Determination of FFA, Tri-, Di-, and Monoglycerides in Ethyl Biodiesel from Acid Oil of Rice Bran Oil Refinery

Abstract

A Method of high performance size exclusion chromatography (HPSEC) with evaporative lightscatteringdetector was developed for analysis of tri-, di-, and monoglyceride (bound glycerols) fatty acidethyl ester and free fatty acids in biodiesel. The separation of the analytes on a phenogel 100Å column (300mm X 7.8 mm ID, 5μm) eluted with toluene containing 0.5 % tetrahydrofuran (THF) is better than straightTHF or toluene. Baseline separation of all the above solutes can also be achieved when acetone,dichloromethane, ethyl acetate or acetic acid is used in place of THF. However, 0.25% acetic acid in toluenewas found to be the best mobile phase modifier. Ethyl biodiesels of rice bran acid oil which werederived from simultaneous esterificaton and transeterification of the acid oil with sulfuric acid at 75°C atdifferent molar ratios of FFA:ethanol (between 1:25 to 1:480) were analyzed by HPSEC eluted with 0.25%acetic acid in toluene. The results show that about 98% FAEEs (biodiesel) could be obtained in less than 30min at 1:480 molar ratio of FFA:ethanol.

Keywords : Free Fatty Acid / Glycerides / High Performance Size Exclusion Chromatography(HPSEC) / Biodiesel / Rice Bran Acid Oil