Patent ID: 8384028

Claim:
An MS/MS mass spectrometer comprising: a first mass separator for selecting, as a precursor ion, an ion having a specific mass from among various kinds of ions; a collision cell, containing an ion guide for transporting ions by a radio-frequency electric field while converging those ions, for making the precursor ion collide with a predetermined gas to dissociate the precursor ion by collision-induced dissociation; a second mass separator for selecting an ion having a specific mass from among various kinds of product ions generated by the dissociation of the precursor ion, the first mass separator, the collision cell and the second mass separator being linearly arranged; a) lens electrodes respectively provided at an entrance end and an exit end of the collision cell; b) a voltage-applying means for applying a DC voltage to one or both of the entrance lens electrode and the exit lens electrode; and c) a control means for controlling the voltage-applying means so that, when an ejection of ions into the first mass separator is halted, a pulsed DC voltage for either pulling or repelling the ions within the collision cell is applied to the aforementioned one or both of the lens electrodes in order to remove the ions from the collision cell.