Pyrolysis-Gas Chromatography-High Resolution Mass Spectrometry with Soft Ionization for Increased Confidence of Polymer Characterization

Significance of the Topic

Polymer characterization is essential for ensuring material safety, performance and regulatory compliance, particularly as the use of recycled and biobased plastics continues to expand. Traditional pyrolysis-GC with high-energy electron ionization often leads to extensive fragmentation, limiting the ability to confirm molecular formulas and detect trace additives or contaminants.

Objectives and Study Overview

This study compares classical pyrolysis-GC/EI-Tandem Quadrupole MS with a novel pyrolysis-APGC-QTof MS configuration. The goal is to assess the analytical benefits of soft atmospheric pressure ionization, high-resolution accurate mass acquisition and MSE data mode for enhanced polymer analysis in both standard materials and commercial biobased plastic films.

Methodology and Instrumentation

Samples of polymer standards and biobased plastic bags were pyrolyzed in a CDS 5000 system, followed by GC separation on an Rtx-5MS column. Two MS setups were used:

• System 1: Xevo TQ-GC with EI source (70 eV, m/z 10–650).
• System 2: Xevo G2-XS QTof with APGC source (soft ionization, m/z 10–1500) operating in MSE mode (low energy 6 V; high energy 15–45 V).

Key Results and Discussion

The APGC-QTof MS approach yielded richer pyrograms with more chromatographic features and clearer molecular ion signals. For polystyrene, the tetramer ion at m/z 416.2504 was only observed under APGC due to reduced fragmentation. In Nylon 6 samples, the protonated molecular ion (m/z 194.2374) appeared exclusively in the soft ionization spectra. MSE acquisition provided simultaneous accurate masses of precursor and fragment ions, facilitating structural elucidation of unknown components like erucamide in bioplastic samples via MassFragment software.

Benefits and Practical Applications

• Enhanced detection of molecular ions improves elemental composition confirmation.
• Soft APGC ionization streamlines analysis by eliminating the need for chemical ionization source changes.
• MSE mode supports confident structural elucidation of additives and contaminants.
• Applicable to complex post-consumer, industrial and biobased polymer materials.

Future Trends and Opportunities

Advancements in soft ionization techniques and high-resolution mass analysis will drive more routine use of pyrolysis-APGC-QTof systems for polymer research. Integration of automated software tools for fragment assignment and database searching will further enhance throughput and identification confidence. Emerging applications may include in-line quality control, contaminant screening and life-cycle studies of sustainable plastics.

Conclusion

Pyrolysis-APGC-QTof MS with soft atmospheric pressure ionization and MSE acquisition offers a powerful and time-efficient workflow for detailed compositional analysis of polymers. The approach overcomes limitations of traditional EI-based methods, enabling reliable detection of molecular ions, accurate mass measurement and robust structural characterization of both known and unknown polymer-related compounds.

References

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