Fig. 1From: Simple isocratic method for simultaneous determination of caffeine and catechins in tea products by HPLCThe HPLC chromatograms of standard samples (1 gallic acid, 3 caffeine, 4 epicatechin, 5 epigallocatechin gallate) each at a concentration level of 8 μg/ml, 2 internal standard i.e., β-hydroxyethyl-theophylline (10 μg/ml) (a) and CTC black tea (1 gallic acid, 2 β-hydroxyethyl-theophylline, 3 caffeine, 4 epicatechin, and 5 epigallocatechin gallate (b)Back to article page