Alkyl lead compounds in air

Tetra-alkyl lead compounds in air Personal monitoring with atomic absorption analysis or electrothermal atomization or X-ray fluorescence spectrometry or on-site colorimetry 9... 

MDHS 14 General method for the gravimetric determination of respirable and total dust MDHS 15 Carbon disulphide MDHS 16 Mercury vapour in air Laboratory method using hopcalite adsorbent tubes, and acid dissolution with cold vapour atomic absorption spectrometric analysis MDHS 17 Benzene in air Laboratory method using charcoal adsorbent tubes, solvent desorption and gas chromatography MDHS 18 Tetra alkyl lead compounds in air Continuous on-site monitoring method using PAC Check atomic absorption spirometry... 

MDHS9 Tetra alkyl lead compounds in air (personal monitoring). 

Radzuik, B., Thomassen, Y. and van Loon, J.C. (1979) Determination of alkyl lead compounds in air by gas chromatography and atomic absorption spectrometry. Anal. Chim. Acta, 105, 255-262. 

Fig. 166. Lead-response chromatogram from a 70-1 air sample, showing the presence of alkyl lead compounds in order of increasing retention time the four peaks are from trimethy1-ethyl-dime thyldiethyl-, methyltriethyl- and tetraethyllead. The baseline drift is due to single-beam operation of the spectrometer.

Air Lead Five tetra-alkyl lead compounds GC eluent introduced into flame-heated ceramic tube placed in light path. H2 introduced prior to tube to give diffusion flame 0.25mgPbmr3 Hewitt and Harrison (1985)... 

No more than 10% of the total lead escapes collection by filtration (and therefore no more than 10% of the total lead is expected to be in a gaseous form). This was shown to be the case at an underground garage where alkyl lead compounds might be expected to be at a maximum in ambient air (7). 

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. 

Evidence for the existence of a natural source of tetraalkyllead compounds comes from analysis of air from the open sea, from coastal, and from estuarine areas, since 1 to 30 ng/m tetraalkyllead was observed [61] further evidence was found from abnormally high alkyllead to total lead ratios, which have been observed in atmospheric samples in Morecambe Bay, U.K. [60]. It was speculated that these tetraalkyllead emissions arise from methylation of lead compounds in coastal and estuarine intertidal areas [61]. The hypothesis of a natural source was supported by additional measurements [132, 174] see also [46, 133, 134]. However, according to recent results on transformation rates and lifetime of alkyllead species in the atmosphere it is not necessary to invoke the hypothesis of the natural alkylation of lead to explain the enhanced alkyllead to total lead ratios [182]. Also no indication of a large-scale natural source for tetraalkyllead compounds was found in other work [22], and determination of atmospheric content of tetraalkyllead compounds gave no indication for the occurrence of natural methylation processes of lead(ll) compounds [23] see also [48, 69, 70, 73]. The origin of trialkyllead species in rural pigeons (Columba livia) was associated in part with natural sources of tetraalkyllead in the environment [135], and also the presence of small amounts of Pb(CH3)4 in fish (Coho Salmon, Yellow Perch, Sucker, Rock Bass, Sunfish) from various lakes and rivers in Ontario, Canada, was taken as an indication for the possibility of environmental methylation or in vivo methylation of lead in fish [95] see also [93]. It was considered conceivable that bacteria in fish intestines or in fish tissue could methylate lead compounds [93, 94, 101, 178]. 

Oxidative processes are very characteristic for pyrazoline derivatives such as dihydroheteroaromatic compounds. However, oxidation of pyrazolines is not a widely used preparative method for the synthesis of the appropriate pyrazoles owing to numerous side reactions following heteroaromatization, and other pathways are usually applied to obtain pyrazoles [66]. It should be noted that pyrazolines unsubstituted at positions 1 and 3 are very unstable compounds and easily decompose in air, with nitrogen elimination. Introducing alkyls or aryls in these positions leads to an increase of their stability but oxidative destruction is also possible, for example, under the action of nitrous acid [116, 117]. 

Speciation of lead in air and atmospheric particulates is still a topic of great environmental relevance. Sodium tetrahydroborate may be used to hydrogenate inorganic lead ions and alkyl-lead species.60 As in the study by Balls outlined above, cryogenic trapping may again be used to trap temporarily the plumbane and alkyl- and tetraalkyl-lead compounds, which are then released sequentially by heating for detection by flame AAS. 

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