Patent ID: 8030611

Claim:
A mass spectrometer comprising: an ionization chamber for producing ion species by ionizing a sample; a mass separator for separating a plurality of the ion species according to their mass-to-charge ratios by scanning the mass-to-charge ratio; a detector for detecting an intensity of detection of the ion species for every mass-to-charge ratio, the mass-to-charge ratio at which a peak of a mass spectrum appears is extracted based on the intensity of detection; a setting unit for setting a mass number of a target ion divided by a natural number as a measuring upper limit based on the mass-to-charge ratio at which the peak appears; and a dissociation chamber for producing a fragment ion by selecting the target ion from the ion species and dissociating the target ion; wherein the mass separator separates a plurality of the fragment ions according to their mass-to-charge ratios in a range whose upper limit is the measuring upper limit, and the detector detects the intensity of detection of the fragment ion for every mass-to-charge ratio.