Real-time measurement of phase partitioning of organic compounds using a proton-transfer-reaction time-of-flight mass spectrometer coupled to a CHARON inlet

Abstract

Abstract. Understanding the gas–particle partitioning of semivolatile organic compounds (SVOCs) is of crucial importance in the accurate representation of the global budget of atmospheric organic aerosols. In this study, we quantified the gas- vs. particle-phase fractions of a large number of SVOCs in real time in an urban area of East China with the use of a CHemical Analysis of aeRosols ONline (CHARON) inlet coupled to a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS). We demonstrated the use of the CHARON inlet for highly efficient collection of particulate SVOCs while maintaining the intact molecular structures of these compounds. The collected month-long dataset with hourly resolution allows us to examine the gas–particle partitioning of a variety of SVOCs under ambient conditions. By comparing the measurements with model predictions using instantaneous equilibrium partitioning theory, we found that the dissociation of large parent molecules during the PTR ionization process likely introduces large uncertainties to the measured gas- vs. particle-phase fractions of less oxidized SVOCs, and therefore, caution should be taken when linking the molecular composition to the particle volatility when interpreting the PTR-ToF-MS data. Our analysis suggests that understanding the fragmentation mechanism of SVOCs and accounting for the neutral losses of small moieties during the molecular feature extraction from the raw PTR mass spectra could reduce, to a large extent, the uncertainties associated with the gas–particle partitioning measurement of SVOCs in the ambient atmosphere.

Characterization of biogenic volatile organic compounds and their oxidation products at a stressed pine forest close to a biogas power plant

“…Besides, we found that the concentrations of particulate C4H7O1-2 + showed increased values from early nighttime (18:00-20:00) to midnight (0:00-2:00 of the next day). As mentioned before, the fragmentation of cis-pinonic acid in the CHARON-PTR-ToF-MS can produce the fragment ions C4H7O + , C6H11O2+ and C10H15O2 + (Gkatzelis et al, 2018;Peng et al, 2023;Muller et al, 2017;Leglise et al, 2019). Furthermore, we observed a similar diurnal pattern of C4H7O + and C10H15O2 + in the particle phase, suggesting that the nighttime increase of particulate C4H7O + was likely contributed by the fragmentation of cis-pinonic acid.…”

“…CC BY 4.0 License. fragment ions (C4H7O + , C6H11O2+ and C10H15O2 + ) were generally higher than the parent ion C10H17O3 + (Leglise et al, 2019;Peng et al, 2023). In this study, we found that only a small fraction of the cis-pinonic acid parent ion C10H17O3 + was detected by the CHARON-PTR-ToF-MS compared to the fragment ions C4H7O + , C6H11O2 + and C10H15O2 + (Fig.…”

“…3d) are most likely fragments from C9-10-monoterpene derived oxidized products which are prone to fragmentation in the CHARON-PTR-ToF-MS (Gkatzelis et al, 2018). Leglise et al, (2019) and Peng et al, (2023) further confirm the fragmentation of oxygenated organic compounds inside the CHARON-PTR-ToF-MS via the loss of neutral water, carbonyl, or carboxyl groups (-H2O, -CO and -CO2).…”

“…For instance, cis-pinonic acid (C10H17O3 + ) a monoterpene oxidation product as detected by the CHARON-PTR-ToF-MS can produce the typical fragment ions of C4H7O + , C6H11O2+ and C10H15O2 + (Peng et al, 2023;Leglise et al, 2019). Furthermore, the relative abundance of https://doi.org/10.5194/egusphere-2024-1768 Preprint.…”

Sources of organic gases and aerosol particles and their roles in nighttime particle growth at a rural forested site in southwest Germany

“…The groups of CxHyO0-2 + showed higher concentrations during nighttime. Previous studies have reported that CxHy + can be attributed to hydrocarbon-like compounds or the fragmented ions of oxygenated ions through 305 the neutral loss of water (-H2O), a carbonyl group (-CO) and a carboxyl group (-CO2) (Gkatzelis et al, 2018b;Peng et al, 2023). The time series of CxHy + strongly correlated with CxHyO1 + (r = 0.98) and CxHyO2 + (r = 0.82), suggesting that they were mainly contributed by the fragmentation of oxygenated ions at higher masses.…”