摘要:

Proceedings of the Society for Analytical Chemistry Analytical Division Chemical Society Proc. SOC. Analyt. Chem. Vol. 9 No. 6 Pages 123-144 CONTENTS Reports of Meetings . . . . 123 Analytical Methods Committee I24 Particle Size Analysis Group.. 127 Summaries of Papers “Nuclear and Electron Magnetic Resonance in Analytical Chemistry” .. .. 128 “Inorganic Gas Analysis by Gas Chromatography . . .. 137 Notices .. .. .. .. 141 The Chemical Society’s Library 141 Papers Accepted for The Analyst 142 Publications Received . . .. 143 Forthcoming Meetings Back Cover June 1972 PAYCAL Vol. 9 No. 6 ~ Members may buy personal copizs a t tha special price o f5.00 June 1972 PROCE ED1 N GS 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 PI rsidefit C.Whailey Hon. Tr2asurer H m . 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. A t t r i l l Assistant Editor P. C. Weston Proceedings i s 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 SELECTED ANNUAL REVIEWS OF THE ANALYTICAL SCIENCES Volume I - 1971 CONTENTS Molecular-sieve Chromatography - D. M. W. Anderson I. C. M. Dea and A. Hendrie Photoluminescence and Chemiluminescence i n Inorganic Analysis - L. S. Bark and P. R. Wood Recent Developments i n Activation Analysis - T. B. Pierce (A.E.R.E. Harwell) Atomic Absorption Spectroscopy - P. Platt (Colgate-Palmolive Ltd. Salford) Catalytic Methods i n Analytical Chemistry - G. Svehla (Queen’s University Belfast) (Edinburgh University) (University of Salford) 269 pages €5.00 Obtainable from- The Society for Analytical Chemistry Book Department 9/10 Savile Row London W I X IAF

ISSN:0037-9697    

DOI:10.1039/SA97209FX021

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY Forthcoming Meetings-continued fvorn back covey June-continued Tuesday 27th SALFORD NORTH WEST REGION AUTOMATIC METHODS and ELECTROAXALYTICAL GROUPS “Water-insoluble Enzymes,” by Professor S. ,4. Barker. “Enzyme Electrodes,” by B. Fleet. “Use of Enzynies in Automatic Analysis,” by D. B. Roodyn. “Trace Analysis by Enzyme Inhibition and Activation,” by A. Toumhend. Room 918 Maxwell Building The University Salford; 11.15 a.m. on “The Use of Enzymes in Analysis.” SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY Forthcoming Meetings June Wednesday 21st SCOTTISH NORTH WEST and NORTH EAST KEGIOXS with MICROCHEMICAL to Friday 23rd METHODS ATOMIC SPECTROSCOPY CHROMATOGRAPHY AND ELECTROPHORESIS STIRLING and RADIOCHEMICAL METHODS GROUPS on “Selectivity in Trace Analysis.” Discussion on “Detection Limits” to be introduced by G.I;. Kirkbright and Plenary Lecture-“Selectivity in Trace Element Analysis,” by A . A. Smales. “Automatic Hollow-cathode Analysis for Trace Elements in High ‘!’cmperature “The Determination of Small Amounts of L41uminium in Steel by Atomic “The Use of Separation Procedures for Atomic Absorption Spectroscopy in “Some Factors Governing Limits of Detection in Separation Systems,” by “2-Alkyl-substituted Quinolinols as Solvent Extraction Agents,” by F. R. “Auto-oxidation of Stilbenes,” by P. Spahr and E. lT. Truter. “Selectivity in the Application of Activation Techniques Based on the Measure- ment of Prompt Radiation Emitted During Charged-particle Irradiation ” by T.B. Pierce. “The Mass-spectrometric Determination of Small Amounts of Gases Particu- larly in Coated Particle Fuels,” by J. W. McMillan B. L. Taylor and G. J. Weldrick. “The Analysis of Impurities in Inorganic Matrices by Flameless 14tomic Absorption Spectrophotometry,” by C. W. Fuller. “Combined Electrolysis and Atomic Absorption for the Extraction and Deter- mination of Metals in Biological Materials,” by T. F. Hartley and D. J . Ellis. Plenary Lecture-“Selectivity in rrace Analysis the Detection and Estimation of Compounds,” by H. Egan. “Some Sources of Contamination in Trace Analysis,” by R. 0. Scott and A. M. Ure. “Practical Improvements in the Selectivity of Neutron Activation Analysis,” by R. F. Coleman. “Problems in the Determination of Oxygen in Steel by Reducing Fusion,” by G.D. Hall. “Programmed Elution Thin-layer Chromatography as a Technique in the Selective Analysis of Phenols,” by J. M. Philp. “Trace Analysis by GC - MS,” by E. Clayton. “Pitfalls in the Measurement of Drug Availability,” by J. P. Glynn. “A New Gas Chromatography Detector Tunable to a Wide Range of Elements,” by W. R. McLean D. L. Stanton and G. E. Penketh. “Spark Source Mass Spectrometry,” by K. B. Wrigley. “Some Applications of Heteropoly Acids for Amplification Procedures in Atomic Absorption Spectroscopy,” by H. N. Johnson G. F. Kirkbright and Professor T. S. West. “Trace Metal Analysis in the Sub-nanograni Range Using Anodic Stripping Voltammetry,” by I. Frascr. The University Stirling. D. A. Pantony. Alloys,” by I(. Thornton. Absorption Spectroscopy,” by R. H. Jenkins. Clinical Chemistry,” by H. T. Delves. R. R. Goodall. Haba G. H. Kazi and D. A. Pantony. [continued inside back covey Printed by W Heffer & Sons Ltd Cambridge England

ISSN:0037-9697    

DOI:10.1039/SA97209BX023

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

June 1972 Vol. 9 No. 6 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY Reports of Meetings ORDINARY MEETING AN Ordinary Meeting of the SAC/Analytical Division was held on Wednesday and Thursday May 17th and 18th 1972 in the Department of Chemistry University College Swansea. The subject of the meeting was “Research Topics in Analytical Chemistry.” On May 17th the Chair was taken for the first session by Professor R. Belcher Vice- Pre;ident of the SAC/Analytical Division and the following papers were presented and discussed “Candoluminexencea Potential Flame Technique for Trace Inorganic Analysis,” by S. Bogdanski; “The ‘Sensitised’ Catechol Violet Reaction and its Utilisation in the Spectro- photometric Determination of Tin in Steel,” by A. Ashton A.G. Fogg and D. Thorburn Burns; “The Determination of Tin in Steels by Solvent Extraction Followcd by Atomic Absorption Spectrophotometry,” by A. Sowerbutts and J. B. Headridge ; “Amalgam Reduc- tion of Titanium(IV),” by G. A. East. The Chair was taken for the second session by Mr. J. D. R. Thomas Chairman of the Western Region and the following papers were presented and discussed “Thermometric and Enthalpimetric Determination of Some Nitrogen-con- taining Bases and Some Physiologically Active Alkaloids,’’ by L. S. Bark and J. K. Grime; “Simultaneous Spectrofluorometric Determination of Tetracaine and Procaine or Bznzocaine,” by A. C. Mehta; “Studies Concerning Metal Chelates of 1-Hydroxyanthraquinone,” by Mrs. M. Jackson and M. A. Leonard; “Thermal Studies and Gas Chromatography of Some Metal Beta-Diketonates,” by J.Warren and A. G. Smeeth. On May 18th the Chair was taken by Professor R. Belclier and the following papers were presented and discussed “The Trace Determination of Peroxides in Hydrocarbons,” by I. J. Thomson and G. C. Bell; “The Determination of Free and Total Fluoride in Milk,” by J . A. W. Dalziel and A. V. Dangi; “Trace h4etals in Soils by Ultramicro Atomic Spectro- metry,” by A. Oborne and Professor T. S. West; “Microwave Excited Detectors for Gas Chromatography,’’ by R. M. Dagnall and P. Whitehead; “Some Consequences of the ‘Auto’ Degradation of Polystyrene-based Exchangers,” by G. M. Armitage S. J. Lyle and V. C. Nair ; “Mutual Interferences Between the Atomic Absorption Determination of Calcium and Some Other Elements,” by A. Harrison and J.11. Ottaway ; “Spectrophotometric Study of the Acid - Base Equilibria in Aqueous Solutions of the 1,4-Benzodiazepines,” by I. Davidson and W. I;. Smyth; “Developments in Photoelectron Spectroscopy,” by S. I<. Hasanuddin. MIDLANDS REGION A JOINT Meeting of the Region with the Loughborough University of Technology Chemical Society was held at 4.15 p.m. on Tuesday May IBth 1972 in the Edward Herbert Building University of Technology Loughborough. The Chair was taken by the Chairman of the Region Mr. P. G. W. Cobb. The following paper was presented and discussed “The Plasma Torcli-\VIiat is i t ? Wliat will it do?” by S. Greenfield and P. B. Smith. A plasma torch was demmstrated by the speakers. EAST ANGLTA REGION AN Ordinary Meeting of the Region was held at 2.30 p.m. on Friday May 26th 1972 in the Lecture Theatre Block University of East Anglia Norwich.The Chair was taken by the Vice-chairman of the Region Mr. J. S. Leahy. The subject of the meeting was “Safety and Legal Aspects of Food Additives” and the following papers were presented and discussed “Determination of Traces of Toxic Metals in Foodstuffs by Atomic Absorption Spectroscopy,” by G. Nelson and D. L. Smith; “Analytical Aspects of Food Additives and Packaging,” by I. E. Burrows ; “Packaging Legislation- Some Analytical Requirements,” by M. W. Robertson. 123 124 ANALYTICAL METHODS COMMITTEE [PYOC. SOC. AqzaZyt. Clzem. MICROCHEMICAL METHODS GROUP THE eighty-third London Discussion Meeting of the Group was held at 6.30 p.m. on Wed- nesday May loth 1972 in the Senior Common Room Imperial College London S.W.7.The Chair was taken by the Chairman of the Group Mr. S. Bance. A discussion on “The Handling of Unstable Samples” was introduced by I. Dunstan and W. G. Duncombe. BIOLOGICAL METHODS GROUP THE Summer Meeting of the Group was held at 2.15 p.m. on Thursday May l l t h 1972 at the Central Veterinary Laboratory Ministry of Agriculture Fisheries and Food New Haw Weybridge. The Chair was taken by the Chairman of the Group Mr. J. W. Lightbown. After an introductory talk by Mr. I. Davidson Head of the Biological Products and Standards Department members toured the laboratories. AN Ordinary Meeting of the Group was held at 2.30 p.m. on Thursday May 25th 1972 a t the Pharmaceutical Society 17 Bloomsbury Square London W.C.l. The Chair was taken by the Chairman of the Group Mr. J. W. Lightbown. The following papers were presented and discussed “Statutory Requirements for Toxi- cological Examination and Control of Plastics,” by D. W. Plester; “Practical Problems in Examination and Control of Plastics for Pharmaceutical Use,” by J. E. Pentelow. RADIOCHEMICAL METHODS GROUP A MEETING of the Group was held at 10.30 a.m. on Thursday May 4th 1972 at the Labora- tories of the Analytical Sciences Division A.E.R.E. Harwell. The meeting took the form of a tour of the Laboratories primarily to see the wide range of radiochemical analysis that is undertaken there.

ISSN:0037-9697    

DOI:10.1039/SA9720900123

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

124 ANALYTICAL METHODS COMMITTEE [PYOC. SOC. AqzaZyt. Clzem. Analytical Methods Committee WHEN in April 1924 the Council of the Society then the Society of Public Analysts and Other Analytical Chemists set up the Standing Committee on Uniformity of Analytical Methods it laid the foundation of what is now known as the Analytical Methods Committee. The decision to institute this Standing Committee was taken in the light of “A Plea for Standardisation” delivered at a meeting of the Society in December 1923 by M. S. Salamon. The pages of The Analyst for this period indicate however that the plea was by no means generally accepted and for this reason the Standing Committee was given power to act only as a clearing house for standardised methods put forward by groups of interested analysts the Society being unwilling to accord its authority to these methods.This state of affairs continued until 1929 when Mr. E. Hinks the first Chairman of the Standing Committee delivered a further plea for wider acceptance of uniform methods of analysis in his Retiring President’s Address to the Society. The first Honorary Secretary of the Committee was Mr. W. H. Simmons. Originally two Sub-committees were set up-Essential Oils and Milk Products-and this number increased only slowly up to 1935. In that year the Committee was reconstituted and re-named as the Analytical Methods Committee still with Mr. Hinks as Chairman and Mr. Simmons as Secretary. In 1942 Dr. E. B. Hughes replaced Rlr. Hinks as Chairman and in 1946 Mr. Simmons after 22 years as Honorary Secretary resigned and was succeeded by Dr.D. C. Garratt. The period between 1935 and 1955 was one of considerable activity and it was during this period that the difficulties in the Committee’s method of working became most apparent. Since the Committee’s inception the work of the Sub-committees had been carried out by voluntary effort and this system has been retained. However until 1955 the administration of each Sub-committee was carried out by honorary secretaries appointed from amongst their members and as in many instances the demands of both their own organisations and the Sub-Committees increased during this period it eventually became apparent that this system militated against the rapid publication of standard methods of analysis. June 19721 ANALYTICAL METHODS COMMITTEE 125 When in 1953 the Association of British Chemical Manufacturers approached the Society for assistance in Pdrmulating standard methods of analysis for trade effluents the Analytical Methods Committee was asked by the Council to represent the Society in this venture and it was immediately obvious that if recommended methods were to be prepared and published in a reasonable time secretarial assistance would be needed.In 1954 the Society launched an appeal to industry for financial assistance in setting up a permanent secretariat and the response was quite adequate to enable the objective to be achieved. At the same time it was decided to reorganise the Committee and the new Committee held its first meeting on February 2nd 1955 under its newly appointed Chairman Tlr. D. C. Garratt and with Dr. C. H. Tinker as Secretary.Dr. Tinker resigned in 1963 and was replaced by Mr. 1’. W. Shallis who previously had been Assistant Editor of The Analyst. In 1;ebruary 1956 a trust formed under tlie Chairmanship of Mr. Justice Lloyd- Jacob was set up to administer tlie donations received from industry. Dr. J. H. Hamence has been Honorary Secretary of the Trustees since the Trust Fund was set up and he was also Treasurer of the Fund until 1964 when it was decided that it would be more convenient for the Honorary Treasurer of the Society also to be Treasurer of the Fund. ilfembevs of the ’4 nalytical Ll.lefhod.s Conamitlee Standing (r- -K) -Dv. E. J . Newman iWr. P. W . Shallis (Secretavy) Mr. A . G. Hill -11~. C . Meredith I l v . I<. A . Williams M r . A . M . Humphrey Mr. S. C . Jolly Dr. S. M .Herschdoerfer. Seated (L-R)-UY. H . Jcgan Dv. U . C . Garratt (Chairman) MY. C . FYhalley (Presidenl) IMr. 13. Bishop Dr. S. W . Hanson LWv. I t . Sinav Talks between representatives of the Society and of the Pharmaceutical Society of Great Britain led to the formation in 1956 of a Joint Committee to recommend methods of assay for crude drugs the Society’s interests being represented by the Analytical Methods Committee but the secretariat has been provided by the A.11 .C. Subsequently this Joint Committee has as a result of tlie successful completion of much of its original work on crude drugs considered its future and decided that it still has a useful function to perform in the broader field of drugs generally and in 1965 it widened its terms of reference. The constitution of the Committee has to cover all aspects of analytical chemistry and membership is chosen accordingly; the Honorary Officers of the Society serve on the Com- mittee during their terms of office.FUNCTION AND POLICY 01; THE COMMITTEE- The Committee meets at about two-monthly intervals. It receives and discusses progress reports either from the Chairman or Secretary of the Joint Committees and Sub-Committees. At one of the meetings during each year all Chairmen are invited to attend to present progress reports for tlie preceding 12 months and to discuss future plans. 126 ANALYTICAL METHODS COMMITTEE [Proc. SOC. A nalyt. Chem. The Committee also receives and critically examines proposals for new work to be undertaken from its own members or from outside. If new projects are approved Council is notified and the Committee appoints a Chairman who is required to gather his own membership which is submitted to the Committee for approval.The Committee is also required occasionally to deal with other matters pertaining to standard metliods of analysis referred to it by the Council. All reports from Sub-Committees and Joint Committees are submitted to the Committee for approval for publication and when approved Council is notified before publication is carried out. The Committee is also responsible for the publication of a collection of all its standardised methods and of a bibliography of recognised methods of analysis. The Committee works essentially in areas where there is a distinct need for recommended methods but avoids fields where other organisations are known to be working.THE SUB-COMMITTEES- The constitution of a Sub-committee is the responsibility of its Chairman and is approved by the Committee. Each member is appointed as an individual not as a representative of his company or organisation and his services to the Sub-committee are given voluntarily. In most instances Sub-Committees carry out by collaborative effort work on stan- dardising published methods of analysis although in a few instances in recent years this approach has proved inadequate and some original investigational work has been undertaken by individual members on behalf of the Sub-Committees. When work on any particular project is completed a report for publication is drafted which after having been approved by the Committee is published usually in The Analyst. Sub-Committees are not permanent ; when their terms of reference have been met they are disbanded.JOINT COMMITTEE WITH THE PHARMACEUTICAL SOCIETY AND ITS PANELS- Within its terms of reference which originally covered only crude drugs but have more recently been widened to include work on any drug the Joint Committee with the Pharma- ceutical Society functions in a similar way to the Analytical Methods committee. It sets up panels of experts to investigate problems in drug analysis and considers the recommenda- tions of the panels before passing them to the Analytical Methods Committee for approval for publication. These panels also are not permanent and are disbanded on completing their remits. THE ANALYTICAL METHODS TRUST- The Trust Fund was set up in 1956 under the Chairmanship of the Hon.Mr. Justice Lloyd- Jacob. Essentially the Trustees administer the monies received by donation to the Trust Fund by arranging investments and approving expenditure. The Deed of Trust also permits the establishment and maintenance of research scholarship in analytical chemistry and it was realised that the prestige of the Analytical Methods Committee could be much enhanced in this way. The first research scholar was Mr. (now Dr.) T. T. Gorsuch who over a period of 2 years carried out at Harwell under the direction of Dr. A. A. Smales his now well known “Radio- chemical Investigations on the Recovery for Analysis of Trace Elements in Organic and Biological Materials.” Dr. Gorsuch’s report under this title which provided much useful information on problems that had for a long time been troubling analysts concerned with determining trace elements in organic matter was published in The Analyst.In 1960 Dr. J. H. Stevenson was appointed as the second research scholar to investigate bioassay methods for determining pesticide residues in foodstuffs. Dr. Stevenson completed 1 year’s work at Rothamsted but was unable to continue. One other investigation was sponsored by the Trust Fund and this was the work carried out by Dr. T. B. Pierce at Oxford on the determination of small amounts of silver in trade effluents. OFFICIAL STANDARDISED AND RECOMMENDED METHODS OF ANALYSIS- Soon after the reorganisation of the Committee in 1955 the work of the Standard Methods Committee of the Society was transferred to it. In its original conception this work consisted in collecting and publishing in one volume the standard methods of analysis of this and other June 19721 PARTICLE SIZE ANALYSIS GROUP 127 Societies and Associations.The Committee was however disturbed by the lack of progress being made in this work and in 1959 Mr. S. C. Jolly was appointed Publications Secretary specifically to handle the collection and editing of these standard methods. The final objective was also modified and it was agreed that the book should contain standard methods produced by the Analytical Methods Committee and all the Joint Committees with which it was associated together with an expanded and revised version of the Society’s bibliography of standard methods. This objective was reached with the publication early in 1963 of “Official Standardised and Recommended Methods of Analysis.” A supplement containing the methods published since 1963 a revised bibliography arid an index was published in 1067.A second edition is now nearing completion under the supervision of Dr. N. W. Hanson who recently took over this work. The recent meeting of the A.M.C. (the 98th meeting since its reconstitution) was the Annual Meeting attended by all Chairmen of the Sub-committees to present reports on the work done during the year and much useful discussion ensued. The Chairman of the Joint Panel of the Analytical Standards Sub-committee and the Microchemical Methods Group Mr. E. Bishop presented to the meeting the final draft of its revision of “Reference Substances and Reagents for Use in Organic Micro-analysis.’’ Revision of these specifications last published about 10 years ago had taken a little over 2 years and involved the general im- provement of most of them together with the deletion of some materials from the lists and the addition of others. The revised specifications which had previously been accepted by the Microchemical Methods Group Committee were approved by the A.M.C. for publication. At the request of B.S.I. these specifications will now be submitted to I.S.O. as draft inter- national specifications and will also be submitted to I.U.P.A.C. for consideration as I.U.P.A.C. specifications. The published recommendation by the Analytical Standards Sub-committee of sodium carbonate as a primary standard for use in acid - base titrimetry has been accepted by I.S.O. as an international recommendation.

ISSN:0037-9697    

DOI:10.1039/SA9720900124

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

June 19721 PARTICLE SIZE ANALYSIS GROUP 127 Particle Size Analysis Group THE Particle Size Analysis Group had its origin in the Particle Size Analysis Sub-committee of the Analytical Methods Committee of the Society. In 1965 this Sub-committee then under the Chairmanship of Mr. E. Q. Laws set up an ad hoc committee to consider the forma- tion of a Particle Size Analysis Group of the Society. Subsequently in January 1966 the formation of the Group was approved by the Council of the Society. The Inaugural Meeting was held on February 17th 1966 when Dr. T. Allen was elected Chairman and Dr. V. T. Crow1 Honorary Secretary and Treasurer. The Group owes much to the efforts of these two founder members and to the other officers who have served it since. Particularly notable is the contribution of the late Professor H.Heywood not only to the Group but also the field of particle size analysis as a whole. LEFT-DY. li. Mavshall (Chaivman) RTGHT-DY. M . J . GYoves ( Vice-Chairman) The stated object of the Group is to encourage assist and extend the knowledge and study of particle size analysis but there is now an increasing and welcome tendency to use the more general terms “powder characterisation” or “particle characterisation.” As far 128 [Proc. SOC. Analyt. Chem. as the Society is concerned this is an unusual subject as it attracts scientists and technologists in disciplines other than chemistry. Physicists mathematicians pharmacists chemical engineers and many others are included among the membership of the Group. That there is a wide interest in the subject has been further shown by the large attendances at the Particle Size Analysis Conferences held by the Society in 1966 and 1970.These attracted many overseas visitors. It is anticipated that now the Society has become the Analytical Division of the Chemical Society future conferences and Group meetings will be even more popular. NMR AND EMR IN ANALYTICAL CHEMISTRY LEFT-MY. M . W . G. Buvt (Honovavy Secvetavy and l‘veasuvev) RIGHT-DY. N . G. Stanley- Wood ( H O ~ W U ~ J I .A ssistant Secvefavy) Particle size analysis provides a rich and diverse field of study and many Group meetings of which there are usually four each year are devoted to particular techniques e.g. sieving sorptometry and sedimentation. However the Group Committee has always realised that the subject of particle size analysis is only a part of the more general field of powder technology and with this in mind at least one meeting is arranged each year to deal with the applications of particle characterisation to other sciences and to industries involved in work with powdered materials.Recently this policy has been extended to arranging visits to establishments with special interest in powder technology. Earlier this year the Group visited Warren Spring Laboratory a t Stevenage and a visit to the British Ceramic Research Association a t Stoke-on-Trent has been included in the programme for 1973. The next Group meeting in 1972 will be on September 13th and 14th at Salford University when there will be an informal colloquium on “Techniques for Particle Characterisation.” It is intended that this meeting should provide a greater opportunity to discuss the problems of individual members than is possible at most Group meetings and it is hoped that the informal atmosphere will encourage a free exchange of ideas and technical knowledge that will be of particular benefit to newcomers to the field.

ISSN:0037-9697    

DOI:10.1039/SA9720900127

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

128 NMR AND EMR IN ANALYTICAL CHEMISTRY [Proc. SOC. Analyt. Chem. Nuclear Magnetic Resonance and Electron Magnetic Resonance in Analytical Chemistry The following are summaries of two of the papers presented at a Meeting of the SAC/ Analytical Division held on February 2nd 1972 and reported in the March issue of Proceedings (p. 53). Purity Control by Nuclear Magnetic Resonance BY I. J. LAWRENSON (Division of Chemical Standavds National Physical Laboratovy Teddiuzgton Middlesex) IN highly purified samples of organic compounds the impurities are often chemically very similar to the main material and quantitative elemental analysis is not sensitive enough for the determination of small concentrations of such related compounds. Thus for samples of organic compounds of purity greater than about 99 mol per cent.physical methods of purity measurement must be used. June 19721 NMR AND EMR IN ANALYTICAL CHEA3MISTRY 129 Chemists have long been aware of the importance of studying the behaviour of a material as it melts and have gauged the purities of specimens by the sharpness of the melting-points. During recent years advances in temperature control and measurement have made cryo- scopy the study of melting behaviour a powerful tool for the measurement of purity. For samples that do not decompose at their melting-points cryoscopy provides reliable methods of general applicability for the assessment of purity. Both dynamic and static cryoscopic methods are in use for the determination of the purities of specimens of organic compounds. In dynamic methods heat is added to or taken away from the sample at a controlled rate and conclusions about the amount of impurity present are drawn from the consequent temperature changes of the sample.Static methods make use of some physical property that is different for solid and liquid material. The chosen property is measured for the liquid the solid and the sample under investigation and the fraction of liquid in the sample is found by linear interpolation. The property may be for example heat content volume or dielectric constant. At the N.P.L. we have developed a static technique,l using nuclear magnetic resonance (NMR) to measure the liquid fraction for the determination of the purities of samples of organic compounds. This technique has been called nuclear magnetic resonance cryoscopy. In a solid material containing nuclei with magnetic moments where the molecules are held rigidly in the crystal lattice the width of the NMR absorption is large because of interaction between the nuclear dipoles.2 However in a liquid rapid molecular re-orientation and diffusion average out this interaction and the resulting NMR absorption is of narrow width.In fact the ratio of the absorption width from a solid material to that from the liquid is typically lo4. The NMR spectrum of a partially molten sample therefore consists of a narrow line due to the molten fraction superimposed on a much wider line due to the solid. As the intensity of an NMR signal is directly proportional to the number of nuclei giving rise to that signal the fraction of sample melted can be readily determined. In the experiments described here two types of NMR spectrometer have been used.One was a high-resolution instrument in which the probe assembly had been modified so as to maintain the temperature of a non-spinning sample within about 0.01 I<. Spectra were recorded on charts and were cut out and weighed in order to obtain intensities. The other was a Quantity Analyser (Newport Instruments Limited) a commercial instrument designed for the determination of oil or water in solid materials. A modified probe assembly was fitted to this instrument to maintain a 2 cm3 sample within 0.05 K. The output of this spectrometer was displayed on a digital voltmeter. With both instruments the fraction of material melted at any temperature was found by measurement of the intensity of the narrow signal from the liquid at that temperature and at a temperature just above that at which the sample was wholly liquid.For a system in which the impurity is not soluble in the solid material the fraction molten f at a temperature Tabs below the melting-point of an absolutely pure sample To is expressed by the equation Tobs = To - N / f A .. . . . . * * (1) .. .. .. ’ (2) where N is the mole fraction of impurity present and A the cryoscopic constant is given by A = AHf/RTo2 .. AHf being the enthalpy of fusion and R the gas constant. Therefore the reciprocal of the fraction melted plotted against the temperature will yield a straight line. In Fig. 1 are shown graphs obtained by the use of the high-resolution spectrometer for observations on some samples of phenol containing water as impurity. The graphs are linear and from the slopes the values of the impurity can be found from known values for the heat of fusion of phenol.In Table I are shown the values obtained by this technique for a series of such phenol samples. Samples 9 and 10 are N.P.L. Standard Samples sample 8 is a commercial sample and the others were prepared from N.P.L. Standard Sample with water added in known amounts. The “measured purity’’ is that determined by the NMR cryoscopy technique while the “established purity” is that calcu- lated from the purity of the starting material which had been measured by a different technique and the amount of added water. I30 NMR AND EMR I N ANALYTICAL CHEMISTRY jl-’voc. SOC. Aualyt. Chcm. \ 20 1 G 50 100 l/fraction molten Fig. 1 . Relation between reciprocal of thc fraction molten and the temperature for sainplcs of phenol containing water as impurity.The samplc numbers refer to Table I A quicker method involves measurement at a single temperature. Equation (1) shows that at a given temperature the amount of impurity is directly proportional to the fraction melted. The experimental results show that the difference between the value of purity determined at one temperature only and that determined from analysis of measurements at several temperatures may be 0.1 mol per cent. for a sample of purity 97.0 rnol per cent. but will be only about 0.02 mol per cent. for a sample of purity 99-9 mol per cent. TABLE I MEASURED PURITIES OF PHENOL SAMPLES Sample number 1 2 3 4 5 6 7 8 9 10 Measured purity mol per cent. 97-82 97.95 98.79 99.12 99.32 99.45 99.50 99.78 99.91 99.92 Established purity mol per cent.98.05 98.07 98.89 99.26 99.01 99.73 99.47 99.97 99.97 - When the impurity forms solid solutions the impurity dissolves in both solid and liquid phases of the main material and the situation is a little more complex. Fig. 2 shows the reciprocal of the fraction melted plotted against temperature for three samples of phenol each containing one of the three cresols. For phenol containing 9-cresol the graph is linear showing that solid solutions are not formed but for phenol containing either o- or Ytz-cresol the graphs are curved showing the existence of solid solutions. Equation (1) does not apply but must be replaced by where d = k / ( 1 - k ) k being the ratio of the concentrations of the impurity in the solid and liquid phases respectively at equilibrium.It is assumed in the derivation of this equation that thermodynamic equilibrium exists throughout the system including the solid phase and that k is a constant (that is the liquidus and solidus of the appropriate phase diagram are linear). Tobs = To - N/A(d +f) . . . . . . * * (3) Equation (3) can be rewritten as f = “ / A (To - Tobs)] - d .. .. ’ (4) June 19721 NMR AND EMR I N ANALYTICAL CHEMISTRY 131 Therefore the fraction melted f plotted against (To - Y'obs)-' should yield a straight line of slope N / A and intercept -d. Fig. 3 shows such a graph for one sample of phenol containing 9-cresol and for another sample containing o-cresol. The former sample yielded a straight line through the origin showing that d = 0 and that a solid solution is not formed.The sample containing o-cresol gave an almost linear graph but with some curvature at low temperatures. I I 0 10 20 l/fraction molten Fig. 2. Relation between the reciprocal of the fraction molten and the temperature for samples of phenol containing one of the three cresols as impurity. A phenol con- taining p-cresol; €3 phenol containing o-cresol and C phenol containing m-cresol I - Fig. 3. Rclation between the fraction molten and ( T o - Tobs)-l for samples of phenol containing a cresol as impurity. A phenol containing p-cresol; and B phenol containing o-cresol If a straight line is to be obtained the assumptions made in the derivation of equation (4) must be valid i.e. total equilibrium must exist between the impurity contained in the liquid and solid phases and k must be constant.All the samples were frozen slowly as rapid quenching of the molten material in a refrigerant often led to the formation of mixed crystals even for systems that do not normally form solid solutions whereas slow cooling of the same material did not? When a molten sample of a mixture that forms solid solutions is cooled slowly the first solid to separate has the composition defined by the solidus. On further cooling more solid is deposited and this has a different composition. Diffusion of impurity in the solid may be very slow or even negligible so that the frozen sample will consist of layers of differing purity the outermost layer being the most impure. On warming the process is reversed the outer most impure layer melting first so that the fraction melted at a given temperature will be greater than if total equilibrium had existed.The graph of f against (To - Tabs) will be curved. However the composition of the last solid to melt TABLE I1 MEASURED PURITIES OF PHENOL SAMPLES CONTAINING A CRESOL Measured purity Established purity Impurity mol per cent. mol per cent. pCresol . . 91.59 91.25 94.73 94.65 o-Cresol . . 90.03 95.18 m-Cresol . . 98.35 95.39 89.79 89.81 95.43 98.19 95.22 89.72 132 NMR AND EMK IN ANALYTICAL CHIJMISTKY -1’7OC. SOC. A Pba&. ChCl92. will be the same as if total equilibrium had existed so that such a graph will tend to a straight line at higher temperatures and the slope of this line will still be proportional to the impurity. In Table I1 are shown the experimentally determined values of purity of several samples of phenol containing a cresol.Measurements using NMR cryoscopy on a more routine basis have been made with the Quantity Analyser and these must be interpreted in a manner slightly different from that described above. A graph of the reciprocal of the apparent fraction melted as measured on the Quantity Analyser against temperature is shown in Fig. 4. The graph is curved the curvature being opposite to that obtained for solid solutions (see Fig. 2). l/apparent fraction melted Fig. 4. Relation between the reciprocal of the apparent fraction melted as measured by the Quantity /Inrtlyser and the temperature of measurement for a commercial sample of phenol The reason for this curvature lies in the design of the Quantity Analyser. The amplifiers are gated so that signals from only part of the magnetic field sweep are amplified in order that lines from liquids only are measured.The gate width is typically 160 pT (1.6 G) while the magnetic field inhomogeneity over the 2 cm3 sample volume is about 30 pT. Additional circuitry prevents part ACDE (Fig. 5) of the line from a solid being measured but the part ABC may still be measured as signal. The ratio of the part ABC to the whole line FABCG depends on the line shape. I t may be too small to measure or may be as large as 0.05 for a substance where the solid has a very narrow line. The curvature in the graph for phenol (Fig. 4) results from approximately 1 per cent. of the line from the solid being recorded with the line from the liquid. The apparent fraction melted f’ as measured on the Quantity Analyser is related to the true fraction melted f by where s is the ratio of the area ABC to area FABCG (Fig.5). f’ = f + (1 - f ) S . . . . . . . . . . (5) Tobp = TO - N(l - s)/A(f’ - S) . . * . * - (6) When the Quantity Analyser is used equation (1) must be replaced by This equation describes the curve shown in Fig. 4. A value must be found for s before the purity of a sample can be measured by the Quantity Analyser. Both X and s can be determined simultaneously by an iterative least-squares procedure if a computer is availalile ; alternatively the apparent fraction of liquid f ’ can be found by measurement at a tempera- ture sufficiently low that the true molten fraction f is negligible when s is equal to f ’; a third method involves solution of the pair of simultaneous equations obtained from equation (6) bv measurement at two temneratiires.There are several possible ways of doing this. June 19721 XMR AKD EMK I N ANALYTICAL CHEMISTKY 133 Calculations by computer on the sample of commercial phenol by using the value known for To gave a value of 0.23 rnol per cent. for the impurity content and a value of 0.0105 mol per cent. for the solid contribution s. (Measurements with the high-resolution spectrometer had given a value of 0.22 mol per cent. for the impurity content as shown in Table I.) The value of To may be uncertain either because of errors in the temperature measure- ment or because the melting-point of an absolutely pure sample is not known accurately. The results shown (Fig. 4) gave an impurity content of 0.23 rnol per cent. for To equal to 40.9 "C. Use of different values for To in the range 41.9 to 38.7 "C (the highest temperature at which a measurement off was made) changed the value of the impurity content by 0.01 mol per cent.for each 0.2 K change in To. Rearrangement of equation (6) shows that the impurity content N is proportional to f' at a given temperature. A quick method of purity determination requiring only a single measurement at a given temperature is possible with the Quantity ,\nalyser if the value of the solid contribution s is known. A series of single measurements on the sample of com- mercial phenol at 32.6 "C gave values corresponding to impurity content of 0.23 0.21 0.29 0.22 0.26 and 0-22 mol per cent. when s was taken to be equal to 0.0105. Changing the assumed value of s by as much as +0.0015 altered each calculated value of impurity content by only PO-02 mol per cent.Moreover each measurement took only 2$ minutes after tlie sample had been brought to the required temperature. KMR cryoscopy is widely applicable to compounds containing liydrogen or fluorine that do not decompose on melting. However the technique cannot be readily used with some globular molecules such as cyclohexane which have very narrow lines from the solid p1iase.l Just below its melting-point solid cyclohexane exhibits a line width of only 2 pT (20 mG) and it is impossible to resolve with accuracy the lines from the solid and liquid phases. I qcn..-r I luup I - - H Vig. 5 . NhIR line shape from a solid material as the magnetic field H is swept; AC is the gate width of the amplifiers l/apparent fraction molten (graph A ) 1 0 10 20 30 l/apparent fraction molten (graph B ) Fig.6 . Relation between the reciprocal of the apparent fraction meltcd as measured by the Quan- tity -4nalyser and the temperature of iiieasurement for samples of Gardona. A sample of purity 84 mol per cent.; and B sample of purity 99.72 mol per cent However solid materials exhibiting considerable molecular motions and quite narrow lines can be examined successfully. For example the commercial pesticide Gardona contains selveral methyl groups which because of their rapid re-orientation give rise to a narrow line from the solid. Conventional broad-line measurements show the line width to be 300 pT (3 G). Fig. 6 shows plots of temperature against reciprocal of apparent fraction melted for two samples of Gardona. One is highly impure; analysis of the experimental results for tlie other yields a value of 0.28 rnol per cent.for the impurity content and a value of 0-04 for the solid contribution s. 134 [Proc. SOC. Analyt. Chenz. NMR cryoscopy as a method of purity measurement offers several advantages over the other cryoscopic techniques. The requirements for accurate temperature control are not particularly stringent because a small molten fraction (approximately 1 per cent .) can readily be measured. In fact it may be kept at all times in a sealed container and this may be coloured or even opaque. The method could be used to measure the purity in different parts of a sample where the impurity is not evenly distributed as in a zone-refining tube. After a batch of samples has been brought to the required temperature in for example an oil-bath each determination of purity may take as little as 2+ minutes.NMR AND EMR IN ANALYTICAL CHEMISTRY The sample is not contaminated in any way. Above all the technique is much quicker than other cryoscopic methods. REFERENCES 1. 2. 3. Herington E. F. G. and Lawrenson I. J. J . Appl. Chrwt. Lond. 1969 19 337. Andrew E. R. “Nuclear Magnetic Resonance,” Cambridge University Press Cambridge 1955. Herington E. F. G. and Lawrenson I. J. J . Appl. Clwn. Lond. 1969 19 341. Electron Magnetic Resonance as an Analytical Tool BY B. D. FLOCKHART (Depavtvnent of Chemistry The Queen’s University Relfact R T9 5-4 G :Vort hern Ireland) ELECTRON magnetic resonance (EMR) was first observed by Zavoiskii in 1945 the discovery preceding that of nuclear magnetic resonance (NMR) by a few months.The two techniques are basically the same-the alignment of magnetic moments by an applied d.c. magnetic field and the re-orientation of these by the absorption of incoming electromagnetic radiation. The essential difference between the techniques is that in NMl3 it is the nuclear magnetic nioiiients tliat are being re-orientated whereas in ENR it is the electronic magnetic moments. Cliemical analysis by ENR suffers however from a serious drawback it is applicable only to elements or compounds that possess an unpaired clectron. The method will therefore never rival NMR in its importance to the analyst but within its range it is unexcelled both for sensitivity and speed. Moreover the restricted origin of EnfR can sometimes be turned to advantage in that rcsults from a paramagnetic substance can be obtained independently of the surrounding diamagnetic material which ma)- swamp tlie required information in a less selective method of measurement.The presence of electric charge and intrinsic spin angular momentum confers on an electron a magnetic moment and so it will interact with an applied magnetic field. L4ccording to quantum theory the value of the spin is t measured in units of Planck’s constant divided by 2 ~ . There are therefore two allowed spin orientations and in the presence of a magnetic field these orientations have different energies. Transitions between the magnetic energy levels may be induced by electrornagiietic radiation whose frequency satisfies the resonance condition where hvo is the quantum of energy of the incident radiation /3 is the Bolir niagneton and g the proportionality factor is a measure of the contribution of the orbital magnetism to the total magnetic moment of the unpaired electron.The resonance transitions can be observed by varying either the strength of the applied magnetic field H or the frequency of the radiation. In practice the frequency is fixed and the magnetic field is swept slowly through the resonance condition. All commercially available EMR spectrometers operate in the microwave region of the spectrum. In most EMR studies frequencies of 9000 to 10 000 MHz (microwave X-band) have been used and the magnetic field needed for a sample with g = 2 is about 3200 to 3600 G. EMR spectra therefore represent a plot of intensity of energy absorption against field strength and line widths are given in gauss (1 G = lo-* T).Line positions are stated in terms of g-values (= hvo//3H,) which makes the measurements independent of the spectrometer that is used. In various forms of spectroscopy including higli-resolution SMR the output of the detection system appears as absorption lines or “peakq.” Most ERIR spectrometers using high-frequency modulation of the magnetic field and a phase-sensitive detector record the 1 1 ~ 0 = gPHo June 19721 NMK AND EMR I N ANALYTICAL CHEMISTRY 135 first derivative of the absorption. This method of presentation has considerable advantages in sensitivity and resolution where broader resonance lines are being observed as in EMR. Greater sensitivity is also obtained by working at low temperatures. The distribution of electrons between the two spin states is given by the Maxwell - Boltzmann expression n,/n = exp (-hvo/kT) where nl is the number of electrons in the lower energy state and n2 that in the upper k is Boltzmann's constant and T is the thermodynamic temperature.As T is reduced the difference between n2 and n1 increases so that a larger net absorption of microwave energy occurs. Accessories are commercially available that allow variable temperature operation between -180 and +300 "C and the liquid nitrogen Dewar flask allows fixed low-temperature study of samples at -196 "C. To facilitate observation of faint transient signals the output from an EMR spectrometer can be fed to a computer of average transients (CAT). A signal- to-noise improvement factor of l/x is obtained where x is the number of times the spectrum is run.When using EMR spectroscopy as an analytical tool three basic parameters deduced from the resonance spectrum are of particular importance. (i) HyperJine splitting-If the unpaired electron is in an orbital embracing one or more magnetic nuclei its magnetic moment will interact not only with the applied magnetic field but also with the nuclear magnetic moments. As a nucleus of spin I may adopt any of 21 + 1 orientations with respect to the direction of the applied field the vector sum of the external field and the nuclear field will have 21 + 1 possible values. But electronic spin transitions occur when Interaction with a nucleus of spin I will therefore split an otherwise single resonance line into 21 + 1 components. This is termed hypevjne splitting and the arrangement of the resulting group of lines is called the ?zy$ep.fine stmcture of the spectrum.When an electron interacts with one nucleus all components of the hyperfine structure are of equal intensity and are separated from one another by the same distance which is termed the hypevfine coupling constant. From the number of lines in the spectrum the spins of the nuclei with which the electron is interacting can be deduced; from the intensity ratio distribution the number of equivalent nuclei with which it is interacting can be deduced; and from the hyperfine coupling constants it is possible to deduce something about the molecular electronic wave function. Although the detailed interpretation of an EMR spectrum is of course not always possible it is the occurrence and analysis of the hyperfine splitting that frequently makes high-resolution EMR such an important tool for analytical purposes.g-value-If the microwave frequency is held constant a measurement of the field strength a t which resonance occurs determines the value of the g-factor associated with the particular system. An electron with no orbital angular momentum has a g-value equal to that of the free electron spin i.e. 2.00232. For almost all organic radicals g is within 0-5 per cent. of the free-spin value. Therefore if two or more chemical species of radical with different g-values are present serious overlapping of the spectra is likely to occur. The g-value is not nearly as useful as the hyperfine splitting for distinguishing different organic radical spectra but if the spectra are poorly resolved it may be the only determinable quantity that can be used to identify the species.With organic radicals precise g-values are essential. In transition-metal ions the orbital contribution to the electronic magnetic moment is often high and g-values differing considerably from 2.00232 are found. In such instances g-value variation can be very useful for identification purposes. Signal intensity-Relative spin concentrations for species with the same line width and shape function are readily determined by measuring the ratio of signal amplitudes (peak-to-peak height on the first derivative curve) for samples of identical size recorded under identical conditions. If Ns and N are the numbers of unpaired electrons in the two samples where h and h are the signal amplitudes.both Gaussian) but the line widths differ the relevant equation is Happlied + Hlocal = H o (ii) (iii) NSlN2 = hl/h If the line shape functions are the same (e.g. NJN2 = hl AH12/h2 AH22 136 KMR AND EMR I N AKALYTICAL CHEMISTRY JI'YOC. S O C . IZLdyt. Chem. where AH and AH are the line widths. Otherwise the area under the absorption curve obtahed by double integration of the derivative signal must be used. In the absence of saturation the area under the absorption curve is proportional to the number of unpaired spins in the sample and is independent of the nature of the species involved. In principle therefore an absolute spectrometer calibration should be possible. Because the actual area under an absorption curve depends on many instrumental factors such an absolute calibra- tion is seldom attempted in practice.Instead standardisation is achieved by the use of samples with known concentrations of spins. For the best result the standard sample should have a line width and intensity comparable with those of the spectra to be measured. The choice of suitable standard samples is wide and no ideal standard has been found. For organic radical spectra the most commonly used standard is 1 l -diphenyl-2-picrylhydrazyl (DPPH) each molecule of which has one unpaired electron. Carbon samples formed at about 500 "C and diluted with an inert powder are useful secondary standards. Solutions of manganese(I1) sulphate and of vanadyl salts have been frequently used as primary standards for aqueous systems. Some EnilR spectrometers incorporate electronic integrators so that starting from the first derivative either the first integral or the second integral is immediately available.With spectrometers that give only a derivative output integration can be the most time consuming part of an analysis. Procedures €or the double integration of the first derivative curve that are suitable for use with a desk calculator or involve the use of an analytical balance have been described in the literature. SENSITIVITY AND ACCURACY- With the Spectrometers at present available the limit of detection is about 5 x 1O1O AH spins where AH is the line width. For a line width of 1 G this corresponds to about mol or a concentration of 10-9 to 10-10 M. In practice to obtain a reasonably well resolved spectrum a considerably higher concentration ( to 1 0 - 7 ~ ) is used and in aqueous solutions the sensitivity is lower.The finite lifetime of short-lived paramagnetic species may also be a limiting factor in their detection. Application of the Heisenberg uncertainty principle shows that for a species with g = 2 the line width introduced by the energy uncertainty AHs is given by where At is the mean lifetime of the species. For high sensitivity work the uncertainty broadening should not be greater than about 1 G and so the lifetime of the species should not be much less than 1 ps. When peak-to-peak height on the derivative presentation can be used for comparison purposes the error in spin concentration measurements should not exceed +5 per cent. in favourable cases. Spin concentrations that have been determined by comparing the areas obtained by double integration of the derivative traces for the sample and the standard may be in error by *SO per cent.Therefore although the sensitivity of the EhlR method is high the accuracy of quantitative measurements of spin concentrations is often low. AH (10-7/nt) G SCOPE AND APPLICATIONS- EMR is limited to the detection of unpaired electrons and is consequently restricted to paramagnetic substances. Paramagnetism occurs in (a) all atoms and molecules that have an odd number of electrons; ( b ) molecules that have an even number of electrons but not all the electron spins are paired; (c) many compounds and salts of transition metals rare-earth metals and trans-uranic elements; (d) organic and inorganic radicals ; ( e ) semiconductors ; and (f) colour centres in crystals. The EMR technique offers a powerful means of detecting identifying and quantitatively determining paramagnetic materials especially when only small amounts or low concentrations are available.The method has the added advantage that no chemical preparation or destruction of the sample is required. polymer chemistry pyrolysis catalysis to enzyme - substrate reactions and to the investi- gation of organometallic compounds as they occur in proteins and similar substances. With living cells the non-destructive feature of EMR is particularly attractive. The ability to obtain radical concentrations directly from the spectra makes the technique very useful for EhIR has been applied to studies in electrochemistry photochemistry radiochemistry, June 19721 INORGANIC ANALYSIS BY GAS CHROMATOGRAPHY 137 measuring the concentration of radical intermediates as a function of time. The use of continuous flow cells has enabled EMR to be applied to process control. For example an EMK system monitoring crude oil on its way to cracking columns can detect excessive concentrations of vanadium ion and instigate protection for the catalysts. Further information regarding the use of EMR as an analytical tool and references to pertinent original literature can be found in a recent artic1e.l REFEREXCE 1. Flockhart R. D. “Nuclear Magnetic Resonance and Electron Spin Resonance Methods,” in ililson C. L. and Wilson D. W. Edztovs “Comprehensive ilnalytical Chemistry,” Volumc Ilc Elsevier Amsterdam 1971.

ISSN:0037-9697    

DOI:10.1039/SA9720900128

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

June 19721 INORGANIC ANALYSIS BY GAS CHROMATOGRAPHY 137 Inorganic Analysis by Gas Chromatography The following is a summary of the paper presented at a Meeting of the Western Region held on February 17th 1972 and reported in the March issue of PYocEedI'1zg.s (p. 54). Gas Chromatography of Metal Chelates BY W. I. STEPHEN (Department of Cheiqaistvy Univevsity of Birmingham P.O. Box 363 13i~wii?igJia~n 1.5) THE tremendous advantages that gas - liquid chromatography has over many other tech- niques of separation have prompted several studies of its potential in inorganic analysis. Isolated examples of organometallic compounds subjected to gas - liquid chromatography have shown the feasibility of the technique but these can in no way be considered as being generally applicable to routine inorganic analysis because the particular compounds are not readily obtained in quantitative yield and many are unstable or susceptible to hydrolysis.If gas chromatography is to be used for metal separation metal purification and metal analysis then it is desirable that the metals in question should react readily with a single reagent (or type of reagent) to give quantitative yields of tlie metal compounds and these compounds must possess certain properties that meet tlie requirements for separation and analysis by gas chromatography. Two properties are paramount-sufficient volatility and thermal stability. Although for example metal carbonyls alkyls and alkoxides have these properties it is certain simple types of metal clielates that have proved most worthy of further study. Of the great variety of chelating agents available tlie simple P-diketones were initially indicated as being suitable reagents that might provide metal compounds of the requisite volatility solubility and thermal stability for their successful elution from a gas-chromato- graphic column.Ledererl suggested that metal acetylacetonates might prove amenable to gas chromato- graphy but it was Biermann and Gesser2 who described the first successful gas-chromato- graphic elution of the acetylacetonates of beryllium aluminium and chromium. This was followed by reports from Rrandt and Heveran3 on several metal diketonates but particularly cliromium( 111) acetylacetonate. Moshier and Sievers4 reviewed progress to 1965. The metal compounds to be used for gas chromatography must possess certain properties if they are to be of value in metal analysis.Most important the compounds must be volatile enough to be chromatographed in the gas phase; secondly they must be stable at the temperatures required to maintain sufficient vapour pressures for chromatographic elution ; thirdly they should be easily formed and isolated particularly from aqueous media; and finally it is desirable for them to have special properties of value for easy detection e.g. halogen in electron-capture detectors. All these factors point to the use of P-diketones and particularly the fluorinated ligands derived from acetylacetone namely trifluoro- acetylacetone (TFA) and hexafluoroacetylacetone (HFA). These ligands form stable highly volatile chelates with aluminium(III) beryllium(II) chromium( IIT) rhodium(II1) and several other metal ions.138 [Proc. Soc. A TzaZyt. Chew. Chelates of H F A were first examined by Moshier and Sieved who found them to be more readily eluted than the acetylacetonates and trifluoroacetylacetonates at column temperatures only a little above room temperature. Aluminium( III) beryllium( 11) and chromium(II1) HFAs are exceptionally volatile and elute before the solvent in many chroma- tograms. One difficulty is that several metal HFAs are formed with coordinated water which makes chromatography more difficult perhaps as a result of dehydration and poly- merisation during chromatography. One serious disadvantage of HFA which precludes it5 more widespread adoption is its readiness to form a tetrahydroxy compound by reaction with water- INORGANIC ANALYSIS BY GAS CHROMATOGRAPHY 0-H 0 O H O H CF3-C=CH-C-CF3'2H,0 + CF,- -CH,- C-CF I I I 11 I I I OH OH which is a much poorer coordinating moiety than the anhydrous P-diketone.Nost attempts at isolating metal HFAs from aqueous solution have been unsuccessful and this may be the reason. HFA is useful in that it reacts with some metals particularly those in Groups IVR VB and VIB to form mixed complexes that are volatile and readily c.hromatograplied. TiCl + 2H.HFA + TiCI,(HFA) + 2HC1 These mixed complexes however are susceptible to hydrolysis even hy atmospheric moisture and special precautions are needed when handling thein. Nevertheless useful separations such as tantalum from niobium are possible. Another very useful ligand is dipivalylmethane (DPM) (the pivalyl group is the tertiarl- butyl group attached to carbonyl i.e.the trimetliylacetyl group)- n u s CH3 I CH3 I H,C-C-C-CH,-C-?-C,H II I 0 CH 1 II H,C 0 Many of its chelates are volatile and very stable. A family of useful ligands based at least 011 one pivalyl group is readily formed by straightforward methods of synthetic cliemistry- C H,-C-CH 2-C-C (C H ,) II II Acetylpivalylmetliane (APM) 0 0 CF,-C -CH,-C-C (CH,) Trifluoroacetylpivalylmetliane (TPM) ll 0 II 0 C,F5-C-CH,-C-C (CH,) Pent afluoropropanolylpivalylmethane (PPhI) I/ 0 II 0 C,T;,-C-CH,-C-C (CH,) Heptafluorobut anoylpivalylmet liane (H €%I) ll 0 11 0 Our initial interest was not so much in the application of gas - liquid cliromatography to the determination of metals via chelates that were readily chromatograpl~ed (e.g. beryllium and chromium) but to study the possibilities of chromatographing the so-called chelates of the alkali metals.I t had been reported that the alkali metal DPMs were volatile but in our experience could not be chromatograplied. I t was hoped to obtain more volatile and thermally stable alkali metal compounds from a ligand in which bulky alkyl groups suitably substituted with fluorine would protect the coordinated alkali metal from hydrolysis and dissociation Ideally a fully fluorinated DPM would have proved an interesting ligand but synthetic difficulties with this compound led Again P-diketone complexes were indicated. June 19721 INORGANIC ANALYSIS BY GAS CHROMATOGRAPHY 139 us instead to the preparation and study of 1 -[undecafluorobicyclo(2.2.l)lieptan-l-y1]-4,4,4- trifluorobutan-2,4-dione otherwise known as perfluoronorbornoyltrifluoroacetylmetliane whose sodium chelate is remarkably thermally stable and readily sublimable (250 "C; 0.5 torr) with no evidence of polymeric species in its mass spectrum (NaLj- 454).5 This sodium P-ketoenolate could be chromatographed at 220 "C provided that tlie column had been conditioned by several large injections of the substance.Better results were obtained however from studies of the lithium sodium and potassium enolates of HPM and PPRI which have been examined by thermal analysis mass spectrometry and gas chromatography. The alkaline earth metals have also presented problems in that the chelates with ligands such as DPM TPM PPM and HPM show complex mass spectra as a result of ready poly- merisation in the source of the instrument. Such chelates cannot be chromatographed.Elemental analysis and thermoanalytical studies have indicated that these clielates are hydrated ; this prevents ready volatilisation in the gas-chromatographic apparatus because at the temperatures necessary to volatilise the chelates the coordinated water molecules are removed and polymerisation of the compounds then ensues. The anhydrous compounds can be chromatographed quite successfully but show adsorption and displacement effects that make the measurement of retention times rather difficult .6 The chromatography of divalent metals as conventional P-diketonates is not very satisfactory; thus the chromato- graphy of lead P-diketonates results in very pronounced tailing of tlie chelate peaks. How- ever the volatility of these chelates can be used mass spectrometrically and very small amounts of lead can be determined by the technique of integrating the molecular ion c ~ r r e n t .~ These difficulties with divalent metals have led us to study tlie behaviour of monothio- P-diketones in the hope that the S-0 system would prove more useful for divalent transition metals. Pure chelates of Pb2+ Cd2+ Zn2+ Co2+ Co3+ Ni2+ and Pd2+ have been prepared from monothioacetylacetone (HT-A) and their thermal stabilities have been measured by thermal analysis. The nickel chelate sublimes completely and sliows unusually high thermal stability. Each chelate gives a good mass spectrum the molecular ion being the highest mass indicated. Very small amounts of the nickel chelate have been determined by the integrated ion current technique. Gas chromatography in PTFE columns is good for several 'd (T-T FA) 2 0 4 8 1 2 Time/m i nutes Fig.1. Separation of Ni(T-TFA), Pd(T-TFI\) and Pt(T-TFX) at 170 "C on a column of 2.5 per cent. Apiczon L on "Uni- versal I3" support 140 INORGANIC ANALYSIS BY GAS CHROMATOGRAPHY [Proc. Soc. ARaZyt. Chem. of these clielates and enables the separation of nickel cobalt and palladium as their chelates with HT-A to be achieved-the first example of the separation of three divalent metal complexes by gas chr~matography.~,~ The monothio derivatives of TFA TPM PPM and HPM and their chelates have also been prepared. The increased volatility of these chelates particularly of HT-TFA allows chromatography at much lower column temperatures. An example of this is given in Fig. 1 which shows the chromatography of Ni(T-TFA), Pd(T-TFA) and Pt(T-TFA),.This is tlie first recorded chromatogram of any platinum chelate and the first successful separation of three transition metals in the same Periodic G r o ~ p . ~ J ~ Of significance too is the fact that beryllium(II) aluminium(II1) and chromium(II1) do not react with H(T-TFA) so that some separations can be effected before chromatography. The general ease of formation of these monothio complexes and ease of extraction into non-polar organic solvents are particular attributes of these sulphur-containing ligands. Exploitation of the nickel thio-TFA system has been made for a variety of analytical purposes. R. S. Barratt has recently described this work in his Elwell Award paper.1 The method is summarised as follows. The nickel solution is treated at pH 4-5 to 5.0 with a solution of H(T-TFA) in hexane.Excess of H(T-TFA) is removed with 0.01 ni sodium hydroxide solution and the hexane solution of tlie chelate is analysed by gas - liquid chromato- graphy on a PTFE column packed with 5 per cent. silicone gum rubber (E350) on “Universal €3’’ support. The use of an electron-capture detector gives good sensitivity as little as 5 x 10-11 g of nickel can be detected and nickel concentrations down to 0.01 pg ml-1 have been determined. Interferences are minimal mercury proving the most troublesome. Copper is removed as sulphide and large amounts of cobalt are removed by masking with cyanide at pH 7-0. The method has been applied to the determination of trace amounts of nickel in instant tea and margarine.13 Further aspects of P-diketone chemistry of interest in gas-chromatographic applic a t’ ions concern the preparation of so-called P-ketoamines in which the enol function of the p- ketoenol is replaced by an amino or substituted amino group- R-C-CH2-C-R’ + KH2R” + R 4- CH,-C-R’ 0 0 I I XR“ I/ /I /I 0 11 R-C-CH =C-R’ I NHR” With the available P-diketones a wide range of new and interesting ligands becomes a reality.The use of secondary amines (bulky and otherwise) in place of ammonia offers an additional means of steric influence on subsequent chelation reactions. Preliminary results on amino-TFA and amino-TPN indicate a limited range of chelation reactions Cu2+ Ni2+ Pd2+ and Pt2+ forming chelates but that cliromatography is quite practicable a t temperatures of about 170 “C. Again selective chelation with divalent metal ions appears to occur.Another useful system concerns the ligands obtained by reacting compounds such as ethylenediamine with P-diketones to form the interesting tetradentate ligands in which two P-diketone residues are bridged by ethylenediamine or substituted ethylenediamines. Thus bisacetylacetoneethylenediimine H,(enAA,) forms chelates readily- with metal ions such as Cu2+ Ni2+ Co2+ Pd2+ and Pt2+. These chelates are volatile at temperatures above 200 “C but more useful properties are obtained with H,(enTFA,) readily prepared as a stable white crystalline compound. The unusual thermal stability of these chelates is indicative of the almost porphyrin-like structures and the volatility of tlie chelates is well within the useful gas-chromatographic range.H,(enTPM,) has proved troublesome to isolate but we have recently prepared pure chelates with Ni2+ Cu2+ and Pd2+. The solubility of these chelates in hydrocarbon solvents is quite remarkable and the volatility and thermal stability are high ; the chromatography of these chelates is interesting and some useful separations should be possible at much lower temperatures than with H,(enTFA2). June 19721 THE CHEMICAL SOCIETY’S LIBRARY 141 The use of gas chromatography for metal analysis offers high selectivity and sensitivity. Applications may be rather limited at the present time but with further studies of the various ligand systems described above the prospects for useful new methods particularly for trace amounts of metals look very good. 1. 2. 3. 4. 5 . G . r 8. 9. 10. 11. 12.13. REFERENCES Lederer M. Nature 1955 176 462. Biermann W. J. and Gesser H. Analyt. Chem. 1960 32 1525. Brandt W. W. and Heveran J . E. Paper presented at 142nd National Meeting American Chemica2 Moshier R. W. and Sievers R. E. “Gas Chromatography of Metal Chelates,” Pergamon Press Belcher R. Dudeney A. W. L. and Stephen W. I. J . Inorg. Nucl. Chem. 1969 31 625. Belcher R. Jenkins C. R. Majer J. R. Stephen W. I. and Uden P. C. Analytica Chim. Acta Belcher R. Majer J . R. Stephen W. I. Thomson I. J. and Uden P. C. Ibid. 1970 50 423. Stephen W. I. Thomson I. J. and Uden P. C. Chew. Commu~z. 1969 269. Belcher R. Stephen W. I. Thomson I. J. and Uden P. C. J . Inorg. N z d . Chem. 1971 33 _ _ _ _ ~ _ _ . Chem. Commun. 1970 1019. ____.- J. Inorg. Nucl. Chem. 1972 34 1017. Barratt R. S. P r o ~ . S O ~ . Analyt. Chem. 1972 9 86. Barratt R. S. Belcher R. Stephen W. I. and Uden P. C. Analytica Chim. .4cta 1972 59 59. Society Atlantic City N.J. Sept. 9-14 1962. Oxford 1965. 1972 60 109. 1851.

ISSN:0037-9697    

DOI:10.1039/SA9720900137

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

June 19721 THE CHEMICAL SOCIETY’S LIBRARY 141 The Chemical Society’s Library THE following publications of analytical interest have been added to the Library since the STAXDARD VETH HODS FOR THE EXAMINATIOX OF WATER AND WASTEWATER. 13th Edition. American A STATISTICAL MANUAL FOR CHEMISTS. 2nd Edition. E. L. BAUER. Academic Press. 1971. FIELD IONIZATION MASS SPECTROMETRY. H. D. BECKEY. Pergamon Press. 1971. CHEMICAL METHODS OF SILICATE ANALYSIS. A HANDBOOK. H. BENNETT and K. A. REED. Academic last list appeared in Proceedings (1972 9 99). Public Health Association. 197 1 . I’ress. 1971. 142 PAPERS ACCEPTED FOR T H E A N A L Y S T [PYOC. Soc. Analyt. Chew. HANDBOOK OF FLUORESCENCE SPECTRA OF AROMATIC MOLECULES. 2nd Edition. I. B. BERLMAN. Academic Fress. 1971. THE CURRENT STATUS OF LIQUID SCIKTILLATIOK COUXTING.(Based on the Proceedings of an International Symposium on the Current Status of Liquid Scintillation Counting held a t Massachusetts Institute of Technology March 31-April 3 1969.) Edited by E. D. BRANSONE. Grune and Stratton. 1970. AND THEIR ALLOYS). W. T. ELWELL and n. F. WOOD. Pergamon Press. 1971. ANALYTICAL CHEMISTRY OF MOLYBDENUM AND TUNGSTEK (IICCLUDING THE ANALYSIS OF THE METGLS KEACTIONS OF MOLECULES AT ELECTRODES. Edited by N. S. HUSH. Wiley-Interscience. 1971. ANALYTICAL CHEMISTRY OF SULFUR AND ITS COMPOUNDS. Parts 2 and 3. Edited by J. H. KARCHMER. TREATISE ON ANALYTICAL CHEMISTRY. Part I Volume 9. I. M. KOLTHOFF et al. Wiley-Interscience. CHEMICAL FALLOUT CURRENT RESEARCH 02 PERSISTENT PESTICIDES. M. W. MILLER and G. G. BERG. FAR-INFRARED SPECTROSCOPY.K. D. MOLLER and W. C. ROTHSCHILD. Wiley-Interscience. 1971. APPLICATIONS OF INFRARED SPECTROSCOPY IS BIOCHEMISTRY BIOLOGY AND MEDICINE. F. S. PARKER. INFRARED SPECTRA OF LABELLED COMPOU:JDS. S . PINCHAS and I. LAULICHT. Academic Press. 1971. AUTOMATION IN ANALYTICAL CHEMISTRY. Techr,ico:i Symposium London 1969. Technicon Instruments THE IDENTIFICATION OF ORGANIC COMPOUNDS. A MANUAL OF QUALITATIVE ASD QUANTITATIVE METHODS. INORGANIC TITRIMETRIC ANALYSIS CONTEMPORARY AIETHODS. Marcel COMPREHENSIVE ANALYTICAL CHEMISTRY. Volume 2C. Edited by C. L. WILSON and D. W. WILSON. PREPARATIVE GAS CHROMATOGRAPHY. Edited by A ZLATKIS and V. PRETORIUS. Wiley-Interscience. PERIODICAL Wiley-Interscience 1972. 1971. Charles C. Thomas. 1969. Plenum Press. 1971. Co. Ltd. 1971. 7th Edition (4th English Edition). S. VEIBEL. G. E. C. Gad. 1971. Dekker. 1971. Elsevier. 197 1. 1971. W. WAGNER and c. J . HULL. Dynamic Mass Spectrometry. 1970. Volume 1.

ISSN:0037-9697    

DOI:10.1039/SA972090141b

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

142 PAPERS ACCEPTED FOR T H E A N A L Y S T [PYOC. SOC. Analyt. Chew. Papers Accepted for Publication in The Analyst THE following papers have been accepted for publication in The Analyst and are expected to appear in the near future. “Determination of Cyclamate in Soft Drinks by Reaction with Nitrous Acid. Gas- Liquid Chromatography of Cyclohexene and of Cyclohexyl Nitrate,” by J. A. W. Dalziel R. M. Johnson and A. J. Shenton. “The Identification of Antioxidants in Polyethylene by Gas Chromatography,” by J. A. Denning and J. A. Marshall. “An Automated Method for the Dztermination of Lead in Calcareous Materials Utilising Liquid Ion Exchange,” by F. J. Bmo and R. J. Crossland. “A Colorimetric Method for the Determination of Chloral Hydrate,” by S. S. Kamat V. P. Barve and H. S. Mahal. “Determination of Thorium in Bovine Bone by Neutron-activation Analysis,” by S. Ohno and T. Ichikawa. “A Method of Processing Data from Automatic Microphotometers for Emission-spectro- graphic Analysis,” by B. L. Taylor and F. T. Birks. “A Comparison of Some Methods for the Determination of Triazine Herbicides in Water,” by C. E. McKone T. H. Byast and R. J. Hance. “Determination of Mercury Indium and Tellurium in Mercury Indium Telluride,” by E. J. Workman. “Species Identification of Heat-sterilised Canned Fish by Polyacrylamide Disc Electro- phoresis,” by I. RiI. Mackie and T. Taylor. “The Quantitative Separation of Chromium(V1) from Other Metals with a Strongly Basic Anion-exchange Resin,” by A. $1. Mulokozi. “The Determination of Sulphur in Lubricating Oil Fractions and in Fuel Oils-A Coulo- metric Method,” by Jean P. Dixon.

ISSN:0037-9697    

DOI:10.1039/SA9720900142

出版商:RSC    

年代:1972

数据来源: RSC

摘要:

SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHERIICAL SOCIETY ERRATUM APRIL (1972) ISSUE p. 101 (inside back cover) 15th line. For “$1.60” read “$61.60.”

ISSN:0037-9697    

DOI:10.1039/SA972090143b

出版商:RSC    

年代:1972

数据来源: RSC