Effect of temperature on the chromatographic retention of ionizable compounds. III. Modelling retention of pharmaceuticals as a function of eluent pH and column temperature in reversed-phase liquid chromatography

GAGLIARDI, L. G.; C. B. CASTELLS *; RÀFOLS, C.; ROSÉS, M.; BOSCH, E.

JOURNAL OF SEPARATION SCIENCE - (Online)

Wiley Interscience

Lugar: Weinheim (Alemania); Año: 2008 vol. 31 p. 969 - 980

1615-9314

We propose a general simple equation for accurately predicting the retention factors of ionizable compounds upon simultaneous changes in mobile phase pH and column temperature at a given hydroorganic solvent composition. Only four independent experiments provide the input data: retention factors measured in two pH buffered mobile phases at extreme acidic and basic pH values (e. g., at least ± 2 pH units far from the analyte pKa) and at two column temperatures. The equations, derived from the basic thermodynamics of the acid-base equilibria, additionally require the knowledge of the solute pKa and enthalpies of acid-base dissociation of both the solute and the buffer components in the hydroorganic solvent mixture. The performance of the predictive model is corroborated with the comparison between theoretical and experimental retention factors of several weak acids and bases of important pharmacological activity, in mobile phases containing different buffer solutions prepared in 25% w/w ACN in water and at several temperatures.