A neutron activation analysis method for determining Yb, Dy, Ho, Sm and La impurities in europium oxide with sensitivities
of 10−5 to 10−7% is described. The method is based on a preliminary concentration of the rare earth elements by reducing europium(III) with
zinc to europium(II), and separating the trivalent rare earth elements by extraction chromatography. After neutron irradiation,
the individual radioisotopes of the rare earth elements are separated by using KU-2 cation exchange resin and ammonium α-hydroxyisobutyrate
solution as the eluant.