Measurement and modeling of solubility of gliclazide (hypoglycemic drug) and captopril (antihypertension drug) in supercritical carbon dioxide

The solubility of drugs in supercritical carbon dioxide (ScCO₂) is crucial information for crystal engineering designs and pharmaceutical applications. A semi-flow apparatus was used to measure the solubility of gliclazide and captopril in ScCO₂ at 308.2 K, 318.2 K, and 328.2 K within the pressure range of 10.0–18.6 MPa. The newly measured solubility data were correlated and confirmed to be self-consistency with four semi-empirical correlation models: Chrastil, Méndez-Santiago & Teja (MST), Bartle, and Kumar & Johnston (K-J). The newly measured data were then used to evaluate the accuracy of three approaches based on the Peng-Robinson equation of state (PR EOS). PR EOS combining with the Wilson model through the Wong-Sandler mixing rule with two adjustable parameters shown excellent fit with experimental data, while PR EOS combining with the COSMO-SAC model through the MHV1 mixing rule provided reasonable solubility prediction without adjustable parameters.