Patent ID: 6852970

Claim:
A mass spectrometer, comprising: an atmospheric pressure chemical ionization source having a primary ionization part for generating a primary ion by means of electric discharge of a reagent gas, a secondary ionization part for generating an ion of a sample gas by a reaction of said primary ion and said sample gas, and a hole disposed between said primary ionization part and said secondary ionization part as a passage for said primary ion to enter from said primary ionization part into said secondary ionization part while said secondary ionization part being maintained at negative pressure as compared with said primary ionization part; a mass spectrometric part for performing mass spectrometric analysis of said ion generated in said secondary ionization part; a mixing portion for mixing said sample gas to be introduced into said secondary ionization part with a dilution gas; means for controlling a flow rate of said dilution gas for flowing through said mixing portion; and means for controlling a flow rate of said sample gas for flowing through said mixing portion, wherein mixed gas obtained by mixing said sample gas with said dilution gas is introduced into said secondary ionization part.