| 摘要 |
An IMS 4 comprises a plurality of apertured plate or ring electrodes, adjacent electrodes supplied with opposite phases of an AC or RF voltage, and with an axial DC voltage gradient applied along at least a portion of its length. Preferably the ion tunnel IMS has an upstream section (4a in figure 7a) formed of a first plurality of electrodes with a first DC voltage gradient, and a downstream section (4b) formed of a second plurality of electrodes with a second DC voltage gradient. Also disclosed is a mass spectrometer comprising an ion mobility spectrometer 4 and a mass filter 5, operated in combination to onwardly transmit ions having a first charge state in preference to ions having a second charge state. This may be achieved by varying the mass filtering characteristic of mass filter 5, i.e. by varying its mass/charge ratio cut-off, in synchronisation with the pulsing of ions into the IMS 4. |
