Analysis of BTEX-MTBE by Purge and Trap (P&T) Concentration and Determination by Gas Chromatography and Photoionization Detection (GC/PID)

Significance of the Topic

The trace analysis of BTEX and MTBE is critical for environmental monitoring and public health assessment. These volatile organic compounds are common water and soil contaminants originating from petroleum products and fuel additives. Their toxicity and mobility in subsurface environments make sensitive and rapid detection methodologies essential for compliance with regulatory standards and remediation programs.

Objectives and Study Overview

The present work evaluates a robust purge and trap concentration approach coupled with gas chromatography and photoionization/flame ionization detection to quantify BTEX and MTBE at sub-part-per-billion levels. The aim is to demonstrate method performance in terms of linearity, precision, detection limits, and throughput.

Used Instrumentation

• Purge and Trap System: OI Analytical Eclipse 4760 with 4551A autosampler and LV-20 standard additions module
• Gas Chromatograph: Agilent 7890A
• Detector: OI Analytical 4450 tandem PID/FID
• Column: Restek Rxi-624Sil MS (30 m × 0.25 mm ID, 1.4 µm film)

Methodology

A Tenax trap collected analytes during an 8-minute purge at 45 °C using helium. Desorption and bake cycles followed with stepped temperatures. The LV-20 module injected internal standard and surrogates at precise volumes. GC parameters included a split ratio of 50 ∶ 1, carrier helium flow of 0.8 mL/min and an oven program from 50 °C to 230 °C over 12.1 minutes. Calibration ranged from 0.5 to 400 ppb using seven-point standards. Method Detection Limits, Initial Demonstration of Proficiency, and Lower Limit of Quantitation were verified per EPA Methods 8021B and 8000D.

Main Results and Discussion

• Calibration showed excellent linearity (R2 ≥ 0.9992) and precision (RSD ≤ 5.9 %).
• MDLs met 40 CFR criteria with sub-ppb detection capability.
• IDP recoveries ranged within 70–130 % and LLOQ accuracy within ±20 %.
• Instrument response was stable for all analytes including internal and surrogate standards.

Benefits and Practical Applications

The method provides a fast (≈15-minute cycle), sensitive, and rugged solution for routine BTEX-MTBE monitoring in environmental and industrial laboratories. It supports compliance with underground storage tank regulations and broader water quality programs.

Future Trends and Potential Applications

• Integration of mass spectrometric detectors for enhanced specificity
• Miniaturized and field-deployable P&T-GC systems for on-site screening
• Automation and data analytics for high-throughput environmental surveillance

Conclusion

This study confirms that the P&T-GC/PID/FID configuration achieves reliable quantitation of BTEX and MTBE at trace levels while maintaining rapid sample turnaround and compliance with regulatory performance criteria.

References

1. Leusch F., Bartkow M. A Short Primer on BTEX in the Environment and Hydraulic Fracturing Fluids; Griffith University, 2010.
2. Irwin R. Environmental Contaminants Encyclopedia; National Park Service, 1997.
3. USEPA Method 8021B, Aromatic and Halogenated Volatiles by GC/PID/FID, Rev. 3, 2014.
4. USEPA Method 8000D, Determinative Chromatographic Separation, Rev. 4, 2014.