Analysis of PAHs in Edible Oils by Online Enrichment, Matrix Removal and Fluorescence Detection

Significance of the topic

Polycyclic aromatic hydrocarbons (PAHs) arise from incomplete combustion of organic matter and represent a significant carcinogenic hazard in foodstuffs. Edible plant oils can accumulate PAHs during processing and require sensitive monitoring to ensure consumer safety. European regulations limit benzo(a)pyrene to 2 ppb and four key PAHs to 10 ppb in oils, driving demand for analytical methods that combine sensitivity, speed, and minimal sample preparation.

Objectives and overview of the study

This work demonstrates a direct analysis approach for PAHs in edible oils using an Agilent 1260 Infinity LC System. The method integrates online enrichment, matrix removal, column switching, and sensitive fluorescence detection to meet EU performance criteria without conventional saponification and extraction steps. Calibration and validation address the major PAHs regulated in Europe.

Used methodology and instrumentation

The analytical workflow is based on donor-acceptor complex chromatography for selective trapping of PAHs and backflush matrix removal, followed by gradient separation on a dedicated PAH column and fluorescence detection.

• Agilent 1260 Infinity Quaternary Pump for sample loading, column cleaning and solvent exchange
• Agilent 1260 Infinity Binary Pump for gradient separation of PAHs
• Agilent Standard Autosampler with 100 µL injection at ambient temperature
• Agilent FLD detector with excitation at 260 nm and emission channels at 350, 440, 500 nm
• Thermostatted Column Compartment with 6-port/2-position valves for online column switching
• Enrichment column: Agilent ChromSpher Pi 3.0×80 mm; Analytical column: ZORBAX Eclipse PAH 3.0×250 mm, 5 µm
• Software: Agilent OpenLAB CDS ChemStation Edition for LC and LC/MS Systems

Main results and discussion

Calibration curves for benzo(a)anthracene, chrysene, benzo(b)fluoranthrene and benzo(a)pyrene show excellent linearity from 0.5 to 10 ppb (r2 > 0.9997). Chrysene LOQ was 0.5 ppb (S/N = 10) and LOD 0.2 ppb (S/N = 2.5); calculated LOQs for other PAHs were < 0.31 ppb and LODs < 0.05 ppb, surpassing EU requirements. Precision at 10 ppb yielded retention time RSDs < 0.06 % and peak area RSDs < 1.1 %. Carryover was below 0.2 % for all studied PAHs. Matrix spikes in sunflower oil at 2, 5 and 10 ppb delivered accuracy within 100–120 % and RSD < 2 %, meeting EU criteria.

Benefits and practical application of the method

• No off-line sample preparation or labor-intensive cleanup
• Reduced analysis time through automated online enrichment and column switching
• High sensitivity and compliance with European legislation for PAH monitoring
• Suitable for routine QA/QC and research laboratories

Future trends and possibilities of use

Adaptation of the online enrichment approach to additional oil types and other food matrices can broaden applicability. Coupling with mass spectrometry would extend detection to non-fluorescent contaminants. High-throughput configurations and miniaturized systems may support regulatory screening and real-time quality control in industrial processes.

Conclusion

The presented LC/FLD method offers a rapid, sensitive and robust solution for direct determination of regulated PAHs in edible oils. Online enrichment and automated matrix removal eliminate laborious sample preparation while delivering performance that exceeds EU detection limits, facilitating routine compliance testing.

Reference

1. European Commission Directive 835/2011 on maximum levels of PAHs in foodstuffs.
2. European Commission Directive 2005/10/EC on sampling and analysis of benzo(a)pyrene.
3. K Dost and C Ideli, Determination of PAHs in edible oils by HPLC/UV-VIS detection, Food Chemistry 133 (2012) 193–199.
4. F Van Stijn, M A T Kerkhoff, B G M Vandeginste, Determination of PAHs in edible oils by online donor-acceptor chromatography and HPLC with fluorescence detection, J Chromatogr A, 750 (1996) 263–273.
5. A Barranco, R M Alonso-Salces, E Corta, L A Berrueta, B Gallo, F Vicente, M Sarobe, Comparison of donor-acceptor and alumina columns for PAH clean-up from edible oils, Food Chemistry 86 (2004) 465–474.