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 ±â€¯0.167, pK2 = 7.130 ±â€¯0.050, pK3 = 8.661 ±â€¯0.042 and pK4 = 12.354 ±â€¯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 ±â€¯0.440) µM, (3.594 ±â€¯0.400) µM and (0.308 ±â€¯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 ±â€¯1.318) µM, (11.283 ±â€¯3.114) µM and (0.0120 ±â€¯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.

Solid-contact Hg(II)-selective electrode based on a carbon-epoxy composite containing a new dithiophosphate-based ionophore.

The experimental results herein concern a novel ion-selective electrode manufactured with an inner solid contact based on a new ligand O,O'-(2,2'-biphenylene)dithiophosphate pentyl (PenDTF). This electrode displays high selectivity toward the Hg(II) ion even in the presence of different divalent ions. The electrode also exhibited a good Nernstian response to Hg(II) (33.7±1.0 mV decade(-1)) over an ample concentration range (5.3×10(-7)-1.0×10(-2) mol L(-1)), with a detection limit of (6.1±1.7)×10(-7) mol L(-1). As a result of design, the electrode can be used for many experiments, simply renewing its contact surface with emery paper, without giving rise to a significant response deviation, exhibiting a variation coefficient of 3%, capable of being tested within the 0-5 pH interval. The electrode was used satisfactorily as indicating electrode during the potentiometric titration of Hg(II) ions with EDTA.