The invention aims at providing a method for online-analyzing organic
monomer chlorine or
bromine isotope, which adopts a direct negative
chemical ionization to replace an original complex organic
monomer conversion process. The method is characterized by including the steps: A. gathering
chlorine or
bromine substitute; B. separating
gas chromatography: placing the gathered
chlorine or
bromine substitute into the
gas chromatography to be separated; C. conducting negative
chemical ionization: components analyzed through
chromatography directly flow into a negative chemical
ion source through acapillary column, the negative chemical
ion source replaces an original
electron bombardment source configured on an
isotope ratio
mass spectrum to conduct the negative
chemical ionization; D.
mass spectrometric detecting: on a gas
isotope ratio
mass spectrum, selecting a faraday receiving cup corresponding to
mass number of chlorine or bromine substitute directly, and receiving electronegative isotope fragment ions generated by the negative chemical
ionization. The process is conducted under high
vacuum state, and degree of vacuum is higher than 1.0*10<-3> Pa. The method greatly simplifies aprocess of online-analyzing organic
monomer chlorine or bromine isotope and can form various special devices for detecting organic monomer isotope ratio.