Ozone measurement with silica cartridges and HRGC-MS analysis

Abstract

Ozone in ambient air is collected onto silica gel cartridges impregnated with pentafluorophenylhydrazine (PFPH) and 1,2-di(4-pyridyl)ethylene (DPE), so that the pyridine-4 aldehyde formed by DPE oxidation is converted into the corresponding PFPH derivative (PPH). The latter product is determined by HRGC/MS. Since the ozonolysis reaction proceeds stoichiometrically on the cartridge, there is no need for calibration in the gas phase with a standardized ozone source. When compared with UV photometry analyzers, this active chromatographic method (ACM) demonstrates a very good accuracy (ACM/UV photometer = 0.97) and precision (12.0–14.0%) under both laboratory and field sampling conditions at ozone concentrations of 20–200 μg m^–3 and exposure times of 1–3 h. The sampling performance was found to be insensitive to relative humidity (r.h.) variations in the 25–90% range and any interference effects could not be observed from various agents, except light, which can be eliminated by using an aluminium shelter. The detection limit for ozone achievable with the ACM in air samples collected at 0.5 L min^–1 for 1 h was found better than 0.5 μg m^–3.