Sirolimus solubility in supercritical carbon dioxide: Measurement and modeling

The solubility of drugs in supercritical carbon dioxide is a key parameter in their processing. This study focuses on sirolimus, an immunosuppressive drug used in organ transplantation. Its solubility in supercritical carbon dioxide was measured using a static gravimetric method. Measurements were carried out at pressures ranging from 12.5 MPa to 25.0 MPa and temperatures from 313 K to 328 K. The findings revealed a molar fraction range of sirolimus between 1.20 × 10⁻⁶ and 2.73 × 10⁻⁶ and a direct solubility behavior in the investigated domain. The experimental data were correlated using several models. These included semi-empirical density-based models (Chrastil, Mendez-Santiago and Teja, Bartle et al., Kumar and Johnston, Sparks et al., and Sodeifian et al.), as well as equation of state-based models (Soave-Redlich-Kwong and Peng-Robinson). The results indicated that Sparks et al. and Soave-Redlich-Kwong showed the lowest average absolute relative deviation (AARD%) and the corrected correlation coefficient (R_adj) of 4.12 %, 0.978 and 05.18 %, 0.980 respectively.