The filter paper partition chromatographic method for the quantitative determination of total ascorbic acid is used for determination of human blood ascorbic acid. The percentage recovery is 101-102%. A comparison is made of this method with Roe-Kuether colorimetric method and photoelectric titration method for the total ascorbic acid determination. The results indicate that 2-ketogulonic acid is not present in human plasma.

It has been proved chromatographically that the substances in human urine interfere 2,6-dichlorophenol indophenol visual titration method are mainly thiosulfates, cysteine and an unknown substance with Rf of 0.5 (Rf of ascorbic acid = 0.28). Ketonic substances present in urine interfere the ascorbic acid estimation with 2,4-dinitrophenylhydrazine colorimetric method. The amount of these interfering substances present in human urine is usually high, so that erroneous results are obtained with both methods, even in the case of large amount of ascorbic acid in the sample.Formaldehyde at pH 2.0 can not condense with ascorbic acid quantitatively, so that the results obtained by formaldehyde condensation method are considerably lower than that obtained with Kuo and Chen's filter paper partition chromatographic method.Our results indicate that the last mentioned method is the most convenient and accurate one for the quantitative analysis of ascorbic acid in urine.

Iodine was used as an oxidant instead of brimine in the 2,4-dinitro-phenylhydrazine method for the determination of total ascorbic acid content in vegetables. The excess of iodine was removed with a small amount of crystalline thiourea. This process of oxidation was simple, safe and rapid.With this modified method, the ascorbic acid content of 18 vegetables were determined. The ascorbic acid values thus obtained with iodine were sometimes slightly lower than those with bromine, but were higher than those with paper chromatographic method.

(1) The contents of total ascorbic acid in 129 kinds of vegetables and fruits in Kaifeng were determined by means of both Kuo-Chen's paper ch-romatographic method and Schaffert-Kingsley's 2,4-dinitrophenyIhydrazine colorimetric method.(2) Our results indicated that the 2,4-dinitrophenylhydrazine colorimetric method was not specific in determining the total amount of ascorbic acid contents in acid extracts of vegetables and fruits and thus usually gave false results. Such extracts must be first separated from interfering substances before determination. Kuo and Chen's paper chromatog-raphic method is most suitable for this purpose.