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- Author or Editor: J. Campbell x
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Abstract
Electrospray ionization mass spectrometry (ESI-MS) was used for the study of cyclization of organic chelating compounds (chelators). Four chelating compounds were studed: Symmetrical ethylenediaminediacetic acid (s-EDDA), Unsymmetrical ethylenediaminediacetic acid (u-EDDA), N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA), and N-(2-hydroxyethyl)iminodiacetic acid (HEIDA). The chelators were cyclized with treatments of acids and heating. The open and cyclized form of the chelators were semi-quantified by both positive and negative ion modes ESI-MS. The kinetics of chelator cyclization was studied as a function of reaction temperature and the pH of the matrix. The cyclization of s-EDDA was found to be a pseudo-first order reaction in s-EDDA and overall second order. The cyclizations of HEIDA and HEDTA are reversible reactions. Higher temperature and lower pH favors cyclization.
Abstract
Several organophosphorus compounds including tributyl phosphate (TBP), bis-2-(ethylhexyl) phosphate (D2EHP), and dibutyl butyl phosphonate (DBBP) were used as extractants at the Hanford site. The mass spectral fragmentation patterns of various organosphosphorus compounds have been interpreted and used to predict the identity of phosphate-related components and their degradation products in tank waste.
Abstract
Three tissue-equivalent cylindrical wound phantoms with varying activities of DU metal imbedded at varying depths were used to compare the efficiencies of a bismuth germinate (BGO) detector, a sodium iodide (NaI), and two identical wound probes with smaller sodium iodide crystals. Our results show that the BGO detector had the highest efficiency (1.0·10-3) and the lowest minimum detectable activity (MDA = 5.8 kBq) for the shallow depth DU phantom, relative to the other detectors. The BGO detector also had the highest peak efficiencies (1.7·10-3 and 5.8·10-4) and the lowest MDAs (3.5 and 10.0 kBq) for the medium and deep phantoms, respectively. Other detectors' performance data are presented.
Abstract
A method has been developed at Pacific Northwest Laboratory (PNL) to remove normal paraffin hydrocarbon (NPH) from radioactive waste samples prior to gas chromotography/mass spectrometry analysis of semivolatile components. The effectiveness of the cleanup procedure was demonstrated for all the EPA semivolatile target list compounds. Blanks and spiked actual waste samples were utilized in the development and validation study. Approximately 95% of the NPH was removed from the single-shell tank samples. The recoveries were good for most of the target compounds. Results were compared with those obtained by utilizing EPA method 3630. The recoveries were much better for the PNL-developed method.
Abstract
Considerable attention has been focused on chelators such as ethylenediaminetetraacetic acid (EDTA) and N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA), which form water-soluble complexes with most heavy metals. Most radionuclides are included in this class of constituents. As a result, chelator complexes have become very important environmentally because of their tendency to enhance the mobility of heavy metals through the soil and potentially contaminate groundwater. In addition, there is a correlation between chelator concentration and crust formation/gas release. The chelators are a class of compounds whose low volatility and high polarity preclude analysis by gas chromatography/mass spectrometry (GC/MS) without prior derivatization. Waste samples from a double-shell storage tank at Hanford were derivatized with BF3/methanol and analyzed using GC/MS. Results indicate the presence of EDTA, HEDTA, nitrilotriacetic (NTA), and citric acid. Nitrosoiminodiacetic acid was identified and determined to be an artifact of the derivatization procedure; it is assumed to arise from nitrosation of iminodiacetic acid in the waste sample.
Abstract
Because of the cost and limited availability of isotopically enriched thallium (>92%203Tl), its use in the203Tl(p, 3n)201Pb nuclear reaction necessitates chemical recovery. An adaptive method has been developed and evaluated. After the separation of201Pb, the203Tl(I) is oxidized to203Tl(III) by Cl2, Br2 or [Fe(CN)6]−2, precipitated as Tl(OH)3 with NaOH and subsequently converted to Tl2O3 by heating. Due to potential loss during recovery, the solubilities of Tl(OH)3 and Tl2O3 in aqueous solution as a function of pH have been studied using the internal tracer202Tl (T=12.2d), produced during cyclotron irradiation. Effective solubility product constants have been determined to be 5.4·10−48 and 2.5·10−47 for Tl(OH)3 and Tl2O3, respectively.
Abstract
Ion-pair chromatography was tested for its applicability in determining monobutyl phosphate (MBP) and dibutyl phosphate (DBP), which are degradation products of tributyl phosphate, in Hanford tank wastes. In tests with simulant waste mixtures, tetrahexylammonium bromide, an ion-pairing agent, was used to complex with all three phosphate species. Recovery studies indicated that ion-pairing chromatography is quantitative for determining the analytes in spiked samples. Initial results demonstrated that DBP could be detected easily and was fairly well separated from other peaks, but MBP was frequently lost due to large negative peaks. Then a preconcentration column procedure was used to clean up the waste-sample matrix, and the negative peaks disappeared. Results indicated that 80% of MBP and 90% of DBP could be recovered. Most of the radioactivity was removed from actual waste tank samples so that additional sample preparation could be performed safely in a fume hood rather than a hot cell. Dibutyl phosphate was identified in an actual tank waste, but MBP was not found; this result was confimed by ion chromatography with conductivity detection.
Abstract
Matrix-assisted laser desorption/ionization coupled with time-of-flight mass spectrometry (MALDI/TOF-MS) was used for the analysis of low-molecular phosphate compounds found in Hanford tank wastes. The mass spectra of these compounds indicate protonated peaks as well as sodium adducts. Analytical methods presently utilized for the analysis of the phosphate-related organics are both time consuming and labor intensive. A promising alternative is MALDI/TOFMS. The MALDI process produces both positive and negative ions directly and very little sample is required. In addition, there is limited sample preparation and minimal hazardous waste production.
