Highly sensitive and selective determination of uranium in natural waters through a novel solidified floating organic drop microextraction method coupled with spectrophotometric determination

Ultra trace amounts of uranyl ions were extracted using a reliable, simple and selective solidified floating organic drop microextraction (SFODME) method, and determined by UV-Vis spectrophotometry. Di-2-ethylhexylphosphoric acid (HDEHP) was applied as the complexing ligand during the microextraction process, and Arsenazo III (AIII) was used as the chromogenic reagent through spectrophotometric determination. The effects of important experimental parameters on the formation of UO2-AIII complex and color development were studied. Other important experimental parameters affecting microextraction recovery such as type and volume of extracting organic solvent, acid concentration of sample solution, ligand concentration, stirring rate, extraction time and temperature, and salt addition were also evaluated and optimized. Under the optimized conditions, a linear response was obtained over the range of 0.8-75 ng mL(-1) for uranyl ions. The interfering effect of some foreign ions on the extraction and determination of uranyl ions was also investigated. Limit of detection, relative standard deviation and enrichment factor of the proposed SFODME-UV method were obtained as 0.1 ng mL(-1), 3.7% and 125, respectively, for uranyl ions. The proposed method was applied successfully for the extraction and determination of uranyl ions in natural water samples. The results of the proposed SFODME method and those reported by official standard method were in good agreement.