摘要:

Electroanalytical Group and Fine Chemicals and Medicinals Groupof the Royal Society of ChemistryE S E A C '966th European Conference on ElectroanalysisUniversity of Durham25th - 29th March 1996- Chemical Sensors, Arrays, Chemometrics- New Technologies and Materials- Environmental, Industrial and Clinical ApplicationsDetails from:Professor A. K. Covington, Department of Chemistry, University of Newcastle, Newcastle upon TyneNE1 7RU, UK. Tel: +44 (0)191 222 6785; Fax: +44 (0)191 222 6929E-mail: a.k.covington 63 newcastle .ac.ukGordon F. Kirkbright Bursary 1996In 1985 a fund was established as a memorial to Gordon Kirkbright and his contributions toanalytical spectroscopy and to science in general. The fund is administered by the Committeeof the Association of British Spectroscopists (ABS) and by the ABS Trust.The purpose ofthe award is to enable promising young scientists of any nation to attend a recognisedscientific meeting or to visit a place of learning.Applications are invited for the 1996 Gordon Kirkbright Bursaries. The award is notrestricted to spectroscopists.Full details and application forms can be obtained from Dr T L Threlfall, Department ofChemistry, University of York, Heslington, York, YO1 5DD, UK.Tel: +44 (0)1904 432576 ; Fax: +44 (0) 1904 432516Completed application forms must be received no later than 30 April, 19966 COUNTRYDo not affix Postage Stamps if posted in Gt. Britain,Channel Islands, N. Ireland or the Isle of Man1II I8 YOUR JOB TITLEPOSITIONBUSINESS REPLY SE RVlCELicence No. WD 106Q 1Reader Enquiry ServiceThe AnalystThe Royal Society of ChemistryBurlington House, PiccadillyLONDONW1E 6WFEnglandIIIIIIIIIIIIIIIIIIIIIIII

ISSN:0003-2654    

DOI:10.1039/AN99621BP003

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

"AnalystThe Analytical Journal Of The Royal Society Of ChemistryAssociate Scientific Editors*Chairman: Professor James N. Miller(Department of Chemistry, Loughborough University of Technology, UK)Dr Y ngvar Thomassen (Arbeidsmiljo lnstituttet,Oslo, Norway)Professor Colin S. Creaser (Department ofChemistry and Physics, Nottingham TrentUniversity, UK)Professor Pankaj Vadgama (Department ofMedicine, University of Manchester, UK)Professor Malcolm R. Smyth (Department ofChemical Sciences, Dublin City University, Eire)'All ASEs are also members of the Analytical Editorial Board.US ASSOCIATE EDITOR, Julian F. TysonDepartment of Chemistry, University of Massachusetts, Box 3451 0 Amherst, MA 01 003-451 0, USATelephone: +1 413 545 0195; Fax: +1 413 545 4846; E-mail: TYSON@CHEM.UMASS.EDUAnalytical Editorial BoardChairman: Professor J.N. Miller (Loughborough, UK)M. Cooke (Sheffield, UK)A. G. Davies (London, UK)A. G. Fogg (Loughborough, UK)G. M. Greenway (Hull, UK)S. J. Hill (Plymouth, UK)R. M. Miller (Gouda, The Netherlands)H. S. Minhas (Cambridge, UK)B. L. Sharp (Loughborough, UK)Advisory BoardN. W. Barnett (Victoria, Australia)K. D. Battle (Leeds, UK)A. M. Bond (Victoria, Australia)R. G. Brereton (Bfistol, UK)U. A. Th. Brinkman (Amsterdam, The Netherlands)A. C. Calokerinos (Athens, Greece)P. Camilleri (Harlow, UK)P. R. Coulet (Lyon, France)D. Diamond (Dublin, Eire)L. Ebdon (Plymouth, UK)H. Emons (Julich, Germany)J. P. Foley (Villanova, PA, USA)M. F. Gin6 (Sao Paulo, Brazil)J.D. Glennon (Cork, Eire)L. Gorton (Lund, Sweden)S. J. Haswell (Hull, UK)A. Hulanicki (Warsaw, Poland)S. Lunte (Lawrence, KS, USA)F. Palmisano (Palermo, Italy)J. Pawliszyn (Ontario, Canada)T. B. Pierce (Harwell, UK)J. ROZiCka (Seattle, WA, USA)1. L. Shuttler (Uberlingen, Germany)K. Stulik (Prague, Czech Republic)J. D. R. Thomas (Wrexham, UK)K. C. Thompson (Rotherham, UK)M. Thompson (Toronto, Canada)M. Valcarcel (Cordoba, Spain)C. M. G. van den Berg (Liverpool, UK)J. Wang (Las Cruces, NM, USA)I. D. Wilson (Macclesfield, UK)Publishing Division, AnalyticalManaging Editor, Harpal S. MinhasDeputy Editor, Sarah J. R. Williams Editorial Secretaries: Claire Harris; Frances ThomsonTelephone: +44(0)1223 420066; Fax: +44(0)1223 420247; E-mail: ANALYST@RSC.ORGProduction Division, AnalyticalProduction Manager, Janice M.GordonProduction Editor, Caroline Seeley Technical Editors: Yasmin Khan, Ziva Whitelock, Roger A. YoungSecretary: Lesley TurneyTelephone: +44(0) 1223 420066; Fax: +44(0) 1223 423429; E-mail: ANALPROD@RSC.ORGFor enquiries relating to manuscripts from receipt to acceptance, contact the Publishing Division, andfor enquiries relating to manuscripts post-acceptance contact the Production Division, Royal Society ofChemistry, Thomas Graham House, Science Park, Milton Road, Cambridge, UK CB4 4WFAdvertisements: Advertisement Department, The Royal Society of Chemistry, Burlington House,Piccadilly, London, UK W1 V OBN. Telephone +44(0)171-287 3091.Fax +44(0)171-494 1 1 34.Information for AuthorsFull details of how to submit material for publicationin The Analyst are given in the Instructions toAuthors in the January issue. Separate copies areavailable on request.The Analyst publishes original research papers,critical reviews, tutorial reviews, perspectives,news articles, book reviews and a conferencediary.Original research papers. The Analystpublishes full papers on all aspects of the theoryand practice of analytical chemistry, fundamentaland applied, inorganic and organic, includingchemical, physical, biochemical, clinical,pharmaceutical, biological, environmental,automatic and computer-based methods. Paperson new approaches to existing methods, newtechniques and instrumentation, detectors andsensors, and new areas of application with dueattention to overcoming limitations and tounderlying principles are all equally welcome.Full critical reviews. These must be a criticalevaluation of the existing state of knowledge on aparticular facet of analytical chemistry.Tutorial reviews.These should be informallywritten although they should still be a criticalevaluation of a specific topic area. Some historyand possible future developments should be given.Potential authors should contact the Editor beforewriting reviews.Perspectives. These articles should provideeither a personal view or a philosophical look at atopic relevant to analytical science. Alternatively,they may be relevant historical articles.Perspectives are included at the discretion of theEditor.Particular attention should be paid to the use ofstandard methods of literature citation, includingthe journal abbreviations defined in ChemicalAbstracts Service Source Index.Whereverpossible, the nomenclature employed should followIUPAC recommendations, and units and symbolsshould be those associated with SI.Every paper will be submitted to at least tworeferees, by whose advice the Editorial Board ofThe Analyst will be guided as to its acceptance orrejection. Papers that are accepted must not bepublished elsewhere except by permission.Submission of a manuscript will be regarded as anundertaking that the same material is not beingconsidered for publication by another journal.Associate Scientific Editors.For the benefit ofall potential contributors wishing to discuss thescientific content of their paper(s) a Group ofAssociate Scientific Editors exists. Requests forhelp or advice on scientific matters can be directedto the appropriate member of the Group (accordingto discipline). Currently serving Associate ScientificEditors are listed in each issue of The Analyst (andAnalytical Communications).Manuscripts (four copies typed in double spacing)should be addressed to:H. S. Minhas, Managing Editor, orJ. F. Tyson, US Associate EditorAll queries relating to the presentation andsubmission of papers, should be addressed to thePublishing Division and any correspondenceregarding accepted papers and proofs, should bedirected to the Production Division for The Analyst.Members of the Analytical Editorial Board (whomay be contacted directly or via the Editorial Off ice)would also welcome comments, suggestions andadvice on general policy matters concerning TheAnalyst.There 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 payable on a US clearing bank, shouldbe sent directly to The Royal Society of Chemistry, Turpin Distribution Services Ltd., Blackhorse Road, Letchworth, Herts, UK SG6 1 HN.Turpin Distribution ServicesLtd., is wholly owned by the Royal Society of Chemistry. 1996 Annual subscription rate EC f487.00, USA $923.00, Rest of World f499.00. Purchased with AnalyticalAbstracts EC f951 .OO, USA $1 804.00, Rest of World f975.00. Purchased with Analytical Abstracts plus Analytical Communications EC f 1 123.00, USA $21 29.00,Rest of World fll51 .OO. Purchased with Analytical Communications EC f610.00, USA $1 156.00, Rest of World f625.00. Air freight and mailing in the USA byPublications Expediting Inc., 200 Meacham Avenue, Elmont, NY 1 1003.USA Postmaster: Send address changes to: The Analyst, Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003. Second class postage paid atJamaica, NY 11431. All other despatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outside Europe. PRINTED IN THE UK.0 The Royal Society of Chemistry, 1996. All rights resewed. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form,or by any means, electronic, mechanical, photographic, recording, or otherwise, without the prior permission of the publishers

ISSN:0003-2654    

DOI:10.1039/AN99621FX005

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

ANALAO 121 (2) 95-274, 17N-24N (1 996) FEBRUARY 1996I Ill IllCONFERENCE PAPERSFOREWORD 9597105111119127133REVIEWS139CHEMOMETRICS/STAT I ST I C S163169SAMPLE HANDLING173177183ATOMIC SPECTROSCOPY/SPECTROMETRY18919520 1'""An a I y s tThe analytical journal of The Royal Society of ChemistryCONTENTSSAC 95: An International Conference on Analytical Chemistry-R. A. YoungDeconvolution of Overlapping Chromatographic Peaks by Means of Fast Fourier and HartleyTransforms-Anastasios Economou, Peter R. Fielden, Andrew J. PackhamRaman Spectroscopic Determination of Thymidine Nucleoside Structures in Nucleotides-RosarioEscobar, Pedro Carmona, Marina MolinaComparison of Chemical Modifiers for the Determination of Vanadium in Water and Oil Samples byElectrothermal Atomization Atomic Absorption Spectrometry-Nikolaos S.Thomaidis, Efrosini A. PiperakiGas Phase Detection of Cocaine by Means of Immunoanalysis-Torsten Ziegler, Oliver Eikenberg, UrsulaBilitewski, Michael GrolCaesium Ion-selective Electrodes Based on Crowned Benzoquinones-Michael G. Fallon, David Mulcahy,William S. Murphy, Jeremy D. GlennonObservations on the Behaviour of Some Trifluoroacetophenone Derivatives as Neutral Carriers forCarbonate Ion-selective Electrodes-Tomasz Sokalski, Dariusz Paradowski, Joanna Ostaszewska,Magdalena Maj-Zurawska, Jozef Mieczkowski, Andrzej Lewenstam, Adam HulanickiRecent Developments in the Determination of Precious Metals-A Review-Yi Bin QuCombined Benedetti-Pichler/Stange-Poole Sampling Equation for Two-component ParticulateMixtures-Lu Zheng, Byron KratochvilMulticomponent Analysis by Flow Injection Using a Partial Least-squares Model.Determination of Copperand Zinc in Serum and Metal Alloys-Oscar Herndndez, Francisco Jimbnez, Ana Isabel Jimbnez,Juan Jose AriasUse of Poly(ethy1ene terephthalate) Plastic Bottles for the Sampling, Transportation and Storage of PotableWater Prior to Mercury Determination-D. D. Copeland, M. Facer, R. Newton, P. J. WalkerDevelopment of a Stand-alone Affinity Clean-up for Lysergic Acid Diethylamide in Urine-John M. Francis,Derek H. CrastonFlow Injection Method for the Determination of Methotrexate With a Column-packed Oxidizing Agent-Samy Emara, Saeid Razee, Abdel-Nasser El-Shorbagi, Tsutomu MasujimaDistribution of Selenium in Human Blood Plasma and Serum-lain Harrison, David Littlejohn,Gordon S.FellRapid and Reliable Method for the Determination of Aluminium in Bone by Electrothermal AtomicAbsorption Spectrometry-Shida Tang, Patrick J. Parsons, Walter SlavinTransport of Nickel, Cobalt, Iron and Chromium to the Atom Cell During a Hydride GenerationProcess-Torild Wickstrom, Walter Lund, Ragnar ByeCH EM1 STRYInformationServices Cambridge, EnglandTypeset and printed by Black Bear Press Limited,Continued on inside back cover-0003-2654(199612:1-MOLECULARSPECTROSCOPY/SPECTROMETRY20521 121 9S E PA R AT1 0 N SC I E NC E223229233239243SENSORS249255259ELECTROANALYTICAL26326927 1273Measurement of Carbon-1 3 : Carbon-1 2 Ratios by Fourier Transform Infrared Spectrometry-AndrewKindness, lain L.MarrCarbon Dioxide-enhanced Luminol Chemiluminescence in the Absence of Added Oxidant-Zhang-HuaLan, Horacio A. MottolaApplication of Near-infrared Reflectance Spectrometry to the Analytical Control of Pharmaceuticals:Ranitidine Hydrochloride Tablet Production-Elena Dreassi, Giuseppe Ceramelli, Piero Corti, Piero LuigiPerruccio, S. LonardiAntimony Speciation in Freshwater Plant Extracts by Using Hydride Generation-GasChromatography-Mass Spectrometry-Matthew Dodd, Spiros A. Pergantis, William R. Cullen, Hao Li,Guenter K. Eigendorf, Kenneth J. ReimerDetection of Veterinary Drugs in Foodstuffs Using Gel Permeation-G. Biancotto, R. Angeletti,R.D. M. PiroSome Comments on the Determination of Microcystin Toxins in Waters by High-performance LiquidChromatography-Roland W. Moollan, Bruce Rae, Alistair VerbeekDetermination of Alkylphenol Ethoxylate Non-ionic Surfactants in Trade Effluents by Sublation andHigh-performance Liquid Chromatography-Naairn M. A. Ibrahirn, Brian B. WhealsDirect Determination of 7-Hydroxycoumarin and 7-Hydroxycoumarin-glucuronide in Urine by UsingCapillary Electrophoresis-Declan R. Bogan, R. D. Thornes, M. Tegtmeier, E. A. Schafer, Richard0’ KennedyColloidal Gold Supported Onto Glassy Carbon Substrates as an Amperometric Sensor for Carbohydratesin Flow Injection and Liquid Chromatography-lnnocenzo G. Casella, Angelo Destradis, Elio DesimoniPyrite as Sensor for Potentiometric Precipitation Titrations-M. M. AntonijeviC, B. Vukanovic, R. MihajlovicPiezoelectric Crystal Sensor With a Plasticized Poly(Viny1 Chloride) Coating for Determination of TraceAmounts of Ethanol Vapour-Ke-Min Wang, Zhong Cao, Hui-Gai Lin, Shi-Hua Wang, Bin-Feng Wang,Ru-Qin YuDetermination of Cinnamic Acid in Human Urine by Differential-pulse Polarography-Valdir S. Ferreira,Cristo B. Melios, Maria Valnice B. Zanoni, Nelson R. StradiottoERRATACORRESPONDENCECUMULATIVE AUTHOR INDEXNEWS AND VIEWS 17N Book Reviews18N Conference Diary22N Courses23N Papers in Future Issues24N Technical Abbreviations and AcronymsCover picture: Determination of precious metals (see p. 139). Image kindly supplied by IAS Marketing forFisons Instruments, Elemental Analysis, Winsford, UK

ISSN:0003-2654    

DOI:10.1039/AN99621BX007

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, February 1996, Vol. 121 17N Book Reviews Principles and Applications of Electrochemistry. 4th Edition By D. R. Crow. Pp. xi + 282. Blackie. 1994. Price f16.99. ISBN 0-7514-0168-4. This book has been written along conventional lines describing the classical concepts fundamental to electrochemistry. This edition of the book is the fourth, the first having been published in 1974. It is aimed at a level suitable for second and third year undergraduate students. Each chapter has set problems with brief solutions in the back of the book. No specific references are given in the text but a listing (topic-wise) of books for further reading is provided in the back. The book is in two halves: the first sets out the fundamentals of electrochemistry such as ionic interactions and equilibria, then it goes via conductivity and double-layers to electrode potentials and electrode processes.The second half is devoted to the principles of applications including electroanalytical techniques, determi- nation of fundamental physical parameters such as stability constants, and corrosion and batteries. ‘this book is very well written: it clarifies the theory and manages to make it look compar- atively simple and interesting. I warmly recommend this book as a course text to teach students the principles of electro- chemical theory. ’ It is difficult to make a book at the introductory level of this topic interesting. There is (for me at least) sufficient mystery in equations on chemical potentials that I would like to do without them. However, this book is very well written: it clarifies the theory and manages to make it look comparatively simple and interesting.The classical electrochemical theory on electrical double-layers, and topics like the double-layer thickness and zeta-potential, and models by Helmholtz, Goey and Chapman, and Stern, are fascinating attempts to explain physico-electro- chemical phenomena theoretically. Fortunately the actual derivations have been placed in appendices making the book more readable and interesting. I warmly recommend this book as a course text to teach students the principles of electrochemical theory. Dr. C. M. G. van den Berg 4/90185A University of Liverpool Bioluminescence and Chemiluminescence. Fundamen- tals and Applied Aspects Edited by A. K. Campbell, L.J. Kricka and P. E. Stanley. Proceedings of the 8th International Symposium on 5ioluminescence and Chemiluminescence, Cambridge, UK, September 7994. Pp. xviii + 672. Wiley. 1995. Price f90.00. ISBN 0-471-95548-5. Chemiluminescence (CL) and its enzyme-catalysed version, bioluminescence (BL), are currently greatly in vogue for research in many fields. Not least of these are its analytical applications, resulting from its great sensitivity, selectivity and wide variety of systems that can be used. This book provides short papers (maximum of 4 pages) of lectures and posters presented at the above conference, and published with com- mendable speed. The conference itself is highly respected, well attended and truly interdisciplinary. The papers are divided into sections covering CL itself (19 articles), CL and BL as a signal (6), luminescence in the environment (12), in medicine (48), and in education (5), methods for ATP and firefly luciferase analyses (25), molecular biology (25) and imaging (10).A large number of the articles refer to analytical applications, including immunoassays, enzyme assays, ATP and bacterial testing, etc. There is a subject index. Alan Townshend 5190053 K University of Hull S I Chemical data. 3rd Edition By Gordon Aylward and Tristan Findlay. Pp. xii + 180. Wiley. 1994. Price f9.95. ISBN 0-471-33554-1. This is the third edition of this compendium of chemical data and follows some twenty years after the second. Its primary aim is to provide a concise and inexpensive source of data for teachers and to this end, as far as possible, all the constants are given for a temperature of 25 “C.The authors admit that this is not the normal convention, but it is more convenient in a teaching environment, where comparison of the various con- stants is often required. An additional feature of this edition, is the inclusion of Safety Data for all the compounds that are listed. This is effectively abbreviated and uses the terminology used by the UK Health and Safety Executive (HSE). While it is not a substitute for full safety data sheets, it does provide a swift check on the properties of many compounds. The book consists of a series of tables, starting with the ‘S I System’, a list of fundamental constants and conversion factors. Up to thirteen properties are listed for each of the elements, while for inorganic compounds, up to eighteen properties are listed, including a considerable amount of thermodynamic data.This table is sixty-five pages in length and while it does not contain as many compounds as the CRC Hand Book, it lists most of the common compounds and supplies more data for most of them. Properties of organic compounds occupy twenty- five pages and only the most common compounds and twenty amino acids are included, but again the data is extensive, including standard enthalpy, Gibbs energy and molar heat capacity, as well as the usual properties and the hazard data. The book continues with some forty pages containing twenty-seven tables covering a wide range of topics from crystal forms, shapes of molecules and bond length, to stability constants, electronegativities and ionization potentials as well as a wealth of enthalpy information. A table showing the electronic configuration of the elements is followed by an Appendix which fully explains the use of the hazard information and lists a large range of materials by hazard. ‘modest price means that it is very good value for money for anyone who requires access to such data.’ The sources of the data are well indexed and the tables appear to be essentially error free. The book certainly meets the needs of its target audience, but is also a useful source of reference data, on the more common materials, of use to any chemist. The modest price means that it is very good value for money for anyone who requires access to such data. Colin Watson 5/90060C Ilford

ISSN:0003-2654    

DOI:10.1039/AN996210017N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

18N Analyst, February 1996, Vol. 121 Conference Diary Date Conference 1996 March 3-8 7-8 10-15 19-23 20-21 24-28 25-29 3 1 4 4 April 9-10 9-12 9-12 17-18 17-1 9 22-23 Locat ion 47th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy USA Chicago, Second Annual Genetic Screening and Diagnosis of Human Diseases USA San Francisco, Advances in the Formulation and Processing of Injectable Dispersed Pharmaceuticals UK Cambridge, International Solvent Extraction Conference Melbourne, 1996 (ISEC '96) Australia External Sourcing of R & D (extRaD '96) Manchester, UK 29th International Meeting of the ESRDG of the RSC: ESR Spectroscopy of Inorganic Radicals and Metal Ions in Inorganic and Biological Systems ESEAC '96,6th European Conference on Electroanalysis UK Edinburgh, UK Durham, 7th International Symposium on Supercritical Indianapolis, Fluid Chromatography and Extraction USA 1996 Northeastern Environmental Symposium East Rutherford, 26th International Symposium on Environmental Analytical Chemistry Scanning '96 TAC 96 Thermal Analysis and Calorimetry Symposium VIIth International Symposium on Luminescence Spectrometry in Biomedical Analysis-Detection Techniques and Applications in Chromatography and Capillary Electrophoresis Computer and Process Validation in the USA Vienna, Austria Monterey, USA Leeds, UK Nice, France Manchester, Pharmaceutical and Fine Chemical Industries UK Contact The Pittsburgh Conference, 300 Penn Center Boulevard, Suite 332, Pittsburgh, PA 15235-5503, USA Cambridge Healthtech Institute, 1037 Chestnut Street, Newton Upper Falls, MA 02164, USA Tel: +I 617 630 1300.Fax: +1 617 630 1325 E-mail: chi@healthtech.com Dr. J. A. Clements, Room 403, Royal Pharmaceutical Society of Great Britain, 1 Lambeth High Street, London, UK SE1 7JN Tel: +44 (0)171 735 9141. Fax: +44 (0)171 735 7629 Dr. R. W. Cattrall, Secretary Organising Committee, ISEC '96, School of Chemistry, La Trobe University, Bundoora 3083, Victoria, Australia Tel: +61 3 9479 2539. Fax: +61 3 9479 1399 E-mail: r.w.c.@latrobe.edu.au Spring Innovations, 185A Moss Lane, Bramhall, Stockport, Cheshire, UK SK7 1BA Tel: +44 (0)161 440 0082. Fax: +44 (0)161 440 9127 Dr. C. C. Rowlands, Department of Chemistry, University of Wales Cardiff, P.O. Box 912, Cardiff, UK CF13TB Dr. A. G. Fogg, Loughborough University of Technology, Loughborough, Leicestershire, UK LEll 3TU Tel: +44 (0) 1509 263171. Fax: +44 (0) 1509 233163 Mrs.Janet Cunningham, Barr Enterprises, 10120 Kelly Road, P.O. Box 279, Walkersville, MD 21793 USA Tel: +I 301 898 3772. Fax: +1 301 898 5596 Sandy Galla, ISC Exhibit Management Co., P.O. Box 313, Shelton, CT 06484-0313 Tel: +1 203 926 9300. Fax: +1 203 926 9722 Professor Dr. M. Grasserbauer, Institute for Analytical Chemistry, Vienna University of Technology, Getreidemarkt 9/15 1, A- 1060 Wien, Austria Fax: +43 1 5867813 Mary K. Sullivan, Foundation for Advances in Medicine and Science, P.O. Box 832, Mahwah, NJ Tel: +1 201 818 1010. Fax: +1 201 818 0086 E-mail: fams@holonet.net Dr. C. J. Keattch, P.O. Box 9, Lyme Regis, Dorset, UK DT7 3BT Tel: +44 (0) 1297 442221. Professor 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 Spring Innovations, 185A Moss Lane, Bramhall, Stockport, Cheshire, UK SK7 1BA Tel: +44 (0)161 440 0082. Fax: +44 (0)161 440 9127 07430-0832, USAAnalyst, February 1996, Vol. 121 19N Date 23-26 28-115 May 5-8 6-8 6-10 9-1 1 13-14 19-22 19-24 20-22 20-23 20-24 23-25 June 4-7 9-13 ~~~~ Conference Analytica Conference '96 Contact Location Munich, Germany Congress Center, Messegelande, D-80325 Munchen, Germany Tel: +49 89 5107 159. Fax: +49 89 5107 180 AOCS Education/Meetings Department, P.O. Box 3489, Champaign, IL, USA 61826-3489 Tel: +1 217 359 2344.Fax: +1 217 351 8091 87th AOCS Annual Meeting and Expo Indianapolis, USA Gramado, Brazil Centro de Ecologia, Universidade Federal do Rio Grande do Sul, C.P. 15007,91501-970 Port0 Alegre, Brazil Tel: +55 51 2281 633. Fax: +55 51 3361 568. E-mail: Ceneceifl .ufrgs.Br Dr. N. Haagsma, Utrecht University, Faculty of Veterinary Medicine, P.O. Box 80.175, NL-3508 TD Utrecht, The Netherlands Tel: +31 30 535365. Fax: +31 30 532365 Francoise Chavel, Executive, Secretary, European Optical Society, B.P. 147-91403 Orsay Cedex, France Tel: +33 1 69 85 35 92. Fax: +33 1 69 85 35 65. E-Mail: francoise.chavel@iota.u-psud.fr Swedish Academy of Pharmaceutical Sciences, P.O. Box 1 136, S-1 1 1 81 Stockholm, Sweden Tel: +46 8 723 50 00. Fax: +46 8 20 55 11 Spring Innovations, 185A Moss Lane, Bramhall, Stockport, Cheshire, UK, SK7 1BD Tel: +44 (0)161 440 0082.Fax: +44 (0)161 440 9127 Mercedes Gomez, Laboratory of Toxicology and Biochemistry, School of Medicine, c/o San Lorenzo 21, E-43201 Reus, Spain Tel: +34 77 759376. Fax: +34 77 759322 Mary L' Abbe, Nutrition Research, Health Canada, Ottawa, ON K1A OL2, Canada Tel: +1 613 957 0924. Fax: +1 613 941 6182 E-mail:mlabbe@ hpb.hwc.ca Michael Carl, Milschwirtschaffliche Untersuchungs und Versuchsanstalt Mempten, Postfach 2025, D87410, Kempten, Germany Tel: +49 8315 2900. Fax: +49 8315 290100 BESB 2; Anita Moberg, Swedish Environmental Protection Agency, S- 10648 Stockholm, Sweden Tel: +46 8 698 1000. Fax: +46 8 689 1504 E-mail: am@ environ.se Professor D. P. Sandra, IOPMS, Kennedypark 20, B-8500 Kortrijk, Belgium Tel: +32 56 204960. Fax: +32 56 204859 Romanian Society of Analytical Chemistry, 13 Boulevard Republicii, Sector 3, 70346 Bucharest, Romania Tel: +40 1 631 00 60.Fax: +40 1 631 2279 International Colloquium on Process Related Analytical Chemistry in Environmental Investigations EuroResidue 111, Third International Conference on Residues of Veterinary Drugs in Food Veldhoven, The Netherlands 2nd European Symposium and Exhibition on Photonics in Manufacturing I1 Paris, France 2nd Symposium on Biotechnology-From the Gene to Finished Product Stockholm, Sweden Boston, USA Barcelona, Spain Chiral USA '96 4th International Symposium on Metal Ions in Biology and Medicine 9th International Symposium on Trace Elements in Man and Animals Banff, Canada Symposium on Dairy Quality Assurance Sonthofen, Germany 2nd International Symposium & Workshop on Biological Environmental Specimen Banking (BESB 2) Stockholm, Sweden 18th International Symposium on Capillary Chromatography Riva del Garda, Italy XIIIth National Conference on Analytical Chemistry Craiova, Romania 3rd Nordic Festival of Mass Spectrometry Thorleif Lavold Jr./Gunilla Hugo, Fisons Instruments, Nordic AB, Gardsfogdevagen 16, S-161 70 Bromma, Sweden Tel: +46 8 629 24 00.Fax: +46 8 627 52 20 Glenda Bland, Global Meeting Planning Tel: +44 (0)1222 700053. Fax: +44 (0)1222 700665 E-mail: 10046.1402@compuserve.com Lund, Sweden 8th International Conference on Metalorganic Cardiff, Vapour Epitaxy UK20N Analyst, February 1996, Vol. 121 Date 10-1 1 10-14 13-14 16-2 1 17-2 1 30-517 July 1-3 8-1 2 15-19 17-19 Conference 6th Conference on Total Reflection X-Ray Fluorescence Analysis and Related Methods (Part 1) 11th International Converence on High-Power Particle Beams (BEAMS '96) 6th Conference on Total Reflection X-Ray Fluorescence Analysis and Related Methods (Part 2) HPLC '96: 20th International Symposium on High Performance Liquid Phase Separations and Related Techniques 2nd European Symposium and Exhibition on Optical Instrument and Systems Design Resonance Ionization Spectroscopy and Its Applications, RIS-96 9th International Symposium on Polymer Analysis and Characterization (ISPAC-9) XVI International Congress of Clinical Chemistry 9th International Conference on Quantitative Surface Analysis 8th Biennial National Atomic Spectroscopy Symposium (BNASS) August 11-16 20-23 7th International Symposium on ICORS '96: XV International Conference on Raman Spectroscopy Pharmaceutical and Biomedical Analysis (PBAT '96) ~~ Locat ion Eindhoven, Netherlands Prague, Czech Republic Dortmund, Germany California, USA Glasgow , UK Pennsy iv ania, USA Oxford, UK London, UK Surrey, UK Norwich, UK Pittsburgh, USA Osaka, Japan 21-23 Fourth International Symposium on Capillary York, Electrophoresis UK Contact Dr.D. K. G. de Boer, Philips Research Laboratories, WB21, Prof. Holstlaan 4, NL-5656 AA Eindhoven, The Netherlands Tel: +31 40 74 2859. Fax: +31 40 74 3075 E-mail: deboerd@prl.philips.nl Dr. Jiri Ullschmied, Conference Co-Chairman, Institute of Plasma Physics, AS CR, Za Slovankou 3, Prague 182 00, Czech Republic Fax: +422 858 6389.E-mail: BEAMS96@ 1PP.CAS .CZ Dr. D. K. G. de Boer, Philips Laboratories WB21, Prof. Holstlaan 4, NL-5656 AA Eindhoven, The Netherlands Tel: +3 1 40 74 2859. Fax: +3 I 40 74 3075 E-mail: deboerd@prl.philips.nl Mrs. Janet Cunningham, Barr Enterprises, 10120 Kelly Road, P.O. Box 279, Walkersville, MD 21793, USA Tel: +I 301 898 3772. Fax: +1 301 898 5596 Francoise Chavel, Executive Secretary, European Optical Society, B.P. 147-91403 Orsay Cedex, France Tel: +33 1 69 85 35 92. Fax: +33 1 69 85 35 65. E-mail: francoise.chavel@iota.u-psud.fr Sabrina Glasgow, Conference Secretary, Department of Chemistry, The Pennsylvania State University, 184 Materials Research Institute Building, University Park, PA 16802-7003 USA Tel: +I 814 865 0200.Fax: +1 814 863 0618 E-mail: scg4@psuvm.psu.edu Prof. John Dawkins, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, UK LEI 1 3TU Fax: +44 (0)1509 233163 Mrs. Pat Nielsen, XVIth International Congress of Clinical Chemistry, P.O. Box 227, Buckingham, UK MK18 5PN Fax: +44 (0) 1280 6487 Professor J. E. Castle, University of Surrey, Department of Materials Science and Engineering, Guildford, Surrey UK GU2 5XH Tel: +44 (0)1483 259150. Fax: +44 (0)1483 259508. E-mail: j.castle@surrey:ac.uk Ms. Brenda Holliday, BNASS Secretariat, Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge, UK CB4 4WF Tel: +44 (0)1223 420066. Fax: +44 (0)1223 423623 Professor S. Asher, Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA Professor Susumu Honda, Faculty of Pharmaceutical Sciences, Kinki University, Kowakae 3-4-1, Higashi Osaka 577, Japan Fax: +81 6 721 2353 Dr.T. L. Threlfall, Industrial Liaison Executive, Department of Chemistry, University of York, York, UK YO1 5DD Tel: +44 (0) 1904 432576. Fax: +44 (0) 1904 4325 16 E-mail: j s20@ york. ac.ukAnalyst, February 1996, Vol. 121 21N Date Conference 25-30 XXIII EUCMOS September 1-7 8-13 9-1 1 9-13 10-14 11 15-20 16-18 Euroanalysis IX Locat ion B alatonfiired, Hungary Bologna, Italy CLEO '96: European Conferences on Lasers Hamburg, and Electro-Optics Gerrnany Sixth International Symposium on Field Flow Ferrara, Fractionation Italy 14th International Conference on High Resolution Molecular Spectroscopy Czech Republic Prague, International Symposium and Exhibition on Biomedical Optics IV Austria Graz, 22nd Annual Meeting of the British Mass Spectrometry Society UK Swansea, 21st International Symposium on Stuttgart, Chromatography Germany The Third International Conference on Applications of Magnetic Resonance in Food Science Nantes, France October 3-4 Validation in Capillary Electrophoresis York, UK November 4-8 International Symposium on the Industrial Johannesburg, Application of the Mossbauer Effect South Africa 1997 January 4-9 The Fourth International Symposium On: Giza, New Trends in Chemistry The Role of Egypt Analytical Chemistry in National Development Contact Professor Dr.J. Mink, Department of Analytical Chemistry, University of VeszprCm, P.O.Box 158, H-8201 VeszprCm, Hungary Professor Luigia Sabbatini, Euroanalysis IX, Dipartimento di Chimica, Universith di Bari, Via Orabona, 4, 70126 Bari, Italy Tel: +39 80 544 2020. Fax: +39 80 544 2026 CLEO/Europe '96, Institute of Physics, Meetings and Conferences Department, 47 Belgrave Square, London, UK SWlX 8QX F. Dondi, Department of Chemistry, University of Ferrara, Via L. Borsari, 46, 1-44100 Ferrara, Italy Tel: +39 532 291154. Fax: +39 532 240709 Dr. V. Spirko, Academy of Sciences of the Czech Republic, J. Heyrovsk, Institute of Physical Chemistry, Dolejskova 3, CZ-18223 Praha 8, Czech Republic Francoise Chavel, Executive Secretary, European Optical Society, B.P. 147-9 1403 Orsay Cedex, France Tel: +33 1 69 85 35 92. Fax: +33 1 69 85 35 65. E-mail: francoise.chavel@iota.u-psud.fr Dr. Fred Mellon, Institute of Food Research, Norwich Laboratory, Norwich Research Park, Colney, Norwich, UK NR4 7UA Tel: +44 (0)1603 255299. Fax: +44 (0)1603 452578 E-mail:fred.mellon@ bbsrc.ac.uk GDCh-Geschaftsstelle, Abt. Tagungen, Vanentrappestr. 40-42, Postfach 90 04 40, D-6000 Frankfurt am Main 90, Germany Tel: +49 69 791 7358. Fax: +49 69 791 7475 G. J. Martin or V. Foucault, FacultC des Sciences, Laboratoire de Resonance MagnCtique NuclCaire et RCactivitiC Chimique, U.R.A. - CNRS 472, 2 rue de la Houssiniitre, 44072 Nantes Cedex 03, France Tel: +33 4037 3169. Fax: +33 4074 9806 Dr. T. L. Threlfall, Industrial Liaison Executive, Department of Chemistry, University of York, York, UK YO1 5DD Tel: +44 (0) 1904 432576. Fax: +44 (0) 1904 432516 E-mail: js20@york.ac.uk Herman Pollak, Mossbauer Laboratory, University of the Witwatersrand, Private Bag 3, WITS 2050, Johannesburg, South Africa Tel: +27 11 716 4053/2526. Fax: +27 11 339 8262. E-mail: isiame@physnet.phys.wits.ac.za Professor Dr. M. M. Khater, Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt Tel: +5727213. Fax: +5727288

ISSN:0003-2654    

DOI:10.1039/AN996210018N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

22N Analyst, February 1996, Vol. I21 Courses Date Conference Locat ion 1996 March 26 Intermediate HPLC Training Course Macclesfield, UK 26-29 Analysis and Examination of Foods and Reading, Other Materials UK 27 Intermediate HPLC Training Course Macclesfield, UK 28 Intermediate HPLC Training Course Macclesfield, UK April 23-24 HPLC Troubleshooting Courses Macclesfield, UK May 19-22 1996 International Symposium, Exhibit & Washington D.C., Workshops on Preparative Chromatography, USA Ion Exchange, and Adsorption/Desorption Processes and Related Techniques 21-23 HPLC Beginners Training Course Macclesfield, UK June 18-19 HPLC Toubleshooting Courses Macclesfield, UK July 23-25 Problem Solving for Analytical Leaders York, UK August 18-2 1 Capillary Electrophoresis Course York, UK September 3-5 HPLC Beginners Training Course Macclesfield, UK 7 Workshop in Field Flow Fractionation Ferrara, Italy Contact Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SKll 6PJ Tel: 01625 613848.Fax: 01625 616916 Robert F. Radford, The Old Thatched Post Office, Sulhamstead Hill, Sulhamstead, Berkshire, UK RG7 4DE Tel: +44 (0) 734 3041 10. Fax: +44 (0) 734 323438 Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SK11 6PJ Tel: 01625 613848. Fax: 01625 616916 Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SKll 6PJ Tel: 01625 613848. Fax: 01625 616916 Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SKI 1 6PJ Tel: 01625 613848. Fax: 01625 616916 Janet Cunningham, Barr Enterprises, P.O. Box 279, Walkersville, MD 21793 USA Tel: +1 301 898 3772.Fax: +I 301 898 5596 E-mail: J a n e t b m aol.com Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SKll 6PJ Tel: 01625 613848. Fax: 01625 616916 Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SK11 6PJ Tel: 01625 613848. Fax: 01625 616916 Dr. T. L. Threlfall, Industrial Liaison Executive, Department of Chemistry, University of York, York, UK YO1 5DD Tel: +44 (0) 1904 432576. Fax: +44 (0) 1904 432516 E-mail: js20@york.ac.uk Dr. T. L. Threlfall, Industrial Liaison Executive, Department of Chemistry, University of York, York, UK YO1 5DD Tel: +44 (0) 1904 432576. Fax: +44 (0) 1904 432516 E-mail: js20@york.ac.uk Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SKll 6PJ Tel: 01625 613848. Fax: 01625 616916 F. Dondi, Department of Chemistry, University of Ferrara, Via L. Borsari, 46,I-44100 Ferrara, Italy Tel: +39 532 291154. Fax: +39 532 240709 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)1223 420066. Fax: +44 (0)1223 420247. E-mail:Analyst@RSC.ORG.

ISSN:0003-2654    

DOI:10.1039/AN996210022N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, February 1996, Vol. 121 23N Future Issues Will Include Quantification of Gas Phase Sidestream Cigarette Smoke Components Using Fourier Transform Infrared Spectroscopy- S. Keith Cole, Patricia Martin Determination of Trace Amounts of Reduced Glutathione by a Chemical Oscillating Reaction-Dolores Perez-Bendito, Rafael Jimenez-Prieto, Manuel Silva Retention Properties of a Spacer Bonded Propanediol Sorbent for Reversed-phase Liquid Chromatography and Solid-phase Extraction-Colin F. Poole, Donna S. Seibert, Michael H. Abraham Polarographic Behaviour of Sulfadiazine, Sulfamerazine, Sulfa- methazine and their Mixtures. Abilities of Partial Least Squares Methods in the Resolution of the Non-additive Signals of these Compounds-T. Galeano Diaz, A. Guiberteau Cabanillas, M.I. Acedo Valenzuela, F. Salinas Selective Detection of Aroma Components by Acoustic Wave Sensors Coated with Conducting Polymer Films-Michael Thompson, David C. Stone, Zhiping Deng Determination of Ethyl Alcohol in Beer by Dual-pulse Staircase Voltammetry in Flow Injection-Y. S. Fung, S. Y. Mo Amperometric Determination of L-Malic Acid in a Flow Injection Manifold Using Packed Bed Enzyme Reactors-M. I. Karayannis, Mamas I. Prodromidis, Stella Tzouwara- Karrayanni, Pankaj Vadgama, Andrew Maines Enzymic Method for Determination of Ethanol and Methanol- Ulyana M. Mizgunova, Galina A. Zolotova, Inga F. Dolmanova Resolution of Multicomponent Mixture Spectra in Mid-infrared Spectroscopy Using Spherical Projection Factor Analysis- Application to Real Data Including a Six-component Mixture Set-R.G. Brereton, Stephen P. Gurden, John A. Groves Silicones and Their Analysis in Biological Matrices. A Review-Michael Thompson, Biljana Cavic-Vlasak, Dennis C. Smith Flow Injection Fluorimetric Determination of Fluoride or Phosphate Based on their Inhibitory Effect on the Photo- oxidation of Acridine Catalysed by Iron(m)-Tomas Perez- Ruiz, Carmen Martinez-Lozano, Virginia Tomas, Antonio Sanz Comparative Study of the Ratio Spectra Derivative and Partial Least Squares Methods to the Simultaneous Determination of Atrazine and Ametryn in Groundwaters-F. Garcia Montelongo, R. Corbella Tena, M. A. Rodriguez Delgado, M. J. Sanchez Filled Fluorosilicone as Matrix Material for Ion-selective Membranes-S. Adam, C. Dumschat, S. Alazard, M. Knoll, K. Cammann Solid-phase Extraction of Heavy Metal Ions on a High Surface Area Titanium Dioxide (Anatase)-E. Vassileva, I. Proinova, K. Hadjiivanov 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 WlV OBN, UK. Tel: +44 (0)171-437 8656. Fax: +44 (0) 171 -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.

ISSN:0003-2654    

DOI:10.1039/AN996210023N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

24N Analyst, February 1996, Vol. 121 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. AAS ac AID ADC ANOVA AOAC ASTM bP BSA BSI CEN CPm CMOS c.m.c. CRM CVAAS cw CZE dc DRIFT dPm DELFIA DNA EDTA ELISA emf ETAAS EXAFS EPA FAAS FAB FAO-WHO FIR FT FPLC FPD GC GLC HGAAS HPLC ICP id INAA IR ISFET iv im IGFET ISE LC LED LOD atomic absorption spectrometry alternating current analogue-to-digital analogue-to-digital converter analysis of variance Association of Official Analytical Chemists American Society for Testing and Materials boiling point bovine serum albumin British Standards Institution European Committee for Standardization counts per minute complementary metal oxide silicon critical micellization concentration certified reference material cold vapour atomic absorption spectrometry continuous wave capillary zone electrophoresis direct current disintegrations per minute diffuse reflectance infrared Fourier transform spectroscopy dissociation enhanced lanthanide fluorescence immunoassay deoxyribonucleic acid ethylenediaminetetraacetic acid enzyme linked immunosorbent electromotive force electrothermal atomic absorption spectrometry extended X-ray absorption fine structure spectroscopy Environmental Protection Agency flame atomic absorption fast atom bombardment Food and Agriculture Organization, far-infrared Fourier transform fast protein liquid chromatography flame photometric detector gas chromatography gas-liquid chromatography hydride generation atomic absorption spectroscopy high-performance liquid chromatography inductively coupled plasma internal diameter instrumental neutron activation infrared ion-selective field effect transistor intravenous intramuscular insulated gate field effect transistor ion-selective electrode liquid chromatography light emitting diode limit of determination assay spectrometry World Health Organization analysis LOQ mP MRL mRNA MS NIR NMR NIST od OES PBS PCB PAH PGE PIXE PPt PPb PPm PTFE PVC PDVB QC QA REE rf RIMS rms rPm RNA SCE SE SEM SIMS SIMCA S/N SRM STM STP TIMS TLC TOF TGA TMS tris TRIS uv UVNIS VDU XRD XRF YAG Commonly Used Symbols M Mr r S U limit of quantification melting point maximum residue limit messenger ribonucleic acid mass spectrometry near-infrared nuclear magnetic resonance National Institute of Standards and Technology outer diameter optical emission spectrometry phosphate buffered saline polychlorinated biphenyl pol ycyclic aromatic hydrocarbon platinum group element particle/proton-induced X-ray parts per trillion (1012; pg g-') parts per billion (109; ng g-l) parts per million (106; pg g- ) pol y (te trafluoroethylene) poly(viny1 chloride) pol y (divin yl benzene) quality control quality assurance rare earth element radio frequency resonance ionization mass spectrometry root mean square revolutions per minute ribonucleic acid saturated calomel (reference) electrode standard error scanningkurface (reflection) secondary-ion mass spectrometry soft independent modelling of class signal-to-noise ratio Standard Reference Material scanning tunnelling (electron) standard temperature and pressure thermal ionization mass thin-layer chromatography time-of-flight thermogravimetric analysis trimethylsilane 2-amino-2-( hydroxymethy1)- propane-1,3-diol (ligand) Z-amino-2-(hydroxymethyl)- propane-l,3-diol (reagent) ultraviolet ul traviole t-visible visual display unit X-ray diffraction X-ray fluorescence yttrium aluminium garnet emission electron microscopy analogy microscopy spectrometry molecular mass relative molecular mass correlation coefficient standard deviation atomic mass

ISSN:0003-2654    

DOI:10.1039/AN996210024N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

95 Analyst, February 1996, Vol. 121 Foreword SAC 95: An International Conference on Analytical Chemistry In planning the 1995 version of the Society for Analytical Chemistry Conference, which was held in the University of Hull on July 11-15, the conference organizers decided to make two major changes to the traditional format. The first change was to have all of the submitted papers presented as posters, the programme or oral presentations being composed entirely of invited papers. The second change was to reduce the length of the Scientific Programme to three days. To this end, the Friday afternoon was reserved for social events while the whole of the Monday plus the Tuesday morning were devoted to a national conference, also on the subject of Analytical Chemistry, entitled Research and Development Topics in Analytical Chemistry.The latter meeting is organized annually by the same organiza- tion as the SAC conferences, namely the Analytical Division of The Royal Society of Chemistry, and is devoted to descriptions. in oral or poster form, of recent research projects by students of analytical chemistry in British and Irish universities. The thinking behind this move was that some of the students might be able to stay on and visit all or part of the SAC Conference, while some of the SAC conferees could hear the students giving their lectures and view their posters. A further innovation at the SAC Conference was to include a discussion period at the end of many of the poster sessions in which each presenter showed a few overheads and used them to expand on the theories behind the work described in their poster. Discussion was moderated by one of the Invited or Plenary Lecturers from the corresponding lecture session and some of these sessions were a great success. In all, the meeting was made up of 6 plenary lectures, 28 invited lectures and 200 poster presentations and was attended by about 300 people.This issue of The Analyst contains six papers from the conference. Other papers have already been or will soon be published in Analytical Communications, while it is probable that future issues of The Analyst or the Journal of Aiialytical Atomic Spectrometiy will feature further papers, which can be identified by the appropriate footnote to their title. The organizers hope that the papers will prove useful and of interest to readers of The Analyst and, for those who attended the Conference, a reminder of the excellent science that was described and discussed in July, 1995, in Hull. R. A. Young Publications Liaison Member, Organizing Committee

ISSN:0003-2654    

DOI:10.1039/AN9962100095

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

97 Analyst, February 1996, Vol. 121 (97-104) Deconvolution of Overlapping Chromatographic Peaks by Means of Fast Fourier and Hartley Transforms* Anastasios Economou, Peter R. Fielden? and Andrew J. Packham Department of Instrumentation and Analytical Science, UMIST, P.O. Box 88, Munchester, UK M60 IQD Chromatographic peaks usually exhibit an exponentially Gaussian modified peak profile that is characterized by a tailing behaviour at the end of the peaks. As a result of this modification of the ideal peak shape, the peaks lose their symmetry and, most importantly, become broader. An unfortunate consequence of this broadening effect is that the resolution between adjacent peaks decreases as compared to the ideal case in which purely Gaussian symmetrical peaks would be considered. In addition to various chemometrical techniques developed to increase the separation of overlapping peaks, methods based on deconvolution in the frequency domain can be exploited.The principle of this latter family of deconvolution methods rests on the division of the frequency spectrum of the signal to be deconvoluted by the frequency spectrum of a judiciously chosen deconvoluting signal. In this paper, the analytical characteristics and utility of deconvolution is assessed with emphasis on aspects of resolution enhancement, data distortion, linearity and signal-to-noise ratios. Keywords: Deconvolution; chromatogsaphy; tailing peak; Fourier- trunsform; chemometrics Introduction Fourier deconvolution of purely symmetrical Gaussian, Lorentzian2 and voltammetric3 peaks has been shown to result in narrower peak profiles, thereby improving the resolution between adjacent peaks in analytical chemistry.Traditionally, the deconvolution has been performed by deriving the discrete Fourier spectrum of the analytical signal and the discrete Fourier spectrum of an appropriate deconvoluting function. The deconvoluting function is usually a peak-shaped function with a peak shape similar (though not necessarily identical) to the expected peak shape of the analytical peaks. After some initial signal manipulation, the former spectrum is divided by the latter spectrum and the inverse Fourier transform is calculated to produce the final deconvoluted signal. The discrete Fourier transform, FV), of a digital time domain signal, x(k), is given by: N 1 F ( f ) = -c N- ‘s(k) N X = O forf = 0, I, 2 ,..., N - 1 ( I ) where N is the number of samples and k is the sample number.The inverse discrete Fourier transform reconstitutes the digital time domain signal from the frequency domain signal: * Presented at The SAC ’95 Meeting, Hull, UK, July 1 I-IS, 1995. + To whom correspondence should be addressed. isin - fork = 0, 1,2 ,..., N - 1 x(k) = C ” - ’ F ( f ) f = O ( c o s p - N 2n$.k N ) 2Jlfk (2) Earlier, a new deconvolution procedure for symmetrical peaks, based on the Hartley transform, rather than the conventional Fourier transform, has been proposed.4 The discrete Hartley transform H(f) of the time domain signal x(k) is given by.5 forf = 0, 1, 2 ,..., N - 1 (3) The inverse discrete Hartley transform is given by: N 2J-!$.k x(k) = x ” - l H ( I ) f = O (cos - N fork = 0, 1 , 2 ,..., N - 1 (4) For chromatographic peaks, the situation is more complex because the peak shape is more often asymmetrical.A sample introduced into a chromatographic system will be subject to various effects as a result of its interaction with this system. Consider a single active component and its concentration distribution with respect to time, t, measured from the point of injection. The input concentration of the system, i(t), can be represented by the rectangular sample plug introduced into the flowing carrier stream. The output concentration of the system, o(t), will be represented by the response recorded at the end of the experiment. The chromatographic system responds to the input pulse in a certain way given by the impulse response function, r(t).A chromatographic system can be described as a linear system. This is usually a valid approximation since, for analytical purposes, operation must be confined within the linear range of the chromatographic system. For such a linear system, the input, i(t), the output, o(t), and the impulse response, s(t), are related according to the general convolution theorem:6 o(t) = r(t) €3 i(t) ( 5 ) where €9 signifies convolution operations. Given that the input, i(t), is a very narrow, rectangular plug of sample, it can be approximated by a unit impulse function, 6, which, by definition, has unity value.7 Eqn. 5 then becomes: (6) Eqn. 6 implies that the output of the chromatographic system will be a good estimate of the system impulse response, provided that the input concentration profile can be approxi- mated by a unit pulse.In a chromatographic system, the impulse response, r(t), is composed of two contributions. (a) A factor, g(t), representing the broadening of the concentration profile o(t) = 6 €3 r(t) = 1 @ r(t) = r(t)98 Analyst, February 1996, Vol. 121 due to several diffusion and mass-transfer mechanisms within the analytical column. This broadening contribution is usually approximated by a symmetrical peak profile. The peak shape is usually Gaussian.8 (7) where A is the peak height; t is the time measured from the moment of injection; tR is the retention time of the peak; and s is the standard deviation of the peak. (b) Various first-order extra-column effects (such as the detector dead volume; the injector dead volume; mixing effect of connectors; etc.).These effects will distort the symmetry of the peak by adding a tailing component at the end of the peak. The extra-column contribu- tions can be collectively represented by an exponential term, e(t).8 e(t) = exp (- z) where T is the time constant of the exponential contribution. The impulse response can then be expressed as the convolution of the two contributing effects. By combining eqns. 7 and 8, the following formula is derived: (9) r(t) = b(t) 63 e(t) Substituting eqn. 9 into eqn. 6: r 8 exp (- f ) Eqn. 10 suggests that the final recorded output will be a convolution of the Gaussian shape with an exponential term. The resulting peak will be termed an exponentially-modified Gaussian (EMG) peak.8 Thus: The shape of the EMG peak will resemble the familiar tailing peak shapes usually obtained in chromatography.The four most important parameters on an EMG peak are: (i) the retention time of the peak, tR (that determines the peak position); (ii) the standard deviation of the peak, s (that determines the peak width); (iii) the time constant of the exponential part, T (that determines the behaviour of the tailing part of the peak; and (iv) the peak height, A . The Fourier deconvolution of exponentially-modified peaks has been treated mathematically .9 For this purpose, simulated EMG peaks were deconvoluted by means of the discrete Fourier transform, using an EMG deconvoluting function. It has been shown that deconvolution had the effect of sharpening the peaks although the peak shapes and areas after deconvolution may be substantially modified with respect to the initial shapes.9 However, in most applications involving overlapping peaks, measurement of the peak heights will be more precise than the determination of peak areas.The use of peak areas is limited owing to the large errors associated with determining the peak areas resulting from minor errors in drawing the baseline.8 In this work, peak heights will be considered rather than peak areas. The deconvolution for tailing chromatographic peaks will be assessed with emphasis on the analytical aspects of the method such as the signal-to-noise ratios, linearity, resolution enhancement and potential data distortion.Deconvolution based on the fast Fourier transform (FFT) will be compared to deconvolution based on the more efficient fast Hartley trans- form (FHT). Finally, the method will be applied to some simple chromatographic data and the results will be discussed. Experimental Reagents All the chemicals in this work were of analytical-reagent grade. Water was purified in an Elgastat Option 3 water purifier equipped with a Maxima unit (Elga Ltd., High Wycombe, Buckinghams hire, UK). Apparatus The chromatographic system consisted of a Kontron Analytical (Zurich, Switzerland) (Model 410) LC peristaltic pump, a Rheodyne (Cotati, CA, USA) HPLC injection valve (Model 7125) equipped with a 10 p1 injection loop and a Philips Analytical (Cambridge, UK) LC-UV HPLC detector set to a detection wavelength of 250 nm.Separation of the phenol- chlorophenol mixture was performed using a Waters Millipore (Milford, MA, USA) Nova-Pak C18 column (150 X 3.9 mm) while the acetone-phenol-toluene mixture was separated in a Hichrom C8 column (Hichrom Ltd., Reading, Berkshire, UK). A Midas Chromatography Datastation (Comus Instruments Ltd., Hull, UK) was used to acquire the chromatograms. A mobile phase of methanol-water (8 + 2), de-gassed with helium, was used throughout at a flow rate of 1 ml min-1. Software Programming The software used for this work was LabVIEW for Windows (National Instruments, Austin, TX, USA). LabVIEW contains extended libraries for signal processing and was selected for convenience of use, speed, flexibility, and compatibility with the Windows environment and platform independence capabil- ities. The data acquired by the Midas system were initially converted into an ASCII spreadsheet format and could then be directly imported into LabVIEW.The structure of the deconvo- lution program was similar for the deconvolution of simulated peaks or acquired data and is shown in Fig. 1. Simulated peaks were generated by convoluting symmetrical peaks with an exponential term. All the parameters of the peaks and exponential term were user-adjustable. The signal array was rotated-translated (as will be discussed below) and padded with zeros to at least double its length so that the total number of points was a power of two. The deconvoluting peak was generated with the same number of points as the signal to be deconvoluted and wrapped around.Padding and wrapping around was necessary in order to convert circular deconvolution to linear, as discussed elsewhere.10 The total number of points should be a power of two to take advantage of the fast implementations of the Fourier and Hartley transforms. The signal spectrum (Fourier or Hartley) was calculated and divided by the spectrum of the deconvoluting function. The deconvo- luted signal was inverse-transformed, inverse-rotated-trans- lated and filtered before display. Results and Discussion Effect of the Deconvoluting Time Constant In order to investigate the effect of the deconvoluting peak time constant, a simulated system consisting of two identical EMG peaks with standard deviation s, and time constant t, has been deconvoluted with an EMG peak with standard deviation sd = s,.The value of the deconvoluting peak time constant, zd, was varied and its effect on the deconvoluted signal was observed. Although the heights of the two peaks were identical in the original data, the peak height of the second peak appearedAnalyst, February 1996, Vol. 121 Generate Gaussian PeaW 99 Generate exponential term(s) higher owing to the contribution of the tailing part of the first peak. Three regimes can be distinguished: (i) when the time constant of the deconvoluting peak is lower than the time constant of the analytical peaks (i.e., td < t,), the deconvoluted peaks retain their EMG shape after deconvolution [Fig. 2(a)]. This observation can be verified by noticing that, after deconvolution, the second peak is still higher than the first peak, indicating that the deconvoluted peaks do possess a tailing end.The same observation can be visually made for the exposed tailing end of the second peak. As td increases, the time constant of the deconvoluted peak decreases as indicated by the fact that the peak height of the second peak after deconvolution decreases [Fig. 2(b)]. As a result, higher values of zd benefit resolution by causing a decrease in the tailing of the deconvo- luted peaks; (ii) when the time constant of the deconvoluting peak became equal to the time constant of the analytical peaks (i.e., td za), the tailing part of the deconvoluted peaks is completely eliminated and the deconvoluted peaks are turned to Gaussian [Fig.2(c)]. This property is verified by the observa- tion that both peaks in the deconvoluted signal have the same height. The resolution within this regime is already significant; and (iii) when the time constant of the deconvoluting peak is greater than the time constant of the analytical peaks (i.e., td > t,), the deconvoluted peaks remain Gaussian but a negative sidelobe appears at the end of the tailing end of the peaks (this sidelobe is only visually apparent at the end of the second peak [Fig. 2(6)]. This effect has been observed previously.9 The resolution keeps increasing with increasing zd. Ideally, the peaks after deconvolution should be Gaussian so that the better resolution can be achieved and contributions from tailing ends are eliminated.So, one should operate in the region in which td = t,. However, analytical signals usually consist of multiple peaks with different standard deviations. In this case the selection of the best time constant of the deconvoluting peak becomes more complicated. If too low a time constant is Convolute Gaussian peak(s) with exponential term(s) selected, narrow peaks will be turned into Gaussian after deconvolution but wider peaks will not be significantly affected. Conversely, if too high a time constant is chosen, wider peaks will be turned into Gaussian, as well as narrow peaks, but negative sidelobes will appear at the tailing ends of the narrower peaks. Therefore, the selected value of Td will be a compromise between elimination of the tailing of the deconvoluted peaks and minimization of the sidelobes at the end of the peaks.For n multiple analytical peaks with time constants T , , ~ , T , , ~ , . . ., z ~ , ~ , and provided that the ratio of the maximum over the minimum time constants among the peaks is less than 2 [i.e., max (t,,l, z,2 . . ., z,,,)/min (za,1, ‘ta,2, . . ., z,,J S 21 the optimum time constant of the deconvoluting peak, zd, should lie between the minimum and maximum time constants of the analytical peaks, i.e. min @,,I, ~ , 2 , .. ., ta,J < zd max (%,I, ~ , 2 ..., L,J (12) Generate noise Generate baseline Effect of the Deconvoluting Standard Deviation To assess the effect of the deconvoluting peak standard deviation, sd, a simulated system consisting of two identical overlapping EMG peaks with standard deviation s, and time constant t, have been deconvoluted with an EMG peak with time constant td = t,.The standard deviation of the deconvoluting EMG peak, sd, was varied and its effect on the deconvoluted system was observed. Two regimes could be observed in terms of the effect of s, on the deconvoluted signal: (i) when the deconvoluting peak standard deviation is much lower than the standard deviation of the analytical peaks (i.e., sd << so), the deconvolution causes only a marginal improvement in the resolution between the peaks [Fig. 3(a)]. However, as sd increases with respect to s,, the resolution between the two peaks increases after deconvolution [Fig. 3(b) and (c)]; and (ii) as soon as the standard deviation of the deconvoluting peak data Add noise and baseline to multipeak response Import data from spreadsheet file I Derive the FFT of the I - Rotate and translate the signal Generate deconvoluting Generate exponential symmetrical peak analytical signal Convolute symmetrical peak with exponential term to the same number of points as the analvtical sianal I signal J.Inverse rotate-translate the deconvoluted signal Wrap around the deconvoluting signal . -W Display results Derive the FFT of the deconvoluting signal ,-d Divide the FFT’s I - - I I Derive the IFFT L 1 1 Filter the deconvoluted 1 \ / f I100 Analyst, February 1996, Vol. 121 0.040 0.030 0.020 0.010 0.000 -0.010 3 -0.020 c .- C -0.030 .+ -0.040 $ 0.040 0.030 0.020 0.010 0.000 -0.01 0 -0.020 -0.030 -0.040 100 150 200 250 300 350 400 0.040 0.030 0.020 0.010 0.000 -0.01 0 3 -0.020 - .- S 3 -0.030 $ .= -0.040 e 100 150 200 250 300 350 400 (b) - - - - C - - - 1 1 1 1 1 v a, 0.040 g 0.030 v) v) LT 0.020 0.01 0 0.000 -0.010 -0.020 -0.030 -0.040 100 150 200 250 300 350 400 0.040 0.030 0.020 0.010 0.000 -0.010 -0.020 -0.030 -0.040 100 150 200 250 300 350 400 Time (arbitrary units) Fig.2 The effect of td of the deconvoluting EMG peak with sd = 8 points on the deconvolution of two EMG peaks located at points 230 and 260 with standard deviations s , , ~ = s,,~ = 10 points and time constants = T , . ~ = 10 points. Time constant of the deconvoluting peaks: (a) td = 2 points; (h) td = 5 points; (c) td = 10 points; and (d) td = 15 points. Traces: A, individual peaks; B, signal before deconvolution; and C , signal after deconvolution multiplied by - 1.0.040 0.030 0.020 0.01 0 0.000 -0.010 -0.020 -0.030 0.040 0.030 0.020 0.010 0.000 -0.01 0 -0.020 -0.030 -0.040 100 150 200 250 300 350 400 100 150 200 250 300 350 400 Time (arbitrary units) Fig. 3 The effect of sd of the deconvoluting EMG peak with td = 10 points on the deconvolution of two EMG peaks located at points 230 and 260 with standard deviations = s , , ~ = 10 points and time constants. T , , ~ = T , , ~ = 10 points. Standard deviation of the deconvoluting peak: (a) sd = 2 points; (h) sCf = 5 points; ( c ) sd = 8 points; and (6) sd = 10 points. Traces: A, individual peaks; B, signal before deconvolution; and C , signal after deconvolution multiplied by - 1.Analyst, February 1996, Vol. 121 101 becomes equal (or greater than) the standard deviation of the analytical peaks (i.e., sd 3 s,), the deconvoluted peaks are oversharpened and sidelobes start to appear at the foot of the deconvoluted signal [Fig.3(d)]. The magnitude of the sidelobes increases as the value of sd increases above the value of s,. This latter situation corresponds to the physically meaningless operation of trying to produce deconvoluted peaks of negative width.3 In order to achieve the maximum resolution without oscillations, the deconvoluting peak standard deviation should be slightly lower than the standard deviation of the analytical peaks. In the case of n multiple peaks with different standard deviation s ~ , ~ , s,2 . . ., s , , ~ the standard deviation of the deconvoluting peak should be lower than the standard deviation of the narrowest peak, i.e.(13) Sd < min (S,,lr sa,2, . . * ? Sa,n) Effect of the Deconvoluting Peak Type Two deconvoluting functions have been used; EMG shape (eqn. 11) and the exponentially modified Lorentzian (EML) function. The latter type of peak can be generated by convoluting a Lorentzian function, l(t), with an exponential term, e(t). The Lorentzian function, l(t), is given by the formula] *: A l(t) = (1+-) The exponential contribution is given by eqn. 8. Hence, the EML peak can be expressed as: Deconvolution, with both the deconvolution peak types (i.e. EMG and EML), exhibits a marked improvement in resolution. The resolution enhancement is very similar for both deconvolut- ing functions (Fig. 4). As expected, the Gaussian deconvolution peak produced the best baseline [Fig.4(a)] while the Lorentzian peak produced a negative going oscillation at the front and tailing ends of the deconvoluted peaks [Fig. 4(b)]. The effects of the time constant, zd, and standard deviation, s,, of the deconvoluting EML function are similar to the effects of these parameters on the EMG deconvoluting function, as discussed in previous sections. Linearity The measurement of the height of overlapping peaks usually involves errors associated with the incomplete separation of the peaks. Indeed, as the simple case of two overlapping peaks demonstrates, the height of the second peak tends to be enhanced by the contribution of the tailing part of the first peak. This effect gives rise to a systematic positive error in the determination of the second peak height.The relative values of this error will mainly depend on the time constants, the retention times and the relative peak heights of the two peaks: the higher the time constant and peak height of the first peak and the closer the retention times, the more pronounced the enhancing effect on the second peak will be. Thus, the effect will be more pronounced in the case of small and narrow peaks occurring close to the tailing end of much wider and taller peaks. However, the first peak will only be marginally affected. So, even if the underlying mechanism producing the peaks is linear (i.e., the height of individual peaks increases linearly with concentration), the determination of peak heights may involve large errors.Deconvolution will be, in principle, able to correct or minimize the systematic positive error in determining the height of the second peak, at least to some extent. The errors in the determination of the peak height of the second peak, before and after deconvolution, are compared in Fig. 5. As expected, a wider first peak, Fig. 5(b), gives rise to higher errors than narrow first peaks, Fig. 5(a). However, the errors after deconvolution are much lower than the errors before deconvolu- tion. The choice of zd and sd of the deconvoluting peak will be crucial in this step since both these parameters will affect the resolution, as discussed previously. Under suitable circum- stances, the measurement of the deconvoluted peak heights will not involve any errors and the heights will be accurately determined.The example in Fig. 6 demonstrates this latter point; by observing the recommendations in eqns. 12 and 13 for the selection of sd and td, the error in the determination of the second peak was eliminated completely after deconvolution at the expense of a small sidelobe after the second peak (this sidelobe is due to the fact that td is higher than z,,Z). Before deconvolution, an error of 40% was calculated for the determination of the peak height of compound 2. It is interesting to note that, as in the case of symmetrical peaks, the absolute peak ratios after deconvolution are not preserved but the linearity of all the peaks is maintained.' Comparison Between the Fourier and Hartley Transforms It has been shown previously that the use of the conceptually simpler Hartley transform can be used for the deconvolution of symmetrical Gaussian, Lorentzian and voltammetric peaks.4 The FHT is twice as fast as the FFT and uses half the memory 0.040 0.030 0.020 0.010 0.000 -0.01 0 -0.020 5 -0.030 .g -0.040 2 100 150 200 250 300 350 400 - 0.040 0.030 - .- $? % = 0.020 v) 0.010 0.000 -0.010 -0.020 -0.030 -0.040 I I 1 I I I 1 100 150 200 250 300 350 400 Time (arbitrary units) Fig.4 Comparison between (a) EMG; and (b) EML deconvoluting peak with standard sd = 8 points and td = 10 points for the deconvolution of two EMG peaks located at points 230 and 260 with standard deviations sU,l = sUs2 = 10 points and time constants T ~ , ~ = T , , ~ = 10 points. Traces: A, individual peaks; B, signal before deconvolution; and C, signal after deconvolution multiplied by - 1.102 Analyst, Februaiy 1996, Vol.121 than a conventional FFT method. However, an important requirement for the application of the Hartley transform is that the deconvoluting function is even (i.e., symmetrical). In the particular case of symmetrical peaks, it can be shown that deconvolution using the Hartley transform is mathematically equivalent to using the Fourier tran~form.~ Although pure Gaussian, Lorentzian and voltammetric deconvoluting peaks do fulfill this requirement, their exponentially modified versions do not. Obviously, the higher the ratio of sd over ~d of the exponential term, the more the EMG deconvoluting peak approaches a symmetrical shape. Therefore, the success of applying the Hartley transform will depend on the requirements placed upon the value of the ratio S,/Q of the deconvoluting peak. An empirical recommendation is that the FHT can be used if the condition s,/T~ 3 4 is fulfilled.Background Correction The implementation of the discrete Fourier and Hartley algorithms requires that the numerical values of the first and last points of the recorded signal are equal to zero. If this requirement is not met, serious errors in the calculation of the frequency spectra will result. 12 Two methods that can be used to accomplish this task are rotation-translation and windowing of the signal. The first method involves subtracting from the signal array, x(k), the straight line, h(k), that passes through the first W, I 0 1 0 2 0 ~ 4 0 m ~ 8 0 o Separation (tH,,-tH,Z), points "0, 1 5 1 * c 100 i .1 A\ ', I 0 I I I , 1.- A \I 10 20 30 40 W W 7 0 Sci)arntion (tU.I-tR.2), points Fig. 5 Comparison of errors in determining the peak height of an EMG peak 2 at the tailing end of another EMG peak 2A, before and B, after deconvolution as a function of the separation between the two peaks. Time constants of both peaks tu,i = = 10 points. (a) Peaks 1 and 2, s,, I = s,,~ = 10 points, and (b) peak 1 = 20 points and peak 2 s,,~ = 10 points. Height ratios: peak 2/peak 1 = 1/3. The deconvoluting peak was an EMG peak with sd = 8 points and td = 10 points. 0.mO- 0.m- 2 I \ 1 .P: 0.8 0.7 5 0.6 0.5 2 0.4 $ 0.3 - - D - c g 0.2 g 0.1 0.0 -2 -1 0 1 2 3 4 Concentration of compound 2 (arbitrary units) Fig. 6 (a) Simulated standard additions for an EMG peak 2 located at point 260 at the tailing end of a wider EMG peak 1 located at point 220 before (A) and after (B) deconvolution with a EMG peak with sd = 8 points and td = 8 points. Conditions of the overlapping peaks: height ratio: peak 2/peak 1 = 1/3; s,,~ = 12 points and su,2 = 10 points; tu,l = 10 points and peak 2 z,.~ = 5 points. (b) Standard additions plots A, before and B, after deconvolution.1 ;A I ' , I ' I ', 0.020 0.010 rn 0.000 -0.01 0 -0.020 5 -0.030 h c .- -0.040 .- c 100 150 200 250 300 350 400 2 0.040 I c ." - - - v 8 0.030 0 U E 0.020 U 0.010 0.000 -0.010 -0.020 -0.030 -0.040 100 150 200 250 300 350 400 Time (arbitrary units) Fig. 7 Comparison between an (a) Hamming and (b) rectangular FIR filter for lowpass filtering of deconvoluted data.Initial S/N ratio = 20. Low-pass cut-off frequency at the 46th harmonic. Overlapped EMG peaks located at points 260 and 230 with s,,~ = s , , ~ = 10 points and T~,] = T , , ~ = 10 points. The deconvoluting peaks was also EMG with sd = 8 points and td = 10 points. Traces: before (A) and after (B) deconvolution.Analyst, February 1996, Vol. 121 103 1.4 and last points. A new background-subtracted array, x’(k), is thus formed12: x[(n - 1)l- -do) ~ ’ ( k ) = ~ ( k ) - b(k) = ~ ( k ) -x(O) - N - 1 f o r k = 0 , 1 , 2 ,..., N - 1 (16) where x(0) is the first point of the data array and x[(n - l)] is the last point of the data array. The new array, x’(k), is used for the deconvolution operation; after deconvolution, the straight line, b(k), is added back to the deconvoluted signal (an operation referred to as inverse rotation-translation).The second method involves multiplication of the data array with a window function that approaches smoothly the value of zero at the two ends of the array. A comparison of the two methods has shown that the rotation-translation operation is superior to the window method, especially in the presence of very sloping baseline^.^ Thus, background correction in this work was accomplished by means of the rotation-translation method. - ‘ phenol (4 B Effect of Noise It has been widely recognized that deconvolution by means of Fourier transform is sensitive to noise in the original data.99’3 This sensitivity has been attributed to the division operation of small numbers in the frequency domain that give rise to artifact noise components in the spectrum before the inverse trans- f ~ r m .~ . ’ ~ Under all circumstances, the signal-to-noise (S/N) ratio after deconvolution will be lower than the initial S/N ratio. In general, attempts to increase the resolution (by using higher 6.0000 5.7500 5.5000 sd values) will result in even poorer S/N ratios.4.13 The artifact deconvolution noise will be distributed in the whole frequency range but only components of relatively low frequency are of importance for the accurate representation of the analytical peaks. This property allows the application of low-pass filtering of the deconvoluted signal. Different types of filters, both infinite impulse response (FIRF) and finite impulse response (FIRF), have been assessed.The usual limitations of selectivity versus spectral leakage associated with digital filters must be considered.14 Filters that have steeper cut-off slopes (such as a rectangular FIRF) will be more frequency-selective at the expense of leakage effects that produce oscillations in the deconvoluted signal. Less selective filters (such as Butterworth IIRF’s or Hamming and Kaiser FIRF’s) are preferable as the S/N ratios after deconvolution are lower. An example is illustrated in Fig. 7, in which a rectangular and a Hamming filter are compared for filtering deconvoluted EMG peaks with a S/N ratio of 20 in the original data. The low-pass filter cut-off frequency will need to be carefully controlled and can be selected by deriving and comparing the power spectra of the raw data and the deconvoluted signal; the useful frequency compo- nents that must be retained will be confined to the lower range of the frequency spectrum.It should be noted that filtering will introduce a group delay in the deconvoluted signal which will manifest itself as a shift of the peak locations. This shift can be easily compensated for by a reverse shift of the deconvoluted array. phenol / \ I \ - - “ 1 \ - ‘? ‘\ A a a 6.2500 6.5000 I . . (4 - chlorophenol (4 I 6.2500 I- 5.2500 - 5.0000 - 4.7500 - 4.5000 - - - - 4.2500 - 4.0000 - 1 1 1 1 -1 n 50 60 80 100 120 140 160 180 200 220 250 6.0000 - 5.7500 - 5.5000 - -- - - _ ---_- ‘- 5.2500 - 5.0000 - 4.7500 - 4.5000 _ - - - - p ~ ’ 42500 - 50 60 80 100 120 140 160 180 200 220 250 Time/102 min Fig.8 Application of the deconvolution procedure to overlapping phenol- chlorophenol chromatographic peaks. Concentrations: phenol 2.8 X g ml-1, chlorophenol 2.5 X 10-3 g ml-1. Deconvoluting peaks: (a) EMG peak with sd = 3 points and td = 4 points, and (b) EML peak with sd = 3 points and td = 4 points. Traces: before (A) and after (B) deconvolution. The deconvoluted data were filtered with a Hamming low-pass FIRF with cut-off at the 50th harmonic. 1.2 1 .o 0.8 0.6 0.4 0.2 a 2 -0.0 50 100 150 200 250 300 350 400 450 $ 0.7 9 0.6 0.5 0.4 0.3 0.2 0.1 -0.0 50 120 140 160 180 200 220 240 260 280 300 Time/102 min Fig. 9 Application of the deconvolution procedure to a chromatogram for the separation of 4.1 x 10-3 g ml-* acetone, 2 X g ml-l phenol and 1 .O x 10-3 g ml-1 toluene.The deconvoluting peak was an EMG peak with sd = 2 points and td = 0.5 points. (a) The whole chromatogram, and (b) magnified region between 1 and 3 min. Traces: before (A) and after (B) deconvoluted. The deconvoluted data were filtered with a Hamming low- pass FIRF with cut-off at the 50th harmonic.104 Analyst, February 1996, Vol. 121 Applications The proposed procedure has been applied to simple chromat- ographic separations. Fig. 8 illustrates the effect of deconvolu- tion on the separation of phenol and chlorophenol using an EMG and EML deconvoluting function. Owing to the sig- nificant overlap between the two peaks and their tailing nature, the height of the second peak appears higher than it should be (as compared with the same concentration of the pure compound). Deconvolution corrected for this effect as a result of the narrower response-time profile afforded by the operation.The sidelobes appearing after deconvolution are a combined result of the filtering step and the amplification of pump pulsations. A second application was the separation of a sample involving the components: acetone; phenol; and toluene (Fig. 9). After deconvolution, the resolution between acetone and phenol was improved, no distortions of the data occurred, the initial S / N ratio was only marginally decreased and the peak ratios for all the peaks remained constant. Moreover, the low sd/ ‘td ratio of the deconvoluting peak (in this case the s&d ratio was set to the value of 4) allowed the application of the FHT. References 1 2 Engblom, S. O., J . Electroanal. Chem., 1990, 296, 371. Kauppinen, J. K., Moffat, D. J., Mantsch, H. H., and Cameron, D. G., Appl. Spectr., 1981, 35, 271. 3 4 5 6 7 8 9 10 11 12 13 14 Kirmse, D. W., and Westerberg, A. W., Anal. Chem., 1971, 43, 1035. Bracewell, R. N., The Fast Hartley Transform, Oxford University Press, New York, USA, 1986. O’Neil, M. A., BYTE, 1988, 13, 293. Lynn, P. A., and Fuerst, W., Digital Signal Processing, John Wiley, Chichester, 1994, revised edn., pp. 34, 385. Lynn, P. A., and Fuerst, W., Digital Signal Processing, John Wiley, Chichester, 1994, revised edn., p. 14. Poole, C. F., and Poole, S. K., Chromatography Today, Elsevier, Amsterdam, 1991, pp. 25-28. Fellinger, A., Anal. Chem., 1994,66, 3066. Press, W. H., Flannery, B. P., Teukolsky, S . A., and Vetterling, W. T., The Art of Scientific Computing, Cambridge University Press, Cambridge, 1989, pp. 449454. Brereton, R. G., Chemometrics, Ellis Horwood, Chichester, 1990, p. 198. Hayes, J. W., Glover, D. E., Smith, D. E., and Overton, M. W., Anal, Chem., 1973,45,277. Kauppinen, J. K., Moffat, D. J., Cameron, D. G., and Mantsck, H. H., Appl. Optics, 1981, 20, 1866. Economou, A., and Fielden, P. R., Anal. Chim. Acta, 1995, 305, 144. Paper 5105445A Received August 15,1995 Accepted September 8,1995

ISSN:0003-2654    

DOI:10.1039/AN9962100097

出版商:RSC    

年代:1996

数据来源: RSC