Studies on the Flavanols in Tea (Part 1):A Method for the Quantitative Determination of Flavanols by Paper Partition Chromatograpy
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概要
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For the determination of individual flavanols in tea leaf or green tea a paperchromatographic method is proposed from results of investigations of various estimating, conditions.<BR>A weighed sample (1-2g. of fresh leaf or 100-200mg. of powderd tea) is extracted with acetone and an aliquot of the solution (corresponds to ca.2 mg. of fresh leaf) is subjected to chromatography. Two-dimensional ascending chromatography is carried out on 23×19cm. Whatman No.<BR>1 paper using phenol-water (3:1) and a butanol-acetic acid-water mixture (4:1:2). The dried chromatogram is sprayed uniformly with a minimum volume of diluted diazotized sulfanilic acid.<BR>The preparation of diazotized sulfanilic acid is as follows:To a solution of sulfanilic acid in 1.75% hydrochloric acid (0.5%) is added an equal volume of 0.5% aqueous sodium nitrite solution. This reagent is used for the preliminary revelation of flavanols after being diluted to 1/5-1/10 concentration with deionized water and for color reaction of the estimating solution after mixing with 2.5 volume of sodium acetate buffer (2%).<BR>The detected spots are cut out and the flavanols are eluted from the paper with 9ml. of hot water. To these eluates is added 0.35ml. of diazosulfanilic acid solution buffered with sodium acetate and make up to 10ml. with water. The colored eluates are placed in a bath at 35°C. for 30 min. and after being cooled to room temperature the absorbances at 420mμ of them are measured spectrophotometrically. The calibration curve by use of each standard flavanol is available for the determination.<BR>This method will ensure the determination of 10-50μg. of catechins with 1.5-9.3% of coefficients of variation.
- 日本茶業技術協会の論文
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