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Re: GC-FID Noise
Posted: Wed Jun 15, 2011 4:01 am
by thohry
You can try to isolate the column from the FID and see if the signal is still high, then you can find out the reason. The quality of compressed air is also one of the reasons. You may have to put in a zero air filter.
Re: GC-FID Noise
Posted: Wed Jun 15, 2011 7:17 am
by Peter Apps
So you have some long term drift in standing signal. Does this affect your analysis ? Have you done any of the troubleshooting that has been suggested ?
Peter
Re: GC-FID Noise
Posted: Wed Jun 15, 2011 7:23 am
by Axar
So you have some long term drift in standing signal. Does this affect your analysis ? Have you done any of the troubleshooting that has been suggested ?
Peter
I've changed some traps but had no chance to check result yet. I don't know how it can affect my analysis.
Re: GC-FID Noise
Posted: Wed Jun 15, 2011 8:39 am
by Peter Apps
The first thing that you need to do is to remove the column from the detector, plug the connection, and check the baseline and whether it drifts. This will immediately tell you whether the carrier gas is part of the problem.
Unless you know that this is a problem with an actual analysis you might well be worrying abut nothing.
Peter
Re: GC-FID Noise
Posted: Wed Jun 15, 2011 5:54 pm
by aldehyde
What are your flow settings?
If you have just air and hydrogen (no make up) does the signal drop? I have seen contaminated gases do exactly this.
If you have contamination in air/hydrogen lines it may be difficult to tell if there is an effect.
Is this plumbed directly between gas tanks and GC or is there common gas supply to other working instrument?
Re: GC-FID Noise
Posted: Fri Jun 24, 2011 7:29 am
by Axar
Well, It is revealed, that traps had not been replased for years at this GC. I'm going to check all of them. (moisture trap in H2-generator and Hydrocarbon trap at air flow are firts at a row).
My bad, I should be more accurate with instrument's past next time.
Thanx for your assistance!!!
Re: GC-FID Noise
Posted: Sat Jun 25, 2011 4:57 pm
by aldehyde
Once a trap is saturated with hydrocarbons/the oxygen scrubber is depleted it turns into a sponge that just emits constant levels of contamination rather than helping you
.
A very common problem.
Re: GC-FID Noise
Posted: Sun Jun 26, 2011 5:33 pm
by Axar
A very common problem.
Yeah! I'm in process of recovering H2O trap from moisture now. Still I want to place air generator away from HPLC's. But I don't think you can help me in conversation with my boss
