Gas-wall partitioning of oxygenated organic compounds: Measurements, structure-activity relationships, and correlation with gas chromatographic retention factor

Abstract

Gas-wall partitioning of 50 oxygenated organic compounds was investigated by using gas chromatography to monitor time-dependent gas-phase concentrations of authentic standards added to a large Teflon environmental chamber. Compounds included C8- C14 monofunctional ketones and alcohols, C5-C9 monoacids, and C4-C10 diols with linear and cyclic structures. Measured time constants for reaching gas-wall partitioning equilibrium ranged from ∼10 to 100 min with an average value of ∼30 min and exhibited no obvious trend with compound structure, whereas the extent of equilibrium partitioning to the walls ranged from ∼0 to 100% and increased with increasing carbon number and with functional group composition in the order ketones < alcohols > monoacids < diols. When results were modeled using an approach analogous to one commonly used to describe absorptive gas-particle partitioning in terms of compound vapor pressure and aerosol mass loading it was determined that the absorptive properties of the Teflon film walls were equivalent to 2-36 mg m-3 of liquid organic aerosol particles. These results, when combined with those obtained in previous studies, indicate that most multifunctional products formed from the oxidation of atmospherically important hydrocarbons including isoprene, monoterpenes, aromatics, and alkanes have the potential to undergo significant partitioning to the walls of Teflon chambers and thus be lost from further chemical reaction and secondary organic aerosol formation as well as from gas and particle analyses. Two approaches for estimating equilibrium gas-wall partitioning in such studies are presented: one is a structure-activity relationship based on the absorptive gas-wall partitioning model and the other involves the use of observed correlations between gas-wall partitioning and compound retention on a gas chromatographic column.