Cloud point extraction associated with differential pulse voltammetry: preconcentration and determination of trace uranyl in natural water

Abstract

A procedure for the electroanalytical determination of uranyl ions pre-concentrated from natural water by cloud point extraction (CPE) is developed in this study. CPE parameters, such as surfactant concentration, extractant concentration, pH and additive concentration were optimized. After CPE, the solution was diluted for electrochemical determination by differential pulse voltammetry (DPV) with a mercury film electrode (Hg-GCE). The current response of uranyl showed a linear relationship with concentration from 10 nmol L⁻¹ to 1 μmol L⁻¹. The hyphenated method combining CPE and DPV achieved a detection limit of uranyl as low as 0.15 nmol L⁻¹. The presence of some foreign ions interfered greatly with the current response of electrochemical detection. Therefore, the hyphenated technique combining CPE and DPV is important because the CPE step provides selectivity against the co-existing metal ions for electrochemical detection. No interference was seen from the representative foreign metal ions in the CPE-DPV method. The developed method was successfully applied for the determination of uranyl ions in natural water. The average recovery using CPE-DPV in real samples varied from 94.4% to 103.2% and the precision was comparable with that of inductively coupled plasma mass spectrometry (ICP-MS), indicating the good accuracy and precision of the method developed. This hyphenated technique could have greater potential applications for the determination of uranyl ions in aqueous environments.