Square peaks on FID and tCd

[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.

[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

[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

[Peter Apps]

Off scale peaks ?

Peter

[chromatographer1]

Yes, Peter, but without the additional information we are all just guessing.

I hope fshah24 complies.

Rod

[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