DETERMINATION OF SELENIUM AND ARSENIC IN MINERAL WATERS WITH HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY

A continuous flow hydride generation (HG) technique was applied for the determination of Se and As in highly mineralized mineral waters. The atomization was performed either conventionally in a heated silica tube or in the graphite furnace after collection and thermal decomposition of the hydrides. In most cases the determination of As in real samples was not subject to serious problems. Significant matrix effects were found only for mineral waters with higher Mg, Na and sulfate concentrations. With the conventional flow through HG technique reasonably good linearity (r=0.998) and satisfactory precision [relative standard deviation (RSD)<5%] were obtained in the concentration range from 1 to 50 mug l-1. For the determination of lower concentrations of As and Se, in situ preconcentration in the graphite furnace was applied. Within 120 s of hydride introduction for As and 150 s for Se at a sample flow rate 0.5 ml min-1, favourable preconcentration factors were obtained that yielded a limit of detection (3sigma(b)) of 0.02 mug l-1. The precision of this procedure was satisfactory in the concentration range 0.5-10 mug l-1, the RSD being 2-16% for both elements under investigation.