Chromatography Forum

Hi all,

According to ECN table, HCHO and HCOOH have no response in FID. Anyone has ever tested this? No peaks or just tiny peaks?

Thanks

There will be response. However these are both somewhat reactive/polar and do not give good peak shapes when trying to assay "as is".

haiedc,

Response but very, very poor. Better to do this with argon ionization detector (with my well known bias) or, I have it from a very reliable source, you can use a methanizer and FID combination. Thick film PDMS will work pretty well for this application.

Best regards.

No response is wrong, or at beat an exaggeration.

But remember even WATER can be seen as a small peak on an FID, so formaldehyde and formic acid giving a small response is no surprise.

(and no one argue with me on this on theoretical grounds as I did residual solvent determinations for decades with the first peak always being the water peak using porapak Q packed columns. Water (steam) doesnt ionize in the flame necessarily but it does change the electron flow between the FID elctrodes and give a 'response'.)

A TCD, an argon or helium ionization detector will detect both analytes with excellent sensitivity. Buy what you need when you need it.

rodney george
consultant

No response is wrong, or at beat an exaggeration.

But remember even WATER can be seen as a small peak on an FID, so formaldehyde and formic acid giving a small response is no surprise.

(and no one argue with me on this on theoretical grounds as I did residual solvent determinations for decades with the first peak always being the water peak using porapak Q packed columns. Water (steam) doesnt ionize in the flame necessarily but it does change the electron flow between the FID elctrodes and give a 'response'.)

A TCD, an argon or helium ionization detector will detect both analytes with excellent sensitivity. Buy what you need when you need it.

rodney george
consultant

Thanks all for replying. Talking about H2O response, I have never seen, but CS2 really gives response, and very low providing that it is used as a diluter.

Th FID is essentially a carbon counter. With these molecules a much smaller fraction of the MW is carbon, compared to a larger similar molecule. One reason for the poor FID response.

Rodney is correct, you will see peaks, small ones, but you will also see really bad chromatography, as these are extremely polar compounds.
Good luck,
Bill