摘要:

ANPRDI 17(1) 1-38 (1980) ISSN 0306-1 396 ANALYTICAL PROCEED I NG S PROCEEDINGS OF THE ANALYTICAL DIVISION OF THE CHEMICAL SOCIETY Hon. Secretary P. G. W. Cobb Hon. Assistant Secretaries D. I. Coomber, O.B.E.; D. C. M. Squirrel1 Secretary Miss P. E. Hutchinson J. M. Ottaway (Chairman) H. J. Cluley "P. Gray J. N. Miller 'Ex officio members President R. Belcher P. C. Weston G. E. Penketh T. B. Pierce W. H. C. Shaw D. Simpson January 1980 Hon. Treasurer J. K. Foreman Assistant Editors Mrs. J. Brew, R. A. Young Publication of Analytical Proceedings is the responsibility of the Analyst Publications Committee: A. Townshend 'P. C. Weston J. Whitehead All editorial matter should be addressed to The Editor, Analytical Proceedings, The Chemical Society, Burlington House, London, W1V OBN.Telephone 01 -734 9864. Telex 268001. Advertisements: Advertising Department, The Chemical Society, Burlington House, Piccadilly, London, W1 V OBN. Telephone 01 -734 9864. Hon. Publicity and Public Relations Officer Dr. A. Townshend, Department of Chemistry, University of Birmingham, Birmingham, B15 2TT Editor, Analyst and Analytical Proceedings @ The Chemical Society 1980 SYMPOSIUM ON Advances in Applied HPLC Wednesday February 20th 1980 at the Department of Chemistry, University of Edinburgh This Joint Meeting is to be organised by the Scottish Region in associ- ation with the Chromatography and Electrophoresis Group and the Association of Clinical Biochemists. Topics include a Plenary Lecture on future prospects for HPLC by Professor J. F. K. Huber (Vienna), selective sample handling by Professor R. W. Frei (Amsterdam), polypeptide hormones by Dr. E. C. Nice, optimisation for preparative-scale HPLC by Dr. J. C. Kraak (Amsterdam). The Meeting closes with a panel discussion on aspects of Prep-HPLC, chaired by Professor J. H. Knox. Further details from, and registration forms to, Dr. Diana Simpson, Analysis for Industry, Factory 2, Bosworth House, High Street, Thorpe-le-Soken, Essex, Tel. 025584-771 4, before February 8th.

ISSN:0144-557X    

DOI:10.1039/AP98017FX001

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

2 RESEARCH AND DEVELOPMENT TOPICS Anal. Pvoc. Research and Development Topics in Analytical Chemistry The following are summaries of six of the papers presented at the Research and Development Topics in Analytical Chemistry meeting of the Analytical Division held on July 4th and 5th, 1979, at the University of Edinburgh. A further paper, by Aziz-Alrahman and Headridge, appeared in full in the October 1979 issue of The Analyst (p. 944). Summaries of a further six papers will appear in a future issue of Analytical Proceedings. Use of a Piezoelectric Sensor as a Continuous Monitor of Atmos- pheric Pollutants S. Cooke and T. S. West and P. Watts The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen, A B9 2Q J Ministry of Defence, Porton Down, Wiltshire The decrease in frequency that is caused by deposition of a small mass of material on the surface of a piezoelectric crystal oscillator has been known qualitatively for some time and is used regularly in order to obtain fine control of oscillator frequencies.Mathematical deriva- tions of the relationship between frequency and added mass have been made by Lostis,l Sauerbrey2 and St~ckbridge.~ The Sauerbrey derivation is most frequently used : -Am x F A x d x t AF =January, 1980 RESEARCH AND DEVELOPMENT TOPICS 3 where AF is the frequency change, F the initial frequency, Am the added mass, A the area of the deposit, d the density of quartz and t the thickness of the crystal. This linear relationship between frequency change and added mass enables a crystaJ oscillator to be used as a microbalance device with a theoretical detection limit of 10-12 g.2 The quartz-crystal device has been used as a moisture detector by coating the crystal with a hygroscopic compound and relating the mass of adsorbed water to the atmospheric water ~ o n t e n t .~ Subsequently, piezoelectric crystals coated with various adsorbant materials have been reported as sensors for other gases, including sulphur d i ~ x i d e , ~ - ~ nitrogen dioxidelot1l and ammonia.12 Methods reported so far, however, are concerned with the analysis of discrete gas samples and show little or no advantage over conventional techniques that employ liquid absorbants to preconcentrate the sample before analysis, e.g., the West - Gaeke procedure for sulphur dioxide.13 It was decided, therefore, to investigate the potential of the piezoelectric sorption detector as a continuous monitor of trace atmospheric constituents.This moisture detector was later developed into a commercial instrument .5 Equipment The detector element was a 9-MHz, AT-cut, quartz crystal (10 x 10 x 0.18 mm) (Quartz Crystal Co. Ltd., New Malden, Surrey), vibrating in the thickness shear mode. The frequency of the crystal was monitored by use of a digital counter, the output of which was converted to analogue form and displayed on a chart recorder. A gas-mixing system was used in order to simulate the low analyte concentrations required to assess the performance of the detector. Calibrated gas mixtures (Rank Hilger Ltd.) containing approximately 50 p.p.m. (V/V) of analyte gas were diluted in two stages to the re- quired levels.The water content of the diluent gas was continuously variable and the final water content of the mixture was monitored by means of a capacitance hygrometer (Shaw Moisture Meters Ltd., Model SH). This monitoring was necessary as water was known to be involved in the reaction between sulphur dioxide and amines and was, therefore, likely to affect the detector response. The detector crystal was housed in a stainless-steel double- impinger cell similar to that used by Karmarkar and G~ilbault.~ This design has been shown to provide the best contact between the detector coating and the gas stream and hence to give the greatest s e n ~ i t i v i t y ~ , ~ ~ ; however, with this arrangement volatile coating materials tend to bleed much more quickly from the crystal surface than with other cell designs.14 Detector Performance The initial investigation of the sorption detector as a gas sensor was conducted using sulphur dioxide as the analyte gas.A brief examination of several possible coating materials was made and triethanolamine was found to be the most sensitive. The triethanolamine detector responded to a sample of sulphur dioxide with an initial steep decrease in frequency followed by a gradual approach to equilibrium. This signal was superimposed on a base line of steadily increasing frequency (typically 2-3 Hz min-l). The base line drift, caused by the bleed of coating material from the surface of the crystal, was not completely regular and proved to be the main factor in determining the system's detection limit.Detector sensitivity The mass of sulphur dioxide that is adsorbed on to the detector coating can easily be calcu- lated from the Sauerbrey equation. The rate at which sulphur dioxide is adsorbed can, therefore, be calculated from the slope of the frequency - time profile over the first 2-3 min of exposure (before equilibrium is approached). The rates of adsorption calculated for 1.2 p.p.m. (Y/V) of sulphur dioxide passing over the detector at 50 ml min-l demonstrated that a large proportion (80-90%) of the sulphur dioxide passing into the cell during this initial pre- equilibrium stage was adsorbed. These results were checked by observing the response of two matched detector cells placed in series in the gas line.The second detector was exposed only to the sulphur dioxide that was not retained on the first. A comparison of the initial frequency slope for the two detectors again showed that an adsorption efficiency of 80-90% was obtained. Thus, in terms of sensitivity alone there is only a limited scope for further improvement in detector performance.4 RESEARCH AND DEVELOPMENT TOPICS Anal. Proc. Variation of response with coating mass The detector response increases linearly with the mass of adsorbant material but, as the coating bleed rate and the detector response time also increase with coating mass, the best detection limit is generally obtained with a light coating. A coating of approximately 20 pg of triethanolamine (equivalent to a frequency decrease on coating of about 12 kHz) was deposited on each side of the crystal; smaller amounts of coating were difficult to apply repro- ducibly .Variation of response with detector temperature The detector temperature was varied by immersing the cell in a thermostatic water-bath. An increase in temperature was found to decrease the equilibrium response by a considerable amount; the response at 40 "C was less than a quarter of that at 20 "C but, on the other hand, the response time was greatly improved so that only 30 min were required for equilibrium at 40 "C compared with 70 min at 20 "C. Detector calibration graphs Calibration graphs were obtained over the range 0.01-140 p.p.m. (V/V) of sulphur dioxide at detector temperatures of 20 and 30 "C. The response in each instance was linear up to about 10% of the coating saturation level, after which negative deviations from linearity were observed.Coating saturation occurred after a response of approximately 5.5 kHz. Within the linear range, the detector showed greater sensitivity at 20 than 30°C for low sulphur dioxide concentrations, but the temperature effect was much less severe at concentrations near to saturation. The linear range was 0.1-0.4 p.p.m. (V/V) at 20 "C and 0.05-2.0 p.p.m. (V/V) at 30 "C; the response at the top of the range was about 500 Hz in each instance. Membrane shielded detector cells It was thought that the high coating bleed rate associated with the impinger cell might be alleviated by the introduction of a gas-permeable membrane between the impinger gas jet and the detector element.A membrane (Celanese Plastics Ltd., Celgard 2500) was, therefore, introduced into the cell, and although this reduced the bleed rate by a factor of ten, the detector response time was increased to well over 2 h. Conclusions The potential of the piezoelectric sorption detector as a continuous gas monitor has been clearly shown. The electronic system is capable of resolving &O.l Hz, which is equivalent to a sulphur dioxide concentration of 0.000 1 p.p.m. (V/V) at a detector temperature of 20 "C. This performance can only be realised, however, if a solution to the problem of coating bleed is found. The minimum measurable frequency change of a triethanolamine-coated crystal is limited by coating bleed to about 10 Hz (which is equivalent to 0.01 p.p.m.of sulphur dioxide at 20 "C). One solution to this problem might be to have the active adsorbant sites situated in a polymer matrix. Alternatively, a search might be made for efficient involatile compounds, such as some silver salts that have recently been shown to act as efficient adsorbants for ammonia gas.15 Although an uncoated AT-cut crystal is not particularly prone to changes in temperature, it is advisable to maintain the temperature within &1 "C during a series of measurements. The massive stainless-steel block device provides reasonable stability under normal laboratory conditions and its temperature can easily be thermostatically con trolled. The other major problem with the sorption detector is that the relatively slow response time results in considerable smoothing of a continuous concentration versus time graph.There are, however, several ways in which the response time might be decreased: (i), by raising the temperature; (ii), by decreasing the mass of the coating material; or (iii), by increasing the gas flow-r ate. These procedures all have potential disadvantages: (i) and (iii) increase the coating bleed rate and (i) and (ii) reduce the absolute detector sensitivity, although with (ii) this dis- advantage can be offset by a decreased bleed rate so that a decrease in coating mass should not adversely affect the detection limit. Careful optimisation of all experimental conditions withJanuary, 1980 RESEARCH AND DEVELOPMENT TOPICS 5 regard to the tendency of a particular coating material to bleed, and the relative importance of sensitivity and speed for a particular application should, however, enable some improvement to be made, particularly if more stable adsorbant materials can be found.It is in this area of coating materials that most further work should be concentrated. We are grateful to the Ministry of Defence for the award of a studentship to S.C. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. References Lostis, M. P., J . Phys. Radium, 1959, 20, 25 s. Sauerbrey, G., 2. Phys., 1959, 155, 206. Stockbridge, C. D., “Vacuum Microbalance Techniques,” Volume 5, Plenum Press, New York, 1963, King, W. H., Anal. Chem., 1964, 36, 1735. King, W. H., U.S. Pat., 1969, No. 3, 427,864. Hartigan, M. J., PhD Thesis, University of Rhode Island, 1971. Guilbault, G.G., and Lopez-Roman, A., Environ. Lett., 1971, 2, 35. Guilbault, G. G., and Lopez-Roman, A., Anal. Lett., 1972, 5 , 225. Karmarkar, K. H., and Guilbault, G. G., Anal. Chim. Acta, 1974, 71, 419. Street, D. C., and West, T. S., Unpublished results. Karmarkar, K. H., and Guilbault, G. G., Anal. Chim. Acta, 1975, 75, 111. Webber, L. M., and Guilbault, G. G., AnaE. Chem., 1976, 48, 2244. West, P. W., and Gaeke, G. C., Anal. Chem., 1956, 28, 1916. Cooke, S., PhD Thesis, University of Aberdeen, 1979. Glass, E. B.-I., Edmonds, T. E., and West, T. S., Work in progress. p. 193. Pollution Studies in the Clyde Sea Area Jane L. Smith- Briggs Depavtment of Chemistry, University of Glasgow, Glasgow, G12 8QQ The Clyde Sea Area extends northwards of a line along 55”15’N, that is, from Finnart Point to the Mull of Kintyre.It has a total area of 2 500 km2 and receives the wastes and effluents of 2.5 million residents. The main contributors to pollution of the Clyde Sea Area are domestic sewage, industrial effluents and the dumping of sewage sludge and dredge spoils. There are inputs of treated, untreated and partially treated sewage in the upper and lower estuaries and along the Ayrshire coast. Industrial effluent releases come from a variety of manufacturing processes, for example, nylon plant, distillery and oil refinery wastes. Some 1.4 x 106 tonnes per year of wet sludge from sewage and industry are dumped in deep water south of Garroch Head; also 3 x 105 tonnes of wet sediment are dredged annually from the Clyde navigation channel and dumped near the mouth of the Holy Loch.This research is designed to assess the effects of these pollutants on the natural sedimentary rbgimes. It consists of two parts, therefore : firstly, to investigate unpolluted sediments in terms of sedimentation rates and trace metal concentrations; and secondly, to study, in the same terms, areas considered to be environmentally endangered. The “polluted” areas chosen for study were Irvine Bay (adjacent to the ICI Ardeer plant), Garroch Head (which receives sewage sludge) and the mouth of the Holy Loch (receiving the dredge spoil). The Arran Deep and the south of Loch Long were selected as the natural sites. Recent sedimentation rates are derived by using both the 210Pb dating methodl and by observing the 13’Cs and 134Cs concentrations in sediment profiles.Levels of the latter species in the Clyde area are dominated by the output and subsequent transport of radiocaesium from the British Nuclear Fuels Ltd. fuel reprocessing plant at Windscale in Cumbria. Therefore, the first appearance of radiocaesium at depth in the sediment profile corresponds approximately to the horizon deposited immediately after the initial output from Windscale in 1958. Pre- industrial sedimentation rates are obtained by using 14C dating and palaeomagnetic methods. The trace metals under study are copper, nickel, zinc, iron, manganese, chromium, lead and aluminium, all except the last being measured by flame atomic-absorption spectroscopy. Aluminium is determined by neutron-activation analysis.6 RESEARCH AND DEVELOPMENT TOPICS Anal.PYOC. The sediment samples were retrieved by using three coring devices, gravity, box and craib corers. The cores were divided into 1-cm sections, using plastic implements to avoid con- tamination. The sediment was weighed while wet and then dried, at 80 “C, to a constant mass. It was subsequently homogenised with a mortar and pestle. Sediment samples of 3-5g are taken for the 210Pb and trace-metal determinations. For both procedures the sediment has to be totally dissolved. This dissolution is achieved by a series of strong acid leaches using hydrochloric, nitric and hydrofluoric acids. The leachates are combined and made up to a total of 500 ml. A spike of 208Po is added to the sediment initially so that an extraction and detection efficiency for 210Po can be assessed; 25ml of leachate are then taken for tcace metal analysis, 100 ml for 210Po and 250 ml for 226Ra analysis.The 210Pb dating method arises from the fact that, within the 238U natural decay series, a precursor of 210Pb is the gaseous nuclide 222Rn. Because of its mobility as a gas, some 222Rn escapes from continental rocks into the atmosphere, there decaying with its 3.8-d half-life to form 210Pb. The 210Pb in particulate form is subsequently rained out on to the land and surface waters where it decays with its 22 year half-life. In the sediment, therefore, there are two types of 2loPb including “supported” 210Pb, which is in secular equilibrium with the 238U activity of sedimentary minerals, and is decaying with the half-life of 238U (4.5 x 109 years). There is also, however, the “unsupported” or excess 210Pb component precipitated from the atmosphere.If we can measure the excess 2loPb in a sediment profile we can determine the rate of sediment accumulation from the rate of decrease of excess 210Pb activity. The excess 2loPb concentration can be obtained by determining the activity of supported 210Pb and the total activity of 210Pb present. The former is measured by determining the 226Ra concentration, and the latter by measuring the concentration of 21OPo.2 2lOPo is the granddaughter of 210Pb and, with a half-life of 148 d, will be in secular equili- brium with all of the 21°Pb present. The analytical procedure is based on the fact that under certain conditions of pH and temperature polonium spontaneously deposits on to silver.The 100-ml volume solution of dissolved sediment is reduced by heating to approximately 15 ml. Hydroxylammonium chloride is added, the pH adjusted to 2 and the solution heated to 85 “C. A silver disc (2.5 cm in diameter) is introduced, precautions being taken so that only one side is available to polonium, and the solution stirred at 85 “C for 4 h (see Fig. 1). The sections were sealed in polythene bags and frozen until used. This excess 210Pb decays with its own 22 year half-life. Magnetic stirrer Fig. 1. Polonium plating cell. All dimensions are in Subsequently, the disc is a-counted by using a surface barrier detector, amplifier and multi- As 208Po is deposited and counted with the same efficiency as The proximities of the centimetres.channel analyser assembly. 210Po, the concentration of 210Po in the sample can be determined.January, 1980 RESEARCH AND DEVELOPMENT TOPICS 7 2O*Po and 210Po cc energies (5.1 1 and 5.308 MeV, respectively) make high-resolution counting essential. It is therefore reasonably assumed to be in secular equilibrium with the “supported” 210Pb com- ponent. Radium-226 is measured by sealing 250 ml of dissolved sediment in an equilibration flask and allowing 222Rn to grow in, with its 3.8-d half-life to secular equilibrium, The radon is then extracted by flushing with helium and transferred to an a-scintillation detector (see Fig. 2).3 The detector is comprised of a hollow sphere coated with zinc sulphide. The a- particles emitted by 2z2Rn and its daughter interact with the zinc sulphide to produce photons, which are subsequently counted on a photomultiplier and scalar assembly.Radium-226 is a precursor to both 222Rn and 210Pb in the 238U natural decay series. Helium manometer 1 lid COP - acetone traps spiral trap Fig. 2. 222Rn emanation system. Flame atomic-absorption analysis is used to determine iron, manganese, copper, chromium, zinc, nickel and lead in the 25-ml aliquot of dissolved sediment. The equipment used is an Instruments Laboratory 151, with background correction via a deuterium lamp. The samples are measured along with standards prepared in the same matrix. Aluminium is measured by means of neutron-activation analysis. Approximately 0.2 g of dried sediment is placed inside a small plastic vial, which is subsequently marked and flame sealed. This vial, and a similar one containing a standard, are irradiated together for 60 s and counted immediately after for 2 min on an 80 cc Ge(Li) detector. The neutron-activated product, 28A1, has a half-life of 2.3 min, 27Al(n,y)28A1, with a y decay mode at 1.78 MeV.Because both sample and standard have identical geometries and have been exposed to the same neutron-flux, etc., the concentration of aluminium in the sample is derived directly from a comparison of the activities and the amount of aluminium in the standard. The analytical procedure for radiocaesium does not involve any chemical pre-treatment . A known amount of dried and ground sediment is placed in a smdl sample bottle and y- counted on a 100 cc Ge(Li) detector for a period of (usually) 800 min.Caesium-137 (t+ = 30.0 years) decays via 2/3- modes to form 137Bam (t+ = 2.55 min). Barium-137m decays by y-emission and, because it is in secular equilibrium with 137Cs, the activity of the observed y radiation is equal to the activity of lS7Cs. Caesium-134 (it = 2.05 years) has 3/3- and 9y decay modes. The efficiency of the system is determined by counting known radiocaesium concentrations. References 1. 2. 3. Koide, M., Soutar, A., and Goldberg, E. D., Earth Planetary Sci. Lett., 1972, 14, 442. Flynn, W. W., Anal. Chim. Ada, 1968, 43, 221. Ferrante, E. R., Gourski, E., and Boulenger, R. P., in Adams and Lowder, Editovs, “The Natural Radiation Environment,” Chicago University Press, Chicago, 1964, p.353.8 RESEARCH AND DEVELOPMENT TOPICS Anal. Proc. Concentration Procedures for Trace Element Analysis by Spark Source Mass Spectrometry Karen H. Welch and Allan M. Ure The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen, A B9 2Q J , Scotland Spark source mass spectrometry (SSMS) is a sensitive, multi-element technique which has been applied at The Macaulay Institute for Soil Research to the analysis of soils, rocks, plants and biological material~l-~ The technique used has been described in and employs an AEI MS702R mass spectrometer with a hydraulically pressed electrode; this electrode is prepared from a mixture of 25 mg of finely ground (particle size less than 150 pm) sample and 25 mg of pure aluminium powder (particle size less than 70 pm) containing iridium and indium as the internal standard elements.The mass spectrum obtained by sparking the sample electrode against a pure aluminium counter-electrode is recorded on an Ilford Q2 photographic plate from which element contents are found after evaluation by microdensitometry. Although SSMS has a uniformly high sensitivity for most elements, typically 0.01-1 p.p.m. with aluminium metal as the conducting material, some elements, such as the noble metals, have abundances in natural samples that are too low for direct analysis. For this reason alone pre-concentration procedures are necessary. These elements, together with copper and silver, because of their similar properties, form the first group of elements for which a common group concentration procedure is sought.For most of the elements in a second group, arsenic, bismuth, lead, antimony, selenium, tin, tellurium and thallium, which are of geochemical, environmental and biological interest, a group concentration procedure is required, not only on the grounds of sensitivity, but also to obtain freedom from the interference effects caused by matrix compounds. This is the case in the determination of selenium by SSMS in liver ash. Two spectra for simulated liver ash are shown in Fig. 1 (a) and (b) ; one was obtained before and one after the application of a cemen- tation concentration procedure discussed below. This concentration procedure is successful in removing elements forming molecular ionic species, which overlap the selenium (and arsenic) isotopic lines required for analysis.For SSMS analysis, the sample must be a conducting solid and the concentrate should, therefore, ideally take this form. This criterion restricts the method of concentration to procedures such as co-precipitation, electrochemical and cementation techniques or adsorption on activated carbon. Of these methods the application of a co-precipitation method is des- cribed and the development of a cementation procedure discussed. Electrochemical methods of deposition have not been attempted although they have considerable potential, especially for single element determination. Collection by activated carbon was not considered because of the interference effects arising in the spectra from carbon species.6 Concentration by Co-precipitation The particular co-precipit ation technique used was chosen because it was already established and in use for the trace-element analysis of soil extracts and plant material by optical-emission spectrographic methods and considerable experience in its use was available at the Macaulay Institute.The main objections to the method are firstly, that it is a relatively slow laboratory procedure, and secondly that it requires an ashing stage in order to remove the organic reagents before SSMS analysis and this may lead to the loss of volatile elements. I t does, however, provide high concentration factors (up to 400-fold) for a large group of elements of biological and geological importance, for many of which the method has been shown to be quantitative.'^^ The concentration procedure is outlined in Fig. 2.This technique was applied to acetic acid extracts9 of various soils and, in Table I, typical results obtained by SSMS analysis of the concentrates are compared with d.c.-arc spectro- graphic analysis of the concentrates and, for copper, zinc and cadmium, with direct analysis of the soil extracts by atomic-absorption spectrometry. As can be seen from Table I, good agreement was obtained between the SSMS analysis and the other techniques for this group of biologically important elements. Other elements determined by SSMS in concentrates from extracts of soils in acetic acid and likely to be collected quantitively by this procedure include arsenic, niobium, selenium, thorium, uranium and tungsten. The acetic-acid extractableJanuary, 1980 RESEARCH AND DEVELOPMENT TOPICS 9 'I 81 Fig.1. Interfering ions 40Ca3SC1+ a t m/z 75, 30K37C1+ and 41K36C1+ a t m/z 76, 40Ca37Cl+ and 42Ca36C1+ a t m/z 77, soK,+ at m/z 78 and 40Ca,+ and 3QK41K+ a t m/z 80, shown in the spec- trogram of a simulated liver ash ana- lysed directly Fig. l(a), are absent in the spectrogram from a concentrate [Fig. l(b)] prepared by a cementation procedure. The line a t m/z 81 in (a) and (b) is due to 27A13+. I I Evaporate r'l HCL solution Precipitate (pH 5.2) with quinolin-8-olI 30-40 mg ash Fig. 2. Concentration by co-precipi- tation with aluminium using quinolin-8- 01 - tannic acid - thionalide. Phosphate, alkalis and alkaline earths left in solution. TABLE I ACETIC ACID (0.5 N) EXTRACTABLE CONTENTS OF TOPSOIL BY SSMS* AND OTHER^ METHODS Micrograms per gram of oven-dried soil.Soil A Soil B w v 7 Element SSMS Other? SSMS Other? Cd co Cr c u Mo Ni Pb Sn V Zn 0.12 0.45 0.33 0.46 0.01 0.38 0.38 0.04 1.3 2.9 0.08 0.47 0.28 0.39 <0.03 0.38 <0.5 (0.5 1.3 2.0 0.03 0.08 0.29 0.13 (0.01 0.21 0.20 (0.02 1.1 1.4 0.05 0.07 0.19 0.20 <0.03 0.20 €0.3 ~ 0 . 5 0.94 1.2 *SSMS analysis of concentrate. TSpectrographic analysis of concentrate or atomic-absorption spectrometric analysis of soil extract.10 RESEARCH AND DEVELOPMENT TOPICS Anal. Proc. contents of these element in the concentrates, and the total contents in the soil, both deter- mined by SSMS, are shown in Table I1 for two soils. TABLE I1 TOTAL SOIL CONTENTS DETERMINED DIRECTLY AND ACETIC ACID EXTRACTABLE SOIL CONTENTS DETERMINED IN CONCENTRATES BY SSMS FOR SOME ELEMENTS THAT ARE LIKELY TO BE EFFECTIVELY COLLECTED BY THE QUINOLIN-S-OL - TANNIC ACID - THIONALIDE CONCENTRATION PROCEDURE Micrograms per gram of oven-dried soil. Soil A Soil B -- Total Extractable Total Extractable Element content content content content As 2.9 0.01 2.4 0.003 Nb 20 0.01 17 0.02 Se 0.28 0.004 0.10 0.003 Th 4.5 0.06 5.9 0.06 U 2.0 0.07 1.9 0.02 w 0.76 0.005 ~ 0 .5 <0.003 Development of a Method for Concentration by Cementation The general equation for a cementation reaction can be represented as follows: %A*+ + yB (solid) = XA (solid) + yBG+ where B is a metal less noble than A. Aluminium metal has been used industrially as a cementant in solution-purification processes.lO In the cementation, for example, of gold from solution by aluminium, the aluminium reduces the ionic goId to elemental gold, which is deposited on to the aluminium surface.In theory, aluminium should reduce all those elements which lie below it in the electrochemical series and interest lay in determining whether the aluminium powder used to make sample electrodes for SSMS could function as a cementant to collect groups of elements from solution. This would provide a simple procedure for direct collection on to the electrode material and thus minimise contamination problems arising from elaborate chemical pre-treatments. Various methods of mixing aluminium powder with solutions were investigated but in most of these methods it proved difficult to collect the aluminium powder after cementation.This problem was largely overcome by placing 50 mg of aluminium powder in a short, narrow PTFE column, and by drawing the sample solution through the column three times in suc- cession by gentle suction from a water-pump. Three passes provided optimum recovery. The apparatus is shown schematically in Fig. 3. Fig. 3. Schematic diagram of cementation apparatus : X, sample solution reservoir (100 ml); Y, cementation column (3 mm diameter, 6 mm length) of aluminium powder in a PTFE tube; 2, water-operated vacuum pump.January, 1980 RESEARCH AND DEVELOPMENT TOPICS 11 Most cementation procedures have been carried out in acidic media, generally in hydro- thloric acid. Acid strength is one of the factors that is known to affect the rate of the cemen- cation reactionll and its effect varies from element to element.For example, for palladium, reduction has been shown to be effected best in acidic solutions, whereas for platinum, better results are achieved in alkaline solutions.12 Because, however, of the high solubility of finely powdered (less than 70 pm) aluminium powder in hydrochloric acid at strengths greater than 0.1 N, and because a group concentration was envisaged, the acid strength was fixed at 0.06 N hydrochloric acid throughout. Recoveries of silver, gold, copper and lead as chlorides, collected by cementation from 0.06 N hydrochloric acid at room temperature, are shown in Table 111. Recoveries of 80-100y0 were obtained for silver, gold and copper with a relative standard deviation of & 1-16%, but for lead the recovery was much poorer, 37%, and the relative standard deviation very much greater, & 34%.Nitrate is known to interfere with cementation reactions,13 and as the standard solutions of silver and lead are more usually prepared from the nitrates and also as aqua regia digests were envisaged for soil and sewage sludge sample preparation, a brief investigation of this effect was undertaken. The effect of using solutions of the nitrates of silver, gold, copper and lead in 0.06 N hydrochloric acid was to reduce the recovery of all of the elements to less than loyo, an exception being gold, which was almost unchanged. The recoveries were calculated from atomic-absorption spectrometric analysis of solutions pre- pared from the aluminium powder concentrates and verified by analysis of the initial and residual solutions.TABLE I11 PERCENTAGE RECOVERIES ON ALUMINIUM AT ROOM TEMPERATURE FROM 0.06 N HYDRO- CHLORIC ACID CONTAINING 1 mg 1-1 OF COPPER, 2 mg 1-1 OF LEAD, 0.04 mg 1-1 OF SILVER AND 0.2 mg 1-1 OF GOLD AS CHLORIDES Recovery, yo 100 82 83 37 Ag Au c u Pb Relative standard deviation, yo & l +16 f l 0 f34 The recoveries of arsenic, antimony, selenium, tin, tellurium and thallium from solution by means of a similar procedure using aluminium powder as a cemetant were found to be negli- gible. If, however, the aluminium was amalgamated by drawing a solution of mercury (11) chloride (40 mg 1-1) through it prior to cementation the recoveries were substantial, particularly for selenium. These recoveries are shown in Table IV, which also shows those for osmium, palladium, platinum and rhodium.Preliminary investigations have indicated that recoveries of the elements palladium, platinum and rhodium can be appreciably increased by heating the sample solution in a modified column. Typical results obtained when the sample solution is heated to 60 "C prior to being drawn once through a column are also shown in, Table IV. TABLE IV CONTAINING 1 mg 1-1 OF ARSENIC, ANTIMONY, SELENIUM, TIN, TELLURIUM AND THALLIUM and 1 mg 1-1 OF OSMIUM, PALLADIUM, PLATINUM AND RHODIUM PERCENTAGE RECOVERIES ON AMALGAMATED ALUMINIUM FROM SOLUTIONS Solution temperature w Element 25 "C 60°C As Sh Se Sn Te T1 0 s Pd Pt Rh 20 30 100 30 0 15 26 20 50 50 77 20 65Aaal. Proc. A comparison between the recoveries of silver, gold, copper and lead on amalgamated and unamalgamated aluminium revealed that there was no significant difference between the two sets of results and in all further experiments the aluminium powder was amalgamated in the column before use.Having established that amalgamated aluminium appeared to be able to collect all except one of the elements of interest, tellurium, a few natural samples were studied. A European sewage sludge and two Scottish soil samples ( 5 g ) were digested three times with 25ml of aqua regia (6 N re-distilled hydrochloric acid - nitric acid, 3 + 1). After each addition the digest was evaporated to dryness on a steam-bath. In order to remove nitrate from the residue it was treated three times with 6 N hydrochloric acid, evaporating the solution to dryness after each addition.Then, 50 ml of 0.06 N hydrochloric acid were added and the solution filtered before being drawn through the amalgamated aluminium cementation column. An SSMS analysis had previously been carried out directly on the ashed sewage sludge and the results are compared with SSMS analysis of the aluminium cementation concentrate inTable V. 12 RESEARCH AND DEVELOPMENT TOPICS TABLE V TRACE ELEMENT CONTENTS OF A EUROPEAN SEWAGE SLUDGE Micrograms per gram of air-dried sludge. Element Analysis of ash c u 450 Se - As - Rh - Pd - 25 0.05 Pt Au 0.92 T1 0.04 Pb 180 Bi 20 - 2 Analysis of cementation concentrate 330 0.3 0 03 0.18 0.08 25 0 02 0 05 0.75 0.06 130 10 There was good agreement between the silver, gold, bismuth, copper, lead, platinum and thallium results.The elements arsenic, osmium, palladium, rhodium and selenium, which were observed and determined in the aluminium concentrate, were not detected in the ashed material. This may be due, in part, to the loss of volatile elements during the ashing stage but it also reflects the improved detection limits obtained following concentration. In the aluminium concentrates obtained from both soil samples arsenic, palladium , selenium and thallium were also detected, as is shown in Table VI. For those elements which could be determined by semi-quantitative spectrographic analysis of the soil ashes, reasonable agree- ment was found between these and SSMS analyses of the aluminium concentrates. The discrepancies may occur because amounts extracted by an aqua regia digest will approach, TABLE VI TRACE ELEMENT CONTENTS OF TWO SOIL SAMPLES Micrograms per gram of air-dried soil.Acid igneous Ultra-basic parent material parent material && SSMS* Spec.? SSMS* Spec.? Ag 0.01 <1 0.06 <1 Au 0.04 t l 0.05 <1 cu 3 10 350 300 Pb 5 9 1 4 * SSMS = Analysis of cementation concentrate from aqua regia digest by spark source mass spectro- t Spec. = Analysis of soil ash by semi-quantitative optical-emission spectrography. metry.January, 1980 RESEARCH AND DEVELOPMENT TOPICS 13 but will not always be quantitatively equal to, the total element content measured by spectrographic analysis of the solid soil material. One of the authors, K. H. Welch, thanks the trustees of the Analytical Chemistry Trust Fund of the Chemical Society for the award of an SAC Research Studentship.1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. References Ure, A. M., Bacon, J. R.. Berrow, M. L., and Watt, J. J., Geoderma, 1979, 22, 1. Ure, A. M., and Bacon, J. R., Geochim. Cosmochim. Acta, 1978, 42, 651. Ure, A. M., and Bacon, J. R., Proc. Anal. Div. Chem. Soc., 1976, 13, 124. Ure, A. M.. and Bacon, J. R., Analyst, 1978, 103, 807. Bacon, J. R., and Ure, A. M., Anal. Chim. Acta, 1979, 105, 163. Bacon, J. R., and Ure, A. M., “Advances in Mass Spectrometry,” Volume 8, in the press. Scott, R. O., and Mitchell, R. L., J . Soc. Chem. Ind., 1943, 62, 4. Mitchell, R. L., and Scott, R. O., J . Soc. Chem. Ind., 1947, 66, 330. Scott, R. O., Mitchell, R. L., Purves, D., and Voss, R.C., “Spectrochemical Methods for the Analysis of Soils, Plants and Other Agricultural Materials,” Consultative Committee for Development of Spectrochemical Work, Bulletin 2, 1971, The Macaulay Institute for Soil Research, 1971, p. 23. Bratt, G. C., and Newman, 0. M. G., Ras. Disclosure, 1976, 147, 66. Pandey, U. M., Chem. Era, 1976, 12, 357. Hawley, J. E., Wark, W. J., Lewis, C . R., and Ott, W. L., Can. Min. Metall. Bull., 1951, 474, 669. Svehla, G., Editor, “Comprehensive Analytical Chemistry,” Volume 111, Elsevier, Amsterdam, 1975, p. 242. Evaluation of Diskpin Samples for the Sampling and Analysis of Liquid Iron and Steel J. McCaig, A. Cunningham, J. Lindsay and J. Little and J. M. Ottaway Chemical Laboratory, Ravenscraig Works, British Steel Corporation, Motherwell, Lanarkshire Department of Pure and Applied Chemistry, University of Strathclyde, Cathedral Street, Glasgow, G1 1XL Technological advances have caused the speed and diversity of modern steelmaking processes to increase rapidly, necessitating the provision of a rapid, accurate analytical service that is able to provide data on the chemical composition of liquid melts at various stages of the refining process.The speed and dynamic nature of modern processes such as L.D. basic oxyge n steel- making has continued to demand even faster analysis from the analyst in order that process control can be carried out within the stringent time limits available. Sophisticated computer-controlled techniques such as optic a1 emission spectrometry and X-ray fluorescence spectrometry are used routinely in the British Steel Corporation Ravens- Craig Works to enable the two demands of speed and accuracy to be met.These analytical techniques have been developed to the extent where it is unlikely that their speed will be surpassed in the immediate future and thus it became apparent that any further savings in the time of analysis would only accrue by streamlining the slowest stage in the system, the sampling and sample preparation operation. The first step in doing this was to select a uniform sample form to replace, if possible, the four completely different forms of sample at present in use. Of the various commercial sampling devices available it was decided to select a paddle and pin shape (Diskpin) rather than cylindrical, as the former type fulfils a multi-purpose role by providing a disk section for spectrometry and a pin section for the rapid determination of ele- ments such as carbon, sulphur, nitrogen or acid-soluble aluminium.Sample preparation times for paddle and pin samples are much reduced, because time-consuming sectioning or drilling prior to analysis is unnecessary. The Diskpin sample had the added advantage of being available in both immersion and pneumatic modes for areas where immersion was impractical, e.g., the continuous casting mould. Initial sampling trials with the Diskpin sampling devices were used to define the appropriate technique for each process area and also to highlight areas where the sampling devices could be14 RESEARCH AND DEVELOPMENT TOPICS Anal.PYOC. improved. The three improved devices will be described only very briefly but consisted basically of a mild-steel disk-shaped mould with a silica pin entry channel encased in resin- bonded sand and held in a cardboard support tube. Metal caps protected the assembly from slag and the pneumatic sampler was hermetically sealed to allow suction of the liquid metal into the mould to occur when a partial vacuum was applied. The immersion samplers filled due to the action of ferrostatic pressure when immersed in liquid metal and the final sample shape was formed due to liquid metal chilling in the disk and entry channel to give the uniform sample shape shown in Fig. 1. Fig. 1. The Diskpin sample. The results of sampling trials carried out with these devices are indicated in Table I.TABLE I SUMMARY OF SAMPLING TRIALS Process area Technique Sampler Success rate, yo Steelmaking convertor . . . . .. .. Immersion 513-005 97 Steelmaking ladles . , .. . . .. Immersion 5 13-004 98 Ingot moulds . . .. , .. .. .. Pneumatic 5 13-002 97 Casting tundish . . .. .. .. .. Pneumatic A 1 3-002 9s Torpedo ladles . . .. . . . . .. Immersion 5 13-004 < 10 Blast furnace runner . . .. .. . . Pneumatic 5 13-002 40 The addition of titanium to the sample mould meant that a wide range of steel types could be sampled successfully even in highly oxidised conditions such as are found in “rimming” steels. Low success rates experienced when sampling liquid iron were due mainly to the sample mould failing to chill the liquid iron satisfactorily, which resulted in loss of metal and unsatis- factory samples.A comparison of the various sampling operations involved is shown in Table 11, with approxi- mate times for each operation. It can be seen that the Diskpin offered substantial savings in time over two of the established techniques and offered a practical alternative for sampling liquid steel. Further work is under way to define a suitable device for sampling liquid iron. Analytical Examination of Diskpin Samples A series of Diskpin samples drawn concurrently with the established cylindrical samples were analysed by emission spectrometry for the main elements of interest, viz., carbon, silicon, sulphur, phosphorus, manganese and aluminium. Good agreement was obtained as reflected by the values of the regression line for each ele- ment shown in Table 111.January, 1980 RESEARCH AND DEVELOPMENT TOPICS TABLE I1 COMPARISON OF SAMPLING TIMES 15 Operation Sampling .. .. .. .. . . Stripping . . .. . . .. .. Cooling . . .. .. .. . . Preparation time- Spectrometry . . . . . . .. Combustion . . . . .. .. Total time .. . . . . .. Sampling time/s r I Spoon and mould Immersion cylinder Diskpin A 120 10 10 10 15 20 30 150 60 60 120 340 60 120 355 60 20 170 TABLE I11 REGRESSION DATA FOR DISKPIN AND CYLINDRICAL SAMPLES Element Slope of regression line Intercept Carbon . . .. . . 1.01 9 x 10-5 Silicon . . .. .. 0.99 4 x 10-4 Sulphur .. .. 1.03 7 x 10-4 Phosphorus . . .. 1.01 4 x 10-4 Manganese . . .. 1.00 7 x 10-3 Aluminium . . .. 1.00 8 x The reproducibilities of replicate analyses by emission spectrometry of the Diskpin, cylinder and standard spectrometric samples were determined and the Diskpin sample exhibited marginally improved precision over the established sample for carbon, silicon, phosphorus, manganese and aluminium, although both sample types were significantly less reproducible than the standard samples, which are specially homogenised for spectrometric analysis.The Diskpin sample was examined for possible heterogeneity both across and through the sample section. This is of paramount importance in metallurgical analysis, where only a small area and mass of the sample is atomised for analysis and thus local imperfections caused by variation in metallurgical structure or inclusions can have a drastic influence on the final result if they occur within the focal region of the spark.This examination was carried out by analysing a group of Diskpin samples of different compositions at four discrete positions at each of twelve discrete levels through the section of the sample utilising emission spectrometry. Results obtained for carbon, silicon, sulphur, phosphorus, manganese, nickel, copper, chromium, molybdenum and aluminium were obtained from the Diskpin and standard samples. A statistical classification of the variances produced was used to demonstrate the presence of heterogeneity for these elements, which, although statistically significant, was considered small enough to render the Diskpin sample acceptable for the routine technical classification of steels. These results were also used to confirm the random nature of the heterogeneity, which sug- gested that no specific depth of preparation was required prior to spectrometric analysis being carried out.The pin section of the sample was also examined with a view to determining the suitability of the pin for the rapid determination of carbon, sulphur nitrogen and acid-soluble aluminium for process control purposes. This was carried out by comparing the analysis of the disk and pin sections of the samples selected using the techniques outlined in Table IV. TABLE IV COMPARISON OF ANALYSES OF DISK AND PIN SECTIONS OF DISKPIN SAMPLES Element Analytical method Slope of regression line Intercept Carbon .. . . Combustion - non-aqueous titration Sulphur . . . . Combustion - titration Nitrogen .. . . Carrier - gas fusion Aluminium . . . . Automated spectrophotometry 0.99 6 x 1.01 7 x 10-4 1 .oo 1 x 10-4 0.97 1 x 10-316 RESEARCH AND DEVELOPMENT TOPICS Anal. PYOC. Repli- cate analyses of discrete samples taken along the pin length for carbon, sulphur, nitrogen and aluminium gave reproducibilities approximating closely to the precision of the technique used for each element, and this confirmed the homogeneity of the pin section and confirmed its suitability for rapid control analysis of these elements. The suitability of the pin section for use in the method for the rapid determination of acid- soluble aluminium1 reported by Gale has been demonstrated and is now in routine use. The general applicability of the Diskpin device has been demonstrated for the routine analysis of liquid steel in the Ravenscrajg Works. Further work is continuing to develop a device suitable for sampling liquid iron and modified devices that give an improved representa- tion of the aluminium content of liquid melts.The authors thank the Ravenscraig Laboratory of the British Steel Corporation for facilities to carry out this work. Good agreement was obtained between the disk and pin sections for these elements. Reference 1. Gale, P., British Steel Corporation, Research Report CC/1/78, 1977. Some Applications of Inductively Coupled Plasma Emission Spectrometry to the Determination of Toxic Trace Elements G. F. Kirkbright, D. L. Millard and R. G. Snook Department of Chemistry, Imperial College of Science and Technology, London, S W7 2A Y The combination of the inductively coupled plasma (ICP) with multi-channel or even single- channel spectrometers has provided the analyst with a powerful optical emission spectro- metric technique for the determination of elements at trace, minor and major levels in many types of sample.The most important advantages that this combination of instrumentation has over other spectrometric techniques are the extended linear calibration ranges obtained (typically six orders of magnitude with respect to concentration) and the absence of inter- ferences in the ICP source itself. Solution samples are normally introduced into the plasma by the use of pneumatic nebulisa- tion and for most solution applications the pneumatic nebuliser is an ideal device for intro- duction of the sample into the ICP.There are, however, limitations to the use of pneumatic nebulisation. For example, the solution uptake rate may be altered if the viscosity of the sample solution changes from one sample to another, although this can be compensated for by correct and careful matching of standards. Another more difficult situation to deal with occurs when nebulising solutions with high dissolved solids contents, which frequently block the orifice of the nebuliser. More recently, ultrasonic nebulisation has been employed as a technique for sample introduction and its application frequently leads to superior detection limits than are obtainable with pneumatic nebulisation. It may be necessary, however, to employ desolvation procedures to minimise the adverse effects observed in the plasma owing to increased sample solution loading of the plasma.Even when employing desolvation pro- cedures certain undesirable effects may be observed if temperature stability of the desolvation apparatus is not maintained. A disadvantage of both nebulisation procedures is the relatively large volume of solution (1-2 cm3) required for each analysis, although Greenfield and Smith have devised a system for the nebulisation of microlitre volumes of so1ution.l In our laboratory we have investigated an alternative sample introduction system, which employs a resistively heated graphite rod to vaporise the analyte from small sample volumes (10-20 p1) directly into the injector of the ICP torch and hence into the axial injector channel of the ICP.The graphite rod is enclosed in a glass chamber (volume 1 dm3), which is connec- ted to the injector tube of the ICP torch with 0.5 m of plastic tubing. Volumes of 10 pl of solution can be applied to the graphite rod through a sampling port in the chamber using a micropipette and can be desolvated and subsequently vaporised into the ICP by applying pre-programmed heating cycles to the graphite rod. The vaporised analyte is carried to the plasma on a continuously flowing stream of argon that passes through the glassJanuary, 1980 RESEARCH AND DEVELOPMENT TOPICS 17 chamber. This procedure frequently leads to superior detection limits than are obtainable with pneumatic nebulisation as the analyte passes through the axial channel as a pulse of sample, giving rise to a transient analyte atomic-emission signal.This transient signal is detected at the photomultiplier of the single-channel spectrometer and recorded on a potentiometric chart recorder, enabling accurate peak-height measurements to be taken. Under the optimum conditions reported previously2 we have established that for many elements calibration graphs can be obtained over five orders of magnitude with respect to concentration of the analyte present and detection limits of 10-10 to 10-l2g can also be obtained using the graphite rod as a sample introduction device. The precision of these determinations is acceptable, with relative standard deviations of typically about 0.05. For most of the elements investigated, inter-element effects and interference effects have been absent. For some of the more volatile toxic elements investigated, however, we observed a marked increase in emission intensity in the presence of concomitant elements. The best example of this is the effect of selenium(V1) on the observed emission intensity of cadmium and arsenic.In the absence of selenium(V1) a calibration graph for cadmium plotted on double logarith- mic axes was rectilinear over a concentration range of only two orders of magnitude and showed a slope of 1.5; the detection limit for cadmium under these conditions was g. In the presence of 10 pg of selenium(VI), however, a graph on similar axes was rectilinear over four orders of magnitude; the resulting detection limit for cadmium was 10-l1g. As no similar effect was observed when cadmium solutions in the absence and presence of selenium were nebulised into the ICP it was thought that the effect is due to an inter-element effect in the vaporisation apparatus rather than an interference in the plasma source.Stabilisation of the volatile elements by selenium during pre-vaporisation heating cycles was ruled out as the effect was still observed if the analyte and selenium(V1) solutions were placed in different depressions in the graphite rod (thus precluding intimate mixing on the rod). Washing experiments were undertaken to assess the extent of possible deposition of the elements in question along the connecting tube from the vaporisation chamber to the ICP torch injector and it was found that in the absence of selenium appreciable deposition of cadmium occurs, resulting in poor transport efficiency to the plasma; in the presence of selenium, however, the deposition of cadmium is much reduced.Radiotracer experiments were then undertaken to quantify the effect of selenium on the transport efficiency of cadmium to the plasma. The distribution of 115Cdm (i4 = 47 d) in the vaporisation apparatus and connecting tube was determined, and also the amount of 1Wdm delivered to the injector tip of the plasma torch in the presence and absence of selenium- (VI). These results are summarised in Table I, and clearly indicate that the enhancement of observed emission intensity is a result of increased transport efficiency, by prevention of deposition of the volatile elements on the walls of the vaporisation chamber and connecting tube to the plasma.We believe from evidence presented by microscope slides of the vaporised material collected 1.0 cm above the graphite rod that the transport of analytes to the plasma is facilitated by the formation of dry condensed aggregates of material a few centimetres above the graphite rod after vaporisation. These dry aggregates are successfully transferred to the ICP torch. When considering the more volatile elements, however, there appears to be an insufficient path length between the graphite rod and the walls of the glass chamber to allow the analyte vapour phase to cool to form aggregates, and deposition therefore occurs. The TABLE I DISTRIBUTION OF CADMIUM-115111 ON MANIFOLD, CONNECTING TUBE AND INJECTOR TIP Distribution of Cd, yo* A Cd concentration/ Concomitant 7 pg cm-3 ion (10 p g ) Chamber Tubing Injector tip 0.1 - 44 17 9 1.0 - 40 22 18 10.0 - 38 18 38 0.1 Se(V1) 7 4 63 1.0 Se(V1) 9 8 64 10.0 Se(V1) 7 5 59 * Expressed as percentage of Cd applied to graphite rod.18 RESEARCH AND DEVELOPMENT TOPICS Anal.PYOC. addition of concomitant elements such as selenium(V1) assists the formation of aggregates and therefore enhances the transport efficiency of the volatile elements to the plasma. The use of the graphite rod vaporisation apparatus as a sample introduction device has permitted the determination of many trace elements in a variety of sample types. For example, ten elements have been determined successfully in uranium solutions using a sample volume of lop1 of solution applied to the graphite rod, and 10-fold superior detection limits than observed using pneumatic nebulisation have been obtained.Similarly, the direct determination of toxic elements such as lead, cadmium and zinc has been performed on bovine serum with no sample pre-treatment other than the addition of a surfactant (Triton X) to assist in “wetting” the graphite rod, 0.5% of sodium sulphide solution to stabilise volatile elements during drylng and 0.1% of selenium(V1) to prevent deposition of these elements in the connecting tube of the apparatus. These additives can be prepared as a single solution and simply added to sample solutions in situ on the graphite rod to provide a rapid method of analysis requiring only small sample volumes. References 1.2. Greenfield, S., and Smith, P. B., Anal. Chim. Acta, 1972, 59, 341. Gunn, A. M., Millard, D. L., and Kirkbright, G. F., Analyst, 1978, 103, 1066. Application of Differential Spectrophotometry to the Determination of Fluoride Using AFBS C. Jordan Department of Analytical Chemistry, The Queen’s University of Belfast, Belfast, B T9 5A G , Northern Ireland Fluoride can be determined with the use of a calibration line prepared using Deane’s pro- cedurel for AFBS. This procedure, an example of the only positive absorptiometric method for fluoride, is based on the colour of the ternary complex formed between AFBS, La and F- in aqueous solutions of fixed pH (around 4.7) with an AFBS to La ratio of 1 : 4. Solutions are prepared by adding various aliquots of standard sodium fluoride solution to a mixture of AFBS in a constant ionic strength buffer followed by addition of lanthanum(II1).After 20 min, the transmittance (T) of each solution (x) can be measured at 635 nm against an AFBS - La blank (s) in the ordinary way [giving T(x/s) readings] and the calibration line drawn by plotting -log T(x/s) against the fluoride concentration (C, or C,) : -log T(x/s) = A(x/s) = €C,Z The fluoride concentration of an unknown solution can be read from the calibration line if its absorbance, A (x/s), is known. The uncertainty in the value of this concentration, due to the uncertainty S , in the transmittance measurements, is usually quoted2 by reference to -0.434 s c - c - T(x/s)logT(x/s) ST which reaches a minimum of about 3 x S, at T(x/s) = 0.368.As-the scale reading error makes an important contribution to S , in the older type of spec- trophotometer, it is reasonable to expect that this type of error, and hence the photometric error, could be reduced by scale expansion. This scale expansion can be achieved by either electrical or “chemical” means. With chemical scale expansion, standard solutions of the analyte are used to set the ends of the %T scale of the spectrophotometer. The three possi- bilities arising from this differential approach are detailed by Reilley and Cra~ford.~ As other worker^^-^ have already pointed out that, in practice, the trace analysis and ulti- mate precision techniques do not necessarily lead to any gain in precision, it was decided that, of the two, only the more general, ultimate precision technique would be used.Thus, in the following, the ordinary technique for fluoride determinations with AFBS is compared with the transmittance ratio and ultimate precision techniques only.January, 1980 RESEARCH AND DEVELOPMENT TOPICS 19 If the 100yoT point is set with reference solution r in the beam (concentration Cr) and the OyoT point is set with reference solution R (concentration C,) then the reading on the expanded yoT scale, which we shall call the relative transmittance, Trel, is related to the ordinary transmittances of solutions x, r and R by If Beer's law holds for the sample, equations (1) and (3) give For the transmittance ratio technique, T(R/s) = 0 and equation (4) simplifies to -log Trel = -log T(x/r) = J C x + log T(r/s) (54 and the calibration graph will be linear (intercept # 0).precision calibration graphs of -log Trel against C, are non-linear. The trace analysis and ultimate Photometric Error Contribution The photometric error associated with the use of these differential methods can be deduced' by applying the law of propagation of errorsS to equation (4), giving We therefore expect [from equation (6a)l a decrease in the photometric error, for a given solution, as T(r/s) decreases and/or T(R/s) increases, i.e., as scale expansion is increased. (For the more general case, the original paper of Reilley and Crawford3 should be consulted.) As increased scale expansion is achieved, however, one finds that STrel tends to increase (Table I). TABLE I EFFECT OF SCALE EXPANSION ON THE STANDARD DEVIATION OF THE TRANSMITTANCE MEASUREMENTS, ST,,^ C , CR Scale ST'reI 'T'rel x t0.05, Technique x los/,, x 1 0 6 / ~ expansion x 103 d G Ordinary, n = 6 Transmittance ratio, 9% = 6 Ultimate precision, n = 3 0 Shutter 1.00 1.17 1.23 6 Shutter 1.67 2.05 2.15 7 1.82 2.02 2.12 8 2.01 2.06 2.16 9 2.18 1.94 2.04 7 13 4.41 7.2 17.9 8 12 6.80 11.6 28.8 was determined for each technique from n parallel %T measurements. emptied and re-filled and the spectrophotometer readjusted for each measurement. The cell was The net effect of changes in T(r/s) and T(R/s) on the photometric error [calculated using equations (6a and 6b)l is shown in Fig.1. Fig. 1 shows that, while there is a net reduction in the photometric error when the transmittance ratio technique is used, there is a net increase in the photometric error with the ultimate precision technique where is increasing more rapidly than T(r/s)-T(R/s) is decreasing.This can be traced to the poor medium-term stability of the SP500 instrument and the relatively long time required with the ultimate precision technique to place the sample solution in the spectrophotometer beam once the expanded scale has been set up.20 RESEARCH AND DEVELOPMENT TOPICS Anal. PYOC. Effect of Scatter In addition to considering the photometric error contribution, one should also make an allowance for the scatter of the points about the calibration line. This is easiest achieved by carrying out a linear regression analysis on the calibration points, the ultimate precision results being made amenable to analysis by converting Trel readings into T(x/s) values using equation (3) and treating the calibration line as if it had been obtained by the ordinary technique.We can then represent all the calibration lines by equation (5a), which can be rewritten as where a = intercept on the y-axis and b = E = slope of line. Application of the law of propagation of errors to this expression permits one to deduce that the maximum relative concentration error with 95% confidence limits, associated with a concentration determination from this line, is given by7 [tor.1-' x $I2 = [ (,,34sT}]2 + [ %I2 + S b dfi y-a IT(x/r) Y-U (7) where S, and s b are the standard deviations of the intercept and slope, respectively, and are evaluated during the linear regression analysis of the results.We see immediately that the first term of equation (7) makes allowance for the photometric error while the other two allow for the scatter of the points about the line. Linear regression analysis of the N experimental points also permits the calculation of the actual error, ACF, involved in calculating C, from a given experimental point Yo with the regression equation. Thus, where ACF is given by9 As with equation (7), the error decreases as N, n and b (or E ) increase. ACF is at a minimum if the middle of the calibration line is used (yo = 7). Fig. 2 shows how the actual relative con- centration error, ACIC, varies with the number of parallels (n) and with the concentrations of the reference solutions (Cr and C,) and that of the sample (C,).The variation of the maximum relative concentration error, Sc/C, with n, Cr, C, and C,,l0 assessed by equation (7), exactly parallels the results shown in Fig. 2 except that the values are approximately 2.5 times as large. We see that the so-called ultimate precision technique actually leads to a considerable loss in precision over the ordinary technique (especially as Cr and C, approach one another) whereas the transmittance ratio technique, despite the limited scale expansion possible here, leads to a net increase in precision as T(r/s) is decreased (Cr increased). In conclusion, it can be said that it would be a waste of time using the ultimate precision technique in an attempt to increase the precision of a spectrophotometric method unless the effect of instrumental drift on the transmittance measurements can be kept low either by using a new generation spectrophotometerwith good medium-term stability or, less expensively, by obtaining a thermostated compartment with three matched cells for the old type of spec- trophotometer. The latter alternative would reduce s, by minimising the time required to place the sample solution into the beam once the expanded scale was set up. Unless this modification is available, the old type of spectrophotometer such as the SP500 is best suited to the transmittance ratio technique, which can lead to useful decreases in both the photometric and overall error, especially for low-transmittance samples. It is probably for this reason, as well as that of simplicity and convenience, that the latter technique has been the most widelyJanuary, 1980 EQUIPMENT NEWS 21 (n=31 oc 0 h c W v “ u c 9 6 7 8 9 10 11 12 13 14 CF ( X I 06)/M Fig. 1. The photometric error, as assessed by (6 a,b), for the ordinary a, transmittance ratio 0 and ultimate precision - .-.--. techniques, for values of Cp ranging from 6 to 13 x 10-6 M. The curve numbers refer to the values ( x lo6) of C,/Ca used to set the ends of the transmittance scale. Those curves labelled with a prime correspond to n = 6; otherwise n = 3. 0 6 9 6’ 0’ 7’ 8’19’ ” 7 8 9 10 11 12 13 14 CF(X106)/M Fig. 2. The actual over-all error, as assessed by (8), for the ordinary a, transmittance ratio 0 and ultimate precision - . - . - . techniques, over the range CF = 9-13 x M. The curve numbers refer to the values ( x 106) of C,/C, used to set the ends of the transmittance scale. Those curves labelled with a prime correspond to n = 6; otherwise n = 3. used differential method to date, having been used for the determination of often relatively high concentrations of about 20 elements in a wide variety of media, with S,/C values as low as 0.1% claimedll (although this is for the photometric error contribution alone). 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. References Deane, S. F., and Leonard, M. A., Analyst, 1977, 102, 340. Willard, H. H., Merritt, L. L., and Dean, J. A., “Instrumental Methods of Analysis,” Fifth Edition, Reilley, C . N., and Crawford, C . M., Anal. Chem., 1955, 27, 716. Shigematsu, T., and Tabushi, M., Bull. Inst. Chem. Res. Kyoto Univ., 1958, 36, 127; Anal. Abstr., Bontnik, B., Chem. Anal. (Warsaw), 1964, 9, 717; Anal. Abstr., 1965, 12, 6357. Ingle, J. D., Anal. Chem., 1973, 45, 861. Jordan, C., MSc Thesis, Queen’s University of Belfast, 1978. Nalimov, V. V., “The Application of Mathematical Statistics to Chemical Analysis,” Pergamon Press, Davies, 0. L., and Goldsmith, P. L., Editors, ‘‘Statistical Methods in Research and Production,” Jordan, C., and Leonard, M. A., Microchem. J., to be published. Svehla, G., Talanta, 1966, 13, 641. Van Nostrand, New York, 1974, pp. 92-97. 1959, 6, 3332. Oxford, 1963, p. 34. Oliver and Boyd, Edinburgh, 1972, p. 206.

ISSN:0144-557X    

DOI:10.1039/AP9801700002

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

ANALYTICAL DIVISION DIARY 36 Analytical Division Diary, continued Tuesday, 19th, 4.15 p.m.: Lough- borough February, continued Contact: Mr. A. F. Fell, Department of Pharmacy, Heriot-Watt University, 79 Grassmarket, Edinburgh, EHI 2HJ. (Tel. 031 -225-8432, Ex. 225). Midlands Region, jointly with the Lough- borough University Chemical Society. There's Death in the Pot (I1 Kings, 4,40). The need to find food has been a major preoccupation of mankind from prehistoric days to the present time. The lecture will describe how the legal and scientific control of our food supplies was achieved in the past and how it is maintained under present-day conditions. Speaker: F. C. Shenton. Lecture Theatre JOOl , Edward Herbert Building, University of Technology, Lo ug h boro u g h, Lei cesters h i re.Contact: Mr. H. E. Brookes, 35 Dunster Road, West Bridgford, Nottingham, NG2 6JE. (Tel. 0602-231769). Scottish Region, Chromatography and Electrophoresis and Joint Pharma - ceutical Analysis Groups, j o i n t 1 y with Wednesday, 20th, 9.10 a.m.: Edinburgh the Association of Clinical Biochemists. Advances in Applied High-perform- ance Liquid Chromatography. Introductory Remarks by G. C. Cochrane. Plenary Lecture: "Present and Future Perspec- tives in HPLC," by Professor J. F. K. Huber. "Extrathermodynamic Relationships in lon-pair HPLC," by E. Tomlinson. "Mechanisms of lon-pair Separation of Bio- logically Important Compounds," by R. A. Hartwick. "The Analytical and Preparative HPLC of Polypeptide and Protein Hormones from Normal and Pathological Calcitonin-secreting Tissues," by E.C. Nice. "Pre-concentration and Selective Sample Handling in HPLC," by Professor R. W. Frei. "Derivative and Diode Array Detectors in HPLC," by A. F. Fell. "Optimum Conditions for HPLC on the Prepara- tive Scale," by J. C. Kraak. Panel Discussion on Optimisation in Preparative H PLC. Anal. Proc. Department of Chemistry, West Mains Road, The University, Edinburgh. Registration is necessary. Cost f16 to CS and ACB Members, f 2 0 to non- members and f 5 to students. Closing date February 8th. Contact: Dr. D. Simpson, Analysis For Industry, Factories 2/3, Bosworth House, High Street, Thorpe-le-Soken, Essex, C016 OEA.(Tel. 025-584- 771 4). Wednesday, 20th, 10.30 a.m.: Berkeley Radiochemical Methods Group. Radiochemical Measurements in Industry. "Applications of Radioisotopes in the Chemical Industry," by A. A. Heslop. "The Use of Radiochemical Techniques in the Evaluation of Nuclear Fuel Performance," by D. Bradbury, D. Reed, I. Robins and S. Tyfield. Sodium Reactor Systems," by A. Hooper. Analysis in Industry," by J. W. McMillan. "Studies of Radioactivity Transport in Liquid "Some Applications of Nuclear Microprobe "Radiotracers in Water Movement," by K. White. Berkeley Nuclear Laboratories, Central Electricity Generating Board, Berkeley, G lou cesters h i re. Registration is necessary. Cost f 6. Closing date February 11 th.Contact: Dr. A. R. Ware, Central Radio- chemical Laboratory, Scientific Services Centre, CEGB, Canal Road, Gravesend, Kent. (Tel. 0474-51 122, Ex. 235). Tuesday, 26th, 4.30 p.m. : Swansea Western Region, jointly with the South West Wales Section of CS/RIC. "Two Dimensional Gas Chromatography," by D. R. Deans. Chemistry Department, University College, Swa nsea. Contact: Mr. J. G. Jones, Wessex Water Authority, P.O. Box 95, The Ambury, Bath, Somerset, BAI 2YP. (Tel. 0225-31 3500). The Electroanalytical Group meeting on Wednesday, 27th: Sheffield Gas Sensors has been postponed. ANALYTICAL DIVISION DIARY January, 1980 Analytical Division Diary, continued January, continued A small commercial exhibition is to be held in conjunction with this meeting. Byng Kenrick Suite, The University of Aston, Birmingham.Registration is necessary. Cost E l 0 to include buffet lunch, tea and coffee. Closing date January 16th. Contact; Mr. H. E. Brookes, 35 Dunster Road, West Bridgford, Nottingham, NG2 6JE. (Tel. 0602-231 769). FEBRUARY Friday, Ist, 7 p.m. : Moreton North West Region, jointly with the South Cheshire Branch of the Pharma- ceutical Society and the Liverpool and District Section of CS/RIC. "Drug Metabolism and Pharmacokinetics in the Pharmaceutical Industry," by D. Case. The meeting will be preceded at 6 p.m. by a buffet, kindly provided by E. R. Squibb 8 Sons. Numbers are limited to 70 and registration is necessary. Closing date January 25th.E. R. Squibb 8 Sons, Reeds Lane, M oreton, Wi rral. Contact: Mr. G. Davison, Research Department, Kodak Ltd., Acornfield Road, Kirby, Merseyside, L33 7UF. (Tel. 051 -546-21 01, Ex. 127/118). Wednesday, 6th, 10.30 a.m.: London Analytical Division, in conjunction with the Special Techniques Group. Recent Advances in Organic Mass Spectrometry in Analytical Chem- istry. This meeting will deal with mass spectrometry techniques applied to organic substances including combina - tions with gas chromatography and high - pressure I iq u id chromatography. " Recent Developments in I on isat ion Techniques," by Professor K. R. Jennings. "Combined High Pressure Liquid Chromato- graphy- Mass Spectrometry," by D. E. Games. "The Analysis of Marine Sterols by GC - MS Techniques," by J.A. Ballantine. "Applications of Ion Kinetic Energy Spectro- scopy Using a Double-focusing Instrument of Reversed Geometry," by Professor J. H. Beynon. "Selected ton Monitoring," by B. J. Millard. "Advances in Protein/Glycoprotein Structure Determination," by H. R. Morris. 37 Scientific Societies Lecture Theatre, 23 Savile Row, London, W.1. Registration is necessary. Cost f 7 with lunch and f2 without. Closing date February 1 st. Contact: Miss P. E. Hutchinson, Analytical Division, The Chemical Society, Burlington House, London, W1 V OBN. (Tel. 01 -734-9971). Wednesday, 13th, 6.30 p.m.: London South East Region, Microchemical Methods and Atomic Spectroscopy Groups. Sophistication i n I nst r u men ta t i on- Has it Gone Too Far? Discussion Meeting.The increasing complexity of modern instrumentation often makes it difficult for the prospective purchaser, or the analyst with a specific problem to solve, to decide which technique, accessories, facilities, etc., are essen tia I to his requirements. Recent advances in electronics and greater use of abbrevi- ations such ICP, DSC, LSI, VDU, ETA, etc., prompt the question "Sophistication in Instrumentation-has it GoneToo Far ?" Speakers: J. E. Cantle and D. A. Pantony. Southside Senior Common Room, Princes Gardens, Imperial College, South Ken si n g ton, London, S. W. 7. A charge of 50p will be made at the meeting to cover the cost of refresh- ments.Registration is required. Closing date February 6th. Contact: Mr. D. J. Willis, Rank Hilger, Westwood Industrial Estate, Margate, Kent. (Tel. 0843-24261 ). Thursday, 14th, 4.15 p.m.: Aberdeen Scottish Region, jointly with the Aberdeen and North of Scotland Section of CS/RIC and the Aberdeen University Chemica I Society. Enzymes in Chemistry. Enzymes are involved in an increasing number of analytical procedures, both in sample pre-treatment and in the measurement step. The lecture will cover both aspects, and show how enzymes are used in a wide variety of analyses. Speaker: A. Townshend. Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen. [continued on p. 36 Aspects of Hazardous Materials will be introduced by D.W. Sutcher. Europa Lodge Hotel, Darlington, County Durham. Registration is necessary, Cost f6 Analytical Division Diary JANUARY Tuesday, 22nd, 4 p.m. : Belfast Contact: Mr. C. L. Denton, Jioxide International Limited, Central Labora- tories, Portrack lane, Stockton-on- Northern Ireland Sub- Committee. Tees, Cleveland, (Tel. 0642-63571 ). "Scanning Electron Microscopy and Electron Probe Micro Analysis in Forensic Science," by v. L. Beavis. Chemistry Department, The Queen's Uni- ve rsi t y, Belfast Thursday, 24th, 10.30 a m , : Birming- ham Mid/ands Region, jointly with the West Midlands Region of the Association Contact: Mr. W. J. Swindali, Depart- of Clinical Biochemists. Practical lmmunoassay : The Present ment of Chemistry, David KeSr Building, Queen% University, €3elfast, BT9 SAG. State, of the Art. (Tel. 0232-661 11 1, Ex. 4428). Wednesday, 23rd, 7.1 5 p.m. : Darling- ton Chairman's Introduction by Dr. D. N. Raine. "An Overview of Imrnunoassay," by Professor V. Marks. "Techniques of lodination," by Professor W. R. North East Region; Annual General Butt. "Fluorescence-linked Immunoassay," by J. N. Miller. "Chemiluminescence-linked Irnmunoassay," by Meeting followed by a Discussion Meeting' A discussi*n On Safety J. S. Woodhead. "Enzyme-linked Irnmunoassay," by M. J. O'Su Ilivan. '"Immunoprecipitation and the Centrifugal Fast Anafyser," by I. Deverill. [continued inside back cover including dinner. Printed by Heffers Printers Ltd Cambridge England

ISSN:0144-557X    

DOI:10.1039/AP98017BX003

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

January, 1980 EQUIPMENT NEWS 21 Equipment News Ultraviolet - Visible Spectrophotometer than 1 s, to be known as the HP8450A, will be A spectrophotometer that can measure and available in Europe later this year. A large display a 200-800 mm wide spectrum in less dynamically allocated data storage is provided22 EQUIPMENT NEWS Anal. Proc. so that analytical information can be stored in the digital memory during each run. The output may be sent automatically to an optional printer-plotter or to any number of input-output devices that can be inter- connected with the Hewlett-Packard Interface Bus (IEEE Standard 488). For use with other data systems, an RS232C serial interface is pro- vided. An integral computer automatically controls the instrument during the analysis, and up to 100 methods, each with up to 20 lines of instructions, can be stored and recalled.The optical system incorporates an aberration- corrected holographic grating with excellent stray light characteristics, efficiency and resolu- tion. The only moving part in the optical system is a high-precision, computer-controlled beam director which serves up to five sample positions located in an easily accessible sample area. Hewlett-Packard Ltd. , King Street Lane, Winnersh, Wokingham, Berkshire, RGll 5AR. Contact: Arthur Wood. Tel. Wokingham 784774. Ultraviolet Spectrophotometers A non-scanning Model 550A spectrophotometer and a scanning Model 550s are based on the Models 552 and 554, and are equipped with double-beam optics, grating monochromator and microcomputer electronics. The non-scanning Model 550A is intended primarily for analyses at a fixed wavelength, and includes double-beam optics, grating mono- chromator for the wavelength range 195-900 nm with 2-nm resolution, automatic source and filter change, and yoT, A and CONC scale with easy-to-read illuminated digital displays. The scanning Model 550s is provided with five-speed wavelength drive by stepper motor, permitting spectra scanning using a chart recorder; it can also record the 1st and 2nd derivatives of a normal spectrum.Perkin-Elmer Limited, Post Office Lane, Beaconsfield, Buckinghamshire, HP9 lQA. Tel. Beaconsfield 6 16 1. On-line Mass Spectrometer A mass spectrometer for on-line qualitative and quantitative analysis of the gases evolved in the process of coal gasification has been introduced, the CVC Superspec 600 Process Gas Analyser.With a fast response time it can detect gases at levels of 5 p.p.m. (0.0005~0) over a mass range from 0 to 600 a.m.u. Designed to tolerate the harsh environmental conditions typically encountered in petrochemi- cal plants, it is also useful for monitoring the underground burning process of combustion gases such as CO (10-35y0), CO, (0.1-50y0), (20-9074) , He (10-1 000 p.p.m.), H,S (50-5 000 p.p.m.), etc., from one or more gas streams. CVC Scientific Products Ltd. , Eastheath Avenue, Wokingham, Berkshire, RGll 2PW. Tel. Wokingham 787348. CH, (0.1-15%), H2 (O.1-40%), 0 2 (0.1-21%), N2 Laser Source Spectrometer The Model LS-3 Laser Source Spectrometer pro- vides spectral measurement over a wide range with orders of line-width resolution better than 0.000 1 cm-l.The spectra are rapidly Cali- brated and fully resolved by the use of a lead- salt tunable diode laser, with wavelength adjust- ment by electrically powered cryogenic tempera- ture control, thus providing a nearly complete coverage up to a 100cm-l interval. The spectrum can be displayed on an oscilloscope. Spectra-Physics Ltd. , Laser Products Division, 17 Brick Knole Park, St. Albans, Hertfordshire, AL1 5UF. Plasma Emission Spectrometers Two plasma emission spectrometers, Spectra- span I11 and IV, can determine most elements at trace to major constituent levels in a variety of complex matrices such as biological materials, natural and effluent waters and seawater, with a wide linear dynamic working range.Difficult elements such as boron, phosphorus, silicon, refractory metals and rare earths can be determ- ined with ease. The spectrum produced by the d.c. argon plasma at temperatures of 6 000- 10 000 K permits the choice of ionisation state lines as high as second order. An echelle grat- ing spectrometer is used, with maximum energy throughout at or near its blaze angle for maxi- mum efficiency. Techmation Ltd., 58 Edgware Way, Edgware, Middlesex, HA8 8 JP. Tel. 01-958-31 11. High- performance Fluorescence Spectro- photometer The Model 650-40 fluorescence spectrophoto- meter is a high-performance instrument with microprocessor control of ordinate and abscissa function. The optical system, with a wave- length range of 200-850 nm, employs concave gratings driven by stepper motors under microprocessor control.Selections from the keyboard include scan speed , auto-zero, zero suppression, integration, concentration, response time and photomultiplier gain. The excitation or emission monochromator can be scanned at aJanuary, 1980 EQUIPMENT NEWS 23 rate of 960 nm min-l for automatic location of peak maximum. Perkin-Elmer Ltd., Post Office Lane, Beacons- field, Buckinghamshire, HP9 IQA. Tel. Beaconsfield 6 16 1. smaller amounts of sample, standard and diluent than many other automatic dilutors. Corning Medical, Corning Ltd., Halstead, Essex, CO9 2DX. Variable Band Pass Filters Variable band pass filter sets contain five long wavelength cut-off filters and five short wave- length cut-off filters. Each filter is 50 nm from its neighbours, and is individually wavelength- tunable down to the next filter.A combination of two filters will provide any band width throughout the visible spectrum. Also avail- able are an ultraviolet blocking filter and an infrared blocking filter. Melles Griot B.V., Industrial & Scientific Optics, Nieuwe Kade 10, Postbus 567, Arnhem, The Netherlands. Tel. 085-22901 1. Atomic-absorption Spectrophotometer The Model 4000 atomic-absorption spectro- photometer offers the performance of the Model 5000, but without the sequential multi-element capabilities. The full system employs built-in memory for all instrumental conditions for six elements, microcomputer-controlled gas control system, manual six-lamp turret, background correction for UV and visible range, automatic setting of wavelength with or without peaking, automatic selection of the lamp for background correction and automatic intensity control.An auto-sampler is also incorporated. Perkin-Elmer Ltd., Post Office Lane, Beacons- field, Buckinghamshire, HP9 IQA. Tel. Beaconsfield 6 16 1. Thermo Circulator A new Thermo Circulator is designed to pass thermostatically controlled liquid through jacketed spectrophotometer cell holders or cells to maintain a constant temperature. Other uses are, for example, refractometers, viscometers, culture flasks, blood gas analysers, chromato- graphic columns and density gradient tubes. Perkin-Elmer Limited, Post Office Lane, Beaconsfield, Buckinghamshire, HP9 1QA. Tel. Beaconsfield 6 161. Dilutor The Corning 800 dilutor, designed for Models 435 and 455 flame photometers, has been modi- fied for use with the earlier models 430 and 450.The 800 dilutor incorporates a platen-type driven roller pump which gives longer tube life and minimises the risk of blockages, and requires Turbomolecular Pump Gas Chromato- graph - Mass Spectrometer A turbomolecular pump replaces oil diffusion pumps to obtain an operational vacuum, saving, in the case of the 5985B gas chromatograph- mass spectrometer systems, 20 min in pump down-time and even more in the venting cycle. The absence of hot oil virtually eliminates the 30-min cool-down cycle. Hewlett-Packard Ltd., King Street Lane, Winnersh, Wokingham, Berkshire, RGl 1 5AR. Contact : Arthur Wood. Tel. Wokingham 784774. Light and Electron Microscope A combination light and electron microscope is now available, the IS1 LEM-2000.It allows a specimen to be examined and photographed in both modes (LM and TEM) on a single instru- ment. A specimen can be observed in the light electron microscope ( 5 0 - 5 0 0 ~ ) and then in the transmission electron microscope (250-45 000 x ), which shares the same specimen stage. Sections stained for the LM up to 1.5 pm thick may be examined using specific colour identification (LM) and high-resolution (TEM) imaging. Extra large grids, 7 mm in diameter, permit the use of sections up to 5 mm square. International Scientific Instruments, Water- witch House, Exeter Road, Newmarket, Suffolk. Contact: Steve Chapman. Tel. 0638-5031. Microscope The Fluorestar laboratory microscope is specific- ally designed for fluorescence techniques. Facilities are provided for incident light, trans- mitted light or mixed illumination examinations, and plug-in “fluoclusters” are provided with matched exciter filter - dichroic beam splitter - barrier filter combinations.Reichert- Jung UK, 820 Yeovil Road, Slough, Berkshire, SL1 4JB. Tel. Slough 31351. Photon Counting Photomultipliers Two photomultipliers, Type D341 with an S20 photocathode for response in the visible - infra- red region and the D347 with a bialkali cathode for minimal dark count, are for photon counting and similar low light level applications. A thermionic background count of 40 C.P.S. at 20 “C and about 1 C.P.S. at -20 “C is typical from a 2.5 mm diameter photocathode, giving good signal to noise performance.The pulse24 EQUIPMENT NEWS Anal. Proc. rise time is of the order of 1.3 ns at 2 kV operat- ing voltage. The 50-MHz counting capability coupled with the low background rate allows operation over a dynamic range of the order of EM1 Electron Tubes, Bury Street, Ruislip, Middlesex. Contact: Mr. A. Fletcher. Tel. Ruislip 30771. 107. Infrared Spectra Interpretation A new applications programme, SEARCH, is designed to interpret and identify infrared spectra. Used with the Perkin-Elmer Infrared Data Station, SEARCH interprets a spectrum in terms of the molecular functional groups present in the unknown molecule. A library of 2 000 spectra of selected compounds accompanies the SEARCH software on one side of a micro disk, and by comparing the unknown spectrum with this, SEARCH details the best 15 matches. Perkin-Elmer Ltd., Post Office Lane, Beaconsfield, Buckinghamshire, HP9 1QA. Tel.Beaconsfield 6 16 1. High-performance Liquid Chromato- graphy Equipment A high-pressure septum injector for high- performance liquid chromatography, which overcomes the problem of column clogging and development of leaks, gives as high an injection efficiency as injection valves. An electrically operated tube-cutting machine, which provides square, burr-free ends on both +g- and %-in tubing with i.d. down to 0.008 in, is also now available. Scientific Glass Engineering (UK) Ltd., 657 North Circular Road, London, NW2 7AY. Tel. 01-452-6244. Automated Gel Permeation Chromato - A gel permeation chromatography system in- cluding a Series 1 LC pump, LC-100 column oven, a selection of GPC columns, Sigma 10 data station, gel permeation chromatography soft- ware and complete user instructions is now offered.Perkin-Elmer Limited, Post Office Lane, Beaconsfield, Buckinghamshire, HP9 1QA. Tel. Beaconsfield 6 161. SZraPhY Injector Accessory A continuous rate injector accessory, the Dohrmann CRI, is used in sensitivity MCTS- 30D microcoulometric sulphur and the DN 1 O / 100 chemiluminescent nitrogen analyser, and can be fitted to other instruments. The injector uses an electronically controlled stepper motor to advance the sample syringe plunger and gives a repeatability better than f20 p.p.b. at con- centrations from 0 to 1000 p.p.b., making possible the routine analysis of sulphur and halogens below 0.1 p.p.m.The CRI also pro- cesses the analyser signal and gives a direct digital display of concentration in p.p.m. Techmation Ltd., 58 Edgware Way, Edgware, Middlesex, HA8 8JP. Tel. 01-958-3111. 2 000-V Power Supply The Model 1420 is intended for use with any electrophoretic system and is especially useful for isoelectric focusing applications. Three readout meters are calibrated for high and low ranges for each of the parameters. A mode switch is fitted to enable a constant voltage (0-2 000 V), a constant current (0-150 mA) or a constant power (0-300 W) to be used. Bio-Rad Laboratories Ltd., Caxton Way, Holywell Industrial Estate, Watford, Hertford- shire, WD1 8RP. Tel. Watford 45517. Balances The Alpha 22 series of electronic balances is alphanumeric with a clear LED readout, having an 8-mm display.All models are dual range, with capacities of 2 kg to 0.1 g and 200 g to 0.01 g, and all have a fully subtractive tare. The HC22/51 model also includes a store and recall facility, and can be interfaced with calculators, printers, etc. Oertling Ltd., Orpington, Kent, BR5 2HA. Contact: Mr. G. B. Hough. Tel. 0689-25771. Balances A new series of toploading industrial systems- orientated balances, the PK range, include three high-resolution, single-range balances and two high capacity models equipped with the Mettler DeltaRange. The PK models have high-speed readout and a built-in self-function check, and are self-calibrating. A. Gallenkamp & Co. Ltd., P.O. Box 290, Technico House, Christopher Street, London, EC2P 2ER.Tel. 01-247-3211. Infrared Dryer The LP15 infrared dryer can be used with any Mettler electronic top-loading balance. Closing the hood of the dryer switches on the twin-tube infrared radiators. Using the LP15 with a Mettler PC balance and GC301 application input device any sample mass can be used with the microprocessor automatically making all necessary ratio calculations. A. Gallenkamp & Co. Ltd., P.O. Box 290, Technico . House, Christopher Street, London, EC2P 2ER. Tel. 01-247-3211.January, 1980 EQUIPMENT NEWS 25 Refrigerated Centrifuge The Chilspin refrigerated centrifuge has a temperature range of 4-15OC. It will accept the same angle and swing out heads as the MSE Super Minor and has a maximum capacity of 600ml. Rotational speed is variable up to 6 100 rev min-' with an angle head giving 3 760g maximum and up to 4 500 rev min-l with a swing out head to give a maximum RCF of 6 710 g.A. Gallenkamp & Co. Ltd., P.O. Box 290, Technic0 House, Christopher Street, London, EC2P 2ER. Tel. 01-247-3211. Rotary Evaporator The 349 rotary evaporators are available as the standard model or cold trap model. The 349 evaporators include a cool-running induction motor with adjustable speed controls. A new vacuum-tight greaseless rotary seal is designed to keep frictional heat and wear to a minimum. In the cold trap model a new cold trap arrangement is used for the concentration of volatile solutions and freeze-drying applications. For the conversion of the standard model to the cold trap model and vice veysa, accessory kits containing glassware and fitments are available.Coming Ltd., Laboratory Division, Stone, Staffordshire, ST15 OBG. Tel. 078583-2121. Stirrer Vessel A new stirrer vessel is available from Schleicher & Schull that has two filter areas and two pres- sure sources. By simply changing an adaptor element, filter areas of 12.5 or 70cm2 can be obtained. The stirrer vessel can be fitted with the Schleicher & Schull ANTLIA pneumatic pump, making the unit completely self-con- tained, or it can be connected to an existing stationary pressure source. In addition to normal ultra- and micro-filtration with mem- brane filters, it is now possible to use large-area filter-papers and glass-fibre filters. The com- plete stirrer vessel can be autoclaved a t 121 "C.Anderman & Co., Ltd., Central Avenue, East Molesey, Surrey, KT8 OQZ. Tel. 01-979-8112. High-pressure Fittings Conversion fittings with a pressure rating to 30 000 lb in-2 are now available, which allow the user to connect existing high-pressure systems to any standard tubing or piping systems. The new fittings are machined from high-quality 316 stainless steel. The male high-pressure ends are designed for use in existing i- , 8- and &in high- pressure ports. Conversions are easily made to standard tubing and piping systems using i-, #- and Q-in Swagelok tube fitting ends, tube socket weld ends, or male and female NPT threaded ends. Techmation Ltd., 58 Edgware Way, Edgware, Middlesex, HA8 8JP. Tel. 01-958-3111. Magnetic Hot-plate Stirrer A magnetic hot-plate stirrer, which auto- matically reverses direction every 6 s, has a top plate covered in white Deconyl high-density nylon to resist most spillages and abrasion.Called the AUTOREV-H, the unit operates within the voltage ranges of 100/110 V a.c., 60 Hz, or Z00/250 V a.c., 50 Hz, with other voltages available to order, and has a controll- able speed range of 100-1 450 rev min-l. Cabbum Sterilizers Ltd., 9 Towerfield Road, Shoeburyness, Essex. Tel. 03708-6266. Freeze Dryer Accessories A wide range of manifolds and chambers are available for use with the VirTis research and pilot production freeze dryers. Tiered mani- folds are available for product drying in ampoules or flasks up to 2 1 or a variety of sizes in one run. A range of vertical manifolds are designed for volume drying viral and bacterial cultures in ampoules or bottles, and where critical control of temperature is not required. Large-port drum manifolds permit processing of shell-frozen materials in large containers (typically 10-15 1).Techmation Ltd., 58 Edgware Way, Edgware, Middlesex, HA8 8JP. Tel. 01-958-3111. Digital pH Meters Digital and analogue pH meters are available with a wide range of compatible electrodes, in both LED or LCD forms. The CD60, with its 13 mm liquid crystal display, provides an accuracy of 0.02 pH unit when used with a standard electrode. Attachment of the PSlOO adaptor converts this battery-powered model to mains operation. The CD300 can select the read-out range of either 0-14 pH, 0-99 mV or 0-9.99 v. Semat (UK), 89 Lakeside Road, London, N13 4PS.Tel. 01-886-8948. Digital pH Meter A hand-held digital pH meter, Model 3050, is mains or battery operated, and has a liquid crystal display to give good visibility even in bright sunlight. Electronic Instruments Ltd., Hanworth Lane, Chertsey, Surrey, KT16 9LF.26 EQUIPMENT NEWS Anal. Proc. Syringes The range of modular micro-syringes manu- factured by the Unimetrics Corporation of Anaheim, Calif., are designed for maximum accuracy and reproducibility, and are available in both gas- and liquid-tight versions. Replace- able needle syringes in all capacities from 1 pl to 1 ml are available. Anderman & Co. Ltd., Central Avenue, East Molesey, Surrey, KT8 OQZ. Tel. 01-979-81 12. Filter Holder A disposable filter holder, the FP 030, is com- pletely sterile and pyrogen free, and available with either 0.2 pm, 0.2 pm hydrophobic, 0.45 pm or 5 pm pore size Triton-free cellulose acetate membrane filter.With a large 5.7 cm2 filter area, the maximum operating pressure is 7 bar and the holders are fitted with a standard Luer thread and taper connector. Anderman & Co. Ltd., Central Avenue, East Molesey, Surrey, KT8 092. Tel. 01-979-8112. Plasma Cleaner A table-top electrodeless r .f. discharge apparatus requires only the addition of a standard vacuum roughing pump to enable it to remove trace contaminants from internal reflection plates and windows, treat surfaces to improve adhesion, sterilise surgical instruments or plates prior to implantation and clean microscopic slides for preparation of smears, removal of photo resist, etc.Harrick Scientific Corp., Croton Dam Road, Box 867, Ossining, N.Y. 10562, USA. Tel. 914- 762-0020. Full Flow Quick- Connects A new series of Swagelok Quick-Connects with *-in female NPT ends, designed for maximum flow and fast, leak-tight connections on rigid or flexible tubing, piping lines and hydraulic hose assemblies, has been introduced. The new QF4 series Quick-Connects are available in brass and 3 16 stainless-steel barstock construction. Ser- vice ratings are 5 000 lb in-2 in brass and 10 000 lb in-2 in 316 stainless steel. Tempera- ture ratings depend on O-ring materials, with recommended maxima of 250 O F for Buna and 450 O F for Viton. Manchester Valve & Fitting Co. Ltd., 12 Rufford Court, Hardwick Grange, Warrington, Cheshire, WAl 4RF.Tel. 0925-822662. Universal Concept Terminal The basic Vector UCT system contains a 74-key keyboard, two 9-digit displays, a 40-column alphanumeric matrix printer, the 6-position keylock, micro-computer, power supply and 5 Eurocard slots for function expansion. The keyboard module includes an interface card for the microprocessor bus and a software routine to read the ASCII codes generated by the keys, with the display module having an interface card and control software. The printer module includes a printer driver card, audible alarm source and software for generating alpha- numeric characters a t a rate of 40 C.P.S. The UCT is based on the Vector 8085A-based MMD85-P Eurocard, containing 1280 bytes of RAM, 8K EPROM sockets, parallel I/O, opto- isolated serial 1/0 and bus buffering.Two Vector MMD-M88 memory expansion cards raise total system memory capacity to 24K EPROM space and 17K RAM. The software is in a modular form. The recent Vector MMD-DDS dual-disk micro-computer development system enables the UCT system to be programmed in FORTRAN, BASIC or ASSEMBLER language. Vector International, Research Park, B-3044 Haasrode, Belgium. Scintillation Counter A microprocessor-controlled liquid scintillation counter, the TRI-CARB 460, is available in two versions : the 460C cassette loading system with data processing and the 460D cassette loading with full data processing facilities including DPM calculations. Both include a video dis- play unit, system control panel and built-in hard copy printer.The data processor outputs are fully compatible with RS232 for connection to on-line computers. The sample handling system comprises cassettes each having a capacity of 10 samples. When fully loaded the instrument will accom- modate 460 samples at any one time. In addition to the standard sample chain a second sample changer offers the means to measure single urgent samples quickly and conveniently without altering the operating conditions already set for the main batch. The microprocessor control system can store up to fifteen separate programs. A built-in microprocessor-based calculator system, the Spectraliser, captures the entire radionuclide spectrum for coincidence threshold to infinity, and selects regions within pre-set upper and lower limits to determine spectral indices of the sample or counting efficiency.Pre-set measurement regions for sH, 14C, la51 and 32P as single and dual label nuclides are inco rpor- ated, or regions for specific attention based on the approximate keV of the radionuclide expected to be present can be set. Tel. 32(16) 23 08 94.January, 1980 EQUIPMENT NEWS 27 Packard Instruments Ltd. , Caversham Bridge House, 13-17 Church Road, Caversham, Berk- shire, RG4 7AA. Tel. 0734-478235/478065. Ultraviolet Oscillographs Autograph 8 and Autograph 6 are UV oscillo- graphs having 8- and 6-in chart widths, respect- ively. The Autograph 8 incorporates up to 25 channels , with a servo-controlled speed range from 1 mm min-1 to 5 m s-1. Remote-control facilities and automatic lamp start are in- corporated.Bryans Southern Instruments Ltd., Willow Lane, Mitcham, Surrey, CR4 4UL. Tel. 01-640- 3490. Gel Electrophoresis Equipment Three vertical slab gel electrophoresis units fabricated from clear acrylic sheet consist of an upper and lower buffer reservoir attached to a rigid vertical plate support. Silicone rubber seals on the upper reservoir provide a leak-free seal. The Model 40 unit incorporates a gel casting area of only 83 mm width by 1.4 mm thickness and separation distances of 34mm. For separating complex protein mixtures the Model 200 general purpose unit, which can incorporate a high-efficiency cooling system, uses a gel 175 mm wide by 1.4 mm thick with a separating length of 136mm. The Model 400 unit, which also uses a gel 175mm by 1.4mm but with a separating length of 336 mm, is designed for use in poly-nucleotide sequencing.When using radioactively labelled substances autoradio- grams can be produced by covering the gel in Savan-wrap and placing it directly on to stan- dard X-ray film. Shandon Southern Products Ltd., 93 Chad- wick Road, Astmoor, Runcorn, Cheshire. Tel. Runcorn 66611. Personal Environment Monitor The 3M 3500 Organic Vapour Monitor is a watch- sized badge designed to act as a personal dose meter for personnel exposed to potentially hazardous organic vapour environments. The monitor is self-contained, lightweight and does not require a sampling pump. Clipped to the collar close to the wearer's breathing zone, it provides a precise measurement of personal exposure by sampling vapours at constant rates.Desorption occurs within the closed monitor, which can be submitted for analysis by conven- tional gas chromatography. Using data sup- plied by 3M, the mass of the compound can simply be computed and converted into parts per million. Occupational Health and Safety Products Group, 3M United Kingdom Limited, 3M House, P.O. Box 1, Bracknell, Berkshire, RG12 1JU. Tel. Bracknell 58297. Size Measurement The Coulter Nano-Sizer determines average particle size in suspensions and emulsions in the over-all range 0.04-3.0 pm. For the analysis only the refractive index and viscosity of the suspending liquid are required. The built-in micro-compu ter performs the calculations , which are displayed digitally to three significant figures. Fine Particle Group, Coulter Electronics Ltd., Coldharbour Lane , Harpenden, Hertfordshire, AL5 4UN.Tel. Harpenden 63151. Pulse Generator A pulse generator with an accurate crystal source requires only to be switched to one of the two frequency ranges provided (99.99 or 999.9 Hz full-scale) and four digits to set for the desired frequency. Crystal reference and digital setting gives the instrument almost absolute accuracy. Litre Meter Ltd., Unit 9, Park Street Indus- trial Estate, Aylesbury, Buckinghamshire, HP20 1ET. Contact: Mr. I. Mercer. Tel. 0296-20441. Toepler Pump An improved version of an automatic Toepler pump used to determine the dissolved gas content of fluids, particularly non-volatile fluids such as oils, is available. The equipment auto- matically controls the entry of the oil to the evacuation chamber and pumps the evolved gases to the measuring burette.The gas col- lected in the measuring burette can be passed directly into a gas chromatograph for analysis. International Research & Development Co. Ltd. , Fossway, Newcastle upon Tyne, NE6 2YD. Tel. 0632-650451. Digital Thermometer The Tempcheck Digital Thermometer has been redesigned to give a smaller unit, 112 x 68 x 34mm, with a working temperature range of -200 to + 1200 "C. Rechargeable batteries built in with plug-in charger, improved cold junction compensation and better LED display are included. Anwill Instrument Co., 26 Knowles Street, Rishton, Lancashire. Tel. Great Harwood 886555.28 EQUIPMENT NEWS Anal. Proc. Automated Control for HPLC A chromatography control module offers analysts increased automatic operation facilities and greater computing power.The chromato- graph is controlled by a single microprocessor- based unit with a built-in data handling system. Multiple programmed runs can be stored in the unit’s memory, permitting long-term un- attended operation. The module connects with any liquid chroma- tograph in the LDC range, A full alpha- numeric keyboard with shielded display screen shows the instructions, analysis status and parameter files in plain language rather than in codes. A digital tape cassette system and the provision of LDC BASIC gives the module mini- computer capability and the two-pen printer- plotter and data acquisition system adds the power of two computing integrators at low cost per channel, presenting a hard copy of all data and chromatograms in an easily interpreted format.Laboratory Data Control, Shannon Inter- national Airport, Ireland. Contact : Richard Graham. Tel. Limerick 61266. Literature The May/June 1979 Edition of Measurement Computation News includes information on the HP 9800 System 45B computer, an advanced real-time spectrum analyser the HP 3582A, and a micro-processor laboratory learning course using the HP 5036A. Hewlett-Packard Ltd., King Street Lane, Winnersh, Wokingham, Berkshire, RG11 5AR. Tel. Wokingham 784774. An illustrated brochure on computer graphics can be obtained from Tektronix Inc., Informa- tion Display Group, P.O. Box 500, Beaverton, Ore. 97077, USA. The June 1979 issue of the Hewlett-Packard Journal is devoted to articles on the use of the HP300 computer.Hewlett-Packard Ltd., Central Mailing Dept., Van Heuven Goed- hartlaan 121, 1180 AM Amstelveen, The Netherlands. A booklet describes the latest modules in Tracor’s 900 Series liquid chromatograph. Solvent programming, sample injection and pump system modules, which incorporate the latest liquid chromatography technology, are included, as are the 970A variable-wavelength UV absorbance detector with automatic scann- ing option, and the Model 965 selective photo- conductivity detector. Techmation Ltd., 58 Edgware Way, Edgware, Middlesex, HA8 8JP. Tel. 01-958-3111. A paper is available describing the automatic measurement of chemical oxygen demand by Johnson COD meter in the sewerage systems of a Swedish pulp mill.The results of correlation studies between BOD and COD analyses for various wastewater types are included. Tech- mation Ltd., 58 Edgware Way, Edgware, Middlesex, HA8 8JP. Sigma Technical Bulletin No. 585 gives full details of a method for measuring calcium in serum or plasma. The chromogenic indicator used is cresolphthalein complexone. Sigma London Chemical Co. Ltd., Diagnostic Products Department, Fancy Road, Poole, Dorset, BH17 7NH. Tel. 0202-733114. A thermal analysis reprint entitled “Thermal Analysis: Useful Tool for Quality Control in a Complex Era” is available. Examples are reported for the three basic techniques : differen- tial scanning calorimetry, thermogravimetric analysis and thermomechanical analysis. Perkin-Elmer Ltd., Post Office Lane, Beacons- field, Buckinghamshire, HP9 1QA.Tel. Beaconsfield 6 161. A Chromatography Accessories catalogue is fully illustrated and includes details of ancillary chromatography equipment ranging from ab- sorbants to the Zippette solvent dispenser. Packard Instruments Ltd., 13-17 Church Road, Caversham, Berkshire, RG4 7AA. Contact: Mr. C. Horne. Tel. 0734-478235. A Nucleonics Accessories brochure giving details of an extensive range of scintillation cocktails, reagents, vials and reference materials for liquid scintillation and automatic gamma counting techniques is available. Packard Instruments Ltd., 13-17 Church Road, Caversham, Berkshire, RG4 7AA. Contact: Mr. C. Horne. Tel. 0734- 478235. A leaflet entitled “DO your switches switch off when the going gets tough” describes the Giannini range of Enviro-Switches. The con- tacts are enclosed within a welded chamber and are operated externally by magnetic action.Push-button switches, rotary switches, plungers, key-lock switches and limit switches are also described. Techmation Ltd., 58 Edgware Way, Edgware, Middlesex, HA8 8JP. Tel. 01-958- 3111.January, 1980 ANALYTICAL CHEMISTRY TRUST 29 International Labmate is available as a guide to suppliers of laboratory equipment, scientific instruments and chemicals. In addition, a card- reply service for a range of advertisers is in- cluded. Labmate similarly contains a card- reply service for advertisers of scientific instru- ments. Both publications are available from Labmate Ltd., Newgate, Sandpit Lane, St. Albans, Hertf ordshire. Tel. 07 2- 7 5 55 7 4. The May/June 1979 issue of International Laboratory contains articles on the use of HYLC for multi-component serum analysis, micro- processor-controlled HPLC, reproducibility in a two-pump gradient HPLC and preparative liquid chromatography. Quantitative thin- layer chromatography is the subject of a paper, as is also transmission scanning acoustic micros- copy for non-destructive testing, high-energy plasma excitation and high-resolution spec- trometry] inductively coupled argon plasma spectroscopy, and co-ordinated surface analysis with scanning electron microscopy, electron probe microanalysis and electron microscopy. Articles on recent advances in polymer charac- terisation by gel-permeation chromatography and multi-dimensional gas chromatography are also included. International Scientific Communi- cations Inc., Sycamore House, Woodside Road, Amersham, Buckinghamshire, HP6 6AA. Tel. Amersham 22703/21005. New Materials A reference material “PreciFlo” is available for calibration of continuous flow analysers. Pre- pared from bovine material to obviate the risk of hepatitis, the material has high values for cholesterol and triglycerides and includes y- glutamyl transpeptidase. Roehringer Corporation (London) Ltd., Bell Lane, Lewes, East Sussex, BN7 ILG. Tel. Lewes 71611.

ISSN:0144-557X    

DOI:10.1039/AP9801700021

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

January, 1980 ANALYTICAL CHEMISTRY TRUST 29 The Analytical Chemistry Trust An article describing the creation of the Trust published in the September, 1977, issue of and the ways in which the interest accruing Proceedings. The statement of account for the from the invested capital of the Trust Fund is year ending December 31st, 1978, is presented used to further the objects of the Trust was below. The Chemical Society Analytical Chemistry Trust Fund Income and Expenditure Account for the Period Ended December 31st, 1978 INCOME L Income from Book sales . . . . .. .. .. .. . . 8 694 Income from Investments . . .. .. .. .. .. .. 44 984 Interest on Loan and Deposit Accounts . . .. .. .. .. 22 834 76 512 Less : EXPENDITURE Contribution to expenses of CS Analytical Division .. .. . . 10 549 Studentships, Grants and Prizes . . .. .. .. .. . . 4 053 Gold and Silver Medals . . . . . . .. .. .. .. 416 Audit and Professional Fees - . . . .. .. .. .. 560 Postages, Travelling and Sundry expenses . . .. .. .. 2 712 18 290 EXCESS OF INCOME OVER EXPENDITURE CARRIED TO BALANCE SHEET fj58 222 -30 CORRESPONDENCE Balance Sheet as at December 31st, 1978 INVESTMENTS AT COST Balance as a t October lst, 1977 . . .. .. .. A d d : Investments Purchased During the Period . . k .. .. 560 251 . . .. 460 535 Anal. PYOC. Less: Cost of Investments Disposed of CURRENT ASSETS Deposit Accounts with Banks . . Investment Deposit Account . . Income Tax Recoverable . . .. Cash at Bank .. .. .. Sundry Debtors . . .. .. Less : CURRENT LIABILITIES Sundry Creditors . . .. .. FINANCED BY TRUST CAPITAL ACCOUNT Balance as at October lst, 1977 A d d .- Profit on sale of Investments . . .. .. .. . . .. .. . . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. k 1 020 786 .. a . 360 401 660 385 .. .. .. .. .. .. .. .. .. .. 266 000 49 200 20 786 2 501 5 555 .. .. .. .. .. .. INCOME AND EXPENDITURE ACCOUNT Balance as at October lst, 1977 . . .. .. . . .. .. A d d : Excess of Income over Expenditure for the Period . . .. 344 042 33 613 310 429 517 465 148 263 665 728 246 864 58 222 305 086 k970 814 NOTE-The sum of $289.20 is held in a blocked savings account at the Standard Bank Limited, Salisbury, Rhodesia.

ISSN:0144-557X    

DOI:10.1039/AP9801700029

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

30 CORRESPONDENCE Anal. PYOC. Correspondence Correspondence is accepted on all matters of interest to analytical chemists. Letters should be addressed to the Editor, Analytical Proceedings, The Chemical Society, Burlington House, London, WIV OBN. Oil and Fat Extraction Sir, time factor in the investigation concerned. I have duly read the reply of Dr. Hersch- Moreover, although he now states that the doerfer (Proc. Anal. Div. Chem. SOC., 1979, 16, methods recommended in this Report are 312) to my trenchant criticisms (Proc. Anal. intended to be used as reference methods, the Div. Chem. SOC., 1979, 16, 276) and note his heading of the Report clearly indicates that it is admission of the subordinate part played by the concerned with general methods, there being noJartuary, 1980 PUBLICATIONS RECEIVED 31 suggestion that it is intended for reference purposes only.Further, let me emphasise that our method, which goes unmentioned, combines time with reliability, as the Sub-committee members would have realised had any of them made comparative time tests as we did originally on cocoas with a maximum fat content of 24%. Accepting the fact that my two fellow APA members approved every word of the Report, I draw my own conclusions accordingly. Re- garding the late Dr. Pearson, with whom I had much friendly professional correspondence, I would say that he, being dead, yet speaketh on page 13 of the 6th Edition of “The Chemical Analysis of Foods,” where he obviously enter- tains no doubt whatsoever regarding the efficiencies of the successors to the outdated Soxhlet apparatus, pointing out that, with them, estimation can be completed in a much shorter time than with the preceding form of fat extractor. To bring the year forward from 1945 to 1961, let me quote from the supplements page (S11) in the APA Bulletin for that year, in which I cite my figures for the oil content (before and after grinding) of a sample of meat and bone meal, 1Q h total extraction time being proved sufficient : Oil extracted by light petroleum Before grinding .. 5.3% 5.5% 5.7% 5.7% After grinding . . 5.9% 5.9% + h l h 1&h 2 h By reason of its high level of efficiency our method is, incidentally, in use in various labora- tories, Avon, Lancashire, West Yorkshire, Newcastle and BFMIRA being amongst them. Moreover, perhaps it would not be too much to infer that the preference for copper(I1) sulphate as against mercury(I1) oxide as the catalyst in the determination of nitrogen stems from the comparative determinations conducted by me in Leeds in 1956, published first for limited circulation and later in J .Ass. Publ. Anal., 1976, 14, 29. (Former Public Analyst and Oficial Agricultural Analyst for the Cities of Leeds and Wakefield) “I’ey”, 3 Great Brockeridge, Westbury-on- Trym, Bristol, BS9 T Y3 C. H. Manley Sir, I see that the question of the merits of different kinds of oil extraction apparatus is again leading to public correspondence. More because I like to support Mr. Manley’s oft- repeated insistence on the merits of the hot solvent extraction, that his apparatus affords, than from any wish to comment on the delibera- tions made about fish products, I find myself just raising my eyebrows at Dr.Herschdoerfer’s bland assurance that all members of his Sub- Committee approved every word of a particular report. The great snag with democracy in science is that people who sit on committees do get tired, and after a while those who work a t the bench tend to succumb to those whose life is spent in committee, yielding in effect to the philosophy, “What they say is good enough.” One is reminded of Lewis Carroll’s comment about there being nothing like hay for a cold. Alice, everyone will remember, was told that this did not mean that there was nothing better! The statement as it stood was correct. Committee documents have a way of following the same reasoning. In these days of published EEC methods of analysis, all of which must have been approved by committees, and which cheerfully re-hydrolyse already hydrolysed material, or direct opera- tives to do such things as pipette concentrated sulphuric acid, one finds oneself at odds with the concept of arriving at scientific truth by vote. Collaborative studies in recent years have almost destroyed my faith in the idea that analytical chemistry is an exact science, and I suspect that curiosities get into committee- approved methods of analysis, because results that come together towards agreement as participants become more familiar with a pro- cedure also follow changes of words that happen to have been made in the most recent committee meetings. It is Post hoc-Ergo propter hoc (whatever that means). A. C. Bushnell County Analyst, Lancashire County Council, County Laboratory, County Hall, Preston, PR1 8XN There is a lot of it about.

ISSN:0144-557X    

DOI:10.1039/AP9801700030

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

Jartuary, 1980 PUBLICATIONS RECEIVED 31 Publications Received Annual Reports on Analytical Atomic Spectroscopy, Reviewing 1978. Volume 8. Edited by J . B. Dawson and B. L. Sharp. Pp. xii + 273. London: The Chemical Society. 1979. Price fT17.50; $38.50. Fundamentals of Mathematics and Statis- tics for Students of Chemistry and Allied Subjects. C. J . Brookes, I. G. Betteley and S. M. Loxston. Pp. viii + 496. Chichester, New York, Bris- bane and Toronto: John Wiley. 1979. Price L6.95 (softback).32 FIFTH SAC CONFERENCE Critical Evaluation of Equilibrium Con- stants in Solution: Part B: Equilibrium Constants of Liquid - Liquid Distribution Systems. Critical Evaluation of Equili- brium Constants Involving 8-Hydroxy- quinoline and its Metal Chelates. Prepared for publication by J.Starq, Yu. A. Zolotov and 0. M. Petrukhin for the Inter- national Union of Pure and Applied Chemistry M y t i c a l Chemistry Division Commission on Equilibrium Data. I UPA C Chemical Data Series-No. 24. Pp. vi + 35. Oxford, New York, Toronto, Sydney, Paris and Frankfurt : Pergamon Press. 1979. Price $12. Composite Flour Technology Bibliography. D. A. V. Dendy and Ruth Kasasian for the Tropical Products Institute. Pp. vi + 74. London: HM Stationery Office. 1979. Price ,cl2 (softback). The Markets for Mint Oils and Menthol. Peter Greenhalgh for the Tropical Products Institute. Pp. xii + 171. London: HM Sta- tionery Office. 1979. Price L3.80 (softback). The Utilisation of Waste Heat Produced During the Manufacture of Coconut Shell Charcoal for the Centralised Production of Copra. G. R. Breag and A. P. Harker for the Tropical Products Institute. Pp. vi + 21. London: HM Stationery Office. 1979. Price fj0.95. Anal. PYOC.

ISSN:0144-557X    

DOI:10.1039/AP9801700031

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

32 FIFTH SAC CONFERENCE Anal. PYOC. Conferences and Courses Process Analytical Instrumentation School March 16-21, 1980, Coventry The continuing growth in the use and impor- tance of process analytical instruments in various sectors of industry has created a need for many personnel to acquire a background knowledge of the principles, capabilities and applications of such instruments. This infor- mation is not normally included in higher educa- tion courses and what definitive articles are available are scattered in the literature. The Institute of Measurement and Control, over the past years, has organised a number of unique residential courses on this topic, the sixth of which will be held from March 16 to 21, 1980, at the University of Warwick. The lecturers are acknowledged experts, having considerable industrial experience in their subjects. To ensure maximum benefit to participants course notes are provided and group projects are included that will give an opportunity to use the knowledge thus gained to provide answers to real, on-line, industrial analytical problems.Numbers on this course are limited to 50 and further details, including the programme and registration form, can be obtained from Mr. M. J. Yates, Institute of Measurement and Control, 20 Peel Street, London, W8 7PD. Postgraduate School on Aspects of Toxico- logical Testing Methods April 14-18, 1980, London The School will be held at Chelsea College, Manresa Road. The following aspects of test- ing for toxicity will be considered in the lec- tures. Pathological : Acute Toxicity ; Chronic Toxicity ; Autoradiography.Biochemical : TheJanuary, 1980 CONFERENCES Use of Isolated Hepatocytes ; Covalent Bonding to Cellular Macromolecules ; Changes in Urinary Enzymes and Plasma Enzymes as Toxicological Markers ; Altered Porphyrin Excretion ; Neuro- toxicity ; Dermatological Reactions ; Protein Binding ; Glutathione Depletion. Carcinogenic : Bacterial Mutagenicity Tests ; Endoplasmic Reticulum Degranulation ; Sisterchromatid Exchange. Regulatory : United Kingdom, EEC and United States Regulatory Requirements. There will be an opportunity, in the seminars, for members of the school to give short com- munications or poster presentations. Application forms can be obtained from Mr. R. E. Marshall, School Secretary, Department of Pharmaceutical Sciences, The Pharmaceutical Society of Great Britain, 1 Lambeth High Street, London, SE1 7JN.Meetings and Courses on Microscopy The 1980 programme of the Royal Microscopical Society contains the following events of interest to analysts. April 13-18, Course on Principles of Electron Microscopy (Leeds) ; April 13-18, Course on Specialised Transmission Electron Microscopy (Leeds) ; April 15-17, Meeting on Microscopy in Ceramics (Leeds) ; April 16, 4th Annual Electron Microscopy Meeting (Leeds) ; July 21-25, Course on Photomicrography (Uxbridge) ; July 21-25, Course on Polarised Light Microscopy (Uxbridge) ; September 15-19, Course on Fluorescence Microscopy (Oxford) ; and September 22-26, Course on Specialised Scanning Electron Microscopy for Biologists and AND COURSES 33 Materials Scientists (Cambridge).The pro- gramme also contains advance notice of a course to be run in 1981, on January 5-8, on X-ray Microanalysis of Thin Films (Manchester) . For further details contact The Administra- tor, Royal Microscopical Society, 37/38 St. Clements, Oxford, OX4 1AJ. Micro 80 August 18-22, 1980, Brighton This conference, which will take place a t the Metropole Hotel, Kings Road, is an international conference on microscopy together with an international exhibition on modern microscopes and ancillary equipment. It is to be organised by the Royal Microscopical Society. The sessions will cover SEM Instrumentation and Analysis, SEM Applications and Developments (Materials), Microanalytical Methods for SEM, STEM, etc., Materials STEM: Convergent Beam and Micro-diffraction Techniques, SEM Bio- logical and Medical Preparation and Ancillary Techniques, SEM Biological and Medical Diag- nostic and Research Applications, Polymers and Fibres, Microscopy of Viruses and Resin Embedding in Microscopy. Papers are invited for all sessions and abstracts should be submitted by April 15, 1980, to The Administrator, Royal Microscopy Society, 37/38 St. Clements, Oxford, OX4 1A J . Further information on the conference is also available from this address.

ISSN:0144-557X    

DOI:10.1039/AP980170032b

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

January, 1980 CONFERENCES AND COURSES 33 Scottish Region Meeting The Scottish Region, together with the Chromatography and Electrophoresis and Joint Pharm- aceutical Analysis Groups and the Association of Clinical Biochemists, will be holding a Meeting on February 20th, 1980, entitled “Advances in Applied High-performance Liquid Chromatography” (see Analytical Division Diary for details). Among the invited speakers from abroad will be Professor J. F. K. Huber and Professor R. W. Frei; some notes on Professor Frei’s career and research work follow. Biography R. W. Frei was born in 1936 in Geneva, and took his Diploma in Chemistry in Switzerland. Later, in 1965, he was awarded a PhD in Analytical Chemistry in the USA. Following postdoctoral work with D. E. Ryan a t Dalhousie University, Halifax, Canada, he was appinted Assistant Professor in 1966 and Associate Professor in 1969 at the same University.From 1972 to 1977 he was head of analytical research at Sandoz Ltd., in Basle, and since 1977 he has been Professor and Head of the Department of Analytical Chemistry at the Free University of Amsterdam. Professor Frei has research interests in the physical separation sciences, spectroscopy and electrochemistry as analytical tools for deter- mining organic pollutants and pharmaceutically active compounds. He is Editor of the International Journal of Environmental Analytical Chemistry and the Journal of Toxicological and Environmental Chemistry Reviews and an Editorial Board member of the Journal of Liquid Chromato-34 SCOTTISH REGION MEETING Anal.Proc. graphy. Professor Frei is also author or co- author of about 150 scientific publications including several books and reviews in various fields of analytical chemistry. Research Current research activities are centred around the topic of selective sample handling and detection. Reaction detectors are of prime interest and several projects are in progress. Reaction Detectors Fluorescamine - aniline reaction detector The reaction of aminophenols and various substituted chloroanilines with fluorescamine to form fluorescent derivatives is being studied. For chloroanilines, which are interesting from a persistent pollutant point of view, the reaction works well, with reaction times of up to 1 min. Besides being relevant as a selective and sensi- tive detection technique it serves conveniently as a model system for the study of band- broadening effects in the tubular reactor designs used for this investigation. The aim is to use this very selective detection principle for the trace determination of important substituted aniline pollutants in waters or biological matrices.Extraction detectors based on ion-pairing principle This development is based on a dynamic micro-extraction principle for fluorescent ion- pairs. The basis is the ion-pair formation between tertiary amines (drugs, pesticides or their metabolites) and the highly fluorescent dimethoxyanthracene sulphonate (DAS) . The ion-pair, which is formed immediately after leaving the column, is extracted into the organic phase of a segmented continuous-flow system and detected in a fluorescence detector.Band broadening in such an extraction detector is found to be primarily caused by the phase separator. Other band broadening phenomena are suppressed by segmenting the flow with air bubbles and/or immiscible organic solvents. A critical study of the effect of various reactor designs, mixing Ts, extraction spiral dimensions, phase separators and the miniaturisation of these units on band broaden- ing is being carried out. Air and solvent segmentation systems are also being compared. Interesting modifications of this approach are normal-phase separation on silica gel instead of reversed-phase separation and the use of the mobile phase, viz., chloroform, as the extraction medium. Photochemical reaction detectors The principle involves the use of post-column and on-line photochemical reactors to either catalyse another continuing reaction (i.e., hydrolysis, redox) or to induce new reactions with or without reagent addition.The detec- tion signals (ultraviolet - visible, fluorescence or electroanalytical) of the resulting products can then be used for a more selective and sensitive determination of suitable compounds separated by HPLC. An air-cooled xenon lamp reactor has been designed. The first successful tests were carried out with the drug clobazam, which is converted to highly fluorescent derivatives upon irradiation. The influence of reactor design on band broadening and the feasibility of using segmen- tation techniques for longer photochemical reactions is being studied.Pre-concentration and Selective Sample Handling This work is based on earlier observations that compounds of relatively low polarity are retained completely on the hydrophobic surface of chemically bonded reversed-phase (C18) materials. Dibutyl phthalate (DBP) and di-2- ethylhexyl phthalate (DEHP), which are widely used as softeners in plastics, have been studied, and pre-column techniques that permit collec- tion of up to 1-1 water samples on 2-mm long pre-columns containing 5- pm particles of C,, material developed. Following the on-line transfer of sample and step gradient separation it is possible to determine concentrations of these phthalates in the 0.1 p.p.b. range with good recovery and reproducibility. Adsorption - desorption phenomena, loading capacity, re- coveries, lifetime and performance of pre- columns as a function of different particle sizes and qualities of support materials, sampling flow-rates, pre-column construction and other parameters are being investigated.Concentra- tion factors of up to 10 000-fold can be obtained with this technique. The principle has been successfully extended to other pollutants, such as PCB’s and chloroanilines, with the idea of coupling pre-concentration techniques of chloro- anilines with the fluorescamine post-column reaction detector. In addition to trace enrichment the pre- column concept can serve other functions, such as selective sample clean-up, possibly via on- column reactions, protection of the separation column, field sampling and automatic sample handling.Several of these aspects have been investigated with drugs and pesticides.January, 1980 SCOTTISH REGION MEETING 35 The concept of pre-concentration on hydro- phobic surfaces can also be used in analogy for relatively polar compounds on polar surfaces. This idea is being studied for the urea herbicides metoxuron, linuron and diuron, again with the purpose of clean-up and trace enrichment and as an approach to residue analysis of these species. In addition, an on-column catalytic hydrolysis on silica gel can be used to hydrolyse rapidly and selectively these ureas to the corresponding anilines for derivatisation purposes. The anilines are then derivatised in a pre-column or post-column mode to yield derivatives with good detection properties for liquid chromatography (fluorescamine reaction) or for gas chromatography (fluoro derivatives for electron-capture detection).Development of Polarographic Detectors for HPLC A study of the design and development of mercury drop detectors for dynamic flow systems is being undertaken. The first version has as new features a horizontally placed mercury capillary and a pin moveable against the capillary opening in order to reduce dropping time. In the meantime two further improved designs have also been developed. The mercury capillary and the reference electrode now have a conical outlet, which permits a better seal, further miniaturisation for low dead volume designs and the reduction of drop size without the moveable pin. A new approach to measuring time constants and response volumes for such detectors has been proposed.The electrochemical detectors tested, while being complementary to other HPLC detectors, show a reproducibility and sensitivity at least comparable with a good ultraviolet detector. The selectivity, the response time and the linear dynamic range are better for optimally designed electroanalytical cells. Finally, a fourth version is now being con- structed, which permits the use of pulsed techniques. The improvement in noise, detec- tion limit and over-all performance is being tested. These detectors are partly applied in conjunction with suitable chemical reactions in a pre- or post-column mode. A recent applica- tion is described below. Application to selective detection of organo- sulphur compounds The studies are based on complexation phenomena of selected organosulphur com- pounds with the mercury surface of our DME detector.The over-all reaction is as follows Hgo + 2 Th -+ Hg(Th)22+ + 2e (Th = thiourea compound) The resulting electrical current is proportional to the concentration of Th. The unusual aspect of this detection mode is the use of the anodic range of the mercury electrode. All of the sulphur compounds tested that contain a thio- carbonyl group can be detected at a potential of about + 180 mV. The removal of oxygen is not necessary. The major advantage of our DME detector, aside from being simple and of low cost, is the selectivity, which permits the determination of such compounds in a complex matix with a minimum of sample handling. As an example, ethylenethiourea was determined directly in urine samples. More fundamental work on the actual complexation phenomena a t the mercury surface is in process. Room- temperature Phosphorimetry and its Analytical Potential Phosphorescence has for a long time been assumed to be usually only observable under low-temperature conditions (77 K). This has been one of the main reasons for its neglect up to now, particularly within analytical chemistry. In this project we have begun systematically to explore the possibilities of measuring phosphorescence under room-temperature conditions and to study parameters such as internal and external heavy atom effects, the nature of the solvent (its viscosity and oxygen content) and their effect on phosphorescence at room temperature and on life times.

ISSN:0144-557X    

DOI:10.1039/AP9801700033

出版商:RSC    

年代:1980

数据来源: RSC