URANIUM SPECIATION IN SOLUTION BY TIME-RESOLVED LASER-INDUCED FLUORESCENCE

Complexation studies of radionuclides (such as uranium) are important to perform in order to predict their migration behavior in natural systems. Time-resolved laser-induced fluorescence, which is a very selective and sensitive method for actinide and lanthanide analysis, is used to study the interactions between uranyl cation and hydroxide ions at low uranium concentration (0.4 mu M). The principle of the study is based on time resolution and spectral convolution since free uranyl ion (UO22+) and first hydroxide complex give specific fluorescence spectra characterized by their spectral shift and fluorescence lifetime. Spectroscopic data (main fluorescence wavelengths, half-bandwidth, lifetime) for the first hydrolyzed complex UO2OH+ are obtained. From experimental spectra and time-resolved spectral convolution, the proportion of each species (free uranyl, complexed uranyl) can be estimated at different pH.