Solid phase extraction in the analysis of squalene and tocopherols in olive oil

Solid phase extraction (SPE) is only marginally employed in the official EU methods on the characteristics of olive oil. In the present study a SPE procedure was optimised for the subsequent extraction of squalene and α-tocopherol prior to HPLC of triacylglycerols. Squalene elution from a silica cartridge was achieved with 10 ml of n-hexane whereas α-tocopherol was isolated using 2 × 10 ml n-hexane/diethylether, 99:1, v/v. For both constituents, the precision of the SPE procedure (squalene: CV % = 4.4–6.4, n = 5; α-tocopherol: CV% = 5.3, n = 7) and the mean recovery (squalene: 88 ± 9% and 85 ± 4% for 700 and 4000 mg/kg levels of addition; α-tocopherol: 88 ± 6% and 91 ± 3% for 70 and 225 mg/kg levels of addition, respectively) were satisfactory with regards to those reported using other HPLC procedures with or without sample pretreatment. The results of the present study can be proved useful in the official control of virgin olive oil.