A Novel Method of Analyzing Free Fatty Acid Content in Triacylglycerol Mixtures using 1H-NMR

Brett Matthew, Breshears


Biodiesel has become a popular option as a potential renewable energy source because pure vegetable oils can be easily transesterified into methyl esters by using a base catalyst. Used vegetable oils (UVOs), such as cooking grease, may be an environmentally friendly source of biodiesel.  However, UVOs are challenging to transesterify because the triacylglycerol molecules have hydrolyzed, resulting in the formation of free fatty acids (FFAs). These FFAs ultimately hinder formation of the desired methyl ester product. This problem can be alleviated by using a titration, which indirectly determines the quality of the oil by determining FFA content.  While a titration is reliable, it can be time intensive and inaccurate. Proton NMR was investigated as a more reliable method to quantitate FFA content. By comparing the ratio of the proposed diacylglycerol moiety relative to the glycerol peak and determining the acid number via titration, a correlation was found.  Thus, analyzing the diacylglycerol moiety relative to the glycerol peak could be a quick and effective way of determining the FFA content of an oil sample


Biodiesel, Acidity, 1H-NMR

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