Ozone Quantification by Selected Ion Flow Tube Mass Spectrometry: Influence of Humidity and Manufacturing Gas of Ozone Generator.

The quantification of ozone by SIFT-MS was investigated in conditions suitable with an industrial emission context (high ozone demand, dry air/oxygen as the manufacturing gas of the ozone generator, and high humidity levels beyond saturation at room conditions). Ozone reacts with four negative precursor ions available in the SIFT-MS device (NO2-, O2-, HO-, and O-), each precursor ion having its specific domain of linearity. For a high ozone concentration range, only NO2- and O2- have resulted in a linear behavior (between 1 and 100 ppmv of O3 for NO2-, between 1 and 50 ppmv of O3 for O2-). No water interference was identified during ozone measurements by SIFT-MS using NO2- and O2- precursor ions, even with extreme humidity levels. The presence of nitrogen oxide contaminants (due to the use of dry air as the manufacturing gas of the ozone generator) affected the ozone quantification by SIFT-MS. It is critical for NO2- precursor ions, whose rate constant varied as a function of NO2 concentrations. With O2- precursor ion, ozone was successfully measured in the presence of nitrogen oxides; however, the secondary chemistry must be taken into account.