Estimation of critical point, vapor pressure and heat of sublimation of pharmaceuticals and their solubility in supercritical carbon dioxide

Abstract

The critical point and vapor pressure of pharmaceuticals are required in the calculation of their solubility in supercritical fluids by using an equation of state. The experimental critical point of many pharmaceuticals are not accessible due to their temperature sensitivity, also the experimental vapor pressure of many pharmaceuticals are not available at temperatures at which the supercritical extraction is usually accomplished. In this study, four group contribution methods are used to estimate the critical point and acentric factor of eight pharmaceuticals. The estimated properties are evaluated in predicting the vapor pressure and enthalpy of sublimation of the pharmaceuticals by using the Peng Robinson equation of state. The most accurate critical points are employed to calculate the solubility of the pharmaceuticals in the supercritical CO2 by using the Peng Robinson equation combined with two mixing rules. The AARD of 7.28% indicates the good performance of the Wong Sander mixing rule.