Ozone measurement with silica cartridges and HRGC-MS analysis

Ozone in ambient air is collected onto silica gel cartridges impregnated wi th pentafluorophenylhydrazine (PFPH) and 1,2-di(4-pyridyl)ethylene (DPE): s o that the pyridine-4 aldehyde formed by DPE: oxidation is converted into t he 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 standar dized ozone source. When compared with UV photometry analyzers, this active chromatographic method (ACM) demonstrates a very good accuracy (ACM/UV pho tometer = 0.97) and precision (12.0-14.0%) under both laboratory and field sampling conditions at ozone concentrations of 20-200 mug m(-3) and exposur e times of 1-3 h. The sampling performance was found to be insensitive to r elative humidity (r.h.) variations in the 25-90% range and any interference effects could not be observed from :various agents, except light, which ca ll be eliminated by using an aluminium shelter. The detection limit for ozo ne achievable with the ACM in air samples collected at 0.5 L min(-1) for 1 h was found better than 0.5 mug m(-3).