4-Aminoquinoline including Hydroxychloroquine (HCQ), amodiaquine (AQ), Chloroquine (CQ) are a quinoline with an amino group at the fourth position with a basic side chain. They are generally used as antimalarial medications. HCQ and CQ were recommended by the World Health Organization on March 2020 for use as a possible treatment to coronavirus. Long-term administration of 4-aminoquinoline drugs can be associated with toxic side-effects on the outer retina and the retinal pigment epithelium, making their determination in biological samples important. Several methods have been used for 4-Aminoquinoline compounds analysis, such as spectrophotometry, immunological, electrophoresis, chromatography, and electroanalytical methods. Electrochemical methods are preferable because they are simple, providing quick analysis and more sensitive performance. Until now, numerous electrochemical methods have been used to detect these drugs. Nevertheless, the utilization of later techniques is limited. This review describes different electrochemical sensors which are used for 4-aminoquinoline electroanalysis in complex matrices such as pharmaceuticals and biological fluids. For this, the fundamental analytical performance of the chosen sensors is investigated. The selectivity and oxidation mechanisms for 4-aminoquinoline reported in the literature were discussed. Also, the application of these sensors for 4-aminoquinoline monitoring in biological and environmental samples is reported.

This research covers the development of a green, sensitive, selective, and simple electrochemical strategy for the detection of ciprofloxacin (Cipro) in biological fluids, wastewater, and drug samples. Herein the carbon paste electrode was modified using reduced graphene oxide and clay composite based on the electrochemical reduction of GO (ErGO-Clay@CPE). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry were used for the electro-characterization of ErGO-Clay@CPE, and the results supported that the ErGO-Clay improved the electrode's conductivity and surface area. Moreover, the electrochemical performance was inspected by differential pulse voltammetry (DPV) and chronoamperometry in phosphate buffer (PB, pH=6). The data demonstrated a magnificent sensitivity of ErGO-Clay@CPE regarding Cipro. Under the optimized operating conditions, the electro-analytical response was linearly related to the Cipro concentration in the range of 0.03-2.0-50.0 µM with a lower detection limit (DL = 3 × SDblank / P) and sensitivity of 2.24 nM and 96.28 µA µM-1 cm-2, respectively. Furthermore, the ErGO-Clay@CPE was applied to identify the Cipro in drugs, wastewater, and urine samples, with satisfied recoveries.