Illustration of important mechanisms controlling mass transfer in supercritical fluid extraction Original Research Article

Supercritical fluid extraction profiles are presented for various model systems. The purpose is to illustrate some mechanisms encountered in supercritical fluid extraction by using simplified systems and also to give examples of how pre-extraction steps can be utilized to improve the mass-transfer rate. Extraction of clevidipine (a calcium antagonist) from different, allegedly inert materials, showed significant differences in extraction efficiency. Extraction from stainless-steel beads gave complete recovery with pure carbon dioxide, whereas the extraction from filter paper required the addition of 4% methanol. This indicates that interactions between matrix and analyte can be strong and that a modifier can be used, not only to increase solubility in the carbon dioxide, but also to break analyte/matrix bindings.