Selectivity enhancements for the determination of thorium by flow-injection analysis through the formation of the Th-DTPA-HQS fluorescent ternary complex.
Addition of diethylenetriaminepentaacetic acid (DTPA) to the fluorescent binary complex of thorium and 8-hydroxyquinoline-5-sulfonic acid (HQS) forms the Th-DTPA-HQS fluorescent ternary complex. The formation of this ternary complex enhances the selectivity for the determination of thorium. Excesses of DTPA and HQS are used as reagents in flow-injection analysis to detect thorium. The excess DTPA effectively masks potentially interfering ions by preventing the formation of fluorescent binary metal-HQS complexes. The presence of lanthanides and transition metals does not interfere with the thorium detection with this method (the ratio of molar intensity for metals to molar intensity for thorium is <0.3% with the exception of lutetium, for which molar intensity ratio is 1.34%). The detection limit for thorium is 12 ng ml(-1).
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Department of Chemistry, The University of Calgary, 2500 University Drive N.W., Calgary, Alberta, Canada.
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CA