Solubility of norfloxacin and ofloxacin in supercritical carbon dioxide

This work presents the solid solubility in supercritical carbon dioxide (scCO2) of two fluoroquinolone-type antibacterial drugs, namely norfloxacin and ofloxacin. Experimental data were obtained at 308.2 K, 318.2 K and 328.2 K in a pressure range from 10.0 up to 30.3 MPa using a static analytical method and correlated using density based equations. Equilibrium solubility data (mole fraction) were found to be between 1.4 × 10−6 and 24.4 × 10−6 (for norfloxacin) and 0.4 × 10−6 and 1.3 × 10−6 (for ofloxacin). Experimental data were correlated with density-based models (Méndez-Santiago-Teja, Bartle, Chrastil and Sparks models) with global average absolute relative deviations (AARD) equal to 34% for norfloxacin and 19% for ofloxacin, being the lowest deviations obtained from the Sparks’ model (27% for norfloxacin and 8.6% for ofloxacin). Those models were not able to correctly describe the dependence of the solubility of norfloxacin with the solvent density and lower deviations are only obtained if temperature dependent parameters are considered (5.0% and 4.3% for norfloxacin and ofloxacin, respectively).