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ABSTRACT: In this work, spectrophotometer was used as a detector for the determination of uranium from water, biological, and ore samples with a flow injection system coupled with solid phase extraction. In order to promote the online preconcentration of uranium, a minicolumn packed with XAD-4 resin impregnated with nalidixic acid was utilized. The system operation was based on U(VI) ion retention at pH 6 in the minicolumn at flow rate of 15.2 mL min(-1). The uranium complex was removed from the resin by 0.1 mol dm(-3) HCl at flow rate of 3.2 mL min(-1) and was mixed with arsenazo III solution (0.05 % solution in 0.1 mol dm(-3) HCl, 3.2 mL min(-1)) and driven to flow through cell of spectrophotometer where its absorbance was measured at 651 nm. The influence of chemical (pH and HCl (as eluent and reagent medium) concentration) and flow (sample and eluent flow rate and preconcentration time) parameters that could affect the performance of the system as well as the possible interferents was investigated. At the optimum conditions for 60 s preconcentration time (15.2 mL of sample volume), the method presented a detection limit of 1.1 μg L(-1), a relative standard deviation (RSD) of 0.8 % at 100 μg L(-1), enrichment factor of 30, and a sample throughput of 42 h(-1), whereas for 300 s of the preconcentration time (76 mL of sample volume), a detection limit of 0.22 μg L(-1), a RSD of 1.32 % at 10 μg L(-1), enrichment factor of 150, and a sampling frequency of 11 h(-1) were reported.
Environmental Monitoring and Assessment 05/2012; · 1.40 Impact Factor
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ABSTRACT: A flow injection on-line determination of uranium(VI) after preconcentration in a minicolumn having amberlite XAD-4 resin
impregnated with dibenzoylmethane (DBM) is described. Uranium(VI) is selectively adsorbed from aqueous solution of pH 5.5
in the minicolumn (5.5cm long with 5.0mm i.d.) at a flow rate of 13.6mLmin−1. The uranium(VI) complex was desorbed from the resin by 0.1moldm−3 HCl at a flow rate of 4.2mLmin−1 and mixed with arsenazo-III solution (0.05% solution in 0.1moldm−3 HCl, 4.2mLmin−1), and taken to the flow through cell of spectrophotometer where its absorbance was measured at 651nm. Various parameters
affecting the complex formation and its elution were optimized. Peak height (absorbance) was used for data analyses. The preconcentration
factors of 36 and 143, detection limits of 0.9 and 0.232μgL−1, sample throughputs of 40 and 10 were obtained for preconcentration time of 60 and 300s, respectively. The tolerance limits
of many interfering cations like Th(IV) and rare-earth elements were improved. The proposed method was applied on different
water (spiked tap, well and sea water) and biological samples and good recovery was obtained. The method was also validated
on mocked uranium ore sample and the results were in good agreement with the reported value.
KeywordsDibenzoylmethane–Flow injection–Online preconcentration–Impregnation–Amberlite XAD-4 resin–Uranium
Journal of Radioanalytical and Nuclear Chemistry 04/2012; 289(3):929-938. · 1.52 Impact Factor
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Journal of Radioanalytical and Nuclear Chemistry 01/2012; 292:277-283. · 1.52 Impact Factor
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ABSTRACT: A short, sensitive and reliable spectrophotometric method, which has advantages over all known "wet chemistry" methods for uranium determination with regard to tolerance to common interferences, has been developed for the determination of uranium. Selectivity, molar absorptivity and the determination range of uranium have been enhanced by using 0.07% arsenazo-III as a chromogenic reagent. The use of 3 mol dm(-3) perchloric acid as a medium of determination was found to be excellent in terms of good solvent compatibility on dilution, destruction of organic contamination and simplicity of operation. The uranium-arsenazo-III complex formed instantly, and was found to be stable for more than 3 weeks with constant absorbance. Beer's law was obeyed up to a uranium concentration of 16 microg g(-1), with a molar absorptivity at 651 nm of 1.45x10(5) mol(-1) dm(3) cm(-1) at 24+/-2 degrees C. Only phosphate and citrate at 70-fold excess over uranium interfere seriously, whereas other anions studied could be tolerated up to a 70-fold excess over uranium. Of the cations studied, only Mn(II), Co(II), Ni(II), Cu(II) and Cr(III) decreased the normal absorbance of the complex. Iron(III), Ce(III) and Y(III) enhanced the absorbance. Other cations studied did not affect the absorbance up to a 50-fold excess. The accuracy was checked by determining uranium from standard solutions in the range 10-50 microg g(-1). It was found to be accurate with a 96.0-98.6% recovery rate. The method has been successfully applied to standard reference materials and ore samples at microg g(-1) levels.
Chemosphere 06/2006; 63(7):1165-9. · 3.21 Impact Factor
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ABSTRACT: The extraction of thorium(IV) from nitric acid solutions by di-n-butyl sulfoxide (DBSO) in xylene has been investigated as a function of acid, extractant and the metal concentration. The effect of contact time and diverse ions on the extraction has been examined. Phosphate, fluoride, oxalate and perchlorate reduce the extraction to some extent. The extraction of other metal ions, especially impurities associated with thorium in ores, has been measured under optimised conditions selected for thorium extraction. Na(I), K(I), Ca(II), Sr(II), Mn(II), Fe(II), Ni(II), Zn(II), Pb(II), Al(III), Ti(IV) and Hf(IV) are not extracted. Among the stripping solutions employed for back-extraction, deionized water is found to be the best and more than 99% thorium can be back-extracted in three stages. The extracted species is supposed to be Th(NO3)42DBSO. The extraction is found to be almost independent of the thorium concentration in the range between 4.310–4–4.310–2M and inversely dependent upon the temperature. The values of thermodynamic functions H, G and S for extraction equilibrium have been evaluated to be –19.62.9 kJmole–1, –18.12.0 kJmole–1 and –5.02.9 Jmole–1K–1, respectively.
Journal of Radioanalytical and Nuclear Chemistry 01/1995; 198(2):409-421. · 1.52 Impact Factor
