Electrochemical Sensor Based on a Composite of Babassu Starch, Carbon Black, and Cobalt Phthalocyanine for the Detection of Hydroxychloroquine

This work presents the development of an electrochemical sensor based on a starch film extracted from the Babassu coconut mesocarp flour, carbon black (CB), and cobalt phthalocyanine. Scanning-electron microscopy coupled with energy-dispersive spectroscopy confirmed the presence of each component in composite, by confirming alteration of surface morphology and composition. Raman and Fourier-transform infrared spectroscopy also evidenced surface alteration while atomic-force microscopy revealed increase in rugosity after insertion of CB and cobalt phthalocyanine. The developed sensor was applied for the determination of hydroxychloroquine (HCQ) in both environmental and pharmaceutical (tablet) samples, using linear sweep voltammetry and a 0.1 mol L^-1 phosphate buffer solution (pH = 7.0) as the supporting electrolyte. The method achieved impressive detectability in comparison with literature, with limits of detection (LOD) and quantification (LOQ) of 0.015 μmol L^-1 and 0.052 μmol L^-1, respectively. Recovery studies conducted in pharmaceutical matrices, tap water, and treated water samples yielded values ranging from 100% to 105%, demonstrating the sensor's accuracy. Notably, no electrode fouling was observed after HCQ oxidation, confirming the stability of the modified electrode. These findings underscore the potential of this sensor for environmental monitoring and highlight starch as a sustainable alternative material for immobilizing modifiers on electrodes.