Quadrupole ion trap mass spectrometer having two pulsed axial excitation input frequencies and method of parent and neutral loss scanning and selected reaction monitoring
AssigneesFinnigan Corporation, University of Florida
InventorsJodie V. Johnson, Randall E. Pedder, Richard A. Yost, Michael S. Story
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Abstract
This invention relates generally to a quadrupole ion trap mass spectrometer and method of operation and more particularly to an ion trap mass spectrometer in which pulses of energy of predetermined frequencies are applied across the end caps to independently and sequentially excite ions of different masses trapped in the ion trap to perform parent scanning, neutral loss scanning and selected reaction monitoring.
Claims6
In a quadrupole ion trap mass spectrometer of the type which includes a ring electrode and end caps defining a trap volume,
- means for applying voltages to said electrodes to generate within the ion trap volume trapping fields which trap selected ions,
- means for applying pulses of energy having a frequency which resonantly excites a trapped parent ion, and
- means for applying pulses of energy having a second predetermined frequency following each of said first pulses to excite and eject daughter ions.
The method of scanning a quadrupole ion trap mass spectrometer of the type which includes a ring electrode and end caps defining a trapping volume, comprising the steps of
- introducing ions of interest into said trapping volume,
- applying voltages to said electrodes to provide a trapping field for trapping parent ions having masses over a range of interest,
- maintaining the voltage applied to said ring electrode constant,
- applying first voltage frequency pulses with successive pulses having different frequencies to excite different parent ions and cause said parent ions to resonate and undergo collision-induced dissociation to form daughter ions, and
- applying second voltage frequency pulses at the resonant frequency of a daughter ion to cause daughter ions to resonate and undergo ejection from the ion trap to the detector for the purpose of performing parent scanning, neutral loss scanning and selected reaction monitoring.
Dependencies are inferred from the claim text.