Molecular Speciation of Size Fractionated Particulate Water-Soluble Organic Carbon by Two-Dimensional Nuclear Magnetic Resonance (NMR) Spectroscopy

Abstract

Particulate matter is associated with increased morbidity and mortality; its effects depend on particle size and chemical content. It is important to understand the composition and resultant toxicological profile of particulate organic compounds, the largest and most complex fraction of particulate matter. The objective of the study was to delineate the nuclear magnetic resonance (NMR) spectral fingerprint of the biologically relevant water-soluble organic carbon (WSOC) fraction of size fractionated urban aerosol. A combination of one and two-dimensional NMR spectroscopy methods was used. The size distribution of particle mass, water-soluble extract, non-exchangeable organic hydrogen functional types and specific biomarkers such as levoglucosan, methane sulfonate, ammonium and saccharides indicated the contribution of fresh and aged wood burning emissions, anthropogenic and biogenic secondary aerosol for fine particles as well as primary traffic exhausts and pollen for large particles. Humic-like macromolecules in the fine particle size range included branched carbon structures containing aromatic, olefinic, keto and nitrile groups and terminal carboxylic and hydroxyl groups such as terpenoid-like polycarboxylic acids and polyols. Our study show that 2D-NMR spectroscopy can be applied to study the chemical composition of size fractionated aerosols.

Development of an Integrated Platform to Assess the Physicochemical and Toxicological Properties of Wood Combustion Particulate Matter

“…In this study, the flaming PM 0.1 was significantly more abundant in saturated oxygenated aliphatic groups [ H –C–O] in addition to allylic [ H –C–C], vinylic [ H –C], acetalic [O–C H –O], and aromatic [ H –Ar] species compared to the larger PM fractions (Figure A, F, G), suggesting that the bioactive compounds responsible for SPDEF promoter activity could be among these organic functional groups. [ H –C–O] represents the region for alcohols, ethers, and esters, whereas both [ H –C–O] and [O–C H –O] functionalities point to the presence of straight-chain or cyclic carbohydrates. ,, In previous studies, authors have found that hydrophilic compounds, specifically sugars, drive SPDEF and MUC5AC expression to the same extent as wood smoke extract, affirming that the high abundance of oxygenated organics observed in pine flaming PM 0.1 is likely driving bioactivity. ,− Those studies showed that chemical fractionation of the wood smoke extract resulted in an enhanced activation of the SPDEF promoter, suggesting that wood smoke contains chemical constituents that can either drive or inhibit the promoter activity. Chemical analyses of the wood smoke extract identified oxalate and levunilate species to be the active constituents that were responsible for inducing SPDEF and MUC5AC expression .…”

“…85 In this study, the flaming PM 0. 53,55,81 In previous studies, authors have found that hydrophilic compounds, specifically sugars, drive SPDEF and MUC5AC expression to the same extent as wood smoke extract, affirming that the high abundance of oxygenated organics observed in pine flaming PM 0.1 is likely driving bioactivity. 60,86−88 Those studies showed that chemical fractionation of the wood smoke extract resulted in an enhanced activation of the SPDEF promoter, suggesting that wood smoke contains chemical constituents that can either drive or inhibit the promoter activity.…”

Multidimensional Analytical Characterization of Water-Soluble Organic Aerosols: Challenges and New Perspectives

“…Using this chemometric approach, Duarte et al [9] demonstrated that the watersoluble compounds isolated from urban aerosol samples (Aveiro, Portugal) consist of at least two classes of compounds: one is rich in both carboxylic and hydroxyl functional groups, and it has an aliphatic character, and the other entails lignin-derived structures. Another set of NMR-based multidimensional methodologies that have emerged for the structural analysis of water-soluble OA are the 2D liquid-state NMR techniques [33,[70][71][72][73]. These techniques have proven to be very useful to solve the spectral information overlaid in 1D NMR spectra by separating the data into a second frequency dimension.…”

“…The combination of the data from some of these 2D liquid-state NMR techniques, namely 1 H-1 H homonuclear (COSY and total correlation spectroscopy (TOCSY)) and 1 H- 13 C heteronuclear (HSQC and HMBC) connectivity, improve the spectral resolution and provide a deeper insight into the C-H backbone of the organic compounds from the atmospheric aerosols [69]. Although the use of liquid-state 2D NMR techniques to water-soluble OA analysis seems to be still very limited, the existing studies [33,[70][71][72][73] have demonstrated the potential of these high-resolution NMR techniques for a comprehensive description of the substructures present in aerosol WSOM, as well as to identify molecular fingerprints of the different aerosol sources and formation mechanisms. Conceivably, one of the most important drawbacks of these techniques is the time required for signal acquisition, which can reach several days, thus limiting its application, at least on a routine basis.…”

“…Nevertheless, as reviewed by Duarte and Duarte [43,69], the keys to developing accurate knowledge about the structural features of water-soluble OA also lies in the development of analytical procedures taking advantage of the synergistic application of all of the aforementioned NMR techniques (i.e., 1D solid-state NMR, 1D and 2D liquid-state NMR), as well as their association with other advanced analytical techniques, namely HR- Another set of NMR-based multidimensional methodologies that have emerged for the structural analysis of water-soluble OA are the 2D liquid-state NMR techniques [33,[70][71][72][73]. These techniques have proven to be very useful to solve the spectral information overlaid in 1D NMR spectra by separating the data into a second frequency dimension.…”