Gasoline organolead compounds

The vast majority of measurements of organolead compounds in the environment do not constitute evidence for biomethylation of lead. Most environmental organic lead comes from incomplete combustion or spillage of methyl- or ethyl-lead gasoline additives (viz tetraalkylleads or TALs). A literature search will produce several hundred TAL or ionic alkyllead results, but few of them are evidence for methylation in or by the environment. 

TABLE 17. Limit of lead content of gasoline (in 1988)111, and consumption of gasoline and organolead compounds (in 1989) (modified from References 111 and 113)... 

The addition of an organolead compound to motor gasolines raises octane numbers, but not uniformly. The incremental increase depends on the composition of the base stock fuel, the particular lead compound employed, the increasing amount of lead compound added, the method of testing, etc. As an extremely crude indication, it may be assumed that 2 ml of tetraethyllead per gallon will result in roughly 10 octane numbers appreciation in the fuel. 

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 chemistry of organolead compounds in the environment has been reviewed elsewhere [93-96], but a few salient aspects are summarized here. First, tetra-alkyllead compounds are volatile Henry s Law constant of 4.7 x 10" and 6.9 X 10" (Pam )/mol for tetramethyl and tetraethyllead, respectively, according to Wang et al. [97]. However, only a small fraction of the Pb leaving an automobile as exhaust is in this form, e.g., typically 0.1-10% [95]. In addition to the relatively low emission factor from leaded gasoline combustion, tetra-alkyllead compounds are rapidly decomposed by homogeneous gas phase reactions such as photolysis, reaction with ozone, triplet atomic oxygen, or hydroxyl radical [98,99] with half-lives of less than 10 h in summer and 40 h in... 

Organolead compounds have been extensively used for many years as antiknock agents in gasoline. Although this use has been banned in developed countries, they are still in use in many developing countries. As a result, enormous amounts of these compounds have been, and still are, discharged into the atmosphere. Therefore, there is a significant... 

The use of a helium MIP as a detector for compounds separated by GC has been mentioned and will be discussed in Chapter 12, but has been used for the determination of thiophene in benzene at ppb levels F, C, N, and S in gasoline organolead and organomanganese compounds in gasoline and elements in sediment and coal. The website at www.jas.de provides a number of application notes. 

The atomizer overcomes many of the difficulties involved in commercial furnace carbon atomizers. Based on this atomizer Robinson et al developed the procedure described below for the analysis of organolead compounds in gasoline. 

Dupuis and Hill have demonstrated the use of a hydrogen atmosphere flame ionization detector (HAFID) 48-452 modified from a commercial FID as a selective gas chromatographic detector for the determination of organolead compounds in gasoline. By a simple one to ten dilution of a leaded gasoline, alkyllead compounds were detected with no interference from overlapping chromatographic peaks of hydrocarbons. Detection limits were calculated to be 7.3 x 10"" g/s of lead. 

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