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 μg 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.

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This study evaluated the total concentrations of Cd, Cr, Cu, Pb and Zn in sediments samples from the São Gonçalo channel, Patos-Mirim lagoon complex, RS state, Southern Brazil during 2013 autumn, winter and spring, and 2014 summer. Ultrasound-assisted extraction method was employed to extract metals from the sediment samples. The sample powder was mixed with HNO3 and HF in an ultrasonic bath during 60 minutes at 25 oC. The limits of detection were 0.002; 0.026; 0.83; 0.386 and 0.44 mg kg-1 for Cd, Cr, Cu, Pb and Zn, respectively. The accuracy of the method was confirmed by analysis of two sediment certified reference materials and its precision was determined by the values of relative standard deviation lower than 9.1%. The concentrations obtained ranged from 0.11 to 0.58 mg kg-1 for Cd; 14.7 to 38.4 mg kg-1 for Cr; 3.9 to 102.0 mg kg-1 for Cu; 1.6 to 3.11 mg kg-1 for Pb; and 29.3 to 126 mg kg-1 for Zn. These values did not exceed the probable effect levels (PEL). Simplicity, low cost and high efficiency are some of the qualities of the method, making it adequate for routine analysis.