To improve GC-FID resolution for CH₄ and CO, optimize the column type, length, and diameter, adjust temperature programming and carrier gas flow rate, and ensure proper injection techniques. Regularly maintain the column and detector, ensure high-purity samples, and adjust integration settings in your data analysis software.

Dear Mohammed Bajiri,

You are right when you describe the FID peaks as not analysable. Unfortunately, I don't know which GC manufacturer you use. However, I think that the flow rates of the detector are atypical, at least for the GC-FID devices that I know (Agilent)

There the fuel gas composition is 45 m/min H2, 450 ml/min air and 45 ml/min auxiliary gas N2

The auxiliary gas is of particular importance here, as the FID is a flow-dependent detector. If this flow is too low, there will be a loss of sensitivity and/or signal broadening. The auxiliary gas flow also depends on the column used. Capillary columns are usually operated with a low carrier gas flow. With these columns, the column eluate must be additionally accelerated; this is achieved by the auxiliary gas flow. The correct setting for your fuel gases can usually be found in the GC manual or on the Internet. Perhaps you can set the auxiliary gas higher and then observe whether anything changes.

Otherwise, I agree with Dr Balamurugan Krishnamoorthy that you should optimise the GC parameters and, if necessary, also think about the separation column.

Good luck and best wishes

Joachim Horst

Thank you for all the valuable responses. I will follow up yours suggestions.

Hi Mohammed Bajiri,

If you could share complete information of the chromatographic conditions of the method, then can able to provide specific trials to optimize the method. However please see below.

Improving GC-FID resolution and achieving better peak separation for methane and carbon monoxide can involve several strategies. Here are some potential solutions:

1. Column Selection:

Column Type: Ensure you are using the appropriate column for separating small gases. Capillary columns with a stationary phase designed for gas separation (e.g., PLOT columns) can improve separation.

Column Length and Diameter: A longer column or one with a smaller internal diameter can provide better resolution but may increase analysis time.

2. Temperature Program:

Oven Temperature: Optimize your oven temperature program. A slower temperature ramp can help separate closely eluting peaks.

Isothermal Conditions: Sometimes, running the column isothermally at a temperature that provides the best separation for your compounds of interest can be beneficial.

3. Carrier Gas Flow Rate:

Flow Rate: Adjust the carrier gas flow rate. Lowering the flow rate can increase the resolution but may lead to longer retention times.

Gas Type: Ensure the use of a high-purity carrier gas. Impurities in the carrier gas can cause peak distortion.

4. Injection Techniques:

Injection Volume: Optimize the injection volume. Too much sample can overload the column, causing peak distortion.

Split/Splitless Mode: Experiment with split and splitless injection modes. Split injection can help prevent column overload.

5. Detector Settings:

FID Optimization: Ensure that your FID detector settings are optimized for the best sensitivity and resolution.

Gas Purity: Ensure high-purity hydrogen and air for the FID flame to prevent baseline disturbances and peak distortions.

6. Maintenance and Conditioning:

Column Conditioning: Regularly condition your column to remove contaminants that can affect peak shapes.

Detector Cleaning: Ensure the FID detector is clean and well-maintained.

7. Sample Preparation:

Sample Cleanliness: Ensure samples are free from contaminants that can cause peak distortion.

Consistent Sampling: Ensure consistent sampling techniques to avoid variability in peak shapes.

Experimenting with these variables should help you improve the resolution and peak separation in your GC-FID analysis.

With Regards

Jayaprakash Kanijam

These are the configuration of our GC, along with the background of the hydrogen reaction.

Update to the earlier question: I tried using a blank without any catalyst, and I got a clear resolution. After any reaction comes after the blank reaction, the resolution becomes too good. since we have several line flows, the hydrogen line resolution was affected even after the conditioning step we did, what could be the reason that affects the resolution?