取土壤样品0.5 g,加入硝酸-盐酸-水(1+3+4)混合酸15 mL,先在室温放置过夜,然后在沸水浴上加热2 h,冷却,加入50 g·L-1硫脲-50 g·L-1抗坏血酸(1+1)混合溶液5 mL后，用盐酸(5+95)溶液定容至50 mL,用原子荧光光谱法在选定的仪器工作条件下测定试样溶液中砷量,所采用的硼氢化钾溶液的质量浓度为25 g·L-1。方法的检出限(3s/k)为0.05 μg·L-1,用标准加入法测得的回收率在93%~101%之间。按所提出的方法分析了土壤标准物质(GBW 07403),测得其砷量与认定值一致。

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.