Síntese e aplicação de compósito à base de Zn2SnO4 na detecção eletroquímica de ofloxacino: um estudo experimental e teórico

Abstract

In this work, a methodology was developed for the detection and quantification of ofloxacin (OFL), using an electrochemical sensor based on a glassy carbon electrode modified with a composite formed by zinc stannate and reduced graphene oxide (ECV/Zn2SnO4-rGO), through square wave voltammetry (SWV). Zn2SnO4 was synthesized and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (RS) and scanning electron microscopy (SEM). The SEM images showed aggregation between the components of the developed composite (Zn2SnO4-rGO) amid dispersion with DMF; while the results obtained through SWV indicated chemical synergism between them against the irreversible oxidation of OFL in its protonated form (OFL+), still presenting Ep ≈ 1.2V, reaction mechanism of mixed control and suggesting the participation of two electrons. The chemical synergism between Zn2SnO4 and rGO was also observed by means of electrochemical impedance spectroscopy (EIS), where the lowest resistance to charge transfer (Rtc) was obtained for GCE/Zn2SnO4-rGO. The optimized voltammetric conditions were H2SO4 5.0 × 10−1 mol L−1 pH 0, f = 60 s−1, a = 30 mV e ΔEs = 3 mV. The analytical curve obtained showed a linearity range from 9.99 × 10−8 to 6.62 × 10−6 mol L−1 with r = 0.998; and limits of detection (LD) and quantification (LQ) of the OFL equal to 8,28 × 10-8 mol L−1 e 2,76 × 10-7 mol L−1, respectively, being still compared to those obtained through high performance liquid chromatography (HPLC). The developed sensor was successfully applied to determine OFL in commercial pharmaceutical formulation samples, showing average recovery rates of 100.58%; (DPR = 2.65%) and stability for repeatability (DPR = 3.20%, n = 12); in addition to having demonstrated efficiency even in the presence of several interferers. The chemical-computational studies theoretically evaluated the adsorption of OFL on two different surfaces (Zn2SnO4 and OGr) and indicated greater process efficiency with Zn2SnO4 (Eads = 21.03 eV) compared to OGr (Eads = 1.90 eV); highlighting the relevance of mixed metal oxide in the proposed composite for the electrochemical sensor.