Applicability of a New Versatile Temperature Programmed Thermodesorption System in Single and Multi Column Capillary GC/MS

Importance of the Topic

Trace analysis of volatile organic compounds is critical in environmental monitoring, industrial process control, food and flavor quality assessment, and biomedical studies. On-line adsorption followed by thermal desorption offers significant advantages in sensitivity, reproducibility, and flexibility compared to direct injection of complex or dilute samples.

Objectives and Study Overview

This study introduces a novel, temperature-programmed thermodesorption system (TDS-1) compatible with standard capillary GC/MS setups. The aim is to demonstrate its design features and performance in combination with a cooled programmable temperature vaporization injector (CIS-3), a dual-column switching module, a cryogenic trap, and an on-line mass selective detector.

Methodology and Instrumentation

A porous polymer adsorbent (Carbotrap, 20/40 mesh) is used to capture vapors from gaseous, liquid, or headspace samples. Thermal desorption is carried out in the TDS-1 with a programmable temperature ramp (50 °C to 280 °C at 40 °C/min). Volatiles are refocused in a cold CIS-3 liner (–150 °C to 280 °C at 12 °C/s). A multi-column switching system directs analytes through a precolumn (25 m OV-17) and a main Ultra-1 column (25 m × 0.2 mm, 0.33 µm film) housed in two HP 5890 ovens; a CTS-1 cryotrap is positioned between columns. Detection is achieved by FID monitoring and an HP 5971 MSD scanning 10–350 amu.

Main Results and Discussion

Example 1: An industrial solvent mixture (1,1,1-trichloroethane, perchloroethylene, Shell-Sol) was analyzed in liquid and static headspace modes. The headspace run showed marked enrichment of the most volatile components, illustrating the trap’s preconcentration power.

Example 2: Car exhaust under four conditions (cold/hot engine, with/without catalyst) was compared. The TDS-1/CIS-3/FID system revealed significant reduction of aromatic hydrocarbons when a three-way catalyst operated on a warm engine, demonstrating the approach’s utility in emission testing and catalyst evaluation.

Example 3: Aroma volatiles from milled coffee were profiled by GC/MS. Unexpected furans and dimethyldisulfide were identified, highlighting the system’s sensitivity and the importance of screening for potentially toxic trace components in food products.

Example 4: Heartcuts of mainstream cigarette smoke were collected on Carbotrap and analyzed via dual-column switching with cryotrapping and MSD. Toxic species including 2-methylpropanenitrile, benzene, furans, phenol, and pyrroles were detected, underscoring risks from passive smoking and showcasing selective fractionation capabilities.

Benefits and Practical Applications

• Lower detection limits through on-line enrichment.
• Rapid, reproducible sampling at varied locations.
• Reusability of adsorbent tubes and liners.
• Flexibility for selective pre-separation and heart-cutting.
• Seamless integration with existing GC/MS platforms.

Future Trends and Opportunities

Advances may include integration with liquid chromatography, real-time field monitoring, novel selective adsorbents, miniaturized thermodesorption devices, and coupling with high-resolution mass spectrometry. Applications will expand in environmental surveillance, food safety, clinical diagnostics, and process control.

Conclusion

The programmable temperature thermodesorption system TDS-1, when combined with PTV injection, multi-column switching, and on-line mass spectrometry, provides a robust, sensitive, and flexible platform for trace analysis of volatile organic compounds across diverse sample types.

References

• Bremer R, Hoffmann A, Rijks JA. Applicability of a New Versatile Temperature Programmed Thermodesorption System in Single and Multi Column Capillary GC/MS. AppNote 1/1992, Gerstel GmbH & Co. KG.