Patent ID: 8519328

Claim:
A method of mass spectrometry comprising: providing a first ion guide or ion trap comprising one or more first electrodes and providing one or more exit electrodes downstream of said first electrodes; trapping ions in a mode of operation within said ion guide or ion trap; performing a plurality of cycles of operation, wherein each cycle of operation comprises the steps of: (i) enabling at least some ions to exit said ion guide or ion trap during a first time period T e ; and (ii) thereafter substantially preventing ions from exiting said ion guide or ion trap for a second time period T C ; varying the length or width of said first time period T e in subsequent cycles of operation; the method further comprising providing a quadrupole rod set mass filter/analyzer downstream of said ion guide or ion trap; wherein said quadrupole rod set mass filter/analyzer is scanned or stepped so as to mass filter/analyze ions that exit said ion guide or ion trap.