Accelerated Determination of Microplastics in Environmental Samples Using Thermal Extraction Desorption-Gas Chromatography/Mass Spectrometry (TED-GC/MS)

Significance of the Topic

Microplastics are pervasive environmental contaminants that pose risks to ecosystems and human health. Accurate, high-throughput quantification of these particles in diverse matrices is essential for monitoring pollution, informing regulatory limits, and guiding remediation strategies.

Aims and Overview of the Study

This study demonstrates an automated thermal extraction desorption-gas chromatography/mass spectrometry (TED-GC/MS) workflow for rapid determination of microplastic polymers in environmental samples. The method addresses limitations of imaging techniques and traditional pyrolysis GC/MS by enabling analysis of larger sample masses, full particle size ranges, and reproducible mass-based quantification.

Methodology and Used Instrumentation

• Sample types: filtered surface water, finished compost, house dust, drinking water.
• Thermogravimetric analysis: Mettler Toledo TGA2, alumina crucibles (up to 1 g sample), N₂ purge 30 mL/min, heating 10 °C/min to 600 °C.
• Coupling device: GERSTEL heated transfer module and autosampler robot for automated movement of TD tubes.
• Thermal desorption: GERSTEL TDU 2 for extraction and desorption, splitless mode, cryo-focusing in GERSTEL CIS 4 at –100 °C.
• GC/MS: Agilent 7890B GC with HP-5MS column (30 m × 0.25 mm × 0.25 µm), He carrier at 1 mL/min; Agilent 5977B MSD, EI 70 eV, scan m/z 35–350.
• Sorbent: PDMS bars for trapping evolved pyrolysis products.
• Software: Agilent MassHunter for acquisition, Enhanced ChemStation for data analysis.

Main Results and Discussion

• Seven common polymers (PE, PP, PS, PET, PA, PMMA, SBR) identified via characteristic thermal decomposition markers.
• Limits of detection ranged from 0.06 µg (PS, PP, SBR) to 2.2 µg (PE), with matrix effects raising LOD modestly.
• Quantification by standard addition showed repeatability RSDs of 6–12 % across pyrolysis fragments.
• Environmental concentrations: house dust 21 µg MP per mg, compost 13 µg/mg; surface water fractions from <100 µm to >1 mm contained 73 µg/L total polymers; bottled water PET at 0.193 µg/L.
• Automated cycle time ~2.5 h per sample; capacity of 10 samples/day including blanks.

Benefits and Practical Applications

• High-throughput, fully automated analysis reduces operator time and contamination risk.
• Large sample masses improve representativeness for heterogeneous microplastic distributions.
• Mass-based results align with regulatory monitoring requirements.
• Reduced solvent use and minimized contamination compared to liquid extraction methods.

Future Trends and Potential Applications

• Extension to additional matrices such as soil, biota, and wastewater sludge.
• Integration with imaging methods for combined particle counting and mass quantification.
• Development of novel sorbent materials to broaden analyte scope.
• Standardization of TED-GC/MS protocols for regulatory frameworks.
• Miniaturized or portable TED-GC/MS systems for on-site environmental monitoring.

Conclusion

Automated TED-GC/MS provides robust, reproducible mass-based quantification of microplastics in diverse environmental matrices. Its ability to handle large sample masses, cover broad particle size ranges, and deliver low detection limits positions it as a valuable complement to imaging-based approaches and a practical tool for regulatory and research laboratories.

References

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