The simple radiochemical determination of 90Sr in environmental solid samples by solvent extraction

Determination of ⁹⁰Sr in environmental solid samples is a challenging task because of the presence of so many other radionuclides in samples of interest. This problem was dealt with by radiochemical separation of strontium followed by yttrium separation and Cerenkov counting of the high-energy ??-particle emissions of ⁹⁰Y in order to quantitate ⁹⁰Sr. In this work, an improved method is described for the determination of ⁹⁰Sr in soil samples, through the separation of the daughter ⁹⁰Y at equilibrium. The procedure is based on the HDEHP solvent extraction in combination with liquid scintillation spectrometry (LSS). A low background Quantulus has been optimized for low level counting of Cerenkov radiation emitted by the hard ??-emitter ⁹⁰Y. The analytical quality of the method has been checked by analyzing IAEA Soil-375 reference materials. The analytical method has also been successfully applied to the determination of ⁹⁰Sr for moss-soil samples in inter-laboratory exercises through IAEA??s ALMERA network. The chemical recovery for ⁹⁰Y extraction ranged from 80 to 85% and the counting efficiency was 73% in the window 25?C400 keV.     

Sorption of radionuclides on the container wall during batch migration studies

The sorption of radionuclides on the wall of polypropylene centrifugetubes used for the batch migration study has been investigated. The parametersvaried were solution acidity, contact time, presence and physicochemical propertiesof geomedia. The radionuclides were ⁴⁶Sc, ⁶⁰Co, ⁷⁵Se, ⁸⁵Sr, ¹³⁴Cs and ²⁴¹Am, whichwere all gamma-ray emitters. It has been found that the sorption of radionuclideson the tube wall increased somewhat with increasing solution pH and the contactperiod in the control experiment, but decreased with increasing the cationexchange capacity of geologic materials in the batch experiment. Effects ofsorption on tube wall in the migration study is negligible in most but notall situations and should be corrected, not by the control experiment butby the batch experiment.     

Table for true summation effect in gamma-ray spectrometry

Probabilities of gamma-ray simultaneous emission have been calculated for the determination of correction factors of full-energy peak areas of radionuclides with a complex decay scheme at measurements of gamma-spectra using HPGe detectors. Coincidence probabilities were determined using the Monte Carlo method for the following radionuclides: ²²Na, ²⁴Na, ⁴⁶Sc, ⁵¹Cr, ⁵²Fe, ⁵⁴Mn, ⁵⁶Co, ⁵⁷Co, ⁵⁸Co, ⁵⁹Fe, ⁶⁰Co, ⁶⁴Cu, ⁶⁵Zn, ⁶⁷Cu, ⁶⁸Ge-⁶⁸Ga, ⁷⁵Se, ⁸⁵Sr, ⁸⁸Y, ⁹⁴Nb, ^108mAg, ¹⁰⁹Cd, ¹¹¹In, ¹²⁴Sb, ¹²⁵Sb, ¹²⁵I, ¹³¹I, ¹³²Cs, ¹³³Ba, ¹³⁴Cs, ¹³⁹Ce, ¹⁵²Eu, ¹⁵³Sm, ¹⁵³Gd, ¹⁵⁵Eu, ^166mHo, ¹⁶⁹Yb, ¹⁷⁷Lu, ¹⁸⁶Re, ²⁰⁷Bi, ²⁰⁸Tl, ²¹²Pb, ²¹²Bi, ²⁴¹Am.     

Evaluation of interferences on measurements of 90Sr/90Y by TDCR Cherenkov counting technique

A study to evaluate conditions affecting the determination of ⁹⁰Sr/⁹⁰Y activities in liquid samples by the triple-to-double coincidence ratio (TDCR) Cherenkov counting technique was conducted. The Cherenkov radiation produced by the ⁹⁰Y beta decay was determined using a commercially available Hidex 300 SL liquid scintillation counter. The interferences of sample geometry, including sample counting vial type and volume composition, and sample colour on the TDCR were investigated. The effects of potentially interfering beta and mixed beta–gamma emitters on the TDCR Cherenkov counting of ⁹⁰Sr/⁹⁰Y activities were also examined. The TDCR values were used to quantify counting efficiencies of ⁹⁰Y under different experimental conditions. The results demonstrated that the Cherenkov counting efficiency of ⁹⁰Y is independent of sample volume and counting vial size. The effect of colour quenching was examined using yellow and brown food-grade dyes. The TDCR correction for colour quenching was found to be effective. An evaluation of counting efficiency of different beta-emitting radionuclides demonstrated that strong gamma emissions can contribute to the Cherenkov counting efficiency. Overall, measured radioactivity values deviated from reference values by ≤7.5 %, which is acceptable for screening applications in emergency situations.     

Multi-element characterization of high-purity titanium dioxide by neutron activation analysis

A radiochemical neutron activation analysis method for the determination of 34 elements in titanium dioxide has been developed. For the assay of indicator radionuclides with short and with long half-lives, the radiochemical separation was performed by anion exchange on a Dowex 1 × 8 column and by combination of cation and anion exchange on a Dowex 50W × 8 and a Dowex 1 × 8 column from HF- and HF/NH₄F-medium, respectively. With both separation modes, a selective removal of the matrix-produced radionuclides ⁴⁶Sc, ⁴⁷Sc and ⁴⁸Sc was achieved. A selective extraction of copper with dithizone from 15 mol/L HF enabled counting the intensive but unspecific 511-keV rays of ⁶⁴Cu for the determination of Cu. The limits of detection achieved were between 0.004 ng/g for Sm and 0.8 μg/g for Sn (via ¹²⁵Sb). The elements La, Mn and Th were determined by instrumental neutron activation analysis only. These techniques were applied to the analysis of two titanium dioxide samples of different purity grade. The results and limits of detection are compared with those of other methods.     

Direct estimation of 90Sr in water samples of spent fuel storage bay using partial counting rate technique

The direct estimation of ⁹⁰Sr by β counting from a mixture of other β and γ emitter is often difficult due to the efficiency variation among the β-emitters and the unknown nature of the sample. This paper deals with use of a combination of β and γ spectrometry measurements in estimating the activity of ⁹⁰Sr, pure β emitter from a mixture of other β–γ emitters in water samples. This procedure offers a simple, easy to use, rapid and a reliable method for ⁹⁰Sr estimation as an alternative to the tedious radiochemical separation procedure in this specific case.     

Application of <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript>-INAA for the determination of essential and toxic elements in medicinal plants from West Pokot County,Kenya

Rapid determination of gross alpha and beta emitters in urine by liquid scintillation counting is discussed. This method is based on direct addition of urine into scintillation cocktail. ²⁴¹Am, ²³⁹Pu and ⁹⁰Sr were selected as model radionuclides. The LSA Hidex 300 SL equipped with Triple-Double-Coincidence-Ratio technique was used for sample measurement. The work focused on optimizing the LSC cocktail to urine volume ratio with respect to the model radionuclides. The overall efficiencies for ²⁴¹Am, ²³⁹Pu and ⁹⁰Sr were greater than 92 %; therefore, this method would be suitable for rapid determination of gross alpha/beta activity.     

Copper‐64‐Alloyed Gold Nanoparticles for Cancer Imaging: Improved Radiolabel Stability and Diagnostic Accuracy

Gold nanoparticles, especially positron‐emitter‐ labeled gold nanostructures, have gained steadily increasing attention in biomedical applications. Of the radionuclides used for nanoparticle positron emission tomography imaging, radiometals such as ⁶⁴Cu have been widely employed. Currently, radiolabeling through macrocyclic chelators is the most commonly used strategy. However, the radiolabel stability may be a limiting factor for further translational research. We report the integration of ⁶⁴Cu into the structures of gold nanoparticles. With this approach, the specific radioactivity of the alloyed gold nanoparticles could be freely and precisely controlled by the addition of the precursor ⁶⁴CuCl₂ to afford sensitive detection. The direct incorporation of ⁶⁴Cu into the lattice of the gold nanoparticle structure ensured the radiolabel stability for accurate localization in vivo. The superior pharmacokinetic and positron emission tomography imaging capabilities demonstrate high passive tumor targeting and contrast ratios in a mouse breast cancer model, as well as the great potential of this unique alloyed nanostructure for preclinical and translational imaging.     

Determination of radionuclidic impurities in <Superscript>99m</Superscript>Tc eluate from <Superscript>99</Superscript>Mo/<Superscript>99m</Superscript>Tc generator for quality control

Technetium-99m is the principal radioisotope used in medical diagnostics; radionuclidic impurity is the major concern of its quality. This work presents a analytical method for sequential determination of all radionuclidic impurities listed in pharmacopoeia including gamma emitters, alpha emitters, ⁸⁹Sr and ⁹⁰Sr. Radioactive decay for removal of ^99mTc, ion exchange and extraction chromatography for removal of ⁹⁹Mo and ⁹⁹Tc are effective for separation of interferences. Gamma spectrometry, LSC with alpha/beta discrimination, and Cherenkov counting using LSC are sensitive methods for measurement of the impurity radionuclides. The detection limits of this method are well meet the requirement of the quality control according to the limitation of the pharmacopoeia.     

Specific energy distribution within cytoplasm and nucleoplasm of a typical mammalian cell due to various beta radionuclides

The use of beta radionuclides for treatment in radiotherapies leads for a need of better understanding of interactions and local energy depositions of beta particles within tissue and tissue equivalent media. The aim of this work is to determine microdosimetric quantities for various radionuclides. Specific energy, z, and its distribution, $ f(z) $ , mean specific energy, $ \bar{z} $ , and its standard deviations, $ \sigma \left( {\bar{z}_{f} } \right) $ , were evaluated for typical single cell where nucleus is the cellular region of interest. Three possible positions of radionuclides were taken into account—cellular membrane, cytoplasm and nucleoplasm. Taking these regions as the source of radiation, microdosimetric quantities were calculated for beta emitting radionuclides: ¹⁹¹Os, ¹⁹⁹Au, ¹⁷⁷Lu, ⁶⁷Cu, ⁷⁷As, ¹³¹I, ¹⁸⁶Re, ³²P, ¹⁸⁸Re and ⁹⁰Y. It was found that low range beta emitters have the largest efficiency and can deliver radiation doses up to 1 mGy per decay. Determination of the specific energy and its distribution for radionuclides is a useful start in order to determine beta emitters for a particular radionuclide therapy.     

Determination of trace elements in carbonates by instrumental neutron activation analysis

A systematic non-destructive determination of eighteen trace elements (F, Na, Cl, Sc, Mn, Zn, Br, Sr, I, Ba, La, Ce, Sm, Eu, Tb, Yb, Th and U) in carbonate samples by thermal neutron activation analysis was developed. Three 0.2–0.5g samples were irradiated for 15 sec (in the case of determination of F), for 3 min (in the case of Na, Cl, Mn, Sr and I) and for 60 hrs (in the case of Sc, Zn, Br, Ba, La, Ce, Sm, Eu, Tb, Yb, Th and U) in the TRIGA MARK II Reactor at a thermal neutron flux of 5·10¹¹ n·cm⁻²·sec⁻¹ (15 sec and 3 min irradiation) and 1.5·10¹²n·cm⁻²·sec⁻¹ (60 hrs irradiation), respectively. According to the half life of the nuclides formed, the activities were measured with a Ge(Li) spectrometer as follows,²⁰F∶15 sec counting after 20–25 sec cooling,²⁴Na,³⁸Cl,⁵⁶Mn,^87mSr and¹²⁸I∶600 sec couting after 30–120 min cooling,⁸²Br,¹⁴⁰La,¹⁵³Sm,¹⁷⁵Yb and²³⁹Np (daughter of²³⁹U)∶3000 sec counting after 1 week cooling,⁴⁶Sc,⁶⁵Zn,¹³¹Ba,¹⁴¹Ce,¹⁵²Eu,¹⁶⁰Tb and²³³Pa (daughter of²³³Th)∶5000 sec counting after 1 month cooling. The errors due to the fluctuation of the neutron flux and the counting geometry were minimized by the use of calcium determined previously with EDTA-titration as an internal standard. The interferences from²⁴Mg(n, p)²⁴Na and²³⁵U(n, fission) reactions were corrected by the activities produced by the reactions in unit weight of magnesium and uranium, and their concentrations in samples measured experimentally. The data of Na, Mn, Zn and Sr were compared with the results obtained by atomic absorption analysis.     

Evaluation of strontium isotope abundance ratios in combination with multi-elemental analysis as a possible tool to study the geographical origin of ciders

In order to evaluate alternative analytical methodologies to study the geographical origin of ciders, both multi-elemental analysis and Sr isotope abundance ratios in combination with multivariate statistical analysis were estimated in 67 samples from England, Switzerland, France and two Spanish regions (Asturias and the Basque Country). A methodology for the precise and accurate determination of the ⁸⁷Sr/⁸⁶Sr isotope abundance ratio in ciders by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) was developed. Major elements (Na, K, Ca and Mg) were measured by ICP-AES and minor and trace elements (Li, Be, B, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Cd, Sn, Sb, Cs, Ba, La, Ce, W, Tl, Pb, Bi, Th and U) were measured by ICP-MS using a collision cell instrument operated in multitune mode. An analysis of variance (ANOVA test) indicated that group means for B, Cr, Fe, Ni, Cu, Se, Cd, Cs, Ce, W, Pb, Bi and U did not show any significant differences at the 95% confidence level, so these elements were rejected for further statistical analysis. Another group of elements (Li, Be, Sc, Co, Ga, Y, Sn, Sb, La, Tl, Th) was removed from the data set because concentrations were close to the limits of detection for many samples. Therefore, the remaining elements (Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba) together with ⁸⁷Sr/⁸⁶Sr isotope abundance ratio were considered for principal component analysis (PCA) and linear discriminant analysis (LDA). Finally, LDA was able to classify correctly 100% of cider samples coming from different Spanish regions, France, England and Switzerland when considering Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba and ⁸⁷Sr/⁸⁶Sr isotope abundance ratio as original variables.     

Measuring alpha and beta activity of filter and swab samples with LSC

Analysis of alpha and beta emitters in aerosol filters and swabs of different materials by liquid scintillation counter is discussed. This method appears suitable for fast determination of activity of radionuclides due to direct alpha and beta separation, measurement in 4π geometry and without sample treatment. The selected group of radionuclides was chosen with respect to military significance, radiotoxicity, and possibility of potential misuse. ⁹⁰Sr and ²³⁹Pu were selected as model radionuclides. Three types of filters were examined, and the attention was also focused on optimizing the type and volume of LSC cocktail. The efficiencies for ²³⁹Pu and ⁹⁰Sr were 90% and 79%, respectively. This method was the most effective for the glass fiber filters measured with the MaxiLight cocktail.     

[161Tb]Tb-Thz-Phe-D-Trp-Lys-Thr-DOTA: A potential radiopharmaceutical for the treatment of neuroendocrine tumors

Thz-Phe-D-Trp-Lys-Thr-DOTA, a conjugate of the DOTA chelator and the Thz-Phe-D-Trp-Lys-Thr pentapeptide, was labeled with ¹⁵²Eu and ¹⁶¹Tb radionuclides, where ¹⁶¹Tb has decay characteristics suitable for its use in cancer therapy. For the [¹⁵²Eu]Eu-Thz-Phe-D-Trp-Lys-Thr-DOTA complex, the biodistribution in nude mice bearing IMR-32 tumors was evaluated for the first time. It was shown that the complexes of the conjugate demonstrate accumulation in the tumor at the level of DOTA-TATE, another peptide conjugate widely used in nuclear medicine for the diagnosis and therapy of neuroendocrine tumors, which allows Thz-Phe-D-Trp-Lys-Thr-DOTA to be considered as a potential biological vector for radiopharmaceuticals.     

The use of liquid scintillation spectrometry as a very sensitive radioanalytical tool for the determination of alpha,beta and monochromatic electron emitting impurities in radiopharmaceutical compounds

Summary Many labeled compounds are used as radiopharmaceuticals (RP), for emission imaging and metabolic radiotherapy and contain as labeling agents γ, β^-, β⁺, monochromatic e^- and α emitting radionuclides (RN). These labeled compounds very often contain unexpected radionuclidic impurities. Some long-lived isotopic and non-isotopic impurities lead to undesirable radiation doses to the patient and his relatives, as well as to medical/paramedical personnel, other than the general population, due to rad-waste of contaminated specimen and excretion of biological fluids. Use was made of liquid scintillation counting/spectrometry (LSCS) for the detection of tiny amounts of charged particle emitting impurities in RPs labeled with ⁶⁴Cu, ⁶⁷Ga, ⁹⁰Y, ⁹⁰Sr/⁹⁰Y, ¹²³I, ¹⁵³Sm, ¹⁷⁷Lu and ²⁰¹Tl.     

Stability of 47Sc-complexes with acyclic polyamino-polycarboxylate ligands

The aim of this study was to evaluate acyclic ligands which can be applied for labeling proteins such as monoclonal antibodies and their fragments with scandium radionuclides. Recently, scandium isotopes (⁴⁷Sc, ⁴⁴Sc) are more available and their properties are convenient for radiotherapy or PET imaging. They can be used together as “matched pair” in theranostic approach. Because proteins denaturize at temperature above 42 °C, ligands which efficiently form complexes at room temperature, are necessary for labelling such biomolecules. For complexation of scandium radionuclides open chain ligands DTPA, HBED, BAPTA, EGTA, TTHA and deferoxamine have been chosen. We found that the ligands studied (except HBED) form strong complexes within 10 min and that the radiolabelling yield varies between 96 and 99 %. The complexes were stable in isotonic NaCl, but stability of ⁴⁶Sc-TTHA, ⁴⁶Sc-BAPTA and ⁴⁶Sc-HBED in PBS buffer was low, due to formation by Sc³⁺stronger complexes with phosphates than with the studied ligands. From the radiolabelling studies with n.c.a. ⁴⁷Sc we can conclude that the most stable complexes are formed by the 8-dentate DTPA and EGTA ligands.     

Extraction-chromatographic system TBP-HBr in radiochemical neutron activation analysis of high-purity materials

The extraction and extraction-chromatographic behaviour of a variety of elements in the TBP-HBr system with concentrations from 0.1 to 7M HBr has been studied. The results allowed the development of simple procedures for radiochemical neutron activation determination of 22 impurity elements (Na, K, Sc, Cr, Mn, Fe, Co, Ni, Cu, Ga, As, Se, Rb, Sr, Zn, Mo, Ag, Sb, Te, Ba, La, Hf and W) in high-purity cadmium and indium samples with detection limits from 1 g g^–1 for Fe and Zr to 0.01 ng g^–1 for Na, Sc, Mn with relative standard deviations < 0.15. To increase the selectivity of the extraction-chromatographic separation, use was made of extraction suppression and co-extraction effects. The procedure for the extraction-chromatographic separation of scandium from a number of other elements is described as an example. The procedure can be used for simultaneous quantitative separation of impurity radionuclides from radiation produced long-life scandium radionuclides in the neutron activation analysis of titanium and vanadium.     

“Multitracer” a new tracer technique — Its principle,features, and application

We established Multitracer, a new versatile radiotracer technique, for simultaneous tracing of a number of elements in various chemical, environmental, and biological systems. Metal foil targets (typically Au, Ag, Ge, Cu and Fe) are irradiated with C, N, or O ions accelerated up to 135 MeV/nucleon by RIKEN Ring Cyclotron. Radiochemical procedures have been developed to remove the target material leaving the nuclides as Multitracer solutions containing various radionuclides of Be, Na, Mg, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Te, I, Ba, Ce, Pm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, W, Re, Os, Ir, Pt, and Hg. Multitracers enable efficient tracing of a number of elements, and comparison of their behavior under strictly identical experimental conditions. Such features will be demonstrated by means of an example of application to a model experiment for the study of removal mechanism of various elements from the ocean.     

Marine Exopolysaccharide Complexed With Scandium Aimed as Theranostic Agents

(1) Background: Exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties. They may represent a new class of ligands to be combined with theranostic radionuclides, such as ⁴⁷Sc/⁴⁴Sc. The goal of this work was to investigate the feasibility of such coupling. (2) Methods: EPSs, as well as heparin used as a drug reference, were characterized in terms of molar mass and dispersity using Asymmetrical Flow Field-Flow Fractionation coupled to Multi-Angle Light Scattering (AF4-MALS). The intrinsic viscosity of EPSs at different ionic strengths were measured in order to establish the conformation. To determine the stability constants of Sc with EPS and heparin, a Free-ion selective radiotracer extraction (FISRE) method has been used. (3) Results: AF4-MALS showed that radical depolymerization produces monodisperse EPSs, suitable for therapeutic use. EPS conformation exhibited a lower hydrodynamic volume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexation with metal for high concentration. The LogK of Sc-EPS complexes have been determined and showing that they are comparable to the Sc-Hep. (4) Conclusions: EPSs are very promising to be coupled with the theranostic pair of scandium for Nuclear Medicine.     

A rapid method for the determination of radionuclides in reactor coolant by ion exchange membranes

This paper deals with a rapid method to determine radionuclides in reactor coolant by anion, cation, and anion-cation exchange membranes. A high pressure filtration device was established to simulate the THOR cooling water sampling system by means of several membranes mentioned above. The experimental results indicate that the adsorption efficiency of each membrane for several radionuclides is /1/ >95% with cation exchange membrane for Zn, Co, Na, Mn, Cu, Cs, Ba, La, W etc., /2/ >98% with anion exchange membrane for I, and /3/ <98% with anion-cation exchange membranes for Fe and Cr. The results are obtained using cooling water of Tsing Hua Open-Pool Reactor and the following radionuclides were identified:^99mTc,¹⁴⁰Ba,¹⁴⁰La,⁵¹Cr,¹³¹I,⁵⁸Co,⁶⁰Co,⁵⁴Mn,⁴⁶Sc,⁵⁹Fe,²⁴Na, etc.