Abstract
(1) The determination of vitamin C by 2,4-dinitrophenylhydrazine(Hyd) method is influenced by the presence of various compounds, for instance, aromatic amino acids, keto acids, sugars, uronic acids, reductone and tannic acid, especially when oxidized with bromine rather than 2,6-dichlorophenolindophenol(Ind) . (2) When the reaction products of Hyd method of various animal and vegetable tissues and their preparations were subjected to thin-layer chromatography(TLC) many colored spots appeared in the chromatogram in addition to the one corresponding to ascorbic acid(AsA). However, the absorption spectra of the colored solutions of many tissues oxidized with Ind corrected with the blank test agreed pretty well with that of pure AsA, when the tissues contained much AsA, but not in the case of those containing little AsA. (3) The determinathion of real total vitamin C by TLC using the colored solution of the Hyd method oxidized with Ind is described in detail. The colored solution is extracted with ethylacetate and subjected to TLC using silica gel G as the adsorbent and toluene・acetone・5% acetic acid as the developing solvent. The fraction correponding to AsA is dissolved in sulfuric acid and determined photometrically at 530 mμ. (4) Comparison of the Hyd values of many fresh tissues oxidized with Ind or bromine with those of TLC showed that those oxidized with Ind and the real vitamin C values by TLC did not differ markedly but those oxidized with bromine were generally much greater than TLC values. (5) Many foodstuffs of animal and vegetable origins showed remarkable AsA values in the Hyd method, whereas the TLC values were negligible, for example, black tea, coffee, cocoa, soy sauce, fruit juice, and bean paste. The TLC method is proved to be useful for testing and determinining the existence of true vitamin C in tissues and products.
