| 摘要 |
A mass spectrometer is disclosed wherein ions having a particular desired charge state are selected by operating an ion mobility spectrometer in combination with a quadrupole mass filter. Precursor ions are fragmented or reacted to form product ions in a collision cell ion trap and sent back upstream to an upstream ion trap. The fragment or product ions are then passed through the ion mobility spectrometer wherein they become temporally separated according to their ion mobility. Fragment or product ions are then re-trapped in the collision cell ion trap before being released therefrom in packets. A pusher electrode of a time of flight mass analyzer is energized a predetermined period of time after a packet of ions is released from the collision cell ion trap. Accordingly, it is possible to select multiply charged precursor ions from a background of singly charged ions, fragment them, and mass analyze the fragment ions with a near 100% duty cycle across the whole mass range.
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