Determination of 4 Arsenic Species in Corn by Reversed Phase Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry with Microwave Assisted Extraction

After corn sample was screened and sieved, an aliquot (0.5 g) was taken and mixed with 7 mL of 0.15 mol·L^-1 nitric acid solution. The mixture was placed into microwave digestion apparatus, and digested at 80, 100, 120 ℃ for 10, 10, 15 min, respectively. The supernatant was passed through a 0.22 μm organic filter membrane after centrifuging for 10 min. The filtrate was introduced into the liquid chromatography, and the mixed solution (pH 4.3) of 5 mmol·L^-1 sodium hexanesulfonate-20 mmol·L^-1 citric acid was used for isocratic elution on the Agilent ZORBAX SB-Aq reversed phase chromatographic column. The 4 arsenic species ［MMA, DMA, As(Ⅲ), As(Ⅴ)］ were determined by inductively coupled plasma mass spectrometry. It was shown that the 4 arsenic species could be separated completely within 4 min; the linear relationships between values of mass concentration and signal intensity were kept in the range of 2-50 μg·L^-1, and the detection limits (3S/N) were 0.041-0.054 μg·L^-1. Test for the spiked recovery was made on blank corn samples at three concentration levels, giving values of recovery in the range of 94.2%-102%, and RSDs (n=6) of the determined values were less than 3.0%. The proposed method was applied to the analysis of the 3 naturally polluted corn samples, and the 4 species of arsenic were all detected, among which the detection amounts of As(Ⅲ) and As(Ⅴ) were higher.