1H Nuclear Magnetic Resonance (NMR) Determination of the Iodine Value in Biodiesel Produced from Algal and Vegetable Oils

A method for the determination of the iodine value in biodiesel produced from algal and vegetable oils has been developed by nuclear magnetic resonance (NMR) spectroscopy. The determination of the Iodine: Value is based on the average molecular weight of the fatty acid methyl ester and the number of double bond, which are calculated from H-1 NMR spectra. The total methyl ester content (% ME) was estimated using the integral Value of the OCH3 group peak at 3.67 ppm and the alpha CH2 at 2.2 ppm. The results obtained from the H-1 NMR method show good correlation (r(2) = 0.9974) with the traditional American Oil Chemists' Society (AOCS) method. The H-1 NMR method does not depend upon the nature of biodiesel feedstock. It is applicable to all methyl biodiesel samples obtained from different raw materials including algal oils. The results show that a higher iodine value indicates less oxidation stability, but there is not a linear correlation between the iodine value and oxidation stability of biodiesel.