Therefore, the high complexity of the
matrix makes the clean-up of the extracts almost mandatory to obtain reliable results, except in cases where the sensitivity of the method is high enough to offer the option of simply diluting the extracts. Hence, clean-up is an important step when extracts are analysed with TOF, which has showed lower sensitivity than other HRMS analyser, such as Orbitrap, in certain food applications [38]. Bearing in mind this and the results obtained in the first experiment, an additional clean-up stage was checked. In this way, three fast clean-up procedures were evaluated: (1) d-SPE with Florisil, (2) d-SPE with C18 and (3) SPE employing Florisil cartridges. For d-SPE clean-ups, 1 mL of sample extract was taken to an Eppendorf tube containing 100 mg of Florisil or C18 dispersive phase. The mixture was shaken in a vortex for 1 min and then it was centrifuged for 5 min at 4,500 rpm (2,264×g). The final extract was collected and was placed in a vial. To test SPE clean-up, 1 mL of the extract was loaded onto the Florisil cartridge. The final extract was collected and placed in a vial for injection. The obtained results are shown in Fig. 2, and it can be observed that they are similar regarding the number of extracted compounds, although slightly better recovery results were obtained when SPE-Florisil was used. Furthermore, the clean-up with Florisil cartridges provided ‘cleaner’ chromatograms (Fig. 1b) with an apparent lower number of interference peaks and slightly better sensibility. Therefore, the generic approach using a SPE clean-up step was chosen and tested at lower concentrations in the further validation: 10 μg kg−1 and 50 μg kg−1.