Simultaneous determination of ascorbic acid, dopamine, and uric acid using graphene quantum dots/ionic liquid modified screen-printed carbon electrode

In this work, graphene quantum dots (GQDs) and ionic liquid (IL) modified screen-printed carbon electrode (GQDs/IL-SPCE) were introduced for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). GQDs were synthesized by directly pyrolyzing citric acid and then dropped onto the surface of IL-SPCE, which was prepared by screen-printing the mixture of IL and carbon ink on a portable substrate. UV-vis spectrophotometry, fluorescence spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to characterize the synthesized GQDs and the modified electrodes. The GQDs/IL-SPCE exhibited excellent electrocatalytic activity for the oxidation of AA, DA, and UA in the mixture solution. Moreover, the anodic peak responses of these three analytes were also resolved into three well-defined peaks. Under the optimized conditions, the linear response ranges for AA, DA, and UA were 25-400 mu M, 0.2-10 mu M, and 0.5-20 mu M, respectively, with low detection limits (sigma/N = 3) of 6.64 mu M, 0.06 mu M, and 0.03 mu M, respectively. The proposed sensor exhibited high sensitivity, low cost and successfully applied for the simultaneous detection of AA, DA, and UA in pharmaceutical products and biological samples.