AFS Determination of Arsenic in Soil of Colliery Reclamation Area

0.5g of soil sample was digested with 15 mL of acid mixture of HNO3-HCl-H2O (1+3+4) first at room temperature overnight, and then heated over a boiling water bath for 2 h. After cooling, 5 mL of mixture of 50 g·L-1 thiourea solution and 50 g·L-1 ascorbic acid solution (1+1) were added and the solution was diluted to 50 mL with HCl (5+95). Arsenic(Ⅲ) in the sample solution was then determined by AFS under the optimum working condition of the instrument using 25 g·L-1 KBH4 solution as reductant to generate AsH3. Detection limit (3s/k) of the method found was 0.05 μg·L-1. Values of recovery found by standard addition method were in the range from 93% to 101%. In the analysis of a soil CRM (GBW 07403) by the proposed method, the result of arsenic obtained was in consistency with the certified value.