ABATEMENT OF VOLATILE ORGANIC-COMPOUNDS BY CORONA DISCHARGE, A STUDY OF THE REACTIVITY OF TRICHLOROETHYLENE UNDER ATMOSPHERIC-PRESSURE IONIZATION CONDITIONS

Non-equilibrium plasma based technologies are currently being develope d for the abatement of volatile organic compounds (VOCs). The promisin g results obtained so far encourage efforts in fundamental research to improve our knowledge of the processes involved. To gain insight into the role played by analyte-derived ionic species we have investigated the ion chemistry of trichloroethylene (TCE), a representative VOC, i n air at ambient pressure by means of an atmospheric pressure chemical ionization commercial mass spectrometer, Different experimental condi tions were examined with regard to the following parameters: ion sourc e temperature, water and TCE concentrations, and extraction potential, Notably, modulation of the variable extraction potential provided a m eans to probe structure and reactivity of the ionic species of interes t. Products resulting from TCE oxidation were observed in the analysis of both positive and negative ions, Particularly prominent is a C2H2C l2O+. species, likely of enol structure, due to reaction with water, A reaction scheme is proposed based on nucleophilic addition of water t o ionized TCE followed by elimination of HCl. The negative ion chemist ry of TCE is dominated by Cl- and its clusters with water and TCE. At low temperature and with water in high concentration very large positi ve and negative ion hydrate clusters (with up to 50 water molecules) c ould be observed. (C) 1997 by John Whey & Sons, Ltd.