Elucidation of the triacylglycerol fraction of menhaden fish oil by using ultra high-pressure NARP-LC/IT-TOF

TAG separation in fish oils represents a challenging and cumbersome task due to the high sample complexity; this may be one reason why their structures have been rarely reported. Such samples contain a large variety of different fatty acids including long-chain polyunsaturated components such as 20:5(n-3) (Ep) and 22:6(n-3) (Dh). Fatty acid (FA) chain length varies between 14 and 22 carbon atoms, with 0 to 6 double bonds. In this work, (NARP)LC based on the use of partially porous octadecylsilica columns, was exploited for separation of the TAGs occurring in a complex fish oil sample, in combination with IT-TOF/APCI MS detection. Up to four identical columns (15-cm length each) were serially coupled, and operated under UHPLC (ultra high pressure liquid chromatography) conditions, to fully exploit the gain in efficiency at the maximum operating pressure allowed. Mass spectra of the analyzed TAGs showed both [M+H]+ and [M+H-COOH]+ ions, formed by cleavage of FAs from the glycerol backbone. In addition, predictable elution order, under non-aqueous reversed-phase conditions, was used to support TAGs identification. Besides, a thorough elucidation of TAG content in menhaden oil is here reported for the first time.