propionic acid analysis

[npc]

Hello,
Hope someone can help out. I am trying to set up a propionic acid analysis using an Agilent 6890N with FID. The column is a RTX-200.

The chromatogram I'd like to get is like the following for volatile free fatty acids.

http://www.chromspec.com/pdf/e/rk91.pdf ... c7902a7650

My sensitivity is very low. I cannot acheive anywhere near the sensitivity of the above. I've tried changing the septum, the liner, cut off the column end. I tried changing the split ratio, temperatures, etc. Propanoic acid at 200ppm comes out at 1.84 and is a very small peak. Valeric acid is the internal std and is very small and poorly shaped at about 2.6. Any suggestions are welcome.

Thanks
NC

[chromatographer1]

Note that there is perhaps a confusion of facts in the note. It states the acid solution concentration is 10 to 20 ng/µL ( injected 0.8µL ) but it also states that the ON-COLUMN concentration is 10 to 20 ng. If the amount of acid on- column is 10 to 20 ng (which appears reasonable for the peaks shown) then if you are trying to see this amount when split at a ratio of 30 or 40:1, then the peaks should be very small indeed, as you state you are seeing in your experience.

Just an observation, but of course, I may have it wrong or be confused myself.

Rodney George
consultant