Authenticity determination of tea drinks in the Chinese market by liquid chromatography coupled to isotope ratio mass spectrometry

Liquid chromatography coupled to isotope ratio mass spectrometry (LC-IRMS) was developed for determinations of caffeine delta C-13 from commercial tea in the Chinese market under lower temperature condition. On the basis of the carbon isotope analysis of 116 commercial tea samples including black tea, Oolong tea, green tea, dark tea, white tea, yellow tea and scented tea, it explained that the range of caffeine delta C-13 for commercial tea were from -26.14 to -33.68 parts per thousand. Partial least-squares discriminant analysis (PLS-DA) modeling of caffeine delta C-13 data indicated that six main types of Chinese tea presented significant difference, and caffeine delta C-13 in Chinese tea was related to the fermented process except yellow tea. The method was also used for measurement of caffeine delta C-13 in the 19 tea drinks, and the results showed that caffeine in the seven tea drinks was not from the natural tea. Thus, LC-IRMS can be very promising tool for evaluation of natural caffeine from commercial tea and tea drinks authenticity.