Patent ID: 7015461

Claim:
A method of ion attachment mass spectrometry for introducing a gas to be detected and an excess-energy absorbing gas into an ionization chamber in which an ion emitter for emitting positively charged metal ions is arranged, and attaching said metal ions to said gas to be detected in said ionization chamber in an atmosphere of said excess-energy absorbing gas so as to ionize the gas to be detected by the metal ions, then performing measurement of mass of the gas by mass spectrometry, comprising a step of preparing in advance a plurality of types of excess-energy absorbing gas, whose mass numbers are mutually different, in the outside of said ionization chamber, a step of performing the measurement by selecting one type of excess-energy absorbing gas from said plurality of types of excess-energy absorbing gas, and introducing it into said ionization chamber, a step of judging whether interference peaks are generated or not by data of said measurement, and a step of performing the measurement by selecting another type of excess-energy absorbing gas from said plurality of types of excess-energy absorbing gas, which generates no interference peak, when judging that the interference peaks are generated.