XRF与ICP-MS法在福建省安溪县和华安县的铁观音茶中元素含量测定的应用研究

安溪是铁观音茶的源产地，茶叶总产值每年数亿元，但不同品质的铁观音茶价格参差不齐，市场上存在以次充好的现象。福建省安溪县和华安县为铁观音主要的茶产地，两县市的茶叶产量市场占有率较高，地理位置毗邻，但茶叶品质和风味各有不同，造成茶叶市场的困扰。铁观音中微量元素种类和含量的检测，对产地的溯源具有重要的意义。采用X射线荧光光谱无标样半定量分析法（XRF）和微波消解/电感耦合等离子体质谱法（ICP-MS）对福建省主要茶产区安溪县（感德、西坪、祥华）和华安县（良村、华丰、仙都）的30份铁观音进行元素含量对比分析。XRF法检测出两县茶样中存在的元素种类有K，Ca，S，P，Mg，Al，Si，Cl，Fe，Mn，Rb，Zn，Na和Sr，但含量上存在一定的差异。根据XRF法检测结果进行快速、准确稀释茶样用于ICP-MS法对比测定金属元素，优化样品前处理方法以满足痕量检测要求。对比发现当测定Ca，Mg，Al，Fe，Mn和Zn金属元素时，相关性系数R2在0.824 8~0.892 8，趋势线斜率在0.806 0~0.944 9，XRF法和ICP-MS法的可比性较好，说明检测这六种元素采用这两种方法皆适合。同1份安溪铁观音茶样采用XRF法的相对标准偏差皆＜6.0%，ICP-MS法的相对标准偏差皆＜3.0%。相对于ICP-MS法，XRF法前处理更简单，耗时少，因此需低成本、快速、简便检测茶样中的Ca，Mg，Al，Fe，Mn和Zn元素含量时，可选择XRF检测法。采用ICP-MS检测出的K，Ca，Mg，Al，Fe，Mn，Rb，Zn，Na和Sr金属元素进行逐步判别分析，通过建立Fisher判别模型对安溪县和华安县铁观音茶样实现有效区分，模型建立的判别函数的产地检验判别率为96.7%，交叉检验判别率为96.7%，对测试样品的识别正确率为100%。ICP-MS法检测金属元素结合逐步判别-Fisher判别分析，对安溪县和华安县铁观音茶样产地溯源具有较强的可行性。

Application of XRF and ICP-MS in Elements Content Determinations of Tieguanyin of Anxi and Hua’an County,Fujian Province

Anxi is the origin of Tieguanyin, with hundreds of millions of gross output values yearly. However, the price of Tieguanyin with different quality is uneven, and the counterfeit and shoddy phenomenon exists in the market. Anxi County and Hua’an County in Fujian Province are the main tea producing areas of Tieguanyin. Although these two counties have a relatively high market share in tea-production and are geographically adjacent, the quality and flavor of tea are different, causing troubles for the tea market. Detecting the types and contents of microelements in Tieguanyin is of great significance in tracing its origin. In the study, standard less semi-quantitative X-ray fluorescence spectrometry (XRF) analysis and microwave digestion-inductively coupled plasma mass spectrometry (ICP-MS) is used to quantitative analyze the element contents of 30 Tieguanyin samples from Anxi (Gande, Xiping, Xianghua) and Hua’an (Liangcun, Huafeng, Xiandu) counties. The element types detected by XRF are K, Ca, S, P, Mg, Al, Si, Cl, Fe, Mn, Rb, Zn, Na, Sr,and there are certain differences in element content. For comparison, we use the ICP-MS method to detect the metallic elements found by XRF. According to the results of the XRF method, tea samples were diluted quickly and accurately for ICP-MS to meet the requirements of trace detection. When detecting Ca, Mg, Al, Fe, Mn and Zn metal elements, the correlation coefficient R2 of the XRF and ICP-MS methods is between 0.824 8 and 0.892 8, and the slope of the trend line is between 0.806 0 and 0.944 9, which shows good comparability. It shows that the XRF and ICP-MS methods are suitable for detecting these six elements. XRF and ICP-MS determined one Tieguanyin sample, the relative standard deviations were less than 6.0% and 3.0%, respectively. Compared with the ICP-MS method, the XRF method is simpler and less time-consuming in the pretreatment. Therefore, when low-cost, fast and easy detection of the content of Ca, Mg, Al, Fe, Mn and Zn in tea samples is required, the XRF detection method is preferred. K, Ca, Mg, Al, Fe, Mn, Rb, Zn, Na and Sr metal elements detected by ICP-MS were used for stepwise discriminant analysis, and the Fisher discriminant model was established to realize the recognition of Tieguanyin tea samples in Anxi County and Hua’an County. The discriminant rate of origin test, cross-validation and test samples established by the model was 96.7%, 96.7% and 100%, respectively. ICP-MS combined with stepwise discriminant analysis is feasible for Tieguanyin tea samples in Anxi County and Hua’an County.