Characterization of At− species in simple and biological media by high performance anion exchange chromatography coupled to gamma detector

Abstract

Astatine is a rare radioelement belonging to the halogen group. Considering the trace amounts of astatine produced in cyclotrons, its chemistry cannot be evaluated by spectroscopic tools. Analytical tools, provided that they are coupled with a radioactive detection system, may be an alternative way to study its chemistry. In this research work, high performance anion exchange chromatography (HPAEC) coupled to a gamma detector (γ) was used to evaluate astatine species under reducing conditions. Also, to strengthen the reliability of the experiments, a quantitative analysis using a reactive transport model has been done. The results confirm the existence of one species bearing one negative charge in the pH range 2-7.5. With respect to the other halogens, its behavior indicates the existence of negative ion, astatide At(-). 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) 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 (211)At-labeled molecules potentially applicable in nuclear medicine.

Advances on the Determination of the Astatine Pourbaix Diagram: Predomination of AtO(OH)2− over At− in Basic Conditions

“…Two anionic species, A and B, were characterized by retention times of 5.2 min and 8.1 min, respectively, with a roughly 1:99 ratio between these two species (see Figure , top). The minor species, A, was identified as At − by comparison of retention times of samples prepared in the conditions in which this species assuredly predominates, both at neutral and acidic pH in reducing conditions.…”

“…The latter is the predominant astatine species at pH=5.5 and oxidizing conditions. According to recent results, this species is AtO(OH), that is, the first hydrolysis product of AtO + . Hence, the HPAEC experiments indicate that a single‐charged B species predominates in basic conditions, and that it converts into AtO(OH) when the pH is decreased, while oxidizing conditions are maintained.…”

“…The first experimentsw ere carried out in a1m m NaOH solution, using aD ionex AS20 anionic exchange column, whilet he NaOH concentrationi nthe eluent was 10 À1 m.T wo anionic species, Aa nd B, were characterizedb yr etention times of 5.2 min and 8.1 min, respectively,w ith ar oughly 1:99 ratio between these two species( see Figure2,t op). The minor species, A, was identified as At À by comparison of retention times of sam-ples prepared in the conditions in whicht his speciesa ssuredly predominates, both at neutral [10] and acidic [7b] pH in reducing conditions.…”

Towards a Stronger Halogen Bond Involving Astatine: Unexpected Adduct with Bu3PO Stabilized by Hydrogen Bonding

“…Consequently, conventional spectroscopic tools are unsuited to get experimental information at the molecular level, which can fortunately be obtained by molecular modeling tools. In fact, at ultra‐trace concentration, only “indirect” experimental method, based for instance on electromobility, chromatography, or competition, can be used …”

Effective bond orders from two-step spin–orbit coupling approaches: The I2, At2, IO+, and AtO+ case studies

“…11 Among the recent experimental highlights, it is worth quoting the determination of the ionization potential of the free atom, 12 or the determination of predominance domains in the Pourbaix diagram (E-pH) of At in aqueous solution. [13][14][15] One should also mention the theoretical prediction of a metallic behavior for condensed astatine, unlike the other halogens. 16 Furthermore, stable At cationic forms (At + and AtO + ) exist in aqueous solution and their coordination chemistry has been experimentally explored by reporting complexation constants with various inorganic ligands.…”