A simple and rapid micromethod for determination of plasma levels of ascorbic acid in Pakistani normal adults

A simple spectrophotometric method has been developed for the determination of the ascorbic acid in human plasma. Method is based on reduction of ferric iron by ascorbic acid into ferrous iron which is then coupled with α, ά-dipyridyl to form a coloured complex. The absorbance of this coloured complex at 525 nm is proportional to concentration of ascorbic acid. The assay is sensitive enough to detect as little as 0.2 μg of vitamin. The recovery of ascorbic acid was in the range of 87%-100%. The mean values of intra-assay and inter-assay coefficient of variation were found to be 6.3% and 17%, respectively. As little as 20 μl of plasma can be used in the reaction with reproducible results. The assay was used to monitor ascorbic acid levels in plasma samples of 21 normal healthy subjects. Mean concentration of plasma ascorbic acid in these normal healthy adults was found to be 8.94 ± 4.1 μg/ml. This value was below the lower limit of normal range of plasma ascorbic acid (10-20 μg/ml) for most Western populations.