Authenticity Assessment of Imported Olive Oil Using Direct Analysis in Real Time Mass Spectrometry

摘要

For the first time HRMS coupled with DART has been employed for authentication studies of olive oil. The ultra-high resolving power of Q-Exactive allowed for more details to disclose, which helped classification of olive oil samples. The spectra profiles of EVOO and ROO samples were completely different in mass range of m/z 50-500 both in positive and negative ion mode. A series of marker ions were shown in all EVOO samples which were not reported by previous studies. One possible reason was that the use of hexane made more non-polar components being extracted. TAGs spectra were not discussed because they were less diagnostic. Some marker components reported previously as elenoic acid, sinapic acid, oleocanthal and ligstroside aglycone present in our studies. We report for the first time that some markers show more than one forms, e.g. elenoic acid has ions of [M+H]~+ and [M+NH_4]~+, while oleocanthal and ligstroside aglycone are both observed as [M+H]~+, [M+NH_4]~+ and [M+H-H_2O]~+. These markers present in all EVOO samples with slight differences in spectra profile and their abundances are used to easily differentiate olive oil grade. DART coupled to Q-Exactive proves to be a powerful tool for rapid characterization of olive oil. The follow up experiments are being focused on distinguishing admixtures of lower grade olive oils with EVOO.