Ferrous tartrate method (method # 1)
Content of tea polyphenols (TP) in tea extracts was
determined by the spectrophotometric method described
by Liang et al. (2003) and Li et al. (2005). One milliliter
of tea extract was transferred into a 25 ml volumetric flask
to react with 5 ml dyeing solution (1 g ferrous sulfate and 5
g potassium sodium tartrate tetrahydrate dissolved in 1000
ml distilled water), 4 ml distilled water and 15 ml buffer
(0.067 M potassium phosphate, pH 7.5). Several minutes
were required for color development. Absorbance readings
were made at 540 nm by a Shimadzu UV-VIS 1601 spectrophotometer,
using a blank solution prepared with distilled
water replacing the tea extract