Tyrosol and Hydroxytyrosol Determination in Extra Virgin Olive Oil with Direct Liquid Electron Ionization-Tandem Mass Spectrometry

Abstract

Extra virgin olive oil (EVOO) is one of the main ingredients of the Mediterranean diet. It is claimed as a functional food for its unique content of health-promoting compounds. Tyrosol (Tyr), Hydroxytyrosol (Htyr), and their phenolic derivatives present in EVOO show beneficial properties, and their identification and quantification, both in their free form and after the hydrolysis of more complex precursors, are important to certify its quality. An alternative method for quantifying free and total Tyr and Htyr in EVOO is presented using an LC–MS interface based on electron ionization (EI), called liquid electron ionization (LEI). This method requires neither sample preparation nor chromatography; the sample is diluted and injected. The selectivity and sensitivity were assessed in multiple reaction monitoring mode (MRM), obtaining confirmation and quantification in actual samples ranging from 5 to 11 mg/Kg for the free forms and from 32 to 80 mg/Kg for their total amount after hydrolysis. Two MS/MS transitions were acquired for both compounds using the Q/q ratios as confirmatory parameters. Standard addition calibration curves demonstrated optimal linearity and negligible matrix effects, allowing a correct quantification even without expensive and difficult to find labeled internal standards. After several weeks of operation, the system’s repeatability was excellent, with an intraday RSD (%) spanning from five to nine and an interday RSD (%) spanning from 9 to 11.

Sample Injection for Real-Time Analysis (SIRTA) Using GC-MS with Cold EI

“…Standard EI ion sources were used during solvent elution such as in electron ionization LC-MS systems (EI-LC-MS) by various researchers, including the group led by Cappiello, as evidenced by their publications. , EI provides a few unique benefits for LC-MS in comparison with ESI and APCI such as library-based identification including at the isomer level, ionization of nonpolar compounds, and the elimination of ion suppression effects. Notably, they have also implemented flow-injection analysis directly into the standard EI ion source without LC separation, − and ref shares similarities with this paper. However, in contrast to SIRTA with Cold EI, flow injection in EI-LC-MS systems required added hardware.…”

“…However, in contrast to SIRTA with Cold EI, flow injection in EI-LC-MS systems required added hardware. Furthermore, flow injection with standard EI typically uses a low, sub-μL/min solvent flow rate (0.4 μL/min , ) and thus can experience relatively long void time. We developed and employed electron ionization LC-MS with Cold EI either with separation or in its flow-injection analysis mode .…”

Correlation Analysis between Dietary Intake of Tyrosols and Their Food Sources and Urinary Excretion of Tyrosol and Hydroxytyrosol in a European Population

“…In fact, these correlations were consistent with previous studies demonstrating the presence of Tyr and/or OHTyr in human or animal urine and plasma after the consumption of the aforementioned foods. Table olives and olive oil are rich sources of Tyr and OHTyr; curiously, whereas in table olives, the amounts of OHTyr are usually higher than Tyr, in olive oil, the opposite occurs [ 26 , 27 ]. Likewise, regardless of the food source, it was observed that OHTyr excretions were usually higher than those of Tyr in urine and plasma [ 13 , 28 ].…”

Exploring Negative Chemical Ionization of Per- and Polyfluoroalkyl Substances via a Liquid Electron Ionization LC-MS Interface

“…As demonstrated in earlier studies, ACN was preferred as the nonpolar solvent over MeOH due to prior experimental evidence that it is best suited to the LEI interface. 37,38,57 All optimized parameters are listed in section 2.5. The base peaks observed in the scan spectra of PFASs were selected as m/z ions for SIM analysis (Table 2).…”

“…Only a few research articles refer to NCI fragmentation 59,60. The fragmentation was governed by the dissociative electron capture mechanism, primarily resulting in the loss of −CH 3 and −COOH terminal groups, along with consecutive loss of fluorine atoms in the fragments, leading to the formation of double and triple carbon−carbon bonds in negatively charged fragments 57. The subsequent loss of fluorine atoms in the fragments, resulting from the impact of low-energy electrons with the analytes, is responsible for most signals appearing in the mass spectrum.…”