RER Consultants

Passau, Germany

RER Consultants

Passau, Germany
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Kwiatek D.,Adam Mickiewicz University | Meinrath G.,RER Consultants | Lis S.,Adam Mickiewicz University
Inorganica Chimica Acta | Year: 2015

An analysis of 17 UV-Vis absorption spectra is presented, collected in a region of the pH/lg(acetate) diagram where the UO2CH3COO+ species prevails. The study was conducted (a) to test a previously determined single component of the UO2CH3COO+ species, (b) to assess the impact of (UO2)2(OH)2 2+ hydrolysis species into numerical peak deconvolution and (c) to study statistical properties of peak deconvolution procedures as a basis for measurement uncertainty assessment. Comparative speciation was performed for a two-species and three-species model, which resulted in different values of U(VI)-acetato formation quotients. The numerical analysis corroborated a detectability of (UO2)2(OH)2 2+ at relative amounts >1%. Lower relative contributions remain ambiguous due to the large Pearson correlation of U(VI) UV-Vis single component spectra. The results of the study show the quantitative deconvolution of U(VI) spectra into single components of UO2 2+, UO2(CH3COO)+ and (UO2)2(OH)2 2+ species. Theoretical U(VI) concentrations are reproduced within a few percent. © 2014 Elsevier B.V. All rights reserved.

Meinrath G.,RER Consultants | Kwiatek D.,Adam Mickiewicz University | Hnatejko Z.,Adam Mickiewicz University | Lis S.,Adam Mickiewicz University
Monatshefte fur Chemie | Year: 2014

As a result of systematic UV-Vis absorption spectroscopy studies in the U(VI) acetate system, the single component spectrum of [UO2CH3COO]+ with characteristic parameters was evaluated and applied in quantitative deconvolution of multicomponent spectra. Free acetate concentrations were obtained by the use of geochemical and probabilistic modelling codes. A total of 51 UV-Vis spectra were collected in a wide range of experimental conditions where coordination of U(VI) by acetate ion was indicated by characteristic variations in the spectra structure as compared to UO22+. Using chemometric data analysis, the resulting factor structure was evaluated to obtain a subset of 14 spectra holding only one coordinated species next to UO22+ (aq). The molar absorption coefficient for the U(VI) monoaceto species was estimated as ε418 = 17.8 ± 1 dm3 mol-1 cm-1. Spectral deconvolution was used to obtain an estimate of the species concentrations which allowed to calculate for each sample the free acetate concentration, the total U(VI) amount and, eventually, to estimate the formation quotient lg β11 = 2.8 ± 0.3 of UO2(CH3COO)+. © The Author(s) 2014.

Lis S.,Adam Mickiewicz University | Glatty Z.,Adam Mickiewicz University | Meinrath G.,RER Consultants | Kubicki M.,Adam Mickiewicz University
Journal of Chemical Crystallography | Year: 2010

The building blocks of the title compound, [UO 2 2+·Cl -·(C 6H 4NO 3)- · (C6H5NO3)] n-uranyl fragment, chloride ion, one deprotonated isonicotinate N-oxide and one isonicotinic acid N-oxide, are arranged in the complicated three dimensional network by means of both coordination and hydrogen bonds. The uraniumion is seven-coordinated, in the fashion intermediate between the pentagonal bipyramid and capped octahedron. The coordination one-dimensional polymer chains are connected by strong carboxyl-carboxyl hydrogen bonds into two dimensional grids. These grids interpenetrate each other like the chain-links. © Springer Science+Business Media, LLC 2010.

Spitzer P.,Physikalisch - Technische Bundesanstalt | Fisicaro P.,French National Laboratory of Metrology and Testing | Meinrath G.,RER Consultants | Stoica D.,French National Laboratory of Metrology and Testing
Accreditation and Quality Assurance | Year: 2011

Traceable measurement of the quantity pH in media outside the limits of the recent IUPAC recommendation requires an alternative to the Bates-Guggenheim convention. The Pitzer's approach to ion interactions is widely appraised and offers a suitable approach to the estimation of single-ion activity coefficients. For this purpose, the underlying electrolyte data need to be consistent and the uncertainty in existing Pitzer's data needs to be assessed. Such an assessment is attempted in this study for pH in potassium acetate buffer medium. The re-evaluation of Pitzer's data from potassium nitrate data revealed inconsistencies and wide uncertainty margins. The uncertainty contribution from binary Pitzer's parameters to an assessment of pH in seawater resulted in an uncertainty in pH of about 0.03 (95% confidence interval). This contribution has to be taken into account in the overall uncertainty budget. Lack of appropriate data for other pH buffer systems (e.g., phosphate buffers) is noted. © 2011 Springer-Verlag.

Lis S.,Adam Mickiewicz University | Meinrath G.,RER Consultants | Glatty Z.,Adam Mickiewicz University | Kubicki M.,Adam Mickiewicz University
Inorganica Chimica Acta | Year: 2010

Spectroscopic speciation of U(VI) solutions holding pyridine carboxylic acid N-oxides in a range pH 2.3-4.5 results in the single component spectrum of the U(VI) isonicotinic acid N-oxide complex. The molar absorption is 14 ± 2 L mol-1 cm-1 at 415.4 nm. The formation constant lg KUL = 2.1 ± 0.2 (k = 2) is derived from solution modelling and by multivariate chemometric analysis. The first crystal structure analysis of a U(VI) pyridine carboxylic acid N-oxide revealed a sheet-like structure where the isonicotinic acid N-oxide binds to the uranyl(VI) both bidentately by the carboxylate group and monodentately by the N-O group. The single component spectrum of the [UO2L]+ (where L- is isonicotinate N-oxide) is compared to the small number of other U(VI) single ligand species. The comparison revealed the possible pitfalls of U(VI) spectroscopic speciation close to the pH region where U(VI) hydrolysis starts to interfere. On basis of the results for U(VI)-L coordination and physicochemical properties of the pyridine carboxylic acid N-oxides some conclusions could be drawn on the likely behaviour of nicotinic acid N-oxide and picolinic acid N-oxide. For the former, complex formation in a narrow range of pH and U(VI) concentrations close to the hydrolysis range of U(VI) might reveal thermodynamic data. In the case of picolinic acid N-oxide, additional experimental evidence is required to characterize suitable conditions. © 2010 Elsevier B.V. All rights reserved.

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