US EPA Method 524.2 with the Tekmar Lumin P&T Concentrator, AQUATek LVA and Agilent 7890B GC/5977A MS

Meaning of the Topic

Purge and trap coupled with gas chromatography/mass spectrometry is a foundational approach for detecting trace levels of volatile organic compounds (VOCs) in drinking water. Accurate measurement of VOCs at sub-ppb levels is essential for regulatory compliance, ensuring public health safety, and supporting environmental monitoring programs.

Objectives and Study Overview

This work applies US EPA Method 524.2 to evaluate the performance of the Teledyne Tekmar Lumin purge and trap concentrator integrated with the AQUATek LVA liquid vial autosampler and an Agilent 7890B GC/5977A MS system. Key goals include establishing linear calibration curves, determining method detection limits (MDLs), and verifying accuracy and precision for a suite of target VOCs in drinking water.

Used Instrumentation

• Teledyne Tekmar Lumin purge and trap concentrator with moisture control system (MCS)
• Teledyne Tekmar AQUATek LVA water-only autosampler
• Agilent 7890B gas chromatograph equipped with an Rtx-VMS capillary column
• Agilent 5977A mass selective detector

Methodology and Instrumentation

Sample Preparation

• Calibration standards prepared in methanol covering 0.2 to 50 ppb for 83 VOCs using Restek VOA MegaMix, Ketone Mix, and 502.2 Calibration Mix.
• Internal standard: fluorobenzene; surrogate standards: 4-bromofluorobenzene and 1,2-dichlorobenzene-d4 at 25 ppb.
• Seven replicate 0.2 ppb samples used for MDL, accuracy, and precision determination.

Purge and Trap Conditions

• Purge time 11 min at 40 mL/min; desorb time 4 min at 250 °C; bake 2 min at 280 °C.
• Moisture control system reduces water vapor transfer by up to 60%, minimizing interference and extending column life.

GC/MS Conditions

• Column: Rtx-VMS 20 m × 0.18 mm × 1 µm; carrier gas helium at 1 mL/min.
• Oven program: 35 °C (4 min), 15 °C/min to 85 °C, 30 °C/min to 225 °C, 2 min hold; total run 14 min.
• MS scan range 35–260 m/z with solvent delay of 0.5 min; transfer line 225 °C, source 230 °C, quad 150 °C.

Key Results and Discussion

Calibration linearity was excellent with response factor %RSD typically below 15%. MDLs ranged from approximately 0.03 to 0.13 ppb across analytes. Accuracy results fell within ±20% of nominal concentrations and precision (%RSD) met the ≤20% criterion. A 30 ppb total ion chromatogram demonstrated sharp, well‐resolved peaks for all compounds with minimal water interference, confirming the efficacy of the moisture control system.

Benefits and Practical Applications

Combined purge and trap automation with moisture control enhances sensitivity and reproducibility for VOC analysis in drinking water. The approach supports regulatory compliance, improves laboratory throughput, and reduces maintenance by minimizing water vapor damage to GC columns.

Future Trends and Opportunities

Advancements may include accelerated GC temperature programs to further boost sample throughput, integration of real-time data analytics and machine learning for method optimization, expansion of analyte panels to emerging contaminants, and development of portable field-deployable P&T-GC/MS systems for on-site monitoring.

Conclusion

The study confirms that the Teledyne Tekmar Lumin P&T concentrator with AQUATek LVA and Agilent 7890B GC/5977A MS meets US EPA Method 524.2 requirements, delivering low MDLs, robust linearity, and reliable accuracy and precision while effectively reducing water interference.

References

• Munch JW US EPA Method 524.2 Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry Revision 4.1 1995