Cloud point extraction of lanthanides with 3-ethylamino-but-2-enoic acid phenylamide from water samples prior to ICP-MS determination

A compound representative of the enaminones class is studied as a new ligand for Cloud Point Extraction (CPE) of lanthanides (La, Ce, Eu, Gd, Er) from aqueous medium. Extraction parameters such as water phase pH, heating temperature, incubation time, type and quantity of surfactant are optimized. Analyte concentrations are measured by ICP-MS after appropriate dilution of the surfactant-rich phase. The extraction system based on the new ligand showed high efficiency for separation of lanthanides from concomitant alkali and alkaline earth elements, which significantly reduces the risk of spectral interferences in real samples. Selectivity of the tested enaminone is compared to the classical ligand 8-hydroxyquinoline. The instrumental drift in sensitivity is corrected by internal standardization with Re. The optimized procedure is applied on water certified reference material and real water samples. Obtained limits of detection are in the interval 0.2-1.3 ng L-1 with 10-fold preconcentration.