You are here:
PRESERVATION OF SULFIDIC WATERS CONTAINING DISSOLVED AS (III)
Citation:
Smieja, J. AND R T. Wilkin*. PRESERVATION OF SULFIDIC WATERS CONTAINING DISSOLVED AS (III). Presented at 226th National Meeting of the American Chemical Society, New York, NY, September 07 - 11, 2003.
Impact/Purpose:
To inform the public.
Description:
Field samples for arsenic analyses are commonly preserved by acidification with hydrochloric or nitric acid. In some suboxic samples, appreciable concentrations of H2S and HS- are observed due to the microbial respiration of sulfate-reducing bacteria. If both As(III) and sulfide are present in natural waters, several reactions are possible. In this study, solutions containing variable concentrations of sulfide (0 to 25 ppm) and arsenite (0.35 to 10 ppm) were subjected to several different preservation treatments. If a near-neutral water sample contained 1 ppm arsenite and as little as 0.4 ppm sulfide, loss of dissolved arsenic was observed upon acidification. These results have implications concerning the practice of acidifying water samples for the purpose of preserving total arsenic values. An alternative three-step preservation method involving base addition, oxidation, and acidification was investigated as an appropriate technique for preserving sulfide-bearing aqueous samples for total arsenic.