离子色谱-电感耦合等离子体质谱联用测定茶叶中4种砷形态

Determination of Four Arsenic Species in Tea by Ion Chromatography-inductively Coupled Plasma-mass Spectrometry

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。

A method was developed for the simultaneous determination of arsenic acid [As（V）], arsenious acid [As（III）], monomethylarsonic acid（MMA） and dimethylarsinic acid（DMA） in tea by ion chromatography-inductively coupled plasma-mass spectrometry（IC-ICP-MS）. Three kinds of extract solutions were compared by extraction efficiency and the separation parameters were optimized. The extraction regent was 0.2 mol·L-（-1） nitric acid with heat-assistant condition for 2 h at 100 ℃. Then the 4 arsenic species were separated by an anion exchange column（Dionex Ion Pac As7, 250mm×2 mm） and detected by ICP-MS. The recoveries of the 4 arsenic species spiked in tea at three levels ranged from90.9% to 125.0% with the relative standard deviations（RSDs, n=4） less than 5.7%. Detction limits of As（V）、As（III）、MMA and DMA were 0.1, 0.2, 0.3 and 0.3 μg·L-（-1）, corresponding to 2.5, 5.0, 7.5 and 7.5 μg·kg-（-1） in tea samples,respectively. This method is applied to investigate the background content of the 4 arsenic species in 4 kind of commercial tea samples, and the content of As（V）, As（III）, MMA and DMA were 0-545.1, 0-147.0, 0-95.2 and 0-86.6μg·kg-（-1）. The contents of inorganic arsenic was higher than that organic arsenic significantly（P〈0.05）, and the average contents were As（Ⅴ）, As（Ⅲ）, MMA and DMA in order. The result shows that this method is simple and precise for the determination and risk assessment of four arsenic species in tea.