The ionization of fluoroquinolones in the presence of differently charged surfactants

Abstract

The pKa values of ciprofloxacin (CPF) and norfloxacin (NRF) were determined potentiometrically, with and without the presence of differently charged micelles, as biomembrane mimetic models. The shift in protolytic equilibria are observed in the presence of surfactants, SDS (ΔpKa1 = +2.02; ΔpKa2 = +0.57); CTAB (ΔpKa1 = -0.09; ΔpKa2 = -0.23) and TX-100 (ΔpKa1 = +0.24; ΔpKa2 = +0.29). The change in distribution of equilibrium forms is most expressed in pH range 6 – 8 which may indicate on potential interactions with molecules of different polarity and charge under physiological conditions.