Dominic Larivière

Automated flow injection system using extraction chromatography for the determination of plutonium in urine by inductively coupled plasma mass spectrometry

An automated system for on-line pre-concentration, separation and detection of plutonium in a urine sample was developed, based on the coupling of a multi-solvent delivery system, remotely-controlled switching modules, and an inductively coupled plasma mass spectrometer (ICP-MS). Effective separation between spectral and non-spectral interferences and Pu was performed viaTEVA selective extraction chromatography. Pu elution from the resin was performed using 0.01 M (NH4)2C2O4, directed to the ICP-MS through a switching module controlled by the multi-solvent delivery unit. The automated flow injection system (AFIS) enables the quantification of Pu isotopes for urinalysis at the sub-mBq L−1 range (DL: 0.21(239Pu), 0.19(240Pu) mBq L−1) in less than 15 min, with a chemical recovery exceeding 70%. The simplicity, speed, and automation of this approach make it attractive for radiological emergency response, especially considering its high daily sample throughput (>80). This throughput is the result of the faster flow rate used for the separation (up to 3 mL min−1) and the reusability of the extraction resin. If a calcium phosphate co-precipitation step is performed prior to loading the sample onto the TEVA resin, improvement in pre-concentration capacity is possible, making the AFIS usable for the assessment of occupational exposures.

Determination of radium-226 in environmental samples by inductively coupled plasma mass spectrometry after sequential selective extraction

A sequential selective extraction procedure for the pre-concentration of radium-226 in complex environmental matrices (i.e. uranium ores and biological samples) was developed and used in conjunction with an inductively coupled plasma collision cell quadrupole mass spectrometer (ICP-CC-Q-MS). In order to measure Ra-226 adequately by mass spectrometry, potential polyatomic interferences created by Ba, Ce, La, Nd, Pb and Sr (88Sr138Ba, 87Sr139La, 86Sr140Ce, 40Ar40Ar146Nd, 18O208Pb), present at high concentrations in the matrix, had to be removed prior to the measurements. A combination of Sr*Spec and UTEVA cartridges was used to separate U, Sr, Pb and Ba from Ra. Subsequently, the eluate containing Ra was loaded onto a Ln cartridge to pre-concentrate Ra and separate it from interference created by Nd, La, and Ce. The entire extraction procedure took a few minutes compared to other Ra-226 chromatographic separations that take several hours. Using this protocol, an absolute detection limit of 0.02 fg (0.75 mBq) was obtained using less than 4 mg of solid sample or 25 mL of liquid sample. This procedure is very robust and can be used to analyze Ra-226 in a variety of matrices in the presence of several interferences.

Cloud point extraction of uranium using H2DEH[MDP] in acidic conditions

A procedure has been developed for the cloud point extraction (CPE) of uranium (VI) using H2DEH[MDP] (P,P-di(2-ethylhexyl) methanediphosphonic acid) with inductively coupled plasma coupled to mass spectrometry (ICP-MS). The method is based on the modification of the cloud point temperature using cetyl trimethyl ammonium bromide (CTAB) and KI. Optimal conditions of extraction were found using a cross-optimization of every parameter (non-ionic and ionic surfactant concentrations, chelating agent concentration, pH and the extraction, and phase separation temperatures). Furthermore, the figures of merit of the methodology were assessed (limit of detection, limit of quantification, recovery, sensibility, and linear range) and are reported. Quantitative extraction (99 ± 0.5%) was obtained in drinking water samples over a wide range of uranium concentrations. The approach was also validated using drinking (SCP EP-L-3 and SCP EP-H-3), and wastewater (SCP EU-L-3) certified materials. Interferences from most critical anions and cations were evaluated to determine the reliability of the method. The proposed method showed robustness since its performance is maintained over a wide range of pH and metal ion concentrations.

Direct determination of 226Ra in environmental matrices using collision cell inductively coupled plasma mass-spectrometry

Direct determination of 226Ra in complex environmental matrices (biological and uranium ore samples) by collision-cell inductively coupled plasma mass-spectrometry was investigated. Possible polyatomic interferences were studied and their effects on 226Ra measurements were determined. The instrumental conditions for optimal signal-to-noise ratio for 226Ra were found. Concentrations of 226Ra in certified reference samples were measured using both external calibration and standard addition approaches. The best precision was obtained by applying standard additions. The absolute detection limit for 226Ra was 1 fg with optimal gas flow rates for the collision cell of 7 ml.min-1 for helium and 4 ml.min-1 for hydrogen.

Sequential automated fusion/extraction chromatography methodology for the dissolution of uranium in environmental samples for mass spectrometric determination.

An improved methodology has been developed, based on dissolution by automated fusion followed by extraction chromatography for the detection and quantification of uranium in environmental matrices by mass spectrometry. A rapid fusion protocol (<8 min) was investigated for the complete dissolution of various samples. It could be preceded, if required, by an effective ashing procedure using the M4 fluxer and a newly designed platinum lid. Complete dissolution of the sample was observed and measured using standard reference materials (SRMs) and experimental data show no evidence of cross-contamination of crucibles when LiBO(2)/LiBr melts were used. The use of a M4 fusion unit also improved repeatability in sample preparation over muffle furnace fusion. Instrumental issues originating from the presence of high salt concentrations in the digestate after lithium metaborate fusion was also mitigated using an extraction chromatography (EXC) protocol aimed at removing lithium and interfering matrix constituants prior to the elution of uranium. The sequential methodology, which can be performed simultaneously on three samples, requires less than 20 min per sample for fusion and separation. It was successfully coupled to inductively coupled plasma mass spectrometry (ICP-MS) achieving detection limits below 100 pg kg(-1) for 5-300 mg of sample.

Hyphenation of flow injection on-line preconcentration and ICP-MS for the rapid determination of 226Ra in natural waters

A novel, sensitive, and rapid method is developed for the preconcentration/separation of 226Ra in natural waters using a flow injection (FI) design based on a sequential on-line ion exchange preconcentration coupled with ICP-MS. 226Ra is extracted using an Ln resin (HDEHP) from the sample at pH 10.6 in the presence of ethylenediamine tetraacetic acid (EDTA) diammonium salt, whereas Ca and Mg, which form stable complexes with EDTA, are not retained on the column. Quantitative elution of 226Ra from the Ln resin is achieved using 5 M HNO3. The separation of Ra from Ba and Sr is subsequently performed by the selective retention of Sr and Ba on an Sr*Spec resin, placed between the Ln resin and the Apex-Q system. In addition to being accurate and rapid for 226Ra determination, this method is effective in eliminating spectral (88Sr138Ba) and non-spectral (Ca, Mg) interferences. Using a 20 mL sample, a detection limit (3σ) of 457 fg L−1 (16.92 mBq L−1) was obtained with a sample throughput of 3.5 samples h−1. The precision for 6 replicate measurements of 5 pg L−1 (185.18 mBq L−1) 226Ra was better than 4%. The method was applied to the analysis of natural waters, where the concentration of 226Ra was found to be in the range 1.2 to 2.4 pg L−1 (44.4 to 88.8 mBq L−1), lower than the maximum acceptable concentration (MAC) for 226Ra of 16.2 pg L−1 (600 mBq L−1), recommended in the Guideline for Canadian Drinking Water Quality.

Radiostrontium and radium analysis in low-level environmental samples following a multi-stage semi-automated chromatographic sequential separation

Strontium isotopes, (89)Sr and (90)Sr, and (226)Ra being radiotoxic when ingested, are routinely monitored in milk and drinking water samples collected from different regions in Canada. In order to monitor environmental levels of activity, a novel semi-automated sensitive method has been developed at the Radiation Protection Bureau of Health Canada (Ottawa, Canada). This method allows the separation and quantification of both (89)Sr and (90)Sr and has also been adapted to quantify (226)Ra during the same sample preparation procedure. The method uses a 2-stage purification process during which matrix constituents, such as magnesium and calcium that are rich in milk, are removed as well as the main beta-interferences (e.g., (40)K, (87)Rb, (134)Cs, (137)Cs, and (140)Ba). The first purification step uses strong cation exchange (SCX) chromatography with commercially available resins. In a second step, fractions containing the radiostrontium analytes are further purified using high-performance ion chromatography (HPIC). While (89)Sr is quantified by Cerenkov counting immediately after the second purification stage, the same vial is counted again after a latent period of 10-14 days to quantify the (90)Sr activity based on (90)Y ingrowth. Similarly, the activity of (226)Ra, which is separated by SCX only, is determined via the emanation of (222)Rn in a 2-phase aqueous/cocktail system using liquid scintillation counting. The minimum detectable concentration (MDC) for (89)Sr and (90)Sr for a 200 min count time at 95% confidence interval is 0.03 and 0.02 Bq/L, respectively. The MDC for (226)Ra for a 100 min count time is 0.002 Bq/L. Semi-annual intercomparison samples from the USA Department of Energy Mixed Analyte Performance Evaluation Program (MAPEP) were used to validate the method for (89)Sr and (90)Sr. Spiked water samples prepared in-house and from International Atomic Energy Agency (IAEA) were used to validate the (226)Ra assay.

Determination of neptunium in environmental samples by extraction chromatography after valence adjustment

Neptunium(V) ions are unstable in acid media, which limits their extraction on chromatographic resins. We developed a novel analytical method to measure Np by either α-spectrometry or inductively coupled plasma mass spectrometry (ICP-MS) after extraction chromatography as Np(VI). We investigated the reactivity of various oxidizing reagents, and determined the retention capacity of Np(IV, V, and VI) on various extraction chromatographic supports. A simple method using two UTEVA resins was used to rapidly detect Np in soil and sediment samples.

Selective recovery of rare earth elements using chelating ligands grafted on mesoporous surfaces

Nowadays, rare earth elements (REEs) and their compounds are critical for the rapidly growing advanced technology sectors and clean energy demands. However, their separation and purification still remain challenging. Among different extracting agents used for REE separation, the diglycolamide (DGA)-based materials have attracted increasing attention as one of the most effective extracting agents. In this contribution, a series of new and element-selective sorbents were generated through derivatisation of the diglycolamide ligand (DGA), grafted to mesoporous silica and tested for the separation of rare earth elements. It is shown that, by tuning the ligand bite angle and its environment, it is possible to improve the selectivity towards specific rare earth elements.

Multi-dimensional extraction chromatography of actinides for alpha and mass spectrometry

A multi-dimensional (MD) separation method using extraction chromatography for the analysis of actinides in environmental samples was developed and tested for alpha spectrometry and ICP-MS. Actinides (Th, U, Np, Pu and Am) were separated into individual fractions using two resins (TEVA/DGA), after valence adjustment initially in 9 M HCl, and in the second dimension, in 3 M HNO3, in order to remove interferences and enable their proper identification and quantification. High separation purity for Th, U, Np, Pu and Am (respectively 98, 100, 94, 98 and 99 ± 2%) were obtained. Reusability of the resins was also demonstrated (≤9). The MD separation scheme was tested on spiked soil and sediment samples as well as on certified reference material (CRM-IAEA-384) dissolved using automated lithium metaborate fusion. Results obtained for actinides by alpha spectrometry and ICP-MS were in excellent agreement with those expected (absolute relative bias: 1.9–23%) and demonstrate the complementarily of the two types of detection.