Room temperature ionic liquid-based dispersive liquid–liquid microextraction of uranium in water samples before spectrophotometric determination

Abstract

A fast, simple and reliable method was developed for the determination of uranium(VI) in water samples based on room temperature ionic liquid dispersive liquid–liquid microextraction (RTIL-DLLME) followed by spectrophotometric determination. This is the first report on the extraction of U⁶⁺ by an RTIL-DLLME method. In this method, uranyl ion was complexed with 4-(2-pyridylazo) resorcinol (PAR) in the presence of cetylpyridinium chloride (CPC), which improved complex extraction into ionic liquid. Room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) and methanol were used as extracting and disperser solvents. The factors influencing the extraction efficiency, such as type and volume of RTIL and disperse solvent, extraction time, pH and concentration of the chelating agent and surfactant, and ionic strength were investigated and optimized. The developed protocol was found to yield a linear calibration curve in the concentration range between 50 and 700 μg L⁻¹ with a limit of detection of 2.4 μg L⁻¹. An enrichment factor of 448 fold was observed for the analyte. The repeatability of the method was satisfactory (RSD = 1.6%) and the total analysis time including microextraction was less than 10 min. The method has been successfully applied for the analysis of uranium in three spiked tap, lake and treated wastewater samples.