摘要:

Proceedings of the Society for Analytical Chemistry Analytical Division Chemical Society CONTENTS Message from The President I7 I Atomic Spectroscopy Group 172 Education and Training in Analytical Chemistry at Educational Establishments 173 “Research Topics in Analytical Summaries of Papers Chemistry” . . .. .. 182 Notice .. .. .. .. 212 The Chemical Society’s Library 212 Publications Received .. 213 Forthcoming Meetings Back Cover Proc. SOC. Anolyt. Chem. Vol. 9 No. 9 Pages 171-214 September 1972 PAYCAL Vol. 9 No. 9 September I972 PROCEEDINGS THE SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY OF Hon. Secretary W. H. C. Shaw Officers of The Society for Analytical Chemistry and the Analytical Division of The Chemical Society President C. Whalley Hon. Treasurer Hon.Assistant Secretaries G. W. C. Milner D. I. Coomber O.B.E.; D. W. Wilson Secretary Miss P. E. Hutchinson 9/10 SAVILE ROW LONDON WIX IAF Telephone 01-734 9864 Editor J. B. Attrill Assistant Editor P. C. Weston Proceedings is published by The Society for Analytical Chemistry and distributed t o all members of the Analytical Division and t o subscribers with The Analyst; subscriptions cannot be accepted for Proceedings alone. Single copies can be obtained direct from The Chemical Society Publications Sales Office Blackhorse Road Letchworth Herts. SG6 I HN (NOT through Trade Agents) price 25p. post free. Remittances MUST accompany orders. 0 The Society for Analytical Chemistry Now published PARTICLE SIZE ANALYSIS I970 THE Society for Analytical Chemistry has published in this book all papers presented at the Second Particle Size Analysis Conference held in Bradford in September 1970 and the full discussions on them. The 35 papers cover all aspects of research into the subject basically covering the 4-year period since the f i r s t conference was held in Loughborough in 1966 and include plenary lectures by the late Professor H. Heywood and by Professor K. Leschonski. The volume is a companion to “Particle Size Analysis” - the report of the First Con- ference also published by the Society. Pp. x + 430 Price f7.75 Obtainable from- THE SOCIETY FOR ANALYTICAL CHEMISTRY (Book Department) 9/10 Savile Row London WIX IAF Members of The Chemical Society may buy personal copies at the special price of f6.25

ISSN:0037-9697    

DOI:10.1039/SA97209FX031

出版商:RSC    

年代:1972

数据来源: RSC

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SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY Forthcoming Meetings-continued from buck cover October Friday Gth BRISTOL Tuesday 10th RICHMOND Wednesday 1 1 th CAMBRIDGE Thursday 12th LONDON IVednesday 18th LIVERPOOL Thursday 19th LONDOX Thursday 19th BURTON-ON- TRENT Friday 20th GLASGOW WESTERN REGION. “Selectrode-The Universal Ion-selective Electrode ’’ by Professor J . Ruzicka. Chemistry Department The University Bristol ; 7 p.m. NORTH EAST REGION Social Meeting and Dinncr. “Consumer Protection,” by M. Kellner. Scotch Corner Hotel Richmond ; 6.30 p.m. ATOMIC SPECTROSCOPY GROUP on “Atom Reservoirs.” “Flames and Alternatives to Flames,” by L. de Galan. “Chemistry of Metals and Free Radicals in Flames,” by P. J . Padley. “Determination of Non-metal Atoms in the Vacuum UV,” by D.Husain. Lecture Room 3 Chemical Laboratory The University Lensfield Road JOINT PHARMACEUTICAL ANALYSIS GROUP. A discussion on “High Pressure Chromatography,” will be introduced by Nl. Pinnegar F. Bailey and K. Wilkins. Pharmaceutical Society of Great Britain 17 Bloomsbury Square London W.C. 1 ; 2.30 p.m. NORTH WEST REGION. “Tablet Manufacture,” by A. W. n’ewberry. Evans Medical Ltd. Speke Liverpool; 6 p.m. BIOLOGICAL METHODS GROUP on ‘Won-prescription ,Intibiotics in ,Animal Food “Flavomycin,” by G. Nesemann. “Virginiamycin,” by B. Boon. “Zinc Bacitracin,” by Mrs. B. Grynne. Pharmaceutical Society of Great Britain 17 Bloomsbury Square London MIDLANDS REGION Scientific Visit. “Analytical Problems in the Brewing Industry,” by G. A. Howard. Allied Breweries (U.K.) Ltd.The Brewery Burton-on-Trent ; 4 p.m. (Number attending restricted to 40). SCOTTISH REGION and EDUCATION AND TRAINIXGROUP on “Training of Food Speakers to include R. M. Johnson. University of Strathclyde Cathedral Street Glasgow G1 1XL; 2 p.m. Cambridge ; 2 p.m. Stuffs Their Nature and Analysis.” W.C.l; 2.30 p.m. Analysts. ” SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY September IVednesday 20th HEREFORD Monday 25th CARD IFF Thursday 28th SALFORD October Monday 2nd LONDON Tuesday 3rd GLASGOW IVeclnesday 4th LONDON Thursday 5th CAMBRIDGE Thursday 5th PRESTON Thursday 5th LONDON Forthcoming Meetings VESTE ERN and MIIILAKDS REGIONS. “Recent Developments in X-ray Fluorescence A4nalysis,” by P. W. Hurley. Henry Wiggin & Co. Hereford; 6 p.m. WESTERN REGION.“Enzymes in Analysis,” by Professor G. G. Guilbault. Chemistry Department University of Wales Institute of Science and Tech- NORTH WEST REGION and THERMAL METHODS GROUP on “Organic _Appli- “The Thermal Degradation of Cellulose in Nitrogen,” by D. Dollimore and “Thermometric Titrimetry,” by L. S. Bark. “Thermal Analysis of Fats and Oils,” by 11. Tresscr. The University Salford ; 2 p.m. nology Cathays Park Cardiff; 3.30 p.m. cations of Thermal Analysis.” B. Holt. ELECTROAKALYTICAL GROUP. “Polymer Membrane Ion-selective Electrodes,” by G. Baum. Theatre D Chemistry Department (Old Building) Imperial College London SCOTTISH REGION joiiztly zoith the Glasgow and West of Scotland Section of the cs. “Selectrode-The Universal Ion-selective Electrode,” by Professor J . IibziEka. Room C129 Chemistry Department University of Strathclyde Cathedral Street Glasgow G1 1XL; 4 p.m.SAC/AD on “Ion-selective Electrodes. ” “Selectrode-The Universal Ion-selective Electrode,” by Professor J . Huziclia. “Selectivity and Sensitivity of Ion-selective Electrodes,” by J. D. K. Thomas. “Measurement Techniques for Ion-selective Electrodes,” by M. J. D. Brand. Scientific Societies Lecture Theatre 23 Savile Row London \V. 1 ; 2.30 p.m. EAST ANGLIA REGION Annual General Meeting followed by an Ordinary Meeting. “Forensic Analysis in the Equine Field,” by RI. S. Moss. Spillers T,td. Research and Technology Centre Station Road Cambridge ; 3 p.m. SORTH WEST REGION. “Environmental Conservation An Analyst’s View,” by G. B. Crump Harris College Preston ; 7.30 p.m. ELECTROANALYTICAL GROUP on “Current Research Topics in Electroanalytical “Some Studies Using Sulphide Ton-selective Electrodes,’’ A. Pathan. “Application of Cathode Ray Polarography to Analysis of Body Fluids ” by “Electrochemical Detectors for High Pressure Liquicl Chromatography,” Additionally two other speakers from the Univcrsity of Southampton and Theatre D Chemistry Department (Old Building) Imperial College T,onclon S.W.7; 6.30 p.m. Chemistry. ” E. d’Essien. b y C. J. Little. Newcastle University. S.W.7. ; 2.30 p.m. [roiztirzzird inside back cover Printed by W Heffer L Sons Ltd Cambridge England

ISSN:0037-9697    

DOI:10.1039/SA97209BX033

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

September I972 Vol. 9 No. 9 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY A Message to All Members from The President I HAVE pleasure in welcoming you to membership of the Analytical Division of the amal- gamated Chemical Society. The Analytical Division during the trial period until 1975 is being run by the Society for Analytical Chemistry and is maintaining the full range of activities previously carried out by that Society (SAC). These include the organisation and financing of the activities of 12 Subject Groups and 6 Regions the running of Divisional meetings and of Symposia and International Conferences. Full details of all these activities may be found in our monthly journal Proceedings of the Society for Analytical Chemistry/ Analytical Division.The Society for Analytical Chemistry will also continue to publish The Analyst Analytical Abstracts Selected Annual Reviews of the Analytical Sciences and its latest publication Annual Reports o n Analytical Atomic Spectroscopy. Three major ventures since amalgamation have been the organisation of a special 2-day meeting in Glasgow to celebrate the 60th Birthday of Professor C. L. Wilson a 2-day sym- posium at the CS Annual Meeting in Manchester and participation in the Euroanalysis I meeting at Heidelberg in August. The meetings in Scotland and in England were very successful and we were extremely pleased to see so many new faces at Manchester. The meeting at Heidelberg was the first combined meeting of the Analytical Societies of the United Kingdom Germany and Holland and it is hoped that this will be the first of a series of European analytical meetings.It is hoped that both old and new members will continue to support the Division’s meetings and will participate in Regional activities. Membership of the Groups has increased considerably and this as will be shown later has caused some difficulties. The Society for Analytical Chemistry will celebrate its Centenary in 1974 with a full- scale International meeting from July 16th to 19th. The Opening Session will be held at the Royal Institution and the rest of the meeting will be based on Imperial College. A cordial invitation is extended to all members of the Analytical Division to participate in this meeting. For the time being the Society and Divisional Councils will both function until a decision is taken by members of the Society on full amalgamation and we are fortunate in being able to communicate regularly with our members through the medium of Proceedings.During 1972 the Society has supplied this journal free to all members of the Division but it is very much regretted that for economic reasons this will not be possible in the future. (Membership has increased from 2300 in the Society to a predicted 6000 in the Division and under the terms of the amalgamation all expenses of the Division until 1975 are to be met by the Society for Analytical Chemistry.) During the year it has also become apparent that because of free membership of the Groups throughout the CS some of the Groups of the Analytical Division are now both numerically and economically unmanageable. Other Divisions have made different arrangements but for members of the Analytical Division the following will apply for 1973- Proceedings will cost L1 per annum.If you purchase it you will receive in addition notices etc. and information on all Division Region and Group activities.* Purchase of Proceedings will also entitle you to free membership of such Groups of the Analytical Division as you wish to join. If you do not wish to purchase Proceedings you may become a member of any of the Division’s Groups on payment of 50p per annum for each Group. (Membership of the Joint Pharmaceutical Analysis Group is free but must be applied for separately). * In order that SAC members should not suffer financially as a result of amalgamation this L1 may be reclaimed through the SAC Office but the initial payment must be made to the CS.I would however appeal to SAC members to forgo this concession if possible to help our finances during the present difficulty. 171 172 A MESSAGE FROM THE PRESIDENT [Proc. SOC. Analyt. Chem. From the start of the 1972-73 Session information about all Group activities will appear in a composite Bulletin and individual notices of meetings will be prepared only in special cases. The Bulletin will appear on a monthly basis but not necessarily every month and will be circulated to Analytical Division members with Proceedings and separately to other CS members who subscribe to the Analytical Division Groups. The Society for Analytical Chemistry has had a long and distinguished history and my Officers and Council are very pleased to join me in welcoming so many new members who have a close interest in analytical chemistry. We believe that this influx of new members will help to enhance the image of analytical chemistry throughout the world. Yours sincerely CLIFFORD WHALLEY President SACIAD.

ISSN:0037-9697    

DOI:10.1039/SA9720900171

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

172 A MESSAGE FROM THE PRESIDENT [Proc. SOC. Analyt. Chem. The Atomic Spectroscopy Group THE history of the Group falls into three distinct periods and during each period there has been a change in the title and to some extent the scope of the Group. Atomic absorption spectroscopy was inaugurated as an analytical technique by Dr. A. Walsh in 1955 and represented an important milestone in the history of analytical chemistry at least as significant as many of the previous discoveries such as polarography or chromato- graphy. In the field of metals analysis this essentially simple and elegant concept was to have a revolutionary effect and its applications have grown steadily since the introduction of commercial instruments in 1960. At its inception an Atomic Absorption Spectroscopy Discussion Panel was formed in 1962 under the auspices of the Physical Methods Group.Dr. (then Mr.) W. T. Elwell was Chairman and Mr. D. Moore Honorary Secretary. An early suggestion that emission flame photometry be included in the scope of the AASDP was rejected except. . . “where its performance would naturally be compared with that of atomic absorption spectroscopy in some specific subjects.” In 1964 the Discussion Panel was reconstituted with full Group status under the title “Atomic Absorption Spectroscopy Group,” a change which marked the growing recognition of the technique as of fundamental importance to the science of analytical chemistry. This decision was to be reversed some years later. LEFT-MY. W. R. Null (Chaivwan) RIGHT-DY. G. F . Kivkbvight ( Vice-Chaivvnan) In 1969 the Group Committee reviewed developments in the field of atomic spectroscopy and felt that it should make itself responsible for covering all aspects of the interaction of light and free atoms involving the three processes of atomic emission absorption and fluores- cence.The third and final change in the Group title to Atomic Spectroscopy Group acknow- ledged this decision and consequently we now are concerned with emission flame photometry (thus reversing the decision of l964) atomic absorption and atomic fluorescence. Spectro- graphers should note that atomic emission obtained by electrical arc and spark excitation falls within the scope of the Group although it must be admitted that the new and attractive methods of atomic absorption and fluorescence tend to have fully occupied members minds to the almost complete exclusion of emission.The Committee has this aspect under review. September 19721 ATOMIC SPECTROSCOPY GROUP 173 In 1969 the 2nd International Conference on Atomic Absorption Spectroscopy was organised by the group under the Chairmanship of Dr. J. B. Dawson and held in the University of Sheffield. Over 400 delegates from twenty countries took part and the first plenary lecture was given by Dr. A. Walsh from Australia. LEFT--MY. C . P. Cole (Hovzovavy Secvefavy and Tveasuver) RIGHT-MY. W . J . Pvice (Hogzovai/y A ssisfavzt Secvefavy) The Committee noted in 1970 the rapidly increasing number of original papers on analyt- ical atomic spectroscopy and decided to form a separate committee to consider the best way of keeping members informed of all these advances.The committee recommended that this could best be done by an annual report which would be a critical appraisal of published work over the past year. Correspondents in twenty countries agreed to co-operate in this venture and report on developments within their spheres of interest. The first volume appeared in June 1972 and reviewed over 1000 references on the subject published during 1971. The number of references received so far this year indicates that this total will be exceeded in 1972. As the range of application of atomic spectroscopy continues to expand and the sophisti- cation and accuracy of instruments increases the Committee has to provide for a steadily growing number of analysts who are interested in the techniques. Meetings have been held in every geographical region and joint meetings with particular research interests and organis- ations are an important aspect of the Group’s activities. The Committee has contributed to the international standardisation of terms used in the technique and has been responsible for the introduction of high purity reagents and standardised solutions through the supply organisations.

ISSN:0037-9697    

DOI:10.1039/SA9720900172

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

September 19721 ATOMIC SPECTROSCOPY GROUP 173 Education and Training in Analytical Chemistry at Educational Establishments A REPORT BY THE EDUCATION AND TRAINING COMMITTEE OF THE SOCIETY FOR ANALYTICAL CHEMISTRY THE constitution of the Education and Training Committee was Dr. W. J. Williams (Chair- man) Mr. J. Bassett Dr. D. Thorburn Burns Mr. J. K. Foreman Dr. J. B. Headridge Dr. G. F. Kirkbright Mr. W. M. Lewis Mr. J. I. Phillips Dr. J. M. Skinner and Mr. C. Whalley (President). Former members were Dr. A. C. Docherty and Mr. L. J. Hamilton. Up to the early post-war years the analytical chemistry content of chemistry courses at Universities and Technical Colleges was relatively well known. It consisted largely of titrimetric gravimetric and qualitative analysis. At Technical Colleges providing courses for A.R.I.C.(usually part-time) inspection of the relatively small number of papers set each year by the Royal Institute of Chemistry would indicate the knowledge of analysis a student was expected to possess and the courses could be assumed to cover this. The past 15 years have seen many changes. Analytical chemistry has and still is undergoing a transformation and its nature is now far more complex. It is doubtful whether any group of present-day analysts would agree either on the definitions of modern analytical chemistry or where its boundaries lie. INTRODUCTION 174 EDUCATION AND TRAINING IN ANALYTICAL CHEMISTRY [Proc. SOC. AnaZyt. Chem. Higher education is also the subject of far-reaching changes that began at about the same time. Several former Technical Colleges have developed into Universities with power to formulate their own courses while several entirely new Universities have been created.New courses and qualifications have been created and others are taking on new forms. The “sandwich” principle by which a student spends a part of his training in industry has become firmly established. Recent changes in the structure of the O.N.C. will produce repercussions at both H.N.C. and Grad.R.1.C. level. Recent government reports on higher education e.g. the Swann Report have made important recommendations that will no doubt produce further changes as will the development of the new Polytechnics. Evening study for O.N.C. and H.N.C. has been largely replaced by day-release while the Grad.R.1.C. is being increasingly pursued by full-time or sandwich courses.In view of these changes the picture regarding the teaching of analytical chemistry is now less clear. It is pertinent and opportune to ask several questions on the current position of analytical chemistry in educational establishments. We may ask- (;) Where is analytical chemistry being taught and how much is being taught? (ii) In how many ways is it possible to obtain a training in analytical chemistry and what is the analytical chemistry content of the various chemistry courses now available ? (iii) How relevant are these courses to present-day needs and to what extent do they reflect modern analytical chemistry ? (iv) Where is analytical research being carried out and how much is being done? Apart from developments at the relatively few centres of excellence where analytical chemistry enjoys a national and sometimes international reputation information is lacking and often out of date.The Education and Training Committee of the Society for Analytical Chemistry was formed in 1968. At one of its earliest meetings it decided that in order to answer some of the above questions a survey of educational establishments was necessary. SURVEY-SCOPE AND RESPONSE Two types of questionnaire were used one for Universities and another for Polytechnics,* Colleges of Technology and other educational establishments. Whenever possible they were addressed to SAC Liaison Officers at establishments. Coverage was restricted to Departments of Chemistry or Science and in consequence such analytical chemistry as is taught in Departments of Metallurgy Pharmacy Biochemistry and Biology is excluded.The general response to the survey is shown in Table I. TABLE I Institution Questionnaires Questionnaires Return sent out returned per cent. Universities . . .. .. 59 Polytechnics . . . . . . 30 Colleges of Further Education. . 27 Medical Schools . . .. 19 Miscellaneous . . . . . . 13 Totals . . .. .. 268 Colleges of Technology . . 120 54 92 24 80 97 81 18 67 13 0s 9 69 215 80.2 (Over-all average) It should be noted that the return of a questionnaire does not imply that analytical activities are involved ; negative information is useful in formulating an accurate over-all picture. “Nil” returns were requested. A more detailed breakdown of replies from Colleges of Technology and Colleges of Further Education is shown in Table 11. * The term Polytechnic will be used for proposed Polytechnics that are still awaiting official approval and for those for which approval has been given.Indeed several such Polytechnics have come into being during the preparation of this Report. September 19721 AT EDUCATIONAL ESTABLISHMENTS TABLE I1 175 Questionnaires Questionnaires Institution sent out returned Colleges of Technology- Area . . .. Local . . .. .. .. 64 Colleges of Further Education .. 27 18 Totals . . . . . . . . 147 115 * * -} 120 33 Some analytical chemistry carried out 39 4 1 44 No* analytical chemistry carried out 25 20 17 71 * Refers to normal lecture courses e.g. H.N.C. L.R.I.C. Some Colleges not involved with such courses however put on short courses involving analytical chemistry or set projects in analytical chemistry.An important aspect of education and training in analytical chemistry is whether the product is satisfactory in employment and if not for what reasons. An accurate assessment of this aspect would entail a comprehensive survey. Nevertheless it was felt that even a limited survey covering a representative cross-section of industry and government estab- lishments would provide useful information on this aspect. This is dealt with later. SURVEY-ANALYSIS OF RETURNS UNDERGRADUATE COURSES AT UNIVERSITIES- Meaningful replies to the questionnaire were received from 54 out of 59 chemistry departments a return of 92 per cent. Furthermore it is known that there are no academic staff members who would describe themselves as analytical chemists in departments from which replies were not received.From the questionnaire it was obvious that the staff in most chemistry departments are trying to educate and train undergraduates to be well rounded pure chemists. However applied chemisty is taught in some of the technological universities which make up about 20 per cent. of the total number of departments. These departments usually have chairs in organic inorganic and physical chemistry and sometimes in theoretical chemistry although frequently theoretical chemistry comes under the wing of physical chemistry. Inorganic and organic chemists constantly use techniques for molecular characterisation and organic chemists in particular also separation techniques. Therefore the undergraduate in our universities usually gets an adequate training in ultraviolet infrared nuclear magnetic resonance electron spin resonance and mass spectrometry and various forms of chromato- graphy.Much of the basic research work into the development of these structural techniques has been and is being done by physical chemists and in our universities the ways in which these techniques are used are usually taught to the undergraduate by inorganic organic and physical chemists. The inorganic and organic research chemist also requires on occasions information involving the techniques of quantitative elemental and compound determinations and qualitative elemental analysis but not to the same extent as the techniques of molecular characterisation and separation. In British universities the development of new methods of quantitative elemental and compound determinations and of qualitative elemental analysis usually falls to the analytical chemist.These latter techniques are taught by analytical chemists or in their absence by other chemists usually to a more limited extent. Because inorganic and organic chemists do not themselves use these techniques to the same extent as structural techniques the teaching of these techniques which include almost all classical analysis and also emission spectroscopy atomic-absorption spectroscopy X-ray fluorescence spectroscopy and electrochemical and radiochemical methods does not receive much em- phasis in many university chemistry departments. However these aspects of analytical chemistry do receive detailed attention in a few universities. It is well known that industrial chemists metallurgists geologists clinical chemists etc.require much more data on quantitative elemental and compound determinations and qualitative elemental analysis than do pure chemists. Therefore it is important that quantitative analytical chemistry should not be eliminated from chemistry courses in British universities since almost all graduate chemists employed in industry and elsewhere rely on quantitative analytical data at some stage of their work. The contents of undergraduate 176 EDUCATION AND TRAINING IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chewz. courses on quantitative analysis should reflect the techniques that are actually being used in modern industry. Of the 54 universities who replied 14 stated that analytical chemistry was completely integrated with other branches of chemistry. In the other departments some attempt was made to quantify the time spent on analytical chemistry.The results are presented in Table 111. TAELE I11 Time spent on analytical Chemistry (theory and practical) in honours courses in three or four yearslhours. . . . . . . . . . . . (25 25-49 50-99 100-200 >zoo In many questionnaires it would appear that analytical chemistry has been dcfined as quantitative elemental and compound determinations and qualitative elemental analysis but in others a wider definition involving at least part of molecular characterisation and methods of separation has been used. This makes a detailed interpretation of the data impossible but when it is considered that the total ntlmber of teaching hours for a student in chemistry in an honours degree course is approximately 1400 it can be seen that quantitative elemental and compound determinations and qualitative elemental analysis receive little attention in some departments.,4 breakdown of teaching time is given in Table IV for a typical department in the largest category shown in Table I11 (100-200 hours). Number of universities in each category . . . . 5 7 7 13 S TAULE IV BREAKDOWN OF THE TIME SPENT ON ANALYTICAL CHEMISTRY IN A TYPICAL Total time spent on lectures tutorials demonstrations and practical work DEPART MEN T Type of analysis S u Is-d i vis ions Ti me spent hours Quantitative elemental and compound Titrimetry and statistics . . .. . . s Electrochemistry . . . . . . .. 7 * . 1 3.5 determinations Gravimctry . . . . . . Analytical spectroscopy . . . . . . 16 j Qualitative elemental analysis Molecular characterisation including Emission spectrography and X-ray U.V.I.R. N.M.R. and mass X-ray diffraction . . . . . . . . 10 J fluorescence spectroscopy . . . . 3 structure determination spectrometry . . .. . . . . 100 1 110 Methods of separation Chromatography and solvent extraction 12 Total . . 1 GO In addition these techniques are used in tliird-year research projects. Three optional courses (6 hours each) on molecular characterisation are also presented to third-year students. In chemistry departments with Professors of Analytical Chemistry special emphasis is given to analytical chemistry. Optional final-year courses in analytical chemistry in addition to the basic courses in this subject are offered at seven Universities. Stajgng-In 21 Departments there are 43 academic staff members with keen interests in analytical chemistry other than molecular characterisation only.The total number of academic staff in University Departments is estimated at about 1500. Therefore about 3 per cent. of the staff specialise in analytical chemistry. The number of staff specialising in analytical chemistry at the 21 Departments varies from one to five. UNDERGRADUATE DEGREE COURSES IN POLYTECHNICS- The teaching of analytical chemistry in undergraduate degree courses a t Polytechnics is considered separately from Universities since the types of course offered are in general different .l An important development in Polytechnics has been the recent introduction of sandwich-type courses leading to degrees of the Council for National Academic Awards. The number of such courses in chemistry or applied chemistry with analytical chemistry as a special option is 13 (in 1971).September 19721 AT EDUCATIONAL ESTABLISHMENTS 177 The more applied nature of these courses and the inclusion of an integrated period of industrial training for the student undoubtedly influences the teaching of chemistry and analytical chemistry in particular in Polytechnics. Projects in analytical chemistry are often an integrated part of such courses. These may arise from work carried out during the industrial training period so that there is emphasis on training the student to deal with analytical problems of industrial importance by using appropriate techniques. Stafing-Replies to the questionnaire were received from 24 Polytechnics a return of 80 per cent. As indicated in the section on L.R.I.C.and H.N.C. endorsement courses several members of staff are usually involved to varying extents in the teaching of analytical chemistry at Polytechnics. Staff who teach analytical chemistry in C.N.A.A. degree courses often act as tutors to students during their industrial training periods and in addition supervise student pro j ec t s. C.N.N.A . degree-Fourteen Colleges gave details of their C.N.A.A. degree courses. Table V shows the number of hours per year allocated to the teaching of analytical chemistry in these courses. An indication is given as to whether the courses are of the thick or thin sandwich type and whether college (C) or industry (I) based. Colleges la 11 and 24 stated specifically that analytical chemistry is offered as a special option in their C.N.A.A.degree course. TABLE V TIME ALLOCATED TO ANALYTICAL CHEMISTRY IN C.N.A.A. DEGREE COURSES Polytechnic per year per year r--h-- 7 Theory/hours Practical/hours Type of sandwich course l a 50 100 Thin C l b Not given 24 Thin c 1 2 64 200 Thin c 1 6 105 320 Thick C 8 100 325 Thin I 9 102 200 Thin c 1 10 3G 70 Thick C 11 20 90 Thin c 12 24 150 Thin c 1 16 80 120 Thin C 17 44 44 Thin C 18 72 72 Thin C 19 94 36 Special scheme C I 21 25 60 Not stated 24 105 145 Thick C It is clear that there is a substantial allocation of time to the teaching of analytical chemistry in most of these courses; an analysis of the time allocated for theory and practical work is given in Table VI. 100 130 Thick TABLE VI DISTRIBUTION OF TIME AMONG C.N.A.A. COURSES Theory/hours per year No. of courses Practical/hours per year No.of courses < 30 4 < 60 2 30-60 3 60-120 6 61-90 3 121-180 3 > 90 6 > 180 5 University degree-Replies to the questionnaire indicated that courses leading to an internal university degree are offered at colleges 12 20 22 and 24 these establishments having recognised teachers of the University of London. External degrees are offered a t colleges 7 10 15 17 and 23. Only three colleges make a formal allocation of lecture time (10 to 15 hours per year) to the teaching of analytical chemistry in this type of course but a significant amount of analytical chemistry is integrated and taught within the traditional subject divisions of inorganic organic and physical chemistry. The time allocated to practical analytical chemistry tends to be in the region of 150 hours per year.178 EDUCATION AND TRAINING IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. NOTES- 1. C.N.A.A. degree courses in chemistry and applied chemistry are not entirely restricted to Polytechnics. One College of Technology has a full time C.N.A.A. degree course in chemistry (10 hours of theory 40 hours of practical work in analytical chemistry) and another offers a C.N.A.A. degree of which the analytical chemistry content is not known. 2. External degrees in chemistry are offered at two non-Polytechnics. At one analytical chemis- try is integrated with other branches of chemistry and a t the other 18 hours (average) of theory and 38 hours (average) of practical work are devoted to analytical chemistry. H.N.C. H.N.D. AND L.R.1.C. COURSES AT POLYTECHNICS COLLEGES OF TECHNOLOGY AND COLLEGES OF FURTHER EDUCATION- Table I1 indicates that from 18 replies analytical chemistry is taught at only one College of Further Education.This type of establishmznt will be excluded therefore from the present discussion. In this section Polytechnics Area Colleges and Local Colleges will be treated together. A total of 122 replies were received. L.R.I.C. or H.N.C. endorsement courses in which analytical chemistry is included are offered at 58 institutions. The distribution is shown in Table VII. TABLE VII L.R.I.C./H.N.C. Offeied including Institution analytical chemistry Not offered Total* Polytechnics . . .. .. 16 10 25 Area Colleges . . .. .. 30 22 64 Local Coleges . . .. .. 4 25 33 Total . . .. .. 58 57 122 * In some establishments analytical activities other than L.R.I.C./H.N.C.are involved. Staflng-In most of the Polytechnics several members of staff (from 3 to 13) are involved with the teaching of analytical chemistry and this clearly represents an important part of the courses. In the other colleges from 1 to 13 members of staff are involved with an average of 3-8. There is wide variation within the group. One institution (No. 24) giving a total of 10 hours of analytical chemistry (theory plus practical work) has 6 staff members; another (No. 35) has only 1 member of staff involved for 100 hours of theory and 250 hours of practical work. Time allocated to analytical chemistry-Table VIII gives the time allocated to analytical chemistry. The 108 hours of theory/216 hours of practical work quoted in several instances is probably based on 3 hours of lectures and 6 hours of practical work per week for three 12-week terms.An analysis of the lecture-time distribution is given in Table IX. MISCELLANEOUS INSTITUTIONS- Medical Schools-Questionnaires were sent out to 19 Medical Schools 13 of whom replied. Two of the schools specifically run limited courses in analytical chemistry as part of the 1st and 2nd M.B. courses and one for M.Clin.Path. and 34.Clin.Biochem. courses. One school provides some teaching in analytical biochemistry about 10 hours per course to B.Sc. Biochemistry students. In addition one Medical School offers a l-week course in separation techniques specifically for medical students. In no instance did the colleges offer specific training in analytical chemistry. SYMPOSIA AND SHORT COURSES- Data concerning the provision of short courses and the organisation of symposia within the broad field of analytical chemistry have been extracted from replies to the questionnaire.The information is listed under the principal establishment headings used above. Universities-No symposia on analytical chemistry were sponsored by universities. Six universities provide short internal lecture courses for interested staff and postgraduate students on analytical topics. Universities often provide facilities for holding SAC Conferences. There were seven nil returns. National Colleges-Of 13 questionnaires sent 9 replies were received. 179 September 19721 AT EDUCATIONAL ESTABLISHMENTS TABLE VIII TIME ALLOCATED TO ANALYTICAL CHEMISTRY IN L.R.I.C./H.N.C. ENDORSEMENTS Theorylhours Practical/hours Theory/hours Practical/hours Institution per year per year Institution per year per year la 27 60 40 (Thin) 86 144 l b 6 12 40 (Thick) 36 108 2 5 24 41 144 180 3 180 216 42 96 192 5 83 116 43 108 216 6 105 245 44 96 208 7 132 264 45 100 250 8 90 180 46 4 6 9 100 198 47 > 60 300 13 120 360 48 102 204 14 100 250 49 110 220 15 60 140 50 108 234 19 92 205 51 324 23 146 219 52 102 187 24 108 270 53 72 72 25 80 210 54 90 210 26 110 150 55 120 180 27 105 210 56 4 5 28 90 180 57 96 168 29 30 70 58 50 99 30 108 216 59 15 80-90 31 3 5 60 36 150 32 108 216 61 120 240 33 108 216 62 120 220 34 4 6 63 108 168 35 Some Some 132" 132* 36 90 180 64 90 170 37 120 140 65 72 234 38 150 150 66 70 105 39* 30 22 67 75 195 68 100 180 * H.N.D.TABLE IX Lecture hours per year No. of institutions Below 10 6 10-25 1 26-50 6 5 1-80 7 Over 80 37 & T ~ ~ ~ ~ - No.47 has been assumed to involve over 80 hours of lectures. The figures clearly indicate that a considerable amount of time is allocated to analytical chemistry in L.R.I.C./H.N.C. endorsement courses with less than 51 hours of lecture time per year given by only 25 per cent. of the institutions. Institution No. 35 is excluded in this analysis. Xo. 40 has been averaged out. Polytechnics-The following is a breakdown of numbers of symposia courses etc. provided by these establishments in 1967-68 and 1968-69; 9 of the 25 establishments who replied did not offer symposia or short courses. Type of course Number of courses l-2-day symposia . . I . 26 l-2-week short courses . . 8 Part-time courses . . .. 31 The subject matter covered in these meetings reflects the current interest in instrumental techniques of analysis including automation.In addition there are a small number repre- senting particular interests of certain Polytechnics e.g analysis of polymers foods and vitamins. A few courses were stated to be of specific applicability such as to teachers sixth-form students and industrial chemists. With very few exceptions the symposia and courses were listed as open. Former Colleges of Advanced Technology-One establishment sponsored two symposia and two others one symposium each. All were concerned with specific aspects of either separation or measurement techniques. 180 EDUCATION AND TRAINING IN ANALYTICAL CHEMISTRY [Proc. Soc. Analyt. Chem. Four establishments offered a total of eight short courses mostly full-time during 1967-68.Of these three were concerned with gas chromatography the remainder com- prising flame photometry ultraviolet spectrometry thin-layer chromatography radio- chemistry and miscellaneous techniques. Colleges of Technology-Of the 47 replies to the questionnaire 25 colleges offer short courses in analytical chemistry. In 11 instances more than one per year were sponsored. The most common subjects were- Chromatography (general) . . .. . . 5 Gas - liquid chromatography . . .. 4 Instrumental/physical methods . . .. 4 Radiochemistry . . .. .. . . 4 As to the nature of the courses (full or part-time open or closed) the data are incomplete but it is evident that over half of the courses are part-time and open. POSTGRADUATE RESEARCH AND POSTGRADUATE COURSES I N ANALYTICAL CHEMISTRY AT UNIVERSITIES POLYTECHNICS AND COLLEGES OF TECHNOLOGY- Universities-In 1968-69 postgraduate research in analytical chemistry was being carried out at 17 universities.All had Ph.D. students the numbers ranging from 2 to 26 and the total numbers were 87 full-time and 5 part-time. Seven universities had M.Sc. students the over-all totals being 14 full-time and 10 part-time. In addition S.R.C.- supported l!l.Sc. courses were running at four universities; a total of 25 full-time and 14 part- time students were involved. Polytechnics-A majority of the colleges do not appear to have offered full-time or part-time postgraduate courses in analytical chemistry during 1967-68 and 1968-69. Two colleges at present offer M.Sc. courses in analytical chemistry one of these courses leading to the M.Sc.(C.N.A.A.) qualification. An increase in the number of such postgraduate C.N.A.A. courses seems probable in the near future. Full-time and part-time research in analytical chemistry leading to the M.Phi1. and Ph.D. degrees can be undertaken at a few colleges. Colleges of Technology-The replies show very little evidence of either postgraduate research or postgraduate courses (not to be confused with short courses). Two persons in all were involved with postgraduate research one part-time for Ph.D. and the other part- time for M.Sc. EMPLOYERS’ VIEWPOINTS Letters were sent to Chief Analysts or others directly concerned with the employment of analytical chemists. Clearly it is important to obtain a personal rather than an official viewpoint and for this reason it was made clear that neither the names of the people nor the organisation would be quoted in the Report but only the viewpoint expressed.Twenty-one replies were received mainly from industry but also including government establishments. The industries are concerned with heavy organic chemicals paints agri- culture dyestuffs fibres plastics pharmaceuticals metals high purity chemicals etc. In order to give some guidance on the type of information of interest recipients were asked- (1) whether they felt generally satisfied with present-day education and training of analytical chemists and if not what changes they would like to see; (2) their views on short courses conferences etc. on analytical chemistry; (3) how they regarded various qualifications as training for potential analytical chemists ; (4) what future changes they saw taking place in analytical chemistry and the impli- cation of this on training; (5) their views on links between industry and educational establishments.In addition comments were invited on other aspects of the training of analytical chemists not covered in the above questions but felt by the person to be important. It should be stressed that this survey is concerned with a small sample only. September 19721 AT EDUCATIONAL ESTABLISHMENTS 181 REPLIES- (Ql) Only seven replies expressed general satisfaction with present-day education and training the main criticism being that the analytical content was very little related to current requirements. Several replies stressed the need for sounder practical work. (Q2) Comments were almost identical all approving of short courses and symposia particularly the specialised ones and those including practical aspects e.g.R.I.C. Summer Schools. However a distinction was drawn in eight replies between these and “conferences.” General conferences were criticised as being of less value except for meeting others working in the same field. The more detailed criticism of conferences included the following points they were low in practical content they gave very little help to the analyst in everyday problems only a small percentage of the papers are of direct utility many second-rate papers are presented on the application of standard techniques to particular situations or academic papers on yet another ligand with little comparison with other reagents. The immediate usefulness of Grad.R.1.C.was stressed and with one exception the H.N.C. was highly praised. Four replies made the point that all the qualifications listed have a part to play; the dependence of the qualification on the establishment from which it was obtained was pointed out in two replies. In addition to the qualifications listed 3f.Chem.A. and B.Pharm. were quoted as being particularly useful in pharmaceutical analysis. (Q4) On future trends almost all replies were unanimous in that they expected a greater degree of instrumental and automated methods of analysis use of computers and more involvement with plant quality control and production. There was less agreement on the implication of this on the future training of analytical chemists at educational establishments but a clear majority accepted that a full training to meet the future needs of analytical chemistry in industry will not be possible.Instead they advocate a sound background in fundamentals so that the person concerned can adapt as the subject evolves. A minority view is that subjects such as computer science chemical engineering electronics and instrument technology will need to be included in future training. It might well be that there is confusion here owing to a clear distinction not having been made between university degrees and A.R.I.C. in which the primary aim is to produce a good chemist and more applied courses such as H.N.C. and L.R.I.C. in which analytical chemistry plays a greater part Several replies to this question stressed the need to retain the basic training in classical methods.(Q5) With one exception and that expressed doubt all replies were in favour of industrial links with education establishments with 13 wanting an increase in such contacts. (Q3) Only the B.Sc. degree and A.R.I.C. emerged without criticism. GENERAL COMMENTS- Few comments were made outside the aspects suggested in the questions. Several comments have already appeared in earlier sections of the report GENERAL COMMENTS AND CONCLUSIONS Mention has been made of limitations due to restricting the survey mainly to Departments of Chemistry. This has particularly affected information of pharmaceutical biochemical and metallurgical analysis. Without doubt the biggest problem encountered in the survey resulted from the variety of ways in which analytical chemistry may be defined and the effect of this on replies.It may well be that the question “What is analytical chemistry? written across one question- naire by a Professor of Chemistry represented a general plea for help in this matter. An obvious method for overcoming this would be to list the various activities within the scope of modern analytical chemistry (a controversial matter in itself) for recipients to 182 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. indicate the ones that are dealt with in their particular establishment. An alternative approach might be to carry out a survey in depth at a limited number of colleges and universities. The survey has indicated where analytical activities are located in higher education. Clearly most analytical chemistry teaching is carried out at Polytechnics and Colleges of Technology whereas research in analytical chemistry is located in relatively few Universities.As teaching is invariably stimulated by a research environment it must be regretted that there is a physical separation of these two activities. It should not be overlooked however that some research on aspects of chemistry related to analytical chemistry e.g. spectroscopy are known to be carried out at some Polytechnics and consultancy work on analytical problems in industry is carried out by some staff members at Polytechnics. Where it applies this probably has a beneficial effect on the teaching of analytical chemistry. Many important aspects of the teaching of analytical chemistry remain obscure. For example analytical teaching is expressed as a time allocation with little information as to content.One would like to know the aspects of analysis dealt with the equipment available the exercises set and the extent to which principles and assumptions are dealt with as opposed to the purely manipulative aspects. Library facilities (journals in addition to books) and use made of them remain an unknown factor. Perhaps most important of all one would like to know more about how courses are designed if indeed they are and what is the motivating force for change. Finally mention should be made of educational activities in chemistry generally. Several organisations including the Royal Institute of Chemistry and I.U.P.A.C. are active in the field of chemical education including its relationship to the needs of industry.2 The Com- mittee for Education and Training in Analytical Chemistry has already made contact with some of these and future work could well be of a collaborative nature. REFERENCES 1. 2. Department of Education and Science “A Plan for Polytechnics and Other Colleges,” H.M. “Report of the Council of the Royal Institute of Chemistry for the Year Ending 30th September Stationery Office London 1966. 1968,” Royal Institute of Chemistry London 1968 p. 4.

ISSN:0037-9697    

DOI:10.1039/SA9720900173

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

182 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. Research Topics in Analytical Chemistry The following are summaries of fifteen of the papers presented at a meeting of the SAC/ Analytical Division on May 17th and 18th 1972 and reported in the June issue of Proceedings (p. 123). A Quantitative Flame Analysis Based on the Phenomenon of BY S. BOGDANSKI Candoluminescence. A New Method for the Determination of Bismuth (Chemistry Department Birmingham University P.O. Box 363 Birmingham B15 2TT) CANDOLUMINESCENCE is the luminescence emitted by certain solids when they are activated by an impinging flame. This phenomenon occurs at temperatures below that necessary for thermal incandescence and can therefore easily be distinguished from black-body radiation. It differs from more common flame-emission phenomena in that the emitting solid does not impart its luminescence to the flame and is not associated with a chemical change occurring to the refractory solids used.The type of solid which has been most studied in candoluminescence is one consisting of a refractory solid solution having a metallic oxide such as calcium oxide as the matrix diluent and a trace amount of an impurity. In this instance the impurity is the activator of a characteristic luminescence in the solid when it is contacted by an impinging hydrogen flame. It is such an activator - matrix system that we have considered for an analytical application the activator being the analyte. Observations of the candoluminescent phenomenon are given in the earliest works in blow-pipe analysis but Donaul was the first to use it as a qualitative analytical method in September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 183 1913.He found that a trace amount of bismuth when added to a preformed calcium oxide bead produced a blue emission from the bead when it was introduced into the edge of a hydrogen flame. I n a similar manner manganese activated a yellow luminescence. Later ~ o r k e r s ~ - ~ extended the list of activators in calcium oxide to include lead tin antimony yttrium lanthanum and many of the rare earth elements each having their own characteristic luminescence. I t was further indicated that the activators had characteristic optimum temperatures for maximum luminescence. In addition to offering selectivity the candoluminescent technique described was very sensitive.I n a calcium oxide based system it was possible to detect 1 ng of manganese and a 0.1 ng of bismuth by using a simple deposition method for introducing the activator to the calcium oxide matrix. By co-precipitating the activator with the matrix 1 ng of yttrium could be detected in 0.1 g of calcium matrix. Although the phenomenon of candoluminescence appears to offer selectivity and sensi- tivity it has never been used as a basis for a quantitative analytical method. This is primarily because the techniques of impinging the flame on the solid have never obtained the repro- ducibility necessary for such an application. EXPERIMENTAL- An Evans Electroselenium Ltd. Model 240 atomic-absorption spectrophotometer was adapted for our candoluminescent studies. Throughout the work the instrument was operated in the emission mode with a 0.4-mm slit.A chart recorder was connected to the 0 to 10 mV output. By coupling an electric motor to the wavelength fine control drive the spectrophotometer could be operated as a scanning instrument. The water cooling device was removed and a sample holder assembly shown in Fig. 1 was positioned in its place. The solid sample to be tested was inlayed into the hexagonal aperture in the head of a 3 cm long Allen screw. This screw was inserted into the accurately positioned assembly so that its head could be reproducibly positioned in the flame from an emission burner in line with the optical system. .- ,Sample De tec tor Fig. 1. Sample holder assembly The centre of a helium-diluted hydrogen flame which became active only when a small proportion of air was added via the aspirator was found to be the most suitable for repro- ducible sample positioning and activation.This flame was free from significant spectral background variation in the region between 340 and 600 nm having only a hydroxyl band emitted at 306nm with its second-order band at 612nm and a small peak at 589nm presumably arising from sodium. The spectra of various concentrations of bismuth in calcium oxide were obtained and are shown in Fig. 2. In order to obtain optimum spectra the detector gain was adjusted for each concentration scanned. As can be observed in Fig. 2 the blue candoluminescence emitted for various concentrations of bismuth activator varied only in intensity and not in wavelength. The broad band at 399 nm characteristic of the bismuth activator occurred superimposed on the hydrogen flame background.184 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY [PYOC. SOC. AnaZyt. Chem. > c vl c a K K 0 .- c .- .- vl .- E W B i I I I 300 400 500 Wave I engt h/n m Fig. 2. Spectra of bismuth a t different concentrations. Concentration of bismuth in calcium oxide (w/w) A 1 per cent.; B 1000 p.p.m.; and C 100 p.p.m. PREPARATION OF SAMPLE AND MEASUREMENT OF CANDOLUMINESCENCE- A co-precipitation of bismuth with the calcium matrix was found to be necessary in order to prepare a homogeneous solid. It was also noted that calcium hydroxide was as suitable a matrix material as calcium oxide and did not alter the spectrum of bismuth. A 1 + 1 mixture of calcium sulphate hemihydrate (plaster of Paris) and calcium hydroxide formed a matrix with the best physical properties in that it became firm and retained a smooth surface and yet could be activated in a similar manner to pure calcium hydroxide.Prior to preparing the sample a calcium solution for matrix preparation was made by dissolving analytical-reagent grade calcium carbonate in dilute nitric acid so that 1 g of calcium is contained in 4 to 10 ml of solution. The bismuth activator solution was a 250 p.p.m. bismuth solution made by diluting a 10 mg ml-1 bismuth solution which was prepared by dissolving bismuth(II1) nitrate pentahydrate in 1 M nitric acid. The sample is prepared by adding the calcium matrix solution (containing 0.5g of calcium) to a 30-ml test-tube followed by the required volume of activator solution and water to make the volume up to 10 ml.Then 1 g of plaster of Paris is added the test-tube is corked and the mixture shaken. An excess of 30 per cent. sodium hydroxide solution is added and the suspension is shaken for 5 minutes and filtered through sintered glass until the pre- cipitate forms a dense cake. This solid is then inlayed in the aperture of the screw and its surface is made smooth. It is heated in a 100 "C oven for 15 minutes after which time it can be positioned in the sample holder assembly. September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 185 The bismuth activated emission is measured at 399 nm and recorded on the chart recorder. The maximum intensity of the emission at 399 nm is a function of the amount of bismuth added to the preparation. A calibration graph obtained by the above procedure is essentially linear from 5 to 1OOOpg of bismuth added and the coefficient of variation remains a t about 10 per cent.over this range. CONCLUSION- The spectra for the other activators already mentioned have been obtained and a detailed examination of these elements will follow. Candoluminescence has been shown to be a useful technique in the determination of bismuth and greater sensitivity is to be expected as the method is refined. REFERENCES 1. 2. 3. 4. Donau J. Monatsh. Chem. 1913 34 949. Neunhoeffer O. 2. analyt. Chem. 1951 132 91. Nichols E. L. Howes H. L. and Wilber D. T. Pubis Carnegie Instn No. 348 1928. Smith E. C. W. Trans. Instn Gas Engrs 1940 90 519. The “Sensitised” Catechol Violet Reaction and its Utilisation in the Spectrophotometric Determination of Tin in Steel BY A.ASHTON A. G. FOGG AND D. THORBURN BURNS (University of Technology Loughborough Leicestershire LE 11 3T U ) THE present British Standards method for the determination of tin in steel is time consuming and an attempt has been made to develop an extractive spectrophotometric method to replace it. After a comparative study of the most popular colorimetric reagents for tin taking particular note of adherence to Beer’s law sensitivity spectral characteristics and repro- ducibility a method in which catechol violet is “sensitised” with cetyltrimethylammonium bromide (CTAB)1 was found to be superior in virtually all respects. Addition of CTAB to the tin - catechol violet system results in a large bathochromic shift of the complex absorption band whereas the band due to the reagent is not moved.The reagent and complex bands are resolved completely with an increase in the molar absorptivity from 6-7 x lo4 to 9-2 x lo4 1 mol-1 cm-l. This CTAB “sensitised” catechol violet finish has been successfully combined with an iodide extraction procedure in which tin(1V) iodide is first extracted from acidic solution into toluene and then back-extracted with sodium hydroxide solution. Hydrolysis problems arising in this procedure were investigated and overcome. Interference from iodine carried over to the final stage was removed by the addition of ascorbic acid. Investigation of the tolerance of the proposed method to other metals found in steels showed that it should be applicable to virtually all steels including stainless steels. The only exceptions are steels with a copper to tin ratio of greater than 20 :1 as insoluble copper(1) iodide causes emulsification in the extraction procedure.A pre-extraction of copper is necessary with steels of this type. The wide applicability of the method is due mainly to the use of lactic acid as a masking agent at the chromogenic stage. Tolerance of molybdenum in particular is greatly increased by its addition. The combined colorimetric finish and extraction procedure has been applied to a range of British Chemical Standards steels. The mechanism of the CTAB “sensitisation” of the catechol violet - tin reaction has been investigated. It has been suggested2 that the presence of CTAB micelles is necessary for the formation of the tin - catechol violet - CTA ternary complex. Spectra taken in the present study at CTAB concentrations well below the critical micelle concentration clearly indicate complex formation.Nevertheless the determination of the critical micelle con- centration of CTAB under the actual test conditions by using surface tension measurements on a Du Nouy tensiometer did show a close correlation between the critical micelle con- centration (0.04 x M) and the concentration of CTAB giving maximum absorbance by the complex (0-055 x A t CTAB concentrations below the critical micelle con- centration precipitation of the ion-association complex was observed. Apparently under M). 186 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. AnaZyt. Chern. analytical conditions the insoluble ion-association complex is dispersed in the micelles formed by the excess of CTAB.It therefore seemed possible that other large cations which were not themselves surface-active could cause the bathochromic shift provided that the non-association complex formed was dispersed in a surfactant that did not interact with the tin - catechol violet anion itself. This was shown to be the case with the basic dye Brilliant green and the surfactant polyvinyl alcohol. Again the large bathochromic shift was evident but unfortunately the hoped-for additive effect of the absorbance of the Brilliant green and the catechol violet which would have led to increased sensitivity was not observed. REFERENCES 1. 2. Dagnall R. M. West T. S. and Young P. Analyst 1967 92 27. Bailey B. W. Chester J. E. Dagnall R. M. and West T. S. Talanta 1968 15 1359. The Determination of Tin in Steels by Solvent Extraction Fol Atomic-absorption Spectrophotometry* BY J.B. HEADRIDGE AND ALAN SOWERBUTTS (Department of Chemistry The University Shefield S 3 7 H F ) A METHOD was described for the determination of 0.001 to 0-25 per cent. of owed by in in irons and steels. The tin from a l-g sample is extracted from an aqueous solution which is 0-5 M in both hydrochloric acid and thiocyanate and 8 per cent. w/v in ascorbic acid into isobutyl methyl ketone. The organic phase is concentrated to a small volume by evaporation and diluted to 10 ml. The tin content of this solution is determined by atomic-absorption spectrophotometry with a nitrous oxide - acetylene flame. Good results were obtained for the determination of tin in twelve B.C.S. irons and steels. The limit of detection was 0.001 per cent.of tin. * The full version of this paper was published in Analyst 1972 97 442. Amalgam Reduction of Titanium( IV) BY G. A. EAST AND E. BISHOP PURSUING earlier work on a possible rate measurement method for the determination of low concentrations of perchloratel by reaction with titanium(III) an attempt was made to define more closely the fractional order dependence on perchlorate. Pseudo-order studies required high concentrations of titanium(II1) in 10 M sulphuric acid. Purified potassium oxodioxalatotitanate(1V) was fumed with Aristar sulphuric acid to remove oxalate hydrated titanium( IV) oxide was precipitated with Aristar ammonia washed well and dissolved in Aristar sulphuric acid to give a 0-25 M solution of titanium(1V) in 10 M sulphuric acid; the concentration of titanium( IV) was verified by gravimetric analysis with a titanium(1V) oxide finish.Specpure mercury and metals of 99.9999 per cent. purity were used to prepare the amalgams. Coarse pale violet crystals separated quickly thus producing a titanium(II1) solution of indeterminate concen- tration. The precipitation was not observed with cadmium lead tin or bismuth amalgams and the deposit was a polysalt containing zinc and titanium(II1) sulphates and possibly hydrogen ion. The crystals were soluble on dilution and it was found that the sulphuric acid concentration had to be reduced to 4.5 M to avoid this crystallisation. The second difficulty arose when the colour of the titanium(II1) solution produced appeared to be much more blue than the expected wine-red and in a kinetic run at X = 482 nm as previously used,l the absorbance instead of decreasing increased four-fold.A spectral scan of the blue solution showed a A,,,. at 528 nm. Repetitive scans at 10-minute intervals of such a solution exposed to the air showed the disappearance of the absorbance at 528 nm and a hypsochromic shift to 482 nm accompanied by a large increase in absorbance (Fig. 1). I t was first thought that because very pure reagents were used purer than in any earlier work the titanium was (Chemistry Department University of Exeter Stocker Road Exeter EX4 4QU) The first difficulty arose with zinc amalgam reduction. September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 187 being reduced to some extent at least to the divalent state the reagents being free from any catalytic impurities which would induce the reaction between hydrogen ion and titan- ium(I1).Such a solution was added to excess of iron(II1) and the iron(I1) produced was titrated with standard dichromate and early results indicated the presence of 16 per cent. of titanium in the divalent state for zinc amalgam and 10 per cent. for cadmium amalgam reduction. Less powerfully reducing amalgams were therefore examined. Cadmium lead and tin amalgams also gave the blue colour and bismuth amalgam gave only a small degree of reduction. All produced the blue-coloured solution and this blue colour persisted in- definitely when the solutions were removed from the amalgam and stored in the absence of air. Chromium made no difference; copper at 1 p.p.m. showed no influence but at 2 p.p.m. proved to be a good oxygen carrier accelerating the take-up of molecular oxygen but was not catalytic in oxygen-free media.The use of liquid amalgams prepared from zone-refined zinc and cadmium and shaking until the blue colour was fully developed gave solutions which on titration with standardised cerium(1V) or permanganate through the intermediate of iron(II1) yielded results for titanium(II1) concentrations that were within 0-5 per cent. of the gravimetric results for the titanium(1V) solutions from which they were prepared. The production of Deliberate addition of catalytic amounts of some metals was tried. n 390 490 590 690 Wavelength/nm Fig. 1. Change of ab- sorption spectrum of a fully reduced titanium(II1) solu- tion when exposed to air with time. Interval between scans 10 minutes; initial titanium(II1) concentration 0.25 M ; medium 4.5 M sul- phuric acid 1.7 1.6 a t m e % n a 1.5 1.4 t I 1 3.0 4.0 Concentration of titaniurn(IV)/10-2 moI I-’ I 0 Fig.2. Spectrophotometric titration of titanium(II1) a t 482 nm initial concentration of titanium(III) 0.105 M in 4.5 M sulphuric acid. Titrant 0.2 M cerium(1V) in 4.5 M sulphuric acid 188 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. titanium(I1) cannot therefore be responsible for the blue colour and an explanation must be sought in the configuration of the titanium(II1) species in sulphuric acid media. It was found that the blue solution is very sensitive to oxidation by air the wine-red colour persists for several days on exposure of the solution to air the consumption of oxidant in titration is always greater for the blue solution than for the wine-red solution no matter how deep the latter colour may be and during amalgam reduction the first colour produced is always wine-red which changes to blue on prolonged shaking.The blue species is formed from the wine-red species but oxygen is required to convert the blue to the red species. In all situations where the more strongly absorbing wine-red species appears both titanium(1V) and titanium(II1) are simultaneously present. I t would appear therefore that the wine-red species is a compound containing titanium in both oxidation states Blue Colourless Wine-red Ti111 + TiIV -+ Ti111 - TiIV and that this compound is oxidised much more slowly than the free solvated titanium(II1) ion. The wine-red colour deepens as titanium(II1) is oxidised until all of it has been converted into the mixed oxidation state compound.Further oxidation causes a diminution in colour intensity until oxidation to titanium(1V) is complete Ti111 - TiIv + oxidant or 0 -3 TiIv This postulate was checked by addition of deoxygenated titanium(1V) solution to the blue solution which immediately turned wine-red and by addition of cerium( IV) equivalent to 1 per cent. of the titanium present in a blue solution which also immediately turned wine-red. Spectroscopic examination showed that a maximum of two species could be present at any time solvated titanium(II1) of Amax. = 528 nm solvated titanium(II1) plus the wine-red polymer of Amax. = 482 nm the wine-red polymer plus colourless titanium(IV) or colourless titanium(1V). To determine the stoicheiometry of the wine-red species a spectrophotometric titration at h = 482 nm was carried out under oxygen-free nitrogen with the result shown in Fig.2. The absorbance increased to a maximum when 50 per cent. of the titanium(II1) had been oxidised and then decreased to zero a t 100 per cent. oxidation. Although the titration curve could be interpreted as showing a rounded top it does show the peculiarity of discontinuity whereby the maximum is traversed by three reasonably linear steps labelled (2) (3) and (4). Extrapolations of the linear sides (1) and (5) and of the steps (2) and (4) cross within about 1 per cent. of the maximum absorbance. The mole ratio of titanium(II1) to titanium(1V) in the polymer is therefore 1 1 in agreement with the results of Goroshchenko and G o d ~ e n a .~ ? ~ The blue solvated titanium(II1) shows a Amax. of 528nm and a molar absorptivity of 0.42 1 mol-l mm-1 and therefore an octahedral splitting energy of 1895 mm-1 or 54.1 kcal mol-l which is consistent with the Laporte-forbidden d - d transition tZg1 + egl. The binuclear complex shows a h,a,. of 482 nm and a molar absorptivity of 8-57 1 mol-1 mm-l indicating a splitting energy of 2075 mm-1 or 59-2 kcal mol-1 which is not consistent with a d - d transition in a single atom but would be consistent with a charge-transfer spectral transition from one atom of titanium to the other in a binuclear oxygen or hydroxyl bridged complex that is tZg titanium(II1) -+ tZg titanium(IV) thus reversing the oxidation state. Probable configurations are Wine-red Colourless H 0 L,TiIILO-TiIVL L,Ti 111’ \iIvL ‘0’ H where L represents solvent molecules or hydrogen sulphate ions.Two conclusions emerge clearly from this investigation. First analytically the prepara- tion of determinate solutions of titanium(II1) as standard reducing titrants by complete reduction of a determinate titanium(1V) solution is viable only if reduction is carried through. to the pure blue colour the indication of this is very sensitive because the much higher molar absorptivity of the binuclear complex makes it easy to observe the disappearance of the last trace of wine-red colour. Such solutions are extremely sensitive to oxygen. If September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 189 the titanium(II1) solution is to be standardised before use then reduction to the maximum intensity of the wine-red colour that is about half reduction will produce a solution with the minimum sensitivity to oxygen and therefore of maximum stability.Furthermore analytically the determination of titanium by reduction for example in a Jones reductor and oxidimetric titration is liable to give low recoveries because the standard procedures do not usually require a sufficiently prolonged reduction time to remove the last traces of the binuclear complex. The solution emerging from the reductor [and usually received in an excess of iron(II1) solution to minimise aerial oxidation] should be inspected for any deviation from the fully reduced blue colour. Second kinetically if a reaction such as that between titanium( 111) and perchlorate is to be followed spectrophotometrically the titanium solution should be less than half reduced so that the wine-red colour A,.= 482 nm can be used and will decrease with elapsed time and not increase. However the formation of the binuclear complex is fast so that it would seem also to be possible to make rate measure- ments by observing the increase in absorbance of the binuclear complex; this approach must be used with caution because of secondary kinetic effects that arise from participation of the polymer in the reaction and the formation of the polymer from the titanium(1V) produced. REFERENCES 1. 2. 3. Bishop E. and Evans N. Talanta 1970 17 1125. Goroshchenko G. and Godvena M. M. Russ. J . Inorg. Chem. 1961 744. Hush N. S . Progr. Inorg. Chem. 1967 8 391. Enthalpimetric and Thermometric Determination of Some Nitrogen- containing Bases and Physiologically Active Alkaloids BY L.S. BARK AND J. K. GRIME (Department of Chemistry and Applied Chemistry University of Salford Salford ,Id5 4 WT Lams.) ENTHALPIMETRIC and thermometric methods for the determination of basic substances have generally utilised either the heat of neutralisation in aqueous media1-* or the heat of dilution of the titrand, or the catalimetric use of the solvent.6-8 The determination of primary aminess by using a diazotisation reaction has been reported. However it was decided to utilise the favourable enthalpy changes involved in a precipitation reaction and in particular to determine the bases by precipitation of the tetraphenylboron derivative by using sodium tetraphenylboron as reagent. This reaction was found to be rapid and reproducible for a particular base and the method has a high sensitivity when applied to the determination of milligram amounts of some bases.Preliminary investigations indicated that a direct titration was not feasible because all the bases do not react at the same rate with the reagent. The relatively low solubility of sodium tetraphenylboron in water (a saturated solution is less than 0.90 M) restricts its direct use as a titrant. Accordingly a back-titration was considered thus keeping an excess of sodium tetra- phenylboron present at all times and ensuring completeness of reaction in a given time. The titration was carried out by using direct injection enthalpimetry. The theory and experimental conditions necessary for this method have been reviewed.1° The need to have standard conditions for determinations of organic functional groups by precipitation reactions has also been discussed.11J2 The method proposed involves the precipitation of the base with a known and excess amount of sodium tetraphenylboron and the subsequent determination of the excess of sodium tetraphenylboron as potassium tetraphenylboron by using a concentrated solution of potassium chloride.The over-all reactions are as follows. (i) Precipitation of the base- RR’R”R”’N+ + B(C,H,),- -+ RR’R”R”’ NB(C,H,) where R R’ R” and R”’ can be hydrogen alkyl or aryl or the compound may be a hetero- cyclic base. (ii) Determination of the excess of sodium tetraphenylboyoa- Na+ + B(C,H,)*- + Kf + c1- + KB(C,H,) + Na+ + c1- 190 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem.The “heat pulse” given by the addition of a fixed volume of potassium chloride solution is a measure of the excess of sodium tetraphenylboron present and thence the amount of base originally present can be calculated. APPARATUS- The injection pipette was specially designed to be submersible and to aid in the efficient mixing of the solutions. The injection apparatus was a %cm3 syringe driven with a synchronous motor and the mixtures were stirred with a rotating multi-paddle stirrer. BASE DETERMINED- The circuit for the basic electrical bridge system has already been reported.12 Compounds containing a primavy amino gvoup- Aniline benzylamine 3-aminopyridine 4-aminopyridine 4-aminoacetophenone and Compounds containing a secondary amino g~oup- Phenylhydrazine hydrochloride N-meth ylaniline diethylamine piperidine and rnorpho- Compounds containing a tertiary amino gvoup- NN-Dimeth ylaniline triet hylamine p yridine hexame t hylenetet ramine acridine and Quaternary ammonium salts and ammonium salts- Tetraethylammonium bromide and ammonium chloride.2-aminobenzoic acid. line. 8-nitroquinoline. RESULTS- All the compounds considered were determined over the range 0.03 x mol; each compound gave results within 1-5 per cent of the theoretical value. The standard deviation of the method is 0.27 mg. FACTORS THAT AFFECT THE METHOD- The endothermic heat of dilution is compensated for and minimised by the exothermic heat of mixing of hydrochloric acid present in the reaction mixture. The acidity of the solution must however be controlled as sodium tetraphenylboron decomposes in strongly acidic solutions.It has been found that 0-1 M hydrochloric acid provides sufficient protons to protonate the base and liberates enough heat during its dilution to provide an overall zero heat of mixing without causing decomposition of the reagent during the time taken for the titration. There is a physical limit to the amount of precipitate that can be effectively stirred and hence a practical limit is imposed in the determination of a particular base by the bulk of precipitate formed. Thus when the series aniline N-methylaniline NN-dimethylaniline is considered the upper limit of determination decreases as the molecular weight of the base increases. DETERMINATION OF ALKALOIDS- The reaction sequence was used to study the determination of some physiologically active alkaloids.The pH conditions were found to be critical and an extensive study of the pH conditions and the time necessary for complete reaction has been carried out by using continuous thermometric titrimetry. Morphine sulphate has been determined at the 10-mg level by using acetate buffer of pH 3 and allowing 10 minutes for reaction before titrating the excess of sodium tetraphenyl- boron. Other alkaloids that have been studied include atropine sulphate quinine sulphate and papaverine hydrochloride. to 0.7 x REFERENCES 1. 2. 3. 4. Parsons J . S. Abstv. Pap. 132nd Meet. Amer. Chem. SOC. 1957 7B. Popper E. Roman L. and Marcu P. Talanta 1965 12 245. Dragulescu C. and Policec $. Studii Cerc. Baza Stiinte TimiSoara Stiinte Chim. 1962 9 33. Ogawa M. Yasuyo N. Tetsu K. and Fujie T. Kyoritsu Y a k k a Daigaku Kenkyu Nempo 1970 15 21.September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 191 5. 6. 7. 8. 9. 10. 11. 12. Vaughan G. A. and Swithenbank J. J. Analyst 1967 92 364. Vajgand V. J. and GaAl F. F. Glasn. Hem. Drujt. Beogr. 1966 31 No. 2 103; Talanta 1967 Vajgand V. J. Kiss T. A. GaAl F. F. and Zsigrai I. J. Talanta 1968 15 699. Vajgand V. J. GaAl F. F. and Brusin S. S. Ibid. 1970 17 415. Yamazaki M. and Takeuchi T. Kogyo Kugaku Zasshi 1969 72 1263. Bark L. S. and Bark S. M. “Thermometric Titrimetry,” Pergamon Press Oxford 1969. Bark L. S. and Bate P. Proc. 3rd Natn. Conf. Analyt. Chem. Brasov Romania 1971 4 335. 14 3451. Analyst 1971 96 881. - Simultaneous Spectrofluorimetric Determination of Tetracaine and Procaine or Benzocaine BY A. C. MEHTA PROCAINE benzocaine and tetracaine are very important drugs as they possess local anaes- thetic properties and one or more of these compounds may frequently be present in illicit drugs.The continually increasing use and abuse of these drugs demand an investigation into the possibility of more rapid and sensitive methods for their determination. The existing titrimetric and absorptiometric methods for their determination are not sufficiently rapid and sensitive and spectrofluorimetry with its unique sensitivity and flexibility was used as a means of solving this problem. This paper describes a simple and sensitive method for the rapid determination of tetra- caine and procaine or benzocaine. The method depends upon the fluorescence of tetracaine in 0.1 M acetic acid and the total fluorescence of tetracaine and procaine or benzocaine in ethanol.In both solvents the absorption and fluorescence spectra involved overlap but this difficulty can be overcome by applying corrections and using selective excitation. Cocaine does not interfere in the determination. The native fluorescence characteristics of these drugs have been investigated in this 1aboratory.l Tetracaine shows weak fluorescence at the wavelength combination of 321 and 374 nm in 0.1 M acetic acid. Its absorption and fluorescence maxima lie at longer wavelengths than those of procaine or benzocaine and therefore excitation at 321 nm should give the tetracaine concentration directly. In practice however the situation is complicated by the fact that procaine or benzocaine if present in large amounts gives slight background fluorescence at 321 and 374 nm giving high values for tetracaine fluorescence.This difficulty is eliminated by drawing calibration graphs for procaine and benzocaine at 321 and 374 nm. The true tetracaine intensity and hence the concentration is obtained by deducting the intensity corresponding to the appropriate concentration of procaine or benzocaine from the observed tetracaine fluorescence. The correction is necessary only if a large amount (five-fold) of procaine or benzocaine is present. The calibration range for all three drugs is from 0 to 5-0 pg ml-l. In ethanol tetracaine procaine and benzocaine give strong fluorescence at 361 347 and 347 nm with major excitation peaks at 315 307 and 308 nm respectively. A t low con- centrations their fluorescence is additive.The ideal situation would be to obtain the com- bined intensity of tetracaine and procaine or benzocaine at 347 nm by exciting themixture in the region of 312 nm. This is not possible however because tetracaine in ethanol has an absorption maximum at 311 nm and this introduces a considerable inner-filter effect. This effect can be made negligible by selectively exciting the mixture at 275 nm at the expense of some fluorescence intensity. Here also three calibration graphs are needed and after de- duction of the intensity corresponding to the concentration of tetracaine the amount of procaine or benzocaine can be found. As all three drugs are strongly fluorescent in ethanol the possibility of carrying out the entire analysis in this solvent was considered before using 0.1 M acetic acid as solvent in the tetracaine determination.In ethanol the ideal wavelength combination for tetracaine deter- mination was found to be 338 and 361 nm 338 nm being the wavelength of selective excitation. Further investigation showed that this wavelength was highly critical because at longer wave- lengths the Rayleigh scattering became significantly high and at shorter wavelengths the other two alkaloids began to interfere. (Department of Chemistry University of A berdeen Old A bevdeen Scotland) The calibration range is from 0 to 0.5 pg ml-l. 192 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. The accurately weighed sample was first dissolved in spectroscopically pure grade ethanol and diluted to a standard volume (stock solution). This solution after dilution with the same solvent was used to obtain the total fluorescence intensity of a mixture at 275 and 347 nm.A suitable aliquot from the stock solution was then carefully evaporated and the residue was dissolved in 0.1 M acetic acid and diluted to a standard volume for the deter- mination of tetracaine at 321 and 374 nm. The procaine or benzocaine concentration was found by difference. Flourescence measurements were made with a Farrand spectrofluori- meter. To allow for the variations in the instrument sensitivity fluorescence measurements were made by comparing the intensity of the sample with that of the reference standard 2-aminopyridine at the same wavelength combination. The standardised intensity L e . the intensity relative to that of the reference standard was then calculated.2 The calibration graphs were obtained by plotting the standardised intensity veysus concentration.Synthetic mixtures were analysed successfully with relative errors of less than 10 per cent. This method could be used for the analysis of mixtures of local anaesthetics or illicit drugs. REFERENCES 1. 2. Mehta A. C. and Chalmers R. A. Chernia Analit. 1972 17 565. Chalmers R. A. and Wadds G. A. Analyst 1970 95 234. Studies Concerning Metal Chelates of l-Hydroxyanthraquinone BY M. JACKSON AND M. A. LEONARD AS part of a general study of reactions underlying the use of hydroxyanthraquinones as reagents in inorganic trace analysis metal chelates of l-hydroxyanthraquinone have been prepared under various conditions. Four metals (nickel cobalt manganese and copper) were utilised in the form of their acetates sulphates chlorides and nitrates as the source of metal.The metal chelates were prepared in a methanol - water mixture pure dioxan dioxan - water and dimethylformamide. The relative amounts of starting materials were varied in the hope of detecting if several complexes of varying composition could be formed. The metal chelates produced were red powders when prepared in alcohol - water dioxan and dioxan - water mixtures. The nickel and cobalt chelates prepared in dimethylformamide proved unique in that they resulted in much darker coloured products. It is interesting to note that under the same conditions as those used for the preparations involving metal acetates metal nitrates chlorides and sulphates were much less suitable for this reaction. The resulting metal complexes were subjected to complete elemental analysis and were also studied by spectroscopic mass spectrometric and thermoanalytical methods.Spectro- scopic studies in the 1700 to 1400 cm-l range proved interesting. l-Hydroxyanthra- quinone has a band at 1673 cm-l which may be associated with the “free” carbonyl group. This is the carbonyl group which is further removed from the hydroxyl group. The band at 1640 cm-I may be attributed to the hydrogen-bonded carbonyl group which suffers a shift from 1673 cm-l. The band at about 1593 cm-1 is associated with vibration within the aromatic ring system. If the infrared spectrum of the nickel chelate of l-hydroxyanthraquinone (made in methanol) is considered then it is observed that the “free” or non-hydrogen-bonded carbonyl band is unaltered in frequency.This tends to suggest that it is absolutely disinterested in the chelation process. The most apparent change is the shift of the “hydrogen-bonded” carbonyl band from about 1640 to about 1620 cm-1 showing involvement of this carbonyl group. The aromatic ring system vibration band is still at about 1590 cm-l but a new and strong band can clearly be seen at about 1520 cm-1. This 1520 cm-1 band has been attributed to carbon-carbon bonds within the new chelate ring system produced. The infrared spectrum of the nickel chelate made in dimethylformamide shows a shifting broadening and intensification of the band previously occurring at 1673 cm-l. This is due to co-ordination of molecules of dimethyl- formamide into the metal chelate structure. This alteration of the “free” carbonyl frequency (Deparhzent of Chemistvy Queen’s University of Belfast Belfast BT9 5AG) September 19721 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY 193 is due to interaction between the quininoid carbonyl frequency and the carbonyl frequency of the dimethylf ormamide.The spectra of the cobalt chelates are exactly similar to those of nickel in this region. For the copper and manganese chelates of 1-hydroxyanthraquinone there is no thickening or intensification of the free carbonyl frequency at 1673 cm-1 and therefore there is no co- ordination of dimethylf ormamide. Thermogravimetric studies on these chelates showed that the nickel chelate (made in methanol) was stable to about 400 "C when the whole complex breaks down to give NiO. The nickel chelate prepared in dimethylformamide showed a substantial weight loss in the region of about 120 "C which corresponded to two molecules of dimethylformamide.Again the cobalt chelates were exactly similar. The copper chelate however fits the traditional image for chelate formation when the ratio of anthraquinone to metal is 2:l. The prepared complexes were analysed for metal content by wet oxidation followed by photometric EDTA titration of the diluted and suitably neutralised digest. Combining ratios for the metal chelates prepared are one nickel atom to one anthra- quinone molecule and two acetate groups for the chelate prepared in methanol with the addition of two molecules of dimethylformamide for the chelate prepared in the latter solvent. The cobalt chelates are exactly similar. For the copper and manganese chelates the ratio of anthraquinone to metal is 2:l.No acetate groups or molecules of dimethylformamide are incorporated into the metal chelate structure. Mass spectrometric analysis confirmed the presence of acetate groups in the nickel and cobalt chelates by showing a high abundance peak at m/e = 60. No such peak was apparent for the copper and manganese chelates. The presence of co-ordinated dimethylformarnide can be confirmed by a study of these metal chelates as hexachlorobutadiene mulls. The solvent molecules show up as a large broad peak in the region 3100 cm-l. Normal solution studies carried out on sulphonated 1-hydroxyanthraquinone have confirmed the combining ratios previously quoted. 1,4-Dihydroxyanthraquinone has two important bands in the 1700 to 1400 cm-l region.The band at about 1635 cm-1 is attributed to a carbonyl group that is adjacent to a hydroxy! group. But this time there is no "free" carbonyl frequency at 1673 cm-1 because both carbonyl groups have hydroxyl groups in the cc-position to them and therefore suffer from the effects of hydrogen bonding. Again there is a band at about 1590 cm-1 associated with the aromatic ring system. A study of the nickel chelate of 1,4-dihydroxyanthraquinone shows a shift in the hydrogen-bonded carbonyl absorption due to involvement of both carbonyl groups. The band due to the aromatic ring system is found at 1550 cm-l and that due to the new chelate ring at 1490 cm-l. The cobalt chelate of 1,4-dihydroxyanthraquinone shows a very similar spectrum. For the copper chelate of this 1,4-derivative there is a very similar spectrum except that the aromatic ring system band occurs at 1570 cm-l.The manganese chelate shows a very similar spectrum to the copper chelate. The infrared spectra of these four metal chelates of 1,4-dihydroxyanthraquinone made in dimethylformamide showed poorly defined peaks and from carbon hydrogen and nitrogen figures it was decided that these compounds were probably non-stoicheiometric. Thermogravimetric studies of the nickel and cobalt chelates showed a gradual loss of water followed by disintegration of the complex. However the copper and manganese chelates are very stable up to about 220 "C and then the complexes disintegrate. From complete elemental analysis the most probable formulae for the chelates were (a) one anthraquinone molecule two atoms of nickel or cobalt and four molecules of water and ( b ) one anthraquinone molecule two atoms of copper or manganese and four acetate groups.Mass spectrometric analysis confirmed the presence of acetate groups in the manganese and copper chelates. No peaks due to acetate were found for the cobalt and nickel chelates. Studies of the cobalt and nickel chelates as hexachlorobutadiene mulls confirmed the presence of co-ordinated water by a broad peak in the region of about 3450 cm-l. The man- ganese and copper chelates showed no such peak. 1,5-Dihydroxyanthraquinone follows a similar pattern to the 1,4-derivative the only detectable differences being due to the fact that the 1,5-dihydroxyanthraquinone chelates are more symmetrical than their 1,4-analogues. The combining ratios are exactly similar and the normal methods of investigation were applied.194 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. Thermal Studies and Gas Chromatography of Some Metal Beta-diketonates BY J. WARREN AND A. G. SMEETH (The City University St. John Street London E.C.l) IN recent years the volatility and thermal stability of metal chelates have become of some analytical interest particularly in the field of gas chromatography of trace amounts of metals.l-' The present study was an attempt to correlate the thermal properties of the metal beta- diketonates in a general way with the structure of the coordinating ligand. The thermal stability and volatility of a number of copper(II) chromium(II1) and cobalt(II1) beta-diketonates were investigated. The groups R, R and R of the beta- diketone R,.CO.CHR,.CO.R were varied so as to alter the nature of the ligand in a syste- matic manner a total of thirty-five ligands being investigated.The substituent groups included hydrogen alkyl fluorinated alkyl naphthyl phenyl benzyl thienyl furyl halo and nitro. Some 3-substituted-pentane-2,4-diones that were not commercially available were synthesised and characterised by gas chromatography mass spectrometry and nuclear magnetic resonance spectroscopy. The chelates of three different metals were studied to determine whether any trends in thermal properties which occurred when the ligand was altered were consistent with the equivalent chelates of other metals. The majority of the chelates were prepared by the direct reaction of the ligand with an appropriately buffered aqueous solution containing the metal in its desired state.8 The cobalt (111) chelates were prepared under oxidising conditions in the presence of either hydro- gen peroxide or nitric acid to minimise the formation of cobalt(I1) chelates.The 3-nitro- 3-bromo- and 3-iodopentane-2,4-dionato chelates were prepared by the respective nitration bromination or iodination of the appropriate metal pentane-2,4-dionates9 The metal chelates were characterised by melting-point and elemental analysis and for the cobalt (111) chelates by nuclear magnetic resonance spectroscopy. The thermal properties of the metal chelates were determined by thermal analysis with a Du Pont 900 thermal analyser. The thermal stability of a metal chelate was assessed in relation to its decomposition temperature recorded by differential scanning calorimetry whilst its volatility was assessed from its behaviour under thermogravimetric analysis.Vapour pressures were also recorded for some of the chromium(II1) chelates with an isoteniscope apparatus and the relative volatilities measured in this way agreed with those measured by thermogravimetric analysis. Isothermal decomposition studies were carried out on some of the copper(I1) chelates and these results were compared with those obtained by differential scanning calorimetry. Thermal analysis was found to be a rapid convenient means of measur- ing the thermal properties of a metal chelate. The nuclear magnetic resonance spectroscopy carried out on the cobalt(II1) chelates for characterisation purposes also gave some information about the electronic density within the chelate ring structure and this was considered in conjunction with the thermal stability of the chelates.The thermal properties of a metal chelate were found to change with the alteration of the nature of the ligand. In general these trends in the relative change of thermal properties were the same irrespective of the metal atom contained in the chelate. It was found that the volatility of the metal chelates investigated is dependent predominantly on the type of ligand used while the thermal stability is dependent on the type of ligand and the metal. It was found that the chelates investigated ranged from highly volatile formed from beta- diketones containing fluorinated alkyl substituents to involatile formed from beta-diketones containing aromatic substituents.Under thermogravimetric analysis the fluorinated chelates started to lose weight in the region of 50 to 100 "C while the chelates that were substituted with aromatic groups started to lose weight in the region of 300 to 400 "C. The thermal stabilities of the chelates investigated ranged from those which are relatively unstable formed from the 3-subsituted-pentane-2,4-diones to the more highly stable chelates formed from beta-diketones containing aromatic groups able to conjugate with the chelate ring. The thermal stability of a chelate was also found to be dependent on its metal atom and in general for a given ligand the thermal stabilities were found to decrease in the order Cr(II1) > Cu(I1) (The Laboratory of the Government Chemist Cornwall House Stamford Slreet London S.E.1) > Co(II1). September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 195 The most stable of the chelates investigated in this study tri-( 1,3-diphenylpropane-1,3- dionato)chromium( 111) formed from chromium (111) and a beta-diketone containing two phenyl groups decomposed at 485 “C under differential scanning calorimetric analysis. These thermal properties of volatility and stability can be explained in terms of the structural and polarity parameters conferred on a chelate by the ligand. Some gas chromatography was carried out on three different columns. The columns were constructed of & inch internal diameter PTFE tubing 3 feet long and packed with (i) 60 to 80-mesh Chromosorb W coated with 5 per cent. w/w of SE-52 silicone gum (ii) 40 to 60- mesh PTFE beads coated with 5 per cent.w/w of SE-52 and (iii) 40 to 60-mesh PTFE beads coated with 1 per cent. w/w of Apiezon L. The columns were run a t temperatures between 125 and 200 “C It was found that the behaviour of the chelates on these columns was consistent with the thermal properties previously measured by thermal analysis. From these experiments it was possible to suggest which types of beta-diketone conferred the optimum properties to a metal chelate desirable for gas chromatography. The chromium(II1) chelates which are particularly stable were found to give favourable gas chromatographic results. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. Barratt R. S. Belcher R. Stephen W. I. and Uden P. C. Analytica Chim. Acta 1972 59 59. Genty C. Houin C. Malherbe P. and Schott R. A n a l y f .Chem. 1971 43 235. Savory J. Mushak P. and Sunderman F. W. Jr. J . Chromat. Sci. 1969 7 674. Booth G. H. Jr. and Darby W. J. Analyt. Chem. 1971 43 831. Moshier R. W. and Sievers R. E. “Gas Chromatography of Metal Chelates,” Pergamon Press Taylor M. L. and Arnold E. L. Analyt. Chem. 1971 43 1328. Foreman J . K. Gough T. A. and Walker E. A. Analyst 1970 95 797. Fernelius W. C. and Bryant B. E. Inorg. Synth. 1957 5 105. Collman J. P. Angew. Chem. I n t . E d n 1965 4 132. Oxford 1965. Determination of Trace Amounts of Peroxides in Light Hydrocarbons BY I. J. THOMSON AND G. C. BELL (Imperial Chemical Industries Limited Petrochemicals Division Billingham Teesside l’S23 1 J B ) A METHOD has been developed for the determination of trace amounts of both easy and difficult to reduce peroxides (1 to 40 p.p.m.of active oxygen) in finished-product buta-1,3- diene C streams and mixed C - C streams. In the method described below peroxides are reduced by hydrogen iodide generated in situ from lithium iodide and phosphoric acid in refluxing isooctanol. Buta-l,2-diene buta-l,3-diene piperylene cyclopentadiene vinylcyclohexene and dicyclopentadiene can interfere in the method by reacting with hydrogen iodide to liberate iodine whereas isoprene methylacetylene and ethylacetylene can remove iodine. Inter- ference from all the hydrocarbons except dicyclopentadiene is overcome by the nitrogen purge step in the method. For finished-product buta-1,3-diene only the purge step can be carried out from 60 ml of lithium iodide-isooctanol reagent but for all other streams this must be done from 40 ml of isooctanol the 60 ml of lithium iodide - isooctanol reagents being added directly after the purge operation.It is important particularly for C streams not to purge directly from the lithium iodide - isooctanol reagent because these streams can contain reactive peroxides which liberate iodine immediately from the reagent at room temperature. Normally the large iodide concentration in the reagent means that all iodine is present as Is- which will not add to unsaturated compounds but because the reactive peroxides produce substantial amounts of free iodine this will react with isoprene or acetylenes during the nitrogen purge at 60 “C. The optimum nitrogen purge conditions developed enable much larger amounts of volatile hydrocarbons to be blown out of the reagent than are typically present in the various streams although the amount of vinylcyclohexene that can be dealt with successfully is lower than for other hydrocarbons.Dicyclopentadiene is not removed during the nitrogen purge operation because of its high boiling-point. Under the conditions of the method dicyclopentadiene breaks down to cyclopentadiene which reacts with hydrogen iodide to give iodine and with remaining dicyclopentadiene to give a dark brown polymer. If only small amounts of dicyclopentadiene are present no polymer is formed but iodine is Liberated iodine is titrated with 0.01 N sodium thiosulphate solution. 196 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [PYOC. SOC. Analyt. Chem. liberated. Interference by dicyclopentadiene can be overcome with acrylonitrile which reacts quantitatively with cyclopentadiene as it is formed under reflux to give a stable colour- less Diels - Alder adduct.Analyses before and after nitrogen purge by using butadiene poly- peroxide and the reactive peroxides present in a mixture of pent-1-ene and 3-methylbut-1-ene as typical of peroxides found in these streams confirmed that these were not removed by the purging operation. The method gives over 96 per cent. recovery of peroxides in the range 1 to 40 p.p.m of active oxygen and the repeatability on successive determinations is good. During a de- termination sample and blank must be kept in an inert atmosphere and this is conveniently done by using solid carbon dioxide. The method gives low consistent blanks and is par- ticularly suited to trace determinations. It can also be adapted to determine trace amounts of dicumyl peroxide.DETERMINATION OF PEROXIDES I N FINISHED-PRODUCT BUTA-1,3-DIENE APPARATUS- Several bubbler assemblies were constructed from 250-ml Quickfit flasks and bubbler units (QF Unit No. MF48/13/250) shortened in the stem so that the bulb of each bubbler rested 3 to 4 mm above the bottom of its 250-ml flask when the unit was correctly seated. Flasks were wrapped in aluminium foil and condensers in black tape to exclude light. REAGENTS- Lithium iodide - isooctanol reagent was prepared by stirring 60 g of lithium iodide monohydrate (Hopkin and Williams Ltd.) finely powdered in a pestle and mortar with 500 ml of isooctanol in a 1-litre tall-form beaker with a sharp-edged four-bladed stainless- steel stirrer. A slow stream of nitrogen was allowed to bubble through the liquid during this operation and dissolution of the solid normally took about 45 minutes.The reagent was stored in an amber bottle under a carbon dioxide atmosphere generated from a small piece of solid carbon dioxide. PROCEDURE- A few small pieces of solid carbon dioxide (10 to 15 g) were added to a flask wrapped in aluminium foil allowed to stand for about 1 minute then 60 ml of lithium iodide - isooctanol reagent were added from a measuring cylinder. The flask was allowed to stand for a further 2 minutes then 50 ml of liquid buta-1,3-diene were added with mixing from a cooled measuring cylinder. The bubbler unit was immediately inserted into the flask placed in a water-bath at 60 “C and nitrogen passed for 20 minutes a t a rate of 130 f 30 1 h-l.After this operation the bubbler unit was lifted clear of the neck of the flask whilst continuing to pass nitrogen. Nitrogen was passed for a further 1 minute to blow any residual solution from the sintered glass tip of the bubbler then a few small pieces of solid carbon dioxide (10 to 15 g) were added to the flask and the bubbler unit removed. The flask was taken out of the bath dried extra solid carbon dioxide added if necessary then 3.0 ml of 30 per cent. orthophosphoric acid solution added by pipette. The flask was then connected to a double-surface water condenser wrapped in black tape and refluxed for 30 minutes on a hot-plate. L4t the end of this period the flask was raised from the hot-plate by slipping a piece of “Syndanyo” board under it and 40 ml of isopropanol were poured down the condenser to stop the boiling and wash down the condenser.The flask was stoppered with a strip of paper placed down the side of the stopper to prevent sticking and cooled in an ice-bath for 10 minutes. The alu- minium foil was removed from the flask and the iodine titrated with 0.01 N sodium thio- sulphate solution shaking the flask vigorously as the end-point was approached. A blank determination was carried out simultaneously taking it through the same heating procedure as the sample but omitting the hydrocarbons. Peroxide oxygen (p.p.m) can be calculated from the formula 1000 1 (B-A) x 8 x 7 x wo September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 197 where A is the volume of 0.01 N sodium thiosulphate required by the blank; B is the volume of 0.01 N sodium thiosulphate required by the sample; and V is the volume of sample taken.DETERMINATION OF PEROXIDES IN C AND MIXED C - C STREAMS For these types of samples the nitrogen purge step must be carried out from 40 ml of isooctanol 60 ml of cooled lithium iodide - isooctanol reagent are then added directly after the purge operation. The remainder of the procedure as described above for finished-product buta-1,3-diene is followed except that 5 ml of acrylonitrile are added to sample and blank before addition of the orthophosphoric acid. The sample size must be chosen according to the dicyclopentadiene content- Dicyclopentadiene content (per cent.) . . 0 to 5 5 to 8 8 to 12 Sample size (ml) . . .. .. .. 50 30 20 The Determination of Free and Total Fluoride in Milk BY J. A. W. DALZIEL AND A.V. DANGI THE analysis of fluoride in milk at the 1.0 p.p.m. level has become important since many Public Health Authorities and the World Health Organisation have proposed the fluoridation of milk supplied to school children as a new vehicle for fluoridation for the prevention of dental caries.1 When fluoride is added to the milk some part of it remains in the free ionic state while the remainder becomes bound to the milk constituents. We have carried out studies on the binding of fluoride ion with the milk constituents viz. milk proteins sugars fats and inorganic ions such as calcium and magnesium. This shows that a significant amount of fluoride is bound to the milk proteins and only a small amount to the calcium and magnesium. The stability constants for the protein - fluoride calcium - fluoride and magnesium - fluoride systems have been determined.Fats and sugars do not show any tendency to bind fluoride. For the determination of total fluoride in milk therefore it is essential to desorb the bound fluoride from the complexing species and then measure the total fluoride in solution. A Willard - Winter distillation followed by a colorimetric finish2 has always been the method of choice. This method although accurate is time consuming and requires skilled attention. This paper describes a method for the determination of free and total fluoride in milk that does not involve ashing or distillation. The free fluoride in milk is measure directly with the fluoride ion selective electrode. The fluoride bound to the proteins is then desorbed from the proteins by the formation of an insoluble complex between a dye and the milk proteins.We have investigated several dyestuffs for this purpose and find that Amido Black 10B recovers virtually all the bound fluoride from the proteins. This dye forms a 1 + 1 insoluble complex with the milk proteins a t pH 2.0. An aliquot of the fluoridated milk sample is mixed with the dye solution which is prepared in 0.3 M citric acid. The protein - dye complex is separated by centrifuging and the clear solution is transferred into a polythene beaker. The pH of this solution is adjusted to 5.5 by the addition of sodium hydroxide solution. The formation of citrate at this pH masks all the calcium and magnesium in the solution. The total fluoride in the solution is then measured with the fluoride electrode.A replicate analysis of a fluoridated milk sample shows that recoveries of fluoride lie between 97 and 100 per cent. The method should be suitable for automatic analysis and the routine monitoring of fluoridated milk. Preliminary studies on this aspect show that up to 20 samples per hour can be analysed for the total fluoride content on a semi-automatic basis. (Depavtment of Chemistvy Chelsea College University of London Manresa Road London S . W.3) The method involved is as follows. REFERENCES 1. 2. “Fluoride and Human Health,” World Health Organisation Geneva 1970. Analytical Methods Committee Analyst 1944 69 243. 198 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. Determination of Trace Amounts of Metals in Soils by Ultramicro Atomic-absorption Spectrometry BY A.C. OBORNE AND T. S. WEST (Department of Chemistry Imperial College of Science and Technology London SW7 2A Y ) AN adequate supply of nutrient elements is essential for healthy crop and livestock gr0wth.l Trace amounts of elements are made available by the weathering of complex silicate minerals and from soil humus. The available trace element concentration is monitored by extraction with various solutions followed by analysis of the extract. Cobalt is a very important trace element and its deficiency in soils causes diseases in live~tock.~-~ It is commonly extracted with 2.5 per cent. acetic acid. The available cobalt content of soils is of the order to 0.1 to 2 p.p,m. of air-dry soil while the total cobalt content is usually 20 to 100 p.p.m. A concentration of greater than 0-3 p.p.m.of available cobalt is necessary for the support of healthy permanent grazing stock.5 Among the methods used to determine trace elements in the extract are ultraviolet - visible absorption spectrophoto- metry emission spectrography and flame-emission atomic-absorption and atomic-fluorescence spectroscopy. Absorption spectrophotometry can be used for most trace elements but the methods are rarely selective and separations and masking agents are often used to improve selectivity. Emission spectrography is often used for soil extracts. The trace elements are commonly precipitated with a mixture of 8-hydroxyquinoline tannic acid and thionalide with aluminium as a carrier and iron as an internal standard. A 500-fold concentration of the trace elements is usually achieved.The precipitate is ignited mixed with carbon powder and packed into an electrode. A d.c. arc is struck and the spectrum recorded.6 The use of flame-emission spectroscopy is usually confined to sodium potassium and calcium because of the limitations of flame-emission spectroscopy for elements that have their most useful lines below 320 to 340nm. Atomic-absorption spectroscopy is finding increasing use in determining elements in soil extracts e.g. the determination of “soluble copper’’ by Varju and Elek.’ Atomic-fluorescence spectroscopy offers the possibility of rapid and sensitive multi- element determinations in a manner not easily possible by atomic-absorption measurements but as a relatively new technique it has not yet been used extensively. 7 Soil Ca D44188 - D44189 2930 D44193 - D46402 5600 D46753 - D46755 855 TABLE I ANALYSES OF STANDARD SOILS Element,* p.p.m.on air-dry soil K 133 183 83 - - - p (as P205) ly; Fe Zn - 20 1.4 27 130 0-93 - - 0.36 60 2.3 51 0.24 - 1.4 - 0.18 40 3.9 11 180 0.30 - cu 7.3 22 1.5 1.2 2.7 2.3 7 Mn 11 11 16 30 78 49 * Cu and Mn were extracted with 0-05 M EDTA solution (EDTA at pH 7.0) ; the others were extracted with 2.5 per cent. acetic acid (pH 2.5). In our studies we have applied atomic-absorption spectroscopy with a carbon filament atom reservoir (CFAR) to the determination of available cobalt in soils. Soil extracts contain large excesses of phosphate magnesium calcium and potassium (Table I). These were found to produce a total suppression of the cobalt signal of 70 to 80 per cent. by using the CFAR. A reduction of this interference was sought through solvent extraction.A number of systems were examined and the extraction of cobalt as the Co(Py),(SCN) complex into isobutyl methyl ketone was finally c h ~ s e n . ~ This step also allowed a ten-fold pre-concen- tration to be made. REAGENTS- All reagents were of analytical-reagent grade. September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 199 APPARATUS- A Hilger Uvispek monochromator (quartz prism) was fitted with an EM1 6256B photo- multiplier and a Brandenburg 472R power supply was used to power the photomultiplier. A Techtron ASL high-intensity cobalt lamp was used as a source powered by a Jobin-Yvon HT supply and a Techtron secondary power supply; the lamp was run a t 18 mA primary current and 400 mA secondary current. The signal from the photomultiplier was amplified with a d.c.amplifierlo and then displayed on an SE Laboratories Type 3006 ultraviolet oscillograph. The optical arrangement was similar to that described by Jackson and West.ll The CFAR was powered by a Zenith “Variac” transformer (0 to 270 V output) via a Keston step-down transformer (maximum output approximately 100 A at 12 V). Clamping / screw Pillar / Gas box U Fig. 1. CFAR design The design of the CFAR is shown in Fig. 1. The filament was 3.2 mm in diameter and had an effective length of 1 cm. A notch 2 mm long by 1 mm deep was filed in the filament. A 3.2 mm diameter filament was necessary so as to provide a large enough area to support 5 p1 of isobutyl methyl ketone which because of its low surface tension could not be applied to a notch in the 2mm diameter filament used previously.The filament was shortened from 1 inch to 1 cm to increase the heating rate. Comparison of filaments made from Mor- ganite WWS Link and Johnson and Matthey Specpure graphite showed that the latter was superior because of its better grain structure. In use the filament unit was enclosed in a glass cell with a removable lid to allow easy sample application. Oxidation of the filament was thereby rendered negligible. Approximately 150 determinations can be made a t full power before the filament needs to be replaced. METHOD- Two grams of air-dry soil were shaken overnight with 80 ml of 2.5 per cent. acetic acid and the extract was filtered and diluted to 100ml. Additions of standard cobalt solution were made to aliquots of the soil extract and 2 ml of each of these solutions were added to a solution 12 per cent.in pyridine and 5 per cent. in potassium thiocyanate in a small screw-top 200 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. bottle. Then 200 p1 of isobutyl methyl ketone were added and the mixture was shaken for 2 minutes to effect extraction. The extraction of each of the three solutions used was carried out in duplicate. After shaking the solutions were allowed to stand for 45 minutes to equilibrate them after which they were centrifuged and analysed. The 240.7-nm cobalt resonance line was used for the analysis. All experimental para- meters were adjusted to give the best signals. A 5-pl volume of the organic extract was taken with a Marburg micro-pipette and placed in the notch of the carbon filament.The isobutyl methyl ketone evaporated off and the filament was raised to red-heat by applying 30 per cent. power for 5 s so as to destroy the complexes and remove pyridine which otherwise gave a scatter peak. After a short cooling period the sample was volatilised at maximum power. The absorption signal which has a rise time of about 100 ms was recorded on the ultraviolet recorder. Up to ten 5-pl samples can be taken easily from the organic layer but normally four aliquots were taken from each solution and the average absorbance was calculated. The average absorbance of each pair of duplicates was found. The concentration of cobalt in the extract was found from graphs of the type shown in Fig. 2. Cobalt in unknown solution p.p.m. Cobalt added p.p.rn. Fig. 2. Typical calibration graph ,4 blank was run to allow for cobalt contamination in the reagents.When this blank had been subtracted from the figure obtained from the calibration graph the soil concentration was calculated on the basis of the weight of air-dry soil taken. RESULTS- Two of them had concentrations near the upper and lower limits of soil concentrations and the third was in the middle range. Three soils were analysed as a preliminary test of the method. The results are summarised in Table 11. Soil D40365 was analysed only once so as to give an estimate of the feasibility of single analyses for screening purposes. The certainty was found to be better than &lo per cent. which would be adequate for screening purposes. The results compare f avourably with those obtained by emission spectrography.Further work is being carried out on other soil samples and the results obtained so far are encouraging in that soils of high and low cobalt content having widely different matrix compositions can be analysed with little difficulty We thank the Macaulay Institute for Soil Research for the provision of soil samples and the Agricultural Research Council for financial support for one of us (A.C.O.). September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY TABLE I1 ANALYSIS OF COBALT IN ACETIC ACID EXTRACTS OF SOIL Cobalt content p.p.m. A I 7 Soil Emission spectroscopy* CFAR D44188 1.1 (1.01 1.2 1.2 0.97) 1.1 D46753 0.18 (0.21 0.17 0.20) 0.19 D40365 0.56 0.51 * Figures supplied by the Macaulay Institute for Soil Research. 201 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.REFERENCES Nikitin A. A. Adv. Agron. 1954 6 183. Stewart J. Mitchell K. L. and Stewart A. B. Emp. J . Ex$. Agric. 1941 9 145. Mitchell R. L. Scott R. O. Stewart A. B. and Stewart J. Nature 1941 148 725. Stewart J. Mitchell R. L. and Stewart A. B. Emp. J . Exp. Agric. 1942 10 57. Mitchell R. L. Soil Sci. 1945 60 63. Mitchell R. L. and Scott R. O. J . Soc. Chem. Ind. 1947 66 330. Varjic M. E. and Elek E. Atomic Absorption Newsletter 1971 10 128. Dagnall R. M. Kirkbright G. F. West T. S. and Wood R. Analyt. Chem. 1971 43 1765. Forsythe J . H. W. Magee R. J. and Wilson C. L. Talanta 1958 1 249. Alger D. Anderson R. G. Maines I. S. and West T. S. Analytica Chim. Acta 1971 57 271. Jackson K. W. and West T. S. Ibid. 1972 59 187. Microwave-excited Detectors for Gas Chromatography BY R. M.DAGNALL AND P. WHITEHEAD (Department of Chemistry Imperial College of Science and Technology London S . W.7) MICROWAVE-EXCITED plasmas have been used as detectors in gas chromatography since 1965 and although their use has been limited they show many potentially interesting and useful properties. The detector used in this study consists of a narrow silica tube (about 15 cm long and 1 or 2 mm bore) connected to the outlet of the gas-chromatographic column through which the carrier gas flows (which at atmospheric pressure must be argon). Around the tube is mounted a microwave cavity connected to a microwave generator. A plasma can be main- tained in the tube by applying greater than about 30 W of microwave power from the generator. All compounds eluted from the column and entering the plasma are broken down into atomic or molecular species or both and emit characteristic electromagnetic radiation.The radiation is recorded via a monochromator a photomultiplier and a chart recorder. By careful choice of wavelength it is therefore possible to record radiation characteristic of an individual atom or molecular species. Furthermore measurements at more than one wavelength can be used to assist in the determination of empirical formulae. Microwave-excited plasmas can be operated at either atmospheric or reduced pressure. The advantage of reducing the pressure in the silica tube to about 10 torr is that helium can be used as the carrier gas. Helium plasmas give less background radiation and possess a higher excitation energy than argon plasmas. For these reasons the initial work on at- mospheric pressure plasmasl-3 was followed by s t u d i e ~ ~ - ~ that were concentrated on low- pressure systems in spite of the greater complexity of a vacuum system.For simplicity an atmospheric argon plasma is used in this study and an attempt has been made to develop a generally useful detector that is capable of high sensitivity and selectivity. Two modes of operation are described which can be used to give simultaneous selective and non-selective detection. The detector has also been used to determine the ratio of hetero-atoms present in the eluates. Of the three major emissions produced by all carbon compounds viz. C, CN and atomic carbon (5163,388 and 247.9 nm respectively) the last proved to be the most sensitive; the signal obtained was also relatively insensitive to slight microwave power variations when operated at about 70 W (the microwave power that gave the best signal to noise ratio).Atomic carbon emission was therefore used for the non-selective determination of organic compounds ; limits of detection of about The emission mode of operation was examined first. 202 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chew. 1 x 10-lo g s-l of carbon with a range of linearity of about 1000 were obtained. The detection limit depends on the charateristics of the photomultiplier - amplifier and monochromator system used. The noise was often limited by the photomultiplier dark current and the sensitivity was improved to g s-l of carbon by using a filter and solar-blind photo- multiplier (Hamamatsu R166). One other useful property of the atomic carbon emission observed in these studies is that for the wide range of simple organic compounds used (containing C1 Br I N S P and 0 atoms) the sensitivity was found to be directly proportional to the weight of carbon in the compound.Selective emissions have been found for compounds containing I Br S C1 and P as well as for W,O (306-4nm) and N (336nm). The intensity of the atomic emission due to I S and P was found to be proportional to the weight of the element in the original compound over a con- centration range of about 1000. The molecular emissions due to C1 and Br were found to be proportional to the square of the elemental concentration which is in agreement with theoretical prediction. The wavelengths used and the limits of detection obtained are shown in Table I together with the selectivities for the atomic emissions over carbon (given as the ratio of response to 1 gram-atom of the element to the response to 1 gram-atom of carbon).The selectivity of the emissive detector is one of its principal advantages. TABLE I SOME LIMITS OF DETECTION AND SELECTIVITY RATIOS Wavelength/ Element nm C 247.9 I 206-2 S 182.0 P 253.5 c1 256* Br 292* :> Band. Limit of detection/ Selectivity ratio g s-1 (with respect to carbon) 1.9 x 10-10 - 1.0 x 10-10 1000 4.0 x 460 3-0 x 150 4.5 x 10-9 2.5 x 1 0 - 9 However one limitation of this detector is that it can be overloaded and the plasma is usually extinguished by approximately milligram amounts of materials ; this imposes an upper limit on the working range of the detector. To avoid overloading the plasma solvents were back-flushed if they eluted after the compounds of interest or if the solvent was eluted before the plasma was not initiated until after the solvent had been eluted.Alternatively a system whereby the main stream by-passes the detector is possible. Most emissive detectors are selective but very few attempts have been made to measure the ratios of emissions for different hetero-atoms in order to determine their ratios in the original compound. This was investigated by using two monochromators mounted one on each side of the plasma so that two different wavelengths could be monitored simultaneously. For example one was set to monitor atomic carbon emission and the other to monitor atomic iodine emission. On the passage of an iodine compound the two peak heights were recorded and their ratio was plotted against the theoretical ratio in the original compound.For the range of different compounds used the result obtained was a straight line passing through the origin. The ratio of peak heights was independent of concentration and of carrier gas flow-rate. Similar results were obtained with the phosphorus and sulphur lines. Hence this method could be used to determine the ratio of C to I P or S in an eluate without any knowledge of the amounts injected. For diatomic emissions the ratio of the peak heights is linearly dependent on the con- centration injected; if the gradients of these results are plotted against the theoretical halogen to carbon ratio in a log - log plot a straight line is obtained with a gradient of 2. Although this can be used for ratio determination it is much less satisfactory than the use of atomic emissions.Another field in which the selectivity of the detector can be used is in the determination of metals as metal chelates by gas chromatography. The response of the detector to the trifluoroacetylacetonates of chromium aluminium scandium indium gallium iron copper Both possessed independent readout systems. September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 203 vanadium and manganese and the acetylacetonates of chromium aluminium and scandium has been investigated. TABLE I1 DETECTOR RESPONSE TO SELECTED ORGANIC COMPOUNDS Compound Acetone .. Diethyl ether . . Ethanol . . lsopropanol . . n-Propanol . . Toluene .. Ethyl iodide . . Carbon tetrachloride Chloroform . . n-Propyl bromide Methyl cyanide Thiophen ..Retention time/ Column* min .. P 2.96 . . P 3.25 .. P 1.92 .. P 3.93 .. P 5-66 * . c 2-91 .. c 0.92 . . c 1.25 .. c 1-05 .. c 0.90 .. c 0.33 .. c 1.30 Range of linearityf I ng s-1 2-1000 2-1000 2-1000 2-1000 2-1000 2-2000 6-6000 2-1 000 2-1000 2-1000 2-1000 2-1000 Limit of detection/ ng s-l 2-1 2.8 1.3 1.3 1.4 1.4 5.8 8.0 5.7 3.3 3.6 2.3 * P = l-m Porapak S column; C = 0.7-m Chromosorb 101 column. * Approximate values. Both columns were used a t 150 "C with an argon flow-rate of 3.6 1 h-I. The response of the detector to the atomic emissions of the various metals was found to be both sensitive and selective. The sensitivities in grams of element per second were generally less than 10-l1 and the selectivities over carbon compounds greater than 1000.One characteristic of this type of emission not shown by the other (wholly organic) compounds used in this study is that the emission is confined to the bottom 10 mm of the argon plasma; this is probably due to the metal plating out on to the walls of the silica tubing in this region. One possible disadvantage of an emissive detector of this type is that it cannot monitor non-selectively as well as selectively. Hence certain compounds could be missed com- pletely. Therefore a study was made of alternative ways of obtaining a response from the plasma to substances in the gas stream. A satisfactory method was found that involves the measurement of reflected microwave power. The experimental arrangement is the same as before with the addition of a reflected power meter between the microwave power supply and the cavity.The output of the meter is connected via a backing-off unit to a recorder hence providing a measure of the microwave power reflected back from the cavity. When an eluate passes through the plasma the microwave power is coupled more efficiently which gives a decrease in the reflected microwave power and hence a signal peak. This method of operation is totally independent of the emissive system and they can both be used simul- taneously under identical operating conditions. TABLE 111 DETECTOR RESPONSE TO A RANGE OF PERMANENT GASES Temperature/ Gas "C Column* Oxygen . . . . . . 25 M Nitrogen . . . . . . 25 M Helium . . .. . . 25 M Hydrogen . . . . . . 25 M Carbon monoxide . . . . 50 M Carbon dioxide . . . . 50 P Nitrous oxide . . . . 50 P Methane .. . . . . 50 P Ethylene . . .. .. 50 P Propylene . . .. .. 150 P n-Butylene . . . .. 150 P Retention time/ min 1.15 1.35 1.00 1.03 2.02 0.73 1.25 0.30 1.2 1 0.52 1.01 Limit of detection/ ng s-l 3.8 2.8 8-8 0.3 3.4 4.2 2.4 1.0 0.9 0 9 1.1 * M = 3-m molecular sieve column; P = l-m Porapak column. 204 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. The reflected-power detector responded to all the organic compounds and gases used in this study including oxygen nitrogen helium and hydrogen. Some limits of detection and ranges of linearity obtained are shown in Tables I1 and 111. Considerable further improvements are possible with this detector because the noise present in the system can be greatly reduced by better stabilisation of the microwave power supply and cavity.Microwave-excited detectors have been found to have considerable potential as practical and versatile detectors for gas chromatography providing sensitive simultaneous selective and non-selective response. Their major area of contribution may prove to be in elemental analysis prior to mass-spectrometric determination of structure. REFERENCES 1. McCormack J. Tong S. C. and Cooke W. D. Analyt. Chem. 1965 37 1470. 2. Bache C. A. and Lisk D. J. Ibid. 1965 37 1477. 3. -,- Ibid. 1966 38 783. 4. -,- Ibid. 1966 38 1757. 5. - ___ Ibid. 1967 39 786. 6. Moy; H. A. Ibid. 1967 39 1441. 7. Braun W. Peterson N. C. Bass A. M. and Kurylo M. J. J . Chromat. 1971 55 237. 8. Dagnall R. M. Deans D. R. Pratt S. J. and West T. S. Talanta 1969 16 797. 9. - Ibid. 1970 17 1009. Some Consequences of the “Auto” Degradation of Polystyrene-based Ion Exchangers BY G.M. ARMITAGE S. J. LYLE AND V. C. NAIR ( University Chemical Laboratory University of Kent at Canterbury Canterbury Kent) POLYSTYRENE-BASED ion exchangers of high quality and from different manufacturers undergo degradation to form water-soluble organic fragments. The vulnerability to de- composition is a function of the degree of crosslinking. The infrared spectra of the fragments obtained have the essential features of the “pure” resin spectra.l With a cation exchanger sulphur analyses of the residues in conjunction with cryoscopic measurements allow an estimate to be made of the residue fragment number-average molecular weight and it is demonstrable that the fragment size is appreciably influenced by the degree of crosslinking (Armitage G.M. Lyle S. J. and Slade M. unpublished results). Mass spectroscopic studies and determinations of the distributions of trace metal ions throw light on the effect of this degradation on the remaining washed ion-exchanger bead; the mass spectra and distri- bution results can be explained in terms of resin oxidation with the introduction of carboxyl groups on the resin matrix. Attention is drawn to the implications for water de-ionisation and the isolation of selected ionic species. Mass spectra of a number of sulphonic acid cation exchangers based on polystyrene crosslinked with divinylbenzene were obtained on an MS 902 mass spectrometer in the m/e range 10 to 300 at a resolution of 2500. Both the source and probe were normally at 160 “C. The effect of crosslinking (percentage of divinylbenzene) and the mode of pre-conditioning of the resins were examined.The most prominent peaks and their assignations (in parentheses) are as follows m/e = 17 (OH) ; 18 (H,O) ; 28 (doublet N < CO) ; 44 (CO,) ; 45 (C,H,O) 48 (SO); and 64 (SO,). Isotope peaks due to 34S in the correct height ratio appear at m/e = 50 and 66. With unconditioned resins taken directly from the shelf and dried at 80 “C the effect of an increase in crosslinking was a steady reduction in the peaks at m/e = 28 and 64. Similar trends were not noted in the other peaks. If the resins were converted to the H-form with 2 M hydrochloric acid washed with distilled water and vacuum-dried at room temperature over phosphorus pentoxide and the spectra taken immediately all the peaks were considerably reduced with only those a t m/e = 17 and 18 remaining prominent.If the resins were con- ditioned and left for a time before the spectra were taken however the peaks all became prominent again. By means of suitably designed control experiments the peak at rn/e = 44 was attributed with considerable certainty to the existence of carboxyl groups on the resin matrix. Because anion exchangers take up carbon dioxide readily it was not possible to obtain unequivocal mass spectra of these substances at mass 44. The time scales suggested that the process of degradation was rapid. September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 205 The uptake of cations for example 144Ce(III) or 8gSr(II) as “carrier-free” isotopes by a sulphonic acid cation exchanger is pH-dependent at constant ionic strength despite the fact that the sul- phonic acid groups are fully ionised over the pH range in question.This pH dependence is greatly reduced as the total metal concentration is raised confirming that the additional capacity conferred by the carboxyl sites is very low. Although glass polyethylene and polypropylene surfaces exhibit a pH-dependent adsorption of hydrolysible metal ions the adsorption is negligible compared with that by the resin and occurs at a higher pH. Di- vinylbenzene-crosslinked polystyrene beads behave in a manner similar to the sulphonic acid cation exchanger except that the overall distribution is reduced owing to the absence of sulphonic acid groups. A similar dependence on pH and metal concentration is noted in the distribution of 144Ce(TTI) and other metal cations between a crosslinked polystyrene anion exchanger and an aqueous phase.The mass spectrometric investigation provides a qualitative estimation of the age and the level of decomposition of stored samples of resin. It permits an estimate to be made of the efficacy of cleaning and conditioning of a resin and it also provides a potential method by variation of the probe temperature of examining aspects of the thermal stability of ion- exchange resins. Analytical methods that depend on the distribution of trace cations between an aqueous and a resin phase are likely to be effected by this secondary exchange behaviour. The elution of “carrier-free” metals from a crosslinked polystyrene sulphonic acid cation exchanger by solutions of pH > 4 is likely to bring this secondary exchange into play.It is then to be expected that elution peak positions will depend on trace metal con- centrations even at constant ionic strength as carboxyl groups will retain metal species more firmly than sulphonate groups. In the determination of stability constants by the ion-exchange method when a “carrier-free” cation may exhibit2 a pH-dependent distribution between the aqueous phase and the resin the assumption that the distribution ratio is in- dependent of pH will lead to error unless appreciable “carrier” is added to the solution. The resin fragmentation may have to be taken into account to avoid interference in the de- termination of a component separated by ion e~change.~,~ The existence of “leached” degradation products explains why mixed (anion and cation) exchange beds are more efficient than separate beds for the de-ionisation of water (Armitage G.M. Lyle S. J. and Slade M. unpublished results). REFERENCES The interpretation presented is supported by distribution experiments. 1. 2. 3. 4. Lyle S. J. and Sani A. R. Analytica Chim. Acta 1965 33 619. Aziz A. and Lyle S. J. J . Inorg. Nucl. Chem. 1969 31 2431. Samuelson O. “Ion Exchange Separations in Analytical Chemistry,” John Wiley New York Mizuike A. in Morrison G. H. Editor “Trace Analysis-Physical Methods,” Interscience New 1963 p. 149. York 1965 p. 148. Mutual Interferences Between the Atomic-absorption Determination of Calcium and Some Other Elements BY A. HARRISON AND J. M. OTTAWAY (Departmepit of Pure and Aflplied Chemistry University of Strathclyde Cathedral Street Glasgow G1 1XL) THE determination of calcium in a wide range of materials is now carried out by atomic- absorption spectrometry.Although many chemical interferences in the atomic-absorption determination of calcium have been reported (see for example references 1 to 3) no syste- matic study of these phenomena has been carried out. The authors described a compre- hensive comparative study of interferences carried out with a Perkin-Elmer 290 atomic- absorption spectrophotometer with an air - acetylene flame burning on a 5-cm single-slot cylindrical burner. Classification into five different types of interference (Table I) was based on the effect of increasing concentration of interferent on the signal from 10 p.p.m of calcium (in sulphate medium) a t an optical path height 11 mm above the top of the burner.In some instances enhancement (+) occurs in others depression (-) whilst in classes A and E both effects occur at different concentrations of interferent. 206 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. SOC. AnaZyt. Chem. TABLE I CLASSIFICATION OF INTERFERENCES IN THE ATOMIC- ABSORPTION SPECTROMETRY OF CALCIUM Group A B C D E Form of interference (&) us. concentration of interfering element Element Cerium( IV) Lanthanum( I1 I) Yttrium(II1) Iron (I I I) Chromium(I1 I) Magnesium hlolybdenum(V1) Thorium(1V) Neodymium(II1) Praseodymium( 111) ~~ Zinc Cadmium(I1) Mercury (I I) Selenium(V1) Tellurium (VI) Ammonium ion Silver(1) Thallium(1) Lithium Sodium Potassium Rubidium Caesium Arsenic(II1) Bismuth( 111) Titanium( IV) Uranium(1V) Tungsten(V1) Vanadium( IV) Zirconium( IV) Aluminium( 111) Niobium (V) Copper( 11) Rhodium( 111) Rhenium(VI1) Cobalt(I1) Indium( 111) Iridium( 111) Manganese (11) Antimony(II1) Ruthenium( 111) Nickel (11) Gold (111) Tin(1I) Germanium( IV) Gallium( I I I) Platinum(1V) Palladium( I I) Effect of adding potassium No effect No effect Interference removed Interference removed - No effect Interference reduced No effect - Interference reduced Interference removed Interference removed No effect Interference reduced - - Interference removed Interference removed Interference reduced Interference removed Interference removed - - - - Interference reduced - - - Interference removed Interference removed Interference removed A study of mutual interferences under comparable flame conditions showed that in most instances an interference on calcium was accompanied by an interference by calcium on the second element.In none of the examples studied which were representative of all the groups (except Group C whose elements could not be determined in an air - acetylene flame) were calcium and second-element signals mutually depressed which suggested that compound formation was an unlikely cause of the interferences. It was found that the addition of a third element could sometimes inhibit the interference September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY 207 of the second element. Many elements appeared to possess this property and hence non- specificity in the releasing mechanism was implied. The alkali metals were effective in many instances and their effect on the mutual interference of calcium and chromium is shown in Fig.1. It can be seen that both the enhancement of calcium and the depression of chromium were effectively quenched by the alkali metals and the concentration required for complete removal is proportional to l/(ionic radus) for each alkali metal. The effect of potassium which was taken as typical on the main classes of interference is shown in Table I. Studies on the alteration of flame composition and optical path height showed that inter- ferences were reduced in high positions under lean-flame conditions. To investigate this effect in more detail the flame was scanned up its height in small increments while the con- centrations of atomic and selected molecular species were monitored across the full working range of flame compositions by absorption and flame emission respectively.This technique gave rise to “isoabsorptiograms” in which similar atomic and molecular densities were en- closed by contours thus mapping out the whole flame. To reduce the rather broad beam from the hollow-cathode lamp two parallel metal plates each with a 1-mm horizontal slit were fitted to the instrument on either side of the flame. When aligned these plates allowed 1-mm sections of the flame to be scanned while lowering of the burner head allowed successive sections of the flame to be examined. T I I t Fig. 1. Effect of alkali metals on the mutual interference of calcium and chromium. Molar ratio of calcium to chromium is 2 1 The use of this technique showed the following- (1) The isoabsorptiogram of ground-state calcium atoms always showed a pronounced ridge of maximum absorbance running diagonally from low to high optical path height as the flame became more fuel-rich.The position of this ridge and the general pattern were found even in the presence of interfering elements although the relative absorbances were raised or 1 owered for enhancement or depression respectively. The emission of C species which was taken as an example of flame radicals showed an extremely pronounced maximum very low in the flame and showed that in a rich flame radicals persist much higher than in a lean flame. (2) (3) (4) (5) Excited calcium atoms maximise moderately high in the flame. Ca+ maximised in the lean flame and always at higher positions than calcium atoms. The emission from CaOH maximised much higher in the flame than calcium atoms.208 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY [Proc. Soc. Analyt. Chem. It appears that it is extremely unlikely that ionisation of calcium plays a large r61e in interference as ions are formed after atoms and also oxide species appear to be formed after calcium atoms so that free atoms cannot be formed via oxide molecules. Maximum calcium atoms appear just after C has disappeared and excited calcium atoms reach a maximum after calcium ground-state atoms. Fig. 2 shows these findings in summary form. Fuel lean =- Fuel rich Fig. 2. Absorptiogram obtained a t various optical path heights and with different flame composi- tions It appears likely that the breakdown of the solid clot is an important factor in the formation of atoms in the flame at least at the lower levels and that the breakdown of the clot takes place by interaction with radicals such as C, CH and H.A possible breakdown sequence might be C, CH Ha Ca*b O,/H,O Solution + Solid matrix Ca atoms<- CaOH so that the nature of the matrix is important and controls the extent of atomisation at any particular position in the flame. As the droplets dry out to form clotlets in the flame some association of the components occurs possibly with the formation at some point of bonding groups of the type -M-0-Ca-0-M- The fact that some elements enhance calcium a t lower concentrations may be due to the flame radicals breaking calcium from the clotlet surface more easily owing to the difference in the bond strengths of -CaO and -MO. At higher concentrations of interferent the amount of calcium a t the surface is reduced as the matrix is composed mainly of interfering atoms so that it is more difficult for radicals to react with calcium and hence the signal is depressed.The effect of adding a third element under these circumstances would be largely that of a matrix buffer that is it operates by preventing interaction between calcium and in- terfering element by physical separation in the condensed phase. The alkali metals are relatively volatile and volatilise in the flame thus leaving the other elements as separate entities. In the study of the calcium - chromium system the molecular metal oxide species were measured by flame emission. During the initial enhancement of calcium by chromium CaOH is also enhanced while the chromium atoms and CrO are both depressed. The presence etc.C a + p September 19721 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY 209 of chromium allows more calcium atoms to be removed from the matrix which gives rise to an increase in CaOH as this has been shown to be produced from calcium atoms. During this time the concentration of chromium atoms is depressed and the preferential splitting of calcium leaves CrO which is more firmly held in the matrix and hence both chromium atoms and CrO are depressed. As the chromium concentration is increased more chromium atoms are released into the flame which makes possible the reaction thus accounting for the subsequent decrease in CaOH with continuing enhancement of calcium and depression of chromium atom matched by an increase in CrO. The results obtained supported this hypothesis. CaOH + Cr -+ Ca + CrO REFERENCES 1 .2. 3. Kamaltrishna T. V. Robinson J . W. and West P. !I,. Analytica Chinz. Acta 1966 36 57. Nocchiccioli C. and Townshend A. Ibid. 1968 41 93. ltubeska I. and Moldan B. Ibid. 1967 37 421. Spectrophotometric Study of the Acid - Base Equilibria of the 1,4-Benzodiazepines BY I. E. DAVIDSON AND W. FRANKLIN SMYTH (Ilepavtnzent of Chemistry Chelsea College University of London -2Innresa Road London S . W. 3) THE 1,4-benzodiazepines are a group of compounds used as hypnotic tranquillisers. Knowledge of the structures of these drug species is of great importance in determining the degree to which they are absorbed by body organs and how they permeate cell membranes. 'To this end pK values of six of these compounds namelv diazepam chlordiazepoxide niedazepam oxazepam nitrazepam and lorazepam were determined by studying the variation of their ultraviolet spectra over the pH range 0 to 14 at a concentration of approximately 5 x lW5 XI.In addition to the pharmacological value of pK data such information is necessary for the determination of suitable pH ranges over which these species can be extracted from biological fluids. NHCH3 H CI I Fig. 1. Structures of six therapeutically important l,&bcnzodiazepincs (a) d i - azepam ; (b) oxazepam ; (c) chlordiazepoxide ; ( d ) nitrazcpani ; ( e ) medazepani ; and (f) lorazepam 210 RESEARCH TOPICS IX ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. The substances are ampho- lytes i.e. they can accept or donate protons. Study of the acid - base behaviour by ultra- violet spectroscopy can lead to postulation as to possible sites of protonation and deprotonation.Approximately M solutions of each compound in AnalaR methanol were prepared and stored under cold conditions as a precaution against possible decomposition. A stock Britton Robinson buffer solution composed of a mixture of 0.04 M boric acid 0.04 M phosphoric acid and 0.04 M acetic acid was prepared which had a pH of just over 2.0. Solutions of known pH were prepared from this solution by adding known amounts of 0.1 N sodium hydroxide solution and measuring the pH on a meter. Experimental solutions were prepared by diluting the appropriate amount of stock benzodiazepine solution with the appropriate buffer to give a drug concentration of 5 x M To extend the pH range studied a t either end of the scale 1 N and 0.1 N hydrochloric acid and 0.1 N and 1 N sodium hydroxide solutions were used.The range from about pH 1 to 13 was scanned for each drug in increments of 1 pH unit to initially determine the approximate position of each pKa value by observation of spectral changes over the whole range. The region around each pKa value was then studied in more detail by using buffers in increments of 0.3 pH units. From the spectra obtained pKa values could be determined using the Henderson - Hasselbalch equation. The wavelength range over which the spectra were scanned was from 200 to 390 nm. The instrument used was a Perkin-Elmer double-beam 137 ultraviolet - visible spectro- photometer operating at a slow scan speed of 8 minutes for the range 200 to 390 nm. Matched l-cm silica cells were used and the reference beam contained a blank of buffer solution con- taining the same amount of methanol as the samples.Nitrogen was flushed through the instrument throughout the operation so as to eliminate possible oxygen absorption at about 210 nm. Structures of six compounds studied are shown in Fig. 1. Wavelength/nm pH dependence of ultraviolet spectra of 2.5 x 10-5 ar solutions of oxazepain in sulphuric acid solutions and Britton Robinson buffers 1 pH 0.40; 2 1.25; 3 1.90; 4 2 - 2 0 ; 5 2.30; 6 2.40; 7 2-55; 8 2.70; 9 3-35; and 10 4.10 Fig. 2. Assuming protonation of each compound in acidic media the existence of an unchanged molecule in neutral solution and deprotonation in basic media the Henderson - Hasselbalch equation could be used to obtain pKa values. Consider the loss of a proton from a neutral molecule- HA = [H+] + [A-] September 19721 RESEARCH TOPICS I N ANALYTICAL CHEMISTR’I‘ -4n equilibrium exists with a constant Ka given by 1.0- 21 1 Therefore which is the Henderson - Hasselbalch equation.By plotting the absorbance of species A- (which if Beer’s law holds is proportional to the molar concentration of A-) we obtain a graph the point of inflexion of which gives the required pK value. Similar reasoning applies to protonation of a neutral molecule. 0.0 Y5 1-4 I I I 1 I I I 1 200 250 300 350 1.2 Wavelengt h/n m Fig. 3. pH dependence of ultraviolet spectra of 2-8 x 10-5 &I solutions of oxazepani in Britton Robinson buffers 1 pH 8-90; 2 9-70; 3 10.10; 4 10-60; 5 11.30; 6 11.60; 7 11.90; 8 12.10; 9 12.20; and 10 12-50 Figs. 2 and 3 show spectral changes for oxazepam in acidic and basic media.For the six compounds studied three namely diazepam medazapani and chlordiaz- epoxide were found to exhibit one pKa value while nitrazepam oxazepam and lorazepam each had two values. All six drugs could be shown to undergo protonation in acid but only nitrazepam oxazepam and lorazepam underwent deprotonation in alkaline media. Such differences in behaviour and the structures of the various drugs existing in certain pH ranges critical from physiological and solvent extraction viewpoints can be explained on the basis of theoretical calculation of the absorption spectrum and mesomeric considerations. The authors acknowledge the co-operation of Dr. J. Goldsmith John Wyeth and Brother Ltd. Taplow Berkshire for providing oxazepam and lorazepam and Dr. D. M. Hailey Roche Products Ltd. Roche Research Unit University of Liverpool for providing nitrazepam diazepam chlordiazepoxide and medazepam.

ISSN:0037-9697    

DOI:10.1039/SA9720900182

出版商:RSC    

年代:1972

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212 THE CHEMICAL SOCIETY’S LIBRARY [Pvoc. SOC. AgzaZyt. Chetn. The Chemical Society’s Library THE following publications of analytical interest have been added to the Library since the last list appeared in Proceedings (1972 9 141). THE DETERMINATION OF IONIZATION CONSTANTS. A LABORATORY >lr\NUAL. gild Edition. 11. ALUERT and E. P. SERJEANT. Chapman and Hall. 1971. Society. 1971. Chemical Society. 1071. ,IIncrican Society €or Testing and Materials. JIETHODS FOR EMISSION SPECTROCIIEMICAL ANALYSIS. JIaterials. 1971. THE RAMAN EFFECT. Volume 1. Edited by A. ANDERSON. Marcel Dekker. 1071. ELECTRON PROBE MICROANALYSIS. 2nd Edition. L. S. BIRKS. Wiley-Interscience. 1071. PHOTOCHROMISM. Edited by G. H. BROWN. Wilcy-Interscience. 1971. SELECTED CONSTANTS OXIDATION - REDUCTION POTENTIALS OF INORGANIC SUBST~YNCES I N AQUEOUS Suarhf ER SCHOOL IN hlAss SPECTROMETRY.University of Sheffieltl 1072. Chemical Society. 1972. SUMMER SCHOOL IN PHOTOELECTRON SPECTROSCOPY. University College of Swansea 1972. Chemical RIOLECULAR SIEVE ZEOLITES. -American Chemical PESTICIDES IDENTIFICATION AT THE RESIDUE LEVEL. ADVANCES IN CHEMISTRY SERIES No. 104. American ADVANCES IN CHEMISTRY SERII<S Nos. 101 AND 102. COMPILATION OF GAS CHROMATOGRAPHIC DATA. Supplement 1 . Edited by 0. E. SCIIUPP and J . s. LEWIS. 197 1 . 6th Edition. .~nicrican society for Testing and SOLUTION. G. CHARLOT et al. Butterworths. 1971. Society. 1972. I. U.P. A.C. 3RD CONFERINTE y.kTION.\LE DE CHIA.IIE ANALITICA BR.\SOV ROMANIA 22-26 SEPT. 107 1. 4 VOlUmeS. A PROGRAXIMED INTRODUCTION TO INFRARED SPECTROSCOPY. B. \v.cOOI< and K. JONES. Heyden. 1972. CHEMICAL ANALYSIS OF ADDITIVES IN PLASTICS. T. I<. CRORIPTON. Pergamon Press. 1971. RECENT ADVANCES I N GAS CHROMATOGRAPHY. Edited b y I. I. DOMSKY and J . A. PERRY. Marcel Dekker. ADVAKCES IN MASS SPECTROMETRY. Volume 6. Edited by A. QUAYLE. Institute of I’ctroleum Hydro- 1971. carbon Research Group Conference Brussels 1070. Institute of Petroleum. 107 1 . SELECTIVE ION SENSITIVE ELECTRODES. G. J . MOODY and J. D. R. THOMAS. Merrow Publishing Co. 1071. September 19721 PUBLICATIONS RECEIVED 213 STRUCTURES 3tECHANISMS AND SPECTROSCOPY 120 PROBLEMS 60 SOLUTIONS FOR THE ORGANIC CHEMIST. J. C. MAIRE and B. WAEGELL. Gordon & Breach. 1971. DETERMINATION OF ORGANIC STRUCTURES BY PHYSICAL METHODS. Edited by I?. C. NACHOD and J. J. ZUCKERMAN.Academic Press. 1971. RECENT TOPICS I N MASS SPECTROMETRY. NATO Advanced Study Institute of Mass Spectrometry Lisbon 1969. Gordon & Breach. 1971. THE DETERMINATION OF IMPURITIES IN NUCLEAR GRADE SODIVM METAL. L. SILVERMAN. Pergamon Press. 1971. SAFETY IN THE CHEMICAL LABORATORY. Volume 2. Edited by N. V. STEERE. A.C.S. Division of Chemical Education. 1971. by H. G. STRUPPE. Akademie Verlag. 1971. NEW YORK 1971. Edited by IRWIN J . GRUVERMAN. Plenum Press. 1971. IVITZ. Hertillon Press. 1971. Volumes 3 and 4. k!SPECTS I N GAS CHROMATOGRAPHY. 6TH SYMPOSIUM ON GAS CHROMATOGRAPHY BERLIN 1968. Edited h~OSSBAUER EFFECT METHODOLOGY. VOlUme 7. 7TH SYMPOSIUM ON R’IOSSBAUER EFFECT METHODOLOGY A SYSTEMATIC APPROACH TO THE INTERPRETATION OF INFRARED SPECTRA. 2nd Edition. LASER RAMAN SPECTROSCOPY. M. C. TOBIN. Wiley-Interscience. 1971. H. A. SZYXI.\NO- PERIODICAL Nuclear Magnetic Resonance. A Specialist Periodical Report. 1072. Volume 1.

ISSN:0037-9697    

DOI:10.1039/SA972090212b

出版商:RSC    

年代:1972

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September 19721 PUBLICATIONS RECEIVED 213 Publications Received The publications listed below have been received by the Editor of The Analyst in which journal Book Reviews will continue to appear. BASIC INFRARED SPECTROSCOPY. By J. H. VAN DER MAAS. Second Edition. Pp. x + 109. London New York and Rheine Heyden & Sons Ltd. 1972. Price A1.25; $3.75; DM11.25. ANALYTICAL ATOMIC ABSORPTION SPECTROMETRY. By W. J. PRICE. Pp. xii + 239. London Sew York and Rheine Heyden & Son Ltd. DMS WORKING ATLAS OF INFRARED SPECTROSCOPY (DMS ARBEITSATLAS DER INFRAROT-SPEKTRO- SKOPIE). (Bilingual). Compiled by NORMAN A. J. LUFF. Pp. vi + 327; Loose-leaf. London Butterworths. Weinheim Verlag Chemie. 1972. Price A7. Editor-in-Chief J . P. REDFERN. Volume 1 Issue 1 May 1972. Pp. 191; Loose-leaf. London Rheine and New York Heyden and Son Ltd.1972. Price L40; $98 per annum including binder and cumulative subject index. SELECTED MEASUREMENT METHODS FOR PLUTONIUM AND URANIUM IN THE NUCLEAR FUEL CYCLE. Edited by CLEMENT J. RODDEN. Second Edition. Pp. xvi + 440. Office of Information Services U.S. Atomic Energy Commission 1972. Price $6. STATISTICAL METHODS IN RESEARCH AND PRODUCTION WITH SPECIAL REFERENCE TO THE CHEMICAL INDUSTRY. Edited by OWEN L. DAVIES and PETER L. GOLDSMITH. Fourth Revised Edition. Pp. xiv + 478. Edinburgh Oliver and Boyd for Imperial Chemical Industries Limited. 1972. Price ,S5. AUSGEWAHLTE METHODEN DER WASSERUNTERSUCHUNG. Band 11. BIOLOGISCHE MIKROBIO- LOGISCHE UND TOXIKOLOGISCKE METHODEN. Edited by G. BREITIG and W. VON TUMPLING. Pp. 128; Loose-leaf. Jena VEB Gustav Fischer Verlag. 1972. Price DM19. GOLDSMITH. Second Edition. Chemical Analysis A Series of MonogmpJzs on Analytical Chemistry and its Applications Volume 12. New York London Sydney and Toronto Wiley-Interscience. 1972. Price LlO.80. THE EXTRA PHARMACOPOEIA (MARTINDALE). Twenty-sixth Edition. Edited by NORMAN W. BLACOW. Pp. xxvi + 2320. London Pharmaceutical Press. 1972. Price L14. SPECTRAL DATA AIKD PHYSICAL CONSTANTS OF ALKALOIDS. Volume VII. By J16i HOLUBEK. Pp. 25 + cards 801-900. Prague Academia Publishing House of the Czechoslovak Academy of Sciences. London Heyden & Son Ltd. 1972. Price u/10.40. 1972. Price L5.80; $15.25; DM62. THERMAL ANALYSIS ABSTRACTS. A New Journal. Lieferungen 1 und 2. SYSTEMATIC ANALYSIS OF SURFACE-ACTIVE AGENTS. By MILTON J. ROSEN and HEXRY L\. Pp. xxviii + 591.

ISSN:0037-9697    

DOI:10.1039/SA9720900213

出版商:RSC    

年代:1972

数据来源: RSC

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214 REPORTS OF THE ANALYTICAL METHODS COMMITTEE [Proc. SOC. Analyt. Chem. REPORTS OF THE ANALYTICAL METHODS COMMITTEE The Reports of the Analytical Methods Committee listed below may be obtained direct from The Society for Analytical Chemistry Book Department 9/10 Savile Row London W1X 1AF (not through Trade Agents) a t the price of lop. to members of the Society and 15p. to non-members. Remittances must accompany orders and be made payable to “Society for Analytical Chemistry.” Additives in Animal Feeding Stuffs Sub-Committee Certain Reports published before 1946 have been omitted from this list but are still available. Report of the Antibiotics Panel The Determination of Penicillin Chlortetracycline and Oxytetracycline Report of the Hormones Panel The Determination of Stilboestrol and Hexoestrol in Compound Report of the Prophylactics Panel The Determination of Nitrofurazone in Compound Feeding Stuffs.Report of the Vitamins (Water-soluble) Panel The Determination of Water-soluble Vitamins ir Report of the Vitamins (Fat-soluble) Panel The Determination of Fat-soluble Vitamins in Diet Report of the Prophylactics in Animal Feeds Sub-committee The Determination of A4mprolium in Report of the Prophylactics in Animal Feeds Sub-committee The Determination of Sulphaquinoxaline. Report of the Prophylactics in Animal Feeds Sub-committee The Determination of Acinitrazole. Report of the Prophylactics in Animal Feeds Sub-committee The Determination of Ethopabate in Report of the Prophylactics in Animal Feeds Sub-committee The Determination of Furazolidone lieport of the Prophylactics in Animal Feeds Sub-committee The Determination of Dimetridazole in Report of the Prophylactics in Animal Feeds Sub-committee The Determination of Dinitolmide Report of the Prophylactics in Animal Feeds Sub-committee The Determination of Amprolium Report of the Prophylactics in Animal Feeds Sub-committee The Determination of Carbarsone in in Diet Supplements and Compound Feeding Stuffs.Feeding Stuffs. Compound Feeding Stuffs. Supplements and Compound Feeding Stuffs. Animal Feeding Stuffs. Feeds. in Feeds. Animal Feeds Revised Method. (Zoalene) in Animal Feeds. Sulphaquinoxaline and Ethopabate when Present Together in Animal Feeds. Animal Feeds. Analytical Standards Sub-committee Sodium Carbonate as a Primary Standard in Acid - Base Titrimetry. Sulphamic Acid as a Primary Standard in Acid - Base Titrimetry.Report No. 15. Application of Gas - Liquid Chromatography to Essential-oil Analysis Interim Report on the Spectral Characteristics of Eugenol. Application of Gas - Liquid Chromatography to the Analysis of Essential Oils. Essential Oils Sub-committee Determination of Linalol in Essential Oils. Determination of Citronellol in Admixture with Geraniol. Part 1 Determination of Cedrol. Fish Products Sub-committee Nitrogen Factor for Cod Flesh. Nitrogen Factor for Coal Fish. Analysis of Meat Extract. Determination of Gelatin in Meat Extract and Meat Stocks Interim Report. Nitrogen Factors for Pork and Nitrogen Content of Rusk Filler (as one reprint). Nitrogen Factors for Beef. Nitrogen Factors for Chicken. Nitrogen Factors for Liver.Nitrogen Factor for Veal. Nitrogen Factors for Turkey. Nitrogen Content of Rusk Filler. Methods for the Destruction of Organic Matter. Notes on Perchloric Acid and its Handling in Analytical Work. The Determination of Lead. The Determination of Small Amounts of Arsenic in Organic Matter. The Determination of Small Amounts of Copper in Organic Matter. The Determination of Small Amounts of Mercury in Organic Matter. The Determination of Small Amounts of Tin in Organic Matter. The Determination of Small Amounts of Zinc in Organic Matter. The Use of 50 per cent. Hydrogen Peroxide for the Destruction of Organic Matter. The Determination of Small Amounts of Tin in Organic Matter. The Determination of Small Amounts of Cadmium in Organic Matter. The Determination of Small Amounts of Copper in Organic Matter by Atomic-absorption Spectroscopy. Meat Products Sub-committee (formerly Meat Extract Sub-committee) Nitrogen Factor for Kidney. Nitrogen Factor for Tongue. Nitrogen Factor for Barley. Nitrogen Factor for Blood. Metallic Impurities in Organic Matter Sub-committee Part 1. Amounts of Tin up to 30 pg. Part 2. Amounts of Tin from 30 to 150 pg.

ISSN:0037-9697    

DOI:10.1039/SA9720900214

出版商:RSC    

年代:1972

数据来源: RSC