摘要:

Proceedinas - - - - ~of the Analytical Division ofThe Chemical SocietyCONTENTS193 Summaries of Papers193 'Silver Medal Lecture'205 'Analytical Aspects of Hazardous217 Equipment News220 Chemical Society Awards221 AD Publicity Officer221 The Analytical Chemistry Trust223 The Harmonisation ofMaterials'Collaborative AnalyticalStudiesIndustrial AnalyticalIn s t ru mentat ionScientific Advisory and AnalyticalServices227 Formation of Specialist Group on227 Future of the Public Analysts228 Publications Received229 CS Autumn Meeting229 Conferences and MeetingsVolume 15 No 7 Pages 193-230 July 197PADSDZ 15(7)193-230(1978)ISSN 0306-1 396PROCEEDINGSOF THEJuly 1978ANALYTICAL DIVISION OF THE CHEMICAL SOCIETYOfficers of the Analytical Divisionof The Chemical SocietyPresidentR.BelcherHon. SecretaryP. G. W. CobbHon. Treasurer Hon. Assistant SecretariesJ. K. Foreman D. I. Coomber, O.B.E.; D. C. M. Squirrel1Secretary Editor, ProceedingsMiss P. E. Hutchinson P. C. WestonProceedings is published by The Chemical Society.Editorial: The Director of Publications, The Chemical Society, Burlington House, London, W1 V OBN.Telephone 01 -734 9864. Telex 268001.Subscriptions (non-members): The Chemical Society, Distribution Centre, Blackhorse Road,Letchworth, Herts., SG6 1 HN.Non-members can only be supplied with Proceedings as part of a combined subscription with The Analystand Analytical Abstracts.0 The Chemical Society 1978EUROANALYSIS 111Dublin, Ireland, 1978The Praesidium of Euroanalysis Ill extends a cordial invitation to participate inthe Conference to be held in Dublin, Ireland, August, 20-25, 1978.The programme includes both General and Special Sessions.TheGeneral Sessions are composed of Plenary Lectures by S. S. Braun, J. T.Clerc, M. Grassenbauer, P. L. Schuller, T. S. West and Yu. A. Zolotov, KeynoteLectures, contributed papers and poster sessions. The Special Sessions willbe concerned with Standard Reference Materials and Education in AnalyticalChemistry.Another feature of the Conference will be exhibitions of equipment andbooks and periodicals.Competitively priced travel and accommodation packages have beenarranged with a travel agent. Prices are quoted from all major British andmany European cities. An example is London: for 6 nights a t a category 3guest house + travel f 104; or at a category 1 hotel for the same period f 163.If you are interested in the Conference write to the Secretariat, EuroanalysisIll, P.8. Box 876, Ballymun Road, Dublin 9, Ireland

ISSN:0306-1396    

DOI:10.1039/AD97815FX027

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

ANALYTICAL SCIENCES MONOGRAPHS No. 3Pyrolysis-Gas Chromatographyby R. W. May, E. F. Pearson and D. ScothernThis monograph attempts to present the available knowledge in a formuseful to the practising analyst, helping in the choice of an appropriatemethod and in the avoidance of the more common pitfalls in this, perhapsdeceptively, simple technique.Chapter 1 serves as an introduction t o gas chromatography and will beof interest to those unfamiliar with the technique. The several methodsof pyrolysis used in pyrolysis-gas chromatography are described inChapter 2; their merits and demerits in particular applications are discussed.The major analytical uses of the technique are presented in Chapter 3;the general analytical 'fingerprinting' aspects described separately fromthe method as applied to specific sample types.Chapter 4 deals with theidentification of the pyrolysis products which are eluted from the chrom-atography column, useful extra information allowing the possibility ofnaming a pyrolysed sample without recourse to a known identical sample.The necessity for increased standardization of the technique of pyrolysis-gas chromatography is discussed in Chapter 5.. Clothbound 117pp 85" x 6" 0 85186 767 7 f7.20 ($14.40)CS Members f5.50ANALYTICAL SCIENCES MONOGRAPHS No. 4Electrothermal Atomization forAtomic Absorption Spectrometryby C. W. FullerAt the present time the two most successful alternatives to the flame appeart o be the electrothermal atomizer and the inductively-coupled plasma. Inthis book an attempt has been made t o provide the author's views onthe historical development, commercial design features, theory, practicalconsiderations, analytical parameters of the elements, and areas of appli-cation of the first of these two techniques, electrothermal atomization.The chapter headings are as follows: History; Theoretical Aspects of theAtomization Process; General Experimental Conditions; Analytical Con-ditions for the Determination of the Elements by Atomic AbsorptionSpectrometry; Applications (Oil and Oil Products; Metals; Rocks, Minerals,and Soils; Waters; Plants; Food and Drugs; Biological Fluids; BiologicalTissues; Air Particulates; Refractory Oxides and Related Materials; OtherAnalytical Applications; Theoretical).Clothbound 135pp 82" x 5" 0 85186 777 4 f6.75 ($13.50)CS Members f5.50THE CHEMICAL SOCIETYDistribution Centre, Blackhorse Road, Letchworth,Herts.SG6 1 HN, EnglandPrinted by Heffers Printers Ltd Cambridge Englan

ISSN:0306-1396    

DOI:10.1039/AD97815BX029

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Vol. 15 No. 7 July 1978 of the Analytical Division of the Chemical Society Silver Medal Lecture The following is the Silver Medal lecture delivered by Dr. J. S. Hislop, the fourth SAC Silver Medallist, at an Ordinary Meeting of the Division held on December 7th, 1977, in London. Gamma Activation Analysis: An Appraisal J. S. Hislop Envivonmental and Medical Sciences Division, AERE, Havwell, Didcot, Oxfordshire, OX1 1 ORA The Oxford English Dictionary defines an appraisal as "a valuation," and the main aim of this paper is to assess the value of y activation analysis and to place it in perspective with respect to the battery of other techniques that are currently available to the analyst.In particular, the advantages and disadvantages of the technique will be compared with those of thermal neutron activation analysis, the activation technique with which the majority of analysts are most likely to be familiar.Gamma activation analysis and certain of its applications have been reviewed by a number of a ~ t h o r s l - ~ and no attempt will be made here comprehensively to review the subject. This lecture will be restricted to certain applications of the technique that have been studied a t Harwell and these will be used to illustrate the various advantages and shortcomings of the method.Activation Analysis Like a number of other analytical techniques, such as X-ray fluorescence or emission spec- trometry, activation analysis is based on the excitation of a particular species into an excited state. Analysis is then based on measurement of the nature and intensity of the radiation emitted when this excited species returns to a more stable state.Unlike X-ray fluorescence or emission spectrometry, however, which involve extra nuclear electrons and in which de- excitation occurs virtually instantaneously, activation analysis involves excitation of the nucleus and, although it may occur instantaneously, de-excitation generally takes a finite time, e.g., seconds, minutes, or even years, to occur.A great variety of species, such as thermal and fast neutrons and charged particles can be, and have been, used for such nuclear excitation. For photonuclear, i.e., y-induced, activation the most common reaction is : i.e., a target atom, with a mass number m, of an element A, with atomic number 2, is bom- barded with a y photon and a product species is formed.This has the same atomic number as the target, but as a neutron has been lost in its production the mass number is reduced by one. If this product is radioactive, then the rate at which it decays or reaches its ground state, and the nature of the radiation it emits, can be used for its identification.In addition, the intensity of the radiation can be used as a quantitative measure of the radioactive species. Bombardment of the same target nuclide with thermal neutrons produces the converse reaction : .. . . * * (2) n+:A -t"f:A+y . . .. 193194 SILVER MEDAL LECTURE Proc. Analyt. Div. Clzem. SOC. Again, the product nuclide has the same atomic number but in this instance, because of neutron capture, the mass number is increased. Other common photonuclear reactions are : * .. . * * (3) y+”,+-zA*+y’ . . . . . . * (4) y + ;A -+ TI!B + ;H .. .. * * (5) y + :A + YrXC + :He + n . . . . Reaction (3) only occurs for nuclides that possess radioactive nuclear isomers and approxi- mately 20 exist with sufficiently long half lives to permit their use for analytical.purposes. Reactions of the type shown in equations (4) and (5), which result in ejection of charged particles, are of importance because they provide alternative product nuclides for analysis, and they introduce the possibility of nuclear interferences, i.e., the product nuclide used for measurement of a particular element by means of reaction (1) may also be produced from other elements of higher atomic number by reactions (4) and (5). Practical Considerations As was stated earlier, the intensity of radioactivity produced as a result of nuclear acti- The factors which deter- vation can be used as a quantitative measure of the target nuclide.mine this activity, A , are as follows: .. * * (6) A = n#o(l - e-hT) .. .. n being the number of target atoms.The isotopic abundance of the target huclide is, there- fore, of importance and indirectly this makes activation an isotopic method of analysis. # is the flux of activating species, whether it be neutrons, charged particles or y rays, 0 is the cross section, or effective area which the target nuclide displays for a particular nuclear reaction and X is the decay constant of the product nuclide and is inversely related to the half life with which it decays. For the majority of nuclides on which y activation is based, the half life is longer than 2 min.T is the irradiation time. In the instance of photonuclear reactions, the cross section, 0, varies in a specific manner with y energy as is shown, for a generalised case, in Fig. 1. The fact that a minimum, or threshold, energy ETI, has to be exceeded before reaction can occur is highly significant, particularly as, for the majority of reactions, this threshold energy is greater than 10 MeV.Such high y energies cannot be achieved from normal isotopic decay processes and consequen- tly use has to be made of high energy electron accelerators, such as betatrons, microtrons, or more commonly, electron linear accelerators (Linacs).This factor, more than any other, has limited the development of y activation and there are probably fewer than 30 machines in the world that are suitable for activation-analysis purposes. Electron accelerators do not produce y radiation directly; the electron beam is used to bombard a heavy metal converter with the resultant production of a continuous y spectrum or bremsstrahlung.As shown in Fig. 1, this spectrum extends up to the energy of the electron beam (El) with an increasing proportion of y radiation at lower energies. From Fig. 1 it can be seen that for photonuclear reactions equation (6) becomes: E, E T 1 A = n f #E 0, dE (1 - e--hT) .. . . - - (7) In principle, therefore, the higher the energy of electrons used the greater the integrated flux of y radiation with energy greater than E,, and hence the greater the activity produced from a given number of atoms.In practice, if an interfering reaction with a threshold energy E,, can produce the same product nuclide as the reaction with threshold ET1, E; should be kept below E,, (Fig. 1). Thus, as with inany other analytical techniques, a com- promise may have to be made between sensitivity and specificity.However, the fact that the electron energy of most accelerators can be readily controlled means that optimum irra-July, 1978 SILVER MEDAL LECTURE 195 diation conditions can be selected for a particular analysis, a feature not readily achieved with neutron activation. Details of y irradiation facilities have been given by a number of author^.^,^,^ Generally, the electron beam (typically 1-2 cm2 in cross section) leaves the vacuum of the accelerator through a thin metal window, crosses an air gap, in which its position and dimen- sion are monitored, and impinges on a cooled, heavy metal target.This produces y rays in the form of a cone (subtending an angle of -10') in the forward direction and samples for analysis require to be positioned accurately within this cone in order to receive maximum y flux.When short-lived radionuclides are of interest, samples are generally transferred to and from the irradiation position using a pneumatic transfer rabbit. Care is required to ensure that samples and simultaneously irradiated standards are subjected to comparable y fluxes or that suitable corrections for y flux variations are made.When nuclides with longer half lives are of interest a rapid transfer system is unnecessary and samples and stan- dards can be irradiated in a series of suitable containers rotated at right angles to the y beam.7 Why Use y Activation? Reference to the literature shows that neutron activation is applicable to a wide range of elements, but there are several elements for which the technique is not particularly well suited.These include the light elements carbon, nitrogen, oxygen and fluorine. Con- sidering the reasons for this in more detail, reference to a chart of the nuclides shows that, for carbon, thermal-neutron capture by the high abundance nuclide 12C produces inactive 13C.On the other hand, thermal-neutron activation of 13C produces active 14C, although the low abundance of 13C and the long half life of 14C result in low levels of induced activity. In addition, 14C decays solely by p- emission, which makes it particularly difficult to identify and measure owing to the weak penetration of ,B- radiation. When using y activation, the (y, n) reaction on high abundance 12C produces llC, which has a half life of 20 min and decays by ,B+ emission, a much more practical combination for analytical purposes. In all instances the highest abundance nuclide produces a radionuclide on (y, n) activation with nuclear properties much more suitable for analytical purposes than the thermal neutron (n, y ) product from lower abundance nuclides. Here then is a group of elements which, it would appear, can be deter- mined much more readily by y activation than by thermal-neutron activation.This obser- vation also illustrates that, in general, y activation makes available an entirely different range of nuclides for analytical purposes than does thermal-neutron activation. A similar situation exists for nitrogen, oxygen and fluorine. Determination of Light Elements llC, 13N, 150 and 18F, the (y, n) products from carbon, nitrogen, oxygen and fluorine, res- pectively, all decay by ,B+ emission.This is typical for neutron-deficient species and necessi- tates, for optimum specificity and sensitivity, that in the determination of the light elements, radiochemical separation from the matrix of the species to be measured be employed.The radiochemical procedures used are generally based on conventional chemical methods, e.g., 18F can be separated by Willard and Winter's distillation,* 1 5 0 and 13N by inert gas fusionllg and llC by combustion.1° The major difference when these techniques are used for radiochemical, as opposed to conventional, separations is that the analysis is based on mea- surement of radioactive species.Thus, after irradiation, blanks from the reagents and apparatus are unimportant. This adds a completely new dimension to light element deter- mination, in that inactive carriers can be added in order to minimise adsorption effects and crucibles and fusion fluxes need not be preconditioned to reduce blank levels. The efficiency of decomposition of stable species, e.g., oxides, carbides and nitrides, is still of concern but a variety of fusion or combustion conditions can be readily used, including those which may be unsuitable in conventional techniques owing to unacceptably high blanks.It should also be borne in mind that the activation process itself may alter the chemical form of the element of interest, simplifying its subsequent separation. The efficiency of recovery of decomposed radioactive species can readily be assessed by using radioactive tracers.196 SILVER MEDAL LECTURE Proc.Analyt. Div. Chem. SOC. A further major advantage of independence from a reagent blank is the ability to remove surface contamination after y irradiation and hence to measure true bulk concentration.This is particularly valuable at low concentrations of oxygen and carbon, which are such ubiquitous elements in the atmosphere. The ability to measure bulk, as opposed to total, concentration can introduce problems in the availability of standardised materials. Table I shows results obtained at Harwell using inert gas fusion to separate 1 5 0 from a series of y-activated metals standardised for oxygen content.In all instances the surfaces of the samples were etched after irradiation and bery- llia was used as an absolute oxygen standard. At high concentrations agreement with the certificated results is satisfactory. At the low concentration in NBS 1094, significantly lower results were obtained by y activation, owing to the removal of the surface oxygen which at this concentration makes a significant contribution to the total oxygen content.This and similar examples highlight the fact that many of the standards available with low concentrations of oxygen, carbon and nitrogen are standards under specified analytical conditions only. TABLE I ANALYSIS OF STANDARD MATERIALS Content found, Standard Certified content n p.p.m. Oxygen- BCS 197/e copper 0.019% 4 214 f 23 NBS 1092 steel 28 p.p.m. 6 29 & 1 NBS 1094 steel 4.5 p.p.m.10 1.9 f 0.2 In practice, y activation is becoming increasingly used as a referee method for determination of the bulk light element content of pure metals and alloys where the presence of these ele- ments within the bulk of the sample can have a significant effect on, for example, the ductility of metals and electrical properties of semiconductors. This is exemplified by the use of y activation as one of the main certification methods adopted by the European Community Bureau of Reference for its oxygen in non-ferrous metals programme.ll From the many examples of the practical application of the method the value of the y activation procedure can be illustrated by consideration of the determination of trace con- centrations of oxygen in sodium.This measurement is of importance in the operation of fast breeder nuclear reactors and there is currently considerable debate as to the accuracy of the various methods used. In the UK the favoured technique involves distillation of the sodium under high vacuum and titration of the residue on the assumption that any oxygen present is in the form of Na,O.Any such indirect procedure with the requirement for rigorous exclusion of oxygen-containing species at all stages of the process is obviously open to criti- cism. On the other hand, comparison of vacuum distillation results with those of y activation shows surprisingly good agreement over a range of concentrations, as is shown in Fig.2. Bearing in mind the entirely different principles on which the analyses are based, this gives confidence in the accuracy of each method. Details of the sampling and chemical separation procedures used for y activation analysis have been described previously.12 The ability, using y activation analysis, to use the sodium itself as an effective barrier against atmospheric oxygen has also proved to be an invaluable feature as oxygen-contaminated sodium and its external container can be discarded after irradiation.This has allowed the technique to be used as a reference procedure by which results from different laboratories can be compared and has also permitted samples to be collected in situations which could not be contemplated when using conventional methods. The limits of detection for the determination of the light elements using y activation are given in Table 11.These limits, obtained by using the short-term irradiation facility at H a r ~ e l l , ~ ? ~ are defined as that mass of element which gives an activity equivalent to twice the standard deviation of the background on the y-ray detection system used, at a time after irradiation sufficient to permit radiochemical separation of the appropriate species.As up to 1 g of sample can be irradiated, the limits of detection for carbon and fluorine are in the parts per billion (lo9) m/m range and for oxygen and nitrogen the tens of parts per billion mlm range.July, 1978 SILVER MEDAL LECTURE 197 \ I I / ET 1 E M E,E,, Gamma energy 1 .o >- c-' v) C a, c-' C C .- .- 0.5 1 Q a, c-' a, .- - lr: 0 60 4 50 F E Q 40 r' .E! 30 a + > .- + g 20 E 0 (II 5 10 0 Vacuum distillation, p.p.rn.m/m Fig. 1. Variation of bremsstrahlung intensity and photonuclear cross section with gamma ray energy. 3 Fig. 2. Determination of oxygen in sodium. Comparison of results obtained by gamma activation and vacuum distillation.The limits of detection quoted assume interference-free conditions because, in all instances, the radionuclide used for measurement of a particular element can also be produced from neighbouring elements in the Periodic Table. As indicated earlier, the magnitude of any such interference is reduced by lowering the irradiation energy. This, in turn, has a detri- mental effect on sensitivity, although for the majority of Linacs this can be compensated for by the increased beam currents available at lower energies. For pure metals and alloys, where relative concentrations of the light elements are unlikely to differ by more than two orders of magnitude, interference effects at irradiation energies below approximately 40 MeV are generally small ; however, whenever possible lower irradiation energies are to be favoured. There are probably only two other practical analytical techniques that can compete with y activation for the determination of total oxygen, carbon and nitrogen at such low con- centrations.One of these is spark-source mass spectrometry (SSMS), provided that a helium cryopump is used to minimise instrument blanks and standardised samples are available from which relative sensitivity factors can be ca1c~lated.l~ The other is charged particle activation analysis (CPAA). This shares with y activation freedom from reagent blanks and the ability to etch the surface after irradiation.However, the limited penetration of charged particles restricts the applicability of the method to surface analysis. Thus, much greater care is required to control the extent of etching, and, if bulk analysis is of interest, it must either be assumed that the surface is representative of the bulk or repeated sequential analyses be carried out into the bulk of the material.On the other hand, if surface analysis only is of interest, CPAA is a much superior technique. This is critically dependent on the basis of the costing system adopted, not to mention such factors as the type and number of samples to be analysed.In general, using the commercial costing system at Harwell for routine analysis of relatively large numbers of samples, costs for y activation are approximately 3-5 times greater than those of conventional methods. Costs A further, increasingly more important, factor when comparing techniques is cost.TABLE I1 DETECTION LIMITS USING ACTIVATION FOR DETERMINATION OF LIGHT ELEMENTS Element Fluorine Carbon Nitrogen Oxygen Irradiation time Limit of detection*/ (at -35 MeV) /min CLg 30 0.002 20 0.002 10 0.02 4 0.05 * Based on mass required to give an activity equal to 20 of detector background at a time sufficient to permit radiochemical separation.198 SILVER MEDAL LECTURE Proc.AnnZyt. Div. Chem. SOC. for SSMS could be 2-3 times more expensive than y activation, but the fact that a large number of elements can be determined simultaneously reduces the cost per element, assuming that a number of elements are of interest. Costs per determination for CPAA should be comparable with those of y activation, although as stated earlier for bulk analyses by CPAA, multiple determinations may be necessary in order to obtain meaningful results.Determination of Other Elements Although historically the determination of carbon, nitrogen, oxygen and fluorine has been one of the most important applications of y activation analysis, and this is likely to continue in the future, it is by no means the only area of application.In theory, the identity and yield of nuclides produced on irradiating a particular element with y photons should be predictable but, unlike thermal neutron activation, there is often a dearth of accurate photonuclear data. A much more realistic and practical approach is to irradiate each element individually and to examine the nature and intensity of the activity produced.This has been carried out by a number of workers under a range of irradiation and counting conditions.14-16 Fig. 3 summarises data obtained at Harwell by using y radi- ation with Em,,, in the range 38-42 MeV and a high resolution germanium (lithium) de- tector as described previ0us1y.l~ Limits of detection, defined as that mass of element pro- ducing an activity equivalent to twice the standard deviation of the detector background at the appropriate y energy, have been quoted along with the identity of the major y-emitting nuclide produced.Generally, the most intense y ray has been used in calculating detection limits. A 1-h irradiation and a count time of 3 h or one half life, whichever is the shorter, have been assumed. To facilitate radiochemical separation of the radioactive species used for analysis the specific activity after a decay time of 1 h has been used in the calculation of limits of detection and, for purely practical reasons, only nuclides with half lives longer than 45min have been considered.With the exception of the light elements, which have been discussed above, and the rare gases, which have not been studied, elements left blank in Fig.3 are unsuited to analysis by y activation, owing either to the nuclear properties of the product nuclide or the presence of significant nuclear interference. Nuclide f o r Analyis Fig. 3. Limits of detection for gamma activation (based on irradiation for 1 h a t about 40 MeV and conditions given in text). Deuterium and beryllium are special cases in that the thresholds for the (y, n) reactions are low, 2.23 and 1.67 MeV, respectively, and hence can be induced by y radiation produced from isotopic decay processes.By measuring prompt neutrons and using a 2 Ci 124Sb source, the limit of detection for beryllium is 0.7 pg, whereas with a 25-Ci 24Na source the limit of detection for deuterium is 1.5Jzdy, 197’8 SILVER MEDAL LECTURE 199 The important aspect of the data shown in Fig.3 is the large number of elements that can be determined by y activation; for the majority of these the limit of detection is below 1 pg. It is also significant that the range of limits of detection is relatively small, and hence there are few elements with very high or very low detection limits, as is the case with thermal neutron activation.Yule has reported the limits of detection obtained by irradiating individual elements for 1 h in a thermal neutron flux of 4.3 x 10l2 neutrons cm-2 s-1 and has calculated limits of detection under somewhat similar conditions to those used here.l7 Using the same criteria for selection of nuclides, of the elements shown in Fig. 3 y activation is suited to the determination of 47 elements compared with 40 by thermal neutron activation. On the other hand, of those elements suitable for y activation, only 44% have a limit of detection below 0.1 pg, whereas the corresponding proportion for thermal neutron activation is 86%.In addition, as the majority of nuclides of interest have long half lives, sensitivity can be improved by increasing the irradiation time.With thermal neutron activation irradiation times of up to weeks may be practicable, whereas for y activation, for economic and practical reasons it is unlikely that irradiation times greater than 1 d will be possible. It can be concluded, therefore, that although y activation can offer a comparable, if not better, elemental coverage than thermal neutron activation the latter technique is, in general, two, three or possibly four orders of magnitude more sensitive.It is of interest to carry out a direct comparison with thermal neutron activation. Analysis Using Radiochemical Separation The ability to produce high levels of activity from a particular element by using neutron activation may be a disadvantage, particularly if that element forms part of the matrix in which a second element has to be measured.This fact can be illustrated by the determination of trace concentrations of nickel in glass, a measurement of importance in assessing the optical attenuation of glass used for fibre optics. Using neutron activation, two reactions, 64Ni(n,y)65Ni and 58Ni(n,p)58Co, are available for the determination of nickel, and in each instance the product nuclides are y emitters with half lives sufficiently long to permit their radiochemical separation.The maj or problem with the neutron activation of glass, however, is the intense 24Na activity induced from sodium present at percentage level concentrations in the matrix. As the half life of 65Ni is 2.6 h it is not possible to allow the 15 h 24Na to decay before separation.Hence, in order to reduce the 24Na activity to acceptable levels, the irradiation conditions must be reduced to a level weli below those that are the optimum for 65Ni production. In practice, at Harwell the estimated practical thermal neutron activation limit of detection for nickel in glass is 0.05 pg. Similarly, by use of the fast neutron activation product WO, the limit of detection is 0.02 pg.In this instance the high thermal neutron cross section of SSCo prevents the use of extended irradiation times as 5 8 C ~ becomes converted to stable 5 9 C ~ during irradiation. Again because of 24Na activity considerations it is impractical to irradiate masses of sample greater than about 200 mg ; consequently, the over-all practical limit of detection when using neutrons at Harwell is 0.1-0.3 p.p.m.Using y activation, nickel can be determined by using the 58Ni(y,n)57Ni reaction and radio- chemical separation of 57Ni as the dimethylglyoxime. As sodium is one of the elements that is least activated (Fig. 3), the matrix presents little problem even under irradiation a t about 40 MeV(E,,,,) for 10 h. Under these conditions the limit of detection is 0.004 pg and as amounts of glass up to 3 g can be irradiated the practical limit of detection for nickel by y activation using the Harwell y irradiation facilities is approximately 0.002 p.p.m.* In this instance, therefore, y activation offers a much more satisfactory approach than neutron activation and if, as is the case for many glasses, significant concentrations of boron are present, neutron activation is not possible at all owing to the high thermal neutron cross section of log.Although a limited number of techniques are already available for the deter- mination of such low concentrations of nickel in glass, e.g., atomic absorption following *Unlike neutron fluxes, y fluxes are difficult to quantise, being dependent on electron energy and current, beam and sample size and design of facility and, in addition, effective flux also varies from element to element. Reference should therefore be made to detailed descriptions of the irradiation facility used.’200 SILVER MEDAL LECTURE Proc.Analyt. Div. Chew. Soc. chemical pre-concentration or spark source mass spectrometry, the availability of an in- dependent absolute procedure free from problems of reagent blank is valuable for assessment of accuracy or for calculation of relative sensitivity factors.This application of y activation followed by radiochemical separation to analytical problems, which do not lend themselves to solution by neutron activation because of unsuitable nuclear properties of either the element of interest or the matrix, is virtually an unexplored area and is certain to expand rapidly as the capabilities of y activation become more widely appreciated. High sensitivity need not be the prime requisite for a technique to be of practical value.Table I11 shows the results obtained during an assessment of the suitability of various tech- niques for the determination of lead in human bone1* prior to carrying out a survey of lead concentrations in bone throughout the UK.The y activation results were obtained by using radiochemical separation of 203Pb. Although these results provide a valuable independent assessment of accuracy, it would be unrealistic to use the technique for the analysis of large numbers of samples if an alternative, satisfactory and more economic procedure was available.From the practical viewpoint, however, the more conventional techniques shown in Table I11 are most satisfactorily applied to ashed, rather than raw, samples. This raises the problem of potential loss of lead during ashing, and a study of the literature shows conflicting evidence for the behaviour of lead during the dry ashing of bone.This behaviour can be readily studied by using y activation.lg TABLE I11 DETERMINATION OF LEAD IN HUMAN BONE ASH Technique Concentration of lead, n p.p.m. Gamma activation 4 15.7 f 0.7 Emission spectrometry 10 15.5 f 0.5 Dithizone - atomic absorption 10 15.3 f 0.3 Dithizone - absorptiometry 12 15.3 f 0.5 Unlike 20gPb (the major thermal neutron activation product of lead) 203Pb is a y-ray emitter with a long half life, and for bone samples with sufficiently high lead concentration (more than 30 p.p.m.), lead can be determined directly in raw bone using high resolution y-ray spectrometry without radiochemical separation.Thus, by measuring the 203Pb activity in raw bone and again after ashing the same sample at each of a number of temperatures, the maximum temperature at which human bone can be ashed without significant loss of lead has been e~tab1ished.l~ This procedure enables the behaviour of lead inherent in bone to be followed, as distinct from the behaviour of the synthetic lead additives that are more generally used in such studies, a factor of particular importance as the chemical form of lead in bone is not known.In fact, it has been shownlg that 203Pb-labelled lead carbonate, chloride and phosphate behave differently from the lead inherent in the bone.This use of high resolution y spectrometry following y activation in order to produce non- destructive, simultaneous, multi-element determination is probably the fastest growing application of y activation. This is particularly so in the environmental field, where there are increasing demands for the multi-element analysis of large numbers of samples.It also brings y activation into direct competition with more conventional multi-element techniques, such as emission spectrometry, spark-source mass spectrometry, thermal neutron activation, X-ray fluorescence and the newer techniques such as charged particle induced X-ray emission.Again, it is only possible here to indicate a limited number of applications of the technique in order to illustrate the salient features. One of the simpler matrices to which the tech- nique has been applied is cellulose filter-paper impregnated with atmospheric particulates.20 In this intance the sample is compressed into a small pellet and irradiated along with a multi- element standard consisting of 20-30 mixed metal oxides, each present at approximately the 50-pg level in a matrix of cellulose.Using a high resolution germanium (lithium) y-ray detector the activities induced in both samples and standards are then measured after a series of decay times, without any post-irradiation chemical treatment. Significantly, and unlike the corresponding spectra produced following thermal neutron activation, few elements dominate the y spectra obtained.In typical urban particulates approximately 20 elements can be quantitatively determined and for several others upper limits can be quoted.20 InJuly, 1978 SILVER MEDAL LECTURE 201 practice, it is found that for air particulates the capability of y activation is very similar to that of X-ray fluorescence and is complementary to that of thermal neutron activation, providing data for such additional elements as Ni and Pb.21 As far as the X-ray emission techniques are concerned, air particulates on filter-paper are an ideal medium because inter-element absorption and enhancement effects are minimised and standardisation can be readily accomplished using suitable solutions evaporated on to the paper.By using y activation the same basic technique as is applied to filter-paper can be applied to a wide variety of other matrices, which would prove difficult for the X-ray methods owing to difficulties in preparation of suitable standards. Fig. 4 shows the high resolution y spectra from two samples of coal taken after decay times following y irradiation of 38 and 67 h, respectively.For these and for other related materials, such as fly ash, soil and rocks, all that was required was to homogenise the sample and com- pare the induced activity with that of a comparable multiple element standard to that used for the analysis of air particulates. Particle size effects, of importance in X-ray methods, are absent and there is no requirement to take into solution, ash, or grind with graphite, as might be required by other techniques such as emission spectrometry, spark-source mass spectrometry or atomic absorption.In coal samples approximately 20 elements, many of particular interest in this type of material, can be determined, e.g., Sb(6, <0.5p.p.m.), Ni(25, 25 p.p.m.), As(1, 1 p.p.m.) and Pb(3.1, 7.4 p.p.m.), along with others such as Ti(80, 15 p.p.m.) and Zr(7.8, 0.9 p.p.m.) not readily measured by other methods.The values quoted in parenthesis are concentrations of elements observed at the decay time shown in Fig. 4 for the power station coal and anthracite, respectively. The ease of standardisation and sample preparation in y activation becomes more valuable as matrices become more complex.For example, in the biological field, elemental balances x i r r '02 i 10' i Zn Pb As Mn Ge Mg Ni Y Ni r. m W W m i Energ ykeV Fig. 4. Gamma spectra from gamma activated coals. A, Calverton coal after 38 h decay; and B, anthracite after 67 h decay. Irradiation and count times 10 and 3 h, respectively.202 SILVER MEDAL LECTURE Proc. Analyt. Div.Chem. SOC. in materials such as diet and faeces can be readily assessed by the analysis of pellets of dried, slurried material. In this area the ability to measure isotopic species is an added advantage over conventional methods; metabolism of elements in different dietary forms can be studied by use of stable isotopic tracers, which subsequently become activated, e.g., in the instance of calcium, inactive 48Ca can be measured via the 48Ca(y, n)47Ca(y at 1297 keV) reaction whereas 44Ca can be measured via 44Ca(y, p) 43K (y at 618 keV).The deep penetration of the energetic activating y rays and the ability to use emitted radiation of relatively high energy means that much larger samples, possibly up to 1 g, can be analysed by using y activation rather than X-ray techniques.This is of particular significance for materials such as soils or sewage sludges, from which it may be difficult to obtain homo- genous samples. Fig. 5 shows the y spectra obtained after a short (10 h) and a long (170 h) decay from a y activated sewage sludge sample. The relatively high concentrations of many elements make the spectra particularly complex, but indicate the range of elements for which technique can be applied.c Fig. 5. Gamma spectra from gamma activated sewage sludge. A, After 10 h decay; and B, after 170 h decay. Irradiation time, 10 h; count times 10 rnin and 2 h, respectively.July, 1978 SILVER MEDAL LECTURE 203 The complexity of these spectra also highlights certain of the interference problems, which must be considered in this type of analysis.Many of these are equally applicable to other types of spectrographic analysis, such as emission spectrometry, particularly when using a direct reader, energy dispersive X-ray fluorescence and spark-source mass spectrometry. Two lines may be of such similar energy that they cannot be resolved, e.g., both iodine and strontium have a y ray at 388 keV. However, the half lives of the two nuclides involved are significantly different, and by decay curve analysis techniques the two components can be readily resolved; this time effect is a parameter not available with other non-activation techniques.Should half lives be comparable, e.g., in the instance of iodine and caesium at 666 keV, it may be possible to measure an alternative line for one of the elements and make a suitable correction on the basis of the relative line intensities obtained from past experience of irra- diating the pure elements; a technique commonly used in X-ray fluorescence.A second type of interference occurs when the same nuclide is produced from more than one element, e.g., 52Mn is produced from both iron and manganese. Again, reference to a published catalogue of y-irradiation products16 or irradiation of the pure elements under comparable experimental conditions enables suitable corrections to be made, provided that one of the elements involved produces a y line at another energy level.Failing this it may be necessary to repeat the irradiation at a lower energy, nearer the threshold of the inter- fering reaction, although this increases the cost of analysis and some compromise between cost and accuracy required may have to be made.As relative cost can be an important factor in the choice of analytical technique it is of interest to consider this factor further. Using the Harwell costing system, it is found that there is little to choose, on a per element basis, between the cost of y activation, neutron activation and X-ray fluorescence for multi- element analysis, provided all elements determined by each of the two activation techniques are of interest.If only a few elements are required X-ray fluorescence is more economical, providing appropriate standard materials are available. Table IV shows typical data obtained in routine y activation analysis of NBS 1571 (orchard leaves).It can be seen that the technique has a wide dynamic range, varying from sub- p.p.m. to percentage concentrations in the same sample without resorting to dilution tech- niques. In many instances, e.g., in rocks and soils, major element composition can be of comparable importance to that of trace elements, particularly if only small amounts of sample are available, as with returned lunar material^.^ The precision of the method, as shown for quadruplicate analyses in Table IV, can be 5%, although care is required to ensure accurate positioning of samples and standards within the y flux in order to attain this precision.TABLE IV ANALYSIS OF NBS ORCHARD LEAVES BY NON-DESTRUCTIVE y ACTIVATION Mean and standard deviation of 4 analyses, p.p.m.m/m unless stated. Element As Ca Cd Mn Mo Nb Ni Mg NDGAA 11 f 0.6 2.2 & 0.05% (0.2 0.61 0.02% 96 f 5 (1.0 (0.3 (2.5 Certificate Element 10 f 2 Rb 2.1 yo Sb 0.11 Sr 0.62 5 0.01% Ti 91 -I: 4 T1 0.5 Pb - Zn 1.3 & 0.2 Zr NDGAA Certificate 3.5 & 0.2 3.0 28 f 0.6 37 96 12 - 0.3 f 0.1 - 40 f 4 31 & 3 28 1.3 f 0.3 - 12.5 f 0.6 12 f 1 45 f 3 From the type of data shown in Table IV, and many other examples quoted in the litera- ture, it is probably realistic to consider the accuracy of the non-destructive y activation method to be approximately &lo%, assuming that due consideration is paid to the effect of interferences, probably the major source of systematic error.In many instances the use of a purely instrumental analytical technique may be justified for the determination of only a single element, particularly if that element is difficult to determine by other methods. Iodine is such an element.The detailed application of y204 SILVER MEDAL LECTURE Proc. Analyt. Div. Chem. SOC. activation to the determination of iodine in a wide range of biological materials has already been described.' A summary of the type of data that has been obtained, along with a com- parison of results obtained by independent laboratories using more conventional pro- c e d u r e ~ , ~ ~ ~ ~ ~ is shown in Table V.TABLE V DETERMINATION OF IODINE IN BIOLOGICAL MATERIALS Iodine, p.p.m. dry mass , 1 RTNAhtZ2 Colorimetry23 Material NDGAA* NBS 1632 (coal) NBS 1571 (orchard leaves) Soil A Soil B Soil C Soil D 3.3 -l 0.3 0.1 f 0.05 2.7 & 0.2 0.17 5 0.01 17.3 f 1.3 - 19.8 f 0.9 34.1 3.6 - 4.9 f 0.9 - - - 24.3 17.2 36.9 4.8 * Instrumental y activation, mean and standard deviation for a minimum of 3 determinations.t Radiochemical neutron activation. This application again shows the value of y activation in providing an independent analytical approach and illustrates that the technique must be considered as a viable, practical method and not just as an academic curiosity of restricted applicability.Conclusion The salient advantageous and limiting features of y activation are summarised in Table VI. Under each heading an indication has been given as to which other techniques share this feature. For precision, accuracy, practical limit of detection, availability and absolute limit of detection an attempt has also been made to assess the relative merit of y activation compared with that of other analytical methods.TABLE VI SUMMARY OF SALIENT FEATURES OF Y-ACTIVATION Advantageous features Freedom from blank Isotopic analysis Bulk analysis/large sample size Ease of sample preparation Ease of standardisation Non-destructive analysis possible Simultaneous multi-element Suitable for light elements Lends itself to automation Precision (f5-10%) Accuracy (f 10%) Practical limits of detection (1 p.p.b- Comparable with- NA, CPA SSMS, >NA, CPA CM, NA NA NA, CPA NA, XRF, CPA, PIXE SSMS, ES, ICP, NA, XRF, PIXE, CPA SSMS, CPA NA, XRF, PIXE XRF, CM, ID, ICP, AA > (NA, GA, CPA) >(ES, SSMS) ID, CM>(NA, GA, CPA, ES, ICP) >(XRF, AA, SSMS) SSMS, NA, ICP, ID >(AA, ES, GA, CPA, XRF, PIXE) .lo p.p.m.) Limiting features Availability Absolute limits of detection (1 ng-10 pg) Multi-element turnround time (weeks or months) CPA, NA NA = Neutron activation, CPA = charged particle activation, SSMS = spark-source mass spectrometry, CM = chemical methods, XRF = X-ray fluorescence, ES = arc-emission spectrometry, ICP = inductively coupled plasma emission spectroscopy, ID = isotope dilution, AA = atomic absorp- tion, GA = y activation, PIXE = proton induced X-ray emission.CM, AA, XRF, ES, ICP >(NA, CPA, PIXE, SSMS, :&!kS. ICP, PIXE, AA, NA, CPA >(XRF, GA, CM) Overall, it can be concluded that y activation is a versatile, widely applicable, although in general less sensitive, complement to thermal neutron activation, the major disadvantage of the method being the relatively small number of suitable irradiation sources available.July, 1978 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS 205 The author would like to take this opportunity of acknowledging the co-operation and assistance he has received from his colleagues in the former Analytical Sciences Division and the Environmental and Medical Sciences Division at AERE, in particular Mr.D. R. Williams and the other members of the y activation section, who have been involved in the various aspects of the work described in this paper. 1 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. References Engelmann, C. in Lenihan, J. M. A., Thomson, S.J., and Guinn, V. P. Editors, “Advances in Activa- tion Analysis,” Volume 2, Academic Press, London and New York, 1972. Kosta, L., Dermelj, M., and Slunecko, J., Pure Ap@. Chem., 1974, 37, 249. Hislop, J. S., “Proceedings of the International Conference on Photonuclear Reactions and Appli- cations, Asilomar, 1973,” USAEC Information Services, Oak Ridge, Tenn., USA, 1973, CONF- Lutz, G., Analyt. Chem., 1971, 43, 93. Hislop, J. S., and Williams, D. R., “The Use of Non-destructive y-activation for the Analysis of Rock and Biological Materials, AERE-R6910, HM Stationery Office, London, 197 1. m7ilkniss, P. E., Hoover, J. J., and Leighton, R. E., Nd. Instrum. Meth., 1967, 56, 120. Williams, D. R., and Hislop, J. S., J . Radioanalyt. Chem., 1977, 39, 359. Hislop, J. S., Pratchett, A. G., and Williams, D. R., Analyst, 1971, 96, 117. Williams, D. R., Hislop, J. S., Mead, A. P., Sanders, T. W., and Wood, D. A., J . Radioanalyt. Chem., Hislop, J. S., Sanders, T. W., Webber, T. J., and Williams, D. R., “The Determination of Carbon in Nickel by High Energy y Photon Activation,” AERE-R8182, HM Stationery Office, London, 1975. Pauwels, J. A., Erzmctall., 1977, 30, 434. Hislop, J. S., Stevens, J. R., and Wood, D. A., J . Radioanalyt. Chem., 1977, 39, 409. Rlackmore, G. W., Clegg, J. B., Hislop, J. S., and Mullin, J. B., J . Electronic Muter., 1976, 5, 401. Kato, T., J . Radioanalvt. Chem., 1973, 16, 307. Segebade, Ch., Lutz, G. J., and Weise, H. P., .J. Radioanalyt. Chem., 1977, 39, 179. Anderson, P., Hislop, J. S., and Williams, D. R., “High Resolution y Spectra of 40-44 MeV y Photon Activation Products,” Part 1, “The Elements Sodium to Molybdenum,” AERE-R7823, HM Stationery Office, London, 1974, Part 2, “The Elements Ruthenium t o Uranium,” AERE-R9021, HM Stationery Office, London, 1978. Yule, H. P., Analyt. Chem., 1965, 37, 129. Hislop, J. S., Parker, A., Spicer, G. S., and Webb, IT. S. W., “The Determination of Lead in Human Hislop, J. S., and Williams, D. R., “Proceedings of Conference on Nuclear Activation Techniques in Hislop, J. S., and Williams, D. R., J . Radioanalyt. Chem., 1973, 16, 329. Cawse, P. A., Editor, “Intercomparison of Analysis of Air Filter Deposits for Trace Elements,” Rook, H. L., J . Radioanalyt. Chem., 1977, 39, 351. Whitehead, B.C., J . Soil Sci., 1973, 24, 260. 730301, pp. 1159-1170. 1978, in the press. Rib Bone,” AERE-R7321, HM Stationery Office, London, 1973. the Life Sciences, Bled, 1972,” IAEA-SM-157/42, TAEA, Vienna, 1972, p. 51. AERE-R8191, HM Stationery Office, London, 1976.

ISSN:0306-1396    

DOI:10.1039/AD9781500193

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

July, 1978 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS 205 Analytical Aspects of Hazardous Materials The following are summaries of five of the papers presented in the Analytical Symposium at the CS/RIC Annual Congress held on April 4-6th, 1978, at the University of Liverpool. Some Aspects of Determining Free Silica in Respirable Dust Samples J. Dodgson, A. P. Middleton and K. J. Pickard* Institute of Occupational Medicine, Roxburgh Place, Edinburgh, EH8 9s U Exposure to dusts containing quartz or other forms of free silica has been recognised as a health hazard for many years.The safe working levels recommended for the UK by the Health and Safety Executive are based upon experience in the USA (ACGIH, la 1971) and stipulate an effective threshold limit value (TLV) for respirable quartz of about 0.1 rng m--3, averaged over an 8-h day, 5-day week. The corresponding TLVs for tridymite and cristobalite are set at half the value for quartz.Respirable dust samples are normally taken at flow-rates * Health and Safety Executive, Occupational Medicine and Hygiene Laboratories, 403 Edgeware Road, London N.W.2.206 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS Proc.AizaZyt. Div. Chzein. SOC. of about 2 1 min-l, giving a total volume of about 1 m3 of air sampled during an 8-h shift, so that for the analysis of personal samples a high degree of analytical sensitivity is required- of the order of 10 pg (10% of the TLV) for quartz. Although chemical methods and differential thermal analysis techniques have been used for the determination of free silica in dust samples, X-ray diffraction (XRD) and infrared (IR) techniques are often preferred because of their greater selectivity, sensitivity and speed of analysis.In particular, XRD and IR techniques involving direct analysis of the dust on the filter used for sampling have considerably simplified the analytical procedures. Outline of Techniques Techniques for the direct on-filter analysis of quartz in respirable dust samples by IR were described in detail by Dodgson and Whittaker.lb Briefly, the absorbance due to the filter material of the sample filter is balanced by placing a similar blank filter in the reference beam of the spectrophotonieter.Absorbance due to quartz is then measured at the doublet at 780 and 800 cm-l and compared with a calibration graph.The choice of filter is important and, in addition to being suitable from a sampling point of view, the filter should have high transmittance of infrared radiation and different filters (of the same type) should “balance.” These requirements for sampling and analysis are met by PVC-based membrane filters (VM filters, PVC filters and DM filters) and by Nuclepore polycarbonate filters.In the present investigations, the XRD techniques used were similar to those described by Crosby and Hamer,2 who modified the method described by Leroux and power^.^ Silver membrane filters were chosen for sampling because of the good background that they give in the X-ray diffractometer, in the region of the quartz diffraction lines. Crosby and Hamer2 measured the intensity of the (101) quartz line and compared this with a calibration graph.Calibration samples were prepared for both the XRD and IR techniques by dispersing a well defined standard quartz sample (X6403) in a dust box and sampling the quartz via appro- priate respirable dust sampling instruments, so as to simulate as near as possible field sampling conditions.The XRD standards were collected on 25 mm diameter silver filters in a BCIRA cyclone, while the IR standards were collected on 37 mm diameter VM-1 filters via a Simpeds cyclone. Comparison of Results from XRD and IR Published a c c ~ u n t s ~ ~ ~ of comparisons between the results of analyses for quartz using IR and XRD have shown reasonably good agreement between the two methods, and this has usually been our own experience in the analysis of quartz in coal mine dusts.However, during the monitoring of a construction site, discrepancies were noted between the apparent percentage quartz content of samples analysed independently and at different times by XRD and IR. The results of XRD analyses consistently indicated quartz concentrations approximately twice those derived from the analysis of samples by IR.In order to investigate these differences a field trial was organised in which side-by-side samples were taken for analysis by XRD and IR. Although there was generally good agreement between the gravimetric concentrations determined from the different samples, analysis of the dust on the silver filters by XRD once again gave quartz contents approximately twice those obtained from IR analysis.In the light of these results, further laboratory studies were undertaken, in particular to investigate possible errors due to unsatisfactory calibrations, particle size effects and inter- f ering substances. Calibration The amounts of dust collected during the field trials were small and the validity of the calibrations at low levels of quartz was therefore investigated.It was found that the IR calibration was linear down to dust loadings on the filter of G0.08 pg mm-2. The XRD calibration, although linear, was found to intercept the abscissa at about 30 pg. This effect was attributed to a shielding effect by the silver filter of quartz particles that had penetrated into the depth of the filter.July, 1978 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS 207 Particle Size Effects The direct effect of particle size on instrumental response in XRD analysis was investigated by Gordon and Harris6 over 20 years ago.For potentially respirable dust (<7 pm in dia- meter) errors of about -+10-20y0 can arise, but if suitable standards are used and appro- priate calibration procedures are followed, these errors are usually not serious.Associated with this particle size effect is the problem of damage (produced during grinding) to the crystalline structure of quartz, which has been extensively discussed,7,8 but which is beyond the scope of the present discussion. The effect of particle size on the IR response to quartz, within the “respirable” particle size range, has also been investigated previously.lb Examination of the IR spectra of samples taken during the field exercises indicated that the particle size of the quartz in these dusts was very similar to that of the standard quartz, so that errors of not more than 5-10% would be expected.The dust deposits on filters taken using cyclones are often non-uniform and can result in differences of as much as 30% in apparent quartz content when analysing (by IR) different areas of filters taken in Simpeds instruments.During the present trial, however, the IR estimates by the direct and disc methods agreed well, indicating that non-uniformity of dust distribution on the Simpeds filters was not a serious source of error in the direct IR analysis. The uniformity of deposits on filters taken for XRD analysis using the Higgins cyclone was investigated using VM-1 filters and IR analysis.The study confirmed that there is a tendency for dust to be concentrated in the central portion of the filter when using this cyclone and also indicated that the magnitude of this centre-spot effect is related to the particle size distribution of the dust being sampled.The area of sample analysed by the X-ray beam will depend upon several factors, including the size of the divergence slit, the angle of diffraction and whether or not a sample spinner is used. In general, however, the beam will preferentially examine the central portion so that any concentration of dust on this part of the filter will result in an overestimate of quartz content.Samples prepared for calibration purposes should therefore be taken using unsettled (or continuously generated) dusts, as these are more likely to be representative of actual dusts sampled. Ideally, the calibration dust should have the same airborne aero- dynamic diameter distribution as the dust to be measured. Interfering Substances Qualitative XRD analysis of dust collected by the filter system on a drilling machine indicated that the dust contained chlorite and muscovite, in addition to quartz. A further possible source of interference was graphite (or other substances) in diesel smoke.None of these substances was thought, on the basis of past experience, to present a serious problem to the IR analysis at the levels present. However, both muscovite and graphite give strong X-ray lines in the region of the strong quartz line (101) at 3.34 A that had been used for analysis. In samples of diesel exhaust, no peak was detected that would have interfered with the determination of quartz.The effect of muscovite interference was assessed by using dust-box samples of the drill dust. The quartz content of the dust was determined by using the strong (101) line and also using the weaker (112) line at 1.81 A (which was ex- pected to be free from interference).It was found that the interference-free (112) line gave quartz contents that were about 2576 lower than the results from the strong (101) line and that these values agree reasonably well with analyses of the same dust by the IR method. The results are summarised in Table I.Conclusion Several possible sources of error have been identified that can lead to differences between results of quartz analysis by IR and XRD analysis. In particular, there is a need for the careful choice of standards and the preparation of calibration samples in a manner that will, as nearly as possible, simulate field sampling conditions, so as to avoid both instrumental and sample distribution effects, which can arise from differences in particle size distributions between samples and standards.Possible sources of interference must also be considered. The exercise illustrated that even well calibrated, self-consistent sampling and analysis208 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS R o c . AnaZyt. Div. Chem.SOC. TABLE I QUARTZ CONTENT OF DRILL DUSTS (yo) XRD analysis Sample .. (101) line (112) line IR analysis r A \ Coarse dust . . .. 42.0 33.0 27.9 Fine dust . . .. 43.5 32.8 30.3 systems require confirmation by independent systems to show that no sources of error have been neglected. References la. “Documentation of the Threshold Limit Values,” Third Edition, American Conference of Govern- mental Industrial Hygienists, 1971.lb. Dodgson, J., and Whittaker, W., Ann. O G C U ~ . Hyg., 1973, 16, 373 and 389. 2. Crosby, M. T., and Hamer, P. S., Ann. Occup. Hyg., 1971, 14, 65. 3. Leroux, J., and Powers, C. A., Staub, 1969, 29, 26. 4. Freedman, R. W., Toma, S. Z., and Lang, H. W., A m . Ind. Hyg. Ass. J . , 1974, 35, 411. 5. Mangia, A., Analyt. Chem., 1975, 47, 927.6. Gordon, R. L., and Harris, G. W., Nature, Lond., 1955, 175, 1135. 7. Moore, G. S. M., and Rose, H. E., Nature, Lond., 1975, 253, 525. 8. Bergmann, I., Cartwright, J., and Casswell, C., BY. J . Appl. Phys., 1963, 14, 390. Analytical Chemistry of the Leblanc Soda Trade” W. A. Campbell Department of Inorganic Chemistry, University of Nezelcastle ~ p o n Tyne, Newcastle .upon Tyne, NE1 7R U The early 19th Century was a period of enthusiasm and optimism concerning the benefits to be expected from the application of chemistry, particularly analytical chemistry, to commerce, agriculture and industry.l In practice, the analytical ingenuity expended was rarely com- mensurate with the commercial returns.Complete analyses of such complex intermediates of the Leblanc process as black-ash or alkali waste demanded high analytical skill, but the value to the manufacturer was minimal. TABLE I ANALYSIS OF BLACK-ASH (1859) BY J.W. KYNASTON, LIVERPOOL Component Sodium carbonate Sodium chloride Sodium sulphate Sodium silicate Sodium aluminate Calcium sulphide Calcium carbonate Calcium bisulphide Calcium hyposulphite Calcium sulphite Caustic lime Content, % 36.878 6 2.528 0.395 4 1.182 0.688 6 28.681 3.315 1 0.435 3 1.152 3 2.178 9.270 3 Component Magnesia Iron sulphide Iron sesquioxide Calcium phosphate} Alumina Charcoal Sand Ultramarine Water (hygroscopic) Total : Content, :h 0.253 7 0.371 0 2.658 1.131 8 7.007 0.901 0.958 9 0.215 8 1UO.2018 Table I shows the results of such an analysis made by slow gravimetric methods2 The distribution of the determined ions among notional salts followed old and complicated rules rooted in 18th Century ideas about affinity.Thus, in the analysis quoted, calcium was determined by the oxalate method and distributed by rule as in Table 11. Process Control Accurate chemical control of the Leblanc process was not possible, as there was no geiieral Essentially, sodium sulphate was * This paper was presented in the Historical Group Symposium.agreement about the mechanisms of the various stage^.^July, 1978 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS TABLE I1 209 DISTRIBUTION OF CALCIUM TO NOTIONAL SALTS Calcium determined by oxalate method gives CaO = 35.109%. In CaS . . . . 22.307 Ca(HS), . . . . 0.234 4 CaCO, .. . . 1.856 4 CaS,O, ... . 0.424 5 CaSO, .. . . 1.016 4 CaO .. . . 9.270 3 (by difference; “caustic lime” in Table I) converted into black-ash (ball soda) by a series of reactions that can be summarised, and oversimplified, as Na,SO, + CaCO, + 4C = Na,CO, + CaS + 4CO The reaction mixture was a pasty mass and not always homogeneous. The carbon monoxide burned off as “soda candles,” after which heating was continued for an indeterminate time.The decision to pour the soda was made by a foreman on the basis of appearance and con- sistency; if poured too soon the ball was said to be “green,” and if too late it was “burnt.” A manager reported, “I have frequently found my judgment entirely at variance with the laboratory test. The test was frequently good but the ball looked bad, and the liquors and ash made from this soda invariably bore out the judgment of the eye against the test.”4 The best that the laboratory could do was a rough disintegration test (ensuring that soda would easily leach out in the lixiviation tank), coupled with a test for undecomposed sulphate.The necessity for speed dictated the use of titrimetric methods as described by Fresenius and M ~ h r . ~ Mohr invented the modern form of burette, and the pinch-clip for closing it. There were two rival burettes, that of Gay Lussac with its fragile capillary tube for delivering the liquid, and the more robust design of the alkali maker Christopher Binks.6 Both suffered from the disadvantage that the contained solution was poured from the top and the instrument returned to vertical for reading. Mohr also introduced normal solutions (1 g-equiv in 1 l), an idea which did not commend titrimetry to British manufacturers working in pounds and gallons. J.J. Griffin, the scien- tific instrument dealer, sought to resolve the difference by introducing a new unit, the septem.’ This was the volume occupied by 7 grains of water, and a decigallon contained 1 000 septems.A standard solution containing 7 grain-equivalents in 1 decigallon was equal in concentration to Mohr’s normal solution: and the relationship between the decigallon and the septem was identical with that between the litre and the cubic centimetre. In fact, most works labora- tories used apparatus graduated in cubic inches, and solution concentrations were chosen for empirical convenience rather than scientific respectability.The manufacturer was usually interested only in the assay of some constituent or quality, and the choice of method depended on the level of skill available in the works laboratory. Thus, in the evaluation of manganese ores (used for converting waste hydrochloric acid into chlorine for bleaching powder), Bunsen’s elegant iodimetric method was not favoured be- cause it was difficult to regulate the evolution of chlorine.Similarly, the oxalate method of Fresenius and Will (absorbing carbon dioxide on soda-lime) was rejected by the Alkali Makers’ Union in 1869. The chosen method was Pelouze’s oxidation of iron(II), which was easy to manipulate although open to chemical criticism.s In skilled hands, matters were different : Lunge’s works laboratory could determine total alkali, chloride, sulphate and sul- phide in tank liquor, all in 20 min.Evaluation of Products The most vital area of interaction between the analyst and the alkali manufacturer was in the sale of soda, which, like bleach, was bought and sold on the analyst’s certificate. In German practice, sulphuric acid was standardised against pure sodium carbonate, and a direct mass - volume relationship established involving no assumptions about formulae or equivalent masses.Such assumptions were implicit in the British practice of relating the volume of sulphuric acid to a mass of putative sodium oxide. Until the Karlsruhe Congress210 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS Proc. AnaZyt.Div. Chem. SOC. (1860) there was little agreement among pure chemists about relative atomic and molecular masses ; not surprisingly, chemical works analysts did not agree on the ratio Na20 :Na,CO,. On Tyneside, pure sodium carbonate was calculated to contain 58.5% of Na20, but on Mersey- side the figure was held to be 59.25%. A broker could make a profit by buying soda on the Newcastle test and selling on the Liverpool test.g Furthermore, analysts often disagreed over the same sample ; “high” and “low” analvsts were well known in the trade, and their‘ results were skilfully employed by the astute. Two explanations were advanced.First was the invasion of the field of chemical analysis by non-professional analysts, often doctors, pharmacists or academics. Drawing their income largely from other sources, these could undercut the conscientious analyst.Glaring cases were reported in Chemical News: in 1871 a “Ph.D., F.C.S.” offered to do any complete analysis for a guinea (Q.Q5),10 and in 1875 (‘a professor” undertook the determination of chlorine in bleaching powder for a shilling (5p). Incompetence was widespread, one analyst detecting the end-point in acid - alkali titrations by taste, and dishonesty was not unknown, for a firm forwarded a certificate of analysis by post before the sample was received.ll The second contributory factor was a general reluctance to publish analytical methods, which many commercial firms saw as their only capital. Moreover, the Chief Alkali Inspector had suggested that a stoker could carry out works tests “armed with burette and beaker” if only he was told how; and an advertisement for an analytical textbook claimed that good results could be achieved by “intelligent foremen and others who are not Following the moves towards organisation among chemists in the 1870s and 1880s, local gatherings of industrial chemists at Glasgow, Liverpool and Newcastle began to urge reform.14 Ferdinand Hurter and George Lunge led programmes of research, training and publication.Thus, although analytical chemistry did not materially assist the conduct of the Leblanc process, that process profoundly influenced analysis : first by compelling the introduction into Britain of titrimetric methods, and later by providing a framework within which men of the calibre of Lunge and Hurter could operate.1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. References Parkes, S., “Chemical Essays,” Second Edition, Volume 1, Baldwin, Cradock and Joy, Lmdon, 1S23 J . Chem. SOC., 1859, 11, 155. Mellor, J. W., “Comprehensive Treatise on Inorganic and Theoretical Chemistry,” Volume 2, Long- Proc. Tyne Chem. SOC., December loth, 1875, 25. Fresenius, K.R., and Mohr, K. F., Justus Liebigs A n n l n Chem., 1853, 86, 129. Sch. Sci. Rev., 1959, 40, 312. Griffin, J . J., “Chemical Handicraft,” Second Edition, J. J . Griffin, London, 1877, p. 286. Lunge, G., “Sulphuric Acid and Alkali,” Second Edition, Volume 3, Gurney and Jackson, London, Trans. Newcastle Chem. SOC., 1874-77, 3, 9 and 101. Chena. News, 1871, 22, 11. Chem. News, 1875, 32, 224.Alkali Inspector, Report No. 26, 1890, p. 16. Chem. News, 1877, 35, 166. J . SOC. Chent. I n d . Loizd., 1883, 2, 441. p. 8. mans, London, 1927, p. 731. 1896, F. 272. Sampling and Analysis of Airborne Pollutants in the Welding Environment Mrs. J. Moreton Chemical Laboratory, Welding Institirte, Abington Hall, Abington, Cambvidgc, C B 1 6A L Sampling and analysis of airborne pollutants generated during welding has been undertaken over a 6-year period at the Welding Institute.Experience has ranged from in-laboratory research to a number of on-site sampling exercises of a trouble-shooting nature. This paper describes the types of environment to be encountered and their sampling and analysis problems. Greater emphasis is given to the techniques of sampling and their applicationJuly, 1978 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS 211 to an on-site situation, as it is in this area where more problems arise.Subsequent analysis of the sample is generally a relatively straightforward exercise involving routine analytical techniques. Welding Environments The term “welding” itself embraces a wide area of processes and applications, and if a number of allied activities to be found in a welding shop (such as heating, grinding, gouging, brazing and cutting) are included, the field is very wide indeed.Each process has its charac- teristic fume and pollutant gas problems but, in general, it can be assumed that the greatest pollutant levels will be encountered with open arc welding processes. These include manual metal arc welding and gas-shielded processes (with either a solid or flux-cored wire).With any given welding process, the nature and extent of the welding fume problem will depend on the plate to be welded, the welding consumables (i.e., electrode or wire), the welding conditions, operator variables and the ventilation conditions. Ventilation conditions can have a vital influence on the magnitude of a welding fume problem.For example, out of doors, fume and pollutant gases are rapidly swept away from the welder, particularly if he takes care to position himself upwind of the job. Nowadays, most indoor welding is carried out with special ventilation aids, and note should be taken of any that are in use during a sampling exercise. A typical arrangement would consist of mobile local extraction equipment for the use of the welder, backed up by general ventilation of the workshop.It is important to note that for local extraction to be efficient, the extractor nozzle must be kept close to the arc. In gas-shielded welding, where a hand-held gun delivers wire from a reel, together with gas for shielding, there is the opportunity to use gun extractors where fumes are sucked back to a filtration unit that is integral with the welding equipment.Only where the toxic hazard is severe or the ventilation inadequate is personal respiratory protection of the welder usually considered. Sampling of Particulate Fume In all of these welding situations, the aim is to maintain airborne pollutant concentrations below their respective threshold limit values (TLVs), as defined in the latest Health and Safety Executive Guidance Note EH15/76.Welding fume has a specific TLV of 5 nig m-3, but it is also necessary to conform to the TLVs of the component parts of the mixture that comprises the fume. This mixture may include oxides of iron, copper, manganese, nickel, chromium, zinc, cadmium, cobalt, sodium, potassium, calcium, titanium, aluminium, etc.(although seldom all at once!), and gases such as carbon dioxide, carbon monoxide, oxides of nitrogen and ozone may also be evolved, as well as some complex organic by-products of paints or solvents used on plates to be welded. TLVs apply to the air the welder is breathing, and relate to an 8-h day or a 40-h working week. Thus, the most important sample to be taken is in the “breathing zone” of the welder, i.e., close to his mouth and nose, although background measurements of pollutants in the workshop atmosphere are also valuable.A British Standards Sub-committee WEE/40 has recently produced a Draft for Develop- ment (DD/54) for sampling and analysis techniques for airborne pollutants found during welding.Part I deals with particulate fumes and Part I1 relates to pollutant gases. DD/54 does not have the status of a British Standard, but ultimately should form the basis for such a standard. The Draft for Development Part I gives details of breathing zone and background fume measurements, with data not only on the principles of sampling and analytical procedures and essential calculations, but also precise working specifications.These include requirements for the pump unit, sampling head, sampling rate, sampling position, filtering medium, handling of test specimens and presentation of results. An appendix gives notes on analytical pro- cedures, and shows a range of constituent concentrations in a typical survey. For particulate fume measurements, commercial equipment is available from a number of firms to conform to the requirements of DD/54.Breathing zone samples should be taken from inside the welder’s headshield, sampling periods should ideally be 1 h, and include arcing and non-arcing periods, representative of a whole working day. The aim should be to collect between 1 and 2 mg of fume, which would be sufficient for a subsequent analysis.212 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS Proc.Analyt. Div. Chem. SOC. In addition to the sampling of welding fume in the breathing zone and background in an on-site situation, there is one other sampling technique that is principally of interest to electrode-consumable manufacturers. This is the Swedish Fume Box Method for measuring the total fume produced by one electrode.This technique is under consideration by the International Institute of Welding as a standard for measuring fume emitted from manual metal arc consumables. In this method, welding takes place through a slit in an otherwise closed box and, as air is drawn through the box, the fume produced is collected on a large, pre-weighed filter. Between 0.2 and 1 g of welding fume will be collected, depending on the type of electrode used, the gauge and the welding conditions.Analysis of Particulate Fume Having collected the fume sample by any of the means described above, analysis will be required. Total fume is determined gravimetrically, using a precise chemical balance, weighing to five decimal places in grams. Individual metal components of the fume can be determined by routine chemical techniques, bearing in mind that the amount from breathing zone and background sampling is small (about 1 mg), and that any method should be capable of detecting an element down to one tenth of its TLV.Factory Inspectorate “Red Book” colorimetric analysis methods exist for a number of elements in welding fume and dust, e.g., zinc, iron and copper, but in general, atomic-absorp- tion spectrophotometry is the most useful tool in this field, allowing a number of elements to be analysed sequentially on the same sample.Atomic-absorption spectrophotometry is recommended as an analytical method in the Draft for Development DD/54. With certain welding processes, fluoride is a component of welding fume, when it should be determined by an ion-selective electrode technique.Gases : Sampling and Analysis For the sampling and analysis of pollutant gases, the same principles as were used for fumes should be applied, although in general the sampling and analysis of gases are carried out in a single stage. Three types of analysis are available: detector tubes, instrumental methods and chemical methods (the chemical methods are not generally suitable for on-site use).A wide range of pollutant gas indicator tubes are available commercially from at least three manufacturers. The normal type of indicator tube is the short-term one, used with a hand-operated pump, and useful for rapid or grab samples. For a few gases, e.g., carbon monoxide, a long-term tube is available, which is suitable for sampling over a whole day with an electrical pump.Both long- and short-term sampling require a special tube for each gas to be analysed. The principle of the indicator tube is similar to that of the “Breath- alyser,” chemical reactions producing a colour change for a given concentration of a particular gas. It is advisable to regard detector tubes as giving a first estimate only of the gas con- centration.Of the three pollutant gases of greatest interest in the welding situation, i.e., carbon mon- oxide, oxides of nitrogen and ozone, accurate instrumental methods are available that are suitable for giving precise on-site readout. Several types of instrument are available, based on principles such as infrared spectroscopy, chemiluminescence or electrolytic reactions.For on-site use, the instrument should be portable (or at least movable), and give direct readout of the gas concentration down to one tenth of the TLV. For monitoring concentra- tions in the welder’s breathing zone, it is important to locate the ends of the gas sampling lines within the welder’s headshield. Filters are located on the input side of the sampling line, preventing particulate fume from clogging the instrument.Even though the instru- ments may give direct meter readout, it is desirable to connect the output to chart recorders, to obtain a measure of the variation in gas concentration over 1 h and to include arcing and non-arcing periods. Shielding gases used in welding, e.g., argon, helium and carbon dioxide, are generally non- toxic but can be asphyxiant if large concentrations are allowed to accumulate in confined spaces.The best approach in this situation is to check that there is sufficient oxygen in the atmosphere, using an oxygen alarm monitor.July, 1978 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS 213 Other pollutant gases that may be found in welding atmospheres, such as phosgene, dichloroacetyl chloride, acetaldehyde and styrene, are not direct by-products of welding, but rather the result of de-greasing, painting or other operations ancillary to welding.In the on-site situation, these gases are usually monitored by detector tubes. Within the laboratory, gas chromatography is an appropriate analytical technique. Conclusion The techniques outlined above have been found to be efficient for the measurement of fumes and gases in on-site tests in a wide variety of different sites.In such on-site measurements, the co-operation of both management and welder is an important part of the sampling exercise. Similarly, in the control of welding pollutants, both management and shop floor have important roles. Scientific instruments in Environmental Monitoring R.S. Barratt Department of Construction and Environmental Health, The University of Aston in Birmingham, Gosta Gveen, Birmingham, B4 7ET An atmosphere is a complex mixture of gases, vapours and particulate matter in suspension. An excess or a deficiency of one component of this mixture may make the atmosphere at best uncomfortable or at worst hazardous. The most important deficiency is, of course, oxygen deficiency, which may occur in a mine, a tunnel, a sewer, or some other enclosed place.The Davy Lamp is a simple monitor for oxygen deficiency; the flame is extinguished. This instrument also serves to indicate quali- tatively that a hazardous environment exists as a result of the presence of a component such as methane or carbon monoxide. It is the measurement of such excesses of contaminants in atmospheres that is the more common need, and as a quantitative determination is usually required, instrumentation is essential.A simple instrument for air quality measurement is the indicator tube, and this method incorporates the essential features of a sampling train. Conditioning of the sample in order to remove interferences is carried out within the tube, and the chemical reactions for an in sit% determination also occur here.The prime mover in the collection of an air sample is the hand bellows, which, being of fixed capacity, also incorporates volume measurement. Sampling by such a method is achieved in a few seconds, but atmospheric concentrations can vary considerably as a result of mechanisms of generation, transport and scavenging.A continuous measurement device can be used to follow these variations in concentration, and such an instrument is an infrared analyser. While infrared analysis is applicable to many atmospheric contaminants, it is most widely used in the determination of carbon monoxide concentrations in enclosed areas and in the open air. Now, a street atmosphere in an urban area would not be expected to be free of carbon monoxide.In fact, localised unhealthy concentrations could be expected in certain areas owing to the discharge of motor vehicle emissions at low levels. Such emissions vary with the operating conditions of vehicles and are high during idling and deceleration. Con- sequently, high concentrations could be expected near to road intersections carrying heavy flows of vehicles.Bayley and Dockerty1y2 investigated such an environment by use of infrared analysis and showed that the threshold limit value of 50p.p.m. was exceeded for only 1.5 min out of 44 d. One would not conclude, therefore, that this constituted a hazar- dous environment. Nevertheless, accumulations of carbon monoxide can occur, particularly in certain poorly ventilated areas, such as in multi-storey car parks, which are a feature of modern city centre developments.Barker and Fox3 reported that tests with indicator tubes in such environ- ments showed concentrations of carbon monoxide up to 120 p.p.m., while in an exit area, where traffic flow was restricted, concentrations reached 210 p.p.m.They also reported measurements of transient levels by another form of instrumentation, an electrochemical214 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS Pvoc. Andy€. Div. Clzewt. Soc. cell. With this continuous recording instrument, levels of up to 450 p.p.m. were observed for short periods. In general, personal exposure to such environments is for limited periods, only, but some people are exposed for long periods and these include those working in the pay-kiosks of car parks.In an investigation of such kiosks4 in an area essentially enclosed on three sides, high levels of contamination were expected and electrochemical analysis confirmed this to be so. In a typical day, peak values over 100 p.p.m. were common for periods of half an hour or more at a time, but the worst situation was recorded on a Saturday before Christmas.From 10.00 the concentration did not fall below 200 p.p.m.; after 11.00 peaks exceeded 400 p.p.m. for much of the time, and between 17.00 and 17.55, the concentration exceeded 500 p.p.m., or ten times the threshold limit value. This could be regarded as a hazardous en- vironment; in fact, complaints of headaches by the employees were common and once or twice a member of the staff did become unconscious.Of course, carbon monoxide is just one component of motor vehicle emissions, and other measurements showed similar high values (see Table I), TABLE I COMPARISON OF AIR QUALITY Concentration/pg m-3 r- -3 Car park kiosk Typical ambient level (8 h ;y-r;ge) (annual mean) Suspended particulates 23 Lead 84 0.75 In an attempt to improve the air quality within the kiosks, air was drawn in from outside the car park to the kiosks.Unfortunately, the first attempt by the consultants to do this failed miserably, and measurements showed that this was due to the air being drawn from a point suffering from contamination by vehicles leaving the car park; the “fresh” air had a carbon monoxide content of 250 p.p.m.! Further tests indicated that in a nearby road the level was 20 p.p.m., but in the intervening shopping precinct the level was 3 p.p.m.By using this as the source of fresh air, it is hoped that an improvement will be possible. Carbon monoxide is not only produced by the motor car; it occurs when there is incomplete combustion of carbonaceous material. In some coal mines, spontaneous combustion is detected by monitoring carbon monoxide concentrations in samples of mine air drawn con- tinuously through plastic tubing from sampling points underground to an analyser a t the ~urface.~ The selection of sampling points in such multi-point systems can be achieved by timer-operated solenoid valves.Clearly, the same principle is applicable to the surveillance of ambient air in many working environments and infrared analysers with a multi-point analysis capability are commercially available. A similar principle has been used for investigating an unusual “hazardous” environment, that of an operating theatre.The instrumental technique favoured for this study was a gas chromatograph, an obvious choice when it is the volatile anaesthetic agents that are the atmospheric components under suspicion.Over the last few years there has been an in- creasing number of accounts suggesting that the chronic exposure of surgical staff to trace concentrations of anaesthetic agents may constitute a hazard. The major anaesthetic agents in question are nitrous oxide, halothane and trichloroethylene, all of which can be detected with adequate sensitivity by an electron-capture detector.A multi-point analysis system was used in this investigation, with ten sample streams being connected in turn to a pneumatically controlled gas-sampling valve ; the whole system was controlled by a timer and solenoid valvesG An inherent disadvantage of gas chromatography for environmental monitoring is the discontinuous process, which precludes continuous monitoring.However, analysis times can be made short and rapid analysis of samples in sequence is possible. The technique allowed sample streams to be analysed at 5-min intervals, and both fixed-point and personal monitoring surveys were carried out. On some occasions, personal monitoring indicated that exposure to certain anaesthetic agents occurred even when such agents were not in use.Volatile anaesthetic agents areJuly, 1978 ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS 215 introduced into the gas mixture of oxygen and nitrous oxide given to the patient by means of a vaporiser, which is adjustable for the required concentration. The unexpected exposures may have arisen as a result of leakage from vaporisers in the “off” position, and this has been shown to occur for many of the vaporisers that are available.’ This introduces a different “hazardous environment,’’ namely the environment of the patient under anaesthesia.There is evidence that the trace contamination delivered from a vaporiser in the “off” position may initiate serious ill effects in susceptible patients.The remedy may seem to be simple, remove the vaporiser from the anaesthetic machine, but it has been showns that there may be as much as 17 pg 1-1 of anaesthetic agent leaking into a 1 1 min-l flow of oxygen in the metal manifold of an anaesthetic machine, even without the vaporiser attached. This contami- nation was traced to up-stream contamination of neoprene sealing rings around the flow meters, and the machine in question had not been used for 2 months.There are many potentially hazardous environments around us and there are many scien- tific instruments available to investigate them. This paper has just described a few practical cases of environmental monitoring which could not have been undertaken without appropriate instrumentation. References 1.2. 3. 4. 5. 6. 7. 8. Dockerty, A., and Bayley, E., Trafl. Engng Control, 1970, 594. Bayley, E., and Dockerty, A., R. SOC. Hlth J . , 1972, 92, 7. Barker, I. W., and Fox, M. F., R. Soc. Hlth J . , 1976, 96, 168. Barratt, R. S., unpublished results. “National Coal Board Scientific Control (1972),” National Coal Board, London, 1972. Thompson, J. M., Barratt, R. S., Belcher, R., and Stephen, W.I., BY. J . Anaesth., 1976, 48, 167. Robinson, J. S., Thompson, J. M., and Barratt, R. S., BY. J . Anaesth., 1977, 49, 745. Robinson, J. S., Barratt, R. S., and Thompson, J. M., BY. Med. J . , 1974, ( i ) , 515. Use of Ultrasonic Instruments in Chemical Plant Containing Hazardous Materials R. C. Asher Instrumentation and Applied Physics Divison, A ERE, Harwell, Didcot, Oxfordshire, OX1 1 ORA Ultrasonic instruments are described that have been developed for use in one particularly hazardous environment, and their potential application in a wide range of other hazardous environments is discussed. The original application was in a nuclear fuel reprocessing plant; this plant combines the hazards of intense nuclear radiation, extremely high radioactive contamination, very corrosive liquors and high toxicity (particularly in the form of plutonium).In the plant, the nuclear fuel (uranium dioxide plus plutonium dioxide clad in stainless steel) is dissolved in concentrated nitric acid and the resulting noxious liquor is passed through mixer - settler units in which liquid - liquid extraction processes separate the fission products, the uranium and the pluton- ium.For safety reasons the plant is contained in sealed concrete cells and is operated remotely, and consequently the instrumentation has to be extremely reliable and easy to maintain. The instruments must not breach the containment of the cells, because otherwise they would become contaminated with corrosive liquors containing radioactive materials and toxic plutonium.Moreover, it is highly desirable that the instruments should be non-intrusive. Two main types of instruments have been developed. Determination of Concentrations of Solutions The problem was to determine the concentration of “heavy metals’’ ( i e . , uranium plus plutonium) at a level of about 60 g 1-1 in solution as nitrates in an organic solvent with a precision of 3 g 1-l. The instrument makes use of the experimental observation that V (the velocity of ultrasound in the solution) depends on the concentration.The empirical relation- ship is V = K + ccT + /?[HIM]216 Pvoc. A Pzalyt. Div. Chenz. Soc. where T is the temperature, [HM] is the concentration of heavy metal in solution and K , a and are constants that have been determined experimentally.Therefore, if V and T are known, [HM] can be calculated. Simple cells have been developed in which V can be determined by transmitting pulsed ultrasound diametrically across a pipe carrying the liquid under examination ; V is calculated from the time interval between the “echoes” from both sides of the pipe. The containment of the plant is not breached and the form of the normal pipework is not changed.Moreover, maintenance work on the ultrasonic probe assembly can be carried out without interrupting plant operation and without contamination by the plant liquor. The features that determine its applicability are the coefficients a and p ; p should be reasonably large and a rather small. Random examples of favourable systems are sugar, maple syrup adulterated with water, sodium carbonate, hexanol contaminated with small amounts of water, fuming nitric acid, concentrated sulphuric acid and aqueous ammonia ; other applications include determining the degree of polymerisation of solutions and the detection, in long-distance pipe- lines carrying petrochemicals, of the instant when a change of product being pumped along the pipeline reaches the receiving station. In two-phase dispersions, i.e., slurries, sludges, suspensions, precipitates and emulsions, etc., it is often possible to determine the concentration of the dispersed phase; examples include a wide range of foodstuffs and many inorganic two- phase dispersions.More complicated situations arise when the concentrations of more than one solute are changing simultaneously.In these instances, useful information can still be obtained ultra- sonically in favourable circumstances either by measuring V at two different temperatures or by determining the attenuation of ultrasound in addition to V . Two-phase dispersions are also systems in which useful information can be obtained by attenuation measurements; by the correct choice of the frequency of ultrasound, it is possible in principle to determine the concentration of the dispersed phase and its particle size.Very simple “saddle probes” that can be clamped to existing pipelines in the plant have been developed. Probes of this type could be installed at a large number of sites in a chemical plant and could transmit data back to a central control room, which could be at a distance of several kilometres or more.ANALYTICAL ASPECTS OF HAZARDOUS MATERIALS This instrument has applications outside the nuclear energy industry. Level and Interface Detection This problem typically arises in large vessels containing liquids in which it is necessary to determine the depth of the liquid and sometimes also the thickness of a lighter liquid floating on its surface.The instrument developed directs a pulsed beam of ultrasound upwards through the liquid and times the intervals before the return of two echoes, one from the inter- face between the two liquids and one from the top surface. The levels can change over the range 15-500 cm and their position can be located with a precision of 0.3 cm.Pulsed columns can also be instrumented by this technique, despite the fact that the interfaces are highly dis- turbed; a microprocessor can be programmed to reject spurious signals. The initial applications of these instruments have been for clear liquids but it has also been shown that useful information can be obtained from the two-phase dispersions provided that lower frequency ultrasound (e.g., 125 kHz) is selected in order to achieve better penetration. The probe head can also be inverted, thus directing the beam of ultrasound downwards instead of upwards. This arrangement can be used to locate the top surface of a sediment or precipitate collecting in the bottom of a vessel such as a “decanter vessel.’’ As in the previous applications, these devices do not breach the containment of the plant; no sensitive component such as an ultrasonic transducer comes into contact with the liquors of the plant and maintenance of the probe can be carried out without interfering with the operation of the plant. A simple modification of the instrument also enables the composition of the liquor to be determined simultaneously under some circumstances. A specialised application of these techniques is in the mixer - settlers themselves, and it demonstrates the considerable amount of information that can be derived ultrasonically from a probe of small volume. Concentrations of both phases in the settler compartment, and the levels of the top surface and of the liquid - liquid interface, are determined by the techniquesJuly, 1978 EQUIPMENT NEWS 217 described above in a total of 10 positions. The electronics system is more complex, largely because of the requirement to record the large mass of data in an easily digestible form. Automatic plant control is a possibility. Use of Ultrasonic Devices Under Flammable Conditions Ultrasonic devices are attractive for use in flammable environments because they consume very little power, the energy pulses are exceedingly small and (because the containment is not breached) the electronic components can be segregated from the flammable environment. Use of Ultrasonic Devices at High Temperatures Nevertheless, high-temperature instrumentation by ultrasonic techniques is possible by (a) artificially cooling the transducer, (b) the use of wave guides to transmit ultrasound to and from the high temperature region and (c) the use of special high-temperature ultrasonic transducers. Conventional ultrasonic transducers are not resistant to high temperatures. Other Ultrasonic Techniques Ultrasonic techniques can also be used in hazarddus environments to determine temperature, flow-rate and pulse amplitude in pulsed liquid extraction columns and for corrosion monitoring.

ISSN:0306-1396    

DOI:10.1039/AD9781500205

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

July, 1978 Equipment EQUIPMENT NEWS 217 In Situ Electrode Cleaner A new automatic cleaning mechanism for pH electrodes is announced. The automatic, pneumatically powered cleaning system con- sists of a control unit, Model 7610, and a wiper mechanism, Model 7611, that is suitable for all EIL 7600 Series pH electrode systems. The wiper mechanism can be simply fitted to existing systems by substituting it for a blanking plug in the system sensor holder.The wall mounting control unit incorporates an air pressure regulator/stabiliser and a timer. The regulator stabilises a mains air supply of 5.7-7.0 bar (80--100 lbf in-2) a t the operating pressure of 4.2 bar (60 lbf in-2) before feeding it to the wiper mechanism. The piston strokes of a pneumatic actuator operate a brush, which periodically wipes the glass membrane of the electrode.The control unit can be adjusted to provide continuous wiping, or eight wipes every 1, 4, 16 or 32 min. Each control unit can operate up to three wiper mechanisms. Electronic Instruments Ltd., Hanworth Lane, Chertsey, Surrey, KT16 9LF. Oxygen Meter A battery-operated dissolved oxygen meter, suitable for both field and laboratory work, is now available.The meter is scaled 0-100 x 2% for measurement of the percentage of dissolved oxygen saturation in water and 0-30 x 1% for measurement in air. The probe is composed of a central platinum cathode with a silver - silver chloride reference anode in a saturated potassium chloride solution. It operates within a temperature range of 5-35 "C and has a switch with on, off and battery test positions.A. Gallenkamp & Co. Ltd., P.O. Box 290, Technic0 House, Christopher Street, London, ECZP 2ER. Photomultiplier Tubes For applications where low dark count is critical, two versions designated types 9862 and 9863 are available with gains of 107 and up to los, pulse rise times of the order of 2 ns, pulse dura- tion of about 4 ns, a dark count of 40 counts s-l and typical peak quantum efficiency of about 22%.These tubes are suitable for all photon counting applications, particularly fast photon correlation requiring very low afterpulsing. Where photoelectron resolution is important the types D295 and D299, with high first dynode gain of (typically) 22 and dark count of about 300 counts s-l, give a single photoelectron resolution of about 70%.EM1 Industrial Electronics Ltd., Astronaut House, Hounslow Road, Feltham, Middlesex. Gas Chromatograph The new 429 Gas Chromatograph combines the existing 428 series features with microprocessor-215 EQUIPMENT NEWS Proc. Awdjyt. Div. Chem. SOC. based control. Built-in, multi-dimensional gas chromatography makes possible an analysis that would only produce an incomplete separ- ation on a single column.The system uses a valveless approach, guaranteeing that the sample does not come into contact with any switching device. A multi-user facility enables a complete analy- sis programme t o be filed under a user table. The system will also accept up to 15 analysis programmes, which can be called up for instant machine setting by the touch of a button.Packard Instrument Ltd., Caversham Bridge House, 13-17 Church Road, Caversham, Berk- shire, RG4 7AA. Liquid Chromatography Column Packing The Haskel, Model 29426, pump system uses a wet-packing or slurry technique for column packing. The system offers compatability with virtually all solvents and rapid pressure build-up to 10 000 Ib in-2. The air-driven pump has an automatic stall in case the system blocks and liquid handling is contaminant free.Olin Energy Systems Ltd., North Hylton Road, Sunderland, Tyne and Wear, SR5 3 JD. Gas-chromatographic Infrared Detector System The Accuspec GC-IR detection system enables any gas-chromatographic column effluents to be examined by infrared spectrophotometry and can be used with most of the commercially available infrared spectrophotometers. The sample is taken from the gas chromatograph and maintained in a heated cell so that a maxi- mum amount of the sample is in the light path.Complete spectra can be run on 10-20 nl of sample materials. EDT Research, 65 Ivy Crescent, London, W4 5NG. Micro - scale Optics High-precision, micro-optical components in- cluding plano-convex lenses, biconvex lenses, achromatic lenses, right-angle prisms and dove prisms are available in sizes starting at 0.7 mm (0.028 in). Melles Griot BV, Industrial & Scientific Optics, Nieuwe Kade 10, Postbus 567, Arnhem, The Netherlands.Laboratory Microscopes Two basic model ranges of Microstar micro- scopes, the 110 and 120, are available with monocular, binocular, or trinocular viewing tubes together with a wide range of options.A focusing, gravity-loaded nosepiece, in which only the nosepiece assembly moves to focus the objective on to the specimen, allows the stage to be rigidly locked to the stand to ensure a stable, vibration-free system unaffected by hand pressure on the stage. The focusing mechanism is enclosed in the microscope stand assembly in order to protect it from dirt and accidental damage.The optical system is infinity corrected with a full range of Planachromatic objectives from 2 . 5 ~ to 1OOx and extra-wide field eyepieces give a field of view of 20. All essential optical surfaces are coated for minimum internal reflection to improve light transmission and image contrast. All of the instruments are equipped with an NA 1.25 Abbe aspheric con- denser and iris diaphragm.All of the micro- scope bodies are inclined 50" and are rotatable through a full 360". The binocular and trin- ocular bodies have converging eyetubes, with independent focusing to the left tube to accom- modate eye refraction differences, and are continuously adjustable for varying interpupill- ary distances.Constant tube length is maintained by internal optical focusing. The trinocular body also incorporates a swing-out prism, allowing all light to be diverted from the viewing position to a camera or viewing screen. The Microstar 110 has a built-in 20 W tung- sten halogen illuminator, with quick-change lampholder, while the Microstar 120 Series has optional 100 W tungsten- halogen or 50 W mercury vapour lamps equipped with three filter turrets, giving a selection of eight filters. Reichert- Jung UK, 820 Yeovil Road, Slough, Berkshire, SL1 4 JB.Lightweight Pocket Microscope A new, lightweight, illuminated, miniature microscope has been designed to be used effectively and easily for the close observation and inspection of detail too small to be seen by the naked eye.This small, pocket microscope, 125 mm long, gives sharp vision with a wide field view at 20 x magnification. Illumination is powered by standard 1.5-V batteries with a screw-base, 2.3 V, 0.2 A bulb. Edmundson Electronic Components Ltd., 30/ 50 Ossory Road, London, SE1 5AN. Ultraviolet Lamp A new, hand-held, ultraviolet lamp is primarily designed for investigating the fluorescence of mineral specimens, but it is also suitable for general purpose use.The lamp contains anJuly, 1978 EQUIPMENT NEWS 219 ultraviolet-emitting fluorescent tube with two filters to transmit either long wave (320-400 nm, peaking at 360 nm) or short wave (250-370 nm, peaking at 290 nm) radiation. Wavelength selection is by a sliding shutter. A. Gallenkamp & Co.Ltd., P.O. Box 290, Technico House, Christopher Street, London, ECZP 2ER. High-performance Vapour Cartridge The high-performance cartridge (CI-200-80-B) has an activated carbon bed sandwiched between an efficient pre-filter and final filter-tube, thus ensuring optimum organic vapour adsorption from air with maximum flow capacity and longer life. The solid-particle filtration efficiency is 99.999% (BS4400 SFP test).Its capacity is greater than 350 g of carbon absorbent with a typical absorption of 70 g. Flow-rates vary from 165 normal m3 h-I, from a single cartridge, to 2 950 normal m3 h-l when used in multiples. Balston Limited, Springfield Mill, Maidstone, Kent. Manometers A range of glass manometers is announced. One is an uncalibrated U-tube and has limbs of 285 mm x 5 mm internal diameter, while another model is calibrated from 0 to 1000 x 2 mm, having one limb with dimensions of 1 085 x 6 mm and a reservoir.The remaining five models are U-tube manometers with centre- zero scales, calibrated variously to read 80-0-80 mm, 260-0-260 mm, 500-0-500 mm, 5-0-5 in and 10-0-10 in. -4. Gallenkamp & Co. Ltd., P.O. Box 290, Technico House, Christopher Street, London, ECZP 2Eli.Bench- top Centrifuge The Minor bench top centrifuge is replaced by the Minor S, which, however, utilises all existing Minor accessories. With a maximum speed of 4 100 rev min-l and maximum g of 2 610, the Minor S incorporates an automatic timer, step- less speed control, lid switch and built-in steel guard bowl. MSE Scientific Instruments, Manor Royal, Crawley, Sussex.Fluorimeter - Densitometer The semi-automatic 720 fluorimeter - densito- meter enables isoenzyme electrophoresis tests to be quantified by colorimetric and fluorimetric methods. Measurements can be made in 12.5 s. The 720 will scan any flat, clear electrophoresis media, such as agarose or cleared cellulose acetate, and its built-in microprocessor controls the automated functions, which include auto zero and auto gain.Each sample fraction is dis- played digitally as a percentage of the total sample scanned. Sample temperature is con- trolled within 1 "C throughout the sample scanning process. The instrument operates on standard 220 V power supplies, but can be specified for operation on 110 V power supplies. Corning Medical, Corning Ltd., Halstead, Essex, CO9 2DX.Oxygen Analysers Oxygen analysers have been developed, which make accurate and stable measurements of oxygen utilising the City Technology oxygen sensor. The sensor can be positioned up to a distance of 30 m from the analyser using a 4-m, pre-coiled, flexible cable with plug and socket connection, or used attached to the instrument. The OTOX 90 is suitable for direct pipe or flange fitting, or for use with pump sampling systems. It operates either from a mains supply or its own integral Ni-Cad battery. The sensor signal is converted to a direct reading of percentage oxygen by volume, displayed by three-digit, high brightness LEDs.A resolu- tion in 0.1% steps from 0 to 35.0% of oxygen is provided. An optional facility is available, providing both an analogue output for automatic proportional control and pen recorders and BCD outputs for data logging.The OTOX 91 is a simpler and more compact version of the OTOX 90 and is designed for field use operating from integral rechargeable Ni-Cad batteries. Digital indication directly in percentage of oxygen is identical with that provided on the OTOX 90.Automatic indica- tion is given for low battery and instrument overload. Both instruments have facilities for pre-set alarm indication to operate either a t excess or deficient air (oxygen) levels. Neotronics Ltd., Building 102, FSTS Site, Stansted Airport, Essex, CM24 8OX. Melting-point Apparatus An automatic melting-point apparatus, the FP61, has a temperature range of 50-300 "C.Accuracy a t 200 "C is *0.5 "C and a t 300 "C & 0.8 "C. It has rapid heating and cooling facili- ties and heating rates of 0.2, 1, 2, 3 and 10 "C min-l can be selected by turning a knob. The melting-point is indicated and held on a digital display, and the melting process can be recorded graphically. A. Gallenkamp & Co. Ltd., P.O. Box 290,220 CHEMICAL SOCIETY AWARDS PYOC.Analyt. Div. Chem. SOC. tions of wall coated open tubular capillary Technico House, Christopher Street, London, ECSP 2ER. Electronic Balance The PS15 electronic top loading balance has a chrome - nickel steel weighing platform measur- ing 320 x 440 mm, with a weighing range of 15 kg. Taring can be carried out over this full range by using the single control bar, and the display reads to 1 g.The digital output per- mits connection t o data receiving and processing equipment. A. Gallenkamp & Co. Ltd., P.O. Box 290, Technico House, Christopher Street, London, ECBP 2ER. Fraction Collector The TJltro Iiac Mark 2 fraction collector is available, giving better control over automated fraction collection. LKB Instruments Ltd., LKB House, 232 Addington Road, South Croydon, Surrey, CR2 8YD.Literature An I S 0 standard sets out a recommended standard layout for a method of chemical analy- sis by gas chromatography and gives calculation formulae for the principal methods of calibra- tion. A new British Standard, BS 5443 “A Standard Layout for Methods of Chemical Analysis by Gas Chromatography,’’ provides comprehensive guidance on the application of this layout.BS 5443, priced a t L4.20, gives as an example a method for the determination of styrene in polystyrene, drafted in accordance with the recommendations. HSI Sales Department, 10 1 Pentonville Road, London, NI 9ND. Determination of trace levels of barium in micro-samples of diatom ash is described in a paper by Bankston and Fisher of the Department of Chemistry, Woods Hole Oceanographic In- stitution, Massachusetts ; a Spectraspan emission spectrometer equipped with the standard d.c.argon plasma jet excitation source and an echelle diffraction grating is used. Using recommended instrument settings, the lowest concentration of barium visible in synthetic standard solutions lay just below 2 p g l-l, which is ,equivalent to 2 pg g-l in the ash.Techmation Ltd., 58 Edgware Way, Edgware, Middlesex, HA8 8JP. A new bulletin describes the use and applica- columns. Packard Instrument Ltd., Caver- sham Bridge House, 13-17 Church Road, Caversham, Berkshire, RG4 7AA. A literature survey on applications of “Uniseal” decomposition vessels in chemical analysis by atomic-absorption spectrometry and other instrumental methods, covering the period 1968- 1977, is available. Uniseal Decomposition Vessels Ltd., P.O. Box 9463, Haifa 31094, Israel. The pharmaceutical section of the AutoAnaZyst for November, 1977, is largely devoted to total haematology automation. Technicon Instru- ments Co. Ltd., Evans House, Hamilton Close, Basingstoke, Hampshire. Infrared News for January, 1978, contains articles on the use of infrared spectrometry in a number of liquid chromatographic analyses, and on the new Model 80 quantitative analysis system. Application notes on the use of infra- red spectrometers in monitoring working atmos- pheres is also included. Wilks Scientific Ltd., 64 Burners Lane, Kiln Farm, Milton Keynes, Buckinghamshire.

ISSN:0306-1396    

DOI:10.1039/AD9781500217

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

220 CHEMICAL SOCIETY AWARDS PYOC. Analyt. Div. Chem. SOC. Chemical Society Awards Corday-Morgan Medal and Prize Three awards for work in different branches of Chemistry, each consisting of a Silver Medal and a monetary prize of 250 guineas, will be made in respect of the year 1977. The awards will be made to chemists of British nationality who, in the judgement of the Council of The Chemical Society, have published during 1977, and in the immediately preceding five years, the most meritorious contributions to experimental chemistry in their respective fields.Can- didates shall not have attained 37 years of age on December 31st, 1977., Copies of the rules of the awards can be obtained from the Local Activities Officer, The Chemical Society, Burlington House, Piccadilly, London, W1V OBN.The Harrison Memorial Prize This prize, which consists of a bronze plaque and a monetary payment of 100 guineas, will be awarded to a chemist who is a natural-born British subject and who has, in the five years ending December lst, 1977, conducted the mostJuly, 19 78 AD PUBLICITY OFFICER 22 1 meritorious and promising original investi- The rules of this award can be obtained from gations in Chemistry and published the results the Local Activities Officer, The Chemical of those investigations in a scientific periodical Society, Burlington House, Piccadilly, London, or periodicals, being under 30 years of age on WlV OBN. December lst, 1978.

ISSN:0306-1396    

DOI:10.1039/AD9781500220

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

July, 19 78 AD PUBLICITY OFFICER The Analytical Chemistry An article describing the creation of the Trust and the ways in which the interest accruing from the invested capital of the Trust Fund is used to further the objects of the Trust was published, together with the financial accounts for 1975/76, in the September, 1977, issue of PYoceedings. The statement of account for the financial year October lst, 1976, to Sep- 22 1 Trust tember 30th, 1977, is presented below.A noteworthy feature is the surplus of kl06 477 from sales of analytical journals and books. This completes the accumulation by the Trust of the Ll50 000 publications surplus which formed one of the terms of the Amalgamation Agreement between the Society for Analytical Chemistry and the Chemical Society.222 ANALYTICAL CHEMISTRY TRUST Proc.Analyt. Div. Chem. SOC. The Chemical Society Analytical Chemistry Trust Fund Income and Expenditure Account for the Year October lst, 1976 to September 30th, 1977 INCOME Surplus arising from Journal Publications and Book Sales Interest on Loan and Deposit Accounts . . . . . . . . . . Income from Ties, Badges and Shields . . .. .. .. .. . . .. Income from Investments . . . . . . . . .. .. .. L zt. 106 477 29 659 7 847 4 TOTAL 143 987 Less : EXPENDITURE Studentships, Grants and Prizes . . .. . . . . .. 2 612 Gold and Silver Medals . . .. .. . . .. . . . . 231 Audit and Professional Fees . . .. . . . . * . . . 822 Postages, Travelling and Sundry Expenses . . . . . . . . 1804 5 469 A138 518 -- EXCESS OF INCOME OVER EXPENDITURE CARRIED TO BALANCE SHEET Balance Sheet as at September 30th, 1977 INVESTMENTS AT cow Balance as at October lst, 1976 .. .. . . . . . . 440 808 A d d : Investments Purchased during the year . . . . . . 308 975 749 783 Less: Cost of Investments disposed of .. . . . . . . 189 532 560 251 CURRENT ASSETS Deposit Accounts with Banks . . . . .. . . . . .. 104 000 Investment Deposit Account .. . . .. . . . . . . 19 500 Income Tax Recoverable . . . . . . .. .. . . 16 145 Cash at Bank .. . . .. . . . . . . . . . . 1305 Sundry Debtors .. . . . . . . . . . . . . 107 547 248 497 Sundry Creditors . . . . . . . . . . . . . . . . 44 419 Less : CURRENT LIABILITIES 204 078 FINANCED BY TRUST CAPITAL ACCOUNT Balance as at October lst, 1976 .. .. .. .. 471 242 A d d ; Transfer from SAC liquidation . . .. .. . . 7 956 Less: Amounts due to SAC Subject Groups . . .. . . 5025 2 931 474 173 A d d : Profit on Sale of Investments . . .. .. .. 43 292 517 4G5July, 1978 HARMONISATION OF ANALYTICAL STUDIES INCOME AND EXPENDITURE ACCOUNT Balance as at October lst, 1976 . . .. .. .. . . A d d .- Excess of Income over Expenditure for the year . . 223 108 346 138 518 246 864 L764 329

ISSN:0306-1396    

DOI:10.1039/AD978150221b

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

July, 1978 HARMONISATION OF ANALYTICAL STUDIES 223 The Harmonisation Studies of Collaborative Analytical ,4 2-day International Symposium on the Har- monisation of Collaborative Analytical Studies was held on March 9th and loth, 1978, in the rooms of the Royal Society, London. The meeting was organised by the Analytical Chemistry and Applied Chemistry Divisions and the Clinical Chemistry Section of IUPAC.Attendance was by invitation, the participants including representatives from most of the international bodies interested in the stan- dardisation of analytical methods. A list of the participating bodies is given in the hppen- dix. The Chairman during the first day was Pro- fessor T. s. West, President of the Analytjcal Division of IUPAC, who opened the proceedings with a short account of the aims and objects of IUPAC.Dr. H. Egan explained the pur- pose of the Symposium. He said there was lack of co-ordination and some overlap in collaborative studies, even on a national basis. It was important to identify the parameters of an analytical method, e.g., accuracy, and to agree on the important ones (including their definition) for the purpose of collaborative study.At the end of this 2-day meeting a further meeting in 2 or 3 years time might seem t o be appropriate. The meeting then received opening state- ments by IUPAC members. Professor H. Freiser (Analytical Chemistry Division) said that limits were often set for deleterious sub- stances before analytical methods had been developed to determine them; for example, of 500 substances the limits for 80% were a t such low levels that no suitable methods were avail- able.He also stressed the importance of sampling. The right number of collaborators involved in a study depended on its purpose-a small number only would be required to investi- gate a method while a much larger number would be needed if the purpose was to see how an average laboratory could cope with a method.Dr. H. Egan (Applied Chemistry Division) said that IUPAC responded to the needs of other bodies in identifying problems. Many of today’s problems related to health or the environment and involved trace analysis, e.g., volatile nitrosamines in foods. Dr. P. Lous (Clinical Chemistry Section) said it was exactly a Century ago that Sir William Gowers introduced the first haemo- cytometer, yet in 1946 eight different methods were being used and no average figures could be agreed.In the early 1960s variable results were being obtained on substances that were being determined routinely every day. Dr. Bl. Roth (Clinical Chemistry Section) said that the accuracy of a method should be related to the particular medical need which the method had to fill.He referred to the IUPAC Quantities and Units in Clinical Chemistry Recommendations, 1973 (Puve A$@. Chenz., 1974, 37, 519), and drew attention to an important development which was the ex- pression of amounts in moles rather than in mass units as the latter yields no biologically useful information. The meeting then heard general statements made by invited participants.Dr. W. Horwitz (AOAC) said the AOAC had been formed nearly 100 years ago (1884) and its first problem was the determination of phosphorus in ferti- lisers where there had been a good deal of disagreement between government chemists and industry. He referred to an AOAC definition of a collaborative study: an inter- laboratory experiment designed to estimate the characteristics of a method.A collaborative study usually involved the trial of one method but it could apply to more, e.g., the IARC study on nitrosamines. A minimum of five laboratories take part and a minimum of six samples is sent to each. The participants224 HARMONISATION OF ANALYTICAL STUDIES Proc. Analyt. Div. Chem. SOC. must follow the directions given and resist their own modifications, although these could be tried in separate experiments. It is im- portant that the participants should not be told the amount present of the substance that they are looking for, beyond giving them an idea of the order of the amount, e.g., about 1 mg kg-l.He criticised the AMC procedures in which participants add their own material, a lower standard deviation is always obtained under these circumstances.Collaborative studies are carried out to check a method, not analysts, i.e., they are not proficiency studies. It is impossible to maximise simultaneously all characteristics, e.g., accuracy and speci- ficity, and it should be decided which is the most important and sacrifice the others in order to obtain it. For a statutory method, e.g., the gravimetric determination of water in a foodstuff, it did not matter for legal purposes whether the method determined water or not so long as this was understood on all sides.Before such a method could be changed, for instance to an automated Karl Fischer method, it is necessary to examine a large number of samples by both methods. Rather than face the legal problems of making the change it might be considered preferable to retain the old method.Dr. Horwitz referred especially to W. J. Youden’s book, “Statistical Tech- niques for Collaborative Tests,” the latest edition of which (1975) had an additional section by Dr. E. H. Steiner on the analysis of variance. In collaborative tests the ratio standard deviation (repeatability) to standard deviation (reproducibility) was usually 0.5- 0.67.In one instance (NBS orchard leaves) the ratio obtained in a study was 0.9. A low ratio suggests that the analyst has used an altered method. Dr. Horwitz stressed the importance of publishing the results of colla- borative studies. He also referred to the costs of such studies and said that the AOAC have accepted studies by other bodies, e.g., CIPAC.Dr. S. S. Brown (International Federation of Clinical Chemists) referred to the collaboration between IFCC and IUPAC (Clinical Chemistry Section). The IFCC set up reference materials and had expert panels on, for example, en- zymes, proteins, nomenclature and the prin- ciples of quality control. An office of reference materials and methods was set up in 1973. Dr. Brown considered three aspects of inter- laboratory trials.The initial stimulus for a trial should come from a professional body. Trials should not be undertaken lightly. Pre- Pre-trial Aspects. liminary trials should be carried out in a few laboratories and the costs should be properly estimated. The organisation should be carried out by a small team and not by a large com- mittee, and the team should contain one scientist and one technician ; there should also be a consultant statistician.Participants should be given the fullest information and a time limit. There should be adequate supplies of test material and these supplies should be homogeneous. There should be two-way communication during the trials and three months should be allowed for each stage. One variable should be studied a t a time and the maximum information should be extracted from limited data.An unexpected finding may have to be specially investigated by one or more laboratories. There should be a meeting of all participants (plus the statistician) at least once during the trial. In-trial Aspects. Post-trial : pzcblication. Dr. C. T. Greenwood (International Asso- ciation for Cereal Chemistry) said that the Association was founded in 1955 with Head- quarters in Vienna.There are currently 33 member countries. The purpose of the Asso- ciation was to study problems of analytical methods in cereal and flour chemistry, standard- isation of methods and the establishment of close relations between scientific research and the practical side of the industry.The main activities are carried out by study groups, e.g., those on sampling, moisture determination and particle size determination, and there are at present 34 such groups. Contact is maintained with many other international bodies, e.g., ISO, AOAC, and the FAO/WHO Codex Alimentarius Commission, and the standard methods are eventually published as IS0 methods. Mr. E. A. Walker (International Agency for Research on Cancer) discussed the special problems involved in selecting a method for the determination of volatile nitrosamines, where it was impossible a t the outset to single out one contender for collaborative study because several methods were proposed with radically different approaches.A co-operative study was conducted in which each laboratory analy- sed identical samples spiked with several nitrosamines by any method they chose.Most of the gas-chromatographic techniques selected had responded well to this approach, even a t levels of added nitrosamine down to 5 or 10 pg kg-l. The choice initially of a single method would have resulted in the loss of participant interest, although such a choice would have beenJuly, 1978 HARMONISATION OF ANALYTICAL STUDIES 225 desirable for legal purposes.Perhaps a study of this sort should be described as co-operative rather than collaborative. Mr. Walker sugges- ted that IUPAC might set up a central registry of projected and continuing collaborative studies in order to avoid overlap and waste of resources. Dr. L.-A. Appelqvist (Nordic Committee on Food Analysis) said that his Committee is a joint body of the four Scandinavian countries and was formed in 1947.It attempted to produce methods that were as general as possible, independent of commodity. It had already 100 methods, but of 100 food con- taminants of interest methods were only available for 25. There was a lack of suitable reference materials. It usually took 10 years to develop a method, although the method for mercury was an exception to this.J , I. Schultz (ASTM) said that the ASTM was founded in 1898 for the purpose of de- veloping standards for materials and materials testing. The scope is now much broader, en- compassing the development of standards for the characteristics and performance of materials and materials testing. Its range of interest covers metals, plastics, medical devices, chemi- cal analysis and mechanical testing. He also disclosed that 40% of NBS standards related to the metal industries and that there was still a need for more metal standards.J . M. Hutchinson (FAO) said that the Codex Alimentarius Commission was established in 1962 and that there were now 114 member countries. The Commission is an inter-govern- mental body aiming to elaborate food stan- dards so as to protect the consumer against health hazards and fraud and to ensure fair practices in the trade. It works through general subject committees, commodity com- mittees and regional co-ordinating committees.There are five general subject committees dealing with Food Hygiene, Food Additives, Pesticide Residues, Food Labelling and Methods of Analysis and Sampling.Methods of analysis for Codex Standards are recommended by the Commodity Committees for examination and endorsement by the Methods of Analysis and Sampling Committee. Preference is given to official methods elaborated by international organisations dealing with food. Methods applicable to a group of commodities are pre- ferred to those which only apply to an individual commodity.A joint Codex/ISO/AOAC meeting held in September 1975 agreed on the need for harmonisation and on future collaboration to deal with the greater use of inter-laboratory testing at the international level. Dr. S. M. Lewis (International Committee for Standardisation in Haematology) said Dr. Lous had referred to the early work in haematology.By the 1920s several methods were available but discrepancies were wide. The ICSH was founded 15 years ago, initially because of the chaotic situation in haemo- globin measurement, Proposals were accepted from any national haematological Society. A tentative standard was subject to co-operative study over 5 years, after which it was pro- mulgated as a standard. The ICSH co- operated with the International Atomic Energy Agency and with the Community Bureau of Reference.Dr. Lewis pointed out that many measurements in haematology had to be regarded as being qualitative. Mr. J. F. Lovett (CIPAC) said that the handbook issued by CIPAC contained methods for 60 pesticides and that the new edition would include infrared spectra for all of these compounds.The handbook was a complete compendium aimed at giving all the information required in one place. Dr. A. Berlin (EEC Health and Safety Directorate) said that in 1973 the Council of Ministers of the EEC set up the first Environ- mental Action Programme which includes specific action to reduce and/or prevent pollu- tion. Lead was considered to be a priority pollutant requiring urgent action.Owing to the low blood levels expected the testing of analytical techniques for lead determination was of paramount importance. Three inter- comparison programmes have been carried out so far involving more than 60 laboratories. Each laboratory could use the method of its choice ; a reference laboratory organised technical seminars. Two individuals visited a large number of participating laboratories over a short period of time and they not only served as analysts but as guinea pigs by providing a sample of their own blood a t each laboratory they visited.In parallel with blood lead determinations tests have been carried out in a number of laboratories to standardise a method of determining ALAD (enzymic activity of delta-aminolevulinic acid) which gives an evaluation of exposure to lead.Another collaborative study is on LD,, determination. Five compounds covering a range of solubilities have been given to rats for LD,, determination. The weight of the test animal and the method of administration have been found to be very important. Dr. A. Carruthers (ICUMSA) said the aims of his organisation were to develop methods that can be applied in most industrial sugar226 HARMONISATION OF ANALYTICAL STUDIES PYOC.Analvt. Diu. Clzem. SOC. laboratories. Tentative methods were tested and became official after 4 years. Proceedings were issued every 4 years. The AOAC manual by Youden and Steiner was used. Mr. W. van der Eijk (EEC/BCR) said that the Community Bureau of Reference had no laboratory of its own and had to rely on the co-operation of several laboratories making measurements by methods of proven accuracy and precision.If possible, two or more methods were used by each laboratory. Each reference sample issued was accompanied by a technical report giving full details. The HCR covered all fields except the nuclear field, as it was formed under a treaty of the Economic Community and not of Euratom.Prof. G. Ghersini (ISO) said that IS0 con- sisted of the national standards institutes of 84 countries, At present, the main task of IC/47 is to define analytical methods and, to date, 400 methods have been standardised. Attention is also devoted to the general har- monisation of these standardisation activities and norms for drafting standard methods are being prepared. The second day of the Symposium com- menced with a general discussion of principles for collaborative studies under the Chairman- ship of Dr.Roth. The following criteria were listed for discussion : precision, accuracy, sen- sitivity, limit of detection, practicability, applicability and specificity. Dr. Egan sugges- ted a general definition of each term should be agreed, following which it might be possible to agree on which criteria were the most irn- portant. He referred to a document that he had tabled in which definitions for precision (reproducibility), accuracy, limit of detection and sensitivity were given, based on recent IUPAC and IS0 definitions.Varying views were put forward on the definition of precision. The Chairman said that clinical chemists preferred to use the term “imprecision.” Prof.Ghersini (ISO) referred to the recent draft IS0 document (ISO/DIS 5725) “Precision of Test Methods-Determination of Repeatability and Reproducibility.” In a discussion on sen- sitivity and limits of detection Dr. Egan said that the correct definition of sensitivity was based on the slope of the response curve.Professor West stated that the IUPAC de- finition of limit of detection was based on the extrapolation of this curve. Dr. E. D. Schall (AOAC) referred to the use of limit of deter- mination. Mr. Walker said the limit of detection was not always necessary, e.g., when p.p.m. levels were required its inclusion could lead to unnecessarv work being done. -, Dr. Egan suggested that applicability was more useful than specificity and Professor West considered it better to state interferences.The question was discussed of the advisability of naming suppliers of reagents and instruments in the description of a method. Mr. C. Mere- dith (BSI) said the difficulty could be over- come by using the phrase “The following. . . . . has been found satisfactory,” as this did not rule out other sources, but names some that are known to be satisfactory.Ilr. Egan took the chair a t the final afternoon session. He suggested it would be of value to have a directory of organisations that sponsor collaborative analytical studies, which would include continuing studies. Professor H. W. Niirnberg (IUPAC Analytical Division) said that people should be asked where the main problems exist and where they feel justified in asking for collaborative studies.Dr. Egan suggested the possibility of IUPAC circulating a questionnaire to obtain the necessary in- iormation for future action. A further meeting might be held followed by a wider Conference in 2 years time. Mr. Meredith stated that definitions of criteria should be available by then and Dr.Berlin requested that a working document should be prepared and put before the meeting. Dr. Egan said this would need to be prepared by one of the existing bodies and not by a working party. Professor Freiser suggested taking the Youden - Steiner manual as a basis and Dr. Egan said that people could be asked whether they would be prepared to accept this. The following were suggested for membership of a working party : IUPAC (three branches), IFCC, ASTM (pos- sibly also representing NBS), AOAC and ISO.APPENDIX Participating Organisations Association of Official Analytical Chemists Collaborative International Pesticides Analy- EEC Agriculture Directorate (EEC/Ag) EEC Community Bureau of Reference (EEC/ EEC Customs Union (EEC/GUD) EEC Environment and Consumer Protection EEC Health and Safety Directorate (EEC/ European Brewery Convention (EBC) Food and Agriculture Organisation (FAO) International Agency for Research on Cancer (AOAC) tical Council (CIPAC) BCR) Service (EEC/ECP) HSD) (IARC)July, 1978 INDUSTRIAL ANALYTICAL INSTRUMENTATION 227 International Commission for Uniform Methods lUPAC Analytical Chemistry Division (IUPAC International Association for Cereal Chemistry lUPAC Clinical Chemistry Section (IUPAC International Committee for Standardisation Nordic Committee for Food Analysis (NMKL) International Dairy Federation (IDF) International Federation of Clinical Chemistry International Office of Cocoa and Chocolate Cbsewevs- International Organisation for Standardisation (ASTM) International Wine Office (OIV) IUPAC Applied Chemistry Division (IUPAC UK Assay Offices (UKAO) of Sugar Analysis (ICUMSA) Analytical) (ICC) Clinical) in Haematology (ICSH) World Health Organisation (WHO) (I FCC) (OICC) American Society for Testing and Materials British Standards Institution (BSI) Chemical Society, Analytical Division (CS/AD) US National Bureau of Standards (NBS) (ISO) Applied)

ISSN:0306-1396    

DOI:10.1039/AD9781500223

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

July, 1978 INDUSTRIAL ANALYTICAL INSTRUMENTATION 227 Future of the Public Analysts Scientific Advisory and Analytical Services The Association of Public Analysts has pub- lished an 8-page report of the above title, which reviews the development of these services over the last 100 years, examines the present situation in relation to current local and national requirements, considers future demands and makes a number of recommendations.The report criticises the lack of coordination and resources to meet the increasing demands for services under new legislation, criticises Central Government for its lack of guidance to the Local Authorities, and deprecates the establishment of additional small laboratories by some Councils, which has led to wasteful duplication of resources. Recommendations include the designation of Public Analysts also as Scientific Advisers, involved in the whole spectrum of scientific228 PUBLICATIONS RECEIVED Proc.Analyt. Div. Chew. SOC. services within the Local Authorities, and the For further information, contact Dr. L. E. development within every County or group of Coles, Mid-Glamorgan Public Health Authority, Counties of a comprehensive scientific service Institute of Preventive Medicine, The Parade, through which all Local Authority scientific Cardiff, CF2 3UJ. matters would be channelled.

ISSN:0306-1396    

DOI:10.1039/AD978150227b

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

228 PUBLICATIONS RECEIVED Proc. Analyt. Div. Chew. SOC. Publications Received Atlas of Metal - Ligand Equilibria in Aqueous Solution. J. Kragten. Translation Editor, Mary Masson. Ellis Horwood Series in Analytical Chemistry. Pp. 781. Chichester: Ellis Horwood. New York, London, Sydney and Toronto : Halsted Press. Distributed by John Wiley in Australia, New Zealand, South-east Asia, Canada, Europe and Africa; and by Halsted Press in North and South America and the rest of the world.1978. Price f135. Potentiometric Water Analysis. Derek Midgley and Kenneth Torrance. Pp. xii + 409. Chichester, New York, Brisbane and Toronto: John Wiley. 1978. Price f116.50; $36.50. Principles of Field Ionization and Field Desorption Mass Spectrometry. H. D. Beckey. International Series in Analy- tical Chemistry, Volume 61.Pp. xvi + 335. Oxford, New York, Toronto, Sydney, Paris and Frankfurt: Pergamon Press. 1977. Price $35; f119.50. Analytical Notes : A Summary of Inorganic Methods of Chemical Analysis. H. J . Boniface. Pp. 64. Wolverhampton : Sigma Technical Press. 1978. Price f13.50 (softback). Viruses and Trace Contaminants in Water and Wastewater. Edited by Jack A. Borchardt, James K.Cleland, William J. Redman and Gordon Oliver. Pp. xiv + 249. Ann Arbor, Mich.: Ann Arbor Science Publishers. 1977. Price Q8.60. Collision Spectroscopy. Edited by R. G. Cooks. Pp. xiv + 458. New York and London: Plenum. 1978. Price $54.60. Automatic Potentiometric Titrations. G. Svehla. International Series in Analytical Chemistry, Volume 60. Pp. x + 219.Oxford, New York, Toronto, Sydney, Paris and Frank- furt: Pergamon Press. 1978. Price $29.50; f116.50. Tables of Standard Electrode Potentials. Guilio Milazzo, Sergio Caroli and V. K. Sharma. Pvoject of the Electvochemistvy Commission of The International Union of Pure and Applied Chemistry. Pp. xvi + 421. Chichester, New York, Brisbane and Toronto: John Wiley. 1978. Price fT17.50; $35 (softback).Affinity Chromatography. Jaroslava Turkova. Jouvnal of Chvomato- graphy Libvavy, Volume 12. Pp. x + 405. Amsterdam, Oxford and New York : Elsevier. Distributed by Elsevier North-Holland in USA and Canada. 1978. Price $69.75; Dfl 167. Chimie ghkrale et minkrale. Tome 1. Nomenclature, atomistique Donnkes sur les Solides et sur les Solutions. Tome 2. Constantes physico-chimiques Renseigne- ments pratiques.Maurice Bernard and Florent Busnot. Tome 1, pp. xxx + 1-253. Tome 2, pp. xxx + 254-550. Paris: Dunod. 1978. Price Fr43 (Tome 1); Fr47 (Tome 2). The Sampling and Initial Preparation of Sewage and Waterworks’ Sludges, Soils, Sediments and Plant Materials Prior to Analysis. 1977. Department of the Environment/National Water Council. Methods for the Examination of Watevs and Associated Materials.Pp. 13. London: HM Stationery Office. 1978. Price Chemical Oxygen Demand (Dichromate Value) of Polluted and Waste Waters. 1977. (Two methods, one tentative). Department of the Environment/National Water Council. Methods for the Examination of Waters and Associated Materials. Pp. 14. London: HM Stationery Office. 1978.Price i l . fTo.90. Amenability of Sewage Sludge to Anaero- bic Digestion. 1977. Department of the Environment/National Water Council. Methods for the Examination of Waters and Associated Matevials. Pp. 10. London: HM Stationery Office. 1978. Price fT0.70.July, 1978 CS AUTUMN MEETING Determination of the pH Value of Sludge, Soil, Mud and Sediment; and Lime Re- quirement of Soil (1977 version).Department of the Environment/National Water Council. Methods for the Examination of Waters and Associated Materials. Pp. 11. London: HM Stationery Office. 1978. Price A0.75. Treatise on Analytical Chemistry. Part 111. Analytical Chemistry in Industry. Volume 4. Section D (Continued). Phy- sical Testing Methods for the Character- ization of Materials. Edited by I.M. Kolthoff, Philip J. Elving and Fred H. Stross. Pp. xxx + 686. New York, London, Sydney and Toronto: John Wiley. 1978. Price A27.50; $50. Trace Elements in Human Hair. Vlado ValkoviC. Pp. x + 194. New York and London: Garland STPM Press. 1977. Price $19. Essays on Analytical Chemistry in Memory of Professor Anders Ringbom. Edited by Erkki Wanninen. Pp. xiv + 607. Oxford, New York, Toronto, Sydney, Paris and Frankfurt: Pergamon Press. 1977. Price $55. Water Analysis : Some Revised Methods for Limnologists. F. J. H. Mackereth, J. Heron and J . F. Talling. Scientific Publication No. 36. Pp. 122. Far Sawrey, Ambleside : Freshwater Biological Asso- ciation. 1978. Price A2.50 (non-members). 229

ISSN:0306-1396    

DOI:10.1039/AD9781500228

出版商:RSC    

年代:1978

数据来源: RSC