Supersonic jet/multiphoton ionization/mass spectrometry of dioxins formed by the thermal reaction of phenols in the absence and presence of an FeCl3 catalyst

Dioxins, which are thermally produced from several precursor molecules, wer e investigated by supersonic jet/multiphoton ionization/time-of-flight mass spectrometry (SSJ/MPI/TOF-MS). Dibenzofuran and dibenzo-p-dioxin were effi ciently generated from o-chlorophenol and also from phenol after a chlorina tion reaction with FeCl3. The present technique was employed for the contin uous monitoring of a specified isomer, e,g,, m-chlorophenol, which is forme d at relatively low temperatures by chlorination of phenol with FeCl3, A di merization reaction that forms a dibenzo-p-dioxin, e.g,, dichlorodibenzo-p- dioxin from 2,4-dichlorophenol, at relatively high temperatures was also in vestigated. The number of chlorine atoms in the dioxin molecule was largely correlated with the number of chlorine atoms in the precursor molecule. Ho wever, some unexpected compounds, which probably occur by dechlorination an d rearrangement reactions, were also found. Thus, the SSJ/MPI/TOF-MS techni que represents a sensitive, as well as selective, analytical method for mon itoring thermally generated dioxins.