Optimized Polycyclic Aromatic Hydrocarbons (PAHs) Analysis Using Triple Quadrupole GC/MS with Hydrogen Carrier

Importance of the Topic

The analysis of polycyclic aromatic hydrocarbons (PAHs) is critical for monitoring trace contaminants in food, water, soil, and air. Recent helium shortages have driven demand for alternative carrier gases in gas chromatography. This work demonstrates a robust method combining hydrogen carrier gas with triple quadrupole GC/MS for sensitive and reliable PAH detection.

Aims and Overview of the Study

This study aims to adapt a conventional helium-based PAH GC/MS method to hydrogen carrier gas while preserving chromatographic resolution, sensitivity, and quantitative performance. Key objectives include optimizing column dimensions, inlet conditions, MRM transitions, and collision energies for hydrogen.

Methodology and Instrumental Setup

• Gas Chromatograph: Agilent 8890 GC with a pulsed splitless inlet (40 psi until 0.75 min).
• Carrier Gas: Ultra-high-purity hydrogen at constant flow (0.65 mL/min).
• Column: DB-EUPAH, 20 m × 0.18 mm ID × 0.14 µm film thickness, initial pressure 4.85 psig.
• Mass Spectrometer: Agilent 7000D triple quadrupole MS with Inert Extractor Source and 9 mm XTR lens.
• Ionization and Collision: Electron ionization; nitrogen collision gas at 1.5 mL/min; collision energies optimized automatically via MassHunter MRM Optimizer.
• Temperature Program: Inlet 320 °C; source 325 °C; transfer line 320 °C; oven ramp 60 °C (1 min) → 200 °C at 25 °C/min → 335 °C at 8 °C/min (6.33 min).

Main Results and Discussion

• Chromatography: Hydrogen carrier increased resolution of late-eluting PAHs (e.g., benzo[b/k/j]fluoranthenes) versus helium.
• Sensitivity: For 26 of 27 target PAHs, signal-to-noise exceeded 3 at 0.1 pg; acenaphthylene LLOQ set at 0.25 pg.
• Linearity: Calibration R² > 0.999 for 24 analytes (0.1–1 000 pg) and > 0.996 for 26 analytes; acenaphthylene R² = 0.9999 (0.25–1 000 pg).
• Accuracy and Precision: At 100 pg, most analytes quantified within ±4% of target; dibenz(a,h)anthracene within ±9%. Internal standards showed RSD ≤ 7.5% across the calibration range.

Benefits and Practical Applications

• Eliminates reliance on helium, securing method continuity amid supply constraints.
• Maintains high sensitivity and wide dynamic range for regulatory and research QA/QC.
• Enhances chromatographic separation of critical isomers, improving quantitation confidence.
• Reduces system downtime through optimized inlet liners and extractor lens configuration.

Future Trends and Possibilities of Application

Further developments may include expansion to other environmental and food-related contaminants, integration with automated data processing and AI-driven peak deconvolution, and application of hydrogen carrier methods in portable GC/MS platforms for on-site monitoring.

Conclusion

The optimized triple quadrupole GC/MS method using hydrogen carrier gas delivers robust, sensitive, and accurate PAH analysis across a broad calibration range. Key innovations—column sizing, high-temperature zones, extractor lens, and automated collision energy tuning—address common challenges and ensure reliable performance.

Used Instrumentation

• Agilent 8890 Gas Chromatograph with pulsed splitless inlet.
• Agilent 7000D Triple Quadrupole Mass Spectrometer with Inert Extractor Source and 9 mm XTR lens.
• DB-EUPAH GC column (20 m × 0.18 mm ID × 0.14 µm).
• Agilent Universal Low Pressure Drop inlet liner (5190-2295).
• MassHunter Acquisition software with MRM Optimizer.

References

• A. Andrianova and B. D. Quimby, Optimized PAH Analysis Using Triple Quadrupole GC/MS with Hydrogen Carrier, Agilent application note 5994-2192EN, 2020.