In this work, three vapor generation methods (photochemical vapor generation, cold vapor generation with NaBH4 or with SnCl2) coupled with atomic absorption spectrometry were compared for the analysis of mercury (Hg) in pure glycerin and residual glycerin from biodiesel production. For these methods, a simple sample treatment step was employed through a dilution with formic acid or water and all parameters used were optimized. The limits of detection for the methods PVG-CV AAS, CV AAS with NaBH4, and CV AAS with SnCl2, were 0.12, 0.11, and 0.04 mu g L-1, respectively. Because no adequate certified reference material was available, the accuracy was evaluated by assessing the recoveries of Hg2+ spikes in all samples (84%-108.3%). When methods were compared, the PVG-CV AAS presented adequate sensitivity and simplicity, and provided a direct approach to the generation of Hg vapor from glycerin samples while promoting green chemistry. In addition, PVG-CV AAS provided limits of detection that are comparable to conventional methods for the determination of Hg by vapor generation.