US EPA Method 624 using the Teledyne Tekmar Atomx XYZ and Thermo Scientific™ ISQ™ 7000 Mass Spectrometry (MS) System Coupled with a Thermo Scientific™ TRACE™ 1310 Gas Chromatograph (GC)

Importance of the Topic

Volatile organic compounds in industrial and municipal wastewater pose significant environmental and public health risks. Accurate quantification of these compounds is essential for regulatory compliance, process control, and safeguarding water resources. Advanced sample preparation and analytical techniques help laboratories achieve the sensitivity and reliability required for trace level VOC analysis.

Objectives and Study Overview

This study applies US EPA Method 624 to wastewater samples using a modern purge and trap system coupled with gas chromatography mass spectrometry. The goals include establishing calibration performance, determining method detection limits, and evaluating initial demonstration of capability accuracy and precision while assessing the impact of moisture on analytical results.

Methodology and Sample Preparation

A 50 parts per million calibration standard containing 31 VOCs was prepared in methanol and diluted to produce a water calibration range from 0.5 to 200 parts per billion. Three internal standards and three surrogate standards were spiked at 30 parts per billion. Seven replicates at 0.5 ppb and seven at 5 ppb were analyzed to calculate method detection limits, precision, and accuracy. Key purge and trap parameters included a 5 milliliter sample volume, controlled purge and sweep flows, and a water bake rinse sequence to reduce moisture transfer to the analytical column.

Used Instrumentation

• Teledyne Tekmar Atomx XYZ purge and trap system featuring an advanced moisture control system and efficient trap cooling design
• Thermo Scientific TRACE 1310 gas chromatograph equipped with a narrow bore column and optimized oven temperature program
• Thermo Scientific ISQ 7000 single quadrupole mass spectrometer operated in full scan mode from 35 to 260 atomic mass units

Main Results and Discussion

Calibration curves for all 31 target compounds exhibited linearity with relative standard deviations below 18 percent. Method detection limits ranged from approximately 0.08 to 0.32 parts per billion. Initial demonstration of capability at 5 parts per billion showed accuracy between 81 and 119 percent and precision below 16 percent. Total ion chromatograms confirmed well resolved peaks and minimal interference from residual moisture.

Benefits and Practical Applications

Implementation of the Atomx XYZ system with enhanced moisture control reduces water vapor carryover and extends column lifetime. High sample throughput is achieved through reduced cycle times and an 84 position autosampler. The validated protocol meets regulatory requirements and offers laboratories a robust solution for trace VOC monitoring in wastewater and other aqueous matrices.

Future Trends and Opportunities

Further improvements may arise from faster GC oven temperature ramps and alternative column chemistries that shorten analysis times. Integration with automated data review software and expansion to larger compound lists will support high throughput environmental monitoring and industrial process control. Emerging detectors and software advances will enhance sensitivity and selectivity for complex sample matrices.

Conclusion

This work demonstrates that US EPA Method 624 can be reliably performed on wastewater samples using the Atomx XYZ purge and trap system coupled with TRACE 1310 GC and ISQ 7000 MS. The methodology delivers low detection limits, robust precision and accuracy, and minimal water interference. Opportunities to reduce cycle time promise further productivity gains for analytical laboratories.

Reference

• US EPA Appendix A to Part 136 Methods for Organic Chemical Analysis of Municipal and Industrial Wastewater Method 624 Purgeables 1984