title: Identification of the geometrical isomers of α-linolenic acid using gas chromatography/mass spectrometry with a binary decision tree.
abstract: Gas chromatography, using a highly polar column, low energy (30 eV) electron ionization mass spectrometry and multivariate curve resolution, are combined to obtain the mass spectra of all eight geometrical isomers of α-linolenic acid. A step by step Student's t-test is performed on the m/z 50-294 to identify the m/z by which the geometries of the double bonds could be discriminated. The most intense peak discriminates between cis (m/z 79) and trans (m/z 95) at the central (carbon 12) position. The configuration at carbon 15 is then distinguished by m/z 68 and 236, and finally the geometry at carbon 9 is determined by m/z 93, 173, 191 and 236. A three-question binary tree is developed based on the normalized intensities of these ions by which the identity of any given isomer of α-linolenic is accurately determined. Application of Bayes theorem to data from independent samples shows that the complete configuration is determined correctly with a minimum probability of 87%.
authors.affiliation: School of Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Leila
authors.initials: L
authors.lastname: Hejazi
authors.forename: David Brynn
authors.initials: DB
authors.lastname: Hibbert
authors.forename: Diako
authors.initials: D
authors.lastname: Ebrahimi
mesh_terms: D001499:Bayes Theorem; D003663:Decision Trees; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D007536:Isomerism; D017962:alpha-Linolenic Acid / Q000737:chemistry*
chemical_list: D017962:alpha-Linolenic Acid