Simultaneous determination of uric acid and ascorbic acid at the film of chitosan incorporating cetylpyridine bromide modified glassy carbon electrode

A glassy carbon electrode (GCE) modified with the film composed of chitosan incorporating cetylpyridine bromide is constructed and used to determine uric acid (UA) and ascorbic acid (AA) by differential pulse voltammetry (DPV). This modified electrode shows efficient electrocatalytic activity and fairly selective separation for oxidation of AA and UA in mixture solution. UA is catalyzed by this modified electrode in phosphate buffer solution (pH 4.0) with a decrease of 80 mV, while AA is catalyzed with a decrease of 200 mV in overpotential compared to GCE, and the peak separation of oxidation between AA and UA is 260 mV, which is large enough to allow the determination of one in presence of the other. Under the optimum conditions, the anodic peak currents (I (pa)) of DPV are proportional to the concentration of UA in the range of 2.0 x 10(-6) to 6.0 x 10(-4) M, with the detection limit of 5.0 x 10(-7) M at a signal-to-noise ratio of 3 (S/N = 3) and to that of AA in the range of 4.0 x 10(-6) to 1.0 x 10(-3) M, with the detection limit of 8.0 x 10(-7) M (S/N = 3).