Patent ID: 8207495
Filing Date: 2012-06-26
Classification: H01J

Abstract:
1. A quadrupole mass spectrometer, comprising a high vacuum analysis chamber; a quadrupole mass filter composed of a main rod electrode for selectively allowing an ion having a specific mass-to-charge ratio to pass through; a multipole pre-filter composed of a plurality of pre-rod electrodes that introduce ions to the quadrupole mass filter, wherein the quadrupole mass filter and the multipole pre-filter are provided in the analysis chamber; a voltage generator for applying a first direct current bias voltage and a radio-frequency voltage to each pre-rod electrode of the pre-filter and applying a second direct current bias voltage and the same radio frequency voltage to the quadrupole mass filter, the first direct current bias voltage and the second direct current bias voltage being different; and a controller for controlling the voltage generator in such a manner that the first direct current bias voltage is changed in accordance with a mass-to-charge ratio of an ion to be allowed to pass through the pre-filter, wherein the first direct current bias voltage is the same for all pre-rod electrodes.