Fast Analysis of Low Level BTEX using the Agilent Micro GC with Sample Concentrator

Importance of the Topic

Accurate and rapid detection of low-level BTEX (benzene, toluene, ethylbenzene and xylenes) is vital for environmental monitoring, workplace safety and regulatory compliance. Conventional micro-GC systems often struggle to reach sub-ppm detection thresholds, limiting their utility in trace analysis.

Objectives and Study Overview

This application note evaluates the performance enhancements achieved by coupling an Enrichment and Desorption Unit (EDU) sample concentrator to an Agilent 490 Micro GC. The study aims to lower detection limits for nine aromatic hydrocarbons by pre-concentrating ambient or bagged samples prior to chromatographic analysis.

Methodology and Instrumentation

• Agilent 490 Micro GC with a 4 m CP-Sil 5 CB column, operated at 100 °C.
• EDU sample concentrator using Tenax TA adsorption tubes for trapping analytes.
• Sampling: 240 s at 450 mL/min, adsorption at 30 °C; desorption at 180 °C for 120 s; transfer to GC with helium carrier gas.
• Chromatographic separation and detection by thermal conductivity detector (TCD), controlled via Agilent EZChrom 3.3.2 software.

Main Results and Discussion

• Analysis time for BTEX separation: ≈3 minutes, with total cycle time of 10–12 minutes including enrichment.
• Enrichment factors ranged from ~150× for benzene up to ~243× for m/p-xylene, depending on breakthrough volumes (700–1,400 mL).
• Estimated detection limits improved from 1–2 ppm (direct injection) to 4–7 ppb with sample enrichment—a 140–240× enhancement.
• Repeatability (30 successive injections at ~1 ppm) yielded RSDs between 1.0 % and 1.9 % for all compounds at optimized sampling times.

Benefits and Practical Applications

• Enables trace-level monitoring of volatile organics in field or mobile laboratories.
• Maintains fast analysis throughput while achieving ppb-level sensitivity.
• Compact footprint and low gas consumption support on-site environmental or industrial air quality assessments.

Future Trends and Potential Applications

• Integration with real-time air monitoring networks and wireless data transmission.
• Development of novel sorbent materials for broader compound coverage and higher capacity.
• Automation enhancements for unattended, continuous environmental surveillance.

Conclusion

Coupling the EDU sample concentrator to the Agilent 490 Micro GC significantly enhances low-level BTEX detection, achieving ppb-range limits with robust repeatability. This approach offers a powerful tool for rapid, on-site trace gas analysis.

Reference

• Duvekot C., van Loon R. Fast Analysis of Low Level BTEX using the Agilent Micro GC with Sample Concentrator. Agilent Technologies Application Note 5991-0819EN, 2012.