The Thermo Scientific LTQ XL linear ion trap mass spectrometer provides high sensitivity full scan MS along with in-depth MSn (CRM) capabilities. A single quadrupole offers Selected Ion Monitoring, and a triple quadrupole adds Selected Reaction Monitoring. A linear ion trap goes further by enabling Consecutive Reaction Monitoring, where the selected ion is fragmented into a product ion, and then the resulting product ion further fragmented in additional consecutive steps. Each additional fragmentation step makes compound identification more certain and simplifies structural characterization.