New Equilibrium Autoclave for Determining Solubility and Melting Point of Solid Solute in Supercritical Fluids. 1. Determination of Solubility of Levonorgestrel in Supercritical Carbon Dioxide.

A new equilibrium autoclave has been designed for determining the solubility of a solid solute and its melting point in supercritical carbon dioxide (ScCO2) with static method inexpensively but accurately. The solubility of levonorgestrel in ScCO2 was measured in this vessel at temperatures ranging from 313 to 323 K and pressures ranging from 10 to 18 MPa. The solubility of levonorgestrel was determined to rise with the increase of pressure at a constant temperature. The crossover point occurred between 14 and 15 MPa. Experimental data were correlated by three semiempirical models (Chrastil, Bartle, and Mendez-Santiago–Teja models). All models achieve excellent correlations to the solubility data with an average absolute relative deviation (AARD (%)) ranging from 7.92 to 9.51%. [ABSTRACT FROM AUTHOR]