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

A continuous flow hydride generation (HG) technique was applied for th e determination of Se and As in highly mineralized mineral waters. The atomization was performed either conventionally in a heated silica tu be or in the graphite furnace after collection and thermal decompositi on of the hydrides. In most cases the determination of As in real samp les was not subject to serious problems. Significant matrix effects we re found only for mineral waters with higher Mg, Na and sulfate concen trations. With the conventional flow through HG technique reasonably g ood 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 S e, in situ preconcentration in the graphite furnace was applied. Withi n 120 s of hydride introduction for As and 150 s for Se at a sample fl ow rate 0.5 ml min-1, favourable preconcentration factors were obtaine d that yielded a limit of detection (3sigma(b)) of 0.02 mug l-1. The p recision of this procedure was satisfactory in the concentration range 0.5-10 mug l-1, the RSD being 2-16% for both elements under investiga tion.