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KEEP ABREAST OF THE LATEST ADVANCES INSCANNING ELECTRON MICROSCOPY BY SUBSCRIBING TOThe Journal of Scanning MicroscopiesSCANNING provides an international and interdisciplinary medium for the rapid exchange of informationamong scientists interested in scanning electron microscopy. Areas of specific interest are emergingmodalities; applications; product evaluations; instrumental aids and accessories; specimen preparationmethods; image procewing; computation and interpretation; methods for correlating information obtainedby scanning electron microscopy and other microscopical techniques; analytical methods; signal detectionand processing; electron specimen interactions; practical problems of electron optics; stereometry; stere-ology; applications of SEM containing novel features of technique which could be adopted in other prob-lem areas.Book reviews, calendar, letters.If you would like to receive each issue of SCANNINGplease fill in the coupon below or write with remittance to:SCANNING, c/o FAMS, Inc.Box 832, Mahwah, NJ 07430-0832Telex: 220883 TAURFax: 201 -81 8-0086Phone: 201 -81 8-1 01 0Order can be serviced only if accompanied by remittance in U.S. funds drawn on a US. bank.Checks should be made payable to FAMS, Inc.Please enter a subscription to SCANNING.0 U.S. and Canada: I enclose $175 (individual rate) or $325 (institutional rate) for 8 issues 19960 Foreign: I enclose $175 plus $10 postage (individual rate) or $325 plus $45 postage (institutional rate)for 8 issues 1996-----------------------------------------------------------------------------,NameAddresGordon 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, 1996.Focus on BiopesticidesPLUS, new for 1 996, monitorsthe use of natural organisms, their genes and theirsecondary metabolites in crop protection.Thenewsletter is edited by Len Copping, who is well-known for his work in this area. Product, companyand market news are brought together each month inan easy-to-read format with valuable analysis andcomment. Focus on BiopesticidesPLUS will be essentialreading for all those working in the sector.With Focus on BiopesticidesPLUS you can:scan ALL the relevant news in one placegain information vital to your businessbe alerted to news you would otherwise misskeep up with legislation and environmental concernsread about forthcoming conferences and key eventsSubscribe to Focus on BiopesticidesPLUS and stay intouch with this developing sector!A FREE sample issue is available now.To claim yourcopy, simply complete and return the slip below. .............................................Please send me a FREE sample issue ofFocus on BiopesticidesPLuSName .......................................................................Position ....................................................................0 rga n i zat ion ............................................................Address .......................................................................................................................................................................................................................................THE ROYALReturn to: SOCIETY OFAlison Hey, The Royal Society of Chemistry, CHEMISTRY @*- Thomas Graham House, Science Park,Milton Road, Cambridge CB4 4WF, U.K.Tel: +44 (0) 1223 420066Fax: +44 (0) 1223 423429TOLL FREE (US only): 1-800-473 9234 *& informationServiceInternational Conference on Analytical ChemistryJune 15-21, 1997Moscow University, Moscow, RussiaAIMSThe objective of the conference is to highlight the most recent developments in the field of analytical science, specifically in thesubject areas identified below.Presentations will be given in the form of plenary and contributed lectures as well as postersessions.It is hoped that the poster sessions will be used to encourage scientists of different generations to exchange ideas andshare experiences in their respective fields.SCOPEThe following major topics will be discussed at the conference:Analytical chemistry: Philosophical aspectPreconcentration (including solid phase extraction)ChemometricsChromatography (GC, HPLC, TLC, IC etc.)and related techniques (CE)Molecular spectroscopy (IR, Raman)Nuclear methodsKinetic methodsBioanalytical chemistryAnalysis of new materials(including high-purity materials)Sampling and sample treatmentOrganic analytical reagentsQuality assurance/quality controlAtomic spectroscopy (absorption emission,Mass spectrometryElectroanalytical methodsExpress test methodsAnalysis of raw materialsAnalysis of food and agricultural productsClinical analysisfluorescence, XRF, lasers)ORGANISING COMMI TTEEChairperson, Yu A. ZolotovVice-chairmen, B.F.Myasoedova, V.A. Davankov and V.G. KoloshnikovGeneral secretary, L.N. KolomietsYu A. Karpov, I.N. Kiseleva, P.N. Nesterenko, G.I. Ramendik, O.A. Shpigun, S.I. Sinkov, 1.1. Smirenkina,B.Ya. Spivakov, M.M. ZaletinaINTERNATIONAL SCJENTIFIC COMMITTEF,Chairman, Yu A. ZolotovF. Adams, BelgiumR. Barnes, USAM. Novotny, USAH. Englehardt, GermanyT. Fujinaga, JapanM . Grasserbauer , AustriaB. Welz, GermanyA. Hulanicki, PolandB. Welz, GermanyE. Mentasti, ItalyB.F. Myasoedov, RussiaV.A. Davankov, RussiaH. Frieser, USAE.Pungor, HungaryI. Havesov, BulgariaJ.F.K. Huber, AustriaT Yotsuyanagi, JapanM.I. Karayannis, GreeceCONFERENCE SECRETARIATFor further information please contact :H. Akaiwa, JapanC. Boutron, FranceH. Pardue, USAK. Niemax, GermanyP.G. Zambonin, ItalyI.Kuselman, IsraelS. Tsuge, JapanV . G. Koloshnikov , RussiaG. Werner, GermanyJ.G.H. dii Preez, South AfricaJ.A. Perez-Bustamente, SpainL. Sommer, Czech RepublicW. Lindner, AustriaF. Macasek, SlovakiaM. Valiente, SpainH.M. (Skip) Kingston, USAM. Widmer, SwitzerlandYu. A. Karpov, RussiaDr L. N. Kolomiets,Scientific Council on Chromatography RAS, Leninsky Prospect 31, 117915 Moscow, Russia.E-mail : Iarionov@lmm.phyche.msk.suTel: 7 (095) 952 0065; 7 (095) 955 4685 Fax: 7 (095) 952 0065; 7 (095) 952 530Vllth INTERNATIONAL SYMPOSIUM ON LUMINESCENCE SPECTROMETRYIN BIOMEDICAL ANALYSIS -DETECTION TECHNIQUES AND APPLICATIONS IN CHROMATOGRAPHY ANDCAPILLARY ELECTROPHORESISUniversitb de Nice (Sophia Antipolis), FranceApril 17-19, 1996Organized by the University of Ghent (Belgium) in collaboration withthe University of Nice, the University of Tokyo and the Complutense University of MadridThis symposium envisages to report on the current status and future developments in the field ofluminescence techniques (fluorescence, chemiluminescence, electroluminescence, bioluminescence,phosphorescence and combinations with chromatography, capillary electrophoresis or immuno-assays) usedin drug quality control, clinical, chemical, biochemical, pharmaceutical, toxicological, food, environmentalanalyses and related areas.Original research papers can be submitted by registered participants to be presented in a general postersession; upon invitation, oral presentation may be suggested.A.Alsina, SpainA.C. Calokerinos, GreeceB.J. Clark, EnglandJ. Crommen, BelgiumA. De Leenheer, BelgiumN. J. Dovichi, CanadaR. Fellous, FranceR.S. Givens, USAC. Gooijer, The NetherlandsScientific CommitteeG. Gubitz, AustriaN.A. Guzman, USAR. Haugland, USAH.T. Karnes, USAJ.R. Lakowicz, USAD. Lerner, FranceJ.N. Miller, EnglandK. Nakashima, JapanT.A. Nieman, USAOrganizing CommitteeW.R.G. Baeyens (Chairman), BelgiumD. De Keukeleire, BelgiumM. Rouillard, FranceK.Imai, JapanB. Del Castillo, SpainLocal Organizing CommitteeG. Van Der Weken, BelgiumC. Rawoens (Secretary), BelgiumL. Liuani-Cuvelier, FranceA. Van Overbeke, BelgiumInvited SpeakersJ.-J. Aaron, FranceW. Adam, GermanyH. Lingeman, The NetherlandsD.L. Massart, BelgiumJ.J. Santana Rodriguez,A. Sanz Medel, SpainS.G. Schulman, USAH.H. Tannesen, NorwayA. Townshend, EnglandC. Van Peteghem, BelgiumT. Vo-Dinh, USAX. Xhang, ChinaSpainG. Rao, USAA. Rieutord, FrancePublication: Proceedings of the conference will be published in The Analyst subject to the usual refereeingprocedures. Authors should send three copies of the manuscript to the Managing Editor, The Analyst TheRoyal Society of Chemistry, at the address given in this journal, before the meeting or, at the latest, at themeeting, so that the paper can be processed rapidly.The manuscript should be in accordance with theInformation for Authors for The Analyst.The proceedings of the conference may be ordered directly from The Royal Society of Chemistry. Orderforms for this purpose will be made available at the meeting.Abstracts will be disseminated separately.Information: Professor Wiily R.G. BAEYENS, Symposium Chairman, University of Ghent, PharmaceuticalInstitute, Department of Pharmaceutical Analysis, Laboratory of Drug Quality Control, Harelbekestraat 72,8-9000 Ghent (Belgium). Fax: +32 9 221 4175; Tel: +32 9 221 8951; E-mail: willy.baeyens@rug.ac.blyticalOVER 40 YEARS ATTHE TOP!The premier source of current awarenessinformation in analytical chemistry since 1954is NOW EVEN BETTER, providing:Enhanced CoverageImproved CurrencyMore Detailed IndexingComprehensive AbstractsAnalytical Abstracts is also available as anonline and CD-ROM database.You need to keep up to date withdevelopments in analytical science- Analytical Abstracts can help!Contact us today for further information:Business DevelopmentThe Royal Society of ChemistryThomas Graham HouseScience Park, Milton RoadCambridge CB4 4WF, UKTel: +44 (0) 1223 420066Fax: +44 (0) 1223 423429E-mail: MARKETING @ RSC.ORGTHE ROYALSOCIETY OFCHEMISTRYInformationService

ISSN:0003-2654    

DOI:10.1039/AN99621BP007

出版商:RSC    

年代:1996

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN99621FX009

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

ANALAO 121 (3) 1 1 R-32R, 275-378, 25N-40N (1 996) MARCH 199611111‘””An a I y stIThe analytical journal of The Royal Society of ChemistryCONTENTSREVIEWSTUTORIAL REVIEWSCHEMOMETRICSISTATISTICSPERSPECTIVESAMPLE HANDLINGMOLECULARSPECTROSCOPY/SPECTROMETRYSEPARATION SCIENCEBIOANALYTICALSENSORS11R29 R27527928528929730330931 732 1325329333339345Compounds of Agricultural Significance Using Environmental Analytical Supercritical Fluid Extraction-AReview-lain A. Stuart, John MacLachlan, Arthur McNaughtanOriented Immobilization of Antibodies and Its Applications in lmmunoassays and Immunosensors-Bin Lu,Malcolm R. Smyth, Richard O’KennedyWhat Exactly is Fitness for Purpose in Analytical Measurement?-Michael Thompson, Tom FearnFormulation Optimization of Novel Multicomponent Photoprotective Liposomes by Using Response SurfaceMethodology-Yannis L.LoukasSense and Traceability-Michael ThompsonInfluence of Selected Natural Complexants on the Mobilization and Purging of Copper From AqueousMedia Into Supercritical Carbon Dioxide-Jin Wang, William D. Marshall, Donald S. GambleDevelopment of a Rotatory and Continuous Liquid-Liquid Extraction Technique for Phenolic Compounds inWine-E. R. Bru, C. G. Barroso, R. Cela, J. A. Perez-BustamanteEvaluation of Anasorb CMS and Comparison With Tenax TA for the Sampling of Volatile OrganicCompounds in Indoor and Outdoor Air by Breakthrough Measurements -Maria P. Baya, Panayotis A.SiskosMulti-element, Multi-media Method for the Determination of Airborne Elemental Emissions by InductivelyCoupled Plasma Atomic Emission Spectrometry-David Eugene Kimbrough, I.H. ‘Mel’ SuffetSpectrofluorimetric Determination of Trace Amounts of Aluminium With SalicylaldehydeSalicyloylhydrazone-Chongqiu Jiang, Bo Tang, Chen Wang, Xiaogang ZhangGas Chromatographic Determination and Negative-ion Chemical Ionization Mass SpectrometricConfirmation of 4,4’Methylenebis(2-~hIoroaniline) in Urine via Thin-layer ChromatographicSeparation-Weh S. Wu, Roman S. Szklar, Roy SmithSimultaneous Determination of Trace Amounts of Copper, Nickel and Vanadium in Sea-water byHigh-performance Liquid Chromatography After Extraction and Back-extraction-Yoshio Shijo, HidetoshiSato, Nobuo Uehara, Sachiko AratakeDevelopment and Evaluation of a Chemiluminescent lmmunoassay for Chlortoluron Using a CameraLuminometer-M.Fawaz Katmeh, G. Wynne Aherne, Derek StevensonMicrotitre-plate Enzyme-linked Ligand-Sorbent Assay of Riboflavin (Vitamin B2) in Human Plasma andUrine-Andrzej KozikFluorescence Optical Sensor for Low Concentrations of Dissolved Carbon Dioxide-Beat Muller, Peter C.HauserElectrochemical Activation of Screen-printed Carbon Strips-Joseph Wang, Maria Pedrero, HenningSakslund, Ole Hammerich, Jose PingarronTHE ROYALSOCIETY OFC H EM1 STRYI ~forfnationServices Cambridge, EnglandTypeset and printed by Black Bear Press Limited,Continued on inside back cover-0003-2654(199613:1-E L ECTRO AN A LY TIC A L351357363369OTHER METHODS373377iDetermination of Trace Levels of Niguldipine in Urine and Blood by Adsorptive Stripping Voltammetry atthe Hanging Mercury Drop Electrode-Gottfried Stubauer, Dagmar ObendorfPreparation of Microelectrodes: Comparison of Polishing Procedures by Statistical Analysis ofVoltammetric Data-Terence J.Cardwell, Jan Mocak, Jose H. Santos, Alan M. BondReference Electrode for Potentiometric Analyses in Corrosive Media-Daniel A. Lowy, Liviu OniciuDetermination of Ethanol in Beer by Flow Injection Dual-pulse Staircase Voltammetric Detection-YingsingFung, Songying MoTowards the Characterization of Bitumen-Mineral Interactions in a Natural Asphalt-Clayton Smith,Lutchminarine Chatergoon, Robin WhitingCUMULATIVE AUTHOR INDEXFACSS 1996: ANNOUNCEMENT AND CALL FOR PAPERSNEWS AND VIEWS 25N29N34N35N39N40NBook ReviewsConference DiaryCoursesConference Reports-Malcom R. Smyth, Ru-Qin YuPapers in Future IssuesTechnical Abbreviations and AcronymsCover picture: Analysis of compounds of agricultural significance (see p.11 R). Photograph kindlysupplied by lain Stuart, Glasgow Caledonian University, UK with thanks ot the Scottish AgriculturalCollege (SAC), UK

ISSN:0003-2654    

DOI:10.1039/AN99621BX011

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, March 1996, Vol. 121 25N Book Reviews Ion Exchange and Solvent Extraction Edited by Jacob A. Marinsky and Yizhak Marcus. Pp. xvi + 448. Marcel Dekker. 1995. Price $195. ISBN 0-8247-9382-X. This book, which is volume 12 in the series of advances in ‘Ion Exchange and Solvent Extraction’, is devoted solely to ion exchange. It contains 9 chapters written by prominent re- searchers in the field and covers a wide range of experiences. A number of the authors are from Russia and China and the current work of these scientists is made readily accessible in this volume in well written and easy-to-read chapters. The book will be valued by the expert but also by those who wish to keep up with the latest developments in particular ion- exchange topics. Chapter 1 describes a fundamental study of the separation of the rare earth elements by high-pressure ion exchange chroma- tography (HPIEC).It starts with a comparison between classical ion-exchange chromatography and HPIEC and is concerned with the large scale separation of the elements. Chapter 2 is titled ‘Ion Exchange in Countercurrent Columns’ and is an easy-to-read, well written account of countercurrent ion ex- change which gives particular attention to the various designs of contactors and techniques. ‘The book will be valued by the expert but also by those who wish to keep up with the latest developments in particular ion-ex- change topics. ’ In chapter 3 there is an excellent review of the methods for recovering elements from sea-water. As the authors point out, sea-water is a virtually untapped source of mineral wealth and procedures for extracting the elements are common to every nation wishing to use this source since the nature of sea-water is the same around the world.Ion exchange has played a major role in this work and the authors describe existing methods for recovering macroelements as well as microelements. The chapter is extremely well referenced with 300 literature citations. Chapter 4 is an account of the author’s research in developing a theory for intraparticle kinetics in selective ion- exchange systems. This has been tested experimentally and the results support the proposal that chemical reactions have a very large effect on the kinetics. These processes are discussed in considerable detail. In chapter 5 , there is a very good account of research into studying the metal ion complexes which form in the ion-exchanger phase.These are often different from the complexes formed in solution and reasons for this are suggested. Spectroscopic methods are used as well as distribu- tion methods. One very interesting aspect is the use of NMR spectroscopy to evaluate stability constants in the ion-ex- changer phase. This has considerable potential in systems with a moderate ligand exchange rate and with suitable ligands. Phosphate is one such example since the 3lP nucleus is commonly studied in NMR and the chemical shift change is related to different complexes. The kinetics of ion-exchange is further discussed in chapter 6. In this work, an examination is made of the rates of ion exchange from the point of view of heterogeneous mixtures of ion exchangers.Mixtures of ion exchangers will have different particle sizes, capacities and separation factors and the kinetic processes of exchange are examined in light of these para- meters. Both batch systems and the stirred flow cell technique are discussed. One aim of the work is to obtain a better understanding of ion exchange in soil, which is a mixture of different types of ion exchangers. Chapter 7 gives a comprehensive account of the evaluation of the electrostatic effect on metal ion-binding in polyanion systems. Carboxylate, sulfate, sulfonate and phosphate polyions and their gel analogues have all been studied. It has been shown in this work that the Gibbs-Donnan concept can be applied to any polyanion irrespective of its nature.In chapter 8, an examination is made of the ion-exchange equilibria of amino acids. Ion exchange has been the most successful method for the separation of amino acids and extensive work has been done on the topic. As the author points out, the mechanisms are still not well understood and the theory is far from complete. Chapter 9 contains a very interesting discussion of the selectivities of inorganic ion exchangers. There are a large number of inorganic ion exchangers and there is considerable information about their selectivities in the literature, much of which is tabulated in the chapter. There are more than two hundred literature references in the work. The author stresses the difficulty in providing a quantitative basis for selectivity in these materials but, no doubt, the wealth of information contained in this chapter will assist in this regard.R. W. Cattrall Sl90036K La Trobe University, Melbourne, Australia Electrophoresis of Enzymes: Laboratory Methods By G. M. Rothe. Springer Lab Manual. Pp. xii + 308. Springer-Verlag. 1994. Price DM 98.00. ISBN 3-540-581 14-6 The separation and characterization of enzymes is of interest not only to the research scientists in the fields of biochemistry, genetics, biotechnology and molecular biology, but also to clinical chemists, pathologists and enzymologists in the diag- nosis of diseases. This book is divided into 7 chapters. An introduction to enzyme classification and nomenclature is presented in chapter 1, which also provides an overview of the structure, size and source of enzymes and isoenzymes with their EC numbers in an easy-to-read table. Chapter 2 describes methods for the extraction of enzymes from plant, animal and human tissues, micro-organisms, cells and sub-cellular organelles.A step-by- step description is given for each example providing details on sample preparation, methods of homogenization or disintegra- tion, buffer salts and equipments used for extraction and procedures for the concentration of diluted enzyme extracts, with tables and notations in the margin adding to the main text (a feature to be found in all chapters). A section on the handling of mammalian (including human) blood and the preparation of serum, erythrocytes, leucocytes, lymphocytes, platelets and polymorphs is particularly useful to the clinical enzymolo- gists.Chapter 3 is devoted to methods for the separation of native enzymes using cellulose acetate, starch gel and polyacrylamide gel electrophoresis, including gradient and 2-D electrophoresis. There is an extensive listing of equipment, reagents and chemicals required for the execution of the methods, with illustrations (diagrams and photographs) on the experimental procedures. Methods for the determination of size and charge of enzymes are also given. Chapter 4 describes sodium dode- cylsulfate (SDS) electrophoresis and summarizes methods used to re-nature enzymes after SDS electrophoresis. Chapters 5 and26N Analyst, March 1996, Vol. 121 6 are devoted to the techniques of enzyme detection and visualization following electrophoresis, with the former con- centrated on the chemistry of visualization and the latter on specific staining protocols, together with suitable electro- phoretic systems, for more than 100 different enzymes.The final chapter is an introduction to the methods of data acquisition from enzyme patterns produced by electrophoresis. A few examples were given to illustrate the calculation of population genetics. This chapter is a little superficial and could have been left out since specialized books in this field are available. The reference lists given for each chapter are adequate. The index, however, is totally insufficient. ‘an invaluable practical guide for a wide application of ‘classical’ electrophoretic techniques. ’ I found the book reasonably well written and readable.It provides an invaluable practical guide for a wide application of ‘classical’ electrophoretic techniques. The book is useful to all who are interested in the electrophoresis of enzymes, but will be especially liked by postgraduate and postdoctoral research workers. As a practical manual for the laboratory it may be better if the book is soft-bound in a loose leaf style to enable easy viewing at the bench. This will also reduce the price, making it more attractive to postgraduate students. Future editions should perhaps also include the modem techniques of capillary electrophoresis, isotachophoresis and immunoblotting techniques. C. K. Lim 51900076 MRC Toxicology Unit, Leicester Infrared and Raman Spectroscopy. Methods and Appli- cations Edited by Bernhard Schrader.Pp. xx + 788. VCH. Wein- heim. 1995. DM298.00. ISBN 3-527-26446-9. Like ripples from a disturbance in a lake, the scope and applications of infrared and Raman spectroscopy spread ever wider. It is manifestly impossible for a single writer to deal with the whole subject. Hence, the approach of the present volume, where the task is entrusted to eighteen specialist spec- troscopists, all from mainland Europe. It is pertinent to question the value of the resulting near-encyclopaedic volume, and for whom it is intended. In the preface the general editor merely remarks that it has been written for graduate students as well as for experienced scientists who intend to update their knowl- edge. This leaves a good deal to the imagination.In all probability it will be used as a reference volume and will be found more frequently in the libraries of scientific institutions rather than on the personal bookshelves of active spec- troscopists. In compiling a reference work of this type the editor has the unenviable task of trying to ensure that there is sensible coverage of all pertinent topics and that the various contributors write to a reasonably uniform standard, both in terms of lucidity and depth of scientific content. The book will be assessed by these two criteria. The first major chapter is a general survey of the theory of the vibrational spectroscopy occupying about fifty pages. This results in a condensed treatment of questionable value. There are already very adequate texts covering this topic and the space would have been better used to expand some of the remaining chapters.Foremost among these is the vibrational spectroscopy of organic substances. This adopts the sensible approach of integrating the infrared and Raman techniques but it lacks the breadth and depth to be useful to neophytes. Furthermore, the treatment is very uneven. For example, much is said about the C=C stretching vibrations of monoolefins, particularly a series of rather obscure cyclic compounds of this type, but no mention is made of the considerable value of the corresponding out of plane deformation modes for structural diagnostic work. The corresponding section on inorganic compounds is sound, but a somewhat extended treatment would have been advanta- geous.Biopolymers are covered adequately, but twenty-eight pages on this subject and twenty-six on conducting polymers is surely out of proportion. Other polymers receive very short shrift and it is curious that although the theory and practice of measurements with polarized radiation is considered, no mention is made of orientation studies on polymers, other than in the specialized field of liquid crystals. ‘this book certainly contains much useful material, but it brings to mind the proverbial curate’s egg.’ The book concludes with a huge chapter of two hundred and twenty-eight pages covering a very wide range of special techniques and applications. These include topics as diverse as vibrational optical activity, infrared reflection techniques, spectrometric control of continuous extraction processes, studies of fast reactions and intermediates, and high-pressure and high- and low-temperature measurements.Within this chapter the account of near infrared spectroscopy is the least satisfactory. It fails wholly to cover the wide range of analytical applications that have emerged during recent years. To summarize, this book certainly contains much useful material, but it brings to mind the proverbial curate’s egg. 51900480 W. F . Maddams Banstead, Surrey New Physico-chemical Techniques for the Character- ization of Complex Food Systems Edited by E. Dickinson. Pp. xii + 356. Blackie Academic and Professional. 1995. f75.00. ISBN 0-7514-0252-4. In a series of short chapters by acknowledged experts, this book describes some of the most up-to-date techniques which can be used to understand the structure-function relationships in food systems.For the most part authors have done extremely well in summarizing the theoretical and experimental principles under- lying the techniques without assuming too much background knowledge on the part of the reader. This is obviously much easier for some subjects than others. (Some of the NMR techniques might be a little hard for the uninitiated to follow, but this is more than made up for by the excellent illustrative examples of application to food systems). Throughout, back- ground references are provided for the more interested reader, and care seems to have been taken to ensure that only up-to-date publications are referenced. Recent developments in ‘traditional’ electron microscopy, i.e., SEM and TEM, are described.Only a passing reference is made to environmental SEM, but of all the chapters in the book this provides some of the most clear, convincing and impressive images of food structure I have seen, which is a measure of the pedigree of these techniques compared with the confocal laser scanning microscopy and scanning probe microscopy covered in subsequent chapters. The latter concentrates mainly on atomic force microscopy. Jumping to the last chapter in the book, imaging on a much larger scale via NMR is describedAnalyst, March 1996, Vol. 121 27N very thoroughly. The author makes no bones about some of the complexities and pitfalls in trying to interpret images, but the potential for following real processes in vivo is tremendously exciting.The two chapters on scattering: dynamic light scattering (DLS) and neutron scattering/reflection describe how colloidal and adsorbed surfactant structure may be obtained via these techniques. Good overviews are given of the modeling considerations which are required to extract information from these techniques. The DLS chapter emphasizes the develop- ments being made to extract information from concentrated colloidal systems. The chapter on ultrasonics illustrates the key role that this techique is also likely to play in characterizing such systems in the future. Chapters on electron spin resonance, infrared spectroscopy (including microscopy) and solid state NMR provide examples of where extremely specific chemical information may be extracted from highly complex systems.The chapters on fracture mechanics and biopolymer rheology are more general overviews of these subjects, whilst the chapter on dynamic surface tension measurement introduces some novel experi- mental and analytical methods which illustrate the significance of this subject to foam and emulsion stability. New methods of data analysis are described which enable macromolecular conformation and interactions to be obtained from ultra- centrifugation data. I would recommend this book to any scientist who is searching for techniques which might be used to characterize food/biomolecular systems, or undergraduates who wish to obtain a basic overview of these techniques and learn how they might be applied to foods (or indeed any other biological system).Dr. Brent Murray 519006IA University of Leeds, Leeds ~ Nuclear Techniques in Soil-Plant Studies for Sustainable Agriculture and Environmental Preservation. Proceed- ings of a Symposium, Vienna, 17-21 October 1994. Jointly Organized by IAEA and FA0 Pp. 736. International Atomic Energy Agency. Vienna. 1995. Price OS2 120. ISBN 92-0- 100895-3. The challenge of continuing to provide food for an increasing population, while at the same time avoiding deterioration of soil, water and air, is probably the most pressing problem facing mankind today. Soil is a finite resource exploited for food, fibre and some energy production, which is under pressure from these demands and from the effects of possible climate change. The concept of soil sustainability encompasses the ability to improve and sustain crop yields in the long term and the maintenance of environmental quality. This book aims to promote the use of nuclear techniques as tools in such studies.It is directed primarily, but not exclusively, towards work in developing countries, and indeed acts as an outlet for the results of some of the work already being undertaken in these areas. Following the formal remarks of the opening session, which includes an overarching keynote address, the proceedings are divided into eight sessions. These deal with: recent develop- ments in analytical methods and equipment; fertilizer use and management studies; biological nitrogen fixation in sustainable cropping systems; soil organic matter studies and nutrient cycling; water use and management studies; plant physiological aspects in crop production; environmental pollution and preservation; soil conservation, soil erosion and desertification.Each session is introduced by an invited paper giving a general overview of some aspects of the topic, followed by papers on specific studies. The numbers of papers per session vary between 3 and 8, with a total of 48 presented papers. In addition, there are short (2 pp.) summaries of 25 posters. This format results in considerable variation in the quality and type of paper, from some excellent reviews to results from single experi- ments. Most attention is paid to the two major plant nutrients N and P, which present problems not only of supply to plants but also of pollution if misused, and to C, as organic matter turnover is a vital aspect of soil sustainability.This degree of attention also reflects the use of well established techniques using l3C, 14C, 15N and 32P. The last session contains two papers that present some interesting new techniques using fallout radionuclides to measure soil erosion. Much of this work uses 137Cs, as caesium binds strongly to clays and has a relatively long half-life, making it an ideal marker for following the movement of eroded soil particles. ‘overall provides a useful collection of papers. ’ Like most conference proceedings, this is a mixture of quality and emphasis, but overall provides a useful collection of papers. It is well produced in a uniform style, although the 16 pages that list the session chairmen, secretariat and participants could have been better used to provide a subject index.My main reservation, which is probably inevitable given the organiza- tions behind the conference, is the emphasis on big science and international programmes. Nuclear techniques clearly have an important part to play in helping to solve some of these problems, but this ability may need to be better targeted. Statements such as ‘chemical fertilizers have played, and will continue to play, a key role in increasing food production in the nutrient poor soils of the tropics’ worry me. They seem to be promoting more of the same type of research, while ignoring such considerations as the cost of fertilizers and their polluting potential if misused, They also ignore the indigenous knowl- edge of people who have grown crops in these soils for generations, and who probably know more about them than scientists flown in by big international organizations.There is mounting evidence that small-scale cropping may be more productive than intensive agriculture in these areas. We need to understand better the processes involved and how they affect the environment. Now there is a challenge that might benefit from the use of nuclear techniques. Dr. I . D. Pulford 5190062 J University of Glasgow, Glasgow Encyclopedia of Spectroscopy By Heinz-Helmut Perkampus. Pp. 670. VCH. Weinheim. 1995. DM 148. ISBN 3-527-29281 -0. Having initially agreed to review this encyclopedia, I then wondered how one could meaningfully do so. When the book arrived, I dipped into it for an initial feel and then found that I was reading all kinds of spectroscopic notes.Increasingly, I looked up many of the spectroscopic effects and techniques that I had heard of over the years but had not really understood, e.g., the Nuclear Overhauser Effect (p. 409) and browsed further. It is an excellent book which one can settle down with and emerge with one’s spectroscopic interest refreshed and stimulated. The encyclopedia is a translation of the original Perkampus’s ‘para Lexicon Spectroscope’ by Hilde-Charlotte and Roger Granter and reads very well. The English and German names and titles are given for each entry, the former leading in each case. The material covered includes historical notes (useful for28N Analyst, March 1996, Vol.121 people unfamiliar with a new field), succinct descriptions of over-all techniques, instrumentation, chemical and physical materials, details of spectroscopic theory and optical com- ponents. One criticism is that the diagrams seem somewhat dated in presentation and cramped at times. But all of the necessary detail is there and people keen enough to read entries in this book will be able to follow the (often) complex diagrams. It will be very useful for working spectroscopists to have this encyclopedia in their bookcase. But also, in compiling this encyclopedia, Perkampus has given particular attention to the applications of spectroscopy in the biological, medical and environmental sciences. Indeed, in his introduction, he makes the point that many environmental problems would not have been identified so readily without the sensitivity of environmental spectroscopic analysis.The wide range of applications that uses spectroscopy as their central operating method emphasizes the need for an encyclopedia such as this for scientists who have not specialized in spectros- COPY. ‘I recommend it to any person involved in spectroscopy or spectroscopic analysis as an interesting read and very useful reference book. The book is well produced and comprehensively cross- referenced. The translators have taken the opportunity to replace the predominantly German original references with similar citations in English as far as possible. I recommend it to any person involved in spectroscopy or spectroscopic analysis as an interesting read and very useful reference book.Even at ca. 570-75, this encyclopedia is reasonable in the context of today’s book prices. Malcolm F . Fox 519002 7A De Montfort University, Leicester Developments in the Analysis of Lipids Edited by J. H. P. Tyman and M. H. Gordon. Pp. vii + 206. Royal Society of Chemistry. 1994. Price f45.00. ISBN 0-851 86-97 1-8. This book reports the proceedings of a one day meeting held at the University of Newcastle-upon-Tyne on the ‘Development in the Analysis of Fats and other Lipids’ organized jointly by the Lipid Group of the Royal Society of Chemistry and the Oils and Fats Group of the Society of Chemical Industry. Although the style of the text is somewhat disconcerting, the content of the book illustrates the considerable progress in the development of new analytical methods in the area of lipid chemistry and the application of these methods to elucidate the structures of lipids and to estimate, for example, the extent of adulteration of oils in certain foodstuffs.All the articles are written by authors who are well respected in their particular field of expertise and it is this aggregation of expert knowledge which enables the book to be of such a high scientific standard. The book consists essentially of two sections: the first covering new extraction and chromatographic methods and the second concentrating on spectroscopic and physical methods. The chapters on supercritical fluid extraction and chromatography are particularly illuminating and give examples of how these relatively new techniques have been assimilated quickly and effectively into the armoury of lipid analytical methodology. The hyphenated technique of liquid chromatography linked to gas chromatography demonstrates the potential in using such a fairly novel technique in assessing potential adulteration of edible fats and oils, whereby minor components can be monitored in a semi-automated manner. There are also chapters on the separation of chiral lipids by high-performance liquid chromatography and the use of a variety of chromatographic techniques in the analyses of phenolic lipids. ‘All the articles are written by authors who are well respected in their particular field of expertisey The second section is concerned mostly with the analysis of lipids by instrumental techniques such as nuclear magnetic resonance, mass spectrometry and neutron diffraction. Al- though the first two techniques have been used extensively in lipid analysis, the third is not one which is normally associated with the analysis of biological materials. However, the potential has been demonstrated but it is unlikely that neutron diffraction will become a technique which lipid analysts are clambering to use! Many of the chapters give an introduction to the theory of the technique under discussion and all the papers have an extensive reference section. The book is highly specialized and will be of value to those scientists who are actively involved in lipid analysis or lipid research. Dr A. Smith 41902 16E The Macaulay Land Use Research Institute A berdeen

ISSN:0003-2654    

DOI:10.1039/AN996210025N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, March 1996, Vol. 121 (29R-32R) 29R Tutorial Review Oriented Immobilization of Antibodies and Its Applications in lmmunoassays and I m m u nosensors Bin Lua, Malcolm R. Smytha* and Richard O’Kennedyb a School of Chemical Sciences, Dublin City University, Dublin 9, Ireland h School of Biological Sciences, Dublin City University, Dublin 9, Ireland The immobilization of antibodies on solid-phase materials has been used in many areas such as purification, diagnostic immunoassays and immunosensors. Problems associated with the loss of biological activity of the antibodies upon immobilization have been noticed in many cases. One of the main reasons for such loss is attributed to the random orientation of the asymmetric macromolecules on support surfaces. In this paper, the approaches for achieving oriented coupling of antibodies to increase the antigen binding capacity are reviewed.Some issues such as steric hindrance caused by neighbouring antibody molecules, the distance between an antibody and the support surface and the use of antibody fragments are dealt with. Some applications of the oriented immobilized antibodies in immunoassays and immunosensors are examined. Keywords: Orientation; antibody; immobilization; immunoassay; immunosensor Owing to their high specificity, antibodies immobilized on various supports have been widely used for different purposes. In immunoaffinity chromatography, antibodies immobilized on traditional affinity gels or porous particles are employed to separate proteins from dilute mixtures under mild conditions.’ The use of immobilized antibodies in diagnostic immunoassays has expanded considerably in recent years.2 Immunosensors, in which antibodies are immobilized on optical fibres, electrodes or semiconductor chips for the detection of antigen^,^-^ represent another promising application.Numerous coupling strategies have been developed for immobilizing antibodies on different solid surfaces through the formation of defined linkages in which glutaraldehyde, carbodiimide and other reagents such as succinimide ester, maleinimide and periodate are widely used. However, problems associated with the loss of biological activity upon immobilization of antibodies are noticeable in many cases. When antibodies are covalently attached to solid supports, their specific binding capacity is usually less than that of soluble antibodies.One of the main reasons for this reduction is attributed to the random orientation of the antibodies on support surfaces. The asymmetric macromolecule immunoglobulin G (IgG) is composed of two different fragments, F(ab’)2 and Fc (Fig. 1). The Fc fragment contains antibody effector functions, so it has no antigen binding affinity. The F(ab’)2 fragment contains two identical Fab’ fragments. The antigen binding site * To whom correspondence should be addressed. is positioned at the amino end of each fragment. In normal coupling schemes, coupling does not discriminate between possible attachment points near or removed from the specific binding site (or sites), which results in spatial orientation of antibodies on the supports that might prohibit formation of an antibody-antigen complex (Fig. 2).For instance, if multiple lysine groups are present on the surface of an antibody molecule, multiple attachment might occur. This may result in Fig. 1 Schematic diagram of an antibody molecule and its fragments. The molecule can be subdivided into two parts. The Fc fragment contains the antibody effector functions, such as complement activation, cell membrane receptor interaction and transplacental transfer.6 The F(ab’)z fragment contains two identical Fab’ fragments, which are held together by the disulfide linkages in the hinge (H) region. The Fab’ fragment (antigen- binding site-containing fragment) consists of the heavy (H) and light (L) variable (V) chains (VH and V,) and the constant ( C H I and CL) chains.Other segments are the Fv (variable fragment) consisting of the VH and VL chains and the Fd fragment which contains the VH and C H I chains. The carbohydrate moieties locate at the c H 2 domain and the binding sites for Fc receptors (protein A, protein G and recombinant protein A/G) locate between the domains of CH2 and cH3. Inactive Parttally active Fully active Fig. 2 coupling procedure. Ideal representation of IgG antibody immobilized by random30R Analyst, March 1996, Vol. 121 different orientations of the antibody on the support surface depending on which lysine group binds to the support. When immobilization occurs through the antigen binding sites on the Fab’ portions, the ability of that antibody to bind antigen may be severely impaired or eliminated entirely.To eliminate these drawbacks, several approaches for achieving oriented antibody coupling have been developed. In one scheme, antibodies were bound to Fc receptors on solid supports, such as protein A, protein G or recombinant protein A/ G [Fig. 3(a)]. These Fc receptors bind to the Fc portion of many IgG subclasses, leaving the antigen-specific sites free. Another strategy for oriented coupling relies on the chemical or enzymic oxidation of the IgG carbohydrate moiety [Fig. 3(h)]. Im- munoglobulins contain carbohydrate moieties linked mainly to the CH2 domain of the Fc fragments. Under mild conditions, the hydroxy groups of the carbohydrates can be oxidized to aldehyde groups without significantly impairing the active sites of the antibody. The oxidized antibodies can then be im- mobilized to hydrazide-activated supports via their oxidized groups by forming covalent hydrazone bonds.The third method is to utilize the sulfhydryl group of the Fab’ fragment to create an oriented antibody fragment [Fig. 3(c)]. This can be achieved by first making F(ab’):! with pepsin digestion, followed by reduction of the sulfide bond between monovalent Fab’ fragments, or by using artificial Fab’ fragments produced by molecular genetic techniques. The sulfhydryl group formed in the C-terminal region of the fragment can be used to couple the fragment to an insoluble support in such a way that its antigen binding site is available for interaction with antigen. The approach to binding antibodies to immobilize the Fc receptors on solid surfaces is by no means a new concept.The first Fc receptor immobilized on a solid support was protein A. Protein A was found in the cell wall of Staphylococcus aureus. In 1978, Gersten and Marchalonis7 linked antibody to protein A-Sepharose to improve its antigen-binding capacity. The procedure circumvented the problem of random antibody- matrix coupling inherent in the cyanogen bromide technique. Subsequently, Schneider et a1.8 modified the technique by generating the affinity cross-linked matrices with dimethyl pimelimidate. The immunoaffinity columns on which antibod- ies were cross-linked were stable and had larger antigen-binding capacities. This scheme was further modified by Sisson and Castor,g the linkage between the protein A-immobilized matrix Fig. 3 Representation of approaches for achieving oriented antibody immobilization. (a) Antibody binds to Fc receptors on solid supports; (b) antibody is coupled to the solid support via an oxidized carbohydrate moiety on its CH2 domain of the Fc fragment; (c) monovalent Fab’ fragment is bound to insoluble support via a sulfhydryl group in the C-terminal region of the fragment.and the bound immunoglobulin being enhanced. After the modification, almost all bound antibody was coupled to the matrix and full antigen-binding capacity of the antibody was reserved, which indicated that the cross-linker does not interfere with the variable region of the IgG molecules, and the antibody is positioned on the gel matrix in an orientation that allows maximum antigen binding.In this scheme, the Fc receptor is the key element for the oriented immobilization of the IgG antibody. It is expected that the receptor has the same affinity to all IgG isotypes to make the receptor-coupled support a universal inducing matrix for oriented IgG immobilization. Protein A has been used success- fully to bind the Fc portion of IgG from many mammalian species. However, it fails to react with IgG from several other species such as goat, sheep, cow and horse.10 A more versatile and efficient alternative to protein A for binding IgG isotypes is protein G, which is found in the cell wall of Streptococcus human pathogenic strains of the Lancefield group G. Protein G has some advantage over protein A because it reacts with more IgG isotypes and it reacts less with other immunoglobulins such as human IgM and IgA.ll However, it does not bind strongly to several IgGs with which protein A reacts well.The third generation of IgG-binding Fc receptor, recombinant protein A/ G, has recently been developed. Recombinant protein A/G is a gene fusion product secreted from a non-pathogenic form of Bacillus. The secreted protein A/G is designed to contain four Fc binding domains from protein A and two from protein G.12 This makes it combine the IgG-binding profiles of both protein A and protein G. Recently, all three kinds of Fc receptors have been successfully immobilized on different affinity gels to bind IgG antibodies. Several commercial products for preparing oriented IgG columns by using these immobilized Fc receptors have appeared recently.13 The concept of oriented immobilization of antibodies relying on the oxidation of IgG carbohydrate moieties appeared about 10 years ago.O’Shannessy and Quarles14 demonstrated in a preliminary experiment that periodate-oxidized goat antibody retained its biological activity after binding to a hydrazide- containing solid support. Subsequently, a general method for binding glycoproteins with specific sites to hydrazide supports was described by O’Shannessy and Hoffman.15 Subsequently, antibodies from several species were investigated by the same workers16 to determine their ability to bind to hydrazide gels and to determine the activity of the bound antibody. Parameters such as the pH of the oxidation, the pH of the binding and coupling time was optimized.The antigen-binding capacity of the antibody coupled to the supports (mol Ag bound/mol Ab coupled) ranged from 0.6 to 1.35, depending on the size of the bound antigen. The activity was three times larger than that of the same antibody bound to the same support through their E- amino groups. Prisyazhnoy et aZ.17 used a similar method for coupling oxidized rabbit anti-mouse IgG to two different gel supports. They suggested that the antigen-binding capacities ranged from 1.1 to 1.6, depending on the support used. Note that several workers have succeeded in detecting the dramatic increase in the antigen-binding capacity of periodate- oxidized polyclonal antibodies, but failed to detect any significant alteration in the capacity of periodate-oxidized monoclonal antibodies.Matson and Little18 suggested that both the antigen-binding site and the carbohydrate moiety of the monoclonal antibody could have been damaged during the affinity purification and excessive oxidation, so milder condi- tions for the purification and the conversion into aldo-IgG should be examined. Highsmith et al. 19 attributed the situation to the presence of carbohydrate moieties in the Fab’ regions of some monoclonal antibodies. However, the data from Solomon et al.’s report20 indicated that enzyme oxidation of monoclonal antibodies before the oriented immobilization improved the specific capacity of the antibodies. They used neuraminidaseAnalyst, March 1996, Vol. 121 31R and galactose oxidase, instead of periodate, to oxidize the carbohydrate moieties on the monoclonal antibodies. The treatments produced a maximum of two aldehyde groups per mole of antibody, compared with 3.2-4 aldehyde groups obtained after periodate oxidation.These enzyme-oxidized antibodies possessed a higher antigen binding activity than the corresponding chemically oxidized antibody immobilized on the same matrix. An example of utilizing the sulfhydryl group of Fab’ fragments to create an oriented antibody fragment on solid surfaces is that developed by Prisyazhnoy et al.17 Fab’ fragments from rabbit IgG were immobilized on to a Sepharose matrix derivatized with the maleimide group and approximately half of the coupled Fab’ fragments retained their antigen- binding capacity.Jimbo and Saitos have developed a technique for the fabrication of oriented Fab’ fragments immobilized in organic films on semiconductor substrates and suggested that a fairly high density of immobilized Fab fragments (6 X 10” cm-2) was obtained. Recently, Lu et ~1.21 studied the effects of the orientation of the Fab’ fragments on the antigen-binding capacity. The Fab’ fragments of rabbit anti-human IgG were immobilized in an oriented form on derivatized silica slide surfaces containing pyridyl disulfide groups, and in random form to glutaraldehyde-bound silanized silica slide surfaces. After immobilization, a higher surface density of the oriented fragment (1.6 X 10l2 cm-2) was obtained. The changes in orientation of the immobilized fragments drastically influenced the antigen-binding capacity of the fragments.The activity of the fragments in oriented form was about three times higher than that in random form. Such immobilized fragments could find extensive applicability in the design of immunosensors for monitoring soluble antigens. Although efforts have been made to develop new schemes to increase the biological activities of immobilized antibodies, little work has been done to compare the properties of the antibodies immobilized by the different techniques. Alarie and Sepaniak22 compared two of the above coupling schemes by immobilizing Fab’ fragments or intact antibody on silica beads via the cross-linker 2-fluoro- 1 -methylpyridinium toluene-4-sul- fonate (FMP) or immobilized protein A, respectively. Although the loadings of the antibody on two surfaces were nearly the same, the immobilized Fab’ fragments exhibited only half the activity of the intact antibody coupled via protein A.They attributed the loss in the activity to the reduction of the disulfide linkages in Fab’ fragments. However, the random adsorption of the fragments on the silica surfaces might be another reason for the loss.2’,24 In addition to the orientation of surface-coupled antibodies, several other factors, such as steric hindrance caused by neighbouring antibodies at high surface concentration, the distance between coupled antibodies and the support surface and the modified conformation, also influence antigen-binding capacity. Matson and Little’s and other workers25326 have studied the relationship between the activity and surface antibody concentration.Their results showed that steric hin- drance created by crowding of adjacent antibody molecules immobilized via oriented or random coupling mechanisms lead to the same net effect, a decrease in antigen-binding efficiency. Spitznagel and co-~orkers2~,~8 studied the effects of surface density and orientation on the immobilized antibody and antibody fragments. For all immunosorbents, a high protein loading led to relatively low specific activities. At higher loading, the activity of the immobilized whole antibody was lower for the large antigen than for the small hapten, whereas no effect of the hapten size on the activity was observed for either immobilized Fab’ or Fv fragments. No significant changes in the conformation of active immobilized antibodies were observed.The most interesting results in the study were that immobilized Fv fragments had the highest binding capacities, which indicated that removing unnecessary protein domains can be beneficial for improving the total capacity of immunosor- bents. As mentioned above, antibody IgGs are multi-fragment glycoproteins that may be dissected into individual fragments using proteases. The preparation of homogeneous antibody fragments by enzymic digestion can be difficult, and often conditions have to be optimized for each antibody. By contrast, molecular genetic techniques can be used to produce defined fragments of any immunoglobulin. Current molecular genetic techniques do not allow for the correct functional expression of whole antibody molecules.However, most expression vectors which are from plasmids that propagate in Escherichia (E. coli) could be used to express correctly recombinant light- and heavy-chain genes. Antibody fragments are easily manipulated using the expression vector available. Various fragments, which include Fab’, F(ab’)2, Fd and Fv, have been manipulated in numerous protocols.29-32 The resulting fragments have been shown to retain the antigen-binding activity of the parent molecule. Furthermore, this technology is not limited to the production of conventional immunoglobulin fragments and has been extended to the generation of novel fragments which have been produced by either isolating variable-region gene seg- ments or by inserting stop codons into heavy- and light-chain genes.33.34 The relatively inexpensive production of the anti- body derivatives opens up the possibility of developing new immunoassay agents.The schemes for oriented immobilization of solid antibodies on supports have been applied in the fabrication of different immunosensors. An immunosensor based on microelectronic techniques in which an antibody was immobilized on to the gate surface by means of immunochemical membranes containing protein A has been reported.35 Flow injection electrochemical enzyme immunoassays for theophylline using protein A immunoreactors have been developed.36.37 Fluorescence flow injection immunoassay for testosterone using protein A and for insulin using protein G immunoreactors have also been developed.38.39 Kaku et al .40 described an enzyme immunoelec- trode in which anti-insulin IgG was anchored on partial hydrophilic polypropylene membranes containing protein A, and suggested that the formation of the oriented antibody improved both the sensitivity and dynamic range of the sensor.Konig and Gratzel4’43 have studied piezoelectric immuno- sensors for the detection of the human herpes viruses and T- lymphocytes, in which three different methods of immobiliza- tion (via polyethylenimine, silane or protein A) were evaluated. The best results in terms of sensitivity, reproducibility and re- usability were obtained with the protein A immobilization method. Recently, Owaku et al.44 developed an optical immunosensor in which the antibody binds to a double monolayer protein A film formed by Langmuir-Blodgett film techniques.Several immunosensors based on the immobiliza- tion of the Fab’ fragments have been produced.5345-47 Betts and co-~orkers45,~7 have demonstrated that dansylated Fab’ frag- ments were useful in the fabrication of selective, sensitive, self- contained and re-usable fibre-optic-based immunosensors for the antigens of human serum albumin and several haptens. In conclusion, an examination of the literature has revealed that oriented coupling techniques offer several potential advantages over random coupling methods, which have resulted in the better separation in immunoaffinity chromatography and higher sensitivity in immunoassays. In general, the antigen- binding capacity using the former is a factor of 2-8 higher than efficiencies obtained with random coupling methods, and the thermodynamic and kinetic properties of oriented antibodies tend to be more uniform, thus simplifying operation with solid supports.However, more work needs to be undertaken to elucidate the mechanisms of orientation and the effects of steric hindrance and of modified conformation in particular situations.32R Analyst, March 1996, Vol. 121 It is expected that this area of the research will continue to expand in the years to come. This work was supported by a grant from Forbairt under the Basic Research Grant Scheme (SC/95/240). References 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17 18 19 20 21 22 23 Janson, J. C., Trends Biotechnol., 1984, 2, 31. Carlsson, R., Glad, C., and Borrebaeck, C.K. A., BiolTechnology, 1989, 7, 567. Ogert, R. A., Brown, J. E., Singh, B. R., Shriver-Lake, L. C., and Ligler, F. S., Anal. Biochem., 1992, 205, 306. Rosen, I., and Rishpon, J., J . Electroanal. Chem., 1989, 258,27. Jimbo, Y., and Saiti, M., J . Mol. Electron., 1988, 4, 111. Staines, N., Brostoff, J., and James, K., Introducing Immunology, Mosby, St. Louis, 1993. Gersten, D., and Marchalonis, J., J . Immunol. Methods, 1978, 24, 305. Schneider, C., Newman, R. A., Sutherland, D. R., Asser, U., and Greaves, M. F., J. Biol. Chem., 1982, 257, 10766. Sisson, T. H., and Castor, C. W., J . Immunol. Methods, 1990, 127, 215. Longone, J. J., J. Immunol. Methods, 1978, 24, 269. Eliasson, M., Anderson, R., Olsson, A., Wigzell, H., and Uhlen, M., J. Immunol., 1989, 142, 575.Eliasson, M., Olsson, A., Palmcrantz, E., Wiberg, K., Inganas, M., Guss, B., Lindberg, M., and Uhlen, M., J . Biol. Chem., 1988, 263, 4323. ImmunoTechnology, Catalog and Handbook, Pierce Chemical Co., USA, 1992-93. O’Shannessy, D. J., and Quarles, R. H., J . Appl. Biochem., 1985, 7, 347. O’Shannessy, D. J., and Hoffman, W. L., Biotechnol. Appl. Biochem., 1987, 9,488. O’Shannessy, D. J., and Hoffman, W. L., J . Immunof. Methods, 1988, 112, 113. Prisyazhnoy, V. S., Fusek, M., and Alakhov, Y., J. Chromatogr., 1988,424,243. Matson, R. S., and Little, M. C., J. Chromatogr., 1988, 458, 67. Highsmith, F., Regan, T., Clark, D., Drohan, W., and Tharakan, J., BioTechniques, 1992, 12,418. Solomon, B., Koppel, R., Schwartz, F., and Fleminger, G., J . Chromatogr., 1990, 510, 321.Lu, B., Xie, J., Lu, C., Wu, C., and Wei, Y . , Anal. Chem., 1995, 67, 83. Alarie, J. P., and Sepaniak, M. J., Anal. Chim. Acta, 1990, 229, 169. Lin, J., Chang, I., Andrade, J. D., Herron, J. N., and Christensen, D. A., J. Chromatogr., 1991,542, 41. 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 Lin, J., Andrade, J. D., and Chang, I., J . Immunol. Methods, 1989, 125, 67. Strauss, W. M., Broze, G. J., Miletich, J. P., and Null, H. R., Biotechnol. Appl. Biochem., 1987, 9,462. Sada, E., Katoh, S., Sukai, K., Tohma, M., and Kondo, A., Biotechnol. Bioeng., 1986, 28, 1497. Spitznagel, T. M., and Clark, D. S., BiolTechnology, 1993,11, 825. Spitznagel, T. M., Jacobs, J. W., and Clark, D. S., Enzyme Microb. Technol., 1993, 15, 916. Jespers, L.S., Roberts, A., Mahler, S. M., Winter, G., and Hoogenboom, H. R., BiolTechnofogy, 1994,12, 899. Abrams, C., Deng, Y., Steiner, B., O’Toole, T., and Shattil, S. J., J . Biol. Chem., 1994, 269, 18781. Tavladoraki, P., Benvento, E., Trinca, S., De Martinis, D., Cattaneo, A., and Galeffi, P., Nature (London), 1993, 366,469. Brinkmann, U., Reiter, Y., Jung, S-H., Lee, B., and Pastan, I., Biochemistry, 1990,29, 1362. King, D., Byron, O., Mountain, A,, Weir, N., Harvey, A., Lawson, A., Proudfoot, K., Baldock, D., Harding, S . , Yarranton, G., and Owen, R., Biochem. J., 1993, 290, 723. Riechmann, L., Foote, G., and Winter, G., J . Mof. Biol., 1988, 203, 825. Colapicchioni, C., Barbaro, A., Porcelli, F., and Giannini, I., Sens. Actuators B, 1991, 4, 245. Palmer, D. A., Edmonds, T. E., and Seare, N. J., Anal. Lett., 1993,62, 1425. Palmer, D. A., Edmonds, T. E., and Seare, N. J., Analyst, 1992,117, 1679. Palmer, D. A., Evans, M., Miller, J. N., and French, M. T., Analyst, 1994,119,943. Khokhar, M., Miller, J. N., and Seare, N. J., Anal. Chim. Acta, 1994, 290, 154. Kaku, S,, Nakanishi, S., and Horiguchi, K., Anal. Chim. Acta, 1989, 225, 283. Konig, B., and Gratzel, M., Anal. Chem., 1994, 66, 341. Konig, B., and Gratzel, M., Anal. Lett., 1993, 26, 1567. Konig, B., and Gratzel, M., Anal. Chim. Acta, 1993, 281, 13. Owaku, K., Goto, M., Ikariyama, Y., and Aizawa, M., Anal. Chem., 1995,67, 1613. Betts, T. A., Catena, G. C., Huang, J., Litwiler, K. S., Zhang, J., Zagrobelny, J., and Bright, F. V., Anal. Chim. Acta, 1991, 246, 55. Boitieux, J. L., Desmet, G., Wilson, G., and Thomas, D., Ann. N . Y . Acad. Sci., 1990, 613, 390. Bright, F. V., Betts, T. A., and Litwiler, K. S., Anal. Chem., 1990,62, 1065. Paper 5f06085K Received September 14,1995 Accepted November 14, 1995

ISSN:0003-2654    

DOI:10.1039/AN996210029R

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

34N Analyst, March 1996, Vol. I 2 I Courses Date 1996 April 23-24 30-1 1/7 May 19-22 20-23 20-23 21-23 2 1-23 28-30 June 3-5 3-7 18-19 July 1-2 1 -5 23-25 Conference Location HPLC Troubleshooting Courses Macclesfield, UK Environmental Analysis and Assessment Silwood Park, UK 1996 International Symposium, Exhibit & Workshops on Preparative Chromatography, USA Washington D.C., Ion Exchange, and AdsorptionlDesorption Processes and Related Techniques Modern Practice Gas Chromatography Laboratory Health and Safety HPLC Beginners Training Course Mass Spectrometry of Peptides and Proteins Seventeenth Annual Introductory HPLC Short Course Advanced HPLC Radioisotope Techniques HPLC Toubleshooting Courses Fourier-Transform Infrared Spectroscopy Summer School in Spectroscopic Interpretation Problem Solving for Analytical Leaders West Chester, USA Loughborough, UK Macclesfield, UK Manchester, UK West Chester, USA Widener, USA Loughborough, UK Macclesfield, UK Manchester, UK Manchester, UK Y ork, UK Contact Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SKI 1 6PJ Tel: 01625 613848.Fax: 01625 616916 Continuing Education Centre, 558 Sherfield Building, South Kensington, London, UK SW7 2AZ Tel: +44 (0)171 594 6881/6882. Fax: +44 (0)171 594 6883. E-Mail: cpd@ic.ac.uk Janet Cunningham, Barr Enterprises, P.O. Box 279, Walkersville, MD 21793 USA Tel: +1 301 898 3772. Fax: +1 301 898 5596 E-mail: Janetbarr@aol.com Sally Stafford, Hewlett Packard, Little Falls Site, 2850 Centerville Road, Wilmington, DE 19808-1 610 Tel: +1 302 633 8444. Joyce Motyka, Centre for Hazard and Risk Management (CHaRM), Loughborough University, Loughborough, Leicestershire, UK LEI 1 3TU Tel: +44 (0)1509 222175. Fax: +44 (0)1509 610361 Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SKI 1 6PJ Tel: 01625 613848.Fax: 01625 616916 Dr. N. H. P. Smith, Chemistry Department, UMIST, P.O. Box 88, Sackville Street, Manchester, UK M60 1QD Tel: +44 (0)161 200 4491. Fax: +44 (0)161 236 7677 Bill Champion, DuPont Merck Pharmaceutical Co., PRF Building, Chambers Works, Deepwater, NJ 08023 Tel: +1 609 540 4826. Jim Alexander, Rohm and Haas Laboratories, 727 Norristown Road, Spring House, PA 19477 Tel: + I 215 619 5226. Dr. P. Warwick, Department of Chemistry, Loughborough University, Loughborough, Leicestershire, UK LEI 1 3TU Tel: +44 (0)1509 222585.Nikki Rathbone, HPLC Technology Ltd, Macclesfield, Cheshire, UK SKI 1 6PJ Tel: 01625 613848. Fax: 01625 616916 Dr. N. H. P. Smith, Chemistry Department, UMIST, P.O. Box 88, Sackville Street, Manchester, UK M60 1QD Tel: +44 (0)161 200 4491. Fax: +44 (0)161 236 7677 Dr. N. H. P. Smith, Chemistry Department, UMIST, P.O. Box 88, Sackville Street, Manchester, UK M60 1QD Tel: +44 (0)161 200 4491. Fax: +44 (0)161 236 7677 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 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/AN996210034N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, March 1996, Vol. 121 35N Conference Reports First Asia Pacific Symposium on Biosensors, Wollongong, Australia: December 4-6, 1995 This symposium was held at the scenic campus of the University of Wollongong set just beneath Mount Keira. It was organized by Professor G. Wallace (Intelligent Polymers Research Laboratory), and aimed to bring together scientists and industrialists in the Asia Pacific region working in the area of biosensors, to review recent scientific advances in this subject, as well as to discuss how the technology can by commercialized. The theme of commercialization was the subject of both the first and final talks. In the opening lecture, Dr. B. Cornell (AMBRI) gave an interesting account of how two companies in the biosensor area had gone about commer- cializing their respective products.He suggested that the best approach was for inventors to keep a low profile for as long as possible and not to oversell their technology, then to negotiate the field of use and maintain a clear strategy. In his address, Dr. N. Furlong (CSIRO) looked to the future and suggested that although very few biosensor products had emerged to-date in the market place, there was still scope for them to emerge, particularly in the environmental area (pesticide residues, hydrocarbon residuals, toxins, gaseous emissions, etc.). He suggested that some of the problems to date had been caused by the fact that ‘proteins are much smarter than those who choose to work with them’. New products would have to out-perform existing methods in terms of sensitivity, selectivity, time of analysis and cost, and provide new performance in terms of real- time measurements.In the main body of the conference, there were a number of interesting presentations. Dr. H. Weetall (NIST) discussed recent advances made in self-assembly of protein pores of 1-2 nm in diameter which could lead to the development of highly sensitive and specific sensors for cations and protein antigens and antibodies. He also alluded to work going on to develop an artificial retina based on the electro-optical properties of bacteriorhodopsin on semi-conducting electrodes, and on the use of tightly focused laser light trapping for the sub-attomolar detection of antigens (10-100 molecules in 1 pl of sample). Professor M. Haskard (University of South Australia) discussed the advances in microelectronics as they related to sensor array design, and how arrays of 100 X 100 are in the process of being developed on single chips.The use of neural networks to aid in the processing of information was discussed both by Professor M. Haskard and Dr. D. Levy (University of Sydney). The requirement for such data processing is needed for instruments such as the electronic nose. In his presentation, Dr. T. Gibson (University of Leeds) described how the ‘bloodhound electronic nose’ that is currently being developed as a commercial product based on a conducting polymer array can be used for odour monitoring. Since each individual has a characteristic odour, such an instrument could have widespread application from forensic science to cosmetics.It could also find use for the detection of bacterial or fungal contamination, monitoring of water quality, measurement of food volatiles, and the detection of oestrous in cows. The use of conducting polymers for studying biomolecular interactions was further discussed by Professor G. Wallace, who showed how large species such as antibodies and whole cells could be incorporated in the conducting polymer matrix. The theme of miniaturization was addressed by several speakers. Professor M. Haskard described how complete gas chromatographs and mass spectrometers could be micro- engineered on silicon wafers in dimensions of 2 in2. These may prove to be near-ideal sensors in the future, as they will be portable and therefore amenable to on-the-spot analysis.My talk described the development of a prototype clinical instru- ment for monitoring glucose and lactate in critical care situations. The system developed so far, is based on the combination of a microdialysis sampling system, a micro-total analysis system for solvent delivery and a micro-biosensor array detector. This development was a result of a joint collaboration between DCU, St. Vincent’s Hospital, Dublin, University of Vienna, Max Delbruch Centre (Berlin) and Ciba-Geigy (Bade). Dr. R. John (University of Wollongong) then described how a biosensor system could be incorporated directly in a micro- dialysis probe. Such instruments required multi-electrode potentiostats to operate the system, and the use of LabVIEW (National Instruments) for representation of the data (Le., virtual instrumentation).Many other themes were presented relating to specific transducers and on how particular molecules could be im- mobilized on their surfaces. The proper orientation of antibody molecules is still, however, proving difficult to solve. The use of sol gels is on the increase both in terms of new fibre optic and amperometric biosensors. Dr. D. Kaplan (US Army, Natick) and described some elegant studies on how pesticides such as parathion and methyl parathion would be detected at the ppb level based on the use of molecular assemblies incorporating alkaline phosphatase and measurement of the inhibition by c hemiluminescence. It was a very interesting meeting both in the scientific and social senses. The conference dinner was held in Carringtons, where the after-dinner entertainment was led by the conference chairman, giving excellent renditions of some Irish folk songs.Dr. A. Karayakin (Moscow State University) then sang some tearful Russian love songs, and we were also treated to an Australian poem from Dr. M. Imisides (University of Wollon- gong) and a classical guitar piece from Dr. N. Pasco (Lincoln University, New Zealand). Dr. D. Tallman (University of North Dakota) is to be congratulated for his ‘Stamina Award’. The darts trophy went to Dr. A. Hodgson and Mr. A. Mimnett of the ‘home’ team, who narrowly defeated myself and my Dutch colleague, Dr. W. von Bennekom (University of Utrecht). As ever, the seafood and Chardonnay was of excellent quality, and I am sure that everyone went home well satisfied, if a little tired from the travel and the inevitable late nights! The next conference in the series will be held in New Zealand in 1997.Professor Malcom R. Smyth Dublin City University, Ireland36N Analyst, March 1996, Vol. 121 BCEIA ’95, Beijing, China: October 24-27, 1995 The sixth Beijing Conference and Exhibition on Instrumental Analysis (BCEIA), a biennial international event (nicknamed ‘The Chinese PittCon’) was attended by 364 analysts. A general plenary session was opened by Professor E. Wang (Changchun Institute of Applied Chemistry) and a welcome address was given by Professor Xuewen Wu (Chinese Society of Magnetic Resonance). The first plenary lecture was given by Professor I. Giaever (Rensselaer Polytechnic Institute, Troy, New York, USA), the 1973 Nobel laureate for physics.Professor Giaever described in the lecture his very intelligent device Electronic Cell-substrate Impedance Sensing (ECIS) with cells cultured on 0.001 cm2 gold-film electrodes. The impedance is measured when cells attach and spread on these electrodes, their insulating membranes constraining the current and forcing it to flow beneath and between the cells. In the section entitled ‘Electron Microscopy’, Long Ba (University of Science and Technology, Hefei) reported that the fractal pattern in semiconductor/metal bilayer was sensitive to the non-equilibrium state of the Ge-Au/Au and Ge-Au-Ga/Au bilayer films. TEM was used to observe the microstructure change, and the fractal dimension was estimated.S. Zhou (Institute of Aeronautical Technology, Nanchang) determined the fractal dimension of fractured surfaces of steel samples under different heat treatments by secondary electron line scanning using an electron probe microanalyser. Microstructure evolution during the high-temperature corrosion and formation of nickel oxide on a nickel substrate was studied by M. Shao (Institute of Chemical Metallurgy, Beijing) using a specially designed scanning electron microscope. The surface layer microstructure of high manganese steel containing niobium was analysed by Zhongliang Shi (Jiao Tong University, Shanghai) using TEM. F. Li (Institute of Physics, Beijing) tested their empirical method for correcting the distortion of electron diffraction intensity by means of the structural information obtained from a high resolution electron microscope image, the tested sample being a crystal of high-temperature superconducting oxide YBa2Cu307 - x.Y. Takai (Osaka University, Osaka, Japan) described his method of defocus-modulation image processing which utilized through-focus images and a bipolar weighting function for the spherical aberration correction. H. Ris (University of Wisconsin, Madison, WI, USA) reported that high resolution SEM revealed a new structure on the intra-nuclear surface in a study of the nuclear pore complex and associated structures in nuclei isolated from Xenopus oocytes. G. Min (Peking University, Beijing) used electron microscopy and STM for in vitro investigation of the lamin assembly. In the joint symposium ‘Surfaces and Interfaces in Materials’ D.B. Williams (Lehigh University, Bethlehem, USA) described the detection of monolayer-level Gibbsian segregation such as Bi films on grain boundaries in Cu using X-ray energy- dispersive spectrometry. A study of the thin layer of oxygen at the boundary of copper shows that Cu is present as divalent CuO rather than monovalent Cu20. F.-R. Chen (Tsing University, Hsinchu, Taiwan) applied the energy filtering image technique coupled with TEM to study the interfacial segregation of Bi in the Cu and Au grain boundary and interfacial reaction of diamond film on silicon substrate. Y. Ishida (University of Tokyo, Japan) used high-resolution electron microscopy (HREM) to examine atomic structures of grain boundaries in vapour-grown diamond foil, nanocrystalline carbon 60, and buckled structures in heavily deformed carbon nanotube in searching new carbons as structural materials. Z.Zhang (Beijing Laboratory of Electron Microscopy, Beijing) used cross-sectional HREM to examine the diamond/silicon interface for diamond films prepared by hot-filament enhanced CVD on silicon substrate. These studies are very important as diamond film possesses a unique combination of properties and, therefore, may be regarded as the most suitable candidate for applications ranging from wear- resistant coating, optical windows for visible and infrared transmission, and high temperature electronic devices. Shun-Ichiro Tanaka (Research Development Corporation of Japan, Yokohama, Japan) described the electron stimulated desorption (ESD) process in TEM.D. H. Ping (Institute of Metal Research, Shenyang) reported the HREM studies of nanocrystalline-Pd(n-Pd), Ti-Ni-Si, Fe- Mo-Si-B and Ti-Si-Nd alloys. J. Dai from the same institution studied Ti(CN)-TiBZ multi-phase ceramics, NiAl matrix com- posite reinforced by TiB2 and Tic particulate. S. Horiuchi (National Institute for Research in Inorganic Materials, Ibaraki, Japan) examined the unusual microstructures at the boundary and surface of boron nitride crystals by using high resolution TEM (HRTEM). Y. Bando from the same institution developed a 300 kV analytical TEM with a field emission gun for elemental analysis at sub-nanometer to nanometer level re- gions. S. Wen (Institute of Ceramics, Shanghai) discussed the use of HREM for studies of Ni(Pd) particles, as these particles have been made for a variety of catalytic applications which very much depend upon their surface structure and composition.M. Avalos-Borja (Instituto de Fisica, Ensenada, B.C., Mexico) used HREM to identify crystalline nano-phase in catalysts such as bismuth molybdate, palladium on amorphous silica and tungsten on alumina (phosphorus promoted). V. S. Raghunathan (Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, India) used HREM to examine the defect structures in bulk and thin-film YBa2- CU307 - x. In the mass spectrometry session, Z. Guo (Peking University, Beijing) presented a very impressive overview of the Peking University AMS. According to N. M. M. Nibbering (University of Amsterdam, The Netherlands), the sophistication of high-performance mass spectrometers has reached such a level that they can be considered as complete laboratories by themselves. That is, following generation of ions (synthesis), species with a particular mlz value can subsequently be selected, modified and brought into reaction with suitable substrates, after which the ionic reaction products are detected and analysed.Examples have been shown including the reactions between metal carbonyl anions with methyl formate in the low-pressure cell of a Fourier transform ion cyclotron resonance MS. P. Van Espen (University of Antwerpen, Belgium) discussed the 3-D characterization of microscopic objects and surfaces by imaging SIMS. S. Yang (National Centre of Biomedical Analysis, Beijing) described the use of electrospray ionization (ESI) MS in biomedical research including determination of the molecular mass of proteins up to about 100 kDa with an accuracy better than 0.01% and the analysis of low mass (< 1000 Da) compounds. The liquid introduction probe for an ESI source has been designed by C.M. Whitehouse (Analytica of Branford, Brandford, USA) to especially accommodate interfacing with a capillary electrophoresis separation system. The isotope dilution MS has been used by K. G. Heumann (University of Regensburg, Germany) for elemental trace analysis of substances used in the production process ofAnalyst, March 1996, Vol. 121 37N microelectronic devices and the elemental speciation in the environment. S. Zhao (Zhongshan University, Guangzhou) described MALDI TOFMS.M. Rentzea (Max-Planck-Institut fur Medi- zinische Forschung, Heidelberg, Germany) studied electron- impact induced cyclization mechanisms of 1,12-bis- (dimethylamino)benzo[c]phenanthrenes using a four-sector MS. An ICP source was coupled by J. Cantle (UG Elemental Analysis, Winsford, Cheshire, UK) to a magnetic sector MS equipped with seven Faraday detectors. Isotopic ratio measure- ments revealed levels of internal and external precision comparable to those obtained using thermal ionization. A. Raith from the same institution reported the use of laser ablation (LA) to extend the capability of ICP-MS to the direct analysis of conducting and insulating solid materials. LA-ICP-MS pro- vides a full elemental coverage within minutes with minimal sample preparation.Russian scientists reported the use of continuous MS monitoring of the important uranium hexafluoride production process in nuclear industry (B. G. Djavaev, V. M. Golik, Ural Electrochemical Integrated Plant, Novouralsk, Russia). The session ‘Spectroscopy’ covered a wide variety of techniques. B. Huang (Xiamen University, Xiamen) reviewed the echelle spectrometers used for spectrochemical analysis. An electrothermal vaporization unit has been optimized by A. Golloch (Gerhard-Mercator University, Germany) for sample introduction into ICP for a new mercury determination system. The vaporization of tin or indium intermetallic compounds with the matrix modifier palladium was observed by K. Yasuda (Instrument Division, Hitachi, Japan) in ETAAS using TEM.A major disadvantage of electrothermal analyses has been the relatively long cycle time for each measurement cycle, The key point is the possibility of simultaneous multi-element analysis. The transverse heated atomizer (THGA) as described by W. Schrader (Bodenseewerk Perkin-Elmer, Germany) allows the use of identical conditions for volatile and non-volatile elements. G. Meng (Central Iron and Steel Research Institute, Beijing) used circular dichroism spectra of DNA to study the interaction of cisplatin and DNA. H. Chen (Changchun Institute of Applied Chemistry, Chang- chun) described a laser two-photon ionization technique in combination with conductimetry for sensitive detection of photo-absorbing molecules not only in non-polar solvents or on metal surface but also on aqueous solution surface.L. Luo (Institute of Rock and Mineral Analysis, Beijing) used the artifical neural network for the treatment of X-ray fluorescence (XRF) analysis data. Y. Harada (Shimadzu, Japan) described the IR microspectroscopic mapping as a powerful 3-D tool for material analysis. In the ‘Chromatography’ session, S. Terabe (Himeji Institute of Technology, Japan) discussed the ways of coupling the micellar electrokinetic chromatography (MEKC) as a mode of CE with MS, the problem to be solved being associated with the fact that ionic surfactants used in MEKC are hardly compatible with ESI. Three different approaches for MEKC-MS have been tested: ESI-MEKC-MS using high molecular surfactants; ESI- MEKS-MS employing the partially filling technique; and an atmospheric pressure ionization (APS1)-MEKC-MS.The APSI seems to have some advantages over ESI. K. Ballschmiter (University of Ulm, Germany) discussed the coupling of GC, LC, and CE with selective and sensitive detection devices such as different modes of MS. J. Pesek (San Jose State University, USA) discussed the surface modifications to support materials for HPLC, HPCE and electrochromatography . The hydride surface formation and the process of adding organic groups via hydrosilation are very practical approaches. It has been shown that the same approach used on porous silica can also be applied to capillary walls in order to make surfaces compatible with a wide variety of analytical situations. H. Liebich (University of Tubingen, Germany) reported the use of CE for the analysis of DNA fragments from angiotensis-I converting enzyme gene allowing the recognition of a deletion/ insertion polymorphism of the gene.The research on CE undertaken in the Institute of Chemistry, Beijing, has been reviewed by A. Zhu. Optical isomers of drugs such as timolol maleate, propanolol, brufenum and secobarbital were resolved by MEKC with the addition of beta-cyclodex- trin. The multi-column systems for separation of complex samples including isomers have been studied by P. Lu (Institute of Chemical Physics, Dalian). The analysis of an 86-pesticide mixture using capillary GC with electronic flow controller has been reported by S. Shibamoto (Shimadzu, Kyoto, Japan). H. Han (Institute of Chemistry, Beijing) reported the analysis of neurotransmitters of microdialysis samples using CE coupled with laser-induced fluorescence (LIF) detection. To improve the sensitivity of LIF, a fibre-coupled intensified ICCD was used by the same group to reach a mass detection limit below attomole level.H. Henriksson (University of Uppsala, Sweden) reported the chiral recognition using HPLC stationary phases immobilized with cellulose degrading enzymes cellobiohydrolase 1 (CBH 1) and enndoglucanase 1 (EG 1). CBH 1 phase showed much better resolution than EG 1 phase for chiral drugs. In the ‘Magnetic Resonance’ session, M. Hong (Fujian Institute of Research on the Structure of Matter, Fuzzhou) reported interesting research on transition metal cluster chem- istry using NMR and related tools.Using 13C CP/MAS NMR, Q. Chen (East China Normal University, Shanghai) observed the slow crystallization process of polyethylene at room temperature after melt-quenching. S. Zhang (Institute of Applied Chemistry, Changchun) discussed the research on the agents used in clinical NMR techniques enhancing the imaging contrast between the normal and diseased tissues or indicating the status of organ function or blood flow. Many kinds of Gd”1 compound have been tried and the results were quite encouraging. An interesting report on the automated assignment of proton resonance from 2D and 3D NMR spectra of proteins has been given by B. C. Sanctury (McGill University, Montreal, Canada). The algorithm was based on graph theory, fuzzy mathematics and pattern recognition.Carbon fibre has become an important material for industry, and 13C NMR is a suitable tool for investigation. Most carbon fibres contain free radicals and the unpaired electrons would couple strongly with the surrounding 13C nuclei, causing interferences to the NMR signal. J. Zhou (Institute of Physics, Wuhan) discussed the use of dynamic nuclear polarization to overcome the aforementioned problem. In the ‘Electroanalytical Chemistry’ session, H. D. Abruna (Cornell University, USA) discussed the process of the underpotential deposition of Cu on Pt on the basis of in situ surface EXAFS and X-ray standing waves. W. Gopel (University of Tubingen, Germany) discussed the molecular recognition process of chemical sensing based on supramolecular and biomimetic structures involving modified siloxanes, calixarenes, etc.The biosensors based on chemically modified electrodes were reviewed by S. Dong (Institute of Applied Chemistry, Changchun). J. Deng (Fudan University, Shanghai) described a sensitive and stable version of glucose biosensor based on immobilization of glucose oxidase in electropolymerized poly(o-aminophenol) film on a platinized glassy carbon elec-38N Analyst, March 1996, Vol. 121 trode. L. Gorton (University of Lund) modified CPE with enzymes for monitoring the fermentation process of producing biofuel from lignocellulose. D. Jagner (University of Goteborg and Chalmers University of Technology, Sweden) described the calibration-free stripping potentiometry of trace elements in nanomole concentration range based on the Faraday law.A. G. Fogg (Loughborough University of Technology, UK) reviewed the studies on sensors based on stripping voltammetry for the analysis of sulfonamides and thiols. K. Oldham (Trent University, Canada) presented the results of his theoretical treatment of the voltammetric effects of microelectrode geometry. S. Kihara (Kyoto Institute of Technology, Japan) reported the theoretical analysis for voltammetry of ion transfer at an interface between two immiscible electrolyte solutions (VI- TIES). The catalysis by enzymes entrapped in hydrated reversed micelles is a new trend in molecular biology. Making use of this concept, J. M. Pingarron (Complutense University of Madrid, Spain) developed the amperometric biosensors in reversed micelle systems as working media. This approach has some advantages as it is possible to solubilize both hydrophilic and hydrophobic substances, and it is easy to control the water content and immobilize the enzymes onto the electrode surfaces because enzymes are scarcely soluble in such reversed mi- celles. The electrochemistry of fullerenes and their derivatives has been studied by D. H. Evans (University of Delaware, Newark, USA). Some acidic species such as tert-BuCsoH have been reported. About 160 manufacturers and companies from 13 countries and regions exhibited their latest analytical instruments and related products. The Chinese analytical instrumentation in- dustry has made significant progress during the past few years. The BCEIA '95 was really a great success. The seventh BCEIA will be held in October 1997, but the location will move to Shanghai. The author of this report sincerely thanks Professor Y. Zhang, the deputy head of BCEIA Program Committee Office, for her valuable information and help. Professor Ru-Qin Yu Department of Chemistry and Chemical Engineering, Hunan University, China

ISSN:0003-2654    

DOI:10.1039/AN996210035N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, March 1996, Vol. 121 39N Future Issues Will Include Mediaeval Stained Glasses of Pisa Cathedral (Italy): Their Composition and Alteration Product-Andrea Orlando, Filippo Olmi, Gloria Vaggelli, Mauro Bacci Application of Partial Least Squares as an Alternative to Single Wavelength Molar Absorption Coefficients for Predicting Concentrations. Application to Electronic Absorption Spec- trometry of Chlorophyll-alpha-Y. Fukunaga, Pedro W. Araujo, Dragan A. Cirovic Influence of the Method of Calculation of Noise Thresholds on Wavelength Selection in Windows Factor Analysis of Diode- array High-performance Liquid Chromatography. Application to Chlorophyll Degradation Mixtures-R. G. Brereton, Abdallah K. Elbergali, Ali Rahmani Flow Dissolution of Diphenylcarbazide for Chromium(v1) Determination-Osvaldo E.Troccoli, Francisco J. Andrade, Mabel B. Tudino Thin Plastic Film Colorimetric Sensors for Carbon Dioxide: Effect of Plasticizer on Response-Andrew Mills, Lela Monaf Autocatalytic Decomposition of Cobalt Complex as an In- dicator System for the Determination of Trace Cobalt and Infectors-Takao Yotsuyanagi, Masatoshi Endo, Masahito Ishihara Determination of Impurity Elements in Graphite by Acid Decomposition-Inductively Coupled Plasma Atomic Emission Spectrometry-Kazuo Watanabe, Jun Inagawa Determination of Cadmium, Copper and Lead in Cervine Liver and Kidney by Slurry Injection Electrothermal Atomic Absorp- tion Spectrometry-William D. Marshall, Yanxi Tan, Jean- Simon Blais Electrochemical Reduction at Mercury Electrode and Differ- ential-pulse Polarographic Determination of Dibucaine-M.San M. Fernandez-Marcote, M. Callejon Mochon, J. C. Jimenez Sanchez, A. Guiraum Perez Organic Microheterogeneous Systems in Kinetic Analysis. Non-covalent Polymeric Assemblies. A Review-Dolores Perez-Bendito, Maria Lopez Carreto, S. Rubio Conditions of Solid-phase Extraction of Agricultural Chemicals in Waters by Using the Partition Coefficient of Octanol- Water-Motoshi Nakamura, Masatoshi Nakamura, Shinkichi Yamada Thermal Lens Determination of Vanadium(v) and its Activators by Reaction of Oxidation on Aniline by Bromate Ions- Michael A. Proskurnin, Nataliya V. Osipova, Vera V. Kusnetsova, E. K. Ivanova, A. G. Abroskin Future Prospects for the Analysis of Complex Biological Systems Using Microcolumn Liquid Chromatography-Electro- spray Tandem Mass Spectrometry-John R.Yates, Ashley L. McCormack, Andrew J. Link, David Schieltz, Jimmy Eng, Lara Hays Artificial Neural Networks and Partial Least Squares Regres- sion for Pseudo-first-order With Respect to the Reagent Multicomponent Kinetic-Spectrophotometric Determina- tions-Marcel0 Blanco, J. Coello, Hortensia Iturriaga, Santiago Maspoch, Miguel Redon, Nuria Villegas Automation of a System for Titrimetric Measurements. Cata- lytic Thermometric Titrations of Organic Bases-Biljana F. Abramovic, Sanja D. Tepavcevic, Borislav K. Abramovic, Ferenc F. Gaal Proton Nuclear Magnetic Resonance Determination of Hexam- ethylenetetramine in the Presence of Formaldehyde and Urine-Bruno Jaselskis, Gary L. Madsen, David S. Crumrine Influence of Pesticide-Soil Interactions on the Recovery of Pesticides Using Supercritical Fluid Extraction-John R.Dean, Ian J. Barnabas, Susan P. Owen Flow Injection Fourier Transform Infrared Determination of Paracetamol in Pharmaceuticals-Miguel de la Guardia, Zouhair Bouhsain, S. Garrigues Kinetic Separation of Amperometric Sensor Responses- Robert J. Forster Moisture-activated, Electrically Conducting Bioadhesive Inter- faces for Biomedical Sensor Applications-A. D. Woolfson Characterization of Carbon Paste Electrodes In Vitro for Simultaneous Amperometric Measurement of Changes in Oxygen and Ascorbic Acid Concentrations In Vivo-Marianne Fillenz, John P. Lowry, M. G. Boutelle, Robert D. O'Neill Detection of Quinine and its Metabolites in Horse Urine by Gas Chromatography-Mass Spectrometry-R. G.Brereton, Cevdet Demir, M. C. Dumasia Chronoamperometric Method Used to Study the Effect of Lanthanide Ions on the Initial Kinetics of Glutamate Dehy- drogenase-Xiao Xia Gao, Wen Kuan Xin Novel Approach to Speciation of Aluminium by Employing Fast Protein Cation-exchange Liquid Chromatography-In- ductively Coupled Plasma Atomic Emission Spectrometry- Bojan Mitrovic, Radmila Milacic, Boris Pihlar Solvent Ex trac tion-S equen tial Injection Without Segmentation and Phase Separation Based on the Wetting Film Formed on a Teflon Tube Wall-Gary D. Christian, Yongyi Luo, Rashed Al-Othman, Jaromir Ruzicka 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)17 1-287 9798. Telecom Gold 84: BUR2 10. Electronic Mailbox (Internet) LIBRARY@RSC.ORG. If the material is not available from the Society's Library, the staff will be pleased to advise on its availability from other sources. Please note that copies are not available from the RSC at Thomas Graham House, Cambridge.

ISSN:0003-2654    

DOI:10.1039/AN996210039N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

40N Analyst, March 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 A D ADC ANOVA AOAC ASTM bP BSA BSI CEN cpm CMOS c.m.c. CRM CVAAS cw CZE dc DRIFT DELFIA DNA EDTA ELISA emf ETAAS EXAFS EPA FAAS FAB dPm FAO-WHO FIR FT FPLC FPD GC GLC HGAAS HPLC ICP id INAA IR ISFET iv im IGFET ISE LC LED LOD LOQ 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 assay electromotive force electrothermal atomic absorption spectrometry extended X-ray absorption fine structure spectroscopy Environmental Protection Agency flame atomic absorption spectrometry fast atom bombardment Food and Agriculture Organization, far-infrared Fourier trans form fast protein liquid chromatography flame photometric detector gas chromatography gas-liquid chromatography hydride generation atomic absorption high-performance liquid inductively coupled plasma internal diameter instrumental neutron activation infrared ion-selective effect transistor intravenous intramuscular insulated gate field effect transistor ion-selective electrode liquid chromatography light emitting diode limit determination limit of quantification World Health Organization spectroscopy chromatography analysis 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 I-IllS rpm RNA SCE SE SEM SIMS SIMCA S/N SRM STM STP TIMS TLC TOF TGA TMS tri s TRIS uv UV/VIS VDU XRD XRF YAG Commonly Used Symbols M Mr r S U 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 polycyclic 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-1) poly(tetrafluoroethy1ene) poly(viny1 chloride) poly(diviny1 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 scanning/surface (reflection) electron microscopy 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 spectrometry thin-layer chromatography time-of-flight thermogravimetric analysis trimethylsilane 2-amino-2-(hydroxymethyl)- propane- 1,3-diol (ligand) 2-amino-2-(hydroxymethyl)- propane-l,3-diol (reagent) ultraviolet ultraviolet-visible visual display unit X-ray diffraction X-ray fluorescence yttrium aluminium garnet emission analogy microscopy molecular mass relative molecular mass correlation coefficient standard deviation atomic mass

ISSN:0003-2654    

DOI:10.1039/AN996210040N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, March 1996, Vol. 121 (275-278) 275 What Exactly is Fitness for Purpose in Analytical Measurement? Michael Thompson" and Tom Fearnb a Department of Chemistry, Birkbeck College, University of London, Gordon House, 29 Gordon Square, London, UK WCIH OPP h Department of Statistical Science, University College London, Gower Street, London, UK WCI E 6BT Fitness for purpose is the principle universally accepted among analytical scientists as the correct approach to obtaining data of appropriate quality. Yet few analytical scientists or end-users of data are in a position to specify exactly what quality of data is required for a specific task. A definition of fitness for purpose based on minimal expected loss is proposed in this paper. This idea enables one to develop optimal strategies for apportioning resources between sampling and analysis, and for balancing technical costs with end-user losses due to error.Keywords: Fitness for purpose; loss functions; quality; sampling Introduction A definition of fitness for purpose (FFP) is 'the property of data produced by a measurement process that enables a user of the data to make technically correct decisions for a stated purpose'.' FFP therefore refers to the magnitude of the uncertainty associated with a measurement in relation to the needs of the application area. In some fields of analysis only a very small relative uncertainty can be tolerated. For instance, a very high accuracy would be called for in an analysis used for negotiating a price for a consignment of scrap gold. In contrast, in geochemical prospecting for gold, where the purpose is essentially to distinguish locations that contain low but interesting concentrations of gold from those that do not, a relative uncertainty of 20% is probably all that is required.In the latter case a highly accurate analysis would be not only unnecessary but also prohibitively expensive. Two general conclusions can therefore be drawn: first, FFP demands sufficient but only necessary accuracy in analysis, and second, purely scientific requirements may be constrained by financial considerations. The uncertainty used to express FFP is strongly related to all aspects of data quality in analytical science. The relationships among these concepts and practices are shown schematically in Fig. 1. A capability for expressing FFP quantitatively and a method for estimating the appropriate value are evidently prerequisites for conducting effective proficiency test$ inter- nal quality control3 and method performance studies (collab- orative trials).4>5 In some areas of analysis this requirement for quantitative information has already been addressed.For example, in applied geochemistry and environmental science, minimal requirements for quality of sampling and analysis have been formulated in relation to the needs of interpretation, although financial constraints have yet to be included in the models.6-10 In clinical biochemistry, empirical rules on data quality have been related to variations between and within patients.11.12 In other areas the interdependence between costs and the quality of data has been noted but not developed into a useful too1.l3,I4 A minimal expected loss approach has been touched upon but not developed.15 At present, however, there seems to be no systematic approach to estimating the uncertainty that specifies FFP.In common practice, FFP criteria are based simply on professional experience. While the value of that cannot be gainsaid, a demonstrably correct estimate is more likely to dispel contention. This paper investigates the possibility of a rational approach to FFP in some typical situations involving end-user decisions based on data obtained by the chemical analysis of a sample. General Approach to Fitness for Purpose Costs of Sampling and Analysis Typically when we analyse a material, we first take a sample and then analyse it.Consider the result x of such a process, which can be broken down as follows: x = true value + sampling error + analytical error from which we have the uncertainty of x expressed as a variance v given by v = v,,, + v, where vSam and vm are the variances of the uncertainties associated with sampling and analysis, respectively. What is the optimum relationship between the values of v,, and v, in the Fig. 1 Relationship between fitness for purpose expressed as uncertainty and other concepts and practices relating to quality in analytical science.276 Analyst, March 1996, Vol. 121 context of end-user requirements? This relationship is akin to a well known problem in sample survey statistics.16 The answer depends in part on the relative costs of sampling and analysis.First, we need to consider the costs of improving precision. Higher precision implies higher costs for both the analyst and the sampler. Suppose the cost of an analysis by a particular method characterised by Oan = 1 is B (where Oan = G). What is the cost of a result with double that precision, i.e., (3, = O S ? We could always achieve the improved precision by using the mean of four separate results obtained by the original method at a cost of 4B. In practice, we would be more likely to modify or change the method to achieve the required precision. Nevertheless, at worst we do not need to spend more than 4B. Consequently, we can say that the cost of analysis L, is limited by L, = B/v, (1) L,, = A/vs, (2) The constants A and B would be established at some fixed value of variance in a particular method.Eqns. (1) and (2) could be called the ‘cost rules’ for sampling and analysis. To put these costs into context, we have to consider the financial losses Lend that would be incurred by the end-user of the data as a result of the total error involved in obtaining the measurement. That would depend on the specific purpose to which the data would be put, but in general we could anticipate that increased errors resulting from higher uncertainty variances would have a financial penalty for the end-user. Therefore, there must be optimum values of v,, and Van at which the loss function L given by Likewise, the cost of sampling is limited by L = Lend + L a m + Lm is minimized. We suggest that this minimum defines values of v,, and van that are ‘fit for purpose’.Optimal Division of Resources Between Sampling and Analysis This optimization can be considered in two parts: first, what choice of v = v,, + v, balances cost with potential loss?, and second, what is the best division of resources between sampling and analysis at that particular value of v? Initially, we consider the second question, which can be posed as finding min ($+$ (3) given a fixed v = v,, + v,. This kind of constrained minimization can be effected by use of a Lagrange multiplier h. If we define f = A/vsa, + B/van + h(vS, + van - V ) the minimum is found by solving the simultaneous equations After some algebra, we find at the minimum which gives I A “-=v‘- van B The combined cost of this optimal sampling and analysis is D/v, where D = ( f l + f l ) 2 .Eqn. (5) is an important general result applicable to allocating resources between sampling and analysis in a wide range of situations. The first part of the optimization can now be defined as minimizing the loss function L = Lend + D/v with respect to the variance v, which is then subsequently apportioned between v,, and v , according to Eqn. (4). Some examples of this procedure follow. (Readers should note that the symbol L is used generically throughout the paper to indicate the particular loss function under consideration at that point.) Establishing the Value of a Commodity by Analysis Consider the case where a lot of a material is being valued by assay of the principal constituent.This is a common reason for conducting analysis. As a general approach, we consider a situation where the loss to the end-user due to the total error E in obtaining the measurement increases with the magnitude of the error in some way. As a specific example we could postulate that Lend = CE2 where E = x - c, c is the true concentration of the analyte and C is a constant. This is called the ‘cost function’, and is illustrated in Fig. 2. The cost function adopted here implies that errors in either direction cause a loss to the end-user and it markedly penalizes large errors. The total cost is therefore L = C E ~ + D / V In any particular instance, the value of E will be unknown but its distribution may be known or assumed. Then we may consider the expected cost (the prior expected loss), which is the expectation of L over the distribution of E, i.e., E(L) = C E ( E ~ ) + D/v If the sampling and analytical methods are unbiased, E will have a mean of zero and a variance v, so that E ( E ~ ) is just v, and E(L) = Cv+ D/u This is minimized when which gives v = e v,, = v m v , = V I K whence Thus, by adopting a particular cost function we are able to establish optimum (fit for purpose) values for sampling and analytical uncertainties.Error ( E ) Fig. 2 combined sampling and analytical error. A hypothetical quadratic cost function based on the magnitude ofAnalyst, March 1996, Vol. 121 277 An alternative and reasonably realistic type of loss function that could be considered is Lend = c I E I illustrated in Fig. 3. Then the total loss would be L = C l ~ l +Dlv To find the expected loss, we need further assumptions about the distribution of E.In particular, if E - N(O,a*), then E( I E I ) = a m , so that I E(L) = C - '," +D/v Again, this is minimized by setting the derivative to zero, which gives v = [ 2 4 $ ] ": v,, = v 6 v, = v JT Hence, when these simple cost functions are used, algebraic solutions to the minimization are obtainable. Not all simple cost functions provide algebraic solutions, however. Use of an Empirical Cost Function Rather than use a general symmetrical loss function as above, we could construct an empirical function that refers to specific end-user requirements. For example, the end-user might specify a maximum tolerable loss due to errors in the process of making the measurement.Loss would be occasioned by the total error E having a positive value and, as a consequence, the purchaser paying for more of the analyte than was actually present in a consignment of the commodity. A tolerable loss could, for instance, be defined in relation to a limit E~ on the error. Of course, the average error would be zero, but the loss function used here represents an extreme aversion to overpayment. The loss function investigated takes the form 0 if E < EI C if E b E~ I Loss = L illustrated in Fig. 4. The expected cost function would be E(L) = CPr(E b ~ 1 ) + Dlv and if we assume E - N(O,v), then where Q, is the standard normal cumulative distribution function. Error (E) Fig. 3 of the combined sampling and analytical error. A hypothetical cost function proportional to the absolute magnitude This expression cannot be minimized analytically, but a variety of other methods are available to obtain a solution.For example, given the parameters A = &1000, B = &loo, C = S10000 and ~1 = I, simply plotting the cost L as a function of a = fi (Fig. 5 ) shows a minimum of about &3300 at a total standard deviation of about 1.2 units. Moreover, the plot shows the rapidly escalating costs of using a smaller uncertainty than necessary compared with the costs of above-optimal un- certainty. The indication, perhaps unexpected, is that we should in this instance err, if at all, on the side of higher uncertainty. That is probably sufficient information for most purposes. Manufacture of a Material with an Upper Bound for an Impurity Consider the manufacture of a material that has an upper limit y 1 for some undesirable but ubiquitous constituent.This is another common reason for conducting analysis. If a batch of the material is prepared and found by analysis to be above the limit, then it must be discarded. It is possible to construct a hypothetical system with these characteristics that illustrates the estimation of a fitness for purpose criterion. Let us assume that the cost L,f, of the manufacture of a batch varies with the intended level ( c ) of the contaminant: the lower the intended level the greater the cost of production, according to the equation L,fr = R + SIC where R and S are constants. As before, the cost of sampling and analysis is given by Ltot = L,,, + L, = D/v so the prima facie cost of preparing a batch of the product is L' = L,f, + Lto, = R + SIC + D/v El Error ( E ) Fig.4 an arbitrary limit E ~ . An empirical loss function where loss occurs only if error exceeds 6000 1 3000 I I I I 0.0 0.5 1 .o 1.5 2.0 Total standard deviation Fig. 5 The loss associated with the empirical loss function in Fig. 4, as a function of combined standard deviation of sampling and analysis, showing the magnitude and shape of the function near the minimum.278 Analyst, March 1996, Vol. 121 /“=2 /c:4.5 5 f j- 20 0 1 2 3 4 5 6 7 8 9 1 0 1 1 Concentration unlts Fig. 6 Hypothetical system balancing manufacturing costs against costs of sampling plus analysis. When the targetted concentration of a contaminant c = 2 units there is virtually no chance of batch rejection, given the distribution of the measured concentration y’.For the optimal solution, when c = 4.5 and the combined standard deviation of sampling and analysis 0 = 1.4 units, there is a probability of about 0.07 that the resulting measurement exceeds the limit y1 - 20. Suppose, however, that the level of contaminant actually achieved (y) varies around the intended mean according to the distribution y - N(c,o,?) where oJc = 0.25. A proportion of the batches will be wasted if they are rejected by the analytical test. If p is the probability of rejection for a single batch, then the long-run proportion of batches accepted is 1 - p and the effective cost per accepted batch is R + S/c + D/v L’ E(L) = - - - 1 - P 1-P The value of p is determined by both the distribution of the batch concentration and the uncertainty of sampling and analysis (Fig.6). A rational policy would be to retain the batch so long as the analytical measurement was below the specifica- tion limit for the analyte y1 by at least two standard deviations of the measurement error. Hence, writing o = 6, we have R + S/c + 0 1 0 2 1 - Pr(y’ > y1 - 20) E(L) = where y’ is the measured value of y. If the distribution of y’ given c is then the expected loss is E(L) = R + S/c + D/a2 y1- 20 - c @( v m ) This cost function can be minimized numerically with respect to the intended concentration c and the uncertainty variance. For a given choice of parameters, contours of cost can be plotted as a function of c and 0.For example, if we choose R = &200, S = &1000, D = 2200 and y1 = 10 concentration units, the cost function shown in Fig. 7 is obtained. This shows a minimum batch cost of &561 at 0 = 1.4 concentration units with a target concentration of the contaminant at c = 4.5 units. Under the optimum conditions, about 7% of the batches are rejected. It would be possible to elaborate the cost function further by considering the possible penalties associated with false accep- tance of a batch of product that in fact did not comply with requirements. However, that consideration is beyond the scope of this paper. 0 3 2 I I I I 0 1 2 3 4 CT Fig. 7 Production costs as a function of the targeted concentration c of the contaminant and the combined standard deviation of sampling and analysis u.shown as contour lines with a well defined minimum. sampling and analysis should be appropriate, given the purpose of the measurement and the likely consequences of error. A natural way to formalize this idea is to set up optimization situations of the type presented above. However, the point of this paper is not to recommend the particular loss functions in the examples but to demonstrate (i) that there are well established methodologies for dealing with this type of problem and (ii) that the solutions are often fairly simple. In practice, it would often be difficult to quantify costs and losses exactly. Further, it may not be possible to implement an optimal solution exactly-we would tend to use the available methods of analysis and sampling that best approximated the optimum requirement.Even so, a knowledge of where the optimum lies and the shape of the minimum, given a reasonable guess at the costs, will at least serve as a warning when the proposed sampling and analytical methods are not appropriate. This will not always be because methods of smaller uncertainty should be used-sometimes the warning will be that expensive methods are not justified by the purpose for which they are proposed. References 5 6 7 8 9 10 11 12 13 14 15 16 Thompson, M., and Ramsey, M. H., Analyst, 1995, 120, 261. Thompson, M., and Wood, R., Pure Appl. Chem., 1993,65,2123. Thompson, M., and Wood, R., Pure Appl. Chem., 1995,67,649. Accuracy (Trueness and Precision) of Measurement Methods and Results, IS0 5725 : 1994, International Standards Organization, Geneva, 1994. Horwitz, W., Pure Appl. Chem., 1995, 67, 332. Handbook of Exploration Geochemistry, Vol. 2: Statistics and Data Analysis in Geochemical Prospecting, ed. Howarth, R. J., Elsevier, Amsterdam, 1983, pp. 92-107. Ramsey, M. H., Thompson, M., and Hale, M., J. Geochem. Explor., 1992, 44, 23. Ramsey, M. H., Appl. Geochem., 1993,2, 149. Ramsey, M. H., in Sampling of Environmental Materials for Trace Analysis, ed. Markert, B., VCH, Weinheim, 1994, pp. 93-108. Thompson, M., and Maguire, M., Analyst, 1993, 118, 1107. Tonks, D., Clin. Chem., 1963, 9, 217. Fraser, C. G., Petersen, P. H., Ricos, C., and Haekel, R., Eur. J . Clin. Chem. Clin. Biochem., 1992, 30, 31 1. Lundell, G. E. F., Znd. Eng. Chem., Anal. Ed., 1933, 5, 221. Horwitz, W., J. Assoc. Off. Anal. Chem., 1983, 66, 1295. Massart, D. L., Vanderginste, B. G. M., Deming, S. N., Michotte, Y., and Kaufman, L., Chemometrics: a Textbook, Elsevier, Amsterdam, Hansen, M., Sample Survey Methods and Theory, Wiley, New York, 1988, pp. 141-147. 1953, pp. 221-223. Conclusions If fitness for purpose is to mean anything concrete, the concept must be based on the premise that the resources allocated to Paper .5/06045A Received September 13, I995 Accepted November 9, I995

ISSN:0003-2654    

DOI:10.1039/AN9962100275

出版商:RSC    

年代:1996

数据来源: RSC