摘要:

'""Aria I ys tThe Analytical Journal of The Royal Society of ChemistryAnalytical Editorial BoardChairman: A. G. Fogg (Loughborough, UK)M. Cooke (Sheffield, UK)H. M. Frey (Reading, UK)J. M. Gordon (Cambridge, UK)G. M. Greenway (Hull, UK)S. J. Hill (Plymouth, UK)D. L. Miles (Keyworth, UK)J. N. Miller (Loughborough, UK)R. M. Miller (Gouda, The Netherlands)B. L. Sharp (Loughborough, UK)M. R. Smyth (Dublin, Ireland)Y. Thomassen (Oslo, Norway)P. Vadgama (Manchester, UK)Advisory BoardJ. F. Alder (Manchester, UK)A. M. Bond (Victoria, Australia)J. G. Dorsey (Cincinnati, OH, USA)L. Ebdon (Plymouth, UK)A. F. Fell (Bradford, UK)J. P. Foley (Villanova, PA, USA)M. F. Gine (Sao Paulo, Brazil)T. P. Hadjiioannou (Athens, Greece)W. R. Heineman (Cincinnati, OH, USA)A.Hulanicki (Warsaw, Poland)I. Karube (Yokohama, Japan)E. J. Newman (Poole, UK)J. Pawliszyn (Waterloo, Canada)T. B. Pierce (Harwell, UK)E. Pungor (Budapest, Hungary)J. R6iiEka (Seattle, WA, USA)R. M. Smith (Loughborough, UK)K. Stulik (Prague, Czechoslovakia)J. D. R. Thomas (Cardiff, UK)J. M. Thompson (Birmingham, UK)K. C. Thompson (Sheffield, UK)P. C. Uden (Amherst, MA, USA)A. M. Ure (Aberdeen, UK)C. M. G. van den Berg (Liverpool, UK)A. Walsh, KB (Melbourne, Australia)J. Wang (Las Cruces, NM, USA)T. S. West (Aberdeen, UK)Regional Advisory EditorsFor advice and help to authors outside the UKProfessor Dr. U. A. Th. Brinkman, Free University of Amsterdam, 1083 de Boelelaan, 1081 HVAmsterdam, THE NETHERLANDS.Professor P.R. Coulet, Laboratoire de Genie Enzymatique, EP 19 CNRS-Universite ClaudeBernard Lyon 1, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex,FRANCE.Professor 0. Osibanjo, Department of Chemistry, University of Ibadan, Ibadan, NIGERIA.Professor F. Palmisano, Universita Degli Studi-Bari, Departimento di Chimica CampusProfessor K. Saito, Coordination Chemistry Laboratories, Institute for Molecular Science,Professor M . Thompson, Department of Chemistry, University of Toronto, 80 St. GeorgeProfessor Dr. M. Valcarcel, Departamento de Quimica Analitica, Facultad de Ciencias,Professor J. F. van Staden, Department of Chemistry, University of Pretoria, Pretoria 0002,Professor Yu Ru-Qin, Department of Chemistry and Chemical Engineering, Hunan University,Professor Yu.A. Zolotov, Kurnakov Institute of General and Inorganic Chemistry, 31 LeninUniversitario, 4 Trav. 200 Re David-70126 Bari, ITALY.Myodaiji, Okazaki 444, JAPAN.Street, Toronto, Ontario, CANADA M5S 1Al.Universidad de Cordoba, 14005 Cordoba, SPAIN.SOUTH AFRICA.Changsha, PEOPLES REPUBLIC OF CHINA.Avenue, 117907, Moscow V-71, RUSSIA.Editorial Manager, Analytical Journals: Janice M. GordonEditor, The AnalystHarpal S. MinhasThe Royal Society of Chemistry,Thomas Graham House, Science Park,Milton Road, Cambridge, UK CB4 4WFTelephone +44(0)223 420066.Fax +44(0)223 420247. Telex No. 818293 ROYAL.US Associate Editor, The AnalystDr Julian F. TysonDepartment of Chemistry,University of Massachusetts,Amherst MA 01003, USATelephone +I 413 545 0195Fax +I 413 545 4490Assistant EditorsSarah Williams Yasmin KhanEditorial Secretary: Claire HarrisAdvertisements: Advertisement Department, The Royal Society of Chemistry, BurlingtonHouse, Piccadilly, London, UK WIV OBN.Telephone +44(0)71-287 3091. Telex No. 268001.Fax +44(0)71-494 1134.Information for AuthorsFull details of how to submit material forpublication in The Analyst are given in theInstructions to Authors in the January issue.Separate copies are available on request.The Analyst publishes papers on all aspectsof the theory and practice of analyticalchemistry, fundamental and applied, inor-ganic and organic, including chemical,physical, biochemical, clinical, pharma-ceutical, biological, environmental, automa-tic and computer-based methods.Papers onnew approaches to existing methods, newtechniques and instrumentation, detectorsand sensors, and new areas of applicationwith due attention to overcoming limitationsand to underlying principles are all equallywelcome. There is no page charge.The following types of papers will beconsidered:Full research papers.Communications, which must be on anurgent matter and be of obvious scientificimportance. Rapidity of publication isenhanced if diagrams are omitted, but tablesand formulae can be included. Communica-tions receive priority and are usually pub-lished within 5-8 weeks of receipt. They areintended for brief descriptions of work thathas progressed to a stage at which it is likelyto be valuable to workers faced with similarproblems.A fuller paper may be offeredsubsequently, if justified by later work.Although publication is at the discretion ofthe Editor, communications will be ex-amined by at least one referee.Full critical reviews, which must be acritical evaluation of the existing state ofknowledge on a particular facet of analyticalchemistry.Every paper (except Communications) willbe submitted to at least two referees, bywhose advice the Editorial Board of TheAnalyst will be guided as to its acceptance orrejection. Papers that are accepted must notbe published elsewhere except by per-mission. Submission of a manuscript will beregarded as an undertaking that the samematerial is not being considered for publica-tion by another journal.Regional Advisory Editors.For the benefitof potential contributors outside the UK andN. America, a Group of Regional AdvisoryEditors exists. Requests for help or advice onmatters related to the preparation of papersand their submission for publication in TheAnalyst can be sent to the nearest member ofthe Group. Currently serving RegionalAdvisory Editors are listed in each issue ofThe Analyst.Manuscripts (four copies typed in doublespacing) should be addressed to:H. S. Minhas, Editor, orJ. F. Tyson, US Associate EditorParticular attention should be paid to the useof standard methods of literature citation,including the journal abbreviations definedin Chemical Abstracts Service Source Index.Wherever possible, the nomenclatureemployed should follow IUPAC recommen-dations, and units and symbols should bethose associated with SI.All queries relating to the presentation andsubmission of papers, and any correspon-dence regarding accepted papers andproofs, should be directed either t o theEditor, or Associate Editor, The Analyst.Members of the Analytical Editorial Board(who may be contacted directly or via theEditorial Office) would welcome comments,suggestions and advice on general policymatters concerning The Analyst.Fifty reprints are supplied free of charge.The Analyst (ISSN 0003-2654) is published monthly by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road,Cambridge, UK CB4 4WF.All orders, accompanied with payment by cheque in sterling, payable on a UK clearing bank or in US dollars payableon a US clearing bank, should be sent directly to The Royal Society of Chemistry, Turpin Distribution Services Ltd., Blackhorse Road,Letchworth, Herts, UK SG6 IHN. Turpin Distribution Services Ltd., is wholly owned bythe Royal Society of Chemistry. 1993Annual subscriptionrate EC f340.00, USA $641.00, Canada f384.00 (excl. GST), Rest of World f366.00. Purchased with Analytical Abstracts EC f718.00, USA$1 351 .OO, Canada f811 .OO (excl. GST), Rest of World f772.00. Purchased with Analytical Abstracts plus Analytical Proceedings EC f851.00, USA$1 601 .OO, Canada f961 .OO (excl. GST), Rest of World f915.00. Purchased with Analytical Proceedings EC f432.00, USA $812.00, Canada f487.00(excl. GST), Rest of World f432.00. Airfreight and mailing in the USA by Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003.USA Postmaster: Send address changes to: The Analyst, Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003. Second classpostage paid at Jamaica, NY 11431. All other despatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outsideEurope. PRINTED IN THE UK. 0 The Royal Society of Chemistry, 1994. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, ortransmitted in any form, or by any means, electronic, mechanical, photographic, recording, or otherwise, without the prior permission of thepublishers

ISSN:0003-2654    

DOI:10.1039/AN99419FX005

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

ANALAO 1 19(2) 165-366, 13N-24N (1 994) FEBRUARY 1994I I'"An al y s tThe analytical journal of The Royal Society of ChemistryCONTENTSGUEST EDITORS 165 Dr Arnold Fogg, Professor Brian BirchFOREWORDC 0 N F E R E N C E PA P E R S166 International Symposium on Electroanalysis in Biomedical, Environmental, and Industrial Sciences,Loughborough University of Technology, 20-23 April 1993167 Dynamic Separation of Mobile Species Transfer Processes at Polymer Modified Electrodes Using theElectrochemical Quartz Crystal Microbalance-A. Robert Hillman, Noelle A. Hughes, Stanley Bruckenstein175 Electrochemical Immobilization of Enzymes. Part VI. Microelectrodes for the Detection of L-Lactate Basedon Flavocytochrome 9 Immobilized in a Poly(pheno1) Film-Philip N. Bartlett, Daren J.Caruana181 Functionalized Cyclodextrins as Potentiometric Sensors for Onium Ions-Paul S. Bates, Ritu Kataky, DavidParker187 Hand-held Instrumentation for Environmental Monitoring-Gwyn Williams, Claudius D'Silva191 Prediction of Gas Sensor Response Using Basic Molecular Parameters-Jonathan M. Slater, John Paynter197 Mathematical Model of Toxicity Monitoring Sensors Incorporating Microbial Whole Cells-Barry G, D.Hag g ett203 Selective Membrane Electrodes for Analysis-J. D. R. Thomas209 Tubular Potentiometric Detector for Flow Injection Based on Homogeneous Crystalline MembranesSensitive to Copper, Cadmium and Lead-Isabel M. P. L. V. 0. Ferreira, Jose L. F. C. Lima21 3 Horseradish Peroxidase Assay-Radical Inactivation or Substrate Inhibition? Revision of the CatalyticSequence Following Mass Spectral Evidence-Ramin Pirzad, Jeffrey D.Newman, Anthony A. Dowman,David C. CowellTUTORIAL REVIEW 21 9 Tutorial Review. Advanced Electroanalytical Techniques Versus Atomic Absorption Spectrometry,Inductively Coupled Plasma Atomic Emission Spectrometry and Inductively Coupled Plasma MassSpectrometry in Environmental Analysis-Pierre M. Bersier, Jonathon Howell, Craig Bruntlett233 Simple Solid Wire Microdisc Electrodes for the Determination of Vitamin C in Fruit Juices-Amiel M.Farrington, Nidhi Jagota, Jonathan M. Slater239 Voltammetric Determination at Platinum Microelectrodes of Water in Acetone-based Solutions With LittleSupporting Electrolyte-Malgorzata Ciszkowska, Zbigniew Stojek243 Development of Amperometric Sensors for Uric Acid Based on Chemically Modified Graphite-Epoxy Resinand Screen-printed Electrodes Containing Cobalt Phthalocyanine-Markas A.T. Gilmartin, John P. Hart,Brian J. Birch253 Development of a Disposable Amperometric Sensor for Reduced Nicotinamide Adenine DinucleotideBased on a Chemically Modified Screen-printed Carbon Electrode-Steven D. Sprules, John P. Hart,Stephen A. Wring, Robin Pittson259 Voltammetric and Amperometric Studies of Thiocholine at a Screen-printed Carbon Electrode ChemicallyModified With Cobalt Phthalocyanine: Studies Towards a Pesticide Sensor-John P. Hart, Ian C. Hartley265 Organic-phase Application of an Amperometric Glucose Sensor-Emmanuel I. Iwuoha, Malcolm R. Smyth269 Evaluation of Amperometric Detection at a Glassy Carbon Electrode for the Liquid-ChromatographicDetermination of Antihypertensive Substances-M.Aranzazu Goicolea, Zuririe Gomez de Balugera, M.Jesus Portela, Ram6n Barrio273 Rapid Scanning Voltammetric Detection in Flowing Streams-Jonathan M. Slater, Esther J. Watt279 Batch and Flow Determination of Uranium(v1) by Adsorptive Stripping Voltammetry on Mercury-filmElectrodes-Anastasios Economou, Peter R. Fielden, Andrew J. Packham287 lonophore/lonomer Films on Glassy Carbon Electrodes for Accumulation Voltammetry. Investigation of aLead(ii)-lonophore Damien W. M. Arrigan, Gyula Svehla, John Alderman, William A. Lane293 On-line Determination of Chromium by Adsorptive Cathodic Stripping Voltammetry-Andrew M.Dobney,Gillian M. GreenwayTypeset and printed by Black Bear Press Limited,Cambridge, EnglandContinued on Inside Back Cover-0003-2654[199412:1-PAPERSCOMMUNICATIONSNEWS AND VIEWS29930530931 932332733333934936535336513N19N24.NVoltammetric Behaviour of Thallium(w) at a Solid Heterogeneous Carbon Electrode Using lon-pairFormation-Wolfgang Diewald, Kurt Kalcher, Christian Neuhold. Ivan Svancara, Xiaohua CaiDetermination of Nitrate in Carbon Black by Using a Nitrate-selective Electrode-Ricardo Perez-Olmos,Jose M. Merino, lzaskun Ortiz de Zarate, Jose L. F. C. Lima, Ma ConceiCao 6 . S. M. MontenegroApplication of Catalytic Stripping Voltammetry for the Determination of Organic Sulfur Compounds at aHanging Mercury Drop Electrode: Behaviour of Cysteine, Cystine and N-Acetylcysteine in the Presence ofNickel lon-Florinel G. Banica, Josino C.Moreira, Arnold G. FoggDifferential-pulse Adsorptive Stripping Voltammetry of the Diuretic Torasemide at a Hanging Mercury DropElectrode-Marta Fernandez, Rosa M. Alonso, Rosa M. Jimenez, Maria J. LegorburuVoltammetric Study of the Extractant 4-Methyl-N-quinolin-8-ylbenzenesulfonamide at a Carbon PasteElectrode-Angel Abelairas. Maria J. Puertollano, Rosa M. Alonso. Maria P. Elizalde, Rosa M. Jimenez,Marta HuebraSpectroelectrochemistry of Nickel(ii) Complexes of N,N'-Bis(salicyla1dehyde-o-Phenylenediamine andN,N-Bis(2-hydroxy-l -naphthaldehyde)-o-Phenylenediamine Using an Optically Transparent Thin-layerElectrode-M. S. El-Shahawi, W.E. SmithDetermination of Ultra-trace Amounts of Selenium(iv) by Flow Injection Hydride Generation AtomicAbsorption Spectrometry With On-line Preconcentration by Coprecipitation With Lanthanum Hydroxide-Guanhong Tao, Elo H. HansenDetermination of Metallic Elements in Catalysts by Flame Atomic Absorption Spectrometry-OswaldPlatteau VA Simple Laser-induced Fluorescence Detector for Sulforhodamine 101 in a Capillary ElectrophoresisSystem: Detection limits of 10 Yoctomoles or Six Molecules-Da Yong Chen, Karin Adelhelm, Xiao LiCheng, Norman J. DovichiA Retention Index For Micellar Electrokinetic Chromatography-Eric S. Ahuja, Joe P. FoleyOptimization of the High-performance Liquid Chromatography Assay for Virginiamycin Determination inMineral Premixes-Philippe Blain, Eric Demaesschalck. Isabel Van Rompaey, Francis GosseleCUMULATIVE AUTHOR INDEXBook ReviewsConference DiaryPapers in Future IssuesCover picture: Video print of a Nafion joint used for earthing in capillary electrophoresis.Print kindlysupplied by Dr Jonathan Slater. Department of Chemistry, Birkbeck College.Second International Symposium onHormone and Veterinary Drug Residue AnalysisCongress Centre Oud St. Jan, Bruges, Belgium,May 31-June 3, 1994The above symposium will cover the following topics: sample pre-treatment, extraction and clean-up procedures(SPE, SFE, IAC, gel permeation, etc.) in drug residue analysis; analysis of hormone and veterinary drug residues;chromatographic techniques (high-performance liquid chromatography, capillary gas chromatography, thin-layerchromatography, etc.) and their detection by spectroscopic (UV, IR, MS, luminescence, etc.), electrochemical andother methods (FID, ECD, etc.); immunoaffinity techniques and immunoassays (RIA, CLIA, ELISA, FIA, dipsticktechnology, etc.); other techniques applied to hormone and veterinary drug residue analysis in biological samples ofhuman and animal origin; metabolism, pharmacokinetics and toxicology of these compounds; quality control andreference materials; stability of residues in food of animal origin; legal aspects and control mechanisms regardingresidues of veterinary drugs in food; and problems concerning consumption of meat originating from hormone treatedanimals with regard to doping analysis.All papers must be presented in English.No simultaneous translation will be provided.The deadline for receipt of abstracts is March 1, 1994.The symposium papers will be published in The Analyst, subject to the usual review process. The manuscripts shouldbe written in accordance with the Instructions for Authors for The Analyst, and be handed to the Secretariat before theend of the symposium.For further information contact: Prof. C. Van Peteghem, Symposium Chairman, Faculty of Pharmaceutical Sciences,University of Ghent, Harelbekestraat 72, B-9000 Ghent, Belgium.Phone: (32) 9/221.89.51 ext. 235Fax: (32) 9/220.52.4

ISSN:0003-2654    

DOI:10.1039/AN99419BX007

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, February 1994, Vol. 119 13N Book Reviews Practice of Thin Layer Chromatography. Third Edition By Joseph C. Touchstone. Pp. xvi + 378. Wiley. 1992. Price f 56.00. ISBN 0-471 -61 222-7. This book is the third edition and, in keeping with the first two, is aimed as a practical aid for practitioners of thin-layer chromatography. The text tries to maintain a practical tone throughout and provides information on a wide range of topics. Chapters cover fundamental topics such as preparation of plates, mobile-phase composition, plate development and visualization. These are covered in depth with sufficient detail to allow practical application. In contrast, chapters on ‘fringe’ subjects such as sample preparation and ‘special techniques’ were poorly covered and only provided a flavour of the subject and not a working knowledge.Most chapters were supported with numerous but often dated references. While dated references were relevant to subjects such as plate and mobile phases, for subjects such as TLC-MS, references from 196& 70s render the text of historical interest only and of no practical help. The scant covereage of subjects like chiral TLC and bonded TLC phases indicates the need to update the text in some areas. ‘The text provides a wealth of experience and is full of useful practical tips and hints’. As well as a practical aid this text is useful reference book for TLC equipment suppliers providing detailed plate order- ing information and supplier’s addresses and telephone numbers. The text is well layed-out, containing numerous diagrams and photographs and is supported by a substantial index and glossary.This book could be used as a useful reference manual as well as a practical aid in any TLC laboratory and could justify its place in the library. P. Martin Electrode Kinetics for Chemists, Chemical Engineers, and Materials Scientists By Eliezer Gileadi. Pp. xviii + 598. VCH. 1993. Price DM1 89.00. ISBN 1-56081 -561 -2 (VCH Publishers); 3-527- 89561 -2 (Verl ag sg esel Ischaft). This was a book to which I warmed with reading. Correspond- ingly, this review becomes more favourable as it progresses. The initial reaction is that this might be another ‘standard’ text for electrochemistry-a view reinforced by familiar thermo- dynamically-oriented early sections, even including figures from earlier ‘standard’ texts.The question then is ‘what does the author’s presentational style add?’ For example, are there any new ways to present the relationship between electro- chemical rate constant and potential, or what else, at this level, can be added to descriptions of the hydrogen, oxygen and chlorine systems? The emphasis is on physical concepts, rather than mathe- matical detail or experimental techniques. In both respects, this makes the book complementary to some other texts and has the advantage that it will not date so rapidly. In respect of techniques, two points are noteworthy. First, the author focuses entirely on electrochemical methods: the plethora of physical and spectroscopic techniques employed by many electrochemists are not covered.This is not a criticism, merely a statement of the author’s choice. Second, the present limitations of (electrochemical) techniques are clearly stated, and likely developments anticipated. The merits of the book became more apparent when practical issues were explored. For example, the reader (student?) is given clear instructions on how to extract the desired parameter (rate constant, double layer capacitance, etc.) from experimental data. Unlike many books, this includes advice on data regimes likely to yield reliable parameters, and is supplemented by cautionary tales on the use of models and empirical correlations. Particularly well presented sections were those on interme- diates and electrosorption (amongst the fundamentals) and fuel cells, batteries and electroplating (amongst the applica- tions).In the latter cases, the discussion assumed no prior knowledge yet managed to reach the present state of knowledge and suggest areas for future development. From a student’s viewpoint, I offer minor criticisms and general praise. The figure numbering system is unusual, the use of units is occasionally inconsistent, and the use of the subscript ‘ad for ’activation control’ in an area employing alternating current methods might be misleading. Despite this, the style is clear and readable and the book takes the reader from zero expertise to a fair appreciation of the topic. I will find this a useful book and recommend it. A . R. Hillrnan Biomolecular Spectroscopy. Part A Edited by R. J. H. Clark and R. E. Hester.Advances in Spectroscopy. Volume 12. Pp. xx + 384. Wiley. 1993. Price f 120.00. ISBN 0-471 -93806-8. In common with many earlier volumes in the series, the editors of this volume have commissioned authoritative reviews of developing areas of the title field from established workers in each area. The book is not, therefore, a compre- hensive review of the field, but a collection of reviews of distinct areas within the field. For the current volume (one of two), the reviews, each forming a separate chapter, cover: Infrared spectroscopic studies of retinal proteins; Ultraviolet resonance Raman studies of proteins and related model compounds; Raman, resonance Raman and FTIR studies of enzyme-substrate complexes; Structure-function relation- ships in cytochrome c peroxidase via resonance Raman spectroscopy and site-directed mutagenesis; Genetically inser- ted tryptophans in protein spectroscopy; Raman microspec- troscopy of single whole cells; Surface-enhanced Raman spectroscopy and its biomedical applications; and Quantita- tive determinations of conformational disorder in biological membranes by FTIR spectroscopy. ‘The stated aim of the editors is that the volume be of interest to researchers, technologists, teachers and graduate and undergraduate students.In this volume, they have succeeded’ This approach has advantages and disadvantages. The main disadvantage is the sense of being given detailed city street maps without a map of the country. From a general spectroscopist’s point of view, the result is less than satisfac- tory; as the chapter topics show, it is difficult to see the range of applications of particular spectroscopic techniques, since each appears in many chapters.Conversely, the arrangement by biochemical topic makes the volume far more readable than a simple list of applications by technique, and the14N Analyst, February 1994, Vol. 11 9 complementary nature of different spectroscopic and bio- chemical techniques appears in particularly sharp relief. For the practising biomolecular researcher, this is ideal. Overall, I felt that the advantages of the approach far outweighed the disadvantages in this instance. Though the individual reviews vary in breadth of coverage, all make interesting reading. The more general reviews are without exception well structured and clear.Each presents a readable account of the state-of-the-art in the chosen area. The theory of spectroscopic techniques is not generally covered except where details require explanation; experimen- tal concerns, on the other hand, are given a welcome prominence. Most of the reviews cover the available litera- ture, taking specific examples to develop their themes, though one or two concentrate more closely on the authors’ own work. Chapters typically provide 70-100 references, which extend into 1992. In addition, there is a short index, which includes cross-references to spectroscopic techniques and specific materials. The stated aim of the editors is that the volume be of interest to researchers, technologists, teachers and graduate and undergraduate students.In this volume, they have succeeded. I look forward with interest to seeing Part B. S. Ellison Supercritical Fluid Engineering Science. Fundamentals and Applications Edited by Erdogan Kiran and Joan F. Brennecke. ACS Symposium Series 574. Pp. xii + 410. American Chemical Society. 1993. Price US $98.95. ISBN 0-8412-2513-3. This book contains selected papers presented at the Sympo- sium on Supercritical Fluids held at the American Institute of Chemical Engineers Annual Meeting in Los Angeles in November 1991. As such it concentrates on current preoccu- pations in the field, with regard mainly to industrial process. There is an introductory chapter by the editors on the Current State of Supercritical Fluid Science and Technology, which sets the present areas of research into the context of this developing subject.As the title implies, both fundamental studies and applica- tions are covered; reports on fundamental studies are grouped into two sections. The first of these covers phase behaviour and transport properties. Studies in this area have a compara- tively long history: current interest, well represented in this volume, is tending towards systems that are more complex in terms of components and phase behaviour. Systems contain- ing polymers and surfactants are included. Experimental measurement and correlation or prediction of diffusion coefficients are discussed in one chapter. The second ‘fundamental’ section is on molecular inter- actions and simulation. This covers an area in which there has been burgeoning interest in recent years.It is centred around concepts of local structure and clustering in supercritical fluids, which appears to affect many types of process in the medium. Chapters are included in which structure is studied theoretically by molecular dynamics simulation in the bulk and using integral-equation theory in the bulk and on surfaces. Chapters on experimental studies of molecular interactions by FTIR, fluorescence and chromatography are included. In two chapters the relationship between local structure and ther- modynamic quantities are discussed. The section contains a useful review of reactions in supercritical fluids, mostly studied by spectroscopic techniques, in which the effect of local structure often features. The final section on ‘applications’ could be more lengthily described as a series of research studies aimed towards potential applications.It does, however, give a good snapshot of current thinking on applications. The well-established technique of supercritical fluid extraction is represented by a chapter on the separation of mesophase pitch (for the production of carbon fibres) with supercritical toluene, one on the extraction of organic components from aqueous slurries, and another on the extraction (combined with thermal decomposition) of coal with tertiary butanol. There is a theoretical chapter on the optimization of the established technique of supercritical fluid chromatography. There are some fundamental studies of processes: of gas hold-up under supercritical conditions; of the structure of polymer foams, produced in supercritical fluids, by light scattering; and of processes involving reverse micelles by dynamic fluorescence.Three of the chapters involve processes in supercritical water: the modelling of oxidation; the separation of salts; and the removal of heteroatoms from organic compounds. Other newer areas for applications are represented by chapters on the production of small particles for pharmaceutical purposes, and on the use of supercritical fluids for recycling of rubber by depolymerization. Most of this book is thus not of direct interest to analytical chemists: exceptions being the chapters on the optimization of supercritical fluid chromatography and the use of the tech- nique to study molecular interactions. Neither is it an introduction to the subject of supercritical fluids for those with no background in the subject. It would be useful for those with some knowledge of the subject who wish to keep up with current research interests in supercritical fluids and many of the concepts discussed are relevant to the theory of super- critical fluid extraction and chromatography.A . A . Clifford Treatise on Analytical Chemistry. Part 1. Thermal Meth- ods. Second Edition. Volume 13 Edited by James D. Wineforder. Pp. xviii + 406. Wiley. 1993. Price f79.00. ISBN 0-471-80647-1. If the reader is expecting a comprehensive review of analytical methods using thermal analysis (TA) then he will be disappointed; thus there is little on the analytical application of TA to polymers, apart from a brief mention in Chapter 3 and the use of pyrolysis techniques in Chapter 5 and there are only a few references to DSC and none to dynamic mechanical thermal analysis (DMTA or DMA) in wide use throughout industry.If, however, the reader is interested in one or more of the subjects treated then the book has real value. The first chapter The Application of TA to Kinetic Evaluation of Thermal Decomposition first reviews the relative advantages of the programme-determined tempera- ture control and rate-determined temperature control meth- ods. The chapter deals fully with a complex subject in a balanced and helpful manner. The inclusion of thermometric titrations and enthalpimetric analysis may surprise some but the techniques are within the scope of TA. The methodological principles and the apparatus required are first described.Sections covering theory and practice follow. The remainder of the chapter covers the determination of stoichiometries, kinetic parameters and specific analytical uses. It is not comprehensive but surveys selected examples which illustrate the range of applications. Chapter 3 on Thermogravimetry is most comprehensive and well-presented. A brief introduction is followed by a review of apparatus. This is clear and helpful although more stress should have been placed on the use of computers in data acquisition and processing, since these have superseded chartAnalyst, February 1994, Vol. 11 9 15N recorders. The authors emphasize that TG is a dynamic technique depending on several variables. The bulk of the chapter is a systematic treatment of the application of TG to both inorganic and organic materials including plastics and rubbers, petroleum products, pharmaceuticals, medical and biological applications and natural products.Lastly there is a brief section devoted to TG in combination with other methods. The chapter on thermodilatometry and ceramics deals with equipment and methodology briefly and is followed by selected examples drawn from glass, crystalline materials, whitewares and refractories as well as silicon nitride. The treatment is up-to-date and covers all aspects of ceramic usage including engineering ceramics. The chapter Pyrolysis Techniques covers a specific aspect of evolved gas analysis, namely the production of pyrolysis products and their identification.The pyrolysers themselves are discussed along with the methods used to identify the evolved species; gas chromatography and mass spectrometry or a combination of both. The range of applications is extensive and the chapter concludes with some recent illustrative examples with references to earlier work. The Application of TA to Problems in Cement Chemistry chapter covers all aspects of cement chemistry and admix- tures. It emphasizes that TA methods are used to study all stages in the production cycle from the raw materials through to the aged product, as well as improvements to the cement- making process. The treatise is well written with few errors but it is clear from the references cited that the book has had a long gestation period. In summary, it is not a general volume covering analytical techniques using TA but its coverage of the subjects treated makes it a welcome addition to the relatively small number of texts on thermal analysis.J . P. Redfern Molecular Luminescence Spectroscopy. Methods and Applications: Part 3 Edited by Stephen G. Schulman. Volume 77 in Chemical Analysis. A Series of Monographs on Analytical Chem- istry and Its Applications. Pp. xii + 468. Wiley. 1993. Price f81 .OO. ISBN 0-471-51 580-9. This book examines the latest developments in molecular luminescence spectroscopy and is the third part of the series of books devoted to this topic (the contents of Parts I and I1 are conveniently reproduced at the front of the book). The first chapter reviews chemiluminescence with the emphasis on the range of chemical reactions that produce light.It provides a good overview for anyone unfamiliar with this phenomenon, but would have been improved by an in-depth exposition of applications. Bernard Valeur has contributed a useful chapter on fluorescent probes. It reviews the characterisics and the physical and structural parameters measurable by probes. Table 2.1 (p. 27) provides a valuable overview of applications of fluorescent probes and a source of reviews and books on this topic. Photochemical fluorimetry is a new approach to analysis that involves a UV-initiated photoreaction of a photochemi- cally unstable analyte, followed by fluorimetric detection of the photo-products. Chapter 3 reviews this topic and describes its application to pharmaceutical, clinical and environmental analysis.Matrix effects are a troublesome source of inter- ference in many analytical techniques. Organized bile salt media (Chapter 4) offer an interesting approach to ensuring a uniform micro-environment for analysis that is free of matrix effects. The bile salts extract the analyte in situ, thus minimizing perturbations due to other components present in the sample. Holiday and Wild provide an in-depth account of spectral hole-burning (Chapter 5). Spectral hole-burning material has potential applications in optical computing, optical data storage, holography, and molecular computing and each of these applications is explained and exemplified. Chapter 6 (Near-infrared luminescence spectroscopy) dis- cusses the utility of near-infrared (NIR) (750-1500 nm) spectroscopy in protein labelling (e.g., indocyanine green labels), HPLC detection, and enzymic assay (e.g., xanthine oxidase).In Chapter 7, Tamm and Kalb describe in detail microspectrofluorimetric techniques on supported planar membranes. The chapter by Schenk covers clinical applica- tions of luminescence spectroscopy. The section on selected organic substances would have benefited from some com- ments on the relative importance of the fluorimetric methods described. For example, serum albumin is usually measured by colorimetric dye binding methods in most routine clinical laboratories. Likewise, serum cholesterol is mostly measured using a cholesterol oxidase based assay. The final and longest chapter in this book reviews the fundamental aspects and applications of laser-excited molecular fluorescence. It includes an account of flow cytometry (principles, instrumen- tation, detection, data acquisition and analysis, and calibra- tion) and covers the application of this technique with particular emphasis on a specialized use of flow cytometry , namely the classification of phytoplankton.The editors of this book have assembled an interesting group of topics and this book will be a useful reference source for both the expert and novice luminescence spectroscopist. L. J . Kricka Practical Surface Analysis. Volume 2. Ion and Neutral Spectroscopy Edited by D. Briggs and M. P. Seah. Pp. xviii + 738. Wiley. 1992. 2nd edn. Price f90.00 (Volumes 1 and 2 combined set: f 160.00; US $359.00). ISBN 0-471 -92082-7.This book is a natural adjunct to the Editors’ earlier volumes concerned with what was once generally called electron spectroscopy for chemical analysis. The present tome, how- ever, is concerned with more recent developments that make use of more massive particles, ions or atoms, as a probe, or as secondary emitted particles, and the application of these interactions with matter for analysis. The first chapter presents an overview of the surface analysis scene, but as far as I can remember, this has been almost completely ‘lifted’ from the editors’ earlier publica- tions, with little attempt to address the eponymous subject matter of this book. Techniques covered in the book range, in usage and applicability, from the popular to the exotic. Of the ten chapters, four or five are explicitly concerned with secondary ion mass spectrometry (SIMS).The two extremes of this technique, static SIMS, in which the target ablation is minimized by the use of a low intensity incident beam, and dynamic SIMS, in which the irradiated surface is continually removed by an intense incident beam, are both well covered. Static SIMS can be termed the mass spectro- scopy of surfaces, and dynamic SIMS is particularly suited to the study of composition with depth. The two aspects of the SIMS experiment are comprehensively discussed both theore- tically and also illustrated with examples. The instrumentation associated with these techniques is also described and the performance of various types of instrument is illustrated by results, including SIMS images.16N Analyst, February 1994, Vol.1 I9 Of more specialist interest is the technique of sputtered neutral mass spectrometry (SNMS). In any SIMS-type experi- ment, of all the species emitted, ions are very much in the minority, with neutral species (atoms and molecules) being the most numerous. All embodiments of SNMS techniques rely on some method of separating the secondary ions and neutrals from each other, ionizing the latter and then directing them into a suitable mass spectrometer. Practitioners in the field of SNMS would appear to have a choice of incident probe: ions, electrons or photons, and a choice of post- ionization methods; electron impact, or laser (non-resonant or resonant) multiphoton ionization being favoured. The advan- tages of SNMS over SIMS are in the areas of quantification and improved detection limits.Of even more esoteric interest are the chapters on the family of ion scattering spectroscopies of which Rutherford back-scattering (RBS) is the most important commercially. These techniques are fundamentally different to the low energy (no more than a few tens of keV) techniques referred to so far. In the first instance, ISS is characterized by higher incident energies (from several tens of keV to upwards of MeV) and the fact that the particles detected are not secondary emitted ions but are primary particles which have undergone some energy exchange with the atoms in the target. The information obtained, too, is different; the content being much more orientated to the structural rather than the compositional. This book is extensively referenced as would be expected, but I was puzzled at the inclusion of an appendix on angle- resolved electron stimulated ion desorption, which to my mind, verges on the excessively abstruse for a book that purports to be about practical surface analysis.I was particularly pleased, though, to see the appendices about reference standards and computer simulations, and I was especially encouraged by the appendices on sputtering yields and isotopic abundances, which enhances further the book’s day-to-day usefulness. This book, by its very nature as a reference work and handbook, cannot be close to the leading edge of research. However, I would rate it as an invaluable guide for any laboratory specializing in ion-based surface analysis tech- niques.It should be close at hand for every instrument operator working in the field. In the light of more recently discovered phenomena and very recent work, one might ask whether the editors are considering the preparation of a third volume in this series- one concerned with scanning probe techniques-I for one, should very much welcome it. Nigel S . Clarke Supercritical Fluid Extraction and its Use in Chromato- graphic Sample Preparation Edited by S. A. Westwood. Pp. xii + 170. Blackie Academic & Professional. An imprint of Chapman & Hail. 1992. Price f45.00. ISBN 0-7514-0089-0. This publication is a compilation of contributions edited by Dr. Steve Westwood. He is well known and respected as a chromatographer and an active supporter of the use of supercritical fluids in analysis and in this book he has combined contributions from many of the leading researchers in the field of supercritical fluid extraction (SFE).The scene is set in a short Foreword by Professor Dai Games in which he stresses the importance of effective sample preparation and summarizes the main features of extraction with supercritical fluids. The real substance of the book begins with an introduction to the use of SFE by Dr. Tony Clifford. This provides a comprehensive theoretical treatment of SFE and the factors that need to be considered when attempting an extraction. Dr. Steve Hawthorne, who is one of the most prolific publishers of papers on analytical SFE, contributes Chapters 2 and 3. His first contribution covers the methodol- ogy of off-line SFE where the extracted analytes are collected in a device that is independent of the instrument to be used for the measurement.This is probably the most widely applied mode of SFE and Dr. Hawthorne covers all aspects of the available technology options in detail. In his second contribu- tion Dr. Hawthorne covers one of his main areas of research, namely the practice and application of SFE coupled on-line to gas chromatography (GC). He describes the options available for coupling the two techniques and discusses in detail the use of both split and on-column injectors. The selection and optimization of the SFE-GC method, the choice of extraction fluid, and the quantitative aspects of the technique are also covered.The next two chapters cover the coupling of SFE to supercritical fluid chromatography (SFC). Chapter 5 by Professor Keith Bartle and co-workers describes the equip- ment and techniques required to couple SFE with capillary SFC. The tabulated reference summaries, giving the reader the main technical highlights of each paper, are a particularly useful feature of this chapter. Chapter 6 by Dr. Ian Anderson deals with coupling SFE with packed column SFC and begins with a detailed comparison of packed and capillary SFC. The mechanisms of coupling and instrumental considerations are then discussed followed by some applications and ideas for future developments. The final contribution by Professor Larry Taylor and Dr. Howard covers the options available for coupling SFE with high-performance liquid chromatography.It covers both off-line and on-line modes and concludes with a tabulated reference summary containing molecular structures of the analytes examined. In summary, this is a comprehensive text in which experts in the field cover each subject area. The written word is illustrated by the many chromatograms and schematic dia- grams and this book provides not only an informative text but a practical experimental guide to the theory and practice of SFE as an analytical sample preparation tool. T. P. Lynch DECHEMA Corrosion Handbook: Corrosive Agents and Their Interaction With Materials. Volume 11. Chlorine Dioxide and Seawater Edited by Gerhard Kreysa and Reiner Eckerman. Pp. x + 296. VCH Weinheim. 1992. Price DM 775.00; f286.00.ISBN 1-56081 -749-6 (VCH Publishers): 3-527-26662-3 (VCH Verlag sgesel Isc haft). As the authors of this reference handbook explain in their preface, corrosion presents an enormous economic burden to industrialized parts of the world. Estimates of cost range from 2 to 4% of gross national product. The reasons for this large cost become apparent when instances of corrosion in daily life (e.g., rusting of car bodies), are extrapolated to infrastructure and buildings ( e . g . , corrosion of reinforcing bars in concrete), and process and manufacturing industries of all types from foodstuffs (tin cans), to offshore drilling technology (oil rigs, pipelines and refineries). Prevention and control of corrosion depends on choosing the most appropriate material of construction or protective measure for the corrosive environment in question. This choice is invariably a balance between corrosion resistanceAnalyst, February 1994, Vol.11 9 17N and cost effectivity. In order to manage this fine balancing act the corrosion engineer requires ready sources of information concerning suitable materials of construction for their parti- cular problem area. The Dechema series of corrosion handbooks represent a long established, starting point and information source for materials selection. The format of the handbook is to present survey tables of materials likely to be considered for use in the subject corrosive environment. The materials cited in the survey tables include extensive lists of metals and their alloys, non- metallic inorganic materials, e.g., refractory materials, glass, carbon and graphite, organic materials from natural fibres to plastics and paints (the latter of particular importance as organic coatings are frequently the most cost effective corrosion prevention measure) and materials with special properties, e.g., seals and packing.A general rating of the corrosion behaviour of each material is given in symbol form, resistant to unsuitable. The reader is then referred to the body of the text for detailed descriptions of corrosion behaviour. The body of the text begins with an introduction to the corrosive properties of the environment in question. This volume of the Dechema corrosion handbook considers chlorine dioxide and sea-water. Chlorine dioxide is used as a disinfectant for drinking water, a bleaching agent for food, pulp and paper and textiles and as a deodorizer for sewage sludges.Corrosion problems can occur during its manufacture and at the point of use. Seawater causes corrosion problems in many key industries, e.g., oil production, desalination, shipping, construction. Both sections of the handbook describe the problems that occur in these environments, e.g., pitting corrosion, environ- mentally induced cracking, biofouling and the mitigating or exacerbating influence of other factors, such as temperature, pH, flow rates, aeration. Methods of corrosion prevention are also described. These introductions are relatively brief. They give an overview of the issues but it is not altogether clear what the target audience is, as they are not fundamental enough for the novice nor detailed sufficiently for the specialist. How- ever, they do serve to point the reader to further reading via an extensive bibliography .Detail is reserved for the discussions of the corrosion behaviour of the materials of engineering significance. Here, particularly, with the metal alloys, the extraction of relevant data from the cited references provides an immediate source of corrosion rate information for given conditions. This is a good starting point to focus in on the most appropriate prevention measures. Overall, the Dechema corrosion handbook is a readable reference book with clearly set out text, tables and graphs and a large bibliography, however, some understanding of corro- sion science is required to utilize the information presented.This understanding is necessary to apply critical consideration to the data, given that small differences in chemical composi- tions, pressures, temperature etc., can have a significant impact on corrosion behaviour. B. J . Hepburn A Practical Guide to HPLC Detection Edited by Donald Parriott. Pp. x + 294. Academic Press. 1992. Price US $59.95. ISBN 0-1 2-545680-8. Many books have recently been published on the theory and practice of HPLC. This one is different in that it is restricted to the important question of detection systems. The book includes 9 chapters that have been prepared by invited authors on different detection methods. Four chapters are devoted to more widely used methods of detection, such as refractive index, UV/visible light absorbance, fluorescence and electro- chemical.These provide very comprehensive descriptions of apparatus design and operating principles followed by discus- sion on applications. These chapters are generally well presented and include several useful examples illustrating the advantages and limitations, plus giving practical hints on their applications. The book then includes some chapters on other more specialized detection modes. These include one on diode array detectors. Following a description of equipment and prin- ciples, the author goes on to discuss the unique features of these detectors including the multitude of data manipulations that are now available when detector outputs are interfaced with even relatively routine laboratory PCs.Applications discussed include the potential for simultaneous multi- wavelength monitoring, the use of library routines for the verification of identity based on UV spectra as well as chromatographic retention times and the possibilities of evaluating the homogeneity of chromatographic peaks. A chapter on mass spectrometry essentially concentrates on instrumentation including different ionization modes, inter- facing methods including transport, particle beam, direct liquid introduction, thermospray, continuous flow FAB and atmospheric pressure ionization, the advantages of the various modes and the use of MS/MS techniques. A chapter on post column derivatization techniques describes various designs of reactors including pumpless systems, hollow fibre, solid-phase and photochemical reactors and then goes on to describe a selection of the more widely applied post-column reactions. The final chapter covers other modes of detection.It includes more detailed sections on radioactivity, infrared, light scattering and optical activity detectors with briefer accounts of the less widely used element specific and nuclear magnetic resonance detectors and followed by very brief mentions of HPLC-GC and HPLC-TLC methods and detec- tors based on Raman spectroscopy, dielectric constant, viscometry and ultrasonic transmission. This is a very interesting volume, which should be of value to students of HPLC and to more experienced practitioners who require information on alternative detection systems. Although most chapters are well written it is considered that in many cases they would have benefited from more up-to-date references.G. P. Carr Trace '89. Trace Elements in Health and Disease Edited by Professor G. T. Yuregir, Professor 0. Donma and Associate Professor L. Kayrin. Pp. viii + 634. Cukurova University Publishing Company. 1991. Price f45.00. ISBN 975-487-000-4. This book represents the collected proceedings of the Third International Congress on Trace Elements in Health and Disease held at Adana, Turkey, from March 31 to April 8, 1989, and includes material from 9 invited lectures, 30 oral and 40 poster presentations. While the editors have obviously gone to a lot of trouble to collect all this material together, including retypesetting all the text and tables, the time this must have taken is reflected in the fact that the book was published in Turkey in 1991 and I am reviewing it in 1993.In a book of this size one has to expect that a lot of the material will be very variable, the articles range in quality from very good to extremely poor and cover nearly every aspect of analytical, biomedical and clinical trace element research. There is no subject grouping, the papers are collected into invited, oral and poster sections, which means that analytical18N Analyst, February 1994, Vol. 11 9 methodology ends up being considered next to some more esoteric philosophical discussion of benefits of trace elements. The content is mainly devoted to research from countries in the Middle East and Indian sub-continent, and in fact this is where the value of the book lies.It is unlikely that much of the material published in this book would see the light of day in the western world (e.g., studies on the variations in Na, K, Mg, Ca and Cu levels during Ramadan fasting), and yet read selectively there is a great deal of information concerning the levels of essential and non-essential toxic trace elements in countries such as Pakistan and Turkey. One interesting article considered the increase in Pb content of meat from being ( i ) served at the side of a busy road and (ii) supplied to the purchaser wrapped in newsprint. In order of popularity, copper and zinc were the subject of 34 papers (it would appear it was measured for nearly every conceivable disease or surgical operation!), Se, 12 and Pb, 8 with a scattering of reports on Al, Cd and Li .The problem with any book of conference proceedings is that rarely is there any form of refereeing. Some of these papers range from in-depth presentations to one or two sides of text, which appear to be no longer, and contain similar information to an abstract. While it is understandable of the editors to want to produce a full record of the conference, some selection would have improved the overall quality of the material. What was very noticeable was the almost complete lack of any analytical methddology validation, comparison or quality control applied in any of the papers. History has shown us that trace element research is a minefield for those who ignore the dangers of contamination and very few papers even mention any of the precautions that were taken.Again it is distressing to see yet more papers discussing the ETAAS determination of Pb and Se and with the authors finding the same results and conclusions as found by everybody else, information that is readily available in the literature. How- ever, it is clear that the conference organizers realise that quality control is an important issue and the first invited paper was on this topic. In conclusion, with selected reading, and with a degree of caution applied to those results presented without any analytical validation, some useful information is contained within this book. However, reading this book did provide me with the rare pleasure of finding the following opening sentence to one of the papers, ‘From primeval time when amoebae emerged out of the watery soup surrounding them, some decided to stay while others returned to their familiar birth place.’ I shall treasure that late night memory for a long time.. . Ian L. Shuttler Instrumentation in Analytical Chemistry 1988-1 991 Edited by Louise Voress. Pp. xvi + 478. American Chemical Society, 1992. Price US $28.95. ISBN 0-8412- 2202-9. This book is a continuation of the series begun in 1973 and is designed to provide readers with updated overviews of analytical techniques and instrumentation drawn from articles originally published in Analytical Chemistry’s ‘A’ pages. The book covers the period 1988 to 1991 and includes sections on: Robotics, Computers and Laboratory Data Management; Atomic and Molecular Spectroscopy; Electroanalytical Chemistry and Chemical Sensors; Separations; Mass Spectrometry and Surface Analysis.By its very nature this book covers an incredible array of subjects, ranging from Fuzzy Sets; Applications to Analytical Chemistry through Chemical Sensors for Bedside Monitoring of Critically Ill Patients, to Ellipsometry for Thin-Film and Surface Analysis, consequently, there is something here for everybody. Although, as I dipped into the various subjects that initially interested me, before moving on into more esoteric areas way outside my expertise, I wondered why anybody should want to buy such a book; all these articles are collected together from the ‘A’ pages of Analytical Chemistry, which are readily available in most University libraries (one would hope!).While attractive to have them all bundled together for the prospective buyerheader, I wonder just how relevant some of these are. Take as an example, a newly employed analytical chemist working in an inorganic analysis laboratory who may be involved in assisting in the purchase of a new ICP-AES instrument. He or she may well delight on the two articles from Bonner Denton’s group, which discuss the use of Charge Transfer Device Detectors, but may not find a detailed discussion of the physics underlying Fourier Trans- form Ion Cyclotron Resonance Mass Spectrometry all that useful. The articles vary from current state-of-the-art overviews, which are enough to get you interested and rushing off to the library to investigate some of the more detailed literature, to full blown detailed descriptions with all the attendent math- ematics that are a sure cure for late night insomnia. Consequently, the articles vary quite widely in their intended audience. Some sections appear to have found the right mixture. As an example, I found the section on Separations, superb, the last time I seriously had to consider chromato- graphy was during my final year GRSC studies (a long time ago), and these articles considerably improved my current knowledge of these techniques. They are well written, explain what the technique can do, how it does it, what are its advantages and disadvantages and where it is likely to be going. All in a style and content suitable for both undergradu- atedgraduates and more experienced chemists who want to improve their knowledge. However, some of the other articles I found extremely difficult to appreciate and required a return to some of my instrumentation text-books to fill in some of the underlying knowledge, which was assumed to be present in the readers mind. The aim of the book is to provide a chronicle of recent progress in a number of measurement science areas that will be found useful and informative by both research specialists and students of analytical chemistry. That the book sum- marizes many of the recent changes in analytical measurement science is without question, and will enable one to keep abreast of these changes. However, if you are a regular reader of Analytical Chemistry, then you will already have seen these. The book achieves its aim but I am still left wondering if I would personally buy a copy. I would recommend our library to purchase one, but feel that the wide spread of topics, while an advantage for use in a multi-user environment, acts as a disadvantage to the graduate or post-graduate buyer who tends to be more selective in his or her purchases on the grounds of a limited budget. My advice is to try and get your library or supervisor to buy a copy! Ian L. Shuttler

ISSN:0003-2654    

DOI:10.1039/AN994190013N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, February 1994, Vol. 119 19N Conference Diary Date Conference 1994 March 1 ‘Good Automated Manufacturing Practice in the Pharmaceutical Industry’ 7-11 4th International Symposium on Trends and New Applications in Thin Films 8-1 1 Laser Applications to Chemical Analysis 12-13 207th ACS National Meeting, Membranes for Biomedical and Biotechnological Separations Location London, UK Dresden, Germany Snow King Resort, Jackson Hole, Wyoming, USA San Diego, CA, USA 13-16 Third European Federation of Corrosion Estoril, Workshop on Microbial Corrosion Portugal 13-18 207th American Chemical Society National San Diego, CA, Meeting USA 16-18 International Course on (Bio)-Analytical Leiden, Mass Spectrometry The Netherlands 27-30 International Federation of Automatic Galveston, TX, Control (IFAC) Symposium on Modeling and Control in Biomedical Systems USA April 6-8 Electroanalysis: A Tribute to Professor J.D. Cardiff, R. Thomas UK 10-13 ANATECH 94: 4th International Symposium Mandelieu La on Analytical Techniques for Industrial Process Control France Napoule, 10-15 207th ACS National Meeting and 5th Mexico City, Chemical Congress of North America (with Sessions of Analytical Chemistry, Environmental Chemistry, Chemical Health and Safety, etc.) Applications of Radioanalytical Chemistry Hawaii, Mexico 10-16 3rd International Conference on Methods and Kailua-Kona, USA 12-14 13th Pharmaceutical Technology Conference Strasbourg, France Contact Management Forum Ltd, 48 Woodbridge Road, Guildford, Surrey, UK GU1 4RJ Tel: +44 (0)483 570099.Fax: +44 (0)483 36424 Frank Richter, TU Chemnitz, FB Physik, PSF 964, D-09009 Chemnitz, Germany Fax: +49 371 852491 Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, DC 20036-1023, USA Tel: + 1 202 223 0920. Fax: + 1 202 416 6100 Dr. Peter Edelman, Ciba Corning Diagnostics Corporation, 63 North Street, Medfield, MA 02052, USA CCsar Sequeira, Instituto Superior TCcnico, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal, or A. K. Tiller, Corrosion Centre, 23 Grosvenor Gardens, Kingston-upon-Thames, UK KT2 5BE, or D. Thierry, Swedish Corrosion Institute, Roslagsvagen 101, Hus 25, S-10405 Stockholm, Sweden Department of Meetings, American Chemical Society, 115516th St., NW, Washington, DC 20036, USA Tel: +1202 872 4396. Symposium Secretariat, Mrs.F. J. Velthorst, LACDR, P.O. Box 9502,2300 RA Leiden, The Netherlands Tel: +31 (71) 274341. Fax: +31 (71) 274277 IFAC Biomedical Symposium, University of Texas Medical Branch, Box 55176, Galveston, TX 77555- 5176, USA Tel: + 1 409 770 6628 or 770 6605. Fax: + 1 409 770 6825 Dr. J. M. Slater, Department of Chemistry, Birkbeck College, University of London, 29 Gordon Square, London, UK WClH OPP Tel: +44 71 380 7474. Fax: +44 71 380 7464 ANATECH 94 Secretariat, Elsevier Advanced Technology, Mayfield House, 256 Banbury Road, Oxford, UK OX2 7DH Tel: +44 (0)865 512242. Fax: +44 (0)865 310981 Mr. B. R. Hodson, American Chemical Society, 1155-16th Street N.W., Washington, DC 20036, USA Tel: +1 202 872 4396. Ned A Wogman, Battelle, Pacific Northwest Laboratories, P.O. Box 999, P7-35, Richland, WA 99352, USA Tel: +1509 376 2452.Fax: +1509 376 2373 Professor Mike Rubinstein, 13th Pharmaceutical Technology Conference, 24 Menlove Gardens North, Liverpool, UK L18 2EJ Tel: +44 51 737 1993. Fax: +44 51 737 107020N Analyst, February 1994, Vol. 1 I9 Date 12-15 17-19 18-22 19-22 May 7-12 8-12 8-13 8-13 9-13 16-19 16-20 16-20 23-25 24-27 24-27 29-116 Conference Location The Royal Society of Chemistry Annual Chemical Congress UK Liverpool, International Symposium on Volatile Organic Montreal, Compounds (VOCs) in the Environment- 6th International Conference on Near Infrared Spectroscopy ANALYTICA’94: 14th International Conference on Biochemical and Instrumental Analysis Food Structure Annual Meeting 85th AOCS Annual Meeting & Expo HPLC ’94, Eighteenth International Symposium on Column Liquid Chromatography CLEO ’94: Conference on Lasers and Electro-Optics Focus 94-The Annual National Meeting and Exhibition of the Association of Clinical Biochemists 24th Annual Symposium on Environmental Analytical Chemistry Deauville Conference: 13th International Symposium on Microchemical Techniques; 2nd Symposium on Analytical Sciences 24th International IAEAC Symposium on Environmental Analytical Chemistry ISPAC 7: International Symposium on Polymer Analysis and Characterization 3rd Symposium on Molecular Chirality International Symposium on Metals and Genetics: Toxic Metal Compounds in Environment and Life 5; Interrelation between Chemistry and Biology 42nd ASMS Conference on Mass Spectroscopy Quebec, Canada Lorne, Australia Munich, Germany Toronto, Ontario, Canada Atlanta, GA, USA Minneapolis, MN , USA Anaheim, CA, USA Brighton, UK Ottawa, Canada Montreux, Switzerland Ottawa, Ontario, Canada Les Diablerets, Switzerland Kyoto, Japan Toronto, Ontario, Canada Chicago, IL, USA Contact Dr.J. F. Gibson, Scientific Secretary, The Royal Society of Chemistry, Burlington House, London, UK W1V OBN Tel: +44 71 437 8656. Fax: +44 71 437 8883 Symposium Chairman, Dr. Wuncheng Wang, US Geological Survey, WRD, P.O. Box 1230, Iowa City, IA 52244, USA. Tel: +1 319 337 4191, Fax: +1 319 354 0510; or Co-Chairmen, Dr. Jerald Schnoor, University of Iowa, Department of Civil and Environmental Engineering, Iowa City, IA 52242, USA. Tel: +1319 335 5649, Fax: +1 319 335 5777; and Dr.Jon Doi, Roy F. Weston, Inc., 1 Weston Way, West Chester, PA 19380, USA Tel: +1215 524 6167. Fax: +1 215 524 6175 NIR-94, Peter Flinn, Pastoral and Veterinary Institute, Mt. Napier Road, Private Bag 105, Hamilton, Victoria 3300, Australia Tel: +61 55 730915. Fax: +61 55 711523 Munchener Messe- und Ausstellungsgesellschaft mbH, Analytica ’94Nerbung Postfach 12 10 09, D-8000 Munchen 12, Germany Tel: +49 89 51 07 143. Fax: +49 89 51 07 177 Dr. Om Johari,, SMI, Chicago (AMF O’Hare), IL Tel: + 1 708 529 6677. Fax: + 1 708 980 6698 AOCS EducationMeetings Department, P.O. Box 3489, Champaign, IL 61826-3489, USA Tel: +1217 359 2344. Fax: +1 217 351 8091 Ms. J. E. Cunningham, Barr Enterprises, P.O. Box 279, Walkersville, MD 21793, USA Tel: +1 301 898 3772. Fax: +1 301 898 5596 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: + 1 202 223 9034.Fax: + 1 202 416 6100 Focus 94, P.O. Box 227, Buckingham, Buckinghamshire, UK MK18 5PN Tel: +44 2806 613. Fax: +44 2806 487 Dr. M. Malaiyandi, CAEC, Chemistry Department, Carleton University, 1255 Colonel By Drive, Ottawa, Canada K1S 5B6 Tel: +1 613 788 3841. Fax: +1613 788 3749 D’Conference 94, 7 rue d’Argout, 75002 Paris, France Tel: +33 1 42 33 47 66. Fax: +33 1 40 41 92 41 Dr. James F. Lawrence, Food Additives and Contaminants, Health and Welfare, Tunney’s Pasture, Ottawa, Ontario, Canada K1A OL2 Secrbtariat, ISPAC 7, CERMAV-CNRS, BP 53 X, 38041 Grenoble Cedex, France Professor Terumichi Nakagawa, Symposium on Molecular Chirality (SMC), Faculty of Pharmaceutical Sciences, Kyoto University, Yoshida-Shimoadachi-cho, Sakyo-ku, 606 Japan Fax: +81 48 471 0310 (Professor Hara) Professor B.Sarkar, Department of Biochemistry, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1x8 60666-0507, USA DC 20036-1023, USA ASMS, 815 Don Gaspar, Santa Fe, NM 87501, USA Tel: +1 505 989 4517.Analyst, February 1994, Vol. 11 9 21N Date Conference Location Contact 30-216 14th Nordic Atomic Spectroscopy and Trace Naantali, Ari Ivaska, Abo Akademi University, Laboratory Analysis Conference Finland of Analytical Chemistry, Biskopsgatan 8, SF-20500 Abo Turku, Finland 30-116 Scandinavian Symposium on Infrared and Bergen, Dr. Alfred Christy, Department of Chemistry, Raman Spectroscopy Norway University of Bergen, N-5007 Bergen, Norway June 1-3 1-3 5-7 5-7 5-1 1 6-8 8-11 12-15 13-15 15-17 15-18 16-17 Second International Symposium on Hormone and Veterinary Drug Residue Analysis Biosensors 9 L T h e Third World Congress on Biosensors VIth International Symposium on Luminescence Spectrometry in Biomedical Analysis-Detection Techniques and Applications in Chromatography and Capillary Electrophoresis VIth International Symposium on Luminescence Spectrometry in Biomedical Analysis-Detection Techniques and Applications in Chromatography and Capillary Electrophoresis 24th ACHEMA Conference on Plasma Science 6th International Conference on Flow Analysis 1994 PREP Symposium and Exhibit 4th International Symposium on Field-Flow Fractionation 16th Symposium on Applied Surface Analysis (ASSD) The Second International Symposium on Speciation of Elements in Toxicology and Environmental and Biological Sciences 14th International Symposium on Environmental Pollution Bruges, Belgium New Orleans, USA Bruges, Belgium Bruges, Belgium Frankfurt, Germany Santa Fe, NM, USA Toledo, Spain Washington, DC, USA Lund, Sweden Burlington, MA, USA Loen, Norway Toronto, Canada Professor C.Van Peteghem, Symposium Chairman, Faculty of Pharmaceutical Sciences, University of Ghent, Harelbekestraat 72, B-9000 Ghent, Be Igi um Tel: +32 9 221 89 51 (ext. 235). Fax: +32 9 220 52 43 Kay Russell, Conference Department, Elsevier Advanced Technology, Mayfield House, 256 Banbury Road, Oxford, UK OX2 7DH Tel: +44 (0) 865 512242. Fax: +44 (0) 865 310981 Professor Dr.Willy R. G. Baeyens, Symposium Chairman, University of Ghent , Pharmaceutical Institute, Department of Pharmaceutical Analysis, Laboratory of Drug Quality Control, Harelbekestraat 72, B-9000 Ghent, Belgium Tel: +32 9 221 89 51. Fax: +32 9 221 41 75 Professor Dr. Willy R. G. Baeyens, Symposium Chairman, University of Ghent, Pharmaceutical Institute, Dept. of Pharmaceutical Analysis, Lab. of Drug Quality Control, Harelbekestraat 72, B- 9000 Ghent, Belgium Tel: +32 (0) 9 221 89 51. Fax: +32 (0) 9 221 41 75 Dechema, Theodor Heuss-Allee 25, P.O. Box 970146, D-W-6000 Frankfurt am Main 97, Germany A. Perratt, Los Alamos National Laboratory, Group X-10, MS D-406, P.O. Box 1663, Los Alamos, NM 87545, USA Professor M. ValcBrceVDr. M. D. Luque de Castro, (Flow Analysis VI), Departamento de Quimica Analitica, Facultad de Ciencias, E-14004 Cordoba, Spain Tel: +34 57 218616.Fax: +34 57 218606 Ms. Janet Cunningham, Symposium1Exhibit Manager, Barr Enterprises, P.O. Box 279, Walkersville, MD 21793, USA Tel: +1 301 898 3772. Fax: +1 301 898 5596 Dr. Agneta Sjogren, The Swedish Chemical Society, Wallingatan 24, tr. S-111 24 Stockholm, Sweden Fax: +46 8 106 678 Joseph Geller, Geller Microanalytical, 1 Intercontiental Way, Peabody, MA 01960, USA Tel: + 1 508 535 5595. The Second International Symposium on Speciation of Elements in Toxicology and in Environmental and Biological Sciences, Yngvar Thomassen, National Institute of Occupational Health, P.O. Box 8149 DEP, N-0033 Oslo 1, Norway Dr. V. M. Bhatnagar, Alena Chemicals of Canada, P.O.Box 1779, Cornwall, Ontario, Canada K6H 5v7 Tel: +1 613 932 7702.22N Analyst, February 1994, Vol. 11 9 Date 16-17 19-21 19-24 20-23 27-117 Conference Location 18th International Conference on Analytical Chemistry and Applied Canada Chromatograph y/Spectroscopy Toronto, The 5th Nordic Symposium on Trace Elements in Human Health and Disease Loen, Norway 20th International Symposium on Bournemouth, Chromatography UK 2nd Oxford Conference on Spectroscopy Ringe, NH, USA Special FEBS Meeting on Biological Membranes Suomi-Finland Espoo, July 3-7 International Chemometrics Research Meeting 18-22 XI11 International Congress on Electron Microscopy 20-22 Seventh Biennial National Atomic Spectroscopy Symposium August 2-6 8-12 14-18 21-26 29-219 The Second Changchun International Symposium on Analytical Chemistry(C1SAC) IGARSS '94: 1994 International Geoscience and Remote Sensing Symposium International Symposium on Bacterial Polyhydroxyalkanotes (ISBP '94) 208th ACS National Meeting (with Sessions of Analytical Chemistry, Environmental Chemistry, Chemical Health and Safety, etc ) 13th International Mass Spectrometry Conference Contact Dr.V. M. Bhatnagar, Alena Chemicals of Canada, P.O. Box 1779, Cornwall, Ontario, Canada K6H 5V7 Tel: +1 613 932 7702. Yngvar Thomassen, Trace Elements in Human Health and Disease, National Institute of Occupational Health, P.O. Box 8149 DEP, N-0033 Oslo, Norway Tel: 47 22466850. Fax: 47 22603276 Mrs J. A. Challis, Chromatographic Society, Suite 4, Clarendon Chambers, 32 Clarendon Street, Nottingham, UK NG1 5JD Tel: +44 602 500596.Fax: +44 602 500614 Dr. Art Springsteen, Labsphere Inc., P.O. Box 70, North Sutton, NH 03260, USA Tel: +1603 927 4266. Professor Timo Korhonen, Biochemical Society, European Federation of Biochemical Societies (FEBS), Department of General Microbiology, University of Helsinki, Mannerheimintie 172, SF- 00300 Helsinki, Finland Veldhoven (Eindhoven), The Netherlands The Netherlands Paris, France Hull, UK Mrs. Gerrie Westerlaken, Conference Organizing Bureau VNW, Postbus 1558,6501 BN Nijmegen, Tel: +3180 234471. Fax: +31 80 601159 B. Jouffrey, SFME 67, rue Maurice Gunsbourg, 94205, Ivry sur Seine cedex, France Tel: +33 1 46702844. Fax: +33 1 46708846 Dr. Steve Hill, Department of Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, Devon, UK PL4 8AA Changchun, China Pasadena, CA, USA Montreal, Quebec, Canada Washington, DC, USA Budapest, Hungary Professor Quinhan Jin, Department of Chemistry, Jilin University, Changchun 130023, China Tel: +86 431 82233 (ext. 2433).Fax: +86 431 823907 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: +1 202 223 9034. Fax: +1 202 416 6100 ISBP Secretariat, Conference Office, McGill University, 550 Sherbrooke St. West, West Tower, Suite 490, Montreal, Quebec, Canada H3A 1R9 Tel: +1514 398 3770. Fax: +1514 398 4854 Mr. B. R. Hodson, American Chemical Society, 1155-16th Street N.W., Washington, DC 20036, USA Hungarian Chemical Society, H-1027 Budapest, Hungary Tel: +36 1201 6883.Fax: +36 1 15 61215 DC 20036-1023, USA September 5-6 First International Symposium on Coimbra, Profa. Dra. Ana Maria Oliveira Brett, Neuroelectrochemistry Portugal Departamento de Quimica, Universidade de Coimbra, 3049 Coimbra, Portugal Tel: +351 39 22826. Fax: +351 39 27703 5-9 7th International Symposium on Synthetic Tiibingen, Dechema, P.O. Box 970146, D-W-6000 Frankfurt Membranes in Science and Industry Germany am Main 97, GermanyAnalyst, February 1994, Vol. 11 9 23N Date 11-16 12-15 12-15 13-18 18-22 19-21 19-21 19-23 21-23 21-23 22-24 25-28 25-30 26-30 Conference Location EUCMOS XXII: XXIInd European Congress on Molecular Spectroscopy Germany Essen, Separations for Biotechnology 3rd International Symposium on Environmental Geochemistry Reading, UK Krakow , Poland 3rd International Symposium on Mass Spectrometry in the Health and Life Sciences Geoanalysis 94: An International Symposium on the Analysis of Geological and Environmental Materials San Francisco, CA, USA Ambleside, UK The Second International Conference on Applications of Magnetic Resonance in Food Science The Fourth Annual CIM Field Conference Aveiro, Portugal Sudbury, Ontario, Canada XIIIth International Symposium on Medicinal Paris, Chemistry 7th International Symposium on Environmental Radiochemical Analysis 5th International Symposium on Pharmaceutical and Biomedical Analysis 12th National Conference on Analytical Chemistry 5th International Symposium on Chiral Discrimination 1994 European Workshop in Chemometrics 16th International Symposium on Capillary Chromatography October 2-7 29th Annual Meeting of the Federation of Analytical Chemistry and Spectroscopy Societies PREP '94: 11th hternatiohd Symposium on Preparative and Industrial Chromatography 3-6 France Bournemou th, UK Stockholm, Sweden Constanta, Romania Stockholm, Sweden Bristol, UK Riva del Garda, Italy St.Louis, MO, USA Baden-Baden, Germany Contact GDCh-Geschiiftsstelle, Abt. Tagungen, Varrentrappestr. 40-42, Postfach 90 04 40, D-6000 Frankfurt am Main 90, Germany Tel: +49 69 79 17 358. Fax: +49 69 79 17 475 SCI Conference Office, 14/15 Belgrave Square, London, UK SWlX 8PS Tel: +44 71 235 3681. Fax: +44 71 823 1698 Helios Rybicka, Faculty of Geology, Geophysics and Environmental Protection, University of Mining and Metallurgy, Al. Mickiewicza 30, PL- 30-059 Krakow, Poland Tel: +48 12 333290.Fax: +48 12 332936 Marilyn Schwartz, Department of Pharmaceutical Chemistry, University of California, San Francisco, D. L. Miles, Analytical Geochemistry Group, British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham, UK NG12 5GG Tel: +44 602 363100. Fax: +44 602 363200 Dr. A. M. Gil, Department of Chemistry, University of Aveiro, 3800 Aveiro, Portugal CA 9413-0446, USA 1994 CIM Field Conference, c/o Sudbury Geological Discussion Group, P.O. Box 1233, Station B, Sudbury, Ontario, Canada P3E 4S7 CONVERGENCESDSMC '94, 120 avenue Gambetta, 75020 Paris, France Fax: +33 1 40 31 0165 Dr. P. Warwick, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, UK LEll 3TU Tel: +44 509 222585 or +44 509 222545. Fax: +44 509 233163 Swedish Academy of Pharmaceutical Sciences, P. 0. Box 1136, S-11181 Stockholm, Sweden Tel: +46 8 245085. Fax: +46 8 205511 Dr. G.-L. Radu, Romanian Society of Analytical Chemistry 13 Bul. Carol I, Sector 3, 70346 Bucharest, Romania Swedish Academy of Pharmaceutical Sciences, P. 0. Box 1136, S-111 81 Stockholm, Sweden Tel: +46 8 245085. Fax: +46 8 205511 Janice Green, School of Chemistry, University of Bristol, Cantock's Close, Bristol, UK BS8 1TS Tel: +44 (0)272 303030 (ext. 4421) or +44 (0)272 303672. Fax: +44 (0)272 251295 Professor Dr. P. Sandra, I.O.P.M.S., Kennedypark 20, B-8500 Kortrijk, Belgium Tel: +32 56 204960. Fax: +32 56 204859 FACSS, P.O. Box 278, Manhattan, KS 66502-0003, USA Tel: +1301846 4797. GDCh-Geschiiftsstelle, Abt. Tagungen, Varrentrappestr. 40-42, Postfach 90 04 40, D-6000 Frankfurt am Main 90, Germany Tel: +49 69 79 17 358. Fax: +49 69 79 17 475 Entries in the above listing are included at the discretion of the Editor and are free of charge. If you wish to publicize a forthcoming meeting please send full details to: The Analyst Editorial Office, Thomas Graham House, Science Park, Milton Road, Cambridge, UK CB4 4WF. Tel: +44 (0)223 420066. Fax: +44 (0)223 420247.

ISSN:0003-2654    

DOI:10.1039/AN994190019N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

24N Analyst, February 1994, Vol. 119 ~~ Future Issues will lnclude- Thin-layer Chromatographic Spray Reagent for the Screening of Biological Materials for the Presence of Carbaryl-Vitthal B. Patil and Murlidhar S. Shingare Improvement in the Determination of Aromatic Carbons in Petroleum Fractions by Proton Nuclear Magnetic Resonance Spectroscopy-A. E. Navarro Fr6meta Integrated Optical Immunosensor for s-Triazine Determina- tion: Regeneration, Calibration and Limitations-Frank F. Bier, Ralf Jockers and Rolf D. Schmid Spectrophotometric Determination of Vanadium(iv) and Vanadium(v) In Each Other’s Presence. A Review-M. J. C. Taylor and J. F. van Staden pH Indicator Based Ammonia Gas Sensor: Studies of Spectral Performance Under Variable Conditions of Temperature and Humidity-Radislav A.Potyrailo, Sergiy P. Golubkov, Pavlo S. Borsuk, Petro M. Talanchuk and Evgeniy F. Novosselov Interlaboratory Comparison of Instruments Used for the Determination of Elements in Acid Digestates of Solids- David Eugene Kimbrough and Janice Wakakuwa Solubility of Barium(ii) Taurodeoxycholate-Emilio Bottari and Maria Rosa Festa On-line and Off-line Voltammetric Methods for the Determi- nation of Nickel in Zinc Plant Electrolyte-Alan M. Bond, Robert I. Mrzljak, Terence J. Cardwell, Robert W. Cattrall, Roger W. Knight, 0. Michael G. Newman and Bruce R. Champion X-Ray Fluorescence Analysis of Ferroalloys: Development of Methods for the Preparation of Test and Calibration Samples- -Aurora G. Coedo, Maria Teresa Dorado, Carlos J. Rivero and Isabel G. Cob0 Response Surfaces for the Determination of Arsenic(iii) by Hydride-generation Atomic Absorption Spectrometry and Flow Injection-Peter D.Wentzell, Nils G. Sundin and C. Hogeboom Vapour-phase Acid Digestion of Micro Samples of Biological Material in a High-temperature, High-pressure Asher for Inductively Coupled Plasma Atomic Emission Spectrometry- -Dulasiri Amarasiriwardena, Antoaneta Krushevska, Mark Argentine and Ramon M. Barnes Flow-through, Microwave-treated Digestion Chamber for Automated Sample Preparation Prior to Inductively Coupled Plasma Spectrochemical Analysis-Ramon M. Barnes and Laura J. Martines Stewart Voltammetric Determination of Dopamine in the Presence of Ascorbic Acid at Overoxidized Polpyrrole-Indigo Carmine Film-coated Electrodes-Zhiqiang Gao, Beshen Chen and Minxian Zi Determination of 2,2,2-Trichloroethanol in Plasma and Urine by Ion-exclusion Chromatography-Hisaaki Itoh, Shigero Ikeda and Norio Ichinose On-line Sample Preparation for the Determination of Ribo- flavin and Flavin Mononucleotides in Foodstuffs-Gillian M.Greenway and Nsanyi Kometa Poly(viny1 chloride) Matrix Membrane Electrodes for the Selective Determination of Buformin-Mona A. Ahmed Comparative Study of Metal Ion Interactions With Wool Keratin Using Chemometrics-Serge Kokot, Jing Cheng and Nigel Gill Sensitive Determination of Sulfur Concentration in Steel by Spectrophotometry With a Waveguide Capillary Cell-Koichi Chiba, Isamu Inamoto, Kin-Ichi Tsunoda and Hideo Akaiwa High-field Magnetic Resonance Studies of the Molecular Motion of tert-Butyl Compounds in Liquid and Solid Phases: the Binary System tert-Butyl Iodide-Carbon Tetrachloride- Dagfinn W.Aksnes and L. Kimitys Ionic Reaction Mechanisms in Pre-mixed Flames Disclosed by Stable-isotope Labelling-Helge Egsgaard, Elfinn Larsen, Lis Vinther Kristensen, Per Solgaard and Lars Carlsen Comparison of Fourier Transform Raman Spectra of Mam- malian and Reptilian Skin-A. C. Williams, B. W. Barry and H. G. M. Edwards Laser-induced Photoacoustic Signal Phase Study of Stratum Corneum and Epidermis-R. D. Snook, M. L. Baesso and J. Shen Nanosecond Time-resolved Infrared Spectrometry: a Compa- rative View of Spectrometers and Their Applications in Organometallic Chemistry-Martyn Poliakoff, Michael W. George and James J. Turner Impact of Mass Spectrometry in Surface Analysis-J. C.Vickerman Microvoltammetric Techniques and Sensors for Monitoring Neurochemical Dynamics In Vivo. A Review-Robert D. O’Neill Determination of Low Levels of Nitrogen Oxides in Gas Streams by High-performance Liquid Chromatographic De- termination of the Saltzman Complex-Julie D. Willis, Chris J. Dowle, Andrew P. Malyan, Robert D. Liversidge and Peter Cullen Real-time Biomolecular Interaction Analysis Using the Reso- nant Mirror Sensor-N. J. Goddard, D. Pollard-Knight and C. H. Maule Determination of Octadecadienoic Acids in Human Serum: a Critical Appraisal-Gordon Read, Nigel R. Richardson and David G. Wickens COPIES OF CITED ARTICLES The Royal Society of Chemistry Library can usually supply copies of cited articles. For further details contact: The Library, Royal Society of Chemistry, Burlington House, Piccadilly, London W1V OBN, UK. Tel: +44 (0)71-437 8656. Fax: +44 (0)71-287 9798. Telecom Gold 84: BUR210. Electronic Mailbox (Internet) LIBRARY@RSC.ORG. If the material is not available from the Society’s Library, the staff will be pleased to advise on its availability from other sources. Please note that copies are not available from the RSC at Thomas Graham House, Cambridge.

ISSN:0003-2654    

DOI:10.1039/AN994190024N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, February 1994, Vol. 11 9 165 International Symposium on Electroanalysis in Biomedical, Environmental and Industrial Sciences Guest Editors Dr Arnold Fogg PhD, DSc, ARTCS, C.Chem., FRSC Arnold Fogg joined ICI at Blackley in pharmaceutical analysis at the age of 16 and continued study, eventually full-time, at the Royal Technical College, Salford. Faced with a choice of national service, schoolteaching or further study, he went to Aberdeen University to study for a PhD under Bob Chalmers and Wolf Moser. In 1961 he came to Loughborough College of Advanced Technology, now Loughborough University of Technology, expecting that his stay would be about three years. In 1981 he was made Reader in Analytical Chemistry, and he has just taken an early retirement package including one-third re-engagement for research, after 32 years at Loughborough, including 24 years as course tutor (welfare) to the MSc course in analytical chemistry. Arnold has published some 200 papers, the majority of which are on electroanalytical chemistry: 90 of these papers are in The Analyst.Arnold has been a committee member of the Electroanalytical Group of The Royal Society of Chemistry continuously since 1970, holding the offices of Chairman and Honorary Treasurer. He tried to escape recently to allow in newer blood but was co- opted to run the two symposia at Loughborough. He served extensively on the Midlands Region committee, being honorary secretary in the early 1970s, and also on the Special Techniques Group committee. He was elected to the Analytical Division Council in 1984, and was a Vice-president from 1988-90.He is currently Chairman of the Analytical Editorial Board of the RSC. He won the 1989 Royal Society of Chemistry Award for Electroanalytical Chemistry, and has just been awarded a Distinguished Service Award by the Analytical Division Council. One of his main interests is travel, which is just as well as since 1981, when their son and daughter had both flown the nest, his wife’s career has taken her, until recently, to Hounslow, Liverpool and Aberdeen. Other interests include archaeology and history, and during this second excursion to North East Scotland he ‘discovered’ the Pictish Symbol Stones and is now a member of the Pictish Arts Society based in Edinburgh. He has strong research links with the Czech Republic, Brazil, Portugal, Spain and Malaysia among other places, and is an active member of the Portuguese Electrochemical Society.Professor B. J. Birch BSc, PhD, C.Chem., FRSC Brian J. Birch was born in 1942. He attended the University of Liverpool, graduating in 1963 with second-class honours in Chemistry. He then moved to the University of London where he undertook research into the ‘Statistical Thermodynamics of Ion- exchange Equilibria’ which led to the award of a PhD degree in 1966. In the same year Dr. Birch joined Unilever Research at Port Sunlight as a Physical Chemist, concerning himself with the physical chemistry of surfactant solutions. After some years Dr. Birch gained the opportunity to indulge his interest in analytical science when he moved to the analytical area (he claims that this interest was fired as an undergraduate when he analysed a sample of cobalt hexamine that he had synthesized and got it right!). While working in this area he became reponsible for the development of novel analytical methods for components of detergent raw materials and products. His research interests also included metal-ligand equilibria using precision titrimetry with computer data handling and chemical speciation using a variety of electrochemical techniques.In 1984 Dr. Birch transferred to Unilever’s Colworth House laboratory in Bedfordshire to work on chemical sensors. In particular, he has worked on disposable sensors for glucose and its major metabolites in whole blood, sugars, organic acids, pH values and bacteria in foods, and trace metals and inorganic anions in water.Another interest has been novel, on-line, process and effluent sensors for peracids in plant cleaning solutions, temperature, conductivity, pH and dissolved oxygen in water. In all he has produced 104 internal reports, 6 patents and 35 externally published papers. Brian Birch has also been active for a long time within the Royal Society of Chemistry, of which he is a Fellow. He is a past member of the Council of the Analytical Division and a Past Chairman (present Treasurer) of the Electroanalytical Group. He has also been a Council member of the Industrial Division of the Royal Society of Chemistry, part of the management team of the DTULINK Molecular Sensors Programme, a member of the Industrial Analytical Instrumentation Panel of the Institute of Measurement and Control and a member of the M25 Measurement and Control Club of the University of Hertfordshire. In recent years Birch has accepted a position of a Visiting Professor at the University of Luton, where he is amember of the Academic Board. He is also an advisor for the MSc(Ana1ysis) course of Birkbeck College, London and the External Examiner in Instrumental Analysis at the University of the West of England. Over the years he has been the Industrial Supervisor of 15 PhD students. Professor Birch is married with three children.

ISSN:0003-2654    

DOI:10.1039/AN9941900165

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

166 Analyst, February 1994, Vol. I I9 Editorial International Symposium on Electroanalysis in Biomedical, Environmental, and Industrial Sciences, Loughborough University of Technology, 20-23 April 1993 This symposium was the eighth in a series of symposia organized by the Electroanalytical Group of the Analytical Division of the Royal Society of Chemistry. Those in 1977 and 1979 were held at Chelsea College (University of London) under the direction of Dr. W. Franklin Smyth (now at the University of Ulster in Coleraine), and in 1981, 1983 and 1987 at University of Wales Institute of Science and Technology (now University of Wales College of Cardiff) by Dr. (now Professor) J. D. R. (Ron) Thomas. In 1985 the symposium was merged with the 30th IUPAC Congress at Manchester in the form of a session on ‘New Electrochemical Sensors’.In 1989 the symposium came to Loughborough for the first time (see special issue of The Analyst, December 1989). Thus, this was the second symposium to be held in Loughborough, and the arrangements followed a similar format to the previous meeting. This time (after their experience in 1989) the local organizers succeeded in finding time to attend most of the lectures! The symposium was opened by Professor Jim Miller (Professor of Analytical Chemistry, and Pro-Vice Chancellor of the University), Professor John Dawkins (Head of the Department of Chemistry) and Professor Arthur Covington (acting for the Chairman of the Electroanalytical Group). Many modem themes of electroanalytical chemistry were covered in the scientific programme, but emphasis was placed on pollution and process monitoring. The papers in this issue, highlight the quality and diversity of topics covered at the meeting, but the organizers thank all contributors for their splendid papers and posters.One highlight among many was the work of Professor Robert Hillman (now at the neighbouring University of Leicester) and Professor Stanley Bruckenstein on the electrochemical quartz crystal microbalance: to those of us with a more broad interest in analytical chemistry this technique seems to have wider implications in gravimetric analysis in addition to its fascinating use in electrochemistry. The symposium dinner within the University was appreciated by all, and the evening visit was to Snibston Discovery Park a short distance away, on the other side of Charnwood Forest hill, from Loughborough. This is at Coalville, which as its name suggests, is in what used to be the Leicestershire coalfield.Snibston, which is the largest newly-built science and industry museum to be built in the UK for 50 years, incorporates a recently closed and preserved pithead. The original Snibston Discovery shafts were sunk by the railway engineer George Stephenson in 1832, he built the permission of Leicestershire County council) first railway line in the area, the Leicester to Swannington railway. Artifacts from local medieval coalpits are also displayed in a reconstruction. The commentary and enthusiasm of the curator, Stuart Warburton, made the visit particularly memorable. Those participants who were required to stay overnight at the end of the symposium enjoyed a minibus trip to Southwell Minster and Sherwood Forest. The next symposium venue is mooted to be in the City of Durham, to be organized by Professor Arthur Covington, and we look forward to seeing old and new friends there. (Reproduced by kind Professor Brian J. Birch Unilever Research Sharnbrook, Bedfordshire Dr. Arnold G. Fogg Loughborough University of Technology, Leicestershire campus A view of the Loughborough University of Technology

ISSN:0003-2654    

DOI:10.1039/AN9941900166

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

167 Analyst, February 1994, Vol. 119 Dynamic Separation of Mobile Species Transfer Processes at Polymer Modified Electrodes Using the Electrochemical Quartz Crystal Microbalance' A. Robert Hillman Department of Chemistry, University of Leicester, Leicester, UK LEI 7RH Noelle A. Hughes Merck, Sharp and Dohme, Shotton Lane, Cramlington, Northumberland, UK NE23 9JU Stanley Bruckenstein Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14214, USA Galvanostatically controlled electrochemical quartz crystal microbalance measurements on poly(viny1ferrocene) modified electrodes demonstrate temporal separation of mobile species transfers. This approach may provide selectivity in analytical applications involving target species preconcentration in a surface-immobilized film.Dynamic separation of ion, salt and neutral molecule (e.g., solvent) transfer processes is optimized via the applied current. Mechanistic issues relating to mobile species transfers and polymer relaxation processes are rationalized in terms of a generalized multi-dimensional version of the scheme-of-squares. Keywords: Modified electrode; redox polymer; mobile species transfer; electrochemical quartz crystal microbalance Introduction Analytical Exploitation of Modifid Electrodes The uptake of solution species by a surface-immobilized film (commonly a polymer) on an electrode surface has consider- able analytical application1.2 and future potential. Careful choice of film chemistry allows preconcentration and selectiv- ity. In the first case, partition coefficients from solutions as large as 105 have been reported.3 Selectivity may be as broad- based as charge type4.5 or size,6 or as sophisticated as host- guest chemis try7 or an ti body-an tigen recognition.8 Immobilization of the target species in the film on the electrode surface is only the first part of the problem: detection and determination remain. For electroactive spe- cies, electrochemical detection is .simple, rapid, economic and, above all, of high precision. This gives, for example, access to the determination of many metal ions.24 If the entrapped species are electroinactiveg or, deceivingly, only a fraction of them are in electronic communication with the electrode,") then spectroscopic determination can be useful. Detection Methods Electrochemical and spectroscopic detection methods have the advantage of providing some selectivity via the potential * Presented at the International Symposium on Electroanalysis in Biomedical, Environmental and industrial Sciences, Loughborough, Leicestershire, UK, April 20-23, 1993.and wavelength variables, respectively. However, they suffer from the disadvantage that they are not generally applicable. For spectroscopy, there are also uncertainties in molar absorptivities: the environment in the polymer is very different to that in solution and may be variable from film to film (see ref. 2 for examples). Our longer-term objective is to develop an accompanying detection methodology of general applicability and with clearly defined sensitivity factor(s). Gravimetric detection satisfies these requirements: all species contribute to film mass, with a sensitivity factor determined by molar mass and reaction stoichiometry.The technique employed to monitor film mass is the electrochemical quartz crystal microbalance (EQCM). 11 This technique is an in situ variant of the quartz crystal micro- balance (QCM),** in which changes (AflHz) in the resonant frequency of a quartz crystal oscillator are a measure of changes (AMlng cm-2) in areal density (film mass per unit area). Provided that the film is rigid,l3,14 Af and AM are related by the Sauerbrey equation:IS Af = - (2/p~)AMfo2 (1) where p is the density of the crystal, v is the wave velocity within it and f o is the base frequency of the crystal. This simple conversion of frequency change to mass change is only applicable if the film can be shown to be rigid: crystal impedance measurements16 show this to be the case for poly(viny1ferrocene) (PVF) at any degree of redox conversion in aqueous sodium perchlorate solutions.For the 10 MHz AT- cut quartz crystals used in this work AM (g cm-2) = -4.426 x 109 Af (Hz) (2) The EQCM has been used to study a variety of aspects of polymer film chemistry on electrode surfaces, from deposition (by precipitation17 or electropolymerization13~14), through film conditioning's to over-all exchange of ions and solvent with the bathing solution.19-25 (For a review of this area, see ref. 11.) The Problem and a Solution When the film redox state changes, both ion and neutral species (notably solvent) transfers occur.In studying these processes, the generality of detection by mass is both the strength and the weakness of the EQCM technique. The advantage is that no transferring species escapes detection. The complication is that all transferring species contribute to168 Analyst, February 1994, Vol. 11 9 the over-all mass change. In short, we observe everything, but may distinguish nothing. We previously proposed a thermody- namic means to separate the contribution of the individual species to the over-all mass change on redox switching of an electroactive polymer film .26 Although the method26 is relatively simple, it necessarily involves determination of film mass changes in a series of different solutions, spanning the range of permselective and non-permselective conditions.This may not be compatible with the analytical requirements, even presuming that equilibrium is achievable. We therefore sought an alternative approach, in which measurements involving a single solution could provide the required informa- tion. The separation strategy explored in this work relies on the fact that different species transfer at different rates.27 This necessarily means that the mass response during a transient experiment will be dominated by different species at different times. A galvanostatic control function is used. The elec- troneutrality condition then dictates the transfer rate of the (fastest) transferring ionic species. Variation of the applied current (i) effectively controls the experimental timescale (z), because t is given by QT/i, where QT is the charge required for total redox conversion of the film.At appropriately low applied current (long timescale) the expectation is that all mobile species transfers (ions and neutrals) will be able to keep pace with the imposed current. As the current is increased we expect sequential failure of individual kinetic steps to keep pace with the current. We refer to this as ‘freezing out’ of the kinetic processes. Our intention is to delineate conditions that facilitate this separation and to identify the species able to transfer on different timescales. The differing sensitivities of the charge and mass data (to ions and to ions + neutrals, respectively) considerably aid this assignment. To summarize, our analytical strategy involves uptake of solution species by a surface-immobilized polymer film, accompanied by gravimetric (EQCM) determination of film mass changes. The fundamental problem that is addressed is the separation of the total mass response into components associated with the individual species enterindleaving the polymer film.The objective of this paper is to demonstrate that mobile species transfers can be temporally resolved. Our approach contrasts with previous work (reviewed in ref. 11) in two respects: first, the separation procedure is kinetic (rather than thermodynamic26) and, second, the electrochemical control function is galvanostatic (rather than potentio- static20.28). Theory Analysis of the data presented here requires use of two procedures we have described recently: a visual representa- tion of the reaction sequence29 and a means of separating charged and neutral species transfers.28.3” The purpose of this section is to reproduce those aspects required to follow the Discussion; the reader is referred to the original papers for a fuller exposition.Visualization of Contributory Processes: the Scheme-of-cubes We consider four processes to occur on redox switching of an electroactive polymer film: a change in oxidation state, a change in solvation state,? a change in salt content and a change in polymer configuration. A priori, we have no knowledge of the ordering of these steps. On an appropriately + We refer here to ‘free’ solvent present in the film, rather than that intimately bound to mobile ions present in the film.We consider ‘bound’ solvent to be a part of the entity that it solvates. long timescale, the over-all reaction occurring on film redox switching between reduced (R) and oxidized (0) states can be written [R,uSv(C+A-)]p --* [O,(U - w)S(V - x)(C+A-)]p + wsS + xsC+A- + e- (3) where subscripts P and S denote polymer film and solution species, respectively, C is the electrolyte cation and A is the electrolyte anion. The solvent (S) and salt (CA) contents of R and 0 are spelled out via the stoichiometric coefficients u, v , w and x ; these need not be integral. Under permselective conditions, v = x = 0, a key simplification we make use of experimentally (see below). The EQCM is sensitive to changes in polymer configuration through the associated solvent (and other neutral molecule) transfer.Although the observed process in this case, solvent transfer, is also seen in its own right as an ‘independent’ process, the underlying process here is different. Solvent transfer associated with different processes is, in principle, distinguishable on the basis of the differing timescales of the underlying processes. For example, one might expect solvent transfer driven by polymer configurational changes to occur on rather longer timescales than those driven directly by changes in redox state (polymer charge). A shorthand nomenclature used to describe the states in the reaction given in eqn. (3) is summarized in Table 1. As reduced PVF films are more hydrophobic than oxidized PVF filrns,20 we denote an equilibrated reduced film by R, and an equilibrated oxidized film by ObS.Each contributory process to the over-all reaction in eqn. (3) is represented by an orthogonal reaction coordinate.29 For the simple case of the ‘broken-in’l*Jl PVF films studied here, there is only one transformation in each coordinate. By analogy with the 2-D scheme-of-squares32.33 for ‘EC’-type processes, we use a 1 x 1 x 1 scheme-of-cubes29 (shown in Fig. 1) to represent the course of the reaction in eqn. (3) under permselective conditions. Changes in the film oxidation, solvation and configuration states are represented by changes in the x, y and z coordinates, respectively. Under non-permselective con- ditions ( v # 0, x # 0), a 1 x 1 x 1 x 1 hypercube is required;34 for simplicity, the Discussion section focuses on the pictorial representation of the 3-D (permselective) case, although the principles are identical in the 4-D (non-permselective) case.Separation of Charged and Neutral Species Transfers This separation relies on the fact that the charge passed (Q/ C cm-2) is related only to population changes of ionic species, whereas the mass change (AMIg cm-2) is related to population changes of both ionic and net neutral species. By taking the difference in the population changes of ‘ions’ and ‘ions + Table 1 Nomenclature for polymer film species State Possibilities Coordinate Oxidation state* 0 = oxidized X R = reduced Y Solvation state+ S = more solvated = less solvatedt Polymer configuration5 a for reduced state 2 b for oxidized state * Main symbol. t Superscript. + This absence of a superscript does not necessarily imply that the film contains no free solvent at all. merely a lesser amount than the ‘S’ state.5 Subscript. The designation of configuration ‘a’ (‘b’) as that for a fully equilibrated reduced (oxidized) film is arbitrary.Analyst, February 1994, Vol. 11 9 169 neutrals', one can extract the population change for 'neut- rals',28*30 denoted by the symbol Q. For convenience, the subtraction is carried out with quantities expressed in the units of areal density (g cm-2). In the general case of the reaction in eqn. (3), the mass change (AMnon-perm) at any point in the redox conversion, referred to an initial reduced (uncharged) film, is given by AMnon-perm = mAArA + msArs + mcAArcA (4) where m and AT, respectively, denote the molar mass and film population change (mol cm-2) of the designated species.The counter ion population change can be calculated using Faraday's law: ArA = -Q/zAF ( 5 ) where zA = -1 and F = Faraday's constant. From eqns. (4) and ( 5 ) , we calculate the contribution to the film mass change associated with neutral species (here, solvent and salt) transfer: @n"n-Perm = msArs + mcAArcA = AM"o"-Perm - Q ~ A I F (6) where we have taken into account the uni-negative charge of the transferred counter ion. Under permselective conditions [x = y = 0 in the reaction in eqn. (3)] eqns. (4) and (6) reduce to eqns. (7) and (8), respectively: AMPerm = t?ZAArA + msArs @Perm = msArs = AMPerm - QmA/F (7) (8) As pointed out previously,30 there is a parallel set of equations to (4) and (6)-(8) in terms of differential, rather than integral, quantities.* analogue voltages and the Af versus t transients were captured using a Keithley (Cleveland, OH, USA) Series 570 data acquisition system interfaced to an IBM ATX computer. Potentials were measured and are quoted with respect to an aqueous saturated calomel electrode. Applied currents were in the range 50-600 PA. The galvanostat was set to change the sign of the applied current as the measured potential reached 0.0 and 0.7 V; these potentials were chosen to span the PVF+/O redox potential, 0.304 V in 0.1 mol dm-3 NaC104 and 0.251 V in 3 mol dm-3 NaC104.20 The counter electrode was a platinum gauze in a separate compartment. Measurements were made at room temperature, 20 & 2 "C. Reagent grades and purification procedures were as described previously .2*-28 Solutions were purged with argon, and the argon stream was directed over the solution during data acquisition.Poly(vinylferrocene) films were deposited electrochemic- ally from PVF solutions in 0.1 mol dm-3 tetrabutylammonium per~hlorate-CH~Cl~.~~ The coated electrodes were then rinsed with water and transferred into aqueous polymer-free NaCIO4 solutions (in which the films are rigid16) for the experiments reported here. The films were 'broken-in'18 prior to acquisition of the data reported here. Coverages or electroactive sites (determined by slow-scan voltammetry) spanned the range 10 < rlnmol cm-2 < 30. Results The results of two typical galvanostatic experiments, on the same film in the same solution (representing permselective conditions), at different applied currents are shown in Figs.2 and 3. The difference between the two experiments, the significance of which is discussed below, is approaching an order of magnitude in their timescale. The dotted lines Experimental The EQCM instrumentation has been described else- where.20-35 The quartz crystals (International Crystal Manu- facturing, Oklahoma City, OK, USA) were 10 MHz AT-cut, coated with gold electrodes of active area 0.23 cm2. All experiments were carried out under current control, using an Oxford Electrodes (Oxford, UK) galvanostat . Frequency differences relative to a reference crystal were converted to Fig. 1 1 x 1 x 1 cube representation of the redox, solvation and configuration states for a broken-in PVF film.Nomenclature as in Table 1 * The choice between using differential and integral quantities depends on whether one wishes to consider instantaneous fluxes or populations, respectively. YUYV 7 3000 E 2500 5 2000 g 1500 .- 4- c 5 1000 5 0 0 f 500 -500 I I I I I I I I 0 5 10 15 20 25 30 35 40 VS Fig. 2 EQCM data for redox switching of a PVF film (r = 23.7 nmol cm-2) under galvanostatic control with an applied current of 50 PA. Solution, 0.1 mol dm-3 NaC104. A, AM; B, QIM,F; and C, <I> 2500 N 'E 2000 0) 2 1500 3 + c 0 0 500 5 0 3 -500 I I I I I 0 0.5 1 1.5 2 2.5 3 3.5 Fig. 3 Analogous experiment to that of Fig. 2, but at an applied current of 400 PA. Labels signify species present at different points (see Discussion) t Is170 Analyst, February 1994, Vol.119 represent the injected charge (Q) as a function of time (t); for galvanostatic experiments, these traces are necessarily linear, with slopes of opposite sign in the oxidizing and reducing half- cycles. The charge data are presented in terms of the equivalent mass of counter ion, QmAIF, the first term of the right-hand side of eqn. (7). The solid lines represent the measured mass changes, calculated from EQCM frequency changes according to eqn. (2). The broken lines are values of @perm, calculated according to eqn. (8). We begin with a series of qualitative observations on the AM and @ data, develop a qualitative model for the underlying processes and finally extract quantitative transfer rate information. From Figs. 2 and 3, we note: ( a ) failure to return to the initial mass at the end of cycle 1, the mass at the end of the cycle is greater than at the start; ( b ) the mass of the oxidized state is the same for cycles 1 and 2 in each case; (c) the over-all mass change is a function of applied current, i.e., experimental timescale; ( d ) the AM versus t plots are curved, this is more obvious for the Q, versus t plots, representing the neutral species component of A M ; and (e) the curvature on the AM versus t and Q, versus t plots is more marked during oxidation than reduction.Observations ( a ) and ( b ) indicate different ‘initial’ reduced states, but the same ‘final’ oxidized states for cycles 1 and 2 irrespective of the applied current. Data for cycles beyond the second cycle showed no further changes.Observation (c) shows that the reaction in eqn. (3) is incomplete within the shorter timescales (higher currents) accessible in this work. Extending this point, observation (4 (in particular the @ versus t plot) reveals that solvent transfers more slowly than counter ion. The AM trace in Fig. 3 is coincident with the Q trace for approximately the first 250 ms of oxidation, so @perm = 0 for t < 250 ms. Thus the primary objective of temporal resolution of mobile species transfer has been successful. Finally, observation ( e ) shows that the kinetic limitations on neutral species, here solvent, transfer are different for entry into and exit from the polymer. All the experiments conducted under the permselective conditions (0.1 mol dm-3 NaC104) of Figs.2 and 3 were repeated under non-permselective conditions (3 mol dm-3 NaCIO4). Analogous qualitative behaviour, illustrated by Fig. 4, was found; quantitative differences (see below) are a result of the non-zero value(s) of salt stoichiometric coefficient(s) in the reaction in eqn. (3). Discussion Qualitative Model We describe the processes occurring in Figs. 2 and 3 by means of the 1 x 1 X 1 cube of Fig. 1. The requirement is to identify the relative timescales of the three processes involved and the order in which they occur. 4000 I I y 3500 3000 2500 cn *g 2000 2 1500 4 500 c 8 1000 = o -500 ‘ I I I I I I I I 0 1 2 3 4 5 6 7 8 t 1s Fig. 4 current of 200 pA and in 3 mol dm-3 NaCIO? Analogous experiment to that of Fig. 2. but at an applied The expectation for a fast electron transfer system, such as PVF, is that charged species transfers (coupled electrodion motion) will be faster than neutral species transfers. This is borne out by the data of Fig.3 in the early stages of each switching step, where the observed film mass change ( A M ) and the anion contribution to the mass change (QlmAF) are coincident. We are able to discount the possibility that the transfer of cation (in the opposite direction) is significant for two reasons. Firstly, whether the cation in question were sodium or proton (from the solvent), the mass change would be in the opposite sense to that observed (it?., the film would become lighter instead of heavier on oxidation, and vice versa on reduction) . Secondly, for sodium ion, under permselective conditions (low electrolyte concentration), there is no cation available in the film for even transient expulsion.Finally, the variation of mass change at the current reversal points (see below) signifies that solvent transfer is not complete on the faster timescale (higher current) experiments. The failure of the system to return to the initial reduced state is a consequence of slow relaxation across the left hand (R) face of the cube in Fig. 1. Potential transients, to be discussed elsewhere, demonstrate that the slow process is polymer relaxation, Rb + R,. Attainment of the same oxidized state (at 0.7 V), but different reduced states (at 0.0 V), on multiple cycling demonstrates that the solvatiod polymer relaxation rates are different for the reduced and oxidized films. Between runs, the film was held at 0.0 V for an extended period (typically 30 min) to allow equilibration of the reduced state to R,.To summarize, in each switching direction, the order of timescales for the contributory processes is electrodion transfer < solvent transfer < polymer reconfiguration. Polymer reconfiguration from the ‘oxidized’ to the ‘reduced’ configuration is markedly slower than the reverse process (but see below). In terms of the nomenclature of Table 1, we represent a complete redox cycle, commencing from an equilibrated reduced film by: for the oxidation half-cycle and for the reduction half-cycle. On the timescale of all the experiments reported here, the final step of reaction sequence (lo) does not occur, i.e., the process stops at Rb. We thus represent the first cycle of Figs.2 and 3 by Fig. 5. In this figure, Ra -+ 0, + 0,’ + o b s o b s + RbS + Rb + R, (9) (10) Fig. 5 Schematic cube scheme for the first redox cycle of a PVF film under permselective conditions (as in the first half of Figs. 2 and 3 ) . Nomenclature as in Table 1Analyst, February 1994, Vol. 11 9 171 shaded and unshaded areas denote unaccessed and accessed states, respectively; six of the eight total states are accessed in the first cycle. Note that the polymer reconfiguration steps are: in the oxidation and R b + Ra (12) in the reduction direction. As they involve different species it is not surprising that there is a disparity in rates. We note that the slower of the two processes, reaction step (12), involves relatively unsolvated species.This is consistent with the notion that solvent should facilitate chain motion. The second (and subsequent) cycles involve interconversion of Rb and o b s . The absence of ‘b’ + ‘a’ reconfiguration at the end of cycle 1 confines subsequent cycles to the lower plane of Fig. 5. This situation is represented by Fig. 6, in which only four of the eight states are accessed. We note that both the electrodion and solvent transfer processes during oxidation in cycle 1 R,+ O,+ 0,s- ... (13) and in cycle 2 (or subsequent) involve different species. In principle, there will be different transfer rates for these processes, which involve the polymer in configurations ‘a’ and ‘b’. There is some evidence, albeit rather slight, for this difference in Fig.3: compare the curvature of the CD versus t plots in scans 1 and 2. In summary, we are able to (a) cause complete conversion (R, e o b s , on very long timescales), (b) ‘freeze out’ polymer reconfiguration (on slow/intermediate timescales) or (c) ‘freeze out’ polymer reconfiguration and solvent transfer (on short timescales).s All this can be seen in Fig. 3. To illustrate the point, the curves are labelled with species accessed at different times. For PVF under the conditions employed here, the progres- sive ‘freezing out’ of the component processes with increasing current is summarized in Table 2. Shaded and unshaded cells, respectively, represent regions of kinetic and apparent ther- modynamic control. In the experiments reported here, we have access to the first five of the six cells.We note that the ordering of the non-electrochemical rates will depend on the polymer, the direction of redox switching and experimental variables such as solvent, electrolyte nature and temperature. Whatever the ordering, the procedure described here is applicable. Quantitative Interpretation In order to exploit this successful strategy of temporal separation of mobile species transfers for analytical purposes, we need to do two things: prove the identity of a mobile species and quantify the timescale on which its transfer occurs. In short, we must answer the question ‘What timescale should be employed for the determination of a chosen species?’. The issue of identity was trivial for the permselective case, where only water and counter ion were transferred.In this section we make the qualitative deduction for the non-permselective case (illustrated by the data of Fig. 4) and quantify the solvent transfer rate for both cases. We consider the ‘end-to-end’l mobile species population changes in the film as a function of experimental timescale. Fig. 7 shows end-to-end A@ data for two series of experi- ments, under permselective and non-permselective conditions (0.1 and 3 mol dm-3 NaC104, respectively). For the perm- selective experiments A@ represents solvent transfer and for the non-permselective experiments it represents salt + solvent transfer, in each case within the interval of the redox half- cycle. Applying the approximate ‘constant solvent transfer’ Table 2 Identifying the rate-limiting step 1600 1400 1200 YE 1000 s600 800 400 200 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 (i/pA)- f Fig.7 Plots of Q, versus i-$ for a PVF film in A, 0.1 (solvent) (Figs. 2, 3 and analogues) and B, 3.0 (salt) (Fig. 4 and analogues) mol dm-3 NaC104 Fig. 6 Schematic cube scheme for the second (and subsequent) redox cycle(s) of a PVF film under permselective conditions (as in the second half of Figs. 2 and 3 ) . Nomenclature as in Table 1 In these experiments, we chose to manipulate the experimental timescale via 11 By ‘end-to-end’ we imply the change between consecutive switches of the current sign, i.e., between the times at which the potential reaches 0.0 and 0.7 V. the imposed current.172 Analyst, February 1994, Vol. I I9 concept,37 and assuming that it holds in a dynamic sense, the differences between pairs of points represent salt transfer, as indicated by the inlaid text.Since z is equal to QT/i, the x-axis of Fig. 7 represents ti. On long timescales (to the right of the plot), the extent of neutral species transfer is independent of timescale. We interpret this to indicate that solvent (and salt, in the non-permselective case) transfer is complete within the half-cycle, regardless of any delays in the early stages of switching. As the timescale is decreased (moving to the left of the plot), a timescale is reached at which this is no longer the case. It is apparent that this timescale is the same for both series of experiments. From this we deduce that the species whose transfer then becomes rate limiting is the same under both permselective and non- permselective conditions.Water is the only candidate, as it is the only neutral species transferred under permselective conditions. Consequently, for the non-permselective case, salt transfer is faster than solvent transfer, and is on shorter timescales than those accessed in this work. At short timescales (high currents), A@ is observed to be proportional to i-5. We can rationalize this as follows. According to Fick’s law, the diffusional flux jlmol cm-2 s-l = D(dc/dx) = {D/xt}iAc (15) where D is the diffusion coefficient for water in the polymer, Ac is the difference in water concentrations between the film and solution, and we have approximated the differential as a linear gradient. The integrated form of eqn.(15) is ATs/mol cm-2 = 2{Dt/n}eAc (16) Using eqn. (8), this gives Q, = 2ms(DQ/ni}~Ac showing that Q, versus i-f plots should be linear (as observed) and of slope 2ms{ DQ/x}AAc, from which D can be estimated. In order to proceed, we require a value for Ac (= csoln - cfilm). Ellipsometric data38 yield a volume concentration for fer- rocene sites of about 2 x 10-3 mol ~3171~. Reduced, ‘broken- in’ PVF films contain about five water molecules per redox site.18 Hence, cfilm = 0.01 mol ~ m - ~ so that Ac = 0.045 mol ~ m - ~ (approximately the external solution as pure water). By using the data of Fig. 7, we then obtain D = 3 x lO-*3 cm2 s-1. We recognize that this treatment assumes that the diffusion coefficient of water in the film is independent of film water content, and is most probably overly simplistic.The general problem of the diffusion of a species taking into account the possibility of a concentration-dependent diffusion coefficient requires information not generally available. The treatment of this problem, originating with Boltzmann and discussed by Crank,39 leads to the conclusion that the P behaviour observed by us is not diagnostic of concentration (in)dependent diffusion. Consequently, the value of D reported is uncertain to this extent. Future studies might be aimed at the use of larger currents (shorter timescales), with the objective of reaching a second break in the short time data of the non-permselective plot in Fig. 7. This would, in an analogous fashion to eqn. (17), lead to a diffusion coefficient for salt in the polymer film.Conclusions Galvanostatically controlled switching of electroactive films on an EQCM can facilitate kinetic separation of mobile species transfers. Migrational transport of ions is faster than diffusional transport of neutral species. Unexpectedly, the gravimetric response may differ from one redox cycle to another, depending on the prior history of the film. These history effects will be a key factor in ‘real’ applications, where a sensor may be ‘rested’ prior to a series of determinations. For redox switching of PVF films in aqueous media, the relative rates of the contributory processes are ion transfer > salt transfer > solvent transfer > polymer reconfiguration. The initial film state is determined by its pre-history and the final state by the experimental timescale.A scheme-of-cubes model can explain the variation of PVF film mass changes under kinetically controlled conditions. In the light of this model, we rationalize the apparent problems of reproducibility for polymer modified electrodes in terms of slow polymer relaxation processes and/or failure to control film history. Furthermore, discrepancies in the observations of different workers employing ‘identical’ polymer films may also be attributable to differing film histories and/or experimental timescales. We thank the NSF (CHE-9115462) for financial support and the SERC (GWC 32946) for an equipment grant. References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Biosensors and Chemical Sensors: Optimizing Performance Through Polymeric Materials, eds.Edelman, P. G., and Wang, J., ACS Symp. Ser., vol. 487, American Chemical Society, Washington, DC, 1992. Hillman, A. R . , in Electrochemical Technology of Polymers, ed. Linford. R., Elsevier Applied Science, London, 1987, pp. 103-239 and 241-291. Szentirmay, M. N., and Martin, C. R., Anal. Chem.. 1984, 56. 1898. Cox, J. A., and Kulesza, P. J., J. Electroanal. Chem., 1983,159, 337. Wang, J., Greene, B., and Morgan, C., Anal. Chim. Acta, 1984, 158. 15. Beer, P. D., Kocian, O., Mortimer, R. J., and Ridgway. C.. Analyst, 1992. 117, 1247. Kutner, W., and Doblhofer, K.. J. Electroanal. Chem.. 1992. 326, 139. Ebersole, R. C., and Ward. M. D., J. Am. Chem. SOC., 1988, 110, 8623. Bruce, J. A., and Wrighton, M. S., J.Am. Chem. SOC., 1982, 10474. Scott, N. S., Oyama, N., and Anson, F. C.. J . Electroanal. Chem., 1980, 110,303. Buttry, D. A., in Electroanalytical Chemistry, ed. Bard, A. J., Marcel Dekker, New York, 1991, vol. 17, pp. 1-85. Methods and Phenomena, Volume 7: Applications of Piezoelec- tric Quartz Crystal Microbalances, eds. Lu, C., and Czanderna. A. W.. Elsevier, Amsterdam, 1984. Glidle, A., Hillman, A. R., and Bruckenstein, S., J. Electro- anal. Chem., 1991. 318,411. Muramatsu, H.. Ye. H., Suda, M., Sakuhara. T., and Ataka. A., J. Electroanal. Chem., 1992. 322, 311. Sauerbrey. G. Z., 2. Phys., 1959. 155,206. Glidle, A., Gonsalves. M., and Hillman, A. R., unpublished work. Hillman, A. R., Loveday, D. C.. and Bruckenstein. S., Langmuir, 1991,7, 191. Hillman. A. R., Hughes, N. A., and Bruckenstein, S., J. Electrochem. SOC.. 1992,139, 74. Varineau, P. T., and Buttry, D. A.. J. Phys. Chem., 1987, 91, 1292. Hillman. A. R., Loveday, D. C., and Bruckenstein, S.. J. Electroanal. Chem., 1989,274. 157. Hillman, A. R.. Swann. M. J.. and Bruckenstein. S.. J. Electroanal. Chem., 1990.291. 147. Borjas, R.. and Buttry, D. A., J. Electroanal. Chem., 1990,280, 73. Daifuku. H., Kawagoe, T., Yamamoto, M.. Ohsaka, T.. and Oyama, N., J. Electroanal. Chem.. 1989, 274, 313.Analyst, February 1994, Vol. I I9 173 24 25 26 27 28 29 30 31 32 33 Naoi, K., Lien, M., and Smyrl, W. H., J. Electrochem. SOC., 1991, 138,440. Inzelt, G., and Bacskai, J., Electrochim. Acta, 1992, 37, 647. Hillman, A. R.. Loveday, D. C., Swann, M. J., Bruckenstein, S., and Wilde, C. P., Analyst, 1992, 117, 1251. Hillman, A. R., Loveday, D. C., Bruckenstein, S., and Wilde, C. P., Faraday Trans., 1990,86,437. Hillman, A. R., Loveday, D. C., and Bruckenstein, S., J. Electroanal. Chem., 1991, 300, 67. Hillman, A. R., and Bruckenstein, S., Faraday Trans., 1993,89, 339. Hillman, A. R., Swann, M. J., and Bruckenstein, S., J. Phys. Chem., 1991,95,3271. Schroeder, A. H., Kaufman, F. B., Patel, V., and Engler, E. M., J. Electroanal. Chem., 1980,113, 193. Jacq, J., Electrochim. Acta, 1967, 12, 1345. Albery, W. J., and Hitchman, M. L., in Ring Disc Electrodes, Clarendon Press, Oxford. 1971, ch. 5 , pp. 38-72. 34 Hillman, A. R., and Bruckenstein, S., Faraday Trans., 1993,89, 3779. 35 Bruckenstein, S., and Shay, M., Electrochim. Acra, 1985, 30, 1295. 36 Hillman, A. R., Loveday, D. C., and Bruckenstein, S.. Langmuir, 1991, 7, 191. 37 Bruckenstein, S., and Hillman, A. R., J. Phys. Chem., 1991,95, 10748. 38 Hillman, A. R., Loveday, D. C., Swann, M. J., Eales, R. M., Hamnett, A., Higgins, S. J., Bruckenstein, S., and Wilde, C. P., Faraday Discuss., 1989,88, 151. 39 Crank, J., Mathematics of Diffusion, Oxford University Press, Oxford, 1956, p. 148. Paper 31047406 Received August 6, 1993 Accepted November 15, 1993

ISSN:0003-2654    

DOI:10.1039/AN9941900167

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, February 1994, Vol. 1 I9 175 Electrochemical tmmobilization of Enzymes Part Vl.* Microelectrodes for the Detection of L-Lactate Based on Flavocytochrome Immobilized in a Poly(pheno1) Film* Philip N. Bartlett and Daren J. Caruana Department of Chemistry, University of Southampton, Highfield, Southampton, UK SO9 5NH The adsorption of flavocytochrome bz at a 25 pm diameter platinum microelectrode, followed by immobilization in an electrochemically polymerized phenol film, was found to be a reproducible method for the fabrication of microelectrodes responsive to L-lactate. Fabrication of enzyme microelectrodes in this manner is simple and produces electrodes that respond rapidly to L-lactate. The immobilization in the poly(pheno1) film has no effect on the specificity of the enzyme for L-lactate over p-chlorolactate and reduces the direct electrochemical interference from uric acid, acetoamidophenol and ascorbate.The stability of the resulting enzyme electrode is discussed. Keywords: Flavocytochrome b2; microelectrode; poly(pheno1); mediation; L-lactate determination Introduction Miniaturization of biosensors for in vivo applications has attracted much attention in recent years. 1 4 The fabrication of small sensors incorporating enzymes normally involves com- plex and delicate techniques. In this work we use an electrochemically polymerized film grown on the surface of a 25 pm diameter microelectrode to immobilize an enzyme. The enzymic activity in the film is studied to assess the effect this method of immobilization has on the enzyme, with a view that it could be used as a step in the fabrication of a small, functional biosensor.Electropolymerization has been successfully used to immo- bilize enzymes at electrode surfacess-6 and to reduce interfer- ences and fouling in amperometric biosensors.7-9 Electro- chemical polymerization has a number of significant advantages as an approach towards biosensor fabrication. First, the method is flexible and can be readily controlled. Second, it is simple to carry out. Third, the polymer deposition is localized at the electrode surface so that the method is suited to the spatially localized deposition of enzymes on to microelectrode arrays. In this work, poly(phe- nol) was used as the electropolymerized film to produce a thin layer on an electrode surface coated with pre-adsorbed enzyme.Previous work by our group has shown that films of electropolymerized phenol, or phenol derivatives, deposited on platinum macroelectrodes are suitable for the immobiliz- ation of glucose oxidase and that the immobilized enzyme retains enzymic activity.1° The use of poly(pheno1) films for immobilizing enzymes is attractive because it produces a thin insulating polymer over the surface of the electrode.11 An * For Part V of this series, see ref. 15. t Presented at the International Symposium on Electronalysis in Biomedical, Environmental and Industrial Sciences, Loughborough, Leicestershire, UK, April 2&23, 1993. advantage of having a thin layer of enzyme is that the response time of the sensor is much reduced.12 Also, it has been shown that poly(pheno1) films provide some permselectivity at the electrode surface, which may reduce fouling of the electrode surfacel3.14 and provide some selectivity against potential interfering species such as ascorbate, uric acid and acetoamidophenol .Recently, we have reported that glucose oxidase can be immobilized on a 25 pm diameter platinum microelectrode using poly(phenol).l5 The activity of the glucose oxidase was measured by the reduction of hydrogen peroxide produced by the enzyme at a platinum surface maintained at +0.9 V versus a saturated calomel electrode (SCE) under steady-state conditions. The immobilization of enzymes on microelec- trodes can be used to produce biosensors that have fast response times, for use with small sample volumes and for in vivo applications.It has recently been found that lactate is an important compound in knee synovial fluid for the diagnosis of arthritis; in this instance only a few microlitres are available for analysis16 so that a small sensor, responsive to lactate, is required. There are three main enzymes that can be used as the biological component of a biosensor for lactate: (i) lactate oxidase, which is a multi-unit, large protein of approximately 370 kDa with complex kinetics and for which the structure is unknown17; (ii) lactate dehydrogenase, which is a reduced nicotinamide adenine dinucleotide-dependent enzyme that does not have a prosthetic group's; and (iii) flavocytochrome 62 (FC-62) which is a well characterized enzyme with flavin mononucleotide (FMN) and haem prosthetic groups and for which the molecular structure is known and well charac- terized.19 In this study FC-62 immobilized on a 25 pm diameter platinum disc has been used to produce a microelectrode responsive to L-lactate.Flavocytochrome 62 (L-lactate: cytochrome c oxidoreduc- tase, EC 1.1.2.3) is found in the inter-membrane space of yeast (Saccharomyces cereviszae) mitochondria where it cat- alyses the oxidation of L-lactate to pyruvate with subsequent electron transfer to cytochrome c.20 The molecule is a tetramer of M, 230000. Each sub-unit contains two function- ally distinct domains, one binds FMN and the other a protohaem IX.21 The active site of the enzyme is located in the FMN domain of each sub-unit and is not absolutely specific for L-lactate, but is capable of oxidizing a number of a-hydroxy acid substrates such as P-chlorolactic acid, although the enzyme shows greatest activity with L-lactate .22 The molecular structure of FC-62 has been elucidated at a resolution of 2.4 A and the catalytic mechanism has been studied intensively.23~24 The native enzyme does not exhibit any direct electron transfer in the presence of a substrate at bare metal electrodes. Flavocytochrome 62 can potentially be used as the biolog- ical component of a biosensor for L-lactate.Kulys and SvirmickaBs produced a sensor for lactate by mixing FC-b2176 Analyst, February 1994, Vol. 119 with powdered N-methylphenazinium 7,7,8,8-tetracyano- quinodimethanide, which was then spread on a platinum electrode and covered with a dialysis membrane.The resulting sensor had a response time of 0.5-0.7 min and an operating potential between -0.03 and +0.4 V versus Ag-AgCl. The enzyme electrode was stable for 3-9 d and the loss of activity was attributed to de-activation of the enzyme. More recently, StaSkeviCiene et a1.26 described the entrapment of FC-b2 on glassy carbon electrodes modified with Carbon Black. In this system the surface quinoidal groups on the Carbon Black were thought to serve as mediators. This allowed the working potential of the electrode to range from -0.2 to -0.1 V versus the SCE, which was effective in reducing interference from ascorbic acid. The response time of this enzyme electrode was 1-1.5 min. Clearly, miniaturization of these sensors is not a trivial task.The use of poly(pheno1) to immobilize FC-62 seems an attractive technique for producing a microelectrode respons- ive to L-lactate. In this work, tetrathiafulvalene (TTF+) is used as the mediator to transfer electrons from the FMN of the enzyme to the electrode surface. The reaction scheme is shown below: L-lactate + FC-b2(ox) + pyruvate + FC-b2 (red) Film FC-62 (red) + 2TTF+ + FC-b2 (ox) + 2'ITF Film 'ITF+?TF++e- Electrode In this paper, previous work on the immobilization of glucose oxidase on a microelectrode15 is extended to the preparation of an electrode responsive to L-lactate by immobilizing FC-b2 in poly(pheno1) on a 25 pm diameter platinum disc. The performance and stability of the fabricated enzyme electrode are discussed. Experimental Reagents All solutions were freshly prepared with water purified by a Whatman (Maidstone, Kent, UK) WR50 RO/de-ionizing system followed by use of a Whatman STILLplus carbon filter.Phenol (Fisons, Loughborough, Leicestershire, UK) solution was freshly made up before use in 0.10 rnol dm-3 disodium hydrogenorthophosphate buffer, pH 7.0 (Fisons analytical reagent), containing 0.1 mol dm-3 sodium chloride (Fisons). Flavocytochrome b2 from Saccharomyces cerevisiae, prepared by the method of Black et al.27 and stored in ammonium sulfate precipitate in the presence of lactate at 4 "C under nitrogen, was a gift from Bruce Moore (Oxford). Measurements of the electrode responses were performed in 0.10 mol dm-3 piperazine-N, N'-bis(ethane-2-sulfonic acid) (PIPES) (Sigma St.Louis, MO, USA), the pH being adjusted to 7.0 with 0.10 mol dm-3 hydrochloric acid (Fisons analytical reagent). All solutions were sparged with nitrogen for at least 20 min, directly before use, to remove dissolved oxygen. L(+)- Lactic acid sodium salt (Sigma), DL-a-hydroxybutyric acid sodium salt (Sigma), P-chlorolactic acid sodium salt (Sigma) were all made up in PIPES buffer (pH 7.0) and stored at 4 "C. Tetrathiafulvalene chloride (TTF+CI-) was prepared by dissolving TTF+ (99% ; Fluka, Buchs, Switzerland) in diethyl ether (99y0 ; Prolabo, Paris, France) and passing chlorine gas (99%; Aldrich, Milwaukee, WI, USA) over the top of the solution until a dark precipitate appeared; the TTF+CI- precipitate was filtered off, allowed to dry and stored under nitrogen at 4 "C.Uric acid (Aldrich), ascorbic acid (Aldrich), 4-acetoamidophenol (Sigma) and FMN sodium salt (Sigma) were used without further purification. Instrumentation All measurements were made using a conventional three- electrode system consisting of a large-area platinum-gauze counter electrode, an SCE and a platinum microelectrode, unless otherwise stated. All potentials are reported with respect to the SCE. The potentiostat was purpose built and incorporated a Faraday cage to reduce noise. It was used in conjunction with a Bryans (Mitcham, Surrey, UK) 60000 series x-ylt recorder and a Keithley (Reading, Berkshire, UK) digital voltmeter. All measurements were carried out at room temperature in an undivided cell unless otherwise stated. The solution was stirred with a purpose-built air-powered stirrer to facilitate mixing on addition of aliquots of substrate.Flow injection measurements were made using the same potentios- tat, but connected in a two-electrode configuration using a laboratory-made calomel as the combined reference and counter electrode and with the microelectrode as part of a purpose-built flow system based on a Pharmacia (Uppsala, Sweden) P-1 single-channel pump and an Omnifit (Cam- bridge, UK) 1106 sample injector valve. A 200 pl sample and flow rate of 1.4 cm3 min- were used. Non-linear least-squares fitting of the experimental responses to the theoretical expression was carried out using the SigmaPlot program (Jandel) , on a 486 microcomputer, Microelectrode Fabrication Platinum wire (Goodfellow Metals, Cambridge, UK) of 25 pm diameter was sealed in soft glass capillaries and the end sections were polished, first using 'wet and dry' paper followed by successively finer grades of diamond lapping compounds (Engis, Maidstone, Kent, UK ) down to 0.1 pm.All electrodes were stored in buffer solution at all times. Before any experiment each electrode was cycled in 2.0 mol dm-3 sulfuric acid (Aldrich AR grade) between -0.2 and +1.5 V for approximately 15 min. Enzyme Immobilization The electrode was immersed in a solution containing approxi- mately 1.6 mg cm-3 FC-b2 in 0.10 mol dm-3 disodium hydrogenorthophosphate buffer at pH 7.0 that was 0.10 rnol dm-3 in sodium chloride and 0.01 rnol dm-3 in L-lactate, purged with nitrogen and allowed to stand for 15 min in open circuit.The electrode was then transferred to a growth solution containing 0.10 rnol dm-3 phenol and 0.01 rnol dm-3 L-lactate, also purged with nitrogen. The electropolymeriza- tion was carried out by maintaining the electrode at 0.0 V for 20 s and then stepping up the potential to +0.9 V and keeping it there for 8 min. The electrode was then stepped down to 0 V, disconnected after 20 s and washed for 5 min in stirred PIPES buffer solution. For the stability measurements the enzyme microelectrodes were kept in PIPES buffer solution, purged with nitrogen and containing either L-lactate or L- lactate and FMN at 4 "C, between measurements. Results Theory The steady-state current for an electrode coated with a thin film containing FC-b2 is given bylo where A is the electrode area, iobs is the observed current for TTF+ detection, KM and kcat describe the reaction of the enzyme with L-lactate, k is the rate constant describing the re- oxidation of the mediator, I is the thickness of the immobilized layer, ex is the enzyme concentration in the layer, Ks and KA are the partition coefficients, and s, and a , are the bulk concentrations of the substrate and mediator, respectively.Analyst, February 1994, Vol.119 177 The parameter a describes the balance between the detection of the reduced mediator, B, at the electrode surface and its loss to the bulk solution and is given by where X, is the diffusion layer thickness, DB,soln and DB are the diffusion coefficients of B in the solution, KB is the partition coefficient of B in the film, and 4 < a < 1.For a microdisc electrode XD is replaced by the electrode radius, ro.3 By using eqn. (1) we can fit our data from studies of the current for the enzyme-coated electrode as a function of the concentration of substrate, the concentration of mediator and the enzyme loading and we can determine the kinetics for the reaction in the immobilized layer. Responses to L-Lactate The inset in Fig. 1 shows responses to the addition of aliquots of L-lactate solution at a 25 pm diameter FC-b2-poly(pheno1)- modified electrode at +0.2 V in PIPES buffer solution containing 2.0 mmol dm-3 TTF+Cl-. The response of the electrode is rapid and is determined by the mixing time in these experiments. In control experiments in which the 20 10 0 100 200 300 Time/s I I I I I 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 [Lactate] / mmol dm3 Fig.1 Response curves for three different 25 pm diameter FC-b2- poly(pheno1) modified microelectrodes recorded at +0.2 V versus SCE in PIPES buffer pH 7.0 containing 2.0 mmol dm-3 TIT+. The background currents were between 15 and 20 PA. The solid lines are the non-linear least mean squares best fits of the data to eqn. (1) the fitting parameters are given in Table 1. The inset shows current responses for a 25 pm diameter FC-b2-poly(phenol) modified microelectrode. Each step corresponds to a change in L-lactate concentration of 0.166 mmol dm-3 enzyme was omitted there was no detectable (CO.1 PA) response to additions of lactate under these conditions. The reproducibility of the fabrication of these enzyme electrodes is good, as shown in Fig.1 where L-lactate concentration is plotted against current response for electrodes fabricated on different days and using different growth solutions of the same composition. When the same experiment was carried out on a macroelectrode under the same conditions, similar results were obtained and the current densities obtained for both size electrodes were equivalent: 13.9 pA cm-2 for the macroelec- trode and 14.6 pA cm-2 for the microelectrode. The kinetic parameters calculated from eqn. (1) for the responses obtained from these enzyme electrodes are presented in Table 1. Eqn. (1) predicts that the response at high L-lactate concentration can be limited by the reaction of the mediator with the enzyme rather than by the enzyme substrate kinetics.We have observed this effect in our experiments; Fig. 2 shows results for lactate determination at two different concentra- tions of TTF+. At the lower TIT+ concentration the current clearly saturates at a lower value, showing that in this instance the plateau current is dependent on the rate of re-oxidation of the enzyme by TTF+ . Kinetic parameters from the analysis of this data according to eqn. (1) are presented in Table 1. To study this effect further we investigated the effect of varying the TTF+ concentration at a fixed (saturating) L-lactate concentration of 10 mmol dm-3. As shown in Fig. 3 the current is initially dependent on the TTF+ concentration, but becomes independent of TTF+ at high concentrations. The solubility of TTF+ in our electrolyte solution was found to be 2 mmol dm-3 by spectrophotometric measurements.In this instance the fit to eqn. (1) is poor, but the situation is complicated by the effect of partitioning of the TTF+ species into the film and possibly by interactions wtih the enzyme.29 Specificity and Stabiliiy Flavocytochrome b2 is not entirely specific for L-lactate, but also oxidizes other a-hydroxy acids such as DL-chlorolactate, DL-fluorolactate, DL-bromolactate and L-glycerate. Fig. 4 shows the current response of an enzyme electrode to L-lactate and DL-chlorolactate; the calculated relative rate for the two substrates at the enzyme electrode is 0.32, while the literature value for the relative rate in homogeneous solution21 is 0.35. The close agreement between the two indicates that the selectivity of the enzyme is not greatly perturbed by electro- chemical immobilization in the poly(pheno1) film.The stability of these enzyme electrodes was also studied and compared with the stability of the free enzyme in buffer solution. Fig. 5 shows data collected for electrodes stored Table 1 Kinetic parameters from non-linear least-squares best fits of data to eqn. (1) aK&cated & a d KM (1 -k kca,/kKAam) /cm s- /mol cm-2 s-1 L- Lactate [large Pt electrode (0.38 cm2)]- L- Lactate (25 pm diameter electrode)- 2.0 mmol dm-3 TIT+ 4.5 x 10-4 8.46 x 10-11 2.0 mmol dm-3 TIT+ 595A 6.0 x 10-4 7.9 x 10-11 595B 5.2 x 10-4 6.6 x lo-" 596 6.0 x 10-4 7.4 x 10-11 2.0 mmol dm-3 'ITF+ 0.5 mmol dm-3 TTF+ 6.1 x 10-4 13 x 10-4 8.1 x 10-11 5.2 x 10-11 Chlorolactate (25 pm diameter electrode)- 2.0 mmol dm-3 TTF+ 1.5 x 10-4 2.6 x lo-" KM 1.96 x 10-7 1.3 x 10-7 1.3 x 10-7 1.2 x 10-7 1.3 x 10-7 0.4 x 10-7 1.8 x 10-7178 Analyst, February 1994, Vol.11 9 (a 1 80 r 1 0 1 .o 2.0 3.0 3.5 [Lactate] I mmol dm4 Fig. 2 Response curves for the same lactate microelectrode, in pH 7.0 PIPES buffer containing 2.0 mmol dm-3 (0) and 0.5 mmol dm-3 TTF+ (0) recorded at + 0.2 V versus SCE. The background currents were 20 and 8 PA, respectively. The solid lines are the non-linear least mean squares best fits of the data to eqn. (1) the fitting parameters are given in Table 1 0 0.5 1.0 1.5 2.0 2.5 pF+] / mmol dm3 Fig. 3 Response curves for microelectrode modified with FC-bz- poly(pheno1) held at +0.2 mV in pH 7.0 buffer containing 'ITF+ and adding 5.0 mmol dm-3 lactate.The background current varied from 2 to 20 pA 70 60 20 10 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 [Substrate] / mmol dm4 Fig. 4 Response curves for the same lactate microelectrode, for p- chlorolactate (V) and lactate (0), recorded at +0.2 V versus SCE in pH 7.0 PIPES buffer containing 2.0 mmol dm-3 ?TF+. The solid lines are the non-linear least mean squares best fits of the data to eqn. (1) the fitting parameters are given in Table 1 under three different conditions: in the presence of lactate in de-oxygenated buffer; in de-oxygenated buffer without lac- tate; and in the presence of lactate and FMN. The activity of the free enzyme in solution falls steadily under all three conditions, although in aerobic solutions, and especially in the presence of FMN, the loss of activity is accelerated.The activity of the enzyme electrode shows two phases: a rapid fall after the first day, followed by a steady fall in activity, which mirrors the activity of the free enzyme in solution under all three conditions. It is interesting that the addition of flavin adenine dinucleotide does not accelerate the loss of activity of the immobilized enzyme as it does for the enzyme in solution. This could be due to the poly(pheno1) film protecting the enzyme from the FMN in solution. Interferences The major potential interfering species encountered in in vivo measurements, or in whole blood, are ascorbate, uric acid and 0.5 0.4 0.3 0.2 80 60 40 0.6 100 0.6 0.5 0.4 0.3 0.2 0.1 I I I P 1 2 3 4 5 0 ' Time/d Fig.5 Stability of microelectrode modified with FC-b2-poly(phenol) (V), and FC-b2 (0) stored at 4 "C in de-oxygenated PIPES buffer pH 7.0 containing: (a) no lactate; (b) 5.0 mmol dm-3 lactate; (c) 5.0 mmol dm-3 lactate and 1.0 mmol dm-3 FMN. The enzyme in homogeneous solution was assayed by recording the decrease in absorbance at 420 nm in PIPES buffer pH 7.0 containing 5.0 mmol dm-3 lactate and 1.0 mmol dm-3 [Fe(CN)6]-3 at 25 "C. (Each point represents the mean of 4 determinations)Analyst, February 1994, Vol. 11 9 179 acetoamidophenol. In principle, the phenol film should help to block the reaction of these interfering species at the platinum electrode. 13 Cyclic voltammograms were recorded for these three species at typical physiological Concentrations at a clean platinum microelectrode, at a poly(pheno1)-coated platinum microelectrode and at a poly(phenol)/FC-b2-~oated platinum microelectrode.The results were very similar to those obtained for poly(pheno1) films containing glucose oxidase15; the poly(pheno1) coat significantly reduces the interference from all three species, and incorporation of the enzyme into the film only slightly increases its permeability. In practice it is necessary to compare the responses to the interfering species with the responses obtained for lactate. However, there is a further problem in the system in its present form because there is a homogeneous chemical reaction between Tl"F+ and ascorbate. To overcome this it will be necessary to avoid the use of TTF+ in the bulk solution, and experiments to overcome this problem by immobilizing the mediator within the film are under way.Flow Injection Measurements Fig. 6 shows the response of the enzyme microelectrode in a flowing system to injection of three different concentrations of L-lactate. The reproducibility is good and the responses show the same type of concentration dependence observed for quiescent solutions. The electrode response is stable in the flowing stream; in a continuous flow of L-lactate (5 mmol dm-3) the current was stable for 50 min before any depletion of current was observed. Discussion The method of immobilizing FC-bz for the construction of a microelectrode responsive to lactate is reproducible, as shown by the kinetic parameters for replicate electrodes presented in Table 1.The first column shows the effective electrochemical rate constants for the enzyme electrode at non-saturating substrate concentrations, and these are derived from the initial part of the calibration graph. The second column shows the limiting flows for the enzyme electrode at saturating substrate concentrations. The values in the last column, derived from those of the previous two by division, are the equivalent of the Michaelis constants for the enzyme elec- trode.30 The table also shows that the kinetic parameters obtained for both the macro- and microelectrodes are comparable, suggesting that we have a thin layer of entrapped 90 r 80 . 50 40 L Ll L L L 0 200 400 600 800 lo00 1200 1400 Time/s Fig. 6 Response of 25 pm diameter microelectrode modified with FC-b2-poly(pheno1) in a continuously flowing stream of 2.0 mmol dm-3 TTF+ in PIPES buffer pH 7.0.Injections were 200 p1 of the flow-through solution containing: A, 5.0; B, 0.5; and C, 0.1 mmol dm-3 L-lactate. Flow rate, 1.4 ml min-1 enzyme that is unaffected by radial diffusion, which would be observed at a microelectrode with a thick film containing enzyme. We can deduce the current densities that are expected on the basis of a monolayer coverage of enzyme on the electrode surface and by assuming that the enzyme molar activity (kcat) and KIM are unchanged from their homogeneous solution values, Assuming an enzyme coverage of FC-62 of 5 X 1O-IO mol cm-2 (determined by taking into account the surface covered by one enzyme molecule) and taking kca, and KM to be 200 s-1 and 0.4 x mol dm-3, respectively,21 we calculate an expected current at the microelectrode (assuming that the rate of re-oxidation of the enzyme is not rate limiting) of 90 PA.This is close to the experimentally obtained value of about 70 pA and indicates that this method of immobilization produces highly active films. The stability of this enzyme microelectrode is less satisfac- tory. A similar problem with immobilized FC-62 was observed by StaSkeviCiene et al. ,26 who attributed the loss of activity to inactivation of the enzyme. The instability of the enzyme in homogeneous solution is not entirely understood; the loss of activity could be due to loss of the flavin group andor haem. The specificity of FC-62 is not changed significantly on immobilization in the poly(pheno1) film.This is encouraging as it suggests that the active site of the protein is not adversely affected by the immobilization technique. This is consistent with our findings for glucose oxidase immobilized in the same types of film.15 From our studies of the effects of interfering species in the glucose oxidase-poly(pheno1) system we concluded*5 that the most effective way of eliminating interference is to lower the working potential of the enzyme electrode to below +0.2 V. In the present work we have done this by using TTF+ as a redox mediator. TTF+ is small and is able to diffuse into the poly(phenol)-enzyme film; in addition, it can be used at +0.2 V. However, there are two problems with the use of TW+: first, the reduced form is only sparingly soluble; second, the TIT+ is readily reduced by ascorbic acid. We are currently investigating the possibility of entrapping the mediator within the enzyme polymer layer in an attempt to circumvent these problems.Although the FC-62 electrode presented here may not be suitable for use in an in vivo sensor in its present state it may be possible to alter certain characteristics, e.g., by making the enzyme more stable or increasing the KIM value to extend the linear substrate-limiting region. Examples of both the increased stability of proteins and the alteration of the enzyme kinetics by molecular biological techniques have been demon- strated in the literature.31 Despite these limitations, the present work demonstrates that the use of electropolymerized films provides an effective technique for the immobilization of an enzyme at a microelectrode surface.The authors thank H. A. 0. Hill, S. K. Chapman and Bruce Moore for the generous supply of FC-62 and helpful dis- cussion. This work was supported by an SERC studentship for D. J. C. References 1 Reach, G., and Wilson, G. S., Anal. Chem., 1992,64, 381A. 2 Alcock, S. J., Danielsson, B., and Turner, A. P. F., Biosens. Bioelectron., 1992, 7, 243. 3 Engasser, J.-M., and Horvath, C., in Applied Biochemistry and Bioengineering, Volume I , Immobilised Enzyme Principles, ed. Wingard, L. B., Katchalski-Katzir, E., and Goldstein, L., Academic Press, New York, 1976, pp. 127-220. 4 Bartlett, P. N., Tebbutt, P., and Whitaker, R. G., Prog. React. Kinet., 1991, 16, 55.180 Analyst, February I994, Vol.I19 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Bartlett, P. N., and Whitaker, R. G., Biosensors, 1987188, 3, 359. Bartlett, P. N., and Whitaker, R. G., J. Electroanal. Chem., Interfacial Electrochem., 1987,224,37. Sasso, S . V., Pierce, R. J., Walla, R., and Yacynych, A. M., Anal. Chem., 1990,62, 1111. Geise, R. J., Adams, J. M., Barone, N. J., and Yacynych, A. M., Biosens. Bioelectron., 1991,6, 151. Centonze, D., Guerrieri, A., Malitesta, C., Palmisano, F., and Zambonin, P. G., Fresenius’ J. Anal. Chem., 1992,342,729. Bartlett, P. N., Tebbutt, P., and Tyrrell, C. H., Anal. Chem., 1992, 64, 138. McClarley, R. L., Irene, E. A., and Murray, R. W., J. Phys. Chem., 1991,954 2492. Ballarin, B., Brumlik, C. J., Lawson, D. R., Liang, W., Van Dyke, L. S., and Martin, C. R., Anal. Chem., 1992,64,2647. Christie, I. M., Vadgama, P., and Lloyd, S., Anal. Chim. Acta, 1993,274, 191. Wang, J., Chen, S., and Lin, M., J. Electroanal. Chem. Interfacial Electrochem., 1989, 273, 231. Bartlett, P. N., and Caruana, D. J., Analyst, 1992, 117, 1287. James, M. J., Cleland, L. G., and Rofe, A. M., J. Rheumatol., 1992,19, 1107. Massey, V., and Hemmerich, P., in The Enzymes, ed. Boyler, P. D., Academic Press, New York, 1975, vol. 12, p. 191. Harrington, T. J., Gainer, J. L., and Kirwan, D. J., Enzyme Microb. Technol., 1992,87,428. Chapman, S . K., White, S. A,, and Reid, G. A., Adv. Inorg. Chem., 1991,36,257. 20 21 22 23 24 25 26 27 28 29 30 31 Appleby, C. A., and Morton, R. K., Nature (London), 1954, 173, 749. Lindqvist, Y., BrandCn, C., Mathews, F. S., and Lederer, F., J. Biol. Chem., 1991,266, 3198. Dikstein, S., Biochim. Biophys. Acta, 1959, 36, 397. Miles, C. S., Rouvibre-Fourmy, N., Lederer, F., Mathews, F. S., Reid, G. A., Black, M. T., and Chapman, S. K., Bwchem. J., 1991,285, 187. Xia, Z., and Mathews, F. S., J. Mol. Biol., 1990,212,837. Kulys, J., and Svirmickas, G. S., Anal. Chim. Acta, 1980, 117, 115. StaSkeviEiene, S. L., CCnas, N. K., and Kulys, J., Anal. Chim. Acta, 1991, 243, 167. Black, M. T., White, S. A., Reid, G. A., and Chapman, S. K., Biochem. J., 1989, 258,255. Pons, S., and Fleischman, M., Anal. Chem., l987,59,1391A. Bartlett, P. N., and Bradford, V. Q., J. Chem. SOC., Chem. Commun., 1990,16, 1135. Albery, W. J., and Bartlett, P. N., J. Electroanal. Chem., Interfacial Electrochem., 1985, 194, 211. Wilkinson, A. J . , Fersht, A. R., Blow, D. M., Carter, P., and Winter, G., Nature (London), 1984,307, 187. Paper 31041 960 Received July 19, 1993 Accepted August 3I, I993

ISSN:0003-2654    

DOI:10.1039/AN9941900175

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, February 1994, Vol. 11 9 181 Functionalized Cyclodextrins as Potentiometric Sensors for Onium Ions' Paul S. Bates, Ritu Katakyt and David Parker Department of Chemistry, University of Durham, South Road, Durham, UK DHl3LE Functionalized, lipophilic a-, fl- and y-cyclodextrins were synthesized and their suitability as onium ion-selective, potentiometric sensors investigated. Selective binding was apparent for N&+, NMe4+ and NEt4+ ions with peroctylated a-, p- and y-cyclodextrin, respectively. The phenomenon of complexation was evidenced by 1H and 14N nuclear magnetic resonance relaxation-time measurements and by electrospray mass spectrometry. Nernstian responses were also evident for acetylcholine chloride, dopamine hydrochloride and the surfactant myristyltrimethylammonium bromide.A particularly good sensor for NMe4+ is peroctylated fl-cyclodextrin with o-nitrophenyl octyl ether as plasticizer. A sensitivity of 60 mV decade-1 was found at 310 K, with a limit of detection, -log a , of 5.8, and -log kr' for Na+ , 3.8, for K+ , 3.2, and for NH4+, 3.5. The response of 'blank' membrane electrodes comprising poly(viny1 chloride), solvent mediator, and additive was compared with the equivalent electrode response for membranes containing functionalized cyclodextrins. In each instance, the electrode response was substantially enhanced and stabilized by the presence of the lipophilic cyclodextrin. The effect of using either 1.0 mmol dm-3 NMe4Cl or 0.01 mol dm-3 analyte as inner filling solution was compared, and, with 1.0 mmol dm-3 N&Cl, was found to enhance electrode performance.Keywords: Cyclodextrin; tetraalkylammonium; potentiometric sensor; electrospray mass spectrometry Introduction Most of the work that has been reported on the binding of tetraalkylammonium ions by synthetic receptor molecules has focused on anionic molecules where the primary binding interaction is coulombic. 1-3 However, to devise an ionophore that can function in a potentiometric sensor, a neutral receptor is required to avoid cation and pH interference. Complexes of quaternary onium ions with n- and n-donors have been studied previously, and were shown to involve CHa++.--X interac- tions.4 It was found that the interaction of H20 and MeOH with NMe4+ and NEt4+ was much weaker (from measure- ments of the dissociation energies of the complexes in the gas phase) than with the more polarizable Bu20, and that polyethers gave the highest values consistent with multiple additive CH-..O interactions.In NMe4+ a low-level MNDO (minimum neglect of differential overlap) calculation reveals that 72% of the positive charge resides on the 12 peripheral hydrogens, so that a fairly strong electrostatic component may be expected for the CH.--O interaction. Although CH---O hydrogen bonds are not as common as NH.--O or OH.--O bonds, they are well defined crystallographically, and a recent * Presented at the International Symposium on Electroanalysis in Biomedical, Environmental and Industrial Sciences, Loughborough, Leicestershire, UK, April 20-23, 1993. + To whom correspondence should be addressed. analysis of the Cambridge Crystallographic Databases revealed that nine out of ten of the shortest CH-a-0 interactions found in accurate neutron diffraction structures, involve NCH*+ as the hydrogen-bond donor.With these thoughts in mind, we have been studying the complexation and detection of various charged onium ions using lipophilic cyclodextrins (CDs). An alkylated CD cavity consists of an array of oxygen lone pairs that may be involved in binding to an included onium-ion guest. Indeed, the cavity of an alkylated p-CD (diameter, -8 A) matches well the size of a small tetraalkylammonium ion, (NMe4+, 6.94 8,; NEt4+, 8.00 A). The potentiometric response of sensors incorporating various lipophilic peroctylated a-, p- and y-CDs to different onium ions was studied under standard conditions.Experimental Reagents and Chemicals The synthesis and characterization of the functionalized CDs 1-6 (Fig. 1) used in membrane preparation has been reported elsewhere .6,7 Ammonium chloride, tetramethylammonium chloride, tet- raethylammonium chloride, dimethylammonium chloride, tetraethylammonium chloride, dimethylammonium chloride, tetrabutylammonium chloride, acetylcholine chloride, choline chloride, and myristyltrimethylammonium bromide were obtained from Sigma (Poole, Dorset, UK). Tetrapropylam- monium chloride was obtained from Kodak (Clwyd, UK). These salts were dried under reduced pressure (50 "C, 0.01 mmHg) prior to use. High relative molecular mass poly(viny1 chloride) (PVC), o-nitrophenyl octyl ether (oNPOE) and bis(tert-butylpentyl) adipate (BBPA) were obtained from Fluka (Buchs, Switzerland).Sodium tetrakis[3,5-bis(trifluoro- methyl)phenyl]borate (TKB) was synthesized in this labora- tory. Chloride salts of sodium, potassium, calcium, mag- nesium, and ammonium were obtained from BDH (Poole, Dorset, UK) and were of analytical-reagent grade. All the salts were dried before use and standard solutions were prepared in de-ionized water (Milli Q, Millipore-Waters, Milford, MA, USA). Potentiometnc Ion-selective Measurements Electroactive membranes were prepared incorporating 1.2% ionophore, 65.6% oNPOE, 32.8% PVC, and 0.4% TKB or 2.0% ionophore, 65.6% BBPA, and 32.4% PVC. 'Blank' membranes were prepared with 65.6% oNPOE, 34.0% PVC, and 0.4% TKB (Fig. 1, Table 1).The membranes were cast by a controlled-evaporation method according to published procedures .8 A Philips IS(561) electrode body (Philips Analytical , Eindhoven, The Netherlands) was used to mount the electro- active membranes. A Philips RE1 saturated calomel electrode was used as reference electrode. For measurements with the182 Analyst, February 1994, Vol. 11 9 surfactant myristyltrimethylammonium bromide the refer- ence electrode was a Philips double-junction RE3DJ elec- trode with a 10% KN03 solution salt bridge; measurements were made in discrete solutions at ambient temperature. Calibration and selectivity measurements, for all other analytes, were made by a constant dilution technique de- scribed previously.9 Measurements were made at 310 K. Activities were calculated from activity coefficient values obtained from the GAMPHI database (which uses the Pitzer equation) .lo Fixed-interference method (FIM) selectivity coefficients (Table 3) were calculated from 1: n=6,R,R'=octyl,(0.) 2: n=7,R,R'=octyl,@) 3: n=8,R=octyl, R'=methyl,(y) 4: n=6,R=octyl,R'=methyI 5: n=6,R=octyl,R'=acetyI 6: n=7,R=octyl,R'=rnethyI R'O y2gH1 H3 7 0 9 10 Dopami ni u rn C,,H,N+Me,Bi Myristyltrirnethylammonium bromide CH,COOCH,CH,N+(CH,),CI- Acetylcholine chloride Fig.1 Structures of compounds discussed in the text. 14: Function- alized CDs used as ionophores; 7, membrane additive; and 8-10, where k r ' is the selectivity coefficient, ai, the activity of the primary ion, aj the activity of the interferent, and zi and zj, the respective charges.Electromotive Force Measurements in Cells Without Liquid Junctions The electromotive forces (e.m.f.s) of cells comprised of peroctylated a-, p- or y-CD and a 'blank' membrane electrode against an Ag-AgC1 reference electrode (RE-1B Ag-AgC1, Biotech Inst., Luton, Bedfordshire, UK) were measured to eliminate errors arising from residual liquid-junction poten- tials and to obtain a measure for the relative values of the cell free energy, -AGcell. The measurements were made in 0.1 and 0.01 mol dm-3 analyte solutions at ambient temperatures using a Molspin quadrupole input meter (Molspin, Newcastle- on-Tyne, Tyne and Wear, UK). The electrodes were allowed to reach equilibrium before voltages were read. Nuclear Magnetic Resonance Measurements A Bruker AC-250 or Varian VXR-400 MHz instrument was used to record 1H nuclear magnetic resonance (NMR) spectra.Measurements of *H and 19F relaxation times (7'1) were made with de-gassed 0.001 mol dm-3 solutions (90% CDC13, 10% CD3CN) containing the ionophore and the alkylammonium salt (as its trifluoroacetate) . The mean value of eight determinations was used for three separate experi- ments. A Bruker AM 500 instrument operating at 36.1 MHz was used to record 14N NMR spectra. Electrospray Mass Spectrometry Measurements Measurements of electrospray ionization mass spectra" were made using a VG Quattro-BQ quadrupole instrument (VG Instruments, Altrincham, Cheshire, UK) with an atmospheric pressure electrospray source and a mass range for singly Table 1 Electrodes used in this work Electrode Composition A Ionophore 1-oNPOE-TKB B Ionophore 1-BBPA C Ionophore 2-oNPOE-TKB D Ionophore ZBBPA E Ionophore 3-oNPOE-TKB F Ionophore 3-BBPA G 'Blank'-oNPOE-TKB H Ionophore 4-BBPA I Ionophore 5-BBPA J IonoDhore 6-oNPOE-TKB analytes L Table 2 Size-selective response of electrodes A-G to onium ions.Electrode slopes are shown in mV decade-'. Numbers in parentheses are the limits of detection (-log a). Inner filling solution, 1.0 mmol dm-3 NH4Cl Electrode response/mV decade- Analyte A NH4Cl 57 (4.9) Me2NH2CI 5 Me4NCI 13 (1.8) Et,NCI 22 (3.0) Pr4NCI 55 (3.5) Bu~NCI 60 (4.6) Dopamine HCI 61 (4.5) B C D E F G - No response No response - 2 52 (4.0) 35 (3.4) No response - lO(1.9) 58(5.7)* M(4.8) - 2.5 (2.0) 47.5 (2.0)t - 60(3.6) - 60(3.5) - 45.0 (2.5)f - 60(3.2) - 60(4.2) - 55.0 (2.5)* - 28(3.6) - 42(4.0) 37.5(2.9) - 61(5.4) 60(4.4) - * 60 (4.6) with 0.01 mol dm-3 Me4NCI as inner filling solution.t No response with 0.01 mol dm-3 Me4NCI as inner filling solution. * These electrodes required 60 h conditioning before a stable potential was reached.Analyst, February 1994, VoE. 11 9 183 charged ions of 4000. Samples of the CDs in propan-2-01 (typically, 20-50 pmol pdm-3) were introduced into the source at a flow rate of 5 pdm-3 min-I. Mass-scale calibration employed the ammonium adducts from polypropylene glycols 2000 and 3000 (1 pg pdm-3), which were introduced into the source at a flow rate of 5 pdm-3 min-I. Ammonium acetate (10 mmol dm-3), tetramethylammonium trifluoroacetate (0.2-2 mmol dm-3), ephedrinium trifluoroacetate (0.2 mmol dm-3) or myristyltrimethylammonium bromide (0.5 mmol dm-3) solutions in propan-2-01 were added to the CD sample solution.Agreement between the observed and calculated mlz values was within 0.5 u. Results and Discussion Potentiometric Ion-selective Studies Size selectivity A qualitative 'size-selective' pattern emerges from the elec- trode responses depicted in Table 2 and Fig. 2. The peroctylated a-CD (A in Table 2) shows a Nernstian response to NH4+, whereas the peroctylated p- (C in Table 2) and y-CD (E in Table 2) show no response. In the presence of K+, however, the peroctylated a-CD (A) response is suppressed [for K+, -log kFO' = 0.1 (Table 3)]. The peroctylated p-CD (C and D in Table 2) responds to the larger dimethylam- monium ion with sub-Nernstian slopes of 52 and 35 mV decade-', respectively, with oNPOE or BBPA used as solvent Fig.2 Size selectivity of the functionalized CDs mediator. Electrodes fabricated with peroctylated a- and y- CDs (A, B, E, and F in Table 2) did not respond to the dimethylammonium ion. The electrode based on peroctylated p-CD (C and D) responds in a Nernstian manner to the tetramethylammonium ion. The response was particularly good when oNPOE was used as plasticizer with 1.0 mmol dm-3 NKCl as inner filling solution: a slope of 58 mV decade-' was found with a limit of detection, -log a , of 5.8 at 310 K. With 0.01 mol dm-3 NMe4CI as inner filling solution, the slope was 60 mV decade-' and the limit of detection, -log a , 4.6. Selectivity over Na+, K+, and NH4+ ions was excellent (Table 3).With the divalent cations Ca*+ and Mg2+ as interferents, the electrode slope reduced to 33.0 mV decade-'. The slopes were reproducible. The larger 'cavity' in peroctylated y-CD appeared to respond best to the bulkier NEt4+ ion (E and F). With the larger NPr4+ and NBu4+ ions, all three functionalized CDs appeared to respond in a Nernstian manner. This could be a function of the PVC- oNPOE-TKB (G in Table 2) contribution to the over-all electrode response, which is discussed in the following section. The sensors based on peroctylated a- and p-CD (A, B, and C) responded well to the catecholamine dopamine, giving a Nernstian response and with a limit of detection, -log c , of 4.0 (Tables 2 and 3). Interference from Ca2+ and Mg2+ was low (-log kf"'for Ca2+, 3.3, and for Mg*+, 3.2).Interference from K+ and Na+ was more marked (-log kTt for K+, 1.5, and for Na+, 1.8). The observed electrode response was independent of the plasticizer used. This is probably because the aryl moiety is included in the CD cavity (see under Mechanism of Onium Ion Recognition). These results are in accord with previous studies,12 which have shown that these lipophilic CDs are excellent chiral sensors for P-arylamino alcohols with minimal interference from Group Ia and IIa cations. A P-CD-uNPOE-TKB (C and D) electrode with 0.01 mol dm-3 acetylcholine as inner filling solution responded in a Nernstian manner to acetylcholine, with a slope of 60 mV decade-', and a limit of detection, -log a , of 5.1. Interference from K+, Na+ , NH4+ , and Ca2+ was fairly low (Table 3).The selectivity over the more hydrophilic analyte choline chloride was encouraging with -log k T t = 1.5. This sensor also responded well to the cationic detergent myristyltrimethylam- monium bromide at concentrations below its critical micelliza- tion concentration. A slope of 58 mV decade-' at 292 K was observed with a limit of detection, -log [c], of 6.5. The response with the corresponding 'blank' membrane was sub- Nernstian (G) (Fig. 3). Effect of Plasticizer, PVC, and Additive Studies by Masadome et a1.13 have shown that anionic sites present as impurities in the plasticizer and in PVC generate permselectivity in plasticized membranes towards cationic and anionic surfactants. The plasticizer itself does not respond to the presence of the surfactant.Table 3 Typical selectivity coefficients, -log k y t (fixed interference method), of some electrodes using onium ion analyte in a 0.1 mol dm-3 interferent background Interferent Electrode Anal yte K+ Na+ Ca2+ Mg2+ NH4+ Choline+ 1-BBPA (B) Dopaminiurn+ 1.5 1.8 3.3 3.2 1-NPOE (A) NH4+ 0.1 1.9 ZoNPOE (C) Acetylcholine+ 3.5 4.5 - 3.2 1.8 - - - - - - - ZoNPOE (C) NMe4+ 2.9 3.5 R* R* 3.5 * R = reproducible. In mixed-ion solution, the slope was reproducible, but reduced to 33.0 mV decade-' with a limit of detection (-log a) of 5.2.184 Analyst, February 1994, Vol. I1 9 In order to study the relative responses of ‘blank’ mem- branes versus membranes incorporating the functionalized CD ionophores, studies were undertaken to compare mem- branes comprising oNPOE-TKB-PVC (G) with similar membranes incorporating the ionophores A, C, and E for the analytes NEt4+, NPr4+, and NBu4+.The electrodes construc- ted with the ‘blank’ electroactive membranes required much longer conditioning times ( 4 0 h) before a stable e.m.f. reading was observed. The corresponding electrodes incor- porating the ionophores required overnight conditioning. The 200 > E E ILi GI00 0 4 5 6 7 -Log[cl Fig. 3 Comparison of the response of 2-oNPOE-TKB (electrode C) and the ‘blank’, oNPOE-TKB-PVC (electrode G), to myristyl- trimethylammonium bromide 200 > E E > ’c: loo 0 1 2 3 4 -Log[cl Fig. 4 Comparison o.f the response of 2-oNPOE-TKB (electrode C) and the ‘blank’ (electrode G) to NMe4Cl. A, Electrode G (inner filling solution, 0.01 rnol dm-3 NMe,Cl); B, electrode G (inner filling solution, 0.001 mol dm-3 NH4Cl); C, electrode C (inner filling solution, 0.01 mol dm-3 NMe4Cl); and D, electrode C (inner filling solution, 0.001 rnol dm-3 NH4Cl) response of the ‘blank’ membranes was always sub-Nernstian with limits of detection (-log a) of approximately 2.0 (Table 2).The observed response was also dependent on the inner filling solution used. Using the ‘blank’ (G), NMe4+ electroac- tive membrane (conditioned in 0.01 mol dm-3 NMe4+), with 1.0 mmol dm-3 NH4C1 as inner filling solution, the electrode slope was 47.5 mV decade-’ down to -log a = 2.1, whereas no response was observed with 0.01 mol dm-3 NMe4+Cl- as inner filling solution. Cyclodextrins are believed to form 1 : 1 inclusion complexes with the analytes used in this study.14-16 Incorporation of functionalized CDs in ‘blank’ membranes dramatically improves their response characteristics towards onium ions (Fig.4) and minimizes interference from alkali and alkaline earth metal cations. Free Energy Calculations Free energies for cells without liquid junctions were calculated from e.m.f. measurements made in 0.1 and 0.01 mol dm-3 analyte solutions (Fig. 5 and Table 4). The electrode slopes for these discrete solution measurements (as compared with continuous dilution measurements) tend towards super-Nern- stian behaviour between 10-2 and rnol dm-3 solutions of analyte (approximately 65 mV decade- at ambient tempera- tures). Similar super-Nernstian behaviour, which is time dependent, has been observed previously by Moody et a1.17 who attributed the phenomenon to slow changes in the environment of the charged species within the membrane phase.Super-Nernstian behaviour was not observed with the faster continuous-dilution measurements. The free energy values (Fig. 5) obtained suggest the following. (i) The alkyl chain is ‘bound’ by the functionalized a-CD. The binding becomes stronger as the chain length increases to four carbon atoms. (ii) The functionalized p-CD shows size-selective onium-ion binding. This effect is super- imposed on the less well defined alkyl chain inclusion. The poor response of the peroctylated p-CD-oNPOE electrode (B) to NEt4+ may, in fact, be due to a high binding constant inhibiting efficient ion exchange on the timescale of the measurement.(iii) Functionalized y-CD is apparently not size-selective . Mechanism of Onium Ion Recognition A comparison of the response of the electrodes incorporating functionalized a- and f3-CD (A, B, C, D, H, I, J) to onium ions is instructive (Table 5). Peroctylated a-CD with BBPA (B) as plasticizer responded poorly to all of the onium ions exam- ined, except to the arylammonium ion, dopaminium. This may be because the aryl moiety enters the CD cavity and ion recognition is further enhanced by O-H.--O and NH--.O Table 4 Values of -AG (kJ mol-I) calculated from the e.m.f. of the cells, Ag]AgClIanalyteImembrane11.0 mmol dm-3 NH4Cl I AgC1-Ag - AG/kJ mol- A [Analyte]/mol dm-3 Anal yte 0.1 0.01 MeN4Cl 18.8 (195)* 12.8 (133) EtN4Cl 23.4 (243) 17.1 (177) PrNjCl 28.6 (296) 22.0 (228) BuN~CI 32.5 (338) 26.7 (276) ~~ ~ C E G [ Analyte]/mol dm-3 [Analyte]/mol dm-3 [Analyte]/mol dm-3 0.1 0.01 0.1 0.01 0.1 0.01 32.0 (332) 26.0 (270) 31.8 (330) 25.9 (269) 23.5 (244) 16.6 (173) 35.0 (362) 28.6 (296) 33.3 (346) 27.0 (280) 32.6 (340) 26.3 (273) 23.7 (246) 18.9 (190) 33.1 (343) 28.5 (295) 30.7 (318) 24.5 (254)t 30.4 (315) 24.3 (252) 28.8 (298) 23.0 (238) 29.4 (305) 23.5 (244)t * Values in parentheses are the e.m.f.readings at equilibrium. t These e.m.f. readings were not taken at equilibrium; the values were drifting upwards even after the electrodes had been in solution for 48 h.Analyst, February 1994, Vol. 11 9 185 hydrogen-bond formation between the -OH or NH3+ group of the catecholamine and the glycosidic or C-6 oxygens of the CD.In addition, weak, but stabilizing C-H--.O interactions between the guest molecule and the CD may occur. Such weak but directing interactions have been observed in detailed structural analyses of p-CD inclusion complexes. 18 A peroctylated a-CD, in which any residual OH groups were capped with methyl groups, was also screened as an ionophore (H). It responded very poorly to NH4+. The response was improved [slope, 50 mV decade-', limit of detection (-log a ) , 3.21 when 2,6-dioctyl-3-0-acetyl-a-cyclo- dextrin (1) was used instead. This behaviour suggests that the mechanism of ion sensing of the simple ammonium ion NH4+ is very different from that involving recognition by the functionalized CD of the larger alkylammonium ions. The ammonium ion may undergo stabilizing NH...OH interactions involving residual hydroxyl groups in 'peroctylated' a-CD.On average, there are 15.4 octyl groups in the 'per-octyl' a-CD used, with 2.6 free OH groups.3 In the methylated, perocty- lated a-CD (H), where there are less than 0.5 residual OH groups,3*7 the ammonium ion is less well bound and only a sluggish response was noted. In the acetylated peroctylated a- CD (1) ionophore, ammonium ion recognition may be enhanced by hydrogen bonding between the carbonyl oxygen and the ammonium ion. When BBPA is replaced by the more polar plasticizer oNPOE, the electrode response (A) to the ammonium ion is almost ideal, although interference from Na+ and K+ is severe (Table 3). This behaviour, again, may reflect the weakness of the interaction involving the ammo- nium ion and the hydrogen-bond acceptor in the substituted CD .r - 0 E 2 P Fig. 5 Plot of -AG versus increasing alkyl onium ion chain length. Measurements of e.m.f. were made in the cells, Ag-AgC110.1 mol dm-3 analyte I membrane IO.001 mol dm-3 NH4CI I AgC1-Ag. A, a-CD; B, (3-CD; and C, y-CD. TMACI, tetramethylammonium chloride; TEACl, tetraethylammonium chloride; TPACI, tetrapropyl- ammonium chloride; and TBACl, tetrabutylammonium chloride Table 5 Electrode responses, showing the relationship between analyte structure, ionophore, and plasticizer Electrode Anal yte 1-BBPA (B) 1-BBPA (B) 1-BBPA (B) 1-BBPA (B) 1-BBPA (B) 1-BBPA (B) 4-BBPA (H) S-BBPA(1) 1-oNPOEITKB (A) ZBBPA (D) ZoNPOERKB (C) 60NPOERKB (J) NH4+ NH3Me+ NH2Me2+ NMe4+ Dopaminium NEtj+ NHj + NH4+ NHj+ NMe4+ NMe4+ NMe4+ Electrode response/ mV decade-' 49.0 (3.6)* 11 .O (1.5) No response 10.0 (1.9) 22.0 (3.0) 61 .O (5.4) 25.0(2.0) 50.0 (3.0) 57.0 (4.9) 48.0 (4.0) 58.0 (5.7) 61.5 (5.0) The peroctylated p-CD sensor with BBPA (D) as plasti- cizer, responded to NMe4+ with a slope of 48 mV decade-' and a limit of detection, -log a , of 4.1.The response was improved considerably when oNPOE-TKB was incorporated in the membrane instead of BBPA (C), (a slope of 58 mV decade-' and limit of detection, -log a , of 5.8 was found). With the p-CD ionophore in which residual OH groups had been capped with methyl groups (J) ( i e . , methylated peroctyl p-CD), the electrode response using oNPOE and TKB was Nernstian at 310 K, with a limit of detection, -log a , of 5.2.The factors suggest that ion recognition may involve stabiliz- ing and orienting C-H...O interactions between the glycosidic 0 atom of the CD cavity wall and the charge-polarized C-H bonds of the NMe4+ ions. Further NMR investigations concerning the mechanism of onium-ion recognition are being carried out and will be reported elsewhere. 19 Preliminary NMR Studies of Complexation The 1H NMR longitudinal relaxation time ( T1) for the methyl hydrogens in Me4N+ was measured in the absence and presence of peroctyl a- (1) and p-CD (2). The change in Tl in the presence of 1 equiv of the CD derivative was -0.15 s with 1, and -0.21 s with 2; Tl increased slightly in the presence of the larger y-CD analogue (A Tl = +O. 13 s). Parallel measure- ments of the changes in the 19F relaxation time (for the trifluoroacetate counter ion) showed an increase in TI in the presence of 2 (ATIF = +0.46 s), but a decrease in the presence of the peroctylated y-CD. These observations may be interpreted in terms of binding of NMe4+ by 1, and to a greater extent by 2, leading to a reduction in the effective correlation, tc, for the methyl protons as they are bound by a species with a free volume approximately 103 times larger than that of 'free' NMe4+.The trifluoroacetate counter ion may be relatively closely ion- paired to the NMe4+ in the CDC13-CD3CN solvent and inclusion of the NMe4+ ion by the CD causes more effective ion separation. With the y-CD, the observed reduction in 19F Tl could be associated with inclusion of the CF3C02- ion by the bulkier CD.A more sensitive probe for onium ion inclusion is to observe directly the quadrupolar 14N nucleus. The 14N NMR spectra for Me4N+ were obtained (36.1 HMz), and the linewidth of the 14N resonance was measured as 2 was added incremen- tally. The resonance due to NMe4+CF3C02- was initially sharp [oa (half line width) = 0.6 Hz], but increased as further 2 was added, from 0.8 (1 equiv), 0.9 (2 equiv), 1.4 (5 equiv) to 320 Hz after the addition of 12 equiv of 2. In the complex [NMe4+.2], the local free volume is approximately 103 times 3453.7 3355.2 Complexation with 3256.7 I C,,H,NMe3+ in ESMS+ 2600 2sbo 3d00 3iOO 3400 3600 m/z Fig. 6 capped with methyls) and myristyltrimethylammonium bromide Electron spray mass spectrum of 6 (peroctyl p-CD, end- * Figures in parentheses, limits of detection.186 Analyst, February 1994, Vol.11 9 larger than that of ‘free’ NMe4+ so the associated rotational correlation time for the 14N nucleus (dominated by the quadrupolar relaxation mechanism) increases accordingly. This may be expressed as follows: where JC is a constant, x 2 is the nuclear quadrupolar coupling constant, tq is the quadrupolar relaxation time (= Tl = T2) and tq is equal to tc, the effective rotational correlation time for the 14N nuclear quadrupole. An estimate of the change (with volume) of the reorientational correlation time may be made from the Stokes-Einstein-Debye equation: t, = 413 nr3 qlkT where r is the radius of the assumed spherical rotating molecule, q the viscosity of the medium and k the Boltzmann’s constant.For NMe4+, r is about 3.5 8, and for the complex [NMe4+.2], r is about 30 8,. Hence the sensitivity of the 14N NMR linewidth to changes in z, is apparent. Electrospray Mass Spectrometry The use of electrospray mass spectrometry (ESMS) for the characterization of lipophilic CD derivatives such as 1 and 2 has been reported recently.11 When a solution of tetramethyl- ammonium trifluoroacetate in propan-2-01 was mixed with a propan-2-01 solution of the CD 2, large peaks were observed for the NMe4+ complex at 2892.3,3004.3,3116.8, and 3229.9 u. These correspond to the NMe4+ complexes with octylated 2 bearing 15, 16, 17, and 18 octyl groups, for which the calculated masses are 2892.4, 3004.6, 3116.8, and 3229.0. No peaks due to the complex [(NMe4)2.2]2+ were observed at lower mass.This is in contrast to the behaviour of the ammonium adducts where strong peaks due to [(NH4)2.2]2+ were observed.7 Permethylation of the residual OH groups in 2 is achieved readily by reaction with methyl iodide in the presence of sodium hydride in tetrahydrofuran. This methyl-capped derivative also formed a well defined 1 : 1 complex with NMe4+, with large peaks at 2976.4,3074.9,3173.3, and 3271.0 (cf., calculated values of 2976.5, 3074.7, 3172.9, and 3271.1). Complexes with NEt4+ could also be discerned in a parallel manner. With 2, a competition experiment was performed whereby the CD solution was mixed with a 0.2 mmol dm-3 solution of the NMe4+ salt in the presence of 10 mmol dm-3 ammonium ions. The major complex observed (about 2: 1 over the peaks due to the NH4+ complex), was the NMe4+ complex, in agreement with the good selectivity observed potentiome trically . Complex formation was also observed by ESMS with other trimethylammonium ions. With myristyltrimethylammonium bromide, a 1:l complex was observed for both 2 and its methyl-capped derivative.In the former instance, peaks at 3186.9 (3186.9), 3298.3 (3299.2), and 3409.3 (3411.4) were observed, corresponding to complexes with 16, 17, and 18 octyl groups, respectively. In the latter case (Fig. 6), peaks at 3256.7 (3257.1) [16 octyls, 5 methyls + NC17H38+], 3355.2 (3355.3) [17 octyls, 4 methyls + NC17H38+], and 3453.7 [I8 octyls, 3 methyls + NC17H38+] were distinct. With 2 and acetyl choline, 1 : 1 adduct formation was also indicated, with peaks at 3077.3 (3076.7), 3189.0 (3188.9), 3301.5 (3301.1), and 3413.3 (3413.3) due to the 16, 17, 18, and 19-octylated complexes, respectively. Spectra due to the complex with choline were weaker, but discernible at the expected masses.The characterization of these complexes by ESMS is strong supporting evidence for the formation 1 : 1 complexes between tetraalkylammonium ions and the lipophilic CDs 1 and 2, and their methyl-capped derivatives. Conclusions Functionalized a-, p- and y-CDs recognize long- and short- chain alkyl onium ions and aryl onium ions. Functionalized p- CD appears to be the most size-selective towards the alkylammonium ions. Both functionalized a- and p-CDs respond well to arylammonium ions with minimal interference from alkali and alkaline-earth metal cations.The more polar plasticizer oNPOE and the additive TKB enhance response towards alkylammoniun ions whereas arylammonium ions respond equally with either oNPOE or BBPA as plasticizer. These lipophilic CD ionophores appear to be well suited to sensing a wide spectrum of onium ions. More work is being carried out using diverse analytes, and further studies are directed towards understanding the recognition mechanism. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 References Meric, R., Vigneron, J.-P., and Lehn, J.-M., J. Chem. SOC., Chem. Commun., 1993, 129. Schneider, H. J., Schiestel, T., and Zimmermann, P., J. Am. Chem. SOC., 1992, 114,7698. Vogtle, F., Merz, T., and Wirtz, H., Angew. Chem. Int. Ed. Engl., 1985, 24,221. Deakyne. C. A., and Meot-Ner, M., J. Am. Chem. SOC., 1985, 107,469 and 474. Kennard, O., Supramol. Chem., 1993, 1, 277. Bates, P. S., Kataky, R., and Parker, D., J. Chem. SOC., Chem. Commun., 1992, 153. Bates, P. S., Kataky, R., and Parker, D., J. Chem. SOC., Chem. Commun., 1993,691. Craggs, A., Moody, G. J., and Thomas, J. D. R., J. Chem. Educ., 1974, 51, 541. Kataky, R., Nicholson, P. G., Parker, D., and Covington, A. K., Analyst, 1991, 116, 135. Goldberg, R. N., Manley, J. L., andNuttall, R. L., Gamphi-A Database of Activity and Osmotic Coefficients for Aqueous Electrolyte Solutions, NBS, Technical Note 1206, US Govern- ment Printing Office, Washington, DC, 1985. Bates, P. S., Parker, D., and Green, B. N.. J. Chem. SOC., Chem. Commun., 1993,693. Kataky, R.. Bates, P. S., and Parker, D., Analyst, 1992, 117, 1313. Masadome, T., Wakida, W., Kawabata, Y., Imato, T., and Ishibashi, N., Anal. Sci., 1992, 8 , 89. Lavandier, C. D., Pelletier, M. P., and Reinsborough, V. C., Aust. J. Chem., 1991,44,457. Satake, I., Ikenque, T., Takeshita, T., Hayakawa, K., and Maeda, T., Bull. Chem. SOC. Jpn., 1985, 58,2746. Saenger, W., Angew. Chem. Int. Ed. Engl., 1980, 19, 344. Moody, G. J.. Owusu, R. K., and Thomas, J. D. R., Analyst, 1987, 112. 121. Steiner, T., and Saenger. W., J. Am. Chem. SOC., 1992, 114, 10146. Bates, P. S., Kataky, R.. and Parker, D., J. Chem. SOC., Perkin Trans 2, in the press. Paper 3103301 E Received June 9, 1993 Accepted October 14, 1993

ISSN:0003-2654    

DOI:10.1039/AN9941900181

出版商:RSC    

年代:1994

数据来源: RSC