Integrated sample preparation and speciation analysis for the simultaneous determination of methylated species of tin, lead and mercury in water by purge-and-trap injection-capillary gas chromatography-atomic emission spectrometry

Abstract

A sensitive and interference-free automated method for the simultaneous speciation analysis of methylated species of mercury, tin and lead, and also inorganic mercury in water, using purge-and-trap injection–gas chromatography–atomic emission spectrometry, was developed. The ionic species are volatilized from the sample after ethylation, using sodium tetraethylborate, in acetate buffer medium of pH 5 and preconcentrated on a capillary cryogenic trap. Desorption is effected by linear heating of the trap, followed by separation of the analytes by capillary gas chromatography and selective simultaneous detection by microwave-induced plasma atomic emission spectrometry. Detection limits of 0.15, 0.20 and 0.60 ng l^–1 for methylated tin, lead and mercury species, respectively, and 2 ng l^–1 for inorganic mercury can be obtained, on the basis of a 10 ml sample volume. Examples of results for the analysis of river- and soil run-off water samples are given.