Analysis of Permanent Gases and Methane with the Agilent 6820 Gas Chromatograph

Significance of the Topic

Permanent gas analysis plays a crucial role in petrochemical, chemical and energy industries by monitoring trace levels of CO, CO2, O2, N2 and CH4 to ensure process efficiency, catalyst performance and product quality.

Study Objectives and Overview

This application focused on evaluating the Agilent 6820 Gas Chromatograph with single-filament Thermal Conductivity Detector for the determination of permanent gases and methane at ppm levels. The study configured a flexible system using valves and capillary PLOT columns for selective separation and detection.

Methodology and Instrumentation Used

• Agilent 6820 GC with purged packed inlet and single-filament TCD
• 10-port gas sampling/backflush valve and 6-port isolation valve for column switching
• HP-PLOT Q columns (15 m and 30 m, 0.53 mm ID) and HP-PLOT Molesieve 5A column (30 m, 0.53 mm ID)
• Carrier gases: hydrogen for routine analysis and helium for fuel cell gas mixtures
• Dynamic blending of 100 ppm standard to 10 ppm using Scott Specialty Gases standard
• Data acquisition with Agilent Cerity QA/QC software at 5 Hz

Key Findings and Discussion

Baseline separation and stable responses were achieved for permanent gases at both 100 ppm and 10 ppm levels using hydrogen carrier. The single-filament TCD offered low noise and drift. The PLOT Molesieve 5A column retained O2, N2, CO and CH4 while PLOT Q separated CO2 and light hydrocarbons. Fuel cell gas mixtures were resolved using helium carrier; hydrogen appeared as a negative peak until polarity was reversed for a positive response.

Benefits and Practical Applications of the Method

• High sensitivity and stability for low-ppm detection
• Modular configuration enables analysis of light hydrocarbons (C1–C8) with FID
• Rapid response and minimal dead volume
• Applicable to petrochemical QA/QC, natural gas, refinery streams and fuel cell development

Future Trends and Opportunities

Further improvements in capillary PLOT columns and detector designs will reduce detection limits and enhance selectivity. Integration of automated blending, advanced data processing and compact GC platforms will support emerging needs in hydrogen purity analysis and environmental monitoring.

Conclusion

The Agilent 6820 GC with single-filament TCD and capillary PLOT columns provides robust, sensitive and flexible analysis of permanent gases and methane down to 10 ppm, making it a valuable asset for industrial and research laboratories.

References

1. ASTM D2504-88(1998) Standard Test Method for Noncondensable Gases in C2 and Lighter Hydrocarbon Products by Gas Chromatography
2. ASTM D1946-90(2000) Standard Practice for Analysis of Reformed Gas by Gas Chromatography
3. China National Standard GB/T3394-93 Ethylene and Propylene for Industrial Use – Determination of Trace Carbon Monoxide and Carbon Dioxide
4. Roger Firor, Automated Dynamic Blending System for the Agilent 6890 Gas Chromatograph: Low Level Sulfur Detection, Agilent Technologies Publication 5988-2465EN
5. Roger Firor, Capillary Gas Chromatography Systems for Permanent Gases and Light Hydrocarbons, Agilent Technologies Publication 228-125