Stopped-flow kinetic determination of a binary mixture: Simultaneous determination of europium and cerium

A kinetic method is proposed for the simultaneous determination of europium(II) and cerium(III), based on their inductive action on the Cr(VI)-iodide redox reaction in weak acidic medium. The reaction rate was followed by the stopped-flow spectrophotometric technique using starch-iodine complex as indicator. The method can be used for the determination of europium and cerium after reduction with zinc metal powder in the concentration ranges 0–2.1 and 0–1.8 μg/ml, respectively. The detection limits are 0.015 μg/ml Eu and 0.010 μg/ml Ce. 100 to 1000 times higher concentrations of other rare earth metal ions and Th4+, Al3+, Mn2+, Hg2+, Co2+, Ni2+, Cu2+, Pb2+ do not interfere. The method is applied to the determination of europium and cerium in a synthetic sample and in barium yttrium fluoride fluorescent material, with relative standard deviation of about 4%.