Extech 2026 Preview: The Benefits of GC×GC–MS to Analyze Recycled Polyolefines in Food Contact Material Applications

Your talk at Extech¹ is focused on the characterization of recycled polyolefines as future food contact materials. What is the rationale behind this research?
This research is directly linked to the goals of the European Union and its European Green Deal, which aims to make Europe the first climate-neutral continent by 2050 and to decouple economic growth from resource use.² To support this transition, significant regulatory changes have been introduced: Regulation 2025/40 (PPWR)³ sets minimum recycled content requirements for all plastic packaging, while Regulation 2022/1616 defines “Novel Technologies” to promote the development of recycling methods and facilitate the market introduction of recycled products.⁴

While there are recycling technologies available producing recycled PET considered safe for food contact, polyolefins remain a major challenge. Research has shown that certain recycled polyolefins exhibit genotoxic activity in an Ames MPF test, though the underlying causes are largely unknown. Moreover, the analytical strategies for safety assessment are not yet fully established, and data on typical input contamination, effective decontamination technologies, and their efficiencies are still limited. We hope to be able to fill some of these gaps in our current research.

What types of sample preparation and chromatography do you use in this research? How do they influence the chromatographic profile?
We combined mostly three sample preparation strategies: solvent extraction, migration testing and headspace solid-phase microextraction (HS-SPME). Solvent extraction aims for comprehensive recovery of extractables, providing a broad view of substances present—depending on the solvent used—but may overestimate realistic exposure. Migration testing simulates transfer in actual use-conditions and aligns better with exposure-oriented safety evaluation and regulatory compliance. HS-SPME efficiently captures volatile species and we use it for sensitive detection of odorous trace components to evaluate the smell of the material. The chromatographic techniques are based on one dimensional gas chromatography coupled to flame ionization detection (GC–FID) or mass spectrometry (GC–MS) and comprehensive two-dimensional gas chromatography mass spectrometry (GC×GC–MS), but also on liquid chromatography mass spectrometry (LC–MS) to be able to cover the broad range of substances and polarities present.

What advantages does comprehensive two-dimensional GC (GC×GC–MS) provide over conventional GC–MS in resolving complex mixtures from recycled packaging materials?
Conventional GC–MS often struggles with unresolved complex mixtures, as the sheer chemical complexity of PCR plastics exceeds the separation capacity of a single column. The major advantages of GC×GC are captured in the well-known “5S” concept: it resolves co-eluting compounds by coupling orthogonal columns, enhancing separation and selectivity; it improves detection of trace contaminants through peak focusing (sensitivity); it enables the analysis of a large number of compounds in a single run (speed); and it produces structured chromatograms that reveal chemical patterns across additives, oligomers, and degradation products. Overall, GC×GC provides a more complete and interpretable chemical profile, which is essential for the quality assessment of recycled materials.

Which classes of contaminants are most frequently detected in recycled polyolefins? How effectively can chromatographic methods distinguish between polymer-related compounds and external contaminants?
It is important to mention that “recycled polyolefins” is a very general term for a very heterogenous material stock. We have to keep in mind, that during recycling, flakes from different quality and origin can be mixed together and are co-extruded into new products. Therefore, optimizing the entire recycling process— from the source of waste to the efficiency of sorting, washing and decontamination—is crucial. It is directly related to chemical composition and complexity we observe in the chromatograms. It determines not only the quality of the final material but also whether it may be suitable for food contact applications. In general, the chemical profile can be divided into polymer-related compounds, including residual monomers, oligomers, and additives like stabilizers and plasticizers, as well as degradation and reaction products of these substances. Additionally, external contaminants such as food residues or cosmetic ingredients can be present, and some compounds may originate from both intrinsic or extrinsic sources. GC×GC fingerprinting is a powerful analytical tool that helps classify and profile these compounds, but complete certainty regarding their origin is rarely achievable.

Which analytical challenges remain in detection of potential genotoxic compounds and in linking chromatographically detected compounds to positive Ames MPF genotoxicity results?
Major challenges are that genotoxic compounds are a heterogenous compound class, that do not mark themselves as being genotoxic in the chromatogram (unfortunately). Modern instrumental analysis can separate and detect those individual compounds, but definitive identification and a reliable risk assessment are frequently not achievable. In contrast, the Ames MPF bioassay provides only a binary yes/no result for the mutagenic activity of a sample extract. The remaining challenge, therefore, is to link specific compounds or chemical classes detected by instrumental analysis to the positive signal observed in the bioassay.

How can chromatographic techniques be optimized to identify compounds responsible for off-odours in recycled polyolefin food-contact materials?
We also see for the volatile, odour-active compounds that a GC×GC separation is often preferred due to the overloading with the intrinsic aliphatics in one dimensional analysis. Regarding sample preparation, a lot has been studied and reported in the scientific literature, comparing different approaches, such as head space-solid phase micro extraction (HS-SPME) and conventional static HS or purge and trap attempts. Furthermore, GC conditions have to be optimized, i.e. by using cryogenic oven cooling to detect the most volatile substances, by using on-column injectors to prevent artefact formations.

What analytical workflow combining GC and LC techniques is most effective for assessing the overall safety and quality of recycled packaging materials?
We know that there is currently not a single technique available that can cover all aspects needed for a proper safety assessment or compliance testing. Our approach is to combine GC-based methods for volatile and semi-volatile compounds, with LC-based methods for non-volatile or polar substances utilising the three discussed sample preparation methods. This captures a broad chemical space. When paired with bioassays, it allows us to link chemical composition to potential biological effects, providing a better assessment of safety and quality.

Do you find that the sample preparation stage in chromatography is sometimes overlooked? Should there be more research into sample preparation? If so, in what areas?
Yes, the sample preparation stage is often underappreciated, even though it largely determines which portion of a complex mixture is actually measured. In my view, it is just as important as developing advanced chromatographic or detection techniques, because it determines whether the data truly reflects the chemical space. For recycled polyolefins, we currently lack standardized workflows optimized for this heterogeneous material. Samples are often present as flakes or pellets and require homogenization before further treatment; a variety of sample preparation and analysis techniques are applied across different labs. Moreover, industry would greatly benefit from miniaturized, high-throughput methods, ideally fully automated, to enable consistent process control. Clearly, there is still a lot of work to be done in this area.

Is there anything else you want to add in relation to Extech 2026?
I am very much looking forward to ExTech 2026, to an inspiring scientific program, engaging discussions and to novel strategies and emerging trends in sample preparation.

References
1. https://www.extech2026.uliege.be/cms/c_20456371/en/extech-2026
2. European Commission – Communication from the commission of the European parliament, the European council, the council, the European economic and social committee and the committee of the regions: The European Green Deal. Brussels, 11.12.2019. COM(2019) 640 final.
3. Regulation (EU) 2025/40 of the European Parliament and of the Council of 19 December 2024 on packaging and packaging waste, amending Regulation (EU) 2019/1020 and Directive (EU) 2019/904, and repealing Directive 94/62/EC. PE/73/2024/REV/1. OJ L, 2025/40, 22.1.2025, ELI: http://data.europa.eu/eli/reg/2025/40/oj.
4. Commission Regulation (EU) 2022/1616 of 15 September 2022 on recycled plastic materials and articles intended to come into contact with foods, and repealing Regulation (EC) No 282/2008. C/2022/6146. OJ L 243, 20.9.2022, pp. 3–46 ELI: http://data.europa.eu/eli/reg/2022/1616/oj.