Application of multivariate optimization to electrochemical determination of methyldopa drug in the presence of diclofenac at a nanostructured electrochemical sensor

In the present paper, for the first time multivariate optimization based on central composite rotatable design (CCRD) coupled with response surface methodology (RSM) was used to optimize all effective experimental variables for determination of methyldopa (MD). A simple and sensitive carbon nanocomposite electrode has been developed for the electrochemical trace determination of MD in the presence of diclofenac (DCF) in phosphate buffer solution. This sensor was designed by incorporation of Cu(OH)2 nanoparticles into the carbon paste electrode (CPE). The nanocomposite was characterized by scanning electron microscopy (SEM). Applicability and suitability of Cu(OH)2 nanoparticles/CPE for determination of MD were checked in details using different methods such as differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry (CA). Using DPV, the prepared sensor showed good sensitivity for the determination of MD in the presence of DCF in the range of 2.0-450.1 μM, with a detection limit (S/N = 3) of 0.61 μM. The proposed electrochemical sensor was also used for the determination of MD in some real samples.