MS/MS scan methods for a quadrupole/time of flight tandem mass spectrometer

• Main Authors: Chernushevich, Igor, Thomson, Bruce
• Format: Patent
• Language: English
• Published: 14.01.2003

This invention relates to mass spectrometry including multiple mass analysis (MS/MS) steps and final analysis in a time of flight (TOF) device or in general any orthogonal mass spectrometry system. This invention is more particularly concerned with such a technique carried out in a hybrid tandem quadrupole-TOF (QqTOF) spectrometer and is concerned with improving the duty cycle of such an instrument for parent or precursor ion scanning and like operations, or more generally to improving the duty cycle over a wide mass range for any type of scan. 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 ion 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.