HPLC-HG-AFS Determination of 4 Arsenic Species in Plant Samples

The plant sample was ultrasonically extracted with 0.15 mol·L^-1 nitric acid solution for 2 times. After centrifugation, the extraction solution was purified by the CNW IC-Guard RP column, then introduced into HPLC using Hamilton PRP-X100 chromatographic column as stationary phase and 25 mmol·L^-1 (NH₄)₂HPO₄-HCOOH solution(pH 6.0) as mobile phase in isocratic elution. The 4 species of arsenic (arsenite, dimethylated arsenic, monomethylated arsenic and arsenate) in sample solution were completely separated within 9 min, then the 4 species of arsenic were determined by HG-AFS with 22.5 g·L^-1 potassium borohydride solution as reductive agent and 1.2 mol·L^-1 hydrochloric acid solution as carrying current. The results showed that linearity relationships between peak area and mass concentration of the 4 species of arsenic were kept in the same range of 5-100 μg·L^-1, with detection limits (3S/N) in the range of 0.20-0.46 μg·L^-1. Values of recovery obtained by standard addition method were found in the range of 80.0% to 101%, and RSDs (n=6) of the measured values were found in the range of 2.1% to 5.0%. The proposed method was used for determination of plant samples including rice, mustard, swamp cabbage, lotus root, citrus leaves, and all of samples contained high mass fraction of arsenite (0.053-0.81 mg·kg^-1) while monomethylated arsenic was not detected, with percentage of the total arsenic species measured between this method and national standard method of GB 5009.11-2014 in the range of 84.2%-104%.