Europium speciation by time-resolved laser-induced fluorescence

Time-resolved laser-induced fluorescence has been used to investigate Eu complexes formed with a few main ligands encountered in natural waters: hydroxide, carbonate and humic substances. By varying pH and concentrations of ligands at fixed europium concentration and ionic strength, it was possible, together with free europium Eu3+, to identify spectrally and temporally carbonate complexes, namely Eu(CO3)+, Eu(CO3)2- and Eu(CO3)33- and humate complexes EuHA. For hydroxide complexes, no differences were found in terms of fluorescence spectra and lifetimes. A spectral interpretation is described by using deconvolution for all systems