US EPA Method 624 with the Tekmar Lumin and the PerkinElmer® Clarus® 600 GC/SQ 8T MS

Importance of the Topic

The reliable detection of volatile organic compounds (VOCs) in wastewater at trace levels is vital for environmental protection, regulatory compliance, and public health. US EPA Method 624 is a well-established protocol for concentrating and analyzing VOCs in aqueous matrices, but it often transfers excess water to the GC/MS system, leading to chromatographic issues and extended cycle times.

Study Objectives and Overview

This application note evaluates the performance of the Teledyne Tekmar Lumin Purge and Trap (P&T) concentrator coupled with a PerkinElmer Clarus 600 GC and Clarus SQ 8T MS, following US EPA Method 624. The primary goals are to demonstrate improved water removal without dry purge, maintain method detection limits (MDLs), achieve acceptable calibration linearity and precision, and increase sample throughput.

Methodology and Instrumentation

Water samples were spiked with a Volatiles MegaMix® standard and calibration mixes to prepare standards from 0.5 ppb to 200 ppb. Internal standards (bromochloromethane, 2-bromochloropropane, 1,4-dichlorobutane) and surrogate standards (pentafluorobenzene, fluorobenzene, bromofluorobenzene) were used to assess accuracy and precision. Seven replicate 0.5 ppb samples determined MDL, precision, and accuracy.

Instrumentation Used

• Teledyne Tekmar Lumin P&T with Moisture Control System (MCS) and AQUATek 100 autosampler
• PerkinElmer Clarus 600 GC: Restek Rtx VMS column, helium carrier
• PerkinElmer Clarus SQ 8T MS: scan 35–260 m/z, transfer line 200 °C, source 200 °C

Main Results and Discussion

Water vapor removal by the MCS eliminated the need for a dry purge step, preserving early-eluting VOC peaks with minimal water interference. Calibration curves for 30 target compounds showed correlation coefficients (r2) >0.99 for most analytes, with relative standard deviations (%RSD) of response factors below 12%. MDLs ranged from 0.07 to 0.59 ppb. Seven replicates at 0.5 ppb yielded accuracy between 93% and 114% and precision (%RSD) under 13% for most compounds. Chromatograms of 0.5 ppb and 30 ppb standards confirmed sharp peak shapes and resolution. Stability tests over 30 injections (≈10 hours) demonstrated internal and surrogate standard drift below 10% RSD.

Benefits and Practical Applications

• Enhanced water removal without dry purge saves up to 2 minutes per sample.
• Maintained low MDLs and strong calibration fit ensure regulatory compliance.
• Improved throughput enables more than double the samples per shift.

Future Trends and Potential Applications

Integration of advanced moisture control in P&T systems will likely become standard to streamline GC/MS analyses across environmental and industrial labs. Further miniaturization and automation, coupled with software-driven method optimization, may reduce analysis time and operator intervention. Expanded applications could include headspace analysis of solids, soil gas monitoring, and on-site field deployable systems.

Conclusion

The Tekmar Lumin P&T with MCS and AQUATek 100, paired with the Clarus GC/MS platform, successfully implements US EPA Method 624 without dry purge. It achieves low detection limits, robust calibration, and precision, while significantly increasing sample throughput by reducing cycle time.

Reference

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