TY - JOUR
T1 - Discrimination Among Geometrical Isomers of α-Linolenic Acid Methyl Ester Using Low Energy Electron Ionization Mass Spectrometry
AU - Hejazi, Leila
AU - Ebrahimi, Diako
AU - Guilhaus, Michael
AU - Hibbert, D. Brynn
PY - 2009/7
Y1 - 2009/7
N2 - There is a consensus that electron impact ionization mass spectrometry is not capable of discriminating among geometrical isomers of unsaturated fatty acid methyl esters (and in general olefinic compounds). In this paper, we report the identification of all eight geometrical isomers of α-linolenic acid, one of the few essential ω-3 fatty acids that has attracted great attention, using low-energy electron ionization mass spectrometry. Three electron energies 70, 50, and 30 eV were studied and the mass spectrum of each isomer was obtained from the analysis of different concentrations of a standard mixture of α-linolenic acid methyl ester geometrical isomers to ensure the robustness of the method. Principal component analysis was employed to model the complex variation of m/z intensities across the isomers. Only using the data of 30 eV energy was complete differentiation among geometrical isomers observed. The unique cleavage pattern of the α-linolenic acid methyl ester isomers leading to a benzenium ion structure is discussed and general fragmentation rules are derived using the mass spectra of over 300 compounds with different kinds and levels of unsaturation. Application of the proposed method is not limited to α-linolenic acid. It can potentially be used to identify the geometrical isomers of any compounds with an olefinic chain.
AB - There is a consensus that electron impact ionization mass spectrometry is not capable of discriminating among geometrical isomers of unsaturated fatty acid methyl esters (and in general olefinic compounds). In this paper, we report the identification of all eight geometrical isomers of α-linolenic acid, one of the few essential ω-3 fatty acids that has attracted great attention, using low-energy electron ionization mass spectrometry. Three electron energies 70, 50, and 30 eV were studied and the mass spectrum of each isomer was obtained from the analysis of different concentrations of a standard mixture of α-linolenic acid methyl ester geometrical isomers to ensure the robustness of the method. Principal component analysis was employed to model the complex variation of m/z intensities across the isomers. Only using the data of 30 eV energy was complete differentiation among geometrical isomers observed. The unique cleavage pattern of the α-linolenic acid methyl ester isomers leading to a benzenium ion structure is discussed and general fragmentation rules are derived using the mass spectra of over 300 compounds with different kinds and levels of unsaturation. Application of the proposed method is not limited to α-linolenic acid. It can potentially be used to identify the geometrical isomers of any compounds with an olefinic chain.
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U2 - 10.1016/j.jasms.2009.02.027
DO - 10.1016/j.jasms.2009.02.027
M3 - Article
C2 - 19318230
AN - SCOPUS:67649336591
SN - 1044-0305
VL - 20
SP - 1272
EP - 1280
JO - Journal of the American Society for Mass Spectrometry
JF - Journal of the American Society for Mass Spectrometry
IS - 7
ER -