Distribution Coefficient of Actinides and Lanthanides in Extraction Chromatography: Trends, Variability, and Applications

Extraction chromatography (EC) has become one of the most effective techniques for the separation of actinides and lanthanides, combining the high selectivity of solvent extraction with the simplicity and versatility of column chromatography. Central to EC is the distribution coefficient (Kd), a fundamental parameter that governs metal ion retention, predicts separation behavior, and enables the rational design and optimization of chromatographic processes for applications ranging from isotope production and nuclear medicine to nuclear fuel cycle research and environmental monitoring. Despite its critical importance, comprehensive and standardized analyses of Kd data for extraction chromatographic resins remain lacking. Existing data are fragmented across vendor specifications, technical monographs, and individual research reports, often exhibiting significant inconsistencies even for identical resin-element systems. This review provides a comprehensive compilation and critical evaluation of Kd values reported for commercially available extraction chromatographic resins developed by Eichrom Technologies and TrisKem International, together with representative laboratory-developed resins. Trends, discrepancies, and the key factors governing Kd variability are systematically examined to provide a unified understanding of resin performance. The review further demonstrates how the informed interpretation of Kd data can guide resin selection, optimize chromatographic separations, and improve the reliability of nuclear and radiochemical analyses. By consolidating and critically assessing the available literature, this work establishes a valuable reference for the rational design of separation strategies in nuclear fuel cycle research, isotope production, radiochemical analysis, and environmental monitoring.