EFFECT OF SUPERCRITICAL CARBON-DIOXIDE PRESSURIZED WITH HELIUM ON SOLUTE SOLUBILITY DURING SUPERCRITICAL-FLUID EXTRACTION

Carbon dioxide cylinders, pressurized with a helium headspace, find routine use as a soh ent in analytical supercritical fluid extraction(SFE). In this study, the solubilities of soybean oil in neat supercritical carbon dioxide (SC-CO2) and CO2 with entrained helium were measured at 70 degrees C and three different pressures. The oil solubility was found to be substantially diminished when the CO2/He source was used, presumably by the presence of small amounts of helium dissolved in the extraction fluid. The recorded reductions in solubility (30-50 wt %) should be taken into account in performing and optimizing SFE with helium-pressurized cylinders.