SOYBEAN OIL TRIACYLGLYCEROL ANALYSIS BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY COUPLED WITH ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION MASS-SPECTROMETRY

Soybean oil triacylglycerols from genetically modified soybean lines were conclusively identified by reversed-phase high-performance liquid chromatography coupled with mass spectrometry with atmospheric pressure chemical ionization. Atmospheric pressure chemical ionization is a soft ionization technique which gives simple spectra for triacylglycerols. Spectral identification of the triacylglycerols was based on the molecular [M + 1](+) ion and the 1(2)-, 2(3)- and 1(3)-diacylglycerol fragments. Triacylglycerols identified in high-stearic and high-palmitic soybean varieties were quantitated by reversed-phase high-performance liquid chromatography with flame-ionization detection. There was excellent agreement between the fatty acid composition calculated from the triacylglycerol composition and the fatty acid composition obtained by gas chromatography of the transmethylated oils. The oils of the modified soybean varieties, compared to typical soybean oil, contained increased content of triacylglycerols known to be more oxidatively stable, such as linoleoyloleoylstearoyl, linoleoylpalmitoylstearoyl, and linoleoyldipalmitoyl glycerols, and less triacylglycerols like trilinoleoylglycerol, known to decrease oxidative stability. This study showed that the atmospheric pressure chemical ionization technique is suitable for mass spectral identification of neutral molecules, such as triacylglycerols, which do not contain a chargeable functional group.