Mass spectrometry on-line monitoring and MS² product characterization of TiO₂/UV photocatalytic degradation of chlorinated volatile organic compounds

On-line Mass Spectrometry and MS 2 are applied to monitor and identify the by-products and total mineralization products of TiO 2 /UV photocatalytic degradation of four chlorinated volatile organic compounds (VOCs): trichloroethylene (TCE), tetrachloroethylene (TeCE), chloroform, and dichloromethane. Selected multiple ion mass spectrometry monitoring using characteristic 70 eV electron ionization ionic fragments monitors in real time the destruction of the starting VOC and the formation of by-products, i. e., the degrees of VOC mineralization, as a function of the flow and relative humidity of the carrier gas (synthetic air). Several by-products were detected: phosgene for TCE, TeCE, and chloroform; dichloroacetyl chloride for TCE; and trichloroacetyl chloride for TeCE. Cl 2 and CO 2 were also detected as final mineralization products of the four chlorinated VOCs. Structural characterization of by-products was accomplished via MS 2 collision-induced dissociation of molecular ions or characteristic ionic fragments.