Ascorbate
was detected at an applied potential of 0.6 V, with the gain set at
100 nA by an LC 4B amperometric electrochemical detector
(Bioanalytical Systems, West Lafayette, IN). Ascorbate was eluted as a single peak with a retention time of 5.5 min. Peaks
were integrated with a ChemStation (Hewlett Packard). Ascorbate
concentrations were calculated on the basis of a calibration
curve and are expressed in mol/L (33).