Patent ID: 8604420

Claim:
A mass spectrometer for analyzing ions according to selected mass-to-charge ratios comprising: an ion source for ionizing a sample; an ion storage portion for repeatedly performing a storing operation for storing ions generated by the ion source and an expelling operation for repeatedly expelling the stored ions as pulsed ions; a quadrupole mass filter for receiving the pulsed ions expelled by the ion storage portion and permitting only desired ions to pass having the selected mass-to-charge ratio defined by selected AC and DC voltages supplied to the quadrupole mass filter; a detector for detecting the pulsed ions passed through the quadrupole mass filter and outputting an analog signal responsive to a detection intensity; and a controller for controlling said selected AC and DC voltages supplied to the quadrupole mass filter, said controller for maintaining said voltages constant while pulsed ions are passing through the quadrupole mass filter and repeatedly changing the selection voltages while pulsed ions are not being introduced in the quadrupole mass filter.