Strange peak on FID and PFPD

[Noxi]

Hi everybody,

I work on a GC-17A. My system is equipped with two lines:
- one connected to a FID, with a Restek ShinCarbon ST 80/100 column
- one connected to a PFPD, with a Agilent GS-GasPro column
I use the first line for analyzing methane, and the second line for sulphur compounds. I work on natural gases.

Everything seems to work fine, but on my both channel, I have a very strange peak (the first one), and I can't find what it is... Maybe someone can help me ?
I put a chromatogram for example. It is FID response. For PFPD it is a negative peak.



Thank you for any help

[CE Instruments]

My guess would be that it is the disturbance peak from the injection, technically the balance gas. If correct the balance gas has more conduction in the FID than your carrier for FID and less for PFPD. As it is there in excess it is good that the the peak is very small and not surprising it has a tail.

[Noxi]

Great ! Thank you for the reply !