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 timedependent gas-phase concentrations of authentic standards added to a large Teflon environmental chamber. Compounds included C 8 -C 14 monofunctional ketones and alcohols, C 5 -C 9 monoacids, and C 4 -C 10 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.

Effects of gas–wall partitioning in Teflon tubing and instrumentation on time-resolved measurements of gas-phase organic compounds

“…(15), the value of C w,t = 4 g m −3 reported above is equivalent to ∼ 10-30 mg m −3 of liquid organic aerosol in an 8 m 3 chamber. This is comparable to the values of C w determined in FEP Teflon chambers: 16 mg m −3 for 1-alkenes and 24 and 78 mg m −3 for 2-ketones (Matsunaga and Ziemann, 2010;Yeh and Ziemann, 2015), where values from Matsunaga and Ziemann (2010) were recalculated with c * values obtained using SIMPOL.1 (Pankow and Asher, 2008). The similarity in C w values indicates that gas-wall partitioning of organic compounds is similar for PFA and FEP Teflon.…”

“…This approach seems reasonable, considering the nature of the processes involved, the dependence of gas-wall partitioning on c * (Matsunaga and Ziemann, 2010;Krechmer et al, 2016), and the observation that the extent of partitioning of an organic compound in a Teflon chamber correlates well with its retention time measured by gas chromatography (Yeh and Ziemann, 2015). Based on the chamber results, we assume that the rate of absorption of a compound into the walls is controlled by gas-phase diffusion to the walls (and thus does not depend on mass accommodation) and treat absorption and desorption as first-order processes.…”

“…The equilibrium reached in this process can be conveniently described using a model that is analogous to gas-particle partitioning theory (Matsunaga and Ziemann, 2010), in which the chamber walls are treated as an equivalent mass concentration of liquid organic aerosol, C w . Values of C w reported by Matsunaga and Ziemann (2010), Yeh and Ziemann (2015), and Krechmer et al (2016) ber, a range indicating that a significant fraction of organic products formed from oxidation reactions regularly studied in environmental chambers (and even some less-volatile precursors) will be absorbed into the walls at equilibrium. Using typical values for C w and the timescale for reaching gas-wall partitioning equilibrium, one can incorporate the effect into box models to estimate the effect of partitioning on chamber measurements, as has been done in several studies of secondary organic aerosol yields (Matsunaga and Ziemann, 2010;Shiraiwa et al, 2013;McVay et al, 2014;Bian et al, 2015;Krechmer et al, 2015;La et al, 2016).…”

“…These properties also make Teflon the material of choice for environmental "smog" chambers, most of which are constructed using fluorinated ethylenepropylene (FEP) or perfluoroalkoxy (PFA) Teflon film (Hallquist et al 2009). Although it has been known for decades that Teflon is permeable to small organic compounds (Yi-Yan et al, 1980;Chemours, 2016), only recently have environmental chamber studies shown that it can also absorb large gaseous organic compounds in an equilibrium partitioning process that is rapid (timescale ∼ 10-60 min), reversible, and independent of the age of the chamber (Matsunaga and Ziemann, 2010;Yeh and Ziemann, 2015;Zhang et al, 2015;Krechmer et al, 2016;Ye et al, 2016). The equilibrium reached in this process can be conveniently described using a model that is analogous to gas-particle partitioning theory (Matsunaga and Ziemann, 2010), in which the chamber walls are treated as an equivalent mass concentration of liquid organic aerosol, C w .…”

Technical Note: Development of chemoinformatic tools to enumerate functional groups in molecules for organic aerosol characterization

“…In this work, positional information of FGs are used only for conjugated aldehyde, ketone, and ester with an alkene or benzene ring (Table 1, substructures 40-48). With regards to the use of SIMPOL.1, vapor pressure predictions can also be improved by updating coefficients for the model with new estimates (Yeh and Ziemann, 2015).…”