A simple eco-friendly carbon paste modified electrode using chitosan-CaO nanocomposite for the voltammetric detection of the antibiotic ornidazole in real samples

Herein, an eco-friendly, simple, inexpensive electrochemical sensor for the antibiotic ornidazole (ORN) was developed based on a carbon paste electrode modified by chitosan-CaO nanocomposite (Chi-CaO-NC/CPE). Eggshell waste was utilized to prepare CaO-NPs which were then combined with chitosan (Chi) to obtain Chi-CaO-NC/CPE. The prepared Chi-CaO-NC/CPE was characterized by different techniques such as XRD, FTIR, SEM, and EDX. The produced sensor showed higher electrocatalytic activity toward ORN in (0.1 M) PBS (pH 7.0) than the unmodified CPE. The influence of pH and scanning rate on the reduction peak of ORN implies that the reduction process of ORN at the Chi-CaO-NC/CPE surface was a diffusion-controlled reaction with four electrons and four protons. Additionally, under ideal conditions, differential pulse voltammetry (DPV) revealed that the cathodic current was directly proportional to ORN concentrations within two various detection ranges of 0.015–0.3 μM and 0.3–4.5 μM. The limit of quantification (LOQ), and the limit of detection (LOD) were 0.0138 μM and 4.13×10⁻³ μM, respectively. Moreover, the fabricated sensor provided acceptable selectivity towards ORN, good stability, and repeatable response, with recoveries ranging from 95.8 %–102.0 %; this electrode was also successful in detecting ORN in commercial tablets and milk samples.