Patent ID: 7381948

Claim:
A method for calibrating a mass spectroscope that includes an ion source for generating ions, an ion trap, and a detector for detecting ions output from said trapping space, said method comprising: a first step of acquiring a first mass spectrum by trapping an ionized sample of which the mass number is known using said ion trap, discharging all of the trapped ions, and then detecting them with said detector; a second step of acquiring a second mass spectrum by trapping a new ionized sample of which the mass number is known using said ion trap, discharging particular ions by resonance based on a predetermined set condition, and then detecting the remaining ions with said detector, wherein said first and said second steps are repeated for a predetermined number of times while said set condition is varied, and a ratio of intensity of said first mass spectrum to that of said second mass spectrum is calculated under each set condition so as to determine an ion resonance condition based on a change in said intensity ratio, and wherein a resonance condition of said ion trap is set based on the preceding steps.