Development of High Performance Liquid Chromatography for Lanthanide Separation

Nuclear fission produces multiple lanthanide isotopes, many of which yield valuable insights into the type and origin of nuclear material. The ability to carefully separate and analyze selected lanthanide radioisotopes can be a key tool for nuclear forensic applications. However, adjacent lanthanides are notoriously difficult to separate from each other due to their very similar chemistry. One effective method for separation of lanthanide cations is High Performance Liquid Chromatography (HPLC). HPLC techniques have long been used to separate lanthanides, and our goal is to modernize our current capabilities through the development of a new test system. The chemistry is well developed, selective stripping of trivalent lanthanide cations from a cation exchange resin using α-hydroxyisobutyric acid (HIBA), but instrumentation advances yield scope for process improvements. Recently, a new HPLC system has been installed comprising of quaternary pumps, columns, fraction collectors and a Diode Array detector that allows for post column on-line analysis. Addition of PAR (4(-Pyridylazo) resorcinol)) for post column derivatization facilitates accurate determination of lanthanide cation elution using the diode array detector. The yellow to red color change upon lanthanide complexation is monitored through absorbance at both 414 and 530 nm. Initial work focused on determination, and then removal, of resin impurities that interfered with colorimetric detection. Single lanthanide cations were then run through the HPLC to â??mapâ?? the system before moving to more complex mixtures. Finally, the impact of variations in HIBA concentrations and solution pH has been studied for a lanthanide separation of relevance to nuclear forensic applications, the separation of Eu, Sm, Tb and Y. Eu and Sm are adjacent lanthanide elements while Y behaves like a lanthanide element adjacent to Tb.

 LA-UR-16-25242