Spectrophotometric determination of tannins in tea samples using alpha and alpha'-dipyridyl and tiron

ABSTRACT

Tannins are determined spectrophotometrically in Indian, Kenyan and Ceylon tea samples using direct and indirect methods In the direct method excess amount of Fe[III] is added to tea sample followed by alpha, alpha ['] -bipyridyl at pH 4.4 and the absorbance of Fe [II]- alpha, alpha ['] -bipyridyl complex is measured at 522 mm. In the indirect method an excess amount of Fe[III] is added to the sample followed by Tiron reagent and the absorbance of the formed Fe[III]-Tiron complex is measured at 620 nm