“…However, due to their similar size and charge (all predominantly reside in the +III oxidation state), all of the elements within the Ln series, especially nearest neighboring Lns, exhibit relatively similar chemistry, so separating mixtures of these elements is a formidable task. In the past, a number of techniques have been used to effect the separation of individual Ln elements and reviews of these techniques are available from the literature [2,3]. To this end, cation exchange chromatography using alpha-hydroxyisobuturic acid (␣-HIB) is widely considered to be the most effective methods for separating these elements.…”