Copper nanoparticles encapsulated in reduced graphene oxide electrode (CuxrGO1-x) for the electrochemical quantification of metformin in water

Electrochemical oxidation of anti-diabetic metformin (MTF) drug was studied on glassy carbon electrode (GCE) prepared by electroplating of copper nanoparticles (Cu NPs) on reduced graphene oxide (rGO). Results showed that the crystallite size and dispersity of Cu NPs on rGO sheets controlled the redox characteristics of CuxrGO1-x. Voltammetry revealed faradaic Cu(II)/Cu(I) redox current at specific anodic potentials as a function of MTF concentration due to biguanide Cu(II)-MTF complexation. rGO, an electron promoter, improved the current density while lowering the overpotential of MTF oxidation. Both the electrochemical surface area (ECSA) and reaction sensitivity were optimal at the Cu to rGO mass ratio of 7:3 for MTF detection. The electrode also exhibited high degree of reproducibility, selectivity, and recovery in 0.1 M of phosphate buffer solution and pH 12. There was a high degree of linearity between anodic current and MTF concentration in the range of 2 to 70 & mu;M at a slope of 1.375 & mu;A/& mu;M and detection limit of 0.09 & mu;M by differential pulse voltammetry (DPV) technique.