A New Method to Extend Applicable Potential Range of Mercury-filmed Glassy Carbon Electrode and Its Analytical Application

Electrochemical behavior of mercury-filmed glassy carbon electrode(GCE) in base solution containing hypoxanthine and the electrocatalytic oxidation of ascorbic acid by hypoxanthine at the Hg-filmed GCE were studied.It was found that addition of a definite amount of hypoxanthine to the base solution was profitable in respect for inhibition of stripping of mercury from the electrode at high potentials,improving the stability and extending applicable potential range of the Hg-filmed GCE.It was also found that in a base solution of pH 1.81,a sensitive irreversible oxidative wave relative to ascorbic acid was observed at its peak potential of 0.25 V(vs.Ag-AgCl electrode).Linear relationship between peak current(Ip) and concentration of ascorbic acid was obtained in the range of 5×10-5-2.4×10-3mol·L-1,with detection limit of 8×10-6mol·L-1.The proposed method has been used in the analysis of vitamin C tablets giving values of RSD(n=7) of 1.3% and of recovery in the range of 101.2%-104.5%.