HPLC determination of catechins in tea leaves and tea extracts using relative response factors

A simple high performance liquid chromatographic analysis of tea catechins using relative response factors has been developed. The separation system consisted of a C18 reversed-phase column, a gradient elution system of methanol/water and orthophosphoric acid, and a photodiode array detector. Relative response factors for catechins are given on different columns and relative to different references. It has been shown that the relative response factors for catechins are quite similar at 210 nm of detection under different analytical conditions (different columns, different elution systems, and different HPLC instruments). (+)-Catechin was selected as the reference compound for calculating the relative response factors of the catechins. Using this method, not every catechin is needed as a reference standard, making the method ideal for rapid, routine analysis, especially for those laboratories where catechin standards are not readily available. The method is applicable to all kinds of tea, tea extracts and some tea containing products. It is especially useful for the determination of (+)-gallocatechin and (+)-catechin, which often are regarded as being present below detectable limits when detected at 280 nm, and (−)-catechin gallate, which takes a long time to elute in isocratic systems.