The concentration of cerium in TBP was obtained from the difference between the introduced and remaining concentration of cerium in the nitric aqueous phase after extraction with TBP. The concentrations of cerium in the aqueous solutions were determined thanks to Induced Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) with argon as plasmogenic gas and c-Myc tag cross-flow nebulizer working at 2.56 bar. Optimum working conditions were: radio frequency 27.12 MHz; incident power 1200 W; Labtam GMK nebulizer; rf power 5 W; observation height 14 mm; argon coolant flow rate 10 dm3.min−1; argon carrier flow rate 1 dm3.min−1; intergraph period 10 s; resolution 0.004 nm; peristaltic pump flow rate 1 cm3.min−1; wavelength cerium 380.152 nm.
Also, the concentrations of cerium present in the aqueous sample were determined by ICP-AES using a calibration curve. A standard stock solution of cerium (1 g.L−1) was diluted to prepare 5 solutions with different concentrations of cerium in the 0–0.04 g.L−1 range in aqueous media. The same matrices were used for the standard and sample solutions (i.e. same concentration of TBP dissolved in water and same concentration of nitric acid) in order to compensate chemical and spectral interferences.