A rapid method for α-spectrometric analysis of radium isotopes in natural waters using ion-selective membrane technology

226Ra and 137Cs determination by inductively coupled plasma mass spectrometry: state of the art and perspectives including sample pretreatment and separation steps

Achieving precise and accurate quantification of radium (²²⁶Ra) and cesium (¹³⁷Cs) by inductively coupled plasma mass spectrometry (ICP-MS) is of particular interest in the field of radiological monitoring and more widely in environmental and biological sciences. However, the accuracy and sensitivity of the quantification depend on the analytical strategy implemented. Eliminating interferences during the sample handling step and/or during the analysis step is critical since presence of matrix elements can lead to spectral and non-spectral interferences in ICP-MS. Consequently, before the ICP-MS analysis, multiple sample preparation approaches have been applied to purify and/or pre-concentrate environmental and biological samples containing radium and cesium through years, such as (co)-precipitation, solid phase extraction (SPE) or dispersive SPE (dSPE). Separation steps using liquid chromatography and capillary electrophoresis can also be useful in complement with the abovementioned sample preparation techniques. The most attractive sample handling technique remains SPE but efficiency of the extraction procedures is currently limited by sorbent specificity. Indeed, with the recent advances in ICP-MS instrumentation, it becomes indispensable to eliminate residual interferences and improve sensitivity. It is in this direction that it will be possible to meet analytical challenges, e.g. analyzing radium and cesium at concentrations below the pg L^-1 range in complex matrices of small volumes, as they are found for instance in pore waters or in biological samples. Development of new innovative sorbents based for example on hybrid and nanostructured materials has been reported with the aim of enhancing sorbent specificity and/or capacity. In the present review, the performances of the different analytical approaches are discussed, followed by an overview of applications.

Optimal methods for preparation, separation, and determination of radium isotopes in environmental and biological samples

In recent years, radium has attracted considerable attention primarily because of the rapid increase in unconventional (fracking) drilling technology in the United States and around the world. One of the major radionuclides of interest in unconventional drilling wastes is radium isotopes (²²⁴Ra, ²²⁶Ra, ²²⁸Ra). To access long-term risks associated with radium isotopes entering into the environment, accurate measurements of radium isotopes in environmental and biological samples are crucial. This article reviews many aspects of radium chemistry, which includes recent developments in radiochemical separations methods, advancements in analytical techniques followed by a more detailed discussion on the recent trends in radium determination.

Accuracy of methods for reporting inorganic element concentrations and radioactivity in oil and gas wastewaters from the Appalachian Basin, U.S. based on an inter-laboratory comparison

Accurate and precise analyses of oil and gas (O&G) wastewaters and solids (e.g., sediments and sludge) are important for the regulatory monitoring of O&G development and tracing potential O&G contamination in the environment. In this study, 15 laboratories participated in an inter-laboratory comparison on the chemical characterization of three O&G wastewaters from the Appalachian Basin and four solids impacted by O&G development, with the goal of evaluating the quality of data and the accuracy of measurements for various analytes of concern. Using a variety of different methods, analytes in the wastewaters with high concentrations (i.e., >5 mg L-1) were easily detectable with relatively high accuracy, often within ±10% of the most probable value (MPV). In contrast, often less than 7 of the 15 labs were able to report detectable trace metal(loid) concentrations (i.e., Cr, Ni, Cu, Zn, As, and Pb) with accuracies of approximately ±40%. Despite most labs using inductively coupled plasma mass spectrometry (ICP-MS) with low instrument detection capabilities for trace metal analyses, large dilution factors during sample preparation and low trace metal concentrations in the wastewaters limited the number of quantifiable determinations and likely influenced analytical accuracy. In contrast, all the labs measuring Ra in the wastewaters were able to report detectable concentrations using a variety of methods including gamma spectroscopy and wet chemical approaches following Environmental Protection Agency (EPA) standard methods. However, the reported radium activities were often greater than ±30% different to the MPV possibly due to calibration inconsistencies among labs, radon leakage, or failing to correct for self-attenuation. Reported radium activities in solid materials had less variability (±20% from MPV) but accuracy could likely be improved by using certified radium standards and accounting for self-attenuation that results from matrix interferences or a density difference between the calibration standard and the unknown sample. This inter-laboratory comparison illustrates that numerous methods can be used to measure major cation, minor cation, and anion concentrations in O&G wastewaters with relatively high accuracy while trace metal(loid) and radioactivity analyses in liquids may often be over ±20% different from the MPV.

A review of the analytical methodology to determine Radium-226 and Radium-228 in drinking waters

Radium-228 (228Ra) and Radium-226 (226Ra) isotopes in drinking water are significant from the aspect of radiation protection and human health. In this paper, the three most common preconcentration methods, i.e.coprecipitation, absorption and evaporation, were reviewed with emphasis on routinely measurement techniques. The reviewed measurement techniques include low background γ-spectrometry, α-spectrometry and liquid scintillation counting. The γ-spectrometry technique is the good selection, when the maximum sensitivity is considered. The Environmental Protection Agency guideline has provided the maximum concentration level 0.74 Bq/L for 226Ra and 228Ra. Also, the World Health Organization guideline limit is 1 Bq/L and 0.1 Bq/L for 226Ra and 228Ra, respectively.

Simultaneous determination of gross alpha, gross beta and ²²⁶Ra in natural water by liquid scintillation counting

The determination of gross alpha, gross beta and (226)Ra activity in natural waters is useful in a wide range of environmental studies. Furthermore, gross alpha and gross beta parameters are included in international legislation on the quality of drinking water [Council Directive 98/83/EC]. In this work, a low-background liquid scintillation counter (Wallac, Quantulus 1220) was used to simultaneously determine gross alpha, gross beta and (226)Ra activity in natural water samples. Sample preparation involved evaporation to remove (222)Rn and its short-lived decay daughters. The evaporation process concentrated the sample ten-fold. Afterwards, a sample aliquot of 8 mL was mixed with 12 mL of Ultima Gold AB scintillation cocktail in low-diffusion vials. In this study, a theoretical mathematical model based on secular equilibrium conditions between (226)Ra and its short-lived decay daughters is presented. The proposed model makes it possible to determine (226)Ra activity from two measurements. These measurements also allow determining gross alpha and gross beta simultaneously. To validate the proposed model, spiked samples with different activity levels for each parameter were analysed. Additionally, to evaluate the model's applicability in natural water, eight natural water samples from different parts of Spain were analysed. The eight natural water samples were also characterised by alpha spectrometry for the naturally occurring isotopes of uranium ((234)U, (235)U and (238)U), radium ((224)Ra and (226)Ra), (210)Po and (232)Th. The results for gross alpha and (226)Ra activity were compared with alpha spectrometry characterization, and an acceptable concordance was obtained.

Determination of radium isotopes in environmental samples by gamma spectrometry, liquid scintillation counting and alpha spectrometry: a review of analytical methodology

Radium (Ra) isotopes are important from the viewpoints of radiation protection and environmental protection. Their high toxicity has stimulated the continuing interest in methodology research for determination of Ra isotopes in various media. In this paper, the three most routinely used analytical techniques for Ra isotope determination in biological and environmental samples, i.e. low-background γ-spectrometry, liquid scintillation counting and α-spectrometry, were reviewed, with emphasis on new methodological developments in sample preparation, preconcentration, separation, purification, source preparation and measurement techniques. The accuracy, selectivity, traceability, applicability and minimum detectable activity (MDA) of the three techniques were discussed. It was concluded that the MDA (0.1mBqL(-1)) of the α-spectrometry technique coupled with chemical separation is about two orders of magnitude lower than that of low-background HPGe γ-spectrometry and LSC techniques. Therefore, when maximum sensitivity is required, the α-spectrometry technique remains the first choice.

Determination of 226Ra in aqueous solutions via sorption on thin films and α-spectrometry

An improved spectrometric method to determine the 226Ra activity in aqueous solutions is described. The method involves two stages, a preconcentration stage of 226Ra sorption onto a thin manganese layer and a measurement stage using alpha-spectrometry. Manganese oxide thin films were prepared and characterized with X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses. The thin films were found to follow the XRD patterns and chemical formula of the K-birnessite layered exchanger. The preconcentration of radium was studied relative to the initial radium concentration, pH and salt concentrations. The preconcentration kinetics was studied as a function of manganese surface, solution volume and salt concentration. Extensive Monte Carlo calculations were performed to optimise the detection of alpha-particles. In this way, the thin film preparation procedure as well as the radium sorption and the measurement conditions were optimised and detection limits lower than 0.5 mBq L(-1) were obtained for 2d of procedure completion. The method was validated with IAEA standards and it was applied for the determination of 226Ra in bottled waters and also wastewaters from the major thermoelectric plant in Greece. Moreover, the 226Ra distribution coefficients (K(d)) of two differently prepared powder manganese oxides, a crystalline silicotitanate and an aluminium-pillared montmorillonite were determined by gamma-spectrometry. 226Ra sorption experiments on silicotitanate thin films were performed and improvements in resolution and reduction of exposure time were observed.

Selective extraction of naturally occurring radioactive Ra2+

Organic extractants play a significant role in the selective removal of radioactive cations from waste streams. Although, literature on the selective removal of man-made radioactive material such as Americium (Am) is widespread, the selective removal of naturally occurring radioactive material such as Ra2+ is only mentioned sporadically. This tutorial review deals with the selective extraction of the highly radiotoxic Ra2+. Special attention is paid to different types of organic extractants used.