Determination of copper, cadmium, lead, bismuth and selenium(iv) in sea-water by electrothermal vaporization inductively coupled plasma mass spectrometry after on-line separation

Abstract

A procedure for the determination of Cu, Cd, Pb, Bi and Se^IV in sea-water by electrothermal vaporization inductively coupled plasma mass spectrometry, after on-line separation using a flow injection system, is proposed. Matrix separation and analyte preconcentration was accomplished by retention of the analytes complexed with the ammonium salt of O,O-diethyldithiophosphoric acid on C₁₈ immobilized on silica in a minicolumn coupled directly to the autosampler arm of the vaporizer. The methanol used as eluent was vaporized after being automatically injected into the graphite tube, prior to the vaporization of the analytes. The conditions for the on-line complexation and separation as well as the vaporizer temperature program were optimized. The recoveries from sea-water ranged from 90 to 110%. The accuracy of the method was tested by the analysis of two certified sea-waters, CASS-3 and NASS-4, from the National Research Council of Canada. The concentration of Bi in these sea-waters was below the method detection limit. The relative standard deviation was below 10% (n=6). The throughput was 22 samples h^–1 and the volume of sample consumed was only 2.3 ml. Tl and As^III were also separated but their complexation in sea-water was not efficient.