采用液相色谱-原子荧光光谱法测定大米中亚砷酸盐［As(Ⅲ)］、砷酸盐［As(Ⅴ)］、一甲基胂酸(MMA)和二甲基胂酸(DMA)等4种砷形态的含量。大米样品(1.00 g)中加入0.10 mol·L-1硝酸溶液10 mL,置于95 ℃水浴中热浸提取120 min,使4种形态砷的化合物溶出。提取液冷却后在Hamilton PRP X-100阴离子交换柱上进行色谱分离。用调节至pH 6.0的20 mmol·L-1 NH4H2PO4溶液作流动相(流量为1.2 mL·min-1)淋洗可使上述4种形态的砷化合物很好分离。用原子荧光光谱法分别测定各形态砷的含量。砷的质量浓度在5.00~500 μg·L-1范围内与其峰面积呈线性关系。上述4种形态砷的检出限(3S/N)依次为0.099,0.18,0.15,0.040 μg·L-1。加标回收率在94.7%~104%之间,测定值的相对标准偏差(n=6)在3.0%~7.4%之间。

LC-AFS was applied to the determination of 4 kinds of arsenic species including arsenite ［As (Ⅲ)］, arsenate ［As (Ⅴ)］, monomethylarsonic acid (MMA) and dimethylarsonic acid (DMA) in rice. Four chemical species of arsenic in rice were extracted from 1.00 g of rice sample by soaking the sample in 10 mL of 0.10 mol·L-1 HNO3 solution in a water-bath at 95 ℃ for 120 min. After cooling, the extract was introduced into the LC-AFS instrument and chromatographic separation was carried on a Hamilton PRP X-100 anion exchange column, by using 20 mmol·L-1 NH4H2PO4 solution (pre-adjusted to pH 6.0) as mobile phase (at a flow-rate of 1.2 mL·min-1), the 4 species of arsenic was separated nicely and determined separately by AFS. Linear relationship between values of peak area and mass concentration of arsenic was obtained in the range of 5.00-500 μg·L-1. Detection limits (3S/N) found for the 4 arsenic species were 0.099, 0.18, 0.15, 0.040 μg·L-1 respectively. Test for recovery was done by standard addition method, giving results in the range of 94.7%-104%, and values of RSDs (n=6) found were ranged from 3.0% to 7.4%.