Chromatography Forum

Hi everyone,
I am having problem with the make up gas in the FID of a 6890 Agilent.
After I have cleaned the jet replaced it and installed the column, the FID flame does lit only if the make up gas is set to below 40.
Using a method with higher make up gas flow will cause the flame to go on and off continually.
Today I run some blanks and standards and the flame goes off when the solvent front hit the detector.
Any clue on what can cause this and how I can solve it?

Best Regards,

Alice

Hello

Makeup gas flow is too high. It should be somewhere between 5-40ml/min.
Higher flow will not improve anything and it can blow flame.
Just set it to lower value (25 ml/min) and it will be ok.

Regards

Tomasz Kubowicz

The normal flows in an Agilent FID is that the column flow PLUS the makeup flow should be about 30ml/min ( with the hydrogen flow at 30ml/min). So if you are running a capillary column at 2ml/min, makeup should be 28ml/min. If you are running 1/8 inch packed columns at 30 ml/min, you basically do not need any makeup flow.

Gasman

I NEVER used make up gas more than 40ml/min

The normal flows in an Agilent FID is that the column flow PLUS the makeup flow should be about 30ml/min ( with the hydrogen flow at 30ml/min). So if you are running a capillary column at 2ml/min, makeup should be 28ml/min. If you are running 1/8 inch packed columns at 30 ml/min, you basically do not need any makeup flow.

Gasman

That's what we do also.

Alice,

Try starting at 20ml/min and if it lights and runs ok, inject a standard at 20ml/min, 25ml/min, 30ml/min, 35ml/min and 40ml/min and see what the sensitivity does. You will probably see it begin to drop off by the time you reach 40ml/min. Choose the flow that gives the best sensitivity and stability for your methods.