Electrochemical Oxidation of Ciprofloxacin on COOH-Functionalized Multi-Walled Carbon Nanotube-Coated Vitreous Carbon Electrode

摘要

This study deals with the use of a COOH-functionalized multi-walled carbon nanotube-coated glassy carbon electrode (f-MWCNT-coated GCE) to investigate the electrochemical oxidation of ciprofloxacin (CIP). The electrochemical behavior of CIP is investigated using cyclic voltammetry and square wave voltammetry in PBS buffer aqueous solutions. Cyclic voltammograms have shown that (1) CIP provided a well-defined irreversible oxidation peak at a potential of around 1 V and (2) modifying glassy carbon electrode surface by MWCNT leads to a significant improvement 3.6 and 1.5 folds of the electrochemical response as compared to that at bare GCE, and MWCNT-coated GCE, respectively. This improvement in the electrocatalytic activity of the electrode is attributed to the decrease of the charge transfer resistance. The influence of some controlled parameters (scan rate, pH, successive potential scans, and SMX concentration) on the electrochemical oxidation of CIP is studied. It has been shown that CIP oxidizes according to a diffusion-controlled mechanism involving the transfer of one electron and two protons. Furthermore, this study demonstrates that the zwitterionic form of CIP is thermodynamically more reactive to electrochemical oxidation than the cationic and anionic forms. Under optimized conditions, a linear calibration curve was obtained by square wave voltammetry for CIP in the concentration range 5-100 mu M with a detection limit of 0.16 mu M. The f-MWCNT-coated GCE showed great improvement, as compared to bare GCE, in the anodic oxidation reactivity of CIP with high simplicity of preparation, selectivity, repeatability, and reproducibility. Also, CIP analytical determination was performed successfully, using f-MWCNT-coated GCE, in-hospital effluent, treated domestic wastewater effluent, and natural water source, allowing promising and feasible applications in on-site environmental monitoring.