Analysis of Polymer Extracts by Gas Chromatography-High Resolution Time-of-Flight Mass Spectrometry With Electron and Chemical Ionizatio

Importance of the Topic

Profiling extractables and leachables from polymeric materials is essential for ensuring product quality, safety, and regulatory compliance. Uncharacterized residual monomers, additives, or degradation products can compromise performance and lead to contamination of packaged goods.

Objectives and Study Overview

This study evaluated the use of gas chromatography–high resolution time-of-flight mass spectrometry (GC-HRT) with both electron ionization (EI) and chemical ionization (CI) to comprehensively characterize extractables in three polymer systems: rubber, polyurethane foam, and siloxane/thermoplastic polyurethane (TPU).

Methodology and Instrumentation

The workflow involved:

• Sample Preparation: 2 g polymer beads extracted in 15 mL acetonitrile or isopropanol with stirring at 37 °C, filtration, and concentration.
• Instrumentation: LECO Pegasus GC-HRT equipped with EI and CI sources.
• GC Conditions: Agilent 7890 GC with Restek Rxi-5Sil MS column (30 m × 0.25 mm ID, 0.25 µm df); split 3:1 injection; oven program 60 °C (2 min) to 190 °C at 10 °C/min, then to 250 °C; helium at 1.0 mL/min.
• MS Conditions: Transfer line 300 °C; source EI 250 °C/CI 225 °C; CI reagent gas 5% NH₃ in methane; mass range m/z 50–650 (EI) and 180–1400 (CI); resolution 25,000 FWHM; 6 spectra/s; PFTBA internal calibration.

Main Results and Discussion

Rubber Extract:

• Detected radical inhibitors (BHT, methylene-bisphenol), oligomers (tetramethylcyclohexane derivatives) with mass accuracy ±0.5 ppm.

Foam Extract:

• Identified 2,4- and 2,6-toluene diisocyanate along with antioxidant additives via EI-HRT spectral matching and CI-HRT confirmation (mass accuracy within ±0.8 ppm).

Siloxane/TPU Extract:

• Resolved a homologous series of methylated cyclosiloxanes (D4–D17) using accurate mass XICs in CI mode (average accuracy 0.43 ppm).

The combination of hard and soft ionization provided complementary fragmentation and parent-ion information, enabling confident formula assignments and structural confirmation.

Benefits and Practical Applications

This approach permits:

• Robust quality control of polymer products.
• Detection of adulteration or unexpected impurities.
• Safety assessment of extractables in contact materials.

Future Trends and Opportunities

Advances may include:

• Integration of high-throughput MS libraries with machine learning for automated identification.
• Coupling GC-HRT with ion mobility or two-dimensional chromatography for enhanced separation.
• Development of portable high-resolution GC-MS systems for field testing.

Conclusion

GC-HRT with EI and CI ionization demonstrated high confidence in identifying a wide range of polymer extractables with excellent mass accuracy and spectral quality. This method supports comprehensive chemical profiling important for materials development and compliance.

Reference

• Alonso DE, Binkley J, Patrick J. Analysis of Polymer Extracts by Gas Chromatography-High Resolution Time-of-Flight Mass Spectrometry With Electron and Chemical Ionization. LECO Corporation, St. Joseph, MI, USA.