Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples

The radiometric methods, alpha (α)-, beta (β)-, gamma (γ)-spectrometry, and mass spectrometric methods, inductively coupled plasma mass spectrometry, accelerator mass spectrometry, thermal ionization mass spectrometry, resonance ionization mass spectrometry, secondary ion mass spectrometry, and glow discharge mass spectrometry are reviewed for the determination of radionuclides. These methods are critically compared for the determination of long-lived radionuclides important for radiation protection, decommissioning of nuclear facilities, repository of nuclear waste, tracer application in the environmental and biological researches, these radionuclides include ³H, ¹⁴C, ³⁶Cl, ⁴¹Ca, ^59,63Ni, ^89,90Sr, ⁹⁹Tc, ¹²⁹I, ^135,137Cs, ²¹⁰Pb, ^226,228Ra, ²³⁷Np, ²⁴¹Am, and isotopes of thorium, uranium and plutonium. The application of on-line methods (flow injection/sequential injection) for separation of radionuclides and automated determination of radionuclides is also discussed.     

Determination of 241Am in Environmental Samples: A Review

The determination of ²⁴¹Am in the environment is of importance in monitoring its release and assessing its environmental impact and radiological risk. This paper aims to give an overview about the recent developments and the state-of-art analytical methods for ²⁴¹Am determination in environmental samples. Thorough discussions are given in this paper covering a wide range of aspects, including sample pre-treatment and pre-concentration methods, chemical separation techniques, source preparation, radiometric and mass spectrometric measurement techniques, speciation analyses, and tracer applications. The paper focuses on some hyphenated separation methods based on different chromatographic resins, which have been developed to achieve high analytical efficiency and sample throughput for the determination of ²⁴¹Am. The performances of different radiometric and mass spectrometric measurement techniques for ²⁴¹Am are evaluated and compared. Tracer applications of ²⁴¹Am in the environment, including speciation analyses of ²⁴¹Am, and applications in nuclear forensics are also discussed.     

Determination of plutonium and other transuranic elements by inductively coupled plasma mass spectrometry: A historical perspective and new frontiers in the environmental sciences

Inductively coupled plasma mass spectrometry (ICPMS), particularly with sector field mass analyzers (SF-ICPMS), has emerged in the past several years as an excellent analytical technique for rapid, highly sensitive determination of transuranic elements (TRU) in environmental samples. SF-ICPMS has advantages of simplicity of sample preparation, high sample throughput, widespread availability in laboratories worldwide, and relatively straightforward operation when compared to other competing mass spectrometric techniques. Arguably, SF-ICPMS is the preferred technique for routine, high-throughput determination of ²³⁷Np and the Pu isotopes, excepting ²³⁸Pu, at fg-pg levels in environmental samples. Many research groups have now demonstrated the SF-ICPMS determination of ^239 + 240Pu activities, ²⁴⁰Pu/²³⁹Pu and other Pu atom ratios in several different application areas. Many studies have examined the relative contribution of global fallout vs. local/regional Pu sources in the environment through measurement of ²⁴⁰Pu/²³⁹Pu and, in some cases, ²⁴¹Pu/²³⁹Pu and ²⁴²Pu/²³⁹Pu. “Stratospheric fallout”, which was deposited from thermonuclear tests, conducted largely during the 1952–1964 time period, is characterized by a well-defined ²⁴⁰Pu/²³⁹Pu of ~ 0.18, while most other sources have different ratios. Examples of local/regional Pu sources are the Nevada Test Site, the Chernobyl plume, and accidents at Palomares, Spain and Thule, Greenland. The determination of Pu activities and atom ratios has stimulated much interest in the use of Pu as a marine tracer; several studies have shown that Pu is transported over long distances by ocean currents. ²⁴⁰Pu/²³⁹Pu ratios > 0.20 in sediments and seawater of the North Pacific are ascribed to ocean current transport of fallout from the Pacific Proving Ground. In nuclear forensics, much effort is focused on detection and fingerprinting of small amounts of TRU in environmental samples consisting of bulk material or individual isolated particles. Activity measurements of ^239 + 240Pu, determined by SF-ICPMS, have the potential to supplement and/or replace ¹³⁷Cs as a tracer of erosion, deposition, and sedimentation. Undoubtedly, the application of SF-ICPMS in TRU analysis will continue to expand, witness new developments, and generate interesting unforeseen applications in upcoming years.     

Determination of As,Cd, Pb,and Hg in urine using inductively coupled plasma mass spectrometry with the direct injection high efficiency nebulizer

The application of the large-bore direct injection high efficiency nebulizer (LB-DIHEN) for the determination of arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) in urine by inductively coupled plasma mass spectrometry (ICP-MS) is described. The LB-DIHEN is compared with the standard method using a concentric pneumatic nebulizer and cyclonic spray chamber. In addition to the toxicological significance of As, Cd, Pb, and Hg, these elements represent a cross-section of analytical issues including spectral interferences (e.g., ⁴⁰Ar³⁵Cl⁺ on ⁷⁵As⁺ and ⁹⁸Mo¹⁶O⁺ on ¹¹⁴Cd⁺) and memory effects (Hg). In this study, the low sample consumption of the LB-DIHEN is used to reduce the volume of urine needed for analysis, and to reduce the volume of final diluted sample required for analysis. Eliminating the spray chamber and reducing the dead volume of the nebulizer reduces memory effects, especially for analytes such as Hg. The Dynamic Reaction Cell (DRC) is used in this study to attenuate the background level of ArCl⁺ in spite of the increase in the solvent load and, in turn, the urine matrix (chloride) delivered to the plasma by the LB-DIHEN. This is the first report on coupling the LB-DIHEN to a standard autosampler for unattended sample analysis. The robustness of direct injection nebulization for routine analysis and the issues associated with automation of the sample introduction process are discussed. Although the figures of merit (sensitivity, limit of detection, and precision) determined for both nebulizers are slightly poorer for the LB-DIHEN than for the concentric pneumatic nebulizer, there is not a clinically significant difference between the results for both sample introduction systems. The accuracy of results is assessed using archived urine materials that are circulated by several different proficiency testing (PT) programs and external quality assessment schemes (EQAS). Results obtained using the LB-DIHEN were within the acceptable range established by a consensus pool generated using different methods, none of which are likely to be using direct injection nebulization. Internal quality control sample results obtained using the LB-DIHEN were compared to those obtained using the conventional nebulizer. Reported results were similar for both nebulizers. Thus, these results show that the LB-DIHEN is certainly feasible for the analysis of urine specimens.     

Interaction of <Superscript>99</Superscript>Tc onto bentonite and influence of Fe(II) and (Ca,Mg) ion exchange in its interlayers

⁹⁹Tc is a redox active radionuclide, which is present as contaminant at a number of sites where nuclear fuel cycle operations have been carried out. The aim of our research was study of bentonite interaction with Fe and Fe²⁺ cation and these influences on the migration behavior. Radioanalytical and analytical methods were used for the concentration and chemical forms of ⁹⁹Tc determination. It was found that Fe²⁺–Ca²⁺, Mg²⁺ ion exchange should be considered as a process of reaction among the corrosion products of carbon steel container and bentonite in the environment of radioactive waste repository.     

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.     

Rapid determination of Cs and precise Cs/Cs atomic ratio in environmental samples by single-column chromatography coupled to triple-quadrupole inductively coupled plasma-mass spectrometry

For source identification, measurement of ¹³⁵Cs/¹³⁷Cs atomic ratio not only provides information apart from the detection of ¹³⁴Cs and ¹³⁷Cs, but it can also overcome the application limit that measurement of the ¹³⁴Cs/¹³⁷Cs ratio has due to the short half-life of ¹³⁴Cs (2.06 y). With the recent advancement of ICP-MS, it is necessary to improve the corresponding separation method for rapid and precise ¹³⁵Cs/¹³⁷Cs atomic ratio analysis. A novel separation and purification technique was developed for the new generation of triple-quadrupole inductively coupled plasma-mass spectrometry (ICP-MS/MS). The simple chemical separation, incorporating ammonium molybdophosphate selective adsorption of Cs and subsequent single cation-exchange chromatography, removes the majority of isobaric and polyatomic interference elements. Subsequently, the ICP-MS/MS removes residual interference elements and eliminates the peak tailing effect of stable ¹³³Cs, at m/z 134, 135, and 137. The developed analytical method was successfully applied to measure ¹³⁵Cs/¹³⁷Cs atomic ratios and ¹³⁵Cs activities in environmental samples (soil and sediment) for radiocesium source identification.     

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.     

Analytical Methods for the Determination of 90Sr and 239,240Pu in Environmental Samples

Artificial long-lived radionuclides such as ⁹⁰Sr and ^239,240Pu have been long released into the environment by human nuclear activities, which have a profound impact on the ecological environment. It is of great significance to monitor the concentration of these radionuclides for environmental safety. This paper summarizes and critically discusses the separation and measurement methods for ultra-trace determination of ⁹⁰Sr, ²³⁹Pu, and ²⁴⁰Pu in the environment. After selecting the measurement method, it is necessary to consider the decontamination of the interference from matrix elements and the key elements, and this involves the choice of the separation method. Measurement methods include both radiometric methods and non-radiometric methods. Radiometric methods, including alpha spectroscopy, liquid scintillation spectrometry, etc., are commonly used methods for measuring ^239+240Pu and ⁹⁰Sr. Mass spectrometry, as the representative of non-radiometric measurement methods, has been regarded as the most promising analytical method due to its high absolute sensitivity, low detection limit, and relatively short sample-analysis time. Through the comparison of various measurement methods, the future development trend of radionuclide measurement is prospected in this review. The fully automatic and rapid analysis method is a highlight. The new mass spectrometer with ultra-high sensitivity shows strong analytical capabilities for extremely low concentrations of ⁹⁰Sr, ²³⁹Pu, and ²⁴⁰Pu, and it is expected to develop determination methods with higher sensitivity and lower detection limit.     

Losses of technetium during various steps in the development of a procedure for environmental samples

A key aspect of the development of a procedure for the measurement of technetium in environmental samples is that each step should be optimized to achieve maximum recovery.⁹⁹Tc and^95mTc have been the tracers used for the determination of yields in steps involving anion exchange, leaching, ashing, solvent extraction, precipitation and evaporation. The results thus obtained are discussed.     

Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP–MS with multiple ion counters

This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC–ICP–MS)—a Nu Plasma HR—equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the ²³⁵U/²³⁸U, ²³⁶U/²³⁸U, ¹⁴⁵Nd/¹⁴³Nd, ¹⁴⁶Nd/¹⁴³Nd, ¹⁰¹Ru/(⁹⁹Ru+⁹⁹Tc) and ¹⁰²Ru/(⁹⁹Ru+⁹⁹Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred μm to about 1 mm and with surface alpha activities of 3–38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA–MC–ICP–MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15–20 min (excluding MC–ICP–MS optimization and calibration). The ¹⁰¹Ru/(⁹⁹Ru+⁹⁹Tc) and ¹⁰²Ru/(⁹⁹Ru+⁹⁹Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in ¹⁴⁶Nd of about 3–5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The ²³⁵U/²³⁸U and ²³⁶U/²³⁸U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously published results from the bulk analysis of contaminated samples originating from the vicinity of Chernobyl. Thus, the ²³⁵U/²³⁸U ratios measured in ten microsamples varied in the range from 0.0073 (corresponding to the natural uranium isotopic composition) to 0.023 (corresponding to initial ²³⁵U enrichment in reactor fuel). An inverse correlation was observed between the ²³⁶U/²³⁸U and ²³⁵U/²³⁸U isotope ratios, except in the case of one sample with natural uranium. The heterogeneity of the uranium isotope composition is attributed to the different burn-up grades of uranium in the fuel rods from which the microsamples originated. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Non-conventional measurement techniques for the determination of some long-lived radionuclides produced in nuclear fuel a literature survey

The results of a literature survey on non-radiometric analytical techniques for the determination of long-lived radionuclides are described. The methods which have been considered are accelerator mass spectrometry, inductively coupled plasma mass spectrometry, thermal ionization mass spectrometry, resonance ionization spectrometry, resonance ionization mas spectrometry and neutron activation analysis. Neutron activation analysis has been commonly used for the determination of¹²⁹I and²³⁷Np in environmental samples. Inductively coupled mass spectrometry seems likely to become the method of choice for the determination of⁹⁹Tc,²³⁷Np and Pu-isotopes. The methods are discussed and the chemical separation methods described.     

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.     

Determination of technetium-99 from complex matrix

This paper reports an approach that can be used for efficient separation and determination of ⁹⁹Tc (as pertechnetate) after contamination of the environment by nuclear materials. The samples were decomposed by fusion in a mixture of potassium hydroxide and potassium nitrate. After fusion, technetium remains as the pertechnetate anion (TcO₄ ^?). The technetium was isolated from the sample by technique combining solvent extraction, anion exchange, then, again, solvent extraction. After separation, ⁹⁹Tc was measured by isotope-dilution mass spectrometry with ⁹⁷Tc as spike. This method yielded nanogram detection limits for ⁹⁹Tc.     

Simultaneous separation and determination of thallium in water samples by high‐performance liquid chromatography with inductively coupled plasma mass spectrometry

An analytical method for separation and determination of thallium species in water using high‐performance liquid chromatography with inductively coupled plasma mass spectrometry was developed. The composition and concentration of mobile phase, injection volume, and pH value were optimized respectively with an anion or cation exchange column. The results showed that Tl(I) and Tl(III) were effectively separated using anion exchange column Hamilton PRP‐X100, with the mobile phase consisting of 200 mmol/L ammonium acetate and 10 mmol/L diethylenetriaminepentaacetic acid (pH = 4.2). When using a Dionex cation exchange guard column, CS12A, 15 mmol/L HNO₃, and 3 mmol/L diethylenetriaminepentaacetic acid as the mobile phase, Tl(I) and Tl(III) could be effectively separated. The detection limits of the methods were 3–6 and 9–12 ng/L, respectively. In a solution containing Fe ions and oxalic acid, a significant quantity of Tl(I) was oxidized. Fe ions and oxalic acid in the water samples did not interfere with high‐performance liquid chromatography‐inductively coupled plasma mass spectrometry measurement results.     

Impact of Different [Tc(N)PNP]-Scaffolds on the Biological Properties of the Small cRGDfK Peptide: Synthesis,In Vitro and In Vivo Evaluations

Background: The [^99mTc][Tc(N)(PNP)] system, where PNP is a bisphosphinoamine, is an interesting platform for the development of tumor ‘receptor-specific’ agents. Here, we compared the reactivity and impact of three [Tc(N)(PNP)] frameworks on the stability, receptor targeting properties, biodistribution, and metabolism of the corresponding [^99mTc][Tc(N)(PNP)]-tagged cRGDfK peptide to determine the best performing agent and to select the framework useful for the preparation of [^99mTc][Tc(N)(PNP)]-housing molecular targeting agents. Methods: cRGDfK pentapeptide was conjugated to Cys and labeled with each [Tc(N)(PNP)] framework. Radioconjugates were assessed for their lipophilicity, stability, in vitro and in vivo targeting properties, and performance. Results: All compounds were equally synthetically accessible and easy to purify (RCY ≥ 95%). The main influences of the synthon on the targeting peptide were observed in in vitro cell binding and in vivo. Conclusions: The variation in the substituents on the phosphorus atoms of the PNP enables a fine tuning of the biological features of the radioconjugates. ws[^99mTc][Tc(N)(PNP3OH)]– and [^99mTc][Tc(N)(PNP3)]– are better performing synthons in terms of labeling efficiency and in vivo performance than the [^99mTc][Tc(N)(PNP43)] framework and are therefore more suitable for further radiopharmaceutical purposes. Furthermore, the good labeling properties of the ws[^99mTc][Tc(N)(PNP3OH)]– framework can be exploited to extend this technology to the labeling of temperature-sensitive biomolecules suitable for SPECT imaging.     

Quantitative Speciation of Arsenic in Water and Sediment Samples from the Mokolo River in Limpopo Province,South Africa

The Mokolo River is disposed to environmental contaminants such as arsenic (As) due to its proximity to several anthropogenic activities. Speciation of As in water and sediment samples from Mokolo River is crucial to evaluate the level and distribution of As in the river and underlying sediment since toxicity depends on its chemical forms. In this study, As species in water and sediment were determined by developing a new method for sediment extraction. Effective microwave-assisted extraction of As species in sediment samples was achieved using 0.3?M (NH₄)₂HPO₄ and 50?mM EDTA, which showed no species interconversion during extraction. The chromatographic separation and detection of As(III), dimethylarsinic acid (DMA), monomethylarsonic acid, and As(V) in water and sediment samples were achieved by coupling to high-performance liquid chromatography to inductively coupled plasma mass spectrometry. Baseline separation of four As species was achieved in 12?min using gradient elution with 10 and 60?mM NH₄NO₃ at pH 8.7 as the mobile phase. The analytical figures of merit and validation of analytical procedures were assessed and adequate performance and percentage recoveries ranging from 81.1 to 102% for water samples and 73.0–92.0% for sediments were achieved. The As species concentration in water and sediment samples was found to be in the range of 0.304–4.99?µg?L^?1 and 74.0–92.0?ng?g^?1, respectively. DMA was not detected in both water and sediment samples.     

Radiochemical determination of technetium-99

The radiochemistry of technetium-99 is reviewed and the different measurement techniques are compared. Experimental results on sorption of technetium on two different types of ion exchange resins using^99mTc and^95mTc as chemical yield tracers are presented. Spectra calibrations of liquid scintillation counter using^95mTc as chemical yield tracer of⁹⁹Tc are discussed.     

Reliable determination of 237Np in environmental solid samples using 242Pu as a potential tracer

This paper reports an analytical method for rapid determination of neptunium (²³⁷Np) in environmental solid samples exploiting automated sequential injection (SI)-based anion exchange separation. Pivotal issues on analytical method performance were investigated including sorption behavior of ²³⁷Np onto various AG 1-type anion exchangers; suitability of ²⁴²Pu as a tracer for ²³⁷Np determination in environmental solid samples; and long-term chemical stability of tetravalent Np. Experimental results revealed that the degree of resin cross-linking has a significant influence on the separation efficiency in terms of chemical yields of ²³⁷Np and removal of interfering nuclides. Although ca. 30% of sorbed Np onto AG 1-×4 was stripped out during HCl rinsing step for the removal of Th, chemical yield ratios of ²³⁷Np to ²⁴²Pu were proven steady with an average value of 0.67 ± 0.04 (n = 15) under selected experimental conditions. Disulfite-8 M HNO₃ was selected as a redox pair for valence adjustment to Np(IV) and the tetravalent Np in the sample solution was demonstrated to be stabilized for up to 5 days under 3 °C. The analytical results for reference materials showed a good agreement with the expected values, thereby demonstrating the usefulness of ²⁴²Pu as a non-isotopic tracer for ²³⁷Np chemical yield monitoring. The on-column separation procedure fosters rapid analysis as required in emergency situations since each individual sample can be handled within 2.5 h, and leads to a significant decrease in labor intensity compared to conventional batch-wise protocols.     

Determination of rare-earth elements in uranium-bearing materials by inductively coupled plasma mass spectrometry

A novel and simple analytical procedure has been developed for the trace-level determination of lanthanides (rare-earth elements) in uranium-bearing materials by inductively coupled plasma sector-field mass spectrometry (ICP-SFMS). The method involves a selective extraction chromatographic separation of lanthanides using TRU™ resin followed by ICP-SFMS analysis. The limits of detection of the method proposed is in the low pg g⁻¹ range, which are approximately two orders of magnitude better than that of without chemical separation. The method was validated by the measurement of reference material and applied for the analysis of uranium ore concentrates (yellow cakes) for nuclear forensic purposes, as a potential application of the methodology.