SPECIATION OF ARSENIC(III) AND ARSENIC(V) IN SEDIMENT EXTRACTS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROPHOTOMETRY

Determining the redox states of arsenic (As) in environmental samples is important due to the pronounced differences in toxicity and mobilit y of the various forms. We have combined the separation capabilities o f high-performance liquid chromatography (HPLC) with the sensitivity a nd element specificity of hydride generation atomic absorption spectro metry (HGAAS) to determine arsenite [As(III)] and arsenate [As(V)], wh ich have been shown to be the most toxic and prevalent forms of As in soil and water. The HPLC-HGAAS technique gave retention times of 2.2 a nd 4.2 min for As(III) and As(V), respectively. Detection limits of 20 0 pg of As (0.8 mu g L(-1) As in solution) were obtained for both As(I II) and As(V). The technique was used to determine As(III) and As(V) i n deionized water and 1 mM PO4 sequential extracts of estuarine sedime nt, coal fly ash, and saline evaporation pond sediment Coal fly ash co ntained no detectable deionized water-extractable As(III) or As(V), bu t contained appreciable PO4-extractable As(V). The As(III) species was detected in all extracts of estuarine sediment, though 1 mM PO4 relea sed primarily As(V). Evaporation pond sediment also contained primaril y PO4- extractable As(V).