Method for mass spectrometry and chromatograph mass spectrometer

A chromatograph mass spectrometer including a chromatograph and a mass spectrometer combined together, comprising:

• a medium supplier configured to supply a medium as a mobile phase or carrier gas;
• a passage configured to introduce, into the mass spectrometer, the medium supplied from the medium supplier, wherein a substance is initially adhered to a wall surface of a member forming the passage, and the substance is configured to separate from the wall surface and mix into the medium;
• an ionizer configured to ionize the medium together with the substance mixed into the medium;
• a measurement executer configured to perform a mass separation and a measurement of an ion or ions having one or more previously determined mass-to-charge ratios generated from the substance in the ionizer, using a plurality of measurement conditions which differ from each other in a value of voltage applied to at least one electrode included in one or more electrodes provided in the mass spectrometer;
• and
• a voltage value determiner configured to determine a value of voltage applied to each of the one or more electrodes so that an intensity of each of the ion or ions having the one or more mass-to-charge ratios satisfies a previously determined criterion.