The study of conditions for the preparation and application of99Mo−99mTc generators starting from irradiated molybdenum metal

⁹⁹Mo−^99mTc generators were prepared starting from irradiated molybdenum metal instead of MoO₃ in order to use reactor irradiation space more economically. The adsorption of molybdenum as sodium molybdate on different kinds of alumina was investigated. The effect of the pH of the column and the aqueous phase concentration of molybdenum were studied and related to the elution yield of^99mTc. A study of the radiation damage effect indicated that generators having a high elution efficiency of 90% could be prepared in the 100–600 mCi range. The losses of⁹⁹Mo were minimized to 10⁻⁵-10⁻⁴% and those of alumina to 2–5 μg/ml eluate.     

Separation of iodine produced from fission with a porous metal silver column in99Mo production

In Argentina, at the Ezeiza Atomic Center,¹³¹I is produced by wet distillation of natural tellurium dioxide irradiated with thermal neutrons in a pool-type reactor. In order to recover the¹³¹I present in the production process of fission⁹⁹Mo obtained by irradiation of UAL_x/Al targets (with 90% enriched uranium) a separation method was developed. Iodine isotopes can be separated from a sodium hydroxide solution containing fission products using a column filled with alternate beds of glass microspheres and porous metal silver. Tests with tracers were performed in radiochemical laboratory. Following this results, a series of tests with higher activities (3 TBq of⁹⁹Mo and 0.7 TBq of¹³¹I) were carried out in hot cells. Molybdenum passes through the silver column, while¹³¹I retention was 92–97% in tracer test and 90% in optimised hot cell tests. This result depends on several facts that are discussed. An initial separation of iodine isotopes diminishes radiation damage on ion-exchange resin used in the subsequent molybdenum purification, improving its retention and elution yield.     

The determination of metals at ppb levels by thin-film x-ray fluorescence spectrometry after coprecipitation with a molybdenum carrier complex

A method is described for the determination of iron, cobalt, nickel, copper, zinc, cadmium and lead in water at μg 1^-1 levels, in which the metals are coprecipitated with a molybdenum—pyrrolidinedithiocarbamate carrier complex. The precipitate is collected as a thin film on a membrane filter (0.4-μm pore-size) and analysed directly by x-ray fluorescence spectrometry. Detection limits, for 100-ml water samples and counting times of 200 s per element, are 1 μg metal l^-1 or lower. Total dissolved metal concentrations are obtained without boiling or u.v. irradiation of the water sample. The method is applicable to river and estuarine waters and is not affected by dissolved organic matter.     

Determination of trace molybdenum in biological and water samples by graphite furnace atomic absorption spectrometry after separation and preconcentration on immobilized titanium dioxide nanoparticles

A new method has been developed for the determination of trace molybdenum based on separation and preconcentration with TiO₂ nanoparticles immobilized on silica gel (immobilized TiO₂ nanoparticles) prior to its determination by graphite furnace atomic absorption spectrometry (GFAAS). The optimum experimental parameters for preconcentration of molybdenum, such as pH of the sample, sample flow rate and volume, eluent and interfering ions, have been investigated. Molybdenum can be quantitatively retained by immobilized TiO₂ nanoparticles at pH 1.0 and separated from the metal cations in the solution, then eluted completely with 0.5 mol L^?1 NaOH. The detection limit of this method for Mo was 0.6 ng L^?1 with an enrichment factor of 100, and the relative standard deviation (RSD) was 3.4% at the 10 ng mL^?1 Mo level. The method has been applied to the determination of trace amounts of Mo in biological and water samples with satisfactory results.     

Chemical effects of (n, γ) nuclear reaction on (Mo6Cl8)Cl4

The chemical effects of⁹⁸Mo(n, )⁹⁹ Mo reaction on molybdenum(II) chloride [(Mo₆Cl₈)Cl₄] have been studied. Retention, thermal and radiolytical annealing were determined. It was found that this molybdenum compound has low retention, a negligible tendency to thermal annealing and a virtual insensitivity to hydrolysis. For practical application in the enrichment of⁹⁹Mo by the Shilard-Chalmers method, molybdenum(II) chloride [(Mo₆Cl₈)Cl₄] appears to offer good prospects.     

Chemical and radiochemical evaluation of the purity of99mTc extracted by MEK

Solvent extraction separation of^99mTc from⁹⁹Mo using methyl ethyl ketone(MEK) has been found to be an effective method of obtaining^99mTc of medicinal purity from low specific activity⁹⁹Mo. The authors have investigated the effect of alkali and molybdenum concentration on the extraction of⁹⁹Mo and^99mTc into methyl ethyl ketone. The possibility of methyl ethyl ketone forming enol and condensation products and its effect on the final extraction efficiency and purity of^99mTc has been studied. Sodium molybdate has been found to have a good salting out effect on^99mTc pertechnetate and hence^99mTc extraction can be better accomplished from low specific activity⁹⁹Mo solutions. The ketone seems to form traces of condensation products in the extraction procedure. These have been found to be coextracted with^99mTc into MEK but did not affect the extractability of^99mTc. It was observed that neutral alumina column removes these condensation products from MEK containing^99mTc. Alternately these could be filtered off by acidification of the final aqueous^99mTc solution. The studies indicate that under optimum experimental conditions methyl ethyl ketone separates^99mTc from⁹⁹Mo with high efficiency and yields^99mTc of high purity suitable for use in nuclear medicine in the form of various labelled compounds.     

A novel technique for the separation of99mTc from99Mo

A new technique for the separation of^99mTc from low specific activity⁹⁹Mo is reported. A separation based on the principle of precipitation of⁹⁹Mo as calcium molybdate has been investigated. On precipitating⁹⁹MoO ₄ ^2– from alkaline solution as calcium molybdate under controlled conditions, the^99mTcO ₄ ^– is found to remain quantitatively in the supernatant solution with little carry-over of⁹⁹Mo. This calcium molybdate (⁹⁹Mo) could be redissolved and reprecipitated at regular intervals, yielding^99mTc quantitatively in aqueous neutral solutions. Calcium molybdate precipitates containing up to 1.5 GBq of⁹⁹Mo and 130–180 mg of molybdenum were prepared and evaluated. The performance in terms of repeated^99mTc separation gave yields of 75–93% with acceptable readionuclidic and radiochemical purity.     

The isotopic composition and atomic weight of molybdenum

The isotopic composition of molybdenum in a shelf reagent standard (MoO₃, 99.99%), 13 molybdenites, and three iron meteorites has been determined with a thermal ionization mass spectrometer. No especially-evident variations of molybdenum isotopes among these samples have been found. The mass fractionation of molybdenum occurring in isotopes during the measurements is discussed and our preferred natural abundances of molybdenum isotopes are:⁹²Mo, 14.7287 ± 0.0010;⁹⁴Mo, 9.2118 ± 0.0006;⁹⁵Mo, 15.8935 ± 0.0011;⁹⁶Mo, 16.6731 ± 0.0011;⁹⁷Mo, 9.5692 ± 0.0007;⁹⁸Mo, 24.2289 ± 0.0017;¹⁰⁰Mo, 9.6950 ± 0.0007. Thus, the atomic weight of molybdenum is 95.9415 ± 0.0001 (the value currently accepted by IUPAC [IUPAC Inorganic Chemistry Division, Pure Appl. Chem., 63 (1991) 991] is 95.94 ± 0.01). The uncertainties correspond to the 95% confidence limit calculated from all the terrestrial and meteoritic samples.     

3-Hydroxy-2-(2-thienyl)-4H-chromen-4-one as a new reagent for the extraction and trace determination of molybdenum(VI)

A simple, sensitive and selective method for the extraction and trace determination of molybdenum(VI) has been developed; it is based on its reaction with 3-hydroxy-2-(2-thienyl)-4H-chromen-4-one (HTC) in sulphuric acid medium. The 1:2 Mo (VI)-HTC yellow complex is quantitatively extractable into chloroform (_max 420 nm) and is stable for more than 4 h. The procedure eliminates the interference of a large number of metal ions and complexing agents. Beer's law is obeyed in the range of 0–2.85 g Mo/mL with a molar absorptivity, Sandell's sensitivity and standard deviation of 5.28×10⁴ L mol^–1 cm^–1, 0.0018 g Mo/cm² and ±0.0054, respectively. The method has successfully been used for the spectrophotometric determination of molybdenum in steel samples.     

Determination of cadmium in grains by isotope dilution ICP–MS and coprecipitation using sample constituents as carrier precipitants

A coprecipitation method using sample constituents as carrier precipitants was developed that can remove molybdenum, which interferes with the determination of cadmium in grain samples via isotope dilution inductively coupled plasma mass spectrometry (ID-ICPMS). Samples were digested with HNO₃, HF, and HClO₄, and then purified 6 M sodium hydroxide solution was added to generate colloidal hydrolysis compounds, mainly magnesium hydroxide. Cadmium can be effectively separated from molybdenum because the cadmium forms hydroxides and adsorbs onto and/or is occluded in the colloid, while the molybdenum does not form hydroxides or adsorb onto the hydrolysis colloid. The colloid was separated by centrifugation and then dissolved with 0.2 M HNO₃ solution to recover the cadmium. The recovery of Cd achieved using the coprecipitation was >97%, and the removal efficiency of Mo was approximately 99.9%. An extremely low procedural blank (below the detection limit of ICPMS) was achieved by purifying the 6 M sodium hydroxide solution via Mg coprecipitation using Mg(NO₃)₂ solution. The proposed method was applied to two certified reference materials (NIST SRM 1567a wheat flour and SRM 1568a rice flour) and CCQM-P64 soybean powder. Good analytical results with small uncertainties were obtained for all samples. This method is simple and reliable for the determination of Cd in grain samples by ID-ICPMS. Figure Overview of a coprecipitation method using sample constituents     

On the separation of molybdenum and technetium crown ether as extraction agent

Separation of⁹⁹Mo and^99mTc can be performed with high selectivity using the crown ether 2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclooctadeca-2,11-diene /DB18C6/ diluted with nitrobenzene. The high efficiency is attributed to the rather low extractability of molybdenum as compared with that of technetium.     

A novel method of the separation/preconcentration and determination of trace molybdenum(VI) in water samples using microcrystalline triphenylmethane loaded with salicyl fluorone

It is the first time that triphenylmethane was used as an adsorbent to preconcentrate and separate trace amount of molybdenum in water samples. The effects of different parameters, such as acidity, stirring time and various metal ions, the amounts of triphenylmethane and salicyl fluorine, etc. on the enrichment yield of molybdenum have been studied to optimize the experimental conditions. Under the optimum conditions, molybdenum can be adsorbed on the surface of microcrystalline triphenylmethane loaded with salicyl fluorone by the intermolecular action strength. The possible reaction mechanism for the enrichment of molybdenum was discussed in detail in this paper. Mo(VI) can be completely separated from Pb(II), Co(II), Cu(II), Cr(III), Ni(II), Hg(II), Zn(II), Cd(II), Fe(III) and Al(III) in the solution. The proposed method was successfully applied to the determination of trace amount of molybdenum in various water samples by spectrophotometry after preconcentration using microcrystalline triphenylmethane. The preconcentration factor is from 83 (500 ml water sample was enriched to 6.0 ml) to 166 (1000 ml water sample was enriched to 6.0 ml). The detection limit is 1.3 × 10⁻⁵ mg l⁻¹ and the linearity is maintained in the concentration range 3.8 × 10⁻³ to 0.36 mg l⁻¹ with a correlation coefficient of 0.9998. The recoveries are in the range of 93.5-104%. The relative standard deviation is 1.8-2.9%. Analytical results obtained with this novel method are very satisfactory.     

Production of99Mo and its application in nuclear medicine

Molybdenum-99 is produced in large quantities as the parent radioisotopes of^99mTc, which has been used recently in nuclear medicine. The neutron capture reaction on molybdenum and the nuclear fission of uranium are used for the large scale production of⁹⁹Mo. The products by these methods are used properly according to the objects of diagnosis. In this paper, the production of⁹⁹Mo is reviewed and the development of the production in JAERI is outlined.     

A simple method for the activation analysis of mercury in fish by using iodinated resins

After irradiation and decay periods, samples are dissolved in 20 min in a sulfuric-nitric acid mixture containing a metavanadate salt. The aqueous phase is neutralized and passed through an iodinated resin which selectively isolates mercury from all other interfering radionuclides. The activity of¹⁹⁷Hg is determined by γ-spectrometry using a thin Na(Tl) detector. A sensitivity limit of 2.5 ppb^* is obtained and the relative standard deviation of the method is 6.7% at a level of 85 ppb.     

Determination of molybdenum in hair and wool by neutron activation analysis

Neutron activation analysis was applied to the determination of molybdenum in hair and wool. Ashed samples of hair and wool were irradiated for 15 min at a flux of 5·10¹³ n/cm²/sec to produce ¹⁰¹Mo. An acid solution of the ash was first boiled in the presence of sodium bromide and bromate to volatilize bromine (⁸⁰Br and ⁸²Br radioisotopes interfere) and then extracted with 0.1% α-benzoinoxime in chloroform to remove ¹⁰¹Mo from other interfering radionuclides. The ¹⁰¹Tc daughter from ¹⁰¹Mo was measured over the 0.31-MeV γ-ray photopeak after allowing the separated ¹⁰¹Mo to decay for 15 min. The molybdenum concentration in hair varied from 0.02 to 0.13μg/g while wool was found to contain 0.04–0.58 μg/g.     

Improved processes of molybdenum-99 production

Two improved processes of⁹⁹Mo production have been developed on laboratory scale. The first one allows to purify Mo of natural isotopic composition from tungsten impurities from 64 to <10 ppm by using preferential adsorption of tungsten on hydrated tin(IV) oxide (SnO₂ nH₂O) before irradiation in a nuclear reactor. The second process deals with the separation of pure fission product⁹⁹Mo from²³⁵U irradiated in a reactor. Two versions of separation process for production of fission⁹⁹Mo have been developed. Both versions start with the dissolution of²³⁵U oxide target in nitric acid and are based on sequential use of alumina and anion exchange resin AG® 1-X8 columns. The yield of⁹⁹Mo in both versions is 80–89%.     

Fission yields of molybdenum in the Oklo natural reactor

The isotopic compositions of molybdenum in six uranium-rich samples from the Oklo Zone 9 natural reactor were accurately measured by thermal ionization mass spectrometry. The samples were subjected to an ion exchange separation process that removed the isobaric elements zirconium and ruthenium, with high efficiency and a low blank. Molybdenum possesses seven isotopes of which ^92,94,96Mo are unaffected by the fission process, enabling the raw data to be corrected for isotope fractionation by normalising to ⁹²Mo/⁹⁶Mo, and to use ⁹⁴Mo to correct for the primordial component in each of the fission-produced isotopes. This enables the relative fission yields of Mo to be calculated from the isotopic composition measurements, to give cumulative fission yields of 1:0.941:0.936:1.025 for ^95,97,98,100Mo, respectively. These data demonstrate that the most important nuclear process involved in reactor Zone 9 was the thermal neutron fission of ²³⁵U. The consistency of the relative cumulative fission yields of all six samples from different locations in the reactor, implies that Mo is a mobile element in the uraninite comprising Zone 9, and that a significant fraction of molybdenum was mobilized within the reactor zone and probably escaped from Zone 9, a conclusion in agreement with earlier published work.     

Determination of molybdenum in biological materials by combined extraction of99Mo and99mTc

Combined extraction of⁹⁹Mo and its daughter-product^99mTc enables a rapid determination of molybdenum in biological samples by neutron activation analysis. A procedure and its application to standard kale powder and standard animal blood are reported.     

A99Mo-99mTc generator based on the use of zirconium molybdophosphate-99Mo gel

A modified⁹⁹Mo–^99mTc gel generator is described. The present generator uses an insoluble zirconium molybdophosphate (ZrMP) gel tagged with⁹⁹Mo. Molybdenum-99 is chemically combined in the gel structure and cannot be eluted from the matrix. The presence of phosphate increases the chemical stability of the gel and decreases the molybdenum breakthrough. The prepared gel is sufficiently porous to permit ready diffusion of^99mTcO ₄ ^– which can be cluted with saline in yields of up to 90%. The gel was found to contain 25.1% Mo, 21.9% Zr, and 0.7% P in a molar ratio of 1.09:1.0:0.09, respectively. The high molybdenum content of the gel allows the use of cheap, non-polluting (n, )⁹⁹Mo. The eluted^99mTc was of high purity and can be used for medical and pharmaceutical applications.     

A Sulfoxide Reduction Method Using Low Valent Molybdenum Acetates

It has been demonstrated that molybdenum(III) ion is effective for deoxygenation of sulfoxides.¹ However, since this reagent was generated by treatment of molybdenyl chloride with zinc dust, the role of some suspended metal in the sulfoxide reduction cannot be assessed. In order to conclusively establish the reducing capability of low-valent molybdenum ions for sulfoxides we have carried out experiments with Mo species obtained in a manner that the suspicion of active metal participation is exonerated.