Estudo eletroanalítico de pirogalol empregando um sensor à base de carbono

Abstract

Pyrogallol (PG) is a phenolic compound widely used as an antioxidant additive, as a hair straightener and in the development of photographs, however some studies have shown that this compound is mutagenic. Thus, this work describes an electroanalytical study of PG using a carbon paste electrode. In this sense, different types of carbon based pastes were prepared to evaluate which one would be more promising to be used as an electrochemical sensor for PG quantification. The materials studied (graphite, carbon black and carbon nanotubes) were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. The sensor using pure carbon black showed better current density for PG than the other materials tested. The scan speed study showed that the analyte oxidation process is transport limited. From these studies it was possible to estimate the number of electrons involved in the PG oxidation reaction, as well as the charge transfer coefficient of this process. In the study of the pH of the solution, it was observed that the highest currents were observed in an acidic medium and in an acetate buffer solution. The study of the potential as a function of pH showed that the anodic peak potential does not depend on the pH of the medium. The study of the effect of the presence of dissolved oxygen on the PG current density showed that it influences the analytical signal of the system. After optimizing the experimental parameters it was possible to obtain a wide range of linear response from 0.1 µmol L 1 to 10 mmol L-1 for PG and a good detection limit (LD) of 0.036 µmol L-1 . The electrode selectivity was tested on different species that may be present in samples containing PG, which showed that some substances that oxidize very easily can interfere. Finally, the electrode was applied for the determination of PG in water and oil samples showing recovery values between 98.64% and 102.50%, suggesting good accuracy.