Retention mechanisms of reversed-phase liquid chromatography: determination of solute-solvent interaction free energies.

Mean-field statistical thermodynamics theory has recently been developed to account for the partitioning of solutes from aqueous mobile phases into reversed-phase liquid chromatography stationary phases. Several predictions are tested here against an extensive data base of nearly 350 sets of experiments. In agreement with theory, we find that (i) the dependence of retention on mobile phase composition can often be suitably linearized through use of a type of composition plot recently suggested by Dill, (ii) retention measurements can be used to determine the binary interaction constants of solutes with solvents, and (iii) ET-30 solvent probe experiments appear to provide a direct measure of the binary interaction constants. This work suggests that the simple random-mixing approximation for solutes with solvents is often useful even for complex chromatographic solutions.