Uranium oxide clusters by laser desorption ionization during MALDI-TOF MS analysis of uranium(VI)

Laser desorption ionization (LDI) mode of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS) analysis of urani um(VI) leads to the formation of uranium oxides clusters, as with fast atom bombardment (FAB). Different uranium clusters than those with FAB were obs erved. Three different fan-lilies of formula (UO2)(x)O-y(+), and two of for mula (UO2)(x)O-y(2+) were found. While x increases, the O:U ratio tends to 3. The relationship between neighboring clusters can be described as (UO2)( x)O-y(+)<----> (UO2)(x-1)O-y-1(+)+UO3. The formation of clusters can be eli minated using some matrices, and a more sensitive uranium determination wit h a detection limit down to 10(-12)M is possible.