Use of Graphene Modified Glassy Carbon Electrode in Cyclic Voltammetric Determination of Ascorbic Acid

Nano-graphene was prepared by the method of Hummers, and graphene modified glassy carbon electrode (GCE) was prepared by addition of 5 μL of suspension of nano-graphene in distilled water dropwise onto surface of GCE. Electrochemical behavior of ascorbic acid (AA) at the modified electrode was studied by cyclic voltammetry in phosphate solution of pH 4.0 as supporting electrolyte in the potential range of -0.4-0.8 V (vs.Ag/AgCl). As shown by the experimental results, a significant oxidation peak was observed at 0.173 V, and the oxidation peak current was found to be higher than that obtained at bare GCE. The interferences of epinephrine, uric acid and dopamine were avoided completely. Based on these findings, a selective method for determination of AA by cyclic voltammetry was proposed. Linearity range between 8.00×10-6 and 1.0×10-3mol·L-1 was obtained, with detection limit (3S/N) of 1.0×10-7mol·L-1. The proposed method was used in the analysis of samples of Vitamin C tablets, and values of recovery found were in the range of 96.3%-104.4%.