Thermodynamic modeling of naringenin protonation equilibria in NaClO4 aqueous solutions by specific ion interaction theory and Pitzer equations

Abstract

The protonation equilibria for the flavonoid naringenin were studied at 25∘C using combined multi-wavelength spectroscopic and pH-potentiometric methods as a function of the ionic strength. Over a wide range of ionic strengths, 0.10–3.00 mol dm−3, the investigation was performed in different aqueous solutions of NaClO4 as the background electrolyte. The dependence on ionic strength of protonation constants was modeled by the Brönsted–Guggenheim–Scatchard Specific Ion Interaction Theory (SIT) and Pitzer approaches. Apart from the values of SIT interaction coefficients and Pitzer parameters, the protonation constants at infinite dilution (zero ionic strength) were obtained. On the basis of these results, it was found that Pitzer mode l gives more satisfactory results rather than the SIT method. Ionic strength dependence of protonation constants for the flavonoid naringenin was investigated at 25∘C using combined spectroscopic and potentiometric methods in different aqueous solutions of NaClO4 (0.10–3.00 mol dm−3). The SIT and Pitzer equations were used for thermodynamic modeling of dependence on ionic strength of the protonation equilibria.