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Gas phase titration
Gas phase titration
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Gas phase titration (GPT) provides a potentially primary method for ozone analysis, which is an alternative to the conventional method of UV photometry. With optimal design of the GPT system, particularly the flow control system and the reaction vessel, the titration reaction
NO + O3 NO2 + O2
goes virtually to completion. The ozone amount fraction is quantified through the change of mole fraction of either NO or NO2 traceable to gravimetrically produced standards. The BIPM GPT system is designed for the determination of O3 in the range (0 to 1) µmol mol–1. The apparatus incorporates three different gas analysers: chemiluminescence (for NO and NO2); UV photometry (for O3); and Fourier transform infrared spectroscopy (for O3, NO and NO2).

FTIR spectroscopy has the advantage of being simultaneously sensitive to the three main species of interest (O3, NO and NO2) as well as to the possible trace contaminant and side product species (H2O, N2O, HNO3) and indeed to any infrared active gas species. The spectra below were collected in one GPT experiment using a 6.4 m pathlength gas cell.