Partition coefficients and polymer-solute interaction parameters by inverse supercritical fluid chromatography

Inverse supercritical fluid chromatography (ISFC) is used to measure partition coefficients of five polar and nonpolar organic solids between supercritical CO2 and cross-linked poly(dimethylsiloxane) (PDMS) swollen with CO2. Polymer-solute interaction energies, which are determined from the partition coefficients, correlate with the heats of vaporization of the pure solutes. These interaction energies can be determined at ambient temperature for solutes that are too nonvolatile to study by inverse gas chromatography. Binary and ternary phase equilibria are modeled with lattice fluid theory including a term to account for the degree of polymer cross-linking. Experimental results indicate that solute adsorption on the support phase, which can be severe in packed columns, is negligible with the use of capillary columns.