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Supercritical fluid extraction is a potential technique for the purification of pharmaceutical products containing residual solvents. The solubilities of the drugs in supercritical carbon dioxide are being measured as part of a program in which the potential applications of this technology are being investigated. The solubilities of three inhibitors of inflammatory activity, Ketoprofen, Piroxicam, and Nimesulide, in supercritical CO2, measured using a dynamic saturation technique, are reported at pressures between 100 bar and 220 bar and at two temperatures:  312.5 K and 331.5 K. These chemicals have relatively high solubilities with values ranging from 4 × 10-6 to 15 × 10-4 mole fraction. The solubilities exhibit a clear dependence on the solvent density, and this has been used to provide a simple and precise correlation of the data.

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The equilibrium solubilities of 0-and m-hydroxybenzoic acid in 3.5 mol ?6 acetone-C02 and 3.5 mol % methanol-C02 binary mixtures were measured at temperatures between 318 and 328 K and pressures in the range of 90-200 bar using a continuous flow apparatus. The solubility isotherms in these ternary systems exhibit a retrograde vaporization phenomenon and a common upper crossover pressure for each ternary system. Moreover, the results demonstrate that the addition of small amounts of cosolvents to C02 increase significantly the solubility of 0-and m-hydroxybenzoic acid. A molecular thermodynamic model was developed based on the Scatchard-Hildebrand regular solution and Flory-Huggins theory using the concept of component solubility parameters to obtain the unlike-pair molecular interactions between the solute and cosolvent. An effective volume fraction term that reflects the "preferential" solvation of the solute by the cosolvent molecules was included in the model development to account for differences between the bulk solvent environment and that in the immediate vicinity of the solute molecule.

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