FID problem on GC.

[JeromAldivia]

Hello everybody.
After recently changing the column on a GC6850 FID (Agilent), the FID can't ignite no more.
I cleant the jet, then changed it, same result. A technician from Agilent told me to reduce the "Lit offset" on my method, same result.
The gas filters are OK, so are the flows.
Has anybody already encounter such a problem ?
Thank you for your replies,
Jerome.

[chromatographer1]

Four things are needed for a FID to light:

An elimination of any leak or blockage disturbing the gas flow.
Proper rate of flow of fuel.
Proper rate of flow of air.
Properly operating ignitor.

One or more of these is missing. Eliminate the problem one step at a time until you find the problem.

best wishes,

Rod

[Consumer Products Guy]

Did you check each gas flow at the FID outlet with a flow meter?

Carrier
Hydrogen
Air
Make-up gas

Do you see the resistance wire glowing when it's trying to ignite? Did you measure ohms resistance/continuity of the ignitor?

[JeromAldivia]

The gas flows displayed by the software are good but I'm waiting for the delivery of a flow-meter to plug in the outlet of the FID.
The ignitor works fine, I can see the incandescent lightning above the FID.
Thanks for your help.

[MSCHemist]

Be sure to check for leaks in any of the gas supply lines, and column connection, and the FID unit itself. Leaks can prevent a FID from lighting or staying lit.

Some FID's are just a pain in the butt to light. My 5890-FID I've been over and over it it just is such a bear to light. I have to shut off makeup, sometimes turn up the H2 and blow on it and sometime I still resort to a barbeque lighter and cursing the whole time.

[JeromAldivia]

I tried to ignite the detector without make-up gas, but it didn't work.
How do I know if there are gas leaks without a flow-meter ? Is it possible ?
Thank you all the members for having replied my request !

[chromatographer1]

You can improvise a homemade bubble meter for an approximate check. Note the 35cc/min hydrogen is different from the 400cc/min of air. Makeup is usually around 20-40cc/min
Sometimes if the alignment of the flame tip (or its base) is off, a match does a better job of lighting the flame.
Sometimes a leak around a flame tip will diffuse the gases so nothing will light.

good luck,

Rod

[MSCHemist]

For the gas supply lines you can drop 50%IPA/water inbetween the nut and tube and see if it bubbles. You can probably do the same for the column/FID connection if you cool it to ambient.

[Bigbear]

I know it sounds "kooky", but sometimes when my FID's don't ignite I gently blow a puff of air down the detector ( from the side). IE do NOT put your face directly above the detector.

[JeromAldivia]

Hello everybody.
Finally, we found out it was the manifold that is defective...
Thank you all very much for your help & propositions !

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