Supercritical CO2 impregnation of silica microparticles with quercetin

Supercritical carbon dioxide has been used to develop two methods for the impregnation of porous silica beads with a natural antioxidant, quercetin. These methods involved batch and semi-continuous supercritical impregnations. The first experiments performed in batch mode helped to understand the influence of pressure, temperature, duration, and the presence of a co-solvent on the impregnation efficiency. A co-solvent was added due to the low solubility of quercetin in supercritical CO2 under the operating conditions studied. In the range of temperatures and pressures studied, the best operating conditions, i.e., those that led to the highest quantity of quercetin impregnated (300 mu g of quercetin per g of silica), were 10 MPa and 323 K with ethanol as co-solvent for 2 h. These operating conditions, highlighted through the batch mode experiments, were subsequently applied to the semi-continuous process. This approach provided an impregnation ratio of 240 mu g of quercetin per g of silica.