Organolead specific compounds

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... 

In this overview, we have limited our discussion to the speciation of four important organometals, each presenting specific analytical features, in environmental samples organomer-cury, organoarsenical, organotin, and organolead compounds. Their uses, presence in the environment, toxicity and threat to human health are also briefly discussed. 

ICP-AES. These detectors are element specific, avoiding most chemical and spectral interferences, and also sufficiently sensitive to quantify the organolead compounds in most environmental samples. The LODs obtained on trimethyllead after ethylation with CGC-MIP-... 

MS HPLC HPLC-heated nebulizer-ESI source Compound-specific LOD e.g., 10 pg 1 organolead compounds in water Commercial systems 430... 

Basic work on the gas chromatography, respectively, of tetraethyllead and tetramethyllead has been reported by Pollard et al and by Abel et al. They are of the opinion that electron capture detection, while sensitive, is not specific enough nor is it a very easy method of detection of organolead compounds. It requires extreme care, cleanliness, and rigid adherence to microchemical techniques. 

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. 

Concentrations of Pb(CH3)4 and other tetraalkyllead compounds in atmospheric samples, which have been measured at different locations with species specific analytical methods, are listed in Table 11. Tetraalkyllead concentrations in indoors air were found to correspond closely with those in outdoors air [24]. More data on concentrations of alkyllead compounds in ambient air have been obtained with analytical methods which measure volatile organolead compounds or total organolead [28 to 55,173]. However, these data, being based on different sampling and analytical procedures, are difficult to compare see also [56 to 64]. According to [5], the results given in [28, 29, 32, 33] are probably unreliable. In this context it has to be considered that the majority of the nonfilterable (molecular) lead seems not to be organic in nature [58, 59] recently also tri- and/or dialkyllead compounds have been determined besides Pb(CH3)4 and other tetraalkyllead compounds in both urban and rural air in the vapor phase and in atmospheric aerosols [27,174] see also [182]. For analytical procedures to determine Pb(CH3)4 in atmospheric samples, see Section 1.1.1.1.1 on p. 75. 

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(C2H5)4 directly by furnace AAS (see, e.g., Refs. [319, 320]) 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 specific case. 

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