Direct metabolic fingerprinting of olive oils using STELDI-MS

A new and rapid approach for analysis of olive oil has been developed using sorptive tape-like extraction in combination with laser desorption ionization mass spectrometry (STELDI-MS). This powerful combination has some great advantages, as no-separation steps, solvent-free, matrix-free, and no sample preparation. The olive oil compounds are analyzed by LDI-MS, directly from the sample spot in a thin-layer chromatography (TLC) plate. Chosen samples represent products commonly used as adulterants in extra virgin olive oil (EVOO) and the main monitored ions were lipid adulteration markers. Analytical procedures consisted of profiling the main fatty acids (m/z 255 – palmitic acid, 279 – linoleic acid, 281 – oleic acid and 283 – stearic acid), triacylglycerols (m/z 901 – LLL and 907 – OOO) and some phenolic compounds (m/z 169 – gallic acid, 193 – ferulic acid and 195 – 2(4-hydroxyphenyl) ethyl acetate) in extra virgin olive oil (EVOO), olive oil (OO), hazelnut oil (HO) and soybean oil (SO). Compound identification was confirmed by analysis of collision-induced dissociation (CID) products in positive (ion [M+Na]⁺) and negative mode (ion [M−H]⁻). This method is simple, fast and efficient in identifying compounds that can be used to recognize different levels of adulteration, oxidation and hydrolysis of vegetables oils.