A semi-quantitative outline of the effects of molecular parameters on retention properties in a chromatographic system was obtained by combining the classical and molecular thermodynamic approaches to the problem of solute distribution between the stationary and the mobile phase. The treatment deals with isotropic, nonelectrolyte systems containing an elastomer as a principal component of the stationary phase. The procedure consists in applying a mean-field lattice-fluid model to compute the sensitivities of the macroscopic properties to perturbations in the molecular parameters of a reference system in four representative regimes of mobile phase density. The reference system is typical of open-tubular, capillary supercritical fluid chromatography (SFC) and the four density regimes typify the operating conditions of gas chromatography, low-density SFC, near-critical SFC and high (liquid-like) density SFC. Swelling of the stationary polymer with the absorbed mobile phase fluid is included in the procedure. The density-dependent patterns of the molecular parameters relevant to the pertinent retention and thermodynamic properties are presented and discussed.