A highly specific and sensitive diazotized sulfanilamide reagent is synthesized for determination of tea catechins. The reagent is employed both as spray reagent for selective visualization of tea catechins on two-dimensional paper chromatograms (sensitivity <1 microg of d-(+)-catechin) and for their spectrophotometric quantification in the crude extracts of tea polyphenols isolated from fresh or dried tea shoots. The formation of yellow color (lambda(max) = 425 nm) between catechins and diazotized sulfanilamide was investigated and made the basis of a simple and sensitive spectrophotometric method for estimation of the total and individual catechins in different tea cultivars. At 425 nm, the absorbance was linear (r = 0.999) over the (0.4-8.0 microg/mL) concentration range of d-(+)-catechin.

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