ヒドラジン法によるアスコルビン酸各型の分別定量について

抄録

The 2,4-dinitrophenylhydrazine method for fractional determination of ascorbic, dehydroascorbic and diketogulonic acids according to Roe was examined and the improved conditions were described : In the presence of oxyhemoglobin, ascorbic acid (AsA) is oxidized to dehydroascorbic acid (DAsA) during deproteinization. For preventing the oxidation of AsA in blood during deproteinization, blood is hemolyzed with water, followed by addition of stannous chloride and metaphosphoric acid. For reduction of DAsA to AsA H_2S is passed through the deprotenized solution containing SnCl_2,adjusted to pH 3 with sodium acetate and the whole is kept at 37℃ for 2 hours. H_2S is expelled by N_2 or CO_2 after addition of thiourea. The solution is filtered and determined, whereby DAsA is practically completely reduced to AsA leaving"diketogulonic acid"as itself. The difference from the total AsA is assumed to be the DAsA. In fresh animal and vegetable tissues the sum of DAsA and diketogulonic acid is small as compared with the total ascorbic acid. In such cases, the determination of"diketogulonic acid"can be practically simplified as follows : The solution deproteinized with 5% metaphosphoric acid without indophenol oxidation is kept at 37℃ for 15 minutes after equilibration with H_2S, followed by addition and dissolution of thiourea and kept further at 37℃ for 20 minutes.