摘要:

ROYAL SOCIETY OF CHEMISTRY ANALYTICAL DlVlS ON ANNUAL GENERAL MEETING and RETIRING PRESIDENT'S ADDRESS Owing to circumstances beyond the Division's control the above two events were postponed and did not take place on Friday, March 2nd, 1984. The revised date for them is Tuesday, June 5th, 1984. For further information contact Miss P. E. Hutchinson, Analytical Division, The Royal Society of Chemistry, Burlington House, Piccadilly, London, WIV OBN. RSC ANALYTICAL DIVISION NORTH WEST REGION A Meeting on FLOW INJECTION ANALYSIS will be held at the Thornton Research Centre, near Chester on April I l t h , 1984 The speakers at the meeting will be J. N. Miller, A. P. Wade, A. Shaw, P. Worsfold, A. Townshend and J. F. Tyson. It is hoped that there will be a small exhibition of FIA equipment. For further information contact Mr. E. R. Adlard, Shell Research Ltd., Thornton Research Centre, P.O. Box 1, Chester, CHI 2SH.

ISSN:0144-557X    

DOI:10.1039/AP98421FX008

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

126 CHEMICAL SPECIATION IN AQUEOUS SOLUTIONS ANALYTICAL DIVISION DIARY RSC/AD: ELECTROANALYTICAL GROUP A Meeting on will be held at Chelsea College, London on April 5th, 1984 Papers to be presented and discussed include: "Speciation of Metals in Natural Water Conditions by Potentiometry and Voltammetry," Dr. J. Buffle (Geneva University); "Organic Speciation of Metals in Seawater," Dr. C. M. G. van den Berg (Liverpool University); "Potentiometric Sensors in Chemical Speciation," Professor N. lshiboshi (Kyusho University); "Metal - Ligand Formation Constants by Potentiometric - Computing Techniques," Dr. K. Murray (UWIST); "Chemical Speciation in Soil Science," Dr. T. Edmonds (Loughborough University); "Horizons in Chemical Speciation," Dr. M. Whitefield (Marine Biological Association, Plymouth). Further details can be obtained from Dr. B. J. Birch, Unilever Research, Port Sunlight, Quarry Road East, Bebington, Wirral, Merseyside, L63 3SW. Electronically typeset and printed by Heffers Printers Ltd, Cambridge, England

ISSN:0144-557X    

DOI:10.1039/AP98421BX010

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

ANPRDI 21(3) 89-126 (1984) March 1984 Analytical Proceedings Proceedings of the Analytical Division of The Royal Society of Chemistry AD President S. Greenfield Hon. Treasurer D. C. M. Squirrel1 Hon. Secretary R. Sawyer 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, LEll 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 G. J. Dickes L. C. Ebdon A. C. Moffat J. M. Skinner J. D. R. Thomas A.M. Ure "P. C. Weston "G. W. Kirby J. Whitehead +Ex officio members All editorial matter should be addressed to: The Editor, Analytical Proceedings, The Royal Society of Chemistry, Burlington House, Piccadilly, London, WIV 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 0144-557x3 is published monthly by The Royal Society of Chemistry, Burlington House, London, WlV 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 lHN, England. 1984 Annual Subscription price if purchased on its own: UKf53.00, Rest of World f56.00, 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. Editorial Euroanalysis V Euroanalysis V will be held later this year, from August 26th-31st, in Cracow, Poland.The second Circular was issued recently and "Circular 3" will be available this month and will include a detailed programme of events. If you are not already on the mailing list and would like more information you should write to Euroanalysis V. Professor Zygmunt Kowalski, Academy of Mining and Metallurgy, 30-059 Cracow , Poland, Al. Mickiewicza 30. The main features of the scientific programme were published in the Second Circular and include four Plenary Lectures and ten Keynote Lectures. including that of G. Nickless from the UK. The topics of the Plenary Lectures will cover some important specific topics in analytical chemistry. such as "Chemical Analysis of Space Materials" (Yu.J. Belyaev. USSR) and Flow-Potentiometric Stripping Analysis (D. Jagner, Sweden). The other two Plenary Lecturers will open Special Sessions at the conference. Thus. a Session on Computer Based Analytical Chemistry will be headed by a lecture from R. E. Dessy of the USA entitled "Microprocessor Systems for Data Processing in Analytical Chemistry.'' In addition, a Special Session on Speciation in Trace and Environmental Analysis will be opened by the Plenary Lecture, "Specimen Bank- Our Link with the Future" by H. W. Nurnberg (West Germany). Although Euroanalysis I11 was held in Dublin in 1978, offers by the Analytical Division of the Royal Society of Chemistry to host a Euroanalysis Conference have never received majority support within FECS. For such an offer to be successful in the future, I believe it is essential that members of the Division should individu- ally show strong support for Euroanalysis meetings, and there could be no better opportunity to demonstrate this than at Cracow in 1984. I am sure that the conference will be successful and that our hosts, the Polish Chemical Society and the Committee on Analytical Chemistry of the Polish Academy of Science, will ensure that all participants find their visit to Poland a stimulating and enjoyable experience. Nowadays our colleagues from Poland and other east European countries appear to find it increasingly difficult to attend conferences outside Eastern-bloc countries and Cracow will provide a marvellous opportunity to meet and have informed discussions on a fully European-wide basis. If you are thinking about going to Cracow, don't hesitate. Maybe a strong UK delegation could persuade more of our European friends to attend SAC 86. J. M. OTTAWAY 89

ISSN:0144-557X    

DOI:10.1039/AP9842100089

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

90 REPORTS OF MEETINGS Anal. Proc., Vol. 21 Reports of Meetings Midlands Region The twenty-ninth Annual General Meeting of the Region was held at 6.30 p.m. on Tuesday, November 15th, 1983, at Trent Polytechnic, Nottingham. The Chair was taken by the Chairman of the Region, Professor J. N. Miller. The following office bearers were elected for the forthcoming year: Chairman-Dr. P. B. Smith. Vice-Chairman-Mr. J. E. W. Tillman. Honorary Secretary-Mr. H. E. Brookes, 35 Dunster Road, West Bridgford, Nottingham, NG2 6JE. Honor- ary Treasurer-Dr . J. F. Tyson. Honorary Assistant Secretary-Dr. A. Braithwaite. Members of Commit- tee-Dr. R. K. Bramley, Dr. A. G. Fogg, Dr. C. L. Graham, Dr. V. J. Jennings, Dr. A. M. G. Macdonald, Professor J. N. Miller (ex officio) and Mr. D. M. Peake. Mr.H. Pugh and Mr. W. G. Harris were re-appointed as Honorary Auditors. Microchemical Methods Group The fortieth Annual General Meeting of the Group was held at 1.40 p.m. on Friday, December 9th, 1983, in the Linnean Society, Burlington House, London, W. 1. The Chair was taken by the Chairman of the Group, Professor D. T. Burns. The following office bearers were elected for the forthcoming year: Chairman- Professor D. T. Burns. Vice-Chairman-Dr, E. J. Newman. Honorary Secretary-Mr. P. R. W. Baker, 55 Braemar Gardens, West Wickham, Kent, BR4 OJN. Honorary Treasurer-Mr. M. R. Cottrell. Members of Committee-Mr. P. G. Baker, Mr. R. Goulden, Mr. J. Mendham, Dr. B. A. Plunkett, Mr. B. T. Saunderson and Mr. C. A. Watson. Mr. S. Bance and Mr. H. I. Shalgosky were re-appointed as Honorary Auditors.Special Techniques Group The thirty-ninth Annual General Meeting of the Group was held at 1.50 p.m. on Tuesday, December 6th, 1983, at Imperial College, London, S.W.7. The Chair was taken by the Chairman of the Group, Professor D. Betteridge. The following office bearers were elected for the forthcoming year: Chairman-Dr. A. F. Taylor. Vice-Chairman-Dr. J. F. Alder. Honorary Secretary- Mr. J. Huddleston, Building 10.2, Instrumentation and Applied Physics Division, AERE, Harwell, Didcot, Oxfordshire, OX11 ORA. Honorary Treasurer-Mr. A. G. Ferrige. Members of Committee-Professor A. Bailey, Professor D. Betteridge (ex officio), Mr. J. T. Davies, Mr. P. Hampson, Dr. C. M. Jenden and Dr. L. W. Tetler. Dr. D. Christopher and Professor J.N. Miller were re-appointed as Honorary Auditors. Atomic Spectroscopy Group The nineteenth Annual General Meeting of the Group was held at 2 p.m. on Thursday, December 15th, 1983, at the University of Technology, Loughborough. The Chair was taken by the Chairman of the Group, Dr. E. J. Newman. The following office bearers were elected for the forthcoming year: Chairman-Dr. E. J. New- man. Vice-Chairman-Dr. A. Townshend. Honorary Secretary-Mr. D. J. Willis, Hilger Analytical Ltd., Westwood Industrial Estate, Ramsgate Road, Margate, Kent, CT9 4JL. Honorary Treasurer-Dr. G. B. Marshall. Honorary Assistant Secretary-Mr. C. A. Watson. Members of Committee-Dr. J. F. Alder, Dr. N. W. Barnett, Dr. A. R. Date, Mr. M. Davies. Dr. L. C. Ebdon (ex officio), Mr. P. W. Hurley and Dr.P. B. Smith. Mr. R. P. Blakemore and Mr. D. B. Ratcliffe were re-appointed as Honorary Auditors. Chromatography and Electrophoresis Group The nineteenth Annual General Meeting of the Group was held at 1.45 p.m. on Thursday, December 22nd, 1983, at Chelsea College, Manresa Road, London. S.W.3. The Chair was taken by the Chairman of the Group, Dr. G. H. Jolliffe. The following office bearers were elected for the forthcoming year: Chairman-Dr. R. M. Smith. Vice-Chairman-Dr. R. G. Hopkins. Honorary Secretary and Treasurer-Dr. D. Simpson. Analysis For Industry, Factories 213, Bosworth House, High Street, Thorpe-le-Soken, Essex, C016 OEA. Members of Committee-Dr. F. K. Butcher, Dr. A. F. Fell, Dr. P. J. Houghton, Dr. G. H. Jolliffe (ex officio), Mr. N. C. McTaggart (co-opted) and Dr. F.Smith. Mr. G. Mitchell and Mr. J. S. Wragg were re-appointed as Honorary Auditors. Automatic Methods Group The eighteenth Annual General Meeting of the Group was held at 1.45 p.m. on Wednesday, December 14th, 1983, at the Scientific Societies Lecture Theatre. 23 Savile Row, London, W.l. The Chair was taken by the Chairman of the Group, Mr. D. G. Porter. The following office bearers were elected for the forthcom- ing year: Chairman-Dr. K. J. Saunders. Vice- Chairman-Mr . S. G . Farrow. Honorary Secretary- Dr. C. J. Jackson, Health and Safety Executive, Occupational Medicine and Hygiene Laboratories, 403 Edgware Road, London, NW2 6LN. Honorary Treasurer-Dr. A. Braithwaite. Honorary Assistant Secretary-Mrs. E. Evans-Terlecki. Members of Com- mittee-Professor D.Betteridge, Dr. A. Law, Mr. K. Leiper, Mr. J. Martin, Dr. G. W. Moody and Dr. R. Narayanaswamy. Dr. J. E. Page and Mr. R. Sawyer were re-appointed as Honorary Auditors. Thermal Methods Group The nineteenth Annual General Meeting of the Group was held at 5 p.m. on Monday, November 7th, 1983, at the Bonnington Hotel, London, WC1. The Chair was taken by the Chairman of the Group, Dr. G. M. Clark. The following office bearers were elected for the forthcoming year: Chairman-Dr. P. G. Laye. Vice- Chairman-Dr. D. V. Nowell. Honorary Secretary- Dr. C. J. Keattch, Industrial and Laboratory Services, P.O. Box 9, Lyme Regis, Dorset. Honorary Treasurer- Dr. R. H. Still. Members of Committee-Dr. G. M. Clark (ex officio), Professor F. P. Glasser, Mr.P. J. Haines, Mr. M. J. Hardy, Dr. G. R. Heal, Mr. R. J. Howes and Dr. T. J. Lever. Dr. A. Dyer and Dr. D. Griffiths were re-appointed as Honorary Auditors.March, I984 USE OF COMPUTERS IN THERMAL ANALYSIS 91 Particle Size Analysis Group The eighteenth Annual General Meeting of the Group was held at 2 p.m. on Wednesday, November 30th. 1983. at the Linnean Society, Burlington House, London, W. I . The Chair was taken by the Chairman of the Group. Dr. R. Wilson. The following office bearers were elected for the forthcoming year: Chairman-Dr. R. Wilson. Vice-Chairman-Dr. N. G. Stanley-Wood. Honorary Secretary and Treasurer-Mr. J . E. C. Harris. MQAD, Ministry of Defence. Puriton. Bridgwater, Somerset, TA7 8AD. Honorary Assistant Secretary- Dr. N. A. Orr. Members ofCommitree-Dr. T. Allen. Dr. L. T. Bayvel, Mr. M. W. G. Burt, Mr. G. Butters (co-opted), Mr. R. W. Lines (co-opted), Mr. P. J . Lloyd, Dr. A. Rood and Mr. A. van Santen. Mr. P. W. Shallis and Mr. J. Spence were re-appointed as Honor- arv Auditors. Radiochemical Methods Group The seventeenth Annual General Meeting of the Group was held at 9 a.m. on Thursday, November 17th, 1983, at the MAFF Fisheries Laboratory. Lowestoft. Suffolk. The Chair was taken by the Chairman of the Group, Dr. A. Dyer. The following office bearers were elected for the forthcoming year: Chairman-Dr. A. Dyer. Vice- Chairman-Mr. J. Eakins. Honorary Secretary-Mr. M. A. Crook, London School of Polymer Technology, Polytechnic of North London, Holloway Road, Lon- don, N7 8DB. Honorary Treasurer-Dr. G. Ayrey. Members of Committee-Dr. R. M. Lee, Dr. A. B. MacKenzie, Miss M. J. Minski, Dr. L. V. C. Rees, Mr. L. A. Richards, Dr. J. R. Thornback and Dr. A. R. Ware (ex officio). Mr. G. Farmer and Dr. P. Johnson were re-appointed as Honorary Auditors.

ISSN:0144-557X    

DOI:10.1039/AP9842100090

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

March, I984 USE OF COMPUTERS IN THERMAL ANALYSIS 91 Use of Microprocessors and Computers in Thermal Analysis The following are summaries of five of the papers presented at a Joint Meeting of the South East Region and the Thermal Methods Group held on November llth-l2th, 1982, at Fulmer Grange, Stoke Poges, Buckinghamshire. Implementation of a Thermal Analysis - Computer System J. M. Barton Materials and Structures Department, Royal Aircraft Establishment, Farnborough. Hampshire The interfacing of a thermal analyser with a desk-top computer system is described. The advantages of the ability to read experimental data over a wide output range, together with easily modified software, are demonstrated by examples of applications of differential scanning calorimetry (DSC) . Instrumentation The system comprises a DuPont 990 Thermal Analyser linked to a Hewlett-Packard 9835B computer.The analogue signals from the thermal analyser are sampled by a Solartron Series 3 analogue scanner connected to a Solartron 7055 digital voltmeter (DVM). The DVM has a resolution of 1 pV and an autoranging facility. This confers the advantage that low-level signals can be read with precision, while large signal excursions can be automatically accommodated. Communication between the computer and the DVM is provided by the IEEE-488 interface. An external counter was constructed to form an interface betweer, the computer’s external clock and the scanner. On receipt of command pulses at pre-selected intervals from the clock the scanner is stepped in turn around 3 input channels, each analogue signal being digitised and stored in the computer. After completion of the experiment the data can be processed and stored on the internal magnetic tape cassette.Output of the processed data is to an external VDU, printer or plotter. A comprehensive range of software has been developed in the extended BASIC language of the computer to cover DSC, thermomechanical analysis, dynamic thermomechanometry and thermogravi- metry. An advantage of the high level language is that programs can be readily modified or extended for special applications, such as testing the fit of data to quantitative models. Examples of Applications Advantages of the use of on-line data processing can be found in all areas of thermal analysis, and some of these advantages are illustrated by the following examples of applications to DSC measurements.92 USE OF COMPUTERS IN THERMAL ANALYSIS Anal.PYOC., Vol. 21 Determination of Polymer Glass Transition Temperature Using DSC The glass transition temperature (Tg) is characteristic of the amorphous phase, and it is a temperature at which major changes are observed in many physical properties. DSC is well established as a method for determining Tg by observation of the discontinuity in heat capacity that accompanies the transformation from a glass to a viscous liquid state on heating. The Tg is a molecular relaxation phenomenon and in macro-molecule$. it: often shows a diffuse character, associated with a broad distribution of relaxation times. It is also pmplicated by the dependence of the relaxation rates on the thermal history of the sample.In practice, a number of different operational definitions of Tg can be used, and it is useful to incorporate several of these into the same computer program. As an example of this application a DSC scan was obtained at a heating rate of 20 K min-1 on a sample of polystyrene. The DSC scan is shown as a graph of heat flow against temperature in Fig. 1. The endothermic peak in the glass transition region is typical of a sample that has been stored in the glassy state, resulting in a relatively low free volume fraction (the effect known as physical ageing'). Approximately linear regions of the curve above and below the glass transition are defined by four reference temperatures digitised from the plotter.Data in the linear regions are then analysed by linear regression to produce linear extrapolations from each side of the transition. Four different methods of defining the Tg are applied as follows. The inflection temperature (T,) is found by differentiation using a seven-point smoothing routine. The tangent at Ti is calculated and plotted. A second characteristic temperature, the extrapolated onset temperature (To,,) is calculated as the simultaneous solution of the equations representing the extrapolated low temperature (glass) line and the tangent at inflection. Thirdly, the mid-point temperature ( Tmid) is defined as the intersection of the line that is the locus of the mid-point between the extrapolated glass and liquid lines and the experimental curve.Finally, the fictive temperature ( Tf) is determined? This is defined as the temperature at which the equilibrium liquid has the same enthalpy as that of the glass, and it corresponds to the intersection of enthalpy curves extrapolated from well below and above the Tg. r I X -8 30 50 70 90 110 130 Tern peratu rePC Fig. 1. DSC scan at 20 K min-' heating rate on polystyrene. Tf is given by the equation TI T3 F p 1 - C,,)d T = (Cp-Cpg) dT . . . . . . . . -4 , I Tf TZ where T2 and T3 are the glass and liquid reference temperatures shown in Fig. 1, Crll and Cp, are the liquid and glass heat capacities extrapolated from above and below the transition region, respectively, and Cp is the experimental heat capacity. This is illustrated in Fig. 2, where the area ABCD represents the left-hand side of equation 1, and area TzDC represents the right-hand side.Heat flow can be used as the ordinate because it is proportional to heat capacity at a constant heating rate. Firstly. the area T2DC is found by trapezoidal integration, and Tf is then found by an iteration with a starting value of Tf = T3 - 0.2. The area ABCD is calculated by integration of the linear regression equations for theMarch, 1984 USE OF COMPUTERS IN THERMAL ANALYSIS 93 liquid and glass lines between the temperature limits T3 and Tf. Successive decrements of 0.2"C are applied to Tf, and the calculation repeated, until this area equals area T2DC, at which point the required limiting fictive temperature is defined. While the other three definitions of Tg are rather empirical, the fictive temperature has the advantage of being independent of the shape of the curve within the transition zone.For a sample of given thermal history, Tf should be independent of heating rate in the DSC experiment, provided that temperature lags within the sample are insignificant. The polystyrene sample gave the four characteristic temperatures: To,,, 106.8; Tmid, 106.7; Ti, 110.2, and Tf, 98.9 "C. When the same sample was held above Tg to erase previous thermal history, rapidly cooled to room temperature and re-scanned at 20 K min-1, the corresponding temperatures were 104.9, 108.5, 110.9, and 106.9 "C, respectively. The 8°C higher value for Tf reflects the greater entropy (free volume) state of the quenched sample. Monitoring Exothermic Reactions by Differential Calorimetry Although it is a misnomer to refer to isothermal DSC, the DSC instrument is widely used in the isothermal mode to monitor the kinetics of exothermic reactions.The method involves the insertion of a sample pan containing the reactants into the DSC cell, with its empty reference pan, previously equilibrated at the required reaction temperature. This insertion of the sample produces an initial endothermic offset in the output, and temperature equilibrium is regained within about 2 min. Then the heat flow signal follows the enthalpy change due to the reaction. Finally, after the reaction is complete, the output reaches a steady value. The base line is usually obtained by backwards horizontal extrapolation of the final output level, to produce an intersection with the rapid upsweep of the output signal that follows the initial non-equilibrium transient.This intersection is taken as the zero of the time scale for the reaction, and the distance between the horizontal base line and the experimental heat flow curve is assumed to be proportional to the rate of reaction. There is a window of temperature within which this method can be applied. If the temperature is too low the reaction will be so slow that the output lies within the noise band of the instrument. On the other hand, at too high a temperature a significant degree of reaction will occur during the initial period between sample insertion and the establishment of approximate isothermal conditions. The apparent heat of reaction will be low in value and the time scale zero will be in error. By using the computer, quantitative data can be obtained in the initial part of the reaction, the true non-linear base line can be determined, and the operational window can be extended to higher temperatures.These procedures are demonstrated by some results obtained on the reaction of phenyl glycidyl ether and 2-ethyl-4-methylimidazole to form a 2 : 1 molar adduct. An earlier investigation on the kinetics of a T2 I 1 I I 1 I 90 110 130 Te m peratu re:"C Fig. 2. Illustration of the method for determining the fictive temperature, Tf. for polystyrene. 200 0 -200 > E -400 52 -600 -800 -1 000 I 1 I I I 2 4 Time/m i n 6 Fig. 3. DSC output the reaction of phenyl glycidyl ether and 2-ethyl-4-methylimidazole at 122 "C.The solid line represents the initial run and the broken line is from the repeat run on the reacted sample.94 USE OF COMPUTERS IN THERMAL ANALYSIS Anal. Proc., Vol. 21 this reaction used the conventional DSC method, assuming a horizontal base line, in the temperature range 80-120 "C.5 The DSC data for a run at 122°C on a 4.6-mg sample of the reaction mixture contained in a hermetically sealed aluminium pan are shown in Fig. 3. After completion of the reaction the sample pan was removed from the cell. The cell was re-equilibrated at 122OC, and the experiment repeated with the same sample and pan to obtain the non-linear base line shown in Fig. 3. Because the manual sample insertion cannot be repeated in exactly the same time interval there is a slight mis-match of the time scales of the experiment and base line runs.The time shift was found to be 1.7 s from plots of the early part of the data on an enlarged time scale, and this value was used by the computer to shift the base line data to match the experiment at the minimum of the initial transient endotherm. The heat flow versus time plots obtained from the present method and the conventional horizontal base line, in Fig. 4, show the differences in both the shapes and areas of the exothermic peaks. Plots of 10 1 Tirne/rnin Fig. 4. Exotherm profiles obtained by using the actual base line (solid line) and the linear base line (broken line). apparent heat of reaction against temperature obtained in the temperature range 80-150 "C are given in Fig.5 for the two methods. Use of the true base line yields an approximately constant value for the heat of reaction ( Q ) , with a mean value of 456.7 J g-1, while the horizontal base line gives an apparent decrease in Q with increasing temperature. The results are complicated by the fact that the temperature is increasing rapidly in the early part of the reaction, and this needs to be taken into account in any kinetic interpretation of the data. 500 1 Fig. linear base line; B.March, 1984 USE OF COMPUTERS IN THERMAL ANALYSIS 95 Conclusions The use of data acquisition and processing by computer extends the range of measurements that are available by thermal analysis. Methods of data analysis, which would be tedious to apply manually, can be readily applied by computer.The examples presented here are on the application of DSC to the determination of Tg and the monitoring of exothermic reactions, but advantages are gained by the use of computer processing in the whole range of thermal analysis techniques. References 1. 2. 3. 4. 5. Struik, L. C. E . , “Physical Ageing in Amorphous Polymers and Other Materials,” Elsevier, Amsterdam, Moynihan, C. T., Easteal, A. J., and DeBolt, M. A., J . Am. Ceram. SOC., 1976, 59, 12. Flynn, J. H.. Thermochim. Acta, 1974. 8, 69. Richardson, M. J . , and Savill, N. G., Polymer, 1975, 16, 753. Barton, J. M., and Shepherd, P. M., Makromol Chem., 1975, 176, 919. 1978. ua‘ca rrocessing aysrerns T o r I nermai nnaiysis N. J. Manning Stanton Redcroft Ltd., Copper Mill Lane, London, SW17 OBN Data processing using a computer system is obviously attractive to thermal analysts in allowing the rapid accurate determination of results.Computer systems, however, have specific problems of interfacing and data handling, some of which are discussed here in relation to DAPS 2 (Data Acquisition and Processing System). At Stanton Redcroft we have assembled a product based on a common BASIC programmable computer (CBM 4032). This system is versatile, easily tailored to specific requirements and has the other advantage of providing a computer for general laboratory use. It has also allowed us to concentrate on two crucial areas, i.e., computer interfacing and the data requirements peculiar to thermal analysis systems. System Outline The system (Fig. 1) is controlled by a CBM 4032, which is a well known, robust machine that is in wide use throughout the UK.The system includes high resolution graphics, a high speed digital tape unit, twin floppy disk drives, a computer interface and a digital plotter. The tape unit is used as an extension to the memory of the CBM 4032 and allows data to be recovered if the equipment is accidently switched off during an experiment. The floppy disk system is used to provide a semi-permanent storage medium for the thermally generated data. The data is stored in sequential files as real numbers (e.g., temperature/OC, time/s, DTA/mV), which allows easy access to the data for specialist applications. Thermal analysis equipment unit High speed resolution graphics digital tape CBM 4032 (Including high CBM-8050 dual-drive floppy disk unit board) unit A4-size digital colour plotter Fig.1. Schematic diagram of DAPS 2. The standard software programmes include the facility to expand areas of curves. determine peak temperatures and times, mass changes, extrapolated onset and offset temperatures and times, glass96 transition temperatures, etc., and to plot the results on an A4 size chart in colour. and data, as indicated below. USE OF COMPUTERS IN THERMAL ANALYSIS Anal. Proc., Vol. 21 In designing the above system it was necessary to consider carefully the constraints of the equipment Data Constraints Thermal analysts are generally used to dealing with analogue data; indeed, one of our objectives in producing a system was to generate an output which was comparable to that of an analogue system.It must always be remembered, however, that computer systems are digital and in essence are more comparable to sophisticated dot recorders than the traditional strip chart or X- Y recorders. Bearing this in mind let us consider the constraints of the various types of signal used in thermal analysis. Temperature (thermocouple) It is immediately obvious, when plotting any digitised thermally generated signal, that the noise level is apparently very much higher than when using a chart recorder. In fact, the relatively slow response time and inbuilt smoothing of the chart recorder is responsible for this. The generation of usable data from a digital system therefore requires a limited amount of smoothing. This is relatively simple in the case of the temperature signal, however, as a recording rate of 1 s-1 or even 1 every 2 s is sufficient to describe the curve. DTA, DSC The data constraints are much more severe for DTA (or DSC) signals because of signal size (pV) and required response time.However, this is also an area in which there is a distinct advantage in using data processing, because the faster response time of the system actually allows greater resolution of fine detail. In order to allow a reasonable description of the curve a minimum sampling rate of 2 s-1 must be possible, and smoothing of the DTA signal should be minimal in order to avoid loss of detail. It is also easy to introduce inadvertently offsets or distortion of small microvolt signals as a result of interactions with the computer system, such as earth loops.The system therefore includes good quality isolation amplifiers on all inputs to isolate the computer system from the thermal analysis equipment. Mass (TG), displacement (TMA), etc. The constraints of other thermally generated data, such as TG and TMA, are similar, requiring limited smoothing and data manipulation and maximum sampling rates of around 1 s-1. Care must be taken, however, in the selection and smoothing of data as a significant proportion of the noise may be non-random. Data Selection and Interfacing Having broadly defined the data constraints it is necessary to consider the mode, selection and storage of data. For example, to store every point of a DTA - temperature curve whilst sampling at the necessary rate would require over 20K h-1 of storage.It is not necessary, however, to store all of this data. The important features are significant differences in the thermally generated input and areas of little or no change can be described with very few points. If, therefore, we select data for storage on the basis of the change in the thermally generated signals it is possible to reduce the amount of storage required by 20 or 30 times, despite the necessity to store time as an extra parameter. This process is not as simple as it first appears, however, because the significance of a given change varies according to range, noise levels and signal characteristics. A careful analysis of noise levels and an intimate knowledge of the instrumental and data characteristics are therefore required in order to implement such a system of data compression. It is also much simpler to implement when controlling data selection in real time via the central computer.The DAPS 2 system therefore includes an interface which allows sampling interval to be controlled by the CBM4032 computer during experiments. Other important considerations of interfacing are the interfacing standard used and the degree of precision required after digitising the incoming signals. The Stanton Redcroft Data Acquisition Unit (DAU) was designed to give a resolution of 1 part in 20 000. This allows a precision of 0.1 "C for both K- and R-type thermocouples over their normal operational temperature range. In terms of the DTA input, for example, a maximum input equivalent to 1000 pV has a step size of 0.05 pV, which is slightlyMurch, I984 USE OF COMPUTERS IN THERMAL ANALYSIS 97 less than the inherent signal noise.The advantages of such resolution are that the high precision allows various levels of detail to be determined from a single experiment with a minimal amount of operator skill. The interface is designed to the IEEE 488 standard. This gives the choice of a wide variety of computer and peripherals, whilst allowing faster data transfer rates than the RS 232 standard. Conclusion The DAPS 2 system is a robust equipment package that provides a useful, convenient method of acquiring and processing thermal data based on a common proved computer system. It facilitates the calculation of the common thermal parameters with the ability to give report-ready A4 size colour graphs of the experimental data.The methods of data collection and compression allow a minimal amount of data storage (thus minimising the subsequent processing time) without loss of detail. The Use of a Microcomputer in Kinetic Analysis G . R. Heal Department of Chemistry and Applied Chemistry, University of Salford, Salford, M5 4WT Microprocessors have been appearing in thermal analysis equipment for some time now. Many units have temperature programmers, which give rates of heating variable to 0.1 "C min-1 for any type of thermocouple, and much smoother control than with previous types. The logging systems record data, convert EMF to temperature, smooth and differentiate data, integrate areas and display results on a screen, or print them on chart paper.Systems have been developed to calculate the purity of routine samples and to print full reports directly on to a recorder, together with the curves obtained. One unit at least can record data on a disc system, for recall later, to compare old and new samples. Of course these sophisticated systems cost a lot of money, and some researchers may wish to computerise their older equipment or to buy cheaper units and adapt them. This paper will be concerned with our experiences in adding a microcomputer to thermal analysis equipment and the results that can be obtained. Choosing a Computer Computers in thermal analysis are often concerned more with logging and presenting large amounts of data and less with processing results. The types that have only a display screen for output are therefore not as useful.A printer can be added to virtually any system, but a good printer costs f500 to over 21 000. We have therefore chosen the Rockwell AIM 65 microcomputer because it has a built-in miniature printer and costs f450 if bought complete with 4K memory, BASIC chips, an ASSEMBLER chip and a case. It then becomes feasible to use one microcomputer per instrument instead of multiplexing. The printer uses thermally sensitive paper, and heaters in the printing head produce blue characters at the rate of 2 lines s-1. The paper is only 6 cm wide and accommodates a maximum of 20 characters. This is not very convenient for programming, but is satisfactory for printing the logged values. BASIC text lines automatically overflow on to a second line if they contain more than 20 characters.There is also a one-line display of 20 characters, made up of light-emitting diodes, which can be used as an alternative to the printer to save paper when programs are being developed. An interface for connection to a teletype or VDU is provided, using a 20-mA loop mode. The 4K ROM chips contain the miniature operating system or monitor that controls the operation and testing of the whole system. Two more optional 4K ROMs contain a BASIC interpreter, which means that the main programs can be written and modified in a familiar high-level language. The signals from instruments are usually analogue in nature, so analogue to digital converters (ADCs) are required. There are types now available which are specially designed for connection to microcomputers.In order to control the ADC and transfer the data, many program instructions have to be executed. Although this could be carried out in BASIC, it is far easier, faster, more efficient and uses less store if ADC control is carried out from machine code sub-routines called from a main BASIC program. It is possible to carry out entry of machine code instructions directly but it is a tedious task. A better method is to enter low-level routines in a mnemonic code called ASSEMBLY language. This is then passed through an ASSEMBLER program to convert it to machine code. An assembler program is available on another 4K ROM chip for the AIM 65.98 USE OF COMPUTERS IN THERMAL ANALYSIS Anal. Proc., Vol.21 The AIM 65 has two multi-pin plugs at the rear. One of these can be used to increase the memory size. The other is an applications connector and is used to attach to ADCs via a versatile interface adaptor (VIA) and also allows connection to a standard cassette tape recorder. The tape recorder can be used to store BASIC programs, mnemonic code ASSEMBLY programs or binary machine code or, with some modification of the system, to store data.’ A power supply has to be added to provide 5 V d.c. at 2 A and 24 V d.c. at 2.5 A for the printer. The AIM 65 is available from two main suppliers.2.3 The circuit and the operation of the machine code routines have been described previously.4 Several types of main program are now in use with an AIM 65 linked to a Stanton TG 750 thermal balance via amplifiers.5 The 10-mV outputs of the control unit and the sample thermocouple are converted to 2.2 V and digitised by ICL 7109 ADCs.The program converts the thermocouple e.m.f. to temperature via a polynomial equation, calculates the rate of change of mass and temperature with respect to time by a smoothing procedure,”S and then prints mass, rate of change of mass, temperature and rate of change of temperature. Another version logs mass and temperature and stores the figures in a buffer. When the buffer is full, the computer starts the cassette tape, stores the buffer contents and stops the tape again. The buffer then refills. A much larger program to analyse kinetics by the non-isothermal method is held on another AIM 65, with extra memory to make up 36K of RAM.This program reads back the data from the cassette tape, carries out a complete analysis for activation energy and pre-exponential factor and finds the best equation to fit the data. If the microcomputer is to be dedicated to one piece of equipment and up to three standard programs, then the storage of programs on a cassette tape can be dispensed with and the program put on EPROMS (Erasable Programmable Read Only Memories), which plug in on the board or extension sockets. References 1. West, S., and Nunneley. F.. Interactive (Rockwell International Annaheim), 1981 (No. 5). 6. 2. Pelco (Electronics) Ltd.. 26/27 Regency Square, Brighton, Sussex. 3. Portable Microsystems Ltd., 18 Market Place, Brackley, Northants. 4. Heal, G. R . , and Openshaw, J .D.. Micro. 1981, 41 (October), p. 100. 5. Heal, G. R., in Dollimore, D . . Editor, “Proceedings of the 2nd European Symposium on Thermal Analysis, 6. Savitzky. A. and Golay, M. J . E.. Anal. Chem., 1964, 36, 1627. 7. Steiner, J . , Termonia, Y., and Deltour, J . . Anal. Chem., 1972.44, 1906. 8. Madden, H. H . , Anal. Chem.. 1978, 50, 1383. Aberdeen, 1981”, Heyden, London, 1981. p. 72. On-line Microcomputer System for Simultaneous Thermal Analysis - Mass Spectrometry P. A. Barnes, *S. €3. Warrington Chemistry Section, School of Health and Applied Sciences, Leeds Polytechnic, Calverley Street, Leeds, LS1 3HE and S. W. Taylor Computer Unit, Leeds Polytechnic, Calverley Street, Leeds, LS1 3HE The use of a mass spectrometer (MS) with thermal analysis equipment dates from the pioneering work of Langer and Gohlke.1 Since then the advantages of the simultaneous use of these techniques have become so widely appreciated that it is not uncommon for the cost of what used to be regarded as a mere specific gas detector to very considerably exceed that of the thermal analysis equipment to which it is connected.The powerful combination of TA - MS can be used for chemical analysis, to study the behaviour of complex materials on heating and to investigate the kinetics of decomposition processes. The equipment used has been described previouslyz.3 and was developed for all three purposes (Fig. 1). However, it is in the context of the analysis of kinetic results that the application of on-line data acquisition becomes important. In essence the problem is to store and process the very large amounts of information that can be produced in a very short period of time from the mass spectrometer and the thermal analysis system.* Present address: Stanton Redcroft Ltd.. Copper Mill Lane. London. SW17 OBN.March, 1984 TG 750 USE OF COMPUTERS IN THERMAL ANALYSIS DTA Micro- furnace 67 1 B & 674 99 Fig. 1. Schematic arrangement of the TA - GC - MS system. Data Acquisition and Processing System The previous system for recording data involved a 6-channel x - r recorder to monitor the 4 channels of the MS operating in the selected-ion monitoring (SIM) mode. Whilst this was satisfactory as a recording medium, each trace was offset in the x direction to enable the recorder peFs to pass each other.This caused slight errors in relating events on the different traces, a great deal of inconvenience in interpretation and a loss in accuracy as the peak areas were measured manually. In order to overcome, or at least reduce, these problems the following system was developed. Firstly the number of channels was increased to eight to allow further information to be stored. The nominal accuracy of the chart recorder used is 0.25% f.s.d. or 1 part in 400. By using a 12-bit analogue to digital converter (ADC), the potential accuracy is increased over 10-fold to 1 part in 4096. The maximum sampling rate of the ADC used is 500 Hz, which means that far more results can be obtained so that the experimental curves can be defined more accurately. Furthermore, experiments of very short duration (1 s) can be studied in theory, although the requirement of reaching reaction temperature in a small fraction of the total reaction time results in a practical minimum time of approximately 10 min.The high sampling rate can still be of benefit, however, as the signal can be averaged to reduce the effects of noise. There is provision in the software for averaging any specified number of readings, each taken at 500 Hz. In addition, it is possible to choose the interval between these averaged readings so that no matter what the length of the experiment, the appropriate number of points required to define the kinpit curves adequately can be obtained. In a typical instance, this gives perhaps 500 points, each beifig an average of 20 individual readings. The ADC provides a choice of input levels covering 50 mV to 10 V and these, as well as uni- or bipolar input, are selected via the software.As the CBM 4032computer is an %bit machine the control program for the 12-bit ADC was not straightforward and was therefore written in 6502 ASSEMBLER language, as was the link program to the Honeywell mainframe computer. The CBM 4032 has 32kbytes of RAM, which means that in principle some 8 000 data points can be stored for each experiment. The number can be increased, of course, by dumping to disc during a run. The data storage medium, floppy discs, was determined by the capacity and read - write speed requirements, which ruled out the use of tape. Cost considerations militated against a hard disc and the Commodore 4040 twin disc drive was therefore chosen.This provides 170 kbytes on each single-sided 5%in disc. The twin unit facilitates the making of back-up discs. which is essential. The CBM 4032 microcomputer has been fitted with a high resolution board (300 x 200 pixels), which enables the results to be displayed as raw data, a-time curves or as processed by the usual solid-state decomposition kinetic equations. A hard copy can be obtained of the high-resolution screen using an Epson MX80 I1 printer. The results can also be sent to a Honeywell 66 mainframe computer for true high resolution plotting using the standard G I N 0 package. Conclusions A versatile system has been developed. using commercially available units. It has proved reliable in use, has saved a great deal of time, once commissioned. and has enabled far more detailed and accurate anaivsis of kinetic data to be performed than was possible previously.With minor modifications it could be used to process results from almost any instrument.100 USE OF COMPUTERS IN THERMAL ANALYSIS 1 0 0 0 Om. Anal. Proc., Vol. 21 output matching unit Mass signal 0 0 0 References 1. 2. 3. Langer, H. G . , and Golhke, R. S., Anal. Chem., 1963, 35, 1301. Barnes, P. A . , in Wood, J . , Lindquist, O., Helgesson, C.. and Vannerberg. N . , Editors, “Reactivity of Solids Barnes, P. A., Stevenson, E., and Warrington, S. B . , J . Thermal. Anal., 1982, 25, 299. (Proceedings of the 8th ISRS),” Plenum Press, New York, 1977. Balance 1 Start ] Cold A Furnace junction T T 1 T - Furnace T a L h I r a I ‘ Controlled I Computer Controlled Thermobalance D.C. Kilioh Materials Research Department, Cement and Concrete Association, Slough, SL3 6PL The construction of a computer controlled thermobalance based on a Stanton Redcroft TG 750 furnace, a CI Electronics microbalance and a Data General Nova 2 computer is described. The computer acts as furnace controller, data logger, calculator and plotter. The heating regime is under program control and TG and DTG curves are produced automatically. The decision was made some years ago to build a computer controlled thermobalance to replace older equipment and to provide a thermobalance that would give more flexibility in controlling the heating regime. The over-all aim of the operation was to improve the quantitative analysis of hydrated cement samples. At the time commercial systems either did not supply the facilities required or were too expensive.Program 7r The Apparatus The CI Electronics Mark 2C electrobalance has a total capacity of 1 g with a repeatability of k0.5 pg; used with the standard control box it gives 500-mV output for full scale deflection. This is then reduced Ah Scanner power - 0 ,, Thyristor Volts controller power A X - Y plotter Voltmeter Nova +q Discstore 2 Fig. 1 . TGA - computer interconnections. adj. , T I Analogue Controlled voltage volts outMarch, 1984 USE OF COMPUTERS IN THERMAL ANALYSIS 101 to 1U mV by using the manufacturer's Universal Matching circuit. Normally a 20 mg sample is weighed on the 25-mg scale and the mass loss measured on the 10-mg scale.The balance mechanism is arranged in a gas-tight bell-jar above the furnace. The sample pan is suspended in the furnace 250 mm below the beam. The Stanton Redcroft TG 750 furnace is continuously water cooled, has a maximum operating temperature of 1 000 "C and a maximum heating rate of 100 "C min-1. It has a very fast response time and will attain isothermal conditions within a few seconds. The atmosphere normally used is dry nitrogen (upward flow): however, other gases can be used provided corrosive agents are not allowed to enter the balance bell-jar. The furnace wall temperature is monitored by a nickel - chromiumhickel - aluminium type K thermocouple, and the sample temperature by a 13% platinum - rhodium/platinym thermocouple on a fixed plate 0.5 mm below the sample pan.The furnace is heated via a suitable transformer by a Eurotherm thyristor power controller, which in turn is controlled by the minicomputer. The data logging system consists of a multi-channel scanner with separate channels for mass, furnace temperature, sample temperature and voltage signals, the output of which goes to a Solartron digital voltmeter reading k 16 mV to 1 yV resolution. This corresponds to k 1 pg for the mass scale, 0.025 "C for the furnace thermocouple and 0.1 "C for the sample thermocouple. The maximum logging speed for this resolution is 10 s-1, but in practice the logging on all channels occurs within 0.4 s once every 4 s. The computer system is controlled by the Nova 2 minicomputer. The speed of the central processor unit and its ability to operate under interrupt control make multi-tasking for the thermobalance and other equipment possible. (The computer controls and logs five other completely separate experiments simultaneously.) The computer has 64 kbytes of 16-bit word core memory and operates using ASSEMBLY and BASIC languages.A 44 k configuration of the operating system (DG Standalone operating system), BASIC compiler, logging and output routines leaves 20 k for BASIC programs. The mV signals are stored in 15 bits (k 16 383), and 64 readings are buffered in memory for each channel before being transferred to floppy disc. The interconnection of the various parts of the apparatus is shown in Fig. 1. Program and Output of Results After taking the initial mass of the sample, setting the heating rate and the maximum temperature and setting up the gas flow, the program enters the 4-s control loop. On each scan the thermocouple -0. C m z m . rn 2 -0.: r" 0 UI -0.: 1 100 200 300 400 500 600 700 800 Sample temperaturePC Fig. 2. Plotter output, showing curve for a hydrated Portland cement. Heating rate, 2°C min-l.102 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS Anal. Proc., Vol. 21 millivolts are converted to temperatures by using an interpolation routine and values from the appropriate British Standard (these values are stored on disc). The difference between the furnace temperature and the computed set point is the input to the software proportional controller, which controls the numerical value given to a digital to analogue converter. This in turn outputs a 2 10 V signal to the thyristor power controller linked to the furnace. The sample temperature is computed using a polynomial fit to a calibration graph of sample temperatures versus plate temperature obtained by prior experiment using ICTA calibrated magnetic samples.' Values of mass and temperature are printed out every minute on a printer and stored on disc throughout the run (about 6 000 readings for 730 "C at 2°C min-I). These values are plotted out at the end of the test (Fig. 2). The DTG curve is obtained by straight-line regression of 64 values (about 8 "C) of mass and corrected sample temperature; the line is drawn point to point. The apparatus is very adaptable with respect to the heating regime and to data processing; the former can readily be changed to suit any test programme, e.g., non-linear or bi-linear heating rates, isothermal steps, etc., and this promises to be its major advantage. Reference 1. ICTA-Certified Reference Material (GM 761). National Bureau of Standards, Washington, DC, USA.

ISSN:0144-557X    

DOI:10.1039/AP9842100091

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

102 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS Anal. Proc., Vol. 21 Applications of Atomic Spectroscopy to Environmental Analysis The following are summaries of four of the papers presented at a Joint Meeting of the South East Region and the Atomic Spectroscopy and Automatic Methods Groups held on February 16th, 1983, at the Occupational Medicine and Hygiene Laboratories, Health and Safety Executive, Cricklewood, London. The Application of Automated X-ray Spectrometry to Environmental Analysis N. G. West Health and Safety Executive, Occupational Medicine and Hygiene Laboratories, 403 Edgware Road, London, Nw2 6LN Introduction Over the past decade, X-ray spectrometry has been used widely for the analysis of both air and water samples in the environmental field.' Its range of application and the techniques used for sampling are illustrated in Fig. 1.In all instances, the sampling procedure fulfils two vitai functions in relation to the WATER AIR Suspended Gaseous Suspended Dissolved particulates contaminants particulates i sor Filtration Precipitation/ nge Filtration t d,// Adsorption/ r . . . . . ............................... Thin deposit on filter substrate Application of X-ray spectrometry in environmental analysis. Fig. 1. subsequent analysis by X-ray spectrometry. Firstly, it acts as a pre-concentration stage for the contaminants in the air or water sample: without pre-concentration, the X-ray spectrometry technique is insufficiently sensitive for most environmental analyses. Secondly. it provides a means of presentingMarch, 1984 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS 103 the sample to the spectrometer in a convenient form, as a deposit on a filter paper or similar substrate.Providing the deposit is “thin” (low mass per unit area), then X-ray spectrometry is, in-many respects, the ideal analytical technique. The filter deposit can be analysed directly with no sample preparation and multi-elemental data obtained rapidly and non-destructively. This may be contrasted with other atomic-spectrometric techniques, such as atomic-absorption spectrometry or inductively coupled plasma emission spectrometry, which require complete dissolution of the sample and are therefore much more costly in terms of staff time. Theoretical Considerations An understanding of certain basic theory is necessary if the spectroscopist is to avoid a number of potential pitfalls in thin specimen analysis by X-ray spectrometry.The relationship between the secondary X-ray intensity ( I ) and the mass fraction ( C ) of an element in a sample of thickness d is given by: 1 - e-pd . . . . . . . . . . . . I = kC (7) (1) 1.1 = pp cosec q, + p, cosec W2 where k is a calibration constant, p, and ps are the mass absorption coefficients for primary and secondary radiation, I ) ~ and v2 the incident and take off angles and p is the sample density. For homogeneous thin specimens, the product ppd is very small, and by series expansion: hence e-Fpd x 1 - ppd i = k C p d . . . . . . . . . . . . Equation 2 represents a linear relationship between the secondary X-ray intensity and the mass of the element per unit area (Cpd).It is important to realise that the relationship is independent of the mass absorption coefficient of the sample and the analysis is therefore not subject to matrix effects. The limiting condition for this approximation to hold within 5% is given by ppd d 0.1. This is commonly referred to as the thin specimen criterion.* It has been assumed in this simple theory that the sample is homogeneous, but in practice this is not generally the case for filter deposits. Most deposits consist of discrete solid particles and are therefore inhomogeneous, making it necessary to consider two further effects, penetration of particles into the filter matrix, resulting in absorption of radiation by the matrix, and absorption of radiation within the individual particles forming the deposit, i.e., a particle size or composition effect. The first of these two effects is very much more severe for a high atomic number matrix depth filter than for a low atomic number matrix screen filter. In practice, this means that whenever possible, an organic membrane or Nuclepore filter should be chosen in preference to a glass fibre filter.This has the added advantage that the metal contamination levels are generally very much lower than in glass fibre filters. If a depth filter is considered essential for a particular application then absorption correction procedures have been developed for the analysis .3 Particle size effects can be accommodated by using a modified version of equation 2 which includes an attenuation factor, A .. . . . . . . . . . . i = A k C p d (3) This equation applies to particulate deposits, which either meet the thin specimen criterion or are in the form of monolayers. There are a number of algorithms in the literature that may be used to calculate A for a given particle size and composition. The most convenient to use in practice for the prediction of particle size effects is that due to Criss4 1 A=-------- (1 +ba)2 . . . . . . . . . . . . (4) where a is the particle diameter and b a calculated coefficient related to the mass absorption coefficient of the particle. One further feature of filter analysis by X-ray spectrometry, which can result in serious analytical errors, is the effect of variation in secondary X-ray sensitivity across the exposed area of the filter.If the variation is significant then errors will arise unless both standards and unknown samples have the same104 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS Anal. Proc., Vol. 21 pattern of deposition over the filter. Problems are commonly found when attempting to analyse non-uniformly deposited unknowns by using uniformly deposited standards. Applications Three examples of the use of X-ray spectrometry in environmental analysis have been chosen to illustrate the range of application of the technique. Two examples are from work carried out at the Occupational Medicine and Hygiene Laboratory, London, and the third based on a published paper from the US Naval Research Laboratory, Washington, DC. Monitoring Toxic Metal Particulates in Workplace Air The sampling of factory atmospheres is carried out by HM Factory Inspectorate to ensure that workers are not exposed to unacceptably high levels of airborne toxic substances. The main source of guidance for occupational hygienists in assessing conditions in a factory is the list of Threshold Limit Values (TLVs) published annually by the American Conference of Governmental Industrial Hygienists.5 The TLVs refer to airborne concentrations of substances and represent conditions under which it is believed nearly all workers may be repeatedly exposed without adverse effects.Samples presented to the laboratory consist of thin particulate deposits on 25 mm diameter organic membrane filters and an analysis may be requested to determine any of twenty toxic metals, e.g., arsenic, cadmium or platinum. The filters are analysed directly on a Philips PW1450 X-ray spectrometer using a molybdenum primary X-ray tube, the optimum choice for the range of emission lines measured.For the noble metals, gold, silver, rhodium and platinum, a sputtering technique is used to prepare calibration standards, but for other metals a variant of the puff6 technique is preferred. A dust cloud of known composition is generated in a small glass dust chamber and sampled with the same equipment as used in the factory, The deposit collected on the filter is accurately weighed on a microbalance to provide a standard. For most applications it is important that particle size effects are very small (<5%) in the standard filter deposit.This is achieved by checking the particle size distribution by optical or electron microscopy and assessing it in terms of calculated particle size effects. Examples of such calculations based on equation4 are given in Table I; this procedure is analogous to the calculation of the thin specimen criterion for the sample matrix. The average particle size of the deposit can be reduced, if required, by increasing the time allowed for the dust to settle prior to sampling. TABLE I SECONDARY X-RAY INTENSITY DUE TO PARTICLE SIZE EFFECTS Molybdenum target primary X-ray source. Compound Emission line Particle diametedpm MAXIMUM LIMITING PARTICLE DIAMETERS FOR 5% REDUCTION IN 0.7 2.7 PbO;? LB c r 2 0 3 KCY CdO KCY 5.7 LCY 0.4 ZnO K a 2.9 c0304 KCY 2.6 On the basis of the figures given in Table I, it might be expected that particle size effects would limit the application of the X-ray spectrometry technique.The limiting particle diameters are small and there is no simple method of applying corrections to real samples whose particle size distribution and minerology are unknown. However, extensive comparison of X-ray spectrometry and atomic- absorption spectrometry results on workplace samples has shown that, in practice, particle size effects are not significant for the K emission lines of elements with atomic number >19(potassium) or for the L emission lines of the very heavy metals ( e . g . , lead). For metals with atomic number in the range 40 to 56 it is necessary to measure both the K and L lines to cover the full analytical range since the K line is insufficiently sensitive to determine very low levels.The normal procedure is for the K line result to be accepted at levels above three times the detection limit for the K line and the L line result to be used at lower levels. The L line may be subject to considerable particle size effects (-do%), but these are generally not of great significance at low concentrations. Table I1 lists the detection limits for a number of metals covering a range of atomic number. In all instances, apart from the cadmium Kar emission line, it is possible to determine airborne concentrations as low as l/lOth TLV on a 120-1 air sample.March, 1984 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS 105 TABLE I1 DETECTION LIMITS Detection limit/pg Detection limit/m m-3 1/10TLV/ Element Emission line (25-mm filter) ( 120-1 sample! mg m-3 0.60 0.005 0.015 1.24 0.01 0.005 Cd KCY La 0.16 0.001 3 0.005 Zn KIX 0.58 0.005 0.5 co KCY 0.24 0.002 0.005 Pb LP Detection limit = 3.290,.- I .*’ * un-, = Standard deviation of results obtained on 24 blank filters.Monitoring Soluble Trace Elements in Natural and Waste Waters It has generally been assumed that atomic-absorption spectroscopy and inductively coupled plasma emission spectroscopy are unrivalled for the analysis of soluble trace elements in water because the sample can be introduced directly into the instrument. However, when sampling relatively remote sites, rivers, lakes, reservoirs, etc., then transport of the water samples to the base laboratory can cause problems.In particular, there may be cross-contamination between the container and the sample and also the physical bulk of the sample presents difficulties. It has been proposed by Panayappan and co-workers8 that these problems can be circumvented by carrying out a simple sample preparation procedure on site, such that the soluble elements are returned to the laboratory in the form of a precipitate on a filter. Providing the precipitate conforms to the thin specimen criterion, then X-ray spectrometry becomes competitive with other techniques in terms of analytical performance and convenience. The recommended precipitation procedure consists of adding solutions of polyvinylpyrrolidone and thionalide to a 250-ml sample of the water. The advantage of this combination of precipitants over ion exchange resins or other precipitating agents is that the presence of high concentrations of calcium and magnesium in natural waters does not interfere with the precipitation of the trace elements.The detection limits obtained for a range of trace metals and metalloids are comparable with those which can be achieved by using inductively coupled plasma emission spectrometry. 0 I I I I 2 4 6 8 Exposure, TLV-hou rs 10 Fig. 2. Calibration plot for arsine using a diffusive sampler. Standard atmosphere concentrations: X. $ TLV; 0 , 1 TLV; +, 2 TLV; m, 4 TLV. TLV for ASH, = 0.16 mg m-3.106 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS Anal. Proc., Vol. 21 Monitoring Gaseous Contaminants in Workplace Air This is a relatively new field of application for the technique but one which holds considerable potential with regard to monitoring long term average concentrations of inorganic gases, such as arsine, hydrogen sulphide and mercury vapour.It may also be applied to the measurement of organic vapour contaminants, providing the organic species contains an element of atomic number >8. For presentation to the spectrometer, it is necessary to adsorb the gas on to a suitable substrate, either charcoal cloth, in the case of organic vapours. or reagent-impregnated papers. for the inorganic gases.9 The established method of sampling requires a pump to draw air through the adsorbent, but in recent years an alternative has been developed in the form of the diffusive sampler. These devices sample by gaseous diffusion and are particularly suited to monitoring personal exposures of workers in that they do not need a heavy and expensive sampling pump.The combination of diffusive sampling with direct analysis of the substrate by X-ray spectrometry offers a very simple sampling and analysis procedure. Calibration standards are prepared by exposing the diffusive samplers in a standard atmosphere of the contaminant and an example of a calibration plot for the determination of arsine (AsH3) by measurement of the arsenic Kar emission line is shown in Fig. 2. Exposure is assessed in TLV-hours (Le., exposure for 1 h at a concentration level equivalent to the TLV) and it can be seen that the relationship is linear up to at least 10 TLV-hours. Conclusions X-ray spectrometry is well suited to the analysis of most types of environmental samples, providing the correct sampling procedures are adopted. For many applications it has a clear advantage over other atomic-spectrometric methods in terms of the simplicity of the analytical procedure.1. 2. 3. 4. 5 . 6. 7. 8. 9. References Dzubay. T. G.. Editor, “X-ray Fluorescence Analysis of Environmental Samples,” Ann Arbor Science. Rhodes. J. R.. Pradzynski. A.. Sieberg, R. D.. and Furuta. T.. in Ziegler. C . A., Editor, “Application of Adams, F. C., and Van Grieken, R. E.. Anal. Chem.. 1975, 47. 1767. Criss, J. W.. Anal. Chem., 1976. 48. 179. American Conference of Governmental Industrial Hygienists, “Threshold Limit Values for Chemical Leroux, J . , Stauh-Reinhalt. Luff, 1969. 29, 19. Currie, L.A.. in Dzubay. T. G.. Editor. “X-ray Fluorescence Analysis of Environmental Samples.” Ann Panayappan, P., Venezky. D. L., Gilfrich, J . V., and Birks. L. S.. A n d . Chem., 1978. 50, 1125. West. N. G.. Purnell. C. J . . Brown. R. H., and Withers, E., in Russ. J. C.. Barnett. C. S.. Predecki. P. K., and Leyden, D. E., Editors, ”Advances in X-ray Analysis, Volume 25.“ Plenum Press, New York. 1982, 1977. Low Energy X- and Gamma Rays.’‘ Gordon and Breach, New York. 1971, pp. 317-333. Substances and Physical Agents in the Work Environment.” ACGIH, Cincinnati. OH, USA, 1981. Arbor Science. 1977. pp. 289-306. pp. 181-187. Automated ICP-Atomic-emission Spectrometry-its Application to the Work of the Health and Safety Executive A. M. Howe and C. J. Jackson Health and Safety Executive, Occupational Medicine and Hvgiene Laboratories, 403 Edgware Road, London, NW2 6LN A variety of atomic-spectrometric techniques are available at the Occupational Medicine and Hygiene Laboratories (OMHL) for the analysis of occupational and environmental samples of interest to the Health and Safety Executive (HSE).These techniques include atomic-absorption spectrometry (AAS), inductively-coupled plasma atomic-emission spectrometry (ICP - AES) and both energy- dispersive and wavelength-dispersive X-ray fluorescence spectrometry (ED- and WDXRF). This paper discusses the applicability of one of these, namely ICP - AES. with particular reference to work undertaken for the Factory and Industrial Air Pollution Inspectorates of HSE in respect of: the evaluation of workplace exposures to metal dusts, fumes and vapours; the analysis of factory stack emissions; and the analysis of a wide variety of bulk materials associated with problems related to the working environment.March, 1984 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS ICP - Atomic-emission Spectrometry 107 In order to make use of the classical technique of atomic-emission spectrometry (AES) for elemental analysis, it is desirable to use an excitation source that has the attributes of high sensitivity, good stability, sufficiently high excitation temperature to produce emission lines from a large number of elements, minimal interferences (spectral, chemical, ionization or contamination), good reproducibil- ity and convenience of operation. In addition, it is necessary to use a spectrometer that has good resolution, high optical efficiency, stability, wide spectral range, appropriately selected fixed analyte lines or the ability to slew rapidly to operator selected lines, and adequate data reduction facilities for the production of analytical results appropriately corrected for interference effects as necessary.Conventional arc and spark sources, combined with direct reading polychromators, have many of these attributes, and have been used for many years for the analysis of suitably prepared solid samples in, for example, the steel industry. However, such sources are of little practical use for the analysis of the wide range of environmental samples that are either in liquid form (water, biological fluids, etc.), or exist as dusts, fumes or vapours, which have been collected into a suitable absorbing solution or on to some form of solid support (membrane filter, glass-wool pad or solid-adsorber tube).The development of various plasma sources has transformed this situation as these are best suited to liquid or gaseous sample presentation. Whilst three different mechanisms have been used to generate plasmas suitable for analytical use, namely inductive coupling,’ d.c. arc2 and microwave induction,3 it appears that the inductively-coupled plasma is by far the most versatile. Following the development of the inductively-coupled plasma by Reed’s in the early 1960s it was realised that this device offered attractive possibilities for the vaporization, atomization and excitation of solution samples injected into it.Greenfield.6 in the UK, and Fassel,’ in the USA, independently developed the argon plasma source into a form suitable for use as an analytical device. Relatively poor detection limits were quoted in Greenfield’s and Fassel’s pioneering work in the mid-l960s, but since then quite dramatic improvements in performance have been reported. These improvements have resulted primarily from progressive refinements in the reduction of electronic interference. improvements in impedance matching and better production and injection of sample . aerosols into properly shaped plasmas.8 It is now generally accepted that for most elements as good, or in many cases better, detection limits are obtainable on real samples for compromise simultaneous analysis by ICP - AES than by flame AAS.Specification of OMHL’s ICP - Atomic-emission Spectrometer The ICP - emission spectrometer in use at OMHL consists of a 37-channel Bausch & Lomb ARL34000C vacuum polychromator with an air-path 1 m scanning monochromator linked into the 38th channel. The ICP source unit, which is of Bausch & Lomb design, is a 2.5-kW, 27.12-MHz crystal-controlled system. The spectrometer, together with a 250-capacity Gilson autosampler, continuous hydride unit and off-peak correction unit (SAMI), is under the control of a DEC PDP 11/03 microprocessor-based computer system. Because the spectrometer is used for a very wide range of analyses, considerable effort was expended in selecting the analyte channels. The major factors that had to be considered were: the need to maximise sensitivity for those elements of greatest environmental significance; the need to limit spectral interferences from those elements likely to be present at the highest concentration; and the need to cover elements in metallurgical samples, slags and drosses, etc., and in standard fusion fluxes.To a large extent these requirements have been met; the analytes chosen together with their wavelengths, and detection limits (in 10% perchloric acid) for simultaneous operation are indicated in Table I. The relatively poor performance of arsenic, antimony, selenium and tellurium will be noted; for these elements recourse is made to hydride generation when trace levels are being determined. The choice of line for magnesium and calcium was governed by the fact that the most sensitive lines are too sensitive; trace levels of these elements are of little significance but there is often interest in percentage levels in a range of bulk samples.Applications of ICP - AES at OMHL Sample Preparation and Analysis Procedure The majority of samples received for ICP - AES analysis require acid dissolution or alkaline fusion, and to overcome transport effects associated with physical factors, such as viscosity and density, it has108 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS Anal. Proc., Vof. 21 proved desirable either to adopt dissolution procedures where the final acid strength is adjusted to a known value, or to make use of internal standardization procedures. TABLE I RESULTS OBTAINED WITH BAUSCH g, LOMB ARL34000C Detection limits are reported for compromise simultaneous operation in 10% perchloric acid.ICP - ATOMIC EMISSION SPECTROMETER IN OMHL Detection limit (2a)l Element Wavelength/nm ng ml-1 328.07 3.9 308.21 13.7 193.70 35.9* As I B I 249.68 28.2 Ba I1 455.40 0.4 Be I1 313.04 0.1 Bi I 223.06 32.0* C I 193.09 17.4 Ca I1 317.93 5.9 Cd I1 226.50 3.4 c o I1 228.62 1.8 Cr IT 267.72 2.0 c u I 324.75 1.7 Fe IT 259.94 1.5 Hg 1 184.95 4.6 K I 766.49 71.9 Li I 670.78 1.4 Mg I1 279.08 19.4 Mn I1 257.61 0.5 Mo I1 281.62 5.3 Na I 589.00 24.9 Ni I1 231.60 7.0 P I 178.29 37.1 Pb I1 220.35 28.7 Pd I 360.96 19.2 S I 180.73 36.9 Sb I 206.83 52.9* Se I 196.03 92.9* Si I 288.16 13.9 Sn 11 189.90 16.3* Te I 214.28 46.0* Ti I1 337.28 5.0 TI I1 190.86 238 v I1 311.07 2.3 w I1 239.71 17.8 3 ; Zn Ii Zr 11 202.55 343.82 4.7 3.7 * Detection limits can be improved by the use of hydride generation techniques.For the former approach, experience has shown that a final composition of 10% perchloric acid is ideal and, where appropriate, samples are prepared and analysed in this acid. Too close an adherence to this procedure can cause certain problems. Some elements, especially when present in significant amounts, hydrolyse and precipitate (e.g., molybdenum, silicon and tin). Others, such as arsenic and antimony, may be volatilized (depending on oxidation state, anions present, etc.). In such instances, and where fusions are necessary, the dissolution technique employed necessarily involves work-up into a different acid and/or acid strength; indeed, the latter may be unknown if substantial amounts of acid have been boiled off.In these instances the procedure adopted has been to use an internal standard to compensate for these effects; beryllium is selected for this purpose as the emission line at 313.0nm shows all of the characteristics required of an internal standard line. It suffers from virtually no spectral interferences, it is very sensitive, so that only a small concentration need be added, and it is very rarely found in a sample in which it is not expected.March, 1984 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS 109 Spectral interferences are a further factor that needs to be considered. Such interferences occur when spectral lines overlap, or when an intensity shift occurs due to recombination of electrons and ions.Corrections can be applied either using factors generated by nebulizing pure element solutions (on-peak), or by off-peak measurement of the intensity shift. The occurrence of significant interferences in occupational and environmental analysis is fortunately uncommon; nevertheless, corrections are built into the data reduction programs and applied as necessary. Applications At OMHL, ICP - AES is used for the analysis of a very varied range of sample types. Some of the more important of these, in the field of occupational and environmental analysis, are: membrane filters and glass-wool pads (analysed to determine Al, Be, Mg, Na. etc.); impregnated filters (Hg); cellulose thimbles and cotton-wool pads (As, Cd, Mo, Pb, Se, Sn and Zn); solid-adsorber tubes (Hg); impactor samples (Cd, Ni and Pb on A1 foils): cyclone wash liquors (Cd and Pb); wipe tissues (Be); bulk samples (from electrostatic precipitators or bag-houses; from cyclones; raw materials, process chemicals, and waste products; paints and glazes for “soluble” metal content; together with a variety of materials associated with environmental and occupational investigations).In passing it should be noted that WDXRF is used for the analysis of the majority of relatively straightforward samples of airborne particulate matter collected on membrane filters or glass-wool pads.9 As little or no sample preparation is required, this is the most cost-effective technique for such analysis. A particular advantage of the multi-element capability of the ICP-AES system is its ability to produce data concerning analytes other than those specifically requested.This is something that would not normally be obtained when analysis is carried out using WDXRF or AAS and has proved to be a useful service for our customers. A specific example of this is concerned with stack sampling of emissions of molybdenum. Several works are monitored regularly, and until recently only this element has been requested for determination. However, since ICP - AES has been introduced, significant levels of arsenic, selenium and tin have been noted in addition to molybdenum. A typical set of results obtained is shown in Table 11. As a consequence of this additional facility, arsenic and selenium are now requested as a matter of course in these samples.TABLE I1 ANALYSIS OF STACK EMISSIONS FOR MOLYBDENUM, ARSENIC AND SELENIUM, SAMPLED BOTH ON CELLULOSE THIMBLES AND COTTON- WOOL PADS MO/PLg As/!% Sampled on cellulose thimbles (1 ft3 air volume)- 10 23 21 11 20 24 31 530 4 6OO Sampled on cotton-wool pads (1 ft3 air volume)- 2 800 50 39 31 19 22 59 45 23 6 13 13 8 c4 6 Sell@ 150 20 20 60 170 130 280 590 230 230 120 160 Quality Control Quality control is very important in any analytical department and OMHL’s procedures fall into three types. Firstly, instrumental quality control is monitored by running a known reference solution at regular intervals throughout a sample run. This can be particularly important as up to 250 samples can be taken by the autosampler. By using this method instrumental drift is monitored and, if necessary, a run can be aborted or the data drift-corrected.110 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS Anal.Proc., Vol. 21 Secondly, internal quality control covering the whole sample preparation and analysis procedure is achieved by utilizing reference samples, where they are available, and monitoring the result against the certified value. This is of most relevance to bulk samples, such as slags, drosses, paint samples, etc. Thirdly, OMHL participate in both a HSE quality control scheme and the National Institute of Occupational Safety and Health (NIOSH) PAT scheme. *O Both involve membrane filter analysis; OMHL and HSE’s seven regional laboratories take part in the HSE scheme, and some 300 laboratories world-wide participate in the NIOSH scheme.The latter involves the analysis of four filters, each separately treated with varying levels of cadmium, lead and zinc standard solution; data are compared with the mean result obtained by about 75 reference laboratories (after any outliers have been adjusted). OMHL’s over-all performance, illustrated in Table 111, is considered to be most acceptable. TABLE I11 PERFORMANCE OF OMHL IN NIOSH PAT SCHEME. SAMPLES ANALYSED UNDER COMPROMISE SIMULTANEOUS CONDITIONS IN 10% PERCHLORIC ACID For round 71- OMHL data/ Analyte Cd 12.1 18.5 12.9 6.5 Pb 77.6 56.5 35.7 60.5 Zn 181.0 104.5 80.9 124.3 Mean data for rounds 65-6917 1-72- Mean OMHL levell Mean NIOSH Analyte Pg reference level/pg 11.6(4 44.0(6] 140.9 :::$:{ Cd Pb Zn 141.3 * Based on data from about 75 reference laboratories.NIOSH reference value*/pg 12.0 18.5 12.8 6.5 77.0 55.5 35.3 60.3 178.3 104.3 81.8 124.6 Mean of individual OMHL/NIOSH ratio (+lo). % 99.55 t 2.08 99.87 k 1.73 99.90 k 4.75 Conclusions Although purchased with the need to undertake a wide range of metallurgical analyses very much in mind, ICP - AES has been successfully applied to the analysis of occupational and environmental samples and has some positive advantages over alternative techniques. References 1 . 2. 3. 4. 5. 6. 7. 8. 9. 10. Greenfield. S . . McGeachin, H. McD.. and Smith. P. B.. Talanta, 1976. 23. 1. Greenfield, S . , McGeachin. H. McD.. and Smith. P. B.. Tulanta, 1975. 22, 1. Greenfield. S.. McGeachin. H. McD.. and Smith. P. B.. Talanru, 1975.22. 553. Reed, T. B.. J. Appl. Phys., 1961, 32. 821. Reed, T. B.. J. Appl. Phys.. 1961. 32. 2534. Greenfield. S . . Jones, I. L.. and Berry. C. T.. Analyst, 1964, 89. 713. Wendt. R. H.. and Fassel, V. A.. Anal. Chem., 1965. 37, 920. Fassel. V. A.. Pure Appl. Chem., 1977. 49. 1533. West, N. G.. Anal. Proc., 1984, 21. 102. Schlecht, P.. and Shulman. S.. “Proficiency Analytical Testing Program Statistical Protocol,” NIOSH. Cincinnati. OH, USA. 1982.March, I984 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS 111 Automated Atomic-absorption Spectrometry in Occupational Health Monitoring N. J. Smith Health and Safety Executive, Occupational Medicine and Hygiene Laboratories, 403 Edgware Road, London, NW2 6LN A study of the literature shows that in occupational health monitoring atomic absorption, and more particularly graphite furnace atomic absorption, is finding ever greater use for the analysis of toxic metals in biological samples.This approach to the analysis, coupled with automated sampling, brings the advantages of improved precision and unattended operation. Part of the work at the Occupational Medical Laboratory of the Health and Safety Executive is concerned with the biological monitoring of workers exposed to a range of toxic metals. The analysis of lead and cadmium in blood is a heavy routine commitment and this is handled by automated atomic absorption with electrothermal atomisation. However, with arsenic and mercury, use has been made of continuous flow and HPLC techniques for the automated analyses of these elements.The development of these techniques has been in parallel with the introduction of quality control procedures and the improvement in performance resulting from automated techniques has been validated by participation in external quality assurance programmes. Lead is a ubiquitous element, and of the heavy metals known to be toxic to man it is the one that has been most studied. For those exposed in industry, the determination of blood lead is a good index of current exposure. Its determination in blood has developed from colorimetric procedures, through Delves cup techniques employing flame atomic absorption, to the use of automated graphite furnace atomisers. In the Health and Safety Executive laboratories, a technique used for some time was the labour-intensive punched paper disc method. in which blood spotted on to filter paper was allowed to dry and then discs were punched out and placed in a graphite cup in an atomic-absorption instrument for lead determination.The imprecision in the method was largely due to variability of the paper. This method has since been replaced by a liquid sampling procedure, whereby whole blood is diluted by a Triton X-100 - nitric acid mixture and 2 0 4 sample aliquots are used for analysis. This has allowed a manual method to be replaced by a sophisticated atomic-absorption system, with automated sample handling facilities giving good quality control. In addition, the use of a modern programmable diluter makes the crucial stage of sample aliquotting and diluting operator independent.Furthermore, the flexibility now offered by microprocessor controlled furnace atomisers, with their capability of being able to produce a high temperature to remove carbon build-up in graphite tubes, allows within-run coefficients of variation of between 2 4 % to be achieved for the routine analysis of lead in blood. A further development at the HSE laboratories has been to incorporate the use of data handling facilities (data collection, analysis and calculation), thereby reducing considerably the time an operator needs to spend on the analyses. However, it must be recognised that even sophisticated automation can be a very precise way of leading the analyst to the wrong answer. In order to overcome this danger, samples should be analysed in a true duplicate fashion and quality control checks should be incorporated into the system at regular intervals.In addition, participation in a recognised quality assurance programme is advantageous as this will allow the accuracy to be monitored. There currently exists a recognised quality assurance scheme for the analysis of lead in blood. It is known as the National External Quality Assurance Scheme for Blood Lead and is organised jointly by HSE and the staff of the Wolfson Laboratories, Queen Elizabeth Hospital, Birmingham. It operates on a regular basis, whereby participants in the scheme receive a quality control sample of blood every 2 weeks for analysis. The results submitted by the participating laboratories are computed and a print-out of the data is produced which gives a consensus mean value and standard deviation and, for each participating laboratory, an appropriate score which is a measure of how its results deviate from the consensus mean value.The average score for the last ten results is also computed for each laboratory. and this indicates the performance by that laboratory over a period of about 5 months. This scoring system is supplemented at intervals by a graph showing how the performance of each laboratory has progressed over a period of many months. The lessons that have been learnt from the analysis of lead in blood are proving to be of use in the development of automation of the analysis of cadmium in blood. Between-laboratory coefficients of variation are about 15-20”/0 for this analysis. This lower precision is probably attributable to both the lower levels of cadmium in blood and its higher volatility.requiring a more careful control of analytical parameters. However, with the increasing awareness of the toxicity of cadmium. it is essential that the methodology be improved to attain better precision of results. This is especially important in relation to any guidelines that may be produced for monitoring the exposure of workers to this metal.112 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS Anal. Proc., Vol. 21 Some of the recent approaches to the analysis of cadmium in blood have adopted a matrix modification procedure using nitric acid at a strength of 1 M to precipitate protein, with the supernatant analysed directly for cadmium. Whilst this has attractions of simplicity, in our experience nitric acid at that strength has a deleterious effect on graphite tubes.A more recent approach adopted by Delves.1 using graphite furnace atomic absorption, has been to employ a matrix modification with phosphate , together with use of oxygen during the charring stage of the analysis cycle. The addition of phosphate permits the use of higher ashing temperatures without loss of cadmium and the selective use of oxygen assists in the decomposition of organic material without causing an undue deterioration of the graphite tubes. The method, whilst not being particularly rapid because of the long programme cycle, does lend itself to automated operation with the added benefit of good precision. Typical coefficients of variation for within-run and between-run values are 2.6% and 5.4%, respectively, at 20 pg 1-1.The method also permits very good discrimination between unexposed and occupationally exposed levels. The application of automated AAS to the analysis of arsenic and mercury in urine can now be considered. At the HSE laboratories. we have developed procedures which illustrate very well how the techniques of HPLC and of continuous flow analysis, coupled to an atomic-absorption monitor as a detector system, can be utilised. The uptake of arsenic by workers exposed to either the metal or its compounds can be assessed by monitoring the excretion of arsenic in urine. However, a determination of the total urinary arsenic does not allow differentiation between occupational exposure and dietary intake, nor does it give any idea of the metabolic transformations that have occurred.It has been found that by using HPLC various arsenic species in urine can be separated. The technique involves injecting an aliquot of urine on to an anion exchange column. The species which can be eluted from the column with phosphate buffer are then fed into a continuous flow system for acidification before reduction of the individual arsenic species with borohydride. The generated arsines are then swept by carrier gas into a silica absorption tube mounted in an air - acetylene flame. The system currently in use at HSE allows for the separation of arsenic(III), arsenic(V), dimethylarsinic acid and methylarsonic acid, which are the major species resulting from exposure to inorganic arsenic.The determination of mercury in urine can be handled in a similar way. Mercury. being monatomic at room temperature, lends itself to cold vapour atomic absorption. One method for the analysis of this metal in urine involves digestion with potassium permanganate and destruction of the excess permanganate before final reduction of the mercury with tin(I1) chloride. The wet digestion procedure can be easily handled by a Technicon AutoAnalyzer system, urine aliquots being sampled automatically. A key feature of the technique is the use of a de-bubbler in the system that allows for the liquid phase to be separated from the mercury vapour, which can then be swept into a mercury monitor acting as an absorption cell. Control of the system is monitored by incorporating both quality control and drift control samples into the run.Fifteen to twenty samples can be annlysed in 1 h. A question now arises concerning the value and cost benefits to be gained from automation. A survey of the literature on the analysis of toxic metals in biological samples over the last few years shows that in many instances there was an unacceptable degree of imprecision in the results obtained. Whilst, in part, this may have been attributable to earlier and less refined instrumentation, nevertheless it is known that automation brings an improvement in precision in the critical steps of an analysis over and above that attainable by manual techniques. It goes without saying that if a study is to be performed where levels of toxic metals in biological fluids are to be correlated with other biochemical parameters, then the precision and accuracy of the methods are of paramount importance.A simple example illustrating the benefits of improved precision exists for the analysis of lead in blood. At the present time, a statutory value exists for lead workers whereby if their lead level exceeds 80 yg per 100 ml, they are suspended from that particular lead process. Clearly, all efforts to improve precision and accuracy at this level are justified, both in economic terms and from the health and safety viewpoint. The final factor concerns the cost benefits to be achieved from automation in atomic absorption. The purchase of an autosampler does not involve a large capital outlay. It may only contribute 10-15% of the total package cost and will certainly pay for itself in terms of the number of samples that can be processed as well as contributing to improved analytical precision.Reference 1. Delves. H. T . , and Woodward. J.. At. Spectrusc., 1981. 2 . 65.March, 1984 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS Cooling Tower Timbers: Sampling and Analysis for Arsenic, Chromium and Copper 113 C. W. Fuller and D. J. M. Clare Centrcl Electricity Generating Board, Midlands Region, Scientific Services Department, Ratcliffe-on-Soar, Nottingham, NG11 OEE Three types of material can be used for the packing in the water distribution system within large cooling towers: asbestos cement, plastic and wood. Although all three materials have their advantages, the preferred material of construction is wood because of its relative cheapness.One of the problems associated with the use of wood is its susceptibility to soft rot. Soft rot differs from wet and dry rot both in the fungi responsible for attack and in its effect on the attacked timber. With wet and dry rot the attack occurs in depth through the thickness of the timber, or may occur in the middle of a piece of timber leaving the outer layers intact. Soft rot on the other hand attacks and destroys the cellulose of the cell walls in the outer layers of the timber. It leaves the surface of the wood soft when still wet and cork-like, with shrinkage cracks, when dry. Attack occurs progressively inwards and with time the thickness of the timber may be reduced to such an extent that it fails due to insufficient mechanical strength.Failure may occur within a period of 7 years. In order to overcome this problem preservatives and methods of impregnation have been developed that can prolong the lifetime of timber to 25-30 years. The recommended preservatives consist of a mixture of copper, chromium and arsenic compounds. The BSI specifications [BS 4072 (1974)] for these preservatives are given in Table I. The copper and arsenic are precipitated as insoluble chromates when the solutions come into contact with wood. Copper is the main fungicidal component, but arsenic is important in preventing attack by copper-tolerant fungi. Other preservatives which contain only copper and chromium have been used in timber, but these are less effective than the arsenic containing preservatives.TABLE I BSI SPECIFICATIONS FOR WOOD PRESERVATIVES FOR USE WITH COOLING TOWER TIMBERS Percentage mlm Component Type A Type B Cu, as CuS04.5H20 32.6 35 .0 Cr, as K2Cr2070r Na2Cr207.2H20 41.0 45.0 As, as As205.2H20 26.4 20.0 Timbers have to be analysed for their preservative content for three distinct reasons. During construction. The efficiency of the treatment process must be confirmed to ensure that the projected lifetime of the timber will be achieved. For this purpose both bulk analysis and depth profiles of the treated timber will be necessary. During operating lifetime. It is necessary, at regular intervals, to confirm the projected lifetime of timber. Depth profiling of the wood is of major importance as the residual wood, which would initially have been at the centre of the timber, may be less well treated than the original outer layers of wood.The projected lifetime of the remaining wood will therefore be less than might otherwise be expected. At the end of the operating lifetime. It is essential to know qualitatively the elemental composition of timber at the end of its lifetime to determine the correct method of disposal. Any material containing arsenic must be disposed of at an approved site according to the Department of the Environment's recommended procedures. Sampling Guidelines for sampling are given in BS 5666, Part 1. 1978. Good sampling of treated timber is of paramount importance; for this reason it is worthwhile emphasising a few important factors. Firstly, timber normally consists of both sapwood and heartwood.As heartwood absorbs significantly less preservative than sapwood, it is important to ensure that the timber analysed is representative of the total supply. Secondly, samples from the ends of a piece of timber will be non-representative of the timber in general. Owing to penetration of preservative along the grain of the wood the preservative loading here is more uniform over the cross-section of the timber than that found in the bulk of the114 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS Anal. Proc.. Vol. 21 timber. Samples for analysis should therefore be taken 30-50cm away from the ends of a piece of timber (Figs. 1 and 2). Thirdly, the absorption of preservative is not uniform within the grain of the wood; samples must therefore be taken across the grain to obtain representative results.Fourthly, wood samples for bulk analysis should be from a complete cross-section of the timber. This avoids bias in the results caused by variations in preservative absorption through the various faces of the timber (Fig. 3 and Table 11). Samples should be obtained by slicing or sawing through the complete section of timber. Drillings through a timber sample will invariably produce inaccurate results as a consequence of the non-homogeneous absorption of preservative in the timber. Fifthly, the variation of preservative loading within timber is normally quite large. When analysing a consignment of timber to ascertain whether it meets the specification for preservative content. it is essential therefore to take sufficient samples to ensure a representative result.m I. Depth below surfaceimm Q Fig. 1. The variation of preservative loading with depth at the end of a piece of timber. A. K2CrZ07; €3. CUSO,. SHz0; C , A S ~ O ~ . ~ H ? O . 16 12 8 4 0 2 4 6 8 Depth below surfaceimm 3 Fig. 2. The variation of preservative loading with depth 50 cm from the end of a piece of timber. Lines A, B and C are as in Fig. 1. Analytical Methods Atomic Absorption Spectrometry (AAS) Recommended procedures are given in BS 5666. Part 3,1979. The powdered wood samples ( 5 g) are leached with sulphuric acid (50ml) and hydrogen peroxide (lOml) at 75°C for 30 min. Sufficient sodium sulphate solution is added to give a concentration of 0.3% mlVafter final dilution. The samples are filtered and diluted to 250 ml.The elements arsenic. chromium and copper are determined by using standard AAS conditions and matrix matched standards. TABLE I1 A COMPARISON OF SURFACE ANALYSIS WITH BULK ANALYSIS OF TIMBER SAMPLES BY AAS Preservative loading in timberikg m-3 Sample B As205 .?HZ0 K2Cr207 CuSOj.SHZ0 Surface . . . . 7.2 15.1 10.2 Bulk . . . . 3.3 7.1 5 . I Inductively Coupled Plasma - Optical Emission Spectrometry (ICP - OES) The solutions obtained from the AAS procedure described above can also be used for the simultaneous determination of arsenic, chromium and copper by ICP - OES. Although this technique offers no advantages in terms of accuracy and precision, it does offer significant savings in time when a large number of samples are to be analysed. Table I11 shows a comparison of results obtained by the two atomic-spectrometric procedures.March, 1984 ATOMIC SPECTROSCOPY IN ENVIRONMENTAL ANALYSIS 115 X-ray Fluoresence Spectrometry (XRFS) Two XRFS procedures can be used. Pressed discs, which have been prepared from powdered wood samples, can be analysed using standard conditions. The instrument is calibrated by use of wood samples that have been analysed previously by the AAS procedure. TABLE IT1 A COMPARISON OF RESULTS OBTAINED USING AAS AND ICP - OES Preservative loading in timberlkg m--3 - As205.2H20 K2Cr2O7 CUSO~. 5H20 r ,- Sample ICP AAS ICP AAS ICP AAS A . . . . 2.8 2.8 5.3 5.4 3.9 4.1 B . . . . 3.7 3.3 7.0 7.1 5.0 5.1 c . . . . 2.5 2.6 4.9 5 .o 3.3 3.4 This procedure is relatively rapid and provides the average concentration of arsenic, copper and chromium in the sample. Alternatively, discs of wood, 40 mm in diameter, which have been cut directly from the timber and then sanded slightly, can be analysed directly. The instrument is calibrated using wood samples that have been prepared in the same way. It is essential, however, that the standards used for calibration have been correctly analysed by AAS. As the XRFS procedure provides information on the surface concentrations of preservatives in the samples, the values for arsenic, chromium and copper used for the standards must also relate to the surface concentrations and not to the bulk (average) concentrations. O x L Y 2 Face of timber, triangular cross-sectio n Fig. 3. The variation of preservative loading on each face of a timber with a triangular cross-section. Lines A, B and C are as in Fig. 1. This technique provides an ideal procedure for the rapid determination of the distribution of preservatives with depth in timbers. To achieve this, disc samples are progressively sanded away and the surface analysed after each layer has been removed. Graphs of preservative loading with depth can then be prepared, Figs. 1 and 2. The technique can also be used as a rapid method for semi-quantitatively determining the levels of arsenic, chromium and copper when deciding on disposal procedures for used timbers. This paper is published by permission of the Central Electricity Generating Board.

ISSN:0144-557X    

DOI:10.1039/AP9842100102

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

116 CHEMISTRY OF THE FIRTH OF CLYDE Anal. Proc., Vol. 21 Chemistry of the Firth of Clyde The following is a summary of one of the papers presented at a Joint Meeting of the Scottish Region of the Analytical Division of the RSC, the South West Scotland Section of the RSC and the Andersonian Society, held in the Thomas Graham Building of the University of Strathclyde on November 25th, 1982. Chemistry of the Firth of Clyde A. J. N. Haig and 6. S . Miller Clyde River Purification Board, Rivers House, Murray Road, East Kilbride, Glasgow, G75 OLA The Firth of Clyde, which lies on the west coast of Scotland, is a complicated system of shallow estuaries, deep fjordic sea lochs and open coastal waters with an area of about 3 000 km2 and a volume of about 100 km3. It supports a rich flora and fauna, serves as an important centre for tourism, fishing, shipping and other industries, and receives liquid wastes derived from over half of Scotland’s population and industry.’ Chemistry is one of the most important of the many disciplines used by the Clyde River Purification Board in performing its statutory task of preventing or controlling pollution by effluents, and as the legislative basis of this duty changes (to meet new national and international needs) so too the role and emphasis of the Board’s chemical studies are changing.Established national legislation*-4 has, for over a decade, empowered the Board to control discharges to defined tidal waters which, by virtue of their form, hydrography and effluent loadings, have a history of pollution or are extremely vulnerable.Chemistry has played its part in a wide spectrum of pollution surveys,S including those examining the nature and extent of the main pollution problems (e.g., oxygen depletion and eutrophication in poorly-flushed area+’), the effect of certain waste disposal practices (e.g., sewage sludge dumping*), the origin and fate of particular contaminants [ e . g . , polychlorinated biphenyls (PCBsg)], the practical application of tracers ( e . g . , coprostanollO), the settirig of discharge licences on the basis of receiving water standards,” and the use of modelling techniques. 12 Most of our monitoring “effort” has focused on biochemical oxygen demand/dissolved oxygen and on dissolved nutrients, i.e., non-conservative parameters having a severe, yet localised impact.A feature of recent years has been the growth of international legislation. Some is designed to combat pollution by substances which, because of their persistent, toxic and bioaccumulable characteristics, pose a risk beyond the strictly local context. For example, the UK has signed the Paris Convention13 and an EC Directive,14 thereby pledging itself to eliminate pollution by groups of particularly harmful (or “black list”) substances, and to limit strictly pollution caused by certain less harmful (or “grey list”) substances. Other EC legislation has been adopted to safeguard water quality for particular usage; thus, some areas within the Firth of Clyde have been designated “shellfish- growing waters” under the appropriate Directive.lS The UK cannot honour its international obligations in full until new national legislation16 is implemented, but the Convention and Directives have already imposed an added burden of monitoring upon the Board, and to meet this we are diverting effort away from studies of non-conservative parameters.An example of a survey that supplies data relevant to the Board’s needs, to the Convention and to the two E C Directives mentioned above, is the “Mussel Watch.” This well-established monitoring approach17 takes advantage of the fact that the common mussel, Mytilus edulis, an edible shore-dwelling shellfish, is able to concentrate in its tissues certain persistent contaminants present in the surrounding seawater, By monitoring the mussel’s body-burdens, which reflect long term exposure to the biologically available fraction of these substances, it is possible to identify “hot-spots” and trends in environmental levels present.Some years ago, in common with others,18,19 the Board20 initiated a programme of intensive mussel watch surveys to monitor certain trace metals and organohalogens; this paper presents some results for three organochlorines that have occurred in elevated levels in the Firth, namely DDT, dieldrin and PCBs. DDT is a pesticide, the usage of which, once considerable in agriculture, horticulture and veterinary practice, is now restricted. Dieldrin was, until its recent replacement by “Eulan” and other chemicals, widely used as a mothproofing agent in the woollen and carpet manufacturing industries of which Kilmarnock, in Ayrshire, is an old-established centre.PCBs are used as dielectric fluids in closed systems, mainly in the electrical industry in capacitors and transformers, and as locating agents. SomeMarch, 1984 CHEMISTRY OF THE FIRTH OF CLYDE 117 former uses (e.g,, in hydraulic fluids and heat transfer systems), which were dispersive in that they allowed PCBs to enter the environment, were stopped in the UK about 10 years ago. Clearly, the amounts of these substances entering the Firth should be diminishing. Table I shows the levels of these compounds, analysed by using a modification of the method of Wells and Johnston,J1 in mussels collected in early spring from selected sites in the Firth of Clyde. Table I1 provides a comparison of these data with those reported for other British estuaries and sea areas.By using the 1982 data, and taking as our standard the mean level plus one standard deviation recorded at control sites in fairly remote parts of north-west Argyll (giving standards of 26.9 ng g-1 total DDT, 4.0 ng g- 1 dieldrin and 39 ng g-1 PCBs, all as wet mass), sites with elevated levels can be identified. On this basis all of the Firth of Clyde sites were PCBs hotspots, 2 sites (Ardmore and Shandon) were DDT hotspots, and 2 sites (Shandon and Kilmun) were dieldrin hotspots. Shandon, on the Gare Loch, which emerges as a hotspot for all three organochlorines in this survey, was also found to be a DDT and PCBs hotspot in a survey performed in 1977.19 The hotspot sites are now the subject of further study.LEVELS OF TOTAL Site Ardmore Shandon Portkil Bay Gourock Kilmun Dunoo n Mean TABLE I DDT, DIELDRIN AND PCBs (as ng g-I WET MASS) IN Mytilus edrilis FROM THE FIRTH OF CLYDE. 1981 AND 1982 DATA Mean wet PCBs National massig Total DDT Dieldrin (as 1254) reference 1981 1982 1981 1982 1981 1082 1981 1982 NS 322 784 0.8 2.1 28.7 31.6 7.2 <0.6 168 117 NS 256 862 2.9 3.0 41.9 31.2 12.2 6.3 194 87 NS 254 803 2.1 2.1 22.2 20.7 2.0 2.9 120 80 NS 234 773 2.4 2.4 25.0 11.2 5.9 4 . 6 204 6.7 NS 171 817 1.9 1.6 31.8 18.2 10.4 4.7 223 142 NS 175 763 2.2 1.1 39.1 22.5 6.7 <0.6 151 104 2.1 2.1 29.8 22.7 7.4 2.6 177 100 Grid Standard deviation (k) 0.7 0.7 6.8 7.8 3.6 2.5 38 27 TABLE I1 LEVELS OF TOTAL DDT, DIELDRIN AND PCBs (AS ng g-1 WET MASS) I N Mytilus edulis REPORTED FROM THE FIRTH OF CLYDE AND OTHER BRITISH WATERS Countrylarea Firth of Clyde 1981 Firth of Clyde 119821 North-west Argyll (1982) Forth and Tay Scotland Medway England Total DDT 22-4 1 11-32 11-28 2& I20 < 3-64 11-72 4 - 2 4 Dieldrin PCBs Reference 2-12 151-223 This paper 0-6 67- 142 This paper 0-4 <1&39 This paper < 1 00-600 <10-70 22 10-1 205 <1-413 19 4-12 70-162 23 10-40 < 1-8 24 The results of two consecutive surveys can hardly be expected to form a sound basis for detecting trends but, as Table I shows, the mean concentrations of the three organochlorides were much lower in 1982 than in 1981.Whilst this is encouraging, and consistent with the expected reduction in input of these substances to the Firth, the surveys will be repeated in future years so that temporal changes in concentration can be examined more closely and any trends identified with certainty.References 1. NERC, “The Clyde Estuary and Firth. An assessment of present knowledge,” NERC Series C. Nu. II, 1974. 2. HM Government, “Rivers (Prevention of Pollution) (Scotland) Act 1965 Chapter 13,” HM Stationery 3. HM Government, “The Ayrshire River Purification Board (Prevention of Pollution) (Tidal Waters) Order 4. HM Government, “The Clyde River Purification Board (Prevention of Pollution) (Tidal Waters) Order 5 . Hammerton, D., Newton, A. J., and Leatherland, T. M., Wat. Pollut. Control., 1981, 80, 189. 6. Mackay. D. W., and Leatherland, T. M., in Burton, J. D., and Liss, P. S., Editors, “Estuarine Chemistry.” 7 . Mackay, D. W., and Halcrow, W., in “Fresh Water on the Sea,“ Association of Norwegian Office, London.1968,” Statutory Instrument 1968 No. 1892 (S. 168), HM Stationery Office, London. 1968,” Statutory Instrument 1968 No. 1891 (S. 167), HM Stationery Office, London. Academic Press, London, 1976, p. 185. Oceanographers,” Oslo, 1976, p. 109.118 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. EQUIPMENT NEWS Anal. Proc., Vol. 21 Halcrow, W., Mackay, D. W., and Thornton, L., J. Mar. Biol. Ass. U. K., 1973, 53, 721. Waddington, J. I., Best, G. A., Dawson, J. P., and Lithgow, T., Mar. Pollut. Bull., 1973,4, 26. Goodfellow, R. M., Cardoso, J., Eglinton, G., Dawson, J. P., and Best, G. A., Mar. Pollut. Bull., 1977,8, Hammerton, D., Newton, A. J., and Allcock, R., Eff7. War. Treat., 1980,20, 261. Curran, J. C., Appl. Math. Modelling, 1981, 5 , 137. HM Government, “Convention for the Prevention of Marine Pollution from Land-based Sources,” Treaty Series No. 64, 1978, Cmnd 7251, HM Stationery Office, London. EEC Council Directive 76/464/EEC, OJ NoL 129, 18.5.1976, p. 26. EEC Council Directive 79/923/EEC, OJ NoL 218, 10.11.1979, p. 47. HM Government, “Control of Pollution Act 1974,” Chapter 40, HM Stationery Office, London. Goldberg, E. D., Mar. Pollut. Bull, 1975,6, 111. Davies, I. M., and Pirie, J. M., Mar. Biol. 1980, 57, 87. Cowan, A. A,, Environ. Pollut., Ser. B., 1981,2, 129. CRPB, “Annual Report for the Year Ending 31st December, 1980,” Clyde River Purification Board, Wells, D. E., and Johnstone. S. J. J. Chromatogr., 1977, 140, 17. Holden, A. V., and Topping, G., Proc. R. Soc. Edinburgh, Sect. B, 1972,72, 189. Wharf, J. R., and Van Den Broek, W. L. F., Mar. Pollut. Bull., 1978,9,76. ICES, “Cooperative Research Report No. 72,1977,” International Council for the Exploration of the Sea, 272. Glasgow. Copenhagen, Denmark, 1977.

ISSN:0144-557X    

DOI:10.1039/AP9842100116

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

118 EQUIPMENT NEWS Anal. Proc., Vol. 21 Equipment News Infrared Detectors Developed by Mullard Ltd., the P1645/46 pyroelectric detectors are claimed to function longer than thermo- couples. They exhibit a substantially flat response. Typically they have a measured noise equivalent power of 0.8 X 10-10 W Hz-*. Amperex Electronic Corporation, Slatersville RI 02876, USA. X-Ray Spectrometry Tube A side window X-ray tube equipped with a scandium anode for sequential spectrometry analysis is announ- ced. It is designed for the detection of light elements ranging from carbon to scandium. Philips Electronic Instruments, 85 McKee Drive, Mahwah, NJ 07430, USA. Accessory for Emission Analysis A torch tip is available, providing an alternative to replacing the complete torch in the Boumans induc- tively coupled plasma source.Pye Unicam Ltd., York Street, Cambridge, CB 1 2PX. Non Destructive Analyser COAT 95 is broad-spectrum software system for the non-destructive analysis of metallic coatings. It is intended for use with Philips PV9500 automated energy-dispersive spectrometers which employ DEC LSI-11 computers. Pye Unicam Ltd., York Street, Cambridge, CB12PX. Gas Chromatograph Based on the Sigma 3B, the Sigma 300 is a compact, multi-detector, single- or dual-column instrument. It features dual ramp temperature programming. There are seven detector options and up to three detectors may be installed and operated simultaneously. Optional RS232C compatible computer communications allow parameters such as oven, detector and injector temper- atures to be set and monitored from a large computer system.Perkin-Elmer Ltd., Post Office Lane, Beaconsfield, Buckinghamshire, HP9 1QA. Chromatography Accessory The Siemens Total Transfer system features a live T-piece fitted with a cold trap between a packed and a capillary column. After a sample is injected on to the packed column, the components giving peaks of interest can be deposited in the cold trap whilst other compo- nent peaks are switched to a monitor detector for quantification. The trap will contain peaks from a series of injections. Heating it releases trapped components on to the capillary column for analysis by the main detector. V. A. Howe & Co. Ltd., 12-14 St Ann’s Crescent, London, SW182LS.119 March, 1984 EQUIPMENT NEWS Gas Chromatograph Digital Electronic Thermometers The Shimadzu GC-Mini 3 instrument measures 305 x 500 X 280 mm and weighs 24 kg.It features a current loop interface to allow programming from the C-R2A A range of miniature instruments consists of three models: the Model TI'X181 covers the range from -55 to +180"C, the Model TTX483 from -50 to +400"C and the Model TTX1082 from -40 to + 1 000 "C. Camlab Ltd., Nuffield Road, Cambridge, CB4 1TH. Immersion Heaters The Immersoheat range of heaters is suitable for heating liquids up to 300 "C. integrator. It has five step multi-linear programming capabilities, with ten files for optional programming. The temperature range is from - 100 to +399 "C. Dyson Instruments Ltd., Sunderland House, Station Road, Hetton, Houghton-le-Spring, Tyne and Wear, DH5 OAT. HPLC Data System The Model 450 disc-based data system - controller provides up to four channels of HPLC control, indepen- dent multi-channel data acquisition, data reduction, storage and management.Software packages include an option for storage and manipulation of spectral data from the Model 165 detector. Beckman-RIIC Ltd., Progress Road, Sands Indus- trial Estate, High Wycombe, Buckinghamshire. Fluid Cell for HPLC The microCel1 features a cross-flow optical design minimising thermal and flow noise without a heat exchanger. It can be retrospectively fitted to spectro- Monitor variable wavelength detectors. The spectro- Monitor D can be purchased with a factory-installed microCel1. Laboratory Data Control (UK) Ltd., Milton Roy House, High Street, Stone, Staffordshire, ST15 8AR.Automatic Sampler for Thin-layer Chromatography The CAMAG Automatic TLC Sampler I is micropro- cessor controlled and takes about 12min to apply sixteen individual samples, e.g., three calibration sam- ples and five unknowns, all in duplicate, to a 10 X 10 cm HPTLC plate. Baird and Tatlock (London) Ltd., P.O. Box 1, Romford. RM1 IHA. Refractive Index Detector The SP6040 is a deflection-type differential refractive index detector. Its long focal length provides high sensitivity. A temperature control system is featured. Spectra-Physics Ltd., 17 Brick Knoll Park, St. Albans, Hertfordshire, AL15UF. Camlab Ltd., Nuffield Road, Cambridge, CB4 1TH. PTFE Tubing Sub-Lite-Wall tubing is extruded in dimensions down to 0.025 mm i.d. with uniform wall thickness of 0.178 mm or, for example, a 1.52mm i.d.with wall thickness of 0.038 mm. Zeus Industrial Products, Inc., P.O. Box 298, Rari- ton, NJ 08869, USA. Balances The Oertling LA 164 electronic fourth-place analytical balance features touch-sensitive function keys posi- tioned in-line with the digital display. A number of optional extras are available. W. & T. Avery Ltd., Smethwick, Warley, West Midlands. B66 2LP. Digital Pump System The Aquarius is a fully programmable self-priming peristaltic pumping system especially suited for dispens- ing media in microbiology laboratories. V. A. Howe & Co. Ltd., 12-14 St. Ann's Crescent, London, SW182LS. Automated Microscope The Polyvar Telematic incorporates a motorised nose- piece with push-button selection of objective plus automatic condenser selection.Reichert-Jung UK, 820 YeoviI Road, Slough. SLl4JB. Autoclave The Swiftlock Series 3000 autoclaves feature three independent adjustable programmes. The Supercool120 SAC SILVER MEDAL Anal. Proc., Vol. 21 models employ a mechanical refrigeration system. Alternatively, a simple mains water cooling system is offered. Astell Hearson, Equipment Division. Cray Road, Sidcup. Kent, DA14 5BZ. Centrifuge Rotor A new swing-out rotor for the maker's T52 and T62 bench top centrifuges carries four square buckets, each accepting samples of 250 ml, or four Universal or McCartney bottles. or a larger range of smaller tubes and bottles up to 100mm long. DNA Synthesiser The System 1 is a microprocessor controlled DNA synthesiser which can be operated manually, automatic- ally or in a combination of the two modes.It uses licensed phosphoramidite chemistry and can synthesise 15 or more bases automatically, each base addition occurring in a half hour or less. Beckman-RIIC Ltd., Progress Road, Sands Indus- trial Estate, High Wycombe, Buckinghamshire. Literature An application booklet on the 1500 series of Fourier transform infrared spectrophotometers describes the instruments and covers a range of experiments. Perkin-Elmer Ltd., Post Office Lane, Beaconsfield, Buckinghamshire, HP9 1QA. A leaflet describes fingertight fittings for liquid chro- matography. Field Instruments Co. Ltd., P.O. Box No. 113, Weybridge, Surrey, KT13 8BJ. Literature is available on equipment and accessories for thin-layer chromatography.Field Instruments Co. Ltd., P.O. Box No. 113, Weybridge, Surrey, KLT13 8BJ. An applications brochure is available on the Shimadzu IP2a isotachophoretic analyser. The process is based on Clandon Scientific Limited. Lysons Avenue. Ash Vale, Aldershot, Hampshire, GU12 5RQ. Rheological Test and Measuring Instruments Computerised systems have been added to the Brab- ender OHG range of instruments. The Plati-Corder can now automatically evaluate and print out measuring data. The data processing unit can be adapted for use with existing units. The Elatest combines the use of a computer with an electronic balance. The H-A-G-E moisture tester is also fully automatic. The Engelmann & Buckham Group, William Curtis House, Alton, Hampshire, GU34 1HH. ion mobilities- when high voltage is applied. London, SW182LS. V. A. Howe & Co. Ltd., 12-14 St. Ann's Crescent, A brochure describes the 52-21 series of high speed centrifuges. It includes details of the J2-21M program- mable centrifuges and of the range of standard and special rotors available. Beckman-RIIC Ltd., Progress Road, Sands Indus- trial Estate, High Wycombe, Buckinghamshire.

ISSN:0144-557X    

DOI:10.1039/AP9842100118

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

120 SAC SILVER MEDAL Anal. Proc., Vol. 21 SAC Silver Medal Nominations are invited for the award of the SAC Silver Medal, which is for the encouragement of young scientists working in any field covering the practice and teaching of analytical chemistry. The award is accom- panied by a cash prize and is normally made annually to the candidate who, in the opinion of the AD Council, has made the greatest contribution and whose work has made the most significant impact in any branch of analytical chemistry. In addition, the future promise of the candidate is taken into consideration. It is hoped to provide an opportunity for the successful candidate to deliver a lecture to the Division on a suitable occasion subsequent to the presentation of the Medal. The rules are as follows- 1.The award of the Silver Medal will normally be considered annually by the Honours Committee, acting on behalf of the Council of the Division, but an award may not be made if it is considered that the work of no candidate reaches the required standard. 2. Candidates must be British subjects of 38 years of age or under in the year in which the award is considered. Evidence of age will be required. 3. The merits of the candidate’s work may be brought to the notice of the Council by any person (being a member of the Analytical Division of the Royal Society of Chemistry) who desires to recommend the candidate by letter addressed to The President, Analytical Division. The Royal Society of Chem- istry. The letter should be accompanied by a short statement on the candidate’s career (date of birth.education and experience, degrees and other quali-March, 1984 CONFERENCES AND MEETINGS fications, special awards, etc., with dates, and any other relevant information) and a list of titles of, and references to, papers or other works published by the candidate, independently or jointly. One reprint of each paper (or other work) for which reprints are available should be submitted. 4. The award will be made on an over-all assessment of the candidate's contribution, the impact of hidher work and hidher future promise in any field covered by the principles, teaching and practice of the analytical sciences. No restriction is placed as to where the work is conducted. 5 . The Committee assessing the, applications shall be at liberty to call any candidate for interview. 6 . The successful candidate will receive the sum of f l O O in addition to the Medal. 7. The decision of the Council shall be final. 8. Any alteration to these Rules shall be subject to the approval of the Council. Recommendations for the next award should be made to The President, Analytical Division, The Royal Society of Chemistry, Burlington House, London, W1V OBN, by March 31st, 1984. 121

ISSN:0144-557X    

DOI:10.1039/AP9842100120

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

March, 1984 CONFERENCES AND MEETINGS 121 Courses Thermal Methods of Analysis April 2-6, 1984, Loughborough This course will be organised by, and held in, the Department of Chemistry of the University of Tech- nology. It will cost 2250, including residence and all meals. For further details contact Miss C. D. Newton, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, LEI 1 3TU. High-performance Liquid Chromatography September 10-14, 1984, Brighton This residential school, which is to be organised by the Royal Society of Chemistry, will be held in the University of Sussex, Falmer. The school will attempt to inform its participants of the latest developments of this technique, while providing relative beginners with the necessary background information to appreciate those developments.In addition to lectures, seminars and practical sessions will be provided. The lecturers will be Dr. G. B. Cox, Mr. B. B. Wheals, Professor J . H. Knox, Dr. R. P. W. Scott, Dr. J . N. Done, Professor J. F. K. Huber, Professor C. Horvath, Dr. J . C. Kraak, Dr. J . V. Dawkins and Dr. C. F. Simpson. For further information contact Ms. L. A. Hart, Royal Society of Chemistry. 30 Russell Square, London. WClB SDT.122 ANALYTICAL PROCEEDINGS Anal. Proc.. Vol. 21 RSC ANALYTICAL DIVISION A Meeting on PRINCIPLES OF AUTOMATION AND APPLICATIONS OF ROBOTICS will be held at The Scientific Societies Lecture Theatre, 23 Savile Row, W.1 on Wednesday and Thursday, 9- 10th May, 1984 This meeting is organised jointly by the Automatic Methods, Microchemical Methods and Special Techniques Groups of the Analytical Division, with the Microcomputer and Microprocessor Group of the RSC. The first day will be devoted to Automated Analysis, and the second to Robotics. It is hoped to arrange practical demonstrations of robot arms, etc. The fee will be f60 to RSC members and f80 to non-members (to include lunches, etc.) One-day registration is possible. There is also a Symposium Dinner on the Wednesday evening. The closing date for registration is 27th April. Further details from Dr. C. J. Jackson, Occupational Hygiene Laboratory, HSE, 403 Edgware Road, London, NW2 6LN. For travel arrangements contact: Commercial Trade Travel, Tel.: 01 -405 5469/8666

ISSN:0144-557X    

DOI:10.1039/AP984210121b

出版商:RSC    

年代:1984

数据来源: RSC