Correlation of solid solubilities of pharmaceutical compounds in supercritical carbon dioxide with solution model approach

Experimental solubility and thermodynamic modeling of empagliflozin in supercritical carbon dioxide

The solubility of empagliflozin in supercritical carbon dioxide was measured at temperatures (308 to 338 K) and pressures (12 to 27 MPa), for the first time. The measured solubility in terms of mole faction ranged from 5.14 × 10^–6 to 25.9 × 10^–6. The cross over region was observed at 16.5 MPa. A new solubility model was derived to correlate the solubility data using solid–liquid equilibrium criteria combined with Wilson activity coefficient model at infinite dilution for the activity coefficient. The proposed model correlated the data with average absolute relative deviation (AARD) and Akaike’s information criterion (AIC_c), 7.22% and − 637.24, respectively. Further, the measured data was also correlated with 11 existing (three, five and six parameters empirical and semi-empirical) models and also with Redlich-Kwong equation of state (RKEoS) along with Kwak-Mansoori mixing rules (KMmr) model. Among density-based models, Bian et al., model was the best and corresponding AARD% was calculated 5.1. The RKEoS + KMmr was observed to correlate the data with 8.07% (correspond AIC_c is − 635.79). Finally, total, sublimation and solvation enthalpies of empagliflozin were calculated.

Correlation of the solubility of solid hydrocarbons in supercritical CO2 using different equations of state and mixing rules

The supercritical extraction process is a technique that has increasingly been applied in various industries in recent years. Solubility determination in the supercritical region is the key feature for this process. However, high expenses and time consuming experiments for this task obligates the need for process modeling. In this study, a thermodynamic model is proposed to correlate the solubility of solid hydrocarbons, namely, 1-hexadecanol, 1-octadecanol, anthracene, benzoin, fluorene, hexamethylbenzene, mandelic acid, naphthalene, palmitic acid, phenanthrene, propyl 4-hydroxybenzoate, pyrene and stearic acid in supercritical conditions, using Peng?Robinson (PR) and Soave?Redlich?Kwong (SRK) equations of state with one-parameter van der Waals (vdW1) and two-parameters (vdW2) and covolume dependent (CVD) mixing rules. For the above combination of equations of state and mixing rules, binary interaction parameters were determined, utilizing the differential evolution optimization strategy. The validity of the model was assessed by comparing the experimental solubility data with the results obtained from thermodynamic model based on average absolute relative deviation (AARD). An empirical correlation was proposed for the correlation of the solid solubilities in supercritical CO2. For each compound, the constants of this equation were obtained in such a manner to correlate the solubility at different temperatures and pressures.