Systematic Study of the Positional Analysis of Triglycerides Using High Performance Liquid Chromatography and Electrospray Tandem Mass Spectrometry

A large set of YXY/YYX and XYZ types of triglycerides were synthesized and analyzed by the electrospray ionization mass spectrometer. The collisional-induced dissociation spectra of various adducts formed via electrospray were obtained and characterized. The calibration plots for several systems of positional isomers were constructed and the sensitivities of the collision-induced dissociation spectra to the position of the fatty acids along the glycerol backbone were compared. The influence of compositional fatty acid moieties on the sensitivity of positional analysis was also studied. It was found that the sensitivities of the collision-induced dissociation spectra to the position of the fatty acids on the glycerol backbone are highly dependent on the cation and the compositional fatty acid moieties. However, the lithiated adducts proved to provide the best overall sensitivity to fatty acid position. The reliability of a model developed to predict the collision-induced dissociation spectra of XYZ-type triglycerides was compared for the different cations used to form the triglyceride adducts and overall the prediction model based on the collision-induced dissociation spectra of lithiated triglycerides was found to be most reliable. The application and significance of high performance liquid chromatography used in conjunction with mass spectrometry for positional analysis were investigated using synthetic triglyceride mixtures and complex triglyceride extract (peanut oil). Three systems studied in this thesis, one dimensional reversed-phase high performance liquid chromatography system, one dimensional Ag+ normal-phase high performance liquid chromatography system and two dimensional Ag+ normal-phase/ reverse-phase high performance liquid chromatography system, were compared on the basis of the precision in measuring the relative abundances of the diacyglycerol product ions in the collision-induced dissociation spectra of [M+NH4]+ parent ions acquired during the analyses of a standard mixture of YXY triglycerides. It was demonstrated that the reliability and precision of positional analysis of TAG can be greatly enhanced using two dimensional chromatographic methods. It was also shown that the chromatographic separation of positional isomers can be utilized to obtain the collision-induced dissociation spectra of pure positional isomers