Ascorbic and dehydroascorbic acid measurement in human serum and plasma.

Plasma supplemented with ascorbic acid was prepared; the stability of these samples was characterized and the accuracy of the supplementation was established. Studies on the accuracy, precision, and sources of methodological bias in the measurement of ascorbic acid were summarized. Measurements of the ratio of ascorbic acid to dehydroascorbic acid in clinical samples was evaluated and was shown to be relatively constant in plasma taken from blood stored at 12 degrees C for 6 h. These results imply that whole blood has the capacity to maintain a constant ascorbic-dehydroascorbic acid ratio and suggest that this ratio may be of physiological significance.