Simultaneous Electrochemical Determination of Serotonin, Melatonin and Tryptophan using A Glassy Carbon Electrode Modified with CuNi-CeO2-rGO Nanocomposite

In the presented study, for the first time, simultaneous electrochemical measurement of serotonin (Ser), melatonin (Mel) and, tryptophan (Trp) was discussed. The CuNi-CeO2-rGO 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 CuNi-CeO2-rGO/GCE has the lowest electron transfer resistance (Rct) in comparison to GCE and was suitable for electrochemical applications. The synthesized compounds were analyzed by powerful methods including Transmission electron microscopy (TEM) and, X-ray Diffraction (XRD). At the CuNi-CeO2-rGO/GCE, three oxidation peaks appeared with Ipa= 27, 20.1 and 24 μA for Ser, Mel, and Trp and the peaks separation of ΔEp (Ser and Mel) =201 mV, and ΔEp (Mel and Trp) =136 mV in the electrochemical potential window of 0.1-1.0 V. In optimum DPV condition and pH=7, a dynamic range of Ser (0.008-23 μM), Mel (0.008-21 μM) and Trp (0.008-23 μM) with the detection limit of 0.0058, 0.0061 and 0.0063 μM for Ser, Mel, and Trp, respectively, were acquired. The provided modified electrode was successfully used to monitor of the analytes in human biological fluids. The data using the suggested sensor and HPLC method were in good agreement without significant difference.