C N H O and mineral element stable isotope ratio analysis for authentication in tea

Abstract In this work, the potential of C, N, H, O and mineral element stable isotope ratios and chemometric methods as a tool to first authenticate Chinese tea according to their blend raw materials was examined. Forty-four multi-elemental stable isotope ratios of four batches of Chongqing tuo tea (n = 27 for each batch) were determined by the EA-IRMS and ICP-MS methods. The clustering results of HCA and PCA were worse than that of PLS-DA, BP-ANN, and LDA. The PLS-DA model displayed good model performance (R2X = 0.57, R2Y = 0.74, and Q2 = 0.653). By BP-ANN, the total correct authentication rates for model training and external validation were 100% and 91.2%, respectively. The best performance was obtained by LDA, the total correct authentication rates for model training, cross-validation and external validation were 100%, 100% and 96.9%, respectively. δ2H, δ18O, 98Mo/95Mo, 96Mo/95Mo, and 98Mo/96Mo were markers for enabling the accurate authentication of Chongqing tuo tea according to formulas. This study has contributed toward generalizing the use of multi-elemental stable isotope ratio fingerprinting as a promising tool for testing the authenticity of tea worldwide.