Supercritical CO₂ Extraction of Organic Solvents from Flunisolide and Fluticasone Propionate

In this work, Class 2 and Class 3 solvents contained in two corticosteroids, flunisolide (Fluni) and fluticasone propionate (Fluti), were reduced to a few ppm by supercritical CO₂ extraction. The process was carried out at pressures from 80 to 200 bar, temperatures of 40 °C and 80 °C, and at a fixed CO₂ flow rate of 0.7 kg/h. The results demonstrated that CO₂ density is the key parameter influencing the extraction kinetics and the solvent final residue. In particular, in the range investigated, optimal pressure and temperature conditions for the extraction of residual organic solvents were found working at 200 bar and 40 °C, which corresponds to a CO₂ density of 0.840 g/cm³. Operating in this way, total organic solvent residues were reduced from 13,671 ppm and 326 ppm to 12 ppm and 10 ppm for Fluni and Fluti, respectively.