Speciation of inorganic lead and trialkyllead compounds by flame atomic absorption spectrometry following continuous selective preconcentration from aqueous solutions

A new method for the speciation of inorganic lead and trialkyllead compound s involving the selective separation of the analytes in a continuous system and their subsequent introduction into a flame atomic absorption spectrome ter was developed. The proposed flow system consists of two units. In the f irst unit, total inorganic lead at concentrations from 8 to 200 ng ml(-1) i s continuously precipitated as lead chromate and the filtrate, containing t rialkyllead cations, is collected in a vessel, the precipitate then being d issolved in diluted acid and driven to the instrument. In the second unit, trimethyllead (TML+) and triethyllead (TEL+) cations at ng ml(-1) levels ar e complexed with sodium diethyldithiocarbamate and retained on a C-60 pre-c onditioned fullerene column; the mixture of both species was resolved by co nditioning the sorbent column with n-hexane or isobutyl methyl ketone solve nts. Detection limits of 1-2 ng ml(-1) can be achieved by using a sample vo lume of 50 ml. Special attention was given to the reliability and robustnes s of the global flow injection method in assessing its applicability to bot h types of organolead compounds and inorganic lead present in different pro portions. Trimethyllead provides the poorest results as consequence of its low adsorption constant on C-60; however, the three different types of spec ies (Pb2+/TML+/TEL+) can be effectively determined in proportions from 1:1: 1 to 30:12:1 with relative errors less than 10%. (C) 1999 Elsevier Science B.V. All rights reserved.