Fabrication of CoHCF-PAni and MWCNTs hybrid modified CPE for electrochemical determination of thioridazine by voltametric method

Conducting polymers are known to be compatible with biological molecules when in a neutral aqueous solution, and hence, they are extensively used in the fabrication of accurate, fast, andinexpensive devices, such as biosensors and chemical sensors in medical diagnostic laboratories (1). Transition metal hexacyanoferrates (MHCFs), represent an important class of mixed-valence compounds that have been studied extensively for many years. MHCFs are widely employed inmany fields, such as sensors, electroanalysis, and electronic devices (2). Wide application havebeen found of these compounds due to interesting properties such as ion-exchange properties, electrochromism, mixed-valence electrical conductivity, and high catalytic activity (3). Amongthe various conducting polymers, polyaniline (PANI) has been considered most attractive because of its high conductivity, good redox reversibility, environmental stability and facile method of preparation (4). Among the MHCFs, cobalt hexacyanoferrate (CoHCF) catchesscientists’ eyes. In this compound, both the cobalt and iron elements have two oxidation states of (II) and (III) leading to a multitude of compound stoichiometries and redox states. CoHCF has wide applications in molecular magnets,optomagnets, humidity sensors, electrochromic devices as well as electrocatalysis (5). Electrochemical response of cobalt hexacyanoferrate-polyaniline hybrid and multi-walled carbonnanotubes-modified carbon paste electrode (MWCNTs/CoHCF/PAni/MCPE) toward thioridazine (Tz) was studied by means of cyclic voltammetry (CV) and differential pulsevoltammetric (DPV). The modified electrode displayed an obvious increase in the peak current compared to the bare carbon paste electrode (CPE). The results indicated thatMWCNTs/CoHCF/PAni/MCPE remarkably enhanced electrocatalytic activity towards the oxidation of Tz. The effects of pH, modifier amount, scan rate, and time of accumulation has been examined. Under the optimum conditions, the anodic peak current increases linearly withincreasing Tz concentration in the ranges of 1.0×10−7–1.0 ×10−4M of Tz with a linear correlation coefficient (R2) of 0.995 with a low detection limit of 0.03 μM by calibration curve with DPV as a sensitive method for Tz. The measurement repeatability of the MWCNTs/CoHCF-PAni/MCPE was examined and the relative standard deviation (RSD) was obtained 2.7% for ten successive assays. Seven modified electrodes showed an acceptablereproducibility with RSD of 3.5%. The interferences of some ions and organic compounds havebeen investigated. In addition, successful applicability of the electrode in the real sample ( blood serum) was studied and good accuracies were obtained.

Keywords:

Cobalt hexacyanoferrate , Poly aniline , Carbon paste , Electrochemical determination , Nanocomposite , Hybrid , Thioridazine