For the first time, simultaneous determination of levodopa (LD), uric acid (UA) and tyramine (Tyr) has been investigated at a glassy carbon electrode modified with functionalized multi-walled carbon nanotubes and quercetin. The simple modification of electrode was performed through the electrodeposition of quercetin on a functionalized multi-wall carbon nanotube immobilized on the surface of a glassy carbon electrode (Q/fMWCNT/MGCE). Electrochemical properties of the modified electrode were investigated by electrochemical impedance spectroscopy (EIS). Also, the electrocatalytic properties of Q/fMWCNT/MGCE toward the electrocatalytic oxidation of LD, UA and Tyr were studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The Q/fMWCNT/MGCE offered substantially lower overpotential for electro-oxidation of LD, UA and Tyr in phosphate buffer solution (pH 7.0) compared with Q/GCE, fMWCNT/GCE and bare GCE. Differential pulse voltammogram peak currents of LD, UA and Tyr increased linearly with their concentration at the ranges of 0.90–85.0 M, 1.0–125.0 M and 0.70–75.0 M, respectively and the detection limits for LD, UA and Tyr were sequentially 0.381 M, 0.575 M and 0.647 M. Furthermore, this sensor was employed for the simultaneous determination of LD, UA and Tyr in biological and pharmaceutical samples and the obtained results were found to be satisfactory
