IMPROVEMENTS IN MS/MS SCAN METHODS FOR A QUADRUPOLE/TIME OF FLIGHT TANDEM MASS SPECTROMETER

摘要

There is provided a method of effecting mass analysis on an ion stream, the method comprising passing the ion stream through a first mass resolving spectrometer, to select parent ions having a first desired mass-to--charge ratio. The parent ions are then subject to collision-induced dissociation (CID) to generate product ions, and the product ions and any remaining parent ions are trapped; the CID and trapping can be carried out together in a linear ion trap. Periodically pulses of the trapped ions are released into a time of flight (TOF) instrument to determine the mass-to-charge ratio of the ions. The delay between the release of the pulses and the initiation of the push- pull pulses of the TOF instrument are adjusted to maximize the duty cycle efficiency and hence the sensitivity for a selected ions with a desired mass-to-charge ratio. This technique can be used to optimize the performance for a parent ion scan, and MRM scan or a neutral loss scan.