The Preservation of Ascorbic Acid in Drawn Samples of Blood*

In clinical or experimental studies of blood ascorbic acid, it is obviously important to maintain the ascorbic acid at its original level until analysis has been made. Pijoan, Townsend, and Wilson (1) reported a loss of about one-half of the vitamin C of blood plasma when the latter stood for 90 minutes at room temperature. Pijoan and Klemperer (2) recommended the addition of 1 mg. of KCN per cc. of blood as a preservative of ascorbic acid. Friedman, Rubin, and Kees (3) observed no loss in plasma ascorbic acid in 160 minutes at ice box temperature and reported the use of KCN to be unnecessary. Farmer and Abt (4) reported that KCN does not prevent loss of ascorbic acid in blood and that its use is objectionable, because it gives enhanced values owing to the decolorizing action of KCN upon 2,6-dichlorophenol indophenol. Cushman and Butler(5) observed a variation in t.he decolorization of indophenol by KCN, depending upon the lot of KCN used, the pH of the reaction, and the concentration of KCN. These authors found that the use of KCN in the amounts recommended by Pijoan and Klemperer does not necessarily invalidate the results, but that there is no advantage in its use. We have made studies of the stability of ascorbic acid in blood, using the method of Mindlin and Butler (6) for its determination. In agreement with Pijoan, Townsend, and Wilson (1) we found a steady decrease in the ascorbic acid of plasma removed from the red cells when allowed to stand at room temperature. We attempted to prevent this loss by the use of antioxidants which