Prediction of the Solubility in Supercritical Fluids Based on Supercritical Fluid Chromatography Retention Times

An improved method for the rapid prediction of solubilities of solutes in supercritical fluids is proposed. The method is based on the measured retention times of solutes eluting from packed and capillary supercritical fluid chromatography (SFC) columns. The solubilities in CO₂ of four polycyclic aromatic hydrocarbons were estimated with an average error of about ±30% using retention data obtained by packed column SFC. For more polar compounds, which may interact strongly with the stationary phase in packed columns, capillary column SFC gave better results. Agreement to better than 35% was found between the solubilities obtained by this method and those obtained gravimetrically for compounds with a variety of functionalities. Several factors have been investigated, including the relationship between solubility and the reciprocal of the capacity factor, the effect of temperature, and the effect of the stationary phase.