Radchenko V, Engle J W, Wilson J J, Maassen J R, Nortier F M, Taylor W A, Birnbaum E R, Hudston L A, John K D, Fassbender M E
Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, United States.
Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, United States.
J Chromatogr A. 2015 Feb 6;1380:55-63. doi: 10.1016/j.chroma.2014.12.045. Epub 2014 Dec 18.
Actinium-225 (t1/2=9.92d) is an α-emitting radionuclide with nuclear properties well-suited for use in targeted alpha therapy (TAT), a powerful treatment method for malignant tumors. Actinium-225 can also be utilized as a generator for (213)Bi (t1/2 45.6 min), which is another valuable candidate for TAT. Actinium-225 can be produced via proton irradiation of thorium metal; however, long-lived (227)Ac (t1/2=21.8a, 99% β(-), 1% α) is co-produced during this process and will impact the quality of the final product. Thus, accurate assays are needed to determine the (225)Ac/(227)Ac ratio, which is dependent on beam energy, irradiation time and target design. Accurate actinium assays, in turn, require efficient separation of actinium isotopes from both the Th matrix and highly radioactive activation by-products, especially radiolanthanides formed from proton-induced fission. In this study, we introduce a novel, selective chromatographic technique for the recovery and purification of actinium isotopes from irradiated Th matrices. A two-step sequence of cation exchange and extraction chromatography was implemented. Radiolanthanides were quantitatively removed from Ac, and no non-Ac radionuclidic impurities were detected in the final Ac fraction. An (225)Ac spike added prior to separation was recovered at ≥ 98%, and Ac decontamination from Th was found to be ≥ 10(6). The purified actinium fraction allowed for highly accurate (227)Ac determination at analytical scales, i.e., at (227)Ac activities of 1-100 kBq (27 nCi to 2.7 μCi).
锕 - 225（半衰期 = 9.92天）是一种发射α粒子的放射性核素，其核性质非常适合用于靶向α治疗（TAT），这是一种针对恶性肿瘤的有效治疗方法。锕 - 225还可作为铋 - 213（半衰期45.6分钟）的发生器，铋 - 213是TAT的另一个有价值的候选物。锕 - 225可通过质子辐照钍金属产生；然而，在此过程中会同时产生长寿命的锕 - 227（半衰期 = 21.8年，99%为β⁻衰变，1%为α衰变），这将影响最终产品的质量。因此，需要精确的分析方法来确定锕 - 225/锕 - 227的比例，该比例取决于束流能量、辐照时间和靶材设计。反过来，精确的锕分析需要将锕同位素与钍基质以及高放射性活化副产物有效分离，特别是质子诱导裂变形成的放射性镧系元素。在本研究中，我们引入了一种新颖的选择性色谱技术，用于从辐照后的钍基质中回收和纯化锕同位素。实施了阳离子交换和萃取色谱的两步序列。从锕中定量去除了放射性镧系元素，最终的锕馏分中未检测到非锕放射性核素杂质。分离前添加的锕 - 225加标回收率≥98%，钍中锕的去污系数≥10⁶。纯化的锕馏分能够在分析规模下，即锕 - 227活度为1 - 100 kBq（27 nCi至2.7 μCi）时，实现对锕 - 227的高精度测定。
