Navegando por Palavras-chave "coumarin"

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    Electrochemical study of simple coumarin and its determination in aqueous infusion of Mikania glomerata
    (Sociedade Brasileira de Química, 2014-03-01) Miyano, Daniela Miwa [UNIFESP]; Lima, Thays [UNIFESP]; Simões, Fabio Ruiz [UNIFESP]; La-Scalea, Mauro Aquiles [UNIFESP]; Oliveira, Hueder P. M.; Codognoto, Lucia [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Universidade Federal do ABC Centro de Ciências Naturais e Humanas
    The present study aims the development and application of an electrochemical method for simple coumarin determination in aqueous media by using a boron-doped diamond electrode (BDDE). The studies were carried out at pH 8.0 by cyclic voltammetry (CV) and registered an irreversible reduction process controlled by diffusion with the peak potential recorded around -1.6 V. The square wave voltammetry analysis (SWV) showed the reversible behavior of the electrochemical reduction of coumarin at the same pH. Additionally, the reversibility of the process was improved by increasing the solution pH. The chronoamperometry study showed that the coumarin reduction process involves two electrons. From the optimized SWV parameters, the analytical curve was constructed in a linear range between 0.5 × 10-5 and 10.0 × 10-5 mol L-1. The limits of detection and quantification were 1.5 × 10-6 mol L-1 and 4.5 × 10-6 mol L-1, respectively. The coumarin was determined in an aqueous infusion of Mikania glomerata, showing recovery values between 92 and 104%.
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    Photophysical properties of coumarin compounds in neat and binary solvent mixtures: evaluation and correlation between solvatochromism and solvent polarity parameters
    (Sociedade Brasileira de Química, 2014-05-01) Moreira, Leonardo Marmo; Melo, Mirian M. de; Martins, Priscila A.; Lyon, Juliana Pereira; Romani, Ana Paula; Codognoto, Lucia [UNIFESP]; Santos, Sandra C. dos; Oliveira, Hueder Paulo Moisés de; Universidade Federal de São João Del Rei Departamento de Zootecnia; Universidade do Vale do Paraíba Instituto de Pesquisa e Desenvolvimento; Universidade Federal de São João Del Rei Departamento de Ciências Naturais; Universidade Federal do ABC Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas; Universidade Federal de São Paulo (UNIFESP); Universidade Federal de Pelotas Centro de Ciências Químicas, Farmacêuticas e de Alimentos; Universidade Federal do ABC Centro de Ciências Naturais e Humanas
    This work studied the fluorescent and solvatochromic properties of coumarin and its derivatives aiming to contribute in the elucidation of the excited state behavior of the molecule in solvent mixtures. This approach has been developed through a set of measurements involving different solvent ratios, which present distinct dielectric constants. The excitation and fluorescence maxima were largely blue-shifted with increasing participation of the organic solvent and the Stokes shifts were unusually low in mixtures with lower solvent polarity parameter, Δf. The emission intensity of coumarin was extremely sensitive to the polarity and the different structural conformations of solvents. These results influenced the spectroscopic behavior and explain the deviation from the linearity of the Lippert-Mataga relationship. The use of fluorescence spectroscopy makes the understanding of the behavior of the systems studied when in the presence of different environments being extremely important for the identification and characterization of coumarin in different pharmaceutical formulations.