Patent ID: 8188426

Claim:
A quadrupole mass spectrometer including: an ion source for ionizing a sample molecule; a quadrupole mass filter selectively allowing an ion having a specific mass to pass therethrough among ions generated in the ion source; and a detector for detecting ions having passed through the quadrupole mass filter, the quadrupole mass spectrometer comprising: a) a quadrupole driving means for applying, to respective electrodes forming the quadrupole mass filter, a voltage obtained by adding a direct current voltage and a radio-frequency voltage; and b) a control means for controlling the quadrupole driving means to sequentially change the direct current voltage and an amplitude of the radio-frequency voltage depending on the mass, and to change a ratio of the direct-current voltage to the amplitude of the radio-frequency voltage depending on a scanning rate so that the ratio UN of the direct current voltage U and the amplitude V of the radio-frequency voltage is relatively reduced for a relatively high scanning rate, when a mass scanning is conducted in such a manner that the mass of ions passing through the quadrupole mass filter is sequentially changed.