distance such that a beam of this divergence just fills the capillary orifice. Calculated optimum distances are 24.7 46.5 and 400mm corresponding to first second and third order reflections respectively. The basis for optimizing intensities transmitted by tapered capillaries taking into account reflectivity of the glass and number of reflections has recently been examined in detail by Lindgren and Selin29 and will not be considered further here. Resolution in transmitted beam To illustrate the intensity profile perpendicular to the axis of a 100 mm long capillary of entrance and exit diameters of 200 and 10 pm with a point source at 40 mm from the capillary entrance the results of calculations for distances of 2 and 10 mm from the capillary exit are shown in Fig.7. Considering first the profile at 10mm from the end of the capillary calculations (Fig. 7B) show that the intensity profile comprises 7 bands. The central band corresponds to rays that are transmitted directly through the exit orifice without any reflec- tion. The first two sidebands correspond to rays that have undergone a single reflection. The second and third pairs of sidebands have suffered two and three internal reflections I A -0.10 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10 Distance perpendicular to the axis of the capillan//mm Fig.7 Computer-calculated intensity profile perpendicular to the axis of the 100mm long capillary that tapers from 200 pm diameter entrance to 10 pm diameter exit with a source-to-capillary distance of 40 mm. The profiles are plotted for capillary-to-sample distances of A 2mm and B 10mm. The central band in the profile for 10mm corresponds to rays transmitted directly (no reflections). The pairs of sidebands correspond to annular bands transmitted after 1 2 or 3 reflections respectively Table 5 100 mm long capillary that tapers in diameter from 200 to 10 pm; source-to-capillary distance is 40 mm Distance from capillary entrance/mm 90.5-100 (end) 82.3-96.7 75.0-82.3 0-75.0 Regions of the capillary measured as distance from capillary entrance that contribute to transmission by multiple reflection in a Contribution to transmission characteristics Transmission of first order reflections Transmission of second order reflections (first reflection) Transmission of third order reflections (first reflection) Does not contribute to the transmission characteristics of the capillary as fourth and higher orders would exceed the critical angle and are therefore extinguished.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL.9 1191 respectively. The overall width of this profile is about 135 pm which is a little larger than that calculated for a 10 pm parallel- bore capillary (Table 2). Whether or not these sidebands are resolved into separate components depends on the observation distance from the capillary exit. At 2 mm from the capillary substantial overlap occurs such that individual sidebands merge into a single distribution which has an overall spread of about 35 pm (Fig.7A). Transmission through tapered capillaries having a small taper angle When equivalent calculations are undertaken for a capillary having a much smaller taper angle (taking as an example a capillary with dimensions 10 pm entrance diameter 2 pm exit diameter and 100 mm long) the characteristics described above are influenced by the larger number of reflections that can be supported (in view of the smaller taper angle). Calculations using eqn. (6) show that a capillary with this taper angle could support up to 63 reflections. However the ray-tracing program shows that for the particular dimensions modelled (in particu- lar a capillary length of 100mm and a source-to-capillary distance of 5 mm) 50 reflections occur partial data for which are listed in Table 6.These data are plotted in Fig. 8 and show that again individual segments of the capillary support rays having a finite number of reflections. First order reflections can only occur from the capillary section between 70.5 and 100 mm from the entrance whereas the fiftieth order reflection can only occur for rays first striking the 0.2-0.3 mm segment of the capillary closest to the source. In this example the only region of the capillary which does not make some contribution to the transmitted beam is the 0-0.2mm segment closest to the source an observation that is sensitive to changes in source-to-capillary distance. However it should be noted that if reflection losses are taken into account only about 4.5% of Table 6 Regions of the capillary measured as distance from capillary entrance that contribute to transmission by multiple refection in a 100 mm long capillary that tapers in diameter from 10 to 2 pm; source- to-capillary distance is 5 mm Range of distances along capillary from which the first reflections are transmitted/mm (from entrance) Order of reflection 70.5- 100 54.5-70.5 44.0-54.5 36.1-44.0 3 1 .O-36.4 - 48 49 50 - 0.4-0.5 0.3-0.4 0.2-0.3 0.2-0.3 31.0 44.0 70.5 100 I 50 1 I 36.4 54.5 Fig.8 Segments of a tapered-bore capillary of entrance diameter 10 pm exit diameter 2 pm and length 100 mm that contribute to the reflection of rays transmitted after multiple reflections. This capillary has a much smaller taper angle than that shown in Fig.6 and the block section shows the segments from which the first reflection occurs of a ray that undergoes 1-50 reflections before emerging from the exit distances being shown inmm from the source end of the capillary. Source-to-capillary distance is 5 mm the rays that undergo 50 reflections will emerge from the exit. With such a large number of reflections the intensity profile of the transmitted beam appears as a single broadened distri- bution when reasonable capillary-to-sample distances are con- sidered (Fig. 9). This beam is computed to have a spread of about 20 pm at a distance of 2 mm from the 10 pm exit orifice and about 100 pm at 10 mm from the exit.Validating Results From the Model The results and conclusions presented in the above sections have been based on the application of simple trigonometry incorporated in the ray-tracing model. Direct experimental verification of results has not been possible owing to lack of access to appropriate instrumentation. Indeed some difficulty might be encountered in fabricating tapered capillaries (par- ticularly those with a large taper angle) to a uniformity and accuracy required for comparison with exact numeric model- ling. However validation of the computer model presented here has been possible by applying our ray-tracing results to experimental data of Denisov et ~ 1 . ~ ~ These workers investi- gated the transmission properties of dihedral waveguides com- prising two slabs of flat and smooth silicon-rich glass 800 or 150 mm long and 30 mm thick.The entrance and exit distances between the two plates were carefully controlled. Measurements were made using the 6.93 keV radiation from a cobalt anode tube which was passed through a pyrolitic graphite crystal to serve as a monochromator and then through slit collimators to restrict the angular divergence of the beam transmitted through the waveguide. Experimental results taken from the paper27 are reproduced in Fig. lO(u) for the 150mm long waveguide having an entrance of 200 pm and an exit of 10 pm. These data are compared with results computed by the ray-tracing model for a 150 mm glass capillary tapering from a 200 pm entrance orifice to a 10 pm exit orifice assuming a point source of diameter 20 pm placed 30 mm from the capil- lary and a relevant critical angle of 3.8 mrad.Comparison of these two profiles shows good agreement between both the band structure and relative intensities. Indeed the computer model gives sidebands of equivalent angular divergence to the experimental measurements and the correspondence between numbers of sidebands indicates that the model agrees with the experimental results in the maximum number of reflections supported by this waveguide configuration [3 as computed by eqn. (6)]. Differences that are observed between these profiles can be accounted for by experimental uncertainty and assump- tions made in the ray-tracing model. The good agreement between these experimental and computed profiles is taken as support for the validity of data from the computer model -0.10 -0.08-0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10 Distance perpendicular to the axis of the capillary/mm Fig.9 Computer-calculated intensity profile at a distance of A 2 mm and B 10mm of rays transmitted through the tapered capillary featured in Fig. 81192 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1 I I 1 I I 1 (b) I I m -0.008 -0.006 -0.004 -0.002 0 0.002 0.004 0,006 0.008 Angular divergence (radians) relative to the axis of the capillary Fig. 10 Comparison of experimental and calculated intensity profiles (a) experimental data for the angular divergence of transmitted rays for a 150 mm long waveguide comprising of two plates of silica glass in a dihedral orientation having an entrance of 200 pm and an exit of 10 p digitized from Fig. 4 of Denisov et al.27 and (b) computer- calculated angular divergence profile for a 150 mm long capillary that tapers from 200 pm diameter entrance to 10 pm diameter exit with a 20 pm source at a distance of 30 mm from the capillary which gives confidence to the predictions discussed in earlier sections of this paper.Conclusions Results from the computer modelling of the transmission properties of parallel-bore capillaries have yielded useful infor- mation about design criteria in optimizing the performance of a laboratory X-ray microprobe. Results confirm earlier exper- imental work that source-to-capillary distance must be optim- ized to maximize transmitted intensities.In particular if the source is placed too far away from the capillary transmitted intensities will be reduced significantly because only a fraction of the cone of X-rays that could be transmitted by the capillary will strike the entrance orifice. However all X-rays striking the entrance orifice with an angle of divergence of < 8 relative to the capillary axis can in principle be transmitted through the capillary either directly or after one or more reflections irrespective of the length of the capillary. A proportion of reflection losses will however occur so that transmitted inten- sities from shorter and larger diameter capillaries will be slightly greater because the number of reflections supported by such configurations is smaller.In this respect the ‘gain facter’ used by some other workers is not a useful figure-of- merit in optimizing capillary dimensions. This factor calculated as the ratio of the total intensity transmitted through the capillary to the intensity that would be transmitted through a pinhole placed in the position of the exit orifice does not reliably reflect variations in the intensity of rays transmitted through the capillary but rather is sensitive to changes in capillary dimensions particularly length. An interesting con- clusion from the present study is that the intensity of X-rays transmitted from a point source through a parallel-bore capil- lary is in theory independent of capillary diameter (ignoring reflection losses) providing in each case the capillary entrance is placed at an optimum distance from the point source. The transmission properties of tapered-bore capillaries have also been modelled and represent a more complex picture.To illustrate performance a capillary of inlet orifice diameter 200pm exit orifice diameter 10pm and length 100mm is shown to support a maximum of three reflections. Higher orders of reflections were not possible from a point source because of the property that after each reflection the angle of divergence increases by twice the taper angle of the capillary and higher orders of reflection would exceed the critical angle before emerging from the capillary. The model shows that the capillary can be divided into discrete segments from which the first reflection occurs of a ray that is reflected one or more times before emerging from the capillary.Since the above capillary has a relatively large taper angle the first three- quarters length of the capillary adjacent to the source does not contribute to the transmitted beam because successive reflections of rays that are reflected from this region exceed the critical angle before having an opportunity to emerge from the exit orifice. The computer model shows that the profile of the X-ray beam emerging from the capillary has an annular band structure if observed at a distance of at least 10 mm from the capillary exit. This profile comprises a central band which corresponds to the direct transmission of rays and annular side bands which correspond to successively higher orders of reflection.Computations using the model have been extended to a capillary which has a much smaller taper angle (10 pm entrance diameter 2 pm exit diameter 100 mm length). The same criteria described above apply except that with this capillary up to 50 reflections can occur. In this case the transmitted beam profile does not separate into distinguishable sidebands at practical capillary-to-sample distances owing to the small differences in angular divergence between the 50 reflections supported by this configuration. Verification of the performance of the ray-tracing model was achieved by comparison with experimental results reported by Denisov et a1.,27 good agreement being observed between the number and angular divergence of bands observed in the transmitted profile.The authors are very grateful to the Natural Environment Research Council for a research award under which this investigation was carried out and to the anonomous reviewers for suggesting improvements to the text. References Gilfrich J. V. X-ray Spectrom. 1990 19 45. Golijanin D. M. and Wittry D. B. in Microbeam analysis 1988. Microprobe X-ray puorescence new developments in an old technique ed. Newbury D. E. San Francisco Press San Francisco Wittry D. B. and Golijanin D. M. in Microbeam analysis 1988. Detection limits in microprobe X-ray Juorescence analysis ed. Newbury D. E. San Francisco Press San Francisco pp. 394-396. Jones K. W. and Gordon B. M. Anal. Chem. 1989 61 341A. Bassett W. A. and Brown G. E. Ann. Rev. Earth Planet. Sci. 1990 18 387. Lu F.-Q.Smith J. V. Sutton S. R. Rivers M. L. and Davis A. M. Chem. Geol. 1989 75 123. Jaklevic J. M. Giauque R. D. and Thompson A. C. X-ray Spectrom. 1990 19 53. Rivers M. L. Sutton S. R. and Jones K. W. Synchrotron Radiat. News 1991 4 23. Wu Y. Thompson A. C. Underwood J. H. Giauque R. D. pp. 397-402.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1193 10 11 12 13 14 15 16 17 18 19 20 Chapman K. Rivers M. L. and Jones K. W. Nucl. Instrum. Methods Phys. Res. Sect. A 1990 291 146. van Langevelde F. Tros G. H. J. Bowen D. K. and Vis R. D. Nucl. Instrum. Methods Phys. Res. Sect. B 1990 49 544. van Langevelde F. Bowen D. K. Tros G. H. J. Vis R. D. Huizing A. and de Boer D. K. G. Nucl. Instrum. Methods Phys. Res. Sect. A 1990 292 719. Gilfrich N. L. Leyden D. E. and Erslev E. A. Adu. X-ray Anal. 1990 33 593. Nichols M. C. Boehme D. R. Ryon R. W. Wherry D. Cross B. and Aden G. Adv. X-ray Anal. 1987 30 45. Boehme D. R. Adv. X-ray Anal. 1987 30 39. Rindby A. Engstrom P. Larsson S. and Stocklassa B. X-ray Spectrom. 1989 18 109. Engstrom P. Larsson S. Rindby A. and Stocklassa B. Nucl. Instrum. Methods Phys. Res. Sect. B 1989 36 222. Larsson S. Engstrom P. Rindby A. and Stocklassa B. Adu. X-ray Anal. 1990 33 623. Carpenter D. A. X-ray Spectrom. 1989 18 253. Carpenter D. A. Lawson R. L. Taylor M. A. Poirier D. E. Morgan K. Z. and Haney G. W. in Microbeam Analysis 1988 A scanning X-ray microprobe with capillary collimation ed. Newbury D. E. San Francisco Press San Francisco pp. 391-393. Carpenter D. A. Taylor M. A. and Holcombe C . E. Adv. X-ray Anal. 1989 32 115. 21 22 23 24 25 26 27 28 29 30 31 32 Carpenter D. A. and Taylor M. A. Adv. X-ray Anal. 1991 34 217. Furata K. Nakayama Y. Shoji M. Nakano H. and Hosokawa Y. Rev. Sci. Instrum. 1991 62 828. Engstrom P. Larsson S. Rindby A. Buttkewitz A. Garbe S. Gaul G. Knochel A. and Lechtenberg F. Nucl. Intrum. Methods Phys. Res. Sect. A 1991 302 547. Stern E. A. Kalman Z. Lewis A. and Lieberman K. Appl. Opt. 1988 27 5135. Thiel D. J. Stern E. A. Bilderback D. H. and Lewis A. Physica B 1989 158 314. Thiel D. J. Bilderback D. H. Lewis A. and Stern E. A. Nucl. Instrum. Methods Phys. Res. 1992 137 597. Denisov E. L. Glebov V. I. and Zhevago N. K. Nucl. Instrum. Methods Phys. Res. 1991 308 400. Yamamoto N. and Hosokawa Y. Jap. J. Appl. Phys. 1988 27 L2203. Lindgren I. and Selin E. X-ray Spectrom. 1993 22 216. Parratt L. G. Phys. Rev. 1954 95 359. Vetterling W. T. and Pound R. V. J . Opt. Soc. Am. 1976,66 1048. Nakazawa H. J. Appl. Crystallogr. 1983 16 239. Paper 4100965 G Received February 17 1994 Accepted May 6 1994

ISSN:0267-9477    

DOI:10.1039/JA9940901185

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1195 Determination of Ultra-trace Amounts of Cobalt in Ocean Water by Laser-excited Atomic Fluorescence Spectrometry in a Graphite Electrothermal Atomizer With Semi On-line Flow Injection Preconcentration" Alexander I. Yuzefovsky Robert F. Lonardo Mohui Wangt and Robert G. MichelS Department of Chemistry University of Connecticut Storrs CT 06269-3060 USA A method has been developed for the determination of trace and ultra-trace amounts of cobalt in sea-water. Samples of CASS-2 Nearshore Seawater and NASS-4 Open Ocean Water reference materials from the National Research Council of Canada were employed. Laser-excited atomic fluorescence spectrometry in an electrothermal atomizer (ET-LEAFS) was used and integrated with semi on-line flow injection microcolumn preconcentration.For cobalt the effects of pH on the preconcentration efficiency the concentration of the chelating agent and the distribution of cobalt in the ethanol eluate were studied. A bonded silica with octadecyl functional groups (C,8) in a 10 kl column was employed for preconcentration of cobalt in ocean water. Ocean water volumes of 0.40 and 1.00 ml were required for the determination of cobalt in CASS-2 and NASS-4 respectively. These volumes were almost two orders of magnitude smaller than those required by inductively coupled plasma mass spectrometry and some other competitive techniques. The preconcen- tration factors were 5- and 12.5-fold for CASS-2 and NASS-4 respectively. The detection limits (3s) based on 12.5-fold preconcentration were 0.08 and 1 .O ng I-' for cobalt in aqueous standard solutions and in Ocean Water Reference Materials respectively.Results for the determination of cobalt in CASS-2 and NASS-4 showed that there were no significant differences between the certified values and the measured values based on Student's t-test at the 95% confidence level. The relative standard deviations for the determinations of the concentrations of cobalt in CASS-2 and NASS-4 were 9 and 13% respectively. Keywords Laser-excited atomic fluorescence spectrometry; graphite furnace; flow injection; cobalt; ocean water; preconcentration The determination of trace amounts of cobalt in natural waters'-' is of great interest because cobalt is important for living species as complexed vitamin BI2.Vitamin BI2 is present in human and animal cells in the forms of adenosylcobal- amin(m) and methylcobalamin(1v). The deficiency of cobalt in ruminants usually results in different types of anaemia. Toxicological effects of large amounts of cobalt include vaso- dilation flushing and cardiomyopathy in humans and animals. The importance of cobalt in human and ruminant nutrition has led to work on the determination of cobalt in soils plants feedstuffs herbage natural waters and fertilizers. Investigations have extended to the biochemistry of cobalt in animals humans microorganisms and enzyme^.^-^ However there is still very little information available concerning the distribution and speciation of cobalt in the environment owing to analytical difficulties.There are two major problems in the determination of cobalt in ocean water. Firstly the high salt content of the ocean water matrix has often resulted in analytical inaccuracies. Secondly the concentration of cobalt in ocean water is below or very close to the detection limit of the most sensitive analytical techniques." For the direct determination of cobalt in aqueous standards the most recent detection limits reported were 0.1 pg I-' for electrothermal atomic absorption spec- trometry (ETAAS) by Slavin;" 7 ng 1-' for inductively coupled plasma mass spectrometry (ICP-MS) by Akatsuka et al.;' and 0.1 and 1.5 ng 1-' reported for laser-excited atomic fluorescence spectrometry in an electrothermal atomizer (ET-LEAFS) by Remy et and Irwin et ~ l .' ~ respectively. Detection limits for cobalt of between 1.0 and 3.0ng1-' have routinely been achieved with ET-LEAFS. * Presented at the XX Annual Meeting of the Federation of Analytical Chemistry and Spectroscopy Societies (FACSS) Detroit MI USA October 17-22 1993 as paper No. 0639. On leave from Chengdu College of Geology Chengdu People's Republic of China. $ To whom correspondence should be addressed. Recently flow injection microcolumn preconcentration has been employed to pre-treat samples prior to analyses in a variety of ways,14 and can be integrated with any of the techniques mentioned above. The technique addresses the two main problems of ocean water analyses as it allows for simultaneous matrix separation and analyte preconcentration during a fairly short analysis time.Flow injection preconcen- tration procedures reduce the sample consumption and are more rugged methods of analyses than other procedures. RdiiEka and Arndal'' demonstrated that extraction procedures for metals as their chelates from aqueous samples can be simplified miniaturized and automated by flow injection- sorbent extraction techniques. For example the chelate is formed in the flow stream sorbed onto c18 bonded silica eluted and then transferred into the detection system. One ancillary advantage of this flow injection procedure is that the apparatus is closed to the environment which reduces the likelihood of contamination. This is a critical consideration for the determination of ultra-trace amounts of metals in ocean water. For on-line flow injection determination of trace and ultra- trace amounts of cobalt in water Hirata et a1.I6 reported a detection limit of 2.9 mg 1-l by flame atomic absorption spec- trometry (FAAS) interfaced with ion-exchange column precon- centration.Backstrom and Danielsson17 reported 10 pg 1-' as the detection limit for cobalt by ETAAS interfaced with liquid- liquid extraction. A lower detection limit of 0.2 pg 1-l was reported by Fang et for ion-exchange column preconcen- tration interfaced with an ICP. Sperling et aLi9 employed c18 microcolumn separation and preconcentration with ETAAS for the determination of ultra-trace amounts of cobalt in natural waters. A detection limit of 1.7 ng I-' was reported for cobalt based on 700-fold preconcentration. Zhang et a1." obtained a detection limit of 0.47 ng I-' for cobalt in ocean water through the use of cathodic stripping square-wave voltammetry. Christian2' obtained a detection limit of 3 ng I-' for cobalt in sea-water through a reductive precipitation tech-1196 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL.9 nique using ICP-MS. The lowest detection limits for cobalt in ocean water reference materials have been obtained by flow injection microcolumn preconcentration interfaced with an ICP-MS instrument and were 50 ng 1-1 by Beauchemin and Berman;22 0.2 ng 1-' by McLaren et al.,23 with 50-fold precon- centration of the sample; and 0.1 ng I-' by Akatsuka et based on 90-fold preconcentration of the sample. It was anticipated that ET-LEAFS would be more sensitive than all or most of these approaches which was the stimulus for the work reported here.There were three aims addressed in the present work. The main goal was to realize the potential of the use of flow injection semi on-line microcolumn preconcentration in con- junction with ET-LEAFS. Femtogram detection limits can be routinely achieved by ET-LEAFS.11,24-26 Such detection limits are 1-4 orders of magnitude lower than those of ETAAS. In addition the linear dynamic range can be up to five orders of magnitude greater than that for ETAAS. Commercial electro- thermal atomic absorption equipment can be employed with- out modification. Thus a flow injection semi on-line microcolumn preconcentration system can be interfaced in the same way with ET-LEAFS as for ETAAS.27 All these features make flow injection ET-LEAFS a promising technique for the determination of ultra-trace amounts of elements in samples with detection limits comparable to or better than ICP-MS.A second aim was to decrease the sample consumption as much as possible and at the same time maintain good precision and accuracy. Sample volumes of only 400 and 100Op1 for CASS-2 and NASS-4 respectively were realized in the present work for the preconcentration of cobalt. This preconcentration volume was between ten and several hundred times smaller than the volumes required for other techniques for the same reference material^.^"^'^* A third aim of this work was to continue the investigation of sodium diethyldithiocarbamate (NaDDC) as a separating reagent with a c18 c o l ~ m n .~ * ~ ~ This approach has been ~ s e d ~ . ' ~ ~ ' successfully to preconcentrate and separate ultra- trace amounts of lead copper and cadmium by flow injection ETAAS for sea-water reference materials. Ethanol was used as the eluent to extract the heavy metal-DDC chelate complexes from the c18 column for direct introduction into a graphite furnace. The analytical conditions such as pH and flow rate were optimized. The preconcentration efficiencies for cobalt on a c18 10 pl column pre-loaded with NaDDC and an unloaded column were compared. Experimental Apparatus The instrumentation for ET-LEAFS (Table 1) has been dis- cussed in detail and is summarized briefly here. An excimer laser which was operated with xenon chloride (308 nm) at a repetition rate of 500 Hz was used to pump a tunable dye laser.Rhodamine 610,o-( 6-diethylamino-3-diethyl- imino-3H-xanthe-9-yl) benzoic acid (Exiton Dayton OH USA) was employed as the laser dye at concentrations of 0.91 and 0.30gl-' in absolute methanol for the oscillator and amplifier dye cells respectively. The frequency doubled output was passed through beam expansion to adjust the beam diameter to 2-3 mm before passage through the atomizer. The atomizer was a Perkin-Elmer HGA-500 graphite tube furnace equipped with an AS-40 autosampler and a L'vov platform. Both windows of the furnace were angled to reduce the stray laser background r a d i a t i ~ n . ~ ~ Cobalt atoms were excited at 304.4 nm. Fluorescence was detected at 340.5 nm in a scheme termed front-surface ill~mination.~~ An off-axis ellipsoidal mirror with an aluminium reflective surface and overcoated with magnesium fluoride was employed to collect the fl~orescence.~~ Table 1 ET-LEAFS instrumentation Component and Model No.Excimer laser EMG 104 MSC Dye laser FL 3002E Boxcar averager 162 165 Photomultiplier tube (PMT) Monochromator H-10 Graphite furnace HGA-500 9893QB-350 Triggering circuitry Data processing software Off-axis ellipsoidal mirror AlMgF coated f = 140 mm; f2 = 260 mm ~ ~~ Manufacturer Lambda Physik Acton MA Lambda Physik Acton MA PAR Princeton NJ USA Thorn-EMI Fairfield NJ ISA Metuchen NJ USA Perkin-Elmer Norwalk CT Laboratory made Asyst Software Rochester NY USA Aero Research Associates Port Washington NY USA USA USA USA USA The detection system consisted of a photomultiplier tube a preamplifier with a gain of ten and a boxcar integrator with a gate width of 5 ns a gate time constant of 0.5 ps and an output time constant of 10ms.The data processing was carried out with a personal computer Dell PC 200-80286. The integrated signal peak area was employed throughout the work. The graphite furnace temperature programme for the determination of cobalt in the ethanol eluate is given in Table 2. For preliminary work on the optimization of the analytical conditions for the determination of cobalt a Perkin-Elmer Model 5000 atomic absorption spectrometer with Zeeman- effect background correction was employed with an HGA-500 graphite furnace and an AS-40 autosampler. A cobalt hollow cathode lamp was operated at 20 mA. The absorption signals were processed with a Model 2108 personal computer WYSEpc 286 which was directly connected to the RS 232C/TTY port of the spectrometer.The graphite furnace temperature programme for the determination of cobalt in the ethanol eluate was similar to the one used for ET-LEAFS (Table 2). The flow injection semi on-line microcolumn preconcen- tration system (Fig. 1 ) was identical to that discussed pre- v i o ~ s l y . ~ ~ The c18 microcolumn was attached to a three-way valve (Rainin Instrument Co. Woburn MA USA) by means of 0.8 mm i.d. poly( tetrafluoroethylene) (PTFE) tubing (Rainin). The valve was used to direct solution through the column in either direction. Switching of the three-way valve was performed manually. Important details of the various steps in the procedures for flow injection labelled 1-4 in Fig.1 are discussed below. In the present work a 10 pl cylindrical microcolumn was employed for the sample analysis. For some preliminary studies an NaDDC loaded c18 column was used. To prepare the NaDDC loaded C column Table 2 Graphite furnace temperature programme for the determi- nation of cobalt by ETAAS and ET-LEAFS in the ethanol eluate Time/s Temperature/ Argon flow rate/ Step "C Ramp Hold ml min-' 1* 90 5 75 300 2 1000 5 40 300 3 20 1 5 300 5 2650 1 5 300 4 2200/2400t 0 7 O$ "Two sequential drying steps were used to dry the two 4Opl aliquots of the sample. t On the atomization step 2400 "C was used with ETAAS 2200 "C was used with ET-LEAFS (to reduce the black-body radiation gener- ated by a graphite furnace).2. Read.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1197 Pe ri st a It ic Pump 3-Way valve -1 Microcolumn *- I J I I GraDhite furnace II IV v Fig. 1 Schematic diagram of the flow injection system (three-way valve in a sampling position) for ETAAS/ET-LEAFS. Arabic numbers correspond to procedural steps 1-4 described in the text. The arrows indicate the flow directions of the ethanol and aqueous solutions during the various steps; The containers I-V were used as follows I mixture of sample and NaDDC solutions; 11 sub-boiled distilled water; 111 ethanol eluate collector; IV waste solutions; and V ethanol the basic CI8 column was rinsed with ethanol for 3min and air dried for 1 min. Then 400 pl of a 0.05% NaDDC solution (in a buffer of pH 9) was passed through the column.This implies that DDC functional groups were pre-adsorbed onto the surface of the c18 particles in the column?7 Finally the c18 column was again air dried for 1 min. The flow rate to load the sample (0.15mlmin-') was comparable to the flow rate that was used by S l a ~ i n ~ ' with a cylindrical column but was slower than the flow rates that were used by Fang et aL2 (2.1 ml min-') and Sperling et aL3 (3.0 ml min-') with conical columns. The limitation in flow rate was due to the back pressure of the column which primarily depends on some physical characteristics of the system such as dimensions column capacity particle size and extent of compaction of the packing material. The same flow rate was employed for both preconcentration of the analyte onto the column and elution of the analyte from the column.Higher flow rates were attempted but could not be achieved. Reagents Sodium DDC (J. T. Baker Chemicals Phillipsburg NJ USA) which is soluble at pH values above about 7 was initially dissolved in a buffer solution (0.06 moll-' ammonia+ 0.03 mol 1-1 acetic acid pH 9). Ultimately during the cobalt preconcentration step the pH of the sample plus buffer solution was adjusted to the optimum range of 2.0-2.5 as discussed later. Other reagents included ultra-pure nitric acid (J. T. Baker Chemicals); absolute ethanol 200 proof (AAPER Alcohol and Chemicals Shelbyville KY USA). Reversed-phase silica bonded with an octadecyl functional group (CIS) 40 pm (J. T. Baker Chemicals) was used as the solid sorbent.The CASS-2 Nearshore Seawater and NASS-4 Open Ocean Water reference materials for trace metals which as delivered have a pH of 1.6 were obtained from the National Research Council of Canada Ottawa Ontario Canada while sub-boiled distilled water prepared immediately prior to all analyses was used throughout. Cobalt standard solutions in the concentration range of 0.05-5.00 pg 1-' were prepared daily by stepwise dilution of a 1000 mg 1-' stock solution (J. T. Baker Chemicals) with 0.2% v/v nitric acid. It was vitally important to maintain control of the contami- nation throughout all the experiments because the flow injec- tion system had some containers that were partially open to the environment during the analytical cycle. The following procedure was employed.All samples and standards were prepared in a class 100 (US Federal 209b) clean-air hood and on a class 100 clean bench. All containers and pipette tips used in this work were cleaned by soaking them first in 20% laboratory-reagent grade nitric acid for approximately 24 h followed by a rinse with de-ionized water then a rinse with a (1 + 1 v/v) mixture of 0.05% NaDDC in buffer solution and 0.2% nitric acid and a final rinse with sub-boiled distilled water.27 The 0.05% NaDDC solution for both the cleaning procedure and the determination of cobalt in CASS-2 was purified in advance by pumping the solution through a 500 pl CI8 conical column. For NASS-4 the purification of the NaDDC solution was performed twice because of a much lower concentration of the analyte in the sample.Recommended Procedure One of the important factors that affected the preconcentration efficiency for cobalt on a C column was the pH of the mixture of the sample and NaDDC. It was found that the optimum pH range for the preconcentration of cobalt was between a pH of 1.7 and 4.0 (Fig. 2). This was taken into account in step 1 of the following procedure for the preparation of sample-NaDDC mixtures. For the determination of cobalt in CASS-2 in step 1 400 pl of ocean water sample were mixed with 200 pl 0.05% NaDDC in the pH9 buffer. The pH of the resultant mixture was 2.5. For the determination of cobalt in NASS-4 in step 1 1000 p1 of ocean water sample were mixed with 400 ~10.05% NaDDC in the buffer at pH 9. The pH of the resultant mixture was 2.4.Hence the acidities of both CASS-2-NaDDC and NASS-4- NaDDC mixtures lay in the optimum pH range. The resultant mixture of each sample was held in an autosampler cup and pumped directly through the column at a flow rate of 0.15 mlmin-'. This allowed the CoDDC chelate to be adsorbed onto the column. In step 2 100 p1 of sub-boiled distilled water were passed through the column in the same direction and at the same flow rate in order to rinse out the residual ocean water matrix retained on the column. In step 3 ethanol was passed through the column at the same flow rate as the sample solution but in the reverse direction in order to extract the CoDDC chelate. An autosampler cup equipped with a PTFE plug on the top was used as the collector for the ethanol eluate.The plug was employed to prevent evaporation of the ethanol eluate from the container. A small hole in the plug allowed the eluate to be poured in and to be taken out of the collector by the autosampler (Fig. 1; 111). In step 4 the ethanol eluate which contained the analyte was delivered by the autosampler directly onto the L'vov platform. The first 80 pl of ethanol eluate were collected and then introduced into the electrother- mal atomizer in two separate deliveries with sequential drying of each 40 p1 aliquot. II " a 0.10 1 .o 3.0 5.0 7 .O 9.0 PH Fig. 2 Effect of pH on the preconcentration efficiency for cobalt (800 pg of cobalt in 400 pl standard with 200 pl of 0.05% NaDDC solution). A 10 p1 unloaded CI8 column was used1198 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL.9 Results and Discussion The experimental section of this project was carried out in two parts. In the first part all the experimental conditions such as flow rate volume of the column and pH of the sample- NaDDC mixture were optimized on the flow injection ETAAS system because the laser system was not available for the experimental work. In the second part of the project the determination of ultra-trace amounts of cobalt in CASS-2 and NASS-4 was carried out by flow injection ET-LEAFS by use of the conditions optimized by ETAAS. E ~ p e r i e n c e ~ ~ ’ ~ ~ with electrothermal atomization has indicated that there is no difference between the techniques of absorption and fluor- escence in terms of the optimization of analytical methods because all the physico-chemical processes are identical when the same furnace is used for both.Fluorescence detection merely improves the sensitivity by several orders of magnitude and the furnace transients always appear temporally identical for both spectrometric methods of detection. It is often useful to optimize the methodology on the simpler atomic absorption instrumentation because of the operational and maintenance difficulties of working with excimer pumped dye lasers. It is expected that this will change in the near future as dye lasers are substituted with solid-state lasers. Nature of the C Column In previous both unloaded and NaDDC loaded c18 columns with different shapes and volumes were compared with respect to the distribution of copper and cadmium in the eluate.It was found that a cylindrical c18 column had an advantage over a conical column because most of the analyte was distributed in the first portion (30 pl) of the eluate. However for a conical column the analyte was distributed over more than 100 pl of the eluate. Therefore a cylindrical c18 column was employed throughout. Diethyldithiocarbamic acid (HDDC) behaves as a bidentate univalent anionic ligand and forms very stable chelates with most of the heavy-metal ions.34-36 The effect of pH on the preconcentration efficiency of copper and cadmium with the proposed flow injection system was discussed in detail pre- v i o ~ s l y . ~ ~ It was pointed out that the pH had a significant effect on the preconcentration efficiency of the analyte when either NaDDC loaded or an unloaded column was used.Furthermore it was shown that the preconcentration efficiency for copper could change by more than one order of magnitude within the pH range between 4.0 and 8.0. This report contra- dicted earlier work by Fang et aL2 and Sperling et aL3 They stated that the formation of metal-DDC complexes and their subsequent preconcentration on a column did not depend on pH. Here the same effect was investigated for cobalt. A series of analyte solutions in the pH range from 1.7 to 8.5 was prepared. The total volume of the analyte solution was held constant at 600 p1. The analyte solution was a mixture of 400 p1 of a standard that contained 800 pg of cobalt and 200 p1 of 0.05% NaDDC solution. Different acidities in this series of analyte solutions were achieved by changing the concentration of the nitric acid in the 400 pl of cobalt standard.It was found that the optimum pH range for cobalt in terms of the precon- centration efficiency was between a pH of 1.7 and 4.0 (Fig. 2) and the preconcentration efficiency slightly degraded at pH values higher than 4.0. These results together with the data obtained earlier,27 show that the optimum pH range was different for different elements. The preconcentration efficiency of cobalt was not as strongly dependent on pH as it was for copper and cadmium. Nevertheless this effect could not be ignored. The pH values used in the present work for CASS-2 and NASS-4 were 2.5 and 2.2 respectively. The distributions of analyte in the ethanol eluate after preconcentration of cobalt on an unloaded column and on a NaDDC loaded c18 cylindrical column are shown in Fig. 3.A comparison of signal sizes obtained for cobalt indicated that there was no difference between these two types of cylindrical c18 columns in terms of the distribution and the preconcen- tration efficiency of the analyte. The unloaded c18 column was chosen for the analysis of ocean water samples. a comparison of various sizes of c18 cylindrical columns showed that 10 pl was the optimum volume for the column in terms of the preconcentration efficiency and the distribution of copper and cadmium in the ethanol eluate. Hence in the present work a 10 p.1 unloaded C18 cylindrical column was employed throughout. In previous Effect of the Concentration of NaDDC Solution A series of 400 pl standards which contained 800 pg of cobalt mixed with 200 pl of NaDDC solutions to give a concentration range of from 0.01 to 0.20% m/v was preconcentrated on the c18 column by use of the procedure described above.The concentration of analyte in the ethanol eluate was measured for each solution. The results indicated that with a 10 pl unloaded C18 column the preconcentration efficiency for cobalt was almost constant over a wide range of NaDDC concen- trations from 0.03% to 0.20% (Fig. 4). A concentration of 0.05% m/v NaDDC was chosen. These results were similar to those obtained for preconcentration of copper and cadmium.27 Effect of Standing Time on the Mixtures of Sample and NaDDC Solutions During a preliminary set of experiments it was observed that the integrated absorbance values of the analyte degraded when mixtures of NaDDC with each sample were allowed to stand in autosampler cups for more than 20-30min (Fig.5). This phenomenon was considered to be a threat to good precision because of the relatively long period of time that was required for each sample to be loaded onto the C column. To avoid possible degradation in the precision of the analyses the effect 0.20 (a) 1 0.15 0.10 S!? 0.05 0 m f! $ 0 a 0.20 E Q 0 c 0.15 - 0.10 0.05 0 I 1 Volume of ethanol eluate/ml Fig. 3 Distribution of cobalt (800 pg of cobalt in 400 pl of standard) in the ethanol eluate after preconcentration on an (a) unloaded and (b) NaDDC loaded 10 p1 CIS columnsJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL.9 1199 0.20 1 0 0.05 0.10 0.15 0.20 INaDDCl(%) Fig. 4 Effect of the concentration of NaDDC on the preconcentration efficiency for cobalt (800 pg of cobalt in 400 pl of standard) 0.20 1 C D 0 100 200 S t a n d i n g ti me/m i n Fig. 5 Effect of standing time of the mixture of cobalt (800 pg of cobalt in 400 p1 of standard) and NaDDC (400 p1 of 0.05% NaDDC) on the preconcentration efficiency for cobalt A mixture was open to the air; B air C oxygen and D hydrogen gases were bubbled through the mixture tration efficiency of the analyte the solutions were passed through the preconcentration column within 20 min of prepar- ing the sample mixture. Effect of the Matrix in Ocean Water The presence of large amounts of matrix materials in ocean water requires preliminary separation from the sample prior to analysis. An investigation was carried out to determine whether or not dilution could be useful to remove interferences given sufficient analytical sensitivity. The results (Fig.6) showed that the laser scatter signal from a CASS-2 solution injected directly into graphite furnace was at least one order of magnitude larger than the fluorescence signal from 10 pg of standard cobalt which was equivalent to the amount of cobalt in 400 pl of CASS-2 reference material. Further dilution experi- ments indicated that the scatter signal for the matrix was so large that it was impossible to isolate the fluorescence signal of the analyte from the laser scatter without prior separation on the c18 column. Preconcentration allows separation of most of the matrix elements such as alkali and alkaline earth elements from cobalt and other heavy-metal ions but residual matrix elements can still be retained on the column.The retained matrix is rinsed into the detection system along with the analyte by the of standing time on the integrated absorbance values of cobalt was investigated in more detail. A series of mixtures of 200 p1 of 0.05°/~ NaDDC with 400 p1 of cobalt standard (800 pg of cobalt) was allowed to stand in autosampler cups open to air for the different periods of time. Thereafter cobalt from each mixture was preconcentrated on the CI8 column and the preconcentration efficiency was meas- ured. For mixtures that stood in containers for longer than 20-30 min before they were pumped through the c18 column the integrated absorbance values for cobalt decreased as a function of time.It was postulated that the effect was due to the decomposition of the chelating reagent in the sample- NaDDC mixtures. In order to identify the nature of this effect the experiment was repeated with different gases bubbled through the sample-NaDDC mixture. It was expected that if the driving force of the effect was oxidation of DDC by oxygen from the air or from the sample solutions an oxidative environment (oxygen gas) should accelerate the process and a reductive environment (hydrogen gas) should inhibit it. In order to keep the experimental conditions all the same air was also bubbled through the sample-NaDDC mixture as a reference point. It was found that the integrated absorbance values for cobalt did not depend on the nature of the gases that were passed through the mixtures.Moreover the signals decreased more rapidly as a function of time compared with the case when the mixtures were just open to the air. A clear explanation for these observations could not be found. It is possible that the stirring caused by the gases accelerated the kinetics of the process of decomposition of DDC molecules. It is also possible that some photo- or thermo-degradation process(es) took place in the sample solutions. This was not investigated further. To avoid possible losses of the preconcen- 304.360 304.400 304.440 Excitation wavelength/nm Fig. 6 Excitation spectra for cobalt A 20 pl of 0.025 pg 1-' solution of CASS-2; and B cobalt 10 pg in aqueous standard.Monochromator slit-width 0.5 mm (4 nm bandpass) and An = 340.5 nm e 0 0 5 0 Time/s 5 Fig. 7 Absorbance profiles for 500 pg of cobalt (a) without and (b) (c) ( d ) in the presence of residual ocean water matrix materials (a) cobalt in 400 pl of standard solution A = 0.073 s; (b) (c) ( d ) cobalt spiked in 400 pl of CASS-2; (b) without rinsing step A=0.085 s; (c) rinsed with 50 p1 of 0.02% nitric acid A =0.043 s; and ( d ) rinsed with 50 pl of sub-boiled distilled water A =0.074 s1200 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 eluate and can affect the precision and accuracy of the determination of cobalt in the ocean water. In previous work a washing step was a necessary part of the separation procedure prior to elution with ethanol.27 In order to find the best washing reagent for the removal of residual matrix retained on the CI8 column 500pg of cobalt were spiked into 400 pl aliquots of ocean water and either sub- boiled distilled water or 0.02% nitric acid was used during the washing step.The recoveries of the cobalt in the ethanol eluates were compared with the absorbance value obtained Table 3 Comparison of the efficiencies of the different volumes of the sub-boiled distilled water rinse of the residual matrix materials ~~ ~ Volume of sub-boiled distilled water/ Pl 20 0.072 50 0.074 100 0.072 150 0.057 Cobalt integrated abs o r bance/s * * Results were obtained by use of 500 pg of cobalt spiked in 400 pl of CASS-2. directly from 500pg of cobalt in an aqueous solution [Fig.7(a)]. For the first mixture the washing step was omitted completely and as expected the presence of the residual matrix in the eluate solution manifested itself as a large spike in the absorbance profile [Fig. 7(b)]. For the second and the third mixtures equal amounts of 0.02% nitric acid [Fig. 7(c)] and sub-boiled distilled water [Fig. 7 ( d ) ] were employed respectively to rinse out the residual matrix. From the results obtained it was clear that the use of 0.02% nitric acid gave worse recovery of the analyte than sub-boiled distilled water. Sub-boiled distilled water which gave essentially 100% recov- ery was used as the washing solution during all subsequent analyses. Different amounts of sub-boiled distilled water were used to find the optimum volume that was required for the separation of the residual matrix from the analyte.The results (Table 3) indicated that any amount of water rinse between 20 and 100 pl could be employed for the removal of the residual matrix. It was also observed that a further increase in the amount of water rinse to more than 100 pl resulted in a decreased integrated absorbance signal for cobalt owing to the leaching of some portion of the analyte from the C column. It could have been useful to buffer the water rinse Table 4 Comparison of results (in ng 1-l) for the determination of cobalt in ocean water reference materials; data are f95% confidence limits Reference material Certified value Present work* CASS-2 NASS- 1 NASS-2 4+1 - 4+1 - NASS-3 NASS-4 -tt 4.4 f 0.6 (13 n = 5 ~ Zhang et a1.t Sperling et a1.S Akatsuka et a1.6 23 t 0.4 27+4 -7 (2 n=6)11 (15 n=5)11 - - 3.9 f 0.4 - 4.8 f 0.4 - - (10 n=4)1i (8 n=8)11 - - 3.1 f0.5 (16 n=6-12**)11 * Analytical volume of ocean water 0.4 ml (CASS-2) 1.0 ml (NASS-4).t Ref. 20; Analytical volume of ocean water 10 ml. $ Ref. 19; Analytical volume of ocean water 5.6 ml (CASS-2) 28 ml (NASS-2). 6 Ref. 5; Analytical volume of ocean water 900 ml. 7 Not available. 11 RSD% n =number of determinations. ** The number of samples was not specified exactly for cobalt. t'f NASS-4 had not been certified at the time of this analysis but NASS-4 was nominally the same as NASS-1 2 3 ref. 37. Table 5 Detection limits for cobalt and performance of different techniques Work Method Present work Flow injection Zhang et al.11 Stripping square- Sperling et al.tt Flow injection Akatsuka et al.fl Flow injection ET-LEAFS wave voltammetry ETAAS ICP-MS [nstrumental Method Ocean water Column packing- detection limit/ detection limit/ detection limit*/ Concentration separating reagent ng 1-' ng I-' ng 1-' factor CI8-NaDDC 17 0.081 1 .w 12.5 C1,-NaDDC low 1.7 7 m - Silica-immobilized 7 8-h ydroxyquinoline * Estimated for the NASS Open Ocean Water reference materials.Based on the preconcentration factors for each method or as indicated. t Based on the variability (3s) of an aqueous blank. $ Estimated from the instrumental detection limit based on 12.5-fold preconcentration of the aqueous standards. 6 Calculated from measurements of the variability (3s) of the procedural blank which was 1.8 ng 1-'.7 Detection limit probably controlled by contamination of ethanol with cobalt. /I Ref. 20. No preconcentration was done. ** Not available. tt Ref. 19. $$ Ref. 11. &j Based on the calculation that 40 p1 of eluate were collected from 28 ml of sample. fl Ref. 5. 11 11 Estimated minimum concentration of cobalt in ocean water that can be determined ref. 5.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1201 but this was not tried owing to the risk of contamination and because the procedures described here already provided accu- rate results. When air was allowed through the column before the water rinse it did not degrade the effectiveness of the removal of the retained matrix materials and did not affect the preconcen- tration efficiency for cobalt.These data contradicted previous observations where the presence of air in the column signifi- cantly degraded the effectiveness of the removal of the residual matrix from the column during the determination of copper in CASS-2.” An explanation for this difference could not be found. Results for the Ocean Water Sample Analysis Ultra-trace amounts of cobalt were determined in CASS-2 and NASS-4 Ocean Water reference materials (Table 4). Aqueous calibration proved possible. There was no difference found between the integrated absorption signal for cobalt from the ethanol solution with and without chemical modification with magnesium nitrate. Hence no chemical modifier was employed not only because it was not necessary but also to minimize the risk of contamination.The results indicated that both the precision and the accuracy of the method were satisfactory compared with the certified and values from other works. The relative standard deviations ( RSD) for the determinations of cobalt in CASS-2 and NASS-4 were 9 and 13% respectively (Table 4). Based on Student’s t-test at the 95% confidence level there were no significant differences between the meas- ured values and the values for the determination of cobalt in certified CASS-2 and non-certified NASS-4. There is a possibil- ity that some of the manual procedures used could have had some degradation effect on the precision of the technique. Detection limits for cobalt by a variety of techniques are presented in Table 5. The ET-LEAFS instrumental detection limit was determined after subtraction of an aqueous blank signal by extrapolation of the analytical curve to a signal level equal to three times the standard deviation of 16 measurements of the blank.Calculations for the detection limit of the present method were based on the instrumental detection limit and the 12.5-fold preconcentration factor. The ocean water detec- tion limits were measured from the standard deviation of the procedural blanks (3s) except where noted in Table 5. Despite the order of magnitude better instrumental detection limit of ET-LEAFS the ocean water detection limit for cobalt in the present work was essentially the same as that achieved by other techniques in Table 5. Although ET-LEAFS was nominally sensitive enough to perform the determination of such small amounts of cobalt without the preliminary precon- centration of the sample on the C column the preconcen- tration procedure was required to separate the matrix from the sample.The procedure introduced contamination via the reagents which negated the improvement in detection limit caused by preconcentration. This is evidenced by the pro- cedural blank level of 1.8 ng 1-’ (Table 5 ) . The same precision and accuracy of a n a l y s e ~ ~ ’ ~ ~ ~ ~ was achieved as those obtained by the alternative techniques dis- cussed in the literature but the present method required less ocean water with volumes at least 1-2 orders of magnitude smaller than those used by other workers (Table4). If the volumes of the ocean water were to be increased the detection limit and the overall precision and accuracy of the method would possibly improve further with caveats about reagent borne contamination.The authors are very grateful to James W. McLaren of the National Research Council of Canada Marine Analytical Chemistry Standards Program for provision of several ocean water standards. Also we thank John T. McCaffrey and Susan McIntosh of Perkin-Elmer Walter Slavin of Bonaire Technologies Zhang Li of AMSPEC and our colleague Evelyn G. Su all of whom helped with parts of this work. This work was supported by an American Chemical Society Division of Analytical Chemistry Fellowship sponsored by Perkin-Elmer (awarded to A.I.Y.). This research employed some equipment that was purchased under grant number GM32002 from the National Institutes of Health.M.W. was supported by grants from the Government of the People’s Republic of China and the University of Connecticut Research Foundation. 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 30 31 32 33 References Porta V. Abollino O. Mentasti E. and Sarzamini C. J. Anal. At. Spectrom. 1991 6 119. Fang Z.-L. Sperling M. and Welz B. J. Anal. At. Spectrom. 1990 5 639. Sperling M. Yin X. and Welz B. J . Anal. At. Spectrom. 1991 6 295. Azeredo L. C. Sturgeon R. E. and Curtius A. J. Spectrochim. Acta Part B 1993 48 91. Akatsuka K. McLaren J. W. Lam J. W. and Berman S. S. J. Anal. At. Spectrom. 1992 7 889. Frieden E. Biochemistry of the Essential Ultratrace Elements Plenum New York 1984. Mertz W. Trace Elements in Human and Animal Nutrition Fifth Edition Academic Press New York 1987.Lavi N. and Altassi Z. B. Analyst 1990 115 817. Blanchflower W. J. Cannavan A. and Kennedy D. G. Analyst 1990 115 1323. Boniforti R. Ferraroli R. Frigieri P. Heltai D. and Queirazza G. Anal. Chim. Acta 1984 33 162. Slavin W. Graphite Furnace AAS. A Source Book Perkin-Elmer Ridgefield CT 1984. Remy B. Verhaeghe I. and Mauchien P. Appl. Spectrosc. 1990 44 1633. Irwin R. L. Wei G.-T. Butcher D. J. Liang Z. Su E. G. Takahashi J. Walton A. P. and Michel R. G. Spectrochim. Acta Part B 1992 41 1497. Carbonell V. Salvador A. and de la Guardia M. Fresenius’ J. Anal. Chem. 1992 342 529. RfiLiEka J. and Arndal A. Anal. Chim. Acta 1989 216 243. Hirata S. Honda K. and Kumamaru T. Bunzeki Kagaku 1987 36 678.Backstrom K. and Danielsson L. G. Anal. Chim. Acta 1990 232 301. Fang Z.-L. Xu S. and Zhang S. Anal. Chim. Acta 1987 200 35. Sperling M. Yin X. and Welz B. J. Anal. At. Spectrom. 1991 6 615. Zang H. Wollast R. Vire J.-C. and Patriarche G. J. Analyst 1989 114 1597. Christian J. D. Environ. Lab. 1993 5 10. Beauchemin D. and Berman S. S. Anal. Chem. 1989 61 1857. McLaren J. W. Mykytiuk A. P. Willie S. N. and Berman S. S. Anal. Chem. 1985 57 2907. Butcher D. J. Dougherty J. P. Preli F. R. Walton A. P. Wei G.-T. Irwin R. L. and Michel R. G. J. Anal. At. Spectrom. 1988 3 1059. Wei G.-T. Dougherty J. P. Preli F. R. Jr. and Michel R. G. J . Anal. At. Spectrom. 1990 5 249. Sjostrom S. and Mauchien P. Spectrochim. Acta Rev. 1993 15 153. Wang M. Yuzefovsky A. I. and Michel R. G. Microchem. J. 1993 48 326. Dougherty J. P. Preli F. R. McCaffrey J. T. Seltzer M. D. and Michel R. G. Anal. Chem. 1987 59 1112. Goforth D. and Winefordner J. Anal. Chem. 1986 58 2598. Yuzefovsky A. I. Lonardo R. F. and Michel R. G. Anal. Chem. in the press. Slavin W. Perkin-Elmer Norwalk CT personal communi- cation 1993. Dougherty J. P. Preli F. R. and Michel R. G. Talanta 1989 36 151. Butcher D. J. Irwin R. L. Takahashi J. Su E. G. Wei G.-T. and Michel R. G. Appl. Spectrosc. 1990 44 1521.1202 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 34 Cheng K. L. and Ueno K. Handbook of Organic Analytical Reagents CRC Press Boca Raton 1982. 35 Stary J. Solvent Extraction of Metal Chelates Pergamon 37 McLaren J. W. National Research Council Canada Institute for Environmental Science personal communication 1993. Morrison G. H. and Freiser H. Solvent Extraction in Analytical Chemistry Wiley New York 1957. Oxford 1964. 36 Paper 31073274 Received December 13 1993 Accepted June 30 1994

ISSN:0267-9477    

DOI:10.1039/JA9940901195

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL O F ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1203 Role of Barium Chemical Modifier in the Determination of Fluoride by Laser-excited Molecular Fluorescence of Magnesium Fluoride in a Graphite Tube Furnace* Alexander I. Yuzefovsky and Robert G. Michelt Department of Chemistry University of Connecticut Storrs CT 06269-3060 USA Some improvement in the determination of fluorine in urine and tap water by use of laser-excited molecular fluorescence spectrometry of magnesium monofluoride in a graphite tube furnace has previously been reported. The use of barium as a chemical modifier increased the size of the signal by a factor of 100. The work reported in the present paper was carried out in an attempt to elucidate the mechanism of the enhancement of the magnesium fluoride fluorescence by barium and to explain some other experimental characteristics of the method such as the vaporization temperature which was lower at 1800 "C than the 2400-2700 "C reported by other workers.The mechanism of formation of gaseous magnesium fluoride molecules from sodium fluoride and magnesium nitrate solutions in a graphite tube furnace during atomic absorption measurements was investigated with and without the presence of barium. It was shown that without chemical modification the formation of magnesium fluoride in the gaseous phase proceeded mainly via interaction between magnesium difluoride molecules and excess of free magnesium atoms [Mg(g) + MgF2(g)+2MgF(g)]. The efficiency of this process was fairly low primarily because of the difference between the vaporization temperatures of the reacting species (1 400 "C for magnesium difluoride and 1800 "C for magnesium vaporized as magnesium oxide). The presence of barium changed the mechanism of formation of magnesium fluoride. It was calculated that the formation of barium difluoride rather than magnesium difluoride was thermodynamically preferable in the first step of the mechanism.Experimental data indicated that the formation of magnesium fluoride then proceeded with higher efficiency than without barium because the reaction Mg(g) + F(g)-+MgF(g) followed the appearance of magnesium from magnesium oxide and fluorine from barium difluoride at coincidental temperatures in the range 1700-1 900 "C. Keywords Flu0 rin e ; lase r-excited molecular flu0 rescen c e spec tro rn e try; m agn esiurn fluoride ; barium ; graphite furnace In a previous publication' significant improvements in the determination of fluorine in urine and tap water by use of laser-excited molecular fluorescence spectrometry (LEMOFS) of magnesium monofluoride in a graphite tube furnace were reported. Excess of magnesium was added to the samples in order to promote the formation of the magnesium fluoride The method was extraordinarily sensitive with a detection limit of 0.3 pg.This detection limit allowed the determination of low levels of fluorine in a urine standard reference material by use of simple aqueous calibration. Physico-chemical inter- ferences were removed by dilution of the sample which was permitted by the high sensitivity of the method. The sensitivity of the analysis was aided by the use of barium as a chemical modifier which increased the temporal peak area by a factor of 100.The work reported in the present paper was carried out in an attempt to elucidate the mechanism of the enhance- ment of the magnesium fluoride fluorescence by barium and to explain some other experimental characteristics of the method such as the vaporization temperature which was lower at 1800 "C than reported by other workers (2500-2700 "C)."' In order to develop the method described above Butcher et al.' used as the standard fluorine in the form of sodium fluoride (NaF) added magnesium in the form of magnesium nitrate [Mg(N03)2 20 pg as Mg] and barium in the form of barium nitrate [Ba(NO,) 1.65 pg as Ba].These aqueous solutions were injected into the graphite furnace dried at 200 "C charred at 800 "C and cooled down to 20 "C before the fluorescence signal of magnesium fluoride was measured upon vaporization at 1800 "C. It was proposed that after decompo- sition of sodium fluoride (NaF) and magnesium oxide (MgO) at high temperature in the gas phase free fluorine reacts with * Presented at the XIX Annual Meeting of the Federation of Analytical Chemistry and Spectroscopy Societies (FACSS) Philadelphia PA USA September 20-25 1992 as paper No. 289. t To whom correspondence should be addressed. magnesium atoms to produce stable diatomic magnesium fluoride (MgF) molecules. The excess of magnesium moves the equilibrium of the following reaction to the Mg(g) + MgF,(g)-+2MgF(g) (1) In ref.1 there were three results that were not satisfactorily explained. Firstly why was the optimum vaporization tempera- ture for magnesium monofluoride between 1700 and 1900 "C which was approximately 1000°C lower than reported by other in analogous experiments? Secondly why did the addition of barium nitrate as the chemical modifier increase the sensitivity of the magnesium fluoride by a factor of loo? Thirdly why did an excess of barium nitrate beyond the optimum that produced the 100 times enhancement mentioned above strongly depress the fluorescence signal of magnesium fluoride? In order to provide a starting point for an explanation of these phenomena Butcher et a/.' proposed a based on the predication of the ability of barium to produce gaseous barium carbides in a graphite furnace.This mechanism was based on the paper b; Styris7 that described the formation of gaseous magnesium from involatile magnesium oxide (boil- ing-point 3600 "C8) according to the reaction BaC2(g)+2MgO(l/s)-+2Mg(g)+Ba(g)+2C0 (2) This reaction in turn would produce the excess of mag- nesium in the gas phase that is a necessary for conversion of magnesium difluoride in to magnesium fluoride according to reaction (1). The explanation of Butcher et al.' was not satisfactory for various reasons. Firstly why does gaseous fluorine which is extremely reactive at high temperature not react with barium carbide? As a result of this type of reaction it could be expected that a significant amount of fluorine could be lost owing to the formation of barium difluoride according to the reaction BaC,(g)+2F(g)~BaFz(g)+2C(s) (3)1204 JOURNAL O F ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL.9 The Gibbs energy per mole of gaseous products (AG*T/y) can be compared for reactions (2) and (3) at 2000 "C which is fairly close to the optimum temperature reported by Butcher et al.' According to the Second Law of Thermodynamics the most favourable reaction is that with the smallest positive or largest negative change in free energy per mole of reactant. For reaction (3) AG*2000~C/~ = - 857.72 kJ which is much more negative than for reaction (2) where AG*2000~C/~ = -92.048 kJ.' This means that reaction (3) has a higher prob- ability of occurrence than reaction (2). Thermodynamic infor- mation to describe the behaviour of barium carbide in the gaseous state could not be found so the calculations used here were based on data for barium carbide in the liquid/solid states.However this is unlikely to result in a different con- clusion because the difference between AG*=/v for reactions (2) and (3) would most likely have been larger rather than smaller for gaseous barium carbide as eqn. (3) represents a homogeneous reaction and (2) is a heterogeneous reaction. In addition for the case without the addition of any chemical modifier a magnesium monofluoride signal was observed even though it is 100 times smaller than in the presence of barium and this requires more explanation than that given by Butcher et al.' Remy" stated that the most stable compounds of the alkaline earth elements are the dihalides.For example at 1700 "C magnesium oxide in the presence of fluorine produces magnesium difluoride according to reaction (4) which has a AG*,~OOOC/V = - 246.856 kJ (4) The occurrence of the magnesium monofluoride is exper- imentally clear,' which indicates that an explanation must be available for the generation of excess of magnesium at the optimized temperature ( 1 700-1900 "C) to allow reaction (1) to proceed. Therefore the work reported in the present paper sought to understand the lower than expected vaporization temperature the increase in sensitivity caused by barium nitrate and the depression of the magnesium monofluoride signal by excess of barium nitrate. Why is fluorine not lost as barium fluoride? Finally without any modifier what processes govern the formation of magnesium monofluoride? Note that for the chemical reactions discussed here only major products are shown and the thermodynamic calcu- lations were performed based only on these products.With eqn. (4) as an example the oxygen from the right-hand side of the reaction after transfer from the reaction zone into the gaseous phase of the furnace could react further with gaseous carbon to produce some CO or CO but these 'secondary reactions' do not significantly affect the mechanisms that are proposed here. Accordingly such reactions are not considered in detail in the remainder of the present paper. Chemical modifiers such as barium nitrate have been widely employed in atomic absorption spectrometry (AAS) in the context of stabilized temperature platform furnace (STPF) technology6?" and are also used in laser-excited atomic fluor- escence spectrometry (LEAFS) and LEMOFS.Many workers have attempted to systemize the practice of the use of chemical modifiers12-14 but such reviews have demonstrated that the physico-chemical reactions involved during the vaporization cycle have often been very complicated contradictory and poorly understood. A better understanding of the chemistry of the reactions in the graphite furnaces should facilitate the appropriate selection of chemical modifiers for particu- lar analyses. The work described in the present paper demon- strates one instance where simple spectrometric measurements with an atomic absorption instrument together with thermo- dynamic calculations can make a contribution to this endeavour.Experimental A11 measurements were made by AAS with a Perkin-Elmer Model 5000 spectrometer equipped with Zeeman-effect back- ground correction an HGA-500 graphite furnace and an AS-40 autosampler. Standard hollow cathode lamps ( HCLs) were used as light sources. Argon which contained less than 1 x oxygen was the sheath gas for the atomizer. Spectrometric measurements which were made during the atomization step were taken under gas-stop or gas-flow (300 ml min- ') conditions. Standard experimental conditions such as wavelength lamp currents and slit-widths for spectro- metric measurements were chosen according to S l a ~ i n . ~ In the experiments with magnesium the samples were vapor- ized from standard platforms made from anisotropic graphite or from laboratory-made tantalum platforms which were used to exclude the possibility of significant interactions between oxide and carbon during the atomization step.15 Tantalum platforms were made from 0.05 mm thick tantalum foil and were 8 x 3 mm in size with rims 1 mm high.16 The furnace heating programme was chosen according to Slaviq6 except for the atomization temperature which was varied between 1700 and 2500 "C.In experiments on the thermal decomposition of magnesium difluoride MgF and sodium fluoride NaF solid samples were used in some cases (salts were of 99.99% purity from Aldrich Chemicals Milwaukee WT USA). Particles of the fluorides with total mass between 100 and 300 pg were placed directly on a standard graphite platform by use of tweezers.Then the platform on which the particles were set was placed into the graphite furnace and the sample was heated slowly (7 "C s-') from 1000 "C while the absorption signals were recorded. In experiments on the decomposition of barium oxide a solution of Ba(NO,) was used. The heating programme consisted of a drying step at 150"C a pyrolysis step at < 1200 "C and atomization with a slow heating rate of 7 "C s-' while the absorption signals were recorded. All experiments were repeated at least 3-5 times to achieve good reproducibility. A slow heating rate was used where appropriate to compensate for the thermal lag in the tempera- ture of the platform relative to the graphite tube. This meant that the platform would be at the same temperature as the wall during the measurements of absorbance.At the normal analytical fast heating rates the platform temperature tends to lag behind the wall temperature by 200-300°C. Results and Discussion The experiments were separated into two parts. The first part was designed to investigate the mechanism of the formation of gaseous molecules of magnesium monofluoride from sodium fluoride and magnesium nitrate without any barium modifier. The second part was designed to investigate the mechanism of the formation of gaseous magnesium monofluoride from the same components but with the presence of a barium salt modifier. Formation of Magnesium Monofluoride From Sodium Fluoride and Magnesium Nitrate Without Barium Modifier The slow heating rate vaporization curve of sodium as it evolved from the decomposition of solid sodium fluoride salt in the graphite tube is shown in Fig.1. Sodium atoms appeared in the gaseous phase at a temperature at least 500°C lower at about 1250 "C than the literature' boiling-point of sodium fluoride (b.p. 1695 "C m.p. 993 "C) which could be a result of the involvement of carbon from the graphite surface in the reduction of sodium fluoride. It was assumed that decompo- sition of sodium fluoride on a graphite platform proceeds by the following reactions NaF(s/l)-+Na(g) + F(g) or (5)JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1205 I I I 1000 1400 1800 2200 TemperaturePC Fig. 1 Vaporization curve of an individual NaF solid particle (x 100 pg) from a graphite platform The reactive fluorine atoms in the form of F(g) and/or F,(g) almost certainly interact with solid and/or liquid mag- nesium oxide formed on the platform by the decomposition of magnesium nitrate to produce stable magnesium difluoride according to reaction (4).The following experiments supported this thesis. The vaporization of magnesium from magnesium difluoride salt by measurement of magnesium atomic absorption signal is shown in Fig. 2(a) and the vaporization of the same metal from a mixture of magnesium oxide and sodium fluoride salt in Fig. 2(b). In the latter case magnesium and sodium fluoride were introduced onto the platform in the form of a magnesium 0 0.8 + Q 0.4 f! v) 2 0 0.8 0.4 0 1000 1400 1800 2200 TemperaturePC Fig. 2 Vaporization curves of Mg from a graphite platform (a) indivi- dual MgF particle about 300pg in mass; (b) mixture of individual particles of NaF ( ~ 1 0 0 p g ) and 5 pl of lOOOpgml-' Mg(NO,) solution; and (c) mixture of individual particle of NaF (x 100 pg) and 20 pl of 1000 pg ml-' Mg(N03)2 solution nitrate solution and a solid salt respectively.A comparison of Fig. 2(u) and (b) indicates that the appearance temperature of the thermal dissociation is about the same at about 1400"C in both cases. Thus it appears that both curves are the result of decomposition of the same molecule magnesium difluoride which is only possible for the mixture of magnesium oxide and sodium fluoride if reaction ( 6 ) occurs first M€Fz(s/l)-+MgF(g) + F(g) MgF,(s/U + MgF,(g) -+MgF(g) + F(g) or ( 6 ) When the concentration of magnesium oxide was signifi- cantly increased and the concentration of sodium fluoride was kept the same two peaks were observed in the magnesium thermal dissociation curve [Fig.2(c)]. The first one was prob- ably due to the decomposition of magnesium difluoride. The second was possibly due to the decomposition of magnesium oxide. Note that although it does not have a significant effect on the present arguments the small delay in the vaporization temperature of magnesium difluoride in Fig. 2(b) and (c) compared with (a) could be explained in terms of the formation of a carbon film on the sample particles owing to the presence of an excess of metal o ~ i d e . ' ~ ' ~ Butcher et ul.' observed only a fairly small magnesium fluoride fluorescence signal without the presence of the barium modifier.According to the thesis of eqn. ( l ) it is necessary to have an excess of free magnesium atoms in the gas phase in order to produce a significant amount of gaseous magnesium fluoride from magnesium difluoride. In Fig. 2(c) it is indicated that in the presence of excess of magnesium only a small fraction of the magnesium vaporizes as magnesium difluoride while most of it is vaporized as magnesium oxide beginning at a temperature that is more than 250°C higher. Optimization of the atomization temperature given by Butcher et al.' indicated that in the presence of barium the sensitivity at 1700-1900 "C is better than at all higher tempera- tures. This is logical given the observations from Fig. 2(c) that there is not a sufficient excess of magnesium for reaction (1) to proceed until temperatures above about 1700 "C which is after the magnesium difluoride has already vaporized and probably mostly diffused out of the furnace.At higher tempera- tures between 2000 and 2700 "C the sensitivity drops steadily.' An increase in the rate of diffusion of both magnesium mono- fluoride and magnesium difluoride from the furnace would result in less signal from magnesium monofluoride and more importantly less time for the excess of magnesium to inter- act with magnesium difluoride to produce magnesium mono fluoride. Formation of Magnesium Monofluoride From Sodium Fluoride and Magnesium Nitrate with Barium Modifier The addition of barium nitrate as a chemical modifier enhanced the magnesium monofluoride fluorescence signal by a factor of 100.Now two concurrent reactions (4) and (7) can occur during the decomposition of sodium fluoride reaction (9 as a result of the presence of barium oxide 2BaO(s/l) + 2F2(g)+2BaF2(s/l)+ O,(g) (7) In order to decide which reaction is preferable the AG*T/v for both reactions was calculated. It was assumed that these reactions must occur in a range of temperatures up to a maximum of 1200 "C which was the highest possible tempera- ture of the complete decomposition of sodium fluoride from the graphite platform (Fig. 1). An inspection of the results of calculations of the Gibbs energies for reactions (4) and (7) through the temperature interval between 500 and 1200 "C always showed a preference for reaction (7) over (4).For example at 1200 "C the difference between the AG*T/v values of the two reactions was 83.68 kJ mol-' which favours reac-1206 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 0.8 m m c (u 0 (D + g 0.4 z 0 tion (7) and this difference increased with decrease in tempera- ture BaF2(s/l)+Ba(g)+2F(g)+ [BaF(g)?] or BaF,(s/l)+BaF,(g)-+Ba(g)+ W g ) + CBaF(g)?l (8) For both reactions (4) and (7) together with reaction (8) and without barium modifier reaction (6) free fluorine appears in the gas phase after the thermal dissociation of the corresponding fluorides but the temperature of vaporization of barium fluoride is higher than the other fluorides and approaches the vaporization temperature of magnesium oxide [Fig. 2(c)]. This statement can be verified by the following results in Fig.3(u) is shown the slow heating rate vaporization curve of barium as it evolved from decomposition of barium fluoride. Barium and sodium fluoride were introduced onto the platform in the form of a solution of a metal nitrate and a particle of a solid salt respectively. The fluoride appeared on the platform according to reaction (7) between barium oxide produced during pyrolysis of barium nitrate salt and fluor- ine produced during decomposition of sodium fluoride. In addition the results in Fig. 4(u) were obtained by atomization of the same mass of magnesium from a graphite platform under normal analytical conditions and the variation in absorption signal with atomization temperature is shown in . 1200 1600 2000 TemperaturePC Fig.3 Vaporization curves of Ba from a graphite platform A mixture of 10 pl of 1000 pg ml-' Ba(NO& solution and individual particles of NaF (z 100 pg); and B 20 p1 of 1000 pg ml-' Ba(NO,) solution 1600 1800 2000 2200 2400 TemperaturePC Fig. 4 Relationship between absorption signal and atomization tem- perature for 15 pg of Mg from Mg(NO,) solution A from a graphite platform; and B from a tantalum platform the figure. It can be seen that the two processes of vaporization of magnesium from magnesium oxide [Fig. 4(u)] and fluorine from barium difluoride [Fig. 3(a)] occur at the same tempera- ture. In this instance the formation of magnesium monofluor- ide molecules occurs in the gas phase [reaction (9)] as a result of a collision of the two free atoms Mg(g) +F(g)+MgF(g) (9) For simplicity it can be assumed that each collision of the two different types of free atom produces one diatomic mol- ecule and that the collision frequency per unit volume depends directly only on the number density of both atoms.I9 The residence time of gas-phase atoms in a tube furnace is depen- dent upon temperature which affects the rate of diffusion from the tube.The significant decrease in the fluorescence signal of magnesium fluoride at temperatures higher than 1800 "C reported by Butcher et al.' was probably the result of the decreased residence time of atoms in the gas phase which activated a lesser number of collisions in a gas phase. As a significant excess of magnesium was used,' it seems reasonable to assume that the collision frequency depended on the concen- tration of free fluorine atoms in the gas phase.The following conclusions can be drawn. Without a barium modifier the relatively weak signal of magnesium fluoride was due to free atoms of magnesium and fluorine that appeared in the gas phase at different optimum temperatures. The concen- tration of magnesium atoms reached a maximum just as the concentration of fluorine atoms was significantly decreased [Fig. 2(c)]. The presence of a barium modifier significantly delayed the appearance of free fluorine atoms in the gas phase by pro- duction of relatively more thermostable fluorides. Magnesium and fluorine atoms vaporized at the same temperature which meant that each atom reached its highest concentration in the gas phase simultaneously.These conditions produced the highest concentration of gaseous magnesium fluoride molecules in the graphite tube. The existence of optimum concentrations of barium chemical modifier can be explained as follows according to the mechan- ism that was proposed above an increased amount of barium caused an excess of free barium atoms in the gas phase after the decomposition of barium oxide. The slow heating rate vaporization curve of barium as it evolved from the decompo- sition of barium nitrate is shown in Fig. 3(b). This appearance temperature for barium atoms coincides approximately with the optimum temperature for the formation and detection of magnesium fluoride. It follows that when the number of free barium atoms in the gas phase increased beyond the optimum the number of collisions between barium and fluorine atoms became significant.These interactions can happen directly via collisions [eqn. (10u)l or through interaction of barium and magnesium fluoride [eqn. (ll)] Ba(g) + F(g)+BaF(g) (10) (11) Both reactions dramatically decrease the number of mag- nesium monofluoride molecules and with further increased barium concentration would depress the fluorescence signal of magnesium monofluoride completely as reported in ref. 1. As a last comment for discussion an attempt was made to explain the decomposition of magnesium oxide in a graphite tube at the rather low temperature of 1800 "C [Fig. 2(c)]. There has been controversy concerning the theories of the formation of free metal species in the gaseous phase of the graphite furnace.The most comprehensive theory is the reduction of oxides by carbon (ROC) the mechanism of which was first proposed by L'vov and Savin2' and has been exten- sively investigated over the last ten years in different labora- torie~."-~~ Some contradictions in the details of the ROC theory have r e ~ e n t l y ~ ' ~ ~ been pointed out. The ROC theoretical mechanism is based on two concurrent Ba(g) + MgF(g)-+BaF(g) + Mg(g)JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY NOVEMBER 1994 VOL. 9 1207 autocatalytic reactions the first reaction occurs on the surface of the graphite tube and the second reaction occurs on the surface of the oxide The appearance temperature of metal atoms in the gas phase produced via the ROC mechanism has been shown to be significantly lower than the appearance temperature of atoms produced by thermal decomposition.'1~'4 In other words if all the assumptions hold true the ROC mechanism is always preferable relative to thermal decomposition. The difference in the analytical signal and atomization temperature of mag- nesium due to the two possible mechanisms is demonstrated in Fig.4. The same mass of sample was vaporized from two different surfaces graphite (a) and tantalum (b) and the results were compared. When the graphite platform was used the ROC mechanism was assumed to be the predominant mechan- ism for the formation of gaseous metal atoms. A tantalum platform was used to prevent interactions between carbon and oxide so that the decomposition of the metal oxide developed via thermal decomposition.Consequently the results in Fig. 4 show that the maximum absorbance signal for magnesium produced by thermal decomposition occurred at a temperature about 500 "C higher than for magnesium produced according to the ROC mechanism. Despite the above discussion there remains some doubt about why the optimum vaporization temperature in the present work was lower at 1800°C than the 2500-2700°C reported by other workers with' and without3 barium nitrate. Unfortunately previous workers did not provide the data that were obtained to optimize the vaporization temperature. Hence it was difficult to discern whether or not the experimen- tal conditions had been properly optimized in their work. At the same time the reported sensitivities for their methods were lower by more than one order of magnitude compared with the work by Butcher et al.' The lack of data and the contradictory results between researchers make it difficult to rationalize why these other researchers used such high vaporiz- ation temperatures.Throughout the present paper it was tacitly implied that all the information derived from atomic absorption measurements are directly transferable to molecular fluorescence measure- ments. This is not true per se since molecular fluorescence could also be affected by a change in collisional environment but the present workers could find no reason to disbelieve this implication in the context of the data presented above. This work was supported by an American Chemical Society Division of Analytical Chemistry Fellowship sponsored by Perkin-Elmer (awarded to A.I.Y.).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 References Butcher D. J. Irwin R. L. Takahashi J. and Michel R. G. J. Anal. At. Spectrom. 1991 6 9. Dittrich K. Hanisch B. and Stark H. J. Fresenius'Z. Anal. Chem. 1986,324,497. Anwar J. Anzano J. M. Petrucci G. and Winefordner J. D. Microchem. J. 1991 43 77. Searcy A. W. in Progress in Inorganic Chemistry ed. Cotton F. A. Wiley Interscience New York 1963 vol. 3. Frech W. Lundberg E. and Cedergren A. Prog. Anal. At. Spectrosc. 1985 8 257. Slavin W. Graphite Furnace AAS A Source Book Perkin-Elmer Norwalk CT 1984. Styris D. L. Anal. Chem. 1984 56 1070. Handbook of Chemistry and Physics ed. Weast R. C. CRC Press Cleveland OH 62nd edn. 1982.Barin I. Knacke O. and Kubaschewski O. Thermochemical Properties of Inorganic Substances Springer-Verlag New York 1977. Remy H. Anorganische Chemie Akademische Verlagsgesellschaft Geest & Portig K.G. Leipzig 1972. Slavin W. Manning D. C. and Carnrick G. R. At. Spectrosc. 1981 2 137. Tsalev D. L. and Slaveykova V. I. J . Anal. At. Spectrom. 1992 7 147. Tsalev D. L. Slaveykova V. I. and Mandjukov P. V. Spectrochim. Acta Rev. 1990 13 225. Tsalev D. L. Bibliography Chemical Modification in Electrothermal Atomization Atomic Absorption Spectrometry 1973-1989 RP 143 Bodenseewerk Perkin-Elmer Uberlingen 1991. L'vov B. V. Spectrochim. Acta Part B 1989 44 1257. L'vov B. V. Nikolaev V. G. Novichikhin A. V. and Polzik L. K. Spectrochim. Acta Part B 1988 43 1141. L'vov B. V. Dokl. Akad. Nuuk SSSR 1985 283 1415. Welz B. Curtius A. J. Schlemmer G. Ortner H. M. and Birzer W. Spectrochim. Acta Part B 1986 41 1175. Atkins P. W. Physical Chemistry W. €3. Freeman San Francisco 1982. L'vov B. V. and Savin A. S. Zh. Anal. Khim. 1982 37 2116. L'vov B. V. Polzik L. K. Romanova N. P. and Yuzefovsky A. I. J. Anal. At. Spectrom. 1990 5 163. Gilmutdinov A. K. Zacharov Y. A. and Ivanov V. P. Zavod. Lab. 1989 55 31. Bendicho C. and de Loos-Vollebregt M. T. C. Spectrochim. Acta Part B 1990 45 547. L'vov B. V. Spectrochim. Acta Part B 1989 44 1257. Holcombe J. A. Styris D. L. and Harris J. D. Spectrochim. Acta Part B 1991 46 629. Round Table Discussion XXVII-CSI Pre-Symposium J . Anal. At. Spectrom. 1992 7 471. Paper 31075691 Received December 24 1993 Accepted June 30 1994

ISSN:0267-9477    

DOI:10.1039/JA9940901203

出版商:RSC    

年代:1994

数据来源: RSC