2017 EPA Method Update Rule and EPA Method 624.1

Significance of the topic

Analyzing volatile organic compounds (VOCs) in industrial discharges and environmental waters is critical for protecting public health, supporting regulatory compliance, and ensuring reliable quality assurance/quality control in analytical laboratories. Recent advances in instrumentation and method performance allow laboratories to achieve greater sensitivity and precision while addressing an expanded list of target compounds.

Objectives and study overview

This work evaluates updates introduced by the 2017 EPA Method Update Rule and the revised EPA Method 624.1. The study aims to harmonize Method 624.1 criteria with those of EPA Method 8260B/C, expand the analyte scope, and optimize purge-and-trap GC/MS parameters to increase sample throughput and analytical robustness.

Methodology and Instrumentation

The performance-based approach employs:

• Purge-and-Trap System: OI Analytical Eclipse 4760 with a #10 trap containing Tenax®, silica gel, and carbon molecular sieve.
• Carrier Gas and Conditions: Zero-grade helium at 40 mL/min, 11 min purge at 45 °C; desorb at 190 °C for 0.5 min; bake at 240 °C for 3 min.
• Gas Chromatograph: Agilent 7890A with a 30 m Rtx-VMS capillary column (0.25 mm ID, 1.4 µm film); temperature program from 40 °C to 220 °C over 14.25 min.
• Mass Spectrometer: Agilent 5975C operating in full scan mode (35–300 amu) with a transfer line at 250 °C.
• Calibration and QC: Eight-point calibration (2–200 ppb, extended for difficult compounds), initial demonstration of capability at 50 ppb, and MDL evaluation following 40 CFR Part 136.

Main results and discussion

Calibrations for over 100 VOCs consistently met RSD thresholds of 35% (Method 624.1), 15% (Method 8260B), and 20% (Method 8260C). Initial Demonstration of Capability (IDOC) and Method Detection Limits (MDLs) fell within required limits. Recoveries ranged from 60% to 140%, with relative percent differences below 30%. The expanded analyte list aligns with Method 8260, facilitating concurrent reporting.

Benefits and practical applications

• Combined QC criteria allow simultaneous processing under Methods 624.1 and 8260, reducing laboratory workload and increasing throughput.
• Modern purge-and-trap and GC/MS technologies deliver improved precision, sensitivity, and faster cycle times.
• An extended analyte roster supports comprehensive environmental monitoring and industrial discharge testing under current regulations.

Future trends and potential applications

Emerging developments such as automated sample handling, high-resolution mass spectrometry, and real-time monitoring systems will further enhance VOC analysis. Integration with data analytics, remote sensors, and portable platforms promises faster decision-making and broader field applications.

Conclusion

The 2017 EPA Method Update Rule and Method 624.1 leverage advances in purge-and-trap GC/MS to achieve superior analytical performance compared to earlier protocols. Harmonizing QC criteria with Method 8260 enables laboratories to expand analyte coverage, improve productivity, and maintain stringent regulatory compliance.

References

1. USEPA Method 624.1: Purgeables by GC/MS, December 2014.
2. USEPA Method 8260B: Volatile Organic Compounds by GC/MS, Rev. 2, December 1996.
3. USEPA Method 8260C: Volatile Organic Compounds by GC/MS, Rev. 3, August 2006.
4. USEPA 40 CFR Part 136, Appendix B: Definition and Procedure for the Determination of the Method Detection Limit.
5. Parr, J.L. Proposed Changes to the Clean Water Act, Methods 608, 624, and 625. NELAC Institute, 2017.
6. Parr, J.L. 2016 Chemistry Standard, Volume 1, Module 4. NELAC Institute, 2017.
7. Burrows, R. Why We Need a Standard on Calibration. NELAC Institute Environmental Measurement Methods Expert Committee, 2017.