摘要:

ThAna I y stThe Analytical Journal Of The Royal Society Of ChemistryAssociate Scientific Editors*Chairman: Professor James N. Miller(Department of Chemistry, Loughborough University of Technology, UK)Dr Yngvar Thomassen (Arbeidsmiljo Instituttet,Oslo, Norway)Professor Colin S. Creaser (Department ofChemistry and Physics, Nottingham TrentUniversity, UK)Professor Pankaj Vadgama (Department ofMedicine, University of Manchester, UK)Professor Malcolm R. Smyth (Department ofChemical Sciences, Dublin City University, Eire)*All ASEs are also members of the Analytical Editorial Board.US ASSOCIATE EDITOR, Julian F. TysonDepartment of Chemistry, University of Massachusetts, Box 34510 Amherst, MA 01003-451 0, USATelephone: +I 413 545 0195; Fax: +1 413 545 4846; E-mail: TYSON@CHEM.UMASS.EDUAnalytical Editorial BoardChairman: Professor J.N. Miller (Loughborough, UK)A. G. Davies (London, UK)A. G. Fogg (Loughborough, UK)S. J. Hill (Plymouth, UK)A. Manz (London, UK)R. M. Miller (Gouda, The Netherlands)H. S. Minhas (Cambridge, UK)B. L. Sharp (Loughborough, UK)P. C. White (Glasgow, UK)N. W. Barnett (Victoria, Australia)K. D. Bartle (Leeds, UK)A. M. Bond (Victoria, Australia)R. G. Brereton (Bristol, UK)U. A. Th. Brinkman (Amsterdam, TheA. C. Calokerinos (Athens, Greece)P. Camilleri (Harlow, UK)P. R. Coulet (Lyon, France)D. Diamond (Dublin, Eire)L. Ebdon (Plymouth, UK)H. Emons (Julich, Germany)J. P. Foley (Villanova, PA, USA)M. F. Gine (Sao Paulo, Brazil)L. Gorton (Lund, Sweden)S. J.Haswell (Hull, UK)Advisory BoardA. Hulanicki (Warsaw, Poland)S. Lunte (Lawrence, KS, USA)F. Palmisano (Bari, Italy)J. Pawliszyn (Ontario, Canada)T. B. Pierce (Harwell, UK)J. RDtiCka (Seattle, WA, USA)I. L. Shuttler (Uberlingen, Germany)K. Stulik (Prague, Czech Republic)J. D. R. Thomas (Wrexham, UK)K. C. Thompson (Rotherham, UK)M. Thompson (Toronto, Canada)M. Valcarcel (Cordoba, Spain)C. M. G. van den Berg (Liverpool, UK)J. Wang (Las Cruces, NM, USA)I. D. Wilson (Macclesfield, UK)Netherlands)Publishing Division, AnalyticalManaging Editor, Harpal S. MinhasDeputy Editor, Sarah J. R. Williams Editorial Secretaries: Claire Harris; Frances ThompsonTelephone: +44(0)1223 420066; Fax: +44(0)1223 420247; E-mail: ANALYST@RSC.ORGProduction Division, AnalyticalProduction Manager, Janice M.GordonProduction Editor, Caroline Seeley Technical Editors: Judith Frazier, Ziva Whitelock, Roger A. YoungSecretary: Lesley TurneyTelephone: +44(0) 1223 420066; Fax: +44(0) 1223 423429; E-mail: ANALPROD@RSC.ORGFor enquiries relating to manuscripts from receipt to acceptance, contact the Publishing Division, andfor enquiries relating to manuscripts post-acceptance contact the Production Division, Royal Society ofChemistry, Thomas Graham House, Science Park, Milton Road, Cambridge, UK CB4 4WFAdvertisements: Advertisement Department, The Royal Society of Chemistry, Thomas Graham House,Science Park, Milton Road, Cambridge, UK CB4 4WF.Telephone +44(0)1223 432243. Fax +44(0)1223 42601 7.information for AuthorsFull details of how to submit material for publicationin The Analyst are given in the Instructions toAuthors in the January issue. Separate copies areavailable on request.The Analyst publishes original research papers,critical reviews, tutorial reviews, perspectives,news articles, book reviews and a conferencediary.Original research papers.The Analystpublishes full papers on all aspects of the theoryand practice of analytical chemistry, fundamentaland applied, inorganic and organic, includingchemical, physical, biochemical, clinical,pharmaceutical, biological, environmental,automatic and computer-based methods. Paperson new approaches to existing methods, newtechniques and instrumentation, detectors andsensors, and new areas of application with dueattention to overcoming limitations and tounderlying principles are all equally welcome.Full critical reviews.These must be a criticalevaluation of the existing state of knowledge on aparticular facet of analytical chemistry.Tutorial reviews. These should be informallywritten although they should still be a criticalevaluation of a specific topic area. Some historyand possible future developments should be given.Potential authors should contact the Editor beforewriting reviews.Perspectives. These articles should provideeither a personal view or a philosophical look at atopic relevant to analytical science. Alternatively,they may be relevant historical articles.Perspectives are included at the discretion of theEditor.Particular attention should be paid to the use ofstandard methods of literature citation, includingthe journal abbreviations defined in ChemicalAbstracts Service Source Index.Whereverpossible, the nomenclature employed should followIUPAC recommendations, and units and symbolsshould be those associated with SI.Every paper will be submitted to at least tworeferees, by whose advice the Editorial Board ofThe Analyst will be guided as to its acceptance orrejection. Papers that are accepted must not bepublished elsewhere except by permission.Submission of a manuscript will be regarded as anundertaking that the same material is not beingconsidered for publication by another journal.Associate Scientific Editors.For the benefit ofall potential contributors wishing to discuss thescientific content of their paper(s) a Group ofAssociate Scientific Editors exists. Requests forhelp or advice on scientific matters can be directedto the appropriate member of the Group (accordingto discipline). Currently serving Associate ScientificEditors are listed in each issue of The Analyst (andAnalytical Communications).Manuscripts (four copies typed in double spacing)should be addressed to:H. S. Minhas, Managing Editor, orJ. F. Tyson, US Associate EditorAll queries relating to the presentation andsubmission of papers, should be addressed to thePublishing Division and any correspondenceregarding accepted papers and proofs, should bedirected to the Production Division for The Analyst.Members of the Analytical Editorial Board (whomay be contacted directly or viathe Editorial Office)would also welcome comments, suggestions andadvice on general policy matters concerning TheAnalyst.There is no page charge.Fifty reprints are supplied free of chargeThe Analyst (ISSN 0003-2654) is published monthly by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge,UK CB4 4WF.All orders, accompanied with payment by cheque in sterling, payable on a UK clearing bank or in US dollars payable on a US clearing bank, shouldbe sent directly to The Royal Society of Chemistry, Turpin Distribution Services Ltd., Blackhorse Road, Letchworth, Herts, UK SG6 1 HN. Turpin Distribution ServicesLtd., is wholly owned by the Royal Society of Chemistry.1996 Annual subscription rate EC f487.00, USA $923.00, Rest of World f499.00. Purchased with AnalyticalAbstracts EC f951 .OO, USA $1 804.00, Rest of World f975.00. Purchased with Analytical Abstracts plus Analytical Communications EC f 1 123.00, USA $21 29.00,Rest of World fl151 .OO. Purchased with Analytical Communications EC f610.00, USA $1 156.00, Rest of World f625.00. Air freight and mailing in the USA byPublications Expediting Inc., 200 Meacham Avenue, Elmont, NY 1 1003.USA Postmaster: Send address changes to: The Analyst, Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 1 1003. Periodicals postage paid atJamaica, NY 11431. All other despatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outside Europe. PRINTED IN THE UK.0 The Royal Society of Chemistry, 1996. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form,or by any means, electronic, mechanical, photographic, recording, or otherwise, without the prior permission of the publishers

ISSN:0003-2654    

DOI:10.1039/AN99621FX054

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

ANALAO 121(12) 1747-1992, 169N-178N (1996) DECEMBER 1996ICONFERENCE PAPERSFOREWORD 1747GUEST EDITORS 1749ORAL PRESENTATIONS 17511759176317691775)I1779178917951801180518711817POSTER PRESENTATIONS 182318291835183918451851185518631869'""An al y s tThe analytical journal of The Royal Society of ChemistryCONTENTSThe Sixth European Conference on ElectroanalysisProfessor David Parker, Professor Arthur K. Covington, Professor Brian J. Birch and Dr. Arnold G. FoggRigid Carbon-Polymer Biocomposites for Electrochemical Sensing-A Review-Salvador AlegretRecent Evolution of Luminescent Photoinduced Electron Transfer Sensors-A Review-A. Prasanna deSilva, Thorfinnur Gunnlaugsson, Terence E. RiceSensing of Transition Metals Through Fluorescence Quenching or Enhancement-A Review-LuigiFabbrizzi, Maurizio Licchelli, Piersandro Pallavicini, Donatella Sacchi, Angelo TagliettiDirect Monitoring of Formaldehyde Vapour and Detection of Ethanol Vapour Using Dehydrogenase-basedBiosensors-Manus J.Dennison, Jennifer M. Hall, Anthony P. F. TurnerChromogenic Reagents-Mark Dolman, Andrew J. Mason, K. R. A. Samankumara Sandanayake, AndrewSheridan, Alastair F. Sholl, Ian 0. SutherlandMicro-optical Ring Electrode: Development of a Novel Electrode for Photoelectrochemistry-Gaelle I.Pennarun, Colin Boxall, Danny O'HareElectrochemical Studies of Zinc in Zinc-Insulin Solution-Rui M. Barbosa, Luis M. Rosario, Christopher M.A. Brett, Ana Maria Oliveira BrettTitrations With Electrogenerated Halogens in the Diffusion Layer of an lnterdigitated MicroelectrodeArray-DuSan Bustin, Stanislav Jursa, Peter TomCikElectrochemistry of the Nitroprusside Ion.From Mechanistic Studies to Electrochemical Analysis-HelenaM. Carapuca, Joao E. J. Simao, Arnold G. FoggHot-wire Electrodes: Voltammetry Above the Boiling Point-Peter Grundler, Andreas Kirbs, TadesseZerihunElectrochemical and Thermal Behaviour of Calcium-selective Membranes-Arthur K. Covington, EugeniaTotuOver-oxidized Polypyrrole-modified Carbon Fibre Ultramicroelectrode With an Integrated Silver/SilverChloride Reference Electrode for the Selective Voltammetric Measurement of Dopamine in ExtremelySmall Sample Volumes-Xueji Zhang, Bofidar Ogorevc, Gabrijela TavCar, lrena Grabec SveglImpedance Spectroscopic Study on Single-piece All-solid-state Calcium-selective Electrode Based onPolyaniline-Tom Lindfors, Johan Bobacka, Andrzej Lewenstam, Ari lvaskaSensitive and Specific Electrochemical Sensors for Charge-diffuse Cations: Use of Lipophilic Cyclodextrinsand an Enzyme Relay for the Determination of Acetylcholine-Ritu Kataky, David ParkerDetermination of Total Arsenic in Soils by Differential-pulse Cathodic Stripping Voltammetry-I.Eguiarte,R. M. Alonso, R. M. JimenezSolid-phase Extraction Coupled With Electrochemical Detection for the Determination of the HerbicideBromofenoxim in Water Samples at Low- and Sub-pg I-' Levels-lrena Grabec Svegl, Bofidar Ogorevc,Milko NoviC, Emilio BenfenatiDetermination of Small Amounts of Analytes in the Presence of a Large Excess of One Analyte FromMulti-analyte Global Signals of Differential-pulse Voltammetry and Related Techniques With the SignalRatio Resolution Method-Zorana Grabaric, Bofidar S.Grabaric, Miquel Esteban, Enric CasassasWall-jet Flow Cell for Stripping Potentiometry-Roongroje Ratana-ohpas, Waraporn Ratana-ohpas,Proespichaya Kanatharana, Daniel JagnerInterpretation of Speciation Measurements on Labile Metal-Macromolecular Systems by VoltammetricTechniques-J. L. Garces, F. Mas, J. Cecilia, J. Galceran, J. Salvador, J. PuyBehaviour of the Current in a Membrane-covered Disc Microelectrode Under Steady-stateConditions-Josep Galceran, Jose Salvador, Jaume Puy, Joan Cecilia, David J. GavaghanMass Transport-controlled Steady-state Currents for Methanol in a Flow Injection System-JoannaGadomska, Mikolaj Donten, Zbigniew Stojek, Leif NyholmTHE ROYALCHEMISTRYInformationServicesTypeset and printed by Black Bear Press Limited,Cam b r I dg e , EnglandContinued on inside back cover-0003-2654C 1991 12.1-18731877188118851891189719031907191 1PERSPECTIVE 1917Construction and Response Characteristics of a Sulfite/Hydrogensulfite-selective All-solid-state ContactElectrode Based on the 4-Methylpiperidinedithiocarbamate Complex of Mercury(i1)-lbrahim Isildak, CemalYigit, Humeyra BatiComparison of Indirect Cathodic Stripping Voltammetric Methods Based on Accumulation of Mercury,Copper(i) and Nickel Salts or Complexes at a Hanging Mercury Drop Electrode: Determination of2-Mercaptobenzothiazole-Arnold G.Fogg, Razali Ismail, Rahmalan Ahmad, Florin G. BanicaIn Situ External Reflection Fourier Transform Infrared Spectroscopic Study on the Structure of theConducting Polymer Poly(parapheny1ene)-Pia Damlin, Carita Kvarnstrom, Ari lvaskaHigh-performance Liquid Chromatographic Determination of Phenols Using a Tyrosinase-basedAmperometric Biosensor Detection System-Olubunmi Adeyoju, Emmanuel I . Iwuoha, Malcolm R. Smyth,Dona1 LeechReagentless Amperometric Glucose Dehydrogenase Biosensor Based on Electrocatalytic Oxidation ofNADH by Osmium Phenanthrolinedione Mediator-Maria Hedenmo, Arantzazu Narvaez, ElenaDominguez, loanis KatakisDetermination of Poly(ethy1ene glycol)^ in Environmental Samples by the Indirect TensammetricMethod-Andrzej Szymanski, Zenon LukaszewskiDetermination of Copper(ii) by Anodic Stripping Voltammetry Using a Flow-through System-A.Economou,P. R. FieldenEffect of Different Experimental Parameters on the Potbntiometric Evaluation of Blood Electrolytes UsingK+ as a Test Cation-Cristina M. R. R. Oliveira, M. J. F. Rebelo, M. F. G. F. C. CamdesInfluence of Surface-active Compounds on the Response and Sensitivity of Cholinesterase Biosensors forInhibitor Determination-G. A. Evtugyn, H. C. Budnikov, E. 6. NikolskayaElectroanalysis for the Purpose of Environmental Monitoring and Specimen Banking: Is There aFuture?-Hendrik Emons, Peter OstapczukSAMPLE HANDLING19231929MOLECULARSPECTROSCOPY/SPECTROMETRY19351939SEPARATION SCIENCE19431949195519631969SENSORS19751979I 9831989Flow System for Liquid Sample Introduction in Arc/Spark Excitation Sources-Carlos Roberto Bellato,Celio PasquiniRapid and Accurate Determination of Manganese in Washing Powders Using Alkali Fusion and InductivelyCoupled Plasma Techniques-Kym E.Jarvis, John G. Williams, Bridget C. H. Gibson, Eric Temmerman,C. De CuyperSimultaneous Stopped-flow Determination of Paracetamol, Acetylsalicylic Acid and Caffeine inPharmaceutical Formulations by Fourier Transform Infrared Spectrometry With Partial Least-squares DataTreatment-Zouhair Bouhsain, Salvador Garrigues, Miguel de la GuardiaContinuous Monitoring of Ozone in Air by Reflectiometry-Nobuo Nakano, Akihiro Yamamoto, KunioNagashimaSensitive Densitometry for the Determination of Platelet-activating Factor and Other Phospholipids inHuman Tears-Toshihisa Ohyama, Chiyo Matsubara, Kiyoko TakamuraVolatile Organic Metabolites Associated With Some Toxic Fungi and Their Mycotoxins-Anna-LiisaPasanen, Sanna Lappalainen, Pertti PasanenDetermination of Volatile Organic Compounds in Air Using a Dehumidified and Ventilated DiffusiveSampler, Thermal Desorption and Gas Chromatography With Flame Ionization Detection-Ying Sing Fung,Zucheng WuGas Chromatographic Analysis of Chlorophenolic, Resin and Fatty Acids in Chlorination and CausticExtraction Stage Effluent From Kahi-grass-C. Sharma, S.Mohanty, S. Kumar, N. J. RaoDirect Determination of Butyl- and Phenyltin Compounds as Chlorides Using Gas Chromatography andFlame Photometric Detection-Gaetane Lespes, Catherine Carlier-Pinasseau, Martine Potin-Gautier,Michel AstrucCalcium Biosensing With a Sol-Gel Immobilized Photoprotein-David J. Blyth, Sarah J. Poynter, David ARussellAmperometric Biosensor for Tyrosinase Inhibitors in a Pure Organic Phase-Qing Deng, Shaojun DongDetermination of Trace Amounts of Antimony(ii1) by Differential-pulse Anodic Stripping Voltammetry at aPhenylfluorone-modified Carbon Paste Electrode-Soo Beng Khoo, Jing ZhuCUMULATIVE AUTHOR INDEXNEWS AND VIEWS 169N Book Reviews171 N Conference Diary176N Courses177N Papers in Future Issues178N Technical Abbreviations and AcronymsCover picture: Rose Window in Durham Cathedral. Photograph kindly supplied by Professor David Parker,University of Durham, UK

ISSN:0003-2654    

DOI:10.1039/AN99621BX056

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, December 1996, Vol. 121 169N Book Reviews Electrochemical Phase Formation and Growth. An Introduction to the Initial Stages of Metal Deposition By E. Budevski, G. Staikov and W. J. Lorenz. Pp. xi + 410. VCH. 1996. Price DM198.00; oS1465.00; sFr192.00. ISBN 3-527-29422-8. The experiment which brought many of us into chemistry and even more of us into electrochemistry must surely be the electroplating of a copper coin with nickel. The secret that underlies the beauty of this process is expanded upon in this new book. The importance of the subject can be immediately appreciated from the author index which reads like a Who’s Who of Modern Electrochemistry. The subject of metal deposition has its roots in the time of Michael Faraday but by far the greatest advances have come since the advent of modern surface science and in particular scanning probe microscopy (SPM).This book covers most of the subject from simple mechanisms of electrocrystallization to surface modification. It is written in an authoritative manner which is mostly easy to follow. One aspect of this book which should be especially commended is the large number of well-chosen, clear diagrams which bring the subject to life. I can cynically foresee many of these being reproduced world-wide for the introductions to PhD Theses. ‘the finish is brilliant’ The authors gently introduce the reader to the fundamentals of electrocrystallization and go on to discuss structural and dynamic properties of crystalline metal surfaces. The important topic of underpotential deposition is covered in great detail in Chapter 3 including the thermodynamic, kinetic and structural aspects of the subject.The book logically moves on to bulk phase formation covering forms of growth, nucleation rates and substrate effects. It then goes on to discuss the growth of crystalline faces. Readers are brought up to date in Chapter 6 with surface structuring and modification relying largely on the technique of SPM. It was nice to see subjects like ultrathin metal films on semiconductors encompassed within this review. On initially reading the contents I was immediately drawn to the final Chapter entitled ‘Outlook’ but I was disappointed to find only two paragraphs, the only defect in an otherwise crystal clear coverage of the subject. Many of the chewy aspects of metal deposition are neatly put in the appendices such that the faint hearted may tip-toe over them on the way to the index.This book will be an excellent guide for those entering the field and an informative reference for those already lost amongst the tall grass. In conclusion this book is very much like our early experiments, coating coins, the subject is covered completely and with the colour diagrams acting as brightners, the finish is brilliant. Andrew Abbott 619009.53 Leicester University Modern Practice of Gas Chromatography. Third Edition Edited by Robert L. Grob. Pp. xii + 888. Wiley. 1996. Price f70.00. ISBN 0-471-59700-7. ___________ ____ ___________________._ This is one of the most comprehensive books on gas chromatography which I have read and the editor, Robert L.Grob, has become a household name among those involved in gas chromatography. One of my criticisms about the previous edition was the lack of information on tandem techniques such as GC-MS, but this has now been fully rectified in this latest book. The volume is separated into three parts, Theory and Basics, Techniques and Instrumentation, and Applications. In Part I , the first two chapters, as might be expected, are concerned with the history and theory of chromatographic separation tech- niques and are written by Grob himself. These would be most useful to students of the technique. This is followed by theoretical and practical chapters on column selection and optimizing separations and show the considerable advances which have been made from the early days of crude packed stainless-steel or glass columns.The modem fused-silica capillary column has come a long way since even the glass capillary columns of a few years ago. It was almost regarded as an art to successfully install these in the GC without breaking them. ‘one of the most comprehensive books on gas chromatography which I have read’ The first chapter of Part 2 gives a comprehensive description of the different types of detectors available including the more unusual ones such as the microwave plasma detector or the useful Fourier transform infrared detector. A section on detector data handling is also included. This is followed by a new chapter on GC-MS and describes the different types of instrumentation available such as quadrupoles, ion traps and sector instruments. To some extent, the development of simple low cost quadrupole mass selective detectors has probably been the biggest advance in GC techniques since the capillary column and considerably increase the specificity of the technique. This is followed by a useful chapter on qualitative and quantitative analyses and a chapter on the various types of modern GC inlet or injector ports available to the chromatographer.The final part of the book, and often the most difficult one to get right, is on the practical applications of GC. In this case, however, I feel that Grob has been successful in giving a balanced overview of the many applications and uses of GC. Invited experts have written chapters on Physiochemical Measurements (one of the more unusual applications), Pet- rochemical Analysis, Polymer Analysis, Clinical Applications, Forensic Science and finally Environmental Applications.As well as providing the student with information on the practical uses of GC, these chapters also provide useful methods for the experienced chromatographer. In summary, this is a book which would be useful in any laboratory carrying out GC or GC-MS analyses. The technique has come a long way since the days when autosamplers were instruments designed for bending syringe needles and pen recorders were designed to cut off the ink supply in the middle of a run. The modern GC is now a precision instrument taken very much for granted where good results can almost be guaranteed at the touch of a button. This book certainly does the technique justice.John Blanchjlonw- 61900746 Department of Agriculture for Northern Ireland Belfast Nuclear Magnetic Resonance. Concepts and Methods By Daniel Canet. Pp. x + 260. Wiley. 1996. Price f24.95. ISBN 0-47 1-96145-0. This is an interesting addition to the spectroscopists’ library of NMR reference books, which repays study. It is not a ‘how-to’170N Analyst, December 1996, Vol. 121 book in the usual sense but rather a book for the spectroscopist wishing to deepen his or her knowledge of ‘modern’ NMR experiments. The five chapters cover an introduction to the subject, the mathematics and quantum mechanics relevant to modern methodologies, spin relaxation, spin dynamics and molecular motions, and a survey of multipulse and multi- dimensional methods.Chapter One is intended to be understandable by under- graduate students, covering as it does, the principles of chemical shift and J-coupling. One of the features of the book is the use of quantum mechanics. The sections containing these more mathematical approaches are in smaller type face so that less interested readers can skip them and read only the more descriptive passages. However, since some of the mathematical sections are quite long, much of the value of Chapter One may be foregone by the less mathematically-inclined reader. In addition, some of the important information for undergraduate spectroscopists, e.g., second order effects in spectra, typical proton chemical shifts, and exchange of labile protons receive only brief mentions.’a book which will help the reader under- stand some of the concepts in modern NMR’ Chapter Two starts by covering the Bloch equations and an introduction to density and product operators (small print), the section on the latter being followed by a more descriptive section outlining the rules for analysing pulse sequences. These sections are one of the strengths of the book. After the excursions into the abstract in Chapter Two, Chapter Three returns the reader to the more usual ground of signal averaging, Fourier transformation, quadrature detection and data process- ing. The latter topic includes a very brief survey of non-FT methods. These topics are treated very quickly and the references to the original literature (as elsewhere in the book) are not extensive.However, the practice of citing the first application in NMR of, for example, maximum entropy, may give some useful gateways into the NMR literature. Chapter Four deals with dynamic phenomena, starting with TI and T2 determinations and moving on to explanations of the NOESY and ROESY experiments. The final chapter treats multipulse experiments such as selective excitations, polariza- tion and coherence transfer in a largely non-mathematical way, but draws on the rules developed in Chapter Two to help explain the effects of pulse sequences. In summary, this is not an exhaustive introductory text but it is a book which will help the reader understand some of the concepts in modern NMR. The undergraduate student with an interest in quantum mechanics will enjoy the book, but its more likely appeal is to graduate students and those involved in NMR as practising spectroscopists.Richard Smith 6190040B SmithKline Beecham Pharmaceuticals Harlow Microelectronics Technology. Polymers for Advanced Imaging and Packaging Edited by Elsa Reichmanis, Christopher K. Ober, Scott A. MacDonald, Takao lwayanagi and Tadatomi Nishikubo. ACS Symposium Series 614. Pp. xii + 564. ACS. 1995. Price US$134.95. ISBN 0-841 2-3332-2. As with other ACS Symposium Series publications this volume provides a snapshot of the state of the art in a particular field, in this case research in polymers for microelectronic applications. Much of the work described here was presented in a symposium held at the ACS meeting in April 1995. The contributions are grouped into three sections dealing with chemically amplified resist materials and processes, novel chemistries and ap- proaches for sub 0.25 pm imaging, and polymer dielectrics for microelectronic applications.In each case a brief introduction to the section is provided by one of the editors. Within each section, the individual contributions, many from industrially based research groups, describe aspects of current research in the different areas. These articles are prepared to a high standard and the overall quality of production of this volume is good. An excellent index is provided to help the reader to access the information distributed within the various contributions con- tained therein. ‘a snapshot of the state of the art in polymers for microelectronic applications’ Polymeric materials find widespread use in the microelec- tronics industry, indeed, without polymers as photoresists, dielectrics and packaging materials there would be no micro- electronics industry.Their utility arises from the ability of the chemist to design and synthesize materials with appropriate properties and functionality and the ease with which these materials can be processed. A significant current motivation in the development of the microelectronics industry is the desire to pack more components into ever smaller spaces in order to achieve enhanced performance. The drive towards sub 0.25 pm feature size places stringent requirements on photoresist technology. Basically a photoresist is a radiation sensitive polymer which can be coated onto the substrate, exposed to a suitable radiation source through a mask or by direct write technology and then developed to leave some areas of the underlying substrate exposed and others protected so that chemical etching or other treatment can be carried out on the exposed regions.Frequently after this stage the residual photoresist is also removed prior to further processing. One approach to developing resist with high sensitivity and contrast is to use chemical amplification by the photogeneration of acidic species which then catalyse a subsequent chemical transformation of the polymer. The overall quantum efficiency is then greatly enhanced by this chemical step. However to understand and control such chemistries it is necessary to understand the coupled reaction and diffusion processes occurring within the polymeric layer following irradiation.This area forms the topic of the papers in the first section of the volume. To achieve ever smaller feature size demands the use of radiation of ever shorter wavelength to overcome the fun- damental diffraction limitation. In turn this requires the development of new photoresists which combine the required physical, chemical and photochemical properties. Work on such photoresist development forms the topic for the second section of this volume and includes papers on the design of resist for use with ArF excimer laser radiatrion (193 nm) as well as other novel dry-developed resist chemistries. The final section deals with the development of novel polymer dielectrics. These are the materials which serve as adhesives, encapsulants and substrates, Again the drive to place larger numbers of components into ever smaller areas places stringent require- ments upon the polymers used as dielectrics in such applica- tions. In this case it is necessary to develop materials which can be used in very thin continuous layers to insulate one part of the circuit from another. In this application thermal stability is crucial. A challenge in this area is to reduce the relative permittivity, E, of the polymer below the value of about 2.3 found for highly fluorinated material. P. N . Bartlett 6l90068B University of Southampton

ISSN:0003-2654    

DOI:10.1039/AN996210169N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, December 1996, Vol. 121 171N Conference Diary Date Conference 1997 January 4-9 12-16 12-17 20-24 25-28 26-30 29-3 1 Location The Fourth International Symposium On: Analytical Chemistry in National Development International Conference on Flow Injection Analysis-ICFIA 97 USA Giza, New Trends in Chemistry The Role of Egypt Orlando, 1997 European Winter Conference on Plasma Gent, Spectrochemistry First Asia-Pacific EPR/ESR Symposium 9th Sanibel Conference on Mass Spectrometry ‘Quadrupole Ion Traps’ 9th International Symposium on High Performance Capillary Electrophoresis and Related Microscale Techniques Validation in Pharmaceutical Analysis February 2-6 The Australian and New Zealand Society for Mass Spectrometry 16th Conference (ANZSMS 16) 3-5 2nd Symposium on Macromolecules Used as Pharmaceutical Excipients-New Opportunities, Characterization and Applications 18-1 9 Inbio ’97 Industrial Biocatalysis: The Way Ahead 19 Advances in Analytical Chemistry: Miniaturisation and Sensors Belgium Hong Kong Sanibel Island, FL, USA Anaheim, USA York, UK Hobart, Tasmania, Australia Stockholm, Sweden Manches ter, UK Hudders field, UK Contact Professor Dr.M. M. Khater, Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt ICFIA 97, Sue Christian, P.O. Box 26, Medina, WA Fax: +I 206 454 9361. E-mail: sue@flowinjection.com. L. Moens, Secretariat, 1997 European Winter Conference, Laboratory of Analytical Chemistry, University of Gent, Proeftuinstraat 86, B-9000, Gent, Belgium Tel: +32 9 264 66 00. Fax: +32 9 264 66 99.E-mail: plasma97@ rug. ac. be. Professor C. Rudowicz, Chairman, LOC & IOC, City University of Hong Kong, Department of Physics and Materials Science, 83 Tat Chee Avenue, Kowloon, Hong Kong Tel: +852 2788 7787. Fax: +852 2788 7830. E-mail: apsepr@ cityu.edu.hk. American Society for Mass Spectrometry, 1201 Don Diego Avenue, Santa Fe, NM 87505, USA Tel: +I 505 989 4517. Fax: +1 505 989 1073. Shirley Schlessinger, Symposium Manager, HPCE ’97, 400 East Randolph Street, Suite 1015, Chicago, IL 60601, USA Tel: +1 312 527 2011. Dr. J. Clements, Room 403, Pharmaceutical Society, 1 Lambeth High Street, London SE1 7JN, UK Tel: +44 (0)171 735 9141. Fax: +44 (0)171 735 7629. 98039-0026, USA Mures Convention Management, Victoria Dock, Hobart, TAS 7000, Australia Tel: +61 002 312121.Fax: +61 002 344464. E-mail: mures@hba.trumpt.com.au; WWW:http://www.csl.edu.au/ANZSMS/anzsms 16.html. The Swedish Academy of Pharmaceutical Sciences, P.O. Box 1136, S-111 81 Stockholm, Sweden Tel: +46 8 723 50 00. Fax: +46 8 20 55 11. E-mail: academy@swepharm.se or visit http://www .swepharm.pharmsoft.se. Spring Innovations Ltd., 185A Moss Lane, Bramhall, Stockport, Cheshire, UK SK7 1BA Tel: +44 (0)161 440 0082. Fax: +44 (0)161 440 9127. Dr. Roger Jewsbury, Dept. Chemical and Biological Sciences, University of Huddersfield, Yorkshire HD1 3DH Tel: +44 (0)1484 472177. Fax: +1 (0)1484 472182. E-mail: r.a.jewsbury@hud.ac.uk Internet: http://www.hud.ac.uk/schools/ applied-sciences/chem/aac97 .htm.172N Analyst, December 1996, Vol. 121 Date Conference 20 Validative Methods in the Pharmaceutical Industry March 9-14 16-21 17-19 23-27 April 13-17 14-19 19-22 21-25 28-29 30-2/5 May 4-8 CANAS '97 Colloquium Analytische Atomspektroskopie 48th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy Fundamentals and Applications of Total-Reflection X-Ray Fluorescence Electrophoresis '97 213th American Chemical Society National Meeting Genes and Gene Families in Medical, Agricultural and Biological Research: International Congress on Isozymcs Scanning 97 9th Seventh International Symposium on Biological and Environmental Reference Materials (BERM-7) Computer & Process Validation in the Location Cork, Ireland Freiberg/S achsen, Germany Atlanta, GA, USA Dortmund, Germany Seattle, WA, USA San Francisco, CA.USA Texas, USA Monterey, CA, USA Antwerp, Belgium Manchester, Pharmaceutical and Fine Chemical Industries UK Flavours and Fragrances Warwick, UK PBA '97, 8th International Symposium on Pharmaceutical and Biomedical Analysis USA Orlando, FL, Contact Dr.Gerry Montgomery, The Royal Society of Chemistry, Burlington House, Piccadilly, London WIV OBN, UK Tel: +44 (0)171 437 8656. Fax: +44 (0)171 440 3320. E-mail: montgomery@rsc.org. G. Werner, Universitat Leipzig, Institut fur Analytische Chemie, Linnestrasse 3, D-04103 Leipzig, Germany Tel: +49 0341 973 6101. Fax: +49 0341 973 61 15. Linda Briggs, The Pittsburgh Conference, 300 Penn Center Blvd., Suite 332, Pittsburgh, PA 1523.5-5503, USA Tel: +1 412 825 3220, +I 800 825 3221. Fax: +1 412 825 3224. Mrs M. Becker, Institut fur Spektrochemie und Angewandte Spektroskopie, Bunsen-Kirchhoff-Str.1 1,44 139 Dortmund, Germany Tel: +49 23 1 1392 230. Fax: +49 23 1 1392 120. David Wiley, Electrophoresis Society, P.O. Box 1987, Lawrence, KS 66044-8897, USA Tel: +1 913 843 1221. Fax: +1 913 843 1274. E-mail: dwiley@allenpress.com. Department of Meetings, American Chemical Society, 115516th St. NW, Washington, DC 20036, USA Tel: +1 202 872 4396. Fax: +1 202 872 6128. E-mail: natlmtgs@acs.org. Mrs. Janet Cunningham, Barr Enterprises, 101 20 Kelly Road, P.O. Box 279, Walkersville, MD 21793, USA Tel: + I 301 898 3772. Fax: +1 301 898 5596. Mary K. Sullivan, FAMS Inc., SCANNING 97 Program Committee, Box 832, Mahwah, NJ Tel: + I 201 818 1010. Fax: + I 201 818 0086. E-mail: fams@holonet net; Internet: http://www.scanning-fams.org. J.Pauwels, Institute for Reference Materials and Measurements, Retieseweg, B-2440 Geel, Belgium. Tel: +12 14 571 722; or Wayne Wolk, US Department of Agriculture, 10300 Baltimore Blvd, Beltsville, MD 20705, USA Tel: + I 301 504 8927. Spring Innovations Ltd,, 185A Moss Lane, Bramhall, Stockport, Cheshire, SK7 1BA Tel: +44 (0)161 440 0082. Fax: +44 (0)161 440 9127. Elaine Wellingham, Conference Secretariat, Field End House, Bude Close, Nailsea, Bristol BS19 2FQ, UK Tel: +44 (0)1275 8533 1 1. Fax: +44 (0)1275 85331 1. E-mail: confsec@dial.pipex.com. 07430-0832, USA Shirley E. Schlessinger (Symposium Manager), Suite 1015, 400 East Randolph Drive, Chicago, IL, 60601, USAAnalyst, December 1996, Vol. 121 173N ~~~~ Date 12-13 12-16 18-22 27-28 June 1-4 1-5 1-5 2-4 2-5 3-5 15-19 15-2 1 16-20 ~~ Conference Chiral USA '97 Location Boston, USA European Symposium on Photonics in Manufacturing I11 19th International Symposium on Capillary Chromatography and Electrophoresis IInd Miniaturisation in Liquid Chromatography versus Capillary Electrophoresis Conference 1997 International Symposium, Exhibit & Workshops on Preparative Chromatography, Ion Exchange, and Adsorption/Desorption Processes and Related Techniques 45th ASMS Conference on Mass Spectrometry and Allied Topics Paris, France Wintergreen, VA, USA Ghent, Belgium Washington, DC, USA Palm Springs, CA, USA Geoanalysis '97,3rd International Conference Vail, CO, on the Analysis of Geological and Environmental Materials 5th Symposium on Analytical Sciences 6th Annual Course on Practical Methods of Digestion for Trace Analysis LIMS '97, 11th International LIMS Conference and Exhibition 27th International Symposium on Environmental Analytical Chemistry International Conference on Analytical Chemistry European Symposium on Environmental Sensing I11 USA Nice, France Amherst, MA, USA The Hague, Netherlands Jekyll Island, GA, USA Moscow, Russia Munich, Germany Contact Spring Innovations Ltd, 185A Moss Lane, Bramhall, Stockport, Cheshire, UK SK7 1BA Tel: +44 (0)161 440 0082.Fax: +44 (0)161 440 9127 or Brandon Associates, PO Box 1244, Merrimach, NH 03054, USA. Tel and Fax: +I (630) 424 2035. Francoise Chavel, Executive Secretary, European Optical Society, B.P. 147-9 1403 Orsay Cedex, France Tel: +33 1 69 85 35 92.Fax: +33 1 69 85 35 65. E-mail: francoise.chavel@ i0ta.u-psud.fr. Joy Wise, P.O. Box 4153, Frederick, MD 21705-4153, USA Tel: +1 301 473 8311. Fax: +1 301 473 8312. E-mail: Wisejoy@aol.com. Prof. Dr. Willy R. G. Baeyens, Chairman MINI-LC 11, University of Ghent, Faculty of Pharmaceutical Sciences, Department of Pharmaceutical Analysis, Laboratory of Drug Quality Control, Harelbekestraat 72, B-9000 Ghent, Belgium Tel: +32 9 264 80 97. Fax: +32 9 264 81 96. E-mail: willy.baeyens@rug.ac.be 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. American Society for Mass Spectrometry, 1201 Don Diego Avenue, Santa Fe, NM 87505, USA Tel: +1 505 989 4517.Fax: +1 505 989 1073. Belinda Arbogast, USGS, Dever Federal Center, Box 25046, MS 973, Denver, CO 80225, USA Tel: +1 303 236 2495. Fax: +1 303 236 3200. E-mail: plamothe@helios.cr.usgs.gov. Deauville Conference 97, SAS 5th Symposium on Analytical Sciences, Nicko & Cri Associes, 7 rue d'Argout, F-75002 Paris, France Tel: +33 1 42334766. Fax: +33 1 40419241. E-mail: dcjc@compuserve.com, http://ourworld.compuserve.com/homepages/dcja/. Beverly Lissner, Questron Corporation, 4044 Quakerbridge Rd., Mercerville, NJ 08619, USA Tel: +I 609 587 6898. Fax: +1 609 587 0513. Conference Secretariat, LIMS 97, 45 Hilltop Avenue, Hullbridge, Hockley, Essex, UK S S 5 6BL Tel: +44 (0)1702 231208. Fax: +44 (0)1702 230580. E-mail: 101320.161 7@compuserve.com. J. A. de Haseth, Department of Chemistry, University of Georgia, Athens, GA 30602-2556, USA Tel: +1 706 542 1968.Fax: +I 706 542 9454. E-mail: jekyllsymp@sunchem.chem.uga.edu. Dr. I,. N. Kolomiets, Scientific Council on Chromatography of the Russian Academy of Sciences Leninsky Prospect 31, 117915 Moscow, Russia Tel: +7 95 952 0065. Fax: +7 095 952 0065. E-mail: Iarionov@Imm.phyche.muk.su. Frangoise Chavel, Executive Secretary, European Optical Society, B.P. 147-9 1403 Orsay Cedex, France Tel: +33 1 69 85 92. Fax: 33 1 69 85 33 65. E-mail: francoise.chavel@iota.upsud.fr.174N Analyst, December 1996, Vol. I21 Date 16-20 22-27 30-3/7 Conference European Symposium on Environmental and Public Safety I1 HPLC '97, 21st International Symposium on High Performance Liquid Phase Separations and Related Techniques Analytical Science and the Environment 30-3/7 6th European ISSX Meeting July 18-23 2 1-25 23-26 International Symposium on Optical Science, Engineering, Instrumentation 4th International Conference on Laser Ablation 4th International Conference on the Biogeochemistry of Trace Elements August 10-15 18-22 25-28 25-29 11th International Conference on Fourier Transform Spectroscopy 13th International Symposium on Plasma Chemistry VII Flow Conference IMSC '97-14th International Mass Spectrometry Conference September 7-1 1 111th AOAC International Annual Meeting and Exposition ~~~ ~ Location Munich, Germany Birmingham, UK Newcastle, Northumbria, UK Gothenburg, Sweden San Diego, CA, USA Monterey, CA, USA Berkeley, CA, USA Athens, GA, USA Beijing, China Aguas de Sao Pedro-Piracicaba, Brazil Tampere, Finland San Diego, CA, USA Contact Francoise Chavel, Executive, Secretary, European Optical Society, B.P.147-91403 Orsay Cedex, France Tel: +33 1 69 85 35 92. Fax: +33 1 69 85 35 65. E-mail: francoise.chavel@iota.u-psud.fr. HPLC '97 Symposium Secretariat, ICC, Broad Street, Birmingham B1 2EA, UK Tel: +44 121 200 2000. Fax: +44 121 643 0388. The Secretary, Analytical Division, The Royal Society of Chemistry, Burlington House, Piccadilly, London W1V OBN, UK Tel: +44 (0)171 437 8656. Fax: +44 (0)171 734 1227. Meeting Secretariat, 6th European ISSX Meeting, c/o The Swedish Academy of Pharmaceutical Sciences, P.O. Box 1136, S-1 1 1 81 Stockholm, Sweden Tel: +46 8 723 5000. Fax: +46 8 20 551 1. SPIE, P.O. Box 10, Bellingham, WA 98227-0010, USA Tel: +1 360 676 3290.Fax: +1 360 647 1445. E-mail: spie@spie.org, http://www.spie.org/. Richard E. RUSSO, Lawrence Berkeley Laboratory, MS 90-2024, Berkeley, CA 94720, USA Tel: +1 510 486 4258. Fax: +1 510 486 4260. E-mail: rerusso@ lbl.gov;http://cola97 .ornl.gov. I. K. Iskandar, U.S. Army Cold Regions Research and Engineering Laboratory, 72 Lyme Rd., Hanover, NH 03755, USA Tel: +1 603 646 4198. Fax: +1 603 646 4561. E-mail: iskander@ crrel .usace.army .mil. James A. de Haseth, Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556, USA Tel: +I 706 542 1968. Fax: +1 706 542 9454. E-mail: dehaseth@dehrsv.chem.uga.edu. Lin He, Secretary ISPC-13, The Chinese Society of Theoretical and Applied Mechanics, 15 Zhing Guan Cun Road, Beijing 1000080, China Fax: +86 10 62559588.E-mail: cstam@sun.ihep.ac.cn. Henrique Bergamin Filho, CENA-USP, Caixa Postal 96, 13400-970 Piracicaba, SP, Brazil Tel: +55 194 335122. Fax: +55 194 228339. E-mail: flow97@aguia.cena.usp.br. 14th IMSC Congress Secretariat, c/o Congress Management Systems, P.O. Box 151, SF-00141, Helsinki, Finland Margreet Lauwaars, P.O. Box 153,6720 AD Bennekom, The Netherlands. Tel: +31 318 418725; Fax: +3 1 3 18 41 8359; or Derek Abbott, 80 Chaffers Mead, Ashtead, Surrey, UK KT2 1NH Tel: +44 372 274856. Fax: +44 372 274856.Analyst, December 1996, Vol. I 2 1 175N Date 7-1 1 7-1 2 8-1 2 8-12 8-12 15-19 21-26 Conference 214th American Chemical Society National Meeting 11th International Conference on Secondary Ion Mass Spectrometry (SIMS XI) 4th International Conference on Nanometer Scale Science and Technology Biomedical Optics V World Congress and Exhibition of the International Society for Fat Research (ISF) Locat ion Las Vegas, NE, USA Orlando, FL, USA Beijing, China Poland Kuala Lumpur, Malaysia 3rd International Symposium on Speciation of Port Douglas, Elements in Biological, Environmental and Toxicological Sciences Australia Queensland, XXX Colloquium Spectroscopicum Melbourne, Internationale Australia October 5-10 4th International Symposium on Environmental Geochemistry Vail, c o , USA 14-18 BCEIA '97, The 7th International Beijing Shanghai, Conference and Exhibition on Instrumental Analysis China 25-31 24th Annual Meeting of the Federation of Providence, RI, Analytical Chemistry and Spectroscopy USA Societies 26-29 8th Symposium on Handling of Almeria, Environmental and Biological Samples in Chromatography.26th Scientific Meeting of the Group of Chromatography and Related Techniques of the Spanish Royal Society of Chemistry Spain Contact Department of Meetings, American Chemical Society, 115516th St. NW, Washington, DC 20036, USA Tel: + I 202 872 4396. Fax: +1 202 872 6128. E-mail: natlmtgso acs.org. SIMS XI, 1201 Don Diego Ave., Santa Fe, NM 87505, USA Tel: +1 505 989 4735. Fax: +1 505 989 1073. Shijin Pang, Beijing Laboratory of Vacuum Physics, Chinese Academy of Sciences, P.O. Box 2724, Beijing 100080, People's Republic of China Tel: +86 10 256 8306. Fax: +86 10 255 6598. E-mail: pang@image.blem.ac.cn. Francoise Chavel, Executive Secretary, European Optical Society, B.P.147-91403 Orsay Cedex, France Tel: +33 1 69 85 35 92. Fax: +33 1 69 85 35 65. E-mail: francoise.chavel@iota.u-psud.fr. Mary Belding, Meetings & Exhibits Department, ISF Secretariat, P.O. Box 3489, Champaign, IL 61826 3489, USA Tel: +1 217 359 2344. Fax: +I 217 351 8091. E-mail: meetings@aocs.org. Dr. J. P. Matousek, Department of Analytical Chemistry, University of New South Wales, Sydney, NSW 2052, Australia Tel: +61 2 3854713. Fax: +61 2 3856141. E-mail: j . matousek@ unsw .edu. au. The Meeting Planners, 108 Church Street, Hawthorn, Victoria 3 122, Australia Tel: +61 3 9819 3700. Fax: +61 3 9819 5978. E-mail: http://www.latrobe.edu.au/CSIconf/XXXCSI.html. R. C. Severson, U.S. Geological Survey, Federal Center, Box 25046, MS 973, Denver, CO 80225, USA Tel: +I 303 236 5514. Fax: +1 303 236 3200. E-mail: iseg@helios.cr.usgs.gov. BCEIA '97 General Service Office, Room 585, Chinese Academy of Sciences Building, San Li He, Xi Jiao, P.O. Box 2143, Beijing 100045, China Tel: +86 10 8511133 Ext. 1585, +86 10 8511814. Fax: +86 10 8511814. E-mail: bceia@aphyOl .iphy.ac.cn. Jo Ann Brown, Federation of Analytical Chemistry and Spectroscopy Societies, 210B Broadway Street, Frederick, MD 21701, USA Tel: +1 301 694 8122. Fax: +1 301 694 6890. E-mail : jbrownsas@ aol .corn M. Frei-Hausler, IAEAC Secretariat, Postfach 46, CH-4123 Allschwil 2, Switzerland Fax: +41 61 482 08 05.

ISSN:0003-2654    

DOI:10.1039/AN996210171N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, December 1996, Vol. 121 1773 biosensor reported for formaldehyde vapour, by Guilbault.14 He detected formaldehyde with a detection limit of 10 ppb, while enzymic methods could detect formaldehyde typically in the ppb range, with one assay reporting a detection limit of 120 ppt v/v. As a demonstration of formaldehyde sensing, this biosensor has been successful. However, further work needs to be carried out to improve the stability of the enzyme, which is poor. When steady-state amperometric responses were used as a measure of ADH biosensor response, a linear response was obtained up to approximately 250 ppm ethanol vapour. This ability of the RMs to concentrate the vapour is ideal for sensing low levels of ethanol, but is not suitable for sensing the high levels of ethanol vapour routinely encountered in everyday applications (100-1 000 ppm).Alternatively, the ADH bio- sensor could be used for measuring ethanol vapour, if the exposure times are short, i.e., the concentration of ethanol partitioned in the gel phase is very low and ADH is not substrate saturated. Enzyme stability remains a major problem owing to the poor stability of ADH. Improvements in enzyme purifica- tion and stabilization would greatly enhance further develop- ment of practical ethanol vapour biosensors. If the problem of biosensor stability (i.e., enzyme stability and gel stability) could be overcome, then this formaldehyde biosensor could successfully compete with conventional meth- ods of formaldehyde detection. Its small size compared with the conventional techniques which have to include pumps makes it portable.This formaldehyde biosensor compares well with conventional portable techniques. The limit of detection of this biosensor has not been determined yet, but could possibly be much lower than 1.2 ppb. If exposure times were increased then even lower levels might be determined. References 1 2 3 4 5 6 7 8 9 10 11 Hobbs, B. S., Tantram, A. D. S., and Chan-Henry, R., in Techniques and Mechanisms in Gas Sensing, ed. Moseley, P. T., Norris, J. 0. W., and Williams, D. E., Adam Hilger, Bristol, 1991, pp. 161-181. Dennison, M. J., Hall, J., and Tumer, A. P. F., Anal. Chem., 1995,67, 3922. Fendler, J. H., in Membrane Mimetic Chemistry, Wiley, New York, Zulauf, M., and Eicke, H. F., J . Phys. Chem., 1979, 83, 480.Bardana, E. J., and Montanaro, A., Ann. Allergy, 1991, 66, 441. Environmental Protection Agency, Fed. Regist., 1984, 49, 21 870. Main, D. M., and Hogan, T. J., J . Occup. 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Paper 61038541 Received June 3,1996 Accepted July 30, 1996 13-14, 574.

ISSN:0003-2654    

DOI:10.1039/AN996210176N

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

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Phys. Chem., 1987, 91, 3934. DeAngelis, T. P., and Heineman, W. R., J . Chem. Educ., 1976, 53, 594. Kozlowski, M., Smyrl, W. H., Atanasoska, Lj., and Atanasoski, R., Electrochim. Acta, 1989, 34, 1763. Tyler, P. S., Kozlowski, M. R., Smyrl, W. H., and Atanasoski, R. T., J . Electroanal. Chem., 1987, 237, 295. Kozlowski, M. R., Tyler, P. S., Smyrl, W. H., and Atanasoski, R. T., Electrochim. Acta, 1988, 194, 505. Carlsson, P., Holmstrom, E., Uosaki, K., and Kita, H., Appl. Phys. Lett., 1988, 53, 965. Kucernak, A. R. J., Peat, R., and Williams, D. E., J.Electrochern. Soc., 1991, 138, 1645.Eriksson, S., Carlsson, P., Holmstrom, B., and Uosaki, K., J. Appl. Phys., 1991, 69, 2324. Compton, R. G., Eklund, J. C., and Nei, L., J . Electroanal. Chem., 1995, 381, 87. Albery, W. J., Archer, M. D., and Egdell, R. G., J . Electroanal. Chem., 1977,82, 199. Bartlett, P. N., and Deards, P., presented at Electrochem '94, Edinburgh, September 1994. Albery, W. J., Bartlett, P. N., Lithgow, A. M., Riefkohl, J., Romero, L., and Souto, F. A., J . Chem. SOC., Faraday Trans. I , 1985, 81, 2647. Williams, D. E., Kucernak, A. R. J., and Peat, R., Electrochim. Acta, 1993, 38, 57. Kucernak, A. R. J., Peat, R., and Williams, D. E., Electrochim. Acta, 1993, 38, 71. Hutton, R., and Williams, D. E., Anal. Chem., 1995, 67, 280. Cohen, C. B., and Weber, S.G., Anal. Chem., 1993,65, 169. Casillas, N., James, P., and Smyrl, W. H., J . Electrochem. Soc., 1995, 142, L16. Symanski, J. S., and Bruckenstein, S., J . Electrochem. Soc., 1988, 135, 1985. Szabo, A., J . Phys. Chem., 1987,91, 3108. Kuhn, L. S., Weber, A., and Weber, S. G., Anal. Chem., 1990, 62, 1631. Kriger, M. S., Cook, K. D., and Ramsey, R. S., Anal. Chem., 1995,67, 385. Wightman, R. M., and Wipf, D. O., in Electroanalytical Chemistry, ed. Bard, A. J., Marcel Dekker, New York, 1989, vol. 15, pp. 267- 3.51. Zak, J., and Kuwana, T., .J. Electroanal. Chem., 1983, 150, 645. Kalapathy, U., Tallman, D. E., and Hagen, S., J . Electroanal. Chem., 1992, 325, 65. Tallman, D. E., Anal. Chem., 1994, 66, 557. 43 44 45 46 47 48 49 so 51 52 53 54 5.5 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 Fleischmann, M., Bandyopadhyay, S., and Pons, S., J .Phys. Chem., 1985,89, 5537. Fleischmann, M., and Pons, S., J . Electroanal. Chem., 1987, 222, 107. Smythe, W. R., J . Appl. Phys., 195 1 , 22, 1499. Wopschall, R. H., and Sham, I., Anal. Chem., 1967, 39, 1527. Papeschi, G., Costa, M., and Bordi, S., J . Electrochem. Soc., 1981, 128, 1518. Svetlicic, V., Tomaic, J., Zutic, V., and Chevalet, J., J . Electroanal. Chem., 1983, 146,71. Svetlicic, V., Zutic, V., Clavilier, J., and Chevalet, J., J . Electroanal. Chem., 1985, 195, 307. Sagara, T., and Niki, K., Langmuir, 1993, 9, 831. Zutic, V., Svetlicic, V., Clavilier, J., and Chevalet, J., J . Electroanal. Chem., 1987,219, 183. Shez, E. I., and Corn, R. M., Electrochim.Acta, 1993, 38, 1619. Kuwabata, S., Nakamura, J., and Yoneyama, H., J . Electroanal. Chem., 1989, 261, 363. Guadalupe, A. R., Liu, K. E., and AbruAa, H. D., Electrochim Actu, 1991, 36, 881. John, S. A., and Ramaraj, R., J . Chem Soc., Faraday Trans., 1994. 90, 1241. Svetlicic, V., Zutic, V., Clavilier, J., and Chevalet, J., J . Electroanal. Cltem., 1987, 233, 199. Clavilier, J., Svetlicic, V., Zutic, V., Ruscic, B., and Chevalet, J., J . Electroanal. Chem., 1988, 250, 427. Lezna, R. O., de Tacconi, N. R., Hahn, F., and Ariva, A. J., J . Electroanal. Chem., 1991, 306, 259. Earner, B. J., and Corn, R. M., Langmuir, 1990, 6, 1023. Naujok, R. R., Duevel, R. V., and Corn, R. M., Langmuir, 1993, 9, 1771. Svetlicic, V., Clavilier, J., Zutic, V., Chevalet, J., and Elachi, K., J.Electroanal. Chem., 1993, 344, 145. Danzinger, R. M., Bar-Eli, K. H., and Weiss, K., .I. Phys. Chem., 1967, 71, 2633. Albery, W. J., and Foulds, A. W., J . Photochem., 1979, 10, 41, and- references cited therein. Bauldreay, J., and Archer, M. D., Electrochim. Acta, 1983, 28, 1515. Faure, J., Bonneau, R., and Joussot-Dubien, J., Photochem. Photo- hid., 1967, 6, 331. Unwin, P. R., and Bard, A. J., Anal. Chem., 1992, 64, 113. Murthy, A. S. N., and Reddy, K. S., J . Chem. Soc., Faraday Trans. 1. 1984,80, 2745. Chen, X., Zhuang, J., and He, P., .I. Electroanal. Chem., 1989, 271, 257. Ju, H., Zhou, J., Cai, C., and Chen, H., Electroanalysis, 1995, 7, 1165. Karyakin, A. A., Strakhova, A. K., Karyakina, E. E., Varfolomeyev, S. D., and Yatsimirsky, A. K., Bioelectrochem. Bioenerg., 1993, 32, 35. Beddard, G. S., Kelly, J. M., and van der Putten, W. J. M., J . Chem. Soc., Chem. Commun., 1990, 1346. Marcus, R., Annu. Rev. Phys. Chem., 1964, 15, 155. Duonghong, D., Ramsden, J., and Gridtzel, M., J . Am. Chem. Soc., 1982,104,2977. Kelsall, G. H., and Williams, R. A., J . Electrochem. Soc., 1991, 138, 931. Zhao, Z., Boxall, C., and Kelsall, G. H., Colloids Surf, 1993, 73, 145. Paper 6103942A Received June 5,1996 Accepted September 5, I996

ISSN:0003-2654    

DOI:10.1039/AN996210177N

出版商:RSC    

年代:1996

数据来源: RSC

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Analyst, December 1996, Vol. 121 1793 0.140 r 0.125 d E - 0.120 -. 0.115 0.1 10 0.105 ' I L I I I -1.3 -1.2 -1.1 -1.0 -0.9 -0.8 EIV Fig. 8 Batch injection analysis of insulin at MTFE on a glassy carbon substrate (diameter 5 mm). [Insulin]: 5.0, 10.0, 50.0 and 100.0 pmol 1-I; peak height increases with increasing concentration. Injections of 100 pl of solution. Other experimental conditions as in Fig. 3. batch injection analysis can be employed for the determination of zinc in small sample volumes. This technique is very promising for application to the determination of zinc arising from the zinc-insulin complex released into the extracellular fluid during exocytosis from pancreatic @-cells. References Hedeskov, C. J., Physiot. Rev., 1980, 60, 442. Orci, L., Vasssali, J. D., and Perrelet, A., Sci.Am., 1988, 260, 85. Efendic, S., Khan, A., and Ostenson, C. G., Diahete Metah., 1994,20, 81. Derewenda, U., Dercwenda, Z. S., Dodson, G. G., and Hubbard, R. E., in Insulin, ed. Cuatrecasas, P., and Jacobs, S., Springer, Berlin, 1990, ch. 2. Howell S. I., and Tyhurst, M., in The Secretory Process, ed. Poisener, A. M., and Trifarii, J. M., Elsevier, Amsterdam, 1982, vol. 1, ch. 4. 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 2s 26 Blundell, T., Dodson, G., Hodgkin, D., and Mercola, D., in Advances in Protein Chemistry, ed. Anfinsen, C. B., Jr., Edsall, J. T., and Richards, F. M., Academic Press, New York, 1972, pp. 279402. Ferrer, R., Soria, B., Dawson, C. M., Atwater, I., and Rojas, E., Am. J . Physiol., 1984, 246, C520. Perez-Armendariz, E., Atwater, I., and Rojas, E., Biophys.J., 1985, 48, 741. Hales C. N., and Randle, P. J., Biochem. J., 1963, 88, 137. Kekow, J., Ulrichs, K., Muller-Ruchholtz, W., and Gross, W. L., Diabetes, 1988, 37, 321. Millar, J., Slamford, J. A., Kruk, Z. L., and Wightman, R. M., Eur. J . Pharm., 1985,109, 341. Leszczyszyn, D. J., Jankowski, J. A., Viveros, 0. H., Diliberto, E. J., Near J. A., and Wightman, R. M., J . Neurochem., 1991, 56, 1855. 0' Neill, R. D., Analyst, 1994, 119, 767. Huang, L., Shen, H., Atkinson, M. A., and Kennedy, R. T., Proc. Natl. Acad. Sci. USA, 1995,92,9608. Stankovich, M. T., and Bard, A. J., J . Electroanal. Chem., 1977,85, 173. Trijueque, J., Sanz, C., Monlebn, C., and Vicente, F., J . Electroanal. Chem., 1988, 251, 173. Trijueque, J., and Vicente, F., An.Quim., 1990, 86, 538. Trijueque, J . , Vicente, F., Martinez, F., and Vera, J., Port. Electrochim. Acta, 199 1, 9, 399. Honeychurch, M. J., and Ridd, M. J., Electroanalysis, 1996, 8, 49. Wojciechowyki, M., and Balcerzak, J., Anal. Chem., 1990, 62, 1325. Brett, C. M. A., Oliveira Brett, A. M., and Mitoseriu, L. C., Anal. Chem., 1994,66, 3145. Brett, C. M. A., Oliveira Brett, A. M., and Mitoseriu, L. C., Electroanalysis, 1995, 7, 225. Brett, C. M. A., Oliveira Brett, A. M., and Tugulea, L., Anal. Chim. Acta, 1996, 322, 151. Cox, J. A., and Gray, T. J., Anal. Chenz., 1989, 61, 2462. Stamford, J. A., Palij, P., Davidson, C., Jorm, C. M., and Phillips, P. E. M., in Neuromethods, ed. Boulton, A,, Baker, G., and Adams, R. N., Humana Press, Clifton, NJ, 1995, 27, pp. 81-1 16. Blundell, T., Dodson, G., Hodgkin, D., and Mercola, D., in Advances in Protein Chemistry, ed. Anfinsen, C. B., Jr., Edsall, J. T., and Richards, F. M., Academic Press, New York, 1972, p. 325. Paper 6103650C Received May 28, 1996 Accepted July 25, 1996

ISSN:0003-2654    

DOI:10.1039/AN996210178N

出版商:RSC    

年代:1996

数据来源: RSC

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Analyst, December 1996, Vol. 121 1747 Foreword The Sixth European Conference on Electroanalysis The Sixth European Conference on Electroanalysis (ESEAC ’96) was held in Durham, UK, on March 25-29, 1996. Previous meetings of the European Society for ElectroAnalysis were held in Dublin (1 986), Turku (1988), Gijon (1990), Noordwijkerhout (1992) and Venice (1994). Durham is, like Venice, a World Heritage Site, and a city which offers a delightful and spectacular setting for an international meeting. The castle, founded by William the Conqueror in 1072, scene of the Conference Banquet, and the magnificent Norman Cathedral dominate the city, standing high on a rocky, tree-clad outcrop around which the River Wear meanders. The University is the third oldest in England. after Oxford and Cambridge, and like them is a collegiate university.The meeting was organized by the RSC Electroanalytical Group (Analytical Division) in conjunction with the RSC Fine Chemicals and Medicinals Group (Jndustrial Division). Some 150 delegates coming from 25 countries in Europe and outside, ranging from Romania, Turkey, the Urals and Thailand, to the East, and to Alberta and Mexico to the west, made the ocasion a memorable event despite the cool March weather. The general theme of the meeting, electroanalytical chem- istry, covered a range of diverse topics encompassing potentio- metric and amperometric sensors and biosensors, micro- fabrication, sensing mechanisms and applications in industry, environmental and clinical analysis. This issue of The Analyst contains 31 papers featuring some 30% of the 18 invited lectures and 24 other oral presentations, and some 20% from the Durham Castle, the Normun Keep.75 posters displayed in two sessions. Some of the other contributions have been published elsewhere, and others may appear in later issues of The Analyst. Initial disappointment at the inability of the first invited lecturer, Meyerhoff (Michigan), to attend due to indisposition, was soon dispelled by the organizing committee’s contingency plan being brought into operation with Parker (Durham) starting the session with an excellent review lecture on the applications of funtionalized cyclodextrins in electroanal ysis. The cover photograph on this issue of the Rose Window in Durham Cathedral was featured as a slide in this lecture illustrating a well defined array reminiscent of size-matched complexation of guest species.Parker’s group is represented here by some recent work (1 829). Specially noteworthy among the invited lectures on electro- analytical topics, featured here, include important reviews by Alegret (17.5 1) on carbon-polymer biocomposites and Emons (1 9 17) on the use of electroanalysis in environmental monitor- ing. Others, which attracted particular interest, were voltam- metry above the boiling point by Griindler, (1 805), Ogorevc (1839) on carbon fibre nanoelectrodes, and the work of some very active Spanish groups (1 863, 1891, 1855, 1845, 1835). Complementary sessions, organized by the RSC Fine Chem- icals and Medicinals Group, were devoted to luminescent sensors and biosensors. Excellent lectures by de Silva (17.59) and Fabrizzi (1763) focussed attention on developments in the design and synthesis of ion-selective luminescent systems, and Sutherland (1775) reviewed his important work on the develop- ment of chromogenic cryptands.Turner ( 1769) described recent innovations in biosensors for gases. The juxtaposition of scientists whose main work embraces sensor design and synthesis with the more physically based electroanalytical community led to some positive interdisciplinary interactions. The consensus impression gained from the conference, and well conveyed by this selection of the work presented in Durham, is that electroanalysis is a vibrant, scientifically1748 Analyst, December 1996, Vol. 121 Conference excursion to Hadrian' s Wall stimulating and profitable area of research, ESEAC '98 is scheduled for 24-28 May 1998 in Coimbra, Portugal (CMA Brett, tel./fax +351 39 35295). Arthur K. Covington Department of Chemistry Univer.sit_)! of' Newcastle upon Tyne

ISSN:0003-2654    

DOI:10.1039/AN9962101747

出版商:RSC    

年代:1996

数据来源: RSC

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Analyst, December 1996, Vol. I21 1749 Guest Editors Professor David Parker, Professor Arthur K. Covington, Professor Brian J. Birch and Dr. Arnold G. Fogg Professor David Parker, MA, DPhil, C.Chem, FRSC David Parker was born in County Durham in 1956 and was educated at Christ Church, Oxford gaining a first-class degree in chemistry in 1978. He undertook research in the Dyson Perrins Laboratory working with Dr. John Brown, examining the mechanism of asymmetric homogeneous catalysis. He left Oxford in 1980 and enjoyed a NATO fellowship in Strasbourg, working with Professor Jean-Marie Lehn on various aspects of macrocyclic chemistry. The appointment to a lectureship at Durham University in 1982 brought him back to his native North-East. In 1989 he was promoted to a senior lectureship and in 1992 he took up a Chair in Chemistry.Professor Parker has published over 160 papers and a dozen patents on a variety of themes involving solution complexation phenomena. These include chirality and catalysis, electroactive materials and sensors, the targeting of metal complexes in vivo and a good deal of synthetic work and solution complexation chemistry related to the development and application of macrocyclic chemistry which most recently has focused on lanthanide coordination chemistry. In 1988 he was awarded the Hickinbottom Fellowship by The Royal Society of Chemistry and the following year he gained a Corday-Morgan medal and prize. He received the TCT Research Prize in Organic Chemistry in 1991 and in 1996 he won the Interdisciplinary Award of the RSC for his work on tailored and targeted metal complexes.He has served on Perkin Council and on various other RSC committees and is currently Chairman of the UK Macrocyclic Group and Chairman of the Department of Chemistry at Durham. He maintains strong contacts with various industrial organi- sations particularly Celltech Therapeutics and Guerbet s.a. but has also worked closely with Zeneca, ICI, Glaxo and the Cookson group. Professor Parker is married and has three energetic children and maintains a strong interest in cricket, golf and gentle fell- walking. Professor Arthur K. Covington, B.Sc., Ph.D, D.Sc. Arthur K. Covington received the degrees of B.Sc., Ph.D and D.Sc. from the University of Reading, where he worked with J. E. Prue on the application of glass electrodes to precise thermodynamic measurements.After a period in industry, he went in 1958 to Kings College in the University of Durham, which in I963 became the University of Newcastle upon Tyne, to join the electrochemistry group of W. F. K. Wynne-Jones. In 1966, he spent 6 months sabbatical leave with R. G. Bates at NBS Washington, USA, working on the heavy water pD scale. In Newcastle, he broadened his solution chemistry interests to include NMR measurements on preferential solvation in mixed solvent electrolyte solutions, and Kaman measurements of dissociation of moderately strong acids. He became Senior Lecturer in 1969, Reader in Physical Chemistry in 1971, and was awarded a personal Chair in Electroanalytical Chemistry in 1985. His contributions to solution chemistry were recognized by the award of the 1983-4 R.A. Robinson Medal and Lecturership in Malaysia, and of the 1987 Sigillum Magnum of Bologna Ilniversity. In 1986, he received the RSC Medal for Electroanalytical Chemistry. As Chairman of a British Standards Institution Technical Committee since 1973, he has been responsible for the preparation of the British Standards on pH measurement, pH meters, glass, ion-selective electrodes and reference electrodes. He has been associated with the IUPAC Commission on Electroanalytical Chemistry since 1979 and is currently UK National Representative. He was responsible for the preparation of the 1985 IUPAC recommendations on pH, and later recommendations on pH determinations on natural waters arising out of a programme of NERC-supported work in association with FBA Ambleside and MBA Plymouth.Re- cently, his work has been concerned with the application of ISEs and ISFETs to clinical measurements, establishing the reference method for ionized calcium in blood plasma, and developing a method for measurement of pH in heart muscle. Since 1983 he1750 Analyst, December 1996, Vol. 121 has been a member of the IFCC Working Group on Selective Electrodes. Professor Covington retired in September 1995 after 37 years in Newcastle and his retirement was marked by a joint Analytical and Faraday Divisions Autumn Meeting Symposium in Sheffield, ‘Ions in Solution’. He continues, as Emeritus Professor, his research in Newcastle and other activities. He recalls wryly, that, at an Electrochemical Group Committee meeting over 3 years ago, he agreed to organise ESEAC ’96 with the statement that he would ‘have plenty of time to do it’ as he would, by then, be retired! Professor Brian J. Birch, B.Sc., Ph.D, C. Chem., FRSC Professor Birch’s biography was published in The Analyst, 1994, 119, 165. At the beginning of 1995, Brian moved full time to the University of Luton, where he holds the Chair in Measurement Science. He is based at the Research Centre within the university, where he is engaged in building the University’s portfolio in this area. In addition to obtaining several research contracts with major industrial customers, he has been awarded recently a ROPA project funded by EPSRC. He is the Division’s 1996 Theobald lecturer. Dr. Arnold G. Fogg, B.Sc., Ph.D, D.Sc., ARTCS, C. Chem., FRSC Dr Fogg’s biography was published in The Analyst, 1994, 119, 165.

ISSN:0003-2654    

DOI:10.1039/AN9962101749

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Analyst, Decwnhei- 1996, Vol. 121 ( I 751-I 758) 1751 Rigid Carbon-Polymer Biocomposites for Electrochemical Sensing* A Review Salvador Alegret Grup dc Sensors i Biosensors, Departament de Qui'mica, Uniwrsital Autdnoma de Barcelona, 08293 Bellatei-ra, Catalonia, Spain This paper reviews the use of biocomposite materials in the construction of amperometric biosensors. These rigid composites are formed by dispersing graphite particles in assorted polymers (especially epoxy resins). These composites are bulk-modified biologically (adding enzymes and cofactors) and chemically (blending mediators and catalysts). Keywords: Biocomposites; conducting composites; rigid c*arbon-polyniei- hioconiposites; amperometric biosensor; elrc~ti.ochemic.al seiisor; reijien) Introduction Most strategies in analytical chemistry today call for complex instrumentation and considerable support, including special laboratory facilities and highly skilled personnel.Chemical sensors are a key element of novel strategies applied to analytical instrumentation. Sensors and sensor-based devices provide original solutions without the need for complex instruments or a huge support infrastructure. Chemical sensors are devices that are small, robust, portable and easy to use. Additionally, they do not need reagents to operate and they can yield reliable information continuously. A chemical sensor has two distinctive parts: a selective recognition component (receptor) and an element (transducer) that converts the primary signal produced by the receptor during the recognition event into a more useful secondary signal.The nature of the primary signal can be thermal, mass, electro- chemical or optical and usually has to be transduced to an electrical signal. This secondary electrical signal contains the codified chemical information from the sample. Several disciplines have to converge in the design of these devices. The design of sensors with biological recognition components such as enzymes, immunological species, che- moreceptors and DNA strands is receiving great attention nowadays. The chemical selectivity shown by these biocom- ponentc is very high. Sensors of this kind are known as hiosc~nsors. Biosensor science and technology use physical and chemical immobilization procedures to couple biological recog- nition elements to appropriate transduction devices.Generally, the biological material is fitted on the surface of transducers using complex and wet immobilization procedures. However, these procedures are seldom suitable for mass production. Amperometric biosensors, usually formed by biologically surface-modified voltammetric electrodes, are gaining increas- ing importance owing to their high reliability, robustness and sencitivity. I Efforts continue to increase the quality of the electrochemical response. Additionally, new materials and ' Prcscnted 'it the 6th European Conference on Electroanalysis, Durham. March 25-29. 1996. immobilization techniques are being tried for the mass produc- tion of these devices. In this context, the present review covers recent work in the field of amperometric biosensors based on new types of materials known as hiocomposites.These materials are formed by rigid conductive composites based on carbon-polymer matrices where the biological material (enzymes) as well as other modifiers (cofactors, mediators, catalysts, additives, etc.) are jointly bulk-immobilized. Conducting Composites A composite is formed by the combination of two or more phases of different nature. Each phase maintains its individual traits, but the mixture may show new physical, chemical or biological properties. If one of the phases is an electrical conductor, the overall electrical properties of the conducting composite will be determined by the nature, the relative content and the distribution of each phase. Electrical resistance depends on the connectivity of the conductor particles in the matrix of the composite.Several conductimetric chemical sensors are based on the disruptive action of organic vapours on the conducting filaments of the material.2J Simple and inexpensive all-solid-state potentiometric sensors have been developed by replacing the metal substrate with a graphite+poxy or a metal- epoxy composite. These composites are mouldable before curing so sensors of different shapes and sizes can be constructed. Ion-selective membranes adhere better to these materials and the resulting devices are simple and inexpensive, show prolonged lifetimes4.5 and the quality of their response is acceptable for analytical applications. An extensive review of ion-selective electrodes based on conducting epoxy composites appeared recently.6 Conducting Composites for Amperometric Sensing The polymer gives the biocomposite a certain physical, chemical or biological stability.The biocomposite acquires particular electrochemical traits from the distribution of the conductive phase in the bulk and, consequently, on the surface of the biocomposite. Carbon materials (graphite, carbon black, etc-.) are ideal conductive phases for composites used in amperometric sensors. These materials have a high chemical inertia and show a wide range of working potentials. They also have a low electrical resistance (approximately 1 0-4 52 cm) and a crystal structure responsible for low residual currents. If the surface of a macroelectrode is reduced, the signal and the associated noise also diminish.In microelectrodes, accord- ing to Oldham,7>8 the perimeter of the sensing surface has a greater influence on the signal. By means of this edge effect, non-linear diffusion is established and the quality of the signal is enhanced. This enhancement is shown by a higher signal-to- noise ratio and lower detection limits. These features and their1752 Analyst, December 1996, Vol. 121 inherent small size have raised interest in microelectrodes. However, the low currents produced call for complex and expensive instrumentation. If small sensors are not required, an alternative is to build carbon fibre arrays separated by an insulating matrix and connected in parallel.9 The signal produced by this macroelectrode formed by a carbon fibre ensemble is the sum of the signals of the individual microelectrodes.The size of the resulting signal is equivalent to the signal produced by a carbon rod of the same active surface but showing the signal-to-noise ratio of a microelectrode. The construction of these ensembles is difficult. However, an equivalent device can be constructed when a composite is made of small conductive particles dispersed in a polymer matrix. Additionally, these devices are easier to build. The selectivity and sensitivity of an amperometric sensor are greatly enhanced if the surface is modified with certain chemical and biological species. One of the key advantages of composite-based sensors is the ease of bulk modification compared with the modification of the surface of a pure conductor, which is usually complex and costly.Conductive composites are modified easily because of their plasticity before curing. Modifying fillers can be blended into the matrix, conferring new abilities on the resulting composite. These new abilities include immobilization of reagents involved in the electrochemical reaction, electrocatalysis, preferential preconcentration and surface structuring. Soft versus Rigid Conductive Composites Adams'O proposed the use of soft carbon pastes to build amperometric transducers. These pastes are built by mixing an inert conductor (e.g., graphite powder) with a non-conducting liquid (e.g., paraffin oil, silicone, Nujol). This insulating liquid has a specific viscosity and the paste has a certain consistency. The resulting devices are easy to prepare and inexpensive and can be coupled to simple instruments.However, these pastes have limited mechanical and physical stability, especially in flow systems. Additionally, the pastes are dissolved by some non-polar electrolytic solvents, leading to a deterioration of the signal. The general degradation of these devices occurs quickly and has limited their use to the research laboratory. Reviews on chemically' 1 and biologically12 mod- ified carbon paste electrodes have appeared recently. On the other hand, amperometric sensors and biosensors based on rigid composites do not show the problems mentioned above. Further, the fabrication of these devices can be adapted for mass production at a low cost. Rigid Carbon-Polymer Biocomposites Rigid Carbon-Polymer Matrices Creasy and co-workers reported the copolymerization of styrene with divinylbenzene (a cross-linking agent) and vinyl- ferrocene (a modifier), using carbon black' 3 (semigraphitic carbon particles) or carbon fibre9314 as a conductor.This was the basis for the construction of chemically bulk-modified elec- trodes. These devices showed better physical properties (the sensing surface was renewable by polishing) and enhanced chemical traits (they were stable in organic solvents) compared with carbon paste electrodes. Wang and co-workers used a commercially available graphite epoxy resin (Grade RX, Dylon, Cleveland, OH, USA) to build chemically and biologicallyI6 bulk-modified electrodes. The use of this commercial compos- ite rendered the Fabrication of the sensors easier, quicker and more reproducible than the procedure proposed earlier by Creasy and Shaw.9 The approach followed by Wang and co- workers for the preparation of rigid biocomposites was the first report concerning this procedure and these materials.It has been adapted in our laboratories using a non-conducting epoxy (Epo- Tek H77, Epoxy Technology, Billerica, MA, USA), graphite powder (Merck, Darmstadt, Germany) (particle size below 50 pm), biological materials and additives. All these elements are mixed to build a particular biocomposite. l7,lx Our procedure has been expanded to include other polymer matrices such as silicone, polymethacrylate, polyester19 and polyurethane. All these polymers can be prepared it? situ, they readily admit the biological material and additives (catalysts, mediators, co- factors, etc.), they have a simple curing process and are commercially readily available. Graphite-Teflon electrodes were developed originally for vol tammetric and amperometric applications .2",2l These mate- rials with bulk-immobilized enzymes have served for the development of biosensors.22-z4 In this particular instance, the graphite and the powdered Teflon are mixed with the other ingredients and the mixture is pressed to form pellets.Biological Materials and Other Modifiers Immobilized in Rigid Carbon-Polymer Matrices The immobilization of some lyophilized en7ymes (oxidases, peroxidases, dehydrogenases and cholinesterases) in rigid carbon-polymer matrices has been reported (see Tables 1 4 ) .In some instances, the enzyme is covalently bonded to graphitG2 or silica25 particles before blending it to the polymer matrix. Different redox mediators and catalysts have been added to the biocomposites in order to enhance their selectivity and sensitivity. These modifiers may be substances related to ferrocene,1"22.26 tetrathiafulvalene27 and tetracyan- oquinodimethane25 or a metallic catalyst such as gold and palladium28-30 or platinum.31 Dehydrogenase biocomposites have been produced featuring the nicotinamide adenine dinu- cleotide (NAD+) cofactor.32,33 This has opened up the possibil- ity of reagentless biosensors for alcohols and lactate. An alcohol biosensor has been developed by confining dry yeast to a graphite-epoxy matrix. '6 Eisenia hicyclis, an alga, has also been immobilized in a graphite-epoxy matrix, forming a composite used in bioaccumulation assays and in the voltammetric measurement of metal ions.1 6 In our laboratories, biocomposites based on immunospecies immobilized in graphite-polymer matrices are being tried. These biocomposites have a surface that may be regenerated by polishing after each immunological assay.34 Preparation of the Biocomposites and Biosensor Construction The biocomposites are prepared very easily. The powdered graphite is dispersed homogeneously by hand with the appro- priate amount of polymer. According to Tallman and Petersen,x these materials can be classified as dispersed composites since the conductor particles have an equal opportunity to occupy any point throughout the matrix.The polymer material is activated when its components are blended. The activation happens when a volatile fraction evaporates or when a hardener, catalyst or initiator acts on the resin. The resin may be epoxy, silicone, methacrylate, polyester or polyurethane (see Table 1). The contents of the graphite, the modifier (enzyme, catalyst, mediator) and the additives are optimized for a particular polymer matrix. Graphite particles are smaller than 50 pm.19 The goal is to achieve the maximum electrical conductivity and the highest response quality with an appropriate biocomposite rigidity. Graphite content may vary from 20% (epoxy) to 60% m/m (silicone).I9 As mentioned earlier, there is a commercial epoxy that already contains the graphite. 16 The fraction of biological material may vary from 1 % (acetylcholinesterase)35 to 25% m/m (tyrosinase).l 6 The homogeneous mixture is introduced 2-3 mm into a tube made of PVC, glass, etc. A metal disk coupled to a wire is usedAnalyst, December 1996, Vol. 121 1753 to contact the composite inside the tube. The ensemble is left at room temperature or slightly higher (40 "C) for one or more days as needed by the curing of the polymer. When it is hardened, the biocomposite is polished with abrasive papers of decreasing grain size. If the matrix is Teflon,22~~~ the granular polymer is mixed with graphite in mass proportions of 7 + 3. The biological material is previously immobilized on particles of graphite powder22 or is homogenized with Teflon and graphite particles at -20 OC.23 Once mixed, the material is pressed at 7000 Table 1 Glucose biosensors based on rigid conducting biocomposites Biocomposite components (% m/m) c Linear response range (mmol I-') 0.1-5 0.1-5 0.2-5 0.4-20 0.1-5 0.05-5 2.5-30 0.2-1'- 0.0 1-2 1-10 gl-'-'- 1-6-1 0.1-2 0.1-5 '"ippl vel'sus Ag/AgCI/V +1.15 +].I5 +1.1 +1.15 +1.1 +1.15 +0.9 +0.8 +0.9 +0.5 +0.3 +O.15 +0.2 Mediator/ catalyst Enzyme* GOD (2) GOD (2) GOD (2) GOD (2) GOD (2) GOD (2) GOD (20) covalently bound to graphite GOD ( 1 5 ) GOD (20) GOD (1.5) GOD (2) Carbon Polymer Graphite (19) Epoxy (79) (Epo-Tek H77) Graphite (49) Epoxy (49) (Epo-Tek H302) Graphite (49) Methacrylate (49) (Sealer-Healer 1540) Graphite (62) Silicone (36) (Sellaceys) Graphite (36) Polyester (62) (Resipol 9 144) Graphite (60) Polyurethane (38) P" 7.0 7.0 7.0 7.0 7.0 7.0 7.4 7.4 7.0 7.4 6.5 7 .0 7.0 Ref.19 19 19 19 19 This 22 work 28 29 16 26 27 This work Graphite (10) Teflon (70) (7A Dupont) Graphite (15.8) Epoxy (63.0) Graphite-epoxy (Dylon) (54) (Epo-Tek H77) Gold (1 1.8) and 1 ,l'-Dimethyl TTFl (19.7) palladium (7.9) ferrocene (26) Graphite (15.8) Epoxy (63.0) (Epo-Tek H77) Silicone (28) (Sellaceys) TTF, TCNQI: (70) ' Glucose oxidase (GOD) (100-200 U mg-I). + Flow-injection. 1 TTF = tetrahiafulvalene; TCNQ = tetracyanoquinodimethane. Table 2 Rigid conducting biocomposite-based biosensors for phenol and phenolic substrates Linear response range (pmol 1-I) Ref. 16 Biocomposite components (5% m/m) Eappl Ag/AgCl/V -0.2 vei'sus -0.2 -0.1 -0.1 -0.1 -0.05 PI3 (working solution) 7.4 (methanol 50% v/v) Carbon/ polymer Catalyst Substrate Graphite-epoxy Catechol' (Dylon) (92.5) Enzyme Tyrosinase (7.5) Dopamine Phenolics Phenol 50-350 0.Y 1" 1 0.04*,' 1 .OW.' 42 43 30 6.7 Mushroom tyrosinase (5) (6300 U mg- I ) Mushroom tyrosinase (3 (12600 U) Tyrosinase (1) (2400 U mg Phenolics Catechol Phenol Catechol Phenol 6.0 Graphite-epox y ( D y W (99) 6.0 (acetonitrile 5-20% v/v) (methanol 5-20% v/v) 6.0 Tyrosinase (1) Tyrosinase (1.8) (2400 U nig-1) (3900 U mg-I) Grapi te-epoxy Gold (8) Catechol (Dylon) (79) Palladium ( 12) Phenol Graphite (1 8) Catechol Graphite-Teflon (10-30%) (80.2) 30 0.2-25' 23 7.0 (methanol 10% v/v) * Detection limit.1 Flow iiijection.I754 Analyst, Decwnher 1996, Vol. 121 kg cm-2, producing 2 mm thick disks. These pellets are coupled to a tube to form an electrode.According to Tallman and Peterseqx these materials can be classified as consolidated composites, since the conductor particles extend throughout the matrix in a random, reticulated fashion with regions of pure insulator and pure conductor. num electrodes.36337 It is known that carbon electrodes that have metal particles (Pt, Ru, Rh, Pd, etc-.) on their surface show great catalytic action.3X.39 The same happens when the metal is dispersed in carbon pastes.3() The addition of catalysts (gold, palladium) to a GOD graphite-epoxy biocomposite for the oxidation of hydrogen peroxide increases the stability of the signal and reduces the response time. Further, the oxidation potential of hydrogen peroxide is lowered by 250 mV.l* This decrease is also found in experiments with carbon rods where Au-Pd was sputtered to the surface of the electrode."' Therefore, metal bulk-modified composites represent more viable alternatives than those surface-modified electrodes produced by sophisticated technologies.However, the inclusion of metal catalysts in the biocomposite does not hinder the action of the usual interferents found in biological samples (ascorbic acid, uric acid, etc.1.28 On the other hand, it has been observed in our laboratory that this material retains the enzymic activity in dry storage for more that 1 year. The lower working potential and the higher quality of the signal observed in biocomposi tes containing Au-Pd has permitted the use of these materials in flow injection systems. Biosensors with these materials have been used to monitor glucose in fermentation processes.29 Artificial electron acceptors may be added to the biocompo- site.These substances act as electron mediators between GOD Amperometric Biosensors Based on Rigid Carbon-Polymer Biocomposites Glucose Biosensors Several glucose biosensors based on biocomposites have been reported (see Table 1). Glucose oxidase (GOD) has been used in our laboratory as an enzyme model to study the biocatalytic characteristics of rigid conducting biocomposites that feature immobilized enzymes. This oxidase is compatible with matrices of graphite and several polymeric materials such as epoxy resins, polymethacrylate, silicone, polyester, polyurethane and Teflon. These biocomposites have been applied to glucose measurement based on the direct oxidation of the hydrogen peroxide produced by the action of the enzyme [see Fig.1 (A)]. This happens at extreme potentials (0.9-1.15 V versus Ag/ AgCI) (see Table I). When a graphite-polymer composite is used, a shift towards more positive potentials is observed compared with measurements realized with graphite or plati- Table 3 Rigid conducting biocomposite-based biosensors for hydrogen peroxide and organic peroxide substrates PH mediator (working solution) 7.4 hexacyano- ferrate(1r) o-pheny lene diamine 7.4 7.4 Linear re spon \e range (nimol I-') Ref. 16 Biocomposite components (5% m/m) E.'PPl Carbon/ polymer Mediator/ l'f2YSI4.5 catalyst Substrate Ag/AgCl/V H202 -0.2 Enzyme Horseradish peroxidase (25) Graphite-epox y ( D y W (75) Horseradish peroxidase (1 5 ) (94 U mg-I) Horseradish peroxidase covalently bound to graphite (16) Organic -0.2 peroxides 47 Graphite ( 10) Teflon (70) Ferrocene (4) H202 0.0 Butan-2-one peroxide 2.5 pmol 1 I ' 22 20-200 pmol 1 * I 3.0 pmol I-'* H202 0.0 Butan-2-one peroxide Butan-2-one Ferrocene H202 -0.1 7.4 22 (acetonitrile 90% v/v) (reversed 1-100 pmol I-] micellar media) 7.4 1-60 pmol 1 ~ 24 7.4 ?-0.02 48 Horseradish peroxidase Graphite Teflon Horseradish peroxidase (1 5 ) (90 U mg- I ) mixed with human serum albumin ( 5 ) Hz02 -0.25 B utan-2-one peroxide '!-0.05 Cumene peroxide peroxy- benzoate hydro- peroxide terr-Butyl tel-r-Buty 1 H Z 0 2 -0.35 ' L O .I '?-(I. I ?- 1 0.005-0.5 19 Horseradish peroxidase (2) (318 U mg-I) peroxidase (2) peroxidase ( I .9) Horseradish Horseradish Graphite (1 9) EPOXY (79) Graphite (20) Graphite ( 19.6) Epoxy (76.6) Epoxy (78) H202 -0.3 7.0 0.03-7 31 Platinum (1.9) H202 -0.05 7.0 0.09-9 31 * Detection limit.-1 Flow injection.Analyst, December 1996, Vol. 121 1755 and the electrode [see Fig. l(B)] and include 1 ,l'-dimethylfewo- ceneI6.'6 and tetrathiafulvalene.'7 The addition of these media- tors permits the use of working potentials in the range 0.5-0.15 V. The action of interferents is greatly reduced at these working potentials. In the biocomposite modified with tetrathiafulva- lene, ascorbic acid interference is reduced by 90% and the detection of uric acid is negligible.27 Phenol Biosensors Biocomposites featuring tyrosinase have been used in biosen- sors for (see Table 2). In this enzyme system, the species produced electrochemically (catechol) is also the enzyme substrate (see Fig.2). This amplifies the electrochemical response.44 That is the reason for the low detection limits found in these biosensors (see Table 2). However, Onnerfjord et al.,43 using tyrosinase-based rigid biocomposites, found detection limits higher by one to two orders of magnitude than those produced by thyrosinase biosensors based on carbon pastes. If gold and palladium particles are introduced into the biocomposite, an increase in current is achieved. 30 On the other hand, the products of the enzyme reaction (quinones) are highly unstable in water. Furthermore, they polymerize quickly into polyphenols that block the enzyme, and may passivate the electrode.Wang et al.42 reported a 4% decrease in the response of a tyrosinase biosensor after 10 successive discontinuous measurements of 1 X 10-5 mol 1-1 phenol samples. This decrease was explained as being due to slow fouling of the measuring surface by the products of the reaction. This deleterious effect may be minimized by working in flow ~ y s t e m s ~ ~ 3 ~ 3 or renewing the surface of the biocomposite by polishing. Tyrosinase keeps its biocatalytic action when confined to graphite+poxy matrices for moderate periods of times (3% decrease in 10 d with the device in dry storage at 4 "C). However, the biocatalytic activity could be regained after polishing (7040% of the original activity for catechol).4' Wang et al.42 proposes that this stabilizing effect may be due in part to the protective action of the epoxy matrix, not unlike the reported effect in non-aqueous media.4"46 This tyrosinase-graphite-epoxy biocomposite has been used to measure phenols in a partially aqueous medium containing 50%16 or 5-20%30 v/v methanol and 5-20% v/v acetonitrile.") Amperometric biosensors incorporating tyrosinase-graphite- Table 4 Biosensors for bilirubin, alcohols, lactate and pesticides, based on rigid conducting biocomposites Biocomposite components (% m/m) Enzyme Bilirubin Horseradish Yeast (20) oxidase ( 5 ) peroxidase ( 5 ) (Sac i hul-omyes cel-r\~i.siuP) Yeast alcohol dehydrogenase (7.5) (350 U mg-I) Lactate dehydrogenase (6) (148.7 U mg-I) aterase ( 12) ( 1 120 U mg-1) Acetylcholine Acetylcholine esterdse covalently bound to silica (2) Butyrylcholine esterase covalcntly bound to silica (2) Carbon/ Cofac lor/ polymer mediator Graphite-epox y (Dylon) (90) Graphite-epoxy NAD+ ( 10) (Dylon) (82.5) Graphite-epoxy NAD+ (12) (Dylon) (82) Graphite ( 1 7.6) Epoxy (70.4) Substrate Bilirubin Ethanol Alcohols Ethanol Ally1 alcohol Propan- 1-01 Butan- 1-01 Propan-2-01 Lactate Acety lthiocholine P" E"Wl mediator Linear versus (working response Ag/AgCl/V solution) range Ref.-0.2 7.4 4-1 00 pmol I- I 49 hexacyanoferrate( 1 1 ) +0.6 7.4 16 hexac yanoferrate( 11 I ) NAD+ +0.7 7.4 32 04.4 rnmol 1- I (-5.8 mmol I-' 0-8.2 mmol 1-1 0-1 1.7 mrnol 1- 13-32 mmol 1- I 0.5-20 mmol 1-11 +0.7 7.4 0.08 mmol 1-1 33 +0.7 7.0 Graphite (18) TCNQ (9)t Acetylthiocholine +0.3 7.5 Epoxy (7 1 ) Graphite (18) TCNQ (9):i Epoxy (7 1 Butyrylthiocholine +0.3 7.0 5-120 pmol I-' 35 20 pg I-]* carbofuran 27 pg I-' paroxon carbaryl dichlorvos 20 pg 1-1 22 pg I-' 2.5-1 00 pmol 1- I 25 2.2 pg 1 - 1 ' carbofuran 27.5 pg 1-1 paroxon carbaryl 2.0 pg I-' 5-100 pmol I- I 25 22.1 pg 1 - 1 - 2.8 pg 1-1 3.6 ug I-' carbofuran paroxon chlorfenvinphos * Detection limit.+ Flow injection. * TCNQ = 7,7,8,8-tetracyanoquinodimethane.1756 Analyst, December 1996, Vol. 121 Teflon biocomposite have been developed for the detection of catechol.23 Studies of the operational stability of the bio- composite response in organic media (10% v/v methanol or acetonitrile) were carried out in the flow injection mode. Better stability was achieved in methanol.23 Tyrosinase shows poor selectivity with respect to phenol substrates.The reported selectivity sequences for different tyrosinase biocomposites show inconsistencies among them- selves42.43 and with conventional tyrosinase biosensors. The hydrophobic nature of the graphite-epoxy resin modifies the selectivity sequence. Peroxide Biosensors Horseradish peroxidase (HRP) has been immobilized in rigid carbon-polymer matrices. This is the basis for the development of sensors for hydrogen peroxide and small organic peroxides. The first reports in literature follow the approach shown in Fig. 3(A). Reducing agents, such as hexacyanoferrate(I1) ion16 or o-phenylenediamine,47 are added to the solution to regenerate the enzyme to its reduced form. In this way, the oxidized form of these mediators can be detected at lower voltages (-0.2 V versus Ag/AgCl) than those used for the direct detection of hydrogen peroxide (see Glucose Biosensors section). Perox- idase has been immobilized with the mediator ferrocene in graphite-Teflon mat rice^.^^,^^ This opens up the possibility of developing reagentless sensors, capable of working at potentials around 0.0 V versus Ag/AgCl.These devices simplify the measurement process as they function as direct sensors that do a-D-glucose It p-D-glucose ~~ ox , GOD 2H+ 2H' 6-gluconolactone \red 1 n H20 D-gluconate + H+ ox Fig. 1 Reaction sequences for the amperometric detection of glucose using biocomposite electrodes: (A) GOD-graphite-polymer biocomposite; and (B) GOD-mediator-graphite-polymer biocomposite. I Biocomposite 2H' + 2Hi I 2H+ Fig.2 phenolic substrates using a tyrosinase-graphite-polymer biocomposite. Reaction sequence for the amperometric detection of phenol and Fig. 3 Reaction sequences for the amperometric detection of hydrogen peroxide and organic peroxide substrates using biocomposite electrodes: (A) mediated HRP-graphite-polymer biocomposite (mediator in solution or in biocomposite); and (B) mediatorless HRP-graphite-polymer bio- composite. not require additional reagents. The rapid response shown by these biosensors makes them ideal for flow applications.zz The biocomposite HRP-ferrocene-graphite-Teflon is stable in a medium of acetonitrile water (9 + 1 v/v). Biosensors based on this composite have been applied to the determination of hydrophobic organic peroxides in this mediumz2 and in reversed micellar media.24 Biocomposites based on HRP-graphite-epoxy have been used to prepare mediatorless biosensors where direct electron transfer takes place between the active sites of the enzyme and the graphite particles when the substrate is present 19,31,48 [see Fig.3(B)]. We have observed31 that the addition of platinum particles in these biocomposites permits one to work with a lower potential than the optimum working potential of unmodi- fied HRP-graphite-epoxy biocomposite electrodes (see Table 3). The trend of sensitivity for mediatorless biocomposites4~ is in accordance with data obtained for o-phenylenediamine- mediated HRP-carbon paste electrodes47 : hydrogen peroxide > butan-2-one peroxide > tert-butylperoxy benzoate > cumene peroxide > tert-butyl hydroperoxide.The response and surfxe-to-surface reproducibility have been improved by mixing HRP with human serum albumin (HSA).48 This can be attributed to the stabilizing effect of HSA on HRP during the curing process of the graphite-epoxy resin (reaction of epoxy with amino groups), similarly to glutar- aldehyde inactivation of pure enzymes due to a cross-linking reaction with amino groups.48 Bilirubin Biosensor The co-immobilization of HRP and bilirubin oxidase in a graphite-epoxy composite and the addition in solution of ferrocene as a mediator complete the construction of a bilirubin biosensor,49 as seen in Fig. 4 and Table 4. The rapid passivation induced by the adsorption of bilirubin or biliverdin calls for frequent polishing of the surface of the biosensor.The renewable surfaces associated with graphite-polymer biocom- posites lend themselves well for this task. Alcohol Biosensors The co-immobilimtion of alcohol dehydrogenase (ADH) and NAD+ in a graphite-epoxy matrix has allowed the development of reagentless alcohol biosensors32 (see Table 4), following the scheme shown in Fig. 5(A). This type of biosensor shows a rapid decrease of the signal on continuous use owing to a fouling of the biocomposite, incomplete recycling of NAD+- NADH system or a loss of this cofactor. If the surface is polished, the initial activity is restored reproducibly. ADH from yeast, used in these biocomposites, oxidizes primary alcohols quickly (with the exception of methanol). Secondary alcohols are also oxidized but more slowly. The sensitivity sequence of these biosensors (i.e., ethanol > ally1 alcohol > butan-1-01 > propan- 1-01 > propan-2-01) is slightly different to the sequence observed for the same enzyme in solution.32 I biliverdin 0, 2H+ 2H' Fig.4 Reaction sequence for the amperometric detection of bilirubin using a biocomposite electrode: mediated bilirubin oxidase (BOX)- horseradish peroxidase (HRP)-graphite-polymer biocomposite (mediator in solution).Analyst, December 1996, Vol. 121 1757 In the first paper in which Wang and Varughese16 singled out polishable and robust biological electrode surfaces, they reported a graphite-epoxy biocomposite containing dry yeast. These materials had enzyme activity blended into the rigid conductive composite.The resulting alcohol biosensor worked in a buffered medium containing the cofactor and hex- acyanoferrate(II1) as a mediator [see Fig. 5(B)]. Lactate Biosensor Following the strategy mentioned earlier [see Fig. 5(A)], lactate dehydrogenase (LDH) and the cofactor NAD+ have been immobilized in rigid matrices consisting of graphite and epoxy33 (see Table 4). The resulting reagentless biosensors may experience a rapid decrease in sensitivity, as found in ADH- NAD-graphite-epoxy biocomposites. Owing to the high work- ing potential (0.70 V versus Ag/AgCl) needed for the regeneration of NAD+, these biosensors show significant interferences from several species such as acetaminophen, ascorbic acid and uric acid. These biosensors have a fast response and are suitable for continuous-flow measurements. In flow injection procedures, where the sample is briefly in contact with the sensor, passivation effects are much less noticeable than in discontinuous measurements.33 Pesticide Biosensors Organophosphorus and carbamate pesticides have been deter- mined with biosensors based on biocomposites containing acetyl~holinesterase.2~~~~ This enzyme hydrolyses both its natural substrate and thiocholine esters.The hydrolysis of acetylthiocholine produces thiocholine. This electroactive spe- cies is detectable at a potential of 0.7 V versus Ag/AgCl applied to the biocomposite. Fig. 6(A) shows the biosensor response to the substrate. This response is inhibited if organophosphorus and carbamate pesticides are present. This enzyme inhibition is irreversible, calling for the renewal or the reactivation of the enzyme content in the electrode surface either by replacing more enzyme or by regenerating it with special reagents.Biosensors based on rigid biocomposites are an attractive proposition here, since this enzyme ‘reloading’ is achieved by simple polishing of the biosensor surfxe. If the mediator TCNQ Biocomposite Fig. 5 Reaction sequences for the amperometric detection of substrates (S) as alcohols or lactate using biocomposite electrodes: (A) dehy- drogenase-NAD-graphite-polymer biocomposite; and (R) mediated dehy- drogenase-graphite-polymer biocomposite (cofactor and mediator in solution). @ H,O + thiocholine Fig. 6 Reaction sequences for the amperometric detection of thiocholine esters using biocomposite electrodes: (A) cholinesterase-graphite-polymer biocomposite; and (JS) cholinesterdse-mediator-graphite-polymer bio- composite.The enzymic hydrolysis of thiocholine esters is inhibited by the presence of some pesticides. (7,7,8,8-tetracyanoquinodimethane)25 is added to the bio- composite [see Fig. 6(B)], thiocholine can be detected at a potential of 0.3 V versus Ag/AgCl, curtailing the effect of interferents. Biocomposites made of butyrylcholinesterase- TCNQ-graphite-epoxy have been prepared for the measure- ment of butyrylthiocholine at this same potential25 (see Table 4). If the origin of the cholinesterase (electric eel, horse serum and bovine erythrocytes) is altered, serious inconsistencies are noted in the biocomposites prepared due to the leakage of the enzyme.A satisfactorily reproducible response is attained only with acetylcholinesterase from bovine erythrocytes. If the enzyme is immobilized on silica particles for stability, good reproducibility is attained regardless of the origin of the enzyme. This step does not alter the curing process of the biocomposite.25 Conclusions Biosensors based on rigid polymer-graphite composites are a recent development and examples of their design and applica- tion are still scarce in the literature (see Tables 1 4 ) . However, several advantageous qualities of biocomposites based on rigid graphite-polymer mixtures can be envisaged from the present review. The preparation procedure for these biocomposites is simple and involves dry chemistry techniques for the most part.In some cases, the enzyme has first to be immobilized on some sort of support particles. Before curing, these biocomposites are highly mouldable. This permits the easy construction of amperometric sensors of various shapes (cylindrical, planar, tubular, flow-through, etc.), and sizes. After curing, these materials are very stable from a mechanical point of view. The surface is stable, rigid and polishable and can be drilled or otherwise altered mechani- cally. The components of the sensing surface can be controlled by defining their content in the bulk. The presence of enzymes, cofactors, mediators, additives, etc., on the sensing surface can be tailored by adjusting their content in the bulk of the biocomposite. Biosensors prepared with the techniques described here have great biological stability.The biocomposite acts as an im- pervious reservoir for the biologically active components. The decrease in sensitivity on the surface is recovered by a simple polishing procedure. Each new surface yields reproducible results if all the individual components of the biocomposite are dispersed homogeneously in the bulk. Epoxy resins and Teflon are employed as polymer matrices because they are well known materials. They provide chemical stability and the resulting biosensors can be used in partially aqueous media (methanol-water, acetonitrile-water, etc.). The morphology, size and distribution of the conducting particles define the behaviour of the biosensor as a microelec- trode array. These microelectrode arrays or ensembles show efficient mass transport and a better electrochemical response (high signal-to-noise ratio, low detection limits, fast response times). The resulting biosensors are suitable for flow systems because of these electrochemical, chemical, mechanical and biological features.Finally, the preparation of the biocomposites and the construction of the biosensors are inexpensive. Final Remarks Surface characterization is a key point in understanding the function of modified electrodes. This knowledge is useful in the design of surface microstructures suitable for the construction1758 Atialyst, December 1996, Vol. 121 of more selective sensors. Surfaces of the type reviewed here have not been studied thoroughly. Scanning tunnelling micros- copy (STM) has been useful in the study of graphite distribution in the surface of an ADH-NAD-graphite-qoxy biocompo- site,32 but this technique cannot produce useful information about the other non-conductive components of the material.The biosensors reviewed here (see Tables 1-4) have been constructed manually in cylindrical shapes. Thick-film tech- nologys" may be the fastest, most reproducible and economical way of mass producing biosensors. Screen printing and ink-jet printing techniques have shown great potential in this respect. These procedures have been used for the sequential deposition of the layers on the device (conductor. receptor, mediator, permselector, insulator, etc.). Using the biocomposites de- scribed here, these methods can be transformed into one-step processes.s1-s4 In this fashion, the printing process becomes simpler and more reproducible. Biocomposites can be rendered more fluid and applied as inks for these methods of mass production.The coupling of the biocomposites mentioned here and printing processes for the production of biosensors have great promise. This work is in progress in our laboratories. All the biocomposites reviewed have been developed for using in amperometric devices. 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ISSN:0003-2654    

DOI:10.1039/AN9962101751

出版商:RSC    

年代:1996

数据来源: RSC