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Accretion Reactions Characterized in Unflavored Electronic Nicotine Delivery System (ENDS) Aerosols by Hydrophilic Interaction Liquid Chromatography Coupled to High-Resolution Quadrupole Time-of-Flight Mass Spectrometry (HILIC/QTOF-MS)
SARAH SUDA PETTERS, Yue Zhang, Jin Yan, Caz Nichols, Timothy Fennell, Michelle McCombs, Kamau Peters, Jonathan Thornburg, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 264
Working Group: Health-Related Aerosols
Abstract
Electronic nicotine delivery systems (ENDS), including electronic cigarettes (e-cigs), are an emerging health concern due to the relatively unknown health consequences of long-term use. Large differences in aerosol generation, due to a variety of factors such as coil temperature, e-liquid content, and nicotine carrier, result in large and often uncharacterized variabilities in e-cig aerosol composition. Recent studies reveal that thermal breakdown of ENDS carrier liquids (humectants including propylene glycol and glycerol) and added flavors yield volatile aldehydes and decomposition products. Many ENDS aerosol characterization studies focus on volatile compounds and the development of gas-phase chemical characterization methods and have potentially missed oligomerization reactions occurring in heated e-liquid mixtures. Here we use hydrophilic interaction liquid chromatography coupled with electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (HILIC/ESI-HR-QTOFMS) to demonstrate that accretion reactions forming C-O-C bonds can occur in unflavored e-cig aerosols. We identify ether, acetal, and heterocycle formation from humectants and first-generation thermal decomposition products. Additional chemical characterization, including comparison to authentic standards and MS/MS fragmentation spectra, were used to confirm the identities of some of the measured compounds. These oligomerization reactions alter the vapor pressure, solubility, reactivity, and other physicochemical properties of the aerosol by raising the molecular weight and altering functional group composition. In contrast to the heated gas chromatography methods preferred for the detection of volatile and semi-volatile humectants, flavors, nicotine and aldehydes in prior e-cig and tobacco research, we developed a lower temperature HILIC/ESI-HR-QTOFMS method that separates polar molecules. Results reveal that, in addition to previously known volatile irritants, higher molecular weight organic compounds of lower volatility are produced in e-cig aerosols. We demonstrate that e-cig aerosol oligomers can be detected and characterized using HILIC/ESI-HR-QTOFMS, thus enabling more detailed research examining the physical properties, composition, biomarkers of exposure, and potential toxicological effects of e-cig aerosols.