Characterization of Industrial Plastics Using Pyrolysis With Atmospheric Pressure Gas Chromatography Coupled to High- Resolution Mass Spectrometry

Importance of the Topic

With growing emphasis on circular economies and sustainable materials, accurately characterizing recycled plastics ensures product safety and performance in industrial applications.

Objectives and Overview

This study develops an analytical workflow combining pyrolysis with atmospheric pressure gas chromatography-high resolution mass spectrometry (APGC-HRMS) and multivariate statistics to differentiate virgin and recycled polyamide-based plastics and identify chemical markers unique to each sample type.

Methodology

Samples of virgin pellets, recycled regrinds, and molded gears were analyzed. Each ~0.2 mg sample underwent single-shot pyrolysis at 600 °C. Volatile products were separated on an Rtx-5MS column via an Agilent 7890 GC and ionized softly using APGC, followed by QTof HRMS acquisition in MSE mode. Data processing and library screening were performed in UNIFI, and PCA/OPLS-DA statistical analyses utilized EZInfo.

Instrumentation Used

• FrontierLab EGA/PY-3030D Pyrolyzer
• Agilent 7890 GC with Rtx-5MS (30 m×0.25 mm, 0.25 µm)
• Waters APGC source and Xevo G2-XS QTof MS
• Waters MassLynx 4.2, UNIFI, and EZInfo 3.0 software

Main Results and Discussion

Base peak intensity pyrograms highlighted the complex mixture of pyrolyzates. Library screening detected common pyrolysis products across samples but could not alone resolve differences. PCA clearly separated blanks, virgin, and recycled plastics, while OPLS-DA S-plots identified ions significantly upregulated in each group. Tentative identification of markers, such as N-vinylcaprolactam and 4-(1-methyl-1H-pyrazol-4-yl)-4-propoxypiperidine, was achieved using accurate masses, isotope pattern matching, and in silico fragmentation in UNIFI’s Discovery Tool.

Benefits and Practical Applications

• Minimal sample preparation with direct pyrolysis
• Soft ionization preserves molecular ions for elemental composition determination
• Statistical workflows facilitate rapid discrimination of material types
• In-house library expansion enables streamlined future screening

Future Trends and Applications

Advances may include integration of machine learning for automatic marker discovery, expanding spectral libraries for a broader range of polymers, and coupling with complementary techniques to enhance structural characterization. Regulatory demand for recycled plastic traceability will drive adoption of these hyphenated approaches.

Conclusion

The combined pyrolysis-APGC-HRMS and multivariate statistical strategy provides a robust, high-throughput method to characterize and distinguish virgin versus recycled industrial plastics, aiding quality control and supporting circular economy initiatives.

Reference

1. European Commission. A European Strategy for Plastics in a Circular Economy. 2018.
2. Tsuge S., Ohtani H., Watanabe C. Pyrolysis-GC/MS Data Book of Synthetic Polymers. 2011.
3. Plumb R., Johnson K., Rainville P., et al. UPLC/MSE: A New Approach for Generating Molecular Fragment Information for Biomarker Structure Elucidation. Rapid Commun. Mass Spectrom. 2006;20:1984–1994.
4. Stevens D., Cabovska B., Bailey A. Detection and Identification of Extractable Compounds from Polymers. Waters Application Note 720004211. 2012.
5. Riches E., Goshawk J., Da Costa J., Jones G. Discrimination Between Commercial Lubricant Oils Using Mass Spectrometry and Multivariate Analysis within UNIFI. Waters Application Note 720006406. 2018.
6. Schweighuber A., Gall M., Fisher J., et al. Development of an LC-MS Method for the Semiquantitative Determination of Polyamide 6 Contamination in Polyolefin Recyclates. Anal Bioanal Chem. 2021;413:1091–1098.
7. Cabovska B. Screening Workflow for Extractable Testing Using the UNIFI Scientific Information System. Technical Note 720005688. 2016.