微波消解-四级杆电感耦合等离子体质谱法测定茶叶中有益和有害金属

目的]全面迅速了解茶叶中微量元素含量,提高我国茶叶品质并指导合理科学饮茶。方法]采用HNO_3-H_2O_2体系微波消解茶叶样品,四级杆电感耦合等离子体质谱法(Q-ICP-MS)测定了茶叶中As、Cd、Co、Cr、Cu、Mn、Ni、Pb、Tl、V和Zn 11种有益和有害金属元素。通过优化Q-ICP-MS仪器测定条件和选择合适的同位素进行测定,克服了质谱干扰;通过采用在线加内标校正、减小取样量至0.04 g和控制微波消解温度大于180℃,消除了有机碳引起的基体效应。结果]在最优的试验条件下,重复测定茶叶标准物质(GBW10052)中11种元素的相对误差为-18.50%~14.30%,精密度为1.5%~8.9%,说明该方法准确可靠。同时,对市售5种茶叶中11种金属元素进行测定,结果与文献报道的中国茶叶重金属元素平均值基本一致,并且与文献报道一样,显示出中国茶叶重金属含量高于日本的趋势。结论]该方法操作简便、快速、准确,适合推广应用。

Determination of Beneficial and Harmful Metals in Tea by Quardrupole Inductively Coupled Plasma Mass Spectrometry Combined with Microwave Digestion

Objective] To understand the content of trace elements in tea comprehensively and rapidly,to improve the quality of Chinese tea and to guide rational and scientific tea drinking.Method]Tea samples were digested with HNO3-H2O2 in microwave system,and then eleven elements including As,Cd,Co,Cr,Cu,Mn,Ni,Pb,Tl,V and Zn were determinded by a quardrupole inductively coupled plasma mass spectrometry.In order to avoid mass interferes,an optimized mass system and interference-free isotopes were choosed.On-line internal standard,decreasing sample mass to 0.04 g and setting microwave tempreture grater than 180 ℃ eliminated matrix effect caused by organic carbon.Results] Under optimized experimental condition,determine errors of a tea standard material (GBW10052) were ranging from-18.50％ to 14.30％,and precisions ranged from 1.5％ to 8.9％,which showed that using this method to determine metals in tea samples could achieve ccurate and reliable results.Measurement results of eleven metals in five marketed tea samples were almost the same with reported average level of Chinese tea,both of which were higher than Japanese tea.Conclusion] This method is suitable to spread considering the simple and fast procedure and accurate results.