| 摘要 |
A tandem mass spectrometer is disclosed having a collisional damping cell that slows down and adapts an ion beam, from a time-of-flight mass spectrometer (TOF MS) to a second mass spectrometer, preferably an orthogonal TOF MS. The cell provides a substantial damping of the energy of the ions in multiple collisions with a gas. An RF-only quadrupole is used to spatially focus the ion beam in the collision cell. As result, the operation of second mass spectrometer can be decoupled from the rest of the instrument, or in some cases with the energy being sufficiently damped the pulsed nature of the primary ion beam can be partially preserved and used to enhance the sensitivity of the second mass spectrometer. An ion selector passes only stable parent ions of interest, thereby introducing ions into the cell at a well controlled low energy. The ion beam can be injected into the collision cell with or without separation as well as with or without fragmentation. Thus, the results obtained with the second mass spectrometer can be used to control each individual step of the tandem MS, including ion formation in the source, ion focusing, metastable fragmentation in the first time of-flight spectrometer, primary ion selection and fragmentation in the cell as well as provide mass analysis of fragment ions. By using a high repetition rate laser at increased energy levels, the acquisition of data is significantly accelerated and adjustments on each individual step may be conveniently automated. The MS analysis can be also applied to analysis of analytes from continuous ion sources by using an orthogonal pulser in the first TOF MS to modulate the beam followed by spatial focusing of the pulsed beam.
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