Evaluation of Direct Analysis for Trace Elements in Tea and Herbal Beverages by ICP-MS

In general, inductively coupled plasma mass spectrometry (ICP-MS) food analysis requires numerous sample treatment steps that imply an increase of analysis time and the use of chemicals. In this study, the main objective was to evaluate the applicability of the direct analysis by ICP-MS to determine twelve elements (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se and Zn) in tea and herbal beverages. Direct analysis method was compared with two other sample treatments: minimum treatment (acid dilution) and using a destructive method (microwave assisted digestion). Besides the lowest time of analysis, direct analysis provides a reliable response and agrees with the “green chemistry” principles. High sensitivity was also observed by low values of limits of detection and quantification, in general, below 2.5 µg L-1. The method accuracy was evaluated by spiked experiments and values ranged between 82 and 120%. Low values of coefficient of variation were also observed, 2 to 17%, for all analytes. The method exhibited applicability for commercial tea samples as well as for drinks made by herb infusion.

一般而言，采用电感耦合等离子体质谱法（Inductively coupled plasma mass spectrometry, ICP-MS）进行食品分析时，需开展多步样品前处理，这会延长分析时长并增加化学试剂的使用量。本研究的核心目标为评估ICP-MS直接分析法在茶与草本饮料中测定12种元素（Al、As、Ba、Cd、Cr、Cu、Fe、Mn、Ni、Pb、Se、Zn）的适用性。本研究将该直接分析法与另外两种样品前处理方案进行对比：一是极简前处理（酸稀释法），二是破坏性前处理（微波辅助消解法）。相较于其他方法，直接分析法不仅分析耗时最短，还可获得可靠的检测结果，且符合"绿色化学"原则。该方法同时具备优异灵敏度，检出限与定量限均较低，整体低于2.5 μg·L⁻¹。通过加标回收实验评估该方法的准确度，其回收率介于82%至120%之间。所有待测物的变异系数均处于较低水平，区间为2%至17%。该方法可有效应用于市售茶样品以及草本浸制饮料的检测分析。