Yee C. Chiew

Solubility of cholesterol and its esters in supercritical carbon dioxide with and without cosolvents

Abstract The solubilities of cholesterol and its esters—cholesteryl acetate, cholesteryl butyrate and cholesteryl benzoate—in supercritical carbon dioxide were measured using a dynamic flow method. We also examined the effect of a polar cosolvent, namely methanol or acetone, on the solubility of these compounds in supercritical carbon dioxide and found that the solubilities of these compounds are enhanced several fold depending on the pressure of the system. The solubility data were correlated using the Peng–Robinson equation of state (PR EOS) and density-based correlations. Model parameters for the systems studied are obtained through data regression.

Influence of supercritical CO2 pressurization on the phase behavior of mixed cholesteryl esters

Evidences indicating the presence of phase transformations in the mixed cholesteryl benzoate (CBE) and cholesteryl butyrate (CBU) under the supercritical CO(2) pressurization, by means of differential scanning calorimetry (DSC) and X-ray diffraction (XRD), are presented in this work. These include (1) the DSC heating curve of pure CBU; (2) the DSC heating curves of CBU/CBE mixtures; (3) the XRD spectra of pure CBU; (4) the XRD spectra of CBU/CBE mixtures; (5) CBU and CBE are miscible in either solid phase or liquid phase over the whole composition range. As a result of the presence of these phase transformations induced by pressurization, it could be deduced that a solid solution of the CBU/CBE mixture might have formed at the interfaces under supercritical conditions, subsequently influencing their dissolving behaviors in supercritical CO(2).