Adsorption and thermal release of highly volatile compounds in silica aerogels

This work reports the adsorption/desorption behaviour of two highly volatile compounds (1-menthol and 2-methoxy pyrazine) in hydrophobic and hydrophilic silica aerogels where CO2 is used as an effective solvent to deliver these compounds to the inner surfaces of the aerogels. The thermal desorption behaviour of both substances depends intimately on the strength of the interactions of the absorbed substance with the type and availability of hydrophobic and hydrophilic surface groups in each aerogel. For example, as much as similar to 50 wt% of either compound remains absorbed on the hydrophilic aerogel surface at temperatures of similar to 250-300 degrees C, whereas these same compounds are released from the hydrophobic aerogel at 100-150 degrees C lower temperatures. The results reported here provide insight into the application of silica gels as delivery/storage devices with potential applications in the food, drug, flavors, and other allied industries. (C) 2008 Elsevier B.V. All rights reserved.