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Title: Speciation model selection by Monte Carlo analysis of optical absorption spectra: Plutonium(IV) nitrate complexes

Abstract

Standard modeling approaches can produce the most likely values of the formation constants of metal-ligand complexes if a particular set of species containing the metal ion is known or assumed to exist in solution equilibrium with complexing ligands. Identifying the most likely set of species when more than one set is plausible is a more difficult problem to address quantitatively. A Monte Carlo method of data analysis is described that measures the relative abilities of different speciation models to fit optical spectra of open-shell actinide ions. The best model(s) can be identified from among a larger group of models initially judged to be plausible. The method is demonstrated by analyzing the absorption spectra of aqueous Pu(IV) titrated with nitrate ion at constant 2 molal ionic strength in aqueous perchloric acid. The best speciation model supported by the data is shown to include three Pu(IV) species with nitrate coordination numbers 0, 1, and 2. Formation constants are {beta}{sub 1}=3.2{+-}0.5 and {beta}{sub 2}=11.2{+-}1.2, where the uncertainties are 95% confidence limits estimated by propagating raw data uncertainties using Monte Carlo methods. Principal component analysis independently indicates three Pu(IV) complexes in equilibrium. (c) 2000 Society for Applied Spectroscopy.

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Nuclear Materials Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
Publication Date:
OSTI Identifier:
20217412
Resource Type:
Journal Article
Journal Name:
Applied Spectroscopy
Additional Journal Information:
Journal Volume: 54; Journal Issue: 6; Other Information: PBD: Jun 2000; Journal ID: ISSN 0003-7028
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; CHEMICAL ANALYSIS; MONTE CARLO METHOD; ERRORS; SPECTRA UNFOLDING; PLUTONIUM COMPOUNDS; EXPERIMENTAL DATA

Citation Formats

Berg, John M., Veirs, D. Kirk, Vaughn, Randolph B., Cisneros, Michael R., and Smith, Coleman A. Speciation model selection by Monte Carlo analysis of optical absorption spectra: Plutonium(IV) nitrate complexes. United States: N. p., 2000. Web. doi:10.1366/0003702001950436.
Berg, John M., Veirs, D. Kirk, Vaughn, Randolph B., Cisneros, Michael R., & Smith, Coleman A. Speciation model selection by Monte Carlo analysis of optical absorption spectra: Plutonium(IV) nitrate complexes. United States. doi:10.1366/0003702001950436.
Berg, John M., Veirs, D. Kirk, Vaughn, Randolph B., Cisneros, Michael R., and Smith, Coleman A. Thu . "Speciation model selection by Monte Carlo analysis of optical absorption spectra: Plutonium(IV) nitrate complexes". United States. doi:10.1366/0003702001950436.
@article{osti_20217412,
title = {Speciation model selection by Monte Carlo analysis of optical absorption spectra: Plutonium(IV) nitrate complexes},
author = {Berg, John M. and Veirs, D. Kirk and Vaughn, Randolph B. and Cisneros, Michael R. and Smith, Coleman A.},
abstractNote = {Standard modeling approaches can produce the most likely values of the formation constants of metal-ligand complexes if a particular set of species containing the metal ion is known or assumed to exist in solution equilibrium with complexing ligands. Identifying the most likely set of species when more than one set is plausible is a more difficult problem to address quantitatively. A Monte Carlo method of data analysis is described that measures the relative abilities of different speciation models to fit optical spectra of open-shell actinide ions. The best model(s) can be identified from among a larger group of models initially judged to be plausible. The method is demonstrated by analyzing the absorption spectra of aqueous Pu(IV) titrated with nitrate ion at constant 2 molal ionic strength in aqueous perchloric acid. The best speciation model supported by the data is shown to include three Pu(IV) species with nitrate coordination numbers 0, 1, and 2. Formation constants are {beta}{sub 1}=3.2{+-}0.5 and {beta}{sub 2}=11.2{+-}1.2, where the uncertainties are 95% confidence limits estimated by propagating raw data uncertainties using Monte Carlo methods. Principal component analysis independently indicates three Pu(IV) complexes in equilibrium. (c) 2000 Society for Applied Spectroscopy.},
doi = {10.1366/0003702001950436},
journal = {Applied Spectroscopy},
issn = {0003-7028},
number = 6,
volume = 54,
place = {United States},
year = {2000},
month = {6}
}