| abstract |
A mass spectrometer is disclosed comprising an ion mobility spectrometer and an ion attenuation means arranged to attenuate ions within a range of mass-to-charge ratios with undesired charge states. In a preferred embodiment, parent or precursor ions having a specific mass to charge ratio are transmitted by a first mass filter 2 before being temporally separated in an ion mobility separator 8. An ion gate 9 is synchronized with the operation of the mobility spectrometer so that only ions having said particular mass to charge ratio and a desired charge state are onwardly transmitted to a collision, fragmentation or reaction cell 10. |