Simultaneous Determination of Five Catechins and Caffeine in Tea by HPLC and Differentiation of Teas by Cluster Analysis

A method was developed for simultaneous determination of five catechins((-)-gallocatechin,(-)-epigallocatechin,(-)-epigallocatechin-3-gallate,(-)-epicatechin,(-)-epicatechingallate) and caffeine by HPLC with diode array detection(DAD).The tea extract was separated on a C18 column which was then eluted with methanol and 0.05% trifuoroacetic acid solution in gradient elution mode.The chromatograms were simultaneously detected by DAD at λ210 nm for(-)-gallocatechin(GC) and at λ278 nm for the other components.Time of flight mass spectroscopy(TOF-MS) was used for qualitative analysis of real tea sample,the results showed that five catechins and caffeine were baseline separated,indicating that the six components could be determined accurately.The method has been used to determine the catechins and caffeine in 33 tea samples with satisfactory results.Cluster analysis has been used to classify 33 tea samples reasonably and to differentiate the qualities of the tea by using the concentrations of the six components as indices.