Simultaneous Analysis of Three Greenhouse Gas Components, CH4, CO2, and N2O

Significance of the Topic

Monitoring major greenhouse gases such as methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) is critical for assessing emission sources and evaluating mitigation strategies. CH4 and N2O have much higher global warming potentials than CO2, making sensitive and simultaneous analysis of all three gases essential for environmental research, regulatory compliance and process control.

Objectives and Overview of the Study

This study demonstrates a simple gas chromatographic method for simultaneous determination of CH4, CO2 and N2O using the Shimadzu Nexis GC-2030. Three measurement approaches were compared: split injection with a Dielectric-Barrier Discharge Ionization Detector (BID), splitless injection with BID, and splitless injection with BID-FID series connection. Key goals included achieving high sensitivity, good separation of adjacent peaks (e.g. CH4 and atmospheric krypton) and elimination of complex electron capture detector (ECD) procedures.

Instrumentation Used

• Gas chromatograph: Shimadzu Nexis GC-2030
• Gas sampler: MGS-2030 with 1 mL loop
• Injection unit: SPL-2030 (split and splitless liners)
• Detectors: BID-2030 and FID-2030
• Column: MICROPACKED ST 2 m × 1 mm I.D. (flow calculation via 250 m × 0.5 mm I.D., df 10 μm section)

Methodology and Instrumentation

Three analytical modes were established:

• Split injection (1:4) with BID detection
• Splitless injection with BID detection for increased N2O sensitivity
• Splitless injection with BID-FID series connection for improved CH4 selectivity

Operating conditions included He carrier gas at 9 mL/min, a temperature program from 35 °C to 275 °C, BID discharge gas flow of 50 mL/min at 280 °C, and FID makeup H2/air flows. A short metal capillary linked the BID vent to the FID for co-detection in the BID-FID mode.

Main Results and Discussion

All three gases were resolved and quantified:

• Split mode separated CH4, CO2 and N2O with baseline separation of CH4 from Kr (resolution 0.95).
• Splitless BID detection increased N2O peak area but reduced CH4/Kr resolution (0.76).
• BID-FID series connection restored CH4 selectivity by detecting CH4 on FID (Kr is not seen by FID), while retaining high sensitivity for CO2 and N2O on BID.

Calibration curves over 1–100 ppm CH4, 10–1000 ppm CO2 and 0.1–10 ppm N2O showed excellent linearity (R² > 0.998). Atmospheric measurements yielded CH4 ≈ 1.9–2.2 ppm, CO2 ≈ 427–443 ppm and N2O ≈ 0.31 ppm, in close agreement with theoretical values. Five-run reproducibilities were better than 1.5 % RSD and signal-to-noise ratios exceeded 10 for all analytes.

Benefits and Practical Applications of the Method

• Simultaneous high-sensitivity detection of CH4, CO2 and N2O without ECD.
• Simple GC configuration using BID and optional FID in series.
• Reliable quantification for environmental monitoring, process control and research.

Future Trends and Potential Applications

Advances may include extending the approach to additional trace gases, integrating automated sampling for continuous monitoring, developing portable GC systems for field use, and coupling with advanced data analysis for real-time emission tracking. Improvements in detector design and column technology could further enhance sensitivity and resolution.

Conclusion

The Nexis GC-2030 combined with BID and optional FID series connection provides a robust, sensitive and straightforward solution for simultaneous analysis of the three principal greenhouse gases. This method offers linear calibration, good reproducibility and avoids complex ECD procedures, making it suitable for laboratory and field applications in environmental and industrial settings.