Electroanalysis of Ascorbic Acid in Fresh Orange Juice Using a PTH/MWCNTCOOH-RGO/CS/CuO Film Modified Carbon Paste Electrode

The incorporation, characterization, and analytical ability of an ascorbic acid (AA) voltammetric sensor, based on the PTH/MWCNTCOOH-RGO/CS/CuO modified carbon paste electrode (CPE), were studied. The nanocomposite was prepared via an in situ chemical polymerization route. The structural characterization, surface morphology, and thermal analysis of the modified polymers were confirmed. The kinetics and mechanism of the oxidation process of AA on the modified electrode were studied via scan rate analysis. The quantitative detection of AA was achieved effectually by a square wave voltammetry (SWV) technique. The proposed voltammetric sensor exhibited high performance in 0.1 M phosphate-buffered solution (PBS) at pH 3. In the pH range 3 to 7 AA undergoes irreversible oxidation via transfer of 2H+/2e-. The proposed sensor showed a wide linear range (5 µM to 2 mM) and a low detection limit (0.613 µM). Additionally, the reproducibility and stability (at the 1 mM level) expressed in terms of relative standard deviation (RSD) was 2.13% and 1.98% respectively. The practicality of the proposed sensor was confirmed by the successful detection of ascorbic acid in fresh orange juice and the recovery was between 107.9% and 92.63%, with excellent accuracy.