Spontaneous decay of oxidized ascorbic acid (dehydro-L-ascorbic acid) evaluated by high-pressure liquid chromatography.

We applied high-pressure liquid chromatography to assess the decomposition of the oxidized form of vitamin C, dehydro-L-ascorbic acid. We selected experimental conditions that might represent a wide variety of clinical and research procedures. Decay of dehydro-L-ascorbic acid proceeded much more rapidly at high pH (7-8) than at low pH (3-5) and was more rapid at 37 or 45 degrees C than at 0 or 23 degrees C. When evaluated at pH 6.6, the percent decay was somewhat more rapid from an initial concentration of 1000 mumol/L than at 5-10 mumol/L. The analytical procedure (HPLC) provided useful information about the rate of decay under various conditions. This may facilitate future biological and clinical studies that require a distinction between the oxidized and reduced forms of vitamin C.