Analysis of triacylglycerols by reversed-phase high pressure liquid chromatography with direct liquid inlet mass spectrometry

Natural triacylglycerols were resolved by high pressure liquid chromatography on Supelcosil LC-18 columns using a gradient of 30–90% propionitrile in acetonitrile as eluting solvent. The effluent was admitted to a quadrupole mass spectrometer via a direct liquid inlet interface. The mass spectra of the solutes were recorded in the chemical ionization mode. The triacylglycerol elution profile was obtained from the total ion current. Individual molecular species of the triacylglycerols were identified from the (MH)+ and the (MH—RCOOH)+ ions. The reversed-phase system allowed the separation of triacylglycerols on the basis of both carbon number and double-bond number, as well as of certain critical pairs of triplets of triacylglycerols with the same partition number. The method is applicable to the determination of triacylglycerol composition of both plant and animal fats. The minimum amount of sample which is required is about 50 ng in the scanning mode. However, 100 times more material must be injected in the liquid chromatograph because only 1/100th of the effluent is being injected into the mass spectrometer.