Solubility and Thermal Degradation of Quercetin in CO(2)-Expanded Liquids

The solubility of quercetin and its thermal degradation was studied in CO(2)-expanded ethanol and ethyl lactate. An equipment setup was constructed that enabled the separation of the products of degradation while quantifying the solubility of quercetin. Three different conditions of temperature were analyzed (308, 323, and 343 K) at 10 MPa. Higher solubility and thermal degradation of quercetin were observed for CO(2)-expanded ethyl lactate in comparison with CO(2)-expanded ethanol. At the same time, as the amount of CO(2) was increased in the CO(2)-expanded liquids mixtures, the thermal degradation of quercetin decreased for almost all the conditions of temperature considered in this work. The importance of considering thermal degradation while performing solubility measurements of compounds that are thermally unstable such as quercetin was highlighted.