Two Methods to Perform the New US EPA Method 1628 with GC/MSD: Traditional Helium Carrier Gas and Hydrogen Carrier Gas

Importance of the Topic

Polychlorinated biphenyls (PCBs) are persistent organic pollutants with known carcinogenic potential that bioaccumulate in the environment. Reliable analytical methods are critical for monitoring PCB contamination in water, soil, sediment, biosolids, and tissue to support regulatory compliance and environmental protection. The US EPA Method 1628 provides a standardized low-resolution GC/MS approach for simultaneous quantitation of selected PCB congeners and screening of all 209 congeners.

Objectives and Overview of the Study

This study aims to develop and compare two analytical workflows for EPA Method 1628 using traditional helium carrier gas and an alternative hydrogen carrier gas. Both methods target the quantitation of 65 PCB congeners using low-resolution mass spectrometry with selective ion monitoring (SIM) and screen all 209 congeners. The hydrogen-based method is adapted via Agilent MassHunter Method Translator to maintain performance while reducing analysis time and reliance on helium.

Methodology and Instrumentation

• Sample Analytes: 209 native and 35 isotope-labeled PCB congeners.
• Helium Carrier Gas Method: Agilent 8890 GC coupled to 5977C MSD with extractor ion source; two Agilent J&W 30 m × 250 µm × 0.5 µm columns joined by a purged union for backflushing; helium flow and temperature gradient optimized per EPA 1628.
• Hydrogen Carrier Gas Method: Same GC/MS hardware with stainless steel tubing for hydrogen delivery; two Agilent J&W 20 m × 180 µm × 0.36 µm columns; HydroInert ion source; initial hydrogen method generated via MassHunter translator and refined for faster gradient and SIM timing.

Main Results and Discussion

Both methods achieved baseline separation of non co-eluting PCB congeners within 40 minutes under helium and within a shorter runtime using hydrogen without compromising resolution. Calibration curves for representative congeners PCB 11 and PCB 180 demonstrated linearity across 2.5–5 to 200 ppb using true isotopic dilution. The regulatory requirement for resolution between congeners 28 and 31 (valley < 80% of peak height) was met in both workflows. Hydrogen carrier gas delivered comparable chromatographic performance, maintained method detection limits at single-digit ppb, and reduced total analysis time by approximately 20–30%.

Benefits and Practical Applications

• Reduced operating costs through substitution of hydrogen for helium.
• Increased sample throughput due to shorter run times.
• Maintained compliance with EPA 1628 performance criteria for sensitivity, resolution, and quantitation.
• Flexible implementation in environmental monitoring, QA/QC laboratories, and industrial analytics.

Future Trends and Potential Applications

Advances in GC/MS method translation and hydrogen-inert hardware may further accelerate high-throughput screening of persistent organic pollutants. Broader adoption of hydrogen carrier gas can mitigate helium supply challenges and reduce laboratory carbon footprints. Integration with automated sample preparation and high-resolution mass spectrometry could extend this approach to emerging contaminants beyond PCBs.

Conclusion

Two robust GC/MSD methods for EPA Method 1628 have been validated using helium and hydrogen carrier gases. The hydrogen-based workflow, developed via Agilent MassHunter Method Translator, achieves comparable sensitivity and resolution while reducing analysis time and operational costs. Both approaches reliably detect and quantify PCB congeners down to single-digit ppb levels, supporting environmental compliance and quality assurance.

Reference

1. US EPA. Learn about Polychlorinated Biphenyls (PCBs). https://www.epa.gov/pcbs/learn-about-polychlorinated-biphenyls (accessed May 1, 2024).
2. US EPA. Method 1628: Polychlorinated Biphenyl (PCB) Congeners in Water, Soil, Sediment, Biosolids, and Tissue by Low-resolution GC/MS using Selected Ion Monitoring. July 2021.