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

Alternative titleHigh resolution LC-MS profiling of triaclglycerols and targeted regioisomer abundance determination in omega-3 enriched fish oils
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DOIResolve DOI: http://doi.org/10.1016/j.foodchem.2012.12.059
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TypeArticle
Journal titleFood Chemistry
ISSN03088146
Volume139
Issue1-4
Pages655662; # of pages: 8
SubjectTriacylglycerols; Omega-3 fatty acids; Eicosapentaenoic acid; Docosahexaenoic acid; Fish oil; Multi-stage mass spectrometry; Regioisomer analysis
AbstractReversed-phase high performance liquid chromatography (RP-HPLC), followed by post-column addition of lithium salts and electrospray ionisation triple-stage mass spectrometry (ESI-MS³) 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-MS³ 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. Standard solutions of TAGs containing different ratios of the regioisomeric pairs MME/MEM, PPE/PEP, PPD/PDP, EEP/EPE and DDP/DPD (M = 14:0, P = 16:0, E = 20:5, D = 22:6) were analysed by ESI-MS3 with a quadrupole linear ion trap instrument. Methodology developed on the standards was applied to quantifying the relative isomeric abundances of EPA and DHA in several fish oil samples. DHA was preferentially located at the sn-2 position in both DHA-containing TAGs studied, while EPA was either observed at near equal levels in all positions, or predominantly at the sn-1 and -3 positions in some cases. The analysis protocol allows for quantification of the designated regioisomers in one simple, rapid chromatographic procedure using a single column and has the advantage of specificity over other methods for the positional analysis of TAGs, since it eliminates interferences associated with co-eluting TAGs of the same molecular weight that yield isobaric diacylglycerol-like product ions.
Publication date
PublisherElsevier
LanguageEnglish
AffiliationNational Research Council Canada; Aquatic and Crop Resource Development; Measurement Science and Standards
Peer reviewedYes
NRC number54023
NPARC number21268598
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Record identifier8059b2b7-66cb-4ed2-b039-cdccf88d79aa
Record created2013-10-25
Record modified2016-05-09
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