Identification of microplastic particles in environmental water and food using pyrolysis GC with high resolution Orbitrap mass spectrometry

Importance of the Topic

Microplastics have emerged as ubiquitous environmental contaminants due to their small size (1 µm–5 mm) and persistence. They carry toxic additives and adsorb pollutants, entering food chains and posing risks to ecosystems and human health. Rapid and reliable analytical methods are needed to monitor their occurrence and identify polymer types in water and food matrices.

Objectives and Study Overview

This study demonstrates the application of pyrolysis-gas chromatography coupled with high-resolution Orbitrap mass spectrometry (py-GC–Orbitrap MS) for detecting and identifying common polymer particles in stormwater, milk, and meat samples. The goal was to validate the method’s selectivity, sensitivity, and suitability for routine environmental and food analysis.

Methodology and Used Instrumentation

Sample preparation involved filtration of 1 L stormwater through sequential glass fiber filters, freeze-drying and grinding of milk and steak, and spike with deuterated polystyrene as internal standard. A double-shot protocol combined thermal desorption (100 °C to 300 °C) for matrix clean-up with pyrolysis (650 °C) for polymer breakdown. Key instrumentation:

• Frontier Multi-Shot Pyrolyzer EGA/PY-3030D with Auto-Shot Sampler
• Thermo Scientific TRACE 1310 gas chromatograph with TG-5SilMS column (30 m × 0.25 mm × 0.25 µm)
• Thermo Scientific Orbitrap Exploris GC 240 mass spectrometer (EI source, 60 000 FWHM at m/z 200, sub-ppm mass accuracy)
• Software: Compound Discoverer for library screening; Chromeleon CDS for targeted data processing

Main Results and Discussion

Polymer standards (PS, PP, PVC, PMMA, PC, PET) yielded characteristic pyrolysis products such as styrene, styrene dimers, methyl methacrylate, bisphenol A, and benzene. In stormwater, benzene, naphthalene, and fluorene matched PVC signatures. Milk and meat samples exhibited styrene, α-methylstyrene, and toluene but lacked PS dimers/trimers, preventing definitive PS confirmation. High-resolution extraction (±5 ppm) effectively isolated target ions against complex backgrounds, outperforming nominal mass approaches.

Benefits and Practical Applications

The py-GC–Orbitrap workflow enables rapid, automated screening of microplastics in challenging matrices with high selectivity and sensitivity. Double-shot analysis reduces matrix interferences and improves detection of submicron particles below microscopy limits. The method supports environmental monitoring, quality control in food production, and regulatory compliance.

Future Trends and Applications

Advancements may include expanded HRAM libraries for broader polymer coverage, coupling with machine learning for automated pattern recognition, and integration into portable platforms for in-field screening. Further work on quantitative calibration and the analysis of emerging polymer blends will enhance real-world applicability.

Conclusion

Py-GC–Orbitrap MS with double-shot analysis provides a powerful tool for identifying microplastic polymers in complex environmental and food samples. Its high resolution, mass accuracy, and targeted workflows minimize false positives and enable routine surveillance of microplastic pollution.

References

1. He D. et al. Microplastics in terrestrial ecosystems: a scientometric analysis. Sustainability 2020;12:8739.
2. Okoffo E.D. et al. Pressurized liquid extraction combined with double-shot pyrolysis GC–MS for plastics in biosolids. Sci Total Environ 2020;715:136924.
3. Akdogan Z., Guven B. A critical review of microplastics in the environment. Environ Pollut 2019;254:113011.
4. Cai Y. et al. Migration and transformation of microplastics in inland waters. Int J Environ Res Public Health 2022;19:148.
5. Dris R. et al. Microplastic contamination in Greater Paris urban areas. Environ Chem 2015;12:592.
6. Rauert C. et al. Tire wear particles in Australian urban tributary. Environ Sci Technol 2022;56:2421.
7. Tsuge S., Ohtani H., Watanabe C. Pyrolysis-GC/MS data book of synthetic polymers. Elsevier 2011.