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

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

[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。

[ 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 HN03 - H202 in microwave system,and then eleven ele-ments 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 °C 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. Measure-ment 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.