A rapid isotope dilution inductively coupled plasma mass spectrometry procedure for uranium bioassay

Negative health effects of uranium taken into the human body are related to both the chemical toxicity of the metal and its radioactivity. A simple and reliable isotope dilution ICP-MS uranium bioassay technique was developed in this study. Use of this technique at Los Alamos National Laboratory has not been previously described. Dilute urine was introduced to a Perkin Elmer DRC II quadrupole ICP-MS via a PFA high solids nebulizer and a PFA cyclonic spray chamber cooled to 2 °C. Urine samples acidified, digested, and diluted 5× generate a solution that is roughly 10% HNO₃ that can be analyzed by ICP-MS to measure uranium concentrations >54 pg/mL and uranium isotopic ratios with high enough precision and accuracy to determine if the uranium in a urine sample is natural. A three-stage rinsing routine is run between each sample to minimize urine salt deposition and uranium memory effects. Regular use of this rinsing routine minimizes instrumental drift and has produced a running ²³⁸U background of <7 cps.     

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 3 h. 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 6 h 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. ²³⁹Pu, ²⁴²Pu, ²³⁷Np, ²⁴³Am, ²³⁴U, ²³⁵U and ²³⁸U were measured by ICP-MS, while ²³⁶Pu, ²³⁸Pu, ²³⁹Pu, ²⁴¹Am, ²⁴³Am and ²⁴⁴Cm 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.     

Comparison of ICP-MS and SIMS techniques for determining uranium isotope ratios in individual particles

The determination of uranium isotope ratios in individual particles is of great importance for nuclear safeguards. In the present study, an analytical technique by inductively coupled plasma mass spectrometry (ICP-MS) with a desolvation sample introduction system was applied to isotope ratio analysis of individual uranium particles. In ICP-MS analysis of individual uranium particles with diameters ranging from 0.6 to 4.2 μm in a standard reference material (NBL CRM U050), the use of the desolvation system for sample introduction improved the precision of ²³⁴U/²³⁸U and ²³⁶U/²³⁸U isotope ratios. The performance of ICP-MS with desolvation was compared with that of a conventionally used method, i.e., secondary ion mass spectrometry (SIMS). The analysis of test swipe samples taken at nuclear facilities implied that the performance of ICP-MS with desolvation was superior to that of SIMS in a viewpoint of accuracy, because the problems of agglomeration of uranium particles and molecular ion interferences by other elements could be avoided. These results indicated that ICP-MS with desolvation has an enough ability to become an effective tool for nuclear safeguards.     

Spectrophotometric Determination of Uranium(VI) with Chlorophosphonazo-mN by Flow Injection Analysis

Abstract

A sensitive and selective spectrophotometric flow injection analysis (FIA) method with chlorophosphonazo-mN has been developed for the determination of uranium(VI) in standard ore samples. Most of interfering ions are effectively eliminated by the masking reagent of diethylenetriaminepentaacetic acid (DTPA). In the U(VI)-chlorophosphonazo-mN system, the maximum absorption wavelength is at 680 nm and Beer's law is obeyed in the range of 1 to 15 μg ml^?1. The correlation coefficient of the calibration curve is 0.9998, the sampling frenquency is 60 h^?1, and the detection limit for uranium(VI) is 0.5 μg ml^?1. The composition of the U(VI)-chlorophosphonazo-nN complex was established to be 1:2 by flow-through spectrophotometric and conventional molar ratios methods.     

Determination of Mercury in Urine and Seawater by Flow Injection Vapor Generation Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

A simple and inexpensive laboratory-built vapor generator was used with inductively coupled plasma mass spectrometry (ICP-MS) for the determination of mercury in urine and seawater samples. The applications of vapor generation ICP-MS alleviated the non-spectroscopic interferences and the sensitivity problem of mercury determination encountered when the conventional pneumatic nebulizer was used for sample introduction. The concentration of mercury was determined by isotope dilution method. The isotope ratio of mercury was calculated from the peak areas of each injection peak. The repeatability of the peak areas and isotope ratio determinations of seven consecutive injections of 1 ng mL^?1 Hg solution were 2.3% and 2.2%, respectively. This method has a detection limit of 0.07 ng mL^?1 for mercury. This method was applied to determine mercury in a CASS-3 nearshore seawater reference sample, NASS-4 open ocean seawater reference sample, NIST SRM 2670 freeze-dried urine reference sample and several urine and seawater samples collected from National Sun Yat-Sen University. The results for the reference samples agreed satisfactorily with the reference values. Results for other samples analyzed by the isotope dilution method and the method of standard additions agreed satisfactorily. Precision was better than 10% for most of the determinations.     

Determination of thorium and uranium in activated concrete by inductively coupled plasma mass spectrometry after anion-exchange separation

A sensitive analytical method was established for the determination of Th and U in activated concrete samples. The method combines an anion-exchange separation step with an ICP-MS determination technique. In the ICP-MS measurement, a few μg mL^–1 of Al and Ca, a few ng mL^–1 of Mn, La, Ce, Nd and Pb and pg mL^–1 amounts of Li, Zr, Nb and Ba coexisting in the anion-exchange fraction of Th and U did not interfere. No adverse interference effects were observed in real sample analyses. The obtained detection limits (3σ, n = 10) of Th and U were 2.3 and 1.8 pg mL^–1, respectively. The analytical precisions for ca. 5 μg g^–1 Th and ca. 1 μg g^–1 U in real activated concrete samples were equally less than 7% RSD. The accuracies obtained by the analysis of GSJ rock standard samples were –18.1 to 0.4% for the Th determination and –14.0 to –5.7% for the U determination. The method uses the conventional absolute calibration curve. The internal standard calibration is unnecessary.     

Determination of ultra-trace levels of cobalt by ion chromatographic separation and chemiluminescence detection

A luminol chemiluminescence detection/flow injection analysis technique coupled with ion chromatography (IC) has been examined for the selective determination of cobalt (II) at pg ml^?1 levels. A barium chloride solution was used as an eluent in the IC to separate cobalt(II) from interferents. When a 100-μ1 sample injection volume was used, the detection limit was 1.0 pg ml^?1 cobalt; the minimum detectable amount of cobalt was 100 fg. The calibration graph was linear above 10 pg ml^?1 and the linear dynamic range extended over six orders of magnitude. The relative standard deviation for ten replicate measurements of 30 pg ml^?1 cobalt was 3.8%. The results of the analysis of a synthetic sample corresponding to a boiling-water reactor coolant and some commercially available copper(II) standard solutions are given.     

Determination of uranium in process stream solutions from uranium extraction plant employing energy dispersive X-ray fluorescence spectrometry

Energy dispersive X-Ray fluorescence (EDXRFS) method is developed and standardized for the determination of uranium on routine basis in various process stream solutions, covering a vide range of concentrations from 0.1 to 400?g?L^?1, from an Uranium Extraction Plant at Nuclear Fuel Complex. The method has been applied to aqueous stream samples. Except for dilution, no much sample preparation was involved in the analysis and accordingly the experimental parameters were optimized. The calibration curve in the range of 0.1?C10?g?L^?1 of U was drawn manually using synthetic standard solutions prepared from U₃O₈ powder and L?? (13.61?keV) line of uranium was used for the measurements. The results from EDXRFS method are compared with other methods and are found to be in good agreement. The EDXRFS measurements carried over a range of 0.1?C350?g?L^?1 of uranium have shown a RSD of ±1?C5%. Also, the limitations of reported methods in literature and the advantages of present method are highlighted in the paper.     

Determination of Pu concentration and its isotope ratio in Japanese soils by HR-ICP-MS

High resolution-type ICP-MS was applied to the analysis of ²³⁹Pu and ²⁴⁰Pu in soil samples. The detection limit of Pu was about 0.001 pg^.ml^-1 (ppt) in the sample solution or about 0.0005 pg in a total sample. This method was used to determine concentrations of Pu and its isotopic ratios in several soil samples collected from different areas in Japan. Concentrations of Pu in surface soils collected from forests were significantly higher than those in soils from agricultural fields. The ²⁴⁰Pu/²³⁹Pu atom ratios observed were usually 0.17-0.19, except for one very low ratio (0.037) found in the Nishiyama area (Nagasaki).     

Development of an accurate,sensitive, and robust isotope dilution laser ablation ICP-MS method for simultaneous multi-element analysis (chlorine,sulfur, and heavy metals) in coal samples

A method for the direct multi-element determination of Cl, S, Hg, Pb, Cd, U, Br, Cr, Cu, Fe, and Zn in powdered coal samples has been developed by applying inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with laser-assisted introduction into the plasma. A sector-field ICP-MS with a mass resolution of 4,000 and a high-ablation rate laser ablation system provided significantly better sensitivity, detection limits, and accuracy compared to a conventional laser ablation system coupled with a quadrupole ICP-MS. The sensitivity ranges from about 590 cps for ³⁵Cl⁺ to more than 6 × 10⁵ cps for ²³⁸U⁺ for 1 μg of trace element per gram of coal sample. Detection limits vary from 450 ng g⁻¹ for chlorine and 18 ng g⁻¹ for sulfur to 9.5 pg g⁻¹ for mercury and 0.3 pg g⁻¹ for uranium. Analyses of minor and trace elements in four certified reference materials (BCR-180 Gas Coal, BCR-331 Steam Coal, SRM 1632c Trace Elements in Coal, SRM 1635 Trace Elements in Coal) yielded good agreement of usually not more than 5% deviation from the certified values and precisions of less than 10% relative standard deviation for most elements. Higher relative standard deviations were found for particular elements such as Hg and Cd caused by inhomogeneities due to associations of these elements within micro-inclusions in coal which was demonstrated for Hg in SRM 1635, SRM 1632c, and another standard reference material (SRM 2682b, Sulfur and Mercury in Coal). The developed LA-ICP-IDMS method with its simple sample pretreatment opens the possibility for accurate, fast, and highly sensitive determinations of environmentally critical contaminants in coal as well as of trace impurities in similar sample materials like graphite powder and activated charcoal on a routine basis. Figure LA-ICP-IDMS allows direct multi-element determination in powdered coal samples     

Vertical distribution of uranium concentrations and 235U/238U atom ratios in the coastal water off Aomori, Japan: A survey prior to the operation of a nuclear fuel reprocessing facility

Summary From the viewpoint of environmental radioactivity monitoring, the determination of uranium and its isotope ratio is important for identifying and assessing the environmental impact of any unexpected release from nuclear facilities. In this work, a survey was conducted to determine ²³⁸U concentrations and ²³⁵U/²³⁸U atom ratios in coastal waters off Rokkasho Village, Aomori, Japan, where several uranium-related nuclear facilities have been operating since 1992, and a newly constructed nuclear fuel reprocessing plant is scheduled to be commissioned in 2006. Seawater samples were analyzed directly after a 10-fold dilution using isotope dilution sector-field ICP-MS. Based on the results, we concluded that there is no observable uranium contamination in the investigated sites. In addition, for the first time, a correlation between uranium concentration and salinity was established in coastal waters using the SF-ICP-MS technique.     

Determination of 234U/238U isotope ratios in environmental waters by quadrupole ICP-MS after U stripping from alpha-spectrometry counting sources

The ²³⁴U/²³⁸U isotope ratio has been widely used as a tracer for geochemical processes in underground aquifers. Quadrupole-based inductively coupled plasma mass spectrometry (ICP-MS) equipped with a high-efficiency nebulizer and a membrane desolvator was employed for the determination of ²³⁴U/²³⁸U isotope ratios in natural water samples. The instrumental limit of detection for ²³⁴U was at the low pg L⁻¹ level with very low sample consumption. Measurement precision (²³⁴U/²³⁸U) was 3–5% for bottled mineral water with elevated uranium concentration (>1 μg L⁻¹). For the analysis of groundwater samples from the Almonte-Marisma underground aquifer (Huelva, Spain), uranium was stripped from stainless steel planchets that had previously been used as radiometric counting sources for alpha-particle spectrometry. Potential spectral interferences from other metals introduced during the dissolution were investigated. Matrix-matched blank solutions were needed to subtract the background on ²³⁴U due to the formation of platinum argides, and to allow for mass bias correction and background correction. The Pt appears to be an impurity present in the stainless steel, either as a minor component by itself or after extraction from the anode and a subsequent uranium electrodeposition. The ²³⁴U/²³⁸U isotope ratio data were in very good agreement with those of alpha spectrometry, while precision was improved by a factor of up to 10 and counting time was reduced down to ~20 min (10 replicate measurements).     

Determination of thorium and uranium in activated concrete by inductively coupled plasma mass spectrometry after anion-exchange separation

A sensitive analytical method was established for the determination of Th and U in activated concrete samples. The method combines an anion-exchange separation step with an ICP-MS determination technique. In the ICP-MS measurement, a few μg mL^–1 of Al and Ca, a few ng mL^–1 of Mn, La, Ce, Nd and Pb and pg mL^–1 amounts of Li, Zr, Nb and Ba coexisting in the anion-exchange fraction of Th and U did not interfere. No adverse interference effects were observed in real sample analyses. The obtained detection limits (3σ, n = 10) of Th and U were 2.3 and 1.8 pg mL^–1, respectively. The analytical precisions for ca. 5 μg g^–1 Th and ca. 1 μg g^–1 U in real activated concrete samples were equally less than 7% RSD. The accuracies obtained by the analysis of GSJ rock standard samples were –18.1 to 0.4% for the Th determination and –14.0 to –5.7% for the U determination. The method uses the conventional absolute calibration curve. The internal standard calibration is unnecessary. Received: 14 March 1999 / Revised: 13 July 1999 / Accepted: 15 July 1999     

Isotopic and ultratrace analysis of uranium by double-focusing sector field ICP mass spectrometry

An analytical method for the ultratrace and isotopic analysis of uranium in radioactive waste samples using a double-focusing sector field ICP mass spectrometer is described. In high-purity water a detection limit for uranium in the lowest fg/mL range has been achieved. Under optimum experimental conditions (²³⁵U/²³⁸U ≈ 1), the precision in ²³⁵U/²³⁸U isotopic ratio determinations has been determined as 0.07% RSD. With the isotopic standard U-020 (²³⁵U/²³⁸U = 0.0208) a precision of 0.23% RSD at the 100 pg/mL level using ultrasonic nebulization has been achieved. With ²³⁴U/²³⁸U isotopic ratios of down to 10^–5, the values obtained by double-focusing sector field ICP-MS and alpha spectrometry were in agreement. Received: 27 February 1997 / Revised: 10 Juni 1997 / Accepted: 12 June 1997     

Rapid determination of 237Np and Pu isotopes in water by inductively-coupled plasma mass spectrometry and alpha spectrometry

A new method that allows rapid preconcentration and separation of plutonium and neptunium in water samples was developed for the measurement of ²³⁷Np and Pu isotopes by inductively-coupled plasma mass spectrometry (ICP-MS) and alpha spectrometry. ²³⁸U can interfere with ²³⁹Pu measurement by ICP-MS as ²³⁸UH⁺ mass overlap and ²³⁷Np via peak tailing. The method provide enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then moving Pu to DGA resin for additional removal of uranium. The decontamination factor for uranium from Pu is almost 100,000 and the decontamination factor for U from Np is greater than 10,000. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration is performed using a streamlined calcium phosphate precipitation method. Purified solutions are split between ICP-MS and alpha spectrometry so that long and short-lived Pu isotopes can be measured successfully. The method allows for simultaneous extraction of 20 samples (including QC samples) in 4?C6 h, and can also be used for emergency response. ²³⁹Pu, ²⁴²Pu and ²³⁷Np were measured by ICP-MS, while ²³⁶Pu, ²³⁸Pu, and ²³⁹Pu were measured by alpha spectrometry.     

Use of chromatographic pre-concentration for routine uranium bioassay analysis by ICP-MS

Routine monitoring of urine is an effective way to detect occupational intake of radioactive material. Historically, determinations of uranium isotopic ratios have been performed by radiochemical separation followed by alpha spectrometry. With recent advancements in technology, inductively coupled plasma-mass spectrometry (ICP-MS) has become widely available for the determination of trace metals as well as radioactive nuclides with long half-lives, such as ²³⁸U in urine. Furthermore, ICP-MS measurements of ²³⁸U do not require radiochemical separation since the number of atoms in the sample is determined instead of the number of alpha particles emitted. However, this method does not provide good sensitivity for the determination of ²³⁵U due to its shorter half-life. An improved procedure using pre-concentration of uranium and determination by ICP-MS decreases the detection limit by a factor of ten or greater with only slight increase in total analysis time. The method also has the capability of accurately determining the isotopic ratio of the sample, which is very important in cases where enriched or depleted uranium is involved.     

Determination of U isotope ratios in sediments using ICP-QMS after sample cleanup with anion-exchange and extraction chromatography

The determination of uranium is important for environmental radioactivity monitoring, which investigates the releases of uranium from nuclear facilities and of naturally occurring radioactive materials by the coal, oil, natural gas, mineral, ore refining and phosphate fertilizer industries, and it is also important for studies on the biogeochemical behavior of uranium in the environment. In this paper, we describe a quadrupole ICP-MS (ICP-QMS)-based analytical procedure for the accurate determination of U isotope ratios (²³⁵U/²³⁸U atom ratio and ²³⁴U/²³⁸U activity ratio) in sediment samples. A two-stage sample cleanup using anion-exchange and TEVA extraction chromatography was employed in order to obtain accurate and precise ²³⁴U/²³⁸U activity ratios. The factors that affect the accuracy and precision of U isotope ratio analysis, such as detector dead time, abundance sensitivity, dwell time and mass bias were carefully evaluated and corrected. With natural U, a precision lower than 0.5% R.S.D. for ²³⁵U/²³⁸U atom ratio and lower than 2.0% R.S.D. for ²³⁴U/²³⁸U activity ratio was obtained with less than 90 ng uranium. The developed analytical method was validated using an ocean sediment reference material and applied to an investigation into the uranium isotopic compositions in a sediment core in a brackish lake in the vicinity of U-related nuclear facilities in Japan.     

Determination of Ultra Trace Amounts of Uranium (VI) by Adsorptive Stripping Voltammetry Using L-3-(3, 4-dihydroxy phenyl) Alanine as a Selective Complexing Agent

Abstract

The spectrophotometric behavior of uranium (VI) with L-3-(3, 4-dihydroxy phenyl) alanine (LDOPA) reagent revealed that the uranium can form a ML₂ complex with LDOPA in solution. Thus a highly sensitive adsorptive stripping voltammetric protocol for measuring of trace uranium, in which the preconcentration was achieved by adsorption of the uranium-LDOPA complex at hanging mercury drop electrode (HMDE), is described. Optimal conditions were found to be a 0.02 M ammonium buffer (pH 9.5) containing 2.0 × 10^?5 M (LDOPA), an accumulation potential of ? 0.1 V (versus Ag/AgCl) and an accumulation time of 120 sec.

The peak current and concentration of uranium accorded with linear relationship in the range of 0.5–300 ng ml^?1. The relative standard deviation (at 10 ng ml^?1) is 3.6% and the detection limit is 0.27 ng ml^?1. The interference of some common ions was studied. Applicability to different real samples is illustrated. The attractive behavior of this reagent holds great promise for routine environmental and industrial monitoring of uranium.     

Uranium isotopes in carbonate aquifers of arid region setting

Groundwater in arid and semiarid regions is vital resource for many uses and therefore information about concentrations of uranium isotopes among other chemical parameters are necessary. In the study presented here, distribution of ²³⁸U and ²³⁵U in groundwater of four selected locations in the southern Arabian peninsula, namely at two locations within the United Arab Emirates (UAE) and two locations in Oman are discussed. The analyses of the uranium isotopes were performed using ICP-MS and the results indicated a range of concentrations for ²³⁵U and ²³⁸ U at 3–39 ng L^?1 (average: 18 ng L^?1) and 429–5,293 ng L^?1 (average: 2,508 ng L^?1) respectively. These uranium concentrations are below the higher permissible WHO limit for drinking water and also comparable to averages found in groundwater from similar aquifers in Florida and Tunisia. Negative correlation between rainfall and uranium concentrations suggests that in lithologically comparable aquifers, climate may influence the concentration of uranium in subtropical to arid regions.     

New methodology for uranium analysis in swipe samples for nuclear safeguards purposes

Environmental swipe sampling for safeguards purpose has been used by International Atomic Energy Agency since 1997, being a powerful tool to detect undeclared materials and activities. This work describes a new methodology for swipe samples analysis based on ultrasound-assisted acid leaching and compares it with traditional total digestion bulk analysis. The proposed method requires few preparation steps, decreasing the risk of contamination, reduced amounts of reagents and a good option to extract uranium from swipe sample. In a real case study, the swipe samples were collected in a conversion plant at IPEN/CNEN, Brazil. The measurements were carried out by ICP-MS and the results showed relative error lower than 0.96 % for uranium isotopic ratios for the certified reference material (NBS U200). The uncertainties were estimated by following the ISO GUM, with a confidence level of 95 %. The uncertainties percentage for n(²³⁵U)/n(²³⁸U) ratio of the samples ranged from 2.5 to 4.3 %. The values of uranium isotopic ratio obtained for each method demonstrate the viability of using the methodology proposed in this work.