Fast radiochemical separations for neutron-deficient short-lived nuclides

We review both simple and exotic radiochemical techniques used for the separation, purification, and analysis of neutron-deficient short-lived nuclides. These range from classical wet-chemical methods to automated and instrumental techniques. We give special attention to chemical adjuncts of the He-jet recoil-transport technique and to high-resolution mass spectrometry. We also review recent developments in biological applications, including¹³N production and use.     

The application of inorganic exchangers to radiochemical separations on neutron-activated high-purity materials

Résumé Cet article traite de l'utilisation d'échangeurs minéraux dans l'analyse destructive de matériaux de grande pureté, en particulier pour la détermination systématique d'un grand nombre d'éléments. On indique brièvement des améliorations récentes dans la méthode permettant d'évaleur mathématiquement les modes de séparation radiochimique à l'aide des échangeurs minéraux. On décrit les modes de séparation dans le cas du dosage des impuretés dans de l'aluminium et du zinc de haute pureté. Les résultats pour plusieurs échantillons de zinc obtenus par purifications successives sont donnés, ces résultats mettent en évidence l'évolution de la distribution des différentes impuretés. On présente aussi les résultats obtenus dans le cas d'un échantillon de zinc choisi comme étalon.      

Use of tetracycline as complexing agent in radiochemical separations

The use of the antibiotic agent tetracycline for analytical purposes in solvent extraction procedures is presented. Individual extraction curves for the lanthanides, zinc, scandium, uranium, thorium, neptunium and protactinium were obtained. Separation of those elements one from another, and of uranium from selenium, bromine, antimony, barium, tantalum and tungsten was carried out. In all cases benzyl alcohol was the diluent used to dissolve tetracycline hydrochloride. Sodium chloride was used as supporting electrolyte for the lanthanide separations and sodium perchlorate for the other elements mentioned. Stability or formation constants for the lanthanide complexes as well as for thorium complex with tetracycline were determined by using the methods of average number of ligands, the limiting value (for thorium), the two parameters and the weighted least squares. For the lanthanides, the stability constants of the complexes Ln(TC)₃ go from 9.35±0.22 for lanthanum up to 10.84±0.11 for lutetium. For the Th(TC)₄ complex the formation constant is equal to 24.6±0.3. Radioisotopes of the respective elements were used for the determinations. When more than one radioelement was present in an experiment, a multichannel analyser coupled to Ge(Li) or NaI(Tl) detectors was used for counting the activities. When only one radioisotope was used, counting of the radioisotopes was made with a single-channel analyser (integral mode counting) coupled to a NaI(Tl) detector. Uranium was determined by activation analysis (epithermal neutrons). Radioisotopes of the elements were obtained by irradiation in the IPEN swimming-pool reactor. The natural radioisotope^{2 3 4}Th was used as label in the thorium experiments. In some separation procedures such as in the case of the pair uranium-neptunium, and of the pair scandium-zinc, the separation was obtained by properly adjusting the pH value of the aqueous phases, before the extraction operation. In other cases, addition of masking agents to the extraction system was required in order to perform the separation between the elements under study. In this way ethylenediaminetetraacetic acid (EDTA) was used as masking agent for scandium and the lanthanides in order to allow separation of uranium from those elements. Diethylenetriaminepentaacetic acid (DTPA) was used as masking agent for thorium in order to extract uranium into the organic phase. Separations of protactinium from thorium, and of uranium from protactinium and thorium, were accomplished by using sodium fluoride as masking agent for protactinium and DPTA as masking agent for thorium and protactinium at the same time. In the case of the separation of the lanthanides one from another it is necessary to resort to a multi-stage extraction procedure since the stability constants for those elements are too close.     

Single-step radiochemical separations by column procedures in activation analysis

Some single-step column procedures are described for both individual and group activity separations. Besides the usual ion-exchange techniques, other methods such as reverse-phase chromatography, isotopic exchange and the use of resins converted into special forms were used. Fast and simple selective separations from 2N hydrochloric acid are reported for Mo(VI), Cu(II), Sb(V), and for AsO₄^3- + PO₄^3- from both 2 N hydrochloric acid and I N sulfuric acid; for Cu, Sb and As + P, the selectivity can be greatly increased by using a guard bed of resin in normal form. By combining the different techniques a single-step separation scheme for 6 elements (Mo, Au, Zn, As, Cu, Sb) in 2 N hydrochloric acid was developed; this allows high chemical recoveries, high cross-decontamination and very large decontamination from ²⁴Na to be reached, so that application for biological sample analysis can be envisaged. Simplified two-stage column separations for Au + Sb and Cu and Fe + Sb and Zn from concentrated hydrochloric acid (cationic and anionic resin beds coupled) are also reported.     

Atom-at-a-time radiochemical separations of the heaviest elements: Lawrencium chemistry

The isotope²⁶⁰Lr, produced in reactions of¹⁸O with²⁴⁹Bk, was used to perform chemical experiments on lawrencium to learn more about its chemical properties. These experiments involved extractions with thenoyl trifluoroacetate, elutions from cation exchange resin columns with ammonium alpha-hydroxyisobutyrate, and reverse-phase chromatography using hydrogen di(2-ethylhexyl) orthophosphoric acid to investigate the chemical properties of Lr. The results from the elutions gave information about the ionic radius of Lr(III) which was found to elute very close to Er. An attempt to reduce Lr(III) with hydroxylamine hydrochloride was unsuccessful.     

Possible radiochemical separations of anionic radionuclides by amorphous hydrous titanium dioxide

Ion-exchange selectivities towards oxoanions and halide ions were studied for radio-chemical applications by an amorphous hydrous titanium dioxide (Am-HTDO) as functions of pH and concentration. The selectivity series was found to be Mo(VI)<W(VI)<P(V)<As(V)<Sb(V) for micro-amounts at pH 9 and Br^–Cl^–F^– for macro-amounts. A feasibility was suggested for radiochemical separations of³²P by³⁵Cl(n,)³²P and⁷⁷Br by⁷⁵As(, 2n)⁷⁷Br, and selective removal of anionic radionuclides.Synthetic Inorganic Ion-Exchange Materials. XLIII.