基于ASE提取IC-ICP-MS联用测定茶叶中Cr(Ⅲ)和Cr(Ⅵ)的研究

采用加速溶剂萃取(ASE)-离子色谱(IC)-电感耦合等离子体质谱(ICP-MS)法测定,建立了茶叶中Cr(Ⅲ)和Cr(Ⅵ)的分析方法。样品使用0.04 mol/L EDTA二钠盐和硝酸铵溶液(p H为7.0~7.5)在80℃和1 600 psi压力下提取,C18固相萃取(SPE)净化。以0.075 mol/L的硝酸铵作为流动相,AG7色谱柱分离后用ICP-MS测定。结果表明,Cr(Ⅲ)和Cr(Ⅵ)在0~10.0μg/L线性关系良好,检出限均达到0.03μg/L。以实际茶叶样品为基体,在1.0μg/L浓度水平下,Cr(Ⅲ)和Cr(Ⅵ)的加标回收率分别为86.2%~89.2%、78.8%~79.4%,RSD4%(n=7)。该方法具有自动化程度高和同时测定2种价态的优点,适合批量、准确测定茶叶中2种价态铬的含量。

Determination of Cr(Ⅲ) and Cr(Ⅵ) in Tea by IC-ICP-MS based on ASE Extraction

A method for determination and analysis of Cr (Ⅲ) and Cr (Ⅵ) in tea was established by IC-ICP-MS). The samples were extracted with 0.04 mol/L EDTA disodium salt and ammonium nitrate solution (pH=7.0~7.5) under pressure at 80℃ and 1600 psi, then were purified with solid phase extraction (SPE) with C18. With 0.075 mol/L ammonium nitrate solution as mobile phase, the AG7-HC ion chromatographic column was separated and detected by ICP-MS. The results showed good linear relationships (r2=1.0) were obtained between Cr (Ⅲ) and Cr (Ⅵ) in the range of 0~10.0 mg/L and the detection limit were all 0.03 mg/L. With practical tea samples as matrix, the recoveries of Cr (Ⅲ) and Cr (Ⅵ) were in the range of 78.8%~89.2% at concentration of 1.0μg/L, and the relative standard deviations (RSDs) were less than 4.0%(n=7). The results indicated the method had advantages of high degree automation and simultaneous determination of 2 valence states, which was suitable for the batch and accurate determination of Cr(Ⅲ) and Cr(Ⅵ) contents in tea.