Behaviour of some dialkyl- and trialkyl-lead compounds in the hydride-generation procedure using a non-dispersive atomic-fluorescence detector

The method of generating covalent hydrides by reduction with sodium tetrahydroborate was applied to aqueous solutions containing traces of R(3)Pb(+) and R(2)Pb(2+) compounds (R = methyl, ethyl). For each compound the effects of sample acidity, sodium tetrahydroborate and hydrogen peroxide concentrations, reaction-vessel and transfer-line materials, were measured and the experimental conditions defined for obtaining maximum sensitivity. Experimental evidence indicating the formation of organolead hydrides during the reduction step at room temperature was adduced. The reaction efficiency was found to be 90% for trimethyl-, triethyl- and diethyl-lead and 59% for dimethyl-lead. In the case of inorganic lead the efficiency was only 27%. Without an intermediate preconcentration step, the detection limits obtained for trimethyl-, triethyl-, dimethyl- and diethyl-lead (3 times the standard deviation) were 3-5 ng of lead per litre. A procedure for discriminating between R(3)Pb(+), R(2)Pb(2+) and Pb(2+) compounds is proposed.