Separation of calcium-48 isotope by crown ether chromatography using ethanol/hydrochloric acid mixed solvent

• Published in: Journal of Chromatography A 2015-10, Vol.1415, p.67-72
• Main Authors: Okumura, Shin, Umehara, Saori, Fujii, Yasuhiko, Nomura, Masao, Kaneshiki, Toshitaka, Ozawa, Masaki, Kishimoto, Tadafumi
• Format: Article
• Language: English
• Subjects: Benzo-18-crown-6 ether; Ca-48; Crown ether; Double beta decay; HETP; Isotope separation
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2015.08.057

•Benzo-18-crown-6 ether resin was synthesized for chromatographic separation of Ca-48.•Ca ions are adsorbed on the resin in concentrated HCl/ethanol mixed solution.•Ca adsorption is controlled by HCl added to ethanol at any mixing ratios.•Heavy isotope Ca-48 is enriched at the front boundary of chromatogram.•Flame photometry was applied to the measurement of Ca concentration. Benzo-18-crown-6 ether resin embedded in porous silica beads was synthesized and used as the packing material for chromatographic separation of 48Ca isotope. The aim of the present work is to develop efficient isotope enrichment process for double β decay nuclide 48Ca. To this end, ethanol/HCl mixed solvent was selected as the medium for the chromatographic separation. Adsorption of calcium on the resin was studied at different HCl concentrations and different ethanol mixing ratios in batch-wise experiments. A very interesting phenomenon was observed; Ca adsorption is controlled not by the overall HCl concentration of the mixed solvent, but by the initial concentration of added HCl solution. Calcium break-through chromatography experiments were conducted by using 75v/v% ethanol/25v/v% 8M HCl mixed solvent at different flow rates. The isotope separation coefficient between 48Ca and 40Ca was determined as 3.8×10−3, which is larger than that of pure HCl solution system. Discussion is extended to the chromatographic HETP, height equivalent to a theoretical plate.