Characterization of α‐ and γ‐linolenic acid oils by reversed‐phase high‐performance liquid chromatography‐atmospheric pressure chemical ionization mass spectrometry

Triacylglycerols of oils rich in α‐ and/or γ‐linolenic acids were analyzed by reversed‐phase high‐performance liquid chromatography (HPLC) coupled with atmospheric pressure chemical ionization mass spectrometry [(APCI)MS]. The (APCI)MS spectra of most triacylglycerols exhibited [M + H]+ and [M ‐ RCOO]+ ions, which defined the molecular weight and the molecular association of fatty acyl residues, respectively. Reversed‐phase HPLC resulted in, at least, partial separation of triacylglycerols containing α‐ and/or γ‐linolenic acid moieties. Molecules containing α‐linolenic acid residues exhibited a relatively weaker retention by the stationary phase than the corresponding molecules containing γ‐linolenic acid residues. Good separation of triacylglycerols of cloudberry seed oil, evening primrose oil, borage oil, and black‐currant seed oil was achieved. The molecular species identification of separated components was based on the (APCI)MS data as well as on the elution properties of triacylglycerols on reversed‐phase HPLC. This study demonstrated the efficiency of HPLC‐(APCI)MS in determining the molecular species compositions of triacylglycerols in complex natural mixtures. Good quality mass spectra could be extracted even from minor chromatographic peaks representing 0.2% or less of the total triacylglycerols.