NRC-8, EuCheMS International Conference on Nuclear and Radiochemistry

Characterization of At- and AtO+ species in simple media by high performance ion exchange chromatography coupled to gamma detector. Application to astatine speciation in human serum.

17 Sept 2012, 17:30

1h 30m

Como, Italy

Poster Chemistry of radioelements and Super Heavy Elements research Poster Session

Speaker

Dr Andrea Sabatié-Gogova (Subatech, Ceisam, France)

Description

Astatine is a rare radioelement belonging to the halogen group. Considering the trace amounts of astatine-211 produced in cyclotrons, its chemistry cannot be directly evaluated by usual spectroscopic tools. Analytical tools, provided that they are coupled with a radioactive detection system, may be an alternative way to study its chemistry. In the present research work, High Performance Ion Exchange Chromatography (HPIEC) coupled to a gamma detector (γ) was used to evaluate astatine species under reducing and oxidizing conditions. Also, to support the reliability of the experiments, a quantitative analysis using a reactive transport model has been done [1]. Under reducing conditions, results confirm the existence of one species bearing one negative charge in the pH range of 2-7.5. With respect to the other halogens, its behavior indicates the existence of a negative ion, astatide At- [2,3]. The methodology was successfully applied to the speciation of the astatine in human serum. Under fixed experimental conditions (pH 7.4-7.5 and redox potential of 250 mV/ENH) astatine exists mainly as astatide At- and does not interact with the major serum components. Also, the method might be useful for the in vitro stability assessment of 211At-labelled molecules potentially applicable in nuclear medicine. Under oxidizing and acidic pH conditions, a peak corresponding to one species holding one positive charge, in agreement with the literature proposed species [4,5], has been shown. It was defined as AtO+. A change in speciation occurs as the pH changes from 1 to 4. Also, starting with At- at pH 7 under reducing conditions, a change in speciation was observed as the potential increases. In both experiments, this species was eluted in the void volume showing neutral species. A complementary experimental competition method based on liquid/liquid extraction and modeling [6,7] has confirmed the exchange of one proton indicating the probable formation of AtO(OH). The thermodynamic hydrolysis constant obtained by quasi-relativistic quantum calculations [7,8] has also confirmed this species. 1. A. Sabatié-Gogova, J. Champion, S. Huclier, N. Michel, F. Pottier, N. Galland, Z. Asfari, M. Chérel and G. Montavon, Analytica Chimica Acta 2012, 721, 182. 2. G.-J. Meyer, Chromatographie Trägerfreier Anorganisher Formen von Jod-123 und Astat-211 und ihre Verwendung zur Halogenierung von Uracil and Desoxyuridin, Berichte Nr.1076, Kernforschungsanlage Jülich, Jülich, 1974. 3. K. Roessler, W. Tornau, G. Stoecklin, J. Radioanalytical Chemistry 1974, 21, 199–209. 4. A. Cavallero, K. Rossler, Radiochimica Acta 1989, 47, 113–117. 5. D. K. Tyung, I. V. Dudova, V. A. Khalkin, Radiokhimiya 1973, 16 (4), 548-553. 6. J. Champion, C. Alliot, S. Huclier, D. Deniaud, Z. Asfari and G. Montavon, Inorganica Chimica Acta 2009, 362, 2654-2661. 7. J. Champion, C. Alliot, E. Renault, B. M. Mokili, M. Cherel, N. Galland and G. Montavon, The Journal of Physical Chemistry A 2010, 114, 576-582. 8. J. Champion, M. Seydou, A. Sabatié-Gogova, E. Renault, G. Montavon and N. Galland, Physical Chemistry Chemical Physics 2011, 13, 14984-14992.