Chromatography Forum

Hi Guys,
I am new to GC-FID. I am experiencing wavy baselines (8mins to 10 mins) each time after I do maintenance. This is apparent on both front and back columns.

My setup is:
GC 7890A
Front inlet - Front Column - Front FID
Back inlet - Back Column - Back FID

Is this a norm on a dual column FIDs? IMO, I feel dual inlet/dual column/dual FIDs are more sensitive; i.e. a new problem will surface each time after a maintenance is done.
I do not have such experience with single inlet/column/FID GCs.

Cheers,
Michael

p/s how do i upload an image to this site?

Hello

If you see wavy baseline on both detectors it could be gases quality - carrier gas and/or makeup gas. Check traps (if you have them) or install them.
The reason can be columns contamination. If you want to eliminate inlet/column contamination just cap FID with blank nut and observe baseline.

Sensitivity has nothing to do with channels configuration (dual or single)

Regards

Tomasz Kubowicz

If you have problems with dual systems but not with single systems in the same lab, check to make sure you have enough gas flow to the dual instruments to handle two columns instead of just one. If each channel is competing for the gas supply then you could have wavy baseline like you describe because you are not getting consistent flows.

1-check your carrier gas purity and hydrocarbons.
2-check your columns bake out and maintenance and thermal program.