Analysis of Mixed Polymer Sample as Microplastics using Pyrolysis GC/MS

Significance of the Topic

Microplastic pollution in marine and terrestrial environments poses a serious ecological and health risk due to bioaccumulation of toxic substances. Accurate identification of polymer composition in mixed microplastic samples is essential for understanding their environmental impact and guiding mitigation strategies.

Objectives and Overview of the Study

This work demonstrates a qualitative approach to identify individual polymers in a mixed microplastic sample by using pyrolysis gas chromatography–mass spectrometry (Py-GC/MS). A model sample containing fragments of polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) was analyzed to evaluate the method’s selectivity and sensitivity.

Methodology

Approximately 0.05 mg of each polymer fragment was placed in a pyrolysis cup with wool to prevent sample loss. Pyrolysis was conducted at 600 °C, and the resulting volatile products were transferred to a GC column with a temperature program from 40 °C to 320 °C. Helium served as the carrier gas, and the system operated in split mode (1 : 50). Mass spectral data were collected in scan mode (m/z 29–700) and selected ion monitoring (SIM) mode to target characteristic pyrolysis fragments.

Instrumentation Used

• Pyrolyzer: EGA/PY-3030D multi-shot pyrolyzer with AS-1020E auto-sampler (Frontier Laboratories Ltd.)
• GC-MS: Shimadzu GCMS-QP™2020 NX
• Column: UA-5 (MS/HT) 30 m × 0.25 mm × 0.25 μm
• Ionization: Electron impact (EI); source temp. 230 °C; interface temp. 300 °C

Main Results and Discussion

The total ion chromatogram (TIC) of the mixed sample exhibited a complex profile, making polymer assignment difficult by scan data alone. SIM chromatograms targeting specific m/z values allowed clear identification of each polymer: long‐chain C20 alkanes and alkenes for PE; branched heptenes and undecenes for PP; styrene and multiring compounds for PS; and benzene, chloroindan, dihydronaphthalene, and azulene for PVC. This targeted approach enabled unambiguous polymer detection in a complex mixture.

Benefits and Practical Applications

• High selectivity and sensitivity for individual polymer identification in mixed samples
• Rapid qualitative screening suitable for environmental microplastic surveys
• Capability to distinguish polymers even at low mass (sub-mg) levels

Future Trends and Potential Applications

Expanding the library of pyrolysis markers will allow analysis of a broader range of polymer types. Integration with quantitative calibration strategies could transform this approach into a semi-quantitative or fully quantitative tool. Coupling Py-GC/MS with automated sample preparation or online sampling systems may enable high-throughput monitoring of microplastic contamination in water, soil, and biota.

Conclusion

Py-GC/MS in SIM mode provides a robust qualitative method for identifying multiple polymers in a mixed microplastic sample. The technique’s sensitivity and specificity support its adoption for environmental monitoring and research into microplastic distribution and fate.

References

(1) M. Fisher and B. M. Scholz-Böttcher, Environ. Sci. Technol., 51, 5052–5060 (2017)
(2) S. Tsuge, H. Ohtani, C. Watanabe, Pyrolysis-GC/MS Data Book of Synthetic Polymers, Elsevier, 2011