Development of a method for rapid analysis of Ra-226 in groundwater and discharge water samples by ICP-QQQ-MS

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.

Development of a reference material for analysing naturally occurring radioactive material from the steel industry

Accurate measurement of naturally occurring radionuclides in blast furnace slag, a by-product of the steel industry, is required for compliance with building regulations where it is often used as an ingredient in cement. A matrix reference blast furnace slag material has been developed to support traceability in these measurements. Raw material provided by a commercial producer underwent stability and homogeneity testing, as well as characterisation of matrix constituents, to provide a final candidate reference material. The radionuclide content was then determined during a comparison exercise that included 23 laboratories from 14 countries. Participants determined the activity per unit mass for ²²⁶Ra, ²³²Th and ⁴⁰K using a range of techniques. The consensus values obtained from the power-moderated mean of the reported participant results were used as indicative activity per unit mass values for the three radionuclides: A₀(²²⁶Ra) = 106.3 (34) Bq·kg^-1, A₀(²³²Th) = 130.0 (48) Bq·kg^-1 and A₀(⁴⁰K) = 161 (11) Bq·kg^-1 (where the number in parentheses is the numerical value of the combined standard uncertainty referred to the corresponding last digits of the quoted result). This exercise helps to address the current shortage of NORM industry reference materials, putting in place infrastructure for production of further reference materials.

Simple and sensitive determination of radium-226 in river water by single column-chromatographic separation coupled to SF-ICP-MS analysis in medium resolution mode

This article describes a novel and simple method to measure ultra-trace ²²⁶Ra in river water samples at fg L^-1 (mBq L^-1) levels as a means for surveying ²²⁶Ra in an unintended contamination in river water. To simplify the procedure, a single column was used for separation and purification; 10 mL of AG 50W-X8 resin was packed into a 10 mL Eppendorf pipette tip, which was used as a separation column. A 500 mL sample solution was loaded, and interfering elements were removed with 80 mL 4 M HCl in 20% ethanol. Subsequently, Ra together with Ba was eluted by 20 mL 5 M HNO₃ prior to SF-ICP-MS analysis; this allows the naturally existing Ba in water samples to be employed as a yield tracer for ²²⁶Ra analysis. Using the medium mode of SF-ICP-MS, the instrumental detection limit of 380 fg L^-1 (10 mBq L^-1) was obtained. An extremely low method detection limit of 0.46 fg L^-1 (0.02 mBq L^-1) was achieved with 500-fold pre-concentration. Finally, the developed technique was applied to analyze natural water samples collected from Japanese rivers, in which the ²²⁶Ra concentrations varied in the range of 0.7-49.6 fg L^-1 (0.03-1.82 mBq L^-1).

A new rapid protocol for 226Ra separation and preconcentration in natural water samples using molecular recognition technology for ICP-MS analysis

A new rapid protocol for ²²⁶Ra separation and preconcentration in natural water samples was developed before its determination by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). For this purpose, the commercially available Ra specific resin AnaLig^® Ra-01 was used. This resin shows a high selectivity for radium in a large range of acid concentrations and no affinity or possible elution of ²²⁶Ra interfering elements. The distribution coefficients of Ra and other elements over a wide range of acid (HCl and HNO₃) concentrations were obtained. Due to the high radium selectivity, the new developed protocol uses only 50 mg of dry resin and its performance was evaluated using 100 mL of three natural waters with different ionic strengths, spiked with a known quantity of ²²⁶Ra. Radium was successfully separated and preconcentrated yielding recoveries ranging between 72% and 86%. In parallel with the characterisation of the resin sorption properties, a detailed study of polyatomic interferences was performed on our ICP-MS allowing to identify the prominent elements favouring interferences at m/z = 226. Furthermore, a ²²⁶Ra sensitivity comparison between different ICP-MS instruments and configurations was done in order to determine high sensitivity conditions for radium analysis.

High Throughput, Direct Determination of 226Ra in Water and Digested Geological Samples

A method was developed for direct measurements of ²²⁶Ra in water samples with triple quadrupole inductively coupled plasma mass spectrometry (ICP-QQQ). The limit of detection was 0.42 pg L^-1 226Ra (15 mBq L^-1, 0.42 pCi L^-1), which is compliant with the specifications for methods used for routine analysis of drinking water quality according to European and U.S. regulations. The use of N₂O as reaction gas ensured that no separation before analysis was necessary. Water samples with high total dissolved solids (conductivity >100 mS cm^-1) were also successfully analyzed after a simple dilution, yet the associated detection limit was higher (17 pg L^-1, 0.61 Bq L^-1, 16 pCi L^-1). ²²⁶Ra content in soil and rock samples was determined with the same method after acid (HNO₃ + H₃PO₄) digestion and dilution, resulting in a limit of detection of 0.75 ng kg^-1 (27 Bq kg^-1, 0.74 nCi L^-1). Analysis of water samples was achieved within 2 min on a running instrument, while the preparation and analysis of 15 geological samples can be completed in 3 h. The key advantages of this direct analysis method are short preparation time, low labor intensity, low sample input (2 mL for water samples, 0.2 g for geological material), high sample throughput (2 min sample to sample, >150 samples measured in 8 h), and use of standard ICP-QQQ hardware. Overall, the proposed method offers a new opportunity for measuring a large number of samples with minimal effort and, in turn, for improving emergency preparedness, environmental monitoring, and data collection for environmental modeling.

The behaviour of 226Ra in high-volume environmental water samples on TK100 resin

Accurate, low-level measurement of ²²⁶Ra in high volume water samples requires rapid pre-concentration and robust separation techniques prior to measurement in order to comply with discharge limits and drinking water regulations. This study characterises the behaviour of ²²⁶Ra and interfering elements on recently developed TK100 (Triskem International) extraction chromatography resin. Distribution coefficients over a range of acid concentrations are given, along with an optimised procedure that shows rapid pre-concentration and separation of ²²⁶Ra on TK100 resin is achievable for high volume (1 L) water samples without the need for sample pre-treatment.