▎ 摘　　要

A modified pencil graphite electrode as electrochemical devise was constructed by the modification with graphene oxide (GO) and phosphomolybdic acid (PMA) for the determination of methyldopa drug. The response of the electrode indicated an increase in the electrode surface and a catalytic effect, which occurred due to the chemisorptions of polyoxometalate on the graphene oxide surface. Differential pulse voltammetry (DPV) technique was applied to investigate the response of electrode to methyldopa and its determination. The modified electrodefeatures were specified using energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy and X-ray diffraction analysis (XRD). To attain the maximum electrochemical response, the efficacies of diverse parameters like scan rate, pH and characteristics of the electrolyte solution were optimized. After the optimization process, the calibration curve was linearly obtained in the concentration range of 4.9 x 10(-10)-1.0 x 10(-7) M whit a low detection limit of 1.2 x 10(-10) M. The procedure was applied for the measurement of MD in human blood serum, urine and milk samples.