Absorption of Semi-Volatile Compounds in Oiled Impaction Substrates: Measurement of Pyrene Absorption

Abstract

ABSTRACT. Oiled impaction substrates have been used to prevent particle bounce during the collection of size-segregated aerosol samples, which have been analyzed for trace-level airborne organic compounds, including polycyclic aromatic hydrocarbons (PAHs). The use of the oiled impaction substrates, however, may introduce another sampling artifact-the absorption of semivolatile species from the gas phase which could arti cially increase the amount of PAHs attributed to the aerosol. In this article, laboratory measurements of the absorption of a particular PAH, pyrene, from the gas phase to impaction substrates of polytetra uoroethylene membranes impregnated with dibutyl phthalate are reported. Overall mass transfer coef cients are determined from the data. These results are used to calculate the absorption of gas phase PAHs during sampling of size-segregated atmospheric particles. Criteria are developed to determine if the absorption artifact is negligible. The rst criterion requires that the analyte be negligibly soluble in the oil; this criterion is met by none of the impaction oils reported in the literature. The second criterion is that species do not have time to reach an equilibrium distribution between the gas phase and impaction oil; this criterion is met for nonvolatile species, those with vapor pressures equal to or less than that of benzo[a]pyrene (3.5 3 10 6 Pa). We recommend that oiled impaction substrates be used only if the absorption artifact is expected to be negligible on the basis of these criteria.

Removal of Naphthalene, Phenanthrene, and Pyrene by Sorbents from Hot Gas

“…The CO2 was released at low temperatures, as a result of the decomposition of acid surface groups. CO has their origin from weakly acidic, neutral, and basic groups (19), which are thermally more stable, and therefore was released at higher temperatures. Np, Phe, and Py molecular parameters (molecular volume and mean diameter) were calculated according to Bondi (20) and are shown in Table 2.…”

Seasonal Variation of the Particle Size Distribution of n-Alkanes and Polycyclic Aromatic Hydrocarbons (PAHs) in Urban Aerosol of Guangzhou, China

“…Other special devices such as diffusion denuders and foam plugs were not used due to the difficulties in applying these devices. And greased substrates didn't also utilize due to absorption of gas phase compounds in the grease film, especially when collecting samples over periods of days (Allen et al, 1999). At each sampling period, the samples were collected for 6 consecutive days.…”

Observations of Twelve USEPA Priority Polycyclic Aromatic Hydrocarbons in the Aitken Size Range (10–32 nm Dp)

“…The sampling system consisted of a Nano-MOUDI impactor (10 nm < Dp < 56 nm) behind a MOUDI impactor (56 nm < D p < 2.5 µm), both running at 10 liters per minute (lpm) by masking two-thirds of the MOUDI orifices. While oiled impaction collection matrices have been used to prevent particle bounce, their use has been shown to cause absorption of semivolatile species from the gas phase, thus artificially increasing the amount of PAHs attributed to the particle phase (Allen et al 1999 Samples from the five nightly collection periods allowed sufficient PAH mass on each size bin for accurate polycyclic aromatic hydrocarbons (PAHs) quantification by HPLC with selective fluorescence detection (Eiguren-Fernandez and Miguel 2003). Although denuders were not used in this study, aerosol dynamic considerations indicate that the use of denuders-commonly used to remove vapor-phase species to minimize sampling artifacts-may actually promote sampling artifacts for particles between 10-30 nm D p .…”