Voltammetric Differentiation of Dopamine and Ascorbic Acid at Glassy Carbon Electrode Modified with Carboxylic Acid Groups Functionalized Single-Walled Carbon Nanotube

摘要

The single-walled carbon nanotubes (SWNT), functionalized with carboxylic acid groups, modified glassy carbon electrode (GCE) and its application for the voltammetric differentiation of dopamine (DA) and ascorbic acid (AA) had been described. Scanning electron microscope (SEM), fourier transform infrared spectra (FT-IR), electrochemical impedance spectroscopy (EIS) and other electrochemical techniques had been used to characterize the SWNT modified GCE (SWNT/GCE). Using different charged catecholates and ascorbic acid in PBS pH 7.0, the changes in electrode processes and accumulation or exclusion of analytes at the electrode surface were shown to be controlled by electrostatic interactions with the surface groups. As a negatively charged linker at pH 7.0 the SWNT film combined with the positively charged DA to induce the accumulation of DA and thus promoted the electron transfer reaction of DA. However, due to the electrostatic repulsion, the negatively charged SWNT film restrained the electro-oxidation of the negatively charged AA. Based on the different electrochemical behaviors of DA and AA at SWNT/GCE, the modified electrode can be used for the voltammetric differentiation of DA and AA. In the presence of AA, the differential pulse voltammetric (DPV) peak current for the oxidation of DA increased linearly with DA concentration over the range of 6.0 × 10~(-6) and 1,65 × 10~(-4) mol L~(-1) with a correlation coefficient of 0.998. The detection limit (S/N = 3) for the determination of DA was 4.7 × 10~(-7) mol L~(-1).