Chromatography Forum

No problem detected when I don't inject (condition only). No problem when I inject from an empty vial.

I think you're right Peter, I should call the technician and use the guarantee before it expires. And before the problem gets worse.

If the technician can explain the problem I'll post the solution here.

@WillyOne: Ok, that will be useful for the technician I think.

Thank you all for the response!

Jeremy

A bit weird problem. As I know the FID signal cannot be below 0, and if you are coming near this the system should assume that FID has been flamed out, and would try to reignite it, what would be shown a spikes on chromatograph, so it has to be something with configuration of signal.
Do you use column compensation, if yes then turn it of and try injecting again.

Are you using an analogue out to a data station or direct digital ? I guess that you are using an analogue out as the GC cannot give a negative output in pA via digital..... Unless you have a column compensation subtracted from the actual chromatogram ?? Analogue system , it needs a baseline zero value set.

As I see it there are two problems. first the "negative" of the output, perhaps due to the above and secondly why on this GC only you have a baseline that dips post injection before rising slowly. The dip you see is unusual and is not characteristic of a specific problem. If under warranty get the supplier in. If not you need to check everything from the injector, gases, column to the detector.

Very odd you run Hydrogen carrier then add Helium make up. You can probably manage without make up and save money.

Anevo,

A long shot but check on your GC itself to make sure that the zero is not set to some value. On a 7890, look at Analog Out and scroll down to zero and see that it is set to zero.

Best regards,

AICMM

Hi everyone,

after few month and a complete revision by several (!!!) Agilent technicians, the issue was solved.

A technician has changed the whole FID collector assembly and everything goes normally after that. He said the original piece had a malfunction, but nothing visible.

Unfortunately Agilent says it will cost to much to fix what's wrong with this FID so I don't have other explanation than a malfonction

Thanks all of you for the help.

Regards
Anevo

Thanks for the feedback, I'm glad you are up and running again.

Peter