Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 51 (2018)

Improved method for preparation of no-carrier added 28 Mg tracer
H. Kikunaga,∗1,∗2 H. Haba,∗2 Y. Komori,∗2 and S. Yano∗2∗1∗2

Research Center for Electron Photon Science, Tohoku University
RIKEN Nishina Center- 225 -0.5 M oxalic acid. The solution was passed through acation exchange resin column (Muromac 50W×8, 100–
200 mesh, 1 mL) to adsorb 28 Mg isotopes. The resin
was washed with 0.2 M HF for Be elimination, 0.5 M
oxalic acid for Al elimination, and 0.5 M HCl for Naelimination. The 28 Mg isotopes were eluted from thecolumn with 2 M HCl.
The chemical yield of the separation procedure, determined by γ-spectrometry of 28 Mg, was approximately 85% and radioactivity other than 28 Mg was notdetected in the Mg fraction.
㻜㻚㻡㻌㻹㻌㻴㻞㻯㻞㻻㻠㻜㻚㻞㻌㻹㻌㻴㻲
㻌㻮㼑㻙㻣㻌㻺㼍㻙㻞㻠
㻌㻹㼓㻙㻞㻤<LHOG Magnesium is involved in important physiologicalactivities such as many enzymatic reactions. The isotope 28 Mg, which has the longest half-life (21.6 h1) )among radioactive magnesium isotopes, is useful in biological sciences as a radioactive tracer.2,3) We plan
to provide a no-carrier added 28 Mg tracer producedin the 27 Al(α, 3p) reaction to applicants through, forexample the Supply Platform of Short-lived Radioisotopes for Fundamental Research. In a precious paper,4) we attempted to separate 28 Mg from an Al target, focusing on reducing waste radioactive materials.
However, there was an unwanted problem that the obtained tracer contained nuclide 7 Be. In this work, wereport an improved method for the preparation of nocarrier-added 28 Mg tracer in addition to the procedureof beryllium elimination.
Magnesium-28 was produced at either the RIKEN
K70 AVF Cyclotron or the AVF Cyclotron at CYRIC,Tohoku University. The target stack of 7 Al foils(99.9% pure) with a thickness of 100 µm was irradiated with an α-particle beam with a beam energy of50 MeV and a mean current of approximately 3 µA.
First, the conditions for the separation of 28 Mg from7
Be were searched for. The irradiated Al targets weredissolved in 12 M (mol/dm3 ) HCl. A portion of it,
containing 0.1 mmol of Al and trace amounts of 7 Be,24Na, and 28 Mg, was heated to dryness and adjusted to0.5 M oxalic acid. The solution was passed through acation exchange column (Muromac 50 W×8, 100–200
mesh, 1 mL), which adsorbs Al(III), 7 Be,24 Na, and28
Mg ions, following which the resin was washed with
7 mL of 0.5 M oxalic acid to eliminate Al(III) and 5 mLof 0.2 M HF. The elution curves of the cation-exchange
separation is shown in Fig. 1. The 7 Be ions are eluted
completely within 5 mL of 0.2 M HF, whereas the 24 Naand 28 Mg ions are retained onto the column.
Next, the procedure to eliminate 7 Be was incorporated into the previous procedure.4) The improved
chemical scheme is shown in Fig. 2. The irradiated
Al targets were dissolved in 9 M HCl and then diluted with water to 15 mL. The 28 Mg isotopes wereco-precipitated with iron hydroxide by adding 2 mg ofFe(III) and 15 mL of 6 M NaOH and separated fromAl, Na, and Be ions. The precipitation of iron hydroxide was dissolved in 9 M HCl. The solution waspassed through an anion exchange resin column (Muromac 1×8, 100–200 mesh, 1 mL), which adsorbs Fe(III)ions, and the resin was washed with additional 9 M
HCl. The eluate was heated to dryness and adjusted to











9ROXPH P/  Fig. 1. Elution curves for the cation exchange separationof Be, Na, and Mg.

Fig. 2. Chemical procedure for the preparation of nocarrier added 28 Mg tracer.

References
1) R. B. Firestone, V. S. Shirley, Table of Isotopes, 8th ed.
(John Wiley and Sons, New York, 1996).
2) C. Schimansky, J. Plant Nutr. 8, 467 (1985).
3) K. Tanoi et al., Plant Soil 384, 69 (2014).
4) H. Kikunaga et al., RIKEN Accel. Prog. Rep. 50, 260(2017).