Spectro-electrochemical characterization and quantification of Rutin in aqueous media

From UV-Vis spectrophotometric measurements the acidity constants of Rutin in aqueous media, at 25 °C and 0.1 M ionic strength, were determined as: pK₁ = 4.392 ± 0.167, pK₂ = 7.130 ± 0.050, pK₃ = 8.661 ± 0.042 and pK₄ = 12.354 ± 0.020 and the molar absorptivity coefficients of all the Rutin pH-dependent species were reported as a function of wavelength. Furthermore, the electrochemical behavior of Rutin at neutral pH was investigated using a bare carbon paste electrode, CPE. It was found that both: Rutin electrochemical oxidation and reduction are reversible, adsorption-controlled processes, involving 2 electron transfers. Moreover, the bare CPE was used for the electrochemical quantification of Rutin in neutral aqueous media, displaying the following features: (1.078 ± 0.440) μM, (3.594 ± 0.400) μM and (0.308 ± 0.014) μA μM^-1 for the detection and quantification limits and sensitivity, respectively, within the 1-11 μM linear range. Meanwhile the spectrophotometric method displayed the following analytical features: (3.385 ± 1.318) μM, (11.283 ± 3.114) μM and (0.0120 ± 0.0001) AU μM^-1 for the detection and quantification limits and sensitivity, respectively within the 11-110 μM linear range. In like manner, the bare CPE is also shown as a robust electrochemical sensor that allows Rutin quantification even in the presence of ascorbic acid, commonly found in Rutin samples.