Chromatography Forum

My FID will not stay lit when the makeup gas is introduced above 35 mL/min. Any ideas out there?

My FID will not stay lit when the makeup gas is introduced above 35 mL/min. Any ideas out there?

Stay below 35 mL/min.

Clean or replace FID jet.
Change hydrogene:air ratio and respective flows.
Is your column properly installed in FID ? I guess it's capillary.

Need better answers - provide more information

Is there a particular reason that the flow of your makeup gas needs to be that large? I generally operate at H2:Air:Makeup 30:300:25 for my old systems and I go with the Agilent-recommended 35:350:20 for my newer systems. I've never had a need to go any higher than that with my makeup gas. I get nice, quiet baselines and good peak shapes with these parameters.

What make up are you using? Helium, nitrogen, hydrogen?

Best regards,

AICMM

What make up are you using? Helium, nitrogen, hydrogen?

Best regards,

AICMM

Hydrogen as makeup gas for FID ?

IMHO not possible. Correct me if I'm wrong.

Never underestimate the ability of anyone to make an error, even a grave one.

Granted you would be doubling the amount of H2 normally used in a FID, but it would run rich, and if it did, the flame geometry might be distorted enough to go out. Sorta like dumping a gallon of gasoline on a lit match and putting it out.

It is more likely that an excess of makeup is just keeping the mixture too lean to keep burning. One might increase the H2 flow, but why? Like a previous poster stated: Use less than 35 mL/min of makeup. Really. and why not?

best wishes

Rod

Thanks all. I think I was thinning the mixture too much. I set it at 20 mL/min and it's working great now.

h

For future knowledge, a moisture impurity in your makeup gas can cause the FID flame to die upon introduction of makeup gas. We've seen this happen from time to time at labs in very humid locations.

Do you really think that even the highest ambient humidity makes makeup gas more humid ?

h