ISSN:0144-557X    

DOI:10.1039/AP98421FX023

出版商:RSC    

年代:1984

数据来源: RSC

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ANPRDI 21(7) 233-278 (1984) July 1984 Hon. Secretary R. Sawyer Analvtical Proceedinis Proceedings of the Analytical Division of The Royal Society of Chemistry AD President P. G. W. Cobb Hon. Treasurer D. C. M. Squirrel1 Hon. Assistant Secretary D. I. Coomber, O.B.E. Hon. Publicity Secretary Dr. J. F. Tyson, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, LEI 1 3TU Secretary Miss P. E. Hutchinson Editor, Analyst and Analytical Proceedings P. C. Weston Senior Assistant Editors Assistant Editor Mrs. J. Brew, R. A. Young Ms. D. Chevin Publication of Analytical Proceedings is the responsi- bility of the Analytical Editorial Board: J. M. Ottaway (Chairman) L. S. Bark L. C. Ebdon A.M. Ure A. G. Fogg *P. M. Maitlis A. C. Moffat B. L.Sharp J. D. R. Thomas *P. C. Weston *Ex officio members All editorial matter should be addressed to: The Editor, Analytical Proceedings, The Royal Society of Chemistry, Burlington House, Piccadilly, London, W1V OBN. Telephone 01-734 9864. Telex 268001. Advertisements: Advertising Department, The Royal Society of Chemistry, Burlington House, Piccadilly, London, WIV OBN, Telephone 01-734 9864. Analytical Proceedings (ISSN 0144-557X) is published monthly by The Royal Society of Chemistry, Burlington House, London, W1V OBN, England. All orders, accompanied by payment, should be sent to The Royal Society of Chemistry, The Distribution Centre, Black- horse Road, Letchworth, Herts., SG6 IHN, England. 1984 Annual Subscription price if purchased on its own: UK €53.00, Rest of World €56.00, US $106.00, including air speeded delivery.Air freight and mailing in the USA by Publications Expediting Inc., 200 Meacham Avenue, Elmont, N.Y. 11003. USA Postmaster: Send address changes to: Analytical Proceedings, Publications Expediting Inc., 200 Meacham Avenue, Elmont, N.Y. 11003. Second class postage paid at Jamaica, N.Y. 11431. All other despatches.outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outside Europe. PRINTED IN THE UK. @The Royal Society of Chemistry, 1984. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photographic, recording, or otherwise, without the prior permission of the publishers.Annual General Meeting of the Analytical Division The twelfth Annual General Meeting of the Analytical Division of the Royal Society of Chemistry was held at 4.00 p.m. on Tuesday, June 5th, 1984, at the Scientific Societies Lecture Theatre, 23 Savile Row, London, W.l. The Chair was occupied by the President, Professor S. Greenfield, PhD, CEng, MIM, CChem, FRSC. The Report of the Council for the year ending March, 1984, was presented by the Honorary Secretary and adopted. The Scrutineers, Mr. C. A. Watson and Mr. R. A. Young, reported that no ballot had been required for the Officers of the Division and the following would therefore serve for the coming year- President-P. G . W. Cobb, CChem, FRSC, Immediate Past President-S. Greenfield. Vice-Presidents-D. T.Burns and T. B. Pierce. Honorary Treasurer-D. C. M. Squirrel Honorary Secretary-R. Sawyer. Honorary Assistant Secretary-D, I. Coomber Other Members of Council-The Scrutineers further reported that 768 valid ballot papers had been received and that votes had been cast in the election of Ordinary Members of Council as follows: B. J. Birch, 421; H. E. Brookes, 373; G. J. Dickes, 398; A. G. Fogg, 370; H. Hughes, 363; J. N. Miller, 434; G. W. C. Milner, 340; E. J. Newman, 474; J. M. Ottaway, 463; J. E. Page, 300; A. M. Ure, 402; J. Whitehead, 423; W. J. Williams, 326. The President declared the following to have been elected Ordinary Members of Council for the ensuing 2 years: B. J. Birch, H. E. Brookes, G. J. Dickes, J. N. Miller, E. J. Newman, J. M. Ottaway, A. M. Ure and J.Whitehead. D. Betteridge, C. L. Denton, A. C. Docherty, L. C. Ebdon, M. C. Finniear, G. F. Kirkbright, P. Morries and J. D. R. Thomas, having been elected Members of the Council in 1983, will, by the Rules of the Division, remain Members of the Council for 1984/5. G. A. Best (Chairman of the Scottish Region), J. G. Jones (Chairman of the SAC 86 Executive 233 DGA. (Programmes Secretary).234 REPORTS OF MEETINGS Committee), C. J . Keattch (Chairman of the Group Liaison and Policy Committee), M. A. Leonard (Chairman of the Northern Ireland Region), A. Mathias (Chairman of the North West Region), J . Newham (Chairman of the North East Region), J . M. Ottaway (Chairman of the Analy- tical Editorial Board), E. B. Reynolds (Chairman of the Western Region), H . I. Shalgosky (Chair- man of the South East Region and of the Analytical Abstracts Editorial Committee), P. B . Smith (Chairman of the Midlands Region), G. M . Telling (Chairman of the East Anglia Region), J . F . Tyson (Honorary Publicity Secretary), J . N. Miller (Chairman of the Programmes Committee) and A. J . Harrison (Chairman of the Analytical Methods Committee) will be ex officio members of the Council for 1984/5. The Honorary Officers and new Members of Council will assume their duties on July 18th. The Annual General Meeting was followed by the Address of the Retiring President, Professor S. Greenfield, entitled “Sauces Other Than ICPS. ” Anal. Proc., Vol. 21

ISSN:0144-557X    

DOI:10.1039/AP9842100233

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

234 REPORTS OF MEETINGS Anal. Proc., Vol. 21 J. G. Jones. The following office bearers were elected for the forthcoming year: Chairman-Mr. E. B. Reynolds. Vice-Chairman-Dr. P. Tackla. Honorary Secretary and Treasurer-Mr. F. W. Sweeting, Wessex Water Authority, Bristol Avon Division, P.O. Box 95, The Ambury, Bath, BA1 2YP. Members of Committee-Mr. K. W. C. Burton, Dr. L. C. Ebdon, Mr. J. G. Jones (ex officio), Mr. G. F. Lewis, Dr. G. Nickless and Dr. J. D. R. Thomas. Mr. E. A. Hontoir and Dr. E. J. Newman were appointed as Honorary Auditors. Reports of Meetings North West Region The fifty-ninth Annual General Meeting of the Region was held at 6.30 p.m. on Thursday, January 19th, 1984, at Pilkington Brothers PLC, Lathom, Lancashire. The Chair was taken by the Chairman of the Region, Dr.A. Mathias. The following office bearers were elected for the forthcoming year: Chairman-Dr. A. Mathias. Vice-Chairman-Mr . P. Morries. Honorary Sec- retary-Mr. G. Davison, Kodak Ltd., Chemical Division, Research Department, Acornfield Road, Kirkby, Merseyside. Honorary Treasurer -My. B. Taylor. Honorary Assistant Secretary- Mr. T. E. Hanley. Members of Committee- Mr. E. R. Adlard, Dr. G. M. Anthony, Professor L. S. Bark (co-opted), Dr. A. Dyer (ex officio), Dr. M. Hitchman, Professor G. F. Kirkbright, Dr. R. Miller and Dr. C. Peacock. Mr. G. W. Earnshaw and Mr. M. Green were re-appointed as Honorary Auditors. Western Region The twenty-ninth Annual General Meeting of the Region was held at 6 p.m. on Friday, January 13th, 1984, in Lecture Theatre 4, School of Chemistry, The University, Bristol.The Chair was taken by the Chairman of the Region, Mr. South East Region The ninth Annual General Meeting of the Region was held at 2.15 p.m. on Tuesday, December 13th, 1983, in the Linnean Society Lecture Theatre, Burlington House, London W.l. The Chair was taken by the Chairman of the Region, Dr. S. J. Lyle. The following office bearers were elected for the forthcoming year: Chairman- Mr. H. I. Shalgosky. Vice-Chairman-Mr. G. F. Phillips. Honorary Secretary-Dr. A. H. Andrews, Beecham Pharmaceuticals, Clarendon Road, Worthing, Sussex, BN14 8QH. Honorary Treasurer-Mr. W. B. Chapman. Honorary Assistant Secretary-Mr. P. J. O’Neil. Members of Committee-Professor D. Betteridge, Mr. D. Blair, Dr. J. E. Firth, Mr. R. Goulden, Mr.D. W. Houghton, Dr. S. J. Lyle (ex-officio) and Dr. A. Ware. Dr. J. E. Page and Mr. D. C. M. Squirrel1 were re-appointed as Honorary Audi- tors. Northern Ireland Region The third Annual General Meeting of the Region was held at 5.15 p.m. on Thursday, October20th, 1983, in the Chemistry Department, Queen’s University, Belfast. The Chair was taken by the Chairman of the Region, Dr. M. A. Leonard. The following office bearers were elected for the forthcoming year: Chairman-Dr. M. A. Leonard. Vice-Chairman-Dr. G. Svehla. Honorary Secretary and Treasurer-Mr. W. J. Swindall, Department of Chemistry, David Keir Building, Queen’s University, Belfast, BT9 5AG. Members of Committee-Professor D. T. Burns, Mr. E. L. Donaldson and Mr. R. A. Hall. Mr. V. L. Beavisand Mr.C. Wilson were re-appointed as Honorary Auditors. Education and Training Group The thirteenth Annual General Meeting of the Group was held at 4 p.m. on Monday, December 12th, 1983, in the Music Room, University ofJuly, 1984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS 235 Strathclyde Staff Club, GIasgow. The Chair was taken by the Chairman of the Group, Mr. A. F. Smith. The following office bearers were elected for the forthcoming year: Chairman-Mr. A. F. Smith. Vice Chairman-Dr. J. D. R. Thomas. Honorary Secretary-Dr. L. A. Gifford, Depart- ment of Pharmacy, University of Manchester, Oxford Road, Manchester, M13 9PL. Honorary Treasurer-Mrs. M. I. Arnold. Members of Com- mittee-Dr. E. J. Greenhow (ex officio), Dr. E. K. Harrison, Dr. C. W. McLeod. Dr. N. T: Crosby and Mr.D. G. Porter were re-appointed as Honorary Auditors. Joint Pharmaceutical Analysis Group The fourteenth Annual General Meeting of the Group was held at noon on Thursday, March, 8th, 1984, at the Pharmaceutical Society of Great Britain, 1 Lambeth High Street, London, SE1 7JN. The Chairman, Mr. C. A. Johnson, welcomed 32 members of the Group to the meeting. The Honorary Secretary presented the Annual Report for 1983. The scrutineers’ report of the ballot for the new committee members was presented. The Com- mittee of Management for 1984 will be as follows: Chairman-Dr. A. H. Andrews. Honorary Secre- tary-Dr. B. V. Fisher. Immediate Past Chair- man-Mr. C. A. Johnson. Ordinary Members- Dr. A. F. Fell, Mr. T. M. French, Mr. D. C. Hunt, Miss M. L. Rabouhans, Dr. N. Randall and Dr. P. R. Wood. Members nominated by the Sponsoring Bodies-Dr. G. Thomas (Pharma- ceutical Society of Great Britain), Mr. G. F. Phillips (RSC, Analytical Division) and Professor W. B. Whalley (RSC, Professional Affairs Board).

ISSN:0144-557X    

DOI:10.1039/AP9842100234

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

July, I984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS 235 Short Papers in Pharmaceutical Analysis The following are summaries of seven of the papers presented at a Meeting of the Joint Pharmaceutical Analysis Group held on October 13th, 1983, at the Pharmaceutical Society of Great Britain, London, S.E. 1. The Effect of Solvent Composition on the Retention of Ten Beta-adrenoceptor Antagonists in a Reversed-phase Ion-pair HPLC System N. H. Day and G. D. Parr Department of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD This study was designed to investigate the effect of changing solvent composition on the chromatographic retention of a series of 10 beta-adrenoceptor antagonists of widely varying lipophilicity by using reversed-phase ion-pair (RP IP) HPLC with the aim of analysing mixtures of these drugs in an in vitro sample. Many biopharmaceutical compounds and their metabolities are polar compounds, and as such are difficult to isolate and subsequently assay.Compounds such as the beta-blockers that are ionised throughout the normal pH range at which most HPLC columns are stable ( e . g . , pH 1.5-7.5) are eluted rapidly from the column in an RP system, close to the solvent front. Thus, selective determination of mixtures is difficult. The use of ion-pairing agents promotes retention of these highly ionised compounds by (in effect) making them less polar in nature. There are several parameters that can be changed in order to control the retention and selectivity of analysis of compounds in RP IP HPLC. Nine important factors have been discussed in detail by Tomlinson et al.1 This study is concerned with changing the concentrations of organic modifier and pairing ion in an RP system.Increasing the concentration of pairing ion will lead to an increase in retention, and as the concentration of organic modifier is increased, retention will decrease. Materials and Methods A Cecil CE 2010 HPLC system was used with a Cecil CE 2112 ultraviolet detector (Cecil Instruments Ltd., Cambridge). The injector was a Rheodyne Model 7125 syringe loading sample injectorAnal. Proc., Vol. 21 (Rheodyne Inc., California, USA) with a loop injection volume of 20 pl. The column was a Partisil ODS (CIS, 10 pm) of 25 cm length (Jones Chromatography Ltd., Llanbradach, Mid Glamorgan). The recorder was a Spectra Physics SP 4100 computing integrator (Spectra Physics, California, USA).Absorbance spectrum determinations were made in a Perkin-Elmer Model 550s spectrophotometer with a Perkin-Elmer 561 chart recorder (Perkin-Elmer Ltd., Beaconsfield, Buckinghamshire) using Spectrosil far ultraviolet 1 cm optical cells (Thermal Syndicate Ltd., Wallsend, Tyne and Wear). The solvent consisted of acetonitrile (HPLC grade, Blackford Wells Ltd., Coalville, Leicestershire) in a 20, 30 or 40% mixture with orthophosphoric acid (Fisons Scientific Apparatus, Loughborough, Leicestershire) (20 mmol dm-’), with and without the addition of 1-heptanesulphonic acid, sodium salt (SHS) (Fisons) at 2 and 4 mmol dm-3, making a total of 9 eluents. The solvents were passed twice through a sintered glass filter to remove any particles and then after the addition (where necessary) of SHS were sonicated for 30 min to reduce dissolved gases.The standard solution of each drug was made up to a concentration of 1 mmol dm-3 in hypotonic solvent (15% acetonitrile in 20 mmol dm-3 orthophosphoric acid). This solution was chosen to aid the identification of the solvent front. Serial dilutions of these standards were made at 25 pmol dm-3 and these were used for the determination of the absorbance spectra of the drugs between 260 and 210 nm. The HPLC detector was set to measure at a wavelength of 210 nm for all of the samples; whilst this was not the em,,. for all the drugs, the absorbance was sufficient, and if greater sensitivity was required then the detector wavelength could be adjusted to the appropriate E ~ , ~ , .The flow-rate was set at approximately 2 cm3 min-1 and the column pressure at this flow-rate varied between 70-85 bar. All measurements were made at room temperature. 236 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS Results In developing an HPLC system, the capacity factor should be adjusted to be between 1 and 5, such that the retained peak neither appears too close to the unretained peak, nor takes too long to emerge from the column. The individual capacity factors (Table I) showed that certain solvent compositions were not appropriate for some drug combinations, e.g., alprenolol, propranolol and betaxolol were all too well retained (with capacity factors in excess of 5) in any of the 20% acetonitrile eluents for this composition to be of practical use.Some of the capacity factors for pairs of drugs were too close together to permit their resolution in a mixed sample. For example, sotalol and atenolol have capacity factors too close together in all of the solvents studied to allow resolution of a mixture of these two drugs. A similar problem exists for mixtures of oxprenolol and labetalol in certain eluents. TABLE I CAPACITY FACTORS FOR RECOMMENDED ELUENTS 20% MeCN and 30% MeCN and 40% MeCN and Drug 2 mM SHS 2 mM SHS 2 mM SHS . . . . . . . . . . . . . . 0.638 5 0.412 3 0.458 3 . . . . . . . . . . . . . . 0.750 0 0.403 5 0.437 5 Sotalol Atenolol Timolol . . . . . . . . . . . . . . n 3.153 8 1.258 6 0.958 3 Acebutolol . . . . . . . . . . . . I 3.876 9 I 1.344 8 Metoprolol .. . . . . . . . . . . 3.969 2 1.552 6 Oxprenolol . . . . . . . . . . . . 6.476 9 2.325 9 Labetalol . . . . . . . . . . . . . . 8.046 2 2.305 3 11.2551 J . . . . . . . . . . . . 3.619 5 1.875 0 . . . . . . . . . . . . 3.796 5 1.877 6 0 3.931 0 1.979 6 Alprenolol 11.369 Propranolol 12.538 Betaxolol 13.738 . . . . . . . . . . . . The capacity factor was reduced as a logarithmic function of acetonitrile concentration, which is in keeping with the theory that retention is a function of partitioning between the mobile and stationary phases. As the stationary phase was predominantly non-polar octadecylsilica, together with a small proportion of uncapped polar silanol groups according to the CI8 loading of the column, increasing the organic solvent strength by increasing the volume fraction of acetonitrile would be expected to reduce the interaction of non-polar solutes with the stationary phase.For most of the drugs, retention was increased by the addition of SHS; the exceptions were the 4 mmol drn-3 SHS concentration with 40% acetonitrile, which for sotalol, atenolol, metoprolol, oxprenolol, labetalol and propranolol had a lower capacity factor than the corresponding 2 mmol dm-3 SHS concentration (some examples can be seen in Figs. 1 and 2 which show graphs of log capacity factor against acetonitrile volume fraction). All theJuly, 1984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS 0.2 0 - 0 m w w- w >. -0.2 0 .- -0.4 - 237 20 30 40 Acetonitrile, YO VIV Logarithm capacity factor plotted against acetonitrile volume fraction: 0, atenolol, 0 mM SHS; V, atenolol, 2 mM SHS; 0, atenolol, 4 rnM SHS; 0, sotalol, 0 mM SHS; V, sotalol, 2 mM SHS; W , sotalol, 4 mM SHS.other drugs in all solvents behave as for betaxolol (Fig. 2) in showing a consistent increase in capacity factor with added SHS. This apparent anomaly may have been because the retention maxima for these drugs had been reached at a concentration lower than 4 mmol dm-3, and thus at this top concentration, a tailing off in retention had occurred, probably due to micellization of the ion-pairing agent which renders the solute ions soluble. There was also an apparent anomaly whereby the retention of sotalol and atenolol increased between 30 and 40% of acetonitrile with zero SHS. We believe this to be due to these solutes of poor lipophilicity showing a tendency to adsorb on to the uncapped silica residues at high organic eluent concentrations. The use of an ODS-2 column with no uncapped silica residues should not show this effect.Fig. 1. 1.2 - 1.0 - 0 m w - + w 0.8 - .- 0 - Q 0.6 - 0 , - -I 0.4 - 0.2 - t 0' I 1 I 20 30 40 Logarithm capacity factor plotted against acetonitrile volume fraction: 0, betaxolol, 0 mM SHS; V, betaxolol, 2 mM SHS; D, betaxolol, 4 rnM SHS; propranolol, 0 mM SHS; V, propranolol, 2 mM SHS; W, propranolol, 4 r n M SHS. Acetonitrile, O/O VIV Fig. 2. In summary, using the results of this study we suggest solvent conditions for the determination of various sets of beta-blockers in mixed solution. Sotalol and atenolol could not be resolved in any of the solvent systems tried, and in many solvents oxprenolol and labetalol were difficult to resolve.The suggestions are listed in Table I with the recommended drug - eluent combinations in boxes. We acknowledge with thanks donations of the respective drugs from Astra Pharmaceuticals Ltd., Ciba-Geigy Ltd., Glaxo Group Research Ltd., ICI Ltd., LERS Synthelabo, May & Baker Ltd. and Merck Sharp & Dohme. NHD received a studentship from Ciba - Geigy Ltd., and also a B.A. Bull Postgraduate Scholarship, which financed a visit to the Department of Pharmacy, University of238 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS Anal. Proc., Vol. 21 Amsterdam. NHD thanks Professor E. Tomlinson (Amsterdam) for initial discussions regarding this work. The comments of Dr.A . H. Short (Nottingham) are also acknowledged. Reference 1. Tomlinson, E., Jefferies, T. M., and Riley, C. M., 1. Chrornatogr., 1978, 159,315 Potency of Polymyxin B, and B2 Fractions by Turbidimetric Assay and by Agar Plate Diffusion Assay J. H. Barnard Central Analytical Laboratories (Biological), The Wellcome Foundation Limited, Temple Hill, Dartford, Kent, DA 1 5A H Commercial Polymyxin B Sulphate contains, by mass, two major active components, designated Polymyxin B1 (relative molecular mass 1203) and Polymyxin B2 (relative molecular mass 1 189).1 Other active components are also present in small amounts.2 Polymyxin B Sulphate is a decapeptide antibiotic that acts like a cationic detergent by binding to cell membranes and causing leakage of the cytoplas tic con tents .3 All Polymyxin molecules have a heptapeptide head with a tripeptide hydrophobic tail.The heptapeptide head displaces divalent cations and binds electrostatically to negatively charged molecules in the cell membrane. It is probable that the hydrophobic tripeptide chain enters the membrane lipid structure to disrupt membrane lipid packing and increase the permeability of the membrane. Polymyxins B1 and B2 differ only in the fatty acid residue terminating the tripeptide chain. Polymyxin B1 terminates in a methyloctanoic acid residue and Polymyxin B2 terminates in a methylheptanoic acid residue.4 Thus, Polymyxins B1 and B2 have a similar antibiotic mechanism and may be expected to have a similar quantitative antibiotic effect. Samples of Polymyxin B1 and B2 have been made available by Dumex and the improved turbidimetric assay method reported here has enabled a comparative study to be made of the antibiotic potencies of Polymyxin B, and B2 in the traditional agar plate diffusion assay and a nutrient broth turbidimetric assay.Materials An ti b io tics Polymyxin B, and B2 fractions from Polymyxin B Sulphate, manufactured by Dumex and by Pfizer, were prepared by HPLC and donated by Dr. H. Sogaard, Dumex Ltd. They were present as solutions containing 1 mg ml-1 and stored at - 120 "C above liquid nitrogen, and were found to be approximately 90% pure by HPLC.4 USP Reference Standard for Polymyxin B Sulfate, Batch No. I, was used. World Health Organisation, 2nd International Standard for Polymyxin B , established 1969: Batch No.Polymyxin B 67/301, was also used. Bacterial Strains obtained from the Wellcome Culture Collection, Beckenham. Klebsiella aerogenes ATCC 10031 and Bordetella bronchiseptica ATCC 4617 (NCTC 8834) were Media Bacto Antibiotic Medium 3 (Penassay Broth), obtained from Difco Ltd. Polymyxin Agar Difco-Bacto Medium 10, obtained from Difco Ltd. Experimental Turbidimetric Assays Eight turbidimetric assays were undertaken on five occasions over 2 weeks. The turbidimetric assay method, as supplied by Dumex, gave large ranges within a dose and overlap between doses, so the method was modified according to principles outlined in reference 5.July, 1984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS 239 The method, as used, is as follows. Freshly prepared, refrigerated, unsterilised Penassay broth was inoculated with sufficient Klebsiella aerogenes ATCC 10031 to raise the initial absorbance by a factor of 0.08 absorbance unit in a 1 cm light path cell at 580 nm.Test and standard solutions were diluted in sterile de'ionised water to levels of 35, 29.5 and 25 U ml-1; 1 ml portions of the solutions were then dispensed into sterile Pyrex glass tubes, The tubes were randomised according to a randomised block design and 9 ml of cold (4 "C) inoculated broth were added to each tube. The assay was transferred to a water-bath at 29 "C. After 3 h incubation, the growth was stopped by plunging the racks into a water-bath at 80 "C for 1 min. The absorbance was read at 580 nm. Agar Plate Diffusion Assays Twelve agar plate diffusion assays were undertaken on five occasions over 2 weeks.Each was based on a three-dose multiple assay, randomised, block design with five replicates at each dose level. The dose levels were 150, 75 and 37.5 U ml-1; 320 ml of molten Polymyxin agar were inoculated with Bordetella bronchiseptica ATCC 4617 (NCTC 8834) at 50°C and poured on to a level glass plate 280 mm X 280 mm, fitted with an aluminium frame. When the agar was set, 8 x 8 9-mm wells were cut and the plugs removed. The standard and test materials were diluted with sterile, de-ionised water to assumed potencies of 150,75 and 37.5 U ml-1 of Polymyxin B Sulphate. The wells were then filled with 0.1 ml of test or standard solution in accordance with randomised block designs. The plates were pre-diffused at room temperature for about 5 h, incubated at 37 "C for 9 h and the inhibition zones were then measured.All assays (turbidimetric and agar plate) included two standard materials, two B1 and two B2 fractions. Statistical Analysis design" in the European Pharmacopoeia.6 The basic statistical analysis followed that given for the "3 dose multiple assay, randomised block Results and Discussion Turbidimetric Assays means of all the individual estimates. fractions from either supplier giving estimates of the same order. Table I lists the combined potency estimate for each preparation. These represent the geometric The B1 and B2 fractions were shown to be of similar potency when assayed turbidimetrically, Agar Plate Diffusion Assays The combined potency estimates listed in Table I involve only the statistically satisfactory estimates.There was an obvious difference between the potency of the B1 and Bz fractions when assessed by this method. The difference in potency is of the same order as that found by other workers over the last 20 years (see Table 11). The ratios of B2 to B1 were very similar in each instance. The apparent differences in results between the turbidimetric assay and the agar plate diffusion assay are probably related to the mechanisms of the two assays, which are quite different. A turbidimetric assay depends on the concentration of a dissolved or suspended drug slowing the growth of a culture, while in an agar plate diffusion assay the concentration of a dissolved drug stops the growth to give the zone edge. Because Polymyxin B1 and B2 are very similar in structure, the disruptive effect of either TABLE I POTENCY OF POLYMYXIN B1 AND POLYMYXIN B2 FRACTIONS BY THE TWO MICROBIOLOGICAL ASSAY METHODS Potency by Potency by turbidimetric agar plate Manufacturer Material assay diffusion assay Dumex Polymyxin B, 8 921 5 941 Polymyxin B2 8 796 10 223 Pfizer Polymyxin B, 8 302 5 590 Polymyxin B2 8 183 9 498240 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS Anal.Proc., Vol. 21 fraction on bacterial cells is likely to be similar. This is supported by the results of the turbidimetric assay, where the potency of B1 and B2 were very much the same. In the agar plate diffusion assay the drug has a concentration gradient from a high concentration in the well to a low concentration away from the well.The zone edge forms when the critical concentration of the antibiotic meets the critical population of dividing b a ~ t e r i a . ~ The critical population of dividing bacteria occurs at the same time all over one agar plate, so the implication is that Polymyxin B2 has diffused further than Polymyxin B1; that is, the two fractions have different diffusion characteristics in the agar plate. TABLE I1 RELATIVE POTENCIES OF POLYMYXIN B1 AND POLYMYXIN B2 FRACTIONS BY THE AGAR PLATE DIFFUSION Year of Potency B1/ Potency BZ/ Potency ratio Source of assay U mg-1 U mg-1 B,/B Assay carried out by antibiotics 1963 7 136 12 320 1.726 Wellcome Wellcome 1973 6 220 10 220 1.643 Haemers and De Moerloose7 Not stated 1982 5 941 19 223 1.721 Wellcome Dumex 1982 5 590 9 498 1,699 Wellcome Pfizer 1982 10 090 16 170 1.603 Dumex* Dumex * The Dumex results were quoted in their document as micrograms activity of milligrams base, where 1 pg is defined as 10 Units, i.e., 1 mg = 10 000 Units.The results have been converted to Units by the Dumex criteria. As the average potency of 11 manufacturing batches by agar plate diffusion assay was 7 734 U mg-l and not 10 OOO U mg-1, the potencies for Dumex results quoted above are overestimated. METHOD CAL, Dartford CAL, Dartford CAL, Dartford It is likely, because Polymyxin B2 is more potent on agar plate diffusion assay than Polymyxin B1, that this reflects in the potency of a mixture of two fractions, such as Polymyxin B Sulphate as bought from a manufacturer. It is therefore important that any standard used to establish the potency of a batch of commercial Polymyxin B Sulphate should be as similar as possible in the contents of B1 and B2 to the test material.Potencies that are established with dissimilar standard and test material may well only be applicable at the dose levels used on the agar plates and may be different at other levels. The differences in the potency estimation of Polymyxin B1 and B2 by the agar plate diffusion assay may therefore be an artifact of the method. Turbidimetric assay may be a better measure of the in vivo action of Polymyxins than the agar plate diffusion assay. Work has been carried out to relate HPLC studies of Polymyxin B Sulphate with the potency achieved on agar plate diffusion assay, but at present the biological potency of heterogeneous Polymyxin B Sulphate cannot be accurately related to HPLC traces; there is still a need for microbiological assays.An HPLC analysis of Polymyxin cannot distinguish between a Polymyxin with a potency of 6 500 U mg-1 and one of 8 000 U mg-1. However, once the potency of a batch of antibiotic is established, all products containing that batch can be assayed for potency by HPLC by comparing the amount of Polymyxin B1 fraction present and relating it back to the original material. References 1. 2. 3. 4. 5. 6. 7. Kalasz, H., and Horvath, C., 1. Chromatogr., 1981, 215, 295. Nakajima, K., Chem. Pharm. Bull., 1967, 15, 1219. Storm, D. R . , Rosenthal, K. S., and Swanson, P. E., Ann. Rev. Biochem., 1977, 46, 723. Fisher, B. V., and Raja, R. B . , Anal. Proc., 1982, 19, 137.Kavanagh, F., Editor, “Analytical Microbiology,” Volume 1, Academic Press, London and New York, 1963. European Pharmacopoeia, 1st Edition, 1971. Haemers, A . , and De Moerloose, P . , Farm. Tijdschr. Belg., 1973. 50, 262.July, I984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS Stability of Oral Vitamin K-a Comparison of an HPLC and Derivative Spectrophotometric Method R. F. Haines-Nutt and P. Adams Regional Quality Control Laboratory, SWRHA, Torbay Hospital, Torquay, South Devon 24 1 Haemorrhagic disease of the newborn (HDN) is a bleeding disorder occasionally seen in the first few days of life. It is characterised by a deficiency of the four vitamin K (phytomeniadione) dependant clotting factors (11, VII, IX and X). Although the disease can be fatal, it can be treated easily with Vitamin K injection given prophylactically at birth.This was once a common practice but has tended to fall into disuse for a number of reasons, the major one being the low incidence of the condition in the 1970s. In Exeter, for instance, the incidence level for the period 1972-80 was less than 1 in 20000 live births.’ Other major reasons were the trauma to the neonate caused by the injection and, in view of the low benefit of the practice, the cost was quite high: a Lancet leading article in 1978 quoted a cost to the NHS of flOO 000.2 For these reasons, therefore, the practice developed in about 50% of all hospitals of giving vitamin K only to those babies considered to be at risk. In the period November, 1980, to March, 1981, however, six cases of HDN were reported in Exeter.None had been given vitamin K at birth, and of the six, three died and one required bowel resection. Exeter, therefore, returned to the practice of giving vitamin K by injection routinely to every newborn baby.’ The paediatricians, however, were still unhappy at the trauma caused to the babies. Additionally, they were also aware of the increasing number of accidental administrations of ergometrine plus oxytocin in adult dosages to neonates.3 The confusion arises because both of these preparations are present as 1-ml amber ampoules in labour wards. Two questions therefore arose: could vitamin K protect against HDN when given orally?; and how long was it clinically useful when removed from the ampoule? The manufacturers were unable to answer either query.However, they stated that the contents were unstable in air and unsuitable for use in multi-dose containers. We were asked to investigate the stability of vitamin K. Experimental We were interested in mimicking “in use” conditions; ampoules of phytonienadione injection were, therefore, opened and the contents placed in either clear or amber bottles. The bottles were then stored in: clear bottle at room temperature in the shade; amber bottle at room temperature in the shade; amber bottle at room temperature exposed to bright sunlight; and amber bottle in a refrigerator. The tops of some bottles were also removed for 1 hour per day to simulate their use on the ward. The amount of phytomenadione remaining in terms of the percentage of the original amount was measured.The BP assay for the injection is very involved and time consuming. The BP assay for the raw material is a simple UV assay and we wondered if this could be modified to produce a rapid method for indicating stability. We looked, therefore, at the UV spectrum of the solution over several weeks. These showed little change at the A,,,. of 249 nm, but elsewhere in the spectra changes were apparent, particularly for those solutions stored in clear bottles. The fact that degradation was occurring in these solutions was confirmed by TLC using the BP method [cyclohexane - ether - methanol (80:20: 1) on silica gel GF254 plates]. Fresh samples were found to contain one major spot, trans-phytomenadione, and 4 other spots, cis-phytomenadione, menadione, the preservative and a breakdown product.Upon storage in clear bottles a total of nine spots was observed. The bottles stored in the refrigerator, however, showed little change. It seemed, therefore, that the solution might have a clinically useful shelf life if stored in a refrigerator but that alternative methods of assay were required. We decided to use derivative spectroscopy as it is an extremely rapid method requiring no more laboratory time than the simple zero order method. Although the theory of derivative spectrophotometry has been around for some 30 years,4 it is only comparatively recently that inexpensive apparatus has been readily available and the technique is beginning to gain in popularity. Mixtures present a problem in spectrophotometry, particularly where the absorbance of one component is presented as a narrow band and is overlapped by components with wide absorbance bands.This is the case with phytomenadione, where the finer detail is lost upon degradation, to be replaced by a broader, less will defined absorbance band. Under these circumstances, increasing derivative order should progressively flatten out the wider bands and increase apparent band sharpening, thus increasing the analytical sensitivity (approximately lO-5% using the fourth derivative).242 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS Anal. Proc., Vol. 21 A standard phytomenadione was purchased and methanolic solutions of it were prepared. Second order derivative analyses were performed on a series of these freshly prepared standards.Peak to trough measurements at approximately 249 nm were plotted as a function of concentration and found to be linear, passing through the origin. With the passage of time the amount of phytomenadione present, particularly in the clear bottles, decreased. However, the bottles that were protected from the light or stored in the refrigerator showed little change. In order to confirm these findings we used an HPLC assay. The method employed a reversed-phase column (Spherisorb 50DS), a simple solvent system of 100% methanol and detection at 270 nm. The standard phytomenadione was found to consist of two peaks by HPLC analysis, the larger attributed to trans-phytomenadione and the very much smaller peak, cis-phytomenadione (5%).A chromatogram of a suitably diluted preparation of phytomenadione was shown to consist of 3 peaks, the largest peak being trans-phytomenadione, with two much smaller peaks attributable to cis-phytomenadione and a breakdown product. Menadione, a breakdown product identified by TLC, was eluted with the solvent. Other breakdown products were well resolved using this system and did not interfere with the quantitative analysis of either cis- or trans-phytomenadione. Results The results using both methods are shown in Table I. TABLE I PERCENTAGE PHYTOMENADIONE REMAINING AS A FUNCTION OF TIME Timeld HPLC 2nd derivative Bottle* 4 7 14 21 42 I 66 49 40 31 23 I1 85 79 65 56 31 I11 97 97 96 96 89 IV 100 100 100 100 99 I 66 46 43 33 28 I1 81 80 61 53 29 111 96 94 96 93 87 IV 100 100 100 100 97 * I Clear, sunlight; I1 amber, sunlight; I11 amber, shade; IV amber, 4°C.When these results are plotted against each other, the two sets of results should be identical, giving a straight line passing through the origin. Regression analysis showed close statistical agreement between the two sets of data. The correlation coefficient was 0.996 with a slope of 0.970, the intercept being only 1.4% away from the origin. If quantities of breakdown products possessing very similar spectral properties to phytomenadione had been encountered, second derivative spectroscopy would have been expected not to yield such good results, because the peak at 249 nm would have been made up not only of the large phytomenadione presence but also those of other breakdown products.In the event, however, the final breakdown product presented a wide absorption band against which phytomena- dione could easily be resolved. Conclusion The results from the two methods indicated that phytomenadione, once removed from the ampoule, is very stable if stored at 4 “C. After 6 weeks of storage under such conditions degradation was found to be minimal. Even when stored at room temperature in an amber bottle, in the shade, degradation was seen to occur at a sufficiently slow rate for clinical use. However, when stored in a clear bottle or an amber bottle in sunlight, very rapid degradation occurred, the clear bottle being the worse of the two. Removal of bottle tops for 1 hour per day, simulating “in ward” use, produced no difference in degradation. Thus, this study has allowed clinicians to use vitamin K orally, overcoming problems associated with the intramuscular route.Analysis from both HPLC and second derivative UV spectrophotometric methods was found to be fast and simple (the derivative method being the faster of the two). The results were highly reproducible.July, 1984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS 243 The indication is that derivative spectrophotometry, stiIl in its infancy, will play a greater role in pharmaceutical analysis. References 1. 2. Editorial, Lancet, 1978, 755. 3. 4. McNinch, A. W . , Orme, R. L’E., and Tripp, J . H . . Lancer, 1983, (i), 1089. Whitefield, M. F., and Salfield, S. A. W., Arch. Dis. Child., 1980. 55, 68. Hammond, V. J . , and Price, W. C., Opt.SOC. Am., 1953,43. 924. The Analysis of Medicinal Products Using Capillary Gas Chromatography J. E. Pearse The Laboratory of the Government Chemist, Cornwall House, Stamford Street, London, SEI 9NQ Capillary gas chromatography (GC) is not a new technique, having been in existence since gas chromatography was first developed. 1 However, for various reasons capillary columns have only relatively recently become widely available commercially. This fact, together with other more recent developments in the field, such as fused silica capillary columns2 and bonded phases,3 and the inherent advantages of analysis time and sensitivity, accounts for the increasing popularity of capillary GC. These advantages mean it is increasingly becoming the technique of choice for many analyses.Strictly speaking, capillary GC includes “micropacked columns”; however, the term is generally used to describe chromatography in “open tubular’’ type columns, including wall coated, porous layer and support coated columns. The “open tubular” character of these columns has a profound effect on the chromatographic process.4 In packed columns, support material increases the liquid phase volume and decreases the gas phase volume. In comparison, with open tubular columns the so-called phase ratio, p, of gas phase to liquid phase is greatly increased. As column diameters decrease and the phase ratio increases analysis times also increase, but the relative retentions remain the same. The net effect is that the over-all separation increases; alternatively, the same degree of resolution can be obtained but with the system optimised for a much shorter analysis time.The open tubular construction also offers less resistance to gas flow, so that very long columns can be used with minimal pressure drops, and a more efficient column in terms of plates per metre. Thus, in comparison with conventional packed columns, the length is increased and the diameter decreased. The very high plate values obtainable increase the range of potential analytes, reduce requirements for variation in stationary phases and yield very narrow peaks of greater height for a given mass of analyte, thus increasing sensitivity. Although capillary columns offer great advantages in terms of performance, certain practical difficulties inherent in their use have to be overcome.Firstly, low carrier gas flow-rates mean that “dead space” must be kept to a minimum, especially at the inlet and detector. Secondly, the sample capacity of capillary columns is much less than packed columns, hence specialist injection techniques are required. Pre-column concentration, splitless injection and split injection are three such techniques.5 This last is arguably the most convenient for general use. The other major problem is encountered with the detector; when the optimum flow-rates used for flame-ionisation detectors are maintained the flame will not endure. The solution is to provide an auxiliary or make-up gas. The subsequent increase in sensitivity is due to a greater mass of analyte reaching the detector in a given time.This is the essence of capillary techniques; although smaller samples are used the very sharp peaks give greater peak heights and effectively more sensitivity. Examples This series of examples illustrates the versatility of the technique; details of chromatographic conditions are given in Table I. The first example employs the high resolution obtainable with capillary GC as a “fingerprint” technique. This sample, referred to the Laboratory of the Government Chemist for approval under the Diseases of Animals Act 1950, was said to contain cresylic creosote and high boiling tar acids (a mixture of a number of components in both instances). Examination of the sample and comparison with244 Anal. Proc., Vol. 21 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS TABLE I EXAMPLES OF ANALYSES WITH OPEN TUBULAR COLUMNS The analyses below were performed on a Varian 3700 gas chromatograph.Flame-ionisation detection was used initially in all instances. The columns were of the wall coated open tubular type (0.31 mrn i.d.) and a split injection technique was used. Number 1. 2. 3. 4. 5. 6. 7. Column 50 m ov- 1 50 m ov- 1 50 m ov- 1 50 m ov- 1 25 m Carbowax 20M 25 m ov-101 25 m ov-101 Temperature Analyte 80 "C (3 min) 40 "C min- to 190 "C and HBTA 40 "C Benzene Cresylic creosote 140 "C (10 min) 12 "C min- I to 250 "C 225 "C (10 min) Atropine 10 "C min- 1 to 285 "C 35 "C (7 min) 25 "C min- I to 100 "C 60 "C (5 min) 15 "C min-1 to 250 "C 100 "C Benzothiazoles 5 "C min-' to 250 "C Phthalate and sulphonate plasticisers Alcohols, aldehydes and ketones Di-n-but ylamine Matrix Disinfectant mixture Microscopy mounting medium PVC tubing Comfrey tea & belladonna Acetone Rubber Rubber relevant standards using capillary GC provided both quantitative and qualitative confirmation of sample content.In the second example concern was expressed about the possible benzene content of a microscopy mounting medium. Capillary GC of the headspace gases revealed that the volatile components of the sample consisted mainly of the isomers of xylene with toluene present as a minor constituent. The benzene content was shown by standard addition to be less than 2 parts per billion, illustrating the high sensitivities obtainable. In a third application a marked decrease in flow-rate in an anaesthetic machine occurred, causing a very serious problem.Infrared spectroscopy revealed that the tubing was composed of PVC heavily plasticised with dL(2-ethylhexyl) phthalate, together with phenyl and cresyl pentadecanesulphonates. After extracting some of the tubing with halothane, an anaesthetic used in the machine, capillary GC revealed the phthalate and sulphonate plasticisers to be present at levels of 4.3% and 9.2'/0, respectively. Apart from any physical obstruction caused by the presence of these compounds it was also found that they reduced significantly the volatility of the halothane, causing a further decrease in flow-rate in the anaesthetic machine. A fourth problem concerned the possible contamination of various batches of comfrey tea with belladonna, suspected after initial examination by microscopy.As the presence of these two herbs together is an abnormal occurrence, no official methods of analysis existed. The method developed for the analysis was based on modified pharmacopoeia1 methods.6 The comfrey tea was subjected to percolation with ethanol and solvent extraction. Silylation followed by capillary GC was used to separate the atropine from the other components. Atropine was found in various samples at levels between 0.1 and 0.3% mlm; these figures were, in turn, used to determine the belladonna content of the tea. The high resolving power of capillary GC proved very useful for this complex mixture (Fig. 1) as only minimal "clean-up" was required, reducing potential losses. The ease with which capillary GC can be linked to the mass spectrometer is very useful in identifying trace levels of unknown contaminants. For example, this laboratory receives samples of acetone that is used to store pituitary glands prior to the preparation of human growth hormone. The levels of contaminants in this acetone are therefore carefully monitored (Table I, item 5).Methanol, ethanol, acetaldehyde, butan-2-one and 4-hydroxy-4-methylpentan-2-one have been identified and quantified as being present at parts per million levels. Identification is achieved by comparison of the retention time with standards and by mass spectrometry. Mass spectrometry was also used to identify an unknown in another example (Table I, item 6). Some samples of sheath-type catheters, which were found to cause irritation in use, were received. As a specification was not available, extracts of satisfactory and irritating catheters were compared.The "fingerprints" obtained (Fig. 2) revealed one component present in significant amounts which was notJuly, 1984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS 245 Atropine Jh 1 15 10 5 0 Ti me/min Fig. 1. Gas chromatogram of comfrey tea contaminated with belladonna. found in the satisfactory catheters. This unknown was identified by capillary GC - mass spectrometry and found to be di-n-butylamine; quantitative analysis showed a level of 3.8 mg per catheter. Because butylamines are used as accelerators for the vulcanising process in rubber production7 and di-n-butylamine is a known skin irritant ,8 the presence of this compound was thought to be the cause of the problem.The final example concerns a sample of water autoclaved in contact with rubber closures (Table I, item 7). Initial studies with ultraviolet spectroscopy indicated the presence of strongly absorbing species. Solvent extraction and subsequent capillary GC mass spectrometry identified three benzothiazole derivatives at parts per million levels in the original autoclave solutions. c L L Di-n-butylamine / 0 5 10 15 20 25 Tim e/m i n Fig. 2. catheter. Gas chromatogram of extract from irritating246 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS Anal. Proc., Vol. 21 Conclusion Capillary GC is a flexible and sensitive method for the analysis of highly complex mixtures. Theoretical considerations dictate that capillary techniques are associated with higher resolving power and our practical experiences confirm this fact.The higher resolution, greater sensitivity and ease of interfacing with mass spectrometry make the advantages of capillary GC outweigh any practical difficulties experienced with the technique. References 1. Desty, D. H., Haresnape, J. N.. and Whyman. B. H. F., Anal. Chem.. 1960, 32. 302. 2. Lee, M. L., and Wright, R. W., J. Chromatogr., 1980, 184, 235. 3. Dandeneau. R. D., and Zerenner, E. H.. J. High Resolut. Chromatogr. Chromatogr. Commun., 1979. 2. 4. Grob, K.. and Grob, G., J. High Resolut. Chromatogr. Chromatogr. Comuun.. 1979, 3 , 109. 5. Grob. K.. and Grob. K.. J. High Resofut. Chromaragr. Chromatogr. Commun.. 1978. 1. 57. 6. "British Pharmacopoeia 1980," Volume 11. HM Stationery Office.London. p. 566. 7. Taylor. R., and Son, P. N.. in Mark, H. F.. Othmer. D. F.. Overberger. C. G., and Sealong, G. T., Editors, "Kirk Othmer Encyclopedia of Chemical Technology," Third Edition. Volume 20, Wiley Interscience, New York. 1982, p. 337. Bretherick, L., and Muir. G. D., in Bretherick, L., Editor, "Hazards in The Chemical Laboratory," Third Edition, The Royal Society of Chemistry. London. 1981, p. 218. 351. 8. Improved HPLC Analysis of Oxmetidine and its Metabolites in Biological Fluids G. S. Murkitt, R. M. Lee and R. D. McOowall SK&F Research Ltd., Department of Drug Analysis, The Frythe, Welwvn, Hertfordshire. AL6 9AR The original assay for estimating oxmetidine in plasma was based on the extraction and chromatography first developed for cimetidine.* This procedure used normal phase silica columns, which worked efficiently for plasma samples in which the only circulating drug-related material was the unchanged compound. However, in patients with an inefficient clearance mechanism, or in excretory biological fluids such as urine and bile, the presence of the sulphoxide metabolite caused a problem. Sulphoxides of oxmetidine and cimetidine are extracted by the procedure described below and appear on chromatograms from silica columns after some 20 min. Such retention seriously reduces the throughput of samples, because the unchanged oxmetidine and an internal standard can be eluted with base line separation within 5 min of injection. In addition creatinine in urine, with a retention of some 15 min, also causes delays.To turn this situation to advantage, new chromatographic separations using reversed-phase techniques were devised so that the sulphoxide was eluted before the parent drug. A different internal standard was found and the mobile phase optimised, so that all three eluates of interest appeared within 4 min of the injection of extracted samples. The new method including the liquid - liquid extraction procedure was as follows. Extraction Procedure After the addition of the internal standard, samples of plasma, urine or other biological fluid were adjusted to pH 9.0 with carbonate buffer. Five millilitres of octan-1-01 were added and mixed with the sample for 15 min, using a blood cell suspension mixer. The organic phase was next separated from the aqueous phase by centrifugation at 1500g for 5 min.Octanol (4.5 ml) was transferred to a second polypropylene centrifuge tube containing 3 ml of 0.02 moll-' hydrochloric acid and the same rotary mixing and centrifugation technique was used to re-extract the compound into the acid and to separate the phases. The octanol layer was then removed by centrifugation and 2.5ml of the acid layer transferred to a clean polypropylene tube, to which 250 pl of acetonitrile or ethanol were added and the liquids vortex mixed, before saturating the whole with solid potassium carbonate (about 5 g). This has the effect of salting out the organic solvent into a discrete layer after centrifugation (1 500g for 5 min). This layer was removed and stored at -20 "C pending HPLC separation and analysis.July, I984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS 247 The efficiency of the extraction procedure has been tested by spiking samples of urine and plasma, and extracting them in the manner described. Both produced about 60% recovery, compared to a theoretical maximum of 75%, i.e., when recovered volumes are taken into account.An additional step before the extraction of bile and urine samples enabled the assay of the glucuronide conjugates of oxmetidine and its sulphoxide. Each sample was divided into two aliquots; one was extracted as described to give the “free” oxmetidine and sulphoxide concentrations; the other aliquot was incubated with P-glucuronidase to hydrolyse the two conjugates to aglycones, followed by the usual extraction. This gave a measure of “total” oxmetidine and sulphoxide.The concentrations of conjugated oxmetidine and sulphoxide were obtained by subtracting the respective “free” from “total” values. Chromatography The normal phase, first used for plasma samples, made use of a 5 pm silica (Lichrosorb) column, 250 X 4.6 mm, with an eluting mobile phase consisting of acetonitrile, methanol, water and 0.88 sp.gr. ammonia in the proportion 200:30: 10: 1.5 by volume. The use of these solvents in the mobile phase is to a large extent dictated by the absorption maximum for oxmetidine, which occurs at 226nm. Reversed-phase chromatography was performed initially with a 150 X 4.6 mm Ultrasphere ODS column of 5 pm particle size maintained at 75 “C. The mobile phase was 0.02 moll-’ camphor- sulphonic acid in a 70: 30 by volume mixture of acetonitrile and water.This system worked well for urine and bile samples, enabling a throughput of 15 samples h-1 using a WISP automatic injector. Under these conditions, creatinine was eluted in the void volume, oxmetidine sulphoxide, oxmetidine and the internal standard were separated cleanly with a run-time of 4min and there were no peaks of significance to the integrator with longer retention times. However, this system had one disadvantage in that the extraction of plasma samples produced peaks on the chromatogram, at relevant retention times, when no oxmetidine was present in the samples. At this stage the strategy was to select the assay procedure best suited to the biological fluid to be analysed.2 Unexpected Change All of the chromatographic systems described so far had given excellent peak-shape and base-line resolution for components of interest.After a considerable period of using the reversed-phase system for urine samples, a replacement Ultrasphere ODS column was found that produced asymmetrical peaks and incomplete resolution. Another column from the same batch gave similar results, and it was discovered that the manufacturer had changed the method of end-capping the residual silanol groups in the C18 column. For the manufacturer this represented a more efficient process and yielded a “purer” reversed-phase column. For the separation of oxmetidine and its sulphoxide, the silanol groups, in combination with the modifier (camphorsulphonic acid), were an essential part of the chromatography.Consultation with the manufacturer indicated that it would not be possible to obtain the Ultrasphere ODS columns as manufactured originally and so a further change of mobile phase would be required, which suited the degree of end-capping of the new column. A mixture of acetonitrile, methanol and water in the proportions 11:44:45 by volume, with the addition of 0.095 ml 1-1 of pentanesulphonic acid adjusted to pH 3.0 with sulphuric acid prior to the addition of the organic solvents, gave results as good as those previously found. However, the final solvent in the extraction had to be ethanol (as the use of acetonitrile produced divided peaks) and the injection volume had to be limited to 20 pl to avoid poor resolution. The greatest advantage of the new system was that endogenous material extracted from plasma no longer produced peaks on a relevant part of the chromatogram, so that all biological fluids could now be assayed by a single method.3 This experience with oxmetidine illustrates a general problem for all drugs that produce metabolites more water soluble than the parent material.The use of normal-phase silica columns will result in long run-times because of the retention of “polar” metabolites. However, in many cases the use of “well-covered” CI8 columns may also present problems if the silanol groups are part of the chromatographic reaction which yields the required retention values for basic drugs. We thank Mr. J. Hobbs, Altex Scientific, for helpful advice during the early stages of this work.248 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS References 1.2. 3. Lee, R. M., and Osborne, P. M., J . Chromatogr., 1978, 146, 354. Lee, R. M., and McDowall, R. D., J . Chromatogr., 1983, 273, 335. McDowall, R. D., Murkitt, G . S., and Lee, R. M., J . Chromatogr., in the press. Anal. Proc., Vol. 21 Comparison of HPLC and Spectrophotometric Analysis of Four Sulphonamides Present in a Medicated Animal Feed Pre-mix Stephen D. Revett and Michael E. Tenneson Peter Hand (GB) Limited, Analytical Laboratory, Tom0 Estate, Creeting Road, Stowmarket, Suffolk, IP14 5A T This paper covers work carried out to determine four commonly used sulphonamide drugs, sulphadimidine, sulphamerazine, sulphathiazole and sulphaquinoxaline , in animal feed pre-mixes using: the AOAC direct UV methodl; the AOAC spectrophotometric method2; and a novel HPLC method .3 For the purposes of the trial a typical “pig rearer” pre-mix was used and spiked with varying amounts of the sulphonamides concerned to give a level of 1% total sulphonamide. Such a pre-mix contains fat soluble vitamins, B-group vitamins and minerals, all of which, when mixed together, may give potential stability and analytical problems. Experimental Direct UV Method’ The sample was extracted with alcohol, dilute ammonia solution and, after warming on a steam-bath, made up with alcohol; a portion of this was evaporated to dryness and made up to volume with 0.1 M sodium hydroxide. A spectrum was obtained from 220-400 nm using a Pye-Unicam SP8-300 UV - visible spectrophotometer fitted with an autocell.The absorption was noted at the maximum and compared with a standard solution prepared similarly. Spectrophotometric Method2 The sulphonamide was extracted from the sample with dilute sodium hydroxide solution and an aliquot acidified with dilute hydrochloric acid and diluted to volume in distilled water. A portion of this aliquot was added to a 50-ml calibrated flask and 1 ml of 0.1% sodium nitrite solution, followed by 1 ml of 0.5% ammonium sulphamate solution and, finally, 1 ml of 0.1% N-( 1-napthy1)-ethylenediamine dihydrochloride solution were added, mixed well and left to stand for 3 , 2 and 10 min, respectively, after each addition. The absorbance of the coloured solution (purple) was read at 545 nm against a reagent blank on a Pye-Unicam SP8-300 UV - visible spectrophotometer fitted with an autocell.Standard solutions were prepared similarly. HPLC Method3 The sulphonamide was extracted from a sample using methanol - dimethylformamide (80 + 20), a portion centrifuged and finally diluted by using the solvent system. The HPLC running conditions were: HPLC fitted with constant volume pump (Dupont Module 870); UV detector, 254 nm (Dupont UV spectrophotometer); automatic injector, 20 yl injection volume; Zorbax ODS column, 4.6 mm X 25 cm, 5 pm; oven temperature, 35 “C; flow-rate, 1.0 ml min-1; solvent system, water - methanol - acetonitrile (3 + 1 + 1). TLC Separation4 Silica gel plates were prepared and 1OOpl of the sample solution (as prepared in the direct UV method) were spotted on to plates A and B.Plate A was developed in (93 + 7) methanol - chloroform and plate B in (90 + 10) methanol - chloroform. Viewed under short wave UV light the sulphonamides can be seen to be separated and can then be identified by removal of the spot from the plate, dissolution in 0.1 M sodium hydroxide solution and measurement of the absorbance at the maximum.July, 1984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS 249 Results Three different possibilities were studied. The first was spiking the blank pre-mix with a single sulphonamide to give a level of 1% sulphonamide (Table I). TABLE I RECOVERY OF 1% OF A SINGLE SULPHONAMIDE Average recovery, ‘/o Colorimetric Sulphonamide uv method HPLC Sulphat hiazole . . . . . . . . . . 102.4 101.3 100.2 Sulphamerazine . . . . . . . .102.0 101.5 99.7 Sulphadimidine . . . . . . . . 102.5 100.4 loo. 1 Sulphaquinoxaline . . . . . . 101.7 101.9 99.8 Blank* . . . . . . . . . . . . . . 3,6,3.5,3.8,0 0 0 * The blank value will vary depending on which sulphonamide is being measured. If the analyst is unaware of which sulphonamide is present then, by spectrophotometric methods, recoveries may vary from 26 to l26%, depending on the sulphonamides concerned. By means of HPLC the sulphonamide can be immediately identified and measured. The second possibility was spiking the blank pre-mix with equal amounts of two sulphonamides to give a level of 1% total sulphonamide. Results from these samples gave recoveries of up to 225% by spectrophotometric methods, depending on whether or not the analyst was aware of what was present in the sample.HPLC gave near 100% recoveries of all sulphonamides. The third possibility involved spiking the blank pre-mix with equal amounts of four sulphonamides to give a level of 1% total sulphonamide. Like the pairs of sulphonamides, recoveries by spectrophoto- metric analysis gave very high values (up to 468%). By HPLC all four sulphonamides were separated completely with near 100% recoveries (see Fig. 1). Discussion Analysis of samples containing one sulphonamide by the direct UV method gave slightly high recoveries due to the effect of the vitamins present in the pre-mix. The precision was reasonable, but the assay is non-specific and requires TLC separation to determine precisely which sulphonamides are present in the sample. The non-specificity is the major disadvantage of this method, particularly when Sulphadimidine H 2 N e S 0 2 * N H - ( > c H 3 Sulphaquinoxaline CH3 Sulphamerazine ,CH, H2N43-S02.NH4==J - - - ‘CH3 Sulphaquinoxaline Fig.1 ( a ) , HPLC trace showing base line separation of the four sulphonamides; (6), HPLC trace of the blank pre-mix.250 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS Anal. Proc., Vol. 21 the analyst is unaware which sulphonamide or sulphonamides are present, and results will vary greatly. With the colorimetric method accuracy is greater as there is no interference from the constituents of the pre-mix, there being little or no reaction between them and the reagents. The precision is slightly worse than for the direct UV method, due to problems encountered in the “colouring up” stage.The three reagents must be added exactly as described in the method, with the correct time between each addition, otherwise the solutions will not colour up consistently. Again, the method is non-specific. all four sulphonamides reacting in the same way to give the type of complex with absorption maxima at around 545 nm. The maxima are not sufficiently far enough apart to allow accurate determination of mixtures by calculation. Again. problems arise when more than one sulphonamide is present and TLC is needed to identify them. Sample preparation is the least straightforward of the three methods because of the addition of the three reagents and the increased time per sample that it causes. The HPLC determination of sulphonamides offers greater accuracy, precision, simplicity and, above all, specificity when compared with other methods.Sample preparation is straightforward. and complete separation of a mixture of all four sulphonamides was found with near 100°/~ recoveries. Blank mixes, i.e., the complete pre-mix extracted in the same way, gave no response at the retention times of the four sulphonamides (see HPLC traces). A small peak due to the B-group vitamins appears well before the first sulphonamide (sulphathiazole); the fat soluble vitamins are not extracted because commercial preparations are gelatin coated and this is not broken down by the methanol - dimethylformamide solution. Other pre-mixes may contain amino acids, such as lysine or methionine, but although these will be extracted their retention time is very long and poses no problem under the conditions stated. By HPLC not only are the sulphonamides identified immediately but they can be measured at the same time.References 1. 2. 3. 4. “Official Methods of Analysis of the Association of Official Analytical Chemists,” Association of Official Analytical Chemists, Washington. DC. 1980. 42.161. “Official Methods of Analysis of the Association of Official Analytical Chemists,” Association of Official Analytical Chemists, Washington, DC. 1980. 42.172. Method PH 001, Peter Hand (GB) Ltd.. Stowmarket. “Official Methods of Analysis of the Association of Official Analytical Chemists.” Association of Official Analytical Chemists, Washington. DC, 1980. 42.165. AMICA: A Stopped Flow Analytical Control System for Small to Medium Sized Laboratories K.Wiegand, D. Watson and C. Cates Quality Control, Ciba-Geigy Pharmaceuticals Division, Wimblehurst Road, Horsham, West Sussex, RH 12 4A B The demands for improved efficiency within the analytical control laboratories of all companies have increased considerably over the last few years. Constraints such as shorter production runs and their diversity, the need for flexible use of equipment, lead times reduced by tight inventory control, greater need for analytical precision and accuracy, and control of wages and capital costs, have all influenced the efficient performance of analytical laboratories. A change in emphasis from the use of more traditional systems of analysis has been necessary in order to accommodate these modern-day demands, particularly to incorporate the advantages provided by the development of microprocessor controlled equipment.Within the Swiss laboratories of Ciba - Geigy the relative merits of various analytical systems were evaluated to see how they could provide answers to these efficiency parameters, particularly for the small to medium sized laboratory with short analytical runs of a wide range of products. The AMICA (acronym for Automatic Modules for Industrial Control Analysis) was developed as one such system. AMICA, a system based on stopped flow and incorporating microchip technology, was developed by Ciba - Geigy in conjunction with Hamilton of Switzerland over a 3-year period. At the beginning of 1983 it was launched as a commercial product in this country.Description of the Technique The principal component of the AMICA system is the liquid processing unit, which is a stopped flowJuly, 1984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS 25 1 instrument. Stopped flow was initially conceived by Q. H. Gibson' in 1954 as a means of studying fast reaction kinetics in solution. Since then many attempts have been made to exploit the speed of the stopped flow method, but it was not until the development of precision stepper motor driven syringes and microprocessor control that its potential in industrial control laboratory automation was fully realised. Basically, the stopped flow measurements made by the AMICA system involve drawing a sample and a reagent or diluent solution into two precision glass syringes at pre-determined mixing ratios.The solutions are then positively displaced by the plungers through several mixing elements and then on to a measuring device, such as a spectrophotometer or electrochemical detector (see Fig. 1). The Prep-set Extraction Prep-set is a low cost, low technology system designed to simplify several unit operations involved in the preparation of samples for analysis. These include dissolution, milling, sedimentation, centrifuga- tion, liquid - liquid extraction, solid - liquid extraction and filtration. The main component of prep-set is a 50-1111, screw capped, polypropylene tube to which solid samples are added together with an appropriate amount of solvent and a stainless-steel milling sphere. Dissolution is effected by loading the sample tubes into a rack and shaking, after which any insoluble matter can be separated by forcing a filter cylinder fitted with a filter disc through the solution.Alternatively, the solutions can be centrifuged in siru. Once dissolution is complete the sample racks load directly on to the autosampler. A silicone foil cover is placed over each rack; this serves two purposes. Firstly, it reduces evaporation when volatile solvents are being used, and secondly, it wipes residue off the sample probe to prevent carry-over (see Fig. 2). Although prep-set is not a completely automated system its robust construction and chemical inertness make it suitable for a wide variety of samples. Also, because of its low cost, old or worn items can be cheaply replaced as and when necessary.Reagent -=GP Mixing chamber Precision syring Measuring unit Shaking Sieve date Filtration Fig. 1. The liquid processing unit. Fig. 2. Prep-set extraction apparatus. Comparison of AMICA With Other Automatic Analysis Systems Until recently the only commercially available continuous flow analysers were those based on segmented flow, such as the AutoAnalyzer. In segmented flow the analytical stream is broken into segments by air bubbles which were considered necessary in order to limit longitudinal dispersion of the sample, promote mixing by generating turbulent flow and reduce carry-over by removing the boundary layer on the walls of the analytical conduits, between segments. Although the applications of segmented flow analysers are numerous there are a number of factors, inherent in this type of system, which limit its usefulness in industrial control analysis.Firstly, a disproportionate length of time is required for the system to reach a steady state when only short runs are being performed. Secondly, because the operational parameters can change significantly during some analytical runs, coupled with relatively imprecise aspiration rates, the results from a run must be regularly quantified by use of standard solutions.252 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS Anal. Proc., Vol. 21 Thirdly, and possibly most importantly, each manifold is purpose built for a particular analysis; thus, for laboratories performing several kinds of analysis during a day, a significant proportion of the total time is spent preparing the analyser for use.In 1970 the concept of flow injection analysis (FIA) was introduced by the electrochemists Nagy, Feher and Pungor.2 The basis of FIA involves the injection of highly reproducible volumes of sample into a continuous analytical stream. Unlike segmented flow systems FIA operates only in the laminar flow region, where the associated fluid dynamics are well understood; thus, the design of FIA manifolds tend to be based more on theoretical considerations than empirical data. However, whilst FIA systems have overcome most of the problems associated with segmented flow analysers, as well as having very fast sampling rates (over 300 h-1 when coupled to AAS, flame emission or ICP - flame emission spectrometry), the basic problem of versatility, in the industrial control field, still remains.AMICA was designed to incorporate the advantages of continuous flow systems, such as fast sampling and precision mixing, with those of a discrete method like versatility, accuracy and precision. Whilst AMICA cannot achieve the sampling rates possible with FIA systems, nor perform the range of chemistries carried out by segmented flow analysers, its ability to change from one analysis to another in a matter of minutes whilst providing highly precise results makes it a very powerful instrument in the industrial control field. The Equipment as Commercially Available The AMICA system is modular in design, incorporating several interconnected instruments which will now be discussed (see Fig. 3). Fig. 3. Block flow.Parallel Mettler Keyboard t S pect ro - Auto- Waste diagram of the AMICA hardware arrangement. The broken lines represent liquid Microcomputer C-6000 and Printer P-6100 The computer is a PSI80,64 kB computer from Kontron. It has a 9-in screen and two 5Y4-k floppy disc drives. Communication with the peripheral instruments is either via RS232C interfaces or via an octocoupler and relay contacts. The computer is connected to the P-6100 printer via the parallel interface port. This printer is bidirectional and prints 80 columns with 10 characters in-1 horizontally with a maximum speed of 440 lines min-1. Liquid Processing Unit A-5000 The liquid processing unit (LPU) incorporates two stepper motor driven precision syringes, each provided with a three-way valve. The syringes dispense into a mixing block, which may be fitted with an electrode for potentiometric measurements or connected to the spectrophotometer A-5200 for photometric analysis.All parts in contact with liquids, except the syringe barrels, are made of PCTFE, making the system inert to practically all types of reagent. The LPU communicates with the other devices in the system via RS232C serial interfacings.July, 1984 SHORT PAPERS IN PHARMACEUTICAL ANALYSIS Autosampler A-5300 253 Sampling is performed by a probe mounted on a moving holder, which is capable of movement in the x , y and z planes. The probe is also capable of detecting the presence of liquid in the sample tubes by having a liquid detector integrated into the probe assembly, which operates by using the dielectric effect.The base of the sampler can accommodate up to 50 samples (5 racks, each containing 10 sample tubes). Spectrophotometer A-5200 This is a single beam instrument, which is completely controlled by the computer C-6000 via an RS232C link. The measuring range is from -0.3 to 4 absorbance units over a wavelength range of 195-900nm, with a spectral band width of 2nm. The photometer also possesses two optional ports, which can accommodate additional items such as an automatic flow-cell changer or a chart recorder. Sodium Diclofenac Content Uniformity in Voltarol Retard Tablets This is an example of an analysis that was previously performed routinely at Horsham by a manual colorimetric procedure, in which the active ingredient, sodium 0-[(2,6-dichlorophenyl)-amino]phenyl acetate, was nitrated with 5~ aqueous nitric acid to give a coloured derivative with a maximum absorbance at about 380 nm.The analysis is now carried out on AMICA by bichromatic photometry. This involves reading the absorbance of the test solution at the maximum and minimum wavelengths in the UV range, then subtracting the latter from the former to give the true absorbance. Table I gives some typical results for this analysis. TABLE I AMICA ANALYSIS OF SODIUM DICLOFENAC . . . . . .<O. 1% Precision (rsd based on 10 determinations) Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .<0.2% Carry over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <O. 1 % I COMPARISON OF AMICA RESULTS WITH THOSE FROM MANUAL DETERMINATIONS Batch AMICA (mean), % Manual (mean), YO G603 102 102 G604 103 102 G605 102 103 AMICA Photometric Assay Sample solutions containing one Voltarol Retard tablet in 40.0cm3 of methanol are prepared by using the Prep-set.A standard sodium diclofenac solution is also prepared corresponding to the nominal conc;enbra&ion in the sample solutions (025%. rnlV). The basis of the assay requires the sample and standard to be diluted with methanol by a factor which is termed the dilution ratio and defined as the total volume dispensed divided by the volume of diluent. This dilution is performed in order to bring the absorbance to a value convenient for measurement and in order to carry it out the UV spectrum of the solution is scanned on AMICA. The range of absorbances acceptable by the software lies between 1 and 2, with a target value of 1.5 AU; thus, if the absorbance at maximum wavelength falls outside this range new dilution ratios are calculated by the software until the criterion is achieved.From the printout of the UV absorption spectrum the minimum and maximum wavelengths, along with the required dilution ratio, can be obtained. These and other parameters. such as sample and standard masses, dilution volumes, flow cell size and choice of syringe, are then used to compile a method, which is stored in the software and can be recalled for subsequent analyses. Other Routine Analyses now Performed on AMICA Table I1 lists some other routine analyses for which AMICA is now used.254 Type of Analysis Potentiometric titrations Photometric titrations . . Spectrophotometry . . . . SHORT PAPERS IN PHARMACEUTICAL ANALYSIS TABLE 11 ANALYSES NOW PERFORMED ON AMICA Anal. Proc., Vol. 21 Example . . . . . . .1. Determination of Fe(I1) in iron(I1) sulphate tablets by titration with Ce(1V) 0.1 MTBAH 2. Assay of sulphonamide compounds by non-aqueous titration with 3. Assay of weak bases (primary and secondary amines) by NAT with 4. Standardization of various titrimetric solutions, including HCl. NaOH, 0. I M HCIOi Ce(SO,),. Na2S203, I,, TBAH, HCIOJ. AgNO, . . . . .l. Most of the standardizations performed potentiometrically can be performed by this method using an internal indicator 2. Determination of water in tablet masses by KF titration . . . . . . .l. Content uniformity of practically all dosage forms where the active ingredient absorbs strongly in the UV or visible region 2. Multi-component analyses of dosage forms with 2 o r 3 active ingredients Conclusion Since the introduction of the Amica system into the quality control laboratories at Horsham the advantages noted to date have been as follows. Firstly, the ability to perform many different kinds of analysis quickly and with a high degree of precision and accuracy. In practically all instances the relative standard deviations based on ten replicate samples are less than 0.2%. Secondly, the ability to automate analyses using solvents other than water with a similar degree of precision and without damage to the system. Solvents ranging from concentrated sulphuric acid to dimethylformamide have all been used successfully on AMICA. Thirdly, the ability to change the system from one analysis to another in minutes. For instance, a change from a photometric to a potentiometric configuration is performed simply by disconnection of the flow cell inlet tubing and installation of the titration cell and electrode. From there the required software is loaded and the system is ready for use. Although far outweighed by the advantages there are some disadvantages to this kind of system. Firstly, the accuracy obtainable with solid samples is limited by the accuracy to which they can be diluted. Secondly, relatively large sample volumes are required, especially for potentiometric work. Thirdly, multi-reagent assays are not possible. Fourthly, the cost, between f20 000 and f25 000, makes it a very substantial investment for any laboratory to undertake. However, for the laboratory that performs a wide range of techniques and which requires a system that can cope with short and varied production runs whilst maintaining a high degree of precision, the AMICA system represents a very cost effective solution. References 1. 2. Gibson, Q. H . , and Roughton, F. J. W., Proc. R. Soc. London, Ser. B , 1955, 143, 310. Nagy, G., Feher, Z., and Pungor, E., Anal. Chim. Actu, 1970, 52, 47.

ISSN:0144-557X    

DOI:10.1039/AP9842100235

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

July, 1984 THE ANALYSIS OF SURFACE COATINGS AND RAW MATERIALS 255 The Analysis of Surface Coatings and Raw Materials The following are summaries of two of the papers presented at a Joint Meeting of the Analytical Division and the Oil and Colour Chemists Association held on February 8th, 1984, at the Scientific Societies’ Lecture Theatre, 23 Savile Row, London, W. 1 . Analysis of Coatings Failures by X-ray Photoelectron Spectroscopy J. F. Watts Department of Merallurgy and Materials Technology, University of Surrey, Guildford, Surrey, GU2 5XH In applying an analytical method to the analysis of an organic coating - metal substrate system that has failed, either in service or as the result of some form of accelerated test, there are certain criteria which must be met. These include the following.Firstly, it should be possible to define accurately the locus of failure (preferably at an atomistic level), i.e., did cohesive or adhesive failure occur in the region of the metal to polymer junction? Secondly, as failure often occurs as the result of exposure to an aggressive environment [e.g., water or salt (NaCI) solution], it is desirable to monitor the concentration of these species at the failed interface. Thirdly, the action of such aggressive media may bring about chemical changes only a few atom layers deep at the interface, which lead to adhesion loss. Consequently any analysis technique used must be very surface specific. In addition there is the rather more obvious requirement that polymeric materials can be analysed without sample degradation, desorption of labile species, or electrostatic charging; this effectively precludes the use of electron, and most ion probe, methods.The analytical technique best suited to such investigations is X-ray photoelectron spectroscopy (XPS). In this paper the use of XPS will be illustrated by examples of recent work on the adhesion and subsequent failure of two markedly different organic coatings on mild steel. X-ray Photoelectron Spectroscopy The basis of XPS is the irradiation of a material with a beam of low energy X-rays, typically aluminium Ka (hv = 1486.6eV). Interaction of the X-ray photons with the sample results in photoionisation of the atoms, brought about by the ejection of electrons, the binding energy (&,) of which is less than the X-ray photon energy (hv).The kinetic energy of these photoelectrons (Ek) is then analysed in an electron spectrometer so that an intensity versus electron energy spectrum can be plotted. The binding energy of the emitted electrons (&) can be expressed as where w is the spectrometer work function. The binding energy of an electron is characteristic of both the energy level within the atom from which it emerged, and, in the majority of instances, the chemical environment (valence state) of that atom. Although the X-rays penetrate some distance into the sample, only those photoelectrons generated very close to the surface escape into the vacuum chamber of the spectrometer. Consequently, XPS yields a very surface-specific analysis; in practice, the analysis depth is generally quoted as 4-6 nm, although it depends to some extent on experimental variables.Theoretical and practical considerations of the XPS experiment can be found in standard texts; see, for example, references 1 and 2. The work described herein was carried out using a VG Scientific ESCA 3 Mk I1 electron spectrometer interfaced to a VG 3040 datasystem based on a DEC PDP8e computer. For each specimen a survey spectrum was recorded together with high resolution spectra of the regions of interest. Quantification of the XPS results was achieved by using the appropriate sensitivity factors, mainly those of Jorgensen and Berthou.’ Eh = hv - Ek - w Polybutadiene Coated Mild Steel The Nature of the Polymer - Metal Bond To establish the quality of the polymer - metal bond lap shear test specimens were assembled from a coated panel.These specimens consistently failed at loads of about 2kN, and examination of the failed interface by both optical and scanning electron microscopy indicated that failure had occurred in an adhesive manner. XPS analysis of the “metal” and “polymer” interfacial surface of a failed joint, however, showed that failure had occurred in a cohesive manner within the polymer. Both spectra indicated the presence of carbon and oxygen; there was no iron in the surface analysis.4256 THE ANALYSIS OF SURFACE COATINGS AND RAW MATERIALS Anal. PrOC., VOl. 21 In order to investigate the chemical nature of polymer - metal bonding a novel method of interface analysis has been developed. The oxide and polymer layers can be removed from the substrate by dissolution of the metal in an anhydrous solution of iodine in methanol. By mounting the resulting duplex couple, oxide uppermost, in the spectrometer it is possible to erode the surface by bombardment with argon ions, stopping at appropriate intervals to carry out XPS analysis.In this manner it is possible to approach the oxide - polymer interface through the oxide. With the polybutadiene coating there exists a reacted zone between the polymer and the oxide, containing iron(I1) rather than the iron(II1) ions that are characteristic of the bulk oxide.5 As polybutadiene cures by an oxidative mechanism it is clear that it has acted as a reducing agent for the iron oxide, the interface being better described as an iron(I1) containing interphase zone between the polymer and the oxide.Cathodic Disbondment of the Polybutadiene Coating Cathodic disbondment occurs when a coated, pre-damaged panel exposed to an aqueous environment is polarised cathodically . Such polarisation may be the result of an externally applied potential (as with cathodically protected structures such as ships and pipelines), or the development of discrete anodic and cathodic sites on the metal surface (this situation occurs in the salt-spray test used in the paint industry). Both types of polarisation have been investigated by exposing pre-damaged polybutadiene coated steel panels to 0.5 M salt solution. The panels were either cathodically protected at -1 500 mV,6 or at the free corrosion potential (FCP). After 10 d exposure the panel at the FCP showed severe rusting at the defect.Blistering and rusting under the coating was evident within 1-2 mm of this defect. The rest of the polymer appeared intact but could easily be peeled from the substrate. In the instance of the cathodically protected panel, blistering (but, of course, no rusting) was clearly seen over several square centimetres around the defect. The coating between the blister and the electrolyte ring (sealed on to the panel to contain the salt solution) was still adhering to the substrate, but could easily be peeled back, as described above. Samples were cut from the substrates of these tests, and the substrate and coating of a slightly longer test, for XPS analysis; the results of these analyses are given in Table I.TABLE I IDENTIFICATION OF SURFACE ANALYSES OF SPECIMENS FROM THE POLYBUTADIENE DISBONDMENT EXPERIMENTS Code D4M1 D4M2 D4M3 D5M1 D5M2 D30M1 D30P1 D30M2 D30P2 Timeld 10 10 10 10 10 15 15 15 15 Potential/ Interfacial mV surface - 1500 Metal - 1500 Metal - 1500 Metal FCPJ: Metal FCPS Metal - 1500 Metal - 1500 Polymer - 1500 Metal - 1500 Polymer Position Near defect Near limit of disbond Near electrolyte ring* Near defect* Near electrolyte ring" Near defect Near defect Near limit of disbond Near limit of disbond Atom concentration, '/o - Assignment C 0 Fe 35.6 47.1 6.5 36.7 43.8 6.5 66.8 27.4 2.2 63.4 28.7 Trt 58.0 30.8 1.0 48.6 42.6 1.3 61.5 30.4 0.4 48.4 43.6 3.9 61.0 31.7 1.0 Na 7.7 9.2 3.6 6.7 7.4 5.4 5.5 3.4 6.0 CI of failure type 3.1 3.8 Trt 1.3 2.9 2.1 2.2 0.7 0.4 Type I1 Type 11 Type 1 Type 1 Type 1 Type I1 Type I1 Type I1 Type I1 * Not disbonded.t Tr = trace. $ FCP = free corrosion potential. For the cathodically protected specimens the analyses from within the blistered zone (D4M1, D4M2, D30M1 and D30M2) show a low level of carbon together with an oxygen concentration of about 45%, and a significant iron signal from the substrate. The specimen from the peeled zone (D4M3) shows much higher carbon, lower oxygen and very little iron. It is, however, quantitatively very similar to those analyses from the panel at FCP (D5M1, D5M2), indicating a similar failure mode. We haveJuly, I984 THE ANALYSIS OF SURFACE COATINGS AND RAW MATERIALS 257 401 20 Oils Fe 2p3/2 // 100 80 8 s 2 60 4- .- Q) 4- - 40 20 0 200 400 600 800 1000 1200 0 Binding energylell Na Is I 0 Is I Cls I Na KLLI Fe 2~312 .I iW P, I I 200 400 600 800 1000 1200 B i nd i ng en e rg yleV Fig. 1. Substrate XPS survey spectra showing (a), Type 11, and ( b ) , Type I failure of polybutadiene. designated these failure models Type I1 and Type I; XPS survey spectra of both types of failure are presented in Fig. 1. The large excess of sodium to chlorine in all of the analyses of Table I show that alkaline conditions prevailed underneath the coating, even when it was not totally detached from the substrate. The two failure modes probably result from different diffusion paths for the active ions, Type I failure occurring as a result of downward diffusion of the cation reaching, but not penetrating the interphase zone.The near interphase polymer is weakened by a build up of sodium and hydroxyl ions. For the Type I1 failure lateral diffusion of these ions can take place from the defect, attacking the interphase zone directly. This leads to failure in the oxide - interphase region. The interphase zone segregates with the polymer coating on failure, whereas in the Type I mode it remains adhering to the metal substrate. Accordingly, the surface analyses from the polymer interface following Type I1 failure D30P1, D30P2) and the substrate interface following Type I failure (D4M3, D5M1, D5M2) are remarkably similar. x 12 2 (D c. c 8 i x 4 n -u .- 40 80 120 160 200 0 Time/d Fig. 2. Disbondment area as a function of time for the epoxy coating. A , 1 pm polish; a, emery abrasion; V, alkali clean; ., grit blast.258 THE ANALYSIS OF SURFACE COATINGS AND RAW MATERIALS Anal.Proc., Val. 21 Mild Steel Coated with a Fusion Bonded Epoxy The epoxy powder coating was applied to steel panels pre-treated in a variety of ways to provide a range of surface topographies. Cathodic disbondment tests were then carried out and the extent of coating delamination as a function of time for the four pre-treatments is shown in Fig. 2 . 7 This shows the kinetics of delamination to be very dependent on surface roughness. Once again, specimens were cut from both coating and substrate for surface analysis. The large data set obtained precludes tabular presentation and our preferred method of presentation is to plot the concentration of a particular element versus the surface roughness (Ra value).This enables comparisons of variations in surface composition with surface pre-treatment to be made “at a glance.” Two such graphs, for the substrate concentration of carbon and coating iron, are shown in Fig. 3. These results indicate no major difference in the locus of failure with surface treatment. However, the gradual increase in iron on the coating surface is consistent with the fracture of protruding oxide asperities, i.e., an increasing proportion of cohesive failure of the oxide. 60 50 - C 9 $ 40 1 8 .;i E 30 20 in t (a’ c I I I I 0 1 2 3 4 0 1 2 3 4 Ra value 1 ” Fig. 3. coating iron. Elemental composition at the disbonded epoxy interface. ( a ) , Substrate carbon; ( b ) , By analysis of the high resolution XPS spectra,8 a three-stage failure process can be identified.The rate controlling step passes from the oxide reduction at the defect to the cathodic area exposed (which controls the flux of cathodically generated hydroxyl ions), and finally to the interfacial path length. The failure is predominantly adhesive in nature, unlike the situation that exists when the polymer is applied to an inorganic conversion coating, where a mixed mode of failure is observed.9 Conclusions The analysis of failures from two different coating - substrate systems has been described. It has been shown that in the instance of polybutadiene coated steel XPS can identify three different loci of failure. By careful specimen preparation it has also proved possible to understand something of the nature of polymer - metal bonding.The rate of failure of the epoxy coating on cathodically protected steel depends on the substrate surface profile. The mechanism of failure, deduced from XPs analysis of the failed interface, is not, however, variable with this parameter. References 1. 2. 3. 4. 5. 6. Castle, J . E . , in Van der Biest, O., Editor, “Analysis of High Temperature Materials,” Applied Science Briggs, D., and Seah, M. P., “Practical Surface Analysis by Auger and Photoelectron Spectroscopy,” John Jorgensen, C. K . , and Berthou, H., Furuday Disc. Chem. SOC., 1972, 54, 269. Castle, J. E., and Watts, J . F., in Leidheiser, H., Editor, “Corrosion Control by Organic Coatings,” NACE, Watts, J. F., and Castle, J. E . , J . Muter. Sci., 1983, 18, 2987. British Gas Corporation Specification: PS/CW6.Publishers, London, 1983, pp. 141-188. Wiley, Chichester, 1983. Houston, Texas, USA, 1981, pp. 78-86.July, 1984 THE ANALYSIS OF SURFACE COATINGS AND RAW MATERIALS 259 Watts, J . F . , and Castle, J. E . , in Hirsch, L. H., Editor, “1983 International Gas Research Conference,” Watts, J. F . , and Castle, J . E., J . Muter. Sci., in the press. Watts, J . F., 1. Muter. Sci., in the press. 7. 8. 9. Government Institutes Inc., Rockville, MD, pp. 262-273. Plasma Erosion: An Ultra-rapid Method for Predicting Paint Film Durability N. A. R. Falla Paint Research Association, Waldegrave Road, Teddington, Middlesex, TW11 8LD One of the most valued properties of a paint is durability. A car is expected to retain the showroom finish for as long as possible and the time and cost involved in the exterior painting of houses is such that most people prefer not to have to repeat the exercise for a good many years.Paint manufacturers recognise the importance that their customers attach to durability and are continually reformulating to obtain improved performance. The problem is that it is possible to make new paints very much faster than they can be tested by natural exposure. A durable paint system can be expected to have a potential life in excess of 10 years and a natural exposure test, i.e., exposing painted panels to the weather and waiting for signs of paint failure, can require several years to obtain results. There are a number of other disadvantages associated with natural exposure testing.(a) There is a problem in selecting a representative site. Possibilities include rural, industrial, marine, sub-tropical and desert environments, all of which may give rise to different degrees of paint degradation. (b) Most exposure sites experience significant seasonal variations in the weather. Panels first exposed during January may well degrade differently from those first exposed in June. (c) Significant annual variations in weather are not uncommon. Thus a 3-year exposure period that includes an abnormally hot summer or a very severe winter may well give anomalous test results. It is these limitations that have forced the paint industry to use accelerated artificial test methods for the prediction of durability. These methods can never completely replace natural exposure testing, but they are used to an increasing extent as a means of selecting promising formulations for further evaluation.For many years the UK industry has relied mainly on a weathering test, based on the carbon arc lamp, and originally developed for assessing oil-based coatings.' The industry is now faced with the evaluation of systems of considerably enhanced durability and is being offered test methods employing alternative light sources such as the xenon arc or fluorescent mercury lamp.2 The work described in this paper is one of the current Paint Research Association projects that is funded jointly by the Materials Chemicals and Vehicles Requirements Board of the Department of Industry and by Members of the Paint Research Association.The objective of this project is to evaluate oxygen plasma erosion as a method for accelerated durability testing. Experimental The work was carried out using a Plasmaprep 100 plasma generator manufactured by Nanotech (Thin Films) Ltd., Prestwich, Manchester. This consists of a cylindrical glass vacuum chamber into which oxygen can be bled to produce a pressure of 1 mmHg. Radiofrequency power (20 W at 13.56 MHz) is fed into the chamber, via a set of capacitor plates mounted around the circumference, to produce an oxygen plasma. The precise composition of this plasma is a matter of some debate but it is known that oxygen ions and free electrons are present and that the number of positive and negative charges are approximately equal. It is also believed that active oxygen species are formed and that electromagnetic radiation is emitted in the visible, ultraviolet and vacuum ultraviolet regions of the spectrum , 3 However, it is certain that an oxygen plasma is an extremely aggressive environment so far as organic materials are concerned.A paint film placed in the plasma chamber degrades rapidly and after exposure for a few minutes the binder is eroded to leave unbound pigment particles at the surface of the film. Smith and Falla4 have used scanning electron microscopy and X-ray photoelectron spectroscopy to show how the effect of plasma erosion compares with more conventional accelerated techniques. Samples of paint to be evaluated were spread on glass panels to give a dry film thickness of 25 pm. Air-drying paints were stored for 14 days before testing whereas thermally cured coatings were tested260 THE ANALYSIS OF SURFACE COATINGS AND RAW MATERIALS Anal.Proc., Vol. 21 immediately after stoving. A number of panels were produced for each paint and these were exposed to the plasma in turn so as to produce a series of panels with an increasing period of exposure. The degree of degradation produced was measured in terms of loss of gloss using a Sheen Instruments 60" specular glossmeter. Results The initial evaluation of the method was carried out using two paints that were known to differ significantly in durability, viz., a long oil air-drying alkyd and a stoving acrylic formulation where the acrylic was known to be the more durable. The results are shown in Table I. TABLE I DURABILITY OF ALKYD AND ACRYLIC PAINT 60" gloss, Yo Time of exposure/ min 0 5 10 15 30 45 60 120 Alkyd 80.5 83.5 45.0 43.0 25.5 23.5 21 .o 18.5 Acrylic 85.5 81.0 76.0 68.0 28.0 15.5 12.0 10.5 A second evaluation was then carried out using two long oil alkyd paints both pigmented with titanium dioxide.These paints differed only in the grade of titanium dioxide used in the formulations and an accelerated weathering test1 showed that paint 1 was more durable than paint 2. The results are shown in Table 11. TABLE I1 DURABILITY OF ALKYD PAINTS Time of exposure/ min 0 2 4 12 16 32 64 a 60" gloss, O/o Paint 1 81.0 87.8 89.5 42.3 36.3 26.5 20.8 18.0 Paint 2 70.8 76.8 54.8 21 .o 13.5 10.0 7.0 5.8 Discussion The gloss results in Table I show that there are marked differences in the resistance of the two paints to plasma erosion.After 10 min the alkyd had undergone a significant loss of gloss whereas the acrylic took between 15 and 30 min to reach the same state. The initial increase in gloss noted for the alkyd is believed due to the "polishing" action of the plasma. The two alkyd paints (Table 11) also showed detectable differences in durability, with paint 1 showing a greater resistance to plasma erosion than paint 2. It is clear from these initial results that oxygen plasma erosion has considerable potential as an accelerated weathering method. It has been shown capable of correctly predicting major differences in durability such as those between the alkyd and the stoving acrylic. The comparison of the two alkyd paints gave results in agreement with those obtained using conventional accelerated weathering.These results also showed that by reducing the time interval between exposures it was possible to obtain fairly precise differentiation between paints of similar formulation. The major advantages of plasma erosion over other forms of accelerated weathering are the savings in both time and cost. Plasma erosion can produce in 10 min degrees of degradation that can takeJuly, 1984 DIAS AT UMIST. PART I 261 several thousand hours to attain by using a carbon arc weatherometer.’ The plasma generator is also about one third of the price of the carbon arc weatherometer and is considerably cheaper to operate. Despite these advantages, it is unlikely that oxygen plasma erosion is destined to supersede all other forms of accelerated weathering. It is more probable that, over a period of time, correlations between plasma erosion and other forms of weathering will be extended to a point where the plasma technique can be used as a rapid method for selecting those formulations worthy of more detailed study. References 1. 2. BS 3900: Part F3: 1971, “British Standard Method of Test For Paints: Resistance to Artificial Weathering (Enclosed Carbon Arc) ,” British Standards Institution, London, 1971. American Society for Testing and Materials, “Standard Recommended Practice for Operating Light- and Water-exposure Apparatus (Fluorescent UV-condensation Type) for Exposure of Non-metallic Materials,” ANSIIASTM G53-77, ASTM, Philadelphia, 1977. 3. Hollahan, J. R., and Bell, A. T., “Techniques and Applications of Plasma Chemistry,” Wiley, New York, 1974. 4. Smith, G. W., and Falla, N. A. R., “Development of Modern Instrumental Methods for Surface Analysis,” Paint RA Technical Report TR/1/84, Faint Research Association, Teddington, 1984.

ISSN:0144-557X    

DOI:10.1039/AP9842100255

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

July, 1984 DIAS AT UMIST. PART I 261 Analytical Chemistry in UK Universities, Polytechnics and Colleges This series of articles began in 1978 with an article on analytical work within The Queen’s University of Belfast (August issue, p. 248). Two more articles appeared, on UWIST (May, 1979, p. 169), and Wolverhampton Polytechnic (July, 1979, p. 215). Now, after a lengthy interval, we present the first part of a two-part article on DIAS at UMIST, a department which had not even been formed when the last item in the series was published. Anyone wishing to write an article describing analytical science in their department is invited to send it to the Editor of Analytical Proceedings, who will also be pleased to advise on the general content of the articles. DIAS at UMIST Themes and Images.Part I M. A. Browne and G. F. Kirkbright Department of Instrumentation and Analytical Science, University of Manchester Institute of Science and Technology, P.O. Box 88, Manchester, M60 lQD Introduction The Department of Instrumentation and Analytical Science (DIAS) at UMIST was formed in 1980. Its broad aims and concepts were to unite the disciplines of analytical, industrial and medical instrumentation to create a department concerned with teaching and research and to develop a coherent approach to “Measurement Science” in these areas. The first 3 years of existence of DIAS have seen its rapid growth so that at the end of 1983 it was composed of more than 100 research and support staff, including seven full-time permanent academic staff. The Department operates an intensive full-time one-year MSc course with an enrolment for the 1983184 session of 32 students.This rapid growth has seen exploration into new areas of instrumentation even amidst the current environment of restrictions in university finance. This has been possible primarily because of the initial investment from UMIST in the creation of the Department and the extensive research grant and contract funding obtained from industry and public institutions. In the short lifetime of DIAS well over fl.8 million has been attracted in external funding in this way; during the 1982/83 session the external research grant income per member of academic staff exceeded flOO 000. The 1982/83 academic year saw the completion of the first stage of the academic development of DIAS; the Department has now become established as a full member department of the UMIST academic community and its support has been further consolidated by the Science and Engineering262 DIAS AT UMIST.PART I Anal. Proc., Vol. 21 Research Council, who recognise the Department as its Centre for Instrumentation and Analytical Science via the SERC Specially Promoted Programme in Instrumentation and Measurement and via research grants and studentships. Traditional research interests of the staff in the Department are concerned with spectroscopy, electrochemistry, flow measurement and ultrasound technology. Considerable interest also exists in the development of integrated measurement systems employing modern microelectronics. New areas of interest in our research are, perhaps, more interesting and include the development of chemically sensitive fibre optic sensing devices, the application of ultrasound techniques to ophthalmic and dental studies, physical parameter measurements (temperature, level, pressure and flow) using fibre optic sensors and the development of sensors for three-phase flow measurements.Earlier research concerned with instrumentation for continuous measurement of neck movement (see Fig. 1) has now been extended to develop a similar system to monitor back movement. New projects have been initiated concerned with microwave spectrometry and mass spectrometry for on-line applications. One of the themes that is seen to be developing within the Department concerns instrumentation for imaging applications; this ranges over a very broad field of discipline including video image processing and robotics applications, ultrasound and NMR imaging for examination of skin and other tissues and laser scanning thermal wave imaging via the photoacoustic effect for the examination of biological samples, solid-state devices and industrial materials.The development of fibre-optic based instrumentation systems for transduction and both physical and chemical parameters now forms a major DIAS research interest. Fig. 1. Instrumentation for monitoring continuous neck movement. This article will attempt, in two parts, to present an overview of the type of research undertaken within the Department of Instrumentation and Analytical Science at present and to give some insight into the range of projects and the current themes in departmental research.These interests are naturally reflected in the teaching activities and duties of the department (particularly at postgraduate level). There thus follows a review of some of the activities concerned with analytical, medical and industrial instrumentation research. Imaging Techniques-an Emergent Theme Thermal Wave Imaging Most applications of the photoacoustic effect, in which periodically interrupted radiation falling on solid, liquid or gaseous samples results in a periodic heat generation which can be detected using a microphone transducer, have been used to obtain absorption spectra and undertake qualitative and quantitative studies concerned with difficult samples, viz., those highly opaque or transparent.' Much of the pioneering work in this technique has been undertaken by DIAS staff; while these applications continue, more recently attention has turned to the possibility of using the photoacoustic effect for imaging applications.If light is absorbed at or below the surface of the solid sample by a defect, inclusion or interface, a modulated heat flow will be generated within the sample. The thermal wavesJuly, 1984 DIAS AT UMIST. PART I 263 that result can be analysed with respect to their amplitude and phase to produce information concerning surface features and sub-surface features. By scanning an amplitude-modulated, focused light source (laser) across the surface of a sample and recording the photoacoustic response it is thus possible to construct a three-dimensional image that is characterfstic of the optical and thermal properties within parts of the sample under investigation.A schematic diagram typical of the types of photoacoustic imaging systems developed at DIAS is shown in Fig. 2. Several systems have now been 1 * , Beam expander Laser - Chopper Berm scanner Fig. 2. Schematic diagram of photoacoustic imaging system. Controlling Lock-in computer . amplifier 4 developed that employ both high power krypton ion lasers and small helium neon laser systems; a compact low cost thermal wave imaging system suitable for commercial development is under construction at present. Recent publications2-4 have demonstrated the qualitative and quantitative manner in which this technique can be employed to study multi-layer and thin-film samples and to detect inclusions and defects in small solid samples with resolution on each of the X-Y-2 axes of the sample of approximately 5 pm.A typical example of results obtained in this type of study is shown in Fig. 3. A low cost laser-scanning photoacoustic spectrometer is also under development via BTG funding (see Fig. 4). Focusing optics Fig. 3. Photographic colour film (images of different layers). t 1 I264 DIAS AT UMIST. PART I Anal. Proc., Vol. 21 Fig. 4. Low cost laser scanning thermal wave imaging system under development. Correlation Photoacoustic Spectroscopy A potentially useful field of application for photoacoustic spectroscopy is in the study of depth-related features in multi-layer or inhomogeneous systems.Generally, this has been achieved by measuring the photoacoustic spectrum of the sample at a number of different modulation frequencies. The modulation frequency employed controls the observation of the photoacoustic signal correspond- ing to different thermal diffusion lengths and thus the depth within the sample from which the signal can be observed and detected. A more suitable method for obtaining depth-related photoacoustic information from the sample is to monitor the photoacoustic impulse reponse. The simplest method by which this response can be obtained is to illuminate the sample with a brief pulse of light in an appropriate wavelength. It is then possible to monitor the pressure change as the heat generated by the sample absorption diffuses to the surface and then into the surrounding gas in the photoacoustic cell.The depth within the sample at which the heat is generated is directly related to the time taken for the heat to diffuse to the surface and cause a pressure wave in the gas in the cell. The recorded impulse response thus provides an interpretable record of the optical absorption of the sample and the distribution of energy deposition within the sample. Although simple to implement, pulse techniques can be relatively inefficient as the sample is illuminated only for a very small fraction of the total measurement time. This results in a low duty cycle and poor signal-to-noise ratio, which can be improved only by signal averaging or increasing the incident radiant intensity of the pulse.To improve the performance of single pulse methods, work has been carried out in DIAS at UMISTS-7 in which multi-frequency test signals, combined with cross-correlation signal recovery techniques, are employed to obtain the photoacoustic impulse response of samples. The test signal employed for the work decribed is a pseudo-random binary sequence (PRBS). This function has two levels and can switch from one to the other only at certain time intervals; the probability of the function switching after any one time interval is 0.5. The sequence is fixed, reproducible and N time intervals in length where N is the odd integer. Correlation of this type of signal with itself (auto-correlation) yields a function identical with the auto-correlation function of a sample impulse.From this it follows that correlation of the input PRBS signal into the system with the resultant output signal from the system (cross-correlation) yields the impulse response of the system. PRBS modulation can be imposed on to a white light source by placing into the light path a rotating metal disc cut to provide a PRBS in the incident beam. This is achieved by dividing the disc into N sectors and removing the sectors corresponding to one level of the PRBS while leaving in place those corresponding to the other. The small portion of the modulated light beam can be taken to a photodetector to produce the electrical analogue of the optical signal and this can be cross-correlated with the output from the photoacoustic cell to produce an impulse response for the sample under examination.Figs. 5 and 6 show isometric projections of the impulse response photoacoustic spectra at 32 different wavelengths for pubescent and mature lettuce leaves. These display two main features, an ultraviolet absorption band centred at about 310 nm, which can be attributed to cuticular absorption, and a band in the visible region of the spectrum with an absorption maximum at about 670nm, which can be attributed to chlorophyllJuly, 1984 DIAS AT UMIST. PART I 265 absorption. The spectra contain information concerning the depth distribution of these features. These studies show great promise for the study of the diffusion of organic species into semi-transparent biological materials and for the study of the transport mechanism in inorganic and organic polymer membranes.730 Fig. 5 . Impulse response PA spectra for pubescent lettuce leaf (wavelength increased in 15-nm steps). Ultrasound and Imaging Ultrasonics is now well established for the purpose of non-destructive testing in industry and has found some applications in medicine. A familiar example of the diagnostic use of ultrasonics is the examination of the foetus in utero to establish growth rates or abnormalities. In addition, ultrasonics is widely used therapeutically utilising the heating effect of high energy ultrasound as it passes through tissue. In all diagnostic applications, however, the energy levels are maintained well below those at which permanent changes to tissue are detectable. There is significant potential application for ultrasonics in dermatology, particularly with respect to imaging applications.Measurement of the thickness of the dermis and epidermis is important to dermatologists, skin biologists, cosmetic scientists, etc., and this can be undertaken invasively or non-invasively.8 It is important that any skin thickness mesurement should allow repetition of the measurement of the same area of skin with or without a lesion, in order to collect dynamic data concerning, for example, the healing process. The only method other than ultrasonics that permits this is the use of xeroradiography, and with extreme care it is possible to obtain epidermal thickness measurements using this technique. However, the excessive amount of ionising radiation that may be introduced by an extended study of a particular area of skin in this way makes the technique unattractive.Pulse-echo studies using ultrasonics have 730 Fig. 6. Impulse response PA spectra for mature lettuce leaf (wavelength increased steps). in 15-nm266 DIAS AT UMIST. PART I Anal. Proc., Vol. 21 Fig. 7. Ultrasonic echoes from upper and lower surfaces from the epidermis. significant potential as an alternative technique. Using modern transducers such as polyvinylidene difluoride (PVDF) in the form of a plastic film, focused ultrasound beams may be produced. The transducer here is housed within a small cup-like container holding water and this acts as the coupling path for the sound between the transducer and the skin.9 With a transducer 25pm in thickness a resolution of approximately 30 pm has been achieved in current work in DIAS.Fig. 7 shows the results of the use of an early instrument devised in our laboratories; the results relate to the inside surface of the forearm. The upper trace is the unprocessed ultrasound signal and the lower trace is a rectified version. The first echoes received are from the upper epidermal region and the second from the lower epidermal region. From these signals the time differences between the epidermal echoes can be obtained and these data can be converted to a thickness measurement. In the particular case illustrated, using the appropriate velocity figures, we obtained a thickness for the epidermis of approximately 80 pm. Measurement of epidermal thickness in this non-invasive manner promises to be of immense benefit in the monitoring of the response to treatment of psoriasis and chronic eczematous patches of the skin.") The results mentioned above were obtained with a stationary transducer. If the transducer is made to traverse the skin then the effect observed is for the echoes to move as the ultrasonic beam interrogates -- I I Fig.8. B-scan of outer forearm.July, 1984 DIAS AT UMIST. PART I 267 skin areas with slightly different thickness dimensions. Also, as the beam scans across the skin, various structural details may be interrogated. This is similar to the conventional B-scan ultrasound system which as mentioned earlier finds wide applications in obstetrics. The difference between the devices devised in DIAS and typical obstetrics B-scanner systems is simply that the dimensions involved are much smaller.Normally only a I-cm scan is made across the skin so that depth imaging occurs to no more than approximately 2 or 3 mm. Primary interest, however, is the first millimetre of the display obtained (Fig. 8). It can be seen that the system is capable of obtaining data from the hairs above the skin, from the epidermis and from structures within the dermis, as well as showing the boundary between the dermal and sub-dermal regions. The resolving power of the system at present under test is better than 50pm along the axis of the ultrasonic beam and investigations are currently being made directed towards the use of a much higher frequency transducer, which should improve the actual resolution considerably.With work currently in hand for skin imaging it is conceivable that the cross-sectional images of the structure of the skin may be sufficiently detailed to permit the diagnosis of skin disease, which at present requires biopsy. It is likely that ultrasonic imaging will be able to distinguish between cysts and tumours and between dermal masses and epithelial structures; in this manner the technique should provide an extremely important clinical aid to diagnosis. This non-invasive form of “biopsy” will therefore provide a rapid and inexpensive diagnostic technique and may indeed assist the outcome of treatment of many patients with small skin tumours. A considerable interest exists in the measurement of blood flow in the skin and a number of techniques have been devised to enable such measurements in vivo.The range of techniques includes the use of radioisotope methods, thermal dilution techniques and, more recently, the application of infrared laser sources in combination with the Doppler effect to obtain blood velocity measurements. The fact that ultrasound is proving to be useful as a technique for imaging the structure of skin suggests that an ultrasound Doppler system can be devised for blood flow measurements. Ultrasonic energy at approximately the same frequency currently used for imaging is used to obtain Doppler shift data from moving red blood cells. A number of advantages accrue from the use of ultrasonics rather than laser techniques to obtain Doppler shift data. Of these the most important is that by the use of “range gating,” the depth into the skin from which flow data are obtained can be controlled.The accurate characterisation of blood flow to the skin by ultrasonic techniques will prove extremely helpful in distinguishing ischaemic disorders from others. It should also allow the monitoring of disordered cutaneous vasculature after attempts at treatment. This “functional” use of ultrasound technology could well be one of its more important analytical applications. Nuclear Magnetic Resonance Imaging The imaging of tissue in vivo has become of special recent interest using proton nuclear magnetic t t t ++4 Radio- 1”I I current I ( C) (d NMR imaging. ( a ) , Representation of nucleus without magnetic field applied; (b), nucleus with field applied; (c), radiofrequency field applied; (d), radiofrequency switched off but receiver on.I Fig. 9.268 DIAS AT UMIST. PART I Anal. Proc., Vol. 21 resonance techniques. As hydrogen is highly abundant in the body and exhibits high NMR sensitivity it is an ideal nucleus for such examination. The usual NMR procedure for imaging is to apply a strong magnetic field (0.05-1T) along the body to be studied (see Fig. 9). The nuclei then align with their magnetic moments along the applied field; a radiofrequency pulse is then applied perpendicular to the main field by means of a coil arrangement alongside the body. This radiofrequency pulse is tuned to the precession frequency of the nuclei. The pulse causes some of the nuclei to precess and tip. At this point the nuclei are in phase, and after the pulse is removed the nuclei continue to precess, slowly recovering to realign with the main field (spin - lattice relaxation, T I ) and due to local variations in the field (due either to local chemical variations or field inhomogeneities) the spins de-phase (spin - spin relaxation, T2).The precessing nuclei can be sensed by the radiofrequency voltages that they induce in receiver coils situated close to the samples. These signals reflect, as previously stated, water content and the decay times give information about the tissue under investigation. Variations in relaxation times have now been widely observed between healthy tissue and tumours. The technique has thus been shown to offer a vast range of clinical applications and is currently only in its infancy.In order to provide spatial information, field gradients are employed. The precession frequency then varies along the gradient; if the resulting relaxation signal can be frequency analysed (by Fourier transform) then a map of nuclei and their behaviour can be produced (see Fig. 10). The signals arising from the excited Frequency+ Fig. 10. Relaxation with field gradient applied to provide spatial information. and relaxing nuclei are frequently weak and always buried in noise. When the signal to noise ratio (SNR) is poor signal averaging must be performed. Fig. 11 shows the main components required for an NMR imaging system and this type of system has been developed by DIAS staff in conjunction with the Department of Physics, Mairchester University. At the present time investigations areconcerned with the gtiner5lion of the opriate field gradients within the magnet in order to yield spatial information.The point makes this use of NMR in DIAS different from other research is the aim to produce high resolution images from small volume samples. To date, the main direction of NMR imaging research has been towards whole body or head scanning; applications envisaged in our Display 0 L F Pulse generator ' - Computer Coil systems Fig. 11. Block diagram of typical NMR imaging system.July, 1984 DIAS AT UMIST. PART I 269 research, however, involve deriving information from much smaller samples, such as fingers, to observe abnormalities, for example, in dermal tissue or cartilage. The information obtained in this way should prove to be extremely useful in the diagnosis and treatment of a number of clinical disorders ranging from arthritis to psoriasis.Optical Imaging and Image Analysis for Industrial Applications Work is currently in progress on the development of a simple, low-cost image sensor measurement system which may enhance the performance of a range of industrial robots that are used for arc welding of relatively simple contours. The very unstable and intense radiation emitted by the welding arc and its concomitant sparks has previously been treated as a source of noise which might interfere with visual seam tracking during welding. For this reason visual tracking has been undertaken during an auxiliary pass preceding welding. In most visual tracking a laser diode is used as the light source for pattern line projection.This structured light source approach requires 2-dimensional sensing and as a result subsequent data processing is complex. In the work being undertaken in DIAS a quite different view has been taken; irradiation from the welding arc and concomitant sparks has itself been used as the source for visual tracking of the seam." The principle of the identification is based on surface grey level detection along a single line perpendicular to the welding torch movement, at some constant distance ahead of the point to be weided (see Fig. 12). Because a human welder is able to distinguish the edge positions in spite of a very strong filter to protect his eyes a similar effect should be observable with the vision sensor, particularly while the most intense area, very close to the welding point, is masked.After filtering the data from the sensor we expected to obtain a grey level distribution similar to that shown in Fig. 12(b). Co-ordinates of the darkest points should then be a measure of the seam deviation from the direction of movement of the welding torch. level Grey T (' 3L \ Deviation L Fig. 12. Principle of passive seam detection technique: (a), envisaged configuration; ( b ) , surface grey level profile. No light source or projector is needed in this method and only a single line camera. A 256-element CCD line scan image sensor appears sufficient and these are sufficiently rapid. The first investigations have involved observing the MIG welding process with a static vidicon camera.(The camera is shielded from the direct light of the arc by a reflector and views the scene through a filter lens from a welder's goggle.) The action is recorded on a video tape recorder and taken to the laboratory for analysis; the data is then led to an Apple I1 microcomputer through a simple interface, which allows single lines from frozen frames of video to be digitised. A number of lines are collected and stored on disc as data files. These files are used as raw data. The main aim of the initial investigation has been to prove that it is possible to extract the seam position from line images of the surface, while viewed in the light of the real welding arc. The level of noise is very high and random in the images. Considerable data filtering is therefore required to improve the signal to noise ratio. Simple time averaging is achieved by extended exposure time; spatial averaging can be achieved by using the transport registers as summers and shifters, summing a time series of shifted images.This provides a combination of spatial and temporal averaging. Thus, the CCD line scan sensor offers the possibility of being mounted remote from its control and processing hardware and this is desirable in a hostile environment. A programme of270 EQUIPMENT NEWS Anal. Proc., Vol. 21 experiments concerned with different surface preparation of the workpiece and the examination of workpiece profiles that are not flat is at present being undertaken. In this two-part article concerned with research programmes current within DIAS at UMIST we hope to reflect many aspects of current problems and endeavour in the area of measurement science. The theme in the first section of this review has been imaging; in the concluding section to follow we hope to illustrate themes of sensor and systems research. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. References Kirkbright, G. F., and Castleden, S. L., Chem. Br., 1980, 16, 661. Kirkbright, G. F., and Miller, R. M., Analyst, 1982, 107, 798. Kirkbright, G. F., and Miller, R. M., Anal. Chem., 1983, 55, 502. Kirkbright, G. F., Miller, R. M., and Rzadkiewicz, A . , J. Phys. Colloq. C6, 1983, 10, 249. Kirkbright, G. F., Miller, R. M., Spillane, D. E. M., and Vickery, 1. P., J. Phys. Colloq. C6, 1983, 10,243. Kirkbright, G. F., Miller, R. M., Spillane, D. E. M., and Sugitani, Y., Anal. Chem., 1984, in the press. Kirkbright, G. F., Miller, R. M., Spillane, D. E. M., and Vickery, 1. P., Plant Physiol., 1984, in the press. Payne, P. A . , Ultrasonics Dermatol., Skin Forum, 1983, 2 ( 2 ) . Payne, P. A , , and Quilliam, R. M., Bioeng. Skin, 1983, 4, 97. Payne, P. A., RNM Images, 1983, 24. Browne, M. A . , and Falkowski, J. L., “Passive Visual Sensing for Arc Welding Processes,” “Proceedings of the International Conference on Optical Techniques in Process Control ,” The Hague, The Netherlands, 1983.

ISSN:0144-557X    

DOI:10.1039/AP9842100261

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

270 EQUIPMENT NEWS Anal. Proc., Vol. 21 Equipment News Atomic Absorption Spectrophotometer The Shimadzu AA646 is a microprocessor- controlled flame-emission instrument, featuring a high speed, double frequency, simultaneous pho- tometric system. By using high frequencies to actuate the light source, the flame noise in the low frequency area is minimised and a high signal to noise ratio is thus assured. V. A. Howe & Co. Ltd., 12-14 St. Ann’s Crescent, London, SW 18 2LS. Monochromator The THR 1000 l m monochromator - spectro- graph from Jobin - Yvon is of modular design and is thus capable of optimisation for specific appli- cations and adaptable for other, future needs. It can be used over a wide spectral range from infrared to ultraviolet. It is equipped with a stepping motor driven by the Spectralink system.Diagnostic Spectrometer The Model 251 diagnostic spectrometer, first developed for the Princeton University Plasma Fusion Laboratory by Schoeffel McPherson, has been further refined by R. J. Fonk and R. V. Yelle. It features a curved micro-channel plate with optical fibre reducer conduit and diode array giving the ability to detect single photon events. Intersci Ltd., 21 Symonds Lane, Linton, Cambridge, CB1 6HY. X-ray Diffraction Tube A new sealed tube, the long fine-focus tube is announced. With a focal area of 0.4 x 12mm, it eliminates the need to use a wider receiving slit to obtain optimum peak heights. It is available in a variety of anode materials. Pye-Unicam Ltd., York Street, Cambridge, CB12BX. Software for Gel Permeation Chromatography The GPC+ program resides on an 8K PROM chip which plugs into the maker’s SP4200 comput- ing integrator.It provides a custom dialog for modifying the integrator for relative molecular mass distribution calculations. It also enables the calculation and plotting of calibration curves by using point to point linear, quadratic or cubic fits of the data. Spectra-Physics Ltd., 17 Brick Knoll Park, St. Albans, Hertfordshire, AL1 5UF. EDT Research, 14 Trading Estate Road, Lon- don, NWlO 7LU.July, 1984 EQUIPMENT NEWS 271 HPLC Columns The short column length of the 3 X 3 columns (so-called because they are 3cm long and use 3,pm packing materials) eliminates the high back pressures and shorter column life associated with many microparticulate columns.Perkin-Elmer Limited, Post Office Lane, Beaconsfield, Buckinghamshire, HP9 1QA. Digital Thermometer The Jenway Model 1004 hand-held instrument offers switchable resolution at 1 .O "C over the range from -100 to +500"C or 0.1 "C over the range from -50 to +200"C. Lenton Thermal Designs Limited, 12/14 Fair- field Road, Market Harborough, Leicestershire, LE16 9QA. HPLC Pre-column The C130B is 2 cm long and has replaceable frits. Included in the kit is a funnel designed to screw on to the pre-column. Field Instruments Co. Ltd., 1-5 Baker Street, Weybridge, Surrey, KT13 8AE. Multi-titration System The MTS800 can permanently store 31 user- programmable titration modules. By pressing 3 mode keys, the user can select to have his methods performed as end-point titrations, inflection point titrations or Karl Fischer titra- tions.One or two end-points and up to nine inflection points can be identified in one titration. V. A. Howe & Co. Ltd., 12-14 St. Ann's Crescent, London, SW18 2LS. Multimeter The PWA1 meter offers measurement of pH, conductivity, redox, ionic strength and tem- perature in most water and chemical samples. It offers four measurement ranges: 0-14 pH, 0-2 1 999 mV, -50-+199.9 "C and conductivity over six ranges from 0-199.9mS down to 0-19.9 pS. Jenway Ltd., Gransmore Green, Felsted, Dunmow, Essex, CM6 3LB. Titration System The Hamilton AMICA system is a closed liquid system. It can be used to determine the purity of chemicals and pharmaceuticals by non-aqueous titrations of weak organic acids with, for example, tetrabutylammonium hydroxide as titrant.V. A. Howe & Co. Ltd., 12-14 St. Ann's Crescent, London, SW18 2LS. Oxygen Analyser The 756A low concentration analyser is available in six switched ranges down to 0.1-10 v.p.m. and features single-point calibration, linear analogue meter indication and a range of linearised voltage - current outputs. Servomex Ltd., Crowborough, Sussex, TN6 3DU. Air Sampling Pump A new pump incorporates a time modulation sampling mode. An example of its use is in dust sampling, where a process flow-rate is required; the pump allows typical tests of 1-2h to be extended to an entire 8-h shift without changing the total sample volume or flow-rate. SKC Ltd., Hamworthy Trading Estate, Daw- kins Road, Poole, Dorset, BH15 4JW. Formaldehyde Monitor The Model SA9400 provides continuous measurement of formaldehyde in air.It operates on the Lutidin Method and has a sensitivity better than 25 p.p.b. Advanced Medical Supplies Ltd., 19 Holder Road, North Lane Industrial Estate, Aldershot, Hampshire. Balances The Shimadzu EB series of electronic balances features automatic stability detection through a choice of four time averaging bands, automatic zeroing, the facility to hold a stabilised value even after the sample has been removed from the pan and data output for connection to the EP 40 printer or an RS232-C buffer unit. V. A. Howe & Co. Ltd., 12-14 St. Ann's Crescent, London, SW18 2LS. Balances Six new models are being added to the PE series of electronic balances. Two of them, the PE360272 EQUIPMENT NEWS Anal.Proc., Vol. 21 and PE3600, feature DeltaRange, which covers one sixth of the entire weighing range and can be recalled with the touch of a button. It enables heavy containers and small quantities of ingredi- ents to be weighed on the same balance. Mettler Instrumente AG, CH-8606 Greifensee, Switzerland. Ovens The Plus series is available in three sizes with internal volumes of 75, 150 and 2251. All can incorporate an optional blower in addition to the built-in fan, providing an air change rate of up to 500 h-I. A wide variety of shelf options are available. Gallenkamp, P.O. Box 290, Technic0 House, Christopher Street, London, EC2P 2ER. Gamma Counting System The LB2102/500R multi-crystal counter has the features of the LB2101 multi-channel instrument with the addition of a 63K memory Apple IIe microcomputer.Laboratory Impex Limited, Lion Road, Twickenham, Middlesex. Water-baths Four thermostatic units feature a polypropylene tray with heater, circulating pump and tempera- ture control circuit. The operating range is from ambient to +50°C with a control accuracy of +0. 1 “C. PolyScience Corporation, P.O. Box 48312, Niles, Illinois 60648, USA. Transmission Electron Microscope The EM 410 LS dedicated life science instrument features a new column design in which minimum magnification has been reduced from that of its predecessor, the EM 410. A normalisation con- trol has been introduced which, coupled with an easily reproducible specimen position , affords accurate reproducibility of magnification over a long period.Pye Unicam Ltd., York Street, Cambridge, CB12PX. Data Logger The Oscillostore P12 has 12 channels, the func- tion and range of which can be modified using plug-in adaptors. The adaptors are available for d.c. 4-20 mA signals (with programmable scaling) and temperatures with platinum measuring resis- tors or thermocouples. Siemens Limited, Siemens House, Wind- mill Road, Sunbury-on-Thames, Middlesex, TW16 7HS. Chart Recorders A range of instruments features electronic control of the chart drive by stepped motor over the 11 speeds between 0.1 mm min-1 and lOmm s-l in both directions. V. A. Howe & Co. Ltd., 12-14 St. Ann’s Crescent, London, SW18 2LS. Flexible Hose Cajon PTFE-lined stainless steel flexible hose with end connections up to 1 in is now available.Standard integral 316 connections are either O-ring coupling glands or tube adaptors for use with Swagelok tube fittings. Swagelok (UK) Ltd., 3 Kelvin Close, Science Park North, Birchwood, Warrington, WA3 7PB. Continuous Line Recorders A range of one, two or three pen models is available with a choice of writing techniques (ink, fibre tip or heated stylus) and each of the pens will respond to a range of electrical signals via plug-in modules. Hartmann & Braun Limited, Moulton Park, Northampton, NN3 1TF. Literature A brochure describes components for microbore HPLC. These include the microMetric pump and spectroMonitor D detector with microcell fluid cell. Laboratory Data Control (UK) Ltd., Milton Roy House, High Street, Stone, Staffordshire, ST15 8AR.A catalogue details a range of 5 and 3 pm Hypersil packing materials, pre-packed and empty col- umns and the maker’s packing pump for HPLC. Shandon Southern Products Ltd., Chadwick Road, Astmoor, Runcorn, Cheshire, WA7 1PR. A leaflet, “Chromatographic News,” describes a new capillary column for the analysis of C1-Clo hydrocarbons. Alltech Associates (Europe) Ltd., 39 New Street, Carnforth, Lancashire, LA5 9BX.July, 1984 RONALD BELCHER MEMORIAL LECTURESHIP A brochure gives information on the Chromoscan range of microprocessor controlled scanning den- sitometers available in a number of options to suit individual needs. They are available with visible and ultraviolet light sources and can operate in transmission, reflectance or fluorescence modes. Joyce-Loebl, Marquisway, Team Valley, Gate- shead, NEll OQW. Four leaflets describe accessories for the maker’s Model 240C elemental analyser. These are acces- sories for carbon in steel/refractories analysis, mineral carbonate analysis, liquids and unstable materials sample handling systems and oxygen analysis. Perkin-Elmer Limited, Post Office Lane, Beaconsfield, Buckinghamshire, HP9 1 QA. A data sheet describes the Karl Fischer Turbo Titrator, which automatically measures water content in solids and other samples that resist mixing. The data sheet includes a list of possible applications. GCA Corporation, 209 Burlington Road, Bed- ford, Massachusetts 01730, USA. A brochure describes the Radiometer MTS800 multitration system. Radiometer A/S, Emdrupvej 72, DK-2400, Copenhagen NV, Denmark. A brochure describes the Magiscan 2 image processing system, which can analyse images from optical and electron microscopes, photographs, negatives, film and real life objects. A leaflet gives advance information of a programmable video interface for the transmission of slow scan video signals to the Magiscan system. Joyce Loebl, Marquisway, Team Valley, Gateshead, NEll OQW. 273

ISSN:0144-557X    

DOI:10.1039/AP9842100270

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

July, 1984 RONALD BELCHER MEMORIAL LECTURESHIP 273 Analytical Division Distinguished Service Award Nominations are invited for the Division’s Dis- tinguished Service Award, the Rules for which are as follows: 1. The aim of the Award is to recognise274 MASS SPECTRAL DATABASE exceptional voluntary service over a period of years to the Analytical Division of The Royal Society of Chemistry (including that to the Society for Analytical Chemistry). 2. The Award shall normally be in the form of an illuminated address which may be accom- panied by such additional recognition as Council of the Division shall agree. 3. Nominations for the Award will be invited annually from members of Council of the Division, and may be received from any member of the Division. They shall be made in writing, with supporting evidence, to the President of the Analytical Division, Royal Society of Chemistry, Burlington House, London, W1V OBN. 4. Nominations shall be considered by the Honours Committee of the Analytical Divi- sion, which shall recommend to Council of the Division (a) to whom an award should be made, ( b ) the nature of the award or ( c ) that no award should be made. 5 . The Award shall be made by the Council of the Analytical Division, which must approve any alteration of these Rules. Nominations for the Award should be sent to the President of the Analytical Division before August 31st, 1984. Anal. Proc., Vol. 21

ISSN:0144-557X    

DOI:10.1039/AP984210273b

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

274 MASS SPECTRAL DATABASE Anal. Proc., Vol. 21 HP 5987A GC - MS System, and on magnetic tape direct from Wiley. For further information , contact Gary Craig, Manager, Database Marketing, John Wiley & Sons, 605 Third Avenue, New York, NY 10158, USA. Mass Spectral Database John Wiley & Sons has signed a licence agree- ment with the Nicolet Instrument Corporation for Nicolet to distribute the Wiley/NBS Mass Spec- tral Database as from March 5th, 1984. The agreement was announced at the Pittsburgh Conference and Exposition on Analytical Chemistry and Applied Spectroscopy in Atlantic City, NJ, USA, March 5th-8th, 1984. Nicolet will make the Wiley/NBS file available as a Mass Spectra Library with automatic on-line compound identification using Enhanced Prob- ability Based Matching (EPBM). The database will be offered as an optional part of Nicolet’s mass spectrometry instrumentation package. The Wiley/NBS Mass Spectral Database, the largest known collection of mass spectral data in the world, combined information from Wiley’s “Registry of Mass Spectral Data” and the National Bureau of Standards’ “National Insti- tute of Health - Environmental Protection Agency (NIH - EPA) Database.” It offers direct access to more than 80000 spectra of approxi- mately of 68 000 different chemical compounds. The combined Wiley/NBS databases are already available through Hewlett-Packard for its

ISSN:0144-557X    

DOI:10.1039/AP984210274a

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

276 THE CHROMATOGRAPHIC SOCIETY Anal. Proc., Vol. 21 Publications Received Developments in Food Colours-2. Edited by John. Walford. DeveZopments Series. Pp. x + 257. Elsevier Applied Science. 1984. Price f28. ISBN 0 85334 244 X. The aims of this second volume are to discuss technical advances in the food coloration field since the appearance of Volume 1 and to examine the progress made in understanding the need for regulating the use and controlling the quality of colours permitted for use in foodstuffs. The chapters are as follows: “Regulatory Approaches to Food Coloration” by L. E. Parker; “Analysis of Synthetic Food Colours” by G. Wadds; “The Influence of Colour on Sensory Perception and Food Choices” by F. M. Clydesdale; “Synthetic Certified Food Colours of the USA” by R.K. Johnson and F. J. Lichtenberger; “Natural Col- ours in Food” by A. J. Taylor: “Adverse Reac- tions to Food Additives and Colours” by K. Miller and S. Nicklin; and “Future Trends” by F. J. Francis. Methods for The Examination of Waters and Associated Materials. Standing Committee of Analysts (to Review Standard Methods for Quality Control of the Water Cycle); Department of the Environment, National Water Council. HM Stationery Office. The Determination of Hydrocarbon Oils in Waters by Solvents Extraction, Infrared Absorp- tion and Gravimetry 1983. Pp. 20. 1984. Price f2.75. ISBN 0 412 24390 3. Methods for The Examination of Waters and Associated Materials. Standing Committee of Analysts (to Review Standard Methods for Quality Control of the Water Cycle); Department of the Environment, National Water Council.HM Stationery Office. Sampling of Non-planktonic Algae (Benthic Algae or Periphyton) 1982. Pp. 27. 1984. Price f3.15. ISBN 0 11 751725 9.July, 1984 AOAC COMMITTEES Iron and Manganese in Potable Waters by Atomic Absorption Spectrophotometry 1983. Pp. 20. 1954. Price f2.75. ISBN 0 11 751727 5. 277 High Performance Liquid Chromatography, Ion Chromatography, Thin Layer and Column Chro- matography of Water Samples 1983. Pp. 99.1984. Price f6.25. ISBN 0 11 751726 7. Classical Methods for the Characterization of Oils, Fats and Waxes by Saponification, Hydroxyl, Iodine and Acid Values 1983. Pp. 27. 1984. Price f3.20. ISBN 0 11 751729 1. Methods of Enzymatic Analysis. Third Edition. Volume IV. Enzymes 2: Esterases, Glycosidases, Lyases, Ligases.Edited by Hans Ulrich Bergmeyer. Pp. xxiv + 426. Verlag Chemie. 1984. Price DM230. ISBN 3 527 26044 7 (Verlag Chemie); 0 89573 234 3 (Verlag Chemie International). HPLC Analysis of Biological Compounds. A Laboratory Guide. William S. Hancock and James T. Sparrow. Chromatographic Science Series, Volume 26. Pp. x + 361. Marcel Dekker. 1984. Price SFrllO. ISBN 0 8247 7140 0. Steric Exclusion Liquid Chromatography of Poly- mers. Edited by Josef JanCa. Chromatographic Science Series, Volume 25. Pp. xvi + 329. Marcel Dekker. 1984. Price SFr153. ISBN 0 8247 7065 X. Instrumental Liquid Chromatography. A Prac- tical Manual on High-Performance Liquid Chro- matographic Methods. Second, Completely Revised Edition. N. A. Parris. Journal of Chromatography Lib- rary, Volume 27. Pp. xiv + 432. Elsevier. 1984. Price $86.50; Dfl225. ISBN 0 444 42061 4 (Vol. 27); 0 444 41616 1 (Series). AOAC Committees The March, 1984, issue of the AOAC’s news sheet The Referee contains a form for the use of persons wishing to serve on the AOAC’s methods and standing committees. For further information on the work of the committees or a copy of the application form contact Rita Comotto Bahner at the Association of Official Analytical Chemists, 1111 N. Nineteenth St.-Suite 210, Arlington, VA 22209, USA.

ISSN:0144-557X    

DOI:10.1039/AP984210276b

出版商:RSC    

年代:1984

数据来源: RSC