EGA for Polymer Identification Using the Pyroprobe

Importance of Topic

Rapid and reliable identification of polymeric materials is critical across industries such as plastics manufacturing, recycling, environmental analysis and quality control. Many polymers are insoluble and non-volatile, posing challenges to traditional chromatographic techniques. Evolved Gas Analysis (EGA) coupled with mass spectrometry provides a straightforward approach to generate characteristic degradation products that serve as molecular fingerprints for polymer identification.

Objectives and Study Overview

This work demonstrates a streamlined method for polymer identification using a CDS 6000 Series Pyroprobe directly interfaced to a mass spectrometer. Key aims include:

• Evaluating direct transfer of pyrolysate to MS without GC separation.
• Establishing heating protocols to distinguish polymer types and additives.
• Building a spectral library for automated identification of unknown samples.

Instrumentation Used

• Pyroprobe 6000 Series (CDS Analytical) with programmable filament.
• Short deactivated fused-silica transfer line (1 m × 0.10 mm) replacing the GC column.
• Quadrupole mass spectrometer with helium carrier gas and split interface.
• CDS Polymer Library for spectral matching.

Methodology and Instrumentation

Samples are loaded into a quartz pyrolysis tube and subjected to a two-stage heating program: initially held at 250 °C for 3 minutes to vaporize additives, then ramped at 100 °C/min to 800 °C. Evolved gases are transferred through the short fused-silica capillary under split conditions (100:1) to maintain MS vacuum. The MS interface, valve oven and transfer line are held at temperatures between 300 °C and 315 °C. Mass spectra are collected continuously versus temperature, generating time-resolved pyrolysis fingerprints. Averaged spectra over the full run facilitate library comparisons.

Main Results and Discussion

EGA profiles of known polymers containing bisphenol A revealed distinct peak temperatures correlating with thermal stability. Early peaks at 250 °C indicated additive evolution in epoxy powder-coat samples. Unknown clear plastics subjected to the same protocol yielded averaged spectra that, when searched against the CDS Polymer Library, correctly identified the material as polyethylene terephthalate (PET). Additional examples, including polyurethane foam and phthalate-containing vinyl toys, confirmed the method’s ability to detect both polymer backbones and low-mass additives.

Benefits and Practical Applications

The direct EGA-MS approach offers:

• Rapid analysis with total run times under 15 minutes.
• Minimal sample preparation and no need for solvents.
• Simultaneous detection of polymer fragments and semi-volatile additives.
• Automated library matching for routine QA/QC and failure analysis.

Future Trends and Opportunities

Integration of high-resolution MS and advanced data processing will improve deconvolution of complex pyrolysate mixtures. Expanded spectral libraries incorporating copolymers and flame retardants will broaden applicability. Coupling EGA-MS with hyphenated techniques such as infrared detection or thermal analysis can enhance structural elucidation and quantitation.

Conclusion

The direct coupling of a CDS 6000 Series Pyroprobe to mass spectrometry enables fast, solvent-free identification of polymers and their additives by thermal decomposition. The technique’s simplicity, speed and compatibility with automated library searches make it a valuable tool for polymer analysis in research and industrial settings.

Reference

Tom Wampler. "EGA for Polymer Identification Using the Pyroprobe," Application Note, CDS Analytical, LLC, Oxford PA, USA.