STUDY THE CONCENTRATION CHANGE OF ARSENIC AND SELENIUM SPECIES IN SAMPLE PRESEVATION, SAMPLE PREPARATION FOR ELEMENT SPECIATION BY HVG – AAS METHOD COMBINES WITH CHEMOMETRICS

Abstract

   It is very essensial for Chemical Speciation of elements to find out the suitable sampling, sample presevation and sample preparation methods so that there is no change in dominant forms and losing of analytes. This study concentrated on the effect of pH, contaner‟s materials, present of iron(III) and dissolved oxygen in samples. The absorption of total trace asenic and selenium on the surface of glass containers had been recognised if sample pH was above 6, concentration of Fe(III) was excess 200 ppb or samples were kept for a long time. The oxidizing process of As(III) to As(V), Se(IV) and SeMt to Se(VI) occured if oxygen was not removed. The determination of asenic and selenium species will be carried out with satisfied results in synthesis samples if the water samples are kept at pH around 2 using nitrogen for removing oxygen in Teflon container at 40C within 48h of analyzing. The effect of Fe(III) in water sample was eliminated by using 0,2 M EDTA.