l-Menthol crystal micronized by rapid expansion of supercritical carbon dioxide

Rapid expansion of supercritical solutions (RESS) is a promising alternative for micronizing various materials including l-menthol of which dissolution would be mainly controlled by its particle size and morphology. The aim of this work is to study the effect of ethanol co-solvent, pre-expansion temperature and pre-expansion pressure on the size and morphology of l-menthol crystals micronized by rapid expansion of supercritical CO2 in prior to their microencapsulation. Calculation of l-menthol dissolution in supercritical CO2 (SC-CO2) was conducted, suggesting that the appropriate pre-expansion temperature would be below 50 °C. Verification based on FT-IR analysis suggested that the fine particles of l-menthol crystals with controlled size and morphology could be prepared by rapid expansion of supercritical CO2 without any structural change.