Characterization of Capillary Molecular Sieve and Carbonized Molecular Sieve Columns for the Separation of Permanent Gases using an FID with ARC in-jet Methanizer

Significance of Permanent Gas Separation

The separation of permanent gases and light hydrocarbons is critical in industries such as environmental monitoring, petrochemical processing, and quality control. Fast, reliable analysis under isothermal conditions supports high-throughput laboratories and ensures accurate quantification of trace components.

Study Overview

This application note compares four capillary columns—two conventional molecular sieves and two carbonized molecular sieves—using a flame ionization detector (FID) with an in-jet methanizer (Jetanizer™). The aim is to assess retention behavior, peak shape, theoretical plate count, noise, and repeatability for a standard gas mixture containing methane, carbon monoxide, carbon dioxide, acetylene, ethylene, and ethane.

Methodology and Instrumentation

The analysis employed a Shimadzu GC-2030 equipped with an LVO-2030 and a 6-port gas loop sampling valve. Four capillary columns were tested:

• HP-PLOT MS5A (30 m × 0.53 mm × 50 μm)
• CP-Molsieve 5A (25 m × 0.53 mm × 50 μm)
• GS-CarbonPLOT (30 m × 0.53 mm × 3 μm)
• CarboBOND (25 m × 0.53 mm × 10 μm)

Common conditions:

• Isothermal oven (100 °C for molecular sieves; 60 °C for carbonized)
• Injector 200 °C, FID 400 °C with He makeup, H₂ and air flows
• 1 mL gas loop injection, 7:1 split, He carrier at 36.6 cm/s

Results and Discussion

Molecular sieve columns:
The HP-PLOT MS5A eluted methane at 3.05 min and CO at 4.04 min, with sharper peaks and higher theoretical plates than CP-Molsieve 5A (4.71 min and 7.24 min). HP-PLOT MS5A showed lower tailing factors and narrower half-widths.

Carbonized columns:
The GS-CarbonPLOT delivered higher efficiency (more plates, smaller HETP) and lower peak widths for most analytes compared to CarboBOND, which exhibited broader late-eluting peaks (ethylene, ethane). Tailing factors indicated moderate asymmetry under these isothermal conditions.

Noise and repeatability:
Zero-free noise was lowest on CP-Molsieve 5A and highest on GS-CarbonPLOT. All columns demonstrated excellent retention time repeatability (RSD < 0.04 %), with CarboBOND showing the highest area and height variability for CO and CO₂.

Practical Benefits

The HP-PLOT MS5A and CarboBOND columns are recommended for analyses requiring minimal retention of heavy analytes and high separation efficiency. For enhanced CO₂ and hydrocarbon resolution, carbonized sieves—particularly GS-CarbonPLOT—offer superior theoretical plate counts. The Jetanizer enables FID detection of permanent gases without additional hardware.

Future Trends and Opportunities

Further optimization under temperature programming or use of universal detectors (BID, TCD) could expand applicability to other permanent gas mixtures. Emerging column coatings and advanced methanizer designs may improve inertness for reactive gases like CO and CO₂. Integration with high-throughput sampling systems will support rapid environmental and industrial screening.

Conclusion

All four columns achieved reliable separation and repeatability. HP-PLOT MS5A and CarboBOND excelled in peak sharpness and plate counts for heavier components, while carbonized sieves delivered enhanced efficiency for lighter gases. Column choice should balance retention strength, inertness, and resolution based on target analytes.

Reference

Shimadzu Scientific Instruments. SSI-GC-2101: Characterization of Capillary Molecular Sieve and Carbonized Molecular Sieve Columns for Permanent Gas Separation. First Edition January 2021.