RESUMO
In this work, the electrochemical behavior of the glycosylated flavonoid kaempferitrin was studied, and an electroanalytical methodology was developed for its determination in infusions of Bauhinia forficata using a boron-doped diamond electrode (BDD). The electrochemical behavior of the flavonoid was studied by cyclic voltammetry, and two irreversible oxidation peaks at 0.80 and 1.0 V vs Ag/AgCl were observed. The influence of the pH on the voltammograms was examined, and higher sensitivity was found at pH 7.0. The electrochemical process corresponding to peak 1 at 0.80 V is predominantly diffusion-controlled, as the study shows at varying scan rates. An analytical plot was obtained by square wave voltammetry at optimized experimental conditions (frequency = 100 s-1, amplitude = 90 mV, and step potential = 8 mV) in the concentration range from 3.4 µmol L-1 to 58 µmol L-1, with a linearity of 0.99. The limit of detection and limit of quantification values were 1.0 µmol L-1 and 3.4 µmol L-1, respectively. Three samples of Bauhinia forficata infusions (2 g of sample in 100 mL of water) were analyzed, and the KF values found were 5.0 × 10-4 mol L-1, 3.0 × 10-4 mol L-1, and 7.0 × 10-4 mol L-1, with recovery percentages of 98 %, 106 % and 94 %, respectively. Finally, experiments were performed with two other flavonoids (chrysin and apeginin) to compare and propose an electrochemical oxidation mechanism for kaempferitrin, which was supported by quantum chemical calculations.
Assuntos
Técnicas Eletroquímicas , Quempferóis , Oxirredução , Quempferóis/química , Quempferóis/análise , Técnicas Eletroquímicas/métodos , Glicosilação , Eletrodos , Bauhinia/química , Teoria Quântica , Flavonoides/química , Flavonoides/análise , Limite de Detecção , Diamante/químicaRESUMO
In order to obtain higher agricultural yields, the use of chemical substances has been increased to prevent the proliferation of pests, as well as ensuring durability in the storage of the food produced. Such substances are known as pesticides that may well present risks to human health and the environment. In the presence of metal ions, these substances can interact forming new species with different characteristics. Carbendazim (MBC) is an example of a harmful pesticide, which has atoms of nitrogen and oxygen in its structure that can form complexes with metal ions. Thus, in this work has studied the interaction between the copper (II) metal ion and carbendazim and its formation in natural water. The Cu-MBC complex showed a reduction peak of 0.007 V and an oxidation peak of 0.500 V, with characteristics of a quasi-reversible process under a glassy carbon electrode. By anodic stripping voltammetry, a different behavior was observed in the interaction of copper and carbendazim in ultrapure water and Billings dam water; however, it was possible to observe the complex in both samples. Carbendazim in the presence of the metal shows lower oxidation potential value, indicating the influence of the metal on the electrochemical response of the pesticide.