The Determination of Low Level Benzene, Toluene, Ethyl Benzene, and Xylenes (BTEX) in Drinking Water by Headspace Trap GC/MS

Importance of the Topic

Benzene, toluene, ethyl benzene and xylenes (BTEX) are volatile organic compounds regulated as toxic pollutants and commonly found near petroleum sites. Monitoring these analytes in drinking water at trace levels is vital for ensuring compliance with environmental standards and safeguarding public health.

Goals and Overview of the Study

This work aimed to develop a headspace trap GC/MS method that surpasses the detection limits specified in EPA Method 524.2 for BTEX in water while maintaining or improving all method performance criteria. The study evaluates method sensitivity, linearity, precision and water management efficiency.

Methodology and Instrumentation

A PerkinElmer TurboMatrix Headspace Trap system was employed to volatilize and preconcentrate BTEX from water samples using a Carbopack B & X trap. Samples were equilibrated at 80°C for 8 minutes followed by a 2-minute dry purge to remove water. The trap was heated from 35°C to 260°C and held for 2.5 minutes before introduction.
Chromatographic separation utilized an Elite 624 column (20 m × 0.18 mm × 1.0 µm) with the oven programmed from 40°C (0.5 min) to 185°C at 35°C/min. Helium served as the carrier gas. A PerkinElmer Clarus SQ 8S GC/MS, operating in full scan mode (35–350 amu), provided molecular identification and enhanced detection sensitivity.

Main Results and Discussion

The method achieved signal-to-noise ratios between 240:1 and 670:1 at 0.02 ppb for individual BTEX compounds. Calibration exhibited excellent linearity (r² ≥ 0.9993) over 0.02–60 ppb. Precision at 1 ppb showed relative standard deviations below 3% for all analytes. Chromatograms demonstrated clear separation of BTEX from water with a 2-minute dry purge, and a 4 ppb standard produced well-resolved peaks within a 4-minute run time.

Benefits and Practical Applications

• Sub-ppb detection limits well below EPA requirements
• Rapid analysis (~4 min per sample, enabling up to 72 samples per 12 h)
• Robust water management minimizing matrix interferences
• Molecular confirmation via full scan MS reducing false positives
• Enhanced uptime and reduced maintenance compared to purge-and-trap systems

Future Trends and Potential Applications

Advancements may include coupling headspace trap GC/MS with two-dimensional chromatography for complex matrices, integration with automated sample handling, field-portable GC/MS systems for on-site monitoring and leveraging artificial intelligence for data interpretation and predictive maintenance.

Conclusion

The presented headspace trap GC/MS approach using a Clarus SQ 8S system delivers a fast, sensitive and reliable method for trace BTEX analysis in drinking water. It meets and exceeds EPA Method 524.2 criteria, offering laboratories an effective solution for routine environmental monitoring.

References

• Marotta L. The Determination of Low Level Benzene, Toluene, Ethyl Benzene, and Xylenes (BTEX) in Drinking Water by Headspace Trap GC/MS. PerkinElmer Application Note; 2011.
• US EPA Method 524.2: Determination of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry.