ICP-MS Determination of 10 Mineral Elements in Pu-Erh Raw Tea and Origin Traceability of Pu-Erh Raw Tea Combined with Chemometry Method

Referrig to national standard of GB 5009.268-2016, contents of 10 mineral elements (Pb, Cd, Mg, Al, K, Ca, Mn, Fe, Cu, Zn) in 90 Pu-erh raw tea samples from 3 different regions of Yunnan province were determined by inductively coupled plasma mass spectrometry (ICP-MS) with microwave digestion. Cluster analysis, principle component analysis and linear discriminant analysis were carried out to examine the feasibility of mineral elements analysis in identifying the geographical origin of Pu-erh raw tea for screening out the effective indicators in Pu-erh raw tea origin assessment. As shown by the results, linear relationships between mass concentrations of 10 mineral elements and response value ratios of analyted elements to internal standard elements were kept in the same range of 1.0-100.0 μg·g^-1, with detection limits (3s) in the range of 0.002-1 μg·g^-1, and the determined values on tea reference material were basically consistent with the confirmed value. Contents of 10 mineral elements in Pu-erh tea from different regions were different. 90 Pu-erh tea samples were divided into 3 groups from the cluster analysis of mineral elements, which was basically consistent with the actual classification results. The samples were classified into two categories by principle component analysis, and the cumulative variance contribution rate was 80.381%. 7 elements of Pb, Cd, Ca, Mn, Fe, Cu, Zn were introduced into locality discrimination models. Base on the models, the initial inspection and cross inspection of samples from 3 different origins were carried out, with the recognition rate of 100%. The models were used for external inspection of Pu-erh raw tea samples from Baoshan, and the recognition rate was 0.