Novel Sc-imprinted polymer resin for applications in radiochemistry Ruslan Cusnir and Marietta Straub Institute of Radiation Physics, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland Introduction: Solid-phase extraction (SPE) is a common method used for chemical separation of radionuclides. Conventional ion-exchange resins employ a broad range of extractants which are adsorbed on the surface of supporting polymer particles. Unlike these resins, ion-imprinted polymer (IIP) resins contain a metal-binding ligand, which is incorporated via covalent bonds within the polymer backbone. Synthesising such polymers in the presence of a metal ion template provides a versatile platform for preparing resins specific for the extraction of a desired radionuclide. An IIP synthesised by imprinting with Y 3+ ion has been applied for the chemical separation of 90 Sr( 90 Y), 241 Am and 225 Ac traces in the environmental and biological samples [1-4]. Methods: To synthesise a Sc-imprinted resin (Sc-IIP), polymerisation of styrene and divinylbenzene in the presence of a picolinate ligand HL1 [3] was carried out in an aqueous emulsion under a nitrogen atmosphere. Sc (III) perchlorate was added stoichiometrically to provide a template for ion imprinting. Polymer particles were filtered off, washed with ethanol and acetone, and refluxed overnight in tetrahydrofuran (THF) to remove unreacted organic molecules. Once filtered off and washed with THF, ethanol and acetone, polymer was dried overnight at 65 °C. Dry polymer was sifted through a 71 µm vibratory sieve shaker, then stirred overnight in a suspension with 2 M HCl in the presence of 10 % ethanol to remove Sc template. The resulting polymer was washed with water until neutral pH, dried at 65 °C and sifted through 71 µm. To characterise the resin, SPE columns were prepared containing 1 g of Sc-IIP suspended in water in the presence of 10 % ethanol to improve wetting. Results: A Sc-IIP resin was synthesised with a chemical yield of 90 %. Solid-phase extraction experiments showed quantitative retention of Sc when loaded at pH 2-3, with no loss of Sc from column upon washing with H 2 O(H + ) at pH 2-3. Sc was released from the resin using 1 M HCl. The extraction capacity determined for Sc (III) was 2 mg per g of resin. A control experiment using an inert resin synthesised without Sc (III) template showed no retention of Sc. Chemical separation of Sc (III) in the presence of a tenfold excess of Ca 2+ showed quantitative retention of Sc, which was released with 1 M HCl with no residual Ca 2+ detected. Conclusion: A novel ion-imprinted polymer resin was synthesised by emulsion polymerisation using Sc (III) ion as a template. The resin is suitable for the chemical separation of Sc (III) from Ca (II) and can be applied for the extraction of a medical radioisotope 44 Sc produced by irradiation of Ca targets in a cyclotron. Covalent binding of the Sc (III) extracting ligand tightly incorporated within the polymer backbone provides a potential application of this resin in a microfluidic configuration using the electrochemical stripping instead of solvent elution. References
1. Chauvin A.S. et al., Chem. A. Eur. J. , 12 (2006) , pp. 6851-6864 2. Chaplin J.D. et al., Anal. Chem. , 93 (2021) , pp. 11937-11945 3. Froidevaux P. et al., J. Radioanal. Nucl. Chem. , 330 (2021) , pp. 797-804 4. Cusnir R. et al., Anal. Chim. Acta , 1194 (2022) , 339441
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