A method for determining regioisomer abundances of polyunsaturated triacylglycerols in omega-3 enriched fish oils using reversed-phase liquid chromatography and triple-stage mass spectrometry.

Reversed-phase high performance liquid chromatography (RP-HPLC), followed by post-column addition of lithium salts and electrospray ionisation triple-stage mass spectrometry (ESI-MS(3)) of lithiated TAG adducts, is shown to provide a useful method for the positional analysis of triacylglycerols (TAGs) in fish oils containing eicosapentaenoic (EPA, 20:5) and docosahexaenoic acids (DHA, 22:6). One prominent fragmentation pathway in the ESI-MS(3) of these adduct ions involves the loss of a fatty acid from the sn-1/3 position in the first step followed by the loss of an α,β-unsaturated fatty acid from the sn-2 position in the second. Regioisomeric TAGs of the type ABA and AAB produced abundant product ions - [ABA+Li-RACOOH-R'BCHCHCOOH](+) and [AAB+Li-RACOOH-R'ACHCHCOOH](+) - the relative intensities of which were dependent on the position of acyl substituents.

Quantitative analysis of positional isomers of triacylglycerols via electrospray ionization tandem mass spectrometry of sodiated adducts.

Herein we report a reversed-phase high-performance liquid chromatography tandem mass spectrometry (RP-HPLC/MS/MS) method for the analysis of positional isomers of triacylglycerols (TAGs) in vegetable oils. The fragmentation behavior of [M + X](+) ions (X = NH(4), Li, Na or Ag) was studied on a quadrupole-time-of-flight (Q-TOF) mass spectrometer under low-energy collision-induced dissociation (CID) conditions. Mass spectra that were dependent on the X(+) ion and the nature and position of the acyl substituents were observed for four pairs of 'AAB/ABA'-type TAGs, namely PPO/POP, OOP/OPO, LLO/LOL and OOL/OLO (where P is 16:0, palmitic acid; O is 18:1, oleic acid; and L is 18:2, linoleic acid).

Liquid chromatography-atmospheric pressure photoionization-mass spectrometry analysis of triacylglycerol lipids--effects of mobile phases on sensitivity.

In this work, we evaluate the performance of liquid chromatography-atmospheric pressure photoionization-mass spectrometry (LC-APPI-MS) for non-aqueous reversed phase analysis of six triacylglycerol model compounds using six binary mobile phases including MeOH/iPrOH, MeOH/CHCl(3), MeOH/CH(2)Cl(2), CH(3)CN/iPrOH, CH(3)CN/CHCl(3), and CH(3)CN/CH(2)Cl(2). All mobile phases give comparably good separation performance on a Gemini C(18) column with carefully adjusted gradient elution programs. APPI sensitivity varies from one mobile phase to the other without dopants; however use of dopants brings sensitivity to comparable levels for all mobile phases.