It is shown for improved mass analyzer. The mass analyzer, an ion injector that is configured to use to provide a plurality of ions for analysis (90) and (30), adapted ion selected to receive the plurality of ions from the ion syringe (30) a unit, for the detection / analysis, and a ion-selective unit that provides only ions having a selected mass to charge ratio. Ion selection unit has one external electrode (95) and a plurality of internal electrodes (100,105,110,115). A plurality of ions provided by the ion injector (90) is received in intrusion region between the outer electrode (95) and a plurality of internal electrodes (100,105,110,115). The electrodes of the ion selection room, the power supply system is connected. The power system, the adapted plurality of to apply to at least one oscillating voltage of the internal electrodes, the mass-to-charge ratio of unselected ions, can separate ions of a selected mass to charge ratio to become.