Development of candidate reference method for accurate determination of four polycyclic aromatic hydrocarbons in olive oil via gas chromatography/high-resolution mass spectrometry using C-labeled internal standards.

We developed an isotope-dilution gas chromatography/high-resolution mass spectrometry (ID-GC/HRMS) method for the accurate determination of four polycyclic aromatic hydrocarbons (PAHs) in olive oil. The clean-up steps were optimized to sufficiently remove co-extracted oil matrix using the EZ-POP NP dual-layer and NH solid-phase extraction (SPE) cartridges. However, the cleaned sample still contained some matrix residues, which caused a bias. When C-labeled PAHs were used as the internal standards instead of deuterated PAHs, the recovery results improved in both low- and high-resolution MS conditions. Furthermore, the HRMS analysis facilitated to obtain more accurate results. The accuracy and precision of the optimized ID-GC/HRMS method were validated using PAH-fortified (0.5, 3, and 6 μg/kg) olive oil. The recoveries and relative standard deviations obtained for all the PAHs/levels were 97.5-102% and ~1%, respectively. Measurement uncertainties were generally within 5% (with a 95% confidence level).