Chromatograph mass spectrometer

A chromatograph mass spectrometer comprising:

• a measurement unit in which a chromatograph and a tandem mass spectrometry section capable of an MS/MS analysis are combined together;
• a controller configured to perform a chromatograph mass spectrometric analysis by controlling the measurement unit so as to operate the tandem mass spectrometry section to cyclically perform analysis cycles, where each of the analysis cycles includes at least a first mass spectrometric analysis in which a measurement of ions is performed over a predetermined mass-to-charge-ratio range and an MS/MS analysis by data independent acquisition in which ions included within each of a plurality of windows formed by dividing the mass-to-charge-ratio range are designated as a precursor ion;
• a window selector configured to select, during an execution of an analysis cycle, a window among the plurality of windows for an MS/MS analysis by data dependent acquisition which is irregularly performed in an ongoing analysis cycle, based on intensity information obtained for each of the plurality of windows from an MS/MS spectrum acquired by the MS/MS analysis by data independent acquisition;
• a precursor-ion determiner configured to determine a precursor ion corresponding to the window selected by the window selector in a mass spectrum acquired by the first mass spectrometric analysis in the ongoing analysis cycle, based on peak information included within a mass-to-charge-ratio range of the window;
• and
• a data-dependent-acquisition condition setter configured to inform the controller of the precursor ion determined by the precursor-ion determiner, as the precursor ion for the MS/MS analysis by data dependent acquisition which is irregularly performed in the ongoing analysis cycle.