Inorganic ion-exchangers: Their role in chromatographic radionuclide generators for the decade 1993-2002

Production, radiochemical separation and electrochemical concentration of No-carrier-added 52Mn: An emerging PET radiometal

Recently, there has been significant interest in 52Mn (T½ = 5.6 d) as a relatively long lived radiometal for PET imaging of cancer. In this study, we have produced 52Mn from natural Cr metallic powder target via 52Cr (p, n) 52Mn reaction in a particle accelerator. An efficient radiochemical separation method based on selective precipitation of Cr as Cr(OH)3 followed by electrochemical purification and concentration of 52Mn was developed for isolation of no-carrier-added (nca) 52Mn from the irradiated target. The overall radiochemical separation yield of the process was >75 %. After separation, 52Mn was obtained with >99.5 % radionuclidic purity and >97 % radiochemical purity. The apparent molar activity of 52Mn was determined to be 2.2 ± 0.1 MBq/nmol and it was found suitable for preparation of radiopharmaceuticals. As a proof of concept, [52Mn]Mn-DOTA-E[c(RGDfK)]2 was prepared with 98.8 ± 0.4 % radiolabeling yield and the radiochemical stability of the formulation was maintained over a period of 7 days under physiological conditions. Overall, this strategy is viable for obtaining nca 52Mn in a suitable form for radiopharmaceutical preparation and would potentially increase the availability of this radiometal for clinical PET imaging in foreseeable future.

TcGenerator Development: Up-to-DateTcRecovery Technologies for Increasing the Effectiveness ofMoUtilisation

A review on theMosources available today and on theTcgenerators developed up to date for increasing the effectiveness ofMoutilisation is performed in the format of detailed description of the features and technical performance of the technological groups of theMoproduction andTcrecovery. The latest results of the endeavour in this field are also surveyed in regard of the technical solution for overcoming the shortage ofMosupply. The technological topics are grouped and discussed in a way to reflect the similarity in the technological process of each group. The following groups are included in this review which are high specific activityMo: the current issues of production, the efforts of more effective utilisation, and the high specific activityMo-basedTcgenerator andTcconcentration units; low specific activityMo: theMoproduction based on neutron capture and accelerators and the direct production ofTcand the methods of increasing the specific activity ofMousing Szilard-Chalmers reaction and high electric power isotopic separator; up-to-date technologies ofTcrecovery from low specific activityMo: the solvent extraction-basedTcgenerator, the sublimation methods forMo/Tcseparation, the electrochemical method forTcrecovery, and the column chromatographic methods forTcrecovery. Besides the traditionalTc-generator systems, the integratedTcgenerator systems (Tcgenerator column combined with postelution purification/concentration unit) are discussed with the format of process diagram and picture of real generator systems. These systems are the technetium selective sorbent column-based generators, the high Mo-loading capacity column-based integratedTcgenerator systems which include the saline-eluted generator systems, and the nonsaline aqueous and organic solvent eluent-eluted generator systems using high Mo-loading capacity molybdategel and recently developed sorbent columns.Tcconcentration methods used in theTcrecovery from low specific activityMoare also discussed with detailed process diagrams which are surveyed in two groups forTcconcentration from the saline and nonsalineTc-eluates. The evaluation methods for the performance ofTc-recovery/concentration process and for theTc-elution capability versus Mo-loading capacity of generator column produced using low specific activityMosource are briefly reported. Together with the theoretical aspects ofTc/Moand sorbent chemistry, these evaluation/assessment processes will be useful for any further development in the field of theTcrecovery andMo/Tcgenerator production.

Radiochemical Studies on the Separation of Cesium, Cobalt, and Europium from Aqueous Solutions Using Zirconium Selenomolybdate Sorbent

A procedure for removal and separation of Cs, Eu and activation product of Co using zirconium selenomolybdate was developed. Interactions of134Cs(I),152,154Eu(III), and60Co(II) ions from HNO3acid solutions with zirconium selenomolybdate matrix, dried at 50°C, have been individually investigated by the batch equilibration method. The sorption behavior of the three ions showed a selectivity sequence in the following order: Cs(I) > Eu(III) > Co(II). The breakthrough capacities of zirconium selenomolybdate for Cs(I), Eu(III) and Co(II) were found to be 0.82, 0.45, and 0.18 mmol/g of the sorbent, respectively. A mixture of the three radionuclides (1×10−2 M each) in 140 mL of1×10−2 M HNO3solution was passed through 1 g zirconium selenomolybdate chromatographic column. Thereafter, quantitative elution of the retained Co(II) was achieved with 14 mL of1×10−1 M HNO3acid solution leaving Eu(III) and Cs(I) strongly retained onto the column. Quantitative elution of Eu(III) was achieved by passing 22 mL2.5×10−1 M HNO3. About 89% of the retained Cs(I) was eluted with 32 mL of 2 M NH4Cl solution at a flow rate of 0.5 mL/min.

One-dimensional Ti–O based nanotubes as ion exchanger: synthesis, characterization and application in radiochemical separation of carrier-free 137mBa from 137Cs

Hydrogen titanate nanotubes (H2Ti3O7) were synthesized by hydrothermal process using 10 M NaOH and TiO2 anatase powder. The material synthesized was characterized by powdered X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to ensure the structural and morphological details of the above said nanotubes. This nanosized material behaved as a cation exchanger and it was employed to separate carrier-free 137mBa from 137Cs in column chromatographic technique using 1.0 M HNO3 as eluting agent.

Availability of yttrium-90 from strontium-90: a nuclear medicine perspective

Yttrium-90 (T(½) 64.1 hours, E(βmax)=2.28 MeV) is a pure β⁻ particle emitting radionuclide with well-established applications in targeted therapy. There are several advantages of ⁹⁰Y as a therapeutic radionuclide. It has a suitable physical half-life (∼64 hours) and decays to a stable daughter product ⁹⁰Zr by emission of high-energy β⁻ particles. Yttrium has a relatively simple chemistry and its suitability for forming complexes with a variety of chelating agents is well established. The ⁹⁰Sr/⁹⁰Y generator is an ideal source for the long-term continuous availability of no-carrier-added ⁹⁰Y suitable for the preparation of radiopharmaceuticals for radionuclide therapy. The parent radionuclide ⁹⁰Sr, which is a long-lived fission product, is available in large quantities from spent fuel. Several useful technologies have been developed for the preparation of ⁹⁰Sr/⁹⁰Y generators. There are several well-established radiopharmaceuticals based on monoclonal antibodies, peptides, and particulates labeled with ⁹⁰Y, that are in regular use for the treatment of some forms of primary cancers and arthritis. At present, there are no generators for the elution of ⁹⁰Y that can be set up in a hospital radiopharmacy. The radionuclide is procured from manufacturers and the radiopharmaceuticals are formulated on site. This article reviews the development of ⁹⁰Sr/⁹⁰Y generator and the development of ⁹⁰Y radiopharmaceuticals.

In situ X-ray diffraction study of cesium exchange in synthetic umbite

The exchange of Cs(+) into H(1.22)K(0.84)ZrSi(3)O(9)·2.16H(2)O (umbite-(HK)) was followed in situ using time-resolved X-ray diffraction at the National Synchrotron Light Source. The umbite framework (space group P2(1)/c with cell dimensions of a = 7.2814(3) Å, b = 10.4201(4) Å, c = 13.4529(7) Å, and β = 90.53(1)°) consists of wollastonite-like silicate chains linked by isolated zirconia octahedra. Within umbite-(HK) there are two unique ion exchange sites in the tunnels running parallel to the a-axis. Exchange Site 1 is marked by 8 member-ring (MR) windows in the bc-plane and contains K(+) cations. Exchange Site 2 is marked by a larger 8-MR channel parallel to [100], and contains H(2)O molecules. The occupancy of the Cs(+) cations through these channels was modeled by Rietveld structure refinements of the diffraction data and demonstrated that there is a two-step exchange process. The incoming Cs(+) ions populated the larger 8-MR channel (Exchange Site 2) first and then migrated into the smaller 8-MR channel. During the exchange process a structural change occurs, transforming the exchanger from monoclinic P2(1)/c to orthorhombic P2(1)2(1)2(1). This structural change occurs when Cs(+) occupancy in the small cavity becomes greater than 0.50. The final in situ ion exchange diffraction pattern was refined to yield umbite-(CsK) with the molecular formula H(0.18)K(0.45)Cs(1.37)ZrSi(3)O(9)·0.98H(2)O and possessing an orthorhombic unit cell with dimensions a = 10.6668(8) Å, b = 13.5821(11) Å, c = 7.3946(6) Å. Solid state (133)Cs MAS NMR showed there is only a slight difference between the two cavities electronically. Valence bond sums for the completely occupied Exchange Site 1 demonstrate that Cs-O bonds of up to 3.8 Å contribute to the coordination of the Cs(+) cation.

Concentration of rhenium from dilute sodium chloride solutions

The conditions for the desorption of rhenium from the anion exchange resin Dowex 1-x8 by HNO3, HCl, H2SO4 and NaOH were determined. The solution (5.0?10-3 mol dm-3 Re in 0.15 mol dm-3 NaCl) was passed through a column containing 0.10 g of the resin. The total sorbed amount of rhenium was 0.20 g/g of the resin. It was then eluted by the corresponding eluent in the concentration range up to about 3.0 mol dm-3. The highest elution efficiency and the most favourable elution profile were found with 3.0 mol dm-3 HNO3. Over 77 % of the sorbed rhenium was found in the first 5 ml of the eluate. Practically all the rhenium was recovered with 20 ml of the acid. Under the given experimental conditions, HCl and H2SO4 were less favourable while NaOH was not applicable, due to very low efficiency of rhenium elution.

Sorption of rhenium on alumina under dynamic conditions

The sorption of perrhenate anion on alumina from aqueous solutions of sodium chloride was investigated under dynamic conditions. The initial concentrations of rhenium were in the range of 2.7x10-2-2.7 mmol/dm3. The breakthrough curves as the function of Re and NaCl concentrations (0.12-0.20 mol/dm3), pH 2-6 and flow rate 3-10 ml/min were determined. According to the experimental results, it was concluded that the breakthrough capacities, the capacities at c/c0 = 0.5, the total column capacities and the utilization degrees (column efficiency) increase with increasing Re and NaCl concentrations and decreasing pH. The optimal flow rate was found to be 3 ml/min. At pH2 and c0 = 2.7 mmol Re/dm3, the total capacity was found to be Q 0.9 max = 2.1x10-2 mmol Re/g Al2O3. The data for perrhenate anions fit with a Henry-type isotherm. It was found that, under the above mentioned conditions, the value of the Henry constant K H was 7.8x10-3 dm3/g and the Gibbs energy change, ?G was -0.5 kJ/mol.