Metabolic profiling approach to determine phenolic compounds of virgin olive oil by direct injection and liquid chromatography coupled to mass spectrometry

•Metabolic profiling approach to determine phenolic compounds of olive oil.•Possibility of implementing direct injection of olive oil into the LC.•Exhaustive optimization and evaluation of possible matrix effect.•21 compounds (belonging to different chemical classes) were determined.

A LC-MS method involving direct injection of extra-virgin olive oil (EVOO) - after a simple dilution - for determining its phenolic compounds has been developed. Optimization of the most appropriate solvent for sample dilution, selection of the optimum oil/solvent ratio, and establishment of column cleaning strategy and maximum number of injections were some of the most relevant steps. Then, the analytical parameters of the method were evaluated, establishing LOD (from 3.3 to 31.6 µg/L) and LOQ, precision (RSD values for inter-day repeatability were found between 3.49 and 6.12%), and trueness (within the range 89.9-102.3% for 1.0 mg/L) and checking possible matrix effect (which was no significant). Three kinds of calibration were used: external standard, standard addition and calibration in a phenols-free matrix, which was subsequently applied to quantify the phenolic compounds in 16 EVOOs (from 6 cultivars). A total of 21 compounds were determined without the need of using any extraction protocol.