Mystery Spike GC-FID with Methane

[Ceomgenus]

I'm getting started with some research in a lab using a new GC-FID. To get started, I thought I would try and construct some calibration curves. I decided to start with Methane so that I can get a feel for the unretained times also.

The sample I am running is just methane in nitrogen, but I keep getting two spikes on my chromatogram. I ran the sample through GC-MS to try and figure what the second one is, but the GC-MS only gave me one carbohydrate spike - Methane.

I also ran a sample of just nitrogen to make sure it wasn't anything inside the GC-FID, and there was no response.

Any impurities in the sample should have shown up in the GC-MS, and any impurities in the equipment should have shown up when I ran a sample of nitrogen. Does anyone have any ideas?

[Don_Hilton]

What was the source of your methane and how big was the second peak on the FID? What mass range were you using on the GC/MS?

Unless you are using one of the very pure grades of methane, espect traces of other stuff in it.

[HW Mueller]

Just for the record: Methane is a hydrocarbon, not a carbohydrate.