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建立了茶叶中砷酸根As(V)、亚砷酸根As(III)、一甲基砷(MMA)和二甲基砷(DMA)的离子色谱-电感耦合等离子体质谱(IC-ICP-MS)检测方法。比较了3种提取方式对茶叶中4种砷形态的提取效率,优化分离条件,通过加标回收试验考察了方法准确度及精密度。以0.1 mol/L硝酸水溶液为提取试剂,石墨消解仪100℃消解2h,上清液供IC-ICP-MS分析。4种砷形态采用Dionex Ion Pac AS7阴离子交换柱(250 mm×2 mm)分离,使用ICP-MS检测。通过加标回收试验考察方法准确度及精密度,在3个加标水平上各形态的回收率在90.9%~125.0%范围,RSD(n=4)小于5.7%。As(V)、As(III)、MMA和DMA的检测限分别是0.1,0.2,0.3,0.3μg/L,即2.5,5.0,7.5,7.5μg/kg茶叶。采用该方法对市售茶叶中的4种砷形态含量进行调查分析,As(V)、As(III)、MMA和DMA本底含量分别在0~545.1,0~147.0,0~95.2,0~86.6μg/kg之间。无机砷含量与有机砷之间差异显著(P<0.05),平均含量从高到低依次为As(Ⅴ)、As(Ⅲ)、MMA和DMA。本结果表明,该方法简单、精确,可用于茶叶中4种砷形态的准确定量和风险评估。
An ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) method was developed for the determination of arsenate As (V), arsenite As (III), monomethylarsone (MMA) and dimethyl arsenate (DMA) Detection method. The extraction efficiency of four kinds of arsenic in tea leaves was compared by three extraction methods. The separation conditions were optimized. The accuracy and precision of the method were investigated by spike recovery test. 0.1 mol / L nitric acid solution was used as extraction reagent, and the graphite digestion device was digested at 100 ℃ for 2 hours. The supernatant was analyzed by IC-ICP-MS. Four arsenic species were separated on a Dionex Ion Pac AS7 anion exchange column (250 mm × 2 mm) using ICP-MS. Through the spiked recovery test, the accuracy and precision of the method were investigated. The recoveries of all the three spiked forms were in the range of 90.9% ~ 125.0% at 3 spiked levels with RSD (n = 4) less than 5.7%. The detection limits for As (V), As (III), MMA and DMA were 0.1, 0.2, 0.3 and 0.3 μg / L, ie 2.5, 5.0, 7.5 and 7.5 μg / kg of tea leaves, respectively. The contents of As (V), As (III), MMA and DMA in the commercially available tea were investigated by using this method. The contents of four kinds of arsenic were 0 ~ 545.1,0 ~ 147.0,0 ~ 95.2,0,0 ~ 86.6 μg / kg. The content of inorganic arsenic was significantly different from that of organic arsenic (P <0.05). The average content of inorganic arsenic was As (Ⅴ), As (Ⅲ), MMA and DMA from high to low. The results show that the method is simple and accurate and can be used to accurately quantify and assess the four arsenic species in tea.