Comparis Analytical Techniques for Inorganic Pollutants R. F. Coleman Laboratory of the Government Chemist London, England
T h e interest in the concentration of pollutants has never been greater. An increasing number of laboratories are involved in the measurement of a wide range of substances in environmental samples, and much of the current research in analytical chemistry is directed toward improved methods of analysis for this purpose. T h e main aim of this paper is to provide some background data which will assist in the selection of the appropriate technique for current and future problems. This is a very wide ranging subject, and I must draw some boundaries, albeit artificial ones, because a pollutant may sometimes be a nutrient, just as t o a gardener a weed is merely a plant in the wrong place rather than something inherently undesirable. I shall limit the discussion to inorganic pollutants, but I shall ignore radioactive and also gaseous pollutants such as sulphur dioxide and oxides of nitrogen which require specialised techniques. In effect, this paper will discuss analytical methods which are applied to inorganic pollutants found in food, water, or collected on air filters from the atmosphere. The choice of the appropriate technique
depends upon many factors; in addition to the inherent characteristics of t h a t technique, it is very much dependent upon the nature of the requirement for analysis as well as the availability of particular kinds of samples. I propose, therefore, to start off with the kinds of operational requirements which one is likely to meet, follow this by a brief description of sampling techniques and problems which are common to all kinds of analysis, and then discuss the analytical techniques themselves in relation to these requirements and sampling problems. Operational Requirement I t is of vital importance to try and understand the complete problem. Sometimes analysis is not required a t all in the initial stages because the analysis of a few samples may be misleading if the problem has not been properly formulated. All too often, the analysis of samples is requested without any thought being given to the value of the data and the valid conclusions which can be drawn from it. There are essentially three different kinds of operational requirement in which analysis can play an important
part. T h e first might be the unexpected problem when a known or unknown pollutant is affecting the health of workers or the external population. T h e analytical chemist is then expected to provide some data rapidly s o t h a t necessary appropriate corrective action can be taken. In such circumstances, the appropriate technique should be capable of giving a rapid answer, be comprehensive and wide ranging, and initially, only qualitative or semiquantitative answers may be required. The second typical requirement is to study the effects of a single or. a t the most, a few elements or compounds on the environment, for example, lead effluent from an industrial plant or on a larger scale. the lead content of the diet of the whole popula. tion. In such cases, one can select a technique which is appropriate for that particular element. If there are a large number of samples, automation may be necessary. Alternatively, several laboratories may collaborate in the study. In this case, it i q essential that intercomparison of particular samples is undertaken a t the beginning of the survey to ensure compatibility of analytical data. Careful plan-
A N A L Y T I C A L C H E M I S T R Y . V O L . 46, NO. 12. OCTOBER 1974 * 9 8 9 A
ning of the sampling programme is also essential. The third requirement involves the analysis of a large number of elements simultaneously. These are often long-term background studies designed to monitor the environment and identify changes which have a health or economic significance. Naturally, multielement techniques are preferred in such surveys, and often some form of automation is necessary to handle the large number of samples generated. Sampling Sampling is a difficult andcomplex problem, and very often insufficient attention is paid to it. The results obtained in many surveys bear little resemblance to the true state of affairs because of changes occurring in the samples, between the source and the laboratory. In some cases, it is possible to avoid sampling altogether by making the measurements in situ. For example, selective ion electrodes may be used for the determination of certain pollutants in flowing streams of liquid. The sampling of water has been reviewed by Spencer and Brewer ( I ) , but general solutions to all the problems are not known a t the present time. Contamination and loss of trace elements during storage has been responsible for much erroneous data on the concentration of trace elements in the literature. Robertson (2) has shown major losses of some elements from unacidified seawater stored in polythene and glass. If it is important to distinguish between ions in true solution and suspended matter, filtration should be carried out as soon as possible. Hamilton and Minski (3) showed very significant differences between river waters analysed as sampled and after the addition of acid. The increase in concentration of many elements is attributed to the dissolution of particulate matter. The same authors found that soft water tends to extract more elements from contaihers than hard water. Cawse and Pierson ( 4 ) have described a remote sampling station for airborne dust and rainwater which has been used satisfactorily for several years. Rainwater is collected monthly in a polythene funnel and bottle, while airborne dust is collected by drawing air through a filter paper in a polypropylene duct. While it is relatively easy to sample in order to measure the concentration of a constituent in a particular foodstuff, sampling of the normal diet of a population is much more difficult. Harries et al. ( 5 )have described the organisation of a total diet study which involved local purchase of foodstuffs and cooking in about 20 colleges in different areas of England and 990A
Wales in order to give a good geographical coverage of population centres and allow for regional variations in the diet. Sample Preparation The sample preparation will naturally depend upon the analytical technique to be used; however, there are some guiding principles which are common. Obviously, care must be taken to avoid contamination of the sample from the laboratory atmosphere, containers, and reagents. Tolg (6) reviews procedures involved in sample preparation and also methods of decomposing and dissolving samples for trace analysis. Hamilton et al. (7) considers the laboratory environment, sample preparation, and ashing procedures specifically for multielement analysis of biological materials. Analytical Methods The analytical techniques which have found the widest application in the study of inorganic pollutants are compared below on the basis of sensitivity, accuracy, precision, multielement capability, and range of application. In addition, where possible, the future trends in each technique will be discussed. Microscopy. Although neglected by many analytical chemists, optical microscopy is particularly suited to the examination of particulate matter. It is a comprehensive technique capable of detecting as little as gram quickly and with relatively simple apparatus. In addition, it provides information, not only on the elemental composition, but also the compounds present and in many cases the crystalline form. Identification of particles is greatly assisted by using the classification system of McCrone and Delly (8). Each particle is characterised by six parameters, e.g., colour, shape, and birefringence and can be compared with over 1000 substances in “The Particle Atlas.” The groups of particles with the same classification can be differentiated on the basis of additional attributes such as density and refractive index and by direct comparison of the unknown with photomicrographs. The next logical step is to use the scanning electron microscope. It shows the shape and surface of relatively large particles (1-100 p) better than the polarising microscope because of the superior depth of field, and with magnifications of up to 30,00OX, it is suitable for the identification of submicron particles also. A third advantage is the ability to determine the chemical composition of tiny single particles by energy dispersive X-ray analysis. “The Particle Atlas” contains electron micrographs of
A N A L Y T I C A L C H E M I S T R Y , VOL. 46, N O . 12. OCTOBER 1974
IOOX, IOOOX, and 10,OOOX and the Xray spectrum of many particles. With transmission electron microscopy diffraction patterns of individual submicron particles may be obtained. With this technique my laboratory identified the presence of traces of talc in maize starch. The latter is used as a lubricant for surgeons’ gloves, and talc is forbidden because of the possible deleterious effects of talc inside the body. This is a formidable analytical problem since direct X-ray diffraction on the bulk powder does not reveal talc, and magnesium oxide is also present to improve the free running characteristics of the powder and would greatly exceed the magnesium concentration due to talc. Optical and electron microscopy are particularly suited to troubleshooting and for a preliminary examination of many types of samples. Atomic Spectroscopy. It is convenient to discuss atomic absorption, atomic fluorescence, and atomic emission together because of their similarities and the complementary nature. Atomic absorption is particularly suited to the analysis of trace pollutants in studies involving one or a few elements. More than 60 elements can be determined by the technique, and it has become the most widely used technique for such applications. Winefordner et al. (9) have written an excellent review of theoretical and experimental aspects of atomic absorption, fluorescence, and emission flame spectroscopy. In addition to comparing the sensitivity of the three techniques, the review discusses the theoretical limitations of different types of excitation and the possible interference effects. Stone and Warren ( I O ) review the modern instrumentation available for atomic absorption and give practical advice to assist in the selection of spectrometers from the wide range now available. Although electrodeless discharge lamps and lasers have been used for atomic absorption, the hollow cathode lamp is still used in the vast majority of applications. The latter are available for over 60 elements and now have a fairly long life and adequate stability. The flame is the most widely accepted method of generating atoms for absorption. A variety of fuels and oxidants have been investigated, but for most purposes, air-acetylene (temperature, 2400°K) and nitrous oxideacetylene (temperature, 3200°K) are satisfactory. The latter is particularly satisfactory for refractory compounds. As with any technique, atomic absorption suffers from various types of interference. However, these are not generally serious, and in flames the mechanisms are well understood so that they can be reduced or eliminat-
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A N A L Y T I C A L CHEMISTRY. V O L . 46, NO. 12. OCTOBER 1974
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ed. Spectral interferences rarely occur in atomic absorption spectroscopy because of the simple absorption spectra and narrow lines emitted by hollow cathode lamps. Variations in the relative proportions of ground state atoms and ionised states can occur if the matrix contains easily ionised elements such as potassium. This is fairly readily avoided by adding a sufficiently large quantity of the element to standards in order t o swamp the matrix effect. Chemical interferences owing to compound formation between the element being determined and interfering substances do exist but are often broken down by the use of high-temperatures flames or by adding a releasing agent which preferentially binds the interferent. For example, lanthanum is widely used for this purpose as it will bind a variety of oxy-anions. Physical differences in samples such as viscosity can influence the formation of aerosols and cause errors if the samples and standards are not adequately matched. Samples containing a high salt content can cause scattering of radiation; thus, an absorption effect is detected other than that . owing to the element to be measured. Many modern instruments contain a second light source which can eliminate background absorption and substantially increase precision and limits of detection in such samples. An indication of the sensitivity of current flame atomic absorption procedures is given in Figure 1. Typically, the precision of analysis is 1-3% for concentrations more than 10 times the limit of detection. In principle, the accuracy should be of a similar order because of the limited interference in the technique; however, in practice the sampling and sample preparation procedures often introduce larger errors. A variety of techniques have been developed to increase the applicability of atomic absorption. For example, the determination of mercury by flame atomic absorption is rather insensitive. However, by reducing mercury to the elementary form, it can be vapourised in a current of air into an absorption tube and then the absorption measured in the cold state. This technique is widely used to determine the mercury level of foods and other biological materials ( 1 1 ) .The measurement of arsenic can be improved by production of arsine from the solution (12),which can then be led directly into the flame and the absorption integrated over time, or by collection in a balloon and subsequently discharged into the flame. Either of these two techniques can determine submicrogram quantities of arsenic. Similarly, the reduction of selenium to hydrogen selenide prior to the introduction into the flame has improved the sensi992A
Figure 1. Limits of detection in atomic spectroscopy
tivity of the technique ( 1 3 ) .A variety of flameless cells are now commercially available, such as graphite tube furnaces, graphite rod atomizers, and tantalum ribbon atomizers. These devices are electrically heated and produce temperatures up to 3000'K and are suitable for the less volatile refractory elements. T h e marked improvement in sensitivity of the graphite atomiser methods over flame sources is indicated in Table I. The precision of analysis is much worse than for flame methods, typically 5-25% depending on the type of atomiser and type of sample. T h e interferences have not
ANALYTICAL CHEMISTRY, VOL. 46, NO. 12, OCTOBER 1974
been adequately studied, and insufficient information is available on the interaction between solution and gaseous state with carbon. Various physical interferences have been noted in some applications, apparently inhibiting the volatilisation of the sample. Atomic absorption is widely used within the Laboratory of the Government Chemist for trace analysis of foods, water, and dust samples when the requirement is for one or a few specific elements such as lead, arsenic, cadmium, and mercury. Simultaneous multielement analysis is difficult by atomic absorption, but various
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schemes have been reported (14) for the rapid sc!quential analysis of many elements. Since 1964 when Winefordner and Vickers (15) demonstrated analytical applications of atomic fluorescence, many papers relating t o this technique have appeared. A review by Browner ( 1 6 )provides a good background description of the technique and allows the reader to make a reasoned choice between this and atomic absorption and flame emission spectrometry. At the present time, there are no commercial instruments available for atomic fluorescent spectrometry which must limit its general availability. It offers comiderable improvement in detection capability for many elements, particularly those with principal resonance lines below 320 nm, but the instrumental drawbacks inherent in its nature have delayed its wider acceptance. It is essential to have a highintensity stable source of the required wavelength. Many workers are now using therrrostatic electrodeless discharge lamps, and these seem to offer the best solution a t the present time. Atomic fluorescence has the same limited interference problems as absorption; in addition, quenching processes could cause problems. Most of the development work on fluorescence spectrometry uses nonflame cells since this reduces the possibility of quenching and still maintains good atomisation efficiency. Multielement analysis is more readi1.y achieved with atomic fluorescence than absorption, and a spectrometer foi*the simultaneous determination of up to six elements has been described. As with most multielement techniques, the operating conditions will be a compromise. Atomic emission has developed significantly in the last decade and is now applied to a large range of elements. T h e sensitivity, compared with ahsorption snd fluorescence techniques, is irldicated in Figure 1. Busch and Morrison ( I 7 ) have reviewed the multielement capability of flame spectroscopy and conclude that emission is the technique most easily adapted for this purpose. although it is not the most sensitive of the three techniques for many elements. T h e high-frequency plasma sources for spectroscopy first used by Greenfield et al. (18)are now becoming widely accepted, and commercial sources coupled with direct reading spectrometers ,are available. Scott et al. (19) have investigated plasma sources extensively and have developed a compact system ideally suited to practical multielement analysis. A pneumatic nebulizer feeds the aerosol produced from the solution directly into a plasma. T h e high temperature (7500’K) eliminates most chemical in994A
terferences observed with other emission sources; thus, simple standard solutions can be used to calibrate complex mixtures. T h e stability of the sys. tem is good, and precisions of about 1%(relative standard deviation) for sub-ppm solutions have been achieved. T h e detection limits with a plasma source for most elements are lower than flame atomic absorption or fluorescence. T h e technique seems well suited t o the multielement analysis of biological samples. following removal of organic matter and dissolution of the sample. Mass Spectrometry. T h e attraction of mass spectrometry for the analyst is the simplicity of the spectra. In theory, a spectrum of a mixture will contain only discrete lines for each isotopic species present, but in practice, some interference from compounds and hydrocarbons is always present. T h e spark source is usually used for ionisation for elemental analysis because of the relatively uniform ion formation for all elements. For analysis of environmental samples, it is usually necessary t o remove the organic material and mix the residue with graphite in order to prepare conducting electrodes for the spark source. Hamilton e t al. (20) have studied the procedure extensively for biological materials, and Brown and VOSsen (21 1 have applied it t o air pollution samples on filters. Several instruments are available commercially with two-stage magnetic and electrostatic separators and ion detection by photographic plate or electrically by using photomultipliers. T h e method is most sensitive using photographic plates with exposure times of about 1 hr, and almost all elements can be detected down to ppb levels. Electrical detection is less sensitive but more rapid; in the scanning mode typical sensitivity limits are 0.1 ppm, taking about 10 min for examination of the full mass range, and 0.01 ppm by peak switching to examine
specific elements. Direct semiquantitative analysis is possible without standards with an accuracy of about a factor of three. For quantitative analysis it is essential t o measure the relative sensitivity of ionisation and detection of each element by using standards prepared in a matrix similar to the sample. In this way, the accuracy can be about fl0-25%--lower for electrical detection and higher for photographic methods. Although the spark source has been used for many years for elemental analysis, it has serious limitations, and Gray (22) has shown that a plasma source has many desirable features for ion formation prior to mass separation. A solution of the sample to be analysed is sprayed directly into a capillary arc plasma, and the gases from the plasma plume directly enter the vacuum system through a small orifice in a thin wall. T h e ions are focused and directed into a second chamber with a quadrupole filter. T h e quadrupole mass filter permits only one mass number to pass through it. but by scanning, a complete mass range can be examined and recorded. Currently. the low mass end of the spectrum contains a complex collection of peaks owing to nitrogen, oxygen, and hydrogen compounds, but above mass 55 the background is very small. Mass spectrometry gives the best coverage of elements a t the ppb concentration range (Table 11) and is well suited to studies requiring a large number of elements. T h e careful sample preparation necessary for spark sources limits the rate of analysis, but this may improve with the development of the plasma source. Isotope dilution procedures are capable of giving some of the most accurate determinations for trace elements. Although not likely to be used on a routine basis for analysis of pollutants, they d o offer the possibilities of providing an absolute method suitable
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A N A L Y T I C A L C H E M I S T R Y . V O L . 46, NO. 12. OCTOBER 1974
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Mass spectrometry Neutron activation analysis
ferences Multielement technique Excellent sensi tivi ty Plasma source promises rapid analysis Freedom from contamination Excellent sensitivity for some elements Applicable to wide variety of matrices Direct examination often feasible May be nondestructive Multielement technique Rapid Simple technique and equipment Excellent sensitivity for some elements
for the standardisation of secondary techniques. T h e principle of the method is very simple; the concentration of a n element is determined from the change produced in a natural isotopic composition by the addition of a known quantity of the same element, the isotope ratio of which has been artifically altered. A given amount of sample is equilibrated with a known quantity of an isotopically enriched spike; the element is extracted, and its new isotopic ratio measured by mass spectrometry. Since only isotopic ratios are involved, the extraction does not have to be quantitative. Isotope dilution techniques are capable of accuracies of the order of 0.1% for many elements a t trace concentrations. The National Bureau of Standards has already used the technique to standardise the determination of calcium in blood and also lead in blood. I t is hoped t h a t through certified reference materials and methods such as isotope di1ution;it will be possible to obtain compatible data for these elements throughout many laboratories. X - r a y S p e c t r o m e t r y , X-ray fluorescence spectrometry is well suited to the determination of the elemental composition of pollutants because in many cases, limited sample preparation is required, and the technique is nondestructive. All elements of atomic number greater than 11, i.e., sodium, can be analysed. Traditionally, the technique has used wavelength dispersion as a method of separating the X rays emitted from the sample, but with the recent availability of silicon
and germanium X-ray detectors of high resolution, energy dispersive spectroscopy is possible and often simpler. Gilfrich e t al. (23) have reviewed X-ray spectrometry for particulate air pollution samples and conclude t h a t there are two problems with solid-state detectors which are limiting in t h a t application. First of all, the resolution is not adequate to separate the K-alpha line of one element from the K-beta line of the next lower atomic number in the region of sulphur to nickel; thus, all these elements will require mathematical unfolding to determine X-ray intensities. Also, the solid-state detectors are limited to about lo4 counts/sec a t their best resolution, and long count times would be necessary to get adequate counting statistics for multielement analysis. Because of these limitations, they conclude t h a t large-scale quantitative analysis requires the resolution obtainable from crystal spectrometers, and for routine analysis the only practical approach is the use of multichannel wavelength spectrometers, because of the time required for the wavelength scanning mode. At our own laboratory we have found X-ray spectrometry very useful for the analysis of food samples; the sample preparation is simple, merely requiring freeze drying followed by grinding a t liquid nitrogen temperatures in order to produce a fine powder suitable for presentation to the X-ray beam. It has been particularly useful for light elements, e.g., sulphur and phosphorous, which are difficult
to determine by most spectrographic techniques. The limit of detection for most elements by wavelength dispersive spectroscopy is in the range 0.1-1 wg, with concentration limit depending on the sample size, shape, and physical form. X-ray spectrometry is mainly used for multielement analysis but often does not have adequate sensitivity for all the elements of interest in biological samples. N e u t r o n A c t i v a t i o n Analysis. The radiation of a sample with neutrons transforms some of the atoms of each element present into a radioactive form. These radioactive atoms can be separated and detected more easily than stable atoms. For many years activation analysis was probably the most sensitive analytical technique, but this is no longer the case, and the merits of the technique must be assessed on other properties such as cost, availability, and range of elements analysed. I t is not easy to sum up activation analysis because its performance depends upon many different attributes-first of all, the specific nuclear properties of the element concerned, the equipment available for measurement of induced activities, and the nature of the sample itself. One of the prime advantages of activation analysis is its freedom from contamination, provided the sample is not contaminated prior to irradiation; then, one does not have to worry about subsequent contamination from reagents. After irradiation the measurement
ANALYTICAL CHEMISTRY, V O L . 46, NO. 12. OCTOBER 1974
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of induced activity may: use direct instrumental methods for discriminating between the radiations emitted from each element present; rely on complete radiochemical separation with simple nonspecific detectors; or use group separations, e.g., Goode et al. (24),to reduce the complexity of each sample to more manageable proportions. The improvement in the sensitivity and resolution of germanium detectors over the last five years has encouraged more use of the direct method. However, for biological samples the intense radiation from sodium and chlorine usually makes some preliminary separation essential if a wide range of elements is to be determined. An example of how the technique can be applied to analysis of pollutants is given by Pierson et al. (25) in their work on the composition of rain and dust in the atmosphere. The samples of filter paper or rain were irradiated for 20 sec; then the gamma spectrum of each sample was measured a few minutes after irradiation and a t further times over the subsequent 24 hr, with sodium iodide detectors. The spectra were compared with those from standards by the method of linear regression analysis with a computer; about eight elements could be determined in this way. Samples were then irradiated for one week, and gamma spectra obtained over a period of several weeks with germanium detectors, and a further 20 elements determined. This example indicates direct access to a reactor for short and long irradiation; a variety of detection systems and computer data processing are necessary for successful routine multielement analysis by activation techniques. If these requirements cannot be met, then other techniques are likely to offer a better solution to the analytical problem. Electrochemical Methods. Polarographic methods of analysis have been used for trace analysis of specific trace metals for many years, but the technique has many limitations and has not been so widely used as many spectrographic techniques. However, the related technique of anodic stripping voltammetry has been applied, increasing in recent years to the analysis of water samples and other solutions. The sensitivity of the technique is obtained by initially concentrating the trace elements into a small volume of mercury by electrolysis, a t a more negative potential than the reduction potential of the trace element, over a period of 10-60 min. The element is then anodically stripped from the mercury in a few seconds with a linearly varying potential. The current peaks for the metal oxidation of the elements in the mercury are displayed 996A
on an X-Y recorder. The technique is particularly useful for elements such as copper, lead, zinc, and cadmium and can be extended to about 12-20 elements, although it is unrealistic to expect more than about six elements to be determined simultaneously in a solution. Multicell units are available commercially and, of the order of 100 samples per day, can be analysed with a precision of 5 1 0 % a t the 10-100 nanogram level. Conclusions In this review the most practical methods of analysis for pollutants have been discussed. Table I11 summarizes the advantages and limitations of the various technqiues. There may have been a bias toward multielement techniques, because I believe t h a t most laboratories in the future will need to consider a wider range of elements. A variety of techniques of adequate sensitivity for the trace analysis of bulk samples are available, and it is important to relate the analytical problem to the overall requirement so that a rational and economical choice can be made.
(17) K.W. Busch and G.H. Morrison, Anal Chem., 45,713 (1973). (18) S. Greenfield. I.L.W. Jones. and C.T. Berry. Analyst. S9, 713 (1964): (19) R.H. Scott, V.A. Fassel, R.N. Kniseley, and D.E. Nixon, Anal. Chem., 46,75 (1974). (20) E.I. Hamilton, M.J. Minski, and J.J. Cleary, sci. Total Enuiron., 1, 341 (1972/73). (21) R. Brown and P.G.T. Vossen, Anal. Chem., 42, 1820 (1970). (22) A.L. Gray, Proc. Soc. Anal. Chem., 11, 182 (1974). (23) J.V. Gilfrich, P.G. Burkhalter, and L.S. Birks, Anal. Chem., 45,2002 (1973). (24) G.C. Goode, C.W. Baker, and N.M. Brooke, Analyst, 94, 728 (1969). (25) D.H. Pierson, P.A. Cawse, L. Salmon, and R.S. Cambray, Nature, 241,252 (1973).
Acknowledgment The author acknowledges useful discussions with many members of the staff of the Laboratory of the Government Chemist but particularly R.G. Stone, D.E. Henn, S. Isherwood, and K.L.H. Murray. References (1) D.W. Spencer and P.G. Brewer, C R C , Crit. Reu. Solid State Sei., 1, 401 (1970). (2) D.E. Robertson, Anal. Chim.Acta, 42, 544 _ _ _ 17968). ...,. (3) E.I. Hamilton and M.J. Minski, Enuiron. Lett., 3 (11, 53 (1972). (4) P.A. Cawse and D.H. Pierson. AERE Report R-7134, 1972. (5) J.M. Harries, C.M. Jones, and J.O’G. Tatton, J . Sei. Food Agr., 20, 242 (1969). (6) G. Tolg, Talanta, 19, 1489 (1972). ( 7 ) E.I. Hamilton, M.J. Minski, and J.J. Cleary, sei. Total Enomin., 1, 1 (1972). (8) W.C. McCrone and J.G. Delly, “The Particle Atlas,” Vols 1-4, 2nd ed., Ann Arbor Sci. Publ., Ann Arbor, Mich., 1973. (9) J.D. Winefordner, V. Svoboda, and L.J. Cline, CRC, Crit. Rev. Anal. Chem., 1, 233 (1970). (10) R.G. Stone and J. Warren, Lab. Equip. Digest, 49 (April 1974). (11) W.R. Hatch and W.L. Ott, Anal. Chem., 40,2085 (1968). (12) E.F. Dalton and A.J. Malanoski, A t . Absorption Newslett., 10 (4), 92 (1971). (13) E.N. Pollock and S.J. West, ibid.,12 ( l ) ,6 (1973). (14) L.E. Ranweiler and J.L. Moyers. Enciron. Sei. Technol., 8, 153 (1974). (15) J.D. Winefordner and T.J. Vickers, Anal. Chem., 36, 161 (1964). (16) R.F. Browner, Analyst, in press (1974). ~~
ANALYTICAL CHEMISTRY. VOL. 46, NO. 1 2 , OCTOBER 1974
Ronald F. Coleman was appointed head of Research and Special Services a t the Laboratory of the Government Chemist in 1973. The laboratory provides analytical service and advice on chemical matters to government departments in the United Kingdom, particularly in the fields of revenue and environmental protection. He obtained a BSc degree from the University of London in 1953 and then spent nearly 20 years a t the Atomic Weapons Research Establishment Aldermaston. His research has been mainly connected with nuclear chemistry but he has wandered into many different areas in collaboration with other workers. In the late 1950’s, he was studying fast neutron and heavy ion reactions and simultaneously used fast neutrons for activation analysis. In 1963 he started using thermal neutron activation techniques to solve many problems in forensic science, geochemistry, and medicine. He has published about 50 papers in nuclear and analytical chemistry.
