Separation of rosemary antioxidant compounds by supercritical fluid chromatography on coated packed capillary columns

Antioxidant compounds in rosemary extracts obtained by supercritical fluid extraction (SFE) were separated by supercritical fluid chromatography (SFC) on packed capillary columns. The columns contained silica particles coated with SE-54 (5% phenyl, 95% methyl silicone) and Carbowax 20 M [poly(ethylene glycol)]. The use of coated packed capillary columns allowed the separation of polar compounds by SFC with neat CO2. The SFC conditions were selected on the basis of previous work. High pressures (up to 370 atm; 1 atm = 10,325 Pa) and moderate temperatures (up to 100 °C) were used to separate the compounds responsible for the antioxidant activity such as carnosic acid and carnosol while lower pressures were sufficient to separate the compounds of the essential oil.