Simultaneous determination of catechins, caffeine and other phenolic compounds in tea using new HPLC method

We conducted a high-performance liquid chromatographic analysis of tea for eight catechins (epigallocatechin gallate, epigallocatechin, epicatechin gallate, epicatechin, gallocatechin gallate, gallocatechin, catechin gallate and catechin), caffeine and eight other phenolic compounds (epigallocatechin 3-O- (3″-O-methyl) gallate, epigallocatechin 3,5-di-O-gallate, chlorogenic acid, 3-O-caffeoylquinic acid, 4-O-p-coumaroylquinic acid, 5-O-p-coumaroylquinic acid, coniferin, 1,4,6-tri-O-galloyl-β-d-glucose). Using an octadecylsilyl column and a gradient elution system of water–methanol–ethyl acetate–phosphoric acid, all of these compounds were separated within 40 min. The validity of this method was confirmed by the quantitative measurement of eight catechins and caffeine. The detection limits of these compounds were within the range of 1.4–3.5 ng. All the analyses exhibited good linearity up to 1500 ng, and the accuracies for the analyses were 96–103%.