SPME/GC Analyses of Sulfur Gases and VOCs, Using a New Carboxen/PDMS Fiber

Importance of the topic

The ability to sample and analyze trace levels of sulfur gases and volatile organic compounds (VOCs) is critical in environmental monitoring, industrial quality control, and public health. Traditional methods often involve bulky thermal desorption units and complex sample preparation steps. Solid phase microextraction (SPME) offers a solvent-free, rapid alternative that simplifies workflows while maintaining or improving sensitivity for challenging analytes.

Goals and overview of the study

This work introduces a novel 75 µm Carboxen™/polydimethylsiloxane (PDMS) SPME fiber designed to capture very volatile and low molecular weight compounds. The study demonstrates its performance in two applications: extraction of trace sulfur gases from air and headspace sampling of VOCs from water samples spiked at sub-ppb levels.

Methodology and instrumentation

The Carboxen/PDMS fiber was evaluated under the following conditions:

• Extraction of sulfur gases in a 250 mL air bulb at 1 ppm, 5 min headspace sampling at ambient temperature.
• Desorption in a gas chromatograph injection port at 250 °C for 2 min.
• Separation on a 30 m Supel-Q™ PLOT column (0.32 mm ID), oven program from 45 °C to 250 °C.
• Detection using GC/MS (quadrupole) scanning m/z 32–125.
• Comparison of VOC responses for Carboxen/PDMS versus PDMS/divinylbenzene and 100 µm PDMS fibers at 0.5 ppb spiked water samples following US EPA Method 524.

Main results and discussion

The Carboxen/PDMS fiber achieved sensitive extraction of sulfur compounds down to ppb levels, resolving six target analytes (carbonyl sulfide, methyl/ethyl mercaptan, dimethyl sulfide, carbon disulfide, dimethyl disulfide). In VOC headspace experiments, it outperformed both PDMS/DVB and thicker PDMS fibers, delivering higher response factors for a broad range of halogenated and aromatic compounds. The enhanced adsorption arises from the high surface area of the Carboxen adsorbent, enabling efficient trapping of very volatile species.

Benefits and practical applications

Key advantages include:

• Elimination of thermal desorption hardware and solvent usage.
• Wide volatility range: from small sulfur gases to larger aromatic VOCs.
• Faster sampling and analysis cycles suitable for routine labs.
• Compatibility with manual and automated SPME samplers.

Potential uses span environmental air monitoring, drinking water compliance testing, flavor and fragrance profiling in food matrices, and monitoring off-gassing in petrochemical processes.

Future trends and opportunities

Further work could explore soil-gas characterization, multiplexed field deployable SPME devices, and integration with high-throughput autosamplers. Expanding the fiber chemistry palette may extend SPME applicability to polar solvents and emerging contaminants. Coupling SPME with real-time detection platforms or portable GC/MS units represents another promising direction.

Conclusion

The 75 µm Carboxen/PDMS SPME fiber offers a robust, versatile tool for trace analysis of highly volatile analytes. Its superior adsorption properties simplify workflows and enhance detection limits, making it an attractive option for diverse analytical contexts.

Reference

Shirey R. SPME/GC Analyses of Sulfur Gases and VOCs Using a New Carboxen/PDMS Fiber. The Supelco Reporter. 1997;16(1):6–7.