Performance of EPA Method 8270 using Hydrogen Carrier Gas on SCION GC MS

Importance of the topic

Analyzing semi-volatile organic compounds (SVOCs) by GC-MS is vital for environmental monitoring, regulatory compliance, and contamination assessment. The rising cost and limited supply of helium have prompted laboratories to explore hydrogen as an alternative carrier gas. This shift requires careful consideration of hydrogen’s reactivity and safety, making robust instrumentation and optimized methods essential for reliable results.

Objectives and study overview

This study evaluates the performance of a helium-free SCION GC-MS system under the parameters of EPA Method 8270 when operated with hydrogen carrier gas. Key objectives include meeting method specifications for tuning, calibration, sensitivity, and spectral quality across diverse SVOCs and matrix types.

Methodology and instrumentation

The analytical workflow employs:

• Pulsed split injection (0.5 µL at 40 psi × 0.3 min) to minimize residence time and prevent inlet reactions.
• Single goose-neck 4 mm open inlet liner to avoid glass wool and compound degradation.
• SCION-5MS capillary column (20 m × 0.18 mm × 0.18 µm) with oven program from 45 °C to 310 °C.
• Hydrogen carrier gas at 1 mL/min.
• SCION Select Helium Free mass spectrometer with axial ion source, transfer line at 300 °C, ion source at 330 °C, and scan range 45–500 Da.
• Calibration using 76 target compounds from 0.075 ppm to 200 ppm; dichloromethane as solvent; internal standards at 40 ppm.
• Compound Based Scanning (CBS) for mixed scan mode acquisition.

Main results and discussion

Key findings include:

• Successful auto-tuning with DFTPP meeting all acceptance criteria.
• Linear calibration curves (R² > 0.995) across both standard and extended low-level ranges.
• System performance checks (SPCCs) and continuing calibration checks (CCCs) passed method limits with RSDs typically below 10 %.
• Minimal reactivity observed with hydrogen, as indicated by response factor stability and low background after instrument conditioning.
• High-quality library matches (>96 %) for all 76 analytes using NIST database searches, demonstrating spectral integrity.
• Robustness confirmed by 50 consecutive injections of a sludge extract, showing negligible drift in surrogate recoveries and calibration check concentrations.

Benefits and practical applications

The validated method offers:

• Reduced operating costs and dependency on helium supplies.
• Maintained or improved sensitivity and precision for complex matrices.
• Enhanced spectral quality via axial ion source to minimize protonation and matrix effects.
• Streamlined workflows with CBS for easy method setup and data acquisition.

Future trends and applications

Emerging directions include:

• Broader adoption of hydrogen carriers in routine GC-MS analyses.
• Advancements in ion source design to further mitigate reactive gas effects.
• Integration of high-throughput data processing and automated quality control.
• Extension of method 8270 adaptations to new environmental and industrial matrices.

Conclusion

The SCION helium-free GC-MS platform successfully meets and exceeds EPA Method 8270 requirements using hydrogen carrier gas. It delivers robust performance, reliable quantitation, and high spectral quality across a wide range of SVOCs and challenging sample matrices.

References

• US Environmental Protection Agency. Method 8270: Semi-Volatile Organic Compounds by GC-MS.
• SCION Instruments. Application Note AN0018: Performance of EPA Method 8270 using Hydrogen Carrier Gas on SCION GC-MS.