Purge & Trap Using a Quartz Tube Microtrap

Significance of the Topic

Volatile organic compounds (VOCs) in water are critical markers of environmental contamination and product quality. Achieving sensitive and reliable analysis at low part-per-billion levels requires robust sample preparation and introduction techniques.

Objectives and Study Overview

This application note presents a simple approach for purge-and-trap sample introduction into gas chromatography (GC) using a quartz tube microtrap housed in a Pyroprobe system. The study evaluates the method’s ability to quantify trace VOCs in aqueous matrices at sub-ppb levels.

Methodology and Instrumentation

The procedure involves:

• Filling a quartz Pyroprobe tube with Tenax sorbent and securing it with quartz wool plugs.
• Conditioning the microtrap at 350 °C.
• Purging an aqueous sample with helium through the trap to collect volatiles.
• Thermal desorption of analytes by rapid heating of the coil filament at the start of the GC run.

Instrumentation Used

• Pyroprobe 5200 with interface at 325 °C.
• Filament heated to 350 °C for trap conditioning and desorption.
• Heated valve oven and transfer line at 325 °C.
• GC/MS with a 30 m × 0.25 mm, 5 % phenyl methyl silicone column.
• Helium carrier gas with a 50:1 split ratio.
• Oven program: 40 °C (2 min) ramped at 10 °C/min to 300 °C.

Main Results and Discussion

Purging 5 mL water samples spiked at 40 ppb yielded distinct chromatographic peaks for a range of volatile analytes and demonstrated negligible carryover in blank runs. Extending the approach to 10 mL samples at 10 ppb confirmed reliable detection and quantification in the low ppb range.

Benefits and Practical Applications

The microtrap purge-and-trap technique offers:

• Low detection limits in aqueous matrices.
• Efficient preconcentration of diverse VOC classes.
• Simplicity of sample introduction using standard vials.
• Compatibility with routine GC/MS workflows for environmental, pharmaceutical, and food analysis.

Future Trends and Possibilities

Advancements may include novel sorbents for enhanced selectivity, integration with automated, high-throughput autosamplers, coupling with high-resolution mass spectrometry for improved compound identification, and portable field-deployable systems for on-site monitoring.

Conclusion

This application of a quartz tube microtrap in a Pyroprobe system streamlines VOC analysis in water at ppb levels, combining sensitivity, reproducibility, and operational simplicity suitable for diverse analytical settings.

Reference

1. CDS Analytical, LLC. Application Note: Purge & Trap Using a Quartz Tube Microtrap.