Simultaneous determination of dopamine, uric acid and nitrite using carboxylated graphene oxide/lanthanum modified electrode

A bare glassy carbon electrode (GCE) was reformed by carboxylated graphene oxide/lanthanum, and the modified electrode, called GO-COOLa/GCE, was fabricated for simultaneously detecting dopamine (DA), uric acid (UA) and nitrite (NO 2 − ) by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometry. Several factors which affected the electrocatalytic activity of the GO-COOLa/GCE electrode, such as the effect of pH, scan rate and concentration were studied. Due to the combination of carboxylated graphene oxide and lanthanum ions, the GO-COOLa/GCE sensor showed rapid response, excellent selectivity and high catalytic performance toward the electrooxidation of DA, UA and NO 2 − . In optimized conditions, two linear response ranges for determining DA were obtained over ranges of 0.01-1.96×10 2   μM and 1.96×10 2 -1.23×10 3   μM with detection limit of 0.018   μM (S/N   =   3). And the responses of the GO-COOLa/GCE electrode for UA and NO 2 − were linear in the region of 1-1.53×10 3   μM and 1-2.75×10 3   μM with detection limits of 0.058   μM and 0.070   μM, respectively. Furthermore, this reformed electrode was successfully used to the detection of DA, UA and NO 2 − in real urine and serum samples, showing its promising application in the electroanalysis of real samples.