Determination of (R)-(+)- and (S)-(-)-Nicotine Chirality in Puff Bar E-Liquids by 1H NMR Spectroscopy, Polarimetry, and Gas Chromatography-Mass Spectrometry

Disposable electronic cigarettes - chemical composition and health effects of their use. A systematic review

OBJECTIVE

Despite the rising popularity of disposable e-cigarettes, little is known about their chemical characteristics, or their impact on users' health. This work attempts to summarize current knowledge about chemical composition and known health effects of disposable e-cigarettes.

METHODS

The literature search was performed in February and March 2024 in Pub Med and Science Direct databases (no time range) by the terms 'disposable electronic cigarette', 'disposable e-cigarette', 'disposable e-cigs', 'cig-a-like e-cigarette', 'cig-a-like electronic cigarette'.

RESULTS

Disposable e-cigarettes contain: nicotine, humectants (propylene glycol, glycerin), flavoring agents (diacetyl, acetoin, triacetin, p-menthone, triethyl citrate, ethyl maltol, 3-hexen-1-ol, methyl anthranilate, α-terpineol, perillartine, benzyl alcohol, vanillin, melonal, methyl dihydrojasmonate, and γ-decalactone), cooling agents (WS-3, WS-23, menthol), carbonyl compounds (acetaldehyde, formaldehyde, propionaldehyde, acetone, acrolein) volatile organic compounds (VOCs) (benzene, ethanol, methanol, styrene, acetylpirazine and 2,3,5-trimethylpyrazine), metals and inorganic compounds (chromium, nickel, manganese, lead, aluminum, and zinc) and reactive oxygen species. Furthermore, there was some evidence of nicotine dependence, risk of cancer and adverse respiratory effects of using disposable e-cigarettes.

CONCLUSIONS

Despite the fact that disposable e-cigarettes contain significantly less toxins compared to combustible cigarettes, they include compounds that are absent in such products that may provide health risk in prolonged usage. In addition, there is a limited number of data on the health effect of disposable e-cigarettes, especially in long time period, for never-smokers. Therefore, due to growing popularity of disposable e-cigarettes among young people, who choose them when initiating nicotine use, further research on their long-term impact of on the users' health is necessary.

[Safety of use of electronic cigarettes: A systematic review of bronchopulmonary, cardiovascular and cancer risks]

As the effects of electronic cigarettes (ECs) have rapidly become widely known, we propose to take stock of recent findings on the bronchopulmonary and cardiovascular adverse effects (AEs) and the risks of cancer occurrence entailed by EC use. METHOD: We carried out a search from 2018 to October 19, 2023 on PubMed, adopting the PRISMA guidelines (2020) with the following keywords in "Titles and abstracts": electronic cigarette, or e-cigarette, or ENDS, AND safety or toxicology or effect or health effect, using "Systematic Review" as a filter. The inclusion criteria were: systematic review of in vitro or in vivo studies in English or French dealing with the risks of ECs for the bronchopulmonary system, the cardiovascular system, or cancer occurrence. CONCLUSION: Twenty-eight systematic reviews on the adverse effects (AE) of electronic cigarettes (EC) in selected humans show that the toxic substances they generate can cause cancers and increase the risk of cardiac and pulmonary disorders. New studies on the potential dangerousness of EC use are essential and urgent.

Plant-Derived and Synthetic Nicotine in E-Cigarettes: Is Differentiation with NMR Spectroscopy Possible?

To circumvent regulatory frameworks, many producers start to substitute plant-derived nicotine (tobacco-derived nicotine, TDN) by synthetic nicotine (tobacco-free nicotine, TFN) in e-cigarette products. Due to the higher costs of enantiomeric synthesis and purification of TFN, there is a need to develop an analytical method that clearly distinguishes between the two sources. To trace nicotine's origin, its enantiomeric purity can be postulated by 1H NMR spectroscopy using (R)-(-)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (BNPPA) as a chiral complexing agent. Low-field (LF) NMR conditions were optimized for this purpose even using a small amount of e-liquid sample (limit of quantification 8 mg/mL nicotine). All investigated products were found to contain one isomer (most likely (S)-(-)-nicotine). A direct 13C NMR method at natural abundance has been validated to differentiate (S)-TDN and (S)-TFN in e-cigarettes produced using nicotine of different origin. The method is based on calculation of the relative 13C content of 10 C-positions of the nicotine molecule with intraday and interday precisions below <0.2%. The method was applied to 12 commercial e-cigarette products labeled as containing TDN and TFN. Principal component analysis (PCA) was applied to the relative peak areas to visualize the difference between studied products. The LF 1H NMR method is a good alternative to expensive high-field NMR to differentiate between a racemate mixture and single optical isomers, whereas only high-precision 13C NMR can be used to distinguish (S)-TDN and (S)-TFN in e-cigarettes after appropriate sample extraction.

Enantiomeric Analysis of Chiral Drugs Using Mass Spectrometric Methods: A Comprehensive Review

Chirality plays a crucial role in the drug development process, influencing fundamental chemical and biochemical processes and significantly affecting our daily lives. This review provides a comprehensive examination of mass spectrometric (MS) methods for the enantiomeric analysis of chiral drugs. It thoroughly investigates MS-hyphenated techniques, emphasizing their critical role in achieving enantioselective analysis. Furthermore, it delves into the intricate chiral recognition mechanisms inherent in MS, elucidating the fundamental principles that govern successful chiral separations. By critically assessing the obstacles and potential benefits associated with each MS-based method, this review offers valuable insights for researchers navigating the complexities of chiral analysis. Both qualitative and quantitative approaches are explored, presenting a comparative analysis of their strengths and limitations. This review is aimed at significantly enhancing the understanding of chiral MS methods, serving as a crucial resource for researchers and practitioners engaged in enantioselective studies.

Evaluating the Role of Nicotine Stereoisomer on Nicotine Pouch Abuse Liability: A Randomized Crossover Trial

INTRODUCTION

Many oral nicotine pouch (ONP) brands use synthetic nicotine, which typically contains a racemic (50:50) mixture of nicotine's two stereoisomers: S-nicotine and R-nicotine. Because tobacco-derived nicotine contains more than 99% S-nicotine, the effects of R-nicotine in humans are not well known. We compared systemic nicotine exposure and product appeal of ONPs containing more than 99% S-nicotine versus racemic nicotine.

AIMS AND METHODS

N = 18 adult smokers (Mage = 45 years, 66.7% male, 77.8% White) enrolled in a three-visit single-blind, randomized crossover study. During each visit, participants used one wintergreen-flavored, 3 mg nicotine ONP for 30 min following at least12 h nicotine abstinence. Study ONP #1 contained more than 99% S-nicotine and the other two study ONPs contained racemic nicotine (collapsed for analyses). Plasma nicotine assessments and measures of withdrawal relief occurred at t = 0, 5, 15, 30, 60, and 90 min; measures of product appeal were assessed following ONP use.

RESULTS

Using the ONP with more than 99% S-nicotine resulted in greater plasma nicotine concentration from 15 to 90 min (p < .0001) and greater maximum plasma nicotine concentration than the ONPs with racemic nicotine (M = 9.9 ng/mL [SD = 2.5] vs. M = 5.7 ng/mL [SD = 2.8], respectively; p < .0001). Product liking and withdrawal relief were similar across ONPs, although participants reported more "bad effects" when using the ONP with more than 99% S-nicotine.

CONCLUSIONS

Participants reported few subjective differences in ONPs according to nicotine stereoisomer, but plasma nicotine concentration was greater for ONPs using more than 99% S-nicotine. ONPs with more than 99% S-nicotine (vs. racemic nicotine) might be better substitutes for cigarettes, but research into other ONP characteristics (eg flavors, freebase nicotine) is needed to inform regulation.

IMPLICATIONS

Little is known about the effects of racemic (vs. S-) nicotine in humans. In a sample of adults who smoke cigarettes, we identified that oral nicotine pouches containing racemic nicotine exposed participants to less nicotine than oral nicotine pouches containing only S-nicotine, but both types of oral nicotine pouches held similar, moderate appeal. Additional research evaluating the roles that flavorings, total nicotine concentration, and freebase nicotine play in the abuse liability of oral nicotine pouches would inform comprehensive product regulations to support public health.

Nicotine Formulation Influences the Autonomic and Arrhythmogenic Effects of Electronic Cigarettes

INTRODUCTION

Evidence is mounting that electronic cigarette (e-cig) use induces cardiac sympathetic dominance and electrical dysfunction conducive to arrhythmias and dependent upon nicotine. A variety of nicotine types and concentrations are available in e-cigs, but their relative cardiovascular effects remain unclear. Here we examine how different nicotine forms (racemic, free base, and salt) and concentrations influence e-cig-evoked cardiac dysfunction and arrhythmogenesis and provide a mechanism for nicotine-salt-induced autonomic imbalance.

METHODS

ECG-telemetered C57BL/6J mice were exposed to filtered air (FA) or e-cig aerosols from propylene glycol and vegetable glycerin solvents either without nicotine (vehicle) or with increasing nicotine concentrations (1%, 2.5%, and 5%) for three 9-minute puff sessions per concentration. Spontaneous ventricular premature beat (VPB) incidence rates, heart rate, and heart rate variability (HRV) were compared between treatments. Subsequently, to test the role of β1-adrenergic activation in e-cig-induced cardiac effects, mice were pretreated with atenolol and exposed to either FA or 2.5% nicotine salt.

RESULTS

During puffing and washout phases, ≥2.5% racemic nicotine reduced heart rate and increased HRV relative to FA and vehicle controls, indicating parasympathetic dominance. Relative to both controls, 5% nicotine salt elevated heart rate and decreased HRV during washout, suggesting sympathetic dominance, and also increased VPB frequency. Atenolol abolished e-cig-induced elevations in heart rate and declines in HRV during washout, indicating e-cig-evoked sympathetic dominance is mediated by β1-adrenergic stimulation.

CONCLUSIONS

Our findings suggest that inhalation of e-cig aerosols from nicotine-salt-containing e-liquids could increase the cardiovascular risks of vaping by inducing sympathetic dominance and cardiac arrhythmias.

IMPLICATIONS

Exposure to e-cig aerosols containing commercially relevant concentrations of nicotine salts may increase nicotine delivery and impair cardiac function by eliciting β1-adrenoceptor-mediated sympathoexcitation and provoking ventricular arrhythmias. If confirmed in humans, our work suggests that regulatory targeting of nicotine salts through minimum pH standards or limits on acid additives in e-liquids may mitigate the public health risks of vaping.

Reliable biological indicator identification and evaluation of tobacco-derived nicotine using an ultra-sensitive gas chromatography-tandem mass spectrometric method

Several countries have exempted synthetic nicotine from existing regulatory frameworks, resulting in the widespread substitution of synthetic nicotine (SN) in almost all e-cigarette products available. However, it remains uncertain whether the purported synthetic nicotine is indeed genuine SN. There is a need to develop biological indicators and an analytical method that more clearly distinguishes between the two sources. Impurities in neat tobacco-derived nicotine (TDN) were characterized and identified through non-targeted and targeted analysis. Gas chromatography-tandem mass spectrometry (GC-MS/MS) conditions were optimized for detecting biological indicators in e-cigarette products. Nine tobacco-related alkaloids were identified and selected as biological indicators for TDN. A liquid-liquid extraction and GC-MS/MS quantitative method were developed to detect nine biological indicators in e-cigarette products with the limit of quantification ranging from 0.2 to 4.2 µg L-1 using 0.5 mL of e-liquid. This method was applied to 50 e-cigarette brands purchased in the Korean market. The developed method was able to easily and accurately identify the origin of nicotine even using a small amount of e-liquid sample. It is expected that effective e-cigarette regulation will be possible if the nicotine biological indicator and high-sensitivity analysis method developed in this study are used.

Nicotine and Cardiovascular Health: When Poison is Addictive - a WHF Policy Brief

Nicotine is universally recognized as the primary addictive substance fuelling the continued use of tobacco products, which are responsible for over 8 million deaths annually. In recent years, the popularity of newer recreational nicotine products has surged drastically in many countries, raising health and safety concerns. For decades, the tobacco industry has promoted the myth that nicotine is as harmless as caffeine. Nonetheless, evidence shows that nicotine is far from innocuous, even on its own. In fact, numerous studies have demonstrated that nicotine can harm multiple organs, including the respiratory and cardiovascular systems. Tobacco and recreational nicotine products are commercialized in various types and forms, delivering varying levels of nicotine along with other toxic compounds. These products deliver nicotine in profiles that can initiate and perpetuate addiction, especially in young populations. Notably, some electronic nicotine delivery systems (ENDS) and heated tobacco products (HTP) can deliver concentrations of nicotine that are comparable to those of traditional cigarettes. Despite being regularly advertised as such, ENDS and HTP have demonstrated limited effectiveness as tobacco cessation aids in real-world settings. Furthermore, ENDS have also been associated with an increased risk of cardiovascular disease. In contrast, nicotine replacement therapies (NRT) are proven to be safe and effective medications for tobacco cessation. NRTs are designed to release nicotine in a slow and controlled manner, thereby minimizing the potential for abuse. Moreover, the long-term safety of NRTs has been extensively studied and documented. The vast majority of tobacco and nicotine products available in the market currently contain nicotine derived from tobacco leaves. However, advancements in the chemical synthesis of nicotine have introduced an economically viable alternative source. The tobacco industry has been exploiting synthetic nicotine to circumvent existing tobacco control laws and regulations. The emergence of newer tobacco and recreational nicotine products, along with synthetic nicotine, pose a tangible threat to established tobacco control policies. Nicotine regulations need to be responsive to address these evolving challenges. As such, governments should regulate all tobacco and non-medical nicotine products through a global, comprehensive, and consistent approach in order to safeguard tobacco control progress in past decades.

Tobacco-derived and tobacco-free nicotine cause differential inflammatory cell influx and MMP-9 in mouse lung

BACKGROUND

Electronic nicotine delivery systems (ENDS) or electronic cigarettes (e-cigarettes) aerosolize an e-liquid composed of propylene glycol (PG) and vegetable glycerin (VG) as humectants, flavoring chemicals, and nicotine. Nicotine naturally occurs in two isomers R- and S-nicotine, with tobacco-derived nicotine (TDN) composed of S-nicotine, and tobacco-free/synthetic nicotine (TFN) composed of a racemic mixture of R- and S-nicotine. Currently, there is limited knowledge of the potential differences in the toxicity of TFN versus TDN. We hypothesized that exposure of TFN and TDN salts to C57BL/6J mice would result in a differential response in lung inflammation and protease/ antiprotease imbalance.

METHODS

Five-week-old male and female C57BL/6J mice were exposed to air, PG/VG, PG/VG with TFN salts (TFN), or PG/VG with TDN salts (TDN) by nose-only exposure. Lung inflammatory cell counts, cytokine/chemokine levels, and matrix metalloproteinase (MMP) protein abundance and activity levels were determined by flow cytometry, ELISA, immunoblotting, and gel zymography, respectively.

RESULTS

Exposure to the humectants (PG/VG) alone increased cytokine levels- IL-6, KC, and MCP-1 in the BALF and KC levels in lung homogenate of exposed mice. While no change was observed in the cytokine levels in lung homogenate of TDN aerosol exposed mice, exposure to TFN aerosols resulted in an increase in KC levels in the lungs of these mice compared to air controls. Interestingly, exposure to TDN aerosols increased MMP-9 protein abundance in the lungs of female mice, while exposure to TFN aerosol showed no change. The metabolism of nicotine or the clearance of cotinine for TFN exposure may differ from that for TDN.

CONCLUSION

Exposure to humectants, PG/VG alone, induces an inflammatory response in C57BL/6J mice. TFN and TDN salts show distinct changes in inflammatory responses and lung proteases on acute exposures. These data suggest variable toxicological profiles of the two forms of nicotine in vivo. Future work is thus warranted to delineate the harmful effects of synthetic/natural nicotine with humectants to determine the potential toxicological risks for users.

Emerging ENDS products and challenges in tobacco control toxicity research

Electronic nicotine delivery systems (ENDS) continue to rapidly evolve. Current products pose unique challenges and opportunities for researchers and regulators. This commentary aims to highlight research gaps, particularly in toxicity research, and provide guidance on priority research questions for the tobacco regulatory community. Disposable flavoured ENDS have become the most popular device class among youth and may contain higher nicotine levels than JUUL devices. They also exhibit enhanced harmful and potentially harmful constituents production, contain elevated levels of synthetic coolants and pose environmental concerns. Synthetic nicotine and flavour capsules are innovations that have recently enabled the circumvention of Food and Drug Administration oversight. Coil-less ENDS offer the promise of delivering fewer toxicants due to the absence of heating coils, but initial studies show that these products exhibit similar toxicological profiles compared with JUULs. Each of these topic areas requires further research to understand and mitigate their impact on human health, especially their risks to young users.

Tobacco-Derived and Tobacco-Free Nicotine cause differential inflammatory cell influx and MMP9 in mouse lung

Electronic nicotine delivery systems (ENDS) or electronic cigarettes (e-cigarettes) have propylene glycol (PG) and vegetable glycerin (VG) as humectants, flavoring chemicals, and nicotine. Nicotine naturally occurs in two isomers R- and S-nicotine, with both tobacco-derived nicotine (TDN) composed of S-nicotine and synthetic nicotine (TFN) composed of a racemic mixture of R- and S-nicotine. Currently there is limited knowledge of the potential differences in the toxicity of TFN vs TDN. We hypothesized that exposure of TFN salts to C57BL/6J mice will result in a differential response in inflammation and lung protease and antiprotease imbalance compared to TDN salts exposed mice. We studied the toxicological impact of these isomers by exposing mice to air, PG/VG, PG/VG with TFN salts, or PG/VG with TDN salts by nose-only exposure and measured the cytokine levels in BALF and lung homogenate along with MMP protein abundance in the lungs of exposed mice. Exposure to the humectants, PG/VG, used in e-cigarettes alone was able to increase cytokine levels-IL-6, KC, and MCP-1 in BALF and KC levels in lung homogenate. Further, it showed differential responses on exposure to PG/VG with TDN salts and PG/VG with TFN salts since PG/VG with TDN salts did not alter the cytokine levels in lung homogenate while PG/VG with TFN salts resulted in an increase in KC levels. PG/VG with TDN salts increased the levels of MMP9 protein abundance in female exposed mice, while PG/VG with TFN salts did not alter MMP9 levels in female mice. The metabolism of nicotine or the clearance of cotinine from TFN may differ from the metabolism of nicotine or the clearance of cotinine from TDN. Thus exposure of humectants alone to induce an inflammatory response while PG/VG with TFN salts and PG/VG with TDN salts may differentially alter inflammatory responses and lung proteases in acute exposures. These data suggest the harmful effects of synthetic/natural nicotine and PG/VG and potential toxicological risk for users.

Scalemic natural products

Covering: up to the end of 2022The area of scalemic natural products is often enigmatic from a mechanistic standpoint, since low optical purity is observed in compounds having multiple contiguous stereogenic centers resulting from mechanistically distinct biogenetic steps. A scalemic state is rarely the result of a sloppy enzymatic activity, rather resulting from the expression of antipodal enzymes/directing proteins or from the erosion of optical purity by enzymatic or spontaneous reactions. Evidence for these processes is critically reviewed, identifying the mechanisms most often associated to the enzymatic generation of scalemic natural products and also discussing analytical exploitations of natural products' scalemicity.

Cardiopulmonary Impact of Electronic Cigarettes and Vaping Products: A Scientific Statement From the American Heart Association

Vaping and electronic cigarette (e-cigarette) use have grown exponentially in the past decade, particularly among youth and young adults. Cigarette smoking is a risk factor for both cardiovascular and pulmonary disease. Because of their more limited ingredients and the absence of combustion, e-cigarettes and vaping products are often touted as safer alternative and potential tobacco-cessation products. The outbreak of e-cigarette or vaping product use-associated lung injury in the United States in 2019, which led to >2800 hospitalizations, highlighted the risks of e-cigarettes and vaping products. Currently, all e-cigarettes are regulated as tobacco products and thus do not undergo the premarket animal and human safety studies required of a drug product or medical device. Because youth prevalence of e-cigarette and vaping product use was as high as 27.5% in high school students in 2019 in the United States, it is critical to assess the short-term and long-term health effects of these products, as well as the development of interventional and public health efforts to reduce youth use. The objectives of this scientific statement are (1) to describe and discuss e-cigarettes and vaping products use patterns among youth and adults; (2) to identify harmful and potentially harmful constituents in vaping aerosols; (3) to critically assess the molecular, animal, and clinical evidence on the acute and chronic cardiovascular and pulmonary risks of e-cigarette and vaping products use; (4) to describe the current evidence of e-cigarettes and vaping products as potential tobacco-cessation products; and (5) to summarize current public health and regulatory efforts of e-cigarettes and vaping products. It is timely, therefore, to review the short-term and especially the long-term implications of e-cigarettes and vaping products on cardiopulmonary health. Early molecular and clinical evidence suggests various acute physiological effects from electronic nicotine delivery systems, particularly those containing nicotine. Additional clinical and animal-exposure model research is critically needed as the use of these products continues to grow.

Synthetic nicotine e-liquids sold in US online vape shops

Synthetic nicotine (relative to tobacco-derived, or "natural" nicotine) is an emerging feature of e-cigarettes including e-liquids in the online marketplace. This study investigated a total of 11,161 unique nicotine e-liquids sold in online stores in the US during 2021, using keyword matching approach to identify the feature of synthetic nicotine based on product description texts. We showed that in 2021, 2.13% of nicotine-containing e-liquids in our sample were marketed as synthetic nicotine e-liquids. About a quarter of the synthetic nicotine e-liquids that we identified were salt-based; the nicotine strength varied; and those synthetic nicotine e-liquids had a variety of flavor profiles. Synthetic nicotine containing e-cigarettes are likely to remain in the market and manufacturers might market those products as "tobacco-free," to attract consumers who this feature as healthier or less addictive. It is important to monitor synthetic nicotine in the e-cigarette marketplace and assess how this feature influences consumer behaviors.

A Systematic Review of Analytical Methods for the Separation of Nicotine Enantiomers and Evaluation of Nicotine Sources

The introduction of synthetic nicotine by the tobacco industry, also promoted as tobacco-free nicotine, presented new challenges for analytical chemists working in tobacco regulatory science to develop and optimize new methods to assess new nicotine parameters, namely enantiomer ratio and source. We conducted a systematic literature review of the available analytical methods to detect the nicotine enantiomer ratio and the source of nicotine using PubMed and Web of Science databases. Methods to detect nicotine enantiomers included polarimetry, nuclear magnetic resonance, and gas and liquid chromatography. We also covered methods developed to detect the source of nicotine either indirectly via determining the nicotine enantiomer ratio or the detection of tobacco-specific impurities or directly using the isotope ratio enrichment analysis by nuclear magnetic resonance (site-specific natural isotope fractionation and site-specific peak intensity ratio) or accelerated mass spectrometry. This review presents an accessible summary of all these analytical methods.

Stable isotope characterization of tobacco products: A determination of synthetic or natural nicotine authenticity

RATIONALE

"Tobacco-free" or synthetic nicotine products have appeared in some markets, increasing potential health risks and regulatory compliance challenges. Currently, there are few reliable methods for the determination of authenticity of natural and synthetic nicotine. Analytical techniques based on stable isotopes have broad application prospects in the traceability and identification of agricultural products.

METHODS

Tobacco leaves from four main tobacco production regions in China and different types of tobacco products were extracted with n-hexane and 5% sodium hydroxide to obtain nicotine extracts. Subsequent stable isotope mass spectrometry was performed by analyzing δ2 H, δ13 C, and δ15 N values of nicotine.

RESULTS

Firstly, results from a batch of 233 samples indicated stable isotopes were closely related to climate and geographical locations and provide a basis for a determination of the origin of tobacco leaves. In addition, the δ2 H values had significant differences between natural and synthetic nicotine and the results indicate a δ2 H value of -163.0‰ could be the threshold for assessing synthetic and natural nicotine. Finally, a total of 239 results further validated the δ2 H value as a metric for source authentication of commercial tobacco products.

CONCLUSIONS

Synthetic (S)-(-)-nicotine could be accurately and quickly identified using the method developed by measuring δ2 H values in a qualitative manner. To our knowledge, this is the first time a stable isotope mass spectrometry technique has been used for distinguishing the source of nicotine. This technique will aid in the accurate identification, labelling, and regulation of synthetic nicotine-based tobacco products.

Kinetics of Aldehyde Flavorant-Acetal Formation in E-Liquids with Different E-Cigarette Solvents and Common Additives Studied by 1H NMR Spectroscopy

Flavorants, nicotine, and organic acids are common additives found in the e-liquid carrier solvent, propylene glycol (PG) and/or glycerol (GL), at various concentrations. Some of the most concentrated and prevalent flavorants in e-liquids include trans-cinnamaldehyde, vanillin, and benzaldehyde. Aldehyde flavorants have been shown to react with PG and GL to form flavorant-PG and -GL acetals that have unique toxicity properties in e-liquids before aerosolization. However, there is still much that remains unknown about the effects of different e-cigarette solvents, water, nicotine, and organic acids on the rate of acetalization in e-liquids. We used 1H NMR spectroscopy to determine the first-order initial rate constant, half-life, and % acetal formed at equilibrium for flavorant-acetal formation in simulated e-liquids. Herein, we report that acetalization generally occurs at a faster rate and produces greater yields in e-liquids with higher ratios of GL (relative to PG). trans-Cinnamaldehyde acetals formed the fastest in 100% PG-simulated e-liquids, followed by benzaldehyde and vanillin based on their half-lives and rate constants. The acetal yield was greatest for benzaldehyde in PG e-liquids, followed by trans-cinnamaldehyde and vanillin. Acetalization in PG e-liquids containing aldehyde flavorants was inhibited by water and nicotine but catalyzed by benzoic acid. Flavorant-PG acetal formation was generally delayed in the presence of nicotine, even if benzoic acid was present at 2-, 4-, or 10-fold the nicotine concentration, as compared to the PG e-liquids with 2.5 mg/mL flavorant. Thus, commercial e-liquids with aldehyde flavorants containing a higher GL ratio (relative to PG), little water, no nicotine, nicotine with excess organic acids, or organic acids without nicotine would undergo acetalization the fastest and with the highest yield. Many commercial e-liquids must therefore contain significant amounts of flavorant acetals.

Research method of rapid determination of chiral pesticide fenpropathrin enantiomers in fruit and vegetable puree by supercritical fluid chromatography

A method is firstly established for the separation and determination of fenpropathrin enantiomer residues in apple puree, strawberry puree, and tomato puree considered as a supplementary food for infants by supercritical fluid chromatography. After the sample was extracted with acetonitrile and cleaned up by a solid phase extraction column, then it's separated by a CHIRALPAK AD-3 chiral column with a gradient elution at a flow rate of 1.0 mL/min using methanol and supercritical carbon dioxide as the mobile phase, detected by ultraviolet detector at 230 nm wavelength and quantified with the external standard method. The limits of quantification of the two fenpropathrin enantiomers were both 0.2 mg/kg, the linear ranges were 1.0-20.0 mg/L with linear correlation coefficients greater than 0.9992, the recoveries in the spiked samples at 0.2, 0.4 and 2.0 mg/kg were from 80.6% to 105%, and the relative standard deviation reached 2.6%-7.7%. This method has the advantages of convenient operation, good resolution and environmental protection, which can satisfy the requirement of determination for fenpropathrin enantiomer residues in fruit and vegetable puree as a supplementary food for infants. This article is protected by copyright. All rights reserved.

Analysis and differentiation of tobacco-derived and synthetic nicotine products: Addressing an urgent regulatory issue

There is significant regulatory and economic need to distinguish analytically between tobacco-derived nicotine (TDN) and synthetic nicotine (SyN) in commercial products. Currently, commercial e-liquid and oral pouch products are available that contain tobacco-free nicotine, which could be either extracted from tobacco or synthesized. While tobacco products that contain TDN are regulated by FDA Center for Tobacco Products, those with SyN are currently not in the domain of any regulatory authority. This regulatory difference provides an economic incentive to use or claim the use of SyN to remain on the market without submitting a Premarket Tobacco Product Application. TDN is ~99.3% (S)-nicotine, whereas SyN can vary from racemic (50/50 (R)/(S)) to ≥ 99% (S)-nicotine, i.e., chemically identical to the tobacco-derived compound. Here we report efforts to distinguish between TDN and SyN in various samples by characterizing impurities, (R)/(S)-nicotine enantiomer ratio, (R)/(S)-nornicotine enantiomer ratio, and carbon-14 (14C) content. Only 14C analysis accurately and precisely differentiated TDN (100% 14C) from SyN (35-38% 14C) in all samples tested. 14C quantitation of nicotine samples by accelerator mass spectrometry is a reliable determinate of nicotine source and can be used to identify misbranded product labelled as containing SyN. This is the first report to distinguish natural, bio-based nicotine from synthetic, petroleum-based nicotine across a range of pure nicotine samples and commercial e-liquid products.

Interconversion of nicotine enantiomers during heating and implications for smoke from combustible cigarettes, heated tobacco products, and electronic cigarettes

Physiological properties of (R)-nicotine have differences compared with (S)-nicotine, and the subject of (S)- and (R)-nicotine ratio in smoking or vaping related items is of considerable interest. A Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS) method for the analysis of (S)- and (R)-nicotine has been developed and applied to samples of nicotine from different sources, nicotine pyrolyzates, several types of tobacco, smoke from combustible cigarettes, smoke from heated tobacco products, e-liquids, and particulate matter obtained from e-cigarettes aerosol. The separation was achieved on a Chiracel OJ-3 column, 250 × 4.6 mm with 3-μm particles using a nonaqueous mobile phase. The detection was performed using atmospheric pressure chemical ionization (APCI) in positive mode. The only transition measured for the analysis of nicotine was 163.1 → 84.0. The method has been summarily validated. For the analysis, the samples of tobacco and smoke from combustible cigarettes were subject to a cleanup procedure using solid phase extraction (SPE). It was demonstrated that nicotine upon heating above 450°C for several minutes starts decomposing, and some formation of (R)-enantiomer from a sample of 99% (S)-nicotine is observed. An analogous process takes place when a 99% (R)-nicotine is heated and forms low levels of (S)-nicotine. This interconversion has the effect of slightly increasing the content of (R)-nicotine in smoke compared with the level in tobacco for combustible cigarettes and for heated tobacco products. The (S)/(R) ratio of nicotine enantiomers in e-liquids was identical with the ratio for the particulate phase of aerosols generated by e-cigarette vaping.