Identification of microplastics in water and food using pyrolysis GC with high resolution Orbitrap mass spectrometry

Significance of the Topic

Microplastics have emerged as pervasive contaminants in environmental and food matrices. Their small size allows them to enter water sources and the food chain, carrying potentially toxic additives and environmental pollutants. Identifying and quantifying microplastics is critical for assessing human exposure risks and informing regulatory actions.

Objectives and Study Overview

This study aimed to evaluate pyrolysis–gas chromatography combined with high-resolution Orbitrap mass spectrometry as a technique to detect and identify common polymer residues in milk, meat, and surface water. By comparing standard polymers with real samples, the research sought to demonstrate sensitivity, selectivity, and throughput advantages over conventional spectroscopic methods.

Methodology and Instrumentation Used

Sample Preparation:

• Stormwater samples (1 L) were spiked with deuterated polystyrene, filtered through 1 µm and 0.7 µm glass fiber filters, dried, and transferred into pyrolysis cups.
• Milk and meat (steak) were freeze-dried, milled to a homogeneous powder, spiked with deuterated polystyrene, and extracted via pressurized liquid extraction using dichloromethane at 180 °C and 1 500 psi.

Instrumentation:

• Frontier multi-shot pyrolyzer coupled to a Thermo Scientific TRACE™ 1310 GC.
• Thermo Scientific™ Orbitrap Exploris™ GC 240 mass spectrometer.
• Data processing with Thermo Scientific™ Compound Discoverer™ and Chromeleon™ CDS software.

Main Results and Discussion

Pretreatment by thermal desorption significantly reduced background signals, facilitating polymer marker detection. Characteristic pyrolysis products from standard polymers were catalogued. In stormwater, benzene, naphthalene, and fluorene signals indicated PVC presence. High-resolution extraction windows (±5 ppm) improved selectivity compared to simulated unit-mass filtering. Milk and meat extracts showed styrene, allylbenzene, α-methylstyrene, and toluene, suggesting possible polystyrene contamination; however, absence of styrene dimers prevented definitive confirmation.

Benefits and Practical Applications

• The py-GC–Orbitrap approach delivers rapid, high-throughput screening of bulk microplastic content beyond microscopy limits.
• High mass accuracy enables discrimination of polymer markers in complex matrices.
• Automated sample introduction and targeted data workflows support routine environmental and food safety monitoring.

Future Trends and Potential Applications

Advances may include expanded high-resolution spectral libraries to cover diverse polymer additives and environmental contaminants. Integration with machine-learning-based spectral deconvolution could accelerate marker discovery. Miniaturized pyrolizers and online coupling with liquid handling systems may enable higher sample throughput and field-deployable platforms.

Conclusion

Pyrolysis-GC coupled with Orbitrap mass spectrometry provides a powerful tool for confirming and characterizing microplastics in water and food samples. Its high sensitivity, selectivity, and automation support comprehensive monitoring strategies addressing emerging microplastic pollution challenges.

Reference

No external literature was cited beyond the study under review.