A simple and fast high performance liquid chromatographic method for five catechins and caffeine using an ODS column and a water-acetonitrile-formic acid mobile phase system was developed. The catechins (epicatechin, catechin, epigallocatechin, epigallocatechin gallate, epicatechin gallate) and caffeine were separated by an acetonitrile gradient within 20 min. The detection limit of the method was approximately 10 ng for all the compounds (by injecting 10 mL). Several green, black and instant

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... as were analysed using this method. By using the studied compounds as chemical descriptors, linear discriminant analysis was performed and complete differentiation of the green, black and instant teas was achieved. Experimental Reagents and standard solutions Methanol and acetonitrile (Romil, Cambridge, UK) were of HPLC grade. Milli-Q (Millipore, Bedford" MA, USA) treated Fig. 1 Structures of catechins and caffeine. This journal is