摘要:

~ ROYAL SOCIETY OF CHEMISTRY AN ALY TI CAL D IVI S I 0 N NORTH WEST, NORTH EAST AND SCOTTISH REGIONS Joint one-day meeting MONITORING INDUSTRIAL ENVIRONMENTS University of Manchester, December 5th, 1984 Details of this meeting are available from Mr. P. Morries, 2 Rothesay Road, Crumpsall, Manchester, M8 6JA (Tel. 061 -740-7354). ~ CHALLENGES TO CONTEMPORARY DAIRY ANALYTICAL TECHNIQUES ANRLYTICRL TO COMCMPCNRRV CttALL€NG€S DAIRY TccHNIQucs Softcover 350pp 0 85186 925 4 Price f 16.00 ($29.00) RSC Members f 12.00 Special Publication No. 49 Over many years international organizations, national organizations and private concerns have prepared standardized methods of analysis for food products, including milk and milk products, for purposes of quality control, assessment of nutritive content, enforcement of legal requirements and affirmation of safety.This activity is concerned with identifying the most appropriate current methodology and codifying it in authoritative documents. The object of this book is to appraise the problems that will be faced by analysts of dairy products in the future and examine the means that are likely to be used to solve them. Brief Contents: Collaborative Studies and Reference Materials; Determination of Major Constituents: Automated, Instrumental Methods; Determination of Micro-constituents: Advanced Methods; Determination of Compounds Formed during Processing and Storage (Artefacts) and Contaminants. Non-RSC members should send their orders to: The Royal Society of Chemistry, Distribution Centre, Blackhorse Road, Letchworth, Herts SG6 lHN, England. RSC members should send their orders to: The Royal Society of Chemistry, Membership Office, 30 Russell Square, London WClS 5DT.

ISSN:0144-557X    

DOI:10.1039/AP98421FX032

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

411 ANALYTICAL DIVISION DIARY October, I984 THINKING OF BUYING A FLAME ATOMIC ABSORPTION S PECTRO PHO TOME TER? Before committing yourself, read the Analytical Methods Committee’s report on the subject in Analytical Proceedings February, 1984, p. 45 and evaluate the available instruments by using the AMC comparison procedure. If you do not have February Analytical Proceedings, or do not wish to write in the one that you do possess, reprints of the report may be purchased from: Dr. J. F. Tyson, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, LEI 1 3TU, price f2.00 ($5.00). SPECIAL ISSUE OF THE ANALYST MARCH 1984 The March 1984 issue of The Analyst contains 46 papers presented at SAC 83 - The 6th International Conference on Analytical Chemistry, held in Edinburgh, 17th-23rd July 1983.The papers presented cover the most important areas of analytical chemistry and provide a valuable overview of the conference. The March issue of The Analyst contains the 4 plenary lectures, as listed below, as well as 42 other papers presented. Plenary Lectures: Recent Developments in Fluorescence and Chemiluminescence Analysis - James N. Miller. Improved Detection Capabilities - Milos Novotny . Capillary Separation Methods: a Key to High Efficiency and Design and Application of Neutral Carrier-based Ion-selective Electrodes - W. Simon, E. Pretsch, W. E. Morf, D. Ammann, U. Oesch and 0. Dinten. Continuum Source Atomic-absorption Spectrometry: Past, Present and Future Prospects - Thomas C. O’Haver. Single Issue Price: RSC Members fAO.00 ($18.50). Non-RSC Members $15.00 ($27.50). ORDERING: Non-RSC members should send their orders to: The Royal Society of Chemistry, Distribution Centre, Blackhorse Road, Letchworth, Herts SG6 lHN, England. RSC Members should send their orders to: The Royal Society of Chemistry, Membership Officer, 30 Russell Square, London WClB 5DT. PAYMENT SHOULD ACCOMPANY ORDER. Electronically typeset and printed by Heffers Printers Ltd, Cambridge, England

ISSN:0144-557X    

DOI:10.1039/AP98421BX034

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

ANPRDI 21 (10) 351-41 2 (1 984) October 1984 Hon. Secretary R. Sawyer Proceedings of the Analytical Division of The Royal Society of Chemistry AD President P. G. W. Cobb Hon. Treasurer D. C. M. Squirrel1 Hon. Assistant Secretary D. I. Coomber, O.B.E. Hon. Publicity Secretary Dr. J. F. Tyson, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, LEI 1 3TU Secretary Miss P. E. Hutchinson Editor, Analyst and Analytical Proceedings P. C. Weston Senior Assistant Editors Assistant Editor Mrs. J. Brew, R. A. Young Ms. D. Chevin Publication of Analytical Proceedings is the responsi- bility of the Analytical Editorial Board: J. M. Ottaway (Chairman) L. S. Bark L. C. Ebdon A. G. Fogg *P. M. Maitlis A. C. Moffat B. L. Sharp J. D. R. Thomas A.M. Ure *P. C. Weston *fx officio mem bers All editorial matter should be addressed to: The Editor, Analytical Proceedings, The Royal Society of Chemistry, Burlington House, Piccadilly, London, WIV OBN. Telephone 01-734 9864. Telex 268001. Advertisements: Advertising Department, The Royal Society of Chemistry, Burlington House, Piccadilly, London, WIV OBN. Telephone 01-734 9864. Analytical Proceedings (ISSN 0144-557X) is published monthly by The Royal Society of Chemistry, Burlington House, London, W1V OBN, England. All orders, accompanied by payment, should be sent to The Royal Society of Chemistry, The Distribution Centre, Black- horse Road, Letchworth, Herts., SG6 IHN, England. 1984 Annual Subscription price if purchased on its own: UK f53.00, Rest of World f56.00, US $106.00, including air speeded delivery.Air freight and mailing in the USA by Publications Expediting Inc., 200 Meacham Avenue, Elmont, N.Y. 11003. USA Postmaster: Send address changes to: Analytical Proceedings. Publications Expediting Inc., 200 Meacham Avenue, Elmont, N.Y. 11003. Second class postage paid at Jamaica, N.Y. 11431. All other despatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outside Europe. PRINTED IN THE UK. @The Royal Society of Chemistry, 1984. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photographic, recording, or otherwise, without the prior permission of the publishers. New Members of Council Dr.Brian Birch was born at Barrow-in-Furness, Cumbria, in 1942 and educated at the Grammar School, Ulverston. In 1960 he began to study chemistry at Liverpool University, followed in 1963 by a PhD course at London University, under the supervision of Professor J. E. Salmon. The subject of the research was the thermo- dynamics of ion-exchange resins. On its comple- tion, in 1966, he joined Unilever Research, Port Sunlight Laboratory, to explore the fundamental physical chemistry of surfactant solutions. During this time, his undergraduate interest in analytical science was reawakened and, after some years, he transferred to the analytical arm of Unilever Research, to exploit aspects of electroanalytical chemistry. Since then, he has developed instrumentation and methodology in the areas of ion-selective electrodes, polarography and tit- rimetry, and applied these to detergent-based products and raw materials.Of late, his thoughts have turned to the interactions between analytical instrumentation and computing technology. Not only to do more and better analysis, but to provide understanding of the underlying scientific questions. This chemometric approach to analytical science will probably occupy more time in the future, together with his involvement in chemical sensor development. Dr. Birch has been involved with the Analytical Division for many years, mainly in the Electro- analytical Group of which he is a past Chairman and Secretary and the present Treasurer. He is married with three children and lives in North Wales, where dealing with the house and “gar- den” at present takes all his hobby hours.He has learnt new skills of bricklaying, demolition, car- pentry and plumbing and has successfully (to date) resisted the family blandishments regarding goats, chickens and geese. He has recently, however, succumbed to bees. Harold E. Brookes was educated at the Mundella School, Nottingham, and was fortunate enough, in 1930, at the depth of the great depression, to join the Analytical Department of Boots Pure Drug Company on leaving school. In those days, 35 1352 NEW MEMBERS OF COUNCIL Anal. Proc., Vol. 21 Dr. B. J . Birch Mr. H . E. Brookes only the affluent and brilliant (who won scholar- ships) were able to study at a University, so he eventually obtained a London University external degree in 1941 after attendance at Nottingham University College evening classes.He was trained in analytical chemistry, using primarily chemical reactions, by meticulous chemists with a vast store of knowledge and considerable manipulative skill. Pride in one’s ability was inculcated then and used to control the quality of materials under supervision. He was fortunate, too, in gaining analytical experience of the considerable range of products and raw materials dealt with by Boots. From 1939 to 1949 he was engaged in finding substitutes for important ingredients of medical products and reformulating them. Brookes re- turned to analysis exclusively, as a Section Head in the Standards Department, Pharmaceutical Division, on Dr. D. C. Garratt’s appointment as Chief Analyst.The former became Head of the Pharmaceutical and Chemical Divisions succes- sively. At this time he became an ARIC followed by FRIC. During this time analysis was changing from chemical reactions to physical determinations. This meant abandoning many elegant and differ- ent chemical procedures, which was inevitable in order to speed up analysis and drastically reduce costs. Nevertheless it is a cause for regret that the skills and knowledge of the chemistry involved are no longer of use. In 1966 Brookes moved to become the Head of Standards Office, Quality Control (previously Standards Department), in the Boots Company. The Office is concerned principally with the maintenance of quality of the Company’s own brand of consumer goods from factory to con- sumer.Although his responsibilities were pri- marily administrative, products were regularly referred to the analytical laboratory. During his periods of responsibility for analy- tical work, he has been a member of a number of British Pharmacopoeia Committees, viz., Assay of Galenicals, Organic and Inorganic Com- pounds, and Assay of Tablets and Capsules. He has also been a member of two British Phar- maceutical Codex Committees: Pharmacognosy B and Formulary Standards. All of these Com- mittees were responsible for drawing up legal standards for medicinal substances and prescrib- ing the methods of analysis to be used. Member- ship of the Sub-committee of the AMC for Essential Oils and the BSI Committee for the same materials were also part of his.interests.Although having joined the (then) Society of Public Analysts and other Analytical Chemists in 1944, it was not until 1950, with the encourage- ment of Dr. Garratt, that a more active part was taken in the Society. H. E. Brookes has served as a member of Council on several occasions, including one spell as a Vice-president. He has been a member of the following committees: the now defunct Publi- ’ cations Committee, Programmes, Finance, and Group Liaison and Policy, He was a member of the 1968 SAC Conference Executive. In 1978 he was presented with the Distinguished Service Award. In the Midlands Section (now Region) he has been a member of the Committee many times and is a past-Chairman. He was Vice-chairman of the Birmingham International Symposium 1969, Chairman of the Midlands Region Local SAC Conference 1977 Committee and a member of the SAC Conference Executive Committee. He served on the Royal Institute of Chemistry Regional Committee as a member and Chairman and was a Regional Member of the RIC Council and Professional Services Committee.In 1979 he retired from gainful employment and imme- diately became the Honorary Secretary of the Midlands Region; his first Committee meeting was on the day that he retired. Brookes has two sons, both electronics engin- eers, the elder with a family in San Francisco, the other a member of a marine seismic exploration party liable to be required anywhere at sea. His interests are still sailing-dinghy racing (although now unable to race himself), music and dilettante photography.A biography of Mr. G. J. Dickes appeared in Proc. Anal. Div. Chem. SOC., 1976,13,148 on the commencement of his first period of service on Council. Having been partly educated in the much maligned town of Chipping Sodbury he persevered, by part-time study, to obtain hisOctober, 1984 NEW MEMBERS OF COUNCIL 353 ARIC qualification by courtesy of the Bristol Merchant Venturers’ Technical College, which has since undergone many metamorphoses to become the Bristol Polytechnic. As a student technician in the Bristol Public Analyst’s Labora- tory he learnt the “wrinkles” of practical analy- tical chemistry (vital, yet little appreciated by today’s push-button analysts) before passing on to the University of Bristol’s Long Ashton Research Station.In 1960, having been promised the opportunity of obtaining a research degree he promptly passed his army medical and became one of the last National Servicemen; the promise was never fulfilled on his civilian return. (“How do we know that you haven’t forgotten all the chemistry you ever knew?”) True, being attached to Military Intelligence in Germany was a far cry from developing analytical methods for the deter- mination of pesticide residues, but he neverthe- less got back into the groove and returned to the Bristol Public Analyst’s Laboratory in 1964 with the specific task of developing and applying analytical methods for the determination of food additives and contaminants. He was later to publish many methods in this field and co- authored “Gas Chromatography in Food Analy- sis.” In 1972 he obtained the MChemA and was subsequently elected to Fellowship of the RIC and RSH, and following local government reor- ganisation he was appointed an Assistant Scien- tific Adviser for the new County of Avon.This has entailed supervising the analysis of air, water and land samples for pollutants to enable assess- ment of environmental impact. He joined the SAC in 1967 and is a previous Chairman of the Western Region and the Micro- chemical Methods Group Committees. He has served on all of the publications committees and retains a food interest in being the AD represen- tative on the United Kingdom Council for Food Science and Technology; he is also serving on the SAC 86 Executive. Seeing his present position as mostly political with a smattering of science, he is aptly linked with his MP in the RSC Parliamentary Link Scheme and, having been the RSC representative on the Federation of European Chemical Socie- ties Working Party on Chemistry and the Envi- ronment, he now finds himself its second Chair- man.Having been a keen Bristol Rovers fan in his youth, he maintains the clinical expertise of modern football is not as exciting as the kick and rush stuff of the 1950s. Points-to-point and National Hunt Racing at Cheltenham, Wincanton and Chepstow have remained a keen interest (no hooliganism here, yet!) but winemaking has given way to antique collecting. Not being an academic, he has no ambition to be AD President, but fancies running a down-market art gallery with his wife in his beloved Cotswolds. Mr.G. J . Dickes Dr. J . Newham John Newham is currently Principal Lecturer in Physical Chemistry at Newcastle upon Tyne Polytechnic, and Chairman of the North East Region. Born in Kingston upon Hull in 1936 and educated at Hull Grammar School and at the University of Hull, he graduated with first class honours in chemistry in 1956. After three further years at Hull as a postgraduate student working with Professor G . C. Bond on the kinetics of catalytic hydrogenolysis, he carried out similar work as a postdoctoral fellow at Northwestern University in Evanston, Illinois, and at the University of Edinburgh. In 1964 he joined the Department of Chemistry at the Rutherford College of Technology, which in 1971 became part of Newcastle Polytechnic.Application of an interactive teaching style to physical and analy- tical chemistry, combined with the development of new courses and of research interests in catalysis and subsequently in trace element analy- sis and speciation, have provided a busy schedule with which to fill most weekdays and evenings. He is co-author of 14 research publications to date, and of a number of major course docu- ments. In 1967 Dr. Newham joined the SAC and became a member of the North East Regional Committee in 1969. Involved in the local commit- tee for the Durham SAC 71 International Confer- ence, he fondly recalls leading a conference excursion to Holy Island (a round trip of about 140 miles) in elderly motor coaches (an economy measure), with drivers who appeared to have only the haziest notion of local geography, and remembers the joy of delegates on discovering their eventual safe return to Durham in the late evening.In 1978 he returned to the North East Committee to serve as Honorary Treasurer,354 NEW MEMBERS OF COUNCIL becoming Vice-chairman in 1981. Other activi- ties have included membership of the Newcastle Section Committee of the Royal Institute of Chemistry, and involvement with the Open Uni- versity. Dr. Newham is married with one son and two daughters. His other interests include gardening, occasional fell walks and music. Anal. Proc., Vol. 21 Mr. H. I. Shalgosky is the new Chairman of the Analytical Abstracts Editorial Committee and also Chairman of the South-East Region. In 1949, after graduating and passing the examination to become an Associate of the Royal Institute of Chemistry, he joined the Atomic Energy Branch of the Chemical Inspectorate in the Royal Arsenal at Woolwich.This lively laboratory, under Mr. A. S. Nickelson, was developing and applying the newer analytical techniques to the stringent demands and new materials of the infant nuclear power industry. He enjoyed developing polarographic methods, first using classical d.c. instruments and later the new “cathode-ray polarographs” developed in-house by H. M. Davis and Joyce Seaborn. When the UK Atomic Energy Authority was formed in 1954, the Woolwich laboratory became part of Dr. Albert Smales’ Analytical Branch at Harwell. Soon after, Mr. Shalgosky began work on X-ray fluorescence spectrometry, using the first complete commercial spectrometer imported into the UK.In 1962, he took charge of the Chatham Outstation of Woolwich until 1966, when both laboratories moved into new, purpose- built accommodation at Harwell. He successively became leader of the Chemical Analysis and Environmental Safety Groups, Project Manager of the Physico-Chemical Measurements Unit and the Hazardous Materials Service, and in 1981 was appointed Head of the Environmental and Med- ical Sciences Division. He has served on the committees of the Physical Methods, Special Techniques and Micro- chemical Methods Groups of the Analytical Division and of the Environment Group of the Industrial Division. He is married to an art teacher; they have two daughters and enjoy gardening in a small hamlet close to the Ridgeway of the Berkshire Downs and the ancient monu- ment of the White Horse of Uffington.They were attracted there by the resemblance to their native Wolds of East Yorkshire. Allan M. Ure obtained his first degree, BSc, at St. Andrews in 1945, awarded (in absentia and in error to George Ure) while serving as a radar lii Mr. H . I . Shalgosky Dr. A. M . Ure time to allow him to complete his honours degree in chemistry in 1948. He gained his PhD, in 1954, at Aberdeen University with a thesis “The Appli- cation of Electronics to Spectrochemistry” after joining the Department of Spectrochemistry at The Macaulay Institute for Soil Research in Aberdeen. Since then he has continued working in this Department, on the development of instrumental techniques for the determination of trace and major elements in soils and plants by atomic-emission and -absorption spectrometry.He was responsible for the introduction of simul- taneous multi-element flame photometry for rou- tine analysis of soil extracts as early as 1954 and has seen flame methods of analysis develop from the Lundegardh emission technique to current atomic-absorption methods, and more recently to inductively coupled plasma emission spec- trometry. He has been active in atomic absorp- tion since about 1960 and is still contributing original papers in this field. His current interests are in the development of practical spectrochem- ical methods for the determination of trace elements in materials of agricultural interest. More recently, the evolution of techniques of spark-source mass spectrometry for comprehen- sive quantitative inorganic analysis has been his chief pre-occupation and this has strengthened his interest in the geochemical aspects of trace element chemistry. He has a long involvement with the Analytical Division and gave his first talk at a meeting of its predecessor, the SAC, in Glasgow in the early 1950s. He has held the office of Chairman of the Scottish Region and been a member of Council, of the Programmes and Analytical Methods Committees and of the Analytical Editorial Board.For the past few years he has been the Royal Society of Chemistry representative in the DOE Standing Committee of Analysts. He is also an associate member of Commission V-4 (Spectrochemical Nomenciat- officer in the RNVR. The mistake was rectified in ure) of IUPAC. As scientific secretary for theOctober, 1984 HONORARY PUBLICITY most recent (SAC 83) Conference held in Edin- burgh he was responsible for the arrangement of the scientific programme. Currently he serves as scientific secretary of the DAFS Consultative Committee for Spectrochemical Work. In his present post as Head of a Department of Spectrochemistry involved in techniques ranging SECRETARY’S COLUMN 355 through atomic emission and absorption, infrared, ultraviolet and visible molecular absorp- tion, spark and thermal ionisation in organic mass, electron paramagnetic resonance and Mossbauer spectroscopy, he has little time for activities other than a little gardening. He has not indulged in hare-calling since 1980.

ISSN:0144-557X    

DOI:10.1039/AP9842100351

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

October, 1984 HONORARY PUBLICITY SECRETARY’S COLUMN 355 Honorary Publicity Secretary’s Column Even though I say it myself, the Division’s Schools’ Lecture programme has proved a great success, with capacity audiences turning out on nearly every occasion. A number of Regions have already started planning for next year when Professor Alan Townshend will be the Schools’ Lecturer. With a bit of luck, a Schools’ Lecture will become a regular part of every Region’s programme. The glossy brochure has also gone over in a fairly big way, in that nearly all of the 5000 copies have been distributed. A second edition, with minor revisions, is planned and it is hoped that these will be available for the start of the academic year. Just write and let me know how many you want. I have been in touch with Regional and Group committees concerning (a) the general efficacy of the Divisional publicity machinery (Groups Bulletin, Regional Mailings, etc.), and (b), the suitability or otherwise of venues chosen for meetings. The responses to (a) indicate that the publicity obtained for meetings through the Div- isional office is, on the whole, satisfactory.However, if you think differently, let me know. This has arisen from discussions at Group Liaison and Policy (GLP) Committee concerning the attendance at meetings, a subject that crops up at Region and Group Committee meetings from time to time. GLP has also initiated an exercise to review Group structure following discussions between Special Techniques and Automatic Methods Groups. However, there does not seem to be any strong move away from the status quo.There will. though, be strong Group participa- tion in the next SAC Conference (July 20-26, 1986, at Bristol University); the strongest of all will be that of the Atomic Spectroscopy Group which, together with the Spectroscopy Group of the Institute of Physics, will be holding the 3rd Biennial National Atomic Spectroscopy Sympo- sium in conjunction with SAC 86. The 3-BNASS part of SAC 86 will be from the Wednesday to the Friday (July 24-26). The first circular for the conference has recently appeared. Recent conferences have included Analyti- con 84 in London, September 4-6 (could this develop into a European “Pittsburgh”?) and the regular RSC Autumn meeting (September 18-20 at Hull University). The analytical theme for this was “The Analysis of Drugs and Their Metab- olites.”The Annual Congress in 1985 will be at St.Andrews, March 25-28, at which the AD theme will concern fossil fuels. In the summer of 1985 the Ninth International Symposium on Column Liquid Chromatography will be held, July 1-5, Edinburgh, followed by the 7th International Meeting on NMR Spectroscopy, July 8-12, in Cambridge and Flow Analysis I11 (the third in the series of international conferences on continuous flow analysis with emphasis on flow injection techniques), September 5-8, Birmingham. The future of Autumn Meetings has come under scrutiny at Divisional Affairs Board and it has been decided to hold at least one more, reduced in length to two nights and with an effort to revert to the original concept of involving younger people.This will be in 1986, of course, as there will not be an Autumn Meeting in 1985 because of the IUPAC Congress, September 9-13 in Man- Chester. This is followed immediately by PSA 85, September 16-20, at Bradford University. Returning north of the border for a moment the Scottish Region is celebrating its 50th AGM on November 9 this year with a lecture by Professor J. F. K. Huber on “The Evolution of Modern Chromatography” at 4.00 at the Royal Society of Edinburgh, followed by a dinner - dance in Edinburgh University Staff Club at which the speakers will be the Division’s President, Peter Cobb, and the Rt. Hon. Tan1 Dalyell M.P. Not to be outdone, the North West Region i s celebrating its 60th AGM on November 2,1984, with a dinner at Salford University.The Regional flavour of the menu will be continued throughout the evening when Professor Stuart Bark will deliver an address entitled “Reminiscences on the North West Region. ” Forthcoming Divisional meetings include356 OBITUARIES Anal. Proc., Vol. 21 “Laser Applications” (October 24), “Process Control” (December 5) and “Modified Elec- trodes” (February 6, 1985). The Division may also be involved with the British Association meeting at Strathclyde University in 1985. Turning to analytical publications, the Books and Reviews Committee has given the go- ahead to the production of a volume concern- ing aspects of the history of analytical chemistry. This will be compiled by Professor Thorburn Burns and will consist of reprints and added material, The publication of Volume 14 of the Annual Reports on Analytical Atomic Spectro- scopy (ARAAS) is also guaranteed.The second edition of “The Chemical Analysis of Water” should be out in 1985, as should the new version of “Official and Standardised Methods of Analy- sis.” Computerised production of “Analytical Abstracts” commenced in April and retrospective computerisation (to 1980) is planned. Analytical Proceedings will increase in size to A4 (the same as The Analyst) from January, 1985. The Analy- tical Editorial Board is considering starting a new journal in the field of analytical atomic spec- trometry. Now for some awards. Professor I. M. Koltoff has been awarded the second Robert Boyle Medal and Professor M. Grasserbauer (of the Institute of Analytical Chemistry, Technical Uni- versity, Vienna) the 1985 Theophilus Redwood Lectureship.Silver medals have been awarded to Dr. M. S. Cresser (University of Aberdeen, Soil Science Department) and Dr. J. F. Alder (UMIST, Department of Instrumentation and Analytical Science). Dr. J. Marshall (University of Strathclyde, Department of Pure and Applied Chemistry) has been awarded the Hilger Spectro- scopy Prize for his work in the field of electrother- mal atomisation. The Atomic Spectroscopy Group will be awarding another Hilger Prize in 1984; nominations must be made through a Group Committee member. Copies of the regula- tions are available from the Group Honorary Secretary, Mr D. Willis. Dr. W. I. Stephen (University of Birmingham) has been awarded *he first BDH AnalaR Gold Medal for his work on analytical reagents.Professor D. Thorburn Burns has been elected a Fellow of both The Irish Academy of Sciences and of the Royal Society of Edinburgh, while Professor J. H. Knox has been elected a Fellow of the Royal Society. The International Council of Scientific Unions has a Scientific Committee on Problems of the Environment (SCOPE) which publishes news of its projects in a “Newsletter.” The most recent of these contains an outline of the Global Cycling of Toxic Metals project and the activities of the Metal Cycling Sub-committee. Other projects include the “Environmental Effects of Nuclear War” and “Mussel Watch 11.” SCOPE reports can be obtained from John Wiley and Sons Ltd., Baffins Lane, Chichester, Sussex, PO19 lUD, and details of SCOPE activities, which obviously involve considerable analytical input, can be obtained from the Secretariat, 51 Boulevard de Montmorency, 75016 Paris, France. Further details of any of the above items may be obtained, in the first instance, from Miss P. E. Hutchinson, Secretary of the Analytical Division of the RSC, at Burlington House. J. F. TYSON

ISSN:0144-557X    

DOI:10.1039/AP9842100355

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

356 OBITUARIES Anal. Proc., Vol. 21 Obituaries Dr. Harold Egan The news of the death of Dr. Harold Egan on June 28th, whilst attending a CHEMRAWN Conference in the Netherlands, was received with great sadness by his many colleagues in the UK and around the World. Born on December 23rd 1922, he was educated at Chiswick County School, Acton Technical College and Imperial College, London, where he obtained BSc, PhD and DIC degrees. After three years in the Biochemistry Department of St. George’s Hospital, he joined the Department (later Laboratory) of the Government Chemist in 1943. Between 1943 and 1981, when he retired, he rose rapidly through the Laboratory, assuming the post of Government Chemist in 1970. He was the only Government Chemist to have risen through the ranks and, in so doing, contributed to a wide range of investigations, particularly in food, drug and pesticide analysis, with special reference to trace determinations. As Govern- ment Chemist, his advice on many aspects of chemistry was frequently sought by Government Departments to assist them in formulating or implementing their policies.He published more than 100 papers on many aspects of analytical chemistry and was a frequent Iecturer at confer- ences. Dr. Egan had many scientific interests outside the Laboratory. He was a Visiting Professor in the Chemical Sciences faculty of the University of East Anglia and previously had held a similarOctober, 1984 OBITUARIES 357 appointment in food science at Queen Elizabeth College, London. He was an active participant in the Society for Analytical Chemistry and, follow- ing the merger with the Royal Society of Chem- istry, became a member of the Council of the Analytical Division.He supported the Analytical Methods Committee both personally and via the LGC. At the time of his death he was completing a new edition of Official, Standardised and Recommended Methods of Analysis for publica- tion by the Society. He had been Editor-in-Chief for the International Agency for Research on Cancer on a series of volumes on Selected Methods of Analysis for Environmental Carcino- gens. He had extensive international interests. An active member of IUPAC for many years, he had served as Secretary and President of the Applied Chemistry and Food Chemistry Divisions. He was President of the International Academy of En- vironmental Safety in 1980-1981.He organised the first International Conference on the Har- monisation of Collaborative Studies in Helsinki and had made arrangements for a follow-up con- ference in Washington in October, 1984. He was the AOAC representative in the UK and actively encouraged individuals and companies to partici- pate in the development of new analytical methods through collaborative studies. Dr. Egan had many hobbies, particularly as a collector. His interest in coins (which he collected avidly) led to the Fellowship of the Royal Numismatic Society. He was also a member of the British Hallmarking Council. He spent many hours searching through bookshops and had an extensive collection of old and rare books, particularly relating to London. He married in 1948 and his wife Daphne and son Geoffrey survive him.Harold Egan will always be remembered by his friends and colleagues for his great energy, which he applied in all aspects of his professional and personal life. Widely known and respected inter- nationally for his contribution to analytical chemistry, his presence will be sorely missed following his untimely death. R. F. COLEMAN Professor G . F. Kirkbright The untimely death of Gordon Frank Kirkbright of the University of Manchester Institute of Science and Technology, on July 8th, has robbed analytical science in the United Kingdom of one of its foremost exponents and, in the opinion of the writer, arguably its most able analytical researcher and teacher. As the first appointed Professor of Analytical Science in UMIST’s Department of Instrumentation and Analytical Science, founded in 1980, Gordon Kirkbright was responsible with his two fellow Professors for the institution of an interdisciplinary Department of Analytical studies, the like of which we have not previously seen in the UK.A totally new concept had been put into practice and under his dynamic leadership as Head of Department in the first 3 years of its existence DIAS had succeeded mar- vellously and perhaps even beyond the expecta- tions of its founders. Its continued success will be a most fitting memorial to him and would be the one which he himself would probably have valued most of all. Born in Wales in 1938, Gordon Kirkbright took an honours degree in Chemistry at the University of Birmingham in 1959.As an undergraduate he was a good student but not remarkable, except for an outstanding skill in dealing with the identifica- tion of the odd, fiendish, mixtures of inorganic compounds that used to be given to students as part of their over-all training in didactic thought and manipulative skills by the late Professor Ronald Belcher. The newly graduated Kirkbright opted to do research in analytical chemistry in Professor Belcher’s research school under the direction of Dr. Bill Stephen, and having found his niche under their benevolent guidance Gor- don Kirkbright really began to shine and quickly became recognised as one of the group’s most promising students. Having gained his doctorate in 1962 Gordon and his wife Ann spent a postdoctoral research year at the University of Virginia in Charlottesville, where his interests, capabilities and particularly his awareness of cause and effect in chelation reactions for trace analysis were stimulated by Professor John Yoe, one of the finest American analytical-reaction men of the time.He did not join the so-called “brain drain” by staying on in the USA, as so many British researchers did in the 1350s and 1960s, but returned to Europe in 1983 to take up a DISR (now SERC)/NATO Fellowship in Profes- sor Hans Malissa’s Department of Analytical Chemistry at the Technical University of Vienna. However, Dr. Kirkbright never settled down to the work on dithiocarbamates there, and in 1964 he transferred the remaining 8 months of his fellowship to the newly formed research group in analytical chemistry that had been set up in 1963 at the Imperial College of Science and Technol- ogy in London, and began his work on spectro- scopic techniques of trace analysis which shaped the rest of his career.There, with Dr. Roy Dagnall, Dr. Bernard Fleet and the writer, he was responsible, with the eager and enthusiastic assistance of a succession of very talented358 OBITUARIES Anal. Proc., Vol. 21 students, for the setting up of a research group that made a prominent contribution to progress in analytical chemistry in the 1960s and early 1970s. His work first on organic reagents for molecular absorption spectrophotometry and molecular fluorescence spectrometry expanded out into atomic-absorption and atomic-fluorescence spec- trometry, into microwave and radiofrequency plasma emission spectrometry, electrothermal atomization, optoacoustic spectrometry, and so on.His research within these areas on the separated flame technique was particularly ele- gant and quite unique, and the basic contributions he made to the measurement of atomic profiles in flames in relation to temperature and flame gas composition, repeated later with the non- chemical plasma “flame,” was also a major contribution. His work on the Shopolskii effect and on the photoacoustic effect typified his intense interest in unusual and off-beat pheno- mena, e.g., the split or separated flame men- tioned above. His success in harnessing these and other phenomena to the benefit of trace analysis, and to the satisfaction of his intellectual curiosity, reveal his genius and capacity as a scientific researcher.His pupils of those days are many and are to be found prominently the world over. As a supervisor of research students he was diligent and generous with his time and meticulous in his attention to detail. Although he was no easy taskmaster and expected much he was never stinting of his own input or unduly critical and it speaks volumes both for his science and his personality that all his research students respec- ted and admired him and, to a man (or woman), inevitably became his friends. They have reason to look back with pride and affection. At Imperial College, from 1964-1980, Gordon Kirkbright rose from Assistant Lecturer through the ranks to Reader in 1977 and became recog- nised world-wide for his innovations and exper- tise particularly in atomic spectroscopy.In the mid-1970s increasingly his attention was focused on electronics and microprocessors in instrumentation and Professor R. N. Haszeldine’s vision of a new synthesis of analytical chemistry, instrumentation and biological science in DIAS fired Gordon Kirkbright’s imagination utterly and completely. To UMIST, in 1980, Professor Kirkbright brought not only an established reputation in the analytical techniques of the 1960s and the up- front technology of the 1970s but also, at one extreme, an unusually good knowledge of chem- ical reactions learned at the hands of his mentor and life-long friend, the late Ronald Belcher, and at the other, an appreciation of and capability in microprocessors, optical fibre technology and the new physical sciences and devices that will un- doubtedly shape the future of analytical techno- logy in the closing two decades of this century.Gordon Kirkbright was the first Silver Medal- list of the Society for Analytical Chemistry, now the Analytical Division of the Royal Society of Chemistry (1973), and became the 16th Society for Analytical Chemistry Gold Medallist in 1983. He also held the Royal Society of Chemistry’s Award for Analytical Spectroscopy (1981). He was active in many national and international committees concerned with analytical chemistry, and to very good effect. These achievements and marks of distinction arose out of his career pre-1980 as an analytical chemist, in a sense his first career, and whilst it is perhaps pointless to speculate what new honours and distinctions might have come his way in his post-1980 career as an analytical scientist, it seems beyond doubt that they would, in due course, have been many. Professor Kirkbright has had a profound effect on the shaping of analytical science in the UK and there is little doubt that it will be a lasting one. He enriched the lives of all who were fortunate enough to be associated with him in his all too brief career as a scientist and will be remembered with a sense of wonderment for his energy and drive, and with affection for his personality. Our deepest sympathy goes out to his wife Ann, who was his constant companion and his sheet anchor in life’s storms, and to his children, Suzanne and Clare, who are, with Ann, the principal losers. We will long remember him. T. S. WEST

ISSN:0144-557X    

DOI:10.1039/AP9842100356

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

October, I984 CHEMICAL SPECIATION IN AQUEOUS SOLUTION Chemical Speciation in Aqueous Solution 359 The following are summaries of five of the papers presented at a Meeting of the Electroanalytical Group held on April 5th, 1984, at Chelsea College, London, S.W.3. Measurement of Organic - Metal Interactions in Seawater Constant M. G. van den Berg Department of Oceanography, University of Liverpool, Liverpool, L69 3BX The study of trace metal complexation in seawater is of importance as speciation may affect the geochemical pathways and bioavailability of these metals. Only in the last decade has it become known that at least a few elements occur largely associated with organic material. Most evidence is available for copper.'-9 which is selected for many complexation studies because it tends to form relatively stable complexes.The results of these studies vary greatly and appear to depend on the technique used: methods relying on extraction of the organic metal fraction generally produce the smallest organic copper fraction of about 3-80%,5-8 those relying on its electrochemical determination by anodic stripping voltammetry (ASV) produce intermediate values of 45-80°/0, 1-3 whereas methods based on equilibration techniques (with Mn02 or ion exchangers) produce values of 97-99% organic c ~ p p e r . ~ ? ~ The extraction methods rely on the adsorption of the organic metal fraction on anion exchangers or pre-packed columns of the SEP-PAK type, usually followed by a methanol extraction and injection into an atomic-absorption spectrophotometer. This is the most convenient and fastest technique, but the least information is obtained, as only the amount of (probably) organic metal that adsorbs is measured.The total ligand concentration, as well as the conditional stability constant of the metal - organic complexes formed, is obtained by measuring the free metal concentration as a function of a number of metal additions, by ASV or by equilibration with Mn02 or ion exchangers. With the ASV technique the assumption needs to be made that the organic complexes are kinetically inert, i.e., that there is no complex dissociation during the plating step. The calculated stability for such complexes would be too small if such dissociation took place. Little evidence is available to support this assumption, but generally ASV techniques'-3 have produced smaller organic copper fractions than can be calculated from equilibrium methods.4-9 Clearly, comparative measurements are necessary to elucidate this matter.The problem is that investigations in our laboratory have shown that different complexing sites may become available at different metal concentrations (weaker complexes at higher metal levels). So, differing results can often be due to that effect. Cathodic Stripping Voltammetry (CSV) Recently a new voltammetric technique has been developed, which is based on the apparent adsorptive behaviour of metal complexes with certain organic complexing ligands. The degree of adsorption is directly related to the dissolved metal concentration and is measured by reduction of the metal complexes adsorbed on to the HMDE.Thus, the concentrations of nickel and cobalt can be determined in the presence of dimethylglyoxime (DMG).") copper, iron, uranium and vanadium in the presence of catechol,11-13 and zinc in the presence of aminopyrrolidine dithiocarbamate (APDC). l 4 The sensitivity of this technique is superior to that of ASV as the metal is collected in a monomolecular layer on the electrode. A reduction efficiency of 100% is therefore obtained, and the detection limits typically are of the order of 10-10 M (or better) after just 2 min collection. A further advantage of this technique is that elements that have a reduction potential within the stability constraints of water can be determined voltammetrically, without the necessity (for ASV) of reduction to the metallic state.The method has been called CSV because of the cathodic direction of the current, but it has also been called adsorption voltammetry. 1s Ligand competition will take place if other complexing ligands are present in addition to those added for metal analysis. Addition of EDTA to seawater, for instance, will reduce the size of the copper - catechol reduction peak. The actual competing effect depends on the products of the conditional stability constants, KIML, and the free ligand concentration, [L'] (not complexed by the metal). The ratio of i,, the current in presence of natural competing ligands Lx, over iP,(), the current in absence of such ligands, is given by'? where [A'] is the free concentration of adsorptive ligand, A ( e .g . , catechol, DMG or APDC). i,/ip.o = K'MA [A']I(K'MA[A'] + K ' M L [L'])360 CHEMICAL SPECIATION IN AQUEOUS SOLUTION Anal. Proc., Vol. 21 The height of the copper peak is normally suppressed by natural organic material in seawater at low catechol concentrations [Fig. l(a)].’ As a result the maximum peak height for copper is obtained at a higher catechol concentration than after ultraviolet irradiation of the sample [UV SW in Fig. l(a)],17 which eliminates the competing, organic ligands. The sensitivity (peak height/metal concentration) at a given catechol concentration below that needed to produce the maximum peak height in such seawater is therefore less than in absence of competing ligands. This property can be used to determine the ligand concentration (or the “complexing capacity”) in the sample by means of a stepwise metal titration of the sample.The ligands have been saturated when the sensitivity is the same as in the absence of ligands. The progress of the titration is followed by plotting the measured CSV peak height against the total (inital plus added) metal Concentration, as shown schematically in Fig. l(b) (the straight line through the origin represents the sensitivity for free metal). Log[catecholl--+ CM ---) Fig. 1. ( a ) , Effect of the catechol concentration on the CSV peak height of copper in seawater before (SW) and after (UV SW) irradiation; ( b ) , diagrammatic representation of a complexing capacity titration as determined by CSV with ligand competition. The straight line is the sensitivity in the absence of complexing ligands. The final result of the determination of the ligand concentration therefore looks similar to that obtained by ASV.However, an important difference is that collection at the elctrode is the result of adsorption of a negligibly small fraction of the surface active metal - organic complexes, MA, at a potential more positive than the reduction potential of the complex. No dissociation of the natural organic complexes can therefore take place during the measurement, and the concentration of MA is determined in true equilibrium conditions. In practice it has appeared that a long period of about 15 h is needed for the metal to equilibrate with the natural ligand, L, in seawater,’6 probably as a result of major cation competition.The concentration of the free metal ion, [M”+], is then calculated from”: [Mnf] = ip/(Sa’) where S is the sensitivity, which is calibrated by standard additions after saturation of L, and a’ = a M + EMMA, = the inorganic alpha-coefficient of the metal, and a M A = the alpha-coefficient due to the formation of MA: The concentration of ML is obtained from where CM = the total metal concentration [see Fig. l(b)]. Values for the conditional constant and the ligand concentration are then calculated from a plot of [M”+]I[ML] as function of [Mnf]. This technique has been successfully applied to complexes with copper using catechol,17 and for zinc with APDC.16 Optimal ligand concentrations are 2 X 10-5 M for catechol and 4 X 10-5 M for APDC. The effective ligand competition for copper exerted by this concentration of catechol can be calculated from &MA, and is equal to about 400 in seawater at p1-I 7.7.A low concentration (10-9-10-XM) of a strong chelator (log KML of 11-12) can compete successfully for copper in these conditions, and complexes of such stability have indeed been detected in seawater. 17 The conditional stability constant for the formation of ZnAPCD has been calibrated in seawater of variable salinity against NTA,16 and @MA = K’MA [A’] + PIMA* [A’]* [ML] = C M - idsOctober, 1984 CHEMICAL SPECIATION IN AQUEOUS SOLUTlON 361 it has been found that 4 x 10-5 M APDC produces a value for aMA of only about 2, which is similar to that caused by inorganic complexation of this metal. Preliminary measurements of copper complexation with this technique revealed two types of complexing ligands or sites, present in concentrations of 1 and 3 x 10-8 M , and with values for log KCuL of 12.2 and 10.2, respectively, in a sample from the South Atlantic.Slightly higher ligand concentrations of 3 and 6 x 10-8 M were found for zinc in a different sample from oceanic origin having values for log KIZnL of 8.4 and 7.5, respectively. These results compare well with those obtained with other equilibrium techniques.".' However, the CSV technique is more sensitive than previous methods (unless radiotracers are used) and is less prone to cause contamination because of the greater simplicity of the procedure. Although the technique of ligand competition has until now only been applied to copper and zinc, in principle the same can be attempted with other metals that can be detected by CSV, such as nickel(II), uranium(V1) and iron(II1). The predominant form of uranium is the U022+ ion, which is strongly complexed by CO<- ions.This metal is an unlikely candidate for organic - metal interactions in seawater, although significant interactions may occur in interstitial waters. The degree of interaction of nickel with dissolved organic material is possibly similar to or slightly less than that of zinc, as its hydrolysis constant is not much different from that of zinc. 18 Investigation into the organic complexation of this metal tnay therefore be of interest. Iron is a solid hydroxide forming metal because of its low solubility. In fact its solubility is only about 1-2 X lo-* M , so in estuaries (usually containing much higher concentrations) it largely occurs as colloidal hydroxides.Its interaction with organic material has been suggested. 1') Determination of its complexing capacity by titration is difficult because of its low solubility. However, CSV measurements with catechol before and after ultraviolet irradiation and acidification of filtered samples revealed that only a small fraction of supposedly dissolved iron is available for complexation by catechol prior to ultraviolet irradiation.20 This is evidence that a significant fraction of iron is indeed organically bound in estuarine waters. These preliminary results suggest that organic - metal interactions in estuarine and seawater may well be of importance to the geochemical cycling of many metals.1. 2. 3. 4. 5. 6 . 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. References Batley, G. E., and Florence, T. M., Mar. Chem., 1976,4, 347. Duinker, J . C., and Kramer, C. J. M., Mar. Chem., 1977, 5 , 207. Hasle, J . R., and Abdullah, M. I . , Mar. Chem., 1981, 10, 487. Hirose, K., Dokiya, Y., and Sugimura, Y . , Mar. Chem., 1982, 11, 343. Kremling, K., Wenck, A., and Osterroht. C., Mar. Chem., 1982, 10, 209. Mackey, D. J., Mar. Chem., 1983. 14, 73. Mills, G. L., Hanson, A. K . , Jr., Quinn, J . G.. Lammela. W. R., and Chasteen, N. D., Mar Chem.. 1982.11, Sugimura, Y . , Suzuki, Y . , and Miyake, Y . , J . Oceanogr. SOC. Japan, 1978, 34, 93. van den Berg, C . M. G., Mar. Chem., 1984, 14, 201. Pihlar.B., Valenta, P.. and Niirnberg, H . W., Fresenius 2. Anal. Chem., 1981, 307, 337. van den Berg, C. M. G., Anal. Lett., 1984, in the press. van den Berg, C. M. G., and Huang. Z . 0.. J . Electround. Chem., 1984, in the press. van den Berg. C. M. G., and Huang. Z . Q., Anal. Chim. Acta. 1984, submitted for publication. van den Berg, C. M. G., Tulanfu. 1984, in the press. Meyer, A., and Neeb, R., Fresenius' Z . Anal. Chem., 1983, 315. 118. van den Berg, Mar. Chem., submitted for publication. van den Berg, Mar. Chem., 1984, in the press. Turner, D. R., Whitfield, M., and Dickson, A. G., Geochim. Cosmochim. Actu, 1981. 45, 855. Sholkovitz. E. R., Earth Planet Lett.. 1978. 41, 77. van den Berg, C. M. G., Buckley, P. J . M., Huang. Z . Q.. and Nimmo, M., in preparation.355. Potentiometric Sensors for Chemical Speciation Nobuhiko lshibashi Department of Applied Chemistry, Faculty of Engineering, Kyushu University, Hakozaki, Higashiku, Fukuoka 512, Japan The selective sensitivity of ion-selective electrodes (ISEs) to individual ions is important for chemical speciation, the selectivity being expressed by the selectivity coefficient of the Nikolskii equation.362 CHEMICAL SPECIATION IN AQUEOUS SOLUTION Anal. Proc., Vol. 21 However, selectivity coefficient values deduced by methods such as the mixed solution method and the separate solution method are not always constant, but vary according to the method employedand the conditions of measurement.1.2 An alternative methods6 has been proposed for the determination of selectivity coefficients of liquid ion exchanger type electrodes.This is based on measurement of the true bi-ionic potential and gives selectivity coefficients characteristic of the electrode membranes. The following summarises the ion selectivities of cation- and anion-exchanger membrane electrodes as well as those electrodes based on neutral carriers as determined by the author’s method.3-6 For liquid ion exchanger membrane electrodes, the relationship between selectivity and solvent species in the membrane is discussed, while for the neutral carrier electrodes the relationship between selectivity and carrier concentration is described6 with data on potassium ISEs being presented .7 The influence of membrane composition on selectivities is also mentioned for a lithium electrode.It is often necessary and useful to employ ISEs in analysis under conditions of flowing sample. In order to avoid the influences of streaming potential and renewed electrode membranes on the electrode potential the use of the “base line supporting electrolyte solution” (BLSS) is recommended.8 This solution consists of an indifferent electrolyte at high concentration and a primary ion at low concentration. Oleophilic ion-exchange rnembranesg.10 wetted with an appropriate organic solvent are mentioned as these are suitable for the detection of anions in flowing solutions. Finally, there are illustrations of the simultaneous detection of alkali metal ions with neutral carrier type membrane electrodes of low and high selectivity during HPLC analysis. In this respect, a microdetector with a tubular ISE may be used for the analysis of samples of less than 1 mm3.Selectivity Diagrams for Liquid Ion-Exchanger Membranes Selectivity coefficient data for various monovalent cations referred to the sodium ion are summarised diagrammatically in Fig. 1 for cation exchanger membrane electrodes. The selectivity coefficient of an appropriate ion, B, against Na+, kE, B , is represented by the distance of B from the Na+ position in terms of logarithmic units. More generally, the selectivity coefficient of a B ion over an A ion, kr;9‘B is given by the distance between the ions B and A. The selectivity coefficients shown in Fig. 1 were determined with electrodes set up as a bi-ionic system and were independent of the ion-exchanger site species.Apart from an overview of the selectivity relation between various ions, Fig. 1 shows the large influence of membrane solvent on selectivity. When 1,Z-dichloroethane is used as the membrane solvent, the membrane gives the greatest selectivitv for tetraalkvlammonium ions over alkali metal ions. Nitrobenzene and o-nitroDhenv1 octvl ether arialso quite g&od solvents for ions positioned at the right r I I I I I I Na+ K+Rb+Cs+ TMA+ TEA+ TPA+ I 1 1 1 1 I I Na+ K+Rb+Cs+ TMA+TEA+ TPA+ I 1 I I I 1 Na+ K+Rb+ Cs+ TMA+ TEA+ TPA+ Rb+Cs+TEA+ K+ Na+TMA+ TPA+ Cs+K+ TEA+ TMA+ Rb+ Na+ TPA+ * * 1 , 1 1 1 , 1 1 1 1 , 1 1 1 -1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 Log& Kt,S hand end as against io& at ihe l&t Membrane solvent Nitro benzene o-Nitrophenyl octyl ether 1,2-Dichlorethane Decan-I -01 Tri-n-butyl phosphate Fig.1. Selectivity diagram for liquid cation exchanger electrodes for various membrane solvents. TPA+, (C5H,,),N+: TEA+, (C2H5),N+; TMA+.October, I984 CHEMICAL SPECIATION IN AQUEOUS SOLUTION 363 hand end. Decan-1-01 and tributylphosphate do not give selectivity for any ions. Thus, for example in the analysis of sodium ion with an electrode containing decan-1-01 in the membrane there is little discrimination between sodium and other coexisting ions. A similar diagram was constructed for liquid anion exchanger electrodes. The similar solvent effects to those in Fig. 1 have been observed for anion selectivites (Fig. 2).4,5+11,12 I Benzenesulphonate Benzoate phthalate I I I Membrane solvent N itrobenzene 1,2-Dichloroethane Chloroform Decan-I -01 0 1 2 3 4 5 6 LogkE,k Fig.2. Selectivity diagram for liquid anion exchanger electrodes. Alkali Metal Ion Selectivity of Crown Ether Based Membrane Electrodes The selectivity coefficient of crown ether based membrane electrodes for an appropriate alkali metal ion, B, over the reference Na+ was shown to depend in three ways on the total concentration of the crown ether in the electrode membrane when sodium forms a 1 : 1 complex with the crown ether: log kpi.B = constant - log C, log kr;B = constant log kp;.B = constant + log C, where C, is the total concentration of crown ether in the membrane. According to these principles, electrode membranes of high selectivity towards potassium were developed by using naphtho-15- crown-5 and related crown ethers.' The PVC membrane electrode consisting of PVC (0.4 g), o-nitrophenyl octyl ether (1 .O g), naphtho-15-crown-5 (0.08 g) and potassium dipicrylaminate (0.4 mg) gave a k g h , value of 4 x 10-4. The lithium ion selectivity of dibenzo-14-crown-4 based membrane increases by adding organo- phosphorus compounds, such as trioctylphosphine oxide.13 This is attributed to increased distribution of lithium ion into the membrane. (i) when the B ion forms no complex with crown ether (ii) when the B ion forms a 1 : 1 complex (iii) when the B ion forms a 2 : 1 complex Application of ISEs as Detectors in HPLC and FIAX." Electrode potential oscillates and drifts when an ISE is used in the detection of ions flowing through narrow tubing. This change may arise from streaming potentials phased with the pumping of solutions and changes of electrode surface.Such potential variations are decreased by using BLSS as the carrier stream. A mixed solution of sodium nitrate (1 M ) and sodium chloride (1 x 10-5 M ) is useful as BLSS for the chloride ISE detector, while a BLSS for the nitrate ISE detector can be based on sodium sulphate (0.5 M ) and sodium nitrate (1 x 10-5 M ) . Increased conductivity brought about by adding a high364 CHEMICAL SPECIATION IN AQUEOUS SOLUTION Anal. Proc., Vol. 21 concentration of an indifferent electrolyte (sodium nitrate for the chloride ISE and sodium sulphate for the nitrate ISE) reduces the streaming potential, while addition of a primary ion at low concentration decreases the changes of the electrode surface and maintains it near to the original state. By using the BLSS, simultaneous detections of chloride, bromide, iodide and thiocyanate with the chloride solid membrane ISE, and detections of nitrite, etc., have become possible with good reproducibilities.An ion-exchange resin membrane with an oleophilic exchange group, such as the trioctylbenzyl- ammonium group, has been applied as an electrode in a HPLC detector. This membrane system has such a great affinity for organic solvents that it is possible to hold an organic solvent in aqueous medium. Electrodes using this membrane can detect anions at various sensitivities by altering the membrane- absorbed solvent.10 Application of Neutral Carrier Based Membrane Electrodes to HPLC Detection of Alkali Metal Ions The relationship between the selectivity of electrodes and their sensitivity during HPLC detection has been examined for the three electrode membranes based on each of the three crown ethers.Sequences of sensitivity were as follows: (i) phenylbenzo-15-crown-5 based electrode: K+>Rb+ >Cs+>Na+ ; (ii) dibenzo- 14-crown-4 based electrode: Li + >Na+>K+ >Rb+ >Cs+ ; (iii) naphtho-12-crown-4 based electrode; Na+=Rb+-K+-Cs+>>Li+. These sequences are in agreement with the selectivity order for the respective electrodes. For the simultaneous detection of alkali metal ions, the naphtho-12-crown-4 based membrane electrode is better, as it has almost equal sensitivity for sodium, potassium, rubidium and caesium ions.A micro-HPLC or FIA detector with a tubular PVC ISE has been developed for very small samples, the effective detector volume being less than 0.1 mm3. By using such a microdetector, it is possible to detect alkali metal ions in just 0.07 to 0.3 mm3 of sample solution. The author is grateful for the facilities of the laboratory of Dr. J. D. R. Thomas, UWIST, Cardiff, at the time of preparing this lecture. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. References Moody, G. J., and Thomas, J. D. R., “Selective Ion-Sensitive Electrodes,” Merrow Publishing Co., Koryta, J . , “Ion-selective Electrodes,” Cambridge University Press, 1975, p. 64. Yoshida, N., and Ishibashi, N., Chem. Lett., 197.4, 493. Jyo, A . , Torikai. M., and Ishibashi, N., Bull. Chem. SOC. Jpn, 1974, 47,2862.Jyo, A . , Mihara, H., and Ishibashhi, N., Denki Kagaku, 1976, 44, 268. Jyo, A., Seto, H., and Ishibashi, N., Nippon Kagakukai-shi (J. Chem. SOC. Jpn, Chem. lnd. Chem.), 1980, Yamauchi, M., Jyo, A.. and Ishibasi, N.,Anal. Chirn. Acta, 1982,136,399. Ishibashi, N., and Jyo, A., Asahi Garasu Kogyo Gijutsu Shoreikai Kenkyu Hokoku, 1978, 33, 47. “Proceeding of the International Meeting on Chemical Sensors,” (E202), Kodansha, Elsevier, 1983. p. 570. Imato, T., Jyo, A., and Ishibashi, N., Anal. Chem., 1980, 52, 1893. Ishibashi, N., Kagaku no Ryoiki, 1975,29, 1. Ishibashi, N., Bunseki, 1976, 4, 209. Ishibashi, N., and Imato, T., to be published. Watford, 1972. 1423. Metal - Ligand Formation Constants by Potentiometric Titration and Computing Tee h n iqu es K. Murray and P.M. May Department of Applied Chemistry, UWIST, Cardqf, CFI 3 N i J Although potentiometry is a very precise technique for the determination of formation constants it is seldom possible to analyse data to the precision of the experimental measurements, which for glass electrodes can routinely be as good as 0.1 mV or better. The problems arise because of the existence ofOctober, I984 CHEMICAL SPECIATION IN AQUEOUS SOLUTION 365 systematic errors that very often have effects an order of magnitude greater than 0.1 mV and which are particularly acute in work at low ionic strengths. These systematic errors may take the form of changes in ionic strength due to changes in complexation, variations in liquid junction potentials, imperfect selectivity of electrodes, inability to calibrate electrodes sufficiently well, the presence of contaminants and errors in analytical concentrations of components.Not only do these errors have direct effects on optimized formation constant values but they can seriously affect the identification of complex species present in solution. In order to tackle some of these problems a program library called ESTA (Equilibrium Simulation for Titration Analysis) has been developed. It presently consists of 5 main programs and about 75 sub-routines written in standard FORTRAN 77. The effects of ionic strength changes are overcome by solving the mass-balance equations using formation constants corrected to the calculated ionic strength at each titration point using an extended Debye - Hiickel expression.If selectivity coefficients are known for the major interfering ions, corrections for the problems of imperfect selectivity of electrodes can also be applied. The electrode equation used includes a liquid junction term based on Henderson’s equation. In addition, there is a facility to optimise the electrode intercept, the electrode slope and the component concentrations. This permits internal calibration of the electrode system and allows the worker to tackle the problems of inaccurate concentrations and the presence of contaminants. ESTA has three facilitiss that provide useful information on the identity of species. Firstly, plots of the formation functions 2 can be obtained. The nature of the dominant species can often be deduced from the shapes of th_ese curves.Secondly, plots of a deprotonation function, Q, versus pH can be obtained. The term Q is defined as the average number of protons released, per metal ion, upon complexation. Comparing this with the average number of protons that would exist on each ligand molecule if there was no metal present allows one to calculate, for a-given-metal to ligand stoicheiometry, the number of protons on predominant complexes. Both Z and Q plots provide a useful means of comparing observed and calculated data. Thirdly, it is possible to calculate formation constants for individual species at each titration point, each species being regarded as the only remaining complex required to produce agreement between calculated and observed data at the point. , Information provided by the constancy of the calculated formation constants over regions of the titrations, and the extent to which the complex forms, can be useful in choosing species as well as providing initial estimates of their formation constants.On the other hand, when one wishes to obtain “best” values based on a least-squares procedure over a whole system of titrations, the ESTA optimiser is used. It enables the worker to optimize simultaneously formation constants, vessel and burette concentrations, the electrode intercept and slope and the initial vessel volume. The sum of squares of residuals can be minimised with respect to e.m.f.s or total electrode ion concentrations and can be weighted or unit-weighted. Based on a set of formation constants, concentrations, electrode parameters and a sequence of titration volumes, it is possible to simulate titrations, producing an output file containing the e.m.f.s calculated at each titration point.This file has a format identical with that required by ESTA as input but this data necessarily contains no experimental errors. This facility is useful for examining the effect of an error in a titration parameter. By imposing the error in question in the simulated data file and then performing the calculation again, a pattern of residuals which reflects the effect of the change can be generated. It is also possible to impose random errors (chosen for normal distributions of user supplied variances) in any of the titration parameters, except the formation constants, before simulating the titration.The resulting file represents real titration data more closely because it contains unknown random errors. As the formation constants are known exactly, these data files can be used to investigate the effectiveness of different approaches to analysing the data. Readers who are interested in obtaining a copy of the programs, either on magnetic tape or via the IPSS network, should contact the authors.366 CHEMICAL SPECIATION IN AQUEOUS SOLUTION Anal. Proc., Vol. 21 Chemical Speciation in Soil Science by Electroanalytical Techniques T. E. Edmonds Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, LE11 3TU One of the goals of soil science is an understanding of the mechanisms of nutrient uptake by plants growing in soil.To achieve this target, and reap the obvious rewards in terms of improved agricultural practice, it is essential that the concentration and form of a trace element or major nutrient in the soil solution, and the factors that control these, are known and understood. It is tempting to think that the required data can be obtained from a study of the soil solution only, but this approach takes no account of the fact that soil is a three phase system, and that studies on an isolated component may not accurately reflect the complete situation. Electroanalytical techniques contribute information that is primarily about the soil solution, but there are other areas of more conventional soil chemistry, where these techniques can also make their mark. Electroanalytical Contributions The elements of biological significance to plants are shown in Table I; three types of element are defined, essential, functional and those of potential significance.The majority of these elements can be determined by electroanalytical techniques. There are five distinct areas in which electroanalytical techniques have been applied to soil chemistry, viz., the determination of the free metal ion concentration in solution, measurement of the form of an element, measurement of the parameters that control the form of an element, characterization of complexes between nutrient species and soil polysaccharides, and direct in-situ measurements. TABLE I ELEMENTS OF BIOLOGICAL SIGNIFICANCE TO PLANTS Potentially Essential Functional significant Na K Ca Mo Mn Fe co c u Zn B C N P 0 S CI Mg Cr Ni Si Se Br I Rb cs Be Sr Ba Ti W Au Cd Al Ge Sn Pb As Sb F Ag Hg Free Metal Ion Concentration Determination of the free metal ion concentration in soil solution is of fundamental importance, because this species enters into all equilibria between different forms of the metal ion in solution. Both polarographic and potentiometric methods have been successfully applied to these types of determination.1.2 In the differential-pulse polarographic determination of molybdenum, it is the sensitivity of this technique that is of advantage. Thus, measurements can be carried out on simple salt solution extracts of soils, as opposed to the determination of molybdenum in extracts obtained by more aggressive reagents. The latter, although ostensibly providing data on the availability of molybdenum to a plant over a growing season, do not permit the determination of the free molybdate species activity (or concentration) in the soil.Equilibrium models of soil systems need these data.October, I984 CHEMICAL SPECIATION IN AQUEOUS SOLUTION 367 The determination of the pH effect on free and total copper in displaced soil solutions utilises a copper sensitive ion-selective electrode (ISE) for the determination of the former. In this instance, the ability of the ISE to distinguish between free and bound forms of a trace element is most useful. In order to measure the very low concentrations of free copper in solution, a technique employing metal ion buffered solution and matching standards is used.This enables measurements of free copper to be made down to the nanomolar range.2 Form of an Element For many years soil chemists have succesfully employed the concept of the chemical form of an element (as opposed to a knowledge of the exact chemical species). To a certain extent these forms can be identified with the two thermodynamic descriptors of soil nutrient status, quantity( Q) and intensity(l).3 Typically the relationship is as depicted in Table 11. The determination of Q/Z curves and/or the fractionation of an element by selective extraction has provided many useful data. Unfortunately, these data take a considerable time to obtain, so that these methods cannot be considered as routine. However, in the past few years this situation has changed. The determination of the Q/Z curve for potassium in a soil can now be undertaken in around 75 min, as opposed to the 20 h that was previously required.4 Essentially the rapid technique employs a titration method by using an ISE.The titration furnishes the potassium concentration (an estimate of Q), whilst an empirically derived equation is used to obtain the activity ratio of potassium with respect to magnesium and calcium (an estimate of potassium’s intensity value). The cation-exchange capacity of the soil is also required, but this is a measurement that is routinely made on soils in any case. Another electrochemical technique that has made significant inroads into the routine determination of the chemical form of an element is electroultrafiltration (EUF) . Essentially, EUF is a synthesis of ultrafiltration and electrodialysis.The method was first described by Bechold in 1925, but has only recently gained popularity for soil studies, due no doubt to the availability of commercial instrumentation.5 As yet there is no satisfactory theoretical treatment for the technique. In spite of this shortcoming, the ability of EUF to remove soil nutrients selectively and rapidly from different nutrient pools of varying intensity has been readily exploited. TABLE I1 RELATIONSHIP BETWEEN NUTRIENT FORM AND SOIL NUTRIENT STATUS Nutrient Geochemical Nutrient form location status I I Unavailable Component of primary minerals secondary Quantity minerals active surfaces, or as compounds complexes, or Intensity Intermediate Component of Labile Sorbed on to Soil solution Labile, soluble t simple ions 5 Chemical Parameters That Control The Chemical Form The effects of pH and redox potential on the chemical form of an element are well known.Many workers have attempted to make measurements of these parameters using conventional electrochem- ical techniques. Unfortunately, too much of this kind of work has taken no account of the fact that soil is a three-phase system, and that to a large extent these electrochemical parameters cannot be regarded as having a unique value in such a heterogeneous system. Thus, it is a relatively simple operation to insert two platinum electrodes into soil and measure a potential difference between them; it is an entirely different matter to relate this measurement to a redox potential.The latter can only be carried out with due regard to the nature of the redox couples involved and the contributions that each part of the couple make to the exchange current. In addition it should be borne in mind that the368 CHEMICAL SPECIATION IN AQUEOUS SOLUTION Anal. Proc., Vol. 21 polysaccharides that make up the soil humic and fulvic acid fractions will absorb on to platinum electrodes and may radically alter the surface properties. In an attempt to overcome some of these problems, Ding et al.6 developed an amperometric determination of the “redox capacity’’ of paddy fields. Essentially, these authors inserted a pair of electrodes (wax impregnated graphite working electrode and silver - silver chloride reference electrode) into the soil and measured the current at +0.35 and +0.70 V versus silver - silver chloride.These currents correspond to the reduction plateaux of the iron and manganese couples. Although, as the authors pointed out, accurate measurements that are capable of detailed interpretation could not be made with this system, useful predictions of paddy field fertility were possible. Characterisation of Complexes The problems of measuring the stability constants of the complexes that are formed between trace metals in the soil and the humic and fulvic acid fractions of soil organic matter are similar to those pertaining to the studies of natural waters.7.8 Unlike natural waters, however, the clay surfaces in soil may play a dominant role in complexation, for there is ample evidence that humic and fulvic acids are sorbed on to these surfaces.In this respect polarographic studies, in which sorption of the polysaccharides on to the mercury drop occurs, may in some respects provide a better model for the soil than for the natural water situation. There are very few of these studies on soil systems. Cadmium complexation by soil-derived fulvic acid has been studied using normal-pulse polarography with variable pulse duration.9 The latter technique also provided a useful diagnostic criterion for determining whether the complex was adsorbed or not. The stability constant between copper and polymaleic acid (a synthetic analogue of soil fulvic acid) has been determined by differential-pulse polarography.1o Some studies have also been made on the complex formed between humic acid and aluminium at a pH of 4.00.11 Undoubtedly, the application of polarographic techniques to studies of trace metal complexation in soils is in its infancy.A major advantage is the technique’s ability to simulate the adsorption of metal ion - soil organic matter complexes. However, before this potential can be fully realised, a rigorous theory will be needed to relate the two situations. In-situ Measurement Although in-situ measurements of redox potential and pH have been attempted in soil, very little else has been tried in the way of direct electrochemical measurement. The advantages of making in-situ measurements are obvious, particularly from the point of view of continuous monitoring, and yet little progress has been made. Clearly the requirements for electroanalytical monitors are that they are rugged, reliable and inexpensive devices.Perhaps the two most promising candidates here are ion-sensitive field effect transistors,’* and carbon firbre microfaradaic electrodes. l3 Conclusions The current use of electroanalytical techniques by soil chemists is significant but by no means extensive. The three advantages of these methods that should lead to their greater employment are sensitivity to chemical form, portability and elemental coverage. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. References Edmonds, T. E., Commun. SoilSci. Plant Anal., 1982, 13, 1. Sanders, J. R., J. Soil. Sci., 1982, 33, 679. Bache, B. W. , “Proceedings of the International Seminar on Soil Environment and Fertility Management in Intensive Agriculture, Tokyo 1977.” Society for the Science of Soil and Manure of Japan, Tokyo, Japan, 1977, p.777. Parra, M. A., and Torrent, J., Soil Sci. SOC. Am. J . , 1983, 47, 355. Nemeth, K., Plant Soil, 1982, 64,7. Ding, C. P., Liu, Z. G., and Yu, T. R., Soil Sci. , 1982, 134, 252. Greter, F.-L., Buffle, J., and Haerdi, W., J . Electroanal. Chem., 1979, 101, 211. Buffle, J., and Greter, F.-L., J. Electroanal. Chern., 1979, 101, 231. van Leeuwen, H. P., “Electroanalysis in Hygiene, Environmental, Clinical and Pharmaceutical Chemistry,” Edmonds, T. E., Pu Guogang and West, T. S., Anal. Chim. Acra, 1981, 129,69. Ritchie, G. S. P., Posner, A. A., and Ritchie, 1. M., J. Soil Sci., 1982, 33, 671. Sibbald, A., Covington, A. K., and Carter, R. F., Clin.Chem., 1984, 30, 1. Edmonds, T. E., and Ji Guoliang, Anal. Chirn. Acra, 1983, 151, 99. Elsevier, Amsterdam, 1980, p. 383.October, 1984 CHEMICAL SPECIATION IN AQUEOUS SOLUTION Models for Speciation of Alkali and Alkaline Earth Metal Ions in Body and lntracellular Fluids 369 Matthias Otto and J.D.R. Thomas Department of Chemistry, Bergakademie Freiberg, 9200 Freiberg, GDR Department of Applied Chemistry, UWIST, P. 0. Box 13, King Edward VII Avenue, Card$f, CFl 3XF The importance in clinical chemistry of knowing the free ion concentrations of metals such as calcium, magnesium, potassium or sodium in biological samples, rather than their bulk concentrations, is now beyond doubt. Despite the successful analysis of ionised sodium, potassium and calcium in blood and urine or of sodium, potassium and magnesium in tissue cells, problems arise if magnesium is to be determined in the presence of calcium at the same concentration level in blood and urine, or if calcium determinations are required in the presence of excess magnesium, as with intracellular measurements.Such difficulties are due to the limited selectivity of today's most popular sensors for calcium and magnesium speciation. These sensors are ion-selective electrodes (ISEs) based on liquid membranes prepared from organophosphate' or neutral carrier2 sensor materials. In spite of the fact that calcium sensors with selectivity coefficients over magnesium as low as 4 x 10-5 M are now available,2 the specificity is inadequate if intracellular calcium ions are to be analysed at free concentrations lower than 10-6 M in the presence of 1-6 mM of magnesium.3 ISEs for magnesi~m1~4 completely lack selectivity with respect to calcium ions, necessitating new approaches for the determination of ionised magnesium in blood or urine samples in the presence of calcium.The aim of the work described here is firstly to demonstrate how the responses of calcium ISEs are affected by magnesium ions at intracellular concentration levels, and secondly to develop a new calibration strategy for the simultaneous determination of ionised calcium and magnesium and also of potassium and sodium. The second aim has the objective of analysing free concentrations of all four components in any of serum, urine and cell fluids. Mixture Calibration of Ionised Calcium and Magnesium At present, calibration of free calcium ion concentrations for intracellular ISE measurements down to 10-7 M is carried out either by serial dilution of solutions containing the metal ion and complexing ligands, such as EGTA, EDTA or NTA in an appropriate concentration ratio, or by changing the pH value of a solution with fixed metal - ligand concentrations.In order to cover a wide dynamic calibration range (10-7-10-3 M) standard solutions from at least two different ligands have to be prepared.'-5 Both calibration methods approach the conditions found in vivo in a rather limited manner, because in the cell the concentration of calcium buffering ligands as well as the pH value vary > 1:; E -200 + E L l j -120 I I I I I I I 0 2 4 6 -80 I Volume of 0.01 M Ca*+/cm3 I Fig.1. Simulated titrations of EGTA alone and of ligand mixtures with a 0.01 M calcium ion solution. M HEDTA, 5 x 10-4 M NTA, pH = 7.6 Composition of titrand solution: 5 x buffered by tris(hydroxymethyl)aminomethane, ionic strength = 0.1 M. M EGTA, 5 x370 CHEMICAL SPECIATION IN AQUEOUS SOLUTION Anal. Proc., Vo1. 21 only slightly. In an attempt to overcome some of the shortcomings, a recent method6 is based on adjusting the free calcium ion concentrations by adding calcium ions to EGTA at pH 7.4. Basically, this method is a titration of EGTA with Ca2+ ions. Therefore, the method lacks precision in the unbuffered region near the equivalance point. Because of the limitations, the method for the calibration of free calcium ions may be improved by using a mixture of ligands rather than a single complexing agent.This kind of calibration ensures that the metal ion is highly buffered at any calibration point, giving much better reproducibility than is possible with a single ligand. The effects of adding a second ligand [N-(2-hydroxyethyl)- ethylenediaminetriacetic acid, HEDTA] and a third ligand (nitrilotriacetic acid, NTA) to EGTA solutions was simulated with a computer program (we used ESTA7) that solves the mass balance equations in a multi-component system (Fig. 1). In the presence of all three ligands the e.m.f. changes are small and the equivalance points are obscured because of competing equilibria among the different metal - ligand complexes. In this way, and as can be seen from Fig.2, free calcium ion concentrations can be adjusted between 10-8 and 10-3 M by a single titration of 50 cm3 of the ligand mixture with 5 cm3 0.02 M Ca*+ ion solution. The agreement between theoretical and experimentally determined free Ca*+ ion concentrations is reasonable down to about 10-7 M Ca2+. 25 > E -25 & 0 v) cn 2 -75 + E W -125 al -175 8 6 4 2 I -Log [Ca2+] Calibration graph for free calcium ion concentrations using an organophosphate (calcium bis{di[4-( 1,1,3,3-tetramethylbutyl)phenyl]phosphate)sensor and dioctylphenyl phosphate solvent mediator), PVC membrane ISE based on titration of a three-ligand system (50 cm3) with 0 . 0 2 ~ calcium chloride solution: x, in 0.1 M NaCI, +, in 0.1 M Kcl; 0, serial dilution of unbuffered calcium chloride solutions.The line represents the calculated dependence for the following electrode parameters: slope = 27.1 mV, and intercept = 56.0 mV. Ligand concentrations and pH as in Fig. 1. Fig. 2. Deviations from linearity occur in the presence of 0.1 M sodium chloride as the supporting electrolyte at 1.6 X 10-7 M free calcium ion concentrations and with 0.1 M potassium chloride solution at 1 X 10-7 M Ca2+. Thus, the limiting factor for measurements at even lower concentrations is due to the restricted selectivity of the electrode with respect to alkali metal ions. ISE calibration of calcium ions of low concentrations in the presence of magnesium at typical intracellular concentrations is shown in Fig. 3 for a neutral carrier electrode.2 Despite good selectivity of the calcium sensor at 1.3 mM free Mg*+ concentration the interfering effect of 6 mM Mg2+ solutions on calcium concentrations lower than 10-6 M is quite obvious. Therefore, intracellular determinations of free calcium ion concentrations can be carried out with use of today’s calcium ion sensors only if the influence of free magnesium is taken into account.This constraint means that the concentration of magnesium has to be determined simultaneously. Multiple Analysis of Calcium, Magnesium, Potassium and Sodium Simultaneous analysis of caicium and magnesium was tested under the even more difficult conditions when both metal ions are present at the concentrations found in blood or urine samples. The approach was generalized by including ISEs for testing free potassium (valinomycin based ISE) and sodium (glass electrode) in order to permit the determination of all four components in biological fluids.October, I984 CHEMICAL SPECIATION IN AQUEOUS SOLUTION > E 2 0 fn -20 3 $ JO 0 b d o x 371 2 1 , xx;ox:x , , , - 60 0 o o o o o o x x x x x x 9 8 7 6 5 4 3 - LogICa2+l Fig.3. Mixture calibration of Ca2+ and Mg2+ ions at intracellular concentration levels by means of a neutral carrier electrode. pH 7.6, ionic strength 0.1 M (KCI), 10-3 M EGTA, 10-3 M NTA; x, 1.35 mM free Mg2+ (4.83 X l o - 3 ~ total Mg2+), 2.53 x 1 0 - 3 ~ HEDTA; 0, 6 mM free Mg2+ (1.74 x ~O-’M total Mg2+), M HEDTA. A calibration set consisting of 15 different mixtures of the components was designed to cover typical concentrations found in blood and urine, namely 10-250 mM of Na+ or K+ and 0.5-5 mM of Ca*+ or Mg2+. Computational analysis of the four component system by means of ordinary least squares analysis (OLS) gave unsatisfactory results, except for Na+ ion determinations (Table I). The poor accuracy with the use of ordinary regression analysis is thought to be a result of deviations from linear calibration curves for some of the sensors caused by the interaction of ions on the surface of the membranes or by non-constant selectivity coefficients. TABLE I ANALYSIS OF FREE CONCENTRATIONS OF CALCIUM, MAGNESIUM, POTASSIUM AND SODIUM Relative prediction errors,* % Data analysis Na+ Ca2+ Mg*+ K+ OLS 2.0 31 450 34 PLS 1.9 4.2 13 4.0 * Calculated as [~(Cactual-Cpredicted)2/~:actual 11’2. In order to overcome the limiting constraints, ordinary multiple regression was replaced by partial least squares analysis (PLS) in principal components. By use of the PLS algorithm the four components could be analysed from their mixtures with reasonable accuracy, as is shown in Table I. This result is encouraging as it demonstrates that free magnesium ions can be determined in the presence of calcium at the same concentration level by means of a non-specific sensor. Therefore, the analysis of intracellular free calcium ions in the presence of an excess of magnesium is seen to be possible by the agency of a calcium ion sensor that is not truly specific. One of the authors (M. Otto) gratefully acknowledges the support of the British Council in respect of a postdoctoral fellowship tenable at UWIST. The authors also thank Dr. P. M. May and Dr. K. Murray (UWIST, Cardiff) for their generous help in using the computer program ESTA. References 1. 2. 3. 4. 5. 6. 7. Moody, G. J . , and Thomas J . D. R., Ion-Sel. Electrode Rev., 1979, I , 3. Simon, W., Ammann, D., Oehme, M., and Morf, W. E . . Ann. New York Acad. Sci., 1978, 53. Pozzan, T., Rink, T. F., and Tsien, R. Y., J . Physiol.. 1981, 318, 12P. Lanter, F., Erne, D., Ammann, D . , and Simon, W., Anal. Chem., 1980, 52, 2400. Craggs, A., Moody, G. J . , and Thomas, J . D. R., Analyst, 1979, 104, 412. Bers, D. M., A m . J . Physiol., 1982, 242, C404. Murray, K., and May, P. M., “ESTA Users’ Manual,” Department of Applied Chemistry, UWIST, Cardiff, CFl 3XF, 1984.

ISSN:0144-557X    

DOI:10.1039/AP9842100359

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

372 FLOW INJECTION ANALYSIS Arid. Proc., Vol. 21 Flow Injection Analysis The following are summaries of four of the papers presented at a Meeting of the North West Region held on April 1 1th. 1984, at the Thornton Research Centre, Chester. Introduction E. R. Adlard Shell Resetrrch Ltd.. Thorfitori Research Ceritrc. P. 0. B0.u 1, Chester, C'H 1 3SH At this meeting six papers were presented. ranging from the principles of flow injection analysis (FIA), through optimisation techniques to specific applications such as the determination of drugs and their metabolites in blood and serum. In addition there was a small exhibition of commercially available FIA equipment by three instrument companies. In FIA a small sample is injected into a flowing liquid stream which may act its both a carrier and reagent.After controlled dispersion and reaction (which need not be complete) the sample is detected by a suitable monitor. A typical simple example would be the analysis of an acidic plant stream by titration. The carrier in such a case would be an alkaline stream containing indicator in its alkaline colour and the detector would be a spectrophotometer or colorimeter. On injection of the acidic sample a "peak" of the indicator in its acid form would pass through the detector and from the area of the peak, the concentration of the alkaline carrier and the size of the acid sample the same information can be obtained as would be derived from a conventional acid - base titration. The difference is that FIA obviously lends itself to automation and is capable of an analysis every 30 s or less.Other examples would be the determination of specific metallic ions in solution utilising known colorimetric reactions for quantitation (after calibration) and the measurement of blood alcohol with an electrometric detector. Sample sizes of 25-100 pl are typical with flow-rates of 1-S ml min-1 through tubing of about 0.5 mm diameter. The degree of dispersion of the sample can be controlled by varying these parameters and optimising them for a particular analysis. In summary. it can be said that FIA is well suited for the cheap, rapid and accurate analysis of large numbers of liquid samples, especially when a simple detector such as a colorimeter can be employed. It is not suitable for the one-off analysis in a research environment when background information about the composition of a sample may be small or even non-existent .Flow Injection Analysis: Fundamentals and Recent Developments J. N. Miller Department of Chemistry, Loiighhoroiiyh University of Techtiology. Loiighborough, Leicestershire. L E 1 1 3 TU Since the introduction of Flow Injection Analysis (FIA) nearly 10 years ago, it has aroused great interest in analytical laboratories, and the introduction of commercially available equipment has accelerated its adoption in many areas. The outstanding features of FIA are its extreme simplicity and its flexibility; it can be applied to an astonishing range of problems. It has been the subject of at least two books, and the number of original papers on FIA is rapidly increasing.Here, the fundamental features of the method are described and some recent advances in techniques and applications are summarised. FIA Principles In FIA the sample is introduced into an unsegmented flowing stream of reagent in a very reproducible manner; several methods are now available. The sample bolus is carried downstream to a detector in conditions of controlled dispersion, possibly undergoing one or more reactions en route. In simple protocols only one sample is present in the stream at a time. but in some cases, e . g . , where stopped-flow analysis is needed, a train of samples can be introduced. Complex manifolds, involving the use of several reagents, can be used; in some instances reagent economy is obtained by injecting the reagent in the same fashion as the sample, and merging the two zones downstream.Reaction kinetics can be studied and physico-chemical parameters such as diffusion coefficients and viscosities determined. Dispersion The dispersion of the sample is controlled by the tube internal diameter (commonly ca. 0.5 mm), by the flow-rate (often 1-5 ml min-1) and by the sample volume. It can be further controlled by theOctober, 1984 373 employment of coiled reaction tubes and by the use of packed-bed or pearl-string reactors. Dispersion in FIA experiments can be controlled between very small values (i.e., not much greater than 1) and very large values (10-100 or more). The dispersion ( D ) is defined as the concentration of the injected sample divided by the peak concentration of the sample zone at the detector.When an intrinsic property of an analyte is under study (e.g., colour, pH, pCa). a low-dispersion (D = 1) system is clearly desirable; for many reaction systems, i.e., when the analyte has to be converted into a more easily detectable derivative, a medium dispersion ( D = 3-10) is needed; there is increasing interest in the use of very high dispersion (D > 10). FLOW IN J ECTl ON AN ALY SlS Manifolds and Detectors The number of detectors used in conjunction with FIA is very large. Most early experiments utilised absorptiometric or electrochemical detectors, but more recently many others have been used, including atomic spectrometers (in which the presence of a nebuliser inevitably affects the experimental conditions) and chemiluminescence detectors (where the FIA system is especially valuable in providing highly reproducible mixing of the reactants). The scope of the FIA method has been further widened by the development of systems permitting dialysis, gas diffusion, solvent extraction and other sophisticated techniques.and FIA titrations have attracted considerable interest. Recent Developments and Future Prospects The scope of FIA methods shows every sign of continuing to expand, and this development is paralleled by new developments in technique and apparatus. Considerable interest has been aroused by the production of matchbox-sized FIA manifolds, with the "tubing" formed as grooves in a block of Perspex or similar material. When FIA is coupled with spectrometric detectors, the use of fibre optics is obviously indicated, and such methods may permit the use of detectors far removed from the flowing stream.FIA methods using packed-bed reactors have not so far found much application, but there is great scope for their use in cases where the packed bed has a highly specific activity, e.g., as an immobilised enzyme or an immunoadsorbent. Calibration methods using FIA will find wide use, and the use of FIA to study molecular interactions is another encouraging development. The portability of the equipment makes it especially suitable for environmental and clinical analyses, and FIA immunoassays have been demonstrated. In some of these applications FIA provides analytical opportunities not available by any other approach, and its future success in the real world of analytical chemistry seems assured.Bibliography Riiifka. J . , and Hansen, E. H . . "Flow Injection Analysis." Wiley, New York, 1981. Proceedings of the International Conference on Flow Analysis, Amsterdam, 1979, Anal. Chim. Acfa, 1980, 114. Proceedings of the Second International Conference on Flow Analysis. Amsterdam. 1982. Anal. Chim. Acta, 1983, Stewart, K. K.. Anal. Chem.. 1983. 55, 931A. Rgiieka, J . , Anal. Chem., 1983, 55. 1040A. 145. Optimisation of Conditions for Flow Injection Analysis D. Betteridge,* A. F. Taylor and A. P. Wade* BP Research Centre, Chertsev Road, Sunbury-on-Thames, Middlesex. TW16 7LN Flow injection analysis (FIA) is a very versatile form of continuous flow analysis. In a simple system a sample plug is injected into a flowing stream of a reagent.Reaction follows as the plug becomes dispersed by the action of the flow and molecular diffusion. The product concentration is monitored at a point, or points, downstream, usually spectrophotometrically. I For many wet chemical analyses an FIA procedure is to be preferred to existing manual methods on several counts. These include increased throughput (samples per hour), improved experimental repeatability.2 a decrease in the amount of reagent consumed and increased safety when handling toxic or dangerous materials.3 Many manual analytical methods have therefore been adapted for FIA. 1.2 * Also of The Chemistry Department, University College Swansea, Singleton Park, Swansea, West Glamorgan, SA2 8PP.374 FLOW INJECTION ANALYSIS Anal.Proc., Vol. 21 The full measure of the gains to be obtained from converting from a suitable existing manual procedure is usually realised only when a multivariate optimisation technique such as the modified simplex is used in the FIA method development.4 This is because the experimental variables of an FIA system (flow-rate, sample size, coil length, reagent concentration, pH, etc.) interact.4 Commonly used univariate techniques are not well suited to such systems,s and may lead to erroneous conclusions as to the optimum values for the variables. The modified simplex approachj.6 is well suited to such systems. It is now becoming routinely used in chemistry,’ thanks greatly to the early work of Morgan and Deming.5 Although there are still relatively few published applications of the method to FIA, where applied, rapid method development has been achieved.4-~10 In more recent years several “further modified” modified simplex procedures have been described.1’-16 The version used here is based on Nelder and Mead’s original method6 and incorporates several of the better modifications suggested and some more that we have found useful.Examples of its use appear in the l i t e r a t u r e . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 7 - ~ ~ We would suggest that all the methods published are of use. Their relative performance is dependent on the response surfaces being explored. The use of response functions with modified simplex optimisation allows a number of FIA parameters to be optimised simultaneously. Instead of just peak height (sensitivity), a function of sensitivity and throughput, or sensitivity and cost, can be used.Workers in this laboratory, in conjunction with another group, have recently used a response function to optimise out the effect of an interferent.”) This was Peak height for pure sample Peak height for sample plus Response = excess ofinterferent The response was improved from 0.25 to 0.84 in 15 experiments. No further impovement was obtained in subsequent univariate confirmatory experiments. A number of problems have been observed in some systems. Precipitation may lead to poor repeatability. Therefore, a set of conditions with suboptimal sensitivity but good repeatability may be preferred.8 In our recent study of a 12-variable FIA - solvent extraction system for uranyl determination (based on that of Baban20 and similar to that of Lynch et al.,3 except using cheaper reagents), it was found that under certain high flow-rate conditions, the separation stage became unstable. This led to a poor base-line and unacceptable repeatability. It was found that a function combining sensitivity with repeatability/stability was a better parameter to monitor than just sensitivity (peak height). The function was R = z/(o + 1) where = mean peak height (mm) and u = standard deviation of peak heights (mm) for typically 7-10 consecutive replicate samples. In another FIA system we are currently developing, the presence of sample decreases the peak height obtained (i.e., an inverse method). The detection limit is required to be as low as possible. We are therefore using - R = (zhlank - hsarnple)/(‘blank + usample -k l) In conclusion, the use of a well chosen response function in conjunction with a modified simplex optimisation procedure is a good way of rapidly developing new FIA methods and improving the performance of existing methods.We thank the British Petroleum Company pic for a research studentship to A.P.W. 1 . 2. 3. 4. 5 . 6. 7. 8. 9. References Rfiiifka, J . . and Hansen. E. H . . “Flow Injection Analysis,” Wiley. New York, 1981. Betteridge, D . . Anal. Chem.. 1978, 50, 832A. Lynch, T. P.. Taylor, A. F . , and Wilson, J . N . . Analyst. 1983. 108. 470. Betteridge. D.. Sly, T . J . , Wade, A. P., and Tillrnan, J . E. W.. Anal. Chem., 1983, 55. 1292. Morgan, S. L.. and Deming. S. N . , Anal. Chem.. 1974, 46, 1170.Nelder. J . A . , and Mead, R . , Computer J . , 1965, 7 . 308. Deming, S. N . , and Morgan, S. L., Anal. Chim. Acfa, 1983, 150, 183. Bourke. G. C. M . , Stedman, G., and Wade. A . P . , Anal. Chim. Acra, 1983. 153, 277. Janse, T . A . H. M.. van der Wiel. P. F. A . . and Kateman. G . , Anal. Chim. Acra. 1983, 155, 89.October, 1984 FLOW INJECTION ANALYSIS 375 10. 1 1 . 12. 13. 14. 15. 16. 17. 18. 19. 20. Lynch, T. P . , Kernoghan, N. J., and Wilson, J . N . , Analyst., 1984, 109, 843. Routh, M. W . , Swartz, P. A., and Denton, M. B . , Anal. Chem., 1977, 49, 1422. Ryan, P. B . , Barr, R. L., and Todd, H. D., Anal. Chem., 1980,52, 1460. van der Wiel, P. F. A., Anal. Chirn. Acta, 1980, 122,421. Betteridge, D., Wade, A. P., Neves, E. A., and Gutz, I ., An. Simp. Bras. Electroquim. Electroanal., 3rd, Aberg, E. R., and Gustavsson, A. G. T., Anal. Chim. Acta, 1982, 144, 39-53. van der Wiel, P. F. A., Maassen, R . , and Kateman, G . , Anal. Chim. Acta, 1983, 153, 83. Wade, A. P., Anal. Proc., 1983,20, 108. Belchamber, R. M., Betteridge, D., Chow, Y. T., Sly, T. J., and Wade, A. P.,Anal. Chim. A m , 1983,150, Wade, A. P., Anal Proc., 1983, 20, 523. Baban, S . , PhD Thesis, University of Wales, 1982. 1982,2, 411. 115. Practical Aspects of Flow Injection Analysis A. Shaw Tecator, Cooper Road, Thornbury, Bristol, BS12 2UP A study of the available publications relating to flow injection analysis (FIA) shows the applicability of this relatively new technology by analytical chemists in a wide variety of disciplines.The underlying principles of FIA need to be understood in order to obtain the best performance from the developed FIA system. This paper illustrated some of the practical considerations that can be employed in the development of colorigenic FIA methods based on well established chemistries that often form the basis of official or standard manual methods. A direct comparison of the manual and FIA methods for the determination of aqueous nitrite in the range 10 pg 1-1 to 1.5 mg 1-1 (as N) shows the immediate benefits of short sample residence times together with excellent repeatability of the FIA method. The normal range of the variables in an FIA system (sample size, flow-rates, tube diameters, reaction coil lengths, etc.) were discussed and related to the rules governing sample dispersion.Specific effects of changes in sample size were related to detector output and sample residence times in order to illustrate the observation that larger samples occupy a greater proportion of the FIA system and can limit the sample throughput with a relatively small gain in sensitivity. Various arguments necessary to the successful development of a colorimetric FIA method were illustrated in some detail, with particular emphasis given to the early testing of the chosen methodology, The importance of checking the system response at this early stage is that it is almost always rewarded within 1 min of the first injection. Once this initial system response is quantified, the chemist can then apply value judgements tempered with a knowledge of the “rules” and amounts in FIA in order to achieve the desired objective.The author favours this approach for colorimetric FIA assays, as the required degree of optimisation can be quickly achieved without the need to resort to extensive and time-consuming calculations. A detailed example of the rationale employed in the development of a colorimetric FIA method for iron (range 0.02-1.0mgl-~) using ferrozine as the chromophore was illustrated. The resultant flow scheme was evaluated and a direct comparison was made for the determination of aluminium (range 0.01 -0.2 mg 1-1) using pyrocatechol violet reagent. This comparison illustrates that a sensitive FIA method for one parameter can be readily adapted to another parameter with the minimum of alterations to the system.Clearly, in such an instance, the reagents need to be changed and the molar absorptivities of the coloured complexes should be of a similar order of magnitude. The above comparisons can also exemplify the rapid changeover from one parameter to another and where the second parameter can be run satisfactorily within minutes of the first, even though in this instance iron is known to interfere specifically with the aluminium chemistry. A selection of the mechanics of an FIA system were discussed with emphasis given to sample injection (with and without valves), manifold designs and phase techniques. The techniques included gas diffusion, dialysis (including stopped flow), solvent extraction and packed reactors together with examples of their use in FIA systems.On-line sample dilution using dialysis or zone sampling were also discussed. Detector outputs were characterised, with emphasis on the fact that the concentration profile represented by a typical FIA peak could be quantified by measurement of peak heights, area or width, and the merits of each were discussed. In addition, the measurement of sample concentration at any376 FLOW INJECTION ANALYSIS Anal. Proc., Vol. 21 point in the peak (“dynamic attenuation”) was illustrated and its use was related to the investigation of specific interferences and their resultant effect on peak shape. A further manipulative procedure was shown where specific and non-specific interferences can be overcome by an automated standard additions process that is broadly applicable and produces a validated result by interpolative means, while at the same time leaving the standards and the majority of the sample mutually uncontaminated. Optimisation was discussed and the merits of formal iterative procedures (modified simplex optimisation) and informal procedures were evaluated. Whichever procedure is adopted, it is particularly important to be absolutely clear which parameters are to be optimised in order to achieve a balanced system of the required performance.A fully automated, microprocessor-controlled and commercially available FIA system (Tecator FIAstar) was shown for routine sequential analysis and colorimetric method development. Clinical Applications of Flow Injection Analysis Paul J. Worsfold Department of Chemistry, University of Hull, Cottingham Road, Hull, H U6 7RX Flow injection analysis (FIA) can be considered as a sample transport and on-line sample treatment system, and as such there is scope for its application in most analytical laboratories. Current interest in the technique is exemplified by recent publications1.2 and by the introduction of several commercial FIA systems.At the present time, however, routine application of FIA (particularly in the field of clinical chemistry3) is very limited in spite of its many attractions, e.g., speed, versatility, simplicity and economy. The application of gradient techniques, the versatility of manifold design and the use of FIA as a sample transport system are described below, with particular reference to clinical applications. Gradient Techniques With conventional continuous-flow FIA a transient signal is obtained as the sample zone passes through the detector.When using stopped-flow FIA a particular segment of the sample zone is arrested within the detector and the rate of reaction is monitored. This approach can be used to overcome high and variable background signals from the sample matrix or to increase the sensitivity of relatively slow reactions. An example of the former is the determination of alcohol in whole blood samples via alcohol dehydrogenase catalysed degradation .4 The method provides a rapid (80 samples per hour) low-cost procedure with no sample pre-treatment required, and an acceptable precision and accuracy as compared with headspace gas chromatography. An example of the latter is the turbidimetric determination of human serum IgG via immunoprecipitation with a selective antiserum .5 The speed (40 samples per hour), reproducibility and cost of the method compare favourably with the routinely used radial immunodiffusion technique.Versatile Manifold Design FIA can be used routinely as a dedicated high throughput analyser, but owing to its versatility and rapid response it can also be used for carrying out multi-parameter tests on small sample batches and as an emergency (stat) analyser. Furthermore, the manifold design can be easily modified to accommodate a variety of on-line processes, e.g. , dialysis, immobilised enzyme reactors, gas diffusion and solvent extraction, and a variety of detection systems are FIA compatible.An example of this versatility is given by the determination of plasma glucose using FIA.6 The protein matrix is removed by an on-line dialyser and hydrogen peroxide is produced using an immobilised glucose oxidase coil. A variety of detection methods can then be employed, e.g. , spectrophotometric, chemiluminescence and amperometry, in order to monitor the hydrogen peroxide. Sample throughputs in excess of 80 samples per hour can be obtained using 30-pl samples, with individual results available less than 1 min after injection. Reagent consumption is minimal and precision and accuracy are comparable with those obtained using standard methods. FIA as a Sample Transport System In its simplest form FIA provides a means of transporting samples to the detector quickly and reproducibly.An example of this is the use of FIA coupled with an inductively coupled plasma - optical emission spectrometer (ICP - OES) for a multi-element serum determination .7October, 1 984 FLOW INJECTION ANALYSIS 377 Results showed that by introducing small discrete sample slugs (20 pl) of serum into the plasma, as opposed to continuous serum aspiration, there were minimal matrix effects, and, therefore, no sample pre-treatment was required. In general terms FIA can be used for sample transport whenever an inherent property of the sample is being measured. Such a system is easily automated and provides more rapid and reproducible results than comparative manual batch procedures. Conclusions FIA is a solution handling system that is compatible with a variety of chemical processes and detection systems, and it also lends itself to automation.It has numerous areas of application, one of which is in the general field of clinical analysis, and it is particularly suited to smaller clinical laboratories where expensive discrete and segmented continuous-flow analysers are not available; References 1. Anal. Chim. Acta, 1943, 145, 1-226. 2. RfiiiEka, J . , and Hansen, E. H., “Flow Injection Analysis,” Wiley, Chichester, 1981 3. Rocks, B., and Riley, C., Clin. Chem., 1982,28, 409. 4. Worsfold, P. J . , RiiiEka, J., and Hansen, E. H., Analyst, 1981, 106, 1309. 5. Worsfold, P. J., and Hughes, A., Analyst, 1984, 109, 339. 6. Worsfold, P. J . , Farrelly, J . , and Matharu, M., Anal. Chim. Acta., in the press. 7. McLeod, C.W., Worsfold, P. J., and Cox, A. G. Analyst, 1984, 109, 327. Flow Injection Analysis Combined with Atomic-absorption Spectrometry Julian Tyson Department of Chemistry, University of Technology, Loughborough, Leicestershire, LE11 3 TU Most flow injection analysis (FIA) systems can be considered to consist of a sample injector, a manifold and a detector. Further, the dispersion effects that occur between injection and detection are usually considered to be due to the manifold design, with the injector and detector making a small, constant contribution. However, owing to the method by which an atomic-absorption spectrometer converts the sample to atomic vapour, there is an apparent contribution to the dispersion effects from the detector. The extent of this contribution depends on the particular nebuliser design but may be equivalent to a mixing chamber of 100 pl volume.Also, the basic performance of the nebuliser changes considerably with flow-rate. The nebulisation efficiency has been observed to increase from 10 to 40% as the flow-rate was reduced from 9 to 1 ml min-1.1 The practical consequence of this is that low dispersion values cannot be achieved unless a large volume is injected, which in turn will reduce the sampling frequency. On the other hand, if peak area is measured, detection limits may be almost the same as for conventional nebulisation owing to the improved precision and nebulisation efficiencies obtained with flow injection at low flow-rates.’ The exponential peak shapes can be used as the basis for the calculation of dispersion values.2 The applications of FIA - AAS fall into three main categories, namely those concerning (a) matrix effects, (b) sample pre-treatment and (c) calibration methods. Matrix Effects It is possible to introduce small volumes of samples whose composition would not allow continuous conventional nebulisation. For example, we have shown that it is possible (a) to determine magnesium in solutions containing up to 32% m/V of sodium chloride, (b) to tolerate up to 50% V/Vof glycerol (a 10% reduction in intensity occurs at this level compared with a 70% reduction for conventional nebulisation) and (c) determine lead as the dithizonate in carbon tetrachloride. In this area of application the flow injection features are similar to those of “discrete” nebulisation3 but with the additional benefit that the nebuliser is continuously washed by the carrier stream.Sample Pre-treatment In the simplest instance, the dispersion effects can be used to dilute the sample and “add” a reagent (such as a spectroscopic buffer) contained in the carrier stream. A more economical method of reagent addition is to use the merging zone configuration.4 High dilutions (up to 1 3 0 ~ ) have been achieved with a zone sampling manifold.5 Sample clean-up and pre-concentration has been achieved using378 THE ANALYST IN COURT Anal. Proc., VoL 21 solvent extraction procedures.6 So far these methods have involved continuous sample introduction and so are not true flow injection. The most recent of these methods describes a procedure for extracting Cd, Cu, Fe, Pb, Ni and Zn as dithiocarbamates into Freon 113 followed by back-extraction.’ The flow-rate of 200 pl min-1 is too slow for flame AAS but the system would be compatible with the use of an electrothermal device.A column of Chelex-100 resin has also been used for pre-concentration and clean-up.8 After removal of the metal (Pb, Cd, Cu and Zn) from the sample (up to 2 ml), the resin column is back-flushed with acid. Detection limits as low as 1 p.p.b. were reported. It is also possible to generate volatile hydrides using an FIA method. The determination of bismuth in the range 1-100ng (in 700 pl) at the rate of 180 samples h-1 has been described.9 Cali bration Met hods A flow injection analogue of the standard additions method has been decribed in which the sample is used as the carrier and the standards are injected.;! Careful selection of the dispersion value is required in order to achieve the appropriate ratio beween interferent and analyte concentrations.10 The use of an exponential gradient chamber to produce a continuous concentration gradient for calibration purposes has been proposed.11 This is not FIA as the instrument is used in the conventional nebulisation mode although, in principle, flow injection introduction could be used and the concentrations calculated corrected via the known dispersion of the manifold.Finally, a method hased on measuring the width of the peak has been proposed for extending the concentration range upwards.12 For exponential peaks, the width is proportional to a simple logarithmic function of the concentration. The range 1-1000 p.p.m. of Mg was covered with a fairly insensitive instrument. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. References Wolf, W. R., and Stewart, K. K., Anal. Chem., 1979, 51, 1201. Tyson, J. F., Appleton, J. M. H., and Idris, A. B., Anal. Chim. Actu, 1983, 145, 159. Cresser, M. S., Prog. Anal. At. Spectrosc., 1981, 4, 219. Zagatto, E. A. G., Krug, F. J., Bergamin, F’., H., Jmgensen, S. S., and Reis, B. F., Anal. Chim. Actu, Reis, B. F., Jacintho, A. O., Mortatti, J., Krug, F. J., Zagatto, E. A. G., Bergamin, Fo., H., and Pessenda, Nord, L., and Karlberg, B., Anal. Chim. Acta, 1983, 145, 151. Backstrom, K., Danielsson, L.-G., and Nord, L., Analyst, 1984, 109, 323. Olsen, S., Pessenda, L. C. R., Rfiiitka, J., and Hansen, E. H., Analyst, 1983, 108, 905. Astrom, O., Anal. Chem., 1982, 54, 190. Tyson, J. F., and Idris, A. B., Analyst, 1984, 109, 23. Tyson, J. F., and Appleton, J. M. H., Talanta, 1984, 31, 9. Tyson, J. F., Analyst, 1984, 109, 319. 1981, 104,279. L. C. R., Anal. Chim. Actu, 1981, 123, 221.

ISSN:0144-557X    

DOI:10.1039/AP9842100372

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

378 THE ANALYST IN COURT Anal. Proc., VoL 21 ANNUAL CHEMICAL CONGRESS The Annual Chemical Congress of The Royal Society of Chemistry was held at the University of Exeter on April 16th to 19th, 1984. A symposium entitled The Analyst in Court was organised by the Analytical Division. The Analyst in Court The following are summaries of eight of the papers presented at the Annual Chemical Congress. Opening Address R. F. Coleman Laboratory of the Government Chemist, Cornwall House, Stamford Street, London, SE1 9NQ Analytical chemistry is widely applied to the solution of problems of relevance to Government Departments, more so than any other branch of chemistry. Some investigations are required to provide information to help in the formulation of policy; for example, knowledge of the nature and extent of the nutrients in the diet or of the tar, nicotine and carbon monoxide content of cigarette smoke can beOctober, 1984 THE ANALYST IN COURT 379 used to guide officials in their consideration of public health issues.Nevertheless, the bulk of analytical chemistry underpins the regulatory role of Government, at national, international and local levels. The analytical chemist plays a vital role in the framing of appropriate legislation that can be adequately monitored and, where necessary, enforced through the Courts. Where infringements of such laws appear to have taken place, the analytical chemist will frequently provide a factual basis on which to consider the offence. During the Symposium a wide variety of different criminal and civil cases in which the analytical chemist plays a vital role were discussed.In these opening comments I shall only sketch briefly the complete framework that needs to be considered to ensure the maximum effectiveness of the expert witness in Court. This includes: 1. Advising on procedures that can be effective in law enforcement and provide a cost-effective means of establishing an infringement before the legislation is presented to Parliament or the Statutory Instrument is introduced. 2. Providing the necessary background information that will enable legal and illegal operations to be differentiated. 3. Establishing a laboratory procedure that will ensure the provision of reliable measurements at all times. 4. Evaluating and interpreting all analytical data relevant to a particular problem and presenting evidence to the Court.The responsibility for workable legislation, of course, rests with the civil servants in the Government Department concerned. This should, and usually does, involve close co-operation with scientists in the public sector. Outside organisations, such as learned societies, can influence the Parliamentary procedure and I suggest that this is an important function for such bodies as the RSC. Some draft EC regulations that will become binding on Member States will also require careful examination and, frequently, considerable discussion and amendment is necessary before they are in an acceptable form that is consistent with UK practice. Many of the problems that could occur in the enforcement of legislation can be avoided by giving careful consideration to the analytical methodology at the drafting stage.The background information necessary for the interpretation of analytical data, relevant to particular cases, may arise from a wide range of sources. Wherever possible, it should be subjected to external scrutiny rather than relying on the accumulated wisdom of an expert witness that cannot be independently verified. For example, the evidential value of blood grouping tests depends on the frequency distribution of blood groups in humans, which has been established for medical rather than forensic purposes. The acceptable errors in measurements and sampling to be used in assessing borderline cases should be based on a careful evaluation of the particular methods and matrices involved and will usually require inter-laboratory studies.Until recently, much of the evidence presented in the UK Courts has been accepted because of the standing, or otherwise, of the expert witness presenting the evidence. Laboratory examinations, however, are often team efforts and therefore demand a laboratory quality and management system that is capable of ensuring that measurements are reliable, meet specified standards and avoid mistakes through careful checking procedures. I suggest this is likely to be most readily achieved by external laboratory accreditation of the test procedures and indeed the whole laboratory. The establishment of the National Test Laboratory Accreditation Scheme (NATLAS) three years ago has primarily impacted on laboratories providing services for companies involved in trade.I suggest it is very relevant to laboratories providing services to the Courts and it would not surprise me if lawyers do not, soon, start asking for some form of accreditation in addition to an assessment of the individual qualities of the expert witness. I do not intend to discuss here the evaluation and interpretation of analytical data, relevant to particular problems, for the presentation in Court. Several of the papers in the Symposium address this particular issue. Finally, I should draw attention to the scale of the problem with which we are dealing. Whilst Court actions may arise through ignorance or careless mistakes on the part of the defendant, the vast majority arise through trying to obtain an unfair advantage over other sections of society or individuals.This can often be expressed in monetary terms and the sums involved on a national scale can be huge. The “black economy” in the UK was estimated by the Keith Report to be about 7% of the gross domestic product. This represents a loss of about f4 billion in income tax and about f500 million in VAT. Whilst the analytical chemist can play only a limited part in combating this particular form of crime, document380 THE ANALYST IN COURT Anal. Proc., Vol. 21 examination that involves not only handwriting and typewriting comparisons but also examination of papers and inks is very relevant. The seizures of illegal drugs in this country last year amounted to a street value of about $50 million, and this is often said to be only about 10% of the total drugs traffic, i.e., f500 million.HM Customs and Excise (HMCE) collect a total of about f10 billion in duties on road fuel, beer, wines and spirits and excise duties on imports. Most traders behave perfectly legally and only a relatively small number try to evade payment of duties. The support given to HMCE by analytical chemists acts both as a deterrent to illegal trading and provides support for the prosecution of those who evade taxes and duties. Even these sums are small compared with the total cost of goods purchased by consumers that should be safe and to approved standards of quality or performance. At present, the resources devoted to enforcement of legislation with direct relevance to the consumer are relatively small but will be adequate so long as major suppliers do their best to comply, and are not threatened by less scrupulous organisations who will risk detection and conviction for short-term gains.Recent Investigation of Fungal Toxins B. Caddy Forensic Science Unit, University of Strathclyde, 204 George Street, Glasgow, G1 1XW Poisoning with Cortinarius Mushrooms Our involvement with mushroom poisonings began in 1980 in Lairg, Sutherlandshire, and concerns two young males and one female on a camping holiday. While the males went hill walking the girl stayed behind to cook the main meal of the day. She picked mushrooms which she identified as the edible Chanterelle, but which were Cortinarius speciosissimus. All were taken ill 3 days later (the latent period can be up to 20 days), experiencing typical Cortinarius poisoning symptoms of intense thirst, gastric disturbances, vomiting and persistent headaches, a sensation of coldness and impaired renal function. The girl also suffered a particularly heavy menstrual period.The Cortinarius group of mushrooms are the largest in Europe and about 250 examples are found in the UK. Of these, several are known to be toxic, especially C. speciosissimus, C. orellanus, C. gentilis and C. splendens, and others are suspected as being so. All workers in this field agree that toxicity resides in those materials, isolated from the mushroom, which demonstrate fluorescence when irradiated with ultraviolet light.l.2 Structural Elucidation Three compounds, cortinarin A, B and C, were isolated from a methanolic extract of the dry powdered mushroom C.speciosissimus by preparative thin-layer chromatography (TLC). These three compounds were found to be soluble in alcohols, water and especially dilute aqueous alkali. They were insoluble in apolar solvents. Elemental analysis of cortinarin A and B showed the presence of carbon, hydrogen, sulphur, nitrogen and by implication oxygen. Their reactions with various chromogenic reagents suggest that the cortinarins are all polypeptides and that cortinarin B may contain a phenolic moiety whereas cortinarin C may possess an indole having positions 2 and 3 free. These views are supported by the ultraviolet spectra of all three cortinarins, with the spectra of the fluorescent compounds showing great similarity to that of phalloidin, a toxic principle of the fungus Amanita phafloides, but at a lower wavelength.The ultraviolet spectrum of cortinarin C was found to be similar to that of psilocin, except that there was no bathochromic shift on the addition of alkali. It was, however, identical with the ultraviolet spectrum of 4-methoxy-N,N-dimethyltryptamine. Hydrolysis studies showed the presence of threonine, ornithine, phenylalanine, lysine, glycine, alanine, valine, leucine, isoleucine and one other compound that gave a positive reaction to ninhydrin. Cortinarin B produced similar results. By making use of the reaction sequences used by Wieland and Wieland3 for the elucidation of the structures of the phallotoxins, we were able to produce two non-fluorescent compounds, one each from cortinarin A and B, by treatment with Raney nickel. These compounds reacted strongly with acidified p-dimethylaminobenzaldehyde @-DAB), giving a purple colour.Further, the ultraviolet spectra of these two hydrogenated compounds showed a shift to shorter wavelength of about 6nm and were similar to the spectrum of cortinarin C. Subsequent partial hydrolysis of these hydrogenated cortinarins with trifluoroacetic acid produced, in each instance, a single compound that reacted with both acid p-DAB and ninhydrin reagents. Further analysis of the total acid hydrolysates of cortinarin A and B byOctober, I984 THE ANALYST IN COURT 381 two-dimensional TLC of the dansylated amino acids showed that both a tryptophan derivative and cysteine were present. In addition, the ultraviolet spectrum of these compounds showed a single band at 300nm, which was considered to be due to the presence of an oxindole. However, amino acid analysis of a hydrolysate of either cortinarin A or B that had been previously treated with Raney nickel showed that cysteine had been replaced by alanine.These observations indicated that the chromophores of cortinarin A and B consist of a condensation product of cysteine with a tryptophan derivative. The substituted tryptophan unit was isolated by column chromatography on Sephadex LH-20 from a total acid hydrolysate of cortinarin A that had been previously hydrogenated with Raney nickel. The free indole nucleus was liberated by incubation with the enzyme tryptophanase to yield 4-methoxyindole, identified by comparison (NMR, TLC, UV) with the product obtained by methylation of psilocin and treatment with the same enzyme.The amino acid sequence of cortinarin A following treatment with both Raney nickel and trifluoroacetic acid was determined using the standard Edman degradation and this was confirmed by low-resolution mass spectrometry of the acetylated and permethylated compound and shown to be alanine from cysteine, threonine, glycine, phenylalanine, 4-methoxytryptophan, valine, ornithine, leucine and isoleucine. Configuration of the amino acids was determined by digestion with both D- and L-amino acid oxidase when all but threonine were shown to have the L-configuration. The probable structures of cortinarin A, B and C can therefore be represented by the formulae in Fig.1 .4 The three compounds are interconvertable, methylation of cortinarin B with diazomethane yielding cortinarin A while hydrogenation of cortinarin A with Raney nickel gives cortinarin C . (a) *I (b) I Phe-OC-CH-NH-Val-Orn --he- OC-CH -NH-Val-Orn I *$ I Gly- Thr-NH-CH- LGIy- ,co 'Isoleu Ll Fig. 1. Structures of cortinarins A, B and C. (a) R=OCH3, cortinarin A; R=OH, cortinarin B. ( b ) cortinarin C. Asterisks indicate major points of comparison. Distribution of the Cortinarins Amongst Mushrooms of the Genus Cortz*narius High-performance liquid chromatography (HPLC) was selected as the method of analysis and the original systems employed a 5-pm Spherisorb silica column (25 cm x 4.5 mm i.d.) developed with the solvent system hexane - ethanol (9 + l), the eluate being monitored by ultraviolet absorption at 270 nm.Unfortunately, this system does not resolve cortinarin B and consequently a reversed-phase alternative consisting of a 5-pm octadecylsilane silica column (25 cm x 4.5 mm i.d. ,) developed with the solvent system acetonitrile - water (1 + 3) was preferred.6 Only three species have so far been found to contain cortinarin B (Table I). Toxicity is probably associated with the combined concentrations of cortinarin A and B. Toxicology of the Cortinarins Initial toxicity studies have been carried out on cortinarin A and B by intraperitoneal administration to male BKA mice. Of the mice poisoned with cortinarin A (5 mg), one died after 4 days and the others, when killed 2 weeks after dosing, showed kidney damage that ranged from mild to severe.Mice given cortinarin B (5 mg) also showed renal damage with two mice dying after 4 days. In both instances the kidneys of the poisoned mice were enlarged and also showed a blue fluorescence when examined under ultraviolet light. These kidneys were then extracted with methanol and a compound isolated whose properties coincided with the sulphoxide of cortinarin B prepared by oxidation of cortinarin B with peracetic acid. This suggests that cortinarin A might undergo 0-demethylation and S-oxidation prior to exerting its effect on renal tissue. This is an agreement with the work of Nieminen eta/.' Although the mechanism of action of the cortinarins is at present unknown, there are a number of similarities between these toxins and the posterior pituitary hormone vasopressin.Both compounds act on the distal tubules and collecting ducts of the nephron, resulting in water retention. Vasoconstriction,382 THE ANALYST IN COURT Anal. Proc., Vol. 21 Concentrations TABLE I ANALYSIS OF CORTINARIUS SPECIES FOR CORTINARINS A, B AND C adsorption-phase HPLC. expressed as % dry mass of mushroom. Values in parentheses were obtained by Cortinarin A, Cortinarin B, Cortinarin C, Species '/O m/V YO m/V O/O m/V C. speciosissimus . . . . . . . . 0.47 (0.47) C. orellanus . . . . . . . . . . . . 0.42 (0.43) C. orellanoides . . . . . . . . . . 0.45 (0.45) C. pinicolu . . . . . . . . . . . . 0.19 (0.20) C. callisteus . . . . . . . . . . . . 0.20 (0.18) C. turmalis . . . . . . . . .. . . 0.32 (0.33) C. rnucifluus . . . . . . . . . . 0.05 (0.06) C. betuletorum . . . . . . . . . . 0.28 (0.28) C. triviulis . . . . . . . . . . . . 0.10 (0.12) C. torvus . . . . . . . . . . . . . . 0.01 (0.012) 0.60 0.20 (0.20) 0.52 0.24 (0.12) 0.47 0.20 (0.19) - 0.028 (0.03) 0.19 (0.19) 0.05 (0.043) - 0.07 (0.076) 0.05 (0.04) 0.06 (0.06) - 0.12 (0.15) - - - - causing hypertension and a sensation of coldness, increased gut motility and stimulation of the uterus are also pharmacological effects produced by both cotinarius toxins and vasopressin. There are also similarities in the structure - activity relationships of the compounds (Fig. 2). The presence of a cyclic structure, a phenolic group at position 2, phenylalanine at position 3 and the presence of a basic amino acid (lysine for cortinarin A) are all apparent in both structures.It seems likely, therefore, that the toxins act at similar receptor sites to vasopressin in the kidney but, unlike the hormone, have an extremely long half-life. This hypothesis has still to be tested. * I "3 Phe -0C-CH-NH-Ala- Pro -AArg-Gly I CH2 2 *OH Fig. 2. Comparison of the structures of cortinarin B [Fig. l ( a ) ] and vasopressin. Asterisks indicate major points of comparison. Conclusions Clearly, it has been established that the Cortinarius toxins are widely distributed amongst mushrooms of the genus Cortinarius. Their structures have been elucidated and their resemblance to vasopressin noted. The author expresses his thanks to Dr. I. R. Tebbett for the experimental work reported here.References 1. Grzymala, S . , Bull. SOC. Mycol. Fr., 1962, 78, 394. 2. Testa, E.. Rass. Micol. Ticin., 1970, 2 , 89. 3. Wieland, T., and Wieland, O., in Kadis, S., Ciegler, A . , and Ajl, S. J . , Editors, "Microbial Toxins," Volume 8, Academic Press, New York and London, 1972, p. 249. 4. Tebbett, I . R . , and Caddy, B . , Experientia. 1984. 40. 441. 5. Tebbett, I. R . , and Caddy, B . , J . Chromatogr., 1983, 268, 535. 6. Tebbett, I. R . , and Caddy, B . , J . Chromatogr., 1984, 283, 417. 7. Nieminen, L., Mottonen, M., Heikkila, H . , Z . Naturforsch., 1975, 30, 668.October, I984 THE ANALYST I N COURT Judgement-a Gamble by Interpretation Out of Fact. An Industrial View of Regulatory Analysis P. 0. Dennis Brooke Bond Liebig, Group Technical Division, Trojan Way, Croydon, CRO 4XL 383 The judgements given in a case if it proceeds through various Courts, and possibly to the House of Lords, are not necessarily consistent, yet in cases involving food law the scientific facts are rarely, if ever, disputed.It is the interpretations put upon them by the enforcement authorities and by the industry concerned that may be very different. Judgement is made by the Court after it has accepted an interpretation of the facts. These facts usually include the results of chemical, physical or biological analysis. The analyst therefore has an important part to play in producing a convincing interpretation of the facts. The industrial analyst has available a vastly greater knowledge of his products and those made by his competitors than has the enforcement authority.He can therefore interpret a set of analytical facts in a much wider and more accurate context than that available to the enforcement authority. Nevertheless, the very inconsistency of the courts indicates that the interpretation they accept of both the facts and the law as applied to them is something of a gamble and hence so is their judgement. Analysis and the Criminal Law The criminal law controls the manufacture and sale of foods with regard to the environment that a factory creates both within and without its walls. Thus the Health and Safety at Work Act, the Clean Air Act and various river and water pollution laws all necessitate analytical monitoring and control to ensure compliance with them. Compliance with food law concerned with compositional standards, adulteration and contamination and the use of food additives similarly requires the application of analytical science.Analysis and the Civil Law Because all law is applicable in all general circumstances the Sale of Goods Act, the law of contract and of master and servant apply to the supply or the sale of food. A civil contract for the supply of food will always require compliance with the Food and Drugs Act and regulations made under it, and frequently the purchaser requires his own special standards to be met. The application of the civil law, as of the criminal law, requires the services of regulatory analysis. Industrial Regulatory Analysis Industry requires the results of analysis to control its production activities, quality assurance programmes, purchasing of new materials, recovery and re-working of materials and shelf-life of its products.Information concerning the composition of its products is necessary for industry to be able to help in the creation of sensible and acceptable legal standards for products and answer questions from professional quarters, consumer organisations and the public concerning its products. Enforcement of Regulatory Services The nature of food law and the procedure it requires to be used to enforce it led to a system mainly based on compositional standards and the examination of samples taken at the point of sale. This usually results in very limited factual information being available to the enforcement authorities upon which they must make a decision.Further, the system fosters the thought, sometimes erroneously, that the compositional requirements and the levels at which they are set are a measure and even a guarantee of the quality of the product. The concept of value as a ratio of quality to cost has no place in the present system. The manufacturer, on the other hand, takes an almost diametric approach to his products. His first concern is to make a product highly acceptable to the consumers against those of their needs he aims to satisfy, whatever those needs may be. He then sets about ensuring that his products are wholesome and fit for human consumption whilst allowing the chemical compositions of the products to be as they may. If necessary, he then has to adjust a product to comply with any prescribed compositional standard with the hope that such adjustments have not altered the product in a way that makes it no longer able to fulfil the need he started out to satisfy.To regulate the composition of his product he needs to analyse it sufficiently to be sure, as far as statistics will allow, of his analytical facts. Certainly there will still be anAnal. Proc., Vol. 21 element of uncertainty in them and therefore his interpretation and subsequent judgement will be a gamble, but he knows the odds, and they are usually not less than 95% in his favour. His use of regulatory analysis is both necessary and effective. 384 THE ANALYST IN COURT The Future There is a vast pool of knowledge and expertise within industry. Much of the food industry employs qualified scientists who are members of the Institute of Food Science and Technology, a professional and qualifying body that requires adherence to a Code of Professional Conduct by its members. It seems reasonable to suppose that better systems of enforcement than the present one could be devised, ones based on co-operation between industry and the enforcement authorities, codes of practice, self-certification and possibly licensing of plants.This is not to ,abandon necessarily the existing point of sale sampling provisions, rather it is to extend the system, as has already been done extremely successfully for weights and measures by the latest Weights and Measures Acts and regulations made under them. Meat Products: Interpretation of Proximate and Other Analyses C.Hitchcock and D. Favell Unilever Research, Colworth Laboratory, Sharnbrook, Bedford, MK44 1 LQ Meat is defined as the flesh, including fat, of any animal or bird normally used for human consumption. In addition to muscle and its integral connective tissue, this definition covers skin, rind, gristle, sinew, tendon and ligament in amounts naturally associated with the flesh used, as well as permitted offal such as heart, liver, kidney, tongue and head meat. Under existing regulations, meat products are required to contain a minimum meat content, and food analysts attempt to provide an accurate measure of this parameter. In chemical terms, raw meat contains variable proportions of water, lipid, myofibrillar proteins, sarcoplasmic proteins, connective tissue proteins, blood proteins and many minor organic and inorganic components.Traditional proximate analysis involves the determination of total nitrogen [N (Kjeldahl)], water [W (volatile at 105 "C)], fat [F (extractable into organic solvent)] and ash [A (residue on ignition)]. Observed levels of N, W, F and A are subject to the usual sampling and experimental errors, but their interpretation in terms of familiar concepts such as total meat content often introduces considerable uncertainty, because of the biological variation in the composition of meat itself and the complexity of modern meat products. The classical approach to the determination of meat levels therefore involves establishing the average nitrogen content of meat, and using this factor to convert observed nitrogen levels (N) to calculated protein (P) and raw fat-free meat levels (M).This introduces an uncertainty which is often neglected; indeed different factors' are used for different samples, e.g., P = 6.25N (over-all dietary protein,), P = 5.57N (collagen); N = 0.0355M (beef), N = 0.0345M (pork). These figures suggest an accuracy of conversion that is not justifiable for individual samples. Total meat levels are calculated as (M + F); extraneous fat and water are defined by setting an arbitrary limit on F and W compared to (M + F). Lean meat (visual lean) is defined as being free of visible fat, and is calculated by adding to M an allowance (up to 0.1M) for interstitial fat that cannot be trimmed off.' In a product made from a particular small piece of meat, biological variation alone can lead to errors of 510% in the crucial estimation of M, if an average factor is used.For instance, the currently accepted factor for pork products (3.45%) is calculated from a range whose extremes are 3-4'/0*: average values are 3.91% (pork back) and 3.64% (pork back after trimming off the associated fat and connective tissue)3; 3.21% (trimmed fore-end) and 3.47% (trimmed hind leg)3; 3.26% (whole carcase, live weight 150 lb) and 3.65% (whole carcase, live weight 310 lb).* The use of a multiplicity of these factors is hardly practicable as the origin of the meat is seldom known in detail; however, the grand average of 3.45% is useful within the limitations outlined. In comminuted products the effect of variations between individual animals and between anatomical positions is alleviated somewhat by the scale of mixing, but further uncertainty can now arise because of the effects of processing and the possible addition of other nitrogenous ingredients, particularly proteins in the form of connective tissue, blood, milk, wheat, soya and other vegetable proteins.While the Kjeldahl method will continue to provide convenient and useful analytical data, it cannot distinguish between individual proteins in a mixed meat product. More sophisticated approaches are being tested, including histology, electrophoresis, immunoassay, peptide - amino acid analysis andOctober, 1984 THE ANALYST IN COURT 385 indirect methods involving non-protein analytes associated with the protein to be monitored. In particular, collagen in connective tissue is often determined through its content of the characteristic amino acid hydroxyproline (H); this again involves factors ( e .g . , dry collagen, 7.2H; wet connective tissue, 37H) which, like the nitrogen factors, are useful but only approximate. Because muscle protein (actomyosin) contains the unusual amino acid NT-methylhistidine, its levels can similarly be determined with the same reservations.4 The direct specific determination of the major meat proteins themselves can therefore be envisaged; however, non-meat proteins do not often contain such convenient markers. Wheat protein from rusk is normally measured indirectly by calculating the carbohydrate level by difference and assuming that 2% of its mass corresponds to the wheat protein nitrogen; this factor is again an appraximation, and moreover is only applicable when all of the carbohydrate is due to wheat rusk and not to more refined polysaccharide ingredients ( e .g . , farina) now in use. More general direct methods for the determination of individual proteinaceous ingredients in meat products are now being established, of which enzyme-linked immunosorbent assay (ELISA) is recommended.5 An ELISA procedure for soya protein6 has been ring-tested with encouraging results; specificity and accuracy are satisfactory when appropriate standards are used, but the precision needs improvement . 7 References 1. Sawyer, R . , in Birch, G. G . , and Parker, K. J . , Editors, “Control of Food Quality and Food Analysis,” 2. Analytical Methods Committee, Analyst, 1961, 86, 557.3. Harrison, N . , J . Assoc. Public Anal., 1983, 21, 59. 4. Jones, D . , Shorley, D., and Hitchcock, C., J . Sci. Food Agric., 1982, 33, 677. 5. Hitchcock, C. H. S., and Crimes, A . A . , Anal. Proc., 1983, 20, 413. 6. Hitchcock, C. H. S . , Bailey, F. J . , Crimes, A . A . , Dean, D. A. G., and Davis, P. J . , J . Sci. Food Agric., 7. Crimes, A. A., Hitchcock, C. H. S., and Wood, R . , J . Assoc. Public Anal., 1984, in the press. Elsevier Applied Science Publishers Ltd., Ripple Road, Barking, Essex, 1984, pp. 39-64. 1981,32, 157. The Independent Consultant as Civil Forensic Scientist and Referee D. Simpson Analysis For Industry, Factories 213, Bosworth House, High Street, Thorpe-le-Soken, Essex, C016 OEA I begin with an indicative (not exhaustive) summary of the types of dispute which may be encountered in independent practice.Types of Dispute Working Conditions Apart from the relatively small number of incidents that give rise to criminal proceedings, there are many instances in which there is a wish to improve working conditions and to meet complaints, and these involve establishing the circumstances in objective and quantitative terms. Accident or insurance claims may make it necessary to compare working environments, arrangements of machinery and processes, and so forth. Usually in our experience the parties concerned cooperate fully with the attempt by the independent expert to establish facts. Environment Environmental matters arise not only within factories and working establishments but in many different situations-in domestic premises, public buildings, harbours and the open air.Apart also from the great variety of sites that may be involved, the actual nature of any dispute can vary greatly. One endeavours to undertake an investigation under typical conditions, and so to eliminate as far as possible the element of fantasy or speculation that does sometimes arise. Manufacturing The manufacturing establishment can generate many problems: with its specifications for materials and products, with faults, with special overseas or domestic legal requirements, with patents, machinery supplies, new developments, additives, finishes, modifications, terminology, test methods, language, contracts and the understanding or misunderstanding of these.No matter how well run anAnal. Proc., Vol. 21 establishment may be the question of maintaining uniform quality and standards will always require attention. 386 THE ANALYST IN COURT Suppliers of Goods and Services Good operating practices, of course, are not only required of manufacturing establishments-a similar approach is essential also in warehousing, transport in its various forms, retail distribution and other service activities. Claims can arise from defects or alleged defects, failure to supply as specified within the delivery period, from failures of refrigeration, taint, accident, inadequate stock control, defective packing and so on. The Public at Large Finally, I would mention the public at large and its requirements for independent help not only with complaints in respect of a great variety of foods and manufactured goods but also its lively interest in topics such as the deterioration of materials, the condition of ponds, waterways and the sea and occasionally some extraordinary forms of damage to paint finishes.Discussion So it is that the independent organisations have a varied clientele for forensic work or arbitration, including insurance companies, loss adjusters, solicitors and barristers, farmers, companies, architects and surveyors, conservancy boards, consumer and public protection and other official agencies. The independent organisations and individual consultants advertise comparatively little and have been overshadowed, so that it is not always appreciated to what extent they can be of help.Their resources are limited, even constrained, but a surprising number of practices exists, and together they constitute a substantial store of knowledge, experience, judgement and skill. For most fields of knowledge, even remote ones, some independent expert will be available. He or she may be found through an appropriate professional organisation, by a search of the literature and publications or by recommendation. He would be bound by the code of ethics of the appropriate professional organisation and normally would be well qualified and equipped with some years of practical experience. In addition to training. some of the qualities he must have would be as follows. (i) Ability to command the attention and respect of the Court; (ii) ability to study and to assimilate quickly detailed and often voluminous documentation; (iii) ability to listen and to judge; (iv) ability to convey reasons, often complex and technical, in clear terms; (v) plus a considerable amount of patience (sometimes with the client).I feel that an analytical training may be particularly suitable for work of this nature, as the analyst will be accustomed to dealing with samples from many different activities, and will define the nature of a problem, apply control techniques and so forth. Most analytical work involves some degree of investigation, and often this is a large element. In every new problem there are certain essential questions to examine: (i) what are the technical considerations? (ii) what are the merits of the technical reports and arguments on both sides? (iii) what are the defects? (iv) does the issue turn on these technical matters and can they be resolved? Sometimes a dispute cannot be resolved in the technical sense-as in the case, for example, of material supplied to one standard not complying with another different one.A number of practical examples were given of the types of problems encountered and the approach adopted in each instance, including consumer products, allegations of contamination by airborne particles, accidents, sensitivity to monomers, and so forth. In doing so an attempt was made to emphasise the similarities between cases and certainly there are many of these. Often, however, the situation appears ambiguous-or perhaps “amorphous” would be a better word.The client may be uncertain as to his own requirements. He may not appreciate the position of the independent expert as a witness of the Court. To some extent the expert can guide events and determine a course of action, but circumstances and personalities may well intervene. It is not always easy to obtain full information from the parties and this can make matters a little difficult, especially if the consultant is not called in-as does happen-until only a short time before the hearing. Searching for each piece of information can be a delicate task and perhaps painful to the client-a little like the dentist searching for the toothOctober, 1984 THE ANALYST IN COURT 387 causing the pain. Occasionally the opposite extreme arises and one is swamped with documentation, some having no relevance to the case, and difficulty may be experienced from time to time as a result of the supply of incorrect information. It may be desirable, or necessary, to spend time explaining to the client what form of analysis is really needed.In the first instance “full analysis” may have been requested, while much of this will not be relevant. Then there is the choice of method, controls, etc. If there is an expert “on the other side” the same samples will have to be taken and divided. The problem may arise of putting results tactfully to a client who is relying upon one to give answers showing that he is not at fault. The adversary system that has developed and become established in British Courts has many great advantages and it can often be a pleasure to hear disputes in which much heat and even passion have been aroused being explored politely, delicately, objectively and thoroughly by opposing counsel.It is useful to remember that for every opinion there may be a contrary one that someone will be prepared to express. Experts will be called by the defendant as well as by the plaintiff and one may sometimes wonder in advance what the other expert witness will say-but in my experience those on both sides invariably are on good terms and if the analytical results are known it is unusual to find that they vary to any extent. There may be differences in interpretation but again this might occur because one of the analysts has been given information not available to the other. The Development of Statutory Methods of Analysis and Sampling for Foodstuffs Roger Wood Ministry of Agriculture, Fisheries and Food, 65 Romney Street, London, SW1 P 3RD Prior to the accession of the UK to the European Community (EC) in 1973 there were, effectively, no methods of analysis for foodstuffs in Regulations made under the Food and Drugs Acts.Since accession, a considerable number of such methods have been introduced and this introduction appears to be an irreversible trend. It has therefore been necessary to cope with a different situation in which Central Government, and for foodstuffs this means the Ministry of Agriculture, Fisheries and Food (MAFF), has played a significant role in developing and prescribing defined methods of analysis for foodstuffs. It has also been necessary to ensure that, as far as is practicable, these prescribed methods are satisfactory and some indication will be given as to how this is, hopefully, achieved. In addition, some indication will also be given of possible future developments in this area-the most important of which is that sampling procedures may also be incorporated into legislation.General Reasons for Statutory Methods of Analysis and Sampling in Foodstuffs When statutory methods for foodstuffs were first being developed in the UK there was considerable criticism received by MAFF that they were being discussed at all. There were many objections to the loss of the traditional freedom of the analyst to choose his own method as he thinks fit. The principal driving force for the adoption of statutory methods comes from EC activities, as all EC Directives for Foodstuffs adopted under the Food Harmonisation Programme, be they additive, contaminant or commodity orientated, state amongst their Articles that “methods of analysis and sampling shall be drawn up to verify the provisions of the Directive.” In addition, it is stated such methods will be adopted by the Community under the Standing Committee for Foodstuffs procedure.Ideally, the “parent” EC Directives should be negotiated at the same time as the methods of analysis or sampling Directives, but what often happens in practice is that the parent commodity Directive is negotiated and adopted and the methods Directives are then negotiated subsequently! There are strong scientific reasons for developing statutory methods; the strongest of these is the link between the values of criteria in a Standard and the methods used to ascertain these values.In many instances such values are obtained by empirical methods, i.e., the value is dependent on the method used and the application of two different methods to the same sample would result in two different values. In such a situation it is very difficult to argue against a method being prescribed by legislation. This fact is recognised by the Codex Alimentarius Commission in that organisation’s “General Principles for the Selection and Establishment of Codex Methods of Sampling and Analysis”; these General Principles may be considered to form the best text on the subject.388 THE ANALYST IN COURT Anal. Proc., Vol.21 It should be emphasised that the reasons for having statutory methods of sampling are just as applicable when sampling procedures are considered, i.e., the link between the value of criterion in the Standard and method of sampling is as strong, or even stronger, than in the case of analysis. This would be best illustrated by a practical example of this in an adopted EC Directive. The common standard of a maximum of 1.5% fat content in dried skimmed milk powder has been agreed by the Community (see the Preserved Milk Directive). That value may be assessed by various methods for fat determination, all of which may give a different result when applied to the sample. To prevent this, the Community has adopted a single procedure for fat content applicable to these samples (see the first Methods of Analysis for Preserved Milk Products Directive).However, there is still no agreement in the Community on the application and enforcement aspects of the Standard. In some Member States ( e . g . , in the UK) the Standard would be interpreted as meaning that every item as sold should conform to it. However, the Standard may be interpreted in other Member States that the average of, say, ten individual items (whether analysed separately or bulked) should conform to the limit of 1.5%, but that some individual items may be in excess of 1.5%. This could mean that manufacturers in the former Member States need to produce dried skimmed milk powder to a higher specification (lower fat content) than those manufacturers in the latter Member States (or alternatively, that the consumers in the former Member States are better protected than in the latter). Such differences between the Member States are occurring even with agreed commodity standards.It is to eliminate differences in interpretation of this type between Member States of the requirements or intent of food compositional standards that the issue of sampling, as well as methods of analysis, must be resolved within the Community. Procedure for Adoption of EC Directives on Methods of Analysis and Sampling Draft Directives on methods of analysis and sampling are sent from the appropriate Commission Working Groups to the Standing Committee for Foodstuffs for adoption. This Committee acts under a “qualified majority” procedure; it will therefore be immediately clear that the development of the methods of sampling Directives as well as the methods of analysis Directives are different from the parent commodity Directives in that a unanimous vote is not required for them to be subsequently adopted by the Community.This means that no one Member State has a veto in this area and that it could, therefore, be forced to adopt a method with which it was in fundamental disagreement; indeed, this has already happened to one of the “large” Member States and emphasises the need for consultation in this area at an early stage within the UK. Methods of Analysis Validation Procedure for Potential Statutory Methods Potential statutory methods in the UK will be either nationally or Community “inspired.” In both instances it is now MAFF policy to carry out a collaborative trial to evaluate the analytical characteristics of the method under consideration whenever possible.Before the method is subjected to collaborative trial it is thoroughly evaluated at one of the Government laboratories, either at the Laboratory of the Government Chemist or MAFF, or another specialist laboratory if appropriate. It is at this stage when a method’s applicability to a range of samples or substrates will be most thoroughly tested. It is hoped that this evaluation will ensure that there will be no challenge to the applicability of the method in Court. The method is then subjected to a collaborative trial to evaluate its analytical characteristics, and those of repeatability and reproducibil- ity in particular, at different concentration levels, etc.MAFF Collaborative Studies Programme Initiation The collaborative studies programme was initiated about 5 years ago in response to the changing requirements of foodstuff legislation. It remains the most effective procedure for testing and evaluating potential statutory methods. Most of the participants in the trials are Public Analysts together with Government laboratories and industry as appropriate. The results of the trials are normally available as reports, which are given in journals such as that of the Association of Public Analysts.October, I984 THE ANALYST IN COURT 389 D iff icu 1 ties The trial programme has run into a number of difficulties since its inception, caused in the main by lack of experience of the organisers of the trials.Such inevitable difficulties which have been encountered include: (a) trial too complex; (b) trial using methods that had been inadequately pre-tested; (c) trial using inhomogeneous samples; (d) trial using samples of “unauthenticated” origin; (e) trial using participants who were too inexperienced to be able to return “reasonable” results because of lack of pre-trialling. Benefits The main benefit of the collaborative trial programme is that it provides information on which the method being tested can be judged satisfactory or not from the legislative point of view. The main benefit to the “Analyst in Court” is that he has information on which he can justify the validity of his own results. In particular he can: ( i ) assess whether his laboratory is performing satisfactorily or not by seeing whether the results obtained satisfy the repeatability clause that is specified in each method; (ii) assess the range within which the true analytical result will fall from the reproducibility value of the method as obtained from the collaborative trial.It will thus ensure that a prosecution is taken to Court in which the analytical result will not be challenged on the basis of analytical variability, as opposed to sampling error. It is important, however, that the analyst does check his own personal accuracy by the use of reference materials, as using collaborative trial results will not tell him how accurate his own experimental results are. Future developments It is expected that the development of statutory methods will continue at much the same rate as at present, given the strong pressure for this to happen from the Community and that reference materials in the foodstuffs area will become more widely available-especially reference materials that certify criteria which are method dependent.This will be a relatively new concept for reference materials which, until now, have been mainly concerned with discrete chemical entities, e.g., trace elements. Methods of Sampling General It may be expected that sampling and analysis will become more formally “linked” than has been the case in the past as both procedures become prescribed by legislation. Sampling in this context is not the procedure whereby samples are physically obtained, but only the numbers of items that are taken and the interpretation that is to be placed on any analytical results.The main reason for the possible elimination of the different sampling systems in the Community has already been described. There is a move towards acceptance sampling schemes, certainly within the other Member States of the Community, and possibly within the UK in future. If this does occur the analyst will, in Court, not only have to be aware of the analytical interpretation of his results on each sample, but will also be expected to make an interpretation on the sampling plan on which he is recommending the rejection of a lot on the basis of the sample he had analysed in his own laboratory. There will also be a need to educate the Courts on the statistical approach and terms used in such sampling plans.For these reasons, it is worthwhile outlining the present developments in the sampling for foodstuffs area. Action That has Been Taken by the EC It was a result of UK and some other member States’ worries about the potential development and implementation of unsatisfactory sampling Directives, unsatisfactory in the sense that they would conflict fundamentally with our UK or their own practice and law, that the Community agreed to draw up a questionnaire on the sampling and enforcement provisions that take place in each member State with a view to seeing if any harmonisation of approach could be achieved. In the event this exercise never really “got off the ground” and was overtaken by events in the Codex Alimentarius Commission forum.Action That has Been Taken by the Codex Alimentarius Commission The work that is taking place or has taken place under the Codex Alimentarius Commission umbrella has been particularly useful and will have an impact far greater than is often the case with CodexTHE ANALYST IN COURT Anal. Proc., Vol. 21 390 activities. Many Governments may well not have yet appreciated exactly what Codex has already achieved. General Principles for the Establishment or Selection of Codex Sampling Procedures The General Principles for methods of analysis have already been adopted by the Codex Alimentarius Commission and are published in the appropriate section of Fifth Edition of the Procedural Manual of the Commission. The General Principles for the establishment or selection of methods of sampling have recently been developed by the Codex Committee on Methods of Analysis and Sampling (CCMAS) and were sent to the Codex Commission in July 1983; they were adopted at that Commission meeting and subdivide methods of sampling into four types.It is recommended that the sampling plans for compositional criteria are predominantly based on variables procedures with unknown standard deviation. As such, they can be considered to be not in agreement with the standard practice of Member Governments, such as the UK, which uses an “every-i tem-must-compl y ” sys tem. Codex Questionnaire on Sampling/Enforcement Systems for Foodstuffs The CCMAS decided to find out the differences that exist in the different countries that subscribed to the Codex organisation regarding their sampling and enforcement systems for foodstuffs.This, it was hoped, would enable detailed background information to be obtained to allow the extent of any agreement on Codex sampling systems to be estimated over and above that for foodstuffs moving in international trade referred to above. The questionnaire was drawn up by the UK delegation to CCMAS. Of the 13 countries that gave detailed comments, 8 used acceptance sampling schemes for compositional standards, 4 used every-item-must-comply-type systems and one used a mixture of both, depending on the commodities under consideration. Some of the countries that replied were EC Member States and of these, some used acceptance sampling plans, i.e., even within the Community so-called harmonised Community standards are not harmonised at all, especially as different sampling regimes, when applied to the same samples, produce different results regarding acceptance of the lot and interpretation of commodity standards.This non-harmonisation of so called harmonised standards is appreciated within the European Community Commission and it may be expected that a determined effort will be made to obtain truly harmonised standards for foodstuffs at some stage. Notes for Guidance for Codex Commodity Committees It was agreed by delegates to the last CCMAS meeting that, provided the General Principles for the Establishment or Selection of Codex Sampling Procedures were adopted by the Codex Alimentarius Commission, then “Notes for Guidance” should be drawn up to inform delegates to Codex Commodity Committees exactly what the implications are of the General Principles having been accepted.The delegations of the UK and the USA were to collaborate in preparing these Notes, which have now been finalised. The most important aspect emphasised in the Notes is that it will be necessary for delegates to Codex Commodity Committees not to go to such Committees with the pre-conceived idea of taking the value of any particular criterion in a Standard from their own national legislation and negotiating for the same value in an equivalent Codex Standard. Guidance will be given for the probabilities associated with individual plans and it will then be for the delegates to the Commodity Committees to select the degree of confidence that they wish to have in their sampling plans. However, as an over-all principle, the Codex has now accepted the use of acceptance sampling plans, and now needs to tie the values of criteria in the Standards to such plans.The importance of this work is such that it will make Governments think of the components of a complete Standard, i.e., the value of criteria, the method of analysis to obtain the value of an individual item in a sampling plan and the method of sampling to interpret the analysis results of each item and so obtain the current over-all result, at the same time without letting the methods of sampling and analysis be elaborated subsequently. Once this thinking is accepted in the Codex it must have repercussions in the European Community.October, I984 THE ANALYST IN COURT “Use Reference Samples Rather than Reference Methods“ 391 H.T. Delves Chemical Pathology and Human Metabolism, University of Southampton, Southampton General Hospital, Tremona Road, Southampton, SO9 4XY Biological monitoring of populations to determine the degree of their environmental exposure to lead by means of blood lead analysis requires the participating laboratories to be able to demonstrate analytical accuracy and good inter-laboratory agreements if valid comparisons of data obtained within and between nations are to be made. Evidence is presented here to show that these requirements may be met by allowing laboratories to use their own analytical methods, provided that their analyses are controlled by using reference materials as common internal quality control samples.This is a practical alternative to collaborative studies in which each laboratory uses the same reference method. The data presented were obtained during population studies of lead in whole blood that were carried out by member States of the European Economic Community over the period 1977-82. EC Directive In 1977, the European Commission (EC) published a directive (EC.77/312) that required all Member States to undertake two screening campaigns for lead in their populations, co-ordinated across the Community and separated by an interval of at least 2 years. The Directive called for a minimum of 50 persons per million inhabitants of the country to be included in each campaign and specified three particular categories from which groups were to be studied: (1) persons in major urban areas with populations greater than 500000, i.e., in the UK these were London, Birmingham, Liverpool, Manchester , Leeds, Sheffield and Glasgow ; (2) populations exposed to specific sources of lead, e.g., those living near lead works, living in regions with plumbiferous soils, living near motorway interchanges or receiving a “plumbosolvent water supply”; and (3) critical groups, e.g., children. Sampling was to be carried out on groups of at least 100 persons in group 1 and also in group 2 as far as this was feasible.Reference levels of lead in blood were set, taking into account known relationships between dose and effect and where these levels are exceeded the Member States were required to take all appropriate measures, i.e.? check validity of results, taking action to trace exposure sources and inform (in the UK) the GP responsible for any individual with a high blood lead. These reference levels were a maximum of 20 pg per 100 ml for 50% of the population examined, a maximum of 30 pg per 100 ml for 90% of the population examined and a maximum of 35 pg per 100 ml for 98% of the population examined. (It should be noted that the EC have not used SI units for blood lead concentrations; for consistency these conventional units will continue to be used here). Member States were required to nominate laboratories, to inform the Commission of the analytical methods used, to organise, in conjunction with the Commission, intercomparison programmes and to examine the results of these programmes with a view to improving the comparability of the methods of analysis.The necessity for these requirements was obvious because the first campaign was to involve initially 56 laboratories in 9 Members States of the EEC. In the UK, the nominated laboratories were the Supra-Regional Assay Service (SAS) Laboratories, which had been established in 1972 by the DHSS for blood lead analyses, plus an associated laboratory in Scotland. Because of this laboratory’s interest in and experience of environmental lead studies of children, the author was elected to represent the SAS laboratories on the UK Steering Group responsible for implementing the EC Directive with responsibilities for all aspects of blood lead analysis from sample collection to quality control.Common Internal Quality Control In 1977, independently of the EC Directive, the SAS laboratories had begun to use common internal quality control (IQC) blood samples as a means of improving inter-laboratory agreement. Originally the concept of W. B. Yeoman. then the Director of the Regional Toxicology Unit at Dudley Road Hospital, Birmingham, this system utilised two samples of whole blood prepared from one large pool of compatible blood. The pool was divided into two halves. to one of which was added a known concentration of lead so that the difference in lead concentrations would be accurately known. Aliquots of each of the two samples were sent to all participating laboratories where they were analysed. From the results, accepted concentration limits were ascribed.Each of the laboratories was required to analyse both IQC samples, in duplicate. with every batch of 10 test samples. The results of392 THE ANALYST IN COURT Anal. Proc., Vol. 21 both IQCs that bounded each batch of 10 test samples had to fall within their accepted limits for the results of the test samples to be accepted. If any of the results of the IQCs were outside their accepted limits then no results on test samples were to be accepted for that batch and no further analyses were to be carried out until the source of the error had been identified and rectified. The general principles of this common IQC system are similar to others used in many laboratories, but the specific and unique features are that each laboratory uses the same IQC samples with the same limits of acceptance and the same protocol.Acceptable concentration limits were set for the IQCs using the consensus mean as the most probable value with consideration given to the recovery of added lead and to the shape of the distribution of results. Fixed concentration limits of k1.5 pg per 100 ml (low IQC) to k4.0 pg per 100 ml (high IQC) were set about the respective means. These limits were narrower than those given by the mean k two standard deviations to encourage laboratories with the results at the extremities of the distributions to modify their methods. The efficacy of the common IQC system was assessed in an external quality assessment (EQA) programme. The inter-laboratory agreement of the SAS laboratories, which was already good, improved from a relative standard deviation of 10.3% to 8.0% for the &week periods immediately before and after the instigation of the common IQC system.National Representatives responsible for implementing the EC Directive were persuaded to adopt this type of common IQC system for laboratories undertaking the blood lead analyses. An initial evaluation of a limited supply of IQCs available from the UK by 30 other European laboratories was encouraging (Table I). The group mean concentrations of lead agreed well with the reference method of isotope dilution mass spectrometry (IDMS) and both data sets gave quantitative recovery of added lead. The proposed reference method using atomic-absorption spectrometry with electrothermal atomisation (ETA-AAS) gave slightly lower values and a lower recovery of added lead.These data showed that, at that time, there was no suitable reference method for blood lead analysis for environmental surveys because IDMS was too slow and could not be used for large numbers of samples, and the ETA-AAS method required improvement. Subsequent inter-laboratory studies with fresh IQCs were not so good, with mean recoveries ranging from only 89% to 93% of the added lead. However, further improvements were observed as laboratories participated in an external quality assessment programme. TABLE I FIRST INTERNATIONAL EVALUATION OF UK IQC BLOOD SAMPLES IDMS = isotope dilution mass spectrometry; ETA-AAS = atomic-absorption spectrometry with electrothermal atomisation; micro-FAAS = microsampling cup flame atomic-absorption spectrometry; ASV = anodic-stripping voltammetry.UK limits: orange 17 k 3, blue 70 k 4 pg per 100 ml. Blood lead/pg per 100 ml Reference methods Participants , 7 IDMS ETA- AAS Micro-FAAS ETA-AAS, ASV, . No.of No.of IQC Mean S.D. Mean S.D. Mean S.D. labs. analyses Orange . . . . 13.21 - 11.0 - 15.2 2.1 30 296 Blue . . . . . . 65.52 - 59.1 - 65.6 4.6 30 302 Recovery,% . . 101 93 97 CEC External Quality Assessment Programme An external quality assessment (EQA) progrmme for blood lead analysis was implemented by the CEC with the aims of assessing the comparability of the analytical data reported by the laboratories and ensuring that only those laboratories with good analytical performances would take part in the monitoring excercise.The EQA began in 1978 with two pre-survey phases and continued until 1981 with one phase during each survey (1979, 1981) and one between-survey phase in 1980. During each phase, samples of blood were sent at frequent intervals for analysis by the participants. Replicated samples and samples with added lead were included in this EQA programme to assess the repeatability and accuracy of the analyses. An assessment of the validity of the group median values in these terms may be made from Table 11. The performances of individual laboratories were assessed relative to the group median values. A minimum level of acceptability in the EQA programme was one in which more than 60% of results fellOctober, 1984 THE ANALYST IN COURT TABLE I1 CEC - EQA BLOOD LEAD ANALYSIS: REPEATABILITY AND RECOVERY DATA Group median value/yg per 100 ml 393 Phase 1* Sample Type of No.specimen a b New 6 7 5 Human blood 16 17 7 Bovine blood 5 6 8 Sample 7 + 10 yg per 100 ml 15 16 9 Sample 7 + 20 pg per 100 ml 25 26 10 Sample 7 + 40 pg per 100 ml 43 46 ] IQC 36 37 6 Sample 5 + 20 pg per 100 ml 37 37 * Phase 1, November 1978 to February 1979; phase 2, June 1979 to August 1979. - C 7 37 17 36 6 16 26 45 Phase 2* - - 17 36 9 18 27 46 within an inner zone and more than 80% of results within an outer zone about the group median values. The boundary lines for these zones were the linear extrapolations of k 1.5 pg per 100 ml at 10 pg per 100 ml to f2.5 pg per 100 ml at 60 pg per 100 ml for the inner zone (zone A in Fig. 1) and exactly twice these limits for the outer zone (zones A + B + C in Fig.1). This constraint resulted in the reduction of the number of participants from an initial 56 laboratories in the pre-survey phases of the EQA programme to 33 laboratories that finally participated in the monitoring excercise. In the UK, four out of six nominated SAS laboratories satisfied the EQA criteria at all phases and reported data for the surveys. The results for the UK laboratories in phase 3 are given in Fig. 1 and show an over-all performance of 71 YO and 96% of 134 results within the inner and outer zones, respectively. -6 ' 1 1 I I I I I I I I I I 5 10 15 20 25 30 35 40 45 50 55 60 Median valvedpg dl-' Fig. 1. Results for four UK SAS laboratories (0, 0, 0, m) in CEC - EQA programme, shown as differences from group median values.Parentheses indicate two or more coincident results. Interchange of Survey Samples for Repeated Analysis An additional measure of the validity of the blood lead data for the UK surveys was obtained from the results of exchanging 10% of all survey specimens between paired UK laboratories and also between these laboratories and the CEC reference laboratory at Ispra in Italy. An acceptable level of agreement for this comparison was set at a difference of <4 1.18 per 100 ml for at least 80% of results, with not more than 10% of results differing by 6 pg per 100 ml or greater. In the 1981 campaign a total394 THE ANALYST IN COURT Anal. Proc., Vol. 21 of 358 blood samples with lead concentrations ranging from 5 to 60 pg per 100 ml were exchanged.The results for the two pairs of UK laboratories were, respectively, 98.4% and 99.2% of results agreeing within 4pg per 100ml or less and only 1% and 0.8% differing by 6yg per 100ml or more. The agreement between the UK laboratories and the CEC reference laboratory is shown in Fig. 2. The distribution of the differences is almost Gaussian, with 94.9% of results agreeing within 2 pg per 100 ml and 99.5% agreeing within 4 pg per 100 ml. 1 w Y 0 +2 +4 +6 +8 0 -6 -4 -2 Difference in blood lead, UK- lspra (pg per 100 mi) Fig. 2. Distribution of observed differences in blood lead concentrations between UK SAS laboratories and the CEC Reference Laboratory at Ispra for inter-laboratory analysis. 358 survey samples from UK 1981 campaign were analysed by each of two UK laboratories and by the Ispra laboratory, giving 716 paired results between any UK laboratory and Ispra.The blood lead concentration range of the samples was 5-60 pg per 100 ml. Maximum differences (arrowed) were i-7 and -5 pg per 100 ml for UK minus Ispra; over-all bias, +0.106 pg per 100 ml. (Reproduced from reference 1 with permission of the Department of the Environment.) Conclusions Improvements in inter-laboratory agreements for blood lead analyses have been achieved by laboratories using common IQC samples with a strict quality control protocol. The validity of the analytical data obtained using the common IQC system have been demonstrated by good analytical performances in an international EQA programme. These data plus the excellent level of agreement obtained from the analyses of exchanged survey specimens provide evidence of the validity of the UK results and of their comparability nationally and internationally. It is reasonable to suggest that similar IQC schemes could be established for other types of analyses and that a practical way of improving inter-laboratory agreement for these analyses would be established more easily by using reference materials as common IQCs rather than reference methods.Reference 1. Department of the Environment, Pollution Report No. 10, HM Stationery Office, London, 1983. Analytical Quality Assurance in United Kingdom Public Analysts' Laboratories D. W. Lord County Analyst, Lancashire County Council, County Hall, Preston, PR1 8XN The 47 UK Public Analysts' Laboratories engage in a very wide range of analytical work, for example in the fields of foodstuffs, drugs, agricultural materials, water, waste disposal, building materials, health and safety, consumer goods and air pollution.Such a wide range of work necessitates methods of analysis being drawn from or developed from an equally wide range of recognised sources. Illustrative of these sources are the following. For foods, European Economic Community, Association of Official Analytical Chemists, British Standards Institution, Analytical Methods Committee; for drugs, European Pharmacopoeia; for agriculture, UKOctober, I984 THE ANALYST IN COURT 395 Regulations; for water, Department of the Environment Standing Committee of Analysts; and for health and safety, Health and Safety Executive, National Institute of Occupational Safety and Health.Some of these sources of reference provide with the method of analysis its performance characteristics. Where that is the case, the data assists the individual Public Analyst’s Laboratory in its analytical quality assurance. For example, generally associated with AOAC methods are the results of collaborative testing, giving values of repeatability and reproducibility standard deviations.’ Thus, before adopting an AOAC method an individual laboratory can compare its performance with published data and in the longer term continue to compare performance with a suitable quality control procedure. Similarly DOE water methods generally list the performance characteristics of total or within batch standard deviation, limit of detection, sensitivity, etc.2 Some BSI methods quote British Standard repeatability,3 some NIOSH and EPA methods indicate both a measure of precision and a quality control procedure (sometimes based on spiking experiments).When using methods so described the individual Public Analyst’s Laboratory has quantitative measures to develop its own quality assurance procedures. Many published methods have neither the backing of collaborative testing nor an indication of performance in terms of precision, bias, etc. ; in these circumstances individual laboratories have devised their own systems of internal validation and quality control. Given the extremely wide range of work, the wide range of method sources, the number of Public Analysts Laboratories and their geographical separation, it is perhaps not surprising that different systems of internal analytical quality assurance have been built up over the years.Similarly, individual Public Analyst’s Laboratories have participated in different external systems which assist in quality assurance, some engaging in collaborative trials organised by the Analytical Methods Committee, the Ministry of Agriculture, Fisheries and Food, the Association of Official Analytical Chemists, the Canadian Food and Drugs Authority and the International Union of Pure and Applied Chemistry. Without necessarily decrying the differences in the approach of individual laboratories the Association of Public Analysts has devised a protocol for analytical quality assurance which attempts to standardise the AQA procedures used by Public Analysts.The Association, which is the body that links professional interests of the individual Public Analysts, defines analytical quality assurance as “The Internal and External systems which evaluate a laboratory’s performance and provide for a continuing process of monitoring that performance.” The AQA protocol recommended by the APA is in two parts: firstly, a minimum quality assurance procedure recommended to be achieved internally by an individual laboratory; and secondly, a system of inter-laboratory collaborative testing. The essential elements of the internal quality assurance protocol are as follows. Documentafionlsystem of work. Each method of analysis adopted by a laboratory should be properly documented.There should be training in the application of the method and a system of work that ensures its continued effective use. Performance characteristics. Each adopted method should be validated in order to define: the limit of detection; the within laboratory repeatability precision; and the within laboratory recovery. Quality controlprocedure. A minimum quality control rate of 10% is recommended for each method in regular use. In association with the prescribed performance characteristics the AQA protocol also recommends the minimum amount of data to be used initially to define those characteristics. Limit of detection is defined as the smallest concentration of a constituent for which one can be 95% confident that the constituent can be detected by the method.4 A minimum of eight analytical results is recommended for calculation, viz., Limit of detection = tSb + tS, where Sb = standard deviation calculated from four blank determinations; S , = standard deviation calculated from four sample determinations at a level close to the blank; and t = critical value for the t test (95% probability).Precision is usefully defined in terms of replication experiments, viz., within laboratory repeatability precision (w,) is the maximum absolute difference (95% probability) between two analytical results obtained by the same method in one laboratory. The repeatability precision is applicable to analytical results produced by different analysts on different days using different reagents, etc., and is calculated from wp = t f l s , where S, = standard deviation of replicates under the conditions specified and t = critical value from396 THE ANALYST IN COURT Anal. Proc., Vol.21 the t test (95% probability). For the initial calcualtion of Wp it is recommended that a minimum of six replicates is taken at one appropriate level of concentration. The protocol recommends that a useful indicator of bias is a series of spiking or recovery experiments from which the following are calculated: within laboratory recovery mean value (W,,), which is the mean recovery value (%) calculated from a series of recovery experiments using the same method in one laboratory where recovery results are produced by different analysts on different days using different reagents, etc.; and within laboratory recovery standard deviation (WRS), which is the standard deviation of the series of recovery experiments.Is is also recommended that the values should be initially calculated from a minimum of six recovery experiments carried out at one appropriate level of concentration by two or more analysts over a suitable period of time. It is a fundamental part of the protocol that as a method is put into general use the number of replicates and recovery experiments be increased at the one initial level and at other levels of concentration. Thus, the values of Wp and W,, can be re-estimated, updated and extended over a period of time. Whilst the protocol emphasises the value of spiking experiments it also encourages the use of reference materials to test bias in the results. A few appropriate reference materials are available from the Community Bureau of References and from The National Physical Laboratory.6 Public Analysts are, in fact, actively engaged in assisting the Community Bureau of Reference in investigating the development of further reference specimens.The last part of the internal AQA scheme deals with quality control procedures. Every tenth analysis is recommended to be accompanied by a check on one or more of recovery, precision and the reference specimen. Acceptable quality control checks are those falling within the previously defined performance characteristics (W,,, W,,, W,, or reference specimen data) and control charts are recommended to assist in long term monitoring. In addition to the internal scheme outlined above is the protocol for analytical quality assurance via a system of inter-laboratory collaborative testing. The protocol has the aims of: firstly, assessing the performance of a method through collaborative testing; and secondly, carrying out further collaborative testing with the same method to assess whether performance is being upheld. This is not intended for methods which have already been collaboratively tested but principally for those with little or no performance data. The design of APA collaborative trials is following broadly BS5497 (reference 3) and the guidelines indicated by Wilson.7 The essential stages in organisation of the APA trials are outlined below: the 47 laboratories have been formed into regional groups to allow combinations of around eight laboratories per trial; a Standing Advisory Group on collaborative testing has been formed within the Assocation to act in an advisory capacity to each of the regional groups; methods will be tested at three concentration levels (generally two replicates at each level); each trial has a co-ordinating laboratory responsible for carrying out initial validation work and for testing the homogeneity of trial samples; trial results are co-ordinated and assessed by the co-ordinating laboratory and the Standing Advisory Group and values of British Standard repeatability and reproducibility calculated. In one form or another Public Analysts have operated internal analytical quality assurance schemes since their formation. The move to the standardised internal AQA scheme described can be regarded as a logical development of existing schemes to assist in the co-ordination of effort and to ensure that maximum benefit is derived from the data generally. Whereas this standardisation is becoming established, the external collaborative testing scheme is in its infancy. At the time of writing, three collaborative trials are under way. It is anticipated that the experience of organising such trials will promote the development of the protocol described. Public Analysts will continue to take part in established collaborative testing systems such as those organised by the AOAC, RICE, etc., but will also have available a viable in-house system to form an essential part of over-all laboratory analytical quality assurance. References 1. 2. Youden, W. J., and Steiner, E. H . , “Statistical Manual of the Association of Official Analytical Chemists,” Department of the Environment, “General Principles of Sampling and Accuracy of Results,” “Methods for Association of Official Analytical Chemists, Washington, D.C., 1975. the Examination of Waters and Associated Materials,” HM Stationery Office, London, 1980.October, 1984 EQUIPMENT NEWS 397 3. 4. 5 . 6. 7. “Precision of Test Methods,” BS5497, Part 1, British Standards Institution, London, 1979. Caulcutt, R., and Boddy, R., “Statistics for Analytical Chemists,” Chapman and Hall, London, 1983. “Catalogue of BCR Reference Materials,” Commission of the European Communities, Brussels, Belgium, National Physical Laboratory, “Certified Reference Materials and Transfer Standards,” Department of Wilson, A. L., Analyst, 1979, 104, 273. 1983. Industry, London, 1982.

ISSN:0144-557X    

DOI:10.1039/AP9842100378

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

October, 1984 EQUIPMENT NEWS 397 Equipment News Computing Integrator for Chromatography The Shimadzu C-R3A is a single-channel inte- grator with printer - plotter, capable of measur- ing all peaks by trapezoidal and tangential base line calculation techniques. Calculations include normalisation, internal and external standard, single, double and multi-point calibration. It has 176k of user Random Access Memory available for programming, and a VDU and dual floppy disk drive can be added. Dyson Instruments Ltd., Sunderland House, Station Road, Hetton, Houghton-le-Spring, Tyne and Wear, DH5 OAT. Analysis of Volatiles by Gas Chromatography A thermal-desorption cold trap injector has been developed for automated desorption and cold trapping of volatiles and subsequent injection in a capillary chromatographic system.Chrompack UK Ltd., Unit 4, Indescon Court, Millharbour, London, E l 4 9TN. Cryogenic Control Module for Gas Chromato- The Model 520 allows programmes to be run between +450 and -79 "C on the makers' Mega Series gas chromatographs. Thermal shocks to fused silica or glass capillary columns are avoided at the start of the cryogenic phase by pre-mixing the coolant in the oven's fan chamber. Erba Science (UK) Ltd., Headlands Trading Estate, Swindon, Wiltshire, SN2 6JQ. Purge and Trap Concentrator The Tekmar LSC-2 is a Bellar and Lichtenberg type system designed for the analysis of drinking and industrial waters. Volatile organics are purged from the aqueous sample, adsorbed on to a trap and thermally desorbed for subsequent chromatographic separation.The LSC-2 does this automatically, controlling the start of a gas chromatograph program or being controlled by a gas chromatograph or computer. Analysis Automation Ltd., Southfield House, Eynsham, Oxford, OX8 1JD. Constant Rate Syringe The CR-700 is adjustable and delivers repeatedly identical sample volumes at identical injection graphy rates. Volume increments as small as 0.1 1-11 can be set by a micrometer device. There are three syringes in the series, of capacities 1-20 1-11, 2-50 1-11 and 10-200 1-11. V. A. Howe & Co. Ltd., 12-14 St. Ann's Crescent, London, SW18 2LS. Micro-scale Gradient System for HPLC The Model 344M is designed for use with 2-mm columns. It employs the Model 114M pump, which features user selectable flow ranges of 0.001-1.00 ml min-1 or 0.01-9.99 ml min-1.A low column dynamic mixer is incorporated, which blends and mixes even difficult solvents at low flow-rates. Beckman-RIIC Ltd., Progress Road, Sands Industrial Estate, High Wycombe, Buckingham- shire. Ultraviolet Detector for HPLC The LC-95 is a variable wavelength ultraviolet- visible detector with a noise level specified at +0.00001 absorbance units measured at 240 nm. The standard wavelength range is 190-700 nm and a cut-off filter protects against second-order radiation at wavelengths above 400 nm. Three self-aligning , quick-change flow cells are avail- able: an 18 1-11, 16 mm path length flow cell with instrumental band width of 50 1-11; a 4.5 p1 cell with band width of 20 pl; and a 1.4 1-11 cell with band width of 10 1-11.Perkin-Elmer Ltd., Post Office Lane, Beacons- field, Buckinghamshire, HP9 1QA. Liquid Chromatography System The Routine 100 is a fully programmable system. When combined with a suitable detector and recorder or data handling device it becomes a computer automated liquid chromatography system. Its main elements are the ISS-100 auto-398 EQUIPMENT NEWS Anal. Proc., Vol. 21 sampler, the Series 10 pump unit and the SSV-1 solvent selection valve. Perkin-Elmer Ltd., Post Office Lane, Beacons- field, Buckinghamshire, HP9 1QA. Ion Chromatography Using Standard HPLC The IonoSpher A ion-exchange column, intro- duced in co-operation with Akzo, is suitable for the analysis of inorganic anions by a method developed by Buytenhuys. Aromatic counter ions are used to make the components detectable with a refractive index detector.Chrompak UK Ltd., 61 Shrubbery Road, London, SW16. pH Electrodes A range of Orion electrodes is announced. It includes an epoxy bodied electrode, which gives the same readings as the other Ross electrodes, viz., stable to 0.01 pH in less than 30 s even in samples varying from one another by 50 "C. Electrode drift is less than 0.002 pH d-1. MSE Scientific Instruments, Manor Royal, Crawley, Sussex, RHlO 2QQ. Digital Thermometer The Jenway 1001 Series covers a temperature range of -30 to +45 " c to an accuracy of 0.3% k last digit and a resolution of 1.0 "C. It is designed for use with a variety of NiCr/NiAl thermo- couples. Automatic cold junction compensation is standard. Lenton Thermal Designs Ltd., 12/14 Fairfield Road, Market Harborough, Leicestershire, LE 16 9QQ.Digital Thermometer The Model 1003 features switch-selectable "F or "C measurement within the ranges -30 to +1200 "C or -20 to +1999 OF, and switchable resolutions of 1.0 or 0.1 "C or OF. Accuracy is assured at 0.5% +_ 0.5 "C or 1.0 OF. Automatic cold junction compensation is standard. Jenway Ltd. , Gransmore Green, Felsted, Dun- mow, Essex, CM6 3LB. Cool Plasma Asher Available complete with refluxing heater, the CPA-1 can handle samples such as PVC, PTFE, polyamide, polyesters, leather, coal, sugar, graphite and active carbon. Up to 3 g of organic or biological material can be ashed within a few hours, with oxygen being excited to a plasma at low pressure using a high frequency field (27.12 MHz).It features a sample chamber with an integrated condenser of quartz glass, which mini- mises volatility losses for elements such as arsenic and selenium. All volatile elements except mer- cury remain in the condenser; mercury can be detected quantitatively by means of a gold absor- ber in the return pipe. Paar Scientific Ltd., 594 Kingston Road, Raynes Park, London, S.W.20. Atomic-absorption Spectrophotometer The Shimadzu AA670 atomic absorption - flame emission instrument, having been instructed to determine any chosen element , will automatically select the optimum lamp current, slit width, gas flow-rates and type of flame; it will then run the analysis and present the operational parameters, the working curve, the absorbance curve and the processed data.A motorised lamp turret can accept eight hollow cathode lamps, and placing of the correct lamp in the optical path is automatic. V. A. Howe & Co. Ltd., 12/14 St. Ann's Crescent, London, SW18 2LS. Microscope The Olympus Vanox-S photographic research microscope features automatic control of the main adjustments: intensity, objective selection and Kohler illumination are automatically set to suit the chosen objective. Any one of the three cameras (two 35 mm and one large format) can be brought into operation by pressing a switch. Also featured are reflex viewing and autofocusing for low power objectives. Gallenkamp, P.O. Box 290, Technic0 House, Christopher Street, London, EC2P 2ER. Surface Area Analyser The Micromeritics FlowSorb 2300 uses a gas flow sorption system to perform rapid BET measure- ments on particulate matter.It permits the analysis of sample surface area from 0.01 to over 1000 m2 g-1 with a reproducibility of typically better than 0.5%. Only one injection calibration is required per day. Coulter Electronics Ltd., Northwell Drive, Luton, Bedfordshire, LU3 3RH. Data Management and Control System for Fluorescence Activated Cell Sorting The Consort 40, launched by Becton Dickinson, is based on the PDP 11 computer with 256k Random Access Memory. Information is stored on one of three options: a double sided, double- density floppy disk (2.04 Mbyte) and two Win- chester - floppy disk combinations (8.8 and 31.4 Mbyte). Built-in software provides one-, two- or three-dimensional dot plots or histograms to show the relationship between cells of various types or sizes. Laboratory Impex Ltd., Lion Road.Twicken- ham, Middlesex.October, 1984 EQUIPMENT NEWS 399 Fluorophotometer The Fluorotron Master consists of a precision optical scanning head coupled to a dedicated computer, with a visual display, dual disk drive and a data - graphic printer. Software is designed to suppress artifacts and enhance the required data. The standard protocol is for scanning in a cell. Options include an anterior chamber adaptor and specialised anterior chamber soft- ware. Coherent (UK) Ltd., Cambridge Science Park, Milton Road, Cambridge, CB4 4BH. Clinical Chemistry Analyser The Kem-0-Mat 2 has been improved by the addition of software. Throughput is up to 320 samples h-1 in the end-point mode or 280 samples h-1 in the kinetic mode.Automatic initial self- test programs and subsequent continuous moni- toring are featured. User definable quality con- trol mean and confidence limits can be set and data are accumulated at two levels automatically. Levey - Jennings plots are available from the standard printer. Coulter Electronics Ltd., Northwell Drive, Luton, Bedfordshire, LU3 3RH. Diluter - Dispenser Hamilton have developed Microlab MT for use with Micro-Titer plates. It incorporates a single drive motor which drives four syringes, giving four independent liquid lines. Reproducibility and accuracy are within 99%. The MT can accept up to 99 user-written programs, each with up to 96 steps. V. A. Howe & Co. Ltd., 12-14 St. Ann's Crescent, London, SW18 2LS.Water Resistivity - Conductivity Measurement The Thornton range of meters includes the 4 h - h analogue triple scale 822 and its digital counter- part, the 832. The 822 incorporates a 0-10 V d.c. output for direct connection to a recorder. Each recorder can operate with two sensor cells, and there is a choice of cell selector switch boxes for four or twelve readouts. Electrodes are made of titanium with dual thermistors for automatic temperature compensation referenced to 25 "C. Semat Technical (UK) Ltd., 223 Hatfield Road, St Albans, Hertfordshire, AL1 4UN. Battery-portable Dissolved Oxygen Meter The EIL Model 7135 is accurate to 0.01 p.p.m. and gives a digital readout of oxygen concentra- tion in the range 0-19.99 mg 1-1 or 0-199.9% saturation over a temperature range of -5 to +50 "C.It comes complete with the EIL Model 7136 combined oxygen and temperature sensor. Kent Industrial Measurements Ltd., Analytical Instruments, Hanworth Lane, Chertsey, Surrey, KT16 9LF. Multi-range Meter A cased version of the Harmony dual read-out, digital - analogue programmable panel meter is announced. The case is for a standard DIN aperture and is held to the panel from the rear by two clamp screws. Sifam Ltd., Woodland Road, Torquay, Devon. Low-temperature Freezer The Sanyo MDF-440 incorporates a dual freezing system which circulates two types of refrigerant through different compressors. This system will keep the temperature inside the freezer at -40 "C, even if the outside temperature reaches 35 "C. Storage capacity is 15 ft3. The unit incor- porates a no-frost design rigid polyurethane foam insulation. Gallenkamp, P.O.Box 290, Technic0 House, Christopher Street, London, EC2P 2ER. Vortex Mixer The Thermolyne Maxi-Mix I1 allows several tubes to be vortexed together. The mixing action can be smoothly varied from 100 to 3000 rev min-1. Clandon Scientific Ltd., Lysons Avenue, Ash Vale, Aldershot, Hampshire, GU12 SRQ. Electromagnetic Flow Meters The Veriflux VTC range, designed for use with conductive liquids and slurries, consists of nine flow meters covering nominal bores from 0.015 to 640 m3 h-1. Accuracy is +0.5'/0 of actual flow independent of fluid viscosity, density and tem- perature. Kent Industrial Measurement Ltd., Flow Pro- ducts, Oldens Lane, Stonehouse, Gloucester- shire, GLlO 3TA. Spectrophotometer The Shimadzu IR435 is a fully microprocessor controlled infrared recording instrument.The optical system is double-beam optical attenuation with a globar light source, featuring three-stage400 EQUIPMENT NEWS Anal. Proc., Vol. 21 automatic intensity adjustment. The dual grating monochromator offers a selectable changeover of grating in the range 1400-1100 cm-1. A parallel head printer enables simultaneous printout of spectrum and frame, and an effective multiple recording capability. V. A. Howe & Company Ltd., 12-14, St Ann’s Crescent, London, S W 18 2LS. Diffractometer The PW 1840 X-ray powder diffractometer incor- porates a solid-state detector and a self adjusting divergence slit, which is integrated with the X-ray source, permits rapid alignment and ensures stable, highly reproducible operation.Designed particularly for routine sample screening in industry and health care, the instrument is also suitable for educational use. Pye Unicam Ltd., York Street, Cambridge, CB12PX. Multi-column GC Analysis A satellite oven and a dual-valve switching unit are available for use with the Shimadzu GC-9A and GC-9AM gas chromatographs. The satellite oven is linked to the main oven through an independently heated metal tube; it can house capillary columns, or glass or metal packed columns, and can be equipped with a cryogenic unit. The automatic switching valve unit includes two independently operated six-way valves, each with its own electronically actuated switch con- trol. Dyson Instruments Ltd., Sunderland House, Station Road, Hetton, Houghton-le-Spring, Tyne and Wear, DH5 OAT.Splitless Injector Control Module for Gas Chro- matography The SL 516 module is compatible with the maker’s Mega Series gas chromatographs and with their 4000 Series instruments. and replaces the existing Model SL 416. Erba Science (UK) Ltd., Headlands Trading Estate, Swindon, Wiltshire, SN2 6JQ. Variable Wavelength Detector Two new versions of the spectroMonitor 111, Model 1204A, detector are announced. One includes the maxN Series high efficiency, high pressure fluid cell; the other includes both the maxN cell and a digital display of absorbance. Both versions feature a linear sensitivity range of 0.001-2.00 a.u.f.s. Laboratory Data Control (UK) Ltd., Milton Roy House, High Street, Stone, Staffordshire, ST15 8AR.Autozero Accessory Module A stand-alone module is available for use in conjunction with the maker’s complete line of detectors. The unit will compensate for L0.7 a.u. of background offset. The Autozero function can be triggered remotely by a switch closure from any data system controller or autosampler. Laboratory Data Control (UK) Ltd., Milton Roy House, High Street, Stone, Staffordshire, ST15 8AR. Capillary Gas Chromatography Retention Index Library The library, from Sadtler Research Laboratories, is available in both printed and fully digitised formats, and it can be used independently or together with gas chromatography - mass spec- trometry or gas chromatography - Fourier trans- form infrared. In addition to retention index data the library provides for each compound its Chemical Abstracts name and available synonyms, molecular formula and structure, rela- tive molecular mass, melting-point , boiling-point , CAS Registry Number, Sadtler infrared grating and vapour phase numbers, Sadtler proton and carbon- 13 nuclear magnetic resonance numbers and Sadtler ultraviolet - visible number.Heyden and Son Ltd., Spectrum House, Hill- view Gardens, London, NW4 2JQ. Portable X-ray Fluorescence Outokumpu of Finland have increased the sensi- tivity of their X-Met battery powered X-ray fluorescence analyser so that it can determine nickel, copper, iron, zinc and calcium in trees, humus and dried peat samples, on site and within a few minutes. It has been found that the metal 8October, 1984 EQUIPMENT NEWS 401 content of plants often corresponds to that of the soil they are growing in.By measuring the elements present in trees over a fairly wide area it is possible to construct a map and then examine it for zones of anomalous concentrations. Clandon Scientific Ltd., Lysons Avenue, Ash Vale, Aldershot, Hampshire, GU12 5QR. Automated Quality Control The Amica system combines the features of several analysers and it has capabilities for sample preparation, automatic sampling, either discrete or on-line, and mixing of liquids in variable ratios. The analysis can be performed by photometry, photometric titration or potentiometric titration. Developed by Hamilton in co-operation with Ciba-Geigy AG, Basle, the system has found many pharmaceutical applications.V. A. Howe & Company Ltd., 12-14 St. Ann's Crescent, London, SW18 2LS. Relative Humidity Meter The Series 5500 hand-held instrument also reads temperature. Offering a resolution of l % , it uses two sensors, one measuring the dry temperature and the other the wet temperature of air drawn across them by a sealed fan. Separate sensors for air, liquid or surface temperature are available and provide operation within the range from -30 to +150 "C to an accuracy of k0.5 "C. Jenway Ltd.) Gransmore Green, Felsted. Dun- mow, Essex, CM6 3LB. Conductivity Meter The CM21 is a portable instrument. Its linear calibration has a width of 3% in showing the range 1-10 yS, but it is connected to a 5-range multiplier control, which takes the reading in multiples of 10 to the 10000-100000 yS scale.Automatic tem- perature compensation is provided. Datronix Controls Ltd., Datronix House, Lower King's Road, Berkhamsted, Hertford- shire, HP4 2AE. Conductivity Detector The conductoMonitor TI1 is designed to measure continuously the electrical conductivity of solu- tions containing organic anions and inorganic cations. It features closed loop active temperature control of the cell, so that no temperature correction - compensation adjustment is ever required. The noise specification is 1 nS (1% at 0.1 yS range) and background drift is 10 nS h-1 (10% at 0.1 yS range). Also featured are a sensitivity range of 0.1 yS-10mS (in 11 steps) and selectable response active filtering of 0.05, 0.1,0.5, 1.0and5.0~. Laboratory Data Control (UK) Ltd., Milton Roy House, High Street, Stone, Staffordshire, ST15 8AR. Portable Meters Three meters are announced. The ECO 291 reads dissolved oxygen in both percentage saturation and concentration units, with a resolution of 0.1% and 0.1 p.p.m. The measurement range is 0-199.9% saturation or 0-19.9 p.p.m. The ECC 251 measures conductivity over four ranges, and can function as a digital thermometer. The ECM 202 is a pH - ion meter and can be used with all pH and ion-selective electrodes. It has a resolu- tion of 0.01 pH unit or 1 mV over the range 0-51999 mV, and it can be used as a digital thermometer in the range form -30 to +150 "C. All three instruments feature automatic temper- ature compensation. EDT Research, 14 Trading Estate Road, Lon- don, NWlO 7LU. Oxygen Analysers The Teledyne Model 340 series of instruments are now available with a new Food Bag Sampling (FBS) Adapter, providing a method for checking the oxygen content inside food packages.They include an integral hypodermic-type needle and small syringe to pierce the food package and draw a sample into the adapter. Analysis Automation Ltd. ) Southfield House, Eynsham, Oxford, OX8 IJD. Combined Isokinetic Sampling Probe and Electro- static Precipitator The TSI Model 3110 provides a means of collect- ing a sample of airborne particulates from ducts and stacks at temperatures up to 220 "C. No pumps or flow controllers are required and isokinetic sampling is maintained automatically over a range of air speeds. Bristol Industrial and Research Associates Ltd., P.O. Box 2, 6 Combe Road, Portishead, Bristol, BS20 9JB.Diluter - Dispenser The Hamilton Microlab "P" has a microprocessor controlled motorised plunger which will drive any one of a variety of the maker's syringes, allowing dispensing of volumes between 0.5 p1 and 50 ml with an accuracy better than 99% and reproducibility of 99.7%. Dispensing and diluting programmes can be fed into the 2k memory. Volume, speed, function, direction, number of step and error are all digitally displayed. V. A. Howe & Company Ltd., 12-14 St. Ann's Crescent, London, SW18 2LS.402 EQUIPMENT NEWS Anal. Proc., Vol. 21 Light Element Microanalysis The ECON IV Detecting Unit provides a means of extending the micro-analytical range from uranium down to boron with improved efficiency for virtually all scanning electron microscopes.It has a mechanical locking device for positive I vacuum seal, along with a choice of beryllium window, thin window or full open position. Interlocking circuitry and cabling allow the win- dow changing mechanism to be interfaced to the vacuum of the scanning electron microscope. EDAX International Inc., P.O. Box 135, Prairie View, IL 60069, USA. Macro Pipettor Tips A Macro Tip for volumes of 1-5 ml is available. It is graduated in 250-p.1 sections and is suitable for most pipettors, although an adapter is required in some instances. Hughes & Hughes Ltd., Elms Industrial Estate, Church Road, Harold Wood, Romford, Essex, RM3 OHR. Micro Pipettors An Ultra-Micro positive displacement pipettor covering the range from 0.5 PI to 5 1-11 has been added to the maker’s range of pipettors.At the other end of the scale there is an adjustable volume pipettor for the range 0.5-2.0 ml. A thin-walled tip minimises operating force and so extends the piston life. Scientific Glass Engineering (UK) Ltd., Pot- ters Lane, Kiln Farm, Milton Keynes, MKll 3LA. Balances and Balance Conversion Mettler have added six new PE electronic preci- sion balances to their range. The various models in the series cover a weighing range up to 6 kg. The user can select either metric or the most important non-metric mass units. Mettler’s Lab- Pac will convert “standard” laboratory balances into multi-function weighing machines. It consists of a Mettler GE 305 application input device and four programme keys, which enable the balance to find the net total, perform percentage determi- nations and weighing, animal weighings, mean value, standard deviations and to show result indications in metric and non-metric units.Gallenkamp, P.O. Box 290, Technic0 House, Christopher Street, London, EC2P 2ER. Centrifuges A range of Heraeus - Christ centrifuges is avail- able. The Haemofuge A is for the rapid determi- nation of the cell volume of blood. The Biofuge A is a combined microlitre haematocrit centrifuge; angle rotors for up to 40 microtubes of different sizes can be inserted as well as a 24-place haematocrit rotor. The Biofuge B has a capacity of up to 160 microtubes; it accommodates a drum rotor for 8 interchangeable tube racks for micro- litre tubes of different sizes.The Medifuge is a small centrifuge for the physician’s laboratory; it is equipped with an angle rotor for 12 tubes of 15 ml. The Varifuge K is fully refrigerated, with temperature control from -30 to +40 “C and the ability to spin 4 x 750 ml. V. A. Howe & Company Ltd., 12-14 St. Ann’s Crescent, London, SW18 2LS. Electrophoresis Reagents Three additions to the Electran range are announced: a new Grade 1 acrylamide with an acrylic acid content below 10 p.p.m., N, N’- bisacrylylcystamine as a cross-linker for soluble polyacrylamide gels (gels can subsequently be solubilised with a thiol reagent such as ethane- thiol), and agarose for isoelectric focusing (it exhibits essentially zero electroendosmosis). BDH Chemicals Ltd., Poole, Dorset. Electrophoresis Kit The SPE-I1 Paragon kit is designed with high resolution in the gammaglobulin region.It con- tains Paragon Blue stain (amido black deriva- tive) and Paragon Violet stain (coomassie blue derivative). The stains are specific for diagnostic determinations of proteins in human serum, urine and CSF. The kit will help, for example, in the diagnosis of multiple sclerosis, with detection of myelomas and oligoclonal bands.October, 1984 EQUIPMENT NEWS 403 Beckman-RIIC Ltd., Progress Road, Sands Industrial Estate, High Wycombe, Buckingham- shire. Therapeutic Drug Monitoring Reagent Kit Analysis with the kit evaluates quinidine and its clinically active derivatives, quinidine-n-oxide, dihydroquinidine , 3-hydroxyquinidine and quini- dinediol. Developed as a homogenous nephelo- metric inhibition immunoassay for the maker's immunochemistry systems, the kit enables the single point assay to be performed as a STAT procedure providing a result in 80 s, or as a routine test. Beckman-RIIC Ltd., Progress Road, Sands Industrial Estate, High Wycombe , Buckingham- shire.Identification of Cancer-causing Chemicals Mutascreen is a fully automated system in which testing is done on bacteria, making use of the fact that carcinogens also act as mutagens. A set of test wells is filled with bacteria that have lost the ability to manufacture histidine; also placed in the tubes are the test substance and some liver enzymes that tend to activate many carcinogens. If the test substance is a mutagen, some of the bacteria will be altered so that they can once again produce the amino acid essential for their growth and colonies of bacteria will appear, causing turbidity.Labsystems Inc., P.O. Box 48723, Chicago, USA. Tube Fittings Tube fittings are now available with I S 0 threads to allow direct connections between fractional and metric size tubing. They connect both frac- tional and metric tubing to equipment with BSP, DIN or JIS threads and ports. Materials include 316 stainless steel, brass and carbon steel in sizes up to Y2 in and 18 mm. Swagelock (UK) Ltd., 3, Kelvin Close, Science Park North, Birchwood, Warrington, WA3 7PB. Controllers Versapak Class 94 microprocessor based process controllers offer accuracy up to 0.05% and a wide variety of input actuations output forms. The prime display consists of 4 digits to indicate and set sequentially all parameters.There is an integral automanual station to provide manual override and ease of process start-up. Honeywell Control Systems Ltd., Honeywell House, Charles Square, Bracknell, Berkshire, RG12 1EB. Signal-conditioning Amplifier The System 2279 offers a gain that is variable from 0 to +72 dB in 6-dB steps, with an accuracy of kO.1 dB. Input impedance is 1MQ and the input d.c. bias current is less than 100 nA. A colour coded bar-graph level indicator in 3- or 6-dB steps is featured. The instrument is compatible with any of the maker's computer interfaces. Kemo Ltd., 9-12 Goodwood Parade, Elmers End, Beckenham, Kent, BR3 3QZ. Microprocessor Development System With the K85 computer and its multi-purpose target board, the MTB-1, the user can specify, design, program, test, modify and de-bug micro- based control units for one-off or low volume production.The main features are in-circuit emulation, full symbolic assembler, de-bug pro- grams, STD or Euro Bus expansion and eprom programmer. Kimberry, 29 Thorney Hedge Road, Chiswick, London, W4 5SB. Particle Counting and Sizing The Kratel Model F features a precision sensor which counts and measures particles using the extinction method. A choice of sampling systems based on vacuum and positive pressure is offered. By choice of sensor, particles in the range 1-6000 pm equivalent diameter can be measured and any liquid (including corrosive ones) can be used as carrier fluid. Sample regulation can be controlled on a time basis which can be set manual to infinity, or automatically using a microprocessor or coupled minicomputer.SEMAT Technical (UK) Ltd., 223 Hatfield Road, St. Albans, Hertfordshire, AL1 4UN. Thermal Analysis System The 7 Series is controlled by the makers' 7500 Professional Computer, which permits multi- tasking instrument operation and data analysis. Modules for the 7 Series include the DSC 7 power compensating differential scanning calor- imeter, offering heating and cooling rates up to 500 "C min-1, and the TGA 7 thermogravimetric analyser provided with automatic furnace cooling and with an optional high temperature furnace for operation up to 1500 "C. The 7 Series is supported by TAS 7, a library of thermal analysis software. Perkin-Elmer Ltd., Post Office Lane, Beacons- field, Buckinghamshire, HP9 1QA.Freeze Dryer The Supermodulyo is a free-standing unit with a castor mounted base. This large capacity unit has automatic hot gas defrosting, a horizontal con- denser for easy removal of ice plugs and an azide404 EQUIPMENT NEWS Anal. Proc., Vol. 21 proof condensing and vacuum system. Access- ories include drum manifolds, a column manifold with 24 ports, a modular heated tray assembly and a shelf unit with stoppering facility. Edwards High Vacuum, Manor Royal, Craw- ley, West Sussex, RHlO 2LW. Gas Blenders The QB100 series instruments provide fresh, accurately blended gas mixtures in set percentage steps or to p.p.b. levels. Two instruments are available: the QBlOl Gas Divider, which mixes two gases (primary and diluent) to give fixed concentration blends from 10% to 90% in 10% steps with a repeatable accuracy to '/2% of selected range, and the QB102 blender, which generates a continuously variable range of gas mixtures, from percentage to p.p.b.levels. The QB102 is available in brass or stainless steel and with fixed total output flow-rates of 1 or 5 1 min-1, giving dynamic dilution ranges of 1000 : 1 and 5000 : 1, respectively. Quantitech Ltd., 75 Garamonde Drive, Wymbush, Milton Keynes, Buckinghamshire, MK8 8DD. Freeze Dryer The SB9 bench-top centrifugal freeze dryer has a 1 1 capacity with a built-in spin-freeze facility. A plastic window over the condenser allows obser- vation of the ice build-up on the low temperature condenser. The standard carrier plates hold up to 116 0.5 ml ampoules.The refrigeration unit has an extraction rate of 120 kcal h-1 at -35 "C. A leaflet gives details of the SB9 and the maker's range of high vacuum pumps. Javac (UK) Ltd., 3 Waverley Lane, Farnham, Surrey, GU9 8EB. Viscometer The AVS 400 automatically carries out data collection, measurement, calculation and print- out. It stores the number of measurements required together with the viscometer constant, calculates the mean value of flow time and the absolute or relative viscosity and provides hard copy of the results. Schott-Gerate GmbH, Im Langgewann 5 , Post- fach 11 30, D-6238 Hofheim/Taunus, FRG. Computers The Series 7000 Professional Computers contain 640 kilobytes of RAM as standard. In an inte- grated workstation, a Series 7000 computer is complete with a detachable keyboard, colour or monochrome graphics display and Winchester and floppy disc drives.Two models are available: the PE 7500 and the PE 7300. An extensive range of software for instrument control, data collec- tion, data storage and graphical manipulation is available for a number of analytical techniques. Perkin-Elmer Ltd., Post Office Lane, Beacons- field, Buckinghamshire, HP9 1QA. Literature A brochure on interference-free trace metal determination with graphite furnace atomic- absorption spectrometry explains the technique and describes graphite furnaces, background correctors, autosamplers, data handling and the stabilised temperature platform furnace (STPF) system. Perkin-Elmer Ltd., Post Office Lane, Beacons- field, Buckinghamshire, HP9 IQA.A 12-page catalogue gives details of gas and liquid chromatography instruments, chromatography data systems and Labnet communication systems. Included is information on the SP9200 labnet computer, which allows a chemist to control and operate chromatographic analysers and data systems from one workstation. Information is also given on special purpose software programs, the (SP)3 series of pre-programmed PROM chips, such as GPC+, OPTIM 1 and AUTOSCAN. Spectra-Physics, Ltd., 17 Brick Knoll Park, St. Albans, Hertfordshire, AL1 5UF. A 12-page brochure describes the capabilities of ion chromatography, giving details of the 2000i ion chromatograph and accessories. The applica- tion of the technique is illustrated with a series of chromatograms, each accompanied by an expla- nation.Dionex (UK) Ltd., Eelmoor Road, Farn- borough, Hampshire, GU14 7QN.October, I984 PUBLICATIONS RECEIVED 405 Three publications are available from Erba Science. One describes the Model 1106 CHN-0-S elemental analyser and its capability for fully automatic operation with the HEC 960 laboratory computer. The second presents the Model 1500 nitrogen analyser and its use with the HEC 960. The third gives an account of an optional kit which allows conversion of the NA automatic nitrogen analyser to handle large non- homogenous carbon samples of up to 100 mg without additional preparation. Erba Science (UK) Ltd. , Headlands Trading Estate, Swindon, Wiltshire, SN2 6JQ. A catalogue, “Laboratory and Industrial Elec- trodes,” covers pH, ion selective, reference and metal electrodes, as well as temperature compen- sators; it also gives details on glass specification and mem brane profiles.Kent Industrial Measurements Ltd. , Analytical Instruments, Hanworth Lane, Chertsey, Surrey, KT16 9LF. An application study sheet describes the use of the DMA35 digital density meter at Beecham Products Ltd. for raw material analysis and quality control on finished products such as Ribena and Quosh, primarily for specific gravity evaluations. The DMA35 is portable and gives an accuracy of kO.001 g cm-3 on a density measuring range of 0.5-1.999 g cm-3. Paar Scientific Ltd., 594 Kingston Road, Raynes Park, London, SW20. A brochure, Number 55, describes an economy gas purifier made from Y4-in wall acrylic material and available with %-in nickel plated brass or stainless-steel fittings. Alltech Associates, Applied Science Ltd., 9a New Street, Carnforth, Lancashire, LA5 9BX. Leaflets describe three microprocessor controlled centrifuges, the RotantdP bench centrifuge, the RotixdRP refrigerated centrifuge and the Rot0 SilentdRP large size refrigerated centrifuge. Andreas Hettich, Postfach 4255, D-7200, Tuttlingen. A high voltage measurement catalogue details additions to the Ross VD and VMP range of precision high voltage probes and dividers, which cover the range 10-900 kV. A range of matching displays, line drivers and fibre-optic data links is also available. Hartley Measurements Ltd., Unit 4, Bear Court, Daneshill East, Basingstoke, Hampshire, RG24 OQT. A leaflet describes a new autodiluter, with which any sample size from 5-500 p1 can be programmed from a touch key pad, together with reagent volumes of 5 p1-5 ml. Gallenkamp, P.O. Box 290, Technic0 House, Christopher Street, London, EC2P 2ER. A leaflet describes the Disc Centrifuge sub- micron particle size analyser designed to produce comparative size distribution curves in the range 0.01 to 60 pm. Joyce-Loebl, Marquisway, Team Valley, Gate- shead, Tyne & Wear, NEll OQW. A brochure describes a range of instruments and their application areas. These range from mic- rodensitometry and electrophoresis, through digital image analysis and particle sizing, to the latest thin solid film technology. Joyce-Loebl, Marquisway, Team Valley, Gates- head, Tyne & Wear, NEll OQW. A leaflet describes a range of portable pH meters. Five models are described. Channel Electronics (Sussex) Ltd., PO Box 58, Seaford, Sussex, BN15 3JB. A booklet, “Preparative Density Gradient Cen- trifugations,” written by A. Fritsch of the Pasteur Institute , discusses principles and practical aspects of zone and isopycnic centrifugation. Beckman-RIIC, Progress Road, Sands Indus- trial Estate, High Wycombe, Buckinghamshire.

ISSN:0144-557X    

DOI:10.1039/AP9842100397

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

October, I984 PUBLICATIONS RECEIVED 405 Publications Received Continuous Culture 8: Biotechnology, Medicine and the Environment. Edited by A. C. R. Dean, D. C. Ellwood and C. G. T. Evans. Pp. 332. Ellis Horwood. 1984. Price f35. ISBN 0 85312 727 1 (Ellis Horwood); 0 470 20042 1 (Halsted Press). Electron Spin Resonance. Volume 8. Edited by P. B. Ayscough. Pp. xvi + 509. Royal Society of Chemistry. 1984. Price f59; $106. ISBN 0 85186 821 5; ISSN 0305 9758. Methods in Enzymology. Volume 96. Biomem- branes. Part J. Membrane Biogenesis: Assembly and Targeting (General Methods, Eukaryotes). Edited by Sidney Fleischer and Becca Fleischer. Pp. lvi + 901. Academic Press. 1984. Price $79. ISBN 0 12 181996 5.406 CONFERENCES AND MEETINGS Topics in Enzyme and Fermentation Biotech- nology, Volume 8. Edited by Alan Wiseman. Pp. 179. Ellis Hor- wood. 1984. Price &21. ISBN 0 85312 466 3 (Ellis Horwood); 0 470 20058 8 (Halsted Press); ISSN 0140 0835. Anal. Proc., Vol. 21

ISSN:0144-557X    

DOI:10.1039/AP9842100405

出版商:RSC    

年代:1984

数据来源: RSC