High-Throughput Determination of Ultratrace Actinides in Urine by In-Line Extraction Chromatography Combined with Quadrupole Inductively Coupled Plasma Mass Spectrometry (EC-ICP-MS).

Determining actinides in urine is vital for occupational exposure monitoring and radiological emergency response because of the toxicity and radiological dose effects of actinides on human health. Traditional radiochemistry analytical methods used to determine actinide concentrations in urine are time-consuming (sample analysis takes several days) and are hindered by a variety of technical and instrumentation-related obstacles. A high-throughput, fully automated, precise, and accurate in-line method was developed for determining five actinides (241Am, 239Pu, 237Np, 232Th, and 238U) at ng/L levels in urine using extraction chromatography combined with quadrupole inductively coupled plasma mass spectrometry (EC-ICP-MS). In this method, the five actinides were successfully separated with the required sensitivity, peak shape, and resolution using a simplified single Eichrom TRU column with a Dionex ICS-5000 system. The separated actinides were subsequently injected into an in-line PerkinElmer (PE) NexION 300D ICP-MS for quantitative determination. The sample-to-sample run time was 23 min for automatic chemical separation and quantification using only 0.5 mL of urine. The limits of detection (LOD) obtained using this method were 0.015, 0.022, 0.039, 4.5, and 2.4 ng/L for 241Am, 239Pu, 237Np, 232Th, and 238U, respectively. The method routinely had a chemical yield of >84% as well as a linearity (R2) coefficient of ≥0.999 for the calibrators. The method proved to be rapid, reliable, and effective for actinide quantification in urine and therefore is appropriate for radiological emergency response incidents.

Rapid procedure for actinides and 90Sr analysis in emergency urine spot samples applied in the GHSI-RNWG emergency intercomparison exercise.

A rapid radiochemical separation method for quantification of 90Sr, plutonium, americium, curium, uranium and thorium isotopes in urine spot samples has been developed. The validation and suitability of the method has been tested in the emergency intercomparison exercise organised by the Global Health Security Initiative/Radio-Nuclear Threats Working Group. Excellent results were obtained with bias of -0.07 (239Pu) and -0.11 (90Sr). CIEMAT Laboratory also fulfilled the established reporting schedule and submitted the results within 72 hours, as required.

RETROSPECTIVE METHOD VALIDATION AND UNCERTAINTY ESTIMATION FOR ACTINIDES DETERMINATION IN EXCRETA BY ALPHA SPECTROMETRY.

Two essential technical requirements of ISO 17025 guide for accreditation of testing and calibration laboratories are the validation of methods and the estimation of all sources of uncertainty that may affect the analytical result. Bioelimination Laboratory from Radiation Dosimetry Service of CIEMAT (Spain) uses alpha spectrometry to quantify alpha emitters (Pu, Am, Th, U and Cm isotopes) in urine and faecal samples from workers exposed to internal radiation. Therefore and as a step previous to achieving the ISO 17025 accreditation, the laboratory has performed retrospective studies based on the obtained results in the past few years to validate the analytical method. Uncertainty estimation was done identifying and quantifying all the contributions, and finally the overall combined standard uncertainty was calculated.

Thin extractive membrane for monitoring actinides in aqueous streams.

Alpha spectrometry and solid state nuclear track detectors (SSNTDs) are used for monitoring ultra-trace amount of alpha emitting actinides in different aqueous streams. However, these techniques have limitations i.e. alpha spectrometry requires a preconcentration step and SSNTDs are not chemically selective. Therefore, a thin polymer inclusion membrane (PIM) supported on silanized glass was developed for preconcentraion and determination of ultra-trace concentration of actinides by α-spectrometry and SSNTDs. PIMs were formed by spin coating on hydrophobic glass slide or solvent casting to form thin and self-supported membranes, respectively. Sorption experiments indicated that uptakes of actinides in the PIM were highly dependent on acidity of solution i.e. Am(III) sorbed up to 0.1 molL(-1) HNO3, U(VI) up to 0.5 molL(-1) HNO3 and Pu(IV) from HNO3 concentration as high as 4 molL(-1). A scheme was developed for selective sorption of target actinide in the PIM by adjusting acidity and oxidation state of actinide. The actinides sorbed in PIMs were quantified by alpha spectrometry and SSNTDs. For SSNTDs, neutron induced fission-fragment tracks and α-particle tracks were registered in Garware polyester and CR-39 for quantifications of natural uranium and α-emitting actinides ((241)Am/(239)Pu/(233)U), respectively. Finally, the membranes were tested to quantify Pu in 4 molL(-1) HNO3 solutions and synthetic urine samples.

[Interest and limits of inductively coupled plasma mass spectrometry (ICP-MS) for urinary diagnosis of radionuclide internal contamination]. / Intérêt et limites du couplage plasma induit par haute fréquence - spectrométrie de masse (ICP-MS) pour le diagnostic urinaire d'une contamination interne par un radionucléide.

After a review of radiometric reference methods used in radiotoxicology, analytical performance of inductively coupled plasma mass spectrometry (ICP-MS) for the workplace urinary diagnosis of internal contamination by radionuclides are evaluated. A literature review (covering the period from 2000 to 2012) is performed to identify the different applications of ICP-MS in radiotoxicology for urine analysis. The limits of detection are compared to the recommendations of the International commission on radiological protection (ICRP 78: "Individual monitoring for internal exposure of workers"). Except one publication describing the determination of strontium-90 (ß emitter), all methods using ICP-MS reported in the literature concern actinides (α emitters). For radionuclides with a radioactive period higher than 10(4) years, limits of detection are most often in compliance with ICRP publication 78 and frequently lower than radiometric methods. ICP-MS allows the specific determination of plutonium-239 + 240 isotopes which cannot be discriminated by α spectrometry. High resolution ICP-MS can also measure uranium isotopic ratios in urine for total uranium concentrations lower than 20 ng/L. The interest of ICP-MS in radiotoxicology concerns essentially the urinary measurement of long radioactive period actinides, particularly for uranium isotope ratio determination and 239 and 240 plutonium isotopes discrimination. Radiometric methods remain the most efficient for the majority of other radionuclides.

An emergency bioassay method for actinides in urine.

A rapid bioassay method has been developed for the sequential measurements of actinides in human urine samples. The method involves actinide separation from a urine matrix by co-precipitation with hydrous titanium oxide (HTiO), followed by anion exchange and extraction chromatography column purification, and final counting by alpha spectrometry after cerium fluoride micro-precipitation. The minimal detectable activities for the method were determined to be 20 mBq L(-1) or less for plutonium, uranium, americium and curium isotopes, with an 8-h sample turn-around time. Spike tests showed that this method would meet the requirements for actinide bioassay following a radiation emergency.

Rapid methods for the isolation of actinides Sr, Tc and Po from raw urine.

Rapid methods for the isolation and analysis of individual actinides (Th, U, Pu, Am/Cm) and Sr, Tc and Po from small volumes of raw urine have been developed. The methods involve acidification of the sample and the addition of aluminum nitrate or aluminum chloride salting-out agent prior to isolation of the desired analyte using a tandem combination of prefilter material and extraction chromatographic resin. The method has been applied to the separation of individual analytes from spiked urine samples. Analytes were recovered in high yield and radionuclide purity with separation times as low as 30 min. The chemistry employed is compatible with automation on the ARSIIe instrument.

Separation of actinides using capillary extraction chromatography-inductively coupled plasma mass spectrometry.

Trace levels of actinides have been separated on capillary extraction chromatography columns. Detection of the actinides was achieved using an inductively coupled plasma mass spectrometer, which was coupled with the extraction chromatography system. In this study, we compare 30-cm long, 4.6 mm i.d. columns to capillary columns (750 microm i.d.) with lengths from 30 cm up to 150 cm. The columns that were tested were packed with TRU resin. We were able to separate a mixture of five actinides ((232)Th, (238)U, (237)Np, (239)Pu, and (241)Am). This work has application to rapid bioassay as well as automated separations of actinide materials.

Rapid determination of actinides in urine by inductively coupled plasma mass spectrometry and alpha spectrometry: a hybrid approach.

A new rapid separation method that allows separation and preconcentration of actinides in urine samples was developed for the measurement of longer lived actinides by inductively coupled plasma mass spectrometry (ICP-MS) and short-lived actinides by alpha spectrometry; a hybrid approach. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration, if required, is performed using a streamlined calcium phosphate precipitation. Similar technology has been applied to separate actinides prior to measurement by alpha spectrometry, but this new method has been developed with elution reagents now compatible with ICP-MS as well. Purified solutions are split between ICP-MS and alpha spectrometry so that long- and short-lived actinide isotopes can be measured successfully. The method allows for simultaneous extraction of 24 samples (including QC samples) in less than 3h. Simultaneous sample preparation can offer significant time savings over sequential sample preparation. For example, sequential sample preparation of 24 samples taking just 15 min each requires 6h to complete. The simplicity and speed of this new method makes it attractive for radiological emergency response. If preconcentration is applied, the method is applicable to larger sample aliquots for occupational exposures as well. The chemical recoveries are typically greater than 90%, in contrast to other reported methods using flow injection separation techniques for urine samples where plutonium yields were 70-80%. This method allows measurement of both long-lived and short-lived actinide isotopes. (239)Pu, (242)Pu, (237)Np, (243)Am, (234)U, (235)U and (238)U were measured by ICP-MS, while (236)Pu, (238)Pu, (239)Pu, (241)Am, (243)Am and (244)Cm were measured by alpha spectrometry. The method can also be adapted so that the separation of uranium isotopes for assay is not required, if uranium assay by direct dilution of the urine sample is preferred instead. Multiple vacuum box locations may be set-up to supply several ICP-MS units with purified sample fractions such that a high sample throughput may be achieved, while still allowing for rapid measurement of short-lived actinides by alpha spectrometry.

Uncertainties in estimation of intakes of actinides for dose reconstruction cases.

Intakes and doses arising from exposure to actinides must be reconstructed from historical bioassay data for the purposes of worker compensation and for epidemiology studies. The usual default assumption is that a series of urine activities is the result of a constant chronic intake. In reality, the urine activities will most likely arise from a random sequence of discrete intakes. In order to investigate the accuracy of the constant chronic assumption, we have created virtual urine datasets using Monte Carlo modelling and these were used as input to the code IMBA(1). Comparisons of estimated intakes with those used as input allow the uncertainties in the procedure to be estimated. The effects of incorrect assumptions about the scattering factors, activity median aerodynamic diameter (AMAD) and solubility can also be examined. The results show that the constant chronic assumptions leads to remarkably reliable estimates of intake, even for datasets generated by just a few intakes per year. The estimate of intake is fairly robust against mis-assignment of scattering factor and AMAD. However, as is well-known, the correct assignment of solubility is crucial in obtaining reliable estimates of intake and dose.

Study of the U/Am separation with supported calix[6]arene in the aim of urinary actinides analysis.

The aim of this work is to propose an alternative radiochemical procedure for the analysis of U, Pu and Am in urine, which is one of the controls used to monitor workers exposed to risk of internal contamination with actinides. Previous studies have demonstrated the extraction efficiency of these molecules towards uranium and plutonium, the affinity of calix[6]arenes bearing hydroxamic acid groups (LHH3) and carboxylic groups (LCH3) towards americium were studied in this paper by solvent extraction. The results showed that LHH3 and LCH3 have a very good affinity for americium and enhance the possibility of separating Pu from U and Am. Experiments were performed to perfect the separation of U/Am. The immobilisation of these calixarenes on polymer supports was also investigated for routine applications. Supported calixarenes LCH3 and LHH3 presented the same performances as those obtained in a liquid-liquid system and, hence, are a promising system for the analysis of actinides. These molecules and their uses have been protected (patent pending).

Potentialities of mass spectrometry (ICP-MS) for actinides determination in urine.

The applicability of inductively coupled plasma-mass spectrometry (ICP-MS) for determining actinides in urine was investigated. Performances of ICP-MS including detection limit and analysis time were studied and compared with alpha spectrometry performances. In the field of individual monitoring of workers, the comparison chart obtained in this study can be used as a guide for medical laboratories to select the most adequate procedure to be carried out depending on the case in question (the radioisotope to be measured, the required sensitivity, and the desired response time).

New purification protocol for actinide measurement in excreta based on calixarene chemistry.

The determination of actinides concentration level in excreta, mainly urine is currently carried out to monitor people potentially exposed to alpha emitters. To measure actinides in such samples, specific analytical protocols have been set up. The chemical purification uses different chromatographic columns to selectively separate the actinides and each fraction, after electroplating, is measured by alpha spectrometry. To reach 1 mBq l(-1) of U, Pu or Am using these protocols, 6 days equally distributed between the chemical purification and the measurement are necessary. The protocol proposed here is based on a single extractant, the 1,3,5-trimethoxy-2,4,6-tricarboxy-p-tert-butylcalix[6]arene, used to selectively separate U, Pu and Am from the urinary matrix prior to be measured. Using this analytical protocol, U and Pu are quantitatively and selectively recovered in two different acidic backextraction solutions whereas Am is quantitatively and selectively recovered in the organic phase. Furthermore, the purification stage is considerably shortened. The uranium and plutonium amounts are measured in aqueous phases using alpha spectrometry or inductively coupled plasma-mass spectrometry, whereas Am is measured in the organic phase using alpha liquid scintillation (photon/electron-rejecting alpha liquid scintillation).

Method for actinides and Sr-90 determination in urine samples.

The primary goal of radiation protection in decommissioning and decontamination of the old nuclear facilities of the CIEMAT is to monitor and minimize exposure of personnel. Monitoring programs include determination of actinides and 90Sr in biological samples. A technique for the sequential measurement of low levels of 239Pu, 241Am and 90Sr in urine samples has been developed. The method involves coprecipitation of these radionuclides as phosphates from bulk urine sample. Separation of Plutonium is carried out using a conventional anion exchange technique. Americium and strontium isolations are achieved sequentially by chromatographic extraction (Tru.Spec and Sr.Spec columns) from the load and rinse solutions coming from the anion exchange column. Plutonium and Americium measurements are performed by alpha spectrometry. The mean recovery obtained is 80% and the detection limit for 24 h urine sample (1.41) is 0.6 mBq L-1. 90Sr determination is made by liquid scintillation counting. The detection limit in this case is 1.1 E-01 Bq/L.