A highly sensitive and selective fluorescence quenching method has been developed for the determination of trace tungsten in environmental samples using dibromohydroxyphenylfluorone (DBHPF) as an emission reagent. In the presence of 0.04 mol/L of sulphuric acid and acetyltrimethylammonium bromide, tungsten(VI) reacts with DBHPF to form a 1 : 3 red complex within 5.0 min. In order for the DBHPF-tungsten(VI) complex to form, the fluorescence intensity of the reagent solution was quenched linearly by adding 0.1 to 1.0 µg of tungsten(VI) in 25 mL of solution. This was measured at 528 nm with excitation at 495 nm. In this work, a standard addition method was investigated and used for sample analysis. The decrease in fluorescence intensity of the reagent solution (ΔF) was linear for 0 ∼ 0.9 µg of tungsten(VI) in 25 mL of solution, and the detection limit (3 s) of the standard addition method was found to be 0.012 ng/mL of tungsten(VI). The effects of various metal and nonmetal ions were studied in detail. The experiments clearly showed that most foreign ions can be tolerated in considerable amounts; in particular, 50-fold Mo(VI), V(V), Zr(VI) and Ti(IV) do not interfere, and the selectivity of the proposed method is better than other previously described methods. Moreover, the method proposed here is very stable and simple, the fluorescence intensity of the solution can remain almost unchanged for 2.0 h at room temperature, and the method has been used successfully to determine tungsten in environmental samples.
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Document Type: Research Article
School of Chemical and Materials Engineering Southern Yangtze University† Wuxi 214036 People's Republic of China
Department of Food Science and Engineering Nanjing Economy University Nanjing 210003 People's Republic of China
School of Chemistry and Chemical Engineering Jinan University Jinan 250022 People's Republic of China
Publication date: August 1, 2004
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