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 (NO 2 - , O 2 - , HO - , and O - ), each precursor ion having its specific domain of linearity. For a high ozone concentration range, only NO 2 - and O 2 - have resulted in a linear behavior (between 1 and 100 ppmv of O 3 for NO 2 - , between 1 and 50 ppmv of O 3 for O 2 - ). No water interference was identified during ozone measurements by SIFT-MS using NO 2 - and O 2 - 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 NO 2 - precursor ions, whose rate constant varied as a function of NO 2 concentrations. With O 2 - precursor ion, ozone was successfully measured in the presence of nitrogen oxides; however, the secondary chemistry must be taken into account.