title: Novel characterisation of minor α-linolenic acid isomers in linseed oil by gas chromatography and covalent adduct chemical ionisation tandem mass spectrometry.
abstract: Discrimination between polyunsaturated fatty acid isomers with three double bonds is a great challenge, due to structural similarities and similar polarities. In this study, we report the identification of four minor geometrical isomers of α-linolenic acid (ALA) present in linseed oil samples: (9E,12Z,15E)-, (9Z,12Z,15E)-, (9Z,12E,15Z)- and (9E,12Z,15Z)-octadeca-9,12,15-trienoic acids, chromatographically resolved by gas chromatography (GC) using a new and highly polar ionic phase column (SLB-IL111). Gas chromatography-electron ionisation mass spectrometry (GC-EIMS) determined that the four unknown compounds were C18:3 n-3 isomers. The positional 9-12-15 C18:3 configuration was achieved by covalent adduct chemical ionisation tandem mass spectrometry (CACI-MS/MS) while geometrical configuration was established with analytical standards based on relative retention. We hypothesised that these isomers are formed during linseed oil deodorisation and postulate preferred and unfavoured isomerisation pathways of ALA.
authors.affiliation: Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
authors.forename: P
authors.initials: P
authors.lastname: Gómez-Cortés
authors.affiliation: Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Brenna
authors.affiliation: Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
authors.forename: P
authors.initials: P
authors.lastname: Lawrence
authors.affiliation: Instituto de Investigación en Ciencias de la Alimentación (CSIC-UAM), Nicolás Cabrera 9, Universidad Autónoma de Madrid, 28049 Madrid, Spain. Electronic address: mafl@if.csic.es.
authors.forename: M A
authors.initials: MA
authors.lastname: de la Fuente
mesh_terms: D015525:Fatty Acids, Omega-3 / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D007536:Isomerism; D008043:Linseed Oil / Q000032:analysis / Q000737:chemistry*; D017962:alpha-Linolenic Acid / Q000737:chemistry*
chemical_list: D015525:Fatty Acids, Omega-3; D017962:alpha-Linolenic Acid; D008043:Linseed Oil
keywords: CACI-MS/MS; Geometrical isomer; Isomerisation; Omega-3 fatty acids; SLB-IL111; α-Linolenic acid
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