Analysis of Gas Sample Using Single-Oven MDGC

Significance of the Topic

Multidimensional gas chromatography (MDGC) enhances the separation of complex gas mixtures by coupling columns of different selectivities. Implementing MDGC in a single-oven configuration reduces instrument footprint and cost while maintaining high resolution. This capability is essential for applications in petrochemical analysis, environmental monitoring, and quality control where accurate quantification of hydrocarbons and permanent gases is required.

Aims and Study Overview

This study presents two approaches for gas sample analysis using a Shimadzu GC-2010 Plus system: single-oven MDGC for separating C1–C5 hydrocarbons and inorganic gases, and detector-switching analysis for routing sample fractions to the most suitable detector (FID or TCD).

Methodology

The workflows consisted of:

• Single-Oven MDGC Heart-Cutting: A non-polar Rtx-1 column and a Molsieve 5A PLOT column were arranged with a flow-switching device. Methane and permanent gases were directed to the TCD, while higher hydrocarbons were heart-cut to the second column and detected by the FID.
• Detector-Switching Analysis: A micro-packed Shincarbon-ST column was used with a switching device to route early-eluting permanent gases to the TCD and later hydrocarbons to the FID. A manufacturer’s pressure–flow table ensured optimal carrier gas flow in the packed column.

Used Instrumentation

• Gas Chromatograph: Shimadzu GC-2010 Plus
• Columns:
  • Rtx-1 (30 m × 0.32 mm I.D., 5 µm)
  • Molsieve 5A PLOT (25 m × 0.32 mm I.D., 30 µm)
  • Micropacked Shincarbon-ST (2 m × 1 mm I.D., 80/100 mesh)
• Detectors:
  • TCD at 200–280 °C, make-up He 20 mL/min
  • FID at 280–300 °C, H2 40 mL/min, Air 400 mL/min, make-up He 30 mL/min
• Switching Device and Restrictors (0.5 m × 0.15–0.18 mm I.D.)

Main Results and Discussion

Chromatograms from the MDGC method showed clear separation of methane, ethane, ethylene, propylene, and C4 isomers, as well as n- and iso-pentane. Permanent gases (N2, O2, CO, CO2, H2) were resolved on the Molsieve 5A column and detected by TCD. Detector-switching analysis achieved efficient routing of early eluting gases to the TCD and hydrocarbons to the FID, demonstrating the flexibility to optimize sensitivity for different compound classes.

Benefits and Practical Applications

• Reduced instrument complexity by using a single oven for MDGC.
• Improved separation of isomeric hydrocarbons and permanent gases in a single run.
• Flexible detector assignment maximizes sensitivity and dynamic range.
• Applicable to environmental, petrochemical, and industrial quality control laboratories.

Future Trends and Possibilities of Use

Integration of software-driven switching programs and automation will streamline method development. Emerging column materials and advanced detectors (e.g., mass spectrometry) can further enhance selectivity and sensitivity. Remote monitoring and data analytics will support real-time decision making in process control and environmental compliance.

Conclusion

The single-oven MDGC and detector-switching strategies demonstrated here provide a compact, cost-effective solution for comprehensive gas analysis. By combining complementary columns and routing capabilities, laboratories can achieve high-resolution separations and tailored detection for a wide range of applications.