Uranyl Ion Extraction into Room Temperature Ionic Liquids: Species Determination by ESI and MALDI-MS

The extraction of uranyl nitrate by TBP in two room temperature ionic liquids (RTILS), viz. 1-alkyl-3 -methyl imidazolium (Cnmim, n = 4 and 8) cation with hexafluorophosphate anion and, for comparison purposes, in dodecane has been studied. The species extracted were determined by slope analysis, UV-VIS spectra and supported for the first time by two known soft ionization mass spectrometric techniques, viz. MALDI-MS and ESI-MS. The results show that the extraction mechanisms differ in the two RTILS, as cation exchange is more likely for a butyl substituted RTIL, C4mimPF6 as noted in literature, whereas the formation of a neutral adduct (i.e., UO2(NO3)22TBP) by a solvation mechanism is operative for octyl analogue, C8mimPF6.