Dear Gabriel, 

The main reasons to make the derivatization of fatty acids (their free form) are due to their high polar tendency to form hydrogen bonds  and the polar carboxyl functional groups must first be neutralized to distinguish between the slight differences exhibited by unsaturated fatty acids. 

Please verify the following websites:

http://www.sigmaaldrich.com/analytical-chromatography/analytical-products.html?TablePage=105120181

http://lipidlibrary.aocs.org/index.cfm

The AOCS Lipid Library® is a great reference when it comes to lipid analysis.

Thank you so much, it was quite helpful

Because fatty acids are non-polar and would just plug the top of the GC column upon injection.  By derivatizing the fatty acids into Methyl esters you are making them volatile (turn into a gas) and FID detectable.

Wow, thank you!

Dear colleague,      

there is f possibility to analyze free fatty acids using no esterification or trans-esterification steps; well known FFAP ("Free Fatty Acid Phase) is used to chromatograph underivitized FA.  This stationary phase  is prepared by  linking PEG20M molecules (and terminating their HO-ends) with nitro-terephtalic acid and ensures quite symmetric oeaks of such FA sorbates and relatively high max working temperature. But

  1) chromatographic efficency parameters of FFAP separation (although needing no preliminary sample derivatization) is somewhat  worse than that  of  "usual"   stationary phases;

  2)  gas chromatography of  free fatty acids on such polar phases as PPAP (compared to GC of FA  alkyl- or TMS- esters) requires much higher column temperatures (approx. +50C); it is undesirable - temperature increase causes sharp decrease of column efficiency. 

   That's why this method is not capable to resolve isomeric FA peaks (positional or geometric isomers). But it is often used to analyse technologic mixtures of short FA (such as C6-C12) owing to it's simplicity. Oh,  methylation  of low molecular weight FA is not easy problem; and FFAP separation of quite simple FA mixtures in isotermic conditios requires several minutes (without any preliminary chemical work).

Thank you so much

My experience with SP2380 column is that free fatty acids (FFA) elute in broad peaks; the width is in the range of several seconds, while the FAME elute in peaks

Incredible, thank you!