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DOI:10.1039/AP98219FX017

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年代:1982

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ANALYTICAL DIVISION DIARY June, 1982 SHORT COURSE STATISTICS FOR ANALYTICAL CHEMISTRY Reprint of an fmportant Analytical Chemistry Review July 5th - 7th, 1982 SIOO (80) The full course fee includes all meals and accommodation: fee in pa rent heses exc I ud es accommodation. Further details from and application to: Miss C. D. Newton, Department of Chemistry, Loug h boroug h University of Technology, Loug hborough, Leicestershire, LEI 1 3TU (Tel: 0509-631 71 Ex. 351 ). In an attempt to ensure that major developments in chemistry reach as wide an audience as possible the RSC is to make available a reprint of an important review which was published in Chemical Society Reviews Vol 10, No 1, pp 11 3-1 58 entitled : Modern Analytical Methods for Environmental Polycyclic Aromatic Compounds by K.D. Bartle, M. L. Lee, and S. A. Wise Polycyclic aromatic compounds are major pollutants of the environment, originating from many sources. This paper reviews the techniques that are available for identification and analysis and provides the reader with a comprehensive and authoritative source of information on the subject. The paper is divided into the following sections: INTRODUCTION; SAMPLE PREPARATION; CHROMATOGRAPHIC METHODS; MASS S PECTROM ETRY; SPECTROSCOPIC M ETH 0 DS This review, which contains more than 400 references, will be of interest to environmental, petroleum and analytical chemists. A copy may be purchased for f 2.50 ($5.00) by sending a stamped addressed envelope measuring 6" x 9" minimum. together with your remittance, to: Dr. A. Kabi, The Royal Society of Chemistry, UKCIS, The University, NOTTINGHAM, NG7 2RD England 347

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年代:1982

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ANPRDI lS(6) 287-348 (1982) June 1982 Hon. Secretary R. Sawyer Analytical Proceedinas I - Proceedings of the Analytical Division of The Royal Society of Chemistry AD President L. S. Bark Hon. Treasurer D. C. M. Squirrel1 Hon. Assistant Secretary D. 1. Coomber, O.B.E. Hon. Publicity Secretary Dr. A. Townshend, Department of Chemistry, University of Hull, Hull, HU6 7RX Secretary Miss P. E. Hutchinson Editor, Analyst and Analytical Proceedings P. C. Weston Senior Assistant Editor Assistant Editors R. A. Young Mrs. J. Brew, Mrs. P. A. Fellows Publication of Analytical Proceedings is the responsi- bility of the Analytical Editorial Board: J. M. Ottaway (Chairman) J. M. Skinner G. J. Dickes J. D. R. Thomas 'G. W. Kirby A. M. Ure J. N. Miller 'P. C. Weston G. E. Penketh 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, WlV OBN. Telephone 01 -734 9864. Telex 268001. Advertisements: Advertising Department, The Royal Society of Chemistry, Burlington House, Piccadilly, Andytical 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 n g es to : Analytical Proceedings, P u bl ica t io ns Expediting Inc., 200 Meacham Avenue, Elmont, N.Y. 11 003. Second class postage paid at Jamaica, N.Y. 11431. All other despatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outside Europe. PRINTED IN THE UK. Q The Royal Society of Chemistry 1982 London, W1 V OBN. Telephone 01 -734 9864. Editorial First Biennial National Atomic Spectroscopy Symposium Both The Analyst and Analytical Proceedings publish significant numbers of papers describing important developments in the field of analyti- cal atomic spectrometry. The Analytical Editorial Board was therefore delighted to note the organisation of a new national symposium on this subject, the first of which is to be held in Sheffield next month from 13-15th July.The major international conference covering this field, the Colloquium Spectroscopicum Internationale (CSI), is organised every two years, and although it was held in Cambridge in 1979, the desire of other nations to undertake the responsibility for organising the meeting is so great that the return of the CSI to the UK will be some years ahead. A UK national symposium will therefore afford British analysts, involved in the development and use of atomic spectrometric methods, an important meeting point for the dissemination of new ideas and discussion of continuing problem areas. The First Biennial National Atomic Spectro- scopy Symposium is being organised jointly by the Atomic Spectroscopy Group of the Analyti- cal Division of the RSC and the Spectroscopy Group of the Institute of Physics.Apart from contributions from UK authors, a number of key papers will be presented by international workers of high repute. Some details of the programme are published on page 343 of this issue of Analytical Proceedings and this pro- gramme indicates that the meeting should be of genuine interest to many practising analytical chemists, The Analytical Editorial Board hopes to publish many of the papers presented a t this meeting in a Special Issue of The Analyst early in 1983. Although the normal method of publication of the papers given at Analytical Division meetings is via extended summaries in Analytical Proceedings, the Board has for some time been encouraging more authors to submit suitable original material for publica- tion as full papers in The Analyst, in preference to the more restrictive format of Analytical Proceedings. Many of the papers in the pro- 287288 ROBERT BOYLE (1627-1691). PART I1 Anal. PYOC. gramme for the first Biennial Atomic Spectro- weather in Sheffield in July is dubious, but scopy Symposium appear to be in this category they have put together an interesting pro- and i t is expected that publication in a single gramme which promises to provide a scientifi- issue of The Analyst will provide a detailed cally stimulating occasion, and the Analytical permanent record of the significant develop- Editorial Board wishes them every success with ments reported at this meeting. this new venture. Whether the organisers can promise fine J. M. OTTAWAY

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DOI:10.1039/AP9821900287

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年代:1982

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288 ROBERT BOYLE (1627-1691). PART 11 Anal. PYOC. Robert Boyle (1627-1691): A Foundation Stone of Analytical Chemistry in the British Isles Part II.* Literary Style, Specific Contributions to the Principles and Practice of Analytical Chemical Science D. Thorburn Burns De9artment of Analytical Chemistry, The Queen‘s University of Belfast, Belfast, BT9 6AG, Northem Ireland Boyle’s Literary Style and the Origin of the Content To assess Boyle’s contributions to chemistry it is necessary to examine his work in relation to that of his predecessors and contemporaries. Reading Boyle’s scientific work1 requires an amount of dedication because, as expressed for example by Thorndike, “Boyle is notorious as having one of the most tiresome literary styles on record. It is diffuse and rambling, apologetic and deprecatory, and without adequate terminal facilities. .. . Another detriment to perusal of Boyle’s writings is their over elaborate and con- fusing subdivision into books, parts, essays, dis- courses, sections, titles, chapters, observations and what-not, to say nothing of profuse pre- liminary prefaces by publisher and author.”a A number are written in the form of familiar discourse and informal conversation, which adds neither to the clarity nor rapidity of transmission of thought. In the midst of the prolixity and verbiage occur strikingly prescient statements and illuminating opinions such as those on the nature of an element, of heat, and of sound. Of an element: “And, to prevent mistakes, I must advertize you, that I now mean by Elements, as those Chymists that speak plainest do by their Principles, certain Primative and simple, or perfectly unmingled bodies; which not being made of any other bodies, or of one another, are the Ingredients of which all thosecalled per- fectly mixt bodies are immediately compounded and into which they are ultimately re~olved.”~e~a Of the mechanical origin, or production of heat : “the nature of it [heat] seems to consist mainly, if not only, in that mechanical affection * For Part I, see Anal.Proc., 1982, 19, 222. of the matter we call local motion. . . .”Ka6a Of sound: of the air.”’08a “Sound . . . consists in an undulating motion The content of Boyle’s writings has three distinct components. The first, or traditional, is the result of his reading of a great variety of authors.The second, or experimental, is the outcome of his own researches or those of his assistants in the laboratory. The third compon- ent is a mass of information and misinformation acquired as a result of conversation or corres- pondence with many different people : naviga- tors, travellers and “credible persons,” men of every occupation and rank. “Strange Re- ports”@J0 interested him and excited him. This third element is far more traditional than experi- mental. The extent of Boyle’s reading can only be judged from the references and acknowledge- ment in the texts he gives to others, on which point he is generous and very fair and if refer- ences are omitted the reasons are stated. NO more detailed evaluation is possible for regret- ably Boyle’s library was sold piecemeal and not catalogued.1l Boyle made numerous experiments, observa- tions and deductions using inorganic and organic materials,la many of which have individual analytical interest.His main themes and systematic studies, apart from the nature of elements and the validity of fire analysis, dis- cussed in Part I, can be divided into (i) solution chemistry, (ii) measurement and applications of specific gravity measurements and (iii) clinical chemistry. These systematic studies were reported mainly in texts, several of which were largely analytical in content. Incidentally,June, 1982 ROBERT BOYLE (1627-1691). PART 11 289 these are less prolix and as a consequence much easier to read. Analysis of Solutions Boyle’s contributions to the analysis of solu- tions are concerned with acid - base indicators, reagents and reactions for specific substances and their limits of detection and the systematic examination of mineral waters.Although some reactions of acids and bases with vegetable juices had been noted earlier,13-16 it was Boyle who first observed that all acids turned such blue juices red and that all alkalis turned them green. Further, he noticed that some substances caused no colour change, and these Boyle classified as neither acid nor alka- line, neutral, or as in Boyle’s terminology, “adiaphorous” (from the Greek, indifferent). Thus Boyle effectively disposed of the acid - alkali theory of matter begun by Helmont and taken up by Tachenius, Lemery and Kunckel. 6 b ,16 Boyle was the first to describe a fluorescent acid - base indicator,17t18 extract of Lignum nephriticum, and an inorganic acid - base indicator, the cuprammine ion, He appears to have been particularly fond of using the extract of Lignum nephriticum, and described the effects of concentration, acidity and angle of viewing on the cerelous blue colour.lsa The earliest account of the wood known to Boyle was that of Monardes.The botanical origin of the material used by Boyle was established by Safford as Esyenhardtia p o l y ~ t a c h a . ~ ~ t ~ ~ The major active fluorescent constituent has recently been established as a hydroxy trimethoxyiso- flavone.21 Boyle also refers to this indicator in Sceptical Chymi~t,~b Experimenta Observationes Physicae,lob An Essay on the Porousness of Solid Bodies 22 9 23 a and Mineral Waters. 24 Many of the colorimetric reactions used by Boyle for analytical purposes are in Experiments and Considerations Touching Colours17 (Fig.1), which may rightly be considered as a landmark in the history of analytical chemistry. Although extract of gall nuts had been known since the days of Pliny25v26 as a reagent for iron, Boyle24g27 a noted its reactions with other metals, and that it did not always detect iron, discussed the preparation and stability of the reagent solution and the sensitivity of the reaction for iron; “one part of dissolved rnarcasite com- municated a tincture to (61 440) sixty-one thousand four hundred and forty parts of infusion of gall~.”2~b In a search for other reagents particularly to detect toxic metals, Boyle developed the use of hydrogen sulphide for copper and lead; he did E X P E R I M E N T S A N D CONS1 DERATI ONS L T o t l E x p e ri rn ::;a1 Hi It or y O F C O L - O U R S .Fig. 1. Title page to “Experiments and Considera- tions Touching Colours” (1 664). not obtain a precipitate for arsenic, probably owing to the solution being alkaline.28 Szabad- vary has confirmed the efficiency of Boyle’s r e ~ i p e ~ ~ c for the production of an aqueous solution of hydrogen ~ u l p h i d e . ~ ~ The preparation of fresh water from sea water was of considerable concern to the Navy a t the time30 and Boyle was “commanded by the King, to show His Majesty an Experiment. . . to examine the Freshness and Saltness of Water”31e32 ; using silver nitrate solution he could detect less than a thousandth part of salt ; this method is alluded to in Mineral A convenient summary of most of Boyle’s work on reagents and reactions is given in Experimenta & Observationes Physicae.l0a Analysis of solutions prior to Boyle has been reviewed by D e b ~ s , ~ ~ who cites most of the previous work and that of his contemporaries including T.Willis, but omits mention of the only two references cited by Boyle in Mineral Waters (Fig. 2), namely Dr. Lister’s De Fontibus Medicatis AngZia34s35 and “the curious little tract of the French Mineral Waters, that was brought our Author in English. . . .”36 The reason Boyle omitted to consult or transcribe from other authors was to present an independ- ent and experimentally based view a t the time of the Witty - Simpson controversy, 3 7 ~ 3 8 which had been referred to the Royal Society and aroused a lively correspondence in Philosophical290 ROBERT BOYLE (1627-1691).PART I1 Anal. Proc. Transactions as well as a series of polemical tracts; abstracts of these are given by Short.3B Apart from a clash of personalities the contro- versy concerned the interpretation of results obtained with galls due to instability of the sample of mineral water, the nature of vitriol and of the role of sulphur in the water. Boyle dealt satisfactory with the reactions with extract of galls including the limit of detection for iron. Speciation of sulphur remained a problem and was the basis of the Lucas - Rutty mineral water controversy in the eighteenth century.40 SHORT MEMOIRS FOR T H E Natural Experimental HISTORY Mineral Waters.OF Addrefid By way of Letter to a Friend. ~ By tlic Honourable Fcllow of thc Royal Society. R O B E R T B O T L E , I. 0 N D 0 ‘V, ’rinted for ~ r m n c ! Smith at the Prince’s Arms in St.i’adJ Church-Yard. 168:. .- - -- - - -- . Fig. 2. Title page to “Memoirs for the Natural Experimental History of Mineral Waters” (1684-85). Boyle’s scheme for the examination of mineral waters was more detailed and a considerable advance on those of earlier workers and his contemporaries such as Lister, Du Clos and G~idott,~’ and most later writers up to the time of Bergman42 and K i r ~ a n ~ ~ used only a small number of reagents and tests. The book is brief and fragmentary yet gives a clear insight into Boyle’s experimental approach and his know- ledge of the limitations of the experiments. A set of suggested geographical and mineralogical observations (Titles 1-1 7) are followed by physi- co-chemical examination of the water (Titles 1- 30), these are summarised in Table I; few details are given as it was assumed that the reader was familiar with Boyle’s earlier works.Certain of the titles have extended notes; those on the gall test, hydrogen sulphide and specific gravity are the most detailed. The book con- cludes with consideration of mineral water as a medicine. For certain elements, such as copper, Boyle was aware of numerous characteristic reactions. The blue - green colour of copper in a solution of aqua fortis (concentrated nitric acid) per- mitted him to determine whether silver was contaminated with copper.18b Similarly, copper gave a “grass green” solution with spirit of saltloa (hydrochloric acid) and an “azure” with any “urinous spirit”108 (ammonia solution), a colour which was destroyed if acid was added.A further test for copper was the black colour produced with a solution of “volatile tincture of sulphur” (hydrogen sulphide) .24C Copper and some of its compounds would also show green in another menstrum-a flame. Boyle44 also knew that silver did not colour the flame.4sa He noted the blue flame with nitre and the dazzlingly bright flame of charcoal with sodium nitrate,45b the blue flame of sulphur‘c and the mixed blue and yellow flame of organic compounds.46*47a Coloured flames had been noted before; what was new was the use to which Boyle put his knowledge, to characterise compounds and to detect impurities.Measurement and Application of Specific Gravities The principle of weighing bodies in air and water dates from the time of Archimedes, but it was Boyle who first drew the attention of physicists and chemists to the importance of specific gravity measurements. References are scattered through many of his works to the use of specific gravity in the analysis and identifica- tion of materials. He first alludes to its use in the second tome of Usefulness of Exflerimental PhiEosophy48 with regard to the examination of salts for agricultural purposes.49a In Gemsso he outlines the hydrostatic methods18 with a “tender Ballance,” disposes, on the basis of density, of the theory that crystal (i.e., quartz) was but ice hardened by long and intense cold,61* argues that certain gems contain “metalline pigment”61a and records the density of various ~tones,~lb bitumen, coa1,Slc etc.Explicit instructions are given for a new “essay-in~trurnent”52~63 (see Fig. 3 here, “Fig. 27” therein), which he used to examine gold coins and assay alloys of gold and silver and other alloys. This is put forward as novel “as in our case, Gold, that Chymists and (as)say- Masters as fain to examine by the fire, we examine by water.”53a Boyle’s major work on the subject Medicina Hydrostati~a,~~ (Fig. 4) was the first tract inJzcne, 1982 ROBERT BOYLE (1627-1691). PART I1 291 TABLE I STAGES IN BOYLE’S SCHEME FOR THE PHYSICO-CHEMICAL EXAMINATION OF MINERAL WATER 1.Temperate. 2. Specific gravity. 3. Transparency or opacity. 4. Precipitation or standing, exposed to air or 6. Examination by microscopy. 6. Colour. 7. Odour. 8. Taste. 9. Change in transparency, colour, odour or taste sealed. upon storage, open or sealed. 10. Viscosity. 11. Specific heat. 12. Rate of putrefaction. 13. Colour changes with tannin-containing ex- tracts. 14. Precipitates formed with salts, acids, ammonia, bases. 16. Amount of common salt in residue after evaporation. 16. Acidity. 17. Examination of distillate. English on the determination of specific gravity. The title was borrowed from Santorio’s Medicina Stutica and as Fultonss notes he might have extended his apologies to include a ‘medicina,” as the book is essentially a monograph devoted to a specialised branch of physical testing of materials.The hydrostatic balance was shown in the frontispiece and is reproduced in Fig. 3 (“Fig. 26” therein). Boyle knew how to deal Fig. 3. An Essay Instrument (Fig. 27) These 64 and and Hydrostatic Balance (Fig. 26). are re-engraved67 from the are fairly exact copies. 18. Residues after total evaporation or distillation 19. Resolution of residues after partial evaporation. 20. Effect of boiling under hermetic seal. 21. Amount of dry residue. 22. Separation of dry. residue into soluble and 23. Relative amounts of soluble and insoluble 24. Effect of heat on saline portion of residue. 26. Crystal forms of saline portion of residue. 26. Saline portion of residue, acidic, alkaline or neutral. 27. Examination of insoluble portion of residue, effect of heat, acids, ammonia, etc.28. Loss and colour changes on ignition. Colour formed on fusion with powdered glass. 29. Uses, as these may indicate ingredients. 30. Imitation of mineral water to aid identification of nature and amounts of constituents of a natural water. to dryness. insoluble fractions. residue. with materials that were less dense than water or dissolved in water; indeed, almost every problem is discussed, and he also used a density bottle. Results were expressed in decimal form, e.g., rock crystal 2Eo. Results for the great variety of materials examined were given in an alphabetical “Table” at the end of the b00k.~~a Boyle noted, for example, the great difference between the gravity of true and artificial crabs-eyes, of clear interest to the physician as his patient.When Davies wrote a review on the subject in 174tP he cited Boyle’s results and considered them accurate. For many chemicals differences from present day results might be due to purity ; results for many materials showed good agree- ment with modern results.ss TABLE I1 COMPARISON OF A SELECTION OF BOYLE’S SPECIFIC GRAVITY RESULTS Substance Boyles8 Gold . . .. . . 19.64 Mercury.. .. . . 14.00 Lead . . .. . . 11.32 Iron . . .. . . 7.64 Tin . . .. . . 7.32 Sodium chloride . . 2.14 Borax . . .. . . 1.71 Quartz .. . . 2.66 Copper . . .. . . 9.00 Modernss 19.30 13.6 11.34 8.92 7.86 7.28 2.17 1.73 2.64 Boyle also used specific gravity measurements in the examination of blood,60 urineeo and mineral waters.a4 In Mineral Waters he dis- cussed the problem of obtaining good balances for the purpose; he could weigh 3 oz t o 0.5 g, i .e . , 93 g to 3 mg.292 ROBERT BOYLE (1627-1691). PART I1 Anal. PYOC. ipebicfna rgpbtottntta? : HYDRO STATICKS 0 R, Appfyed to the M A T E R I A MEDXCA. How by the Wei hc that divers Bodies, us’d in Pf fick, have in Water; one may dif!over Whether they be Genuine or Adulterate. To wbicb isjibjop’d A Previous Hydroitatical Way of ERirnating 0 R E S. S I I E W I N G , 1 I Fig. 4. Title page to “Medi- cina Hydrostatica” (1690). Clinical and Biochemical Analyses Attitudes to Boyle’s Memoirs for the Natural History of Humane Bloodso (Fig. 5) vary from “a disappointing treatise,”2 “the most important of Boyle’s medical writings . . . the beginning of physiological chernistry”,66 “the first true clinical chemist”s1 and “exhibited an analytical eleg- ance which it is difficult to emulate today.”6a The most critical discussion is by Hall,63 who argues that i t is mistaken to regard that Willis, Lower, Boyle, Mayow and Hooke were precur- sors to the experimental investigation of phys- iology and medicine and the majestic results obtained in the nineteenth century.Manie4 avoids the problem by considering that the subject began in the nineteenth century. Boyle was not the first to attempt to analyse blood; for example, Needham read a paper on the subject to the Royal Society in 167tjs5: “. . . we find two seemingly unlike parts of it, vis the grumus and the serum; yet when we come to analise them by fire, we find them to consist of the same parts viz.phlegm, spirit, if I may so call it, volatile salt, oil, fixed salt, and earth . . . , but with this difference in propor- tion. . . .” Boyle’s advances were in the increase in the number of “titles,” questions or tests and his characterisation of certain of the components. The style of writing is very similar to that of Miweral Waters; in certain instances the titles are supported by experiments and observations. The headings under which blood should be examined included colour, taste, smell, tempera- ture, specific gravity, various factors which aided or prevented coagulation and examination of the products of dry distillation. Boyle could not make up his mind if the volatile alkalis, spirits of urine and hartshorn were the same as spirit of blood, owing to problems of purity.s6” On the “fixed salt” he was definitive and by a variety of tests showed the presence of sodium chloride or more particularly chloride.6’Jb The product tasted of sea salt, and was not acidic since it did not turn syrup of violets green; on adding oil of vitriol (concentrated sulphuric acid) it reacted like common salt, “corroding with great violence and with much foam and smoke,” and gave a white precipitate with solution of silver in aqua fortis (concentrated nitric acid). But the most elegant demonstra- tion of all was when he floated some gold on aqua fortis : the acid did not dissolve the metal but when he added “our powdered salt into the liquor, which being thereby turned into a kind of aqua regia, did in a trice, without the assist- ance of heat, totally dissolve it.” The residue of the dry distillation of Caput mortum or Terra damnata “was not pure ele- mentary earth, since it had a fine red colour, very like that of calcothar of vitriol (red iron oxide) .”6sb Had he applied a confirmatory test,June, 1982 ROBERT BOYLE (1627-1691).PART I1 293 he would have been the first to discover iron in blood. Boyle’s assistant in the work on blood and on salts of the air was John Locke, whose notebook is extant .67 Humane BZood was published with a dedicatory preface to “the very Ingenious and Learned Doctor J[ohn] L[ocke].” Boyle considered that other liquors of the human body such as gall, spittle and milk should be examined; however, he only gave details of the examination of urine in addition to those already discussed on blood.He was aware that much could be learnt from the liquor “skilfully handled,” as phosphorus is made from urine.46 The “Titles of the Frst CZu~sis”~~c for the natural history of humane urine emitted by healthy men (Titles 1-31) follow a similar pattern to those on blood and were a consider- able advance on the Paracelsian chemical dis- section of ~ r i n e . ~ * ~ ~ ~ This dissection of urine was nothing more than distillation to be carried out in a gauged cylinder, the shape of which was to correspond to the human body (Fig. 6). A under attack earlier; Boyle indicated more could be learnt than from merely the vulgar analysis of urine by distillation. One must conclude that although Boyle could not deal with the organic subtleties of blood and urine he made significant advances in their inorganic analysis.Conclusions Examination of Boyle’s writings on analytical chemical topics, and those of his predecessors and contemporaries, show him to be the leading exponent of the subject of his period. The major areas of his work are considered to be in solution chemistry, measurement and applica- tion of specific gravities and clinical chemistry. The distinguishing features of the work are the detailed and critical approach and in his frequently expressed pleasure in experimental work. Boyle’s scientific work began and ended with studies of the air; his last work, The General History of the Air71 was published post- humously. Boyle did not achieve an analysis of air or appreciate its function in combustion, but gave accounts of aqueous particles in the air, 72S of salts in the air,72b of sulphur ., . ,7ac and hence might be given the appellation of “the first environmental chemist .” The title “Father of Modern Chemistry” is clearly deserved, as he was active in many areas of current concern, particularly in analytical chemistry over a wide range of application. VIVORVM In addition to those noted in Part I, the author further thanks A. B. Scott for assistance with latin texts and R. Doggart (Ulster Hospital) for data on aspects of the history of clinical analysis. Fig. 6. The “anatomical furnace” for the distillation of urine and diagnosis of the locus morbi. From “Aurora Thesaurusque Philosophorum Paracelsi with ‘Anatomia Viva Paracelsi’,” Basileae (1577).careful examination of the various fractions of the distillate as well as the residue was supposed to reveal the type of disease as well as its location in the body. Uros~opy~~ had been References 1. “The Works of the Honourable Robert Boyle. In Six Volumes. To which is Prefixed a Life of the Author. A New Edition,” J. and F. Rivington et al., London, 1772. 2. Thorndike, L., “A History of Magic and Experi- mental Science, Volume VIII, The Seven- teenth Century,” Columbia University Press, New York, 1958. 3. Boyle, R., “The Sceptical Chymist: . . . ,” J. Caldwellfor J. Crooke, London, 1661. [The second edition was printed by H. Hall for R. Davies and B. Took, London, 1680.1 4. Ref. 1, Volume I, pp. 458-661; (a), Volume I, p.562; (b), Volume I, p. 519; (c), Volume I, p. 625. 5. Boyle, R., “Experiments Notes &c About the Mechanical Origine of or production of divers particular Qualities,” E. Flesher for R. Davis, London, 1675. 6. Ref. 1. Volume IV, pp. 230-354; (a), Volume IV, p. 244; (b), Volume IV, p. 284.294 ROBERT BOYLE (1627-1691). PART I1 Anal. Proc. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. Boyle, R., An Essay of the Great Effects yf Even Languid and Unheeded Motion. . . , M. Flesher for R. Davis, London, 1685 (also an anonymous edition, 1685). Ref. 1, Volume V, pp. 1-70; (a), Volume V, p. 13. Boyle, R., “Experimenta & Observationes Physicae: . . . to which is added a small collection of Strange Reports, . . . ,” J.Taylor and J. Wyat, London, 1691. Ref. 1, Volume V, pp. 564-609; (a), Volume V, p. 578; (b), Volume V, p. 579. Feisenberger, H. A., “The Libraries of Newton, Hooke and Boyle,” Notes Rec. R. Soc., London, 1966, 20, 42. Partington, J. R., “A History of Chemistry,” Volume 11, Macmillan, London, 1961, pp. Baker, A. A., “A History of Indicators,” Chymia, 1964, 9, 147. Eamon, W., “New Light on Robert Boyle and the Discovery of Colour Indicators,” A mbix, 1980, 27, 204. Thorburn Burns, D., “Edward Jorden M.D. (1569-1632) : Early Contributions to Solution Analysis,” Proc. Anal. Div. Chem. SOL, 1979, 16, 219. Boas, M., “Robert Boyle and Seventeenth Century Chemistry,” Cambridge University Press, Cambridge, 1958. Reprinted by Kraus Reprint Co., New York. 1976. Boyle, R., “Experiments and Considerations Touching Colours .. . ,” H. Herringman, Anchor, New Exchange, London, 1664. Reprinted by Johnson Reprint Corp., New York, 1964. Ref. 1, Volume I, pp. 662-788; (a), Volume I, pp. 729-735; (b), Volume I, p. 775. Safford, W. E., “Lignum Nephriticum-Its History and an Account of the Remarkable Fluorescence of its Infusion,” Ann. Rep. Smithsonian Inst., 1915, p. 271; Government Printing Office, Washington, 1916. Partington, J. R., “Lignum Nephriticum,” Ann. Sci., 1955, 11, 1. Thorburn Burns, D., Grimshaw, J., and Gargan, P.E., unpublished work. Boyle, R., “Experiments and Considerations About the Porosity of Bodies, in two Essays,” S. Smith, London, 1684. Ref. 1, Volume IV, pp. 759-793 ; (a), Volume IV, p. 792. Boyle, R., “Short Memoirs for the Natural Experimental History of Mineral Waters .. . ,” S. Smith, London, 1684/5. (Reviewed in Phil. Trans., 1685, 15, 1063. Holland, P., Translator, “The Historie of the World. Commonly Called, The Naturall Historie of C. Plinius Secundus,” A. Islip, London, 1601. Thorburn Burns, D., Leonard, M. A., and Swindall, W. J., Educ. Chem., 1981, 18, 80. Ref. 1, Volume IV, pp. 794-821; (a), Volume IV, p. 803; (b), Volume IV, p. 817; ( c ) , Volume IV, p. 807; (d), Volume IV, p. 813; (e), Volume IV, p. 810. Thorburn Burns, D., Townshend, A., and Carter, A. H., “Inorganic Reaction Chem- istry. Volume 2. Reactions of the Elements and their Compounds. Part A: Alkali Metals to Nitrogen.” Ellis Honvood, Chichester, 1981, Chapter 5. 486-549. 29. Szabadvary, F., “Early Preparation and Analytical Use of Hydrogen Sulphide,” Talanta, 1959, 2, 156.30. Maddison, R. E. W., “Studies on the Life of Robert Boyle, F.R.S., Part 11, Salt Water Freshened,” Notes Rec. R. Soc., London, 1952, 9, 196. 31. Boyle, R., “Way of Examining Waters as to Freshness and Saltness,” Phil. Trans., 1693, 17, 627. 32. Ref. 1, Volume V, pp. 744-750. 33. Debus, A. G., “Solution Analysis Prior to Robert Boyle,” Chymia, 1962, 8, 41. 34. Lister, M., “De Fontibus medicatis Angliae . . . ,” Eboraci, 1682; Second Edition, W. Kettilby, Londini, 1684. 35. Keynes, G., “Dr. Martin Lister: A Biblio- graphy,” St. Pauls Bibliographies, 1981. 36. Du Clos, [S. C.], “Observations on the Mineral Waters of France Made in the Royal Academy of Sciences,” H. Faithorne and J. Kersey, St.Pauls, 1684. [The original edition in French (1675) was reviewed a t length in Phil. Trans., 1676, 11, 612.1 37. Poynter, F. N. L., “A Seventeenth Century Medical Controversy : Robert Witty versus William Simpson,” in Singer, C., Editor, Science, Medicine and History,” Oxford University Press, London, 1953. 38. Coley, N. G., “Cures without Care,” “Chymical Physicians and Mineral Waters in Seventeenth Century English Medicine,” Med. Hist., 1979, 23, 191. 39. Short, T., “The Natural, Experimental and Medicinal History of the Mineral Waters of Derbyshire, Lincolnshire and Yorkshire particularly those of Scarborough . . . ,” F. Gyles, London, 1734. Sullivan, W. K., “Memoir of Byran Higgins and of William Higgins with a Short Notice of Irish Chemists and the State of Chemistry in Ireland Before the Year 1800,” Dublin Quart.J . Med. Sci., 1836, viii, 465. 41. Thorburn Burns, D., “Thomas Guidott (1638- 1705), Physician and Chemist ; Contfjbution to the Analysis of Mineral Waters, Anal. Proc., 1981, 18, 2. 42. Bergman, T., (Cullen, E., Trandatm), “Physical and Chemical Essays,” J. Murray, London, 1784. 43. Kirwan, R., “An Essay on the Analysis of Mineral Waters,” J. W. Myers, London, 1799. 44. Boyle, R., “The Origine of Formes and Quali- ties. . . ,” H. Hall, Oxford, 1666. 45. Ref. 1, Volume 111, pp. 1-137; (a), Volume 111, pp. 80-82; (b), Volume 111, p. 88. 46. Boyle, R., “New Experiments, and Observa- tions, Made upon the Icy-noctiluca . . . ,” R.E. for B. Tooke, London, 1681/2. 47. Ref. 1, Volume IV, pp. 469-505 ; (a), Volume IV, p.498. 48. Boyle, R., “Some Considerations Touching the Usefulnesse of Experimental Naturall Phil- osophy . . . The Second Tome . . . ,” H. Hall, Oxford, 1671. 49. Ref. 1, Volume 111, pp. 392-494; (a), Volume 111, p. 407. 50. Boyle, R., “An Essay About the Origine & Virtues of Gems . . . ,” W. Godbid for M. Pitt, London, 1672. 40.June, 1982 SAFETY IN ANALYTICAL LABORATORIES 295 51. Ref. 1, Volume 111, pp. 516-561; (a), Volume 111, p. 536; (b), Volume 111, p. 547; (c), Volume 111, p. 556. 52. Boyle, R., “A New Essay Instrument. . . with Uses Thereof. . . ,” Phil. Trans., 1675, 10, 329. 53. Ref. 1, Volume IV, pp. 204-213; (a), Volume IV, p. 205. 54. Boyle, R., “Medicina Hydrostatica or Hydro- staticks Applyd to the Materia Medica . . . To which is subjoyn’d A Previous Hydrostatical way of Estimating Ores,” S.Smith, London, 1690. (Reviewed in Phil. Trans., 1686-1692, 16, 488.) 55. Fulton, J. F., “A Bibliography of The Honour- able Robert Boyle,” Second Edition, Claren- den Press, Oxford, 1961. 56. Ref. 1, Volume V, pp. 453-507; (a) Volume V, 57. Shaw, P., “The Philosophical Works of the Honourable Robert Boyle,” Volume 11, W. Inny, R. Manby and T. Longman. London, 1738. 58. Davies, R. “Tables of Specific Gravities, Extracted from Various Authors ; with Some Observations upon the Same,” Phil. Trans., 1748, 45, 416. 59. Weast, R. C., and Astle, M. J., Editors, “CRC Handbook of Chemistry and Physics,” 59th Edition, CRC Press, West Palm Beach, USA, 1978. 60. Boyle, R., “Memoirs for the Natural History of Humane Blood . . . ,” S. Smith, London, 1684. 61. Winsten, S., “The Skeptical Chemist,” Clin. Chern., 1969, 15, 739. pp. 505-507. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. Lines, J. G., “A Chronicle of the Development of Clinical Chemistry,” IFCC Newsl., 1977 (Oct.), 3. Hall, A. R., “Medicine and the Royal Society,” in Debus, A. G., Editor, “Medicine in Seventeenth Century England,” University of California Press, Berkeley, CA, 1974. Mani, N., “The Historical Background of Clinical Chemistry,” J . Clin. Chem. Clin. Biochem., 1981, 19, 311. Needham, W., in Birch, T., “The History of the Royal Society of London, . . . as a supplement to The Philosophical Transactions,” Volume 111, A. Millar, London, 1756. Ref. 1, Volume IV, pp. 595-759; (a), Volume IV, p. 623; (b), Volume IV, p. 609; (c), Volume IV, p. 601. Dewhurst, K., “Locke’s Contribution To Boyle? Researches on The Air and on Human Blood, Notes Rec. R . SOG. London, 1962, 17, 198. Debus, A. G., “The English Paracelsians,” Oldbourne, London, 1965. Debus, A. G., “The Chemical Philosophy: Paracelsian Science and Medicine in the Sixteenth and Seventeenth Centuries,” Volumes I and 11, Science History Publishers, New York, 1977. Brian, T., “The Pisse-prophet or Certaine Pissepot Lectures . . . ,” E.P. for R. Thrale, London, 1637. Boyle, R., “The General History of the Air . . . ,” Awnsham for J. Churchill, London, 1692. Ref. 1, Volume V, pp. 609-743; (a), Volume V, p. 622; (b), Volume V, p. 626; (c), Volume V, p. 635.

ISSN:0144-557X    

DOI:10.1039/AP9821900288

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

June, 1982 SAFETY IN ANALYTICAL LABORATORIES 295 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. The Semantics of Safety “Then you should say what you mean,” the March Hare went on. “I do,” Alice hastily replied; “at least-at least I mean what I say-that’s the “Not the same thing a bit!” said the Hatter. “Why, you might just as well say Alice in Wonderland LEWIS CARROLL same thing, you know.” that ‘I see what I eat’ is the same thing as ‘I eat what I see!’.’’ We all know what we mean when we refer to safety “rules,” but unless we mean what we say we are probably using the wrong word.The Oxford Dictionary defines “rule” as “a principle, regulation or maxim governing individual con- duct.” Within this definition, however, there can be a wide spectrum of intentions. “Keep to the left,” for example, does not preclude an occasional move to the centre or right; it indicates a priority. “Keep to the left,” one may argue, is not a rule, but a warning. Many of us, however, see all rules in this light. “Rules,” we say, “are made to be broken.” Another way of regarding rules is to see them as an insurance policy. A manager lays down a rule, possibly accepting that it may be broken or even knowing that it will be broken.He may conceivably be aware that, if the job is to296 SAFETY IN ANALYTICAL LABORATORIES Anal. PYOC. be done efficiently, it has to be broken. The rule is there to be hidden behind. It is a means of absolution in the event of the ulti- mately inevitable mishap. It does not neces- sarily fbllow that managers making such rules are being unscrupulous. In many instances it is a matter of their not thinking carefully enough about the division of responsibility between the manager and the managed. Consider, for example, the plant operator who is required to drain water from the base of a hydrocarbons storage tank. The rules require him to be on hand to spot the interface. The reality is that he has other jobs to do.Whose fault is it when hydrocarbon goes down the drain? So let us mean what we say. When we put up a “No Smoking’’ sign, let us not refer to it as a “rule” (to be broken) but as a mandatory instruction. When we say “No Smoking,” we mean that smoking is not tolerated and disci- plinary action will result if anyone is found smoking. Looked at from the legalistic point of view, this is the only way to avoid the situation, where, after a fire, it can be said, “Oh yes, there was a ‘No Smoking’ sign, but everyone knew that management paid only lip service to it.” It must be clear by now that the point being made here is that safety is not merely a matter of “rules.” There are relatively few areas where we would wish to, or indeed could, lay down mandatory instructions for a laboratory.Each laboratory will have its own particular problems, but perhaps the following seven items might appear on most lists of mandatory instructions : 1. Smoking is forbidden at all times in designated “No Smoking” areas. 2. Approved dust masks must be worn in areas so designated. 3. Eye protection must be worn at all times in designated areas. 4. Full eye protection must be worn when pouring corrosive materials from a Winchester bottle or other large container. 5. No member of staff is allowed to work alone in any laboratory without written permission. 6. Pipetting or siphoning by mouth is for- bidden. 7. Staff must not carry out electrical work on equipment using 240-V a.c. mains without written approval. Having eliminated rules and replaced them with a few mandatory instructions, the manager responsible for establishing safe practices might well ask what else is to be done.His quandary arises possibly because he is regarding safety as something to be built on top of a job, some- thing separate from the job itself. Now, it is true that there are aspects of laboratory life where special safety procedures are required. For example, it is essential that everyone in a laboratory is thoroughly familiar with the procedures to be followed in the event of fire or toxic gas release. These procedures have to be clearly defined and rehearsed. Then there is, of course, legislation, which must be obeyed to the letter. An example is the Highly Flammable Liquids and Liquefied Petroleum Gases Regulations 1972.Failure to comply with, for instance, the requirements of these regulations on the limits to the highly flammables stored in a laboratory could entail prosecution. By far the greatest and most important part of safety in the laboratory, however, is in- separable from the job itself. Safe experiments are experiments correctly performed. A safe worker is one who thinks about what he is doing and never does anything beyond his competence. There is no definition of a “competent person” but clearly appropriate training and experience are paramount. It should be expected, but never assumed, that someone who has passed “0”-Level Chemistry will have learned and understood some of the basic dos and don’ts of laboratory work. For example, the “0”-Level pupil should know the hazards of adding water to concentrated acid, that many liquids are flammable, that some substances can react vigorously and exothermi- cally and that many chemicals are toxic.The rest is a matter of training, especially by working under supervision and by learning from the experience of others. I t is here that guidelines and Codes of Practice play their part. The chief point to be remembered about guidelines and Codes of Practice is that they are by their very nature advisory. Their purpose is to establish a standard or level of performance. They need not be followed but they must be equalled. Whether a Code of Practice is purely voluntary or has been drawn up or approved by the Health and Safety Commission the standard it sets must be maintained.I t is not, however, to be regarded as a set of rules. Failure to observe any provision of an approved Code of Practice is not of itself cause for legal proceedings but there is a mandatory requirement to adopt an equally effective practice. To summarise, then, let us define what a laboratory safety manual should contain. There are five types of information which should be provided.June, 1982 SAFETY IN ANALYTICAL LABORATORIES 297 Firstly, there should be a statement of policy on health and safety, setting out arrange- ments for safety and indicating where various responsibilities lie. Secondly, there should be the mandatory instructions to be obeyed by everyone. It is perhaps worth taking a leaf out of the Good Book; in it there are only 10 commandments ; the mandatory instructions should not exceed their number.Thirdly, there should also be the emergency procedures- what to do in the event of fire, etc. These too are to be followed by everyone except those with specially defined duties, e.g., Fire Wardens. Above all, they must be rehearsed. Fourthly, it should be made clear to all readers of the Manual what is legally required of management. The onus is on the manager to ensure compli- ance with legislation, but all staff have to be aware of what the legislation stipulates. Fifthly, the largest part of the Manual should comprise the guidelines, the advice, the reminders given to staff on how experiments should be carried out. This important part of the Safety Manual is a compendium of guidance, a handbook, which laboratory workers cannot be expected to memorise but to which they should refer when embarking on new experi- ments. It should be a repository of the wisdom gained by experience and it should be regularly reviewed and revised in the light of new experi- ence. The Safety Manual should be a living document, not a set of dead stone tablets. So, have a fresh look at your Safety Manual. Does it contain all these items? It is clear about what is mandatory and what is advisory? Are its readers also clear on these matters? Does it say what you mean?

ISSN:0144-557X    

DOI:10.1039/AP9821900295

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

June, 1982 SAFETY IN ANALYTICAL LABORATORIES 297 Address of the Retiring President This address was delivered after the Annual General Meeting of the Analytical Division held on March 12th, 1982. Reflections on Analytical Chemistry L. S. Bark Department of Chemistry and Applied Chemistry, University of Salford, Salford. Lancashire, M5 4 WT It is always useful, when presenting a paper, to examine two points: (1) what is the purpose of the paper?; and (2) does the title summarise the paper, or does it ask a question? The purpose of this paper is to summarise some of my views on the present role and position of analytical chemistry in the scientific community in general, and in the British context in particular. I hope also that it will stimulate some reflection on opinions regarding analytical chemistry as it now affects those involved in that field.Anal. Proc.Two of the questions that may be asked are: (a), what is a reflection?; and (b), what is analytical chemistry? A reflection need not necessarily be a true representation of the object reflected; indeed, it will never be so even with a perfectly plane surface-even in such perfect conditions it will be handed. If the reflecting surface is uneven or curved then some apparent distortion of the image will occur. When the reflecting surface has been subjected to the non-uniform forces encountered by a President of the Analytical Division of the Royal Society of Chemistry, at a time when those industries, universities and Government establishments which employ professional analytical chemists are under the pressures of economic constraints and sociological changes, then it should not be surprising that the reflection may appear to be superficially distorted.When the image is received on surfaces that may have encountered somewhat similar economic forces, then the image finally interpreted may be somewhat confused. Thus, it is preferable not to define precisely what is meant by “reflections” but to proceed to “what is analytical chemistry?” There have been so many superficial definitions-especiall y of late-that it is appropriate to ask: (i), why are there so many definitions? ; and (ii), what does a self-styled practising, professional analytical chemist mean by such a styling? These questions may be answered by examining where so-called speculative science and industrial analysis fit into the general industrial and educational scenes.1 Most industry can only have a continuing existence if it is profitable, so the end-product must be industrial Profitability.This can be achieved only if one solves an industrial problem. This, in a chemical industry, can occur in economic reality only if one has industrial intelligence, which can generally be obtained from suitable chemical information. To obtain this suitable chemical information for a completely new problem one may, and generally will, require the use of sj!wculative science. This last will have been, or may have to be, evolved at a research institution-be it university, polytechnic, Government establish- ment or industry, and then developed into a basic scientijc technique.From this basic scientific technique it is necessary for a professional analytical chemist to evolve a method capable of being used as an industrial method of analysis. This will give a Physical result-which may be a change in mass or volume, a physical measurement of a radia- tion, be it absorbed or emitted, nuclear, electronic, atomic or molecular, or an electrical para- meter such as conductance, capacitance or resistance. The result will have to be transmogrified into chemical information, which then completes the circular path by being used to provide industrial intelligence. Educational establishments fit into this pattern in various ways. In the present research environment, whilst they are not the only source of speculative science, if one uses-as a source of measurement-the number of publications dealing with speculative science then they are the main source.This is the domain of the scientist; it may be that he is fundament- ally a chemist, physicist, biochemist, biologist or mathematician, or a combination of any or all of these, but his main purpose, in this particular context, is to provide the idea, which will be the embryo of the solution to the problem. This idea must have novelty-it is generally unusual, in that once formulated it may become part of the obvious. However, the idea may lie dormant for some years, as the scientist having provided the idea may be content to allow it to do so. The next step is the development of the basic scientific work into a scientific and possibly analytical technique. This process is the domain of the analytical scientist, who may incident- ally be an analytical chemist.If the technique is primarily used to solve chemical problems, then whether or not the analytical scientist realises this or, realising this, admits it, at this point he is acting as an analytical chemist. The domain for the development of the technique and its extension into a usable form as a method that will eventually give industrial intelligence is that of the professional analytical chemist. When, and only when, this large sweep has been made can the method be used as a $re- scribed and, if appropriate, a routine method of analysis. It is at this stage in its development that knowledge of the routine method generally reaches the “scientific lay public,” i.e., those chemists and other scientists who are not professional analytical chemists for this purpose.The part of the whole, which becomes evident to the scientific public, is that of obtaining 298 ADDRESS OF THE RETIRING PRESIDENTJune, 1982 ADDRESS OF THE RETIRING PRESIDENT 299 physical results using the prescribed method. These determinators must not be confused with professional analytical chemists. They have an extremely limited domain and are not expected to do any more than obtain physical results, using whatever instruments the professional analytical chemist has decreed. At this time, the most important step is to use the physical results to obtain chemical information. To convert this chemical informa- tion into industrial intelligence is the domain of the professional analytical chemist.There remain the two areas of the circle; those of the solving of a particular industrial problem and the essential area of industrial profitability. Here, the professional analytical chemist has to have skills in communication, management, a sound knowledge of the particular industry, often a knowledge of the legal requirements and a reasonable sense of industrial economics. In “domain terms” this is the domain of the professional analytical consultant, who is probably labelled as the Chief Analyst. The ideal professional analyst has been described.2 The centre of this array is a good chem- ist. As Thompson2 indicated (Fig. l), industry’s needs are for a psychologically robust, lateral-thinking, logical and numerate, good, knowledgeable chemist, who has received a more than adequate training in practical work. It is not considered to be educationally or industri- ally sound to have the training and education of a chemist so unbalanced that the theoretical This is the domain of the determinator.This is the domain of the analytical chemist. Fig. 1. The attributes of the ideal industrial analyst. aspects are taught at the expense of the practical aspects. Most graduate analysts should have sufficient practical expertise and “feel” to be able to assimilate new techniques with ease and confidence. This is essential, as it is axiomatic that during the course of such an analyst’s career he will need to learn many new techniques. There is no doubt that- 1.2. The average length of career of a professional analytical chemist is at least 25-30 years. During the last 25-30 years there have been many new techniques advanced, many of which are no longer in general or in frequent use. These techniques would be “new” to many recently qualified professional analysts. This situation is not peculiar to professional analytical chemists; it applies, to some extent, to all professional chemists. I t is, probably, of greater significance to the exponents of analytical chemistry, as advances in other branches of chemistry, generally, can only follow relevant advances in analytical chemistry. Teachers of professional analytical chemists, be they teaching in educational institiitions or in industry, and perhaps more especially their critics, must recognise this situation and act300 ADDRESS OF THE RETIRING PRESIDENT Anal.Proc. accordingly. If one accepts the concept of an ideal analytical chemist where, then, does the ideal professional analytical chemist obtain these attributes? The over-all answer is “at all stages of the development of his career.” However, in more detail, the points in his career where these are most likely to be initiated and expanded vary from parameter to parameter. There is no doubt that the nucleus of this cell has to be a good, sound training in general chem- istry. Modern institutional educators will ensure that, for an undergraduate, this includes education and training in such parameters as- 1. Observation and scientific deduction. 2. The use of instruments of all types, and not just those which are electrically or electronic- ally based.3. An awareness of the scientific method and the philosophy inherent in accepting and applying the regimen implicit in the scientific method. 4. The. use of statistics, applied to appropriate data and used to provide chemically mean- ingful conclusions. 5 . The need for the results to be reliable. For this purpose it will be necessary to inculcate good chemical and analytical manipulative techniques. This parameter will undoubtedly require an acquisition of the basic skills of analytical science and especially of analytical chemistry. 6. The need to communicate. Findings and conclusions must be communicated, in a reasoned and easily assimilated manner, to those who are to use them for any purpose, In order to have progress in any field, but especially in those whose proponents rely on the results and the expertise of others, the analytical chemist, who in general will produce these results which enable progress to be made in the work of others, must have the ability to communicate his findings and his conclusions.Probably during the latter part of the undergraduate-type training, and certainly during the first part of organised graduate training, whether it be in universities or in polytechnics, or extra-mural to them, there is the necessity to begin the lengthy process of learning how to be more than a determinator. This involves, as it has always done, being able to innovate and to plan experiments, which processes frequently require lateral thinking and cross-fertilisation between techniques and disciplines. This process is essential to ensure that techniques appropriate to the solution of the particular analytical problem are optimally used.In most modern and up to date analytical organisations, this will require the professional analytical chemists to be able and ready to use modern computational methods for statistical evaluation and possibly for discrimination of relevant analytical signals from random noise. Each, and all, of these parameters requires that the professional analytical chemist develop and maintain a professional pride, a justifiable conviction that he has the knowledge and the ability to solve the particular problem to hand. As the professional analytical chemist progresses, he will inevitably have to manage, not only resources but also personnel, because he will need to lead and often teach a team of junior analysts and determinators. He will also be subjected to various pressures, both economic and otherwise. There may be pressure brought on him to save time and hence money, and thence increase profitability by decreasing the number of non-profit-making and superficially costly steps and by accepting approximations, or the results of other analysts, in order to make decisions on results and evidence which may be analytically insufficient for his particular purpose.To be able to resist these pressures, the professional analytical chemist must be “psychologically robust.” In this way he may be able to make the optimum contribution to the over-all industrial plan.It may not be pleasing, but unfortunately it is true, that he will be prevented from making a full contribution in these later stages unless there is equal recognition of the professional standing of the analytical chemist and those involved in planning and management. This involves other chemists, other professionals, recognising and accepting the professional status of the analytical chemist. Such a recognition of equality will not be achieved easily, indeed it may be thought that it will be denied him whenever possible. In the USA, as well as in the UK, there are growing indica- tions that the analytical chemist must be involved in participative management. At a recent Symposium on Managerial Affairs in Analytical Chemistry, held in 1980 in New York, an oft- repeated theme was the desirability of greater analytical chemists’ involvement in industrial problem-solving.“Greater involvement of the analytical chemist in the totality of a problemJune, 1982 ADDRESS OF THE RETIRING PRESIDENT 301 as opposed to narrow-minded data generation pays a number of dividends, including improved morale for the analyst and greater scientific prod~ctivity.”~ Also, it must be realised that the analytical chemist, himself, may be at fault. A quotation from the ACS Meeting3 exempli- fies this : “Too often the analytical chemist is considered, and allows himself to be considered, merely as a pair of skilled hands. The extent of this problem has been aggravated further by management policies which do not fully utilise the professional capabilities of the analytical chemist .” A recent report was issued in the UK by the SERC,4 who set up a Working Group following consideration of a “Report of the Analytical Sciences Panel,” and gave to it terms of reference that included the use made of analytical scientists by industry and the kinds of recruits needed in this area.Unfortunately, although some of the recommendations are acceptable and will be supported by many professional analytical chemists, I feel that they may lack universal credibility and fail to gain widespread acceptance, because the terms of reference have been drawn far too narrowly with respect to “industry.” The requirements of those sectors of industry dealing with foodstuffs, pharmaceuticals and agrochemicals are, at best, scarcely considered, and those of the relevant departments of Local and Central Government seem to have been ignored.The current activities, structures and trends in analytical chemistry in the public sector, including Research Councils, have been discussed.6 In 1980 there were, in Government employment, over 2 600 chemists, which is approximately 15% of the total 17000 members of the Scientific Civil Service (SCS). Of these, 36% were analytical chemists, employed in many important sections of Government Service, and it has been indicated that the SCS seeks graduates with the correct attitudes of mind “to solve the total problem’’ and particularly those who could, after further training, relate their work to broader issues and explain and present their results to a wide audience.The SERC report4 seems to intend that promotion of analytical science will be at the ex- pense of analytical chemistry. As the description of analytical science used is “a very broad area, broader in concept than traditional analytical chemistry, even when coupled with modern instrumental methods,” it does not indicate an awareness of what the tasks of modern professional analytical chemists are ; it seems probable that some of their recommendations will be ignored, especially by those who see no need to alter the statw quo. Indeed, by their conclusion that although it is “not possible to give a precise definition of analytical science, but it is possible to identify five different analytical scientist categories in industry,” viz., the chemical analyst, the specialist analyst, the instrument technologist, the production analyst and the instructor, the chances of acceptance of equality between the professional disciplines in chemistry seem to have been decreased or even removed.It is becoming evident that there is a need for a real recognition of the role for professional analytical chemists. The conclusion of the SERC Working Group that “the scope within the SERC research grants scheme for departments to obtain equipment which may be used for teaching is adequate-the case . . . to make special provision for teaching equipment to promote analytical science (and presumably artalytical chemistry) is not strong and could be counter-prod~ctive,”~ certainly conflicts with my views and with those expressed recently by a leading American industrialist,6 who predicts a severe shortage of analytical chemists in the 1980s.Such a shortage in the USA may result in a new type of “brain-drain” from the UK, with the few PhD-holding analytical chemists who are trained here being attracted by an industry that is prepared to contribute to attract more undergraduates to chemistry, and to analytical chemistry in particular.’ Similar progressive steps are needed in the UK, and an acceptance of non-equality of professionalism by analytical chemists, based on the recent SERC report, will not help progress. Unless we, the professional analytical chemists, take active steps to remedy the UK situa- tion, it will become gradually but definitely worse. The future of analytical chemistry in the UK lies in the hands of the analytical chemists. Let us decide it advantageously. These last are not insignificant. References 1. Bark, L. S., “Academic - Industrial Bridges in Analytical Chemistry,’ ’Paper presented at RSC Autumn Meeting, September 1981, Leeds, Reported in Anal. Proc., 1982, 19, 269.302 RESEARCH AND DEVELOPMENT TOPICS Anal. PYOC. Thompson, R. J . , Paper presented at RSC Autumn Meeting, September 1981, Leeds, Reported in Pietri, C. Report of 182nd ACS Meeting, New York, Anal. Chem., 1981, 53, 1481A. Report of the Analytical Sciences Working Group (Chairman: J. J . Turner), CC. 81-173, Science and Dunstan, I., Paper presented at RSC Autumn Meeting, September 1981, Leeds, Reported in Anal. Logan, T. J . , Anal. Chem., 1981, 53, 1476A. Editor’s Column, Anal. Chem., 1981, 53, 1290A, 1969. 2. 3. 4. 5. 6. 7. Anal. PYOC., 1982, 19, 269. Engineering Research Council, Swindon, 198 1. PYOC., 1982, 19, 269.

ISSN:0144-557X    

DOI:10.1039/AP982190297b

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

302 RESEARCH AND DEVELOPMENT TOPICS Anal. PYOC. Research and Development Topics in Analytical Chemistry At the start of the meeting the AD President, Professor L. S . Bark (L), presented the eighth Society for Analytical Chemistry Silver Medal to Dr. A . C . Moffat The following are summaries of thirteen of the papers presented at the Research and Develop- ment Topics in Analytical Chemistry Meeting of the Analytical Division held on June 30th and July lst, 1981, at the University of Salford. Effect of Organic Solvents on the Atomic Absorption of Tin in Air - Hydrogen Flames: Some Anomalies and Some Intriguing Flame Chemistry Jamil Anwar and lain L. Marr Chemistry DeFartment, The University of Aberdeen, Meston Walk, Old Aberdeen, AB9 2 UE Tin exhibits an exceptional behaviour in its flame chemistry, and although impressive advances have been made in flame spectroscopy in general, some basic mysteries related to this element remain unsolved.The unusual behaviour can be observed both in emission and in atomic-absorption spectroscopy. Gilbert1 found that the atomic lines emitted by tin were 1000 times more intense when a propan-2-01 solution was aspirated into an air - hydrogen flame than when the solution was purely aqueous. The atomic-absorption sensi- tivity for tin is higher in hydrogen flames than in acetylene flarne~,~,~ and even higher in the cool hydrogen - argon diffusion flame,3 suggesting that temperature alone is a relatively unimportant parameter in affecting the atomisation of tin in these flames. As with emission, chemical reactions are thought to be responsible for this unusually high absorption by tin in cooler flames.The effect of organic solvents on tin absorption, particularly in hydrogen-supported flames, is also interesting because statements in the literature concerning the effect are not in agree- ment. The first, much quoted subsequently in books and papers, is by Harrison and Juliano, who found that absorption by tin in an air - hydrogen flame was highly depressed by the presence of organic solvent^.^ however, reported enhancement of absorption by organic solvents, while Vickers et aL6 found no We may summarise three statements. Gibson etJune, 1982 RESEARCH AND DEVELOPMENT TOPICS 303 difference in the absorption by aqueous and 60% propan-2-01 solutions of tin in an air - hydrogen flame.Our present work is related to this effect in general, and in particular to these anomalies in the literature. During our work on developing a method for the determination of tin in organotin com- pounds by atomic-absorption spectroscopy, we found that the effect of solvents depended very much on the fuel - oxidant ratio, not only in magnitude but in direction as well (Fig. 1). It was found that solvents increased the absorption in fuel-lean flames and depressed it in fuel-rich flames, while in stoicheiometric flames the nature of the effect depended on the concentration of solvent in the mixed aqueous sample solution. A number of solvents including butanone, acetone, butanol and ethanol were tested, and all gave the same kind of picture, the variation being simply one of magnitude.The significance of the height of measurement above the burner was also checked : it was found that relative depression could be decreased by looking higher up in the flame. This part of the work confirmed that the maximum absorption sensitivity, which was that observed for purely aqueous solutions, could not be observed in the presence of organic solvents, but that nevertheless the depression caused by them could be significantly reduced and rendered insensitive to moderate changes in the proportion of solvent [in the mixture if the fuel - oxidant ratio, the burner height and the mixed solvent composition were all optimised. We were able to take advantage of these findings to select suitable conditions under which a wide range of organotin compounds and inorganic tin salts could be analysed by aspirating into the flame a multi-component solution in which both organic and inorganic compounds could be dissolved.' With samples in the range 5-10 mg, tin at the 30% level could be determined with a relative standard deviation of 0.6%, in a mixed solvent consisting of water, hydrochloric acid, ethanol and butanone.In the second part of the work we attempted to explore the facts behind these surprising changes. We started by looking at physical parameters, including nebulisation efficiency and flame temperature, but neither of these was found fully responsible for the changes observed. We then adopted three approaches to a study of the flame: visual observation, spectroscopic measurement, and gas-chromatographic analysis of the flame gases.In the first case it was noticed that when an aqueous solution was aspirated into an air - hydrogen flame, the flame remained almost colourless, but in the presence of organic solvents a bluish green cone appeared above the burner slot. This cone disappeared at high fuel - oxidant ratios and high solvent concentrations but remained fairly luminous in stoicheio- metric flames with a moderate amount of solvent. The height of the cone depended on three factors: fuel flow-rate, concentration of organic solvent in the aqueous mixture and nature of the solvent. Secondly, we identified and attempted to quantify various species in the flame by emission and absorption spectroscopic methods. This approach was concerned with various radicals in the flames; CH and C, were determined by measuring their emission at 431 and 516 nm, respectively, and OH by its emission at 309 nm.The copper hydride emission method was used to measure H radical concentration, and CH, was determined by absorption measure- ments at 216 nm. As an example of the results obtained by this approach, Fig. 2 shows the variation in methyl radical concentration with change in butanone concentration in the mixed solvent, for different flame mixtures, which can be compared with Fig. 1 for the depression of the tin signal. The correlation between CH, concentration and depression of the tin signal is clearly seen. Similar correlations have been observed when working with other solvents . Thirdly, as it was not possible to detect spectroscopically many of the intermediate species present in the flame, and particularly the final products, we decided to analyse samples of flame gases from different parts of the flame by gas chromatography.A number of products have been detected by this method. For example, when aspirating butanone - water mixtures, we found and determined light hydrocarbons (CH,, C,H,, C,H,, C2H6, C,H6, C,H,), oxides of carbon (CO, CO,) and oxidation fragmentation products (CH,OH, C,H,OH, CH,.CO.CH,) as well as the flame gases themselves (H2, N,, 02). One thing was interesting, that most of these gases, particularly the hydrocarbons, were concentrated in the bluish green cone mentioned earlier. Fig. 3 shows the variation in hydrocarbon concentration with increasing height above the burner for different fuel - oxidant ratios; in all instances the maximum hydrocarbon con- Later work was to prove the importance of this internal cone.304 Anal.PYOC. RESEARCH AND DEVELOPMENT TOPICS I- I 5 10 15 20 5 10 15 20 25 Concentration of butanone, YO V/V Concentration of butanone, % V/V Fig. 2. Effect of butanone concentra- tion on absorption by the methyl radical tion on absorption of tin at 224nm. at 216 nm. Fuel mixtures as in Fig. 1. Fuel mixture: A, rich hydrogen flame; A, Rich hydrogen flame; B, stoicheio- B, stoicheiometric; C, lean. metric; C, lean. Fig. 1. Effect of butanone concentra- centration is found still inside the cone. Fig. 3 also shows the corresDondinp variation in the tin atomic absorption signal in and abov; the cone.hydrocarbons is associated with very low tin absorption signals. It is evidentlthat tKe presence of u Height above ' 4 8 1 2 16 20 24 2C burner /mm 1 I I I I l l 4 8 12 16 20 24 28 Height above burner /mm Fig. 3. (a) Variation in hydrocarbon concentration with increasing height above the burner compared with (b) variation in the absorption by tin with increasing height above the burner. Conclusions The conclusions that have been drawn so far from these results can be summarised as follows. Firstly, the solvent molecules are pyrolysed in the lower region of the air - hydrogen flame, particularly in the cone when it is visible. Secondly, the extent of this region in the flame depends on the fuel - oxidant ratio, the concentration of organic solvent in the solution and the nature of the organic solvent. Thirdly, recombination reactions involving dissociated hydrogen atoms and radicals produced by pyrolysis of the solvent molecules result in depletion of hydrogen atoms in the lower regions of the flame (confirmed by measurements made using the CuH method).This depletion is associated with a corresponding depression of the tin atomic absorption signal in these regions of the flame. Fourthly, in lean flames, and when the solutions contain only a moderate amount of organic solvent, the radical reactions occur low in the flame, below the part where the tin absorption is measured. There is then no apparent interence in the determination of tin, and indeed there may be an improve- ment in sensitivity caused by the increased nebulisation efficiency given by the added solvent. The determination of tin in mixed solvents then becomes a practical proposition.Jzcne, 1982 RESEARCH AND DEVELOPMENT TOPICS 305 References 1.2. 3. 4. 5. 6, 7. Gilbert, P. J., in “Proceedings of the Xth Colloquium Spectroscopicum Internationale,” Spartan Capacho-Delgado, L., and Manning, D. C., Spectrochim. Acta, 1966, 22, 1505. Rubeska, I., Spectrochim. Acta, 1974, 29B, 263. Hamson, W. W., and Juliano, P. O., Anal. Chem., 1969, 41, 1016. Gibson, J. H., Grossman, W. E. L., and Cooke, W. D., Anal. Chem., 1963, 35, 266. Vickers, T. J., Cottrell, C. R., and Breakey, D. W., Spectrochim. Ada, 1970, 25B, 437. Man-, I. L., and Anwar, J., Analyst, 1982, 107, 260. Books, Washington, 1963, pp.171-215. Determination of Volatile Trace Metals in Coal by Analytical Atomic Spectroscopy J. R. Wilkinson and L. Ebdon and K. W. Jackson Defiartment of Environmental Sciences, Plymouth Polytechnic, Drake Circus, Plymouth, Devon, PL4 8A A Department of Chemistry, Shefield City Polytechnic, Pond Street, Shefield, S1 1 WB With the proposed increased use of coal, some environmental concern has been expressed concerning the presence of volatile toxic metals even at trace levels. We have been concerned with developing analytical methods for the routine determination of such elements in coal. Determination of Mercury Both atomic-absorption spectrometry (AAS) and atomic-fluorescence spectrometry (AFS) have been used to determine mercury at the ng g-1 level using flame and cold-vapour atom cells.Methods for the generation of mercury vapour vary but reduction with tin(I1) chloride solution1 has proved most popular. AFS enjoys a number of advantages for mercury determinations over AAS, e.g., greater sensitivity and linear working range, fewer problems from molecular absorption, the opportunity of using a windowless cell and hence avoiding fogging of cell windows. A method for the cold-vapour AFS of mercury based on tin(I1) chloride reduction and using a microwave-excited electrode- less discharge lamp as the excitation source was developed. The gas-sheathed atom cell consisted of a bundle of capillary tubes glued around the channel delivering mercury to the optical path.2 Argon passed through these tubes, producing a laminar flow around the atom cell, reducing quenching and preventing lateral diffusion of mercury.Front surface illumi- nation reduced scattered and background radiation. A continuous-flow system was used in which two peristaltic pumps delivered reductant and mercury simultaneously to a constant level reduction cell. The problems of complete dissolution of coal using wet-ashing conditions sufficiently mild to prevent mercury losses by volatilisation are considerable. Many workers have combusted coal in air or oxygen3-5 to release mercury but conflicting opinions exist as to the need to use catalysts or auxiliary oxidants. We have successfully used non-oxidative pyrolysis under nitrogen to liberate mercury from coal followed by collection in acidified potassium perman- ganate solution.6 In the method developed, a linear working range from 0.2 to 10oO ng ml-l of mercury was established with a detection limit of 0.045 ng ml-1 (corresponding to 1.13 ng g1 of mercury in coal using a 2-g sample).The accuracy and precision of the method were con- firmed by the analysis of a number of coal samples with known mercury contents and found to be excellent, e.g., for NBS SRM 1632a, bituminous coal, certificate value 130 & 30 ng g-l, we obtained a mean value of 134.1 ng g1 from nine replicate determinations with a relative standard deviation of 3.5%. The latter is usually more sensitive, Determination of Arsenic and Selenium The determination of arsenic and selenium by hydride generation AAS has proved markedly Sodium tetrahydroborate(II1) solution is more popular than other contemporary methods.306 RESEARCH AND DEVELOPMENT TOPICS Anal.Proc. commonly used as reductant and both argon - hydrogen - entrained air flames and heated quartz tube atom cells have been used.' Flame cells offer greater simplicity and, in the method developed, sample and sodium tetrahydroborate( 111) solution were pumped via a mixing coil to a reduction cell which acted as a gas - liquid separator.8 The hydrides evolved were swept by a small flow of argon to a hydrogen flame burning on a borosilicate glass tube of 8.5 mm i.d. Arsenic and selenium were determined by AAS using hollow cathode lamp sources or by AFS using microwave-excited electrodeless discharge lamps as sources. The lower volatility of arsenic and selenium, relative to mercury, permitted wet ashing and a rapid, yet safe, perchloric acid digestion method was developed.Coal (0.5g) was mixed with perchloric acid (25ml) and heated gently until effervescence began; after the initial vigorous reaction had subsided the solution was heated until complete dissolution. A lanthanum hydroxide co-precipitation step was included to remove transition metal interferentsg and the precipitate was dissolved in hydrochloric acid (5 M) prior to hydride generat ion. Detection limits obtained were 0.8 ng ml-l by AAS and 0.34 ng ml-l by AFS for arsenic and 0.5 ng ml-l by AAS and 0.13 ng ml-l by AFS for selenium, with linear working ranges typically from 2 to 100 ng ml-l. Quantitative recoveries of both arsenic and selenium from standard coals were achieved using both AAS and AFS, eg., for NBS SRM 1632a, bitu- minous coal, certificate values 9.32 & 1 pg g-l of arsenic and 2.6 0.7 pg gf of selenium, we obtained values of 9.34 and 9.27 pg g1 of arsenic and 2.58 and 2.59 pg g1 of selenium by AAS and AFS, respectively. 0.15 pg gl of arsenic and 0.9 & 0.3 pg g-1 of selenium, we obtained values of 0.32 and 0.33 pg g-1 of arsenic and 0.90 and 0.90 pg g-l of selenium by AAS and AFS, respectively.Typically relative standard deviations for these determinations were in the range 1-3%. For SRM 1635, sub-bituminous coal, certificate values 0.42 Direct Aspiration of Coal Slurries into an Inductively Coupled Plasma The intractable nature of coal poses analytical problems, and any method combining matrix destruction and analyte atomisation into one step immediately attracts interest.Analysis of finely powdered coal as an aqueous slurry is one such method. Previous slurry analyses have focused largely on flame AAS methods,lO,ll although d.c. arc plasmas have been used.12 In such studies problems have been encountered with precision and in attempts to achieve calibration using aqueous solutions. The inductively coupled plasma (ICP) offers an atom cell of higher temperature and, under certain conditions, longer residence time ; this should aid complete matrix destruction and atomisation. Hence it may be possible to achieve equivalent sensitivity using the ICP for slurry and aqueous concentrations. The free-running Radyne R50P generator, demountable torch and 0.5-m scanning mono- chromator used have been described previ0us1y.l~ In this instance a laboratory-constructed Babington-type nebuliserf4 was used.This nebuliser was constructed from a rod of PTFE (13 mm diameter, 40 mm long) drilled with a 0.4-mm diameter hole through which the argon injector gas issued. Slurries were pumped so that they flowed down a groove in which the exit of the argon was centrally situated. The nebulised fraction was led to the plasma via a double-pass cloud chamber. Coal slurries in the range 0.1-25y0 m/V were prepared in an aqueous solution of Triton X-100 (0.5% V / V ) . The effects of particle size (in the ranges 4-38, 38-53, 53-63, 63-125 and 125-250pm), sample pumping rate (in the range 0.67-5.0mlmin-l) and slurry con- centration on the observed manganese emission were investigated.For our nebuliser the preferred sample pumping rate was 1.4-2.0 ml min-1 and the signal increased linearly with increasing slurry concentration up to approximately 20% m/ V. Particle size was critical, particles in the range 38-53 pm producing at least twice the signal of particles in the range 53-63 pm. Particles of 70 pm and greater produced small signals, probably owing to inefficient atomisation of such large particles. It is suggested that complete atomisation occurs only for particles of 10 pm of less,l5 and our results tend to confirm this. Analysis of the ash of the different particle size fractions by AAS has shown, however, that there is no significant difference in manganese concentration with variation in particle size.The plasma performance was optimised using the variable step-size simplex methodls for signal to background ratio at the manganese 403.1-nm atom line in both argon- and nitrogen- cooled plasmas. The argon-cooled plasma gave the best results because of the much lowerJune, 1982 RESEARCH AND DEVELOPMENT TOPICS 307 background observed. Optimum conditions were shifted in favour of longer residence times and increased observation heights compared to those observed using aqueous solutions.l6 No build-up of carbon on the injector tip has been observed and the method shows con- siderable promise for the direct analysis of trace metals in finely powdered coal samples. 1. 2. 3. 4. 6. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. References Hatch, W. R., and Ott, W.L., Anal. Chem., 1968, 40, 2085. Ebdon, L., Wilkinson, J . R., and Jackson, K. W., Anal. Chim. Acta, 1981, 128, 45. Lo, F. C., and Bush, B., J . Assoc. Ofl. Anal. Chem., 1973, 56, 1509. O'Gorman, J. V., Suhr, N. H., and Walker, P. L., Jr., Appl. Spectrosc., 1972, 26, 44. Jones, P., and Nickless, G., Proc. SOC. Anal. Chem., 1973, 10, 269. Ebdon, L., Wilkinson, J. R., and Jackson, K. W., Analyst, 1982, 107, 269. Godden, R. G., and Thomerson, D. R., Analyst, 1980, 105, 1137. Thompson, M., Pahlavanapour, B., Walton, S. J., and Kirkbright, G. F., Analyst, 1978, 103, 568. Thompson, M., Pahlavanapour, B., Walton, S. J,, and Kirkbright, G. F., Analyst, 1978, 103, 705. Willis, J . B., Anal. Chem., 1975, 47, 1752. O'Reilly, J . E., and Hicks, D. G., Anal. Chem., 1979, 51, 1905.Mohamed, N., Brown, R. M., Jr., and Fry, R. C., Appl. Spectrosc., 1981, 35, 153. Ebdon, L., Mowthorpe, D. J., and Cave, M. R., Anal. Chim. Acta, 1980, 115, 171. Babington, R. S., Pop. Sci., 1973, May, 102. Fuller, C. W., Hutton, R. C., and Preston, B., Analyst, 1981, 106, 913. Ebdon, L., Cave, M. R,, and Mowthorpe, D. J., Anal. Chim. Acta, 1980, 115, 179. Some Recent Developments in Chemical Ionisation Mass Spectrometry J. A. Page Shell Research Ltd., Sittirgbourne Research Centre , Sittingbourne, Kent, ME9 8A G Chemical ionisation (CI) mass spectrometry is a technique whereby the ionisation of the substance of interest is effected by ion-molecule reactions rather than by electron ionisation. The spectrum of a substance produced by chemical ionisation is different from the spectra produced by other ionisation techniques and the analytical and scientific usefulness of the method stems from the unique character of the CI spectra.The technique was first intro- duced in 1965 and in the years since it has greatly advanced in scientific importance and application. To appreciate fully the chemical ionisation (CI) technique a brief comparison must be made with electron impact (EI) ionisation. Under EI conditions sample molecules are ionised by impact with energetic (70 eV) electrons to form odd-electron ions by removal of an electron. The process is extremely fast and the ion produced acquires up to 10 eV of energy, causing it to undergo extensive fragmentation. The fragment ions are formed by a series of competing consecutive unimolecular decompositions which makes them difficult to predict.By comparison, ions formed by ion-molecule reactions, as in CI, are generally even-electron species formed with significantly lower internal energy. The salient features of the CI spectra are that little fragmentation is observed, the ions constituting the spectra tend to be located at the higher mass end of the spectra and the (M + 1)' and/or (M -l)+ ion intensities are relatively large. Ionisation Processes The ionisation of the reagent molecules in the system is almost always effected by EI. The CI process may be represented in a general way by the equations R + e + R + R + + M + M $ + R .. .. . . - - (2) where R is the reagent gas, R+ is a stable reagent ion produced from R, M is the additive molecule under investigation and M+ are the ions constituting the CI mass spectrum of M.308 RESEARCH AND DEVELOPMENT TOPICS Anal.PYOC. The important aspect of the CI technique is the fact that with different kinds of reagent ions different kinds of reactions will be involved in the production of the CI spectra. For example, if CH5+ is used, the reaction occurring is proton transfer and the reaction is an acid - base type, but if N2+ is used then electron transfer occurs and the chemistry is oxidation - reduct ion. The most commonly used ion - molecule reaction is that of proton transfer. This may be represented as follows: M + AH++MH++A Base Acid AH = PA(A) - PA(M) (PA = proton affinity) For this reaction to occur, PA(A) <PA(M). Further, as the exothermicity of this reaction lies in the newly formed bond ( i e ., MH+), then the greater the exothermicity of the reaction the greater will be the fragmentation of MH+, as shown in Table I. TABLE I SOME USEFUL REAGENT GASES AND THEIR PROTON AFFINITIES Reagent gas Reagent ion (acid) Proton affinity'lk J mol-1 Hydrogen . . .. .. Decreasing fragmentation 930 Methane .. .. .. P&+ Isobutane . . * . . . C4H,+= Ammonia .. .. . . NH4+ Dimethylamine . . . . (CH,),NH,+ Thus by the choice of suitable reagent gas: 1. the energetics of the sample ion formation may be controlled to give either ions charac- teristic of the relative molecular mass or abundant fragment ions characteristic of mol- ecular structure (both may be required to solve a typical analytical problem); 2.the type of structural information in the resulting mass spectrum may be varied; different CI reagent gases undergo different ion - molecule reactions with the same sample molecule and each type of ion- molecule reaction yields new structural information about the sample. Selective Reagent Gases for Positive Chemical Ionisation There have been many reviews of C12J discussing the use of a variety of reagent gases, the most widely documented reagent gas being methane.4 Methane, however, undergoes a strong acid - base reaction and is therefore not suitable for all classes of compounds, e.g., oligasaccharides or peptides. Isobutane, a milder reagent gas, has not been found ideal experimentally in this laboratory because, although it is a better reagent for these compound classes, as it is a hydrocarbon it contaminates both the source and source resolution slits extremely rapidly. Ammonia has been preferred as a more suitable milder reagent gas.The reagent ions generated are mainly NH4+ with some (NH,),H+ and (NH3),H+. These ions act as weak Bronsted acids and will only protonate strongly basic compounds, i.e., amides5 and amines5 and some aJ/3-unsaturated ketones6 However, NH4+ ions act as weak electrophiles towards a wide range of other organic compounds, the spectra exhibiting a single ion corresponding to (M + NH4)+. This is illustrated for amygdalin, a glycoside, in Fig. 1. Even though this molecule contains a number of labile hydroxyl groups, the relative molecular mass can readily be determined from the (M + NH4)+ ion.In contrast to this result, the EI and CI (methane) spectra are completely devoid of ions in the relative mol- ecular mass region of the spectrum. Nitrogen oxide3 forms NO+, which functions as an electrophile, hydride abstractor and electron oxidising agent, depending on the type of organic functional groups present in the sample molecule, and can be used to identify these functional groups. However, as it is a strong oxidising agent it destroys the mass spectrometer filaments very rapidly. Recent work has been carried out on selective reagent gases.Jane, 1982 RESEARCH AND DEVELOPMENT TOPICS 309 100 - - 40 t CN 0 H OH H OH 239 20 0 - 150 1 , 1 1 l l , I I I I 179 Ill 111,l I * I I I I I I I l l I I Ill mlz 100 Fig. 1. CI (ammonia) mass spectrum of amygdalin.Ammonia does not react readily with alcohols, phenols, hydrocarbons, nitro compounds, etc., and our recent research has been to investigate methylamine and dimethylamine as suitable alternatives to ammonia. Results have shown that reagent ions formed from dimethylamine undergo electrophilic reactions with a wide range of compounds, including cyanoethers, multifunctional biological compounds, nitro compounds, etc., forming more intense adduct ions than are formed with ammonia. Aldehydes and ketones, however, undergo reactions with dimethylamine ions, (CH,),NH,+, possibly forming Schiff base type adducts. Negative Ion Chemical Ionization Negative ion mass spectrometry has been little used in the investigation of structural and analytical problems, however, as negative ions are formed in much lower abundance than positive ions.This is due mainly to the strong dependence on the electron beam energy and source tempera- ture and to the fact that many compounds do not form molecular anions under EI conditions. Over the past 5 years the interest in negative ion mass spectrometry has been revived, mainly because the source conditions employed for chemical ionisation have greatly increased the sensitivity for the production of negative ions. The large increase in negative ion currents observed when the ion source pressure is increased to above Torr to 1 Torr can be attri- buted to a large population of thermal electrons generated under these conditions. Under negative CI conditions, negative ion spectra can be produced in two ways: by electron capture (1) and by reagent ion NCI (2) : Under low-pressure EI conditions negative ions are also generally produced... .. - (1) A B + e +AB- .. .. AH+B--+HB+A- .. .. .. * * (2) Electron Capture The ionisation of a sample by the capture of thermal electrons is not "chemical ionisation" in the true sense but it produces spectra that show features characteristic of a CI spectrum,310 RESEARCH AND DEVELOPMENT TOPICS Anal. PYOC. ie., intense ions in the relative molecular mass region and little fragmentation. This tech- nique has been used by Dougherty et aZ.,' Hunt and Crow8 and Hass et aZ.,9 the advantage being an increase in sensitivity compared with other ionisation techniques. This has been reported3 to be 100--1000 times greater than for positive CI in some instances, the success being due mainly to the development of derivatisation procedures which facilitate the intro- duction of groups that enhance the formation of molecular anions M-*.Pentafluoro- benzaldehyde and pentafluorobenzoyl chloride are good reagents for this purpose. ( b ) 80 - $? 60 - 40 - 20 - -- Reagent Ion Negative Chemical Ionisation In reagent NCI, the negative ions are formed by ion - molecule reactions (2), and much research has been devoted to developing negative reagent ions. In reagent NCI the reagent ion acts as a Bronsted base to abstract a proton from a sample molecule, i.e., the acidity of the sample to be studied will determine its reactions. This is therefore complementary to positive ion CI. The versatility of the technique again lies in the choice of reagent gaslions for the class of compound to be studied.C1-, a weak base, was investigated in this laboratory as it had been reportedll to interact with almost all organic compounds. C1- ions can readily be formed from CH2C12 or CHCI,, although in this laboratory CC12F2, available as Freon 12, was found to be more convenient to use. CH,C12 and CHCl, produce ions that are both temperature and pressure dependent, i.e., C1-, HC12-, CC13- and CHC14-, whereas Freon gave a reproducible reagent ion spectrum and was clean to use. Good C1- attachment spectra were obtained for oligosaccharides, glycosides, many pesticides and a wide range of compounds. C1- is therefore particularly Recent reviewslO of negative ions discuss the process in more detail.248 M- 363 CI 105 \ 0 I l I I l l l l I l l ~ ~ i ' ~ ' l l I I l 1 y _ ~ 80 - ' 60- - -- 40 20 - O r ( c ) 80 - 60 - $? -. 40 - 20 - I I M + CI- 398 155 35 153 71 248 I l l . I 0 , 2 7 6 100 r M+H+ ,364 I 1.1 1. I .I 1 I I I ' I I I , .LI , 1 ,I , 0 - 100 1 . 1 4 . 1 I!. ' I , ' I I l i t - I I I I I I I I 200 300 mlz 400 100 200 300 mlz 400 100 200 300 m/z 400 Fig. 2 . CI mass spectra of Barnon: (a) PCI (methane); (b) electron capture; and (c) NCI (chloroform).June, I982 RESEARCH AND DEVELOPMENT TOPICS 311 suitable for the selective ionisation of these components in a mixture (of, for example, hydro- carbon compounds). Fig. 2 shows the complementary nature of the CI techniques for the analysis of Barnon,” a herbicide. It can be seen that for single ion monitoring of small impurities, electron capture would be most sensitive, giving an intense fragment ion at m/x 248, whilst for relative molecular mass determination C1- NCI gives better sensitivity than methane PCI.The latter could be used for structural confirmation, as some fragmentation remains. OH-, a stronger base that can be formed from the reaction of dinitrogen oxide - methane, hydrogen, methanol,l2 etc., reacts with “acidic” compounds and its use for selective ionisation in mixtures should also prove valuable. Recent results have also shown OH- CI to be much more sensitive than methane CI for the identification of steroids. In conclusion, the CI techniques at present available have greatly enhanced the analytical potential of mass spectrometry to determine the relative molecular masses of complex biological and organic compounds, elucidate structures by studying the chemical reactions undergone by these compounds and monitoring extremely low concentrations in gross mixtures.1. 2. 3. 4. 6. 6. 7. 8. 9. 10. 11. 12. References Walder, R., and Franklin, J. L., I n t . J . Mass Spectrom. Ion Phys., 1980, 36, 85. Hunt, D. F., Prog. Anal. Chem., 1973, 6, 359. Hunt, D. F., and Sethi, S. K., in “High Performance Mass Spectrometry: Chemical Applications,” Munson, M. S. B., and Field, F. H., J . Am. Chem. Soc., 1966, 88, 2621. Dzidic, I., J. Am. Chem. SOC., 1972, 94, 8333. Dzidic, I., and McCloskey, J. A., Org. Mass Spectrom., 1972, 6, 939. Dougherty, R. C., Dalton, J., and Biros, F. J., Org.Mass Spectrom., 1972, 6, 1171. Hunt, D. F., and Crow, F. W., Anal. Chem., 1978, 50, 1781. Hass, J. R., Friesen, M. D., Harvan, D. J., and Parker, C. E., Anal. Chem., 1978, 50, 1474. Jennings, K. R., Phil. Trans. R. SOC. Lond., 1979, A293, 125. Tannenbaum, H. P., Roberts, J. D., and Dougherty, R. C., Anal. Chem., 1975, 47, 49. Smit, A. L. C., and Field, F. H., J . Am. Chem. SOC., 1977, 99, 6471. A C S Symposia, American Chemical Society, Washington, D.C., 1978, p. 150. * Barnon is a Shell trade-mark. Py ro I yt ic Met hods A p pl ied to Quantitative T h i n - layer Chromatography Samuel J. Lyle and M. Saber Tehrani Chemical Laboratories, University of Kent at Canterbzkry, Canterbury, Kent, C T 2 7NH Thin-layer chromatography (TLC) is a versatile, inexpensive technique for the separation of a mixture into its constituent chemical components.However, quantitative measurement, following TLC, is generally not straightforward. Existing in situ techniques or those applied following elution of the separated component from the chromatogram frequently lack accuracy or sensitivity.1,2 In an attempt to increase the range of available techniques some work, summarised here, has been carried out to explore the application of pyrolysis - gas chromato- graphy to such determinations. In the scheme adopted, the zone supporting the separated constituent is cut along with the backing plate from the chromatogram and transferred to a pyrolysis chamber. I t is worth noting that the underlying portion of the backing plate acts as sample support or holder and the sample is pyrolysed while still adsorbed on the thin-layer substrate.By means of a carrier gas the pyrolysis products are swept directly on to the gas-chromatographic column for separation and detection. The height or area of the detector output corresponding to the yield of a well resolved pyrolysis product is used as a measure of the amount of the constituent on the thin-layer substrate. Experimental Furnaces of the tubular or hot-filament types were designed and tested as pyrolysers; a version of the former was eventually considered to be most suitable for present purposes.312 RESEARCH AND DEVELOPMENT TOPICS Anal. Proc. It consisted essentially of a quartz tube (15 x 0.7 cm i.d.) connected by a narrower bore tube (1.5mm id.) to the gas-chromatographic column.A rod made from stainless steel tipped with a piece of quartz tube (2 x 0.6 cm 0.d.) was designed to push the sample to the hot zone of the furnace. This zone occupied a 2-cm length of the furnace tube and it had a temperature gradient from its centre of about 7 "C cm-l at 530 "C. Furnace temperatures up to 1100 "C could be provided by the externally wound heater. The gas chromatograph used was a Pye Series 104 instrument equipped with a flame-ionisation detector and a glass column (160 x 0.35 cm id.) packed with Porapak Q (50-80 mesh). Results and Discussion Preliminary experiments were conducted using either poly(viny1 chloride) (PVC) or a partially hydrolysed poly(viny1 acetate) (PVA) ; standard solutions were prepared in cyclo- hexanone and water, respectively.Known volumes of each solution were transferred to small pieces of thin quartz, the solvent was removed by evaporation and the quartz plate introduced to the furnace by means of the push-rod device. A pyrolysis temperature of 440 "C and a gas-chromatographic oven temperature of 180 "C were found to be satisfactory operating temperatures. A typical pyrogram obtained for PVA is presented in Fig. 1. The major products of pyrolysis are acetaldehyde and crotonaldehyde for PVA, whereas PVC yields toluene, benzene and a pentene. Deter- minations of PVA and PVC were based on the height of the crotonaldehyde and benzene peaks, respectively. Calibration graphs were rectilinear for each polymer over the ranges of sample sizes investigated; these were 0.10-8.Opg for PVA and 0.35-8.0p.g for PVC.Pyrograms and peak heights were reproducible. For example, the coefficient of variation for PVA determination within the sample range quoted above was about 2% for 3-5 replicate measurements. The carrier gas was nitrogen at 50 ml min-l. 9 7 5 3 1 0 Time/m i n Fig. 1. A pyrogram for PVA pyrolysed a t 440 "C with separation of the decomposition pro- ducts on Porapak Q at 180 "C. A, Crotonaldehyde; and B, acetaldehyde. Aluminium foil was used as the backing plate in the TLC as it is easily cut and does not volatilise at the temperatures employed. The aluminium in the form of 0.1 mm thick sheet was cut into pieces 5 x 20 cm and heated in a furnace a t 600 "C for 12 h to remove any adsorbed organic material. The aluminium was coated with silica gel G (13% gypsum binder) in the usual way.A pair of scissors or a punch can be used to cut the separated zone from the developed plate; a square of 6mm side or a disc 6mm in diameter was suitable. It is desirable to have a well resolved spot as small as possible for removal and pyrolysis. Organic binder cannot be used and the layer on the plate for TLC should be as thin as is compatible with the separation to be achieved. Use of a punch to remove theJune, 1982 RESEARCH AND DEVELOPMENT TOPICS 313 separated zone is preferable because the area, and hence the total amount taken, is more easily reproduced. Having established that reproducible results are obtainable and with due regard for the constraints already discussed, the method was applied to the determination of some water- soluble vitamins and to several amino acids.The vitamins examined were L-ascorbic acid (vitamin C) , calcium D-pantothenate (vitamin B,) and pyridoxine hydrochloride (vitamin B6). The mixture was run on silica gel G and the revealing agent for locating the vitamin- containing zone on the plate was iodine vapour for vitamins & and c and ammoniacal silver nitrate reagent for vitamin B,. The solvent system for development of the chromatogram was acetic acid - acetone - methanol - benzene (5 + 5 + 20 + 70) as used by Gaenshirt and Malzacher.3 Rectilinear calibration graphs were obtained for samples of each vitamin in the range 0.2-3 pg on pyrolysis. The amino acids tested were L-cystine, L-proline, L-glutamic acid, L-methionine and DL- leucine.They were separated on silica gel G using butan-1-01 - acetic acid - water (4 + 1 + 1) for chromatographic development. Pyrolysis temperatures were within the range 410- 560 "C and they were selected to maximise production of the pyrolysis product on which the quantitative measurement was based. Rectilinear calibration graphs were obtained for amounts between about 0.3 and 3 pg of individual amino acid. Iodine vapour was a suitable revealing agent with the limit of detection varying from 0.1 to 0.5 pg depending on the amino acid. Conclusion The pyrograms obtained for the polymers, vitamins and amino acids tested were repro- ducible, permitting the determination of each substance within the group. In all of the experiments the reproducibility was such that the main sources of experimental variation related to sample handling or volumetric transfer of the sample solutions to the thin-layer plates.A new sample can be introduced into the furnace as soon as all the volatile pyrolysis products of the previous sample have emerged from the gas-chromatographic column. Thus, the time required for a single measurement can vary from a few minutes to 30 min or more, depending on the retention times of the pyrolysis products. Introduction of a sample into the furnace takes about 30 s, so that the gas chromatography will usually determine the rate of analysis. The sensitivity of the method is dependent on the limit of detection of the constituent to be determined on the thin-layer plate; this in turn depends on the revealing agent or physical method available.The method proposed here may be compared with existing methods for quantitative TLC based on elution procedures or in sih scanning techniques. Problems associated with elution are avoided and, unlike densitometric methods, surface unifoiwty of the thin layer is unimportant. From statistical checks it would appear that a single measurement can provide a reliable result, whereas in applying either elution or densitometric methods replicate determinations would be needed to give mean values of comparable reliability.lS2 At present the main limitations would appear to relate to restrictions on materials for TLC, location of the separated component on the plate and the need to generate volatile decompo- sition products by pyrolysis.Backing plates and binding agents, organic in origin, are ruled out and materials for the former are confined to those readily cut with minimum disturbance to the supported thin layer. Location on the plate is restricted to physical methods such as fluorescence in ultraviolet light or to the use of simple involatile, and thus generally inorganic, chemical revealing agents. Development solutions leaving organic residues on the thin-layer substrate are undesirable and stationary phases sensitive to water vapour are unsuitable for the gas chromatography. 'The proposed technique makes use of equipment the major items of which are to be found in most chemical laboratories, and it enables a quantitative analysis to be performed on mixtures containing involatile constituents for which gas chromatography alone would be inadequate.References 1. 2. 3. Lyle, S. J., and Saber Tehrani, M., J . Chromatogr. Sci., 1979, 17, 317. Lyle, S. J., and Saber Tehrani, M., J . Chromatogr., 1979, 175, 163. Gaenshirt, H., and Malzacher, A., Naturwissenschaften, 1960, 47, 297.314 RESEARCH AND DEVELOPMENT TOPICS Anal. PYOC. Analysis of Quaternary Ammonium Compounds by Pyrolysis - Gas Chromatography A. Christofides and W. J. Criddle Department of Chemistry, UWIST, Cardifl, CF1 3NU Numerous publications1 s 2 have appeared describing the application of pyrolysis - gas chroma- tography (PGC) to macromolecular materials for qualitative and quantitative investigations of structure and stability. To date, however, comparatively little published work has appeared showing the uses of PGC in similar studies of low molecular mass materials, in particular of compounds having low volatility, which normally precludes their study by gas chromatography.The present investigation indicates PGC developments recently made on one such group of compounds, viz., the industrially and pharmaceutically important quaternary ammonium compounds, and currently this study falls into two main areas. Firstly, a fundamental approach to the factors influencing compound stability, and associated qualitative and quantitative examination of the breakdown products formed during pyrolysis of quaternary ammonium compounds having both organic and inorganic anions. Secondly, analytical applications of PGC to the qualitative and quantitative determination of quaternary ammonium compounds in pharmaceutical preparations.Fundamental Study Recently published work3 has shown that for a range of model trimethylphenyl ammonium compounds having different inorganic anions, viz., OH-, C1-, I-, Br-, F-, SO,,-, Po,'-, and pyrolysed by direct injection in aqueous solutions, the variable anionic moeity had no detectable effect on the thermal stability, or the nature and yield of the main product of the reaction, i.e., the tertiary amine (reaction 1). + - A PH(CH,),NX --+ PhN(CH,), + [CH3X]* . . .. * * (1) The mechanism proposed was one involving free radical formation : + A + PhN(CH,),X-- PhN(CH,), + CH; -+ CH,X + PhN(CH,), +x- * ' (2) However, work currently in progress on a series of compounds having organic anions (Table I) shows that such ions can have an influence on the thermal stability of the com- pounds.TABLE I Compound Temperature at which Temperature for pyrolysis is detectable/ maximum base yield/ "C "C Trimethylphenylammonium acetate . . .. . . 135 Trimethylphenylammonium monochloroacetate .. 125 Trimethylphenylammonium dichloroacetate . . .. 125 Trimethylphenylammonium trichloroacetate . . .. 120 275 260 225 225 Table I1 clearly indicates that the presence of chlorine in the anion serves to decrease the thermal stability of the compound. Applying the same mechanistic approach as that suggested for the compounds with inorganic anions, ester formation would be expected along with the tertiary base: A Ph(CH,),&CO,CCI, - PhN(CH,), + CC1,C02CH, .. - (3) * Low molecular mass products.J m e , 1982 RESEARCH AND DEVELOPMENT TOPICS 315 However, the highly chlorinated ester, once formed, would be expected to hydrolyse and decarboxylate successively forming carbon dioxide, methanol and chloroform, the ester being merely a transient intermediate: H O CCl,CO,CH, --% CH,OH + CCl,CO,H CHC1, + CO, * * (4) Gas chromatography - mass spectrometry (GC - MS) studies have confirmed the presence of carbon dioxide, methanol and chloroform as being the only significant compounds formed and these are currently being quantified. It should be noted that aqueous solutions have been used throughout this section of work to allow for the general use of a flame ionisation detector, which gives little or no response to water.The effect of a solvent peak is thus largely removed, although a response due to water and stationary phase is observed using phthalate ester columns in the GC - MS studies. Applications main reactions involved were : Initial studies were carried out on the analytical application of PGE by Cannard and Criddle4 in the development of a technique for the determination of the commercially available and widely used ICI herbicides, paraquat (l,l’-dimethy1-4,4’-bipyridylium chloride) and diquat (1,l ’-ethylene-2,2’-bipyridylium bromide) in aquatic systems. The 2:Br- - I AH2-C”, 1 + 2CHSCI - - --- (5) + (CH2Bd2 - - - - - (6) The 2,2’- and 4,4’-bipyridyl peaks were clearly separated, thus allowing paraquat and diquat to be determined simultaneously, a marked improvement on the standard spectrophotometric methods then available.Subsequently, further development work by Choi, Criddle and Thomas5 resulted in a new assay procedure for the widely used germicidal agent, Cetrimide, in a number of pharma- ceutical preparations (see Table 11). TABLE I1 Preparation Cetrimide concentration, yo Reported Found A f \ Savlon hospital concentrate . . . . 15.0 15.05 f 0.10 Savlon lotion . . .. .. . . 5.0 5.08 f 0.10 Savlon cream . . .. . . . . 0.5 0.56 f 0.02 Cetavlex cream . . .. .. . . 0.5 0.51 f 0.02 Table I1 shows good agreement between the reported levels of cetrimide and those found using the technique. Further work is continuing with studies on the germicidal agent hexadecylpyridinium chloride. This is a considerably more powerful germicide than cetrimide and is therefore used in markedly smaller concentrations in the pharmaceutical preparations currently available. The pyrolysis of hexadecylpyridinium chloride yields two main products :316 RESEARCH AND DEVELOPMENT TOPICS Anal. PYOG. Basic studies equating the pyrolysis temperature to the degree of compound pyrolysis have been carried out, in this instance in methanolic solutions using both the direct injection technique for temperatures up to 450 "C and a CDS 190 Pyroprobe for temperatures up to 1000 "C (Table 111). The low volatility of the main product, viz., hexadecyl chloride, results in a high retention volume and the peak is well clear of the large solvent peak. TABLE I11 Degree of pyrolysis (% molar yield of Degree of pyrolysis (yo molar yield of Temperaturel'C hexadecyl chloride) Temperature/"C hexadecyl chloride) 460 30.3 1000 22.8 376 18.0 850 36.4 300 10.7 650 Although Table I11 shows a maximum yield of hexadecyl chloride at temperatures in excess of 450 "C, the direct injection method at this temperature was chosen because of the greater analytical facility obtained, the Pyroprobe technique being time consuming as a result of the equilibration required after each pyrolysis. Several preparations are currently being investigated, the simplest of which, an anti- bacterial mouthwash (Merocets, Merell), has already been examined and the result of 0.051 % m/m for hexadecylpyridinium chloride compares well with the reported value of 0.05%. Pyrolysis techniques for other antibacterial preparations, viz., sprays and lozenges, are in the course of development, but such preparations require preliminary separation procedures before successful pyrolysis studies can be made. Direct pyrolysis of these preparations results in highly complex pyrograms, unsuitable for analytical interpretation. We thank the Science Research Council for financial support for this work (to A.C.). References 1. 2. 3. 4. 5. May, R. W., Pearson, E. F., and Scothern, D., "Pyrolysis-Gas Chromatography," The Chemical Urwin, W. J., J. Anal. Appl. Pyrol., 1979, 1 (i)/(ii), 89. Criddle, W. J., and Thomas, J., J . Anal. Appl. PyroE., 1981, 2 (iv), 361. Cannard, A. J., and Criddle, W. J., Analyst, 1975, 100, 848. Choi, P., Criddle, W. J., and Thomas, J., Analyst, 1979, 104, 451. Society, London, 1977.

ISSN:0144-557X    

DOI:10.1039/AP9821900302

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

316 RESEARCH AND DEVELOPMENT TOPICS Anal. PYOG. Developments in Grafting Organophosphate Ion Sensors to Polymer Matrices P. C. Hobby, G. J. Moody and J. D. R. Thomas Chemistry Department, University of Wales Institute of Science and Technology, Cardiff, CF1 3N U Introduction The introduction of liquid ion exchanger membrane electrodes, e.g. , the calcium electrode reported by Ross1 in 1967, gave ion-selective electrodes a new dimension. Ross used a solu- tion of calcium bis(didecy1phosphate) sensor in di-n-octylphenyl phosphonate (DOPP) solvent mediator supported on a Millipore filter. The design of such electrodes imposed considerable constraints and was greatly simplified by incorporating the liquid ion exchanger in a poly(viny1 chloride) (PVC) matrix, conveniently cast as a master membrane and from which 8-10 smaller sensor discs can be cut for electrode fabrication.2June, 1982 RESEARCH AND DEVELOPMENT TOPICS 317 The sensor and the solvent mediator liquid ion exchanger system of calcium ion-selective electrodes have been the subject of much subsequent research resulting in significant improve- ments.In particular, a better sensor for calcium electrodes is based on calcium bis{di-[4- (alky1)phenyllphosphate) with DOPP solvent m e d i a t ~ r . ~ , ~ This system has an extended pH range and enhanced selectivity for calcium over sodium and magnesium compared with the early Ross liquid ion exchanger. Unfortunately, the operational lifetimes of PVC membrane electrodes are not necessarily extended owing to the finite solubility of sensor and/or mediator components in the analyte samples, especially in flowing cell arrangements.Recent work of Oesch and Simon5 indicates that the rate of loss of the plasticiser and/or ionophore from the polymeric phase into the sample solution determines the lifetime of PVC membrane electrodes based on neutral ligands. Similarly, potassium ions are rapidly leached from the sensor disc of PVC potassium ion- selective electrodes, while the resistance of the sensor disc eventually approaches that of PVC alone.6 Attempts have been made to improve the selectivity' and extend the lifetime of these electrodess-12 by minimising, or ideally, totally offsetting leaching of the active components by immobilising the sensor component by covalent bonding to a polyner background. A calcium ion-selective electrodelOJ1 has been made by crosslinking a poly (styrene-b-butadiene)- triblock copolymer with triallyl phosphate and diallyl phosphonate groups.The organo- phosphorus groups were hydrolysed to give alkyl phosphate or phosphonate anions as immobilised ion-exchange sites. This electrode showed improved mechanical properties, such as robustness and lifetime, but its calcium ion-selectivity over other cations did not match that of normal PVC membrane electrodes. An alternative grafting approacha involved phosphorylating a vinyl chloride - vinyl alcohol copolymer [VAGH , Union Carbide (UK) Ltd.] with mono-n-decyl dihydrogen phosphoric acid to give a covalently bound alkyl phosphate sensor. The polymeric sensor was then mixed with PVC, plasticised with DOPP, to produce a calcium ion selective electrode.Ex- tended lifetimes were, however, not obtained, although the immobilised sensor sites showed similar calcium over sodium and magnesium selectivities as the Orion 90-20-02 calcium liquid ion exchanger that was used as a comparison. This work has been extended in this study, particularly with regard to immobilising the improved alkylphenyl sensor which has proved so successful in the normal PVC-matrix membrane electrodes. TABLE I SUMMARY OF CALCIUM ION-SELECTIVE ELECTRODE PROPERTIES FOR MEMBRANES CONTAINING PHOSPHORYLATED PRODUCT VAGH PI VAGH PI1 Specification (free acid) Standard? (free acid) Detection limit1? in CaCl,/M . . .. . . 4.8 x 6.6 x 8 x SlopelmV decade-l . . .. .. .. . .30 (25 "C) 32 (25 "C) 32 (35 "C) Long term drift/mV d-l . . .. .. .. 6 1 6 Dynamic response time+ (1 cm3 of lo-' M Tris pH-buffered calcium-containing solution added Detection limit17 in Tris pH buffered CaCl,/M . . 4 x 2 x - Static response time dilute to concentrated/min 1-6 1-6 1-6 to 10 cm3 of M CaC1,) . . .. .. 1 1 1 Operational lifetime/weeks . . .. .. .. 2-3 2-3 51 Selectivity coefficients (mixed solution method in water) K!&B (5 x M)* . . . . .. . . 1.2 1.3 Considerable interference Kg:Mg (5 x 10-4 M)* . . .. .. . . 4.8 x 1.7 x lo-, 1.2 x lo-, Standards 3 x 10-6 32 (36 "C) 1-6 1 - 1 7-9 Nil 1.2 x 10-3 * Concentration of interferent. t Taken from master membrane containing PVC 0.17 g, DOPP 0.36 g and calcium bis(di-n-decyl- 1 Still under evaluation. 8 Taken from master membrane containing PVC 0.17 g, DOPP 0.36 g and calcium bis(di-[4-(1,1,3,3- phosphate) 0.04 g. tetramethylbutyl)phenyl]phosphate } 0.04 g.318 RESEARCH AND DEVELOPMENT TOPICS Ana2.Proc. Phosphorylation of Vinyl Chloride - Vinyl Alcohol Copolymer In order to obtain phosphorylated VAGH, purified vinyl chloride - vinyl alcohol (VAGH) copolymer is phosphorylated by a modification devised by Blackburn et aZ.13 for insoluble polymers. Thus, the appropriate organo dihydrogen phosphate [- 1.30 g] previously dried in a vacuum dessicator over silica gel, is added to a solution of 4.00 g (0.0055 mol of hydroxyl) of similarly dried copolymer VAGH in 20 cm3 of freshly distilled pyridine. To this is added a solution of 2.25 g (0.011 mol) of dicyclohexylcarbodiimide in 20 cm3 of pyridine, the mixture is shaken for 1-3 days at 20-35 "C followed by separation and purification of the phosphorylated polymer product.The synthetic stage can be represented as follows: I % 3 0-P-OH where R = -CI0Hz1 in mono-n-decyl dihydrogen phosphoric acid obtained by the procedure of reference 14; where R =* C8Hq7 in mono-4-(1,1,3,3- tetramethylbutyllphenyl dihydrogen phosphoric acid obtained by the procedure of reference 15. 'R 0 Grafted free acid sensor Grafted calcium sensor The product obtained by phosphorylating with monodecyl dihydrogen phosphoric acid (VAGH PI) has been compared with mono+( 1 lJ3,3-tetramethylbutyl)phenyl dihydrogen phosphoric acid (VAGH PII) 0 I 0 I 0-P-OH 0- P-OH CH3 I I I o ~ c 1 0 H 2 1 '*F2CH2- T-CH. CH3 CH3 VAGH PI VAGH PI1 Evaluation of Phosphorylated Product Infrared spectra of the phosphorylated polymers show a drastic reduction in OH absorption at 3400 cm-l and a new strong broad band appears at 1000 cm-l, assigned to POC activity.Further evidence for successful phosphorylation comes from phosphorus analyses of -2% after Schoniger oxygen flask combustion.Is The phosphorus content is maintained even after prolonged soxhlet extraction of the grafted polymer with boiling methanol. Several batches of free acid VAGH PI and of free acid VAGH PI1 have been synthesised, all with similar infrared patterns and of the following phosphorus contents. VAGH PI Mean yo P = 1.88, s.d. 0.08 (6) VAGH PI1 Mean yo P = 2.11, s.d. 0.08 (2)June, 1982 RESEARCH AND DEVELOPMENT TOPICS 319 Assuming the specified 6% m/m poly(viny1 alcohol) in the copolymer VAGH, the mean phosphorus assays are equivalent to about 65-70y0 conversion of the original hydroxyl sites.The VAGH PI material varied in its solubility in the tetrahydrofuran used in electrode membrane fabrication, according to batch. Nonetheless, the performances of electrodes made from membranes cast from the VAGH PI (0.05 g), plus PVC (0.12 g) and DOPP (0.36 g), were generally similar to each other and also to the comparison model based on calcium bis(di-n- decyl phosphate) (Table I). A similar brief evaluation of VAGH PI1 has been carried out with respect to the comparison model based on calcium bis{di- [a-( 1,1,3,3-tetramethylbutyl)- phenyllphosphate) (Table I). Leaching Effects Various master membranes have been suspended horizontally under the surface of stirred, de-ionised water (50 cm3) in covered beakers at 35 "C and the water changed at intervals over several weeks.Each water batch was examined for sensor and mediator by thin-layer chromatography and by atomic-absorption spectroscopy for calcium content. The results establish that calcium as well as di [4-( 1,1,3,3-tetramethylb~tyl)phenyl]phosphate anions are leached from the non-grafted sensor matrix, at least during the first 19 d (Table 11). How- ever, no mediator could be detected during this stage, although control runs with di-n-octyl- phenyl phosphonate established that this material could be detected on thin-layer chromato- graphic plates in amounts greater than 10 pg. Results for comparison were obtained for the grafted sensor VAGH PII, both free acid and calcium forms.No organic species were detected for the grafted calcium sensor but free calcium was detected in the leach waters (Table 11). This can be attributed to the higher than theoretical calcium analysis of about SyO, possibly due to calcium carbonate entrapment in the acid to calcium salt conversion. TABLE I1 SUMMARY OF LEACHING EXPERIMENTS ON MEMBRANES CONTAINING .COPOLYMER VAGH PHOSPHORYLATED WITH MONO-4- (1 , 1,3,3-TETRAMETHYLBUTYL)PHENYL DIHYDROGEN PHOSPHORIC ACID Non-grafted membrane Calcium bis {di[4- (1 , 1,3,3-tetra- methylbuty1)phenyl)phosphate } VAGH PI1 grafted sensor membrane A f A I f 7 (CaX,) + DOPP Acid form Calcium form TLC TLC TLC Days of (-A-, Ca, Daysof I-A-, Ca, Daysof ,---A-> Ca, leaching CaX, DOPP p.p.m.leaching HX DOPP p.p.m. leaching CaX, DOPP p.p.m. 0.9 1 - - 0.1 1 - - 0.4 0.4 2 - - Nil 2 - - 0.4 1 + - Nil 5 - - 0.2 2 + - - 0.1 6 + - 0.1 5 - + Nil 8 - - 1.3 9 + - 0.2 8 - + Nil 12 - - 0.3 19 + - 0.3 12 - + 29 - - Nil 18 - + Nil 18 - 40 - - Nil Mass loss = 1.7% A h f > I \ I 'L A Mass loss = 2.2% Mass loss = 2.4% Conclusion The calcium ion-selective electrode membranes obtained from phosphorylated polymer Further approaches are sensors show reduced leaching of the organic phosphate sensor. being studied in order to otherwise improve electrode properties. The authors thank the Science and Engineering Research Council for a studentship (to P.C.H.) under the CASE scheme in association with the Central Electricity Research Laboratories, Leatherhead, Surrey.320 RESEARCH AND DEVELOPMENT TOPICS Anal.Proc. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. References Ross, J. W., Science, 1967, 156, 1378. Moody, G. J.. Oke, R. B., and Thomas, J. D. R., Analyst, 1970, 95, 910. RfiiiiJka, J., Hansen, E. H., and Tjell, J. C., Anal. Chim. Acta, 1973, 67, 155. Moody, G. J., Nassory, N. S., and Thomas, J . D. R., Analyst, 1978, 103, 68. Oesch, U., and Simon, W., Anal. Chem., 1980, 52, 692. Davies, J . E. W., Moody, G. J., Price, W. M., and Thomas, J. D. R., Lab. Pract., 1973, 22, 20, Kimura, K., Maeda, T., Tamura, H., and Shono, T., J . Electroanal. Chem., 1979, 95, 91. Keil, L., Moody, G. J . , and Thomas, J . D. R., Analyst, 1977, 102, 274. Cutler, S. G., Meares, P., and Hall, D.G., J. Electroanal. Chem., 1977, 85, 145. Ebdon, L., Ellis, A. T., and Corfield, G. C., Analyst, 1979, 104, 730. Corfield, G. C., Ebdon, L., and Ellis, A. T., Anal. Proc., 1981, 18, 112. Freiser, H., and Martin, C. R., Anal. Chem., 1981. 53, 902. Blackburn, G. M., Brown, M. J . , Harris, M. R., and Shire, D., J. Chem. SOC. ( C ) , 1969, 676. Nelson, A. K., and Loy, A. D. F., Inorg. Chem., 1963, 2, 776. Craggs, A., Delduca, P. G., Keil, L., Key, B. J . , Moody, G. J., and Thomas, J . D. R., J . Inovg. NucC. Belcher, R., and MacDonald, A. M. G., Talanta, 1958, 1, 185. International Union of Pure and Applied Chemistry, “Recommendations for Nomenclature of Ion- selective Electrodes,” Appendices on Provisional Nomenclature, Symbols, Units and Standards, No. 43, IUPAC Secretariat, Oxford, 1975.Chem., 1978, 40, 1483. Automated Determination of Nanogram Amounts of Phosphorus by Molecular Emission Cavity Analysis 1. H. El-Hag* Department of Chemistry, University of Birmingham, P.O. Box 363, Birmingham, B15 2TT Molecular emission cavity analysis (MECA)1 is a flame photometric technique that relies on a cool flame source to generate band emissions, such as those from S,, BO, and HPO. The conventional manual method involves depositing the microlitre-volume sample into a cavity cut into the end of a rod, which is introduced manually to the flame, so that the emission generated within the cavity is viewed by the detector. The reproducibility of this method is unsatisfactory for fast emitting species because variables such as the exact time of injection, cavity residence time in the flame and cooling time after analysis need precise control.The Automated Instrument It includes automated sample injection into the cavity and automatic movement of the cavity in and out of the flame. A Varian ASD-53 automatic sample dispenser is used for the injection of solutions into the MECA cavity after simple modification of its electrical circuitry. It includes a rotating carousel module which can hold up to 25 samples, an injector and a control unit. The moveable cavity device consists of a synchronous motor, a gearbox and an egg-shaped cam driving a precision stainless-steel tube which moves forwards and backwards following the shape of the cam. The cam is connected to an electronic timer, which controls the residence time of the cavity in the flame in the range 5 4 5 s and the cooling time between successive injections between 10 and 270 s.As the tube moves forward, it tilts the cavity holder from the vertical position in which the sample is injected to the horizontal position in which it enters the flame, in view of the detector. The automatic device described is designed to overcome these shortcomings. The complete arrangement is shown schematically in Fig. 1. Results Initially, the device has been used for the determination of phosphorus anions, based on the measurement of the green HPO emission band generated in a carbon cavity in a hydrogen- based flame. Phosphorus anions can be determined at the nanogram level after ion-exchange to remove cationic interferences.All condensed phosphates give the same response as * Present address : Department of Chemistry, The University, Hull, HU6 7RX.Jztrte, 1982 Moveable Injector cavity module * device , +- Monochromator +- Photomultiplier 321 Recorder Control unit Fig. 1. Block diagram of the automated MECA analyser. orthophosphate but phosphite and hypophosphite are more sensitive. graphs are obtained for inorganic phosphates in the range 25-250 ng of phosphorus. detection limit for hypophosphite is 3 ng of phosphorus. up to nine times with the operator dialling up the number of readings required. advantage is its improved reproducibility. 50 p.p.m. (250 ng) of phosphorus as KH,PO,.gave a relative standard deviation of 1.5%. as well as applications to other elements.Linear calibration The It can automatically repeat each determination Its major For example, 10 peak height measurements of Work in progress includes the determination of phosphorus in detergents and fertilisers, The system is easy and convenient to use. Reference 1. Bogdanski, S. L., Burguera, M., and Townshend, A., C.R.C. Crit. Rev. Anal. Chew., 1981, 10, 186. Determination of Selenium in Biological Material ; Comparison of Three Atomic Spectrometric Methods A. A. Brown* and J. M. Ottaway G. S. Fell Department of Pure and Applied Chemistry, University of Strathclyde, Cathedral Street, Glasgow, G1 1 X L Department of Pathological Biochemistry, University of Glasgow, Royal Infirmary, Glasgow, G4 OSF For over 100 years after its discovery, selenium was considered solely as a toxic element. But, in 1957, Schwarz and Foltzl demonstrated that a small amount of selenium was essential for animals.Selenium-responsive deficiency diseases have been found in numerous species and the practical importance of adequate selenium nutrition in the economic production of farm livestock is considerable.2 Human requirements for selenium were often postulated but convincing evidence was lacking until Van Rijj et aL3 demonstrated reversible clinical and biochemical effects upon provision of supplemental selenium during prolonged intravenous nutrition. Biochemical evidence of selenium depletion can be found in severe gastrointestinal disease.*v5 Epidemio- logical studies of children in areas of China also indicate a reversible selenium deficiency.6 Analytical methods suitable for the investigation of the human nutritional requirements of selenium should be both sensitive enough to measure nanogram amounts and sufficiently rapid and reliable for hospital laboratory use.The preferred method in agricultural science has been based on a molecular fluorimetric procedure,' but over the past few years the tech- nique of hydride generation atomic-absorption spectrometry (HGAAS) has been introduced8 for selenium analysis. This method has been applied to the assay of selenium in human whole blood, blood plasma, urine and a variety of liquid nutrients used in supplementary fee ding.,^^ The procedure requires the prior wet digestion of samples with acid mixtures but a graphite furnace atomic absorption method now allows direct analysis of selenium in blood plasma.Hydride generation atomic fluorescence spectrometry (HGAFS) is potentially a more sensitive technique and an instrument that was purpose-built for HGAFS has been con~tructed.~ This paper compares the analytical performance of these three techniques when applied to a variety of biological materials. * Present address : Pye-Unicam Ltd, York Street, Cambridge.322 RESEARCH AND DEVELOPMENT TOPICS Anal. Proc. Experimental Hydride Generation Atomic-absorption Spectrometry (HGAAS) A Perkin-Elmer 360 spectrometer was used with the MHS-10 hydride system. This system utilises a long path length silica cell, heated by an air - acetylene flame, to atomise the gaseous selenium hydride. The selenium 196.0 nm line was used at a 2.0 nm band pass.The light source was a Perkin-Elmer radiofrequency electrodeless discharge lamp, operated at 6 W. The reductant solution was 3% m/V sodium tetrahydroborate in 1% m/V sodium hydroxide solution. All biological materials were digested by using a mixture of nitric and perchloric acids. The digestion procedure required 0.2 ml of whole blood, 0.5 ml of plasma or 2 ml of urine or nutrient solution and digestion with nitric acid (5 ml) plus perchloric acid (2 ml). The heating block was a Technicon BD 40, programmed to give 100 "C (1 h), 150 "C (1 h) and 200 "C (1 h). After cooling, hydrochloric acid (2 ml) and water (5 ml) were added and the mixture heated to 80 "C for 30 min in order to convert selenate to selenite. The cooled mixture was made up to 25 ml with water and this solution used for hydride generation.Standards were made by addition of selenium (0-100 ng) to hydrochloric acid (2 ml) and perchloric acid (2 ml) and then made up to 25 ml with water. The selenium absorbance at 196.0 nm was measured on a potentiometric chart recorder, using the peak height mode. Hydride Generation Atomic-fluorescence Spectrometry (HGAFS) A laboratory-constructed atomic-fluorescence system was used, with a microwave selenium electrodeless discharge lamp (EDL), a minimate monochromator (Spex) , a "solar blind'' photomultiplier (Hanonamatsu) and a "lock-in" amplifier (Brookdeal). Various designs of atomisers and hydride generation systems were investigated. An electrically heated silica tube atomisation system gave the lowest detection limits, The initial design assumed that the gaseous hydride would be thermally decomposed in the heated silica tube and that the lifetime of the selenium atoms would be long enough to permit emission of EDL-excited atomic fluorescence above the atomiser head, which was shielded by a stream of hot inert argon.The measured temperature inside the silica tube was between 800 and 1000 "C, and it was noted that when the shielding gas flow was low (less than 1 1 min-1) a small hydrogen diffusion flame was evident on the atomiser head, which produced an improvement in atomis- ation efficiency. Although this hydrogen flame increased the background noise, an over-all increase of 50 times in signal to noise ratio was observed.The hydrogen diffusion flame originated from gas produced during the decomposition of sodium tetrahydroborate, which then spontaneously ignited on the heated silica tube. When an electrothermal atomiser is used with the MHS-10 hydride system, the total gas flow (hydrogen plus inert carrier gas) is low and gives rise to longer residence times for atoms of selenium in the optical path of the spectrometer compared with those found in a conventional hydrogen diffusion flame. Sample preparation for HGAFS also required prior acid digestion of samples and the generation of selenium hydride, as described previously for the HGAAS method. Graphite Furnace Atomic-absorption Specrometry (GFAAS) A Perkin-Elmer 5000 spectrometer was used with the HGA-500 electrothermal atomiser.The heating cycle for the furnace involved a two-stage drying programme (100 and 130 "C), ashing at 1100 "C and atomisation at 3000 "C (ramp rate 1, gas flow 10 ml min-l, 4 s). The sample volume was 20 pl, and the selenium absorbance was measured at 196.0 nm while using deuterium arc background correction. A standard graphite furnace tube was preferred for plasma samples, although marginally greater sensitivity was obtained for aqueous selenium standards with a pyrolytically coated tube. Sample preparation for the GFAAS method needs only 1 + 1 dilution of plasma with 0.1% nickel solution. This should be prepared from analytical-reagent grade nickel nitrate because other nickel nitrate solutions as used for atomic absorption standards contain nitric acid, which precipitates plasma proteins. Calibration is by the standard additions pro- cedure.If more than 20 plasma samples are to be analysed, then five can be measured by standard additions and an average calibration graph derived, against which the other samples can be compared.June, 1982 RESEARCH AND DEVELOPMENT TOPICS Results and Discussion 323 Hydride Generation Atomic-absorption Spectrometry (HGAAS) up to 100 ng of selenium. of selenium. 25 ml of solution) was 1 ng of selenium (average of 10 determinations). interferences were found for acid-digested whole blood, plasma, urine or liquid nutrients. The sensitivity was 2.5 ng of selenium (sample volume 25 ml), while the linear range was Precision (yo RSD) was from 4 to 8% within the range 10-100 ng The detection limit (twice the standard deviation of long of selenium in No chemical Accuracy was established by satisfactory inter-laboratory comparisons.Hydride Generation Atomic-fluorescence Spectrometry (HGAFS) The detection limit (twice the peak-to-peak noise of the background signal) was 1.4 ng of selenium and the precision (yo RSD) within the range 10-200 ng of selenium was 6 7 % (average of 10 determinations). Accuracy was confirmed by comparison with hydride generation atomic-absorption spectrometry. Graphite Furnace Atomic-absorption Spectrometry (GFAAS) The linear range was up to 200 ng ml-l of selenium, The precision (% RSD) for a plasma sample containing 51 ng ml-l of selenium was 5.4% (average of six determinations). The detection limit in the diluted sample was 5 ngml-l, which corresponds to 10ngml-l in the original plasma.Accuracy was confirmed by comparison with hydride generation atomic-absorption spectrometry. Interferences were compensated for by standard-addition calibration ; however, whole blood and urine samples could not be assayed owing to severe matrix effects.lOJ1 The linear range was up to 600 ng of selenium. The sensitivity was 98 pg (on a 20-4 plasma sample). Applications The concentration of selenium in whole blood and blood plasma varies with the population studied, because of marked geographical differences in dietary selenium intake. In the UK, the reference range for whole blood is from 170 to 220 ng ml-l and for plasma from 80-140 ng ml-l. Urine excretion varies according to recent dietary intake, but an average value would be 40 ng ml-l of urine.The amounts of selenium found in liquid nutrients used in hospital practice fall into two categories : firstly, fluids given parenterally, such as glucose, saline and crystalline amino acid mixtures, contain less than 2 ng ml-l; secondly, fluids given by naso- gastric tube, some of which are derived from whole protein, contain 5-20 ng ml-l.g The HGAAS method can reliably measure selenium in whole blood, plasma, urine and “tube feed’’ solutions. Although prior acid digestion is required, this can be safely left for unattended operation and 100-150 duplicate digestions can easily be accomplished and 100- 150 duplicate digestions can easily be accomplished within a working week. However, the digestion procedure does add a reagent blank of about 2 ng per sample and strict temperature control is important, necessitating a programmable heating block.The GFAAS procedure avoids pre-digestion. Sample preparation is simple and each analysis takes 15-20 min. Only a small volume of sample is required and the analytical performance is adequate for plasma selenium determinations. However, GFAAS is limited by matrix effects for other types of sample, and the need for the addition of nickel at a relatively high concentration contaminates the furnace system. There is a need for efficient optical back- ground correction. There is also a tendency for the nickel, which is added to the plasma at a level of 500 pg ml-l, to precipitate plasma proteins and give erratic results. Furthermore, the lifetime of the graphite tubes is short as a result of the high atomisation temperature required.The HGAFS system has a wider linear range than the other techniques, thus reducing the need for repeat analyses of samples with larger amounts of selenium. The detection limit is similar to that of HGAAS and superior to that of GFAAS. Further improvements in the detection limit will be obtained as higher intensity EDL light sources become available. The atomic-fluorescence system could be used for whole blood, plasma and “tube feed” solutions; however, pre-digestion with acid would still be required. Also, the long-term stability of laboratory-made selenium EDL sources is not established and no commercial version of this324 RESEARCH AND DEVELOPMENT TOPICS Autal.Proc. instrumentation is available. None of the techniques described can measure selenium at less than 2 ng ml-1 and therefore cannot fully define theselenium content of some intravenous nutrients. However, the daily intravenous selenium requirement is about 30 pg and the HGAAS and GFAAS methods have been found useful in monitoring patients receiving selenium supplements during intravenous feeding. 1. 2. 3. 4. 5. 6. 7. 8 . 9. 10. 11. References Schwarz, K., and Foltz, C. M., J . Am. Chem. Soc., 1957, 79, 3292. Underwood, E. J ., in “Trace Elements in Human and Animal Nutrition,” Fourth Edition, Academic Van Rijj, A. A., Thomson, C. D., McKenzie, J. M., and Robinson, M. F., Amer. J . Clin. Nutr., 1979,32, Fell, G. S., Shenkin A., Main A., Russel R., Brown A.A., and Ottaway, J. M., R o c . Nutr. SOL, 1979, Fell, G. S., Stromberg, P., Main, A., Spooner R., Campbell, R., Russel, R., Brown, A. A., and Ottaway, Young, V., N. Engl. J . Med., 1981, 304 (20), 1228. Ihnat, M., J . Assoc. Off. Anal. Chem., 1974, 57, 368. Nakahara, T., Kobayashi, S., Wakisaka, T., and Musha, S., Appl. Spectrosc., 1980, 34, 194. Brown, A. A., PhD Thesis, Strathclyde University. in the press. Saeed, K., and Thomassen, Y., Anal. Chim. Acta., 1979, 110, 285. Manning, D. C., At. Absorpt. Newsl., 1978, 17, 107. Press, 1977. 2076. 39, 30A. J. M., Proc. Nutr. Soc., 1981, 40, 76A. Problems in the Simultaneous Determination of Chloride and Bromide in Organic Compounds D. Thorburn Burns and B. K. Maitin De$artment of Analytical Chemistry, The Queen’s University of Belfast, Belfast, BT9 5AG, Northern Ireland Many organic compounds of pharmaceutical interest contain two or more of the halogens.Hence, a method that could achieve the simultaneous, precise and accurate determination of all halogens present in a compound would be advantageous for assay and for quality control purposes. Mutual interference has always been a problem in the simultaneous determination of halides in admixture, particularly so for chloride and bromide. A large number of methods based on various techniques have been proposed but no reliable method has been described to date.1 Experimental The direct potentiometric titration using a silver nitrate solution as titrant has been re- examined in detail. Titrations were carried out using a silver billet indicator electrode in conjunction with a mercury - mercury(1) sulphate reference electrode and an Orion 901 microprocessor ionalyser for accurate potential measurement.A precalibrated “AGLA” micro-syringe burette, operated by a micrometer, was used for the accurate delivery of the small volumes of titrant required in the final procedure. Results and Discussion Using conventional, i . e . , dilute, titrant solution, conditions problems arise from : small potential changes at the end-points ; speed and stability of the electrode response ; mixed crystal formation ; and location of the end-points. The quantitative mineralisation and recovery of inorganic halides from organic compounds is a further very important aspect of the analysis. Electrode Response possible to obtain appreciable potential jumps a t the end-points.I t has been found that by the use of a concentrated silver nitrate titrant solution it is A 0.2 M silver nitrateJame, 1982 RESEARCH AND DEVELOPMENT TOPICS 325 solution gave distinct potential breaks for 0.01-0.04 mmol of each halide in 50-90 ml of solu- tion. The use of a concentrated titrant solution also improves both the speed and the stability of the electrode response. Repeatability can be further improved if a 1 min time interval is allowed after each addition of titrant near the equivalence points. Mixed Crystal Formation Mixed crystal formation, because of the closeness of the solubility products (AgC1 = 1.78 X 10-lo; AgBr = 5.25 x lO-l3) and compatibility of crystal lattices (face-centred cubic), is the most serious problem in the simultaneous determination of chloride and bromide. The error due to mixed crystal formation can be reduced to a reproducible minimum by flocculating the precipitate as it is formed.Upon flocculation rapid exchange occurs and the distribution of chloride and bromide between solid and solution approaches that expected for the formation of ideal homogeneous distribution mixed crystals.2 Several electrolytes were examined and potassium aluminium sulphate was found to be the most suitable. In the absence of alum an enhanced non-reproducible bromide value was obtained owing to co-precipitation of chloride. When using flocculation a reproducible value, close to theoretical value, was obtained (Fig. l), 2 ml of 0.05 M alum being sufficient under the conditions described above; an excess has no adverse effect.0 -40 -80 -120 3 -160 - 0 - z -200 -240 -360 -400' I I ' ' ' I I ' ' 0 1.35 2.70 4.05 -40 - -80 - -120 - m -160 - + - 0 .L - -200 - - .- ' -240 - -280 - -320 - -360 - <r 0 1.35 2.70 4.05 -400. I I I I' ' I ' Volume of titrant x 10-Vml Volume of titrant x 10-'/ml Fig. 1. Computer-drawn titration graphs showing the effect of The Theoretical alum on the titration value. silver nitrate solution is 0.2 M and the sample 0.0008 M. titration value is 0.199 8 ml. The alum is added in graph (b). Location of the End-point It is of prime importance to locate the titration end-point precisely and accurately. Simple graphical methods are tedious and subject to reading errors; a variety of mathematical procedures to overcome the problems have been de~cribed.~ The second derivative method, which derives from the work of Hostetter and Roberts4 (now commonly called Kolthoff's method5) , and Gran's procedure,e using data before and after the equivalence point regions, were examined.Both methods gave similar accuracy but Gran's method, using 8-10 points before the end-points, was the most precise. The calcula- tions can be conveniently carried out using a programmable desk calculator with printout. Mineralisation and Recoveries oxygen flask combustion. busted by using cellulose powder (30-40 mg) as a combustion aid. Under suitable conditions quantitative recovery of inorganic halide can be achieved by The sample is wrapped in several folds of filter-paper and com- The size of the platinumAnal. PYOC.gauze should be small enough so that it is entirely inside the flame during the combustion, otherwise distillation of the compound and soot formation are unavoidable. Hydrazine hydrate was found to be a suitable reducing agent for use in the absorption solution and does not interfere in the final titration if the solution is acidic. Hence, absorption solutions, after acidification, can be titrated directly. Additions of ammonium vanadate (4 drops of 1 % m/V) to the solutions followed by gentle heating catalyses the conversion of any bromate, formed after the combustion, to bromide. 326 RESEARCH AND DEVELOPMENT TOPICS Standardisations and Analytical Results The silver nitrate solution was standardised by use of a mixture of M.A.R.grade s-benzyl- thiouronium chloride and 9-bromobenzoic acid as reference compounds,’ and the chloride and bromide factors calculated incorporating the blank values from the paper. Several organic and pharmaceutical compounds were analysed, the results being both precise and accurate, as is shown in Table I. TABLE I ANALYSIS OF ORGANOHALOGEN COMPOUNDS Each result is the average of ten replicate determinations except for compounds Nos, 1 and 5, which are the average of nine determinations. Bromide f A * - Standard Calculated, Found, Error, deviation, Calcyted, Compound % % % % /o 1 N- (4-Bmophenyl) 4’- (2-chloro-4-ni trophen yl) - thiourea CIsH,BrCIN 08 . . 20.66 20.61 -0.05 i 0 . 0 4 9.17 2 1-[1-(4-Bromophenylm~thyl)-4-pip~~idinyi]:5- chloro-2-( trifluoromethyl)-1H-benzimidazole 3 Bromocllphenyl hyd&mine hydrochloride ‘ C,,H,BrNO.HCl .. .. .. 21.65 21.56 0.00 k0.05 9.56 5 a-Bromo-pchloroacetophenone ClC,H,COCH,B; * 34.22 34.24 +0.02 k0.17 15.18 C,H,@rClF,NI . . 16.90 16.99 +0.09 *0.06 7.50 4 Bromosalicylchloranilide CI~HHpBrCiNO, . . 24.47 24.46 -0.01 *0.07 10.88 Chloride P Found, Error, dewation, St++d % % % 9.21 + O M *0.04 7.49 -0.01 *0.04 9.54 -0.02 i0.07 10.90 +0.02 k0.04 15.24 +0.06 iO.18 References 1. 2. 3. 4. 5. 6. 7. Williams, W. J., “Handbook of Anion Determination,” Buttenvorths, London, 1979, p. 291. Bowers, R. C., Hsu, L., and Goldman, J. A., Anal. Chem., 1961, 33, 190. Svehla, G., “Automatic Potentiometric Titrations,” Pergamon, Oxford, 1978, p. 187. Hostetter, J. C., and Roberts, H.S., J . Am. Chem. SOG., 1919, 41, 1919. Kolthoff, I. M., and Laitinen, H. A., “pH and Electrotitrations,” Wiley, New York, 1944, p. 110. Gran, G., Analyst, 1962, 77, 661. Microchemical Methods Group and the Analytical Standards Sub-committee of the Analytical Methods Committee, Analyst, 1972, 97, 740. Applications of Non-aqueous Catalytic Thermometric lodimetry G. L. Jeyaraj and E. J. Greenhow Iodine in dimethylformamide has been used to titrate amines, amides, dithiocarbamates and phosphorodithioates in non-aqueous so1ution.l The end-point was located by an increase in the rate at which the temperature of the titration solution, containing ethyl vinyl ether as a thermometric indicator, rose as soon as iodine appeared in excess, the free iodine catalysing the indicator reaction.In a further evaluation of catalytic thermometric iodimetry we have studied the effect of using different solvents for the sample, different vinyl ethers as indicator reagents and alternatives to iodine, namely iodine monochloride, iodine monobromide, iodine trichloride and iodophenyl dichloride, as titrants. Dimethylformamide and acrylonitrile proved to be superior to propylene carbonate, toluene, 1,4-dioxan, tetrahydrofuran, diethylformamide, dimethylacetamide and dimethyl sulphoxide in terms of the sharpness of the end-point achieved when they were used as solvents for the sample in conjunction with dimethyl- Chemistry Department, Chelsea College, Manresa Road, London, S W3 6LXJune, 1982 RESEARCH AND DEVELOPMENT TOPICS 327 formamide as the solvent for the titrant.Divinyl ether and 2-chloroethyl vinyl ether were ineffective as thermometric indicators, while n-butyl and isobutyl vinyl ethers, although effective as indicators, were inferior to ethyl vinyl ether with respect to end-point sharpness. Similarly, there was no improvement in the sharpness of the end-point inflection when iodine was replaced by the alternative titrants. However, it was found that an improvement in end-point sharpness could be effected by using a mixture of ethyl vinyl ether and 1,3-dioxolan as the indicator reagent instead of ethyl vinyl ether alone (Fig. 1). Presumably, copoly- merisation of ethyl vinyl ether with 1,3-dioxblan occurs at a faster rate than the homopoly- merisation that has been assumed to be the indicator reaction of ethyl vinyl ether alone.The mechanism of the reaction occurring when iodine in dimethylformamide is added to ethyl vinyl ether in the same solvent was investigated by terminating the reaction by shaking the final titration mixture with aqueous sodium thiosulphate, separating the non-aqueous layer and analysing this layer by using capillary gas liquid chromatography - mass spectro- metry. In addition to solvent and unreacted monomer, two major constituents, ICH,CH- (OC,H,)CH,CH(OH) (OC,H,) and I [CH,CH(OC,H,)],CH,CH(OH) (OC2H5), were identified, thus confirming the occurrence of a polymerisation process initiated by the iodonium ion. The hydroxy terminating group must originate from the aqueous thiosulphate. The iodimetric method was evaluated for the determination of sodium, potassium, rubidium, caesium and mercury( 11) iodides, lithium, sodium and potassium bromides, ammonium, sodium, potassium, mercury(II), mercury(I1) potassium, zinc, barium, lead(II), cobalt(I1) and iron(II1) thiocyanates, sodium azide, and three organic thiols (mercaptothiazoline, mercapto- benzothiazole and mercaptobenzoxazole) .When titrated in dimethylformamide solution, the alkali metal iodides gave titration values corresponding to the formation of a triiodide, i.e., to a reaction stoicheiometry of about 2 (Fig. 2). With mercury(I1) iodide the end-point was indicated at a lower titration value than that for the solvent, dimethylformamide, alone, suggesting that this non-ionisable compound does not undergo reaction with iodine but itself catalyses the indicator reaction.The alkali metal bromides gave indistinct, rounded, end-point “inflections,” again approximating to a reaction stoicheiometry of 2. 1 ~ 0.1 M Iodine in DMF -b 0.1 M Iodine in DMF Fig. 2. Catalytic thermometric titration Fig. 1. Effect of 1,3-dioxolan on end- of alkali metal iodides in dimethylformamide. point sharpness in catalytic thermometric Solvent, 2 ml of dimethylformamide plus iodimetry (blank titrations). The values on 1 ml of ethyl vinyl ether. The values on the graphs indicate the ratio of ethyl vinyl the graphs represent the sample, its amount ether to dioxolan. in milligrams and the stoicheiometry (in parentheses). The metal thiocyanates and ammonium thiocyanate were readily soluble in dimethyl- formamide and gave titration curves with sharp end-point inflections (Fig.3). In all instances, except in the titrations of Hg(SCN), and HgK(SCN),, the reaction stoicheiometries corre- sponded to the formation of polyiodides and ISCN. For example, sodium, potassium and ammonium thiocyanates formed the triiodides : MSCN + 21, = MI, + ISCN while barium thiocyanate formed the hexaiodide : Ba(SCN), + 41, = BaI, + 2ISCNAnal. Proc. The reactions with Hg(SCN), and HgK(SCN), resulted in titration values that could be explained if it is assumed that HgI,, rather than HgI,, is the reaction product with the mercury(I1) ion. This would be expected from the result obtained when HgI, was titrated in dimethylformamide. Ammonium, sodium and potassium thiocyanates are soluble in acrylonitrile also and when these solutions were titrated with iodine in dimethylformamide the end-point inflections were sharp, but they corresponded to reaction stoicheiometries of 5, and not 4, as were obtained with dimethylformamide as the sample solvent.To explain this discrepancy, it is proposed that in acrylonitrile, a solvent in which the thiocyanates are not readily ionised, a free radical mechanism predominates, leading to the reaction : 2MSCN + 51, = 2M15 + (SCN), 328 RESEARCH AND DEVELOPMENT TOPICS As the ratio of acrvlonitrile to dimethvlformamide in the final titration solution is reduced the reaction 1 0.1 M Iodine in DMF Fig. 3. formamide. vinyl ether. Catalytic thermometric titration of thiocyanates in dimethyl- Solvent, 2 ml of dimethylformamide plus 1 ml of ethyl The values on the graphs are as for Fig.2. Sodium azide is not readily soluble in dimethylformamide but dissolves in dimethyl sulph- oxide to yield a solution that can be diluted with 2 volumes of dimethylformamide without precipitation occurring. On titration a sharp end-point inflection occurs, corresponding to the reaction : 2NaN3 + 31, = 2Na1, + 3N, When thiols are titrated with iodine the usual product is a disulphide, but in catalytic thermometric iodimetry reaction stoicheiometries were found to be lower than the expected stoicheiometry of 1 , being 0.06 for mercaptothiazoline, 0.3 for 2-mercaptobenzothiazole and 0.13 for 2-mercaptobenzoxazole. In an earlier study of the titration of toluene and aliphatic thiols2 it was suggested that low reaction stoicheiometries could be explained by the effect of a competing reaction in which the ethyl vinyl ether adds to the thiol group, thus preventing reaction with iodine.The ready addition of acrylonitrile to thiols under alkaline conditions has been found to be reversible with 2-mercaptobenzothiazole and 2-mercaptobenzoxazole.a The acidic thiol groups of these last two compounds can be titrated with alkali, using catalytic thermometric titrimetry, because this reversible reaction occurs rapidly,3 but it is apparent that the addition reaction between ethyl vinyl ether and these two thiols, although it may be reversible, particularly in the case of 2-mercaptobenzothiazole (stoicheiometry 0.3) , is too slow in the reverse direction for the iodimetric oxidation to disulphide to proceed to completion during the course of the titration.June, 1982 RESEARCH AND DEVELOPMENT TOPICS References 1.2. 3. Greenhow, E. J.. Chem. Rev., 1977, 77, 835. Greenhow, E. J., Chem. Ind., 1973, 697. Greenhow, E. J., and Dajer de Torrijos, L. A., Anabyst, 1979, 104, 801. 329 New Developments in Fluorescence lmmunoassay H. Thakrar and J. N. Miller Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, LEl 1 3T U Among the several types of homogeneous fluorescence immunoassay is the energy-transfer assay first described by Ullman and co-workers1 In this method the sample antigen competes with the analogous labelled antigen for binding sites on antibodies that also have fluorescent labels attached.The labels on the antigen and antibody are so chosen that, when the labelled molecules are in specific combination, short-range energy transfer effects take place, leading to a reduction in the fluorescence of the donor label and possibly an enhanced fluorescence of the acceptor label. These labels are normally attached to the antigen and antibody, re- spectively. Most work thus far has utilised fluorescein as the donor group and rhodamine as the acceptor,2 but this combination is far from ideal3 and at least one other pair of labels has been found to be ~aluable.~ This paper describes studies of further pairs of labels, in particular involving eosin as an acceptor group. This group might be expected to have two advantages; the bromine atoms in the eosin nucleus might produce large quenching effects (by the heavy- atom mechanism) on any neighbouring fluorophors, and the eosin group itself may show delayed fluorescence and pho~phorescence.~,~ These triplet state phenomena, which have millisecond lifetimes, may facilitate the removal of the short-lived (nanosecond) background fluorescence of blood serum and other biological samples. Experimental Fluorescence measurements were made in 10 mm silica cuvettes at a temperature of 25 "C, using an MPF-44B instrument (Perkin-Elmer, Ltd., Beaconsfield, Buckinghamshire) ; corrected spectra were recorded using the DCSU-2 accessory.Human serum albumin (hsa, lOOyo pure, Hoechst, London) and rabbit anti-albumin antibodies (Dakopatts, obtained through Mercia Brocades Ltd., Weybridge, Surrey) were labelled with fluorescein isothiocy anate, quinacrine mustard (Sigma Ltd., Poole, Dorset), fluorescamine (Roche Diagnostics Ltd., Welwyn Garden City) and eosin isothiocyanate (Polysciences Inc., Warrington, PA, USA, obtained through International Enzymes Ltd., Windsor, Berkshire) using conventional procedures.Fluorochrome to protein (F : P) ratios were determined spectrophotometrically. Results and Discussion Substantial overlap of the fluorescence spectra of fluorescein conjugates and the excitation spectra of eosin conjugates was verified. This is one requirement for efficient fluorescein-to- eosin energy transfer. Such energy transfer was demonstrated by adding eosin-labelled antibodies to an albumin-fluorescein conjugate (1.31 nM, F: P = 1.5). Fluorescence measure- ments were made after 20 min incubation in the dark.The magnitude of the quenching of fluorescein (520 nm) and the enhancement of the eosin (545 nm) depended on the F:P ratio of the eosin-labelled antibodies, the fluorimeter bandwidth, and the antibody: antigen (Ab : Ag) ratio. Enhancements of up to 40% at 545 nm were observed using lightly-labelled (F : P m 4) antibodies and substantial quenching (< 60%) at 520 nm was obtained when using more heavily-labelled (F: P M 10) antibodies. The addition of unlabelled albumin reversed these effects, and as little as l0-lo M albumin could be determined in pure solution (loA9 M in diluted serum) using an antibody conjugate with F : P = 4, an Ab : Ag ratio of 6 and fluorimetry at 545 nm. The addition of human immunoglobulin G to a mixture of eosin-labelled antibodies and fluorescein-labelled albumin had no effect on the fluorescence intensities at either wave-330 RESEARCH AND DEVELOPMENT TOPICS Anal.R o c . length, thus showing the specificity of the assay. Eosin conjugates were found to be stable when stored in the dark at 4 “C. These results demonstrate that the fluorescein - eosin dye pair behave similarly to the fluorescein - rhodamine pair in a conventional energy transfer assay. The magnitudes of the quenching and enhancement effects are similar, and similar shortcomings (band width effects, small Stokes shifts leading to direct excitation of the eosin acceptor groups, etc.) are apparent.3 In efforts to relieve these problems, two further donor labels were investigated, with eosin as the acceptor in each case.Using fluorescamine-labelled albumin (F: P = 6), eosin-labelled antibodies (F:P = 3 4 ) showed a 40% enhanced fluorescence signal at 545 nm (excitation wavelength, 390 nm) . Little corresponding fluorescarnine quenching was observed, probably because of a compensating enhancement effect observed with all fluorescamine-labelled antigens.’ The eosin enhancement effect could be used to detect M albumin in pure solution. When quinacrine mustards was used as the donor fluorescent label, experiments were per- formed by mixing quinacrine-labelled albumin( F: P = 2) and eosin-labelled antibody (F: P = 6). The quinacrine fluorescence at 490 nm was reduced by about 60% (excitation wave- length, 420 nm) and the reversal of this effect could be used to detect 10-lo M albumin in pure solution.A further advantage of using quinacrine or fluorescamine as the donor dye was that the eosin fluorescence at 490 nm was negligible in the experimental conditions used, so the fluorescence background due to the reagents was minimised ; unfortunately, endogeneous serum fluorescence is higher at 490 nm than at higher wavelengths. Despite earlier suggestions that eosin groups bound to proteins were thereby protected from oxygen quenching of the triplet state,5,6 it was found that measurable delayed emissions from eosin conjugates could, in practice, only be obtained when samples were thoroughly deoxy- genated. Further work on the use of “triplet state labels” is in progress.J.N.M. thanks the Medical Research Council for an equipment grant, and H.T. thanks the Science and Engineering Research Council for a Research Studentship. 1. 2. 3. 4. 5. 6. 7. 8. References Ullman, E. F., Schwarzberg, M., and Rubenstein, K. E., J. Biol. Cham., 1976, 251, 4172. Ullman, E. F., Bellet, N. F., Brinkley, J . M., and Zuk, R. F., in Nakamura, R. M., Dito, W. R., and Tucker, E. S., Editors, “Immunoassays : Clinical Laboratory Techniques for the 1980’s,” Alan R. Liss, New York, 1980, pp. 13-43. Lim, C. S., Miller, J . N., and Bridges, J . W., Anal. Bzochem., 1980, 114, 183. Miller, J . N., Lim, C. S., and Bridges, J . W., Analyst, 1980, 105, 91. Cherry, R. J., Oppliger, C . M., Schneider, G., and Semuza, G., Biochemistry, 1976, 15, 3653. Garland, P. B., and Moore, C.H., Biochem. J., 1979, 183, 561. Miller, J. N., Lim, C. S., and Bridges, J . W., submitted for publication. Chen, R. F., Arch. Biochem. Biophys., 1976, 172, 39. Acoustic Emissions from Chemical Reactions Malcolm Joslin Department of Chemistry, University College of Swansea, Swansea, SA2 8PP It has been found that during the course of many chemical reactions acoustic emissions can be detected with the aid of a microphone and amplifier. Out of the 50 reactions tested so far, only 10 have failed to give a detectable resp0nse.l This technique is proving to be a useful way of monitoring reactions and shows great analytical potential. Whereas physical effects account for many of these signals, some chemical influence is also indicated and an investigation into possible sources of these emissions is being carried out using mathematical processes such as pattern recognition, Experimental Two approaches have been used in this work; in one, an over-all plot of the entire acoustic energy given out during the course of a reaction is made and in the other individual signals,June, 1982 RESEARCH AND DEVELOPMENT TOPICS 331 taken over lOOps, are recorded.The signals are collected by a broad-band transducer and then amplified and filtered, leaving only the ultrasonic component in the range 50 kHz- 5 MHz. This information may be fed directly on to a chart recorder to give an over-all plot or individual signals can be collected by a transient recorder and transferred to a mini- computer where they are recorded permanently on floppy discs.Results Over-all Acoustic Energy Plots Before investigating possible analytical applications of this technique, the relability of the system had to be tested. This was done by repeating a reaction between solid sodium hydrogen carbonate and copper sulphate solution a number of times over several days. Fig. 1 shows three of these plots, which are surprisingly similar considering the crudity and complexity of the reaction. The start of the reaction is accompanied by a large burst of Base line I Base line I Time 4 Fig. 1. Plot of acoustic energy for reaction between 2.78 g of solid sodium hydrogen carbonate and 150 ml of 0.62 M copper sulphate solution. energy (thousands of individual signals superimposed on each other) which then decays over 10-15 rnin.Such a complicated reaction, however, can tell us nothing about the source of any particular indi- vidual signal. Therefore, concentrated sulphuric acid and its reactions with both water and sodium hydroxide were studied as these represented a homogeneous environment with supposedly no physical emission sources. Fig. 2 shows that acoustic emission is indeed observed in both these reactions. A small burst occurs on injection of one reagent, which is then followed after about 13 s by a second, much larger, burst of emission which then decays to a number of individual signals. The temperature response of a nickel - chromium- thermocouple is also included in this figure, showing no deviation during this second burst, The two peaks at the summit of the burst are apparent in every plot.332 RESEARCH AND DEVELOPMENT TOPICS Anal.PYOC. which indicates that the emission in this situation is not solely a result of the exothermicity of the reaction. 1 min 41 1st addition 2nd addition I Time Fig. 2. Plot of acoustic energy for the addition of approximately 6-ml aliquots of sodium hydroxide solu- tion into concentrated sulphuric acid. The following reaction systems have also been followed acoustically and demonstrate the analytical merit of the technique. (i) An ion-exchange reaction between an aluminosilicate clay charged with sodium ions and aluminium sulphate solution produces emission for several minutes, with greatest intensity at the beginning. The integrated curve produced from this is in broad agreement with that produced conventionally by an ion-selective electrode.(ii) A solution of iodate, peroxide and malonic acid in the presence of starch oscillates between blue and colourless regularly2 with the acoustic trace also oscillating, following these colour changes faithfully. (iii) A gelation between sodium carbonate solution and calcium chloride solution is indicated by a build-up of emission over about 15 min. The break-up of this gel can also be observed over the next hour in the form of isolated intense bursts of sound. (iv) The uptake of water by anhydrous copper sulphate crystals can be monitored acoustically. (v) The recrystallisation of solid copper sulphate from a saturated solution gives out more than 20 signals per second for over 1 h during crystal growth.Individual Signal Anal ysfs Fig. 3 shows four typical signals, as recorded from concentrated sulphuric acid reactions. If the assumption is made that these signals originate from a small number of discrete sources, then similarities should occur between those signals emitted from the same source. To test this, signal properties have to be measured and compared. The most useful manipulation is made by computing the frequency intensity spectrum (power spectrum) for each signal. This is achieved by calculating the square of the Fourier transform; the resulting spectrum will then display the component frequencies which make up the complex wave of the signal. The median frequency of this spectrum can then be calculated, which gives one value to describe the whole signal.It has been found that most of these frequencies lie in either of two bands, one around 100 kHz and the other at 650-750 kHz. It is possible, therefore, that some environmental factor is favouring the transmission of signals of certain frequency. However, the recording equipment is known to have a flat response over a wide range of frequencies and other possible causes have been eliminated by changing the reaction vessel (from glass to plastic and metal) and also the reaction solvent (from aqueous to various organic solvents). It would seem, therefore, that there must be some chemical significance attached to this effect but, if so, it can only be in the broadest sense as a wide selection of reactions produce the same frequency bands. This type of study can be extended by also measuring the amplitude and variance of each signal.A three-dimensional graph can be plotted with median frequency, amplitude and variance each representing one axis. A signal can be diplayed as a single point on this graph and can then be plotted along with a number of other signals from the same reaction.June, 1982 RESEARCH AND DEVELOPMENT TOPICS 333 Signals arising from the same source will then plot as a closely spaced group or cluster. This is a basic form of pattern recognition.3 Twelve reactions have so far been studied in this way and in virtually all instances 3-5 clusters have been well defined. It remains to be seen if these clusters have any real chemical significance or if there is any cross-correlation between clusters produced from different reactions, which would then indicate a common source.0.05 I I 1 0.025 0 t -0.02 U -8 - -0.05 Q 0.05 E 0.025 a 0 -0.02 -0.05 ‘ I I I I I I 0 25.6 51.2 76.8 102.4 0 25.0 51.2 76.8 102.4 Time@ Fig. 3. Typical individual acoustic signals from reactions between concentra- ted sulphuric acid and sodium hydroxide. Discussion By monitoring the over-all acoustic energy of a reaction ( i e . , acoustic power verszcs time) Its main advantages a totally novel means of following a chemical reaction has been found. are as follows: (a) the apparatus is very simple but has also been shown to be reliable; ( b ) the probe is non-intrusive and can therefore be used with closed-vessel systems; ( c ) the detection system is sensitive; (d) there may be a quantitative relationship between acoustic energy and the extent of reaction ; ( e ) this technique may well be able to monitor systems that are not easy to follow by conventional techniques (such as gelation).Although some of the detected emission can be credited to physical occurrences such as the bursting of gas bubbles or breaking up of solid reagent, the evidence of homogeneous reactions strongly indicates that these emissions are also chemically linked. As yet, the analysis of individual signals has not enabled us to identify these sources but has, at least, managed to group signals which, it would seem, arise from the same source. The clustering technique also shows that the grouping of these signals is not solely caused by the median frequency values tending to fall into two bands, the reason for which has still to be identified.Despite the present uncertainty of the origins of all these emissions, this method appears to have the makings of a simple but powerful analytical tool. References 1. 2. Betteridge, D., Joslin,. M. T., and Lilley, T., Anal. Chem., 1981, 53, 1064. Horlick, G., and Hieftje, G. M., in Hercules, D. M., Hieftje, G. M., Snyder, L. R., and Evenson, M. A., Editors, “Contemporary Topics in Analytical and Clinical Chemistry,” Plenum Press, New York, 1978, Volu,me 3, Chapter 4. 3. Batchelor, B. G., Practical Approach to Pattern Classification,” Plenum Press, London, 1974, pp. 46-49, 215 and 222-225.334 RESEARCH AND DEVELOPMENT TOPICS Anal. PYOC. Analysis of Romano- British Pottery A. Tubb and G. Nickless Department of Inorganic Chemistry, School of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS Archaeologists are concerned with reconstructing the behaviour of past civilisations. Very often physical remains are the only clues available for consideration. On any article four pieces of information are required: (i) use; (ii) burial site; (iiz) age; and (&I) source of origin.The source of origin is often more uncertain than the other three points and techniques that can provide such information are useful. A possible approach is to analyse samples chemically and hopefully produce a concentration “fingerprint” characteristic of the manufacturing site. Chemical analysis of pottery has been used to correlate composition and pr~venance.l-~ Analytical Method For pottery samples of archaeological interest, non-destructive techniques may appear superficially to be ideal tools for analysis.Unfortunately they are not, partly because sample and standard matching is very awkward without some sample preparation, and partly because many of these techniques are expensive and not widely available. Atomic-absorption spectrophotometry (AAS) is relatively cheap, available, rapid, accurate and simple to operate. The disadvantage of destroying the sample is probably not important for most pottery samples. Large volumes of broken pottery are found on most sites, and these are generally available for destructive analysis. In order for the results to have any statistical significance a large number of samples must be analysed.A rapid and simple dissolution technique is required. Clays are aluminosilicates, and the commonest dissolution technique is acid digestion (using hydrofluoric and perchloric acid), which is a hazardous operation producing a solution prone to interference effects in AAS, so reducing the precision of the analysis. Lithium metaborate fusion techniques are safer and easier to handle than direct acid digestions and they produce a solution matrix that is protected to a large extent from interferences in AAS.“’ Lithium metaborate (800 mg) was mixed thoroughly with 400 mg of the dry finely powdered sample in a platinum crucible. The mixture was fused for 20-30min at 920°C in the oxidising flame of a Meker burner, producing a glass that was rapidly cooled by a cold air jet.The mass loss was determined and the glass powdered in a stainless-steel mill. The powder (500 mg) was dissolved in 50 ml of 1.5 M nitric acid to give a solution containing 1400 pg ml-1. The effort and time required for the dissolution of the Li+ is comparable to that required for acid digestion. Lithium is more easily ionised than most of the other elements present in the matrix. The large excess of Li+ allows it to act as an ionisation buffer, preventing ionisation of the other elements in the AAS flame. Lanthanum, also present in excess, acts as a releasing agent, thereby preventing the formation of complexes in the flame. The sample is only a small proportion of the total matrix, so large variations in the relative elemental composition of the sample can be tolerated without altering the over-all matrix effect.Nitric acid shows fewer interference effects than most other acids, which is why it was selected. The concentration of the acid and storage in plastic gives the samples a long shelf- life (several months). Higher sample concentrations can be tolerated in nitric acid than in most other acids and precipitation from stored samples has not been noted. Dinitrogen oxide - acetylene flames were used for the determination of all elements, except sodium and potassium, which were determined by flame emission using an air - acetylene flame. The hotter flame prevents interference by providing an environment too energetic for the formation of stable complexes. The considerable attempts to avoid and compensate for matrix effects were useful because of the high interferences usually found in solutions of aluminosilicates.In this instance all of the elements gave linear calibration graphs over the concentration ranges of interest. Consequently, no sample dilution was required for any elements, unlike the equivalent wet acid digestion technique. Samples and standards were also closely matched.June, 1982 RESEARCH AND DEVELOPMENT TOPICS 336 Table I gives the accuracy and precision for replicate analyses of British Standard Firebrick No. 269, and lists the elements determined in the samples. TABLE I ACCURACY AND PRECISION OF THE ANALYTICAL METHOD Reported No. of Standard composition of Element determinations Result, % deviation, yo the standard, % Aluminium (Al,O,) .. .. Iron (Fe,O,) . . .. .. Magnesium (MgO) . . .. Calcium (CaO) . . .. Titanium (TiO,) . . .. Manganese (MnO) . . .. Barium (BaO) . . .. Sodium (Na,O) . . .. Potassium (K,O) . . .. 32.4 3.17 0.86 0.19 1.28 0.027 0.34 2.68 - 2.0 33.9 &- 0.2 0.9 3.31 f 0.04 1.1 0.93 f 0.05 1.6 0.22 f 0.02 3.7 1.48 f 0.04 1.2 0.02 f. 0.005 3.5 - 3.6 0.36 f 0.04 1.2 2.62 & 0.10 Samples Samples were taken from known kiln sites at Llanedeyrn and Caldicot (both near Cardiff), Gloucester College of Art site, Ashley Rails and Islands Thorns in the New Forest. These samples can be used to ascertain whether chemical composition is correlated with the site of origin. Results The results were examined by principal co-ordinate analysis. In this type of analysis a similarity matrix is calculated. The similarity between items is related to their Euclidean separation in space. From the similarity matrix the principal co-ordinate analysis seeks to create artificial co-ordinates that will reproduce the distances.In this instance each sample has nine variates so the separations in nine dimensions are calculated and used to produce the similarity matrix. Co-ordinates that try to reproduce the data in the matrix are then calculated sequentially. The first co-ordinate calculated contains most information, the last least. The first two co-ordinates generated can then be plotted as scattergrams to give a two-dimensional representation of the data, which contains about 60% of the total informa- tion available. This is often sufficient to allow an objective assignment of origin to about 90% of the samples. The principal co-ordinate plot is shown in Fig. 1. Co-ordinate 2 Co-ordinate 2 Fig. 1. Principal co-ordinate plot Fig. 2. Principal co-ordinate plot using the data obtained from all atomic- using only iron, magnesium, calcium absorption results. 1, Samples from and potassium results. Code as for Gloucester; 2, samples from Wales; Fig. 1. 3, samples from the New Forest.336 EQUIPMENT NEWS Anal. PYOC. In this instance a maximum of nine co-ordinates would be required to reproduce all of the information content of the data. The last co-ordinates found contain very little information and can be ignored. The co-ordinates can be related to the variates (elemental concentra- tions). In this instance iron, potassium and magnesium concentration data gave higher contributions to co-ordinate 1 than the other elements. Calcium is the major contributor to co-ordinate 2. Fig. 2 shows the principal co-ordinate plot obtained when the less useful elements are discarded and only iron, potassium, magnesium and calcium data are used. Conclusions The method is a rapid and simple technique for the analysis of aluminosilicates and related samples which shows few matrix effects when examined by AAS. The results are sufficiently precise to allow principal co-ordinate analysis to resolve pottery samples into groups corre- lating with their sources of origin. We acknowledge with very grateful thanks the help, advice and encouragement that Dr. A. J. Parker gave to us. We thank Mr. G. C. Boon (National Museum of Wales), Mr. J. Rhodes (Gloucester City Museum) and Mrs. P. Saunders (Salisbury City Museum) for supplying the samples. The computer programs were compiled with the help and advice of Dr. S. Evan of the University of Bristol Computer Centre, whom we thank for her invaluable help. We also thank the Science Research Council for supplying the funds that made this project possible. References 1. 2. 3. 4. 5. 6. 7. Goodyear, F. H., Sci. Archaeol.. 1970, 2 (2), 17. Catling, H. W., Archaeometry, 1963, 6, 2. Allen, R. O., Lukenback, A. H., and Holland, C. G., Archaeometry, 1975, 17, 69. Hughes, M. J., Cowell, M. R., and Craddock, P. T., Archaeometry, 1976, 18, 19. Ingamells, C. O., Anal. Chim. Acta, 1970, 52, 323. Apt, K., and Gladney, E., Anal. Chem., 1975, 47, 1484. Boar, P. L., and Ingram, L. K., A.nalyst, 1970, 95, 124.

ISSN:0144-557X    

DOI:10.1039/AP9821900316

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

336 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. Automatic Pipette The Eppendorf Varipette 4710 can accurately pipette any volume between 2 and 1000 p1, the required volume being displayed digitally. It is available in sizes of 2-10, 10-100 and 100- 1000 pl. Anderman Co. Ltd. Circle 501. Syringe Filter Holders Schleicher and Sciihll holders are manufactured in stainless steel or polycarbonate. The former type accepts 13 and 25mm diameter filters, and the latter 25 and 50 mm diameter filters. The holders have standard Luer connections suitable for Schleicher and Schiill three ring syringes, the ANTLIA pump or sterile dis- posable syringes.Anderman Co. Ltd. Circle 502. Small- scale Pressure Filter Pressures up to 7 bar can be applied to the Schleicher and Schull ANTLIA filter, enabling viscous or extremely turbid solutions to be filtered through membrane filters with a pore size of only 0.01 pm. Anderman Co. Ltd. Circle 503. Air Conditioning Units The Branca Idealair range includes sizes from 500 to 700m3 h-1 supply air and a cooling capacity of 0.5-3.5 T. A range of extras is available. Certified Climate Ltd. Circle 504. Non-ferrous Reference Materials These materials are used for the calibration of X-ray fluorescence and optical emission spectro- meters. They are in the form of discs 40 mmJ w e , 1982 EQUIPMENT NEWS 337 or more in diameter and not less than 10mm thick. A range is available, including brasses, bronzes, gunmetals and nickel silvers. BNF Metals Technology Centre.Circle 505. Oil-in- Water Analyser The OCMA-200 analyser is a portable instru- ment which extracts water with a solvent and determines the hydrocarbon content down to 1 p.p.m. with a non-dispersive infrared analyser. The unit has a standard range of 0-20 p.p.m. with optional ranges of 0 to 50, 100 and 200 p.p.m. A variety of solvents may be used, including carbon tetrachloride and fluoro- chloro-based solvents such as 316. A solvent recovery system is available as an extra. Horiba Instruments Ltd. Circle 506. Mume Furnace The Type 30400 has a 36 x 36 x 36cm heating chamber, automatic control to f 5 "C over the range 93-982 "C, and an LED digital readout.It is constructed with lightweight ceramic fibre insulation, resulting in faster heat- up, greater energy efficiency and larger chamber size compared with the overall volume. Thermolyne Corp. Circle 507. Heater for Radiation Dosimeter A variation of the DB-4 Dri-Block has been produced for annealing the discs used in Pitman radiation measuring badges. This is necessary to return the disc to a zero level after use. Techne Cambridge Ltd. Circle 508. Clamp Meters This range is designed for the measurement of a.c. current and voltage in conductors up to 30 mm diameter (54 mm for the PK210). All measure voltage up to 600V. The currents measured are PK110, 0-300A (5 ranges): PK111, 0-60A (5 ranges); PK210, 0-3000A (6 ranges); and PK300 (digital) 0-1000 A.Channel Electronics (Sussex) Ltd. Circle 509. Scanning Electron Microscope The Model JSM-35CF will resolve to 5nm. Image brightness is automatically corrected when the specimen is moved or parameters changed. An alignment wobbler is fitted for adjustment of the objective aperture. The specimen stage can be reset to position co- ordinates, rotate and tilt with high accuracy. JEOL (UK) Ltd. Circle 510. Pre-packed HPLC Columns Merck Hibar RT columns are 4 mm in diameter and are available in lengths of 250 and 125 mm. They are supplied with a zero dead volume reducer a t each end together with a test chromatogram and a computer printout giving the performance data of the column. Replace- ment columns (Hibar EC) are also supplied without reducers or data.BDH Chemicals Ltd. Circle 511. Gamma Counter The Berthold LB2100 contains 12 borehole scintillation counters into which 15 mm vials containing the RIA samples are loaded. All twelve channels can be counted simultaneously. Evaluation and printout of results is carried out by means of a microprocessor. Three ver- sions are available; the Ratio and RIA versions have single isotope windows for 1261, 67C0, 76Sc and 61Cr; the RIA PLUS also includes a window for 67C0/1251. The internal memories are pro- tected for up to 3 months in the event of a power failure. Laboratory Impex Ltd. Circle 512. Laboratory Blenders Waring revolving knife blenders are available with capacities from 12 to 4000m1, with a timer, variable speed and glass or stainless- steel containers.Astell Hearson. Circle 513. Ion Chromatograph Columns New plastic columns are available with an inert plastic support for the resin. These are more durable than glass, and the resins used enable up to seven ions to be separated and identified in 20 min. Dionex (UK) Ltd. Circle 514. PTFE-lined Stainless-steel Hose Cajon stainless-steel hose is rated to 3 000 lb in-2 and 450 O F , and reinforced by an overbraid of 304 SS. It is available in lengths of 12, 24 and 36in with either tube adaptors or O-ring coupling gland ends. Techmation Ltd. Circle 515.338 EQUIPMENT NEWS Anal. PYOC. Manual ELISA Reader This reader will read 96 well ELISA plates having either U -shaped or flat-bottomed wells. There is also a built-in cuvette reader which will accept all semimicro and standard 1 cm path length cells.A beam of light from a quartz - halogen lamp is projected through the plate and a 10nm band pass filter on to a silicon detector. The measured light intensity is displayed on a digital readout. The reader may also be used as a colorimeter, a range of filters being available. Artek Systems Corp. Circle 516. pH Electrodes In Orion electrodes the silver chloride or calomel reference is replaced by a new system. This is claimed to give stable readings to 0.01 pH in under 30 s, three to five times better accuracy than with conventional elec- trodes, and drift of less than 0.002 pH per day. MSE Scientific Instruments. Circle 517. Power Supply for Electrophoresis The ISCO 494 provides constant power down to zero level.It can be modified to incorporate an electrically floating remote sensing voltage control. It is designed to meet IEC high- voltage safety recommendations. MSE Scientific Instruments. Circle 518. Photon Detection System This system allows simultaneous measurement of anode current and anode pulse rate, giving a dynamic range of lo8. Computer programs are available for measurements in numerous modes. A range of photomultipliers is also available. EM1 Electron Tubes. Circle 519. Photomultipliers The 9903 Series typically have a quantum efficiency of 25-27% at 400 nm, an over-all sensitivity of 50Alm-1 at llOOV, a dark current of 0.5 nA at 50 A 1 m-1 and a pulse rise time of 2.5 ns. The 9903B is suitable for high-energy physics and the 9903L for spectro- metry.Fused silica versions are available. EM1 Electron Tubes. Circle 520. Mass Spectroscopy Microcomputer Pro- grams The MASSLAB is the first in a series of MICROLAB specialised software programs. Computer Science would be interested in hearing from analysts or others with pro- gramming experience to examine the possibility of co-operating with them. Computer Science. Circle 521. Surface Analysis Technique for Mass Spectrometry The Saddle Field FAB-GG gas gun provides a neutral beam of fast atoms. It does not need the addition of a charge exchange cell to produce atoms, and it can be mounted on to a customer-constructed mass spectrometer FAB source. Ion Tech Ltd. Circle 522. Monochromator/Spectrograph The Jarrell-Ash Monospec-18 is designed for OEMs.It can be used as a scanning or fixed- grating instrument. Measuring 6.5 x 5 x 6.5 in, it has a focal length of about & m with a throughput of f/3.1 and a resolution of 0.6 nm, with wavelength accuracy better than fl nm. Anaspec Ltd. Circle 523. Atomic-absorption Spectrophotometry System A new version of the SP9 system incorporates the PU 9095 Video Furnace Programmer and PU 9090 computer. The video information centre details every element in both its flame and furnace sections. The Data Graphics System allows a signal to be captured on video and expanded for detailed examination. The signal can be shown as corrected absorption or atomic absorption plus background. Display of calibration with up to five standards is available. There is a built-in printer.Pye Unicam Ltd. Circle 524. Spectrophotometer The Model Lambda 5 UV/VIS incorporates video display and “Soft Keys.” Absorbance, transmittance and first to fourth derivative spectra are displayed on a hard-copy printer/ plotter with full listing of operational para- meters. Perkin-Elmer Ltd. Circle 525.June, 1982 EQUIPMENT NEWS 339 Gas Chromatographs Six versions of the SIGMA 3B are available: single electron-capture detector, single nitro- gen - phosphorus detector, single channel split/ splitless capillary, dual flame-ionisation detec- tor, dual-channel hot-wire detector, and a gas analyser combining a gas sampling valve with a dual channel hot wire detector. Perkin-Elmer Ltd. Circle 526. Gas Chromatograph The PU 4500/14 thermal conductivity model produces a linear range of 104.Typical response is 10 000 DPSU, corresponding to a detectability of 6 x g ml-1 for toluene. The detector is interchangeable with other Pye Unicam ionisa- tion detectors. Pye Un.icam Ltd. Circle 527. Gas Chromatograph The HP 5790A features push-button control, digital display, RS-232C compatibility, built- in diagnostics and a direct approach to inter- facing for recorders, integrators and data systems. The oven, which is calibrated to &0.05 "C a t 130 OC, accommodates fused silica capillary columns allowing retention time reproducibility of f 0.005 min. Hewlett-Packard Ltd. Circle 528. Microprocessor-controlled Autosampler The Model AS- lOOB automates liquid sample injection into any Sigma series gas chromato- graph. Features include manual, automatic or remote control, variable analysis time from 1 to 999 min, up to three injections per vial, sample number identification, use of micro- vials and variable flush facility.Perkin-Elmer Ltd. Circle 529. Computing Integrator The Shimadzu C-R1B has a built-in printer/ plotter providing chromatogram, analysis para- meters and data on the same chart. Peak detection sensitivity is determined auto- matically and a number of quantitative calculations are provided. Dyson Instruments. Circle 530. Oxygen Trap Kit A regenerable coiled unit is available for removing oxygen from GC gas supplies. It has a visible indicating section. Alltech Associates UK Ltd. Circle 531. Silica Polyimide Tubing for GC Synthetic and natural fused silica tubing is available for use in gas chromatography up to 400 "C in lengths of 0-100 and 101-500 m in both 250 and 320 pm dimensions.Field Instruments Co. Ltd. Circle 532. Stainless-steel Unions Zero dead volume unions are available for connecting flexible vitreous silica columns and tubing. The bore incorporates glass-lined tubing to ensure an inert connection. The unions are available for both small- and wide- bore columns. Scientific Glass Engineering (U K) Ltd. Circle 533. Wavelength Detectors for HPLC The Model 788 dual variable-wavelength detec- tor simultaneously measures light absorbance a t two wavelengths. Information is displayed on a dual-pen recorder and the signals can be processed to give sum, quotient and difference of the two signals. The Model 791 fixed-wavelength detector detects UV-absorbing compounds a t selectable wavelengths.Both models are adaptable to existing LC systems. Micromeritics Instrument Corp. Circle 534. HPLC Columns Two columns are available for analysis of poly- nuclear aromatics. The 202TP5 will resolve dibenz (a,h) anthracene and benzo(ghi)perylene. The 201TP5 will resolve benzo(b)fluoranthene and perylene. Chromacol Ltd. Circle 535. Caps for GC/HPLC Autosamplers A range of aluminium crimp caps is available in two sizes, 11 and 8 mm. They are in red to allow colour coding of samples. Chromacol Ltd. Circle 536.340 ANALYTICAL PROCEEDINGS Anal. Pro The CILAS Granulometer is NOT a pure research tool. Just because ... the CllAS 71 5 Granulometer gives you a 1 6 point printed size analysis of particlesfrom 1 to 192 microns as well as displaying a curve of the particle size distribution which updates itself every second to show the effect of agglomeration or dissolving, you may be led to suspect that it might be a research tool.Just because ... it gives you a choice of weight percentage undersize, weight percentage oversize, surface area, sieve corrections, media particle size, a histogram print-out on demand and an indication of sample concentration, you may be forgiven for believing that it is a pure research tool, but to do so is to overlook its main feature which is that it does it all in less than 5 minutes with repeatability better than 2 percent without any need for calibration. So if you want to use the CllAS 71 5 Granulometer for quality control or formulation of powder products the Granulometer is for you.If you want to use it for pure research, we can't stop you - in fact why not ring us on Abingdon (0235) 331 33 for further information or a demonstration of its not pure research capabilities. Spectron Optical Holdings Ltd Ashville Trading Estate, Nuffield Way Abingdon. Oxon OX1 4 1 TD Telephone (0235) 331 33 Telex837261 SPECTO Circle A403 for further information. THE ROYAL SOCIETY OF CHEMISTRY Annual Reports on Analytical Atomic Spectroscopy Vol. 10 Edited by J. B. Dawson and B. L. Sharp This volume reports on current developments in all branches of analytical atomic emission, absorption and fluorescence spectroscopy with references to papers published and lectures presented during 1980. Much of the information is in tabular form for ease of reference. Hardcover 342pp 0 851 86 71 7 0 f 36.00 ( $80.00) Still available: Vol. 3 (1 973) 0 85990 253 6 f 10.50 ($22.00) Vol. 4 (1 974) 0 85990 254 4 f 15.00 ($32.00) Vol. 5 (1975) 0 85186 757 X f18.50 ($39.00) Vol. 6 (1 976) 0 851 86 747 2 f23.50 ($50.00) Vol. 7 (1 977) 0 85186 737 5 f22.75 ($48.00) Vol. 8 (1 978) 0 851 86 630 1 f 22.75 ($48.00) Vol. 9 (1 979) 0 851 86 727 8 f34.00 ($72.00) Orders t o The Royal Society of Chemistry, Distribution Centre, Blackhorse Road, Letchworth, Herts SG6 1 HN snnmarschod UNDERSTANDING SPECTROSCOPY: PRACTICAL APPUCATIOMS OF ABSORPTION AND FLUORESCENCE SPECTROSCOPY. Courw fw flbS, including malr, lccomodnkn md mum bmklot. Same bursaries to defray costs will k milrbk for Funkn details horn Prof. J.N. Miller, Dopt. of Chrnhy, mhbarouph vniiity. Englad. LEll3N.Td.0508 63171 Circle A404 for further information.

ISSN:0144-557X    

DOI:10.1039/AP9821900336

出版商:RSC    

年代:1982

数据来源: RSC

摘要:

Jzcne, 1982 OBITUARY 341 Obituary Robert Lyell Mitchell Dr. R. L. Mitchell died on February 7th, 1982, after a short illness following a slow decline in health over the previous year. He was Head of the Department of Spectrochemistry a t The Macaulay Institute for Soil Research, Aberdeen, from 1937 to 1968, Deputy Director of the Institute from 1955 to 1968, Director from 1968 to 1975, and a Fellow of the Institute from 1975 until his death. Dr. Mitchell was born in Edinburgh on June 3rd, 1910, and educated a t Bathgate Academy, where he gained a scholarship (The Newlands Bursary) tenable a t the University of Edinburgh. There he studied chemistry under Professor J. P. Kendall and graduated BSc with First Class Honours in 1931. Subsequently, as a Department of Agriculture for Scotland Research Scholar, he was awarded in 1934 the degree of PhD of the University of Aberdeen, most of the work having been carried out at the newly-established Macaulay Institute.The last year of his studies, however, was spent with Professor Wiegner in the Agricultural Chemistry Department of the Federal Technical High School in Zurich, where he saw Lundegiirdh- type spectrographic equipment operated by Hans Pallman. This, i t might be said, was the beginning of his career as a spectroscopist, as he foresaw the potentiality of the technique as a means of improving the determination of both major and trace elements in soils and plant materials, and thus help in the elucidation of problems associated with the deficiency or excess of elements in plant and animal nutrition.This was always his primary objective, spectro- scopy being a means of achieving it. Following his period a t Zurich Dr. Mitchell returned to the Macaulay Institute and, after a visit to Henry Lundeghdh’s laboratory in Stockholm, he persuaded his Director (the late Sir William Ogg) and the Department of Agri- culture for Scotland to provide flame spectro- graphic equipment, primarily for the determina- tion of the alkali and alkaline-earth metals. The development of the technique for soil analysis provided a description, probably the first in spectroscopy, of an inter-element effect, that of aluminium on the determination of calcium, and of a method for its suppression. A visit to Professor Mannkopff’s laboratory a t Gottingen, in 1937, showed Dr.Mitchell that the use of a high-temperature carbon arc as a source of excitation would enable not only more elements to be determined than could be achieved with a flame, but that powder samples, such as soils and plant ashes, could be analysed directly. By 1938-1939 he had installed Mannkopff’s arc system but, although i t was the best then available, it was soon found that the sensitivity was insufficient for the determination of some biologically-important elements. With the help of Dr. R. 0. Scott and others, the variable internal standard method and the preliminary concentration technique using mixed organic reagents (quinolin-8-01, tannic acid and thionalide) were developed, methods still employed, virtually unchanged, a t the Macaulay Institute and many other laboratories through- out the world.The levels involved are of the order of 0.01-10 mg kg-l for such elements as chromium, cobalt, nickel, molybdenum, lead, zinc, copper and manganese. In 1948 he pub- lished “The Spectrochemical Analysis of Soils, Plants and Related Materials” (Technical Com- munication No. 44 of the Commonwealth Bureau of Soils), which included detailed des- criptions of the methods in use at the Institute. The continuing demand for this book resulted in its re-publication, with an Appendix, in 1964. The requirement for the analysis of several hundred samples per day, especially for the major elements, soon encouraged Dr. Mitchell to adopt direct-reading techniques. With the assistance of Dr. A. M. Ure, who joined his department in 1948, a 3-channel flame photo- meter was built for the simultaneous determina- tion of sodium, potassium and calcium.This was followed by a laboratory-built porous-cup solution-spark instrument for the determination of magnesium, and later a 49-channel cathode layer arc emission spectrometer was purchased. Dr. Mitchell developed atomic-absorption methods and an instrument for the determina- tion of cobalt in soil extracts was designed and built in his department before suitable commer- cial instruments were available. In addition to the trace element facilities he formed a unit in his department, under Dr. V. C. Farmer, to study the inorganic and organic constituents of soils using infrared and ultraviolet absorption techniques. Because Dr. Mitchell’s interest in spectro- scopy had an essentially practical bias, most of his investigations concerned the distribution of trace elements in plants, soils and their parent rocks, particularly insofar as they concern342 PUBLICATIONS RECEIVED Anal.Proc. plant and animal nutrition and, of his approx- imately 90 publications, more than half are on this aspect of his work. For his part in the advancement of the knowledge of trace element problems Dr. Mitchell was awarded the Research Medal of the Royal Agricultural Society of England in 1963, and, for his services to trace element analysis, the Society for Analytical Chemistry’s Gold Medal in 1975. Besides giving lectures in the USA, Canada, Australia, New Zealand, the USSR and many European countries, Dr. Mitchell served on the committees of numerous organisations dealing with the determination and implications of trace elements in agriculture. From 1952 to 1978 he served on the Editorial Board of Spectrochimica Acta. He was a Fellow of the Royal Society of Chemistry and of the Royal Society of Edinburgh, and a member of other scientific organisations including the Geo- chemical Society and the British Society of Soil Science. Dr. Mitchell’s outside interests included photography and mountaineering and he was a member of the Alpine Club, the Swiss Alpine Club, the Scottish Mountaineering Club and the Cairngorm Club. After his retirement in 1975, Dr. Mitchell continued to publish fundamental papers on the distribution, mobility and importance of trace elements in soils. He was a world-wide auth- ority on this subject and for this and his valuable contributions to analytical spectroscopy he will be long-remembered and greatly missed. Dr. Mitchell remained a bachelor and is survived by his younger brother, David. R. 0. SCOTT

ISSN:0144-557X    

DOI:10.1039/AP9821900341

出版商:RSC    

年代:1982

数据来源: RSC