| 摘要 |
An object of the present invention is to provide a method of discriminating singly-charged ions from multiply-charged ions by the use of an ion trap type mass spectrometer which is an inexpensive mass spectrometer. <??>This object is achieved by a mass-analyzing method using an ion trap type 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, comprising a 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 said 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, and a fourth step of scanning said main high frequency voltage and ejecting ions from said mass analyzing unit and detecting thereof. <??>With this, chemical noises can be reduced dramatically. <IMAGE>
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