Thermal Desorption of Gasoline Range Hydrocarbons from Soil using a Pyroprobe

Importance of the Topic

Rapid screening of hydrocarbon contamination in soils and detailed analysis of polymer additives in industrial formulations are essential for environmental monitoring and quality control. Hyphenated GC–IR methods such as Pyroprobe thermal desorption and GPC–IR coupling combine precise sample introduction with molecular level identification of volatile and semi-volatile compounds.

Objectives and Overview

This application note presents two case studies: direct thermal desorption of gasoline-range hydrocarbons from soil using a Pyroprobe system, and separation of complex polymer mixtures in silver ink paste via GPC–IR hyphenation. The goals are to demonstrate sensitivity, selectivity, and minimal sample preparation requirements.

Methodology and Instrumentation

Soil samples were loaded into a quartz tube and heated in the Pyroprobe coil filament at controlled temperatures (200 °C for desorption; 300 °C blank tests) to release hydrocarbons without inducing matrix pyrolysis. Volatiles were trapped and analyzed by GC–MS. In parallel, GPC–IR was employed to fractionate a polymer ink paste and record full FT-IR spectra of each fraction for component identification.
Used Instrumentation

• Pyroprobe 5200 with quartz tube and sorbent trap
• GC–MS system: 30 m × 0.25 mm 5% phenyl methyl silicone column, helium carrier, split injection
• GPC–IR setup capturing full mid-IR range for hyphenated analysis

Main Results and Discussion

Thermal desorption at 200 °C efficiently liberated spiked gasoline-range hydrocarbons at 100 ppm without significant interference from native soil organics. Blank runs confirmed minimal background volatiles. GPC–IR analysis of the silver ink paste separated three distinct polymer components, assigned as Polymer A (aliphatic polyester resin), Polymer B (aliphatic polyurethane), and Component C (latent cross-linker), by matching IR bands to reference spectra.

Benefits and Practical Applications

• Minimal sample preparation and rapid screening of environmental contaminants
• Selective thermal desorption prevents matrix degradation
• Detailed IR spectral information aids in polymer identification and additive profiling
• Applications in environmental monitoring, quality assurance, polymer formulation, and forensic analysis

Future Trends and Opportunities

Advancements in trap media, lower-temperature desorption protocols, and expanded FT-IR spectral libraries will enhance detection limits and compound specificity. Integration with AI-driven spectral interpretation can further streamline environmental and materials analysis workflows.

Conclusion

Pyroprobe thermal desorption coupled to GC–MS and hyphenated GPC–IR represent powerful analytical strategies for rapid, selective, and detailed characterization of low-level hydrocarbons in soils and complex polymer formulations. The approaches offer significant advantages in speed, sensitivity, and structural elucidation.

Reference

1. D. White and L. Beyer. Journal of Analytical and Applied Pyrolysis, 50 (1999) 63–76.