Patent ID: 6787767
Filing Date: 2004-09-07
Classification: H01J

Abstract:
A mass-analyzing method using an ion trap mass spectrometer which is equipped with a ring electrode and one pair of end cap electrodes and temporarily traps ions in a three-dimensional quadrupole field to mass-analyze a sample, comprisinga first step of applying a main high frequency voltage to said ring electrode to form a three-dimensional quadrupole field, a second step of generating ions in a mass analyzing unit or injecting ions from the outside and trapping ions of a predetermined mass-to-charge ratio range in said mass analyzing unit, a third step of applying a supplementary AC voltage having a plurality of frequency components between said end cap electrodes and scanning the frequency components of said supplementary AC voltage, said supplementary AC voltage having a first frequency component with a voltage (V1) at least high enough to eject ions in resonance and a second frequency component with a voltage value (V2) high enough to excite ions in resonancs but not high enough to eject ions in resonance, and a fourth step of scanning said main high frequency voltage and ejecting ions from said mass analyzing unit and detecting thereof.