A dynamic dilution system-based evaluation of the procedure adopted for determining ozone precursor volatile compounds.

A dynamic dilution system was created to evaluate the performance and the reliability of ozone precursor volatile organic compound (VOC) sampling ("TO-Can" canisters) and analysis (thermal desorption/gas chromatography/flame ionisation detection) techniques used by the "Laboratoire Interregional de Chimie du Grand Est (LIC)". Different atmospheres of VOCs were generated at concentrations between 0.8 and 25 ppb, with temperatures of 0, 10, 20 and 30 degrees C, and with relative humidities of 0, 30, 50, 70 and 90%. These conditions are generally representative of those commonly observed in ambient air in the eastern France. This dynamic dilution allows the simulation of a wide range of scenarios (concentrations, temperatures and relative humidities). After assessing the capacity and performance of the system, it was applied in order to evaluate the recoveries and stabilities of VOCs from canisters used for the collection and analysis of two mixtures of VOCs. The first mixture contained six alkanes (ethane, propane, butane, pentane, hexane and heptane), and the second contained five alkenes (ethene, propene, butene, 1-pentene and 1-hexene), five aromatics (benzene, toluene, ethylbenzene, m-xylene and o-xylene), acetylene, and 1,3-butadiene. No significant losses of alkanes from the canisters were observed after 21 days of storage, and good recoveries of alkanes from the canisters (>80%) were obtained regardless of the concentration, the temperature and the relative humidity. However, losses of certain aromatics were noted at low relative humidity.