Fast and selective reversed-phase high performance liquid chromatographic separation of UO 2 2+ and Th 4+ ions using surface modified C 18 silica monolithic supports with target specific ionophoric ligands.

Reprocessing nuclear-spent fuels is highly demanded for enhanced resource efficacy and removal of the associated radiotoxicity. The present work elucidates the rapid separation of UO 2 2+ and Th 4+ ions using a reversed-phase high-performance liquid chromatographic (RP-HPLC) technique by dynamically modifying the surface of a C 18 silica monolith column with target-specific ionophoric ligands. For the dynamic modification, four analogous aromatic amide ligands, N 1 , N 1 , N 3 , N 3 , N 5 , N 5 -hexa(alkyl)benzene-1,3,5-tricarboxamide (alkyl = butyl, hexyl, octyl, and decyl) as column modifiers were synthesized. The complexation properties and retention profiles of the amide-based column modifiers for the selective and sequential separation of UO 2 2+ and Th 4+ ions were investigated. In addition, the selective separation of UO 2 2+ and Th 4+ ions among the competitive ions of similar chemical properties were also studied. The ionophore immobilized C 18 silica monolith columns demonstrated a varying degree of retention behavior for UO 2 2+ and Th 4+ ions (UO 2 2+ is retained longer than Th 4+ under all analytical conditions), eventually leading to rapid separations within a period of ≤5 min. A 0.1 M solution of 2-hydroxyisobutyric acid (HIBA, 1 mL min -1 ) served as the mobile phase, and the qualitative and quantitative assessment of the sequentially separated 5f metal ions was achieved through post-column derivatization reaction, using arsenazo(iii) as a post-column reagent (PCR; 1.5 mL min -1 ) prior to analysis using a UV-vis detector, at 665 nm ( λ max ). The developed technique was further evaluated by standardizing various analytical parameters, including modifier concentration, mobile phase pH, mobile phase flow rate, etc. , to yield the best chromatographic separation. Also, the conceptual role of alkyl chain length (in the modifier) on the retention behavior of the studied metal ions was evaluated for cutting-edge future applications.