A theoretical investigation of the kinetic energy of ions trapped in a radio-frequency hexapole ion trap

The kinetic energy dependence of ions trapped in a radiofrequency (RF) hexapole ion trap was calcd. as a function of space charge, mean free path, mass, RF potential and charge. The av. kinetic energy of the ions increases with increasing space charge, mean free path and the ion charge state. For a trapped ion in a given Coulombic field, the mass of the ion and the amplitude of the applied RF potential did not affect the av. kinetic energy. The consequences for multipole-storage-assisted dissocn. (MSAD), in which ions are accumulated for prolonged periods of time in the multipole ion trap of an electrospray ion source, are discussed. As a result of radial stratification inside the ion trap, MSAD can lead to the preferential excitation of ions with larger m/z values. Such discrimination would have neg. consequences for the detection of labile noncovalent adducts, which are normally detected at higher m/z values than their constituent species. [on SciFinder (R)]