PACKED-MICROBORE SUPERCRITICAL FLUID CHROMATOGRAPHY WITH FLAME IONIZATION DETECTION OF ABUSED VEGETABLE-OILS

Packed-column supercritical fluid chromatography with flame ionization detection (SFC-FID) has been applied to the analysis of abused vegetable oils. Previous studies have shown that packed-column SFC-FID of polar solutes is difficult due to the unshielded surface silanols on SFC stationary phases. The use of a polymeric resin-based stationary phase or high-temperature water saturation with a bonded-silica column eliminates the problem. With the use of the polymeric resin-packed column, silanophilic interactions are non-existent. High-temperature water saturation of the carbon dioxide mobile phase provides water as a modifier at levels of 2 to 3 mole%, levels previously unattained in packed-column SFC. At this concentration, water notably minimizes fatty acid interactions with the bonded-silica column, yet allows the use of FID. These two chromatographic approaches are illustrated on lipid-containing samples such as oil from storage-abused soybeans and a commercial frying fat. Chromatograms obtained by packed-column SFC-FID are compared with separations attained using capillary-column SFC. Packed-microbore SFC-FID results show a linear correlation with free fatty acid content determined by a standard titration method.