Electrochemical determination of dopamine at the surface of carbon paste electrode modified with Ni-MWCNT/TiO2NPs nano-composite

In this research, a simple and selective electrochemical sensor with high-sensitivity was proposed to detect dopamine. For this purpose, a nanocomposite consist of nickel-multiwalled carbon nanotubes and titanium dioxide nanoparticles was used to modify the carbon paste electrode. The surface morphology of the modified sensor was evaluated by field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectrometry (FTIR). Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques were used to analyze of the proposed modified electrode electrochemical behavior and to characterize dopamine. The modified electrode used in this study showed an excellent electro-oxidation response to the presence of dopamine. In addition, to optimize the electrochemical sensor response, any change in the voltammetric behavior of dopamine under different pH and scan rates conditions were investigated and phosphate buffer solution was used for this purpose. Under optimal conditions, the dopamine electrocatalytic peak currents are linearly dependent on the dopamine concentration in the range of 0.3-100 µM and the detection limit of 11.68 nM was calculated for it. Also, electrochemical parameters such as the transferred electrons number and the electron transfer coefficient were estimated. The present study findings showed that the sensor has high sensitivity, low detection limit, fast response, long-term stability, significant repeatability and reproducibility, high selectivity and recovery, as well as excellent performance in analyt detection in the real samples, which proves that the proposed electrode can be used in food, medical and environmental applications. The proposed method is simple, fast and inexpensive and can be used as a valuable analytical tool in quality control of the pharmaceutical industry.