Identification of the geometrical isomers of α-linolenic acid using gas chromatography/mass spectrometry with a binary decision tree

Leila Hejazi, David Brynn Hibbert, Diako Ebrahimi

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

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%.

Original languageEnglish (US)
Pages (from-to)1233-1238
Number of pages6
JournalTalanta
Volume83
Issue number4
DOIs
StatePublished - Jan 1 2011

Keywords

  • Bayes theorem
  • Fatty acid methyl ester
  • GC/MS
  • Geometrical isomers
  • Structure elucidation
  • Unsaturated fatty acid

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