Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 53

Decontamination of Po in the 211 Rn/211 At generator system
K. Aoi,∗1,∗2 K. Kawasaki,∗1,∗2 S. Maruyama,∗1,∗2 M. Higashi,∗1,∗3 K. Washiyama,∗4 A. Yokoyama,∗1,∗3I. Nishinaka,∗5 D. Mori,∗1 Y. Wang,∗1 and H. Haba∗1
The short path length and high linear energy transfer of α particles are expected to enable targeted alpha therapy for the treatment of tumor. A promising nuclide among various α emitters is 211 At with ahalf-life of 7.21 h, which has gained popularity owing
to its appropriate life and potential to synthesize labeled compounds as a halogen element. This has been
the motivation behind several preclinical studies on Atchemistry.1) To improve the availability of 211 At, thedevelopment of a 211 Rn/211 At generator would be useful for expanding nuclide production away from accelerator facilities because 211 Rn, which has a half-life of
14.6 h, is the parent nuclide of 211 At.2) However, Po
isotopes such as 207 Po and 206 Po, which are known tobe harmful to the human body, may contaminate theAt sample owing to decay from the Rn products. We
aim to study the wet chemistry processes by using adsorption chromatography resins for an At solution freefrom Po contamination.
In this study, 211 At was produced via the209
Bi(α, 2n) reaction at the RIKEN AVF cyclotron anddelivered to Kanazawa University. The irradiated Bi
target was dissolved in 2 mL of 6 M HNO3 and mixed
with 10 mL of H2 O to prepare a 1 M HNO3 solution,
2 mL of which was used to extract the 211 At nuclide
into 18 mL of dodecane solvent.
Aliquots of the dodecane solution were subjected
to back extractions into several solutions of various
HCl concentrations. 2 mL of each solution was fed toadsorption chromatography columns ﬁlled with eithera cation-exchange resin, DGA resin, or TEVA resin
through a conditioning process in advance. The eluted
solution from the column and the eluent due to additional washing with 2 mL of two solutions with thesame HCl concentration were subjected to liquid scintillation counter (LSC) measurement to determine the211
At radioactivity.
The results of the measurement of 211 At radioactivity after puriﬁcation with adsorption chromatography columns demonstrate that the recoveries for DGA
resin and cation-exchange resin were ca. 50% at mostat 0.01 M HCl and were better than that for TEVA
resin. This suggests that the species of At may have
∗1
∗2
∗3
∗4

∗5Graduate School of Natural Science and Technology,Kanazawa University
Institute and College of Science and Engineering, Kanazawa
University
Fukushima Global Medical Science Center, Fukushima Medical University
Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology
RIKEN Nishina Center- 193 -Fig. 1. Recovery of 211 At radioactivity and elimination ofPo depending on the ascorbic-acid concentration.

a variety of oxidation states that aﬀect adsorption
in columns. Therefore, another experiment was performed to change their oxidation states by using a reductant agent and to conﬁrm the eﬀect of reduction
with cation-exchange resin.
Similarly to the experiment described above,
aliquots of the dodecane solution were subjected toback extractions into 0.01 M HCl solution, which had
been adjusted to the solutions with 0.01, 0.1, and 1%
ascorbic acid. The HCl solutions were fed to a column
ﬁlled with cation-exchange resin that was conditioned
well in advance. The eluent from the column was collected and subjected to the LSC measurement in thesame manner as above.
The recovery of 211 At radioactivity with ascorbic
acid as a reductant agent is shown in Fig. 1 together
with Po elimination data taken with the Po activity
produced in the JAEA tandem accelerator. It wasfound that the 211 At recoveries are improved to 80%,and the elimination of Po was successful under thesame condition.
References

1) F. Guérard, J. -F. Gestin, M. W. Brechbiel, Cancer Biother. Radiopharm. 28, 1 (2013).
2) E. Maeda et al., J. Radioanal. Nucl. Chem. 303, 1465
(2015).