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205 6. ANALYTICAL METHODS The purpose of this chapter is to describe the analytical methods that are available for detecting and/or measuring and monitoring lead in environmental media and in biological samples. The intent is not to provide an exhaustive list of analytical methods that could be used to detect and quantify lead. Rather, the intention is to identify well-established methods that are used as the standard methods of analysis. Many of the analytical methods used to detect lead in environmental samples are the methods approved by federal organizations such as EPA and the National Institute for Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are approved by groups such as the Association of Official Analytical Chemists (ADAC) and the American Public Health Association (APHA). Additionally, analytical methods are included that refine previously used methods to obtain lower detection limits, and/or to improve accuracy and precision. 6.1 BIOLOGICAL MATERIALS Blood Urine Serum, Cerebrospinal Fluid. There are several methods for the analysis of lead in biological samples. The most common methods currently used are flame atomic absorption spectrometry (AAS), graphite furnace atomic absorption spectrometry (GFAAS), anode stripping voltammetry (ASV), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Spectrophotometric methods also exist and were commonly used in the past; however, they are not as sensitive or reliable as the newer methods. According to Grandjean and Olsen (1984), GFAAS and ASV are the methods of choice for the analysis of lead. In order to produce reliable results, background correction must be applied. Other specialized methods for lead analysis are inductively coupled plasma-mass spectrometry (ICP-MS), X-ray fluorescence spectroscopy (XRFS), neutron activation analysis (NAA), differential pulse anode stripping voltammetry, and isotope dilution mass spectrometry (IDMS). The most reliable method for the determination of lead at low concentrations is IDMS (EPA 1986a; Grandjean and Olsen 1984), but due to the technical expertise required and high cost of the equipment, this method is not commonly used. It is primarily used for the development of certified standard reference materials by which other methods can determine their reliability since results of lead analyses from numerous laboratories often do not agree (Fell 1984). Details of several methods used for the analysis of lead in biological samples are presented in Table 6-1. Concentrations of lead in blood, urine, serum, and cerebrospinal fluid have been used as indicators of exposure to lead. Measurement of lead in blood is the most common method of assessing exposure. Sample preparation usually consists of wet ashing the sample with strong acid and heat, and redissolving the residue in dilute acid prior to analysis so that all lead species are converted quantitatively to the same lead compound (NIOSH 1977a, 1977d, 1977e, 19778, 1977h). Preparation methods not requiring wet ashing have also been used with good results (Aguilera et al. 1989; Delves and Campbell 1988; Manton and Cook 1984; NIOSH 1977f; Que Hee et al. 1985a). For samples analyzed by ICP-MS, ASV, AAS, and GFAAS, sensitivity is in the low- to sub-ppb (2.4-15 ppb) with good accuracy and precision (Aguilera et al. 1989; Delves and Campbell 1988; NIOSH 1977d, 1977e, 1977f, 1977g, 1977h; Que Hee et al. 1985a)., A comparison of IDMS, ASV, and GFAAS showed that all three of these methods can be used to reliably quantify lead levels in blood (Que Hee et al. 1985a). ACGIH recommends quantification of blood lead by the GFAAS. For analysis of urine, chelation and solvent extraction, followed by atomic absorption for quantification is the recommended method (ACGIH 1986). Estimated accuracy reported for an IDMS technique was excellent (Manton and Cook 1984). Sensitivity and precision were not reported by the `.authors, but they are generally considered to be excellent (EPA 1986a; Grandjean and Olsen 1984).