AUTOMATIC METHOD FOR ONLINE PREPARATION OF FATTY-ACID METHYL-ESTERS FROM OLIVE OIL AND OTHER TYPES OF OIL PRIOR TO THEIR GAS-CHROMATOGRAPHIC DETERMINATION

Fatty acids in oils were on-line methylated with acetyl chloride in methanol by dissolving 10-120 mg of oil in 100 ml of n-hexane, followed by continuous transesterification of the triglycerides, and flushing of residual reaction products by circulating a water stream through the derivatization manifold, after which the n-hexane phase from a membrane separator containing the fatty acid methyl esters was injected (5 mu l) via a valve into the injection port of a gas chromatograph. Comparison of this transesterification method with the manual method involving saponification with methanolic sodium hydroxide and esterification with boron trifluoride in methanol (Official Method of Analysis) revealed good agreement between the results provided by both for olive and other vegetable oils as well as codfish oil.