Determinação eletroanalítica de acetaminofeno sobre eletrodo modificado com nanopartículas de ouro, nanotubos de carbono e ftalocianinas de cobalto

Abstract

This work describes the development of a simple electroanalytical methodology for quantification of acetaminophen (ACOP) using square-wave voltammetry (SWV). A glassy carbon electrode modified with gold nanoparticles (AuNp), functionalized multi-walled carbon nanotubes (fMWCNT) and cobalt (II) phthalocyanine (CoPc) was prepared and characterized by cyclic voltammetry (CV), SWV and electrochemical impedance spectroscopy (EIS). The optimum experimental conditions, such as pH, supporting electrolyte and square-wave voltammetric parameters were investigated. From the data analysis of the optimization of experimental conditions, the oxidation of ACOP was characterized as a quasi-reversible and as a proton-dependent process, and with the reaction mechanism which allowed to calculate equal number of protons and electrons (two protons and two electrons) and the standard rate constant ks value is equal to 59.0 ± 2.5 s–1. Study of the electrolyte was carried out in four different buffer solutions and the influence of pH was also evaluated, with the best results obtained at pH 5.0 McIlvaine buffer. The frequency (f), amplitude (a) and step potential (ΔEs) optimized values were 50 s1, 40 mV e 3 mV, respectively. Under the optimized conditions, calibration curves were linear in the concentration range of 1.49 × 10–6 a 4.76 × 10–5 mol L1 with limit of detection (LOD) of 1.35 × 10–7 mol L1 and limit of quantification (LOQ) of 4.50 × 107 mol L1. Repeatability and reproducibility were evaluated based on the relative standard deviation values (RSD), which were equal to 4.56% and 2.38%, respectively, demonstrating the accuracy of the methodology. Recovery assays were performed to ACOP quantification in drug samples presented in the form of tablets (Tylenol® 500 and Tylenol® DC) oral solution (Tylenol® Drops) and oral suspension (Tylenol® Child). The recovery percentages for samples of Tylenol® 500, Tylenol® DC Tylenol® Drops and Tylenol® Child were 101.34%, 89.91%, 98.61% and 75.76%, respectively. The results obtained by the SWV methodology were compared to the results obtained by ultraviolet-visible spectrophotometry (UV-Vis), showing the advantages to proposed electroanalytical methodology as lower LOD and LOQ values. Therefore, it is evident that the methodology developed in this work is quite suitable for practical applications.