DETERMINATION OF FLAVANOLS, THEOGALLIN, GALLIC ACID AND CAFFEINE IN TEA USING HPLC

An RP-HPLC method for the determination of flavanols (catechins), theogallin, gallic acid and caffeine, including the sample preparation using a solid-phase extraction technique, has been developed. HPLC separation was performed on a Hypersil-ODS column using a gradient method with 2% acetic acid (aq) and acetonitrile as solvents. The method has been applied to green, oolong and black tea samples as well as tea extracts. The contents in different kinds of tea were 0.93-5.74 g/100 g dry mass for epigallocatechin gallate, 0.73-3.25 g/100 g dry mass for epigallocatechin, 0.17-1.16 g/100 g dry mass for epicatechingallate, 0.04-0.48 g/100 g dry mass for catechin, 0.1-0.8 g/100 g dry mass for epicatechin, 0.17-0.97 g/100 g dry mass for theogallin, 0.06-0.62 g/100 g dry mass for gallic acid and 2.25-4.33 g/100 g dry mass for caffeine. Instant tea contained 2-3-fold higher amounts. As expected the contents of flavanols in green teas were higher than in black teas, for gallic acid it was the opposite. Furthermore, the influence of different extraction methods on the contents of these compounds has been investigated.