[Determination of 11 fatty acids and fatty acids methyl esters in biodiesel using ultra performance liquid...

A method for the determination of 11 familiar components in biodiesel was developed using ultra performance liquid chromatography with evaporative light scattering detector (UPLC-ELSD). These components were oleic acid, methyl cis-9-octadecenoate, linoleic acid, methyl linoleate, stearic acid, methyl octadecanoate, methyl linolenate, palmitic acid, methyl hexadecanoate, erucic acid and myristic acid. The sample was dissolved in methanol after extraction from the products. The separation column was an Acquity UPLC BEH Phenyl C18 (100 mm x 2.1 mm, 1.7 microm) and the mobile phase was acetonitrile-water (3:1, v/v). An isocratic elution program was utilized for the separation. The flow rate was 0.3 mL/min and the column temperature was 40 degrees C. The parameters of ELSD were as follows: the plus was 80; the temperature of the drift tube was 45 degrees C; the eluant gas pressure was 172 kPa. The sample was detected by ELSD in only 5 min. The calibration curves of 11 components showed good linearity with the correlation coefficients greater than 0.997. In comparison with other methods, this method is simple, fast, and has a good separation efficiency. The fatty acids and fatty acid methyl esters were separated in one step, thus, the extent of reaction can be confirmed by the determination of their contents. This method can be routinely used for the determination of the fatty acids and fatty acid methyl esters in the reaction products and the final biodiesel.