THE ANALYSTTHE ANALYTICAL JOURNAL OF THE ROYAL SOCIETY OF CHEMISTRYADVISORY BOARD*Chairman: J. M. Ottaway (Glasgow, U.K.)'L. S. Bark (Salford, U.K.)E. Bishop (Exeter, U.K.)W. L. Budde (U.S.A.)D. T. Burns (Belfast, U.K.)L. R. P. Butler (South Africa)H. J. Cluley (Wembley, U.K.)E. A. M. F. Dahmen (The Netherlands)L. de Galan (The Netherlands)A. C. Docherty (Billingham, U.K.)D. Dyrssen (Sweden)G. Ghersini (Italy)J. Hoste (Belgium)A. Hulanicki (Poland)' G . W. Kirby (Glasgow, U.K.)W. S. Lyon (U.S.A.)H. V. Malmstadt (U.S.A.)G. W. C. Milner (Harwell, U.K.)"A. C. Moffat (Aldermaston, U.K.)E. J. Newman (Poole, U.K.)H. W. Nurnberg (West Germany)'T. B. Pierce (Harwell, U.K.)E. Pungor (Hungary)P. H. Scholes (Middlesbrough, U.K.)D. Simpson ( Thorpe-le-Soken, U.K.)'J.M. Skinner (Billingham, U.K.)'J. D. R. Thomas (Cardiff, U.K.)K. C. Thompson (Sheffield, U.K.)*A. M. Ure (Aberdeen, U.K.)A. Walsh, K.B. (Australia)G. Werner (German Democratic Republic)T. S. West (Aberdeen, U.K.)"P. C. Weston (London, U.K.)' J. White head (Stockton- on- Tees, U. K.)J. D. Winefordner (U.S.A.)P. Zuman (U.S.A.)'G. J. Dickes (Bristol, U.K.)*Members of the Board serving on the Analytical Editorial BoafdEditor: P. C. WestonSenior Assistant Editor: R. A. YoungAssistant Editors: Mrs. J. Brew, Miss D. ChevinREGIONAL ADVISORY EDITORSDr. J. Aggett, Department of Chemistry, University of Auckland, Private Bag, Auckland, NEW ZEALAND.Professor L. Gierst, Universit6 Libre de Bruxelles, Facult6 des Sciences, Avenue F.-D.Roosevelt 50,Professor H. M. N. H. Irving, Department of Theoretical Chemistry, University of Cape Town, Ronde-Professor W. A. E. McBryde, Faculty of Science, University of Waterloo, Waterloo, Ontario, CANADA.Dr. 0. Osibanjo, Department of Chemistry, University of Ibadan, Ibadan, NIGERIA.Dr. G. Rossi, Chemistry Division, Spectroscopy Sector, CEC Joint Research Centre, EURATOM, lspraDr. I. Rubeska, Geological Survey of Czechoslovakia, Malostransk6 19, 118 21 Prague 1 , CZECHO-Professor J. R&icka, Chemistry Department A, Technical University of Denmark, 2800 Lyngby,Professor K. Saito, Department of Chemistry, Tohoku University, Sendai, JAPAN.Professor L. E. Smythe, Department of Chemistry, University of New South Wales, P.O. Box 1 ,Professor P.C. Uden, Department of Chemistry, University of Massachusetts, Amhesst, MA 01 003,Editorial: Editor, The Analyst, The Royal Society of Chemistry, Burlington House,Piccadilly, London, W1V OBN. Telephone 01 -734 9864. Telex No. 268001Advertisements: Advertisement Department, The Royal Society of Chemistry, Burlington House,Piccadilly, London, W1V OBN. Telephone 01 -734 9864. Telex No. 268001The Analyst (ISSN 0003-2654) is published monthly by The Royal Society of Chemistry, BurlingtonHouse, London W1V OBN, England. All orders accompanied with payment should be sent directly toThe Royal Society of Chemistry, The Distribution Centre, Blackhorse Road, Letchworth, Herts. SG6 1 HN,England. 1983 Annual subscription rate UK f93.50, Rest of World f 99.00, USA $201 .OO. Purchased withAnalytical Abstracts UK f 226.50, Rest of World f 238.50, USA $487.00. Purchased with AnalyticalAbstracts plus Analytical Proceedings UK €251 .OO, Rest of World €265.00, USA $539.00. Purchasedwith Analytical Proceedings UK fll7.50, Rest of World f 124.50, USA $253.00. Air freight and mailingin the USA by Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 1 1 003.USA Postmaster: Send address changes to: The Analyst, Publications Expediting Inc., 200 MeachamAvenue, Elmont, NY 11003. Second class postage paid at Jamaica, NY 11431. All otherdespatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outside Europe.PRINTED IN THE UK.Volume 108 No 1287 @ The Royal Society of Chemistry 1983 June 1983Bruxelles, B ELGl U M.bosch 7700, SOUTH AFRICA.Establishment, 21 020 lspra (Varese), ITALY.SLOVAKIA.DEN MARK.Kensington, N.S.W. 2033, AUSTRALIA.U.S.A