Solubility of Pholcodine (antitussive drug) in supercritical carbon dioxide: Experimental data and thermodynamic modeling

Abstract

Pholcodine (PHO, Antitussive Drug) solubility in supercritical carbon dioxide (Sc-CO2 ) was measured at temperatures of 308, 318, 328, and 338 K and pressures of 120–270 bar. According to the measurements, mole fractions and solubilities of PHO dissolved in Sc-CO2 ranged in 2.06–5.93 × 10−4 and 0.721–4.212 g/L, respectively. Three types of models were employed for correlating experimental results: 1) three existing empirical and semi-empirical models with three and six parameters, 2) the cubic equation of Peng-Robinson with the conventional temperature-dependent and independent mixing rule; and 3) regular solution with Hansen solubility parameter, Reddy-Madras and Alwi et al. models as solid-liquid equilibrium models. Based on the results, all applied models accurately described PHO solubility in Sc-CO2, although Alwi et al. model led to superior results based on AARD (0.29%) and AICc criterion (-647.697).