Debra A. Bostick

Supramolecular Chemistry of Environmentally Relevant Anions

Publisher Summary This chapter discusses supramolecular chemistry of environmentally relevant anions. The ultimate goal of the studies on the basic chemical aspects of anion receptor design of functional pH-independent systems is to target selective binding of anions of environmental significance. In applications-oriented aspects of the research on the design of separations, strategies for selective and efficient removal of targeted anions have been a major long-term goal. The chapter discusses (1) some of the first synthetic sulfate-selective anion-binding agents; (2) simple, structure-based methods for modifying the intrinsic anion selectivity of a given class of anion receptors; and (3) the first system capable of extracting sulfate anion from acidic, nitrate-containing aqueous media. These initial findings point the way to more effective systems involving receptors with higher selectivity, binding strength, and solubility. The evolution of anion-binding ligands from simple ammonium-based systems through mixed amide/amine and thioamide/amine receptors is reviewed. Thus, the emphasis is largely on synthetic design strategy carried out in the Bowman–James group.

Direct Measurement of Uranium Isotopic Ratios in Soils by Glow Discharge Mass Spectrometry

Since the current methodology mandated by the environmental protection agency (EPA) for the determination of isotope ratios of priority metals in sediments, sludges, and soils is both time consuming and labor intensive, it would clearly be of great value in environmental surveys if there were a procedure capable of direct analysis of these materials with little or no sample preparation. A method that holds promise in this regard is glow discharge mass spectrometry (GDMS). GDMS has several characteristics that make it worthy of evaluation; essentially all elements are amenable to analysis, preliminary results indicate isotopic biases are small, and the determination of isotopic ratios at the sub-ppm level is a reasonable hope since detection limits are in the sub-ppb range. Furthermore, previous studies have indicated that GDMS is a fairly precise method for providing isotopic information with good precision; precisions better than 0.05% relative standard deviation (RSD) have been obtained.

Quantifying multiple trace elements in uranium ore concentrates: an interlaboratory comparison

An intercomparison was organized, with six laboratories tasked to quantify sixty-nine impurities in two uranium materials. The main technique employed for analysis was inductively coupled plasma mass spectrometry in combination with matrix-matched external calibration. The results presented highlight the current state-of-the-practice; lessons learned include previously unaccounted polyatomic interferences, issues related to sample dissolution, blank correction and calibration, and the challenge of estimating measurement uncertainties. The exercise yielded consensus values for the two analysed materials, suitable for use as laboratory standards to partially fill a gap in the availability of uranium reference materials characterized for impurities.

Comparison of active and passive environmental sampling for safeguards applications

Environmental sampling (ES) of surfaces using cotton swipes at nuclear facilities is one of the standard sampling protocols used by International Atomic Energy Agency (IAEA) inspectors to verify treaty compliance. Described herein is a series of studies undertaken to (1) survey a variety of low latent uranium content sampling media for efficacy of collecting nuclear materials and (2) compare active collection of particulates to swipe sampling. Findings from the evaluation of 40 natural and synthetic woven swipes will be presented. Results from a joint Oak Ridge National Laboratory (ORNL) and Savannah River National Laboratory (SRNL) project wherein a variety of passive deposition surfaces and active collections were examined for efficacy of sampling uranium processing effluents will also be detailed. For the swipe material evaluation portion of this work, uranium (U) particulate collection efficiency was evaluated on woven materials as-received and coated with complexants/solvents. The relative merits of each sampling matrix were reviewed on the basis of: (1) latent U background, (2) ease of separating the swipe material from the nuclear components, (3) presence of isobaric interferences from the swipe, and (4) efficiency in collecting uranium from contaminated surfaces. The second series of experiments evaluated the collection characteristics of active aerosol collection versus swipe sampling. ORNL and SRNL are collaborating on the development of the next generation of ES equipment for air grab and constant samples that could become an important addition to the international nuclear safeguards inspector’s toolkit. Described herein are findings from the evaluation of collection efficiency of swipe sampling and active collection using an aerosol contaminant extractor (ACE) developed by SRNL.

Ultra-Low Level Plutonium Isotopes in the NIST SRM 4355A (Peruvian Soil-1)

For more than 20 years, countries and their agencies which monitor radionuclide discharge sites and storage facilities have relied on the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 4355 Peruvian Soil. Its low fallout contamination makes it an ideal soil blank for measurements associated with terrestrial-pathway-to-man studies. Presently, SRM 4355 is out of stock, and a new batch of the Peruvian soil is currently under development as future NIST SRM 4355A. Both environmental radioanalytical laboratories and mass spectrometry communities will benefit from the use of this SRM. The former must assess their laboratory procedural contamination and measurement detection limits by measurement of blank sample material. The Peruvian Soil is so low in anthropogenic radionuclide content that it is a suitable virtual blank. On the other hand, mass spectrometric laboratories have high sensitivity instruments that are capable of quantitative isotopic measurements at low plutonium levels in the SRM 4355 (first Peruvian Soil SRM) that provided the mass spectrometric community with the calibration, quality control, and testing material needed for methods development and legal defensibility. The quantification of the ultra-low plutonium content in the SRM 4355A was a considerable challenge for the mass spectrometric laboratories. Careful blank control and correction, isobaric interferences, instrument stability, peak assessment, and detection assessment were necessary. Furthermore, a systematic statistical evaluation of the measurement results and considerable discussions with the mass spectroscopy metrologists were needed to derive the certified values and uncertainties. The one sided upper limit of the 95% tolerance with 95% confidence for the massic (239)Pu content in SRM 4355A is estimated to be 54,000 atoms/g.

Automated Separation of Uranium and Plutonium from Environmental Swipe Samples for Multiple Collector Inductively Coupled Plasma Mass Spectrometry

A fully automated method for the separation of low-concentration uranium from plutonium in environmental swipe samples has been developed. The offline chromatography system features renewable 1 mL Eichrom TEVA and UTEVA column generation from bulk resin slurry. Discrete fractions of the separated actinides are delivered into user defined vials for future analysis. Clean room background levels were achieved outside of a cleanroom environment with this method. Purification of uranium and plutonium from various sample matrixes and at various concentrations was successful. Major and minor isotope ratios for both elements were measured via multiple collector inductively coupled plasma mass spectrometry and were in good agreement with certified reference values. Validation of the separation method was conducted on archived environmental samples and agreed with values previously reported using standard column chemistry.