Mass spectrometry method and mass spectrometer

A mass spectrometer comprising:

• a reaction chamber into which a precursor ion derived from a sample component is introduced;
• an inert gas introducing section configured to introduce an inert gas into the reaction chamber;
• a hydrogen radical introducing section configured to introduce hydrogen radicals into the reaction chamber;
• an ion detecting section configured to detect ions emitted from the reaction chamber after separating the ions according to a mass-to-charge ratio;
• a first measurement controller which is a controller configured to control the inert gas introducing section and the ion detecting section, the first measurement controller configured to dissociate the precursor ion by collision between the precursor ion and an inert gas molecule to generate product ions, and acquire first product ion spectrum data by detecting the product ions by the ion detecting section;
• a second measurement controller which is a controller configured to control the hydrogen radical introducing section and the ion detecting section, the second measurement controller configured to dissociate the precursor ion by a reaction between the precursor ion and hydrogen radicals to generate product ions, and acquire second product ion spectrum data by detecting the product ions by the ion detecting section;
• and
• a product ion set extractor configured to extract a set of product ions having a predetermined mass difference in the first product ion spectrum data and the second production spectrum data obtained for a same precursor ion.