Method for mass spectrometry

The present invention is the target compound by the charged particle transfer reaction from the target compound, and a mixture of at least one interfering compound samples the at least one charged particle (charged particle) affinity higher additive than interfering compound in containing the sample mixture It relates to a mass spectrometry method which comprises selectively ionized. In according to the mass spectrometry method according to the invention, whereby the interfering compound other than the desired compound contained in the sample was added accompanied by that efficiently control is ionized by the transition reaction of the charged particles, such as protons, electrons of a predetermined additive sample the sensitivity of the ion derived from the target compound to be analyzed by a mass meter can be selectively enhanced.