Investigation of Gas-Phase Products from the NO₃ Radical Oxidation of Δ-3-Carene

Abstract

Organic aerosol in the atmosphere has an impact on climate, visibility, and human health. Oxidation of biogenic volatile organic compounds forms secondary organic aerosols by lowering the volatility of the product molecules and thus enhancing partitioning to the particle phase. The NO 3 -initiated oxidation of Δ-3-carene was studied because it connects the interaction between biogenic and anthropogenic emissions to form aerosols. This work characterized the first-generation gas-phase products of the NO 3initiated oxidation of Δ-3-carene in a 7.4 m 3 Teflon FEP chamber using a Vocus proton-transfer-reaction time-of-flight mass spectrometer (Vocus) and a high-resolution time-of-flight chemicalionization mass spectrometer (CIMS) using iodide adducts. The mass spectra not only show the presence of most of the expected products, including dicarbonyl, hydroxy nitrate, carbonyl nitrate, hydroxy dicarbonyl, and dicarbonyl nitrate but also show significant fragmentation of the parent ions in the Vocus through the loss of water and/or nitric acid and other neutral fragments. Parent and fragment ions were grouped together, taking advantage of gas-wall interactions in Teflon tubing, which separate the molecules by their inlet delay time. After grouping product ions, the Vocus signals were used to determine the gas-phase product yields for the NO 3 + Δ-3-carene reaction. A comparison between the Vocus and iodide CIMS data allowed the sensitivity of the iodide CIMS to be investigated. Understanding the mechanism of the oxidation of Δ-3-carene by NO 3 radicals allows for a better understanding of the sources of organic nitrate in the atmosphere and can improve the interpretation of field data and the representation of this chemistry in models.

Effects of 222 nm Germicidal Ultraviolet Light on Aerosol and VOC Formation from Limonene

“…Previous research has identified both the gas-phase products resulting from the ozonolysis of limonene, as well as the underlying reaction mechanisms. ,,− Expected products for the ozonolysis of limonene (limonaldehyde, limonaketone, limononic acid, keto-limonaldehyde, and keto-limononic acid) are shown in Figure S8. , The product mass spectra observed in this work (Figure S8) have some main oxidation products labeled as the expected parent ion (MH + .) There is significant fragmentation in the Vocus and although there are ways to account for product fragmentation, this was not done here …”

“…There is significant fragmentation in the Vocus and although there are ways to account for product fragmentation, this was not done here. 61 …”

Absorption of VOCs by polymer tubing: implications for indoor air and use as a simple gas-phase volatility separation technique

“…One demonstration was published by Jenks, et al (2023), who use PFA tubing to identify parent-fragment ion relationships in the time series of measurements from a chemical ionization mass spectrometer, where otherwise two different reaction products may have been assigned. This was achieved by flowing reaction products from a Δ-carene oxidation experiment through a 50 m coil of PFA tubing, and identifying signals at different m/z that had the same desorption profiles through the tubing, suggesting a parent-fragment ion relationship.…”

“…However, this phenomenon may also have some practical applications. For example, polymer tubing was recently used to separate isomers and identify fragments of the same species in PTR-MS (Jenks et al, 2023). Additionally, the tubing geometry provides major advantages over larger reactors, chambers, or rooms for studying material-VOC interactions.…”