Stability and optimization of extraction of four arsenic species

The stability of arsenic species was investigated at room temperature and at 4 degrees C. The stability studies were carried out with arsenite, arsenate, methylarsonic acid, and dimethylarsenic acid, which are the most toxic arsenic species present in the environment. The stability studies of solutions of inorganic arsenic species were carried out at a wide range of concentrations and storage times. Whereas solutions of the organic species were stable during long-time storage, solutions of inorganic species were stable only during refrigerated storage. For optimization of the extraction two different yeast samples with arsenic additives were prepared under laboratory conditions. One of the samples accumulated arsenate; the other was enriched with methylarsonic acid during fermentation. In the extraction studies the effects of the extraction method (sonication, shaking), the composition of the solvent, and the extraction time on the efficiency of the extraction were investigated. In the case of yeast the extraction with the 10% methanol:90% water mixture resulted the highest extraction efficiency after the four days of shaking. (C) 1998 Academic Press.