Desenvolvimento de sensor eletroquímico baseado em carbon dots suportados em óxido de grafeno reduzido para determinação de hidroxicloroquina

Abstract

The use of modifiers in carbon paste electrodes (CPE) has been growing every year due to the possibility of improving the performance of the electrode in relation to the selective determination of several analytes. The objective of this work is the development of modified electrodes with a hybrid material based on carbon dots and reduced graphene oxide (CD-rGO), which has a low cost of preparation, high sensitivity, and fast response for the determination of hydroxychloroquine. Graphene oxide (GO) was synthesized by the modified Hummer’s method under mild conditions and reduced with L-ascorbic acid to obtain reduced graphene oxide (rGO), then the carbon dots were synthesized in situ, on rGO matrix, using urea and glucose as precursors, by a hydrothermal route at 180 °C for 5 hours. The hybrid material obtained was characterized using scanning electron microscopy (SEM), fluorescence emission spectroscopy (PL), molecular absorption in the ultravioletvisible region (UV-Vis), Raman and vibrational spectroscopy in the Fourier-transform infrared spectroscopy (FTIR), and x-ray diffractometry (XRD). After the characterizations of CD-rGO, the modified carbon paste electrode (ECO) was applied to the voltammetric determination of commercial hydroxychloroquine tablets and synthetic urine. Parameters such as electrolyte medium, ECO composition, and parameters of differential pulse voltammetry technique were optimized and the electrochemical characterization showed that the ECO electrode has higher sensitivity in the hydroxychloroquine determination than CPE. The optimizations of the parameters of the electrolyte medium and the VPD technique resulted in a significant current gain for the analytical signal of HCQ. With the development of the analytical curve, the limits of detection (LOD) and quantification (LOQ) of 2.40 pmol∙L-1 and 7.99 pmol∙L-1 , respectively, were obtained in a linear response range of 19.90 to 138 pmol∙L-1 and the precision of the developed method showed satisfactory results of repeatability and reproducibility, presenting recoveries between 101.55 and 106.83 %, enabling the use of the ECO as an electrochemical sensor for hydroxychloroquine determination.