Ion trap/time-of-flight mass analyzing apparatus and mass analyzing method

Abstract

An 'ion trap-TOF/MS' capable of calibrating the observed mass for each of an ion trap and a TOF. In the ion trap-TOF/MS, sample ions having known mass numbers and ionized by an ion source are trapped within an ion trap. Auxiliary AC voltages having a frequency component ω are applied to the end cap electrodes of the ion trap to expel unwanted ions out of the ion trap. A measurement process is carried out by applying DC voltages to the ring electrode and the end cap electrodes to expel an ion remaining within the ion trap, and measuring the mass number of the expelled ion by the time-of-flight mass spectrometer. The measurement process is repeated while changing the frequency component ω, and the ion signal intensity measured by the time-of-flight mass spectrometer is compared with a previously stored threshold, thereby making calibration of the frequency component ω for the ion having the known mass number. Thus, the calibrating of the observed mass can be realized for each of the ion trap and the TOF.