Preparation and application of ion exchangers with azacrown‐ether and cryptands to alkali and alkaline‐earth cation separation

Three macrocyclic exchangers are prepared and characterized by grafting on chloromethylated styrene‐divinylbenzene resin, one diazacrown‐ether (7,16‐bis(2‐hydroxyethyl)‐1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane (1)), one cryptand (21‐(2‐aminoethyl)‐4,7,13,16‐tetraoxa‐1,10,21‐triazabicyclo[8.8.5]tricosane (2b)), and one polymeric cryptand (poly(4,7,13,16‐tetraoxa‐1,10,21,24‐tetraazabicyclo[8.8.8]hexacos‐21,24‐ylene‐2,7‐dihydroxyoctamethylene (3)). Separation of alkali and alkaline‐earth cations is studied by liquid column chromatography with these exchangers in water. The separations occur according to the binding properties of the ligands in solution with an increase of the binding constants in the resin. The resolutions obtained are limited by relatively low capacities of the resins (0,4–0,9 mmol Mn+/g) and mainly by slow diffusion of the cations inside the resins.