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FID signal - noise at the apex of the peak
Posted: Tue Jan 04, 2011 7:03 am
by thohry
Hi all,
I just met this situation: the peaks are more noisy at the top, the baseline seems OK (see picture bellow).
That are hydrocarbon peaks (FID) in a Toga analysis. The GC is new.
Thanks for any inputs.
Re: FID signal - noise at the apex of the peak
Posted: Tue Jan 04, 2011 5:58 pm
by Consumer Products Guy
Almost looks like the time about 30 years ago that I forgot to turn the air flow on to the FID detector. Check the basics.
Re: FID signal - noise at the apex of the peak
Posted: Wed Jan 05, 2011 4:20 pm
by thohry
Almost looks like the time about 30 years ago that I forgot to turn the air flow on to the FID detector. Check the basics.
Thanks for your answer. The GC is an Agilent 7890 and brand new. Anyway, I will check the flow rates of H2, Air and see.
Re: FID signal - noise at the apex of the peak
Posted: Wed Jan 05, 2011 10:10 pm
by AICMM
thohry,
How much are you shooting? Is this a standard or is this a standard in oil or is this just the oil? You are a little noisy for an FID but not that noisy, I am guessing that you are running +/- about 0.3 pA? This is high for an FID but not outrageous. If you think this is too high, I would look at your gas supplies for contamination and then I would look for leaks.
Best regards,
AICMM
Re: FID signal - noise at the apex of the peak
Posted: Thu Jan 06, 2011 8:50 am
by thohry
thohry,
How much are you shooting? Is this a standard or is this a standard in oil or is this just the oil? You are a little noisy for an FID but not that noisy, I am guessing that you are running +/- about 0.3 pA? This is high for an FID but not outrageous. If you think this is too high, I would look at your gas supplies for contamination and then I would look for leaks.
Best regards,
AICMM
Thanks AICMM for the input.
I injected standards, not oil and it's about 100 ppm (at max). The noise at the peak apex is about 1.5pA for the later peaks. I have put filters in the carrier gas line and it is better, just a bit.
Regards
Re: FID signal - noise at the apex of the peak
Posted: Thu Jan 06, 2011 9:20 am
by Peter Apps
If the GC is new it should have some kind of guarantee on it, in which case this is Agilent's problem. Did it pass it's installation tests ?
Peter
Re: FID signal - noise at the apex of the peak
Posted: Thu Jan 06, 2011 9:47 am
by thohry
If the GC is new it should have some kind of guarantee on it, in which case this is Agilent's problem. Did it pass it's installation tests ?
Peter
The installation test is OK, it's C14, 15 and C16 peaks and they all are OK.
This one has FID, Ni converter and TCD. I am thinking about the argon cylinder but not so sure.
Thanks and regards
Re: FID signal - noise at the apex of the peak
Posted: Sat Jan 08, 2011 3:35 am
by thohry
Thanks all for replying.
It's now OK after conditioning the column, inlet etc.. and gas filtering.