Determination of selenite and selenate in drinking water: a fully automatic on-line separation/pre-concentration system coupled to electrothermal atomic spectrometry with permanent chemical modifiers |
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Authors: | Jorge Stripeikis Adrián Bonivardi |
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Institution: | a Department of Materials Science, Kitami Institute of Technology, 165 Koen-cho, Kitami 090-8507, Japan b Instrumental Analysis Center, Kitami Institute of Technology, 165 Koen-cho, Kitami 090-8507, Japan |
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Abstract: | A time-based flow injection (FI) separation pre-concentration system coupled to an electrothermal atomic absorption spectrometer (graphite furnace) has been developed for the direct ultra-trace determination of selenite and selenate in drinking water. The pre-concentration of both forms of selenium is carried out onto a micro-column packed with an anionic resin (Dowex 1X8) that is placed in the robotic arm of the autosampling device. Selenite and selenate are sequentially eluted with HCl 0.1 M and HCl 4 M, respectively. The interference of large quantities of chloride during selenium atomisation is prevented by using iridium as a “permanent” chemical modifier. The features of the pre-concentration separation system for both species are: 53% efficiency of retention and an enhancement factor of 82 for a pre-concentration time of 180 s (sample flow rate=3 ml min−1) with HCl elution volumes of 100 μl. The detection limit (3 s) is 10 ng l−1 for the two species and the relative standard deviation (n=10) at the 200 ng l−1 level is 3.5% for selenite and 5.6% for selenate. The addition of selenite and selenate stock standard solutions to tap water samples yields a 97-103% recovery of both species. |
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Keywords: | Flow injection Selenium speciation Electrothermal atomic absorption spectrometry Permanent modifiers Drinking water |
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