ABSTRACT
Abstract: In December 2019, the world experienced a new coronavirus, SARS-CoV-2, causing coronavirus disease 2019 originating from Wuhan.The virus has crossed national borders and now affects more than 200 countries and territories. Hydroxychloroquine has been considered as a drug capable of treating COVID-19. The objective of this work is to establish a simple platform for electrocatalytic detection of hydroxychloroquine in human urine samples and pharmaceutical samples (tablets) using a ZnO@CPE sensor constructed by simple and inexpensive hydrothermal methods using a square wave voltammetry method. The best results are obtained in a PBS electrolyte with irreversible behavior of the hydroxychloroquine complement and controlled by diffusion coupled with absorption phenomena. The ZnO@CPE shifts the oxidation potential of hydroxychloroquine with the formation of a single very intense peak at the position of Epa = 0.5 V/(vs Ag/AgCl) with a shift is ΔEp = 0.1 V(vs Ag/AgCl) compared to the unmodified electrode. The obtained ZnO@CPE hybrid nanocomposite was characterized by different techniques and showed excellent electrocatalytic activity and higher active surface area compared to the bare carbon paste electrode. Under the optimized experimental conditions, the ZnO@CPE sensor showed good analytical performance for the determination of trace amounts of hydroxychloroquine, a wide linearity range from 10-3 M to 0.8 × 10-6 M with a very low detection limit in the range of 1.33 × 10-7 M, satisfactory selectivity, acceptable repeatability and reproducibility. The calculated recovery and coefficient of variation for the two samples analyzed are very satisfactory, ranging from 97.6 to 102% and 1.2 to 2.3% respectively. The proposed applied method and the fabricated sensor offer the possibility to analyze traces of hydroxychloroquine in real human urine and water samples. Graphical abstract: Strategy for the electro-oxidation reaction of hydroxychloroquine on the electro-catalytic surface of the ZnO@Carbon graphite electrode and real-time detection of hydroxychloroquine.
ABSTRACT
The objective of this paper is to evaluate and optimize the experimental parameters of the electro-deposition of silver atom nuclei on a graphite carbon paste to elaborate an electrochemical sensor. The electro-deposition process was performed using the cyclic voltammetry. The electrochemical studies show that the deposited silver micro-particle array offers an excellent electro-catalytic activity towards the NO2 attractor group of the dimetridazole side chain. SEM morphological analysis of the silver deposits indicates the presence of a large number of Ag micro-particles on the graphite carbon with good nucleation. The size of the Ag micro-particles is of the order of 19,7621 µm and their distribution is normal over the entire range of the pulp. DRX analysis of the deposit also indicates that the microcrystalline structure of the silver microcrystals in the deposit is face-centered cubic. The electrochemical behavior of dimetridazole is totally irreversible, the transfer process is controlled by diffusion phenomena on the surface of the electrode covered by a silver deposit realized µAg@CPE. The analytical performance of the constructed electrode shows a good selectivity. Calibration curves for the detection of dimetridazole have been drawn in the concentration range of 3,5 × 10-4 mol/L to 10-6 mol/L using cyclic voltammetry method, with a detection and quantification limits of 6.565 × 10-7 mol/L and 2.216 × 10-6 mol/L respectively. The applicability of the constructed electrode has been tested in real samples including orange juice, tomato juice, tap water. The results obtained show a recovery rate above 94%, which is very satisfactory.
