| 摘要 |
A method of operating a quadrupole ion trap as a mass spectrometer, in which the ion mass to be detected is selected by adjusting the three-dimensional quadrupole storage field to make the .beta.z value of the selected mass equa l to a fixed, predetermined .beta.z value of a narrow range of frequencies excluded from a broadband supplemental RF electric field. The ions are detected to provide a signal corresponding to the amount of the selected ion mass.
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