Cubic plus association (CPA/qCPA) and classical thermodynamic modeling of pharmaceuticals solubility in supercritical carbon dioxide

The processing of pharmaceuticals by supercritical fluids requires the correct assessment and prediction of the solubility of solid compounds in a supercritical fluid. In this work, the solubility of two drugs, namely ibuprofen and salicylic acid, in supercritical carbon dioxide at different temperatures (308–333 K) and pressures up to 35 MPa was regressed using four different thermodynamic models: Soave–Redlich–Kwong equation of state, cubic plus association equation of state, quadrupolar cubic plus association (qCPA), and the regular solution theory tuned by the Flory–Huggins equation. Adjustable parameters of each model were regressed and reported at the studied temperatures. A comparison of the models’ performances showed that CPA and qCPA models with AARD% 1.34 and 2.16 for ibuprofen and 1.63 and 1.65 for salicylic acid are superior to the other applied methods.