Phosphomolybdium Tungstic Acid Colorimetric Method
Phosphomolybdic acid colorimetric method determine Tannin is one of many methods, including hide powder method, casein law, phosphomolybdic acid - Colorimetric hide powder, casein improved method, phosphomolybdic acid colorimetry. Phosphomolybdium tungstic acid colorimetric method is using tannin reduces phosphomolybdium tungstic acid in alkali solution and appears dark blue color, by colorimetric method will test the content, test under 760nm. Use gallic acid as reference substance, phosphomolybdium tungstic acid colorimetric method to test tannin content. Use cold water to filter and extract tannin, then precipitate non-tannin content with casein. The disparity is tannin content. It is accurate than hide powder method which is repeatable and has high sensitivity. Among which phosphomolybdic acid uses sodium tungstate, molybdate, water, hydrochloric acid, phosphoric acid as raw material, add lithium sulfate and bromine, boil and remove excess bromine, solution color should be yellow.
Tannin is also called tannic acid, it is a kind of complex water-soluble polyphenolic compounds have precipitated proteinaceous, widely existed in plants. There are many method to test tannin content, hide powder method is recognized internationally. The main content of hide powder is protein, polyphenols by an amide group to form hydrogen bonds in the molecule a phenolic hydroxyl group and protein incorporated into water-insoluble precipitation, content is tested by weight method.
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