In this study, for the first time, poly hydroquinone / reduced graphene oxide (pHQ-rGO) composite was synthesized and used for modification of the graphite paste electrode (GPE)for simultaneous electrochemical determination of dopamine (DA), acetaminophen (AC), and xanthine (XN). A detailed investigation by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy(FT-IR), field emission electron microscopy (FESEM), transmission electron - microscopy (TEM), electrochemical impedance spectroscopy and electrochemistry methods such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) was performed in order to elucidate the preparation process and properties of the pHQ-rGOmodified graphite paste electrode (GPE/pHQ-rGO). The proposed modified electrode displays intense and indelible electrooxidation response for simultaneous determination of DA, AC and XN to three well-separated peaks in the potential range from 0.4 to 1.1V using CV and DPV methods in a phosphate buffer solution with pH 2.0. Some kinetic and thermodynamic parameters for the electrochemical oxidation of DA, AC, and XN were also determined. Under the optimum conditions, detection limits (S/N=3) of 60, 80and 90nM were obtained for DA, AC, and XN, respectively. Moreover, GPE/pHQ-rGOwas successfully used to determineDA, AC, and XN in real samples.
