 |
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 two gas analysers: chemiluminescence (for NO and NO2) and UV photometry (for O3). The system is entirely automated by software developed at the BIPM. In 2004 the GPT facility participated in the pilot study CCQM-P28, where it was compared with over 20 ozone UV photometers and one other GPT system.
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.
GPT reactants and products measured using the BIPM's FTIR facility.
|
|
Summary
