稻米中5种砷形态提取及HPLC-ICP-MS法测定

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

  • 摘要: 准确定量分析大米中不同形态砷的含量是评价其品质的关键。该文应用高效液相色谱−电感耦合等离子体质谱联用技术(HPLC-ICP-MS),优化了稻米中亚砷酸盐As(Ⅲ)、砷酸盐As(Ⅴ)、一甲基砷(MMA)、二甲基砷(DMA)和砷甜菜碱(AsB)5种常见砷形态的提取及分析方法。结果表明,采用pH值10.22~10.27的10 mmol/L无水乙酸钠、3 mmol/L硝酸铵、2 mmol/L磷酸二氢钠和0.2 mmol/L乙二胺四乙酸二钠混合溶液作为流动相,可很好地分离稻米中的5种砷形态。比较了硝酸−水、磷酸−水、盐酸−水、甲醇−水、纯水不同提取液对稻米中5种砷形态的提取效率,并对提取溶剂的浓度、提取时间、辅助加热方法等条件进行优化选择。研究表明,以1% HNO3水溶液作为提取试剂,在90℃恒温条件下处理3 h,对稻米中砷的提取效果较好。样品中5种砷形态的加标回收率在84.24%~112.75%之间,RSD小于7.74%,检出限在0.2~0.5 µg/L之间。实验表明,此方法适用于含砷稻米中砷的形态分析。

     

    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.

     

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