Photoelectron resonance capture ionization mass spectrometry of fatty acids in olive oil



Photoelectron resonance capture ionization (PERCI) mass spectrometry has been developed for the direct online analysis of organics, including lipids. Analysis is conducted without the need for sample preparation or chemical derivatization such as methylation, foregoing the use of harmful or toxic chemicals. PERCI is currently being adapted towards the analysis of edible oils. Herein, as a proof of principle of the simplicity and potential utility of this method towards the analysis of edible oils, we present the analysis of the prevalent fatty acids (FA) in Tuscan extra-virgin olive oil along with triolein and linolenic acid (LNA) standards. Ionization of olive oil results in little fragmentation of the prevalent FA, which are measured as their molecular ions, [FA–H]. The relative concentrations of these FA determined by PERCI were in good agreement with established values. Further utility of PERCI was demonstrated by interrogation of ozonized LNA and olive oil, with 13 of the 18 anticipated products of the ozonolysis of LNA measured as their molecular anions, [M–H]. Similarly, the PERCI mass spectrum of ozonized olive oil showed all the anticipated ions of the predominant FA, oleic acid, as well as many molecular ions arising from less abundant unsaturated FA.