Extraction and HPLC-ICP-MS Determination of Five Arsenic Species in Rice

Abstract

Accurate quantitative analysis of the content of different species of arsenic in rice is the key to evaluate its quality. By using high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS), the extraction and analysis methods of five common arsenic species were optimized, including arsenite [As(III)], arsenate [As(V)] and monomethyl arsenic (MMA), dimethyl arsenic (DMA) and arsenicbetaine (AsB). The results showed that a mixed solution of 10 mmol/L anhydrous sodium acetate (CH3CHOONa), 3 mmol/L ammonium nitrate (NH4NO3), 2 mmol/L sodium dihydrogen phosphate (NaH2PO4) and 0.2 mmol/L disodium ethylenediaminetetraacetic acid with a pH value of 10.22~10.27 was used as the flow phase, which can well separate the five species of arsenic in rice. The extraction efficiencies of nitric acid-water, phosphoric acid-water, hydrochloric acid-water, methanol-water, and pure water for five arsenic species in rice were compared, and the extraction solvent concentration, extraction time, auxiliary heating method and other conditions were compared and modified. The results showed that using 1% HNO3 aqueous solution as an extraction reagent, with treatment at a constant temperature of 90 ℃ for 3 hours, has a better extraction effect on arsenic in rice. The recovery rates of the five arsenic species in samples were between 84.24% and 112.75%, the relative standard deviation (RSD) was less than 7.74%, and the detection limits were between 0.2~0.5 µg/L. This study indicates that this method is suitable for the analysis of arsenic species in arsenic-containing rice.