Effect of hydrogen carrier gas on Py-GC/MS analysis of polymers Part 3 Library search using existing database

Significance of the topic

Pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) is a cornerstone technique for rapid characterization of polymers in research, quality assurance and failure analysis. Carrier gas choice can influence pyrolyzate composition via hydrogenation, potentially altering mass spectra and affecting library-based identification.

Objectives and overview of the study

This technical note investigates whether hydrogen (H₂) as a carrier gas modifies Py-GC/MS results for common polymers—high-density polyethylene (HDPE), polystyrene (PS), polycarbonate (PC) and styrene-butadiene rubber (SBR)—and whether existing helium-based spectral libraries remain valid under H₂ conditions.

Methodology

Samples (100 µg each of HDPE, PC, SBR; 5 µL PS solution) were pyrolyzed at 600 °C using a Multi-Shot Pyrolyzer (EGA/PY-3030D) directly interfaced to a GC split injector. Separation employed a 30 m×0.25 mm i.d. UA+-5 column (5% diphenyl–95% dimethylpolysiloxane, 0.25 µm film). Carrier gases (He and H₂) were delivered at a constant 1 mL/min flow. Mass spectral data were processed with F-Search against a database compiled under helium atmosphere.

Applied Instrumentation

• Multi-Shot Pyrolyzer EGA/PY-3030D
• Auto-Shot Sampler
• Gas chromatograph–mass spectrometer with UA+-5 capillary column

Main results and discussion

Library search match quality remained ≥95% for all polymers under both He and H₂. Major pyrolyzate peaks and their summed spectra showed negligible hydrogenation effects in H₂, yielding comparable identification scores for HDPE (99%), PS (99%), PC (91–98%) and SBR (93–97%). These findings confirm that existing He-based spectral libraries are directly applicable when using H₂ carrier gas.

Benefits and practical applications

• Enables use of cost-effective hydrogen without compromise to identification accuracy
• Improves analysis speed and operational efficiency in polymer QA/QC
• Maintains reliable library matching for routine industrial and research laboratories

Future trends and possibilities of use

Extending validation to a broader range of polymer types and composite materials will further establish H₂’s utility. Integration with expanded spectral libraries and real-time Py-GC/MS platforms may enhance throughput for environmental monitoring, forensic investigations and advanced materials development.

Conclusion

Py-GC/MS analysis using hydrogen carrier gas yields equivalent polymer identification performance to helium-based methods when applying existing libraries. This supports H₂ adoption for efficient, accurate polymer profiling.

Reference

• Watanabe A et al. Analytical Chemistry 88 (2016) 5462–5468
• F-Search System catalog, Frontier Laboratories Ltd.