摘要:

The AnalystThe Analytical Journal of The Royal Society of ChemistryAnalytical Editorial BoardChairman: A. G. Fogg (Loughborough, UK)K. D. Bartle (Leeds, UK)D. Betteridge (Sunbury-on-Thames, UK)J. Egan (cambridge, UK)H. M. Frey (Reading, UK)D. E. Games (Swansea, UK)S. J. Hill (Plymouth, UK)D. L. Miles (Keyworth, UK)J. N. Miller (Loughborough, UK)R. M. Miller (Port Sunlight, UK)B. L. Sharp (Loughborough, UK)Advisory BoardJ. F. Alder (Manchester, UK)A. M. Bond (Victoria, Australia)R. F. Browner (Atlanta, GA, USA)D. T. Burns (Belfast, UK)J. G. Dorsey (Cincinnati, OH, USA)L. Ebdon (Plymouth, UK)A. F. Fell (Bradford, UK)J. P. Foley (Villanova, PA, USA)T. P. Hadjiioannou (Athens, Greece)W. R. Heineman (Cincinnati, OH, USA)A. Hulanicki (Warsaw, Poland)I.Karube (Yokohama, Japan)E. J. Newman (Poole, UK)T. B. Pierce (Harwell, UK)E. Pungor (Budapest, Hungary)J. RSiiCka (Seattle, WA, USA)R. M. Smith (Loughborough, UK)M. Stoeppler (Julich, Germany)J. D. R. Thomas (Cardiff, UK)J. M. Thompson (Birmingham, UK)K. C. Thompson (Sheffield, UK)P. C. Uden (Amherst, MA, USA)A. M. Ure (Aberdeen, UK)P. Vadgama (Manchester, UK)C. M. G. van den Berg (Liverpool, UK)A. Walsh, K.B. (Melbourne, Australia)J. Wang ( i a s Cruces, NM, USA)T. S. West (Aberdeen, UK)Regional Advisory EditorsFor advice and help to authors outside the UKProfessor Dr. U. A. Th. Brinkman, Free University of Amsterdam, 1083 de Boelelaan, 1081 HVProfessor Dr. sc. K. Dittrich, Institute for Analytical Chemistry, University Lei pzig, Linnestr.3,Professor 0. Osibanjo, Federal Environmental Protection Agency, Federal Secretariat, PhaseProfessor K. Saito, Coordination Chemistry Laboratories, Institute for Molecular Science,Professor M. Thompson, Department of Chemistry, University of Toronto, 80 St. GeorgeProfessor Dr. M. Valcdrcel, Departamento de Quimica Analitica, Facultad de Ciencias,Professor J. F. van Staden, Department of Chemistry, University of Pretoria, Pretoria 0002,Professor Yu Ru-Qin, Department of Chemistry and Chemical Engineering, Hunan University,Professor Yu. A. Zolotov, Kurnakov Institute of -General and inorganic Chemistry, 31 LeninAmsterdam, THE NETHERLANDS.D-0-7010 Leipzig, GERMANY.II, 1st Floor, IKOYI, Lagos, P.M.B.12620, Lagos, NIGERIA.Myodaiji, Okazaki 444, JAPAN.Street, Toronto, Ontario M5S I A l , CANADA.Universidad de Cordoba, 14005 Cordoba, SPAIN.SOUTH AFRICA.Changsha, PEOPLES REPUBLIC OF CHINA.Avenue, 117907, Moscow V-71, USSR.Editorial Manager, Analytical Journals: Judith EganEditor, The AnalystHarpal S. MinhasThe Royal Society of Chemistry,Thomas Graham House, Science Park,Milton Road, Cambridge CB44WF, UKTelephone 0223 420066.Fax 0223 423623. Telex No. 818293 ROYAL.Senior Assistant EditorPaul DelaneyUS Associate Editor, The AnalystDr J. F. TysonDepartment of Chemistry,University of Massachusetts,Amherst MA 01 003, USATelephone413 5450195Fax 41 3 545 4490Assistant EditorsBrenda Holliday, Paula O'Riordan, Sheryl WhitewoodEditorial Secretary: Claire HarrisAdvertisements: Advertisement Department, The Royal Society of Chemistry, BurlingtonHouse, Piccadilly, London, W1V OBN.Telephone 071-437 8656. Telex No. 268001.Fax 071-437 8883.The Analyst (ISSN 0003-2654) is published monthly by The Royal Society of Chemistry,Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK. All orders,accompanied with payment by cheque in sterling, payable on a UK clearing bank or in USdollars payable on a US clearing bank, should be sent directly to The Royal Society ofChemistry, Turpin Transactions Ltd., Blackhorse Road, Letchworth, Herts SG6 1 HN, UnitedKingdom. Turpin Transactions Ltd., distributors, is wholly owned by the Royal Society ofChemistry. 1992 Annual subscription rate EC f276.00, USA $589, Rest of World f310.00.Purchased with Analytical Abstracts EC f604.00, USA $1299.00, Rest of World f669.00.Purchased with Analytical Abstracts plus Analytical Proceedings EC f712.00, USA $1 527.00,Rest of World f791 .OO.Purchased with Analytical Proceedings EC f351 .OO, USA $749.00, Restof World f395.00. Air freight and mailing in the USA by Publications Expediting Inc., 200Meacham Avenue, Elmont, NY 11003.USA Posrmaster: Send address changes to: The Analyst, Publications Expediting Inc., 200Meacham Avenue, Elmont, NY 11003. Second class postage paid at Jamaica, NY 11431. Allother despatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Postoutside Europe. PRINTED IN THE UK.Information for AuthorsFull details of how to submit material forpublication in The Analyst are given in theInstructions to Authors in the January issue.Separate copies are available on request.The Analyst publishes papers on all aspects ofthe theory and practice of analytical chemistry,fundamental and applied, inorganic andorganic, including chemical, physical, biochem-ica I, clinical, pharmaceutical, biolog ica I,environmental, automatic and computer-basedmethods.Papers on new approaches to existingmethods, new techniques and instrumentation,detectors and sensors, and new areas of appli-cation with due attention to overcoming limita-tions and to underlying principles are all equallywelcome. There is no page charge.The following types of papers will be con-sidered :Full research papers.Communications, which must be on anurgent matter and be of obvious scientificimportance.Rapidity of publication is enhancedif diagrams are omitted, but tables and formulaecan be included. Communications receive pri-ority and are usually published within 5-8weeks of receipt. They are intended for briefdescriptions of work that has progressed to astage at which it is likely to be valuable toworkers faced with similar problems. A fullerpaper may be offered subsequently, if justifiedby later work. Although publication is at thediscretion of the Editor, communications will beexamined by a t least one referee.Reviews, which must be a critical evaluationof the existing state of knowledge on a par-ticular facet of analytical chemistry.Every paper (except Communications) will besubmitted to a t least two referees, by whoseadvice the Editorial Board of The Analyst will beguided as to its acceptance or rejection.Papersthat are accepted must not be published else-where except by permission. Submission of amanusqipt will be regarded as an undertakingthat the same material is not being consideredfor publication by another journal.Regional Advisory Editors. For the benefit ofpotential contributors outside the United King-dom and North America, a Group of RegionalAdvisory Editors exists. Requests for help oradvice on any matter related to the preparationof papers and their submission for plmblicationin The Analyst can be sent to the nearestmember of the Group.Currently servingRegional Advisory Editors are listed in eachissue of The Analyst.Manuscripts (four copies typed in double spac-ing) should be addressed to:Harpal S . Minhas, Editor, The Analyst,Royal Society of Chemistry,Thomas Graham House,Science Park, Milton Road,CAMBRIDGE CB4 4WF, UK or:Dr. J. F. TysonUS Associate Editor, The AnalystDepartment of ChemistryUniversity of MassachusettsAmherst MA 01003, USAParticular attention should be paid to the use ofstandard methodsof literaturecitation, includingthe journal abbreviations defined in ChemicalAbstracts Service Source Index. Wherever pos-sible, the nomenclature employed should fol-low IUPAC recommendations, and units andsymbols should be those associated with SI.All queries relating to the presentation andsubmission of papers, and any correspondenceregarding accepted papers and proofs, shouldbe directed either to the Editor, or AssociateEditor, The Analyst (addresses as above). Mem-bers of the Analytical Editorial Board (who maybe contacted directly or via the Editorial Office)would welcome comments, suggestions andadvice on general policy matters concerningThe Analyst.Fifty reprints are supplied free of charge.@ The Royal Society of Chemistry, 1992. Allrights reserved. No part of this publication maybe reproduced, stored in a retrieval system, ortransmitted in any form, or by any means,electronic, mechanical, photographic, record-ing, or otherwise, without the prior permissionof the publishers

ISSN:0003-2654    

DOI:10.1039/AN99217FX009

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALAO 1 17(3) 229-694 (1 992) March 1992The AnalystThe Analytical Journal of The Royal Society of ChemistryCONTENTSXXVll COLLOQUIUM SPECTROSCOPICUM INTERNATIONALE, JUNE 9-14, GRIEG HALL, BERGEN, NORWAY229 CONFERENCE REPORT-F. J. Langmyhr, Y. Thomassen230 CSI Award for Major Scientific Contributions to Analytical Spectroscopy230 A Personal Tribute t o Sir Alan Walsh-L. R. P. Butler231 Sir Alan Walsh-The Scientist and the Man-P. L. Larkins233 Atomic Absorption Spectroscopy-Present and Future Aspects-Ralph E. Sturgeon236 Reflections and Comments from Sir Alan Walsh, FRS237 EDITORIAL-XXVII CSI, Bergen, NorwayKEYNOTE LECTURE239 Spectroscopy From the Hubble Space Telescope-Bruce E. WoodgatePLENARY LECTURES243 Applications of Nuclear Analytical Techniques in Environmental Research-Brit Salbu, Eiliv Steinnes251 Some Considerations Regarding Reference Materials and Their Role in Environmental Monitoring-Anthony R.Byrne259 Particle Induced X-ray Emission and Complementary Nuclear Methods for Trace Element Determination-Sven A. E.267 Application of Multinuclear Magnetic Resonance Spectroscopy t o Solvation and Aggregation Phenomena in289 Principles and Applications of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry-Nico M. M. Ni bberingPAPERS295 Determination of Thallium in Sediments of the River Elbe Using Isotope Dilution Mass Spectrometry With Thermal299 Characterization of Proteins by Mass Spectrometry-Invited Lecture-Peter Roepstorff305 Characterization of High- and Non-boiling Crude Oil Fractions-Invited LectureDieter Severin313 Recent Advances in Surface Analysis-Invited Lecture-J.C. Riviere323 Surface Analysis of Lanthanum-modified Cobalt Catalysts-Invited LectureJeff rey S. Ledford, Young-Man Kim,329 Characterization of lnhomogeneity in High-quality Quartz Crystals-Bernard Viard, Pierre Zecchini335 Recent Advances in Infrared Matrix Isolation Spectroscopy-Invited Lecture-Peter Klaeboe, Claus J. Nielsen343 Evaluation of Intensity Information in High-resolution Gas-phase Fourier Transform Infrared Spectra-InvitedLectureBrenda P. Winnewisser351 In situ Investigation of Solid State Ion Exchange in Zeolites Using Fourier Transform Infrared Spectroscopy-ReinerSalzer, Ute Finster, Frank Roessner, Karl-Hermann Steinberg, Peter Klaeboe355 Solid Phases of Bicyclohexyl Studied With Vibrational Spectroscopy and Calorimetry-A. Horn, P.Klaeboe, C. J.Nielsen, V. S. Mastryukov, B. 0. Myrvold, K. Redford361 Hydrogen Bonding of Tris(diethy1amino)phosphine Oxide, Tris(diethy1amino)phosphine Sulfide, Tris(diethylamin0)-phosphine Selenide and N,NDimethylthioacetamide With Various Proton Donors-Pirkko Ruostesuo, AnneHaapalainenJo ha nssonSolution-Jean-Jacques DelpuechIonization-E. Waidmann, M. Stoeppler, P. HeiningerMarwan Houalla, Andrew Proctor, David M. Hercules365 Vibrational Spectra of Seven Halomethanes-Valdas Sablinskas, Peter Klaeboe, Claus J. Nielsen, Detlev Sulzle371 Infrared Spectra of Tetrahydropyrido[l,2-a]pyrimidin-4-one Derivatives-G. Horvath, I. Hermecz, L.Pusztay, A. I. Kiss375 Application of Infrared Spectrometry t o the Study of Tautomerism and Conformational and Configurational Isomerismin Medical and Biochemical Agents: N,N’-Disubstituted Amidines-Ewa D. Raczynska, Christian LaurenceTypeset and printed by Black Bear Press Limited, Cambridge, England0083-2654(199213-ANALYST, MARCH 1992, VOL. 11737938338739540 140741 341 741 942543 143543944344745345445546 1465469475481487493497501505Determination of Ammonia Using Carbon Dioxide Laser Photoacoustic Spectroscopy Compared With ConventionalSpectrophotometry-Aniko M. Solyom, Gyorgy Z. Angeli, Dane D. Bicanic, Marcel LubbersCalculation of Molecular Thermodynamic Parameters From Incomplete Spectroscopic and Diffraction Data-Vi ktor A.Si pac hevComputer Aided Analysis of Carbon-13 Nuclear Magnetic Resonance Spectra of Multicomponent Mixtures.Part 2.Determination of the Content of Alkadienes in a Light Gasoline-Marek Matlengiewicz, Norbert Henzel,Jean-Claude Lauer, Thierry Laurens, Daniel Nicole, Patrice RubiniDetermination of Trace Elements in Steel by Laser Ablation Inductively Coupled Plasma Mass Spectrometry-HisaoYasuhara, Teruo Okano, Yasuharu MatsumuraFactors t o be Considered in the Preparation of Single and Multi-element Standards for Inductively Coupled PlasmaOptical Emission Spectrometry-N i rma I a Kocherla kotaCombined GeneratorSeparator for Continuous Hydride Generation : Application t o On-line Pre-reduction of Arsenic(v)and Determination of Arsenic in Water by Atomic Emission Spectrometry-Ian D.Brindle, Hosen Alarabi, SamirKarshman, Xiao-chun Le, Shaoguang Zheng, Hengwu ChenIndirect Atomic Absorption Spectrometric Determination of Sulfate in Human Blood Serum-Sarnath Chattaraj,Arabinda K. DasTemperature Dependence of the Absorption Spectra of Nitrogen Oxide, Nitrogen Dioxide and Sulfur Dioxide in theApplication of Differential Optical Absorption Spectroscopy-J. Mellqvist, A. Rosen, H. AxelssonComparative Study of Certified Reference Materials and Quality Control Materials for the Quality Assurance ofBlood-lead Determination-J. Thomas, 6. Anglov, Jytte M. ChristensenStatistical Model for Assessing the Quality and Cost in Inspection Procedures in Forensic and EnvironmentalAnalysis-Willem G.de Ruig, Fred A. Huf, A. A. M. JansenSources of Error in Analytical Gamma-ray Spectrometry-Invited Lecture-Marcel de Bruin, Menno BlaauwDetermination of Aluminium-26 Using a Low-level Liquid Scintillation Spectrometer-Helge E. Bjornstad, Deborah H.Determination of Plutonium-239 + Plutonium-240 and Plutonium-241 in Environmental Samples Using Low-levelRapid Radiochemical Neutron Activation Analysis for Iodine in Urine by Different Separation Techniques-M. Dermelj,Determination of Selenium in Human Diets by Radiochemical Neutron Activation Analysis-Yasser H. El-Hallaq, inci G.Oughton, Brit SalbuLiquid Scintillation Spectrometry-Yu-fu Yu, Helge E. Bjornstad, Brit SalbuZ. Slejkovec, A. R. Byrne, P. Stegnar, S. Hojker, M.Porenta, G. SestakovGokmen, Namik K. Aras, Ali Gokmen1991, BERGEN, NORWAYMEASUREMENTS OF RADIONUCLIDES AFTER THE CHERNOBYL ACCIDENT. XXVll CSI PRE-SYMPOSIUM, JUNE 6-8,FOREWORD-Brit Salbu, Eiliv SteinnesPAPERS PRESENTED AS LECTURESRelationships Between Deposition of Chernobyl Originating Caesium and Ruthenium Radionuclides and Rainfall inEffects of Topography on Caesium-137 in Montane Peat Soils and Vegetation-Edward J. McGee, Peter A. Colgan,Small-scale Variation in Deposition of Radiocaesium From the Chernobyl Fallout on Cultivated Grasslands inVertical Migration of Plutonium-239 + -240, Americium-241 and Caesium-137 Fallout in a Forest Soil Under Spruce-K.Migration Rates of Radionuclides Deposited After the Chernobyl Accident in Various North German Soils-GeraldRadionuclide Mobility and Bioavailability in Norwegian and Soviet Soils-Deborah H.Oughton, Brit Salbu, G. Riise, H.Availability of Caesium Isotopes in Vegetation Estimated From Incubation and Extraction Experiments-Brit Salbu,Comparison of the Uptake of Radiocaesium From Soil t o Grass After Nuclear Weapons Tests and the ChernobylConcept of Seasonality in the Light of the Chernobyl Accident-Asker AarkrogInvestigations of Radiocaesium in the Natural Terrestrial Environment in Norway Following the ChernobylAccident-S. Bretten, E. Gaare, T. Skogland, E. SteinnesDevelopment of a Laboratory Method t o Predict Rapidly the Availability of Radiocaesium-Diane L. Singleton, FrancisR. Livens, Nicholas A. Beresford, Brenda J. Howard, Catherine L.Barnett, Robert W. Mayes, Michael G. SegalCaesium Contamination in Human Milk and Transfer Factor From Diet-Serena Risica, Gloria Campos Venuti, AntoniaRogani, Dante Baronciani, Massimo PetroneIreland-Ian R. McAulay , Diarmuid MoranDavid E. Dawson, Barbara Rafferty, Ciaran O’KeeffeNorway-Lars E. HaugenBunzl, W. Kracke, W. SchimmackKirchner, Dieter BaumgartnerLien, G. 0stby, A. NorenGeorg 0stby, Torstein H. Garmo, Knut HoveAccident-Tone D. Selnax, Per Strand51 ANALYST, MARCH 1992. VOL. 11751 5521525529533539545549550551555559563571577583589595605613619623629637641645649657665Winter Transport of Chernobyl Radionuclides From a Montane Catchment t o an Ice-covered Lake-John E.Brittain,PAPERS PRESENTED AS POSTERSTransfer Characteristics of Radiocaesium From Soils t o Permanent Pasture-Geraldine MacNeill, Jarlath T. Duffy, JohnRadioactive Contamination of Soils in Lower Saxony, Germany, After the Chernobyl Accident-Christiane Beckmann,Different Approaches for Estimating the Deposition of Radiocaesium on Mountain Pasture in Southern Norway-LarsDistribution of Radionuclides in the Environment in Northern Italy After the Chernobyl Accident-Antonella Berzero,Post-Chernobyl Accident Radioactivity Measurements in the Comunidad Autonoma de Valencia, Spain-J. Ortiz, L.Radioactive Contamination of Food Sampled in the Areas of the USSR Affected by the Chernobyl Disaster-Willem G.Helge E. Bjbrnstad, Brit Salbu, Deborah H. OughtonD. Cunningham, Brian Coulter, Sean Diamond, Ian R.McAulay, Diarmuid MoranChristoph FaasE. Haugen, Torstein H. Garmo, 0yvind Pedersen, Helge E. BjornstadPier Angelo Borroni, Massimo Oddone, Vera Caramella Crespi, Nicla Genova, Sandro MeloniBallesteros, V. Serradellde Ruig, Teunis D. B. van der Struijs16-18,1991, LOEN, NORWAYSPECIATION OF ELEMENTS IN ENVIRONMENTAL AND BIOLOGICAL SCIENCES. XXVll CSI POST-SYMPOSIUM, JUNEFOREWORD-Evert NieboerPAPERS PRESENTED AS LECTURESTrace Element Speciation by Anodic Stripping Voltammetry-T. Mark FlorenceSpeciation of Trace Elements in Biological Materials: Trends and Problems-Dietrich BehneUtilization of Two Different Chemical Forms of Selenium During Lactation Using Stable Isotope Tracers: an Example ofOverview of Analytical Methods for Elemental Speciation-Jon C.Van Loon, Ronald R. BarefootChromatographic Techniques in Metal Speciation-Y. K. ChauElemental Speciation by Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry With DirectUse of Radiochemical Methods as Tools for Speciation Purposes in Environmental and Biological Sciences-RitaEffect of Deposition Potential on the Voltammetric Determination of Complexing Ligand Concentrations inSize, Morphology and Composition of Particulates in Aquatic Ecosystems: Solving Speciation Problems by CorrelativeKinetic Aspects of Chemical Speciation-John BurgessSpeciation in Nutrition-Phylis B. Moser-Veillon, A. Reed Mangels, Kristine Y. Patterson, Claude VeillonInjection Nebulization-Sam C.K. Shum, Robert Neddersen, R. S. HoukCornelisSea-Water-Constant M. G. van den BergElectron Microscopy-Gary G. LeppardPAPERS PRESENTED AS POSTERSSize and Charge Fractionation of Aqueous Aluminium in Dilute Acidic Waters: Effects of Changes in pH andUse of an Aluminium-26 Tracer t o Study the Deposition of Aluminium Species on Fish Gills Following Mixing of LimedSelective Extraction and Determination of Metals in Organic Stream Sediments-Marja L. Raisanen, Lea Hamalainen,Temperature-Espen Lydersen, Brit Salbu, A. 6. S. Pole0and Acidic Waters-Deborah H. Oughton, Brit Salbu, Helge E. Bjbrnstad, J. Philip DayLars M. WesterbergDifferential Determination of Chromium(vi) and Total Chromium in Natural Waters Using Flow Injection On-lineSeparation and Preconcentration Electrothermal Atomic Absorption Spectrometry-Michael Sperling, XuefengYin, Bernhard WelzSimultaneous Determination of Chromium(itt) and Chromium(vi) in Aqueous Solutions by Ion Chromatography andChemiluminescence Detection-Bente Gammelgaard, Ole Jbns, Bent NielsenSimultaneous Speciation of Butyltin and Phenyltin Compounds in the Waters of South-west Spain-J.L. Gomez-Ariza,E. Morales, M. Ruiz-BenitezMercury Determination by Cold Vapour Atomic Absorption Spectrometry in Several Biological Indicators From LakeMaracaibo, Venezuela-Marinela Colina de Vargas, Romer A. RomeroPreliminary Study of Metals in Proteins by High-performance Liquid Chromatography-Inductively Coupled PlasmaMass Spectrometry Using Multi-element Time-resolved Analysis-Linda M. W.Owen, Helen M. Crews, Robert C.Hutton, Amanda WalshSpeciation of Mercury in Human Whole Blood by Capillary Gas Chromatography With a Microwave-induced PlasmaEmission Detector System Following Complexometric Extraction and Butylation-Ewa Bulska, HB kan Emteborg,Douglas C. Baxter, Wolfgang Frech, Dag Ellingsen, Yngvar ThomassenPreliminary Study of the Effects of Some Physical Parameters on the Stability of Methylmercury in BiologicalSamples-Milena Horvat, Anthony R. ByrnANALYST, MARCH 1992, VOL. 117669 Determination of Organic Mercury Species in Soils by High-performance Liquid Chromatography With Ultraviolet673 Investigation of Mercury Speciation in Lichens-V. LupSina, M. Horvat, Z. Jeran, P. Stegnar677 Effect of Seafood Consumption on the Urinary Level of Total Hydride-generating Arsenic Compounds. Instability ofArsenobetaine and Arsenocholine-Ann J. L. Murer, Anne Abildtrup, Otto M. Poulsen, Jytte M. Christensen681 Influence of Organic and Inorganic Arsenicals on Glucose Uptake in Madin-Darby Canine Kidney (MDCK)Cells-Bernhard Liebl, Harald Muckter, Erika Doklea, Burckhard Fichtl, Wolfgang Forth685 Influence of Soluble Organic Matter on Cadmium Mobility in Model Compounds and in Soils-Alain Bermond, SergeBourgeois689 NSPEC: A Chemical Speciation Program for Personal Computers-Gregory W. Quinn, David M. Taylor693 CUMULATIVE AUTHOR INDEXDetection-M axi m i I ian Hem pel, Holg e r Hi ntel man n, Rolf- Dieter Wi I ke

ISSN:0003-2654    

DOI:10.1039/AN99217BX011

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, MARCH 1992. VOL. 117 229 XXVll Colloquium Spectroscopicurn Internationale: June 9-14,1991 Bergen, Norway Finn J. Langmyhr (Chairman of the XXVll CSI) Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo 3, Norway Yngvar Thomassen (Vice-chairman and Programme Chairman of the XXVlI CSI) National Institute for Occupational Health, P.O. Box 8749 DEP, N-0033, Oslo I , Norway This traditional biennal conference in analytical spectroscopy was organized for the first time in a Nordic country by the Norwegian Chemical Society. The long and distinguished history of the CSI meetings obligated the Organizing Com- mittee of eight members to provide participants with a similarly satisfying scientific and personal experience. The XXVII CSI attracted 580 registrants and 59 accompanying persons, representing 41 countries and all continents.The scope of the conference covered research in basic theory and instrumentation of atomic, nuclear and molecular spec- troscopy and the application of spec- troscopy to the analysis of a broad variety of matrices. In continuance of the scientific tradi- tion of this conference, 49 invited, ple- nary and keynote speakers reviewed and discussed recent advances. Over the four days of the meeting, a total of 134 contributions were presented orally in parallel sessions, 254 posters were shown and thoroughly discussed. The broad scope is reflected in the papers that constitute the special issues of The Analyst and Journal of Analytical Atomic Spectrometry. The CSI conference conforms to the rules and regulations of the International Council of Scientific Unions, thus ensur- ing sponsorship by the International Union of Pure and Applied Chemistry (IUPAC).At the 35th IUPAC General Assembly in 1989 it was decided to concentrate a significant part of future efforts on projects related to Chemistry and the Environment. To promote this effort the XXVII CSI programme high- lighted the key role of spectroscopy in overcoming environmental problems and in protecting our environment in a special plenary session on the Role of Spectroscopy in Environmental Studies. Two special satellite meetings dealing with this topic were also organized: the pre-symposium ‘Measurement of Radio- Nuclides after the Chernobyl Accident’ and the post-symposium ‘Speciation of Elements in Environmental and Bio- logical Sciences’.The third pre-symposium ‘Graphite Atomizer Techniques in Analytical Spec- troscopy’ emphasized the unique impor- tance of electrothermal atomization in trace element measurements. Increasing concerns about the consequences of both harmful and beneficial constituents in environmental matrices encouraged a great number of analytical spectrosco- pists to meet with other scientists at these satellite meetings for an interchange of knowledge and ideas. Further informa- tion and selected presentations from these meetings are available either in The Analyst or JAAS. To enhance the scientific stature of the CSI further, the present organizing com- mittee awarded Sir Alan Walsh the Award of the XXVII CSI for his out- standing contribution to spectroscopy.Sir Alan’s work covers many fields of spectroscopy ‘and in all his work he has contributed original and applied know- ledge. In particular his investigations into and the final development of the field of atomic absorption spectroscopy stands out in the field of scientific endeavour and his work has found applications in virtu- ally all areas of manS scientific achieve- ment. In making this award, the XXVII CSI is paying tribute to a great but humble man for his inspiration, his leadership, his ability to apply his talent to many fields, and his promotion of knowledge’ as is stated in the award scroll. The organizers and the participants were extremely pleased that Sir Alan and Lady Walsh were both able to travel to Norway.They participated as special guests in the pre- symposium on graphite atomizers and the post-symposium on speciation, and indeed they charmed us all! Acknow- ledgement of credit for the success of the award session must also go to four contributors: L. R. P. Butler (Republic of South Africa), A. Hulanicki (Poland), P. Larkins (Australia) and R. Sturgeon (Canada). Special acknowledgement is owed to Perkin-Elmer and Varian for their generous economic contributions to the XXVII CSI-Award. At the Meeting of the National Del- egates in Bergen a proposal to amend the Constitution of the CSI was passed unani- mously. The new sub-chapter 6 in Chapter 3 reads as follows: ‘On the occasion of each Colloquium a CSI- Award for major contributions to ana- lytical spectroscopy may be presented.The Continuation Committee is respons- ible for the selection of the recipient. The names of Candidates for the Award should be submitted to the Continuation Committee by the National Delegates not later than 6 months before the coming Colloquium. The selection is made by a simple majority vote by the Continuation Committee. The name(s) should be accompanied by a brief summary of the candidate(s) qualifications ’. Owing to the recent dramatic changes in Eastern European countries the XXVII CSI in Bergen became for the first time a meeting-place for the entire spectroscopy family. The response from these countries to the 20000 first circu- lars distributed worldwide was over- whelming and many interesting abstracts were received from outstanding scien- tists.The scarcity of foreign currency made it, however, extremely difficult for most of them to participate. The Organ- izing Committee was pleased to be able to provide funds for the support of 30 participants. Certainly, any meeting of this type depends on the support and sponsorship of a number of organizations and sources. The main source of income was the exhibition of scientific equipment and products. Special acknowledgements must be given to the 28 exhibiting com- panies for their support and their effort in preparing the well attended exposi- tion. Most participants took the oppor- tunity to view the latest instrumentation. We would also like to express our appreciation to all speakers, poster con- tributors and chairmen for their excellent cooperation. Finally, we also thank the editorial staff of the Royal Society of Chemistry for their inestimable support in publishing the great number of contri- butions presented in Bergen. A conference is not only a scientific meeting, but also a social event. The venue of the XXVII CSI was, we feel, a delightful location which all participants enjoyed. During a cheese and wine tasting party, a conference excursion and a farewell party on the fjord after a week of scientific activities, the spectroscopic family demonstrated once again that life is not lived only in the ground state.

ISSN:0003-2654    

DOI:10.1039/AN9921700229

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

1348 ANALYST, AUGUST 1992, VOL. 117 Similarly, any variation in distance between sample and detector in a replicate analysis can contribute towards random error. Possible sources of such error are the variation in the thickness of the bases of the sample holders above the detector. Beckerg calculated that the sample shape variation was 3% for a 1 mm change in the average height of a sample at 5 cm distance from a 13% efficient detector. Similarly, Potts and Husseyg have calculated such variation resulting from reposi- tioning of a sample. They worked on a range of sample-to- detector distances of 5-50 mm and found that a repositioning discrepancy of only 0.2 mm for a source-to-detector distance of 10 mm can cause an error of up to 4% in the measured activity of a sample. Fortunately, in this work, all these errors could be eliminated by counting at large distances from the detector.Total Analytical Variation Taking account of all the analytical uncertainties, the total error for a sample i would be the sum of all absolute and relative random errors consisting of irradiation variation (iv), counting variations (cv) and the counting statistics (cs) error: (4) According to Heydorn and Damsgard,4 analytical variation, a2, becomes insignificant if it is less than one-third of the total variance (9). This can be checked conveniently by calculating the index of determination (ID): For an ID 20.8, the analytical variation is less than one-third of the total variance and can be ignored; therefore, eqn. (2) reduces to: or Experimental Blank Rock Standards Standard samples of similar matrices were needed to check the irradiation variation in this work.Therefore, a synthetic standard was prepared. A blank rock (basalt) of 200 mesh particle size was used as a base matrix because the samples were also siliceous ores. Blank ore, weighing 19 g, was doped with 19 g of a 13 mg kg-1 gold solution (HAuCI4). The mixture was blended on an orbital shaker and then frozen at -30 "C before drying in a vacuum-dryer. After drying, the synthetic standard was re-ground with a Tema swing mill in an agate pot. Finally, it was blended in an end-to-end shaker for 4 h. Reference Materials The reference ores of the Canadian Certified Reference Material Project, MA series, are typical of high and low (waste rock) ore grades from the Macassa Mine at Kirkland Lake, Ontario, Canada.The ore contains quartz, wall rock inclu- sions, carbonates, and small amounts of sulfides, tellurides and native gold. The principal sulfide is finely disseminated pyrite. Most of the gold occurs as an electrum. The high-grade ore, MA-1, was replaced by MA-la and then MA-lb, as they became depleted. The low-grade ore, MA-2, has been replaced by MA-2a. Irradiation Facilities All the samples in this work were irradiated in the CONSORT I1 reactor at Imperial College, London. It is a swimming pool-type reactor of thermal power 100 kW. A number of irradiation facilities are available, two of which were used: a manual epithermal system called CT8 and a new pneumatic epithermal large-volume irradiation system (ELVIS).Both these systems are lined with 1 mm thick cadmium and have epithermal-neutron fluxes of 2.8 x 1014 n m-2 s-' and fast-neutron fluxes of 2 x 1015 n m-2 s-1. Gamma-ray Spectrometry All the samples and standards were counted on a Ge(Li) detector [full width at half maximum (FWHM): 1.8 keV, peak/Compton ratio: 36.3 and efficiency: 8.l%, at 1.33 MeV]. The gamma-ray spectra were measured with an ND6700 multichannel analyser. Results Evaluation of Analytical Errors Irradiation variations A set of twelve 1 g replicates of the synthetic rock standard was prepared in polyethylene containers (18 x 8 mm) and irradiated in the CT8 system to measure the combined effect of neutron-flux variation and the sample geometry. Another batch of synthetic rock standards was then prepared by the same procedure and sixteen 1 g replicates from that batch were used to measure the irradiation variation in the ELVIS.Counting geometry variations The spectrometry system at the reactor centre has a sample changer on which 12 samples can be counted automatically. Small plastic cups (51 mm diameter and 1 mm thick) are used for holding the sample containers over the detector. A slight variation (0.2 mm) in the thickness of these cups was found to contribute a 1% error to replicate variation, at 11 mm. The error was reduced by using those with minimum variation, and eliminated by counting samples at 60 mm from the detector. A second counting geometry error, which was reduced by counting samples at 60 mm, was due to the movement of the sample inside the container (i.e., the sample shape variation).This error was evaluated for those samples measured at 11 mm from the detector by counting a sample six times without shaking and six times with intermittent shaking. Evaluation of Sampling Constants When this work was started, only the core tube system, CT8, was available for epithermal-neutron activation, and CANMET had certified two reference ores: MA-1 and MA-2 (MA-lb and MA-2a were certified later, after their deple- tion). In order to avoid flux variation, two middle positions of CT8 were chosen and so a maximum of 12 capsules (18 X 8 mm) could be placed in them. Therefore, 12 replicates of four sample masses (1, 1.5,2 and 2.5 g) were prepared to carry out the replicate analyses. Replicates larger than 2.5 g could not be irradiated because the irradiation container (18 X 8 mm) only held a maximum of 2.5 g of powdered rock. All the samples were irradiated for 7.5 h. By the time MA-lb and MA-2a were certified, the ELVIS had also been installed. Therefore, two sample masses, 1 and 10 g, were chosen to carry out the analyses on MA-lb and MA-2a. The samples were prepared in containers measuring 18 x 8 mm and 22 X 35 mm, respectively. The capsules were sealed thermally to avoid leakage during pneumatic transfer. Sixteen 1 g replicates were irradiated for 1 h, and sixteen 10 g samples were irradiated for 15 min, sequentially.

ISSN:0003-2654    

DOI:10.1039/AN992170230a

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, MARCH 1992, VOL. 117 23 1 Sir Alan Walsh-The Scientist and the Man P. L. Larkins CSIRO, Division of Materials Science and Technology, Locked Bag 33, Clayton, Victoria 3 168, Australia I would like to start by saying that I am delighted to have been given the oppor- tunity to participate in this presentation of the inaugural CSI-Award to Sir Alan Walsh. I believe that it would be difficult to find a more fitting recipient of this award and I congratulate those who were responsible for this decision. I would like to present to you, briefly, my view of Alan’s work and its impor- tance, and also to give some personal views of Alan derived from working with him for nearly 10 years prior to his retirement in 1976 and in a less formal association since then. Various details of Alan’s early years have been recorded in the literature’-3 so I will give only a very brief summary.Alan was born in Lancashire in England in 1916 and was one of a family of four children; one sister and two brothers. He was educated in England at the Danven Grammar School and then at Manchester University where he studied physics, specializing in X-ray crystallography. He commenced his scientific career in 1939 with the British Non-Ferrous Metals Association working on spectrochemical methods of analysis, and in the short period up to the end of the war he had become a recognized expert in this field, particularly in relation to source units for arc and spark spectrography . In 1946 Alan joined the CSIR (later CSIRO) in Australia as the first member of the Spectroscopy Group which was being formed in the Chemical Physics Section of the division of Industrial Chemistry.He was appointed to carry out research in optical spectroscopy, especially infrared (IR), and he arrived in Australia in April 1947 to commence work in this area. By 1951 he had made a substantial contribution to instrumenta- tion in this field by inventing and patent- ing a double-pass (multiple) monochro- mator4 which gave increased resolution and decreased stray light. A commercial version of this instrument was produced soon after by Perkin-Elmer under licence to CSIRO and production continued for many years. Thus even prior to his work on atomic absorption spectroscopy Alan had established himself as an extremely capable and inventive spectroscopist.Although Alan continued his work and interest in IR spectroscopy until about 1958, the invention of atomic absorption spectroscopy began with a thought which occurred to him one Sunday in March 1952 while he was working in his garden. In this regard he is in company with one of the previous great physicists, Sir Isaac Newton, of whom it is reported that he came to a realization of the laws of gravitation while watching apples falling from trees. Perhaps there is a moral in this; that those among us who aspire to greater things should spend more time gardening. In Alan’s case the realization that the measurement of atomic absorp- tion constituted a possible new method of analysis must have made him quite excited as he then went to the telephone to discuss his new insight with one of his colleagues.His initial attempt at measuring the absorption by atoms in a flame was successful but the more difficult task of convincing the rest of the world of the value of the technique was only just beginning. In fact, when he then demon- strated his results to some of his col- leagues their response was ‘well, so what?’.5 Alan’s initial papers on this topic are quite remarkable, not only because the details of the instrumenta- tion which he proposed are essentially those which are still in use today, but also because in those early papers he pro- posed many of the other variations and developments of the technique which have since been investigated either at CSIRO or by others. Some examples of these techniques are cathodic sputtering for sample atomization, resonance detec- tors and selective modulation.It is interesting to note that in his first paper6 Alan even referred to the possible use of a (vacuum) furnace for sample atomiza- tion, however no work on furnaces was carried out at CSIRO. In regard to the basic technique, Alan has written’ that he ‘had the great good fortune to select flames for atomization and hollow cathode lamps for light sources’. In addition he had used an a.c. detection system to avoid problems from flame emission. I believe that all these choices were not the result of good luck but arose from a thorough understanding of the various possible light sources and atomization and detection systems. This understanding had been gained during his earlier work on arc and spark emis- sion and on IR and Raman spectroscopy.Perhaps the only piece of good fortune was the fact that he had the opportunity to carry out extensive work in both these fields and had a keen interest in, and understanding of, the instrumentation associated with these techniques. Closing the gap between the initial232 thought and the final product of commer- cial standard required extensive work on the part of Alan and the group that he gathered to work on the project. Devel- opment of each of the main components of the atomic absorption instrument required almost a separate research project for each component and the work involved could be discussed at length, but I will indicate the size of the project by reference to the work on light sources.The truly creative part of this work was the initial realization that the problem of the narrow width of flame absorption lines could be overcome by the use of a light source with an even narrower emis- sion line. This represented a substantial departure from existing absorption tech- niques which used continuum light sources combined with a monochroma- tor to provide the required spectral bandwidth. In his Raman spectroscopy work Alan had worked with microwave lamps, and his initial experiments with atomic absorption had involved laboratory dis- charge lamps. While either of these types of lamps could have been chosen for further development he realized that neither would be capable of providing for the elemental coverage inherent in the technique itself. Instead he chose to base further work on the hollow cathode lamp.This was not a trivial decision since, at that time, hollow cathode lamps were generally made by the scientists using them and had only short lifetimes. The aim of the work at CSIRO was to develop these lamps in a sealed form with a reasonable lifetime and to be able to make them for all the elements accessible to the atomic absorption technique. This aim was eventually achieved and the wisdom of the initial choice of the hollow cathode is demonstrated by the fact that they are still the main type of light source used in atomic absorption spectroscopy. Having developed the sealed hollow cathode lamp, work in this area was not abandoned. In association with Jack Sullivan,7 Alan proceeded to develop a modified form of this lamp, which they called a high-intensity (or boosted-out- put) hollow cathode lamp.This modified lamp had the advantages of higher inten- sity combined with narrow linewidths but in this work they were too far ahead of their time. Some of these lamps were produced commercially for a few years in the late 1970s but then interest waned. However, developments in atomic flu- orescence and the introduction of the carbon furnace revived the need for more intense light sources and a more highly developed version of this lamp is now in production by the Australian firm, Pho- tron Pty. Ltd., and is meeting with rapidly growing commercial success. I first became aware of AAS in the early 1960s and I was very impressed. This technique did for inorganic analysis what chromatographic methods, and gas chromatography in particular, had done for organic analysis.Here was a tech- nique which could be used for an enor- mous range of sample types with little or no pre-treatment other than that required to bring the sample into solu- tion. This provided an enormous increase in productivity, as some analy- ses which required a day or more using previous techniques could now be carried out in less than a minute. Apart from the benefit to analytical chemists worldwide which came from the development and promotion of AAS, there were, and continue to be, real and substantial benefits to Australia which result from this work having been carried out within CSIRO. A cost benefit analy- sis carried out in 19698 conservatively estimated the value to the country to that date to be $20-$23 million. An on-going benefit is the fact that this work resulted in the establishment within Australia of two firms which now rank second and third in the world in production of atomic absorption spectrometers.Although there were some small instrument firms operating previously, the manufacture of AAS instruments represented the real birth of the scientific instrument industry in Australia. The benefits from AAS, however, are not all counted in economic terms. Very early in the development of atomic absorption a 7 year old boy had been undergoing treatment in a Sydney (Aus- tralia) hospital for extensive burns. Dur- ing the course of his treatment he devel- oped convulsions and seemed likely to die. An early atomic absorption unit was used to measure magnesium in his blood and this was found to be very low.Treatment with magnesium salts stopped the convulsions and he recovered com- pletely.9 Prior to the introduction of atomic absorption the determination of magnesium in blood was very difficult. Moving now to Alan himself, I believe that perhaps the most important personal characteristic which he brought to his work was enthusiasm. As those working in science will know, the best scientists are not detached observers, but rather they have a keen, almost passionate, involvement in their work and the de- velopment of their ideas, and promote them enthusiastically to their colleagues. In addition to enthusiasm, of course, one has to have something to be enthu- siastic about.In Alan’s case this was not a problem as he often came into the laboratory with new ideas to discuss or new suggestions to overcome problems in current work. In fact there was one memorable occasion when some work was being carried out on a sputtering- fluorescence technique. Alan made a suggestion which it was estimated would improve the results by a factor of about two. He returned to his office but came back a while later with another sugges- tion to give another factor of two ANALYST, MARCH 1992, VOL. 117 improvement. By lunchtime it was esti- mated that he had been back 15 times and simple mathematics indicated that the total improvement resulting from his suggestions should be 2 to the power of 15, i.e., about 32000. Actually, many of the ideas were useful but the improve- ments never reached the estimated figure.Not all of Alan’s ideas fell on receptive ears, however. Alan has occa- sionally related a story concerning a laboratory assistant who worked for him early in the AAS project. Sometime after this person had left CSIRO, Alan was looking through her note book and on one page found the cryptic comment ‘Boss suggests try . . .’, followed by some results. On the next page was the equally cryptic comment ‘Didn’t work’. Some pages on was another note, ‘Boss sug- gests try . . .’, more results and then ‘Didn’t work either’. Of Alan’s various ideas for improve- ment of modification of atomic absorp- tion or related methods, none have met with the success of the original idea, but this is not surprising.The basic simplicity and broad range of application of AAS more than satisfied most analytical requirements for many years. Although some of his ideas were aimed at problems which are now either much reduced in importance or no longer exist, others, such as sputtering-atomization and boos- ted hollow cathode lamps (as mentioned earlier) are now having a renaissance and may well see further development in the future. Another characteristic which stood out in Alan’s approach to his work was the desire to keep it simple. This simplicity was obvious in most of the equipment depicted in the early papers on the subject, and also in developments in areas such as selective modulation. This latter technique effectively put the func- tions of both the light source and monochromator within the lamp enve- lope.Unfortunately, simplicity and ver- satility do not often go together and generally users have opted for versatility with its related complexity. Other characteristics which made it a pleasure to work with Alan were his tolerance and his sense of humour. In my early days at CSIRO as a relatively young scientist, there were times when I made suggestions or offered opinions which were based on inadequate knowledge. I was never ridiculed but mostly had my ideas discussed and from this I learnt much and with little pain. Alan has many humorous stories to tell of the early days of AAS and some of these have appeared in his written accounts of those times.5 During his career Alan has received many honours and awards. I will not try to list them all but among the more prestigious are: being made a Knight Bachelor in 1977, and election to Fellow- ship of the Royal Society and Foreign membership of the Royal Academy ofANALYST, MARCH 1992, VOL.117 233 Sciences, Stockholm. Among his many medals are the Royal Medal of the Royal Society, the Analytical Division of The Royal Society of Chemistry Robert Boyle Medal in Analytical Chemistry, the Talanta Gold Medal and the Maurice Hastler Award of the Society for Applied Spectroscopy (USA). All the honours and awards which he has received over the years have not altered his generous and friendly nature. In fact, he recently agreed to be the subject of a young boy’s school project and readily made the time available to be interviewed. As the young lad noted in the introduction to his report, despite ‘his achievements . . . he still doesn’t get big headed’. In finishing I would like to add a final thought, We are, of course, here to honour Sir Alan Walsh, but it is often said that behind every great man is a great woman and I believe that this is true also for Alan. It would be difficult to find a warmer, friendlier lady than Lady Walsh, Audrey to all her many friends, and I have no doubt that she has been an enormous help to Alan throughout his career. Perhaps this is the area of his life in which he had great good fortune. References Walsh, A . , Chimica, 1980, 34, 427. Willis, J . B . , Hisr. Rec. Ausr. Sc., 1988, 7 , 153. Annual Report, CSIRO Division of Chemical Physics, 1976/77. Walsh, A . , Aust. Phys., 1990, 27, 164. Walsh, A . , Anal. Chem., 1974,46, 698A. Walsh, A., Specrrochim. Acra, 1955, 7 , 108. Sullivan, J . V., and Walsh, A . , Spectro- chim. Acta, 1965,21,721. Brown, A . W., CSIRO Industrial Research News, No. 76, July 1969. Willis, J . B . , Specrrochim. Acra, Parr B, 1980, 35, 653.

ISSN:0003-2654    

DOI:10.1039/AN9921700231

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, MARCH 1992, VOL. 117 233 Atomic Absorption Spectroscopy-Present and Future Aspects Ralph E. Sturgeon Institute for Environmental Chemistry, National Research Council of Canada, Ottawa, Ontario KIA OR9, Canada This XXVII Colloquium Spectroscopi- cum Internationale has chosen to honour Sir Alan Walsh with its first CSI-Award for major scientific contributions to analytical spectroscopy. It is equally an honour and a great privilege to partici- pate in this event and I extend my congratulations to Sir Alan, the recog- nized 'Father of AAS'. Although Sir Alan has published widely in areas of atomic, infrared and Raman spectroscopy, he is universally noted for his pioneering contributions in atomic absorption spectrometry (AAS). Since the initial inception of the concept, as revealed in his landmark paper of 1955,' Walsh perceived the significance of this technique, which would revolu- tionize analytical atomic spectroscopy, and pursued it with the conviction neces- sary to establish it as an acceptable methodology .2 As an instrumental method it has had, until recently, few equals in popularity: as of 1986, AAS was ranked the most significant advance to occur in analytical chemistry in the past 50 years.3 Recent market projections4 suggest a 3.8% sales increase for AA spectrometers in 1991, to be surpassed for the first time by ICP-AES purchases.What does the future hold for AAS? This question has been addressed numerous times in the past2.5-10 and I will attempt to examine this perspective once again. This exercise is most often indulged in with techniques which have been deemed to have evolved through at least several of the latter 'seven stages of instrument develop- ment''() and may be presently residing in the age of senescence.Having already celebrated its 'silver jubilee' more than a decade ago," it certainly merits broad acceptance. The major challenge facing the future of AAS stems from increased competi- tion from newly emerging or 'redis- covered' (e.g., glow discharge) spectro- scopic techniques. Its continued viability will only be assured through successful evolution and adaptation of more pro- ductive instrumen tation. In comparison with other popular state-of-the-art spectrochemical tech- niques, AAS proffers a number of attrac- tive and unique features for routine analyses as well as fundamental investi- gation,",12 not the least of which are its competitive cost per analysis, high detec- tion power [for electrothermal AAS (ETAAS)] and simplistic instrumenta- tion.It is well recognized, however, that the major shortcoming is sample throughput: AAS is, by design, a 'single- element at a time' technique. This can be attributed primarily to the source-detec- tor arrangement and to some extent to the atomizer. If this problem is to be addressed, major changes/modifications will have to be implemented to have any impact on these areas. Current inter- national research efforts have identified and explored a number of options and these will be the target of discussions of this text. Flame AAS (FAAS) suffers most acutely from competition with induc- tively coupled plasma atomic emission spectrometry (ICP-AES).The latters' multi-element capability (fast sequential and simultaneous) and detection power that rivals or surpasses FAAS, especially for the refractory elements, have placed FAAS in a vulnerable position. Instrumentation for FAAS has altered little since Walsh's first description of the method.' Since the introduction of the dinitrogen oxide-acetylene flame by Wil- lis in 1965, there has been no subsequent major advance in flame methods, 'which appear to have reached a plateau of development'.13 Although this statement was made by Walsh more than a decade ago, it remains valid today. A limited amount of research continues to be invested in the design of more efficient burner heads14 but the majority of interest in the fabrication and characteri- zation of new nebulizers and spray cham- bers appears to lie with ICP users.Automation of commercial FAAS instruments is currently well developed, permitting some 500 determinations per hour. However, as has been noted,15 such instruments can be described as multi-sample rather than multi-element in that they repetitively determine the same element in all samples prior to quantifying the next element. An instrumental approach to multi-element capability has been described's using conventional hollow cathode line sources having the capacity for an estimated 1200 determinations per hour-very competi- tive with sequential ICP based instrumentation. Although automation of instrumentation via onboard micro- processor control has revolutionized per- formance and (unattended) sample throughput of FAAS, as well as other atomic spectrometric techniques, it is hoped that the intelligent instrument of the future will go beyond these narrow confines and actively participate in the implementation of quality assurance/ quality control of the data. 16 Although unfortunately still con- sidered within the realm of a laboratory research tool, the wavelength modulated continuum source based instrument con- ceived by O'Haver and colleagues pro- vides an attractive and viable approach to true multi-element AAS when coupled to a high-resolution polychromator. 17.18 When interfaced to photodiode array detectors the optics are simplified by omission of the wavelength modulation19 (as well as the need for multiple PMTSs).Currently, this approach is limited in scope to those elements having reso- nance lines lying above 280 nm because234 ANALYST, MARCH 1992, VOL. 117 of the poor source intensity at shorter wavelengths. This, or course, precludes application to the measurement of many elements of current environmental interest. This limitation may be lifted as a result of promising recent studies aimed at pulsing the continuum source to high intensity levels, thereby boosting the UV output. Moulton et aZ.20 reported a sig- nal-to-noise ratio (S/N) increase of 1.4- fold at 241 nm by using a pulsed con- tinuum source in conjunction with linear photodiode array detection. An improvement factor of 6.7-fold was noted over the case of PMT detection with a non-pulsed lamp.It is expected that significantly greater benefits in S/N will be reaped with larger pulse currents. An alternative approach to achieving the resolution needed for continuum source AAS is by application of inter- ferometry. Although a Fourier transform AA spectrometer provides all of the advantages of other continuum source dispersive systems, it can be subject to a multiplex disadvantage when a practical free spectral range is desired and, at high resolution, suffers from long scan times .21 How will such research impact on the practising analyst and the market for FAAS? The answer of course is little, unless a commercial instrument becomes available. Despite the acknowledged benefits of multi-element capability, fas- ter throughput, comparable detection power and greater dynamic range, the increased complexity of utilizing a high- resolution polychromator offsets the cur- rent cost advantage cited for FAAS over its ICP-AES competitor. This is not the whole picture, however, because such an instrument would also find application with the graphite furnace and this is the area that could revolutionize the use of AAS.A cursory examination of current analytical spectroscopic literature reveals that it is the graphite furnace atomizer that is of prime interest for further development (not only for AAS but as an atomizer for use in a variety of atomic and mass spectroscopic instrumenta- tion). The introduction of the graphite fur- nace by L’vov in 195922 was eventually to elevate AAS to a foremost position amongst preferred techniques for ultra- trace analysis.The reason was clear: all of the inherent advantages of AAS were coupled to a highly efficient atomization device .23 Significant improvements in signal processing, furnace design and operation have occurred in the last decade and many of these are now embodied in the concept of the stabilized temperature platform furnace (STPF) pioneered by Slavin and co-workers.24.25 The remarkable success of this relatively interference free technique has permit- ted extension of the procedure to the analysis of solids and slurries26 and has advanced to the point where the concept of absolute (standardless) analyses may be realistically entertained.27.28 With the recent release of a commercial graphite furnace atomizer (Perkin-Elmer) based on the design of the spatially isothermal cuvette of Frech et aZ.,29 analysts are expected to have even greater freedom from matrix interferences as well as reduced spectral background and memory effects.Of course, matrix effects cannot be completely eliminated even for constant temperature atom- izers.30 Unfortunately, graphite furnace (GF) techniques are also characterized by the single-element-at-a-time AAS syndrome which was further compounded by the need to establish individual atomization programmes optimized for each element or a few broad classes of elements-a situation which turned out to be more inflexible than that encountered by the choice of two different flames in FAAS. Conventional single-channel GF instru- ments usually cannot achieve more than 20-30 determinations per hour in a multi- sample approach.This rate may be increased up to 100 per hour if the furnace cycle time is reduced to a mini- mum using such measures as hot injec- tions, elimination of the drying and/or char stage and reducing the delay between injections by the autosampler.31 Bank et aZ.32733 recently demonstrated the feasibility of flow injection thermo- spray deposition for ETAAS, which boosted potential throughput into the 150-200 per hour range while retaining sensitivity, precision and the use of pl volumes. The excellent scope for the correction of high non-specific back- ground absorption offered by Zeeman- effect systems serves to more easily implement such modifications to the thermal pre-treatment of the sample.Although commercially available 2 and 4 channel instruments (Hitachi and Thermo Jarrell Ash) could serve to increase the multi-sample efficiency of the technique further, increased compe- tition from the now well established field of ICP mass spectrometry (ICP-MS) will eventually require that ETAAS adopts a true multi-element approach to survive. In this respect, the shortcomings of AAS highlighted by Hieftje,’ i.e., those resident in the hollow cathode light (HCL) source and the atomizer, need to be addressed and promising alternatives pursued. Multi-element AAS necessitates a multi-wavelength source and compatible detector. Systems based on multiple HCLs rapidly become impractical with more than only a few elements and with ETAAS any attempt at a rapid sequen- tial measurement will fail.Only con- tinuum sources and cheap tunable lasers inherently meet the necessary require- ments. Dispersive, rather than inter- ferometric means, should be considered as a consequence of the cost and prac- tical limitations associated with the latter.7312J1 Continuum source based approaches are presently the most attractive. Those employing high-resolution poly- chromators with PMT detectors and wavelength modulation have been shown to provide exceptional performance for elements having resonance lines above 280 nm. Here detection limits are gener- ally within a factor of 2-3 of those obtained with line sources, background correction is rapid and accurate and dynamic range can be extended to cover 4-6 de~ades.3~ As noted earlier, useful access to resonance lines lying below 250 nm now appears promising using pulsed continuum sources20~35 but extensive work will be required to evaluate this comprehensively.Schmidt et aZ.35 recently described such an approach, based on an echelle spectrometer and a charge coupled linear array device as detector. Electrothermal AAS detection limits achieved for Cd and Pb at 228.8 and 283.3 nm, respectively, were within a factor of two of their line source counter- parts. The coupling of pulsed continuum sources and diode array detectors should also find application in the domain of coherent forward scattering wherein more intense sources should improve performance. This technique has already demonstrated useful multi-element results with commercial atomizers and 4-6 decades of linear range.36 Hergenroder and Niemax37 recently demonstrated the feasibility of multi-ele- ment ETAAS using temperature and diode current controlled semiconductor diode lasers as sources.With modulated diode laser power (using electro-optic KDP crystals) the signal measured with a photodiode in a non-dispersive system can be subjected to Fourier analysis to separate multiple channels. Rapid square wave diode current modulation permits absorption measurements to be made on/off line for simultaneous back- ground correction or in the wings of the profile for extended linear range. Com- pact multichannel capability may be realistically achieved using optical fibre technology. The availability of diode lasers covering a wider wavelength range is anticipated. Successful solutions to the optical aspects of the multichannel AAS chal- lenge highlight the remaining deficien- cies resident in the atomizer.Presently, separate optimization of thermal parameters is generally required for each element due to either pre-atomization losses or incomplete atomization. Three solutions merit consideration: the quest for and application of a ‘universal’ chem- ical modifier; the elimination of the thermal pre-treatment stage and the application of new atomizers. Multi-element analyses may be heavily dependent upon the use of chemicalANALYST, MARCH 1992, VOL. 117 235 modification techniques in that compro- mise thermal conditions will be utilized. Reduced palladium appears to be emerg- ing as a potentially universal modifier that will be useful for this purpose.38 It should be noted that the need for chem- ical modification techniques should be verified before use on a sample.Manning and Slavin31.39 have presented examples of systems in which adequate perfor- mance can be achieved by eliminating the char stage and modifier completely. The larger background which normally oc- curs is then easily handled with a Zee- man-based system. It is easier to con- ceive of universal compromise conditions in such circumstances. ‘If atomic absorption methods are to be substantially improved, it seems ines- capable that the advances can only result from improved methods of atomization’. This statement was penned by Walsh in 1980.13 With the conventional GF this has included implementation of ideas fostered by L’VOV,~~ i.e., vaporization of samples from a platform placed within the furnace (on which STPF techniques are now based), from a probe subse- quently inserted into an isothermal fur- nace41 and by rapid heating achieved through capacitive discharge.42 The last has proved to be too difficult to utilize routinely because of materials require- ments whereas the performance of the probe technique can generally be matched through application of the simpler STPF concept.43 Similarly, the spatially and temporally isothermal two- step atomizer described by Frech and Jonsson,44 while deemed too complex to justify routine application,45 may provide an excellent vehicle for implementation as an atomizer for multi-element AAS. This configuration is amenable to auto- mation and lends itself more easily to the establishment of compromise conditions.It has been suggested that use could be made of non-thermal atomizers, in par- ticular the rare gas sputter systems which are advantageous in producing a low background and high yield of atomic vapour. A version of the popular glow discharge lamp (Atomsource) has been introduced into the marketplace and configured so as to optimize production of ground-state atoms in the analytical volume.*5 In such systems there is a greater conformity between the composi- tion of the sample and the vapour being analysed, such that matrix effects may be greatly reduced and samples having a range of compositions can be analysed with the same working curve. ‘To date all sputtering work has been concerned with steady-state systems.Would it not be worthwhile considering the use of cathodic sputtering in association with the “total vaporization” method evolved by L’vov?’. This remark by Walsh’3 follows from his early work on sputtering at CSIRO (Australia) and recognizes the significance of L’vov’s approach which has been so successful with the GF. Recent studies by Chakrabarti et aZ.46 confirmed the benefits of transient sput- ter atomization of discrete samples for which absolute detection limits rival those of conventional ETAAS. Although an evaluation of the effect of the matrix is awaited, it is tempting to speculate that such an approach might present an attractive source for multi- element AAS. Non-conductive samples may likely be sputtered via r.f.dis- charges.47 A hurdle to be surmounted in the quest for multi-element AAS is the limited linear range (currently 2-4 decades) , which makes it necessary to undertake multiple dilutions in order to cover the variation of elemental concen- trations present in a typical sample. Several means have been suggested to extend this figure of merit, the most promising working concept for commer- cial instrumentation being use of three- field a.c. Zeeman modulation48 which readily achieves a 5-10-fold wider dynamic range. Alternatively, instru- mentation based on the ‘Smith-Hieftje’ pulsed HCL background correction approach may take advantage of a corre- sponding multi-level current pulse to elicit different source profiles and there- by extend linear range.With continuum source based instruments, the dynamic range can cover 4-6 decades by making use of information in the line wings. Thus, it appears that this obstacle can be easily circumvented with existing tech- nology. The demand for reliable analytical data at ever decreasing concentration levels has outstripped current detection capabilities of ETAAS for many ele- ments. It is for this reason that method- ology for enhancing detection power is evolving at a rapid pace. Such approaches include conventional off-line matrix separation and preconcentration schemes as well as in situ trapping of volatile forms of elements [e.g., hydrides , Ni( C0)4, Pb( C2H5)4] .49 The latter are ultratrace techniques which make specific and profitable use of the GF and are ripe for automation.Throughput, even in the single-ele- ment mode, can be considerably en- hanced utilizing flow injection tech- niques to speed both calibration proce- dures and sample analyses. On-line sam- ple preparation systems for matrix management and analyte preconcentra- tionso751 will have substantial impact on all areas of analytical atomic spectro- scopy in the coming years. More difficult samples will be amenable to quantitation at lower analyte concentrations with greater speed, precision and accuracy. As these developments are likely to influence all instrumentation without prejudice, no relative gains can be claimed by AAS proponents. However, it is evident from the foregoing that greater attention must be paid to enhanc- ing the versatility of GF autosamplers.Software control should permit the user to program the timing and mechanical events associated with this process. It is clear that it should be possible to provide AAS users with multi-element capability using present technology. In this regard, current research directions suggest the suitability of an image detec- tor approach in combination with a pulsed continuum source and a GF or sputtering cell. Means will be devised for coping with the voluminous amount of data generated by the necessary two- dimensional detectors if a significant wavelength range is desired.52 However, in the final analysis, ‘it is unlikely that AAS would, in its over-all capability, surpass those techniques with which it is now competitive’7 (i.e., ICP-AES and -MS).Of course, it is not necessary, performance wise, for future AAS instruments to surpass that of other spectrometric techniques in order to remain viable. Quite apart from its sus- tained contributions to fundamental and diagnostic studies of atomic systems, AAS will continue to be used in a routine analytical capacity. When methods are compared for ultratrace capability, the power of detection and accuracy or reliability become the most important criteria.53 Inductively coupled plasma AES is gradually replacing FAAS and this trend will accelerate as the cost of ICP equipment continues to decline and the demand for multi-element capability rises in the face of environmental chal- lenge and legislation. Electrothermal AAS, however, is currently ‘holding its own’ and will continue to act in a complementary rather than redundant manner to enhance the capability of alternative spectrometric techniques.It is the acknowledged ‘benchmark’ against which all other commercial- and labora- tory research-based atomic spectro- metric techniques (including ICP-MS, LEAFS, LEI, CFS, FANES and FAPES) are currently, and will continue to be, gauged. The decline noted in the total number of AAS publications in the last 5 years7 in no way construes the demise of this technique-it only serves to reflect its broad and unchallenged acceptance. The remarkable fact that publications continue in this already mature discipline reflects the substantial interest of researchers and users alike. Of course, one of the principal advan- tages of absorption measurements is that they are amenable to undertaking abso- lute analyses.This subject has been raised earlier by Ran1154 for the flame and by L’vov27 for the furnace. It would be no great surprise to find analysts using this approach in future, at least for semiquan- ti ta tive work. We are indebted to Sir Alan Walsh for his many contributions to the birth and growth of this fascinating and ubiquitous236 ANALYST, MARCH 1992, VOL. 117 analytical tool. The question posed by 18 Harnly, J. M., Kane, J. S., and Miller-Ihli, 36 Hermann, G., Jung, M., Lasnitschka, G., him2 some 17 years ago: ‘AAS-Stag- N. J.. Appl. Spectrosc., 1982,36, 637. Moder, R., Scharmann, A., and Zhou, X., nant or Pregnant?’, can still be answered 19 Jones, B. T., Mignardi, M.A., Smith, Spectrochim. Acta, Part B, 1990,45,763. with the Same retort . . . ‘the subject has B. w . , and Winefordner, J. D., J . Anal. 37 Hergenroder, R., and Niemax, K., not really been stagnant but merely At. Spectrom., 1989,4,647. Spectrochim. Acta, Part B, 1988,43,1443. 20 Moulton, G. P., O’Haver, T. C., and 38 Schlemmer, G., and Welz, B., pregnant and has now given birth to new Harnly, J. M., J . Anal. At. Spectrom., Spectrochim. Acts, Part B, 1986,41, 1157. 1989,4, 673. 39 Manning, D. C., and Slavin, W., offspring’. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 References Walsh. A., Spectrochim. Acta, 1955, 7 , 108. Walsh, A., Anal. Chem., 1974,46, 698A. Braun, T., Fresenius’ Z. Anal. Chem., 1986,323, 105. Howard, B.. Am. Lab., 1991, Jan., 66. Koirtyohann, S.R., Anal. Chem., 1980, 52,736A. Slavin, W., Trends Anal. Chem., 1987, 6, 194. Hieftje, G. M., J. Anal. At. Spectrom., 1989,4, 117. Sturgeon, R. E., Fresenius’ Z. Anal. Chem., 1990, 337, 538. Slavin, W., Anal. Chem., 1982, 54,685A. Koirtyohann, S. R., and Kaiser, M. L., Anal. Chem., 1982,54, 1515A. Boumans, P. W. J. M., Spectrochim. Acta, Part B, 1980, 35,637. Hieftje, G. M., Fresenius’Z. Anal. Chem., 1990,337,528. Walsh, A., Spectrochim. Acta, Part B, 1980,35, 639. Willis, J. B., Sturman, B. T., and Frary, B. D., J. Anal. At. Spectrom., 1990,5,399. Bernhard, A. E., and Kahn, H. L.. Am. Lab., 1988, June, 126. Hieftje, G. M., Spectrochim. Acta, 1990, 44 (Spec. Suppl.). 113. Zander, A. T., O’Haver, T. C., and Keliher, P. N., Anal. Chem., 1976, 48, 1166. 21 Glick.M. R.. Jones, B. T., Smith, B. W., and Winefordner, J. D.. Anal. Chem., 1989, 61, 1694. 22 L’vov, B. V., Spectrochim. Acta, 1961,17, 761. 23 Falk, H., and Tilch, J., J. Anal. At. Spectrom., 1987, 2, 527. 24 Slavin, W., Manning, D. C., and Canrick, G. R., At. Spectrosc., 1981, 2 , 137. 25 Slavin, W., andcarnick, G. R.. Am. Lab., 1988, Oct., 88. 26 Epstein, M. S., Carnrick, G. R., Slavin, W., and Miller-Ihli, N. J., Anal. Chem., 1989, 61, 1414. 27 L’vov, B. V., Spectrochim. Acta, Part B, 1990,45, 633. 28 Slavin, W.. and Carnrick, G. R., Spectrochim. Acta, Part B, 1984, 39, 271. 29 Frech, W., Baxter, D., and Hutsch, B., Anal. Chem., 1986, 58, 1973. 30 Frech, W., Cedergren, A., Lundberg, E., and Siemer, D. D., Spectrochim. Acta, Part B, 1983, 38, 1435. 31 Slavin, W., Manning, D. C., and Carnrick, G. R., Spectrochim. Acta, Part B, 1989, 44, 1237. 32 Bank, P. C.,de-Loos-Vollebregt, M. T. C., and deGalan, L., Spectrochim. Acta, Part B, 1988,43,983. 33 Bank, P. C. ,de-Loos-Vollebregt, M. T. C., and de Galan, L., Spectrochim. Acta, Part B, 1989, 44, 571. 34 Harnly, J. M., Fresenius’ Z. Anal. Chem., 1986,323, 759. 35 Schmidt, K. P., Becker-Ross, H., and Florek, S., Spectrochim. Acta, Part B, 1990, 45. 1203. Spectrochim. Acta, Part B, 1988,43, 1157. 40 L’vov, B. V., Spectrochim. Acta, Part B, 1978, 36, 153. 41 Littlejohn, D., Cook, S., Durie, D., and Ottaway, J. M.. Spectrochim. Acta, Part B, 1984,39, 295. 42 Chang, S. B.. Chakrabarti, C. L., Prog. Anal. At. Spectrosc., 1985, 8, 83. 43 Wu, S., Chakrabarti, C. L., and Rogers, J. T., Prog. Anal. Spectrosc., 1987, 10, 111. 44 Frech, W., and Jonsson, S., Spectrochim. Acta, Part B, 1982,37, 1021. 45 Lundberg, E., Frech, W., Baxter, D., and Cedergren, A., Spectrochim. Acta, Part B, 1988,43,451. 46 Chakrabarti, C. L., Headrick, K. L., Hutton, J. C., and Bertels, P. C., Spectrochim. Acta, Part B, 1991, 46, 183. 47 Duckworth, D. C., and Marcus, R. K., Anal. Chem., 1989,61, 1879. 48 de Loos-Vollebregt, M. T. C., Koot, J. P., and Padmos, J., J . Anal. At. Spectrom., 1989,4, 387. 49 Sturgeon, R. E., Spectrochim. Acta, Part B, 1989,44, 1209. 50 Karakaya. A.. andTaylor, A., J . Anal. At. Spectrom., 1989,4, 261. 51 Fang, Z., Sperling, M., and Welz, B., J . Anal. At. Spectrom., 1990, 5 , 639. 52 Kolczynski, J. D., Radspinner, D. A., Pomeroy, R. S., Baker, M. E., Norris, J. A., and Denton, M. B., Am. Lab., 1991, May, 48. 53 Tolg, G., Analyst, 1987, 112, 365. 54 Rann, C. S., Spectrochim. Acta, Part B, 1968, 23, 827.

ISSN:0003-2654    

DOI:10.1039/AN9921700233

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

236 ANALYST, MARCH 1992, VOL. 117 Reflections and Comments from Sir Alan Walsh, FRS In a brief speech following the presenta- tion of the inaugural CSI-Award, Sir Alan spoke of his delight and surprise on learning that he was to be the first recipient. The surprise was complete, since he had been totally unaware that such an Award had been proposed. He thanked Pat Butler, Peter Larkins and Ralph Sturgeon for their generous remarks which were in sharp contrast to the apathy and suspicion which greeted the first papers on atomic absorption spectroscopy in the 1950s. He wondered if the delayed impact of these early papers was partly due to them having originated from small and/or remote countries such as Holland, Australia, New Zealand and South Africa. The production in Australia in the late 1950s of ‘do-it-yourself kits’ which per- mitted the construction of the ‘working- man’s atomic absorption spectrometer’ led to rapid acceptance of atomic absorp- tion methods.Sir Alan paid high tribute to all those who took part in the design, Sir Alan and Lady WalshANALYST, MARCH 1992, VOL. 117 construction, marketing and operation of these cost-effective instruments. He felt quite sure that these many contributions had been influential in the decision to present the first CSI-Award to Australia! After the conference Sir Alan reflec- ted that it had been outstandingly suc- cessful. He considered that he had little expertise in most of the subjects being presented (a typically humble comment) but the standard of lecturing had been remarkably high and the discussions lively. The enthusiasm was sustained throughout the proceedings. The social events had been most enjoyable and all participants had appreciated the meet- ings held in remote but beautiful sur- roundings, which contributed to the con- ference being such a happy one. For he and his wife the conference had been a very special occasion. They had been overwhelmed by kindness and the conference organizers had spared no effort to make their visit to Norway a 237 particularly happy one. It had been especially good to see many old friends who they had not met for a long time. Sir Alan and Lady Walsh brought a great deal of pleasure to everyone at the conference, and for this we thank them and wish them good health and happiness for many years to come. We also hope it will not be too long before we meet them both again.

ISSN:0003-2654    

DOI:10.1039/AN9921700236

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, MARCH 1992, VOL. 117 237 Editorial-XXVll CSI, Norway This special issue of The Analyst consists of over 80 papers that were presented either as lectures or posters at the XXVII CSI held in Norway in June, 1991. In addition to the papers published here, there are another 66 papers published in the March issue of JAAS (our sister journal) that deal specifically with atomic spectrometry, making a total of over 140 papers published from this conference (out of a total of 210 submissions). This, I believe, is an indication that although some spectroscopic techniques may be on the decline, spectroscopy in general is still a very active growth area for research and development. All papers have been refereed to the usual high standards expected by our readers and authors, in fact The Analyst and JAAS are proud of the fact that we do not relax the rules or exercise leniency for primary papers presented at conferences.The Analyst also agreed to publish papers from the Pre-Symposium ‘Measurements of Radionuclides After The Chernobyl Accident’ and the Post-Symposium ‘Speciation of Elements in Environmental and Biological Sciences’. These symposia and, of course, the main meeting itself in Bergen were extremely successful and thoroughly enjoyed by all participants, both from an academic viewpoint and socially. The organizers are to be congratulated on providing excellent academic and social programmes. As mentioned by Professors Salbu and Steinnes in their introduction to the papers presented at the ‘Chernobyl’ meeting, very few data obtained as a result of the Chernobyl accident have actually been published.This important issue goes some way towards correcting this situation. However, as a result of the enormous upheavals and problems that have taken place in what used to be the Soviet Union, several of the proofs have not returned. We kept the deadlines open for as long as we possibly could (communication being a problem even before the reforms) but, of course, we had to close the issue at some point. The papers that are still outstanding will be published in forthcoming issues of The Analyst with appropriate footnotes. One thing that was very apparent at both the Pre- and Post-Symposia and the main meeting itself was that analytical chemistry now needs to broaden its horizons further, to include many other areas of research, and that analytical chemists together with scientists from various other disciplines should form interdisciplinary teams working across areas as diverse as speciation of metals in sea-water for toxicology studies and the determination of concentrations of radio- Three members ot the organizing committee of the ‘Chernobyl’ sym osium.L to R: Professor Brit Salbu, Dr Deborah Oughton and Prokkor Eiliv Steinnes nuclides in the environment. If this does not happen then each discipline will have its own definitions and standards that are totally incompatible with those from other disciplines. For example, at the speciation Post-Symposium analytical chem- ists and toxicologists could not even agree on the answer to the question ‘What is a species?’. Clearly, many scientists agree that interdisciplinary co- operation is probably the key to meaningful studies in many areas of scientific research.As will be seen from the variety of papers in this and forthcoming issues, The Analyst strongly supports the idea of including the diverse range of subjects that are now almost inextricably linked with analytical chemistry. We believe that this is an accurate reflection of the way analytical chemistry has expanded over the last few years and truly become ‘analytical science’. We hope you will find this issue provides interesting reading and will prove to be a good source of important (up-to-date and background) information for some time to come. Finally, the next CSI is to be held from Tuesday to Sunday, June 29th to July 4th, 1993, in York, UK.We hope to see you there and look forward to meeting our friends and renewing all the new acquaintances we made in Norway. Harp Minhas EditorThe XXVIII Colloquium Spectroscopicurn Internationale will be held in The University of York, United Kingdom June 29-July 4,1993 This traditional biennial conference in analytical spectroscopy will once again provide a forum for atomic, nuclear and molecular spectroscopists worldwide to encourage personal contact and the exchange of experience. Participants are invited to submit papers for presentation at the XXVIII CSI, dealing with the following topics: Basic Theory, Techniques and Instrumentation of- Applications of Spectroscopy in the Analysis of- Computer Applications and Chemometrics Laser Spectroscopy Environmental Samples Atomic Spectroscopy (Emission, Absorption, Fluorescence) Electron Spectroscopy Geological Materials Gamma Spectroscopy Industrial Products Mass Spectrometry (Inorganic and Organic) Methods of Surface Analysis and Depth Profiling Molecular Spectroscopy (UV, VIS, IR) Mtissbauer Spectroscopy Nuclear Magnetic Resonance Spectrometry Photoacoustic Spectrometry Raman Spectroscopy X-ray Spectroscopy Biological Samples Food and Agricultural Products Metals Alloys PLENARY AND INVITED SPEAKERS The scientific programme will consist of Plenary and Invited Speakers.To date the following scientists have accepted invitations to present keynote lectures: Phnary- Invited- M L Gross, Lincoln, NE R E Hester, York C L Wilkins, Riverside, CA J D Winefordner, Gainemdie, FL F C Adams, Antwerp F V Bright, Bufldo, NY J A Caruso, Cincinnati, OH B T Chait, New York, NY R Donovan, Edinburgh D E Games, Swansea D L Glish, Oak Ridge, TN P Hendra, Southampton F Hillenkamp, Munster J A Holcombe, Austin, 7X J Refher, Stanford, CT B L Sharp, Loughbotough M Sigrist, Zurich M Thompson, London J C Vickerman, Mmhester PRE- and POST-SYMPOSIA In connection with the XXVm CSI a number of symposia and workshops will be organized.EXHIBITION The conference will feature an exhibition of the latest instrumentation. ACCOMMODATION Accommodation has been reserved on campus and in the halls of residence, although hotel accomodation in York will be available if desired. SOCIAL PROGRAMME The scientific programme will be punctuated with memorable social events and excursions of scientific, cultural and tourist interest. The social programme is open to all participants and accompanying persons. For further information contact- THE SECRETARIAT XXVm CSI Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire LEll3TU, UK. Telephone: +44 (0) 509 222575; Fax: +44 (0) 0509 233163; Telex: 34319.

ISSN:0003-2654    

DOI:10.1039/AN9921700237

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, MARCH 1992, VOL. 117 239 Spectroscopy From the Hubble Space Telescope* Keynote Lecture Bruce E. Woodgate laboratory for Astronomy and Solar Physics, NASNGoddard Space Flight Center, Greenbelt, MD 20771, USA Early spectroscopic results from the Goddard High Resolution Spectrograph and the Faint Object Spectrograph on the Hubble Space Telescope (HST) are described, including detection of intergalactic material between the Earth and a quasi-stellar object, observations of a chemically unusual star with large overabundances of heavy metals and material surrounding a nearby star. Planned improvements to the HST by in-orbit interchange include correction for the spherical aberration and the provision of more capable instruments. Keywords: Hubble; space; ultraviolet; spectra; astronomy The Hubble Space Telescope was launched in April 1990 into a low Earth orbit, and shortly thereafter was found to have spherical aberration in its primary mirror.The image contains a diffraction-limited core with about 15% of the light within 0.25 arcsec diameter and 70% within 2 arcsec square depending on wavelength. While far from the planned capability, this is still useful for many imaging projects where the images have high contrast, such as the separation of stars in clusters on morphology studies,'-* particularly with the use of image deconvolution techniques, and for ultraviolet (UV) imaging, although many projects have been deferred until optical corrections have been made, as described below. The effect of spherical aberration on spectroscopy is somewhat less harmful than that on imaging, although critical spectroscopic projects on faint objects must be deferred.For brighter isolated objects, by using smaller apertures, the full planned spectral resolutions can be obtained, and the signal- to-noise recovered by taking longer exposures. Experimental Spectroscopic Instruments The spacecraft and instruments have been described in some detail.3 The two primary spectrographs are the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS); each uses 1 x 512 element photon- counting Digicon detectors. The GHRS has a choice of two apertures, 0.25 arcsec and 2.0 arcsec square, and nominal spectral resolving powers [ = wavelength/instrumental line width (full width at half maximum)] of 2000,20000 and 100OOO over the spectral range 115&3200 A.The FOS has a choice of 11 apertures and nominal spectral resolving powers of 250 and 1300 over the spectral range 1150-8OOO 8,. Results and Discussion Quasar 3C273 The quasar 3C273 is the nearest bright quasar, and the first one discovered, with a red shift z = 0.158, approximately 2 billion light years away z = [(l + v/c)/(l - v/c)]*.5 - 1 where v is the velocity with which the object is receding from the Earth as measured by the Doppler shift. Observations were taken with the FOS at a resolving power * Presented at the XXVII Colloquium Spectroscopicum Inter- nationale (CSI), Bergen, Norway, June 9-14, 1991. of 1300 (Bachall et al.4). The results are shown in Fig. 1. Three types of spectral features are seen. Strong broad red shifted emission lines of H Lyman alpha, C IV, C 111 and Mg I1 provide diagnostics for the quasar itself (marked Q in Fig.1). The 28 absorption lines are explicable on the basis of abundance, atomic physics and ionization considerations and are thought to be from the interstellar gas in our galaxy. The remaining seven absorption lines are all in the wavelength region between the H Lyman alpha lines from our galaxy and from the quasar (marked L in Fig. 1). They are a result of H Lyman alpha absorption from intergalactic clouds in line of sight to the quasar. Two of them are owing to very nearby gas, apparently inside the Virgo cluster, as they are at the correct red shift, and the Virgo cluster is between us and 3C273. These clouds are familiar as a result of ground-based spectroscopy of more distant quasars, where the Lyman alpha lines are red shifted to above 3000 8, with red shifts above z = 1.8.At very high red shifts these absorption lines are so numerous that they are called the Lyman alpha forest. For the stronger lines, other lines such as Lyman beta and higher lines of the Lyman series, and lines from heavier elements have been seen at the same red shift, confirming their identifica- tion. Thus, looking back into the early universe, it appears that intergalactic space was filled with these clouds, some down to a millionth of a galaxy in optical depth; from red shifts above z = 3 down to z = 2, the line density thins out. Before the UV spectroscopic observations from HST, extrapolations of the ground-based data to low red shifts of recent times had led to the expectation that there would be very few Lyman alpha forest lines.Only one or zero lines were expected towards 3C273. Observations were then taken with the GHRS, with higher resolving power and good signal-to-noise (Morris et al.5). The resolving power using the core of the point spread function was 15000. The spectra were deconvolved and smoothed, revealing 16 Lyman alpha lines including the two lines from the Virgo cluster; these 16 lines include those seen by the FOS. These observations, with indications from more recent obser- vations from other quasars, show that the number density is similar at low red shifts to that at z > 2, hence, whatever process was destroying the intergalactic clouds, stopped about 10 billion years ago, thus the clouds are still present.Chi Lupi Observations were made of this chemically peculiar star using the GHRS with the kchelle spectrograph at a resolving power of 87000 over a 10.4 8, range with a signal-to-noise of 96 (Leckrone et ~ 1 . 6 ) . Fig. 2 shows the 2 8, region around the Hg I1 absorption line at 1942.287 A. A spectrum from the240 6 4 2 x 3 = U .- w - Q p z 1 1 0.5 0 ANALYST, MARCH 1992, VOL. 117 (a) - 1200 1300 1400 1 500 1700 1800 1900 2000 2100 2200 1 I I I I I I I I J 2400 2500 2600 2700 2800 2900 3000 3100 3200 WavelengthA Fig. 1 UV spectrum of the quasar 3C273 taken by the FOS at a resolving power of 1300. Features seen are broad emission lines from the quasar (a), absorption lines from the interstellar medium of our galaxy and intergalactic H Lyman alpha lines (L) 2.0 I 1 into account configuration interaction in the atomic physics and possible unidentified line blends.Why do these extreme abundance variations occur? No known nuclear process at the centre of stars or supernovae can cause them. Current work is concentrated on radiatively driven diffusion processes in the outer layers of the star, with the lighter isotopes either being driven away from the star or being ionized into higher ionization stages. In the latter, the overabundance of the lighter isotopes would have to be extremely high in the higher ionization stages. I 1 I I 1941.3 1941.8 1942.3 1942.8 1943.3 WavelengthIA Fig. 2 A 2 8, region of the UV spectrum of the chemically peculiar star Chi Lupi (b), taken with the GHRS at a resolving power of 87000, showing the Hg I1 line at 1942.287 A.The Hg is overabundant compared with the sun by a factor of 105. A spectrum from the International Ultraviolet Explorer (IUE), with a resolving power of 12O00, is shown above (a) for comparison International Ultraviolet Explorer (IUE) satellite is shown for comparison. The shape and depth of this line were compared with theoretical models by Kurucz.7.8 It was necessary to alter the isotopic abundance ratios drastically compared with the Earth, Sun and interstellar space, where 204Hg is 7% of total Hg; on Chi Lupi it is 98.9%. Also, the total Hg is 1 x 105 times more abundant compared with hydrogen than in the Sun. Similarly, with the Pt I1 line at 1942.113 A, wavelength shifts of 3-8 m8, suggest isotope anomalies and large over- abundances compared with the Sun.Interpretation of the line strengths of the Mn I1 and Cr I1 lines at 1942.7 8, must take Beta Pictoris Beta Pictoris is a nearby star, 50 light years away, which is known to have a large dust disc of 1100 AU diameter around it (Smith and Ternleg); (1 AU = distance from Earth to Sun). Observations with the GHRS at high resolving power (R = 1OOOOO) were obtained by Boggess et ~ 1 . 1 0 Fig. 3 shows line profiles of three Fe I1 lines, plotted as a function of velocity with respect to the laboratory wavelength; the thick curve is for January 12 and the thin curve is for February 4. The ground-state line at 2599.4 A can be formed even at low densities.A density of 103 electrons cm-3 is required to excite the 2598.4 8, line and 10s electrons cm-3 is required for the 2739.5 8, line, so their absorption features are from gas close to the star where the densities are higher. An absorption feature (A) at 10 km s-1 is seen only in the ground- state line and so is from a region with density less than 103 cm-3. It may be from an interstellar cloud, but there is some indication of variability, in which case it must occur in an extended low density halo around the star. Other absorption features, particularly E and F, seen in all three lines, must come from the high density regions found only very close toANALYST. MARCH 1992. VOL. 117 241 Fe II h 2599.396 I A Fe II h 2598.37 Fe It h 2739.546 I I I 1 I Heliocentric radial velocity/km s-’ Fig.3 Three line profiles of Fe I1 lines of different lower levels from the nearby star Beta Pictoris, taken by the GHRS, for two different times taken 3 weeks apart. A-F, various absorption features (see text) 0 20 40 60 the star. Here infalling gas clouds at 33 and 52 km s-1 are seen. By comparing spectra taken 3 weeks apart, several infalling clouds at speeds of up to 220 km s-1 have been seen varying with time. This suggests that approximately 100 infall events per year are occurring. Boggess et a1.10 have speculated that there is a ring of gas inside the dust disc, and that instabilities trigger infall either steadily or in surges that develop wider velocity dispersions as they fall down the stellar gravitational well. Other Results A wide range of new spectroscopic results are emerging rapidly from the HST spectrographs.( i ) The sharp core of the HST image has allowed the FOS to separate the spectrum of a weakly active nucleus of a galaxy from that of the surrounding material, showing gas velocities of 20CL1000 km s-1, consis- tent with free fall into a 5 x 106 black hole (Kriss et al.11). (ii) Spectra taken by the GHRS of the giant star Gamma Draconis show fluorescence excitation of emission lines, and a cool absorbing wind of neutral gas away from the star with complex velocity structure (Carpenter et al. 12). (iii) The GHRS spectra of the cool super-giant Alpha Orionis show a circumstellar shell with strong absorption from carbon monoxide, a cool absorbing wind in Mg I1 and a hot emitting wind in C IV and He IT (Carpenter et al.12). (iv) The GHRS spectra of Capella, which consists of two G giant stars in orbit around each other, show complex fluorescence features, with 0 I pumped by H Lyman beta, and S I in turn pumped by 0 I (Linsky et al.13). Both stars have active chromospheres, with self-reversed Mg I1 lines, and have 0 IV and S IV emission with density diagnostic line intensity ratios. Future Improvements Although the current performance of the telescope allows unprecedented high quality UV spectroscopy of isolated targets of moderate and high brightness, a re-visit to the spacecraft planned for 1994 will add the Corrective Optics Space Telescope Axial Replacement (COSTAR), which will correct the spherically aberrated image for the two spectro- graphs and for the Faint Object Camera.This will allow spectroscopy of crowded fields, portions of extended objects, and faint objects; the current Wide Field and Planetary Cameras will also be replaced by one containing correcting optics. Correction for each instrument by the COSTAR will consist of two mirrors placed in front of the focal plane. The first correcting mirror will image the spherically aberrated tele- scope primary mirror onto the second correcting mirror, which will provide an opposite spherical aberration to correct the wavefront. A further re-visit planned for 1997 will replace two of the current instruments with the Space Telescope Imaging Spec- trograph (STIS) and the Near Infrared Camera (NIC), with both of the new instruments containing corrective optics.The STIS will contain two dimensional detectors, allowing imaging along the slit or kchelle spectroscopy with simultaneous high resolution and broad wavelength coverage. By using 1024 X 1024 pixel detectors, it will have a multiplex advantage by a factor of 2048 compared with the 1 x 512 pixel detectors of the GHRS and FOS. The NIC will open up a new spectral range, 0.8-3.5 pm, to the high spatial resolution and low background of the HST. 1 2 3 4 5 6 7 8 9 10 11 12 13 References Astrophys. J . , Special Issue, 1991, 369. Feinberg, R., Sky Telescope, 1991, 81, 14. The Space Telescope Observatory, ed. Hall, D. N. B., NASA Conference Proceedings CP-2244, 1982. Bachall, J. N., Jannuzi, B. T., Schneider, D. P.. Hartig, G. F., Bohlin, R., and Junkkarinen, V., Astrophys. J. Lett., 1991,377, L5. Morris, S. L., Weymann, R. J., Savage, B. D., and Gilliland, R. L., Astrophys. J. Lett., 1991, 377, L21. Leckrone, D. S., Wahlgren, G. M., and Johansson, S. G., Astrophys. J. Lett., 1991, 377, L37. Kurucz, R. L., Astrophys. J. Suppl. Ser., 1979, 40, 1. Kurucz, R. L., in Stellar Atmospheres: Beyond Classical Models, eds. Crivellari, L., Hubeny, I., and Hummer, D. G., Kluwer, Dordrecht, NATO AS1 Series C, ~01341,1991. Smith, B. A., and Terrile, R. J., Science, 1984, 226, 1421. Boggess, A., Bruhweiler, F. C., Grady, C. A., Ebbets, D. C., Kondo, Y., Trafton, L. M., Brandt, J. C., and Heap, S. R., Astrophys. J. Lett., 1991, 377, L49. Kriss. G. A., Hartig, G. F., Armus, L., Blair, W. P., Caganoff, S., and Dressel, L., Astrophys. J. Lett., 1991, 377, L13. Carpenter, K.. Robinson, R., Ebbets, D., Brown, A.. and Linsky, J. L., Bull. Am. Astronom. SOC., 1991, 23,910. Linsky, J. L., Brown, A., Carpenter, K., and Robinson, R., Bull. Am. Astronom. Soc., 1991, 23, 910. Paper I I04355 B Received August 9, 1991 Accepted October 27, 1991

ISSN:0003-2654    

DOI:10.1039/AN9921700239

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, MARCH 1992, VOL. 117 243 Applications of Nuclear Analytical Techniques in Environmental Research* Plenary Lecture Brit Salbu Isotope Laboratory, Agricultural College of Norway, N- 1432 As, Norway Eiliv Steinnes Department of Chemistry, University of Trondheim, AVH, N-7055 Dragvoll, Norway Among nuclear analytical techniques, neutron activation analysis (NAA) is particularly useful for environmen- tal studies. It affords low detection limits for many elements, high specificity and few sources of systematic error, which means that high accuracy is attainable. Neutron activation analysis is particularly useful for trace and ultra-trace analysis of environmental samples (water, soils, rocks and biological material). In trace element work associated with pollution, instrumental NAA is a powerful technique for multi-element surveys, in particular when combined with other spectroscopic techniques.Nuclear techniques, as with most analytical techniques, cannot be used t o distinguish between different physico-chemical forms of an element per se. When used in combination with appropriate separation techniques, however, nuclear techniques can provide valuable information about trace element speciation in environmental and biological systems. From dynamic tracer experiments, i.e., addition of chemically well defined labelled compounds t o environmental systems, valuable information can be obtained on the distribution of species and on microchemical processes influencing the physico-chemical forms. In these laboratories, speciation studies on trace elements in natural waters have been carried out by using instrumental NAA in combination with physical separation techniques, such as dialysis and ultrafiltration, in situ and in the laboratory.Dynamic radiotracer experiments have provided important information a bout processes influencing the speciation of trace elements in aquatic systems. Sequential extraction techniques have proved t o be useful in studies on sediments and soils when combined with NAA. Sequential extractions also provide significant information about the physico-chemical behaviour of radionuclides supplied t o natural soils from the Chernobyl accident. Keywords: Neutron activation analysis; radioactive tracer; trace element; speciation studies; artificial radionuclides Radionuclides and radiation sources can be used for analytical purposes in a wide variety of ways, as shown in Table 1.In environmental research, three of the issues listed in Table 1 are of particular interest, notably neutron activation analysis (NAA), the use of radiotracers and measurements of environ- mental radioactivity. In this paper, the application of these techniques in environmental research is discussed and illus- trated by examples from investigations, mainly performed in these laboratories. Particular emphasis is placed on speciation studies. The additional techniques listed in Table 1 are of more limited use in environmental studies, with the exception of proton-induced X-ray emission, which is dealt with in another paper. * Neutron Activation Analysis in Environmental Research Neutron activation analysis can be carried out with use of a nuclear reactor, a neutron generator or an isotopic source.For environmental investigations, only nuclear reactors are of significant interest. As shown in Table 2, detection limits attained by NAA are very low for many elements, and for a considerable period of time it was the only means of studying a number of elements at the levels at which they exist in many environmental matrices. However, improvements in other techniques such as electrothermal atomic absorption spec- trometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS)2.3 have meant that NAA is no longer the most sensitive technique for many of these elements, but there are still some exceptions, such as some of the rare earth * Presented at the XXVII Colloquium Spectroscopicum Inter- nationale (CSI), Bergen.Norway. June 9-14. 1991. elements. These elements may sometimes be advantageously used as ‘activable tracers’ in the study of environmental processes. Other advantages that could be listed for NAA include a high specificity, in particular when combined with a radio- chemical separation, and few sources of systematic error, which means that high accuracy can be achieved. This has made NAA a particularly useful tool in the certification of reference materials for environmental and other uses. However, NAA also suffers from some disadvantages when compared with several other trace element techniques. Table 1 Possible uses of radioactive nuclides and radiation sources in analysis Activation- Prompt techniques: Neutron-induced gamma emission Proton-induced gamma emission Gamma-gamma resonance Proton-induced X-ray emission Delayed techniques: Neutron activation analysis Photon activation analysis Charged-particle activation analysis Isotope dilution techniques Radiotracer measurements Scattering analysis Absorption measurements Natural radionuclides Artificial radionuclides Addition of radioactivity- Use of radiation sources- Measurements of environmental radioactivity-244 ANALYST, MARCH 1992, VOL.117 Table 2 Detection limits in RNAA for 50 elements under a given set of conditions* Half-life of radio- Element nuclide Na A1 Pt sc Ti V Cr Mn Fe c o Ni c u Zn Ga Ge As Se Br Rb Sr Y-t Nb Mo Ru Rh Pd Cd In Sb Ag 15.0 h 14.3 d 84d 2.25 min 5.8 rnin 3.75 min 2.58 h 5.3 years 2.6 h 12.7 h 14.1 h 83 rnin 26.4 h 35.3 h 18.7 d 64h 66h 39 d 13.5 h 2.3 d 54 min 2.7 d 27.7 d 45 d 244 d 120 d 2.81 h 6.3 min 4.4 min 250 d Half-life Detection of radio- Detection limit/ng Element nuclide limithg 0.5 Te 5 I 0.2 c s 0.01 Ba 20 La 0.1 Ce 2 Prt 0.005 Nd 20 Sm 0.2 Eu 0.5 Gd 0.05 Tb 0.1 Ho 1 Er 0.02 Tm 0.5 Yb 0.01 Lu 0.5 Hf 1 Ta 0.02 w 10 Re 0.2 Ost 0.2 Ir 5 Pt 0.05 Au 0.2 Hg 0.5 TIT 0.002 Th 0.05 U 2 DY 8.0 d 25 .O rnin 2.06 years 11.5d 40.2 h 32.5 d 19.2 h 11.0d 47h 12.4 years 18.6 h 72 d 2.35 h 26.7 h 7.5 h 4.2 d 6.7 d 129 d 42 d 115 d 23.8 h 17.0 h 15.4 d 74 d 3.13 d 2.70d 2.7 d 3.8 years 27.0 d 2.36 d 0.2 0.1 0.1 5 0.01 0.05 0.2 0.5 0.005 0.01 0.2 0.01 0.002 0.005 0.2 0.01 0.05 0.002 0.05 0.01 0.02 0.01 0.1 0.001 1 0.05 0.1 2 0.02 0.05 * Conditions: neutron flux, 2 x 10" n cm-2 s-1; irradiation time, maximum 3 d; induced activity, 50 Bq for short half-lives (t2 <lo h).10 Bq for long half-lives; 15 min decay for short half-lives, 1 d for long half-lives. t Pure 0-emitter, requires extensive separation. Relatively high skill is required from the operator, handling of radioactive material is involved, and the turnover time could be long in many instances. Moreover, it requires access to a nuclear reactor, which is already a problem in some countries and which may gradually become worse in the years to come. In spite of these problems, the full potential of NAA is yet to be exploited in environmental research. The examples shown in the following sections are mainly from work in areas where few other applications of NAA have been reported.Applications of Instrumental Neutron Activation Analysis (INAA) Neutron activation analysis in the purely instrumental mode can, in favourable instances, allow the determination of about 30 elements in environmental samples, and has been widely used in the analysis of, e.g., rocks and minerals,4 air particulates5 and coal and coal products.6 In this paper, examples are shown where INAA is applied to areas not generally recognized to be well suited for this technique. Multi-element studies on trace elements in fresh waters is one area where INAA has proved to be very usefu1,7 particularly in connection with speciation work.*-11 Typically, 15-20 elements can be determined at normal levels in natural fresh waters.12 Another kind of investigation where INAA has been successfully applied is in the analysis of mosses used as biomonitors of atmospheric deposition.The number of elements that can be regularly determined in mosses is about 25, including V, Cr, Mn, Fe, Co, Zn, As, Se, Br, Mo, Sb, Th and U. When additional determinations of the environmen- tally important heavy metals Ni, Cu, Cd and Pb by AAS are Table 3 Evaluation of results from a feasibility study of INAA applied to 50 natural surface soils in Norway's No. of samples where element could be determined quantitatively at Rating existing concentrations Elements Very good 50 Satisfactory 47-49 44-46 37-41 31-36 Marginal 6-19 20-34 Unsatisfactory 4-10 Na, AI, Sc, Cr, Mn, Fe, Co.Br, La, Sm, Hf, Th K, Zn, Sb, U Cs. Ba V, As, Rb, Sr C1, Se, I Ta, Au Ni, Ag Mo; Hg Cd, Ti, Mg Environmental effects t Biological uptake t I K7 Bioavailable species Inert species Active uptake low molecular weight forms, e.g., ions, molecules K2 Passive uptake high molecular weight forms, e.g., colloids, particles I Source Fig. 1 Importance of speciation in natural waters25 added, this forms altogether a strong scheme for this particular type of air pollution study. 13 Recently, however, ICP-MS has proved to be a serious competitor for the analysis of mosses;14 32 elements can be determined, including all the primary pollutant trace elements, with the exception of Se. Instrumental NAA is also useful for the analysis of organic soils15 and humic substances. 16 Previous applications of NAA in soil science have almost exclusively dealt with essentially pure mineral soils, mainly agricultural.Recently, the feasi- bility of INAA for the analysis of natural surface soils in Norway, normally ranging from 60 to 95% in organic matter, was investigated.15 The results of this study are shown in Table 3. Of the 34 elements studied, 27 could be determined in all or most of the 50 samples tested, representing a wide com- positional range. Applications of Radiochemical Neutron Activation Analysis (RNAA) In order to achieve the theoretical determination limits of NAA (Table 2), it is often necessary to use a radiochemical separation procedure, after activation, to remove interfering activation products. The analysis is, in many instances, time and work consuming, and alternative techniques are, there- fore, most often chosen if equally good determination limits can be attained.However, there are still many instances whereANALYST, MARCH 1992, VOL. 117 245 Table 4 Fraction of an element (%) present in low molecular weight forms ( M , <10 kDa)24 Ground water bore-hole Element (Kise) Ca 80 Al 10 sc 20 La 40 Ce ND Cr <5 Mn 50 Fe (1 c o <1 Zn 20 * ND = Not determined. Ground water spring Lake (Astadalen) Tyrifjorden 70 80 70 80 100 30 10 35 <20 ND <20 10 <40 50 < 10 <5 < 10 50 10 5 Lake Trehflrningen 95 75 20 75 30 10 25 35 75 75 Lake Diplane 85 ND 65 30 50 30 ND <5 90 100 River Asta 80 50 40 <5 15 20 70 25 30 20 River Glomma 95 10 10 ND <25 50 65 85 20 55 Coastal waters (Framvaren) ND* ND 50 ND 40 80 ND 20 20 25 RNAA offers the best, and sometimes the only, alternative when dealing with ‘difficult’ elements in environmental research.A few examples are as follows. (i) Trace elements in oceans, in particular when pre-irradiation separation17 or post-irradiation group separation procedures18 are used. Even 25 years ag0,17 the rare earth elements were determined in ocean water at levels of 0.1-1 ng I-‘. (ii) Determination of iodine in complex samples such as plant tissue.19 (iii) Determination of uranium in natural waters.20 100 c Speciation Studies by Nuclear Techniques In environmental trace element research the determination of the total concentration of an element is often only the initial step. If the pathways, mobility and bioavailability of elements are to be elucidated, it is necessary to obtain information about their speciation, i.e., the distribution between different physico-chemical forms, as illustrated in Fig. 1.25 For natural systems, theoretical species calculations most often do not reflect very accurately the real situation, as several important microchemical processes are not included in the models. Electroanalytical techniques are frequently used for direct speciation of labile species, but their working range is fairly restricted both with regard to elements and to natural systems that can be reliably studied. In most other instances no direct speciation method exists, and fractionation procedures fol- lowed by analysis of each fraction are necessary.In such studies, any sufficiently sensitive and accurate technique of analytical determination can be used, including NAA. Another area of nuclear environmental studies where speciation methods are essential is in radioecology, i.e. , the study of pathways of natural or artificially produced radio- nuclides in the environment, leading to the exposure of biota, including man. For a long time the need for information about speciation of environmental radionuclides was not generally recognized. Recent work has clearly demonstrated the impor- tance of such knowledge. In the following, some examples of speciation studies involving either INAA or artificial radio- nuclides in the environment are briefly described. Trace Element Speciation in Water Studied by INAA A number of fractionation techniques are available for trace element speciation studies on water.Fractionation can be based on: ( a ) Size: filtration/ultrafiltration, dialysis, gel filtration. (6) Charge: electrophoresis, ion chromatography, extraction. (c) Chargekize: electrodialysis. (d) Specific grav- ity/density : centrifugation. Trace element speciation studies on natural waters may preferentially include an initial separation step, allowing the distinction between a fraction of low molecular weight and a colloidal fraction (Fig. 1). We have found combinations of some of the above fractionation techniques with INAA very fruitful for this purpose.~10-21-24 The distribution of a trace A B C D 100 ,,,i 5 50 A B C D 100 1’”’ I + A B C D 501i A B C D Fig.2 Distribution of four trace elements in ground water and lake water according to size.*l 0, Ground water: (a) cf = 415 ? 90; (6) cf = 1.6 k 0.4; (c) cf = 102 k 16; and ( d ) cf = 5 t 1 pg 1-1. tzI, Lake water: (a) cf = 61 k 8; (b) cf = 0.4 rf: 0.1; (c) cf = 8 k 1; and (d) cf = 0.6 k 0.1 pg 1-1. Fraction (%): A, >0.45; B, 0.1-0.45; C, 0.005-0.1; and D, <0.005 pm element between low relative molecular mass (a10 kDa) and higher relative molecular mass forms can vary within wide limits in different natural waters, as illustrated in Table 4, depending on factors such as pH, Eh, and the quality and amount of organic carbon. As the speciation of trace elements in a water sample can change rapidly during transport and storage,g fractionation should preferably be carried out in the field.Two specific techniques have been adopted for this purpose. Dialysis in situ8 is carried out by placing a dialysis bag filled with distilled water directly into the natural water under study, and leaving it for a period of time (usually a few days) necessary to establish dialytic equilibrium between species of low relative molecular mass inside and outside the membrane. This technique is less subject to contamination and adsorption losses than, e.g., are conventional filtration/ultrafiltration techniques, and the fraction obtained represents an average over the sampling period. Another very useful technique is in situ ultrafiltration, using hollow fibres21 or cross-flow membranes.26 Compared with traditional ultrafiltration, the hollow fibre has a much larger surface area, which allows a higher flow rate and thereby a larger volume to be filtered within a reasonable time.The larger surface area means high adsorption initially, but saturation of adsorption sites nor- mally occurs within the first 100-200 ml filtered, as conve- niently shown by radiotracer experiments. 1 1 By discarding the246 ANALYST, MARCH 1992, VOL. 117 Total 0.08 (a) t N 0 . 1 pm 0.06 - 0.04 - 0.02 - I- t U - E! 5 0 - L Total 0 m0.1 pm 10 kDa 1.5 - 1.2 - 0.9 - 0.6 - 0.3 - --Eiilnr;wn I 2 24 48 tlh Fig. 3 Size fractionation of 239Pu + 240Pu in effluents from the Sellafield nuclear installation (UK).*9 (a) Sellafield SIXEP effluent and (b) Sellafield Seatank effluent first 250 ml, a fractionated sample of up to 100 1, suitable for further speciation steps, can be obtained.In situ hollow-fibre filtration has been applied in several field studies involving radionuclides26.27 and stable trace elements.21.23 Fig. 2 shows examples from a speciation study21 where samples of ground water and lake water, respectively, were fractionated by filtration/ultrafiltration techniques, and trace elements were determined in the individual fractions by INAA. From Fig. 2 it is evident that these elements show substantially different fractionation patterns, and that their behaviour can differ appreciably between ground and surface waters. Speciation of Artificial Radionuclides in Water Low-level radioactive waste is being discharged into coastal waters from nuclear installations on a regular basis.The following two examples serve to show that the speciation of released radionuclides can vary, according to sources. Hence, the potential environmental harm of a given total amount of a radionuclide in fallout (source term28) or released to a recipient will depend on the speciation of this nuclide in the discharged water. Fig. 3 shows results of size fractionations of 239Pu and 2M)Pu in effluents [Seatank (SIXEP, site ion-exchange plant)] from the Sellafield nuclear installation, UK, after diluting lo00 times with coastal water.29 It appears that although the total Pu concentration is about three times higher in Seatank, the release from SIXEP is of importance as about 70% of the Pu is present in low molecular weight forms, which are potentially Fig. 4 Size fractionation of waste waters from two nuclear power plants in Sweden.30 (a) Forsmark nuclear installation (October 1985); (b) Oscarshamn nuclear installation (September 8, 1987); and (c) Oscarshamn nuclear installation (sampled August 20, fractionated September 8.1987). The numbers on the columns represent the total activity concentration (Bq 1-l) mobile and bioavailable , whereas the corresponding figure for Seatank is only about 5%. Size fractionation of waste waters from two nuclear power plants in Sweden is shown in Fig. 4.30Trends apparent are: (a) different radionuclides show different size distributions; ( b ) there could be significant differences in speciation of the same radionuclide discharged from two different power plants; and (c) the speciation may be strongly dependent on storage conditions prior to discharge.Group Separations Based on Sequential Extractions Since the pioneering work of Tessier et a1.,3* a number of separation schemes have been proposed to distinguish between different operationally defined binding forms of elements in complex environmental matrices such as sedi- ments and soils. This approach is now being introduced for the study of soil-plant transfer of fallout radionuclides from the Chernobyl accident. Based on the sequential extraction scheme used (Fig. 5 ) , Cs isotopes are shown to be strongly bound to components in soil, while 9oSr is far more mobile.32 Even though the technique is operationally defined, the results are remarkably reproducible. Fig. 6 illustrates that the exchange of L37Cs with stable Cs in soil is almost complete except for the slow migration into the mineral lattice (residue).33 On a Bq m-2 basis, results from sequential extractions can be utilized for calculating mobility factors, i.e.,ANALYST, MARCH 1992, VOL.117 247 Fig. 5 Fractionation of (a) %Sr and (b) I3’Cs in soils from a mountain area in eastern Norway using sequential e~tractions.3~ (F1 = H20; F2 = NH40Ac; F3 = NaOAc; F4 = NH20H-HCI; F5 = H202 + HNO,; F6 = 7 mol dm-3 HN03; and Res = residue) Fig. 6 Specific activity of 13’Cs in soil fractions from sequential extractions.33 (F1 = NH40Ac; €2 = NH20H.HCI; F3 = H202 + HNO3; F4 = 7 mol dm-3 HNO,; and F5 = residue). The numbers given represent specific activity (Bq pg-1) distinguishing between mobile and inert species of deposited radionuclides.32 Use of INAA in Screening for Halogenated Organics A total analysis for persistent organochlorine compounds, such as polychlorinated biphenyls in environmental samples, is fairly difficult and expensive.In projects involving a large number of samples it may often be advantageous first to ‘screen’ the samples with respect to a collective parameter such as TPOC (total persistent organochlorine compounds, extracted from a sample by means of a suitable non-polar organic solvent), and subsequently to select samples with high levels for detailed analysis. In recent years, persistent bromi- nated compounds have also received attention in environmen- tal studies. Instrumental NAA is a convenient way of determining the sum of organically bound halogens (CI and Br, and I, if required) in sample extracts based on, e .g , hexane or cyclohexane.34 This approach has been in use in Norway for about 15 years, and several thousand samples have been analysed. Radiotracer Studies Radionuclides play a very important role in environmental research. On the one hand, long-lived, naturally occurring or artificially produced radionuclides are frequently used to study natural processes such as sedimentation rates, and for dating purposes. This is an extensive field of research in itself, and is considered outside the scope of this paper. On the other hand, suitable radioactive tracers can be added to experimen- tal systems to study a wide variety of processes on a short-term basis. Dynamic Tracer Studies If transport, transformation or kinetics is to be investigated, the use of a radiotracer could often represent the only applicable tool.One good example is a recent investigation on the role of aluminium in causing injuries to fish in the mixing zone of limed river water and acid tributaries.35 In a laboratory experiment, a 26AI tracer was added to two containers with limed river water (pH 6) and acid river water (pH 4.9, respectively. Fish were introduced and mixing zones were created by adding to these containers, respectively, acid and limed waters. Only in the originally acid water was 26Al observed on fish gills. The use of fractionation techniques demonstrated that A1 species of low molecular weight, in acid water, polymerize rapidly and precipitate on the fish gills.Hence, Al in the mixing zone tends to be more toxic to fish than Al in the acid tributaries. In non-equilibrium systems, not only the speciation, but also the transformation processes and kinetics involved must be taken into account when assessing biological effects. Another interesting example36 is given in Fig. 7, which shows the migration of 134Cs during electrodialysis as a function of time, as followed by a gamma camera. The apparatus consists of three compartments, divided by a membrane transparent to species below a certain molecular weight. When applying an electric field across the cell, the Csf ions move towards the negative electrode, and can diffuse out of the central compartment into the cathode compartment. If the *34Cs tracer is fixed instead to Prussian blue, a negatively charged compound of high molecular weight, it moves towards the anode, but its migration is hindered by the membrane.Performance of Separation Procedures Radioactive tracers have frequently been used to study methodological aspects in analytical chemistry. In radiochem- ical separations involving a short-lived nuclide it is sometimes possible to add a long-lived radioisotope of the same element to monitor the chemical yield, such as the use of 48V in pre-irradiation separations of V to be determined in biological material by NAA.37 This is an example of isotope dilution analysis (cf. Table l), which is also routinely used in the determination of Pu in environmental samples where a known248 ANALYST, MARCH 1992, VOL. 117 Fig.7 Migration of 134Cs+ during electrodialysis as a function of time, followed by a gamma ~amera3~ 100 1 Volumelml Fig. 8 Adsorption of Zn*+, Cr3+ and Cr04*- as a function of filtration volume during hollow-fibre ultrafiltration, as shown by radiotracers. e, 65ZnCI2 added to solution; 0, 51CrCl3 added to solution; and V , Na251Cr04 added to solution amount of 236Pu or 242Pu is added to the sample prior to radiochemical separation. Radiotracers are also conveniently used to test the perfor- mance of physical separation techniques in speciation work, an example of which is shown in Fig. 8, dealing with the adsorption of 65Zn2+, 5lCr3+ and 5*Cr042- as a function of filtration volume during hollow-fibre ultrafiltration.21 Use of Radiotracers in Speciation Studies Radiotracers are useful for studying the speciation and behaviour of non-radioactive substances.The necessary con- ditions are that the added radioactive component should not significantly increase the total concentration of the substance or elements concerned, and that complete isotopic exchange between the radiotracer and its stable counterpart (all its species) must take place. If the aim is to study the environmen- tal behaviour of a compound not occurring naturally, radioiso- tope techniques are often well suited. In a recent study,38 the sorption behaviour of the pesticide tribenuron on clay mineral particles in water, as a function of pH and suspended matter concentration, was studied by equilibrating 14C-labelled tribenuron with solutions of different pH and illite concentra- tions.The solutions were then subjected to hollow-fibre ultrafiltration, with a nominal molecular weight cut-off of 3 kDa. The association of the pesticide with the suspended , Table 5 Behaviour of stable Fe and added 59Fe tracer in a sample of river water as a function of storage time.39 NAA: Fraction of stable Fe, determined by neutron activation (%); R: fraction of radioactive Fe (%); A: loss by adsorption; IE: removed by ion-exchange filter; C: removed by centrifugation at 3000 rev min-1; and D; dialysable fraction (<lo kDa) Storage time A IE C D NAA 2h 0 81 56 8 24h 0 87 56 5 7d 30 90 70 4 35d 24 94 83 3 R 2h 0 37 8 2 24h 4 61 12 3 7d 23 51 31 2 35d 42 77 50 5 fraction increased with decreasing pH within the range studied (3-6) and increased strongly with suspended load.The possibility of using added radiotracers to study the speciation of a naturally occurring element is somewhat more limited. From Fig. 5 it is obvious that the 137Cs deposited after the Chernobyl accident, 3 years before the actual experiment took place, has not completely exchanged with all forms of stable Cs in the soil. As regards the potentially mobile and plant-available pool of Cs, however, the radiotracer seems to reflect the speciation of stable Cs fairly well. The feasibility of using radiotracers to study the speciation of trace elements in natural fresh waters39 was investigated by adding radiotracer to a recently collected sample and storing it in the laboratory. During the storage period the physico- chemical behaviour of the radiotracer and its stable counter- part was studied by using different separation techniques, and the absorption loss was monitored.The results are shown in Table 5 for Fe. Although the behaviour of the stable and radioactive isotopes of Fe gradually becomes similar, their speciation is not the same even after 35 d. Therefore, until equilibrium conditions are reached, radiotracers added to natural water do not represent adequately the speciation of the corresponding stable elements, but they can be con- veniently used in dynamic experiments, revealing information on the transformation processes and kinetics involved. Conclusions (1) Instrumental NAA still plays a significant role in certain trace element studies. (2) Radiochemical NAA is a valuableANALYST, MARCH 1992.VOL. 117 249 reference technique, and is superior in some specific examples of environmental studies. (3) Neutron activation analysis can be successfully used in physical and chemical speciation studies, after appropriate fractionation steps. The potential of NAA is not being fully exploited. (4) Speciation methods are very important, not only in environmental trace element studies, but perhaps also even more so in investigations on artificial radionuclides in the environment. (5) Radiotracers represent a unique opportunity to study a wide variety of environmental processes influencing stable and radioactive species in ecosystems. Radiotracers often provide the only possibility for studying the transformation processes and kinetics involved.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 References Johansson, S. A. E., Analyst, 1992, 117, 259. Berman, S. S., Paper presented at the XXVII CSI, June 9-14, Bergen, Norway. McLaren, J. W.. Lam, J. W., and Berman, S. S., Paper presented at the XXVII CSI. June 9-14, Bergen, Norway. Laul. J. C.. At. Energy Rev.. 1979. 17, 603. Dams, R., Robbins. J. A.. Rahn, K. A,, and Winchester, J. W., Anal. Chem.. 1970. 42. 861. Steinnes. E . , in Analytical Methods for Coal and Coal Products, ed. Karr, C., Academic Press, New York, 1979, vol. 111, pp. 276302. Salbu, B., Steinnes. E., and Pappas. A. C., Anal. Chem.. 1975, 47, 1011. Benes, P., and Steinnes. E., Water Res., 1974, 8, 947. Benes. P.. and Steinnes, E.. Water Res., 1975, 9, 741. Salbu, B.. Mikrochim. Acta, Part II, 1981. 351.Salbu, B., Steinnes, E., and Bjarnstad, H. E., in Hydrochemical Balances of Freshwater Systems, ed. Eriksson, E., International Association of Hydrological Sciences, University of Uppsala, Uppsala, Sweden (IAHS-AIHS), Publ. No. 150, 1984, pp. Steinnes, E.. in The Determination of Trace Elements in Natural Waters, eds. West, T. S., and Niirnberg, H. W., Blackwell, Oxford, 1988. pp, 152-159. Steinnes. E.. J. Radioanal. Chem., 1980, 58, 387. Steinnes, E., Johansen, O., Rgyset, O., and 0degArd, M.. Environ. Monit. Assess., submitted for publication. Nzumann, R., Steinnes, E., and Guinn, V. P., J. Radioanal. Nucl. Chem., submitted for publication. Riise, G.. and Salbu, B., Sci. Total Environ., 1991: 81/82, 137. Hagdahl, 0. T., Melsom, S., and Bowen, V.T., in Trace Inorganics in Water, Advances in Chemistry Series No. 73, American Chemical Society, Washington. DC, 1968, pp. Jarstad, K., and Salbu. B.. Anal. Chem., 1980,52,672. Johansen, 0.. and Steinnes, E., Analyst. 1976. 101. 455. 203-2 13. 308-325. 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Steinnes, E., Radiochem. Radioanal. Lett., 1973, 16, 25. Salbu. B., Bjamstad, H. E., Lindstrom, N. S., Lydersen, E., Brevik, E. M., Rambaek, J. P.., and Paus, P. E., Talanta, 1985, 32,907. Lydersen, E . , Bjgrnstad, H. E., Salbu, B., and Pappas, A. C.. in Speciation of Metals in Water, Sediments and Soil Systems, ed. Landner, L., lecture notes in Earth Sciences, Springer-Verlag, Berlin, 1987, vol. 11, pp. 85-97. Salbu, B., Riise, G., Bjgrnstad, H.E.. and Lydersen, E., in The Surface Water Acidification Programme, ed. Mason, B. J., Cambridge University Press, Cambridge, 1990, pp. 251-254. Salbu, B., Proceedings of the International Conference on Modern Trends in Activation Analysis, Copenhagen, 1986. vol. Salbu. B.. The Quality of Analytical Data for Modelling Purposes. BIOMOVS Technical Report No. 3, Swedish Radia- tion Protection Institute, Stockholm, September, 1988. Brittain, J. E . , Bjgrnstad, H. E., Salbu, B., and Oughton, D. H., Analyst, 1992, 117, 515. Salbu. B., Bjomstad, H. E., and Brittain. J. E.. J. Radioanal. Nucl. Chem., 1992, 156,7. Salbu, B., Proceedings of the Joint Meeting OECD(NEA)/CEC Recent Advances in Reactor Accident Consequence Assess- ment, CSNI, Rome, Report 1-45, 1988, 1, 55-68. Salbu, B., Bjgrnstad, H. E., Svaeren, I., Prosser, L. S., Bulman, R. A., Harvey, B. R., and Lovett, M. B., Sci. Total Environ., in the press. Salbu, B., and Bjgrnstad, H. E., J. Radioanal. Nucl. Chem., 1990, 138, 337. Tessier, A., Campbell, P. G. C., and Bisson, M., Anal. Chem., 1979, 51, 844. Oughton, D. H.. Salbu, B., and Strand, P., Proceedings of the BIOMOVS Symposium. On the Validity of Environmental Transfer Models, Stockholm, 1990, pp. 235-239. Riise. G., Bjamstad, H. E., Lien, H. N., Oughton, D. H., and Salbu, B.. J. Radioanal. Nucl. Chem., 1990, 142, 531. Gether, J., Lunde, G., and Steinnes, E., Anal. Chim. Acra, 1979. 108, 137. Rosseland, B. O . , Blakar. I. A., Bulger, A., Krogland, F., Kvellestad, A., Lydersen, E., Oughton, D. H., Salbu, B., Staurnes, M., and Vogt, R., Sci. Total Environ.. in the press. Salbu, B., and Rambaek, J. P., in Environmental Consequences of Releases from Nuclear Accidents, ed. Tveten, U., Final Report NKA Project AKTU-200, Nordic Liason Committee for Atomic Energy, Roskilde, 1990, pp. 119-127, Allen, R. O., and Steinnes, E.. Anal. Chem., 1978, 50, 1553. Riise, G., personal communication. BeneS, P., and Steinnes, E., Int. J. Environ. Anal. Chem., 1976, 4, 263. 1, pp. 135-141. Paper 1104755H Received September 13, 1991 Accepted November 18, 1991

ISSN:0003-2654    

DOI:10.1039/AN9921700243

出版商:RSC    

年代:1992

数据来源: RSC