Production of copper-graphene nanocomposite as a voltammetric sensor for determination of anti-diabetic metformin using response surface methodology

Abstract

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 nanocomposite (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 × 106 cm3 mol−1 s−1 and 1.07 × 10−8 cm2 s−1, respectively. Under the optimum conditions, the detection limit and linear dynamic range were found to be 3.4 µM and 10.4–1125.0 µM 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.