US EPA Method 524.2 - Atomx XYZ and Agilent 7890B GC/5977A MS

Significance of the Topic

Trace-level monitoring of volatile organic compounds (VOCs) in drinking water is essential for ensuring public health and regulatory compliance. US EPA Method 524.2 employs purge-and-trap coupled with gas chromatography/mass spectrometry (GC/MS) to concentrate and quantify VOCs, but excessive water vapor transfer can compromise analytical performance and shorten column life.

Objectives and Study Overview

This study compared two desorb times (4 min and 2 min) using the Teledyne Tekmar Atomx XYZ purge and trap system with an Agilent 7890B GC/5977A MS under US EPA Method 524.2. The goals were to evaluate calibration linearity, method detection limits (MDLs), accuracy, precision, and the effectiveness of moisture control in reducing water interference.

Methodology and Instrumentation

Instrumentation:

• Teledyne Tekmar Atomx XYZ purge and trap system
• Agilent 7890B gas chromatograph
• Agilent 5977A mass selective detector

Method summary:

• Calibration standards prepared from 83 target VOCs over 0.2–50 ppb
• Internal standard: fluorobenzene; surrogates: bromofluorobenzene and 1,2-dichlorobenzene-d4
• Purge parameters: 5 mL sample, 40 mL/min purge flow, sample at 20 °C
• Desorb step: 250 °C for either 4.0 min or 2.0 min
• GC oven: 35 °C hold, ramp to 85 °C at 15 °C/min, then to 225 °C at 30 °C/min, total run 14 min
• MS scan: 35–260 m/z, gain factor 10, solvent delay 0.5 min

Main Results and Discussion

• Calibration curves exhibited relative standard deviations (RSDs) below 18% for all analytes, meeting EPA criteria.
• MDLs ranged from approximately 0.06 to 0.30 ppb for both desorb durations.
• Accuracy (±20%) and precision (≤20% RSD) for seven replicates at 0.5 ppb compliance standards were achieved.
• The Atomx XYZ moisture control system reduced water vapor transfer by up to 60%, minimizing peak interference and protecting GC columns.
• Total ion chromatograms of a 30 ppb VOC standard showed well-resolved peaks with negligible water interference for both 4 min and 2 min desorb times.

Benefits and Practical Applications

• Accurate and reliable quantification of trace VOCs in water matrices.
• Extended GC column lifespan due to lower moisture load.
• Enhanced laboratory throughput: approximately 14% reduction in sample cycle time.

Future Trends and Possibilities

• Optimization of GC temperature programs to further reduce analysis time.
• Integration with high-resolution MS for improved compound identification and selectivity.
• Automated data processing, cloud connectivity, and expanded methods for emerging contaminants.

Conclusion

The combined Teledyne Tekmar Atomx XYZ and Agilent 7890B/5977A system effectively implements US EPA Method 524.2, delivering robust calibration, low detection limits, and superior moisture management. Employing a 2 min desorb time maintains analytical performance while improving throughput.

Reference

Munch J.W. US EPA Method 524.2 - Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry, Revision 4.1, 1995.