Using Hydrogen as Carrier Gas: Fast Detailed Hydrocarbon Analysis (DHA) analog to ASTM D6730

Importance of the Topic

The selection of carrier gas in gas chromatography critically affects analysis speed, cost and performance. With increasing helium prices and supply constraints, hydrogen has emerged as an attractive alternative. Its higher diffusivity allows for faster separations without sacrificing chromatographic efficiency, making hydrogen-based methods valuable for high-throughput hydrocarbon analysis in petroleum and petrochemical laboratories.

Objectives and Overview of the Study

This application note evaluates the performance of hydrogen as a carrier gas in detailed hydrocarbon analysis (DHA) analogous to ASTM D6730. Key aims include demonstrating operational cost savings, comparing runtimes and resolution against helium, and establishing safe implementation guidelines for hydrogen in routine GC workflows.

Methodology and Instrumentation

• Instrumentation Used
  
  • Agilent 7890 Series GC system equipped with Flame Ionization Detector (FID)
  • Combi inlet combining pre-fractionating injector and split/splitless (S/SL) injector
  • Silicone capillary analytical column
  • Automated sample injection device
  • AC pre-fractionator for front-end applications (light ends separation and backflush)
• Methods Compared
  
  • ASTM D6729, D6730, D6733 hydrocarbon analysis methods
  • AC Fast DHA front-end application for naphtha and gasoline range
• Carrier Gas Conditions
  
  • Helium vs. hydrogen at optimized linear velocities based on Golay theory
  • Electronic pressure controls to monitor and shut off gas flow under fault conditions

Key Results and Discussion

• Analysis Time Reduction
  
  • Hydrogen reduced runtimes by up to 1 hour across methods (e.g., ASTM D6730: 173 min → 110 min)
  • Table of average runtimes:
    • D6729: 140 min (He) vs. 90 min (H₂)
    • D6730: 173 min vs. 110 min
    • D6733: 137 min vs. 90 min
    • DHA FE: 137 min vs. 90 min
• Chromatographic Efficiency
  
  • Van Deemter profiles show hydrogen maintains low HETP over a wider velocity range, supporting higher flow rates
  • Critical pair separations (e.g., 1-methylcyclopentene/benzene, 1-methylnaphthalene/n-tridecane) are comparable to helium, with resolution differences within ±0.3
  • Overlayed chromatograms confirm nearly identical peak shapes and baseline separation
• Safety Considerations
  
  • Hydrogen handling must comply with relevant regulations and safety protocols
  • Systems employ electronic pressure sensors and automatic shut-off to detect leaks or unsafe conditions

Benefits and Practical Applications

• Operational Cost Savings
  
  • Hydrogen is approximately four times less expensive than helium
  • Estimated savings of several thousand dollars per laboratory per year when switching 5–10 GC systems to hydrogen
• Increased Throughput
  
  • Shorter analysis cycles enable higher sample throughput for QA/QC and research labs
• Data Quality Maintained
  
  • No compromise in resolution or sensitivity compared to helium-based methods

Future Trends and Potential Applications

• Emerging Column Technologies
  
  • Development of new stationary phases optimized for high-velocity hydrogen separations
• Automated High-Throughput Workflows
  
  • Integration of hydrogen carrier flows in fully automated sample prep and analysis platforms
• Broadening Analytical Scope
  
  • Extending hydrogen-based GC to complex petrochemical and environmental analyses

Conclusion

Hydrogen serves as a superior carrier gas for detailed hydrocarbon analysis, offering substantial reductions in analysis time and operating cost without sacrificing chromatographic performance. Laboratories can safely adopt hydrogen with existing GC platforms equipped with electronic safety controls to achieve higher throughput and long-term cost efficiencies.

References

No specific literature references were cited in the original application note.