Abstract: A new method was developed for the determination of 30 polycyclic aromatic hydrocarbons (PAHs) in edible vegetable oils by gas chromatography-tandem mass spectrometry (GC-MS/MS) after freeze defatting. Six deuterium labeled PAHs were used as internal standards. Samples were extracted with acetonitrile-acetone (4:1, V/V) by vortex mixing in a centrifuge tube followed by 5 min centrifugation at 10 000 r/min and freezing at ?80 ℃ for fat solidification. The extract was evaporated in a rotary vacuum evaporator and blown to dryness under nitrogen. The residue was re-dissolved in dichloromethane, and detected using GC-MS/MS in the multiple reaction monitoring mode. The calibration curves for all the analytes showed good linearity (R2 > 0.998) in their respective concentration ranges. The limits of detection (LODs) and limits of quantitation (LOQs) for 30 PAHs were in the ranges of 0.10–1.83 and 0.35–6.11 μg/kg, respectively. The recoveries varied from 67.77% to 119.28% with relative standard deviation (RSDs) of 1.18%–12.47% (n = 6) at spiked levels of 5, 20 and 50 μg/kg. The levels of 30 PAHs in 38 commercial edible vegetable oil samples from 11 different species were investigated using the GC-MS/MS method. The results showed that naphthalene, 2-methylnaphthalene, 1-methylnaphthalene, biphenyl, 2,6-bimethylnaphthalene, acenaphthylene, acenaphthene, 2,3,6-trimethylnaphthalene, fluorene, dibenzothiophene, phenanthrene, anthracene, 1-methylphenanthrene, fluoranthene, pyrene, cyclopenta[c,d]pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene and benzo[a]pyrene were detected in all samples; the detection rates of 5-methylchrysene, perylene, indeno[1,2,3-c,d]pyrene, dibenz[a,h]anthrancene, benzo[g,h,i]perylene and dibenzo[a,l]pyrene were 86.84%, 63.16%, 81.58%, 21.05%, 81.58% and 26.32%, respectively; neither dibenzo[a,e]pyrene nor dibenzo[a,h]pyrene were detected in any of the samples. The total concentrations of 30 PAHs ranged from 92.56 to 905.16 μg/kg, and BAP varied from 1.94 to 7.40 μg/kg, which were at safe levels according to the limit standard.

Key words: edible vegetable oil, freeze defatting, polycyclic aromatic hydrocarbons, gas chromatography-tandem mass spectrometry (GC-MS/MS)