摘要:

Proceedings of the Society for Analytical Chemistry Analytical Division Chemical Society CONTENTS Reports of Meetings . . . . 263 North West Region . . . . 265 Summaries of Papers "Research Topics in "On-line Methods of Analytical Chemistry". . . . 267 Particle Size Analysis" . . 282 SAC Analytical Chemistry Trust Fund . . . . . 286 Notices . . . . . . . . 286 Forthcoming Meetings Back Cover Proc. SOC. Analyt. Chem. Vol. 10 No. 11 Pages 263-286 November 1973 PAYCAL Vol. 10 No. 11 November 1973 PROCEEDINGS THE SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY OF Hon. Secretary W. H. C. Shaw Officers of The Society for Analytical Chemistry and the Analytical Division of The Chemical Society President G . W. C. Milner Hon. Treasurer Hon. Assistant Secretaries J.K. Foreman D. I. Coomber O.B.E. D. W. Wilson Secretary Miss P. E. Hutchinson 9/10 SAVILE ROW LONDON WIX I A F Telephone 01 -734 9864 Managing Editor SAC Publications F. D. Grimmer Assistant Editor P. C. Weston Proceedings is published by The Society for Analytical Chemistry. Members' subscriptions must be sent to The Chemical Society Non-members can be supplied with Proceedings only as part of a combined subscription with The Analyst and Analytical Abstracts Single copies can be obtained direct from The Chemical Society Publications Sales Office Blackhorse Road Letchworth Herts. SG6 1HN (NOT through Trade Agents) price 30p post free. Remittances MUST accompany orders @ The Society for Analytical Chemistry SELECTED ANNUAL REVIEWS of the ANALYTICAL SCIENCES Volume 2 - 1972 CONTENTS The Techniques and Theory of Thermal Analysis Applied to Studies on Inorganic Materials with Particular Reference to Dehydration and Single Oxide Systems - D. Dollimore Developments in Ion Exchange - F. Vernon Thermometric and Enthalpimetric Titrimetry - L. S. Bark P. Bate and J. K. Grime Obtainable from- Pp. vi + 149 f 5.00 ; U.S. $1 3.00 ISBN 0 85990 202 1 The Society for Analytical Chemistry Book Department 9/10 Savile Row London WIX 1AF Members of The Chemical Society may buy personal copies at the special price of f3.00; US. $8.00

ISSN:0037-9697    

DOI:10.1039/SA97310FX038

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

286 NOTICES [Proc. SOC. Analyt. Chem. Forthcoming Meetings-continued front inside back covey Decem ber-continued Thursday 6th JOINT PHARMACEUTICAL A~YALYSIS GROUP. LOKDON Discussion on “Quantitative Thin Layer Chromatography-Scope and Limitations.” Speakers Professor E. J . Shellard and P. Smith. Pharmaceutical Society of Great Britain 17 Bloomsbury Square London W.C. 1 ; 2.30 p..m Friday 7th CARDIFF WESTERN REGION jointly with the South East IVales Section of the CS. “Recent Advances in Molecular Spectroscopy,” by H. A. Willis. University Staff Dining Club Park Place Cardiff; 6.30 p.m. KORTH WEST REGIOS Semi-social Evening.. “Rum,” by J. C. Clark. Edge Hill Training College Ormskirk; 7.30 p.m. Tuesday 18th ORIVISKIRK SOCIETY FOR AKALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY Forthcoming Meetings-continued fvovn back covey December Tuesday 4th XIDLANDS REGIOX jointly with the International Institute for the Conservation of Historic and Artistic Works (LK Group) on “Analytical Techniques for the Museum and Art Gallery.” Introduction by A.E. Werner. “Analytical Techniques with Possible hpplication to the Examination of Museum BIRMIXGHAM Wednesday 5th LONDON Wednesday 5th LOSDOX Thursday 6th YORK Thursday 6th LOXDOS Objects. Session 1 Mossbauer Spectroscopy,” by B. W. Fitzsimmons. “Analytical Techniques. Session 2 Immunological Methods,” by J. K. Miller. “Analytical Techniques. Session 3 Photoelectron Spectroscopy,” by ill. “The Use of Gas Chroniatography and Infrared Absorption Techniques in the “Son-dispersive X-ray Analysis of Ancient Bronze and Faiences ” by H.“Xcrochemical Analytical Techniques Used for the Examination of Objects in “Some Practical Analytical Problems and Their Solutions,” by J . Hedley and City Museum and Art Gallery Birmingham; 10 a.m. Abstracts of papers to be presented and further information with regard to this meeting can be obtained from bIr. S. Rees-Jones City Museum and Art Gallery Birmingham B3 3DH. Thompson. Examination of Paint Media,” by J . hlills. McKerrell. the British PIIuseum,” by M. J. Hughes. A . Cumming. SAC/AD (organised by the AUTOMATIC METHODS GROUP) on “Limitations in “Sample Preparation and Quality Control in Automatic Systems,” by H. J. PI. “Translation of A4utoxnatic Laboratory Methods into Plant Control Systems,” “Problems in Routine Laboratory Automation,” by F. Harper.Scientific Societies Lecture Theatre 23 Savile Rox London ST’. 1 ; 3 p.m. MICROCHEMICAL METHODS GROUP London Discussion Meeting. Discussion on “The Microdetermination of Chlorine Bromine and Iodine in “The Phoenix,” 14 Palace Street London S.W 1 ; 6.30 p.m. XORTH EAST REGION on “Trace Element Analysis in Industry.” “Some Techniques for Trace Element Analysis,” by R. I<. TVebster. “Trace Element Analysis of Inorganic Materials,” by H. J . Cluley. “The Determination of Some Minor Constituents Within the Steel Industry,” “Trace Metal Control in a Chocolate Factory,” by J . W. Colquhoun. Lecture Theatre A101 The University Heslington York; 2 p.m. ELECTROAXALYTICAL GROUP Annual General Meeting; 2.15 p.m. ATo3fIc SPECTROSCOPY GROUP Annual General Neeting ; 2.30 p.m. The AGNs will be followed by a Joint Meeting of the Groups on “Toxic Material “Electrochemical Analysis of the Aquatic Environment,” by \V.J . Stiff. “A Gradient Titration Monitor for Heavy Materials,” by S. K. Das Gupta. “The Use of Atomic Absorption for Determining Toxic Water and Pollution in “Determination of Toxic Metals in XVaters and Waste Waters by Atomic Absorp- Chemistry Department Imperial College South Kensington London S.W. 7 ; Automatic Methods.” Bow en. by B. J . Hulley. Organic Compounds,” to be introduced by S. Bance. by A. D. Ambrose. in Water.’’ Water,” by G. Kickless. tion,” by G. F. Lowden. 2.45 v.m. SOCIETY FOR ANALYTICzlL CHEMISTRY AKALYTICAL DIVISION CHEMICAL SOCIETY Forthcoming Meetings November Wednesday 21st PARTICLE SIZE ANALYSIS GROUP Annual General Meeting followed by an “Study of Emulsion Formation by Light Scattering Methods,” by M.J . Grox-es. “Particle Size Analysis of Particulate Emissions in situ,” by L. Svarovsky. “Automatic Microscope and Field Scanning -\nalysis,” by R. J . -4kers. Pharmacy Department Chelsea College University of London nlanresa Road LOXDON Ordinary Meeting on ‘Tewer Methods of Particle Characterisation.” London S.W.3; 2.30 p.m. Thursday 22nd THERMAL METHODS GROUP Annual General Meeting followed by the lietiring LONDON Chairman’s Address and a meeting on “Temperature Programmed “Kinetic A4nalysis of Thermogravimetric Curves,” by J . H. Sharp (retiring Chair- “Design Considerations in Advanced Systems for DSC,” by 11. Cottrell. “Purity hleasurement by the Nelting Range Xethod-an Easily Computerised “Vapour Pressure Determinations by Temperature Programmed Calorimetry,’’ “Applications of DSC in Physical Chemistry,” by P.J . Haines. “Differential Scanning Calorimetry of Elemental Sulphur,” by B. li. Currell and “The Application of Scanning Calorimetry to the Study of Secondary Explosives,” Royal Astronomical Society Burlington House London W. 1 ; 10.30 a.m. Calorimetry.” man). Method of Computation,” by R. 1. \Y. Hill and B. G. C,ooksey. by H. G. n’iedemann. A. J. Williams. by P. G. Laye. Thursday 29th BIOLOGICAL NETHODS GROUP. Annual General Meeting follow cd by an Ordinary “The Quantification of Potentially Subjectir e Data,” by D H Barry The Kings Arms 77 Buckingham Palace Road London S.11- 1 6.30 p.m. LOKDOK Meeting Friday 30th LONDON MICROCHEMICAL METHODS GROUP Annual General Meeting; 6.30 p.m. EDUCATIOK -4ND TRAININGROUP Annual General Meeting; 6.45 p.m. Room 522 Department of RIetallurgy Royal School of Nines Prince Consort The XGXs will be followed by a Joint Cheese and \Vine Party Common Room Road London S.15’ 7 . Level 7 Department of Metallurgy; 7 p.m. [confi?zzied iizside bnck couey Printed by Heffers Printers Ltd Cambridge England

ISSN:0037-9697    

DOI:10.1039/SA97310BX040

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

November 1973 Vol. 10 No. 11 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY ANALYTICAL DIVISION CHEMICAL SOCIETY Reports of Meetings JOINT MEETING A JOINT Meeting of the SAC/AD (organised by the Chromatography and Electrophoresis Group) with the Chromatography Discussion Group was held at 10.30 a.m. on Wednesday November 7th 1973 at the Scientific Societies Lecture Theatre 23 Savile Row London W.l. The subject of the meeting was “Gas Chromatography.” At the morning session the Chair was taken by Mr. C. E. Waterhouse Vice-president of the SAC/AD and the following papers were presented and discussed “The Role of the Stationary Phase,” by D. F. G. Pusey; “A Study of Antioxidant Behaviour by Gas Chro- matography,” by M. B. Evans. At the afternoon session the Chair was taken by Dr. G. A.P. Tuey Chairman of the Chromatography Discussion Group and the following papers were presented and discussed “The Choice of the Stationary Phase for the Analysis of Basic Drugs,” by A. C. Moffat A. H. Stead and K. W. Smalldon; “Supercritical Fluid Chromatography,” by T. Doran; “Applications of Gas Chromatography to the Analysis of Some Common Waxes and to Wax Mixtures,” by C. A. Blau. CS AUTUJIN MEETIYG THE SAC/AD participated in the CS Autumn Meeting on Thursday September 27th 1973 a t the University of East Anglia Norwich. The Chair was taken by hlr. J. K. Foreman Honorary Treasurer. The subject of the Symposium was “Characterisation of Xaterials” and the following papers were presented and discussed “Characterisation of Inorganic Rlaterials,” by I. R. Green ; “Characterisation of Ceramic Materials,” by P.T. A. Hodson; “The Characterisation of Recovered Hydrocarbons from Arson Debris,” by R. Watt and D. IVillson; “The Use of I W R in the Characterisation of Materials,” by I. K. O’Seill ; “The Electrophoretic Charac- terisation of Proteins in Foodstuffs,” by I. hl. Mackie; “The Characterisation of Proteins in Blood,” by B. H. Parkin; “Characterisation of Fats,” by C. J. Tryner. NORTH WEST REGION A JOINT Meeting of the Region with the North Lancashire Section of the CS was held a t 7.30 p.m. on R’ednesday October 24th 1973 at the Harris College Preston. The Chair was taken by the Chairman of the North West Region Mr. A. C. Bushnell. A lecture on “Recent Advances in Forensic Analysis” was given by F. L. Cann. NORTH WEST REGION ATOMIC SPECTROSCOPY AUTOMATIC METHODS EDUCATION AND TRAINING ELECTROXNALYTICAL MICROCHEMICAL NETHODS AKD RADIOCHEMICAL METHODS GROUPS A JOIST Meeting of the above Region and Groups was held on Thursday and Friday September 20th and 21st 1973 a t the University Salford.The subject of the meeting was “Different Approaches to Trace Analysis.” The title of the first session was “Spectroscopic Techniques for Trace Analysis.” The Chair was taken by the Vice-chairman of the Atomic Spectroscopy Group Dr. R. Smith and the following papers were presented and discussed “Spectroscopic Techniques Principles Scope and Limitations,” by J. H. S. Green; “Analysis of Thin Films and Epitaxial Layers by Spark Source Mass Spectrometry,” by J. B. Clegg and E. J. Xillett; “X-ray Spectrometry in the Analysis of Light Matrices,” by J.D. ITTilson; “The Determination of Some Trace Elements in Silicate Rock by Flame ,4tomic Absorption Spectrophotometry,” by J. Warren; 263 264 REPORTS OF NEETISGS [Proc. SOC. Analyt. Chem. “Luminescence in Inorganic Analysis,” by L. S. Bark; “Use of the Shpol’skii Effect for Analysis of Traces of Polynuclear Hydrocarbons,” by C. G. de Lima and G. F. Kirkbright. The title of the second session was “ Radiochemical Techniques for Trace ,4nalysis.” The Chair was taken by the Chairman of the Radiochemical Methods Group Nr. J. W. RlcAlillan and the following papers were presented and discussed “The Use of Radiochemical Techniques,” by H. J. M. Bowen; “The Determination of the Light Elements C N 0 and F Using High Energy Gamma Photon Activation and Radiochemical Separation,” by J.S. Hislop ; “Autoradiography,” by R. J. McCulloch. The Chair was taken by the Vice-chairman of the North West Region Dr. L. S. Bark and the following papers were presented and discussed “The Use of Probe Techniques,” by T. B. Pierce; “Secondary Ion Microanalysis,” by D. M. Poole; “The Electron Probe Analyser,” by F. T. Ewart. The title of the fourth session was “Pre-concentration and Separation Techniques in Trace Analysis.” The Chair was taken by the Vice-chairman of the Education and Training Group Dr. J. B. Headridge and the following papers were presented and discussed “The Use of Pre-concentration and Separation Techniques,” by R. A. Chalmers ; “The Adsorption of Methyl-substituted 8-Quinolinethiol Chelates,” by G. C. Dickson; “The Use of Pulse Electrodeposition as a Concentration Technique for Atomic Absorption Spectroscopy,” by K.W. Metcalf. The title of the fifth session was “Catalytic and Kinetic Techniques in Trace Analysis.” The Chair was taken by the Chairman of the Automatic Methods Group Dr. J. 11. Skinner and the following papers were presented and discussed “The Use of Catalytic and Kinetic Techniques,” by J. 11. Ottaway; “Automated Enzyme Analysis,” by D. B. Roodyn; “Applica- tions of Enzyme-catalysed Reactions in Trace Analysis,” by A. Townshend. The title of the sixth session was “Electroanalytical Techniques for Trace Analysis.” The Chair was taken by the Chairman of the Electroanalytical Group Dr. B. Fleet and the following papers were presented and discussed “A Comparative Evaluation of Polarographic Techniques for Trace Analysis,” by R.D. Jee; “Electrochemical Detectors for High Pressure Liquid Chromatography,” by C. J. Little and B. Fleet; “Developments in Stripping Voltam- metry,” by I. Fraser. WESTERN REGIOY A JOINT Meeting of the Region with the South East Wales Section of the CS and the UWIST Students Chemical Society was held a t 5.30 p.m. on Thursday October l l t h 1973 a t the University of \Vales Institute of Science and Technology Cardiff. The Chair was taken by the Chairman of the Western Region Dr. J. D. R. Thomas. A lecture on “Catalytic Methods of Trace Analysis” was given by J. 51. Ottaway. The title of the third session was “Probe Techniques in Trace Analysis.” MIDLANDS REGION A JOIXT Meeting of the Region with the UV Group was held a t 2 p.m. on Wednesday October 17th 1973 in the Lecture Theatre The Boots Co.Ltd. Pennyfoot Street Yottingham. The Chair was taken by the Chairman of the UV Group Dr. A. IV. S. Tarrant. The subject of the meeting was “UV and Visible Spectrophotometry of Difficult Samples” and the following papers were presented and discussed “Solid Scattering Samples,” by A. J. Everett ; “UV Spectra of Scattering Low Temperature Matrices,” by 31. Poliakoff ; “Microcell Techniques and Related Problems,” by K. W. Smalldon ; “Fugitive/Photoreactive Samples,” by A. L. Glenn; “Extent of Reaction and Automation,” by J. W. Murfin; “Adsorption on to Cell LValls,” by D. Thorburn Burns. NORTH EAST REGION A SOCIAL Xeeting of the Region was held a t 7 p.m. on Tuesday October 9th 1973 a t the Scotch Corner Hotel near Richmond Yorkshire. The Chair was taken by the Chairman of the Region Mr.J. Whitehead. An informal dinner was followed by a lecture on “Leisure Laughter and Lunatics,” given by G. G. Watson. November 19731 THE NORTH WEST REGION 265 BIOLOGICAL METHODS GROUP 4 DISCVSSION Meeting of the Group was held at 2.30 p.m. on Thursday October l l t h 1973 a t the Pharmaceutical Society 17 Bloomsbury Square London IV.C.l. The Chair was taken by Mr. W. H. Stephenson. A discussion on “Microbial Attributes of Non-sterile Pharmaceuticals and Cosmetics,” was introduced by H. S. Bean D. F. Spooner and N. J Van Abbe. ATOMIC SPECTROSCOPY GROUP A JOINT Meeting of the Group with the Sheffield Metallurgical Society was held a t 7 p.m. on Tuesday October 9th 1973 a t BISRA Hoyle Street Sheffield. The Chair was taken by the Chairman of the Atomic Spectroscopy Group Dr.G. F. Kirkbright. The subject of the meeting was “State of the Art-X-ray Fluorescence and Emission Spectroscopy for Copper and Steel,” and the speakers were H. Hughes and J. K. T’yse. ELECTROXNALYTICAL GROUP A JOIKT lleeting of the Group with the Society of Chemical Industry was held a t 11 a.m. on Monday October 22nd 1973 a t the Society of Chemical Industry 14 Belgrave Square London S.IV.1. The Chair was taken by the Chairman of the Solvent Extraction Group of the Society of Chemical Industry Dr. A. RlcKay and by the Honorary Secretary of the Electroanalytical Group Dr. W. F. Smyth. The subject of the meeting was “Liquid - Liquid Extraction and Ion-exchange in Analytical Chemistry” and the following papers were presented and discussed “Current Uses of Liquid - Liquid Extraction in Analytical Chemistry,” by Professor H. 11. N. H. Irving; “blethods for Identification of Organic Phase Species,” by A. G. Maddock; “Influence of Interfering Ions on the Performance of Liquid Ion-exchange Membrane Electrodes,” by B. Fleet ; “Trapped Liquid Membranes-Nainly in PVC-for Ion Selective Electrodes,” by J. D. R. Thomas. JOINT PHARMACEUTICAL ANALYSIS GROUP THE Group participated in the British Pharmaceutical Conference 1973 on Thursday Septem- ber 13th 1973 a t the School of Pharmacy Brunswick Square London W.C.l. The Chair was taken by the Chairman of the Group Dr. B. A. IYills. The subject of the meeting was “Challenge of Formulation to the Pharmaceutical Analyst,” and the speakers were A. Holbrook K. A. Lees and E. B. Reynolds.

ISSN:0037-9697    

DOI:10.1039/SA9731000263

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

November 19731 THE NORTH WEST REGION 265 The North West Region THE North of England Section now the North West Region is proud to be the oldest Section of the SAC. Other Regions and Groups owe their existence to the successful launching of this Section and this was due largely to the untiring and successful work of G. D. Elsdon ably assisted by S. E. hlelling. Backed in their efforts by North of England Public Analysts and by a number of industrial analysts in the area they persuaded the Council of the SAC to call an extraordinary meeting in Manchester on November 7th 1924 and on that date the North of England Section was born. G. D. Elsdon was appointed acting Honorary Secretary until the rules governing the Section were finally agreed with Council. The objectives of the Section were to raise the status of the SAC to increase its influence and to afford opportunities for members to meet for the discussion of subjects of scientific and professional interest and for the reading of papers on analytical chemistry.The written records and the homely atmosphere which obtains within the Region provide ample evidence that these objectives have been successfully accomplished. Membership was open to all who lived north of Birmingham but this was later modified to cover the area north of tlie line connecting Bangor Stoke-on-Trent Derby and The IVash. From its inception in 1924 until the end of 1946 the Section was (except for an initial grant-in-aid of L l O from Council) entirely self-supporting from an Annual Membership Subscription of 2s 6d (12:~). No subscription was required from members in 1946 when the Section subsisted on the balance of k67 carried forward from 1945.Originally members could 266 THE XORTH WEST REGION [Proc. SOC. Analyt. Chem. enter the SAC by election to the North of England Section and as members of that Section they were exempted from any contribution to the SAC. This concession was withdrawn by Council in 1945 a t the request of the Section’s Committee and after 1946 Council made a grant-in-aid to Sections and Groups and has continued to do so from that date. The Chairman Mr. A . C. Bicshnell wearing the North West Region jewel of ofice. Much of the success of the Section and Region lias been due to the character of its Chair- men and to the quality of its Honorary Secretaries. Since 1924 only nine Secretaries have served the terms of office.The most outstanding were Arnold Lees who served for 15 years and J. B. Stubbs who served for 11 years and only three members have served both as Honorary Secretary and Chairman (G. D. Elsdon J. B. Stubbs and G. F. Longman). In 1932 Council elected the Chairman of the Section as an EX oficio Vice-president of the Parent Society and the Honorary Secretary as an EX-oficio member of Council but the Section records give no indication of the date when these privileges were withdrawn. Nonetheless this is no doubt the precedent for the present practice of electing Regional Chairmen as ex-oficio members of Council. It is of interest to mention that the Section has been honoured on four occasions when past-Chairmen were elected President of the SAC. These were J.T. Dunn (1930) J. Evans (1934) W. H. Roberts (1938) and S. E. JIelling (1944). Mr. J W . Ogleby MV. J . Cottam Dr. L. S . Bark (Honorary Treasurer) (Honorary Secretary) ( Vice-Chairman) From its inception the Section showed a keen interest in the policies and objectives of the Parent Society and has submitted a number of important resolutions for consideration by Council. The most important led to the legal acceptance in this country of the Hortvet technique for the recognition of milk adulteration. These are pri- marily long week-end social meetings a t which members and their wives can meet in a relaxed atmosphere. A special feature of meetings has been its successful Summer Meetings. The present officers are- Chairman . . .. .. . . Mr. A. C. Bushnell Vice-chairman . . .. . . Dr. L. S. Bark Honorary Secretary .. . . Mr. J. Cottam Honorary Treasurer .. . . 3lr. J. W. Ogleby On Kovember 7th 1974 the Region completes the 50th year of its existence and an Anniversary Dinner is being arranged to celebrate the occasion.

ISSN:0037-9697    

DOI:10.1039/SA9731000265

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

November 19i3; RESEARCH TOPICS IN AKALYTICAL CHEMISTRY 267 Research Topics in Analytical Chemistry The following are summaries of ten of the papers presented at a meeting of the SXC/;2D held on July 12th and 13th’ 1973 and reported in the August issue of Proceediizgs (p. 189). The Determination of Nanogram Amounts of Indium Lead and Drugs of Forensic Importance by Enzymic Inhibition BY R. A. SHEIKH (Chrwzistuy Defiavtmmt Bivmi~zghawt U,iiversity P.O. Box 363 BZrnzii4gham Bl5 2TT) ESZVJIES are biological catalysts that control the rate of chemical reactions. h n important characteristic of enzymes is their substrate specificity ; therefore an enzyme will discriminate or select only a limited number of compounds for attack e.g. glucose oxidase catalyses the oxidation of P-D-glucose to gluconic acid Glucose oxtdase ,f3-o-glucose + H,O + 0 n-gluconic acid + H,O Another aspect of enzyme specificity is its stereospecificity towards substrates e.g.in the case of amino-acid oxidases D-amino-acid oxidase effects the deaniination of n-amino-acids to keto acids while on the other hand L-amino-acids are catalytically oxidised by the use of L-amino-acid oxidase. This selectivity of the enzymes and their ability to catalyse reactions of substrates a t low concentrations is of great use in chemical analysis. Enzyme catalysed reactions have been used for analytical purposes for a long time in the determination of substrates activators inhibitors and of enzymes themselves. An enzyme inhibitor is a compound that causes a decrease in the rate of an enzyme catalysed reaction either by reacting with the enzyme or enz5’me - substrate intermediate E + I + E I E + S + E S + E S I In this department methods have been developed for the determination of inorganic ions1?2 and drugs such as lysergic acid diethylamide (LSD) tetrahydrocannabinol (THC) morphines and barbiturates (K.B. O’Xeill and A. Townshend unpublished work) on the basis of enzyme inhibition. For example picogram amounts of silver and mercury can be deter- mined by their inhibition of alcohol dehydr~genase.~ Recently we have developed methods for the determination of indium and lead bj- their inliibition of nicotinamide adenine dinucleotide phosphate (ShDP) linked isocitrate dehydro- genase. The reactions are monitored by following the rate of formation of S-IDPH spectro- photometrically at 340 nm. The methods allowed the determination of 1 to 100 ng of indium and 1 to 70 iig of lead per ml of the reaction mixture.;\Ian>- metal ions interfere and in order to eliminate such interferences an attempt was made to determine indium and lead after their solvent extraction. S-Benzylaniline in chloroform was used to extract indium from a li!ydriodic acid medium but the extractant was also found to inhibit the enzyme. Tributyl phosphate (a 30 per cent. solution in isobutyl methyl ketone) in 3 >I hydrochloric acid containing lithium chloride ( 2 31) as salting-out agent was used to extract lead. B>- this method 45 pg of lead were separated from Ui2.- Bas- and Ca’; in the ratios by mass of 1 100 from HgZr a t 1 50 and from -Ig- at 1 25 and were thus determined without interlerencc from these metals.Traces of drugs such as LSD THC morphines and barbiturates have been determined by their inhibitory effect on enzymes. An investigation of alcohol and lactate dehydrogenases has shown that the former enzyme is more sensitive than the latter to these drugs (R. B. O’Neill and -4. Townshend unpublished work). The sensitivity achieved is between 0.1 and 10 pg which is insufficient t o provide an improvement over conLTentiona1 methods of analysis. In an attempt to achieve greater sensitivity the effect of such drugs was also investigated on other enzymes such as glucose oxidase isocitrate dehydrogenase and glutamate deliydrogen- ase. Glucose oxidase and isocitrate dehydrogenase were found to be unaffected by small amounts of drugs whereas glutamate dehydrogenase was found to be very sensitively inhibited.268 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY LProc. SOC. Anal?$. Chem 80 I I LSD tartrateips ml-’ Fig. 1. Inhibition of glutamate dehydrogenase by LSD tartrate. Incuba- tion of GDH with drug in a unbuffered 0.1 hi sodiuni chloride solution; b un- buffered water; and c pH 7.6 0.05 hi tris(hydroxymethy1)methylamine buffer The activity of glutamate dehydrogenase was measured by following the rate of disappearance of NADH at a wavelength of 340 nm in pH 7.6 buffer. \I’hen the enzyme was incubated with LSD in the presence of 0.1 M sodium ions the sensitivity of the method was increased. Fig. 1 shows the inhibition of glutamate dehydrogenase by various amounts of LSD after incubation with the enzyme in different media; as little as 40 ng of LSD per ml of the reaction mixture can be determined by incubation in 0.1 41 sodium chloride solution.Table 1 summarises the possible determinations that can be made by using glutamate dehydrogenase. This enzyme shows appreciable sensitivity and selectivity in its response to the drugs which encourages the search for even more sensitive enzyme systems. TABLE I IKHIBITIOX OF GLUTAMATE DEHYDROGENASE (GLUTARATE REDUCTION) Concentration a t which inhibition Drug begins/g ml-l LSD tartrate . I ,. * . 4 x 10-8 As-THC .. . . * . .. 4 x 10-5 Morphine hydrochloride . . .. 1 x 10-6 Diamorphine hydrochloride* . . 5 i( 10-6 Phenobarbitone sodium . . . . 1 x 10-4 * Activates the enzyme. The author thanks the Home Office Central Research Establishment for the award of a research scholarship. REFERENCES 1.2. 3. Townshend A and Vaughm A, Talanta 1970 17 289 and 299. - - Ibzd. 1969 16 929 and references therein. Hasani S. M. T. Ph.D. Thesis Birmingham University submitted. November 1973; RESEARCH TOPICS IIi ANALYTICAL CHEhIISTRY The Determination of Mercury (Inorganic and Organic Forms) BY P. JONES AKD G. NICKLESS (Inorganzc Chemistry Department The L'nzcerszty Bristol BS8 1TS) 269 THE two main techniques used for the analysis of mercury in environmental samples are (i) flameless atomic absorption combined with a reduction - aeration method for the determina- tion of inorganic mercury; and (ii) gas - liquid chromatography coupled with electron-capture detection for organomercury compounds. These methods have been studied and their accuracy and precision checked by analysis of standard reference materials and participation in round-robin surveys.Some work has also been carried out on the determination of inorganic mercury by gas chromatography which technique could prove a useful alternative to flameless atomic absorp- tion. (i) REDUCTION - AERATION METHOD WITH FLAMELESS ATOMIC AHSORPTIOX- An open-ended system was evaluated (see Fig. 1) and is based on systems in current use. The inorganic mercury is reduced to the elemental state and is swept out of the solution by a stream of nitrogen. In the normal mode the gases are passed through a drying agent into the absorption cell ; alternatively the gases can be diverted through a silica tube containing gold wire where efficient trapping of the mercury takes place so that any peak obtained is due to molecular absorption.Thus possible interferences from organic vapours or inorganic gases can be assessed. Mercury ~ lamp beam FIOW rneter.1 \ L 16-cm silica cell Silica tube containing gold wit-e \ Magnesium perchlorate drying tube -- 125-ml bubbler Coarse sinter Fig. 1. Mercury reduction - aeration apparatus Of the parameters affecting sensitivity one of the most important is temperature. 11 graph of peak height against temperature produces an S-shaped curve with maximum slope at 20 "C. It is very important that temperature changes between samples should be kept to a minimum a t ambient conditions. Good linear calibration graphs were obtained from the detection limit of 1 ng up to 10pg. Conditions normally used were solution volume 60 ml; solution temperature A0 to 70 "C; and nitrogen flow-rate 300 ml min-1.Coal was the first matrix to be examined and a combustion method was found to be the best way of extracting the mercury. Up to 1 g of the sample was mixed with 1 g of alumina in 270 RESEARCH TOPICS Ih' AXALYTICAL CHERIISTRY ;Proc. soc. A pinlyt. Cheii?. a silica boat. This mixture was heated in a silica tube under a stream of nitrogen and oxygen ( 3 1). The released vapours were then passed through a quartz wool plug at red heat to break down uncombusted organic materials. The mercury was collected in a bubbler con- taining acidic potassium permanganate (1 per cent. m/I; potassium permanganate in 3.5 N sulphuric acid). After complete combustion (approximately half an hour) the solution m:as transferred to a stoppered flask until ready for analysis.The solution must be boiled before analysis to convert all the mercury to the soluble inorganic state. Coal samples from the north Somerset and south Wales coalfields have been analysed. Results from the sampling programme so far are tabulated below .ires Suinber of samples Xverage/pg g-1 Rangelpg g-* North Somerset . . 11 0.14 0.07 to 0.30 South \Tales . . I . 25 0.30 0.02 to 1.44 Illinois (lLS..A.) . . 55 0.18 w0.i to 0.49 The Illinois samples were analysed by Ruch Gluskoter and Kennedy1 and are included for comparison. The coal standard SRN 1630 was used as a check throughout the study; the average value for this from nine determinations was 0.12 pg g-l (certified result 0.13) with a coefficient of variation of 8 per cent. Other solid matrices were examined by the combustion technique these being sediment fish orchard leaves and bovine liver.Samples were either standard reference materials or from round-robin surveys. Good agreement was obtained for saniples containing up to 200 pg g-1 of mercury. The results indicate that the combustion system could be a useful standard technique to check other systems. Its main advantage is that it reduces all sample-; to a common matrix which is relatively free from interferences. ( i i ) GAS CHR031ATOGRAPHY OF ORGAXOMERCL'RY COlfPOCNDS- This technique is now well established2 but it is still difficult to obtain good peak sym- metry reproducibility and sensitivitl-. Long conditioning times combined with repeated injections of standard compounds are essential for optimum I'erforniance. A Pye 104 gas chromatograph fitted with a 'j3Xi electron-capture detector with pulsed d.c.supplj. was used. Conditions with detection limits were Colu I l l I 1 T.iqiiid phase and Compound lengthlft loading Detection limi 's CH,H,gCI . . . . 5 E.G.4. (5 per cciit 1 2 x 1 0 - 1 ? C,H,HgCl . . . . 1 1; G.A. ( 5 per cent J 2 x lo-" €:,G.X. =- monoethylene glycol achpatc polyvster. Support phase = Supasorb (.ASS'-! 80 to 100 iiiesh. Two extraction methods have been examined for the analysis of methylmercury in f i ~ h meat. The latter n.as cliosen because it could be used with relatively small sample masses and its over-all cficiencj- \$:as very high (greater than 95 per cent.). Results for fisli samples in the range 2 to 10 pg g-1 \yere well within one standard deviation of the round-robin means. These are the IVestiiii and Uthe Solomon and Grift4 procedures.GAS CHROXATOGRAPHY OF IKORGANIC VERCURY- TIT-o reagents have been studied for the conversion of inorganic to organic mercurq- in Sodiunz hc~izeizeszilphiilnte C,H,SO,-Sa-This reagent converts inorganic mercury to order to be determined by gas chrornatograpliy following extraction. phenvlmercury and is derived from the Peters reaction of general form- Tlie reaction proceeds smoothly in a weakly acidic solution a t the boiling-point and is quan- titative down t o 0.05 p . ~ . m . ~ Sodium 2,2'-aimet7~itiZ-'3-silapelltai2e-5-sLro?z~~e ( D S S ) (CH,),Si(CH,),SO,-Sa r-This re- agent is a water-soluble trimethylsilyl derivative normally used as a reference substance in nuclear magnetic resonance spectroscopy. Its ability to methylate inorganic mercury was RSOBH 2 HgX -> RHgX + SO + HX Sovember 1973 RESEARCH TOPICS IK AS4LYTICrlL CHEMISTRY 27 1 reported by DeSinione.6 The DSS reagent is very stable in strongly acidic conditions and quantitative yields have been obtained from 0.0018 to 10 p.p.m.I t has been used for total mercurjr determinations on a small number of environmental samples with good agreement with other methods. Results obtained so far with this reagent are very promising. 1. 2 3 3 . 6. J . RE FE RE K c ES lcuch R. R . Gluskotcr H. J . and Kennedy E. J liiznois St. Grol. S?rvv. En7,iv. G c d AYott,s S o . 13 February 1951. Fiihbein. I>.. Ckroiwat. R e v . 1YiO. 13. 133 ,too .’ .’ ‘G ‘.4cla Chrrn. S c a ~ d . 1967 21 1790 (‘the J F, Solomon J and Grift l3 J . A s s . ( I f f . Awalyt C‘hi’:ii 1 9 i 2 5 5 AS3.lones P. and Tlcklcss C . I. Chioniat. 19i3 76 285. Non-dispersive Atomic Fluorescence Using a Non-flame Atom Reservoir Determination of Bismuth BY R P. Moul\jcE R XI D~GNILL €3 L SHARP m i ) T S \I b \ ~ (Liiciizzatiy Depaitnient Ivzpeiial Collrge o,f Sciiiicr a n d Iichizologj I.oiidoji 511 i 2 11‘1 -4 SIMPLE system has been constructed using a microwave-powered electrodeless discharge lamp as an intense atomic line source and a tantalum loop atomiser. The source is focussed by a single lens immediately above the “hot-wire loop” atom reservoir which is viewed directly by a solar-blind photomultiplier tube (Hammamatsu T.17. Co. J/td. RIG6 side-window or R431 end-window). Direct current measurements of the transient fluorescence signal are produced 011 a chart recorder (Fig.1). generator Reflected power meter E.H.T. Supply Back-off unit recorder u t t Circuit for the hot-wire loop atom reservoir . Metered argon gas flow U Fig. 1. Nun-dispersive atomic-fluorcxencc systeiii T,arkins Love Sullivan and Walshl and I’ickers StesTin Muscat and Fariasz have pre- viously given full accounts of the potential of non-dispersive systeiiis in flame media. A Jlarburg pipette was used to deposit 5 pl of analyte sample either in water or isobutpl methyl ketone solution directly on to the “loop.” The loop was dried for 40 s a t a low temper- ature and then flashed a t red heat. Optimum operating conditions were discussed for the argon-sheathing flow-rate source operating conditions and photomultiplier tube voltage to give the best signal to noise ratio. Some discussion was also given of the effect of heating rate on the signal peak height and width as displayed on the recorder.272 RESEARCH TOPICS IX AKALVTICAL CHEMISTRY -Pmc. Soc. AnaLyt. Chew. Analytical measurements were made using a bismuth - iodine and an iodine electrodeless discharge lamp making use of the overlap of the iodine non-resonance line at 206.163 nm with the bismuth resonance line a t 206.17 nm. The photomultiplier tube viewed the various fluorescence lines emitted simultaneously and additively within the response range of the caesium - tellurium photocathode (160 to 320 nm) of the solar-blind photomultiplier tube. The linear range extends from 0.01 to 500 pg cm-3 for both sources and photomultiplier tubes. The detection limits and analytical precision were determined from ten repetitive signals.The results are given in Table I. TABLE I DETECTION LIMITS AKD PRECISIOS Source Detection limit Precision Photomultiplier (electrodeless r-7 r-yA-i tube discharge lamp) p g c 1 r 3 g pg c ~ i i - ~ per cent. R166 1 2 0.043 2.2 2 0.5 8.5 K431 I 0.00i 3.5 x lo-" 0.1 9.0 R166 Bi - I 0,016 8.0 x lo-" 0.9 5.0 R43 1 Bi - I 0.0063 3,2 x lo-" 0.1 6.5 Interference studies were carried out by using previously optimised conditions and various alloy samples were analysed. The bismuth was separated and extracted into isobutyl methyl ketone and an acidified potassium iodide solution was used to produce the iodobismuthate species. TABLE I1 RESULTS FOR BIS~KTH DETERMISATIOSS The results of the determinations are given in Table 11. Bismuth content r Present/ Sample p g cm-3 (aqueous solution) x 0.2 B 0.1 C 0.4 D 0.8 Precision _- 1 per cent.Found./ (10 results) pg c n r 3 0.18 f i 0.093 I 0.39 5 0.80 7 \Ye are grateful to the Jlinistry of Defence for providing a grant to carry out this research and for permission to present this paper. REFERENCES 1. 2. Larkins P. L. 120ve R. N. Sullivan J . V. and Walsh X. Spectvochinz. Acta 1969 24B 187. Tickers T. J Stevin P. J . Muscat V. I. and Farias L. T. Analyt. Chew. 1972 44 930. Thin-layer Phosphorimetry BY L. A. GIFFORD (Depavtmewt of Chemistvy Loiighbovough Unzvevszty of Technology Loughbovough Lezcestevshtvc LE11 3TC) SISCE the introduction of phosphorimetry as an analytical technique by Kiers Britt and iYentworth,l numerous workers have shown phosphorimetric measurements to be extremely sensitive and selective.The selectivity of the techniques has been improved further by combination with thin-layer chromatography. Applications of the combined technique have included the determination of p-nitrophenol in urine2 biphenyl in oranges3 and alkaloids in tobacco.4 In each instance however the sample had to be eluted from the thin layer before measurement. Phosphorescence spectra at 77 "K have been observed from materials ad- sorbed on a variety of supports including silica alumina paper asbestos and glass fibres after immersion in liquid nitrogen in a conventional Dewar flask.j-* It is the intention in this paper to describe a device capable of scanning thin-layer chromatographic strips and measur- ing qualitative and quantitative phosphorescence directly. Yovember 1973 KESEAKCH TOPICS IN ASALYTICAL CHEMISTRY 273 THIN-LAYER PHOSPHOKIMETER- The device consists essentially of two discrete parts the sample holder and the single disc pliosphoroscope.The sample holder is constructed from a hollow copper cylinder closed a t its lower end. The thin- layer strip is attached to the lower end of the drum by means of elastic bands. The drum is then filled with liquid nitrogen and the sample is cooled by conduction. The copper drum is inserted into an air-tight box the function of which is to prevent condensation of water vapour on to the surface of the sample. Two silica windows a t right-angles to each other in the front of the box allow the incident radiation to excite the sample and the emitted radiation to pass to the photodetector. The single disc phosphoros~ope~-~~ allows the isolated observation of phosphorescence on the basis of lifetime.A disc with three rectangular slots equally spaced and rotated by means of a variable-speed motor is mounted in front of the two fixed slits. Excitation radiation passes through the rotating disc and fixed excitation slit to irradiate the sample. 4s the excitation radiation is cut off by the disc the fluorescence decays rapidly and only the long- lived phosphorescence remains. The phosphorescence is then allowed to reach the emission monochromator and photodetector as the disc covering the emission slit opens. A less important feature of the phosphoroscope results in the minimal measurement of scattered incident light. The sample drum is rotated by means of a small variable-speed motor mounted outside the light-tight compartment.When a luminescent component on the strip is a t the focal point of the optical system a signal is registered in the photodetector circuit. The drum can be stopped at any position and the spectral characteristics of each component measured; the position of the drum is a measure of the R value of the component. The amplitude of the signal can be used as a quantitative measure of the component. Phosphorescent lifetimes can be measured from the rate of decay of the luminescent signal after cut-off of the exciting radiation. Fixed to the top of the drum is a canopy which acts as a light trap. APPLICATIOSS- Sawicki and Pfaffs demonstrated the sensitivity of a combined technique in the detection of nanogram amounts of aromatic air pollutants. R'e were able to separate identify and quantitate a mixture of three sulphonamides in microgram amounts by direct spectrophos- phorimetric analysis of a thin-layer chromatogram.13 Electrophoretic separations can also be examined by this technique enabling separations of complex mixtures such as plasma and drug - protein binding phenomena to be studied.Multiple scans can be performed as different wavelengths of excitation and emission. hlodification reactions can be performed on chromato- graphed zones and the amount of data available for the characterisation of unknowns can therefore be greatly increased. The combined technique has great potential for use in pollution control pharmaceutical and biological analysis and other fields where small amounts are to be determined in complex mixtures.1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. REFERENCES Keirs R. J . Britt R. D. and \Ventworth m'. E. Aiqalyt. C h e w 1967 29 202. McCarthy Ur. J. and Winefordner J . D. -4nai.ytica Chim. d c i a . 1966 35 120. ____ J . Ass. O f f . Aizalyt. Chem. 1965 48 915. \\'inefordner J . D. and RIoye H. A, Analylica Ckirpz. rlcta 1965 32 278. Szent-Gyorgi A Science N. Y . 1957 126 751. Zander M. Erdol Kohle 1962 15 362. Sawicki E. and Johnson P. Micvochem. J . 1964 8 85. Sawicki E. and Pfaff J . D. Analytica Chim. Ada 1966 32 521. Hollifield H. C. and Winefordner J. D. Chem. Iizstrur~z. 1969 1 341. Vavilov S. I. and Levshin V. L. Z . Phys. 1926 35 920. Langouet L. Bull. SOC. Sczent. Bretagne 1962 37 11. Housset Y . Dupuy F. and Lochet R. J . Phys. The'oor. Appl. 1968 3 250. Gifford L.A, Miller J . S. Thorburn Burns D. and Bridges J . W. in preparation 274 RESEARCH TOPICS IN ANALYTICAL CHEMISTRY IPvnc. SOC. Aizalyt. Clzt.m. The Solution Chemistry of Simple Phenol-based Complexones and their Anthraquinone Analogues BY G. T. MURRAY AKD 31. A. LEOYARD (Departnzeizt of Analvtzcal Clzewzistry Dnaid I<& Rzcildii~g Quetvz's L'izivevsz'ty of Rrlfust Be!fast BT9 SAC) SINCE its discovery in 1969 the metallochromic indicator alizarin fluorine blue1 has been used extensively and with great success for the determination of the fluoride ion in various matrices. However in spite of this not much work has been carried out on the physical and chemical nature of either the complexone or the binary and ternary complex species formed with lanthanum and fluoride ions reactions which form the basis of the fluoride determination with use of this reagent.By studying a series of simpler complexones in this case reagents based on simple phenols together with selected anthraquinone analogues it was hoped to clarify tlie processes involved in the ionisation of alizarin fluorine blue and the nature of the binary and ternary complexes. For the most part spectrophotometry using absorption in tlie visible and ultraviolet regions of the spectrum was used in the investigation of tlie complexone ionisations and complex formation. The series of reagents chosen for this work is shown in Fig. 1. ,C H COO H CH,-N 0 'C H co o H &OH ,C H COO H *'& C H *- N 0 CH Fig. 1. Phenolic and anthraquinone-based 1-eagents A11 of the complexones were prepared by the usual hIannich condensation reaction involv- ing the parent phenol or alizarin formaldehyde and iminodiacetic acid these reactions being carried out in aqueous media.IOKISATIOK OF STJZPLE COMPLEXONES- Studies on the ionisations of the simple complexones showed normal behaviour for the removal of the first and second protons; that is to say the first and second ionisation steps involved simple one-proton processes. However when the removal of the third proton is considered a different picture is presented and it would appear that perhaps a dimerisation process is occurring. The ph' values for the reagents were determined by making use of their insolubility in the lower regions of the pH scale. Values of 3.98 for o-cresol complexone and 5.01 for m-cresol complexone were calculated.The ph' values were obtained by mathe- matical analyses of the first portions of the relevant pH i ~ c ~ s u s absorbance curves for the complexones according to the equations' 1 [H+;g 1 + - - q - A,K' A and log [ 7 2%tJ = qpH - pK, November 1973 RESEARCH TOPICS I N ANALTTICAL CHEXISTRX- 275 These \$-ere found to be 10.21 for o-cresol complexone and 9.26 for the nz-cresol analogue. STLDIES ON ALIZARIS COMPLEXONE- B y obtaining a series of absorption spectra at different pH values for alizarin fluorine blue not only can we observe the variation of the spectrum but me have a basis for the subsequent mathematical treatments that are available. From the spectra thus obtained two ionisation processes were indicated by the presence of two clearly defined isosbestic point<;. pH iwsz.is absorbance graphs were constructed and analysed according to the equations shown above.The first step was found to be due to a simple one-proton ionisation process whereas the second step showed a process apparently involving only half a proton. However by assuming two overlapping ionisations and with a suitable choice of pk’ and E values a theoreti- cal pH ilersm absorbance cur1.e was constructed which coincided with that obtained experi- mentally. hgain the insolubility of the complexone in the lower pH regions was used to calculate pK,. Fig. 2 shows the suggested ionisation scheme for alizarin complexone together with t h e pK values obtained. These values are in good agreement wit11 those obtained by lngnian . 3 In the case of the binary and ternari- complexes the coinlining ratios were determined from continuous variation (Job) and molar ratio plots and were found to be 1 1 for the alizarin complexone - lanthanum complex and 1 1 1 for tlie alizarin complexone - lantlianurn - fluoride complex.The procedure proposed by BudesinskyJ was applied to the determination of the nuclearity of the complexes and showed 2 2 and 2 2 2 stoicheiometry respectisrely. ITalues for the conditional stability constants were found to be 2.7 x lo6 1 mol-l for the binary species and 2.1 x lo6 1 mol-l for the ternary species a t pH 4.12 Calculations were made by using molar ratio and continuous \,ariation graphs. CHZCOO- .. ( 2 34) CH COO- 1 k K 2 ( 5 401 0 CHZCOO- 0 / . ? 0- CH ,COO- + / 6 ‘C H CO 0- PH 0 ‘CH,COO- Fig. 2. Ionisation scheme for allzariii complexone myhr 1 2 3.1 5 Solid samples of the binary and ternary complexes were isolated and submitted for ele- mental mass spectral and thermogravinietric analysis. The results obtained together with tlie solution data suggested a structure for the complexes similar to that proposed by Lang- Klausen and So~ri-Nekoui.~ REFEKEXCES Leonard 31. A. and West T. S. J . Chewz. SOL. 1960 4477 Keilly C. S. and Sawyer D. T. “Experiments for Instrumental Methods,” McGraw-Hill S e n . York 1961. Ingnian F, Talania 1973 20 135. Budesinsky B. Z . anai.yy2. Chcnz. 1963 195 244. Langmyhr F. J.. Klausen K. S. and Nouri-Xekoui h1. tI. Analytzca Ckiln. Acta 1951 57 341. 276 RESEARCH TOPICS I N ANALYTICAL CHEMISTRY [ P V O C . S O C . Atzalyt. Chem. Solvent Effects in the Catalytic Thermometric Titration of Weak Acids BY E.J. GREESHOW AXD R. HARGITT CATALYTIC thermometric titration has some advantages ol'er normal thermometric titration in that easily measurable temperature changes can often be achieved in situations where this is not possible with the latter method e.g. in the titration of dilute solutions of weak acids and bases. Probably the best known catalytic thermometric procedure for the determination of weak acids in non-aqueous solution is that of Vaughan and Swithenbank,l in which the sample dissolved in acetone is titrated with potassium hydroxide in propan-2-01 When the acid has been neutralised further addition of titrant catalyses the dimerisation of the acetone causing temperature rises of the order of 4 "C. Greenhow2 has shown that acrylonitrile can be used in place of acetone and in this instance a highly exothermic polymerisation process orcurs and the end-point is indicated by a temperature rise which can exceed 30 "C.acids that are insoluble in acrylonitrile can be dissolved in a suitable solvent and only sufficient acrylonitrile to give a measurable temperature rise a t the end-point needs to be added. In a comparison of the acetone - indicator and acrylonitrile - indicator methods for the determination of mono- and poly-basic organic acids Grcenhow and Spencer3 found that with some compounds the end-points indicated by the two methods corresponded to different ratios of titrant to titrand. A more detailed investigation of this phenomenon has been carried out. Lye found that with succinimide phthalimide and 2,fj-di-t-butyl-4-metliylplienol the stoi- cheiometry of the neutralisation reaction depends not only on the procedure used but in the acrylonitrile method also on the nature of the titrant and on the solvent in which the sample is dissolved.Thus in Table I it can be seen that when the sample is dissolved in acrylonitrile only and potassium hydroxide in propan-2-01 is the titrant used the results are almost identical with those obtained by the acetone method. There is a marked change in stoicheiometry when potassium hydroxide is replaced with tetra-n-butylammonium hydroxide in toluene - methanol as titrant. The large reduction in the titrant consumption at the indicated end- point with 2,6-di-t-butyl-4-methylphenol would appear to be due to steric hindrance with the latter titrant. IVith succinimide and phthalimide t h e reduction in the stoicheiometric ratio is even more marked when dimethylformamide is used as the solvent in place of acrylonitrile.TABLE I (Department of Chenzistvy Ciaelsea College University of Londolz Manresa Road London STV3 6 L X ) CATALYTIC THERMOMETRIC TITRATION OF SCCCINI.\IIDE PHTHALIZIIDE ASD 2,6-DI-t-BCTYL-4- JIETHYLPHENOL USISG ACETOSE AKD ACRI'LOSITRILE .1S ESD-POIST ISDICATORS Stoicheiometry of the neutralisation reaction* 2,B-di-t-butyi- Succinimide Phthalimide 4-inethylphenol Titranti Solvent Indicator 0.27 0.51 0.31 K D A S 0.28 0.46 0.31 B D i\s 0.69 0.82 0.26 N n .\s 1.0 1.0 0.97 K AN AN 0.68 0.67 0.27 B -4 N A S 1.0 1.0 1.0 K A -1 * Equivalents of titrant per molecule of sample. 7 Titrants K 0.5 M potajsium hydroxide in propan-2-01; 13 0.1 M tetra-n-butylammonium hydroxide in toluene - methanol and S 0.1 ZI sodium methoxide in methanol.Solvents and indicators A acetone AN acrylonitrile; and D dimethylformamide. The results can then be seen to be similar to those for the potassium hydroxide and tetra-n- butylammonium hydroxide titrants. However with sodium methoxide in methanol as the titrant the reduction in the stoicheiometric ratio is not so great; apparently the titrant and the dimethylformamide solvent have opposing effects. In order to find an explanation for these solvent effects one must consider not only the influence of the solvent system i.e. the sample solvent the indicator monomer and the titrant solvent on the acidic properties of the sample, Sovember 1973; RESEARCH TOPICS IN ANALYTICAL CHEMISTRY 6 L $ 5 - E .4 P 5 3 - 0 2 - 2 - - 0 c Cl .- 2 1 - E 277 - TABLE I1 CATALYTIC THERMOMETRIC TITRATION OF RESORCINOL USIKG ACETOXE AKD ACRYLOSITRILE AS EKD-POINT INDICATORS Stoichciometry of the Indicator Titrant* Solvent neutralisation reaction Acetonc K Acetone 2.0 -icetone (50O.6) K Acrylonitrile (50qb) 2.0 Acrylonitrile K Acrylonitrile 2.0 Xcrylonitrile (50%) B Dimethylforrnamide (5Ooi0) 1.0 Acrylonitrile (3004) B Dimethylformamide (707;) 1.0 Acrylonitrilc (50q6) I< Dimethylformamide (500;) 1.5 Xcrylonitrile B Acrylonitrile 1.3 * Titrants K 0.5 M potassium hydroxide in propan-2-01; B 0.1 11 tetra-11-butplammonium hydroxide in toluene - methanol. but also the conditions and ionic species necessary for initiation and propagation of the indi- cator reaction. The ratio of ion pairs to unpaired and probably solvated ions is almost certainly an important factor controlling the polymerisation process.5 Titrant/ml Fig. 1. Titration of phenol - resorcinol mixtures. Sample size (1.05 mequiv of phenol plus an appropriate amount of resorcinol. Titrant A 0.1 M tetra-n-butylammonium hydroxide in toluene - methanol; and B 0,416 M potassium hydroxide in propan-2-01 (adjusted to 0.1 SI equivalent) Table I1 summarises the results obtained in the catalytic thermometric titration of resorcinol with acrylonitrile and acetone as the end-point indicators dimethylformamide acetone and acrylonitrile as the solvents and potassium hydroxide and tetra-n-butylamnion- ium hydroxide as the titrants. It can be seen that depending on the titration conditions resorcinol titrates as a monobasic acid a dibasic acid or an acid of intermediate strength.In contrast to resorcinol phenol titrates as a monobasic acid under all the conditions listed in I Phenol per cent. 80 60 40 20 0 Resorcinol per cent. (molar) Fig. 2 Titration of phenol - resorcinol mixtures 278 RESEARCH TOPICS I N AK.4LYTICAIL CHEMISTRY P V O C . S O L . -4 mlj't. Ch,enq. Table 11. I t is therefore possible to use catalytic thermometric titration under two sets of conditions to analyst binary mixtures of phenol and resorcinol. The two conditions chosen in the present work were (a) potassium hydroxide titrant and acrylonitrile as both solvent and end-point indicator ; and (b) tetra-n-butylarnmonium hydroxide titrant dimethylformamide as solvent and acrylonitrile as end-point indicator. The results of calibration are shown in Figs.1 and 2 . Preliminary investigations have established that the contents of combined phenol and resorcinol in phenol - formaldehydc and resorcinol - formaldeh).de condensation resins can be determined by the thermometric method and also that tlie ratio of combined phenol to combined resorcinol in mixed phenol - resorcinol - formaldehyde resins can be determined by using the procedure employed for the assay of phenol - resorcinol mixtures. REFEREKCES 1 . 2 . 3 . 1-aughan G. X.. and Swithenbank J J 4wn!yst 1966 90 694. Greenhow E. J Chcin. 4 I d 1972 422. Grcenhow I.? J . and Spencer L. E Ai7a!yst 1053. 98 90. Polarography of 2-Ethylanthraquinone in Sulphuric Acid BY S. R. PORTER V. J. JESSISGS -1. Donsos ASI) J. I\'. OGLEBY ( ~ . ~ % C h ? $ t f l ' ~ O / J ' t c C h i ? i c C O I ' P I 7 t ) ? ' c- 1.1 S F D ) (G~~izt~i.nl Cheiizzcnls Diviszoiz Lnpor.te Iiiiliistpit's Ltd.liooi.jic.id R o a d i l ~ i t l r i i s I.ni7cs.t ~ - I . T H ~ L . ~ S T H R ~ Q ~ I ~ O N E (ZEAQ) is used in conjunction with palladium as a catalyst in tlie auto-oxidation process for the industrial manufacture of hydrogen peroxide.' Its polaro- graphic behaviour has previously been studied in -dimethylforniamide2 and in different alcohol - aqueous base electrolyte mixture^.^ In these studies it has usually been found that tlie electrode process is diffusion controlled. In a search for a suitable electrochemical solvent for 2 E I Q it ivas noted that this com- pound is readily soluble in concentrated sulphuric acid.4 Polarograpli!- has been studied before in concentrated sulphuric acid.5 The reduction waves for several aromatic nitro compounds were reported and $-chloronitrobenzene and p-nitrotoluene u.ere determined.-1nthraquinone was reported to be reduced polarographically. Concentrated sulphuric acid would be a most useful electrochemical solvent for 2EAQ because it requires no addition of supporting electrolyte the current being carried by dissocia- tion reactions in sulphuric acid and the 2 per cent of water present. No mixing of solvents is required to improve the electrical conductivity. Hou-evcr there are some disadvantages with concentrated sulphuric acid. The polarographic cathodic range in this medium is only up to - 0.7 \.' iwszts the mercury pool anode. This had a stable potcntial of - 0.24 1. :IEYSLI.S the niercury(1) sulphate electrode.The range could be extended by dilution with water but this reduced tlie solubility of the 2EAQ. The apparent capillary curve for con- centrated sulpliuric acid found by plotting drop-time against the applied potential mas normal except that the decomposition potential was reached before the electrocapillarj- maximum. Sulphur dioxide gives a reduction xave a t - 0.4 V i'c~sus the anode pool that cannot be removed by passing nitrogen through the solution. However based on the manufacturer's specification that there was not more than 04001 per cent. of material that would reduce permanganate and assuming that this material mas present entirely as sulphur dioxide the concentration of sulphur dioxide would be 2.8 x Assuming SlEek's value for the diffusion coefficient6 of sulphur dioxide which was 2.2 x cm2 s-l the limiting current would only be about 0.12 F A .This is only of the order of 1 per cent. of the limiting currents measured for 2EAQ in the concentration range 0.5 to 5 :< M. All of the polarograms were obtained using a Tinsley pen recording polarograph (type number 19,'3) manufactured by Evershed and T'ignoles Ltd. The scan speed was 2.5 mi' s-' the slow speed of this instrument. The sulphuric acid was of AnalaR grade containing 9848 per cent. W;PZ of sulphuric acid and witli a density of 1.84 g ml-1. nr. November 1973; RESEARCH TOPICS I S ANALYTICAL CHEMISTRY 279 The 2EAQ was recrystallised once from AnalaR grade methanol and had a melting- This was The wave height was The concentration dependence of the limiting current was investigated in the region point of 108 "C; it gave a reduction wave at about - 0.5 1' veysus the pool anode.the potential at which the maximum occurred on the derivati\Te scan. always measured at -0.6 V after allowing for a linear rise in background current. 0.5 to 5 x h i . The dependence in this range was found to be non-linear (Table I ) . TABLE I COSCEKTR.4TIOS DEPEKDEXCE OF THE LIMITIKG CCRREKT FOR THE REDUCTIOK O F PEXQ I S COSCEXTRATED SULPHC'RIC ACID AT 25 "C Concentrationlsr x 0.49 0.98 1.47 1.96 2.94 3.93 4.92 Limiting currcnt/pLX . . 9.83 11.6 15.6 21.6 38.3 61.6 80.6 :/.% mmoi -1 . . . . 20.06 11.84 10.61 11.0.' 13.03 15.67 16.38 The temperature dependence of the reduction wave was investigated between 8.4 and 32 T and the temperature coefficient of the limiting current found to be 3.4 per cent."C-1. The limiting current was found to he independent of the head of mercury in the range from 23.8 to 66.5 cm of mercury. DISCESSIOY- When a polarographic wave is controlled by diffusion of the electroactive species to the dropping-mercury electrode the limiting current is proportional to the square root of the head of mercury.' This has been the case in preyious polarographic studies of 2EAQ. The temperature coefficient of diffusion-controlled waves is usually between 1 and 2 per cent. The large temperature coefficient (3.4 per cent.) of the polarographic reduction wave for 2EXQ in concentrated sulphuric acid and its independence of the liead of mercury suggest that the wave is kinetically ~ontrolled.~ The solubility of anthraquinones in concentrated sulphuric acid is attributed to proto- nation of the carbonyl oxygen atoms.8 I t is possible that the kinetic mechanism is related to an equilibrium between 2EAQ and protonated 2EL4Q assuming that the former is reducible while the latter is not.Further work is required on the spectroscopy of these species in concentrated sulphuric acid and glacial acetic acid in order to try to identif!. the presence of nrotonated PEAQ. lye would also like to establish the control of the reduction wa\.e in acetic acid. glacial 1. 2 . 3 . 1. 5. 6 S ,. REFEREKCES Cronan C. S. C h m . Engng 1959 66. P a r t 7 118 lilabnnovskii E I . and Ezerskaya S. X. Zh. .4 izalit. I<hii~>. 1963 18 980 English translation J Annlyl. Chcnz. C . S . S . K . 1963 18 856. Jennings V J . Forster T. E. and ST'illiams J .Analysf 1Oi0 95 7 1 Kichter I:. Edituv "Bcilsteins Handbuch der Organischen Chcmi 1 s t Siupp 1 emen t J LI li Springer Berlin 1931 James J C . T r a n s . Favndny Soc. 1951 47 1240. \71?ek .A. .I. Coilii Czt:ciz. Chcnz. Conzmtin. 1951 16 465. Zurrian P. "Organic Polarographic -%nalysis," Pergamon Press. Ckfortl I$t(iA 13. 25 (;rake Ji. Tiaizs. Fa~adczy Soc. 1941 37 68. Time-resolved Non-dispersive Atomic Fluorescence by the Carbon Filament Atomisation Technique BY A. F. KISG ASU T. S. \YEST THE non-dispersive atomic fluorescence system described by Larkinsl lias been modified to permit its use with a carbon filament atom reservoir. By utilising the temperature gradient produced in firing the filament it lias been possible to obtain time-resolved fluorescent peaks from a single atomisation of a solution of certain pairs of metals.Xcrowave-excited electradeless discharge lamps were used as primary radiation sources because of their higher atomic line intensity than hollow cathode lamps and the convenience (Ch:.;iiistqi Depnvtiiieizt Imperial College of Science aiid Trchizology L o ~ ~ c i o i z 511.7 2.4 I') 280 RESEARCH TOPICS IS ASALYTICAL CHEMISTRY LProc. SOC. Analyt. Chew. of their preparation. Two lamps one for each of the pair of elements to be determined were run in separate ;-wave (Evenson type) or :-wave (Broida type) resonant cavities. Occasion- ally both cavities were run from one microwave generator using a twin-port divider to direct one half of the incident power to each cavity but more often separate generators were used so as to allow greater individual control over each cavity.Light from each lamp was focussed on to the central notch in the 2-nim diameter carbon filament from which atomisation was effected using separate 1-inch focal length Cassegrain mirror systems. Focussing is by reflection from front-silvered convex toroidal and concave hemispherical mirrors giving minimal absorbance of short wavelength radiation compared with silica lenses and a focal length independent of wavelength. Fluorescent radiation was viewed by a similar mirror system focussed on to the photo- cathode of a Hammamatsu R166 or R431 solar-blind photomultiplier arranged to subtend right-angles to both of the primary radiation sources. A storage oscilloscope was used for signal amplification and read-out. Temperature measurements on the carbon filament indicate that on firing a t maximum voltage there is a linear temperature rise to about 2000 "C after 0.6 s after which the tempera- ture gradient decreases as the maximum of about 3000 "C is approached.By decreasing the applied voltage the initial temperature aeysus time gradient can be reduced to 1000 "C s-l or less. This means that it is possible to atomise one metallic species selectively from a mixture of two on the filament and then to atomise the second after the first has disappeared from the field of view. By using a fast response recorder it is possible to follow this procedure and obtain separate fluorescent peaks for the two elements of the mixture. Preliminary results obtained in this way show that simultaneous determinations are possible for mixtures of mercury with cadmium zinc or bismuth.The similarity in volatility of mercury and cadmium indicates that mercury could be simultaneously determined in a two-element mixture with most common metals. Other pairs of elements for which time- resolved fluorescent peaks have so far been obtained in this study include cadmium and zinc cadmium and bismuth and cadmium and thallium. Calibration graphs for mercury and bismuth from simultaneous determinations of mercury and bismuth mixtures show linear ranges of two or three orders of magnitude depending on the mercury to bismuth ratio studied. h large excess of one element over tlie other tends to decrease the linear range and the slope of the calibration graph. Calibrations were obtainable for mercury - bismuth mixtures in ratios between a 100-fold excess of bismuth and a 10-fold excess of mercury.The range of possible ratios depends on the oscillator strengths of the appropriate fluorescent transitions and on various experimental parameters such as incident line intensity and must of course be such that the fluorescent peaks obtained for each element are both of measurable size. Similar calibrations to the above are obtainable for the other mixtures indicated. It is likely that the best results i.e. the greatest separation of fluorescent peaks will occur with mixtures of less volatile elements which are atomised from the carbon filament a t a point on the temperature zeysus time curve where the temperature gradient is beginning to decrease. \Ye are indebted to NERC for the provision of a research studentship for ,4.F.K REFEREKCE 1.Larkins P. L. Spectvochiln. i l c t a 1971 26B 477. Some Studies in Complexing Ion-exchange Resins BY H. ECCLES AKD F. YERKOS (Depavtwzent of Chetntstiy and Apfilted Chemstry Cnzverszty of Saljovovd Saljovd LawcadLive ;I15 4U'T) PI MAJOR disadvantage of conventional cation exchangers i.e. crosslinked polystyrene sulphonates and methacrylic acid is the lack of selectivity. Ion-exchange chromatography on the latter is dependent on differences in the cation - resin affinities which are determined by the cationic charge. Xovember 19731 RESEARCH TOPICS IN AKALYTICAL CHEMISTRY 281 The first attempt to separate cations on a solid chelating compound was made by Erlen- meyer and Dahn,l who passed aqueous solutions through a column of 8-hydroxyquinoline (oxine) with some success but the method was limited by the solubility of the oxine in the aqueous phase.Various workers have attempted to produce oxine-containing resins both by polycondensation of the ligand with resorcinol and formaldehyde2s3 and by coupling oxine to a polystyrene matrix.3~~ There are drawbacks to both types of chelating resin polycon- densates are usually highly crosslinked with correspondingly low water regains and relatively long equilibration times making them unsuitable for column use whilst polystyrene-based resins involve chemical reactions on the resin with the accumulation of impurities and by- products leading to low over-all conversions and hence low total capacities. A recently investigated oxine-containing e~changer,~ based on a macroporous polystyrene matrix was found to be suitable for column separations of those cations that are capable of forming oxine complexes.As with the monomeric systems the existence of the cation - oxine resin complex was pH dependent and hence the exchanger would remove iron(III) copper and uranyl ions from a solution a t pH 2.8 whereas nickel and cobalt were not retained by the resin below pH 4 while aluminium and zinc were retained above pH 4.8 the alkali metal cations not being retained. Hence iron could be separated from aluminium and copper from cobalt and nickel. All retained cations were rapidly eluted from the column by 2 1\1 hydrochloric acid. The total capacity of the exchanger was low (1 niequiv g-l for copper) compared with the commercially available Dowex 4-1 (4.5 mequiv g-I) which is a polystyrene-based iniinodiacetic acid chelating resin.Dowex A-1 chelates in a similar manner to EDTA and is not therefore very selective which is an advantage in many analytical applications where trace amounts of polyvalent cations can be removed from solutions that contain large amounts of alkali metal sa1ts.j Highly selective chelating ion exchangers have been synthesised and investigated by Bayer,6 based on the condensation of glyoxal with di- and triaminophenols. The resulting resin a glyoxal bis-2-hydroxyani1 was found to be selective for copper and uranium while the mercapto analogue was selective for mercury silver and gold. \lTork has previously been carried out on the synthesis of chelating ion exchangers containing hydroxamic acid as the functional group. Attempts a t synthesis have involved conventional weak cation exchangers (polycarboxylic acids) as starting materials.Con- version into polymeric acid chlorides and subsequent reaction with hydroxylamine in aqueous solution has resulted in resins that possess hydroxamic acid units the resins being specific for iron(II1) .i These resins were reported to be unstable towards relatively concentrated acids and bases and to undergo rearrangements during regeneration. The conversion of polymeric carboxylic acids into acid chlorides is however very difficult. The resins are not reproducible and the percentage conversions are extremely low. Consequently the synthesis of a liydrox- amic exchanger from crosslinked polyacrylonitrile by hydrolysis and condensation with hydroxylamine was attempted. The resulting polymer a white micro-bead exchanger had a water regain of 1.5 g g-l in the hydrogen form with a 50 per cent.saturation time (1,) of 11 minutes for iron(II1) ions making it a suitable resin for column operation Unlike previous exchangers of this class the stability is good no decrease in the observed total capacity for iron(II1) ions (3.5 mequiv g-l at pH 2.7) was observed when the resin was recycled twenty times. TABLE I CAPACITIES OF THE HYDROXAMIC IOK EXCHAKGER Total capacity mequiv g-' p~ of l\ritiout competing In presence In presence Cation equilibration ligand of citrate of EDTX Fe(II1) FelII) c u 3 3 5 co 5 Ni 5 T.r (as VO,+) 3.3 U (as UO,*+) 5 4.1 1.6 3.5 1.0 0.3 0.3 4.2 1.7 0.2 0.7 0.4 0.1 1 .0 0.4 0.1 1.8 1.0 2.6 2.0 - - 282 RESEARCH TOPICS I S ANALYTICAL CHEMISTRY [PE'OC.SOC. A PLalyt. Ch&WZ. Table I shows the total capacities of the resin for various cations at the optimum pH both with and without a competing ligand in the aqueous phase. L'nlike in previous work the resin was found not to be selective for iron(III) high capacities being exhibited for iron(II1) and copper but the highest selectivity was found to be for vanadium which could be completely removed from 1 >I acid solutions. The capacities for copper cobalt and nickel follow the Irving - \T:illiams series and separation of copper from cobalt and nickel should be possible by using column operation. This liydroxamic acid exchanger is cheaper and easier to produce than Dowex A-1 with which it compares favourably for swelling equilibration rates and total capacities and as it has the advantage of being more selective should find application in analytical separation prob- lems.REFERENCES 1. 2. 3. 4. 5. G . 7 . Erlenme);er H. and Dahn. H. Helv. Chiwz. .4cla 1939 22 1369. Pennington L. D.. and Williams RI. B. I n d . Engng Chern. 1959 51 7.59. Yernon F. and Eccles H. Analytzca Chzm Acta 1953 63 403. Davies R. Y ~ Kennedy J . Lane E. S. and Williams J L. J . A p p l . C'hewz. Lond. 1959 368. Riley J . P. and Taylor D. Analytzca Chiin. .4cta 196S 40 4 i Q . Bayer E. Angcw. Chem. 1964 3 32.5. Cornaz J. P. and Deucl H. Expevientia 1954 10 137. Studies on the Solvent Extraction and Atomic-Absorption Spectroscopy of the Noble Metals BY 11. A. ASHT A METHOD was described for the determination of trace amounts of ruthenium osmium and iridium in rhodium sponge.The sponge is dissolved with a mixture of sodium chlorate and concentrated hydrochloric acid in a sealed glass tube a t 250 "C and the diluted solution is extracted with a 1 per cent. w$/V solution of chloroform in methyltriplienylphosphonium chloride. The osmium iridium and most of the ruthenium are extracted into the organic phase which is evaporated to dryness. The residue is dissolved in acetonitrile containing lithium perchlorate and the concentration of noble metals determined by atomic-absorption spectroscopy. The interfering effects of certain noble metals on the determination of ruthen- ium osrniuni and iridium are eliminated when lithium perchlorate is present in the solution. (Clzeiiiistry Departrneizt The Cizivevsity Shcijield S 3 7HF)

ISSN:0037-9697    

DOI:10.1039/SA9731000267

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

282 RESEARCH TOPICS IS ANALYTICAL CHEMISTRY [PE'OC SOC. APLalyt. Ch&ltZ. On-line Methods of Particle Size Analysis Tlie following is a summary of one of the papers presented at a meeting of tlie Particle Size .Analysis Group held on >larch i t h 1973 and reported i n the April issue of Proceedlugs Quality Measurement of Powdered Solids and Viscous Fluids By 9. G. STISLEY-~VOOD* I(. T. LEE+ AKD 11. S. BECK! (p. 7 5 ) . ( Z'h e C?tioevs it?) Bvadjo vd Yorksk ire,) IN fluid flow systems measurable properties such as temperature pressure capacitance and conductivity are known to fluctuate with time and position. These variations are due to thc random motions caused by the eddies and velocity fluctuations in a turbulent fluid. \\'lien a turbulent fluid flow system contains solid particles the concentration at an)' one part is likewise varying with time.Although the general direction of motion of a solid particle in a solid - liquid system is to follow the fluid along its constrained limits or pipe there are random perturbations super- imposed upon the mean particle velocity. Beck and Lee investigating the mass flow of * Postgraduate School of Powder Techiiology. f Undergraduate School of Control Engineering November 19731 OK-LIKE METHODS OF PARTICLE SIZE AXALYSIS 283 solids in a solid - liquid flow system designed a conductivity transducer that measured the conductivity of the flowing slurry. This conductivity measurement was achieved by passing an alternating current between the wall of a pipe and an insulated electrode inserted into the solid - liquid system.A known frequency square-wave carrier produced by a constant-voltage source was modulated as large numbers of particles passed through the electical field of the two electrodes. The carrier frequency of the rectification was stripped off by a low-pass filter and either the resultant voltage measured by an integrating voltmeter or the current measured on a milliammeter. These measurements are thus an indication of the fluctuation of the solid velocities about a mean value provided the resistivity and the velocity of the fluid are con- stant. Fig. 1 shows the relationship between the quality measurements of the solid - fluid system and the concentration of the different sized solid particles. 8 - a ‘1 6 - E > + ._ .- I-’ 0 10 20 30 Concentration per cent m/m Fig. 1. The effect of particle size on mass flow meter calibration curve (sand).Transport velocity 5.35 m s-l. A 1400 t o 2000 p m ; B 600 to 1000 pm; C 210 to 300 pm; and D 150 to 180 p m Within a turbulent fluid there are considered to be stresses that arise from the fluctuating disturbances of the mean x y and z velocity components in a system. These are usually termed Reynold or eddy stresses and exist when there is any form of fluctuating disturbance maintaining the flowing fluid in a state of turbulence. Although the physical nature of turbulence and its development is still far from clear Prandtl von Karman and Taylor have used the analogy that like the small-scale random movement of molecules that is used to describe the kinetic theory of gases there is a mean free path for a fluid particle in fluid dynamics.Taylor in particular used the concept that there was an average size of an eddy that could be used as a scale of turbulence. This scale of turbulence can be measured by the correlation of two turbulent velocity components from two positions along the direction of flow where R(y) is the correlation coefficient falling between the limits unityand zero Do and oy are the turbulent component velocity at two points distance y apart and U 2 is the mean velocity of flow. A correlation function is equivalent to unity when the turbulent velocity components are identical but decreases to zero when the turbulent velocity components become increas- ingly dissimilar. This total dissimilarity or zero correlation is achieved either by measuring the velocity components at the same time but at different positions the Lagrangian co- ordinate concept or at different times at the same position the Eulerian co-ordinate concept.The distance or time depending whether the Lagrangian or Eulerian method is used for the 284 OK-LIKE METHODS OF PARTICLE SIZE AXALYSIS [Proc. Soc. Analyt. Chem. correlation function to become zero is then a measure or scale of turbulence in the flowing system. All of the various correlation functions available play an important part in the statistical interpretation of turbulent dynamic systems. When solid particles are present in a flowing turbulent fluid the solid particles try to follow the turbulent motion of the fluid. Owing to the inertia of the solid particles however the larger particles tend to follow only large eddies while small particles can follow both large and small eddies.It is therefore possible to relate the size of the suspended solid following the fluid eddies to the scale of turbulence of the solid particles within those eddies. The scale of solid particle turbulence can be determined in an analogous manner to that of Taylor's scale of turbulence the distance or time of the correlation function to decrease from unity to zero being a measure of turbulence. Associated with any disturbance pattern of flow caused by Reynolds or eddy stresses is that of pressure disturbances. Both the stress and pressure disturbances will do work and enable energy to be transferred from the mean motion of flow to the disturbance velocities and vice uersa. In this kinetic energy concept each turbulent component can be regarded as being made up of fluctuations or oscillations of differing frequencies and amplitudes.The intensity of turbulence can therefore be separated into its harmonic components producing a spectrum of turbulence (Simmons and Salter 1938). Taylor has shown that there is a connection between the spectrum of turbulence and the correlation coefficient. The mean value of C2 may be regarded as being the sum of the con- tributions from all frequencies and that the correlation coefficient and the spectrum of tur- bulence are Fourier transforms of one another 2my m Ry = SF(1z) cos ~ dn 0 u 4 " 27Tny [To U F(n) = -sRy cos - dy where F ( M ) is the distribution of the frequencies n is the number of cycles per second ifre- quency) y is the distance and C is the mean velocity.0.8 - 0.6 c - G? 0.4 0.2 0 20 40 60 Timeips ( x 100) Time:ps ( x 100) Fig. 2. Correlation coefficients as a function of time delay 3 air dust (bclow 100 pm) ; x 150 t o (a) Transport velocity 3.5 in s-l 180 p m ; + 210 t o 300 pm; . 500 to 1000 Fm; and 0 1400 to 2000 p m . and (b) transport velocity 2.1 m s-l Instead of using Lagrangian co-ordinates it is possible to determine a scale of turbulence for eddies or solid particles in terms of time by using auto-correlation and Eulerian co-ordinates. Since the correlation coefficient and frequency spectrum are Fourier transforms of one another if either is measured the other can be calculated. With multi-sized eddies or disturbances the information received by the sensors is the sum of all the contributions from the various disturbances.In order to evaluate these data, November 19731 OS-LINE METHODS OF PARTICLE SIZE ANALYSIS 285 so that when the correlation functions are normalised so as to give an appropriate size of an eddy or solid particle within an eddy complicated computer analysis is required. The normal- isation of the auto-correlation coefficient for large and small disturbances is shown in Fig. 2. Because the frequency spectrum is a Fourier transform of the correlation coefficient this too can be normalised so that the total energy obtained from the large particles is equal to that of the small particles. The range of frequencies for the small disturbances is greater than that for large disturbances. A ratio of the range of frequencies can then be used to differentiate the large and small disturbances and also evaluate the mean particle size of a solid flowing in these disturbances or eddies.* transducer High-pass filter integrating volt meter r - 7 Low-pass filter I Integrating volt meter e / e p f (particle size) Fig. 3. -4rrangement for particle size measurement. X(t) = waveform from flowing solid - liquid suspension m(t) = signal from a.c. conductivity transducer e e = mean square voltage values from high pass and low pass filter respectively X measure of the mean size can be achieved by allowing the normalised signal to be divided into two and to pass through either a high- or low-pass frequency filter both with the same cut-off frequency (Fig. 3). This division results in an inequality in the mean square value of the two signals. The ratio of this inequality is a function which can give a measure of the mean particle size of the flowing slurry. After calibration of the system with particles of known size this inequality can be used in conjunction with a recorder to give a direct reading of particle size.

ISSN:0037-9697    

DOI:10.1039/SA9731000282

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

286 NOTICES [Proc. SOC. Analyt. Chem. Notices THE COLOUR GROUP (GREAT BRITAIN) THE programme of The Colour Group (Great Britain) for 1973-74 includes the following two meetings- December 5th 1973 3 p.m. a t the Physics Department Imperial College Prince Consort Road London S.W.7. “The New Hunter Colorimeter,” by 11. B. Lloyd. “The New ICI Colorimeter,” by 4 . C. Perry. “The Neotec Internal Quality Analyser,” by R. D. Elliott. January 9th 1974 3 p.m, a t the Institute of Ophthalmology Judd Street London “Digital Filtering in an On-line Spectrophotometer Data System,” by F. J. J. Clarke. Further details can be obtained from the Honorary Secretary of the Group Bliss M. B. Halstead Thorn Lighting Ltd. Research and Engineering Laboratories Great Cambridge Road Enfield Mitldlesex EN1 1UL. IVClH 9QS AUGER ELECTRON SPECTROSCOPY NEETIXG IIIARCH 4TH 1974 CLEVELAND OHIO A JfEETmG of those interested in AES (Auger Electron Spectroscopy) and ESCA (Electron Spectroscopy for Chemical Analysis) is being scheduled for March 4th 1974 in Cleveland Ohio during the week of the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (see Proceedings p. 223). Those interested are requested to write to Mr. Joseph F. IVoodruff Research and Tech- nology Armco Steel Corporation Middletown Ohio 45042 U.S.A.

ISSN:0037-9697    

DOI:10.1039/SA973100286b

出版商:RSC    

年代:1973

数据来源: RSC