Extraction procedure
Extra-virgin olive, sunflower, maize, linseed and sesame oils
were collected in retail shops or department stores from Granada
(Spain). The QuEChERS procedure was as follows: 3 g of sample
was placed in a 50-mL falcon tube. Subsequently, 7 mL of water
and 10 mL of MeCN were simultaneously added to the tube, and it
was mechanically shaken for 10 min. QuEChERS extraction salts
(4 g MgSO4, 1 g NaCl) were added to the tube and it was shaken
again for another 10 min. After that, the sample was centrifuged at
5000 rpm for 5 min. Then, 3 mL of the supernatant was transferred
to the dispersive tube containing 150 mg of Z-Sepþ and
150 mg of MgSO4, stirred in vortex for 2 min and centrifuged
(5000 rpm for 5 min). An aliquot of 2 mL of the MeCN extract was
transferred to a vial, dried under a gentle N2 stream and the final
residue was re-dissolved with 500 mL of H2O:MeOH (80:20 v/v),
shaken by vortex for 2 min, filtered through syringe filters and
injected into the UHPLC–MS/MS system.