Determination of polycyclic aromatic hydrocarbon compounds in edible oils by GC-MS

Importance of the Topic

This study addresses the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils, a critical task for food safety and regulatory compliance. PAHs are persistent, lipophilic, and potentially carcinogenic compounds formed during incomplete combustion of organic matter. Monitoring PAH levels in oils and fats ensures consumer protection and adherence to the European Union maximum limit of 2.0 μg/kg for benzo[a]pyrene in oils.

Objectives and Study Overview

The primary aim was to develop a selective, sensitive, and reproducible method for quantifying nine priority PAHs in sunflower and canola oils. The study combines molecularly imprinted polymer solid-phase extraction (MIP-SPE) with gas chromatography-mass spectrometry (GC-MS) operated in Selected Ion Monitoring (SIM) mode to achieve low detection limits and high linearity.

Methodology and Instrumentation

Sample preparation involved spiking diluted oil with chrysene-d12 as internal standard (100 ng/mL), followed by extraction using SupelMIP™ SPE–PAHs cartridges. Eluates were dried under nitrogen and reconstituted in methylene chloride. Analytical conditions included:

• Shimadzu GCMS-QP2010Plus with AOC-20i+s liquid autosampler
• Rtx-5MS capillary column (30 m × 0.25 mm, 0.25 μm film)
• Splitless high-pressure injection (4 μL, 250 kPa for 2 min)
• Helium carrier, GC oven ramp from 60 °C to 300 °C
• GC-MS interface at 250 °C, ion source at 200 °C, SIM acquisition

Main Results and Discussion

Calibration curves for nine PAHs were linear over 1–100 ng/mL with correlation coefficients (R2) exceeding 0.999. The high-pressure injection and SIM mode yielded detection limits down to 1 ng/mL. Analysis of sunflower and canola oils revealed PAH concentrations generally below 1 μg/kg; benzo[a]pyrene and some high-molecular-weight PAHs were either trace or not detected. The MIP-SPE provided excellent cleanup, minimizing matrix interferences and ensuring reliable quantitation.

Benefits and Practical Applications

This method offers:

• High selectivity through MIP-SPE extraction
• Enhanced sensitivity via SIM-GC-MS and HPI injection
• Robust linearity across a wide calibration range
• Compliance with EU regulatory thresholds
• Applicability for routine QA/QC and research laboratories

Future Trends and Potential Applications

Advancements may include integration of high-resolution mass spectrometry for greater selectivity, automation of sample preparation to increase throughput, application to other lipid-rich matrices, and deployment of portable GC-MS systems for on-site monitoring. Development of faster SPE materials and alternative extraction techniques could further streamline PAH analysis.

Conclusion

The combined use of PAH-selective MIP-SPE and SIM-mode GC-MS with high-pressure injection has been demonstrated as a robust, sensitive, and selective approach for routine determination of PAHs in edible oils, meeting stringent regulatory requirements.

Instrumentation

• Shimadzu GCMS-QP2010Plus
• AOC-20i+s liquid autosampler
• SupelMIP™ SPE–PAHs cartridges

Reference

Supelco Application Note 192, Extraction & Analysis of PAHs in Olive Oil Using SupelMIP SPE–PAH and GC-MS.