Air in Shimadzu2010-GC chromatogram (BID detector)

[BID]

Hello All,

We have a gas-chromatograph device in our petrochemical lab: a Shimadzu 2010 Tracera.
It has a BID (Barrier Discharge Ionization Detector) and has a Micropacked-ST column in it.
We use He as carrier gas.

We want to measure petrochemical gas samples (C2 fraction) and would like to assay the hydrocarbons and the traces of CO; CO2; O2; N2 in it.

The problem is that air is in the chromatogram.
Even after checking for any leaking in the GC and changing the sample-injection method.

How air could get into the system? How could we exclude air? We do not have any idea.

Thank you guys for your helpful suggestions!

Regards,
BID

[yazmer]

Is there air in your sample? Does the balance of your C2 fraction contain air? Is your sample exposed to air at any point? Secondly, if you are using a valco valve, there is always going to be some air in your loop. Having a purge valve on it does help. hopefully the concentration of your desired compounds is in much higher concentration of that air. Also plumbing the valve (inside the oven) after the injection port may help.

[BID]

Thank you for your suggestions Yazmer! Here I have answers for your questions:

Is there air in your sample? No. If yes, then must be only sampling error.

Does the balance of your C2 fraction contain air? No.

Is your sample exposed to air at any point? No.

...if you are using a valco valve... We don't use valco valve. We have purge at the injection port.

Anyway I asked a professional and he suggested that the problem must be around the injection port. But that is all we know.