Comparison of a radiation counting method and ICP-MS for the determination of99Tc in environmental samples

Results of⁹⁹Tc measurements between radiation and non-radiation counting methods were compared using four radiation sources for which⁹⁹Tc has been previously determined with a gas-flow proportional counter or a GM counter. Each⁹⁹Tc source consisted of a stainless steel planchet bound by mylar films. Seaweeds collected from the Irish Sea were analyzed and⁹⁹Tc was electroplated on the planchet. The⁹⁹Tc in each sample was separated and measured again by inductively coupled plasma mass spectrometry (ICP-MS). Tc was continuously removed from each sample with 2M HNO₃ and 2M NaOH. After the solution containing Tc was adjusted to 0.1M HNO₃, Tc was extracted on a novel extraction chromatographic resin to separate it from Ru. The total recoveries for Tc on the planchet samples were almost the same with an average of 91%. The results of⁹⁹Tc measurements by both radiation and non-radiation counting methods agreed well with each other.     

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).     

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.     

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.     

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.     

Radiochenical determination of technetium-99 in LLW by chelation with sodium diethyl dithiocarbamate (NaDDC) and extraction with chloroform

A radiochemical method has been developed for the determination of⁹⁹Tc in low-level radioactive, waste from nuclear facilities, using^99mTc as an internal tracer. Radioactive contaminants were removed by carrier hydroxide precipitation and chelating extraction with NaDDC/CHCl₃ system at pH 4. The final technetium was chelated with NaDDC in 3N HCl solution and extracted selectively into chloroform. The average of radiochemical recovery for various types of LLW sample is about 90%. The decontamination factors for most radioactive nuclides are higher than 10⁵. The detection limit for⁹⁹Tc in a sample of about 10 g is 0.17 pCi/g (6.5 Bq·kg^–1) for a 100-minute count.     

Separation of radioactive strontium from natural samples by means of mixed-solvent anion exchange

A new procedure for isolation and determination of⁹⁰Sr in real natural samples is presented. It consists of bringing natural samples in a soluble form suitable for separation on an ion-exchange column, separation of calcium from strontium by means of the anion exchanger Amberlite CG-400 and 0.25M HNO₃ in methanol as eluent for calcium, and the determination of⁹⁰Sr using a low level -counter after elution with H₂O, scavenging steps and SrCO₃ precipitation. The method was tested with IAEA standards of natural samples with known contents of⁹⁰Sr, and water samples, where the concentration of⁹⁰Sr was previously determined by the standard IAEA procedure. The results obtained show that it is possible to isolate and determine low levels of⁹⁰Sr in natural samples. The procedure is favorable because of the simple separation of radioaactive strontium without using fuming nitric acid.     

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.     

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%.     

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.     

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.

     

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.     

New method for90Sr determination in liquid samples

A method has been developed for measuring⁹⁰Sr activity in liquid samples. After concentrating strontium from the sample by coprecipitation with calcium phosphate, the residue is dissolved in 8N HNO₃ and passed through an extraction chromatographic column (Sr.Spec) containing a new material that selectively retains strontium. This is eluted from the column with 0.05N HNO₃ and counted by liquid scintillation. Measurement is performed using a double window method, that allows a rapid and single determination of⁹⁰Sr.     

The stability of99mTc phosphorus compounds in plasma both in vivo and in vitro

The in vivo and in vitro stability of^99mTc hydroxyethlylidene diphosphonate, 99^mTc methylenediphosphonate and^99mTc pyrophosphate in plasma has been studied using paper chromatographic technique as the analytical tool. The results indicate that the amounts of^99mTc activity found both at the origin and R_f range of^99mTcO₄ ^? for in vivo experiments are slightly greater than those for either in vitro or control experiments. However, this amount of^99mTc activity represents about 0.16–0.4% of the injected dose. Therefore, it is suggested that^99mTc phosphorus radiopharmaceuticals are stable in vivo and neither oxidation nor hydrolysis of these bone imaging agents occurs in the blood.     

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.     

Determination of technetium-99 in environmental samples: A review

Due to the lack of a stable technetium isotope, and the high mobility and long half-life, ⁹⁹Tc is considered to be one of the most important radionuclides in safety assessment of environmental radioactivity as well as nuclear waste management. ⁹⁹Tc is also an important tracer for oceanographic research due to the high technetium solubility in seawater as TcO₄⁻. A number of analytical methods, using chemical separation combined with radiometric and mass spectrometric measurement techniques, have been developed over the past decades for determination of ⁹⁹Tc in different environmental samples. This article summarizes and compares recently reported chemical separation procedures and measurement methods for determination of ⁹⁹Tc. Due to the extremely low concentration of ⁹⁹Tc in environmental samples, the sample preparation, pre-concentration, chemical separation and purification for removal of the interferences for detection of ⁹⁹Tc are the most important issues governing the accurate determination of ⁹⁹Tc. These aspects are discussed in detail in this article. Meanwhile, the different measurement techniques for ⁹⁹Tc are also compared with respect to advantages and drawbacks. Novel automated analytical methods for rapid determination of ⁹⁹Tc using solid extraction or ion exchange chromatography for separation of ⁹⁹Tc, employing flow injection or sequential injection approaches are also discussed.     

Radiochemical measurements of99Tc: Sources and environmental levels

A method of⁹⁹Tc determination has been developed based on sample decomposition followed by purification from interfering elements by hydroxide and oxide precipitations. Technetium is extracted by TBP and electrodeposited onto stainless steel discs from sodium hydroxide solution.⁹⁹Tc^m is used as yield monitor. The method has been applied to study releases from different sources and contents in different samples of atmospheric, terrestrial and marine origin. Results show enhanced⁹⁹Tc/¹³⁷Cs activity ratios for samples collected in recent years which are only expected to be contaminated from fallout from nuclear tests. Integrated fallout measurements did not reflect these enhanced ratios.     

Comparison of recoveries of inogranic and organic incorporated75Se by four mineralization methods of biological material

The recovery of selenium⁷⁵Se added as selenite to human blood and to mixed food, and the recovery of biologically incorporated⁷⁵Se from different rat tissues were determined by using four mineralization methods. The recoveries of⁷⁵Se after dry ashing /HNO₃, Mg/NO₃/₂/ and after three wet digestion methods — 1. HNO₃, HClO₄ 2. HNO₃, HClO₄, H₂SO₄ 3. HNO₃, HClO₄, MgCl₂ were as follows: 50–106%, 96–99%, 92–99% and 97–100%, resp. Losses of⁷⁵Se in wet digestion /HNO₃, HClO₄/ were observed at the end of the procedure, when an excess of acids was evaporated. The addition of MgCl₂ to the digestion mixture prevented the escape of⁷⁵Se and thus permitted the total evaporation of the digest without any loss of selenium.     

Isolation of radioactive strontium from natural samples: A semi-automatic procedure

A procedure for semi-automatic isolation and determination of radioactive strontium from natural samples was developed. The method was tested by the determination of⁹⁰Sr in soil samples and the results obtained were compared to those obtained by the standard procedure. The procedure consists of leaching of strontium (and other cations as well) from soil samples with a water suspension of the cation exchanger Amberlite IR-20, the separation of strontium from other cations, e.g., potassium, calcium, sodium, barium by the anion exchangers Amberlite CG-400 or Dowex Ag 1×8 with 0.25M HNO₃ in ethanol-methanol mixture as eluent in the apparatus specially constructed for this purpose. Determination of⁹⁰Sr was done on the low-level gas-flow β-counter and by Cherenkow counting on the liquid-scintillation counter few hours after the separation. It was shown that this procedure might be successfully applied for rapid determination of⁹⁰Sr in soil samples and other natural samples in a timesaving manner.