Ascorbic Acid Content of Blood

While numerous papers have appeared dealing with the ascorbic acid content of various plant and animal tissues, and urine, only a few refer to the quantity present in the blood. Van Eekelen, Emmerie, Josephy and Wolff, 1 and Emmerie and Van Eekelen 2 deproteinize blood, blood plasma, or serum with trichloracetic acid, precipitate interfering substances, chiefly SH compounds, with mercuric acetate, then treat with H₂S, which not only precipitates the mercury but also reduces that portion of ascorbic acid which in blood occurs in a reversibly oxidized state. The H₂S is later removed by a stream of nitrogen, and the ascorbic acid estimated by titration with 2:6 dichlorobenzenoneindophenol. 3 Gabbe 4 claims that loss of ascorbic acid occurs if a solution of pure ascorbic acid is treated with H₂S in the presence of mercuric acetate, and therefore, omits this step. Tauber and Kleiner 5 describe a method generally applicable to plant and animal tissues (and to blood) in which the essential features of deproteinization, removal of interfering substances, and H₂S reduction are preserved. They estimate the ascorbic acid present either by titration or by its ability to reduce potassium ferricyanide, with subsequent development of Prussian-blue upon the addition of the ferric gum ghatti reagent of Folin and Malmros. 6

Our experience with several of these methods disclosed a number of difficulties. Some of the methods require considerable quantities of blood. Mercuric acetate solutions must not be over two weeks old, or filtrates containing colloidal sulphides may be obtained, particularly when the method is applied to urine. Any colloidal material in the filtrate makes it impossible to obtain a satisfactory endpoint during the titration with the dyestuff. The endpoint with trichloracetic acid filtrates is not sharp.

In the present study, we are chiefly concerned with finding some method whereby the relative ascorbic acid level of blood in infants and children may be determined as an aid in studying subclinical scurvy and following its course under treatment.