I have a group of margarines and want to analyze for the fatty acids (c14-c24) without derivitization. I have a few methods to try for the hplc chromatography and have pda, ri, and elsd. I need a good method for extracting these acids from the margarine. Were I to use bits and pieces from methods I have seen, I would heat to 60 centigrades, filter through sodium sulfate to trap the water, then esxtract with a solvent that would be compatible with my hplc mobile phase - that is the problem. I want to try piggy-backed c18 columns with a water/methanol/acetic acid mobile phase. Chloroform is the preferred extraction solvent that I have seen. Might acetonitrile or methanol be used? Some other solvent?
ves shirley

I work for a company that makes food products and soap; standard practice for total fatty acid profile would be saponify/make methyl esters, then GC on polar column. For free fatty acid distribution, dissolve in pyridine and trimethylsilate, then GC on nonpolar column; alternatively, the sample can be dissolved in petroleum ether, shaken with basic water/methanol, and the triglycerides extracted, then the water/methanol acidified with acetic acid and it extracted with petroleum ether to pull out the free fatty acids, which are then made into methyl esters and GC on polar column.

Anonymous,

Will you provide the methyl esterification conditions?

I really want to dothis with hplc/pda/elsd. Would this be a routine?

1. the sample can be dissolved in petroleum ether,
2. shaken with basic water/methanol, and the triglycerides extracted,
3.then the water/methanol acidified with acetic acid and it extracted with petroleum ether to pull out the free fatty acids

Acidified to what pH?

Then blow down and put the acids into acetonitrile or methanol. Any thoughts?

Shirley: acidification with excess acetic acid or HCl to pH of about 3 will work fine.

Bill: esterification conditions for soaps and free fatty acids.
1. Transfer about 3 g fatty acids and/or soap to a 100 ml volumetric flask.
2. Add about 20 ml 12% BF3/CH3OH or 20 ml 12%sulfuric acid-methanol solution.
3. Heat on the steam bath for 5 minutes.
4. Stopper and cool to room temperature in a cold bath.
5. Add 25 ml petroleum ether, stopper, and mix. Then add saturated NaCl solution to bring the total volume to the middle of the volumetric flask neck. Stopper and invert a few times.
6. Transfer about 1 ml petroleum ether layer to a sample vial and cap.

Triglyceride samples need to be prepped differently, such as saponifying with NaOH or KOH in methanol for 5 minutes on steam bath, then adding the acid-methanol excess, etc., as above.

anonymous:
Basic water/methanol - pH? 10-ish?

Hi ,

Could some one can letme know

what is fatyacids? and some explanation about fatyacids.

fatty acids are carboxylic acids found in fats and oils, ie triglycerides, and are usually biological in nature. They are usually found as esters with the tri-alcohol glycerol, hence the name, triglycerides.