The purification of raw glycerin in biodiesel production can provide economic benefits and help to avoid residue accumulation, thus reducing environmental impacts. In this work, the glycerin obtained from biodiesel production by catalytic transesterification of waste cooking oil was purified by sequential extraction with organic solvents, followed by discoloration with activated coal and monitoring by H-1 NMR spectroscopy. Through sequential extraction with petroleum ether and toluene, in that order, followed by discoloration with activated carbon, 99.2% pure glycerin was obtained. This technique is shown to allow for glycerin purification using less drastic or hazardous conditions than those commonly applied in vacuum distillation. (C) 2014 Elsevier B.V. All rights reserved.