Enhanced mass transport and compound selectivity are possible for low molecular weight components solubilized in a carrier media of supercritical carbon dioxide fluid and subjected to radial thermal field-flow fractionation. In preliminary studies we observed separation of methanol and benzophenone through rapid expansion of carrier fluid at 135 bar from a 100-mu m diameter capillary tube into a larger-bore tube that extended across a 20 degrees C radial thermal gradient. We can only assume that the localized drop in pressure imposed by the rapid expansion of fluid coupled with its behavior when subjected to the thermal gradient have enormous effects on fluid density which appear to be more effective in mass transport than conventional liquid solvents for extending field-flow fractionation to a range of low molecular weight compounds that classically could only be separated by chromatography.