Hydrolysis contributions in U(VI) spectroscopic speciation in acetate media

• Quantitative deconvolution of UV–Vis spectra by up to three single components.
• Theoretical U(VI) concentrations reproduced within a few percent.
• The total number of spectra allows statements on a statistically sound basis.
• Corroborated basis for evaluation of higher U(VI)-acetato species.
• Comparable information unavailable in literature.

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)22+ 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)22+ 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 UO22+, UO2(CH3COO)+ and (UO2)2(OH)22+ species. Theoretical U(VI) concentrations are reproduced within a few percent.

Interference by U(VI) hydrolysis has been observed and quantified next to UO2(CH3COO)+ for five samples. These three-component spectra are interpreted with marginal residuals on basis of the results obtained in this work.Figure optionsDownload as PowerPoint slide