摘要:

KrialystThe Analytical Journal of The Royal Society of ChemistryAnalytical Editorial BoardChairman: A. G. Fogg (Loughborough, UK)K. D. Bartle (Leeds, UK)J. Egan (Cambridge, UK)H. M. Frey (Reading, UK)D. E. Games (Swansea, UK)S. J. Hill (Plymouth, UK)D. L. Miles (Keyworth, UK)J. N. Miller (Loughborough, UK)R. M. Miller (Port Sunlight, UK)B. L. Sharp (Loughborough, UK)M. R. Smyth (Dublin, Ireland)Advisory BoardJ. F. Alder (Manchester, UK)A. M. Bond ( Victoria, Australia)R. F. Browner (Atlanta, GA, USA)D. T. Burns (Belfast, UK)J. G. Dorsey (Cincinnati, OH, USA)L. Ebdon (Plymouth, UK)A. F. Fell (Bradford, UK)J. P. Foley (Villanova, PA, USA)T. P. Hadjiioannou (Athens, Greece)W. R. Heineman (Cincinnati, OH, USA)A. Hulanicki (Warsaw, Poland)I.Karu be (Yokohama, Japan)E. J. Newman (Poole, UK)T. B. Pierce (Harwell, UK)E. Pungor (Budapest, Hungary)J. RSiiEka (Seattle, WA, USA)R. M. Smith (Loughborough, UK)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)P. Vadgama (Manchester, UK)C. M. G. van den Berg (Liverpool, UK)A. Walsh, K.B. (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 HVProfessor Dr. sc. K. Dittrich, Institute for Analytical Chemistry, University Leipzig, Linnestr.3,Professor 0. Osibanjo, Department of Chemistry, University of Ibadan, Ibadan, NIGERIA.Professor 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 LeninAmsterdam, THE NETHERLANDS.D-0-7010 Leipzig, GERMANY.Myodaiji, Okazaki 444, JAPAN.Street, Toronto, Ontario M5S I A I , CANADA.Universidad de Cordoba, 14005 Cordoba, SPAIN.SOUTH AFRICA.Changsha, PEOPLES REPUBLIC OF CHINA.Avenue, 117907, Moscow V-71, RUSSIA.Editorial Manager, Analytical Journals: Judith EganEditor, The AnalystHarpal S.MinhasThe Royal Society of Chemistry,Thomas Graham House, Science Park,Milton Road, Cambridge CB44WF, UKTelephone 0223 420066.Fax 0223 423623. Telex No. 818293 ROYAL.Senior Assistant EditorPaul DelaneyUS Associate Editor, The AnalystDr J. F. TysonDepartment of Chemistry,University of Massachusetts,Amherst MA 01003, USATelephone413 5450195Fax 41 3 545 4490Assistant EditorSheryl YouensEditorial Secretary: N avl ette DennisAdvertisements: Advertisement Department, The Royal Society of Chemistry, BurlingtonHouse, Piccadilly, London, WIV OBN. Telephone 071-437 8656.Telex No. 268001.Fax 071 -437 8883.The Analyst (ISSN 0003-2654) is published monthly by The Royal Society of Chemistry,Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK. All orders,accompanied with payment by cheque in sterling, payable on a UK clearing bank or in USdollars payable on a US clearing bank, should be sent directly to The Royal Society ofChemistry, Turpin Distribution Services Ltd., Blackhorse Road, Letchworth, Herts SG6 1 HN,United Kingdom. Turpin Distribution Services Ltd., is wholly owned by the Royal Society ofChemistry. 1993 Annual subscription rate EC €301 .OO, USA $662.00, Canada €348.00 (excl.GST), Rest of World f331 .OO. Purchased with Analytical Abstracts EC f656.00, USA $1444.00,Canada f758.00 (excl.GST), Rest of World f722.00. Purchased with Analytical Abstracts plusAnalytical Proceedings EC f774.40, USA $1703.68, Canada €894.00 (excl. GST), Rest of Worldf851.84. Purchased with Analytical Proceedings EC f383.00, USA $842.00, Canada f442.00(excl. GST), Rest of World €421.00. Air freight and mailing in the USA by PublicationsExpediting Inc., 200 Meacham Avenue, Elmont, NY 11003.USA Postmaster: Send address changes to: The Analyst, Publications Expediting Inc., 200Meacham Avenue, Elmont, NY 11003. Second class postage paid at Jamaica, NY 11431. Allother despatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Postoutside Europe. PRINTED IN THE UK.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 a l l aspects ofthe theory and practice of analytical chemistry,fundamental and applied, inorganic andorganic, including chemical, physical, biochem-ical, clinical, pharmaceutical, biological,environmental, automatic and computer-basedmethods, Papers on new approaches to existingmethods, new techniques and instrumentation,detectors and sensors, and new areas of appli-cation with due attention to overcoming limita-tions and to underlying principles are all equallywelcome.There is no page charge.The following types of papers will be con-sidered:Full research papers.Communications, which must be on anurgent matter and be of obvious scientificimportance. Rapidity of publication is enhancedif diagrams are omitted, but tables and formulaecan be included.Communications receive pri-ority and are usually published within 5-8weeks of receipt. They are intended for briefdescriptions of work that has progressed to aStage at which it is likely to be valuable toworkers faced with similar problems. A fullerpaper may be offered subsequently, if justifiedby later work. Although publication is at thediscretion of the Editor, communications will beexamined by at least one referee.Reviews, which must be a critical evaluationof the existing state of knowledge on a par-ticular facet of analytical chemistry.Every paper (except Communications) will besubmitted to at least two referees, by whoseadvice the Editorial Board of The Analyst will beguided as to its acceptance or rejection.Papersthat are accepted must not be published else-where except by permission. Submission of amanuscript will be regarded as an undertakingthat the same material is not being consideredfor publication by another journal.Regional Advisory Editors. For the benefit ofpotential contributors outside the United King-dom and North America, a Group of RegionalAdvisory Editors exists. Requests for help oradvice on any matter related to the preparationof papers and their submission for publicationin The Analyst can be sent to the nearestmember of the Group.Currently servingRegional Advisory Editors are listed in eachissue of The Analyst.Manuscripts (four copies typed in double spac-ing) should be addressed to:Harpal S. Minhas, Editor, The Analyst,Royal Society of Chemistry,Thomas Graham House,Science Park, Milton Road,CAMBRIDGE CB4 4WF, UK or:Dr. J. F. TysonUS Associate Editor, The AnalystDepartment of ChemistryUniversity of MassachusettsAmherst MA 01003, USAParticular attention should be paid to the use ofstandard methodsof literaturecitation, includingthe journal abbreviations defined in ChemicalAbstracts Service Source Index. Wherever pos-sible, the nomenclature employed should fol-low IUPAC recommendations, and units andsymbols should be those associated with SI.All queries relating to the presentation andsubmission of papers, and any correspondenceregarding accepted papers and proofs, shouldbe directed either to the Editor, or AssociateEditor, The Analyst (addresses as above). Mem-bers of the Analytical Editorial Board (who maybe contacted directly or via the Editorial Office)would welcome comments, suggestions andadvice on general policy matters concerningThe Analyst.Fifty reprints are supplied free of charge.0 The Royal Society of Chemistry, 1993. Allrights reserved. No part of this publication maybe reproduced, stored in a retrieval system, ortransmitted in any form, or by any means,electronic, mechan ica I, photog rap h ic, record-ing, or otherwise, without the prior permissionof the publishers

ISSN:0003-2654    

DOI:10.1039/AN99318FX001

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

2N ANALYST, JANUARY 1993, VOL. 118 Conference Reports Fourth European Conference on Electroanalysis, ESEAC IV: May 314une 3, 1992, Leeuwenhorst Congress Centre, Noordwijkerhout, The Netherlands Organized under the auspices of the European Society for Electroanalytical Chemistry (ESEAC) and the Royal Netherlands Chemical Society, this was the fourth in a series of meetings that began in Dublin in 1986, and were held subsequently in Turku and Gijon in 1988 and 1990 respcctively, and was attended by approximately 180 participants. The main aim of this series of meet- ings is to promote greater exchange of ideas and results relating to the theory and application of electroanalytical met hods (potentiometry , volt ammetry, coulometry, etc.) in the chemical, bio- logical, industrial and environmental sciences.At this particular meeting, keynote lectures were prcsented by Dr. C. M. G. van den Berg (UK) on metal speciation studies, Dr. C. Amatore (France) on ultramicroelectrodes, Dr. L. Gorton (Sweden) on amperometric biosensors, Dr. H. W. van Leeuwen (The Nether- lands) on environmental electroanaly- sis, Professor J.-M. Kauffmann (Bel- gium) on pharmaceutical and biomed- ical applications and Professor K. Stulik (Czechoslovakia) on electrochemical detection in flow analysis. The pro- gramme also included 21 other oral presentations and over 100 posters. This attests to the great interest and technol- ogical developments in this field of analytical science throughout Europe, and particular praise should be paid to the Conference Chairman, Dr.W. M. van Bennekom and his co-workers for organizing such a scientifically stimulat- ing meeting. The choice of location allowed for many informal discussions among the participants and the social programme, which included a trip to The Hague and a dinner cruise in Rotterdam harbour, complemented well the scientific fare. At the biannual meeting of ESEAC held during this conference, it was decided that the Society should remain ‘a loose associa- tion of electroanalytical chemists in Europe’, and it was decided to start a newsletter under the editorship of Dr. W. Frenzel (Technical University of Berlin). The next meeting of this series will be held in May/June, 1994, in association with the Analytical Division of the Ttalian Chemical Society, at a location to be decided. Malcolm R.Smyth School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland Focus ‘92 Association of Clinical Biochemists National Meeting: June 8-12, 1992, Blackpool, UK One practical expression of analytical biochemistry, of unquestionable impor- tance, is the medical analytical service provided by the clinical biochemist. This largely hospital-based group of analysts serves as the diagnostic reference point for a wide range of diseases, and its contribution of biochemical data is of a scale, quality and versatility that is a match for any other application area. Analysis of ‘clean’ samples is usually not feasible, as contemporary medicine demands a rapid turnaround of data using non-ideal biological specimens often assayed under non-ideal analytical conditions.The annual National Meet- ing of the Association of Clinical Bio- chemists constitutes the major calendar occasion for the profession, and accord- ingly, provides one of the best means of divining current rcsearch themes and development areas. At the Meeting held in Blackpool this year, delegates numbered over 1000, with an ambitious scientific programme comprising a complement of five ple- nary lectures, eight scientific symposia, along with over 250 posters, 27 breakfast workshops, member’s short paper presentations and competitive scientific presentations for trainees. I n addition, there were ‘expert workshops’, com- mercially sponsored seminars and trainee teaching sessions. Although this short report cannot do justice to such an extensive meeting, something of the scientific flavour is presented, which might help define the role of the clinical biochemist.The Meeting was opened by Dr. K. Calman, the Chief Medical Officer, who set the scene on the needs and expecta- tions placed upon clinical biochemistry, and the relevance of research. The traditional ‘light’ topic opening lecture was presented by Dr. G . H. Dodd (Warwick) who gave a comparative description of the natural and artificial (electronic) nose, and the future diag- nostic possibilities of sniffing thc pat- ient; in the general sense, this served as an interesting redefinition of the term non-invasive monitoring. The Boehr- inger Mannheim Award lecture this year was by Professor S. Lieberman (New York) who challenged established con- cepts of adrenal steroid synthesis, and concluded that despite highly reliable analytical data, errors in biological interpretation have prevented us from appreciating true mechanisms and synthetic control points.The scientific symposia ran as twin parallel sessions; particular prominence (the second day) was given to analytical methods with Novel Analytical Tech- niques and Tissue Biochemistry occupy- ing a full day. Professor P. Rolfe (Keele) gave an overview of near infrared moni- toring of brain tissue oxygenation through quantitation of haem-protein spectra, particularly in the vulnerable neonate, and speculated on the further possibility of functional imaging with adaptation of tomographic techniqucs. Dr. K. M. Brindle (Manchester) explained how NMR was now being used to probe expressed intracellular proteins, and in particular how protein enzyme switching and kinetics has been followed.Professor P. J . Sadler (Birk- beck) described NMR with regard to more conventional diagnostic use in body fluid analysis; the clinical advan- tages of simultaneous, multi-metabolite analysis by NMR were not lost on an audience used to having to pre-target assay systems. Dr. R. D. Vaughan- Jones (Oxford) brought together his practial comparative experience of microelectrodes and fluorophore probes used to examine the intracellular and pericellular ionic environment. Dr. S. Sharma (Kodak Clinical Diagnostics) described principles and newer develop- ments in waveguide biosensors, par- ticularly based on surface plasmon res- onance, and realistically assessed future prospects in the context of outstanding,ANALYST.JANUARY 1993, VOL. 118 3N residual problems of biological interfac- ing. Direct sampling of the tissue com- partment by means of a dialysis mem- brane-tipped flow system (microdialy- sis) was reviewed from basics to clinical applications by Professor U. Ungerstedt (Stockholm) who provided some con- vincing evidence of its practical utility and suitability for routine use. Exten- sive, and relatively successful, experience of glucose monitoring by implantable enzyme electrodes, was aired in Professor U. Fischer’s (Karls- burg) presentation; documentation of in vivo data made a refreshing change from the standard rarefied description of in vivo hopes and aspirations of biosen- sors.Professor D . A. Eisner (Liverpool) outlined the latest in ionophore dye use and design to achieve more convenient and meaningful intracellular ion moni- toring. The parallel session in the morn- ing focused on vitamin D, which is undergoing a renaissance of biological interest well beyond the study of bone metabolism. Dr. E. B. Mawer (Man- Chester) presented a profile of vitamin D and its metabolites that illustrated its likely role in influencing cell prolifera- tion and differentiation generally. Some degree of osteoporosis is inevitable with ageing in all of us, so a description of its etiology, progress and management by Dr. W. D. Fraser (Liverpool) were of more than academic interest. Work into the wider biochemistry of vitamin D must be regarded as still being at an early stage, but what is known about calciudbone inter-relationships cer- tainly owes much to the achievements of the analyst.Analytical methods have done much to unravel the biochemistry of Paget’s disease of the bone, but as Dr. S. Ralston (Aberdeen) demonstrated, the precise cause of this quite common condition (considered by some to be viral) remains elusive. Newer markers of bone disease were described by Dr. D. A. Heath (Birmingham), who indi- cated the additional quantitative measure of bone activity these can provide. Biochemical investigation might of course need to begin in utero, especially for inborn errors of metabolism. The parallel session in the afternoon concen- trated on prenatal diagnosis. Genetic aspects were covered by Professor J.M. Connor (Glasgow) who highlighted the need for systematic genetic screening programmes in the identification of chromosomal disorders; inherited disorders giving rise to specific meta- bolic disease were described by Dr. G. T. W. Besby (Manchester). The use of chorionic villus biopsy samples as a source of foetal cells for such diagnostic work is an example of a sampling technique that has proved to be as important as any which might be used by the engineer in an industrial process. Diagnosis of deranged steroid produc- tion in foetuses leading to a failure of cortisol production was a specific disease example reviewed by Dr. M. G. Forest (Lyon). The powerful use of a multiple combination of analytical data (a-fetoprotein, estriol, chorionic gonad- otrophin) in Down’s screening was sur- veyed by Professor N.Wald (London) who showed the urgent need to institute wide use of these parameters. The third day plenary speaker, Professor R. H. Michell (Birmingham), gave a lucid account of the accelerating pace of research and knowledge in the field of secondary (intracellular) mes- senger systems, and of the kaleidoscope of such pathways that may modulate cell action. The morning symposia were on cytokines and free radicals. Cytokines are a very broad range of diffusible signal molecules that effect intercellular signalling and communication in tissue. Professor G. W. Duff (Sheffield) reviewed the general biochemical regu- lation of these agents and where measurement could be of value in diag- nosis. Acute life-threatening situations involve an orchestrated cellular meta- bolic response, and as indicated by Professor B.R. Bistrian (Boston), the major cytokines are intimately involved here. Such an involvement, with the associated breakdown of body protein, can also occur in cancer and as empha- sized by Mr. K. C. H. Fearon (Edin- burgh), is a basis for the cachexia seen in malignant disease. As ever, none of this patho-biology can be unravelled without the correct assay; and Dr. A. T. Meager (National Institute for Biological Stan- dards and Control) reminded the audience of the current state of the analytical art and outlined advances that have resulted in immunoassay super- seding bioassay. The free radical session dealt with the basics of the chemistry of redox reaction mechanisms between the vitamins and free radicals (Professor R.L. Willson, Brunel). The concept of the free radical as a ‘double edged sword’, indispensable in the oxygen economy of the body, yet lethal if out of balance with endogenous antioxidants, was emphasized by Dr. C. Rice-Evans (London). Later radiation induced bio- chemical damage with its mediation by reactive species [e.g., OH’ and ecaJ were discussed by Professor R. B. Can- dall (MRC), and the determination of reactive oxygen species in biological samples by Professor J. Lunec (Leices- ter). The Kone-Award lecture on the fourth day was by Professor 0. Sig- gaard-Anderson (Copenhagen), a pioneer of the assessment of respiratory gas status in the critically ill patient. His revisitation of this established field, but with emphasis on 02-supply problems rather than blood levels, gave many a blood gas expert pause for thought.The subsequent symposia were on intensive care medicine and NHS reforms and changes. Professor R. A. Little (Man- Chester) provided an update on our understanding of the general metabolic response to severe trauma and of the associated changes in energy balance, a classic example of thermodynamics in biology. Mr. J. Macfie (Scarborough) offered some ‘thermodynamic’ solu- tions, notably, the practical means of managing nutritional support and obli- gatory negative energy and nitrogen balance after trauma and sepsis. Just when it was deemed safe to rely upon a central measurement of oxygen to assess its general delivery, Dr.D. Bihari (Lon- don) reminded delegates of the need to determine local delivery, especially to vulnerable tissues, in the circulation ‘front line’ such as of the gut. The newborn have particular vulnerabilities, and Dr. M. L. Chiswick (Manchester) surveyed the instrumental techniques available for oxygen measurement, par- ticularly the transcutaneous Clark elec- trode that has done so much to aid titration of oxygen therapy. The NHS reform symposium, though of more parochial interest to the practising clin- ical biochemist, dealt with the powerful organizational issues of trust hospitals (Dr. T. A. Gray, Sheffield), the Audit Commission assessment on pathology services (Mr. D. Browning, London), future regulation and licensing of hospi- tal laboratories (Dr. D. Burnet, St. Albans) and the shape of things in USA health care (Mr. R. D. Jennings, Wash- ington). The fifth and final day Foundation Award Lecture was delivered this year by Professor J . Whicher (Leeds) on cytokine assays and their utility for research as well as clinical medical practice. Although refined analytical techniques have clearly helped to profile the multi-cytokine environment of the cell, full biological interpretation is clearly some way off and this area is set to expand further. The final session of the Meeting was a robust counter to convention and involved a none-too serious look at a vogue subject: clinical audit. While these meetings continue to satisfy the requirement of the practising clinical biochemist, there is also much that the analytical chemist could find of interest here, and with future participa- tion both scientific communities would receive substantially wider benefit. Pankaj Vadgama Department of Medicine, University of Manchester, Hope Hospital, Eccles Old Road, Salford, UK, M6 8HD

ISSN:0003-2654    

DOI:10.1039/AN993180002N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALAO 1 18( 1 ) 1 N-I 4N, 1-1 22 (1 993)AnalystJanuary 1993The Analytical Journal of The Royal Society of ChemistryCONTENTSNEWS AND VIEWS1 N Foreword-Ernie Newman, President of The Analytical Division2N Conference Reports-M. R. Smyth, P. Vadgama4N Book Reviews9N Conference Diary14N Papers in Future Issues111172329354147535965717379858997101105109111115119VTUTORIAL REVIEW-Applications of Confocal Laser Scanning Microscopy in in-situ Mapping-Martin C. Moss, JeffreyA. Veiro, Scott Singleton, Donald P. Gregory, John. J. Birmingham, Carol L. Jones, Phillip G. Cummins, DianeCummins, Richard M. Miller, Robert C. Sheppard, Vyvyan C. Howard, Nilam BhaskarExtraction of Organophosphorus Pesticides From Soil by Off-line Supercritical Fluid Extraction-Klaus Wuchner, RudyT.Ghijsen, Udo A. Th. Brinkman, Robert Grob, Jacques MathieuSupercritical Fluid Extraction for the Analysis of Liquid Poly(alky1ene glycol) Lubricants and Sorbitan EsterFormulations-Terence P. Hunt, Chris J. Dowle, Gillian GreenwayPreconcentration of Aniline Derivatives From Aqueous Solutions Using Micellar-enhanced Ultrafiltration-EdmondoPramauro, Alessandra Bianco Prevot, Piero Savarino, Guido Viscardi, Miguel de la Guardia, Empar Peris Cardells6-Methoxy-2-methylsuIfonylquinoline-4-carbonyl Chloride as a Fluorescence Derivatization Reagent for Amines inLiquid Chromatography-Tomohiko Yoshida, Youichi Moriyama, Kayoko Nakamura, Hirokazu TaniguchiFast-responding, Fibre-optic Based Sensing System for the Volatile Anaesthetic Halothane, Using an UltravioletAbsorption Technique and a Fluorescent Film-Judith A.Barnard Howie, Peter HawkinsGlass pH Electrodes With Improved Temperature Characteristics. Part 2. Systems With Conventional Inner ReferenceElectrodes-Derek M idg leySimultaneous Determination of Nickel(ii) and Cobalt(ii) by Square-wave Adsorptive Stripping Voltammetry on aRotating Disc Mercury Film Electrode-Anastasios Economou, Peter R. FieldenVoltammetric Determination of Gold Using a Carbon Paste Electrode Modified With Thiobenzanilide-Xiaohua Cai,Kurt Kalcher, Christian Neuhold, Wolfgang Diewald, Robert J. MageeUse of a Quadratic Response Surface in the Polarographic Determination of Lead-B. Lopez Ruiz, G. Frutos, P. SanzPedrero, J. P.MartinVoltammetric Trace Determination of Uranium and Other Transition Metals in Rock Phosphate Samples-NeerjaVerma, Krishna S. PitreIdentification of Trihaloacetaldehydes in Ozonated and Chlorinated Fulvic Acid Solutions-Yuefeng Xie, David A.ReckhowUse of Rapid Scan Correlation Nuclear Magnetic Resonance Spectroscopy as a Quantitative Analytical Method-HerveBarjat, Peter S. Belton, Brian J. GoodfellowMicroanalysis of Bismuth Indium Selenide Thermoelectronic Materials by X-ray Fluorescence Spectrometry WithReference Assays of Indium-Stanislav Kotrly, Jitka Sramkova, Radko Chadima, Josef CermakColumn Preconcentration of Cobalt in Alloys and Pepperbush Using 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenoland Ammonium Tetraphenylborate Adsorbent Supported on Naphthalene With Subsequent Determination UsingAtomic Absorption Spectrometry-Masatada Satake, Tohru Nagahiro, Bal Krishan PuriDetermination of Malonaldehyde in Human Plasma: Elimination of Spectral Interferences in the 2-Thiobarbituric AcidReaction-Anunciacion Espinosa-Mansilla, Francisco Salinas, Amparo Rubio LealSpectrophotometric Determination of Stability Constants of Anti-stepwise Complexes-Shi-Fu Zou, Jie Zhou, Wei-AnLiangSpectrophotometric Titration of Some Thiazine Dyes With Iron(ii) in Buffer Medium in the Presence of Oxalate-K.Vijaya Raju, G. Bangar RajuSimultaneous Determination of Iodide and Nitrite by Catalytic Kinetics-Zhong-liang Zhu, Zhi-cheng GuCUMULATIVE AUTHOR INDEXINSTRUCTIONS TO AUTHORSREFEREEING PROCEDURE AND POLICYIUPAC PUBLICATIONS ON NOMENCLATURE AND SYMBOLISM1993 FACSS: ANNOUNCEMENT AND CALL FOR PAPERSTypeset and printed by Black Bear Press Limited, Cambridge, England0003-2654C199311: 1-

ISSN:0003-2654    

DOI:10.1039/AN99318BX003

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

4N ANALYST, JANUARY 1993, VOL. 118 Book Reviews Principles and Practice of lmmunoassay Edited by Christopher P. Price and David J. Newman. Pp. xvi + 650. Macmillan. 1991. Price f50.00. ISBN 0-333-51 406-8. The thirty year history of immunoassay has seen its rapid and widespread development in many analytical disciplines includ- ing its natural home the clinical biochemistry laboratory. The range of assays that exploit the antigen-antibody reaction and the technology that underpins it are vast and rapidly changing to take into account exciting novel developments. The purpose of this multi-authored volume was to ‘bring together, in one text, current perspectives on some of the fundamental aspects of immunoassay together with the principles of the major techniques in use today’.Although the editors have recognized that in such a rapidly moving field much of the material might be outdated within a few years, the book represents a comprehensive compilation of basic immuno- assay principles and practice, which will be a valuable source of reference for some time to come. The book consists of 22 chapters contributed by eminent and internationally known exponents of the ‘art’ of immuno- assay. Each contribution stands alone as an excellent review of a particular aspect of immunoassay but the chapters are logically organized so that newcomers to the field can easily learn the basic principles of immunoassays and follow how modern assay formats have developed and been refined from the earliest radioimmunoassays. The book begins by describing the nature of the antigen- antibody reaction on which all immunoassays depend and defines some fundamental terms such as avidity, affinity, specificity etc. Next, are two chapters describing how anti- bodies, with the required characteristics for the development of robust, highly sensitive and specific assays, are produced and how molecular biology provides the means of engineering antibody structure so that their properties can be fully exploited for various applications. The theory and design of immunoassays, their optimization, standardization and qual- ity control, methods of automation and the various com- puterized methods available for data reduction are the subject of the next five chapters. The reader should not be dismayed by some of the mathematical content of these chapters as they are clearly set out and are extremely readable.The lengthy but informative chapter on the design and optimization of immunoassays is essential reading for those who wish to understand the concepts behind the development of highly sensitive immunoassays, the recent move towards non-iso- topic immunoassays and the current efforts to develop the assays of the future. A newcomer to immunoassays could be excused for being confused by the vast array of different assay formats, acronyms and nomenclature that are described in the literat- ure. Chapter nine successfully manages to clarify how immunoassays are classified (e.g. heterogeneous versus homogeneous, competitive versus non-competitive) and des- cribes the different types of labels that have been used.Each of the remaining chapters describes one of the variants of immunoassay from those in use now to those that are in various stages of development for future use and applications. These include the classical radioimmunoassay , the different forms of enzyme immunoassay and the more recent use of fluorescent and chemiluminescent labels. Tmmunoassays that do not rely on a labelled component, e.g. light scattering immunoassays are also included. Current and more futuristic developments in assay design are also described in the later chapters. The exciting possibilities for exploiting the physical characteristics of the antibody-antigen reaction for the development of bio(immun0)-sensors using evanescent waves, multi-layer films and immunochromatography are also presented. As the virtues of immunoassays are being recognized in analytical fields that have not traditionally embraced the techniques, this reviewer has often been asked to recommend a suitable text as an introduction to immunoassay; this is one volume I will readily be able to recommend as an excellent comprehensive source of background knowledge.The book is well organized, easy to read and to understand and does not unnecessarily decorate the subject with jargon. The volume will be useful for students as well as research workers about to embark on projects involving the development or use of immunoassays. At the same time I am sure this book will be a constant source of reference to those like myself who have come to depend largely on the use of immunoassays in their work.G. Wynne Aherne ~~ Chromatography Today By Colin F. Poole and Salwa K. Poole. Pp. ix + 1026. Elsevier. 1991. Price US $147.50, Dfl. 295.00 (hard bound); US $75.00, Dfl. 150.00 (paperback). ISBN 0-444-88492-0 (hard bound); 0-444-891 61 -7 (paperback). The authors have assembled a comprehensive volume that emphasizes a fully contemporary approach to an extremely wide analytical discipline, but succeeds in placing the field in a good developmental perspective. The task undertaken is a daunting one and the authors have wisely excluded non- chromatographic analytical separations, wide in application though they are. Even so, the magnitude of the effort needed explains in good measure why no competitive text has been produced in recent years.This camera-ready , word-processor produced book will surely be well received particularly in the more economical paperback format. This is not a book to be followed through in a defined sequence, although, as the authors suggest, it may provide a basis for a (post)graduate level course if care is taken to select material carefully. Rather it provides a resource both to introduce the novice to new areas and, particularly by virtue of its extremely comprehensive reference lists, to act as a resource for the laboratory practitioner. This is very much an applied practical book with many features of a working manual. Mathematical treatments and theoretical discussions are not emphasized, but its strength lies in excellent descrip- tions of instrumentation, experimental characteristics and practical applications.This is clearly a product of working professionals in the chromatographic field who have much experience to impart to the reader. The structure of the book is based upon techniques and instrumentation rather than chemistry and applications. Most theoretical material is covered in the first chapter on fun- damental relationships, which focuses on practical implica- tions of basic ideas and in fact provides a very strong general introduction for the novice with clear indications for the laboratory. Gas chromatography is the ‘senior’ high resolution separation technique and appropriately is covered in the two following chapters focusing in turn upon columns and instrumental aspects, especially detectors.High-performance liquid chromatography is covered in a similar sequence in Chapters 4 and 5. The authors have chosen also to introduceANALYST, JANUARY 1993, VOL. 118 5N high-performance capillary electrophoresis in the latter chapter. Supercritical fluid chromatography and thin layer chromatography are each afforded separate chapters, the latter being covcred in much greater depth than is usual in recent separations texts. Next follows an extremely com- prehensive chapter on sample preparation in which sample introduction, derivatization, concentration techniques and pyrolysis gas chromatography are all covered. This chapter could well have been split into several briefer ones for easier reference. Hyphenated methods are covered in the final chapter with most emphasis on mass spectroscopy and Fourier transform infrared spectroscopy; surprisingly interfaced atomic spectroscopy receives little mention. Overall this is an admirable if rather ponderous book, both in construction and writing style.It is a book best used as a good information source and in this regard is virtually unique and well worthy of acquisition. Peter C. Uden ~~ ~ ~ Report of the Proceedings of the 20th Session, Colorado Springs, June 3-8,1990 International Commission for Uniform Methods of Sugar Analysis. Pp. xxxvi + 410. ICUMSA. 1991. Price f40.00. ISBN 0-905003-1 2-8. The first chapter of this book is a record of three meetings of the executive committee of ICUMSA and reports of social occasions in connection with the sessions. The chapters following deal with the analysis of sugar in various forms- including raw and white sugar, molasses, cane and beet sugars.The general purpose of the text appears to be to review the methods available for each parameter and each product, then to consider and decide what still remains to be done in each field. Details are included of collaborative testing and statistical treatment of the data obtained, with discussion of the various official and non-official procedures, and recommendations as to the priority in the investigation of the methods needed. In addition to procedures such as determination of ash, colour, pH, etc., the methods studied include: polarimetry; infra-red and near infra-red spectroscopy; atomic absorption and emission spectrometry; fluorimetry, gas-liquid, gel-per- meation and high-performance liquid chromatography; ion chromatography and ion-selective electrodes; enzymic proce- dures; rheology; and microbiology.Most chapters contained a referee’s report discussing the state-of-the-art, followed by discussion, results and recommendations. This is a book crammed with detail, which should be valuable to personnel in sugar and related industries; it is recommended to all libraries within organizations such as these. D. Simpson Computational Aspects of the Study of Biological Macro- molecules by Nuclear Magnetic Resonance Spectro- scopy Edited by Jeffrey C. Hoch, Flemming H. Poulsen and Christina Redfield. NATO AS/ Series. Series A: Life Sciences. Volume 225. Pp. x + 464. Plenum. 1992. Price US$l15.00. ISBN 0-306-441 14-4.Computation is playing an increasingly important role in NMR spectroscopy, especially in the study of biological macromolecules. As noted on page one of the book, these days modern NMR facilities often contain more computers than spectrometers. This book is a collection of 37 articles written by participants in a NATO Advanced Research Workshop held in July 1990. The publication date is reasonably soon after the event for material of this kind; it needs to be so, because the reports often become superseded by papers from the same authors in primary journals. The book is largely about the determination of the 3D structures of proteins in solution using NMR methods. Polynucleotides are also mentioned briefly. The editors have taken care to ensure a uniformly high standard of presentation of text and diagrams throughout the book.Unfortunately this is not always the case with multi- authored books based on conference proceedings. The methods for the determination of the structures of small proteins (<lo kDa) are outlined and are now becoming routine. The extension to larger systems (perhaps even 20-30 kDa) is discussed via combinations of multi-dimen- sional COSY, TOCSY and NOESY with 15N and/or l3C enriched proteins. I saw little mention of partial 2H labelling that can sometimes improve resolution, but I might have missed it; the index is too brief (one and a half pages) to help. Most aspects of the problem are addressed, including the acquisition of data, data processing (e.g. increasing the resolution using Prony covariance, or maximum entropy methods), and the calculation of structures based on distance geometry, simulated annealing and molecular dynamics rou- tines.Programs that automate the assignment of multi-dimen- sional spectra are emerging. Indeed several authors offer their programs to readers on request, so this book is a good source of contacts. The reports of round-table discussion sessions address important and difficult questions, such as how many NOE’s are required to define a structure? How do we represent a solution structure or define the precision and accuracy of such a structure? And, should the effects of mobility be taken into account in the analysis of NMR data? For polynucleotides, the power of analysis of the complete relaxation matrix is evident: distances derivable from NOE measurements can be extended beyond 5 A.In summary, this is a well-presented book, of special interest to laboratories involved in the determination of the structures of proteins and polynucleotides in solution by NMR methods. You can find Nobel prizewinner Richard Ernst’s wedding photograph on p. 8, and enjoy his reminiscences of ‘very early, mostly unpublished experiments in computer- aided NMR’ in Chapter 1. It reads as if he enjoyed writing-even though (as he reveals) it was extracted from him by ‘brute force’! Peter J . Sadler Handbook of Surfactants By M. R. Porter. Pp. ix + 227. Blackie. 1991. Price f55.00. ISBN 0-21 6-92902-4; 0-41 2-02491 -8 (USA). Dr. Porter is a consultant in speciality chemicals. His book opens with a summary of the theory of surfactants and a general approach to their use in formulations, with properties of the hydrophilic and hydrophobic groups and a range of suggested sources of further information.However, essentially it is a work of reference covering the wide range of all the main types of agents of this nature available currently, including their nomenclature, general properties and applications. The information about surface-active agents is presented in groups as follows: anionics; non-ionics; cationics; amphoterics; speciality and polymeric materials. (It was of particular interest to find the last since although the basic technology now is well established newer approaches remain open and are not neglected here.) The discussion of anionics includes carboxylates, isethionates, phosphates, sarcosinates, sulfates, sulfonates, sulfosuccinates, related compounds and taurates.The non-ionics include acetylinic and ethoxylate6N ANALYST, JANUARY 1993, VOL. 118 groups, alkanolamides, copolymers, and carbohydrate deriv- atives; the cationics include quaternary ammonium com- pounds, amine and imidazoline salts; and under amphoterics are listed, betaines, glycinates, aminopropionates, and the later imidazoline-based surfactants (following the discovery that an incorrect chemical structure was assigned to earlier products). There is also an interesting discussion of the ecological and safety requirements derived from some of the European directives on the subject. This is a book crammed with useful facts about a wide variety of surfactants, and the author must have performed much hard work in order to amass them.It is written clearly, and the properties, specifications and applications should be of assistance to readers and users of surfactants in a considerable variety of fields. I would recommend the book to libraries in industrial and educational establishments, to students in the field, and, not least, to development chemists and managers. D. Simpson ~~ ~ ~~ DECHEMA Corrosion Handbook: Corrosive Agents and Their Interaction With Materials. Volume 9: Methanol and Sulfur Dioxide Edited by Dieter Behrens. Pp. ix + 375. VCH. 1991. Price DM 775.0, f286.00 (Single Volume Price). ISBN 0-89573- 630-6 (VCH Publishers); 3-527-26660-7 (VCH Verlags- gesel Isc haft).This is the latest in the series of Corrosion Handbooks that provides an updated version in English translation of the well-known Dechema Werkstoff-Tabelle. Like the other volumes, it summarizes an immense amount of information on the resistance of a very wide range of materials to specific corrosive environments, in this case methanol and sulfur dioxide. The sources include journal articles, other compila- tions and trade literature, the latter often being treated with some scepticism. There are well over 600 references in each section, and as in previous volumes a high proportion are to papers published in 1980 or later. The corrosive environments are very broadly defined, and take into account a large number of impurities and also, for methanol, the use of solutions for electro-polishing and metallographic etching.I was surprised to find in this section a reference to one of my own papers, which happened to be on electron microscopy on thin oxide films, and this may give some idea of the pertinacity of the compilers in extracting all relevant information from their sources. Corrosion in process streams in chemical plant, for instance, in methanol synthesis and in flue gas desulfuriza- tion is generously treated, as are problems in gas-turbine engines and fire-side and condensate corrosion in power stations. The coverage of materials is also very wide, and apart from a huge number of industrially important metals and alloys includes such inorganic materials as stone, carbon and asbestos. There are extensive indices, summary tables and notes on materials selection.This volume, like the others in the series, will certainly be in constant use in design offices and consultancies, in spite of the high price. If few people read it like a novel, this will be a pity, as it contains all manner of fascinating items of information one might never come across anywhere else. Given the immense industry of the compilers, and their high degree of success (so far as I have been able to check) in securing accurate information, one does wonder how success- ful such a compilation can hope to be ultimately. Specialists in particular topics, such as, for instance, hot-salt corrosion, will be aware that the coverage is inevitably selective. Apart from this, the technique of selecting one or two points from a paper does lend an ex cathedra air to some judgments on rates of corrosion, which might be inconsistent with other judgments a page or two away.This is particularly the case with heavily researched topics such as the atmospheric corrosion of steel, where too little attention is given to the great decline in sulfur dioxide concentrations in many towns in recent years, which has led to a large fall in rates of corrosion. The English translation is often rather unidiomatic and occasionally difficult to understand without careful re-read- ing, and there are occasional slips such as the use of ‘mm’ where ‘pm’ must be meant (Table 37, p. 210), and the use of ‘mazout’ meaning fuel-oil. These, however, are small defects, and in general the compilers have done their work as well as could possibly be expected.G. 0. Lloyd Reviews in Computational Chemistry. Volume 2 Edited by Kenny B. Lipkowitz and Donald B. Boyd. Pp. xvi + 527. VCH. 1991. Price DM236.00; f85.00. ISBN 1-56081- 51 5-9 (VCH); 3-527-28338-2 (VCH Verlagsgesellschaft). This book is the second volume in a series, covers a range of topics in the field of molecular modelling. The articles are at a level where they will be accessible to a graduate student, but extensive references to publised work make them useful for researchers working in related areas where similar computa- tional problems are encountered. A particularly useful aspect is reference to specific codes and their origins. The volume begins with optimization techniques for the multi-minimum problem.This is an important area of work in mathematics, but the special requirements of chemists are addressed here. Leach reviews numerous methodologies for medium sized molecules while Troyer and Cohen address the problem of proteins. There are two articles on parameterization and empirical force-fields. This area is renowned as being something of a black art, with the rationale behind derivation of these fields often glossed over. These articles give a good insight into this area. Scheiner’s article about hydrogen bonding uses simple systems to illustrate the main points. It shows the difficulty and uncertainty associated with choice of basis set to describe both molecular and intermolecular bonding due to complete- ness, superposition and correlation errors. This is shown especially in calculations of vibrational spectra, where the accuracy of the harmonic approximation is also discussed.In the initial stages of a reaction molecules ‘see’ each other via the electrostatic potential. Politzer and Murray show what can be deduced about reactivity from the potentials of single molecules and the effects of strain. Strain dependence suggests how reactions proceed as molecules deform prior to rebonding. Modern quantum chemistry has many methods (and acronyms!) for doing quantum mechanics wrongly. These semi-empirical methods allow treatment of problems for which full ‘ab initio’ calculations are too computationally demanding. The level of approximation to various parts of the quantum mechanical total energy of several common methods is discussed.The types of systems for which each method is suitable and reasons for breakdown of the approximation in other cases are given. Hall and Kier discuss molecular flexibility, shape and topology via the kappa and phi indices. These methods are used in biologically important materials to discover the active sites, similarities between molecules that lead to similar behaviour and differences that lead to trends in reactivity. Bersuker and Dimoglo review methods of going from one extreme to another, simplifying the results of ab initio (or other) structural calculations, extracting the important features and producing simple parameters to describe parti- cular functions of the molecules.ANALYST, JANUARY 1993, VOL. 118 7N As a whole, the volume presents a wide ranging review of current areas of interest in computational chemistry.The articles are self-contained, requiring little reference to other work. The downside is that the volume as a whole is rather unstructured, there are no clear links between the articles. Specific examples arc cited, but in general the emphasis is on methodologies and limitations of the various techniques rather than specific successes. As such it nicely complements journal papers, which seldom discuss why a certain method was used to tackle a particular problem. The rapid growth of computational chemistry has left a gap between what is generally taught at an undergraduate (and even graduate) level and what is actually done in state-of-the-art research. This series will enable the researcher to bridge the gap. G.J . Ackland The Handbook of Environmental Chemistry. Volume 2. Part F. Reactions and Processes Edited by 0. Hutzinger. Pp. 255. Springer-Verlag. 1991. Price DM 178.00; ISBN 3-540-541 39-X; 0-387-541 39-X. This volume of the series is devoted to four reviews of subjects related to precipitation and sediment adsorption. The final chapter is devoted to a discussion of photochemically gener- ated reactive oxygen species. The authors are drawn from Canada, the USA and Germany, making for international authority. Unfortunately the balance of the book is very much towards the first topic: Wet Deposition, which occupies 163 of the 255 pages of the volume. This may reflect the importance of this input to the ecosystem. The chapter on Wet Deposition is comprehensively written covering many aspects of programme design and types of sampling equipment.These are vital to ensure that any sampling programme produces scientifically accurate results. The analytical chemistry of the various determinands is discussed in broad terms but there is little discussion of the relationship between detection limit of the various techniques and the precision needed for meaningful results. It is pleasing also to see analytical quality control (AQC) discussed, as without a rigorous programme most analytical results will show so much variability as to make conclusions based on the data at best questionable. However, reading this section one is left with the impression that this point is still poorly understood by environmental scientists.The following chapters discuss the Transport of Contami- nants by Colloid-Mediated Processes; these are vital in controlling levels of pesticides and radioisotopes in the environment. Models for transport of contaminants from sediment beds are also discussed as they are also vital in controlling environmental concentrations. These chapters provide a connected core to the review. The final chapter does not fit so well into the theme; however, the data presented suggest that photochemically generated reactive oxygen species play a great role in controlling the concentration of man-made organic compounds. As part of a series this book provides in-depth reviews of particular topics and as such it is to be recommended. N . S. J . Christopher Trace and Ultratrace Analysis by HPLC By Satinder Ahuja. Volume 115 in Chemical Analysis: A Series of Monographs on Analytical Chemistry and Its Applications.Pp. xi + 419. Wiley-lnterscience. 1992. Price f59.00. ISBN 0-471-51419-5. This book extends and complements many of the topics covered in the author’s earlier books on trace analysis for drug compounds and on selectivity and detection in HPLC. It is intended as a discussion of methods for the determination and separation of dilute samples or very small samples. The author defines trace analysis as being at the ppm level and ultratrace as being below this level (less than pg g-1). However, although some sections are specifically directed to these areas a large proportion of the book duplicates material to be found in any of a range of general texts on HPLC.Thus, the book appears to be aimed at the newcomer to HPLC who has to work in trace analysis rather than being aimed at the special problems and applications of techniques devoted to trace analysis for an analyst who is already familiar with less demanding forms of HPLC. It covers the scope of trace analysis, and theoretical considerations with due emphasis on the use of narrow and microbore columns although many of the terms are in general use. However, the assertion that narrow columns produce narrow peaks is contradicted by a table later the same page and a number of other similar broad comments are also unjustified-‘separation time increases rapidly with d,,’. A useful section considers instrumental problems and the difficulty of increasing limits of detection by reducing pump and detector noise.This includes an analysis of the value of different detectors for small samples, including electrochem- ical and mass spectrometric detectors and surprisingly also includes the refractive index detector although its limited response for many compounds is noted. Equally valuable, although it is fairly general, is a discussion on sample pre-treatment before analysis. This is followed by a general description of different mobile phases and elution methods almost all of which is not specific to trace analysis. The last section describes methods to optimize detectability and finally a long section on the applications of trace analysis is provided covering a range of analytes in pharmaceuticals, food and environmental samples.Overall, I feel the book would have been improved if it had focused on trace and ultratrace analysis, rather than being an all encompassing text on HPLC methodology based around trace analysis. Roger M . Smith Sensors. A Comprehensive Survey. Volume 2. Chemical and Biochemical Sensors. Part I Edited by W. Gopel, J. Hesse, J. N. Zemel. Volume edited by W. Gopel, T. A. Jones, M. Kleitz, I. Lundstrom and T. Seiyama. Pp. xvii + 716. VCH. 1991. Single Volume Price DM380.00; f 147.00. (Subscription price DM31 5.00; f 122.00). ISBN 3-527-26768-9 (VCH, Weinheim); 0-89573- 674-8 (VCH, New York). Sensors. A Comprehensive Survey. Volume 3. Chemical and Biochemical Sensors. Part II Edited by W. Gopel, J. Hesse, J. N. Zemel. Volume edited by W.Gopel, T. A. Jones, M. Kleitz, I. Lundstrom and T. Seiyama. Pp. xvii + 514. VCH. 1991. Single Volume Price DM380.00; f 147.00. (Subscription price DM31 5.00; f 122.00). ISBN 3-527-26769-7 (VCH, Weinheim); 0-89573- 675-6 (VCH, New York). These two volumes form part of a comprehensive series on sensors, which is to be published in eight volumes. The emphasis in these particular volumes is in the area of chemical sensors and biosensors, while other volumes in the series will deal with general aspects and fundamentals of sensors, and with physical (thermal, magnetic, optical and mechanical) sensors. The two volumes reviewed here have set out to produce a ‘core’ reference text on chemical and biological sensors, as well as providing an outer ‘shell’ describing the basic physical and chemical background underlying the sensing mechanisms, the technology needed to produce8N ANALYST.JANUARY 1993, VOL. 118 sensors or components, and recent applications. This has been acheived by arranging the two volumes in the following way. The first volume contains several introductory chapters dealing with definitions and historical remarks, before going on to deal with some basic physical chemistry aspects of sensors. The main body of the first volume, however, deals with specific aspects relating to potentiometric, amperome- tric, conductometric, electronic conductivity and capacitance, field effect, calorimetric, optochemical and mass-sensitive sensors. The second volume then begins with a chapter on biosensors before treating applications of sensors in areas such as environmental monitoring and control, biotechnology and clinical diagnostics.These volumes are therefore to be welcomed as a major contribution to the literature on chemical and biological sensors, and along with the other volumes in this series should be on the shelf of every library servicing scientists and technologists interested in this field of endeavour. Malcolm R. Smyth Spectral Atlas of Polycyclic Aromatic Compounds. Volume 3. Including Information on Aquatic Toxicity, Occurrence and Biological Activity Edited by W. Karcher, J. Devillers, Ph. Garrigues and J. Jacob; with contributions from R. Dumler, S. Ellison, J. Florestan and E. Gevers. Pp. 1157. Kluwer Academic. 1991. Price Df1440.00; f 148.00; US$241 .OO.ISBN 0-7923- 1464-6. This volume is the third in a series which make up a ‘Spectral Atlas of PAC’ and this volume contains spectral and other information on 59 compounds. These include 16 nitro derivatives of PAH, 6 oxygenated heterocyclic PAC, 15 sulfur-heterocyclic PAC, 14 methylated or dimethylated PAH and 8 metabolites. The spectra presented for each compound include UV-spectra, fluorescence and phosphorescence Shpol’skii spectra at 15 K, mass spectra (magnetic and quadrupole), NMR spectra (proton and carbon-13 spectra) and IR spectra (in solution and in KBr pellets and including some Fourier-transformed 1R spectra). In addition to the above data, a variety of other basic information is provided such as the chemical formulae, mass number, melting-point, purity, CAS registry and BCR reference material numbers.Of particular value to an environmental scientist such as myself is the physico-chemical data provided, which includes retention indices (HPLC), octanol-water partition coefficients, water solubility and capacity factors. The sub-title of the book refers to a collection of data and/or literature citations of the occurrence, biological activity (bacterial mutagenicity data from Ames tests and animal carcinogenity data) and aquatic toxicity data. In the latter case references relating to nearly 150 compounds are given though no actual data are provided. This book is not one to sit down and read from cover to cover, as despite its 1157 pages there is very little text (less than 20 pages), with information being provided as full page, annotated spectra and tables.With one notable exception, the coverage is remarkably complete and should be of use to many practising environmental scientists as a reference work and aid to identification as well as a guide to the relevant literature (over 1100 references are cited). Much of the information provided would otherwise be very difficult to find and to have it compiled in this volume is clearly very useful. Indexing is by compound and seems to be comprehensive; however, having had only this isolated volume for review I should also like to have seen some cross-referencing to the contents of the other volumes included. The one major gap in the coverage is a complete lack of gas chromatography related data, notably retention indices.This seems a curious omission given that GC-MS was used for the production of the mass spectral data and that GC is a major analytical technique in PAC analysis. To sum up, this is a long and expensive book which should not be considered for purchase in isolation of the other volumes in the series. Nevertheless, to workers in the field of polycyclic aromatic hydrocarbons it is a mine of information and clearly merits inclusion on library shelves. Martin R. Preslon Wilson and Wilson’s Comprehensive Analytical Chem- istry. Volume XXVII. Analytical Voltammetry Edited by G. Svehla; Volume edited by M. R. Smyth and J. G. Vos. Pp. xxv + 578. Elsevier. 1992. Price US$228.00; Df I .445.00. ISBN 0-444-88938-8. I am pleased to be able to recommend this volume on analytical voltammetry to postgraduate scientists in this field.This book is generally well-written, and provides a very large amount of information on analytical applications of vol tam- metry; it is a little weak on applications to natural waters. The chapters in this book were written by different authors, and the quality of the individual chapters varies somewhat. Especially good chapters are those on instrumentation, pharmaceutical applications, and applications to organic and organometallic species in the environment. It is surprising that such overviews can be made interesting reading by careful inclusion of many well-described examples. Similarly the chapter on biological molecules (immunoassays) is interesting and provides many examples, but the material appears to be less well-digested and is harder to read. A chapter on theory is aimed at the beginner and provides equations of electroanalytical or electrochemical importance without derivation. This chapter is unreadable, but references are provided for those who want to take it further. More theory is given in other chapters, notably in those on modified electrodes and biosensors. A chapter on inorganic species in the environment is somewhat weak; it is let down for instance by a review of rather dated methods to determine metal speciation in natural waters. The advice to store samples by freezing to eliminate losses of metals by adsorption on container walls is flawed and does not show familiarity with the topic of natural waters, nevertheless many interesting applications are given. Biolog- ical samples are also discussed in this chapter, but the important production of interferences as a result of sample digestion (and methods to deal with it) is not discussed. The area of sample treatment (very important in order to remove interferences) of biological and water samples is mentioned piecemeal in individual chapters; a thorough treatment is, however, lacking from this book. A chapter on modified electrodes is strong on mechanisms and theory, but comparatively weak on applications. The book ends with a chapter on the interesting topic of biosensors, which is still very much being developed. C. M . G. van den Berg

ISSN:0003-2654    

DOI:10.1039/AN993180004N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993. VOL. I18 9N CONFERENCE DIARY ~ February 31/1-5/2 Symposium on Electronic Imaging: Science San Jose, CA, and Technology USA 8-12 10-12 18 23-26 4th International Conference on the Health and New Delhi, Disease Effects of Essential and Toxic Trace India Elements International Conference on Energy, Karaikudi, Environment, and Electrochemistry Tamilnadu, India Physics and Chemistry of Transmittance Measurements Middlesex, UK Teddington, 2nd International Symposium on Automation, Montreux, Robotics and Artificial Intelligence Applied to Switzerland Analytical Chemistry and 2nd International Conference on Robotics in Laboratory Medicine Conference Manager, IS&T, 7003 Kiiworth Lane, Springfield, VA 22151, USA Tel: + 1 703 642 9090. Fax: + 1 703 642 9094 M.Abdulla, Department of Medical Elementology and Toxicology, Jamia Hamdard, Hamdard Nagar, New Delhi 110062, India Tel: +91 11 643 3685. K. C. Narasimham, Conference Convener, Central Electrochemical Research Institute, Karaikudi-623 006, Tamilnadu, India Tel: +9104565 3161,2368 or 2064. Fax: +91 04565 2088 Dr. G. H. C. Freeman, National Physical Laboratory, Teddington, Middlesex, UK TWll OLW J. van der Greef (Chairman), TNO and University of Leiden, P.O. Box 360, 3700 AJ Zeist, The Netherlands Tel: +31 3404 44144. Fax: +31 3404 5722 8-12 19 23-25 23-26 30 April 3-4 4-8 5-7 6-7 18-2 1 19-21 PITTCON '93, 44th Pittsburgh Conference and Exposition on Analytical Chemistry and Applied Spectroscopy Atlanta, GA, USA Symposium on Possibilities and Limitations of Antwerp, Chiral Separation Techniques Belgium International Symposium on Advanced IR Spectroscopy (AIRS) Japan Tokyo, 7th International Symposium on Instrumental Brighton, Planar Chromatography Sussex, UK The Laboratory Environment: Working with Dangerous Substances London, UK VDI-Meeting on Progress in Thermic, Catalytic and Sorptive Exhaust Cleaning Mannheim, Germany XIIIth World Congress on Occupational Safety New Delhi, and Health India 3rd International Conference on Ion-Beam and Namur, Surface Specific Analysis Techniques Belgium BTS Colloquium (of the British Toxicology Society) on Early Markers of Carcinogenesis Canterbury, Kent, UK 4th International Symposium on Pharmaceutical and Biomedical Analysis USA Baltimore, MD, Anakon '93 Baden-Baden, Germany Mrs.Alma Johnson, Program Secretary, Pittsburgh Conference, 300 Penn Center Boulevard, Suite 332, Pittsburgh, PA 15235-5503, USA Tel: +l 412 825 3220.Royal Flemish Chemical Society (KVCV), Working Party on Chromatography, c/o Dr. R. Smits, BASF Antwerpen N.V., Central Laboratory, Scheldelaan, B-2040 Antwerp, Belgium Tel: +32 3 568 2831. Fax: +32 3 568 3250 Hirokazu Toriumi, AIRS Organizing Committee, Department of Chemistry, College of Arts and Sciences, The University of Tokyo, Komaba, Meguro, Tokyo 153, Japan Tel: +813 3467 1171, ext. 309. Fax: +813 3485 2904 Mrs J. A. Challis, Chromatographic Society, Suite 4, Clarendon Chambers, 32 Clarendon Street, Nottingham, UK NG1 5JD Tel: +44 602 500596. Fax: +44 602 500614 Pauline A. Sim, Gascoigne Secretarial Services, 24 Southfield Drive, Hazlemere, High Wycombe, Buckinghamshire, UK HP15 7HB Tel: +44 494 713664.Fax: +44 494 714516 VDI, Verein Deutscher Ingenieure (Kommission Reinhaltung der Luft), Graf Recke-Strasse 84, P.O. Box 1139, D-W-4000 Diisseldorf 1, Germany National Safety Council, P.O. Box 26754, Siom, Bombay 400022, India Professor G. Demortier, Facultes Universitaires, N-D de la Paix, 22 rue Muzet, B-5000 Namur, Belgium Dr. E. S. Harpur, Sterling Winthrop Research Centre, Willowburn Avenue, Alnwick, North Cumberland, UK NE66 2JH Shirley E. Schlessinger (Symposium Manager), Suite 1015,400 East Randolph Drive, Chicago, IL 60601, USA Tel: +1 312 527 2011. Gesellschaft Deutscher Chemiker, Abteilung Tagungen, Postfach 90 04 40, Varrentrappstasse 40-42, D-6000 Frankfurt am Main 90, Germany1ON ANALYST, JANUARY 1993, VOL.118 20-23 International Symposium on Electroanalysis in Loughborough, Dr. Arnold Fogg, Electroanalysis Conference, Biomedical, Environmental and Industrial Leicestershire , Chemistry Department, Loughborough University Sciences UK of Technology, Loughborough , Leicestershire, UK LEll3TU Messedamm 22, P.O. Box 191740, D-W-1000 Berlin 19, Germany 27 Validating Mu1 ticomponen t Analysis London, Mr. T. 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ISSN:0003-2654    

DOI:10.1039/AN993180009N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993, VOL. 118 Extraction of Organophosphorus Pesticides From Soil by Off -line Supercritical Fluid Extraction Klaus Wuchner, Rudy T. Ghijsen and Udo A. Th. Brinkman Department of Analytical Chemistry, Free University, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands Robert Grob and Jacques Mathieu ENSCT, Laboratoire de Chimie Analytique, 3 18 Route de Narbonne, 31077 Toulouse Cedex, France Supercritical fluid extraction (SFE) conditions were optimized for the isolation of organophosphorus pesticides (OPPs) from soil. Results using pure carbon dioxide and carbon dioxide modified with acetone, ethyl acetate or methanol were compared in terms of recoveries, extraction rates and matrix effects. Despite the good solubility of the OPPs in pure C02, the addition of methanol was necessary t o achieve high recoveries (390%) when spiked soil was extracted.The extent t o which matrix effects, which probably cause the decrease in recoveries, occur depends on both the analyte polarity and the spiking method used. Similar extraction efficiencies were achieved by adding microlitre amounts of the modifier directly t o the soil in the extraction cartridge and by using a pre-mixed gas cylinder. SFE of OPPs in soil was compared with solvent extraction. Keywords: Supercritical fluid extraction; organophosphorus pesticides; soil; optimization; matrix effects The growing interest in supercritical fluid extraction (SFE) as a sample preparation method in analytical chemistry is reflected by the large number of papers and comprehensive reviewsl-3 published and by the many contributions to symposia4.5 in recent years.SFE is increasingly employed as an alternative to the more tedious classical extraction proce- dures, such as Soxhlet and manual solvent extractions with organic solvents. These classical extraction techniques are often the limiting step in the determination of organic pollutants in environmental solids and cause a considerable contribution to waste production in the laboratory. On the other hand, SFE has been shown to be an efficient and rapid technique for the isolation of polychlorinated biphenyls (PCBs),h-") polycyclic aromatic hydrocarbons (PAHs), chlorinated dibenzodioxins,lJ halocarbons15 and other organic pollutantslcp18 from sediments and soils. The widespread use of agricultural chemicals, with more than 1000 pesticides in common use,lg demands efficient and practical analytical methods for the inventory and assessment of the spread of these hazardous chemicals in the environ- ment.There is particular interest in the monitoring of pesticide residues in soil. The utility of SFE for the determi- nation of pesticides has been demonstrated for urea herbi- cides,20-22 chlorinated insecticides,'"24 triazines25 and phen- oxyace tic esters .Zh An important group of pesticides, the organophosphorus pesticides (OPPs), have been the subject of only a few SFE studies, despite their worldwide application in agriculture and their high mammalian toxicity. Ethion was extracted from a freeze-dried grape sample with pure C 0 2 to demonstrate the potential of an on-line coupling of SFE and GC.27 Cortes et a1.28 used methanol-modified C 0 2 for the determination of chlorpyrifos in grass samples.The pesticide was quantitatively recovered and interferences could be eliminated by coupling SFE with micro-LC/GC. Bergna et ~ 1 . 2 9 showed that the extraction of disulfoton and tolclofos methyl from soil was feasible by on-line coupling of SFE and GC. The extractability of a larger number of OPPs with pure and modified C 0 2 under various extraction conditions was dis- cussed by Lopez-Avila rt al.23 Dimethoate, azinphos methyl and coumaphos could not be recovered by pure C02; diazinon was not even extractable with 10% methanol-modified C02. The analytes were added to sand, which has been proposed as a non-sorptive matrix in method development of SFE.30 Other studies showed a decrease in the extraction efficiency due to solute-matrix interactions when relevant environmen- tal samples, such as soil or sediments, were extracted.'".l"26." Obviously, there still is a need for an SFE procedure that permits the efficient isolation of a large number of OPPs from soil.The main objective of this study was the development of an efficient SFE method for the rapid determination of OPPs of varying polarity in soil. The selected set of OPPs covers a wide range of polarity, as indicated by their octanol-water partition coefficient, Kow; log KO, ranges from 0.5 for dimethoate to 5.1 for carbofenthion.32 The extraction conditions, such as pressure and the use of modifiers, were optimized for different matrices (quartz wool, sand, soil) in order to achieve high recoveries (>SO%) in less than 1 h.Two different spiking methods were tested to study analyte-matrix interactions. The results were mainly discussed under the aspect of matrix effects. Practical aspects, such as the method and conditions of modifier addition, were emphasized. No attempt has been made to appreciate fundamental thermodynamic and kinetic SFE parameters, for which some basic treatments and models are available in the literature. Finally, the SFE results were compared with those obtained using a classical solvent extraction method. Experimental Chemicals Diazinon, disulfoton, dimethoate, malathion, parathion ethyl, carbofenthion, azinphos methyl and coumaphos of 9649% purity were obtained from various sources. Ethyl acetate, acetone (both of analytical-reagent grade), methanol (HPLC grade) and anhydrous sodium sulphate (analytical- reagent grade) were purchased from J .T. Baker (Deventer, The Netherlands) and used without further purification. Carbon dioxide (purity 299.99%) and pre-mixed methanol- modified C 0 2 (2% m/m) were supplied by Hoek Loos (Schiedam, The Netherlands) and Intermar (Breda, The Netherlands), respectively. Calibration standards were prepared in ethyl acetate by serial dilution of a stock solution of the OPPs in acetone (0.5 mg ml- 1). The stock solution was used to spike the various matrices. All solutions were stored at 4°C in the dark.12 ANALYST, JANUARY 1993, VOL. 118 Matrices and Spiking Methods Soxhlet-extracted glass-wool was used as an inert matrix.A purified seasand, purchased from J. T. Baker, was also studied. A dried soil with a particle size distribution of <2 pm 1.6%, 2-38 pm 3.1%, 338 pm 88% was used throughout this study. It contained 3.3% of total organic carbon. Two methods were used to prepare a contaminated soil at the 4 and 40 ppm spiking levels. In the spot method, approximately 250 mg of soil were weighed into the extraction cartridge. The soil was then fortified with a known amount of the analytes by adding 20 p1 of the stock solution directly to the soil. In the slurry method, 10-20 g of soil were weighed into a 50 ml flask. After the addition of 20 ml of acetone and an appropriate volume (80 p.1-1.6 ml) of the spiking mixture in acetone, the flask was sealed and its contents were stirred for 3 h.With both methods, the solvent was evaporated to dryness at ambient temperature in a hood for at least 20 h. The completeness of the drying step was controlled by weighing the sample. SFE System All extractions were performed on a laboratory-built SFE system, represented in Fig. 1. The pump heads of the syringe pump (1) (Chrompack, Middelburg, The Netherlands) are cooled to 5 "C. The extracting phase is preheated in a coil (2) and enters the extraction cartridge (4), a 20 X 4 mm i.d. HPLC precolumn (Chrompack), via a stop valve (3) (Alltech, Deerfield, IL, USA). The stop valve is closed during pressurization of the pump and decompression of the extrac- tion vessel. The six-port valve (5) (Valco, Schenkon, Switzer- land) permits selection between two restrictors (6) or the flow of the supercritical fluid to be stopped during static extraction.When a dynamic extraction is performed, the supercritical pressure in the extraction cartridge is maintained by using fused-silica capillaries. The dimensions of the capillaries, which determine the flow rate at a given pressure and temperature, were 15-25 cm x 25 pm i.d. (Chrompack) and 80-100 cm x 50 pm i.d. (SGE, Ringwood, Australia). 9 GC oven 8 Fig. 1 Schematic diagram of the off-line SFE system The restrictors were introduced via a septum into a vial containing 2 ml of ethyl acetate, which contained phorate as an internal standard. The internal standard is used to correct for the loss of collection solvent during extraction.Solvent losses were minimized by condensation of the vapours in a reflux cooler (7). The extraction temperature was regulated by a GC oven (8) (HP 5840A, Hewlett-Packard, Palo Alto, CA, USA). A short 30 cm X 0.25 mm i.d. PEEK capillary (9), connected to a 500 pl syringe (Hamilton, Reno, NV, USA), permitted 50 pl aliquots of the trapping solvent to be taken during extraction. In this way extraction profiles, i . e . , plots of percentage recovery versus extraction time or volume of C02, could be easily monitored. SFE Procedures Extractions were generally performed at 50°C and 250 bar, i.e., at a density of 0.84 g ml-1 for pure C02. The collection solvent and extraction cartridge were heated for 5 min at SO "C before the extraction was started. Dynamic extractions with pure or pre-mixed methanol-modified C02 were carried out at about 0.8 ml min-1 after a static equilibrium period of 1 min.Steady-state extractions were performed by closing the outlet valve (5) for 2 min. The extracted analytes were then transported dynamically to the collection solvent with 1 ml of C02. This procedure was repeated 2-5 times. The effect of modifier on the recovery was determined by adding 5-70 pl of the modifier with a syringe directly to the matrix in the cartridge. In that event, only steady-state extractions were carried out to permit the dissolution of the modifier in the supercritical fluid. The volume and the flow rate of the supercritical fluid were read at the pump and correspond to its fluid state. Conventional Solvent Extraction The spiked soil samples were also extracted by a conventional solvent extraction method, currently used in a laboratory in The Netherlands for the determination of OPPs in A portion of 5 g of soil was placed in a 50 ml Erlenmeyer flask and 20 ml of ethyl acetate were added.The flask was sealed with a septum-lined cap and shaken for 90 min. After decantation, the organic layer was transferred into a closed centrifuge tube. A second portion of 15 ml of ethyl acetate was then introduced into the Erlenmeyer flask. The suspension was shaken for another 90 min and equilibrated overnight. The combined extracts were centrifuged for 10 min at 2000 rpm . GC Analysis The SFE collection solvent and extracts from the conventional extraction technique were dried with anhydrous sodium sulfate and analysed by GC with flame ionization detection (FID) (PU 4450, Pye Unicam, Cambridge, UK), with on-column injection.A 1 pl volume was injected into a 2 m x 0.32 mm i.d. diphenyltetramethyldisilazane (DPTMDS)- deactivated retention gap (B. Schilling, Zurich, Switzerland), connected to a 15 m X 0.25 mm i d . DB-1701 fused-silica column (J & W, Folsom, CA, USA) via a press-fit connector. A Hewlett-Packard 5890 Series I1 GC with a pressure programmable on-column injector was used for thermionic detection. Results and Discussion In the development of an SFE method, several steps can be discerned. First, the pressure, temperature and supercritical fluid composition have to be optimized. To that end, the analytes should be extracted from a simple inert matrix such as glass-wool, filter-paper or sand,3(J to prevent matrix effects.ANALYST, JANUARY 1993, VOL.118 13 These experiments are also necessary for the evaluation of the trapping efficiency of the collection system. Second, a spiked matrix of interest should be extracted in order to reveal the influence of the matrix on the extraction efficiency and to detect interfering co-extractives. It may well be that the extraction conditions will have to be adjusted to overcome matrix effects. Finally, the reliability of the SFE method can be tested by extracting a certified reference material. Extraction of OPPs From Inert Matrices The extractability of the OPPs of interest by pure C 0 2 was determined by dynamically extracting an inert matrix, glass- wool, at 50 "C using pressures ranging from 100 to 250 bar.The spiking solvent was evaporated prior to SFE extraction to avoid changes in the solubility characteristics of the super- critical C02. All OPPs were quantitatively recovered (295%) with only 1.5 ml of liquid CO2 at 250 bar. The analytes could also be dissolved in less dense C02 (50°C' 100 bar), but the extraction rate was lower and at least 3.5 ml of C02 were required. No attempt was made to study the influence of temperature on the extraction efficiency. First, the recoveries obtained by Lopez-Avila et al.23 at 60 and 70 "C were not higher than those achieved at 50°C in our study. Moreover, an increase in temperature will cause a greater loss of collection solvent during extraction, which may adversely affect the trapping efficiency.The high recoveries from the inert matrix demonstrate that ethyl acetate (2 ml) is an efficient trapping liquid. Flow rates between 0.3 and 1 ml min-1 could be applied without any noticeable loss (22%) of the extracted pesticides. In order to compare the performance of our system with that of Lopez-Avila et aZ.,23 a spiked sand sample was extracted dynamically with pure CO2 at SO "C and 250 bar. The recoveries, shown in Fig. 2, are comparable (394%) to those achieved in the experiment with glass-wool. Apparently, the investigated sand sample does not influence the analyte recovery. Better results were found in our study, especially for dimethoate, diazinon, azinphos methyl and coumaphos, which could not be recovered at all with pure C02 in the study of Lopez-Avila et al.The differences in recoveries may be caused by the different nature of the sand samples or more likely the poorer trapping qualities of hexane. 1 nn 1 2 3 4 5 6 7 8 OPP sand, spot spiked soil, spot spiked soil, slurry spiked Fig. 2 Influence of matrix and spiking method on OPP recovery (n = 3). Extraction conditions: 250-300 mg of the spiked material (40 ppm; approximately 10 pg of each compound) were extracted dynamically with pure C02 at 50 "C and 250 bar (25 MPa) at a flow rate of 0.7-0.9 ml min-l. The samples were extracted 24 h after spiking. OPPs: 1, diazinon; 2, disulfoton; 3, dimethoate; 4, malathion; 5 . parathion ethyl; 6, carbofenthion; 7, azinphos methyl; and 8, coumaphos SFE of Spiked Soil Samples, Matrix Effects Spiked soil samples were extracted dynamically with pure C02 at 50 "C and 250 bar to determine the extraction efficiency for a relevant environmental sample.Two spiking methods were used. Although the spot method is frequently used in SFE studies,13,16Jg the less commonly used slurry method143'7 should provide a more realistic evaluation of the influence of solute-matrix interactions on extraction efficiency. In the spot method, a few microlitres of the spiking solution are added directly to the soil in the extraction vessel; the analytes are present in a narrow region, a spot. In our work, the acetone used as the spiking solvent had completely disappeared after 1-2 h. A further distribution of the solutes over the soil sample can only be due to volatilization from the soil surface.However, migration of semi-volatile chemicals, such as OPPs, by volatilization from a dry soil is a very slow process .34 In the slurry method, a suspension of about 10 g of soil in 20 ml of a dilute spiking solution is stirred for 3 h before evaporation of the solvent. Stirring the slurry causes the compounds to spread all over the soil and to interact with the total surface of the soil particles. Further, the analytes can partition between the liquid phase and the whole wetted soil surface during a much longer period of time than in the spot method (about 20 versus 2 h). It can therefore be expected that the analytes will interact with essentially all active sites of the matrix. Active matrix sites for OPPs are localized in the organic matter (e.g., humic material) and clay fraction of the soil .35 Adsorption of solutes on soil involves interaction forces ranging from van der Waals-London interactions to chemical bonding .34 Analyte recoveries after extraction with pure C 0 2 from spot-spiked soil are depicted in Fig.2. The extraction yields were as good as those obtained with the sand sample, except for dimethoate. Its recovery decreased from 94% (sand) to 71% (soil). Apparently no significant interaction of the soil matrix occurs with any of the other OPPs. However, when a slurry-spiked soil was extracted under the same conditions, the extraction was distinctly less efficient. As can be seen from Fig. 2, the extraction yields of disulfoton and azinphos methyl were about 20% lower than for the spot-spiked soil and only 41% of dimethoate was extracted.The recoveries of the remaining OPPs decreased by &13%. Analyte losses due to the evaporation of the larger spiking solvent volume were estimated by conducting a 'blank' slurry-spiking experiment, i . e . , without soil. The observed evaporation losses of 2-8%, which represent an extreme situation, because no particulate matter was present during the solvent elimination step, cannot explain the substantial I C - / A o B 0 1 2 3 4 5 6 CO$m I Fig. 3 OPP recovery (%) versus volume of liquid C02 used in SFE. SFE conditions as in Fig. 2. The slurry-spiked soil was extracted 5 d after spiking. Dimethoate; A, spot-spiked and B, slurry-spiked; azinphos methyl: C, spot-spiked and D, slurry-spiked soil14 ANALYST, JANUARY 1993, VOL.118 decrease in the recoveries of azinphos methyl, disulfoton and dime thoate. An attempt t o improve the OPP recoveries by carrying out SFE at higher pressure (300 bar) was not successful. As can be seen from the extraction profiles of dimethoate and azinphos methyl in Fig. 3, a plateau was rapidly reached (after about 3 ml of C02) when a spot- and a slurry-spiked soil were extracted with pure C02. As expected, increasing the volume of extractant to 9 ml of C 0 2 did not cause a noticeable increase in the recoveries of the OPPs, and neither did exhaustive steady-state extraction with pure C02. The decreased recovery of the OPPs and especially of dimethoate from a slurry-spiked soil implies that part of the analytes is strongly bound to the soil.Despite the good analyte solubility in pure C02, the apolar supercritical C 0 2 cannot compete efficiently with the active matrix sites to displace the sorbed analytes. The plateau of the extraction profile in Fig. 3 indicates the area in which the extraction becomes sorption and/or diffusion limited. The explanation is further supported by the fact that dimethoate, which obviously is the analyte most sensitive to sorption interactions, showed the largest decrease in recovery when testing the slurry-spiking proce- dure, with which interaction with active sites will be most prominent. It was also observed that the C02-extractable percentage of the OPPs decreased with the storage time of the spiked soil. For instance, only 66% of azinphos methyl was recovered after 5 d (cf., Fig.3), compared with 75% after 24 h (cf., Fig. 2). As another example, compare the 40 ppm spiked data in Fig. 2 with those in Table 1. Such an increase of the strongly bound portion of an analyte with time is well known from the literature dealing with sorption processes in soil .34,35 The low extraction yields obtained with the slurry-spiked soil suggest that poor results may also be expected when the extraction of OPPs from field samples is attempted with pure CO?. SFE With Modified C02 The negative influence of solute-matrix interactions on analyte recovery from real samples has been reported in several studies. Incomplete extraction with pure C 0 2 , despite good analyte solubility, has been observed by Mulcahey et uf.1 0 for PCBs, by Onuska and Terry14 for tetrachlorodibenzo- p-dioxins and by Hawthorne et uf.3' for PAHs from sediments and by Engelhardt et al.Z6 for explosives from soil. The extraction efficiency can be increased by using a supercritical fluid having a dipole moment ( N 2 0 , CHCIFS) or by adding an organic solvent as modifier to C 0 2 . Because of practical aspects ( N 2 0 is explosive, CHCIF3 very expensive and NH3 Table 1 Cumulative OPP recoveries (%) as a function of organic modifier used Modifier added to the samplc? Prc- extraction Ethyl Analyte with C03* acetate Acetone Methanol Diazinon Disulfoton Dimethoate Malathion Parathion Carbofenthion Azinphos methyl Coumaphos 72 62 37 72 71 75 67 73 82 71 55 81 80 84 85 80 82 70 61 82 81 80 88 86 82 70 83 84 82 81 99 90 * Slurry-spiked soil (40 ppm) dynamically extracted with 5.5 ml of pure CO? at 50°C and 250 bar.11 d after spiking. i- Subsequent addition of 35 pl of modifier to the C02-pre-extracted soil in the cartridge; 2 min static extraction, followed by 1.0 ml ofCOZ. The procedure was repeated once. toxic), modifiers were used to enhance the extraction effi- ciency. Acetone, ethyl acetate and methanol were selected as modifiers, because they are used in conventional techniques for the extraction of OPPs from soil and sediment.35--37 Table 1 lists the cumulative OPP recovery for a slurry-spiked soil, using these modifiers. Before adding modifier, the soil was exhaustively pre-extracted with pure C02. That is, the increased recoveries observed on subsequent SFE in the presence of modifier reflect the successful competition for the analytes bound to the active matrix sites.As can be seen from Table 1, the recoveries improved with all threc modifiers. Significant mutual differences were observed for the pesti- cides for which the recovery was most seriously affected by the matrix effect, viz., azinphos methyl and dimethoate. With both analytes methanol was the most effective displacer. The effect of the addition of methanol to a C02-pre-extracted soil sample is clearly demonstrated in Fig. 4. Fig. 4(a) shows the gas chromatogram with nitrogen-phosphorus specific detec- tion (NPD) of an SFE extract with pure COT. In Fig. 4(b), the chromatogram obtained after a subsequent extraction of the same sample in the presence of 70 PI of methanol is shown. Fresh trapping solvent was used for the methanol-modified extraction.The distinctly increased recoveries for dimethoate (63%) and azinphos methyl (26%) are clearly observed. In order to study the extraction yield, the analyte recovery was monitored as a function of the number of methanol- modified extraction cycles. Some typical results are presented in Fig. 5 . A plateau is reached for diazinon after a single extraction cycle. The same behaviour was shown by disulfo- ton, malathion, parathion and carbofenthion. Two cycles were required to obtain an extraction efficiency of at least 80% for azinphos methyl, dimethoate and coumaphos (data not shown). With this group, a further increase of 5 4 % could t - m c 0, m .- IS 0 5 10 15 20 Retention time/min Fig.4 GC-NPD traces of SFE extracts from a slurryspiked soil. ( u ) Spiked soil (4 ppm) extracted with 5 ml of pure C 0 2 at 50 "C and 250 bar (25 MPa); ( h ) same soil subsequently extracted with methanol- modified C 0 2 (addition of 70 pl to the soil). For compounds, see Fig. 2. GC conditions: 1 pl injected on-column into a 2 m X 0.32 mm i.d. retention gap, coupled to a 25 m x 0.32 mm i.d. DB-5 column. Temperature programme: 80 "C for 1.5 min. then increase to 280 "C at 10°C min-1. Carrier gas: He at 80 kPa head pressureANALYST, JANUARY 1993, VOL. 118 15 100 s - 80 L- > 60 I 0 1 2 3 4 5 Number of cycles Fig. 5 Plot of analyte recovery versus number of SFE cycles for three OPPs using methanol-modified C02. A 35 yl volume of methanol was added to the soil bcforc steady-state extraction cycle.One cycle corresponds to approximately 1.4 ml of C02. Extraction conditions: 2 rnin static; dynamic purging with 1.0 ml of C 0 2 , 50°C; 250 bar (25 MPa). decompression of the extraction cell for 3 rnin before addition of the next portion of modifier. The spiked soil (40 ppm) was extracted 7 d after slurry-spiking Table 2 OPP recovery using methanol-modified steady-state SFE of soil. Slurry-spiked soil extracted 24 h after spiking. Same conditions as in Fig. 5 cxcept that four cycles were performed ( n = 3). Analysis by GC-FID (40 ppm) and by GC-NPD (4 ppm) Spiking level 4 PPm 40ppm Analyte Diazinon Disulfoton Dimethoate Malathion Parat hion Carbofenthion Azinphos methyl Coumaphos Recovery 95 70 100 96 97 95 103 99 ("/.1 RSD 2 2 3 1 2 2 4 3 ( Y o ) Recovery 89 75 94 92 90 89 94 90 (%) RSD 6 6 5 4 8 6 9 6 (Yo ) be achieved if five instead of two cycles were performed. The slight improvement certainly does not justify the increase in the extraction time from 22 to 55 min. The extraction yields during one cycle could not be further improved by extending the dynamic purging, i.e., by using more than 1 ml of CO-,. Probably the organic modifier is rapidly swept out of the extraction vessel. The static period was varied from 1 to 4 min; 2 min were sufficient for equilibration, which agrees with the results of Onuska and Terry.9 All of the OPPs were extracted efficiently from a slurry- spiked soil at 40 ppm by performing two methanol-modified steady-state extractions.With the exception of disulfoton (see below), the recoveries of all analytes were at least 80%. The adsorption of the OPPs on the soil probably is due to hydrogen bonding or ligand exchange.35 This would explain why the most polar modifier tested, methanol, is the most effective in overcoming the matrix effects. Different extraction yields were obtained using methanol-modified C02 when soil was extracted 1 d after spiking (see Table 2) or 11 d later (see Table 1). The slight decrease in analyte recovery (about 5%) with storage time may be due either to stronger bonding of OPPs to matrix sites or to degradation. In order to evaluate whether the extraction procedure can also be used at lower concentration levels, a soil was slurry Table 3 OPP recovery (% t SD) from spiked soil using SFE or solvent extraction.Slurry-spiked soil (4 ppm) extracted 7-9 d after spiking ( n = 3) Methanol- modified Pre-mixed steady-state modified C02 Solvent Anal yte SFE" dynamic SFEt extraction$ Diazinon Disulfoton Dimethoate Malathion Parathion Carbofenthion Azinphos methyl Coumaphos 92 k 3 63 f 3 111 + 4 101 * 4 95 -r- 3 96 k 5 103 f 5 96 f 2 91 rt 2 66 f 5 104 f 4 97 f 4 98 f 2 92 + 4 102 f 4 93 ?E 5 90 -e 4 65 2 2 75 + 6 90+ 4 96 f 8 93 f 8 95 f 8 91 * 5 * Conditions as in Fig. 5 ; four cycles. cylinder (2% m/m) at 50°C and 250 bar. $ See Experimental for conditions. Dynamic extraction with 3-5 ml of methanol-pre-mixed C 0 2 spiked at the 4 ppm level. The typically 90-95% analyte recoveries obtained at both spiking levels (Table 2) suggest that the present procedure will be applicable over a wider range of concentrations. The relatively low RSD values obtained at the lower spiking level may well reflect the inherently greater selectivity of NPD as compared with FTD. At both spiking levels it was necessary to add at least 30-40 p1 of methanol per cycle to obtain the recoveries quoted above.The addition of only 5 or 15 p1 of modifier yielded lower recoveries, especially with dimethoate and azinphos methyl. On the other hand, the use of 70 instead of 35 pl did not improve results at all. The low recovery of disulfoton is probably caused by degradation. We observed that solutions of disulfoton were not stable when they were exposed to daylight and ambient temperature for longer periods of time. Disulfoton contains a thioether group.Degradation studies on phosphorothiolo- thionates in soil indicate a rapid oxidation to their sulfone and sulfoxide form .35 These degradation products are more polar than the parent compound and, hence, are less extractable. On the other hand, it cannot be excluded that disulfoton interacts strongly with the soil matrix and that none of the tested modifiers could displace the bound pesticide. Performing methanol-modified static extractions takes approximately 11 rnin per cycle (addition of solvent, installa- tion of the cartridge, static period, dynamic purging and decompression) or 20-25 rnin for the two cycles required. On the other hand, the exhaustive dynamic extraction of the 40 ppm spiked soil with pure C02 was complete after 12 min. Consequently, the use of a pre-mixed methanol-modified CO-, cylinder was also studied.Table 3 lists the OPP recoveries obtained with a methanol- modified C02 cylinder at 2% m/m. Dynamic extraction with the pre-mixed phase is seen to be as efficient as methanol- modified steady-state extraction. The high results obtained for dimethoate (104-111%) were due to peak tailing and integra- tion, problems occurring with this analyte during this part of our research. The extraction of all solutes was completed when using 3 ml of premixed C 0 2 . The total time of extraction, including installation o f the cartridge, pre-heating and static equilibra- tion, was only 12 min. Hencc t h c use of pre-mixed modified phases is attractive for routine analysis, because sample handling is minimized.Still, the addition of a modifier to the soil is more appropriate for SFE method development, because different modifiers can easily be tested. Finally, SFE was compared with conventional solvent extraction of a slurry-spiked sample. As can be seen from Table 3, the several sets of data show good mutual agreement, with the precision of the SFE methods being better than that16 ANALYST, JANUARY 1993, VOL. 118 of solvent extraction. For the rest, SFE was more efficient in removing the polar dimethoate from the soil sample. It should be noted, however, that the solvent extraction was not optimized for dimethoate. A major advantage of SFE over solvent extraction, often cited in the literature,*Jg is its speed. This is also true for the extraction of OPPs from soil.Depending on the mode of modifier addition, SFE took 12 or 25 min compared with 3-4 h for solvent extraction (even apart from the overnight equilibration). Conclusions Under optimized conditions, SFE permits the quantitative recovery (290%) of most OPPs from soil in less than 15 min. These high recoveries are obtained by adding methanol to the soil or by using premixed methanol-modified C 0 2 . All OPPs except dimethoate can be quantitatively recovered from inert matrices, such as glass-wool and sand, and from spot-spiked soil samples using pure C02 at 50 "C and 250 bar. However, the extraction yields with pure C02 decrease significantly when the analytes are added to soil by means of the slurry-spiking method. Solute-matrix interac- tions apparently prevent the desorption of part of the spiked analytes, as was especially manifest for dimethoate and azinphos methyl.This confirms that good analyte solubility in the supercritical phase (in our case C02) does not guarantee an efficient extraction from environmental samples. Matrix effects have to be considered as the major factor to be understood, for a successful application of SFE in the field of environmental analysis. The use of a polar modifier, methanol being more suitable than either ethyl acetate o r acetone, completely eliminates these problems. The optimized SFE method is slightly more precise than, and as efficient as, the conventional solvent extraction. Its main advantage however, is the dramatic gain in the time required for sample handling.Future work will focus on the influence of different soil characteristics and of water on solute-matrix interactions and on SFE efficiency. The authors thank Chrompack (Middelburg, The Nether- lands) for the loan of the syringe pump and RIVM (Bilthoven, The Netherlands) for the gift of the soil sample. References Hawthorne, S. B., Anal. Chem., 1990, 62, 633A. Vannoort. R. W., Chervct, J.-P., Lingeman, H . , De Jong, G. J., and Brinkman, U. A. Th., J . Chromatogr., 1990, 505, 45. Analyticul Supercritical Fluid Chromatography and Extraction, eds. Lee, M. L., and Markides, K. E . , Chromatography Conferences, Provo, UT. 1990. Abstructs of the International Symposium on Supercritical Fluid Chromatography and Extraction, Park City, Utah, USA, 1991.Proceedings ,for the European Symposium on Supercritical Fluid Chromatography and Extruction, Wiesbaden, Germany, 1991. Hawthorne, S . B., and Miller, D. J., J. Chromatogr., 1987,403, 63. Schantz, M. M., and Chesler. S . N., J. Chromutogr., 1986,363, 397. 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 Lohlcit, M., Hillmann, R., and Bachmann, K . , Fresenius' J. Anal. Chem., 1991. 339, 470. Onuska, F. I., and Terry, K. A., J. High Resolut. Chromatogr., 1989, 12, 527. Mulcahey, L. J., Hedrick, J. L., and Taylor, L. T., Anal. Chem., 1991, 63, 2225. Hawthorne, S. B . , Miller, D. J . , and Langenfeld, J. J . , J. Chromatogr. Sci., 1990, 28, 2. Hawthorne, S . B., and Miller, D. J . , Anal. Chem., 1987, 59, 1705. McNair, H. M., and Frazicr, J .O., fnt. Lub., 1991, 21, 33. Onsuka, F. I . , and Terry, K. A., J . High Resolut. Chromutogr., 1989, 12, 357. Levy, J . M., and Rosselli, A. C., Chromatographia, 1989, 28, 613. Richards, M., and Campbell, R. M., LCGC Int., 1991, 4, 33. Hawthorne, S. B., Miller, D J.. Walker, D . D., Whittington, D. E., and Moore, B. L., J. Chromatogr.. 1991, 541, 185. Spall, W. D., Martinez, A. A.. and Smith, B. F., in Abstracts of the International Symposium on Supercritical Fluid Chromato- graphy and Extraction, Park City, Utah, USA, 1991, p. 11 I. Pesticide Analysis, ed. Gas, K. D., Marcel Dekkcr, New York. 1981. McNally, M. E. P., and Wheeler, J. R., J. Chromatogr.. 1988, 435, 63. McNally, M. E. P., and Wheeler, J. R., J. Chromutogr., 1988, 447, 53. McNally, M. E. P., and Wheeler, J . R., J. Chromatogr. Sci., 1989. 27, 534. Lopez-Avila, V., Dodhiwala, N. S . , and Beckert, W. F., J. Chromatogr. Sci., 1990, 28, 468. Engelhardt, H., and Gross. A., J. High Resolut. Chromatogr. Chromatogr. Commun., 1988, 11, 726. Janda, V., Steenbekc, G . , and Sandra, P., J. Chromatogr., 1989,479, 200. Engelhardt, H., Zapp, J. and Kolla, P., Chromutographia, 1991, 32. 527. Mapelli, G., Pigozzo. F., Raynor, M. W., and Trestianu. S . , in Proceedings of the 13th Internutionul Symposium on Capillary Chromatogr.. ed. Sandra, P., Huthig. Heidelbcrg, 1991, p. 489. Cortes, H. J. Green. L. S . , and Campbell, R. M., Anal. Chem., 1991, 63, 2719. Bergna, M., Banfi, S . , and Cobelli, L., in Proceedings o f t h e 13th International Symposium on Capillary Chromatography, ed. Sandra, P., Huthig, Heidelberg, 1991, p. 300. Pipkin, W., LCGC Int., 1992, 5, 8. Hawthorne, S. B., Miller, D. J . , and Langenfeld, J . J., in Abstracts of the In ternationul Symposium on Supercritical Fluid Chromatography and Extraction, Park City, Utah, USA, 1991, Borburgh, H. J.,Applicution Note, J . T. Baker, Deventer, 1990. M. deWilde, CIVO-TNO, Scist, The Netherlands, personal communication. Organic Chemicals in the Soil Environment, eds. Goring, C. A. 1.. and Hamaker, J . W., Marcel Dekker, New York, 1972. Khan, S . U.. Pesticides in the Soil Environment, Elscvicr, Amsterdam, 1980. Durand. G., and Barcelo, D.. Anal. Chim. Acta, 1991,243,259. Kjslholt. J . , J. Chromutogr., 1985, 325, 231. Bartle. K . D.. and Clifford, A. A., LCGC Int., 1991, 4, 10. p. 91. Paper 2/01 993 K Received April 16, 1992 Accepted September 30, 1992

ISSN:0003-2654    

DOI:10.1039/AN9931800011

出版商:RSC    

年代:1993

数据来源: RSC

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14N ANALYST, JANUARY 1993, VOL. 118 Future Issues will lnclude- Flow-through (Bio)chemical Sensors- Miguel Valcarcel and Maria Dolores Luque de Castro Flow Injection Chemiluminometric Determination of Epinephrine, Nor- epinephrine, Dopamine and L-Dopa- Nikolaos T. Deftereos, Antony C. Calokerinos and Constantinos E. Efstathiou Dataprocessing by Neural Networks in Quantitative Chemical Analysis-M. BOS, A. Bos and W. E. van der Linden Novel Electrochemical Device for the Detection of Cholesterol or Glucose- John F. Cassidy, Cathriona Clinton, William Breen, Robert Foster and Eilish 0 'Donoghue Novel Usage of Synthetic Detergent to Partition Protein Mixture-Wakako Tsuzuki, Hanae Kasumimoto and Shouichi Kobayashi Isomeric Characterization of Poly- chlorinated Biphenyls Using Gas Chro- matography Fourier Transform Infrared-Gas Chromatography Mass Spectrometry-Doyle M.Hembree, Jr., Norman R. Smyrl, Willard E. Davis and David M. Williams Determination of Formic Acid Vapo-ur Using Piezoelectric Crystals With 4-Ethyl, 3-Thiosemicarbazide and 2,6- D i ace th y lpyridine Coatings-J. A. Munoz Leyva, J. L. Hidalgo Hidalgo de Cisneros, D Garcia, Gomez de Barreda and A. J. Fraidias Becerra Oxazole-based Tagging Reagents for Analysis of Secondary Amines and Thiols by Liquid Chromatography With Fluorescence Detection-Susan M. Lunte, Toshimasa Toyo'oka, Hitesh P. Chokshi, Robert G. Carlson and Richard S. Givens Agarose Gel Electrophoresis System for the Separation of Antibiotics Used in Animal Agricul ture-Michael J. Salva- tore, Stanley E. Katz and Ilya Feygin High-performance Liquid Chromato- graphic Determination of 5-Hydroxyin- doles by Post-col um n F1 uorescence Derivatization-Masatoshi Yamaguchi, Junichi Ishida and Ryuji Iizuka Separation of Chromium and Nickel Using Extraction Chromatography.Application to the Analysis of Alloys- Ricardo 0. Crubellati and Ariel Led e s m a Efficacy of Robust Anova for the Inter- pretation of Data from Collaborative Trials-Michael Thompson, Bart Mer- tens and Margalith Kessler Determination of Non-ionic Surfactants in Waste Water by Direct Extraction With Fourier Transform Infrared Spec- troscopic Detection-B. E. Andrew Direct Determination of Cadmium in Sea-water by Electrothermal Atomic Absorption Spectrometry with Sodium Hydroxide as a Chemical Modifier- Chi-ren Lan Micelle-mediated Methodology for the Preconcentration of Uranium Prior to its Determination by Flow lnjection- Bernard0 Moreno Cordero, Esther Fer- nadez Laespada and Josk Luis PCrez Pavon Protamine-coated Silica Gel as Packing Material for High-performance Liquid Chromatography of Carbohydrates- Shuji Yamauchi, Noriyuki Nimura and Toshio Kinoshita

ISSN:0003-2654    

DOI:10.1039/AN993180014N

出版商:RSC    

年代:1993

数据来源: RSC

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ANALYST, JANUARY 1993, VOL. 118 17 Supercritical Fluid Extraction for the Analysis of Liquid Poly(alky1ene glycol) Lubricants and Sorbitan Ester Formulations Terence P. Hunt and Chris J. Dowle* ICI Wilton Research Centre, P.O. Box 90, Middlesbrough, Cleveland, UK TS6 8JE Gillian Greenway Department of Chemistry, University of Hull, Hull, UK HU6 7RX Additives were selectively extracted from poly(al kylene glycol) (PAG) lubricant formulations using supercritical fluid extraction. The PAG matrix was adsorbed onto silica for the extractions and the extracted analytes were passed through a silica column positioned in-line in the supercritical fluid stream. The selectivity obtained by this method was compared with that obtained by the direct extraction of adsorbed and unadsorbed PAG and by the extraction of unadsorbed PAG through the in-line column.The final procedure was found t o be successful in separating additives from all but the lowest molecular mass PAG oligomers. Further use of this procedure was demonstrated by a stepwise extraction of a sorbitan ester formulation. This gave a chemical-class fractionation of the product and so provided a sample preparation technique for further spectroscopic analysis. Keywords: Supercritical fluid extraction; liquid poly(alky1ene glycol) and sorbitan ester samples; adsorption on silica; in-line silica packed column Supercritical fluid extraction (SFE) has been used extensively in the analysis of solid polymers. 1,2 Supercritical fluid extrac- tion of liquid samples is undertaken less widely because dissolution or entrainment of the matrix can occur.Direct extraction of aqueous samples has resulted in incomplete separations3.4 and although a more promising extractor, incorporating a dip tube, has been used by Ong et aZ.5 to extract cholesterol from egg yolk, this system was not used for more volatile samples. An alternative approach , analogous to thermal desorption in gas chromatography, involves immob- ilizing a sample on an adsorbent bed which is then extracted by a supercritical fluid, Polycyclic aromatic hydrocarbons, chlori- nated hydrocarbons, chlorinated aromatics and organophosp- hate pesticides have been extracted from Tenax resin.6.7 Moreover, Wright et a1.8 using several different adsorbents and extraction fluids showed that the selective recovery between individual solutes can be varied by altering the combination of the adsorbent and the extraction conditions.In this way Alexandrou et al.9 successfully separated poly- chlorinated dibenzo-p-dioxins (PCDDs) from polychlorinated biphenyls and chlorinated benzenes in standard and fly ash extract solutions. The bulk of the solutes were extracted from Florisil with C 0 2 at 20.68 MPa after which the remaining PCDDs were extracted with N20 at 41.37 MPa. Selectivity in the extraction process can also be achieved by passing the effluent from the extraction cell through an adsorbent column. This procedure was used to remove contaminants from seed oil extract by King et a1.10 using an activated carbon column and by Shishikura et aZ.11 to remove cholesterol from butter oil extract using a silica column.Ramsey et aZ.12 cleaned up freeze-dried pig's kidney extracts for on-line drug analysis by mass spectrometry (MS). The polar drugs were adsorbed onto an amino column while the bulk of the non-polar endogenous components were extracted rapidly to waste. The addition of a polar modifier to the supercritical fluid then enabled the drugs to be desorbed to the MS system. Also, Yamauchi et al.13 extracted naphthalene selectively with supercritical C02 at 10 MPa from a mixture of naphthalene and anthracene by passing the extracted solutes through a silica column. Naphthalene eluted through the column but anthracene was adsorbed. The anthracene was then desorbed by increasing the pressure to 25 MPa . * To whom correspondence should be addressed. Poly(alky1ene glycols) (PAGs) are low molecular mass liquid polymers which consist of chains of ethylene oxide (EO) and propylene oxide (PO) units bonded to an alkoxy end-group.The analysis of PAG additives (antioxidants, biocides and anti-corrosion , anti-wear and anti-foaming agents) is hindered by the presence of the PAG matrix and so a method for separating additives from PAG is required. However, both PAG and additives tend to be soluble in supercritical C02. Therefore, the selective extraction of additives from PAG must be achieved by immobilizing PAG on an adsorbent in either of the ways described above. Silica is a powerful adsorbent, acting through hydrogen-bonding with surface silanol groups. It has also been found that for solutes containing nitrogen and oxygen, this mechanism is sup- plemented by coordinate bonding with electron acceptor centres on the surface.*4?15 It is a matrix which should, therefore, be suitable for adsorbing EO-PO polymers.The strong interaction of silica with EO-PO polymers is demon- strated by its use as the stationary phase for the normal phase high-performance liquid chromatography (HPLC) separation of oligomers of ethoxylated acids and alcohols. Furthermore, many workers have chosen to derivatize ethoxylates in order to reduce the strength of the interaction which would otherwise be too strong for the elution of higher oligo- mers.16.17 Similar reasoning suggests that silica could also be used as an adsorbent in the selective extraction of formulations of sorbitan ester (a sugar formed by reaction of sorbitol and lauric acid).Sorbitan mono-ester contains three hydroxyl groups and one cyclic oxygen atom in addition to the ester carbonyl group. These oxygen atoms, and particularly the carbonyl , should exhibit strong hydrogen-bonding interac- tions with silica. This seems to be confirmed by reported normal-phase HPLC and thin-layer chromatography (TLC) separations of other sugars on silica stationary phases which require very polar eluents.18.19 In this paper silica has been used both to adsorb PAG and sorbitan ester samples prior to extraction and to fractionate the extracted solutes in the extraction effluent downstream from the extraction cell. The method has been scaled up to enable 1 g samples to be analysed.This provided fractions of extracted analytes in sufficient amounts to be characterized by nuclear magnetic resonance (NMR) spectroscopy without the interferences from solvents or their impurities frequently found with traditional sample preparation schemes.ANALYST. JANUARY 1993. VOL. 118 Column Fig. 1 back-prcssure regulator Schematic diagram o f thc SFE system. PU = Pump; PH = prc-heating column; SV = switching valve; PM = pressure mcter and BR = Experimental Reagents Extractions were performed on PAG lubricants (Union Carbide, ICI and Exxon) and on sorbitan ester (ICI). Carbon dioxide (SFC grade, Air Products) was used for SFE and capillary supercritical tluid chromatography (CSFC). Samples were adsorbed on 5 pm particle size silica Spherisorb S5W and alumina Spherisorb A5Y (Hichrom).Dichloromethane of HPLC grade was used to slurry samples with the oxides, HPLC grade methanol was used as a polar modifier to the C02 and stabilized tetrahydrofuran (THF) was used as the eluent in the gel-permeation chromatography (GPC j analysis of extracts. All solvents were supplied by either BDH or Fisons Laboratory Supplies. Instrumentation Extractions were carried out using the Jasco (SFC-SFE) system shown in Fig. 1 with a 300 x 7.5 mm column case (Polymer Laboratories) used for the extraction cell. This was positioned in the loop enclosed by the Rheodyne 7000 switching valve SV1 and was heated in the 860-CO oven. A 4.6 mm i.d. adsorption column (Spherisorb S5W or Nucleosil silica, all supplied by Hichrom) was positioned in the loop enclosed by the switching valve SV2, downstream from the extraction cell and outside the oven.Adsorption columns were 250 nim long unless otherwise stated. The switching valves SV1 and SV2 allowed the CO? flow to be passed through either the extraction cell and column or by-passed to the 880-81 back-pressure regulator BR2 via the 875-UV (ultraviolet) detector. A third switching valve SV3 was always by-passed during extractions and the Rheodyne 7037 pres- sure-relief valve BRl was adjusted to give negligible back- pressure and the extraction back-pressure was maintained using a Jasco back-pressure regulator BR2. Samples were analysed by CSFC and GPC. The CSFC system consisted of a Carlo Erba SFC 3000 instrument with a 10 m x 50 pm i.d. biphenyl polysiloxane column (Dionex, UK).The GPC system consisted of a Knauer pump and refractive index (RI) detector, a Pye Unicam temperature controller and a Talbot ASI-3 aut?sampler with a 300 X 7.5 mm 104 8, + 300 x 7.5 mm 500 A column series (Polymer Laboratories). Table 1 Extraction conditions Extraction Back- In-line scheme Methanol pressure Flow ratc adsorption number -COz (%) /MPa Time/min /ml min-1 column 1 0 20 30 1 .o No 0 30 30 1 .0 2 0 30 1380-900 1.0 Y cs 3 0 30 240 4.0 Yes 4 0 30 60 1 .o 5 0 20 I000 1 .0 Yes 6 0 10 60 4.0 Y cs 0 20 1000 I .0 1 0 30 60 4.0 40 30 60 4.0 0 7 90 4.0 0 10 280 4.0 0 15 70 4.0 0 20 70 4.0 0 30 990 1 .0 10 30 70 4.0 40 30 150 4.0 7 Y es Procedure All extractions were carried out at 45 "C with the adsorption column (when used) at ambient temperature.The UV absorbance of extracted solutes was monitored with the detector at 220 nm and extracts were collected in glass collection vessels positioned beneath BR2. The extraction conditions used are listed in Table 1 and after each extraction the SFE system was cleaned by pumping through with 40% MeOH-C02 at 30 MPa. Adsorbed samples were prepared by slurrying a 1 : 5 sample : oxide mixture in dichloromethane and evaporating to dryness. Initially the extraction procedure was optimized for PAG A to determine how sample adsorption onto silica and extraction through an in-line silica adsorption column affects extraction selectivity. To achieve this the extraction selectivity was compared for extractions on free (unadsorbed) PAG A and a PAG A-silica mixture without an in-line adsorption column and for PAG A extractions through in-line adsorption columns packed with silicas of various pore sizes.ExtractionsANALYST, JANUARY 1993, VOL. 118 19 with an in-line adsorption column were then compared for free PAG A, PAG A-silica and PAC A-alumina to investigate how the combination of sample adsorption and an in-line Extractions on Unadsorbed Samples With In-line Adsorption Column column affects the extraction selectivity. Thus free PAC A and a PAGA-silica mixture were each directly extracted with SV2 closed at 20 and 30 MPa using extraction scheme 1 (see Table 1). Free PAG A was also extracted overnight at 30 MPa and 1 ml min-1 with SV2 open so that the CO? flow and extracted solutes were passed through a Spherisorb column (extraction scheme 2).This was repeated for :00 mm Nucleosil columns with pore sizes of 50, 120 and 300 A. PAC A was also extracted through a 50 mm Spherisorb column at 4 ml min-1 (extraction scheme 3). PAG A and mixtures of 0.1 : 0.5 g PAG A-silica and PAG A-alumina were then extracted at 30 MPa for 60 min (extraction scheme 4) through a Spherisorb column and these were compared with an identical PAC A-silica extraction in which SV2 was closed to by-pass the column. The final, optimized method was then used to extract various samples. Hence 1 : 5 g PAG A-silica mixtures were extracted overnight through a Spherisorb column (extraction scheme 2). Further extractions through a Spherisorb column were carried out on 1 : 5 g mixtures of PAGs B and C and sorbitan ester with silica. PAG B was extracted at 20 MPa (extraction scheme 5 ) ; PAC C and sorbitan ester were extracted stepwise from 10 and 7 MPa (CO,) to 30 MPa (40% methanol-C02) (extraction schemes 6 and 7 respectively).PAGs A and B and their extracts were analysed by GPC with a stabilized THF eluent at 1 ml min-1 and ambient temperature. PAG extracts shown by GPC not to contain high molecular mass material were also analysed by CSFC at 100 "C using a C 0 2 pressure gradient of 6 or 1W.5 MPa at 1 MPa min-1. PAG C and sorbitan ester and their extracts were analysed by CSFC: with a temperature gradient o f 100-190 "C at 3 "C min-1 and an asymptotic density gradient of 0.16-0.5 over 30 min (PAG C); at 100°C with an asymptotic C 0 2 density gradient of 0.15-0.55 g ml-1 over 40 min (sorbitan ester).Results and Discussion Direct Extractions (Without In-line Adsorption Column) PAG A and the 30 MPa SFE direct extracts of PAG A and PAG A-silica were analysed by GPC to give a measure of the concentrations of additive. The concentration of additive is proportional t o its GPC peak area expressed as a percentage of the total peak area of the sample (referred to as relative peak area in this paper). These results are presented in Table 2. Although PAG is present in both extracts, comparison of the additive relative peak areas listed in Table 2 shows that the additive concentration is greater in the PAG A-silica extract. This shows that by interacting PAG with silica, the selective extraction of more weakly adsorbed additives is enhanced, although insufficiently to provide a complete separation of the additives from PAG.Table 2 Rclative GPC peak area of additive (total peak area set to 100) for PAG A and PAG A extracts Relative peak area of Sample additive Unextracted PAG A- 7 6 CO? PAG A-silica direct extraction 44 PAG A through-column extraction 29 PAG A-silica through-column 100 30 MPa 1 PAG A dircct extraction extraction Rather than slurrying samples with silica to give adsorbed mixtures prior to extraction it would be simpler to extract the free sample and pass the extracted solutes through a silica column. For PAG A this appears to be successful for relatively short extraction times. After 1-2 h the extract collected from a 1 ml min-' 30 MPa C 0 2 extraction through a silica adsorption column, is a creamy white solid. However, when the extrac- tion is continued overnight for 315 h, the extract becomes an oil resembling the original sample.Moreover, even after 1000 min, the UV absorbance of the extraction effluent from the adsorption column shows no sign of decaying to the pre- extraction value (set to zero). This shows that the additives are not completely extracted and suggests that a final extract would be even further contaminated with PAG. In order to run such an extraction to completion, PAG A was extracted at 4.0 ml min-1 with a shorter SO mm in-line adsorption column. The extract was analysed by GPC for the additive relative peak area which is listed in Table 2. This shows that greater PAG contamination results from this method than for the direct extraction of PAG A-silica. However, enhanced selectivity over the direct extraction of unadsorbed PAG A is achieved.The extraction selectivity can be affected by changing the properties of the adsorption column silica. The UV absorb- ance curves for CO, extractionsoof PAG A through silicas with pore sizes between 50 and 300 A are shown in Fig. 2. It can be seen from this that the extraction rate increases with pore size. This is consistent with a smaller surface area available to adsorb the extracted sample resulting from a larger pore size. As extracts become more contaminated with PAG the further the extraction progresses it might be expected that the lowest concentration of PAG would be found in the 50 A extract. However, the results ot GPC analysis, given in Table 3, show that it is in fact the 120 A extract that is the least contaminated.A possible explanation is that a larger pore size allows the large PAC molecules to enter the silica pores more easily. This should enhance PAG-silica adsorption and improve the extraction selectivity. Owing to these two conflicting tenden- cies an optimumo extraction selectivity is obtained at the intermediate 120 A pore size. Extractions on Adsorbed Samples With In-line Adsorption Column The UV absorbance curves for various 60 min extractions of 0.1 g samples of PAG A with 30 MPa C 0 2 (extraction scheme 4) are shown in Fig. 3. In each instance the sample size and extraction conditions are identical. They show the direct 0 200 400 600 800 Time/min Fig. 2 UV absorbance of 30 MPa C02 extractions of PAG A through 100 mm silica columns with different pore sizes: A, 50; B, 120; and C , 300 A.(Extraction scheme 2)20 ANALYST, JANUARY 1993, VOL. 118 Table 3 Relative GPC peak area of additive for 30 MPa C02 extracts from extractions of unadsorbed PAG A through silica columns of different pore size Pore sizciA Relative peak area of additive 50 120 300 36 56 30 z 600 . 4- x cn .- 2 400 - 0 10 20 30 40 50 Time/min Fig. 3 UV absorbance of 30 MPa COz extractions of: A, 1 : 5 PAG A-silica; B, PAG A through a 250 mm silica column: C, 1 : 5 PAG A-alumina through a 250 mm silica column; and D, 1 : 5 PAG A-silica through a 250 mm silica column. (Extraction scheme 4) extraction of PAG A-silica [extraction (a)] and the through- column extractions of unadsorbed PAG A, PAG A-alumina and PAG A-silica [extractions ( h ) , ( c ) and (d), respectively].Comparison of extraction curves in Fig. 3 shows a marked improvement in the definition of individual peaks for extrac- tion (d) where adsorption of the sample prior to extraction and passing the extracted solutes through an adsorption column are combined. The difference between extractions (b) and (d) cannot be explained by the extra mass of silica (0.5 g) mixed with the sample prior to extraction as this is insignificant compared with the mass of silica contained in the adsorption column. This suggests that adsorption onto the dry silica used in premixing the sample is much stronger than adsorption onto the silica contained in the column in the supercritical fluid stream.It is known from studies in normal-phase HPLC that even non-polar eluents such as heptane are weakly adsorbed on the surface of a silica column to form a monolayer coating of solvent molecules.20 A similar monolayer formed by supercritical C 0 2 on a silica column would force extracted solute molecules to compete with the C02 molecules in this monolayer in order to be adsorbed. This would account for the weaker adsorption. The difference in resolution between the silica and alumina adsorbed samples shows the importance of choosing the right adsorbent in optimizing the extraction selectivity . When a scaled up 1 : 5 g PAC A-silica through-column C 0 2 extraction is run overnight, the UV absorbance curve of the extracted additive shows that the extraction is now completed rapidly after about 600 min whereas the equivalent extraction of unadsorbed silica under identical conditions is still far from complete after 1000 min.Analysis of the PAG A-silica extract by GPC and CSFC shows that it is free of PAG contamination (see Table 2). Therefore, in this extraction additives are selectively extracted from PAG. Similar results are obtained for the 20 MPa through-column extraction of PAG B. The UV absorbance curve, shown in Fig. 4, shows that the PAG B additives are extracted from the silica column in two clearly resolved fractions which were collected separately. The second peak was confirmed as 1000 800 > @ 600 2- cn 4- .- 400 - 200 0 100 200 300 400 500 600 Time/min Fig. 4 UV absorbance of a 20 MPa C02 extraction of 1 : 5 PAG B-silica through a 250 mm silica column (extraction scheme 5 ) Table 4 Molecular mass values for PAG A and PAG B Mass-average Number-average Molecular mass molecular mass molecular mass at peak maximum PAG A 2770 2610 2750 PAG B 3370 2290 3190 z 18.0 -.14.0 12.0 0 lrganox 1010 THF stabilizer 6.0 12.0 18.0 24.0 30.0 36.0 42.0 Tim e/m i n Fig. 5 CSFC trace of 1 : 5 PAG B-silica 20 MPa C02 extract passed through a 250 mm silica column (extraction scheme 5) Irganox 1010 antioxidant by CSFC and NMR. The GPC analysis shows that this Irganox 1010 fraction of the 20 MPa extract is separated from the bulk of the PAG. This result should be expected as GPC analysis gives similar molecular mass values for both PAGs (see Table 4). However, PAG B contains lower molecular mass oligomers not present in PAG A and the CSFC trace of the 20 MPa extract shows that some of these shorter-chain oligomers have been extracted together with Irganox 1010 (see Fig.5 ) . Clearly the higher the molecular mass of a PAG chain, then the more EO-PO groups in the chain are available to be adsorbed onto the silica and consequently the over-all adsorption of a PAG chain is stronger. Fig. 5 shows that a threshold number of groups is needed for a PAG chain to be sufficiently adsorbed for a given set of extraction conditions, with PAG chains below this threshold being extracted. This effect is better illustrated for the stepwise, through- column extraction of PAG C-silica. PAG C has a nominal molecular mass of only 750 and CSFC analysis of its extracts, shown in Fig.6, shows that the first 9-10 oligomers can be extracted by 10 MPa C02. Increasing the extraction pressure to 20 MPa boosts the C 0 2 solvent strength and so allows the further desorption of oligomers 10-15 whilst the remaining longer-chain oligomers are desorbed when the extraction fluid polarity is increased by the addition of methanol. Clearly PAGANALYST, JANUARY 1993, VOL. 118 21 adsorption must be strengthened in order to separate additives from shorter-chain oligomers. Further studies are planned to investigate the possibility of achieving this either by using a different silica or even by changing to a polar, bonded phase such as a diol or amine. Extractions on Sorbitan Ester Having developed the above method for the separation of additives from PAG formulations, the possibility of using it in the analysis of different samples was then considered.Sorbitan ester is a complex mixture of sugars formed by the reaction of lauric acid and sorbitol. Both reactants may contain impurities and the final product contains mono-, di- 60 50 > E 40 . c > KI m .- E: 30 - 20 10 0 6.0 12.0 18.0 24.0 30.0 36.0 42.0 Time/min Fig. 6 CSFC traces of 1 : 5 PAG C-silica extracts assed through a 250 mm silica column. A, C02 (10 MPa); B, COz 6 0 MPa); and C, 10% mcthanol-C02 (30 MPa). (Extraction scheme 6 ) 24.0 26'o 1 I =. 22.0 E 2 20.0 5 18.0 5 16.0 . .- fn CI 14.0 12.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 and tricyclic esters and linear esters. Its CSFC trace is shown in Fig. 7(a). Hence for this sample, the extraction of parts of the sample matrix (as observed in the extraction of PAG C, where it is unwelcome as the aim is to isolate certain trace additives) can be used here to investigate the composition of the matrix itself by providing a potential means of separating it into constituent fractions that are easier to analyse. The stepwise, through-column extraction of this sample (adsorbed onto silica) gives a series of separately collected fractions.The CSFC traces of the main fractions are shown in Fig. 7(b)-V). Comparison with that of the original sample in Fig. 7 ( a ) shows that their compositions are much simpler, which permits less complex spectroscopic analysis to be d'eveloped for different fractions. Initial analysis by 13C NMR suggests that the 7 and 10 MPa COz extracts contain cyclic mono-esters; the 1.5 and 20 MPa C 0 2 extracts contain cyclic di- and tri-esters with some fatty acid (more pronounced in the 20 MPa extract); and the C02 and 10% methanol-C02 extracts contain linear esters.The spectra of the extracted esters were predicted with the assistance of our corporate 13C NMR computerized chemical-shift calculation facility and spectral database. The predictions were confirmed by the subsequent synthesis of the proposed compounds from isomerically pure starting materials. These results confirm that adsorption is enhanced by the addition of further ester carbonyl groups. Also, the greater adsorption of linear compared with cyclic esters may be because they are less sterically hindered in their ability to attach themselves to silica through their oxygen atoms.The 40% methanol-C02 fraction has not been identified. This characterization would be extremely difficult for the original sample. Furthermore, this method creates a separation on the basis of a specific property of the matrix components (their adsorption strength) and should be seen as complementary to 27.0 I 24.0 1 I 15.0 12.0 9.0 11.4 11.2 11.0 10.8 10.6 10.4 10.2 10.0 9.8 14.5 14.0 L I (f' I 12.0 18.0 24.0 30.0 36.0 42.0 48.0 54.0 Time/min 13.5 13.0 12.5 12.0 12.0 18.0 24.0 30.0 36.0 42.0 48.0 54.0 Fig. 7 ( c ) 10 MPa C02 extract; (d) 20 MPa C02 extract; (e) 30 MPa C02 extract; and (f) 30 MPa 40% mcthanol-CO2 extract CSFC traces of sorbitan cstcr and 1 : 5 ester-silica extracts (extraction scheme 7).( a ) Original sample; ( b ) 7 MPa C 0 2 extract;22 ANALYST, JANUARY 1993, VOL. 118 other fractionation techniques, such GPC, which utilize different properties as semi-preparative Conclusions Additives in PAG lubricants cannot be isolated by SFE carried out on free samples because of the relatively high solubilities of both PAG lubricants and their additives in supercritical CO2. The separation is improved by extracting the lubricant sample as a PAG-silica mixture and by passing the effluent from the extraction cell through a silica column. In both instances the sample is adsorbed onto the surface of the silica where additives tend to be more easily desorbed than PAG. This is confirmed by the GPC analysis of the C02 extracts, which shows that the relative areas of additive peaks are greatly increased compared with that for the unextracted sample.When these two procedures are combined so that a PAG-silica mixture is extracted with the extracted solutes passing through a silica column, it is possible to extract less polar additives from PAG exhaustively with only very short PAG chains extracted together with the additives. Further- more, individual additives are desorbed separately in discrete bands which can be collected separately for further analysis. The further application of this method to sorbitan ester resulted in its fractionation into four distinct chemical classes: cyclic monoesters, cyclic di- and tri-esters, linear esters and a highly polar but unidentified fraction. This particular example showed the value of SFE as a sample preparation technique for the spectroscopic characterization of complex mixtures.Thanks to A. Bunn and H. Yates of ICI Wilton Research Centre for NMR analyses. References 1 Cotton, N . J . , Bartle, K. D., Clifford, A . A., Ashraf, S . , Moulder, R., and Dowle, C. J . , J. High Resolut. Chromatogr., 1991, 14, 165. 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Hunt, T. P., Dowle, C. J., and Greenway, G., Analyst, 1991, 116, 1299. Roop, R. K., Hess, R. K., and Akgerman, A.. Supercrit. Fluid Extr. Chromatogr. (ACS Symp. Ser.), 1989. Tiebault, D., Chervet, J. P., Vannoort, R. W., de Jong, G. J., Brinkman, U. A. Th., and Frei, R. W., J . Chromatogr., 1989, 477, 151. Ong, C. P., Ong, H. M., and Li, S. F. Y . , J. Microcol. Sep., 1990, 2, 69. Hawthorne, S. B., and Miller, D. J., J. Chromatogr. Sci., 1986, 24, 258. Raymer, J . H., and Pcllizzari, E. D., Arzal. Chem., 1987, 59, 1043. Wright, R. W., Wright, C. W., Gale, R. W., and Smith, R. D., Anal. Chem., 1987, 59, 38. Alexandrou, N., Lawrence. M. J . , and Pawliszyn, J . , Anal. Chem., 1992, 64, 301. King, J. W., Eissler, R. L., and Friedrich, J . P., Supercrit. Fluid Extr. Chromatogr. (ACS Symp. Ser.), 1988, 63. Shishikura, A., Fujimoto, K., Kaneda, T., Arai, K., and Saito, S . , Agric. Biol. Chem., 1986, 50, 1209. Ramsey, E. D., Perkins, J. R., Games, D . E., and Startin, J . R . , J. Chromatogr., 1989, 464. 353. Yamauchi, Y., Kuwajima, M., and Saito, M., J. Chromatogr., 1990, 515,285. Tret’yakov, N. E . , and Filimonov, V. N., Kinet. Katal., 1972, 13, 815. Filiminov, V. N . , Lopatin, Y. N., and Sukhov, D . A., Kinet. Katal., 1969, 10, 458. Aitzmuller, K., J. Chromatogr. Sci., 1975, 13, 454. McClure, J. D., J. Am. Oil Chem. SOC., 1982, 59, 364. Karamanos, N. K., Tsegenidis, T., and Antonpoulos, C. A., J. Chromatogr., 1987, 405, 221. Koizumi, K., Utamura, T., and Okada, Y., J. Chromatogr., 1985, 321, 145. Brown, P. R., and Hartwick, R. A., High Performance Liquid Chromatography, Wiley-Interscience, New York, 1989. Paper 2103926E Received July 22, 1992 Accepted October 12, 1992

ISSN:0003-2654    

DOI:10.1039/AN9931800017

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993. VOL. 118 23 Preconcentration of Aniline Derivatives From Aqueous Solutions Using Micellar-enhanced Ultrafiltration Edmondo Pramauro and Alessandra Bianco Prevot Dipartimento di Chimica Analitica, Universita di Torino, 10 125-Torino, Italy Piero Savarino and Guido Viscardi Dipartimento di Chimica Generale ed Organica Applicata, Universita di Torino, 10125-Torino, Italy Miguel de la Guardia and Empar Pewis Cardells Departamento de Quimica Analitica, Universidad de Valencia, 46I00-Burjassotl Valencia, Spain The preconcentration of aniline derivatives present in aqueous solutions containing ionic surfactants was performed using the micellar-enhanced ultrafiltration technique. The efficiency of the analyte recovery in the surfactant-rich retentate was significantly improved by exploiting the electrostatic, hydrophobic and specific interactions between the aggregates and the solute molecules.By working at low pH, in the presence of anionic micelles, the quantitative retention of amines having different su bstituent groups can be achieved. The enriched sample can be analysed directly using high-performance liquid chromatography. Keywords: Micellar-enhanced ultrafiltration; aromatic amine; preconcentration; aqueous sample; high-performance liquid chromatography analysis The unique properties of amphiphilic aggregates have been exploited in separation science to improve existing methods and to develop new procedures in which the use of organic solvents is avoided. 1-5 In particular, micellar-enhanced ultra- filtration (MEUF) is emerging as a promising technique for preconcentration and/or removal of organic and inorganic solutes of environmental concern from aqueous media.&" This technique is based on the association of the analytes to suitable surfact ant aggregates, which are successively blocked by membranes having an appropriate pore size.As the mean relative molecular mass of most micelles is generally higher than 10000 Da, membranes with a relative molecular mass cut-off in this range can be used, thus allowing operation at acceptable flow rates. The solute enrichment takes place in the retentate, whereas the permeate contains only small amounts of free surfactant and unbound solute. If biodegradable amphiphiles are used to treat polluted streams, their presence in the permeate does not present environmental problems.The extent of binding of substrates to the aggregates depends on hydrophobic, electrostatic and specific interac- tions operating between the micellized amphiphile molecules and solutes. Only a limited number of lipophilic solutes have been removed or concentrated from aqueous samples using MEUF (phenols, benzene, DDT, chlorinated hydrocarbons, aliphatic alcohols) and there is a lack of information about the basic relationships which control the performance of the process. In most instances, the efficiency of MEUF can be directly correlated to the partition coefficients of the analytes in micellar media, which are in turn dependent on the nature of the surfactant and on the conditions of the medium. For example, the effective removal of some chloroaromatic carboxylic herbicides from aqueous solutions can be accom- plished by regulating the pH and exploiting the electrostatic attraction between the ionized analytes and oppositely charged aggregates.10 Aromatic amines are an important class of anthropogenic compounds of environmental concern. Among their main applications, these harmful products are used in the synthesis of a variety of organic dyes. Hence, they may be present at trace levels in commercial products and in aqueous effluents discharged from dyestuff manufacturing and dyeing plants.]' Their determination in such samples often involves a time- consuming enrichment stage (typically a liquid-liquid extrac- tion from basic solutions), followed by analysis using gas chromatography (GC) or high-performance liquid chromato- graphy (HPLC).As GC usually requires the prior derivatiza- tion of the amines, HPLC is employed in a large number of analytical protocols. The sensitivity of this method varies with the detection mode, but it is sufficiently high to allow the determination of aromatic amines present at trace levels in effluents and environmental samples. 12-15 In the present work, a series of substituted anilines, including some hydrophobic dye intermediates, were separ- ated and concentrated from aqueous surfactant solutions using the MEUF approach. The use of organic solvents, which is required in other preconcentration techniques (e.g., solid- phase extraction) to dissolve the hydrophobic analytes, is avoided.The amphiphiles chosen were sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (HTAB) , which are commonly used and inexpensive products. Owing to their ionic character, these aggregates can exert electrostatic attraction or repulsion towards the amine cations, allowing the partition coefficients of the substrates investigated to be varied. The effects of pH, ionic strength, surfactant concentration and type of micelle on the solute recovery were examined. Experiments performed with some aniline derivatives indi- cated that the MEUF-based enrichment of these analytes can be coupled with micellar HPLC or conventional HPLC analysis without interference problems. Experimental Apparatus A Cary 219 (Varian) and a Uvikon 930 (Kontron) spectropho- tometer were used.Potentiometric measurements were per- formed with a Dosimat 655 (Metrohm) automatic titrimeter. A liquid chromatograph, consisting of a PM 330 pump (Violet) , a Merck-Hitachi LC-4200 ultraviolet/visible (UV/ VIS) detector and an ERC-7512 refractive index detector, was used for the HPLC measurements. Ultrafiltration cells (S-43- 70) supplied by Spectrum and Spectra/Por-C hydrophilic cellulose membranes were also employed. Reagents The aniline derivatives (Fluka and Merck) were used as received. Stock solutions of each compound were prepared in24 ANALYST. JANUARY 1993, VOL. 118 95% ethanol (Merck). The surfactants SDS and HTAB were of analytical reagent-grade (Merck) . Sodium chloride, HCI and NaOH were from Carlo Erba. Acetonitrile, methanol and propan- 1-01 of HPLC-grade (Merck) were used. Doubly distilled water was used throughout.The following heterocyclic intermediates [2-(4-amino-2- hydroxypheny1)benzoxazolesl , used in the synthesis of dis- perse azo dyes water) ,I6 were procedures. 17 (i.e., those dyes that are almost insoluble in prepared according to previously reported CiH I : X = O II: x = s 111: X = NH Procedure Measurement of the binding constants The micellar HPLC technique was mainly used to evaluate the extent of binding between the analytes and the anionic aggregates. The retention data were analysed as a function of the micellized surfactant concentration (c,,) in the mobile phase, according to the Armstrong-Nome partition model. 18 The following equation was used: where V,, V , and V, are the stationary phase, mobile phase and elution volume, respectively, PMw and Psw are the partition coefficients of the solutes between the micelles and the bulk aqueous phase, and between the stationary phase and the aqueous phase, respectively, and V is the paltial molar volume of the amphiphile.The term (PWM - l ) V gives the binding constants to the aggregates (KB).19 Mobile phases containing the micellized surfactants (with- out any organic modifier) were adjusted to the appropriate pH (about S), filtered through a 0.45 pm cellulose filter (Milli- pore) and carefully de-gassed. Each solute was dissolved in the surfactant solution before the runs and 20-50 pl of these samples were injected into the loop. The concentrations of the aniline derivatives were in the range from 1 x 10-3 to 3 X 10-3 mol 1-1.The elution was performed at constant flow rate 1 ml min-I), at room temperature (24 k 1 "C). The stationary phase of the column was LiChrospher 100-CN (10 pm) (Merck). The absorbances of the solutes were monitored at 240 nm. The absorbance variation method20 was also used to estimate the binding constants of some compounds to cationic micelles. The UV absorption of the undissociated analytes was measured at different wavelengths, varying the concentration of the micellized surfactant. The corresponding data were treated according to the following equation: where A , A , and A , are the measured absorbances in surfactant solution, in water and when the substrate is completely bound, respectively. For some polysubstitued hydrophobic compounds, the partition data were estimated by starting from the contribu- tion of each substituent to the free energy of transfer of the molecule to the micelle.The following equations21 are valid within each series of compounds: A p t = Ap*, - Apow = -RT ln(55.5 KB) (3) (4) where Apot is the free energy of transfer per mole of solute from water to micelles and ApoAn is the contribution of the aniline moiety to the total free energy of transfer. The term zApoSubst accounts for the contributions of the substituent groups. Ultrafiltration procedure The experiments were carried out in cylindrical ultrafiltration cells (capacity 70 ml) equipped with a magnetic stirrer rotating slightly above the UF membrane to reduce the concentration polarization effect.The Spectra/Por-C10 hydrophilic cellulose membranes have a relative molecular mass cut-off of about 10000 Da, which is sufficiently small to reject the micelles completely. The membranes were thoroughly washed with water before the runs in order to remove the incorporated wetting agents. A pressure of 300 kPa was maintained in the cell by nitrogen in order to obtain a regular flow of the solution through the membrane. The cells were filled with 30 ml of solution and each run was terminated after the collection of 25 ml of permeate. The stirrer bar was rotated at a constant speed in all the experiments. Each solute was determined both in the retentate and in the permeate by HPLC, according to the following standard procedure: aliquots of 20 pl of retentate solution were injected into the chromatograph, equipped with LiChrocart 125-4 columns (Merck) filled with LiChrosphcr 100 RP-18 (5 pm) stationary phase. Elution was performed using acetonitrile- water (50 + 50).The pH of the eluent was adjusted to about 8 using a borate buffer. The flow rate was kept constant (1 ml min-1) and the wavelength of the UV detector was selected in the range 250-320 nm. Calibration graphs were obtained from the corresponding standards. The analysis of retentate samples was performed in the same way after dilution with the hydro-organic eluent (usually 1 + 9). This step minimizes the interference effects arising from concentrated surfactants and allows the sample viscosity to be decreased. The efficiency of MEUF was estimated through the evaluation of the rejection factor, R , defined as follows: R = 1 - c,/c~ where cp and co are the analyte concentrations in the permeate and in the initial solution, respectively.Each reported R value represents the mean of three independent determinations. Preconcentration-determination experiments The preconcentration of a test mixture of aniline compounds from aqueous dilute solutions was performed using MEUF. Typically, aliquots of 70-100 ml of solutions containing the analytes at the ppb level and each surfactant at a concentration slightly above the critical micellization concentration (c.m.c.) were ultrafiltered until a volume ratio of retentate : permeate in the range 0.07-0.05 was obtained. Working with Spectra/ Por-C 10 membranes under a nitrogen pressure of 300 kPa, about 80 min are necessary for each ultrafiltration run.Samples were taken from the resulting viscous retentate solution with a syringe and immediately analysed by HPLC. As fairly concentrated amphiphile samples are obtained, the HPLC analysis using micellar eluents is recommended in order to eliminate the interference effects arising from concentrated amphiphiles. For example, SDS micellar solu- tions in the concentration range 0.1-0.3 mol 1-1 are able to elute the analytes fairly rapidly, preconcentrated using the same surfactant. The addition of 3% of propan-1-01 to the micellar eluent improves the chromatographic efficiency.2' A LiChrospher 100 RP-18 (5 pm) column was used and the flow rate was kept constant (1 ml min- 1). Ultraviolet detection was performed at 240 nrn for most anilines, whereas for com- pounds 18-20 detection at 340 nm is more sensitive.When HTAB is used to preconcentrate the analytes, the analytical step becomes more difficult because the surfactantANALYST, JANUARY 1993, VOL. 118 25 concentration in the chromatographic eluent is limited by phase separation phenomena (Krafft point). As the surfactant concentration in the eluent must be lower than about 0.04 mol 1-1 at room temperature, the elution becomes much too slow. In these instances, the determination step can be improved by using hydro-organic eluents [usually methanol-water (50 + 50 v/v)] containing an appropriate amount of dissolved cationic surfactant to reduce the interference effects. Higher organic solvent-to-water ratios are recommended to elute highly hydrophobic derivatives, such as compounds 18-20.Results and Discussion Partition and Ultrafiltration Data Most experiments were conducted in the pH range at which the aniline derivatives are present in the undissociated form. The binding constants of the analytes were measured or calculated under the same conditions. The precision of the measurements of K g , expressed as the relative standard deviation, is in the range 8-15%, depending on the hydro- phobicity of the solute.23 The precision of the determination of R is better than 6%. The rejection and partition data for all the compounds investigated are presented in Table 1. Binding constants higher than 2000 1 mol-1 were estimated for the heterocyclic derivatives 18-20 in HTAB micellar solution, from absorbance variation measurements.These lower limit values are in agreement with previous data concerning compounds 18 and 19 in strongly alkaline HTAB solutions, determined using a spectrofluorimetric approach .25 It can be seen that, irrespective of the surfactant used, partitioned compounds having binding constants lower than a threshold value of about 600-700 1 mol-1 are only partially recovered in the retentate. The data also indicate that cationic micelles are more efficient systems, because the positively charged head-groups strongly interact with the x-electrons of the aromatic ring. The results obtained here are in good agreement with previous findings concerning the removal of phenols,6 alcohols* and chloroaromatic pollutants10 from aqueous solutions by MEUF.Table 1 MEUF rejections and binding constants of aniline derivatives in the presence of SDS and HTAB micelles. Experimental conditions: pH 8.0-8.5 SDS HTAB Solute KB/l mol-I R KB/l mol-I R 1: Aniline 2: 4-Fluoroaniline 3: 4-Chloroanilinc 4: 4-Bromoaniline 5: 4-lodoaniline 6: 4-Methylaniline 7: 4-Ethylaniline 8: 4-Isopropylaniline 9: 4-tevt-Butylaniline 10: 4-Nitroaniline 11: 4-Cyanoaniline 12: 3-Fluoro-4-methylaniline 13: 5-Chloro-2-methoxyaniline 14: 2-Chloro-4-fluoroaniline 15: 2-Fluoro-4-bromoaniline 16: 2-Chloro-4-bromoaniline 17: 2-Nitro-4-methylanilinc 18: Compound 1 19: Compound I1 20: Compound I11 23 27 56 75 119 43 79 140 260t 33 27 50 133 707 90-1 220 58 800 lo00 1200 0.34 39* 0.40 0.35 SO* 0.50 0.61 175* 0.85 0.68 240" 0.91 0.87 430* 0.97 0.53 55* 0.61 0.75 110' 0.80 0.86 270* 0.92 0.85 47St 0.95 0.52 180 0.81 0.26 70" 0.55 0.62 94t 0.82 0.85 355 0.94 0.82 225-3- 0.85 0.88 350-t 0.96 0.97 12001- 1.00 0.70 350 0.93 1.00 - 1 .OO 1.00 - 1.00 1.00 - 1.00 * Data taken from ref.24. -3- Binding constants calculated from the hydrophobic contribution of each substituent. In order to improve the performance of MEUF it is necessary to increase the binding constants of the partitioned analytes to micelles by introducing additional interactions. In an attempt to achieve this, the effects of pH and ionic strength were investigated. Effect of pH The rejection factors of all the analytes examined in SDS can be significantly increased by lowering the pH, and this can be attributed to the electrostatic attraction between the anilinium ions and the negatively charged aggregates.The effect is, therefore, related to the mole fraction of the charged form present in the system. In order to evaluate this contribution, the apparent acid constant of some protonated aniline derivatives was determined spectrophotometrically in the presence of SDS and HTAB micelles. The surfactant concen- tration was the same as that of the initial working solutions (2 x 10-2 mol 1-1 for both surfactants). The uncertainty of these measurements is about 15%. The corresponding data are presented in Table 2. Fig. l(a) shows the variation of the rejection factor as a function of pH for some aniline derivatives in SDS. It appears that the effect is particularly important for the more hydro- philic compounds, whereas the electrostatic contribution is less relevant for analytes having larger binding constants. For example, ethylaniline can be quantitatively retained at pH 2-3 Table 2 Apparent acid constants of some anilinium ions in SDS and HTAB micellar media, at an ionic strength of 0.1 mol I-' (NaCI) Compound SDS HTAB Aniline 5.4 4.8 4-Ethylaniline 6.5 5.9 4-Isopropylaniline 6.5 5.8 4-Chloroaniline 5.2 4.0 1 .o 0.9 0.8 0.7 0.6 ~ 2 3 4 5 6 7 8 0.9 c 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 I I I I 1 2 3 4 5 6 7 8 PH Fig.1 Variation of the rejection coefficient with pH in the recovery of aniline (I), 4-chloroaniline (3) and 4-ethylaniline (7) by MEUF. ( a ) 2 x 10-2 moll-1 SDS and (b) 2 x 10-2 moll-' HTAB26 1.0 ANALYST, JANUARY 1993, VOL.118 -- ________ -+--------4 - 16 ---- *---- (at which the protonated form largely predominates) by SDS micelles, whereas at pH 8, about 25% of this solute was found in the permeate. For pH values in the pK,,,,,, range, the contribution of the electrostatic attraction becomes highly significant. Ultrafiltration experiments performed using SDS micelles at pH 2-4 gave quantitative recovery for all the compounds examined. As expected, the effect of pH on the retention yield is the opposite when cationic HTAB micelles are employed [see Fig. 1(6)]. Effect of ionic strength N o significant change in the value of R was observed in MEUF experiments conducted at higher pH with both anionic and cationic micelles, even after addition of 0.1 moll-' of an inert salt (NaCI).In contrast, marked effects were observed when the analytes were present in their protonated form, owing to the lowering of the electrostatic potential of the charged micelles. For the aniline-SDS system, where the electrostatic attrac- tion significantly increases the solute binding to the aggre- gates, the retention efficiency is lower at higher ionic strength. More hydrophobic compounds, such as alkylanilines, showed little effects because the main contribution to the binding is not electrostatic. These different situations are depicted in Fig. 2. The effect of the ionic strength on the rejection of protonated anilines in the presence of cationic HTAB micelles is the opposite, with a significant increase in binding at higher ionic strength for hydrophilic solutes.Effect of surfactant concentration Although the total surfactant concentration has to be mini- mized in MEUF experiments, in order to avoid the formation 1 .o 0.95 0.90 ry 0.85 0.80 0 0.02 0.04 0.06 0.08 0.10 cNaCl/mol I-' Fig. 2 Effect of ionic strength on rejection [SDS] = 2 x 10-2 moll-', pH = 3, added salt: NaCl. Analytes: aniline (l), 4-methylaniline (6) and 4-isopropylaniline (8) of viscous layers above the membrane, this experimental parameter can also be adjusted within certain limits. In particular, an increase in the number of micelles favours the retention of partially bound compounds, whereas the effect is less important for hydrophobic species. The MEUF experi- ments performed at pH 8.0 with compounds 1 and 16 in SDS micellar solutions showed the influence of this parameter (see Fig.3). Preconcentration Experiments The concentration factor in MEUF is limited by the viscosity of the retentate solution and/or by the Krafft point (when ionic surfactants are used). Hence, the preconcentration experi- ments were performed by starting from very dilute surfactant solutions, just above their corresponding c.m.c. The initial concentrations were 2 x 10-3 mol 1-1 (HTAB) and 1 X 10-2 mol 1-1 (SDS). Fig. 4(a) shows the chromatographic profile obtained by working with 0.15 rnol 1-1 SDS (3% v/v of propan-1-01 was added to this eluent), after direct injection of 20 pl of SDS-containing retentate. The separation of two aniline derivatives preconcentrated using HTAB is shown in Fig. 4(6), where methanol-water (50 + 50) (containing 3% v/v of 0.04 rnol 1-1 HTAB) was used as eluent.The inconvenience associated with the injection of concen- trated surfactant solutions into hydro-organic eluents, in particular the poor reproducibility of the peaks and the baseline disturbance, was significantly reduced by working a) 0.9 j- 0.4 f- 24 16 8 Retention time/min 0 0.1 1, I I I 0.01 0.02 0.03 0.04 csos/mol 1-1 Fig. 3 Effect of SDS concentration on rejection efficiency at pH 8.0. Aniline (1) and 2-chloro-4-bromoaniline (16) Fig. 4 ( a ) Separation of aniline derivatives preconccntrated using SDS and eluted with 0.15 rnol 1-1 SDS containing 3% v/v of propan-1-01. Analyte concentration: 7 X lo-' mol 1-'. Compound 5 : 1 x 10V mol I-'. 0.005 a.u.f.s. Detector wavelength: 240 nm. ( b ) Separation of anilines after preeoncentration with HTAB.Eluent: methanol-water (50 + 50) plus 3% v/v 0.04 mol I-' HTAB. Analyte concentration: 1 X 10-6 rnol 1-1. 0.005 a.u.f.s. Detector wavelength: 240 nmANALYST, JANUARY 1993, VOL. I18 27 Table 3 Sensitivity of the HPLC dctcrmination of some aniline derivatives after prcconcentration by MEUF Detection limit/ng Compound SDS HTAB CF* - 1 0.6 14 14 7 0.7 - 14 8 0.8 - 16 2.5 1.2 14/20 5 - 1.3 20 19 - 4.8 20 * cF = Concentration factor. with these surfactant-modified cluents. 'The added surfactant saturates the stationary phase, avoiding abrupt changes in the properties of the packing material when the sample is injected. Moreover, by using recrystallized surfactants, the interfer- ences arising from amphiphile impurities can also be mini- mized. The detection limits obtained by working with several aniline derivatives, after preconcentration of solutions containing 5 x 10-8 moll-' of each analyte, are presented in Table 3.The reported detection limits were determined under the same experimental conditions by injecting decreasing amounts of pure standards. The concentration factor attained is indicated by cF. Quantitative recovery of the analytes in the retentate phase was confirmed. Conclusions The results presented here indicate that effective preconcen- tration of several aniline derivatives from water (or aqueous wastes) can be performed by using MEUF. The percentage recovery of each analyte is related to the corresponding binding constants to the aggregates, which can in turn be increased by selecting the appropriate surfactant, the pH, and other experimental conditions.In particular, experiments conducted in acidic media with anionic micclles allow the quantitative recovery of both hydrophobic and polar derivatives. The retentate samples obtained by using these surfactants (e.g., SDS) can be readily injected into the chromatograph and analysed after elution with aqueous micellar solutions containing the same amphiphile. The use of hydro-organic HPLC eluents to analyse the retentate is also possible if surfactants are added to these solvents and the column is carefully conditioned. The final surfactant concentration in the retentate has to be limited in order to prevent the formation of very viscous layers (gel formation) and/or precipitation.The use of UF units equipped with stirrers rotating just above the membrane surface allows undesirable concentation polarization effects to be minimized. As high concentration factors are desirable when starting from very dilute aqueous samples, amphiphiles having low c.m.c. values (e.g., molecules possessing longer alkyl chains) are, in principle, the best candidates for these MEUF-based separations. Financial support from CNR (Progetto Finalizzato Chimica Fine) and from MURST (Rome) is gratefully acknowledged. References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Armstrong, D. W., Sep. Purif. Methods. 1985, 14, 213. Ordered Media in Chemical Separations, eds. Hinze, W. L.. and Armstrong, D. W.. ACS Symp. Ser.342, Amcrican Chemical Society. Washington, DC, 1987. Surfactants in ChemicallProcess Engineering. cds. Wasan, D. T., Ginn, M. E., and Shah, D. O., Marcel Dekker, New York, 1988. Pramauro, E., and Pelizzetti, E., TrAC, Trends Anal. Cizem., 1988, 7, 260. Surfuctant-Based Separation Processes, eds. Scamehorn, J. F., and Harwell, J . H., Marcel Dckker, New York, 1989. Dunn, R. O., Scamehorn, J . F., and Christian, S. D., Sep. Sci. Technol., 1985, 20, 257. Scamchorn, J . F., Ellington, R. T.. Christian, S. D., Penney, B. W., Dunn, R. O., and Bhat, S. N., AIChE Symp. Ser., 1986. 82, 48. Lane Gibbs, L., Scamchorn, J . F., and Christian, S. D.. Sasaki, K . J., Burnctt, S. L.. Christian. S. D., Tuckcr, E. E., and Scamehorn, J. F., Langmuir, 1989, 5, 363. Pramauro, E., Ann. C'him. (Rome), 1990, 80, 101. Clarke, E. A.. and Anliker, R., in The Handbook of Environ- mental Chemistry, cd. Hutzingcr, O., Springcr-Verlag, Berlin, Vantulder, P. J . M., Howard, C. C., and Riggin. R . M., HPLC Determination of Aromatic Amines in Body Fluids and Commer- cial Dyes, ACS Symy. Ser. 149, American Chemical Society, Washington, DC, 1981, pp. 413-427. Bjorkovist. B., J . Chromatogr., 1981, 204, 109. Lores. E. M., Bristol, D . W., and Moseman, R. F., J . Chromatogr. Sci., 1978, 16, 358. Narang, A. S . , Choudhury, D. R., and Richards, A., J. Chromatogr. Sci., 1982, 20, 235. Barni, E . , Savarino, P.. Carpignano, R., and Larovcrc, R., Dyes Pigments, 1985, 6, 83. Barni, E., Savarino, P., Marzona, M., and Piva, M., J . Heterocycl. Clzem., 1983, 20, 1517. Armstrong, D. W.. and Nome, F., Anal. Chem., 1981,53,1662. Bcrczin, 1. V., Martinek, K., and Yatsimirskii, A. K., Russ. Chem. Rev. (Engl. Trund.), 1973, 42, 787. Sepulveda, L.. J . Colloid Interface Sci., 1974, 46, 372. Bunton, C. A., and Sepulveda, L., J . Phys. Chem., 1979, 83, 680. Dorsey, J. G., De Echcgaray, M. T., and Landy, J. S . , Anal. Clzem., 1983, 55, 924. Pramauro, E.. Minero, C., Saini, G . , Graglia, R., and Pelizzetti, E . , Anal. Chirn. Acta, 1988, 212, 171. Graglia. R., Pramauro, E . , and Pelizzetti, E.. Ann. Chim. (Rome). 1984, 74, 41. de la Guardia, M., Peris-Cardells, E . , Sancenon, J . , Carrion, J . L., and Pramauro, E., Microchern. J., 1991, 44, 193. 1980, VOI. 3A, pp. 181-215. Puper 2/01285E Received March 10, 1992 Accepted August 28, I992

ISSN:0003-2654    

DOI:10.1039/AN9931800023

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993, VOL. 118 29 6-Methoxy-2-methylsuIfonylquinoline-4-carbonyl Chloride as a Fluorescence Derivatization Reagent for Amines in Liquid Chromatography Tomohiko Yoshida, Youichi Moriyama, Kayoko Nakamura and Hirokazu Taniguchi Meiji College of Pharmacy, 1-35-23 Nozawa, Setaga ya, Tokyo 154, Japan 6-Methoxy-2-methylsuIfonylquinoline-4-carbonyl chloride was found t o be a sensitive fluorescence derivatization reagent for primary amines. The reagent reacted with the amines in acetonitrile in the presence of potassium carbonate t o give the corresponding fluorescent amides, which could be separated on a TSK,,, ODs-80TM reversed-phase column with aqueous 55% v/v acetonitrile as eluent. Pentylamine, hexylamine, heptylamine and octylamine were used t o investigate the derivatization conditions.The detection limits (signal-to-noise ratio = 3) of these amines were in the range 0.5-1 .O pmol per 20 PI injection volume. Alcohols did not give any fluorescent products under these derivatization conditions. Keywords: 6-Methox y-2-meth ylsulfon ylquinoline-4-carbon yl chloride; primary amine; fluorescence de riva tiza tio n reagent; h ig h -perform an ce liquid ch ro ma tog rap h y Benzoyl chloride, 1 4-nitrobenzoyl chloride2 and 3 ,5-di- nitrobenzoyl chloride,3 having a carbonyl chloride group, are well known derivatization reagents for the determination of amines by high-performance liquid chromatography (HPLC) with spectrophotometric detection. On the other hand, several fluorescent derivatization reagents such as 5-dimethyl- aminonaphthalene-1-sulfonyl chloride,4 phthalimidylbenzoyl chloride derivatives ,5 3,4-di hydro-6,7-dime t hox y-4-me thyl-3- oxoquinoxaline-2-carbonyl chloride6 and 7-dimethylamino- coumarin-3-carbonyl fluoride7 have been developed for the determination of amines.Quinoline derivatives, in addition to naphthalene, quin- oxaline and coumarin derivatives, are also widely known fluorescent compounds, e.g., quinine sulfate. To the best of our knowledge, however, quinoline derivatives (except for 3-benzoylquinoline-2-carboxyaldehyde8) have not been applied as fluorescence derivatizatian reagents to HPLC with fluorescence detection. In a previous paper,Y several 6-methoxyquinoline-4-carb- oxylic acid derivatives containing an S-atom at the 2-position of the quinoline ring were synthesized, and the fluorescence quantum yields of these compounds were measured. Subse- quently, 6-methoxy-2-methylsuIfonylquinoline-4-carboxylic acid (MSQC) was found to have the highest fluorescence quantum yield, and the quantum yields of MSQC-amide derivatives were about the same as those for amide derivatives of 7-methoxycoumarin-4-carboxylic acidl(1 in an ethanol sol- vent.Moreover, the MSQC-amide derivatives showed the highest fluorescence intensity in acetonitrile, which is widely used as a component of the mobile phase in reversed-phase HPLC. This paper describes the synthesis of 6-methoxy-2-methyl- sulfonylquinoline-4-carbonyl chloride (MSQC-CI), according to a previous method," as a fluorescence derivatization reagent for amines in reversed-phase HPLC.In order to investigate the reactivity of amines with MSQC-CI, pentyl- amine, hexylamine, heptylamine and octylamine were used. The MSQC-CI reagent reacted with these amines in aceto- nitrile in the presence of potassium carbonate to produce the corresponding fluorescent amides. The amides were separated on a reversed-phase column with aqueous 55% v/v acetonitrile. Experimental Reagents and Materials All chemicals were of analytical-reagent grade. All amines used were purified by distillation. De-ionized and glass- distilled water was used. Acetonitrile was of HPLC-grade (Kanto Chemicals). All solvents (Luminazol) for measuring the fluorescence quantum yield were purchased from Wako Pure Chemicals. The MSQC-CI solution (1 mmol 1-1) was prepared by dissolving MSQC-CI (3 mg), synthesized from MSQC as described previously,ll in acetonitrile (10 ml).This solution was stable for 10 h. Apparatus All melting-points (uncorrected) were determined with a Yanagimoto micro melting-point apparatus. Infrared (IR) spectra were recorded in KBr discs with a Hitachi 270-30 infrared spectrophotometer. Mass spectra were obtained with a Jeol DX302 spectrometer. Proton nuclear magnetic res- onance (IH NMR) spectra were recorded with a Jeol JNM-GX400 spectrometer using tetramethylsilane as an internal standard. Fluorescence spectra and fluorescence quantum yield (using quinine sulfate solution in 0.05 mol 1-1 H2SOL1 as a standard solution) were measured12 with a Hitachi F-4000 fluorescence spectrophotometer in a 1 cm quartz cell.Fluorescence Quantum Yield12 First, the excitation spectrum (210-606 nm) was calibrated by using Rhodamine B (5 g 1-1, in ethane-1,2-diol) as a quantum counter at the emission wavelength (640 nm) fitted. Next, the emission spectrum was calibrated by using the diffuser and the attenuator by scanning both the excitation and emission wavelengths (210-603 nm). The emission spectra of the sample solution (MSQC-amide solution in various solvents) and the standard solution (quinine sulfate solution in 0.05 moll-' H2S04) were recorded at an excitation wavelength of 366 nm. Each area (F, or F,) at the peak width at half-height on the spectrum (relative light quantum number-wavenum- ber) obtained was calculated. The fluorescence quantum yield (ax) for the unknown compound was then calculated accord- ing to the following equation: ax = X F,IF, X (nx)2/(ns)2 X E,/E, X c,/c, where Q5 is the quantum yield of the standard, quinine sulfate (0.55), n is the refractive index of the solution, E is the molar absorption coefficient at 366 nm and c is the molarity.Subscripts x and s refer to the unknown compound and the standard, respectively. High-performance Liquid Chromatography For HPLC a Model L-6200 high-performance liquid chroma- tograph (Hitachi) equipped with a Rheodyne 7125 injector (2030 ANALYST. JANUARY 1993, VOL. 118 pl loop) (Rheodyne) was used. A Jasco RC-250 recorder, SIC chromatocorder 12 and a Jasco FP-210 spectrofluorimeter fitted with a 12 PI flow cell were used. The spectrometer was set at an excitation wavelength of 342 nm and an emission wavelength of 448 nm.A TSK,,, ODs-80TM column (particle size 5 pm, 150 x 4.6 mm i.d.; Tosoh) was employed at room temperature. Aqueous 55% v/v acetonitrile was used as the mobile phase at a flow rate of 1.0 ml min-1. Preparation of Fluorescent Compounds (1-10) From Amines The acetonitrile solution (15 ml) of MSQC-CI (0.1 g) was added to the acetonitrile solution ( 5 ml) containing each of the amines (1 g). After the mixture had been allowed to stand for 30 min at room temperature, it was evaporated to dryness in vacuo. The residue was dissolved in a small amount of dichloromethane, then subjected to column chromatography on Wakogel C-200 (Wako Pure Chemicals) with hexane-ethyl acetate-ethanol (46 + 3 + 1, v/v). The blue fluorescent eluate was collected and the solvent removed in vacuo. The residue was recrystallized from dichloromethane-hexane to give the corresponding compounds (1-10, Tables 1 and 2).Derivatization Procedure To a 0.2 ml portion of an acetonitrile solution of the amines were added about 10 mg of potassium carbonate and a 0.2 ml portion of 1 mmol 1-1 MSQC-Cl solution in a polypropylene micro-centrifuge test-tube (1 .5 ml volume). The mixture was allowed to stand at room temperature for 5 min. A 0.05 ml portion of the reaction solution was diluted with mobile phase to 1.0 ml and a 20 p1 portion of the resultant solution was injected into the chromatograph. Results and Discussion Structural Assignment and Fluorescence Properties of Compounds 1-10 The elemental analysis data and spectral data are shown in Tables 1 and 2, respectively. Compounds 1-10, except for compound 9, showed an I R absorption band due to the NH of the secondary amide groups at 3292-3308 cm-1.The 1R absorption bands due to the CO of the secondary amide groups or methylsulfonyl groups was observed at 1622-1660 or 1152-1160 and 1304-1316 cm-1, respectively. The 'H NMR signals due to methylsulfonyl and methoxy protons were observed at 3.30-3.34 (3 H, s) and 3.92-3.98 (3 H, s) ppm, respectively. These data, the mass spectra data and elemental analyses were consistent with the assigned structure of the corresponding carboxyamides. The fluorescence quantum yields and corrected fluores- cence emission maxima (excited at 366 nm) of compounds 1-10 in various solvents are shown in Table 3.The fluores- cence quantum yields of compounds 1-6 (aEtOH = 0.25-0.30) were about the same as those of the amide derivatives (QEtOH = 0.25-0.34) of 7-methoxycoumarin-4-carboxylic acid in an ethanol solvent described by Goya et a1.10 Consequently, it was found that MSQC-CI reacted with amines to form the same intense fluorescent amide derivatives as those derived from 7- methoxycoumarin-4-carbonyl chloride. 10 Moreover, the MSQC-amide derivatives showed the highest quantum yields in acetonitrile, which is widely used as a component of the mobile phase in reversed-phase HPLC. The maxima of the fluorescence spectra in acetonitrile were slightly blue-shifted compared with those in methanol for compounds 1-8. The fluorescence intensities of compounds 1-8 in 55% v/v aqueous acetonitrile as mobile phase were slightly lower than those in acetonitrile.However, the fluorescence quantum yields of these compounds in 55% aqueous acetonitrile were higher than those in methanol. The quantum yield of compound 9 derived from diethylamine was below 0.01 and that of compound 10 derived from aniline was not calculated at the concentration which gave an absorbance of 0.02 at the corrected excitation wavelength (366 nm). 12 Separation of MSQC Derivatives The effect of different organic modifiers in the mobile phase was studied by using the four amines listed in Table 4. The log k' value (k' = capacity factor) of all the amines was smaller Table 1 Analytical data for fluorescent compounds 1-10* Analysis (YO) Calc. (Found) Compound 1 2 3 4 5 6 7 8 9 10 * Me1 ting-poi nt/ "C 206-207 I 74- 1 75 222-223 139- 140 138-139 135-136 164-167 234-235 I41 -1 42 245-246 Yield 68 63 64 81 78 76 71 89 83 86 (Yo) C 54.53 55.89 (55.76) 55.89 57.13 (57.08) 58.27 (58.21) 59.32 (59.09) 61.61 (61.62) 59.65 (59.50) 57.13 (57.05) 60.66 (60.68) (54.73) (55.74) H 5.23 5.63 5.63 (5.66) 5.99 (6.00) 6.33 (6.40) 6.64 (6.68) 4.90 (4.80) 6.12 (6.09) 5.99 (6.21) 4.53 (4.40) (5.39) (5.75) N 9.08 (9.02) 8.69 (8.69) 8.69 8.33 7.99 7.69 (7.63) 7.56 (7.53) 7.73 (7.74) 8.33 (8.34) 7.86 (7.86) (8.64) (8.23) (8.00)ANALYST, JANUARY 1993, VOL.118 31 Table 2 Spectral data for fluorescent compounds 1-10 Compound 1 2 3 4 5 6 7 8 9 10 MS. mlz 308 322 322 336 350 364 370 362 336 356 (M+ 1 IR, v,,,/cm-l NH C=O SO2 1H NMR in CDCI, [6 (ppm)] 3308 1642 1158 1.35 (3 H, t, CH2CH3), 3.33 (3 H, s , S02CH3), 3.61 (2 H, m, CH2CH3), 3.98 (3 H, s , OCH,).6.36 1308 (1 H, br, NH). 7.50, 7.71, 8.08 and 8.09 (each 1 H, aromatic H) 3308 1622 1158 1.06 (3 H, t, CH,CH,CH,), 1.71 and 3.54 [each2 H, m, (CH2)2CH3], 3.34 (3 H, s, SO,CH,), 3.97 1316 (3 H, s, OCH3), 6.26 (1 H, br, NH), 7.51, 7.70, 8.09 and 8.10 (each 1 H, aromatic H) 3300 1622 1158 1.36 [6 H, d, CH(CH3)2], 3.34 (3 H, s, S02CH3), 3.97 (3 H, s, OCH3), 4.39 [ 1 H, m, CH(CH3)2], 1310 6.10 ( 3 H, br, NH), 7.51, 7.68, 8.07 and 8.09 (each 1 H, aromatic H) 3304 1640 1158 1.01 [3 H, t, (CH2)3CH3], 1.49, 1.68 and 3.56 [each 2 H, m, (CH2),CH,], 3.33 (3 H, s, S02CH3), 1314 3.97 (3 H, s, OCH,), 6.27 (1 H, br, NH), 7.51, 7.69, 8.08 and 8.09 (each 1 H, aromatic H) 3296 1644 1154 0.95 [3 H, t.(CH&CH3], 1.42, 1.69 and 3.56 [8 H, m, (CHZ)4CH3]. 3.33 (3 H, s, S02CH,), 3.97 1314 (3 H, s, OCH3), 6.28 (1 H, br, NH), 7.51, 7.69, 8.08 and 8.09 (each 1 H, aromatic H) 3292 1644 1156 0.92 [3 H, t, (CH2)5CH3], 1.36.1.43, 1.68and 3.56 [lOH, m, (CH2)sCH3], 3.33 (3 H, s, S02CH,), 1316 3.97 (3 H, s, OCH3), 6.31 (1 H, br, NH), 7.50, 7.69. 8.08 and 8.09 (each 1 H, aromatic H) 3304 1660 1156 3.30 (3 H, s, SOzCH,), 3.92 (3 H, s, OCH3), 4.74 (2 H, d, CH2), 6.65 (1 H, br, CONH). 7.32-7.44 1304 (5 H, m, C6Hs), 7.50, 7.66, 8.07 and 8.10 (each 1 H, aromatic H) 3308 1642 1160 1.21-2.14(10H,m, cyclicH), 3.33 (3H, s,S02CH3),3.96(3H,s,0CH,),4.09(1 H,m,cyclicH), 1312 6.16 (1 H, d, NH), 7.50, 7.66, 8.07 and 8.08 (each 1 H, aromatic H) 1152 1.07 and 1.38 (each 3 H, t , CH2CH3), 3.12 and 3.71 (each 2 H, br, CH2CH3), 3.32 (3 H, s, 1314 S02CH,), 3.93 (3 H, s, OCH?), 7.08, 7.52, 7.99 and 8.14 (each 1 H, aromatic H) 1156 3.34 (3 H, s, S02CH3), 3.96 (3 H, s, OCH,), 7.25-7.74 (5 H, m, ChHs), 7.50,7.73,8.08 and 8.23 1312 (each 1 H, aromatic H), 8.30 (1 H, br, NH) 1638 1652 3296 Table 3 Fluorescence spectral data for compounds 1-10 Compound Quantum yield (A.,","x/nm)* Acetonitrile 55% Acetonitrile 1 0.56 (437) 0.44 (455) 2 0.54 (438) 0.43 (456) 3 0.46 (438) 0.43 (458) 4 0.56 (437) 0.46 (455) 5 0.50 (438) 0.47 (454) 6 0.56 (438) 0.42 (456) 7 0.61 (438) 0.51 (457) 8 0.30 (436) 0.30 (455) 9 -t --t 10 --$ 4 * Excited at 366 nm and corrected by using Rhodamine B. -t Below 0.01.$ Could not be measured. Methanol 0.27 (456) 0.29 (455) 0.24 (453) 0.25 (454) 0.27 (454) 0.28 (454) 0.31 (456) 0.19 (455) --t --$ Chloroform 0.53 (431) 0.44 (431) 0.56 (431) 0.50 (431) 0.53 (431) 0.57 (432) 0.36 (430) -7 -3 0.55 (430) Cyclohexane 0.1 1 (420) 0.10 (421) 0.09 (422) 0.11 (421) 0.10 (420) 0.10 (420) 0.20 (422) 0.06 (419) -7 -3: Table 4 Effect of organic modifier of mobile phase* Acetonitrile Methanol Tetrahydrofuran Amine Log k' h Log k' h Log k' b Pentylamine 2.45 -0.030 3.23 -0.037 2.70 -0.041 Hexylamine 2.88 -0.034 3.93 -0.045 3.22 -0.048 Heptylamine 3.32 -0.039 4.58 -0.051 3.72 -0.055 Oct ylamine 3.74 -0.043 5.30 -0.058 4.20 -0.062 * Log k' = a + h(x), where x is the modifier concentration.with acetonitrile as modifier than with methanol or tetra- hydrofuran as modifier; therefore, acetonitrile was the most suitable organic modifier in the mobile phase.The MSQC derivatives of pentylamine, hexylamine, hepty- lamine and octylamine were subjected to a separation study on a TSK,,, ODS-80TM reversed-phase column using aqueous acetonitrile as the mobile phase. At acetonitrile concentra- tions higher than 60% v/v, the peak for pentylamine was overlapped by the reagent blank peak, whereas at acetonitrile concentrations lower than 45% v/v the pentylamine peak took longer to elute and there was some broadening of the peak. The best separation was obtained with aqueous 55% v/v acetonitrile as the mobile phase. Fig. 1 shows a typical chromatogram of the MSQC derivatives obtained with a mixture of the four amines (concentration, each 0.05 mmol 1-1) under the selected derivatization conditions. Derivatization Conditions and Reaction With Alcohols The use of acetonitrile as a solvent for the derivatization reaction gave the highest detector response. Pyridine, acetone and tetrahydrofuran gave a lower detector response (about 88, 55 and 32%, respectively, of that obtained in acetonitrile).Dimethylformamide and dimethyl sulfoxide did not yield any detector response for the corresponding amines. Hence, acetonitrile was chosen for the recommended procedure. The uncorrected fluorescence-emission maximum of the MSQC derivative of hexylamine was observed at 448 nm with excitation at 342 nm in the mobile phase (55% v/v acetonitrile solution). Potassium carbonate accelerated the derivatization reaction and the most intense peaks for the amines examined were achieved by the addition of 7-15 mg; about 10 mg were added to the reaction mixture. Potassium carbonate was found to be32 ANALYST, JANUARY 1993, VOL.118 0 10 20 Time/mi n A C D Fig. 1 Chromatogram obtained for the reaction of amines with MSQC-CI. A, Pcntylaminc; B, hexylamine; C, hcptylamine; and D, octylaminc. An aliquot (0.2 ml) of a mixturc of thc amincs (each 0.05 mmol 1 - l ) was treated as dcscribcd undcr Dcrivatization Procedure 15 E 2 10 c 0) a, f Y (D .- 2 5 0 1 2 3 MSQC-Cl/mmol I-' Fig. 2 Effect of MSQC-CI concentration on the tluorescence derivatization. A, Pcntylaminc; B , hexylaminc; C, hcptylamine; and D, octylaminc. An aliquot (0.2 ml) of a mixture of the amines (each 0.05 mmol 1-I) was reacted with various concentrations of MSQC-CI as described under Derivatization Procedure more effective than pyridine, quinuclidine and dibenzo-18- crown-6.Even in the absence of potassium carbonate, the reaction was complete within 3 min at room temperature. However, the peak areas of pentylamine, hexylamine, hepty- lamine and octylamine were about 69-70%0 of those obtained in the presence of potassium carbonate. The dcrivatization reaction of the four amines with MSQC- C1 proceeded rapidly, independently of the temperature (0-100°C); maximum and constant peak areas for the corresponding amines were obtained on allowing the reaction mixture to stand at room temperature for about 3 min. Therefore, a reaction time of 5 min was selected. Maximum and constant peak heights for the four amines (concentration, each 0.05 mmol 1 - 1 ) were obtained at Table 5 Retention times and detection limits of the MSQC derivativcs of primary and secondary amines Amine Prop ylaminc Butylamine Pentylamine Hexylamine Hcpt ylaminc Octylamine Benzylamine 4-Methylbenzylamine 2-Phenylethylamine Cyclohexylamine Dipropylamine Di butylamine Detcction limit*/ pmol per 20 pl min injcction volumc Retention time/ 6.8t 10.9-I- 6.1$ 8.73 12.83 19.4$ 13.7t 21.47 18.0-1 17.0-1 17.5-1 11.43 1 .o I .o 0.5 0.5 0.5 1 .o 1 .o 1 .o 1 .0 2.0 100 100 * The amount in the injection volume (20 pl) giving a signal-to- t Mobile phase: acetonitrile-water (40 + 60).$ Mobile phase: acetonitrile-water (55 + 45). noise ratio of 3. MSQC-CI concentrations greater than about 0.6 mmol 1-1; hence a 1 mmol 1 - 1 MSQC-Cl solution was used (Fig.2). The MSQC derivatives in the final solution were stable for at least 10 d in daylight at room temperature. As reported previously,ll MSQC-Cl reacts with primary and secondary alcohols at high temperatures (100 "C) and long reaction times (60 min) to produce the corresponding fluores- cent esters. However, under the derivatization conditions adopted here, the reaction of MSQC-Cl with primary and secondary alcohols gave no fluorescent products. Calibration Graphs, Precision and Detection Limits The relationship between the peak area and the amount of propylamine , butylamine , pentylamine , hexylamine, heptyl- amine, octylamine and benzylamine was linear from 0.5 pmol to 0.15 nmol per 20 pl injection volume (corresponding to 1 ymol 1-1-0.3 mmol 1 - 1 of sample solution).The precision was established by repeated analyses (n = 10) of the above seven amines. The relative standard deviations were 7.0, 4.4 and 3.5% (propylamine), 6.2,4.5 and 3.1% (butylamine), 7.3, 4.2 and 2.9% (pentylamine), 4.3,3.9 and 2.9% (hexylamine), 5.1, 3.8 and 2.7% (heptylamine), 4.5, 3.8 and 2.7% (octyl- amine) and 4.0,3.2 and 3.3% (benzylamine) at concentrations of 0.005, 0.05 and 0.1 mmol 1 - 1 , respectively. The detection limits (signal-to-noise ratio = 3) ( n = 10) for the primary amines were from 0.5 to 1.0 pmol and those for secondary amines were above 100 pmol per 20 yl injection volume (Table 5 ) . Conclusions The reagent MSQC-CI, which is characterized by a methylsul- fonyl group, readily reacted with primary amines at room temperature to produce the corresponding strongly fluores- cent amides, which were detected with a detection limit of 0.5-1 .O pmol per injection volume.The results presented in Table 5 suggest that 2-phenylethylamine in plasma might be determined with MSQC-Cl by reversed-phase HPLC. More- over, the reaction of MSQC-Cl with alcohols gave no fluorescent products under the derivatization conditions employed. The authors are grateful to Professor T. Nakagawa of Kyoto University for his valuable suggestions. Thanks are due to Professor Y. Shibanuma of this College for measurements of IR spectra and for his advice.ANALYST, JANUARY 1993, VOL. 118 33 References 1 2 3 4 5 6 7 Fitzpatrick. F. A., and Siggia, S., Anal. Chem.. 1973,45,2310. Newsome. W. H., and Panopio, L. G., J . Agric. Food Chem., 1978, 26, 638. Suzuki, Y., and Tsuchiya, N., Bunseki Kuguku, 1981, 30, 240. Yamada, K., and Aizawa, Y., J. Pharmacol. Methods, 1983,9, I. Tsuruta, Y., and Kohashi, K., Anal. Chim. Actu. 1987, 192, 309. Ishida, J . , Yamaguchi, M., Iwata, T., and Nakamura, M., Anal. Chim. Actu, 1989, 223, 319. Fujino, H . , and Goya, S . , Yakugaku Zusshi, 1990, 110,693. 8 9 10 11 12 Beale, S. C., Savage, J . C., Wiesler, D., Wietstock, S. M.. and Novotny, M., Anal. Chem., 1988, 60, 1765. Yoshida, T., Moriyama, Y., and Nakano, S . , Chem. Pharm. Bull., 1992,40, 1322. Goya, S . , Takadate, A., Tanaka, T., and Nakashima, F., Yakugaku Zasshi, 1980, 100,289. Yoshida, T., Moriyama, Y.. and Taniguchi, H., Anal. Sci., 1992, 8, 355. Nishikawa, Y., and Hiraki, K., Analytical Methods of Fluores- cence and Phosphorescence, Kyoritu Press, Tokyo, 1984. Paper 2iO4250I Received June 26, 1992 Accepted August 6, 1992

ISSN:0003-2654    

DOI:10.1039/AN9931800029

出版商:RSC    

年代:1993

数据来源: RSC