Selection of biphasic liquid systems in liquid-liquid chromatography using predictive thermodynamic models

The possibility of using thermodynamic models for screening biphasic liquid systems, including systems for which liquid-liquid equilibrium data are not available, is demonstrated. The liquid-liquid equilibrium in different biphasic systems and the partition coefficients of solutes in these systems are predicted with UNIFAC and COSMO-RS. The predictions are based only on the molecular structure of the solutes and solvents. The advantages and limitations of the two models are explored using fourteen solutes and five biphasic solvent systems. The overall results show that the theoretically selected systems closely match the systems chosen by experimental screening. The experimental work needed for selecting a suitable biphasic system for a given separation problem can be drastically reduced with the help of predictive thermodynamic models.