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Spectrofluorimetric determination of selenium after cloud point extraction

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2008
Güler, Nehir
As compared with the concentration in sample when the detection limit of analyte is low, a preconcentration method can be used. In this study, cloud point extraction (CPE) was used as the preconcentration method. The aqueous solutions of nonionic and zwitterionic surfactant materials become cloudy when its temperature reaches the cloud point temperature and analyte collapses with surface active material. The volume of surfactant rich phase is much smaller than the solution volume and therefore a way high preconcentration factor was obtained. For the cloud point extraction of selenite, a fluorimetric ligand, 2,3-diminonaphthalene (DAN) was used and the hydrophobic Se(IV)-DAN complex formed (4,5-benzopiazselenol) was extracted with Triton X-114. The effects of pH, complexation period, reaction temperature, DAN concentration and surfactant concentration on the extraction efficiency were investigated. The extraction efficiency at the optimized conditions was 98 percent. Spectrofluorimetric determination of selenium was performed at excitation and emission wavelegths of 379 nm and 582 nm, respectively. The detection limit, established as 3s /slope where s is the standard deviation of 9 measurements of 0.020 mg/L Se (IV)-DAN complex after 10 fold preconcentration was 3.7 g/L Se. By using solid surface fluorescence measurements detection limit could be reduced down to 1.2 g/L. The obtained detection limits (3.7 and 1.2 g/L) were sufficiently low for detecting selenite in diverse samples. The accuracy of the method was confirmed by the analysis of trace elements in waste water Standard reference material (EnviroMAT- Waste Water LOW EU-L-1). The interference effects of some anions and cations were also tested.