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Diphenylarsinic acid (DPAA) was extracted selectivity and efficiently from biological samples by a combined solvent extraction with solid-phase extraction and was determined by graphitefurnace atomic-absorption spectrometry (GFAAS). After 0.01 similar to 0.1 g of biological samples were decomposed in 1 ml of 2 M sodium hydroxide by heating (90 similar to 120 degrees C, 2 - 5 h), I ml of water was added. The decomposed solution was shaked for 5 min with 1 ml of chloroform and 4 ml of n-hexane, and the organic layer was discarded. The aqueous layer was adjusted to ca. 0.5 M hydrochloric acid solution by the addition of 2 ml of 2 M hydrochloric acid, and 1 ml of 20% cysteine solution and 1 ml of 40% potassium iodide solution were added to this solution. After 30 minutes, DPAA was extracted with 4 ml of chloroform. This operation was repeated again and combined chloroform layers were evaporated. After the residue was dissolved in 0.5 ml of ethanol, 10 ml of a 1% nitric acid solution was added and mixed well. The mixture was then passed through a 0.45 mu m of membranefilter and 0.2 ml of a 0.05 M EDTA solution was added to the filtrate. The solution was applied on an Oasis HLB cartridge and DPAA was eluted in 6 ml of ethanol. After evaporation of the solvent, the residue was dissolved in I ml of water and DPAA was analyzed by GFAAS. The proposed method could determine DPAA in biological samples, such as mouse brain, liver and kidney with an average recovery of 93%. The coefficient of variation was as low as 15%. The calibration curve was linear between 0 and 50 ng/ml (r = 0.999).