Validation of USEPA Method 524.2 Using a Stratum PTC and the New AQUATek 100 Autosampler

Significance of the topic

Volatile organic compounds (VOCs) in drinking and environmental waters pose significant health and regulatory concerns. Sensitive, reliable and efficient analytical methods are essential to ensure water quality, comply with regulatory limits and enable high-throughput monitoring in municipal and industrial laboratories.

Study objectives and overview

This application study aimed to validate USEPA Method 524.2 by integrating a Stratum Purge and Trap Concentrator (PTC) with the newly introduced AQUATek 100 autosampler, coupled to an Agilent 7890A gas chromatograph and 5975C mass spectrometer. Key performance metrics included reproducibility (%RSD), surrogate percent recovery and method detection limits (MDLs) across multiple calibration runs and over 600 sample analyses.

Methodology and instrumentation

A five-point calibration (0.5–10 ppb, extended ranges for poorly purging analytes up to 100 ppb) assessed linearity and precision. A 25 mL purge volume and standard EPA 524.2 conditions were applied. Surrogate and internal standards in amber vessels dispensed precise aliquots to each sample under controlled pressure. MDLs and recovery were determined by seven replicate analyses over eight days at low concentration levels.

Used Instrumentation

• Stratum Purge and Trap Concentrator with water sample pH option
• AQUATek 100 autosampler with 100-vial carousel, integrated water reservoir and chiller tray (10°C)
• Agilent 7890A gas chromatograph with HP-VOC capillary column (30 m × 0.20 mm × 1.12 µm)
• Agilent 5975C triple‐axis quadrupole mass spectrometer
• Vocarb 3000 adsorbent trap, split/splitless inlet with 1.0 mm liner

Main results and discussion

Calibration curves exhibited excellent linearity with average %RSDs of 6.48%, 7.06% and 6.82% across three separate runs. Over 600 samples processed, all analytes maintained <10%RSD after routine source cleaning. MDLs ranged from 0.03 to 1.12 µg/L, well below regulatory thresholds. Surrogate recoveries for 4-bromofluorobenzene and 1,2-dichlorobenzene-d4 averaged 93% over 224 samples, demonstrating long-term dosing accuracy and system stability.

Benefits and practical application

• Increased laboratory throughput via automated vial handling and auto-blanking reservoir
• Reduced carryover and consistent sample cooling (to 10°C) for integrity preservation
• Enhanced serviceability through pull-out plumbing access compartment
• Precise internal standard and surrogate delivery minimizing reagent waste and cost
• Full compliance with USEPA Method 524.2 and readiness for Method 524.3 requirements

Future trends and opportunities

Advances may include real-time pH monitoring integrated into purge-and-trap schedules, expanded automation for multi-matrices, and remote diagnostics. Adoption of enhanced adsorbent materials and software-driven scheduling can further boost sensitivity and sample throughput, addressing evolving regulatory demands and resource constraints.

Conclusion

The Stratum PTC combined with the AQUATek 100 autosampler and Agilent GC/MS platform meets or exceeds analytical performance criteria for VOC measurement in water per USEPA Method 524.2. It offers robust reproducibility, low detection limits and operational enhancements that streamline laboratory workflows without compromising data quality.

References

• USEPA Method 524.2, Measurement of Purgeable Organic Compounds in Water by GC/MS, Revision 4.1, 1995
• USEPA Method 524.3, Measurement of Purgeable Organic Compounds in Water by GC/MS, Version 1.0, June 2009