Mercury organoleads

Environmental Tin, lead and mercury Organolead, organotin and organomercury compounds Helium plasma (Hewlett Packard) 1-2.5 ng ml"1 Liu et al. (1994)... 

In addition to manufactured organolead compounds, the possibility exists of biological meth-ylation of lead, such as occurs with mercury (see Section 12.7). However, there is a great deal of uncertainty regarding biological methylation of lead in the environment. 

The commercial production of mercury fungicides from organolead compounds is based on patents by Kharasch 184,185). The mercury compounds are used in the disinfection of seeds and grains. Typical compounds are ethylmercuric chloride, ethylmercuric sulfate, ethyl-mercuric phosphate, phenylmercuric acetate, and compounds derived from substituted phenols and ureas. The manufacture of these compounds was reviewed by Whelen in 1957 310>. The alkylation reaction is a general reaction, and a number of additional patents has been issued on methods similar to Whelen s. A representative equation is ... 

Several efforts have been carried out to develop a new aqueous derivatization reagent. Phenylation with sodium tetraphenylborate is a promising procedure for the speciation of several metals. Its application for organomercury analysis has been comprehensively studied [10]. Sodium tetrapropylborate is another reagent that has been investigated for determining organolead, tin, and mercury compounds [1]. However, its application is limited because it is not commercially available. 

Lead, like mercury, causes neurological diseases. The organolead compounds are more toxic than mineral lead salts, since they are non-polar, lipid-soluble, and more readily cross the blood-brain barrier. This disease is related to mental retardation is children, lower performance on I.Q. tests, and hyperactivity. Severe exposure in adults causes irritability, sleeplessness, and irrational behavior. Some have gone as far as to blame anti-social behavior and criminality on sub-clinical Pb poisoning. A correlation between Pb in blood and Pb in air, dust and soils has been observed in many studies. The U.S. Centers for Disease Control has proclaimed a goal of reducing blood lead contents in children below 10 jag/lOOmL. 

The most general route to organolead tricarboxylates, such as aryllead, vinyllead or alkynyllead tricarboxylates, is the metal-metal exchange which can involve mercury-lead, thallium-lead, silicon-lead, tin-lead, boron-lead or zinc-lead transmetallation. 

The other concern in the 1970s and 1980s was whether or not inorganic lead could be biomethylated naturally, as in the case of mercury. In view of the bulk amounts of organoleads being used anyway at the time, this was not likely to be a key consideration in urban areas, but in pristine locations, natural lead methylation and transport might in some circumstances have led to environmental problems. In fact, there has not been any clear demonstration of such methylation, and it is unlikely to be a big environmental problem. Where organic lead compounds are detected in the remote environment, they are at very low levels, probably accountable by transport of these species. Evidence is considered in the next section. 

Organomercury compounds were produced by the reaction shown in eq. (4.39) and they were used for agrochemicals such as disinfectants of seeds. But, their poisonous character was pointed out earlier than that of organolead compounds. In Japan, the use of agricultural mercurials was prohibited in 1968. After that, agricultural organomercury compounds have not been prepared [3]. 

Quimby et al examined the applicability of this type of detector to a range of elements including lead, silicon, phosphorus, mercury and manganese. The results they obtained for organolead compounds are discussed below and those for the other elements are discussed elsewhere. Quimby et al used a microwave emission detection system for gas chromatography which utilizes the TMq] q resonant cavity to sustain a plasma in helium at atmospheric pressure. The effluent from the gas chromatograph is split between a flame ionization detector and a heated transfer line directing it to a small... 

This set-up was used for the determination of a variety of species, e.g. organolead in urban air, volatile metal species in stack gas and fuel burning processes, or volatile selenium and mercury species purged and trapped from seawater. 

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