LC-AFS Determination of 4 Kinds of Arsenic Species in Rice

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%.