Patent ID: 8829434

Claim:
A mass spectrometer comprising: a collision chamber including linear multipolar electrodes, and accelerating fragment ions in a direction along the linear multipolar electrodes by superimposingly applying an AC voltage for collision and a first DC voltage between the linear multipolar electrodes, having a molecule ion collide with a neutral molecule to cause collision induced dissociation of the molecule ion and to generate the fragment ions, and applying a second DC voltage between a front stage electrode and a later stage electrode which are divided from each linear multipolar electrode; a mass spectroscopy unit carrying out mass separation of the fragment ions with mass-to-charge ratios, the fragment ions accelerated in the collision chamber; and a control unit configured to determine the second DC voltage based on the mass-to-charge ratios of the fragment ions to be selected in the mass spectroscopy unit such that velocities of the fragment ions in the collision chamber become equal regardless of the mass-to-charge ratios of the fragment ions.