LC-ICP-MS法研究莲藕中砷的形态分布

Speciation Distribution of Arsenic in Lotus Analyzed by Liquid Chromatography coupled with Inductively Coupled Plasma Mass Spectrometry

本文通过测定莲藕不同砷浓度环境、不同生长阶段和不同器官中总砷及砷的5种形态(亚砷酸盐As(Ⅲ)、砷酸盐As(Ⅴ)、一甲基砷MMA、二甲基砷DMA和砷甜菜碱As B)的含量,研究了莲藕中砷的形态分布规律。采用优化的超声酸提取方法,用1%HNO3在70℃超声提取40 min,25 mmol/L磷酸二氢铵溶液(pH 8.0)为流动相等度洗脱,液相色谱-电感耦合等离子体质谱联用(LC-ICP-MS)法进行测定,各形态提取完全、稳定,8 min内基线分离。高砷环境栽培莲藕的无机砷比率略高于低砷环境的。莲藕在旺盛生长期对砷的富集能力高于结藕期,除藕外,地下部分总砷含量和无机砷比率普遍高于地上部分。结藕期无机砷比率降低,有机砷以As B、MMA和少量DMA形式存在。各器官中无机砷含量比例为29.03%~45.21%不等,可食部分藕和莲蓬中无机砷含量比例最低,有利于食品安全控制。

The speciation distribution of arsenic in lotus was investigated by determining the content of total arsenic and five arsenic species including arsenobetaine（As B）, As（Ⅲ）, As（Ⅴ）, monomethylarsine（MMA） and dimethyarsine（DMA） in different parts of lotus at different growth stages with different arsenic concentrations environment in this study. The arsenic species were extracted by ultrasound with 1% HNO3 solution at 70℃ for 40 minutes, which were analyzed by Liquid Chromatography coupled with Inductively Coupled Plasma Mass Spectrometry with 25 mmol/L NH4 H2 PO4（pH 8.0） as the mobile phase for isocratic elution. The results showed that arsenic species were extracted completely, and baseline separation was achieved within 8 minutes. The inorganic arsenic species ratio of lotus grew in high arsenic environment was higher than that grew in low rsenic environment. The accumulation ability of lotus was better in the period of growth than that in period of root. The ratio of total arsenic and inorganic arsenic in underground parts was higher than that of the above-ground part except lotus root. The ratio of inorganic arsenic decreased in the period of root, where organic arsenic was present in As B, MMA and DMA. The inorganic arsenic species ratios in lotus root and semen nelumbinis were lower than that in any other parts in the ratio range of 29.03%~45.21%, which would help the food security control.