Measurement and correlation for the solid solubility of non-steroidal anti-inflammatory drugs (NSAIDs) in supercritical carbon dioxide

The solubilities for three non-steroidal anti-inflammatory drugs (NSAIDs) of nabumetone, phenylbutazone and salicylamide in supercritical carbon dioxide were measured in this study using a semi-flow type apparatus. The experimental data were taken at 308.2, 318.2 and 328.2 K, over the pressure range from 10 to 22 MPa. The measured results were then correlated using semi-empirical equation presented by Chrastil, and that presented by Mendez-Santiago and Teja. With optimally fitted parameters, these two equations yielded satisfactory results where the average absolute relative deviation (AARD) was below 7%. Furthermore, the solid solubilities of these three compounds and seven other NSAIDs in supercritical carbon dioxide were correlated by applying the regular solution model coupled with a Flory–Huggins term. The solution model, which has fewer parameters than the semi-empirical equations, yielded comparable correlation results. The parameters in the solution model could be generalized for the specific group of NSAIDs. Finally, the predicted solubilities of 10 NSAIDs in supercritical carbon dioxide were demonstrated to be reliable.