US EPA Method 624 with the Tekmar Lumin P&T Concentrator and the Thermo Scientific™ TRACE™ 1310 GC and ISQ™ LT MS

Importance of the Topic

The determination of volatile organic compounds (VOCs) in wastewater is critical for environmental monitoring, public health protection and regulatory compliance. US EPA Method 624 is widely adopted for trace-level VOC analysis, but conventional purge and trap approaches can introduce significant water vapor to GC-MS systems, leading to poor peak shapes, decreased sensitivity for early-eluting analytes and extended analysis times due to dry-purge steps.

Objectives and Study Overview

This application note evaluates the performance of the Teledyne Tekmar Lumin purge and trap (P&T) concentrator, equipped with a novel moisture control system (MCS), coupled to a Thermo Scientific TRACE 1310 GC and ISQ LT MS for US EPA Method 624 analysis. Key aims include:

• Assessing water vapor reduction without a dry-purge step
• Verifying calibration linearity, method detection limits (MDLs), precision and accuracy at sub-ppb levels
• Demonstrating increased sample throughput through reduced cycle times

Methodology and Instrumentation Used

Sample Preparation and Calibration:

• Calibration standards spanned 0.5 to 200 ppb using EPA Method 624 Volatiles MegaMix and Calibration Mix #1
• Internal standards: bromochloromethane, 2-bromo-1-chloropropane, 1,4-dichlorobutane
• Surrogate standards: pentafluorobenzene, fluorobenzene, bromofluorobenzene
• Seven 0.5 ppb replicates for MDL, accuracy and precision determination

Instrumentation Configuration:

• Teledyne Tekmar Lumin P&T concentrator with MCS and AQUATek 100 autosampler
• Thermo Scientific TRACE 1310 GC with Rtx-VMS capillary column (20 m x 0.18 mm, 1 µm film), helium carrier at 0.8 mL/min
• ISQ LT single quadrupole MS: transfer line 230 °C, ion source 300 °C, scan 35–260 amu
• MCS set points: trap bake 280 °C, transfer line 160 °C, moisture control bake 180 °C
• No dry-purge step; total purge time 11 min at 40 mL/min

Main Results and Discussion

Calibration and Detection Limits:

• Excellent linearity across all VOCs with correlation coefficients (r2) > 0.99 for most compounds
• Relative standard deviations (%RSD) of response factors below 10% for target analytes
• MDLs ranged from 0.37 to 0.81 ppb, meeting EPA Method 624 requirements

Accuracy and Precision at 0.5 ppb:

• Average recoveries between 90% and 122% for key VOCs
• Repeatability (%RSD) typically below 9%, demonstrating robust performance without dry purge

Chromatographic Performance:

• Trace-level 0.5 ppb standard showed clear characteristic ions for early-eluting gases with minimal water interference
• 30 ppb standard produced sharp, well-resolved peaks for all VOCs, confirming effective water removal

Stability Over Extended Runs:

• Internal and surrogate standard areas drift remained below 8% RSD over 9–10 hours (27–29 samples)
• MCS provided consistent moisture control, avoiding signal suppression or retention shifts

Benefits and Practical Applications

The Lumin P&T with MCS enables US EPA Method 624 analysis without a dry-purge step, reducing the total cycle time and increasing sample throughput in high-volume laboratories. Improved water vapor removal enhances chromatographic reproducibility, especially for early-eluting VOCs. This approach is directly applicable to municipal and industrial wastewater testing, environmental monitoring programs and quality control laboratories.

Future Trends and Opportunities

Advances may include further integration of moisture control with automated data analysis, adaptation to other environmental matrices (e.g., groundwater, soil leachates), coupling with high-resolution mass spectrometry for non-target screening and miniaturized P&T systems for field deployable workflows. Continued optimization of trap materials and cooling architectures could yield even faster cycle times and lower detection limits.

Conclusion

The Teledyne Tekmar Lumin P&T concentrator, equipped with a moisture control system and operated under US EPA Method 624, delivers reliable, interference-free VOC analysis without the need for dry purge. Calibration, MDL, precision and accuracy data confirm method compliance at sub-ppb levels. Elimination of dry-purge steps shortens analysis cycles, enhancing laboratory productivity and robustness in wastewater VOC monitoring.

References

• Appendix A to Part 136 - Methods for Organic Chemical Analysis of Municipal and Industrial Wastewater - Method 624: Purgeables; US EPA, Promulgated 1984.