Determination of lanthanides by ion chromatography. Separation and retention mechanism

As an extension of our previous studies, in this work, an ion exchange method for the determination of rare earths in a YbF3 matrix, used for optical fibres manufacture, was improved. The separation has been performed on a mixed bed column, IonPac CS5 containing both anion and cation exchange sites, by oxalic and diglycolic acids eluents and post-column spectrophotometric detection. The improvement of the method allowed us to avoid the coelution of Ho and Er in the presence of excess of Yb in the matrix. In addition, a study on the separation mechanism has also been performed, in order to identify the kind of sites involved in the separation process. For this purpose, experiments were performed under anion exchange conditions, using an IonPac AS5 column, and under pure cation exchange conditions, using an IonPac CS2 resin. The study allowed us to state that the mechanism involved is a function of ligand concentration in the mobile phase used.