ACCURATE MEASUREMENTS OF SOLUBILITY AND THERMODYNAMIC TRANSFER QUANTITIES USING REVERSED-PHASE LIQUID-LIQUID CHROMATOGRAPHY

A reversed-phase high-performance liquid chromatographic system, consi sting of polydimethylsiloxane coated on non-porous glass beads as the stationary phase and pure water as the mobile phase, was used to measu re the absolute solubility and the temperature dependence of the solub ility of a series of alkylbenzenes in water in the temperature range 0 -80 degrees C. The system and the method of analysis provide accurate values of the molar free energy, enthalpy, entropy acid reasonable val ues of the heat capacity of transfer of the alkylbenzenes from their o wn liquids into water. The thermodynamic data were analysed in terms o f the Flory-Huggins theory giving combinatorial and non-combinatorial, i.e., interactional, contributions to the free energy of transfer. Al l the data were found to agree very well with literature values. The s uccess of the system is attributed to the liquid nature of the station ary phase, the low surface area-to-volume ratio offered by the support material chosen and the availability of the absolute Value of the vol ume of the stationary phase to calculate the phase ratio.