Phase Behavior of Arbutin in a Mixture of Ethanol and Supercritical Carbon Dioxide

Phase behavior of the ternary systems of arbutin, which is well known to be effective material for skin lightening agent, in a solvent mixture of ethanol and supercritical carbon dioxide was investigated. The solubilities of arbutin in the mixture of ethanol and carbon dioxide were determined as functions of temperature, pressure and solvent composition by measuring the cloud points of the ternary mixtures at various conditions using a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. On the basis of ethanol, arbutin loading was kept at 1.5wt% throughout this study and the pressure and temperature were varied up to 20MPa and 333.15K, respectively. For a range of CO₂ loading less than 33wt% on the basis of ethanol, the cloud point was not observed. On the contrary, solid remained undissolved when CO₂ loading exceeded 54wt%. Between these loadings, steep and thus very sensitive to pressure variation solubility curves, which extends downward to a vaporization boundary, were found.