▎ 摘　　要

In this paper, application of a sensitive electrochemical technique assisted with multivariate optimization methods is presented for measurement of anti-diabetic metformin (MET) drug in pharmaceutical and serum samples. The sensitive electrochemical sensor was modified carbon paste electrode by copper-graphene nano composite (Cu-G/CPE). Firstly, synthesis of graphene (G) and copper-graphene (Cu-G) were performed and X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and N2 adsorption-desorption isotherm were applied to specify the structure of them. FESEM of Cu-G shows carbon sheets were decorated with some dense layer of well-dispersed uniform CuNPs with a type size around 50 nm. Also, the XRD pattern of Cu-G displays several peaks for Cu, which approves the formation of Cu-G nanocomposite. Next, the G and Cu-G are used for modification of a carbon paste electrode (CPE) surface. Results from response surface methodology indicated that solution pH of 12, 11% of Cu-G nanocomposite in the modified CPE, accumulation potential (0.2 V) and accumulation time (80 s) outcomes in the maximal current density. The electrochemical behavior of MET at the Cu-G/CPE surface are investigated by differential pulse voltammetry (DPV), cyclic voltammetry (CV), and chronoamperometry techniques. The electron-transfer coefficient, catalytic rate constant and diffusion coefficient are found to be 0.84, 6.27 x 10(6) cm(3) mol(-1) s(-1) and 1.07 x 10(-8) cm(2) s- 1, respectively. Under the optimum conditions, the detection limit and linear dynamic range were found to be 3.4 mu M and 10.4-1125.0 mu M by DPV technique, respectively. The Cu-G/CPE exhibited good reproducibility, stability and high recovery and it has low cost, low background current, ease of surface renewal. The Cu-G/CPE has better poisoning tolerance ability than bare CPE for electro-oxidation of MET and is a superior sensor for the long-term action. Furthermore, the proposed method can be applied as a valorous analytical method in the quality control of the pharmaceutical industry.