MASS SPECTROMETER

摘要

In a pause time assigned for switching voltage applied to a quadrupole mass filter or other ion transport optical system so as to switch the mass-to-charge ratio of a target ion in an SIM measurement, the polarity of direct-current voltage applied to a pre-quadrupole mass filter is temporarily reversed. The voltage polarity reversal time is changed according to length of the pause time so that the ion intensity can sufficiently rise by the time the next dwell time begins. When the polarity of the voltage applied to the pre-quadrupole mass filter is reversed, the electric charges which lie on an insulating film of contaminants or other substances attached to the surface of the pre-quadrupole mass filter or on an insulating support structure are dispersed, whereby the charge-up is eliminated. Since ions are prevented from passing through, charge-up of a main quadrupole mass filter in the subsequent stage is also reduced.

主权项

1. A mass spectrometer having one or more ion transport optical systems for transporting ions by an effect of an electric field between an ion source and an ion detector, the mass spectrometer being capable of performing an SIM or MRM measurement in which an operation of sequentially performing a mass spectrometry on each of a plurality of ions having previously specified mass-to-charge ratios is cyclically performed, and the mass spectrometer comprising:
a) a voltage generator for applying a direct-current voltage corresponding to the mass-to-charge of an ion to be monitored, to at least one of the ion transport optical systems in the SIM or MRM measurement; and b) a controller for controlling the voltage generator so that, in a pause time during which collection of detection data by the ion detector is suspended in conjunction with a switching of the mass-to-charge ratio of the ion to be monitored, if a polarity of the ion to be monitored in an SIM or MRM measurement is unchanged before and after the switching of the mass-to-charge ratio, then the direct-current voltage applied to the at least one ion transport optical system, while being switched from one specific level to another specific level in the pause time, is temporarily changed to either a level at which the direct-current voltage has a polarity different from the polarity of the direct-current voltage at those specific levels, or a level at which the direct-current voltage has the same polarity as the direct-current voltage at those specific levels yet has a smaller absolute value than the direct-current voltage at any of those specific levels.