Glycerol is a by-product of biodiesel production and is also considered a contaminant in the final product. Current US and EU standards place Limits on the permissible levels of free glycerol and bound (unconverted) mono, di and triglycerides in biodiesel, which can be quantified using gas or high pressure liquid chromatography. We report a method based on thin layer chromatography that can be effectively used to determine the presence of glycerol in biodiesel. Visual and machine (image analysis) detection limits of 0.1% and 0.2% v/v of free glycerol, respectively, were established using this procedure. In conjunction with a suitable sample enrichment procedure, this procedure could provide a cost effective alternative to glycerol detection. (C) 2008 Elsevier Ltd. All rights reserved.