Chromatography-Based Thermal Desorption Method Enables Rapid Screening of Contaminants in Recycled Plastics

As only approximately 10% of plastic products are recycled globally,¹ there is a need for improved technologies grounded in a deeper understanding of material properties. In the packaging sector—the largest driver of plastics demand—odor and potential safety concerns continue to hinder high-quality recycling. Traditional characterization methods typically rely on chromatography and require extensive sample preparation.

A gas chromatography system equipped with thermal desorption and dual flame ionization and mass spectrometric detection (ATD-GC/FID-MS) was established by researchers at Johannes Kepler University Linz (Austria) to analyze recycled materials directly, thereby accelerating technology adaptation and guiding follow-up analyses. A paper based on their work was published in Polymers.¹

Why Is It Difficult to Ensure Chemical Safety in Recycled Plastics?

The recycling of high-quality plastics still faces several barriers that need to be addressed. Considering the chemical cleanliness of the recycled materials, which is crucial for materials that come in contact with medical and food products, any contaminants to the product can result in unpleasant odors or pose health risks to consumers.^2-5 Technologies for the pre-treatment and cleaning of recycled materials require improvements for overcoming these barriers and increasing recycling rates, which, in turn, requires characterization methods for the gathering of knowledge about material inputs (which often fluctuate)and the resulting properties of the recycled materials.

The characterization of contaminants in post-consumer materials remains a challenge. There is an enormous diversity of unknown compounds present in post-consumer material streams, and this diversity demands a great deal of effort to quantitatively extract and isolate them.^6,7 However, the identification and absolute quantification can often be difficult due to analytical standards which are not available for every compound or degradation product formed during recycling. Still, this knowledge is crucial for being able to predict contaminant migration and assessing associated hazards.⁸

What Did the Researchers Do to Meet This Challenge?

For calibration and validation, the researchers introduced liquid standards into TenaxTA-filled tubes via a packed column injector and compared to a loading rig. The injector exhibited losses for higher-molar-mass compounds and solvent-dependent signal shifts. A storage study on compounded recycled polypropylene stored under various conditions showed that samples not frozen in sealed containers should be analyzed within 30 days. Experiments with varying sample geometries demonstrated that higher surface-to-volume ratios increase volatile release and variability in results, highlighting the need for uniform shapes.¹

“Overall,” write the authors of the paper,¹ “ATD-GC/FID-MS provides a rapid screening tool for recyclate quality control and supports the improvement of recycling technologies.”

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References

1. Czaker, S.; Fischer, J. Thermal Desorption Used to Characterize Volatile Organic Compounds of Recycled Plastics. Polymers (Basel) 2026, 18 (7), 792. DOI: 10.3390/polym18070792
2. Cecon, V. S.; Da Silva, P. F.; Curtzwiler, G. W. et al. The Challenges in Recycling Post-Consumer Polyolefins for Food Contact Applications: A Review. Resour. Conserv. Recycl. 2021, 167, 105422. DOI: 10.1016/j.resconrec.2021.105422
3. Fuller, J.; White, D.; Yi, H. et al. Analysis of Volatile Compounds Causing Undesirable Odors in a Polypropylene—High-Density Polyethylene Recycled Plastic Resin with Solid-Phase Microextraction. Chemosphere 2020, 260, 127589. DOI: 10.1016/j.chemosphere.2020.127589
4. Zeng, S.-F.; Zeng, Y.; Guo, P. et al. Characterization of Odors and Volatile Organic Compounds Changes to Recycled High-Density Polyethylene Through Mechanical Recycling. Polym. Degrad. Stab. 2023, 208, 110263. DOI: 10.1016/j.polymdegradstab.2023.110263
5. Commission Regulation (EU) No 10/2011 of 14 January 2011 on Plastic Materials and Articles Intended to Come into Contact with Food; European Commission: Brussels, Belgium, 2025.
6. Franz, R.; Mauer, A.; Welle, F. European Survey on Post-Consumer Poly(ethylene terephthalate) (PET) Materials to Determine Contamination Levels and Maximum Consumer Exposure from Food Packages Made from Recycled PET. Food Addit. Contam. 2004, 21, 265–286. DOI: 10.1080/02652030310001655489
7. Cabanes, A.; Valdés, F.J.; Fullana, A. A Review on VOCs from Recycled Plastics. Sustain. Mater. Technol. 2020, 25, e00179. DOI: 10.1016/j.susmat.2020.e00179
8. Arvanitoyannis, I.S.; Kotsanopoulos, K.V. Migration Phenomenon in Food Packaging. Food–Package Interactions, Mechanisms, Types of Migrants, Testing and Relative Legislation—A Review. Food Bioprocess Technol. 2014, 7, 21–36. DOI: 10.1007/s11947-013-1106-8