Graphitic carbon nitride (g-C(3)N(4))/graphite nanocomposite as an extraordinarily sensitive sensor for sub-micromolar detection of oxalic acid in biological samples

Nanosized graphitic carbon nitride (nano-g-C(3)N(4)) was synthesized using the thermal polymerization of melamine and utilized as a novel electrocatalyst for electrooxidation of oxalic acid (OA). The nano-g-C(3)N(4) was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The electrocatalytic performance of the g-C(3)N(4)-modified carbon paste electrode (g-C(3)N(4)/CPE) was investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The modified electrode showed excellent electrocatalytic activity towards the oxidation of OA. The effects of electrode composition, pH and scan rate on the electrooxidation response of OA were studied. Under optimized conditions, the differential pulse voltammetric response of the electrode was linearly related to OA concentrations between 1 and 1000 μM, with a limit of detection (LOD) of 7.5 × 10(−7) M. The electrode exhibited very high sensitivity of 1945 μA mM(−1) cm(−2) for OA assay. The developed method was successfully applied for the determination of OA in urine samples with satisfactory results.