摘要:

'""AnalystThe Analytical Journal of The Royal Society of ChemistryAnalytical Editorial BoardChairman: J. N. Miller (Loughborough, UK)M. Cooke (Sheffield, UK)C. S. Creaser (Nottingham, UK)A. G. Davies (London, UK)A. G. Fogg (Loughborough, UK)J. M. Gordon (Cambridge, UK)G. M. Greenway (Hull, UK)S. J. Hill (Plymouth, UK)D. L. Miles (Keyworth, UK)R. M. Miller (Gouda, The Netherlands)B. L. Sharp (Loughborough, UK)M. R. Smyth (Dublin, 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. RSiiCka (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 NETHER LANDS.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. Valchrcel, Departamento de Quimica Analitica, Facultad de Ciencias,Professor J. F. van Staden, Department of Chemistry, University of Pretoria, Pretoria 0002,Professor Yu Ru-Qin, Department of Chemistry and Chemical Engineering, Hunan University,Professor Yu.A, Zolotov, Kurnakov Institute of General and Inorganic Chemistry, 31 LeninUniversitario, 4 Trav. 200 Re David-70126 Bari, ITALY.Myodaiji, Okazaki 444, JAPAN.Street, Toronto, Ontario, CANADA M5S 1Al.Universidad de Cordoba, 14005 Cbrdoba, SPAIN.SOUTH AFRICA.Changsha, PEOPLES REPUBLIC OF CHINA.Avenue, 117907, Moscow V-71, RUSSIA.Editorial Manager, Analytical Journals: Janice M. GordonEditor, The AnalystHarpal S. MinhasThe Royal Society of Chemistry,Thomas Graham House, Science Park,Milton Road; Cambridge, UK CB4 4WFTelephone +44(0)223 420066.Fax +44(0)223 420247.E-Mail :Analyst@RSC.ORG(INTERNET)US Associate Editor, The AnalystDr Julian F. TysonDepartment of Chemistry,University of Massachusetts,Amherst MA 01 003, USATelephone +1 413 545 0195Fax +1 413 545 4846Assistant EditorsEditorial Secretary: Claire HarrisSarah Wi I hams Yasmin KhanAdGertisements: Advertisement Department, The Royal Society of Chemistry, BurlingtonHouse, Piccadilly, London, UK W1V OBN.Telephone +44(0)71-287 3091.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 TheAnalystwill 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 to theEditor, or Associate Editor, The Analyst.Members of the Analytical Editorial Board(who may be contacted directly or via theEditorial Office) would welcome comments,suggestions and advice on general policymatters concerning The 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 1 HN.Turpin Distribution Services Ltd., is wholly owned by the Royal Society of Chemistry. 1994Annual 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$1351 .OO, Canada f811 .OO (excl. GST), Rest of World f772.00. Purchased with Analytical Abstracts plus Analytical Proceedings EC f851 .OO, USA$1601 .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.@ 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/AN99419FX036

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

ANALAO 1 19(9) 1925-21 48 1 13N-126N (1 994) SEPTEMBER 1994llllllTUTORIAL REVIEWITUTORIAL REVIEWCRITICAL REVIEW'""AnalystThe analytical journal of The Royal Society of ChemistryCONTENTS1925 Discovering Flow Injection: Journey From Sample to a Live Cell and From Solution to Suspension-JaromirRCI i i C ka1935 Atomic Force Microscopic Determination of Substrate Effects on the Structure of Deposited BiomineralPhosphates-Lorraine M. Siperko, William J. Landis1939 Imaging Glucoamylase by Scanning Tunnelling Microscopy-A. Patrick Gunning, Victor J. Morris, GaryWilliamson, Nigel J. Belshaw, Gerard F. H. Kramer, Marja W. Kanning1943 Imaging Flagella of Halobacteria by Atomic Force Microscopy-Manfred Jaschke, Hans-Jurgen Butt, ElmarK. Wolff1947 Potential Carbon Dioxide Sensing Based on Recognition by trans-[Carbonylhydroxybis-(triphenylphosphine) rhodium(i)] Deposited on Acoustic Wave Devices-P.C. H. Li, M. Thompson1953 Voltammetric Determination of Trace Metals and Organics after Accumulation at ModifiedElectrodes-Damien W. M. Arrigan1967 Adsorptive Cathodic Stripping Voltammetric Determination of Theophylline at a Hanging Mercury DropElectrode-Raqi. M. Shubietah, Ali Z. Abu Zuhri, Arnold G. Fogg1971 Electrochemical Oxidative Determination of Thimerosal in Soft Contact Lens Care Solutions by CyclicVoltammetry-M. Pilar da Silva, Jesus Rodriguez, Lucas Hernandez1975 Determination of Silver(i) by Cyclic Voltammetry at Iodine-coated Electrodes-Mohammed Khair Hourani1979 Voltammetric Study of Salbutamol, Fenoterol and Metaproterenol at Unmodified and Nafion-modifiedCarbon Paste Electrodes-Damien Boyd, Jose Ramdn Barreira Rodriguez, Arturo Jose Miranda Ordieres,Paulino TuAon Blanco, Malcolm R.Smyth1985 All solid-state Poly(viny1 chloride) Membrane Ion-selective Electrodes With Poly(3-octylthiophene) SolidInternal Contact-Johan Bobacka, Mary McCarrick, Andrzej Lewenstam, Ari lvaska1993 Plastic Membrane Electrode for Selective Determination of Diclofenac (Voltaren) in PharmaceuticalPreparations-Saas S. M. Hassan, Ragab M. Abdel-Aziz, Mohamed S. Abdel-Samad1997 Pulsed Amperometric Detection of Thaurnatin Using Antibody-containing Poly(pyrro1e) Electrodes-0, A.2001 Organic-phase Enzyme Biosensor for Moisture Determination in Food Products-Saverio Mannino, MariaStella Cosio, Joseph Wang2005 Phase Change and Viscosity Effects on a Quartz Crystal Microbalance-Daniel James, David V.Thiel,Gillian R. Bushell, W. Ken Busfield, Alan Mackay-Sim2009 Development of a Monitoring Tape for Ammonia Gas in Air Using Rose Bengal-Nobuo Nakano, YoshioKobayashi, Kunio Nagashima201 3 Recent Trends in Chromatographic Procedures for Separation and Determination of Rare Earth ElementsA Review-Manjeet Kumar2025 On-line Trace-level Enrichment Gas Chromatography of Triazine Herbicides, OrganophosphorusPesticides, and Organosulfur Compounds From Drinking and Surface Waters-Yolanda Pico, Arjan J. H.Louter, Jolan J. Vreuls, Udo A. Th. Brinkman2033 Separation of Barium From Associated Elements Using Poly(dibenz0-18-crown-6) and ColumnChromatography-Baburao S.Mohite, Dnyandeo N. Zambare, Bharat E. Mahadik2037 Biogenic Amines in Table Olives. Analysis by High-performance Liquid Chromatography-DamasoHornero-Mendez, Antonio.Garrido-FernandezSadik, M. J. John, G. G. Wallace, D. Barnett, C. Clark, D. G. Laing 1Continued on Inside Back Cover-Typeset and printed by Black Bear Press Limited,Cambridge, England0003-2654C199419;l-20432051205720612067207 12075208120872093209721 0121 0521 0921 13211921 2321 2921 3521 4121 45113N119N124N125NDetermination of BRL 46470 in Human Plasma by High-performance Liquid Chromatography WithUltraviolet Absorbance Detection Followed by Post-column Photochemical Reaction and FluorescenceDetection-Nigel J.Deeks, Richard W. Abbott, Graham D. Allen, Frank J. Hollis, Gerald RhodesBiological Monitoring of Hexamethylene- and Isophorone-diisocyanate by the Determination ofHexamethylene- and Isophorone-diamine in Hydrolysed Urine Using Liquid Chromatography and MassSpectrometry-G. Skarping, M. D. Dalene, H. TinnerbergInvestigation of the Sorbitol Content of Wines and an Assessment of its Authenticity Using Stable IsotopeRatio Mass Spectrometry-M. John Dennis, Robert C. Massey, Tim BigwoodUse of Nuclear and Nuclear-related Analytical Techniques in Studies of Trace and Minor Elements in AirPollution-Borut SmodiS, Boris StropnikSub-stoichiometric Isotope Dilution Analysis for the Determination of Selenium by Liquid ScintillationCounting-A.Ramesh, K. Raghuraman, M. S. Subramanian, T. V. RamakrishnaExtractive Separation and Determination of Thallium and Indium by Liquid Scintillation Counting-N.Rajesh, M. S. SubramanianComparison Between Microwave and Conventional Heating Procedures in Tessier's Extractions ofCalcium, Copper, Iron and Manganese in a Lagoon Sediment-Monica Gulmini, Giorgio Ostacoli, VincenzoZelano, Annamaria TorazzoOne-step Microwave Digestion Procedures for the Determination of Aluminium in Steels and Iron Ores byInductively Coupled Plasma Atomic Emission Spectrometry-Maria Grazia Del Monte Tamba, RobertaFalciani, Teresa Dorado Lopez, Aurora Gomez CoedoEvaluation of the Precision of the Flow Injection Doublet Peak Method-Roger T. Echols, Julian F.TysonSelective Continuous Flow-Stopped Flow-Continuous Flow Determination of Sulfite in White Wines UsingImmobilized Sulfite Oxidase on a Rotating Reactor-Maria Olirnpia Rezende, Horacio A. MottolaContinuous Liquid-Liquid Extraction With On-line Monitoring for the Determination of Anionic Surfactants inWaters-Manuel Agudo, Angel Rios, Miguel ValcarcelFlow Injection Spectrophotometric Determination of Aspartame in Dietary Products-Joaquim de AraujoNobrega, Orlando Fatibello-Filho, lolanda da Cruz VieiraSelective Method for the Spectrophotometric Determination of Vanadium in the Presence of OtherRefractory Elements with 2,2'-lminodibenzoic Acid-Nan Zhou, Chun-Xiang He, Nai-Lin Gu, Pin-GangChenDetermination of Antimony in Waste Water with Chromazurol S by Beta-correctionSpectrophotometry-Hong-Wen Gao, Peng-Fei ZhangCatalytic Spectrophotometric Determination of Nitrite Using the Chlorpromazine-Hydrogen PeroxideRedox Reaction in Acetic Acid Medium-Bing Liang, Masaaki Iwatsuki, Tsutomu FukasawaCatalytic Spectrofluorimetric Determination of Copper Using Aerial Oxidation of Ascorbic Acid in thePresence of o-Phenylenediamine-Susumu Kawakubo, Hirofumi Kato, Masaaki lwatsukiDevelopment of the H-Point Standard Additions Method for the use of Spectrofluorimetry and SynchronousSpectrofluorimetry-P.Campins-Falco, J. Verdu-Andres, F. Bosch-ReigSelective Fluorescence Quenching to Discriminate Between Alternant and Non-alternant PolycyclicAromatic Hydrocarbons: Acephenanthrylene Derivatives as Exceptions to the Nitromethane QuenchingRule-Sheryl A. Tucker, Jason M. Griffin, William E. Acree, Jr, Patrick P. J. Mulder, Johan Lugtenburg, JanCornelisseCharacterization Of The Behaviour Of Nitrogen Dioxide At Low Concentrations in Humid Air WithinAdsorbent Charcoal Sampling Media-C. L. Paul Thomas, Philip J. C. AnsticeDetermination of Bromate and Chlorate via Reduction With Sodium Nitrite-Robert C. Duty, Jesse S. WardCUMULATIVE AUTHOR INDEXBook ReviewsConference DiaryCoursesPapers in Future IssuesCoverpicture: Upper half, photograph of a three-inlet fountain cell; lower half, Flow injection '89. A painting byBroo Serrensen, for full details see pages 1925-1934. Reproduced with permission

ISSN:0003-2654    

DOI:10.1039/AN99419BX038

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, September 1994, Vol. 11 9 113N Book Reviews Applications of Plasma Source Mass Spectrometry. Volume II Edited by Grenville Holland and Andrew N. Eaton. Pp. x + 244. Royal Society of Chemistry. 1993. Price f45.00. ISBN 0-851 86-465-1. This volume is made up of a collection of papers presented at the 3rd International Conference on Plasma Source Mass Spectrometry held at Durham, UK, September 13-18, 1992. Any doubt that ICP-MS is now a full-blooded laboratory work- horse is dispelled by the breadth of applications of the technique. Analysts in the environmental, mining, nuclear, metallurgical and electronic industries will find this volume a useful source of information. The application of ICP-MS to the analysis of electronic chemicals, automotive exhaust gases, radioactive liquid samples, and to the measurement of ’This volume is a useful addition to the growing literature in this area, but it is difficult to recommend it to the specialist’.skin absorption of lead demonstrates the versatility of the technique. However, there is little new on offer to the researcher who is conversant with the literature in their area of expertise. The three non-application papers on glow dis- charge, measurement of isotope ratios and ion kinetic energies in ICP-MS, respectively, are useful reviews of the subject areas. Also thrown in for good measure is a paper by Gray, one of the pioneers of ICP-MS, on how he sees the technique evolving. Although a number of authors have made the effort to bring their contributions to refereed journal standards, a few have fallen short of this criterion.This volume is a useful addition to the growing literature in this area, but it is difficult to recommend it to the specialist. P. Gardiner Division of Chemistry Sheffield Hallam University, UK Capillary Electrophoresis: Principles, Practice and Appli- cations Edited by S. F. Y. Li. Journal of Chromatography Library. Volume 52. Pp. xxvi + 586. Elsevier. 1992. Price U S$225.50 ; DF1395.00. ISBN 0-444-89433-0. The family of methods that comprise capillary electrophoresis (CE) is burgeoning. Hence, it is not surprising that literature on CE is also burgeoning. The expansion includes textbooks so there is now a welcome choice of tertiary literature on the topic. Li’s book is a worthy and weighty contender among these publications. The book aims to provide a comprehensive and detailed reference work for both experienced analysts and newcomers.It has been designed for teaching at advanced undergraduate and graduate levels, in particular for courses in analytical science, biochemistry, environmental science, phar- maceutical analysis and biotechnology . The volume begins with a historical overview and a straightforward description of the various electrophoretic methods encompassed by CE, such as free solution CE, micellar electrokinetic capillary chromatography (MEKC), isotachophoresis, and capillary electrochromatography. The physical phenomena that underpin free solution CE are then covered in more depth. The next two chapters cover every conceivable injection and detection method with clarity and ample referencing.The advantages and disadvantages of each injection and detection method for different applications are expounded fairly. The discussion of detectors (100 pages) is especially strong and complete. Chapter 4 provides a thorough account of column technology. It explains particularly effec- tively the various and versatile treatments of the internal surface of columns with either permanent or reversible coatings. Gel-filled columns are also covered appropriately. The effects of optimum column conditions on separations are well illustrated with a substantial number of electrophero- grams. ’extremely helpful for the new user’ The choice of electrolyte is a crucial factor in CE method development. The importance of this aspect is acknowledged in Chapter 5.The effects of pH, organic modifiers, buffers, cyclodextrins, surfactants, chelating agents and so on are dealt with at some length. Thus, the treatment includes a considera- tion of MEKC and the resolution of the enantiomers of chiral compounds. In the next chapter, special instrumental features and separation methods not found in conventional CE operations are discussed. Examples include buffer program- ming, fraction collection, systematic optimization schemes, coupled HPLC-CE, and capillary isoelectric focusing. In the extensive chapter on applications (164 pages), the anecdotal coverage of a huge range of analytes is sometimes achieved at the expense of detail. The table of analytes, separation conditions and references to original literature, all 19 pages of it, is extremely helpful for the new user looking for precedents for an analysis by CE.The short final chapter contains yet another three pages updating the table. In effect, this last chapter is a stop-press for advances reported in early 1992, along with a short but realistic assessment of the potential for growth in CE. The final sentiment, that CE is becoming one of the most powerful separation techniques ever developed, provides a suitably upbeat finale. The volume closes with a subject index and a list of articles that were in press at the time of publication. It is possible to quibble with some aspects. For example, the diagrams in the book are taken from a very wide range of sources and are not always as illuminating as they could have been.There are also some typographical errors. Some readers might baulk (or snigger) at the concept of a ‘moving stationary phase’ in MEKC. However, the quibbles are not serious and the strengths of the text more than compensate. At the foot of each page, the page number on which the appropriate references is given. This guide is very handy because the references are collated at the end of each chapter rather than at the back of the book. The author is to be congratulated on achieving the objectives for the book. It can be recommended to anyone who wishes to get to grips with a technique that can generate up to thirty million theoretical plates per metre: that should include all separation scientists. Malcolm E. Rose and Darren Wycherley Department of Chemistry The Open University, UK Analytical Chemistry Refresher Manual By John Kenkel.Pp. xvi + 358. Lewis Publishers. 1992. Price f58.00. ISBN 0-87371-398-2. The ambitious aim of this book is to outline all the popular analytical methods for graduates in biology, environmental science, geology etc., who, as the Preface gracefully but unflatteringly describes it, ‘are expected to function as114N Analyst, September 1994, Vol. 119 chemical analysis technicians’. If this sets one’s teeth on edge a little, it is only fair to add that the author certainly does not intend to relegate analytical science to a subordinate position. Indeed, he emphasizes that this is a ‘golden age’ for the subject, not least because of the numerous techniques and applications now available.The difficulty of covering all these methods in a book of moderate length is apparent, but overall this is a very brave attempt. Many of the sections are certainly successful in stimulating the reader’s interest, so it is a great pity that there is no bibliography for each chapter: even references to larger textbooks, monographs or reviews would have been helpful. In reality, it would have been more realistic to claim that most of the core techniques of analytical chemistry are covered: thermal methods, capillary electro- phoresis, chemiluminescence, radiochemical and X-ray methods, and the large range of biospecific analysis tech- niques are not included. ‘this book can be recommended to its intended readership’. Even if these omissions are regarded as inevitable, it is clearly essential for the author to use his 350-odd pages prudently.Inevitably also, the outcome is controversial. More space is devoted to gas chromatography than to all electro- chemical methods combined; the data handling chapter is so short that instrumental calibration graphs are not covered; the atomic spectroscopy chapter gives a page to electrodeless discharge lamps, but almost nothing to background correc- tion; and in the same chapter ICP methods get very short shrift. But there are good points, too: modern methods like LC-MS are at least mentioned, the importance of planning and sampling in the analytical process are rightly emphasized, and the balance between classical and instrumental methods is sensible. There is also a good index.Overall, this book can be recommended to its intended readership. James N . Miller Department of Chemistry Loughborough University of Technology, UK XRF Analysis of Ceramics, Minerals and Allied Materials By Harry Bennett and Graham J. Oliver. Pp. xvi + 298. Wiley. 1992. Price f45.00. ISBN 0-471 -93457-7. This book is about a single variant of X-ray fluorescence (XRF), namely the fused cast bead technique which has been accepted as the basis for both British and International standard methods. It replaces the now dated third edition of ‘Chemical Methods of Silicate Analysis’ (1971), and is intended as a practical tool for analysts faced with samples of non-metallic matrices in quantity and having the use of an XRF spectrometer. The methods aim for results of referee standard on a routine basis.It arises from the authors’ experience at Ceram Research (British Ceramic Research Association), which has a considerable expertise in this area. The book contains no complex maths and all aspects are carefully explained. ‘a practical tool for analFts faced with Samples of non-metallic matrices in quantity and having the use of an XRF spectrometer’. The book takes a didactic rather than an analytical approach: it is not a review of the methods in use in different laboratories, but presents working methods used for a decade in such detailed form that they will be accepted as descriptions of laboratory procedures by such organizations as NAMAS. The book aims towards standardizing procedures, equipment and software, to reduce costs and to make better interlabora- tory comparison of results.The authors provide some background information about the ancillary equipment and procedures, best described as ‘know how’: the book therefore contains some elements of a textbook. Specific instruments are quoted and tests carried out on them to determine the optimum settings: these are valuable guides. For those operating other equipment, the philosophy behind the tests to obtain the optimum settings will be useful. Energy dispersive XRF is not discussed as the authors do not consider it of equivalent value. A chapter on element line selection discusses each element, details the likely interferences, and indicates the probable magnitude of the correction to overcome them. While some of this data could have been presented in table form, it would not have been nearly so useful.Detailed procedures for specific matrices each have a chapter: aluminosilicates, calcium-rich matrices; glasses, glazes and frits; carbides and nitrides and finally ‘Procedures for samples of unknown composition’, which includes materials such as coloured glasses, welding flux, furnace deposits where the possible range of compositions is enor- mous. The chapter on decomposition of samples by fusion will be of wider interest to any involved in atomic spectrometry because of the difficulty of decomposing some of the above matrices. Analysts tempted to simply fuse and forget, or who have found insoluble residues after fusion for solution-based atomic spectrometry would do well to read this chapter.We get here an insight into the running of a busy analytical laboratory and the complex problems it has to solve. One chapter covers a neglected area, loss on ignition, showing some of the complex reactions occurring when silicate based materials are heated to ignition (water, C02, S02, halogens). Useful appendices list typical certified reference materials, with their quoted analyses, continuing the emphasis on careful checking of analytical technique. For its specific purpose, it will be a consistently useful handbook. Michael J . Hughes Department of Scientific Research The British Museum, London, UK Handbook of Affinity Chromatography Edited by Toni Kline. Chromatographic Science Series. Volume 63. Pp. viii + 332. Marcel Dekker. 1993. Price US$135.00.ISBN 0-8247-8939-3. Affinity Chromatography was introduced to biological chemistry over 25 years ago, and rapidly added major weapons to the armoury of laboratories purifying biospecific molecules. Its impact on analytical science was initially less dramatic, but recent years have seen many important applications in trace analysis, as well as in the isolation of antibodies, enzymes and other receptor molecules for use in assay systems. This multi-author volume is designed as an up-to-date handbook and practical guide, and overall it certainly succeeds. The first two chapters of the book deal with support media and immobilization methods. Strangely, although the first chapter is described as an overview, the principles of affinity chromatography (including its problems) are not described, and the book starts very abruptly indeed.However, this chapter is a very detailed source of up-to-date material on stationary phases and immobilization chemistries, with numerous tables and references. By contrast the second chapter is very short, but it does introduce the importantAnalyst, September 1994, Vol. 11 9 115N recent development of perfusion matrices. Alas, the term is not listed in the index: the latter is, as so often, one of the least successful aspects of the book. ‘should be on the shelves of all those interested in biospecific analysis’. The next five chapters, covering 140 pages in all, describe preparative applications of affinity methods in specific areas such as enzymes, nucleic acids and their binding proteins, regulatory and membrane transport proteins etc.The analyst will, while not ignoring these, find more of interest in the concluding chapters, which are collectively entitled ‘Research on Biorecognition’. There is an authoritative description of surface plasmon resonance sensors, a very detailed account of binding constant determinations, and an interesting summary of weak affinity methods (those relying on K A values of only 102-104 1 mol-1) which clearly offer interesting analytical opportunities as abrupt changes of eluent are unnecessary. The last chapter, again a brief one, widens the horizons of the subject by its discussion of ‘paralogue’ methods (using fragments of receptors), mixed mode chromatography (e.g., with a matrix containing ion-exchange as well as affinity groups), and other novel concepts.The book is far from cheap, but it is an important addition to the literature and a stimulating read. It should be on the shelves of all those interested in biospecific analysis. James N . Miller Department of Chemistry Loughborough University of Technology, UK HPLC Detection. Newer Methods Edited by Gabor Patonay. Pp. xii + 236. VCH. 1993. Price 2821 9-X (VCH, Verlagsgesellschaft). DM1 58.00; f65.00. ISBN 0-89573-327-7 (VCH); 3-527- There are probably better books telling the practising analyst what a certain new method of HPLC detection can do for him, but possibly no better text than this to stimulate the interest and ingenuity of researchers keen on developing new analy- tical methods and on state-of-the-art instrumental problem solving.The book comprises nine chapters, each devoted to a continually developing detection method and written by researchers in that area, with a good index and contents summary. A brief glance shows the near impossibility of finding a page that is text only: practically every one has either a table or graph of experimental data, or a schematic diagram. This feature along with the references (from 22 to over 160 in number) at the end of each chapter creates a favourable impression. ’possibly no better text than this to stimulate the interest and ingenuity of researchers keen on developing new analytical methods and on state-of-the-art instrumental problem solving’. is one of the authors of Chapter 4 on near-infrared detection which provides an introductory approach whose ‘goal is to provoke the interest of the scientific community in this new and powerful spectroscopic HPLC detection method’.The editor sets an exemplary standard by covering, in a very balanced way, NIR chromophore properties and labelling, laser diode characteristics, detector configuration, and some results mostly taken from serum protein work. Electrochem- ical methods are covered in Chapter 5 with constant-potential methods as the main focus, with characteristics of mobile phases, detector cell geometry, and detection modes construc- tively reviewed. The challenges of more complex samples, tailored microelectrodes, and novel derivatizations are regar- ded as a spur to further progress. Chapter 6 addresses photothermal detection in which a laser is used in the thermal lens technique, the theory of which is presented to show the relative sensitivity of this method compared with conventional absorption.Single- and double-beam instrumental configura- tions of varying complexity are described with the aid of useful schematic diagrams, and solvent characteristics and very small sample volumes are discussed constructively. FTIR detection is addressed in Chapter 7 initially by comparison with GC-MS and GC-FTIR. Again the problems of solvent-elimination are dealt with in some detail and are presented with many examples from the literature, some of which show instrumen- tal ingenuity at its best. The page on SFC-FTIR, TLC-FTIR, and NIR-HPLC detracts slightly from the main story of this chapter, which otherwise leads easily into Chapter 8 on HPLC-MS, where the obvious problems of phase and interface designs are first addressed, followed by examples including drugs, herbicides, natural products, and various macromolecules. Finally HPLC-NMR is covered and the advantages and disadvantages of the combination are well discussed before coverage of continuous-flow probes and cryomagnet systems.The limited choice of solvents, and solvent signal suppression in flowing liquids are discussed with numerous examples, and the chapter concludes with a summary of further developments and of stopped-flow analy- sis for the identification of unknowns. No extravagant claims are made for any of the techniques: the authors’ style addresses what limits can be reached; what sensitivity can be achieved; and most importantly, what research has to be done for further development.J. R. Johnson Department of Pharmaceutical Sciences University of Strathclyde, UK Gas Chromatographic Retention Indices of Toxicologic- ally Relevant Substances on Packed or Capillary Columns with Dimethylsilicone Stationary Phases By Rokus A. de Zeeuw, Jan Piet franke, Hans Haurer and Karl Pfleger. Report XVlll of the DFG Commission for Clinical-Toxicological Analysis Special Issue of the TlAFT Bulletin. Pp. 408. VCH. 1992. Price DM158.00. ISBN 3-527-27396-4. (VCH, Weinheim); 1-56081 -1 82-X (VCH, New York). Techniques covered range from the relatively common- place, e . g . , electrochemical, to the futuristic, e.g., NMR. Chapter 1 covers laser-based detection generally in high- performance microseparations where the potential and research trends of the combined technologies are outlined.In Chapter 2 luminescence, fluorescence, and phosphorescence are covered with many examples of the advantages and use of long-lived lanthanide luminescence. Similarly, Chapter 3 deals with the sensitivity and the selectivity of chemilumines- cent detection and the labels used in the reactions. The editor This book is an extensive collection of retention data, expressed as retention indices for many drugs, poisons, their metabolites and other substances of toxicological interest. Almost all of this volume is committed to tables but there are five short introductory chapters explaining the background to the collection and outlining the theoretical basis of the Kovats’ indices systems.Details of their calculation are given for both isothermal and temperature programmed analyses. Using the standard approach retention indices windows of k50-60116N Analyst, September 1994, Vol. 119 retention index units were found to be the norm but this can be reduced if a series of standard drugs are used as calibrators. ‘an extensive collection of retention data, expressed as retention indices for many drugs, P O ~ ~ O N , their metabolites and other substances of toxicological interest’. A series of 3 tables are detailed, first listing the drugs alphabetically, the second in order of increasing retention index and the third in order of their CAS registry number. This work has been a mammoth task of data gathering and it also provides data on drug derivatives which are sometimes necessary to achieve good chromatography.The authors are to be congratulated for all of their efforts. I cannot imagine any toxicologically orientated laboratory not being in posses- sion of such a volume. B. Caddy Department of Pure and Applied Chemistry University of Strathclyde, UK Ion Exchange Processes: Advances and Applications Edited by A. Dyer, M. J. Hudson and P. A. Williams. Pp. x + 372. Royal Society of Chemistry. 1993. Price f52.50. ISBN 0-85186-445-7. This volume comprises the 35 papers presented at the Ion-Ex ’93 Conference at the North East Wales Institute in Wrexham, UK, April 4-7, 1993. It was produced in time for distribution at the conference, which is commendable, though as a consequence there is no record of the conference discussions.The first paper by Townsend of Unilever is an excellent and original account of the fundamentals of ion exchange. The remaining papers are loosely grouped under the headings: ‘Ion Exchange in the Nuclear Industry’, ‘Capillary Electro- phoresis’, ‘Water Treatment’, ‘Inorganic Ion Exchangers’, and ‘New Materials’; but it should not be assumed either that the first section, for example, deals exclusively with nuclear applications, or again that all references to water treatment appear in the section so headed. Readers with particular interests should use the subject index to search the whole book. Most of the papers present basic data needed for the design of separation processes for aqueous liquors of all kinds, and one paper, by Croll of Anglian Water Services, goes further in giving a critical overview of process options for plants for nitrate removal from potable waters.Further examples of the separations dealt with include removal of: traces of silicate from ultra-pure water; univalent from polyvalent cations; radiocaesium from nuclear wastes; mineral salts from proteins; cationic from anionic dyes and vice versa; and traces of chlorophyll etc., from edible oils. The last-mentioned is one of the few non-aqueous separations discussed. ‘This volume describes separations and novel ion-exchange materials potentially useful in analytical chemistry’. Many of the separations are potentially useful in analytical chemistry, as also may be some of the novel ion-exchange materials described.Most of the papers, however, though very dependent on chemical analysis, make use of standard techniques, which are only mentioned briefly, if at all. The principal exceptions to this statement are to be found in the first three papers in the capillary electrophoresis section of the volume and in the second paper in the new materials section. Those on capillary electrophoresis deal with novel applica- tions of the technique to aqueous solutions of different classes of dyes, polymeric water treatment additives, and transition metal cations, respectively. The topic of the last paper mentioned is trace metal determination with the aid of a resin coated with a chelating dye (Xylenol Orange). H. A . C. McKay Oxford, UK Practical Polymer Analysis By T.R. Crompton. Pp. xx + 822. Plenum. 1993. Price US$175.00. ISBN 0-306-44524-7. Even the briefest inspections of this single author text shows it to be a remarkable volume. Its sheer size and coverage together with its 2367 references attest to its potential value. Certainly most of the references are pre-1980, but since advances in polymer analysis are few since that date, this is hardly surprising. The book is also remarkable because in part it is as much about polymer ‘characterization’ as about polymer ‘analysis’, and at least those who see themselves as ‘characterizers’ rather than ‘analysers’ will appreciate the distinction. At the other extreme the text is also a laboratory manual, in places giving precise experimental details of how to conduct a particular analytical procedure.‘anyone involved in the use of and research into polymers should acquire a copy of this text to keep along with their copy of “Polymer Handbook”’. Following a brief Chapter 1 (8 pages) which lists polymer types and Chapter 2 (5 pages) which lists the characteristics that need elucidation, the first important chapter is number 3 (15 pages) which relates how to separate a polymer from its additives. This is especially useful because it deals with likely additives in particular commercial polymer types and has some messages for those simply wanting to purify polymers. Chapter 4 (73 pages) is a meaty one covering polymer identification. It is comprehensive and, indeed, ‘forensic-like’. A wide variety of techniques are covered ranging from classical wet and combustiodpyrolysis analyses through to infrared spectral assignment.Strangely, nuclear magnetic resonance spectral identification, which is potentially very powerful, is relegated to a list of spectra in Appendix I, with no critical discussion. Chapter 5 (135 pages) deals not only with polymer analysis, but also with the identification of additives, volatiles and catalyst remnants. This is, of course, a key area and the space allocated is well justified. The coverage of and information within this chapter is remarkable. Chapter 6 (14 pages) returns to the polymer itself and focuses on functional group identification. In many respects this could usefully have been incorporated into Chapter 4. Polymer fractionation and molecular mass characterization is dealt with in Chapter 7 (65 pages).The approach is very practical and the topic is not elevated to some unreasonably higher intellectual level as it sometimes can be. Chapter 9 (115 pages) covers copolymer composition analysis and is packed with information. Again this is a contribution much understated by the book’s title. Likewise Chapter 10 (58 pages) describing polymer microstructure evaluation. Here the term microstruc- ture is used to encompass all aspects of backbone regio- and stereo-isomerism as well as chain branching. The coverage is largely according to specific polymer types. All aspects of thermal, oxidative and photostability are dealt with in Chapter 11 (88 pages). This is very much a chapter for practitionersAnalyst, September 1994, Vol.I I9 117N rather than those with an academic interest. The latter, however, may find some satisfaction in Chapters 12 (34 pages) and 13 (17 pages) dealing with glass transition and melting/ crystallinity, respectively. The treatment, however, is again aimed at those trying to pin down experimental data, rather than those wishing to devise novel theories. One minor detraction in the book for me as an organic polymer chemist is the poor, and in some cases, misleading structural representations of polymers and additives, etc. With modern structure packages for microcomputers this is un- necessary and the publishers in particular need to be held responsible here. Notwithstanding this, however, I believe that anyone involved in the use of and research into polymers should acquire a copy of this text to keep along with their copy of ‘Polymer Handbook’.The author deserves a great vote of thanks for what he has achieved, and deserves significant remuneration for his efforts! D. C. Sherrington Department of Pure and Applied Chemistry University of Strathclyde, UK Statistical Methods in Analytical Chemistry By Peter C. Meier and Richard E. Zund. Volume 723 in Chemical Analysis: A Series of Monographs on Analytical Chemistry and Its Applications. Series Editor, J. D. Winefordner. Pp. xiv + 322. Wiley. 1993. Price f49.50. ISBN 0-471-58454-1. This text gives a rather idiosyncratic description of how a selection of statistical techniques can be applied to certain situations in analytical chemistry. It is written by ‘two passionate analysts’, whose prose style is often rather off-beat.For example they describe one chapter as being ‘all surprise and combination’. The technical content is quite standard in many respects, but is not always discussed in a logical order. The standard statistical concepts and tests are generally well described, with worked examples. The discussion of the different variations on the t-test is particularly useful. The description on analysis of variance (ANOVA) is more superficial, not stating the assumptions that often limit its applicability, and suggesting that it is not capable of testing ‘concrete hypotheses’. Analytical quality control and the estimation of measure- ment uncertainty are one of the major areas where statistical techniques are needed by the analyst, yet they are only covered peripherally in this text.There is no explicit definition of precision, or the methodology for its estimation. Nor is the use of reference materials for the estimation of accuracy described. Detection limits are discussed in more detail but no reference is made to the IUPAC/ISO definition, which is now generally accepted. ‘a useful alternative to the standard texts in this area but it is unlikely to supplant them’. An unexpected omission in the text is the very minor coverage given to multivariate statistical techniques (10 pages) which are now one of the main areas of interest in this field. A later chapter discusses a series of ‘complex examples’ or case studies in which statistics have helped solve particular analytical problems. These form a useful addition to the text, but the objectives of each example are not always easy to discern.A disc is supplied with the book that contains a number of BASIC programs and trial data sets. These programs are useful to illustrate and reinforce the points made in the book. However, many of the operations covered by these separate programs are often available in a single integrated statistical package (e.g., MINITAB) that is likely to be of more use to the reader for future applications. Overall therefore, this book forms a useful alternative to the standard texts in this area (such as Miller and Miller, 1986), but it is unlikely to supplant them. Michael H . Ramsey Department of Geology Imperial College, UK ~ ~~ Capillary Electrophoresis Technology Edited by Norbert0 A.Guzman. Chromatographic Science Series, Volume 64. Pp. xvi + 858. Marcel Dekker. 1993. Price US$165.00. ISBN 0-8247-9042-1. Capillary Electrophoresis Technology contains 30 different chapters written by an impressive list of scientists widely recognized €or their contributions to this new and rapidly expanding area of separation science. This opportunity to access the ideas and opinions of an impressive list of prominents scientists is one of the most important strengths of this book. With over 850 pages it is not surprising that there are few areas of capillary electrophoresis (CE) that are not dealt with in this volume of the Chromatographic Science Series. The contributions to this interesting monograph have been organized into five different sections. The first section, ‘Overview’ opens with a very concise, but comprehensive overview of CE theory, aspects of interest for practical implementation of the technique, and a brief summary of important areas of application.The focus is narrowed slightly in the second chapter, which covers micellar CE in a very brief, but thorough manner. The next chapter in this first section, and, to a large extent the remainder of the chapters in the book, deal with more specialized topics. As has been the goal established by the editors, any of the chapters in this book can be read independently, and in any order the reader wishes. Some chapters deal with subjects that impinge directly on experimental aspects that are of particular importance to anyone new to the area of CE separation technology; subjects in this category would include discussions on buffer systems (Chapter 4), organic solvents (Chapter 5 ) , and chemical treatment of capillaries (Chapter 8).‘Capillary Electrophoresis Technology contains 30 different chapters written by an impressive list of scientists widely recognized for their contributions to this new and rapidly expanding area of separation science’. While anyone interested in CE will find this book a useful addition to their CE library, the newcomer to CE should be aware that this book should not be purchased with the intent of providing a logical, progressive, and in depth introduction to CE. While some important subjects, such as capillary treatment and biopolymer separations, are treated in con- siderable depth, the format of having each chapter stand on its own, leads to considerable duplication of information with some figures being reproduced in two or three different locations. In addition, the format makes it difficult to quickly access important information.Another drawback for the newcomer is that several of the chapters contain narrowly focused descriptions of areas that reflect the interest and opinion of the author. While most of these chapters are still of considerable importance, this narrow focus will be of limited use to the uninitiated; in one instance the information in the chapter deals only with previously unreported data on the separation and analysis of a very specific compound. Another limitation for the newcomer is the very limited discussion of118N Analyst, September 1994, Vol.11 9 quantitative aspects. This is an especially important area because many analysts beginning to apply CE are familiar with liquid chromatography (LC). While there are many similari- ties between LC and CE, many of these similarities are deceptive as there are a number of fundamental differences that must be given proper attention if accurate quantification is to be expected. In spite of some of the drawbacks, as a first book on CE, this book is recommended because of its up-to-date discussion on a number of important aspects of this rapid1 y-growing area of separation science. R. Cassidy Chemistry Department University of Saskatchewan, SK, Canada Intelligent Software for Chemical Analysis Edited by Lutgarde M.C. Buydens and Peter J. Schoen- makers. Data Handling in Science and Technology. Volume 73. Pp. xviii + 348. Elsevier. 1993. Price DF1350.00; US$200.00. ISBN 0-444-89207-9. Routine aspects of analysis may be readily automated including operation of instruments, optimization of instru- ment parameters, comparison of data with reference (library) data, archiving data (databases) and generating reports. The analytical chemist is therefore only required to add to the analytical procedure by contributing knowledge and expertise gained through training and practice. This frequently amounts to the selection of an appropriate method for the analytes of interest in the sample, checking and validation of the results and trouble shooting any problems that become apparent.In essence, the book sets out to show that it is entirely possible to implement computer software in the form of a knowledge- based expert system which reflects the expertise an analyst (expert) would use to evaluate analytical procedures and the data generated from analytical measurements. The book aims to provide the reader with sufficient details and information on expert systems so that he or she may appreciate their application to various instrumental analytical techniques. Sufficient references are appended to each chapter so that the enthusiastic reader could initiate a project to develop an expert system application. It would have been relatively straight forward for the authors to have written a book on the theory and practice of knowledge-based systems.However, it is more difficult to pitch a text such that analysts who are not software engineers can appreciate ‘intelligent software’ and potential applica- tions. Credit should be given to the authors for they have succeeded in compiling a set of chapters, written by them- selves and five others, that are relatively straight forward to follow and clearly demonstrate the application of expert systems. Sufficient theory is included to wet the appetite! ‘it is entirely possible to implement computer software in the form of a knowledge-based expert system which reflects the expertise an analyst would use to evaluate analytical procedures’ An introductory chapter examines the status of automation in analytical laboratories and potential uses of intelligent software: a sound foundation for subsequent chapters.Ana- lytical methodology and the role and ‘expertise’ of analytical chemists is then discussed. This serves to identify the expertise that may form the basis of intelligent software. Development and implementation of expert systems are then considered. Writing the software from scratch would be extremely time-consuming and beyond most analytical chemists. However, expert system development tools are available to ease the task. These are considered at length and supported by examples. The second half of the book looks at case studies and applications. These include expert systems for high-perfor- mance liquid chromatography method development, optimi- zation and trouble shooting, adaptive expert systems for interpretation of 2D-nuclear magnetic resonance spectra and inductive expert systems for classification and identification of mass spectra and airborne particles. Finally, genetic algorithms (a class of optimization software) and neural networks (pattern recognition software utilizing neural-like pathways to associate data) are explained and potential applications for interpreting data are discussed.The final chapter is entitled ‘Perspectives’ and tries to present an honest account (the authors’ words) on the development and application of intelligent software in the analytical laboratory. The book is one of the first to address this topic and succeeds in presenting the information at a level that many analytical chemists should be able to follow.There is also sufficient detail and back-up material in the form of examples and references for those so-inclined to have a go. Alan Braith waite Department of Chemistry and Physics Nottingham Trent University, UK Quality Control in Analytical Chemistry. Second Edition By G. Kateman and L. Buydens. Volume 60 in Chemical Analysis: A Series of Monographs on Analytical Chemistry and Its Applications. Pp. xviii + 318. Wiley. 1993. Price €49.50. ISBN 0-471 -55777-3. The first edition of this useful book has justly become a standard text, and the second edition has made substantial improvements that will ensure it remains so. The structure of the book is methodical and well thought out. It commences with a review of the development of analytical quality control (AQC). The terminology used in AQC can be ambiguous (e.g., accuracy) but the meanings used for this book have been clearly defined. There is an in-depth treatment of the very important, but often ignored, topic of sampling as a source of measurement error. This is set in a sound framework of what the objectives of the analytical process are for a given circumstance. Also discussed are the cases of ‘one-shot’ sampling when the theories discussed (e.g., of Visman, Gy and Ingamells) are of no practical use, and alternative strategies have to be employed. ‘a readable, classic text’ The discussion of analytical data quality is generally comprehensive and authoritative. One minor exception is the lack of discussion on how the precision of an analytical method changes with concentration, and the effect this has on its estimation. Less usual but undoubtedly important measures of analy- tical quality such as cost, sensitivity, safety and measurability are discussed in detail, alongside the more usual parameters, such as precision and accuracy. Coverage of data processing techniques includes lucid descriptions of topics such as information theory, filtering, analysis of variance (ANOVA) and principal component analysis (PCA). The explanation of PCA is particularly clear and comprehensible, without being too over-simplified. Overall I can thoroughly recommend this new edition as a readable, classic text in this increasingly important subject area. Michael H . Ramsey Department of Geology Imperial College, UK

ISSN:0003-2654    

DOI:10.1039/AN994190113N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, September 1994, Vol. 119 119N Conference Diary Date Conference 1994 October Location 2-7 3-7 3-6 5-7 10-13 11-13 11-12 11-13 14-15 17-19 18 20 24-25 24 29th Annual Meeting of the Federation of Analytical Chemistry and Spectroscopy USA Societies ISCMS '94, International Symposium on Chromatography and Mass Spectrometry Russian St. Louis, St. Petersburg, Federation PREP '94: 11th International Symposium on Preparative and Industrial Chromatography Germany Baden-Baden, 9th International Symposium on Capillary Electrophoresis (ITP '94) Hungary Budapest, International Symposium on Chromatographic Bled, and Electrophoretic Techniques Slovenia 6th International Coloquium Solid Sampling with Atomic Spectroscopy The Netherlands Amsterdam, Ecotoxicology Monitoring London, UK 35th ORNL-DOE Conference on Analytical Chemistry in Energy Technology USA Tennessee, CITAC '94 Hong Kong Symposium on Traceability and Comparability of Analytical Measurements Hong Kong 3rd International Symposium on Supercritical Strasbourg, Fluids France Elemental Analysis User Forum Teddington, UK Short Papers in Pharmaceutical Analysis London, UK Data Handling, Automation, Regulation and Technology Conference and Table-Top Exhibition (DART '94) Fundamentals of Toxicology and Chemical Risk Assessment UK Amsterdam, The Netherlands Birmingham, Contact FACSS, P.O.Box 278, Manhattan, KS 66502-0003, USA Tel: + 1 301 846 4797. ISCMS '94, Dr. Alexander Rodin, State Institute of Applied Chemistry, Dobrolubov Avenue 14, 197198 St. Petersburg, Russian Federation Tel: +7 812 238 9786.Fax: +7 812 233 8989 GDCh-Geschaftsstelle, Abt. Tagungen, Varrentrappestr. 4042, Postfach 90 04 40, D-6000 Frankfurt am Main 90, Germany Tel: +49 69 791 7358. Fax: +49 69 791 7475 Dr. Ferenc Kilair, Central Research Laboratory, University of PCcs, Medical School, Szigeti ut 12, H-7643 Pecs, Hungary Tel: +36 72 324 122, ext. 2086. Fax: +36-72 315 864 Dr. M. ProSek, National Institute of Chemistry, SLO-Ljubljana, Slovenia Fax: +386 61 125 9244 Professor Dr. R. F. M. Herber, Coronel Laboratory, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands BICS International, City Headquarters, 1st Floor, Chandos House, 12-14 Berry Street, London, UK EClV OAQ Tel: 1-44 (0) 171 490 2076. Fax: +44 (0) 171 490 2086 W. R. 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Dr. Diana Simpson, Analysis For Industry, Factories 2/3, Bosworth House, High Street, Thorpe-le-Soken, Essex, UK C016 OEA Tel: +44 (0) 255 861714.Analyst, September 1994, Vol. 11 9 121N Date Conference Location Contact 18-22 Joint Oil Analysis Program International Pensacola, Condition Monitoring Conference USA 24-26 5th International Symposium on Advances in Madras, Electrochemical Science and Technology India 30 Clinical Applications of Electroanalysis Edgbaston UK December 13-16 DNA-Fingerprinting: 3rd International Hyderabad, Conference India 15 Recent Advances in Technologies for the Study London, of Drug Metabolism UK 1995 January 8-13 1995 Winter Conference on Plasma Spectrochemistry 29-2/2 7th International Symposium on High Performance Capillary Electrophoresis (HPCE '95) February 6-8 International Conference on Arsenic in Ground Water: Cause, Effect and Remedy 7-10 4th International Conference on Automation, Robotics and Artificial Intelligence Applied to Analytical Chemistry and Laboratory Medicine Alternatives to Chemical Solvents Restricted by the Montreal Protocol 15 19-24 OFC '95: Optical Fibre Communication Conference Technical Support Center, Joint Oil Analysis Program, Building 780, Naval Air Station, Pensacola, FL 32508, USA Tel: +1 904 452 3191.The Secretary, Society for Advancement of Electrochemical Science and Technology, Karaikudi, 623 006, India A. E. Bottom, ABB Kent-Taylor Ltd., Oldends Lane, Stonehouse, UK GLlO 3TA Tel: +44 (0) 453 826661. Fax: +44 (0) 453 826358 Dr. Lalji Singh, Centre for Cellular and Molecular Biology, Hyderabad 500 007, India Fax: +9140 85 1195 Mr. A. Crooks, "Cartref", 35 Queensberry Road, Salisbury, Wiltshire, UK SP1 3PH Tel: +44 (0) 722 334974. Cambridge, UK Janice M. Gordon, Winter Conference on Plasma Spectrochemistry , Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge, UK CB4 4WF Tel: +44 (0)223 420066. Fax: +44 (0)223 420247 Shirley E. Schlessinger, HPCE' 95, Suite 1015,400 East Randolph Drive, Chicago, IL 60601, USA Tel: +I 312 527 2011.Wiirzburg, Germany Calcutta, India Montreux, Switzerland London, UK San Diego, USA D. Chakraborti, School of Environmental Studies, Jadavpur University, Calcutta 700 032, India Tel: +91 33 473 5233. Fax: +91 33 473 4266 SCITEC, Avenue de Provence 20, CH-1000 Lausanne 20, Switzerland Tel: +4121624 1533. Fax: +4121624 1549 Ms. Paula Elliott, Secretary, Analytical Division, The Royal Society of Chemistry, Burlington House, Piccadilly, London, UK W1V OBN Tel: +44 (0)171 437 8656. Fax: +44 (0)171 734 1227 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: +1202 223 9034. Fax: +1202 416 6100 DC 20036-1023, USA March 6-10 PITTCON '95, Pittsburgh Conference On New Orleans, Pittsburgh Conference, Suite 332,300 Penn Centre Analytical Chemistry and Applied USA Boulevard, Pittsburgh, PA 15235-9962, USA Spectroscopy Microscopy Meeting USA Medicine and Science, P.O.Box 832, Mahwah, 28-31 Scanning 95 Seventh Annual International California, Mary K. Sullivan, Foundation for Advances in NJ 07430-0832 USA Tel: +010 1 201 818 1010. Fax: +OlO 1 201 818 0086 Sciences, University of Northumbria at Newcastle, Ellison Building, Newcastle upon Tyne, UK NE1 8ST Tel: +44 (0) 91 227 3517. Fax: +44 (0) 91 227 3519 29-30 Atomic Spectrometry Updates Bristol, J. R. Dean, Department of Chemical and Life UK122N Analyst, September 1994, Vol. 119 Date April 3-6 10-13 23-25 26-28 May 3 7-1 1 7-1 1 16-18 21-26 21-26 28-216 June 5-8 Conference 7th Instrumental Analysis Symposium Annual Chemical Congress (with Analytical Session) 6th International Symposium on Pharmaceutical and Biomedical Analysis 6th International Symposium on Chiral Discrimination New Techniques in Bioanalysis 86th AOCS Annual Meeting & Expo Seventeenth International Symposium on Capillary Chromatography and Electrophoresis Fourth International Conference on Progress Location Madrid, Spain Edinburgh, UK St.Louis, USA St. Louis, USA Bradford, UK Texas, USA Virginia, USA Luxembourg in Analytical Chemistry in the Steel and Metals Industry CLEO '95: Conference on Lasers and Electro- Baltimore, Optics QELS '95: Quantum Electronics and Laser Science Conference 19th International Symposium on Column Liquid Chromatography 5th Symposium on our Environment and 1st Asia-Pacific Workshop on Pesticides July 9-15 SAC 95 10-13 Vth COMTOX Symposium on Toxicology and Clinical Chemistry of Metals USA Baltimore, USA Innsbruck, Austria Convention City, Singapore Hull, UK Vancouver, Canada Contact 7as Jomadas de Analisis Instrumental (JAI) Expoanalitica & Biocierica, Arda Reina Ma Cristina, Palacio no.1, 08004-Barcelona, Spain Tel: +34 3 423 3101. Fax: +34 3 423 6348 Dr. J. F. Gibson, The Royal Society of Chemistry, Burlington House, Piccadilly, London, UK W1V OBN Tel: +44 (0)171 437 8656. Fax: +44 (0)171734 1227 Shirley Schlessinger, 400, East Randolph Street, Suite 1015, Chicago, Illinois 60601, USA Tel: +010 1312 527 2011. Shirley Schlessinger, 400, East Randolph Street, Suite 1015 Chicago, Illinois 60601, USA Tel: +010 1312 527 2011.A. J. Crooks, 'Cartref', 35 Queensbury Road, Salisbury, Wiltshire, UK SP1 3PH Tel: +44 (0) 722 334974. AOCS Education/Meetings Department, P.O. Box 3489, Champaign, IL 61826-3489, USA Tel: +010 1 217 359 2344. Fax: +010 1217 351 8091 Dr. Milton L. Lee, Department of Chemistry, Brigham Young University, Provo, Tel: +1801378 2135. Fax: +1 801 378 5474 R. Jowitt, British Steel plc, Technical, Teesside Laboratories, P.O. Box 11, Grangetown, Middlesbrough, Cleveland, UK TS6 6UB Fax: +44 (0)642 460321 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: +1 202 223 9034. Fax: +1 202 416 6100 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: +1202 223 9034.Fax: +1202 416 6100 HPLC '95 Secretariat, Tyrol Congress, Marktgraben 2, A-6020 Innsbruck, Austria Tel: +43 512 575600. Fax: +43 512 575607 UT 84602-4672, USA DC 20036-1023, USA DC 20036-1023, USA. The Secretariat, 5th Symposium on our Environment, c/o Department of Chemistry, National University of Singapore, Kent Ridge, Republic of Singapore 0511 Fax: +65 779 1691 Analytical Division, The Royal Society of Chemistry, Burlington House, Piccadilly, London, UK W1V OBN Tel: +44 (0)71 437 8656. Fax: +44 (0)71 734 1227 F. William Sunderman, Jr., M.D., Departments of Laboratory Medicine and Pharmacology, University of Connecticut Medical School, P. 0. Box 1292, Farmington, CT 06034-1292, USA Tel: +1203 679 2328. Fax: +1203 679 2154Analyst, September 1994, Vol. 11 9 123N ~~ Date Conference August Location Contact CSI XXIX: Colloquium Spectroscopicum Internationale 27-21 9 27-119 27-30 Leipzig, Germany GDC h- Geschaftss telle , Ab t .Tagungen , Varrentrappestr. 40-42, Postfach 90 04 40, D-6000 Frankfurt am Main 90, Germany Tel: +49 69 791 7358. Fax: +49 69 791 7475 Secretariat, XLVIth ISE Annual Meeting, P.O. Box 1995, Xiamen University, Xiamen 361005, China Tel: +86 592 208 5349. Fax: +86 592 208 8054 Czech Medical Association J. E. Purkyng, EUROTOX ’95, P.O. Box 88, Sokolska 31,120 26 Prague 2, Czech Republic Tel: +42 2 24 915195. Fax: +42 2 24 216836 46th Annual Meeting of the International Society of Electrochemistry (ISE46) Xiamen, China EUROTOX Prague, Czech Republic September 10-14 Ion-Ex ’95, The Fourth International Conference and Industrial Exhibition on Ion Exchange Processes Wrexham, UK Moscow, Russia Ion-Ex ’95 Conference Secretariat, Faculty of Science, The North East Wales Institute, Connah’s Quay, Deeside, Clwyd, UK CH5 4BR Fax: +44 (0) 244 814305 Dr.I. F. Dolmanova, Analytical Chemistry Division, Chemical Department, Lomonosov Moscow State University, 119899 Moscow, Russia Tel: +7 095 939 3346. Fax: +7 095 939 2579 25-28 5th Symposium on ‘Kinetics in Analytical Chemistry’ (KAC ’95) October 1-5 21st World Congress of the International Society for Fat Research (ISF) Mrs. J. Wills, ISF Secretariat, P.O. Box 3489, Champaign, IL 61826-3489, USA Tel: +010 1 217 359 2344. Fax: +010 1 217 351 8091 The Hague, The Netherlands November 5-10 OPTCON ’95 San Jose, USA Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, Tel: + 1 202 223 9034.Fax: + 1 202 416 6100 Dr. M. P. Coward, Chemistry Department, UMIST, P.O. Box 88, Manchester, UK M60 1QD Tel: +44 (0) 61 200 4491. Fax: +44 (0) 61 228 1250 DC 20036-1023, USA 14-15 International Conference for Chemical Information Users Manchester, UK December 17-22 International Symposium on Environmental Biomonitoring and Specimen Banking K. S. Subraimanian, Environmental Health Directorate, Health Canada, Tunney’s Pasture, Ottawa, Ontario, Canada KlA OL2 Tel: +010 1613 957 1874. Fax: +O 101 613 941 4545 Hawaii, USA 1996 February 6-9 June 16-21 July 8-12 Fourth International Symposium on Hyphenated Techniques in Chromatography (HTC 4); Hyphenated Chromatographic Anal ysers Bruges, Belgium Dr. R. Smits, Royal Flemish Chemical Society (KVCV), Working Party on Chromatography, BASF Antwerpen N.V., Central Laboratory, Haven 725, Scheldelaan 600, B-2040 Antwerp, Belgium Tel: +32 3 561 2831. Fax: +32 3 561 3250 HPLC ’96: 20th International Symposium on High Performance Liquid Chromatography San Francisco, USA Mrs. Janet Cunningham, Barr Enterprises, P.O. Box 279, Walkersville, MD 21793, USA Tel: +1301 898 3772. Fax: +1301898 5596 XVI International Congress of Clinical Chemistry London, UK Mrs. Pat Nielsen, XVIth International Congress of Clinical Chemistry, P.O. Box 227, Buckingham, UK MK18 5PN Fax: +44 (0)280 6487

ISSN:0003-2654    

DOI:10.1039/AN994190119N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

124N Analyst, September 1994, Vol. 11 9 Courses Date Conference Location Contact 1994 October 3-4 Course on Capillary Electrophoresis (ITP '94) PCcs, Hungary Dr. Ferenc KilBr, Central Research Laboratory, Medical School, University of PCcs, Szigeti lit 12, H 7643 PCcs Hungary Fax: +36 72315 864 Nevada Technical Associates, P.O. Box 90748, Henderson, Neveda 89009, USA Tel: 010 1 702 564 2798. Dr. M. P. Coward, Chemistry Dept. UMIST, P.O. Box 88, Manchester, UK M60 1QD Tel: +44 (0)61200 4491. Fax: +44 (0)61228 1250 10-14 Environmental Radiochemistry Vienna, Austria Manchester , UK 18-19 Mass Spectrometry for Beginners November 7-8 Short Course on LCMS, SFCMS and CEMS Montreux, Switzerland M. Frei-Hausler, Workshop Office IAEAC, Postfach 46, CH-4123 Allschwil2, Switzerland Dr.A. van den Berg, University of Twente, MESA Research Institute, P.O. Box 217,7500 AE Enschede, The Netherlands Tel: +3153 892 691. Fax: +3153 309 547 21-22 Workshop on Micro Total Analysis (pTAS '94) Enschede, The Netherlands December 15-17 Capillary Electrophoresis Short Course Loughborough, UK Mrs. S. J. Maddison, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, UK LEll 3TU Tel: +44 (0) 509 22575. 1995 April 4-5 Workshop in Chemical Information Retrieval Manchester, UK Rome, Italy Dr. M. P. Coward, Chemistry Department, UMIST, P.O. Box 88, Manchester, UK M60 1QD Tel: +44 (0)61 200 4491. Fax: +44 (0)61228 1250 Dr. S. Faniti, CNR, Istituto di Cromatografia, C.P.10,100016, Monterotondo Scalo, Roma, Italy Fax: +39 6 906 25 849 4-7 Short Course on Chiral Resolution May 10 Education and Training of Chromatographers Dr.D. Simpson, Analysis for Industry, Factories 2/3, Bosworth House, High Street, Thorpe-le- Soken, Essex, UK C016 OEA Tel: +44 (0) 255 861714. Fax: +44 (0) 255 662111 London, UK July 17-19 Techniques Workshop (Chemometrics) Hull, UK Dr. M. J. Adams, School of Applied Sciences, University of Wolverhampton, Wulfruna Street, Wolverhampton, UK WV1 1SB Tel: +44 (0) 902 322141. Fax: +44 (0) 902 322680 September 6-8 5th Workshop on Chemistry and Fate of Modern Pesticides Paris, France Professor M-C. Hennion, ESPCI, Labo. Chimie Analytique, 10 Rue Vauquelin, 75005 Paris, France ~ ~~ 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/AN994190124N

出版商:RSC    

年代:1994

数据来源: RSC

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Analyst, Septern ber 1994, Vol. I1 9 125N Future Issues will lnclude- Object-orientated Programming on Personal Computers- R. G. Brereton Is my Calibration Linear?-Analytical Methods Committee Use of Protein A as an Immunological Reagent and Its Application Using Flow Injection. Review-Derek A. Palmer, Martin T. French and James N. Miller Melatonin, a Hormone Monitored In Vivo by Voltammetry- Francesco Crespi, Emiliangelo Ratti and David G. Trist Calculating Standard Deviations and Confidence Intervals with a Universally Applicable Spreadsheet Technique-J. Kragten Determination of Aluminium by Instrumental Neutron Acti- vation Analysis in Biological Samples With Special Reference to NBS SRM 1577 Bovine Liver-Zeev B. Alfassi and Bernd Rietz Comparative Study of the Chelation Reaction of N-Benzoyl- N-phenylhydroxylamine with Tin(r1) and Tin(1v)-Zhou Nan and Chun-Xiang He Potentiometric Thick-film Sensor for the Determination of the Neurotransmitter Acetylcholine-Norbert Hampp and Christian Eppelsheim Potentiometric Microtitration of Vitamin B1 With Phospho- tungstic Acid by Using a Phosphotungstate-sensitive Elec- trode and Its Application to the Analysis of Pharmaceutical Preparations-Antonio Campiglio Mass Spectrometric Methods for Studying Nutrient Mineral and Trace Element Absorption and Metabolism in Humans Using Stable Isotopes-Fred A.Mellon, Helen M. Crews, Veronique Ducros, John Eagles, Peter Kastenmayer, Joop B. Luten and Brian A.McGaw Determination of Chromium(iI1) and Chromium(v1) in River Water by Electrothermal Atomic Absorption Spectrometry After Sorption Preconcentration in a Microwave Field-Yurii A.Zolotov, Irina Kubrakova, Tamara Kudinova, Andrei Formanovsky and Nicolai Kuz’min Anodic Stripping Voltammetry of Lead, Cadmium and Zinc in the Presence of Copper with an Ion-Exchange Column- Hari Gunasingham and Ruelito R. Dalangin Simultaneous Determination of Chromium(v1) and Tung- sten(v1) Based on Their Catalytic Effect on the Reaction Between Hydrogen Peroxide and Iodide-Zhong-Liang Zhu, Chuan-Qiang Han, Zhi-Cheng Gu and Rong-Mei Chen Supercritical Fluid Extraction of Analytes from Environmen- tal Samples: A Review-John R. Dean, I. J. Barnabas and S. P. Owen 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.1995 E u RO P EAN W I NT E R ROYAL SOCIETY OF CHEMISTRY C ON F E RENCE O N PLASMA 3 PECTROCHEMISTRY 8 -13 Janua y 1995 CAMBRIDGE ANALYTICAL DIVISION Great Britain S CI ENTI F IC PROGRAMME S P EAKE RS The 1995 European Winter Conference will, for the first time, be held in the UK in the historical University City of Cambridge, the centre of some of the most important scientific developments of recent times.The conference will be based upon a single lecture stream featuring five plenary and five invited speakers plus contributed papers. Symposia will include the following topics:- 1) Sample introduction phenomena 2) Glow discharge techniques 3) Fundamental plasma processes 4) Sample preparation and handling 5) Elemental speciation 6) Plasma source mass spectrometry 7) Laser sampling techngques Plenary lecturers will include=- Professor M M s (Univ British Columbia, Catuuiu) Professor K Niemax (ISAS, Dortmund Germany) Professor H M (Skip) Kingston (Duquesne Univ, USA) Professor L Ebdon (Univ Plymouth, UK) Professor J Caruso (Univ Cittcinnat& USA) Invited lecturers will include:- Professor J Olesik (Ohio State Univ, USA) Professor R K Marcus (Clemson Univ, USA) Dr S J Haswell (Univ Huy LIK) Professor R Nesbitt (Univ Southampton, LIK) Dr K Kawabata pokogawa Ana#ytical Systems, Japan) 1995 EUROPEAN WINTER CONFERENCE ON PLASMA SPECTROCHEMISTRY If you would like to receive the final circular and registration form, please complete and return to:- Janice M Gordon European Winter Conference Royal Society of Chemistry Thomas Graham House Science Park Mihon Road tilmbridge CB4 4WF United Kingdom NAME ADDRESS ~_____ I intend to submit a paper/poster on:

ISSN:0003-2654    

DOI:10.1039/AN994190125N

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

1925 Analyst, September 1994, Vol. 11 9 Tutorial Review Discovering Flow Injection: Journey From Sample to a Live Cell and From Solution to Suspension Jaromir RGiiEka Department of Chemistry BG-10 University of Washington, Seattle, WA 981 16, USA Twenty years after its inception, flow injection is seen as an ever-expanding method, as new modifications are discovered such as flow injection cytoanalysis and the flow injection on renewable surfaces technique. In this review, a personal view of the future rather than the history of flow injection is given, with comment on how research is actually being conducted. Keywords: Sequential injection; renewable reactive surface; solid-phase separation; immunoassay; fluorescence microscopy; cell biology; chemical sensor Introduction Amongst the most powerful addictions is a combination of a journey, discovery and creativity.This is undoubtedly the driving force behind many human endeavours, some of which are deemed more noble than others. Science is undisputedly one, and a travel book through one’s scientific journey may be of some interest, although probably not a useful guide. Let us imagine that each such tour starts at a point in space, while opportunity presents itself in any direction, which, however, must be chosen and travelled along. Obviously the element of luck (sometimes called intuition) is equally as important as the effort expended to move forward, if one is to be rewarded by the joy of discovery. The field I selected was analytical chemistry, within which my direction has changed several times, most importantly in the spring of 1974 when the course turned towards a horizon beyond which at that time the unknown territory of flow injection (FI) awaited discovery.Initially this simple idea seemed destined to be an improved tool for automation of serial assays, named appropriately flow injection analysis (FIA). Later, when the outline of the shore appeared, the greater substance to FI was recognized as its compatibility with electroanalytical techniques and spectroscopies became apparent. When it was recognized that FTA could serve as an interface between solution chemistries and analytical instru- ments, the small island on the horizon turned into what medieval travellers called terra incognita, only there were no dragons there, only pitfalls and missed opportunities.Indeed the more we know about FI, the more there is to learn, about its versatility, complexity of its underdeveloped theory, its relationship to chromatography, its place amongst the methods of analytical chemistry and above all about its potential, yet undiscovered applications. This tutorial review is meant to provide room for fantasy by offering vantage points from which future prospects can be gleaned. It will also offer a criticism of the past journey, which could have been travelled more efficientlv. as is so easilv seen in retromect. The Outset In the beginning there was the realization that colorimeter- based serial assays could be carried out more efficiently in a flowing stream of reagent into which the sample was injected as a discrete narrow zone1 and that FIA could be used to carry out serial assays even in a routine laboratory with modest means.2J All that was needed was a multichannel pump, an injection valve, a reaction coil, a flow-through detector and a recorder (Fig.1). Except for the last component, which was replaced when computers invaded laboratories some 10 years later, this basic flow scheme remained essentially unchanged until very recently, when sequential injection (SI) was introduced.4 It would, however, be incorrect to conclude that FI was not being developed during that period, on the contrary its scope has increased enormously, but the focus of Fig. 1 An FI system consists of a two-channel pump, an injection valve. a coiled reactor and a detector (D).The reagent is added continuously to the carrier stream (top) which allows the injected sample zone to be merged with it (centre). The resulting reaction product forms a concentration gradient corresponding to the concen- tration of the analyte throughout the entire sample zone length. Typical flow rates are 1 ml min-1, sample volume 50 p1, residence time 30 s and a samoline freauencv of 2 samdes min-1.1926 Analyst, September 1994, Vol. 119 research was in a different direction.s.6 First, a large number of chemistries and techniques, such as liquid-liquid extrac- t i ~ n , ~ hydride generation ,8 gas diffusion ,9 immunoassayslo and assays with immobilized enzymes,” were integrated into an FI scheme and found many useful applications. Also, a whole range of spectroscopic and electrochemical instruments were gradually adapted as detectors.However, within this first decade of discovery, the aim was to prove that FIA was viable while the main thrust was towards development of serial assays. In other words, there were items at the beginning of this journey when the goal was to show that the ship could sail, while land was beyond the horizon. From today’s perspective, with more than 5000 papers on FI published,’2 such a goal may be seen as too modest, but it should be noted that at that time lectures were given and papers were published, deeming that FI was impractical and too limited to ever be usefu1.13.14 During the second decade, FIA found many applications both in the laboratory and in process control and became known simply as FI1S as it was realized that FI is not only a tool for analysis, but also a generally applicable solution handling technique.Its ability to control and monitor kinetic aspects of automated assays has been recognized, and identified as ‘kinetic advantage’,16 Its ability to enhance the sensitivity and selectivity of electroanalytical and spectroscopic techniques became widely recognized, and was marked by the appear- ance of the first specialized monograph on FI atomic spectroscopy.17 The relationship between FI and chromato- graphy was defined, and the specific features of FI, viz., its ability to exploit concentration gradients and the importance of flow programming, were recognized. An Outlook and a New Course Today it is generally accepted that FI is an impulse-response technique, whereby the initial square-wave input (Fig.2), provided by sample injection, is transformed into a response function by means of a modulator, within which two processes take place simultaneously: physical dispersion of the sample zone within the carrier stream and chemical reactions of the analyte with the surrounding medium.18 As the detector is tuned to detect the species thus processed, the readout takes the form of a peak which reflects both of the above processes. By keeping all the parameters unchanged, except for the amount of analyte, a calibration graph is obtained from the corresponding changes of the response curve. Fig. 2 FI and chromatography belong to the group of so called impulse-response techniques (top) and use the same basic flow scheme (below).They differ, however, in their goals, in their operational characteristics and most visibly in the concept and function of their modulators. It is not incidental that this ‘definition’ equally well accommodates chromatographic and FI techniques, as both methods are based on injection of a well-defined zone into a flowing stream (mobile phase or carrier). The difference is to be found in the construction and function of the modulator. This is a column in chromatography which provides a vast amplification of differences of migration velocities of indi- vidual analytes. Therefore, sample components emerge from the column serially, being sequentially detected, yielding a chromatogram. The function of the reactor in FI is to transform analytes through chemical reactions into species that are selectively quantified by a detector.18 This delineation places in a ‘grey area’ flow schemes where a microcolumn is used either in FI or in chrmatography for one-step (‘all-or- nothing’) analyte separation (a mode originally designed for affinity chromatography). However, even here a more distinct line might be drawn in the future, as the novel technique of flow injection on renewable surfaces (FI-RS) avoids the use of microcolumns by making the stationary phase mobile. I do not believe that definitions have a lasting value, as they reflect the past state-of-the-art and thus maintain the status quo rather than encouraging discovery. (Prior to becoming a globe the Earth was deemed to be flat and the Atlantic Ocean was believed to plunge into an abyss, a view which undoub- tedly discouraged many to sail west.) However, the recent interest in providing better definitions for F119-21 is valuable, as it seeks to define a method rather than a tool.Thus we are landing on a new shore where the next stage of exploration begins. Once again it is difficult to decide which direction to take; however, a brief review of the present state-of-the-art may be of some help. Sequential Injection. A New Look at a Familiar Landscape The first aspect to consider is the change brought about by the introduction of SI,d which, in contrast to the classical FI scheme, relies on preprogrammed flow reversals rather than on continuous forward flow (Fig. 3). Each measuring cycle begins by aspirating a precisely measured volume of a sample solution from a sample line through a multiposition valve into the holding coil by the pump moving in reverse.Next, the valve is switched to the reagent line and a precisely measured volume of reagent is drawn into the holding coil. Lastly, the valve is switched to the detector position and the pump propels the sequenced zones forward. As the central stream- line moves at a rate that is twice the speed of the mean flow velocity, whereas the elements of the fluid more adjacent to the walls move at lesser rates, the cores of the sequenced zones penetrate each other. If then the radial mixing is promoted by a suitable choice of coil geometry, the analyte and reagent zones mix and produce species to be detected. The complex reagent/product/analyte zone can be either propelled through the detector continuously, or stopped within the detector, resulting in measurement of the rate of formation of the reaction product.In this way the stopped-flow approach yields kinetic information and allows for longer reaction times. In contrast to the ‘classical’ FI mode, where the carrier flows from the pump through the valve, reactor and detector continuously and unidirectionally, in SI the selector valve is the hub through which the zones are moved back and forth in a programmed fashion by means of a series of precisely controlled flow reversals.4-18 There is apparently no limit to how many solutions (reagents, samples and standards) or devices (reactor coils, mixing chambers and detectors) can be nested around the valve.Indeed, an SI cluster may serve as a single- and a multichannel analyser. Alternatively, a series of standards can be permanently nested around the valve, being ready for automated recalibration whenever needed. The biggest advantage of Si compared with FI is that there is noAnalyst, September 1994, Vol. 11 9 1927 need for physical reconfiguration of the flow path. Any changes (injected sample volume, reaction time, sample dilution and reagent : analyte ratio) are accomplished via flow programming rather than by physical reconfiguration of the flow path. Indeed SI is fully computer-compatible, as it allows all changes, including system calibration, to be controlled from a computer keyboard, a feature that will allow its future optimization through the use of artificial intelligence.It is amusing to note that while SI could perhaps have been conceived simultaneously with FI in the mid-l970s, it could not have been implemented at that time, as no analytical chemist could have afforded the software capable of controll- ing the SI instrument. However, how does SI differ from FI and what are its drawbacks? The answer lies in the differences in dispersion patterns as observed in FI and SI channels (Fig. 4). The characteristic feature of the FI pattern is that the injected zone flows past a confluence point where two streams merge in a synchronous fashion, so that an equal volume of reagent solution is added to each element of the passing carrier stream. The result is a concentration gradient of an analyte within the constant background of a reagent.As several confluence points can be serially placed on the main carrier line, several reagents can be serially added to the passing analyte zone, thus following the protocol of manual assays which require serial addition of several reagents. The only price paid is the multitude of manifold lines and the need for a multichannel pump. In contrast, no confluence points are used in SI, where the multiposition valve is used to sequence the Fig. 3 An SI system consists of a single-channel high-precision bi-directional pump, a holding coil (HC) a multiposition valve and a detector (D). At the beginning the system is filled with a carrier stream (top) into which a zone of a sample solution (red) and a zone of a reagent (blue) are sequentially aspirated forming a stack in the holding coil (middle).By using flow reversal the zones are propelled through the valve into a detector, while a reaction product (yellow) is being formed. As the stacked zones cannot mutually overlap through their entire length, the concentration gradient of the product is narrower than the entire concentration gradient of the injected analyte. The typical flow rate is 1 ml min-’, the volumes of injected zones are 50 pl and the residence times are 30 s. As SI systems operate in the stop and reverse flow mode the volume of waste generated by SI is much lower than that generated by FI, which usually operates in continuous-flow mode. zones into the holding coil. Such a valve cannot serve as a confluence point as it connects only two (and not three ports) at a time.The result is an initial sharp boundary between adjacent zones and, therefore, only a partial overlap of analyte and reagent peaks is possible. There is also a limitation to the number of zones that can be mixed by a flow reversal in a tubular reactor, three being the maximum.21 Consequently, if several reagents need to be added serially, as is often the case in enzymic assays, the only alternative in SI is the use of a mixing chamber, as was used in the determination of factor XIII, which required six reagents.22 A mixing chamber is also needed when extensive dilution of the analyte is required, typically for process control applications.23 Accordingly, in an SI process control application, a mixing chamber connected to a fibre optic detector has proved successful for the monitoring of total biomass.24 Minimizing the number of mechanical components to two (one pump, one valve) is beneficial for a process control environment as it increases the reliability of the apparatus.For laboratory applications, however, the drawbacks of the SI system, with only one pump, need to be addressed. Therefore, one of the goals for future exploration is to design a flow scheme that combines the advantages of FI and SI and yet has none of their drawbacks. A New Territory: Flow Injection Cytoanalysis Gases, solids and most often liquids are the focus of most analytical chemistry, while biological samples when analysed Fig. 4 In the FI mode (top) the sample zone (S) forms a concentration gradient (red) which is via the confluence point supplied by a steady reagent concentration (R, blue) yielding reaction product (yellow) throughout the entire length of the analyte zone. In the SI mode (below) the sample and reagent zones mutually penetrate, with the result that the zone of the product to be detected (yellow) is sharp and narrow. This explains why the ‘fluidics’ of the SI apparatus and its computer control need to be much more sophisti- cated, as otherwise the volumes of injected zones, their intermixing and the location of the stopped-flow point (t-stop, purple) would be poorly reproduced.(I) denotes the initiation of the sampling cycle on which timing of all events is based, whire H denotes peak height which is used as a readout in continuous-flow mode.1928 Analyst, September 1994, Vol.11 9 are almost always dead rather than alive. Also, those biological materials that find their way to the analytical chemist are macroscopic in nature: serum, tissues, plants and fermentation liquids. Rarely is the analytical chemist faced with typical biological samples such as a group of cells or individual cells. This explains why flow injection cytometry (FIC) and flow injection fluorescence microscopy (FIFMZS) deal with materials normally outside the scope of analytical research. However, instrumental analysis has much to contri- bute to research in biology and the life sciences by designing advanced tools for cell studies, for drug discovery, for the study of membrane processes and of receptors, diagnostics of auto-immune diseases and for genetic engineering. It is beyond the scope of this review to discuss FIC, but the principles of FIFM are briefly reviewed as they are relevant to this story.The technique of observing cells microscopically, while manipulating their chemical environment, is important to many studies in cytochemistry. Indeed, this area of biology has undergone a revolution through the merger of two techniques: fluorescent probe chemistry and (video) fluorescence micro- scopy.26,27 Presently, most of these studies are carried out in batch mode (either in a Petri dish or in a well) by simply squirting the amount of reagent into an open container with a pipette. This technique allows no control over the rate at which the cell comes into contact with the stimulant, nor does it allow this process to be repeated reproducibly.Conse- quently, valuable information on the initial kinetics of the reagentkell interaction is obscured by this manual technique, which also makes it virtually impossible to treat all the cells in the batch investigated in exactly the same manner. Further, removal of reagents (destimulation) from a cell culture by aspirating the entire volume of media is impractical and at best unreliable. The introduction of FI into fluorescence micro- scopy allowed the exposure of cells to be controlled with millisecond reproducibility from a fraction of a second up to as much as a few hours. This was achieved by injecting a zone of stimulant and by propelling it in a defined flow geometry over a group of cells grown on a cover slip [Fig.5 , A]. In this way cells are exposed to well-defined concentration profiles of a desired reagent while their response can be monitored and ~ ~~ quantified. Any sequence of reagents (fluorescent probes, porants, stimulants) can be handled by means of an SI apparatus [Fig. 5 , B] which will allow the desired perfusion protocols to be repeated automatically any number of times on the same group of cells. The fountain cell2* was a key component that made the concept of FIFM practical. Adherent cells, as are routinely grown on a circular cover slip, are, in this device, exposed to an accurately controlled radial flow, which emerges from a central inlet (Fig. 6). The planparallel gap (200 pm thick) between the mounted cover slip and the flat disc forming the body of the fountain cell maintains this flow pattern, which transforms the injected zone of the reagent (or stimulant) into an expanding ring moving towards the circumference of the fountain cell, where the presence of a circular drain ensures uniformity of the radial flow (Fig.7). Thus any cell, or group of cells, regardless of its position on the cover slip, is exposed to exactly the same pulse of reagent.29 This allows the biologist to select a desired single cell, or colony of cells, for a planned impulse-response study, regardless of where the cells have attached themselves to the coverslip (Fig. 8). Also, FIFM avoids any variation of physical variables such as stimulant concentration and cell contact times between experiments run at different times.Further, the peculiar fluidics of the thin layer in the fountain cell allow the observation field to be divided into well-defined fluidically controlled segments. This is achieved by replacing the single central inlet by a cluster of inlets which introduce the liquid into the fountain cell. Thus if Fig. 6 Single inlet fountain cell shown in a side view (left) and top view (right). The carrier stream emerging from the central inlet spreads radially towards a circular drain. The adherent cells grown on a cover slip are perfused and monitored by a microscope. Fig. 7 The zone of Acridine Orange is shown as it emerges from the central inlet into the fountain cell, where it spreads radially, forming a circular concentration gradient.The image obtained by fluorescence video microscopy was enhanced into false colours by NIH Image software. whereby the highest concentration of Acridine Orange is represented by the warmest colour. Fig. 5 Principle A , of FIFM and SI apparatus B, used for this purpose (see text). Typical flow rate is 1 ml min-1, injected zone volume 50 PI. For details of perfusion chamber see Fig. 6 .Analyst, September 1994, Vol. 11 9 1929 three central inlets are used, each supplying a stream flowing at the same rate, three segments of equal size are produced (Fig. 9). This flow pattern allows the same batch of cells, grown on a given cover slip, to be perfused at the same time, with three different stimultants in the same time-concentra- tion protocol.3" FIFM was most recently used to study antibody binding on the surface of viable rat insulinoma cells.Cell surface specific antibodies are widely used to probe specific antigens to determine cell types, immunocyte sub-types and functional activation. The expresssion of cell-specific surface molecules is critical in a variety of cellular analyses and has a clinical relevance, as specific antibodies are detected in a variety of auto-immune disorders including insulin-dependent diabetes. However, current manual techniques, such as that recently developed to monitor islet surface antibodies,31 use the %-well format, and are labour-intensive, time consuming and do not allow monitoring of the initial binding rate. Use of FIFM for the same purpose allowed the assay, which required over 2 h in the manual format, to be performed within 5 min, while the more selective initial binding rate was being moni tored.3' A New Frontier: the Stationary Phase on the Move The tremcndous wealth of solution/surface chemistries, which has been accumulated throughout the development of chro- matographic supports, awaits exploitation beyond their present role as a column material.As in chromatography the solid phase serves the singular task of promoting differences in migration velocities of analytes to aid their separation, FI should become the vehicle to exploit solid-support chemistries for all other analyte/solution handling tasks. Thus, column materials will become useful as sorbents, carriers for reagents and catalysts, filters, retainingkeactive media for immunoas- says, reflectors for spectroscopic detection, pseudo-mem- branes and possibly even as media for solid-state titration.In order to fulfil these diverse functions, a novel and practical way must be found to inject, move, retain, monitor and discharge small amounts of particles within a flow system reproducibly . This new approach, the FI-RS technique, utilizes a key component, the jet ring cell, which serves as an integrated detector and reactor (Fig. 10). Originally designed as a tool for FI microscopy of living cells grown on Cytodex beads, the jet ring cell was used in conjunction with a fluorescence microscope equipped either with a camera or a photomulti- plier.33 Its application to a broad range of analytical tasks was first demonstrated in connection with immunoassays34 and is further expanded on here.The apparatus into which the jet ring cell is integrated consists of a conventional SI system, a rotary flask which maintains beads in a homogenized suspension, and an auxiliary peristaltic pump, which, when stopped, serves as a shut-off valve (Fig. 11). Typically a 50 yl volume of a diluted bead suspension, containing approximately 1.2 x 104 beads each with an average diameter of 35 ym, is aspirated and transported into the jet ring cell. There the beads are trapped, forming a well-defined cylindrical layer of beads (about 1 mm deep, 0.8 mm in diameter) within the confines of the ring and in the focal plane of the microscope. This layer of beads (with a packed volume of about 0.5 yl and weighing 0.1 mg) can easily be perfused; however, the tight packing of the beads perserves the geometry even when the forward carrier flow is stopped. On flow reversal, the reversed jet formed by the ring flushes the beads rapidly out of the system.The beads can be Fig. 8 Rat insulinoma cells grown on a cover slip and stained within the fountain cell by Acridine Orange. The image obtained by fluorescence video microscopy was enhanced into false colours by NIH Image software, whereby the yellow and red colours represent the dye adsorbed in the DNA. Note the uneven distribution of the cellular material grown on the surface of the cover slip. Fig. 10 The jet ring cell (A, and C, side view, B, and D, top view) is designed to capture beads carried by a forward flow (top) into a ring, from which the liquid escapes radially through a circular gap narrower than the diameter of the beads.The planar surface, retaining the bead layer serves as a window for the detector (microscope or optical fibre) used to monitor the spectral changes on the bead surfaces during perfusion. A flow reversal (below) removes all beads instantaneously, as the direction of the jet formed within the circular gap forces the particles away from the window, and out of the system. Typical ring diameter is 0.8 o r 0.5 mm. The bead size is exaggerated for the sake of clarity . Fig. 9 Photograph of three-inlet fountain cell with three separate streams being pumped at equal flow rates from central inlets. Owing to laminar flow in a radial direction two dyed and one clear solution form three segmcnts which remain separated until they reach the circular drain wherc they mix.Thc shadow seen through the cell body is cast by thc inlet tubing.1930 Analyst, September 1994, Vol. 119 injected, retained and monitored with surprising reproducibil- ity, not only when the bead layer is thick and the signal reaches saturation, but also when the fluorescence increases propor- tionally with the number of beads injected (Fig. 12). This is because the beads are being deposited within the ring in a regular pattern, as confirmed by visual observation and recorded by video microscopy. The methodology of FI-RS, still in its infancy, is based on (1) testing the fluidics and of the monitoring system, (2) investigation of the kinetics of the adsorption process, (3) study of solutiodsolid-phase reaction kinetics and (4) calibra- tion of the system and testing the reproducibility of an assay.Testing the fluidics and monitoring is performed by using the beads that have been pre-stained either by a suitable dye, or possibly by the reaction product of the analyte with a desired reagent. The procedure is the same as described in connection with Fig. 12, where selected volumes of the bead suspension are repeatedly injected, retained and discarded under continuous monitoring, while the reproducibility of this process is evaluated by the detector response. At this stage it is important to (a) select beads with suitable mechanical properties,33 (b) adjust the gap in the ring cell such that the Fig. 11 FI-RS apparatus, shown here furnished with a microscope, is based on an SI system, which has been amended by a rotary flask, where the beads are held in suspension, and by an auxiliary peristaltic pump (2).Typically 50 p1 of diluted bead suspension are aspirated into the holding coil (HC) and propelled into the jet ring cell, by means of pump 1 , while pump 2, being in stopped-flow mode, serves as a shut-off valve. Next, the trapped beads are perfused by zones of samples and reagents according to a desired protocol. Finally, while pump 1 is stopped (or the valve shut off), pump 2 is activated, washing the spent beads out to waste. Fig. 12 Polysorb CIS beads (diameter 35 pm), tagged with fluores- cein, were injected by means of an SI system (Fig. 11) into a jet ring cell (Fig.10) and monitored by fluorescence microscopy. Two experimental runs, each consisting of five injections, have been overlaid (red and blue traces) to show the repeatability of the fluidic manipulation and of fluorescence monitoring. The numbers are approximate counts of trapped beads, as obtained independently by assaying the bead suspension by flow cytometry. The injected volumes ranged from 200 pl (46000 beads) to 40 p1 (9200 beads). Decreasing volumes were injected in order to demonstrate the lack of bead carry-over in the system between subsequent injections. beads cannot escape, (c) match the detection area with the probing device (microscope, optical fibre, electrode) and (d) select the appropriate dilution of the bead suspension. Investigation of the kinetics of adsorption begins by injecting a suitable volume of a pristine bead suspension into the jet ring cell, which yields a baseline signal (Fig.13, C), followed by injection of a zone of the label (such as a fluorescence-labelled analyte for immunoassays34), or of the reaction product of an analyte with a colour-forming reagent, or of an analyte alone, if detectable. This results in a transition signal which shows a maximum (A) proportional to the total amount of 1abel.injected. As the unbound label is washed away, the signal declines to a plateau (B), corresponding to the amount of label retained on the solid phase. Finally, the solid phase is removed from the detector by flow reversal (C’). (The relative positions of the levels C and C’ depend on the optical qualities of the beads, such as auto-fluorescence or reflectance .) The amount of retained label B depends on the distribution ratio and kinetics of adsorption and is strongly dependent on the contact time which is very short in-FI-RS.This is because the flow velocities normally encountered in an FI system are fairly high. For tubing with an i.d. of 0.5 mm and for a flow rate of 1000 yl min-1, the central streamline is moving at a velocity of 17 cm s-1.35 Even if the flow is randomized, owing to the presence of beads and to the wall jet velocity profile in the jet ring cell, the flow in the cell will still move at a mean velocity of 85 mm s-1, which results in an average contact time between a 1 mm thick bead layer and any individual element of the fluid as short as 12 ms.Stopping the flow would not solve this problem considering that even a zone as small as 100 yl in a 0.5 mm i.d. tube occupies a length of 500 mm and, therefore, a bead layer of the same diameter corresponds to only 0.2% of the zone length (and as the bead layer is packed, its void volume will accommodate an even smaller fraction of the zone volume). Therefore, slowing the flow rate, while the zone passes through the jet ring cell, is a suitable approach. Further, taking the zone length into account, it is seen that the cumulative contact time under the above conditions is 500 X 12 ms = 6 s, suggesting that an increase in the injected sample volume is the next available option. Therefore, a plot of B Fig. 13 Ten overlaid traces of binding of R-Phycoeritrin conjugated mouse IgGl on anti-mouse IgGl coated agarose beads, monitored by fluorescence microscopy, show the reproducibility of perfusion and binding typical for FI-Rs immunoassay.The bar shows the protocol as the absence and presence of unstained (black) and stained (magenta) beads and the cumulative contact time of the injected zone (red) with the bead layer as the tagged mouse IgGl was perfusing it. As the beads have no auto-fluorescence, the baseline at the beginning of the run (C) in the presence of non-stained beads is the same as at the end (C’) in the absence of beads. Note that there is a large difference between the bound fraction (B) and the peak maximum (A). indicating that only a fraction of the total label has been retained (flow rate 1 ml min-1, volume of injected beads 42 ~ 1 , containing 8400 beads).Analyst, September 1994, Vol.11 9 1931 versus contact time is the critical parameter for optimization of the adsorption yield and sampling frequency.36 Investigation of the reaction kinetics between the analyte and the reactive solid phase follows the same protocol as designed for the study of the kinetics of adsorption. So far, data of this type have been obtained only for FI-RS immunoassays (FI-RSI) of two analytes, one being a small molecule (the herbicide imazethapyr) while the other was a large molecule [mouse immunoglobulin G(IgG) 11. The binding yield of the large protein was low (Fig. 13) but once the complex was formed, the bond was strong as seen from a stable level for B. The small molecule of the imazethapyr analogue reacted much faster (Fig.14); however, the complex formed seemed to be less stable as the level of the bound fraction decreased with time. As predicted, slowing the flow rate increased the yield of binding (Fig. 15). These observa- tions are in agreement with theories of antibody-antigen bond Fig. 14 Three overlaid traces of binding of fluorescein conjugated imazethapyr analogue on anti-imidazoline monoclonal antibody attached to protein A coated sacharose beads as monitored by fluorescence microscopy. The bar shows the protocol as the absence and presence of unstained (black) and stained (magenta) beads and also the cumulative contact time of the injected zone (red) of the tagged herbicide with the antibody immobilized on the beads.As the beads have no auto-fluorescence, the baseline at the beginning of the run (C) in the presence of non-stained beads is the same as at the end (C’) in the absence of beads. Note the small difference between the bound fraction (B) and the peak maximum (A), indicating that a substantial fraction of labelled molecules has been retained (flow rate 1 ml min-1). Fig. 15 Influence of contact time on the binding yield of labelled imazethapyr analogue on anti-imidazoline monoclonal antibody attached to protein A coated sacharose beads. The flow rate was varied between 2.5 ml min-I (blue trace) and 0.12 ml min-1 (red trace). The bar shows the protocol as the absence and presence of unstained (black) and stained (magenta) beads and also the cumula- tive contact time of the fluorescing zone of the tagged herbicide with the antibody immobilized on the beads at the highest (blue) and at the lowest (red) flow rate.As the beads have no auto-fluorescence, the baseline at the beginning of the run (C) in the presence of non-stained beads is the same as at the end (C‘) in the absence of beads. formation, as large molecules are expected to form complexes more slowly, while forming more robust structures than small molecules which react faster. Considering the very short contact times offered by FI-RSI, the yields shown in Figs. 13- 15 are surprisingly high, giving grounds for cautious optimism. They also indicate that the negative impact of the very short contact time between the solid and liquid phase, which is the principal limitation of FI-RS, is compensated by a high concentration of the reactive sites on the surface of the sorbent and by the high yield of the measured product which becomes preconcentrated from the large volume of the analyte zone on to a small area of the probed surface.This explains why the immunoassays discussed in this section have an acceptable sensitivity, yielding feasible calibration graphs in both compe- titive and non-competitive formats.34.36 Reviewing this unexplored terrain is both exciting and challenging: there are many unknowns, such as the mechan- ical, fluidic and optical properties of the beads. Their surface characteristics range from hydrophobic to hydrophilic, from simple ion exchangers to chemically and biologically active functional groups, such as biotin and streptavidin.The availability of labels, particularly fluorescing and enzymic, brings yet another dimension to the versatility of FI-RS. Thus unexpectedly, even catalogues of speciality reagents such as those of Pierce37 or Molecular Probes38 make exciting, albeit sketchy, reading, in a similar way to the travel agent’s alluring brochures. Having now established a new vehicle, the question is: where to go first? The Quest and Goals There are a number of analytical techniques that can potentially benefit from the FI-RS format. Although the viability of competitive and non-competitive immunoassays (FI-RSI) has already been documented,34736 the use of beads as inert filters, reagent carriers, replacements for organic solvents and as reflecting media for optical sensors and also as disposable membranes for chemical sensors has yet to be investigated.FI-RS Preconcentration This is the simplest goal to achieve, as it would deal with analytes that adsorb readily on the solid phase and could themselves fluoresce or absorb radiation in the ultraviolet- visible (UVNIS) or perhaps even the infrared region. provided that the distribution ratio of the analyte is large and the kinetics of adsorption is fast, the monitored signal will increase proportionally with the volume of the sample injected until the sorbent, or detector signal, becomes saturated. As for FI-RS the analyte/solid phase interaction can be selected to be as strong as possible, because there is no need to elute the retained analyte or to regenerate the solid phase, conditions for high selectivity and for a high degree of preconcentration can more easily be fulfilled than if the solid surface needs to be regenerated after each use, such as in chromatography and chemical sensor technology.FI-RS Sensing This is more complex because it involves a chemical reaction of a suitable reagent with an analyte with the aim of producing a species that is adsorbed and then detected by fluorescence or reflectance spectrometry. It may, fortunately, include also irreversible reactions, as the reactive surface is to be discarded after each use. Further, the reagent of choice does not need to be covalently bound to the bead surface because the bead1932 Analyst, September 1994, Vol. 119 suspension may be equilibrated with the reagent solution under such conditions that the reagent is simply adsorbed on the bead surface. This would allow easy access to a vast array of chemical reactions that have so far been unsuitable for chemical sensor technology, which inherently requires com- plete and repeatable restoration of the sensing chemistries and a strong bond between the reagent and membrane phase.Indeed FI-RS sensing avoids two fatal flaws of chemical sensor technologies: the need for a reversible sensing mechanism and prolonged stability of the reagents involved. Preliminary experiments in our laboratory on a model system whereby a jet ring cell has been coupled by means of a bifurcated fibre to a UV-VIS spectrophotometer confirm that reagents such as dithizone, 4-(2-pyridylazo)resorcinol (PAR), and diphenyl- carbazide entrapped on CIS beads are useful for preconcentra- tion and sensing of heavy metals.This is the first stage of the exploration of the feasibility of the concept of an FI-RS chemical sensor system in which spectroscopic or electro- chemical sensors will be coupled to a disposable sensing surface. Although more complex than the ‘stand-alone’ electrode or optrode, FI-RS sensor systems will provide automated recalibration, sample dilution and sensor regenera- tion. In addition to reagent-based chemistries, several other uses of a mobilized solid phase can be envisaged. Hydrophobic beads with an acid-base indicator within the pores filled with air might replace gas diffusion membranes for the sensing of volatile species such as carbon dioxide and ammonia.Inert hydrophilic beads may serve as disposable filters. Immobilized enzymes on hydrophilic beads may serve as pseudo-mem- branes for biosensors for substrate assays while at the same time serving as disposable barriers protecting the transducer surface from unwanted cellular material. Even the oldest analytical technique, titration, might be redesigned to the FI-RS format. By using a bed of a strong ion exchanger with either an indicator adsorbed on its surface or with a pH sensor contracting the ion exchanger beads in a jet ring cell, a solid-phase titration system for the assay of concentrated acids or bases can be envisaged. Ultimately, even simple chromato- graphy on a disposable microcolumn might be contemplated, by using a bead layer or a minute column held within a jet ring cell.With a suitable solvent gradient, analytes would be sequentially eluted, while those species remaining on the solid phase would be monitored and then discarded. Interestingly, these projections are as sketchy and as ambitious as those made many years ago when the potential uses of FIA were contemplated. Although at that time the advantages were seen to be automated sample handling with an increased throughput, on this occasion the projected benefits of the FI-RS technique seem to be many: avoiding regeneration of the solid phase will save time needed for column elution and surface reconditioning; replacing organic solvents with a solid sorbent and avoiding analyte elution will reduce the use of hazardous and expensive chemicals; the use of a minute amount of bead suspension will reduce the cost of the assay and the amount of waste generated (such as with the 96-well plastic trays used in immuno- assays, or the organic solvents used for liquid-liquid extraction) ; reliability of the assay will increase and the danger of carry-over will be reduced as each sample is reacted with a pristine surface; monitoring of initial reaction (binding) rates will not only allow more rapid assays, but is also likely to exploit the ‘kinetic advantage’ of FI further; a wide range of well-characterized carrier beads is commer- cially available ; a vast range of reagent chemistries can easily be accommo- dated on carrier beads without the need for specialized ‘know-how’; FI-RS apparatus can be designed with an ‘open archi- tecture’ to accommodate a wide range of assays.Once again, much time and effort is needed to discover what is practical and what is merely an illusion, what is feasible and what is speculative, what will be accepted and implemented, and what will be rejected as being impractical. The Story Behind This Story There is a touching frankness recorded in the travel logs of old navigators, who strayed and drifted, who spoke of the Deception Pass, the Cape of Hope and of a futile search for the Western Passage and the discovery of lands, which were not meant to be there. In contrast, a scientific paper seems always to be a marvellously straightforward (although not always lucid) description of a well-planned trip, leading directly to a discovery of sorts.This tale, alas, seems to be no exception, and, therefore, the following is meant to correct this misconception. A number of stories can be told about the meandering path which research in FI took, but a recent story, which relates to the development of FI-RS, is telling. Initially, there was a collaboration with Dr. Ole Thastrup, a biologist interested in the kinetics of the flux of calcium in and out of intercellular depots. He kindly guided us through elements of high school biology and ‘high-tech’ fluorescence microscopy, while pat- iently rejecting our numerous inept designs of perfusion chambers, until the fountain cell was brought to him. Ole used the fountain cell, and was so taken by a grand vision that he wrote a grant proposal. This proposal relied on a rapid screening of cells by FIFM with a ‘minor’ modification, which required that cells would not be grown on a coverslip but on Cytodex beads.These beads would then somehow be handled by FI and monitored by a microscope. He received a substantial grant and then called in our debt to him by asking us to design a tool that would handle and monitor suspensions of these very fragile and elastic beads, a task viewed by us at that time as insurmountable. It is now easy to see that the fountain cell is a precursor to the jet ring cell (cf. Figs. 6 and 10); however, this was far from obvious to us when we contemplated various filters and magnetic traps. Develop- ment of the jet ring cell not only facilitated the screening of adherent cells, but also made us aware of the feasibility of the handling and monitoring of all types of suspended matter by FI.Indeed it was Ole’s extraordinary request, which made us consider the handling of suspensions and ultimately led towards the concept of FI-RS. In retrospect it is obvious that throughout the past 20 years the main difficulty has been to change the perception of what the objective of current research might be, as the difficulty in recognizing the true potential of FI. Originally viewed as FIA, the r61e of the technique was to automate manual reagent chemistries, replace test-tubes, laboratory glassware and the air-segmented autoanalyser system (Fig. 16). Although useful and well-motivated, this was a very narrow focus. In the next stage, the relationship between FI and chromatography was recognized, resulting in an increased use of chromatographic components such as valves, fittings, detectors and computers for peak evaluation and instrument control (Fig.17). The theory of flow, designed to fit the mode of operation and needs of chromatography and of chemical engineering, was applied extensively to FI.39 The scope of FI expanded as the range of detectors applied to it grew, but the methodology remained confined within the boundaries of continuous unidirectional flow, perpetuated by the legacy of the Autoana-Analyst, September 1994, Vol. 11 9 1933 lyser and by current chromatographic models. Sequential injection broke through this boundary by applying flow programming and by making the concept of partial reagent=peak overlap, practical.However, it was the venture into biotechnology and the fertile contact with its stimulating challenges that led to the discovery of FI-RS (Fig. 18). Thus, just as an expedition outside the realms of serial assays led to enhancement of instrumental analysis, so a journey outside traditional analytical chemistry will lead to the application of FI to wider aspects of chemical research. This development, which started many years ago,SJj when extraction constants were measured by FI, should gain further acceptance as the undeniable advantages of FI become more widely recognized. The recent FI study of supercritical binary mixtures of carbon dioxide with methanol40 is an example of such pioneering work. ‘Having a point of view about the future’ (G.Hamel, London School of Economics) is no doubt important, yet this Fig. 16 ‘Flow Injection 87’. A painting by Broo Sorensen showing the components of the FI technique as they blend with the analyst’s tools of the trade and with the autoanalyser concept (centre). Fig. 17 ‘Flow Injection 89’. A painting by Broo Sorensen, where FI and chromatographies are surrounded by their shared components on the left and where the similarity of these impulse-response techniques is implied by readouts on the right. Fig. 18 ‘Flow Injection 93’. A painting by Broo Sorensen where merging peaks symbolize sequential injection and the disc the combination of fountain and jet ring cells. does not seem to be quality deemed essential for research in analytical chemistry. However, it is, as otherwise we focus too much on solving a present problem within a familiar area, rather than venturing outside, where there are many opportu- nities to serve the scientific community by designing new tools and methods for advancing research into chemistry, the life sciences and the environment.There is no sailing without a ship, without a skilled crew and supportive fellow travellers. I am truly indebted to many, who bore with me, often for long stretches at a time. On the last leg of this journey, facilities were provided by the National Institute of Health [grant No. SSS-3 (5) R 0 1 GM 54260-21 and by Novo/Nordisk Denmark. Pam Baxter, Cy Pollema, Louis Scampivia and Kurt Scudder together with Ole Thastrup, Ake Lernmark and Gary Christian are those without whom this journey would have been impossible and unenjoyable.Harp Minhas is also to be thanked for encouraging me to write this story. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1.5 16 17 18 19 20 21 22 23 24 25 26 27 28 29 References RGiiEka, J., and Hansen, E. H., Anal. Chim. Acta, 1975. 78, 14.5, Stewart J. W. B.. RGiiEka, J., Bergamin, Fo. H., and Zagatto. E. A. G., Anal. Chim. Acta, 1976, 81, 371. Krugg, F. J., Bergamin, Fo. H., Zagatto, E. A. G., and Jorgensen, S. S., Analyst, 1977, 102, 503. RGiiEka, J., and Marshall, G. D., Anal. Chim. Acta, 1990, 237, 329. RfiiiEka, J . , and Hansen, E. H., Flow Injection Analysis, Wiley, New York, 1st edn., 1981. Valcarcel, M., Luque de Castro, M. D., Flow Injection Analysis. Principles and Applications, Ellis Horwood, Chiches- ter.1987 (Spanish Edition, Cordoba, 1984). Karlberg, B., and Thelander, S., Anal. Chim. Acta, 1978,98, 1. Astrom, 0.. Anal. Chem., 1982, 54, 90. Baadenhuijsen, H., and Seuren-Jacobs, H. E. H., Clin. Chem. (Winston-Salem, N. C.), 1979, 25, 443. Lim, C. S., Miller. J . N., and Bridges, J . W., Anal. Chim. Acta, 1980, 114, 183. Johansson, G.. and Ogren. L., Anal. Chim. Acta, 1983,145,71. Hansen, E. H., Comprehensive FI Bibliography, in preparation. Margoshes, M., Anal. Chem., 1977, 49, 1861. Snyder,.L. R.. Anal. Chim. Acta, 1980, 114, 3. RGiiEka, J., and Hansen, E. H., Flow Injection Analysis, Wiley, New York. 2nd edn., 1988. Pacey, G. E., Hollowell, D. A., Miller, K. G . , Straka, M. R., and Gordon, G., Anal. Chim. Acta, 1986, 179, 259. Burguera, J . L., Flow Injection Atomic Spectroscopy, Marcel Dekker, New York, 1989. RfiiiEka, J., Anal. Chim. Acta, 1992, 261, 3. Fang, Z.. Flow Injection Separations and Preconcentrations. VCH, Weinheim, 1993. van der Linden, W. E., Classification of Analytical Methods Based on Flowing Media, IUPAC Analytical Chemistry Divi- sion, 1989-92, report, in preparation. Gubeli, T., Christian, G . D., and R8iiEka, J., Anal. Chem., 1991. 63, 1680. Guzman, M., Pollema. C., RGiiEka, J., and Christian, G. D., Talanta, 1993.40. 1. Gisin, M., Thommen, C., and Mansfield, K. F., Anal. Chim. Actu, 1986, 179, 149. Baxter. P. J., Christian, G. D., and RfiiiEka, J . , Analyst, in the press. RfiiiEka, J., and Lindberg, W., Anal. Chem., 1992,64, 537. Applications of Fluorescence in the Biomedical Sciences, eds. Taylor, D. L., Waggoner, A. S., Murphy, R. F., Lanni, F., and Birge, R. R.. A. R. Liss, New York. 1986. Methods in Cell Biology, ed. Tartkoff, A. M., Academic Press, New York, 1986. Scudder, K. M., Pollema, C. H., and ReiiEka, J., Anal. Chem., 1992, 64,2657. Pollema. C. H., and RfiZiEka, J., Analyst, 1993, 118, 1235.1934 Analyst, September 1994, Vol. I I 9 30 31 32 33 34 3.5 36 37 Scudder, K. M., Dissertation, University of Washington, 1994. Matsuba, I., and Lernrnark, A., Regional Immunol., 1990, 3, 23. Pollema, C. H., Lernmark, A., and RGiiEka, J., Cytometry, in the press. Riiitka, J., Pollerna, C. H., and Scudder, K. M.. Anal. Chem., 1993,65, 3.566. Pollema, C. H.. and Riiitka. J., Anal. Chem., 1994,66, 1825. Tyson, J. F., J . Flow Injection Anal., 1993, 10, 19.5. Pollerna, C. H., Dissertation, University of Washington, 1994. Life Science and Analytical Research Products. Catalogue & Handbook, Pierce, Rockford, IL, 1994. 38 Haughland. R. P., Molecular Probes. Handbook of Fluorescent Probes and Research Chemicals. Molecular Probes, Eugene, OR, 1992. Hull, R. D., Malick. R. E., and Dorsey, J. G., Anal. Chim. Acta, 1992,267, 1. Dorsey. J . G., paper presented at the Winter Conference on Flow Injection Analysis, San Diego, CA, 1993; unpublished results. Paper 4102055C Received April 6, I994 Accepted May 20, 1994 39 40

ISSN:0003-2654    

DOI:10.1039/AN9941901925

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, September 1994, Vol. 11 9 1935 Atomic Force Microscopic Determination of Substrate Effects on the Structure of Deposited Biomineral Phosphates Lorraine M. Siperko IBM Microelectronics Division, Endicott, N Y 13760-5533, USA William J. Landis Harvard Medical School and Children's Hospital, Boston, MA 021 15, USA Periodicity observed by atomic force microscopy on the surface of two biological crystals, hydroxyapatite (HA) and brushite (DCPD), has allowed identification of crystal planes indicative of preferred orientation on several substrates. From isolated HA crystal clusters, deposited on to a glass substrate, two crystal planes were identified. The (001) and (110) spacings of HA are in agreement with published values taken from crystallographic data. Measurements made on DCPD platelets, deposited on to glass, yielded atomic spacings presumed to be those of the (110) crystal plane.For both minerals, comparison of atomic-scale imaging showed differences between deposits on glass or freshly cleaved mica. Larger scale structure was also found to differ when the mineral deposits were compared on gold, glass and mica. A very ordered structure was found when HA was deposited on to a gold substrate that had been modified with a monolayer of an alkane thiol. These observations suggest that different substrates influence the final structure of the crystals as determined by atomic force microscopic surface characterization. Keywords: Atomic force microscopy; hydroxyapatite surface structure; brushite surface structure; substrate effects Experimental Crystals of HA and DCPD were prepared and characterized as described previousIy.5,22,23 The biominerals, in powdered form, were prepared for AFM imaging by suspending 1 mg of each in 1 ml of absolute ethanol.After gentle sonication of the respective suspensions, aliquots were deposited on to the substrates. Gold substrates, which consist of predominant gold (111) planes, were prepared as described earlier.24 The self-assembled alkane thiolate monolayer substrate was pre- pared according to the method of Porter et al.25 The resulting chemisorbed alkane thiolates were previously found to form densely packed arrays with an average 30" tilt from the surface normal26727 having a ( q 3 x d3)R30° adlayer structure at gold (111) .2*,29 The deposited biomineral samples were dried in air and images were obtained in air with a Digital Instruments (Santa Barbara, CA, USA) Nanoscope I1 atomic force microscope.Silicon nitride integrated tips were used for all the measurements. Low resolution images are presented as unfiltered data. High resolution, atomic-scale images were subjected to low-pass filtering. Neither ultrahigh vacuum nor liquid media were required to obtain the images. No special sample treatments were needed before imaging. Introduction Biomaterials that play a significant role in biological tissue mineralization are being probed by atomic force microscopy (AFM). As many processes occurring in living systems take place at surfaces or interfaces, information gained from surface studies could prove invaluable in elucidating many interactions including those between biominerals and tissues.Biominerals such as hydroxyapatite (HA) and brushite (DCPD) are found naturally in hard tissues such as bones and teeth. The seeding and dissolution kinetics of both minerals have been studied,lJ and certain of their structural properties have been analysed by techniques such as X-ray diffraction and transmission electron mi~roscopy.~-1o Presently, both HA [Calo(P04),(OH),] and DCPD [CaHP04.2H20] have been characterized in this manner,11-13 but the details regarding their surface features remain to be described. The advent of AFM and its use in the study of biological materialsl4-16 has provided the research vehicle for recent investigations of the surfaces of biominerals17-20 and collagen .21 Previous work with AFM has shown surface structural similarities between HA and DCPD,'9J' each deposited on to glass substrate.Subsequent examination of the two types of biominerals deposited on to substrates different from glass indicates that the surface to which the minerals are applied may affect the crystallographic orientation, as observed by AFM. The results of these studies are presented here. Results and Discussion Initial studies into the feasibility of imaging biomineral powders by AFM led to the development of a method for affixing the powders to a substrate.18 Tests of the method on NaCl deposited on to a glass substrate yielded lattice periodicity consistent with literature values for the NaCl face-centred cubic structure observed by AFM under non- ambient ~onditions.3~331 This method has been applied in this paper to atomic-scale and larger imaging of HA and DCPD on very smooth substrates such as glass, mica and gold.The reported measurements made here are accurate within the same limits of error as a series of measurements made on a known standard (NaCI) which was found to be within 5% of the reported value. HA deposited on to glass showed a surface structure that was predominantly the (001) and (110) crystal planes, having measured periodicites of 0.68 and 0.43 nm, respectively. On mica, HA measured atomic distances were larger, but they compared well with Ca-Ca distances reported in the l i t e r a t ~ r e . ~ ~ DCPD atomic-scale images on glass yielded spacings of 0.45 and 0.60 mm, consistent with those reported for the DCPD (110) crystal plane.On mica, however, the observed spacings for DCPD (0.37 nm) were correlated with the reported shortest Ca-Ca distance in a calcium phosphate corrugated sheet structure .33 In addition to these effects of the substrate on preferred crystal orientation, differences in larger scale surface charac- teristics were also noted. HA images on gold, glass and mica1936 Analyst, September 1994, Vol. I 1 9 are shown in Fig. 1. Within a 1000 x 1000 nm scan area, most of the surface features observed when HA is deposited on to gold [Fig. l ( a ) ] arise from the gold itself. Areas between the smooth, flat gold islands consist of HA particles of the order of 400 nm. This agglomeration of particles indicates that the HA is deposited at the gold island edges, rather than on the relatively flat islands themselves.The edges are most likely an area of higher surface energy that provide sites for deposition of large particles. This characteristic gives rise to the appear- ance of vertical furrows that outline the substrate islands. Appearance of the furrows may suggest alignment by the imaging probe; however, over a large range of field we have observed no evidence for alignment. On glass, HA also tends to form clusters, in 'this instance approximately 350 nm in length, as shown in Fig. l ( b ) . The clusters are well-isolated as the glass substrate is essentially featureless and displays no topography that would lend to agglomeration or clustering of (a) particles as do the edges of the large gold islands.On mica, which is composed primarily of relatively flat islands similar to those of gold, the HA forms spherical particles 500-1000 nm in diameter or elongated structures measuring 700-1500 nm. The background structure is not, however, reflective of bare mica. As shown in Fig. l(c), smaller structures with a fan-like shape appear as the background for the larger HA structures on mica. The appearance of both background and larger structures for the HA deposit on mica could be due to the observed area being one of larger concentration; however, no similar background structure was found for HA on glass or gold although concentrations in the ethanolic suspensions were identical. DCPD deposited on gold yields a granular structure over a large (1000 x 1000 nm) area, taken to be representative of the sample surface, as shown in Fig.2(a). In contrast to HA on gold, there seems to be very little clustering o r agglomeration of DCPD, which indicates that there are differences in the Fig. 1 ( a ) HA on gold. 1000 x 1000 nm AFM image. Although this region may suggest tip alignment, this was found not to be the case. For details see test. (b) HA on glass. Cluster shown is approximately 350 nm in length (c) HA on mica. For details see text. Fig. 2 ( a ) DCPD on gold. 1000 X loo0 nm AFM image. For details see text. ( h ) DCPD on glass. Flat platelets appear in the AFM image. (c) DCPD on mica. For details see text.Analyst, September 1994, Vol. 119 1937 interaction of the two minerals with gold.A 500 X 500 nm image of DCPD on glass shows flat platelets, again with no clustering of particles [Fig. 2(b)]. On mica, DCPD is clustered although not to the extent observed for HA on mica. The DCPD spherical deposits on mica range from 500 to 1200 nm in size, and no elongated structures are observed. As with HA on mica, the background structure in the presence of DCPD is not reflective of mica alone. In this instance, web-like features with no crystals apparent at this resolution are detected as shown in Fig. 2(c). Fig. 3 shows a 1000 X 1000 nm image of HA applied as a droplet to a gold substrate that was modified with a monolayer of octadecane thiol. When the thiolate monolayer alone is applied to gold ( 11 1) a very ordered surface, consisting of the methyl-terminated end groups, is the result.25 When HA is applied to such a surface, features characteristic of the monolayer-covered gold arc masked by those attributed to HA.On a large scale, a very ordered surface appears consisting of regular patterns spaced approximately 2500 nm apart [Fig. 3(b)]. Closer inspection reveals that this pattern is composed of small HA particles or clusters of particles approximately 200-350 nm in size, as shown in Fig. 3(c). It is interesting that an order is imposed on the biomineral by such a relatively neutral surface. The terminal methyl groups of the alkane thiol provide a substrate surface that is not only Fig. 3 ( a ) HA on gold substrate that was modified with a monolayer of an alkane thiol. (h) AFM line projection showing 2.500 nm macroscopic periodicity of HA deposited on alkane thiolate modified gold. ( c ) AFM line projection showing that the macroscopic HA structure in (6) is composed of particles approximately 1.50-300 nm in size.chemically unreactive, but also extremely smooth and of very low energy. It is clear that surface order must play a significant role in influencing the structure of the HA deposit. Conclusions In general, it is extremely important to recognize that the surface properties of a particular substrate may have an effect on the structure of certain deposited materials, in this instance the biominerals HA and DCPD. A gold substrate provides an ordered, well-defined and chemically unreactive surface for the force microscopic study of HA and DCPD. The observa- tions that HA and DCPD yield different structures on deposition over gold, HA forming clusters at gold island edges and DCPD forming an apparent continuous structure over the entire gold substrate, indicate that physical interaction, possibly relating to areas of high and low energy sites on the gold surface, influences the deposited mineral structure.The respective surfaces of glass and mica are chemically similar to one another, each composed of relatively large numbers of -OH groups, but the degree of surface order varies and gives rise to different physical properties of glass and mica. The distinct surface orders may account, in part, for the differences observed for HA and DCPD on glass and mica. The importance of surface order is also reflected in the apparent change in structure of HA on a low energy, chemically unreactive, but highly ordered substrate such as alkane thiolate modified gold.An additional consideration in studies of the influence of substrates on deposits is that of surface charge, residing on the surface of both the biomineral and the substrate as the deposit forms from its liquid suspension. AI though precise explanations of the particle substrate interactions are not yet possible because of the complexity of physical and chemical effects, the collective observations presented here indicate clearly that the nature of interfacial interaction deduced from force microscopic imaging depends critically on the choice of substrates to which materials such as biominerals are applied. Consistent data can be obtained through appropriate understanding of possible chemical and physical interactions between the biomineral and ubstrate.Experiments are planned to address these issues. Y The authors thank Professor M. D. Porter of Ames Labora- tory, Iowa State University, for graciously supplying the gold and alkane thiolate-modified gold substrates. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 References Barone, J . P., Nancollas, G . H . , and Tomson, M., Calcif. Tissue Res.. 1976, 21, 171. Zhang, J . , and Nancollas. G . H . , Adv. Znd. Cryst., 1991, 47. Ji, H . , and Marquis, P. M., J. Muter. Sci. Lett., 1991, 10, 132. Landis. W. J . , Moradian-Oldak, J . , and Weiner, S., Connect. Tissue Res., 1991, 25, 181. Landis, W. J . . and Glimcher, M. J . , J. Ultrastruct. Res..1978, 63, 188. Kay, M. I . , Young, R. A . . and Posner, A. S., Nature (London), 1964. 204, 1050. Skinner, H. C. W., Hunt, H . T., and Griswold, J . . J. Phys. E, 1980, 13.74. Curry, N . S., and Jones, D. W., Z. Kristallogr., 1987,181,205. Plovnik, R. J . , J. Cryst. Growth, 1991, 114, 22. Ohta, M . , and Tsutsumi, M . , J. Cryst. Growth, 1981. 56, 652. Grynpas, M. D.. J. Mafer. Sci., 1976, 11, 1691. Glimcher, M. J . , Bonar, L. C., Grynpas, M. D., Landis, W. J . , and Roufosse, A. H . , J. Cryst. Growth. 1981, 53, 100. Lee, D. D., Landis, W. J . , and Glimcher, M. J . , J. Bone Miner. Res., 1986, 1, 425. Binnig, G . , Quate, C. F., and Gerber. Ch., Phys. Rev. Lett., 1986,56. 930.1938 Analyst, September 1994, Vol. 119 15 16 17 18 19 20 21 22 23 24 Freidbacher, G., Hansma, P.K., Ramli, E., and Stucky, G. D., Science, 1991, 253, 1261. Radmacher, M., Tillman, R. W., Fritz, M., and Gaub, H. E., Science, 1992, 257, 1900. Siperko, L. M., and Landis, W. J.. Muter. Res. SOC. Symp. Proc. , 1992, 295, 243. Siperko, L. M., and Landis, W. J., Appl. Phys. Lett., 1992.61, 2610. Siperko, L. M., and Landis, W. J., J. Muter. Sci. Lett., 1993,12, 1068. Landis, W. J., and Siperko, L. M., Connect. Tissue Res., 1992, 27, 125. Siperko, L. M., and Landis, W. J., paper presented at the Atomic Forcekanning Tunneling Microscopy Symposium, US Army Natick RD&E Center, Natick, MA, USA, June 8-10, 1993. Moreno, E. C., Brown, W. E., and Osborn, G., Soil Sci. Suc. Am. Proc., 1960, 24, 94. Roufosse, A. H., Landis, W. J., Sabine, W. K., and Glimcher, M. J., J. Ultrastruct. Res., 1979, 68, 235. Widrig. C. A.. Chune. C., and Porter, M. D., J. Electroanal. 25 26 27 28 29 30 31 32 33 Smith, E. L., Alves, C. A., Andregg, J. W., Porter, M. D., and Siperko, L. M., Langmuir, 1992,8,2707. Laibinis, P. E., Whitesides, G. M., Allara, D. L., Tao, Y.-T., Parikh, A. N., andNuzzo, R. G., J. Am. Chem. Soc., 1991,113, 7152. Porter, M. D., Bright, T. B.. Allara, D. L., and Chidsey, C. E. D., J . Am. Chem. Soc., 1987, 109, 3559. Strong, L., and Whitesides, G. M., Langmuir, 1988, 4, 54. Alves, C. A., Smith, E. L., and Porter, M. D.. J. Am. Chem. Soc., 1992, 114, 1222. Marti, O., Drake, B.. and Hansma, P. K., Appl. Phys. Lett., 51, 484. Meyer, G., and Amer, N. M., Appl. Phys. Lett., 1990,56, 21. Francis. M. D., and Webb, N. C., Calcif. Tissue Res., 1971, 6 , 335. Beevers, C. A., Acta Crystallugr.. 1958, 11, 273. Paper 4100550C Received January 28, 1994 Chemr, 1991, 310, 333. Accepted April 11, 1994

ISSN:0003-2654    

DOI:10.1039/AN9941901935

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, September 1994, Vol. 11 9 1939 Imaging Glucoamylase by Scanning Tunnel I i ng Microscopy A. Patrick Gunning, Victor J. Morris,* Gary Williamson and Nigel J. Belshaw Institute of Food Research, Norwich Laboratory, Norwich Research Park, Colney, Norwich, UK NR4 7UA Gerard F. H. Kramer and Marja W. Kanning Department of Food Chemistry and Microbiology, Wageningen Agricultural University, Wageningen, The Netherlands Images of the enzymes glucoamylase 1 and glucoamylase 2 and G1C (a proteolytically derived C-terminal fragment of glucoamylase 1) have been obtained by scanning tunnelling microscopy (STM). The images of glucoamylase 2 and G1C show that these proteins are nearly spherical globular proteins. In contrast, images of glucoamylase 1 show that it is a dumb-bell shaped globular protein.Problems encountered in (i) imaging these proteins and (ii) validating and interpreting the images obtained by STM are discussed. Keywords: Scanning tunnelling microscopy; atomic force microscopy; scanning probe microscopy; glucoamylase; biomolecule Introduction Scanning tunnelling microscopy (STM) is one of several scanning probe microscopy (SPM) methods which have been used to image biopolymers. Large numbers of proteins have been imaged by STM either as single or as ordered Despite this it is still difficult to obtain reliably, images of uncoated proteins deposited on to sub- strates unless they can be prevented from being swept aside by the STM tip, by for example coaxing the molecules under investigation to form two-dimensional ordered arrays on the substrate, or by covalently attaching them to the substrate.1”- 14 Also, despite the inherent high resolution of STM, at present it has only been possible to obtain molecular resolution in STM images of proteins.This means that the technique cannot rival methods such as X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy in terms of details of structural resolution. However, STM and the other forms of SPM are useful for visualizing large and/or complex protein molecules that are difficult to crystallize. The techniques also offer the advantage of being able to work at ambient temperatures and pressures in air or under liquids, closely matching typical environments for biological systems. 15.16 Complex molecules such as glucoamylase 1 are difficult to crystallize without chemical modification (deglyco- sylation) and are also unlikely to form two-dimensional ordered arrays easily.The large molecular mass of these proteins makes structural analysis by NMR spectroscopy difficult. Hence such complex proteins present a challenge for study by SPM. In order to obtain information on their shape, they have to be imaged as isolated molecules. Given the scarcity of suitably developed methods for covalent attach- ment of molecules to substrates, this is usually the most difficult way to image proteins. In this paper some of the * To whom correspondence should be addressed problems encountered are illustrated through a study of the enzyme glucoamylase 1. Glucoamylase 1 Glucoamylase 1 (glucan-l,4-a-glucosidase, EC 3.2.1.3) from Aspergillus niger is one of two related naturally occurring starch degrading enzymes.Its primary sequence contains two domains: catalytic domain residues 1-470 and C-terminal domain residues 509-616, linked by residues 471-508 contain- ing 70% m/m carbohydrate.l7-19 The second form of glu- coamylase (glucoamylase 2) consists of residues 1-512 of glucoamylase 1 and is essentially the catalytically active part of the enzyme plus the linker peptide. The linker region in glucoamylase 1 is heavily glycosylated containing short oligosaccharides, mainly mannose, 0-linked to serine or threonine.20 The sugars in glucoamylase 1 have been impli- cated in increased thermostability of the enzyme21 and in conferring rigidity to the glycopeptide linker, serving to separate spatially the two domains.’’ Williamson et a1.2’ have observed from NMR measurements that the two domains within glucoamylase 1 tumble at different rates, implying that they are spatially separated, and have also concluded from NMR and circular dichroism (CD) measurements that the linker glycopeptide is extended and rigid.Only preliminary data have been obtained for the crystal structure of glucoamy- lase 2,23 and this required deglycosylation of the enzyme. The two enzymes (glucoamylase 1 and 2) have different roles in nature. Glucoamylase 1 is able to bind and attack granular starch (i.e., insoluble starch) with a high efficiency in addition to starch already in solution, whereas gluycoamylase 2 attacks soluble starch but, lacking the ability to bind granular starch, attacks it only very slowly.24 It has been shown that the C-terminal domain in glucoamylase 1 acts as a binding domain.25 It has been postulated that these properties are utilized by Aspergillus niger, which secretes first glucoamylase 1 and then when sufficient starch has been rendered soluble switches to the production of glucoamylase 2 which requires less synthesis.Experimental Glucoamylase 1 (residues 1-616), glucoamylase 2 (residues 1- 512) and a proteolytically derived fragment named G1C (residues 471-616: C-terminal domain of glucoamylase 1 plus linker glycopeptide) were prepared and purified as described previously.22J5 STM samples were prepared by dissolving the freeze-dried powders in distilled water at a concentration of 1 mg ml-1 and centrifuging at lOOOOg for 10 min to remove large aggregates and denatured protein.The supernatant solution was removed and 2 yl aliquots were deposited on to highly oriented pyrolytic graphite (HOPG). The samples were1940 Analyst, September 1994, Vol. 119 allowed to dry in air at room temperature. The effect of drying glucoamylase 1 in the presence and absence of graphite was determined. A solution of glucoamylase 1 (0.5 mg ml-1) was dried using a speed vac at 30-40 "C in the absence or presence (0, 12, 37 and 51 mg ml-l) of powdered graphite. After drying, an equal volume of 0.02 mol I-' tris(hydroxymethy1)- methylamine hydrochloride (Tris-HCI) of pH 8.0 was added, and after 30 min the samples were centrifuged at 1OOOOg for 5 min.The supernatant solutions were assayed for glucoamylase activity22 and the absorbance of 280 nm was measured. The STM used was a commercial instrument manufactured by WA Technology (Cambridge, UK). Images were recorded in the constant-current mode in air under ambient conditions using electrochemically etched tungsten tips. The quality of the tips was assessed by imaging the HOPG substrate at atomic resolution, before and after examination of the samples. Operating conditions were typically: tunnel current, 50 PA; and sample bias, +800 mV. Results and Discussion The results of the drying experiment shown in Table 1 demonstrate that the graphite retains some glucoamylase protein but that the specific activity of the enzyme is unchanged, except for the highest graphite concentration where the specific activity is 12% lower. These results, when compared with those for the untreated enzyme, demonstrate that: (a) drying and rehydration does not denature glucoamy- lase 1; (b) graphite adsorbs some of the glucoamylase 1 and the enzyme is not fully eluted by Tris buffer; and (c) below a ratio of glucoamylase 1 to graphite of 1: 100 (m/m), no denaturation of the enzyme occurs.This suggests that the glucoamylase 1, when dried on to graphite for STM, is not denatured. A preparative technique widely used in electron microscopy and adopted for STM is to overcoat the molecules with Pt/C. This immobilizes the molecules and the conductive layer aids imaging. However, the resolution achievable is limited by the grain size of the coating, and the evacuation step in the preparative procedure can lead to irreversible changes in protein structure.2 For these reasons the present work has been confined to studies on uncoated molecules.Although surface tension forces may distort the molecules during drying, the above studies suggest that such changes are not irreversible. It is widely accepted that there is considerable force between an STM tip and the surface it scans, making it difficult to image molecules that are not in some way bound to the surface.26 For systems where two-dimensional ordered arrays cannot be formed this very often results in images of the molecules either (i) as amorphous aggregates the size of which increases their likelihood of resisting tipsample forces which would otherwise sweep them clear of the scan area, or (ii) trapped at steps or faults on the substrate surface.The nature of this entrapment of molecules against steps or faults ih the HOPG surface means that images of the molecules are only obtained infrequently and are usually associated with surface defects, raising the possibility of imaging artifacts of the ~ u b s t r a t e . ~ ~ J 8 In several studies of glucoamylase 1 both of these cases have been observed. The images presented in Fig. l(a)-(d) are representative of the small groups of features seen, which have been trapped at a fault on the HOPG surface. There are sufficient images of these clusters to suggest that they are glucoamylase 1 molecules. Fig. 2 is a lower magnification image showing groups of proteins trapped at faults on the HOPG surface.The high magnification images (Fig. 1) show that the molecules are dumb-bell in shape containing two domains. Images of individual glucoamylase 1 molecules were examined at various samples bias and tunnel currents. No significant changes in sample contrast or dimensions were observed, although only positive sample biases were investigated. However, at low sample bias (<700 mV at,a tunnel current of 0.3 nA), streaking was observed, possibly owing to tip-sample interaction. Images of amor- phous aggregates have also been obtained subsequently, but given the apparent dumb-bell shape seen in the images of isolated molecules, it is difficult to deduce the shape of individuals within the aggregates. For the images obtained of isolated molecules an obvious interpretation is that the two bright regions represent the binding and catalytic domains, which in the primary sequence of glucoamylase 1 are Fig.1 Unprocessed STM images of clusters of glucoamylase 1 molecules trapped at surface faults. Image size: ( u ) 38.8 x 38.8; ( b ) 19.4 x 19.4; ( c ) 41.9 x 41.9; and ( d ) 39.6 x 39.6 nm. For all images tunnel currcnt = 100 PA; sample bias = 500 mV. Grey scale (black to white): 0-1.1 nm. Table 1 Effect of drying and rehydration on glucoamylase 1 activity Glucoamylase 1 in supernatant solution Relative after rehydration/ specific Sample treatment vg ml-I activity None 50 100 Drying with: Drying 48 99 12 mg ml- graphite 45 99 51 mgml-l graphite 31 88 37 mg ml-' graphite 34 103 Fig. 2 Unprocessed STM image of clusters of glucoamylase 1 molecules trapped at defects in the HOPG surface. Image size: 449 x 449 nm; tunnel currcnt = 100 Pa; sample bias = 500 mV.Grey scale: 0-5.9 nm.Analyst, September 1994, Vol. 11 9 1941 8 - 6 - > C 3 F4 LL 2 - 0 ~ separated by the linker glycopeptide. This conclusion is premature, however, without any supportive evidence, because the mechanism of image contrast in STM of biomolecules is by no means clear.29 The simplest way of testing this idea is to study the catalytic and binding domains of glucoamylase 1 as separate molecules and compare the images obtained with images of the intact enzyme. This was effected by imaging the related enzyme glucoamyl- ase 2 and the proteolytically derived binding domain fragment G1C described above.These proteins have molecular masses of 5.2 X 104 and 1.1 x 104 Da, respectively, and so would be expected to differ in size. During the preparation and imaging of these two samples their identity was concealed from the operators. This use of blind trials was employed in an effort to avoid operator bias in the collection and analysis of images. Images of both samples were frequently obtained as large amorphous aggregates. Many of the aggregates were simply too large to resolve with any detail, but it was possible to find other regions that were sufficiently thin to achieve molecular resolution. Even so the conditions needed to acquire relatively clean images were fairly low tunnel current (typically 10-50 PA), high bias voltages (typically 800 mV) and slow scan speeds (typically 4 >220 s per image).These conditions combine to give a large tipsample distance and time for the feedback loop of the STM to control the position of the tip above the molecules, thus minimizing streaking caused by t i p sample contact, but also lowering image resolution. The images obtained (examples are shown in Figs. 3 and 4) show - 1 1 1 1 1 1 1 I 1 Fig. 3 Unprocessed STM image of an aggregate of glucoamylase 2 molecules. Image size: 79.9 x 79.9 nm; tunnel current = 50 Pa; sample bias = 800 mV. Grey scale: 0-2.4 nm. Fig. 4 Unprocessed STM image of an aggregate of G1C molecules. Imagc size: 79.5 x 79.5 nm; tunnel current = 100 Pa; sample bias = the proteins to be globular and nearly spherical. The shapes of the proteins are inferred from their measured lateral dimen- sions and calculated molecular size determined from known molecular masses.30 Estimates of shape cannot be based on measured heights from STM which depend on an unknown contrast mechanism and cannot be expected to be equal to the true ‘height of the protein’.Analysis of the sizes of the proteins gives two distinct size ranges,30 which are consistent with known and calculated sizes of the samples supplied.30.31 Therefore, blind analysis of the STM images correctly revealed the identity of each sample. The median sizes for the isolated fragments, glucoamylase 2 and GlC, are 8.5 and 3.0 nm, respectively, based on the analysis of the profiles measured for about 70 molecules. The median sizes for the two bright regions in the images of the intact enzyme glucoamylase 1 are 8.5 and 5.0 nm based on the analysis of profiles of about 20 molecules. Summary of Findings Comparison of the images obtained for the isolated binding domain, GlC, and catalytic domain, glucoamylase 2, suggests that the images obtained of trapped clusters in isolation are indeed of molecules and that the larger bright region in the images corresponds to the catalytic domain within the intact enzyme, glucoamylase 1, and that the smaller bright region corresponds to the binding domain.The measured range of sizes of the catalytic domain within the intact enzyme, glucoamylase 1, is very similar to the range of sizes measured for the catalytic fragment, glucoamylase 2. However, the size range for the binding domain within the intact enzyme, glucoamylase 1, differs slightly from the range of sizes measured for the proteolytically derived binding domain fragment, G1C.The measured sizes indicate that the frag- ment, GlC, is slightly smaller after proteolytic cleavage from glucoamylase 1. A detailed analysis of the sizes of all three of the samples is given elsewhere.30 Having identified the features in the images of the intact enzyme glucoamylase 1 as the domains predicted from the primary structure it is possible to measure the inter-domain spacing and hence infer properties of the glycopeptide linker which seprates them. The histogram shown in Fig. 5 illustrates the variation of inter-domain spacing seen in the images (measured as the distance between centres of domains). The range of inter-domain spacing measured is fairly narrow, implying that the glycopeptide linker is reasonably rigid.The fact that the domains are spatially separated also reveals that the glycopeptide linker is extended. Both of these suggestions are consistent with previous measurements made using NMR 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 Distance between centrednm Fig. 5 Histogram of the measured spacing between the domains in S O 0 mV. Grey scale: 0-3.0 nm. glucoamylase 1.1942 Analyst, September 1994, Vol. 1 I9 spectroscopy and CD.22 The glycopeptide linker region has not been visualized in any of the images of the intact enzyme, glucoamylase 1 or the fragments of it, glucoamylase 2 and G1C. This may be due to the nature of the linker which is rigid and extended, making it possible that it is never directly in contact with the substrate.Also, the linker consists of just a single chain of amino acids coated with sugars, so will be very small by comparison with the domains which seem to dominate the image contrast. If the individual domains are assumed to be spherical with a partial specific volume of 0.74 x m3 g-l, then it is possible to calculate the inter-domain spacing for a fully extended glycopeptide linker. Comparison of this value with the measured inter-domain spacing would suggest about 40% extension of the linker glycopeptide. Conclusions Images have been obtained of the enzyme glucoamylase 1 and fragments of it, glucoamylase 2 and G1C. The images obtained of glucoamylase 1 show that it is a dumb-bell shaped molecule.By comparison of images of the intact enzyme and its constituent parts in isolation, the images of glucoamylase 1 can be validated and the domains within the enzyme can be assigned. Despite the limitations of the technique, this study shows that by adopting a careful and planned approach it is possible to validate and interpret STM images of biomole- cules. Separate studies have been made to demonstrate that the deposition on to graphite does not alter the activity of the enzyme and that the enzyme is not denatured. These studies also provided evidence that a fraction of the enzyme can be tightly bound to graphite. This is consistent with the observa- tion of the enzyme decorating defects on the HOPG surface. The study also demonstrates the potential for STM and SPM to provide new information which is difficult to obtain by, for example, X-ray crystallography, which requires alteration of the molecule by deglycosylation in order to cause it to crystallize. References Faruqui, A.R., Cross, R. A., and Kendrick-Jones, J., J. Appl. Crystallogr., 1991, 24, 852. Welland, M. E., Miles, M. J., Lambert, N., Morris, V. J., Coombes, J. H., and Pethica, J . B., Int. J. Biol. Macromol., 1989, 11, 29. Edstrom, R. D., Meinke, M. H., Yang, X., Yang, R., and Evans, D. F., Ultramicroscopy, 1990,33, 99. Guckenberger, R., Wiegrabe, W., Hillebrand. A., Hartmann, T., Wang, Z., and Baumeister, W., Ultramicroscopy, 1989,31, 327. Miles, M. J . , McMaster, T. J., Carr, H. J., Tatham. T. J., Shewry, P. R., Field, J. M., Belton, P.S., Jeens, D., Hanley, B., Whittam, M., Cairns, P., Morris, V. J., and Lambert, N., J. Vac. Sci. Technol. A, 1990,8,698. 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 McMaster, T. J., Carr, H. J., Miles, M. J., Cairns, P., and Morris, V. J., J. Vac. Sci. Technol. A , 1990, 8,648. Breen, J . J., and Flynn, G. W., J. Phys. Chem., 1992,96,6825. Stemmer, A., and Engel, A., Ultramicroscopy, 1990, 34, 129. Guckenberger, R., Hacker, B., Hartmann, T., Scheybani, T., Wang, Z., Wiegrabe, W.. and Baumeister, W., J. Vac. Sci. Technol. B , 1991,9, 1227. Legget, G. J., Roberts, C. J . , Williams, P. M., Davies, M. C., Jackson, D. E., and Tendler, S. J . B., Langmuir, 1993,9,23.56. Ill, C. R., Keivens, V. M., Hale, J. E., Nakamura, K.K., Jue, R. A., Cheng. S., Melcher, E. D., Drake, B., and Smith, M. C., Biophys. J., 1993, 64, 919. Heck], W. M., Kallury, K. M. R., Thompson, M., Gerber, Ch., Horber, H. J. K., and Binnig, G . . Langmuir, 1989, 5 , 1433. Lindsay, S. M., Tao, N. J.. De Rose, J. A., Oden, P. I., Lyubchenko. Y. L., Harrington, R. E., and Shlyakhtenko, L., Biophys. J., 1992, 61, 1570. Lyubchenko. Y. L.. Lindsay, S. M., De Rose, J. A . , and Thundat, T., J. Vac. Sci. Technol. B, 1991,9, 1288. Drake, B., Prater. C. B., Weisenhorn, A. L., Gould, S. A. C., Albrecht, T. R., Quate, C. F., Cannell, D. S., Hansma, H. G., and Hansma, P. K., Science, 1989, 243, 1586. Haberle, W., Horber, J . K. H.. Ohnesorge, F., Smith, D. P. E . , and Binnig, G., Ultramicroscopy, 1992, 42-44. 1161. Svensson, B., Larson, K., Svendsen, I., and Boel, E., Carlsberg Res. Commun., 1983,48,529. Svensson, B.. Hespersen, H., Sierks, M. R., and MacGregor, E. A., Biochem. J., 1989, 264, 309. Evans, R.. Ford, C., Sierks, M., Nikolov, Z., and Svensson, B., Gene, 1990, 91, 131. Gunnarsson, A., Svensson, B., Nilsson, B., and Svensson, S., Biochemistry, 1984, 145, 463. Shendy, B. G., Rao, A. G. A., and Rao, M. R. R., J. Biosci., 1984, 6, 601. Williamson, G., Belshaw, N. J., and Williamson, M. P., Biochem. J., 1992,282.423. Goluber, A. M., Neustroev, K. N., Aleshin, A. E., andFirsov, L. M., J. Mol. B i d , 1992, 226, 271. Svensson, B., Pedersen, T. G., Svendsen, I., Sakai, T., and Ottesen, M., Carlsberg Res. Commun., 1982,47, 55. Belshaw, N. J., and Williamson, G., FEBS Lett., 1990,269,350. Nawaz, Z . , Cataldi, T. R. I.. Knall, J., Somekh, R., and Pethica. J. B., Surf. Sci., 1992, 265, 139. Clemmer, C. R., and Beebe, T. P., Jr., Science, 1991,251,640. Heck], W. M., and Binnig, G., Ultramicroscopy, 1992, 42-44, 1073. Guckenberger. R., Hartmann, T., Wiegrabe, W., and Baumeis- ter, W., in Scanning Tunnelling Microscopy II, eds. Weisen- danger, R., and Guntherodt, H. J., Springer Series in Surface Science, Springer-Verlag, Berlin and Heidelberg, 1992, vol. 28, Kramer, G. F. H., Gunning, A. P., Morris, V. J., Belshaw, N. J., and Williamson, G., J. Chem. Suc., Faraday Trans., 1993. 89, 259.5. Aleshin, A., Goluber, A., Firsov, L. M., and Montzatko, R. B., J. Biol. Chem., 1992, 267, 19291. ch. 3, pp. 51-98, Paper 4100552J Received January 28, 1994 Accepted March 29, 1994

ISSN:0003-2654    

DOI:10.1039/AN9941901939

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Analyst, September 1994, Vol. 119 1943 Imaging Flagella of Halobacteria by Atomic Force Microscopy Manfred Jaschke and Hans- Jiirgen Butt Max- Planck Institut f u r Biophysik, Kennedyallee 70, 60596 Frankfurt am Main, Germany Elmar K. Wolff Institut f u r Technologieentwicklung und Systemanalyse, Stockumer Str. 10, 58453 Witten, Germany Halobacterial flagella were adsorbed on mica and imaged with an atomic force microscope in air. Different assemblies such as large, net-like structures, and straight flagella aligned by flow were observed. The hypothesis of individual flagellar motors was confirmed by frequent observation of knobs at the end of single flagella. A periodic substructure was observed along flagellar strands with a spacing of 50- 100 nm. The diameter of halobacterial flagella was determined as 11 k 4 nm.The influence of two different preparations on the flagellar profile, and reasons for the distortion of height and width are discussed. Keywords: Halobacteria; flagella; atomic force microscopy; flagellar motor; super-flagella; tip broadening Introduction The atomic force microscope (AFM) invented by Binnig, Quate and Gerber' has become an important tool for imaging surface topographies.* For biologists, the AFM is attractive, because it combines high resolution with the possibility of imaging uncoated and unstained specimens.3-5 In addition, the specimen do not need to be exposed to vacuum. We used the AFM to image flagella of Halobacteria halobium. In contrast to flagella of Escherichia coli,G-8 much less is known about halobacterial flagella.In many bacteria, the flagella operate in bundles and form a left-handed helix. These left-handed helices can only rotate counterclockwise (looking towards the cell body).g Otherwise, the bundles fly apart and the bacteria start to tumble. In contrast, Alam and Oesterhelt") found that flagellar bundles of Halobacteria halobium have a right-handed helix that can rotate in both directions without flying apart. By clockwise rotation, the cell body is propelled forward, while counterclockwise rotation moves the cell in the reverse direction. Signal formation," signal transduction,12 switching between counter- and clock- wise rotation and the swimming behaviour of these bacterial3 have been studied in detail. Besides electron microscopy studies, most investigations have been performed by dark- field microscopy.14 In this way, the swimming mechanisms could be observed directly in vivo.Two possibilities as to how the rotation of flagella in the bundle is generated have been discussed. Either all flagella in a bundle converge into one motor endplate or each flagellum possesses an individual motor. While Spencer's reported that electron microscopy showed that the members of a bundle penetrate the cell surface in a tight coil, Marwan et a1.16 reported that single filaments originate from distinct points of the cell surface. The aim of this study was three-fold. We intended to measure the size of halobacterial flagella. Furthermore, we looked for substructure within individual flagella. Finally, we tried to ascertain whether the flagella of one bundle originate from only one motor endplate or if each flagellum has its own motor.Materials and Methods Cell Growth Conditions For the experiments reported here we used the Halobacterium halobium mutant FIx3 KM1 D1 strain. Cells were grown in complex medium at 39°C under illumination of white light.177'8 This strain was selected because the bacteria showed reproducible properties (size of bacteria, high mobility, similar swimming velocities) under constant growth condi- tions. For preparation of flagella, these cells were grown in 100 ml shake cultures and harvested at the end of their logarithmic growth phase. Preparation of Flagella A dark-field microscope with an oil-immersion condenser (aperture of 1.4) and front lenses with a primary magnification of between 10 and 2 6 ~ was used to monitor all steps of the preparation. We found that adsorption of halobacteria on glass was much weaker than on mica, as many more bacteria could be rinsed off glass with water.Mica was therefore used in all experiments. For flagellar preparation, a cell suspension was applied to an open chamber of about 100 pm depth (similar to the method of Stoeckenius et al.17) on freshly cleaved mica. In order to adsorb the cells and their flagella, the suspension was left in the chamber for at least 30 min. After flushing the preparation several times with a 4 mol I-' NaCl solution to rinse off non- adsorbed cells, an osmotic shock was applied to burst the cell bodies. The osmotic shock was applied in one of two different ways: (1) the sample chamber was rinsed excessively with 8 mmol I-' magnesium acetate to stabilize the flagellar struc- tures on the surface of mica and to clean the sample (referred to as preparation 1); and (2) the preparation of adsorbed cells was directly flushed with distilled water (referred to as preparation 2).A third preparation was also attempted. In this case, the osmotic shock was performed by stepwise reduction of the salt concentration. Although the specimen were also flushed with distilled water several times, the flagella seemed to bear a coating of amorphous salt. As a consequence, the heights and widths of the flagella differed significantly from those obtained by preparations 1 and 2. This third preparation was therefore rejected.I1944 Analyst, September 1994, Vol. I I9 Atomic Force Microscopy All images were taken in air with a NanoScope I1 AFM (Digital Instruments, Santa Barbara, California, USA). The D-Scanner with a scan range of about 13 X 13 pm2 was used. The AFM was operated in the constant-force mode. With scan rates of 7-20 Hz, 20-60 s were required to record one image. Silicon nitride cantilevers with a length of 100 or 200 ym and a sharpened integrated tip were used (Olympus, Tokyo, Japan). The applied forces ranged from between 1 to 10 nN. Results and Discussion The AFM images revealed different assemblies of adsorbed flagella. On a large scale we often observed net-like structures, as shown in Fig. l(a). Nets may arise during adsorption and the subsequent flushing.During these processes, flagellar bundles may partly detach and their flagella may orientate randomly. On the other hand, often flagella of different bundles converge into one strand. This indicates that flagella may also have a tendency to aggregate. Similarly, it is well- known that loose flagella can aggregate spontaneously into thick super-flagella. 10 Single flagella can be distinguished from flagellar bundles by ramifications. Indeed, the best way to detect single flagella is to follow their course up to the end and see whether they bifurcate. This procedure is rather simple and fairly reliable for finding single flagella. Fig. l ( b ) shows individual flagellar fragments, which were aligned by flow during excessive flushing in preparation. As a consequence, all flagella are oriented in the same direction. We did not detect the sine-shaped flagella frequently observed by dark-field microscopy in aqueous medium.10,19 ~ ~~ Often, bundles of flagella protruding from a piece of the bacterial membrane were observed [Fig. 2(a) and ( b ) ] . In Fig. 2(a), nine filaments are seen to form a flagellar bundle. This is in agreement with the results of Houwink20 who found five to 10 filaments in a bundle. These pictures also provide a basis for discussing how flagellar rotation is generated. As the flagellar complex shown in Fig. 2(a) has an extent of 250- 300 nm, it is too large to rotate as a whole. It can also be discerned that the flagella do not converge into a single point, but leave the complex at fairly distinct points.The complex shown in Fig. 2(b) contains a number of knobby substruc- tures. This indicates that the flagella do not originate from a single motor endplate. Furthermore, we often observed knobs at the end of isolated filaments [Fig. l(b)]. The occurrence of these knobs at the end of numerous flagella favours the hypothesis that each flagellum has its own motor. Similarly, Manvan et al. 13 reported that intact flagellar filaments could be isolated, each equipped with a basal body. Many images revealed a substructure of flagellar strands with a periodic character (Fig. 3). The spacing between adjacent vaults in these substructures ranged from 50 to 100 nm. As it is not possible to distinguish unambiguously individual filaments from a group of flagella, we could not decide whether the periodic substructure should be attributed to a single filament or to an assembly of several filaments.The length of most single flagellar fragments ranged from 2.5 to 4 pm. Nevertheless, we found flagella of up to 5.8 pm; this is greater than the value of 3.85 -t 0.10 pm reported for wild-type strains and the values of 3.90 k 0.10 pm and 3.85 k 0.02 pm reported for the mutants L-07 and M-175, respec- tively, by Alam and Oesterhelt.10 Fig. 2 (a) Nine flagella protrude from a piece of the burst bacterial membrane and form a flagellar bundle. As the flagella originate from distinct points, a common motor endplate is unlikely. ( b ) Very often, knobs can be seen at the end of flagella and surrounding residual pieces of the bacterial membrane. This observation favours the hypothesis of single individual motors. Fig.1 ( a ) Large net-like structures of adsorbed flagella were often observed. ( b ) halobacterial flagella aligned by flow during prepara- tion. The knob at the end of many of these flagella might be the flagellar motor complexAnalyst, September 1994, Vol. I1 9 1945 25 Besides length, we also investigated the height and width of adsorbed flagella. For these measurements, about 30 flagella from both preparations were considered, and each flagellum was measured several times at different sites. Fig. 4 shows the measured height distributions obtained via the two prepara- tions. The average height of the flagella is about 6.5 f 1 nm in preparation 1 and about 5.5 2 1 nm in preparation 2. The distibutions of flagellar widths are indicated in Fig.5. The average measured width is 17 k 3 nm in preparation 1 and 48 k 6 nm in preparation 2. Measured heights and widths did not depend on the imaging force. In air, the force between the tip and the sample is largely determined by the meniscus force. Hence, the force could only be varied by between, typically, 2 and 10 nN. With imaging in water, it can be further reduced to 0.1 nN, owing to the absence of the meniscus and reduced van der Waals forces. The initial experiments in aqueous electrolyte solution were not successful, because the flagella were not sufficiently immobilized. - 0 Prep. 1 Fig. 3 The spacing between adjacent vaults ranges from 50 to 100 nm. A periodic substructure can be observed along the flagella. 35 30 & 25 n 5 20 15 10 5 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 Heighthm Fig.4 measured for both preparations (preps.). Height distribution of adsorbed halobacterial flagella in air 0 10 20 30 40 50 60 70 Width/nm Fig. 5 Width distribution of adsorbed halobacterial flagella in air measured for both preparations. Widths were measured at half maximum of the flagellar profile. In Fig. 6, five flagella can be identified; these were prepared according to preparation 1. The flagella are embedded in a layer of cell debris. This layer was found in all preparations. As holes were found in the layer, its thickness could be estimated to 5 k 3 nm. Consequently, the measured heights of the flagella had to be corrected. Assuming that the flagella lay on the mica and were embedded in the layer of cell debris, the heights of the layer (5 nm) and the measured height of the flagella (6.5 nm) must be added.Hence, we obtained a height of 11 f 4 nm for the flagella from preparation 1. The difference to the width of 17 nm might be attributed to broadening of the tip geometry. On the other hand, the height is hardly influenced by the tip geometry. The flagella from preparation 1 thus appear to have a fairly round profile. Possibly, the magnesium ions stabilize the flagellar structures. The diameter of 11 k 4 nm agrees well with the diameter of about 10 nm reported by Typke et aZ.21 We did not find a similar layer of cell debris in samples obtained via preparation 2. As the measured height was of the same order as that of preparation 1, the geometric tip effect should also be of the same order.The average width of the flagella from preparation 2 was thus estimated to be 40 f 10 nm. Obviously, the flagella from this preparation appear to be rather flat and broad. The profiles observed for flagella from preparation 1 appeared more natural, whereas the flagella from preparation 2 appeared to be deformed. In particular, for soft specimens flattening may be a consequence of tight adsorption to the flat mica surface. Flattening can also occur during air-drying as a consequence of the meniscus force.22 In this aspect, the layer of cell debris observed for preparation 1 may stabilize the flagella. It may also immobilize the flagella and prevent distortions that could arise when the flagella are scanned by the tip.Assuming that the flagella are incompressible, the cross- sectional areas should be about the same in both preparations. From the corrected data of width and height, the sectional area of flagella from preparation 1 was estimated to be 95 f 45 nm2 (=x x 112/4 nm2). In making a rought estimate for preparation 2, we assumed that the flagellar profile was elliptic. Taking values of 5.5 nm and 40 nm for the main axes of the ellipse, the sectional area was calculated to be 170 k 70 nm2 (=n x 5.5 X 40/4 nm2). Although both sectional areas are of the same order and agree within their errors, they differ by about a factor of 2. Consequently, other reasons may contribute to the distortions of height and width. It is well known that friction can distort height measure- ments23 but not width measurements.The effect of friction on the apparent height was investigated by rotating the sample. Thereby, the apparent height varied from about 1 to 1.5 nm. This effect applied to the height measurement of flagella from both preparations. Furthermore, the layer of cell debris Fig. 6 Straight strands of individual flagella as obtained from preparation 1. The flagella are embedded in a layer of cell debris.1946 Analyst, September 1994, Vol. 119 observed in preparation 1 and the pure mica used in preparation 2 may cause different tip-sample interactions and hence influence height measurements. In addition, the geo- metric tip effects might differ slightly. Although for both experiments, the same type of cantilever was used, the tip geometry of two different cantilevers may not be the same.Another aspect should be taken into consideration. In peparation 1, the sample was rinsed with magnesium acetate whereas in preparation 2 it was only rinsed with distilled water. Hence, electrostatically bound contaminations are probably more efficiently rinsed off in preparation 1 than in preparation 2 . Conclusions Different assemblies of halobacterial flagella-large net-like structures and single, straight flagella-were observed. The occurrence of these structures was explained in terms of the preparation procedure. Complexes of flagellar bundles and bacterial membrane were found. Flagella did not converge into a single motor endplate, but left the bacterial fragment at distinct points [Fig.2(a) and ( b ) ] . Knobs at the end of several single flagella also confirmed the hypothesis that each flagellum is driven by its own motor. A periodic substructure was found along flagellar strands. The spacing between adjacent vaults of this substructure ranged from 50 to 100 nm. Samples were prepared in two different ways: after the cells had adsorbed to the mica substratum they were rinsed with (1) 8 mmol 1-1 magnesium acetate or (2) distilled water. Significant differences were found in the heights and, in particular, the widths, demonstrating the influence of prepa- ration on the apparent profile of the flagella. If the flagella were rinsed with magnesium acetate (preparation l), the flagella were embedded in a layer of cell debris. Although this layer made it difficult to determine the height of the flagella, we identified a fairly round flagellar profile with flagella having a diameter of 11 k 4 nm.In this case, the layer might even immobilize the flagella. Magnesium ions appear to stabilize the flagellar structure against deformation. No contaminations were revealed on rinsing the mica substrate with distilled water. The adsorbed flagella were deformed and appeared flat and broad. Flattening by adsorption and as a consequence of capillary forces during air drying were probably the main reasons for this deformation. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 References Binnig, G . , Quate, C. F., and Gerber, C.. Phys. Rev. Lett., 1986, 56. 930. Rugar, D., and Hansma, P. K., Physics Today, 1990,43 (Oct.), 23.Engel, A., Annu. Rev. Biophys. Biophys. Chem., 1991,20, 79. Hoh, J. H., and Hansma, P. K., Trends Cell Biol., 1992,2,208. Butt, H. J., Wolff, E. K.. Gould, S. A. C., Dixon Northern, B., Person, C. M.. and Hansma, P. K., J. Struct. Biol., 1990, 105, 54. Macnab, R. M., and Aizawa, S . I., Annu. Rev. Biophys. Bioeng., 1984, 13, 51. Silverman, M., and Simon, M., Nature, 1974, 249, 73. Eisenbach, M., Wolf, A., Welch, M., Caplan, S. R., Lapidus, I. R.. Macnab, R. M., Aloni. H., and Asher. O., J. Mol. Biol.. 1990, 211, 551. Macnab. R. M., Proc. Natl. Acad. Sci. USA, 1977, 74, 221. Alam. M., and Oesterhelt, D., J. Mol. Biol., 1984, 176, 459. Marwan, W., and Oesterhelt, D., J. Mol. Biol., 1986,195,333. Oesterhelt, D.. and Marwan, W., in General Microbiology Symposium, Cambridge University Press, Cambridge, 1990, Marwan, W., Alam, M., and Oesterhelt, D., J. Bacteriol.. 1991, 173, 1971. Macnab, R. M.. J. Clin. Microbiol,, 1976,4, 258. Spencer, M., Nature, 1984, 310. 367. Marwan, W., Alam, M., and Oesterhelt, D.. Naturwissenschaf- ten, 1987, 74, 585. Stoeckenius, W., Wolff, E. K., and Hess, B., J. Bacteriol., 1988, 170, 2790. Wolff, E. K., Bogomolni, R. A., Scherrer, P., Hess, B., and Stoeckenius, W., Proc. Natl. Acad. Sci. USA, 1986, 83, 7272. Alam. M., and Oesterhelt, D., J. Mol. Biol., 1987, 194, 495. Houwink, A. L., J. Gen. Microbiol., 1956, 15, 146. Typke, D., Nitsch. M., Mohrle, A., Hegerl, R., Alam, M.. Grogan, D., and Trent, J., Znst. Phys. Conf Ser. No. 93, 1988, 3, 379. Kellenberger, E., in Cryotechniques in Biological Electron Microscopy, eds. Steinbrecht, R. A.. and Zierold, K., Springer Verglag Berlin, Heidelberg, 1st edn., 1987, pp. 5C56. Zenhausern, F., Adrian, M., Heggeler-Bordier, B., Eng, L. M., and Descouts, P., Scanning, 1992, 14, 212. Paper 4fOO551 A Received January 28, 1994 Accepted April 21, 1994 V O ~ . 46, pp. 219-239.

ISSN:0003-2654    

DOI:10.1039/AN9941901943

出版商:RSC    

年代:1994

数据来源: RSC