Patent ID: 8581184

Claim:
A quadrupole mass spectrometer including a quadrupole mass filter having four pre-rod electrodes provided anterior to four main rod electrodes for selectively allowing a passage of an ion originating from a sample according to a mass-to-charge ratio of the ion, comprising: a) a quadrupole driver including a direct-current voltage source for generating a direct-current voltage whose voltage value changes according to the mass-to-charge ratio of a measurement target, a radio-frequency voltage source for generating a radio-frequency voltage whose amplitude changes according to the mass-to-charge ratio of the measurement target, and a voltage adder for applying, to the main rod electrodes, a voltage produced by adding the direct-current voltage and the radiofrequency voltage, where a response time of the amplitude of the radio-frequency voltage is set to be shorter than a response time of the direct-current voltage when both the radio-frequency voltage and the direct-current voltage are simultaneously changed so as to switch the mass-to-charge ratio of the measurement target, and where the response time of the direct-current voltage is set to be shorter than a period of time required for an ion having a highest mass-to-charge ratio among a target of analysis to pass through the main rod electrodes; and b) a transient voltage supplier for generating, when both the radio-frequency voltage and the direct-current voltage are simultaneously changed so as to switch the mass-to-charge ratio of the measurement target, a voltage corresponding to a transient state of the change of the direct-current voltage and for applying this voltage to the pre-rod electrodes so as to block an ion of a low mass-to-charge ratio that can pass through the main rod electrodes due to a difference in the response time between the radio-frequency voltage and the direct-current voltage while these voltages are being changed.