Switchable solvent based liquid phase microextraction of uranium in environmental samples: a green approach

Abstract

This paper describes a new and green approach for the preconcentration and separation of U(VI) by switchable solvent based liquid phase microextraction (SPS-LPME) and its UV-vis spectrophotometric determination. 1-(2-pyridylazo)-2-naphthol (PAN) as complexing agent was used. Conversion features of triethylamine (TEA) and protonated triethylamine bicarbonate (P-TEA-BC) as a green and cheap switchable solvent pair were used in the presented work. Protonated triethylamine bicarbonate (P-TEA-BC) as the polar form of the switchable polarity solvent (SPS) was successfully synthesized from triethylamine (TEA) via a proton transfer reaction and used for microextraction of the hydrophobic U(VI)–PAN complex at pH 9.0. The relative standard deviation was 2.5% for five repeated determinations of model solutions containing 6 μg L⁻¹ of U(VI). The limit of detection (LOD), the limit of quantification (LOQ) and enhancement factor were 0.3 μg L⁻¹, 1.0 μg L⁻¹ and 40, respectively. The accuracy of the method was evaluated by analyzing certified reference materials and addition-recovery tests. The method was successfully applied to the determination of uranium in water, sediment, soil and rock samples.