Characterization and chemical profiling of green tea samples using capillary electrophoresis combined with chemometrics

Green tea (GT) is made from the leaves of Camellia Sinensis and is the most popular beverage in Asia because of its attractive aroma, taste and health promoting effects. The catechins content is associated to the biological value of tea and it could be used as chemical descriptor and potential indicator of the geographical origin. Besides catechins, xanthines and in particular caffeine are important components of GT, due to their stimulating effects. Cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) was applied to the characterization of GT samples by evaluation of the quantitative profile of catechins and xanthines. The CD-MEKC method showed to be suitable for the simultaneous analysis of these compounds, presenting good performances in terms of selectivity, analysis time and possibility of chiral analysis. The enantioselective analysis made it possible to provide information on sample stability and manufacturing processes. Data analysis was performed by different multivariate exploratory and discriminant techniques to differentiate GT samples according to geographical origin, which is an important factor in order to determine quality and reputation of a commercial GT product. In general, with exception of (-)-epicatechin gallate, the amount of all the compounds was found to be higher in Chinese GT samples compared to those from Japan. The use of excitation–emission matrix fluorescence spectroscopy coupled with chemometric tools was proposed as alternative analytical approach.