1
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Strongin RM, Sharma E, Erythropel HC, Kassem NOF, Noël A, Peyton DH, Rahman I. Chemical and physiological interactions between e-liquid constituents: cause for concern? Tob Control 2025; 34:393-396. [PMID: 38658055 PMCID: PMC11745934 DOI: 10.1136/tc-2023-058546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 04/11/2024] [Indexed: 04/26/2024]
Abstract
Studies of Electronic Nicotine Delivery Systems (ENDS) toxicity have largely focused on individual components such as flavour additives, base e-liquid ingredients (propylene glycol, glycerol), device characteristics (eg, model, components, wattage), use behaviour, etc. However, vaping involves inhalation of chemical mixtures and interactions between compounds can occur that can lead to different toxicities than toxicity of the individual components. Methods based on the additive toxicity of individual chemical components to estimate the health risks of complex mixtures can result in the overestimation or underestimation of exposure risks, since interactions between components are under-investigated. In the case of ENDS, the potential of elevated toxicity resulting from chemical reactions and interactions is enhanced due to high operating temperatures and the metallic surface of the heating element. With the recent availability of a wide range of e-liquid constituents and popularity of do-it-yourself creation of e-liquid mixtures, the need to understand chemical and physiological impacts of chemical combinations in ENDS e-liquids and aerosols is immediate. There is a significant current knowledge gap concerning how specific combinations of ENDS chemical ingredients result in synergistic or antagonistic interactions. This commentary aims to review the current understanding of chemical reactions between e-liquid components, interactions between additives, chemical reactions that occur during vaping and aerosol properties and biomolecular interactions, all of which may impact physiological health.
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Affiliation(s)
| | | | - Hanno C Erythropel
- Chemical and Environmental Engineering, Yale University, New Haven, Connecticut, USA
| | - Nada O F Kassem
- CBEACH, San Diego State University Research Foundation, San Diego, California, USA
| | - Alexandra Noël
- Department of Comparative Biomedical Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
| | - D H Peyton
- Chemistry, Portland State University, Portland, Oregon, USA
| | - Irfan Rahman
- Department of Environmental Medicine, University of Rochester, Rochester, New York, USA
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2
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Rantaša M, Majer D, Finšgar M. A review of analytical techniques for the determination of e-liquid and electronic cigarette aerosol composition. J Chromatogr A 2025; 1748:465859. [PMID: 40106856 DOI: 10.1016/j.chroma.2025.465859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2024] [Revised: 02/21/2025] [Accepted: 03/06/2025] [Indexed: 03/22/2025]
Abstract
Since the introduction of electronic cigarettes (ECs) to the global market, the composition of e-liquids has been a controversial topic. While some consider ECs to be an effective tool for quitting smoking, their primary criticism lies in the uncertain and varied composition of e-liquids. Manufacturers create the desired formulations by mixing different ratios of humectants, flavorings, nicotine, cannabinoids, and cooling agents. However, the health effects of inhaling these compounds are still not well understood. Regular analytical control of e-liquids and aerosols is crucial to gain valuable insights into e-liquid composition, generating new compounds during aerosolization, and the potential impact on human health. This work presents an overview of the analytical techniques used for the qualitative and quantitative determination of e-liquid and aerosol compounds, including a description of the methods used for aerosol collection. Gas and liquid chromatography are the most used analytical techniques for compound determination, followed by nuclear magnetic resonance spectroscopy. Additionally, inductively coupled plasma-mass spectrometry and inductively coupled plasma-optical emission spectroscopy are the most frequently used analytical techniques for elemental determination in e-liquids and their aerosols.
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Affiliation(s)
- Matjaž Rantaša
- Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia
| | - David Majer
- Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia
| | - Matjaž Finšgar
- Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia.
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3
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Page MK, Merzianu AD, Leigh NJ, Goniewicz ML. Stability of Flavoring Chemicals in e-Cigarette Liquids: A Naturalistic Product Aging Study over 24 months. ACS OMEGA 2025; 10:15706-15715. [PMID: 40290923 PMCID: PMC12019726 DOI: 10.1021/acsomega.5c01266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2025] [Revised: 03/10/2025] [Accepted: 03/13/2025] [Indexed: 04/30/2025]
Abstract
Flavoring chemicals commonly used in many consumer products, including pharmaceuticals, foods, and beverages, deteriorate over time. Flavoring chemicals are also common additives in e-cigarette liquid formulations, but their stability in vaping products has not been evaluated. Since e-cigarette liquids are exposed to varying environmental conditions during storage and use, we assessed the stabilities of 20 flavoring chemicals commonly used in vaping products, including benzaldehyde (cherry flavor), menthol (cooling flavor), and vanillin (vanilla flavor). We prepared reference e-cigarette liquids (reference solutions) containing individual flavorings and a mixed liquid with combined flavorings in a 55:45 (v/v) propylene glycol to vegetable glycerin solution. We also purchased 14 commercial e-cigarette liquids. Liquids were stored over 24 months in different temperatures (room and cold) and light exposure conditions (ambient light and dark). Gas chromatography/mass spectrometry techniques were used to measure the concentration of each flavoring chemical at the baseline and after 1, 3, 6, 12, and 24 months. We used a nontargeted approach to identify potential degradation byproducts. Using an air-liquid interface with bronchial epithelial cells and the Neutral Red assay, we also compared the cytotoxicity of selected reference solutions vaped at the baseline and after storage over 24 months. The flavorings in reference solutions stored at ambient temperature and exposed to light were the least stable. Reducing exposure to light and storing reference solutions in cold temperatures delayed the degradation of some flavorings. Tentatively identified byproducts of flavoring degradation found in unstable reference solutions suggested oxidation, hydrolysis, and condensation reactions with solvents. Despite substantial changes in the chemical composition, no significant cytotoxicity differences were detected between fresh and aged reference solutions. Our findings suggest that storing vaping products in dark places and at cold temperatures improves the stability of flavorings in e-cigarette liquids.
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Affiliation(s)
| | | | - Noel J. Leigh
- Department of Health Behavior, Division
of Cancer Prevention and Population Studies, Roswell Park Comprehensive Cancer Center, Buffalo, New York 14263, United States
| | - Maciej L. Goniewicz
- Department of Health Behavior, Division
of Cancer Prevention and Population Studies, Roswell Park Comprehensive Cancer Center, Buffalo, New York 14263, United States
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4
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Effah F, Sun Y, Lin K, Rahman I. A comparative toxicological evaluation of emerging nicotine analogs 6-methyl nicotine and nicotinamide: a scoping review. Arch Toxicol 2025; 99:1333-1340. [PMID: 39937258 DOI: 10.1007/s00204-025-03960-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2024] [Accepted: 01/15/2025] [Indexed: 02/13/2025]
Abstract
Thermal degradation of flavored e-liquids in e-cigarettes (e-cigs) produces oxidants, volatile organic compounds, and heavy metals. Inhalation toxicology studies have revealed exposure to these toxicants may be toxic to humans. These studies informed the FDA's regulation of nicotine-containing E-cigs under the Tobacco Regulation Act (TRA) (2020) and the banning of all flavors in E-cig bars apart from tobacco and menthol. Furthermore, tobacco companies aiming to sell nicotine products on the US market ought to submit a premarket tobacco product application (PMTA) and obtain approval from the FDA before marketing. Nonetheless, because the PMTA process is lengthy/complicated, vape/tobacco companies utilized a loophole in the TRA (2020) and have introduced nicotine analogs in E-cig bars, such as 6-methyl nicotine (6-MN) and nicotinamide, which are not derived from nicotine or tobacco. These companies claim these analogs to be 'safer' alternatives to nicotine while providing similar satisfaction as nicotine. However, the safety profiles of these analogs are entirely unknown. Therefore, in this review, we have extrapolated the current literature on 6-MN and nicotinamide, and speculated their potential mode of toxicity through alterations in intracellular ROS and activation of nicotinic acetylcholine receptors, transient receptor potential ankyrin-1, and NF-κB. These biomolecules are pivotal in the onset and regulation of pulmonary diseases such as COPD, asthma, and lung tumorigenesis/remodeling. Thus, primary research is urgently warranted to inform regulatory agencies of these emerging nicotine analogs' potential adverse health effects. This article provides insightful information on emerging vape products' potential toxicity for environmental toxicology research and regulation.
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Affiliation(s)
- Felix Effah
- Department of Environmental Medicine, University of Rochester Medical Center, 601 Elmwood Avenue, Box 850, Rochester, NY, 14642, USA
| | - Yehao Sun
- Department of Environmental Medicine, University of Rochester Medical Center, 601 Elmwood Avenue, Box 850, Rochester, NY, 14642, USA
| | - Karen Lin
- Department of Environmental Medicine, University of Rochester Medical Center, 601 Elmwood Avenue, Box 850, Rochester, NY, 14642, USA
| | - Irfan Rahman
- Department of Environmental Medicine, University of Rochester Medical Center, 601 Elmwood Avenue, Box 850, Rochester, NY, 14642, USA.
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5
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Harris T. Physical and Chemical Characterization of Aerosols Produced from Commercial Nicotine Salt-Based E-Liquids. Chem Res Toxicol 2025; 38:115-128. [PMID: 39654291 PMCID: PMC11752517 DOI: 10.1021/acs.chemrestox.4c00315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2024] [Revised: 11/15/2024] [Accepted: 11/20/2024] [Indexed: 01/21/2025]
Abstract
Nicotine salt e-liquids are widely used in pod-style and disposable electronic nicotine delivery systems (ENDS). Studying the physical and chemical properties of their emissions can inform their toxicological impact. A prior companion study reported the harmful and potentially harmful constituents (HPHCs) and aerosol particle sizes produced from laboratory-made nicotine salt and freebase nicotine e-liquids to assess the effects of varying nicotine salts and nicotine protonation. This study reports the HPHCs and aerosol particle sizes for commercial brand nicotine salt and freebase nicotine formulations. Several tobacco, fruit, mint, and menthol flavored e-liquids of varying nicotine concentrations were tested with open and closed pod-style ENDS and a disposable ENDS. The nicotine yields showed a positive correlation with aerosol output, and the aerosol nicotine mass fractions reflected the e-liquid nicotine quantities. Benzene, crotonaldehyde, and 2,3-pentanedione were not detected or quantified in any of the aerosols, whereas acetaldehyde, acrolein, diacetyl, and formaldehyde were each quantified in at least one of the tested conditions. The aerosol particle number concentrations indicated that 97-99% of the aerosols for all the ENDS tested were composed of ultrafine (<0.1 μm) and fine (0.1-1.0 μm) aerosol particle sizes, and the mass median aerodynamic diameters ranged from 1.0 to 1.4 μm. The estimated regional deposition fractions and total respiratory depositions were calculated for all the ENDS conditions using a dosimetry modeling program. The calculations predicted depositions would predominantly occur in the pulmonary and head regions with a low total respiratory deposition (≤41%) calculated for all ENDS tested. This study broadens the availability of high-quality and reliable testing data of popular commercial nicotine salt-based ENDS for the scientific and regulatory communities. In conjunction with the previous work on the model e-liquids, these studies offer an extensive examination of the HPHCs and physical aerosol parameters of nicotine salt e-liquids.
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Affiliation(s)
- Trevor Harris
- Office of Science, Center
for Tobacco Products, U.S. Food and Drug
Administration, Silver
Spring, Maryland 20993, United States
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6
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Kassem NOF, Strongin RM, Stroup AM, Brinkman MC, El-Hellani A, Erythropel HC, Etemadi A, Exil V, Goniewicz ML, Kassem NO, Klupinski TP, Liles S, Muthumalage T, Noël A, Peyton DH, Wang Q, Rahman I, Valerio LG. A Review of the Toxicity of Ingredients in e-Cigarettes, Including Those Ingredients Having the FDA's "Generally Recognized as Safe (GRAS)" Regulatory Status for Use in Food. Nicotine Tob Res 2024; 26:1445-1454. [PMID: 38783714 PMCID: PMC11494494 DOI: 10.1093/ntr/ntae123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 04/26/2024] [Accepted: 05/10/2024] [Indexed: 05/25/2024]
Abstract
Some firms and marketers of electronic cigarettes (e-cigarettes; a type of electronic nicotine delivery system (ENDS)) and refill liquids (e-liquids) have made claims about the safety of ingredients used in their products based on the term "GRAS or Generally Recognized As Safe" (GRAS). However, GRAS is a provision within the definition of a food additive under section 201(s) (21 U.S.C. 321(s)) of the U.S. Federal Food Drug and Cosmetic Act (FD&C Act). Food additives and GRAS substances are by the FD&C Act definition intended for use in food, thus safety is based on oral consumption; the term GRAS cannot serve as an indicator of the toxicity of e-cigarette ingredients when aerosolized and inhaled (ie, vaped). There is no legal or scientific support for labeling e-cigarette product ingredients as "GRAS." This review discusses our concerns with the GRAS provision being applied to e-cigarette products and provides examples of chemical compounds that have been used as food ingredients but have been shown to lead to adverse health effects when inhaled. The review provides scientific insight into the toxicological evaluation of e-liquid ingredients and their aerosols to help determine the potential respiratory risks associated with their use in e-cigarettes.
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Affiliation(s)
- Nada O F Kassem
- Health Promotion and Behavioral Science, San Diego State University, San Diego, CA, USA
- Hookah Tobacco Research Center, San Diego State University Research Foundation, San Diego, CA, USA
| | - Robert M Strongin
- Department of Chemistry, Portland State University, Portland, OR, USA
| | - Andrea M Stroup
- Behavioral Health and Health Policy Practice, Westat, Rockville, MD, USA
| | - Marielle C Brinkman
- College of Public Health, The Ohio State University, Columbus, OH, USA
- Center for Tobacco Research, The Ohio State University Comprehensive Cancer Center, Columbus, OH, USA
| | - Ahmad El-Hellani
- Center for Tobacco Research, The Ohio State University Comprehensive Cancer Center, Columbus, OH, USA
- Division of Environmental Health Sciences, College of Public Health, The Ohio State University, Columbus, OH, USA
| | - Hanno C Erythropel
- Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, USA
- Department of Psychiatry, Yale Center for the Study of Tobacco Products (YCSTP), Yale School of Medicine, New Haven, CT, USA
| | - Arash Etemadi
- Metabolic Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Bethesda, MD, USA
| | - Vernat Exil
- School of Medicine, St. Louis University, St. Louis, MO, USA
| | - Maciej L Goniewicz
- Department of Health Behavior, Roswell Park Comprehensive Cancer Center, Buffalo, NY, USA
| | - Noura O Kassem
- Health Promotion and Behavioral Science, San Diego State University, San Diego, CA, USA
- Hookah Tobacco Research Center, San Diego State University Research Foundation, San Diego, CA, USA
| | | | - Sandy Liles
- Health Promotion and Behavioral Science, San Diego State University, San Diego, CA, USA
- Hookah Tobacco Research Center, San Diego State University Research Foundation, San Diego, CA, USA
| | | | - Alexandra Noël
- Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA
| | - David H Peyton
- Department of Chemistry, Portland State University, Portland, OR, USA
| | - Qixin Wang
- Department of Environmental Medicine, University of Rochester Medical Center, Rochester, NY, USA
| | - Irfan Rahman
- Department of Environmental Medicine, University of Rochester Medical Center, Rochester, NY, USA
| | - Luis G Valerio
- Division of Nonclinical Science (DNCS), Office of Science/Center for Tobacco Products, U.S. Food and Drug Administration, Silver Spring, MD, USA
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7
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Wu S, Kim E, Zhao R. Acetal Formation of Flavoring Agents with Propylene Glycol in E-Cigarettes: Impacts on Indoor Partitioning and Thirdhand Exposure. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:21284-21294. [PMID: 38065550 DOI: 10.1021/acs.est.3c08514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
The widespread use of flavored e-cigarettes has led to a significant rise in teenage nicotine use. In e-liquids, the flavor carbonyls can form acetals with unknown chemical and toxicological properties. These acetals can cause adverse health effects on both smokers and nonsmokers through thirdhand exposure. This study aims to explore the impacts of these acetals formed in e-cigarettes on indoor partitioning and thirdhand exposure. Specifically, the acetalization reactions of commonly used flavor carbonyls in laboratory-made e-liquids were monitored using proton nuclear magnetic resonance (1H NMR) spectroscopy. EAS-E Suite and polyparameter linear free energy relationships (PP-LFERs) were employed to estimate the partitioning coefficients for species. Further, a chemical two-dimensional partitioning model was applied to visualize the indoor equilibrium partitioning and estimate the distribution of flavor carbonyls and their acetals in the gas phase, aerosol phase, and surface reservoirs. Our results demonstrate that a substantial fraction of carbonyls were converted into acetals in e-liquids and their chemical partitioning was significantly influenced. This study shows that acetalization is a determinant factor in the exposure and toxicology of harmful carbonyl flavorings, with its impact extending to both direct exposure to smokers and involuntary exposure to nonsmokers.
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Affiliation(s)
- Shuang Wu
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Erica Kim
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Ran Zhao
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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8
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Klupinski TP, Strozier ED, Koebel DD, Lucas EA. Detection of the Synthetic Coolant Menthone 1,2-Glycerol Ketal in an e-Liquid and in Electronic Waterpipe Aerosols Therefrom. Chem Res Toxicol 2023; 36:1355-1360. [PMID: 37439580 PMCID: PMC10529952 DOI: 10.1021/acs.chemrestox.3c00089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
The presence and toxicological risks of synthetic coolants in electronic nicotine delivery systems (ENDS) have not been thoroughly studied. We identified the synthetic coolant menthone 1,2-glycerol ketal (MGK) in a menthol-flavored e-liquid at a concentration of ∼170 μg/mL. We also detected MGK in aerosols resulting from heating the e-liquid with an electronic waterpipe. MGK was initially detected in the e-liquid by two-dimensional gas chromatography-time-of-flight mass spectrometry. To avoid potential analytical artifacts that could result from heating samples in the injection port of the gas chromatograph, quantitation of MGK in the e-liquid was accomplished using a liquid chromatography-tandem mass spectrometry method. Following recent reports identifying other synthetic coolants in e-liquids, these results add knowledge about inhalation exposures from ENDS use and suggest the importance of future research to study the potential inhalation toxicity related to the use of MGK-containing e-liquids in ENDS devices. Furthermore, the results demonstrate the ability to quantify ketals in e-liquids using liquid chromatography methods.
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Affiliation(s)
| | | | - David D Koebel
- Battelle, 505 King Ave., Columbus, Ohio 43201, United States
| | - Eric A Lucas
- Battelle, 505 King Ave., Columbus, Ohio 43201, United States
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9
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Kosarac I, Katuri GP, Kubwabo C, Siddique S, Mischki TK. Quantitation and Stability of Nicotine in Canadian Vaping Liquids. TOXICS 2023; 11:378. [PMID: 37112605 PMCID: PMC10144332 DOI: 10.3390/toxics11040378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 04/05/2023] [Accepted: 04/14/2023] [Indexed: 06/19/2023]
Abstract
Electronic cigarettes (e-cigarettes, vaping products) have become increasingly popular, with recent increases in use associated with closed systems delivering higher concentrations of nicotine. Most vaping products designed as an alternative to combustible cigarettes contain nicotine. A number of published studies have examined the reported concentrations of nicotine in vaping liquids (e-liquids) and found discrepancies between labelled and measured levels. Some discrepancy can also be explained by the lack of stability of nicotine in these types of products. Recently, a chemical analysis method for the quantitative determination of low and high levels of nicotine in vaping liquids was developed. This method uses dilution with acetonitrile prior to analysis with gas chromatograph mass spectrometry (GC-MS) in single ion monitoring mode (SIM). The developed method was validated using a laboratory-prepared vaping liquid as well as commercially available, nicotine-free products fortified with nicotine in the laboratory. The method detection limit (MDL) and the limit of quantitation (LOQ) for nicotine were calculated to be 0.002 mg/mL and 0.006 mg/mL, respectively. The newly developed method was applied to quantify nicotine in commercially available vaping liquids of various flavour profiles and across a wide range of nicotine concentrations, including those with nicotine salts. Furthermore, a subset of vaping liquids were analyzed to elucidate nicotine stability in various product subtypes. After a period of six months of accelerated storage to mimic one year, the overall mean percent of the original nicotine concentration remaining in the salt-based vaping products was 85% (minimum 64%, maximum 99%) while in the free-base nicotine products it was 74% (minimum 31%, maximum 106%). Nicotine stability in vaping liquids was found to be influenced by the nicotine form (pH) of formulation and its chemical composition. Non-targeted, qualitative analysis of chemical composition of vaping products showed that most constituents were identified and found to be remaining in the products following stability trials; however, three new compounds were tentatively identified in some vaping liquids at the end of the stability trials. Stability studies and the accurate quantitation of nicotine in vaping products can help inform product standards related to the safety, quality and utility of vaping products as a smoking cessation tool.
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Affiliation(s)
- Ivana Kosarac
- Tobacco Control Directorate, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - Guru P. Katuri
- Tobacco Control Directorate, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - Cariton Kubwabo
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - Shabana Siddique
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - Trevor K. Mischki
- Tobacco Control Directorate, Health Canada, Ottawa, ON K1A 0K9, Canada
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10
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Kerber PJ, Luo W, McWhirter KJ, Powers M, Peyton DH. Effects of E-Cigarette Flavor Enhancing Capsules on Inhalable Aerosols. Chem Res Toxicol 2023; 36:8-13. [PMID: 36490387 DOI: 10.1021/acs.chemrestox.2c00273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The flavor of inhaled e-cigarette aerosols may be augmented using crushable flavor capsules added to e-cigarettes. For example, Puff Krush contains breakable flavor capsules in a sorbent material. The capsules are crushed, and then, aerosol passes through the saturated sorbent material before inhalation. Herein, we used NMR and GC-MS to identify the capsule medium chain triglyceride (MCT) solvent and flavorants in selected Puff Krush flavor capsules and then determined which molecules from the capsule transfer into aerosols. MCTs from the Puff Krush were not found in the aerosols, and ∼50% of Puff Krush flavorants transferred into the aerosol upon vaping.
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Affiliation(s)
- Paul J Kerber
- Department of Chemistry, Portland State University, Portland, Oregon 97207-0751, United States
| | - Wentai Luo
- Department of Civil and Environmental Engineering, Portland State University, Portland, Oregon 97207-0751, United States
| | - Kevin J McWhirter
- Department of Civil and Environmental Engineering, Portland State University, Portland, Oregon 97207-0751, United States
| | - Marley Powers
- Department of Chemistry, Portland State University, Portland, Oregon 97207-0751, United States
| | - David H Peyton
- Department of Chemistry, Portland State University, Portland, Oregon 97207-0751, United States
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11
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Gschwend G, Jenkins C, Jones A, Kelso C, Morgan J. A Wide Range of Flavoring-Carrier Fluid Adducts Form in E-Cigarette Liquids. Chem Res Toxicol 2023; 36:14-22. [PMID: 36597559 DOI: 10.1021/acs.chemrestox.2c00200] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A range of flavoring molecules are used in electronic cigarette liquids (e-liquids), some of which have been shown to form cyclic acetal adducts with e-liquid solvent components propylene glycol (PG) and vegetable glycerine (VG). The objective of this study was to identify the range of flavoring molecules which form adducts in e-liquid products. Common e-liquid flavoring molecules (N = 36) from a range of chemical class groups were exposed to PG, VG, or methanol and analyzed by GC-MS over a time frame of 4 weeks to identify possible reaction products. Adduct formation was observed, with 14 of the flavoring molecules reacting with methanol, 10 reacting with PG, and 10 reacting with VG. Furfural PG and VG acetals, valeraldehyde PG and VG acetals, veretraldehyde PG and VG acetals, p-anisaldehyde PG and VG acetals, and piperonal VG acetal were confirmed for the first time. Adducts formed by reaction with ketone-containing flavoring molecules were also observed for the first time. The presence of these acetals was confirmed in 32% of commercial e-liquid products analyzed (N = 142). This study has established a range of flavoring molecules which are able to react with solvent components PG and VG in e-liquids under standard storage conditions. These newly identified adducts need to be further assessed to determine their toxicological safety.
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Affiliation(s)
- Grace Gschwend
- School of Chemistry and Molecular Bioscience, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW 2522, Australia.,Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Caitlin Jenkins
- School of Chemistry and Molecular Bioscience, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW 2522, Australia.,Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Alison Jones
- School of Medicine, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW 2522, Australia.,School of Public Health, University of Western Australia, Perth, WA 6907, Australia
| | - Celine Kelso
- School of Chemistry and Molecular Bioscience, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW 2522, Australia.,Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia.,Molecular Horizons, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Jody Morgan
- Molecular Horizons, University of Wollongong, Wollongong, NSW 2522, Australia.,School of Chemistry, Faculty of Science, University of Sydney, Sydney, NSW 2006, Australia
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12
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Alhadyan SK, Sivaraman V, Onyenwoke RU. E-cigarette Flavors, Sensory Perception, and Evoked Responses. Chem Res Toxicol 2022; 35:2194-2209. [PMID: 36480683 DOI: 10.1021/acs.chemrestox.2c00268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The chemosensory experiences evoked by flavors encompass a number of unique sensations that include olfactory stimuli (smell), gustatory stimuli (taste, i.e., salty, sweet, sour, bitter, and umami (also known as "savoriness")), and chemesthesis (touch). As such, the responses evoked by flavors are complex and, as briefly stated above, involve multiple perceptive mechanisms. The practice of adding flavorings to tobacco products dates back to the 17th century but is likely much older. More recently, the electronic cigarette or "e-cigarette" and its accompanying flavored e-liquids emerged on to the global market. These new products contain no combustible tobacco but often contain large concentrations (reported from 0 to more than 50 mg/mL) of nicotine as well as numerous flavorings and/or flavor chemicals. At present, there are more than 400 e-cigarette brands available along with potentially >15,000 different/unique flavored products. However, surprisingly little is known about the flavors/flavor chemicals added to these products, which can account for >1% by weight of some e-liquids, and their resultant chemosensory experiences, and the US FDA has done relatively little, until recently, to regulate these products. This article will discuss e-cigarette flavors and flavor chemicals, their elicited responses, and their sensory effects in some detail.
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Affiliation(s)
- Shatha K Alhadyan
- Department of Pharmaceutical Sciences, North Carolina Central University, Durham, North Carolina 27707, United States
| | - Vijay Sivaraman
- Department of Biological and Biomedical Sciences, North Carolina Central University, Durham, North Carolina 27707, United States
| | - Rob U Onyenwoke
- Department of Pharmaceutical Sciences, North Carolina Central University, Durham, North Carolina 27707, United States
- Biomanufacturing Research Institute and Technology Enterprise (BRITE), North Carolina Central University, Durham, North Carolina 27707, United States
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Non-Targeted Chemical Characterization of JUUL-Menthol-Flavored Aerosols Using Liquid and Gas Chromatography. SEPARATIONS 2022. [DOI: 10.3390/separations9110367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The aerosol constituents generated from JUUL Menthol pods with 3.0% and 5.0% nicotine by weight (Me3 and Me5) are characterized by a non-targeted approach, which was developed to detect aerosol constituents that are not known to be present beforehand or that may be measured with targeted methods. Three replicates from three production batches (n = 9) were aerosolized using two puffing regimens (intense and non-intense). Each of the 18 samples were analyzed by gas chromatography electron ionization mass spectrometry and by liquid chromatography electrospray ionization high-resolving power mass spectrometry. All chemical constituents determined to differ from control were identified and semi-quantified. To have a complete understanding of the aerosol constituents and chemistry, each chemical constituent was categorized into one of five groups: (1) flavorants, (2) harmful and potentially harmful constituents, (3) leachables, (4) reaction products, and (5) chemical constituents that were unable to be identified or rationalized (e.g., chemical constituents that could not be categorized in groups (1–4). Under intense puffing, 74 chemical constituents were identified in Me3 aerosols and 68 under non-intense puffing, with 53 chemical constituents common between both regimens. Eighty-three chemical constituents were identified in Me5 aerosol using an intense puffing regimen and seventy-five with a non-intense puffing regimen, with sixty-two chemical constituents in common. Excluding primary constituents, reaction products accounted for the greatest number of chemical constituents (approximately 60% in all cases, ranging from about 0.05% to 0.1% by mass), and flavorants—excluding menthol—comprised the second largest number of chemical constituents (approximately 25%, ranging consistently around 0.01% by mass). The chemical constituents detected in JUUL aerosols were then compared to known constituents from cigarette smoke to determine the relative chemical complexities and commonalities/differences between the two. This revealed (1) a substantial decrease in the chemical complexity of JUUL aerosols vs. cigarette smoke and (2) that there are between 55 (Me3) and 61 (Me5) unique chemical constituents in JUUL aerosols not reported in cigarette smoke. Understanding the chemical complexity of JUUL aerosols is important because the health effects of combustible cigarette smoke are related to the combined effect of these chemical constituents through multiple mechanisms, not just the effects of any single smoke constituent.
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