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 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.     

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.     

Rapid determination of 99Tc in environmental samples by high resolution ICP-MS coupled with on-line flow injection system

High resolution inductively coupled plasma mass spectrometry coupled with an on-line flow injection system (FI-HR-ICP-MS) was applied to determine the ultra-trace level ⁹⁹Tc in soil. The flow injection system (PrepLab) was composed of two TEVA-Spec^Òresins, reduced remarkably the sample amounts and the analysis time, compared to the conventional analytical methods. In the flow injection system, Mo and Ru were sufficiently eliminated by using the flow injection system, with the decontamination factors of 1.6^.10⁴ and 9.9^.10⁵, respectively. With the present method, it was possible to determine ultra-low level of ⁹⁹Tc in 3-6 g soil at 3–5 hours of analysis time per sample. The relative standard deviation for each sample was less than 4%. The detection limits for ⁹⁹Tc was 85 fg^.ml^–1 (0.05 mBq^.ml^–1), which was calculated from the three times standard deviation of the count rate of the blank.     

Analysis of99Tc atmospheric samples

The analysis of⁹⁹Tc was carried out in filter, peat and rainwater samples. A solvent extraction technique was used to separate Tc from them, where tributylphosphate was the extracting agent. Radiochemical yield was obtained by using^99mTc as an internal tracer. A typical value of 60% was found for it. However, problems encountered in its determination are discussed in the text. Additionally, rainwater samples were analyzed for¹³⁷Cs. This was adsorbed in ammonium phosphomolibdate. Radiochemical yield was obtained by using¹³⁴Cs as an internal tracer.Work partially supported under Contract CAICYT No. 2849/83.     

Determination of 99Tc in environmental samples by anion exchange and liquid-liquid extraction at controlled valency

A method for collecting ⁹⁹Tc from 200-2-400 1 of sea water by anion exchange has been developed. Further decontamination of ^103.106Ru was achieved by repeated evaporation of RuO₄ from 0.05 M sulphuric acid at 100° C, followed by extraction of TcO^-₄ into 5% triisooctylamine-xylene at controlled valency. ^110mAg was precipitated as AgCl. An average overall radiochemical yield of 70% was found for Tc. Decontamination factors were between 3 10⁵ and 2 10⁷ for Ru and 2 10⁵ for Ag. A method for determining ⁹⁹Tc in seaweed by wet ashing and simple extraction into 5% triisooctylamine-xylene is also presented.     

Comparative studies of methylmercury determination in biological and environmental samples

Some parameters affecting the accuracy of various approaches to methylmercury (MeHg) determination in biological and environmental samples were studied. Different isolation techniques (ion-exchange, extraction, volatilization, distillation) and final measurement via cold vapour atomic absorption spectroscopy (CV AA) or gas chromatography (GC) were compared. Results obtained by the various isolation techniques are comparable for almost all biological and environmental samples, except for soils and some sediments, where disagreement between the results obtained by GC and CV AA was found. In order to resolve these problems, a new separation technique based on distillation of MeHg from the sample followed either by CV AA or GC was developed. The new method results in very good recovery and reproducibility (95 ± 2%) for all samples examined (fish, mussel, shrimp, blood, hair, algae, sediment, etc.), is specific for MeHg and provides for its differentiation from other species by an indirect CV AA determination. Gas-chromatographic measurement of the isolated MeHg using different packings and conditioning of the columns is also discussed. The distillation method with GC detection is advantageous in producing cleaner chromatograms and in prolonging the life-time of the packing and the intervals between reconditioning.     

A new very sensitive LSC procedure for determination of Tc-99 in environmental samples

A new method for the determination of Tc-99 in different environmental samples has been developed. The sample is carefully ashed in a muffle furnace and then fused with Na₂CO₃ and K₂CO₃. The first step is an enrichment and purification of TcO ₄ ^– on an anion exchange resin. The Tc is desorbed as a cationic thiourea complex, which is held on a cation exchange resin. The complex is destroyed by oxidation to TcO ₄ ^– with (NH₄)₂S₂O₈ in sulfuric acid. From this solution TcO ₄ ^– is extracted into TBP/toluene and the organic phase is mixed with a scintillation cocktail and counted in an anticoincidence shielded LSC. Tc-99m is used as a chemical yield tracer. The decontamination factors for all important fission and activation products and naturally occurring radionuclides are in the range between > 10⁵ and > 10⁸. The detection limit is about 5 mBq per sample at a counting time of 1000 minutes. The maximum sample amount of plants is 500 g dry weight and therefore the lowest detection limit achievable is 10 mBq/kg. Ashing and dissolution of the samples takes 24 h and 4 analyses are performed by one technician in 8 hours. The chemical yield ranges from 50 to 80%.     

The sequential separation of99Tc and129I in waste samples

A unique procedure permitting the determination of⁹⁹Tc and¹²⁹I in the same portion of sample is presented. Various matrices of environmental waste samples are spiked with⁹⁵Tc and iodide carrier, ashed, fused, and analyzed. The matrices analyzed included various types of filters, resin, evaporator salts, floor silt, sludge and charcoal. The technetium isotopes and iodine isotopes are sequentilly separated by organic extraction techniques.     

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.     

Determination of <Superscript>99</Superscript>Tc in environmental samples and depleted uranium penetrators using ICP-MS

A new method was developed for the determination of ⁹⁹technetium (Tc) by ICP-MS. We report, for the first time, an activity of ⁹⁹Tc for the reference material IAEA-315. For the IAEA-375, IAEA-373 and IAEA-381, our results confirmed the values already reported in the literature. The developed method was used for analysing sediments from the Yenisei river (collected downstream of a nuclear fuel reprocessing plant) and for characterizing corrosion products of depleted uranium penetrators that were fired during the Balkan conflict.     

Selectivity analysis of 99Tc determination by LSC in the field of nuclear decommissioning

Journal of Radioanalytical and Nuclear Chemistry - In this work, two Tc radiochemical isolation methods—a conventional method by Triskem TEVA® resin and a rapid method by Empore?...     

Comparison of two ICP-MS set-ups for measuring 99Tc in large volume water samples

Large volume fjord and seawater samples have been radiochemically prepared for ICP-MS analysis in order to test the robustness of the procedure and to carry out a comparison of two ICP-MS set-ups. A sector field instrument (MicroMass PT2) coupled with an ultrasonic nebuliser and a quadrupole ICP-MS (Perkin-Elmer Elan 6000) coupled with an electrothermal vaporisation (ETV) unit were used. The results showed that the radiochemical procedure was robust, removing Ru and Mo to acceptable levels, and that the two set-ups gave results that were in agreement. The correlation coefficient between the sets of 11 results was 1.0 +/- 0.05. The importance of establishing the matrix effect when using an ETV is discussed.     

Determination of 99Tc in bentonite clay samples using inductively coupled plasma mass spectrometry

A method was developed for the determination of ⁹⁹Tc at low concentrations in clay samples. The chemical treatment of the samples prior to chemical separation and analysis comprised leaching with sulphuric acid/ sodium bromate. After leaching, pertechnetate was extracted with Alamine-336/chloroform and then back-extracted into nitric acid. Detection was carried out using inductively coupled plasma mass spectrometry, ICP-MS. The instrumental detection limit was 0.45 pg/mL, which corresponds to 0.28 mBq/mL. With the use of a desolvating nebuliser, the detection limit was lowered by about a factor of five. The results were compared with a method using radiometric detection. Received: 16 April 1998 / Revised: 12 June 1998 / Accepted: 16 June 1998     

Determination of 99Tc in bentonite clay samples using inductively coupled plasma mass spectrometry

A method was developed for the determination of ⁹⁹Tc at low concentrations in clay samples. The chemical treatment of the samples prior to chemical separation and analysis comprised leaching with sulphuric acid/ sodium bromate. After leaching, pertechnetate was extracted with Alamine-336/chloroform and then back-extracted into nitric acid. Detection was carried out using inductively coupled plasma mass spectrometry, ICP-MS. The instrumental detection limit was 0.45 pg/mL, which corresponds to 0.28 mBq/mL. With the use of a desolvating nebuliser, the detection limit was lowered by about a factor of five. The results were compared with a method using radiometric detection.     

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.     

Investigating the antimony determination in environmental samples by NAA

In recent years, environmental concerns regarding antimony have grown considerably due to anthropogenic processes that have resulted in increasing concentration of Sb in the environment, and also because of its impacts and possible adverse effects to living organisms. Several techniques have been used, to obtain reliable results for Sb, since Sb is present at low level concentration, requiring analytical instrumentation with low detection limits. The neutron activation analysis (NAA) technique has a high metrological level for the determination of several elements in different matrices. However, Sb determination in environmental and biological samples presents some analytical difficulties due to its low concentrations and gamma ray spectrum interferences. The objective of this research was to study on Sb determination in environmental reference materials by NAA. Ten environmental reference materials were selected and analyzed using long period irradiation at IEA-R1 research nuclear reactor. The induced gamma activities of ¹²²Sb and ¹²⁴Sb were measured. Relative errors of the results demonstrated that the accuracy depends mainly on Sb radioisotope measured, the decay time for counting and the sample composition.     

Rapid determination of 226Ra in environmental samples

A new rapid method for the determination of ²²⁶Ra in environmental samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used for emergency response or routine sample analyses. The need for rapid analyses in the event of a Radiological Dispersive Device or Improvised Nuclear Device event is well-known. In addition, the recent accident at Fukushima Nuclear Power Plant in March, 2011 reinforces the need to have rapid analyses for radionuclides in environmental samples in the event of a nuclear accident. ²²⁶Ra (T1/2?=?1,620?years) is one of the most toxic of the long-lived alpha-emitters present in the environment due to its long life and its tendency to concentrate in bones, which increases the internal radiation dose of individuals. The new method to determine ²²⁶Ra in environmental samples utilizes a rapid sodium hydroxide fusion method for solid samples, calcium carbonate precipitation to preconcentrate Ra, and rapid column separation steps to remove interferences. The column separation process uses cation exchange resin to remove large amounts of calcium, Sr Resin to remove barium and Ln Resin as a final purification step to remove ²²⁵Ac and potential interferences. The purified ²²⁶Ra sample test sources are prepared using barium sulfate microprecipitation in the presence of isopropanol for counting by alpha spectrometry. The method showed good chemical recoveries and effective removal of interferences. The determination of ²²⁶Ra in environmental samples can be performed in less than 16?h for vegetation, concrete, brick, soil, and air filter samples with excellent quality for emergency or routine analyses. The sample preparation work takes less than 6?h. ²²⁵Ra (T1/2?=?14.9?day) tracer is used and the ²²⁵Ra progeny ²¹⁷At is used to determine chemical yield via alpha spectrometry. The rapid fusion technique is a rugged sample digestion method that ensures that any refractory radium particles are effectively digested. The preconcentration and column separation steps can also be applied to aqueous samples with good results.     

Radiochemical determination of cobalt-60 in environmental samples

A procedure for the radiochemical determination of (60)Co in low-activity samples of sediment and biological material is described. Cobalt recovery is high and decontamination from tervalent lanthanides and naturally-occurring radionuclides is complete. Cobalt is precipitated with 1-nitroso-2-naphthol, decontaminated from iron by precipitation of the iron as ferric phosphate, extracted into methyl isobutyl ketone, and finally precipitated as cobalt mercury(II) thiocyanate for yield determination and beta-counting.