Determination of low selenium concentrations by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) - interference by perchloric acid

In routine determinations of selenium (Se) by flow injection hydride generation atomic absorption spectrometry (Fi-HG-AAS) technique a home-made equipment from commercially available components were used. An electrically heated quartz tube was used as atomiser. Blank and Se-standard solutions were analysed after wet digestion using an oxidising acid mixture (HNO3/HClO4). An absorption signal at 196.0 nm occurred in reagent blanks and disturbed Se measurements at low concentrations. Searching for the cause of this phenomenon was the purpose of the present work. Influencing factors on light absorption in the quartz tube were studied, which were gas flow rate and gas composition, acidity of carrier, blankand Se-standard solutions, as well as presence of HClO4 in the solutions. When the difference in acidity between carrier-, blankand Se-standard solutions was eliminated, the gas flow stabilised resulting in disappearance of this effect. The main cause of this aberration was found in construction of the quartz tube that has been used in the system. The final detection limit achieved was in the range of 0.10.3 ng Se/ml measuring solution (0.3 ml injection volume) and was limited by the noise of the equipment.