Determination of free glycerol in biodiesel

Within the biodiesel production process, glycerol arises as a side product. This free glycerol is included also in biodiesel in small amounts. Several methods are known to determine it. Some of them are based on gas chromatography (GC). In this paper, a new method is introduced that is based on the extraction of free glycerol into water and its subsequent determination in water solution by high-performance liquid chromatography (HPLC) with refractometric detection. Comparison of the GC and HPLC methods showed that they led to the same results. The new method is reliable and comparatively fast for the determination of free glycerol in biodiesel.