The almighty Flame ionization Detector

The FID was the very first detector in the very first chromatograph in the very first lab I worked. I even was there when it was installed. In that time, I did the classical question: “What does it ionize?”. And the install-GC-Guy said the molecules, it’s just like atomic absorption!

Well, now I know that’s not exactly true…

The source for ions in FID are the intermediates on the oxidation process, mainly the formylium ion CHO+.

This paper do a great job in simplify the yada, yada, yada from some publications in a simple and useful technical information.

Two of that I stress here, First: Anything with carbon tend to decompose to methane on the flame, and the reaction are very similar to my old post (if you didn’t read the post on the Thermoelectrical-chromatographer I say you should).

C2H2 +3H2 → 2CH4

Second: This is why the FID have an equal response per carbon, I mean, same amount of carbon ALMOST same response on detector. Now I can sleep happy.

To ilustrate the FID working, check the flash animation, you'll need flash player.

Flash animation: Dr. Thomas "Red Head" Chasteen, Sam Houston State University.