Solubility of Three Veterinary Sulfonamides in Supercritical Carbon Dioxide by a Recirculating Equilibrium Method

The equilibrium solubility of three pure sulfonamides in supercritical carbon dioxide (SC-CO2) was determined by use of a recirculating flow method. Overall, solubilities were in the part per million range. Solubilities were measured at two temperatures (40 and 60 °C) and at pressures from 131 to 488 bar. Sulfamerazine (SME) was slightly more soluble than either sulfamethazine (SMZ) or sulfadimethoxine (SDM). The maximum solubility determined for the three sulfonamides was at 60 °C (472 to 488 bar), and their solubility range was 6.50 × 10-5 to 10.14 × 10-5 mol·L-1. The data for SMZ and SDM at 40 °C were compared with published data that showed slight differences in the mole fraction versus pressure curve. Our results provide experimental validation that mole fraction solubility increases with pressure above the critical pressure.