Rapid Elution of 226Th from a Two-Column 230U/226Th Generator with Diluted and Buffer Solutions

A radionuclide generator of the short-lived alpha emitter Th-226 was proposed. An original scheme consisting of two in-series chromatographic columns was developed for rapidly producing a neutral citric-buffered eluate of high purity Th-226. The first column filled with TEVA resin retained the parent U-230, while Th-226 was eluted with 7 M HCl solution to be immediately adsorbed on the second column containing DGA resin or UTEVA resin. Having substituted the strongly acidic medium of second column with neutral salt solution, Th-226 was desorbed with diluted citric buffer solution. One cycle of generator milking took 5-7 min and produced >90% of Th-226 in 1.5 mL of eluate (pH 4.5-5.0) appropriate for direct use in radiopharmaceutical synthesis. The U-230 impurity in Th-226 eluate was less than 0.01%. The proposed two-column U-230/Th-226 generator was tested over 2 months including a second loading of U-230 additionally accumulated from Pa-230.