Patent ID: 8866074

Claim:
A tandem mass spectrometer including an ion source that ionizes a compound in a sample, a first mass separating unit that selects an ion having a specific mass-to-charge ratio in various produced ions as a precursor ion, an ion dissociating unit that dissociates the precursor ion, and a second mass separating unit and a detector that perform a mass spectrometry of various product ions that are produced by the dissociation, the tandem mass spectrometer comprising: a) an ion mixing unit that is placed between the ion dissociating unit and the second mass separating unit, and adjusts traveling of ions so that ions are mixed together at least at a time point when the ions are introduced into the second mass separating unit, with respect to various ions ejected from the ion dissociating unit at different timings; b) an analysis controlling unit that switches a condition under which the ion is dissociated in the ion dissociating unit from one to another, and controls an operation of the ion mixing unit so that the ions ejected from the ion dissociating unit during a time period of the switch are mixed together at least at the time point when the ions are introduced into the second mass separating unit; and c) a data processing unit that acquires a mass spectrum based on a detection signal that is obtained by the second mass separating unit and the detector in a predetermined mass-to-charge ratio range during the time period of switching the dissociation condition by the analysis controlling unit.