Analysis of Sterol Glycosides in Biodiesel and Biodiesel Precipitates

Biodiesel is produced by the transesterification of vegetable oils with short chain alcohols, usually in the presence of an alkali catalyst. Minor components in biodiesel exist as a result of unreacted reagents, by‐products, additives, and auto‐oxidation products, such as water, free glycerin, bonded glycerin, free fatty acids, catalysts, residual alcohol, unsaponifiable matter (plant sterols, antioxidants, and hydrocarbons), soaps and polymers. The biodiesel properties, such as cold flow properties, acid number, cetane number, and oxidative stability are oftentimes significantly affected by these minor components. Sterol glycosides, as one of the most important minor components in biodiesel, and due to their polarities and limited solubility, can accelerate precipitate formation even at room temperature and possibly block fuel filters. In this paper, reversed phase high‐performance liquid chromatography with an Evaporative Light Scattering Detector (ELSD) is evaluated for the analysis of sterol glycoside (SG) content in not only biodiesel precipitates but also in biodiesel. SG was found to be a major component in soy biodiesel precipitates and an SG peak was found in biodiesel after concentration by centrifugation.