Apparent Solubility of Natural Products Extracted with Near-Critical Carbon Dioxide

The apparent solubility controls the initial stage of supercritical fluid extraction of natural products, which is most important for the process economics. Based on the literature, data on CO2 apparent solubility of volatile substances from different matrices as leaves, flowers, rhizomes and seeds were collected and compared with their thermodynamic solubility. The adsorption isotherm derived by del Valle and Urrego as a modification of the isotherm proposed by Perrut et al. is universal enough to interpret these data as well as the apparent solubility of vegetable oils from seeds, for which it was originally proposed. When the apparent solubility of minor extract components in CO2 is compared with their thermodynamic solubility, their fraction in the extracted mixture should be taken into account.