Simultaneous Determination of Trace Amounts Ascorbic Acid, Melatonin and Tryptophan using Modified Glassy Carbon Electrode Based on Cuo-CeO₂-rGO-MWCNTS Nanocomposites

In the presented study, for the first time, simultaneous electrochemical measurements of ascorbic acid (AA), melatonin (Mel), and tryptophan (Trp) were discussed. The CuO-CeO2-rGO-MWCNTs nanocomposite was prepared, then applied for amendment of glassy carbon electrode (GCE) surface to the measurement of target analytes using differential pulse voltammetry (DPV) technique. Electrical impedance spectroscopy (EIS) techniques displayed that CuO-CeO2-rGO-MWCNTs/GCE has the lowest electron transfer resistance (R-ct) in comparison to GCE and was suitable for electrochemical applications. The synthesized compounds were analyzed by powerful methods including Scanning Electron Microscopy (SEM) and, X-ray Diffraction (XRD). At the CuO-CeO2-rGO-MWCNTs/GCE, three oxidation peaks appeared at 0.309, 0.631, and 0.855 V for AA, Mel, and Trp and the peaks separation of Delta E-p (AA and Mel)=322 mV, and Delta E-p (Mel and Trp)=224 mV in the electrochemical potential window of 0.0-1.1 V. In optimum DPV condition and pH=5.0, a dynamic range of AA (0.0128 mu M), Mel (0.01-12.6 mu M) and Trp (0.01-13.5 mu M) with the detection limit of 9, 8 and 7.3 nM for AA, Mel, and Trp, respectively, were acquired. The provided modified electrode was successfully used to monitor the analytes in human biological fluids.