Determination of low-level99Tc in environmental samples by high resolution ICP-MS

An analytical method has been developed for the determination of low-level⁹⁹Tc in environmental samples by High Resolution ICP-MS. The method consists of leaching of⁹⁹Tc by HNO₃ and separation by three different solvent extractions with 30% TOA-xylene, MEK, and cyclohexanone. Finally, purification of⁹⁹Tc was made by using an anion exchange resin column to reduce dissolved solids content. The final solution was adjusted to 1M HNO₃ for introducing into the HR-ICP-MS. The accuracy and precision of the method was confirmed to be satisfactory by applying this technique to the determination of⁹⁹Tc in IAEA marine algae sample (AG-B-1). Measurements of⁹⁹Tc using 0.5–2.5 g of sediment samples from the Irish Sea, UK, were successfully performed by the present method.     

Quantification of99Tc by liquid scintillation counting: An evaluation of chemical quenching by liquid chromatographic eluents

The feasibility of utilizing liquid scintillation counting as a detection method for the liquid chromatographic analysis of⁹⁹Tc is evaluated. The chemical quenching of constituents commonly found in liquid chromatographic mobile phases is investigated, and quench corrections are presented. Quantification of⁹⁹Tc is achieved over a concentration range of 10^–3 to 10^–8M on quiescent KTCO₄ solutions, with sample volumes of 0.3 ml, yielding a counting efficiency from 51 to 59% for a narrow 150 channel window. The potential for the double isotope labelling of technetium complexes and the implications of the liquid scintillation counting of⁹⁹Tc in flowing eluents are discussed.     

Preparation and characterization of an extraction chromatography column for technetium separation based on Aliquat-336 and silica gel support

An extraction chromatographic material based on Aliquat-336 anchored on hydrophobized silica gel support was prepared as an ion exchanger. The prepared material appeared to be suitable for the separation of ⁹⁹Tc from environmental matrices in column application. The properties of the material, sorption characteristic and distribution coefficient of ^99mTcO₄ ^-in various media were studied. The prepared sorbent was conditioned by washing with nitric acid. The solution containing ^99mTcO₄ ^- in 0.1M HNO₃ was passed through the column. Tc was eluted from the column by 8M HNO₃. The flow rate was 0.4 ml/min. The chemical yield of technetium during the separation process was determined using ^99mTc tracer and gamma measurement. The sorption recovery of Tc from the prepared sorbent with 0.1M HNO₃ solution was more than 98%, and the desorption recovery from the column using 8M HNO₃ varied between 92-96%. It was found that the prepared sorbent is suitable for the separation of technetium from environmental matrices and radioactive wastes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of99Tc in rain and dry fallout by ICP-MS

Due to the difficulty of⁹⁹Tc analysis, data are insufficient for discussing its behavior in the environment. In this study, we focused on the determination of⁹⁹Tc in rain and dry fallout samples. The samples were collected monthly at Nakaminato, Japan, from June 1993. They were concentrated by heating on a hot plate without any loss of Tc. The solution was filtrated and then a liquid-liquid extraction (LLX) with trioctylamine (TOA), which works as a liquid anion exchanger, was carried out. Technetium was extracted from 5% HNO₃ solution into the organic phase with a high extractability. After being back-extracted from TOA/xylene into 1M K₂CO₃, LLX with cyclohexanone was used to remove ruthenium, which has a stable isotope of mass 99. Technetium was back-extracted into deionized water, and the solution was measured by inductively coupled plasma mass spectrometry (ICP-MS). The average recovery under the experimental conditions was 67% and the instrumental detection limit was 0.04 ppt (0.03 mBq/mL).     

Comparison of the TEVA-Spec resin and liquid-liquid extraction methods for the separation of technetium in soil samples

When ICP-MS is used for⁹⁹Tc measurements, elements which interfere with⁹⁹Tc counting should be removed. In this study, a separation method using a novel chromatographic resin (TEVA·Spec^® resin) was compared with a liquid-liquid extraction (LLX) method for separation and concentration of⁹⁹Tc which was trapped in a solution after combustion of environmental soil samples. The results showed that Tc could be separated from Ru at high recoveries with both separation methods. Molybdenum, however, was not removed by LLX, while more than 99% of Mo in soil samples were removed by TEVA·Spec resin.     

Low-level measurements of actinides and long-lived radionuclides in biological and environmental samples

This paper describes a radiochemical method for the determination of⁹⁹Tc in large volumes of rain, river and seawater. The procedure is based on the reduction of technetium to the +4 oxidation state with potassium disulfite in a slightly acidic medium, followed by iron hydroxide precipitation. After oxidation to the +7 oxidation state, the technetium fraction is purified with iron hydroxide and calcium carbonate precipitations. Technetium (+7) is extracted with TBP (xylene) in 3M H₂SO₄, back extracted in 2M NaOH or ammonia, and the electrodeposition is made in 2M NaOH or H₂SO₄/NH₄OH medium at pH 5–6. The radiochemical yield is determined by gamma counting of the 140 keV gamma ray from⁹⁹Tc^m.⁹⁹Tc is counted on an anti-coincidence shielded GM-gas flow counter. The purity of the⁹⁹Tc plated samples is checked by alpha and beta spectrometry using surface barrier detectors and by gamma spectrometry on Ge(HP) detector. The radiochemical yield of 50–150 l water samples is around 20–60%.     

Separation and concentration of technetium using a Tc-selective extraction chromatographic resin

For⁹⁹Tc separation from environmental samples, liquid-liquid extraction, ion-exchange chromatography and coprecipitation, have been described. Although these methods are removing matrix elements, some combinations of them is necessary for purification and concentration of Tc. Besides, the procedures are time-consuming and generally a week or more is needed to purify Tc in the samples. In this study, a novel extraction chromatographic resin for the separation and preconcentration of Tc from several kinds of solutions is described. The material is shown to retain Tc efficiently and selectively from these solutions. Sorbed Tc is readily recovered using 5 ml of 12M HNO₃ and the recoveries with^95mTc are more than 97% for all sample solutions.     

Extraction of99Mo-molybdophosphate and99mTc-pertechnetate from various acid solutions by bis/2-ethylhexyl/ phosphoric acid

The extractability of⁹⁹Mo-molybdophosphoric acid H₃/PMo₁₂O₄₀/ and^99mTc-pertechnetic acid /PTcO₄/ in 20% (v/v) bis /2-ethylhexyl/ phosphoric acid /HDEHP/ in benzene has been investigated at different concentrations of HCl, HBr and HNO₃ acids. The effect of extractant concentration and diluent on the extractability of molybdophosphoric and pertechnetic acids with 20% (v/v) HDEHP in benzene from different concentrations of HCl acid has also been studied.⁹⁹Mo-molybdo-phosphoric acid was found to be selectively extracted and separated from^99mTc-pertechnetic acid with 20% HDEHP in benzene at an acidity of about 0.49M HCl, HBr and HNO₃. The extractability of H₃/PMo₁₂O₄₀/ from these acids generally follows the decreasing order HBr>HCl>HNO₃. The separation factors /K_d molybdophosphoric/K_d pertechnetic/ were found to be 12.9×10⁵ and 7.6×10⁵ for HBr and HCl, respectively. The extractability of pertechnetic acid follows the order HCl>HBrHNO₃. Benzene is the diluent due to its radiation stability. A new procedure for the separation of^99mTc from⁹⁹Mo was suggested.     

Determination of technetium-99 in soils and radioactive wastes using ICP-MS

Three methods have been used for the determination of ⁹⁹Tc in soils and solid radioactive wastes using ^99mTc as a yield monitor. In the method one and three the samples were leached in low concentrated nitric and sulphuric acid. Many contaminants were then co-precipitated with Fe(OH)₃ in alkali media and Tc in the supernatant was separated using anion-exchange extraction chromatography. There were made also some studies how to improve the chemical recovery of ^99mTc in the process of chromatography. In the method two the sample was ashed and then leached in 8 mol dm⁻³ HNO₃ and after iron precipitation, technetium was separated on chromatographic column. The chemical recovery of ^99mTc was optimized in the process of chromatography and leaching. Typical recoveries of technetium determined with ^99mTc tracer for all these methods were in the range 39 %–87 %. The ⁹⁹Tc activity was measured using proportional low-background beta detector after one week of staying to allow decay of ^99mTc activity. ⁹⁹Tc was also determined by the non-radiometric method using inductively coupled plasma mass spectrometer.     

Study the radiation effects on 4-vinylpyridine-based porous resins in 99Tc adsorption

The 4-vinylpyridine-based porous resins (4VP–DVB and 4VP–DVBQ) were synthesized to adsorb ⁹⁹Tc from radioactive waste. The radiation stability of the synthesized resins were investigated in air, water, HCl, and HNO₃ mediums. The radiolytic degradation of resins was evaluated by the total organic carbon analysis. The weakly basic resin (4VP–DVB) and strongly basic resin (4VP–DVBQ) showed a remarkable resistance to radiation in HCl and HNO₃ solutions respectively. Moreover, adsorption behavior of irradiated 4VP–DVB and 4VP–DVBQ resins toward ⁹⁹Tc was studied by the batch experimental method.

     

Rapid and sensitive determination of pertechnetate in99Mo/99mTc generator eluates by reversed-phase high-performance liquid chromatography

Reversed-phase high-performance liquid chromatography with u.v. detection was applied for rapid and sensitive determination of pertechnetate in⁹⁹Mo/^99mTc generator eluates, using a mixture solvent of acetonitrile and 0.04M aqueous acetate buffer (1/1) containing a few volume percentage of 0.5 M tetra-n-butylammonium hydroxide as the mobile phase. Employing a -bondapak C₁₃ column, the TcO ₄ ^– species was separated, monitored with absorbance at 254 nm, and observed at the retention time of 3.5 min. The detection limit was found to be 5.2·10^–10 g of Tc for each injection. Total Tc contents in the^99mTc eluates from clinically-used⁹⁹Mo/^99mTc generator were analyzed by this technique. The^99mTc (⁹⁹Tc) species was separated from the contaminant⁹⁹Mo. This method was found to be useful for the purification of^99mTc (⁹⁹Tc) as well as the determination of total Tc content.     

Activity standardization of <Superscript>99m</Superscript>Tc using liquid scintillation counting method

The Korea Research Institute of Standards and Science (KRISS) participated in the BIPM.RI(II)-K4.Tc-99 m comparison of activity measurements of ^99mTc. We develop the national primary standard for ^99mTc solution used during the comparison. We use two primary liquid scintillation counting techniques for the standardization: digital coincidence counting with the 4πβ(LS)-γ(NaI(T1))system and triple-to-double coincidence ratio counting. Both methods give consistent results for the specific activity of a ^99mTc solution. Adopting the result from the DCC method as the reference value of the ^99mTc measurement, we evaluate the standard uncertainty of 0.856% for the KRISS primary standard of the ^99mTc activity. The K4 comparison result shows that the newly-established KRISS primary standard lies within the standard uncertainty with the key comparison reference value defined from other ^99mTc measurements.     

Determination and lebels of99Tc in environmental and biological samples

In this paper, the physical and chemical methods used in our laboratory for the measurement of⁹⁹Tc in natural samples are reviewed. Levels of⁹⁹Tc in rainwater, algae, and freshwater samples are given. In addition, and estimation of the radiological impact of⁹⁹Tc to the population, derived from our earliear atmospheric⁹⁹Tc measurements, is presented. For rainwater, levels of¹³⁷Cs are also given for comparison.Work partially supported by the contract PB86-0207 of the Spanish CICYT.     

Exchange labeling of proteins:99mTc labeled transferrin

^99mTc-labeled transferrin was prepared by reduction of^99mTcO ₄ ⁻ ; with stannous DTPA or stannous citrate followed by equilibration of the technetium chelate with human transferrin. The rate of transfer of^99mTc to transferrin in the presence of 0.015M citrate buffer was dependent on pH in the order pH 2.1> pH 7.2> pH 4.1> pH 5.9. The incorporation rate was inversely proportional to the concentration of DTPA and citrate buffer. The replacement of citrate buffer by acetate buffer or oxalate buffer reduced drastically the formation of^99mTc-labeled transferrin at pH 4.1. The formation of^99mTc-labeled transferrin prepared from the reduction of^99mTcO ₄ ⁻ with stannous citrate was faster than that from the reduction with stannous DTPA in the presence of 0.015M citrate buffer and pH 2.5. Equilibration of transferrin with^99mTc-labeled pyrophosphate did not produce^99mTc-labeled transferrin at pH 4.5. The ligand exchange labeling of^99mTc to transferrin in 0.015M citrate did not cause appreciable denaturation of the protein at all pH values. This method also enabled labeling of the protein in a low concentration (2.6·10⁻⁴ M) via tin reduction. Sequential external imaging of the^99mTc-labeled transferrin in Sprague-Dawley rats bearing Walker-256 carcinosarcoma showed optimal tumor localization occurred at 3 hr after injection. In spite of this,^99mTc-labeled transferrin does not appear to be a suitable imaging agent because of the low tumor to blood ratio of^99mTc (0.50±0.17) at 3 hr post injection. This is similar to that of^{6 7}Ga-citrate (0.43±0.15%).     

Isotope exchange between 12-molybdocerate(IV) and sodium molybdate-99Mo in aqueous media

12-molybdocerate(IV) gel labelled with⁹⁹Mo has been prepared via isotope exchange between a column of inactive molybdate matrix and a mobile solution of⁹⁹-Mo-sodium molybdate(VI) in 0.1 mol·dm^–3 HNO₃. The composition and nature of the reaction mixture, concentration of Mo(VI) in the reactants, reaction temperature and/or drying temperature of the gel matrix on the exchange yeild of⁹⁹Mo and time of reaction are explored using the batch equilibration and/or the chromatographic column methods. The obtained material is evaluated for use in preparation of elution-type⁹⁹Mo-^99mTc generators.     

Preparation of99Mo,132Te isotopes and99mTc,132I generators

Adsorption and desorption of⁹⁵Zr−⁹⁵Nb,⁹⁹Mo,¹⁰³Ru,¹³²Te and²³⁹Np in a HCl-alumina system were studied in order to purify⁹⁹Mo and¹³²Te obtained by the cation-exchange separation of fission products and to prepare highly pure^99mTc and¹³²I generators.⁹⁹Mo and¹³²Te, of which radionuclidic purity was over 99.99% and 99.999%, respectively, could be obtained by passing the cation-exchange separated Mo and Te fractions through alumina columns, by washing with HCl and finally by eluting⁹⁹Mo with 1M NH₄OH and¹³²Te with 3M NaOH. In order to raise the recovery of⁹⁹Mo and¹³²Te from the alumina columns, they should be eluted as quickly as possible after the adsorption. The direct use of the alumina column containing⁹⁹Mo or¹³²Te as the generator allowed milking of^99mTc or¹³²I, of which radionuclidic purity was over 99.999%. Milking yields of^99mTc with 0.1M HCl and¹³²I with 0.01M NH₄OH were 77% and 90%, respectively. The latter value was much higher than that in usual performance of the generator.     

Determination of technetium-99 from the aspect of environmental radioactivity

A radioanalytical procedure has been developed for the determination of⁹⁹Tc in environmental samples. The procedure consists of precipitation, solvent extraction, ion exchange, electrodeposition and radiation measurement. Rhenium was used as a non-isotopic carrier of⁹⁹Tc. On the basis of 3σ counting error, the detection limits were 4.9·10^?5 Bq/l, 7.4·10^?3 Bq/kg wet and 7.4·10^?2 Bq/kg dry for water, biota and soil samples, respectively. Sea water, seaweeds (brown algae) and soils were collected to evaluate the present levels of⁹⁹Tc in Japan. The level of⁹⁹Tc in sea water was ca. 1·10^?4 Bq/l around Japan. Among the seaweeds (brown algae), Ishige okamurai showed the highest concentration of 5.8·10^?2 Bq/kg wet tissue and the highest concentration factor of 583. The level of⁹⁹Tc in the organic rich surface soil was ca. 1 Bq/kg dry soil in Fukuoka.     

Sample treatment techniques for the determination of environmental radiocarbon in a nuclear power station area

This report describes the environmental sample treatment techniques for¹⁴C measurement with liquid scintillation counter. The groundwater sample of about 80 liters was collected from well and inorganic carbon was removed by acidification and recirculated gas stripping with the extraction efficiency of more than 98%. The biological samples were freeze-dried and combusted to carbon dioxide in high pressure combustion unit with a combustion efficiency of nearly 99%. The¹⁴CO₂ in the stack effluents was collected by an air bubbler with a collection efficiency of more than 99% for a sampling time of two weeks. Sampling of¹⁴C in reduced form also has been done by passing the gases through a tube furnace with Pt/Al and Pd/Al catalyst. Active and passive sampling methods for atmospheric¹⁴C measurements were compared in detail, and it could be concluded that the uncertainty associated with passive sampling method was quite acceptable for environmental monitoring. The CO₂ trapped in NaOH was precipitated as BaCO₃, and subsequently reconverted to CO₂ for environmental samples and transferred to Carbo-Sorb E^TM for liquid scintillation counting. In case higher precision is the deciding factor, benzene synthesis would be employed with home-made benzene synthesizer.     

Determination of99Tc in fuel leachates using extraction chromatography

A simple technique using a combination of cation exchange and solid phase extraction chromatographic resins has been developed for the separation of⁹⁹Tc from other radionuclides present in nuclear fuel leachates. Quantification of the isolated⁹⁹Tc is accomplished using liquid scintillation counting. The method provides consistently high recoveries (>96%), generates small amounts of waste compared to classical methods, and requires less analysis time.     

Radiochemical separation of99Mo from natural uranium irradiated with thermal neutrons

⁹⁹Mo was separated from uranium and insoluble fission product hydroxides. More than 98% of⁹⁹Mo radioactivity was extracted with bis (2-ethylhexyl)phosphoric acid. The organic phase was washed and⁹⁹Mo was back-extracted from the organic phase with NH₄OH solution. The percent recovery from the organic phase was 91% and the purity of⁹⁹Mo was more than 99%. Pure^99mTc was also extracted from the organic phase with a saline solution. Reversed-phase partition chromatography was used for the purification of⁹⁹Mo from¹³¹I and other fission products (10% HDEHP on kieselguhr bed).¹³¹I and other isotopes were quantitatively eluted with 0.1M H₂SO₄,⁹⁹Mo was eluted using a mixture of 0.5 M HCl and 30% H₂O₂.