Arsenic Speciation in Rice and Soil Containing Related Compounds of Chemical Warfare Agents

Diphenylarsinic acid, phenylarsonic acid, methylphenylarsinic acid (MPAA), dimethylphenylarsine oxide (DMPAO), and methyldiphenylarsine oxide (MDPAO) in soil and rice were extracted, separated by reversed-phase chromatography, and quantified by ICPMS with a membrane desolvating system. For the extraction of arsenicals from rice grain and straw, 68% HNO3 provided better extraction efficiency than water, 50% methanol, or 2.0 mol L−1 trifluoroacetic acid. For the extraction from soil, 68% HNO3 provided better extraction efficiency than H2O, 1 mol L−1 H3PO4, or 1 mol L−1 NaOH. The contaminated soil contained all five aromatic arsenicals along with inorganic arsenicals as main species (5.86 ± 0.19 μg of As kg−1: 60.8 ± 2.0% of total extracted As). After pot experiments, rice straw contained mainly DMPAO (7.71 ± 0.48 μg of As kg−1: 60.5 ± 3.7%), MDPAO (0.91 ± 0.07 μg of As kg−1: 7.2 ± 0.5%), and inorganic As (2.85 ± 0.20 μg of As kg−1: 22.3 ± 1.6%). On the other hand, rice grain contained mainly MPAA (1.17 ± 0.04 μg of As kg−1: 86.7 ± 2.7%). The root uptake of each species from the soil and transport from straw to grains were significantly related to the calculated log K ow values.