Alternative chromatographic processes for no-carrier added 177Lu radioisotope separation

HPLC technique combined with the simple conventional column solid phase extraction (SPE) chromatography using di-(2-ethylhexyl)orthophosphoric acid (HDEHP) impregnated OASIS-HLB sorbent based SPE resins (OASIS-HDEHP) was developed for the separation of no-carrier added (n.c.a) ¹⁷⁷Lu from the bulk quantity of ytterbium target. This combination strategy was based on combining the advantages of the better resolution of HPLC separation of n.c.a ¹⁷⁷Lu from the few milligram level Yb target with the high capacity of the OASISHDEHP column for the separation of ¹⁷⁷Lu from the bulk Yb target. The production batches of several hundred mCi activity of n.c.a ¹⁷⁷Lu radioisotope separated from 50 mg Yb target activated in a nuclear reactor of medium neutron flux (Φ=5·10¹³ n·cm^?2·s^?1) were successfully performed using this combined separation technique. With the target irradiation in a reactor of higher thermal neutron flux or with the parallel run of several separation units, several Ci-s of n.c.a ¹⁷⁷Lu can be profitably produced on a commercial production basis.     

Alternative chromatographic processes for no-carrier added 177Lu radioisotope separation Part I. Multi-column chromatographic process for clinically applicable

The conventional multi-column solid phase extraction (SPE) chromatography technique using di-(2-ethylhexyl)orthophosphoric acid (HDEHP) impregnated OASIS-HLB sorbent based SPE resins (OASIS-HDEHP) was developed for the separation of no-carrier added (n.c.a) ¹⁷⁷Lu from the bulk quantity of ytterbium target. This technique exploited the large variation of lutetium metal ion distribution coefficients in the varying acidity of the HCl solution-OASIS-HDEHP resin systems for the consecutive loading-eluting cycles performed on different columns. The production batches of several hundred mCi n.c.a ¹⁷⁷Lu radioisotope separated from 50 mg Yb target activated in a nuclear reactor of medium neutron flux (Φ = 5·10¹³ n·cm⁻²·s⁻¹) were successfully performed using the above mentioned separation technique. With the target irradiation in a reactor of thermal neutron flux Φ = 2·10¹⁴ n·cm⁻²·s⁻¹ or the parallel run of several separation units, many Ci-s of n.c.a ¹⁷⁷Lu can be profitably produced. The OASIS-HDEHP resin based multi-column SPE chromatography technique makes the separation process simple and economic and offers an automation capability for operation in highly radioactive hazardous environments.     

Separation of Yb as YbSO4 from the 176Yb target for production of 177Lu via the 176Yb(n, γ)177Yb→177Lu process

An effective and simple process for the separation of ¹⁷⁷Lu from neutron-irradiated Yb targets was developed. Irradiated Yb target was dissolved in H₂SO₄ solution and after reduction with sodium amalgam Yb was precipitated in the form of YbSO₄. From 50 mg of Yb irradiated target only 1 mg Yb remains in solution after precipitation and separation of YbSO₄. The overall recovery of ¹⁷⁷Lu is estimated at 73%. Further efficient chromatographic separation of carrier-free ¹⁷⁷Lu from 1 mg of Yb is relatively easy and is described in several papers.     

Rapid isolation of plutonium in environmental solid samples using sequential injection anion exchange chromatography followed by detection with inductively coupled plasma mass spectrometry

This paper reports an automated analytical method for rapid determination of plutonium isotopes (²³⁹Pu and ²⁴⁰Pu) in environmental solid extracts. Anion exchange chromatographic columns were incorporated in a sequential injection (SI) system to undertake the automated separation of plutonium from matrix and interfering elements. The analytical results most distinctly demonstrated that the crosslinkage of the anion exchanger is a key parameter controlling the separation efficiency. AG 1-×4 type resin was selected as the most suitable sorbent material for analyte separation. Investigation of column size effect upon the separation efficiency revealed that small-sized (2 mL) columns sufficed to handle up to 50 g of environmental soil samples. Under the optimum conditions, chemical yields of plutonium exceeded 90% and the decontamination factors for uranium, thorium and lead ranged from 10³ to 10⁴. The determination of plutonium isotopes in three standard/certified reference materials (IAEA-375 soil, IAEA-135 sediment and NIST-4359 seaweed) and two reference samples (Irish Sea sediment and Danish soil) revealed a good agreement with reference/certified values. The SI column-separation method is straightforward and less labor intensive as compared with batch-wise anion exchange chromatographic procedures. Besides, the automated method features low consumption of ion-exchanger and reagents for column washing and elution, with the consequent decrease in the generation of acidic waste, thus bearing green chemical credentials.     

Production of no-carrier-added 177Lu via the 176Yb(n, &;#947;)177Yb &;#8594; 177Lu process

No-carrier-added ¹⁷⁷Lu was produced by the ¹⁷⁶Yb(n,)¹⁷⁷Yb¹⁷⁷Lu process using enriched ¹⁷⁶Yb₂O₃. The radiochemical separation of the nca ¹⁷⁷Lu from the macroscopic ytterbium target was investigated by reversed-phase ion-pair HPLC. Effects of the concentrations of 2-hydroxyisobutyric acid and 1-octanesulfonate in the eluent, the amount of Yb₂O₃, the type and length of the C₁₈ column on the separation efficiency were examined. Under optimum conditions, the nca ¹⁷⁷Lu was obtained in radiochemically pure form from 5 mg of Yb₂O₃ with a separation yield of 84%.     

Accurate determination of half-life and radionuclidic purity of reactor produced <Superscript>177g</Superscript>Lu (<Superscript>177m</Superscript>Lu) for metabolic radiotherapy

Thanks to its favorable decay characteristics, ^177gLu is finding several applications in nuclear medicine, especially for palliative metabolic radiotherapy of cancer and radioimunotherapy. ^177gLu is produced in thermal nuclear reactor either by direct neutron capture ¹⁷⁶Lu(n,γ)^177(m+g)Lu on either natural or enriched ¹⁷⁶Lu target, or by reaction on enriched ¹⁷⁶Yb target followed by negatron decay. The latter method does produce a high radionuclidic purity and high specific activity radionuclide in no-carrier-added form, since ¹⁷⁷Yb decays solely to the ground state ^177gLu. Conversely, the first method does produce a low specific activity ^177gLu in carrier-added form,¹ contaminated by the long-lived radioisotopic impurity ^177mLu. The accurate determination of radionuclidic purity and half-life of ^177gLu carried out by HPGe and LSCS is presented in some details.     

On-line renewable solid-phase extraction hyphenated to liquid chromatography for the determination of UV filters using bead injection and multisyringe-lab-on-valve approach

For the first time, an automatic sample pre-treatment/detection method is proposed for the multiclass determination of UV filters (namely, benzophenone-3, ethylhexylmetoxycinnamate, butylmethoxydibenzoylmethane and homosalate) in environmental samples. The new methodology comprises in-line solid-phase extraction (SPE) of the target analytes by exploiting the bead injection (BI) concept in a mesofluidic lab-on-valve (LOV) format, with subsequent determination by liquid chromatography (LC). The proposed microanalytical system, using a multisyringe burette as propulsion unit, automatically performed the overall SPE steps, including the renewal of the sorbent in each analytical cycle to prevent sample cross-contamination and the post-extraction adjustment of the eluate composition to prevent chromatographic band broadening effects. In order to expedite the LC separation, a C₁₈ monolithic column was applied and an accelerated isocratic elution was carried out by using a cationic surfactant as mobile phase additive. The LOV-BI-LC method was proven reliable for handling and analysis of complex matrices, e.g., spiked swimming pool water and seawater, with limits of detection ranging between 0.45 and 3.2 μg L⁻¹ for 9 mL sample volume. Linear calibration was attained up to 160 μg L⁻¹ for homosalate and up to 35 μg L⁻¹ for the other target analytes, with good reproducibility (RSD < 13%, for 5 different SPE columns). The hyphenated scheme is able to process a given sample simultaneously and within the same time frame than the chromatographic separation/determination of the formerly pre-treated sample, providing concentration values every 9 min. Hence, the sample throughput was enhanced up to 33 times when compared with previously reported off-line SPE methods. A drastic reduction in reagent consumption and effluent production was also attained, contributing to the development of an environment-friendly analyzer.     

Extraction chromatography of thorium ion by solid phase impregnated resins containing bi-functional organic extractants</p> </p>

Summary Macroporous methyl methacrylate polymeric resin (XAD-7) was investigated incorporating both acidic organophosphorous extractant (cyanex-301) and one neutral extractant from the followings: dibenzo 18 crown 6 (DB18C6), 18 crown 6 (18C6) and 15 crown 5 (15C5). The sorption behavior of the solvent impregnated resin (SIR) towards thorium ion, including batch equilibrium, and kinetic operation are described. Different factors affecting the uptake of metal ions and hence, the separation efficiency of the impregnated resins were investigated. The maximum uptakes of Th⁴⁺ were found to be 62.9, 66.7 and 92.6% for DB18C6, 18C6 and 15C5, respectively. Synergistic extraction of various CE towards thorium ion was tested with cyanex-301 to enhance the sorption capacity as well as the selective separation efficiency. A relatively high capacity of the chelating resin towards tetravalent thorium was found. The capacities of the co-impregnated resins were found to be 2.11, 2.42 and 3.85 mmol/g for DB18C6, 18C6 and 15C5, respectively. The impregnated resin containing cyanex-301 and 15C5 can be utilized for selective separation and pre-concentration of thorium ion from nitrate medium in the presence of several interfering metal ions.</p> </p>     

Separation of curium from americium using composite sorbents and complexing agent solutions: part 2

TODGA–PAN composite sorbent and (PhSO₃H)₂–BTPhen in nitric acid solution were employed as a system for separation of curium from americium. The influence of aqueous phase composition (complexing agent and nitric acid concentrations) on weight distribution coefficients and Cm/Am separation factor was studied in batch experiments with trace amounts of ²⁴¹Am and ²⁴⁴Cm. Based on the results obtained, column experiment was designed and conducted. The Cm/Am separation factor of 3.8 ± 0.1 found in batch experiments with TODGA–PAN could be reproduced also in column experiment resulting in good separation of Cm from Am. The efficiency of Cm separation from Am in the TODGA–PAN system was compared with the analogous system with DGA resin (Triskem International). After separation on a 0.5 mL column (φ4.7 × 29 mm) the Cm fraction containing 93% of Cm(III) contained only 3% of Am(III) in optimum conditions.

     

Separation of carrier-free lutetium-177 from neutron irradiated natural ytterbium target

Neutron irradiation of naturally occurring Yb produces small amounts of carrier-free¹⁷⁷Lu activity. Cation exchange chromatography in the displacement development mode using Dowex-50X8, 200–400 mesh resin, and Zn²⁺ as the separating ion was used to separate¹⁷⁷Lu produced in a neutron irradiated Yb target. 0.04M -hydroxyisobutyric acid at pH 4.6±2 and temperature 26±1°C was used to elute carrier-free¹⁷⁷Lu in 70% yield and at a radionuclidic purity greater than 99%.     

Application of different types of resins in the radiometric determination of uranium in waters

The aim of this study is to compare different resins regarding their separation and pre-concentration efficiency for uranium from aqueous solutions and its subsequent radiometric determination by liquid scintillation counting (LSC). The different types of the investigated resins include: (a) a pure cation-exchange resin (Dowex Marathon C), (b) a complex forming resin (Chelex 100) and (c) an impregnated resin (5% diethylene glycol succinate on Chromosorb W-H). The radiometric measurements were performed after mixing of the pre-concentrated aqueous phase with the liquid scintillation cocktail. The effect of experimental conditions such as pH, salinity (e.g. [NaCl]) and the presence of other chemical species (e.g. Ca²⁺ and Fe³⁺ ions or humic acid and silica colloids) on the separation recovery have been investigated at constant uranium/radioactivity concentration. According to the experimental results the maximum chemical recovery differs significantly from one resin to another as a function of either, pH or the other chemical parameters. The optimum pH is found to be 8, 4 and 8 for Marathon C, Chelex-100 and diethylene glycol succinate, respectively. On the other hand, generally Ca²⁺ and Fe³⁺ ions as well as the presence of colloidal species in solution (even at low concentrations) result in a significant decrease of the chemical recovery of uranium, particularly for Marathon C and the diethylene glycol succinate impregnated resins. Generally, among the studied resins Chelex 100 was superior regarding chemical recovery, selectivity, regeneration and reuse.     

Ni(II) ion-imprinted solid-phase extraction and preconcentration in aqueous solutions by packed-bed columns

Solid-phase extraction (SPE) columns packed with materials based on molecularly imprinted polymers (MIPs) were used to develop selective separation and preconcentration for Ni(II) ion from aqueous solutions. SPE is more rapid, simple and economical method than the traditional liquid-liquid extraction. MIPs were used as column sorbent to increase the grade of selectivity in SPE columns. In this study, we have developed a polymer obtained by imprinting with Ni(II) ion as a ion-imprinted SPE sorbent. For this purpose, NI(II)-methacryloylhistidinedihydrate (MAH/Ni(II)) complex monomer was synthesized and polymerized with cross-linking ethyleneglycoldimethacrylate to obtain [poly(EGDMA-MAH/Ni(II))]. Then, Ni(II) ions were removed from the polymer getting Ni(II) ion-imprinted sorbent. The MIP-SPE preconcentration procedure showed a linear calibration curve within concentration range from 0.3 to 25 ng/ml and the detection limit was 0.3 ng/ml (3 s) for flame atomic absorption spectrometry (FAAS). Ni(II) ion-imprinted microbeads can be used several times without considerable loss of adsorption capacity. When the adsorption capacity of nickel imprinted microbeads were compared with non-imprinted microbeads, nickel imprinted microbeads have higher adsorption capacity. The K_d (distribution coefficient) values for the Ni(II)-imprinted microbeads show increase in K_d for Ni(II) with respect to both K_d values of Zn(II), Cu(II) and Co(II) ions and non-imprinted polymer. During that time K_d decreases for Zn(II), Cu(II) and Co(II) ions and the k′ (relative selectivity coefficient) values which are greater than 1 for imprinted microbeads of Ni(II)/Cu(II), Ni(II)/Zn(II) and Ni(II)/Co(II) are 57.3, 53.9, and 17.3, respectively. Determination of Ni(II) ion in sea water showed that the interfering matrix had been almost removed during preconcentration. The column was good enough for Ni determination in matrixes containing similar ionic radii ions such as Cu(II), Zn(II) and Co(II).     

Carrier-free separation of167Tm from Yb,Er and Ho targets by reversed-phase extraction chromatography and preparation for its medical use

Reversed-phase extraction chromatography employing a Daiflon-supported HDEHP column and HCl as eluent was examined for carrier-free separation of¹⁶⁷Tm from a photo-irradiated Yb target and also from particle-bombarded Er and Ho targets. The examination was performed with radioassays of radioactive Tm and Yb tracers and⁵⁷Co--induced X-ray analysis of Er and Ho. An example of the separation of about 1 mCi of¹⁶⁷Tm from a 100 mg irradiated Yb target enriched in¹⁶⁸Yb and a procedure for the final preparation for medical use are described. The YbSO₄ precipitation could be combined with this chromatographic separation of¹⁶⁷Tm from a more massive Yb target of natural abundance, weighing several tens of grams. A procedure for YbSO₄ precipitation is also presented in the Appendix.     

Atmospheric depositional fluxes of cosmogenic <Superscript>32</Superscript>P, <Superscript>33</Superscript>P and <Superscript>7</Superscript>Be in the Sevastopol region

⁹⁰Y was separated from ⁹⁰Sr using an extraction chromatographic resin consisting of 4, 4′(5′)-bis-t-butylcyclohexano-18-crown-6 (DtBuCH₁₈C₆), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide (C₂mimNTf₂), and a polymer (Amberlite XAD-7). Ionic liquid was introduced into the column to improve the separation efficiency. The column showed an excellent performance for the separation of Y from Sr. After the separation, the ratio of ⁹⁰Sr/⁹⁰Y was <2.0 × 10^?5; the column was recycled for >18 times. This study provides preliminary results on columns to produce ⁹⁰Y with a high purity in radiopharmaceuticals.     

Extractive scintillating resin for 99Tc quantification in aqueous solutions

A method utilizing extractive scintillating resin for ⁹⁹Tcmonitoring in aqueous solutions is presented. These extractive scintillatorscombine analyte selective uptake and scintillating properties to produce dualfunctionality analytical resins. These resins were produced by (1) co-locatedextraction chromatographic resin and plastic scintillating beads, (2) immobilizingfluors in macroporous polystyrene supports to which chains of monomethylatedpolyethylene glycol have been grafted and (3) co-immobilizing organic scintillatingfluors and a quaternary ammonium extractant (Aliquat-336) within macroporousacrylic and polystyrene supports. The first and third resins selectively extractpertechnetate ions from dilute acid whereas the second resin selectively extractspertechnetate ions from high ionic strength solutions. These resins were utilizedin ~0.20 ml pore volume columns while ⁹⁹Tc was continually monitoredwith commercially available scintillation detection systems. Manual and automatedmicrofluidics were used to deliver sample and reagent solution for loadingand elution of the ⁹⁹Tc. The detection efficiencies were determinedto be 45 and 70% for acrylic and polystyrene based resins, respectively, andindependent of extractant. Minimum detectable ⁹⁹Tc concentrationusing the Aliquat-336/acrylic-based resin was 6.2 Bq . l –1 for a 50-mlsample and 30-minute count time. The new methodology was applied towards analysisof contaminated groundwater samples and nuclear waste simulants.     

Mercury determination and speciation analysis in surface waters

A sorbent L-cysteine grafted silica gel has been evaluated for separation and enrichment of dissolved inorganic i-Hg(II) and methylmercury CH₃Hg(I) from surface waters at sub-μg L⁻¹ concentrations. Chemical parameters for mercury species enrichment and separation have been optimized. Analytical schemes for the determination of Hg species, using selective column solid phase extraction (SPE) with continuous flow chemical vapor generation atomic absorption spectrometry (CF-CVG-AAS) or inductively coupled plasma-mass spectrometry (ICP-MS) were developed. Possibilities for on-site SPE enrichment were demonstrated as well. The limits of quantification were 1.5 and 5 ng L⁻¹ for dissolved i-Hg(II) and CH₃Hg(I) by CF-CVG-AAS and 1 and 2.5 ng L⁻¹ by ICP-MS with relative standard deviations between 7–12% and 7–14%, respectively. The chemically modified SPE sorbent has demonstrated high regeneration ability, chemical and mechanical stability, acceptable capacity and good enrichment factors. Results for total dissolved mercury were in reasonable agreement with those from independent analyses by direct ICP-MS determinations for river waters and for estuarine water certified reference material.      

Chelating Resins in Analytical Chemistry

Chelating resins, the polymeric complexing compounds, are specific and selective ion exchange resins. A chelating ion exchange resin consists essentially of two components, i.e. a chelating group and a polymeric matrix. The properties of both components affect the selectivity of the synthesized resin. Methods used to synthesize chelating resins are reviewed. The analytical and physical techniques used to characterize the dissociation constant, metal capacity and distribution coefficient of the newly synthesized resin as well as the coordination site, the composition and the formation constant of the metal-resin complexes are discussed. Chelating resins could be used in various forms. Some important features of the analytical application of chelating resins, including selective concentration and separation both in inorganic analysis and organic analysis are also discussed. The techniques by which sorption or separation with the help of chelating resins achieved can be static, dynamic, or chromatographic. After sorptive concentration or separation, the elements can be determined either directly in the sorbent phase, its decomposition residue, the eluent solution after desorption, or the effluent after the solution has been passed through the sorbent. Various objects such as natural waters, geological objects, industrial materials, foodstuffs, coal, fuel oil. shale oil, transuranium elements and biological materials could be analyzed with the help of chelating resins.     

Solid-Phase Extraction of Caffeine and Theophylline from Green Tea by a New Ionic Liquid-Modified Functional Polymer Sorbent

The new ionic liquid-modified polymer sorbent was developed by surface chemical modification of the synthesized polymer particles using ionic liquids. The obtained ionic liquid-modified polymer was successfully used as a special sorbent in a solid-phase extraction (SPE) process to isolate caffeine and theophylline from green tea. A comparison of different SPE cartridges using the blank polymer, C₁₈, and ionic liquid-modified polymer revealed that the highest recovery was obtained using ionic liquid-modified polymer sorbent. Quantitative analysis was carried out by using a C₁₈ column (5 µm, 150 × 4.6 mm) as an analytical column. Good linearity was obtained from 5 × 10^?4 to 0.5 mg/mL (r²>0.999) for the two analytes with relative standard deviations <4.5%.     

Purification and separation of <Superscript>239+240</Superscript>Pu and <Superscript>241</Superscript>Am in biological samples by anion-exchange and extraction chromatography for high resolution alpha-spectrometry analyses

Many biological samples (urines and faeces) have been analyzed by means of chromatographic extraction columns, utilizing two different resins (AG 1-X2 resin chloride and TRU), in order to detect the possible internal contamination of ^239+240Pu and ²⁴¹Am for some workers of a reprocessing nuclear plant in the decommissioning phase. The results obtained show on one hand the great suitability of the first resin for the determination of plutonium, and on the other, the great selectivity of the second one for the determination of americium.     

Recovery of 177Lu from Irradiated HfO2 Targets for Nuclear Medicine Purposes

A new method of production of one of the most widely used isotopes in nuclear medicine, ¹⁷⁷Lu, with high chemical purity was developed; this method includes irradiation of the HfO₂ target with bremsstrahlung photons. The irradiated target was dissolved in HF and then diluted and placed onto a column filled with LN resin. Quantitative sorption of ¹⁷⁷Lu could be observed during this process. The column later was rinsed with the mixture of 0.1 M HF and 1 M HNO₃ and then 2 M HNO₃ to remove impurities. Quantitative desorption of ¹⁷⁷Lu was achieved by using 6 M HNO₃. The developed method of ¹⁷⁷Lu production ensures high purification of this isotope from macroquantities of hafnium and zirconium and radioactive impurities of carrier-free yttrium. The content of ^177mLu in ¹⁷⁷Lu in photonuclear production was determined. Due to high chemical and radionuclide purity, ¹⁷⁷Lu obtained by the developed method can be used in nuclear medicine.