A new time-resolved laser-induced fluorescence spectrometry (TRLFS) data acquisition procedure applied to the uranyl-phosphate system

TRLFS has been used to study the U VI O 2 2+ -PO 4 3- system, in the 1 to 5 pH range, for [PO 4 3- ] = 2 × 10 -3 to 1.02 x 10 -1 M range and [UO 2 2+ ]= 1.2 x 10 -5 M. The data acquisition procedure was based on four different sets of acquisition parameters, which were chosen in order to maximize the fluorescence signal for four different time domains. The fitting procedure used to simulate the corresponding fluorescence decays curves was based on the crosscheck of the fitting results and on the inter-comparison between results for solutions of different concentrations. Five different lifetimes τ 1 to τ 5 were evidenced and associated with five uranyl species (UO 2 (H 2 PO 4 ) 2 , UO 2 H 2 PO 4 + , UO 2 HPO 4 , UO 2 PO 4 - and UO 2 2+ ). The fitting results, moreover, allowed the distinction between mono-, bi- and tri-exponential fluorescence decay behaviours. The isolated fluorescence spectra showed an expected wavelength shift between the fluorescence spectra of all the complexes, except in the case of the (UO 2 (H 2 PO 4 ) 2 , UO 2 H 2 PO 4 + ) couple, which spectra were not distinguishable. Finally, the obtained results have shown that the data acquisition and fitting procedure enabled a complete and reliable characterization of the studied solutions.