Systems and methods for scaling injection waveform amplitude during ion isolation

A mass spectrometer system comprising:

• an ionization source;
• an RF ion trap configured to receive a continuous stream of ions from the ionization source;
• a mass analyzer and an ion detector configured to receive ions from the ion source and to measure an ion flux of each of a plurality of ion species comprising respective mass-to-charge (m/z) values;
• a power supply configured to apply trapping voltages and a supplemental AC voltage waveform to the RF ion trap and to supply voltages to the mass analyzer;
• and
• a computer processor or electronic controller comprising program instructions operable to:
• cause the mass analyzer and ion detector to measure the ion flux of a pre-determined ion species within an ion stream also comprising a plurality of other ion species, the pre-determined ion species having a pre-determined isolation mass-to-charge ratio, (m/z)ISO and the plurality of other ion species having respective different m/z values;
• determine, from the measured ion flux of the pre-determined ion species, a time duration required to accumulate a pre-determined quantity of the pre-determined ion species;
• and
• cause the RF ion trap to receive therein the stream of ions for an accumulation time period having duration, tA, while simultaneously causing the power supply to apply a notched supplemental AC voltage waveform to electrodes of the RF ion trap, the supplemental AC voltage waveform consisting of component frequencies effective to resonantly eject only ion species for which m/z≠(m/z)ISO, the applied supplemental AC voltage waveform further comprising a time-varying amplitude, A(t), that decays with time, t, during at least a portion of the accumulation time period.