RESUMEN
From UV-Vis spectrophotometric measurements the acidity constants of Rutin in aqueous media, at 25⯰C and 0.1â¯M ionic strength, were determined as: pK1â¯=â¯4.392⯱â¯0.167, pK2â¯=â¯7.130⯱â¯0.050, pK3â¯=â¯8.661⯱â¯0.042 and pK4â¯=â¯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⯵M-1 for the detection and quantification limits and sensitivity, respectively, within the 1-11⯵M 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⯵M-1 for the detection and quantification limits and sensitivity, respectively within the 11-110⯵M 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.
RESUMEN
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.