Chromatographic models to predict the elution of ionizable analytes by organic modifier gradient in reversed phase liquid chromatography

The retention of an ionizable analyte under RP-HPLC organic modifier gradient elution is strongly affected by its ionization degree which, in turn, depends on its pKa and on the pH of the mobile phase. The values of both parameters change depending on the mobile phase composition and thus retention becomes a parameter quite difficult to predict, particularly when working in gradient mode. In this work, an equation describing the retention of...