Zinc Oxide Nanostructured-Based Sensors for Anodic Stripping Voltammetric Determination of Darifenacin

Abstract

Herein for the first time, the construction and the electroanalytical applications of novel darifenacin (DFC) voltammetric sensors were described. Zinc oxide nanostructures act as a proper redox mediator and exhibit efficient catalytic activity towards the electrooxidation of the DFC molecule. At the optimum measuring conditions, DFC exhibited an irreversible anodic oxidation peak at 0.880 V with an assumed adsorption-reaction mechanism at the electrode surface. Based on the effect of the pH and the scan rate studies, electrooxidation of DFC takes place through the oxidation of the nitrogen atom (N12) in the five-membered ring of the darifenacin molecule with the participation of one electron and one proton in agreement with the molecular orbital calculations. Calibration curves were linear within the DFC concentration ranging from 0.33 to 6.54 × 10−6 mol l−1 with a limit of detection (LOD) and limit of quantification (LOQ) values of 0.08 and 0.23 × 10−6 mol l−1. The proposed sensors exhibited enhanced performance with high measurement reproducibility and prolonged lifetime. The presented voltammetric approach was utilized for precise determination of darifenacin in biological samples and pharmaceutical formulations with acceptable recoveries compared with the traditional spectrophotometric methods.