摘要:

Proceedinas - - - - - - -of the Analytical Division ofThe Chemical Society394041414243436973747576CONTENTSSociety for Analytical ChemistryAnalytical Division Distinguished1977 Award of the Rank HilgerPresentation of the Fourth SACReports of MeetingsSummaries of PapersGold MedalService AwardSpectroscopy PrizeSilver Medal'Fourth International SACConference'Equipment NewsCorrespondenceRank Hilger Spectroscopy PrizeCoursesAnalytical Division DiaryVolume 15 No 2 Pages 39-76 February 197PADSDZ 15(2)39-76(1978)I SSN 0306-1 396February 1978PROCEEDINGSOF THEANALYTICAL DIVISION OF THE CHEMICAL SOCIETYOfficers of the Analytical Divisionof The Chemical SocietyPresidentD. W. WilsonHon. SecretaryP. G.W. CobbSecretaryMiss P. E. HutchinsonHon. Treasurer Hon. Assistant SecretariesJ. K. Foreman D. I. Coomber, O.B.E.; D. C. M. Squirrel1Editor, ProceedingsP. C. WestonProceedings is published by The Chemioal Society.Editorial: The Director of Publications, The Chemical Society, Burlington House, London, W1 V OBN.Telephone 01 -734 9864. Telex 268001.Subscriptions (non-members): The Chemical Society, Distribution Centre, Blackhorse Road,Letchworth, Herts., SG6 1 HN.Non-members can only be supplied with Proceedings as part of a combined subscription with The Analysrand Analytical Abstracts.@ The Chemical Society 1978Annual Reports on AnalyticalAtomic SpectroscopyVOLUME 6,1976This comprehensive and critical report of developments in analytical atomicspectroscopy has been compiled from over 1650 reports received fromworld-wide correspondents who are internationally recognised authorities inthe field and who constitute the Editorial Board. In addition to surveyingdevelopments throughout the world published in national or internationaljournals, a particular aim has been to include less widely accessible reportsfrom local, national and international symposia and conferences concernedwith atomic spectroscopy.Paperbound 282pp 83"x 6" f18 (CS Members fl3.50)(Still available: Vols. 2-5 covering 1 972 to 1975)Obtainable from : The Chemical Society, Distribution Centre,Blackhorse Road, Letchworth, Herts., SG6 1 H

ISSN:0306-1396    

DOI:10.1039/AD97815FX005

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

February, 1978 COURSES 75Analytical Division Diary, March continuedWednesday, 15th, 2.30 p.m.: LondonSpecial Techniques and A tomic SpectroscopyGroups on “Optical Emission Spectro-scopy-The Future. ”“Solids-Metallurgic Applications,” by“Solution Applications,” by S. Greenfield.Introduction : Customer - User’s Views.P. B. Smith.“Spectrophotometers,” by M. Silvester.“Detectors,” by Dr. Schmitz.“Data Handling,” by A. Sloame.Lecture Theatre C, East Chemistry Building,Imperial College, South Kensington,London, S.W.7.Thursday, 16th: LondonJoint Pharmaceutical Analysis Group.Discussion on “Dissolution Testing.”Pharmaceutical Society of Great Britain,1 Lambeth High Street, London SE1 7JN.Analytical Division : Annual General Meeting ;Address by the retiring President, Mr.D. W.Scientific Societies Lecture Theatre, 23 SavileBiennial Formal Dinner: 7 p.m. for 7.30 p.m.The Chemical Society, Burlington House,Friday, 17th: London2.30 p.m.Wilson; 3 p.m.Row, London, W.l.Piccadilly, London, W. 1.Wednesday, 29th, 6.30 p.m. : LondonMicrochemical Methods and Biological MethodsDiscussion on “Enzymatic Methods of Analy-Savoy Tavern, Savoy Street, London, W.C.2.Groups.sis,’’ to be introduced by D. Hall.Thursday, 30th, 2 p.m. : BradfordParticle Size Analysis Group on “Particles inIndustry-Quality Control.”“Pigments and Extenders in Industry-Quality Control,” by W. Carr.“An Investigation into the Quality of Pro-cessed Montmorillonite Using Develop-ments of Standard Quality ControlMethods,” by J.Dunderdale.“Particle Characterisation for Product Speci-fication in the Pharmaceutical Industry,”by J. Sherwood.“Particulate Control with Respect to LampPhosphors,” by W. G. King.“The Effects of Variation in Particle Size. Distribution on the Mineralogy and AppliedProperties of China Clays,” by G. L. Toms.“The Role of Particle Characterisation inDefence Quality Assurance,” by J. E. C.Harris.D4 Main Building, The University, BradfordAnalytical Division DiaryFEBRUARYTuesday, 21st, 4.15 p.m. : LoughboroughMidlands Region, jointly with the Lough-borough University Student ChemicalSociety.“Analytical Chemistry and Drug Meta-bolism,” by A. C. Moffat.Lecture Theatre J .001, University of Tech-nology, Loughborough.Wednesday, 22nd, 6.30 p.m.: LondonMicrochemical Methods Group.A discussion on “The Karl Fischer Deter-mination,” will be introduced by C. A.Watson.Savoy Tavern, Savoy Street, London W.C.2.Thursday, 23rd, 2 p.m.: BristolWestern Region on “Microprocessors-GrowthSpeakers: D. Betteridge, E. L. Dagless, D. A.The University, Bristol.Point in Analytical Instrumentation.”Newton and R. Reeves.Thursday, 23rd, 4.15 p.m.: AberdeenScottish Region, jointly with the Aberdeenand North of Scotland Section of the CSand the Aberdeen University ChemicalSociety.“Food: Do We Really Know What We Eat?”by J . K. Foreman.Tuesday, ZSth, 7.30 p.m. : SwanseaWestern Region, jointly with the South West“The Impact of Modern Chemical MethodsUniversity College, Swansea.Wales Section of the CS.on Archaeology,” by R.E. ’M. Hedges.Tuesday, 28th, 4 p.m.: BelfastNorthern Ireland Sub-Committee.“The Determination of Halogens,” by M. A.Chemistry Department, Queen’s University,Leonard.Belfast.MARCHWednesday, lst, 2.15 p.m.: LondonBiological Methods Group on “Methods ofAssessing the Allergenic Potential of aNew Drug.”Speakers: J. M. Dewdney, H. Amos and P.Kendall.National Institute for Biological Standardsand Control, Holly Hill, London N.W.3.Wednesday, lst, 2 p.m. : MiddlesbroughNorth East Region and Autovnatic MethodsGroup on “Microprocessors in Analysis.”“Viscosity Measurement,” by D. Deans.“Application of Microprocessors to Electro-chemical Analysis,” by W.F. Farrell, Jr.“Future Possibilities of Microprocessor Tech-nology,” by E. L. Daglish.ICI Petrochemicals Division, HeadquartersOffices, Wilton, Middlesbrough, Cleveland.Tuesday, 7th, 2 p.m. : SheffieldElectroanalytical Group.Discussion on “Electrochemical Gas Sensors,”introduced by I. Bergman.Safety and Health Laboratories (Safety inMines Research Establishment), Red Hill,Sheffield.Wednesday, Sth, 2 p.m. : BrightonSouth East Region on “Recent Advances inPharmaceutical Analysis.”“Preparation and Use in Analysis of aPenicillin Enzyme Electrode,” by C. J.Olliff and J. M. Wright.“chromatography of Prostaglandins-GLC,TLC and HPLC,” by D. Sayers.“NMR-Some Recent Pharmaceutical Appli-cations,” by C. P. Richards.“Thin-layer Chromatography on Silica-CoatedRods: An Evaluation of the Iatroscan,”by W. H. C. Shaw.Lecture Theatre No. 1, Ground Floor,Cockcroft Building, Brighton Polytechnic,Moulsecoomb, Brighton.Friday, loth, 2 p.m. : CarlisleNorth West, Scottish and North East Regionson “Developments in PharmaceuticalAnalysis.”“Separation Techniques in PharmaceuticalAnalysis,” by J. E. Fairbrother.“The Analysis of Drugs and Metabolites byHigh Performance Liquid Chromato-graphy,” by Professor J . H. Knox.“Analysis of Drugs and Metabolites by GasChromatography - Mass Spectrometry,” byN. Haskins.“The Analysis of Dosage Forms by SecondDerivative UV - Visible Spectroscopy,” byA. F. Fell.Crown and Mitre Hotel, Carlisle, Cumbria.Wednesday, loth, 6.30 p.m.: ChepstowWestern Region.Discussion on “PCBs-Their Analysis and itsGeorge Hotel, Chepstow.Implications,” introduced by D. Casey.[continued inside back coverPrinted by Heffers Printers Ltd Cambridge Englan

ISSN:0306-1396    

DOI:10.1039/AD97815BX007

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

March, 1978 ANALYTICAL DIVISION DIARY 113Ana I ytical Division Diary, cont i n uedApril, continuedWednesday, 12th, 2 p.m.: Nottingham ’Midlands Region on “Have You Thought ofUsing a Microscope ? ’’Speakers will include I. G. Holden, B.Scarlett and R. Tomlinson, together withcontributions from McCrone ResearchAssociates Ltd., E. Leitz (Instruments)Ltd., Jeol (UK) Ltd. and Vickers Instru-ments Ltd.Lecture Theatre, The Boots Co. Ltd., Penny-foot Street, Nottingham.Thursday, 13th, 1.45 pm.: BlackburnNorth West Region, jointly with the Lancasterand District Section of the CS, BlackburnCollege of Technology Chemical Society andthe Association of Public Analysts.“The Analysis and Quality Control of Beersand Lagers during and after Processing,’’by P.M. Carpenter.“The Quality Assessment of Wine,” by MissA. J . Fishlock.College of Technology and Design, Blackburn.Tuesday, 25th, 4 p.m. : BelfastNorthern Ireland Sub-Committee.“Microprocessors in Analytical Chemistry,”by T. B. Pierce.Chemistry Department, The Queen’s Univer-sity, Belfast.Wednesday, 26th, 2 p.m.: TauntonWestern Region on “EEC Influence on FoodSpeakers: R. Sawyer, F. C. Shenton and G.Castle Hotel, Taunton.Contaminants Analysis.”Telling.Wednesday, 26th, 10.30 a.m. : Southend-on-Sea.East Anglia Region, jointly with the EasternEngland Region of the Industrial Divisionand the Essex Section of the CS/RIC on“Analytical Methods-Ultimate Sensitivity.”“Sensitivity in Trace Organic Analysis-AMoving Target,” by D.R. Hoar and G. M.Telling.“Sensitivity of Radiochemical Techniques, ”by M. A. Crook.“The Use of Atomic Absorption Spectroscopyfor the Determination of Impurities in HighPurity Inorganic Chemicals,” by G. L.Everett.“The X-ray Spectrophotometer as a TraceAnalysis Instrument,” by D. A. Pantony.Paper from the Water Research Centre,Marlow.College of Arts and Technology, CaernarvonRoad, Southend-on-Sea.CS ATOMIC SPECTROSCOPY GROUPinvite applications for the1978 RANK HILGER SPECTROSCOPY PRIZEThe successful candidate will receive a prize to the value of f75, part of which is tobe used for the purchase of a book(s) for presentation at the Group’s AGM. Theaward will be judged on the basis of the candidate‘s contribution to analyticalatomic spectroscopy.The work need not be theoretical but could cover applic-ations, instrumental modification, accessories, improvements in technique or datahandling. The contribution need not have been published and candidate’s wisheswith respect to publication will be respected.Intending candidates should (1) be under 30 years of age on December 31st,1978; (2) be resident in the United Kingdom; (3) submit, before May 31 st, 1978,a summary of about 500 words, describing their contribution to the theory orpractice of atomic spectroscopy. The summary should be endorsed--by a seniormember of the establishment in which the candidate is employed.Applications should be addressed to the Honorary Assistant Secretary, AtomicSpectroscopy Group, Analytical Division, The Chemical Society, Burlington House,London, W1 V OBNAnalytical Division Diary“Some Problems of Conducting PhysiologicalInvestigations in Hyperbaric Environ-ments,” by R.Carlyle.Wednesday, Gth, 10 a.m.-Seventh Theophilus Redwood Lecture: “Ana-lysis-the Link Between Science andTechnology,” by T. B. Pierce.“Historical Lecture on Analytical Chem-istry,” by W. A. Campbell (HistoricalChemistry Group Session).MARCHWednesday, 29th, 6.30 p.m.: London“Toxicity of Metals,” by I. J. T. Davies.“The Sampling and Analysis of ParticulateFumes and Pollutant Gases in the WeldingField,” by Janet Moreton.“Measuring Personal Exposures to Vapoursin the Petroleum and Petrochemical Indus-tries,” by D. T. Coker.Thursday, 6th, 9.30 a.m.-Microchemical Methods and Biological MethodsDiscussion on “Enzymatic Methods of Analy-Savoy Tavern, Savoy Street, London, W.C.2.Groups.sis,” to be introduced by D.Hall.Late DeliveryThe Society apologises for the lated eliveryof Procecdings in recent months,which has been caused by distributionproblems outside the control of theEditorial office and the printer. It ishoped that these problems have now beenovercome and a normal schedule can nowbe resumed.Thursday, 30th, 2 p.m.: BradfordParticle Size Analysis Group on “Particles inIndustry-Quality Control.”“Pigments and Extenders in Industry-Quality Control,” by W. Carr.“An Investigation into the Quality of Pro-cessed Montmorillonite Using Develop-ments of Standard Quality ControlMethods,” by J.Dunderdale.“Particle Characterisation for Product Speci-fication in the Pharmaceutical Industry,”by J. Shenvood.“Particulate Control with Respect to LampPhosphors,” by W. G. King.“The Effects of Variation in Particle SizeDistribution on the Mineralogy and AppliedProperties of China Clays,” by G. L. Toms.“The Role of Particle Characterisation inDefence Quality Assurance,” by J. E. C.Harris.D4 Main Building, The University, Bradford.“Scientific Instruments in EnvironmentalMonitoring,” by R. S. Barratt.“The Use of Ultrasonic Instruments in Chenii-cal Plant Containing Hazardous Materials,”by R. C. Asher.“The Analysis of Organic Peroxides,” byN. J. Chalkley and C. Whalley.“Problems in the Analysis of HydrofluoricAcid,” by F. Shaw and J. W. Ogleby.The University, Liverpool.Tuesday, 4th, 4 p.m.: GlasgawScottish Region, jointly with the InorganicSection Colloquium Group of the Univer-sity of Strathclyde.“Spectral and Spatial Studies of the Induc-tively Coupled Plasma with PhotodiodeArray Spectrometers,” by Professor G.Horlick.Room C129, Thomas Graham Building,University of Strathclyde, CathedralStreet, Glasgow

ISSN:0306-1396    

DOI:10.1039/AD97815BX011

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Vol. 15 No. 2 Proceedings February 1978 of the Analytical Division of the Chemical Society Society for Analytical Chemistry Gold Medal As announced in the November issue of Proceedings (p. 313), the thirteenth Society for Analytical Chemistry Gold Medal has been awarded to Dr. J . K. Foreman. Jim Foreman was born near Ashford, Kent, in 1928. The start of his secondary education a t the local grammar school coincided with the outbreak of World War 11; a gas mask was compulsory hand luggage and attendance for lessons was limited to one afternoon each week, during which he was given sufficient homework to last, supposedly, for the rest of the week.Full-time teaching shortly became possible by evacuating the school to Witney and making use of three local schools on different days of the week.He returned to Ashford after a year and encountered his first taste of bureaucracy, being summoned before the Education Authorities to explain why he had foresaken the assumed peace of Witney (Coventry was being bombed a t the time !) for the aerial battlegrounds of Kent. Fortunately, many other pupils had done the same and the authorities yielded to the weight of numbers. In 1946 he competed unsuccessfully with returning ex-servicemen for university places.Rather reluctantly he accepted a place at the Medway Technical College although, in the event, the standard of teaching proved to be high and he graduated in 1949 with first-class honours in chemistry. From 1949 to 1951 he worked for the Chcmical Inspectorate a t Woolwich Arsenal in the atomic-energy unit, where he was a member of a team developing methods for determining trace impurities in graphite and beryllium.It was the start of 27 years of varied and challenging work in analytical chemistry, for which he was awarded a DSc by London University in 1976. The 24 years spent at Woolwich were interrupted in 1950 when he was seconded for 6 months to work with Professor Britton a t the (then) University College of the South West a t Exeter.Late in 1951 came the expected ultimatum: “continue the atomic energy work a t Windscale or start your National Service.” The choice was not difficult to make and he almost became a naturalised “marrer” by spending the next 14 years in West Cumberland. In retrospect they proved to be challenging and formative years; rarely does one have the opportunity to join an organisation in its most rapidly growing period.From 1957 until he migrated South in 1966 he was head of the Analytical Research and Development team, serving both the reactors and fuel reprocessing plants. His three main analytical interests, physical methods of analy- sis, separation techniques and automation, developed during this period.The last received its impetus in the early 1960s from his participa- tion in the design and commissioning of a new and higwy instrumented fuel reprocessing plant. He was able to extend this interest to the field of laboratory automation a t the Laboratory of the Government Chemist. His book “Automatic Chemical Analysis,’’ written with Peter Stock- 3940 AD DISTINGUISHED SERVICE AWARD Proc. Analyt.Div. Chem. SOC. w7ell, was published in 1975. Dr. Foreman joined the Laboratory of the Government Chemist in February 1966, being appointed Superintendent of a newly formed Research Division which was set up on the recommendation of a Committee of Inquiry headed by Sir Patrick Linstead. He held the post for 4 years, during which time the Research Division made notable advances in the deter- mination of carcinogenic N-nitrosamines, eluci- dation of the chemistry of dental silicate cements and laboratory automation.Following a brief spell as Senior Superintendent (Environmental Chemistry) he was appointed Deputy Govern- ment Chemist in October 1970. For 12 years he was a member of the Standard Technical Com- mittee on Synthetic Detergents and he served on the Toxicity Sub-committee, and its prede- cessor the Pharmacology Sub-committee, operated jointly by the Department of Health and Social Security and the Ministry of Agri- culture, Fisheries and Food.In October 1977 he was somewhat surprised to be appointed Deputy Director (B) at the National Physical Laboratory. Here, chemis- try forms only a small part of his remit and analytical chemistry even less ; his other responsibilities cover materials applications, numerical analysis and computer science and include the “marketing” of the considerable research capability of NPL.His introduction to SAC committees was through the AMC Fluorine Sub-committee, which he later chaired. He was a founder member and subsequently Chairman of the Education and Training Group and he has also served on the Committee of the Special Tech- niques Group. He was elected to Council in 1971 and appointed Honorary Treasurer of the SAC and CS AD in 1973. In this capacity he was centrally involved in the negotiations leading to the amalgamation of the SAC with the Chemical Society and subsequently with the tortuous process of putting SAC into liquidation. I t has been, on occasions, a complex and demanding office but always a satisfying one.

ISSN:0306-1396    

DOI:10.1039/AD9781500039

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

40 AD DISTINGUISHED SERVICE AWARD Proc. Analyt. Div. Chem. SOC. Analytical Division Distinguished Service Award As announced in the November issue of Proceedings (p. 314), the third Distinguished Service Award of the CS Analytical Division has been conferred on Mr. H. E. Brookes, as a tribute to the numerous contributions he has made over many years to the Society for Analytical Chemistry and, more recently, to the Analytical Division.Company in 1930 under A. D. Powell and J. Eggleston (later to become Honorary Secretary of the Scottish Section of the SAC). In those days only the affluent and the brilliant were able to study at a university and so he eventually obtained a London University external degree in 1941 after attendance at Nottingham University Evening Classes. The award of ARIC followed in 1950 and FRIC in 1955.From 1939 to 1949 he was engaged in the analysis of drugs, fine chemicals and galenicals, as well as in the development of new products. He returned to analysis exclusively as section head in the Pharmaceutical Division of the Standards Department under Dr. D. C. Garratt as Chief Analyst. He later became head successively of the Pharmaceutical and the Chemical Divisions.In 1966 he moved to head of Standards Office, a Division of Quality Control in the Boots Company. The office is concerned principally with the maintenance of quality of the Com- pany’s own brand of consumer goods from Harold E. Brookes was educated at The factory to consumer and the acceptance of the Mundella School, Nottingham, joining the quality of products by the consumer.Even Analytical Department of the Boots Pure Drug though his responsibilities are primarily adminis-February, 1978 trative, the very wide range of manufactured merchandise covered, and hence the variety of potential problems, ensures that he is frequently involved with laboratory analytical matters both externally and internally.Although having joined the then Society of Public Analysts and Other Analytical Chemists in 1944, it was not until 1950, with the encour- agement of Dr. Garratt, that a more active part was taken in the Society. Mr. Brookes has now served as a member of Council on six occasions, including one spell as a Vice-chairman. He has been a member of the now defunct Publications Committee (its place being taken by The Analyst Editorial Committee), the Programmes, Finance and Group Policy and Relations Committees, and a member of the 1968 SAC Conference Executive.In the Midlands Section (now Region) he has been a member of the Midlands Region Com- mittee innumerable times and is a past Chair- man. He was Vice-chairman of the Birming- ham International Symposium in 1969, as well as being Chairman of the Local (Midlands Region) SAC Conference 1977 Committee; for this last event he was also a member of the SAC Conference Executive Committee.He has served on the Royal Institute of Chemistry Council and is, at present, Chairman of the RIC Midlands Region Committee. Other committees of which he has been a member include com- mittees of the British Pharmacopoeia, British Pharmaceutical Codex and the British Standards Institution. Mr. Brookes has also served on the Essential Oils Sub-committee of the Analytical Methods Committee and the Essential Oils Committee of the ISO. His hobbies include sailing-dinghy racing and music. 1977 RANK HILGER SPECTROSCOPY PRIZE 41

ISSN:0306-1396    

DOI:10.1039/AD9781500040

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

February, 1978 1977 RANK HILGER SPECTROSCOPY PRIZE 41 1971 and during this time he obtained ONC, HNC and GradRIC Part I. He then moved to Kingston Polytechnic in order to obtain his GradRIC Part 11, following which (in 1972) he joined the staff of the Metropolitan Police Forensic Science Laboratory. Since 1972, he has been carrying out research under the auspices of Imperial College, London, in order to obtain a PhD degree.The original internal Supervisor was Professor T. S. West, but on his appointment as Director of the Macaulay Institute for Soil Research, the supervision was transferred to Dr. G. F. Kirkbright. The Supervisor a t the Metropolitan Police Forensic Science Laboratory is Dr. R. L. Williams. Mr. Wall has principally been concerned with atomic-absorption spectroscopy and flame- emission and d.c.-arc emission spectrography.The work of the Forensic Laboratory has led him to study the determination of thallium in urine by atomic-absorption spectroscopy and emission spectrography, the determination of six elements in glass fragments by emission spectrography and the determination of lead, cobalt and zinc in paint flakes by use of electrothermal atomisation techniques.Presentation of the Fourth SAC Silver Medal The fourth Society for Analytical Chemistry Silver Medal was awarded to Dr. J. S. Hislop at a meeting of the Analytical Division held at the Scientific Societies Lecture Theatre, 23 Savile Row, London, W.l, on December 7th, 1977. A summary of the Silver Medal Lecture will appear in a future issue of Pyoceedings.Bio- graphical notes on Dr. Hislop appeared in Proceedings, 1977, 14, 50. 1977 Award of the Rank Hilger Spectroscopy Prize The 1977 prize was awarded to Mr. C. D. Wall of the Metropolitan Police Forensic Science Lab- oratories at the Annual General Meeting of the CS Atomic Spectroscopy Group, held on December 6th, 1977. The award has been made for work on “Research and Development in Forensic Applications of Atomic Spectro- copy.^' Mr.Wall presented a paper at the Fifth ARAAS Symposium, which was held in Sheffield in January, 1978. chemicals Ltd., of Bournemouth, from 1966- Colin was Wessex Bio- Presentation of the fourth SAC Silver Medal hy the President, MY. D. W . Wilson, to Dr. J . S. Hislop (R).42 SAC SILVER MEDAL PYOC. Analyt. Div. Chem. SOC. Society for Analytica I Chemistry Silver Medal On the recommendation of its Honours Com- mittee, the Council of the Analytical Division, at its meeting on December 7th, 1977, awarded the fifth Society for Analytical Chemistry Silver Medal to Dr. C . W. Fuller of Tioxide International Ltd., Stockton on Tees, Cleveland.

ISSN:0306-1396    

DOI:10.1039/AD9781500041

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

42 SAC SILVER MEDAL PYOC. Analyt. Div. Chem. SOC. 16th, 1977, at Levington Research Station, Fisons Ltd., Ipswich. The Chair was taken by the Chairman of the Region, Dr. D. Simpson. The following office bearers were elected for the forthcoming year: Chairman-Dr. D. Simpson. Vice-Chairman-Mr J . Dutton. Honorary Sec- retary awd Treasurer-Mr. A. G. Croft, Spillers Ltd., Research and Technology Centre, Station Road, Cambridge, CB1 2JN.Members of Committee-Dr. D. Christopher, Mr. D. J . Evans, Mr. A. W. Hartley, Mr. G. M. Telling and Dr. R. Whiteoak. Dr. A. N. Worden and Mr. C. E. Waterhouse were re-appointed as Honorary Auditors. Reports of Meetings Scottish Region The forty-third Annual General Meeting of the Region was held at 5 p.m. on Friday, November 4th, 1977, at the University of Strathclyde, Cathedral Street, Glasgow.The Chair was taken by the Chairman of the Region, Dr. A. M. Ure. The following office bearers were elected for the forthcoming year: Chairman-Dr. A. M. Ure. Vice-Chairman-Dr. G. C. Cochrane. Honorary Secretary-Mr. A. F. Fell, Department of Pharmacy, Heriot-Watt University, 79 Grassmarket, Edinburgh. Honorary Treasurer -Dr.J . E. Whitley. Honorary Assistant Secretary-Dr. D. E. Wells. Menzbevs of Committee-Dr. P. Bowden, Dr. G. S. Fell, Dr. M. Masson, Dr. J . M. Ottaway, Dr. J. W. Wells and Dr. P. R. Wood. Dr. B. W. East and Mr. J. S. Foster were re-appointed as Honorary Auditors. Midlands Region The twenty-third Annual General Meeting of the Region was held at 6.15 p-m. on Wednesday, November 23rd, 1977, at the Polytechnic, Wolverhampton.The Chair was taken by the Chairman of the Region, Dr. A. Townshend. The following office bearers were elected for the forthcoming year: Chairman-Mr. D. M. Peake. Vice-ChairmanDr. D. N. Raine. Honorary Secretary-Dr. R. S. Barratt, Department of Construction and Environmental Health, University of Aston in Birmingham, Gosta Green, Birmingham, B4 7ET.Honorary Treasurer-Dr. J. N. Miller. Members of Committee-Dr. R. K. Bramley, Dr. A. G. Fogg, Dr. G. C . Gidley, Mr. S. Greenfield, Mr. J. E. W. Tillman and Dr. J. Tyson. Mr. W. G. Harris and Mr. H. Pugh were re-appointed as Honorary Auditors. East Anglia Region The tenth Annual General Meeting of the Region was held at 2 p.m. on Wednesday, November Northern Ireland Sub-committee The first Annual General Meeting of the Northern Ireland Sub-Committee of the Scottish Region was held at 5.15 p.m.on Thursday, October 13th, 1977, at The Queen’s University, Belfast. The Chair was taken by the Chairman of the Sub-committee, Professor D. T. Burns. The following office bearers were approved for the forthcoming year : Chairman-Professor D. T. Burns.Vice-Chairman-Mr. R. A. Hall. Honora.ry Secretary and Treasurer-Mr. W. J. Swindall, Department of Chemistry, David Keir Building, Queen’s University, Belfast, BT9 5AG. Members of Committee-Dr. P. W. Darby, Dr. M. A. Leonard and Dr. G. Svehla. Biological Methods Group The thirty-third Annual General Meeting of the Group was held at 6.30p.m. on Thursday, November 17th, 1977, at the Chemical Society, Burlington House, London, W.l. The Chair was taken by the Chairman of the Group, Dr.J . A. Holgate. The following office bearers were elected for the forthcoming year : Chairman-Dr. J . A. Holgate. Vice-Chairman -Dr. B. A. Wills. Honorary Secretary- Mr. F. W. Webb, Central Analytical Labora- tories (Biological), The Wellcome Foundation, Temple Hill, Dartford, Kent.Honorary Treasurer-Dr. L. Singleton. Honorary Assis- tant Secretary-Dr. A. H. Thomas. Members of CommitteeMr. V. J. Birkinshaw, Dr. M. E. Duncan, Mr. D. J . N. Hossack, Miss F, N. Mulholland and Mrs. M. Pratt. Dr. J . H. Hamence and Dr. M. W. Parkes were re- appointed as Honorary Auditors. Automatic Methods Group The twelfth Annual General Meeting of the Group was held at 2 p.m.on Thursday, Novem- ber 24th, 1977, in the Chemistry Department, Imperial College, London, S.W.7. The Chair was taken by the Chairman of the Group,February, 1978 REPORTS OF MEETINGS 43 Mr. D. C. M. Squirrell. The following office bearers were elected for the forthcoming year : Chairman-Dr. P. B. Stockwell. Vice-Chair- man-Dr. B. Fleet. Honorary Secretary- Mr. D. G. Porter, Laboratory of the Government Chemist, Cornwall House, Stamford Street, London, SE1 9NQ.Honorary Treasurer- Mr. K. H. Wall. Honorary Assistant Secretary -Mr. J . L. Martin. Members of Committee- Dr. D. Betteridge, Mr. C. L. Denton, Mr. F. R. B. Fearn, Mr. S. R. Hill, Mr. D. C. M. Squirrel1 and Mr. J . Stevens. Dr. J . E. Page and Mr. R. Sawyer were appointed as Honorary Auditors. Radiochemical Methods Group The eleventh Annual General Meeting of the Group was held at 2.05p.m.on Thursday, November 17th, 1977, a t AERE, Harwell, Didcot, Oxon. The Chair was taken by the Chairman of the Group, Dr. G. W. A. Newton. The following office bearers were elected for the forthcoming year: Chairman-Dr. G. W. A. Newton. Vice-Chairman-Mr. G. A. Sutton. Honorary Secretary-Mr. M. A. Crook, Depart- ment of Chemistry and Polymer Technology, Polytechnic of the South Bank, Borough Road, London, SE1 OAA. Honorary Treasurer- Mr . D. A. Ginger. Honorary A sszstant Secretary -Mr. J . W. McMillan. Membevs of Committee- Dr. G. Ayrey, Mr. T. H. Bates, Professor J. H. Fremlin, Mr. J . A. B. Gibson, Dr. D. M. Taylor and Dr. A. R. Ware. Mr. G. Farmer and Dr. P. Johnson were re-appointed as Honorary Audi- tors.

ISSN:0306-1396    

DOI:10.1039/AD9781500042

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

February, 1978 REPORTS OF MEETINGS 43 Fourth International SAC Conference The following are summaries of eleven of the papers and posters presented in the Sessions on “Chromatography and Separation,” “Pollution and Environmental Control,” “Microchemical Techniques,” “Computer Techniques,” “Spectrometric Methods,” “Analysis in the Life Sciences” and “Atomic and Molecular Spectrometry” at the Conference, which was held on July 17th-22nd, 1977, in Birmingham.Further summaries of papers and posters from other Sessions at this Conference will appear in a future issue of Proceedings. Summaries of nine of the papers given at the Conference appeared in the January issue of Proceedings (p. 1). Contributions to the Ring Oven Technique-Enzymatic Analytical Methods Herbert Weisz and 1.Vereno” Chemistry Laboratory, University of Fveiburg i . Rv., West Germany The ring oven method, first published in 1954, is basically a special kind of spot analysis on filter-paper, in which the substances to be identified or determined are concentrated in the form of well defined circular lines as a result of the heat barrier action of the central bore- hole of the ring oven heating block.This method has found numerous applications in nearly all fields of analytical chemistry. More than 350 publications have so far appeared on this technique. Of special interest is the use of the technique in air-pollution studies and in radiochemical ana1ysis.l In recent years, enzymatic reactions have found an increasingly important role in analytical chemistry.It seemed interesting to investigate how far such methods can be carried out with the aid of the ring oven technique. Two basic difficulties had to be overcome in order to combine the two methods. Firstly, whereas the usual quantitative ring colorimetry methods are independent of time (the colour intensity of the unknown ring is merely com- pared with that of standard rings), with enzymatic kinetic methods, the reaction time plays the decisive role.This problem has already been solved for inorganic catalysts by combining the simultaneous comparison method with ring oven spot colorimetry in the segment technique, as we have called it.2 The second difficulty is, of course, that enzymes cannot be transferred to the ring zone at the usual temperature of the ring oven (110 “C) without being deactivated.Three different techniques have been developed to solve this problem of determining enzymes, inhibitors and substrates. * Manuscript read by W. Meiners.44 FOURTH INTERNATIONAL SAC CONFERENCE Proc. Analyt. Div. Chem. SOC. A possibility of avoiding the heat barrier is offered by an “adsorption barrier.”3 The ring oven is used only for the preparation of a narrow ring zone consisting of a suitable adsorbent; the enzyme itself is then transferred to the adsorption zone without the use of the ring oven.For our purpose, a barium sulphate adsorption zone proved best. Barium chloride (about 350pg) is washed with water on the hot ring oven into the ring zone; the filter-paper is bathed in 0.05 M sulphuric acid, rinsed well and dried.Filters thus prepared can be stored for a long time. On three points concentric around the middle of the filter-paper, bearing such a narrow barium sulphate adsorption zone, one drop each (1 p1) of the sample solution and of two standard solutions out of the six (I, 11, IV, VI, VIII and X) of the same enzyme are placed to form an equilateral triangle.The filter-paper is placed on a suitable support and, without the use of the ring oven, these three spots are washed into the adsorption zone with a suitable solvent; the three different enzyme spots are thus concentrated in the form of three sharply outlined circular segments within the adsorption zone. A solution of the necessary substrate is sprayed on to the filter-paper and the reaction of the enzyme with the substrate is started simultaneously in all three segments under identical conditions.The order of the changes of colour or fluorescence in the three segments is observed and from this order it is possible to conclude whether the activity of the enzyme to be determined is higher or lower than that of the two standard solutions, or if it is in between.After two further steps with logically selected concentrations of standard solution it is possible to evaluate the activity of the unknown solution. To achieve higher accuracy, two more determinations with different drop numbers of the unknown enzyme solution are carried out. Instead of spraying the substrate on the paper, it is more economical to press it on with a paper ring (5 mm in width) moistened with the substrate solution (100 p1, 0.02 M), fully covering the three segments.The filter and paper ring are placed between two glass plates and gentle pressure is applied by hand. Under the ultraviolet lamp, the appearance of sharp green fluorescent segments is observed. This method can also be used for the determination of inhibitors, if the inhibited enzyme can actually be transferred to the adsorption zone.On all three spots are placed equal activities of the enzyme and three different concentrations of the inhibitor, namely the sample and two standards, and, after a suitable incubation time, these spots are transferred to the adsorption zone. This technique with the adsorption zone can only be applied, of course, if the enzyme to be determined really arrives in the adsorption barrier by migration through the fibres of the filter-paper.If this is not the case, another procedure is needed: the reaction between the enzyme and the substrate must be done in the middle part of the filter-paper. Enzyme and substrate are placed on three points concentric around the middle of the round filter- paper. The three spots contain different activities of the enzyme, namely the unknown and two standards. Consequently, different amounts of substrate will have reacted within a given fixed time, that is to say, until the paper is dried.The different amounts of reaction product thus formed within the three spots are con- centrated in three segments on the hot ring oven in the usual way. From the different intensities of the three segments at that time (and not from the order of their appearance) the concentration of the unknown enzyme solution is evaluated.The general procedure, the subsequent steps with logically selected standard concentrations and the additional evaluations with different drop numbers of the unknown solution are the same as was described above for the adsorption ring procedure. This is the procedure for all of the other determinations to be discussed here. Some insecticides can be determined by their inhibition of a suitable enzyme (acetyl- cholinesterase) .The first method mentioned, using the adsorption zone, is applicable only if the enzyme can be eluted into the adsorption zone. The second method described is only applicable when a thermally stable product is formed that can be transferred to the ring zone on the hot ring oven.If neither of these conditions is fulfilled in a certain enzymatic system, the enzyme itself cannot be determined. Nevertheless, inhibitors and substrates can be determined if the enzyme is added directly to the segments within the ring zone. The sample is transferred to the ring zone and an Substrates can also be determined.Fe bmary , 1978 FOURTH INTERNATIONAL SAC CONFERENCE 45 enzyme solution is sprayed on to all three segments simultaneously to start the reaction, or more economically, the paper ring described above is used.The paper ring is moistened with the enzyme solution and is pressed on to the filter-paper covering the three segments.Table I gives a number of examples for the determination of some enzymes, inhibitors and substrates, carried out with one of the three methods4 Me th o d * A A B €3 B A B C C B C TABLE I EXAMPLES OF DETERMINATIONS COMPOUNDS Enzymes Phosphatase H yaluronidase Acetylcholinesterase Iipase Alcohol dehydrogenase 4-Methylumbelliferyl phosphate Indoxyl acetate Indoxyl acetate 4-Methylumbelliferone heptanoate Ethanol + NADf Inhibitors Copper Hyal nronidase Insecticides : carbaryl, paraoxon Acetylcholinesterase Herbicides : 2,4-D, mecoprop, bentazon Fungicide : phenylmercuryacetate Urease Molybdenum, beryllium Phosphatase Substrates Ethanol Glucose Alcohol dehyclrogenase Glucose oxidase *A, Adsorption zone on the filter-paper; €3, reaction in the middle of the filter-paper; C, direct addition of enzyme to the segments.We did not expect to improve existing methods of enzymatic analysis but intended merely to show how far the simple ring oven can be applied even in this specialised field of analysis. References 1. Weisz, H., “Microanalysis by the Ring Oven Technique,’’ Second Edition, Pergamon Press, Oxford, 1970. 2. 3. 4. Weisz, H., Pantel, S., and Vereno, I., Mikrochim.Acta, 1976, 11, 287. Weisz, H., and Abe, S., MiRrochim. A d a , 1970, 1054. Weisz, H., and Vereno, I., Analytica Chim. A d a , 1977, 91, 229. Trace Analysis Without Matrix Effect Pre-concentration of Phos- phorus in a Solid-state Reaction Z. G. Szabo and 1. Konkoly Thege Institute 0-f INorganic and Analytical Chemistry, I.. ECtuOs Univcrsity, Budapest, Hungary The pre-concentration of components to be determined in a large amount of matrix is increasingly necessary in trace analysis.Pre-concentration in the solid phase can be regarded as a new procedure that favourably expands the possibilities of separation. For example, trace amounts of silicon in alumina can be converted into silicon tetrafluoride after mixing with a slight excess of ammonium fluoride and, after collection in a small amount of sodium hydroxide solution, this can easily be measured spectrophotometrically as molybdosilicic acid.l In this paper we report investigations concerning the pre-concentration and separation of the very small phosphorus content of metals and salts.The principle of the method is completely analogous to that applied to the determination of silicon.In this instance also the preconcentration was carried out in the solid phase. A compound usually containing phosphorus in its highest oxidation state should be reduced quantitatively in order to obtain phosphorus( -111). Magnesium was chosen as the reducing agent.2 The phosphide formed reacts with water t o yield phosphine, which is distilled off and collected in a solution of an oxidising agent, thus separating the phosphorus from the main46 FOURTH INTERNATIONAL SAC CONFERENCE Proc.Analyt. Div. Chem. SOC. components. The usual spectrophotometric determination for phosphorus is then carried out. Calcium phosphate was chosen as a model material, and the over-all equation of the reduction is the following : Ca,(PO,), + 8Mg = Ca,P, + 8Mg0 To collect the phosphine formed on hydrolysis, silver nitrate solution can be used and the amount of phosphine determined either from the amount of silver precipitated or from the excess of silver ions.In most instances, however, the more sensitive spectrophotometric procedure was applied. Experimental and Discussion A mixture of calcium phosphate and magnesium powder was prepared, which corresponds to an 8-fold excess of the latter according to the stoicheiometric equation given above.Reduction of the phosphate was carried out in a horizontal tube furnace. It is of crucial importance that the reduction be carried out in a completely inert atmosphere, as the metal phosphide reacts rapidly with oxygen and water. The pre-heated furnace was flushed with purified argon for half an hour while the small Morgan boat containing the materials was kept in the outer part of the furnace at room temperature.Subsequently it was pushed into the high-temperature region. After reduction, the sample, already cooled to room temperature, was carefully taken out and the boat and contents were dropped as quickly as possible into the small distilling apparatus filled with carbon dioxide.The optimum temperature of the reduction was found to be 560 "C, which is consistent with the value obtained as a result of differential scanning calorimetry investigations. The duration of the reduction was 60 min. Following the reduction, water was released drop by drop from the adapter, containing a bubble-free water column, into the distillation flask.A 100-ml measuring cylinder was used as the receiving flask, in which were placed 25 ml of 10% sodium hydroxide solution and sufficient bromine solution for the colour to remain yellow. Distillation was carried on until approximately 75 ml of solution were collected in the receiving flask. The distillate was acidified with concentrated hydrochloric acid and evaporated prior to spectrophotometric determination.The residue in the distillation flask was investigated several times to determine whether or not it still contained phosphorus as phosphate. Table I shows the results obtained by this method. Thus, the method can be applied to samples containing a large amount of inert material. TABLE I RECOVERY OF PHOSPHORUS AFTER REDUCTION OF PHOSPHATE Phosphine collected in NaOH + Br, solution.Amount of calcium phosphate - magnesium Recovery (1 + 8) mixture taken/g Temperature/"C of phosphate, yo 0.101 3 400 9.4 0.100 0 414 7.0 0.100 0 530 78.2 0.100 5 530 81.0 0.100 0 545 92.4 0.097 4 550 89.9 0.103 8 550 90.3 0.100 4 560 102.6 0.100 1 560 102.9 0.100 2 560 100.0 0.100 1 560 los.s 0.100 0 560 101.0" 0.050 2 560 102.9 0.100 2 4- 0.048 3 6 of CaSO, 56C 102.0 * Phosphine collected in 0.05 N AgXO, solution.February, 1978 FOURTH INTERNATIONAL SAC CONFERENCE 47 The phosphorus in alloys is already present in the oxidation state -111.If this phosphide is soluble in a non-oxidising acid the procedure is as simple as described above. However, some alloys, containing silicon, molybdenum, tungsten, etc., are soluble only in oxidising acids, such as concentrated nitric acid.In these instances, after dissolution, the sample must be evaporated and the solid residue treated as above in order to avoid the interfering effect of the matrix. References 1. 2 . Szabb, Z. G., Zapp, E. I?, and Perczel, S., Microchim. Acta, 1971, 167. Vogel, A. I., “Macro and Semimicro Qualitative Inorganic Analysis,” Fourth Edition, Longman’s Green and Co., London, 1953, p.388. Microcomputers in Analytical Chemistry M. E. Jones, G. C. Gidley” and R. M. Averill Unilever Research, Colworthl Welwyn Laboratory, Unilever Limited, Colworth House, Shambrook, Bedford, MK44 1LQ Despite their importance, several areas of routine analysis such as moisture analysis, pH monitoring, routine atomic-absorption spectrophotometry and nitrogen determination seem to have escaped the attention of the “packaged” system manufacturer.This paper reports on work currently in progress at Unilever research laboratories, a large multi-disciplinary food research centre, on the utilisation of one of the more recent desk-top computers to the process- ing of data from several analytical instruments.These instruments, electronic balances, atomic-absorption spectrometers, chloride meters, etc., are, in general, characterised by their slow (operator-limited) data rate. Our goal is to provide a local data processing capability, which is both flexible and responsive to users requirements while also being cost effective and allowing users with no great expertise in computer programming to cater for their own requirements.A major consideration when providing data processing facilities within a laboratory is whether to make use of an existing centralised computer facility or to provide a local data processing capability. There is usually considerable pressure to adopt the former solution and it is certainly true that in the laboratory, as in the world at large, the fraught issue of centralisa- tion verszbs decentralisation arises. There are, of course, valid arguments for both sides and it is the case that these two approaches are not mutually exclusive.We have opted for the localised approach, which is, however, linked to the central computer system in order to provide a hierarchical data-collection capability that gives the best of both worlds.Flexibility is considered to be of major importance because it is in the nature of the work that day-to-day changes are required. The analyst, as it is he alone who fully understands his own requirements, is probably the best person to cater for his own needs and thus write his own computer program. However, this level of self-sufficiency can only be fostered by the availability of an easily comprehensible system.Also, users require to be able to obtain access to processed data files, correct data entries, enter sample codes, obtain a listing, run a given method, etc. All of these facilities should entail a minimum of overheads in terms of communicating with the system. The level of flexibility and responsiveness implied by these requirements is attained with the system discussed, which embodies a Hewlett-Packard HP9825A computer system supporting HPL, a programming language having much in common with BASIC. The provision of a scientifically orientated language such as BASIC was seen to be an essential pre-requisite to encouraging and promoting this approach. BASIC imposes fewer restrictions on its use than FORTRAN, is easy to learn and has gained wide acceptance in schools and educational establishments.Thus, the analyst’s first line of attack should be to solve his own programming problems. This approach should be possible in most instances without recourse to the resources of the centralised computer group (who would, of course, have to devote time and effort into exploring the nature of the problem, often ab initio). Of course, for less tractable problems specialist advice may be required. *To whom any correspondence should be addressed.48 FOURTH INTERNATIONAL SAC CONFERENCE Proc.Amalyt. Div. Chem. SOC. Desk-top computers, despite offering many sophisticated features, such as high level programming languages, interrupt capability, floppy-disc memory and comprehensive inter- facing options, clearly leave unsolved problems in the area we are considering.These prob- lems manifest themselves when instruments which are scattered about a laboratory of (say) 600 f t 2 or larger must be connected on-line to a data processor. In such circumstances inter- facing difficulties loom large and the probability is that a considerable expenditure of effort will be required.Firstly, owing to the varying electrical and logical signal conventions adopted by each instrument manufacturer, it is unlikely that any instrument will present the same interfacing requirements. This possibility implies a unique interface for each instru- ment. There are many reasons why standardisation in this nebulous area should be encouraged.Indeed, several standard interface specifications have been presented.l However, the measure of success of a particular standard must be based on its acceptance by industry and, until now, no standard has received this accolade. Recently, however, an interface standard2 has been drawn up by instrument manufacturers that shows promise of general acceptance.In fact, several major manufacturers (notably PHewlett-Packard, who were concerned in drafting the specifications) have designed the interface structure of their instruments and computers around this standard. Also, pre-empting full international recognition via the International Electrotechnical Commission (IEC) (Technical Committee No. 66), the Institute of Electrical and Electronic Engineers (IEEE) has accepted and adopted this standard, which has now been designated “Standard Digital Interface for Programmable Instrumentation,” IEEE 488-75. Hopefully, this standard will go some way towards eliminating the present incompatibility between instruments and computer systems and thus resolve the difficulties which arise from the ad hoc interfacing methods currently resorted to. Secondly, although instrument control is clearly provided for with those systems which implement the IEEE 488-75 standard, there remain problems in connecting equipment or instruments that are not clustered about the processor.Transmission line considerations dictate that the input - output bus lines (connection wires) do not exceed a total of 20 m.This can be a severe limitation if instruments are to be located in even a moderately sized laboratory. We have solved this particular problem by interfacing our processor (Hewlett - Packard 9825A) via the HPIB (Hewlett-Packard’s implementation of IEEE 488-75) to a locally designed multiplexer. This multiplexer allows us to share the input - output data bus between several instrument channels.This is possible because the HPIB is capable of transferring data at rates up to 45K bytess-l, while the maximum rate at which data is generated is about 1 byte every 10 s. (The data entry terminals to be described below will present data at 100 times this rate.) Given that the number of channels is 16, the worst conditions occur when all channels are requesting service simultaneously.All channels must be serviced within the time limit imposed by the maximum bus transfer rate. This implies a data-transfer rate on the bus of at least 6K bytes per channel. This rate is well within the capabilities of the IEEE bus. In order to allow for the possibility of all channels requiring service simultaneously, priority interrupting hardware has been incorporated into the multiplexer design.This equipment ensures that only that channel having the highest allocated priority is allowed to interrupt the processor for service. Also, each channel is double-buffered, which doubles the latency time (time spent waiting for the processor to acknowledge and service an interrupt) allowable for a given channel. Essentially, incoming data are stored to prevent loss of data, thus providing some leeway for carrying out operations for which the time involved is critical.The multiplexer conducts all of its transactions with remote instruments and terminals via serial data links. Serial data transmission allows both the economy and reduced complexity of providing duplex (four-wire) cable links (cable and installation costs can be high) along with the necessary optical isolation required to minimise the effects of noise coupling on to the lines.(This latter option would be prohibitively expensive for a 16-line bidirectional bus.) As the complexity of both instrument and terminal interfaces is also reduced, we are able to interface by using a standardised modular approach, which allows for easy expansion in a cost- effective way.This approach allows us to escape the restrictions placed on the maximum bus length and the maximum number of instruments capable of being connected, while retaining the significant benefits that accrue from the use of the Hewlett-Packard HPIB software.February, 1978 FOURTH INTERNATIONAL SAC CONFERENCE 49 A problem arises when working remote from a computer system in that a user has no immediate knowledge of whether or not data are being collected and/or processed correctly, or indeed whether the computer system has failed.In order to provide for this situation, data- entry terminals are being designed. These terminals will allow data to be entered at the instrument. Also, a display of entered data along with system status messages is possible.At present we are using the magnetic-cartridge mass-storagemedium. This is fundamentally limited by its file-access time and data-transfer rate; with any system having a limited fast internal memory it becomes impossible to allow all programs to reside in an internal memory. This implies that programs and data files are swapped in and out of internal memory as the need arises. As more instruments are considered for connection, the point is soon reached at which a magnetic tape system can no longer accommodate the requirement without seriously impairing the performance of the system.The solution to this problem is a disc memory system that will allow high speed disc transfers to and from the internal memory. In conclusion, we are well on the way to achieving our goal, that of providing a cost-effective system to collect and process the data from the smaller, commonplace analytical instrument.This data could be sample codes or data. References 1. 2. “Computer Automated Measurement and Control,” originally drafted by European Standard on Standard IEEE-488-75, IEEE Publications Section, Piscataway, N.J ., 1975. Nuclear Electronics (ESONE) Committee. Ion-exchange Chromatography and Complex Formation. Separation of Metal Ions J. J. Inczedy Institute of Analytical Chemistry, University of Chemical Engineering, Veszflre’m. Hungary By the use of recently introduced high-performance chromatographic techniques excellent resolutions, large plate numbers and short analysis times can be obtained.However, the selectivity of the separations is still an important problem, if trace elements are to be separated from large amounts of matrix elements, or if complicated systems of many components are to be analysed. The way to improve the selectivity is, as in most instances in analytical chemistry, to use selective chemical reactions. One method of increasing selectivity is to prepare ion-exchange resins capable of selective chemical reactions.An exa.mple is the resin with ethylenediaminetriacetic acid groups.] These groups can form 1 + 1 complexes with metal ions, similarly to EDTA: KMR R3- + M2+ + MR- The resin groups, as free ligands, can also take up protons and the extent of complex forma- tion is strongly related to the concentration of acid in the solution.The apparent protonation constants of the resin ligands are as follows2: log& = 11.2; logKz = 7.1; logK, f 4.13 [I (ionic strength) = 0.11. The apparent stability constants of the resin complexes were determined and are presented in Table L2 Using the equilibrium constant data, the pH of an eluting solvent, or the concentration of acid in eluting solvent, can be calculated easily, and thus the selective elution of a given metal ion can be readily performed.Considering the conditional-constant formula intro- duced by Ringborn, and keeping in mind that for a short elution time the distribution coefficient of the metal ion eluted should be less than 0.1, we can deduce simple equations:50 FOURTH INTERNATIONAL SAC CONFERENCE Proc.Analyt. Div. Chem. Soc. where K’MR denotes the conditional constant, DM the distribution coefficient of the metal ion and Q the volume capacity of the resin. Round parentheses denote concentrations in the resin phase and square brackets denote concentrations in the eluting phase. aM(L) and aB,H) are the side-reaction functions of the metal ion and of the resin ligand, respectively. If DM<lO-l, the retention volume is close to the dead volume of the column: <10-1 .. .. .. KMR Q [H+I2 K1K2 -+ [H+I3 KlK2K3 DM zzz Using the equilibrium constant data and equation (l), the pH values that are calculated to be necessary for rapid elution are as follows: Cu2+, <1.07; Zn2+, <1.43; Cd2+, (1.97; Ca2+, <4.0; and Mg2+, (4.5. TABLE 1 STABILITY CONSTANTS OF METAL - RESIN COMPLEXES ( I = 0.1) LogKMR .. .. 18.2 17.1 17.0 15.5 9.2 8.8 8.2 Cation . . . . Cu2+ Zn2+ co2+ Cd2+ Ca2+ Mg2+ Sr2+ The terms in the denominator of equation (1) are changed markedly by changing the hydrogen-ion concentration, and at decreasing pH the desorption of the ion takes place suddenly for a very small pH change. Therefore, very selective separations can be obtained by using stepwise-changing eluting solvent compositions.Selective separations can also be carried out quantitatively when the ratio of the metal ions is high. Another method of carrying out selective ion-exchange chromatographic separations of metal ions is by the use of conventional strongly acidic cation- or strongly basic anion-exchange resins and complex-forming agents in the eluting solvent.By this method almost all of the metal ions can be separated and the order of the metal ions on the chromatogram can be changed as required. If multi-element separations are to be carried out the separations will be of highest efficiency if gradient elution techniques are used, i.e., the composition of the eluting solvent is changing continuously during elution.Because the distribution coefficient depends on eluting solvent composition, and the migration rate is changing during the elution, the retention volume, i.e., the position of the peak on the chromatogram, is to be calculated by solving the following equation: X V where dx denotes the infinitesimal column volume through which the component M moves forward on the addition of dv ml of eluting solvent; X is the total column volume and ‘v is the total eluting solvent volume (retention volume).Let us consider as an example the separation of bivalent metal ions on a cation-exchange column, using oxalate ions as complex-forming agents of constant total concentration, but a with linear pH gradient. KZ M2+ + 2RNa + R2M + 2Na+ The ion-exchange reaction is as follows: where x is the ion-exchange constant.The complex-formation reactions are : P I 8 2 M2+ + L2- + ML M2+ + 2L2- + MLi-February, 1978 FOURTH INTERNATIONAL SAC CONFERENCE 51 The complex-f ormation reactions can be considered to be side-reactions of the ion-exchange reaction and the distribution coefficient can be expressed as follows4 : where CL is the total concentration of oxalate.For calculation of the retention volume the reciprocal value of the distribution coefficient must be integrated during the migration of the component, i.e., the metal ion, from the top to the bottom of the column. As the relationship between the distribution coefficient and the retention volume is complicated, numerical integration, using a mini-computer, is suggested.By this method the calculation can be done easily. If the pH of the eluting solvent is changing linearly from a certain value, pHo, the actual pH will be given by i-1 PH = PH, + b ( V - a s a x ) 1 where i is an integer and b is the pH gradient, expressed in ApH ml-l, while the second term in parentheses is the void volume of the column already passed by the component (a is the void fraction of the column, v is retention volume). The stepwise summation of the reciprocal value of the distribution coefficient, using steps of Av ml, should be carried out until the total column volume is reached: where X is the total volume of the column. The sum of the Av increments gives the volume of eluting solvent necessary to bring the metal ion peak to the end of the column (nAv = V ) . Retention volumes for the separation of copper, zinc and cadmium, using gradient elution, were calculated and compared with the experimental values. The data were as follows: pHo = 2.0; Av = 1 ml; a = 0.4; b = 0.012 pH ml-l; “a+] = 10-1 q; C, (total oxalate) = 10-1 M ; X = 3.08 ml; Q = 1.9 mequiv ml-l. The protonation constants of oxalic acid were logK, = 3.8 and lo@, = 1.4. Ion-exchange and complex-formation constants for copper were KSCuNa = 2.6, log For zinc the values were KxZnNa = 2.2, logp, = 3.7 and log#& = 6.0. For cadmium KZCdNa = 2.6, logfi, = 2.9 and lo@, = 4.7. The calculated (3.5, 64 and 130 ml) and the experimentally determined (3, 70 and 126 ml) retention volumes were in fairly good agreement. = 4.5 and logfi, = 8.9. References 1. 2. Szabadka, 0.. unpublished results. 3.. 4. Szabadka, o., and Incddy, J., unpublished results. Ringbom, A., “Complexation in Analytical Chemistry,” Interscience Publishers, London, 1963. InczCdy, J ., “Analytical Applications of Complex Equilibria,” Ellis Horwood, Chichester, 1976.

ISSN:0306-1396    

DOI:10.1039/AD9781500043

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

52 FOURTH INTERNATIONAL SAC CONFERENCE Proc. Analyt. Div. Chew. SOC. Analytical Problems Concerning Natural Waters Lambert J. Ottendorfer Bundesanstalt f i i y Wassergiite, A-1223 Vienna, Kaisermiihlen, Schiffmiihlenstrasse 1 SO-Postfach 7, Austria The analytical problems of water analysis are clearly divided into three groups. (i) Natural water : ground water, river water, impoundments and reservoirs, and natural (ii) Processed water : drinking water, boiler feed water, water for industrial purposes and (iii) Natural water as under (i) but influenced by treated or untreated, domestic and/or This paper deals only with natural water, concentrating on the various considerations and problems connected with sampling and sample handling, including transportation.Water analysis can be carried out either on a continuous basis using recording and/or data transmission (generally known as water quality monitoring) or by means of taking discrete samples.Natural water contains a large variety of dissolved or dispersed organic matter and very frequently various botanical and zoological species. Many parameters of the water sample therefore undergo very rapid changes immediately after removal from the body of water.In water monitoring, parameters like oxygen saturation and content of suspended solids are very easily influenced by the dimensions of the intake tube and may also depend on whether pressure or suction pumping is used. Only the problems connected with the treatment of single, hand-picked samples will be emphasised in this paper.Each of the three groups mentioned above requires different sampling techniques and sample volumes for the application of specific analytical methods appropriate to the concentration range in question. Several parameters are best determined in the body of water itself parallel to the sampling procedure ( e g . , temperature, pH, electrical conductivity or oxygen content).The characteristics of the body of water must be noted (flow-rate, width, depth, colour, the presence of weeds or algae, the nature of the banks) and included later in the final report. For many parameters samples must be preserved by use of particular additives (for phenols or cyanides, solid sodium hydroxide ; several drops of concentrated sulphuric acid for ammonia and nitrous and nitric nitrogen; mercury(I1) chloride for detergents, etc.).In some instances freezing or deep-freezing can also be used. In order to obtain a maximum of information with a minimum of effort and expenditure, it is necessary to consider from the beginning, i.e., even before the actual picking of the samples, all factors that are likely to influence the quality of the sample or that might affect selection of the most appropriate analytical procedures.It is therefore very important that an gxperienced chemist supervises the sampling. The transportation of the samples to the laboratory provides a few more aspects to be considered. There are two main factors : transportation time from sampling site to laboratory (including the time lag between arrival and the start of the actual analysis), and the sample volume and material of the transport vessel.The time delay mainly affects the biological parameters, but several inorganic constituents participate in the metabolism of organic species (oxygen, carbon dioxide and nitrogen and phosphorus nutrients). As these reactions show high time to temperature ratios it is also important to choose a suitable container to keep the samples on a nearly constant temperature level during transportation.With regard to sample volume, practical experience showed that volumes of less than 100 ml should be avoided. Water bodies containing suspended solids may not be representa- tive because of easily occurring inhomogeneities in the water body. Trace-metal analysis at the parts per million and, much more, at the parts per billion level require very special procedures and careful s4ection of the material and size of the container.Increased sample volumes improve the volume to surface area ratio and reduce the danger of sorption - desorp- tion phenomena. In many instances pre-concentration steps may be necessary, but even then the sample volume should not be less than 2 1.The taking of samples along horizontal or vertical profiles requires very refined equipment, as in oceanographic practice. Taking a series of 20 or more samples without interference and artificial lakes. specially treated water for any other purpose. industrial wastes. These factors affect continuous monitoring or single sampling in different ways.February, 1978 FOURTH INTERNATIONAL SAC CONFERENCE 53 with the surrounding water body, a very common task in limnological analysis, requiresnot only excellent equipment, but also skill and experience.Again, a number of different problems arise. If one considers a muddy sediment in the anaerobic zone, consisting of silt, organic matter, iron(I1) sulphide, fibres from the pulp and paper industry and different types of worms, it may be understood that each of these components can give rise to more than one analytical problem.However, it is very necessary to correlate water and sediment analysis in order to obtain ideas about the origin of possible water contamination. Even more important than experience, skill and well chosen equipment is the thorough planning of the whole sampling expedition.For example, with unexpected hazards, the taking of water samples has to be carried out at the appropriate time and in the correct place as they obviously cannot be repeated. They have been prepared and tested over long periods following co-operation between numerous laboratories and, in many instances, laboratories in many countries. These well known methods give some guarantee that the results obtained are reliable and compatible with similar results from other laboratories or within a series over a period of time. Standard procedures of this kind have been issued at various governmental levels and some are recommended by international institutions : Water Quality Criteria, USA ; Deutsche Einheitsverfahren ; World Health Organization Manual on Analysis for Water Pollution Control; Standard Methods of the Committee for Mutual Assistance "COMECON." It is not surprising that the main features of these compilations agree fairly well, because the required results leave little space for variations in method.There are, of course, some divergences based on the fact that the necessary equipment and reagents are not always available or, in some instances, that several methods are offered ; these clearly indicate that the ideal analytical approach has not yet been found (e.g., alternatives such as ortho- and polyphosphates, anionic and non-ionic detergents).A technique called semi-automatic analysis has been proposed which can save a considerable number of man-hours without loss of accuracy.A series of 6-12 samples is started at short intervals, perhaps 30-60 s, so that step 2 for sample number 1 is effected at the correct time and so on. This technique can be regarded as a forerunner of the AutoAnalyzer technique. This technique has proved to be a valuable tool for laboratories of medium size with a daily sample input that is too low to justify fully automatic equipment, i.e., those having a capacity of about 40-120 samples per hour.Even when automatic equipment is used one should consider very carefully whether the analytical procedures represent an essential variation of the stan- dard methods formerly used. It should be understood that analytical chemistry alone cannot give the complete answer that is required by water management workers.A multi-disciplinary survey including biological and hydrobacteriological investigations can give a fairly accurate answer and, following comparison and correlation of the different findings, some comfort when the results fit together. That the results of water analysis represent far more than a scientific purpose on its own is fortunately nowadays common knowledge.The slow and difficult change from restoration to prevention has been made and it can be hoped that the enormous difficulties with which water management authorities are confronted everywhere can be overcome. The analysis of sediments is closely related to the analysis of the body of water. Standard analytical procedures are available for most of the parameters. Critical Comparison of the Determination of Vitamin BZ in Foods by a High-performance Liquid Chromatographic Method and the "Standard" Microbiological Approach P.J. Richardson, D. J. Favell, G. C. Gidleyand A. D. Jones Unilever Research, ColworthlTVelwyn Laboratory, Unilever Limited, Colworth House, Sharnbrook, Bedford, MK44 1LQ There is increasing interest at the present time in the nutritional value of food, particularly convenience foods which form a significant part of the UK diet.In assessing the status of foods, data on micronutrients, vitamins and trace minerals are required in addition to54 FOURTH INTERNATIONAL SAC CONFERENCE Proc. AnaZyt. Div. Chem. SOC. protein, fat and calorific value. Included in the list of vitamins is vitamin B, (riboflavin), which is specified in proposals for soy protein1 and recommendations for school meals., The generally accepted methods for the determination of vitamin B, are fluorimetry3 and microbiology.* Fluorimetry is not entirely specific, being more correctly a measure of dithionite-reducible fluorescence, while the microbiological method is tedious and time consuming.The use of high-performance liquid chromatography (HPLC) was selected as this technique offered a rapid, specific and sensitive method that could be readily automated.Principle of the Method The method is based on that developed by van de Weerdhof et aL5 Riboflavin is extracted from samples by acid hydrolysis and enzyme treatment. The free vitamin is then chromato- graphed in a buffered solution on a microparticulate silica column and detected in a flow fluorime t er .Acid Hydrolysis We used sulphuric acid and found that changing the concentration had little effect on the response from the detector, although, if the acid was diluted too much, there was a decrease in the response. The optimum concentration is 0.125 M and this was the concentration used throughout the rest of this study.No difference in peak height was observed between standard solutions that had been autoclaved in this way and those that had not, thus showing the stability of riboflavin to this treatment. This method appeared to have no real advantages over the use of acid alone, and several problems were encountered owing to the ammonia produced by hydrolysis of the urea. The first step in the separation is acid hydrolysis in an autoclave at 120 "C.The method of Roy et aZ.,6 using urea and acid, was tried as an alternative. Enzyme Treatment The enzyme used was takadiastase and, as this requires a pH of about 4.6 to function efficiently, the acid added in the first step must be neutralised. Initially a 4 M acetate buffer was used to do this. However, the peak heights obtained from standard solutions of ribo- flavin decreased with increasing buffer concentration.The use of this buffer was, therefore, discontinued, and an amount of sodium hydroxide solution equivalent to the amount of acid was substituted. A small volume of 0.1 M sodium acetate buffer was then added to adjust the pH to the correct value. The original method specified 1 ml of a 10% solution in distilled water, with an incubation time of 30 min.Neither of these was found to be sufficient and the volume was increased to 4 ml with an incubation of 2 h. As a large amount of takadiastase was being used a blank determination was performed. This showed a small amount of riboflavin, but not enough to be significant. We obtained the takadiastase from Serva of Heidelberg.Removal of Precipitated Proteins Filtration through a Whatman No. 541 filter-paper was tested and found to be satisfactory, and so was adopted. Initially, the denatured proteins were removed by centrifuging the extracts. Chromatographic System giving a back pressure of about 300 p s i . The reducing unions at the top and bottom are fitted with 2-pm stainless-steel frits.The column has a high capacity for co-extracted material and is capable of accepting about 150 injections before needing replacement. An Aminco Fluoromonitor fitted with filters giving excitation and emission wavelengths of 457 and 510 nm, respectively. Pump. Sample vaZve. Column. A Jobling Model 4D711 eluent delivery unit, pumping at a flow-rate of 1.5 ml min-l, A Specac six-port injection valve fitted with a 100-p1 loop.A stainless-steel tube (20 x 0.76 cm i.d.) packed with 10-pm silica. Detector.Febrztary , 19 78 FOURTH INTERNATIONAL SAC CONFERENCE Solvent. 0.1 M sodium acetate buffer solution, pH 4.6. The total cost of this system is about fl3200. 55 Initial Comparison Sixty samples that had previously been examined microbiologically were analysed, each in duplicate on two occasions.They were selected from a range of typical meal components and chosen to cover as wide a range of types as possible. Most of these were in the range 0-2 pg g-l of riboflavin with a few in the range 2-20 pg g-l. The results were calculated by comparing the peak heights with those of standards taken through the whole procedure. At this time the samples were not being homogenised with the acid.Comparing the results with those obtained microbiologically it was found that the dessert dishes agreed well, but that in high-protein samples the HPLC results were, on average, 22% low. The reason for this could be poor extraction or the ability of the micro-organism to utilise protein and so grow more rapidly than expected. In order to decide between these explanations a number of samples were re-analysed following homogenisation.Re-examination of Selected Samples Two groups of samples were selected, one for which the HPLC results had previously been low and one for which they had not. The introduction of the homogenisation step caused most of the low results to increase, giving generally good agreement between the two methods.In a few instances there was no change. Where the agreement was previously good it remained so, showing that the increase was not an artifact of the new system. Thus the new procedure outlined above provides data on riboflavin that generally agree well with data obtained by use of the microbiological procedure on a wide range of human foods. The technique is more rapid and sensitive and lends itself to automation, and has now been adopted for routine produce analysis in our laboratory.References 1. 2. 3. “Food Standards Committee Report on Novel Protein Foods,” HM Stationery Office, London, 1974. “Nutrition in Schools,” HM Stationery Office, London, 1975. Horwitz, W., Editor, “Official Methods of Analysis of the Association of Official Analytical Chemists,” Twelfth Edition, Association of Official Analytical Chemists, Washington, D.C., 1975, 43.039- 43.043.Horwitz, W., Editor, “Official Methods of Analysis of the Association of Official Analytical Chemists,” Twelfth Edition, Association of Official Analytical Chemists, Washington, D.C., 1975, 43.139- 43.147. van der Weerdhog, T., Wiersum, M. L.. and Reissenweber, H., J .Chromat., 1973, 83, 455. Roy, R. B., Salpeter, J., and Dunmire, D. L., J. Fd Sci., 1976, 41, 996. 4. 5. 6. Determination of Daunorubicin and Daunoru bicinol in Plasma from Leukaemic Patients Staffan Eksborg and Hans Ehrsson Karolinska Pharmacy, Fack, S-104 01 Stockholm 60, Sweden Daunorubicin, I, is an anthraquinone glycoside widely used for the treatment of acute 1eukaemia.l Generally, it is given as an intravenous infusion, either as the free drug or as a complex with DNA. In the latter instance a reduction of the cardiac toxicity can be postulated2 as proposed from animal model systems.In the present study the doses of daunorubicin given were within the range 0.70-1.50 mg per kilogram of body mass, either as the free drug or as a complex with DNA (mass ratio of daunorubicin to DNA, 1 : 12).Daunorubicinol, 11, the main metabolite of daunorubicin, has been reported to have similar cytotoxic activity to the parent compound. The aim of this work was to devise a fast and reliable method for the simultaneous deter- mination of daunorubicin and daunorubicinol for a comparative pharmacokinetic study after administration of daunorubicin as the free drug and as the DNA complex.56 FOURTH INTERNATIONAL SAC CONFERENCE Proc.Analyt. Div. Chem. SOC. 0 OH NHz I, R = COCH3 II, R = CH(OHlCH3 Proposed Method for the Determination of Daunorubicin and Daunorubicinol in Plasma Plasma (2.00 ml), buffered with 0.2 ml of phosphate buffer, pH 8.1 [ionic strength (p) = 1.01, is extracted with 10.00 ml of chloroform - heptan-1-01 (9 + 1) for 10 min.Seven millilitres of the organic phase are then re-extracted with 0.400 ml of 0.1 M orthophosphoric acid, and 0.050-0.300 ml of the aqueous phase is injected into the liquid chromatograph. The chromatographic system consists of LiChrosorb RP-2 (5 pm) as support and aceto- nitrile - water (1 + 3), acidified with orthophosphoric acid, as mobile phase at a flow-rate of 0.9 ml min-l.Quantitation is based on measurement of peak area using the molar absorptivity of the migrating compounds. Photometric detection at 253.7 or 500 nm was used. Results and Discussion Extraction Procedure The degrees of extraction of daunorubicin and daunorubicinol were found to be strongly dependent on the pH of the aqueous phase (Fig. l), with an optimum value at pH 8.1.3 Using equal phase volumes, the degree of extraction was found to be 97, and 91% for daunorubicin and daunorubicinol, respectively.Quantitative extraction of the two com- pounds was obtained by using the organic and aqueous phases in a ratio of 5 : 1. To avoid an interfering peak in the chromatogram pentan-1-01 was replaced with heptan-1-01, which does not change the extraction profile presented in Fig.1 to any significant extent. Conditions for quantitative re-extraction of daunorubicin and daunorubicinol from the organic phase, used for the initial extraction, into the aqueous phase, injected into the liquid 2 0 5 7 9 11 PH Fig. 1. Influence of pH on the distribution ratio: I, dauno- rubicin ; 11, daunorubicinol. Organic phase, chloroform - pentan-1-01 (9 + 1); aqueous phase, buffer solution ( p = 0.1). (Equal phase volumes.)February, 1978 FOURTH INTERNATIONAL SAC CONFERENCE 57 chromatograph, can be calculated from constants presented in reference 3. volume ratio used in the proposed method the pH should not exceed 1.7.aglycones, formed as metabolite^,^ are excluded. pH 8.1 were not found to be affected by an excess of DNA below 25-fold.At the phase- In this step The degrees of extraction of daunorubicin and daunorubicinol from a buffer solution of Liquid Chromatography Retention time dent on the concentration of acetonitrile in the mobile phase5 (Fig. 2). complete separation of daunorubicin and daunorubicinol within 10 min. SeZectivity The proposed chromatographic system shows a high selectivity when separating anthra- quinone glycosides with minor differences in substitution of the side-chain.5 A high detection selectivity toward co-extracted drugs used in combination therapy, as well as towards co-extracted endogenous compounds that might give retention times identical with those of daunorubicin and daunorubicinol, can be obtained by measuring the eluate photometrically at 500 nm.This results in three to five times lower sensitivity as a result of the higher detector noise and lower molar absorptivity compared with measurements made at 253.7 nm. The retention times of daunorubicin and daunorubicinol were found to be strongly depen- In the proposed method a mobile phase containing 25% of acetonitrile is used, giving a Sensitivity Chromatographic peaks containing 2.3 ng each of daunorubicin and daunorubicinol give a signal to noise ratio The sensitivity of the chromatographic system is illustrated in Fig.3. of 2-3. 30 C .- E \ 20 .- + C ._ + C 0, $ 10 (r: O L L - J 20 25 30 [CH3CNI, % Fig. 2. Effect of mobile-phase com- position on reten- tion time. Sample: I, daunorubicin : 11, daunorubicinol (2.5 nmol of each in 100 p1 of mobile phase).Mobile phase (flow- rate 0.9 ml min-l): acetonitrile - water, acidified with H,PO,. Support, LiChrosorb RP-2 (5 pm). Column, 150 x 4mm. a Tirne/m i n Fig. 3. Sensitivity of the chro- matographic system. Sample : I, daunorubicin ; 11, daunorubicinol [4 x nmol (2.3 ng) of each in 100 pl of mobile phase]. Mobile phase: acetonitrile - water (1 + 3), acidified with H,PO,.Support, LiChrosorb RP-2 (5 pm) . Column, 150 x 4mm. , Measuring wave- length, 253.7 nm. Quantitative determination Quantitative determination is based on measurements of peak area : M = Yube-l .. .. .. . . ..58 FOURTH INTERNATIONAL SAC CONFERENCE Proc. Analyt. Din. Chem. SOC. where M mmol is the amount of sample, Y mm2 is the peak area, u is millilitres of eluting agent per millimetre of chart paper, b is the absorbance per millimetre of chart paper and E 1 mol-l cm-l is the molar absorptivity of the migrating compound.6 The molar absorptivities of daunorubicin and daunorubicinol were found to be identical (7.89 x 1031 mol-l cm-l at 500 nm and 1.92 x lo4 1 mol-l cm-1 at 253.7 nm).From equation (1) it follows that the peak area is independent of chromatographic para- meters such as column efficiency and the capacity factors of the solutes as well as the length and diameter of the chromatographic column used.Recovery and Precision standard deviation) at 25 and 100 ng ml-l of daunorubicin and daunorubicinol (Table I). The recovery from spiked plasma was >goyo, with a precision of better than 10% (relative TABLE I RECOVERY OF DAUNORUBICIN AND DAUNORUBICINOL FROM PLASMA Compound Concentration/ng ml-1 Recovery, * yo Daunorubicin .. . . 100 96.4 f 9.7 Daunorubicin . . .. 25 96.3 f 12.2 Daunorubicinol . . . . 100 98.0 5.2 Daunorubicinol . . . . 25 90.4 f 6.3 * Recovery & relative standard deviation calculated from eight determinations. Samples from Leukaemic Patients A typical chromatogram of a plasma sample from a leukaemic patient treated with dauno- rubicin is shown in Fig.4. Examples of plasma levels of daunorubicin and daunorubicinol after administration of daunorubicin to leukaemic patients as the free drug and as the DNA complex are presented in Fig. 5. l l l l l l l l l J 0 2 4 6 8 Time/min Fig. 4. Chromatogram of plasma from leukaemic patient : I, daunoru- bicin ; I1 daunorubicinol.Mobile phase : acetonitrile - water (1 + 3), acidified with H,PO,. Support, Li- Chrosorb RP-2 (5 pm) . Measuring wave- length, 500 nm. Determined plasma levels : daunorubicin, 370 ng ml-l ; daunorubicinol, 90 ng ml-1. Plasma samples taken after infusion of 1.4 mg of- daunorubicin per kilogram for 45 min. l L L d - d U L l 0 5 10 15 20 2 Time/h Fig.5. Plasma levels of daunorubicin and daunorubicinol after intravenous infusion of daunorubicin : 0, daunorubi- cin ; 0, daunorubicinol. Dose of daunoru- bicin administered: ( a ) , 1.3 mg kg-l as free drug; ( b ) , 0.81 mg kg-l as DNA complex. Further pharmacokinetic studies are in progress. References 1. Bernard, J., Paul, R., Boiron, M., Jacquillat, C., and Maral, R., Editors, “Rubidomycin.Recent Results in Cancer Research,” Springer-Verlag, New York, 1969.February, 1978 FOURTH INTERNATIONAL SAC CONFERENCE 2. 3. 4. 5. 6. Langslet, A., (aye, I., and Lie, S. O., Acta Pharmac. Tox., 1974, 35, 379. Eksborg, S., J. Pharm. Sci., in the press. Takanashi, S., and Bachur, N. R., J. Pharmac. E x $ . They., 1975, 195, 41. Eksborg, S., J.Chromat., in the press. Eksborg, S., and Schill, G., Analyt. C h ~ m . , 1975, 45, 2092. 59 Voltammetric Behaviour of Humic and Fulvic Substances of Natural Waters J. Buffle, A. Cominoli, F.-L. Greter and W. Haerdi Department of Inorganic and Analytical Chemistry, University of Geneva, 121 1 Geneva 4, Switzdand Interaction of Fulvic Acids with the Mercury Electrode The behaviour of fulvic substances at the aqueous solution - mercury electrode interface was studied by means of voltammetric methods.It has been shown that fulvic acids are adsorbed. From the change in the capacitive current measured by d.c. polarography, it can be seen that the adsorption process is the rate- determining step. More than 30 s are necessary for the attainment of equilibrium.The shapes of the electrocapillary curves show that the species adsorbed are anionic even at acidic pH (Fig. 1). The adsorption is stronger in acidic solutions (pH 3.8) than in neutral solutions (pH 6.9). The use of phase-sensitive a.c. polarography at 90 "C and 400 Hz allows the deter- mination of the fulvic acids. The relationship between the concentration of fulvic acids and the decrease of the capacitive current is linear for concentrations between 1 and 30 mg 1-l.+0.1 0 -0.1 -0.5 -1 .o -1.5 PotentialN Fig. 1. Electrocapillary curves of aqueous solutions of fulvic acids at the dropping-mercury electrode. pH, 3.8; drop time, 20 s; electrolyte, 0.1 M KNO,. Potentials measured versus Ag I AgCl I sat. KC1 I 0.1 M KNO, I 1 reference electrode. Fulvic acid concentration: 1, 0; 2, 42.2; 3, 100.0 mg 1-'. These results show that : as the time necessary for the adsorption process is relatively short and fairly independent of the concentration of fulvic substances, this process might well interfere with the techniques using stationary or even dropping-mercury electrodes, even at low concentrations of fulvic substances; and that this adsorption process may be used to develop a new method for measuring the concentration of the adsorbable component of fulvic acids.Interactions between Lead( 11) and Fulvic Acids The interactions between lead and fulvic acids were studied by means of several voltam- metric rneth0ds.l60 FOURTH INTERNATIONAL SAC CONFERENCE Proc. AnaZyt. Div. Chern. SOC. Normal pulse-polarographic results (Fig.9 in reference 2) indicate two important features : 1, the ratio of the limiting current of lead in the presence and absence of fulvic acids is less than one but independent of the concentration of fulvic substances, which indicates that the lead - fulvic acid complexes are not inert; and 2, the half-wave potential is shifted to more negative values with increasing concentrations of fulvic acids.However, the observed shift is much more than that calculated from the stability constants obtained from potentiometric measurements (ion-selective electrodes) .3 Moreover, we found that this shift is also depend- ent on the lead(I1) concentration, which is an unexpected result, especially as fulvic acid i.s present in excess and the complexes are labile.In order to understand the processes that are taking place, a more detailed analysis of the system should be made, using various voltammetric techniques such as those shown in Fig. 2. A quantitative interpretation of this system was made in this way and a schematic diagram of the processes occurring in the solution is shown in Fig. 2. 7/ D.c. polarography Influence of mercury height on current D.c.polarography Influence of mercury height on potential Differential pulse polarograph y i p = f ([A] 1 A.c. polarography Influence of frequency on ip and Ep A.c. polarography Phase-angle measurements Cyclic voltammetri Influence of scan rate and adsorption ti me on i”,i‘p and Ez - Fp /---------- \ --\ \&& PbA km+2j]ad:: \ / / / /‘/ / / ,,/ , / ///// / Potentiometry -- (ion-selective electrode) .- - - - f Pb2+ + n.AZ- f--a PbAL-zn+2’ D.c. polarography i = f(t) curves 4-- Ner nstia n Diffusion :ont ro lled Cyclic voltammetry Influence of adsorption ti me on I: and E‘p Differential pulse polarography Influence of drop time and [Pb(II)It Fig. 2. Schematic diagram of the behaviour of the lead - fulvic acid complexes a t the mercury electrode, as deduced from several potentiometric, polarographic and voltammetric techniques. A represents fulvic substances [ Pb A fl (-%a+ 2’1.The complexation reaction occurring in solution as measured by a potentiometric technique is given at the top of the scheme. The three particles may diffuse to the mercury electrode, and the same equilibrium occurs at the electrode surface.All voltammetric criteria shown here show that: (a), the lead - fulvic acid complex is labile from the polarographic standpoint, i.e., the dissociation and formation processes are extremely fast ; and (b), Nernstian behaviour is observed for the reduction. However, fulvic acids are adsorbed on the electrode surface and modify the surface potential, +. Moreover, lead(I1) may be complexed by the adsorbed fulvic acids, which increases the energy needed for the reduction of lead(I1) and explains why the shift of half-wave potential occurs at more negative values than that expected from potentiometric reults, particularly when large amounts of fulvic acid are adsorbed.It was also expected that this effect would increase with increased adsorption time, which was found to be the case: the peak potential of lead, measured by means of differential pulse polarography, shifts with drop time towards more negative values.The kinetics of this adsorption can be measured, which allows us to extrapolate the curve to zero drop time. In this way it is possible to determine the peak potential that would be obtained if there were no adsorption.The difference between this peak potential and thatFebmary , 19 78 FOURTH INTERNATIONAL SAC CONFERENCE 61 obtained in the absence of fulvic acid is directly proportional to the logarithm of the degree of complexation of lead (a) = [Pb],/[Pb2+], where [Pb], and LPb2+] are concentrations of total and free lead, respectively. By doing this for several concentrations of fulvic acid the degree of com- plexation thus obtained agreesfairly well with that obtained from ion-selective measurements.The over-all results indicate that the lead - fulvic acid complexes are labile. Now the ratio of the limiting current of the complexed and uncomplexed metal ion is proportional to the square root of the ratio of the corresponding diffusion coefficients. Hence the order of magnitude of the relative molecular mass can be estimated. The degree of complexation can be measured from the shift in Etwhen extrapolated to zero drop time.This is very important as even drop times higher than 0.1 s may lead to erroneous results. Finally, the study of the change in E, as a function of time may give an idea of the adsorp- tion properties of the fulvic acids.It must be mentioned that when adsorption times are long, a shoulder on the polarographic wave appears, presumably owing to the fact that the reduction of the adsorbed lead - fulvic acid becomes more important than the direct reduction of the dissolved complex. This effect is particularly noticeable in Fig. 8 in reference 2, which sliows the cyclic voltammetric curve recorded with a stationary mercury electrode after waiting for various lengths of time at the initial potential .It can be seen from this figure that the difference in the cathodic and anodic peak potentials extrapolates to 30 mV for zero adsorption time, which is expected for a reversible system and which agrees with the results obtained by other techniques (Fig. 2). For longer adsorption times, this difference increases, the cathodic peak current increases and its shape becomes more and more symmetrical.All these modifications correspond to the reduction of the complex after it is adsorbed on the electrode. This observation is extremely important from the point of view of speciation measurements in waters, as in anodic stripping voltammetry, which is the most often used voltammetric technique, the adsorption times correspond to the electrolysis time, which is sometimes more than 30 min.This should be borne in mind as otherwise erroneous results for both current and potential readings would be obtained. Conclusion It should be emphasised that: (a), adsorption phenomena may have a marked influence on voltammetric results when applied to natural water systems; (b), the shift in peak potential does not necessarily mean a simple complexation process; and (c), a decrease in current ob- served is not always due to formation of inert complexes.Hence we need to know more about the electrochemical behaviour of the system of interest before trying to interpret the data. Although to try to understand the mechanism at the electrode may lead to a complicated interpretation of the results, it is important to realise that such detailed studies of the test solution, using both potentiometric and voltammetric methods, are necessary in order to choose the best conditions for measuring the parameters of interest.Moreover, in some instances interesting applications may be found by making use of the adsorption phenomena.Firstly, before measuring a degree of complexation in water, it would be preferable to separate at least the three main groups of complexing agents of natural waters, ie., small soluble compounds (which often form labile complexes), large colloids in suspension (which may be treated as if they were completely inert ligands) and the intermediate group (which include most surface- active agents).Such a separation, which can be achieved by ultra-filtration, would certainly facilitate the interpretation of the results because there will be no interaction between these groups during the electrochemical measurements. Secondly, it is important to have a better understanding of the behaviour of the various kind of compounds that constitute the third group.Finally, from the technological point of view there is an urgent need for reproducible voltammetric electrodes that minimise the adsorption effects without loss of sensitivity. Three recommendations regarding the complexation measurement can be made. References 1. 2. 3. Buffle, J . , Greter, F. L., and Haerdi, W., Analyt. Chem., 1977, 49, 216. Buffle, J . , and Greter, F.L.. in preparation. Buffle, J . , Greter, F. L., Nembrini, G., Paul, J., and Haerdi, W., 2. Analyt. Chem., 1976, 282, 339.62 FOURTH INTERNATIONAL SAC CONFERENCE Proc. Analyt. Div. Chem. Soc. MECA Spectroscopy: an Appraisal of its Application to the Measurement of Some Naturally Occurring Phosphorus Compounds D. J. Knowles Department of Chemistry, Preston Institute of Technology, Plenty Road, Bundoora, Victoria 3083, Australia P.Marriott Department of Inorganic and Analytical Chemistry, La Trobe University, Bundoora, Victoria 3053, Australia and S. J. E. Slater Environment Protection Authority, 240 Victoria Parade, East Melbourne, Victoria 3002, Australia The role played by phosphorus in eutrophication processes in natural waters has received much attention and has been reported extensively in the literature. In complex natural water systems it is extremely difficult to predict what the effect of a given discharge of phosphorus- containing wastes will be.Attempts to model these systems are complicated by physical processes as well as assimilations, inter-conversions and sedimentation processes, of both chemical and biological origin, which are incompletely understood.Although the measure- ment of total phosphorus levels in wastes is useful from a monitoring and enforcement point of view, such measurements do not provide any predictive information regarding the avail- ability of that phosphorus to biological processes, which is the crucial consideration. To approach this goal it would be extremely useful to have both qualitative and quantitative knowledge of the chemical forms of phosphorus present.Although it is desirable to be able to determine the various fractions of phosphorus it is also extremely difficult owing to an almost complete lack of direct methods for the determination of many of the forms. For instance, treated and untreated sewage contain simple phosphate, condensed phosphates and organic phosphorus compounds.Direct analysis for all of these components is not possible at present : lengthy hydrolysis and oxidation steps must be carried out and the levels of condensed and organic phosphates calculated by difference. This situation has led to the present attempt to apply molecular emission cavity analysis (MECA) to such systems.MECA has been successfully applied to analogous sulphur systems1,2 and has made possible the direct fractionation and measurement of a wide variety of anionic and organic sulphur species. More recently, the application of MECA to the analysis of single organophosphorus compounds and phosphate rock has been rep~rted.~ The methods currently used for the analysis of aqueous systems for phosphorus are principally based on the conversion of all forms to the simple phosphate form, which is then measured spectrophoto- metrically as a reduced molybdophosphate complex ,4 Arsenic interference can be a significant problem with these methods as arsenate ion reacts in exactly the same manner as phosphate to give a similar colour.This interference can be overcome by carrying out a reduction step before adding the chromogenic reagent.It was also hoped that the present MECA study would provide a method for phosphorus analysis that was not subject to arsenic interference. Methods An Anacon MECA spectrophotometer was used with the burner assembly modified so as to allow the burner to be moved up to the cavity rather than the reverse. This mode was found to give superior reproducibility. Carbon cavities were found to be the most suitable but required regular replacement because of a slow loss of sensitivity with use.The materials investigated were simple orthophosphates, pyrophosphate, adenosine tri- and monophosphates (ATP and AMP) and inositol hexaphosphate (phytic acid), which represent the range of inorganic, condensed and organic phosphorus.The compounds were obtained as their sodium, ammonium or calcium salts. Cationic interferences on the HPO emission at 528 nm were investigated.February, 1978 FOURTH INTERNATIONAL SAC CONFERENCE 63 Results and Discussion Following the method used for the determination of rock phosphate, addition of sulphuric acid was investigated as a means of removing cationic interference and was found to be un- satisfactory. When the concentration of sulphuric acid was made high enough to remove interference effects (-0.3 M) two emissions were observed from sulphur at 528 nm, the wave- length for HPO measurement.The results are shown in Fig. 1. The second of these emissions overlaps the HPO emission and thus makes accurate measurement impossible, The problem of cationic interference was resolved by using an ion-exchange resin to convert all compounds into the ammonium or acid form.1 I 0 6 12 Timeh Fig. 1. Emission from sulphuric acid at 52'3 nm. Table I shows the results obtained for the calibration sensitivities and the peak emission times (t,) for the compounds studied. TABLE I SENSITIVITIES OBTAINED BY USING THE HPO EMISSION AT 528 nrn Compound SensitivitylmV per p.p.m.tmls 2.00 2.0 2.0 (NH,),HPO, (NH,),P,O, 1.59 Phytic acid 1.68 2.2 ATP 1.52 2.8 AMP 1.67 3.0 The results show two features of interest. Under the flame conditions required to achieve good emission characteristics and good sensitivities (hydrogen at a flow-rate of 5 1 min-l, nitrogen at 3.3 1 min-l and air at 4 1 min-l) the t, values for these species lay between 2 and 3 s.Consequently, it was not possible to achieve a time resolution for these different species such as has been observed in the sulphur system. If the flame temperature was lowered, thus reducing the rate of heating of the cavity and enhancing the poss-bility of achieving a time resolution, the sensitivity became too low. The second point of interest is that although the t, values of the organic phosphates, phytic acid, ATP and AMP are similar, so are their sensitivities.Calibration graphs for these three species are linear over the range 0-50 p.p.m. and a figure for the total organic phosphorus as these three compounds could be obtained that would be accurate to at least 610%. The accuracy may be better than this as the calibrations were made with the chemicals as received.They are not readily standardised and thus their purities were not known. If a method of separating the inorganic forms from the organic forms is used (e.g., column chromatography) then MECA spectroscopy may provide a rapid means of determining the total organic phos- phorus content of the material under investigation.As already mentioned arsenic is an interferent in the standard colorimetric analysis of phosphorus, in which it produces a positive interference. The effect of added arsenic(II1) and arsenic(V) on the HPO emission at 528 nm was investigated and the results are shown in Table 11.64 FOURTH INTERNATIONAL SAC CONFERENCE Proc. Analyt. Div. Clzem. SOC. TABLE I1 EMISSION PEAK HEIGHTS (mV) AT 528 nm FOR 50 p.p.m.PHOSPHORUS SOLUTIONS AT VARIOUS LEVELS OF ADDED ARSENIC (p.p.m.) HPO emission at HPO emission at As(II1) concentrations of- As(V) concentrations of- A t \ f A 1 0 0.5 1.5 2.5 0 2 5 10 0 0.5 1.5 2.5 84* 81* 76* 76* 57* 54* 49* 37* 85t 8 l t 80f 78t * Phosphorus present as (NH,),HPO,. t Phosphorus present as H,PO,. The results indicate anincreasing suppression of the HPO emission as the arsenic concen- tration increases.The direction of the interference is opposite to that encountered in the colori- metric determination of phosphorus. The interference would not be serious for those natural situations in which the level of arsenic was below 1% of the level of phosphorus. At low levels of phosphorus this interference presents serious difficulties and further investigation is neces- sary in order to develop a method of suppressing the interference.Aged cavity used. Conclusion As a result of this preliminary investigation it cannot be said that MECA spectroscopy provides a rapid and direct means of fractionating and measuring naturally occurring phos- phorus compounds. This situation probably arises from the fact that the phosphorus exists in very similar chemical environments in most of the compounds studied.However, with further work it is likely that the technique, in conjunction with separation procedures, will prove valuable in this difficult area of analysis. 1. 2. 3. 4. References Belcher, R., Bogdanski, S. L., and Townshend, A., Analytica Chim. Acta, 1973, 67, 1.Belcher, R., Bogdanski, S. L., Knowles, D. J., and Tomnshend, A., Analytica Chim. Acta, 1975, 77, Osibanjo, O., PhD Thesis, Birmingham University, 1975. “Standard Methods for the Examination of Water and Wastewater,” Fourteenth Edition, APHA, 53. AWWA and WPCF, Washington, D.C., 1975. Absorption Spectroelectrochemistry at a Platinum Electrode J. F. Tyson Department of Chemistry, University of Technology, Loughborough, Leicestershire, LE11 3T U and T.S. West Macaulay Institute for Soil Research, Craigiebuckler, A berdeen, A B 9 2Q J In this paper, a novel spectroelectrochemical method involving transmission spectroscopy parallel to an electrode surface, in combination with chronoamperometry and linear-sweep voltammetry, is described and assessed. Experimental Apparatus An ultraviolet - visible spectrometer was constructed from the appropriate components.The cell and electrode assembly consisted of a 2-cm silica cell containing two platinum-plate electrodes mounted horizontally. The cell was fitted with an inlet for oxygen-free nitrogen, a salt bridge (for connection with a saturated calomel reference electrode) and an outlet to remove solutions by suction.A potentiostatic waveform generator was used as a potential source.February, 1978 FOURTH INTERNATIONAL SAC CONFERENCE 65 Method The intensity of the light was monitored during the electrolysis of dilute (containing a few p.p.m.) metal ion and redox indicator solutions as a function of a number of experimental parameters. After recording the absorption value, the solution was removed and the electrode cleaned by applying a high positive potential while washing through with background electro- lyte solution. Results The results for the variation of absorbance with potential difference, wavelength and con- centration for a typical metal (zinc) have already been reported.112 The results for other metal ions are given in Table I.Absorption signals were also obtained from the background electro- lyte alone.TABLE I SUMMARY OF RESULTS Metal Cd c o Cr c u Fe( 111) Mn Ni Pb Zn Plateau region of absorbance versus potential variation/V 1.8-2 .O 1.4-2.0 1.4-2.0 1.6-2.0 1.8-2.0 1.9-2 .O 1.6-2.0 1.8-2.0 0.9-2.0 Linear range of analytical growth curve, p.p.m. 0-15 0-15 0-8 0-15 0-10 0-12 0-20 20-50 0-12 Sensitivity, p.p.m.0.09 0.11 0.05 0.10 0.09 0.08 0.16 0.35 0.08 Amax. at electrode surf ace/nm 215 210 215 235 270, 364 210 208 270 207 Amax. in 10-3 M KOH/nm 215 212 205 237 260, 360 215 210 234 207 The absorbance varied with time, increasing to a maximum value after about 30 s and with distance from the electrode surface; no absorption was detected 0.5 mm from the surface. The absorption was also sensitive to the nature of the pre-treatment; the higher the anodic potential, the greater the absorbances obtained for both metal ion and blank solutions.Discussion The results show that the phenomena observed are due to the production of absorbing species at the electrode surface, which then diffuse out into the bulk solution. It was origin- ally suggested192 that the absorbing species might be an intermediate in the metal-deposition process.On closer examination of this theory two problems become apparent; one thenno- dynamic, the other mechanistic. The Thermodynamic Problem The cathodic potential limit is set by the evolution of hydrogen gas, which obscures the light beam, and it has been calculated that a number of metals (namely nickel, cobalt, cad- mium, iron, chromium, zinc and manganese) will not be deposited within the accessible potential range. However, it is known, though perhaps not widely, that for sub-monolayer coverage of an inert electrode the normal form of the Nernst equation is not valid and an extra term must be introduced to account for the activity of the deposit.3 The result predicted by this form of the Nernst equation is that sub-monolayer amounts of metals will be deposited at potentials more anodic than those required for bulk deposition.This could bring the deposi- tion potentials of most of the metals studied to within the accessible potential range. The Mechanistic Problem Despite the vast amount which has been written in the electrochemical literature concerning the mechanism of electrodeposition, it has proved difficult to obtain a model for electrodeposi- tion that can be examined from the point of view of deciding at what stage interaction of an66 FOURTH INTERNATIONAL SAC CONFERENCE Proc.AnaZyt. Div. Chem. SOC. intermediate with the light beam occurs. However, it appears to be generally agreed that the mechanism is as follow^.*^^ 1.The metal ion reaches the electrified interface by the processes of diffusion, convection and migration. 2. Electrons are transferred by quantum mechanical tunnelling, which occurs when the appropriate conditions have been met. These conditions involve modification of the initial electron energy levels in the metal by application of a potential, and of the final levels by vibration of the metal ion - water molecule bond.3. A surface-adsorbed ionic species (adion) is formed. 4. The adion undergoes a two-dimensional random walk process, during which successive diminution in hydration and increase in the co-ordination by surface atoms occurs until the deposited atom is finally incorporated into the electrode crystal lattice. Difficulties arise when the model is applied to divalent cations, as it is known that electrons are transferred one at a time,6 and the nature and fate of the univalent intermediate that must be formed' is open to speculation.One possibility is that a homogeneous redox reaction (dis- proportionation) occurs, giving rise to the formation of hydrated atoms which may have sufficient life-times to diffuse away from the electrode and interact with the light beam.A study of the theory concerned with charge transfer and electrodeposition did not shed any light on how the surface of the electrode might affect the absorbance intensity. Nature of the Platinum Electrode Surface It is well known that a platinum electrode is not electrochemically inert.8 It is apparent9 that under the conditions used to clean the electrode the surfaces will be coated with platinum oxide.All of the experi- mental evidence has been obtained for strongly acidic electrolytes, in which the final stage is formulated aslo On cathodic polarisation this surface oxide is, of course, reduced. PtOH + Hf + e- + Pt + H,O It is thought that in neutral solution the reduction product could well be the hydroxide ion.Investigation of pH of Catholyte Changes in the pH near to the working electrode during electrolysis were followed by monitoring the absorbance at 552 nm for a solution containing 0.001 yo phenolphthalein. The results showed clearly that the solution became alkaline (pH 10-11) during electrolysis at much lower potentials when the surface was oxidised than when it was oxide free.The results of further experiments indicated that the absorbance signal from the metal ion solutions was observed only when the solution near to the cathode became alkaline. Process Occurring at the Electrode Surface From the evidence that the solution near to the cathode becomes alkaline it was deduced that the absorbances were due to the production of metal - hydroxo complexes.This is supported by a comparison between the absorption spectra obtained at the electrode surface and spectra obtained on making solutions of the metal ions alkaline (see Table I). The absorbance from the background electrolyte alone was attributed to that of OH-. When all of the surface oxide has been reduced the metal - hydroxo complexes dissociate and diffuse out of the light path, causing the absorbance to decrease.Quantitative Basis In deriving the basic relationship, it was assumed that the movement of species in the solu- tion was governed by semi-infinite linear diffusion. An expression relating the absorbance measured normal to the electrode surface was first derived, which was then converted to an expression for absorbance measured along the electrode surface, allowing for the fact that bothFebruary, 1978 FOURTH INTERNATIONAL SAC CONFERENCE 67 the oxidised and reduced species could absorb at the wavelength used.The resulting equation is where A is absorbance, D the diffusion coefficient of both the oxidised and reduced species (assumed equal) in cm2 s-l, t the time after the start of the electrolysis in s, eR the molar absorptivity of the reduced species in 1 mol-l cm-l, c0 the molar absorptivity of the oxidised species in 1 mol-l cm-l, I the path length on the electrode surface in cm, Cob the bulk con- centration of the oxidised species in mol 1-1 and h the height of the light beam in cm.As the absorbance cannot have a value greater than eRC:I, the variation of absorbance with any parameter will have a maximum value when 2 D W / d h = 1.The agreement between the predicted and actual variation of absorbance with concentration, time and height of the light beam for the metal ions was good, considering the limitations of the assumptions made in the derivation. A much better agreement was obtained for organic compounds exhibiting redox behaviour, where it was also possible to verify the agreement between predicted and actual variation of absorbance with wavelength.The organic com- pounds studied included 5-nitro-1,lO-phenanthroline - iron( II/III), o-tolidine and Variamine blue. The redox behaviour of these compounds could easily be distinguished from their acid - base behaviour. The compounds were also studied by oxidation. Analytical Applications Although there has recently been a considerable expansion in the use of the combination of optical and electrochemical methods to study the nature of electrode surfaces, adsorbed species or species in the double layer,11-13 there has been little or no previous application in quantitative analysis because of the inherent lack of sensitivity of these methods. This insensitivity is a result of the very short distance that the light beam travels in the absorbing medium.As far as the determination of metal ions is concerned, the sensitivity of the method is comparable to that of other general colorimetric reagents. It is possible that the method could offer advantages of convenience as it does not require the preparation of a reagent solu- tion and the absorbance values are obtained rapidly.As far as organic compounds are con- cerned the technique would only be of use if the compound of interest increased its absorbance on oxidation or reduction. The technique could also be used to determine diffusion coefficients and for both types of compound the technique could have advantages in being readily adapt- able to a flow-through cell.Passage of the light beam along the electrode surface overcomes this difficulty, 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. References Tyson, J. F., and West, T. S., Natwre, Lond., 1974, 139, 250. West, T. S., Analyst, 1974, 99, 886. Rogers, L. B., and Stehny, A. F., J . Electrochem. Soc., 1949, 95, 25. Matthews, D. B., and Bockris, J. O’M., in Bockris, J. O’M., and Conway, B.E., Editors, “Modern Bockris, J. O’M., and Reddy, A. K. N., “Modern Electrochemistry,” Volume 2, MacDonald, London, Bockris, J. O’M., and Damjanovic, A., in Bockris, J. O’M., and Conway, B. E., Editors, “Modern Bockris, J. O’M., and Despic, A. R., in Eyring, H., Henderson, D., and Jost, W., Editors, “Physical Gilman, S., in Bard, A. J., Editor, “Electroanalytical Chemistry,” Volume 2, Marcel Dekker, New Nadebaum, P.R., and Fahidy, T. Z., Flectrocbim. Actu, 1972, 17, 1659. Tilak, B. V., Conway. B. E., and Angerstein-Kozlowska, H., J . Electroanalyt. Chem., 1973, 48, 1. “Faraday Society Symposium on Optical Studies of Adsorbed Layers at Interfaces,” No. 4, Faraday Delahay, P., and Tobias, C. W., Editors, “Advances in Electrochemistry and Electrochemical Engineer- Strojek, J.W., and Kuwana, T., J . Electroanalyt. Chem.. 1968, 16, 471. Aspects of Electrochemistry,” Volume 6, Butterworths, London, 1971. 1970. Aspects of Electrochemistry,” Volume 3, Butterworths, London, 1964. Chemistry, An Advanced Treatise,” Volume IXB, Academic Press, London, 1970. York, 1967. Society, London, 1970. ing, Volume 9, Wiley, New York, 1973.68 FOURTH INTERNATIONAL SAC CONFERENCE Proc.Analyt. Div. Chem. SOC. Gas-phase Molecular-absorption Spectrometry for the Determination of Cations and Anions in Solution Malcolm S. Cresser Department of Soil Science, University of Aberdeen, Aberdeen, AB9 2UE The development of gas-phase molecular-absorption spectrometry (GPMAS) originated in a search for a rapid and reliable method for the determination of ammonium-nitrogen in Kjeldahl digests of soil and plant samp1es.l Ammonia gas can be displaced from alkaline sample solutions by a current of air, and determined by ultraviolet-absorption spectrometry.Initially, a steam-jacketed 530-mm tube was used as an absorption cel1,l but this was sub- sequently replaced by the 180-mm cell from a standard atomic-absorption spectrometer accessory, the Baird-Atomic A3490 Arsenic/Selenium Detection Unit.A detailed discussion of factors governing the sensitivity of ammonium-nitrogen determination using this cell has been published elsewhere.2 A detection limit of 0.1 pg ml-l or less should be attainable using most commercial atomic-absorption spectrometers. The method can be applied to the determination of any nitrogen-containing species that can readily be converted into ammonia.Nitrate can be determined after reduction with titanium(II1) sulphate at room temperat~re.~ Most a-amino acids are determined after treat- ment with ninhydrin and citric acid in a boiling water bath. For methionine only 15 min are necessary for conversion of the amino acid-nitrogen to ammonia.By using conversion condi- tions similar to those used by Bremner4 for the determination of a-amino acids, quantitative recoveries were observed for leucine, phenylalanine, norleucine and methionine, and satisfac- tory calibration graphs were obtained for these four amino acids over the range 0-50 pg ml-l of amino acid-nitrogen. Because the above procedures are simple, rapid and (provided that a suitable spectrometer is available) inexpensive, it seemed worthwhile to investigate the possibility of determining anionic species by use of a similar approach.A brief study of the ultraviolet-absorption spectra of the gaseous reaction products obtained upon acidification of solutions of sulphide, sulphite and nitrite indicated that it should be possible to determine each of these anions with reasonable sensitivity by means of GPMAS.5 In initial studies the precision attainable for the determination of these species was found to be significantly poorer than that obtained in the determination of ammonia.This was found to be due primarily to the much more rapid rate of evolution of the gaseous reaction products from the anion solutions upon acidification, which rendered the experimental stopper and shake technique inadequate.This problem was overcome by designing a simple reaction vessel, which enabled the acid to be added by direct injection into the sample solutions through which air was already being passed. The air bubbles in this instance provide sufficient turbulence for rapid and thorough mixing in sib.A second factor contributing to the deterioration in precision was found to be the poor stability of the sulphite and sulphide stock and standard solutions in the absence of suitable stabilisers. It was found, for example, that the long-term stability of sulphite solutions could be improved considerably by rendering sample and standard solutions 3 yo with respect to propan-2-01.Sulphide can be determined by measuring the ultraviolet absorbance of hydrogen sulphide at about 200 nm. The limited fine structure observable means that the slit width is much less critical for this determination than for ammonia, and reasonable results can be obtained by using 40-mm silica cells in a solution spectrophotometer of only moderate resolution. Neither the acidity nor the air flow-rate is critical over wide ranges.Injection of 1 ml of 4 M hydrochloric acid into 20-ml aliquots of the sample solution gives satisfactory results. Opti- mum conditions for the determination of sulphite as sulphur dioxide are similar to those observed for sulphide. The author employs 1 ml of 2 M acid plus 15 ml of sample solution containing 3% of propan-2-01. Both species can be determined over the sulphur concentration range 0-25 pg ml-l, the limit of detection being about 0.1 pg ml-l under the conditions des- cribed.The determination of nitrite is somewhat more complicated than that of sulphite or sulphide. The absorbing species in this instance appears to be a mixture of nitrogen oxides and nitrous acid. The fine structure on the absorption spectrum disappears when the gaseous reactionFebruary, 1978 EQUIPMENT NEWS 69 products are dried, which is probably indicative of removal of water vapour eliminating the possibility of the formation of the normal equilibrium concentration of nitrous acid. Although optimum sensitivity is attained at 195 nm, the peak at about 203 nm is normally used. Much higher acidity is required for the sensitive determination of nitrite; a detection limit of 0.1 w 1 - l of nitrite-nitrogen can be achieved by injecting l-ml aliquots of the sample solution into 20-ml aliquots of 8 M hydrochloric acid. The acidity must be very carefully controlled. Under these conditions linear calibration graphs can be obtained up to at least 25 pg ml-1 of nit ri te-nit rogen . The absorbance obtained from nitrite solutions is suppressed by the presence of small amounts of thiosulphate. The decrease in absorbance is reproducible, and constitutes the basis of a useful indirect method for the rapid determination of thiosulphate. Under the condi- tions used, and provided that the nitrite is present in excess, it appears that a 1 : 1 nitrite - thiosulphate reaction takes place. Although for the results reported so far relatively large aliquots of sample solution have been employed, it is possible to use a scaled-down version of the apparatus for the analysis of smaller volumes of sample. By using a 10-ml capacity plastic centrifuge tube as the reaction vessel, for example, successful nitrate determinations have been completed on 150- and 500-p1 aliquots of xylem sap and root sap collected directly from, plant samples6 The precision of the method tends to deteriorate significantly when very small sample volumes are employed, however. Thus, if nitrogen (or argon) is used as a displacing gas, hydrogen sulphide or sulphur dioxide can be introduced into a cool hydrogen - nitrogen - entrained air flame. In this instance a small, purpose-built burner is preferable to those used in flame absorption or emission spectrometers, because the spray chambers in the latter give rise to an excessive dead volume. Moreover, lower flow-rates are generally required in the GPMAS volatilisation techniques. Similar techniques can also be employed in plasma-emission spectrometry. The techniques evolved for GPMAS can also be utilised in emission spectrometry. The author is indebted to Mrs. E. Haw for assistance with much of the experimental work, and to the Science Research Council for financial support. References 1. 2. 3. 4. Bremner, J . M., “Methods of Soil Analysis, Part 2, Chemical and Microbiological Properties,” 5. 6. Cresser, M. S., Analytica Chim. Acta, 1976, 85, 253. Cresser, M. S., Lab. Pract., 1977, 19. Cresser, M. S., Analyst, 1977, 102, 99. American Society of Agronomy, 1965, p. 1238. Cresser, M. S., and Isaacson, P., Talanta, 1976, 23, 885. Cresser, M. S., and McBratney, A., unpublished results.

ISSN:0306-1396    

DOI:10.1039/AD9781500052

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

February, 1978 EQUIPMENT NEWS 69 Equipment News Spectrophotometers Versatile spectrophotometers have been designed to meet the needs of routine analysts as well as research chemists. All of the new range of instruments incorporate holographic gratings, giving photometric accuracies of better than f0.5%. The new range includes Model JY 101, a single-beam, visible-light spectrophotometer with accuracy better than 2 nm and a resolution of lOnm, the JY 105, a more complex single- beam unit incorporating sample thermostating and autozeroing, and the JY 201, which is a double-beam, ultraviolet - visible instrument with accuracy & 0.5 nm that is capable of being controlled by a microprocessor.EDT Research, 65 Ivy Crescent, London, W4 5NG. Plasma- source Analytical Spectrometers Inductively-coupled plasma-emission analytical systems are capable of analysing liquid samples for trace metals down to the nanograms per millilitre level.The high energy output of the plasma (1.5-2.5 kW) is available for the ashing and exciting of even refractory samples with70 EQUIPMENT NEWS Proc. Analyt. Div. Chem. SOC. negligible or zero matrix and inter-element effects. The dynamic range of the instruments can extend to give linear calibrations over six orders of magnitude.Computer interfacing is readily achievable using a PDP 11. EDT Research, 65 Ivy Crescent, London W4 5NG. X-ray Spectrometer The PW 1600 simultaneous X-ray spectrometer is fitted with a 12-position sample changer and a fast printer. This permits the analysis of up to 28 elements in under 1 min and is designed for high volume quality-control analyses in the metal, mining, cement and similar industries.Philips Industries, Scientific and Analytical Equipment Department, Leleyweg 1, Almelo, The Netherlands. Emission Spectrometer The PV 8350 emission spectrometer is a direct reading vacuum spectrometer. Typically, it determines up to 20 elements simultaneously, including carbon, sulphur, phosphorus and boron.Philips Industries, Scientific and Analytical Equipment Department, Leleyweg 1, Almelo, The Netherlands. X-ray Diffraction Generator A high stability constant-potential generator for X-ray diffraction and spectrometry systems, designated PW 1730, can be used for single-tube and two-tube sequential or simultaneous opera- tion.High voltage is variable between 20 and 60kV and the tube current between 10 and 80 mA. The stability of kilovolts and milliamperes is 0.002~0 per 1% mains voltage variation and the temperature drift is 0.002~0 per "C ambient. The maximum output power is 3 kW. Philips Industries, Scientific and Analytical Equipment Department, Leleyweg 1, Almelo, The Netherlands. Rotating Anode X-ray Generator The rotating anode X-ray generator operates at currents up to 300 mA at 50 kV on a focus of 0.5 mm.This generator brings the advantage of short counting and exposure times with focal spot sizes down to 0.1 mm to all crystallo- graphers. The equipment complies with the forth- coming statutory safety regulations under the Health and Safety Act. Elliot Avionic Systems Ltd., Elstree Way, Borehamwood, Hertfordshire. Coloured Glass Filters The square, 50 x 50 mm coloured glass filters are made from virgin Schott material.There are 78 individual filters available from stock. Each filter is supplied with an individual spectrophotometer curve. Melles Griot BV, Nieuwekade 10, Postbus 567, Arnhem, The Netherlands. Liquid Chromatographs Series 3 liquid chromatographs with micro- processor control are now available.The microprocessor enables solvent delivery to be performed automatically, thus improving the instrument's reliability, precision and ease of operation. Series 3 can be operated in iso- cratic, solvent-programme and flow-programme modes. The high-pressure capability, rapid program- ming and unlimited solvent supply give precise and steady flow plus a wide range of flow-rates adjustable from 0.1 ml min-1 when the two pumps are combined.Perkin-Elmer Ltd . , Beaconsfield, Bucking- hamshire. Sample Applicator for Thin-layer Chroma- tography The Linomat I11 automatically delivers a pre- selected volume of sample in the form of a narrow band of pre-selected length from a precision syringe, the sample solution being sprayed on to the plate in a stream of nitrogen directly from the tip of the syringe needle.The quality of resolution is such that mixtures containing a number of dyes can be separated by eluting for just 3 cm. Baird & Tatlock (London) Ltd., Freshwater Road, Chadwell Heath, Romford, Essex, RM1 1HA. Total Organic Carbon Analyser The Dohrmann DC-54 measures total organic carbon down to f 10 p.p.b.The independent measurement of purgeable organic carbon (POC) to a level of f 1 p.p.b. can be used as an indication of haloforms in drinking water. The low detection levels are achieved by a two-step analysis. The 10-ml sample is sparged, inorganic carbon dioxide is removed and the vola- tile organics are reduced to methane. Residual organics are then irradiated with ultraviolet light and the resulting carbon dioxide is sparged and reduced to methane.In both instances a flame-ionisation detector is used for measure- ment. Techmation Ltd., 58 Edgware Way, Edgware, Middlesex, HA8 8 JP.February, 1978 EQUIPMENT NEWS 71 Microcomputer - based Ultraviolet - Visible - Near Infrared Spectrophotometer The microcomputer-controlled double-beam ultraviolet - visible - near infrared spectro- photometer, the Model 340, offers ease of operation, high performance, enabling highly accurate photometric determinations, and versatility in sample handling, which is obtained through convenient instrumental operating conditions and well designed accessories.The microprocessor controls source and filter changes, the stepper motor monochromator drive, the integral X - Y recorder, 0 and 100% transmission calibrations, response times, auto zero and automatic base line correction, etc.The double monochromator covers the range 190-260 nm with a resolution of 0.15 nm and reduces stray light to 0.000 2% transmission a t 300 nm; the microprocessor enables a base line flatness of f 0.001 A in the ultraviolet - visible region and 0.002 A in the near infrared region to be achieved. Perkin-Elmer Ltd ., Beaconsfield, Bucking- hamshire. Gas Chromatographs The Sigma Series is a complete product line of four complementary gas-chromatographic systems with interchangeable components and accessories consisting of: Sigma 1, a system combining one or more gas chromatographs with integral control and data handling; Sigma 2, a multi-detector, microprocessor-controlled gas chromatograph ; Sigma 3, a microprocessor- controlled gas chromatograph ; Sigma 4, an isothermal gas chromatograph; and Sigma 10, a laboratory data system for multiple channels with printer - plotter.Each instrument provides identical chromato- graphic performance. The use of a micro- processor in Sigma 1, 2 and 3 instruments enables certain functions to be performed automatically.Perkin-Elmer Ltd . , Beaconsfield, Bucking- hamshire. Graphite Furnaces The new HGA-220 and the HGA-76B graphite furnaces are compatible with all current Perkin- Elmer atomic-absorption spectrophotometers. As with other Perkin-Elmer furnaces, the radiation passes through a small graphite tube into which the sample is placed.Inert gas flows through the tube from either end, sweeping volatilised matrix material out of the sample inlet port. The furnace programme of drying, charring and atomisation is performed automatically. Maximum power heating, which can be selected by the operator, raises the temperature very quickly to atomise the elements rapidly, thus significantly improving the sensitivity for refractory elements such as titanium and boron, and permitting furnace temperature of 3 000 "C to be reached.A silicon diode temperature sensing device detects the point at which desired temperature is reached and signals the power supply to reduce power. The Perkin-Elmer AS-1 auto- matic sampler can be coupled directly to both the HGA-2200 and the HGA-76B.Perkin-Elmer Ltd., Beaconsfield, Bucking- hamshire. Gas Chromatograph - Mass Spectrometer The high-performance HP 5990 series gas chromatograph - mass spectrometer (GC - MS) , having a more powerful data system composed of a fast HP 2lMXE computer and a dual-disc drive, has been announced. The fully integrated GC - MS incorporates a two-bay data system, with all-digital electronics, a microprocessor-controlled GC, electron- multiplier detector, power supply, analyser vacuum system, inlet vacuum system and a GC - MS membrane interface.An HP 2 1MX E-Series microprogrammable 16-bit computer with 32K words of memory and an HP 7900A dual-disc drive with 5 megabytes of data storage is included. Autotune can set up and calibrate the mass spectrometer automatically to save manual tuning by producing a mass spectrum with a calibrated mass scale and standard peak inten- sities.Hewlett-Packard Ltd., King Street Lane, Winnersh, Wokingham, Berkshire, RG11 5AR. Tissue Dehydrator and Processor The Reichert EM tissue dehydrator is designed to dehydrate up to 45 specimens simultaneously. There are 9 automatically timed stages within an enclosed chamber, the tissue being taken up to 95% alcohol. There is also a provision for immersion in 100% alcohol and propylene oxide. The instrument ensures extremely con- sistent results and complete safety.A complementary instrument, the Reichert EM Tissue Processor, provides a means of automating manual procedures and handles up to 45 specimens simultaneously. It offers up to 10 individually and automatically timed fixing, dehydrating and infiltrating channels, and72 EQUIPMENT NEWS Proc.Analyt. Div. Chem. SOC. accommodates the chemical solution in glass containers within the equipment. An auto- matic “clean” cycle at the end of each pro- gramme ensures the elimination of any possible contamination. Reichert - Jung UK, 820 Yeovil Road, Slough, Berkshire, SL14JB.Suspended Solids Monitors Partech Suspended Solids Monitors are available for either laboratory or field use and all are portable. The range of sensor probes and flow cells allows measurement of suspended solids between 1 mg 1-1 and 10 g 1-1 to be made, and certain models are available with recorder output. Weatherproof enclosures are also available.Baird & Tatlock (London) Ltd., Freshwater Road, Chadwell Heath, Romford, Essex, RM1 IHA. Hi-Volume Air Sampler The Staplex Portable Hi-Volume air sampler measures air flow rate by means of an indirect, variable-orifice meter. This device indicates the pressure drop across an orifice in the light- weight aluminium housing, and is calibrated against a standard orifice on the intake.The air mover is a high-speed, heavy-duty pump and motor, 0.49 hp at 15 600 rev min-l, and is designed for 24-h sampling. The standard unit takes the 102-mm Gelman range of glass-fibre air sampling filters, with a special filter holder available for the 8 x 10 in range of Gelman glass-fibre filters. Gelman Hawksley Ltd., 12 Peter Road, Lancing, Sussex, BN15 8TH. Smoke Density Measurement The National Bureau of Standards - Aminco equipment measures the smoke generation quantitatively in specific density units under controlled radiant non-flaming and flaming exposure.The specimen, 3 x 3 in is placed in front of a radiant source contained within a gas- tight chamber and a simple photometer system measures the change in density. The test can be carried out on materials ranging from plastics, carpets, mattresses and clothing, to electrical cables, conveyor belts, paper, etc.Stanton Redcroft, Copper Mill Lane, London, SW17 OBN. Radiologic Test Tools A range of test tools for simple routine monitor- ing of a number of important parameters in diagnostic radiography and nuclear medicine is available. Test objects are available for peak kilovoltage measurements from 28 to 120 kV, focal spot size check, light beam diaphragm alignment, exposure timer and milliampere seconds setting, mechanical misalignment on tomographic X-ray sets, low contrast and imaging performance of fluoroscopic systems, limits of resolution in zero-radiographic and film - screen mammographic systems and cassette screen - film contact.A sensitometer - densito- meter outfit is available for reproducible light exposure and measurement on X-ray film. For use on gamma cameras, test patterns are available to test the uniformity of detector response, resolution, mapping accuracy and imaged field dimensions. The test objects are supplied either indivi- dually or in sets to suit customers’ particular requirements.D. A. Pitman Ltd., Mill Works, Jessamy Road, Weybridge, Surrey. High Pressure Flangeless Tube Connectors High pressure fluid tube connectors are now available, the Omnifit High Pressure Series. A tube gripper allows the use of flangeless tubing. Connections are leak tight to 1 000 p.s.i. The flow path of an assembled Omnifit connector is tubing to tubing. The fittings are self- centring, leaving no dead volume.The connectors are chemically and biolo- gically inert. They are made of polypropylene, or for highly corrosive environments or an increase in service temperature rating, clear Tefzel. In an assembled connector each tube end has a fitting of Teflon encapsulated in stainless steel that offers a large area of sealing surface. This Teflon - Teflon seal maintains its leak tightness despite inevitable cold flow.Omnifit high pressure fittings are designed for use with Teflon or other plastic tubing having an outer diameter of $G in (1.59 mm). Three bore sizes (0.8, 0.5 and 0.3 mm) of Teflon tubing are available. Zero dead volume fittings with 0.8 mm bore internal passages are also available for the construction of fluid systems. Biolab Ltd., 61 Norfolk Street, Cambridge, CB12LE. Graduated Pipettes Technico graduated pipettes have been modified to meet BS 700:1976, to take advantage of the faster permitted flow-rates. A new range of Technico graduated pipettes is also available. These meet the requirements of BS 700 Class B Type 3, being calibrated for delivery from zero at the top of the scale to theFebruary, 1978 CORRESPONDENCE 73 jet. and sub- Pipettes have the .divisions : in this range have very fast flow For use in conjunction following nominal capacities and with any specific-ion or pH meter, the arm, 1 x 0.01 ml; 2 x 0.02 ml; with counterbalance springs, makes moving 6 x 0.05 ml; 10 x 0.1 ml; and 25 x 0.2 ml. electrodes from beaker to beaker a smooth one- handedaction. Christopher Street, London, EC2P 2ER. MSE Scientific Instruments, Manor Royal, Crawley, RHlO 2QQ, West Sussex. Electrode Arm announced recently, A. Gallenkamp & Co. Ltd., P.O. Box 290, An electrode arm with swivel base has been

ISSN:0306-1396    

DOI:10.1039/AD9781500069

出版商:RSC    

年代:1978

数据来源: RSC