Methanol Peak

[Guilherme]

Dear All Chromatographers,
I have a basic doubt...In theory methanol shouldn't produce signal in FID, but we can run analysis of it (samples or standards). How explain it?

[chromatographer1]

I don't know the theory to which you attest, but by all the theories I have seen methanol SHOULD give a response to FID and it does quite well.

Could you explain your statement in some detail. Perhaps that would get a discussion moving on a thread.

[Guilherme]

I'm reffering about the burning of organic coupounds in the flame. I have read that the covalent bounds C-C produce ions that generate signal. Is it true? Or any covalent bounds can generate signal?

[JI2002]

If a compound can burn in the hydrogen flame and produce ions, it should have response in FID. In this case, MEOH certainly can. If it needs C-C bond, how to expain that methane has good response in FID? that being said, MEOH should have a much weaker response than CH4 because of -OH group.

[chromatographer1]

I have read studies that claim any ionization of a molecule when heated within the hydrogen flame gives a response. Oxidation is not required.
A claim is made that even hexane ionizes effectively at a rate of only 1%.

Even water seems to change the conductivity across the electrode of an FID and gives a very weak response in an FID. That being said, formaldehyde gives a very poor response to a FID, and formic acid gives almost no response at all.

Yet compounds covalently bonded can give a relatively poor response, ie Carbon Disulfide.

Any one know of any studies available out there for review?

[arie2044]

Hi everybody
All Hydrocarbons burn in Hydrogen flame and produce very good signal, so is CH3OH, but the signal is weaker. there is a lot of articles descibing the correlation between the C number and FID response ( i have some). Water in high content just cool the environment and that produse the signal on FID.

Good lake