Chromatography Forum

This is the chromatogram when I monitor my GC system. This is a capillary column with FID detection. An analyst replaced the liner, septum ferrules and then installed her column. The only signal, at first, was just baseline noise, even though there were many injections. Today the column was reinstalled with 10 cm of length from each side of the column cut off. Now, at 50 C I see the following.



Does anyone know whats going on? For some of you more experienced Analysts this might be a no-brain'er. Thanks for any help.

MestizoJoe: there is definitely something going on with your Detector in that it is giving a carbon-burn signal according to a systematic regular cycle which almost resembles an oscillation pattern.
Please provide us with the run parameters and the identity of the compound being analyzed.

have you done any maintenance on your detector recently?

I don't suppose your FID has automatic re-ignition? Your pattern looks like the flame keeps getting ignited then quenched, then re-ignited.

If so I'd try removing the detector, cleaning the area out and sonicaing the torch.

jh1's suggestion is a good one, I have also seen something like this when using a gas generator to supply the make-up nitrogen.

This might also be due to a problem with detector or carrier gas controllers - do you see any fluctuations in pressures and flows ?

Peter

I think JH1 has nailed the issue, it remains to be seen what is causing the re-ignition.

Leaks, flows out of control, deposits in the flame tip, are all possibilities.

Time for someone who is experienced to fix the darn thing.

Do you have anyone like that?

Rodney George
consultant

Yes! Thank you JH1. The flame did repeatedly reignite. The problem was solved when we cleaned the jet which was clogged. I'm not sure if that was the primary issue but once we put the detector back together everything was fine.

Thanks guys.

I am not experienced but I fixed it anyway because I am a nice guy.

You were inexperienced but looks like you are getting more and more of it. Congratulations on the fix.

I hope they appreciate you.

Rodney George

I know you fixed the problem already, but you should also make sure you detector offset isn't set too high.