摘要:

Proceedinas - - - ~~~of the Analytical Division ofThe Chemical SocietyCONTENTS79 Annual General Meeting of theAnalytical Division80 Reports of Meetings81 The President8188 Summaries of Papers88 'Developments in PharmaceuticalAnalysis'91 'Laser Applications in Analysis'94 'Analysis in Archaeology, Art andAddress of the Retiring PresidentAntiquities'104 'Lasers in Analytical Chemistry'107 Rank Hilger Spectroscopy Prize108 Personal and Lightweight Flam-mable Gas Monitors11 0 Conferences and Meetings112 Centenary of The Analyst11 3 Publications Received11 6 Analytical Division DiaryVolume 13 No 4 Pages 79-1 16 April 197April 1976 PADSDZ 13(4)79-116(1976)ISSN 0306-1 396PROCEEDINGSANALYTICAL DIVISION OF THE CHEMICAL SOCIETYOF THEOfficers 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 Chemical 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, Publications Sales Office, Blackhorse Road, Letch-worth, Herts., SG6 1 HN.Non-members can onlv be supplied with Proceedings as part of a combined subscription with The Analystand Analytical Abstracts.0 The Chemical Society 1976ANALYTICAL DIVISIONTIEA modern, wider version of the tie bearing the SAC Coat of Arms is now onsale to members of the CS Analytical Division. The tie, which carries a simp-lified version of the Coat of Arms woven in red, silver and gold as a singlemotif, is available in three different background colours-dark blue, dark greenand maroon. The tie is manufactured in a Crimplene - Terylene mixture.The price of the tie is Al.60, post free. The traditional, narrower versionof the tie is also still ava'ilable at El.10, post free. Orders, accompanied by theappropriate remittance, should be sent to The Secretary, Analytical Division,The Chemical Society, Burlington House, Piccadilly, London, W1V OBN. ,Please make cheques payable to The Chemical Society, and ensure that~ the background colour required on the tie is stated

ISSN:0306-1396    

DOI:10.1039/AD97613FX013

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

114 ANALYTICAL DIVISION DIARY PYOC. Analyt. Div. Chem. SOC.Analytical Division Diary, continuedMay, continued“Agricultural Analysis,” by A. M. Ure.“Food and Water Analysis,” by I. Dale.“Preconcentration Techniques,” by A. M.Ure.Demonstration Session on analytical appli-cations of flame atomisers.“Recent Developments in Instrument De-sign,” by K. J. Mills.“Filament and Furnace Atomisers,” by J. M.Ottaw ay .Demonstration Session on Delves’ cup mer-cury cold vapour, hydride generation cellsand filament and furnace atomisers.Room C133 of the Thomas Graham Building,University of Strathclyde, Glasgow.Wednesday, 26th, 2.15 pm. : LoughboroughChvomatogvaphy and Electvophovesis GYO@and Midlands Region on “AnalyticalChemistry of Drug Metabolites.”“Analytical Problems Involved in the Meta-bolism of Drugs and Foreign Compounds,”by J .W. Gorrod.“The Use of Thin-layer Chromatography inthe Quantitative Analysis of Body Fluids,”by D. A. Stopher.“Gas - Liquid Chromatographic Methods forthe Analysis of Drug Metabolites,” byA. C. Moffat.“The Application of HPLC to Drug Meta-bolism,” by G. Skellern.Lecture Theatre U020, Brockington Ex-tension, TJniversity of Technology, Lough-borough, Leicestershire.The Practising Chemists’A History of theSociety for Analytical Chemistry1874-1 974By R. C. CHIRNSIDE andJ. H. HAMENCE225 pages; 11 platesCS Members f 2.50ISBN 0 85990 100 9f 3-00; u.s.$8.00Obtainable from The Publications Sales Officer,The Chemical Society, Blackhorse Road, Letchworth, Herts.SG6 1 HA p d , 19’16 ANALYTICAL DIVISION DIARY 115Analytical Division Diary, continuedMay, continued Special Techniques Group on “Micropro-cessors-Definitions and Applications.”I t microprocessors and Their Use for theAnalyst,” by D. Newton.“The Use of a Micro-computer for ContinuousData Processing in Conjunction with anInfra-red Spectrometer,” by D. Pooley.“Microprocessors and Titrimetry,” by D.Betteridge.Lecture Theatre A, College Block, ImperialCollege, South Kensington, London, S.W.7.Wednesday, 12th, 2.30 p.m. : London“Enthalpimetric Determination of the Con-stituents of Dolomite,” by M. A. H.Al-Gifri and L. S. Bark.Exeter.Chemistry Department, The University,Wednesday and Thursday, 5th and 6th:LowestoftRadiochemical Methods Gvozzl, on “Radio-analysis and the Marine Environment .”Wednesday, 5th, 2 J3.m.-Introduction and welcome by A.J . Lee.Plenavy Lectuve : “Radioactive Nuclides inthe Marine Environment : Their Occurrenceand Significance,” by J . D. Burton.“Analytical Procedures Used for the Mea-surement of Pu and TransplutoniumIsotopes in Marine and Other Environ-mental Samples,” by C. N. Murray.“Analytical Techniques for Determination ofRadiocaesium in Sea Water and itsDistribution in UK Coastal Waters,” byC. W. 13aker and D. F. Jefferies.Visit to Fisheries Radiobiological Laboratory.Thursday, 13th, 2 p.m. : TeddingtonPavticle Size Analysis Gvoup on “SurfaceEnergy. ”“Particles, Surface Energies and Properties,”by E.D. Hondros.“Specific Surface Areas from Heats ofPreferential Adsorption (Flow Micro-calorimetry),” by C. E. Templer.“Heats of Immersion by Calvert Micro-calorimetry,” by J. Wightman.“Study of the Adsorption of Polar Moleculeson Aluminium Surfaces,” by J. Treverton.National Physical Laboratory, Teddington,Middlesex.Thuvsday, 6th, 9 a.m.-“The Use of Nuclear Techniques for Ele-Wednesday, 19th, 6 p.m.: HerefordAnalytical Division.mental Analysis of the Seabed,” by C. G. Solvent Extractionist Looks at xon _ _Selective Electrodes,” by H. Freiser.Hereford.Clayton.“Some Radionuclides of Interest in theClyde River System,” by M. S. Baxter.“Sediment Dating in Fresh and MarineEnvironments, with Special Reference toR.Tamar,” by E. I. Hamilton.Lovett and J. A. Hetherington.Henry and co. Ltd., Holmer Road,Thursday, 20431, 10.45 a.m. : BetchworthStudies in Irish Sea,,, by B. Biological Methods Group Suvnmev Meeting:Visit to Beecham Research Laboratories,Brocliham Park, Betchworth, Surrey. Visit to Fisheries Radiobiological Laboratory.Fisheries Research Laboratory LectuieTheatre, Ministry of Agriculture, Fisheriesand Food, Pakefield, Lowestoft. GlasgowTuesday and Wednesday, 25th and 26th:ScottisJz Regioa on “Atomic AbsorptionWednesday, 12th, 2.30 p.m. : ColchesterEast Anglia Region on “Ion Selective Elec-trodes.”“Some New Applications of Ion SelectiveElectrodes and Gas Sensing Membranes,”by P. L. Bailey.“The Use of the Fluoride Electrode for theDetermination of Fluorine in BiologicalMaterial and Feedingstuffs,” by G.Lewis,C. W. Clarke and F. J. Salt.“Application of Ion Selective Electrodes toBrewing Analyses,” by G. K. Buckee.North East Essex Technical College andSchool of Art, Sheepen Road, Colchester.Spectrometry.”Tuesday, 25th, 2 J3.m.-“Principles of Atomic Absorption Spectro-metry,” by W. B. Rowston.“Spectral, Physical and Chemical Inter-ferences and Their Control in RoutineAnalysis,” by J. M. Ottaway.Demonstration Session on the setting up andoptimisation of atomic absorption instru-ments.Wednesday, 26th, 9 a.m.-“Clinical Analysis,” by G. S. Fell.[continued on p. 11Analytical Division DiaryAPRILThursday and Friday, 22nd and 23rd:ShefieldAtomic Spectroscopy Group, jointly with theModern Methods of Analysis Group of theSheffield Metallurgical and EngineeringSociety and the Spectroscopy Group of theInstitute of Physics, on “Detection Limitsand Trace Analysis.”Thursday, 22nd, 2.15 9.m.-Round Table on “Detection Limits.”Speakers: R.A. Mostyn, R. Smith, P.Hurley, L. Ebdon and J. Moore.“The Accuracy of Analytical Results : Inter-laboratory Studies in Trace Analysis,” byA. L. Wilson.“The Preparation and Certification of Analy-tical Reference Materials,” by P. D.Ridsdale.“How Clean is Clean?” by J. F. Woolley.Friday, 23rd, 9 a.m.-“Trace-element Analysis of Super AlloysUsing Hollow-cathode Emission Spectro-scopy,” by K. Thornton.“Some Spectrochemical Trace Analysis Tech-niques in Use in MQAD,” by J .Moore andK. A. Mostyn.“Monitoring Residual Elements in Steels byAAS,” by M. S. Taylor.“Trace Elements in Ceramics,” by H. Bennett.“Trace Analysis of Geological Materials, ” byP. J. Moore.“The Determination of Trace Elements inHigh-purity Glasses and Related MaterialsUsed for the Production of High-qualityFibres,” by C. Fuller.“The Use of X-ray Spectroscopy in the Deter-mination of Air-borne Pollutants,” by S. A.Isherwood.“The Determination of Lead in DeciduousTeeth from Children in the City of Birming-ham, “by A. Townshend.“The Analysis of Hazardous IndustrialAtmospheres,” by J . G. Firth, H. Jacksonand R. Foster.“Legal Requirements for Analysis of the En-vironment,” by D. G. Swinburn.Ranmoor House, The University, Sheffield.Thursday, 29th, 2.30 p.m.: LondonBiological Methods Group on “The Anti-bacterial Activity of Contact Lens Solu-tions.” Speakers: A.F. Ross, D. J. G.Davies and P. Cordrey.The Pharmaceutical Society, 17 BloomsburySquare, London, W.C.l.MAYTuesday, 4th, 2 p.m.: BillinghamNorth East Region and Electvoanalytical Gvoupon “Aspects of Fermentation Control.”Speakers: D. G. Wright, A. Edgson andICI Ltcl., Agricultural Division, Billingham,Tuesday and Wednesday, 4th and 5th:ExeterAnalytical Division on “Research and De-velopment Topics in Analytical Chemistry.”Tuesday, 4th, 2.15 p.m.-“Some Studies in Optoacoustic Spectro-scopy,” by A. J. Adams, A. A. King, B. C.Beadle and G. F. Kirkbright.“Cation Adducts of Nonionic Surfactants asIon-selective Electrode Sensors,” by A.M. U.Jaber, G. J . Moodyand J . D. R. Thomas.“Microprocessors in Analytical Chemistry,”by P. David.“Interferometric Atomic Line Profile Mea-surements of Electrodeless Discharge LampSources,” by S. L. Castleden and G. F.Kirkbright.“Problems in Environmental Phthalate Ana-lysis,” by R. D. J . Webster and G. Nickless.“Polarographic Studies of Some ForeignOrganic Compounds in the Aqueous En-vironment,” by J . P. Hart, W. FranklinSmyth and B. J. Birch.“Determination of Silicon in Steel Using aPulse Polarograph,” by A. A. Osakwe.Wednesday, 5th, 9.15 a.m.-“Determination of Trace Metals by In-hibition of Insolubilised Enzymes,” byT. R. Stokes.“The Spectrophotometric Determination ofFluoride Using Sulphonated Alizarin Fluo-rine Blue,” by S. F. Deane.“Determination of Some Trace Elements byCandoluminescence Measurements, ” by S.Karpel.“Determination of Zinc and Cadmium in13iological Samples by Atomic FluorescenceSpectrometry,” by F. E. R. Hussein,G. S. Fell and J. M. Ottaway.“The Determination of Mobile Nitrogen andNitrides in Steel,” by G. D. Long.“Some Analytical Problems Concerning TraceMetal Analysis of Human Placentae,”by A. K. Khera and D. G. Wibberley.“Mechanistic Studies of the Reactions ofSubstituted Triazines with Iron( XI),” byI. H. Hashmi.[continued inside back coverw. Pyggott.Cleveland.Printed by Heffers Printers Ltd Cambridge Englan

ISSN:0306-1396    

DOI:10.1039/AD97613BX015

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

Vol. 13 No. 4 April 1976 Proceedings of the Analytical Division of the Chemical Society Annual General Meeting of the Analytical Division The fourth Annual General Meeting of the Analytical Division of the Chemical Society was held a t 3 p.m. on Wednesday, March loth, 1976, a t The Boots Company Ltd., Pennyfoot Street, Nottingham. The Chair was occupied by the President, Dr. G. W. C. Milner, M.Inst.P., C.Chem., F.R.I.C.The Report of the Council for the year ending March, 1976, was presented by the Honorary Secretary and adopted. The Scrutators, Mr. D. A . Elvidge and Mr. P. C. Weston, reported that the following had been elected officers for the coming year- Pvesident-D. W. Wilson, M.Sc., C.Chem., F.R.I.C. Past Pvesidents sevving o n the Council- G. W. C. Milner, A.A. Smales, T. S. West and C. Whalley. Vice-Pvesidents-H. E . Brooltes, H. Egan and W. H. C. Shaw. Honovavy Tveasuvev- J. K. Foreman. IIonovavy Secvetavy-1’. G. W. Cobb. Honovavy Assistant Secvetavies-D. I. Coomber (Programmes Secretary) and I). C. M. Squirrcll. Othev Membevs of Council--The Scrutators further reported that 57 1 valid ballot papers had been received and that votes had been cast Pvesentatiolz of the eleventh SAC Gold Medal by the Pvesident, Dv.G. W . C. Milnev, to Pvofessov E . Bishop (R). in the election of Ordinary Members of Council as Pollows-D. Betteridge, 352; D. Thorburn Burns, 283; G. 33. Crump, 287; W. T. Elwell, 320; S. Greenfield, 367; G. Nickless, 245; G. E. Penketh, 276; D. I. Rees, 297; D. Simpson, 360; W. I. Stephen, 267.Pvesentatiovz of the fivst Distinguished Sevvice A wavd by the Pvesidevzt to Dv. A . J . Amos, O R E (R). The President declared the following to have been elected Ordinary Members of Council for the ensuing 2 years--D. Betteridge, G. U. Crump, W. T. Elwell, S. Greenfield, 11. I. Rees and D. Simpson. I,. S. Bark, H. E. Ih-ookes, W. J. Price, D. C. M. Squirrell, A. Townshend and J.Whitc- head, having been elected members of the Council in 1975, will, by the rules of the Division, remain members of the Council for 1976. D. C. Garratt (Chaivman of the Analytical Methods Committee), F. J. Bryant (Chaivman of the Analytical Abstracts Committee) , H. J . Cluley (Chaivman of The Analyst Publications Committee), J. B. Dawson (Chaivman of the Analytical Books a.tzd Monogvaphs Committee), J .M. Ottaway (Chaivwzan of the Scottish Region), G. J . Dickes (Chaivman of the Western Region), .F. E. Harper (Chaivman of the Novth East Region), and A. W. Hartley (Chaivman of the East Anglia Region) will be ex o$cio members of the Council for 1976. L. S. Bark (Chaivman of 7980 REPORTS OF MEETINGS Proc. Analyt. Din. Chem. SOC. the Novth W e s t Region) and A.Townshend (Chaivman of the M i d l a n d s Region) are elected members of Council. The Annual General Meeting was followed by the Address of the Retiring President, Dr. G. W. C. Milner, entitled “The Changing Scene in Analytical Chemistry,” and this Address appears on p. 81. At the Informal Dinner held at the George Hotel, Nottingham, in the evening, Dr. Milner presented the eleventh SAC Gold Medal to Professor E. Bishop, and the first Analytical Division Distinguished Service Award to Dr. A. J. Amos, OBE. Biographies of the two recipients were published in the March issue of Pvo Geed i pzgs .

ISSN:0306-1396    

DOI:10.1039/AD9761300079

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

80 REPORTS OF MEETINGS Proc. Analyt. Din. Chem. SOC. Midlands Region The Elwell Award Presentation Meeting was held at 6.30 p.m. on Tuesday, January ZOth, 1976, at Lanchester Polytechnic, Coventry. The Chair was taken by the Chairman of the Region, Dr. A. Townshend. Two papers submitted for the Award were read : “The Determination of Phosphorus Com- pounds by MECA,” by 0. Osibanjo; and “Ana- lytical Aspects of Gas-phase Auger Electron Spectrometry,” by P.A. Hewitt. Reports of Meetings North West Region The fifty-first Annual General Meeting of the Region was held at 6.30 p.m. on Friday, January 23rd, 1976, at the University, Salford. The Chair was taken by the Chairman of the Region, Dr. L. S. Bark. The following office bearers were elected for the forthcoming year: Chaivman-Dr. L.S. Bark. Vice-Chaivman- Mr. J . W. Ogleby. Honovavy Secvetavy-Mr. G. B. Crump, Shell Research Ltd., Thornton Research Centre, P.O. Box 1, Chester, CH1 3SH. Honovavy Tveasuvev-Mr. M. McDonnell. Membevs of Committee-Mr. J. M. Bather, Mr. J. Cottam, Mr. G. Davison, Mr. T. Hodson, Mr. B. Taylor and Dr. P. R. Wood. Mr. E. C. Conchie and Mr. G. F. Hooke were appointed as Honorary Auditors.The Annual General Meeting was followed by a lecture on “Catalytic Methods in Chemical Analysis” by Dr. G. Svehla. Western Region The twenty-first Annual General Meeting of the Region was held a t 6 p.m. on Friday, January 23rd, 1976, at the University, Bath. The Chair was taken by the Chairman of the Region, Dr. W. J. Williams. The following office bearers were elected for the forthcoming year : Chaivvnan Mr.G. J . Dickes. Vice-Chaivman-Mr. M. C. Finniear. Honovavy Secretavy-Dr. G. Nickless, School of Chemistry, The University, Bristol, BS8 1TS. Honovavy Tveasuvev-Dr. D. Betteridge. Menabevs of Committee-Dr. W. Cule Davies, Mr. A. G. Hill, Mr. E. B. Reynolds, Mr. G. Jones and Dr. W. J. Williams. Mr. E. A. Hontoir and Mr. E. Minshall were re- appointed as Honorary Auditors.MY. 0. Osibanjo with the Elwell Aevavd. Mr. Osibanjo’s paper was awarded first prize, and he was presented with the trophy and a cheque for fj15 by Dr. Elwell. North East Region The tenth Annual General Meeting of the Region was held at 7.15 p.m. on Wednesday, January Zlst, 1976, at the Europa Lodge Hotel, Darling- ton. The Chair was taken by the Chairman of the Region, Mr.F. E. Harper. The following office bearers were elected for the forthcoming year: Chaivman-Mr. F. E. Harper. Vice- Chaivman-Dr . H. Hughes. Honovavy Secvetavy -Mr. D. F. Griffiths, Davy Powergas Ltd., Research and Development Division, Bowesfield Lane, Stockton-on-Tees, Cleveland, TS18 3HA. Honovavy Tveasuvev-Mr. G. A. Gray. Honovavy Assistant Secvetavy-Mr. P. J . Burnill. Membevs of Committee-Mr. L. W. Bell, Dr. L. C. Ebdon, Mr. F. C. Shenton, Dr. A. A. Smales, Mr. J. Whitehead and Dr. C. Woodward. Mr. C. N. Bell and Mr. R. H. Jackson were re-appointed as Honorary Auditors.

ISSN:0306-1396    

DOI:10.1039/AD9761300080

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

THE PRESIDENT 81 Address of the Retiring President This Address was delivered after the Annual General Meeting of the Analytical Division held on March loth, 1976. The Changing Scene in Analytical Chemistry G. W. C. Milner Applied Chernistvy Division, A .E.R.E., Havwell, Didcot, Oxfordshive When I was elected President, the term of office was for 2 years, but because of the final amalgamation of the Society for Analytical Chemistry (SAC) with The Chemical Society (CS) from January lst, 1975, this term was extended by a further year so that I could help to82 PYOC.Analyt. Div. Chem. SOC. smooth the transfer operation. Much is expected of your President during his term of office and I can assure you that a great deal was expected of me, during the past 3 years.My period covered three main phases: ADDRESS OF THE RETIRING PRESIDENT (1) the celebration of the Centenary of the SAC in 1974; (2) the negotiation of suitable terms for the final amalgamation of the SAC with the CS so that our activities could be continued in the Analytical Division of the CS; (3) the first year of complete amalgamation with the CS. There has been much to do during the past 3 years and fortunately Council has succeeded in getting through the necessary business.This has been possible only through the endeavours of the Honorary Officers and Members of Council and the hard work of the permanent staff involved. My task has been helped considerably by the good team spirit that has prevailed throughout Council, Committees of Council and many of our other activities. I am sure that the festivities at our Centenary Celebrations in 1974 helped to foster this spirit of good will, and I have been very grateful for it. Important decisions have had to be taken, and these decisions could have far-reaching effects on future generations of analytical chemists in this country. I can only hope that Council has made the right decisions and for the right reasons. Undoubtedly, 50 or 100 years from now the historians will be examining in some detail the records of the happenings in analytical chemistry in these last few years.Because of this, I considered it necessary to put on record some details of the negotiations leading to the amalgamation of the SAC with the CS. This also meets the commitment on me, as your retiring President, to give an account of my stewardship on reaching the end of my term of office.Time alone will be the judge of this. Amalgamation and Its Effects on the SAC Financial Considerations When I became your President in March 1973, the SAC had already completed 14 months of its 3-year period of trial amalgamation with the CS. This period had not been without its problems and difficulties.Council had expected the membership to increase from 2 200 in the SAC to about 4 000 in the Analytical Division (AD) of the CS, but in the event the membership increased to 7 000. This situation arose because at that time each member of the CS had the right to apply for membership of any two Divisions for his basic CS subscrip- tion. Unfortunately, this placed a heavy financial burden on the SAC, who had agreed to fund the activities of the AD throughout the trial period of amalgamation (1972-75).You will therefore appreciate that the SAC was faced with real problems in the very first year of trial amalgamation, but somehow we managed to get through this period, at some cost in financial terms and with a reduction in some services to members.Fortunately, there was good will on both sides to find a satisfactory solution to these problems and various changes were considered. The fact that we had representation on the CS Executive Committee and the CS Council helped considerably in achieving acceptable solutions to the difficulties that faced us. The CS Council decided to change the rules for membership of CS Divisions from January lst, 1974, and this was of substantial help.From that date, CS members had the right to join only one Division for the basic CS subscription, and had to pay an extra E l for each additional Division they wished to join. This change helped us considerably as it reduced the membership of the AD to about 6 000, and also it generated some necessary finance.Also in 1973, the CS Council introduced a fee of 50p for the membership of each Subject Group, and this again helped our finances appreciably. By 1974, the AD had recruited those members of the CS with a genuine interest in analytical chemistry and, moreover, they were making some contribution to the financing of the Divisional activities. Negotiation of Terms for Final Amalgamation One of the major requirements facing the SAC in 1973 and 1974 was to negotiate terms for final amalgamation with the CS that would be acceptable to the Councils of both Societies, and eventually to the SAC members.The Council of the SAC formed an Amalgamation Committee under the President’s Chairmanship. In addition to the Honorary Officers and selected Members of Council, this Committee had a representative from each Regional Committee soApril, 1976 ADDRESS OF THE RETIRING PRESIDENT 83 that it had the benefit of regional thinking on amalgamation.By this means, there could also be some feedback of information to the Regional Committees on the progress of negoti- ations. The purpose of this Committee was to identify the problems involved in negotiations with the CS, and then to discuss them in some detail.The following problems were considered during this period. (a) The correct legal interpretation of the CS/SAC Agreement of January 31st, 1971, which covered the trial period of amalgamation, and also the form of the resolutions to be put to SAC members at an EGM required to be held before December 31st, 1974. ( h ) Staffing matters, including Pension Schemes and the possibility of combining the Scheme for SAC staff with that operated by the CS.(c) The integration of the SAC publishing activities with the CS publications organisation. (d) Problems concerning Regions and Groups. On the above matters, the Committee determined the policy to be followed by a team of six negotiators discussing terms on behalf of the SAC. Their task was to try to negotiate equitable terms with a comparable CS team. This was a fairly formidable task for the SAC negotiators, but in the event they worked extremely well together and they negotiated most effectively.A major difficulty in the negotiations was in ascertaining the correct legal interpretation of Clause 8a(ii) of the CS/SAC Agreement of January, 1971.This clause stated that “SAC members should consider at an EGM and, if thought fit, they should pass a Special Resolution authorising and instructing the Liquidator to transfer the Surplus Assets of SAC to CS to be applied forthwith to a Charitable Trust Fund with objects to be agreed by SAC before the date of the EGM and which shall be similar to those of SAC.” The SAC’S legal advisers were of the opinion that the SAC publishing business was part of the surplus assets, and as such it should be transferred to the Charitable Trust Fund for the Trustees to operate for the benefit of the Fund.The CS negotiators, however, felt that this interpretation did not comply with the pooling of rescources in the true spirit of complete amalgamation.It became clear that the SAC was expected to make an outright transfer of the publishing business to the CS because the Faraday Society had done so with their publications on amalgamation 2 years earlier. In our opinion, the SAC publications were too valuable to pass to the CS without an agreed financial settlement, and we felt that this view would be supported by the SAC membership, particularly as the proposed annual allocation of funds to the AD by the CS after final amalgamation would be insufficient to allow the AD to continue its activities at the level and in the style enjoyed by SAC members before amalgamation.It was important for the SAC to obtain a financial settlement so that the funds could be invested and the interest used to pay for any short-fall in the expenses of the AD in future years.A lump sum settlement in return for the publishing business appeared to us to represent a fair and honourable way of achieving our objective. Independent pro- fessional advice indicated that the SAC publishing business plus the stocks of unsold publica- tions at that time had a market value in the region of E200 000. After several meetings, the CS negotiators accepted the principle of a financial settlement in return for the SAC publishing business, but unfortunately the sum offered initially was much lower than the market value estimated by our advisers.In addition, the CS negotiators considered that their Council would not accept a policy which involved the use of CS liquid assets for this transaction. In this kind of situation, the negotiators had to attempt to achieve a compromise that they considered might be acceptable to the Councils of both Societies. A breakthrough finally came after two meetings of the negotiators in February, 1974, when it became possible to formulate terms acceptable to both sides.The agreed terms were as follows : “In consideration of the transfer of the (SAC) Publishing Business to CS and the release of CS from its obligation to transfer the same to the Charitable Trust, CS hereby agrees as follows : ( a ) CS agrees to transfer to the Charitable Trust the whole of the surplus of receipts of the SAC Publishing Business over the expenses and overheads attributable thereto from January lst, 1975, to September 30th, 1980, and, if necessary, 25% in the accounting period October lst, 1980, to September 30th, 1981.84 ADDRESS OF THE RETIRING PRESIDENT PYOC.A n a l y t . Div. Chewz. Soc. ( b ) The total amount to be transferred by reason of this clause shall not exceed the sum of E150000. (c) For the purposes of calculating the said surplus, the expenses and overheads shall include the direct costs of the staff engaged in the publishing business together with all overhead costs proportionately allocated to the (SAC) Publishing Business.Until September 30th, 1981, or such earlier date by which the sum of El50 000 shall have been transferred to the Charitable Trust, the Trustees shall determine the selling prices of the analytical publications on an annual basis.” We considered this last term to be a vital requirement because of the high inflationary conditions prevailing in 1974 and which were expected to continue a t a high level for several years.Also, the overheads to be allocated to the analytical publications would be much higher in the CS than in the SAC, and this additional charge could be recovered only by increasing the annual subscription rates.The stocks of SAC publications in existence at January lst, 1975, were treated separately. The CS agreed to store, sell and distribute these publications for a period of 5 years for a commission of 10% of all receipts from sales. It was considered that these sales should generate a sum of between E30 000 and E50 000 over a period of 5 years, because the stocks included a newly published quinquennial index for Analytical Abstracts in addition to existing monographs and back issues of journals. The receipts from these sales would be additional to the El50 000 surplus allowed from the sale of the current publications.Hopefully, this settlement should enable the Trustees to accumulate a lump sum of approximately L200 000 over a period of about 5 years. This amount was in general agreement with a realistic valuation of the SAC publishing business in 1974.In addition, the proposed method of raising this large sum of money was considered to be a fairly painless one for the CS. With certain safeguards, which were written into the Agreement, these terms were equitable to the Councils of both Societies. The general membership of the SAC did in fact accept these terms by voting in favour of amalgamation by the necessary majority at an EGM held in London on October 23rd, 1974.The First 9 Months It is now possible to evaluate the performance from the statement of accounts up to September 30th, 1975. The surplus on the journal publications is only El1 102, leaving a total of El38 808 still t o be obtained by 1981.This is disappointing and several factors have contributed to this poor performance, including the following : ( a ) a considerable increase in charges for the printing of the journals in 1975; ( b ) the costly experiment of providing Proceedings free of charge to every member of the Analytical Division in 1975 ; (c) increases in postal rates and in charges for paper and other materials; ( d ) the effects of CS charges for central services. Some action has already been taken to deal effectively with this situation.For instance, Proceedings is no longer sent to AD members free of charge, and the subscription rates for journals have been increased by fairly substantial amounts for 1976. By this action we hope to have increased the surplus for the next 12 months to about E30 000.The income from sales of back issues of the journals and books belonging to the Trustees of the Analytical Chemistry Trust Fund amounted to El5 319. This is a very satisfactory performance for the first 9 months, but it must be appreciated that the annual totals for the next few years may be much smaller than this first total, because the stocks are being de- pleted as the new publications appear in the CS accounts.However, a final amount of about &SO 000 for the Trust Fund should be attainable from this source. How did we fare in the first 9 months of amalgamation? The Analytical Chemistry Trust Fund It was agreed that, in addition to the proceeds arising from the transfer of the SACpublishing business to the CS, this Charitable Trust would also receive all other assets resulting from theApril, 1976 ADDRESS OF THE RETIRING PRESIDENT 85 liquidation of the SAC.The main items of these assets were the investments of a separate Trust Fund set up in 1972 for the funding of SAC Studentships and Fellowships and which had to be dissolved on final amalgamation. This fund was valued at about E200 000 before transfer, and so eventually the new Analytical Chemistry Trust Fund should reach a total valuation of approximately L400 000.Care has been exercised in drawing up the Trust Deed so that only the elected Members of Council, together with the Honorary Officers of the AD, become the Trustees. By this means it is possible to obtain a democratically elected body of analytical chemists charged with the responsibility of applying the income from the Trust for the benefit of analytical chemistry in accordance with the terms of the Trust Deed.The terms and conditions of the Trust Deed have also been carefully formulated for the guidance of the Trustees in discharging their responsibilities. ( a ) Organising lecture tours and conferences in analytical chemistry, and awarding medals and prizes to outstanding workers in analytical chemistry.( b ) Supporting close co-operation with analytical chemists of other countries by organising meetings and exchange visits. (c) Encouraging improvements and developments in methods and techniques for the publication and dissemination of information in analytical chemistry. (d) Providing, or assisting in providing, means for the pursuit of research and investigation into all matters relating to the development of analytical chemistry.( e ) Developing, organising, entering into and carrying out or co-operating in any charitable project or projects which is or are calculated to further the purposes of this Deed. The Trustees will be able to support many activities aimed at improving and enhancing the status of analytical chemistry in the UK, in addition to helping with the finances of the AD.The income from the fund should ensure the continuation of our pre-amalgamation activities at their present level or at an increased level if desired by Council. Council recognised that the non-SAC members of the AD had not been receiving sufficient information on the Division’s meetings and activities during the trial period of amalgamation.As an experiment for 1 year, therefore, it agreed to circulate Proceedipzgs to all members of the AD free of charge during 1975. This kind of experiment could only be contemplated because of the availability of independent finances to supplement the Divisional allocation from the CS General Purposes Fund.It was an interesting experiment because it had the effect of unifying the activities of all analytical chemists in the UK for the first time. It was realised that the value of this exercise would have to be assessed after the first year because of the inevitable escalation in the costs of printing, paper and postage. However, by this means all analytical chemists in the AD were assured of some benefit in the first year from the income from the Analytical Chemistry Trust Fund.Regrettably, I have to report that the experiment has had to be discontinued because of the high costs involved, and PYoceedivzgs is now available to members on a subscription basis. Another responsibility of the Trustees of the Trust Fund is t o arrange and finance good- quality analytical research carried out by research fellows and/or postgraduate students in university, industrial or government laboratories.Up to the present time, the Trustees have funded or are funding the following Studentships: (1) Mr. C. W. McLeod on “Solvated-atom Fluorescence and Absorption Spectroscopy for Analysis,” at Aberdeen University. (2) Mr. K. P. Ranjitkar on “Applications of Candoluminescence in Ultra Trace Analysis,” at Birmingham University. (3) Mr.P. David on “Applications of a Micro-computer to Automatic Analysis,” a t the University College of Swansea and ICI Petrochemicals Division. (4) Mr. A. A. King on “Analytical Optoacoustic Spectrometry,” at Imperial College, London. A disappointing feature of the Studentships so far has been an apparent lack of suitably qualified British students who are willing to carry out research in analytical chemistry.The four Studentships allocated have been awarded to two British students and two overseas These are as follows.86 ADDRESS OF THE RETIRING PRESIDENT Proc. Agzalyt. Div. Chem. SOC. students. No Fellowships have been awarded, but applications have been received mainly from overseas workers wishing to gain research experience in a British university.For those of us committed to the future expansion and development of analytical chemistry in the UK, we must do our utmost to attract some of the best chemistry graduates (preferably with 1st Class Honours degrees) to carry out research in analytical chemistry. Without a steady supply of this type of graduate to our discipline, analytical chemists may have some difficulty in future in continuing on equal terms with those in other branches of chemistry.The challenge is a real one, particularly for the analytical chemistry teachers in universities. I acknowledge that chemistry has lost some of its appeal and that it is no longer favoured by some students at university level. However, our academic members must try desperately hard to recruit some of the brightest of the available students for research in analytical chemistry.The situation would be improved if more Readerships and Professorships in Analytical Chemistry, particularly the latter, could be established in our universities. Unfortunately, the present economic climate in many university chemistry departments may prevent such developments from taking place for some time.Let us do all we can to improve the pro- fessional standing and career prospects of all analytical chemists in this country, whether they are in university, industrial or government laboratories. Analytical Publications Future sales On complete amalgamation there were no problems concerning the assimilation of SAC journals and other publications by the CS.Amalgamation was expected to improve the sales situation by making use of the CS Marketing Department. This organisation would provide the help and experience needed for the exploitation of existing and new analytical publications. The SAC could never justify a separate marketing department, and as a conse- quence the sales of its books and monographs had not really penetrated the American market.The sale of some analytical publications should also benefit from the special arrangements negotiated by the CS with the American Chemical Society. The ACS has agreed to sell CS publications in the USA under very favourable terms compared with those required by commercial publishing organisations. The CS has also negotiated suitable terms for the exploitation of their publications in Japan.There are special problems with the Japanese market which make it difficult for outsiders to penetrate, but the CS has succeeded in making satisfactory arrangements. Any sales promotional activities are most welcome to the Trustees in generating more financial returns. After all, we must not overlook the fact that new funds generated by the sales of analytical publications over the next 5-6 years will be vital in financing some of the activities of future generations of analytical chemists in this country. Although we have completed 1 year of full amalgamation, it is too early to attempt to quantify the effects of the marketing activities and of the special arrangements with overseas organisations on analytical publications.Future viability In his Presidential Address in 1969, the late Mr. A. G. Jones alerted us to the possibility of serious competition for Analytical A bstvacts arising from the computer-based information services of the Chemical Abstvacts Service. He reported the possibility of a two-fold threat. In the short term, it was thought that we might see the appearance of a journal derived from Chemical Abstvacts Covzdensates or from the tape version of Chemical Abstracts itself.In the long term, however, Mr. Jones foresaw a complete revolution in the supply of abstracts information which could supplant our journal completely. In addition, we must not overlook the fact that every year the cost of producing Analytical Abstracts in its present form increases significantly.This is due to annual increases in staff salaries, paper and printing costs, postage rates, etc., which are inevitable in an inflationary situation. We can recover these increases in costs only by passing them on to our subscribers, both members and non-members. A situation is developing in which each annual increase in subscription rate results in a loss in the number of subscribers and eventually this journal may not remain financially viable in its traditional form.The charges for paper, printingApril, 1976 ADDRESS OF THE RETIRING PRESIDENT 87 and postage are outside the control of the CS but staff salaries are within its control, but if its salaries are not kept in line with those paid by other publishers, the CS would quickly finish up with no editorial staff of the standard required to produce the journal.The threat to the future of Analytical Abstracts will come from cost increases in production, as well as from the competition from computerised systems. However, changes in procedure that have helped to keep down costs have already been introduced, and further studies to this end are in progress.The publication of The AfiaZyst and PYoceedings will undoubtedly continue for some time in the future. A threat is already developing to the future of The Analyst from the new CS Synopsis/Microfiche journal, to be published from January, 1977, and the future success of The Analyst may depend on its receiving sufficient papers of high quality from members of the CS and others.It was expected that these activities could be expanded in the event of a serious threat developing to the financial viability of the journals. After a cautious start, this project is now gaining momentum. So far two monographs have been published, and their sales have been en- couraging. Other monographs are in an advanced state of preparation and they should be published in the near future.Volume 1 of “Selected Annual Reviews of the Analytical Sciences” was introduced in 1971, and so far three volumes have been published. Unfortunately, this publication was launched at a time when there was intense competition from other publishers with this type of journal. This competition has clearly affected the demand for “Selected Annual Reviews’’ by outside subscribers in spite of the fact that it is available at a very competitive selling price. A decision was taken recently to change the name of this publication to “Selected Analytical Reviews.” It is no longer committed to an annual publication schedule, and a volume can be published to meet a genuine demand as required. By this means we hope to have a more successful publication, but it is still too early to evaluate the effects of this change.A specialist annual publication on atomic-absorption spectroscopy (ARAAS) is making good progress after only 4 years of publication. This publication is meeting a genuine need for analytical chemists specialising in atomic-absorption spectroscopy, and we are very grateful to the members of the ARAAS Board for their voluntary work in the preparation of manuscripts.The high standard achieved so far is a tribute to this group of dedicated enthusiasts. The financial viability of PYoceedings is causing some concern. In the late 1960s, a decision was taken to publish monographs on a limited scale. The Future for Analytical Chemistry For example, in industry he has to collaborate with the engineer or plant operator to produce the analytical information needed for the efficient operation of the plant.In the biomedical and bio- chemical areas the analytical chemist must work with the medical expert or the biochemist to ensure that these specialists are provided with the right kind of analytical information for the subsequent treatment of disease, disorders and so on.If an analytical chemist is unable to work with other experts who require his support, experience and knowledge, then he is unlikely to survive for very long, either now or in the future. The successful analytical chemist must really become involved in the chemical situations that require his support, and he must understand the chemistry involved. He must get into the situation of being able to identify the analytical problems that exist and then he must possess the ability and the motivation to solve each problem successfully and as quickly as possible.Amalgamation with the CS has served the very valuable purpose of allowing analytical chemists an opportunity of meeting and conversing with chemists of other disciplines. The analytical chemist is no longer isolated in his own small Society, unable to gain reasonable contact with the vast majority of other chemists.In recent years, successive Councils have had the foresight and wisdom to guide analytical chemists along this pathway. The oppor- tunities for discussion and collaboration with other chemists are now a reality within the structure of the CS, and it is up to all analytical chemists to make the fullest possible use of the opportunities available to them both now and in the future.One possible course of action would be to organise joint scientific meetings between the Subject Groups of the Analytical Division and those of other Divisions. Also, the organisation of joint Divisional The ambitious and progressive analytical chemist seldom works alone.88 DEVELOPMENTS I N PHARMACEUTICAL ANALYSIS P I / O C . Andyyt. D i V . ClZCY?Z. .?OC. Sessions might be considered for future CS Annual Congresses. We must experiment with new ideas on collaboration if we are to gain the maximum benefit from the amalgamation of the SAC with the CS. In the fullness of time, of course, we may have other groups of chemists joining the CS. If this is the case, then analytical chemists have wen more to gain from amalgamation provided that they are willing to take the opportunities and that they are prepared t o show some initiative in achieving their aims. Analytical chemists are now in an advantageous situation. We are members of a large Society that has a total membership of over 40000. We are in the unique position that, in addition to some finances coming from annual subscriptions, some Divisional funds arise from the interest on investments in the Analytical Chemistry Trust Fund. This limited financial independence is something that we must safeguard for many years to come. Let us be wise and make the most of our opportunities in this advantageous situation. I feel certain that the Analytical Division of the CS has a long and distinguished future ahead of it, and I look forward with confidence to the future development of analytical chemistry in the UK. Let us all go forward united with confidence and with good will, and let us make the most of our opportunities in the CS.

ISSN:0306-1396    

DOI:10.1039/AD976130081b

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

88 DEVELOPMENTS I N PHARMACEUTICAL ANALYSIS P I / O C . Andyt. D i V . ClZCY?Z. S O C . Developments in Pharmaceutical Analysis The following is a summary of one of the papers presented at a Meeting of the Analytical Division organised by the Scottish Region in conjunction with the Joint Pharmaceutical Analysis Group held on September 16th and 17th, 1975. Summaries of nine of the other papers presented were published in the January issue of Pi1oceedi.Yzg.s (p.6). Some Assay Methods Used in Clinical Pharmacology A. Bye Depavtvnent of Clivzical Pharmacology, Wellcovne Reseavch Labovatovies, Langley Couvt, Beclzenham, Kent, B R 3 3 B S The assays used by clinical pharmacology departments differ from those required by most other departments within the industry in that they are carried out with a small amount of biological fluid containing low concentrations (micrograms to milligrams per litre level) of a known drug.The assays provide essential data on bioavailability and pharmacokinetics of subsequent value to pharmaceutical development, but they rarely themselves have a place in a routine analytical laboratory. Liaison is close between departments (such as research chemistry) that can provide essential preliminary information of ultimate benefit to the development of an assay with the requirements outlined above.Before a new drug is given to man, the eventual assay required can be considered by means of information from animal experiments, in vitm chemical studies and chemical litera- ture searches. The assay procedure selected is developed initially with standards prepared by adding known amounts of drug to the biological material of interest, as the new drug cannot be given to man immediately. When the drug is eventually given to man, samples (plasma, urine, etc.) are received that contain a known drug and/or metabolites at an unknown concentration. The developed assay must be specific and quantitative for the unchanged drug and/or metabolites; the assay must be sensitive enough to follow the drug’s absorption and elimination for at least one half-life; the assay must be rapid enough to allow studies to be completed quickly so that iurther studies can be planned without delay (in practice a minimum of ten assays per technician per day is needed); the assay must have eventual wide application; major modifications depending on the fluid involved should be avoided as these greatly lengthen the development time; also, the apparatus involved should be standard for replication in the field and not limited by its expense.Feeding radioactive drugs to man is avoided unless all feasible attempts at a non-radioactive assay have failed. The assays we use are usually based on solvent extraction as outlined in Brodie’s classic papers in the 1940s.However, the prime requisite for this approach is that the drug can be made insoluble in water, by adjustment of pH, so that it can pass into a water-immiscible organic solvent. For drugs that are essentially soluble in water at all pHs (c.g., amphotericApvil, 1976 DEVELOPMENTS IN PHARMACEUTICAL ANALYSIS 89 compounds, zwitterions and water-soluble neutral drugs) a different method of extraction is needed, e.g., ion-pair extraction or selective adsorption to either antibodies, charcoal or XAD-2 resin.Alternatively, selective sensitive detectors, e.g., polarographjc, can be tried on the unextracted drugs. A typical example of our work is the analysis of our established antibacterial, Septrin, which contains both trimethoprim (TMP) and sulphamethoxazole (SMX) in the proportions 1 + 5. Chemically, TMP is a base (pK, 7.3) and SMX an acid (pK, 5.9).At an early stage, we were set the task of designing an assay for both drugs in urine and plasma but applicable to the other body tissues and fluids. The assay had to be specific, sensitive and quantitative for the study of pharmacokinetics and bioavailability. To choose a suitable assay, we considered the drug levels that should be expected as follows.The dose of sulphonainides alone was known but the effect of the synergist TMP on the dose was not known, nor was the influence of both TMP and SMX on one another in clinical effect and in chemical assay. For SMX, 800mg are administered in each standard dose.This dose was decided from animal work, where the volume of distribution was always lower than total body water, and we therefore expected drug levels in man to be greater than 10 ,ug ml-I. It was known that 1 g of sulphonamides could be safely and effectively given to man but because of our synergistic combination this level was decreased. We also knew from animal data that metabolism of sulphamethoxazole, especially to the N4-acetyl compound, was likely in man, and this was taken into account in designing an assay.In the literature there are several chromatographic and colorimetric methods for deter- mining sulphonamides. We chose a colorimetric method based on the Bratton and Marshall procedure as it was sufficiently sensitive and readily automated by using an AutoAnalyzer.After making allowance for problems specifically related to SMX (see below), we found the method to be reliable and iree from interference by other compounds, possibly because the concen- trations of drug generally observed were in the higher end of the range 10-200,ugml-1 in plasma. Metabolism occurred to about 15% of the total and fortunately N4-acetylsulpha- mcthoxazole was the predominant but not the only metabolite.As the colorimetric Auto- Analyzer procedure relies on the existence of the N4-group as a primary amine, the metabolites must be measured by difference before and after hydrolysis. We found that protein precipi- tation outside the AutoAnalyzer was necessary as the usual dialysis unit was influenced by the relative concentrations of drug and metabolites.Alternatively, several chromatographic methods (gas - liquid, thin-layer and high-performance liquid chromatography) are able to measure both unchanged and individual metabolites in one run, but these methods need a preliminary solvent extraction and are usually more expensive to automate. For TMP, the standard dose was found to be 160mg.Initially, 50mg were given but the volume of distribution was found to be greater than was first thought, as indicated by low plasma levels. I t was known that a 1:20 ratio of TMP to SMX was effective bacterio- logically, so the TMP dose was increased relative to 800mg of SMX until that ratio was achieved in plasma. Also, at that time no assay method was available.We expected a peak drug level of about 2 ,ug ml-I, which is too low for straightforward spectrometry. Although the native TMY fluoresces adequately, we found that fluorescent impurities carried over in extraction procedures limited its use. No chromatographic methods were available. Because of these facts, an assay was developed utilising the antibacterial properties of TMP.I t was known that TMP produced inhibition of folate reductase whereas SMX inhibited the incorporation of p-aminobenzoic acid (pAB) into folic acid. Therefore, by adding pAB to the incubation medium and selecting a suitable micro-organism, an assay was developed that was capable of detecting 0.03 pg ml-l of TMP. With this assay several important factors became apparent in man.Firstly, peak plasma levels were of the order of 0.1-4 pg ml-l after single doses. The plasma disappearance half-life was about 12 h and recovery of the drug in the urine was incomplete, suggesting metabolism. The last fact began to create doubts about the assay as the potential metabolites could also have had antibacterial activity. In the absence of the pure metabolites a t that time a specific chemical assay was favoured.As TMP is relatively non-volatile, the first gas-chromatographic methods were not very successful and quantitative thin-layer chromatography was tedious. Closer study of the fluorescence method revealed that alkaline oxidation of TMP to trimethoxybenzoic acid (TMBA) and subsequent back-extraction into the chloroform enhanced the sensitivity and selectivity.This procedure was developed and became the routine method. The only90 DEVELOPMENTS IN PHARMACEUTICAL ANALYSIS R o c . Annlyt. Din. Chew. SOC. criticism was that metabolites derived from the pyrimidine ring would be assayed with TMP. However, in practice these metabolites were quantitatively insignificant. The major meta- bolite was, in fact, a derivative demethylated in the TMBA moiety and which fortunately has only poor fluorescence properties.The method could detect 0.05pgml-l of TMP in plasma and was applicable to most other body fluids. “Background” fluorescence was mainly associated with the assay reagents, especially in the final chloroform extraction and the water used in making up solutions. Such great care was required in selecting these solvents that even fresh Merck spectroscopic-grade chloroform (of a specific batch) and double glass- distilled water had to be specified.Few problems with drug interference affected this assay but once a high background fluorescence in samples from babies fed on a certain brand of powdered milk occurred. Also, hay feeds given to certain animals taking the veterinary product caused high background fluorescence.Recent advances in high-perf ormance liquid, gas and thin-layer chromatography have begun to compete with the fluorescence method for ease of operation, as the throughput of samples (12 per day per technician) using fluorescence is only just adequate. A comparative drug bioavailability study can generate up to 1000 samples and the drug assay laboratory should not be the bottleneck in such a study. Drug assay development is only part of the work of the Department of Clinical Pharma- cology.Another task is prediction of the test drug’s characteristics in man and its subsequent testing. For this purpose, physico-chemical characteristics in vitro of the drug, e.g., solubility in water at various pHs, partition between aqueous buffers and octanol, pK,, protein binding and dissolution, are related to absorption, distribution and elimination using the standard procedures such as the “ion-trapping” method.We also examine the available in vivo data from the animal experiments, usually carried out using radioactively labelled drugs. Spe- cifically for the TMP - SMX drug combination, both components had similar elimination characteristics in certain animals (rat t, = 30 min; monkey t, M 10 h), different volumes of distribution (TMP > total body water, SMX < total body water) and good absorption (14C-label in animals, in vitro characteristics).Early studies in man were contemporaneous with some of the animal studies mentioned above. The first trials were concerned with drug tolerance of the proposed dose, for which a plasma method is essential in order to establish that the drug is being absorbed.Once a clinically effective dose has been tolerated, the single-dose pharmacokinetics after oral and i.v. dosing are worked out. The facts arising from such studies for TMP - SMX showed that the half-lives of both drugs were similar (about 10 h), the volumes of distribution were 82.3 1 for TMP and 15 1 for SMX and at least half of the drug was recovered unchanged.We also found that after a dose of 160 mg of TMP and 800 mg of SMX, given orally as two tablets, absorption was complete and peak plasma levels of 2-3 pg ml-l were seen for TMP and 40-60 pg ml-l for SMX. These levels, when compared with the in vitro bacteriological data, suggested clinical efficacy, which was later proved.Although the initial sampling times are arrived a t by guesswork (usually causing more samples than necessary to be taken), when the above facts are available sampling times can be worked out expeditiously. Generally, for a drug with a 12-h half-life, plasma is sampled quarter-hourly for 4 h after oral administration, then hourly to 12 h and probably 24-, 48-, 28- and 32-h samples are also taken.For half-lives in excess of 24 h, sampling times after 12 h are suitably extended. Urine is collected for 6 or 7 half-lives, usually in 12- or 24-hourly lots. However, frequent early collections can be valuable for pharmacokinetics. Faeces are not usually collected unless poor absorption is expected or a full balance study is needed. Once the single-dose pharmacokinetics at the prescribed dose are known, studies of multiple- dose pharmacokinetics and comparative bioavailability of dosage forms are made.There- after, studies are usually designed to answer problems encountered in the clinical practice, such as dosages in renal impairment, children and so on.Each drug presents its own problems, and although the above drug example was reasonably trouble free, other drugs have not been so. For the cardiac glycoside digoxin, the daily dose is small (usually 0.25-1 mg) and plasma levels of a few nanograms per millilitre are seen, which requires a very sensitive radio- immunoassay. In addition, intestinal absorption is variable between dosage forms and the therapeutic plasma level range is very small.As toxicity is related to elevated plasma levels, the importance of a rapid reliable assay is obvious. Before a reliable assay was developed,April, 1976 LASER APPLICATIONS I N ANALYSIS 91 digoxin therapy could be hazardous for certain types of patient. Radioimmunoassay was a feasible method for digoxin because it has a large relative molecular mass (781) with poor chromatographic, colorimetric and fluorimetric characteristics a t the therapeutic level (2 ng ml-l) in biological fluids.One of our experimental drugs (a thioxanthone) was present in large amounts in plasma (10 pg ml-l) and numerous methods were possible. However, the most specific method was chosen, which in this instance was gas chromatography as this technique can be automated easily.Problems were caused in assaying one of our drugs (allopurinol) as it was a close structural isomer of hypoxanthine, a naturally occurring nucleotide base. The drug was non-volatile and so chemically similar to its natural isomer that gas-chromatographic and spectroscopic methods were impractical. On careful examination, a small difference in pK, could be ex- ploited by high-performance liquid chromatography (HPLC) using ion exchange, the molar absorptivity being high enough for the sensitivity required.As another example of an HPLC method, an antihistamine (triprolidine) was run on silica columns. However, its peak plasma level was about 8ngml-1, which meant that direct spectroscopic methods of detection were impossible.Theoretically, fluorescence could be used for detection but no workable flow cell for HPLC is available for sensitive fluorescence detection. However, by transferring to thin-layer plates [as HPLC (silica) and thin-layer chromatography are often compatible], drying the plate and scanning with a scanning fluorimeter, the necessary sensitivity could be achieved. This paper has covered only a cross-section of our work and it includes only successful assays. There are still many extremely potent drugs that defy direct chemical analysis but I feel that with the introduction of more and more sensitive but selective techniques (e.g., gas chromatography - dedicated mass spectrometry) that all drugs will be able to be analysed. In some instances, because of metabolism, a parent drug exists very temporarily but then usually one of the metabolites is active and this should be analysed. Several, often expensive, techniques now measure femtogram (lO-l5 g) amounts and pre- sumably the limit will be individual molecules. However, I think that expense is balancing the search for more sensitive methods, otherwise drug regulation authorities will be asking for information that few laboratories could afford to give.

ISSN:0306-1396    

DOI:10.1039/AD9761300088

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

April, 1976 LASER APPLICATIONS I N ANALYSIS 91 Laser Applications in Analysis The following are summaries of two of the papers presented at an Ordinary Meeting of the Division held on December 3rd, 1975, and reported in the December issue of Proceedings (p. 307). Pulsed Laser Techniques and Their Applications E. S. Reid Depavtment of Chemistvy, UYzivevsity of Southampton, Southampton, SO9 5NH A laser source can be controlled much more precisely than any other light source.A care- fully designed laser oscillator can be operated in a single axial and transverse mode, thus providing a collimated, single-frequency beam of radiation.1 If pulsed excitation sources are used, then pulses of a few microseconds duration can be obtained. Even shorter pulses can be obtained by controlling the gain of the laser oscillator (Q-switching) or by constraining a few axial modes to oscillate in phase (mode-locking).Nanosecond-duration pulses can be obtained from Q-switched lasers while picosecond-duration pulses can be obtained from mode-locked lasers. The laser therefore provides a new source of powerful short-duration pulses of visible radiation that have applications in a number of fields of analysis.When a pulsed ruby laser beam is focused down to a point by a lens, power densities of up to 1O1O W m-2 can be produced. The optical electric field strength at these power densities is of the order of lo7 V m-l, which is sufficient to ionise the air through which the beam passes.92 LASER APPLICATIONS IN ANALYSIS Proc. Awalyt.Div. Chem. SOC. An important application of pulsed lasers is therefore the controlled production of ionised plasmas a t points in space that may be far removed from the laser itself. One such appli- cation, in which a laser is used as a means of producing ions for the analysis of solid materials by mass spectrometry, was described in another paper presented at this meeting. The induced dipole (P) generated in materials by an electric field strength ( E ) is given by .. - - (1) p + &yE3+. . . . . where a, /3 and y are the polarisability, hyperpolarisability and second hyperpolarisability, respectively. The first term gives rise to normal linear optical phenomena such as refraction, absorption and scattering, while the terms involving higher powers of E give rise to a large number of non-linear optical phenomena.Because of the small magnitude of p and y , these phenomena are only observable when E is very large. Many non-linear optical effects are observable, however, when pulsed laser beams interact with matter. One such effect, in- volving the PE2 term in non-centrosymmetric crystals such as ammonium dihydrogen ortho- phosphate, is commonly employed to generate radiation of double the frequency of the incident laser beam.2 Frequency doubling is particularly useful in generating laser fre- quencies in the ultraviolet region of the spectrum.Another non-linear effect, involving the yE3 term, has caused much excitement recently. This is a non-linear scattering process involving two laser beams, and is referred to as coherent anti-Stokes Raman scattering (CARS).3 Both laser beams are focused into the same volume of sample.Two pulsed lasers with frequency w , and us are required. By tuning one beam (us) such that ma, - w, = uI1 .. . . .. . . (a) where wE is a Raman-active vibrational frequency of the sample, Raman scattering from the other beam (wD) can be stimulated together with the simultaneous generation of coherent anti-Stokes Raman scattering.This effect generates a collimated beam of frequency higher than w p at a small angle to both incident beams. The advantage of CARS over conventional Raman scattering as an analytical technique is that vibrational information is contained within a collimated beam that can be readily separated from other sources of incoherent radiation.CARS has already proved useful in detecting Raman spectra from fluorescent samples and flame~~9~ and should prove most useful in detecting and analysing gases at low pressures and high temperatures. The CARS experiment is, however, fairly complex and is unlikely to supersede conventional Raman spectroscopy for most routine applications. Powerful, short-duration laser pulses have many applications when time-resolved spectro- scopic information is required.Q-switched and mode-locked lasers have been used to obtain fluorescence, absorption and Raman spectra of short-lived specie^.^-^ Continuously mode- locked gas lasers have been employed to record Raman spectra from fluorescent samples.9 Normally, sample fluorescence is a major problem in recording Raman spectra because of the detection problems involved in recording small signals in the presence of large background signals.The use of mode-locked lasers to alleviate this problem relies on the fact that fluore- scence originates from molecular excited states that have finite lifetimes, whereas Raman signals originate from scattering of the laser pulse and therefore have the same temporal characteristics as the laser pulse.Therefore, if the laser pulse is shorter than the lifetime of the fluorescent excited state, electronic gating systems, which allow signal detection only when the laser pulse is incident upon the sample, can be used to reduce background signals. This technique is limited only by the duration and power of the laser and the efficiency of the gating technique.Another important application of pulsed lasers is the remote sensing of atmospheric pollu- tion. A number of techniques have been devised whereby atmospheric pollution can be monitored by detecting the light scattered from a laser pulse. As the laser pulse travels through the air, the scattered signal can be detected as a function of time, which now gives information concerning the composition of the air as a function of distance from the laser source and detector.The spatial resolution of this technique therefore depends upon the duration of the pulse, while the range depends upon its power.APYil, 1976 I . 2. 3. 4. 5. 6. 7. 8. 9. LASER APPLICATIONS IN ANALYSIS References 93 Lengyel, B. A., “Lasers,” Second Edition, John Wiley & Sons, New York, 1971.Giordmaine, J . A., in Schawlow, A. L., Editov, “Lasers and Light,” Readings from Scienti;fic Ameri- Begley, R. F., Harvey, A. B., Byer, R. L., and Hudson, B. S., J . Chem. Phys., 1974, 61, 2466. Regnier, P. R., and Teran, J . P. E., Appl. Phys. Lett., 1973, 23, 240. Porter, G., Reid, E. S., and Tredwell, C. J., Chew. Phys. Lett., 1974, 29, 469.Porter, G., and Topp, M. R., PYOC. R. Soc., A, 1970, 315, 163. Wilbrandt, R., Pagsberg, P., Hansen, I(. B., and Weisberg, C. V., Chevn. Phys. Lett., 1975, 36, 76. Alkins, J . R., Analyt. Chem., 1975, 47, 752. Van Duyne, R. P., Jeanmaire, D. Id., and Shriver, D. F., Analyt. Chew., 1974, 46, 213. can, Freeman, San Francisco, 1969. The Analysis of Solid Materials by Laser Probe Mass Spectrometry R.A. Bingham AEI Scienti$c Ap@avatzzs Limited, Bavton Dock Road, Uvmston, Manchestev, M31 2LD The conventional method of ionising solid materials for the analysis of trace elements in mass spectroscopy is by the radiofrequency spark. The laser has an appeal as a competitor because of its inert nature and because it provides the possibility of examining small regions of single specimens without the need for special preparation.It provides not only a micro- analytical surface technique because of its small beam diameter capability but also offers the possibility of both bulk and surface analysis with a focused or defocused beam. Three types of high-power pulsed lasers have been examined, CO,, ruby and NdYAG, and their analytical capabilities compared with the conventional spark source. No secondary ionising process was used and the ions were extracted directly from the plasma into an AEI MS7 mass spectrometer.The ruby and NdYAG lasers were Q-switched but the CO, laser was operated in the normal burst mode. The laser beam was fired into the ion-source housing of the mass spectrometer with mirror and focusing lens system fitted internally.Specimen position and focusing lens control could be adjusted from outside the chamber and the region of specimen to be analysed could be viewed through a microscope system. A He - Ne C.W. laser beam could be passed along the same optical path as the pulsed laser and this was used to pinpoint the analysis area. Crater diameters in the range 20-300 pm could be obtained with the ruby and NdYAG lasers but with the CO, system the diameters were 300-400 pm.The spectra were recorded on photoplates, which are able to record all ions in the mass range 6-240 simultaneously, and the effects on all types of ion species were observed. The CO, laser was a solid cathode TEA device having a peak pulse energy of about 300 m J, giving a mean peak power density of about lo8 W ern-,.The visual sensitivity of element detection in the spectra was 2 000 p.p.m. per laser shot. The laser had a maximum repetition rate of 1 pulse s-l. By firing a series of pulses, all recorded on one spectrum, higher sensi- tivity was achieved. Thus, for a sensitivity of 2 p.p.m., 1000 pulses were required, taking 16min to record. The ruby laser produced one pulse every 10s and gave a photoplate sensitivity of 1000 p.p.m.per shot. The pulse power output was 0.25 MW, which could be focused to give a peak power density of 109-1011 W ern-,. A single pulse consumed about 1O-Sg of material from samples such as steel. The NdYAG laser was a commercially available system that had a variable pulse repetition rate from single shot to 50 Hz.Analysis speed was faster with the higher repetition rate and element sensitivity was 2 000 p.p.m. per shot. Samples such as fractured rock surfaces have been examined, selecting individual mineral grains for analysis. Small single samples could also be handled by embedding them in a solid or mounting them on a pin. Ion production from non-conducting materials was the same as from conductors with the ruby and NdYAG systems.Organic substances such as plastics, wood and walnuts were examined and good spectra recorded from rubber. Spectra obtained from the lasers are not as complex as those obtained with the spark source. Multiply charged ion species are lower in intensity and molecular species have rarely been found. It was found that it is not important for specimens to be flat.The resolving power is similar to that given by the spark source.94 ANALYSIS IN ARCHAEOLOGY, ART AND ANTIQUITIES Proc. AnaZyt. Div. Chew. Soc. The CO, laser showed discrimination in the instances of volatile and high boiling point elements, but this was not found to be so for the ruby and NdYAG lasers, with which relative sensitivity factors were around unity. The analysis of NBS standard samples of steel, brass and glass using ruby and NdYAG lasers demonstrated the accuracy of analysis of both metallic and non-metallic materials without the use of standards.The results were obtained by the visual line extinction method and were all within a factor of three of the nominal concentrations. This is com- parable with the accuracy of the spark source under the same experimental conditions.Higher analytical accuracy would be expected by using element correction factors and by measuring line densities by use of a microdensitometer. Reproducibility of element analysis or single shot spectra was &20% with the ruby laser and <lo% with the NdYAG laser. The reproducibility of multiple-shot spectra would be expected to limit at that of the photo- plate emulsion.In addition to the semi-quantitative capability of the laser probe the volume of material consumed in each pulse is small and this feature can be exploited in surface analysis. By defocusing the laser beam, analysis of layers down to a depth of 0.5 prn per laser shot can be achieved and the examination of a layer of gold on brass at a depth of 29 pm was described.Conversely, by focusing the laser to a fine focus, spatial analysis can be obtained across the specimen surface. Line scans or area mapping can be obtained by recording a series of spectra across the area of interest and the photoplate can record all elements at concentrations above 1000 p.p.m. simultaneously, for a single shot. More than one shot in each position would increase the sensitivity according to the number of shots. The NdYAG laser high pulse repetition rate makes it possible to use electrical detection techniques. By using electrical measurement of the laser ion beams individual elements could be monitored to much lower detection levels. A single shot should have an element sensitivity of about 1 p.p.m. Using a repetition rate of from 30 to 50 Hz the spectrum could be scanned over a large mass range, or selected elements peak switched in a similar manner to that currently used with the spark source and with detection limits of the same order (0.1 p.p.m. scanning; 0.01 p.p.m. peak switching).

ISSN:0306-1396    

DOI:10.1039/AD9761300091

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

94 ANALYSIS IN ARCHAEOLOGY, ART AND ANTIQUITIES Proc. AnaZyt. Div. Chem. Soc. Analysis in Archaeology, Art and Antiquities The following are summaries of two of the papers presented at a Joint Meeting of the Micro- chemical Methods, Atomic Spectroscopy and Radiochemical Methods Groups held on Sep- tember 22nd and 23rd, 1975, and reported in the October issue of PYoceedings (p. 264). Analysis and Archaeology-Plenary Lecture John Musty Ancient Momuments Labovatovy, Department of the Envivonvvzent, 23 Savile Row, Londom, W1X 2HE To the archaeologist, the word “analysis” embraces all the activities involved in the examina- tion of excavated material, whether by archaeological or scientific procedures. Thus, the methods of comparing objects can be those employing art history techniques, which seek out significant typological elements and study their evolution, or, for example, the methods of analytical chemistry, which use the abundance of various chemical elements as a criterion.Nowadays, a working partnership exists between the two and the growth of archaeological science has been matched with a parallel development of scientific archaeology, which, with the assistance of the computer, multivariate analysis and other techniques, has raised the typological approach to a new level.Now, typologies are being checked by carbon-14 and other dating methods and it is easy to forget that the carbon-14 revolution is barely 25 years old, as indeed is the application of many other scientific techniques. In the past, typological analysis was used to define “cultures,” to produce dates.A p ~ i l , 1976 ANALYSIS I N ARCHAEOLOGY, ART AND ANTIQUITIES 95 To the archaeologist, the scientific examination of the geological, botanical and faunal remains is also a form of “analysis,” and rightly so.In turn, he will see all types of analysis as leading to the construction of socio-economic frameworks at different periods of time and to the reconstruction of the landscape and man’s influence upon it.In one aspect, early technology, there may be a fusing of many analytical approaches. One will often be seeking to “fingerprint” artifacts so that production centres can be located and an understanding achieved of the manufacturing processes involved. Indeed, the excavator’s “please analyse” may follow the finding of unfamiliar materials (slags, metal residues, etc.) in association with unfamiliar structures involving a furnace element.It is possible to define two broad areas of application of analytical techniques. Level 1 investigations are those concerned with enquiries from individual excavators seeking specific answers to questions related to freshly excavated material.Level 2 investigations are usually of the corpus type, involving comprehensive multi-site comparisons, often employing material from past excavations long since deposited in museums; this type of investigation figures most frequently in the published literature, and it is of interest to consider why this is so. Clearly, there are certain problems that cannot be solved by confining a scientific investi- gation to the material available from a single excavation ; for example, the determination of trading connections.Also, the number of samples in the form of artifacts that can be analysed may be too small in statistical terms to permit valid conclusions to be drawn. However, the advantage of any level 1 investigation is that analytical results, or any other scientific data, can be considered alongside the rest of the excavated evidence.In my view, analysis in archaeology is part of a forensic science exercise in which the excavator and the laboratory scientist are attempting together to reconstruct events that have taken place in the distant past from whatever evidence may have survived. Much greater emphasis could be placed on this form of investigation, as I will demonstrate later, but first I propose to look at the historical development of chemical analysis in archaeological work as it is relevant to my main theme.Added point comes from the reference to Augustus Voelker in Dr. Chirnside’s lecture, “A Composition of Some Days. . . .”l Voelker was described in the minutes of a Select Committee of the House of Commons as a “certain agricultural chemist” who said that “there are not a dozen competent analysts in the Kingdom.” Dr.Chirnside suggests that these remarks were in part responsible for the calling of a meeting on August 7th, 1874, which led to the foundation of the Society of Public Analysts. My interest in Voelker stems from the fact that I have identified him as someone who with others had established a minor tradition in analysis and archaeology as early as 1850 at, surprisingly, Cirencester Agricultural College. Indeed, more detailed research might show that the College was the earliest corporate body showing an interest in archaeological chemistry for, according to Caley,2 apart from papers by Klaproth (the first in 1795) and Sir Humphrey Davy (his last in 1817), only 25 publications appeared on the chemical composition of antiquities up to 1850, and no investigator published more than once.In 1812 Sir Kichard Colt Hoare makes reference to a level 1 investigation. He write^,^ in discussing black earth found on long barrow floors: “A friend of mine was so convinced that it arose from the decomposition of numerous human bodies by means of fire, that he sent some of the soil to two of the most able chyinists of the day, Mr.Hatchett and Dr. Gibbes, to be properly analysed. . . . They both reject the idea. . . . Dr. Gibbes is of the opinion that it arises from the decomposition of vegetable matter.” He also says, of another excavation, that he found a “sword or spear of the warrior, and with it some small bits of cloth, so well preserved, that we can distinguish clearly the size of the spinning, and that it is what we now term a Kersey cloth.” This is the first example I know of textile analysis on archaeological material in Britain. In 1815 Sir Humphrey Davy published a paper on ancient pigments and in 1826 his brother, John, published a study of corrosion in ancient metals.Chemistry text-book writers were also beginning to refer to the analysis of archaeological material, for example Samuel Parkes (1761-1825), the celebrated author of “Chemical Catechism,” who also undertook some analyses. Thus, in a preface to the Twelfth Edition of the “Catechism,” a Mr. Joseph Hodgetts, who was seeing it through the press, Parkes However, before talking more of Cirencester, some earlier work needs mention.Also, in 1810 we have the first analysis of Roman mortar.96 ANALYSIS IN ARCHAEOLOGY, ART AND ANTIQUITIES PYOC. Anaht. Div. Chew. SOC. having just died, writes of Parkes, “for instance the last paper which he ever wrote, ‘On the Analysis of some Roman Coins,’ published in the Jouvnal of Science for July, 1826, during the composition of which he submitted to accurate analysis upwards of 20 coins, costing him the incessant labour of many months, as he made it an invariable rule never to place dependence upon any experiment, till it had been repeated and the same result again obtained.” Hodgett’s account also indicates the amount of effort then needed to undertake even a small number of analyses.However, many of these early contributions were single investigations to satisfy some particular scientific curiosity and it is difficult to judge, without detailed research, the extent of any related archaeological interest.Sir Humphrey Davy seems to have had one as his work on pigments followed a visit to Rome and Pompeii. Later, he also reported on wall plaster from the Bignor Roman Villa and undertook experiments in the conservation of papyri found at Herculaneum.Davy’s visit to Rome during a grand tour during the period 1813-1815 was in many ways unusuaL4 Although France and England were a t war, he travelled first to France with his wife and Michael Faraday, having obtained Napoleon’s permission, carrying with him a small box of chemical apparatus (possibly the first field laboratory).During his travels he heard of a substance which released a violet-coloured gas and he demonstrated that it was a new element similar to chlorine, which he named iodine. From France he travelled to Italy where his interest was aroused by the Roman wall paintings. Immediately on his return to England he was invited to investigate mine explosions and the invention of his celebrated lamp coincided with the publication of his work on ancient pigments.Thus, during the first half of the nineteenth century, a number of individuals applied their scientific skills to the analysis of archaeological material, often once only and not in any corporate way. However, as mentioned previously, one institution, the Royal Agricultural College at Cirencester, founded in 1840, had three scientists on its staff whose interest was more sustained and with a strong archaeological bent, doubtless developed from an interest in Roman Cirencester.Thus in 1850, there appeared the book “Illustrations of Roman Art in Cirencester : The Site of Ancient Corinium,” under the authorship of C. H. Newmarch and James Buckman. He was also helped by John Voelker, Professor of Chemistry, who undertook the glass analysis.In turn, Voelker was succeeded as Professor by A. H. Church, who was to publish in 1867 a “Catalogue of Finds in the Corinium Museum.’’ Church subsequently became Professor of Chemistry in the Royal Academy of Arts and was ultimately knighted. He also published (in 1865) analyses of bronze artifacts found in Great Britain.Evidently then, the conjunction of a Roman site and a group of scientists nearby had interesting repercussions to the benefit of archaeology. In fact, Voelker’s contribution to the Newmarch and Buckman publication shows him to be conscious of this, as if the matter had been debated in the College Senior Common-Room. He writes, “the following analysis of coloured glass, found at Cirencester, will enable me to present additional proof of the great utility of chemistry in general, and the aid which this science is capable of rendering to the archaeologist in his researches, and I hope to contribute something to give that science that recognition amongst archaeologists with which my friend, Professor Buckman, regards the same.” It looks as if he set out to be the founding father of organised archaeological chemistry some 25 years before his words to the House of Commons Select Committee led to the organisation of analytical chemistry.Some of Voelker’s inspiration may have come from Continental work, bearing in mind that he came from Germany. On the other hand, he would seem to have priority in publication.Thus Caley draws attention to Wocel’s papers (1853 and 1855) reporting original bronze analyses, and proposing the possibility of using them to determine provenance. Caley also mentions Fellenberg, with a dozen papers published between 1860 and 1875, and including 200 analyses of prehistoric Central European bronzes. He notes Stolba’s work (1867), but gives special mention to Bibra both for a book (1860) on the composition of copper alloys and a pamphlet published at Leipzig (1873) with a large number of results for the analysis of iron and silver objects.One French worker, Damour, is also mentioned for his work (1864-66) on the density and chemical composition of prehistoric stone objects in relation to parent rock with a view to determining provenance.Up to World War I, this sort of work continued to be the contribution of individuals; Buckman was a geologist and Professor at the College.A p d , 1976 ANALYSIS I N ARCHAEOLOGY, ART AND ANTIQUITIES 97 institutionalised activities were to be more commonplace after 1918, and especially after World War 11. Of the individuals, Professor William Gowland was engaged in what Coghlan has described5 as the first phase of a systematic metallurgical analysis of archaeological material (the second and third phases came at the end of World Wars I and 11, respectively).Gowland’s last paper, “Silver in Roman and Earlier Times,” appeared in 1914(j and we are again reminded of Cirencester by his quotation of determinations of sodium chloride in rain by Professor Kinch of that College.After World War I, the establishment of a laboratory (in 1922) under Dr. Alexander Scott to deal with problems arising from the incorrect war-time storage of British Museum material was a major step forward in the institutional approach and led to the establishment of the British Museum Research Laboratory. In 1937 the Institute of Archaeology was founded and a speech at the opening ceremony contained the significant phrase, “if the essential character of the Institute may be expressed in a word it is this, that it is a laboratory: a laboratory of archaeological science. .. .” World War I1 soon followed and its aftermath resulted in a considerable impetus to archaeological work because of the large excavation programme which preceded post-war reconstruction.This led to a considerable state involvement under the auspices of the Inspectorate of Ancient Monuments (then the Ministry of Works, now the Department of the Environment). One further consequence was the establishment of the Ancient Monuments Laboratory (in 1950) to deal with the finds and scientific interpretation of evidence from the Inspectorate’s excavations.Since then, its activities have expanded to cover geophysics, environmental studies and early technology as well as conservation. The tremendous boost in technical progress made during the War was also capitalised for archaeology by a project for a Research Laboratory at Oxford to work on the archaeological applications of physical science, first put forward in 1950 and finally realised during the early part of 1955.By 1958, Professor Hawkes, writing in the journal Antiquity, could already report an impressive list of achievements by this laboratory-two X-ray fluorescent spectro- meters had been built, optical spectroscopy had been used to analyse prehistoric bronzes, magnetic dating of ceramics was underway and neutron activation analysis was being tried as a new technique.An optical spectrophotometer and a proton magnetometer had been designed, the latter leading to a new geophysical surveying technique utilising magnetic detection, now one of the two principal methods in general use; a veritable explosion of activity, and archaeology was never going to be the same again. Further, the Oxford Research Laboratory for Archaeology and the History of Art (as it was to be called) launched in that year (1958) a house journal, AYchaeovnetvy, for the publication of its results.This has since developed into an international journal and has only recently been joined by another, The J o w n a l of A ychaeologicnl Science. A fifth Research Laboratory, that of the National Museum of Antiquities, Edinburgh, came into being in 1966 and has concentrated on the application of analytical and dating techniques to archaeological problems and research into methods of conservation.These laboratories are the present resources for the scientific examination of archaeological material which are available on a full-time basis in England, Scotland and Wales, although other universities also have some ongoing research, and we will now look at some examples of what is being achieved.In this context, it is important to remember that new material and problems are being generated by approximately 200 new excavation sites a year. Apart from soil, the largest bulk of material removed during an excavation is pottery. Traditionally, this is the type fossil for dating sites, using classifications achieved by the application of subjective criteria; more recently its value has been supplanted, to some extent, by absolute dating methods such as carbon-14 dating or, in some instances, enhanced when methods such as thermoluminescence can be applied directly to it.However, for many sites pottery still remains the dating type fossil. Clearly the maximum use of chemical, petrological and physical techniques to enable accurate “fingerprinting” and grouping of pottery is highly desirable. On those occasions when petrological identity can be established, the results can be spectacular, as, for example, with Dr.Peacock’s finding that Neolithic pottery from Wiltshire contained a suite of minerals characteristic of only one possible source, which was the gabbro that outcrops over about 7 square miles of the Lizard Head in C~rnwall.~ Thus here we98 ANALYSIS IN ARCHAEOLOGY, ART AND ANTIQUITIES Proc.Analyt. Div. Chew. SOC. have evidence for pottery being traded over long distances at a time (around 3000 B.C.) when one might expect all pottery to be of local manufacture. Let us now move to the remainder of man’s material equipment, so often termed “small finds.’’ These usually constitute the third largest component of excavated remains, kitchen refuse, notably animal bones, being the second.Two major problems will be encountered when contemplating analysis of a metal find and the respective solutions can be in conflict. Thus (a) the analyst will be discouraged from damaging the object and (b) he will be faced with a lack of homogeneity in its com- position. If he overcomes objection (a) by using X-ray fluorescence or some other method of surface analysis, (b) will ensure that the various surfaces will all give different results.Possibly lie will then wish he could take the entire object into solution, but will finally have to settle for neutron activation analysis, unless, of course, the fine hole drilled to obtain a 15-mg amount for atomic-absorption spectroscopy is acceptable (and nowadays it usually is).However, it is to be hoped that before he contemplates the removal of the first major obstacle to homogeneous sampling, the corrosion product, he will realise that this carries a great deal of evidence about the object and the history of its immediate environment subsequent to burial.Thus, when level 2 investigations are undertaken on a cleaned object taken from a museum case there may be missing information that could be critical in the interpretation of any analytical results. As a kind of trap it may preserve organic material which was in contact with it during burial. Almost every iron object from a grave will have textile fibres on its surface.Eggs and larvae from corpse- inhabiting insects, etc., may also be found, especially on copper alloy objects, and any wooden attachments to iron objects such as knife handles and scabbards may be represented to a greater or lesser degree as preserved areas or, more commonly, as fossil casts in the corrosion products. In the Ancient Monuments Laboratory, we are finding the scanning electron microscope a valuable tool in this sort of examination.It should also be a matter of routine to X-ray excavated metal objects. This technique will not only reveal the shape of the unmineralised metal in an object, but also provide infornia- tion on construction methods, including the use of inlays of different metals, a well known Saxon technique.An X-ray fluorescence spectrometer of the Milliprobe type is useful for the non-destructive analysis of these inlays, which are normally of gold, silver, brass, bronze or copper. The corrosion product must first be removed and an Airbrasive cleaning plant can be used to do this without “smearing” the inlay. Sometimes mineralisation will have proceeded on all sides of the inlay, which will then survive only in a matrix of corrosion product.Atomic-absorption spectroscopy provides a method that involves minimal destruction for sampling and reasonable speed, although a complementary analytical method (e.g., optical or X-ray fluorescence spectrometry) will be needed to indicate the elements present as a guide to the choice for atomic absorption.X-ray fluorescence spectrometry by itself presents problems because of the matrix effect, but it still has its uses. A recent important level 2 investigation is Dr. Craddock’s survey by atomic-absorption spectroscopy of the composition of Roman “bronze” objects, which showed that many are in fact made from brass.8 It is also of interest that the earliest contain approximately as./, of zinc, which could result only from the use of the cementation process for making brass.I believe he has indications that later Roman brasses contain less zinc, presumably because of the use of re-melted metal. A related type of investigation is one undertaken at the Oxford Laboratory which suggests (on the basis of the determined fineness of the gold) that the gold components of the Saxon jewellery examined came from melted-down coins.g The fact of re-melting has lead Professor Hall of the Oxford Laboratory to express the opinionlo that to analyse bronzes with the hope of determining provenance or relating metal composition to that of ore bodies is a waste of time.However, such analyses can be used to correlate changes in technology such as those I have mentioned.Another frequently quoted example is the work of Smith and Blin-Stoyle, which demonstrated that lead was only a trace element in Middle Bronze Age bronzes but a deliberate addition in the Late Bronze Age.11 Insight into a more specialised area of early technology is provided by McKerrel and In my view, the corrosion product has enormous potential. Given a cleaned object, what can be learned about its composition?A p ~ i l , 1976 ANALYSIS I N ARCHAEOLOGY, ART AND ANTIQUITIES 99 Tylecote in demonstrating that the arsenic content of Bronze Age halberd rivets, but not of the remainder of the weapon, would seem to have been controlled by the smith.12 There is also a largely unexplored area, not subject to problems of re-melting and questions of technology, comprising soil, organic materials and the interaction of organics with the soil.Further, at the limits of decomposition, organic materials become part of the soil and just before the limit is reached their previous existence may be revealed as soil stains that silhouette the parent body. One can attempt a general statement of the analyst’s over-all task in the following terms.He will be concerned primarily with determining the composition of materials to answer questions regarding provenance and identification, methods of manufacture, etc. However, these materials will have been modified during long-term burial (and also in use) because of interaction with the immediate environment leading to chemical, physical and biological change.Although this change may complicate the analytical processes and interpretation of results with respect to the primary material, at the same time the modified material will carry a record of any change in the layers of corrosion product, etc., which can also be read by analysis. Further, it will act as a kind of trap that may retain minute residues of other inorganic or organic materials present in the micro-environment.These, too, can be analysed as a further source of information, and may, in some instances, provide the basis for a dating method. One might also add that anything found in an excavation, including the soil covering the site, should be seen as a potential trap. Finally, it was suggested that I might predict what new analytical methods should be developed. However, in my view, the developments are more likely to be in the refinement of the applications of existing techniques and in the interpretation of results, i.e., increased attention to the underlying methodology.Any analytical technique applied to archaeological material will produce results, but these will remaln merely numbers unless correctly viewed in an archaeological context. As Sir Mortimer Wheeler says in the preface to his book “Archaeology from the Earth,” an “archaeologist is digging up not things but people,’’ to which someone else has rejoindered, “we may be digging up people but we have to face the facts of life that the information comes from things.” Nevertheless, it does no harm to remind oneself from time to time of the ultimate purpose of the study of antiquity: a fuller under- standing of man and his environment.1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. References Chirnside, R. C., Pvoc. Analyt. Div. Chevut. SOL, 1975, 12, 163. Caley, E. R., J . Chem. Educ., 1951, 28, 64. Hoare, K. C., “Ancient Wiltshire,” William Miller, London, 1812. Kendall, J., “Michael Faraday,” Faber and Faber, London, 1955; Hartley, H., “Humphrey Davy,” Coghlan, H.H., in Heizer and Cook, Editovs, “The Application of Quantitative Mcthods in hrchaeo- Gowland, W., Avchaeologia, 1917-18, 49, 120. Peacock, D. P. S., Antiquity, 1969, 43, 145. Craddock, P., Cuvv. Avchaeol., 1974, 4, 43. Hawkes, S., Avchaeol. J . , 1974, 131, 417. Hall, E. T., “The Impact of the Natural Sciences on Archaeology,” Oxford University Press, London, Smith, M.A., and Rlin-Stoyle, A. E., Pvoc. Pvehist. SOG., 1959, 25, 188. McKerrel, H., and Tylecote, R. F., PYOG. Pvehist. Sac., 1972, 38, 209. S. R. Publishers Ltd., East Ardsley, Wakefield, 1971. logy,” Quadrangle Books, Chicago, 1960, p. 1. 1970. Activation Analysis and Archaeometry G. R. Gilmore Univevsities Reseavch Reactov Activation Analysis Sevvice, Risley, Wavvington, WA 3 6 A T Archaeometry is the application of scientific techniques to the study of archaeological and related problems.The application of neutron activation analysis has proved so fruitful that the method is now accepted as routine, particularly in characterisation studies. In this paper some of the many uses of the technique to obtain results that lead to archaeological conclusions are discussed, referring only to a few of the many excellent examples available.100 ANALYSIS I N ARCHAEOLOGY, ART AND ANTIQUITIES Proc.Analyt. Div. Chem. sot. Table I lists a number of materials which, for archaeological reasons, have been analysed by means of activation analysis. It will be useful to indicate the basic attributes of acti- vation analysis that are important for archaeological analysis.It can be said a t the outset that the most common means of activation of archaeological materials is by thermal neutrons, using either reactor or isotopic sources, and also that analysis involving radiochemical separa- tions has found little application. The most important aspect of neutron activation analysis in the present context is the feasibility of simultaneous multi-element instrumental analysis.The simplicity of this type of analysis is important in characterisation studies when it may be necessary to analyse a large number of samples for several elements with a reasonable invest- ment in time and effort. TABLE I ARCHAEOLOGICAL MATERIALS ANALYSED BY NEUTRON ACTIVATION ANALYSIS Natural materials Flint 1 Obsidian J Marble Clays Ores Slags Wood Bone Man-made objects Tools Statuary, ctc.Jade objects Pottery Faience Glasses Tools Statuary Coinage Paper Amber objects Pigments Small objects can be activated as a whole, which is an advantage when sampling of an object is undesirable. Coins, jade and amber ornaments, and faience beads have all been analysed in this way.Obviously, some care is necessary in order to ensure that the degree of acti- vation will not be too great, so that the object can safely be returned to its owner or the museum display cases and it is often more convenient, particularly for the analyst, if a sample can be taken from the object. The amount of information obtained is not restricted by taking only small samples, owing to the high sensitivity of neutron activation analysis.For example, a 50-mg sample of pottery can yield results for 15-20 elements and as little as 1 mg of sample drilled from a coin can permit the analysis of the alloy components and several impurity elements. Fig. 1 shows two copper-based coins sampled by drilling with a 0.5 mm diameter steel drill. Coins as small as 1 cm in diameter and 1 mm thick have been sampled in this way.Reagent blanks do not, of course, exist in instrumental neutron activation analysis and therefore accuracy is good even at trace levels. Characterisation of Archaeological Material It can be expected that in the process of making, for example, pottery, the trace element concentrations in the pottery will reflect the concentrations in the original clay.It can also be expected that clays in different geographical locations will have different levels of the same trace elements. The trace-element pattern of a piece of pottery should, therefore, be characteristic of its origin. This fundamental principle, that the manufacturing origins of an object will be reflected in some way in its trace-element pattern, is the basis of many archaeological studies and, outside archaeology, in the characterisation of crude oils, drugs and industrial products.Reactor neutron activation analysis is particularly appropriate for the characterisation of ceramics because the matrix activities induced by the irradiation are all of relatively short half-life, while many of the useful trace elements have long half-lives and high sensitivity.The ultimate capability of neutron activation analysis in this connection is probably repre-April, 197'6 ANALYSIS I N ARCHAEOLOGY, ART AND ANTIQUITIES 101 sented by the work of Perlman et al. ,l in which a total of 34 elements were measured in standard pottery, using three irradiations and four measurements of y-ray spectra. The simplified procedure adopted by McKerrel12 is tailored to produce results for 10 significant elements from a single irradiation and measurement. 330 400 600 800 1000 Cr2 0 3 , p.p.m.Knossosn I I I 1 I Mycenae 7 1 60 80 100 2 u 330 NiO, p.p.m. Fig. 1. Roman imperial coinage sampled by I:ig. 2. Coilcentrations of chromium and nickel in pottery from Knossos and Mycenac.2 Fig. 2 shows the measured concentration ranges of chromium and nickel in pottery from Mycenae and Knos~os.~ The separation between these ranges for the two groups of pottery means that a sherd of unknown origin could be identified with reasonable certainty by com- parison of its chromium and nickel concentrations. Unfortunately, in many instances, the ele- mental concentration ranges overlap and for satisfactory discrimination many element con- centrations may need to be considered.The difficulty of discrimination increases as the volume of data per sample increases and handling of data by use of computer methods be- comes a necessity. Other materials that have been extensively studied by neutron activation characterisation are flint,4 obsidian and faience. Obsidian is glassy material of volcanic origin and exhibits remarkable homogeneity within a particular flow.The material was used by ancient man to make tools and was a trade commodity. Characterisation of American and Mediterranean obsidians has produced valuable insight into the trade dispersion of the artifact^.^^^ Faience is a silica-based material with a glaze that contains copper. Following earlier studies by a neutron activation analysis of typical beads, Aspinall et al.7 were able to confirm that British beads had higher concentrations of tin than beads from alternative sources, which supports the notion of a local origin.drilling. Metals The analysis of metals differs from the analysis of pottery in several important respects. Firstly, there is considerable metallurgical or numismatic importance in the matrix com- position itself.There has been only slight interest in the measurement of impurity and trace elements in ancient metals by activation methods. A metal matrix will often give rise to radioactive isotopes, which will cause difficulty in the instrumental measurement of both short- and long-lived isotopes. The characterisation of metals with respect to ore sources has received little attention, possibly owing to a prevailing attitude engendered by statements made with great authority, but probably little evidence, that such characterisation is impossible.It is true that the transformation of ore to metalis more profound than that of clay to pottery. However,102 ANALYSIS IN ARCHAEOLOGY, ART AND ANTIQUITIES PYOC.Analyt. Div. Chem. SOC. the mutual solubility of certain metallic elements ensures that, for example, the arsenic content of a copper ore is transferred, almost wholly, into the copper metal. Friedman et aL8 have made attempts to correlate copper ore types, rather than sources, with impurity con- centrations in the metal. Studies of Roman imperial copper-based coinageg have been successful in deducing a possible date for the beginning of exploitation of the mines in present-day Romania and Jugoslavia.Fig. 3 shows a chronological plot of arsenic concentrations, for a range of alloy types, found in coinage minted throughout the Roman Empire. Closer examination of the data for the period at the beginning of the fourth century revealed that only coins minted by Licinius in the Thracian and Macedonian mints contain high ( i e ., greater than 0.2%) levels of arsenic. This suggests that Licinius, or more probably his predecessors Galerius or Diocletian, discovered new sources of copper. Coinage minted by Constantine in this region after 324 AD (when he overthrew Licinius) also contains high levels of arsenic, an interesting indication that coinage was produced as required from the nearest available source of copper with little or no regard for the inflationary consequences.0.8 0.6 x? 0‘ 2 .- c Lc 0 0.4 .- + L + a, c 0 0 0.2 0 A A A k A A 0 0 00 A E, 0 0 0 \ ‘t 8 * ? m - 0 BC I AD 100 200 300 Date of issue 400 Fig. 3. Chronological variation of the concentration of arsenic in the Roman imperial copper- based ~oinage.~ The different symbols represent distinct types of coins.Silver and gold present special problems when large samples, for example whole coins, are to be analysed. The neutron-capture cross-section of both elements is extremely high and causes the centre of a large sample to be shielded from the neutron flux. There are several solutions to the problem. The analyses of the Merovingian coins from the Sutton Hoo hoardlo were corrected by normalising the sum (copper + silver + gold) to 100%.This procedure is adequate unless significant proportions of lead are present. Other worker@ have devised empirical correction curves relating flux depression to composition. Gordusl2 uses a flux-monitor method in order to assess the degree of self-shielding.The technique is only directly applicable to isotopic neutron source irradiations. Gordus has also described the “streak” technique for sampling silver coinage, in which a few hundred micrograms of material are removed from a clean edge of a coin by rubbing across it a roughened quartzA p d , 1976 ANALYSIS I N ARCHAEOLOGY, ART AND ANTIQUITIES 103 rod or tube. Most analyses of silver and gold have concerned only the matrix elements (including copper).Trace elements are difficult to measure because of the long-lived activity of silver-ll0m formed from the silver that is usually present in gold coinage. Radiochemical separations of irradiated drillings have met with some S U C C ~ S S . ~ ~ ~ ~ ~ It is a well known fact that ancient silver always contained impurity amounts of gold.In principle, it is possible to deduce the source of silver on the basis of this characteristic silver to gold ratio. Modern silver is more highly refined and therefore the measurement of this ratio can provide valuable evidence for the authentification of ancient silver. It is unfortunate that normal reactor activation techniques do not allow an instrumental analysis of lead, especially in view of its common occurrence as an impurity and alloy element.On the other hand, the analysis of lead materials is simplified. Wyttenbach15 has examined Roman lead pigs and water pipes, measuring concentrations of copper, arsenic, silver, tin, antimony and gold. Although some interesting information about the construction of the pipes emerged, it was not possible to relate the impurity concentrations to any place of origin, probably implying a wide distribution of lead from different sources.Other Materials Most organic materials contribute very little to the over-all activity of an irradiated sample, most of the activity being due to impurities present. Organic materials do, however, suffer radiation damage, which makes long irradiations inadvisable and to some extent limits the number of elements measurable. Small-scale studies of amber,l6 paper1’ and single flakes of ~ a i n t l ~ ? ~ ~ appear to have been successful in distinguishing between different sources of the material.Concluding Comments Neutron activation analysis is no longer available only to a few fortunate specialists.Hopefully, the examples presented above have illustrated the value of the technique and will stimulate its application to new problems. Perhaps the simplest and most direct way of assessing the usefulness of neutron activation analysis in a new application is to arrange for the irradiation and qualitative examination of a suitable typical sample. Whether the analyst wishes to do this himself or to contract out the work, facilities and services are widely available in various parts of the country and in some situations may even be free of charge. References 1. Perlman, I., and Asaro, I?., Archaeometry, 1969, 11, 21. 2. McKerrell, H., paper presented a t the Symposium on Archaeometry and Archaeological Prospection, 3. Harbottle, G., Archaeometry, 1970, 12, 23. 4. de Bruin, M., Korthoven, P. J . M., Bakels, C. C., and Groen, F. C. A., Archaeometvy, 1972, 14, 55. 5. Aspinall, A., Feather, S. W., and Renfrew, C., Nature, Lond., 1972, 237, 333. 6. Gordus, A. A., Griffin, J . B., and Wright, G. A., “Science and Archaeology,” M.I.T. Press, Cambridge, 7 . Aspinall, A., Warren, S. E., and Crummett, J . G., Archaeonzetry, 1972, 14, 27. 8. Friedman, -4. M., Conway, M., Kastner, M., Milstead, J., Melta, D., andFields, P. R., Science, N . Y . , 9. Coper, L. H., and Gilmore, G. R., Universities Research Reactor Report, URR-5, 1975. 10. Coleman, R. F., and Wilson, A., “Mcthods of Chemical and Metallurgical Investigation of Ancient 11. Thiele, R. W., Aung Khin, U., and Kyaw, U., Archaeonzetvy, 1972, 14, 199. 12. Gordus, A. A., “Methods of Chemical and Metallurgical Investigation of Ancient Coinage,” Royal 13. Randle, K., Wellum, R., and Whitley, J. E., J . Radioanalyt. Clzem., 1973, 16, 205. 14. Meyers, P., van Zelst, L., and Sayre, E. V., J . Radioanalyt. Chenz., 1973, 16, 67. 15. Wyttenbach, A., and Schubiger, P., Archaeometry, 1973, 15, 199. 16. Das., H. A., Radiochem. Radioanalyt. Lett., 1969, 1, 289. 17. Schroeder, G. L., Kraner, H. W., and Evans, R. D., Science, N . Y . , 1966, 151, 815. 18. Houtman, J. P. W., Turkstra, J., “Radiochemical Methods of Analysis,” Volume 1, Intcrnational 19. LUX, F., Braunstein, L., and Strauss, R., “Modern Trends in Activation Analysis,” Natn. BUY. Stand. Oxford, 1975. Mass., 1970, p. 222. 1966, 152, 1504. Coinage,” Royal Numismatic Society, London, 1972, p. 88. Numismatic Society, London, 1972, p. 127. Atomic Energy Agency, Vienna, p. 85. Sflec. Publ. 312, 1969, p. 216.

ISSN:0306-1396    

DOI:10.1039/AD9761300094

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

104 LASERS IN ANALYTICAL CHEMISTRY PYOC. Analyt. Div. Chem. SOC. Lasers in Analytical Chemistry The following is a summary of the paper presented at a Meeting of the Midlands Region held on November 18th, 1975. Lasers: Their Current and Potential Applications in Analytical Chemistry B. L. Sharp Macaulay Institute f o v Soil Iieseavch, Cyaigiebuchlev, A bevdee.tz, AB9 2Q J Lasers possess a number of unique properties and it is useful to begin with a listing and description of their relevance to analytical chemistry.Lasers are capable of yielding high spectral (output per unit band width) and spatial (output per unit area) power densities. Potentially, this property should result in lower detection limits from techniques whose sensitivity is dependent on source power, e.g., fluorescence.High power may also enable saturation of the excited state of a transition to be realised, which results in further sensitivity gains (see Laser-excited Atomic-fluorescence and Saturation Spectroscopy). The low beam divergence of laser sources (less than 1 mrad is typical; lower limit set by diffraction) enables them to be focused to small spots (e.g., ZO-lOOprn), where high power density or spatial resolution is required, e.g., laser vaporisation. Further, the power density is conserved over large distances (no 1/r2 loss), thereby making possible remote sensing techniques.Laser photons are coherent both across the beam section and along the longitudinal axis, i.e., a well defined phase exists over extended regions. This property greatly facilitates the use of interferometric techniques and related methods such as holography, which is routinely used in the production of diffraction gratings.Tunable output can be obtained from the microwave to the vacuum-ultraviolet region of the spectrum, either by line selection or continuous tuning in the ultraviolet - visible or near-infrared regions. A wide range of spectral transitions may therefore be excited and the simultaneous excitation of several transitions is feasible. In addition to variable wave- length, variable band width can also be obtained, ranging over lO-'-lO nm.High excitation selectivity can therefore be achieved and specific line excitation of individual isotopes is possible. Pulsed or Q-switched operation is used when high peak power is required.Very short pulses, down to a few picoseconds, can be obtained and employed in the measurement of excited-state lifetimes. Continuous-wave (c.w.) lasers are preferred for interferometric and optical testing applications. Lasers can yield either continuous or pulsed output. Current Analytical Applications Laser Microprobe Analysis's The output of a pulsed or Q-switched ruby or neodymium glass laser is focused directly on to the surface of the sample.Pulse energies of 1-10 J are typical, with periods of 100 p s when non-Q-switched and 20-100 ns when Q-switched. Spot sizes of 50-500pm can be used so that power densities of 1010-1013 W cm-z are available. The dense vapour plume produced is sufficiently hot to produce ions and emit spectra; generally, however, a spark struck between a pair of electrodes is used to excite the vapour, thereby increasing the line intensity and lowering the limits of detection.The advantages associated with the method are : (i) Small and precise areas of the sample can be analysed, e.g., single mineral crystals in rocks. Representative sampling can be accomplished by varying the spot location and diameter.(ii) Conducting and non-conducting solids can be handled with a minimum of sample preparation and, as no dilution is necessary, contamination is reduced.Afi~il, 1976 LASERS IS AXALYTICAL CHEMISTRY 105 (iii) Vnlike most optical emission techniques, the vaporisation and excitation processes can be separately controiled (e.g., the vapour cloud could be used as the sample input for a mass spectrometer).(iv) Precisions in the 1-2% range can be obtained by summing the results from 50-100 shots. Laser Raman Spectroscopy3 This is an established technique for structural or compositional analysis, which, for its current range of application, is entirely dependent on the availability of laser sources. When incident radiation of arbitrary frequency, vo, impinges on the sample, the radiation scattered at right angles contains frequencies vo & Av, where AV is the Raman shift or Raman frequency and corresponds to one of the vibrational transitions in the molecule.The rotational spectrum appears as a fine structure superimposed over the vibrational band. The intensity relationship can be approximated by the expression where C is a constant, N is the molecular concentration and P is the induced dipole moment.I t should be noted that, to a first approximation, P is proportional to the electric field, E , and therefore P2 is proportional to E2, i.e., to the intensity of the incident radiation. Raman scattering is an extremely weak phenomenon and therefore in order to obtain measurable signals, high power densities are required.As each source line produces a com- plete spectrum, single-line output is preferred and, to take advantage of the fourth-power scattering law, that output should be in the ultraviolet region. In addition, a highly direc- tional source assists the detection optics in discriminating against incident radiation. These requirements are exactly fulfilled by the laser, the most used type being the argon ion laser, which yields up to 15 W C.W.output, principally in two lines at 488.0 and 514.5 nm with line widths of about 0.25 cm-l. Unfortunately, such lasers cost in the region of L5 000-10 000 and the detection optics are also expensive. Nevertheless, Raman spectroscopy is capable of probing many molecules that are not infrared active and is therefore an indispensable tool to the chemist.Remote Sensing4 The detection or determination of chemical species at considerable distances (remote sensing) by using a laser source is perhaps the most exciting and potentially valuable appli- cation currently being considered, not least because it makes use of the unique properties of the laser. In this summary it is possible only to list the available methods and to give some mention to the more important ones. Remote sensing has so far been applied to gaseous species, the detection and sizing of aerosols and to the detection of pollutants on surface water^.^ Gaseous detection has received most attention and the following discussion relates to this subject.The methods employed include (i) Raman scattering, (ii) resonance Raman scattering, (iii) infrared vibrational and rotational fluorescence and heterodyne sensing, (iv) molecular fluorescence from excited electronic states, (v) absorption and (vi) atomic fluorescence.Generally, methods (i)-(iii) are not sensitive enough to measure ambient pollution levels, but may be of use to monitor local concentrations of pollutants such as those from flue outlets and chimneys.Of the remaining three methods, (iv) has not been widely used but (v) and (vi) have proved particularly useful and are discussed below. The difeve.lztial absov9tiol.z technique A few pollutant molecules commonly found in the atmosphere, viz., SO,, NO,, 0, and NOCl, have electronic absorption spectra in the visible or ultraviolet region and can therefore be detected with tunable lasers (normally dye lasers).In the differential absorption technique, the transmitted output of the laser is divided into two frequencies, using a Fabry - Perot interferometer with its free spectral range adjusted to coincide with the peak and trough of an absorption band of the molecule. The gas and particulate matter in the atmosphere act as a distributed Rayleigh and Mie reflector and therefore the absorption due to the106 LASERS IN ANALYTICAL CHEMISTRY PYOC.AizaZyt. Div. Chem. SOC. presence of a pollutant can be observed at the detector and its concentration computed. Using this technique, it is possible to measure 1 p.p.m. levels at a range of several kilometres with 30-m range resolution (i.e., the minimum path length that can be resolved); even lower levels can be determined at shorter ranges, as there is an approximately inverse linear relation- ship between detection limit and range.Difficulties can arise due to overlapping absorption bands and the technique is limited to relatively few molecules. Atomic fluoyesceizce The cross-sections for atomic absorption of radiation are very high, about 10l6 times greater than those for Raman spectroscopy.Potentially, atomic fluorescence can be used for detection at the However, the high absorption coefficient results in depletion of the source beam and, together with self-absorption of the fluorescence, limits the distance to 500 m or less. This problem can be overcome by using the line wings rather than the line centre, but at the cost of decreased sensitivity. The ideal situation is where the material is remote but localised in depth; thus Bowman et aZ.6 measured sodium concentrations in the upper atmosphere layer at a range of 100 km.The principal difficulty with atomic fluorescence is that there is no wavelength shift and therefore the Rayleigh and Mie scattering contribute at the receiving wavelength and may cause the signal to noise ratio to be limited by the background.p.p.m. level at long ranges. In t r a - cavity A b sorp t ion7 In conventional absorbance measurements, a typical lower limit would be about 0.001 absorbance unit, corresponding to about a quarter of the “sensitivity.” To increase the effective absorbance of the species under study, it is possible to use a multipass cell, although losses limit the gain to a few passes only.An alternative approach is to place the weak absorber within the resonator cavity of a tunable laser. The effect is to modify the single pass gain of the cavity and thereby selectively quench the output of the laser. It is estimated that for photons averaging 10 passes through the laser cavity, this is equivalent to about 400 passes through a normal cell.Using this technique, absorbances of 0.0001 or less can be measured and detection limits improved 10-100-fold. Unfortunately, the effect on the output is non-linear and at present the technique can be considered worthwhile only for the determination of very small concentrations for which no alternative methods are available. Laser-excited Atomic-fluorescence and Saturation Spectroscopy The advantages of using a laser to excite atomic fluorescence have been described both t h e o r e t i ~ a l l y ~ ~ ~ and, to some extent, experimentally.lOJ1 The benefits of using a high-powered narrow-line tunable source for atomic fluorescence are obvious, but the major benefits are realised when the source is sufficiently powerful to saturate the excited state of the absorption transition.For a simple system with two energy levels, this means that half the atoms are in the excited state and the following consequences result. (i) As the population of the excited state is maximised, the fluorescence flux and sensitivity are also maximised. (ii) Fluctuations in the input power produce no corresponding change in the fluorescence output.Hence, regulation of the fluorescence with respect to input flux is achieved and gains in signal to noise ratio result. (iii) When the energy-state populations are equalised, absorption is completely balanced by stimulated emission and therefore no net increase in absorption can occur. The result is to minimise the effect of self-absorption and increase the linear range of the growth curve.(iv) The relative effect of quenching is minimised, thereby ob- viating some of the problems of using quenching gases in atomic-fluorescence experiments. Current experiments tend to show that these benefits can be realised but that the lasers now in use do not enable their full potential to be exploited, because of limited power and tuning capability. Conclusions The title of this paper poses the question, “will lasers play an important role in analytical chemistry ?” and one might add the rider, “will analytical chemists be responsible for any developments which do occur ? ”April, 1976 RANK HILGER SPECTROSCOPY PRIZE 107 The above list of applications is by no means exhaustive and does not include optical applications that are related to analytical chemistry.A consistent theme runs through many application descriptions; that the full potential of the laser will be reached only when further development has taken place, yielding firstly a greater tunable range extending further into the ultraviolet region and, in some instances, higher power or energy output.It should also be noted that current analytical techniques normally employ the least expensive satis- factory equipment and therefore, unless lasers become considerably less expensive, future analytical development may be limited to those methods for which the unique properties of the laser are indispensable. Indeed, entirely new analytical techniques may become possible through their development.However, such advances will occur, particularly in the UK, only if analytical chemists can obtain the level of funding required to work with such advanced technologies. It may well be that potential UK users of the future will be forced to buy their equipment abroad or be faced with trying to persuade their wealthier brethren, the physicists, to turn their attention to analytical problems. Certainly the future for lasers appears promising. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. References Scribner, B. F., Puve A p p l . Chem., 1965, 10, 591. Boumans, P. W. J . M., in Grove, E. L., Editov, “Analytical Emission Spectroscopy,” Marcel Deltker, Gilson, T. R., and Hendra, P. J . , “Laser Raman Spectroscopy,” Wiley-Interscience, New York, 1970. Kildal, H., and Byer, R. L., Pvoc. I.E.E.E., 1971, 59, 1644. Measures, K. M., Houston, W., and Bristow, M., Can. Aevonaut. Space J . , 1973, 19, 501. Bowman, M. R., Gibson, A. J., and Sandford, M. C. W., Natuve, Lond., 1969, 221, 456. Keller, R. A,, Zalewski, E. F., and Peterson, N. C., J . Opt. Soc. An%., 1972, 62, 319. Piepmeier, E. H., Spectvochivvz. Acta, 1972, 27B, 431. Piepmeier, E. H., Spectvochivvz. Acta, 1972, 27B, 445. Omenetto, N., Benctti, P., Hart, L. P., Winefordner, J. D., and Xlkemade, C. Th. J., Spectvochinz. Omenetto, N., Hart, L. P., Benetti, P., and Wineforclner, J. D., Spectvochiwz. Acta, 1973, 28B, 301. New York, 1972, p . 222. Acta, 1973, 28B, 289.

ISSN:0306-1396    

DOI:10.1039/AD9761300104

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

April, 1976 RANK HILGER SPECTROSCOPY PRIZE 107 Rank Hilger Spectroscopy Prize The Atomic Spectroscopy Group of the Analyti- cal Division is pleased to invite applications for the 1976 Rank Hilger Spectroscopy Prize. The successful candidate will receive a prize to the value of L75, part of which is to be used for the purchase of a book(s) for presentation a t the Group’s AGM. The award will be judged on the basis of the candidate’s contribution to analytical atomic spectroscopy.Relevant techniques in- clude atomic absorption, atomic fluorescence, atomic emission and X-ray fluorescence. The work need not be theoretical but could cover applications, instrumental modification, accessories, improvements in technique and data handling. The contribution need not have been published and candidates’ wishes with respect to publication will be respected. Intending candidates should : 1 .be under 30 years of age on December 31, 1976; 2. be members of the Chemical Society and resident in the United Kingdom ; 3. submit, before May 31, 1976, a summary of about 500 words describing their contribution to the theory or practice of atomic spectroscopy. The summary should be endorsed by a senior member of the establishment in which the candidate is employed. The Selection Committee may require certain short-listed candidates to provide a more detailed account of their work. Applications should be addressed to the Honorary Secretary, Atomic Spectroscopy Croup, Analytical Division, The Chemical Society, Burlington House, London, W1V OEN.

ISSN:0306-1396    

DOI:10.1039/AD9761300107

出版商:RSC    

年代:1976

数据来源: RSC