Solvatochromic parameter values and pH in aqueous-organic mixtures used in liquid chromatography - Prediction of retention of a series of quinolones

The proportion of the organic modifier and the pH of the mobile phase were optimized in order to separate six important quinolones: ciprofloxacin, norfloxacin, enoxacin, fleroxacin, ofloxacin and pipemidic acid. The mobile phase was optimized by establishing relationships between retention parameters and the Reichardt's E(T)(N) scale of solvent polarity, and between retention and the Kamlet-Taft multiparameter solvent scale of the eluent, using linear solvation energy relationships (LSER). In addition, the effect of liquid junction potentials was studied in cells with commercial potentiometric sensors in order to determine the highest precision and accuracy in pH measurements achievable in acetonitrile-water mixtures used as mobile phases. This pH allows the optimization of the mobile phase pH for the chromatographic separation required.