Organolead compounds determination

TABLE 3. Structural determination of organolead compounds by NMR spectroscopy... 

Determination of Pb(II) and organolead compounds in human urine, after LLE of the complexes with 91 and derivatization Et4Pb as internal standard . The aqueous solution is evaporated to dryness, the sohd residue is derivatized and the alkylated Pb was evaporated into an ETAAS instrument the LOD (SNR 2) was 7 ppb . 

Other applications of gas chromatography to the determination of organolead compounds in non saline waters are discussed in Table 15.17. 

Salih, B. Speciation of inorganic and organolead compounds by gas chromatography-atomic absorption spectrometry and the determination of lead species after pre-concentration onto diphenylthiocarbazone-anchored polymeric microbeads. Spectrochim. Acta B 55, 1117-1127 (2000)... 

Differences in the volatility of the elements and their compounds may also be used for speciation work. Accordingly, it is possible, for example, to determine different organolead compounds such as Pb(CH3)4 and Pb(C2Hs)4 directly by furnace AAS (see e.g. Refs. [284, 285]) or after on-line coupling with chromatographic separations. This approach can be used for other species as well but must be developed carefully for each special case. 

Helium MIPs are excellent for element-specific detection in gas chromatography, as has been commercially realized [451]. In this way, not only are the halogens and other elements relevant in pesticide residue analysis but also organolead and or-ganotin compounds determined down to low concentrations. This makes MIP-AES very useful for speciation work [321, 452]. It has been shown that the delocalized helium MIP gave low detection limits for elements with high excitation potentials... 

The dithizone method has been applied for determining lead in biological samples [44,89,90], waters [8,15,91], soils [92],organic materials [93], plant materials [94,95], air (inorganic lead and organolead compounds) [96-98], silicate minerals [99], steel [2], molybdenum and tungsten [100], silver [34], cadmium [101], cobalt [11,13], boron [45], telluric acid [102], antimony sulphide [103], and gasoline [104],... 

The second interlaboratory study generated detailed discussions one ETAAS technique employed did not include a separation step but the participant stated that EDTA extraction would only extract organic lead compounds this technique was considered to be suitable for the analysis of a simple solution containing only one lead compound but would not be suitable for mixtures of lead species, e.g. the technique would not allow the separation of TriML and TriEL in a natural rainwater sample. In cases where different organolead compounds are to be determined in natural samples or solutions containing different lead compounds, ETAAS should be coupled to a separation technique, e.g. GC or HPLC. 

Other examples of indirect amplification after oxidation with I2 are summarized in Table 2. Especially interesting is the method developed by Amin and Al-Allaf for the amplification of the iodometric determination of organolead compounds, using Scheme 1, because in this case alkyllead and phenyllead compounds show different behavior. Phenyllead reaction products with I2 are extracted quantitatively into an organic phase, whereas in the determination of ethyllead compounds the reaction products... 

Organolead compounds can be associated with airborne particulate matter. A recent study determined the concentration of organolead in airborne particulate matter collected in Oviedo (Spain). The results show concentrations of 1.6-3.6 and 5.5-23.5pgm DML and DEL, respectively. 

Chau et al pointed out that as the authenticity of the compounds to be analyzed must be preserved, any of the digestion methods with acids or alkalis are not suitable, and that extraction seemed to be the method of choice for removing these compounds from samples. For this traction, they adopted benzene as recommended by Sirota and Uthe for the quantitative extraction of tetramethyllead and tetraethyllead from fish homogenates suspended in aqueous EDTA solution. Although ionic forms of lead such as Pb(II), diethyllead dichloride, and trimethyllead acetate do not extract in the benzene phase, any lead compounds that distribute into the benzene phase as tetraalkyllead will be determined. Chau et al421 found that environmental samples can contain other forms of organolead compounds that are extractable into benzene but which are not volatile enough to be analyzed by the GC-AAS technique, hence the need for a speciation specific analytical system. 

Radzuik et al have described a gas chromatographic-atomic absorption method using furnace atomization for the determination of alkyllead compounds in air. Gas chromatography-mass spectrometry was used to identify the separated organolead compounds. In this method, described below, the alkyl lead compounds are condensed from a 70-1 air sample in a series of four traps at - 72°C, separated by gas chromatography and determined by atomic absorption spectrometry with electrothermal atomization. 

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