摘要:

'""Aria I y s tThe Analytical Journal of The Royal Society of ChemistryAnalytical Editorial BoardChairman: J. N. Miller (Loughborough, UK)M. Cooke (Sheffield, UK)C. S. Creaser (Nottingham, UK)A. G. Davies (London, UK)A. G. Fogg (Loughborough, UK)J. M. Gordon (Cambridge, UK)G. M. Greenway (Hull, UK)S. J. Hill (Plymouth, UK)D. L. Miles (Keyworth, UK)R. M. Miller (Gouda, The Netherlands)B. L. Sharp (Loughborough, UK)M. R. Smyth (Dublin, IrelandY. Thomassen (Oslo, Norway)P. Vadgama (Manchester, UK)Advisory BoardJ. F. Alder (Manchester, UK)A. M. Bond (Victoria, Australia)J. G. Dorsey (Cincinnati, OH, USA)L. Ebdon (Plymouth, UK)A. F. Fell (Bradford, UK)J. P. Foley (Villanova, PA, USA)M. F. Gine (Sao Paulo, Brazil)T. P. Hadjiioannou (Athens, Greece)W.R. Heineman (Cincinnati, OH, USA)A. Hulanicki (Warsaw, PolandI. Karube (Yokohama, Japan)E. J. Newman (Poole, UK)J. Pawliszyn (Waterloo, Canada)T. B. Pierce (Harwell, UK)E. Pungor (Budapest, Hungary)J. RSiiCka (Seattle, WA, USA)R. M. Smith (Loughborough, UK)K. Stulik (Prague, Czechoslovakia)J. D. R. Thomas (Cardiff, UK)J. M. Thompson (Birmingham, UWK. C. Thompson (Sheffield, UK)P. C. Uden (Amherst, MA, USA)A. M. Ure (Aberdeen, UK)C. M. G. van den Berg (Liverpool, UK)A. Walsh, KB (Melbourne, Australia)J. Wang (Las 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 HVAmsterdam, THE NETHERLANDS.Professor P.R. Coulet, Laboratoire de Genie Enzymatique, EP 19 CNRS-Universite ClaudeBernard Lyon 1, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex,FRANCE.Professor 0. Osibanjo, Department of Chemistry, University of Ibadan, Ibadan, NIGERIA.Professor F. Palmisano, Universita Degli Studi-Bari, Departimento di Chimica CampusProfessor K. Saito, Coordination Chemistry Laboratories, Institute for Molecular Science,Professor M. Thompson, Department of Chemistry, University of Toronto, 80 St. GeorgeProfessor Dr. M. Valcircel, 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 LeninUniversitario, 4 Trav. 200 Re David-70126 Bari, ITALY.Myodaiji, Okazaki 444, JAPAN.Street, Toronto, Ontario, CANADA M5S 1Al.Universidad de Cordoba, 14005 Cbrdoba, SPAIN.SOUTH AFRICA.Changsha, PEOPLES REPUBLIC OF CHINA.Avenue, 117907, Moscow V-71, RUSSIA.Editorial Manager, Analytical Journals: Janice M. GordonEditor, The AnalystHarpal S. MinhasThe Royal Society of Chemistry,Thomas Graham House, Science Park,Milton Road, Cambridge, UK CB4 4WFTelephone +44(0)1223 420066.Fax +44(0)1223 420247.E-Mail :Analyst@RSC.ORG(lnternet)US Associate Editor, The AnalystDr Julian F. TysonDepartment of Chemistry,University of Massachusetts,Box 34510 Amherst MATelephone +I 413 545 0195Fax + 1 41 3 545 484601003-4510, USAAssistant EditorsSarah Williams Caroline Seeley Yasmin KhanEditorial Secretary: Claire HarrisAdvertisements: Advertisement Department, The Royal Society of Chemistry, BurlingtonHouse, Piccadilly, London, UK WIV OBN.Telephone +44(0)171-287 3091.Fax +44(0)171-494 1134.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 original researchpapers, critical reviews, tutorial reviews,perspectives, news articles, book reviewsand a conference diary.Original research papers. The Analyst pub-lishes full papers on all aspects of the theoryand practice of analytical chemistry, funda-mental and applied, inorganic and organic,including chemical, physical, biochemical,clinical, pharmaceutical, biological, environ-mental, automatic and computer-basedmethods.Papers on new approaches toexisting methods, new techniques andinstrumentation, detectors and sensors, andnew areas of application with due attentionto overcoming limitations and to underlyingprinciples are all equally welcome.Full critical reviews. These must be acritical evaluation of the existing state ofknowledge on a particular facet of analyticalchemistry.Tutorial reviews. These should be infor-mally written although they should still be acritical evaluation of a specific topic area.Some history and possible future develop-ments should be given.Potential authorsshould contact the Editor before writingreviews.Perspectives. These articles shouldprovide either a personal view or a philoso-phical look at a topic relevant to analyticalscience. Alternatively, they may be relevanthistorical articles. Perspectives are includedat the discretion of the Editor.Particular attention should be paid to theuse of standard methods of literaturecitation, including the journal abbreviationsdefined in Chemical Abstracts ServiceSource Index. Wherever possible, thenomenclature employed should followIUPAC recommendations, and units andsymbols should be those associated with SI.Every paper will be submitted to at leasttwo referees, by whose advice the EditorialBoard of The Analyst will be guided as to itsacceptance or rejection.Papers that areaccepted must not be published elsewhereexcept by permission. Submission of amanuscript will be regarded as an under-taking that the same material is not beingconsidered for publication by anotherjournal.Regional Advisory Editors. For the benefitof potential contributors outside the UK andN. America, a Group of Regional AdvisoryEditors exists. Requests for help or advice onmatters related to the preparation of papersand their submission for publication in TheAnalystcan be sent to the nearest member ofthe Group. Currently serving RegionalAdvisory Editors are listed in each issue ofThe Analyst.Manuscripts (four copies typed in doublespacing) should be addressed to:H.S. Minhas, Editor, orJ. F. Tyson, US Associate EditorAll queries relating to the presentation andsubmission of papers, and any correspon-dence regarding accepted papers andproofs, should be directed either to theEditor, or Associate Editor, The Analyst.Members of the Analytical Editorial Board(who may be contacted directly or via theEditorial Office) would welcome comments,suggestions and advice on general policymatters concerning The AnalystThere is no page charge.Fifty reprints are supplied free of charge,The Analyst (ISSN 0003-2654) is published monthly by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road,Cambridge, UK CB4 4WF.All orders, accompanied with payment by cheque in sterling, payable on a UK clearing bank or in US dollars payableon a US clearing bank, should be sent directly to The Royal Society of Chemistry, Turpin Distribution Services Ltd., Blackhorse Road,Letchworth, Herts, UK SG6 IHN. Turpin Distribution Services Ltd., is wholly owned by the Royal Society of Chemistry. 1995 Annual subscriptionrate EC f408.00, USA $749.00, Canada f428.00 (excl. GST), Rest of World f428.00. Purchased with Analytical Abstracts EC f807.00, USA$1472.00, Canada f841.00 (excl. GST), Rest of World f841.00. Purchased with AnalyficalAbstracts plus AnalyticalProceedings EC f925.00, USA$1699.00, Canada f971 .OO (excl. GST), Rest of World f971 .OO. Purchased with AnalyticalProceedings EC f492.00, USA $905.00, Canada f517.00(excl. GST), Rest ofworld f517.00. Airfreight and mailing in the USA by Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003.USA Postmaster: Send address changes to: The Analyst, Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003. Second classpostage paid at Jamaica, NY 11431. All other despatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outsideEurope. PRINTED IN THE UK.@The Royal Society of Chemistry, 1995. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, ortransmitted in any form, or by any means, electronic, mechanical, photographic, recording, or otherwise, without the prior permission of thepublishers

ISSN:0003-2654    

DOI:10.1039/AN99520FX001

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

2N Analyst, January 1995, Vol. 120 Editorial This has been a phenomenal year for the Analyst and also a difficult one as a result of the large increase in the number of papers submitted for publication. Even with a rejection rate similar to that in 1993 we have seen a 45% increase in the number of pages published in 1994 (approximately 2826) over 1993 (1566). The increase in submissions has come about as a result of a determined effort to exapand the coverage of the journal with particular emphasis on biological papers (19% increase); clinical (78% increase); food analysis (33% increase); and geochemical analysis (90% increase). The subject areas we are placing particular emphasis on in 1995 are: chemometricshtatistics; speciation; chroma- tography and electrophoresis; imaging techniques; and bio- materials.However, we encourage submissions in all areas of ana- lytical science. We are also now making a bigger impact in North America, thanks to our US Associate Editor, Dr. Julian Tyson. Papers from the US made up 13% of all published papers in 1994 compared with 9% in 1993. Most of you will have noticed our redesigned cover and new format interior; we may be the oldest, continuously-published English language analytical science journal but, as ever, the papers we publish are at the forefront of current analytical research. We believe the new format reflects this image. The use of colour, where appropriate, inside the journal also helps to promote the understanding and clarity of some difficult principles, particularly in Tutorial Reviews. The electronic revolution in journals publishing seems to have begun in earnest now and many of you have indicated that the RSC has been slow to offer authors the opportunity to submit their manuscripts on disk.This is because the savings expected in time and costs are not substantial. However, we are now accepting manuscripts on disk, but to avoid confu- sion, authors should not send disks with their original manuscripts, but wait until they are asked to carry out revisions such that the information on the disk exactly matches that on the revised hard copy. Using author disks should save us a small amount of time; however, authors should still ensure that they check proofs carefully. As Professor Miller has mentioned in his Editorial, any peer-reviewed journal such as The Analyst stands or falls, mainly, by the quality imparted to it by the referees. Our referees have coped with an incredible amount of work on our behalf throughout 1994 and yet maintained the quality of their reports. We offer them our sincerest thanks and hope that they will maintain the standards of refereeing that we have become familiar with. Finally, 1994 saw a complete change in the personnel working on The Analyst leading to intensive on-the-job training for the new staff concerned and resulting in small backlogs throughout the year. Since then, procedures have been altered to allow a continuous production process as opposed to the batch system used previously. This change has allowed a more even flow of work and will hopefully result in Harp Minhas shorter publication times. Editor

ISSN:0003-2654    

DOI:10.1039/AN995200002N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

ANALAO 120( 1 ) 1-230, 1 N-16N (1 995) JANUARY 1995EDITORIALSCRITICAL REVIEWAMC'""An a I y stThe analytical journal of The Royal Society of ChemistryCONTENTS1N The Analyst at 120-4 N. Miller2N Changes-Harp Minhas1 Methods for Assessing the Authenticity of Orange Juice-Kevin Robards, Michael Antolovich29 Internal Quality Control of Analytical Data-Analytical Methods Committee35 Routine Lead Isotope Determinations Using a Lead-207-Lead-204 Double Spike: a Long-term Assessmentof Analytical Precision and Accuracy-Jon. D. Woodhead, F. Volker, M. T. McCulloch41 Gas Chromatography-Negative-ion Chemical Ionization Mass Spectrometry of Hydrolysed Human Urineand Blood Plasma for the Biomonitoring of Occupational Exposure to 4,4'-Methylenebisaniline-PerBrunmark, Marianne Dalene, Gunnar Skarping47 Determination of Creatinine in Human Serum.Statistical lntercalibration of Methods-M. C. Gennaro, C.Abrigo, E. Marengo, C. Baldin, M. T. Martelletti53 Micellar Liquid Chromatography of Zwitterions: Retention Mechanism of Cephalosporins-Carmelo GarciaPinto, Jose Luis Perez Pavon, Bernard0 Moreno Corder063 1 -Methoxycarbonylindolizine-3,5-dicarbaldehyde as a Derivatization Reagent for Amino Compounds inHigh-performance Capillary Electrophoresis-Shigeyuki Oguri, Chikako Uchida, Yasuko Miyake,Yasuyoshi Miki, Kazuaki Kakehi69 Evaluation, Mechanism and Application of Solid-phase Extraction Using a Dithiocarbamate Resin for theSampling and Determination of Mercury Species in Humic-rich Natural Waters-HAkan Emteborg, DouglasC.Baxter, Michael Sharp, Wolfgang Frech79 Optimization of Atomization Parameters in the Speciation of Organotin Compounds by HydrideGenerationGas Chromatography-Electrothermal Atomic Absorption Spectrometry-P. M. Sarradin, F.Leguille, A. Astruc, R. Pinel, M. Astruc85 Determination of Trace Amounts of Phosphorus in Silicate Materials by Simultaneous Inductively CoupledPlasma Atomic Emission Spectrometry-F. J. Valle Fuentes, S. del Barrio Martin89 Atomic Absorption Spectrometric Determination of Copper and Lead in Silicon Nitride and Silicon Carbideby Direct Atomization-Toshihiro Nakamura, Yuji Noike, Yoshiyuki Koizumi, Jun Sato95 Comparison of Reflux and Microwave Oven Digestion for the Determination of Arsenic and Selenium inSludge Reference Material Using Flow Injection Hydride Generation and Atomic AbsorptionSpectrometry-Rajananda Saraswati, Thomas W.Vetter, Robert L. Watters, Jr.101 Determination of Cadmium and Lead in Vegetables After Activated-carbon Enrichment by AtomicAbsorption Spectrometry-Mehmet Yaman, Seref GuGer107 Rapid Determination of Calcium, Magnesium, Sodium and Potassium in Milk by Flame AtomicSpectrometry After Microwave Oven Digestion-Miguel Angel de la Fuente, Manuela Juarez1 13 Novel Disulfonated Tetrazolium Salt That can be Reduced to a Water-soluble Formazan and its Applicationto the Assay of Lactate Dehydrogenase-Munetaka Ishiyama, Kazumi Sasamoto, Masanobu Shiga,Yosuke Ohkura, Keiyu Ueno, Katsuhiko Nishiyama, lsao Taniguchi11 7 Chemiluminescence Determination of Proteases by Flow Injection Using Immobilized Isoluminol-RobertEdwards, Alan Townshend, Barry Stoddart121 Determination of Volatile Phenols by a Flow Injection Chemiluminescent Quench Method-Hui-shengZhuang, Fan Zhang, Qiong-e Wang125 Kinetic Determination of Propyl Gallate in Edible and Cosmetic Oils With Sensitized Terbium(iii)Luminescence Detection-Sagrario Panadero, Agustina Gomez-Hens, Dolores Perez-Bendito129 Kinetic Determination of Carbirnazole, Methimazole and Propylthiouracil in Pharmaceuticals, Animal Feedand Animal Livers-Ma Soledad Garcia, Ma Isabel Albero, Concepcidn SBnchez-PedreAo, Lorenzo Tobal135 Enzymic Method for the Amperometric Determination of Nicotinic Acid in Meat Products-Takashi Hamano,Yukimasa Mitsuhashi, Nobuaki Kojima, Nobumi Aoki, Masanori Semma, Yoshio Ito, Yoshikiyo Oji7Continued on inside back cover-Typeset and printed by Black Bear Press Limited,Cambridge, England0003-26541199511:l-NEW AND VIEWS1391 4314915516116717117517918318719319720120721 121 521 721 821 9223225228VStudy of the Electrocatalytic Effect of Casein on the Polarographic Reduction of Nickel(i1).Determination ofTotal Proteins in Milk by Polarographic Chronoamperometry-A. Sanchez Perez, M. M. DelgadoZamarreAo, M. B. Turrion Nieves, J. Hernandez MendezDetermination of Cobalt in Blood Using Cathodic Stripping Voltammetry-Beata Godlewska, JerzyGolimowski, Adam Hulanicki, Constant M. G. van den BergComputer Program for Examination of Acids by Conductimetric-Potentiometric Titration-EdwardChromiakDevelopment of an Integrated Thermal Biosensor for the Simultaneous Determination of MultipleAnalytes-Bin Xie, Michael Mecklenburg, Bengt Danielsson, Ove Ohman, Peter Norlin, Fredrik WinquistSelective Piezoelectric Sensors Using Polymer Reagents-Thomas C. Hunter, Gareth J.PriceDetermination of Fluoride in the Presence of Tetravalent Metal Ions With an Ion-selective Electrode:Application to Raw Materials of Fluoride Glasses-Akio Yuchi, Tomoko Niwa, Hiroko WadaDetermination of Pyridoxamine in Urine by Matrix lsopotential Synchronous FluorescenceSpectrometry-J. J. Berzas Nevado, J. A. Murillo Pulgarin, M. A. Gomez LagunaUse of Fluorescamine for the Spectrofluorimetric Investigation of Primary Amines on Silanized Glass andIndium Tin Oxide-coated Glass-Robert Wilson, David J.SchiffrinSimultaneous Spectrofluorimetric Determination of Glycerol and Ethanol in Wine by Flow Injection UsingImmobilized Enzymes-I. L. Mattos, J. M. Fernandez-Romero, M. D. Luque De Castro, M. ValcarcelDetermination of Chloride Ions by Reaction With Mercury Thiocyanate in the Absence of Iron(iti) Using anUltraviolet-photometric, Flow Injection Method-Joanne Cirello-Egamino, Ian D. BrindleDetermination of Micro-amounts of Phosphorus With Malachite Green Using a Filtration-DissolutionPreconcentration Method and Flow Injection-Spectrophotometric Detection-Joko P. Susanto, Mitsu koOshima, Shoji Motomizu, Hiroshi Mikasa, Yoshikazu HoriDerivative Ultraviolet Spectrophotometric Determination of Saccharin in Artificial Sweeteners-Cristina D.Vianna-Soares, Jorge L. S.MartinsSpectrophotometric Determination of Uranium(iv) With Thorin andN-Hydroxy-N,N’-diphenylbenzamidine-Neena Nashine, Rajendra Kumar MishraApplication of Flow Injection Spectrophotometry to the Determination of Dissolved Iron in Sea-water-lrinaYa. Kolotyrkina, Liliya K. Shpigun, Yury A. Zolotov, Alexander MalahoffComparison of Sample Preparation Methods for the Spectrophotometric Determination of Phosphorus inSoil and Coal Fly Ash-Johanna M. SmellerMineral Analysis Using X-ray Powder Data-Nicholas Caios, Colin H. L. Kennard, Lambert K. Bekessy,ERRATUMCUMULATIVE AUTHOR INDEXCOPYRIGHT LICENCEINSTRUCTIONS TO AUTHORSGUIDELINES FOR SUBMISSION ON DISKIUPAC PUBLICATIONS ON NOMENCLATURE AND SYMBOLISMREFEREEING PROCEDURE AND POLICY (1995)FACSS 1995: ANNOUNCEMENT AND CALL FOR PAPERS3N Book Reviews7N Conference Diary12N Courses13N Papers in Future Issues15N List of Abbreviations and AcronymsCover picture: Authenticy of orange juice (see p. 1). Photograph kindly supplied by courtesy of Leeton CitrusJuices

ISSN:0003-2654    

DOI:10.1039/AN99520BX003

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

Analyst, January 1995, Vol. 120 7N Conference Diary Date Conference Locat ion 1995 February 6-8 7-10 9-1 1 9-1 1 15 19-24 International Conference on Arsenic in Ground Water: Cause, Effect and Remedy Calcutta, India 4th International Conference on Automation, Montreux, Robotics and Artificial Intelligence Applied to Switzerland Analytical Chemistry and Laboratory Medicine Fourier Transform Spectroscopy: New Methods and Applications USA Santa Fe, Modern Spectroscopy of Solids, Liquids, and Gases USA Santa Fe, Alternatives to Chemical Solvents Restricted by the Montreal Protocol UK London, OFC '95: Optical Fibre Communication Conference USA San Diego, 6-10 9-10 13-16 24 28-31 28-30 29-30 April 3-6 PITTCON '95, Pittsburgh Conference On Analytical Chemistry and Applied USA Spectroscopy Advances in Genetic Screening and Diagnosis of Human Diseases USA New Orleans, San Fransisco, Trace Elements, Free Radicals, Cytokines, Chromosomal Analysis and Tumour Markers in Clinical Medicine and Biochemistry Kuwait City, Kuwait The L.H.Sutcliffe Magnetic Resonance Symposium, covering ESR and NMR Guildford, UK Scanning 95 Seventh Annual International Microscopy Meeting USA California, Applications of Modern Mass Spectrometric Methods to Plant Science Research Swansea, UK Atomic Spectrometry Updates Bristol, UK 7th Instrumental Analysis Symposium Madrid, Spain Contact D. Chakraborti, School of Environmental Studies, Jadavpur University, Calcutta 700 032, India Tel: +91 33 473 5233. Fax: +91 33 473 4266 SCITEC, Avenue de Provence 20, CH-1000 Lausanne 20, Switzerland Tel: +41 21 624 1533.Fax: +41 21 624 1549 Optical Society of America, Meetings Department, 2010 Massachusetts Ave., N.W., Washington, DC Tel: +1 202 223 0920. Fax: +1 202 416 6100 Optical Society of America, Meetings Department, 2010 Massachusetts Ave., N.W., Washington, DC Tel: +1 202 223 0920. Fax: +1 202 416 6100 Ms. Paula Elliott, Secretary, Analytical Division, The Royal Society of Chemistry, Burlington House, Piccadilly, London, UK W1V OBN Tel: +44 (0)171437 8656. Fax: +44 (0)171 734 1227 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: + 1 202 223 9034. Fax: + 1 202 416 6100 20036-1023, USA 20036-1023, USA DC 20036-1023, USA Pittsburgh Conference, Suite 332,300 Penn Centre Boulevard, Pittsburgh, PA 15235-9962, USA Ben Keddy, Cambridge Healthtech Institute, Bay Colony Corporate Center, 1000, Wirter Street, Suite 3700, Waltham, MA 02154, USA Tel: +1 617 487 7989.Fax: +1 617 487 7937 Hussain Dashti, Department of Surgery, Faculty of Medicine, Kuwait University, P.O. Box 24923, Safat, Kuwait Fax: +965 531 8454 Dr. D. G. Gillies, Department of Chemistry, University of Surrey, Guildford, Surrey, UK GU2 5XH Mary K. Sullivan, Foundation for Advances in Medicine and Science, P.O. Box 832, Mahwah, NJ 07430 0832, USA Tel: + 1 201 818 1010. Fax: +1 201 818 0086 Dr. R. P. Newton, Biochemistry Group, School of Biological Sciences, University College, Swansea, Wales, UK SA2 8PP Tel: +44(0) 792 295 377. Fax: +44(0) 792 295 447 J. R. Dean, Department of Chemical and Life Sciences, University of Northumbria at Newcastle, Ellison Building, Newcastle upon Tyne, UK NE18ST Tel: +44 (0) 91 227 3517.Fax: +44 (0) 91 227 3519 7as Jomadas de Analisis Instrumental (JAI) Expoanalitica & Biocienca, Arda Reina Ma Cristina, Palacio no. 1. 08004-Barcelona, Spain Tel: +34 3 423 3101. Fax: +34 3 423 63488N Analyst, January 1995, Vol. 120 Date 10-13 23-25 2628 May 3 7-10 7-1 1 7-1 1 9-12 14-18 16-18 21-26 2 1-26 21-26 22-24 28-216 June 5-8 11-14 Conference Annual Chemical Congress (with Analytical Session) 6th International Symposium on Pharmaceutical and Biomedical Analysis 6th International Symposium on Chiral Discrimination New Techniques in Bioanalysis Handling of Environmental and Biological samples in Chromatography 86th AOCS Annual Meeting & Expo Seventeenth International Symposium on Capillary Chromatography and Electrophoresis Metal Compounds in Environmental and Life Location Edinburgh, UK St. Louis, USA St.Louis, USA Bradford, UK Lund, Sweden Texas, USA Virginia, USA Jiilich, &Analysis, Speciation and Specimen Banking Germany EMAS 95 on Modern Developments and Applications in Microbeam Analysis France Fourth International Conference on Progress in Analytical Chemistry in the Steel and Metals Industry St Malo, Luxembourg CLEO '95: Conference on Lasers and Elect ro-Op tics USA Baltimore, QELS '95: Quantum Electronics and Laser Science Conference USA Baltimore, ASMS Conference on Mass Spectrometry Atlanta, USA Eighth International Symposium on Polymer Analysis and Characterization (ISPAC-8) USA Sanibel Island, 19th International Symposium on Column Liquid Chromatography Austria Innsbruck, 5th Symposium on our Environment and 1st Asia-Pacific Workshop on Pesticides Singapore Convention City, 1995 International Symposium, Exhibit & Workshops on Preparative Chromatography USA Washington DC, Contact Dr.J. F. Gibson, The Royal Society of Chemistry, Burlington House, Piccadilly, London, UK W1V OBN Tel: +44 (0)171 437 8656. Fax: +44 (0)171 734 1227 Shirley Schlessinger, 400, East Randolph Street, Suite 1015, Chicago, Illinois 60601, USA Tel: +1 312 527 2011. Shirley Schlessinger, 400, East Randolph Street, Suite 1015, Chicago, Illinois 60601, USA Tel: +1312 527 2011. A. J. Crooks, 'Cartref', 35 Queensbury Road, Salisbury, Wiltshire, UK SPl 3PH Tel: +44 (0) 722 334974. Mrs.M. Frei-Hausler, Postfach 46, CH-4123 Allschwil 2, Switzerland Fax: +41 61 482 0805 AOCS Education/Meetings Department, P. 0. Box 3489, Champaign, IL 61826-3489, USA Tel: +1 217 359 2344. Fax: +1 217 351 8091 Dr. Milton L. Lee, Department of Chemistry, Brigham Young University, Provo, UT 84602- 4672, USA Tel: +1 801 378 2135. Fax: +1 801 378 5474 H. W. Durbeck, Institute of Applied Physical Chemistry, Research Center Jiilich (KFA), P.O. Box 1913, D-5170 Jiilich, Germany EMAS Secretariat, RIKILT-DLO, P.O. Box 230, 6700 AE Wageningen, The Netherlands R. Jowitt, British Steel plc, Technical, Teesside Laboratories, P.O. Box 11, Grangetown, Middlesbrough, Cleveland, UK TS6 6UB Fax: +44 (0)642 460321 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: +1202 223 9034.Fax: +1 202 416 6100 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: +1 202 223 9034. Fax: +1202 416 6100 ASMS, 815 Don Gaspar, Santa Fe, NM 87501, USA Tel: + 1 505 989 4517. ISPAC Registration, 815 Don Gaspar, Sante Fe, NM 87501 USA Tel: + 1 505 989 4735. Fax: + 1 505 989 1073 HPLC '95 Secretariat, Tyrol Congress, Marktgraben 2, A-6020 Innsbruck, Austria Tel: +43 512 575600. Fax: +43 512 575607 DC 20036-1023, USA DC 20036-1023, USA. The Secretariat, 5th Symposium on our Environment, c/o Department of Chemistry, National University of Singapore, Kent Ridge, Republic of Singapore 0511 Fax: +65 779 1691 Janet Cunningham, Barr Enterprises, 10120 Kelly Road, P.O.Box 279, Walkersville, MD 21793 USA Tel: + 1 301 898 3772. Fax: + 1 301 898 5596Analyst, January 1995, Vol. 120 9N Date Conference Contact 13-16 ESIS 95-New Infrared Spectroscopy and Microspectroscopy: FTIR and Raman July 2-6 VII International Congress of Toxicology 2-7 12th International NMR Meeting 9-13 3rd International Symposium on Applied Mass Spectrometry in Health Sciences and 3rd European Tandem Mass Spectrometry Conference 13th Australian Symposium on Analytical Chemistry/4th Environmental Chemistry Conference 9-14 9-15 SAC 95 10-13 Vth COMTOX Symposium on Toxicology and Clinical Chemistry of Metals 30-518 XXIInd International Conference on Phenomena in Ionized Gases August 5-10 13-17 20-25 27-219 27-119 27-1/9 27-30 1995 International Symposium on Soil and Plant Analysis 7th International Conference on Flow Injection Analysis 12th International Symposium on Plasma Chemistry CSI XXIX: Colloquium Spectroscopicum Internationale 46th Annual Meeting of the International Society of Electrochemistry (ISE46) Third International Conference on Magnetic Resonance Microscopy EUROTOX Location Lyon, France Seattle, USA Manchester, UK Barcelona , Spain Darwin, Australia Hull, UK Vancouver, Canada Hoboken, USA Wageningen , The Netherlands Seattle, USA Minneapolis, USA Leipzig, Germany Xiamen, China Wiirzburg, Germany Prague, Czech Republic G.Lachenal, Laboratoire des Materiaux Plastiques et Biomateriaux, Universitk Claude Bernard Lyon 1,43 Boulevard du 11 Novembre, 69622 Villeurbanne Cedex, France Jada Hill, The Sterling Group, 9393 W, 110th St., Suite, Overland Park, KS 66210, USA Tel: + 1 913 345 2228.Fax: + 1 913 345 0893 Dr. J. E. Gibson, Royal Society of Chemistry, Burlington House, Piccadilly, London, UK W1V OBN Professor Emilio Gelpi, Palau de Congressos, Departamento de Convencions, Avda, Reina Ma Christina, 08004 Barcelona, Spain 13AC/4EC, Symposium Secretariat, Convention Catalyst Int., GPO Box 2541, Darwin NT 0801, Australia Tel: +61 89 811 875. Fax: +61 89 411 639 Analytical Division, The Royal Society of Chemistry, Burlington House, Piccadilly, London, UK W1V OBN Tel: +44 (0)171437 8656. Fax: +44 (0)171 734 1227 F. William Sunderman, Jr., M.D., Departments of Laboratory Medicine and Pharmacology, University of Connecticut Medical School, P.O.Box 1292, Farmington, CT 06034-1292, USA Tel: +1 203 679 2328. Fax: +1203 679 2154 E. E. Kunhardt, Physics Department, Stevens Institute of Technology, Hoboken, NJ 07030 USA Tel: +1 201 216 5099. Fax: +1201216 5638 Soil and Plant Analysis Council,, Georgia University Station, P.O. Box 2007, Athens, GA Tel: +1706 546 0425. Fax: +1706 548 4891 Gary D. Christian, Department of Chemistry BG-10, University of Washington, Seattle, WA 98195 USA Tel: + 1 206 685 3478. Fax: + 1 206 543 5340 L. Graven, 315 Pillsbury Drive, SE, University of Minnesota, Minneapolis, MN 55455-0139, USA Tel: +1 612 625 9023. Fax: +1 612 626 1623 GDCh-Geschaftsstelle, Abt. Tagungen, Varrentrappestr. 40-42, Postfach 90 04 40, D-6000 Frankfurt am Main 90, Germany Tel: +49 69 791 7358.Fax: +49 69 791 7475 Secretariat, XLVIth ISE Annual Meeting, P.O. Box 1995, Xiamen University, Xiamen 361005, China Tel: +86 592 208 5349. Fax: +86 592 208 8054 Dr. A. Haas, Physikalisches Institute, Universitat Wiirzburg, Am Hubland, D-97074 Wiirzburg, Germany Czech Medical Association J. E. PurkynC, EUROTOX '95, P.O. Box 88, Sokolska 31,120 26 Prague 2, Czech Republic Tel: +42 2 24 915195. Fax: +42 2 24 216836 30612-2007, USA10N Analyst, January 1995, Vol. 120 Date Conference September Location 1-4 3-6 3-8 5-8 10-14 12-15 17-21 24-28 25-28 CSI XXIX, Post-symposium ICP-MS and 11th German ICP-MS Users Meeting Wernigerode , Germany Third International Meeting on Recent Louvain la Neuve, Advances in Magnetic Resonance Application Belgium to Porous Media 6th European Conference on the Spectroscopy Villeneuve of Biological Molecules d' Ascq, France RSC Autumn Meeting.Analytical and Faraday Sheffield, Symposium: Ions in Solution UK Ion-Ex '95, The Fourth International Conference and Industrial Exhibition on Ion Exchange Processes Wrexham, UK 5th International Symposium on Drug Analysis Leuven, Belgium 30th Annual Meeting of the Federation of Analytical Chemistry and Spectroscopy USA Societies 11th Asilomar Conference on Mass Spectrometry-Molecular Structure USA Determination: Activation, Mass Analysis and Detection 5th Symposium on 'Kinetics in Analytical Chemistry' (KAC '95) Russia Philadelphia, Pacific Grove, Moscow, October 1-5 21st World Congress of the International The Hague, Society for Fat Research (ISF) The Netherlands 9-13 ECASIA '95 Montreux, Switzerland 15-20 22nd Annual Conference of the Federation of Cincinnati, Analytical Chemistry and Spectroscopy USA Societies 24-27 BCEIA '9S-The International Sixth Beijing Beijing, Conference and Exhibition on Instrumental Analysis China November 5-10 OPTCON '95 San Jose, USA 14-15 International Conference for Chemical Manchester, Information Users UK Contact Professor Lieselotte Moenke, Department of Chemistry, Martin-Luther University, Halle- Wittenberg, Institute of Analytical and Environmental Chemistry, Weinbergweg 16, D-06120 Halle, Germany Professor J.M. Dereppe, Univcrsitk de Louvain, Place L. Pasteur 1, B-1348, Louvain la Neuve, Belgium Professor J. C. Merlin, ECSBM '95, LASIR, UST Lille Biit. C5, 59655 Villeneuve d'Ascq Cedex, France.Dr. J. F. Gibson, The Royal Society of Chemistry, Burlington House, Piccadilly, London, UK W1V OBN Tel: +44 (0)171437 8656. Fax: +44 (0)171734 1227 Ion-Ex '95 Conference Secretariat, Faculty of Science, The North East Wales Institute, Connah's Quay, Deeside, Clwyd, UK CH5 4BR Fax: +44 (0) 244 814305 Professor J. Hoogmartens, Institute of Pharmaceutical Sciences, Van Evenstraat 4, B-3000 Leuven, Belgium Tel: +32 16 28 34 40. Fax: +32 16 28 34 48 FACSS, P.O. Box 278, Manhattan, KS 66502-0003, USA Tel: +1301 846 4797. Professor R. Graham Cooks, Department of Chemistry, 1393 Brown Building, Purdue University, West Lafayette, IN 47907, USA Dr. I. F. Dolmanova, Analytical Chemistry Division, Chemical Department, Lomonosov Moscow State University, 119899 Moscow, Russia Tel: +7 095 939 3346.Fax: +7 095 939 2579 Mrs. J. Wills, ISF Secretariat, P.O. Box 3489, Champaign, IL 61826-3489, USA Tel: +1217 359 2344. Fax: +l 217 351 8091 EPEL-ECASIA 95, Department des Materiaud LMCH, CH-1015 Lausanne, Switzerland Fax: +4121693 3946 Joseph A. Caruso, FACSS National Office, 198 Thomas Johnson Dr., Suite S-2, Frederick, MD 21702, USA Tel: + 1 301 694 8122. Fax: + 1 301 694 6860 General Service Office, The International Sixth BCEIA, Room 585, Chinese Academy of Science Room, San Li He, Xi Jiao, P.O. Box 2143, Beijing 100045, China Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: +1 202 223 9034. Fax: +1 202 416 6100 Dr. M. P. Coward, Chemistry Department, UMIST, P.O. Box 88, Manchester, UK M60 1QD Tel: +44 (0) 61 200 4491.Fax: +44 (0) 61 228 1250 DC 20036-1023, USAAnalyst, January 1995, Vol. 120 11N Date Conference Locat ion Contact December 17-22 International Symposium on Environmental Hawaii, Biomonitoring and Specimen Banking USA 20-21 2nd LC/MS Symposium Cambridge, UK 1996 January 8-13 1996 Winter Conference on Plasma Florida, Spectrometry USA 21-25 VIth Latin American Congress on Caracas, Chromatography Venezuela February 6-9 Fourth International Symposium on Bruges, Hyphenated Techniques in Chromatography Belgium (HTC 4); Hyphenated Chromatographic Anal ysers March 17-21 3 1 4 4 April 23-36 May 7-9 June 16-21 July 8-12 47th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy USA Atlanta, 7th International Symposium on Supercritical Fluid Chromatography and Extraction USA Indianapolis, Analytica Conference '96 Munich, Germany VIIth International Symposium on Monte-Carlo, Luminescence Spectrometry in Biomedical Monaco Analysis-Detection Techniques and Applications in Chromatograph and Capillary Electrophoresis HPLC '96: 20th International Symposium on High Performance Liquid Chromatography USA San Francisco, XVI International Congress of Clinical Chemistry UK London, September 1-7 Euroanalysis IX Bologna, Italy K.S. Subraimanian, Environmental Health Directorate, Health Canada, Tunney's Pasture, Ottawa, Ontario, Canada K1A OL2 Tel: +1 613 957 1874. Fax: +1 613 941 4545 Dr. J. Oxford, Glaxo Research and Development, Park Road, Ware, Hertfordshire, UK SG12 ODJ R.Barnes, Department of Chemistry, Lederle GRC Tower, University of Massachusettes, P.O. Box 34510, Amherst, MA 01003-4510, USA Tel: +1 413 545 2294. Fax: +1413 545 4490 Irene Romero, Interep SA, P.O. Box 76343, Caracas 1070-A, Venezuela Dr. R. Smits, Royal Flemish Chemical Society (KVCV), Working Party on Chromatography, BASF Antwerpen N.V., Central Laboratory, Haven 725, Scheldelaan 600, B-2040 Antwerp, Belgium Tel: +32 3 561 2831. Fax: +32 3 561 3250 The Pittsburgh Conference, 300 Penn Center Boulevard, Suite 332, Pittsburgh, PA 15235-5503 USA Tel: +1412 825 3220. Fax: +1412 825 3224 Janet Cunningham, Barr Enterprises, 10120 Kelly Road, P.O. Box 279, Walkersville, MD 21793 USA Tel: +1301 898 3772. Fax: +1301898 5598 Congress Center, Messegelande, D-80325 Miinchen, Germany Tel: +49 89 5107 159. Fax: +49 89 5107 180 Prof. Dr. Willy R. G. Baeyens, University of Ghent, Pharmaceutical Institute, Department of Pharmaceutical Analysis, Harelbekestraat 72, B-9000 Ghent, Belgium Tel: +32 9 221 8951. Fax: +32 9 221 4175 Mrs. Janet Cunningham, Barr Enterprises, P.O. Box 279, Walkersville, MD 21793, USA Tel: +1 301 898 3772. Fax: +1301 898 5596 Mrs. Pat Nielsen, XVIth International Congress of Clinical Chemistry, P.O. Box 227, Buckingham, UK MK18 5PN Fax: +44 (0)280 6487 Professor Luigia Sabbatini, Euroanalysis IX, Dipartimento di Chimica, Universith di Bari, Via Orabona, 4, 70126 Bari, Italy Tel: +39 80 242020. Fax: +39 80 242026

ISSN:0003-2654    

DOI:10.1039/AN995200007N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

12N Analyst, January 1995, Vol. 120 Courses Date Conference 1995 February Location Contact 6-10 April 4-5 4-7 May 10 18 21 June 7-12 6-8 16-20 July 17-19 Basic Microbiology: A Practical Guide Campden, UK Workshop in Chemical Information Retrieval Manchester, UK Short Course on Chiral Resolution Rome, Italy Education and Training of Chromatographers London, UK Meat Authenticity: Introduction to Immunoassay Test Kits Techniques for Polymer Analysis and Characterization 4th Annual Course on Practical Methods of Digestion for Trace Analysis 5th Annual Flow Injection Atomic Spectrometry Short Course Campden, UK Sanibel Island, USA Amherst, USA Amherst, USA Capillary Electrophoresis, Routine Method for Montpellier, the Quality Control of Drugs: Practical France Approach Techniques Workshop (Chemometrics) Hull, UK September 6-8 5th Workshop on Chemistry and Fate of Paris, Modern Pesticides France December 18-19 LCMS Training Course Cambridge, UK Training Department, Campden Food and Drink Research Association, Chipping Campden, Gloucester, UK GL55 6LD Tel: +44 (0) 1386 840319.Fax: +44 (0) 1386 841306 Dr. M. P. Coward, Chemistry Department, UMIST, P.O. Box 88, Manchester, UK M60 1QD Tel: +44 (0)61 200 4491. Fax: +44 (0)61 228 1250 Dr. S. Faniti, CNR, Istituto di Cromatografia, C.P.10, I 00016, Monterotondo Scalo, Roma, Italy Fax: +39 6 906 25 849 Dr. D. Simpson, Analysis for Industry, Factories 2/3, Bosworth House, High Street, Thorpe-le- Soken, Essex, UK C016 OEA Tel: +44 (0) 255 861714. Fax: +44 (0) 255 662111 Training Department, Campden Food and Drink Research Association, Chipping Campden, Gloucester, UK GL55 6LD Tel: +44 (0) 1386 840319.Fax: +44 (0) 1386 841306 Dr. Petr Munk, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA Tel: +1512 471 4179. Fax: +1512 471 8696 Nancy Teranto, Questron Corporation, 4044 Quakerbridge Road, Mercerville, NJ08619 USA Tel: +1 609 587 6898. Fax: +1609 587 0513 J. Tyson, Department of Chemistry, LGRC Tower, University of Massachusetts, Box 34510, Amherst, MA 01003-4510 USA Tel: +1413 545 0195. Fax: +1413 545 4846 Professor H. Fabre, Laboratory of Analytical Chemistry, Faculty of Pharmacy, 15 Avenue Charles Flahault 34060 Montpellier, France Tel: +33 67 54 45 20. Fax: +33 67 52 89 15 Dr. M. J. Adams, School of Applied Sciences, University of Wolverhampton, Wulfruna Street, Wolverhampton, UK WV1 1SB Tel: +44 (0) 902 322141. Fax: +44 (0) 902 322680 Professor M-C. Hennion, ESPCI, Labo. Chimie Analytique, 10 Rue Vauquelin, 75005 Paris, France Dr. J. Oxford, Glaxo Research and Development, Park Road, Ware, Hertfordshire, UK SG12 ODJ Entries in the above listing are included at the discretion of the Editor and are free of charge. If you wish to publicize a forthcoming meeting please send full details to: The Analyst Editorial Office, Thomas Graham House, Science Park, Milton Road, Cambridge, UK CB4 4WF. Tel: +44 (0)223 420066. Fax: +44 (0)223 420247.

ISSN:0003-2654    

DOI:10.1039/AN995200012N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

13N Analyst, January 1995, Vol. I20 Future Issues Will lnclude- Sensing With Chemically Modified Carbon Electrodes- John P. Hart and Markas A. T. Gilmartin Adsorptive Stripping Voltammetric Determination of Uranium With Cephradine-Azza M. M. Ali, Mahmoud A. Ghandour and Mahmoud Khodari Quality Concepts and Practices Applied to Sampling-An Exploratory Study-Michael Thompson and M. H. Ramsey Arsenic in Ground Water in Six Districts of West Bengal, India-The Biggest Arsenic Calamity in the World. Part 1. Arsenic Species in Drinking Water and Urine of the Affected People-D. Chakraborti, Amit Chatterjee, Dipankar Das, Badal K. Mandal, Tarit Ruychowdhury and Gautam Samanta Arsenic in Ground Water in Six Districts of West Bengal, India-The Biggest Arsenic Calamity in the World. Part 2.Arsenic Concentration in Drinking Water, Hair, Nails, Urine, Skin-scale and Liver Tissue of the Affected People-D. Chakraborti, Dipankar Das, Amit Chatterjee, Badal Madal and Gautam Samanta Potassium Determination in Soils by Atomic Absorption Spectrometry Using the Slurry Technique- Judy Heinen Brown, Jesus E. Vas, Zully Benzo and Manuela Velosa Iron Metabolism in Rats Consuming Oil From Fresh or Fried Sardines-Pilar Navarro, Pilar Vaquero and Ana Perez- Granados Chromatographic Methods and Procedures for the Determi- nation of Alkyl Ketene Dimer (AKD) in Pulp and Paper Matrices-Brian B. Sithole, Samuel Nyarku and Lawrence H. Allen Selenoprotein P in Serum as a Biochemical Marker of Selenium Status-B. Akkeson, M. Persson-Moschos, W. Huang, T. S. Srikumar and S.Lindeberg Beyond Total Element Analysis of Biological Systems With Atomic Spectrometric Techniques-Alfred0 Sanz-Medel New Concepts of Iron and Aluminium Chelation Therapy With Oral Li (Deferiprone), and Other Chelators-George J. Kon t oghior ghes Speciation and Genotoxity of Butyltin Compounds-Jurgen Kuballa, Eckard Jantzen, Rolf-Dieter Wilken, K. K. Kwan and Y. K. Chau High-performance Liquid Chromatography and Post-column Chemiluminescence Detection for the Simultaneous Determi- nation of Trace N-Nitrosoamines and Corresponding Secon- dary Amines in Ground Water-Chengguang Fu and Hongda x u Analysis of Copper and Lead in Hair Using the Nuclear Microscope: Results from Normal Subjects, Wilson’s Disease and Lead Poisoning-J. J. Powell, F. Watt, J. A. Cargnello, J.P. Landsberg, R. J. Ede and R. P. H. Thompson Elemental Hair Analysis With Nuclear Microscopy and Energy Dispersive X-ray Spectroscopy-J. J. Powell, J. A. Cargnello, P. R. Crocker, F. Watt and R. P. H. Thompson Assessment of Toxic Metal Exposure Following the Camel- ford Water Pollution Incident: Evidence for Acute Mobiliza- tion of Lead Into Drinking Water-J. J. Powell, S. M. Greenfield, J. A. Cargnello, J. P. Landsberg, H. Trevor Delves, I. House, M. D. Kendall, F. Watt and R. P. H. Thompson The Study of Antioxidant Properties of Metal Aspartates and Their Compositions-Igor B. Afanasev, Tatjana B. Suslova, Zinaida P. Cheremisina, Natalia E. Abramova and Ludmila G. Korkina Studies on the Distribution and Characteristics of New Mammalian Selenium-containing Proteins-Dietrich Behne, Christian Weiss-Nowak, Margrit Kalcklosch, Christian West- phal, Hildegard Gessner and Antonios Kyriakopoulos Iron species Involved in Iron Homoeostasis and Toxicity- Robert R.Crichton and Roberta J. Ward Odourant Identification Using the Response Kinetics of Chemically-modified Quartz Piezoelectric Crystals-Alan Mackay-Sim, Bruce W. Saunders and David V. Thiel High-performance Liquid Chromatography With Diode Array Detection for the Determination of 12 Pesticides in Water Using an Automated Solid Phase Extraction-B. Nouri, B. Fouillet, P. Chambon and R. Chambon Indirect, Ion-annihilation Electrogenerated Chemilumines- cence, and its Application to the Determination of Aromatic Tertiary Amines-Gillian M. Greenway and Andrew W. Knight Probing the Characteristics of Metal-binding Proteins Using High-performance Liquid Chromatography-Atomic Absorp- tion Spectroscopy and Inductively-coupled Plasma Mass Spectrometry-Kim A.High, Jean-Simon Blais, Bradley A. J. Methven and James W. McLaren Qualitative and Semi-quantitative Trace Analysis of Acidic Mono-azo Dyes by Surface Enhanced Resonance Raman Scattering-P. C. White, C. H. Munro and W. E. Smith Fractionation of an Antiserum to Progesterone by Affinity Chromatography: Effect of pH, Solvents and Biospecific Adsorbents-Gianfranco Giraudi, Cornelia Parini, Nadia Corocher, Maria A. Bacigalupo, C. Baggiani and Stefan0 Colombi I I COPIES OF CITED ARTICLES ~ The Royal Society of Chemistry Library can usually supply copies of cited articles. For further details contact: The Library, Royal Society of Chemistry, Burlington House, Piccadilly, London W1V OBN, UK. Tel: +44 (0)71-437 8656.Fax: +44 ~ (0)71-287 9798. Telecom Gold 84: BUR210. Electronic Mailbox (Internet) LIBRARY@RSC.ORG. If the material is not available from the Society’s Library, the staff will be pleased to advise on its availability from other sources. Please note that copies are not available from the RSC at Thomas Graham House, Cambridge. I I13N Analyst, January 1995, Vol. I20 Future Issues Will lnclude- Sensing With Chemically Modified Carbon Electrodes- John P. Hart and Markas A. T. Gilmartin Adsorptive Stripping Voltammetric Determination of Uranium With Cephradine-Azza M. M. Ali, Mahmoud A. Ghandour and Mahmoud Khodari Quality Concepts and Practices Applied to Sampling-An Exploratory Study-Michael Thompson and M.H. Ramsey Arsenic in Ground Water in Six Districts of West Bengal, India-The Biggest Arsenic Calamity in the World. Part 1. Arsenic Species in Drinking Water and Urine of the Affected People-D. Chakraborti, Amit Chatterjee, Dipankar Das, Badal K. Mandal, Tarit Ruychowdhury and Gautam Samanta Arsenic in Ground Water in Six Districts of West Bengal, India-The Biggest Arsenic Calamity in the World. Part 2. Arsenic Concentration in Drinking Water, Hair, Nails, Urine, Skin-scale and Liver Tissue of the Affected People-D. Chakraborti, Dipankar Das, Amit Chatterjee, Badal Madal and Gautam Samanta Potassium Determination in Soils by Atomic Absorption Spectrometry Using the Slurry Technique- Judy Heinen Brown, Jesus E.Vas, Zully Benzo and Manuela Velosa Iron Metabolism in Rats Consuming Oil From Fresh or Fried Sardines-Pilar Navarro, Pilar Vaquero and Ana Perez- Granados Chromatographic Methods and Procedures for the Determi- nation of Alkyl Ketene Dimer (AKD) in Pulp and Paper Matrices-Brian B. Sithole, Samuel Nyarku and Lawrence H. Allen Selenoprotein P in Serum as a Biochemical Marker of Selenium Status-B. Akkeson, M. Persson-Moschos, W. Huang, T. S. Srikumar and S. Lindeberg Beyond Total Element Analysis of Biological Systems With Atomic Spectrometric Techniques-Alfred0 Sanz-Medel New Concepts of Iron and Aluminium Chelation Therapy With Oral Li (Deferiprone), and Other Chelators-George J. Kon t oghior ghes Speciation and Genotoxity of Butyltin Compounds-Jurgen Kuballa, Eckard Jantzen, Rolf-Dieter Wilken, K.K. Kwan and Y. K. Chau High-performance Liquid Chromatography and Post-column Chemiluminescence Detection for the Simultaneous Determi- nation of Trace N-Nitrosoamines and Corresponding Secon- dary Amines in Ground Water-Chengguang Fu and Hongda x u Analysis of Copper and Lead in Hair Using the Nuclear Microscope: Results from Normal Subjects, Wilson’s Disease and Lead Poisoning-J. J. Powell, F. Watt, J. A. Cargnello, J. P. Landsberg, R. J. Ede and R. P. H. Thompson Elemental Hair Analysis With Nuclear Microscopy and Energy Dispersive X-ray Spectroscopy-J. J. Powell, J. A. Cargnello, P. R. Crocker, F. Watt and R. P. H. Thompson Assessment of Toxic Metal Exposure Following the Camel- ford Water Pollution Incident: Evidence for Acute Mobiliza- tion of Lead Into Drinking Water-J.J. Powell, S. M. Greenfield, J. A. Cargnello, J. P. Landsberg, H. Trevor Delves, I. House, M. D. Kendall, F. Watt and R. P. H. Thompson The Study of Antioxidant Properties of Metal Aspartates and Their Compositions-Igor B. Afanasev, Tatjana B. Suslova, Zinaida P. Cheremisina, Natalia E. Abramova and Ludmila G. Korkina Studies on the Distribution and Characteristics of New Mammalian Selenium-containing Proteins-Dietrich Behne, Christian Weiss-Nowak, Margrit Kalcklosch, Christian West- phal, Hildegard Gessner and Antonios Kyriakopoulos Iron species Involved in Iron Homoeostasis and Toxicity- Robert R. Crichton and Roberta J. Ward Odourant Identification Using the Response Kinetics of Chemically-modified Quartz Piezoelectric Crystals-Alan Mackay-Sim, Bruce W.Saunders and David V. Thiel High-performance Liquid Chromatography With Diode Array Detection for the Determination of 12 Pesticides in Water Using an Automated Solid Phase Extraction-B. Nouri, B. Fouillet, P. Chambon and R. Chambon Indirect, Ion-annihilation Electrogenerated Chemilumines- cence, and its Application to the Determination of Aromatic Tertiary Amines-Gillian M. Greenway and Andrew W. Knight Probing the Characteristics of Metal-binding Proteins Using High-performance Liquid Chromatography-Atomic Absorp- tion Spectroscopy and Inductively-coupled Plasma Mass Spectrometry-Kim A. High, Jean-Simon Blais, Bradley A. J. Methven and James W. McLaren Qualitative and Semi-quantitative Trace Analysis of Acidic Mono-azo Dyes by Surface Enhanced Resonance Raman Scattering-P. C. White, C. H. Munro and W. E. Smith Fractionation of an Antiserum to Progesterone by Affinity Chromatography: Effect of pH, Solvents and Biospecific Adsorbents-Gianfranco Giraudi, Cornelia Parini, Nadia Corocher, Maria A. Bacigalupo, C. Baggiani and Stefan0 Colombi I I COPIES OF CITED ARTICLES ~ The Royal Society of Chemistry Library can usually supply copies of cited articles. For further details contact: The Library, Royal Society of Chemistry, Burlington House, Piccadilly, London W1V OBN, UK. Tel: +44 (0)71-437 8656. Fax: +44 ~ (0)71-287 9798. Telecom Gold 84: BUR210. Electronic Mailbox (Internet) LIBRARY@RSC.ORG. If the material is not available from the Society’s Library, the staff will be pleased to advise on its availability from other sources. Please note that copies are not available from the RSC at Thomas Graham House, Cambridge. I I

ISSN:0003-2654    

DOI:10.1039/AN995200013N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

Analyst, January 1995, Vol. 120 15N Technical Abbreviations and Acronyms The presence of an abbreviation or acronym in this list should NOT be read as a recommendation for its use. However those defined here, need not be defined in the text of your manuscript. AA AAS ac AID ADC AES AFS ANOVA AOAC ASTM ASV BSA BSI CEN CCD CI CI-MS bP CMOS c.m.c. CME CRM csv CVAAS C.W. CZE dc DME DPP DPV DRIFT DELFIA DNA DMSO EC ECD EDXA EDXRF EDTA EI EIA EIAES dPm EI-MS EIS ELISA emf EPR ETAAS EXAFS EXAPS EPA atomic absorption atomic absorption spectrometry alternating current analogue-to-digital analogue-to-digital converter atomic emission spectrometry atomic fluorescence spectrometry analysis of variance Association of Official Analytical Chemists American Society for Testing and Materials anodic stripping voltammetry boiling point bovine serum albumin British Standards Institution European Committee for Standardization charge coupled device chemical ionization chemical ionization mass spectrometry complementary metal oxide silicon critical micellization concentration chemically modified electrode certified reference material cathodic stripping voltammetry cold vapour atomic absorption spectrometry continuous wave capillary zone electrophoresis direct current dropping mercury electrode disintegrations per minute differential pulse polarography differential pulse voltammetry diffuse reflectance infrared Fourier transform spectroscopy dissociation enhanced fluorescence immunoassay deoxyribose nucleic acid dimethyl sulfoxide exclusion chromatography electron capture detector energy dispersive X-ray analysis energy dispersive X-ray fluorescence spectroscopy ethylenediaminetetraacetic acid electron impact ionization enzyme immunoassay electron-induced Auger electron electron impacthonization mass electron impact spectroscopy enzyme linked immunosorbent electromotive force electron paramagnetic resonance electrothermal atomic absorption extended X-ray absorption fine electron-excited X-ray appearance Environmental Protection Agency spectroscopy spectroscopy assay spectrometry structure spectroscopy potential spectroscopy FAAS FAB FABMS FAO-WHO FI FIA FI-AAS FID FIR FT FTIR FTMS FPLC FPD GC GC-MIP GDL GDMS GLC GM HGAAS HMDE HPLC HRXPS IC ICP ICP-MS id IR ISFET iv im IGFET ISE LA-ICP-MS LC LIMS LM-ICP-AES LMMS LOD LOQ LSV M Mr MIP mP MRL mRNA MS MSD MSPD MIMS NIR MS-MS flame atomic absorption fast atom bombardment fast atom bombardment mass Food and Agriculture Organization, flow injection fluorescence immunoassay flow injection atomic absorption flame ionization detector (GLC) far-infrared (spectroscopy) Fourier transform Fourier transform infrared Fourier transform mass fast protein liquid chromatography flame photometric detector gas chromatography gas chromatography microwave- induced plasma glow discharge lamp glow discharge mass spectroscopy gas-liquid chromatography Geiger-Muller hydride generation atomic absorption spectroscopy hanging mercury drop electrode high-performance liquid high resolution X-ray photoelectron ion chromatography inductively coupled plasma inductively coupled plasma mass spectrometry internal diameter infrared ion selective field effect transistor intravenous intramuscular insulated gate field effect transistor ion-selective electrode laser ablation ICP-MS liquid chromatography laboratory information management system laser microprobe ICP-AES laser microprobe mass spectrometry limit of determination limit of quantification linear sweep voltammetry molecular mass relative molecular mass microwave-induced plasma melting point maximum residue limits messenger ribonucleic acid mass spectrometry mass selective detector tandem mass spectrometry matrix solid phase dispersion membrane inlet mass spectrometry near-infrared (near-IR) spectroscopy spectrometry World Health Organization spectroscopy spectrometry chromatography spectroscopy16N Analyst, January 1995, Vol.120 NMR NIST OES PCB PAH PC PDA PIXE PPt PLS PPb PPm PTFE PVC PDVB QC r RBS REE rev min- rf RI RIA RIMS rms rPm RNA RHE RMSD S Sr SCE SE 1 nuclear magnetic resonance National Institute of Standards and optical emission spectrometry polychlorinated biphenyl polycyclic aromatic hydrocarbons paper chromatography photodiode array particle/proton-induced X-ray parts per trillion (1012) partial least squares parts per billion (109) parts per million (106) poly( tetrafluoroethylene) poly(viny1 chloride) poly (divinyl benzene) quality control correlation coefficient Rutherford (ion) backscattering rare earth element(s) revolutions per minute radio frequency refractive index radioimmunoassa y resonance-ionization mass spectrometry root mean square revolutions per minute ribonucleic acid reversible hydrogen electrode root mean square difference standard deviation relative standard deviation saturated calomel (reference) electrode standard error Technology emission (spectroscopy) SEM SERS SFC SFE SIMS SIMCA SPE SRM STM STP TIMS TLC TOF TGA TCA TMS tris TRIS uv UV/VIS VDU WDXRF WHO XES XPS XRD XRF YAG U scanninghrface (reflection) electron microscopy surface-enhanced Raman spectroscopy supercritical fluid chromatography supercritical fluid extraction secondary ion mass spectrometry soft independent modelling of class analogy, statistical isolinear multicategory analysis solid phase extraction Standard Reference Material scanning tunnelling (electron) standard temperature and pressure thermal ionization mass thin-layer chromatography time-of-flight thermogravimetric analysis trichloroacetic acid trimethylsilane 2-amino-2-(hydroxymethyl)- tris (h y drox y methyl) me thy lamine atomic mass unit ultraviolet ultraviolet-visible (spectroscopy) visual display unit wavelength dispersive X-ray fluorescence spectroscopy World Health Organization X-ray emission spectroscopy X-ray photon spectroscopy X-ray diffraction X-ray fluorescence (spectroscopy) yttrium aluminium garnet microscopy spectrometry propane-l,3-diol

ISSN:0003-2654    

DOI:10.1039/AN995200015N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

Analyst, January 1995, Vol. 120 29 Internal Quality Control of Analytical Data Analytical Methods Committee* Royal Society of Chemistry, Burlington House, Piccadilly, London, UK Wl V OBN It is recognized that effective quality control procedures are essential if analysis is to produce data that are fit for their purpose. This paper outlines the practical approaches to quality control. The control of random error using replication of analysis is described. Different types of reference materials are discussed as a means of controlling systematic error. Keywords: Analytical quality control; accuracy of results; reference materials The Analytical Methods Committee has received and has approved for publication the following report from its Statistical Sub-committee. Report The constitution of the Sub-committee responsible for the preparation of this paper was Dr.M. Thompson (Chairman), Dr. D. W. Brown (from October 1991), Dr. W. H. Evans (until June 1992), Mr. M. J. Gardner, Dr. E. J. Greenhow, Professor R. Howarth, Professor J. N. Miller (from July 1991), Dr. E. J. Newman, Professor B. D. Ripley, Mrs. K. J. Swan, Mr. A. Williams (from June 1992) and Dr. R. Wood, with Mr. J. J. Wilson as Secretary. The Analytical Methods Committee acknowledges financial support from the Ministry of Agriculture, Fisheries and Food. The views expressed and the recommendations made in this paper are those of the Analytical Methods Committee and not necessarily those of the Ministry of Agriculture, Fisheries and Food. Introduction An analytical result cannot be interpreted unless it is accompanied by knowledge of its associated uncertainty. A simple example demonstrates this principle.Suppose that there is a requirement that a material must not contain more than 10 yg g-1 of a particular constituent. A manufacturer analyses a batch and obtains a result of 9 kg g-1. If the uncertainty on the result is 0.1 pg g-1 (i.e. the true result falls within the range 8.9-9.1 pg g-1 with a high probability) then it can be accepted that the limit is not exceeded. If, in contrast, the uncertainty is 2 pg g-1 there can be no such assurance. The ‘meaning’ or information content of the measurement thus depends on the uncertainty associated with it. Analytical results must therefore be accompanied by an explicit quantitative statement of uncertainty, if any definite meaning is to be attached to them or an informed interpreta- tion made.If this requirement cannot be fulfilled, there are strong grounds for questioning whether analysis should be undertaken at all. The second conclusion is that in analysis the measurement uncertainty must be continually reappraised, because it can vary both with time within a laboratory and * Correspondence should be addressed to the Secretary, Analytical Methods Committee, Analytical Division, Royal Society of Chemistry, Burlington House, Piccadilly, London WlV OBN, UK. between different laboratories. This process of continual reappraisal of data quality provides a means of demonstrating and controlling the accuracy of data. The concept of internal quality control of analytical data (IQCAD) should be applicable to all types of chemical analysis.14 The success of IQCAD depends on the way in which it is applied.This, in turn, depends on the nature of the analytical job. Modifications of the practice of quality control will need to be made to accommodate numbers of samples analysed and the frequency with which analysis is undertaken. The purpose of this paper is to provide guidance on the purposes and implementation of QC procedures. It is recog- nized that the quality of sampling procedures determines to a large extent the quality of the measurement produced. However, the assessment of sampling quality is in its infancy. This document is restricted therefore to analytical quality control. Quality Control and Quality Assurance A number of factors contribute to the production of analytical data of adequate quality.Most important is the recognition of the standard of accuracy that is required of the analytical data. This should be defined with reference to the intended uses of the data. It is seldom possible to foresee all of the potential future applications of analytical results. For this reason, in order to prevent inappropriate interpretation, it is important that a statement of the intended accuracy and a demonstration that it has been achieved should always accompany analytical results, or at least be readily available to those who wish to use the data. From the practical point of view, the following factors are important in meeting accuracy requirements. Compliance with Sound Principles of Laboratory Practice and Organization Good laboratory practice or ‘quality assurance’ (in the general sense) is the essential organizational infrastructure that underlines all reliable analytical measurements.It is concer- ned with achieving appropriate levels in matters such as staff training and management, adequacy of the laboratory envi- ronment, safety, the storage, integrity and identity of samples, record keeping, the maintenance and calibration of instru- ments and the use of properly documented methods. Failure in any of these areas might undermine vigorous effects elsewhere to achieve the desired quality of data. In recent years these practices have been codified and formally recog- nized as essential. However, the prevalence of these favour- able circumstances by no means ensures the attainment of appropriate data quality.Availability of Analytical Methods that are Capable of Producing Data of the Required Quality It is important that laboratories restrict their choice of methods to those which have been thoroughly tested and have30 Analyst, January 1995, Vol. 120 been shown to be free from important fundamental flaws, for the types of analysis and materials of interest. However, even a wise choice of method does not exclude the possibility of serious error. A method does not itself possess any inherent performance characteristics for precision or trueness. There is, for a given method, only the potential to achieve a certain standard of accuracy when the method is applied under a given set of circumstances.The entire set of circumstances, including the chosen method, under which analytical results are produced can be defined as the laboratory’s analytical system. The analytical system is responsible for the accuracy of analytical data. It is therefore important to determine and control the performance of the analytical system in order to meet accuracy requirements. This should be the initial aim of any quality control measures undertaken in a laboratory. In summary, the introduction and use of an analytical method is best seen in three parts: (a) The development stage. This is usually undertaken by a single laboratory to meet an analytical need. The outcome is to produce a written procedure that has been subjected to preliminary tests to determine the likely range of application and limit of detection.(b) The validation stage. This should be carried out by a group of laboratories. The ideal approach to validation is for extensive testing of precision and trueness to be carried out in several laboratories on test samples of known composition. This stage aims to produce what is often referred to as a standard method-a method for which there is a range of test data as an illustration of the accuracy that can be achieved. Method validation is outside the scope of this paper, although, as discussed below, it may have elements in common with quality control. (c) The implementatiodapplication stage. This involves incorporation of the method into the analytical system of a given laboratory and the characterization of performance in routine use.It is the stage at which initial trials are followed by quality control tests carried out on a continuing basis. These tests should be regarded as distinct from tests to validate the method [which should have been carried out earlier as part of stage (b)]. The distinction made earlier between validation and implementation of methods is valuable in consideration of two key elements of control over bias: the use of reference materials and participation in interlaboratory tests. Both of these approaches to quality control are used, in a modified form, in method validation. The discussion below of reference materials and interlaboratory tests refers only to their application in routine quality control. Application of Quality Control Procedure Quality control is the term used to describe the practical steps undertaken to ensure that the analytical data are adequately free from error.The practice of IQCAD depends on the use of two strategies, the analysis of reference materials to check on trueness, and of some form of replication to check on precision. In this paper, the term ‘reference material’ is used to denote a test material of specified determinand content; it includes certified reference materials (CRMs), house refer- ence materials (HRMs) and independent calibration (stan- dard) reference materials (SRMs). ‘Test material’ is used as a general term to describe the type of substance analysed by the laboratory. The basic approach to IQCAD involves the analysis of control materials (reference substances or test materials of defined composition) alongside the test materials of interest.The outcome of the control analyses forms the basis of a decision regarding the acceptability of the test data. Two key points are worth noting in this context. First, interpretation, wherever possible, should be based on objective statistical criteria. Second, the results of control analyses should be viewed primarily as indicators of the performance of the analytical system, rather than as a guide to the errors associated with individual test results. Hence changes in the apparent accuracy of control determinations are usually taken to signal changes in the system but cannot be assumed to indicate an identical change for data obtained for test materials analysed at the same time.General approach-statistical control The intrepretation of the results of quality control analyses depends largely on the concept of statistical control. Statistical control corresponds to stability of operation. Specifically, it implies that quality control results can be interpreted as arising from a normal population with mean p and variance 02. Only about 0.3% of results would fall outside the bounds of p k 30, and such results can justifiably be regarded as being ‘out-of- control’, i.e., that the system has started to behave differently. Loss of control is taken to imply that the data produced by the system are of unknown accuracy and hence that they cannot be relied upon. The system thus requires investigation and remedial action before further analysis is undertaken.Results falling outside the bounds p k 20 would be sufficiently unusual (about 5%) to act as a warning of a possible problem. The values of o should be estimated by careful observation of the analytical system over an extended period. Initial estimates may need to be updated as use of the analytical system proceeds. Consideration must be taken when setting control limits of whether individual results or means of several results are to be controlled. Compliance with statistical control should be monitored graphically with Shewhart control charts.5--8 A less visually informative, but numerically equi- valent, approach [by the equivalent method of comparing values of z = (x-X)/o against appropriate values of the normal deviate] is also possible; x is an individual observation and Xis the mean value used as the best estimate of p.The nature of analytical errors It is worthwhile to recognize that two main categories of analytical error may arise. These are random errors and systematic errors (giving rise to imprecision and bias, respec- tively). The importance of categorizing errors in this way lies in the fact that they have different sources, remedies and consequences for the interpretation of data. Random errors determine the precision of analysis. They may be envisaged as causing positive and negative deviations of results about the underlying population mean. Systematic errors are manifested as a displacement of the mean of many determinations from the true value. Two forms of systematic error are worthy of consideration.Persistent bias may affect the analytical system (for a given type of test material). This will apply over a long period and affect all data. Such bias, if it is small in relation to random error, may only be identifiable after the analytical system has been in operation for a long time. It might be regarded as tolerable, provided it is kept within prescribed bounds. The second type of bias is an adventitious form introduced by a failure of the system (e.g., mistaken use of the wrong size of pipette). This form of bias is not to be tolerated, but, because it is often large, it may easily be detected by IQCAD at the time of occurrence. To some extent the division between what is regarded as random and systematic error depends on the time-scale over which the system is viewed.Long-term changes of unknown source in a positive and negative direction could be regardedAnalyst, January 1995, Vol. 120 31 as long-term random effects. Alternatively, if a shorter term view is taken, the same errors could be seen as changes in bias. Another example is ‘drift’. Calibration drift within a batch of analyses is a form of bias. However, its effect is to increase the spread of results of replicate analyses. Hence, it might be observed as a contributor to random error. As ever, the view of performance should be based on the likely consequences on data use. The batch or ‘run’ Quality control envisaged in this paper is largely based on the idea of the analytical batch. The batch can be regarded as a group of one or more test materials that are analysed by a particular method under conditions in which environmental factors that affect data quality are essentially constant, i.e., under ‘repeatability conditions’.Results from a particular batch are associated with one or more control measurements. The batch is thus the operational unit for data quality control. Routine Control of Precision An analytical result ( x ) produced in a laboratory on a particular test material can be regarded as a random sample from a potentially infinite normal population with a mean 1-1 and variance 0 2 , if the analytical protocol is executed under conditions where an approximation to statistical control can be assumed. Although several different measures can be regarded as describing ‘precision’, they are all based on 0.It should be borne in mind that the precision of interest (and therefore that which must be monitored and controlled) can vary according to data use. In a long-term monitoring programme the overall precision of data (including within- and between-batch random errors, often called ‘total’ stan- dard deviation) is important. If comparisons are to be made between observations made in the same batch, only short- term precision (as measured by the within-batch standard deviation) is of interest. Quality Control with Duplicates The simplest control of precision is achieved by duplicated measurements made on real test materials. The measure of precision monitored in this case is within-batch variation. Unless the test materials analysed are uniform, both in gross composition and in determinand level, o can be expected to vary from one test item to another.Several approaches may be applied in different circumstances. (i) All of the test materials are analysed in duplicate, and the differences (xl - x2) are tested against appropriate control limits based on a specified value of o. This method is appropriate for small batches of test materials, where statis- tical control cannot be established. (ii) A random selection of the test materials (of each type and determinand level) is analysed in duplicate. This would be appropriate for large batches of analyses and is particularly applicable to unstable determinands or those for which no reasonably representative reference material may be devised.(iii) A few representative HRMs are analysed in duplicate. This applies to the situation where (a) there are no problems with the representativeness of the control material and stability of reference materials and (b) when similar types of samples are analysed on a regular routine basis. Of these options, (i) and (ii) have the advantage that representativeness (in relation to random error) of the reference material does not have to be assumed. For some applications, it has been noted that the precision of determina- tions on reference materials are often too good, because of the extreme care with which such materials are prepared. In other areas (such as water analysis), however, this objection may not arise. The advantage with option (iii) (provided it is applic- able) is that data can be obtained for the control of both precision and bias at the same time and the performance can be monitored using a mean and range Shewhart chart (see below).Duplicates intended to control within-batch precision must not be placed adjacent to each other in the analytical sequence, otherwise they will reflect only the smallest possible measure of analytical variability. The best spacing for realistic precison control of within-batch duplicates is at random within each batch. Interpretation of Duplicate Data For the simplest approach, each group of test materials used in control measurements should have a small range of composi- tion, so a common within-batch standard deviation of results can be assumed. (a) The differences ( d = x1 - x2) between duplicate pairs should be examined.The expected distribution of the values of d is zero-centred with a standard deviation of q 2 0 . Thus the 95% confidence interval of the differences would be bounded (approximately) by -2u20 and + 2 f i o . However, it is often more convenient to consider absolute differences Id(. In this case the expected mean value is 1.1280 and the upper 95% bound of Id1 is 2.80, or about 30. This treatment is consistent with the I S 0 treatment of repeatability. Only about 1 in 20 absolute differences can be expected to fall above the 30 limit. An unduly high proportion is taken to show that the system is out of control, and is manifesting an unacceptable precision. Only about 1 in a 1000 results should fall above 4.60, corresponding to the action limit on the conventional Shewhart chart.(b) An alternative statistical approach is to form the standardized difference z d = d/V% which should have a normal distribution with zero mean and unit standard deviation. Individual values could be inter- preted on this basis. A group of n such results from a batch could be combined by forming z z d 2 and interpreting the result as a sample from a chi-squared distribution with n degrees of freedom. This alternative treatment is closer to recent trends in interpreting the results of proficiency tests. If test materials have a wide range of determinand concentrations, no common standard of precision can be assumed for the test materials, but a functional relationship between o and the determinand concentration X can still be determined.A linear relationship of the form given below may be expected: o = a + b X where a and b are constants that can be estimated for within-batch precision in the analytical system. If the mean of duplicate results is used as an estimate of the true concentra- tion, X, the expected value for 0 can be calculated. This enables us to extend the duplicate method to wide ranges of determinand concentration, utilizing either of the methods described previously. Precision Control using Reference Materials This may be applied where the reference material is a close analogue of test materials. A reference material is analysed ( n replicates) in each batch of tests and the data plotted on two Shewhart charts, one for the mean result and the other for the range of values.The charts act as a means of monitoring systematic and random errors, respectively. Control limits are32 Analyst, January 1995, VoI. 120 set at +2a and +3a for the chart of mean values. In this case the value for B corresponds to the batch to batch standard deviation of mean (of n replicates) values. Control limits for the range chart are based on estimates of the mean range as indicated in Table 1. Limits for the range chart are calculated by multiplying the mean range by the factor in the table (from BS 6008). Control of Bias Control Materials The bias (p - A‘) of an analytical result is the difference between the mean of the population of analytical results (p) and the true value (X). In routine analysis, p is estimated as the mean of a relatively small number of results.In order to estimate bias, it is necessary to have a working estimate of X . This is achieved by use of a reference material. There is a slight difference when an empirical method is used to measure a chemically ill-defined determinand such as ‘fat’. In that instance, truencss may need to be defined in relation to the consensus of a large number of laboratories’ results. When used in IQCAD as control materials, reference materials act as surrogates for the test samples, and must therefore be representative of the test material (i.e., they should be subject to the same potential sources of error), if a useful check on bias is to be made. To be fully representative, a control material must have the same matrix (in terms of gross composition and in any trace constituents which may have a bearing on accuracy) and it should be in a similar physical form, e.g., state of comminution, as the test materials.There are three other essential characteristics of a control material: it should be adequately stable over the period of interest; it must be possible to divide the control material into essentially identical portions for analysis, to allow its use over an extended period; and it must contain a concentration of the determinand that is appropriate to the range of interest. In practice, it is necessary to make some compromise on the extent to which a control material is representative of test materials. Nevertheless, analysts should always seek to improve the representativeness of their control materials. Certified Reference Materials Certified reference materials (CRMs), when available, are ideal for use as control materials as they are directly traceable to international standards or units.However, several deficien- cies limit the use of CRMs for routine QC, viz. , (a) their cost; (b) the relatively small amounts that may be purchased; (c) the small ranges of matrix and determinand content that are covered, especially for natural materials; (d) the fact that the uncertainty in the certified determinand content may be large in relation to allowable error in the application concerned; and (e) the limitation of the CRM concept to determinands and matrices that are stable. Table 1 Control limits for the range chart No of replicate analyses Warning Action on RM 2 0.04 2.81 0.00 4.12 3 0.18 2.17 0.04 2.99 4 0.29 1.93 0.10 2.58 5 0.37 1.81 0.16 2.36 6 0.42 1.72 0.21 2.22 Multiplier for action and warning limits ( n ) Lower Upper Lower Upper House Reference Materials (HRMs) For most analyses undertaken at present, appropriate CRMs are not available.It therefore falls to individual laboratories or groups of laboratories to prepare their own ‘house’ reference materials (HRMs) in suitable form, and to assign appropriate determinand concentration values to them. Assigning a true value by analysis In principle, all that is required to assign a true value to a stable reference material is careful analysis. However, con- siderable precautions may be necessary to avoid the very biases that IQCAD seeks to eliminate.This usually requires some form of independent check such as may be provided by analysis in a separate laboratory or laboratories and, where possible, the use of methods based on different physical and chemical principles. An alternative way of establishing the determinand concen- tration in an HRM is to carry out a comparison analysis (i. e., under repeatability conditions) with a suitable CRM (. z.e., one which is closely similar in both matrix and determinand concentration). The measured mean value for the HRM is adjusted to allow for the difference found between the mean for the CRM and its certified value. In effect, the CRM is used to calibrate the system for the HRM. This establishes a direct traceability from the CRM to the HRM. Assigning a true value by formulation In favourable instances an HRM can be prepared simply by admixture of constituents of known purity in predetermined amounts.For the formulation to be successful, the matrix constituents must be adequately free from determinand and the added determinand must be from a source independent of the analytical calibration. Problems are often encountered in producing the HRM in a satisfactory physical state or in ensuring that the chemical form of the determinand is realistic. Spiked control materials This is a way of creating a reference material in which a value is assigned by a combination of formulation and analysis. This is possible when a test material essentially free of the determinand is available. This material is spiked with a known amount of determinand, after exhaustive analytical checks to ensure that the background level is adequately low.The reference sample prepared in this way is thus of the same matrix as the test materials to be analysed and of known determinand level-the uncertainty in the assigned concentra- tion is limited only by the possible error in the unspiked determination. However, it may not be possible to ensure that the chemical form of the determinand is the same as in real samples. The use of spiked materials is valuable when the determinand is not stable, so that HRMs cannot be estab- lished, and when analyses are carried out on an ad hoc basis. Recovery checks A limited check on some sources of bias is possible by a check on recovery. This may be useful when determinands or matrices cannot be stabilized and when ad hoc analysis is required.A portion of the test material is spiked with a known amount of the determinand and the ‘recovery’ (the proportion of the added amount detected) is measured. The primaryAnalyst, January 1995, Vol. I20 33 advantages of recovery checks are that the matrix is represen- tative and the approach is widely applicable-most test materials can be spiked by some means. Again, this approach suffers from the disadvantage noted previously regarding the chemical speciation of the determinand. However, it can normally be assumed that poor performance in spiking recovery is strongly indicative of a similar or worse bias for the test material. Spiking and recovery testing as a method of quality control should be distinguished from the method of standard additions (which is a calibration procedure) i.e., the same spiking addition cannot be used to fulfil the role both of calibration and an independent check on accuracy. Standard Reference Materials (SRMs) In some situations it is possible to prepare a control material from pure constituents, for example, a standard solution made from high-purity metals.It is essential that the source of the constituents is independent of that used to obtain calibration materials, otherwise there is no check on bias at all. Checks on purity by spectroscopic or chromatographic means are recom- mended. This type of control material is probably the least useful in that it is at best a check only on calibration bias. However, the limited scope of the control means that it is simple to assign a cause for any bias that is detected.SRMs should be prepared at determinand concentrations at or near the top of the calibrated analytical range. This ensures the maximum power to detect calibration bias. Participation in Interlaboratory Tests Proficiency testing is a periodic assessment of the performance of individual laboratories and groups of laboratories that is achieved by the distribution by an independent testing body of typical materials for unsupervised analysis by the partici- pants .4 Proficiency testing schemes should be used where appro- priate, i.e., where the sample type and determinand concen- tration relate to the samples analysed routinely. They can be regarded as a routine, but relatively infrequent, check on bias.Without the support of a well developed within-laboratory QC system within which a control material is analysed in every batch of analyses, participation in a proficiency test is not an effective means of controlling errors. The advantage of proficiency tests is that they can allow the detection of unforeseen sources of bias. They play a key role in demonstrating the need for remedial action in laboratories with long-term problems in achieving data of appropriate quality, and the efficacy or otherwise of any remedies applied. Moreover, successful schemes demonstrate that participants have the ability to produce data of a given quality on the occasions of the tests, and hence have the potential to do so on other occasions.The limitations of proficiency tests fall into four main categories: (a) they are necessarily restricted in the scope of materials and determinands that can be prepared and circu- lated for testing; the performance of a laboratory in a given test often has to be taken as an indication of its capabilities for a wide range of related analyses; (b) the samples analysed are usually identifiable as check samples and may be analysed with more than usual care, hence the standard of accuracy achieved is not necessarily typical of laboratories’ routine operation; (c) they are repeated over a long time-scale and therefore cannot indicate the short-term variations in quality that can occur within laboratories; (d) they function as good indicators of overall data quality, but do not identify clearly the sources of errors and thereby point to effective remedies.Application of Routine IQCAD Approach to IQCAD versus Analytical Load-Various Cases The practical approach to quality control is determined by the frequency with which batches of analyses are carried out and the size of each batch. Analysis that is performed only occasionally or perhaps in one batch does not lend itself to the statistical interpretation that underlines conventional QC systems. It is not possible under these circumstances to establish and maintain a state of statistical control over the measurement process. Frequent large batches of analyses pose different problems: those of too great a number of QC data and of the possibility of needing to reject large amounts of data if ‘out of control’ is indicated.Guidance on what to do under these different circumstances is given below. Small batches (<20) analysed frequently Recommendation: carry out at least one control analysis of a reference material (spiked as appropriate) per batch. Plot a control chart of individual values. Respond to ‘out of control’ on chart by rejecting the batch of data and (where possible) repeating analyses. Use a variety of duplicate controls if different sample types are analysed at the same time. The frequency of analysis means that sufficient QC data can be generated to establish control. However, it is usually practical to peform only one QC analysis per batch. The frequency of use of control materials recommended above is for general purposes.It may be advisable to use more or permissible to use less under specific circumstances. The deviation of the actual rate of ‘out of control’ determinations from that expected does not usually pose problems. Large batches (>20) analysed frequently Recommendation: carry out one control analysis of a reference material (spiked as appropriate) per 10 test samples. If the batch size varies (but is still large), arrange to standardize on a fixed number of control determinations per batch, say between three and six. Plot a mean and range control chart. Respond to ‘out of control’ on the mean chart by rejecting all data if d l control analyses agree or, if there is only one discordant result, investigate its cause and respond accord- ingly. Respond to ‘out of control’ on the range chart by checking for sources of random error.This is the ideal approach to IQCAD provided that the choice of control material(s) is (are) representative. The use of mean and range charts allows checks on precision and bias (see below). Control data can be relied upon to be normally distributed, so the control system will operate according to statistical expectations. If the concentration range is wide (i.e., spanning a factor of 10 or more), two levels should be represented by appropriate HRMs. Batches analysed infrequentlylad hoc analyses Recommendation: carry out duplicate determinations on at least one third of samples, carry out spiking recovery tests on representatives of all sample types (consider standard addi- tions calibration) and, where possible, analyse at least one independently confirmed reference material for each sample type.Costs of IQCAD The practice of quality control requires extra analytical effort and consequently an apparent increase in costs. The amount of extra work varies with circumstances but is likely to be at least 15%. This figure is not alarming in proper perspective: it34 Analyst, January 1995, Vol. 120 is estimated that 10% of all analyses undertaken are repeated subsequently because of obvious unreliability. More signifi- cantly, the true cost of undetected analytical errors must be substantial, although difficult to quantify. Further, in the current era of the ‘educated customer’, a laboratory will increasingly face loss of custom or legal liability through the production of incorrect data.Conclusions Quality control can in principle determine with a high probability that data released from a laboratory are of appropriate quality. If properly executed, quality control methods can monitor the various aspects of data quality at closely timed intervals, effectively as a continuous part of the analytical process. In intervals where performance falls outside acceptable limits, the data produced can be rejected and, after remedial action, the analysis repeated. It must be stressed, however, that data quality control, even when properly executed, cannot exclude the possibility of important errors. First, it is subject to statistical uncertainty. Second, it cannot usually detect sporadic outliers due to very short-term disturbances in the analytical system or due to mistakes made with individual samples. Third, it cannot usually detect errors that arise from particular samples falling outside the scope of the method validation. Despite these limitations, quality control is the only recourse available under ordinary circumstances for ensuring that good-quality data are released from a laboratory. When properly executed it is very successful. However, it is abundantly clear, from a wide variety of interlaboratory tests, that many laboratories need to give more attention to the use of quality control techniques. References Analytical Methods Committee, Analyst, 1989, 114, 1497. Gardner, M. J . . Manual on Analytical Quality Control for the Water Industry, Water Research Centre, Medmenham, 1989. Kateman, G., and Pijpers, F. W., Quality Assurance in Analytical Chemistry, Wiley. New York, 1981. Mesley. R. J.. Pocklington, W. D.. and Walker, R. F., Analyst, 1991. 116, 975. Control Charts, General Guidance and Introduction, I S 0 7870, International Organization for Standardisation, Geneva, 1993. Shewhart Control Charts, IS0 8258, International Organization for Standardization, Geneva, 1991. Control Charts for A rithmetic Mean with Warming Limits, IS0 7863, International Organization for Standardization, Geneva, 1993. The Application of Statistical Methods to Industrial Standardisa- tion and Quality Control, BS 600, British Standards Institution, London, 1935. Paper 4102721 C Received May 9, 1994 Accepted June 13, 1994

ISSN:0003-2654    

DOI:10.1039/AN9952000029

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

Analyst, January 1995, Vol. 120 35 Routine Lead Isotope Determinations Using a Lead-207-Lead-204 Double Spike: a Long-term Assessment of Analytical Precision and Accuracy Jon. D. Woodhead Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia F. Volker Institute of Petrography and Geochemistry, University of Karlsruhe, Karlsruhe, Germany M. T. McCulloch Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia Lead-isotope data obtained on a multicollector mass spectrometer over a four year period using a 207PP04Pb double spike to correct for the effects of mass discrimination, are reported. Considerable improvements in both precision and accuracy over conventional correction procedures were noted, without recourse to rigorous loading or run conditions.An external precision in 206Pb/204Pb, 207PbPPb and 208PbP”Pb ratios +0.003,0.003 and 0.01 (2 X standard deviation), respectively, is routinely obtainable independent of minor variations in loading and run parameters. Keywords: Lead isotope analysis; double spike technique Introduction In the determination of radiogenic isotope ratios, particularly within the Earth Sciences, a correction is usually made for the isotope mass fractionation effects encountered during thermal ionization mass spectrometry (mass discrimination) by normalization to an accepted ratio of two non-radiogenic isotopes; e.g., for Sr, the ratio *6Sr/g*Sr = 0.1194 is commonly employed. However, of the naturally occurring Pb isotopes only 204Pb is non-radiogenic whereas 2WPb, 207Pb and Pb208 are daughter products from the radioactive decay of U and Th.Consequently, the analytical precision and accuracy of Pb isotope determinations has always been limited by an inability to make such a correction. The recent advent of a ‘new generation’ of multi-sample, multicollector mass spectrometers has led to a rapid proliferation in both the number and quality of Sr and Nd isotope determinations available, highlighting an increased requirement for more accurate and precise Pb isotope data with which to address scientific problems requiring fine resolution. Many factors contribute to mass spectrometer induced fractionation; in particular, relatively subtle variations in filament loading and run conditions can produce marked variations in mass-fractionation characteristics.Although it has been demonstrated that rigorously controlled loadinghnning parameters can produce considerable improvements in precision,’ for whole rock samples such an approach is often not possible or indeed desirable. The usual approach employed is to determine a mass discrimination factor by analysis of a Pb standard with well-known isotopic composition and then apply the same correction factor to all unknowns. With geological materials, however, even if a consistent discrimination factor can be established by a given operator with reference to a Pb isotopic standard [usually National Bureau of Standards (NBS) (now National Institute of Standards and Technology) Standard Reference Material (SRM) 981 (natural lead)], real rock samples rarely run under identical conditions of mass fractionation, for at least two reasons.The first reason is the relative ‘impurity’ of sample Pb compared with standard Pb. Even with very ‘clean’ column chemistry (two column passes, blanks <lo0 pg), trace contaminants such as Cd, Zn and organics affect the performance of the silica gel substrate, often resulting in markedly different behaviour on the filament. This issue is rarely addressed as the ‘real’ values for rock samples are not known; it is simply assumed that a correction factor derived for the standard can be applied to the sample. However, it will be shown below that this may not always be the case. The second reason in contrast to the running of standard Pb, with real samples there is often a lack of prior knowledge of the exact amount of Pb being analysed. This problem is particularly acute for samples that have been acid-leached as a precaution to remove surficial contaminants (these problems have been discussed by McDonough and Chauvel2 and Volker et al.,3 for example), and with very low-level or small samples that are not readily amenable to X-ray fluorescence analysis of Pb content. The resultant variation in both amount of Pb loaded and Pb: silica gel ratio often limits the utility of reference to isotopic standards to determine mass fractionation. Fortunately, these problems are surmountable. DodsonJ showed that a rigorous correction for the effects of mass discrimination was possible by spiking a second sample aliquot with an artificial solution, highly enriched in two isotopes, thereby simulating the presence of two non-radiogenic iso- topes, and Compston and Oversbys and Cooper and Richards6 first routinely applied this ‘double spike’ method to Pb isotope analysis. The technique was not widely adopted at the time but, foreseeing the arrival of multicollector machines and the need for increasingly precise data, Hamelin et al.7 have made a re-evaluation of the Pb double spike procedure.These workers concentrated in particular on the optimization of run parameters and provided an analysis of error propagation in relation to spike: sample ratios but presented little data. We have been using a zo7Pb-204Pb double spike for Pb isotope36 Analyst, January 1995, Vol.120 15.6 n a 4 3 a w 15.5 analysis routinely in our laboratory3,x-lI and here present the first long-term (four year) evaluation of its performance in conjunction with a Finnigan MAT 261 multicollector mass spectrometer. ' Analytical Details Lead was separated from geological materials by conventional HBr/HCI techniques using Teflon microcolumns,'2 Dowex AG 1x8 anion-exchange resin, and two column passes for sample purification. We stress, however, the advantage of using rock chips rather than powders and the need for preliminary acid washing before dissolution to remove any non-magmatic contaminants. Such an approach cannot be applied to older materials where individual mineral phases may have developed different isotopic compositions with time but we believe it should be used without exception for samples of recent age.Total procedural blanks are typically in the range 20-50 pg and always less than 100 pg. Although a 2osPbA02Pb double spike is the theoretical ideal as both isotopes do not occur in natural samples,13 the prohibitive cost and difficulty of obtaining very 'clean' samples of these enriched isotopes makes such a spike unsuitable for routine analytical work. A 207PV04Pb double spike of similar composition to DSII of Compston and Oversby5 was used here (206Pb/204Pb = 0.237, 207Pb/2(]4Pb = 8.714, 2ogPb/204Pb = 0.443). Samples were split for spiking immediately prior to filament loading and mass spectrometry, thus, avoiding potential problems due to variable blank levels in spiked- and unspiked-runs which have hampered previous attempts to use the double spike method.14 Following the methodology of Hamelin et al.,7 in order to control error propagation, the ratio of 204Pb"nknown/2'4Pbspike, designated Q , in the spiked run is maintained within the limits 0.02 < Q < 1, although an exact knowledge of Q (i.e., by weighing) is not necessary unless simultaneous Pb concentration data are required from the analysis. Samples were loaded on single Re filaments with silica gel-H3P04 in a clean air hood. This procedure takes 1-2 h for a carousel of 13 samples and, although a disciplined method is adopted, in particular to avoid blank problems, the rigorous loading and heating sequences advocated by experienced Pb isotope workers, are not necessary (any perturbations in fractionation are corrected by the double spike analysis). Again, during mass spectrometry, precisely controlled heating procedures under manual control or the use of automated heating sequences15 are only necessary in so far as a stable ion beam must be established; the accuracy of the result is in no way compromised.All samples were run on a Finnigan MAT 261 mass spectometer, operated in static multicollector mode. Data acquisition was usually at a filament temperature of about 1100-1200 "C and, typically, consisted of four blocks of data per run, each comprising twelve 8 s integrations (thus, 96 s integration time per block). Baselines were measured every two blocks and gain calibrations every three or four samples. It is difficult to generalize about the degree of within-run precision obtained for each sample run as the speed at which a given sample moves along a mass discrimination trend depends on both the amount of Pb loaded and the condition of the silica-gel substrate through which the sample essentially 'distils'.Hence, low-level samples will tend to move more rapidly along the mass discrimination vector resulting in relatively larger values for within-run precision. With relatively large loads (100 ng), it has been found that four blocks of data are sufficient to provide an internal precision (2 x standard error) of k0.002 or better on 206Pb/204Pb but we do not believe that larger values of within-run precision produce any significant degradation in the final result, after double spike correction. Spiked- and unspiked-aliquots were usually run on the same carousel, each machine 'run', thus, providing six complete analyses plus one blank or standard run. A number of different mathematical solutions for the double spike unmixing analysis have been formulated.16-18 Our data reduction was performed by an iterative technique using a computer program developed for the Macintosh, further details of which can be found in the Appendix. It is relatively easy to perform 26 analyses ( i . e . , two carousels) within 1 d, thus providing 12 unknown analyses plus a standard or blank. Analytical Accuracy for NBS SRM 981 As a preliminary test of the ability of the double spike technique to correct for highly variable degrees of mass fractionation, a single filament load of 40 ng of NBS SRM 981 was run repeatedly to exhaustion (three blocks of data per run), turning up the filament current between runs to exaggerate mass discrimination effects.The resulting raw data are shown in Fig. 1, together with data corrected in conjunc- tion with a single NBS SRM 981 + double spike analysis, run under 'normal' fractionation conditions. These data show that the correction procedure is efficient over a very wide range of mass discrimination , far outside that normally encountered in routine analysis. The method only appears to break down for extreme mass fractionation (point 'x', with corresponding corrected value, point 'y', in Fig. l), presumably as a result of the severe degradation of the signal intensity at this point producing error in the measurement of the 204Pb peak and result ant 206Pb/204P b , 207P b P P b and 20sP bP4P b ratios .As a measure of the long-term accuracy of the double spike technique, raw and double spike corrected data for NBS SRM 981, obtained at the Australian National University over a 37.4 t- 37.2 9 > 37.0 a a 0 0 0 0 ox V 36.6 1 8 Certified/preferred value I I I I ~ ox 0 0 - mooy @Certified value 15.4 I I I I I 16.90 16.95 17.00 17.05 17.10 206 Pbfo4 P b Fig. 1 Results of an experiment in which a single filament load of 40 ng of NBS SRM 981 was run repeatedly to exhaustion, turning up the filament current between runs to exaggerate mass discrimination effects (open circles). Filled circles represent the same data after correction with a single 'double spike' analysis (a mixture of NBS SRM 981 plus ~07PbJ04Pb tracer).See text for details.Analyst, January 1995, Vol. 120 37 period of four years from 1989 to 1993, have been collated in Fig. 2. It is important to note that the dispersion displayed in the uncorrected data does not represent the degree of consistency obtainable by any one analyst under normal conditions; rather it is a compilation of data for seven operators who have used the laboratory, over a period of time in which three different batches of silica gel have been used, and includes early tests of the double spike technique, therefore, encompassing many different analytical situations in terms of sample loading and run conditions. However, this array can be usefully regarded as covering the maximum range in mass discrimination ever likely to be encountered by any one laboratory, and certainly far more than that for any one individual.When the double spike correction is applied to the data using the corresponding double spike runs, most of this dispersion disappears, with all of the resulting corrected data 36.80 36.70 n n > 36.60 0 36.50 36.40 Certified value k 2 SD Doubl6 spike corrected data 15.52 Certified value 2 2 SD, 15.50 a 15.44 204 I .J.w 16.86 16.88 16.90 16.92 16.94 16.96 2wPb/204Pb Fig. 2 Compilation of NBS SRM 981 uncorrected (open circles) and double spike corrected (filled circles) data from this laboratory over the period 1989-93. The uncorrected data represent a compilation for seven operators, over a period of time in which three different batches of silica gel were used and include a number of early experimental runs; thus, they cover a range in mass discrimination far greater than that normally encountered by any one individual. Note, however, that the double spike corrected values all fall within the 2 x s uncertainty assigned to the NBS SRM values.See text for further details. falling well within the range of uncertainty assigned to SRM 981 by the NBS. Note that a residual error visible in these data, and shown in Fig. 2 , does not coincide with the mass fractionation vector; this is in fact a ‘204 error’ line, associated with errors in the measurement of the relatively small 204Pb peak if the beam intensity is low: some of this dispersion could, thus, be reduced further by running larger amounts of Pb to produce beam intensities in the region of = 3 V 2f18Pb or more.These two sets of data, taken in conjunction, firmly establish the validity of the double spike method in producing highly accurate data over an exceptionally wide range of mass discrimination, far beyond that normally encountered in routine analysis. We believe the double spike procedure is particularly powerful when applied to relatively low-level samples (<20 ng). In conventional Pb work, these can cause significant problems, not only because of the potential importance of the blank, but also because the relatively low levels of Pb being run often follow different mass fractionation versus time paths to the standard, resulting in an inappropriate fractionation correction being applied. Analytical Precision (Reproducibility of the Double Spike Correction) The NBS SRM 981 data shown in Fig.2 also provide what might be termed a ‘worst case’ estimate of the analytical reproducibility possible with the double spike method because the uncorrected data cover such a large range of fractionation effects. Table 1 contains a full statistical analysis of the corrected data, from which it is clear that even with the considerable dispersion in uncorrected data, application of the double spike correction results in an external precision, expressed as +2 X standard deviation (s), of 0.004,0.005, and 0.013 on the 206PbPPb, 207PbP4Pb and 208PbP4Pb ratios, respectively. In order to determine whether the technique could provide improvement on data obtained in laboratories where very stringent run conditions are imposed, different aliquots of NBS SRM 981 and a whole-rock sample were processed through the normal chemistry and loading procedures in our laboratories (in addition the whole-rock chips were individually acid-washed prior to dissolution) in an identical way.Each split was then run at the same temperature (1100 “C), with the same heating sequence. These data, shown in Table 2, provide some estimate of the levels of reproducibility possible under ideal conditions using conventional Pb isotope techniques; again an ‘end-member’ situation as, in routine analysis, it is unlikely that such consistency in the amount of Pb loaded could be achieved. The data for the NBS SRM are less dispersed than those for the rock sample and, as both have experienced the same chemistry, this cannot be attributed to blank effects (which are in any case negligible); it must reflect either very minor isotopic heterogeneity in the rock or mass fractionation effects due to trace amounts of contaminants from the rock sample affecting the performance of the silica gel substrate as noted above.Although the reproducibility Table 1 Statistical analysis of double spike corrected NBS SRM 981 data (n = 109), obtained under many different run conditions, i.e., covering a very large range in mass discrimination effects Re 1 at i ve Standard Standard standard Maximum - Isotope ratio Mean deviation error deviation (%) Minimum Maximum minimum 0.010 206Pb/204Pb 16.937 0.0020 0.0002 0.012 16.932 16.942 207 PbF04Pb 15.492 0.0024 0.0002 0.016 15.485 15.497 0.012 208PbFmPb 36.708 0.0064 0.0006 0.017 36.692 36.721 0.02938 Analyst, January 1995, Vol.120 here is excellent, application of the double spike correction provides further improvement by a factor of two, with external precision o n the corrected data for the rock sample -7(]6Pb/ZO4Pb, -7(17Pb/"]JPb and ?08Pb/Z()JPb ratios of 0.0026, 0.0034 and 0.0096, respectively (again expressed as k 2 X s). Comparison of the rock and NBS SRM data in Table 2 confirms our belief that sample Pb, prepared and run under identical conditions to standard Pb, behaves in a different manner during mass spectrometry. Processing for both these Table 2 Replicate analyses (total procedure) for individual samples, under optimum conditions (although the data are reported to three decimal places, statistics were calculated on values to four decimal places) (1) NBS SRM 981, 150 ng loads, with chemistry (two column passes), identical run conditions- Raw data (uncorrected) Double spike corrected Sample 206Pb/ 207pb/ 2OXpb/ ?OhPb/ 207Pb/ 2OXpb/ No. 204Pb 204Pb 204Pb 204Pb 204Pb 204Pb 1 16.887 15.424 36.490 16.937 15.492 36.707 2 16.885 15.422 36.482 16.937 15.493 36.707 3 16.886 15.423 36.486 16.936 15.492 36.704 4 16.886 15.422 36.485 16.936 15.490 36.702 5 16.888 15.424 36.494 16.936 15.491 36.703 Mean 16.886 15.423 36.487 16.936 15.492 36.705 SD * 0.0010 0.0012 0.0043 0.0007 0.001 1 0.0024 SET 0.0004 0.0005 0.0019 0.0003 0.0005 0.0011 RSDt 0.006% 0.008% 0.012% 0.004% 0.007% 0.007% (2) 32 NG 0124 Andesite, Western Bismarck arc, P.N.G.b- Raw data (uncorrected) Double spike corrected Sample 206Pb/ 207Pb/ 2OSpb/ 206pb/ 207pb/ 20Spb/ No.204pb 204pb 204Pb 204Pb 204pb 7-04pb 1 18.632 15.489 38.217 18.695 15.568 38.477 2 18.634 15.492 38.227 18.697 15.570 38.485 3 18.634 15.492 38.228 18.695 15.568 38.478 4 18.629 15.486 38.209 18.693 15.566 38.473 5 18.628 15.485 38.204 18.697 15.570 38.484 6 18.633 15.490 38.221 18.695 15.568 38.477 Mean 18.632 15.489 38.218 18.695 15.568 38.479 18.6877 15.5587 38.4487 SD* 0.0024 0.0031 0.0099 0.0013 0.0017 0.0048 SEt 0.0010 0.0013 0.0040 0.0005 0.0007 0.0020 RSDt 0.013% 0.020% 0.026% 0.007% 0.010% 0.012% (3) K-feldspars, Berridale and Bega batholiths, S . E. Australia(I- Raw data (uncorrected) Double spike corrected Sample 20hPb/ 207Pb/ *"SPb/ 206Pb/ 207Pb/ 208Pb/ BB104 18.099 15.552 37.939 18.153 15.621 38.163 Duplicate 18.087 15.537 37.892 18.153 15.622 38.169 KB22 18.171 15.562 38.022 18.226 15.633 38.253 Duplicate 18.IS9 15.554 37.996 18.222 15.635 38.260 MG-19 18.111 15.503 37.782 18.169 15.577 38.023 Duplicate 18.1 11 15.507 37.805 18.167 15.579 38.039 No. 204pb 204pb 204Pb 204pb 204Pb 204pb ' SD = Standard deviation. + SE = Standard error. -I RSD = Relative standard deviation. 11 Ratios obtaincd by conventional correction procedures, using a mass discrimination factor calculatcd from the NBS SRM 981 data in part (1) on this table. Note the comparison with the double spike corrected data, highlighting the potential loss of accuracy by the use of conventional correction procedures. + Ref.19. 11 Ref. 9. sets of analyses was identical, including the column chemistry and loading procedure. Similar amounts of Pb were loaded on to the filaments in each instance and all were run at about 1100 "C. Reproducibility between individual runs for each sample is excellent, but the NBS SRM and whole-rock samples have experienced consistently different degrees of mass fractionation with values of E (the mass discrimination factor per u) of 0.00149 and 0.00170, respectively. This, coupled with the observation that beam intensities were lower for the same amount of rock Pb, suggests suppression of the ion beam by trace amounts of impurities which were not adequately removed by the chemistry. This is a clear demonstration that, even under optimum conditions, conventional correction procedures for mass discrimination effects are likely to result in some loss of accuracy and, we believe, a strong argument for the application of the double spike technique.It is most unlikely that routine Pb isotope analyses will approach the precison obtained here under these ideal circumstances. However, comparison of the corrected data from both Tables 1 and 2 shows that the double spike technique provides a very high degree of precision, essentially independent of the extent of mass fractionation, producing, for geological samples run under routine conditions, external precision in 206Pb/204Pb, 207Pb/204Pb and 208PbP4Pb ratios of +0.003,0.003 and 0.01 (2 x s), respectively. A brief survey of the literature indicates that most laboratories quote errors on the mass discrimination factor for Pb isotope analyses of about 0.02-0.03% per u.2,12,20,*1. Based on this error, a simplistic calculation using maximum and minimum discrimination factors translates into a range on measured 206Pb/204Pb, 207PbPPb and 2osPb/204Pb ratios of k0.01,0.014, and 0.044, respectively.We conservatively estimate, therefore, that use of the double spike increases precision by a factor of three over conventional mass fractionation correction procedures. Conclusions The use of a 207PbXO4Pb double spike for correction of mass fractionation effects during routine Pb isotope analysis offers increased analytical accuracy and precision without recourse to excessively rigorous loading or run conditions; indeed, tests show that this appears to be largely independent of minor variations in loading/run parameters.An improvement in precision by a factor of three over conventional methods appears to be easily obtainable. In view of the increased requirement for high precision Pb isotope data, and the relatively rapid analysis time offered by modern multicollector mass spectrometers, we consider use of the double spike to be far more advantageous than the use of 'conventional' correc- tion methods. We thank L. Kinsley, G. Mortimer, M. Fanning and J. Richards, all of whom have been involved at various stages in the gradual refinement of our double spike procedures at the Research School of Earth Sciences. J. Hergt, G. Mortimer and two anonymous reviewers provided constructive comments on the original manuscript.Appendix Data Reduction Although exact solutions can be obtained from double spike analysis,17 an iterative method is presented here, which has the advantage that a more complex fractionation law can be incorporated in the solution (in this instance we have used a power law). As described previously, two mass spectrometerAnalyst, January 199.5, Vol. 120 39 runs are required, one being a mixture of the sample and z"7PV04Pb tracer (termed 'mix') and the other an analysis of the unknown sample (termed 'Sa'). The program first determines the apparent 204Pb/207Pb tracer composition in the mixture run [i.e., (204Pb/207Pb)ta mix] using the following spike-sample unmixing equation: (2"Pb/207Pb),, = (204Pb/207Pb)mix - [(204Pb/2'7Pb)sa - (2"4Pb/207Pb) mix] x [ (208Pb/207Pb) mix - (208Pb/207Pb)t]/ [ ( 208Pb/2"7Pb)sa - ( 2"8Pb/207Pb)mix] (1) where the subscripts mix and Sa refer to the measured composition in the mixture and sample runs, respectively, and t is the known ratio in the tracer.A first estimate of the mass discrimination factor in the mixture run (Dmix) is then obtained using Dmix = [(204PbP07Pb),, mix)/(204Pb/207Pb),]*'3 (2) The measured ratios in the mixture run are then corrected for mass fractionation using the above estimate for Dmix. The 208Pb/206Pb ratio of the sample in the mixture run, minus the spike contribution (2°8Pb/206Pbsa mix) is then calculated from an analogous equation to (1) above. Using this corrected ratio an estimate of the mass fractionation in the unspiked sample can then be obtained from the relationship: Ds, = [(20'Pb/206Pb)sa/(20'Pb/206Pb)Sa mix]'" (3) where (208Pb/206Pb)sa) is the ratio measured in the unspiked sample run.This calculation scheme is then iterated several times until the change in the value of Dmix is less than 10-6. If spiking is within the range Q = 0.02-1, then the convergence is rapid within 3 4 iterations. Further details can be obtained from the authors. 2 McDonough, W. F.. and Chauvel, C., Earth Planet. Sci. Lett., 1991, 105, 397. 3 Volker. F.. McCulloch. M. T., and Altherr. R.. Geophys. Res. Lett., 1993, 20, 927. 4 Dodson, M., J. Sci. Instrum., 1963,40,289. 5 Compston. W., and Oversby. V. M., J. Geophys. Res., 1969, 74. 4338. 6 Cooper, J. A., and Richards, J. R., in Hot Brines and Recent Heavy Metal Deposits in the Red Sea, eds. Degens, E. T., and Ross, D. A., Springer-Verlag, New York, 1969, pp. 499-511. 7 Hamelin, B., Mahnes, G., Albarede, F., and Allkgre, C. J., Geochim. Cosmochim. Acta, 1985,49, 173. 8 Richards, J. P., McCulloch, M. T., Chappell, B. W., and Kerrich, R., Geochim. Cosmochim. Acta, 1991,55, 565. 9 McCulloch, M. T., and Woodhead, J. D., Geochim. Cosmo- chim. Acta, 1993, 57, 659. 10 Woodhead, J. D., and Devey, C. W., Earth Planet. Sci. Lett., 1993, 116, 81. 11 Woodhead, J. D., and Johnson, R. W., Contrib. Mineral. Petrol., 1993, 113,479. 12 Manhes, G., Minster, J. F., and Allkgre, C. J., Earth Planet. Sci. Lett., 1978, 39, 14. 13 Todt, W., Cliff, R. A., Hanser. A., andHofmann, A. W., Terra Cognita, 1984, 4, 209. 14 Oversby, V. M., Geochim. Cosmochim. Acta, 1973,37,2593. 15 Gulson, B. L., Korsch, M. J., Cameron, M., Vaasjoki, M., Mizon, K., Porritt, P., Carr, G. R., Kamper. C., Dean, J. A., and Calvez, J.-Y., Int. J. Mass Spectrom. Ion Process., 1984.59, 125. 16 Dodson, M., Geochim. Cosmochim. Acta, 1970, 34, 1241. 17 Gale, N. H., Chem. Geol., 1970, 6, 305. 18 Hofmann, A. W., Earth Planet. Sci. Lett., 1971, 10, 397. 19 Woodhead. J. D., and Johnson, R. W., unpublished work. 20 Galer, S. J. G., MacDougall, J. D., and Erickson. D. J., 111, Geophys. Res. Lett., 1989, 16, 1301. 21 Tatsumoto, M.. Basu, A. R., Wankang, H., Junwen, W., and Guanhong, X . , Earth Planet. Sci. Lett., 1992, 113, 107. References Richards, J. R., Trans. Geol. SOC. S . Afr., 1986, 89, 285. 1 Paper 4/01 4 7 7 0 Received March 14, 1994 Accepted July 29, 1994

ISSN:0003-2654    

DOI:10.1039/AN9952000035

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

Analyst, January 1995, Vol. 120 41 Gas Chromatography-Negative-ion Chemical Ionization Mass Spectrometry of Hydrolysed Human Urine and Blood Plasma for the Biomonitoring of Occupational Exposure to 4,4'-Met hylenebisaniline Per Brunmark, Marianne Dalene and Gunnar Skarping Department of Occupational and Environmental Medicine, University Hospital, S-22185 Lund, Sweden A gas chromatographic-mass spectrometric (GC-MS) method for the biological monitoring of 4,4'-methylenebisaniline (MDA), is presented. MDA was determined in urine and plasma after hydrolysis and analysed as the pentafluoropropionic anhydride derivative. High sensitivity and selectivity were achieved using negative-ion chemical ionization with ammonia as the reagent gas. The hydrolysis procedures for urine and plasma samples were studied under alkaline and acidic conditions.Alkaline conditions gave the highest recovery for both urine and plasma samples. Hydrolyses of urine at 80 "C and of plasma at 100 "C for 16 h were selected owing to the good recovery and precision achieved. Ten analyses of a urine sample containing 11 nmol 1-1 of MDA gave relative standard deviations (s,) within and between assays of 2 and 6%, respectively. The determination of MDA in a plasma sample containing 8 nmol l-1 of MDA gave s, = 4 and 6% within and between assays, respectively (n = 5). For the preparation of samples spiked to 10 nmol l-1 of MDA, the recovery was 97 k 3% for urine samples and 96 k 2% for plasma samples. The detection limit, defined as the blank plus three times the standard deviation of the blank, was 0.2 nmol l-1 for aquous solutions containing an internal standard.Determinations of MDA in urine and plasma from exposed workers showed that the method is appropriate for biomonitoring. Keywords: Hydrolysis; aromatic amine; gas chromatography; negative-ion chemical ionization mass spectrometry Introduction Exposure to methylenebisaniline (MDA) is a well known occupational hazard. Cases of hepatoxic effects' and dermatitis2 in humans have been reported. Carcinogenicity in mice and rats has been reported3, implying that exposure of MDA may be a carcinogenic risk to humans. MDA is used in the production of methylene diisocyanate and as an epoxy resin hardener in paints, rubber, composites and glues. A recent report4 concluded that the occupational exposure is still significant and that skin contact is the dominant exposure route.Dermal uptake is difficult to estimate by monitoring in the work environment. Biomonitoring offers much more powerful methods for assessment of MDA exposure. MDA and its monoacetyl conjugate have been detected in urine from exposed humans.5 Therefore, when monitoring MDA in biological samples, effects of differences in human metabolism should be lessened by a hydrolysis procedure that releases the amine from conjugates. Hydrolyses performed in 5 moll-' NaOH at 80 "C for 2 hs and 3 moll-' HCI at 100 "C for 2 h6 have been reported to be sufficient to release conjugates from the urine matrix. Determinations of hydroly- sed MDA in biological matrices have been based on gas or liquid chromatographic analysis.The derivatization of MDA with perfluoroacid anhydrides was shown to increase the sensitivity for determinations by capillary GC with electron- capture and thermionic detection7. Also, gas chromato- graphy-mass spectrometry (GC-MS) with electron impact ionization of MDA as the pentafluoropropionic anhydride (PFPA) derivative gave high sensitivity, demonstrated by a detection limit of 10 nmol l-1 of MDA in urine.8 Negative-ion chemical ionization (NICI) mass spectrometry has been developed in recent years and is now common in biomedical laboratories. The use of electron-capture detection in NICI- MS has been illustrated for fluorinated derivatives of aromatic amines.9 Studies of the sensitivity of MDA-PFPA by NICI- MS demonstrated detection limits below 10 pmol l-1 of MDA in spiked water samples.'" Most methods for determination of MDA in biological matrices have only been investigated for urine, but MDA has also been detected in rat blood by GC with electron-capture detection11 and in spiked serum by GC-NICI-MS.12 The determination of MDA and N-acetyl- MDA (monoacetyl-MDA, MAMDA) adducts to hemo- globin, as biomarkers of occupational exposure, has been reported.13 However, to our knowledge, biomonitoring by analysis of hydrolysed plasma has not been studied. In this paper, a method for the determination of MDA at sub- nanomolar concentrations in hydrolysed human urine and plasma is described. Experimental Apparatus A Carlo Erba Mega gas chromatograph equipped with an A200S autosampler (Fisons Instruments; Carlo Erba, Milan, Italy) connected to a Trio 1000 quadrupole mass spectrometer (Fisons Instruments; VG-Biotech, Altrincham, UK) was used for the analysis of urine and plasma samples.Injection was performed using splitless injection. The injector temperature was 300 "C and the split-exit valve was kept closed for 1 min after injection. For the chromatographic separation, fused- silica columns with a chemically bonded stationary phase, DB-5 (J & W Scientific, Folsom, CA, USA), 25 m X 0.25 mm i.d. with a film thickness of 0.25 pm, were used. The capillary inlet pressure of helium was 80 kPa. The starting temperature of the column oven was llO"C, kept isothermal for 1 min, then increased at 15 "C min-1 to 300 "C, which was maintained for 2 min.The temperature of the ion source was 200 "C and the GC-MS interface temperature was 300 "C. The solvent delay42 Analyst, January 1995, Vol. 120 was to set to 8 min. The instrument was used in the chemical ionization mode with negative-ion monitoring and ammonia as reagent gas. The dwell time for each ion was 0.1 s and the inter-scan delay was 0.01 s. The pressure in the ion source was about 10-4 mbar. The emission current was 100 PA and the electron energy was 70 eV. The tuning of the instrument was optimized before every sequence of 50-100 samples, with nonafluorotributylamine as a calibrant. Chemicals MDA was obtained from Fluka (Buchs, Switzerland), aceto- nitrile and toluene from Lab-Scan (Dublin, Ireland), pentaflu- oropropionic anhydride (PFPA) from Pierce (Rockford, IL, USA), sodium hydroxide, hydrochloric acid and K2HP04 were from Merck (Darmstadt, Germany) and dideuteriated 4,4'-MDA (2CH2[C6H4NH2]2) (MDDA) and MDA-PFPA derivative from Synthelec (Lund, Sweden).Monoacetyl- MDA (MAMDA) was synthesized by the reaction of equi- molar amounts of MDA and acetic anhydride as described.13 Standard Solutions Stock standard solutions of MDA and MDDA were prepared and further diluted with 0.1 mol 1-1 HCI. MDA-PFPA stock standard solutions were prepared in acetonitrile, and further diluted with toluene. Stock standard solutions were stored in darkness at room temperature. Diluted solutions were pre- pared on the day of use. Sampling and Storage of Samples Urine samples were collected in polyethylene bottles.Samples that were analysed within 2 d were stored in a refrigerator. Samples analysed more than 2 d after sampling were trans- ferred into polyethylene tubes and kept frozen at -20 "C until analysis. Blood samples were collected in heparinized test tubes (Venoject). The tubes were cooled by storage in a refrigerator for a minimum of 1 h. The plasma fraction was then separated by centrifugation (1500g) and transferred into a poly(propy1ene) tube. Separated plasma samples were kept in a freezer (-20 "C) until analysis. Hydrolysis When testing hydrolysis conditions, the internal standard was added in the first work-up step after hydrolysis. Hydrolysis was performed in 5 moll-' NaOH and 3 moll-1 HCI. Samples hydrolysed in acid were prepared as reported previously.8 The preparation described under the work-up procedure was used for alkaline hydrolysis.The hydrolysis was studied for test solutions prepared in the biological matrix, urine and plasma. Urine Urine matrices were tested under alkaline and acidic condi- tions with variation of the hydrolysis time. The concentrations of spiked solutions of MDA, MAMDA and pooled urine from subjects exposed to MDA in urine were all approximately 50 nmol 1-1. Using the previously reported conditions, the duration of the hydrolysis was varied from 0 to 40 h. Plasma When investigating the hydrolysis of plasma, the concentra- tions of MDA, monoacetyl-MDA and pooled plasma from subjects exposed to MDA were about 4 nmol 1-1. The hydrolysis temperature was varied from 60 to 100 "C at a constant hydrolysis time of 16 h.Acidic and alkaline hydro- lyses at 100 "C were studied for hydrolysis times in the range 0-40 h . Work-up Procedure of Urine Samples A 2 ml volume of a urine sample, 50 1.11 of internal standard and 2 ml of 10 moll-1 NaOH were added to a 12 ml test-tube. The sample was hydrolysed at 80 "C for 16 h and cooled to room temperature. A 3 ml volume of toluene was added to the screw-capped tube and the solution was shaken for 10 min and centrifuged at l500g for 10 min. A 2 ml volume of the organic phase containing MDA was transferred into a new screw- capped tube. The sample was derivatized by addition of 20 1-11 of PFPA. The test-tube was immediately shaken for 5 s and the derivatization reaction was completed within 5 min at room temperature. A 2 ml volume of 1.0 mol 1-1 phosphate buffer (pH 7.5) was added, and the tubes were shaken for 5 s and centrifuged at l500g for 10 min to remove excess of reagent.The organic layer was transferred into vials and analysed by GC-MS. Work-up Procedure for Plasma Samples The work-up procedure for plasma samples is similar to that for the urine sample preparation, but the first steps differ and are reported here. To 1 ml of plasma, 50 1.11 of internal standard and 1 ml of 10 mol 1-1 NaOH were added. The sample was hydrolysed at 100 "C for 16 h and cooled to room temperature. A 3 ml volume of toluene and 0.5 ml of water were added, after which the tube was shaken for 10 min. The remainder of the work-up procedure was identical with that for the urine preparation. Quantification For the determinations of the amine-PFPA derivatives, the ions monitored were mlz 470 and 472, corresponding to the [M - 201- ions of MDA-PFPA and MDDA-PFPA.The ratio between the peak area of MDA and that of the dideuteriated internal standard was used for quantification. Standard and blank samples were prepared and analysed within every assay. Results and Discussion Standards The isotopic purity of the dideuteriated internal standard, determined by GC-MS, was found to be 97%. A 3% impurity of non-labelled MDA gave an intercept of the calibration graphs of 0.03. For the evaluation of the hydrolysis procedure, we used the crude mixture from the synthesis of acetyl-MDA. By analysis using HPLC with UV detection (254 nm), the mixture was found to contain approximately 7% of MDA, 86% of MAMDA and 7% of diacetyl-MDA.The stock standard solutions of MDA and MDDA in 0.1 mol 1-1 HCI were stable for at least 2 weeks when stored in darkness at room temperature. Hydrolysis The hydrolysis reactions are complicated and dependent on parameters such as temperature, pH and the time of hydro- lysis. We investigated the hydrolysis of urine and plasma from humans exposed to MDA. Hydrolysis was also studied in urine and plasma spiked with MDA and MAMDA. The concentrations of MDA and MAMDA in urine and plasma were chosen to represent the concentration of MDA in the pooled urine and plasma solutions. The same solutions in equal volumes were used for acidic and alkaline hydrolysisAnalyst, January 1995, Vol. 120 43 studies to achieve comparable results.Within each test 'released MDA' values from the MDA and MAMDA spiked solutions were normalized to arbitrary units with 1.0 as the maximum amount of MDA released. As the 'true' concentra- tion of MDA in the pooled urine and plasma sample is unknown, these 'released MDA' values were normalized separately. The values in the Figs. 2 4 are averages of three measurements. Samples hydrolysed under acidic conditions at 5 "C could not be worked up owing to emulsion formation during extraction. Urine samples The release of MDA for different durations was tested in urine at hydrolysis temperatures of 100 "C for acidic conditions and 80 "C for alkaline conditions. For acidic and alkaline hydro- lyses no increase in released MDA was obtained on increasing the hydrolysis time above 2 h for urine spiked with MDA and MAMDA.For pooled samples (Fig. 1) the release of MDA continued for the whole period studied of 40 h. However, only a small increase was observed after 16 h. Comparing alkaline and acidic hydrolyses, a higher release of MDA (about 25%) was found under alkaline conditions. From these results, alkaline hydrolysis at 80 "C for 16 h was chosen for the analysis of urine samples. Plasma samples The release of MDA after hydrolysis of plasma samples was studied for different hydrolysis temperature and time (Figs. 2 and 3). Hydrolysis for 16 h at 5-100 "C is shown in Fig. 2. For acidic conditions the releases of MDA from the spiked solutions were similar for 60 and 80 "C but lower at 100 "C, indicating a loss of MDA [Fig.2(a)]. Alkaline hydrolysis showed about the same release in the temperature range 60-100 "C. On comparing alkaline and acidic hydrolyses of pooled plasma from exposed persons, a higher release of MDA was seen for the alkaline hydrolysis and the release increased with increase in temperature. The alkaline release of MDA from MAMDA-spiked and pooled plasma was low at 5 "C, showing the necessity for hydrolysis. On altering the duration of the hydrolysis only a small difference was found between long and short hydrolysis times for acidic and alkaline hydrolyses of the spiked samples. The acidic and alkaline hydrolysis of the pooled plasma showed a slightly increasing release of MDA with time (Fig. 3), with a small difference between 16 and 40 h.About a 10% higher release of MDA was seen with alkaline hydrolysis. We adopted alkaline hydrolysis at 100 "C for 16 h when analysing plasma samples from exposed subjects. Interestingly, there were differences in the release patterns of pooled samples compared with samples spiked with MDA 0.2 0 10 20 30 40 Timelh Fig. 1 Release of MDA from pooled urine during acidic and alkaline hydrolysis for 0-40 h . The pooled urine was obtained from exposed volunteers and hydrolysed under acidic conditions at 100 "C and alkaline conditions at 80 "C. A , Pooled urine during alkaline hydrolysis at 80 "C and B. pooled urine during acidic hydrolysis at 100 "C. and MAMDA (Fig. 2). This may indicate a binding to, e . g . , proteins or additional metabolite(s) to those investigated.Except for free MDA, only one metabolite, monoacetyl- MDA, has been found in a human biological matrix. Several other metabolites are likely as they arise from structurally related compounds. The formation of oxidized metabolites of MDA has been shown in metabolism studies by a rabbit microsome model. 14 Oxidized metabolites may react and form covalent bindings to proteins. Covalent bindings to hemo- globin have been found to release under weak hydrolysis conditions. 13 However, bindings to other biomolecules may not necessarily release MDA during hydrolysis. The hydro- lysis procedure should therefore never be expected to release the total amount of 'MDA' in the sample. What can be measured are the free MDA and the fraction of hydrolysable conjugates. For this reason, it is obviously important to study 5 60 80 100 Temp/"C Fig.2 Release of MDA with acidic and alkaline hydrolysis for 16 h at different temperatures. Plasma solutions of MDA and monoacetyl- MDA under (a) acidic conditions: A , MDA and B , MAMDA; and (b) alkaline conditions: A , MDA and B, MAMDA. Diagram (c) shows the hydrolysis of pooled plasma samples from exposed volunteers under A, acidic and B. alkaline conditions. 0.4 I I I I I 0 10 20 30 40 Timelh Fig. 3 Release of MDA from pooled plasma during A , acidic and B. alkaline hydrolysis at 100 "C for 2-40 h. The pooled plasma was obtained from exposed volunteers and hydrolysed under acidic and alkaline conditions at 10 "C.44 Analyst, January 1995, Vol. 120 biological samples from exposed humans when selecting optimum hydrolysis conditions.Further studies on these aspects are in progress. Work-up Procedure The relatively simple work-up procedure gave a high through- put and a short analysis time. The available volume of a plasma sample is often limited and therefore only 1 ml samples are used. Addition of water to the plasma samples was useful to avoid foam formation during the extraction. The work-up may also be performed by liquid-solid extraction of MDA in hydrolysed biological matrices. However, the high concentra- tion of sodium hydroxide demands either neutralization or dilution of the sample. Gas Chromatography-Mass Spectrometry Spectra from the PFPA derivatives of MDA and the internal standard MDDA gave very simple spectra. The fragment corresponding to [M - HF]- dominates the spectrum but also the [M - 2HFl- fragment was apparent, giving ions of mlz 470 and 450, respectively, for MDA. The relative abundance of ions varies with the ion source temperature and the ammonia pressure.Chromatograms of the [M - HF]- ions obtained from urine and plasma samples showed good separation of the MDA-PFPA derivative and the internal standard from the matrix (Fig. 4). Several background peaks were found in plasma samples but they did not interfere with the MDA peak. The urine samples were usually very clean from peaks not originating from MDA. Initial attempts to use methane and isobutane as reagent gases gave about the same NICI mass 10 11 12 13 10 11 12 13 I I I I I I I I 8 9 10 11 12 13 14 15 Retention time/min Fig.4 Selected ion monitoring of ( a ) and (b) a urine sample and ( c ) and (d) a plasma sample from a subject, dermally exposed to 1.5 pmol of MDA. The urine sample was collected in the interval 6.25-8.25 h after exposure and the blood sample 8.25 h after exposure. The urine and plasma samples contain 19 and 4 nmol of MDA per litre of matrix, respectively. For chromatographic conditions, see Experimental. The determined MDA (mlz 470) and the internal standard MDDA (mlz 472) are plotted separately. spectra as ammonia. However, using methane and isobutane contamination of the ion source occurred, and the source had to be rinsed after 1-2 d. The use of ammonia as the ionization gas gave very stable conditions for several weeks of operation. Recovery The over-all recovery was studied by performing the work-up procedure for 10 urine samples and 10 plasma samples spiked with 10 nmol of MDA per litre sample.Comparisons were made with MDA-PFPA standards diluted to the same concentration. The over-all recovery for urine samples was found to be 97 k 3% ( P = 0.05). For plasma samples the over-all recovery was 96 k 2% ( P = 0.05). Calibration Graphs and Linearity Peak area and peak height measurements were both useful for the quantification. The calibration graph was linear up to an MDA: MDDA ratio of about five. For higher relative amounts of MDA the calibration graph bent towards a lower relative response. For this reason, the concentration of the internal standard corresponding to a concentration of one quarter of the highest MDA concentration in the calibration was selected.Calibration graphs in the ranges 0-60 nmol 1-1 for urine and 0-8 nmol 1-1 for plasma were prepared using urine and plasma from unexposed humans. A calibration graph with six concentrations in the range 0-60 nmol of MDA per litre of urine (n = 12) gave a correlation coefficient of 0.999. For the concentration range 0-8 nmol of MDA per litre of plasma ( n = 12), the calibration graph gave a correlation coefficient of 0.998. Repeatability Samples originating from an exposed volunteer were studied. For five analyses during 1 d of a urine sample containing 11 nmol l-1 of MDA, the relative standard deviation (s,) was 2%. Five analyses during 1 d of a plasma sample containing 8 nmol l-1 of MDA gave an s, value of 4%. Reproducibility For peak area measurements during a period of 4 weeks, the s, value was 6% for five preparations of a urine sample containing 12 nmol l-1 of MDA.For peak area measurements during a period of 4 weeks the s, value was 6% for five preparations of a plasma sample containing 8 nmol 1-1 of MDA. The urine and plasma samples were taken from an exposed volunteer. Detection Limit The instrumental detection limit, defined as three times the noise, was 50 pmol 1-1 of MDA for a 1 pl injection volume. The detection limit, defined as the blank plus three times the standard deviation of the blank, was 0.2 nmol l-1 for aqueous solutions containing 4 nmol 1- 1 of internal standard. 15 Biological Monitoring of MDA The proposed method makes possible sensitive and precise determinations of MDA in hydrolysed human urine and plasma.The simple work-up procedure makes a high sample throughput possible and the method has been used in our laboratory for hundreds of samples. This method is suitable for biological monitoring of occupational exposure. For the complete interpretation of the analytical results, with regardAnalyst, January 1995, Vol. 120 45 to the exposure of MDA, further studies are necessary. A study of MDA-exposed workers and volunteers is in progress. MDA will be determined in urine and plasma and the concentrations will be associated with exposure. This work was financially supported by the Swedish Work Environmental Fund and the Medical Faculty at Lund University. References 1 McGill. D. B.. and Motto, J. D., N. Engl. J. Med., 1974, 291, 278. 2 Levine, M. J . , Contact Dermatol., 1983, 9, 448. 3 IA RC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, International Agency for Research on Cancer, Lyon, 1986, vol. 39, 347. 4 Occupational Safety and Health Administration, Fed. Regist., 29, CFR, Parts 1910 and 1926, 1992. 5 Cocker, J., Gristwood, W., and Wilson, H. K., Br. J . Ind. Med., 1986,43, 620. 6 7 8 9 10 11 12 13 14 15 Tijander, A., and Skarping. G., J. Chromatogr., 1990, 511, 85. Skarping, G., Sango, C., and Smith, B. E. F., J. Chromatogr., 1981, 208, 313. Tijander. A,, Skarping, G., and Dalene. M., J. Chromatogr., 1989.479. 145. Trainor. T. M., and Vouros, P., Anal. Chem., 1987, 59, 601. Benfenati, E., Natangelo, M., Fanelli, R., Lualdi, G., and Tridico, R., Microchem. J., 1992, 46, 352. Torteroto, M., Catalani, P., Bianchi, M., Blonda, C., and Pantarotti, C., J. Chromatogr., 1983, 262,367. Avery, M. J . , J. Chromatogr., 1989,488, 470. Bailey, E., Brooks, A. G., Bird, I., Farmer, P. B., and Street, B., Anal. Biochem., 1990, 190, 175. Kajbaf, M., Sepai. O., Lamb, J. H., and Naylor, S.. J. Chromatogr., 1992, 583, 63. Miller, J . C., and Miller, J. N., Statistics for Analytical Chemistry, Ellis Horwood, Chichester, 2nd edn., 1988. Paper 41021 88F Received April 13, 1994 Accepted June 20, I994

ISSN:0003-2654    

DOI:10.1039/AN9952000041

出版商:RSC    

年代:1995

数据来源: RSC