Simultaneous Determination of Free Fatty Acids and Esterified Fatty Acids in Rice Oil by Gas Chromatography

Free fatty acids (FFA) in crude rice oil were selectively and stoichiometrically derivatized to fatty acid N,N-dimethylamides (FADMA) by catalytic condensation at 45 degrees C, and then esterified fatty acids (eFA) were directly converted to fatty acid methyl esters (FAME) at 37 degrees C. The mixture of FADMA and FAME formed in a single test tube was injected into the capillary column of a gas chromatograph (GC). No mutual contamination occurred between FFA and eFA, and reliability of the method was confirmed by comparison between GC data obtained by this method and by a conventional isolation method. The advantages of the present method are that no FFA isolation procedures are required, the reactions proceed under mild temperature conditions, and FFA and eFA can be analyzed simultaneously by GC.

Automated summary

The method selectively and stoichiometrically converts free fatty acids in crude rice oil to fatty acid N,N-dimethylamides and esterified fatty acids to fatty acid methyl esters under mild temperature conditions. The mixture of FADMA and FAME formed can be simultaneously analyzed by GC without the need for FFA isolation procedures.