摘要:

Proceedings of the Society for Analytical Chemistry CONTENTS Proc. SOC. Analyt. Chem. Vol. 3 No. 4 Pages 49-68 Gold Medal . . .. . . 49 “Automatic Analysis” . . .. 52 “Thin-layer Chromatography” . . 58 “Determination of Purity in Organic Materials” . . .. 61 “Economics of Automatic An- Reports of Meetings . . . . 49 alysis” . . . . . . . . 64 Membership changes . . . . 64 Papers accepted for The Analyst 65 Publications Received . . .. 65 Particle Size Analysis Confer- ence 1966 . . .. . . 66 Notices . . .. .. . . 67 Forthcoming Meetings Back cover April 1966 Vol. 3 No. 4 April 1956 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY President of the Society A. A. Smales O.B.E. Hon. Secretary of the Society S. A. Price Hon. Treasurer of the Society D.T. Lewis C.B. Hon. Assistant Secretaries of the Society B.S. Cooper; D. W. Wilson Secretary Miss P. E. Hutchinson 14 BELGRAVE SQUARE LONDON S.W.1 Telephone BELgravia 3258 Editor 1. B. Attrill Proceedings i s published by The Society for Analytical Chemistry and distributed to members and all subscribers to The Analyst without charge Single copies may be obtained direct from the Secretary The Society for Analytical Chemistry a t the above address (NOT through Trade Agents) price 2s. 6d. post free. Remittances payable t o “Society for Analytical Chemistry” MUST accompany orders THE SOCIETY FOR ANALYTICAL CHEMISTRY A Meeting of the Society to mark the Inauguration of the North East Section will be held on the afternoon and evening of Tuesday May 17th 1966 at Stockton-on-Tees The programme will include A visit to the Central Laboratories of British Titan Products Co. Ltd. The presentation of the Society’s Gold Medal t o Mr. H. N. Wilson by the President. A lecture by Mr. R. C. Chirnside entitled “Analytical Chemistry - A Nonconformist View.”

ISSN:0037-9697    

DOI:10.1039/SA96603FX013

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

THE SOCIETY FOR ANALYTICAL CHEMISTRY Forthcoming Meetings-continued May Tuesday 17th STOCKTON-ON- TEES Wednesday 18th LONDON Thursday 19th HUNTINGDON Friday 20th to Monday 23rd LLANDUDNO Tuesday 31st PAISLEY SOCIETY Special Meeting to mark the Inauguration of the North East Section. Presentation of the Society’s Gold Medal to Mr. H. N. Wilson F.R.I.C. “Analytical Chemistry-A Nonconformist View,” by R. C. Chirnside F.R.I.C. Stockton-on-Tees Co. Durham. MICROCHEMICAL METHODS GROUP London Discussion Meeting on “The “The Feathers,,’ Tudor Street London E.C.4; 6.30 p.m. BIOLOGICAL METHODS GROUP Summer Meeting. Visit to Huntingdon Research Centre Huntingdon. NORTH OF ENGLAND SECTION Summer Meeting. The County Hotel The Promenade Llandudno. Ordinary Meeting Saturday morning R. J. Taylor B.Sc.will give an introductory talk to two films entitled “The Social programme. SCOTTISH SECTION One-day Symposium on “Thin-layer Chromatography.” “The Principles of Thin-layer Chromatography,” by E. V. Truter Ph.D. “The Application of Thin-layer Chromatography to Anthraquinone Dyestuff “The Thin-layer Chromatography of Carbohydrates,” by K. C. B. Wilkie “The Thin-layer Chromatography of Lipids,” by W. R. Morrison Ph.D. “The Application of Thin-layer Chromatography to the Analysis of Pesticide College of Technology High Street Paisley; 10.30 a.m. Determination of Fluorine.” Physics and Chemistry of Water” and “Water in Biology.” BSc. A.R.C.S. D.I.C. Chemistry,” by C. G. Haynes Ph.D. B.Sc. Ph.D. B.Sc. F.R.I.C. A.R.C.S.T. Residues,” by J. Thomson Ph.D. A.H.-W.C. A.R.I.C. THE SOCIETY FOR ANALYTICAL CHEMISTRY Forthcoming Meetings April Wednesday 20th MIDLANDS SECTION jointly with the Lea Valley Sub-section of the Royal “Recent Investigations a t the Laboratory of the Government Chemist,” by Luton College of ‘Technology Luton; 6.45 p.m.THERMAL ANALYSIS GROUP on “Characterisation of Residues after Thermal LUTON Institute of Chemistry. D. T. Lewis C.B. Ph.D. D.Sc. F.R.S.H. F.R.I.C. Thursday 21st and Friday 22nd Treatment.” SALFORD Saturday 23rd MRNCHESTER Tuesday 26th LONDON May Wednesday 4th BRISTOL Friday 6th P R E s T o N Thuysday- Tour of the Research Laboratories Pilkington Bros. Ltd. Lathom; 2.30 p.m. Fyiday- “Modern Aspects of Dehydration and Decomposition of Mineral Silicates,” “Physical and Chemical Methods of Characterising Silicas,” by J. A. Hockey.“Differential Thermal Analysis of Edible Fats,” by D. P. J. Moran. “A Method of Thermal Analysis by Measurement of the Electrical Conductivity Conference Room Royal College of Advanced Technology Salford ; 10 a.m. NORTH OF ENGLAND SECTION. “X-ray Fluorescence Analysis,” by R. Twemlow A.R.I.C. Old Nag’s Head Hotel Lloyd Street Manchester; 2.30 p.m. SOCIETY Special Meeting. “Automated Systems for Extra-terrestrial Nuclear Activation Analysis,” by Meeting Room of the Chemical Society Burlington House Piccadilly London by A. A. Hodgson. of Polymers during Carbonisation,” by M. I. Pope. Professor R. E. Wainerdi. W.l; 6.30 p.m. SOCIETY Meeting on “Research Topics in Analytical Chemistry some current “Some Aspects of Titrimetry on the Microgram Scale,” by C. L. Graham B.Sc. “Some Developments in the Use of Oximes as Analytical Reagents,” by “Continuous Substoicheiometric Analysis,” by B.Cooksey L.R.I.C. “Precise Coulometric Titration,” by M. Riles B.Sc. and E. Bishop B.Sc. A.R.C.S.T. F.R.I.C. “A New Fluorimetric Reagent for the Determination of Submicrogram Amounts of Magnesium,” by R. Smith B.Sc. A.R.C.S. “Chromatography of Some First Row Transition Metals on Thin Layers of Substrates Impregnated with Tri-butyl Phosphate,” by G. Duncan B.Sc. A.R.C.T. L. S. Bark BSc. F.R.I.C. M.R.S.H. and R. J. T. Graham M.Sc. Ph.D. A.R.I.C. work in Universities and Colleges of Advanced Technology.” C. Broughton M.Sc. A.R.I.C. A.R.T.C.S. “Some New Inorganic Ion-exchangers,” by G. N. Stradling B.Sc. “Analytical Properties of Heterocyclic Azo Dyestuffs,” by R. G. Anderson School of Chemistry The University Bristol ; 2.30 p.m. NORTH OF ENGLAND SECTION. “Rapid Screening Methods for Drugs,” by M. S. Moss. Preston; 7.15 p.m. B.Sc. and G. Nickless B.Sc. Ph.D. [continued ivtside back cover PRINTED BY W. HEFFER & SONS LTD.. CAMBRIDGE. ENGLAND,

ISSN:0037-9697    

DOI:10.1039/SA96603BX015

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

April 1966 Reports of Meetings Vol. 3 No. 4 JOINT MEETING A JOINT Meeting of the Society (organised by the Midlands Section) with the Birmingham and Midlands Section of the Royal Institute of Chemistry and the Birmingham and Midland Section of the Society of Chemical Industry and the Chemical Society was held at 9.45 a.m. on Wednesday March 30th 1966 in the Chemistry Department Haworth Lecture Hall The University Edgbaston Birmingham 15. The subject of the meeting was “Nuclear Magnetic Resonance and Electron Spin Reson- ance Spectroscopy.” The Chair at the morning session was taken by the President of the S.A.C. Dr. A. A. Smales O.B.E. F.R.I.C. and the following papers were presented and discussed “An Introduction to the Principles of Nuclear Magnetic Resonance Spectroscopy,” by Professor N.Sheppard B.A. Ph.D. ; “Academic Applications of Nuclear Magnetic Resonance,” by J. A. Smith M.A. D.Phil. ; “Analytical Applications of Nuclear Magnetic Resonance Spectroscopy Particularly as Applied to Industry,” by J. K. Becconsall B.Sc. Ph.D. The Chair at the afternoon session was taken by the President of the Birmingham University Chemical Society Professor M. Stacey F.R.S. and the following papers were presented and discussed “Some Aspects of the Nuclear Magnetic Resonance Spectroscopy of Fluorine Compounds,” by L. F. Thomas B.Sc. Ph.D. ; “Introduction to Electron Spin Resonance Spectroscopy and its Applications,” by D. H. Whiffen M.A. D.Phil. DSc. F.R.S. ; “Instrumentation and Experimental Techniques in Electron Spin Resonance Spectroscopy,” by J. K. Brown B.A. Ph.D. NORTH OF ENGLAND SECTION THE forty-first Annual General Meeting of the Section was held at 2.30 p.m.on Saturday January 29th 1966 at the Old Nag’s Head Hotel Lloyd Street Manchester. The Chair was taken by the Chairman of the Section Mr. J. F. Clark MSc. A.R.C.S. D.I.C. F.R.I.C. F.R.S.H. The following appointments were made for the ensuing year Chairman-Mr. J. F. Clark. Honorary Secretary aad Treasurer-Mr. G. F. Longman Unilever Research Laboratory Port Sunlight Cheshire. Members of Committee- Mr. J. B. Aldred Mr. L. s. Bark Mr. A. 0. Jones Mr. F. C. Shenton and Mr. R. Sinar. Mr. C. E. Davis and Mr. H. Pritchard were re-appointed as Honorary Auditors. The Annual General Meeting was followed by an Ordinary Meeting of the Section at which the following paper was presented and discussed “Thermal Analysis with Reference to Inorganic Hydrates,’’ by G.F. Longman B.Sc. F.R.I.C. 49 Vice-Chairman-Dr. W. Cule Davies. 50 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 A JOINT Meeting of the North of England Section with the Newcastle upon Tyne Section of the Royal Institute of Chemistry was held at 6.30 p.m. on Friday March 4th 1966 in the Lecture Theatre The School of Chemistry The University Newcastle upon Tyne. The Chair was taken by the Chairman of the North of England Section Mr. J. F. Clark M.Sc. A.R.C.S. D.I.C. F.R.I.C. F.R.S.H. The following paper was presented and discussed “The Analysis of Standard Metallur- gical Samples,” by P. D. Ridsdale B.Sc. A.I.M. A JOINT Meeting of the Section with the Leeds University Union Chemical Society was held at 6.15 p.m.on Friday March 18th 1966 inathe Lecture Theatre Chemistry Department The University Leeds. A lecture on “Analysis Reborn” was given by Professor C. L. Wilson Ph.D. D.Sc, F.R.I.C. F.I.C.I. The Chair was taken by Dr. W. Cule Davies F.R.I.C. SCOTTISH SECTION THE thirty-first Annual General Meeting of the Section was held at 1.45 p.m. on Friday January 28th 1966 at More’s Hotel India Street Glasgow. The Chair was taken by the Chairman of the Section Mr. J. K. McLellan M.A. B.Sc. F.R.I.C. The following office bearers were appointed for the coming year Chairman-Mr. J. K. McLellan. Vice-Chair- man-Dr. D. M. W. Anderson. Honorary Secretary and Treasurer-Mr. J. W. Murfin Boots Pure Drug Co. Ltd. Motherwell Street Airdrie Lanarkshire. Members of Committee-Mr. W. A. Alexander Dr.R. A. Chalmers Mr. A. L. Cochrane Mr. G. R. Jamieson Mr. R. C. Voss and Mr. A. F. Williams. Mr. J. S. Foster and Mr. A. M. Markson were appointed as Honorary Auditors. After the business meeting a talk on “The Development and Facilities of the New Glasgow Airport” was given by the Airport Manager Mr. R. A. Read D.F.C. AN Ordinary Meeting of the Section was held at 7.15 p.m. on Friday February 25th 1966 at the Paisley College of Technology Department of Chemistry High Street Paisley. The Chair was taken by the Chairman of the Section Mr. J. K. McLellan M.A. B.Sc. F.R.I.C. The following papers were presented and discussed “The Balance Manufacturer Educator or Sycophant?” by M. V. Moorhouse; “Weighed in the Balance and Found Wanting,” by R. A. Chalmers B.Sc. Ph.D. F.R.I.C. NORTH EAST SECTION AN Exploratory Meeting of the Section was held at 7 p.m.on Thursday March 24th 1966 at the County Hall Durham. The Chair was taken by the Chairman-elect of the Section Mr. W. C. J. Smith F.K.I.C. A lecture was given by the President of the Society Dr. A. A. Smales O.B.E. F.R.I.C. on “The Analysis of the Barwell Meteorite.” The following officials and committee were confirmed in office until the next Annual General Meeting Chairman-Mr. W. C. J. Smith. Honorary Treasurer-Mr. A. Hutchinson. Honorary Secretary-Mr. J. Whitehead British Titan Products Co. Ltd. Central Laboratories Portrack Lane Stockton-on-Tees Durham. Members of Committee-Mr. W. C. Coppins Dr. A. C. Docherty Mr. L. R. Flynn Dr. J. R. Gwilt and Mr. F. C. Shenton. A formal request was made to Council to approve the formation of the North East Section.The laboratories of the Durham County Analyst were opened for inspection after the Meeting. April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 51 MICROCHEMICAL METHODS GROUP THE fifty-third London Discussion Meeting of the Group was held at 6.30 p.m. on Wednesday March 16th 1966 at “The Feathers,” Tudor Street London E.C.4. The Chair was taken by the Chairman of the Group Mr. R. Goulden F.R.I.C. A discussion on “The Determination of Molecular Weights” was opened by C. Heitler B.Sc. and W. W. Wright B.Sc. Ph.D. A.R.I.C. SPECIAL TECHNIQUES GROUP AN Ordinary Meeting of the Group was held at 3 p.m. on Tuesday February 22nd 1966 at the Wellcome Building Euston Road London N.W.l. The Chair was taken by the Chair- man of the Group Dr.G. F. Reynolds M.Sc. Ph.D. M.R.S.H. F.R.I.C. The subject of the meeting was “Special Techniques in Gas Analysis” and the following papers were presented and discussed “Some Aspects of Gas Analysis with Gas -Solid Chromato- graphy,” by C. G. Scott D.Phi1. ; “Thermovaporimetric Analysis,” by B. Riley BSc. A.R.I.C. A.I.Ceram. ; “The Determination of Trace Impurities in Permanent Gases With a Mass Spectrometer,” by R. E. Wilson BSc. F.R.I.C. and R. T. Parkinson B.Sc. BIOLOGICAL METHODS GROUP AN Ordinary Meeting of the Group was held at 7 p.m. on Wednesday February 23rd 1966 in the Meeting Room of the Chemical Society Burlington House London W.l. The Chair was taken by the Chairman of the Group Dr. M. W. Parkes. The following paper was presented and discussed “Modern Techniques in the Bacterio- logical Examination of Food,” by Dr.Betty Hobbs. PARTICLE SIZE ANALYSIS GROUP THE Inaugural Meeting of the Group was held at 7 p.m. on Thursday February 17th 1966 in the Meeting Room of the Chemical Society Burlington House London W.l. The meeting was opened by the President Dr. A. A. Smales O.B.E. F.R.I.C. and the following were con- firmed as Officers and Committee Members for the forthcoming year Chairman-Mr. T. Allen. Honorary Secretary and Treasurer-Dr. V. T. Crowl The Paint Research Station Walde- grave Road Teddington Middlesex. Members of Committee-Dr. L. M. Fitzgerald Dr. C. G. L. Furmidge Dr. J. A. Hersey Mr. J. F. Hinsley Mr. G. Treasure and Mr. D. C. Soul. Mr. E. Q. Laws and Mr. C. Whalley were appointed as Honorary Auditors. The business meeting was followed by the first Ordinary Meeting of the Group at which the Chair was taken by the Chairman of the Group Mr. T. Allen M.Sc. The following papers were presented and discussed “Determination of the Surface Area of Fine Particles,” by N. G. Stanley-Wood; “Size Analysis by Optical Microscopy,” by G. L. Fairs; “Size Analysis with the Coulter Counter ; Comparison with Sedimentation and Surface Area Measurements,” by M. J. Thornton.

ISSN:0037-9697    

DOI:10.1039/SA966030049b

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

62 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 Automatic Analysis The following are summaries of papers presented at the Ordinary Meeting of the Society held on November loth 1965 and reported in the December 1965 issue of Proceedings (p. 175). Introductory Talk BY H. E. STAGG (Imperial Chemical Industries Ltd. Dyestufs Division Manchester) MR. STAGG said that he believed the mechanisation of critical analytical procedures was already one of the most important subjects concerning the professional analyst and that within the next decade it might become the most important single topic. He thought that this was due primarily to the advance that the analytical technique itself had achieved during recent years. Twenty-five years ago techniques such as mass spectro- scopy nuclear magnetic resonance spectroscopy X-ray fluorescence and gas - liquid chroma- tography were unknown in the analytical laboratory.Ultraviolet visible and infrared spectroscopic techniques were known but were handicapped by the limitations of the single- beam instruments of poor resolving power and doubtful stability then available and the enormous potentialities of polarography and thin-layer chromatography were virtually unrecognised. The revolutionary changes in technique and the improvements in instrument performance and design that had since occurred had enabled the analyst to provide the chemist in research and development with a wealth of information about the products that he made. Together with these developments there had been two other significant economic changes. One was the steady rise in the cost of labour that had taken place throughout the whole of the post-war period and the other was the sharp rise in competition for export markets.Already the chemical industry and many other attendant industries were experiencing the severe competition that American European and Far Eastern manufacturers were capable of exerting and unless we were prepared to extract the maximum efficiency from our manu- facturing processes these markets would be stolen from us. These were three major reasons why the mechanisation of analytical procedures both in the laboratory and in process control was a matter of necessity. A less pressing reason that deserved mention was the increased amount of restrictive legislation under which the industrial chemist was being entombed.He could no longer discharge unwanted reaction products into the rivers or vent noxious gases into the air. The concern shown by local and national government by the pollution of the atmosphere and rivers and tidal estuaries was proper but the need for industry to prevent such pollution from occurring accidentally required considerable vigilance in monitoring factory effluents and exhaust systems. The cracking of a pipe or the disintegration of a gland packing could occur even in the best-run factories and unless such a mischance was detected quickly serious damage might be caused. The results of the accidental emission of poisonous irritant or malodourous chemicals into the air or into rivers and tidal waters could be both costly and embarrassing to industrial management.Damages were likely to be heavy and in addition there was the cost of litigation as well as the time spent by senior staff in preparing a defence. In considering the necessity for mechanising analytical processes and the methods by which this could be achieved distinction had to be made between the mechanisation of laboratory analyses and the provision of automatic analysis as part of the continuous control of a chemical manufacture. In the laboratory samples were received in discreet form and were fed individually by hand into the machines that performed the reactions and measure- ments constituting the analytical process. This method of working overcame the two most difficult problems associated with the mechanisation of analysis which are respectively the collection and presentation of a representative sample and the detection of mechanical breakdown.It was therefore not surprising that much success had already been achieved in this sphere of activity. April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 53 The mechanisation of process-control analysis however presented an additional set of problems. In addition to providing a method of analysis that would determine separately the components of a comparatively complex mixture some of which might be present in quite small amounts and might exert an effect on quality that was out of all proportion to the amount present it was also necessary to arrange that this analytical test could be carried out repeatedly over long periods of time. The accuracy of the results had to remain constant and the risk of failure had to be small.The design of equipment that would fulfil this exacting specification was not an easy matter and in this field of application engineering successful developments were more difficult to find. They had been most common in the petroleum and petrochemical industries where the products were clean and volatile and less liable to solidify in feed lines and the optical cells could be kept free from accumulated deposit. Nevertheless in other sections of the chemical industry there were already enough examples of continuous on-line analysers in operation to show that the problems could be overcome. This condition was usually fulfilled if the safety of a chemical plant or of the persons operating it was involved. There were many other circumstances in which the cost of development and installation of an on-line analyser could be amply justified by the return that could be obtained e.g.in the manufacture of alkyl benzenes by the Friedel - Craft reaction. If water accident- ally entered the system via the ethylene feedstock it could result in the complete destruction of the aluminium chloride as well as loss in production. Mr. Stagg referred to a case quoted by Fraade in which the cost of catalyst destruction had been estimated at $3700 a month. An on-line analyser to monitor the water content of the ethylene costing only $4000 to install had prevented this from happening. The saving in raw-material cost alone had been over $40,000 a year quite apart from the loss of potential profits resulting from interrupted production representing a 1000 per cent.return. The vital importance of utilising existing plant to the full was not sufficiently recognised in Britain; a shortage that had to be faced by British Industry was that of investment capital. Mr. Stagg knew from his own company that a simple process analyser could raise the output of a plant by as much as 50 per cent. simply by instant recognition of the completion of the reaction. The product could therefore be discharged without waiting for laboratory testing. As operations increased in size and continuous processes replaced batch processes the penalties of error became more serious and the need for quick detection grew correspondingly. The development of automatic analysers was important in another direction also ; with the advent of the computer critical closed-loop control of chemical processes could become a reality but the facilities of the computer could not be fully utilised unless it could be fed with critical analytical data at frequent intervals and this was physically impossible to achieve with manual techniques.The problem of the maintenance of the complicated and delicate devices used also had to be considered. Without the team of people who could carry out analyses by hand depend- ence upon the machine would become absolute and it was important that in the event of failure rapid repairs should be made. There was a serious shortage of maintenance engineers capable of repairing this kind of instrument and unless methods of training inside or outside industry produced such men in sufficient numbers widespread attempts at the automation of chemical processes would be futile.There was therefore an abundance of problems and topics for the new Group of the Society to discuss. Mr. Stagg thought that it might initially wish to confine itself with the mechanisation of purely laboratory analytical methods. Eventually the problem of providing reliable repetitive analyses for the control of manufacturing processes had to be faced and he hoped that the Automatic Methods Group of the Society for Analytical Chemistry would be one of the first to face it. Process Control with Gas Chromatography in Chemical Industry BY DR. HERMANN KIENITZ AND DR. RUDOLF KAISER (Badische A n i l i n und Sodafabrik A ,G. Ludwigshafen Germany) DR. KIENITZ said that essentially automatic gas-chromatographic equipment used in chemical process control gave quite a good performance with an average down-time under ideal con- ditions of 2 hours per month.In practice however difficulties arose resulting in a rise of 54 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 down-time to about 20 hours per month. An investigation of such problems would therefore be worthwhile. It was essential to know the parameters concerned for the automation of chemical equip- ment. These parameters could assume the form either of physical characteristics e.g. temperature pressure mass flow or of the concentrations in the various stages and knowledge of them was necessary for control and checking or even for optimation. Knowledge of the composition of the feed stock and the products of conversion was also needed to give information on the equilibrium conditions or on kinetic mechanisms.Changes in the compositions even of substances in very low concentrations were more sensitive and gave more rapid response than the corresponding physical variables of state. For example gas-chromatographic techniques were 10 times more sensitive to a change in concentration in a distillation column than other techniques to the associated change in temperature. Consequently a control device functioning on changes in concentration would be 10 times more sensitive. Dr. Kienitz divided the automation of analytical processes into the following individual stages conditioning the sample ; introducing the sample ; measurement of the results obtained with an analogue or digital computor ; transformation of the measured values for analytical results into concentrations ; data processing determination of average values statistical analysis and so on.However automation of the individual steps would be inadequate if there was not a control system in the total procedure that would exert some form of critical judgement similar to the human element in manual analysis. This would provide a guarantee for the analytical results and avoid the errors involved in the automatic control of chemical processes. The various types of gas chromatographs available on the market for automatic and periodic gas-chromatographic analysis were mentioned. It was necessary for the process gas chromatograph to accommodate each analytical task individually and for data processing to yield the analytical results in the form desired.Data processing could be used either for statistical purposes or for process control by eliminating fluctuations with the aid of mean values. Continuous and discontinuous sample conditioning were then discussed ; continuous techniques were preferred for gaseous specimens and discontinuous for liquid specimens. The introduction of an internal standard was as important for ensuring reliable analytical results as it was for self-checking of the automatic analysing device. This automatic self- checking of the process gas chromatograph could be extended to include the introduction of the specimen the column in which separation was effected and the detector; thereby simplify- ing maintenance of the instruments. The down-time might be reduced by a factor of ten. Its main pur- pose he said was to provide a representative sample from the sample origin to the sampling system of the analytical device with a minimum of dead-time.Factors such as phase pressure temperature homogeneity and purity of the phase had to conform with the necessary requirements for the accuracy of the measured results. The chemical and physical state of the sample at the point at which it was introduced had to guarantee that the sampling system functioned reliably for as long as possible. However the required quality of the analytical results determined for example the extent to which the phase purity of phase and the thermo- dynamic variables of state had to be maintained within given tolerances. An example cited involved the investigation of a gaseous specimen from a fluidised-bed reactor.Portions of only 0.1 per cent. by volume of the solid phase consisting say of dust from the catalyst could be neglected provided that the amount of solid matter did not accumulate. If however solids were deposited an error would be detected after the fifth analytical sequence and the feed volume would then be reduced by 0-5 per cent. volume. Even if the solid phase did not accumulate it could still cause mechanical damage to the feed system in a short time. But not all of the solids that did not contribute to the final results could be completely removed by sample conditioning; that in fact was not even necessary. The solids should only be removed to such an extent in which they no longer affected the results. The qualitative demands were then dealt with in detail with special reference to taking a representative sample ; transportation to the sample-introducing device ; dead-time ; and chemical and physical variables of state.Dr. Kienitz then continued by describing sample conditioning in detail. April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 55 TAKING A REPRESENTATIVE SAMPLE- The standard devia- tion in the composition of the specimen depended considerably upon the method of sampling or on the ratio of the sample size to the particle-size distribution. This relationship did not hold for liquids and gases as the homogeneity of the specimen at the sample origin was usually unknown. Specimens were usually taken from a single point by tapping of a stream- line in which it was usually assumed that the stream was entirely homogenous at the sample origin.Dr. Kienitz described an example in which it was assumed that the composition of the vapour phase in a distillation column deviated from the original value because of fluctua- tions in temperature or pressure. Small changes in temperature and pressure and in the mass flow of the stream-line could give rise to considerable changes in composition. An entirely satisfactory solution could not be found to the problem of tapping the stream-line a t the correct place and in the correct manner and of leading it to the starting point of the analytical system. The diameter of the opening and its position and orientation to the direction of mass flow were decisive factors when the sample to be tapped off was not locally completely homogeneous. If it was homogeneous then the change in composition with regard to time could be determined without ambiguity.The first significant difference between continuous and discontinuous sample conditioning could be recognised here. If in discontinuous conditioning the cycle was longer than the time required for a mensurable change in concentration a false result might be obtained for the rate of change of concentration. In continuous sample preparation plug-flow predomin- ated and the dimensions were selected so that no error in the rate of change of concentrations could arise. Rapid changes in scattering of measured values could be recognised even when the analytical cycle was reduced. These changes with time were smoothed out with dis- continuous sample preparation in accordance with the time constants of the sampling cycle and the rate of change.If the dimensions describing the cycle mass flow and width of the stream-line were favourably related to one another discontinuous sampling offered a decided advantage for controlling unsteady processes-high rates of change of concentration about an average which although low governed the process and whose trend could be determined. Too little attention had been devoted to the mechanical and physical magnitudes describing the section of the sample preparation concerned with tapping of the stream-line. The sampling of solid granular material presented no difficulties. TRANSPORTATION TO THE SAMPLE INTRODUCING DEVICE- composition of the sample would have to be maintained. To retain the advantage of continuous sample conditioning small changes in the DEAD-TIME- The time-dependent characteristic of the flow of the stream-line through a continuous conditioner and the geometry of the conditioner itself (i.e.effective volume of the whole con- ditioning system with relation to mass flow) governed the dead-time. The discontinuous system could operate more rapidly i.e. have less dead-time than the continuous. If the conditioning system was regarded as a control system (i.e. if the dead-time response time and time constants were investigated) quantitative predictions could be obtained. CHEMICAL VARIABLES OF STATE- The nature and amount of the components of the sample that did not primarily affect the analytical results but damaged the feed system were included. In an emulsion of water and residues in petrol neither the amount introduced nor the solid residues would affect the hydrocarbon composition.Seals in the sample-introducing systems might however be damaged. If the solid residue accumulated it could be determined and then disturbances could be measured. Enrichments in the sample-introducing system affected the absolute amount fed. Enrichments in the separating system qualitatively affected the analytical results. To prevent accumulation in the sample introducing system a greater outlay in the separation of phases or back-flushing the sample-introducing device with solvents was necessary. 56 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 To prevent accumulation of residues in the separating system a greater outlay in the separation of the phases and better treatment of the sample was needed.Solid residues that had originally been loosened could also cause disturbances and because of this the discontinuous system was usually superior to the continuous system. Dr. Kienitz concluded by discussing in detail and by the use of slides the advantages and disadvantages of continuous and discontinuous sample conditioning. Automatic mechanical cleaning e.g. by pressure surges was also feasible. Non-radiometric Instruments for Process Control in the Windscale Nuclear Fuel Reprocessing Plant I3u C. R. MCGOWAN (United Kingdom Atomic Energy Authority Windscale Works SellaJield Curnberland) DR. MCGOWAN described three analytical instruments developed for use in the U.K.A.E.A. irradiated-uranium reprocessing plant at Windscale. The subjects were direct in-line measurement of the ferrous-to-ferric ratio in a process stream by oxidation - reduction potentiometry ; in-line measurement of the ferrous sulphamate Concentration in a non-active feed stream by continuous partial-potentiometric titration ; the measurement of the acidity of plutonium process solutions by automatic coulometric titration of manually presented samples.The function of these instruments was limited to the provision of information on process conditions ; they were not incorporated in a closed control loop. IN-LINE FERROUS-TO-FERRIC RATIO MONITOR- At one stage in the Windscale solvent extraction process a ferrous sulphamate backwash solution is used to reduce plutonium to the inextractable tervalent form in order to separate it from a tributyl phosphate - kerosene solution containing uranium(v1) and plutonium(1v).Complete reduction of the plutonium is essential for high efficiency. The necessary con- ditions can be specified in terms of the ferrous-to-ferric ratio in the aqueous product and this parameter is continuously monitored by redox-potential measurement. A platinum indicator electrode is used with a mercury - mercurous sulphate reference half-cell. The e.m.f. is measured with an electronic millivoltmeter and a resistance thermometer provides temperature compensation. The sensing elements are installed in a small tank in a re- circulating sample loop not in the main stream and are accessible for standardisation with synthetic process solutions. IN-LINE FERROUS SULPHAMATE MONITOR- An in-line analyser is used to measure the ferrous ion concentration in a non-active ferrous sulphamate - nitric acid feed to the process stage referred to above.The sample is delivered at a slow constant rate into a small mixing vessel in which it meets a stream of standard oxidising agent (potassium dichromate solution). The flows are regulated by a pair of gravity-fed injector valves driven by a synchronous motor. The product of the oxidant flow-rate and concentration is a chosen amount smaller than the corresponding product for the sample so that the sample is incompletely oxidised even when its con- centration falls to the lowest point in the required range. The proportion of unreacted ferrous ion and therefore the ferrous-to-ferric ratio varies with the ferrous sulphamate concentration. This ratio governs the redox potential of the mixture which is measured with conventional equipment of the type described above.The method is quite sensitive (a 1 per cent. change in sample concentration produces a potential change of 2 mV) and is capable of good reproducibility ( 5 2 per cent. under plant conditions) but scale curvature severely restricts the useful span. The chief merit of the method is that the use of simple reliable equipment is allowed. AUTOMATIC COULOMETRIC TITRIMETE:R FOR FREE ACID DETERMINATION- This instrument had been developed for determining free acid in aqueous ( 0 . 6 ~ ) and organic ( 0 . 4 ~ ) process solutions containing plutonium and other hydrolysable cations. April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 57 Measured volumes of sample were presented to it manually and thereafter the analysis was fully automatic through to waste disposal and digital presentation of the result.Although this was not an in-line instrument it was a valuable aid to process control as it greatly reduced the analysis lag and considerably decreased analytical costs. It had been constructed to meet a specific need in the former Windscale plutonium-purification plant and is no longer in use. The method was based on a laboratory procedure in which potassium fluoride was used as complexing medium to prevent appreciable hydrolysis of the cations during alkalimetric titration. In the automatic method the titrant was produced by external electrolysis at constant current. The colour change of the acid - base indicator at the equivalence point was detected by a photometer that operated on a relay to switch off the electrolysis current and the flow of titrant.The titre was expressed in units of time; the number of electrical impulses produced by a simple pulse generator during the titration period was recorded by a digital register. The precision (3 x relative standard deviation) was k4.3 per cent. which was adequate for the immediate purpose. The method was inherently sound and there was considerable scope for improvement in performance but the model described was assembled to a schedule that did not allow time for refinement. Some Applications of Radio-isotopes in Chemical Analysis BY J. K. SKREBOWSKI (Imperial Chemical Industries Ltd. Heavy Organic Chemicals Division Billingham Co. Durham) DR. SKREBOWSKI said that methods of analysis based on radio-isotope sources and labelled compounds were now fairly well established in the laboratory.Significant advances had also been made in recent years in the application of fixed sources as the basis of on-stream analysers in chemical manufacturing processes. He thought that the most widely known application of this type was the use of a or P-emitting sources in ionisation detectors for on-stream gas chromatography. In some processes an unambiguous relationship could exist between density and chemical composition and for these y-emitting radio-isotope sources could offer a convenient and simple method of continuous density monitoring. A great advantage of the y-density gauge was that it could be installed (e.g. on a pipe carrying a liquid) directly; both source and detection system were mounted external to the pipe on the vessel containing the medium of interest.For many applications on chemical plant sources of caesium-137 or cobalt-60 were convenient ; both isotopes emitted sufficiently penetrating y-radiation capable of passing through steel walls and they had suitably long half-lives. A number of density gauges with ion-chamber Geiger - Muller tube and scintillation detectors were available commercially. Simple liquid mixtures comprising a minor constituent (e.g. impurity) of relatively high atomic number in a matrix of low mean atomic number (e.g. organic liquid) frequently arose in petrochemical processes. If a sample stream could be arranged to pass through a cell with appropriately thin windows it was then possible to consider the use of radio-isotope sources of low energy radiation (less than 100 KeV).In this region mass absorption coefficients were strongly dependent on atomic number and a simple absorption cell could be constructed to be highly sensitive to variations in concentration of the element of relatively high atomic number. The method was useful when the minor constituent was present at the fractional percentage level and it had been applied to the continuous monitoring of sulphur in refinery streams and the determination of lead (as tetraethyl lead) in petrol and of cobalt in hydrocarbon streams. Sources suited to particular applications could be selected from Bremsstrahlung emitters such as hydrogen3 and promethium-147 or from cadmium-109 and americium-241 sources (available more recently) that emitted monochromatic electromagnetic radiations.Radio-isotope sources of this nature could also be used for analysis by the X-ray fluores- cence technique. It was usual to use the source - detector system in back-scatter geometry in relation to the sample and to select the characteristic radiation by a pulse-height analyser or by a filter system. The limited intensity available from a radio-isotope source prohibited the use of energy-selection methods applied in conventional X-ray tube fluorescence equip- ment and in general the radio-isotope method was not comparable with regard to the limits 58 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 of detection. Nevertheless for on-stream instruments the radio-isotope method offered the important advantages of simplicity compactness and cheapness and was especially useful for the analysis of elements at the level of 100 p.p.m. and above. Other techniques of analysis incorporating fixed radio-isotope sources included the use of p emitters for determining the carbon-to-hydrogen ratio of organic streams and neutron sources in methods based on absorption and scattering properties. Radio-isotope methods were beginning to make a contribution in on-stream analytical instrumentation and with the general trend to automation in chemical processes Dr. Skre- bowski thought it likely that their future contribution would become increasingly significant.

ISSN:0037-9697    

DOI:10.1039/SA9660300052

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

58 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 Thin-layer Chromatography The following are summaries of papers presented at the Joint Meeting of the Thin-Layer Chromatography Group and the Department of Textile Industries of the University of Leeds held from January 5th to 7th 1966 and reported in the March issue of Proceedings (p. 39). Reproducibility of RF Values in Thin-layer Chromatography BY M. S. J. DALLAS ( Unilever Research Laboratory Welwyn Herts.) MR. DALLAS said that if R values in thin-layer chromatography were to be reproducible then it was necessary to describe simultaneously certain experimental details which in part determined them. The paper was concerned principally with the physical factors affecting R values. The most important of these factors were the adsorbent and the design of the developing vessel; a method of controlling the activity was described and a comparison was made between development in ordinary tanks and the development in S-tanks (sandwich chambers).Other physical factors including adsorbent quality layer thickness temperature loading relative mobile phase volume and the distance of migration were discussed. The effects of temperature relative humidity and of silver nitrate concentration on R values on silver nitrate impregnated adsorbents were also discussed. The Place of Thin-layer Chromatography in Pesticide Residue Analysis BY J. THOMSON (Ministry of Technology Laboratory of the Govevnrnent Chemist Covnwall House Stainford Street London S.E.l) DR. THOMSON said that thin-layer chromatography had replaced paper chromatography as a major weapon in the armoury of the pesticide residue analyst.It had been used as a clean-up process a diagnostic method and as a quantitative method. The effect of several essential parameters such as tank size and temperature on the separa- tion of organochlorine and organophosphorus pesticides and herbicides was discussed to- gether with the use of other recently developed techniques such as wedge-layer and multiband- layer chromatography. One major aim of the residue analyst was the production of a unified method of extrac- tion clean-up and analysis of parts per thousand million of pesticide residue. The method should be appljcable to a wide variety of samples and would also enable chlorinated pesticides to be distinguished from organophosphorus pesticides.Thin-layer chromatography had opened new and exciting possibilities in the solution of these problems. Use of Radioactive Tracers in Analysis by Thin-layer Chromatography BY D. A. LAMBIE (Radiochernical Centre Amersharn Bucks.) MR. LAMBIE said that one of the problems of thin-layer chromatography as in other chromato graphic procedures was the detection of colourless substances after they had been separated April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 59 Radioactive tracers (in the form of the appropriate labelled compounds) added to the sample offered an elegant solution to this problem. The radioactive spots on the chromatograms were detected by a variety of means e.g. auto-radiography scanning with a radiation detector such as a Geiger - Miiller counter or a gas-flow proportional counter.Thin-layer chromatography was used in isotope dilution analysis a technique that was of particular value for the examination of complex mixtures as it obviated the need for the quantitative isolation of the constituent of interest. A known weight of the appropriate labelled compound was added to the analytical sample and the constituent of interest that was of course chemically identical with the labelled compound was isolated in a pure state by suitable methods. The change in the specific activity of the compound enabled the amount of constituent in the sample to be determined. A related and more accurate technique derivative dilution analysis was to be preferred for determining trace constituents. This technique was also used when a radio-isotopically labelled sample of the compound of interest was unobtainable provided that a labelled reagent with which it would react reproducibly was available.It was essential for the labelled compounds used in analysis to be radiochemically pure. Thin-layer chromatography was one of the simplest methods for purifying labelled compounds during production and for checking the purity after storage. Fundamentals and Application of Thin-layer Electrophoresis BY J. D. R. THOMAS (Welsh College of Advanced Technology Cathays Park Cardiff Glamorgan) MR. THOMAS said that material which had been prepared for thin-layer chromatography had also been used for separations by electrophoretic methods. Apparatus designed for horizontal paper electrophoresis had been found to be suitable. The behaviour on thin-layer electrophoresis of amines amino-acids and peptides carbo- hydrates phenolic materials (including dyes) and inorganic materials had been studied.The advantages claimed for thin-layer chromatography e.g. enhanced resolution and faster separation had also been seen in thin-layer electrophoresis. If compounds of high water solubility were separated on supports of low adsorptive capacity haphazard zone migration occurred during drying at elevated temperatures. This effect had been overcome by freeze-drying the electrophorograms before applying the detecting reagent. For the effects of heating to be minimal thin-layer electrophoresis could be carried out at an initial loading of around 0.02 watts per cm2 for periods of up to 15 minutes or for longer periods at lower loadings.Loadings of up to 0.07 watts per cm or more were found possible provided adequate steps were taken to dissipate the heat produced. Loadings at the higher end of the range required voltages of up to 50 or 60 volts per cm and had been used for finger-printing studies of amino-acids and peptides. Applications of Thin-layer Chromatography in Anthraquinone Dyestuff Chemistry BY C. G. HAYNES (Imperial Chemicals Industries Ltd. Dyestuffs Division Gyangemouth Stirlingshire) DR. HAYNES said that the introduction of thin-layer chromatography had provided an invalu- able extension to the chromatographic methods already applied extensively to problems in anthroquinone chemistry. The chromatographic behaviour of simple substituted anthra- quinones on thin-layers was compared and contrasted with simple derivatives of other chromo- phores; the effect of orientation of substituent groups in the anthraquinone nucleus was also illustrated and discussed.The effectiveness of thin-layer chromatography for the characterisation of dyestuffs derived from anthraquinone was illustrated by examples taken from three main groups of dyes vix. vat dyes - pigments disperse dyes and wool colours. Emphasis was placed on the various modifications of the technique in its application to development work and process control. The quantitative aspects of the technique in this field were also mentioned. 60 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 Applications of Thin-layer Chromatography to the Study of Propellants BY F. W. S. CARVER (Explosives Research and Development Establishment Waltham Abbey Essex) MR.CARVER commenced by discussing general propellant analysis. Conventional single and double-based propellants mainly consisted of nitric esters. These materials were inherently unstable and unfortunately the breakdown was auto-catalytic with respect to the nitrogen dioxide produced. To make them safe the nitrogen dioxide had to be removed as it was formed usually by adding easily nitrated secondary aromatic amines or their derivatives. The chemical lifetime of a stabilised propellant depended upon the rate of fall of the level of the stabiliser so it was of the utmost importance to be able to separate and determine residual stabiliser contents of aged propellants. Thin-layer chromatography had made it possible to determine stabilisers such as $-nitro- methylaniline 2-nitrodiphenylamine and diphenylamine with an error of 3 to 10 per cent.which was quite adequate for the assessment of chemical lifetimes. Mr. Carver continued by discussing reaction mechanisms. He said that the mechanism of a reaction could be conveniently studied by a combination of thin-layer chromatography and mass spectrometry. The thermal decomposition of several substituted peroxybenzoic acids was discussed and it was shown how the mechanisms of the reactions were elucidated. Some Applications of Thin-layer Chromatography in the Analyses of Fats BY J. A. CORNELIUS (Tropical Products Institute Gray’s I n n Road London W.C. 1) DR. CORNELIUS said that thin-layer chromatography had been used at the Tropical Products Institute for many aspects of fat analysis.It had been found to be a useful ancilliary to gas - liquid chromatography of fatty esters as prior running of the esters on silica-gel plates had enabled the efficiency of the esterification procedure to be checked. This had proved particularly important in the examination of oils of unknown composition as the presence of free fatty acids could give rise to the appearance of misleading peaks. The use of nitromethane in the mobile phase with fatty acid methyl esters on paraffin- impregnated kieselgel had resulted in some separation of esters which normally formed critical pairs for example laurate - linoleate myristate - linoleate and palmitate - oleate. On spraying the chromatograms with ferric chloride - sodium molybdate solution and then heating them saturated esters had given an orange colour and unsaturated esters a blue colou r.It had been found of special value as a rapid semi-quantitative test for the presence of cashew-nut shell liquid on cashew kernels. Thin-layer chromatography had also been used for sterols and carotenoids. A Pre-coated Sheet for Thin-layer Chromatography BY E. ANNE MORRIS MISS MORRIS described the properties of three types (silica gel polycarbonate and polyamide) of Eastman Chromogram sheet The performance of the sheets was compared directly with that of conventional thin-layer chromatography with respect to rate of development of the chromatogram effect of thermal activation on the resolution of mixtures and the purity of compounds recovered from the chromatogram. Suitable and unacceptable solvents for use with the chromogram sheet were disclosed and the technique for impregnating the adsorbent of pre-coated sheets was outlined.Finally the behaviour of some 2,4-dinitrophenylhydrazones amino-acids and sugars was illustrated and discussed. (Kodak Ltd. Harrow Middlesex) April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 61 The Value of Film Chromatography in Chemical Research BY E. V. TRUTER D R . TRUTER said that but for the existence of film chromatography some types of chemical investigation could not have been undertaken with any hope of success. The common feature of these problems had been that the amount of material was small and the number of components large. The way in which film chromatography could be used to characterise unknown compounds was illustrated by considering three types of examples the components of a natural lipid (cabbage wax) ; the products of a chemical reaction (oxidation of cholesterol) ; and the discovery of a new auto-oxidative reaction (linoleic acid). (Textile Chemistry Laboratory The University Leeds)

ISSN:0037-9697    

DOI:10.1039/SA9660300058

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 61 Determination of Purity in High-purity Organic Materials The following are summaries of papers presented at the Ordinary Meeting of the Society held on February 2nd 1966 and reported in the February issue of Proceedings (p. 13). Determination of the Purity of High-purity Organic Materials Methods of Determining Purity in Use in the Chemical Standards Division of N.P.L. BY J. D. Cox (Chemical Standards Division National Physical Laboratory Teddington Middlesex) DR. COX said that Chemical Standards Division of N.P.L. was established in April 1965 when the National Chemical Laboratory was amalgamated with the National Physical Laboratory. Much of the Division’s research programme was concerned with the accurate measurement of the physico-chemical and spectroscopic properties of substances that were important to the British chemical industry or were likely to become so.The measurements embraced properties such as heat capacities heats of formation vapour pressures of liquids and equations of state of gases knowledge of which was needed by chemical engineers for the design of new processes and plant. Both inorganic and organic substances were studied in the Division but Dr. Cox discussed only organic substances. A programme of accurate physico-chemical measurements was only worthwhile if the specimens studied were of high and proven purity. Therefore samples of substances for study were subjected to a variety of physical purification procedures before the measurement programme was begun. The progress of purification was monitored by spectroscopic techniques and by gas - liquid chroma- tography.When it appeared likely that a given specimen had been brought to a purity of about 99.9 per cent. a definitive measurement of purity was attempted. Normally thermal analysis was used but where thermal analysis was inapplicable a combination of techniques generally mass spectrometry and gas - liquid chromatography was used. Dr Cox then described the theory that underlay the three distinct techniques of thermal analysis used in Chemical Standards Division. The basic equation which related the freezing temperature T of a liquid to the fraction of the sample in the liquid state F was- where Tpure was the freezing temperature of the pure liquid (component l) R was the gas constant x2* was the mole fraction of impurity (component 2) present in solution in component 1 and AH was the heat of melting of component 1.The equation which could be deduced by standard thermodynamic arguments applied rigorously only in the limiting condition when x2* -+ 0 i.e. when component 1 obeyed Raoult’s law exactly. For finite values of xa* when component 1 might not obey Raoult’s law exactly the equation became an approxima- tion but experience showed that as long as x2* < 0.005 no significant error arose from the approximation. Two other provisos attendant on the use of the equation had to be borne in mind namely that component 2 should not dissociate when dissolved in component 1 and that component 2 should not form a solid solution with component 1. 62 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 The most accurate experimental method for determining purity by thermal analysis was the calorimetric melting-point method.Dr. J. F. Martin of Chemical Standards Division used adiabatic calorimeters with automatic control and measurement equipment to determine the heat capacities of pure specimens in the temperature range 10" to 450" K. If the melting point of the substance fell in that temperature range the equilibrium melting temperature T was determined as a function of the fraction melted F and the over-all heat of melting of the specimen AH, was accurately measured. A plot of Tagainst 1/F usually gave astraight line which afforded (see equation) a value of Tpure as the intercept at 1/F = 0 and a value of xz* from the slope of the line. The method was illustrated by data for butanol (J.F. Counsell J. L. Hales and J. F. Martin Tram. Faraday Soc. 1965 61 1869). The study of melting behaviour by adiabatic calorimetry provided a reliable method of determining the purity of highly pure specimens because the melting could be carried out very slowly thus assuring the establishment of thermodynamic equilibrium between the solid and liquid phases throughout the melting. It was necessary however to have very sophisticated equipment so that the calorimetric method was only likely to be used in those laboratories which were concerned with the measurement of heat capacities and heats of phase transition. Workers in laboratories concerned with purity measurements only would be better advised to use time - temperature techniques of purity assessment (E.F. G. Hering- ton Analytica Chim. Acta 1957 17 15; R. Handley Ibid. 1957 17 115). For example the time - temperature freezing-point method permitted determination of F and Tpure solely from plots of time versws equilibrium temperature of a liquid sample frozen with agitation under controlled conditions. To solve for the remaining unknowns x2* and AH, it was necessary t o carry out a second time - temperature freezing experiment after the addition of a measured amount of impurity to the liquid; the experiment had to be carried out under the same conditions as in the first experiment particularly with regard to the rate of heat extraction from the sample. Although the method was dynamic a good approach to thermodynamic equilibrium during freezing was obtained by use of an efficient method of agitation of the sample.The successful use of the method was exemplified by data for a sample of ethyl methyl ketone which was assessed as 99.95 moles per cent. pure (R. R. Collerson J. F. Counsell R. Handley J. F. Martin and C. H. S. Sprake J . Chem. SOC. 1965 3697). The method had failed in instances where there was slow approach to equilibrium between solid and liquid phases (often arising from the high viscosity of the liquid) or where a single crystal grew rather than a mass of small crystals with consequent thermal dis-equilibrium. In such instances a value for the purity had often been obtained by the time - temperature melting- point method devised by Mr. R. Handley (Zoc. cit.). In this method heat was applied at a controlled rate to the specimen contained in a silver cell and frozen before the experiment.Temperature measurements as a function of time were made through the melting region then the experiment was repeated after the addition of a known amount of impurity. The calcula- tion of x2* was carried out by a procedure devised by Dr. E. F. G. Herington (Zoc. cit.). The weakness of the time - temperature melting-point procedure was that the method was dynamic and unlike the freezing-point method there was no possibility of agitating the sample. Hence there was doubt whether the system was at equilibrium during melting. Finally Dr. Cox discussed the procedures that were used in Chemical Standards Division when thermal methods of purity determination were not applicable e.g. where a liquid sample could not be induced to form stable crystals or a solid sample decomposed at its melting point or the impurities in a sample formed a solid solution with the host.The latter situation had arisen in an attempt to assess the purity of a synthetic sample of n-docosane C22H&. The impurities in the specimen were known to be other normal paraffins that were likely to form solid solutions with the host. Therefore instead of thermal analysis mass spectrometry and gas - liquid chromatography were used to determine the purity of the sample. There was semi-quantitative agreement between the two analytical techniques on the amount of C, and c 2 6 impurities in the sample but mass spectrometry revealed the presence of a trace of C, impurity that was not shown up by gas - liquid chromatography whilst the presence of a trace of C, impurity was revealed by gas - liquid chromatography but not by mass spectro- metry.This was an illustration of the general point that mass spectrometry was excellent for determining small amounts of impurities with molecular weights higher than the molecular weight of the main component but was less suitable for determining impurities with lower molecular weights. Mass spectrometry and gas - liquid chromatography could in fact be regarded as complementary techniques. April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 63 Dr. Cox summarised by saying that the Chemical Standards Division gave most weight to purity determinations by the calorimetric melting-point technique but use of other tech- niques both thermal and non-thermal often gave added assurance of the validity of the purity assessments made.Some Methods for Determining the Purity of Pharmaceutical Products BY J. H. CHAPMAN (Glaxo Research Ltd. Greenford Middlesex) DR. CHAPMAN divided his talk into two sections in the first he dealt with the problem of establishing that a new generally complex organic material was substantially a single sub- stance. Secondly he reviewed briefly the applicability of existing physcial methods to the problem of identifying and assaying in pharmaceuticals minor components that were closely related to the principal constituent. It was possible for considerable amounts of a closely related material to be present and especially in a previously undescribed substance be almost undetectable by physical measure- ments. Separative methods all suffered from not “failing safe,” and methods that gave a positive indication of purity were particularly desirable.The lecturer discussed only non- separative methods. Solubility analysis had been recommended in several publications but Dr. Chapman wondered whether it was widely used. After considerable experience with the method he had concluded that the results obtained always had to be treated with suspicion and for this reason he now only used the method as a last resort. If several solvents were tried and no impurities were detected in any of them this was strong but not infallible evidence of homo- geneity. The only certain result was that a positive indication of impurity could not be given by a single substance that was stable under the conditions of the analysis. However when a positive result was obtained it was difficult to draw with any degree of certainty conclusions as to the number or amount of the impurities present.Examples were given in which results had been obtained that were subsequently shown to be grossly in error. The amounts of such impurities as were detected were generally found to be exaggerated. Such results associated with satisfactory straight-line plots were attributed to the formation of compounds between the components and this seemed a disconcertingly common phenomenon. Methods for reducing the time taken to reach equilibrium appeared not to have met with success and 3 to 4 weeks was still often required. Pharma- ceuticals frequently decomposed at or below their melting point. Nevertheless this did not exclude the method although evidently its detailed application would be different from that described by Dr.Cox. The differential thermal-analysis procedure seemed likely to be suitable for application to pharmaceuticals. Examination by this method of samples of cortisone acetate griseofulvin and cephaloridine of varying purity had been disappointing but the speaker felt that further examination of the method should be made. Pharmaceuticals were not infrequently fluorescent and a characteristic of pure fluorescent substances was the invariance of their fluorescence spectrum with changes in the excitation wavelength. A convenient method of testing such observations had been described (Weber Nature 1961 190 27). This seemed a potentially useful method although with samples of impure griseofulvin it had failed to indicate the impurity.The detection of impurities in relatively small amounts by ultraviolet and infrared spectroscopy was difficult but the situation had been greatly improved by the application of nuclear magnetic resonance spectroscopy. This method gave spectra consisting of sharp peaks relatively widely spaced thus providing “windows” through which the lesser peaks arising from impurities could better be observed. These points were illustrated with infrared and proton magnetic resonance spectra of a mixture of cortisone acetate and its Al-isomer. However none of these methods permitted general qualitative analysis of mixtures of unknown components. Mass spectrometry on the other hand certainly permitted this in theory although care had to be taken that artifacts were not produced during the volatilisation of mixtures.The The great merits of thermal analysis were evident from the preceding paper. 64 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 resolution in mass spectrometry was such that it seemed probable if the spectra of the com- ponents were truly additive that a computer could handle the data contained in mass spectra of several mixtures containing different proportions of the same components and produce to a satisfactory degree of probability spectra of the separate components. These could then be identified in the normal way and their proportions in the mixtures determined. Equipment capable of performing these operations was already becoming available. In the meantime a very powerful procedure was the combination of mass spectrometry with a separative tech- nique as chromatography. With gas chromatography the two techniques could be coupled particularly readily and this method was now being applied to great advantage in several fields.

ISSN:0037-9697    

DOI:10.1039/SA9660300061

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

64 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 Economics of Automatic Analysis The following is a summary of the paper presented at an Ordinary Meeting of the Auto- matic Methods Group held on January 27th 1966 and reported in the March 1966 issue of Proceedilzgs (p. 42). The Economics of Automatic Analysis BY A. W. FOSTER (Imperial Chemical Industries Ltd. Central Instruments Research Laboratory Reading Berks.) DR. FOSTER commenced by listing the main parts of a complete analysis system beginning with sampling and not finishing until the analysis led to a decision. He detailed the costs involved in all these stages and emphasised the profitability aspect of the decision stage. Where the previous method of analysis was inefficient by modern standards there was rarely any difficulty in making a good case for the use of automatic methods.However the more efficient organisations were moving into a position in which it was necessary to deal with the costs and profit-making aspects much more thoroughly. The lecturer emphasised that costing of methods of analysis in modern systems necessi- tated treating the system as a whole. The analyser took its place with other items of equip- ment on the plant and therefore the profitability estimate meant taking into account not only development installation and maintenance costs but also interest and taxation. Only in simple circumstances could this full economic study be omitted. In most of these a profit statement was given against a simple cost and the critic had plenty of ground for feeling that development and maintenance costs had been ignored.Some interesting examples occurred in which the analyser considered as part of a well designed control scheme enabled a highlyprofitable process to be operated. The first part of the discussion that followed included the manufacturers’ difficulty in determining the specification for analysers that would prove of greatest success. Collabora- tion between analysts and manufacturers was essential and it was highly unprofitable for either to ignore this maxim. Examples were considered where analysers had been failures. These often arose because simple systems had not been fully designed adequate maintenance labour was not available or the plant was not yet ripe for making proper use of such instruments. Various examples were treated briefly. Changes in the Register of Members DEATH WE record with regret the death of Ernest Vernon Browett.April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 65 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 Thiamine in Breakfast Cereals,” by H. N. Ridyard. “Determination of Neomycin,” by R. A. Hoodless. “The Determination of Diethyl Phthalate in Perfumes Lacquers and other Ethanolic “Plant Mineral Analysis with X-ray Fluorescence Spectrometry,’’ by R. Jenkins P. W. “A Simple Method for Preserving Thin-layer Chromatograms,” by H. A. Foner. “The Determination of Parts per 10l2 Levels of Helium-3 in Argon,” by K. R. Melhuish “The Analysis of Fats Containing Cyclopropenoid Fatty Acids,” by G. G. Stone and “Thin-layer Chromatography of Epoxide Resins,” by R. G. Weatherhead. “The Flame-photometric Determination of Traces of Calcium in Lithium Chloride “The Determination of Carbon in Steel by a Dynamic Infrared System,” by G. White Preparations,’’ by W. Hancock B. A. Rose and D. D. Singer. Hurley and V. M. Shorrocks. and H. Chapman. T. W. Hammonds. Contaminated with Aluminium,” by P. Emmott and G. Law. and P. H. Scholes.

ISSN:0037-9697    

DOI:10.1039/SA9660300064

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

April 19661 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 65 Publications Received The publications listed below have been received by the Editor of The Analyst in which journal Book Reviews will continue to appear. TREATISE ON ANALYTICAL CHEMISTRY. Volume 12. Part 11. ANALYTICAL CHEMISTRY OF INORGANIC AND ORGANIC COMPOUNDS. Section B. ORGANIC ANALYSIS (cont.). Edited by I. M. KOLTHOFF and PHILIP J. ELVING. New York London and Sydney Interscience Publishers a division of John Wiley & Sons Inc. SUBMICRO METHODS OF ORGANIC ANALYSIS. By RONALD BELCHER D.Sc. Pp. x + 173. Amsterdam London and New York Elsevier Publishing Company Ltd. 1966. Price 55s. ELECTROCHEMICAL ANALYSIS STUDIES OF ACIDS BASES AND SALTS BY E.M.F. CONDUCTANCE OPTICAL AND KINETIC METHODS. Edited by ROGER G. BATES.Pp. xiv + 100. Washington D.C. U.S. Government Printing Office. 1965. Price 60 cents. KIRK-OTHMER ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY. Second Edition. Volume 7. Di- alysis to Electron-Spin Resonance. Edited by HERMAN F. MARK JOHN J. MCKETTA jun. and DONALD F. OTHMER. Executive Editor. ANTHONY STANDEN. Pp. xvi + 903. New York London and Sydney Interscience Publishers a division of John Wiley & Sons Inc. 1965. Price Ll6 18s. ; price per volume for subscribers to the complete set of 18 volumes L13. CELL K. By RODERICK P. KERNAN D.Sc. Pp. viii + 152. London Buttenvorth & Co. (Publishers) Ltd. 1965. Price 27s. 6d. CHROMATOGRAPHY. By L. SAVIDAN. Edited by D. I. DAVIES. Pp. xiii + 112. London Iliffe Books Ltd. 1965. Price 35s. ABSORPTION SPECTRA IN THE ULTRAVIOLET AND VISIBLE REGION. Volume VI. Edited by DR. L. LANG. Pp. 412 + index pp. 415-442. Budapest Akademiai Kiado. 1965. Price 115s. By L. C. WILLEMSENS and G. J. M. VAN DER KERK. Pp. x + 128. London ILZRO. 1965. Pp. xvi + 383. 1965. Price 113s. July 1964 to June 1965. INVESTIGATIONS IN THE FIELD OF ORGANOLEAD CHEMISTRY. Fvee o n request from the Lead Development Association 34 Bevkeley Square London W. 1. THE MODERN ELECTROPLATING LABORATORY MANUAL. Pp. xviii + 382. HIGH RESOLUTIONUCLEAR MAGNETIC RESONANCE SPECTROSCOPY. Volume I. By J. W. Oxford London New York By REX CONDE ARMET. Teddington Robert Draper Ltd. 1965. Price 115s. EMSLEY J. FEENEY and L. H. SUTCLIFFE. Paris and Frankfurt Pergamon Press. 1965. Price 105s. Pp. xx + 694.

ISSN:0037-9697    

DOI:10.1039/SA9660300065

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

66 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 Particle Size Analysis Conference 1966 This preliminary list of papers accepted for the Particle Size Analysis Conference 1966 is arranged alphabetically by first authors and will be supplemented in subsequent issues of Proceedings. “The Influence of Particle-size Distribution on the Sintering of Ceramic Powders,” by A. G. Adwick and R. J. Warmer (Dounreay Experimental Reactor Establishment,. Caithness) . “Use of the Coulter Counter in Measuring the Particle-size Distribution of Organic Pigment Dispersons,” by J. Beresford W. Carr and G. A. Lombard (Geigy (U.K.) Limited Manchester 22). “Errors Caused by Short-duration Aerosol Sampling with the Cascade Impactor,” by D. A. Blyth and R. G. Picknett (Physical Research Division C.D.E.E.Porton Down Salisbury Wilts.). “An Appraisal of the Use of the Micromerograph for Particle-size Analysis of Manganese Dioxide,” by A. C. Bryant B. S. Freeman and F. L. Tye (The Ever Ready Co. (Great Britain) Ltd. London N.15). “Some Tests of the Mullard Automatic Particle Analyser Type L188,” by G. F. Collins (C.D.E.E. Porton Down Salisbury Wilts.). “Particle-size Analysis by Counting from Electron Micrographs,” by V. T. Crowl (The Paint Research Station Teddington Middx.) . “Surface Area Measurement by Low Temperature Nitrogen Adsorption,” by V. T. Crowl (The Paint Research Station Teddington Middx.) . “A Centrifugal Sedimentation Method for Particle-size Analysis,” by P. Dewell (British Cast Iron Research Association Birmingham). “The Determination of Silver Halide Crystal Size Distributions in Photographic Emulsions using the Zeiss - Endter Particle-size Analyser,” by P.Falcon-Uff and K. F. Leverington (Ilford Ltd. Brentwood Essex). “The Metals Research Image Analysing Computer,” by C. Fisher (Metals Research Ltd. Royston Herts.). “The Particle Size of Emulsions,” by M. J. Groves B. Scarlett and D. C. Freshwater (Boots Pure Drug Company Ltd. Nottingham). “Particle Size by P-Backscattering,” by W. H. Hardwick and B. J. Laundy (Chemical Engineering Division A.E.R.E. Harwell Didcot Berks.). “Characterization of the Powder Particle Shape,” by H. H. Hausner (730 Fifth Avenue New York U.S.A.). “Organisation and Methods of Ore-handling and Sample Preparation at Warren Spring Laboratory,’’ by A. S. Joy T. H. Hughes and G. E. Whale (Warren Spring Laboratory Herts.). “A New Particle-size Analyser of Photo-scanning Type,” by A. Muta N. Saito and Y. Uehara (Central Research Laboratory Hitachi Ltd. Tokyo Japan). Comparative Particle-size Profiles of Some Materials of Interest in Atomic Energy Fuel Fabrication Processes,” by G. Smith and D. J Ferrett (Chemistry Group G.O.T.D. U.K.A.E.A. Winfrith Dorset). “Phosphorescence Microscopy; A Simple Automatic Counting Device for Phosphorescent Particles,” by C. J. P. van Buijtenen and Dr. L. A. Clarenburg (Chemisch Laboratorium Rvo-Tno Rijswijk The Netherlands).

ISSN:0037-9697    

DOI:10.1039/SA9660300066

出版商:RSC    

年代:1966

数据来源: RSC

摘要:

April 19861 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY 67 Notices NORTH OF ENGLAND SECTION SUMMER MEETING THE North of England Section draws attention to its Summer Meeting which will be held at the County Hotel Llandudno from Friday May 20th to Monday May 23rd 1966. Any member of the Society not necessarily a member of the Section will be heartily welcome. THE POLAROGRAPHIC SOCIETY ANNUAL GENERAL MEETING THE Annual General Meeting of the Polarographic Society will be held at 2.45 p.m. on Wednes- day April 27th at the Royal School of Mines Imperial College Prince Consort Road South Kensington S. W .7. The meeting will begin at 2.45 p.m. with a lecture by Dr. M. E. Peover of the National Chemical Laboratory Teddington Middlesex on “Polarographic Characteristics of Organic Compounds in Organic Solvents.” There will be an interval for tea at 4 p.m.followed at 4.45 p.m. by the Annual General Meeting. GORDON RESEARCH CONFERENCES 1966 THIS year’s Gordon Research Conference on Analytical Chemistry will be held at New Hamp- ton School New Hampton New Hampshire U.S.A. from August 22nd to 26th 1966. Applications must be received two months before the date of the Conference and must be submitted in duplicate on the standard application form obtainable with further informa- tion from the Director W. George Parks Department of Chemistry University of Rhode Island Kingston R.I. U.S.A. Lectures scheduled include “Mass Transport in Electro-analytical Methods A Com- parative Treatment ,” by David K. Roe “Chromocoulometry Recent Applications of Current Integration Methods,” by Robert A.Osteryoung “Techniques for Elucidation of Organic Electrode Processes in Polarography,” by Petr Zuman “Computers in Analytical Chemistry,” by N. Rasmussen M. Silberg R. A. Edwards and IT. G. Poll; “Analytical Chemistry of Living Systems,” by Ross U. Robinson ; “Intercorrelations with Nuclear Magnetic Resonance Infrared and Mass Spectrometry,’’ by W. Donald Cooke; “Uses of Pulse Techniques in Nuclear Magnetic Resonance,” by Erwin L. Hahn (Open Session) ; “Spectroscopic Applica- tions of Gas Lasers,” by A. Javan and M. Feld; “Gas Absorption Spectroscopy in the Infrared with a Laser Light Source,” (speaker to be announced). BRITISH STANDARDS INSTITUTION A FEW copies of the following draft specifications issued for comment only are available to members of the Society and can be obtained from the Secretary The Society for Analytical Chemistry 14 Belgrave Square London S.W.l.Draft Specification prepared by Technical Committee CIC/24-Alumina. Draft Specification prepared by Sub-committee CIC/29/1-Solvents for Use in Foodstuffs. 66/3881-Draft B.S. Methods of Test for Alumina. 66/5955-Draft B.S. Specification for Ethyldigol for Use in Foodstuffs. 65 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY [April 1966 THE INSTITUTE OF PHYSICS AND THE PHYSICAL SOCIETY SYMPOSIUM ON LIQUID SCINTILLATION COUNTING THE Institute of Physics and The Physical Society is arranging a Symposium on “Liquid scintillation counting” to be held on October 18th and 19th 1966 at the National Physical Laboratory Teddington Middlesex. The Symposium is primarily intended to afford users of radioactivity measuring equip- ment an opportunity for the exchange and critical discussion of new information on physical and chemical techniques applied in the use of liquid scintillators.It is hoped that the Symposium will be of value both to workers in this field and to those contemplating the use of liquid scintillators. Appropriate introductory survey papers are being arranged on “The scintillation process,” “Apparatus for liquid scintillation counting’’ and “Applications of liquid scintillat ors. ’ ’ It is proposed that following the review papers sessions of proffered papers will be arranged as follows Quenching and quench corrections ; Principles and techniques of sampling preparation ; Supplementary methods ; Applications of liquid scintillators (with particular reference to large volume scintillators and nuclear physics applications).Offers of contributed talks of from 15 to 20 minutes’ presentation time are welcomed. Those wishing to contribute to the conference should submit three copies of an outline not exceeding 300 words in length giving statements of the main points and conclusions to be presented Outlines should be clearly headed with the title of the paper author’s name and the name and the address of his establishment. Offers of contributions should be sent to the Conference Technical Secretary Dr. R. P. Parker Institute of Cancer Research Surrey Branch Clifton Avenue Belmont Sutton Surrey and should arrive not later than July lst 1966. As it is intended to allow ample time for discussion the number of papers that will be presented will be restricted to about 18.It is not intended to publish the Proceedings of the conference and contributors may feel free to publish their papers in suitable journals. Advance registration for attendance at the Symposium will be necessary and further details and application forms are available from the Meetings Officer The Institute of Physics and The Physical Society 47 Belgrave Square London S.W.l. For those unable to attend the Symposium the handbook containing outlines of the talks to be presented will be available for a limited time after the conference from the Institute and Society at a cost of 7s. 6d. to non-members and free to members. Residential accommodation is not being arranged. XIIITH INTERNATIONAL SPECTROSCOPY COLLOQUIUM UNIVERSITY OF OTTAWA CANADA JUNE 1 9 ~ ~ TO 2 3 ~ ~ 1967 THE Canadian Association for Applied Spectroscopy is sponsoring the XIIIth International Spectroscopy Colloquium to be held at Carleton University Ottawa from June 19th to 23rd 1967.Technical sessions are being prepared in the following fields of spectroscopy Information storage and retrieval and education ; Optical emission Flame photometry atomic absorption ; Astrophysical and solar spectroscopy ; Spectroscopic applications in geochemistry and bio- geochemistry; Ultraviolet absorption and fluorescence ; X-ray diffraction fluorescence electron probe ; Infrared-absorption spectroscopy; and Metals analysis. Those wishing to contribute papers should submit three copies of an abstract 400 to 500 words in length. The abstract may be in English French or German and must be received not later than October lst 1966. Residential accommodation will be available at Carleton University and multilingual guides will be available to assist visitors. Exhibitions of instruments and books and tours of scientific establishments will be arranged. A full social programme is also being planned. Further information is available from the Secretary XI11 Colloquium Spectroscopicum Internationale National Research Council Ottawa 7 Canada.

ISSN:0037-9697    

DOI:10.1039/SA9660300067

出版商:RSC    

年代:1966

数据来源: RSC