Mass spectrometer and mass spectrometric method

摘要

There is provided an ion trap mass spectrometer which can detect fragment ions having a low mass and enables high-sensitivity measurement. A mass spectrometer has an ion source generating sample ions; an ion trap having a pair of and endcap electrodes and a ring electrode and accumulating ions generated by the ion source and isolating precursor ions from the accumulated ion and dissociating the isolated precursor ions and ejecting the dissociated ions from the ion trap. A gas introduction hole is arranged in the endcap electrode or the ring electrode for introducing in intermittently-introduced bath gas therethrough into the ion trap. A detector detects the ions ejected from the ion trap. The center axis of the gas introduction hole is arranged so as to pass through a region near the center of gravity of the ion trap.