A Greener Approach to Sensitive Detection of PAHs in Our Food
LC-GC-MS technique could help analysts to overcome issues with existing detection methods
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A myriad of chemicals have been identified that pose risks to human health when they enter the food chain, from pesticides and veterinary drug residues to additives, contaminants and food contact materials. To try and keep consumers safe, public health authorities such as the European Commission and United States Food and Drug Administration set stringent limits on acceptable levels of certain compounds that are permissible in foodstuffs.
To monitor the presence and levels of these compounds, analytical testing techniques and methodologies specific to the target and suitable for the sample medium are essential. The subsequent implementation of these testing procedures thus forms a vital part of the food production and supply chain. Included among the contaminants tested for are polycyclic aromatic hydrocarbons (PAHs), a group of chemical compounds that comprise carbon and hydrogen molecules in a cyclic arrangement.
We spoke to Dr. Mariosimone Zoccali, assistant professor in analytical chemistry at the University of Messina, about a new approach, recently published in Analytica Chimica Acta, that he and his team have been working on to detect PAHs in extra virgin olive oil (EVOO).
Why is the detection of PAHs in food products, and particularly oils, so important?
Mariosimone Zoccali, PhD (MZ):
Detecting PAHs in vegetables oils, particularly in EVOO, is essential because PAHs are a diverse class of organic compounds with known health risks, such as carcinogenicity and genotoxicity. These compounds are primarily introduced into food products through environmental contamination during processes such as milling, air pollution from vehicle emissions and direct contact with contaminated soil. Oils, due to their lipid content, easily accumulate PAHs, which readily solubilize in fats. Since dietary intake is a major source of PAH exposure for non-smokers, monitoring these levels in oils is crucial for food safety. The European Commission has established specific maximum allowable limits for PAHs in oils: 2.0 μg/kg for benzo[a]pyrene and 10.0 μg/kg for the sum of four high-priority PAHs (benzo[a]pyrene, benz[a]anthracene, benzo[b]fluoranthene and chrysene, known as PAH4). These limits highlight the critical need for reliable, sensitive methods to quantify PAHs in oils to protect public health and comply with regulatory standards.
KS:
Methods already exist for PAHs detection, why was a new approach sought? What issues were you hoping to overcome, or areas were you wanting to improve on compared with existing methods?
MZ:
Existing PAH detection methods, such as high-performance liquid chromatography (HPLC) and gas chromatography (GC) hyphenated to different kinds of detectors (e.g., mass spectrometry (MS)), often require complex, multi-step sample preparation that involves significant organic solvent use. This is not only time-consuming and labor-intensive but also environmentally detrimental. Most methods require off-line sample extraction and purification steps, making them less efficient and prone to contamination from external sources.
This study aimed to overcome these issues by developing a streamlined “greener” approach that minimizes solvent consumption and reduces sample handling. A new method was also necessary to improve selectivity and detectability in complex matrices like oils, where high lipid content can lead to interference in detection. The LC-GC-MS technique employed here, especially using the pseudo-multiple reaction monitoring (p-MRM) mode, was chosen to enhance sensitivity, reduce background noise and improve detection limits to meet and exceed current EU requirements.
KS:
How did you approach this challenge? You chose to use LC-GC-MS. Can you tell us more about the methods tested and why you chose this technique?
MZ:
To address the challenges of PAH detection in EVOO, we employed an LC-GC-MS method, with a triple quadrupole mass spectrometer. This technique was selected because of its ability to manage complex samples with minimal preparation while maintaining high sensitivity. Sample preparation was simplified to a single dilution step, avoiding the need for labor-intensive extraction or clean-up, which reduced organic solvent usage to below 8 mL per sample. Moreover, we tested two acquisition modes: the traditional selected-ion-monitoring (SIM) and the advanced p-MRM mode. Results showed that p-MRM outperformed SIM by enhancing specificity and signal-to-noise ratios – essential for accurately detecting PAHs at trace levels. This mode allowed the system to monitor transitions with no mass loss, reducing interference from other ions, which was particularly useful in handling EVOO’s lipid-rich matrix.
KS:
Please tell us about the key findings of the study.
MZ:
The method developed showed high precision and accuracy in detecting and quantifying 16 priority PAHs, including those listed in EU regulations, across a concentration range of 1–200 μg/kg. In tests with EVOO samples, the p-MRM mode allowed for lower detection limits than those required by EU standards, making it possible to detect even minimal PAH contamination levels. Among the 10 EVOO samples analyzed, 3 contained detectable PAHs, though at very low concentrations. The study also showed high reproducibility across both intra- and inter-day analyses, indicating the method’s reliability for routine use. Matrix effects, while present, were manageable within this method’s parameters, as the technique’s selectivity minimized the impact of co-eluting compounds, thus ensuring compliance with stringent EU limits.
KS:
What do these results mean for other scientists working in this field? Do these results have wider implications beyond the analysis of EVOO?
MZ:
This study’s success in minimizing solvent consumption and simplifying sample preparation sets a valuable precedent for food analysis research, especially in alignment with green chemistry practices. The developed LC-GC-MS method, with its high sensitivity, could be applied beyond EVOO to other vegetable oils and lipid-rich foods prone to PAH contamination, providing a template for sustainable, high-precision analysis in the food industry. The technique’s robustness and adaptability for other matrices can help laboratories standardize PAH testing protocols, potentially influencing future guidelines and regulations for food safety monitoring globally. The use of p-MRM acquisition also encourages the broader adoption of this technique in settings where matrix effects typically hinder PAH quantification, demonstrating how advanced MS approaches can improve analytical specificity in challenging samples.
KS:
Were there any limitations to the current study or challenges that remain and if so, how are you hoping to address them in the future?
MZ:
While the method proved highly effective, certain limitations remain, particularly regarding matrix effects. Lipid-rich matrices, like EVOO, contain compounds (e.g., squalene and triglycerides) that can interfere with analyte ionization, leading to signal suppression and affecting sensitivity. The study reported an average signal suppression of 53% in p-MRM mode, indicating the need for continued refinement in managing matrix effects. Future research may focus on further minimizing these effects, potentially through refined chromatography techniques or more selective ionization methods. Additionally, as PAH contamination can vary widely across different food matrices, adapting this method for use in diverse foods could expand its applicability, helping to establish more comprehensive safety assessments across the food industry.
I would also like to underline that the research was funded by a Research Projects of Relevant National Interest and the National Plan of Recovery and Resilience (PRIN PNRR) project called 'RELIABLE' Green analytical methods for PAHs detection in EVOO: From laboratory to smart label (CODE: P2022842MJ_001; CUP J53D23014520001). The 'RELIABLE' project aims to develop sustainable analytical methods based on the use of advanced chromatographic techniques coupled with MS, integrated with 'food grade' electrochemical sensors, to create a fast, selective, sensitive and reliable platform for the detection of contaminants such as PAHs in EVOO, which can also be used by producers or consumers through oil immersion.
