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

On-line Mass Spectrometry and MS2 are applied to monitor and identify the by-products and total mineralization products of TiO2/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 CO2 were also detected as final mineralization products of the four chlorinated VOCs. Structural characterization of byproducts was accomplished via MS2 collision-induced dissociation of molecular ions or characteristic ionic fragments. (C) 1998 American Society for Mass Spectrometry.