pH optimum of the reduction of dehydroascorbic acid by dithioerytritol

Ascorbic acid is a water soluble antioxidant, that is itself oxidized to dehydroascorbic acid. In order to detect dehydroascorbic acid by amperometri it has to be reduced to ascorbic acid beforehand. This reduction was performed with dithioerytritol at pH = 6.0 for 10 min, which is a choice between optimal reaction rate and stability of ascorbic acid. The limit of detection of ascorbic acid is 1.1 pmol making the assay useful for determination of ascorbic and dehydroascorbic acid in small tissue biopsies. Results of this method and a colorimetric method were comparable.