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212 <br /> 6. ANALYTICAL METHODS <br /> 6.2 ENVIRONMENTAL SAMPLES <br /> The primary methods of analyzing for lead in environmental samples are AAS, GFAAS, ASV, ICP-AES, <br /> and XRFS. Less commonly employed techniques include gas chromatography/photoionization detector <br /> (GC,/PID), IDMS, DPASV, electron probe X-ray microanalysis (EPXMA), and laser microprobe mass <br /> analysis (LAMMA). In determining the lead concentrations in the atmosphere and water, a distinction N <br /> between the concentration of lead in the particulate and gaseous or dissolved forms is often necessary. a� <br /> Particulate lead can be separated from either media using a filter technique. The filter collects the C <br /> particulate matter and allows the dissolved material to pass through for separate analysis of each form. cc <br /> As with the analysis of biological samples, the definitive method of analysis for lead is IDMS. However, fA <br /> most laboratories do not possess the expertise or equipment required for this method. Table 6-2 � <br /> summarizes several methods for determining lead in a variety of environmental matrices. C <br /> d <br /> Air. A variety of methods have been used to analyze for particulate lead in air. The primary methods, C <br /> AAS, GFAAS, ICP-AES are sensitive to levels in the low Ag/mI range (0.1-20 ug/m3) (Birch et al. 1980; o <br /> EPA 1988b; NIOSH 1977c, 1977g, 1981, 1984; Scott et al. 1976). Accuracy and precision are generally •C <br /> good. GFAAS is considered to be more sensitive than AAS; however, AAS is not subject to as much C <br /> interference from matrix effects as GFAAS (NIOSH 1977b, 19778, 19771). Detection of particulate lead <br /> by generation of the lead hydride has been used to increase the sensitivity of the AAS technique (Nerin <br /> et al. 1989). Excellent accuracy and precision was reported for this method. ASV has a wide range as to <br /> well as high sensitivity. It is relatively inexpensive compared to other methods (NIOSH 1977b). J <br /> Advantages of ICP-AES are that it has a wide range and allows analysis of several elements at once. tM <br /> C <br /> However, the technique is expensive in terms of equipment and supplies (NIOSH 1981). XRFS has been .e <br /> used to analyze for particulate lead in air (DeJonghe et al. 1981). While sensitivity was good, recovery .E <br /> was highly variable and relatively low compared to other methods. The highest sensitivity was obtained CDL <br /> with IDMS, as expected (Volkening et al. 1988). As previously stated, this is the definitive method for <br /> determining lead in environmental, as well as biological samples. Two sophisticated methods, EPXMA and 0 <br /> LAMMA, have been used to determine the inorganic lead species present in particulate matter in air (Van C <br /> w <br /> Borm et al. 1990). H <br /> 10 <br /> Determination of lead vapor in air requires prior filtering of the air to exclude particulate lead, and C <br /> trapping of the gaseous components. Gaseous lead is also referred to as organic lead or allyl lead, the <br /> .0 <br /> most common being the tetraalkyl species. Organic lead species may be trapped by liquid or solid sorbents, <br /> or cryogenically (Birch et al. 1980; DeJonghe et al. 1981; NIOSH 1978b). Gas chromatography (GC) is <br /> cies. Detection by GFAAS and PID have been reported (DeJonghe, <br /> used to separate the different alkyl spe <br /> et al. 1981; NIOSH 1978b). GFAAS detection is more sensitive than PID, but both have good accuracy. <br /> io <br /> Water. As with air, water can be analyzed for both particulate and dissolved (organic) lead. Particulate Q <br /> lead collected on a filter is usually wet ashed prior to analysis. Comparison of the GFAAS and AAS <br /> methods for particulate lead showed the former technique to be about 100 times more sensitive than the N <br /> latter, although both offer relatively good accuracy and precision'(EPA 1983). GC/AAS has been used 10 (b <br /> determine organic lead, present as various alkyl lead species, in water (Chakraborti et al. 198Chau e1 W4; J <br /> for organic lead analysis was either by organic solvent extraction <br /> al. 1979, 1980). Sample preparation Q <br /> (Chakraborti et al. 1984; Chau et al. 1979) or purge-and-trap (Chau et al. 1980). Sensitivity was in the <br /> ppb to ppt range and reliability was similar for all three methods. Total lead can be determined by <br /> z <br />