ISSN:0144-557X    

DOI:10.1039/AP98219FX029

出版商:RSC    

年代:1982

数据来源: RSC

ISSN:0144-557X    

DOI:10.1039/AP98219BX031

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

ANPRDI 19(9) 421-454 (1982) September 1982 Hon. Secretary R. Sawyer Proceedings of the Analytical Division of The Royal Society of Chemistry AD President S. Greenfield Hon. Treasurer D. C. M. Squirrel1 Hon. Assistant Secretary D. 1. Coomber, O.B.E. Hon. Publicity Secretary Dr. J. F. Tyson, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, LE7 1 3TU Secretary Miss P. E. Hutchinson Editor, Analyst and Analytical Proceedings P. C. Weston Senior Assistant Editor Assistant Editors R. A. Young Mrs. J. Brew, Miss D. Chevin Publication of Analytical Proceedings is the responsi- bility of the Analytical Editorial Board: J.'M. Ottaway (Chairman) J. M. Skinner L. S. Bark J. D. R. Thomas G. J. Dickes A. M. Ute 'G. W. Kirby 'P. C. Weston A.C. Moffat J. Whitehead T. B. Pierce 'Ex officio members All editorial- matter should be addressed to: The Editor, Analytical Proceedings, The Royal Society of Chemistry, Burlington House, Piccadilly, London, W1 V OBN. Telephone 01 -734 9864. Telex 268001. Advertisements: Advertising Department, The Royal Society of Chemistry, Burlington House, Piccadilly, Ana/yfica/ Proceedings (ISSN 01 44-557X) is pub- lished monthly by The Royal Society of Chemistry, Burlington House, London W1 V OBN, England. All orders, accompanied by payment, should be sent to The Royal Society of Chemistry, The Distribution Centre, Blackhorse Road, Letchworth, Herts., SG6 1 HN, England. 1982 Annual Subscription price if purchased on its own: UK f40.00, Rest of World f42.00, US $95.00, including air speeded delivery.Air freight and mailing in the USA by Publications Expediting Inc., 200 Meacham Avenue, Elmont, N.Y. 11 003. USA Postmaster: Send address c ha nges to : Analytical Proceedings, Publications Expediting Inc., 200 Meacham Avenue, Elmont, N.Y. 11 003. Second class postage paid a t Jamaica, N.Y. 1 1431. All other despatches outside the U K by Bulk Airmail within Europe, Accelerated Surface Post outside Europe. PRINTED IN THE UK. Q The Royal Society of Chemistry 1982 London, W1V OBN. Telephone 01 -734 9864. New Members of Council Edmund Bishop, of Yorkshire descent, was educated in the Universities of Glasgow and Strathclyde, taking degrees in chemistry and chemical engineering. After short service in a Public Analyst's laboratory, he joined the Explosives Directorate of the Armaments Research Department.Invalided out in 1944, he became an Assistant Lecturer in the Univer- sity of Strathclyde, moving to a Lectureship in the University of Newcastle-upon-Tyne in 1946. In 1953 he joined the University of Exeter, where he has remained, becoming a Senior Lecturer in 1960, Reader in Analytical Chemistry in 1968 and being appointed to a Personal Chair in 1974. He has always had strong interests in high precision analysis, the mathematical interpretation of analytical processes, analytical electrochemistry, the investigation of reactions, reagents and indicators, and in probing into reaction mechanisms. He has published four books and about 150 papers. He was awarded the SAC Gold Medal in 1976, and the RSC's BDH Chemicals Award for Analytical Reactions and Analytical Reagents in 1980.Bishop joined the Chemical Society in 1939, and the SPA in 1948. He became involved with the Microchemical Methods Group in the 'fifties and was elected to the Group Committee. He was first elected to the Council of the SAC in 1959, and has since served six periods in office. He has been on the Analytical Methods Com- mittee since 1960, being now Deputy Chairman, and has chaired the Analytical Standards Sub- committee, the Complexometric Standards Panel, the Joint Committee on Organic Micro- chemical Reagents and Standards, and some ad-hoc Panels, as well as the BSI Reagents and Standards CIC 26/-/l. In the same context, he has served on BSI C/5 and CIC/-/l, IS0 Plenary TC 47 and TC 47 SC 3, the BNCC of the Royal Society and IUPAC Commissions V-1 on Reac- tions and Reagents and V-5 on Electroanalytical Chemistry.He has also served on the AMC Iron Sub-committee and serves on the Instru- mental Criteria Sub-committee. Again, he has served on the Analytical Chemistry Trust, Publications Policy, Finance, Amalgamation and AnaZyst Editorial Committees, and is a 421422 NEW MEMBERS OF COUNCIL Anal. Proc. member of the Analyst Editorial Advisory Board and the Honours Committee. Married, with two sons and two grand- daughters, Bishop is interested in music, languages, people, food and drink, and is to be seen pedalling frantically around Devon roads, peering through cameras, or thrashing up and down the swimming pool. Professor E . Bishop Dr.C . Burgess Christopher Burgess was born in 1945 in Liverpool. He was educated at the Liverpool Blue Coat Grammar School and Widnes Technical College, following which he took MSc (1969) and PhD (1971) degrees a t Lough- borough University of Technology. His super- visors at this time were Drs. A. G. Fogg and D. Thorburn Burns. He then undertook post- doctoral research at the University of Hong Kong, in 1971 and 1972, and at the University of Southampton, from 1972-1974. Dr. Burgess has produced a number of research publications (21 papers published so far) and two books, “Solution Equilibrium,” which was written in co-operation with F. R. Hartley and R. M. Alcock, and “Standards in Absorption Spectrometry,” edited with A. Knowles of the University of Bristol on behalf of the Ultraviolet Spectrometry Group. He is currently the Head of the Analytical Department at Glaxo Operations UK Limited, situated a t Barnard Castle in County Durham, where his present research interests are the automation and software control of analytical operations, the application of mathematics to analytical chemistry and diode array spectrometry in analytical chemistry.Apart from membership of the Analytical Division, Dr. Burgesses professional activities include Vice-chairmanship of the Ultraviolet Spectrometry Group and acting as an external examiner of Teesside Polytechnic for the CNAA BSc degree and GRSC examinations. Dr. Burgess is married, with one son and two daughters aged 4, 2 and 6 months, respectively. His interests include collecting books and antiques.Dr. Sam Lyle was born in Co. Down, Northern Ireland, in 1931 and graduated with a BSc degree in Chemistry from the Queen’s Univer- sity of Belfast in 1953. He remained a t Belfast for a further year to take an MSc degree under the supervision of Dr. (later Professor) Cecil L. Wilson, with whom he got his first taste for analytical chemistry. At the beginning of 1955 he moved to Birmingham to complete his apprenticeship with Dr. W. I. Stephen in Dr. (later Professor) Belcher’s group at the Univer- sity. After obtaining a PhD degree, in 1957, he spent a short time in a local industrial firm before moving to the University of Durham as a Lecturer in Radiochemistry at the London- derry Laboratory for Radiochemistry, a labora- tory established a few years earlier by Professor F.Paneth who was a pioneer Radiochemist. In January, 1965, Dr. Lyle joined the then newly founded University of Kent at Canterbury as a Lecturer in Chemistry, the first to be appointed. He has remained a t the University, becoming Senior Lecturer (1968) and Reader (1976). With recent retirements, he has ac- quired the doubtful distinctions of not only being the longest serving, but also the oldest member of the full-time academic staff in the Department. Current research interests are in the fields of chemical separations by liquid- liquid extraction, ion-exchange and other forms of chromatography, automatic chemical analy- sis and in the properties of inorganic solids and solid-state reactions. The interest in separa- tions techniques originates in collaborative radiochemical studies in nuclear fission at Durham and in independent work on separations of “carrier-free” activated nuclei from irradiated targets.In 1971 he was awarded the degree of DSc by the Queen’s University of Belfast. Dr. Lyle joined the SAC and the Chemical Society in 1955 and was one of the founder committee members of the Radiochemical Methods Group, serving as Chairman from 1970- 72. He is the present Chairman of the South East Region (having also been associated with the Regional Committee since the Region was established) and has been a member of the Analytical Abstracts Editorial Committee for a number of years. Dr. Lyle is married with a daughter and a son, neither of whom has taken up chemistry as a profession. Outside interests include local history, architecture, sampling wines, preferably other than those produced by himself, and walk-September, 1982 NEW MEMBERS OF COUNCIL 423 ing.From time to time necessity demands the expenditure of additional physical energy in efforts to prevent nature reclaiming her own from the fabric of an ageing house and in the surrounding “over-mature” garden. Mr. D. G. Porter Dr. S. J . Lyle Derrick Porter was born in Bedfordshire in 1934 and went to school a t Christ’s Hospital, where his education followed traditional classical lines. It was probably, therefore, a certain natural perverseness that caused him to seek a scientific career when he left school, and it was the Government Chemist’s Department (as it then was) that provided him with the oppor- tunity.He has been there ever since, which he claims is an indication of the interesting and varied nature of his work rather than tendency to inertia as some of his colleagues believe. After a period spent analysing paints and varnishes he had two enjoyable years with the RAF in Germany servicing and repairing pre- transistor-age airborne radar systems. Shortly after returning to the Laboratory he enrolled a t the nearby Birkbeck College, a unique college of London University whose under- graduate students were all part-time. He recalls that the first year entailed a somewhat hectic struggle to achieve the inter-BSc standard (including physics “from scratch” in 8 months), after which the BSc (Special) chemistry course seemed an oasis of comparative calm.For most of this period he was employed on various aspects of food analysis and he believes strongly that such work provides the best basis for a thorough training in analytical chemistry. In 1961 he joined the Custom House branch of the Laboratory, where he was concerned with the analysis of wines, beers, spirits and (less enthusiastically) sugar. To occupy his evenings he spent 3 years attending the Branch E Food and Drugs course at Chelsea College but, wisely (in his view), he never attempted the examina- tions. Soon after the various branches of the Labora- tory were brought together at the present South Bank site he moved back to the Food Division, where among other activities he developed gas- chromatographic methods for the determination of fat-soluble vitamins.It was at this time, also, that his interest in automation began to form. In 1968, during a year’s paid leave, he acquired an analytical chemistry MSc at Chelsea College. He took this opportunity to make an in-depth study of automation in analysis and on his return to the Laboratory he joined the Research Division to work on automation. In 1978 he became Head of the Automation and Computing sub-division. Mr. Porter joined the SAC in 1961 and the Committee of the Automatic Methods Group in 1974, subsequently serving as Honorary Assist- ant Secretary, Honorary Secretary, Vice- Chairman and currently Chairman. He has been a committee member of the Microcomputer and Microprocessor Subject Group since its formation 2 years ago. He felt very honoured, recently, to be invited to serve on the RSC Oral Examinations Committee.He is a co-organiser of the annual Swansea Summer School of Automatic Chemical Analysis and is a Corres- ponding Editor of the Journal of Automatic Chemistry. Mr. Porter is married, with a daughter and two sons, all currently in pursuit of science degrees. None of them is reading chemistry; he suspects that this is significant, but is not sure why. The absence of his younger son from home now allows him to indulge his hobby of microcomputing to the full. The few spare moments left over from this very absorbing occupation are spent in listening to music. He left school with the very firm resolve never again to indulge in any form of strenuous physical activity. Dr. Peter B. Smith, who is married with one son, is at present the manager of the analytical services group of BCIRA (formerly British Cast Iron Research Association).This position involves him in providing an analytical service to the membership of BCIRA, numbering some 400 firms, both British and overseas, and carrying out research and development particu- larly to improve the cost effectiveness of analysis both at BCIRA and in the ironfounding industry. Typically during a year some 300000 analyses are made on instrumentation ranging through the whole spectrum of analysis424 NEW MEMBERS OF COUNCIL Anal. PYOC. from a computer controlled direct reader, ICP, XRF, to traditional chemical methods. Dr. Smith gained an Honours degree in chemistry a t Sheffield University in 1960 and continued there to obtain a PhD in 1963 on “Reaction Mechanisms of Steroidal Amines.” Proceeding from university he spent 13 years at Albright and Wilson Ltd. before moving to BCIRA. During his years a t Albright he commenced research into high-temperature resins before moving over to join Dr. Greenfield in his pioneering work on the ICP. He is the author or co-author of over 20 technical papers and has presented lectures both in Britain and abroad, culminating in late 1980 with a visit to China to present two papers at the Beijing (Peking) Analytical Symposium. He is a member of some dozen committees concerned both with the Analytical Division and as the ironfounding industry’s representa- tive on various national and international committees concerned with analysis.Dr. P. B. Smith MY. J. Vallance John Vallance, Deputy County Analyst of Durham, is the new Chairman of the North East Region. He was born at Matlock, Derbyshire, and educated a t the Ernest Bailey Grammar School. In 1956 he commenced his training in the County Analyst’s Department of Derbyshire County Council under Mr. R. W. Sutton, and continued under his successor, Mr. J. Markland. He attended Derby and District College of Technology at the same time as his chemist brother, Dr. Victor Vallance, over which some confusion still persists. An external ARIC at Trent Polytechnic was followed in 1973 by the Diploma of Mastership in Chemical Analysis and by the Fellowship of the Institute in 1976. When local government reorganisa- tion took place, in 1974, he moved to County Durham, having been appointed as a deputy to Mr.F. C. Shenton in the Regional Laboratory. He maintains an interest in the advancement of analytical methods, particularly in the field of trace metals analysis, and has recently served on the Standards and Methods Commit- tee of the Association of Public Analysts. It is his contention that the wide variety and ever increasing complexity of the work undertaken in the modern Public Analyst’s Laboratory constitutes a challenge rather than an employ- ment. His involvement in Analytical Division affairs originated in the less time consuming capacity as auditor, but he remains sure that further development can be built on the firm foundations laid by his predecessors in the Region. He cites recent developments, such as the successful special meetings for sixth-form pupils, as ample evidence for optimism in the future of the Region.He is married, with three sons, and his inter- ests include music, being a retired cornet player and a partly reformed brass band enthusiast. Dr. T. S. West is a first class honours chemistry graduate of the University of Aberdeen and took his PhD in analytical chemistry with Professor Belcher a t Birmingham in 1952. He was a DSIR Research Fellow there from 1952-55, when he was appointed lecturer in chemistry. During his years in Birmingham he developed streams of work on absorption spectrophotometry, com- plexometry, spectrofluorimetry, atomic absorp- tion spectrometry, some electrochemistry and organic elemental and functional group ultra- micro analysis.While at Birmingham he was awarded the Royal Institute of Chemistry’s Meldola Medal for 1956. He was awarded the DSc of the University in 1962. In 1963 he was appointed Reader in Analytical Chemistry a t Imperial College, London, and in 1965 he be- came the first holder of the Chair of Analytical Chemistry there. His research group quickly established itself as a leading one in atomic spectroscopy and electroanalytical chemistry and it became one of the world’s most prominent schools of analytical chemistry. During this period Dr. West was particularly proud to be associated with his three team leaders, Dr. R. M. Dagnall, Dr. B. Fleet and Dr. (now Professor) G. F. Kirkbright, all of whom have played a prominent part in the affairs of the Analytical Division.Dr. West’s former pupils now occupy many prominent positions in analytical chem- istry, e.g., in the U.K. Professor D. Betteridge a t Swansea, Dr. M. Williams, Executive Secretary of IUPAC at Oxford, and in many otherSeptember, 1982 RSC ENDOWED LECTURESHIP 425 countries of the world, including the PRC, USA, USSR, Japan and several Commonwealth countries. Dr. West has long been active in the Analytical Division of IUPAC. After serving on its V.3 Commission on Nomenclature, he eventu- ally became Secretary of the Commission and was President of IUPAC’s Analytical Division from 1979-81. In 1981 he became Assistant Secretary General of IUPAC. Within the RSC Dr. West was Honorary Secretary of the (new) Chemical Society from 1972-75 and Chairman of its External Affairs Board.He has served on the Analytical Sub-committee and main Committee of the British National Committee for Chemistry since 1965. In 1975 he was appointed Director of the Macaulay Institute for Soil Research, Aberdeen. Dr. West has won many honours, including the Redwood Lectureship, Gold Medal and Perkin-Elmer Medal of the SAC/ Analytical Division, of which he was President from 1969-71, the Johannes Marcus Spectro- scopy Medal from Czechoslovakia, the Bunseki Kagakukai Medal and Honorary Membership of Dr. T . S . West MY. D. W . Wilson the Japan Society for Analytical Chemistry and Fellowship of The Royal Society of Edinburgh. He has lectured by invitation in all five con- tinents and has published over 420 research papers. Dr. West is married, has three children and one grandson.His main relaxations are gardening, reading and listening to music. A biography of David Wilson appeared in PYOC. Anal. Div. Chem. SOC. in April 1976, when he became President of the Division. Following his Presidency he served on Council as Past President from 1978 to 1980, with a brief interruption by illness early in 1979, which also required a term’s absence as Head of the Chemistry Department of the City of London Polytechnic. The excellence with which the Department flourished during his absence, coupled with some prescience of impending higher educational rapine, persuaded him after much soul searching to accept an offer of early retirement in Septem- ber, 1980. When he reflects upon this decision he bursts into applause, because it has enabled him to transfer his attention from things that must be done to things that are nice to do. Among the latter is sailing, and he has taken advantage of the opportunity not only to sail more, but also to fill the longstanding theoretical and practical gaps in his knowledge by attending evening classes in the School of Navigation of his former Polytechnic. His success rate is classified, but he can claim some certified com- petence in avoiding collisions, in gazing wisely at the weather, and as a radio operator. His interest in the affairs of the Royal Society of Chemistry and of the Division has never flagged. He is currently a member of Committee of the South East Region, and of the Steering Committee of the SAC 83 Conference.

ISSN:0144-557X    

DOI:10.1039/AP9821900421

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

Sefitember, 1982 RSC ENDOWED LECTURESHIP 425 Royal Society of Chemistry Endowed Lectureship, 19 83/84 Nominations to the Theophilus Redwood Lectureship for 1983/84 will be considered by the Society. The Theophilus Redwood Lectureship was founded in 1972 to commemorate the forma- tion in 1874 of the Society of Public Analysts (later the Society for Analytical Chemistry and now the Analytical Division of The Royal Society of Chemistry). It is named after the founder President, Theophilus Redwood. The lecture is given annually, normally at the Annual Chemical Congress, by one of the world’s leading analytical chemists. Further details of this Lectureship, which carries an award of a medal, an honorarium of LlOO and an inscribed scroll, may be obtained from Stanley S. Langer, The Royal Society of Chemistry, Burlington House, London, W1V OBN, to whom members may submit nominations by Tuesday 19 October, 1982.

ISSN:0144-557X    

DOI:10.1039/AP9821900425

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

426 ANALYTICAL DIVISION PUBLICITY SECRETARY Anal. Proc. Safety in Analytical Laboratories This article continues the series of reports on aspects of safety of particular interest to analytical chemists. It is hoped that these articles will provide a forum for further discussion, and correspondence on the individual articles and on all safety matters is invited. This series is written by outside contributors and views expressed in the articles are not necessarily those of the Royal Society of Chemistry. Investigating Incidents Whether 'tis nobler in the mind to suffer the slings and arrows of outrageous fortune, or to take arms against a sea of troubles, and by opposing end them? Hamlet WILLIAM SHAKESPEARE To investigate, or not to investigate: that is the question. Do we treat laboratory mishaps merely as the unavoidable slings and arrows of outrageous fortune or do we seek the underlying causes and try to eliminate them? From a purely technical standpoint there would seem to be no question.Each incident has a cause and the sooner it is revealed the better. As every manager knows, however, this is a gross oversimplification that can lead to a sea of troubles. Laboratory incidents are not mere matters of chemicals and apparatus; directly or indirectly they involve people. From this it follows that we are working in an area where attitudes and trust are important factors. Before we can develop a sound approach toSeptember, 1982 SAFETY IN ANALYTICAL LABORATORIES 427 investigation we must have an accepted system for reporting incidents. The keyword here is “accepted.” Somehow or other management must establish a climate of attitudes in which all incidents, however trivial, are reported as a matter of course.If we exclude the most trivial we present the laboratory worker with the problem of deciding what is not trivial. And we expose him to the embarrassment of feeling that he may be seen to be making a fuss about nothing. Once it is accepted that even the “small graze to left forefinger” should be reported, we are well on the way to ensuring that information will be available when more serious incidents have to be investigated. There will, of course, be laughter, and why not ? The following report was made: “While speak- ing to my supervisor I inadvertently allowed my finger to stray into a piece of glass tubing, in which it got stuck.” The injury in this actual accident was minimal and there was the inevit- able mirth ; but the attitude towards reporting incident was healthy.Perhaps we should agree what we mean by an incident. This rather vague word has been chosen to allow the inclusion not only of acci- dents involving injury but of all occurrences that have implications for safety. It would be unwise to attempt a comprehensive definition. Dangerous occurrences which could have resulted in injury should be included. So, too, should fires, however small. Delayed medical effects, such as dermatitis, which might be attributed to prior contact with chemicals should be regarded as incidents. Equipment failure, for example interruptions to the power supply, may have a bearing on safety.In the end some judgement must be left to the indi- vidual. In any given circumstance one person might discern a potential hazard not immediate- ly recognised by his colleagues. The method of reporting is a matter for local agreement. The choice will be made by the manager, but the views of all involved should be taken into account. Union Safety Repre- sentatives may well insist that their involve- ment should be automatic and formal. What- ever arrangements are agreed it is essential that incident reports are made in writing. In a small laboratory it may suffice to have an incident report book to which all have access. Elsewhere, it may be desirable to have an incident report form on which can be recorded the name of the author, i.e., the person directly involved, the date, time and location of the incident, the names of witnesses, a description of the occurrence and of any injury incurred.There should also be space for brief comments by the supervisor and/or manager. These comments rnzcst be constructive. Criticism of the victim/perpetrator of the incident can only be counter-productive and damaging to the co- operative spirit on which good safety procedures depend. People don’t like being injured; they don’t want to have accidents; nor do they wish to endanger their colleagues. So, if they have made a mistake they should be helped to recog- nise that they have done so and be given advice on how to avoid a recurrence. The persistently accident-prone person is a special problem for the manager.If patient supervision and training are ineffective a search for alternative employ- ment may be necessary. In most cases a report followed by managerial comment will be all that is required. There will, however, be occasions where a formal investigation is desirable or even necessary. The decision to investigate should rest with a senior manager or with the Safety Officer. In reaching this decision the primary consideration should be the need for further information. Is there anything that can be learned from the incident ? Are there any implications for future work? Is there any possibility of, or require- ment for, improvement in work procedures or training? Is the cause of the occurrence fully understood? Does the incident point to wrong attitudes? Is there any evidence that staff have anxieties, justified or not, about the safety aspects of their work? Clearly it is inadvisable to initiate an investigation where none of these considerations indicates any likely benefit.People quickly become disillusioned by an activity that they feel is unnecessary. Given that an investigation is necessary it should be set up and conducted by a prescribed procedure which, however, should allow maxi- mum informality. There are several advan- tages in having an agreed procedure for investi- gations. Firstly, it established who should arrange and chair the event. Secondly, it provides a check list of those who should be present, i.e., all directly involved in the incident, the Safety Officer and any specialists who can contribute, such as an engineer, a Fire Warden, a first aider or medical expert, and so on.The composition of the meeting will thus depend upon the nature of the incident. Union- appointed Safety Representatives should be invited to attend. Not only are they entitled to be present but they can play a useful role. Thirdly, it defines what documentation is required. Finally, the fact that an agreed established procedure is invoked helps to convey to the participants the normality of the event. This last point is especially important. It ‘428 HEADSPACE ANALYSIS Anal. PYOC. should be borne in mind that, however inform- ally the investigation is conducted, the person involved in the incident and his supervisor may be feeling somewhat exposed. It is important, therefore, that the procedure clearly spells out the objective of investigations, i.e., the dis- covery of what can be learned. An investiga- tion must never be regarded as a means of apportioning blame. In some situations this requirement may place considerable demands upon the tact of the Chairman, who will have to ensure that the legitimate discussion of the incident does not become, and is seen not to be, a witchhunt.Most investigations will require only a half hour’s discussion and the subsequent issue of an agreed report, which will include recomrnenda- tions and actions, with a statement of who is to carry out these actions and when they are t o be completed. In some instances, however, there may be a number of issues that will remain submerged unless the Chairman is sensitive to the feelings of those present. A reported incident may be only the tip of the iceberg. The Chairman must listen to what is being said, and he should direct some careful probing towards what is not being said. The incident investigation may occasionally be an opportunity to uncover unspoken anxieties, something rotten in the state of Denmark. This may be mild dissatisfaction over informa- tion systems or near-hypochondriacal apprehen- sion about toxicological hazards, which may or may not be real. It is important that these should be articulated. Once in the open they can be dealt with. Accidents are always regrettable, but an incident can be a valuable sign of unsuspected problems. Properly investigated, i.e., without concern about blame, it can be a bonus. The manager should, like Hamlet’s Lord Chamber- lain, Polonious, say : “If circumstances lead me, I will find Where truth is hid, though it were hid indeed Within the Centre.”

ISSN:0144-557X    

DOI:10.1039/AP982190426b

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

428 HEADSPACE ANALYSIS Anal. PYOC. Headspace Analysis The following are summaries of three of the papers presented at a Joint Meeting of the Special Techniques Group and the East Anglia Region held at Unilever Research Laboratories, Sharnbrook, Bedfordshire, on May 20th, 1981. Analysis for Residual Monomer Levels in Plastics and in Foods N. T. Crosby Defiartment of Industry, Laboratory SE19NQ of the Government Chemist, Cornwall House, Stam ford Street, London, This paper describes the use of headspace techniques for the determination of vinyl chloride monomer (VCM), vinylidene dichloride (VDC), acrylonitrile (AN) and styrene (SM), both in plastics and in foods. The nzcld for analytical control of residual monomer levels arises from the finding that VCM was implicated in acro-osteolysis of the hands and feet and in a rare form of liver cancer in isolated cases of poly(viny1 chloride) (PVC) plant operatives who had worked in a closed environment for several years in contact with relatively high doses of the monomer.Extensive studies on animals1 have confirmed these initial findings. Inevitably, once the VCM story began to unfold, attention was focused equally on other monomers used in food packaging2 although much less is known about their toxicology and potential for hazard. Concern over possible hazard from VCM prompted legislative authorities to take action. The Food and Drug Administration in the USA withdrew approval for the use of PVC resins in contact with alcoholic beverages and the EEC promulgated a Directive3 specifically to control the level of residual monomer in plastic articles and in foods.The Directive imposes a limit of 1 mg kg-l for VCM in finished plastic articles and any transference to the food must not produce a concentration greater than 0.01 mg kg-l of VCM in the food. In both instances, the Directive specifies that headspace gas chromatography shall be used for the determination of residual monomer levels. In the UK, the Materials and Articles in Contact with Food Regula- tions* came into operation on November 26th, 1979, and were subsequently amended in 1980.5 Now that the method of analysis for residual levelsof VCM in food has been approved, a further amendment will be required in the near future.September, 1982 HEADSPACE ANALYSIS 429 Headspace Analysis Table I shows some properties of the monomers of interest that are pertinent to headspace analysis.The boiling-points range from - 13.5 "C for VCM up to 145 "C for styrene. Despite such a wide range, all four compounds are readily determined by using headspace techniques with equilibration temperatures not too dissimilar. Of crucial importance is the distribution of the monomer between the headspace and the solvent in the sampling vial. The low boiling- point of VCM obviously favours a higher concentration in the gas phase by comparison with SM at a similar equilibration temperature. However, the lower solubility of styrene (in aqueous systems) compared with VCM acts in the opposite direction. Monomer Vinyl chloride (VCM) TABLE I PROPERTIES OF SOME MONOMERS Solubility in water at Structural formula Boiling-point/"C 25 "C, % mlm 13.9 0.11 Vinylidene chloride (VDC) Acrylonitrile (AN) Styrene (SM) H\C=C/H H' 31.5 77.5 145 0.021 7.3 0.032 During analysis, the sample is thermostatically maintained at the appropriate temperature inside a sealed vial until equilibrium is attained.A portion of the gaseous phase is then transferred on to the gas - liquid chromatographic column and the analysis continues by con- ventional means. This transfer can be performed manually, using a gas-tight syringe, or automatically by positive pressure valve switching, as in the Perkin-Elmer F40, F42, F45 or HS6 instruments. Manual operations have to be carried out with a great deal of care for quantitative work. The syringe should be pre-warmed to equilibration temperature and the operations carried out in as standardised a manner as possible.The use of a suitable internal standard is essential. Alternatively, the electropneumatic dosing system can be used, particularly when large numbers of analyses have to be made. With this system a relative standard deviation as low as 0.5% can be achieved and the use of an internal standard is not then required. The chief advantage of the headspace technique in this type of work is that preliminary sample pre-treatment processes, such as extraction, distillation or digestion, are not generally required. There is also less contamination of the injection port and chromato- graphic column with high boiling-point components, which increases the life of the column and shortens each chromatographic run. Some comments on the determination of individual monomers follow; a review of suitable techniques has been published by Crosby.2 Vinyl Chloride The chief problem in the analysis of samples for VCM is that as VCM is a gas with only lim- ited solubility in water, it is not easy to prepare standard solutions.A saturated solution contains about 0.2% m/V of VCM at room temperature. Normal laboratory handling opera- tions, e.g., dilution, pipetting or pouring, may involve loss of the gas to the atmosphere. All containers must be tightly stoppered, kept chilled and filled to leave the minimum headspace volume. Aqueous standard solutions can be checked independently by titration after reaction430 HEADSPACE ANALYSIS Anal. PYOC. with potassium bromide - potassium bromate reagent.Standard solutions of VCM can also be prepared by use of organic solvents such as tetrahydrofuran or dimethylacetamide. These are much more stable but the distribution of VCM into the headspace is less favourable and the concentration cannot be checked by an independent assay. Problems of sampling PVC bottles have been illustrated by Crosby2 and the results of a survey of residual levels of VCM in PVC bottles, film and some foods in the period 1974-7 have been reported.6 Calculations based on this survey suggest that the intake of VCM from the average diet will be less than 0.1 pg per person per day. Vinylidene Chloride The presence of an extra chlorine atom in the molecule (Table I) enables an electron-capture detector to be used with greater effect than for VCM, where the sensitivity is no better than the flame-ionisation detector.Gilbert et aZ.7 were able to detect as little as 0.001 mg m-2 (= 0.05 mg kg-l) in films and down to 5 pg kg-l in foods. A MAFF8 Working Party have similarly reported on levels of VDC found in films and food. The maximum intake of VDC from the diet based on these results was calculated to be 1 pg per person per day. Acrylonitrif e AN is a component of several polymers, which may contain up to 70% of AN in conjunction with styrene and/or butadiene. Wherever possible, a nitrogen-selective detector should be used in this type of work at low residual levels of monomer as other constituents frequently interfere. Under suitable conditions, AN can be detected down to 0.1 mg kg-l in plastics and down to 5 pg kg-1 in beverages.Steichen9 recommends dilution of the resin dispersion with water as a means of lowering the detection limit. Styrene Styrene is often present at higher levels than other monomers and has been associated with problems of taint in foods. Unlike the other polymers, polystyrene readily unzips on heating to release the monomer. Headspace techniques have been described by Witheylo and detec- tion limits as low as 1 pg kg-l were achieved with some foodstuffs. Gilbert and Startin” have recently demonstrated that headspace gas chromatography equipment can be successfully coupled with a mass spectrometer as detector. Single-ion monitoring of the column eluate was possible without deleterious effects on resolution.Detection limits ranged from 1 to 15pgkg-1. Hence, just as in any other field of analytical chemistry, it is possible to employ a wide range of different techniques. However, for the determination of residual monomers in plastics and in foods there is no doubt that headspace gas chromatography is the preferred approach. Selective detectors and, in particular, mass spectrometry by single-ion monitoring, offer unequivocal identification and excellent sensitivity for current research and legislative requirements. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. References International Agency for Research on Cancer, “Monograph on the Evaluation of the Carcinogenic Risk of Chemicals to Humans,” Volume 19, IARC, Lyon, 1979. Crosby, N. T., “Food Packaging Materials,” Applied Science, London, 1981.Council Directive of 30 January 1978 on the Approximation of the Laws of the Member States Relating to Materials and Articles Which Contain Vinyl Chloride Monomer and are Intended to Come into Contact with Foodstuffs, Official Journal of the EEC, No. L44, 15 February, 1978. The Materials and Articles in Contact with Food Regulations 1978, SI 1927, HM Stationery Office, London. The Materials and Articles in Contact with Food (Amendment) Regulations 1980, SI 1838, HM Station- ery Office, London. Food Surveillance Paper No. 2, HM Stationery Office, London, 1978. Gilbert, J., Shepherd, M. J., Startin, J. R., and McWeeny, D. J., J. Ckromatogr., 1980, 197, 71. Food Surveillance Paper No. 3., HM Stationery Office, London, 1980. Steichen, R.J., Anal. Chem., 1976, 48, 1398. Withey, J. R., Environ. Health Perspectives, 1976, 17, 125. Gilbert, J., and Startin, J. R., J. Chzromatogr., 1981, 205, 434.September, 1982 HEADSPACE ANALYSIS 431 ldentif ication of Anaerobic Bacteria by Headspace Analysis A. J. Taylor Venereal Diseases Reference Laboratory, London Hospital Research Laboratories, A sh$eld Street, London, E 1 2BL During the mid and latter parts of the 1960s there was much investigation of metabolic end- products of bacteria in the hope that compounds would be found that might be unique to a particular group or species of bacteria. The compounds that received the greatest attention, and which have stood the test of time as regards their usefulness, are the volatile or short- chain fatty acids (SCFA).The volatile acids produced by micro-organisms range from acetic acid, through propionic and the isomers of butyric acid, to valeric and caproic acids. These compounds are easily detected in spent culture media, either after extraction in a solvent such as diethyl ether or by a technique such as headspace analysis. The metabolic origins of such products are not clear. Results of studies carried out largely on the bacterial flora of ruminant animals suggest an amino acid origin for these acids. For example, Bacteroides rurniwocola has been shown to produce the branched chain acids iso- butyric, isovaleric and 2-methylbutyric acid by metabolism of valine, leucine and isolewine, respectively.1 Such acid end-products provide a rapid and reproducible set of characteristics, which have been exploited in the identification of anaerobic bacteria. Infections involving such microbes are usually of endogenous origin, Anaerobes are found in large numbers in the normal flora of healthy persons, especially in the oral cavity, upper respiratory tract and lower gastrointestinal tract. Normally they do not cause a problem, but if the balance of health is disturbed then infection may occur.It has been argued that identification of the infecting organism is of little direct benefit to the patient and that the clinician merely requires a choice of antibiotics that may be used to treat. This approach does little, however, towards increasing our under- standing of the inter-relationships of members of the normal microbial flora and how endogen- ous infections arise.Identification of anaerobes has traditionally depended on differential characteristics familiar to microbiologists for a century: colonial morphology of the isolate; its ability to grow in the presence of selective agents; the shape and Gram stain reaction of the cells; and the results of simple metabolic studies involving fermentation of carbohydrate sub- strates and examination of pH changes. In recent times, gas-liquid chromatography has been increasingly used as a supplement and, to some extent, as a replacement for this traditional approach to anaerobe identification. It is our experience that headspace analysis, in particular, has much to offer in this area of microbiology. The technique is not new to this science, having been utilised to study spoilage organisms in milk.2 We have used the method in the characterisation of anaerobic bacteria isolated from the gut of healthy and diseased individuals. The scheme employed relies on a mixture of traditional methods and gas - liquid chromatography.Isolates were subcultured into 10-ml volumes of pre-reduced chopped meat broth supple- mented with glucose. These cultures were incubated for 3 d at 35 "C. One millilitre volumes of the spent media were acidified with 0.1 ml of 50% sulphuric acid and transferred to chroma- tography sample vials for analysis using either a Perkin-Elmer F40 or F45 automatic gas chromatograph designed for headspace analysis. Sample bottles were maintained at 95 "C for a minimum of 10 min prior to sampling.The machines automatically sampled the vapour phase of each vial. Chromatographs were fitted with flame ionisation detectors and 2 m stainless steel columns of 1/8 in o.d., packed with 15% Carbowax 20M plus 2% phosphoric acid on Chromosorb W 80-100 mesh. The carrier gas was oxygen-free nitrogen passing through the F40 instru- ment at 22 ml min-l. The column oven was set at 135 "C and the detector oven at 200 "C. A 5-s injection period was used. Under such conditions separation of the SCFAs was obtained with the following retention times: acetic acid, 5.0 min; propionic acid, 7.2 min; isobutyric acid, 8.2 min; butyric acid, 10.6 min; isovaleric acid, 12.8 min; valeric acid, 15.2 min; isocaproic acid, 23.8 min; and caproic acid, 27.4 min. Figs. 1 and 2 show typical chromatograms that can be achieved when using this method.Culture 1, Clostridiwn tertium, a Gram-positive bacillus, produces major amounts of acetic and432 HEADSPACE ANALYSIS Anal. Proc. butyric acids with a minor peak of propionic acid. In contrast, culture 2, the Gram-negative coccobacillus Bacteroides distasonis, produces large amounts of four SCFAs, acetic, propionic, butyric and isovaleric acids. 3 i I 4 P b ..d I/ Fig. 1. Chromatogram of SCFA present in a cooked meat culture of Clostridium tertium. Peaks are: a, acetic acid: p, propionic acid ; b, butyric acid. Fig. 2. Chromatogram of SCFA present in a cooked meat culture of Bacteroides distasonis. Peaks are as for Fig. 1 except iv is isovaleric acid. Such chromatograms can be used in two ways. Firstly, a combination of simple cell morphology and gas - liquid chromatogram profile may give an indication as to the identity of an isolate to generic or sub-generic level.Table I shows how the morphological groups of anaerobic bacteria may be sub-divided on the basis of major SCFA end-products. The other major application is one of confirming differential identification between related species. Larsson et aZ.8 showed how two related species of Clostridia, Cl. d@de-and CZ. sporogertes, could be differentiated by quantitative headspace analysis of SCFAs. TABLE I MAJOR SCFAs PRODUCED BY THE FOUR MORPHOLOGICAL GROUPS OF ANAEROBIC BACTERIA Gram-positive rods- No SCFA Lactobacillus spp. Acetic acid only E. lentum Bifido bacterium spp . Clost. histolyticum Propionibacterium spp.Clostridium spp. (f other SCFA) Acetic, propionic Aracitnia spp. Acetic, butyric Eubacterium spp. Gram-negative rods- Acetic acid only B . melaninogenicus B. oralis Acetic, propionic B. fragilis Acetic, butyric Fzssobacterium spp. Acetic, propionic, B. asaccharolyticus butyric, isovaleric Gram-positive cocci- Acetic acid only P . magnus P. saccharolyticus Streptococcus spp. Peptostreptococcus spp. P. prevotii Acetic, butyric P . asaccharolyticus Acetic, isovaleric Pst. anaerobius Gram-negative cocci- Acetic, propionic Veillonella spp. Acetic, butyric A cidaminococcus spp. The speed and sensitivity of such an analysis on isolated cultures has been applied to direct It has been shown that pus or drainage fluids from diagnosis performed on patient specimens.September, 1982 HEADSPACE ANALYSIS 433 patients with an infection of anaerobic origin contain high levels of volatile acids and that acids containing 3 or more carbon atoms (isobutyric acid and beyond) are not found in infections caused by aerobes.* Levels of SCFAs often exceed 10 mM in cases of acute anaerobic infection, and this fact has been used to provide a rapid diagnostic test of great value to the clinician in the choice of antimicrobial therapy, without the delay of 48 h or more often encountered in the culture of anaerobic bacteria.Headspace analysis has been shown to be a very suitable method for carrying out such assay^,^ and the technique has now been expanded to the investigation of bacterial infections of the urinary tract.* References 1.2. 3. 4. 6. 6. Allison, M. J., Afipl. Environ. Microbiol., 1978, 35, 872. Basette, R., and Claydon, T. J., J. Dairy Sci., 1965, 48, 775. Larsson, L., Holst, E., Gemmell, C. G., and Mardh, P-A., Scand. J. Infect. Dis., Sufifil., 1980, 22, 37. Phillips, K. D., Tearle, P. V., and Willis, A. T., J. Clin. Path., 1976,29, 428. Taylor, A. J., in Kolb, B., Editor, “Applied Headspace Gas Chromatography,” Heyden, New York, Coloe, P. J., J. Clin. Path., 1978, 31, 365. 1980. Headspace Methods for the Analysis of Dithiocarbamate Pesticide Residues in Foodstuffs A. R. C. Hill and J. W. Edmunds Ministry of Agriculture. Fisheries and Food, Harpenden Laboratory, Harpenden, Hertfordshire, A L5 2BD Introduction Dithiocarbamates, in the context of this paper, are taken to be those agricultural and horti- cultural fungicides which may be considered to be derivatives of dithiocarbamic acid.They are synthesised by first allowing carbon disulphide and an amine to react in the presence of sodium hydroxide and then either oxidising the product to form a disulphide (e.g., thiram: tetramethylthiuram disulphide), or precipitating it with heavy metal salts, usually to form insoluble polymeric materials of undefined composition (e.g., mancozeb : a manganese- and zinc-containing ethylene bisdithiocarbamate) . Because of their generally poor solubility, these compounds are normally applied to crops as dusts or suspended in water and, for the same reason, it is impossible to purify many of them or make proper solutions for standards. This group of compounds is of very low mammalian toxicity, so why is it necessary to determine the residual amounts present on harvested crops? Firstly, the residues can be significant in their own right as, compared with most other pesticides, relatively large amounts are applied to crops in order to achieve good disease control. Secondly, the ethylene bis- dithiocarbamates can be converted, on the crop but more especially during food processing (cooking, canning, brewing, etc.), to ethylene thiourea (ETU).ETU is not a fungicide but is reputed to be weakly carcinogenic, teratogenic and mutagenic.l ETU tends to be degraded rapidly within living plants and, as it may be produced post-harvest, it is often more appropri- ate to determine the precursor ethylene bisdithiocarbamate in the harvested crops than ETU itself.Relatively few techniques can be applied to the analysis of dithiocarbamates because of their poor solubility. The most popular approach is to decompose them with acids and reducing agents to produce carbon disulphide, essentially reversing the synthesis. The classical method is that of Keppel,2 in which the carbon disulphide is distilled from the reaction mixture and determined colorimetrically. However, carbon disulphide is readily determined by gas chromatography using flame-photometric, electron-capture or certain alkali flame ionisation detectors, especially if it is not in solution but present as a vapour. Hence, headspace methods are an attractive proposition. Practically all of the headspace methods in use today for the analysis of dithiocarbamate residues are derived from that of McLeod and McCully.s The samples are digested in a sealed vessel by hydrochloric acid (about 5 M) containing tin(I1) chloride (about 2%) for about 1 h at 50-80 “C and an aliquot of the headspace gases injected on to the chromatographic column.The response obtained is calibrated with that of similar containers of reagent that have been434 HEADSPACE ANALYSIS Anal. PYOC. spiked with known amounts of carbon disulphide. In our experience, the presence of most types of plant material in the liquid phase has little effect on the partition of carbon disulphide. Calibration can therefore be carried out by substituting the plant material with 50 ml of water. Where such an effect is shown to occur, and the method cannot be calibrated with material known to be untreated, a different technique should be used. It is important to realise that the amount of carbon disulphide injected on to the column, from either calibration standards or the crop samples being analysed, is unknown.ETU is not detected by this method. The type of container used in the analysis may depend on the range of substrates to be analysed but, naturally, it must be well sealed and have aseptum fitted for sample withdrawal. Those which we now use are Schott & Mainz 250-ml bottles with modified polypropylene caps, fitted with 42 mm silicone rubber septa. The headspace volume of these bottles varies over a range of &3% from the mean when they are charged with 150 ml of reagents and 50 g of crop.Drawbacks The principle of the headspace method is very simple, but adapting it to dithiocarbamate residue analysis has its problems. Refinements produced to overcome these problems account for most of the published variations of the basic method. The first problem is to get the crop sample into the bottle, without loss of residues. Where the sample is, for example, of seeds then this is no problem but if it is of a crop such as lettuce or cabbage then the sample has to be broken up, both to get it into the bottle and also to obtain a representative sample (bearing in mind that the residue is not normally uniformly distributed). However, unfortunately, dithiocarbamate residues on fresh crops can be rapidly decomposed if the samples are cut up or otherwise damaged.There is no ideal answer to this problem at the present time; we cut out quarters (or other appropriate fractions) of about 50 g and, breaking the sample as little as possible, fold them up and gently push them into the bottles, taking care not to rub off the surface residues. Variations in sample mass, from 50g, are compensated for by adding more or less acid digesting agent so as to keep the headspace volume constant. For this purpose, 1 g of a leafy crop (which are those to which it applies most) is taken to be equivalent to 1 ml of reagent. As the degradation is essentially irreversible under the conditions used, the second problem is to ensure that the reaction goes to completion. This normally appears to be the case but certainly it is not invariably so.Where, for instance, unusually high concentrations of copper compounds are present, increasing copper( 11) ion concentration can decrease the carbon disulphide production from ethylene bisdithiocarbamates such that essentially no carbon disulphide is produced from crops containing about 10 p.p.m. (fresh mass) of copper; there is little effect upon carbon disulphide production from thiram at this level. Such levels of copper are only likely to occur where copper-containing fungicides have been used on crops. The problem may be associated with ’the formation of extremely stable complexes between copper and these dithi~carbamates~ and, as yet, there is no really satisfactory solution to the problem. The third problem, and this affects all headspace analyses, is removing an aliquot of the headspace gas from the bottle for chromatography.It is essential, of course, that the carbon disulphide distribution should be at equilibrium. For this reason we position the water-bath containing the samples and standards close to the chromatograph and sample the headspace at 80 “C without removing the bottles from the bath. The gas-tight syringes used are rinsed with distilled water, at 80 O C , several times prior to each injection. When sampling the headspace “hot,” it is important not to cool the bottles at all, otherwise the headspace concentration of carbon disulphide falls rapidly, even at temperatures in excess of its boiling-point. Some analysts cool the bottles to ambient temperature before analysis of the headspace, which makes automation easier but can reduce the sensitivity. Sampling the headspace “hot” we find that up to 40-50 samples can be analysed by one person in a day.We have recently introduced a check for leakages from either the reaction bottles or the syringes by spiking all samples and standards with thiophene5 as an internal standard and have found it to give a considerable improvement in both efficiency and reliability. The fourth problem is that of interference. With some crops, such as lettuce, there is little interference from other volatile sulphur compounds and the headspace can be analysed rapidly on a non-polar gas-chromatographic stationary phase at low temperature. With crops such asSeptember, 1982 HEADSPACE ANALYSIS 435 hops, onions and brassicas a separation of carbon disulphide from other volatile sulphur com- pounds, such as hydrogen sulphide, carbonyl sulphide, etc., can readily be obtained on porous polymer columns but the sensitivity of the analysis may be considerably reduced.It has been suggested that there may be naturally occurring compounds that decompose to carbon disulphide under the conditions employed and many laboratories have reported finding very low levels of carbon disulphide (<0.1 mg kg-1 of dithiocarbamate) in apparently un- treated samples. In some instances this may have been a result of contamination with dithiocarbamate formulations (these materials are designed to spread and stick to surfaces; this they do all too readily and can be difficult to remove from glassware, etc.). Certain other fungicides, such as captan and captafol, can also, rather unexpectedly considering their chemi- cal structure, produce carbon disulphide under the conditions employed.Where significant residues (meaning in this context in excess of appropriate maximum residue limits) are found, it is important that they be confirmed by an alternative technique. It is also desirable that the confirmatory technique give some indication of the type of dithiocarbamate present, as the headspace method gives none. Acceptability of Headspace Analysis Bearing in mind the important consequences that the results can have, it is imperative that analytical methods for pesticide residues should be proved to be reliable. The UK Government, the EEC Commission and the FAO/WHO Codex Commission of the United Nations all accept that the best way of proving the reliability of analytical methods, to the satisfaction of all parties, is to subject them to collaborative study by interested laboratories.A “hot sampling” headspace method had been subjected to this tests and, although the results may seem rather variable (mean recovery of three dithiocarbamates, spiked at levels approximating to maximum residue limits, of 84% with a standard deviation of &17%, in a series of 154 analyses) they are sufficiently encouraging, in the analysis of what is generally accepted to be a group of difficult compounds, for the method to be considered by the EEC Commission for adoption as an Official Community Method for dithiocarbamate residues. Refinements to the headspace technique, in the types and sealing of containers, in sampling crops, and in the use of internal standards, have been made by a number of workers since it was studied collaboratively, and these seem likely to improve the reliability of the method to an extent comparable with that obtained by the refinement’ of the original spectrophotometric method for dithi0carbamates.l 1. 2. 3. 4. 5. 6. 7. References “Report of an ad hoc Group on the Relevance of Ethylene Thiourea (ETU) in Ethylenebisdithiocarba- mate (EBDC) Fungicides,” Personal Communication, Groupement International des Associations Nationales de Fabricants de Pesticides, Brussels, 1979. Keppel, G. E., J . Assoc. Off. Anal. Chem., 1971, 54, 628. McLeod, H. A., and McCully, K. A., J . Assoc. Off. Anal. Chem., 1969, 52, 1226. Lesage, S., J . Assoc. Off. Anal. Chem., 1980, 63, 143. Blaicher, G., Woidich, H., and Pilannhauser, W., Emahrung, 1980, 4, 440. Report by the Panel on Determination of Dithiocarbamate Residues, Analyst, 1981, inithe press. Thier, H. P., European Economic Community, personal communication, 2421/VI/79-EN SMH, 1979. molecular models for research Orbit and Minit systems- 17 shapes of coloured atom centres and bonds-for easy construction of models @ Leafield, Oxford OX8 5NY let (000387) Cochraner of Oxford Please mention Analytical Proceedings when replying to advertisements P Circle A404 for further information.

ISSN:0144-557X    

DOI:10.1039/AP9821900428

出版商:RSC    

年代:1982

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436 BIOSIGNIFICANT TRACE ELEMENTS IN SOILS Anal. PYOG. Biosignificant Trace Elements in Soils The following is a summary of the paper presented at a Joint Meeting of the Northern Ireland Region and the Andrews Society held on October 22nd, 1981, at The Queen’s University, Belfast . The Role of Biosignificant Trace Elements in Soils in Relation to Plant and Animal Nutrition as Revealed by the Techniques of Atomic Spectroscopy T. S. West The Macaulay Institute for Soil Research, Aberdeen, AB9 2 3 J The seven trace elements boron, cobalt, copper, iron, manganese, molybdenum and zinc are the only ones known, at present, to be essential for plant life, but chromium, nickel, selenium, silicon, vanadium, bromine and iodine are biofunctional in the sense that they have been shown to have beneficial effects on the growth of some plants under certain conditions. The roles played in plant life by these elements have been discussed, together with the levels and forms in which they occur and the effects caused by their deficiency.l All of these elements except boron are essential to animal life, as are several others.The range of occurrence of these elements in the crustal rocks of the earth and in ten typical soils has also been described, along with the significance of the depleted or accumulated levels at which they exist in soils. The forms of occurrence of bioessential trace elements and various soil management factors control the availability to plants of the soil’s (total) store of trace elements. The roles played by soil pH, redox balance, soil organic matter content and meteoro- logical conditions are also significant .2 Complicating factors, such as contamination of sampled herbage by soil, seasonal variation in the total trace element content of plants, translocation within the plant and the effect of grazing by animals, show that rather than analyse the plant tissues it is generally better to assess the supply from the soil by extracting the latter with selected extractants that can simulate the plants’ ability to take up trace elements from the soil.In many instances these extracts do not have sufficiently high levels of the extracted trace elements to permit direct spectroscopic analysis. Pre-concentration techniques, such as co-precipitation on selected gathering agents, solvent extraction or deposition by cementation, allow analysis to be carried out subsequently.A multi-element capability is particularly important for future trace element work on soils, plants and animals because of the existence of synergic effects, such as that between molyb- denum, sulphur and copper, whereby copper deficiency is induced in ruminants by high herbage levels of molybdenum and sulphur even where the supply of copper is sufficient. The simplicity of the trace element technique of atomic-absorption spectroscopy has to be assessed against its limited sensitivity in the flame mode and its virtual single-channel capabil- ity. Emission techniques, such as (polychromator) spectrography and atomic emission with the inductively coupled radiofrequency plasma are less easy to use, but are inherently capable of higher sensitivity and simultaneous multi-element analysis.Spark-source mass spectro- metry, arguably a technique of atomic spectroscopy, also shows considerable value in the analysis of trace elements in soils, plants and animals3 In general, spectroscopic techniques offer diagnosis of problems before as well as after “incidents” where cause and effect are already known, but by virtue of their more recently acquired versatility and sensitivity they should, in future, become increasingly useful in establishing the existence of hitherto unknown deficiency problems and inter-element syner- gisms. References 1. 2. 3. West, T. S., 1st T. B. Miller Memorial Lecture, “Biosignificance and Analysis of Trace Elements in Agricultural Soils,” Special Publication, North of Scotland College of Agriculture, Aberdeen, 1979. West, T. S., Philos. Trans, R. SOC. London, Ser. B., 1981, 294, 19. Welch, K. H., and Ure, A. M., Anal. Proc., 1980, 17, 8.

ISSN:0144-557X    

DOI:10.1039/AP9821900436

出版商:RSC    

年代:1982

数据来源: RSC

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September, 1982 DEVELOPMENTS AND APPLICATIONS OF DATING TECHNIQUES 437 Recent Developments and Applications of Dating Techniques The following are summaries of two of the papers presented at a Meeting of the Analytical Division held on October 28th, 1981, at 23 Savile Row, London, W.l. Radiocarbon Dating at Oxford Using a Dedicated Accelerator R. E. M. Hedges Research Laboratory for Archaeology, Radiocarbon Accelerator Unit, Oxford University, 6 Keble Road, Oxford, OX1 3QJ Introduction In radiocarbon dating, the “age” of a sample is evaluated from a measurement of the isotopic ratio 14C/12C. Those samples are suitable the carbon atoms of which have been, at some time, in equilibrium with the carbon dioxide in the atmosphere, and in particular this includes living organisms whose main source of carbon is, directly or indirectly, through photosynthesis. As 14C is formed at an approximately uniform rate in the stratosphere (by the reaction of cosmic ray produced neutrons with nitrogen nuclei), such organisms reflect the ambient 14C/12C ratio (although a small amount of isotopic fractionation, measurable by its effect on 13C/12C ratios, also occurs).This has the very low abundance ratio of about one part in 10l2. The “age” of the sample, in this context, is the time elapsed since exchange with atmospheric or related reservoirs of carbon dioxide (e.g., the oceans) ceased, for example, on the death of the living creature. The initial 14C/12C ratio decreases with the half-life of 14C radioactive disintegration, that is, 5730 years. Thus, apart from problems of interpretation (what constitutes equili- brium in a given case, for example) it is sufficient to make only the abundance measurement of 14C for a date.Hitherto this measurement has been made by detecting the rate of beta emission from a sample. Because of the low abundance and long half-life of 14C, samples containing 1-5 g of carbon are required to register adequate counting statistics in a reasonable time. Further- more, the signal to background ratio is not high, typically between five and ten to one, and the ultimate age possible for dating is limited to samples about six half-lives old. The method described here is simply a different way of measuring the abundance ratio, in which 14C is detected by its mass rather than by its radioactivity.It has proved possible to detect about 1% of the 14C in a sample (this would take 80 years by beta counting), so that samples a thousand times smaller can be measured to an adequate precision. Also, the signal-to-background can be greatly improved (to lo4 to 1 or better) so that much older material can be dated. (The ultimate limitation is set by inherent contamination in the sample itself.) As sample size has been a major limitation in both archaeological and environ- mental dating, a freeing of the limits of amount and age should give a great improvement. For example, bones contain only limited amounts of surviving protein, and only large and fairly recent specimens could be dated. But with the new method it becomes possible to date portions from important human skeletons of the pre-Homo sapiens period (e.g., before 40000 BP).This is the justification for embarking on the construction of the necessarily expensive, large and complex equipment. At present, there are about 100 conventional (beta counting) radiocarbon laboratories in the world, and the total number of published dates is in the region of 50000. High Energy Mass Spectrometry The very low abundance of 14C necessitates special approaches if it is to be successfully measured in a mass spectrometer. The likelihood of isobaric molecules means that atomic ions should be selected. The mass difference between 14C and 14N is too small (1 in 104) for separation by high resolution. Furthermore, it is necessary to have an efficient ion source and high beam transmission (also implying a relatively low resolution instrument) in order that the small sample advantages of the method will not be lost.438 DEVELOPMENTS AND APPLICATIONS OF DATING TECHNIQUES Anal.Proc. A major part of the solution is to accelerate the ion beam to energies in excess of 5-10 MeV. At this energy nuclear physics particle detectors can be used, so that the final energy of the particle can be measured with a resolution of 1% or so. In addition, and of greater importance, the rate of energy loss of the ion, as it is stopped in the detector, is characteristic of its nuclear charge, and in this way 14C and 14N can be discriminated even when they have the same energy. Such a detector (which resembles a gas-filled proportional counter with spatial resolution) can detect ions at a rate of up to 5 KHz or so.For an ion source current of 1 yA this corresponds to only lo-’ of the beam. The balance must be eliminated before reaching the detector. In the system adopted by most accelerator radiocarbon laboratories, the acceleration is achieved with a tandem electrostatic accelerator. This has negative ions injected into it at, say, 4-0 KeV, accelerates the ions linearly to an energy corresponding to that of the terminal voltage (in our case between 2 and 3 MV), and then strips the ions at the terminal by colliding the beam with a thin foil or region of differentially pumped gas. At energies of 2-3 MeV, C- ions lose electrons predominantly to give C3+. The positive ion is further accelerated away from the positive potential of the terminal, gaining an extra energy of 3 times the voltage, so that the final particle energy is 8-10 MeV.The effect of the stripper is to destroy molecular ions (although some survive in lower charge states; for example, CH,,+ has been detected following stripping from CH,) . Another important advantage is the discrimination against 14N, since the ion N- is believed not to exist in its ground state. (Some N is injected, in the form of NH-, however.) In addition to the advantages of a tandem acceleration, it is still necessary to use conventional mass spectrometric methods to select mass 14 ions. Fig. 1 shows the beam optical configuration. The injector magnet has a resolution of about 100, and injects mainly 14C-, 12CH 2 , - 13CH-, and “tails” of 12C-, W-, 14NH- and lSO-.The analyser magnet has a mass resolution of about 1000. Fig. 2 shows how, for a given magnetic field and bending radius, different atomic ion masses can be transmitted when they possess a particular energy. Such aberrant particles arise through charge changing collisions in the accelerator leading to a broad energy distribution. However, a further selection can be made, on the basis of velocity (an alternative possibility is to select for energy), and the final mass-selective com- ponent is a Wien filter (crossed electric and magnetic fields). The operation of these three kinematically selective components is sufficient to reduce the flux of unwanted ions to the detector to manageable proportions. Detector Electrostatic Stripper foil -be- at 2.5 MV -c3’ Fig.1. Ion beam configuration for 14C accelerator. Much research has been expended on the design and operation of the ion source. This must be efficient, produce as large a beam of C- as possible, and be free from memory effects, isotopic fractionation and instabilities. The principle of operation is to bombard a target made from graphite (this is prepared from the sample by pyrolysing acetylene) with a beam of Csf. C- isSeptember, 1982 DEVELOPMENTS AND APPLICATIONS OF DATING TECHNIQUES 439 sputtered off with a yield of about lo%, and beam currents of 20-30 pA can be produced with high stability. 20 16 g 12 . ). P Z 8 w 4 0 Particles transmitted by magnet ’ . * * . 4 8 12 16 20 24 : Ma ss/a. m . u . 8 Fig. 2. Methods of kinematic rejection of unwanted ions.Performance and Prospects The accelerator system at Oxford is nearing the final stages of construction after several delays owing to difficulties with the commercially supplied accelerator. When complete it should be the first dedicated system for carbon dating, although other groups, using existing facilities, have shown that dates of limited accuracy can be produced with much larger acceler- ators. To be useful, a measurement with an accuracy of 0.5% is required. Several strategies to reduce systematic errors are called for; these include the use of standards on a cycling basis, the repetitive pulsed transmission of the stable isotopes 12C and 13C through the accelerator, and the avoidance of any isotopically selective elements in the beam handling, such as magnetic steerers and lenses.The ultimate accuracy attainable is not yet known, although it is doubt- ful if it can exceed the best conventional laboratory accuracy, which is 0.1-0.2%. The accelerator system is capable of making a routine measurement within an hour or so, although very old samples will take considerably longer. The theoretical output in a year could be as high as 2000 dates, but this would involve an enormous amount of chemical preparation of samples so that 400 dates a year is a more realistic figure. It is hoped that there will be time available for similar experiments with other nuclides in trace abundance. Many of these are of potential dating interest; for example 10Be, with a half-life of 1.6 Myr. Indeed, the use of high energy mass spectometry, especially for the detection of nuclides in the abundance range from 1 0 - l O to IO-lS, opens up a new analytical field.Other groups have already measured the trace levels of, for example,1291 in meteorites, and experiments are in mind for the detection of such exotic particles as free quarks and nuclides resulting from proton decay. Bibliography “ 1st Conference on Radiocarbon Dating with Accelerators,” University of Rochester, Rochester, N.Y., 1978. “Symposium on Accelerator Mass Spectrometry,” Argonne National Laboratory, Argonne, IL, 1981. Hedges, R. E. M., Archaeometry, 1981, 23, 3. . Thermoluminescence Dating J. Tate National Museum of Antiquities of Scotland, Conservation and Research Laboratories, Government Training Centre Complex, West Granton Road, Edinburgh, EH5 1 JA Principle of the Method Both the clay of pottery and the surrounding burial medium generally contain small amounts of radioactive elements, principly uranium-238, thorium-232 and potassium-40, and their440 DEVELOPMENTS AND APPLICATIONS OF DATING TECHNIQUES Anal. Proc.associated daughter decay products. Each of the parent isotopes have extremely long half- lives, so that, provided secular equilibrium has been attained, the rate of production of radio- active decay “particles” is constant over time scales of some thousands of years. Pottery fabric usually consists of a basic clay mixed, intentionally or fortuitously, with sand or crystalline inclusions which give the pure clay improved working and firing characteristics.Principal among these minerals are quartz and various feldspars, and in contrast to the clay they, particularly quartz, are almost free of radioactive impurities. Although free from radioactive isotopes themselves they will, during the lifetime of the pottery and subsequent burial, be subjected to the radiation from the surrounding clay. Most of the radiation energy is dissipated as heat, but a small fraction is actually absorbed by the crystals. Electrons may be stimulated from their normal states to exited states; most rapidly return to their ground state but some may diffuse through the conduction band to become bound at defects or impuri- ties, the tightness of such binding depending on the electronic environment of the “trap” and on the effective electron energy.The associated electron-deficient site created during ionisa- tion may simply recombine with a free electron or, in the correct circumstances, activate a luminescence centre. The mineral inclusions in pottery are likely to have many different impurities and defects and consequently electron “traps” of different energies. In quartz the principle trap complex of interest in thermoluminescence (TL) may be the substitution of A13+ for Si4+ in conjunction with adalkali metal ion. Ignoring the possibility of quantum mechanical tunnelling, the probability of escape depends on the trap depth and nature and the lattice temperature. As the temperature of the crystal is raised the lattice vibrations become increasingly energetic and electrons may gain sufficient energy to escape from the (probably perturbed) trap sites.In returning to their low energy states a small fraction of the thermally released electrons may combine with activated lumines- cence centres with consequent photon emission. This is exactly what happens when pottery is made and kiln fired, to perhaps 500-1000 “C; the trapped “geological” electrons are released, giving a “time zero” for subsequent accumulation until the present day or any second (high temperature) heating. The thermoluminescence measurement therefore involves estimating the amount of stored energy by the controlled heating of a sample of the pottery and simultaneous measurement of the light emitted. Thermoluminescence glow curves are shown in Fig. 1 from two identical samples from an Iron Age sherd.The first sample was untreated, showing archaeological (“natural”) thermo- r-rr- I I 100 200 300 400 5 Te m per at u rePC 0 Fig. 1. Thermoluminescence glow curves from aa Iron-Age Sherd. luminescence, while the second was given an artificial radiation dose in addition to the archaeo- logical radiation dose before the thermoluminescence was measured. The point is that from measurements of this kind it is possible to characterise the TL versus radiation dose response of the material and so, by extrapolation, determine the magnitude of the archaeological radiation441 September, 1982 DEVELOPMENTS AND APPLICATIONS OF DATING TECHNIQUES dose which the pottery must have received [Fig, Z(a)]. The age of the pottery, or, more pre- cisely, the last high temperature heating event, can then be calculated, provided that the archaeological radiation dose rate can be measured : AD kalpha + beta + gamma Age = where AD is the archaeological radiation dose and the bottom line represents the alpha and beta internal dose rates and the gamma dose rate from the surrounding burial medium.Alpha radiation is less efficient in creating TL than beta or gamma radiation and this is reflected by the factor k ((1) which has to be measured for each sherd. 1 Intercept correction I I 1 I 1 200 100 0 100 200 300 0 200 400 600 Artificial radiation doselrad Artificial radiation doselrad Fig. 2. (a), Thermoluminescence veysus radiation dose for samples before the archaeo- logical TL has been drained; (b), thermoluminescence uemus radiation dose after the archaeological TL has been drained.Archaeological dose = E + I . The criteria that must be obeyed for this dating method to be useable are that the probability of electron escape from deep traps is small, that the increase in the number of trapped electrons (and hence TL) is a linear, or known, function with time, that the firing of the pottery removed all geologically accrued electrons to give a time-zero and that the natural radiation dose rate can be measured. Kinetic studies1s2 indicate that trapped electrons, which cause maxima in the glow curve above about 325 "C, have lifetimes of many thousands of years. Unfortunately, some minerals do not always show this predicted stability and 3 is routine to store samples after known irradiations to test for any anomalous fading.The TL v e m w radiation dose curve is deter- mined from the integral of TL glow curves over appropriate temperature ranges [Figs. 1 and 2(a)], with a correction for non-linearity at low dose levels by irradiating samples from which the natural TL has been drained [Fig. 2(b)]. Radiation Measurements Consideration of the dosimetry within the pottery fabric has given rise to several different techniques. In the fine grain method3 1-8 pm grains are selected from the fabric (after gentle crushing). These grains experience the full alpha radiation dose, in contrast to larger (90- 150 pm) inclusions where the alpha contribution is confined to the outer few micrometres and can be reduced still further by etching in hydrofluoric acid.4 In this instance measurement of the gamma dose rate from the surrounding burial medium becomes relatively more important.In the subtraction technique5 this difference is utilised so that only the internal radiation dose has to be determined, the external gamma dose cancelling out (hence minimising problems about the environmental conditions). An alternative difference method is to measure the TL both from quartz inclusions and from alkali feldspar inclusions, the latter having a large internal beta radiation dose from potassium-40.442 DEVELOPMENTS AND APPLICATIONS OF DATING TECHNIQUES Anal. R o c . Measurement of the alpha radiation dose rate in the pottery is most often carried out by alpha counting using zinc sulphide scintillator screens, and for the beta dose by thermolumines- cence dosimetry using high sensitivity phosphors such as calcium fluorides or calcium fluoride - manganese.’ The gamma dose from the burial surroundings is measured in sit% by burial of a known phosphor for six months or 1 year, or more rapidly by scintillation counting.8 The potassium content can be determined by flame photometry.Other techniques are fission track analysiss and neutron activation. The relative advantages and disadvantages relate mainly to the estimation of any disequilibrium that may have existed or built up during burial owing to loss of radon and thoron in the natural decay chains.1° Dating Projects Archaeological dates for pottery have been produced by several laboratories using fine grain and quartz and feldspar inclusion techniques with generally good agreement with calibrated radiocarbon and known archaeological dates.Careful study of the uncertainties in TL measurement, calibration and environmental factors have lead to over-all uncertainties as low as 6 5 % for routine dating.ll Dates have also been estimated from techniques involving the change in sensitivity of the low temperature peak in quartz (“pre-dose”) and from zircon in- clusions. Zircon grains have high internal radioactivity and thus exhibit the attractive prop- erty of re-accumulating TL naturally, so in principle all radiation calibration problems could be avoided. Unfortunately, the TL may not always be stable.12 Pottery is not the only material suitable for dating; burnt stones and lava may also have had their geological TL erased by heating events, which can be dated in similar manner, although the sample prepara- tion and dosimetry problems are somewhat different. Recent work in this field has been sum- marised by Wintle.l3 Perhaps the most exiting recent project has been the dating of deep sea sediments by TL.14J5 In this instance the mechanism is not heat but is thought to be bleaching by sunlight, possibly combined with grinding while the sediment was being laid down.The development of TL as a possible dating method applicable to both deep sea and terrestrial sediments seems likely to stimulate yet more research with, one hopes, consequent advances in understanding in both geology and archaeology. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. References Fleming, S.J ., “The Acquisition of Radioluminescence by Ancient Ceramics,’’ DPhil. Thesis, Oxford University, 1969. Fleming, S. J ., “Thermoluminescence Techniques in Archaeology,” Clarendon Press, ?“ford, 1979. Zimmerman, D. W., “Thermoluminescence Dating Using Fine Grains From Pottery, -Archaeometry, 1971, 13, 29. Fleming, S. J ., “Thermoluminescence Dating : Refinement of the Quartz Inclusion Technique,” Archaeometry, 1970, 12, 135. Fleming, S. J., and Stoneham, D., “The Subtraction Technique in Thermoluminescence Dating, ” Archaeometry, 1973, 15, 229. Bailiff, I. K., and Aitken, M. J., “Use of Therjmoluminescence Dosimetry for Evaluation of the Internal Beta Dose-rate in Archaeological Dating, Nucl. Inst. Meth., 1980, 173, 423. Mejdahl, V., “A Thermoluminescence Technique for Beta-ray Dosimetry,” irt “Proceedings of the 1st Specialist Seminar on Thermoluminescence Dating, Oxford, 1978,” PACT J., 1978, 2, 35. Liritzis, Y., and Galloway, R. B., “Correlationof Variations in Gamma-ray Dose RatewithMeteorological Factors,” Archaeometry, 1981, 23, 109. Wagner, G. A., “Dose Rate Evaluation for Thermoluminescence Dating by Fission Track Counting, ” Proc. 16 IBt. Con.. Archaeometry Archaeological Prospection, 1976, National Museum of Antiquities of Scotland, 1980. Aitken, M. J., “Dose Rate Evaluation” in “Proceedings of the 1st Specialist Seminar onThermolumines- cence Dating, Oxford, 1978,” PACT J., 1978, 2, 18. Mej dahl, V. , “Thermoluminescence Dating Based on Quartz and Feldspar Inclusions, ” Riso National Laboratory Offprint, Riso, Denmark, 1981. Zimmerman, D. W., “TL Dating Using Zircon Grains,” in “Proceedings of the 1st Specialist Seminar on Thermoluminescence Dating, Oxford, 1978,” PACT J., 1978, 3, 458. Wintle, A. G., “Thermoluminescence Dating : A Review of Applications to Non-pottery Materials,” Archaeometry, 1980, 22, 133. Wintle, A. G., and Huntley, D. J., “TL Dating of Sediments,” in “Proceedings of the 1st Specialist seminar on Thermoluminescence Dating, Oxford, 1978,” PACT J., 1978, 3, 374. Wintle, A. G., and Huntley, D. J., “Thermoluminescence Dating of a Deep Sea Ocean Core,” Nature, 1979, 279, 710.

ISSN:0144-557X    

DOI:10.1039/AP9821900437

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

September, 1982 YOUNG PERSONS MEETING 443 Young Persons Meeting The following is a summary of one of the papers presented at a Meeting of the Electroanalytical Group held on November 19th, 1981, at the Technical College, Paisley. Voltammetric Determination of Phosphate in Blood M. A. Abdalla, N. K. Bsebsu and A. G. Fogg Chemistry Department, Loughborough University of Technology, Loughborough, Leicestershire, LEI 1 3T U Orthophosphate has been determined as 12-molybdophosphate in aqueous acidic molybdate solution by linear-sweep and differential-pulse voltammetry at a glassy carbon electrode in a static system.l The procedure recommended is essentially an anodic-stripping procedure as a positive-going potential scan is used to re-oxidise molybdophosphate reduced at the electrode surface earlier in the scan.These techniques were also applied to the determination of phos- phate, silicate, arsenate and germanate in the solution conditions in which the fl-heteropoly- acids are stabilised by the addition of acetone or e t h a n ~ l , ~ , ~ and to the determination of phos- phate as phospho~anadomolybdate.~ All of these methods have been adapted to the voltam- metric flow-injection determination of the determinands by injection of the pre-formed heteropolyacids into eluents with the composition of the reagent blanks3 By this means 0.01 and 0.1 pg ml-1 of silica and phosphate, respectively, were determined. The application of these static and flow-injection voltammetric methods to the determina- tion of phosphate in blood serum is described in this paper.Experimental Details of the static and flow-injection voltammetric procedures have been given previo~sly.~-~ Wellcomtrol Quality Control sera (BCOl and BC02) were used to test the procedures: solutions were prepared from the dry sera according to the manufacturer’s instructions. To determine the inorganic phosphate in a serum sample, 2.0 ml of serum were added to a small beaker containing 7-8 ml of 15% trichloroacetic acid. This was mixed carefully and filtered into a 50-ml calibrated flask. The precipitate was washed with water and the washings were added to the solution in the flask. Incorrect high values for the inor- ganic phosphate content were invariably obtained if this filtrate was not perfectly clear. The appropriate reagents were added to the contents of the flask and the phosphate was determined voltammetrically in accordance with the procedures given previ~usly.l-~ Calibration graphs were prepared in the range 0.5 x 10-54 x 10-5 M of phosphate.Results and Discussion Initial tests were made of the static aqueous and aqueous acetone methods on a bovine albumin solution (7 g in 100 ml) spiked with phosphate (3.2 mg in 100 ml) : the solution was cleared with trichloroacetic acid. The values obtained using the two methods were 3.11 and 3.15 mg per 100 ml, respectively, with coefficients of variation (four determinations) of 1.7 and 0.3%.. A carbon paste electrode* also gave excellent results with the aqueous system but was unswtable for use with the aqueous acetone system. The results obtained using various procedures for the determination of phosphate with the Wellcomtrol samples are given in Table I.Very high inaccurate results, frequently over twice the certificated value, were obtained using the aqueous acetone and aqueous ethanol systems. It appears that in these acidic, partially non-aqueous, systems containing molybdate organic phosphates in the cleared sera are hydrolysed to, orthophosphates. The vanadomolybdate system gave slightly better values but the differential-pulse voltammetric result on sample BC02 was very high, and this system is probably also better avoided. Satisfactory results were obtained with the simple aqueous system using both the static differential pulse voltam- metric and the flow-injection procedures. The flow-in jection procedure, in particular, is particularly suited to this determination.444 EQUIPMENT NEWS TABLE I Anal.PYOC. DETERMINATION OF INORGANIC PHOSPHATE IN WELLCOMTROL SERA SAMPLES USING VARIOUS STATIC (DIFFERENTIAL-PULSE) AND FLOW-IN JECTION VOLTAMMETRIC METHODS Sample No. BCOl .. .. BC02 .. .. BCOl .. .. BC02 .. .. Certificated inorganic phosphate target value (mg per 100 ml) 4.72 3.22 4.72 3.22 Aqueous system* A - I 1 Flow-injection Static method method 4.75 (1.6%) 4.75 (0.2%) 3.21 (1.3%) 3.16 (0.2%) Vanadomolybdate system* # 1 Flow-injection Static method method 4.91 (1.2%) 4.80 (0.2%) 4.16 (1.2%) 3.36 (0.2%) Aqueous acetone system : static method* 7.30 (0.3%) 7.90 (0.3%) Aqueous ethanol system : flow-inj ection method* 11.1 (2.9%) 6.83 (2.2%) * Figures in parentheses are coefficients of variation on 10 determinations.Since the completion of these studies we have shown6 that phosphate can be determined by direct injection into aqueous acidic molybdate reagent, using a delay loop for molybdophos- phate formation before the detector cell. This procedure has now been optimised, and will be tested for the determination of phosphate in the Wellcomtrol samples. If these tests are satisfactory, the procedure will be further evaluated by analysing a large number of human blood plasma and urine samples. Arrangements have been made to do this in collaboration with a hospital laboratory. M.A.A. thanks the British Council for financial support and the University of Khartoum for leave of absence. N.K.B. thanks the people of the Socialist People’s Libyan Arab Jamahiriya for financial support and leave of absence from El-Fateh University, Tripoli. References 1. 2. 3. 4. 6. Fogg, A. G., and Bsebsu, N. K., Analyst, 1981, 106, 369. Fogg, A. G., Bsebsu, N. K., and Birch, B. J., Talalzta, 1981, 28, 473. Fogg, A. G., and Bsebsu, N. K., Analyst, 1981, 106, 1288. Fogg, A. G., and Bhanot, D., Analyst, 1981, 106, 883. Fogg, A. G., and Bsebsu, N. K., Analyst, 1982, 107, 666.

ISSN:0144-557X    

DOI:10.1039/AP9821900443

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

444 EQUIPMENT NEWS Anal. PYOC. Equipment News Further details of all items reported below are available from the companies concerned. For rapid information please complete the Reader Enquiry Service card (circle the appropriate number mentioned), rather than approaching companies direct. Infrared Spectrometers the Model 783 scans to 200 cm-1. Features The Model 780 Series comprises three instru- include pre-sample chopping and continuous ments: the Model 781 scans from 4 000 cm-l to digital readout of both wavenumber and ordin- 600 cm-l, the Model 782 scans to 400 cm-l and ate value. Spectra are presented on a micro-September, 1982 EQUIPMENT NEWS 445 processor-controlled flow-chart recorder with automatic wavenumber correction. Perkin-Elmer Limited. Circle 50 1. carbohydrates.The detection limit is as low as 10 ng and a complete analysis takes 20 min. Tecator AB. Circle 508. Spectrometer The FX6000 Fourier Transform Infrared Spectrometer employs a “Transept” optical wedge interferometer requiring only a few centimetres’ movement. A complete spectrum can be recorded in 2.5 s. Anaspec Limited. Circle 502. Multi-channel Detection Equipment The B & M Spektronik INF 500 is a 512-channel vidicon camera with a sensitivity range of 0.4-2.0 pm, a dynamic range of lo4 and an analog to digital converter of 12 bits. The IR-AK 128 and IR-AK 256 are diode array cameras with 128 and 256 channels, respectively. Spectral sensitivity is in the range 2.0-25 pm. EDT Research. Circle 503. Atomic Absorption Spectrophotometer The Scintrex AAZ-2 employs a flameless (tungsten strip) source with Zeeman modulation.It enables elements to be registered indepen- dently of background matrix effects. Techmation Limited. Circle 504. Gas Chromatography Systems The Series-40, with a product processing capability of 150 g h-1, and the Series-80, with a 5 t y-l capability, are available with program- mable microprocessor controls. Elf-SRTI. Circle 505. On-column Injection for Gas Chromatographs An on-column injector for open tubular columns is available for use with Sigma Series gas chromatographs. Perkin-Elmer Limited. Circle 506. Liquid Chromatography Systems The Series 4 chromatograph allows the simul- taneous use of up to four different solvents. Provision is made for flow and gradient pro- gramming. Control is from a video-display keyboard.The Series 10 pumping system is a single pump unit in a cabinet, complete with injector mount and column compartment. . Perkin-Elmer Limited. Circle 507. HPLC System The Optilab 5931 liquid chromatograph, com- bining an interference refractometer and a HPLC unit, is intended for analysis of fats and HPLC Columns Bakerbond wide-pore silica gel columns provide resolution of protein mixtures in less than 1 h with recoveries typically above 95 yo. J. T. Baker Chemicals B.V. Circle 509. Electrochemical Detector for HPLC The Model LCA15 features event marker and auto zero facilities. It is almost completely free from static pick-up and can be used without Faraday cages. EDT Research. Circle 510. Integrator for Chromatography The CDPl computing integrator has been up- dated to permit internal and external standardi- sation.The possible number of timed events has been doubled and results can be recalculated using new parameter data. Pye Unicam Ltd. Circle 51 1. Dipping Chambers Made from “Tempax” borosilicate glass, the chambers allow uniform application of reagents to thin-layer chromatography plates. Desaga GmbH. Circle 512. Gas Sampling Bags A selection of sampling bags is available. They can be adapted for subsequent gas chromato- graphy analysis. Field Instruments Co Ltd. Circle 513. Portable Gas Analyser The Series 2000/2200 range of portable gas analysers from Columbia Scientific Industries gives audible alarm of the build-up of ozone (1 p.p.b. to 1 p.p.m.) or oxides of nitrogen (10 p.p.b.to 50 p.p.m.). Accuracy is better than 2% and response time less than 30 s. Techmation Limited. Circle 514. Gas Detector The Tritector CGS-80 detector/alarm monitors and meters toxic gas, combustible gas and oxygen deficiency, providing audio and visual alarms of unsafe conditions. A “chirp” at 8-s intervals indicates a safe atmosphere. Rotheroe & Mitchell Ltd. Circle 515. Personal Monitoring System The Chronotox System comprises a range of sensors (for carbon monoxide, hydrogen sul- phide, phosgene, hydrogen cyanide and other446 EQUIPMENT NEWS Anal. PYOC. gases), a CMOS microprocessor system for storage and either a datagram readout unit or digital readout unit for hard copy documenta- tion. MDA Scientific (UK) Ltd. Circle 516. Personal Monitor The Adsorba is a stainless-steel tube packed with appropriate adsorbents.It can be used as a passive monitor operating by diffusion or, connected to a sampling pump, as an active monitor. Dutom Meditech Limited. Circle 517. pH/Ion Meter The Model ECM2Ol is a digital millivoltmeter suitable for use with ion-selective electrodes. It measures to 0.1 mV with an over-all accuracy of 0.2 mV. EDT Research. Circle 518. pH Electrodes Orion Research refillable models 91-55 and 91-56 have epoxy bodies. The 91-55 has a standard US connector; the 91-56 has a BNC connector. MSE Scientific Instruments. Circle 519. Balances Electronic PE-series balances with Delta Dis- play are available. The GC302 application input unit converts a PE-series balance into a net total, percentage or animal balance.Mettler Instrumente AG. Circle 520. Portable Balances The Ohaus Port-0-Gram (TM) models C200M and C2000M have ranges of 199.9 g (readability 0.1 g) and 1999 g (readability 1 g), respectively. S . Garcia Sales Ltd. Circle 521. Digital Thermometer The KM450, powered by a 9 V PP3 battery, has a range from -30 to +450 "C with a repeata- bility of 1 "C and a typical accuracy of 1.5 "C a t -30 OC to f0.7% above -10 "C. Boro Labs Ltd. Circle 522. Oil Content Analyser A new version of the OCMA-200 portable unit has a dual measuring range of 0-20 p.p.m. and 0-200 p.p.m. I t is intended for the determina- tion of hydrocarbon contamination of surface water. Horiba Instruments Ltd. Circle 523. DNA Electrophoresis Cell The DNA Sub-Cell allows DNA electrophoresis to be run in submarine or agarose bridge modes. It consists of a cell body with removable casting gates, lid and comb holder with 15-well comb.Bio-Rad Laboratories Ltd. Circle 524. Chart Recorders A range of single-pen and double-pen chart recorders features an event marker, electric pen lift and forward, stop and reverse chart drives. V. A. Howe & Company Limited. Circle 525. Literature A brochure gives information on the Biotronix range of fibre-tipped chart-recorder pens. There is also a catalogue describing the Series A Pressure-lok Gas Syringe, which features a positive rear plunger stop to prevent the plunger blowing out of the barrel at high pressures. Field Instruments Co. Ltd. Circle 526. An applications report outlines the use of the CSI 740 portable X-ray fluorescence analyser in analysing air particulates and waste waters for trace elements.Columbia Scientific Industries Corporation. Circle 527. A brochure describes the Camac Micronalab multi-channel analyser, which is available in two formats: as a complete console containing both display and keyboard, or for multi-viewing with free-standing, large-screen display and special function keyboard. Nuclear Enterprises Limited. Circle 528. A leaflet gives details of a portable HPLC system, which employs a microprocessor to select solvent changes and composition. American Research Products Corp. Circle 529. A mini-catalogue provides information on a range of radiation detection devices and access- ories. Among these are a 1 eV-14 MeV neutron measurement system giving same-day answers on exposure, and a radiation alarm system.Dosimeter Corporation. Circle 530. A leaflet describes two instruments for radiation detection. Radiation Alert is portable and combines the features of a geiger counter and a radiation alarm. The Radiation Alert-Mini is a pocket-size personal radiation detector and alarm. Heyden & Son Ltd. Circle 531. Technical literature is available on Merck water- testing products. These include the Aquamerck446 EQUIPMENT NEWS Anal. PYOC. gases), a CMOS microprocessor system for storage and either a datagram readout unit or digital readout unit for hard copy documenta- tion. MDA Scientific (UK) Ltd. Circle 516. Personal Monitor The Adsorba is a stainless-steel tube packed with appropriate adsorbents.It can be used as a passive monitor operating by diffusion or, connected to a sampling pump, as an active monitor. Dutom Meditech Limited. Circle 517. pH/Ion Meter The Model ECM2Ol is a digital millivoltmeter suitable for use with ion-selective electrodes. It measures to 0.1 mV with an over-all accuracy of 0.2 mV. EDT Research. Circle 518. pH Electrodes Orion Research refillable models 91-55 and 91-56 have epoxy bodies. The 91-55 has a standard US connector; the 91-56 has a BNC connector. MSE Scientific Instruments. Circle 519. Balances Electronic PE-series balances with Delta Dis- play are available. The GC302 application input unit converts a PE-series balance into a net total, percentage or animal balance. Mettler Instrumente AG. Circle 520. Portable Balances The Ohaus Port-0-Gram (TM) models C200M and C2000M have ranges of 199.9 g (readability 0.1 g) and 1999 g (readability 1 g), respectively.S . Garcia Sales Ltd. Circle 521. Digital Thermometer The KM450, powered by a 9 V PP3 battery, has a range from -30 to +450 "C with a repeata- bility of 1 "C and a typical accuracy of 1.5 "C a t -30 OC to f0.7% above -10 "C. Boro Labs Ltd. Circle 522. Oil Content Analyser A new version of the OCMA-200 portable unit has a dual measuring range of 0-20 p.p.m. and 0-200 p.p.m. I t is intended for the determina- tion of hydrocarbon contamination of surface water. Horiba Instruments Ltd. Circle 523. DNA Electrophoresis Cell The DNA Sub-Cell allows DNA electrophoresis to be run in submarine or agarose bridge modes. It consists of a cell body with removable casting gates, lid and comb holder with 15-well comb. Bio-Rad Laboratories Ltd.Circle 524. Chart Recorders A range of single-pen and double-pen chart recorders features an event marker, electric pen lift and forward, stop and reverse chart drives. V. A. Howe & Company Limited. Circle 525. Literature A brochure gives information on the Biotronix range of fibre-tipped chart-recorder pens. There is also a catalogue describing the Series A Pressure-lok Gas Syringe, which features a positive rear plunger stop to prevent the plunger blowing out of the barrel at high pressures. Field Instruments Co. Ltd. Circle 526. An applications report outlines the use of the CSI 740 portable X-ray fluorescence analyser in analysing air particulates and waste waters for trace elements.Columbia Scientific Industries Corporation. Circle 527. A brochure describes the Camac Micronalab multi-channel analyser, which is available in two formats: as a complete console containing both display and keyboard, or for multi-viewing with free-standing, large-screen display and special function keyboard. Nuclear Enterprises Limited. Circle 528. A leaflet gives details of a portable HPLC system, which employs a microprocessor to select solvent changes and composition. American Research Products Corp. Circle 529. A mini-catalogue provides information on a range of radiation detection devices and access- ories. Among these are a 1 eV-14 MeV neutron measurement system giving same-day answers on exposure, and a radiation alarm system.Dosimeter Corporation. Circle 530. A leaflet describes two instruments for radiation detection. Radiation Alert is portable and combines the features of a geiger counter and a radiation alarm. The Radiation Alert-Mini is a pocket-size personal radiation detector and alarm. Heyden & Son Ltd. Circle 531. Technical literature is available on Merck water- testing products. These include the Aquamerck448 ROYAL SOCIETY OF CHEMISTRY AWARDS Anal. Proc. Aquaquant and Merckoquant ranges, all top centrifuge, the FP-801 sampler for auto- designed for use outside the laboratory. matic sample preparation, the FP-901 Analyser BDH Chemicals Limited. Circle 532. (semi-automatic nine-channel photometer) and the FP-400 incubator. A brochure describes the Spektra portable Nuclear Enterprises Ltd.Circle 536. photometer for water and effluent analysis. Pre- packed sets of reagents and scales are available The v i r ~ i s Guide to F~~~~~ ~~~i~~ details for the analysis of chlorine, chloride, sulphate, ammonium, nitrate, fluoride, cyanide, Copper, chromate, phosphate, silicate, turbidity, hydra- of freeze-drying accessories including Quickseal valves, which permit the removal of individual flasks and ampoules during the drying process zine and aluminium. without interference to the system vacuum. A range of adaptors enables connection of B19 or B24 cone-ended flasks to the valve. Techmation Limited. circle 537. Semat (UK) Ltd. Circle 533. The Model 2008 digital temperature indicator is described in a leaflet. It covers the range from -50 to +750 O C to an accuracy of 0.5%. It bent without affecting performance. Gard Instrument Services Ltd. Circle 634. features a minerally insulated probe that can be A range Of Salzkotten containers for the and transport of flammable liquids is the subject Of a leaflet. Camlab Limited. Circle 545. A range of digital density meters is described in a brochure. This includes the new DMA 35 hand- held meter. A publication, “Homogeneous Catalysis- JMC Products and Services” contains a summary of Paar Scientific Ltd. Circle 535. the principles of homogeneous catalysis, an account of JMC’s involvement in the low A folder containing leaflets on a range of pressure OX0 process, literature references, Labsystems products for health care and etc. research is available. The products described Johnson Matthey Chemicals Limited. Circle are a nine-channel pipette, the FP-510 bench- 546.

ISSN:0144-557X    

DOI:10.1039/AP9821900444

出版商:RSC    

年代:1982

数据来源: RSC