Simultaneous determination of ascorbic acid, dopamine and uric acid using poly(l-leucine)/DNA composite film modified electrode

A highly selective electrochemical method was developed for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA) using a glassy carbon electrode modified by a poly(l-leucine)/DNA composite film. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to study the electrochemical properties of the modified electrode. The modified electrode shows an excellent electrocatalytic activity towards the oxidation of AA, DA and UA. The separations of anodic peak potentials for AA/DA, DA/UA and AA/UA are 220, 158 and 378 mV (vs. Ag/AgCl) in DPV, respectively. Under optimal conditions, the linear response range for AA, DA and UA are 5.0–750.0 μmol L−1, 0.1–100.0 μmol L−1 and 0.5–100.0 μmol L−1, respectively. The detection limits are 2.0, 0.04 and 0.2 μmol L−1 (S/N = 3), respectively. The present method was applied to the determination of AA, DA and UA in human urine sample and satisfactory results were obtained.