摘要:

Proceedings of the Society for Analytical Chemistry .Analytical Division Chemical Society CONTENTS Proc. SOC. Analyt. Chem. Vol. 10 No. 5 Pages 99-124 Reports of Meetings . . . . 99 The Future of the Analytical Summaries of Papers Chemist . . .. . . 101 “Techniques for Particle Charac- terisation” . . . . . . 108 “Ion-selective Electrodes” . . I18 Papers Accepted for The Analyst 120 Notices . . . . . . . . 122 Correspondence on Arnalga- rnation . . .. . . . . 123 Forthcoming Meetings Back Cover May 1973 PAYCAL Vol. 10 No.5 May 1973 PROCEED I N GS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY Officers of The Society for Analytical Chemistry and the Analytical Division of The Chemical Society G. W. C. Milner President Hon. Secretary W. H. C. Shaw Hon.Treasurer Hon. Assistant Secretaries 1. K. Foreman D. I . Coomber O.B.E. 0. W. Wilson Secretary Miss P. E. Hutchinzon 9/10 SAVILE ROW LONDON WIX IAF Telephone 01-734 9864 Editor J. 8. A t t r i l l Assistant Editor P. C. Weston Proceedings is published by The Society for Analytical Chemistry. Members’ subscriptions must be sent t o The Chemical Society Non-members can be supplied with Proceedings only as part of a combined subscription with The Analyst and Analytical Abstracts. Slngle copies can be obtained direct from The Chemical Society Publications Sales Office Blackhorse Road Letchworth Herts. SG6 IHN (NOT through Trade Agents) price 30p post free. Remittances MUST accompany orders. Q The Society for Analytical Chemistry THE ELEVENTH SAC ANNUAL MEETING on RESEARCH TOPICS IN ANALYTICAL CHEMISTRY will be held at The- University of Sheffield on Thursday afternoon July 12th and Friday morning July 13th 1973 Papers are invited describing work carried out by postgraduate research students in Universities and Colleges and by young research workers i n industrial and other establishments. Contributions are t o be presented by the student or his industrial counterpart during a 20-minute lecture. Those who wish to offer a paper or who have any queries about the meeting should write to- Dr. D. I. Coomber Laboratory of the Government Chemist Cornwall House Stamford Street London SEI 9NQ.

ISSN:0037-9697    

DOI:10.1039/SA97310FX018

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

SOCIETY FOR AKALYTICAL CHEMISTRY ANALYTICAL DIVISIOK CHEMICAL SOCIETY Forthcoming Meetings May Thursday 24th Biological Methods Group Summer Meeting. Visit to Shell Research Laboratories Analytical Chemistry Division and Bio- logical Evaluation Division \Yoodstock Agricultural Research Centre Sitting- bourne Kent; 2.15 p.m. SCOTTISH REGION and ATOMIC SPECTROSCOPY and RADIOCHEMICAL NETHODS GROUPS on “Metals in Clinical Analysis.” “Traces and Tracers-the Limits of Analysis,” by J . 31. -A. Leniham. “Toxicological Applications of Activation Analysis,” by H. Smith “Analysis of Some Clinical Samples by Seutron Activation,” by B. W. East. “The RBle of Lead in Clinical Medicine,” by A. Goldberg. “Xtomic Absorption Techniques in Clinical Biochemistry,” by G. Fell. “Studies on Lead in Blood,” by A.RI. Smith. “Some Applications of Ion Selective Electrodes in Clinical Analysis,” by G. P. Department of Chemistry Thomas Graham Building University of Strathclyde SITTIKG- BOURNE Friday 25th GLASGOW Bound. Cathedral Street Glasgow; 9.45 a.m. June lhursday 14th hTOTTINGHAM JOINT PHARMACEYTICAL AXALYSIS GROUP Meeting for the reading of Original The Boots Co. Ltd. Pennyfoot Street Nottingham; 2.30 p.m. Discussion on “Amalgamation,” to be opened by the President Dr. G. TV C. Lecture Room 203 Haworth Building The University Edgbaston Birmingham XORTH TVEST REGIOS Summer Meeting on “Looking to the Future.” Papers-papers on a wide selection of analytical topics will be read. TT;ednesday 20th MIDLASDS REGION. BIRMINGHAM Milner. 15; 6.30 p.m. Saturday 30th to Sunday Satuvday June 30tj~- July 1st “Carbohydrates-the Present and the Future,” by Professor S . A. Barker; ECCLESTON 2.30 p.m. Coach trip to Southport to visit “New Theatre” at Floral Hall; 8 p.m. Sunday July 1st- “Synthetic and Artificial Foods and their Dietetic Significance,” by Dr. Magnus Pyke; 11 a.m. Coach tour to the \Tinter Hill Television Transmitter; 2.30 p.m. Further details may be obtained from RIr. J . Cottam County Laboratory Blackburn Management Centre Heskin Hall Eccleston. C,ounty Hall Preston PR1 8XN. Printed by Heffers Printers Ltd Cambridge England

ISSN:0037-9697    

DOI:10.1039/SA97310BX020

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

May 1973 Vol. 10 No. 5 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY Reports of Meetings ORDINARY IIEETIKG A?; Ordinary Xeeting of the SAC,IAD was held at 2.30 p.m. on IT’ediiesdaS- \lay 2nd 1953 at the Scientific Societies Lecture Theatre 23 Savile Row London lV.1. The Chair was taken b y the President Dr. G. l V . C. Miher. The subject of the meeting was “Standardisation of Methods and Materials” and the following papers were presented and discussed “The Philosophy of Standards ; the lYork of the Analytical Standards Sub-Committee,” by E. Bishop ; “The Preparation of Certified Reference Materials for the hIetallurgica1 Industries,” by P. D. Ridsdale; “Tlie Preparation of Standard Chemical Substances,” by J. E. Connett ; “Reference Materials for Pharmaceutical Analy-sis,” b y C.A . Johnson. SCOTTISH REGION ASD CHROJIATOGRAPHY AKD ELECTROPHORESIS GKOUP A4 JOIKT Meeting of the Scottish Region and the Chromatography and Electrophoresis Group was held on Thursday and Friday April 12th and 13th 1973 a t The University Dundee. The subject of the meeting was “Aspects of Chromatography.” The Chair a t the first session was taken by tlie Chairman of the Scottish Region llr. IT. Dunnet who introduced Professor R . Foster who welcomed participants to the University. The following papers were presented and discussed “Characterisation of Long-chain Fatty .kids by GLC,” by G. Janiieson; “GLC of lyaxes,” by R. J. Hamilton; “A Method for Determining Free Fatty Acids by Gas Chromatography,” by G. Coclirane; “The Identification of Hydrocarbon Pollutants on Seas and Beaches,” by E.R. _idlard; “Determination of an Isomeric Impurity in Crude Samples of Morantel Tartrate by GLC Analysis of the Products of :i Controlled Degradation Procedure,” by E. Addison E. Davison and P. 1;. 1I:adsworth. The Chair a t the second session was taken by the Chairman of the Clironiatograpliy and Electropliorcsis Group Dr. E. 1’. Truter and the following papers were presented and dis- cussed “Xffinity Chromatography,’’ by K. \Y. lT311iams; “The Potential for High Speed Liquid Chromatography,” by J. H. Knox ; “Determination of Isotopically Labelled Lipids by Combined TLC and GLC,” by 11’. lY. Christie; “TLC and TLE of Ceplialesin,” by P. J. Stevens. \!,.ESTER?rT REGION AKD 3IICROCHEMICAL 3IETHODS GROCP A JOIKT Meeting of the \Vestern Region and the Microchemical Methods Group was held on Thursday and Friday April 5th and Bth 1973 a t the Seale-Hayne *4gricultural College Xeiz-ton Abbot Devon.The subject of the meeting was “The Characterisation and Quality of l:ood and Agricultural Products with Special Reference to 13EC Requirements.” On April bth the Chair a t the first session was taken by the Chairman of the Xcrochemical Methods Group Dr. D. -4. Pantony and tlie following paper was presented and discussed Plriinry Lectiue “Characterisation and Quality of Food and Agricultural Products in the Enlarged EEC,” by T. J. Coomes. The Chair a t the second session was taken by the Vice- C,liairman of the \Yestern Region Dr. \V. J. \Villiams and the following papers were presented and discussed “Current and Proposed Analytical Methods for EEC Legislation and Codex Alimentarius International Standards,” by A.\Y. Hubbard; “Tlie Toxicological Investig a t‘ ion of l;ood Additives,” by P. S. Elias; “Problems Associated with the Examination of Food for Metallic Contamination,” by L. E. Coles. On ,ipril Bth the Chair at the third session was taken by the l‘ice-Chairman of the Nicro- chemical Methods Group Bance and the following papers were presented and discussed “Some Analytical Metho ted to Standards for Fish Quality,” by J. J. Connell; “Instru- mental Methods of Anal mthetic Feeding Stuffs and Intermediates,” by J. 11. Skinner. 99 100 REPORTS OF MEETINGS [Proc. SOC. Analyt. Chem. The Chair at the fourth session was taken by Mr. E. B. Reynolds and the following papers were presented and discussed “The Detection and Characterisation of Trace Aroma Compounds in Foods and Beverages,” by 0.G. Tucknott ; “The Detection of the Adulteration of Milk with Re-constituted Dried Skim Milk Powder,” by B. M. Dougall and D. T. Morgan; “The Application of Trifluoroacetyl Derivatives for the Identification of Amines in Foodstuffs in the Parts per Million Range,” by M. J. Saxby J.P. Chaytor and B. Crathorne. The final session was chaired by Dr. D. A. Pantony and the following papers were presented and discussed “Additives in Animal Feeding Stuffs,” by R. S. Hatfull; “The Determination of Pesticide Residues in Food Crops,” by M. J. Edwards. The meeting included a visit to Brixham Laboratory I.C.I. Ltd. and a tour of the Chemistry and Microbiological Departments and the Botanic Gardens of Seale-Hayne College.MIDLANDS REGION AND SPECIAL TECHNIQUES GROUP A JOINT Meeting of the Midlands Region and the Special Techniques Group was held at 6.30 p.m. on Thursday April loth 1973 in the Haworth Building The University Edgbaston Birmingham. The Chair was taken by the chairman of both Region and Group Mr. S. Greenfield. A lecture on “Optical Correlation Spectrometry for Remote Sensing of Air Pollution” was given by A. R. Barringer. MIDLANDS REGION AN Ordinary Meeting of the Region was held at 4.15 p.m. on Tuesday May lst 1973 in the Edward Herbert Building University of Technology Loughborough. The Chair was taken by the Chairman of the Region Mr. S. Greenfield. A lecture on “Thermal Analysis-How and Why?” was given by J. P. Redfern. NORTH EAST REGION A JOINT Meeting of the Region with the North West Region of the Association of Clinical Biochemists was held at 2 p.m.on Wednesday April l l t h 1973 in the Littlewood Hall General Infirmary Leeds. The subject of the meeting was “Newer Physical Methods of Analysis in Clinical Chemistry.” Following a short welcoming address by Professor G. H. Lathe of the Department of Chemical Pathology the Chair at the first session was taken by the Chairman of the North West Region of the Association of Clinical Biochemists Mr. J. R. Close and the following papers were presented and discussed Introductory Remarks by C. Toothill ; “Ion-selective Elec- trodes,” by W. G. Robertson and R. M. Marshall; “Nuclear Magnetic Resonance,” by J. W. Akitt. The Chair at the second session was taken by the Chairman of the North East Region Mr.J. Whitehead and the following papers were presented and discussed “Radio- immunoassay,” by M. J. Levell; “Analytical Atomic Spectroscopy,” by J. B. Dawson. ATOMIC SPECTROSCOPY GROUP AN Ordinary Meeting of the Group was held at 7.30 p.m. on Monday April 9th 1973 at the Leicester Lounge 44 Glasshouse Street London W.l. The Chair was taken by the Honorary Assistant Secretary of the Group Mr. W. J. Price. A discussion on “Tubes Rods and Ribbons” was introduced by A. R. Knott and K. C. Thompson. CHROMATOGRAPHY AND ELECTROPHORESIS GROUP AN Ordinary Meeting of the Group was held at 10.30 a.m. on Tuesday April loth 1973 a t Labex International Earls Court London. The Chair was taken by the Chairman of the Group Dr. E. V. Truter. The subject of the meeting was “Aspects of Liquid Chromatography” and the following papers were presented and discussed “An Introduction to Liquid Chromatography,” by Mrs.D. Simpson; “A Review of Applications of Liquid Chromatography,” by E. J. Gallacher and R. J. J. Simkins ; “Liquid Chromatography Applied to Coatings Analysis,” by W. Ledger. May 19731 THE FUTURE OF THE AKALYTICAL CHEXIIST 101 THERMAL METHODS GROUP A JOIUT Meeting of the Group with the Department of Chemical Science5 of the Hatfield Poll technic was held on Monday and Tuesday April 9th and loth 1973. The subject of the meeting was “Quantitative Thermal Methods.” On April 9th the Chair at the first session was taken by Dr. D. 5’. Kowell and the following papers were presented and discussed “Thermal -Analysis in Perspective,” by R. C. llackenzie; “Thermosonimetry,” by K.Lmvik; “Design Requirements for Quantitative DTA,” by F. IT. Wilburn. The Chair a t the second session was taken by the Chairman of the Group Dr. J. H. Sharp and the following papers were presented and discussed “The Beginnings oi Thermogravimetry,” by C. J. Keattch “A Study of the Loss of Lattice \\’ater from Crystalline a-Zirconium Phosphate,” by S. E. Horsley and D. 1. Sowell; “The Thermal Decomposition of Yanadyl Oxalate,” by L. F. Jones and L). Dollimore “The Thermal Deconiposition of Calcium Sulphate Hydrate,” by T. P. Lees. On April loth the Chair at the third session mas taken by Dr. R. C. Slackenzie and the following papers were presented and discussed “The Thermal Decomposition of Simple and Complex Oxy-salt Materials,” by D. Dollimore ; “The Production of Carbons by Thermal Degradation of Polymers,” by B. MacEnaney ; “Applications of Differential Scanning Calori- metry to Steroids Cephalosporins and Penicillins,” by R. E. lIvaller ; “Thermometric Titra- tions in Pharmaceutical Analysis,” by L. S. Bark. The Chair a t the fourth session was taken by 11r. R. E. Ii‘aller and the following papers were presented and discussed “The Thermal Decomposition of Pure and Doped Cadmium Carbonate,” by A. 11. Kamel R. Sh. llikhail S. R. el Sazem and D. Dollimore; “The Thermal Degradation of Some PmTa-Substituted Polystyrenes,” by 11. B. Evans R. H. Still and A. Whitehead; “A Fovel Uae of Differential Thermal Analysis in the Determination of Liquid Paraffin in Mixtures with I17hite Soft Paraffin,” by I. Jackson and P. Wood.

ISSN:0037-9697    

DOI:10.1039/SA9731000099

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

May 19731 THE FUTURE OF THE AKALYTICAL CHEXIIST 101 The Future of the Analytical Chemist” BY A. G. JONES (Reseai.ch D~pai,tinent Analytical Diaision Inzperinl Chemical Industvies Limited Plastics Diisisioii P.O. Ror N o . 6 Bessenieif Road Welwyn Garden City He,.t,foudslzire) I WAS asked on August 23rd 1971 if I would give this lecture. At that particular time to ask anyone to talk on such a subject as the future of the anall-tical chemist was undoubtedly an act of faith because in the Midlands especially redundancy or retirement seemed to be the order of the day and a pessimist could be forgiven for wondering if there was any future for anybody. Hence the first thing to be said is that the future of the analytical chemist is very much bound up with technology and its forward development which in turn is considerably more at the mercy of the economic climate than we might have imagined say 10 years ago so whatever our thoughts about the future might be that future is as I suppose it always was at the mercy of uncontrollable events.\1’lien talking about the future of the analytical chemist the future of analytical chem- istry cannot be ignored because the one is so significantly bound up with the other. Analytical clieniists come in all shapes and sizes all ages many different kinds of experience much variety in length of experience and much variety in both initial and on-the-job training so that whatever generalisations I may attempt they will seem to be completely wrong to some people but I hope a t least to generate some discussion. I must also mention that there are many people who carry out analytical operations z.e.they use analytical tools for making analytical measurements but by no stretch of their imagination do they consider themselves analysts-some of them are a positive menace to society in general but this is discussed later. I am prepared to go along with Hume who said lir is “one who is a specialist in the methodology of solving problem having to do with the properties of chemical systems.” One must of course differentiate him from the technician wlio is engaged in routine analysis and from the physical inorganic or organic chemists who although they may spend a major part of their working lives using analytical techniques nevertheless only use those techniques more or less routinely to achieve some specific end. \\:hat then is an analytical chemist? * Presented a t a hIeeting of the Midlands Region held in Birmingham on hiarch 6th 1973.102 THE FUTURE OF THE XKALYTICAL CHESIIST [ P Y O C . ‘4 Ptalyt. Ciacm. \!’hat is analytical chemistry? I think it is best described in tlie words of Dr. Cliirnside as the examination of a material to establish its properties its qualities arid tlie identification and/or determination of the amount of some or all of its constituents. In order to give a broad picture of the analytical chemist’s work I want to consider very briefly the job of the analytical organisation that one might expect to find in any reasonably large industrial company. The analytical department is essentially a service organisation and as such it has a number of functions. I t may (or may not) check the quality of all the raw materials used in the company’s processes.It will check the quality of the company’s products throughout their several stages of manufacture it will support the company’s research and development organisation by providing analyses for pilot plants and by examining the many miscellaneous materials that arise from research work and by a continual evaluation of new analytical techniques it will always be ready to devise such new methods of analysis as may be required. In addition it must support any technical service that the company provides for its customers and in doing so examine competitive materials the quality of which would seem to threaten the company’s trading position either through technical excellence or infringement of patent rights.Finally it must provide various miscellaneous services such as the examination of factory effluents to guard against pollution of rivers and pollution of the atmosphere and so help to protect the health of the workers and often these days to prevent inconvenience to the community surrounding the factory. Some laboratories will also have to cope with physical testing which in other laboratories is taken care of by the physicists. There is therefore an area of analytical work in which the line separating the analytical chemist from the analytical “physicist” in any particular organisation may be drawn as a result of logical thinking by tradition by chance or by sheer opportunism. -in important part of the remit of the industrial analyst is to carry out his tasks at a reasonable cost and the accountants will be making sure that he know just what tliat means.i\Iany analytical chemists work outside industry but almost all have senice functions that are similar to those already mentioned although the emphasis on the individual functions may differ. Having given these definitions it must not be forgotten that the analyst is a chemist ! He may be called upon to look for any of the hundred or so constituent elements of the earth and any of the million or so organic compounds that are possible and thc amount of any one he niay be asked t o look for can range from fractions of a part per million up to 100 per cent, and it may be in a variety of environments. Fortunately for any one analyst his area of interest is inclined to be a little less broad. In order that he can get on with this task he must be trained in chemistry-good honest fundamental chemistry-lie gets to know that hydrated copper sulphate is blue and calcium carbonate fizzes if you put hydrocliloric acid on it.Not only does he know some chemistry but other people get to know that he knows some chemistry -in fact I have heard analysts spoken of as the most chemical of chemists. I t is important to mention this because so many people who start out in life as chemists end up by becoming specialist technologists in very narrow fields forget their chemistry and the number of chemical chemists becomes smaller. To summarise this introductory section the good analyst has got to be a versatile man and he has got to be continually aware of his chemistry. Turning to the future I want first to offer six obvious trutlis- (1) ( 2 ) (3) (4) (6) (6) employers are going to want more for their money; things must be “socially acceptable” ; analytical instrumentation is going to become more complicated; the chemistry will not go away; the analyst must not be content to play “long-stop”; analysts are exploiters and not inventors.At this moment these may seem to be rather disconnected but I hope to demonstrate that they are all important in whatever future the analytical chcmist is going to have. Let us consider the first obvious truth-employers are going to n-ant more for their money. It lias become pain- fully obvious during the past 2 years that anyone who employs people to provide a service As already stated the analytical chemist provides a service. May 19731 THE FUTURE OF THE ANALYTICAL CHEMIST 103 for him is going to do his utmost to want less of them and on every side we are seeing organisa- tions of all kinds pruning their research activities reducing their staffs in various ways and trying their hardest not to recruit.This would seem to suggest that there are going to be fewer jobs for analysts fewer scliool leavers are being recruited at the bottom and fewer graduates would seem to be required for our laboratories at the present time yet among the vacancies one sees advertised there are always a few analytical posts although more often than not these are for people with particular expertise. The tragedy at the present time would seem to be that none o f these jobs are for people over 50 and for such individuals caught up in a redundancy situation it can be a tragedy indeed and a time for agonising reappraisal manpower by black boxes controlled by unskilled button-pushers.The more enlightened employers will have been thinking such thoughts for the past 20 years at least and will realise that some success in this direction is possible; much bitter experience is also possible. How- ever these are early days in automation. Much of our present analytical instrumentation is comparable with the Model T Ford or with even carlicr versions of the motor car. Make no mistake if it is worth doing even the most complex of our present-day instrumental techniques will be reduced to mere button-pushing and programming in the not too distant future-if it is worth doing! l h e r e would seem to be little that cannot be achieved by way of manipulation and reliability if it becomes absolutely essential-if it is cheaper to employ a man to do it then that is how it will be.To return to present-day reality as the pattern of life in the 70s emerges we shall find problems arising in all the various aspects of the environment and I am hopeful that many of these problems will require the use of analytical skills and so will create more jobs. Neverthe- less I think we have all got to consider very carefully what our contribution to “the body politic” really amounts to and to consider whether by the applications of new skills be they clieniical technical or management or just plain thinking we can improve our contribution and give our employer more for his money and furthermore cnjoy ourselves in the process. Those of us who are responsible for staff must think harder how we can employ tliern to the best advantage both for the company and for themselves.I t may he fashionable to talk of consultation and much lip service is paid to the idea and much time wasted in consequence but nevertheless with the salary patterns that are emerging we can no longer expect anything like a quiet life and we must ensure that our staff understand even if they do not want to what it is they get paid for and whether or not they will ever get any more money for doing the same job. Nobody likes to think they have reached tlie end of the road regarding pay increases but inevitably this is going to happen as particularlv in the junior ranks trade unionism influences or even determines salary levels. This is an area remote from chemistry- the beliaviour of niolecules can usually be predicted but when you are dealing with people each is an individual and woe betide you if you try too much generalisation and classification (although for some purposes of course you must try).Having got round to the subject of people we now move on to the second obvious truth- things must be “socially acceptable.” Whether we like i t or not and despite the condition of life we know to exist in inany under-developed parts of the world there are niany people in the civilised world for whom the struggle to survive is a thing of the past and for whom the next goal is improvement in the quality of life whatever that may mean. Thus it has become fashionable to talk of things being socially acceptable-all sorts of things. What you may ask has this got to do with the future of the analytical chemist? ilnalytical chemists being normally very level-headed no-nonsense types have a duty when i t is relevant to help find out the truth about public worries a duty that is going to become more obvious.To explain in more detail- because of various tragic happenings arising from tlie use of chemicals (and I do not niinimise in any way the seriousness of some of tliese happenings) one has the impres- sion from the media that the environment has only recently been discovered and all sorts of people become alerted to all sorts of alarming possibilities. There are of course many alarming possibilities but possibilities must not be turned into apparent realities by sheer incompetence on the part of scientists. I mentioned earlier the activities of “scientists” who make analytical measurements.Early in 1972 there was the “phthalate scare’’-it was being said mainly by biochemists that phthalates were everywhere in the environment and hence a positive menace to our health. These “euvironmentalists” had published experi- niental results that they said demonstrated the presence of plasticisers particularly dioctyl Some employers will be tempted to consider how far they can repla 104 [€‘roc. SOC. -4 iialyt. Chenz. phtlialate in blood human tissue water (including tap and river water) fish (including deep- sea jelly-fish) and various organs of food-producing animals. It seems that they discovered these phenomena when looking for mercury and chlorinated biphenyls. These findings worried not only the PVC manufacturers but also medical scientists engaged in clinical practice and chemists engaged in the analysis of blood and human tissue.Some of the findings reported were clearly absurd for example from tlie work in the estuary of the Mississippi it was found that as much dioctyl phthalate was present in tlie river in 1970 as was produced in the U.S.X. in that year. Eventually a t a conference in September 1972 organised by the National Institute of Environmental Health Sciences of tlie U.S.=1. it was concluded that much of the concern arose from the incompetent use of very sensitive analytical techniques and failure to realise the importance of the analytical “blank.” The main attack on the environmentalists case came from Dr. Fales of the National Heart arid Lung Institute whose main work had been in connection with drug addiction and he liad been required to analyse blood and stomach contents for trace amounts of drugs and their metabolites; it was in this work that lie had found trace amounts of plasticisers and was forced to discover their origin and then find a procedure to eliminate them from his analyses.*is a result he evolved a technique that could detect I p.p.m. of phthalate ester with certainty and yet lie had not been able to find any a t all in his many analyses of human blood. Dr. Fales received con- siderable support from other analytically oriented workers and the conference concluded that tlie reason for the scare had been fully recognised and that it could now be discounted. As one speaker maintained the most serious health hazard presented by phthalates arose from the scientific effort that was diverted from genuine problems.As a follow-up to this conference representatives of the European plastics industry met in Sovember 1972 to discuss the findings and it was revealed that in France several other scares had caused grave concern to the plastics industry and all liad their origin in faulty analyses carried out by medical research workers in French universities. The most serious had been a demand for the total banning of polyethylene for use in contact with food because pesticide residues had been detected in virgin polymer. Another had found alarming migra- tion of stabilisers from PVC. It was agreed that the sensitivity of modern analytical tech- niques in the hands of those untrained in analytical discipline raised grave problems for the industry as a whole and eventually for the community.For some years my staff have been very conscious of the occasional occurrence of plasticisers in solvents bought from major suppliers the impurity arising because of the contact of the solvents with plasticised PVC tubes. To my knon-ledge one manufacturer has placed an upper limit of 1 p.p.m. of high-boiling esters in ether. This seems very reasonable but if it contains 0.5 p.p.m. and 100 ml of the solvent are used and later evaporated to dryness the residue could contain 50 pg of plasticiser which would show up as a major component in a mass spectrometer. Let me remind you of the closing words of a R.I.C. booklet on Pesticide Residues written by J. Thompson and D. C. Xbbott of the Laboratory of the Government Chemist in 1966 “some analytical methods are no\v too sensitive; small residues almost certainly of no toxicological significance whatsoever can be found almost anywhere.” \Ye must be sure that our results are meaningful and that any apparent deviation from what is “socially acceptable” is real and not the result of analytical incompetence.Analysts have a duty not only t o make sure that their work is beyond reproach but to teach other users of analytical techniques of the pitfalls that await their carelessness. This leads to tlie third obvious truth-analytical instrumentation is going to become more complicated. I have already suggested that much of our instrumentation complex though it may be is probably only a t the Model T Ford stage. We have long recognised that our instrumentation has broadly followed two paths-the autoniatic laboratory equipment and the automatic on-line equipment installed on the manufacturing plant-and both create their own financial technical and personnel problems.Let us consider the financing of instrumentation. -4s instruments become more complex they tend t o become more expensive and thus harder to buy. In consequence instruments become harder to sell which creates problems for the instrument manufacturers. As far as the analyst is concerned a partial solution to this problem has developed over the past few years-we are today considerably more amenable than we were 10 years ago to sending our THE FUTURE OF THE ANALYTICAL CHEMIST These occurrences do not surprise me. In the future our analytical methods will become even more sensitive.May 1973; THE FUTURE OF THE AKALYTICAL CHEMIST 105 samples to a central laboratory for processing and far more laboratories exist today that will accept commissioned work. We should rid ourselves of the idea that each of our laboratories must be self-sufficient and we must be prepared to go to consultant laboratories when this can be an advantage. To give a simple but pertinent example-I am occasionally asked by our metallurgist to determine the carbon in steel; I can have this done almost by return of post by a consultant for under f;lO and so it is not worth keeping the equipment and training someone to use it. I keep a check on the facilities offered by consultant laboratories and also on what can be done in other laboratories in my own company.Instruments can also be hired; in the long run this can be more expensive than purchase but in the short term it can have its advantages. We do not of course use the more complex and expensive instrumentation for all our work. Much of this work will continue t o require chemical or simple instrumental treatment and quick analyses with quick communication of results will continue to be very important There will therefore be little prospect of our laboratories being replaced by a solitary postman despatching our samples hither and thither but we can expect to be under increasing financial pressure for some time and so shall have to adapt our methods of working to cope with this situation. I mentioned the technical problems raised by the increased complexity of instrumentation. The machinery itself will be fabricated for us more and more by instrument manufacturers and only by careful and painstaking liaison with them will we get what we want because they have their problems too.The major part of our complex instrumentation is going to be produced by a declining number of instrument manufacturers because of amalgamations and closures. They will become increasingly attracted to producing best-selling lines and less inclined to produce anything that sells less than a dozen. Also part of the complexity of our future equipment will arise from the sort of developments in electronic circuitry we are seeing elsewhere so that more than ever we shall be able to do little in the way of self-service but will require the manufacturers to maintain a really efficient service organisation that does not cease to function because the store-keeper is on holiday.This service is of course going to become more expensive. This is a useful point at which to repeat the fourth obvious truth-the chemistry will not go away. While instrumentation is becoming inore complex so are many of the products that our employers wish t o make-the chemistry is going to become more complex and we must understand it. Furthermore that chemistry is going to get out of the laboratory. Just as we have seen the community at large become conscious of the effects of trace metals on the quality of life so will the effects of trace organic chemicals come to assume greater importance and it could be that we are only just beginning to understand the significance of these traces in the environment.I should point out that the Carcinogenic Substances Regulations 1967 prohibited the manufacture of various chemicals (subject to certain exceptions). While the people con- cerned were affected immediately the importance of this is only slowly making itself felt. For analytical chemists it means that despite the trivial danger associated with the small amounts we are likely to use we must replace these materials in our methods with an alter- native that is just as effective analytically and not known to be carcinogenic at the present time. I mention this now because it represents a concern that no potentially dangerous chemical is used by anybody and all chemicals are potentially dangerous. We are seeing efforts being made t o abolish the use of benzene in laboratories and several other chemicals are also being considered.I therefore suggest that there is considerable potential for analyti- cal work arising from a better understanding of our increased worry about chemicals in the future and I think this is beginning t o be reflected in job advertisements. I now want to introduce the fifth obvious truth-the analyst must not be content to play “long-stop.” By this I mean that he must not sit in the laboratory and wait for people to bring him work. By doing this he accepts that the people who bring in the work are competent to decide when analyses are required and what analysis is possible. We are in an age when the analyst must regard himself as part of the technological team-he must be present at every stage of a new project. While he will not wish to get involved with the actual construction of a plant he will want to be involved with all the consequences of plant design raw material analysis process control analysis sampling effluent quality atmospheric contamination toxic effects on the work force hazards in despatch and carriage of products and so on.All of these 106 THE FUTURE OF THE ANALYTICAL CHEMIST [Proc. SOC. AnaZyt. Chewz. aspects must be considered at the start of a project and not require panic measures when the plant is operational. We can expect factory inspectors river boards etc. to be much more interested in what goes on in chemical plant in the future and the analyst has a part to play. No analyst will spend all his life around new plants but in the course of everyday life the same philosophy will hold-he is a member of a technological team and must do his share of the forward thinking of the organisation having ideas for his own area and so meeting problems half way; he must not be content to sit and wait for instructions.In looking to the future the analyst will constantly be seeking new tools to use and here we come to the last obvious truth-analysts are exploiters and not inventors. This is a generalisation with which some may wish to find fault but most of our present-day techniques have been invented outside the analytical laboratory. However as soon as a new idea has been explained the analysts are certainly good at exploiting it. New tools that are being developed are laser Raman spectroscopy electron spectroscopy in several variants the use of Fourier transforms in infrared and nuclear magnetic resonance spectrometry and further developments in the uses of computers.The analyst has also exploited the use of combina- tions of techniques-in particular the use of gas - liquid chromatography (plus pyrolysis) and thin-layer chromatography with infra-red nuclear magnetic resonance or mass spectrometry. We are seeing the development of new detectors for gas chromatography that embody other techniques such as polarography and coulometry and with liquid chromatography we are using ultraviolet spectrophotometry refractive index and the flame-ionisation detector plus travelling wire. The latest commercially available combination combines the techniques of gas chromatography and atomic emission where the atomic emission results from the passage of the eluent compounds through a microwave-sustained helium plasma discharge.Surely we can expect other combinations to be developed as problems arise. I t may be a truism but I think it pertinent to say that it is the existence of problems which must be solved that produces the new methods-whether the drive for solution of the problem comes from some inner urge (as it did with the early inventors) or from the feeling of a gun held at your head by your employer. I have given a few obvious truths and tried to indicate how the analyst and his craft will be affected in the future. However I have not said much about the analyst himself and what all this means to him nor have I said anything about his training. As I said earlier analysts come in all shapes and sizes all ages and all levels of competence so that generalisa- tions are difficult.However let us consider seniors and juniors where they come from and where they are going. I will begin with the juniors or technicians who come into our laboratories as school- leavers and study by means of day-release taking either the Chemical Technicians Certificate route or the National Certificate route. The latter usually go through ONC and HNC to LRIC-in my experience far fewer these days attempt GRIC largely because most of the people who might have done this only 10 years ago now go to university full time. So more and more the junior will not be expected to proceed beyond LRIC if he reaches that stage. He will be responsible for most of the work in factory laboratories and the more routine work in research laboratories. If he is fortunate and bright enough he can give valuable service by running the most complex instrumentation i.e.gas chromatography X-ray fluorescence mass spectrometry nuclear magnetic resonance and so on and take some part in interpreting results. What is his future? In the past we could regard the analytical laboratory as a staging post for young people in their career-a few would be attracted to the profession and remain while the majority used it as a stepping stone to some other occupation where their experience would be valuable and many of the young ladies would marry and start a family. Now with a sudden break in recruitment we are I think seeing far fewer school-leavers being required and because of a blockage in the system there are fewer opportunities for the 30 year old technicians and so the flow through laboratories has slowed down.Unless this flow can be speeded up again we shall find our junior staff becoming older and wanting more money and yet the work will not change very much so that they could be overpaid for what they do and salaries might be kept down; in that way frustration and unionisation lie. I cannot help feeling that the basic reason for the present upsurge of interest in “representation,” apart from its necessity under the terms of the Industrial Relations Act arises out of boredom with dull jobs that offer little prospect for advancement and hence little “job satisfaction.” This is a dismal prospect. The administration of the laboratory is not going to become any May 19731 THE FUTURE OF THE ASALYTICAL CHEMIST 107 easier and more time will be spent in consultation and communication basically because this part of our staff will on average be less bright than it was in the old days although the behavioural scientists will always insist that we previously used the wrong approach.We must of course retain both our specialists and our generalists since both have a valuable part to play in our work. Here again the recent economic climate has placed a blockage on recruitment so that far fewer graduates in chemistry would seem to have entered our laboratories during the past 2 years than previously. These conditions will probably continue for at least a further 2 or 3 years by which time analytical cheniistry and indeed chemistry as a whole may come to be regarded as an unpromising area for graduate employment and many potential chemists will be looking elsewhere.’1’15th this blockage in recruitment there will in the short term be less opportunities for the younger graduate analysts to move out into process research production and technical service or even other companies which will thus have the effect of slowing up their career. There is another factor that I believe is having an adverse effect on careers in general- the current price of houses. This has been evident for some years and I have had several juniors who had to leave my laboratory because they could not afford to buy a house in the surrounding area but could buy one if they moved away from the south-east. However the south-east no longer has the monopoly of high-cost housing and it seems to me that the future trend is that it is going to become progressively harder for the young married man to move once he has settled into an area particularly when his children are settled in schools.In all of the above I have taken for granted the existence and availability of analytical information to everyone but this requires some discussion. Not many years ago the world of analytical information seemed simple-there were not too many journals in our laboratories we could browse through most of those of immediate interest and we did not have to worry too much about where they came from. There were clouds on the horizon but in general we ignored them. Five years ago I was wondering about the future of Aizalytical Abstracts and vaguely thought that we should see changes within 10 years and yet today it looks exactly the same as it did 6 years ago.But much has happened in 5 years and much more is going to happen in the future and the younger members of our profession especially should take notice. There are now more journals that publish information of interest to analysts and those journals are now expensive. So librarians who have probably had their budgets cut are no longer amenable to buying all the journals that we might wish to have. XIore and more we are having only the contents pages of journals circulated and are making more use of abstracts. This means that we are having to find new ways of discovering what is in the current literature that might be of interest to us and selecting from that the original papers that weguessare the best ones to read. We are therefore seeing an increase in computer searching of the literature and the possibilities for browsing and serendipity are shrinking almost to vanishing point.There are schemes afoot to abolish the publication of original papers as we now know them. Such papers would be stored in central archives and access would be gained through ab- stracts’journals. Such schemes are not finding favour a t the present time and although it might sound cynical I suggest that this will not be really seriously considered until the existing com- mercial journals find themselves in financial difficulty-as they may well do not so far ahead. Publication in microform especially microfiche is slowly developing but the lack of cheap reading devices is holding this back (as it has been for a t least 5 years). So in a world where more information than ever is available communication is becoming more difficult.I am inclined to the view that with the large area of literature that analytical chemists have to cover to see only lists of titles and a few keywords is not enough and we are in real danger of becoming increasingly ignorant. I drew attention to this in my Presidential Address 4 years ago and it is certainly something that should be discussed in detail. It is still my experience that in general analytical chemists do not take enough interest in this part of their business and so may find themselves in difficulty in the future when the traditional sources of information have dried up. I have touched upon some aspects of the future that lies ahead for the analytical chemist. Each person has to make up his own mind about the future and act on those findings but the difficulty is that the rules of the game keep on changing. Thus to the question “is it possible to plan a career in analysis?” I can only answer-is it possible to plan a career anyway and indeed was it ever possible? What of our senior analysts?

ISSN:0037-9697    

DOI:10.1039/SA9731000101

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

108 TECHKIQUES FOR PARTICLE CHARA4CTERISATIOS [PVOC. SOC. .-I Itdyt. ch’I1Z. Techniques for Particle Characterisation The following are summaries of three of the Plenary Lectures presented a t a Colloquium of the Particle Size Analysis Group held on September 13th and 14th 1972 and reported in the November 1972 issue of Proceedhzgs (p. 232). Ancillary Techniques in Particle Characterisation BY H. J. SCULLION AND J. E. C. HARRIS (.Walevials Quality Assuvance Direcdovate Ministvy of Defence Pwiton B v i d p a t e r Somerset) THERE are many useful in which are discussed various ancillary techniques associated with particle characterisation in its broadest sense. In this paper only an outline of a philo- sophy of approach is given and some of the complicating phenomena (e.g. pseudopolg7rnor- phism) that can adversely affect particle size characterisation are mentioned.We summarise the approach as follows- ( a ) ( b ) observation of the particulate; (c) ( d ) preparation of samples; (e) (f) calculation of results. consideration of the purpose of the examination in the light of relel-ant theory; sampling and the sub-division of samples; change in particle characteristics with time; These are not definitive topics but are of course inter-related and overlap. PURPOSE OF EXAlIINL4T1OS- Primarily we are concerned with selecting the technique appropriate to the technological use of the powder. If a powder is to undergo moderate physical working then we know that in preparing it for say sedimentation analysis spatulation of a paste would be appropriate. With (b) in mind one also observes the nature of such a paste (e.g.for dilatancy as a clue to flocculation). In addition we would be careful not to “extrapolate” the use of a technique into an area where the theory is inapplicable e.g. unhindered sedimentation theory to con- centrated systems or viscous pernieametry where molecular flow is significant. If however circumstances force one to make such an extrapolation then great care has to be taken and the results must be treated with reservation. \l‘hen using sedimentometry perhaps practical workers would feel that the system can never be made sufficiently dilute to satisfy theoreticians. Statistical considerations arise and it is pointed out that in any very small volume of the system there is always a probability that more than one particle will be present and hence of more rapid fall.Barfodj applied a Poisson law to such a system. Our inclination would be towards a negative binomial. OBSERVA4TIOS OF THE PART1CULL4TE6- In quasi-routine work the importance of this aspect is frequently underestimated and relevant observations may be missed. The microscopic observation of the orifice on the Coulter Counter the stroboscopic observation used with the disc centrifuge and the intensive (500 W) illumination used7 with a Bound Brooke sedimentometer illustrate “special situation” observations in particle size measurement. General observation usually starts with a simple instrument say a zoom binocular microscope. An image-shearing eyepiece can be brought into use in preliminary work and even if need be petrological microscopy on a universal stage.s In the last instance a particle can be mounted in the centre of what is virtually a glass sphere.Rotation of the sphere enables the morphology of the particle to be viewed from all angles and if required conoscopic measurements can be made. For comparative work one can examine the same sieve-cut taken say from different tender samples. Thus in Fig. 1 marked differences can readily be seen in the same size cut of ammonium perchlorate from different sources. Such material exhibits different techno- logical behaviour illustrating that particle characterisation is not just simple sizing. They may influence fragility and Comminution for example and enhydrous inclusions may leak and cause particle Inclusions9 inside particles may be of interest for various reasons. May 19731 TECHNIQUES FOR PARTICLE CHARACTERISATION 109 (4 (4 Fig.1. Sieve cuts (425 to 500 pm) of ammonium perchlorate samples from four sources (a) Swedish; ( b ) Japanese; (c) French; and ( d ) British 110 TECHNIQUES FOR PARTICLE CHARACTEKISATION rPYOC. SOC. i!nal>d. Chem. adhesion. Batten’s approaches to the investigation of inclusions are of value in some fields,’O as is the use of density gradient col~mns.~f Changes due to polymorphism and pseudopolymorpliism (solvate formation etc.) are conveniently investigated by optical means.8%11 In pharmaceutical work polymorphism is of prime importance and was admirably surveyed by Kuhnert-Brandstatter12 who reported (for the compounds covered) that 63 per cent. of barbiturates and 40 per cent. of sulphonamides were found to exist in polymorphic forms.Besides effects on tabletting the absorption and hence efficacy of drugs (q. cortisone acetate and novobiocin) are very greatly influenced by the polymorphic form of the particulate. Pseudopolymorphism also can be very prevalent in certain fields such as explosives (e.g. Selig Crossman and Silveira reported sixty molecular complexes of diaminotrinitrobenzene13) and pharmaceuticals (e.g. P-oestradioll4 afforded thirty different solvates from thirty solvents). The tiny bubbles produced when a solvate is heated in a drop of silicone oil can be used to distinguish solvates and hydrates from the unsolvated parent compounds.14 A lower mean refractive index and higher crystal asymmetry characterises hydrates and solvates in general (e.g. NaBr cubic R.I. 1.64; NaBr.2HZO monoclinic R.Is.about 1.5). The technique of “dispersion staining’ls has been used to detect minor optical differences between samples of ostensibly similar particles and can be used in suitable instances to detect thin (less than 1 pm) transparent coatings on parti~u1ates.l~ Perhaps the ultimate way of looking at particle morphology is by electron microscopy. In comparing very fine iron powders we found that the G/K ratio* varied from about 1 up to 5 for a series of samples. Examination by Stereoscan showed that the lowest ratio related to spheroidal particles and the highest to “solid sponge” particles thus confirming a diagnosis based on indirect evidence. SAMPLIXG AND SAMPLE SL?B-DIVISIOX- This is a vast subject. Some references of use are Welcher16 on sampling generally .411en2 on particle size aspects and Bowker and Goodel’ on statistical aspects.Dispersions are discussed in another of the papers a t this meeting so in this paper we will describe some of our experience with dry powders. The initial buik sample is probably best taken from a moving stream of powder rather than from a heap during the formation of which segregation might well occur. In Table I using a spinning rifflerl8 modified for use with explosives and employing four operators 1 2 3 and 4 in increasing order of experience we have compared this method of sample sub-division with other procedures. The work was in essence on larger and less dense particles than those p r e v i o u s l y r e p ~ r t e d ~ ~ ~ ~ ~ but it confirmed other workers’ broad conclusions as regards the superiority of the spinning riffler.It is interesting to note that unmixed samples (.N‘z. 0-15 kg of A p1z.t~ 0.16 kg of B) gave (for percentage A content) TABLE I OF A 1+1 nzim 0.3-kg MIXTURE OF PARTICLES OF A (- 3000pm DIAMETER; DEXSITE’ STAXDARD DEVIATIONS CALCCLATED FOR PERCEKTAGE A COWTEKT OF SIXTEEN SUB-SAMPLES 0.9 g ~ m - ~ ) AND OF B (<300 pm DIAMETER; DENSITY 2.2 g ~ m - ~ ) Operator P Scoop sampling -_ 7.09 5.78 - Cone and quartering 5.83 4.06 3.83 1.82 Chute splitting 3.20 1.91 1.50 1.30 Spin riffling 0.91 0.68 0.77 0.81 Technique 1 2 3 4 standard deviations of 0-71 to 1.56 per cent. which are markedly superior to cone and quarter- ing results for mixed samples (viz. 1.82 to 5.83 per cent.). An additional point to be made is that increased precision of the resultant mass of a sub-sample may be of distinct value when a sizing or analytical procedure requires a specimen of closely limited sample mass.Thus i n the work illustrated in Table I the spinning riffler gave a precision (coefficient of variation) of 2.0 to 2-5 per cent. for the masses of sub-samples as compared with 5.3 to 9.0 per cent. for cone and quartering. * The G/Ii ratio is the ratio of specific surface by gas adsorption to specific surface Knudscn flow pcrmeametry. May 1973; TECHKIQUES FOR PARTICLE CHARACTERISATIOS 111 Between dry powders and dispersions there is a wide range of powders wetted to varying extents. Perhaps one of the most common would be damp particulate “cakes” built up on circular filter beds. If one takes say three vertical thief samples at random from each bed then in three beds out of four we expect (in the statistical sense) the three holes to lie on one half of the circular bed rather than being arranged as is usually seen like the vertices of an equilateral triangle.The only point we make is that if random sampling is required one should ensure its achievement by say the use of random numbersz0 to identify the locations bags or drums etc. from which to sample. Semi-intuitive ideas regarding randomness can be misleading. SARIPLE PREPARATION- Sample preparation is linked to the test method which is chosen as far as possible in the light of the envisaged function of the particulate. When one has to dry wetted powders perhaps freeze-drying is the logical approach but a t present we use vacuum drying a t ambient temperature in the presence of desiccant.When a “wet” method of characterisation e.g. electrical zone sensing21 or sedimentation is to be used then other aspects are pertinent. Slower dilution of pastes tends to prevent flocculation. A small sample of suspension taken to observe whether flocculation has occurred should not be subjected to work either by passage through a narrow orifice (hypodermic syringe or pipette) or manipulation under a microscope cover-slip. The effect of temperature rise (especially that generated in an ultrasonic bath used to assist dispersion) may be much greater than might be anticipated. The effect of solubility may similarly be underestimated. When using a Coulter Counter with a fine powder of low solubility in the electrolyte (about 0.005 per cent.) we obtained a fall in count of over 70 per cent.in a few minutes yet when using a 95 per cent. saturated system the final counts were 98.5 to 100 per cent. of the original even after an hour. Thermal analysis techniques can be harnessed in investigating de-gassing conditions for gas adsorption methods of determining specific surface area. A knowledge of particle density is frequently stipulated in certain areas of particle sizing. Fnr this a gas or air comparison pycnometer does not significantly alter the sample and has advantages for use with soluble powders. Of course density measurements can be useful in investigating a lack of uniformity in a ~ystem,4f,22~23 e.g. hydrated (less dense) particles in an unliydrated particulate may be readily indicated on a density gradient column. I 23 days\ . 23 day I I I 2.0 3.0 4.0 Carbon or hydrogen content per cent.Fig. 2 Change in specific surface and carbon or hydrogen content of magnesium oxide with time X carbon; and B hydrogcn 112 TECHNIQVES FOR PARTICLE CHARACTERISATIOX [PYOC. SOC. dizalyt. Chem. In permeametrp a knowledge of particle density is really required only to enable one to calculate the compacted bed inter-particle pore volume and when this can be attained in other ways then measurement of density is not necessary. However a very accurate knowledge of pore volume may be needed for compacted beds of low porosity. As regards the actual technique of bed preparation Burt and Fewtrel124 have found centrifugal compaction to be most satisfactory. \Vhen one uses the sedimentation fluid for determining the particle density then only the density difference is required and despite the definition of Stokes diameter explicit knowledge of particle density is not needed.Some uniformity in “effective” density is of course essential in sedimentometry but not p e Y se in permeametry. For determining the “effective” density of porous particles which is a complex procedure the work of ErgunZ5 and Dollimore et aLZ6 is useful. A similar situation obtains for sedimentometry as for pernieametry. CH.4n’GE I N PARTICLE CHARACTERISTICS WITH TILIE- This aspect has been mentioned above-the crystallisation of amorphous novobiocin can render the drug virtually useless. It is frequently found that newly comminuted powders can alter rapidly in particle size especially if allowed to stand when damp and this factor can be worrying if it has not been previously encountered.The specific surface (S) usually falls very rapidly at first and then more slowly. Thus milled RDX can show a reduction in S trom 7000 to 6500 cm- in a few hours yet about 14 days may be required before 6000 cm-l is reached and thereafter the decrease is slight. The action may be purely physical e.g. associated with the greater solubility of the smallest particles,27 or chemical. We investigated a magnesium oxide powder that declined in specific surface from over 150 m2g-l to 20 m2 g-1 in 55 days and found that S varied smoothly with the uptake of both carbon dioxide and water as shown in Fig. 2. The ancillary equip- ment used was a C H and K analyser from the organic chemistry laboratory. It should be mentioned that milling organic particulates in an aqueous medium can convert a “stubborn” metastable polymorpli into the stable modification e.g.cortisone acetate and HMX. 0.5 0.6 0.7 Porosity Fig. 3. Specific surface area veysus porosity relationships A iron(II1) oxide B copper(I1) oxide; C tungsten; and D barium peroxidc May 1973 TECHNIQCES FOR PARTICLE CHARACTER1S;ITION 113 CALCULATION 01; RES~LTS- Programmable desk calculators and computers are of great value in particle size work. However sources of error can be many and varied e.g. the symbol for a commonly used variable may have only integral value in the language used; and a “best” straight line can be drawn through a set of points arranged as the vertices of a regular polygon. Hence safeguards in programmes are essential especially against “abnormal” ram data.Thus when using the B.E.T. equation in dynamic gas adsorption work one requires besides slope and intercept some measure of goodness of fit (e.g. correlation coefficient). Thus one can replace the usual 2 / 2 spacing by a 1.2589 spacing in micrometer eyepiece graticules and GuruswamyZ8 has outlined the computational advantages of the relationship log 1.2589 = 0.1. Again in I k o u s permeametry a very simple calculation devicezs enables one to follow a por- osity w s u s specific surface relationship in virtually zero calculation time. In Fig. 3 are illustrated the relationships found for four powders two (barium peroxide and tungsten) showing a satisfactory plateau and two indicating the failure of the Carman-Kozeny equation for the systems under test. In fact for copper(I1) oxide the measured specific surface was virtually a linear function of porosity (correlation coefficient 0.996).To sum up we would say that whereas the acquisition of a fundamental knowledge of the basic theory behind all sizing techniques is probably difficult for most workers nevertheless we should aim a t least at some cognisance of the limitations that such theory imposes on any practical sizing operations with which we are concerned (cr~iticnl reviews such as ref. 30 are invaluable). In the light of this the relative importance of various ancillary techniques should become clearer. May we add finally that we feel that microscopy in all its aspects is at present undervalued in particle size characterisation. Devices more modest than programmable desk calculators can be of value.\Ye thank hIr. J. McCormack for preparing the illustrations. 1 . 3 . 4. 5 . 6. ? -. c t . 8 . 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. REFEREXES Parfitt G. D. “Dispersion of Powders in Liquids,” Elsevier London 1969. Allen T. “Particle Size Measurement,” Chapman and Hall London 1968. Silverman L. Billings C. E. and First Y1. W, “Particle Size Analysis in Industrial IIygierie,” British Standards (a) B.S. 346; ( b ) B.S. 4359; (c) B.S. 410; ( d ) B.S. 4522 ( e ) B.S. 1796; (I) B.S. Barfod S Powder Teckrzol. 1972 6 30. McCrone \V C. Draftz R. G. and Delly J . G. “Particle Atlas,” .Inn A4rbor Science Publishers Academic Press N e w York 1971. 3715; (g) B.S. 733. Xiin Arbor. 1967. Allen T in’Groves hi. J. and 1Vyatt-Sargent J . L. Editovs “Particle Size .Inalysis 1970,” Hartshorne N.H. and Stuart A “Crystals and the Polarising Microscope,” Fourth Edition Society for Analytical Chemistry London 1972 p. 164. Edward Arnold London 1970. Gross K. A J . Crysf. Gvowth 1970 6 210. Batten J. ,J. AppZ. Chenz. Biotechnol. 1971 21 163. BlcCrone W. C. “Fusion Methods in Chemical hlicroscopy,” Interscience Se\v Yorlc 1957. Kunhert-Brandstatter M. Puve Appl. Chew. 1965 10 133. Selig W. Crossman G. L. and Silveira V. G. Explosiustoffe 1971 1 . Kuhnert-Brandstatter M and Grimas H. X k r o c h i m . Acta 1968 115. RlcCormack J . Harris J. E. C. and Scullion H. J . Powdev Technol. 1973 7 281 Welcher F. J. Editor “Standard hlethods of Chemical Analysis,” Sixth Edition T-olumc 2 Bowker A. H. and Goode H. P. “Sampling Inspection by Variables,” NcGraw-Hill New York Allen T.and Khan A. A Chem. Evzgt, Lond. 1970 108. Charlier R. and Goosens W Powder Technol. 1970 4 3.51. Kenney J . F. and Keeping E. S. “Mathematics of Statistics,” Part 2 Van Kostrand New Yorlc Allen T. and Marshall K. “The Electrical Sensing Zone Method of Particle Size lIeasurement Published by the authors a t the University of Bradford 1972. Scullion H . J . and McCormack J. Mzcvoscope 1970 18 99. XicCrone 1%’. C. and Hudson W. J . Fovens. Sci. 1969 14 370. Burt M. W. G. and Fewtrell C. A. in Groves &I. J. and Wyatt-Sargent J . L. Edifors o p . cit Ergun S. Analyt. Cltem. 1951 23 151. Dollimore D. Dollimore J and Spooner P. ila Groves $1 J . and Wyatt-Sargent J . L. Editovs Part A \‘an Nostrand Princeton N. J.. 1963. 1952. 1951 p. 162. p. 321. op. cit. p.401. 114 TECHI~IQUES FOR PARTICLE CHARACTERISATIOS CPvoc. SOC. A n a l j k Clzenz. 27. Partington J. R. “Advanced Treatise on Physical Chemistry,” Volume 3 Longmans Green 28. Guruswamy S. “Particle Size Analysis 1966,” Society for Analytical Chemistry London 1967 29. Techlink Pamphlet KO. 777 Ministry of Trade and Industry 1970. 30. Analytical Methods Committee “The Determination of Particle Size. I. London 1952 p. 538. p. 29. Sedimentation Methods,” Society for Analytical Chemistry London 1968. :\ Critical Review of Problems Associated with the Determination of a Size Distribution by Using Sieves with Particular Reference to the Sizing of Marine Sediments BY P. R. KIFF (Defiarlnzent of the Envivonmeizt Hydraulics Reseavch Station l+:allingJoyd Berkshzve) THE factors that control the accuracy of the results obtained by standard sieving procedures fall into the following groups- Sieves .. . . . . Aperture diameter Percentage open area Sieve height Physical properties Total load Shaker .. .. . . Method of agitation Duration of sieving Anall-sis of results . . Weighing accuracy Interpretation of results Powder . . .. . . Particle size distribution Aperture tolerances as described in B.S. 410 1969 become proportionately larger as the aperture diameter decreases and although modern microscopical techniques enable these diameters to be accurately measured the practical aperture size is better obtained by grading a batch of glass beads. Commercial glass beads are usually of a log-normal distribution and if a selected batch is split into representative fractions and sieved through a nest of sieves then the results when plotted on log-probability paper should fall on a straight line.Any individual point that falls off this line can be taken as being of suspect aperture see and corrections can be made accordingly. The percentage open area of the mesh and the height of each sieve were not found to have a noticeable effect on results. The effect of the particle size distribution on the accuracy of results is bound up with the effect of total load. In fact there is an optimum mass of material that produces the maximum rate of saving for each particular aperture size mesh. In practice however for routine determinations the only alternative is to use each sieve in the B.S. f i 1 series for narrow size distributions and perhaps alternate sieves for wider distributions.I t is also necessary when there are considerable amounts of material below the minimum aperture size to be used to remove fines prior to sieving. This is particularly important in the case of sediments that contain dried clay which is very hard and will not break dowi appreciably in the sieving process. Normally a wet sieving process is used to remove the majority of the fines the amount being added to the mass in the sieve pan prior to calculating the size distribution. The physical properties mainly shape and density affect the rate of sieving and air-jet sieves are useful for the low-density irregularly shaped particles. S o difference between air-jet and conventional shaker results was found when a test sample of glass beads was sieved but sieving coal and wood grains (reducing the density) produced increasing differences in size distributions the air-jet showing the finer grading.This implies that the conventional shaker may be adequate for nearly spherical sand particles but does not agitate less dense particles sufficiently. The air-jet sieve agitates less dense particles proportionately more than denser particles and thus will produce a more accurate size distribution of those materials. An important point to note is that when particles are examined under a microscope prior or subsequent to sieving the view is of a two-dimensional object the third dimension not May 1973 TECHNIQUES FOR PARTICLE CHARACTERISATION 115 being visible. In comparing sand and coal grains the general outline of the particles is similar but when the grains are rotated through 90" and the third dimension is measured sand grains are found to be uniform whereas coal grains are found to be much more plate-like.When therefore a specific sieve fraction of sand and coal grains is examined under the micro- scope the coal grains appear to be larger than the sand grains owing to the fact that they pass through the aperture diagonally. The duration of sieving is important in as far as there is a continual increase with time in the amount of material passsing the sieve. The extent of this increase depends on the size distribution and the sieves used. After an initial period in which the rate of passage of material is high the rate decreases until a stage is reached when the smaller particles in the size distri- bution remaining on the sieve are continually chasing the largest aperture of the mesh.Breakdown of particles can also be a factor in this process depending on the nature of the material being sieved. Modern balances are normally accurate enough for the weighing of material on sieves. Depending on the amount of material sieved an accuracy of 0.01 to 0.1 g is usual. At the Hydraulics Research Station one of the purposes of determining the size distribu- tion of sand is to determine the amounts of material passing in or out of an estuary over a complete tidal cycIe. This involves taking samples of water and suspended sediment a t various points across the estuary at various depths and at 30-minute intervals over a 124 hour period. The numbers of samples involved are large and in order to produce results rapidly and economically a knowledge of the relative importance of the different factors that affect sieving is essential.The Use of Gas Adsorption as a Tool in the Study of Surfaces and Pore Structures in Finely Divided Solids BY N. R. THOYIPSOX (Iiiipevial Chemical Industries Limited Mond Divisioiz Research and Development Depar,tment Winxiizgtoii Laboratoiy *\'orthwich Cheshire) BECAUSE of unbalanced atomic and molecular forces surface molecules of solids attract molecules from their surrounding environment. If gases are attracted the phenomenon known as gas adsorption provides one of the best methods for measuring solid surface areas. To use this technique the volume of gas required to form a monomolecular thick layer and also the area covered by one adsorbed molecule need to be known.Type 1 occurs when no multilayer formation exists in the adsorbed gas layer and interpretation in terms of monolayer volume is straightforward. The other types of isotherm arise from niultilayer formation by various mechanisms in the adsorbed layers and interpretation to yield monolayer volumes is usually carried out by using the B.E.T. theory. However in this theory several assumptions are made that most practical cases do not satisfy and the validity of the B.E.T. area should be assessed empirically for each gas - solid system. A41so the importance of micropore filling has not always been appreciated. However equating the rates of condensation and evapora- tion of gas molecules on to and from an adsorbed layer and summing for an infinite number of layers the equation Five classes of adsorption isotherm exist (Fig.1). 1 (C-I) P v ( P S - P T - VmC VmC PS - -.- P results from which the monolayer volume Vm can be obtained ( P = actual pressure; P = saturation pressure a t sample temperature; V = volume adsorbed; and C = constant). In non-porous solids no capillary condensation occurs and with such systems the work of Lippens and de Boer1 showed that the ratio between the adsorbed volume V and the mono- layer volume Vm approximated a single curve when plotted as a function of relative pressure. Knowing the adsorbed layer thickness ( t ) a t one point on the curve it can be calculated for other relative pressures as can also the number of layers of ad-molecules ( n ) assuming a close-packed liquid structure for the adsorbate. The various published "t-curves" show differences mainly in the low-pressure region as might be expected since the substrate surface is not as effectively screened in this pressure region as it is a t higher pressures.Unhindered 116 TECHNQUES FOR PARTICLE CHARACTERISATIOS [Puoc. SOC. A tzalyt. Clzem. multilayer formation will give a straight-line t-plot passing through the origin and of slope determined by the surface area. However in systems with narrow pores that are filled or blocked at low relative pressures the t-plot will exhibit a break and after the pores are filled will follow a t-plot below the original and coiisistent with a solid of lower surface area. If capillary condensation occurs the t-plot can lie above the standard t-plot for a non-porous solid. However Sing2 modified the t-plot method to take micro-pore filling into account and Sing’s modification can give an estimate of the micro-pore volume.+ P - P - P * P Fig. 1. The five types of isotherms The t-plot method is itself restricted in applicability to those systems for which the B.E.T. monolayer capacity is well defined since t is calculated from VjV,. Replacing the function t by one designated C I ~ avoids this limitation where CI is defined as the volume of gas adsorbed at the measured relative pressure divided by the amount adsorbed at a selected relative pressure; 0.4 is usually chosen as the reference relative pressure since any micropore filling takes place below and any hysteresis effects above this relatiw pressure. Thus the reduced standard isotherm is derived empirically and not via a function involving the monolayer volume.So far the technique has been applied to only a few The phenomenon of capillary condensation can have a marked effect on the shape of the adsorption - desorption isotherms for a particular system and study of the isotherm shape can yield valuable information concerning the pore structure of the material under study. The relationship used is that described by the Kelvin equation P -2av~COS4 PS Yk RT In- = which relates the pressure P over a curved liquid surface to the degree of curvature over that surface; yk denotes the radius of curvature of a hemispherical meniscus of a liquid having surface tension a contact angle 4 and molal volume VL and P is the saturated vapour pressure over a plane surface at the temperature of interest. For pores that are not spheri- Mag’ 19731 TECHKIQUES FOR PARTICLE CHARACTERISATION 117 cally symmetrical the Kelvin radius yli is determined by the two main radii of curvature y1 and y 2 i.e.- = y 1 1 (;+$) yk On decreasing the gas pressure above a fully filled pore evaporation will occur and the meniscus will assume a concave surface of gradually decreasing radius as the pressure de- creases so that the Kelvin relationship is maintained. This process continues until the radius of the ineniscus is the same as the pore radius when any further evaporation will cause an increase in radius and as a consequence the pore will empty completely except for the physi- cally adsorbed multilayer film. Similarly on increasing the gas pressure from a low value there can exist a critical pressure a t which pores of a particular radius can suddenly completely fill with condensed liquid.IT-hen the Kelvin equation is applied to pores of various shapes only those with re- entrant angles will be found to require a higher relative pressure to fill empty pores with liquid than to empty already filled pores and thus give rise to the phenomenon of hysteresis in the adsorption - desorption isotherm i e . merely by observing the shape of adsorption - desorption isotherms valuable information can be gained about the types of pores present. To obtain the required adsorption data experimentally can present intriguing problems The ultimate requirement is to determine the amount of gas adsorbed a t various relative pressures both as the pressure is increasing and as it is decreasing. One of two basic tech- niques volumetric or gravimetric is usually used.Both have certain advantages and dis- advantages and the methods are compared below. Because of the low relative molecular mass of hydrogen all studies in which hydrogen is used as adsorbate have involved volumetric techniques but with heavier gases (nitrogen carbon dioxide and krypton) the gravimetric method becomes acceptable from a sensitivity standpoint and by using modern electrobalances mass changes can be measured to an accuracy of 1 2 pg or better. cm3 of nitrogen a t N.T.P. and to measure volume changes to this order of accuracy by volumetric techniques requires very precise thermostatic control of all sections of the apparatus in order to enable the gas laws to be applied with sufficient accuracy. Capillary tubing is used in the volumetric method t o connect the cold sample bulb to the remainder of the apparatus so as to minimise errors due to assumptions made about the temperature gradient in this region.However the use of capillary tubing where temperature gradients exist introduces the necessity of making corrections for thermal transpiration effects so as to obtain a true value for the pressure in the sample bulb an additional source of potential error Mitigating these disadvantages is the pre- cision with which the sample temperature can be controlled and measured when using volu- metric methods compared with that which is possible when using gravinietric techniques. In the gravimetric method no contact between the sample and the walls of the sample vessel can be allowed during a run and any heat transferred to the sample by conduction down the suspension wire or through heat of adsorption effects must be dissipated across an (initially a t least) fairly high vacuum.With the volumetric method the sample is actually in contact with the walls of the sample vessel and conductive heat transfer is good. Apart from this problem of sample temperature temperature control of the remainder of the equipment need be minimal since the gas laws are not used in determining the amount of gas adsorbed. Also thermal transpiration effects do not have any significance since tubing with a relatively wide bore is used in regions where thermal gradients are present. Therrnomolecular flow can cause some errors but normally the effect is small and can be minimised readily. Thus if and when sample temperature control can be accomplished easily the major drawback of the gravimetric method will have been overcome and it could become the tech- nique of choice especially in situations where only small amounts of sample are available since in general much less sample is required when using a highly sensitive vacuum electro- balance in comparison with that required when using conventional volumetric apparatus.This level is equivalent to about &2 x REFERENCES 1. Lippens B. C. and de Boer J. H. J . Catal. 1965 4 319. 2. Sing K. S. W. Chem. & m d . 1967 829. 3. Xicolaon G. A, J . Chinz. Phys. 1969 66 1783. 4. Aldcroft D. Bye G. C. Robinson J. G. and Sing K. S. W. J . A p p l . Chein. Lond. 1968 18 301. 118 IOK-SELECTIVE ELECTRODES [Pvoc. SOC. A tzalyt. C h e w 5. Carruthers J. D. Payne D. L4. Sing I<. S. W. and Stryker J. L. J . Colloid 1,ztcvjuce Sci. 1971 36 6. Bhambhani 31. R. Cutting P. A. Sing K. S. \f7. and Turk 11. H. Ibid. 1972 38 109. 7. Xicolaon G. A. and Teichncr S. J. J . Cizim. Phys. l9G9 66 1816. 205.

ISSN:0037-9697    

DOI:10.1039/SA9731000108

出版商:RSC    

年代:1973

数据来源: RSC

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118 IOK-SELECTIVE ELECTRODES [Pvoc. SOC. A tzalyt. C h e w Ion-selective Electrodes The following is a summary of one of the papers presented a t aMeeting of the S;1C! Analytical Division held on October 4th 1972 and reported in the October 1972 issue of Proceedings (p. 215). Measurement Techniques for Ion-selective Electrodes BY M. J. D. BRL4ND* (ImFerial Chemical Industries Limited Agvicuitural Division Billingham Z’resside) THE renewed interest in potentiometry as an analytical measurement technique that has been apparent in the last few years is largely due to the development of a range of indicator electrodes showing varying degrees of ion selectivity. The applications of ion- elective electrodes are numerous and have resulted in a critical examination of the methods used in analytical potentiometry.Improvements in measuring techniques have been made with the object of increasing accuracy and precision and to allow a greater degree of automation in the analytical process. The results achieved by analytical potentiometry are dependent on the instrumental system used in the measurement and on the method used to convert electrode potential into a meaningful analytical concentration. It is therefore appropriate to consider separately the systems used to measure electrode potentials and of the methods of data treat- ment needed for interpretation. INSTRUMENTAL SYSTEMS- In addition to an ion-selective indicator electrode and a reference electrode the only additional instrument required is some form of high input impedance voltmeter (electrometer). \Vhile the simpler type of low-cost analogue meter is entirely adequate for routine pH measure- ment its precision is too limited for most work with ion-selective electrodes.Electrode potentials can be measured reproducibly to kO.1 m1- and for this kind of precise work a meter with digital read-out is preferred. In addition it is desirable to plot the meter readings on a chart recorder in order to observe when steady-state electrode potentials have been established. It is apparent that the measured potential of an ion-selective electrode is only as reliable as the stability of the reference electrode potential. In the usual types of reference electrode the most common cause of difficulty is in the maintenance of a good liquid junction. The problem may be even more serious in the case of a so-called “double junction” electrode in which a salt bridge is placed between the sample and reference electrode.Here the compo- sition of the salt bridge is critical and it map not always be possible to use the desirable equi- transferrent electrolyte.1 One approach to eliminating the problems associated with liquid junctions is to use a second ion-selective membrane electrode as a reference.2 Such “differential” cells without liquid junction require that the activity of the reference ion remains constant in all solutions to be analysed. In practice this is often not difficult when solutions can be buffered in pH (or some other ion) or when a large excess of an indifferent electrolyte is added so as to mini- mise variations in the activity coefficient. In potentiometric titrations small variations in the activity of the reference ion can be tolerated during the titration.The use of a glass membrane or other high-impedance electrode as a reference may cause electrical problems when the electrometer input circuit is not adequately isolated from ground. h differential input electrometer3 successfully overcomes the difficulties that arise from ground loops present in single high-impedance input circuits. * Present address Technicon Corporation Tarrytown N e w Yorlr 10591 U.S.A. May 1973! IOK-SELECTI\.'E ELECTRODES 119 Differential input amplifiers are particularly advantageous for measurements made in flowing streams which normally cannot be isolated from ground. JIoreover process streams are notorious for the existence of potential gradients often of hundreds of millivolts and such coninion mode potentials are eliminated by the differential amplifier.The technique has also been of value in the laboratory automation of potentiometric measurements using Techni- con XutoXnalpzer systems. In order to handle the small sample volumes necessary in such systems conventional dip-type electrodes must be modified. Glass membrane electrodes can be constructed from capillary glass while crystal and liquid membrane electrodes of conventional types can be converted to a flow-though configuration by the use of specially designed caps. The use of a laboratory automated system has been found to be particularly advantageous in tlie determination of low levels of dissolved hydrogen sulphide in water samples (M. J. D. Brand and A. I V . Remmer unpublished work).Such samples must be rigorously protected from air so as to avoid oxidation of the sulphide and a fully enclosed .lutoA\nalyzer system provides a convenient means of sample handling. The normal segmentation of the sample stream b!- air bubbles was effected with nitrogen gas;. Addition of an air-free solution of sodium hydroxide converted the hydrogen sulphide into sulphide ion which was measured with a sulphide electrode. DaT.4 TRE.4TMENT METHODS- Thc conversion of electrode potentials into activity (or concentration a t constant ionic strength) is most often effected by means of a calibration grapli prepared from standards and plotted on semi-logarithmic axes. This approach is convenient when samples of concentration varying by orders of magnitude or more are analysed. However the precision with which such a grapli can be read is limited.Equivalent instrumental methods include the use of meters and recorder charts with logarithmic scales. A greater degree of instrumental sophi- stication is introduced by the inclusion of an electronic antilogarithmic circuit between the electrometer and read-out device. IYhile direct potentiometry offers experimental simplicity it has been recognised that greater precision can be achieved by standard addition methods with little increase in coin- plerity. Some improvement is obtained by making a single addition but in general methods based on multiple additions are preferred. Such methods can be divided into two basic types depending on whether or not tlie electrode calibration slope is assumed to be known. Methods of the first type are based on tlie procedure described by Gran4 in which a function derived by taking antilogarithms of the Nernst equation is linearly dependent on the known concentra- timi of tlie ion added.The necessary calculations have been minimised by the introduction of antilogarithmic graph paper.j Perhaps the most serious drawback of Gran's method is that it assumes that the slope of the electrode calibration graph is known. Either this is assumed to be Nernstian which may be far from true for some electrodes or it is determined by a prior calibration. This latter procedure is not required from the point of view of mathematical analysis of the data. Two additions provide enough data to determine the unknown concentration as well as the electrode formal potential and calibration slope; for more than two additions the system is mathe- matically overdefined.Unfortunately no simple solution exists to tlie set of simultaneous equations that describe a standard addition experiment. The problem can be sol\Ted rapidly on a computer by using iterative methods and a simple program ADDFIT has been described for this purpose.6 Standard addition methods are related experimentally and mathematically to potentio- nictric titrations. Titrations involving the use of ion-selective electrodes are now numerous' and serve to achieve high precision and to determine species for which no selective indicator electrodes exist. The precision of the method is determined by how well it is possible to locate the equivalence point on the titration curve.* This point may or may not correspond to the point of inflection.The well known finite difference methods of plotting 6E/SV or 82E,,SV as a function of I/ are unlikely to determine the inflection point with high precision altliougli better results are obtained with the reciprocal function 61','8E. Gran's method can be applied to locate the equivalence point although this pre-supposes that the membrane electrode is an ideal indicator electrode which many are not. -1 compromise solution to this problem is to locate the inflection point of the titration graph as accurately as possible and 120 PAPERS ACCEPTED FOR THE AYXLYST [Pvoc. SOC. Aizalyf. Chewa. then to relate this to the equivalence point either theoretically or experimentally by using standards. One approach that suggests itself as a means of locating the inflection point of the titration graph accurately is to use curve-fitting methods to generate an equation for the graph.This can then be differentiated twice and the resulting equation solved in order to locate the end- point. In an attempt to eliminate equations based on the system chemistry a polynomial regression method has been applied in this way. A cubic equation fits the experimental data near to the end point reasonably well and locates the inflection point a t least as well as the better established methods. It is apparent however that further work is necessary in order to establish the optimum form of equation for the numerical analysis of the data. REFERESCES 1. Orion Research Iizc. h'ewd. 1 No. 4 1969. 2. Manahan S. E. Analyt. Chem. 1970 42 128. 3. Brand 31. J . D. and Rechnitz G. A I b i d . 1970 42 616. 4. Gran G. Analyst 1952 77 661. 6 . Orion Research I n c . YewsZ. 2 Xos. 11 and 12 1970. 6. Brand bl. J. D. and Rechnitz F. A Aizalyt. Cheitz. 1070 42 1172 7 . Buck R. P. I b i d . 1972 44 270R. 8. Anfalt T. and Jagner D. Arzalytica Chint. Acta 1971 57 165.

ISSN:0037-9697    

DOI:10.1039/SA9731000118

出版商:RSC    

年代:1973

数据来源: RSC

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120 PAPERS ACCEPTED FOR THE AYXLYST [Pvoc. SOC. dizalyf. Chewa. Papers Accepted for Publication in The Analyst THE following papers have been accepted for publication in The A~znlyst and are expected to appear in the near future. “The Determination of Tin and -Antimony in Lead ,Illoy for Cable Sheathing by -Atomic- absorption Spectroscopy,” by Teresa 31. Quarrell R. J. LV. Powell and H. J. Cluley. “Replacement of Platinum Vessels with a Pressure Device for Acid Dissolution in the Rapid Analysis of Glass by Atomic-absorption Spectroscopy,” by Y. Hendel. “An Improved Plasma Jet System for Spectrochemical Analysis,” by J. F. Chapman L. S. Dale and R. N. Whittem. “An Ultramicro-scale Method for the Determination of the Uranyl Cation,” by Glenn Peter U‘ood. “Interference of Carbon Dioxide Resulting from the Schijniger Flask Conibustion of Organofluorine Compounds in the Titrimetric Determination of Fluorine,” by William F.Heyes. “The Histochemical Detection of Soya ‘Novel Proteins’ in Comminuted Xeat Products,” by 11. Coomaraswamy and F. Olga Flint. “Thermometric Assay of Some Sulphonamides of Pharmaceutical Importance,” by L. S. Bark and J. K. Grime. “The Determination of Di-n-alkyl Phthalates in Cosmetic Preparations by Gas - Liquid Chromatography,” by E. 147. Godly and A. E. AIortlock. “The Determination of Lead in Foods by Atomic-absorption Spectrophotometry,” by R. K. Roschnik. “A Critical Study of Safranine 0 as a Spectrophotometric Reagent Rapid Method for the Determination of Trace .4mounts of Antimony in Steel,” by C. Burgess A. G. Fogg and D. Thorburn Burns.“Ion Polymerisation as a Means of End-point Indication in Son-aqueous Thermometric Titrimetry. The Determination of Catecholamines,” by E. J. Greenhow and L. E. Spencer. “The Determination of Microgram Amounts of Sulphate by Emission Spectroscopy of Barium with a Nitrous Oxide - Acetylene Flame,” by E. A. Forbes. Part IT’. May 19731 PAPERS ACCEPTED FOR THE ANALYST 121 “A Modified Field Test for the Determination of Carbon Disulphide Vapour in Air,” by “An Emanation Method for Determining Radium Using Liquid Scintillation Count- “Residues of Prophylactics in Animal Products. Part 111. The Determination of “A hlultichannel Dispenser - Titrator - pH Stat,” by D. G. Mitchell and K. 11. Aldous. “Spectrophotometric and Chelatometric Determination of Iron(II1) with 3-Hydroxypyri- dine-%thiol,” by Mohan Katyal Miss Veena Kushwaha and R.P. Singh. “The Use of a Laser for Cutting Bone Samples Prior to Chemical Analysis,” by J. Hislop and A. Parker. “Potentiostatic Coulometric Determination of Vanadium Vanadium - Manganese and 1-anadium - Iron Mixtures and the Influence of Chromium on the Process,” by E. Bishop and P. H. Hitchcock. Part V. Comparison of Pattern Theory Tafel Allen and Hickling and Lewartowicz Methods and Apparatus and Procedures for Ramping T’oltammetry,” by E. Bishop and P. H. Hitchcock. The Pre-treatment of Solid Electrodes and a Review of the Effects of Oxidation of Platinum,” by E. Bishop and P. H. Hitchcock. Part VII. Conditional Potentials and Single-scan Voltammetry of Pure I‘anadium(1’) - Yanadium(1V) Systems in Various JIedia at Platinum Electrodes Pre-treated by Five Nethods,” by E.Bishop and P. H. Hitchcock. Part VIII. Single Scan Voltammetry of Vanadium(T’) - Vanadium(1V) in the Presencc of Chromium. Manganese and Iron. and the Kinetic Parameters of the T’anadium E. C. Hunt ITr A. McNally and A. F. Smith. ing,” by K. G. Darrall P. J. Richardson and J. F. C. Tyler. Carbarsone in Poultry Meat,” by R. A. Hoodless and K. R. Tarrant. “blass and Charge Transfer Kinetics and Coulometric Current Efficiencies. “Mass and Charge Transfer Kinetics and Coulometric Current Efficiencies. Part VI. “Mass and Charge Transfer Kinetics and Coulometric Current Efficiencies. “Xass and Charge Transfer Kinetics and Coulometric Current Efficiencies. System a t Platikm Electrodes Pre-treated by Five RIetliods,” by E. Bishop and P. H. Hitchcock. “llass and Charge Transfer Kinetics and Coulometric Current Efficiencies. Part IX. An Examination of the Titanium(1V) - Titanium(II1) System and the Effects of Ultratrace Impurities in Sulphuric Acid,” by E. Bishop and P. H. Hitchcock. “Jlass and Charge Transfer Kinetics and Coulometric Current Efficiencies. Part X. An Examination of the Tin(1V) - Tin(I1) - Tin(0) Systems a t Platinum and Gold Elec- trodes,” by E. Bishop and P. H. Hitchcock. “Determination of the Antioxidant 1,3,5-Trimethql-2,4,6-tri-(3’,5’-di-t-butyl-~’-hydroxy- benzy1)benzene in Feeds,” by G. F. Bories. “Quantitative Determination of the Enantiomeric Purity of Chrysanthemic A4cid in Synthetic Pyrethroids,” by F. E. Rickett. “The Determination of Trace Amounts of Barium in Calcium Carbonate by Atomic- absorption Spectrophotometry,” by F. J. Bano.

ISSN:0037-9697    

DOI:10.1039/SA9731000120

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

122 NOTICES [Proc. SOC. 41znlyt. Chena. Notices INTERNATIONAL SYPIIPOSIUM ON LIQUID SCINTILLATION COUNTING DELEGATES wishing to attend the Symposium on Liquid Scintillation Counting to be held a t the Hotel Metropole Brighton are reminded that if they wish to register at the reduced fee of Sll their fees must reach bIiss P. E. Hutchinson at the Society for A4nalytical Chemistry 9/10 Savile Row London WlX IAF by June 30th 1973. Any registrations after this date will be charged a t &l660. Information on booking for the Hotel JIetropole and for cheaper hotels in the Brigliton and Hove area is also available from Miss Hutchinson. There is a wide range of hotels avail- able at various prices in the area that can be booked through the accommodation service provided for the Symposium. However 111 \7iew of the high demand for accommodation in Brighton during September delegates are advised to book as soon as possible.SEPTEMBER 3RD TO 6TH 1973 BRIGHTON INTERNATIONA4L SYMPOSIUlI O S MICROCHEYIICXL TECHNIQUES ACGUST 19TH TO 24TH 1973 PENKSYLVANI.4 THIS Symposium will be held at University Park Pennsylvania U.S.X. and as in previous ones in 1961 and 1965 it is again being conducted by The Pennsylvania State University through its College of Science. I t is also being organised by the American Nicrochemical Society with the sponsorship of the IUPAC Commission on Xcrochemical Techniques Division of Analytical Chemistry. The Symposium will provide for an interchange of information and ideas among tech- nologists concerning new methods and techniques or unique applications in the field of microchemistry .Technical sessions dedicated to topics of current interest original papers an exhibition of commercial equipment buffet dinner picnic supper banquet and ladies’ programme will be included in the schedule of activities. Over seventy papers will be presented a t sessions including -1utoinated Elemental Analysers-Ten Years Later; Computers in Elemental hnalysis ; Organic Elemental Analysis New Methods and Equipment ; Environmental llicroanall-sis Yew Sensors and Techniques ; AIicroelectrodes; Forensic Analysis Xarcotics and Drugs of -Abuse ; Organic Functional Group Analysis New Directions ; Electroanalytical Advances Including Ion-selectii-e Electrodes ; Nicroscale Separations Advances in Techniques and Methods ; Standards and Standardisa- tion for Microchemistry and hIicroanaljGs ; Trace Analysis Advances in Organic and Inorganic Analysis ; and New Techniques in llicrochemistry.Further details of the technical programme can be obtained from IIr. Howard J. Francis Jr. Pennwalt Corporation 900 First Avenue Icing of Prussia Pennsylvania 19406 U.S.X. and also on this and other aspects of the Symposium from Nrs. D. Butterworth Division of Chemical Standards Kational Physical Laboratory Teddington Middlesex. INTERNATIONAL LISS SPECTROMETRY COSFEKENCE SEPTEMBER 1OTH TO 1 4 ~ ~ 1973 EDINBURGH THE sixth in the series of triennial international mass spectrometry conferences is being held a t Edinburgh University this year. The conference is sponsored by TUPAC and the mass spectrometry organisations of many countries France (GL411S) Germany (DPG-MS) Japan (NSSJ) Great Britain (IP) U.S.X.(ASJIS’ASTJI) L.S.S.R. Italy Belgium Czechoslovakia The Netherlands Sweden and Yugoslavia. The scientific programme will cover niost aspects of mass spectrometry and each topic will be introduced by a review paper given by a leading \wrld authority in tliat field. There will also be a Conference Dinner and a social programme. I’or further information write to JIr. C. H. Maynard .1ssistant General Secretary (.4dmin- istration) The Institute of Petroleum 61 New C,avendisli Street London W1 hI 8XR. w w Nay 1973 SOTICES 123 ALGER ELECTROK SPECTROSCOPY-lIAATERIALS XPPLIC-%TIOXS r\ND QUASTIFICBTIOS OCTOBER 2 4 ~ ~ ASD ~ S T H 1973 TEDDISGTOS A TWO-DAY Conference on “Auger electron spectroscopy-materials applications and quantifi- cation,” organised by the N.P.L.in conjunction with the Thin Films and Surfaces Group and the Naterials and Testing Group of The Institute of Physics is to be held a t the N.P.L. a t Teddington Middlesex on October 24th and 2.311 1973. Themes that will be covered are applications of *\uger electron spectroscopy and related techniques to metals ceramics and glasses in relation to the materials problems of thin films coatings corrosion layers grain boundaries adhesion interface stability etc. The conference will also cover the quantifica- tion of Auger electron spectroscopy dealing with experimental and theoretical aspects of precise systems or general parameters (electron ranges ion sputtering yields etc.) relating to electron spectroscopy for surface studies (i,e. including ESCA APS etc.) Offers of contribu- tions together with a 200-word abstract should be sent to Dr.11. P. Seah Division of Inorganic and Metallic Structure Xational Physical Laboratory Teddington Middlesex TlVl1 OLlT before July 24th 1973. Further details and application forms will be available in June from the Meetings Officer The Institute of Physics 1 7 Belgra1.e Square London ElITlS S Q S . ROYAL hl1CROSCOPICAL SOCIETY JCLV TO DECEMBER 1973 THE Royal RIicroscopical Society’s programme for the second half of 1873 includes the following- Symposium on X-ray Rlicroanalysis of Biological Yaterial in the Electron Microscope. July 6th. llicro 74. July 8th to 12th. London. Course on Modern Xcroscopy. July lGth to 20th. Brunel University. Course on Photomicrography. Juiy 23rd to 27th. Brunel University. Third International Conference on High 1-oltage Electron hlicroscopy. August 27th to Symposium on lIetallographica1 Ilicroanalysis. September 17th to 19th. University of Further information can be obtained from The Aidministrator Royal JIicroscopical Vniversity of Kent at Canterbury. 30th. St. Catherine’s College Oxford. 1-reds. Society Clarendon House Cornmarket Street Oxford OX1 3HA.

ISSN:0037-9697    

DOI:10.1039/SA9731000122

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

SOTICES 123 Correspondence on Amalgamation -AT the beginning of this year Pvoceediizgs inaugurated a correspondence column “to enable nienibers to air their views on the specific subject of ‘=\malgamation’.” So far only one letter has been received and published (February issue). The final decision for or against permanent Amalgamation must be reached in the early autumn of 1974 to be effective from January lst 1975; not much more than 12 months remains f u r any further public expression of members’ views. Members are reminded that tlir correspondence column remains available for this purpose.

ISSN:0037-9697    

DOI:10.1039/SA9731000123

出版商:RSC    

年代:1973

数据来源: RSC