Methanol Analysis in Natural Gas Using an Agilent 990 Micro GC Equipped with the MES (TCEP) Channel

Significance of Methanol Analysis in Natural Gas

Natural gas liquefaction and transportation can be compromised by residual methanol that freezes under low temperatures, leading to pipeline blockages and safety risks. Monitoring trace methanol levels ensures efficient removal processes and safe operations.

Objectives and Study Overview

This study demonstrates a rapid and sensitive method for quantifying methanol in natural gas streams using an Agilent 990 Micro GC equipped with a MES (TCEP) channel. The approach aims to achieve sub-ppm detection, excellent repeatability, and analytical cycle times under three minutes.

Methodology and Instrumentation

Experimental parameters were optimized on a 15 m MES (TCEP) straight channel with helium carrier gas at 200 kPa. Sample injections (40 ms) and 30 s sampling times at 110 °C injector and 65 °C column temperature produced well-resolved peaks for n-C11, methanol, and n-C12. A series of standard gases (11.1 ppm MeOH) were diluted to 3.2 ppm to evaluate detection limits and linearity.

Main Results and Discussion

Chromatograms showed clear separation of methanol eluting after n-C11, with analytical cycles below three minutes. Ten-run sequences yielded retention time RSDs below 0.2 % and area RSDs under 5 %. Methanol displayed a linear response down to 3.2 ppm with a response factor RSD of 2.4 %. The calculated lower detection limit was 1.4 ppm (2 × S/N). Analysis of a real natural gas sample confirmed absence of methanol under typical field conditions.

Benefits and Practical Applications

• Fast, sub-3-minute analysis per run
• Low power and carrier gas consumption for online monitoring
• High sensitivity (LDL 1.4 ppm) and linear quantification
• Excellent repeatability (RT RSD < 0.2 %; area RSD < 5 %)

Future Trends and Potential Applications

Integration of micro GC systems into process control loops can enable real-time monitoring of polar contaminants in natural gas and related streams. Future developments may extend the approach to other reactive or polar analytes in petrochemical and environmental matrices.

Conclusion

The Agilent 990 Micro GC with MES (TCEP) channel offers a robust, rapid, and sensitive solution for trace methanol analysis in natural gas, combining short cycle times, low detection limits, and high repeatability for effective process monitoring.

Reference

1. Bajja, M.; van Loon, R. Analysis of Acetone, MeOH, and Ethanol in Air Using the Agilent 490 Micro GC; Agilent Technologies Application Note 5990-9105EN, 2011.
2. Yue, F. Natural Gas Analysis Using the Agilent 990 Micro GC Equipped with COX and 5CB Channels; Agilent Technologies Application Note 5994-7012EN, 2023.
3. Bajja, M.; van Loon, R. Analysis of Methyl Ethyl Sulfide (MES) in Natural Gas Using the Agilent 490 Micro GC; Agilent Technologies Application Note 5990-8750EN, 2011.