Simultaneous determination of ascorbic acid, dopamine, uric acid, tryptophan, and nitrite on a novel carbon electrode.

A novel carbon electrode for simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), tryptophan (Trp), and nitrite (NO 2 − ) was fabricated by chemical vapor deposition of carbon layers on a Ta wire. The carbon electrodes were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The carbon electrodes are composed of stacked graphene nanosheets. The carbon electrode exhibited excellent electro-catalytic activities, high selectivity and sensitivity toward the oxidation of AA, DA, UA, Trp, and NO 2 − in pH 7.0 phosphate buffer solution. For AA, DA, UA, Trp, and NO 2 − , the corresponding DPV current signals have appeared as five well resolved oxidation peaks with peak potential differences of 204 mV (AA-DA), 152 mV (DA-UA), 312 mV (UA-Trp), and 128 mV (Trp-NO 2 − ). For simultaneous determination, the linear responses for AA, DA, UA, Trp, and NO 2 − were obtained in concentration ranges of 6 to 1500, 0.4 to 100, 1 to 250, 0.4 to 100, and 6 to 1500 μM with detection limits of 5 μM, 0.2 μM, 0.8 μM, 0.4 μM, and 3 μM, respectively. The carbon electrode was proved to be applicable for the determination of the above analytes in serum samples. [ABSTRACT FROM AUTHOR]