ISSN:0306-1353    

DOI:10.1039/AA97909FX001

出版商:RSC    

年代:1979

数据来源: RSC

摘要:

Royal Society of ChemistryAnalytical Sciences MonographsA series of monographs on topics of interest to analytical chemists.The Chemical Analysis of Water-General Principles and Techniquesby A. L. WilsonChemical analysis of water for human consumption has been the subject of countless books,and this volume concentrates on a critical appraisal on the analytical principles involved. Allstages of the analytical process are covered, including: sampling of time, place and techniques;the analysis proper; the reporting of results, and data handling.Hardcover 1Spp 83" x 4"€7.50/$15.00Pyrolysis- Gas Chromatographyby R. W. May, E. F. Pearson and D. ScothernThis volume presents the available knowledge on the subject of pyrolysis-gas chromatography ina form useful to the analyst.Areas covered include: merits and demerits of particular ap-plications; major analytical uses of the technique; identification of the pyrolysis products whichare eluted from the chromatography column, and the necessity for increased standardization.Hardcover I 1 7pp 83" x 6" €7.201 $14.10Electrothermal Atomization for Atomic Absorption Spectrometryby C. W. FullerOne of the successful alternative atomization sources tG the flame is at present electrothermalatomization, and this volume deals with all aspects of this technique, including: history;theoretical aspects; practical considerations; analytical parameters of the elements; and specificareas of application.Hardcover 135pp @" x €6.75/$13.50Dithizoneby H. M. N. H.IrvingAs a result of his long association with analytical techniques using this reagent, the author isable to present in this volume a body of historical and technical data on the subject. Specifictopics include: the properties of dithizone; metal-dithizone complexes and their formulae; thephotochemistry of dithizonates; and organometallic dithizones.Hardcover 112pp @" x 3" €7.25/$14.50lsoenzyme Analysisby D. W. MossThis monograph attempts to draw together the most important experimental techniques whichhave resulted from the modern recognition that enzymes frequently exist in multiple molecularforms. This monograph also indicates the advantages and limitations in isoenzyme studies ofthese modern analytical techniques.Hardcover 171pp 83" x ~"€9.00/$22.@Analysis of Airborne Pollutants in Working Atmospheresby J. Moreton and N. A. R . FallaPart I covers pollution in the welding industry while Part II covers the surface coatings industry. \ Hardcover 194pp 83" x 3" €12.OY1/$32.00\\Further information about any of these publications can be obtained from: The MarketingDepartment, The Royal Society of Chemistry, Burlington House, London W1V OB

ISSN:0306-1353    

DOI:10.1039/AA97909BX003

出版商:RSC    

年代:1979

数据来源: RSC

摘要:

6 Analytical A tomic Spectroscopy 1.2 PLASMAS The now widespread availability of commercial plasma spectrometers has been reflected by a continued growth in the literature describing their use in analytical chemistry. Interest in microwave plasmas has appeared to decline but that in d.c. plasmas, especially their application, has increased, Most of the published reports deal with the r.f. inductively coupled plasma (ICP), but here there has been a noticeable shift towards a more realistic appraisal of the ICP in genuine analytical situations, as evidenced by the numbers of papers that discuss interference effects, unmentioned until recently.Two books (656, 1830) have contained chapters devoted to accounts of the different forms of plasma excitation used for analytical emission spectroscopy.A tomization and Excitation 7 1.2.1 R.f.Inductively Coupled Plasmas 1.2.1.1 Reviews. An authoritative and comprehensive review of the theoretical aspects of r.f. induced discharges has been published in two parts (655, 1087). Readers who prefer a theoretical discussion with fewer equations are directed to that by Robin (652). State-of- the-art reviews have been presented at conferences by Boumans (126, 1089).An insight into the progress of ICP-AES in various parts of the world was afforded by a report (1086) of activities in seven countries. An attempt has also been made to clarify the role of the ICP in practical analyses in comparison with other techniques (2073). It was concluded that of the available multi-element techniques, the ICP offers the greatest versatility and sensitivity. 1.2.1.2 Fundamental Studies. The present knowledge of the excitation conditions in the ICP was well surveyed by Mermet (842) at the CSIIICAS meeting in Cambridge. The author described the various spectroscopic diagnostic methods that have been used with the ICP for the measurement of temperatures, electron number density and metastable density. A study of excitation temperatures and i o n / a t m line intensities in both a conventional ICP and a mini-ICP (see also Section 1.2.1.3) has been presented (588).This work showed that local thermal equilibrium (LTE) did not exist in the low-power Ar plasma either close to the load coil or higher up in the tail flame. Other workers (150) have confirmed this conclusion and shown that desolvation of the sample moved the plasma even further from LTE (see also ARAAS, 1978, 8, Ref. 755). Lovett (1289) has found very broad lines in the ICP spectrum due to emission from autoionizing states with half-widths of as much as 4 A. These were ascribed to the natural line-width of very short-lived (ca. 10-14 s) excited states lying above the ionization limit of the atom.As the concentration of the element, e.g., Ag, Bi, Cd, Cu and Pb, was increased, the contribution of these emissions to the background became significant, posing problems in metallurgical analysis and demonstrating a unique link between atomic and ionic states in the study of plasma mechanisms. There is a growing appreciation that an understanding of analytically important plasma characteristics will be facilitated by an increased recognition of the inhomogeneity of the ICP.Koirtyohann et d. (201) have attempted to delineate separate zones in the plasma by using both a photodiode array detector and a moveable aperture controlled by a stepper-motor. The profiles obtained help explain the conflicting reports found in the literature concerning ionization interferences and optimum power levels.Other workers (737) have also used a computer-coupled photodiode array spectrometer to study spatial profiles of emitting species and provided evidence of the effects of plasma operating conditions and interferents. The alternative “end-onYy view of the ICP can give information on radial distribution patterns and, using an IDES, some interesting results have been obtained (86 1).As would be expected, under normal conditions most elements exhibited their maximum intensities around the centre of the plasma and background intensity was maximal at the skin zone. This distribution was influenced to some extent by operating conditions. Demers (617) has also studied “end-on” viewing in some detail and concluded that this gave superior detection limits with little or no loss in othcr aspects of analytical performance.Barnes et al. (841, 1092) have continued to refine and discuss their computer simulations of the ICP (see also ARAAS, 1978, 8, 7, and 1977, 7, 12). Computed results confirmed the experimental observation that natural convection exerted a negligible effect on the flow and temperature fields in a confined discharge but was a greater influence for a free plasma discharge.In contrast, the effect of conductive heat losses was found to be greater in the confined plasma.8 Analytical Atomic Spectroscopy The introduction of gases other than Ar into the plasma continues to be an active area of research. A He ZCP discharge is particularly interesting as the available excitation energy should be greater than that for an Ar ICP.Using a 54 MHz generator and 6 kW forward power, Robin and co-workers (848) produced a He plasma. Unfortunately, even when 40 1 min-l He was used, only a needle-like discharge was obtained and efforts were being directed towards broadening the plasma sufficiently to permit sample injection. The introduction of small concentrations of He into a conventional Ar plasma did not produce a He-type discharge.Talaat (1094) has maintained an experimental r.f. discharge inside a cylindrical quartz tube using high-velocity He flows at an intermediate pressure. Experi- mental results and thcoretical predictions of the r.f. ionization of He wcre compared. Many European and other spectroscopists continue to use nitrogen as the coolant or outer gas flow and the effects of this have again been discussed (1084).The use of N, in any of the three gas flows has also been studied (1816). When N,/Ar mixtures were used in the aerosol carrier-gas flow, the stability of the plasma was impaired. The use of a N,/Ar mixture in the plasma coolant gas increased both the net analyte and background intcnsities, confirming that a hotter plasma was produced.Little change, however, in detcction limits for 15 elements was obtained. Barnes and Meyer (1299) have investigated both N,/Ar and all N, discharges using a 10 kW, 27 MHz, crystal-controlled r.f. gcnerator. Experimental results suggested that a N, ICP could be operated at lower power than that predicted by a computer model. This model had previously predicted (see ARAAS, 1976, 6, Ref. 314) improved particle decomposition in a N, ICP compared to an Ar ICP. There has been a renewed interest in using air as the coolant gas for the ICP. Ohls and Sommer (654) have used an air/Ar ICP at 27 MHz and 3 kW. Most elements studied showed improved sensitivities in the air/Ar ICP compared to N,/Ar, but detection limits were only improved for about half of the elements.Considerable controversy has in the past been aroused concerning the effects of different plasma parameters, particularly power, on analytical utility. One difficulty in the resolution of such controversies has been that many comparisons have been made with non-optimal conditions. This problem has been compounded because optimization of the ICP is difficult given that the five operating parameters that affect plasma performance (the three gas flows, hcight of observation and power) are closely inter-related.Hopefully this is now a difficulty of the past as two different approaches to optimization have been successfully applied. These wcre the alternating variable search method employed by Greenfield (866) and the variable step-size simplex employed by Ebdon et al.(873). Both groups of workers came to the same general conclusions that low power was optimal for an Ar plasma, but higher power was normally optimal for a N,-cooled plasma. The wide extent of the other para- meters that must be optimized in a particular laboratory situation has also been discussed (2040).The characterization of noise is obviously of importance in this context and a comprehensive study of the noise power spectra of an ICP has been reported (1291). Near the limit of detection the major component was that of 1 /f noise. This noise increased with increasing wavelength. Some very useful lists of prominent lines for ICP analysis have been published this year. One listing of 450 persistent lines for 71 elements (1475) was based on a previously tested empirical relationship between sensitivities in the 4 r ICP and intensities in the NBS copper arc (see also ARAAS, 1978, 8, Ref. 1060). Another listing (1730, 1801) covered the prominent lines of 70 elements in both alphabetical and numerical wavelength order. Additional reference on the preceding topic (W spectrum) - 625.The ICP offers one of the few viable techniques for rare-eurth element analysis. Three different groups have reported on the determination of the lanthanoids by ICP-AES (870, 1275, 1476). In each case various Lines were investigated and limits of detection reported.Atomization and Excitation 9 The line-widths reported and the complexity of the spectra require the use of spectrometers with high resolving powers. The energetic nature of the ICP has led to its use as a source in other spectroscopic techniques.Winefordner and co-workers (1399, 1851) used an ICP as an excitation source for flame AFS. Fourteen elements were studied; promising detection limits and a reduction in spectral interferences were reported. The same system was used to plot three growth curves (the fluorescence, the excitation and the ICP emission growth curves).These showed the absence of self-absorption and self-reversal in the ICP at normal observation heights, even at relatively high concentrations. An ICP has also been used as a source for molecular fluorescence (1096). Interest in the ICP as an ion source for analytical mass spectrometry has been the subject of further study (1288).A small fraction of the ions from the ICP were pumped into a quadruple mass spectrometer. There are few potential interferents above mass number 42 and direct isotopic determinations are possible. We can expect to hear more of this approach in the future. Other references of interest - Ar/C,H, plasma for pyrolysis experiments: 845.Ar/UF Determination of stoicheiometries of heterupolymolybdates and heteropolytungstates by ICP: 2052. lasma for UF, regeneration and product analysis: 1093. 6 P 1.2.1.3 Torches. Of the various developments in torch design reported, by far the greatest interest has been in the so-called “mini-torches”, or reduced gas-flow torches (see also ARAAS, 1978, 8, Ref. 1412). The miniaturized torch of Savage and Hieftje has been further described (210, 733, 860, 1194, 1701).This compact torch was sustained by less than 1 kW of power and consumed less than 8 1 min-1 Ar. Two new torch configurations, with reduced diameter and smoothed contours have been reported (1985). Both power and gas consumption for these 9- and 13-mm diameter torches were lower than for the conventional 18-mm torch and the detection limits for 19 elements were encouraging. Another interesting development was the emergence of a water-cooled torch (844, 1298, 2012, 2042).As the water replaced the cooling function of the outermost argon flow, a tenfold reduction of Ar consumption was achieved with excitation temperaturee comparable to a conventional system. This ICP could be sustained at powers as low as 0.2kW, but as the carrier gas flow-rate available was only about 0.1 1 min-1, there were problems with sample introduction and hence detection limits were not as low as for conventional torches.Torches designed for improved performance with samples in orgaizic solvents have been reported. Boom and Browner (225, 559, 853) have inserted quartz capillaries in the two outer annular channels to produce a laminar flow of the gases.This reduced turbulence and hence improved stability while spraying organics. A new streamlined torch, for the analysis of liquids with organic constituents (1090), has been described. It has been pointed out that at higher power (5 kw) the N,/Ar ICP gives a stable discharge with organic solvents and that no carbon deposits occur (852).A modified Greenfield torch was reported, which was shown to have particular advantage when using Ar as coolant (873). The intermediate tube was flared and the torch was demountable. The three tubes were inserted into a brass support, which also featured replaceable threaded brass jets for control of the tangential gas velocity of the intermediate and outer gas flows; another demountable torch featured threaded and slotted spacers between the coolant / plasma tubes and plasma / injector tubes (1 725).This novel arrangement gave a greater tangential component to the outer gas flow. 1.2.1.4 Sample Introduction. Perhaps no other aspect of ICP-AES would more repay study than sample introduction, Fortunately it is increasingly being recognized that this is often10 Analytical Atomic Spectroscopy the limiting factor controlling the applicability of the ICP.Methods of sample introduction for the ICP have been briefly surveyed (590). Pneumatic nebulization is still the most popular form of sample introduction and the studies of Browner and co-workers (199, 226, 559, 593, 843, 853, 1320) on the chemistry of aerosol transport and the characterization of droplet sizes promises to be of great practical significance.Droplet-size distributions for a variety of pneumatic and ultrasonic nebulizers were characterized in the range 0.01 to 10pm for both aqueous and organic solvents. Information was obtained by laser scattering, electrostatic precipitation and cascade impac- tion.They have found in these studies a new form of interference, aerosol ionic redistribufion, arising from the observation that the relative concentrations of metals in droplets formed from mixed salt solutions are a function of droplet size. Doubtless we will hear more of this effect in future work. Two new cross-flow pneumatic nebulizers have been described (1 320), which are robust and of fixed geometry.Both, it was claimed, ran continually with solutions containing 10% NaCl. One of these nebulizers operated at a net sample uptake rate of 0.2 ml min-1, without loss of analytical signal, by recycling the untransported sample. More detailed descriptions of methods for wetting the injector gas stream to avoid the salt blockages that can m r with conventional concentric nebulizers (see also ARAAS, 1978, 8, Ref. 1424) have been published (51 5, 1541). The complex relationship between the analytical signal and stability, and the characteristics of concentric nebulizers, e.g., pressure, uptake rate, annulus area and flow velocity, has been explored (850). Babington-type nebulizers are becoming increasingly popular. A design fabricated in Teflon and glass was shown to be tolerant to a wide-range of sample flow-rates, 0.2-4 ml min-1, and was operable even with samples containing suspended solids (592).A factorial design-optimization of another promising prototype has been reported (591). A new development was the fritted-disc nebulizer. Sample was allowed to flow across a fine frit 15-ml Buchner funnel while Ar was introduced from the other side.Sample uptake rates as low as 0.02mlmin-1, with a 60% efficiency, were used but problems with drift and memory effects were encountered. The use of an injection cup technique has again (see also ARAAS, 1978, 8, Ref. 1442) been recommended for the rapid analysis of solutions with up to 20 mg ml-1 solids content (1 572). As more workers discover that the practical power of detection of the ICP is somewhat poorer than the lists of “distilled water detection limits” had led them to believe, there is increased interest in pre-concentration techniques and the use of organic solvents.Such solvents not only cause problems at the torch when using the conventional low-power all Ar systems, but also pose problems of sample introduction.A new cross-flow pneumatic nebulizer with adjustable Teflon capillaries and a novel spray chamber has been described (857, 1090). This nebulizer appeared to be well suited to samples dissolved in HF, those with high salt contents, or those dissolved in MIBK. The analysis of wear metals in oils may present an additional problem, namely the presence of metal particulates in the sample.It was reported that, using a conventional nebulizer-spray chamber system, the analyses of samples containing particles greater than 10 pm were not quantitative (1 321). The critical particle size that can be tolerated has been calculated using a theoretical model (600). In other studies of the same problem, attention has been given to appropriate dilution of the sample before aspiration (882, 1698). The formation of vohtile hydrides (see also Section 1.5) is well recognized as an attractive method of circumventing the relatively poor sensitivity for certain important elements.A continuous on-line NaBH, reduction cell for the routine simultaneous deter- mination of As, Ge, Hg, Sb, Se and Te has been described (1306), as well as a more detailed survey of the conditions for Sn and Ge hydride generation (1722).The influence of excess H, on the discharge stability can be important. It has been reported that when using anAtomization and Excitation 11 Ar ICP at a power of more than 2 kW, this factor can be neglected (852). Alternatively, the hydride, e.g., ASH,, may be collected in a liquid Ar cold-trap and the H, allowed to pass to waste (1739).Further studies of electrothermal vaporization of samples into the ICP have been reported (3, 851, 1312, 1697). A carbon rod is generally used as the vaporizer and some interesting transport effects in the tube connecting the vaporizer to the torch have been described. Enhancement of Cd and As signals in the presence of Se appeared to be due to the formation of condensed aggregates.The use of a halocarbon/Ar atmosphere was found to aid the vaporization of refractory compounds, e.g., in the determination of trace metals in uranium or in the determination of B, Cr, Mo, W and Zr using 0.1% trifluoromethane/Ar as the transport gas. Spark sampZing of solids is a technique with considerable attractions for metallurgical analysis. The use of an electronically controlled waveform spark source to sample a metal for ICP excitation has been further described (74, 192, 525, 874).It was reported that the linearity of response of the ICP was maintained and that matrix effects were reduced and precision improved compared to conventional spark excitation. An interrupted arc has also been used for this type of sample introduction, using either conventional metallic samples or briquetted mixtures of copper powder and oxides (877, 2028).Other methods of soZid sampling that have been reported include laser vaporization and direct solid injection. A system using a pulsed C0,-TEA laser to vaporize samples into the injector Ar stream has been shown to give good accuracy when used with reference materials (222).A wide variety of samples, e.g., metals, powders as pellets or on tape, have been analysed using a pulsed ruby laser as the vaporizer (594). A method was developed by Horlick and Salin (211, 595, 736, 1857) for the direct insertion of a graphite cup containing the sample (powders, solids or desolvated liquids) into the central core of the ICP. The sample holder occupied the position normally held by the aerosol tube.The graphite holder became white hot approximately 2 s after insertion, but the inert Ar ensured virtually no graphite consumption. Selective volatilization and thermochemical reactions are possible problems with this new form of sample introduction. Zil'bershtein et al. (224, 875) have developed a similar system that was used successfully for the direct multi-element analysis of thin sticks of oxide, silicate glass, and water evaporated onto carbon.Descriptions of coupled chromatography-ZCP systems have been published. For example, a coupled GC-ICP was employed for the determination of tetraethyl lead in petrol (1610). It has been suggested that GC-ICP is sufficiently accurate and precise to permit the determination of elemental compositions and hence empirical formulae for hydrocarbons and halogens (2003).The utility of the ICP as an HPLC detector has been evaluated for 25 elements (227, 1855). Its ability to detect HPLC peaks composed of EDTA and NTA chelatcs of Cu was compared with that of AAS. Detection limits were comparable, but the ICP possessed the advantage of multi-element capability. 1.2.1.5 Instrumentation. Complete ICP instruments are described in Section 2.4.1, where, it will be seen that there has been a considerable increase in the interest in rapid-scanning sequential instruments. A commercial instrument, based on a microcomputer-controlled rapid-scanning double monochromator, has been announced (535, 55 1, 864, 865, 1 30 1, 1594). Other workers have published accounts of sequential ICP-AES systems using computer- controlled monochromators (1 78, 188, 56 1, 862, 1 179, 1 300, 2039).The importance of high resolution in geological analysis has been demonstrated using gratings of different dispersion in a Paschen-Runge sequential spectrometer (872). It was concluded in this work that a holographic grating was superior, but another study reported12 Analytical Atomic Spectroscopy few advantages of holographic over ruled gratings, especially regarding stray light inter- ferences (6 14).Echelle spectrometers offer very high resolution and reports are beginning to appear concerning their application with ICPs (731, 739, 1290). It is possible that the geometry and light throughput of commercially available echelle spectrometers are unsuited to the ICP source.The use of specific detectors, either AAS or AFS cells, offers excellent “resolution” and a preliminary examination of a Hg detector has been made (213). Specifications for ICP systems have been reviewed (355) with special attention being given to data reporting. An ICP-spectrograph instrument for general survey analysis, using a computerized microphotometer, has been further developed (858).A interactive computer language for a direct-reading ICP spectrometer has been evaluated (10 19). Further details concerning optics, detector systems and data processing are to be found in Chapter 2, Other references of interest - Optical coupling of an ICP to an AA spectrometer: 343. Spectrometer modifications for K determination: 562. 1.2.1.6 Interferences. Assurances that there are no interferences in the ICP are much rarer than in the recent past and largely confined to those who do not operate an ICP for practical analysis. The present climate favours a frank discussion of the few problems that do exist, as one comprehensive discussion evidenced (5%). Sample trartport interferences are still being reported.These, because of the limitcd gas flow available for nebulization, can oftcn be more acute than in FAAS. For example, different acids have been shown to affect the emission from Cu when using both pneumatic and ultrasonic nebulization (1527, 2016). These effects were correlated with the density of the solution. Most workers now use a peristaltic pump routinely to minimize sample up-take rate interferences.The effects, at present unexplained and apparently varying, of easily ionizable elements seem to present a more acute problem. Perhaps some of these phenomena will be explained in future by the aerosol ionic redistribution mechanism (843) discussed in Section 1.2.1.4. Some workers report negligible effects from, for example, Na on K (1050).Others found matching of the Na level necessary when analysing samples following sodium peroxide fusions (650). Similarly, systematic errors caused by easily ionizable elements have been reported (1091) as have methods for dealing with matrix interferences (1281). Robin (652) has commented on the complexity of these phenomena, and has shown that generally they were less severe as the height of observation increased and the carrier gas flow-rate decreased, There was general agreement with these observations (1654, 201 5).Often the observed effects dcvelop similarly for atom and ion lines, contrary to expectation. The effect of K on atom lines was reported to be more severe than that on ion lines (1698). It has been suggested that high concentrations of Na quench metastable Ar and that this was therefore responsible for the effects observed in the analysis of rare-earth minerals (1654).In the miniature ICP, the enhancement by Na of a Ca atom line was greatest (30%) at higher powers and nebulizer gas flows (1285). In contrast, a Ca ion line was only slightly enhanced, and this only at low power. The use of Ce as internal standard to overcome suppressions by K has been recommended (587) as has the use of Li to enhance Pb signals (148).Spectral interferences due to the superposition of lines are enhanced by line-broadening in the plasma, as Robin has noted (652). An excellent tutorial rcview of these phenomena has been presented (847). There have been many reports this year of such interferences (e.g., 883). The greater number of spectral interferences in ICP-AES compared with AAS was commented upon by several authors (548, 879, 1524, 1996).Spectral interferences haveA tomization and Excitation 13 been predicted from wavelength tables and then evaluated in a practical study orientated towards environmental and clinical samples (1 282). Stray light effects continue to cause problems (221, 1541).The use of glass filters was found to be an effective way of reducing the interference of Cu and Ni on 0 s determina- tions (319). Band rejection filters for Ca and Mg have been used to reduce stray light effects on shorter wavelength channels (ca. 200 nm) in a commercial direct-reading plasma spectro- meter (218). A comparison of transmission filters placed before the detectors and a single rejection filter placed at the entrance slit (opaque to 390-4OOnm) for the removal of stray light caused by emission from Ca has been made (1153). The former was found more effective.Various devices for background correction are now in use. A novel triple entrance slit prefaced by an oscillating chopper so that radiation entered alternatively through the central slit and the two adjacent slits was proposed (878).A SIT has been used to provide back- ground correction (862). A spectral window of 5 nm with resolution of 0.01 nm per channel was used. Boumans (863) presented a progress report concerning the use of three silicon photodiodes for automatic background correction. Each was provided with a current t o voltage converter and connected to the measuring circuitry.The line peak was centred on the second photodiode and the other two viewed the background on either side of the line. The nature of micro-wavelength scan background correction systems and their performance on two different instruments has been discussed (616, 1284), as have microcomputer- controlled background-correction systems (705, 1050, 1283, 1308).Other references of interest - Concomitant effects in AAS using a plasma atomizer: 11 13. Influence of concomitants on analytical results: 231. 1.2.2 Microwave-excited Plasmas Research work in the field of microwave-excited plasmas seems to have entered a quiescent period, certainly fewer papers are being published. 1.2.2.1 Fundamental Studies. A comparison has been made of different cavities for micro- wave induced plasmas (MIP) (1696).Of the Beenakker (see also ARAAS, 1977, 7, 16), 3- and +-wave Evenson and +-wave Broida cavities, the former was preferred as being easier to tune, more reproducible and capable of sustaining a He plasma at atmospheric pressure. A plasma at atmospheric pressure, obtained by surface-wave propagation using a surfatron, was reported (1634).Produced within a silica tube, the plasma had a typical electron density of 3X 1014 cm-3 but the gas temperatures were lower than 4000 K. Measure- ments of temperatures and electron densities in the Beenakker cavity have been reported (607, 849). These were shown to vary with gas flow rates and applied power, The combina- tion of this He MIP with a micro-arc sampler, for analysis, was also briefly reported (733, 1194).The characteristics of the MIP, such as the atomization efficiency, have been studied (1 359). Preliminary results suggested good correlation between atomization efficiency and electron temperature, electron density and an energy parameter (power/pressure). The radiative ionization-recombination model has been shown to offer reasonable predictions of the experimentally measured intensity ratios of the H a- and P-lines in a 0.2 Torr He and Ar MIP, but so did a hypothetical thermal model (1888).The absorption intensities, how- ever, were very poorly predicted by the thermal model. A kinetic scheme based on a radiative charge-recombination process was shown to explain the scavenging and other effects observed when 0, is added to a conventional GC-MIP detector (1549).A reduced-pressure plasma operating at 5 kW and a frequency of 2300 MHz was14 A n d y tical A t omic Spectroscopy reported (846). A more conventional MIP has been employed to measure hydrogen isotope ratios in a GC eluant using an oscillating slit mechanism to view alternately the H emission at 656.28 nm and the D emission at 656.10 nm (2045).Agterdenbos et al. (966) have con- tinued their work with sealed MIP-AES and have determined Pb in human serum. The serum was ashed by microwave excited 0,, the Pb extracted with dithiocarbamate and the freeze dried extract sealed in a quartz tube before excitation. 1.2.2.2 Sample Introduction. A variety of approaches continues to be investigated with the MIP.Conventional nebulization is difficult because of the low tolerance of the plasma to water; however, plasmas operated in the Beenakker cavity are more robust in this respect. A new demountable torch has been described, which allowed a conventional cross-flow nebulizer to be used at a flow-rate of 1-2 1 min-1 (735). The plasmas was stabilized by the generation of an annular toroid and operated without desolvation with both pncumatic and ultrasonic nebulizers.Work has continued on laser vaporization of solids for excitation in an MIP (see also ARAAS, 1978, 8, Ref. 1061) (1657). The procedure was applied to the analysis of trace elements in aluminium and zinc samples using both photographic and photoelectric detection. The precision of the method was limited by the small number of photons arriving at the detector.Electrothermal vaporization continues to be a popular way of introducing samples into the MIP. A graphite cord was used to vaporize 1 pl samples and a temperature programme enabled the distortion of the linearity of the peak height caused by 1% KC1 solutions to be removed (855). Peak-height responses linear over 2 to 3 orders of magnitude were thus obtained.Van Dalen et al. (856) reported that use of a carbon rod vaporizer overloaded the plasma with C. Therefore, a home-made Ta furnace was used for the determination of C1, Br, I and S over the mass range 1-4000 ng. Metal oxides have been electroplated onto a wire, which was then used either as a wire loop or moving wire Vaporizer for MIP emission (90). The extraction into CHC1, of Mg from aluminium as the TFA complex, with subsequent vaporization of the chelate into an MIP was reported (641).The low tolerance of the MIP to solvents has encouraged investigation of the hydvide generation technique. Various means of hydride formation and their corresponding sensi- tivities have been reported (89).The H, p!oduced during the hydride generation has been vented and the hydrides condensed in a hquid-N, trap (91, 146). The hydrides were then passed to the MIP via a simple chromatographic column that removed condensed con- taminants. The linear dynamic range of the method extended over 3 orders of magnitude from the ngml-1 level. The most popular application of the MIP is as a GC detector.The advantages of the Beenakker cavity for GC detection of halogens and other elements has been stressed, reported detection limits were in the pgs-1 range (75, 460, 608, 945). The element specificity of the MIP was used to eliminate interferences, found with an electron capture detector, in the determination of polybrominated biphenyls in food (1 385). 1.2.2.3 Capacitively Coupled Microwave Plasmas.The need for ionization buffcrs and hence matrix matching has limited the application of the CMP. This has been stressed in a comparison of the CMP and the ICP for geological analysis (1691). Provided that the appropriate ionic and atomic partition functions are known, the degree of ionization may be calculated by comparing the intensity of atomic and ionic emission.A four-line method (2 atom and 2 ion) has been developed on this basis to calculate the excitation temperatures of atoms and ions and the dcgree of ionization, and hence correct for cationic interference (180, 1721). The method was successfully applied to the determination of Mn in the presence of Sr. By gradual electrical heating of a coal sample, S species were vaporized andAtomization and Excitation 15 introduced discretely into a CMP (1331).Four S species were found using an atmospheric pressure Ar plasma and monitoring at 190.027 nm. The air plasma torch of Hanamura reported last year (see also ARAAS, 1978, 8, Ref. 176) has now been used to detect Pb above an open container of gasoline, and Hg in air (537). A novel background corrector for use with this plasma, consisting of a quartz cell containing vapour of the metal being determined, is being evaluated. 1.2.3 D.c. Arc Plasmas Clearly, the availability of commercial d.c. plasma spectrometers is encouraging a growth in the literature on their applications and interference effects. Several evaluation papers have appeared. It was suggested that the commercial plasma has a sensitivity advantage over a rotating d.c.arc (see also ARAAS, 1975, 5, Ref. 1246), but a disadvantage in respect of the high rate of anode consumption (54). A comparison of the d.c. plasma and the ICP for forensic analysis concluded that the ICP offered better precision and lower detection limits, although this was not based on first hand experience (876). From a study of stray light and spectral overlap problems in the d.c.plasma/echelle spectrometer, it was concluded that these were less severe than those reported for ICP/direct-reading spectrometer systems (1741). Schmidt and Sacks (53) have compared the two-electrode plasma jet, the three-electrode stabilized plasma jet, and the gas-stablized bent-arc and noted the problems in each with sample introduction into the high-temperature regions, and plasma stability.It has been claimed that significant advances have been mad2 in the analytical capabilities of the commercial system by alteration of the electrode con- figuration (to 30" from 75"), the use of a small, 2.4mm, diameter chimney for aerosol introduction and doping the electrode streams with 25% V / V He (55, 603) (see also ARAAS, 1978, 8, Ref. 182). These modifications all seem to favour more entrainment of the aerosol in the plasma. This new system has been characterized using Hg vapour in order to minimize vaporization and desolvation effects (1 322). Using a computer-controlled stepper-motor, the emission of elements in the d.c. plasma has been mapped (604). This improved the selection of optimum conditions for multi-element analysis.The effects of easily ionizable concomitants in the d.c. plasma, the so called "salt- effects", have generated considerable interest. High concentrations of Na, Ca and Mg were found to increase line intensities and background emission, and alter the shape of the plasma (1539). It was therefore concluded that the d.c. plasma could not be used for the direct determination of metals in sea-water.Other workers were able to perform such analyses in the three-electrode plasma by adding appropriate amounts of alkali-metal salts to standards and samples (514, 960), or by buffering with high-purity Li,CO, (952), or other easily ionizable elements (1952). Barium was found to exert similar effects at the centi-molar level and self-enhancement was observed that produced non-linear calibration curves (62).A correction procedure, in which apparent concentration values were fitted to a series of simple regression equations, has been employed to correct for the effects of Ca, K, Na and Si on 19 elements in the analysis of geological waters (1595). By using a LiBO, fusion and 0.4% m/V CsCl buffer, Bankston (58) was able uniformly to minimize matrix effects in geological analyses.Experimental studies of possible solute vaporization mutual interference effects of P on Ba, Ca and Sr and of Ca on A1 have been reported (1986). Ionization buffers were used throughout. The only systematic trends observed were the suppression of Ca emission at 393.3nm by excess of Al. The extent of the suppression was approxin~ately 10% at molar ratios in excess of 20.A simple flow-injection device has been connected in line with the nebulizer flow system of a d.c. plasma spectrometer (61 8). This permitted appropriately16 Analytical Atomic Spectroscopy buffered samples of 50-1OOpl to be injected for the determination of Al, Ca, Mg and P in dental plaque and Zn in skin. As with other forms of plasma, samples may be introduced in a gaseous form. Hydride generation methods have been described for As (65) and As, Sb and Se (1 360). In the latter study, detection limits of 1, 2 and 1 ppb, respectively, were reported. Sediment samples have been heated in an induction furnace in an HCl/Ar atmosphere. The AsC1, formed was trapped and then swept into the plasma (1471). Using CaSO, to enhance the signals and suppress interference from organics, the detection limit quoted was 15 ng. Trace levels of S in various oxidation states have been determined by reduction to H,S by HI (564, 1780). The resultant gas was swept into a d.c. Ar plasma and the emission monitored in the V.U.V. at 180.7 nm. The detection limit was 10 ng S, with less than 2 min required per sample. The factors that governed the rate of H,S evolution and possible interferences were investigated. An interface for coupling the plasma to a GC has been described (454). The heated interface enabled quantitative transfer of relatively involatile organometallics. Detection limits in the range 10-8 to 10-12 gs-1 were reported. Selective detcction of Si with this system has been demonstrated for silylated derivatives (59). Examples of the analysis of complex mixtures by GC-d.c. plasma emission have also been presented (60). A portable GC-d.c. plasma was reported (538) that was capable of separating and detecting Hg species present in air and determining total Hg in air. The sample was either passed through the GC column or collected on Ag and Au before being flushed into the plasma. Other references of interest - Analysis of silver scrap by d.c. plasma: 64. Automation of a multi-channel d.c. plasma emission spectrometer: 81. Wavelength selection for a multi-element d.c. plasma emission spectrometer: 63.

ISSN:0306-1353    

DOI:10.1039/AA9790900006

出版商:RSC    

年代:1979

数据来源: RSC

摘要:

16 Analytical Atomic Spectroscopy 1.3 FLAMES While much of the work reported this year reflects a consolidation of existing knowledge, some significant contributions have been made in three areas. In the study of interference effects, new insights into mechanisms, and original experimental approaches to minimiza- tion have been offered. Several comprehensive investigations of noise and precision have allowed invaluable quantitative comparisons of different flame and instrument types.A great deal of attention has been paid to the study, development and improvement of nebulizers and in particular to micro-sampling devices, which continue to grow in popularity. 1.3.1 Fundamental Studies Few reports of new frame types have appeared this year although an investigation of a N,O/ toluene flame (2063), with a maximum temperature of 2600 K, showed impressive AAS detection limits; Pt 0.03 pug ml-1, Pd 0.04 pg ml-1, Rh 0.05 pg ml-1 and Ir 0.5 pg ml-I.Further study has been made of the O,/C,H,/He flame reported last year (see also ARAAS, 1978, 8, Ref. 207). Its capabilities for AFS have again been compared (1351) with the air/C,H, Aame and its superior quantum efficiency, 2.3-fold for Fe and 5.7-fold for Cr, demonstrated.This arises largely as a consequence of the dilution of quenching species by the He. Improvements in atomization for elements such as Ca were also obtained. At the present stage of development however, both SNR and AF signals are lower. Intriguing possibilities for AES were suggested by an investigation of effective cross-sections for the electron-impact excitation of Cu lines (1 819).Theoretical studies have included an investigation of the chemical equilibria of the species generated in the N,O/C,H, high-temperature flame used in AAS (1258). An important finding was that the equilibrium compositions were profoundly affected by theAtomization and Excitation 17 introduction of aqueous solutions.Rise velocities (1 324) and rise-velocity profiles (1 326) continue to be studied in the air/C,H, flame using the single aerosol droplet technique (see Anal. Chem., 1968, 40, 1860). Additional reference on the preceding topic - 380. The measurement of temperature in small defined regions of a flame has been achieved with a 3-line (Co) spectroscopic method (1726).The measurement zone was defined, in the horizontal plane, by the position at which single aerosol droplets were introduced and, in the vertical plane, by mounting the monochromator on its side with the slits horizontal. The flame itself could be moved in both planes by a stepping-motor to map the temperature distribution. Measurements were in good agreement (within 40-50 K) with published data for the air/C2H, flame. An interesting 3-wavelength pyrometer has been described (1 102) for use in dust explosions and flames, which has potential for analytical application.Temperature was determined by measuring the continuum emission from dust particles at wavelengths of 0.8, 0.9 and 1.0 pm. Additional references on the preceding topic - 1169, 1729, 2062.Several theoretical and experimental studies of noise and its origins in flames have been made. A standardized figure-of-merit for the effect of flame emission noise in FAES, FAAS and FAFS was derived (1650) and used to determine the choice of optimum modulation frequency. A computer-controlled spectrometer system using FAES and FAFS was employed (1653) to determine the predominant type of noise in air/C,H,, N,O/C,H,, N,O/propane, air/H, and iso-octane liquid fuel flames.The precision of single-beam and double-beam instruments was compared and the conclusions drawn that near the detection limit the single-beam was slightly superior to the double-beam instrument, but at higher absorbances analyte absorption noise was predominant and the two instrument types differ little (929, 1 199).Another comparative noise study, between different flame types, produced the conclusion to the great relief of many analysts, that, on the basis of background noise and overall precision, the air/C,H, flame was the best choice for most purposes (602). A comprehensive experimental investigation of the precision of FAES considered the properties of conventional slot and Meker burners i n a commercial AA spectrometer (619). For all types of C2H2 flames, maximum analyte emission signal, SNR, and SBR at high and low analyte concentrations were obtained at near stoicheiometric fuel/ oxidant ratios with the Meker burner.With the slot burner, results were similar except that maximum SBR and maximum SNR for low analyte concentrations required lean-flame conditions.A similar study of FAAS precision with the same instrument (464) presented curves of RSD of absorbance versus absorbance for the elements Al, Co, Cr, Eu, K, Mn, Ni, Pb, Se, Si, Ti and V. An instrumental method for improving the precision of AES (and potentially AAS) measurements in a N20/C,H, flame has been described (1966). This used one channel of a dual-channel instrument for the analyte and the second channel to monitor CN band-head emission.The latter signal was used to stabilize the CN emission by servomechanically controlling the C2H2 flow rate. The improved RSD, demonstrated in the determination of A1 by this method, was superior, by one order of magnitude, to that obtained by using CN as a form of internal standard.While not pcrhaps of immediatc analytical interest, the surprisingly large differences, up to lo%, between the molar absorbances of the isotopes 40Ca, 44Ca and 48Ca in air/C,H, and N,O/C,H, are worthy of note (1746). These were explained in terms of isotope shifts and Lorentz and Doppler broadening effects. Other references of interest - Background absorption correction by Zeeman and other magneto-optic cffccts: 906, 907, 91 3.See also Chapter 2, Section 2.2.1. Oscillator strengths for Cu: 381.18 Analytical Atomic Spectroscopy 1.3.2 Atomization and Interference Studies Research on the mechanisms of atomization and interference continues to make extensive use of the single-droplet generator. In an elegant study (1328), the flame was scanned vertically above an introduced droplet to provide emission intensity versus time information.This was applied in a theoretical model to obtain vaporization and ionization rate constants, which might offer routes to practical methods for reducing vaporization interferences. Another investigation of a single system of Cu and Zn as chloride, nitrate and sulphate employed the single-droplet technique to produce a particle of a controlled size in the flame (98, 459).Vaporization rates and particle trajectories in the flame were studied. An interesting insight into the mechanism of the buffering action of Ba, La and Sr in FAAS has been given by Shcherbakov and Karyakin (1938). They showed that the matrix element interference increased in the order of decreasing crystallographic ionic radius, i.e., Fe (0.74) < A1 (0.51) < Si (0.42).The buffering by Ba, La and Sr was attributed to improved analyte diffusion in the less dense structures formed by the large buffer cation (Sr, 1.12; Ba, 1.34; La, 1.14) compared to the more closely packed structure formed by the matrix element (see also ARAAS, 1978, 8, Ref. 810). The releasing effect of, for example, La on Mg in the presence of phosphate has been studied by using an AAS inhibition- release titration technique (1004). Additional references on the preceding topic - 140, 920, 1542, 1693, 1770. Comprehensive experimental invcstigations of interference in the determination of specific elements include studies on Cr (1897), Ru (1963) and Ta (1049). Fresh examples of specific superpositional spectral interferences have been reported; FeO molecular bands on the Cs 825.1 nm line in FAES (746) and background interference by B on the Pb 405.8 nm line (1078) in FAES and in d.c.Ar arc plasma emission spectrometry. An instrumental selective spectral line modulation approach has been used to reduce interferences in FAES (1327) (see also J. A. Bowman, J. V. Sullivan and A.Walsh, Spectrochim. Acta, 1966, 22, 205). Two flames, one as the sample emission source and the other as the selective modulator were arranged in a dual-beam system. Emission from the source alternately bypassed or passed through the second modulating flame. At wavelengths where emission from the source coincided with absorption by species in the second flame, modulation occurred.Thus an a.c. signal was generated at the spectrometer detector whenever flame background features or element spectral lines were common to both flames. By introducing pure analyte element into the second flame, selective modulation was achieved with a reduction in both narrow-line and broad-band spectral interference effects. Since the modulation occurred only for the narrow absorption-line band-width, a consider- able improvement in the eaective resolving power of the complete instrument resulted.An investigation of the profile of the Ca 422.7 nm resonance line, isolated by a selective modulation technique, has been made using a Fabry-Perot interferometer (9 14). The results demonstrated the sharpening of atomic resonance lines by selective modulation.Interferencc effects by various cations in the detcrmination of Mn (304) have been eliminated by the use of the appropriate flame conditions, i.e., by employing N,O/C,H, in place of air/C,H,, at the expense of a modest (2X) reduction in sensitivity. The perennial problem of Ca interference in the determination of Ba by FAAS was reduced by using a reducing N,O/C,H, (382) or a separated N,O/C,H, flame (751).In the analysis of CU alloys, preheating thc aerosol minimized interferences from the matrix (7 19). Schliercn techniques were used to study (1587) changes in the flames produced by the presence of organic solvents. It was demonstrated that the failure of organic solvents to give the full expected increase in sensitivity from the increased rate of analyte input could be correlated with changes in flame geometry.It has been shown (1715) that organic solvents such as petroleum products, which arc difficult to use with analytical flames, can be accom-Atomization and Excitation 19 modated by the N,O/H, flame. Improvements (10-fold) in detection limits were claimed (1833) for diethyl ether/methanol mixtures in the determination of Mg and Zn in copper and nickel salts by FAAS.The replacement of inorganic acids, such as HC1, by organic acids, such as acetic acid, has been recommended (571), and was reported to minimize the deposition of salts on the burner slot when solutions of high salt content were analysed. This method was investigated with solutions prepared by sodium peroxide fusions with organosilicon compounds in a P a n bomb, followed by dissolution of the melt in acid.Different acids, HI, HCl, HNO, and acetic, were compared. No relationship between salting-up of the burner and solubility of the salt was evident. Noise levels, however, lowest with HI, showed an inverse relationship with the solubility of the sodium salt. Other references of interest - Ca interference suppression, silicate analysis: 796.Enhancement of A1 absorbance by nitrogen compounds: 174. Interference, slag and cement analysis : 922. Mathematical interference correction procedures: 51 1, 1803, 1804. Mineral acid interferences on CaOH emission: 122. Molecular absorption spectra, Na salts: 1799. Suppression of interferences on CaOH emission: 699. 1.3.3 Devices €or Sample Introduction Some of the important parameters of sample transport and atomization have been studied in conventional pneumatic, ultrasonic and high-solids nebulizers using laser Fraunhofer diffraction measurements (1307) to provide data on dynamic particle and droplet size.The apparatus was incorporated into a commercial microcomputer-based AAS instrument and enabled rapid presentation of particle size histograms together with mean and median particle diameter for particles in the size range 2.4-150pm. The fundamentals of aerosol production and transport have been discussd (1319) and used to predict ideal design solutions for practical systems (202). 1.3.3.1 Nebulizers.The improvement of nebulizer design and efficiency has been the subject of a refreshingly systematic new look at the problem employing three different techniques (153, 1295).In the first method the solution was charged electrically, by, for example, applying an electric potential to the nebulizer tip. This produced a 63% decrease in droplet diameter. A second technique made use of the disruptive and exothermic decomposition of thermally unstable compounds, such as hydrazine, dissolved in the solution.In yet another method, by dissolving a highly absorbing dye, such as nigrosin, in the solution thermal dissolution and decomposition was encouraged. Two new pneumatic nebulizer designs of the concentric type (1204, 1365, 1596) with demountable and interchangeable components have been described. A design for a modified Babington-type of nebulizer has been reported (1738) and its operation discussed.The authors pointed out that with this type of nebulizer higher solution flow rates, 50 ml min-1 in this case, were required compared with conventional nebulizers with flow rates of about 5 ml min-1. This design, however, loses some of its attraction for trace-element analysis by using nickel-plated brass in its construc- tion, In a further study of the Babington-type of nebulizcr (546) it was claimed that the formation of a “Babington film” of sample liquid is not essential in recent designs.The same authors advocated the use of homogenates of meat, ~021, etc., with such nebulizers to avoid the use of tedious sample digestion procedures for FAAS or plasma emission analysis. While spectral interferences were found to be low with this preparative method, it would be surprising if chemical and matrix interference effects were not a considerable problem for some elements at least.20 Analytical Atomic Spectroscopy Informative comparisons of nebulizer performance (926, 1998) were carried out for pneumatic (concentric and cross-flow) types, with and without desolvation, and for an ultra- sonic nebulizer with desolvation.Quantitative data presented included comparative analyte delivery rates, pneumatic/concentric, 110 ng min-1; pneumatic/cross-flow, 181 ng min-1; rising to 900 and 81 5 ng min-1, respectively, when used with desolvation. The ultrasonic nebulizer delivered analyte at a rate of 1186 ng min-1. The limitations of desolvation for solutions with high salt contents were illustrated by, for example, a fall from 57.4% absorption, obtained with 0.4ppm Cu in aqueous solution, to 16.6% in 5% sodium chloride solution using the ultrasonic nebulizer.An impact cup interchangeable with a conventional impact bead has been used to reduce the volume of sample reaching the flame and also the droplet size with advantages for solutions containing a high salt content (1 504). 1.3.3.2 Microsampling Devices. Solution microsampling devices for FAAS and FAES continue to proliferate (160, 239, 1942), many with automatic or semi-automatic injection (97, 1763, 1808). They have also been widely reported for flow injection analysis of digests of plant materials for Co and Cu (1458), Cu and Zn (1708), and Cu and Mg (495). 1.3.3.3 Sample Zntroduction by Volatilization. The technique of volatilizing the sample into a flame for atomization has attracted further interest. A graphite furnace atomizer has been used for this purpose (928; see also ARAAS, 1977, 7, Ref, 1062). The apparatus was improved by introducing a slotted quartz T-tube into the flame as the final atomizer. The advantage was a much reduced non-specific light loss by scattering or molecular absorption compared with direct analysis by electrothermal atomizer methods.Results for As, Hg and Se were presented and applications in AFS and ICP-AES considered. Direct current arc volatilization of copper sample from graphite electrodes into an air/C,M, flame (489) has also been described. Cadmium, Pb and Zn were determined by FAAS with detection limits of 0.08, 0.7 and 0.1 1 pg g-1 respectively and the spectral interference from the copper and zinc matrix eliminated.A laser, of the type used in laser microprobe analysers, was applied to volatilize Ag, Au and Ni into an air/C,H, flame (1689) for the surface-analysis of electroplated copper sheets by AAS. The electrically heated graphite chamber-in-flame method (ARAAS, 1977, 7, Ref. 466), which is suitable for solid powder samples, continues to receive attention, mainly by Russian workers. The method has been applied to the determination of elements forming refractory oxides, such as Al, B, Ca, Mo, V and W, and in addition makes use of the reducing properties of a luminous-diffusion flame (303, 1951). The advantages of the technique for solid powder samples were illustrated in the analysis of sulphide ores, which were mixed with graphite powder and placed in the chamber.Cd, Cu, In, Pb, Sb and T1 were determined with detection limits of 7.3X 10-10 g, 3.1 X 10-11 g, 9.3X 10-10 g, 2.1 X 10-9 g and 3.4X 10-9 g, respectively. Further development of the atom-trapping concentration procedure (see also ARAAS, 1976, 6, Ref. 1288) has been reported for Cu (1464). In this technique, sample solution was nebulized in the usual way for fixed periods of time into an air/C,H, in which a water- cooled silica tube was mounted. Copper species collected on the tube were released into the flame and atomized when the cooling water was switched off. Some 50-fold gain in sensitivity was obtained for 0.01 pg ml-1 Cu compared with convcntional FAAS.The principles of the Pt-loop solution microsampler for FAAS have been discussed (1684) and the method applied to the determination of Cd and Pb in drinking water. 1.3.3.4 Injection Methods. The advantages of the direct analysis of solid, powder or slurry samples, in avoiding the problems of a sample digestion and dissolution, still attract con- siderable research despite the obvious difficulties of reproducible sampling, samplc homo-Atomization and Excitation 21 geneity and matrix interferences.Solid metal samples, in the form of rod or wire, etc. were held in a graphite rod and inserted into a flame for analysis by AAS (1751) (see also H. Ramage, Nature, 1930, 126, 279 and K. Govindaraju, J. Morel and N. L’Homel, Geosturidards Newsl., 1977, 1, 137).Aspiration of HCl dramatically increased the signal. Slurries of finely comminuted (<325 mesh) coal in a 0.5% aqueous solution of Triton X-100 were used (215, 530, 1694) for the direct determination of some 23 elements by AAS in air/C,H, or N,O /C,H, flames. Reasonable accuracy (+5-*25% error) and precision (%1-*4%) were claimed. The use of brass-bodied metal screens for sizing the coal powder must leave some doubts, however, about freedom from contamination by Cu and Zn.In comparing this with an XRF method the authors state that the total time for the determina- tion of 12 elements in 6 samples was the same for both methods. I .3.3.5 Chromatographic Sample Introduction. The use of flame spectroscopic detectors iit chromatography continues to grow.The band emission of Se, (principal bands 450-500 nm) was used as the basis for a Se detector (129). The sensitivity for Se and the quenching of emission by carbon compounds were both less than for S. The detection limit for Se was about 2x10-12gs-1. The normally exponential response of S , Se and Te detectors was linearized (329) by providing a high S background.A F-specific detector, using CaF band emission at 529nm, designed for GC (see also 2. Anal. Chem., 1972, 258, 273) has been applied to HPLC (1686). This used an O,/C,H, total-consumption burner with two aspira- tors, one connected to the HPLC output and the other to a solution of Ca(NO,), in methanol / water. A simple low-cost FAFS detector interfaced to a standard liquid chromato- graph (1400) employed a chopped Xe continuum source, a N,-sheathed air/C,H, flame, a 0.1 m monochromator, and synchronous electronic detection. Its performance was discussed and compared with a conventional molecular u.v.-absorption detector.The detection and determination of organic compounds by complexing them with a suitable metal and using a liquid chromatograph with a FAAS metal-specific detector has been discussed and illustrated by the determination of a copper-labelled amino acid, histidine (10 17).A chromatographic support treated with sodium azide and hexamethylphosphorotriamide (HMPT) has been used to concentrate carbon disulphide from air for final analysis by a flame emission method (1 854). 1.3.4 Applications of Lasers The past year has seen continued intense activity in the field of laser applications in analytical chemistry and the separate sub-section initiated in Vol. 8 of ARAAS is repeated in the present volume. A useful book cokering much of the interesting work in this field has appeared in 1979. The book entitled “Analytical Laser Spectroscopy”, contains eight chapters by different authors under the general editorship of Omenetto (1 138).A review of recent developments in tunable lasers for spectroscopy has also been published (2067) and two authors have compared the potential of several laser techniques for individual atom detection (421, 1287). 1.3.4.1 Atomic Fluorescence Spectrometry. A review of the theory and applications of laser AFS has been published (687). Further improvements in limits of detection, using pulsed dye lasers and a specially designed aerosol delivery /flame system, have been described (1 398).This new system was evaluated with respect to long-term stability and to the accuracy and precision achieved in real sample analysis. Another paper from the same group described methods used to overcome problems of molecular fluorescence and scatter observed in the analysis of NBS CRMs (1402).Problems associated with the practical applications of laser AFS have generated more interest this year and Yeung et a!.22 Analytical Atomic Spectroscopy (1349) have described developments aimed at tackling three of the major problems in this field, namely, lack of high intensity tunable U.V. lasers, light scattering, and lack of atom sources with good efficiency and good optical properties.The authors discussed the use of collision-induced non-resonant excitation, wavelength modulation, and introduced the ICP and premixed O,/H, flame as atom cells. The ICP has also been evaluated as an atom cell for laser AFS by Winefordner and co-workers (1 164, 1373). Use of the ICP with a CW dye laser was not recommended as detection limits were worse or not significantly better than those obtained using the ICP in emission mode (1164).The pulsed N,-pumped tunable dye laser was claimed however to be a useful source for gcnerating AFS signals in an ICP and has been evaluated in detail (1373). The measurement of laser AF signals using a graphite furnace as the atom cell was described by Bower et al.(1375). Both conventional furnaces and continuous-flow furnaces were evaluated. Measurements of laser AF in a furnace atomizer have also been reported by Falk and Tilch (934) who claimed a detection limit for Pb of 0.02ppb. Analytical measurements of Na AFS in flames using pulsed dye lasers was reported by Gonchakov et al. (1843) and Daily er al. (345). The former group gave a detection limit of 0.0004ppm and a working range up to 1 ppm using an air/C,H, flame, Experimental observations of the saturation behaviour of Na atoms in a variety of flames have been reported by Omenetto et al.(1348). The intensity ratio of the two AF lines for the yellow Na doublet can be significantly different from the thermal value of 2, depending on the relative values of the quenching and mixing cross-sections of the levels involved.For excitation at 589.0 nm it was predicted that the ratio would be 2 only if the quenching rate and the radia- tive spontaneous rate are much smaller than the mixing rates between the two excited levels. The ratio should decrease on going from a flame with a poor quantum efficiency to a flame with high quantum efficiency.This conclusion was supported by experimental data obtained using six different flames. Saturation using laser excitation has also been evaluated as a method for the determination of the absolute concentration of Na and Mg in air/C2H2 flames (682). The occurrence of energy level saturation using lasers has been confirmed by comparing experimental plots of AF signal versus laser power with theoretically derived expressions (725).Resonance Rayleigh scattering of laser radiation by Na vapour in shielded O2/H,/N,, O,/H,/Ar and O,/C,H,/N, flames has also been described (693). 1.3.4.2 Molecular Fluorescence Spectrometry. The fluorescence spectra of SrOH, CaOH, CrO, MnO and C, (440) and C,, CH, OH, CN in air/C,H, and N,O/C,H, flames (317, 1658) have been characterized.The spectra of flame species extend over a broad wavelength range and contribute significantly to the background signal in AFS mcasuremcnts. These observations indicate the potential of laser AFS for obtaining spatially resolved profiles of species in flames and the E P . Methods for the characterization of the temperature, density of species and quantum efficiencies have already been described (1350).A lascr fluorescence method was used to measure the rotational temperature of the lowest vibrational state of the electronic ground state of OH in an air/CH, flame and this was found to be in equilibrium with the N, vibrational temperature measured by laser Raman scattering (1099). Other references of interest - Effect of thermal variations on the spatial mode structure of a linear flashlamp-pumped dye laser: 2046.Measurement of absolute OH concentrations in low-pressure flames by laser fluorescence: 135. Spin-orbit rclaxation of Pb (SPJ by H after laser excitation: 396.Atomization and Excitation 23 1.3.4.3 Laser-enhanced loni~aiiort Spectrometry (LEI). Considerable advances have again been achieved in the use of optogalvanic detection in trace-element analysis.The principal authors in this field, who now prefer to refer to their technique as laser-enhanced ionization, have produced a stream of original (1551, 1692, 1987) and conference papers (99, 100, 574, 575, 1077, 1352, 1372, 1397). In addition the thesis of Turk is now available (1278) and two US. patent applications (1228, 1277) have appeared, which describe the apparatus and method used for galvanic detection.The method employs a tunable dye laser to promote analyte atoms in a flame or other atom reservoir to a discrete excited atomic level. Thermal ionization from this excited state occurs at an enhanced rate compared to the ground state and the enhanced ionization is detected electrically by applying a voltage across the flame and observing changes in the electrical current through the flame.Both W and Mo rods and plates have been used as electrodes and were placed 12mm apart, with the lower end 6 mm above the 5-cm slot burner head supporting the flame (1692). In Vol. 8 of ARAAS (Section 1.3.4.2, p. 22) preliminary results were reported for five elements indicating that ppb detection limits were achievable and that the magnitude of the difference in energy between the excited atomic state populated by the laser radiation and the ionization energy, referred to as E,*, had a critical effect on sensitivity.In a recent paper, detection limits for 18 elements at 28 wavelengths were reported (1692) that supported the earlier conclusions.In all cases, except for Cu, detection limits were in the ppb range, were comparable to or better than laser AFS and were remarkable for flame measurements. Most of the transitions employed originated from the ground state, but some used the low atom populations in thermally excited states. Acceptable or good detection limits were still achieved as long as the value of Ei* was small.For example Pb at 283.3nm (transition 0-35287 cm-I, Ei* 24533 cm-1) gave a detection limit of 3 ngml-1 whereas at 280.2 nm (transition 10650-46329 cm-1, Ei* 13491 cm-1) a value of 0.6 ng ml-1 was achieved, The detection limit of 100ngml-1 for Cu was ascribed to the large value of Ei* and poor performance was also assumed for elements with high ionization potentials, such as As, Cd, Se and Zn, which have not so far been measured.A mechanism for LEI has been described by means of a model that takes into account the degree of population of the excited state, the exponentially improved ionization rate from the excited state and the depletion of neutral species by ionization ( I 372, 1551). The model was fitted by a least-squares procedure to experimentally measured sensitivities for 14 elements and 23 different transitions.The investigation of ionization interferences in LEI has been reported (575, 1692). Moderately high concentrations of elements such as Na, which are easily ionized thermally, have a serious depressive effect on LET signals. The increased level of electrons in the flame causes an increase in ion recombination rates and hence a depression of signal.It also gives an increased background current, which reduces measurement precision. Serious depression by Na above 10 pg ml-1 was shown for In at 10 ng ml-1 but this was released by application of higher cathode potentials and greater tolerance was found using W plates compared to rods for the cathode. In the presence of easily ionized elements, analysis by standard addition or by using carefully matched standards, or with prior separation using ion-exchange columns (573, was found to be necessary.The application of LEI to the determination of Ni and Mn in alloys was demonstrated (1692). CW dye lasers have been compared with pulsed lasers for LEI using both flame and furnace atomizers (574, 1397). Comparison was also made between LEI and AFS detection.In both cases detection limits were reported to be in the sub-ppb to ppb range with linear dynamic ranges of 4 to 6 orders of magnitude. When using a single laser a maximum photon energy of 4.4eV is available. For elements of high ionization potential, this still leaves an energy gap, Ei*, which is too large for significant thermal ionization to occur.Although two-photon transitions with a24 Analytical Atomic Spectroscopy single wavelength laser have been observed (1692), the sensitivity was poor due to the low probability of such transitions. Attempts have therefore been made to use a second light source to promote the second step in the excitation process. New or improved detection limits were reported for Cd, Cu and Zn by use of a Xe arc continuum source or EDL light sources as supplementary photo-excitation (100).Recent work has included the use of two tunable dye-lasers pumped by a single N, laser (1352, 1987). Improvements in detection limits for 7 elements varying from a factor of 7 to 1600 were reported (1987) compared to the use of a single laser. Other reference of interest - Opto-galvanic spectroscopy in a U hollow-cathode discharge : 726. 1.3.4.4 Other Studies. Resonance ionization spectroscopy determination of Li via a three- photon process involving two separate pulsed lasers tuned to 670.8 and 610.4nm has been demonstrated (179). Li atoms were generated by photodissociation of Li vapour using a third laser. The determination of pg amounts of Na in a flame by photo-ionization has also been reported (1868). The analytical application of acoustic pulses generated in a flame following laser excitation of sodium atoms has been described (1571; see also ARAAS, 1978, 8, Ref. 8). Linear calibration was obtained over the range of 1-100 pg ml-1. A two-photon absorption technique has been proposed for the measurement of atomic 0 in the mesosphere and lower thermosphere (134).Excitation by laser radiation at 225.6 nm using two photons to populate a level equivalent to 130.4 nm resulted in fluorescence at 130.4 and 844.7 nm. It was proposed to use the line at 844.7 nm as the resonance fluorescence is strongly absorbed by ground state 0 atoms. Other references of interest - Coherent optical transient spectroscopy in flames: 132. Redistribution of population among the higher levels of Na in an O,/H,/Ar flame following laser excitation: 1256. 1.3.5 Atomic Fluorescence Spectrometry An instrument designed for multi-element analysis by Xe arc continuum source FAFS and FAES, with which the thirteen elements Ag, Ba, Ca, Cd, Cu, Fey Mg, Mn, Ni, Pb, Si, Sn and Zn were determined in lubricating oil, has been described (1733). The Xe arc source has also been used for automatic correction of the background due to light scattering (1177) in an instrument for the determination of Cd by FAFS. Detection limits of 0.5 and 0.1 pg 1-1 for blood and urine, respectively, and improvements in precision were obtained. Non-dispersive FAFS using an air/LPG flame has been applied to on-line monitoring of Mg in boiler-feed water (938). It has also been used for multi-element analysis of air-filter samples volatilized by a graphite furnace atomizer into an air/C,H, flame. The detection limits for Cd, Fe, Pb and Zn were, respectively, 0.01, 4, 5, and 0.25 pg (1578). 1.3.6 Methods Based on Molecular Emission New developments in molecular emission spectrometric methods of analysis are few. The determination of ammonium-N,, by measurement of the emission intensity of the NH species (bandhead at 336.0 nm) evolved from alkaline solution has becn reported (141). The application of various methods for the determination of S-species in air using flame photo- metric (S,) detectors have been discussed (427, 1269, 1270). Sulphate-S has been determined following reduction of sulphate to H,S using a tin-orthophosphoric acid reagent. The H,S was fed into a MECA cavity where S, emission was measured (580, 1443). The indirect determination of amines and amino acids using MECA has also been reported (1565).

ISSN:0306-1353    

DOI:10.1039/AA9790900016

出版商:RSC    

年代:1979

数据来源: RSC

摘要:

Atomization and Excitation 25 1.4 ELECTROTHERMAL ATOMIZERS With the widespread use and acceptance of ETA in routine analysis, developments in applications would be expected to be more prevalent than fundamental studies of the atomizer and atomization processes, and new methodologies. It is refreshing to find, how- ever, that this is not the case, and that this year there have been a number of papers directed at improving the performance of ETA.There have, for example, been significant develop- ments in the use of tube coatings, temperature optimization and background reduction. It would appear that there is still much scope for improvement and that any complacency over problems at this stage would be dangerous. 1.4.1 Atomizer Design and Modifications Several groups of workers have modified the design of Massmann-type furnaces to allow atomization of samples under isothermal conditions.A graphite platform, similar to that proposed by L’vov (see also ARAAS, 1976, 6, Ref. 1141), has been shown to reduce matrix interferences substantially, especially for the more volatile elements (557, 1016, 1344). An analogous approach involved the use of a wire or rod onto which the sample was deposited and dried prior to its introduction into a pre-heated graphite furnace (463, 1124, 1340, 201 1).Chakrabarti and co-workers (886, 1339, 1341, 1994) have reported enhanced sensitivity for many elements by using a tube atomizer of anisotropic pyrolytic graphite, heated by capacitive discharge and maintained at constant temperature by an auxiliary power supply.Temperatures of up to 3300K, and heating rates of up to 100 Kms-1 were achieved independently of each other, The use of anisotropic graphite resulted in a more even temperature distribution along the length of the tube. To avoid memory effects in the atomization of U, Tarui and Tokairin (636) atomized samples from Ta boats, which were inserted into the graphite tube.Additional reference on the preceding topic - 1190. A device by which direct temperature control of a furnace was achieved by monitoring the thermal expansion of the graphite within a feedback circuit was proposed by Czobik et al. (1200). Wassall (1020), however, stated that only optical feedback systems could successfully cope with the rates of temperature rise achieved by modern furnaces.Research continues on the use of metal carbide coatings, both to prolong tube life and to reduce memory effects. Norval et al. (887, 1233, 1648) employed a cathodic sputtering technique for coating tubes with metals (usually W) prior to the application of a pyrolytic graphite coating. They claimed that over 3000 firings at 3000 K could be achieved with test solutions of 2% V/V perchloric acid and 10% V/V nitric acid.Additional reference on the preceding topic - 888. There have been some interesting papers on the use of metals as atomizers. Sychra et al. (263, 898, 1563, 1564) described a simple W tube furnace, fabricated from two U-shaped metal strips, pressed together to form a tube. The furnace was claimed to give comparable performance to that of commercial graphite atomizers for most elements, but gave superior detection limits and tube lifetimes for the more refractory elements.Ohta and Suzuki (622, 1582, 2018) used a Mo microtube to determine volatile elements, using a sheath gas mixture of Ar and H, to prevent oxidation of the tube and also possibly to provide a reducing atmosphere. Additional references on the preceding topic - 409, 539, 2010.Theoretical calculations by Frigieri and Trucco (1 39) predicted improvements in scnsi- tivity when the internal shape of the tube was tailored to fit the geometry of the hollow- cathode light beam. Practical results have substantiated these predictions (see also ARAAS, 1977, 7, 26 and Refs. 719, 778).26 Analytical A tomic Spectroscopy Other references of interest - Sample introduction: I1 1, 523, 524, 889, 939, 1977. 1.4.2 Atomization Processes A new approach to the investigation of atomization processes has been proposed by L’vov and Pelieva (715, 749). Using a W probe to introduce samples into a preheated commercial graphite atomizer, they concluded that gaseous monocyanides were formed as intermediate species during the atomization of 32 out of 42 elements studied (in particular Al, Ba, Cs, Sr).Dissociation energies of Al, Ga and rare-earth monocyanides (1 81 5) were calculated by applying the second and third laws of thermodynamics, and found to be in agreement with mass spectrometric data. The feasibility of these calculations when related to conventional pulse-heated atomizers has yet to be investigated.Tessari and Torso (1771, 1916) have further extended their theoretical model, which describes atom release from graphite rod atomizers. This model assumes conditions of pseudo-equilibrium at the solid/gas interface. When the model was examined with respect to different gas atmospheres (Ar, He and H2), some inconsistency was found as to whether the major factor was diffusive or convective transport.In a H, atmosphere (8971, local equilibrium at the solid/gas interface was no longer established and atomization was found to be kinetically controlled. Falk and Thann (900) similarly described the processes occurring in the vapour above open atomizers. They concluded that vapour transport was principally diffusive and explained how such information could be used to optimize atomic signals both spatially and temporally. Chakrabarti er al.(1997) have utilized Fuller’s kinetic model (see ARAAS, 1974, 4, Ref. 1131) to describe atomization in their capacitively heated atomizer. Since this atomizer operates virtually at constant temperature, the absorbance is propor- tional to the efficiency with which atoms are initially produced. The authors intend more closely to define this kinetic model in order to design “a perfect atomizer”.Explanations of signal enhancements and depressions based on gas-phase reactions have been forwarded by Eklund and Holcombe (542, 904, 1672, 1709). They have suggested that competition for 0, traces in the gas atmosphere above open atomizers could result in an increase (or decrease) in free-atom populations.It was shown that metal-oxide bond strengths can be used to predict such changes. The controlled electrothermal heating of a graphite crucible in combination with an air/C,H, flame, by Kantor er al. (903, 1478), has been used to study condensed-phase reactions taking place within the furnace. Experimental results on various Cu, Sn and Zn compounds showed close agreement between this technique and differential thermogravimetry as far as initial vaporization temperatures were concerned.In a further study (1009), the same authors added CC1, and CF,C12 to the sheath gas of the furnace and noted that Al, Ca, Co, Cu, Fe, Ga, Mn and Ni were now vaporized at 560-600 “C. This system was seen as being useful for selective volatilization of analytes from refractory matrices.In the first part of a comprehensive study on the atomization of noble metals in a graphite furnace, Rowston and Ottaway (1 180) critically compared thermogravimetric, X-ray diffraction, vacuum deposition and thermodynamic data to support their theory that atomization occurs via evaporation of the metal only. The mechanism of atom excitation in graphite furnace AES has been clarified by Littlejohn and Ottaway (508).Electronic, vibrational and ionization temperature measure- ments wcre used to prove the existence of local thermal equilibrium in commercial tube atomizers operated under static gas conditions. It was concluded that molecular collision was the major process contributing to atom excitation, though radiative excitation was con- sidered significant when a monatomic purge gas, with molecular impurities of less than 0.01 %.was used.Atomization and Excitation 27 Other references of interest - High temperature equilibrium calculations: 101 2. Thermogravimetric studies: 899, 1862. 1.4.3 Interferences The concept of achieving isothermal conditions within pulse-heated atomizers in order to reduce matrix interferences has gained much popularity (see also Sction 1.4.1).The applica- tion of the L’vov platform to commercial graphite atomizers by Manning and Slavin (1642) for example, substantially reduced anion interferences on Pb. This type of work has also caused a resurgence of interest in the constant temperature or Woodriff-type furnace.In some comparative studies this furnace was found to give substantially reduced interferences for Co (891), Mn (1731), Pb (555, 1547, 1716) and Se (106) in a variety of matrices, compared to pulse-heated atomizers of the mini-Massmann-type, In no case was the inter- ference effect greater than 10% in the Woodriff furnace. Interferences caused by molecular volatilization during ashing steps were also reported to be less in Woodriff-type furnaces (165).Additional references on the preceding topic - 467, 556, 648, 1470, 1630, 1838, 1877. The use of matrix modification to reduce interferences has gained in popularity. Koirtyohann et al. (104) described studies of various matrix modifiers used in the determina- tion of Cd, Cu, Fe, Ni and Pb in blood, urine, waters and tissue.They concluded that although no universal reagent has been found, considerable progress towards a general reduction in interferences has been made. Some interesting spectral interferences have recently been recorded. Frigieri and Trucco (919) reported that Co and Fe showed a very strong spectral interference on Cs. It would appear that AE is still superior to absorption for Cs determinations.Iron has also caused some spectral overlap problems when Pb was determined in iron-based alloys (120). The effect was however minimized by selective volatilization of analyte and matrix. An apparent spectral interference of Fe on Se at 204.0 nm was observed by Langmyhr et al. (1494) when determining Se in whole blood. The authors commented that the interference could be reduced by measuring at the 196.0nm Se line.Additional references on the preceding topic - 645, 888, 1444, 1455, 1480, 1583. Other references of interest - Accuracy: 13 1 3. Background correction: 127, 457, 522, 1297, 1935. Contamination: 322. Solvents: 925. Tube lifetime: 1056. 1.4.4 Emission There have been several interesting developments on the use of the graphite furnace as an emission source (885).The mechanism of excitation in commercial tube atomizers has been discussed by Littlejohn and Ottaway (508) (see Section 1.4.2). The same authors showed that for instrumcnts without dynamic background correction, e.g., wavelength modulation, optimization of temperature may be necessary to achieve the best SBR (1461). A graphite furnace with additive excitation has been produced by Falk et al.(895). In this device, the vaporized sample from the graphite tube was excited in a hollow-cathode discharge. Detection limits similar to AAS values and superior to AES values were reported (see also ARAAS, 1977, 7, Ref. 1001). The authors have proposed a non-thcrmal mechanism to explain the processes involved (1688).28 Amlyrical Atomic Spectroscopy Some new equipment for graphite furnace AES has been evaluated by Papp and Bodnar (892, 1008).Different graphites and alternative furnace geometries were examined in an attempt to optimize the atomizer. Other investigations showed that modifications to the graphite tube may improve detection limits (2074). However, no tube design giving the best sensitivity for all elements has yet been proposed.Detailed studies of ionization phenomena in graphite furnaces were reported by Ottaway and co-workers (902). Calculated electron concentrations ranged from 5.2 X 10-16 m-3 at 2558 K, to 1.2X 10-17 m-3 at 2761 K. An attempt was made to produce a simple expression, formulated from the Saha and thermionic emission equations, to predict the degree of ionization under practical conditions, Several reviews of the characteristics of the graphite furnace as an emission source, which demonstrate the potential of the technique.have been published (761, 1362, 1468). Other references of interest - Applications of graphite furnace emission: 1545. Chemiluminescence measurements in a furnace: 1 10. 1.4.5 Advances in Methodology The potential of ETA for the direct analysis of solids continues to be exploited and several on-going studies as well as some novel applications have appeared this year.One of the problems often associated with solid sampling is over-sensitivity. Using less sensitive atomic lines, Backman and Karlson (1682) overcame this problem and determined Ag, Bi, Pb, Sb and Zn in steels and nickel-based alloys.Some erratic results were, however, obtained; these were attributed to sample heterogeneity. Headridge and his group have continued to demonstrate the utility of their induction furnace for the direct analysis of metallurgical samples. Ag (311), Sb and other more volatile metals (1445) were determined in a variety of iron and steel samples. Some difficulties were experienced with Sn and other metals that were retained by the matrix.A similar technique has been employed for the analysis of Bi (491) in chips of nickel-based alloys. Solution analysis and direct solid analysis of mild steels for Pb and Sb were used in homogeneity studies by Frech and Lundberg (1119). Their results indicated that even for sample weights as low as 2 mg, no heterogencity could be detected.The same authors have modified a commercial auto-sampler to accept and deliver solid samples to a furnace held at constant temperature; Bi, Ag, Cd and Zn were determined in steels with improved precision (1675). The importance of isothermal conditions and of peak area measurements was stressed in further work (1112). Several novel applications have been proposed.Nakano et al. (644) analysed Cu, pre-adsorbed on to a Dowex A-1 ion-exchange resin. Nichols and Woodriff (553) atomized trace clenients from APDC precipitates using their constant-temperature furnace. The use of ETA coupled to chromatographic systems has increased. One of the original exploiters of the technique, Van Loon, has with co-workers determined Pb alkyl compounds in air (1562).They passed the eluate from a gas chromatograph directly into a preheated graphite furnace. Copper in different amino acid complexes (436) has been similarly determined after separation of the amino acids on a silica-gel ion-exchange column. Two systems for the analysis of WPLC eluate, using Zeeman AA, have been described. In the first (1774), the continuous mode of operation was compared with a temporary storage mode, which was shown to give a more complete description of the concentration profile.The second (1964) utilized a new furnace design to dstermine organic Pb compounds in automotive exhausts. By using indium chloride band emission measured at 359.9nm (see ARAAS, 1977, 7, Ref, 1590), Gutsche and Rudiger (39) used a graphite micro-furnace as a chloride-specific detector on a GC system.As little as 1.3 ng of chlorine could be determined in this manner. Speciation studies using electro-deposition of metallicA tomizatiorz and Excitatiort 29 species onto graphite tubes were described by Batley and Matousek (195, 1192). Chromium (VI) could be differentiated from Cr(II1) by altering the deposition potential.Acidified NaCl solutions were electrolysed at 3.2-5.2V versus S.C.E. to deposit Ag, Cd, Cu, Pb and Zn on to a W wire, before atomization in a graphite furnace (1193). The method eliminated background problems and could detect 0.3 ppb of Pb. Another area of activity has been biological analysis. A novel application was described by Ottaway and co-workers (1871) who evaluated the use of electrophoresis to separate Cu protein fractions before analysis of the cellulose acctate strips by ETA.A Zeeman spectro- meter was used by Pearson and Pleban (170) to determine Se in human kidney cortex. Magnesium was added to the matrix to prevent Se losses on ashing. The importance of temperature optimization in the determination of Cd in urine samples was stressed by two groups of workers (1544, 1586).Whole blood has also been analysed for Cd (741) by placing an aliquot onto a carbon or filter paper, which was then inserted into an r.f. heated atomizer. In this work aqueous and internal standards were compared. The most novel applications of ETA have bceen reported in the field of eiiviroizmentd analysis. Thompson and Wagstaff (961) used the molecular absorption of a sample as it undergoes evaporation or slow pyrolysis to detect and characterize organic pollutants in natural waters (see also Analyst, 1979, 104, 668). The addition of Ba was found to enhance the absorption signal of B in a graphite tube furnace (502). The method was used to monitor B in natural waters with a rapid sample throughput of 10 samples h-I. No mention of memory effects was given. Airborne particulates have been electrostatically precipitated onto a graphite furnace by Torsi and Desimoni (1749) prior to analysis. L’vov and Pelieva (1839) have investigated the factors affecting the determination of C e using ETA. Ce in steel was successfully determined at the 0.05-0.23% level. Other references of interest - Application of magneto-optics: 124, 200, 912. Rare earths: 2020. Trace impurities in metallic Na by ETA: 1027. Tube cleaning: 479.

ISSN:0306-1353    

DOI:10.1039/AA9790900025

出版商:RSC    

年代:1979

数据来源: RSC

摘要:

A tumizatiurz and Excitatiort 1.5 VAPOUR GENERATION 1.5.1 Hydride Generation In the past year a review of hydride generation methods (see also Section 3.1.1.5) has appeared (2002). The use of hydride generation is no longer confined to the original AAS methods. The introduction of hydrides into the ICP, MIP and d.c. arc plasmas is reported in Sections 1.2.1.4, 1.2.2.2 and 1.2.3, respectively. Labelled 75Se was used to confirm expressions derived to quantify the effects of apparatus design, atomization efficiency and operating conditions on signal absorbance and peak area (967).A patent has been published (1265) that described a new type of heated quartz measurement cell with end pieces made of heat resistant materials such as quartz, ceramic or graphite. The function of the end pieces is to cool down the hot H,, which is formed in the cell, and thus prevent its ignition when it comes into contact with the air.There has been increased interest in the determination of the volatilized metals by nun-dispersive AFS. Nakahara et d. have dcscribcd methods based on NaBH, reduction, and transport of the hydride to an Ar/H, flame where A F was measured non-dispersively following excitation with an EDL.They have applied their apparatus to the determination of As (412), Bi (167, 1589) and Sb (797, 1556), and described in each case, the optimization of conditions and identification of inter-element interferences, Azad et al. (510) reported the30 A 11 a1 y tical A tornic Spectroscopy use of a non-dispersive AFS method for the determination of Se in soil digests.Measure- ments were again made in an Ar/H, flame. Co-precipitation of Se with lanthanum hydroxide or masking with Te have been recommended as methods for the elimination of Cu interference (510, 713). Continuum source AFS has been applied to the determination of metal hydrides formed by NaBH, reduction using dispersive (572) and non-dispersive (wide bandpass interference filter) measurement (573).The Ar/H, flame was used for atomization and a 300 W Eimac Xe arc lamp for excitation. In the non-dispersive measurement system, multi-element determinations were made by separation of the hydride species in a tube filled with gas-chromatographic packing materials. Electrochemical reduction, of As to ASH,, has been used in a non-dispersive AFS method (34), and for the conversion of Sn to SnH, in an AAS method (1835).In both cases a quartz tube atomizer heated to 700 "C was used. Several detailed interference studies have again been reported (1 390, 1882, 1893) and one paper (1390) included some useful hints on methods that can be used to reduce inter-element effects. Taga et al. (1805) described an interesting method which can be used for the determination of Te(IV) and Te(V1) in mixtures.When NaBH, was used on its own, only Te(1V) was reduced to the hydride and determined. Addition of TiCl, as a pre-reductant allowed the determination of both oxidation states of Te. Other references of interest - Antifoaming agent for As in urine determinations: 1980. Automation: 1491.Determination of Sn in a long path absorption tube in a N2/H2 flame: 1779. Use of enhancing reagents in Pb determinations: 632. 1.5.2 Mercury Determination Papers on this subject (see also Section 3.1.1.4) continue to appear in considerable numbers and many of them include minor modifications to the apparatus or procedures used for the cold vapour AAS method, particularly with regard to automation.Two new AFS methods have been described both involving non-dispersive detection of the Hg AF signal (411, 1157). In one method, Hg was electrolytically deposited from solution onto a gold cathode and subsequently released by heating the cathode at 700 "C in a stream of He (1 157). A linear response from 20 pg to 2 p g of Hg with a detection limit of 0.7 pg was achieved.The method was successfully applied to biological material and natural water samples. In the second procedure (41 I), the usual reduction by SnCl, was used and dispersive and non-dispersive AFS methods were compared, The non-dispersive method was linear over the range from the detection limit of 0.05 ng (0.003 ppb) to 1 pg. Non-dispersive AAS methods have been described by Hoffman et al.(1656) and Fuwa et al. (790, 915) that made use of the more sensitive Hg absorption line at 184.9 nm. In both cases the apparatus consisted simply of a Hg lamp [discharge lamp (1656) or EDL (790)], a long-path absorption cell and a V.U.V. sensitive photomultiplier tube. Considerable improvements in sensitivity were claimed in comparison to measurements at the inter- combination line at 253.7 nm.For example (91 5), a characteristic concentration of 0.29 ng (1 5% absorption) and a detection limit of 0.05 ng were achieved for 0.5 ml of solution. The factors affecting the shape of peaks in the cold vapour AAS determination of Hg have been investigated and amalgamation was proposed as a means of overcoming problems due to the variable rate of release of Hg from the reduction cell (1665).Collection of Hg released from the reduction cell on activated charcoal, Au and Ag in various forms has been the subject of renewed interest as a means of increasing the sensitivity of the AAS method. Activated charcoal appears to be the least satisfactory (957,A tomizatioii and Excitatiott 31 1614) as it shows considerable memory effects, slow and incomplete dcsorption, a high affinity for interfering volatile organics (957) and poorer sensitivity than other materials (1614).The use of Ag-coated quartz wool was recommended by two groups of workers (76, 1614) and Au-coated quartz wool by others (1581, 1664). Release of Hg occurred at 650-800 "C. The Au-coated quartz wool was reported to be more efficient for direct collection of Hg from air than was Au wire (1664), and was "nearly" quantitative at flow rates up to 10 1 min-1 and temperatures of 50 "C (1581).Thc use of very thin films of Au on sea sand was preferred t a the same material coated with Ag, as the latter did not retain R,Hg and RHgX was only partially adsorbed (957, 1462). Au or Ag liners applied to graphite furnaces were also found to give improved sensitivity for the determination of Hg by AAS (1566).A home-made electrical furnace was used as an AA detector for the GC determination of alkyl-mercury compounds in fish tissue (1463). A radiotracer study using 197Hg has been used to demonstrate the extent of Hg losses during analysis and the trapping of Hg in a vapour generation apparatus (1943).Other references of interest - Background correction using the wings of the broadened 253.7 ng Hg line: 1941. Comparative study of NaBH, tablets and SnCl, solutions: 1936. Dzterminations of Hg by a Au film Hg detector (resistivity measurement): 2053. 1 S.3 Methods Based on Molecular Absorption Some authors have this year re-discovered the possibility of measuring molecules, particu- larly those containing nitrogen, in the cold vapour or hydride AAS cell by means of their molecular absorption (see ARAAS, 1976, 6, Ref. 1351). Ammonia has been measured at 201 nm with a continuum source or with EDLs with lines in the appropriate region, such as those of As, Pb, Sb or Se (164, 718, 1364). Nitrate and nitrite were determined by prior reduction to NH, (164, 1364). A nitric oxide (NO) hollow-cathode lamp was used as a light source for the measurement of NO in a cold vapour measurement cell (948). The (0, 0) band of the NO molecule at 227nm was used and the light beam was split both in time and space to correct for drift and scatter. Internal calibration was achieved by use of a sealed quartz cell of known length, which could be tilted into the light beam, and contained a fixed concentration of NO. Similar procedures to those described above have been adopted for H,S, SO, and thiosulphate (718, 1364). Boron has been determined by generation of BF, by reaction with calcium fluoride and sulphuric acid. In a high-temperature flame, AA of B, emission of BO, and molecular absorption of BF were all observed (164).

ISSN:0306-1353    

DOI:10.1039/AA9790900029

出版商:RSC    

年代:1979

数据来源: RSC

摘要:

CHAPTER 2 hation 2.1 LIGHT SOURCES The number of applications of lasers as light sources in atomic spectrometry continues to increase, and these are reported in the Sections 1.1.2 and 1.3.4. To justify the general use of AFS rather than AAS, intense stable light sources with good long and short term stability are required. The limitations imposed by currently available sources are largely responsible for the lack of popularity of AFS.EDLs often provide sufficient intensity, but they have gained a reputation for poor stability compared with HCLs. The addition, in 1965, of auxiliary electrodes to HCLs provided an increase in spectral output, but a major limitation of these boosted discharge lumps was that the proximity of the auxiliary electrodes produced a high concentration of charged species in thc region of the sputtering (hollow cathodc) discharge. This limited the magnitude of thc boosting current that could be applied, since excessive line broadening and self-reversal occurred at currents in excess of 100mA.This limitation has been overcome in a demount- able boosted discharge lamp described by Sullivan and Van Loon (490), in which thc water-cooled cathode was in the form of a disc.The charged species formed by the sputtering discharge were swept from that region by a flow of Ar prior to additional excitation by the boosting discharge; thus electrical interaction was minimized. This allowed boosting currents up t o about 500mA t o be used, resulting in high output intensities over narrow line profiles due to the low sputtering currents used.Calibration graphs obtained with this lamp for FAAS showed improved sensitivity and linearity. Detection limits for FAFS were better than those obtained with the old-style boosted-output lamps. A later version of the new lamp was described, which was more suitable for FAFS because the window was placed closer to the discharge (1559). This resulted in a higher numerical aperture (approximately f / 1) and hence further improved fluorescence sensitivity. This lamp had a shorter warm-up time than those of commercial EDLs and non-dispersive FAFS performance was at least as good.Normally, the most successful line sources for volatile elements such as As and Se are EDLs, but a new type of sealed vapour discharge lamp developed by Gough and Sullivan (799, 1678) was reported t o be especially suited t o these elements.The lamp, known as a control!ed temperature-gradient lamp consisted of a vertically mounted tube with an electrode sealed into each end. In operation the volatile element vapours rose slowly from the bottom of the lamp (the anode) and a furnace surrounding the tube controlled the vapour pressure and thus prevented condensation on the cathode.A stable narrow-line output was obtained with reported intensities five times higher than those of EDLs. The performance of the lamp was demonstrated by a detection limit of 16 ngml-1 for As by non-dispersive FAFS. It is well known that the pulsing of hollowcathode Zumps enables higher spectral output to be obtained without serious line broadening.A 6-element HCL was pulsed at 200 mA (duration of pulses 3.2 ms) and provided FAFS detection limits for Ag, Au, Co, Cu, Fe, and Ni of 3 X 10-4, 1.5X 10-4, 6 X 10-4, 4 X 10-5, 6 x 10-4, and 1 x 10-4 ppm, respectively (1950). A circuit for a pulsed HCL power supply has been described (1743). Demountable HCLs frequently employ water-cooling of the cathode to give narrower lines at higher operating currents.Water-cooled HCLs for As and Se (633) were claimed t o have much 3334 Aizdlytical Atontic Spectroscopy reduced warm-up times (only 2-3 min) compared with conventional lamps, and to yield very low detection limits for AAS; e.g., 22 pg for As (197.3 nm) and 40 pg for Se (196.0 nm) with ETA. The reported detection limits of 1.3 and 0.74 ppm, respectively, for these elements in an air/C,H, flame were, however, worse than those normally obtained using EDLs.A further improvement by the same authors (634) replaced the Ne fill gas of the As lamp with a mixture of Ne and H,. They reported enhanced emission, 7-10 times the intensity of a conventional HCL (via the intermediate production of ASH,), which gave a detection limit of 4pg by ETA-AAS.The effect of HCL line-widths on AAS calibration graphs has been investigated (804). Additional references on the preceding topics - 420, 606, 16 13. Commercial electrodeless discharge lamps are more often coupled to r.f. generators than to traditional microwave resonant cavities. Larkins (1 191) has evaluated some commer- cially available r.f. powered EDLs as sources for non-dispersive FAFS.They provided high-intensity narrow spectral lines, and although warm-up times were long (30-60 min) little drift was observed. Walters and Smit (935) found that r.f. powered lamps required thermostatted air sheathing for temperature stabilization. They studied the effects on cmission line profile of temperature, amount of material in the lamp, variation of forward power, and electronic modulation, Peak performance was obtained when the lamps were partly situated in the excitation coil and partly in the thermostatting jacket.These authors have also described a 150 MHz ref. generator for use with EDLs (937). Microwave EDLs acquired in the past a reputation for poor stability. More stable lamps have however been produced by a Simplex optimization of 10 parameters involved in their construction (1 182). Detection limits obtained with these lamps for FAFS were the lowest reported to date.A review of microwave EDLs (441) incorporated a study of fill-gas pressure, amount of filling material, temperature, operating power, etc. Additional references on the preceding topics - 154, 368, 759. The use of an inductively coupled plasma as an excitation source for AFS was investig- ated (1851). It was extremely versatile, since to change elements it was only necessary to spray a different salt into the plasma.Detection limits were generally poorer than those obtained with conventional AFS, but the authors suggested the use of an ellipsoidal reflector behind the plasma to increase the solid angle of emission detected, thus providing better analytical sensitivity.The high cost of an ICP would preclude its use merely as a light source, but in specific instances where line spectral interferences occur in ICP-OES, the fluorescence technique could reduce or eliminate them. The pulsed flashlamp continuum source of Human and Butler (see ARAAS, 1977, 7, Ref. 671), which consisted of a He jet guided spark discharge, has been evaluated for AFS (933). A 5-fold improvement in the detection limits for Au and Pb, compared with those obtained with a 150 W Eimac lamp, was reported. Other references of interest - Continuum source AFS: 413. Flow lamp as a line source: 1662. Laser induced opto-galvanic spectroscopy in a hollow-cathode discharge : 726.Mercury (1 85.0 nm) discharge lamp: 158. Reviews of light sources: 423, 1376, 1969. Selective modulation for sharpening resonance lines: 9 14. Xe arc source correction for light scattering: 1177.Iirstrumentation 35 2.2 OPTICS 2.2.1 Background Correction A lamp combining H, and W sources in the same envelope has been reported, which gave coiztiiiuous spectral emission in the range 190 to 900 nm (1 123).Thus, background correction was extended to those elements with wavelengths greater than 350 nm. Errors in background correction with an ETA have been observed when the radii of the HCL and H, lamp beams were different (635). Wavelength modulation by displacement of a quartz refractor plate is frequently used in emission spectrometers for background correction.A stair-step waveform applied to the plate driver causes a discontinuous wavelength sweep across each analytical line. A digitally programmable waveform generator (1 325) allowed either the complete wavelength range to be swept, or, if the background had already bccn characterized, only the specific wavelengths needed to determine the background were measured; thus a significant saving in analytical time was accomplished. A crystal controlled time-base then allowed each wavelength to be integrated for up to several seconds.The self-drive function generator also providcd a saving in computer overheads, since the computer was only required to collect and process data and not to generate the waveform, A novel method of wavelength modulation for FAFS used a rotating light beam chopper whose four quartz quadrants of different thicknesses provided different degrees of refraction.Square-wave modulation was achieved with a fixed wavelength-scan range (1 374). Additional reference on the preceding topics - 209. Several papers have appeared on the use of Zeeman-eflect AAS for providing back- ground correction when determining trace elements in biological materials by ETA-AAS (170, 612, 613, 909, 1245, 1437, 1785, 1973).Stephens and Murphy (313) have investigated the possibilities of Zeeman background correction in cases of variable background absorp- tion over the spectral multiplet. Additional reference on the preceding topic - 910. Other references of interest - Background correction with photodiode array: 863.Regulated H, lamp power supply: 2047. 2.2.2 Optical Systems A major source of stray light in ICP-OES can arise from the intense cmission lines of Ca and Mg. A band-reflection interference filter centred at 398nm was used to eliminate the Ca 393.4 nm and Mg 396.8 nm lines (1 153). This filter was mounted ahead of the polychromator entrance slit, but where the source of stray radiation was a number of lines or bands spread over a wide wavelength range, band-transmission filters ahead of the individual detectors were used.Wohlers (614) found that although holographic gratings in polychroma- tors reduced stray light generally, interferences from Ca and Mg were not reduced signifi- cantly, It was concluded that the only advantage of holographic gratings was to eliminate ghosts, and this did not justify their general use with KPs.Stray light in FAFS originates from both the source and the flame. Michel et al. (1178) used a double monochromator to reduce flame stray light, the extent of the reduction was dependent on sample type. Source scatter was still significant, however, especially when an air/H, rather than air/C,H, flame was used.When vidicon tubes are used for simultancous multi-wavelength detection, a major limitation is the poor resolution when viewing a wide spectral range. In attempts to obtain3h Analytical A tomic Spectroscopy sufficient resolution, details of some interesting modifications of polychromafors have been published. A vertical array of 6 small mirrors mounted aftcr the diffraction grating of a 0.25 m Czerny-Turner polychromator divided the u.v.-visible spectrum into 6 different 105nm segments (2007).Each segment was then displayed along the horizontal axis at a different vertical position of the 2-dimensional imaging detector. The system provided a spectral resolution slightly better than 1 nm over the range 200-800 nm, which was adequate for molecular spectrometry but would still allow significant spectral interferences if used for multi-element AES. The modification used by Busch et a!.(1707) involved reversing the optical path of a 0.5 m Czerny-Turner polychromator. A multiple entrance slit assembly was placed in the exit plane of the polychromator and this permitted selected spectral regions of 40 nm to be imaged on a SIT vidicon detector mounted in the focal plane of the entrance port (see Section 2.3).Echelle monochromators provide much better resolution than do conventional mono- chromators, but suffcr from “peaking” of the spectral efficiency in the centre of cach ordcr rangc. It has been found that thc efficiency in thc overlap region between o r d m is less than 50% of the maximum on a commcrcial spectrometer (56, 1747).Additional reference on the prcccding topic - 205. A microcomputer-controlled monochromator accessory module, consisting of a pro- grammable exit slit mechanism and a PMT mounted on a moving carriage (453, was attached to a commercial programmable monochromafor. Insertion of a beam-splitter into the optical path of the monochromator produced 2 focal plancs of radiation; one was dctccted via the normal exit slit assembly and the other via the accessory modulc.T h i s systcm could be used for simultaneous dual-element AES, for dctcrmining onc clement with an internal standard, or for simultaneous background correction. Wavelength modulation can compensate for spectral interferences and scatter of exciting radiation in AFS, and can provide increased SNR.This feature has been incorporated into a prcviously described continuum source multi-elemcnt AFS / A E S instrument (see ARAAS. 1975, 5, Ref. 1237) by mounting a quartz rcfractor plate in the slew-scan monochromator (2013). Elements such as Na and K with high wavelength resonance lines (i-e.,, giving pre- dominantly emission signals) were determined with bcttcr SNR than when amplitude modulation of the light source was used.The time-constant of the photon counter, however. prevented thc USC of wavelength modulation frequencies greater than 12.5 Hz and this was not rapid enough to minimize flame background flicker noise. Also, focussing of the optics was adversely affected by thc quartz plate. An improved optical system has becn described (912) for an ETA-AAS system utilizing the Furuday e&ct (see ARAAS, 1978. 8, Ref. 1074). Additional references on the preceding topic - 124, 200, 912. An ingenious application of fibre optics exploited the variation of the speed of light with wavelength through a long optical fibre to provide time-resolved wavelength dispersion (1 363); hence multi-element analysis with a single detector was feasible.A dual-beam arrangement used 2 fibre optics of unequal length to present the sample and reference signals sequentially at the detector. In a second type of instrument a number of optical fibres of different lcngth were used to transmit spatially dispersed light to a single PMT. Other references of intcrcst - Coma dispersion in an Ebert monochromator: 1100.Glass capillary arrays for V.U.V. windows: 1101. Modified spectrometer for timt, wavelength, and spatial resolution of transient signals: 67. Optical system for improved K determination in ICP-OES: 562.Znstrumen tation 37 2.3 DETECTOR SYSTEMS Rapid-scanning photoelectric detectors (e.g., diode arrays and vidicons) generally give poorer detection limits than do PMTs for atomic spectrometry.This is due to their low sensitivity and, in some cases, readout noise associated with scanning the detector. Most workers have favoured their use in multi-element AES rather than AAS, particularly in recent years when using ICP emission sources: though a limitation is the rather narrow spectral range (typically 40nm) that can be viewed if resolution i s to be adequate. The lower resolution requirement of line-source AAS enables a spectral range up to approxi- mately 170 nm to be viewed, and thus elements with resonance lines in the range 200-370 nm could be determined simultaneously.Multiplexing line sources is however difficult, and the spectral lines from a multi-element HCL are often emitted with widely differing intensities.The limited dynamic range of AAS compared with ICP-OES is also a problem for multi- element analysis. Most of the recent work has been directed towards computerized data processing, and data reduction with some associated improvements in analytical performance. Codding (738) examined the precision obtained with a photodiode array AA spectro- meter. The use of a computer for data acquisition and reduction gave precision that was generally similar, though somewhat inferior to, conventional detection systems.Bubert et al. (807, 1473) found that with their 5-element diode array spectrometer (see ARAAS, 1978, 8, Ref. 1065) the SNR was wavelength dependent and they claimed that when high value feed-back resistors were used it was similar to the SNR obtained with PMTs.They used the detector with a GDL for determining Cs, K, Li, Na, and Rb in powdered rock samples with detection limits of 12, 0.3, 0.05, 0.5, and 3.6 ppm, respectively. Also, Al, C, Mg, 0, and Si were determined in limestone. Simplified circuitry and much reduced computational equip- ment have now been described for this equipment (1687). An array of 20 photodiodes with the provision of automatic background correction was used by Boumans (863) as a detector in ICP-OES.Any three of the photodiodes were chosen such that the centre one coincided with a spectral line, while the other 2 detected background, which was thcn electronically subtracted. Diode arrays do not suffer the lag problems of vidicons, and therefore they can be used with pulsed light sources and with ETA devices.Resolution of 0.1 nm with a spectral range of 102nm was claimed (534, 549) when two multiplexed high intensity pulsed HCLs were used for the simultaneous determination of 6 elements by ETA-AAS with independent background correction. Intensified diode arrays were evaluated for multi-element FAES, FAAS, and FAFS by Ingle (198, 734). Using pulsed light sources a 512-point spectrum was obtained in only 5ms. Additional reference on the preceding topic - 57.The first reported use of vidicon tubes for multi-element FAES by Busch and Morrison (ARAAS, 1973, 3, Ref. 623) achieved adequate resolution only by limiting the spectral window to 40 nm. Busch et al. (1707) have now improved the versatility of the system for FAES by using a polychromator in reverse so that the SIT vidicon was mounted in the entrance slit position, while a multiple entrance slit asscmbly in the exit plane allowed selected 40nm windows to be focussed on to the detector.The advantage over the previous system was that any number of 40nm windows could be multiplexed at the detector, and hence careful selection of windows would permit more elements to be determined simultaneously without spectral interference. Detection limits were poorer than previously obtained with this detector and conventional spectrometer, but the new system used fibre optics and their low light throughput was doubtless a disadvantage.Hoffman and Pardue (2007) were able to detect the entire u.v.-visible range (200-800nm) simultaneously with a silicon target vidicon by using a modified polychromator that gave a 2-dimensional stacking of 6 separate 105 nm spectral segments (see Section 2.2.2). Resolu- tion was no better than 1 nm, but if the range was limited to (say) 40 nm pcr segment as38 Analytical Atomic Spectroscopy with thc Busch system, resolution might be sufficient for AES.A limitation was the extra time required to scan 6 segments.A SIT vidicon has been used in conjunction with a slew- scan programmable monochromator for sequential multi-element ICP-OES (1 78, 862). Spectral windows were only 5nm wide and apparently the only reason for using this detector rather than the conventional exit slit/PMT arrangement was to eliminate the need for accurate positioning of the exit slit on the analytical peak; this presumably was at the expense of SNR.An echelle spectrometer with a vidicon detector previously described by Wood et nl. (ARAAS, 1975, 5, Ref. 1377) has been used with a GDL (484, 2054). Additional references on the preceding topic - 825, 827. Thc improved performance of imnge dissector tubes compared with other rapid-scanning devices was described by Pardue and Felkel(206) who used an IDES for multi-element AAS and d.c.plasma OES. Emission performance was similar to that using conventional optics and a PMT, while spectral resolution of 0.04-0.09nm was claimed. Similarly, an IDES has been reported to give detcction limits for continuum source FAFS comparable to those obtained with PMTs (1 659). A computer controlled rapid-scanning FAAS spectrometer with an ID mounted in the focal plane of a 0.5 m Ebert monochromator was described by Aldous (950).A 200 nm spectral window was covered for each grating position, and the instrument was successfully used for the multi-element analysis of potable and waste waters. When a photon counting system is to be used for analytical measurements, characteris- tics of the transfer function relating measured count rate to incident photon flux are important.Increased output linearity can be obtained by adjusting the fraction of the pulses passed by the discriminator, but at the expense of stability and sensitivity. Darland et al. (2000) examined several different photon-counting systems as an aid to optimizing the parameters for given applications.Measurements of pulse-height distribution and linearity wcre shown to provide valuable information about the optimum operating parameters under different experimental conditions, Conventional photon-counting systems are generally considered less suitable than conventional current-mode techniques at high radiative fluxes because of counting losses resulting from pulse overlap. An amplifier / discriminator lprescaler module has been described (2001) which was capable of count rates of greater than 90 MHz and therefore to some extent overcame this limitation.Nau and Nieman (536) solved this problem by combining photon counting and the conventional current-mode detection into a single unit. The instrument automatically switched from one mode t o the other at a pre-determined light level.Instrument control signals, including the selection of photon counting or conventional current mode, amplifier gain, calibration, and counter time-base were provided by hard-wired logic within the instrument, though either manual override or computer interfacing were also possible. Niemczyk et al. (2008) studied the effects of PMT voltage, discriminator setting, and temperature on SNR in photon counting with a PAR Model 1120 amplifierldiscriminator and several commonly used PMTs. They found that under the typical low-light-level operating conditions, the best SNR characteristics were obtained with the highest possible PMT voltage.Cooling the PMT was not considered worthwhile owing to the small improvement in SNR obtained.Resonance detectors contain a low-pressure cloud of analyte atoms that absorb the radiation to be detected; the fluorescence radiation from this cloud is measured by a PMT at right angles to the incident radiation. These dcviccs have good optical efficiency and very high resolving power without the need for a separate monochromator. However, they have never achieved great popularity for AAS because all the atomic absorption lines of an element are detected, and consequently sensitivity for those elements with complex spectra is degraded.Further, as a separate detector is required for each elemcnt this implics high cost. A versatile resonance detector that allowed interchange of elements has been describcd (624). The detector consisted of a flow-through furnace into which desolvated salt particlesInstrumentation 39 were introduced at a low gas flow-rate from an ultrasonic nebulizer system.When an Eimac continuum source was used for AAS, the sensitivity obtained was better than usual for continuum source, but worse than that with a line source. A resonance detector has also been used with a GDL (811, 812). In this case the atomic cloud was produced by sputtering from a cathode containing the elemcnt of interest. Atomic emission interference was eliminated by a pulsing technique.A 4ms current pulse was applied to the detector, which produced an atomic cloud of relatively long lifetime (20-40 ms). By using a gated system, the fluorescence from this cloud was measured a few ms after termination of the current pulse, when atomic emission had subsided almost to zero but the concentration of ground-state atoms was still high.A resolving power of approximately 500000 was obtained. An advantage was that the GDL and dctector both opcrated in an inert gas at low pressure, and so elements with resonance lines in the V.U.V. could be analyzed (e.g., C, P, and S in steel). Multi-element analysis could be accomplished by mounting more than one cathode in the detector and pulsing the cathodes sequcntially.Evaluation of a charge-coupled device as a multi-element detector: 71. Review of new detector systems: 1830. Other references of interest - 2.4 DATA PROCESSING Spectrography, when manually measuring line densities on a photographic plate, can be time consuming and more prone to errors than is OES with photoelectric detectors, With the availability of modern low-cost computers and microprocessors a number of workers have automated these photometric measurements and realized marked improvements in data-processing efficiency. Golightly (6) interfaced a scanning microphotometer to a mini- computer, which rapidly located up to 400 spectral lines, calculated background relative intensities and extrapolated concentrations from stored second-degree polynomial coeficients that described each analytical curve.By using this system with a d.c. arc spectrograph, 64 elements could be determined in 15mg samples of silicate rocks. Bettison and Bundy (783) described a system that allowed a plate to be scanned for the location of 672 lines; the subsequent calculations were completed in 2.5 h plus 30 min operating time.Analogous manual processing by an experienced operator would have taken 6-8h. A Zeiss Schnellfotometer has been automated (824) by interfacing it to a 40 K microcomputer and a floppy disk unit. In addition to a considerable time saving, an improvement in precision was also claimed, Boumans and Bosveld (858) used a computerized microphotomcter in conjunction with a 3.4m Ebert spectrograph for ICP-OES.It was found that the N.B.S. Tables of Spectal Line Intcnsities could be used for line selection provided that appropriate transfcr factors were used to convert the N.B.S. intensities into ICP scnsitivities. Thus, the rclative sensitivities of 452 ICP lines of 71 elcments were computed, together with detection limits for 377 of these lines.The sensitivities of spectral lines of concomitants that interfered with thc most senstive analytical lines were also determined. Computer control of direct reading spectrometers performs several functions, including setting source and software parameters, calibration, data acquisition, data reduction, and outputting the data in suitable format.In addition, the computer may initiate test procedures to ensure that various sections of the spectrometer are operating within specification, and make background corrections and corrections for other interferences. A general discussion of software requirements for performing most of these functions has been prcscnted (1383), and customized systems have been described for ICP-OES (589, 1019) and spark source or ICP-OES (60 1).A time-shared software system for several direct-reading spectrometers was reported (1 384) that allowed FORTRAN programs to be executed simultaneously with40 Analytical Atomic Spectroscopy instrument-control programs. A general purpose minicomputer could control up to 4 spectrometers from 1 or 2 independent graphics terminals.Microprocessor control of commercial AA spectrometers is now standard on the more expcnsive instruments. Several systems have been described (282, 1021, 1957, 2005) including two that had facilities for processing transient signals obtained with electrothermal atomizers (96, 130). The Perkin-Elmer Model 5000 AA spectrometer (see ARAAS, 1978, 8, Section 2.4.2), itself a microcomputer controlled instrument, was interfaced to an external computer (79, 1045).This provided increased capabilities, such as high-speed characteriza- tion of transient signals, automatic background correction in FAES by averaging readings either sidz of the analytical line, and storage of operating parameters. The interfacc was suitable for computers using either the BASIC or FORTRAN languages.Additional references on the preceding topic - 483, 2069. Other references of interest - Algorithm for use with a programmable calculator to process AES data: 1465. Confidence limits for calibration curves with non-uniform variance of data: 2051. Correlation and Fourier transform methods for measurement and analysis of spectral data: 61.Data collection for a microdensitometer: 287. Factors affecting line choice in spectrography: 147. Mathematical expression for the emulsion calibration curve : 1724. Microcomputer controlled monochromator accessory module for dual-wavelength AES: 455 (see also Section 2.2.2). Microprocessor controlled readout system for PMTs: 597. 2.5 COMPLETE INSTRUMENTS 2.5.1 Emission Instruments Plasma source direct readers are now firmly established for routine multi-element analysis.Disadvantages, however, are the compromise operating conditions necessary when several elements are determined simultaneously, and the difficulty of quickly changing elements in the analysis programme, An emerging trend is towards compact and more versatile instru- ments where rapid sequential multi-element analysis is accomplished by using a program- mable slew-scanning monochromator.These instruments are likely to be competitive with AA spectrometers in many cases, and if more than 5 elements are being determined per sample the ICP instrument can provide a faster sample throughput than a fully automated AA spectrometer (548, 879). In addition the versatility of a scanning monochromator allows alternative lines to be easily selected in cases of spectral interference.Perkin-Elmer have produced a dual-purpose ICP-OES /FAAS instrument by coupling a Plasmatherm ICP to a Model 5000 AA spectrometer (1050). The instrument has a stepping-motor driven monochromator, automatic background correction and it is interfaced to an external com- puter.Detection limits with the ICP were generally equal to or better than FAAS and fcwer chemical interferences were evident, but with a spectral band pass of 0.03nm some spectral intcrfcrences were cncountcrcd. Claimed precision was better than 1 %. A rapid-scanning computer controlled ICP spectrometer has been developed by Tnstrumentation Laboratory (551, 864, 865). The programmable doublc monochromator is able to step-scan the spectral range 189-900 nm in only 13 s.The avcrage time to drive from one wavelength to the next is only 3 s, and when each line is integrated for 2 s, 10 elements can be. determined per min. The double monochromator (resolution 0.02 nm) is claimed virtually to eliminate stray light and other types of spectral interference can be compensated for by automatic background correction, which measures and subtracts the background onInstrumentation 41 both sides of the analytical line.An optional second double monochromator allows the number of elements in a given time to be doubled, or it can be used for monitoriiig an internal standard. The optimum viewing position in the plasma can be selected for each element as part of the analysis programme.Haraguchi et al. (178, 862) described a pro- grammable monochromator with a SIT vidicon detector coupled to an ICP source (see Section 2.3). Additional references on the preceding topic - 343, 561, 1300. A 1.5 m Paschen Runge type direct-reading spectrometer has been designed (101 11, which it was claimed allowed the analytical wavelcngths to be changed far more rapidly and easily than in conventional instruments. This instrumcnt uscd dual holographic gratings giving a spectral coverage from 180-500 nm with a linear dispersion of 0.27 nm/mm.Other references of interest - Automatic sampler for a commercial flame photometer: 691, Automatic sampler for a d.c. plasma echelle spectrometer: 81, 208. 2.5.2 Absorption Instruments The multi-element A A spectrometer developed by Salin and Ingle (ARAAS, 1978, 8, Ref. 125) has now been described in more detail (136). Radiation from HCLs, sequentially pulsed at 12.5 Hz, was multiplexed and directed through a monochromator. A mask containing appropriate exit slits was mounted in the focal plane to allow 4 elements to be determined. All radiation was then focussed by means of a mirrored funnel onto a single PMT.The signal for each element was distinguished and integrated by a time-multiplex procedure. The performance of the instrument was evaluated (137) and detection limits were within a factor of 2 of detection limits obtained by conventional single-channel AAS. The poorer SNR with the multi-element system was attributed to stray light, the use of beam splitters, and the pulsing cycle that reduced absolute light levels and hence caused the relative shot noise to increase.The system was also used with an ETA (765) and gave multi-element detcction limits for Cd, Mn, and Pb of 0.2, 2, and 8 ppb, respectively ( 5 pl aliquots). This is probably a better approach to multi-element analysis than using vidicons and SSIDs with their inferior response characteristics, but the use of an image dissector tube would overcome thc need for the mirrored funnel with its stray light problems.This detector has similar SNR perform- ance to a PMT and it would not be necessary to pulse the light sources. Aldous (950) con- structed a multi-element AA spectrometer with an ID mounted in the focal plane of a 0.5 m Ebert monochromator. The instrument was able to monitor a spectral range of 200nm (see also Section 2.3).The versalility provided by a double beam dual-channel A A spectrometer has been described previously with respect to the Instrumentation Laboratory Model 751 (sec ARA AS, 1977, 7, Refs. 1054, 1063; 1978, 8, Refs, 332, 1256). This instrument has now been further updatcd by incorporating a video display (621), as on the Model 551.In addition this new instrument, the Model 951, has achromatic lenses, hence the focal lengths remain constant over the wavelength range 185-860 nm. This instrument was used with a graphite furnace (523) equipped with the automatic aerosol-type sampler (see ARA AS, 1978, 8, Ref, 1354) for the simultaneous determination of Cd and Pb.An additional feature of the instrument, useful for analysis by ETA, is that during the use of background correction, the background absorption and the total absorption (AA + background) can be displayed simultaneously on the video screen. A microprocessor dual-channel instrument has been constructed from commercial components (1930) and used for the simultaneous determination of As and Se in natural water.A throughput rate of 37 samples per hour was claimed.42 A nary tical A t omic Spectroscopy The very high resolving power of echelle monochromators has made continuum source AAS a practical technique. A continuum source echelle wavelength-modulated AA spectro- meter, as described previously by O’Haver and co-workers (ARAAS, 1976, 6, Ref. 596; 1978, 8, Ref. 630), was used with ETA for the determination of 8 trace metals in coal (1335). A multi-element version of the instrument has now been developed (80, 207, 552, 1645). The echelle monochromator was converted to a 20-channel direct readx by inserting a multi-slit cassettc in the focal plane. Background correction and double beam operation were available for all channels and data wcrc output through a 16-channel multiplexed A / D converter interfaced to a dedicated computer.The data acquisition rate was sufficiently fast to permit 100 source-compcnsated background corrected absorbances per second to be measured. Transient events from an ETA could thus be detected. For this, each channel was sampled at a rate of 1 kHz, data being stored immediately on a disk and then removed and processed at the end of the atomization cycle, Detection limits with a flamc were said to be similar to those of conventional AAS above 280nm, but slightly poorer at shorter wave- lengths.The system was used to determine Cr, Cu, Pb, and Zn in body fluids (163). This is probably the most promising approach yet to multi-element AAS, and the system would be useful where AAS methods are already established for determining several metals in the same sample, especially if the continuum source can be improved to provide better SNR at low wavelengths, Additional reference on the preceding topic - 1909.Routh and Bennett (568) described two further new Varian instruments with micro- computer control, providing signal handling and data reduction, and control of instrumental parameters.A new hydride generation accessory suitable for As, Bi, Ge, Sb, Se, Sn, and Te has also been described (993). A new instrument, manufactured in Australia and marketed in the U.K. by EDT Research, is the GC SB900. This compact lightweight low-cost instrument may well be suited to teaching or mobile field testing laboratories. Optional background correction, calculator and hydride generation units are available. Zeeman-AAS, while providing high quality background correction with only a single light source, suffers from the limitation of low analytical sensitivity unless strong magnetic fields are used.An instrument has been described, however, that used a 50Hz sine-wave modulated electromagnet (908, 1297), and sensitivity was claimed to be similar to that of conventional AAS, while curvature of calibration graphs was no more pronounced The magnet consisted of 200 turns of anodized aluminium around a 40 X40 mm core of lamin- ated transformer plate.An 800W power supply delivered up to 25A and provided field strengths up to 10 kG in a 12 mm air gap, which accommodated an ETA between the 10x30 mm pole pieces.The analytical signal was obtained from the log-ratio of the intensities read at zero field and maximum field, respectively (100 Hz modulation). 2.5.3 Fluorescence Instruments A computer-controlled multi-element AFS/AES spectrometer using an Eimac continuum source slew-scanning monochromator and photon counting was previously described by Winefordner et al.(ARAAS, 1975, 5, Ref. 1237). The instrument has now been modified (2013, 1917) by incorporating a quartz refractor plate to allow wavelength modulation (see Section 2.2.2). A continuum source AFS/AES instrument described by Brinkman et al. (1733) was interfaced to a programmable calculator, which allowed the 0.3 m mono- chromator to scan to a programmed set of wavelengths. Data collection and processing were also performed automatically.Although sequential multi-element analysis was feasible, theInstrumentation 43 instrument was used in the single-element mode because of poor long-term stability. The only advantage over conventional single-element systems was that changing from one element to another did not require the source to be changed. Typical detection limits were 0.3, 0.08, and 0.02ppm for Cd, Cu, and Mg, respectively; these are slightly inferior to those normally expected by continuum source FAFS.Salin and Ingle (494) have adapted their time-multiplex AA spectrometer (see Section 2.5.2.) for multi-element FAFS to give better than 1% precision.Table 2.5A - COMMERCIALLY AVAILABLE EMTSSION SPECTROMETERS P P Supplier Reciprocal Focal nm oer mm range/nm m Model Type c~~q;,,$s dispersion/ Wavelength length Type of Source Special features Applied Research Quantometer Laboratories Ltd., 34000C Wingate Road, Luton, Beds., England Applied Research Laboratories Ltd., En Vallaire CH-1024. Ecublens/Lausanne, Quantometer Switzerland 34000D Applied Research Laboratories Ltd., 9545 Wentworth Street, Quantometer P.O.Box 129, B34000C California, U.S.A. Societe Francais d'lnstruments Controlee d'Analyses, B.P. No. 3, Quantotest F 78320, Le Mesnil, 36000 St. Denis, France DR 48 0.465 0.520 or 0,310 0.930 or 0.465 190-820 1.0 DR 48 As 34000C As 34000C As Low voltage high voltage and/or d.c. arc 34000C and/or DR 60 As 34000C As 34000C As As 3400OD 34000C DR 10 0.70 200-400 0.3 Low voltage Full computer control to provide direct concentration print out; full range of options including dual floppy discs, VDUs, fast printers, remote terminals and computer links etc; twin stand facility including Ar, air, hollow cathode, rotrode, plasma etc.Full computer control to provide direct concentration print out; optional local and remote printers, Ar or air excitation stands As 3400CYC, twin stand facility including Ar, air, hollow cathode, rotrode, glow discharge etc, allows for expansion to include a large number of elements and offers comprehensive computer options to handle multiple and complex alloy programmes Small transportable Quantometer with GO-NO GO inspection type electronics Baird Corporation, Spectromet DR 30 0.6 or 0.3 210-590 1.0 Arc or spark; Compact, low-cost direct reader with 125 Middlesex 1000 modular minimum air-conditioning requirements; Turn pike, Bedford, MA 01730, alignment manual master monitor to check slit U.S.A.Spectrovac Baird-Atomic Ltd., 1000 Warner Drive, Spr i ngwood Industrial Estate, Rayne Road, Braintree, Spectromet Essex CM7 7YL, I I England Spectrovac II DR 30 0.6 or 0.3 173-767 1.0 Arc or spark; Compact, low-cost direct reader with 5 modular minimum air-conditioning requirements; a logarithmic read-out; manual master monitor to check slit alignment; dual stand option % DR 60 0.294 190-432 2.0 As Spectromet Automatic optical servo monitor 0.59 190-863 1000 continuously maintains correct slit alignment; logarithmic read out; manual master monitor to check slit alignment; length; dual stand for Ar and air avai la ble i n vacuum 3 temperature-compensated fixed focal 5' DR As Spectromet As Spectromet 11; all photomultipliers 5 1000 0 2 2 0.29 173-432 2.0 60Jarrell-Ash Division t 78-090 Fisher Scientific Co., 590, Lincoln Street, Waltham, MA 02154, 70-310 U.S.A. 420-970 1.5 * 21 0-485 180-3000 180-1500 3.4 180-750 200-6000 0.75 1.0 or 2.0 - 75-1 50 Various availaple in ‘Varisource unit incl.spark, low and high voltage d.c. arcs. -Also versatile controlled wave- excitation source. 96-750 96-785 1500 70-314 Phot. - 1.1 or 0.54 Phot. - 1.0 or 0.24 depending on grating Phot. - 4.4 to 1.1 3.2 to 0.8 1.6 to 0.4 DR DR DR Up to 50 0.54 Up to 50 0.54 Up to 60 0.56 or 0.28 0.34 or 0.17 DR 30 As 70-310 168-500 0.75 As above except 168-500 0.75 controlled \ electronically J peak current 200-800 or 190-400 200-510 or 1 - 5 As above 190-250 As 70-310 3.4 As above Wadsworth Spectrograph; 20 in.camera. Choice of three gratings; N2 purging extends range to 175 nm; optional accessories permit use as direct-reader or scanning spectrometer Computer controlled Choice of 2 gratings Easy interchange to photographic (70-31 0) version I Labtest Equipment 31 0 DR 60 max 0.56 190-900 1.5 Co.Ltd., 11828 La Grange V25 DR 40 max 0.46 170450 1.0 Avenue, Los Angeles, 21 00 DR 30 max 0.46 188-455 1.0 CA 90025, U.S.A. 71 DR 74 max 0.52 170-900 2.0 “Transource’ high-voltage- triggered discharge,. Low- voltage-triggered d.c. arc; ICP all models source for isolution analysis Wavelength in first order: CRT; teletype printer or computer read out systems; dual air/inert gas and solution excitation stand: V25 vacuum for C and S in ferrous materials; ICP can be used on M.B.L.E., t Philips PV Rue des Deux Gares 8300 80, Vacuum 8-1070, Brussels, Belgium Philips Analytical Department, Pye-Unicam Ltd., York Street, Cambridge CB1 ZPX, Philips PV England. 8350 Air DR 60 0.55 170-430 1.5 Triggered (80 lines) or capacitor 0.46 discharge.“Monoalternance discharges” up to 500 Hz; d.c. arc, glow discharge, hollow-cathode DR 40 0.46 177-410 1.0 As for PV 8300 Optional dual air/Ar excitation stand; choice of programmable calculator and computer configurations with dual cassettes or floppy discs; rapid printer; VDU extension options Integrated spectrometer system, including source and readout options as for PV 8300 - t No up to date information supplied.P !ATable ZSA- COMMERCIALLY AVAILABLE EMISSION SPECTROMETERS- continued Supplier Reciprocal Focal nm per mm range/nm m Model Type chNaq;Afls dispersion/ Wavelength length Type of Source Special features ~ Rank-Hi lger Ltd., E 1000 DR 60 0.293-1.155 156-880 1 -5 Various, including Solid-state electronics; microprocessor Westwood, Margate, Polyvac high repetition control available.Dual gratings give 12 Kent CT9 4JL, condensed arc, standard systems to select optimum England ICP, GDL dispersion and wavelength coverage. Special grating if required; dual spark stands microprocessor control available: air or inert gas discharge stands E 960 DR 36 0.546 or 0.741 174.0-447-7 0.75 As ElOD0 Curved entrance and exit slits: Spectrametrics Inc., 204 Andover Street, Andover, MA 01810, U.S.A.AE2 Phot, DR 1 0.06 190-800 0.75 Plasmajet Optimized AE system using a high DRlO DR 20 0.06 190-800 Plasmajet dispersion, high -energy-throughput (inter- chanseab le echelle spectrometer and a high temoerature plasma iet excitation source cassettes) Techmation Ltd., Plasma jet, flame Built ,in computer 58 Edgware Way, ES 9 Phot.- 0.06 19&800 0.75 or arc stand Edgware, Middlesex HA8 8JP, RS 1 DR 1 0.06 190-800 0-75 AS ES9 England (variable wavelength) SDex Industries Inc.. 1870 Scan/Phot. - 1.6 175-1280 0.5 Mu It i-purp ose unit 3880 Park Avenue, U.S.A. Metuchen, NJ 08840, 1702 Scan/Phot. - 1.1 175-1500 0.75 1704 Scan/Phot. - 0.8 175-3500 1 - 0 Glen Creston Instruments Ltd., 1802 Scan/Phot. - 0.8 1&&1500 1 - 0 Direct reading accessory available 16 Carlisle Road, London NW9 OHL, 1269 Scan/Phot.- 0.65 180-1500 1-26 9 Very high resolution England .1" 2 German Democratic multiplying as required; automatic 3 B 2 2 2 2. VEB Carl Zeiss Jena, PGS 2 Phot. - 0.74 or 0.37 200-2800 2.075 Arc or spark Atlas for spectra evaluation; wide choice -, 69 Jena! Carl-Zeiss Str. 1, resolving power; dispersion doubling or $ Republic, transport of cassette; wavelength scale 6. Carl Zeiss Scientific the spectra; wide range of accessories h Instruments Ltd., P.0. Box 43, microspectral analyser 2 Elstree Way, Boreham Wood, Herts. WD6 INH, c, England of precision diffraction gratings; high for quick orientation of the user within available including LMA-10 laser-Table 2.5B - COMMERCIALLY AVAILABLE PLASMA SPECTROMETERS Generator Special features No.of Reclprocal Focal Operat- Type of Type of Type of Supplier Model Type channels “ , p ~ ~ i ~ ~ Output ,i:2 Spectrometer grating nebulizer Power quency/ M Hz Applied Research Quanlometer DR 48 0.930 or 0.465 1.0 2 kW 27.12 Czerny-Turner Ruled Concentric Full computer control to Laboratories Ltd.t 34OOO/lCP or 0.310 replica glass provide direct concentration print-out; full range of options including dual floppy discs, VDU. fast printers, remote terminals and computer links etc. Quanlomepr Scan/DR unllmlted 0.80 1.0 2 kW 27.12 Crerny-Turner Ruled Concentric Automated scanning grating 35000C 0.60 replica glass for waveleng:h.range studies, qualitative analysis on chosen spectrum lines. Full computer control Baird Corporation t Plasma DR 60 0.66 1.0 2.5 kW 27.12 - - - One metre polychromalor with 120 exit slits in a,rigid,focal curve. Da:a aquisition is controlled by a Tektronix 4052 graphic computing system lnstrumenlal ion 100 Scan - 2 . 5 - 2 kW 27.12 Ebert - - M;crocompu:er co;ltrolled Laboratory Inc.Q (Double) scanning double mono- chromator for sequential multi-element analysis; 0.50 profile facilities and 0.40 electronics providing Spectrornet instructions for programming aDoear on video diSDlaV with single keystroke operafion; emission profiles of analytical line appear on video screen for selection of wavelength, of background correction, of inter-element effects and observation of spectral interferences: all circuitry for r.f.power generation, monochromator optics and microcomputer are built into the ins:rument Jarrell-Ash Div., 96975 DR up to 50 0.54 0.75 2 kW r.f. - - - Computer control variable Fisher Scientific channel; concentration print Co. Ltd. t $ out 96-988 OR up t o 5 0 0,54 0-75 - - - - - Computer control; N+l channel scanning attachment, spectrum shiftcr attachment for automatic background Correction; special K and L I channels; data management system New equipment since publication of Volume 8 t No up to date information supplied t Address as in Table 2.5A § Address as in Table 2.5CTable 2.5B - COMMERCIALLY AVAILABLE PLASMA SPECTROMETERS- corztinued h -- Generator Speclal features No.o, Reciprocal Focal Operat- Type of Type of Type ot Supplier Model Type channels ~ ~ p ~ ~ i $ ~ Output i:: Spectrometer grating nebulizer q;zY/ Power Jobin-Yvon t JY 38P Division d'lnstruments, 16-1 8 Rue du Canal, 91160 Longjumeau, France EDT Research, 14 Trading JY 48P Esiate Road, London NWlO, England Kontron GrnbH,, t Plasmaspec 8057 Eching bei System 3 Munchen.Oskar-von-MiIier Plasmaspec Str. 1, System 4 West Germany Scan - - 1.0 Plasmatherm Czerny-Turner Replica Crossflow or Large operative monochromator 1.5 kW 27.12 holographic concentric ( f 5-4 grating size 120x140 2.5 kW glass, or mm) Manual or computer 5 kW ultrasonic conlrolled; constant time Durr-Jobin-Yvon integration or i n ratio mode 2.2 kW 56 4 kW DR 48 0.45 1.0 As Paschen- Master As above Air or vacuum; 86 positions of 0-58 above Runge holographlc photomultipliers.fully 0.69 automatic read-out computer 0.80 option 0.8-1.6 1.0 4tO 27.12 - Scan - 7 kW 7 kW 4t0 27.12 - OR up to 30 0.23-0.46 1.0 - - General purpose - - General purpose Labtest Equipment Plasmascan Scan - - 0.35 2 kW r.f. Czerny-Turner Holographic Crossflow or Microprocessor control. co. * 700 concentric enclosed sample pumping glass, or system, computer read-out ultrasonic system M.B.L.E.t * Philips DR 60 0.55or 0.28 1.0 - r.f. - - - Wavelength range covered In PV 8210 (50 lines) 1st order; remote controlled roving detector; read out by printer, teletype or digital computer systems Integrated spectrophotometer Philips 40 0.695 or 0.35 1.0 - system with built-in source and PV 8250 0.59 or 0.35 read-out options as for PV8210 E \1 2.Phllips DR 40 0.46 1.0 - r.r. - - - Integrated spectrometer system r, PV 8350 including source and read-out a, k Air 0.92 or 0.46 0.46 or 0.23 options as for PV 8210 OR r.f. - Rack- +iilger Ltd., * E 1000 Polyvac DR 60 0*293-1*155 1.5 - r.f. Paschen- Holographic Crossflow or Solid state electronics; dual Runge concentric gratings give 12 standard glass systems to select optimum dispersion and wavelength coverage; special grating I t required; dual spark stands; microprocessor control available E D60 DR 36 0.546-0.741 0.?5 - r.f As above - As above Curved entrancs and exit silts; microprocessor control availablePerkin-Elmer ICP5000 * Corporation 9 Scan - U.V. 0.65 0 . 4 2.5 kW 27.12 - VIS 1.3 Holographic Concentric Complelely au:omated 2 glass seqwntial ICP system can 2 anaiyse up to 20 elements in an operator selectable mu?i-elernent croxamme: analytical parameters ' including wavelength selection, background increment selection and signal handling are programmable ar.d s!orable via standard minicomputer; optical path purgeable permit!ing analysis to 175 nm; optional HGA-500 furnace and gas control systems permit inslrument lo operate as completely automated ICP, flame AA and furnace AA system; ICP sectlon retrofitable t o existing Model 5000 AA speclrophotorneters 0.06 0.75 - d.C.- Echelle - Optimized AES system using Inc. $ Ill inter- As above high-dispersion throughput; Spectrametrics Spectraspan Pho:o/DR 20 integral microprocessor - d.C. - - - High sensitivity even in changeable cassettes - - 0.75 presence of complex matrix solutions with solid contents up to 20% m / V Spectraspan - 1v P W New equipment slnce publication of Volume 8 $ Address as in Table 2.5A 5 Address as In Table 2.5CTable 2 .X - COMMERCIALLY AVATLABLE: ATOMIC ABSORPTION SPECTROMETERS model ~~~~~~~~ Resolution Wavelength Read Automatic Type Of beam nm per mm /nm range/nm out background data correction output Supplier Special features Baird Corporation, 125 Middlesex Turnpike, Bedford, MA 01730, U.S.A.Baird Atomic Ltd., Warner Drive, Springwood Industrial Estate, Rayne Road, Braintree, Essex CM7 7YL, England A51UO Single 3 - 0 0 - 1 186-860 Digital Dz HCL Bit parallel Automatic background correction; BCD (TTL 4-lamp turret; auto zero; integration; levels) curve correction; wavelength scan; flame ignition; gas safety devices; lens optics; emission and fluorescence; optional microprocessor control for up t o 8 standards with re-slope facility, illuminated status indication and date/time clock A3400 Single 6.0 0.2 190-860 Meter or - Digital 4-lamp turret; auto zero; curve correction; integration; flame ignition; wavelength scan; emission and fluorescence; optional microprocessor control for up to 8 standards with re-slope facility; illuminated status indication and date/time clock GBC Scientific GBC Single - 0.5 190-900 Digital - IEEE-488 Dimensions : length 700 mm; Equipment, SB900* width 200 mm; height 225 mrn; Pty.Ltd., optional background correction 7/63. Park Drive. bandenong, . Victoria 3175, Australia EDT Research, 14 Trading Estate Road, London NWlO 7LU, England Hitachi Ltd., t 170-10 Single 2.25 0.4 i90-9ao Nissei Sangyo Co.Ltd., - - Mori 17th Building, 26-55 Toranomon. 1-chome, Mi n ato-Ku, Tokyo, Japan Nissei Sangyo Instruments Inc., 392 Potorero Avenue, Sunnyvale, CA 94086, U.S.A. 70-30 Single ,2.25 0.4 190-900 70-50 Double 2.25 0.1 190-900 70-70 Double 2.25 0.1 190-900 - Meter/ digital optional - Polarized - Zeeman Single lamp mounting, NzO-air simultaneously exchanged; concentration read-out; continuously variable time constant Concentration read-out; time weighted signal averaging; AAS/AES measurement; auto zero; NzO-air simultaneously exchanged Base-line drift correction; curve corrector; time-weighted signal averaging; auto zero Background correction to 1 - 7 absorption unitsNissei Sangyo GmbH, 4 Dusseldorf, Am Wehrhahn 41, West Germany Instrumentation Laboratory Inc., 68 Jonspin Road, W Ilmington, MA 01887, U.S.A. 951* Double/ 2.5 0-04 180-1000 CRT DZ arc in RS232C Microcomputer controlled; calibration si m u I t an- using up to 5 standards; read-out will eously display two elements simultaneously A, 6 , A/B or ATB; jnternal standard and non absorbing line background correction; VDU displays standard signals; automatic gas box is standard feature, optional 4-lamp turret, wavelength scan and built-in alphanumeric printer dual video both channels curve linearized in both channels channel Instrumentation 551 Laboratory (UK) Ltd., Kelvin Close, Birchwood Science Park, Warrington, Cheshire, England 257 Double 2.5 Double 2.5 0.04 180-1000 CRT - video 0.04 180-1000 - RS232C RS232C Microcomputer controlled; calibration curve linearized using up to 5 standards; memory will store up to 10 calibration curves simultaneously; VDU displays standard conditions for each element, the working curve and will show transient signals; fully automated fail-safe gas-box is standard feature; optional background correction, 4-lamp turret, wavelength scan and alphanumeric printer Microcomputer controlled; calibration curve linearized using 2 standards or 5 standards (optional); fully automated gas-box is standard feature; optional background correction; 4-lamp turret, wavelength scan and alphanumeric printer As for 257 m icroprocessor control led, auto-zero; auto conc.; auto curve with up to 3 standards; peak height; peak area, integration time selectable from 0.2 to 60 s; statistics; flame i,gnition optional auto NzO switching and burner head safety interlocks; optional flame and pressure sensing by microcomputer burner control automatic gain control; auto NzO switching, burner head safety interlock; optional DZ arc background correction with automatic intensity RS232C 157 Single 2.5 0.04 180-1000 - - Perkin-Elmer 2280" Single 1.6 0.2 190-860 Digital DZ arc EIA-RS-232C High energy optical system, Corporation, optional Main Avenue, N orwa I k, CA 06856, U.S.A.Perkin-Elmer Ltd ., Beaconsfield, Bucks, HP9 10A, England 190-860 Digital DZ arc EIA-RS-232C As model 2280 but all mirror optics; optional (continued) control ur t No up to date information supplied * New equipment since publication of Volume 8 c 0.2 2380* Double 1.6Table 2.92- COMMERCIALLY AVAILABLE ATOMTC ABSORPTION SPECTROMETERS - continued Single/ Reciprocal Automatic Type of beam nm per mm correction output Supplier Model double dispersion/ ~ ~ ~ ~ ~ ~ ! h 'tid background data Special features (continued) 4000* Double 0.65 0.03 170460 Digital - 1.3 170-900 Bodenseewerk, Perkin-Elmer & Co..GmbH t Postfach 1120, D7770 Uberlingen, West Germany 5000 400 Double 0.65 1.3 Double 1.3 0.03 17M60 Digital - 170-900 0.2 19e860 Digital - 2 way E I A-RS-232C 2 way E IA-RS-232C BCD 410 Double 1/1.6 0.17/0.27 19&860 Digital - - 422 Double 1.3 0.2 190-860 Digital - EIA-RS-232C 432 Double 1/1-6 0.17/0.27 190-860 Digital - - Semi-automated sequential AA system; automatic gain control: instrument can analyse up to 6 elements with little operator participation; analytical parameters, including standardization and signal read-out can be entered and stored internally; digital stepper motor wavelength selection; flame ignition, auto NzO switchover, burner head interlock; optional flame and pressure sensing by microcomputer burner control; optional double-beam background correction for all U.V.and visible wavelengths with automatic intensity control; lamp turret available Completely automated sequential AA system; instrument can analyse up t o 6 elements with minimal operator participation; all analytical parameters, including lamp current, wavelength selection, resolution, gas flows, standardization and signal read-out can be entered and stored using magnetic cards: optional double-beam background correction for all U.V.and visible wavelengths; when used in conjunction with HGA 500 it will provide sequential analysis for up t o 6 elements with the same analytical ease as flame; when used with ICP-emission accessory it will provide sequential multi element analysis for up to 20 elements with operator selectable background parameters Auto zero, auto concentration, integration, curve correction, automatic flame ignition As model 400, but with double-grating monoc hromator As model 400, but with microcomputer electronic key board operation: linearization with up to 3 standards As model 422, but with double-grating m on ochr omat orPye-Unicam Ltd., SP 2900 Double 3 . 3 0.2 190-850 Digital D1 arc BCD 4-lamp magazine; auto zero; integration; 2 standard curve correction; peak-height measurement York Street, with timer; peak area; emission: Cambridge, 0-10 V fast analogue output (0-1 A), CB1 2PX, England 10 mV output for integrated or peak-height reading; simultaneous background Correction as accessory Data d Centre SP 9 Single 4.7 SP 9 - Computer 0.2 190-850 Digital DI HCL - Fully microprocessor controlled data processing by programmable calculator; 3 types of curve correction, statistics, standards additions and other data handling; full calculator ability retained Eight models available with combinations of 4-lamp turret: gas control module with full safety interlocks; scale expansion, 2-standard curvature correction, burner interlock, data output for SP9 computer CO-2V for 0-2 V plus various status and control signals, and 0-10 mV (0-1 A) analogue output as standard Calibration with up to 5 standards i n fixed or variable ratios: peak height and/or peak area; full statistics: running mean; error warnings, built in self-test routines; control of flame autosampler Rank-Hilger Ltd., Atomspek Single 2 . 6 0.1 190-850 Digital HZ HCL Hewlett- 6-lamp turret; autozero and flame Westwood, H 1580 Packard ignition; curve correction; Ramsaate Road, calculator/ integration: programmable calculator M arg ate, Kent CT9 4JL, England printer output available ~~ S himadzu- AA-625 Single 1.9 Seisakusho Ltd., t 14-5 Uchikanda, 1-chome, Chiyoda-ku, AA-630 Single 1.9 Tokyo 101, Japan V.A. Howe & Co. Ltd., 88 Peterborough Road, London AA-640 Single 1.9 SW6 3EP, England (continued) * New equipment since publication of Volume 8 0.2 190-700 Meter or - - Quantitative flame emission; flameless digital capacity; flow lines for air, CZHZ and N2 0 0.2 190-900 Meter or - - Quantitative/qualitative flame digital emission; flameless capacity: flow line for air, Ar, C2H2, NzO, Hz; f!ame monitor, gas pressure monitor, wavelength drive 0.2 190-900 Meter or - Automatic background correction; emission: flameless capacity; flow lines for air, Ar, CZHZ, N20,.Hz; flame monitor, wavelength drive; integration digital quantitative and qualitative flame VI m t No up to date information suppliedTable 2.5C-COMMERCIALLY AVAILABLE ATO M!C ABSORPTION SPECTROMETERS- conliniicd Ln P Single/ Reciprocai Model doubre dispersion/ Resolution Wavelength Read Type Of Special features beam nm Der mn: /nm range/nm out background correction output Supplier (continued) AA-650 Double 1.9 0.2 190-900 Meter or - - digital Automatic background correction; quantitative and qualitative flame emission; built in peak catcher; flameless capacity: flow lines, for air; Ar, C2H2.N20, Hz; flame monitor; gas pressure monitor; wavelength drive; integration Vari an-Tec htr on Pty. Ltd., 679 Springvale Rd., Mulgrave; Vic. 3170. Australia Varian Associates Ltd., Instrument Group, 28 Manor Road, Walton on Thames, Surrey, England Varian Instrument Div., 611 Hansen Way, Palo Alto, CA 94303, U.S.A. AA-275 AA-475 AA-875* Single Double Double I EEE-488 RS-232-C 3.3 0.2 185-900 Digital DZ arc and parallel BCD 3.3 1 . 6 AA-575 Double 3.3 042 185-900 Digital DZ arc 0.05 185-900 Digital DZ arc 0-2 185-900 Digital DZ arc IEEE-488 RS-2 32-c and parallel BCD IEEE-488 and duplex RS-232-C IEEE-488 RS-232-C Parallel BCD Two-lamp turret overcoated reflective optics, automatic gas control system, compatible with samplers, printers, hydride and furnace atomization systems, Intel 8080 with 10 K ROM provides signal processing background correction, absorbance, conversion, integration, 3-standard curve-fitting, peak height and area measurement, lamp current control Two-lamp turret, overcoated reflective optics, automatic gas control system, compatible with samplers, printers, hydride and furnace atomization systems, Intel 8080 with 10 K ROM provides double-beaming background correction, absorbance conversion, integration, 3-standard curve-fitting, peak height and area measurement, lamp current control Computer compatible via two-way RS-232-C, for realtime signal generation and instrument control, new integrated, high sensitivity atomization 2 system.Four-lamp turret compatible with desktop computer, printer, samplers,, hydride and furnace atomization systems, Intel 8080 with 15 K ROM provides double beam background correction, absorbance ? h conversion, integration, 5-standard curve fitting, peak height and area measurement, statistics, self-test and 2 error detection Reflective optics with quartz overcoat; 2 fully microprocessor controlled three standard calibration optional automatic gas-control, +lamp turret 2 acquisition, comprehensive report Q 3AA-775 Double 1.6 0.05 185-900 Digital DX arc Reflective optics with quartz overcoat; fully microprocessor controlled five standard calibration with statistics and standard additions calibration; optional automatic gas-control, 4-lamp turret VEB Carl Zeiss Jena, 69 Jena, Carl-Zeiss Str. 1, German Democratic Republic Carl Zeiss Scientific Instruments Ltd., P.O. Box 43. 2 Elstree Way, Boreham Wood, Herts. WD6 lNH, England ~~~ ~ ~~~ - ~ AASl Single 1.5 - 190-820 Meter DX lamp 1OUmV 4-lamp turret: single or triple pass AASl N equipment) (600 ohms) for optics; autozero: titanium burner potentiometric heads; flow lines for air, C2H2, recorder or absorbance converter automatic flame ignition TECl printer or computer VIOTEC 1; signal output 775 mV (5 K ohms) for linear recording of absorbance N2O; gas pressure monitor, gas flow monitor; burner head safety interlock; (1520 New equipment since publication of Volume 8 t No up to date information suppliedVI Q\ Table 2.5D -COMMERCIALLY AVAILABLE ELECTROTHERMAL ATOMIZERS Special features Temperalure Ramp rale control range S upp I ier Model Type Control unit Baird Corporation* A3470 Graphite Rod programmable, dry ash - ( 2 stages) atomize: max.temp. 3500 "C Fits most AA spectrophotometers; air cooled, uses mains power, inert gas shielding; pyrolytic graphite coating for rods in siru; rapid interchange between flame and electrothermal methods Instrumentation 655' Laboratory 1nc.S 255' Graphite Programmable six stages, Furnace ramp or step from ambient, max.temp. 3500 " C Autosampler Digital timers for sample for flame 8 furnace operation calibrating the deposition, trigger circuitry for auto zeroing & auto spectrometer Perkin-Elmer HGA 400 Graphite Microprocessor unit Corporation$ furnace provides up to 8 steps of controlled heating; temp. ramp time, hold time, gas 8.other furnace and spectrophotometer control functions are programmed by direct keyboard entry; digital displays provide read-out of temp. time and prog. status Feedback from - tungsten temperature sensor True on temperature read-out: LED display; safety interlock system; automatic cell door: automatic cleaning; cell pressurization; convenient solid sampling capacity using micro boats Flame/furnace autosampling technique with auto calibration FASTAC, employs an aerosol deposition technique of introducing aerosol into furnace cuvette, which is at elevated temperature; sample volume, which evaporates on contact with graphite surface, is controlled by length of time sample is sprayed into furnace, allowing the operator to control sensitivity by varying deposition time 1 to 999 s From 2000 "C High .speed, temperature accessory per second to permits rapid heating to temperature 999 s between between 800 and 3000 "C for optimal any two temps.atomization; AS40 autosampler available for automatic insertion of up to 35 samples and blank and 35 standards into the HGA; will also perform automatic method of additions; automatic matrix modification: recalibration; automatic triggering of HGA and instrument read cycle for unattended operation P hot od iodeHGA 500 Graphite furnace Microprocessor unit provides up to 9 steps of controlled heating; temp., ramp time, gas and other furnace & spectrophoto- meter control functions are programmed for each step by direct keyboard entry; digital displays provide read-out of temp, time & programme status; up t o 6 complete programmes can be stored & recalled at the touch of 1 key Photodiode As for HGA 400 Furnace control programmes for up t o 6 different elements may be stored i n 6 programme memories; programme parameters for more than 6 elements can be stored on magnetic cards and recalled with the touch of one button; the optical temperature sensor and digital gas flow control for 2 different purge gases add to the versatility of the furnace programme; when used i n combination with the AS40 microcomputer furnace auto-sampler and the Model 5000 AA up to 35 samples, blank and three standards may be analysed for up to 6 elements, each without operator attention Bodenseewerk, HGA 500 Graphite Microcomputer controlled - - Fits Perkin-Elmer and Zeiss AA Perkin-Elmer & Co.furnace up to nine programme spectrophotometers; water-cooled; GmbH * inert gas shielding; safety features for failure of water, purge gas or tube break; ramp or stepwise increase of temperature plus isothermal phase i n each of the steps; recorder and peak reader control in each step preselectable; gas stop or miniflow, selectable temperature controlled maximum power heating for atomization steps for drying, ashing, sample pretreatment, atomize, tube clean, tube blank etc; max. temp. 3000 "C Pye Unicam Ltd.* SP 9-01 Graphite Programmable, dry, ash, Photodiode - Water-cooled, inert gas shielding, safety features for failure of water, tube life indicator and remote recorder control for 1,2,3 or all phases furnace atomize, tube clean, tube blank, with cancel and delay stages; max. temp. 3000 " C SP9 Video Furnace Graphite 6 phases each program- Photodiode 9 ramp rates Microcomputer control of all functions; furnace mable t o 3000 "C; linear 2-2000 "C s-1 video displays of set parameters and or non-linear temp. ramp on each phase; voltage or temp. control (no adj. t o photodiode sensor) status; storage of 10 furnace programmes; gas stop and recorder control on all phases; built in autosampler controls; fits all current Pye Unicam spectrophotometers SP9 Furnace Graphite furnace SP9 Furnace - Auto-sampler 4 phases each program- Photodiode 9 ramp rates Fits all current Pye Unicam mable to 3000 "C; voltage 2-2000 "C s-1 spectrophotometers or temp. control (no adj. of photodiode sensor) Automatic sampling of 38 - - Microprocessor control of all functions; samples and 2 wash positions selectable number of readings and volume for each sample cup identification, wash system interlock; automatic stop after last sample; fits all current Pye Unicam spectrop hotometers * New equipment since publication of Volume 8 t No up t o dale information supplied * Address as in Table 2.5CTable 2.5D-COMMERCIALLY AVAILABLE ELECTROTHERMAL ATOMIZERS- continued Speclal features Temperature Ramp rate conlrol range Model Type Control unit ul 00 * H1475 Graphite Programmable, dry, ash, No temperature - furnace wait, atomize; max. temp. control or 2600 "C variable ramping Watercooled, inert gas shielding Current stabilized to obtain - G FAZ Graphite Programmable, dry, ash, - atomize; max. temp. reproducible results 3000 "C furnace CRA 90 Graphite Programmable, dry, ash, - furnace atomize; max. temp. graphitetube) 3000 "C threaded raphite tube) graphite cup) 1 7 since publicatlon of Volume 8 25-800 "C s-1 Fits most AA spectrophotometers; water cooled; inert gas shielding and hydr en flame option; automatic rampTold atomization: pyrolytic graphite coating on cup and tubes b j No up to date information supplied 4 Address as in Table 2.5C b

ISSN:0306-1353    

DOI:10.1039/AA9790900033

出版商:RSC    

年代:1979

数据来源: RSC

摘要:

CHAPTER 3 Methodology 3.1 NEW METHODS This Section describes novel methods of analysis that are considered to be of suficient general interest to merit discussion here as well as in the appropriate Section on specific applications. The Section also includes consideration of papers by workers who have made a detailed study of experimental parameters of widespread relevance. 3.1.1 Sample Preparation Techniques 3.1.2.1 Sample Handling and Storage.The accuracy of trace analysis is often critically dependent upon both the preservation of the sample and the minimization of contarninof ion. Unfortunately, in many routine analyses these aspeets are not given the considcration that they merit. Mizuike and Pinta (307) have reviewed contamination problems in trace analysis.Four main types were identified and discussed: airborne contamination, which could be drastically reduced by using clean rooms or hoods; reagent contamination (especially mineral acids), which could be minimized by utilizing various purification tech- niques; apparatus contamination, which could be reduced by judicious selection of materials and cleaning procedures; and finally, and an often overlooked source, the analyst himself/ herself.Guidance for the design and operation of a clean room for trace metal analyses has been given by Gardner (1449). The present status of contamination in trace analysis has been reviewed by the IUPAC Commission of Microchemical Techniques and Trace Analysis (1519). A summary of the contamination problems encountered in 93 different laboratories is given and it is shown that decomposition of the sample is the most critical stage.As an extension to previously approved nomeizclature, (Pure Appl. Chenz., 1979, 51, 43), recommendations for scales of working in analysis in which sample size and comtituent content are classified have also been published (310). Further work on the selection of sampIe containers (see also ARAAS, 1978, 8, 63) has been performed (1 1, 740).It i s generally agreed that acid-washed high-pressure polyethylene or PTFE containers are suitable for most trace element analyses. One study (1 1) found that there was no significant leaching of 11 metals from high-density polyethylene containers into water or nitric acid after 4 years, unfrozen, storage. A bigger problem however was prevent- ing loss of analyte on or into the sample container itself.A rather worrying study on the effect of the time of storage and type of container on the reliability of Cd, Cu, Hg, Pb and Zn determinations in whole blood has been published by Meranger et al. (1314). Within one week almost all determined concentrations changed by at least 10%. Except for Hg, storagc at low temperature was found not to inhibit these changes.No single type of container could be recommended for all elements. Vitreous containers were optimum for Cd and Zn; losses of Cu occurred in all types of container. Loss or gain of Hg from polyethylene and PTFE containers continues to be investigated (78). Sulphur-containing antioxidants in polyethylene have been implicated in such losses, while the addition of HNO, or KMnO, as a preservative to the sample appeared to assist passage of Hg vapour from ambient air through the walls of the sample container (1498). Freezing of the sample or the use of glass containers was advocated to minimize this problem.Matsunaga et al. (477) have recom- mended the use of glass containers, pre-heated to 500 "C or washed with HF, for the determination of Hg in seawater.The samples were acidified with H,SO, to give a final 5960 Analytical Atomic Spectroscopy concentration of 0.2M, and were allowed to stand for 20 days before being analysed. The resulting solutions were then found to be stable for at least another 40 days. The 20-day standing procedure resulted in relcase of additional Wg, which was not initially reduced by SnC1,.It also avoided the use of KMnO,, which increased blank values (see also 3.1.1.4). Additional reference on the preceding topic - 1885. 3. I J.2 Sample Homogenization, Solubilization and Dissolution Procedures. The accuracy of analysis of many food products is limited by the sampling technique. In a procedure that gave highly homogenized samples of canned foods, the contents of the entire can were mixed with 2M HNO,, blended using a high-efficiency sonic-probe homogenizer, allowed to stand for 16 hours, and then sampled after further blending (1065, 1440).The use of organic tissue solubilizers such as tetramethylammonium hydroxide (TMAH) can result in rapid dissolution of tissues with minimal blanks (see also ARAAS, 1974, 4, 148).One gram of soft animal tissue was dissolved in 2 ml of 20% m/V TMAH in methanol (107). The resulting solutions were analysed for Cd, Cr, Cu, Ni, Pb and Zn using ETA with an automatic sampler. It was essential to effect calibration by the method oi standard additions. Julshamn and Anderson (970) have compared a commercial tetra-alkyl tissue solubilizer in toluene with a conventional HNO, /HClO, digestion.For small soft tissue samples, satisfactory results for Cd, Cu and Mn were obtained using the tissue solubilizer, but not for Al. For hard tissues such as bone, the solubilizer did not give complete dissolution. Emulsioizs of oil (1670) and iodine-treated pctroleum (1635) in water have been obtained using various surfactants (see also ARAAS, 1978, 8, 77).With minimal sample preparation and the use of inorganic standards, satisfactory FAAS analyses were achieved. Ghiglione et al. (1728) have continued their work on the dissolution of metal samples using an underwater high-voltage spark discharge (see also ARAAS, 1976, 6, Ref, 315). The resulting emulsions were reasonably stable at a pH of 2.5, but sensitivities were only 60% of those of the equivalent aqueous solutions.The technique was successfully applied to the determination of Cr, Cu, Mn and Ni in low-alloy steels. The determination of trace elements in coal ash and glass has been accomplished using relatively simple dissolution techniques. Satisfactory cold digestion tcchniques with minimal blanks have been reported for glass (42) and coal fly ash (1567).The samplcs were treated with HF/ HC1 and subjected to ultrasonic agitation. An alternative sample-dissolution procedure for coal utilized slurries, produced by an ultrasonic cavitational homogenization, which were nebulized into an ICP using a Babington nebulizer (1361) (see also Section 3.1.4). 3.1.1.3 Sample Digestion and Oxidation Procedures.In view of the increasing sophistica- tion of analytical instrumentation, it is surprising that so little agreement on digestion and oxidation procedures has been achieved. The accuracy of many analytical methods would now appear to depend on the sample preparation technique rather than the type of instru- mentation used. Bock's comprehensive book on decomposition methods for both inorganic and organic materials has now been translated into English (156), and over 3000 references are listed. Various problems concerning dry ashing or wet digestion of organic and biological materials continue to be reported.There still seems to be considerable diszgreement over the relative merits of wet and dry ashing (963). Fetteroff and Syty (1037) found that for the determination Pb in chewing-gum, dry ashing at 500 "C followed by dissolution of the residue in HNO, did not result in complete recovery.It was necessary to evaporate theMethodology 61 HNO, leachates to dryness and re-ash for a further 2 h in order to obtain quantitative recovery. Dry ashing at 480 "C followed by dissolution of the ash in HCl/HF has been recommended (1609) for the analysis of a wide range of elements in refuse. A useful description of the sampling procedure used for this difficult type of sample is given.Prasad and Spiers (1035) found that wet digestion of plant materials with H,SO,/H,O, resulted in poor recovery of Ca and, surprisingly, of Fe and Zn. They recommended dry ashing the samples at 475 "C followed by dissolution of the residue in 2M HCl; this procedure gave results equivalent to a conventional HNO, /HC10, wet digestion.Other workers (773), how- ever, have found problems with a similar dry ashing technique in the determination of Cd, Cu, Mn and Zn in vegetable matter. When this was dry ashed at 450 "C losses were observed from volatilization (typically 5-1 5 % ) and also from conversion of the analytes into forms that were not quantitatively recovered by conventional acid leaching.Both types of losses were found to increase with increasing temperature and at 800 "C the latter type of loss was typically 40-60%. Etherington and Davies (468) have presented evidence that loss of Fe from plant material as iron pentacarbonyl can occur with dry ashing at 500 "C or even with conventional acid digestions.Additional reference on the preceding topic - 331. Polytetrafluoroethylene pressure digestion vessels have been successfully used for many difficult digestion procedures. One such procedure is the digestion of mineral oils by heating 100 mg of oil with 2 ml HNO, at 160 "C for 16 h (1483). The method was compared with dry ashing and oxygen flask combustion and found to possess significant advantages.Price et al, (1574), for the determination of 12 elements, used a PTFE pressure vessel to dissolve a wide range of aluminium alloys using an HNO,/HF digcstion followed by addition of W$O, to complex excess fluoride and minimize interelement effects (see also ARAAS, 1978, 8, 62). A pressure digestion vessel constructed from glassy carbon (1482) has been recom- mended for the decomposition of organic matrices.The main problem with conventional pressure digcstion devices is that they cannot be readily applied to large batches of samples. A method to overcome this, utilizing a miniature multiple-pressure digestion device, has been described (161 1). Thirty-six 1.5 ml polypropylene tubes were held in an aluminium box-section tube rack by their rims and a sheet of silicon rubber was sandwiched over thc top of the tubes, Up to 20 mg of sample could be digested under pressure with the appropri- ate acids, The use of polypropylene however, rather than PTFE, limited the upper working temperature. 3.1.1.4 Sample Preparation for Mercury Analysis. Considering the vast amount of effort that has been expended on the analysis of Hg (see also Section 1.5.2) in environmental samples there is remarkably little consensus of opinion as to the optimal sample prepara- tion procedures, The prodigious rate of publications on this topic shows no signs of abating. Low recoveries of Hg in wet-digested settled sewage and humus tank effluent samples were observed (38) unless the organic material present was completely oxidized by wet digestion on a boiling water bath with an excess of a suitable oxidizing agent.Similarly, other workers (470) have found that digestion with KMnO,/HNO, at 80 "C for 18 h only gave 90% recovery of organic Hg in natural waters. hlillward and Le Bihan (8) have also shown that if inorganic Hg is allowed to equilibrate with humic material in natural waters for 90 min, some of the resulting mercury species were more stable than methylmercury salts, Very poor recoveries were obtained when a standard SnCl, reduction was used.Photochemical oxidation at pH 1 was recommended as a means of destroying the organic matter. This is an increasingly popular method of destroying organic material prior to Hg analysis (8, 470, 496, 1512, 1719); however, the recovery of Hg has been reported to be significantly reduced in the presence of significant amounts of suspended solids (470).The determination of Hg62 Analytical Atomic Spectroscopy in fish tissue usually requires prolonged digestion. Velghe et al. (1048) have rapidly digested fish tissue with H,SO, and injected the resulting solution directly into a Hg generation cell containing SnCl, /CdCl, in acid in order to determine inorganic and phenylmercury, excess of NaOH was then added to liberate methyl- and ethyl-mercury (see also ARAAS, 1973, 3, Ref. 132).An alternative rapid method for total Hg involved a 20-min digestion procedure in which the sample was refluxed with H,S0,/HN0,/V,05 (1047). The procedure was also applied to the determination of Se. 3.1.1.5 Sample Preparation for Hydride Generation Techniques. A particular problem with hydride generation techniques (see also Section 1.5.1) is the production of foam when incompletely digested biological samples react with NaBH,. This has been effectively overcome (1980) by using a new commercial antifoaming agent (DB llOA, Dow Corning, U.S.A.). Undigested urine samples were found to give a complete recovery of As when compared to fully digested samples.Calibration using aqueous standards containing the antifoaming agent was possible. The determination of Pb by hydride generation has been further investigated (632) (see also ARAAS, 1977, 7 , Ref. 295). A comparison of the use of K2Cr207, H,S,O,, and KMnO, as the preliminary oxidizing agent before addition of 5% m / V NaBH, solution was carried out.A sample solution containing 0.25M K,Cr,O, and 0.25M malic acid was recommended. 3.1.2 Pre-concentration Techniques A large number of pre-concentration techniques have been published, yet the interlabora- tory agreement of the results of ultratrace level analysis would appear to leave much to be desired. (1452, 1858; see also ARAAS, 1978, 8, 68).An interlaboratory ccmparison of As, Mo and Se analyses from uranium mill tailings has been reported. (Dreesen, D. R., Gladney, E. S., and Owens, J. W., J. Wat. Pollut. Control Fed., 1979, 51, 2447’). This paper quoted results from an interlaboratory comparison exercise in which Se was determined in a groundwater sample. The results ranged from 40 to 1840 pg 1-1 with a standard deviation of 499pg 1-1.The depressing conclusion was that compliance with regulations for Se in discharges is difficult to justify at present. Problems arise when published methods are adopted for the routine analysis of large numbers of samples since they often require con- siderable attention to detail not immediately obvious from the author’s description. Two useful reviews on pre-concentration techniques have been published (475, 670) and it was generally agreed that no single type of pre-concentration technique could be specifically recommended for a wide range of elements. 3.1.2.1 Solvent Extraction.Multi-element extractions of natural waters using APDC / DDC / CHCl, for Cd, Cu, Ni and Zn followed by ETA analysis (1070) and APDC/2,6-dimethyl-4- heptanone for Cd, Co, Cr, Cu, Fe, Mo, Ni, Pb, V and Zn followed by FAAS (1467) have been reported.The general need for pretreatment of the samples before the extraction step was stressed (1467). Laqua et al. (852) found it necessary to use a third Ar flow to prevent carbon deposition in a 5 kW ICP after an APDCIMIBK multi-element extraction and nebulization of the organic solvent into the plasma.Intense band spectra (see also Section 1.2) limited the usefulness of the technique to elements having their emission lines below 280nm. Additional references on the preceding topic - 31, 171, 638, 1052. Three further solvent extraction systems for lead have been reported: 4-capryl-3-methyl- 1 -phenyl-5-pyrazolone / MIBK (631); Na,S,O, / trioctylmethyl ammonium chloride / MIBK (1126); and ‘Alamine 336’ OT ‘Aliquat 336S’/xylene (10). These appeared to have no significant advantage over conventional systems using APDC and/or DDC.Methodology 63 A method for the selective determination of As(ZZZ), As(V) and organo-arsenic com- pounds has been described by Akemi et al.(354). The samples were solubilized in 6M HCl and the As(II1) extracted into toluene; the As(V) was then reduced to As(II1) by KI and again extracted into toluene.The As in the two toluene extracts was then back extracted into water and determined. The organo-arsenic compounds retained in the aqueous samples were wet ashed and also determined. The As in orchard leaves was found to be wholly inorganic, while 90-100% of the element in algae and shark muscle was organic.Organo-silicones in water (777) have been extracted into pentanol/MIBK (1 : 1) at pH 5-7. Tetramethyldisiloxane-1,3-diol (TMDS) was used as a standard. An RSD of 0.095 at a 1 pgml-1 level of TMDS was claimed (see also ARAAS, 1978, 8, Ref. 1251). A novel method for the determination of barium in the presence of a large excess of Ca has been reported (374).The Ba was selectively extracted as its 18-crown-6 ether into nitrobenzene (this reagent is highly toxic !). Three extractions were necessary. The Ba was then re-extracted in 1M HNO, and determined by AAS using a N,O/C,H, flame. The Ca concentration in the final solution was 0.1% that of the original sample solution. A PTFE porous film disc with a 40pm pore diameter, which allowed the passage of organic solvents but impeded the passage of water (466), was found to be ideally suited for microextractions when only small volumes of organic solvents were used. It is, however, only applicable to solvents heavier than water.The method was tested on orchard leaves, bovine liver and rat whole blood by extraction of Cd and Pb into CC1, using various chelating agents.Other reference of interest - N,O/H, flame for organic solvents: 1715. 3.1.2.2 Ion-exchange Methods. The precision of ion-exchange pre-concentration was found to be improved significantly if a peristaltic pump was used to control the flow of samples through the resin columns (37). Chelex 100 resin has been used to concentrate Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn from seawater (456).After adjustment of the pH to 5.2 the sample was passed through the column. Alkali and alkaline-earth metals were eluted with ammonium acetate prior to elution of the analyte elements with 2x5 ml of 2.5M HNO,. The final extracts were analysed by ETA. Additional references on the preceding topic - 670, 1070. The direct ETA anatysis of small mounts (--I rng) of ion-exchange resins, after passage of the sample solution through a small quantity of the resin, is becoming popular (172, 644, 946, 1043, 1496). This approach has the advantage that natural water samples can be passed through the resin at the time of collection and hence the problems associated with preserva- tion of the sample solutions are effectively overcome, Barnes et al.(1546) have passed 25Oml urine samples through columns containing 100mg of a polydithiocarbamate resin, washed the resin with water and then digested it in 2ml HNOB/H2S0,, to give a 125-times concentration step for trace metals. The resulting solutions were nebulized into an ICP.A similar technique has been applied to geological analysis (1309). It should be stressed (yet again) that it is possible that some elements present in natural waters or biological samples are associated with natural organic com- pounds and are not quantitatively extracted unless a pretreatment step, such as photo- chemical oxidation or wet digestion, is used.The fact that spikes of the analyte are recovered from these types of samples does not guarantee recovery of endogenous analyte. Other references of interest - Au, Pt, ion-exchange pre-concentration: 229.Development of specific ion-exchange resins: 73.64 Analytical Atomic Spectroscopy Non-boiling concentration: 465. Polyurethane foam / 142 pyridylazo)-2-napthol: 293. Speciation /ion-exchange studies: 88. Se, electrochemical pre-concentration: 1493. TI, anion-exchange pre-concentration: 1074. 3.1.2.3 Adsorption Concentration. Concentration of Ag, As, Bi, Cd, Cu, Hg, Se, Sn, Te and Zn has been achieved (1615, 2033) by passing the sample solution at pII 3-6 through a freshly prepared homogenous layer of CuS, MnS or ZnS. The layer was 300-400nm thick and was supported on a 40 mm diameter cellulose nitrate or PTFE filter with a pore size of less than 1 pm. The resulting precipitate was dissolvcd in 2 ml aqua regia and the elements determined by ETA.By using large sample volumes (0.1-6 litres) detection limits of a few ngl-1 were obtained. An additional advantage of the technique was that tlic filters could also be analysed using XRF. Isolation of the analyte from the matrix can occasionally be achieved with simple methods. Jackwerth (628) has Concentrated many trace elements from a lead matrix by dissolving the lead in 20% V / V HNO,, evaporating the solution to near dryness and extracting the precipitated Pb(NO,), with 65% V/V HNO,, Gold has been concentrated from aqueous solutions by adding a large excess of Hg2+ ion, adding SnCl, solution, collect- ing the resulting Hg globule containing the Au and dissolving it in a small volume of aqua regia (729).Additional reference on the preceding topic - 112. 3.1.3 Indirect Methods Indirect methods can prove very useful for specific applications, but it is important to appreciate that the reaction of the determinand with the element finally determined is often not specific. Hence, interference effects can be quite severe and the methods tend to have limited application.The ittdirect determiiiation of phosphate by measuring the Mo or V in phosphovanado- molybdic acid has been recommended for the analysis of iron and steels (724) and biological tissue (1369). The method was claimed t o be an improvement over the more common phosphomolybdic acid system (see also ARAAS, 1978, 8, 65). The formation of phospho- molybdic acid has been used, however, for the analysis of bottom sediments for phosphate (1 778).Vierkorn-Rudolph and Bachmann (1002) have determined nanogram levels of chloride by utilizing the following reactions : C,H,Hg NO, + C1- + C,H,Hg Cli- NO,- CrO, + 2H+ +2C1- -+ CrO,Cl, The covalent reaction products were extracted using CHCl, or CC1, and the Hg or Cr subsequently determined by ETA. +H,O Additional reference on the preceding topic - 338.The determination of the total carboxyl and phenolic content of coat and lignite residues has been achieved (565) by treating the coal with 1M NaOH, washing it with water, then removing the adsorbed Na with HCl and determining the Na by FES. When NaHCO, was substituted for NaOH, only the carboxyl group adsorbed sodium, and thus the carboxyl content could be determined.Carbon disulphide has been determined in fuel gases (927) by absorption in alcoholic KOH and reaction with Cu2f ion to form insoluble cuprous xanthate. This was separated byMethodology 65 filtration, dissolved in acid and the Cu determined by AAS. Other workers (1854) have adsorbed the CS, onto a chromatographic support and subsequently determined the CS, by monitoring S, emission in a cool flame.Non-ionic detergents in natural waters have been determined by extraction into ethyl acetate, evaporation of the extract to dryness, followed by reaction with phospho- molybdic acid in the presence of BaCl, to form an insoluble Mo species. The residual Mo in the filtrate was measured by FAAS (1828). A somewhat simpler method has been pro- posed by Crisp et al.(1487) who used the extraction of a neutral adduct with potassium tetrathiocyanozincate into 1,2-dichlorobenzcne. The Zn was subsequently determined by FAAS after back extraction into 0.1M HCl. Anionic detergents have been determined (305) in natural waters at the ngml-1 level by reaction with Cu(I1) and ethylenediamine to form a ternary complex, which was then extracted into CHC1, and the Cu subsequently deter- mined using ETA.At very low levels interference by natural organic chelating agents was minimized by preferential U.V. photochemical oxidation of the chelating agents prior to the analysis. Zndirecr AAS methods have also been proposed for: As (33), chluroprothixene (1231), cyanates (1612), esters (1 1291, ethinyloestradiol (703), fluoride (1649), sulphate (1248, 1443, 171 7), tannins (1 159) and thiols (1712).Zndirect emission methods have bccn proposed for aliphatic amines and amino acids (1565), fluoride (1540, 1686), sulphate (564, 580) and total sulphur (1468). 3.1.4 Nebulization, Vaporization and Atomization The Babington nebulizer (see ARAAS, 1978, 8, 8, and 1977, 7, 24) continues to gain popularity (546, 591, 592, 1738) and is being used for a wide variety of difficult applications. This nebulizer can satisfactorily nebulize solutions containing a high level of dissolved solids, viscous solutions and even solutions containing suspended solids, such as homogen- ized tissue (546).It can also operate at low Ar flow rates and is thus ideally sl-lited to ICP as well as FAAS analyses. The reported FAAS detection limits were similar to those obtained with a conventional pneumatic nebulizer (591).Ape1 and Duchane (569) described a fritted disc pneumatic nebulizer that was fabricated from a 15 ml Buchner funnel containing a fine frit. The sample was supplied to one side of the frit by a peristaltic pump and, simultaneously, gas was forced through from the other.Nebulization efficiences greater than 60% were obtainable. The device can be thought of as a Babington nebulizer with multiple orifices (see also Section 1.2). Cresser (1364, 1504) has described an impact cup that can be easily fitted to most commercial AAS pneumatic nebulizers. The PTFE cup replaced the impact bead and was positioned so that the nebulized sample was directed on to the inside of the cup.The resulting absorbance signal f o r most elements was rcduced about 12 times and thus the Ca, Mg and Na content of many natural waters could be determined without sample dilution. The fine spray produced resulted in less condensed phasc interference effects. It was possible to incorporate both the cup and the conventional impact bead in the spray chamber and to changc from one to the other without extinguishing the flame.Slurry injection where the solid sample i s ground to a small size, suspended in a suitable solution, such as 0.5% m/V aqueous Triton X-100, and directly nebulized into a flame or plasma is becoming increasingly popular (see ARAAS, 1975, 5, Ref. 1239). The technique has proved extremely useful for coal analysis using conventional pneumatic iiebulization (215, 530, 1694), Babington nebulization (546, 1361) and ETA (215).Compared to conven- tional wet ashing, approximately 15 min of operator time per sample was saved and, in addition, the typical turn-round time was reduced from 2days to 2 h (530). The main66 Analytical Atomic Spectroscopy disadvantage of the technique is decreased accuracy because of increased matrix effects.Careful calibration preferably using slurries containing typical samples that have previously been analysed after conventional wet or dry ashing is recommended. Additional references on the preceding topic - 12, 546, 591, 1444, 1501, 1568, 1588, 1694, 1981. FAAS detection would appear to be ideally suited for flow injection analysis.Some promising results using small volumes of analyte and automated sample injection have been reported (495, 1708). Ure et al. (1464) have mounted a water-cooled silica tube in an air/C,H, flame to concentrate Cu from solutions nebulized into the flame for a fixed period. At the end of the period the cooling water was turned off and the liberated Cu absorbance pulse (10-20s duration) was monitored.A characteristic concentration of 0.8 pg 1-1 was observed (see also RRAAS, 1976, 6, Ref. 1288). Gold, Pd and Pt have been vaporized (1628) by heating silicate samples in a stream of chlorine at 850 OC for 15 min. The volatile metal chlorides were condensed on to a water- cooled gat-top electrode and the metals subsequently determined by OES in a 10 A a.c.arc. Standards were prepared by mixing silica with small portions of the metal chlorides. Two sample preparation techniques were compared for hollow-cathode excitation (805). In the first technique, the cup cathode was coated with a benzene solution of Apiezon N grease and then 20Opl of the sample solution placed in the cup and evaporated to dryness under an i.r. lamp. In the second technique, the electrode was dipped in the sample solution, which was then evaporated to dryness, The first technique was found to be optimal for “cooled” cathodes, while the second was recommended for “hot” cathodes.The use of element-specific spectroscopic detectors for GC and HPLC continues to increase (see Section 1.2.2.3). Plasma detectors are the most popular and these include d.c.Ar plasmas (59, 60, 454), MIP (75, 89, 91, 193, 608) and ICP (1610). Flinn and Aue (129) used a cool flame detector to determine Se in GC effluents by monitoring Se, emission at 475 nm. The response was quadratic as for S, emission. Various methods for coupling flames to HPLC systems have been reported (39, 40, 101, 436, 481, 526). A direct interface to an ETA system (230) has been used to detect Se; Ni was incorporated into the final liquid stream to prevent loss of Se during the dry ashing step.The direct aitalysis of solid samples can result in considerable labour saving, but the main problems are still sample homogeneity and establishing reliable calibration procedures. Langmyhr (1681) has produced a comprehensive review on this subject and concluded that it has great potential, particularly in medicine, biology and environmental analysis.The use of graphite powder was found to improve atomization efficiency and prevent sample fusion in direct ETA of solids, and if the correct operating conditions were employed it was often possible to use simple aqueous standards for calibration (531). Van Loon (1751) has mounted metal samples (in the form of rods or nails) in graphite rods and inserted these into a flame. Refractory samples could be mounted on a Pt wire for insertion.A HC1 solution wds simultaneously nebulized into the flame and the determination carried out by AAS. The results were matrix-dependent but could be used for semi-quantitative sorting of sample types. Uranium determination b y A AS is notoriously insensitive; the characteristic concentra- tion in the N,O/C,H, flame has been improved 5 times by the addition of 10 mg ml-1 Ga to all solutions (1870).Tarui and Tokairin (636) have determincd U by ETA in a graphite tube device and avoided a significant memory effect from carbide formation by placing thc sample in a small Ta boat that was inserted into the tube.Methodology 67 L’Vov and Pelieva (1839) successfully determined cerium in steel in the 0.05-0.23% concentration range by ETA.A comprehensive study of the factors affecting Ce determina- tion was presented and from these studies the authors found that a Ta-lined furnace and the use of the 567 nm absorption line gave the best results. The determination of boron and phosphorus by ETA is limited by poor sensitivity and memory effects.Szydlowski (502) enhanced the B sensitivity and minimized carbide formation by the addition of 1000 pug ml-1 Ba to all solutions. Natural waters were success- fully analysed by this method using a Massmann graphite tube ETA device. Khavezov et al. (1890) used Zr carbide coated graphite tubes to achieve increased P sensitivity, long tube life and to avoid the necessity of adding La to the samples (see also ARAAS, 1978, 8, 66).A P detection limit of 0.05 pgml-1 for a 50 pl sample injection volume was claimed. Garnys and Smythe (463) improved the rate of ETA analyses by pre-drying and ashing samples on a long graphite filament. The filament was inserted through the graphite tube, the temperature raised for atomization and then the filament rapidly moved on to the next sample.The rate of analysis was increased three fold. Other references of interest - ETA-Determination of Tc: 458. ETA-Use of CCI, and CF,Cl, for vaporization: 1009. Graphite capsule in flame atomizer: 717. New pneumatic nebulizer: 1596. Use of organic acids to improve FAAS signal stability: 571. 3.2 DETECTION LIMITS, PRECISION AND ACCURACY Impressive detection limits or good precision are not synonymous with high accuracy. More attention should be given to improving accuracy rather than detection limits, on which considerable eff art and ingenuity are frequently expended. Boumans and Bosveld (1475) and Winge et al. (1730) have independently carried out investigations in computing the relative ZCP sensitivities for up to 10 prominent lines of some 70 elements.Detection limits were estimated from the ratio of peak-to-background intensity for each line, The results were presented in tabular form arranged alphabetically by element. A specific study of optimum ICP emission wavelengths for 18 impurity elements in TiO, has been made (63). Demers (617) has presented the results of an evaluation of the “end-on” viewed ZCP, operating in the horizontal position.It was claimed that with aqueous samples much lower detection limits were obtained than with the conventional configuration, but precision and chemical interference effects were similar (see also ARAAS, 1978, 8, Ref. 1415 and Section 1.2). A method for determining the contribution of separate noise componerzts with respect to source and type, the “noise-study” method, has been tested using an automated AE/AF spectrometer system (602).An evaluation of modulation methods and flame types was used to demonstrate how the magnitude and source of precision limiting noise call be determined. The use of a resistor-capacitor damping device for improving the SNR of transient AA signals was described by Wall and Catterick (41).The authors demonstrated the advantages of the device by using it in conjunction with two commercially available instruments having alternatively digital and analogue damping systems. The accuracy of most methods is critically dependent upon the rnerhod of cdibru~iort. Standard addition was the subject of a detailed study by Ratztaff (1999). Equations were given to demonstrate the effect of increment size on the precision of a standard addition or subtraction method.Use of a “generalized” standard addition method has been postulated (1844) as a means of detecting and quantifying the magnitude of interference effects. The68 Analytical Atomic Spectroscopy determination of Ca in Portland cement employing calibration by standard addition (1643) was shown to result in errors of up to 2896, whereas with matching standards, errors were less than 2%.A wide concentration range calibration method for furnace AAS was described (159) in which the peak width at a chosen fixed height was measurcd. It was claimed that the results obtained by this method were not affected by the numerous optical and electronic factors which cause non-linear response in AAS.The authors reported that a 100-1000 fold range of concentration could be covered by this method. It has been shown that calibratioii graphs for Cr determination by FAAS, in the optimized luminous air/C,H, flame, can exhibit inflexions and/or regions of negative slope (144). ‘The shape of the graph was found to be dependent upon the age of the standards, even when made up in 10% V / V IiNO,.Thcse efects were not observed if a non-luminous flame was used; however this resulted in a significant loss of sensitivity. Other references of interest - Analytical range test: 859. Detection limits of rare earths by ICP-OES: 1275. Preeision and noise in FAAS: 929. Preeision of flame emission measurements : 6 19.Seleetio n and pre-concentration of trace substances: 629. Use of the cathode layer line enrichment to reduce detection limits for noble metals: 13. 3.3 STANDARDS AND STANDARDIZATION 3.3.1 Standards A timely report on the worldwide availability and application of CRMs for trace analysis has been prepared by Koch (308). This report was originally proposed at the 26th IUPAC conference in 1971 and should prove to be extremely useful particularly for those concerned with routine analytical quality control.Alvarez (52) described the preparation and methodology for certification of six plant tissue and food product CRMs issued by the National Bureau of Standards (N.B.S.). The value of such CRMs in the development of reliable methods for obtaining accurate data on the chemical composition of foods in agricultural studies was stressed (1434).The area of fossil fuel analysis has been somewhat neglected in the preparation of CRMs, particularly in view of the increasing use of these fuels as a primary energy source. Reed and Uriano (86) have described two currently avail- able CRMs in this field as wcll as plans for expanding the range.A set of six new silicate “Geochemical Exploration” samples has been produced by the US. Geological Survey (1554) and, in view of inhomogeneity problems with the previous series, work has been carried out on 42 elements by more than 100 laboratories on a co-operative basis. Stoch et al. (Geos. Newsl., 1979, 3, No. 1, 25) have described in a very thorough report the preparation and certification of two samples of Bushweld type chromitc, dctailed statistical treatment of results from 32 laboratories throughout the world was presented .Other references of interest - Feasibility study for preparation of high purity reagent RMs: 6x3. Investigations into homogeneity of metallurgical materials for solid sample ETA: 1119. Pepperbush powder RM: 1934.Methodology 69 3.3.2 Standardization Studies Smith (1452, 1858) has produced a report summarizing interluboratory comparison studies carried out by the South African National Institute for Water Research.Results and methods used for mineral (Part IV) and trace metal (Part V) analysis by 14-16 laboratories were given. For the trace metal study, solutions were prepared by additions of proprietory standard solutions to deionized-distilled water and circulated in polythene containers.The two groups of elements studied were: Group I: Al, Cd, Co, Cry Cu, Fe, Mn, Ni, Pb and Zn; Group 11: Ag, As, Ba, Be, I-Ig, Li, Se, Sr, and V. Almost 95% of the determinations were carried out using AAS techniques. Of the results received, 67% were considered acceptable, 25% acceptable but questionable, and 8% unacceptable.Insufficient data was received for As, Hg and Se. As a result of tests involving 22 laboratories under the auspices of the BITC (Bureau International Technique de Chlore), two methods for the determination of total Hg in water involving the cold vapour technique have been accepted for recommendation as referee methods (171 9).The breakdown procedures recommended were (i) oxidation with HNO, /H,SO,/KMnO, /K2S,08 for domestic waters and domestic and industrial waste and, (ii) U.V. irradiation in the presence of K,Cr,O, and H,SO, or HNO,. Several interlaboratory method studies have been carried out on the determination of Pb in blood (1116, 1198, 1316, 1621). These have shown that there is room for improvement in such areas as the preparation of standard materials and the selection of laboratories with relevant experience (see also Section 3.1.2).The accuracy of 2 reference methods for Na and K in serum by FAES has been confirmed in a survey carried out by 12 laboratories in which manual and semi-automated pipetting techniques were used (325). In an intercomparison of analytical methods for the analysis for traces of Pt and Pd in alloys, Pauwels (19) has shown that both AAS and activation techniques can be used for determining the lower levels of these elements with precision and accuracies equivalent to the uncertainties of the referenee material.XRF, OES and spark source MS, however, were less accurate. The samples used in the study were synthetic alloys prepared by doping pure Cu with Pt and Pd using high-frequency levitation melting.A comparison of two methods for the dissolution of iron ores was studied in a round- robin test on the determination of trace levels of Cr, Cu, Mn, Ni, Pb, Ti, V and Zn by AAS (1898). An acid dissolution procedure involving HCl was found to give more accurate results than a Na,BO, /Na2C0, fusion procedure.With this latter procedure lower values for Cu and Pb were observed and this was attributed to alloy formation with the Pt crucibles during the fusion step. A very large amount of collaborative effort is required before a Standard Method can be published with confidence. Such a method for the analysis of wood preservatives and treated timber containing As/Cr/Cu formulations has been issued (1 160).Arsenic, Cr and Cu are leachcd from the wood by dilute H2S0,/H,0, solution before analysis by FAAS. An alternative photometric procedure is given. The U.K. Department of the Environment / National Water Council has issued tentative AAS mcthods for the determination of Hg and Ca in waters and sewage effluents (1076, 1426) as part of a series of rccommended methods for the determination of water quality.Methods for the determination of both inorganic and organo-mercury compounds using the cold vapour technique are given. It is hoped that the final version of the Ca method will give an indication as to the maximum permissible levels of potential interferents such as aluminium, phosphate and sulphate. Other references of interest - AAS techniques in food analysis: 533.Comparison between ETA and anodic stripping voltammetry for the determina- tion of Pb in geological samples: 659.70 Analytical A tomic Spectroscopy Evaluation of two mineralization methods for plant materials: 1895. Interlaboratory comparison of trace element measurements in marine organisms: 408. Metals in workplace environments, collaborative test of a “Ruggedized Method”: 115.Methods for determination of total Hg in gases: 1666. Sampling and methods for determination of Cd, Cu, Ni and Zn in sea water: 1070. Sn in foods by AAS: 45. TABLES 3.3A.1- 3.3A.5 : REFERENCE MATERIALS Table 3.3A.1 FERROUS METALS AND ALLOYS ~~ ~~ ~ Supplier Finely divided form Solid form Amt fur Standardisierung und Warenprufung (ASMW), 102 Berlin, Wallstrasse 16, D.D.R.Bundesanstalt fur Materialprufung (BAM), 1 Berlin 45, Unter den Eichen 87, Germany Bureau of Analysed Samples Ltd., Newham Hall, Newby, Middlesbrough, Cleveland TS8 9EA, England Bureau National de Metrologie (B.N.M.)., 21 rue Casimir Perier, 7500T-Paris, France Centro Nacional de Investigaciones Metalurgicas, Cuidad Universitaria, Madrid 3, Spain Gosstandart of the USSR, 9 Leninsky Prospekt, 1 1704, Moscow, U.S.S.R.Institut de Recherches de la Siderurgie Francaise, B.P. 129, 78104-Saint Germain en Laye, France Iron & Steel Institute of Japan, Japan Unalloyed & alloyed steels, cast irons, slags, ferro alloys Unalloyed & alloyed steels, slags, cast irons, ferro alloys High purity irons, unalloyed & alloyed steels, slags, cast irons, ferro alloys Unalloyed & alloyed steels, cast irons High purity irons Unalloyed & alloyed steels Unalloyed & alloyed steels, cast irons Unalloyed & alloyed steels, ferro alloys, cast irons, slags Unalloyed & alloyed Unalloyed & alloyed steels Unalloyed & alloyed steels, cast irons steelsMethodology 71 MBH Analytical Limited, Station House, Potters Bar, Herts.EN6 lAL, England Metalimpex, POB 330, H- 1 376 Budapest, Hungary National Bureau of Standards, Office of Standard Reference Materials, Washington, DC 20234, U.S.A. Spex Industries Inc., 3880 Park Avenue, Metuchen, NJ 08840, U.S.A. Swedish Institute for Metal Research, Drottning Kristinas vag 48, S-11428 Stockholm, Sweden South African Bureau of Standards, Private Bag X191, Pretoria, Transvaal 0001 , South Africa Unalloyed & alloyed steels Unalloyed & alloyed steels, cast irons, ferro alloys Unalloyed & alloyed steels, cast irons Unalloyed & alloyed steels, cast irons Unalloyed & alloyed steels, cast irons Unalloyed & alloyed steels, cast irons Unalloyed & alloyed steels, ferro-alloys, slags Ferro alloys Table 3.3A.2 NON-FERROUS METALS AND ALLOYS Supplier Finely divided form Solid form Aluminium Company of America, Alcon Technical Center, Alcon Center, PA 15069, U.S.A.Aluminium Pechiney, High-purity metals, 23 bis, rue Balzac, 75360 Paris Cedex 08, France Amt fur Standardisierung und Sn, Al, Mg base Al, Cu Warenprufung (ASMW), 102 Berlin, Wallstrasse 16, D.D.R.British Aluminium Co. Ltd., Chalfont Park, Gerrards Cross, Bucks. SL9 OOB, England Bundesanstalt fur Materialprufung (BAM), 1 Berlin 45, Unter den Eichen 87, Germany Bureau of Analysed Samples Ltd., High-purity metals, High-purity metals, Newham Hall, Newby, Middlesbrough, Pb base Cleveland TS8 9EA, England A1 base Al, Mg base A1 base Cu, Ni, Al, Mg base Al, Mg, Cu, Ni, Sn, AI.Cu, Ni base72 Analytical Atomic Spectroscopy Table 3.3A.2 NOM-FERROUS METALS AND ALLOYS- cmfinued Supplier Finely divided form Solid form BNF Metals Technology Centre, Grove Lab oratories, D c nchw o rt h Road , Wan ta ge, Oxfordshire, England Canada Centre for Mineral and Energy Technology, c / o Coordinator, CANMET, 555 Booth Street, Ottawa, Ontario K1A OGI, Canada Commissariat a 1’Energie Atomique, (C.E.A.) Cristal Tec, B.P.no 85 Centre de tri, 38041 - Grenoble Cedex, France Centre Technique des Industries de la Fonderie (C.T.I.F.), 44, Avenue de la Division Leclerc, 923 10 - Sevre, France Centre Technique du Zinc, 34, rue Collange, 92300 -Levallois Perret, France Gosstandart of the USSR, 9 Leninsky Prospekt, 11704 Moscow, U.S.S.R. Inco Europe Limited, European Research and Development Centre, Commercial Development Department, Birmingham B16 OAJ, England Japan Brass Makers’ Association, Japan Japan Light Metal Association, Japan Light Metal Smelters Association, Japan Johnson Matthey Chemicals Ltd., Orchard Road, Royston, Herts.SG8 SHE, England Cu base Cu base Cu base Al, Mg base Cu base High-purity metals, Zn base Cu base Ni base Cu base Al, Mg base Al, Mg base Hi gh-puri ty me ta 1s High-punt y me ta IsMethodology 73 MBH Analytical Limited, Station House, Potters Bar, Herts.EN6 IAL, England Mercure Industrie, 13, rue Saulnier, 92800 - Puteaux, France Metalimpex, POB 330, H-1376 Budapest, Hungary Al, Cu, Ni, Zn, Co base High-purity metals A1 base National Bureau of Standards, Office of Standard Reference Materials, Washington, DC 20234, U.S.A.High-purity metals, Al, Co, Cu, Ni, Pb, Mg, Sn, Pb, Ti, Zn, Zr base Al, Cu, Pb, Ni, Ti, Zn, Zr base Planet- Watt ohm, 05310-la Roche de Rame, France Spex Industries Inc., 3880 Park Avenue, Metuchen, NJ 08840, U.S.A. High-purity metals Cu, Pb, Sn base Table 3.3A.3 GEOLOGICAL MATERIALS Supplier Finely divided form Amt fur Standardisierung und Warenprufung (ASMW), 102 Berlin, Wallstrasse 16, D.D.R.Mn, Cr, Sn ores Bundesanstalt fur Materialprufung (BAM), 1 Berlin 45, Unter den Eichen 87, Germany Fe ores Bureau of Analysed Samples Ltd., Fe, Mn, Cr, Al, ores Newham Hall, Newby, fluorspar, sillimanite, Middlesbrough, Na & K feldspar, magnesite, dolomite Cleveland TS8 9EA, England74 Analytical Atomic Spectroscopy Table 3.3A.3 GEOLOGICAL MATERIALS - continued Supplier Finely divided form Canada Centre for Mineral and Energy Technology, c / o Coordinator, CANMET, 555 Booth Street, Ottawa, Ontario KIA OGI, Canada Sb, Co-Mo, Au, Fe, Mo ores syenite, gabbro, ultramafic rocks Centre National de la Recherche Scicntifique, Centre de Recherche Petrographiques et Geochimiques (C.N.R.S./C.R.P.G.), 15, rue Notre Dame des Pauvres, Case Officielle No. 1, 54 500 Vandoeuvre-lez-Nancy , France Commission of European Communities, Community Bureau of Reference (BCR), 200 Rue de la Loi, B-1049 Brussels, Belgium Geological Survey of Japan, Japan Gosstandart of the USSR, 9 Leninsky Prospekt, 1 1704 Moscow, U.S.S.R. International Atomic Energy Agency, Analytical Quality Control Services, Laboratory Seibersdorf, PO Box 590, A-101 1 Vienna, Austria Junta de Energia Nuclear, Cuidad Universitaria, Madrid-3, Spain L.R.M., B.P. 3013, 54000 Nancy Cedex, France National Bureau of Standards, Office of Standard Reference Materials, Washington, DC 20234, U.S.A. National Chemical Laboratory for Industry, Japan South African Bureau of Standards, Private Bag X191, Pretoria, Transvaal 0001, South Africa Ores, rocks Zn, Pb, Sn, Cu ores Rocks Fe ores U ores Lignite Rocks Fe, Al, Cu, Mo, Li, Zn, W ores, fluorspar, Na & K feldspar, clays Rocks Rocks, Fe, Cr oresMethodology 75 Table 3.3A.4 GLASSES, CERAMICS AND REFRACTORIES Supplier Finely divided form Bureau of Analysed Samples Ltd., Newham Hall, Newby, Middlesbrough, Cleveland TS8 9EA, England Centre d'Etudes et de Recherches de L'lndustrie des Liants Hydrauliques, 23, rue de Cronstadt, 750 1 5 - Paris, France Centre National de la Recherche Scientifique, Centre de Recherche Petrographiques et Geochimiques (C.N.R.S./C.R.P.G.), 15, rue Notre Dame des Pauvres, Case Officielle No. 1, 54500 Vandoeuvre-lez-Nancy, France Federation Europeenne des Fabricants de Produits Refractaires (P.R.E.), 44, rue Copernic, 75016 Paris, France L.R.M., B.P. 3013, 54000 Nancy Cedex, France National Bureau of Standards, Office of Standard Reference Materials, Washington, DC 20234, U.S.A. National Chemical Laboratory for Industry, Japan Sheffield University, Department of Ceramics, Glasses and Polymers, Northumberland Road, Sheffield S10 2TZ, England Society of Glass Technology, 20 Hallam Gate Road, Sheffield S10 5BT, England Silica brick, firebrick, magnesite-chrome Portland cement, zircon, high purity silica Cement Glasses (2 available) Refractory materials Refractory materials Lead / barium, opal, high and low boron, soda lime glasses, silica, aluminosilicate and chrome refractories, Portland cements Sodalime silica, silica, high silicic acid - high boric acid glass Potassium oxide-lead oxide-silica glass Glasses (3 available)76 Analytical Atomic Spectroscopy Table 3.3A. 5 ENVIRONMENTAL MATERIALS ~~ ~~~ Supplier Finely divided form Bureau of Analysed Samples Ltd., Newham Hall, Newby, Middlesbrough, Clcveland TS8 9EA, England Institut de Recherches de la Siderurgie Fra ncaise, B.P. 129, 78 104 - Saint Germain en Laye, France Furnace dust (LD) Furnace dust (electric) National Bureau of Standards, Office of Standard Reference Materials, Washington, DC 20234, U.S.A.Orchard leaves, bovine liver, river sediment, urban particulate matter, coal, fly ash, Theat flour, rice flour, yeast, tomato leaves, pine ncedles, spinach, oyster tissue 1 1 i 3 4 5 6 7 8 9 10 11 Table 3.3B SUPPLIERS OF SPECTROGRAPHIC GRAPHITE ELECTRODES Baird Corporation Inc., 125 Middlesex Turnpike, Bedford, MA 01 730, U.S.A.Carbon Products Division, Union Carbide Corp., 270 Park Avenue, New York, NY 10017, U.S.A. (ARL Ltd., Wingate Road, Luton, Beds., England) Labtest Equipment Co., 11828 La Grange Avenue, Los Angeles, CA 90025, U.S.A. Johnson Matthey Chemicals Ltd., 74 Hatton Garden, London EClP lAE, England Le Carbone (GB) Ltd., Portslade, Sussex, England Le Carbone Lorraine, 37-4 1 Rue Jean-Jaures, 92231 Gennevilliers, France Jarrell-Ash, 590 Lincoln Street, Waltham, MA 021 54, U.S.A.Zebac Inc., P.O. Box 345, Bevea, OH 44017, U.S.A. Ringsdorffe-Werke GmbH, 53 Bonn-Bad Godesberg, West Germany (Mining & Chemical Products Ltd., Alperton, Wembley, Middlesex HA0 4PE, England) Spex Industries Inc., 3880 Park Avenue, Metuchen, NJ 08840, U.S.A.(Glen Creston, 16 Carlisle Road, London NW9 OHL, England) Ultra Carbon Corp., P.O. Box 747, Bay City, MI 48706, U.S.A. (Heyden & Son Ltd., Spectrum House, Alderton Crescent, London NW4, England)Methodology 77 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Table 3.3C SUPPLIERS OF STANDARD METAL SOLUTIONS (MS) AND REAGENTS (R) FOR AAS Aldrich Chemical Co., Inc., 940 W.St. Paul Avenue, Milwaukee, WI 53233, U.S.A. (R) J. T. Baker Chemical Co., 222 Red School Lane, Phillipsburg, NJ 08865, U.S.A. (MS, R) Barnes Engineering Co., 30 Commerce Road, Stamford, CO 06902, U.S.A. (MS) BDH Chemicals Ltd., Poole, Dorset BH12 4NN, England (MS, R) Bio-Rad Laboratories, 2200 Wright Avenue, Richmond, CA 94804, U.S.A. (MS) Carlo Erba, Divisione Chimica Industriale, Via C . Imbonati 24, 20159 Milano, Italy (MS) Eastman Organic Chemicals, Eastman Kodak Co., 343 State Street, Rochester, NY 14650, U.S.A. (R) Fisons Scientific Apparatus Ltd., Bishop Meadow Road, Loughborough, Leics. LEll ORG, England (MS, R) Harleco, Div. of American Hospital Supply Corp., 60th and Woodland Avenues, Philadelphia, PA 19143, U.S.A. (MS) Hopkin & Williams Ltd., P.O. Box 1, Romford, Essex RM1 IHA, England (MS, R) V. A. Howe & Co. Ltd., 88 Peterborough Road, London SW6 3EP, England (MS) Instrumentation Laboratory Inc., 11 3 Hartwell Avenue, Lexington, MA 02173, U.S.A. Johnson Matthey Chemicals Ltd., 74 Hatton Garden, London EClP lAE, England (R) Koch-Light Laboratories Ltd., Colnbrook, Bucks., England (R) (Anderman & Co. Ltd., Battlebridge House, 87-95 Tooley Street, London SE1, England) May & Baker Ltd., Dagenham, Essex RMlO 7XS, England (R) E. Merck, D 61 Darmstadt, West Germany (R) Spex Industries Inc., 3880 Park Avenue, Metuchen, NJ 08840, U.S.A. (MS) ALFA Division, Ventron Corp., 152 Andover Street, Danvers, MA 01923, U.S.A. (MS) (MS) (Glen Creston, 16 Carlisle Road, London NW9 O H L , England)78 Analytical A tomic Spectroscopy 10 11 12 13 14 15 16 17 Table 3 3D SUPPLIERS OF ORGANOMETALLIC STANDARDS Angstrom Inc., P.O. Box 248, Belleville, MI 481 11, U.S.A. Baird Corporation Inc., 125 Middlesex Turnpike, Bedford, MA 01730, U.S.A. J. T. Baker Chemical Co., 222 Red School Lane, Phillipsburg, NJ 08865, U.S.A. BDH Chemicals Ltd., Poole, Dorset BH12 4NN, England Burt and Harvey Ltd., Brettenham House, Lancaster Place, Strand, London WC2, England Carlo Erba, Divisione Chimica Industriale, Via C. Imbonati 24, 20159 Milano, Italy Conostan Div., Continental Oil Co., P.O. Drawer 1267, Ponca City, OK 74601, U.S.A. Durham Raw Materials Ltd., 1-4 Great Tower Street, London EC3R SAB, England Eastman Organic Chemicals, Eastman Kodak Co., 343 State Street, Rochester, NY 14650, U.S.A. Hopkin and Williams Ltd., P.O. Box 1, Romford, Essex RM1 lHA, England E, Merck, D 61 Darmstadt, West Germany MBH Analytical Ltd., Station House, Potters Bar, Herts. EN6 IAL, England Division of Chemical Standards, National Physical Laboratory, Teddington, Middlesex TWll OLW, England National Spectrographic Laboratories Inc., 19500 South Miles Road, Cleveland, OH 44128, U.S.A. National Bureau of Standards, office of Standard Reference Materials, Washington, DC 20234, U.S.A. Research Organic/Inorganic Chemical Corp., 1 1686 Sheldon Street, Sun Valley, CA 91 352, U.S.A. ALFA Division, Ventron Corp., 152 Andover Street, Danvers, MA 01923, U.S.A. (Glen Creston, 16 Carlisle Road, London NW9 OHL, England)

ISSN:0306-1353    

DOI:10.1039/AA9790900059

出版商:RSC    

年代:1979

数据来源: RSC

摘要:

CHAPTER 4 Applications EXPLANATION OF THE TABLES Each of the Applications Sections, 4.1 to 4.9, is accompanied by a Table which summarizes the principal analytical features of the references from which the corresponding Section i s compiled. All relevant references are included in the appropriate Table, while the accom- panying text discusses only the more noteworthy contributions. These Applications Tables form a convenient source of information for analysts interested in particular elements, matrices, sample treatments, or atomization systems. In many cases, sufficient detail is given for the analytical procedure to be followed; absence of such detail usually means that the information was not directly available to the compiler of the table, and the original reference should be consulted.The key to the tables is given below. ELEMENT h/nm MATRIX CONCENTRATION TECH. ANALYTE SAMPLE TREATMENT ATOMIZATION REF. The elements determined are listed in alphabetical order of chemical symbol, except that, for space economy, multi-element applications (5 elements or more) are given at the end of some tables. The wavelength, in nanometres, at which the analysis was performed.An indication, necessarily brief, of the material analysed. The concentration range or level of the element in the original matrix, expressed as 9% or pgg-1 for solids and mgl-1 or pg ml-1 for liquids. The atomic spectroscopy technique is indicated by A (absorp- tion), E (emission), or F (fluorescence). The form of the sample, as presented to the instrument, is indicated by S (solid), L (liquid), or G (gas or vapour). A brief indication i s given of the sample pre-treatment required to produce the analyte. The atomization process is indicated by thc abbreviations A (arc), S (spark), F (flame), or P (plasma), usually with some additional descriptive detail. The number refers to the main Reference section, which gives the title of the paper and the name(s) of the author(s), with address. 79

ISSN:0306-1353    

DOI:10.1039/AA9790900079

出版商:RSC    

年代:1979

数据来源: RSC

摘要:

80 Analytical A tomic Spectroscopy 4.1 CHEMICALS 4.1.1 Petroleum and Petroleum Products In a field where the requirement is often for sequential or simultaneous mufti-element analysis it is not surprising to find an increase in papers dealing with ICP-OES. Interest in wear metal analysis continues at a high level with particular attention being paid to particle size effects and the relationship between data produced by different techniques.A series of CRMs, metal decanoates, useful in this field of analysis has appeared and is available from the National Physical Laboratory in the U.K. (772). 4. I . 1.1 Petroleum. Ross and Umland (1483) studied the sample preparation procedures available for petroleum products. Dry ashing, wet ashing, plasma ashing, Schoniger combustion, bomb oxidation, and simple dilution were investigated, with the last two techniques considered best for trace determinations.An investigation into the nature of V compounds in Boscan crudc oil was undertaken by Spencer et at. (1387), using chroma- tography, extraction and ETA-AAS. Porphyrin and non-porphyrin species were separated and characterized. The determination of S in petroleum products down to 100ppb was reported by Alder and Kargosha (W2, 1468).Reductive or oxidative techniques were used to liberate H,S or SO,, which were collected and analysed by monitoring the S , molecular emission in a H,/Ar diffusion flame. 4.1.1.2 Lubricating Oils. It was claimed by Wittmann (506) that the use of a mixed solvent, toluene and glacial acetic acid (1 +4), allowed the determination of the additive elements Ca, Mg and Zn by FAAS, using inorganic salts as standards.Interference from K wns absent. The determination of P, down to OSppm, was described by Tittarelli (1015). The sample was diluted with xylene before injection into a graphite furnace that had been treated with lanthanum nitrate. The Dayton Research Institute has been particularly active in the area of wecr metal analysis.Information has appeared on instrumental comparisons of, e.g., d.c. plasma OES, ICP-OES, rotating-disc electrode OES, ETA-AAS and FAAS (1334, 517, 567, 579), on wear metal particle size effects (600) and on the efficiency of sample introduction systems in AAS and AES (1321). Further work on a particle size independent method has been published by Saba et al. (1695, 598) (see ARAAS, 1978, 8, Ref. 931). Hernandez Mendez et al. (1670) have demonstrated the applicability of the emulsion formation technique to the determination of Pb in lubricating oils. The sample was emulsified using ultrasonic disper- sion in the presence of surfactants and the results obtained by FAAS compared with those from aqueous standards. 4.2.1.3 Gasoline. Bye et af. (1046) investigated the use of both FAAS and ETA-AAS as specific GC detectors for the determination of Pb-alkyls (TML and TEL) in gasoline. The coupling of GC and ICP-OES for a similar purpose was described by Sommer et al. (1610). An emulsion formation procedure for the determination of Pb in petrol was claimed to give acceptable results (1635). Iodine and Aliquat 336 were added as in ASTM D3237, and a gel formed by the addition of an emulsifying agent and water, prior to analysis by FAAS. 4.1.2 Chemicals and Miscellaneous Applications 4.1.2.1 Sample Preparation. General methods for the removal of organic material before the determination of Ni (1683) and Se (1505) by AAS have been produced by the Analy- tical Methods Committee oE the Royal Society of Chemistry.Selenium was determined, after wet oxidation, using hydride generation AAS while Ni was determined by conventional FAAS after wet oxidation and extraction with APDC/MIBK. Alder and Bucklow (1981)Applications 81 produced an interesting method for the determination of Cu, Zn and Cr in carbon cloth, in which the cloth was ground, suspended in a HNO, /sodium hexametaphosphate solution and directly aspirated into a flame.The preparation of refuse material for analysis by FAAS has been discussed by Peck (1609). Complete dissolution was effected by using in turn HNO,/HF, HN03/HC10,, and HCl. The use of tri-n-octylamine in MIBK/toluene (1 : 1) for the extraction of Fe (TIT) from TiI, prior to FAAS analysis was described by Spivakov et al.(716). A novel technique for the determination of As down to 35ppb in TiC1, was presented by Orlova et al. ( 3 3 ) . A molybdoarsenate species was formed and extracted into an MIBKlbutyl acetate mixture in which the Mo was measured by FAAS. Ng and Bhattacharyya (1068) determined Pb in a variety of inorganic materials after extraction into MIBK using NaDDC. A method for the layer-by-layer anulysis of Sb in epitaxial Si was described by Zakharchuk et al.(35). Layers of approximately 0.1 pm thick were removed using HF/HNO,, evaporated to dryness, taken up in H20 and analysed by ETA-AAS. In a similar procedure, Paama and Kuus (742) determined Al, Cu, Fe, Mg, and Mn in silicon semi-conductors. In this case, after removal of a thin layer with HF/HNO,/ethanol etching solution, pure graphite was added and the solution evaporated to dryness.The elements were determined in the residue by using a carbon electrode and a.c. arc OES. An enzyme was used by Ambrosetti et al. (480) to digest photographic-film emulsions for the determina- tion of Pd. The Pd was extracted into toluene with dibutylsulphide for analysis by An indirect method for the determination of Ge in CdS, based on the formation of a molybdogermanate complex, was developed by Pelosi and Attolini (1 174).The Mo was measured, which gave increased sensitivity, Coutinho et al. (927) described an indirect method for the determination of CS, in fuel gases by FAAS. Carbon disulphide was collected in alcoholic KOH containing Cu(I1) and an insoluble Cu xanthate complex was formed; this was filtered, redissolved, and the Cu determined. The method was claimed to be interference free, provided that any H2S was removed using cadmium acetate.Signal instability and drift due to burner salting, often experienced when aspirating aqueous solutions of high salt content, was claimed by Gooch et al. (571) to be considerably reduced by the addition of organic acids such as formic, acetic, propionic and butyric.ETA-AAS. 4.2.2.2 Atomic Ahsorptiori ?Methods. Further work on AsIII BV semi-conductors has been reported by Dittrich et al. (see ARAAS, 1978, 8, 78). The determination of traces of Te and Se in acid solution was investigated using both ETA-AAS and hydride generation with a heated quartz tube (1485). Te was best determined by the former and Se by the latter technique.In another paper ETA-AAS, ETA-AFS and d.c. arc OES were compared for the determination of Te (1484). The best sensitivity was obtained with ETA-AAS. In the analysis of dopant levels in semi-conductors, Demko and Copeland (105) used hydride generation coupled to the Woodriff furnace in order to improve sensitivity and, it was claimed, reducc interferences.The coupling of a lascr microprobe and FAAS for the dctcimination of the thickncss of Ag, Au and Ni layers on a copper substrate was investigated by Kantor et al. (1689). Details of the apparatus were given and depth could be determined to an accuracy of better than 0.1 pm for all three elements. Sukhov and Zolotukhin (1821) have described the determination of Cr, Cu and Mn in silicon/chromium layers on ceramics in which the solid sample was both vaporized and atomized using a Q-switchcd lascr.Spivakov et al. (1 8.10) studied the behaviour of In in both a flarnc and a furnace using aqueous solutions and organic extracts. Molecular absorption spectra were used to study82 A naly tical A tom ic Spectroscopy graphite furnace species such as InCl and I n 0 in order to predict optimum conditions for the determination.After separation by HPLC, vitamin B,, was determined (as Co) by Zeeman AAS in the presence of a large excess of inorganic Co (1272). An extensive discussion on the use of U S for the determination of trace metals in pharmaceutical products has been presented by Rousselet and Thuillier (1989).Interference effects and methods for their elimination along with detailed analytical procedures were given. 4.1.2.3 Atomic Emission Methods. The application of ICP-OES to problems in forensic analysis was discussed by Drenski et d. (1286). The multi-element nature of the technique makes it useful as a fingerprinting device for both proof of origin and ownership. The determination of S in halide salts, using a d.c. plasma, has been reported by Swain and Ellebracht (1780).The S species were reduced to H,S, using HT, and swept into the plasma where S emission was monitored in the V.U.V. region. Lowry and Strube (1736) have applied d.c. arc OES t o the determination of residual C in integrated circuits using Cu electrodes. The presence of Ga was claimed to enhance the emission of Al, As, Be, Ge, Mg, Si, Sn and Zn in the 12A d.c.arc, by facilitating a more uniform distribution of the elements between the electrodes. The determination of trace impurities in silicon by Metastable Transfer Emission Spectrometry has been described by Sutton et al. (194) (see Section 1.3.1). Measurement of the emission downstream of the discharge was fmnd to give a considerable reduction in spectral background.Table 4.1A PETROLEUM AND PETROLEUM PRODUCTS b 2 Element X/nm Matrix Concentralion Sample treatment Atomization Ref.Tech. Analyte 3 Form Al - Lubricating oils Trace levels A Ca 422.7 Lubricating oils 1-6 pg/ml A and additives (in extract) Ca cu c u c u Fe Fe 422-7 Mlneral 011s 1-6 pg/g A - Lubrfcating 011s 324-7 Petroleum products - Gasoline - Lubricating oils - Petroleum products Trace levels A 0-1-2 ,g/ml A 0.03-2.5 pg/mt A ( i n extract) Trace levels A 5 pg/ml level A (in extract) Hg 253.7 Natural gas From 0 . 2 ng/m3 A Mg 285-2 Lubricating oils 0.5-2 ,g/ml A and additives (in extract) L L L L L L L L G L See Fe, ref. 517 Graphite furnace (HGA-2100) Dilute with mixed solvent of toluene+ F Air/C,H, glacial acetic acid (1 : 4).Calibrate with inorganic metal salt standards (Ca, Mg, Zn) Comparison of various treatments for the F Air/C,H, determination of Ca, V, Zn : (A) Dry-ash in Pt at 450 "C (B) Wet-ash with HN03/H,S0,/HCI0, (HGA-72) (C) Combust on filter-paper (Schoeniger (D) Ash in microwave oxygen plasma (E) Digest with HNO, in PTFE bomb (Results obtained via above treatments compared with those from direct solution method using acetic acid/toluol dilution) N,O/C,H, Graphite furnace method) See Fe, ref. 517 Dilute with white spirit Graphite furnace F Air/C,H, (HGA-2100) Comparison of ETA-AAS with photometric method (IP 225/71) Comparison of ETA-AAS with various alternative methods for determining (HGA-2100) Al, Cu, Fe in used engine oils Interference study, related to mineralized F sample solutions (5% H,SO,).For Fe, use oxidizing flame; for V, add K+AI to all solutions. No interferences observed for Ni Collect in cold trap containing Au wool, heat to transfer Hg t o control trap and thence to absorption cell See Ca, ref. 506 F Air/C,H, Graphite furnace Graphite furnace - Cold vapour 517 z 506 1483 51 7 1158 1960 51 7 1639 418 506 wTable 4.1A PETROLEUM AND PETROLEUM PRODUCTS - coiztinued 03 P Element X/nm Matrix Concentration Tech.Analyte Form Sample treatment Atomization Ref. Mo 313-3 Lubricating oils Trace levels A L 315.0 320.9 Na - Fuel oils - E c Na - Fuel oils - E L NI - Petroleum products 5 pg/ml level A L P - Lubricating oils From 0-5 pg/g A L (in extract) Pb Pb 283.3 Gasollne 283.3 Gasollne A L A L Pb 283.3 Lubricatlng oils 1.7-3.0 mg/g A L (1-10 pg/ml in extract) Pb - Fuel oils - E L Treat with HFIHNO,, shake and dilute F N,0/C,H2 with MlBK Application of OES to determination of S - contamination levels of Na, Pb, V. Use polyethylene sampling vessels.Automated on-line method. Mix fuel with F - alcoholic surfactant/H,O diluent See Fe, ref. 1639 F - Dilute ( 1 : 1) with xylem and take 20 aliquots for analysis.Pre-treat (HGA-768) furnace with La(NO,), solution, or, with auto-sampler, add organo-La solution to diluted sample. Dry at 130 "C, ash at 1600 "C and atomize at 2700 "C Combined GC-AAS procedure for F Air/C,H, determination of TML and TEL. (A) For flame AAS, pass GC effluent to burner via heated tube ( B ) For ETA-AAS, dilute ( ~ 5 0 ) and pass sample vapour tangentially to furnace (C) Total lead may be determined by acid-extraction AAS Allow sample (4 ml) to react for 5 min.with 10 drops of 6% solution of I in benzene. Add 1 ml of 5% solution of Aliquat i n Pb-free gasoline+2-5 ml of Emulsogen LBH. Add H,O gradually until gel forms and dilute to 100 ml Prepare emulsion (0.1 g oi1/50 mi) by F Air/C,H, ultrasonic dispersion in surfactant solution (Tween 20 +MSe12/benzene) Sea Na, ref. 1765 s - Graphite furnace Graphite furnace (HGA-70) F Air/C,H, 1695 1765 1811 1639 1015 1046 b 3 s 1635 c' % b s 2. h 1670 2 GI 1765 2S 384 Petroleum products From 6 ng/rnl E (S, band) S 384 Gasoline ( S , band) S 384 Petroleum products (S, band) V - Crude oils V V V Zn Zn Various 318.4 Mineral oils - Petroleum products - Fuel oils 213.8 Lubricating oils 213.8 Mineral oils and additives - Lubricants - Petroleum products Trace levels E (as mercaptan) From 0.1 pg/g E A - 50 pg/ml level A 0-2-0.8 pg/ml A 0.4-1 ' 0 pg/g A (in extract) E - (in extract) A - L, G t G L L L L L L L t (A) Reduce with Na and Devarda's alloy F Air/Ar/H, +HCI, collect H,S in NaOH solution and re-liberate gas into flame (B) Combust, collect liberated SO, in Na teirachloro-mercurate solution and re-liberate into flame - F - Reduce to H,S with Na or Devarda's F Ar/H, alloy, under reflux Isolate and fractionate non-porphyrin V compounds on neutral AI,O,, using IPA/THF mixtures as eluants.Measure individual fractions for V by ETA-AAS. (Procedure involves other separations and other techniques, e.g., NMR, i.r.and MS) See Ca, ref. 1483 F N,O/C,H, Graphite furnace Graphite furnace (HGA-72) See Fe. ref. 1639 F - See Na. ref. 1765 See Ca, ref. 506 s - F Air/C,H, See Ca, ref. 1483 F Air/C,H, Graphite furnace (HGA-72) Comparison of methods for determination F, A - of wear metals. Elements quoted : Ag, At, Co, Cr. Cu, Fe, Mg, Mn, Ni, Pb. Si, Sn (Ti, W, Zn unsatisfactory) (A) Pb in gasoline-Dilute with F - 2-butanone and add I (10-fold excess) to equalize TEL and TML absorbances ( 8 ) Zn, Fe in engine oils-Dilute with 2-butanone and calibrate with metal benzoate solutions (C) Ni, Zn, Fe, Cu, Ca i n asphaltenes- Wet-ash with H,SO, and extract with dilute acid (D) Ca, Mg, Fe in crude oils-as for (C) 942 ,$ % e P ;; -.. 1225 1468 1387 1483 1639 1765 506 1483 393 422 00Table 4.1A PETROLEUM AND PETROLEUM PRODUCTS-continued 00 Element X/nm Matrix Concentration Tech.Analyte Form Sample treatment Atomization Ret. Lubricating oils Various - Trace levels E, A Comparison (on 350 samples) of four methods for wear metals determination : (A) AAS (B) OES - ro-trode method (D) D.c. argon plasma Add mineral acid mixture to oil sample, agitate and dilute with homogenizing reagent.(Comparison of OES and AAS methods for Fe, Ni, Cr, Mg, Cu, Al, Sn, Mo and T i ) Theoretical study of particle size effects Dilute with toluene or MIBK. (Comparison of results with those given by rotrode method) Comparative study of sample transport and particulate size in wear metal determinations by OES (ICP, d.c. arc plasma and rotrode) and AAS Comparative study of sample matrix effects in wear metal determinations by OES (ICP, d.c.arc plasma and rotrode) Elements : Fe, Al, Cr, Cu, Mg, Ni, Ti, Mo (C) ICP F, S - P ICP, D.c. plasma 567 579 598 Various - Lubricating oils (9) pg/g levels E, A F - P D.c. plasma Various - Lubricating oils Lubricating oils Trace levels Trace levels E E A. E P ICP P ICP 600 882 Various - Lubricating oils Trace levels Various 1321 Lubricating oils Trace levels E Various 1334 b oils Various - (7) Various - Used diesel-engine 0.5-50 pg/g A (various elements) E - Results quoted, on 150 samples, for Cu, F - Fe, Pb, Ag, Cr, Zn and Mg Combined GC/ICP system.Applications P ICP include TEL/TML in gasoline, Si in tetra-ethoxysilane and, indirectly, NJargon 1 ethsnol and toluene detection Investigation of use of acid-treated F Air/C,H, suspended metal particle standards, as alternative to organo-rnetallics (argon or N,O/C,H, 1417 1610 Petroleum products Used jet-engine oils p g / g levels A, F 1679Various - Used jet-engine oils Trace levels E L Dilute ( 1 : 9) with xylene.Elements : P ICP 1698 'Q Various - Lubricating oils Trace levels E , F L - - _ 1733 2- ( 8 ) Ag, Al, Cu, Cr, Mg.Ni, Si, Fe % (13) 3 Various - Engine oils (25) Trace levels E , F L - F Air/C,H, 2013 N,0/C2H,Table 4.1B CHEMTCALS AND MTSCELLANEOUS MATERTALS E Element X/nm Matrix Concentration Tech. Analyte Form Sample treatment Atomization Ref. Ag Al As As As AS As Au Ba C C Cd Metal films Organo-Si compounds High-purity t i tani um chloride Colour additive (FD & C Red No. 3) Wood preservatives and timber Antimony compounds Lewisite (in air) Metal films Calcium compounds Organic compounds Integrated circuit residues Plastic utensils From 0.025 pg A (absolute) - A From 35 ng/g A From 1 A - A - A From 0.032 p g A pg/g levels A (absolute) - A 0.1-5.0 mg E (absolute) A - S, G L L L L L, G L, G S, G L L S L Vaporize by laser microprobe and pass F Air/C,H, sample vapour/aerosol to flame See Si, ref. 571 F N,O/C,H, Adjust sample solution to contain 0.2M F - KI and 9M HCI. Form molybdo-arsenate complex and extract into MIBK/ butyl acetate solvent for measurement of Mo by AAS Digest with HNO,, evaporate t o low volume and dilute to 5 ml with H,O. Take 20 aliquots for analysis Extract As, Cr, Cu by leaching with F N,O/C,H, HzSOJH,O, and add Na,SO, solution.(Comparison with colorimetric method) Dissolve in HCI, dilute, add TiCI, solution F and extract with C,H,. Back-extract with H,O. Proceed by arsine generation method, using Zn + HCI Collect in aqueous NaOH bubbler See Ag. ref. 1689 F Air/C2H, Graphite furnace or Ar/H, NJH, + entrained air Graphite furnace Extract Ba ( 2 x 1 6 5 to 5x10-4M) from F N,0/C2H, excess Ca ( 5 x l a 2 M) with 18-crown-6 solvent extraction Ca(OH), and determine Ca in CaCO, formed or in excess Ca(OH), - A D.c.arc Combust in 0,-flask, absorb CO, in F - Extract with HLO; 3% acetic acid: 10% F Air/C,H, ethanol of ethyl ether: 4 % acetic acid. Evaporate extracts t o dryness and redissolve in 1N HNO, 1689 571 33 49 1160 1176 1410 1689 5 374 g 2.k 1230 a, 3 1736 5. 8 760 8 ;* 8 > 0cd Cr Cr Cr c s c u cu c u c u Fe Fe Fe Fe FO Ge Ge 228.8 - 359.3 - - - - 324 * 7 324.7 - 248.3 - - 248.3 313-3 (Mo) 265.1 (doublet) Calcium salts; boric acid; waters Wood preservatives and timber Thin films Carbon cloth Radioactive leachates Rare-earth reagents Wood preservatives and timber Thin films Carbon cloth Rare-earth reagents Ti ta ni um tetra-iod ide Cellulose products Drugs Perchlorate solutions Cadmium sulphide Miscellaneous samples ng/ml levels A A - A A From 0.5 C1g/mf A From 70 ng/g A A - A 7% level A From 50 ng/g A A - - A A 0.1-100 pg/rnl A 40-1 000 pS/O A A + L L S, G L L L L S, G L L L L L L L L Dissolve in H,O and separate Cd on Pt F Air/C,H, electrode (-1 -0 V).Dissolve Cd deposit in hot HNO, (1 : 1) See As, ref. 1160 F Air/C,H, or N,0/C2H, Laser evaporat i on/AAS method - - Grind (< 200 u) and shake with 2% F - HNO, +0.1% Na hexametaphosphate to form suspension - F Air/H, Adjust sample solution to pH 2-3 and F - extract Cu, Fe with oxine, into isobutyl alcohol See As, ref. 1169 F N,O/C,H, See Cr, ref. 1821 - - See Cr, ref. 1981 F Air/C,H, Dissolve 0-5g sample in 50 mi 8M HCI F Air/C,H, and extract ( x 2 ) with lOml of 0.2M tri-n-octylamine in MIBK/toluene (1 : 1).Dilute extract with acetone and (a) measure directly or (b) back-extract Fe with H,O into acetone after HCI washing of original extract See Cu, ref. 27 F - - F - Methods, including AAS, for determination F of F e ( l l ) , Fe(ll1) and total Fe - Graphite furnace Dissolve in conc.HNO,, remove S, add Graphite furnace NH, molybdate and adjust t o pH 1.3-1.5 (HGA-74) with KOH. Shake with pentan-1-ol/diethyl ether (1 : 4). Separate, strip organic phase with NH,OH/NH,CI buffer (pH 9.3) and measure for Mo (Ge/Mo=1/12) Add NaOH to sample solution t o avoid - Graphite furnace Ge loss at ashing stage ( FLA-10) A 1827 2 =1 1160 E* 1821 1981 E? 3 1250 27 1160 1821 1981 27 71 6 1416 1814 1948 1174 1470 00 Wv) Table 4.1 B CHEMICALS AND MlSCELLANEOUS MATERIALS- continued 0 Element X/nm Matrix Concentration Sample treatment Atomkatfon Ref.Tech. Analyte Form Hg In K L i Li Li Mg Mn Mo Na Ni Ni Pb 253.7 Drugs 309.3 Organic extracts: 293.3 aqueous solutions - Hydrochloric acid - Polyamide fibres 670.7 Neutron absorbers (containing boron) - Radiosctive leachates - Drugs 279.4 Thin films - Electrolytes - Hydrochloric acid 232.0 Organic matter - Thin films - Exhaust gas catalysts Trace levels (as LiCI) From 10 ng/ml (in extract) From 70 crg/g (as 6) From 0.05 pg/ml (in extract) 1-2% level - Trace levels From 0.073 pg (absolute) - Pb - Chemicals (FeSO,, ZnO, Trace levels MnSO,, Fe powder) (below 1 p / g ) A A E E A A A A E E A A A A G L L L L L L L L L S, G L L Digest with HNO, and reduce with SnCI, Cold vapour Prepare solutions in 0-1M HNO, w F - H F , Graphite furnace - F - Stir 1 g sample in 100 ml N,O for 1 h F - Digest 1-10 mg sample with HNO, in F - micro-Carius tube at 250 "C.(Indirect method for determination of B "burn-up", producing 7Li species) - F Air/H, - F - - - See Cr, ref. 1821 Adjust to pH 1 - 2 with HCI.Heat graphite A electrode to incandescence, cool and immerse for 20 s in sample solution. Dry in air and use electrodes, in pairs, in a.c. arc discharge A.c. arc - F - Oxidize with H202/H,S0,, destroy excess F H202 with SO, or Na,SO,, dilute and extract with APDC/MIBK Air/C,H, See Ag, ref. 1689 F Air/C,H, - F - Extract Pb from sample solution with NaDDC/MIBK, in the presence of excess NaCN-kNH, citrate Graphite furnace 1168 1840 1804 681 1110 1250 425 1821 14 L 1804 1683 '1, b 1689 3.h 696 2 z 1068 2 0Pd 340.5 Photographic emulsions Pd Pt Rh Ru - Ru (SO,) (S,-band) S 384 S 180.7 Sb - Sb 217.0 Sb 206.8 217.6 231.1 259.8 Exhaust gas catalysts Aqueous solutions Aqueous solutions Nuclear waste materials Aqueous solutions Miscellaneous materials Halide salts Epitaxial silicon layers Explosives residues Phosphoric acid From 9 pg/ml From 0.6 pg/ml ng levels (absolute) From 1-25 CLg/ml 40 ng to 5 pg (absolute, as SO,) From 10 ng (absolute) From 30 pg (absolute) - 0.1-2.5 @/ml A A A A A A E E A A F L L L L L L G G L L 1 4 Extract film (2 drn2) with enzyme solution Graphite furnace 480 8 (Serizyrne) at 37 "C.Remove film, evaporate extract to dryness, treat with HN03/H,02, evaporate t o dryness, treat with HNO3/H,SO4/HCIO,, evaporate to dryness, add KBr/HBr solution+0*2M dibutyl sulphide solution in toluene. Separate toluene phase. - F - 696 (HGA-72) 9, 5. 2 Study of interferences and operating F N,0/C2H:, 1875 conditions. Add L%(SO,), buffer See Pt, ref. 1875 F N,O/C,H, 1875 For most matrices (e.g., condensates, Graphite furnace 361 HCI/CH,OH and NaOH scrubber solutions, Zr/Al waste feeds) treat with HCI and compare with single series of standards in 0.1 N HCI.For solid wastes, fuse with Na,O, and extract Ru with APDC/amyl acetate. Atomize at 2800 'C See Pt, ref. 1875 F N,O/C,H, 1875 Heat sample with reducing agent at F Air/H, 1443 300 "C and pass evolved H,S to MECA system.Prepare reducing agent by heating Sn granules with anhydrous H,PO,, in N, at 290 "C Reduce t o H,S by treatment with HI and P D.c. arc 1780 pass gas t o plasma source Etch with HF/HNO, ( 1 : 70), evaporate Graphite furnace 35 almost to dryness, add 0.2 ml HNO, and evaporate (twice). Dissolve residue in H,O (20-50 420 "C and atomize at 2050 'C Application of Zeeman effect AAS P - 1272 (Sb 217.02 nrn/Pb 217.00 nm) Hydride-evolution method, with F Ar/H, 1556 non-dispersive AFS system (+ MECA cavity) plasma Dry at 100 "C, ash at\o Table 4.1 B CHEMICALS AND MISCELLANEOUS MATERIALS- continued t 4 Element X/nm Matrix Concentration Tech.Analyte Form Sample treatment Atomization Ref. ~~ - ~~~~~~ Se 196.0 Semiconductor fragments - Se - Organic materials 0.1-10 pg/g Si - Organo-Si compounds VO levels Te 214.3 Semiconductor fragments ng levels 238.5 (absolute) Te 214.3 Semiconductor fragments - Ti 365.4 Hydrazine 2-6 ng/ml Ti - Fire-proofed wool - Ti 365.4 Hydrazine Trace levels (0.5-5 pg/rnl in extract) Zn - Carbon cloth - Zr - Fire-proofed woo! - C 324.7 Coke oven gases 0-1-0.5 g/nrn3 ( cs, 1 (CU) (indirect) A L, G A, F G A L E, A, F S, L A L, G A L A L A L A L A t A L Comparison of ETA-AAS and hydride- generation methods.Dissolve sample in H CI/H NO, Digest with HNO,/HCIO, (5 : 1) in Kjeldahl flask, add HN0,/H2S0, (1 : 1) and evaporate to fuming stage. Complete by hydride-evolution method Fuse with Na,O, in pressure bomb and F N,O/C,H, dissolve melt in organic acid, t o improve sensitivity and stability Comparison of ETA-AAS, ETA-AFS and (A) For solution methods, dissolve in A 9 A d.c.(8) For direct method, mix with graphite Graphite furnace (8-1268) Heated SiO, tube Heated SiO, tube Graphite furnace OES methods. (8-1268) HCI/HNO, (1 : 1) powder containing 19'0 Bi,O, See Se. ref. 1485 Graphite furnace Heated SiO, tube (B-1268) Flash-evaporate 100 ml sample to dryness Graphite furnace and dissolve residue in small volume of 0.2% HNO,.Calibrate by standard addition method Add excess F e ( l l l ) solution to overcome F - interferences by SO,, PO,, CIO,, citrate and silicate ions Flash-evaporate and dissolve residue Graphite furnace in acid. Atomize at 2800 "C (HGA-2100) See Cr, ref. 1981 F Air/C,H, Absorb CS, in alcoholic potash and add F - Cu(ll) solution to form cuprous xanthate complex.Filter, convert to soluble Cu salt and measure Cu level See Ti, ref. 1242 F - I 4135 1505 517 1484 1485 521 b 1242 ? 5. b 2057 ' $ 1981 5'4 Vitamin B, 217.0 (indirect) (Pb) Chlorpro- 357.9 (indirect) (indirect) (Ag) Various - (Rare earths) thixene (Cr) Thiols 328.1 Various - (Rare earths) Various - (12) Drugs - Drugs - Isopropanol-water 0.8-20 pmol/ml mixtures Luminescence materials - (M,SiO, type) Inorganic compounds From 1 pg/g (various) (3 elements) From 100 pg/g (8 elements) From 0.1 70 (4 elements) Trace levels High-purity acids and salts High-purity ng/g levels aluminium chloride Various - Trimethylgallium ether Trace levels (9) A %.A L De-sulphurize with K plumbite and F - 1066 A L Add exzess NH, reineckate, filter to F - 1231 3, 0 measure unreacted Pb ( I I ) remove precipitate and determine excess 5‘ Cr in filtrate z A L Add AgNO, solution, filter and dissolve F Air/C,H, 1712 E L Dissolve in HF/H,SO,, precipitate s - 23 precipitated salts in HNO, rare-earth hydroxides with NH,OH and redissolve in HCI. Nebulize solution into spark discharge (as appropriate) +Sc as internal standards E L Decompose with acid and add La or Y S Solution- 1142 spark method E E E Various - Semiconductor materials - A (4) (20) Various - Silicon Trace levels E (61 Various - Hydrochloric acid 0 * 001 -0- 2 c”g/g E L Add H,O-miscible organic solvent, e.g., S - ethanol, acetonitrite, to aqueous sample solution t o improve detection limits rhodanide-diantipyrylmethane, into CHCI,.Evaporate extract onto C powder for analysis. (Elements quoted : Co, Cu, Fe, Mo, Sn, Ti, V, Zn) S Extract sample solution with A - 1145 24 L De-alkylate with HCI, extract Ga as Hollow-cathode 26 butyl acetate, evaporate aqueous phase to dryness and redissolve in HCI/HNO,. Transfei 0.05 ml to graphite hollow cathode. for As, Se, Sb, Te discharge L/G Combined hydride evolution/ETA method Graphite furnace 105 L Comparison of ICP and AAS P ICP 148 G Heat samp!e and carry vapour in flow of P Microwave 194 argon to active nitrogen source.Application of Metastable Transfer discharge Emission Spectrometry (MTES) w wv) Table 4.1 B CHEMICALS AND MISCELLANEOUS MATERIALS- corztiriued L Element X/nm Matrix Concenlration Sample treatment Atomization Ref.Tech. Analyte Form Various ( 4 ) (8) Various Various Various Various ( 5 ) Various (13) Various Various (8) Various (5) - Silicon polymers Trace levels - High-purity Trace levels tungsten compounds - Coating materials - (paint, resin, pigments) - Polyimide resins pg/g levels - Silicon semiconductors Trace levels - Metal decanoates Major levels - Ammonium hydrogen Trace levels fluoride - Gallium p hosp hide Trace levels - Ammcnium bromide 1- 5 ps/s (Fe) 1(Mopg/g (Ba) 1-10 p u g (Mn, Pb, Cu) - Organometallic compounds Major levels A L A L A L A L E S A, E L E S E S E S A L Application of new digestion technique, Graphite furnace 267 for determination of Cu, Zn, Pb, Cr Dissolve compound, e.g., H,WO, or F - 369 (NH,),,W,,0,,.5 H,O, in 10% solution of fCH,),NOH, for determination of Al, Ca, Fe, K, Mg, Mo, Na, Si Review of ETA-AAS applications to Graphite furnace 520 analysis of materials associated with the coatings industry Ash under controlled temperature and F Air/C,H, 639 atmospheric conditions in special quartz vessel.Dissolve ash in acid. Results given for Cu, Fe, K, Na De-grease specimen, air-dry and etch for A A.c. arc 742 1 min by suspension in solution of HNO,/40% HF/C,H,O, (8 : 1 : 1).Add C powder, evaporate to dryness, add KCI solution, dry and excite in electrode cavity to determine Al, Fe, Cu, Mg, Mn Description of preparation, analysis and - - 772 applications of metal decanoates as b spectrochemical reference materials 3 3 a, 3 Study of added-matrix effects (G3O3, A - 792 2 GeO,, graphite, MgO, ZnO) Study of effect of Ca on the determination of At, Si, Be, Mg, Sn, Ge, As and Zn Mix (10 : 1) with graphite powder and A 10 A d.c. 1122 ? ignite gently t o 330 "C.Mix residue with 10% NaCl $ A 12 A d.c. ah F - 1186Various - Calcium salts; electrolytes Trace levels E (8) Various - Chemicals ( 5 ) Trace levels Various - Forensic samples - Various - Drugs (10) Trace levels Various - Cadmium mercury telluride ng/g levels ( 9) Various - Domestic refuse - (11) Various - Red lead ( 7 ) 0.1-100 pg/g A E E, A A A E Various - Firerarm pellets, residues - A Various - Thin films CLg/cm3 levels A A Various - Drugs - L L L L S L S L L L (1) For CaCl,, dissolve 12 g in H,O and (2) For CaCO,, dissolve 12.5 g in HCI F Air/propane/ butane (A), Air/C,H, (6) and (C) dilute to 500 ml (Na, K, Mg) (1 : 1) and dilute to 500 ml (Cu, Fe, Mn, At) N,0/C2H, (3) Na/Li electrolyte, 0.5 g to 500 ml (Li) Flames : (A) Na, K, Li, (B) Mg, Cu, Fe, Automatic flame injection method applied F to determination of Ca, Fe, Cu, Pb and Zn in various chemical salts and mineral acids - P ICP AAS and OES methods for Ca, Ag, Cu, A,F - At, Bi, Ni, Fe, Mg, Pb, Zn Direct method, for Ag, Cu, Fe, Mn, Cr, Al, Na, Mg, Si Ash at 480 "C, digest with HF/HNO, F - (3 : 2) followed by HNOJHCIO, (5 : 2) and heat to fuming.Dissolve i n HCI and dilute to volume (50 m i for 6 g sample). Determine At, Fe, Ca, Mg, K, Na, Sn, Cu ,Zn, Pb, Ni by AAS. (Results compared with those given by ASTM methods) Mix (1 : 1) with C powder and transfer 50 mg to electrode cavity. Cover with 20 mg C powder containing 8% NaCI. (An extraction-concentration method i s also given, for concentrations from 5 ng/g to 10 pg/g). Elements : Cr, Cu, Co, Ni, Fe, Mn and V Use of AAS and NAA to characterize F Air/C,H, materials for As, Sb, Cu, Pb, Au, Fe, Zn Etch metal layers with acid, e.g., F Air/C,H, HCI/H,O at 55 "C (Cu, Ni); HCI/HNO, at 65 "C (Au);; HF at 40 "C (Ta) Mn, (C) Al - Graphite furnace A 15 A a.c. N,O/C,H, Review (50 refs.) F - 1266 2 1279 1286 1405 1409 1609 1626 1631 1866 1925 \oTable 4.1B CHEMICALS AND MISCELLANEOUS MATERIALS- coittirrued W a Element X/nm Matrix Concentration Sample treatment Atomization Ref. Tech. Analyte Form Various - Drugs (20) Various - Various (13) A L Review P - 1969 Graphite furnace E S Study of d.c. arc effects for various A D.c. arc 2068 matrices (SiO,, graphite, albite, CdSO,, NaCI/CaO) and internal standards (Pb. Ge, In, Bi) b b

ISSN:0306-1353    

DOI:10.1039/AA9790900080

出版商:RSC    

年代:1979

数据来源: RSC