ANALYSES OF VEGETABLE OIL TRIACYLGLYCEROLS BY SILVER ION HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH FLAME IONIZATION DETECTION

Silver ion high performance liquid chromatography with a commercially available column with a simple isocratic mobile phase of acetonitrile in hexane and flame ionization detection was employed to separate and quantitate triacylglycerol species of vegetable oils. Coconut, palm, c ottonseed, olive, safflower, sunflower, corn, pumpkinseed, linseed, so ybean, and canola oils were analyzed, as well as randomized corn and s oybean oils, and the blends and interesterified products of corn and s oybean oil with cottonseed oil stearine. Fractionated triacylglycerol species were identified by gas chromatography of their methyl esters. Triacylglycerol composition was obtained by reversed phase and silver ion high performance liquid chromatography of the same oil. Oil fatty acid composition was determined by gas chromatography of the transmeth ylated oil and correlated with that calculated from the triacylglycero l composition by silver ion chromatography of the same oil. The triacy lglycerol separation was mostly based on the total unsaturation of the fatty acids attached to the glycerol moiety. However, partial separat ion of triacylglycerols with the same unsaturation content but differe nt fatty acids indicates that other separation mechanisms, in addition to fatty acid complexation with silver ions, such as adsorption and p artition, are involved. The flame ionization response (area percent) w as determined to be proportional to weight percent for oil triacylglyc erol composition. In addition to analyses of vegetable oils, the effic acy of the silver ion high performance liquid chromatography method wi th flame ionization detection for analyses of margarine base stocks pr oduced from corn and soybean oils was demonstrated.