Spectrophotometric quantitative determination method of tannins in oak bark, alder multiple fruit, and in water extractions from the given source material

National pharmacopeia (XI edition) recommends permanganatometry as the main method of quantitative determination of tannins. The method yields overrated results. In connection with it we have suggested spectrophotometric method of determination based on optical density measurement of coloured reaction products of tannins with iron tartrate reagent with presence of pH 8, 2 buffer.

We used gallic acid as a standard. Subjects of inquiry were: oak bark and alder multiple fruit released by pharmaceutical industry and water extractions from it. We have established wave length in maximum absorption of reaction products of gallic acid and tannins in water extraction with iron tartrate reagent, retention of the colour during the time, ability to follow Bouguer-Lambert-Beer law. There was represented the method of quantitative determination of tannins in water extractions from oak bark and alder multiple fruit, there was ascertained that single determination error was not more then 4,5% when confidence probability was 0,95. The absence of systematic error was proved. We have compared the method of permanganatometry with the spectrophotometric one and found out that the first one yielded overrated results.