Accurate measurements of solubility and thermodynamic transfer quantities using reversed-phase liquid-liquid chromatography

Abstract

A reversed-phase high-performance liquid chromatographic system, consisting of polydimethylsiloxane coated on non-porous glass beads as the stationary phase and pure water as the mobile phase, was used to measure the absolute solubility and the temperature dependence of the solubility of a series of alkylbenzenes in water in the temperature range 0–80°C. The system and the method of analysis provide accurate values of the molar free energy, enthalpy, entropy and reasonable values of the heat capacity of transfer of the alkylbenzenes from their own liquids into water. The thermodynamic data were analysed in terms of the Flory-Huggins theory giving combinatorial and non-combinatorial, i.e., interactional, contributions to the free energy of transfer. All the data were found to agree very well with literature values. The success of the system is attributed to the liquid nature of the stationary phase, the low surface area-to-volume ratio offered by the support material chosen and the availability of the absolute value of the volume of the stationary phase to calculate the phase ratio.