SIMULTANEOUS DETERMINATION OF INORGANIC ARSENIC AND ANTIMONY SPECIES IN NATURAL-WATERS USING SELECTIVE HYDRIDE GENERATION WITH GAS-CHROMATOGRAPHY PHOTOIONIZATION DETECTION

Dissolved arsenic and antimony in natural waters can exist in the trivalent and pentavalent oxidation states, and the biochemical and geochemical reactivities of these elements are dependent upon their chemical forms. A method for the simultaneous determination of As(III) + Sb(III) and As(III + V) + Sb(III + V) has been developed that uses selective hydride generation, liquid nitrogen cooled trapping, and gas chromatography/photoionization detection. The detection limit for arsenic is 10 pmol/L, while that for antimony is 3.3 pmol/L; precision (as relative standard deviation) for both elements is better than 3%. The apparatus is rugged and allows determinations to be made in the field. In addition to determining dissolved arsenic and antimony species, an oxidative digest has been developed to allow the simultaneous determination of the two elements in sediments and biogenic particles. Numerous water and particulate samples have been analyzed by using the described procedures.