Automation of sample processing for ICP-MS determination of 90Sr radionuclide at ppq level for nuclear technology and environmental purposes

An overview of automated flow systems for total and isotopic analysis of strontium and yttrium in samples of environmental interest

Due to the different uses of radioactivity during the last decades, there has been an increase in the concentration of natural and artificial radionuclides in the environment. This, along with some accidents with a high affect public opinion (for example, Chernobyl and Fukushima), have led to the growth and establishment of environmental radioactivity monitoring programs. Currently, trends in legislation and research are focused on the development of accurate, precise, reliable and fast analytical methods with low limits of detection (LOD) for radionuclides determination, such as strontium and yttrium, in environmental samples. In this paper, two comprehensive reviews and four automated analytical systems for total and isotopic determination of yttrium and strontium are presented. The developed methods have been applied in the analysis of environmental samples with low concentrations of these analytes. These methodologies have been automated by exploiting flow analysis techniques, such as multi-syringe flow injection analysis (MSFIA), Sequential injection analysis (SIA) and laboratory-on-valve (LOV) systems, achieving a minimal handling and low consumption of samples and reagents, a significant reduction in waste generation and a high frequency of analysis. In the developed methodologies, some spectrometric methods such as ICP-OES and ICP-MS have been implemented as detection techniques instead of radiometric detectors obtaining a fully automated, low-cost and fast yttrium and strontium determinations.

Radiostrontium determination by combination of automated Sr isolation and "on-column" Cherenkov detection using chromatographic model

A novel analytical solution of non-linear chromatography in case of parabolic isotherm for frontal analysis was obtained by combination of Cole-Hopf and Laplace transform. It was used for simulation of strontium capturing on chromatographic column with aim to improve quantitative determination of low-level 90Sr activities. From the experimentally determined breakthrough curves, the retention factor and the number of theoretical plates were calculated using the Glueckauf and Wenzel relations and by fitting the breakthrough curves for the linear isotherm using MatLab. These were used to simulate the breakthrough curves using a parabolic isotherm solution where the non-linear term of the isotherm was taken as a small negative deviation of the retention factor. On the base of theoretical prediction and experimental data, procedure for automated capturing of strontium on chromatographic column with specific dimension and off line "on-column" Cherenkov detection on commercial ultra low-level liquid scintillation counter was developed. It was shown that analytical solution for parabolic isotherm in comparison with solution for linear isotherm gives better prediction of mass of captured Sr on column filled with small amount of Sr resin and SuperLig®620 in case of elevated Sr concentration, even when non-linear effect is not obvious. The solution also makes it possible to predict the mass of resin required for strontium isolation at 100% yield under given conditions. Considering the limited dimensions of the column, and consequently small mass of the resin in them, it resulted in the low efficiency of the columns, which, however, did not affect the yield in real conditions of isolation. The results have shown that the yields achieved after isolation on SuperLig®620 from real samples are 100%. In addition, it is shown that captured 90Sr can be detected through 90Y ingrowth, on column filled with strontium specific resin, with Cherenkov detection efficiency of at least 50%. The efficiency may be enhanced to 60%, depending on parameters which can affect detection efficiency change (type of column, resin type, surrounding solution, etc.). The developed procedures enable quantitative determination of 90Sr in natural water samples with MDAC below 12 mBq l-1 and solid (soil and vegetation) samples with MDAC below 6 Bq kg-1 within 2-3 days. The proposed solution may easily be implemented in radiochemical laboratories where this type of analysis is routinely done within environmental monitoring or other purposes.

Recent Development on Determination of Low-Level 90Sr in Environmental and Biological Samples: A Review

In the context of the rapid development of the world's nuclear power industry, it is vital to establish reliable and efficient radioanalytical methods to support sound environment and food radioactivity monitoring programs and a cost-effective waste management strategy. As one of the most import fission products generated during human nuclear activities, ⁹⁰Sr has been widely determined based on different analytical techniques for routine radioactivity monitoring, emergency preparedness and radioactive waste management. Herein, we summarize and critically review analytical methods developed over the last few decades for the determination of ⁹⁰Sr in environmental and biological samples. Approaches applied in different steps of the analysis including sample preparation, chemical separation and detection are systematically discussed. The recent development of modern materials for ⁹⁰Sr concentration and advanced instruments for rapid ⁹⁰Sr measurement are also addressed.

Sr-Nd-Hf isotopic analysis of reference materials and natural and anthropogenic particulate matter sources: Implications for accurately tracing North African dust in complex urban atmospheres

We present novel chemical separation protocols for isotopic analysis of low mass aliquots (0.3 mg and 25 mg) of several reference materials and real-world samples of relevance to urban airborne particulate matter (PM) investigations. A high-yielding gravity flow column chromatography scheme was developed for facile and quantitative separation of Sr, Nd, and Hf prior to multi collector - inductively coupled plasma - mass spectrometry (MC-ICP-MS). Because we are interested in isolating and accurately quantitating individual anthropogenic and natural aerosol sources in complex industrial/metropolitan atmospheric environments, laboratory protocols were optimized using National Institute of Standards and Technology Standard Reference Material (SRM) 1648a (urban atmospheric PM), SRM 1633b (coal fly ash), and European Commission standards BCR-723 (vehicular road dust), and BCR-2 (basalt rock standard). Sr, Nd, and Hf procedural blanks from column chromatography were low (averaging only 37 pg, 17 pg, 11 pg, respectively) and recoveries were high (averaging 95%, 82%, and 92%, respectively). A volume-adjustment protocol was established using isotope reference solutions SRM 987 (SrCO₃), JNdi (Nd₂O₃), and in-house Hf standards to dilute the dried samples prior to MC-ICP-MS based on projected uncertainties for low sample masses. ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, and ¹⁷⁶Hf/¹⁷⁷Hf isotopic ratios in SRM 1648a, BCR-723, and SRM 1633b are reported for the first time that can serve as provisional reference values. The novel method was used to characterize isotopic ratios and elemental abundances in two anthropogenic urban aerosol sources, namely motor vehicles and petroleum refining using airborne fine PM collected in a vehicular tunnel and fluidized-bed catalytic cracking catalysts, respectively. Two other important mineral-rich urban PM sources, namely soil (i.e., resuspended crustal material) and concrete/cement dust (i.e., construction activity) were also characterized. These are the first isotopic measurements in these environmental compartments and were compared with literature data for long-range transported North African dust, which is a prominent summertime PM source in urban regions in southeastern United States. We demonstrate the capability of coupled Sr-Nd-Hf isotopes to uniquely trace different mineral dust sources with overlapping elemental composition (Sahara-Sahel region, local soil, and concrete/cement) and accurately isolate various urban PM sources demonstrating the superiority of isotopic markers over elemental tracers.

Flow-Injection Methods in Water Analysis-Recent Developments

Widespread demand for the analysis and control of water quality and supply for human activity and ecosystem sustainability has necessitated the continuous improvement of water analysis methods in terms of their reliability, efficiency, and costs. To satisfy these requirements, flow-injection analysis using different detection methods has successfully been developed in recent decades. This review, based on about 100 original research papers, presents the achievements in this field over the past ten years. Various methodologies for establishing flow-injection measurements are reviewed, together with microfluidics and portable systems. The developed applications mostly concern not only the determination of inorganic analytes but also the speciation analysis of different elements, and the determination of several total indices of water quality. Examples of the determination of organic residues (e.g., pesticides, phenolic compounds, and surfactants) in natural surface waters, seawater, groundwater, and drinking water have also been identified. Usually, changes in the format of manual procedures for flow-injection determination results in the improvement of various operational parameters, such as the limits of detection, the sampling rate, or selectivity in different matrices.

Online Solid-Phase Extraction-Inductively Coupled Plasma-Quadrupole Mass Spectrometry with Oxygen Dynamic Reaction for Quantification of Technetium-99

Quantification of pg/L levels (i.e., 0.6 mBq/L) of radioactive technetium-99 (⁹⁹Tc) was achieved within 15 min in the presence of isobaric and polyatomic interference sources such as ruthenium-99 (⁹⁹Ru) and molybdenum hydride (⁹⁸Mo¹H) at 3-11 orders of magnitude higher concentrations. Online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) with oxygen (O₂) dynamic reaction cell (online SPE-ICP-MS-DRC) was shown to be a thorough automatic analytical system, circumventing the need for human handling. At three stepwise separations (SPE-DRC-Q mass filters), we showed that interference materials allowed the coexistence of abundance ratios of 1.5 × 10^-13 and 1.1 × 10^-5 for ⁹⁹Tc/Mo and ⁹⁹Tc/Ru, respectively. A classical mathematical correction using the natural isotope ratio of ⁹⁹Ru/¹⁰²Ru was used to calculate the residues of ⁹⁹Ru. Using this optimized system, a detection limit (DL; 3σ) of ⁹⁹Tc was 9.3 pg/L (= 5.9 mBq/L) for a 50 mL injection and sequential measurements were undertaken at a cycle of 24 min/sample. For the measurement of a lower concentration of ⁹⁹Tc, an AG1-X8 anion-exchange column was used to study 20 L of seawater. Its DL was approximately 1000 times greater than that of previous methods (70.0 fg/L). Thus, this method withstands coexistences of 5.8 × 10^-18 and 3.5 × 10^-9 for ⁹⁹Tc/Mo and ⁹⁹Tc/Ru, respectively. Spike and recovery tests were conducted for environmental samples; the resulting values showed good agreement with the spike applied.

Development of a numerical simulation method for modelling column breakthrough from extraction chromatography resins

A numerical simulation method has been developed to describe the transfer of analytes between solid and aqueous phases and assessed for a commercially available extraction chromatography resin (UTEVA resin). The method employs an ordinary differential equation solver within the LabVIEW visual programming language. The method was initially developed to describe a closed batch system. The differential equations and kinetic rate constants determined under these conditions were then applied to the flow-through column geometry. This was achieved by modelling the resin bed as a series of discrete vertically stacked sections, thereby generating an array of solid and aqueous concentration values. Axial flow was simulated by the advancement of the aqueous phase values by one array position with the value advancing from the final array position representing the column output concentration. An investigation into the observed difference in breakthrough profiles obtained under repeated conditions revealed the relative tolerance of the numerical simulation method to errors in each input parameter. Additional physical processes such as backpressure and leaching of the extractant were considered as an explanation for observed inconsistencies between experimental and simulated datasets. An elution sequence featuring multiple eluents was also simulated, demonstrating that the prediction of analyte separation sequences is possible. The potential to develop the LabVIEW coding into user friendly software with an extendable kinetic database is also discussed. This software will be a useful tool to radiochemists particularly in the development of new analytical methods using automated separation systems.

Synergy of flow injection system and molecular recognition technology products for rapid determination of 89,90Sr and 210Pb

A rapid, automated separation procedure was developed for radioactive strontium and lead isotope determination. This system includes a portable automated system for the preconcentration and sequential elution of targeting isotopes with an Na₂H₂EDTA solution from solid phase extraction materials, AnaLig®Sr-01 and SuperLig®620, provided by IBC Technologies. Strontium and lead were separated from the majority of matrix constituents to obtain pure fractions of Pb and Sr prior to radiometric detection. In case of barium presence, it can also be fully isolated and completely separated from Sr. The automated procedure can be successfully used for preconcentration and separation from high as well as low radioactivity samples. With only a 1 mL column filled with SuperLig®620, it is possible to isolate Sr and Pb with 100% recovery from 1 L to 2 L of sample at a flow rate of up to 10 mL min^-1 within several hours. ^89,90Sr isotopes can be further determined by Cherenkov counting, while ²¹⁰Pb isotopes can be determined by either gamma spectrometry or liquid scintillation counter. The method was tested and validated using certified standard materials and proficiency test samples. The synergy of automated separation and detection procedures enables the determination of the low level activity of ⁹⁰Sr and ²¹⁰Pb in a short time with detection limits of 20 mBq L^-1 for both isotopes. The proposed method enables lower labour costs, minimal size of apparatuses and columns, low separation time, and reduced secondary waste production. The automated procedure may be easily implemented in laboratories worldwide and can also be used at sampling sites.

Supercritical water pretreatment method for analysis of strontium and uranium in soil (Andosols)

Hydrothermal pretreatment of soils (Andosols) from Ibaraki prefecture (Japan) was used to improve methods for monitoring radioactive Sr and U. Calcined samples were pretreated with subcritical or supercritical water (SCW) followed by extraction with 0.5 M HNO₃ solutions. With SCW pretreatment, recoveries of Sr and U were 70% and 40%, respectively. Experimental recoveries obtained can be described by a linear relationship in water density. The proposed method is robust and can lower environmental burden of routine analytical protocols.

Automatic multicommuted flow systems applied in sample treatment for radionuclide determination in biological and environmental analysis

The presence of artificial and natural radioactivity in the environment is currently a topic of great relevance and ecological interest, even in human health issue, due to the increase of different anthropogenic activities. The use of multicommuted flow analysis techniques (e.g. Multi-Syringe Flow Injection Analysis - MSFIA, Lab-On-Valve - LOV and Lab-In-Syringe - LIS) has allowed the automation of radiochemical procedures to separate and preconcentrate radionuclides in environmental and biological samples. In comparison with the manual approach commonly used in routine analysis for radioactivity monitoring, the automation has enabled the development of highly reproducible methodologies with a great analysis frequency. Moreover, during the analytical procedure, the intervention of the analyst is drastically reduced, minimizing the radiological risk. The automation also offers significant advantages such as minimum consumption of time and reagents, reducing the cost and the generation of waste, contributing to the green chemistry. In this review, several multicommuted flow analysis techniques (MSFIA, LOV and LIS) reported in the last decade applied for the development of automatic sample treatment methodologies, used to separate, preconcentrate and quantify ⁹⁰Sr, ⁹⁹Tc, natural U and ²²⁶Ra in biological and environmental samples are described and critically compared.

Dynamic Flow Approaches for Automated Radiochemical Analysis in Environmental, Nuclear and Medical Applications

Automated sample processing techniques are desirable in radiochemical analysis for environmental radioactivity monitoring, nuclear emergency preparedness, nuclear waste characterization and management during operation and decommissioning of nuclear facilities, as well as medical isotope production, to achieve fast and cost-effective analysis. Dynamic flow based approaches including flow injection (FI), sequential injection (SI), multi-commuted flow injection (MCFI), multi-syringe flow injection (MSFI), multi-pumping flow system (MPFS), lab-on-valve (LOV) and lab-in-syringe (LIS) techniques have been developed and applied to meet the analytical criteria under different situations. Herein an overall review and discussion on these techniques and methodologies developed for radiochemical separation and measurement of various radionuclides is presented. Different designs of flow systems with combinations of radiochemical separation techniques, such as liquid-liquid extraction (LLE), liquid-liquid microextraction (LLME), solid phase extraction chromatography (SPEC), ion exchange chromatography (IEC), electrochemically modulated separations (EMS), capillary electrophoresis (CE), molecularly imprinted polymer (MIP) separation and online sensing and detection systems, are summarized and reviewed systematically.

Flow Chemistry in Contemporary Chemical Sciences: A Real Variety of Its Applications

Flow chemistry is an area of contemporary chemistry exploiting the hydrodynamic conditions of flowing liquids to provide particular environments for chemical reactions. These particular conditions of enhanced and strictly regulated transport of reagents, improved interface contacts, intensification of heat transfer, and safe operation with hazardous chemicals can be utilized in chemical synthesis, both for mechanization and automation of analytical procedures, and for the investigation of the kinetics of ultrafast reactions. Such methods are developed for more than half a century. In the field of chemical synthesis, they are used mostly in pharmaceutical chemistry for efficient syntheses of small amounts of active substances. In analytical chemistry, flow measuring systems are designed for environmental applications and industrial monitoring, as well as medical and pharmaceutical analysis, providing essential enhancement of the yield of analyses and precision of analytical determinations. The main concept of this review is to show the overlapping of development trends in the design of instrumentation and various ways of the utilization of specificity of chemical operations under flow conditions, especially for synthetic and analytical purposes, with a simultaneous presentation of the still rather limited correspondence between these two main areas of flow chemistry.

An Automated SeaFAST ICP-DRC-MS Method for the Determination of 90Sr in Spent Nuclear Fuel Leachates

To reduce uncertainties in determining the source term and evolving condition of spent nuclear fuel is fundamental to the safety assessment. ß-emitting nuclides pose a challenging task for reliable, quantitative determination because both radiometric and mass spectrometric methodologies require prior chemical purification for the removal of interfering activity and isobars, respectively. A method for the determination of ⁹⁰Sr at trace levels in nuclear spent fuel leachate samples without sophisticated and time-consuming procedures has been established. The analytical approach uses a commercially available automated pre-concentration device (SeaFAST) coupled to an ICP-DRC-MS. The method shows good performances with regard to reproducibility, precision, and LOD reducing the total time of analysis for each sample to 12.5 min. The comparison between the developed method and the classical radiochemical method shows a good agreement when taking into account the associated uncertainties.

Rapid analytical method of 90Sr in urine sample: Rapid separation of Sr by phosphate co-precipitation and extraction chromatography, followed by determination by triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS)

A rapid analytical method for determining ⁹⁰Sr in urine samples (1-2 L) was developed to assess the internal exposure of workers in a radiological emergency. Strontium in a urine sample was rapidly separated by phosphate co-precipitation, followed by extraction chromatography, and the ⁹⁰Sr activity was determined by triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS). Measurement in the MS/MS mode with an O₂ reaction gas flow rate 1 mL min^-1 showed no tailing of ⁸⁸Sr at m/z = 90 up to 50 mg L^-1 Sr. The interferences of Ge, Se and Zr at m/z = 90 were successfully removed by phosphate co-precipitation, followed by extraction chromatography with a tandem column of Pre-filter, TRU and Sr resin. This analytical method was validated by the results of the analyses of synthetic urine samples (1.2-1.6 L) containing a known amount of ⁹⁰Sr along with 1 mg of each of Ge, Se, Sr and Zr. The turnaround time for Sr purification from the urine sample and the ⁹⁰Sr measurement by ICP-MS/MS was about 10 h. The detection limit of ⁹⁰Sr was approximately 1 Bq per urine sample, which was lower than 15 Bq per urine after a day of intake giving 5 mSv of unplanned exposure of worker limited by Nuclear Regulation Authority of Japan.

A review of measurement methodologies and their applications to environmental 90Sr

The high fission yield product ⁹⁰Sr has been released into the environment in large amounts due to nuclear weapon tests, nuclear power plant accidents, and nuclear fuel reprocessing industries. It is a long half-life radionuclide (28.9 y), with serious consequences to human health; hence, it is desirable to perform routine monitoring of ⁹⁰Sr in environmental samples. Many ⁹⁰Sr radiometric methods have been developed in the past decades, which generally require complicated separation and purification steps with a relatively long analytical time. Moreover, some nominally rapid methods usually have high method detection limits, making them unsuitable for the environmental samples with ultra-low ⁹⁰Sr levels. In this review, some rapid and practical methods for ⁹⁰Sr routine monitoring are summarized. Different sample pretreatments and major purification procedures for ⁹⁰Sr developed in recent years, such as variable digestion methods and extraction chromatography using Sr resin or DGA resin, are especially described. Additionally, four conventional and widely used β spectrometric and mass spectrometric methods are demonstrated. Finally, ⁹⁰Sr evaluations focusing on contaminated soil and seawater samples collected after the Fukushima Daiichi Nuclear Power Plant accident, and ⁹⁰Sr application as tracers for environmental behavior are also reviewed.

Automated 90Sr Separation and Preconcentration in a Lab-on-Valve System at Ppq Level

A quick, automated and portable system for the separation and determination of radiostrontium in aqueous samples, using Sr-resin and multi sequential flow injection analysis, has been developed. The concentrations of radioactive strontium were determined by flow scintillation counting, allowing for on-line and also on-site determination. The proposed system can determine radioactive strontium at industrial relevant levels without further modification using overall analysis time of less than 10 min per aqueous sample. The limit of the detection is 320 fg·g^-1 (1.7 Bq/g).

A comparison study on the use of Dowex 1 and TEVA-resin in determination of 99Tc in environmental and nuclear coolant samples in a SIA system with ICP-MS detection

This work refers to a comparative study of sorbents widely used in determinations of ⁹⁹Tc such as TEVA resin and Dowex 1. Despite having a similar functional group of quaternary amines, both materials represent different chromatographic methods-extraction (TEVA resin) and anion exchange (Dowex 1)-which provides a diverse range of their properties significant in determination of ⁹⁹Tc in flow conditions. The comparative tests, carried out in a SIA-LOV (Sequential Injection Analysis-Lab-on-Valve) system combined with mass spectrometric (ICP-MS) detection, considered several factors that are crucial from the standpoint of resin´s utility such as sorption capacity, durability, or selectivity, critical in ⁹⁹Tc separation from interferences. The developed and optimized analytical procedure based on the application of the TEVA resin provided determinations of ⁹⁹Tc at minimum detectable limit (MDL) 6.00 mBq L^-1 in 50 min and has been successfully employed in analyses of samples from nuclear industrial and research units (reactor coolant and sewage) as well as from the river surrounding the nuclear reactor. The method proved to be sufficient for routine analysis of water samples in accordance with EPA standards. The reliability of the method was confirmed in the analysis of the BH standard provided by the NPL for inter-laboratory proficiency tests. The ⁹⁹Tc recovery for all real samples was evaluated as 80-100%.

Sequential Injection Analysis System Exploiting On-line Solid-phase Extraction for the Determination of Strontium and Nickel by Microwave Plasma Atomic Emission Spectrometry

A sequential flow-based analysis system with on-line solid-phase extraction (SPE) columns coupled to microwave plasma atomic emission spectrometry (MP-AES) was developed for strontium and nickel determination. Crown ether chromatographic resin and dimethylglyoxime polymethacrylate resin were used for strontium and nickel retention under acidic and basic conditions, respectively; eluted with a nitric acid solution in both cases followed by MP-AES detection. The calculated detection limits were 0.25 μg L^-1 for strontium and 3.56 μg L^-1 for nickel.