Simple and sensitive monitoring of polycyclic aromatic hydrocarbons in edible oils by polydimethylsiloxane/pyrazine-based hyper-crosslinked polymer coated stir bar sorptive extraction followed by gas chromatography-mass spectrometry detection

Background: Edible oils are susceptible to contamination with polycyclic aromatic hydrocarbons (PAHs) throughout production, storage, and transportation processes due to their lipophilic nature. The necessity of quantifying PAHs present in complex oil matrices at trace levels, which bind strongly to impurities in oil matrices, poses a major challenge to the accurate quantification of these contaminants. Therefore, the development of straightforward and effective methods for the separation and enrichment of PAHs in oil samples prior to instrumental analysis is paramount to guaranteeing food safety.

Results: A pyrazine embedded hyper-crosslinked porous polymer, HCP_Pz-TPB, was synthesized via a Friedel-Crafts reaction, utilizing triphenylbenzene (TPB) as the monomer and 2,5-dibromomethylpyrazine as the cross-linking reagent. The material was combined with polydimethylsiloxane (PDMS) using the sol-gel method, and applied as a coating to a dumbbell-shaped stir bar prepared in-house. Using stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS), 15 PAHs in edible oils were successfully quantified. Optimal conditions for the extraction of PAHs were experimentally investigated, with factors such as stirring rate, extraction time, extraction temperature, desorption solvent, and desorption time systematically optimized. The final method demonstrated a broad linear range (0.12-150 ng g^-1), and low limits of detection (0.04-0.28 ng g^-1). The recoveries of PAHs in real edible oil samples ranged from 83.14 % to 128.01 %, with relative standard deviations (RSDs) below 13.47 %.

Significance: This method simplifies PAH extraction by eliminating steps such as saponification, liquid-liquid extraction, drying, and re-dissolution, thus reducing potential analyte loss and errors associated with the inclusion of multiple pretreatment steps typical of conventional methods reported in the literature. Notably, the adsorbent materials prepared in this study can be reused up to 30 times, underscoring its sustainability. The proposed research broadens the diversity of coating choices for SBSE applications while offering a streamlined, cost-effective, and greener alternative for PAH determinations in edible oils via SBSE/GC-MS.