ZnO/functionalized MWCNT and Ag/functionalized MWCNT modified carbon paste electrodes for the determination of dopamine, paracetamol and folic acid

Abstract

In this study, functionalized multiwalled carbon nanotubes (FMWCNT), Ag nanocomposite FMWCNT (Ag/FMWCNT) and ZnO nanoparticles (NPs) were prepared and characterized by different characterization techniques. The prepared materials, pristine-MWCNT (MWCNT), ZnO composite with MWCNT and FMWCNT were used as modifiers of carbon paste electrode (CPE) to study the electrochemical behavior of dopamine (DA) in phosphate buffer solution (pH7.4) by using cyclic voltammetric technique. In that ZnO NPs incorporated with FMWCNT modified CPE (ZnO/FMWCNT MCPE) shows enhanced electrocatalytic activity compared to bare and all other modified CPEs. As a result the ZnO/FMWCNT MCPE was used for further electrochemical studies. From the pH study, it was found that an equal number of electrons and protons are involved in the electrochemical reaction of DA. The calibration curve for DA was obtained in the concentration range of 0.2–5μM. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.025 and 0.08μM, respectively. The ZnO/FMWCNT MCPE showed good stability, repeatability and reproducibility towards DA. Moreover the ZnO/FMWCNT MCPE, Ag/FMWCNT MCPE and bare CPE were used for the study of electrochemical response of paracetamol (PC) and folic acid (FA). At Ag/FMWCNT MCPE, no characteristics voltammetric peaks appeared for PC and FA. The ZnO/FMWCNT MCPE showed good electrocatalytic activity towards PC and FA when compared to bare CPE. The effect of scan rate shows that the electrode process is diffusion controlled for DA, PC and FA. The LOD and LOQ for PC were found to be 0.23 and 0.79μM with a linear range of 0.5–13μM. ZnO/FMWCNT MCPE was effectively applied towards the determination of DA and PC in pharmaceutical samples. The fabricated electrode proved to be an effective sensor for electrochemical investigation of DA in presence of PC and FA.