COMPARATIVE-STUDY OF THE REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF BLACK TEA LIQUORS WITH SPECIAL REFERENCE TO THE THEARUBIGINS

New high-performance liquid chromatographic methods for the analysis of black tea phenolic pigments, using Hypersil ODS, Hypersil octyl wide-pore, and Hamilton PRP-1 columns, and several new results arising from them are presented. Very good resolution of a wide range of phenolic tea pigments, was obtained using a Hypersil ODS column with a citrate buffer, and, for the first time, eight theaflavins were observed in a single chromatogram. Unresolved brown phenolic pigments (thearubigins), ran as a convex broad band on the Hypersil wide-pore and Hamilton PRP-1 columns, and the Hamilton PRP-1 column showed an anthocyanidin to be a significant contributor to liquor colour. The pigments were classified into three groups by chromatographic behaviour: group I, pigments running close to the void volume of the columns; group II, resolved pigments; and group III, unresolved pigments. Group II pigments were divided into four Sub-Groups by their photodiode-array UV-VIS spectra, as follows: subgroup II.1, theaflavins; sub-group II.2, theaflavic acids; sub-group II.3, type I resolved pigments; and sub-group II.4, type II resolved pigments. Pigments in sub-groups II.3 and II.4 were designated as resolved thearubigins, and those in group III as unresolved thearubigins.