I have collected the hexane extract having positive fatty acid test, I'd like to separate the fatty acids from it.
You don't want the fatty acid esters, just the fatty acids?
Try saponification (mix with NaOH in water, heat). You'll get the sodium salt of the fatty acids. Extract with ether to remove non-polar compounds that aren't fatty acids (such as tocopherols). Finally, acidify the aqueous layer and extract the free acids.
What is the quantity of fatty acids you want to separate from the other lipids in the extract? You can use TLC to separate out the unesterified FA. I would not subject the sample to saponification as you will get FA from all of the PL and TAG in the extract. There will be predominantly TAG, but some PL as well.
Understanding your question, you really want to get the existing unesterified fatty acids out of the extract. Using TLC or traditional silicic acid chromatography should enable a reasonable separation, with TLC being the better of the two.
Dear Steven,
Thank you for your advice I will try SPE using anion exchanger.
could you suggest best anion exchanger for FFA.
Hi, you can try the extraction via the SAX (strong anion exchange) cartridge from Phenomenex, which yields feasible separation/isolation.
It depends on what your matrix is. If you can estimate what components may exist in your mixture, the seperation step could be easier. I've read some papers that the authors used vacuum rotary evaporation system to eliminate n-hexane as the solvent, the remaining liquid is exactly what you want. Good luck!
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