Simultaneous determination of ascorbic acid, epinephrine, and uric acid by differential pulse voltammetry using poly(p-xylenolsulfonephthalein) modified glassy carbon electrode

A novel poly(p-xylenolsulfonephthalein) modified glassy carbon electrode was prepared for the simultaneous determination of ascorbic acid (AA), epinephrine (EP) and uric acid (UA). Cyclic voltammetric, chronoamperometric, and differential pulse voltammetric methods were used to investigate the modified electrode for the electrocatalytic oxidation of EP, AA, and UA in aqueous solutions. The separation of the oxidation peak potentials for AA–EP and EP–UA was about 200 and 130 mV, respectively. The calibration curves obtained for AA, EP, and UA were in the ranges of 10–1343, 2–390, and 0.1–560 μmol L−1, respectively. The detection limits (S/N = 3) were 4, 0.1, and 0.08 μmol L−1 for AA, EP and UA, respectively. The diffusion coefficient and the catalytic rate constant for the oxidation of EP at the modified electrode were calculated as 1.40(±0.10) × 10−4 cm2 s−1 and 1.06 × 103 mol−1 L s−1, respectively. The present method was applied to the determination of EP in pharmaceutical and urine samples, AA in commercially available vitamin C tablet, and EP plus UA in urine samples.