Isolation of phenolic antioxidant compounds by SFC

Specially designed chromatographic columns were evaluated for antioxidant compounds separation by supercritical fluid chromatography (SFC) with pure CO2. Columns studied involved the use of commercial octadecylsilica particles (ODS) and silica particles coated with a stationary phase commonly used in gas chromatography, such as CW20M (polyethylene glycol) of high polarity. In order to select the appropriate chromatographic conditions to elute antioxidant compounds of phenolic structure, carnosic acid was selected as a model molecule and a theoretical study of the solubility of carnosic acid was performed. Carnosic acid was eluted using CO2 as mobile phase (without modifiers) with a pressure programming up to 37 MPa (and at different temperatures) but only when coated particles were used. No elution was possible when ODS particles were tested, probably due to the strong interactions of the acid group of the molecule with the active sites remaining in the column. A separation of a complex mixture of a rosemary antioxidant extract (obtained by supercritical fluid extraction) using the columns designed in the present work is shown.