Optimization and scale-up of a microscale ion exchange separation for an adjacent lanthanide pair

Radiolanthanides are important for cancer therapy and diagnostics but are challenging to chemically purify post production because of charge and ionic radii similarities. Conventional-scale ion exchange chromatography is commonly used, often requiring large volumes of costly resins, creating significant radioactive waste, and can be time-consuming. Microfluidic ion exchange separations can advance research and development using minimal resources to inform conventional column chromatography scales. The transition between different separation scales must be well understood to effectively make this transition from microscale separations, particularly for complex separations such as those involving adjacent lanthanides. This work demonstrates proof-of-concept cation exchange separations of the adjacent lanthanides Yb and Tm at the microscale using Dowex 50W X8 resin and α-hydroxyisobutyric acid. The lanthanide separation was optimized at the microscale and scaled up for conventional column chromatographic separation. The microscale separations were indicative of the conventional-scale column separations in their elution profile peak shape and separation factor, but the microscale separations had reduced resolution, likely due to a lower packing efficiency. This study reports the first demonstration of the ion exchange separation of adjacent lanthanides at the microscale, an advance on previously reported Ac-225 and Ra-225 separations, thus paving the way for evaluating more complex separations.