US EPA Method 524.4 with the Tekmar Atomx XYZ and the Thermo Scientific™ TRACE™ 1310 GC and ISQ™ 7000 MS System with an ExtractaBrite Source

Significance of the Topic

Volatile organic compounds (VOCs) are widespread contaminants in drinking water that pose health risks even at trace levels. Accurate monitoring of these compounds is essential for regulatory compliance, public health protection, and quality assurance in water treatment facilities. US EPA Method 524.4, which combines purge-and-trap (P&T) concentration with gas chromatography–mass spectrometry (GC–MS), remains a gold standard for trace-level VOC analysis in aqueous matrices.

Objectives and Study Overview

This application note evaluates the performance of the Teledyne Tekmar Atomx XYZ P&T system coupled to a Thermo Scientific TRACE 1310 GC and ISQ 7000 MS with an ExtractaBrite source. The study aimed to demonstrate linear calibration, method detection limits (MDLs), initial demonstration of capability (IDC), accuracy, precision, and minimum reporting levels (MRLs) for 75 target VOCs in drinking water, as defined by EPA Method 524.4.

Methodology

A 25 ppm multi-compound standard in methanol was diluted to generate a nine-point calibration curve from 0.2 ppb to 50 ppb (r² ≥ 0.995). Three internal standards and three surrogate standards were added to each 5 mL sample to achieve 12.5 ppb. Seven replicates at 0.5 ppb determined MDLs and MRLs; seven replicates at 5 ppb assessed IDC, accuracy, and precision. P&T parameters such as sample volume, purge time, trap bake, and rinse cycles were optimized to minimize water interference and maximize analyte recovery.

• Sample volume: 5 mL
• Purge time: 5.5 min at 80 mL/min
• Desorb temperature: 250 °C for 1 min
• Bake temperature: 280 °C for 6 min

Instrumental Setup

• Teledyne Tekmar Atomx XYZ purge-and-trap concentrator with moisture control system
• Thermo Scientific TRACE 1310 GC with 20 m × 0.18 mm, 1 µm TG VMS column
• ISQ 7000 MS with ExtractaBrite ion source, scan range 35–260 amu

Key Results and Discussion

Calibration linearity exceeded r² = 0.995 for nearly all analytes. MDLs ranged from 0.05 ppb to 0.18 ppb, with most compounds below 0.1 ppb. IDC precision and accuracy fell within ±20%, and MRL confirmation met the required 50–150% UI/LI criteria. Iodomethane and pentachloroethane showed deviations due to limited calibration range and thermal instability. A representative total ion chromatogram of a 5 ppb standard demonstrated sharp peaks and negligible water interference.

Benefits and Practical Applications

The Atomx XYZ system’s rapid trap cooling and enhanced moisture removal reduced cycle time by up to 14%, enabling up to three analyses per hour. Robust valve design and integrated autosampler increase throughput, making this configuration ideal for high-volume environmental laboratories and regulatory agencies.

Future Trends and Potential Applications

Further reductions in GC oven ramp times and alternative column chemistries may decrease analysis time while maintaining resolution. Integration of advanced data processing and machine learning algorithms could streamline peak identification and quantitation. Expanding the method to emerging contaminants and automated on-line P&T–GC–MS platforms represents the next frontier in continuous water quality monitoring.

Conclusion

The combined Atomx XYZ P&T and TRACE 1310 GC/ISQ 7000 MS system reliably meets US EPA Method 524.4 performance requirements for trace VOC analysis in drinking water. The approach delivers excellent linearity, low detection limits, and high throughput, supporting regulatory compliance and safeguarding public health.

References

• Munch DJ. Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry; US EPA Method 524.3 – Rev. 1.0, June 2009.
• Munch DJ, Wendelken SC. Measurement of Purgeable Organic Compounds in Water by Gas Chromatography/Mass Spectrometry Using Nitrogen Purge Gas; US EPA Method 524.4, May 2013.