Preconcentration and spectrophotometric determination of uranium in environmental water samples with various microextraction techniques

In this study, two methods have been developed for preconcentration and spectrophotometrically determination of trace amount of U(VI) ion found in environmental water samples. In ionic liquid based in-situ dispersive liquid-liquid microexraction method (in situ-IL-DLLME) which is one of the developed methods, pyrocatechol violet (PV) and arsenazo III ligands were used for complexation of U(VI) ion. A 1-methyl-3-n-octylimidazolium as ionic liquid and lithium bis(trifluoromethyl)sulfonyl imide salt as anion-exchange reagent were used. Complexation pH, complexation reagent concentration, type and amount of surfactant, molar ratio of ionic liquid to ion-exchange reagent as optimization parameters were investigated. Under optimized conditions, linear working ranges with PV and arsenazo III were obtained as 0.1-10 ppb and 0.2-8 ppb, respectively. Another method developed for preconcentration of U(VI) ion is aqueous two-phase system. In this method, phase separation is succeeded using ionic liquid and inorganic salt. U(VI) ion was determined by complexation with arsenazo III ligand. In aqueous two-phase system, four different ionic liquid (tetraoctylphosphonium bromide, trihexyl tetradecylphosphonium bromide, 1-methyl-3-n-octylimidazolium bromide and tetra-n-octylammonium bromide) and dipotassium hydrogen phosphate inorganic salt were used. Triton X-100 as surfactant was added to medium for contribution to phase formation. Type and amount of added inorganic salt, amount of ionic liquid, amount of surfactant were optimized for each ionic liquid studied. The concentration of ligand and pH for U(VI)-arsenazo III complexation was same as used in situ IL-DLLME method. The developed arsenazo III complexation based in situ IL-DLLME and aqueous two-phase system methods were successfully applied tap water and drinking water samples.