Simultaneous Electrochemical Determination of L-Dopa and Melatonin at Reduced Graphene Oxide-Cu 0.5 Co 0.5 Fe 2 O 4 Modified Platinum Electrode

A novel nanocomposite of reduced graphene oxide (RGO) and spinel Cu 0.5 Co 0.5 Fe 2 O 4 was synthesized and was characterized using fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). A selective and novel sensor was fabricated using this nanocomposite by modifying a Platinum (Pt) electrode by employing the simple drop-casting technique. The modified electrode was then used for the simultaneous electrochemical detection of L-3,4-dihydroxyphenylalanine (L-dopa) and melatonin. Cyclic voltammetry (CV), square wave voltammetry (SWV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were used for the electrochemical characterization and applications of the developed sensor. The results of the optimization processes confirmed that PBS buffer with pH 7 can be used as the best experimental medium for the further studies. The electrooxidation of L-dopa and melatonin was found to be quasi reversible and diffusion controlled. Various electrochemical parameters such as charge transfer coefficient, diffusion coefficient and number of electrons involved in the electrochemical reaction of L-dopa and melatonin were experimentally calculated. The limit of detection from the simultaneous electrochemical determination was found to be 5.83 × 10 −8 M for melatonin and 4.80 × 10 −8 M for L-dopa.