calculation of triglyceride ammount to fatty acid methyl.est

[leo1352]

I can not comment on how to improved the yield of your procedure as I do not have the details - all the steps and reagents.

I am using 3% Sulfuric acid in Isopropanol vol/vol heated up at 100C for 2 hours. The matrix is standard triglyceride cocktail.
Cheers

[Don_Hilton]

From the information you give, I can make reccomendations of a few things to try:

You can try changing the length of time for derivitization. Be sure the isopropanol is as dry as you can get it. (The side reaction is hydrolysis of the esters - and if there is an appreciable quantitiy of water in the isopropanol, you will generate some free acid) Check the procedure for making the sulfuric acid in isopropanol.

[Phycal]

Why use IPA for this reaction? The steric properties of IPA might not give you good results.

I would use dry methanol instead - as the derivatized products are more stable.

Also, I assume you are exracting into another solvent - like chloroform or hexane. Make sure after extraction to put the sample through anhydrous sodium sulfate to dry it. It helps to keep the samples stable.

[leo1352]

Why use IPA for this reaction? The steric properties of IPA might not give you good results.

I would use dry methanol instead - as the derivatized products are more stable.

Also, I assume you are exracting into another solvent - like chloroform or hexane. Make sure after extraction to put the sample through anhydrous sodium sulfate to dry it. It helps to keep the samples stable.

I use IPA since Methyl esters are more volatile and I have experienced lower recovery.(Hexane). also I am mostly interested on Butryric acid which in a DB-225 column comes off early with solvent tail. I use GC-IRMS(have to keep the He back-flush open for 200S to avoid solvent to the reactor).
I am interested to know why IPA esters are less stable?