Gas Phase Reactions of Ions Derived from Anionic Uranyl Formate and Uranyl Acetate Complexes

Abstract

Abstract. The speciation and reactivity of uranium are topics of sustained interest because of their importance to the development of nuclear fuel processing methods, and a more complete understanding of the factors that govern the mobility and fate of the element in the environment. Tandem mass spectrometry can be used to examine the intrinsic reactivity (i.e., free from influence of solvent and other condensed phase effects) of a wide range of metal ion complexes in a species-specific fashion. Here, electrospray ionization, collision-induced dissociation, and gas-phase ion-molecule reactions were used to create and characterize ions derived from precursors composed of uranyl cation (U

Formation and hydrolysis of gas‐phase [UO2(R)]+: R═CH3, CH2CH3, CH═CH2, and C6H5

“…In another set of experiments that are relevant to the present study, electrospray ionization (ESI) and multiple‐stage (MS n ) tandem mass spectrometry were used to create and characterize ions derived from anionic UO 2 2+ ‐formate and ‐acetate precursors . When the levels of background H 2 O are low, [UO 2 (O 2 C─H) 3 ] − fragments by decarboxylation and elimination of CH 2 ═O, ultimately to produce the oxo‐hydride [UO 2 (O)(H)] − .…”

“…The low level of background H 2 O in the LIT also allowed us to revise the intrinsic dissociation pathways for a range of species such as [UO 2 (NO 3 )] + , [UO 2 (ClO 4 )] + , and [UO 2 (O 2 C‐CH 3 ) 3 ] − . For example, with relatively high levels of background H 2 O, CID of [UO 2 (NO 3 )] + generated peaks corresponding to [UO 2 (H 2 O)] + and UO 2 + .…”

“…Recent experiments by our group have demonstrated that lower levels of adventitious H 2 O in a linear ion trap (LIT) mass spectrometer can provide access to fragmentation pathways and reactions for gas‐phase uranyl (U VI O 2 2+ ) complexes that were not observed during previous experiments conducted with a three‐dimensional quadrupole ion trap (QIT) . When H 2 O levels in an ion trap are high, precursor complexes that are isolated for collision‐induced dissociation (CID) tend to undergo association reactions to make adducts or charge reduction reactions to form products such as [UO 2 (OH)] + , [UO 2 ] + , and hydrates of these cations .…”

Collision‐induced dissociation of [UVIO2(ClO4)]+ revisited: Production of [UVIO2(Cl)]+ and subsequent hydrolysis to create [UVIO2(OH)]+

“…CID of [U VI O 2 (ClO 4 )(H 2 O)] + (MS 4 stage, Figure C), created [U VI O 2 (ClO 4 )] + ( m/z 369) by loss of the final H 2 O ligand, and all of the fragmentation reactions to this point were in general agreement with the earlier study that used a 3D ion trap . One notable difference, however, was that the number and relative abundance of H 2 O was significantly lower in the present experiments, consistent with several recent studies by our group …”

“…We have recently demonstrated that dissociation pathways and reactions are revealed in experiments that use a 2D linear ion trap (LIT) that were not observed in prior studies that employed 3D ion traps. For example, in a recent investigation of the MS n CID of U VI O 2 2+ /acn complexes, use of the LIT (with the associated lower levels of background H 2 O) allowed us to sequentially eliminate acn ligands to leave the bare U VI O 2 2+ cation, as well as generate NU VI O + by CID of [U VI O 2 (CN)] + .…”