Colina Blanco Andrea E, Kerl Carolin F, Planer-Friedrich Britta
Department of Environmental Geochemistry, Bayreuth Center for Ecology and Environmental Research (BAYCEER), University of Bayreuth, 95440 Bayreuth, Germany.
J Agric Food Chem. 2021 Feb 24;69(7):2287-2294. doi: 10.1021/acs.jafc.0c06853. Epub 2021 Feb 10.
Inorganic and methylated thioarsenates have recently been reported to contribute substantially to arsenic (As) speciation in paddy-soil pore waters. Here, we show that thioarsenates can also accumulate in rice grains and rice products. For their detection, a method was developed using a pepsin-pancreatin enzymatic extraction followed by chromatographic separation at pH 13. From 54 analyzed commercial samples, including white, parboiled and husked rice, puffed rice cakes, and rice flakes, 50 contained dimethylmonothioarsenate (DMMTA) (maximum 25.6 μg kg), 18 monothioarsenate (MTA) (maximum 5.6 μg kg), 14 dimethyldithioarsenate (DMDTA) (maximum 2.8 μg kg), and 5 dithioarsenate (DTA) (maximum 2.3 μg kg). Additionally, we show that the commonly used nitric acid extraction transforms MTA to arsenite and DMMTA and DMDTA to dimethylarsenate (DMA). Current food guidelines do not require an analysis of thioarsenates in rice and only limit the contents of inorganic oxyarsenic species (including acid-extraction-transformed MTA), but not DMA (including acid-extraction-transformed DMMTA and DMDTA).
最近有报道称，无机和甲基化硫代砷酸盐在稻田土壤孔隙水中的砷（As）形态形成中起了重要作用。在此，我们表明硫代砷酸盐也能在稻谷和大米制品中积累。为了检测硫代砷酸盐，我们开发了一种方法，即先用胃蛋白酶 - 胰蛋白酶进行酶提取，然后在pH 13条件下进行色谱分离。在54份分析的商业样品中，包括白米、蒸谷米、糙米、米饼和米片，50份含有二甲基一硫代砷酸盐（DMMTA）（最高25.6 μg/kg），18份含有一硫代砷酸盐（MTA）（最高5.6 μg/kg），14份含有二甲基二硫代砷酸盐（DMDTA）（最高2.8 μg/kg），5份含有二硫代砷酸盐（DTA）（最高2.3 μg/kg）。此外，我们还表明，常用的硝酸提取会将MTA转化为亚砷酸盐，将DMMTA和DMDTA转化为二甲基砷酸盐（DMA）。目前的食品指南并不要求对大米中的硫代砷酸盐进行分析，只限制无机含氧砷物种（包括酸提取转化后的MTA）的含量，而不限制DMA（包括酸提取转化后的DMMTA和DMDTA）的含量。
