Studies on photochemical vapor generation of selenium with germicidal low power ultraviolet mercury lamp

Photochemical vapor generation (photo-CVG) with flow injection - atomic fluorescence spectrometry was investigated for the determination of selenium, using formic and acetic acids as photochemical reagents. Using a germicidal low power ultraviolet mercury-based lamp, emitting both the 185 and 254 nm Hg lines, mild reaction conditions can be achieved in formic acid medium, where optimal sensitivity was obtained at 0.3-0.5% w/w acid concentrations, whereas the optimal sensitivity could be attained with acetic acid in the range from 12 to 35% w/w. The only volatile Se product identified by gas chromatography-mass spectrometry from formic acid-based photo-CVG was selenium carbonyl. A series of dedicated experiments were performed using photo-CVG and pure dimethylselenide in order to identify reaction pathways contributing to the formation of non-volatile selenium species or to the degradation of volatile selenium species. Under the optimized conditions in formic acid, using 250 ?L sample volume, the limits of detection and quantification were 0.10 and 0.35 ?g L- 1, respectively. The effect of several interfering species was investigated and the method was tested in the analysis of certified reference materials.