Correlation of stoichiometries for Rb+ extraction determined by mass spectrometry and electrochemistry at...

The electrochemical extraction of rubidium at micro water|1,2-dichloroethane (w|DCE) and water|room-temperature ionic liquid (w|RTIL) interfaces housed at the tip of a 25-μm capillary using octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in the TRans Uranic EXtraction (TRUEX) process, was examined. Rubidium is of great interest in a modern spent nuclear fuel cycle as well as toward myocardial perfusion imaging utilizing (82)Sr/(82)Rb isotopic generators. The ligand-to-metal stoichiometry (n:1) and overall complexation constant (β) for interfacial complexation reactions induced by an applied potential were determined by the interfacial electrochemistry. One stoichiometry, n = 2, was observed at the w|DCE interface with β = 3.3 × 10(4). In the w|RTIL system, two rubidium salt solutions were employed: RbNO(3) and RbNO(3) plus Rb(2)SO(4). The former demonstrated a stoichiometry of n = 2 and β = 2.4 × 10(6), while the latter showed n = 4 and β = 3.3 × 10(12). These stoichiometries of the reaction were confirmed by electrospray ionization mass spectrometry, using an emulsion generated by shaking water and DCE phases containing the dissolved metal and ligand, respectively. Both RbCMPO(+) and RbCMPO(2)(+) complexes were observed. The influence of ion pair interactions in this system will be discussed.