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Square peaks on FID and tCd
Posted: Mon Feb 27, 2012 9:53 pm
by fshah24
Hi,
I have 7890A GC with Front FID; Back FID and Aux TCD.
Initially, I used a gas composition of CH4 1
C2H4 1%
C2H6 1%
CO 1%
CO2 80%
N2 15%
O2 0%
H2 1%
Ar 0%
And this gave me nice peaks
I changed the composition to
CH4 10%
C2H4 10%
C2H6 10%
CO 10%
CO2 10%
N2 15%
O2 10%
H2 10%
Ar 15%
And now I started getting square peaks. Can someone help me.
Thanks.
Re: Square peaks on FID and tCd
Posted: Mon Feb 27, 2012 9:58 pm
by chromatographer1
oh come on.
No column or sample size is given.
Let's discuss after you can share these essential details.
I guess you might be thinking column overload.
Share?
Rod
Re: Square peaks on FID and tCd
Posted: Tue Feb 28, 2012 3:21 pm
by AICMM
fshah24,
Might I suggest you also post a chromatogram? FID's are extremely linear and that goes for the the electronics as well so I would very much like to see your chromatogram.
Best regards,
AICMM
Re: Square peaks on FID and tCd
Posted: Tue Feb 28, 2012 3:38 pm
by Peter Apps
Off scale peaks ?
Peter
Re: Square peaks on FID and tCd
Posted: Tue Feb 28, 2012 3:59 pm
by chromatographer1
Yes, Peter, but without the additional information we are all just guessing.
I hope fshah24 complies.
Rod
Re: Square peaks on FID and tCd
Posted: Thu Mar 01, 2012 6:02 pm
by vajjara
In your first injection the CO2 is 80% and in the second injection it is 10 %. In your second chromatogram the peaks are square, meaning amp is saturated, i.,e your CO2 also would have saturated, if this is the case then in your first chromatogram 80 % CO2 must be square i.,e saturated. To solve the problem, (1) attenuate your signal using software.
Vajjara