Método fotoeletroquímico utilizado como ferramenta para a determinação do ácido 3,4,5-tri-hidroxibenzóico e avaliação da sua capacidade antioxidante

Abstract

The present work is based on the development and application of a photoelectrochemical method used as a tool for the determination of the antioxidant 3,4,5-trihydroxybenzoic acid (THBA), a phenolic antioxidant, and evaluation of its antioxidant capacity (AA) in different samples. The method is based on the use of a photoelectrochemical platform based on a fluorine doped tin oxide (FTO) coated glass slide which has been modified with cadmium sulfide (CdS) and poly (D-glucosamine) (p-DG) and subjected to a radiation source (an

LED light emitting diode). The modified electrode was denoted as FTO/CdS/p- DG, showed a fast photoelectrochemical response for analyte detection. The

photoelectrochemical method used showed that there was subsequent decrease in the sensor response as the concentration of antioxidant THBA in solution was increased. The photoelectrochemical assays for AA evaluation were performed by monitoring the photocurrent generated after the addition of 2,2-diphenyl-1- picrylhydrazide (DPPH•

) to the solution and the presence of the antioxidant

studied. Under optimized experimental and operational conditions, the FTO/CdS- p-DG sensor showed a linear concentration range for the analyte in the absence

of DPPH•

from 0.2 to 500 μmol L-1, with a detection limit of 0.1 μmol L-1. In the

presence of the DPPH• radical a concentration range for THBA from 0.5 μmol L- 1

a 8.5 mmol L-1 was observed. The p-DG-CdS/FTO sensor was applied to samples of beverages such teas, juices and red wines. The obtained results suggest that the developed platform is a promising tool for the quantification of the antioxidant THBA and for the evaluation of the antioxidant activity of different food samples such as juices, wines, teas and plant extracts.