Can Electrospray Mass Spectrometry Quantitatively Probe Speciation? Hydrolysis of Uranyl Nitrate Studied by Gas-Phase Methods

Aqueous solutions of uranium(VI) nitrate are probed by electrospray mass spectrometry. The leading cationic species are the mononuclear [UO2(X)(H2O)(3)](+) (X = OH, NO3) along with oligonuclear clusters [UmO2m(X)(2m-1)(H2O)(n)](+). The nature of the anionic ligand X and the cluster size of the ions show a distinct dependence on concentration in the condensed phase. The results are used to deduce a phenomenological relationship between the concentrations of the feed solution and that in the spray process itself.