ABSTRACT
The presence of a buffer gas in quadrupole ion traps (QITs) cools injected ions by reducing the ions’ kinetic energy, thereby enhancing trapping efciency, and serves also as the collision gas for collision-induced dissociation (CID) in tandem mass spectrometry. However, during other events of the analytical scan, having buffer gas inside the QIT can be disadvantageous. During the mass isolation and ejection events, fragile ions can collide with buffer gas atoms/molecules with enough kinetic energy to cause fragmentation and to degrade mass resolution. Currently, commercially available QITs maintain a constant buffer gas pressure of ca 1 mTorr, a compromise between efcient cooling and limiting possible fragmentation of ions.
