Evaluation of flavour profiles in e-cigarette refill solutions using gas chromatography-tandem mass spectrometry

Recent advances in the analysis of electronic cigarette liquids and aerosols: Sample preparation and chromatographic characterization

Electronic cigarette (e-cigarette) usage has risen dramatically worldwide in recent years. It has been publicized as a safer alternative to the conventional combustible cigarette. This, however, has not yet been supported by robust toxicological research evidence. Analysis of the chemical compositions of e-liquids and generated aerosols is an important step in evaluating the toxicity effects of e-cigarettes. Currently, a broad spectrum of analytical methods have been employed for qualitative and quantitative analysis of chemical compositions of e-cigarette liquids and aerosols. The aim of this article is to review the advances in the chromatographic characterization of chemical composition of the latter in the recent five years. In addition, sample preparation methods for e-liquids and aerosols are surveyed and discussed. A study of the relevant literature indicates that, expectedly, gas chromatography and liquid chromatography with a variety of detection systems, particularly mass spectrometry, have been the main analytical techniques used in this field. Sample preparation procedures primarily include headspace sampling, dilute-and-shoot approach, liquid-liquid extraction and sorbent-based extraction for e-liquids and for aerosols (the latter usually with laboratory-built collection devices). Some challenges of current e-cigarette analytical research, and an overview on prospective work are also presented.

Comprehensive characterization of volatile and semi-volatile compounds in e-liquids for electronic cigarette using gas chromatography accurate mass spectrometry

The consumption of electronic cigarettes is a habit with an increasing prevalence, particularly among youths. Knowing the composition of e-liquids used in these devices represents the first step to understand the potential impact of e-smoking in the health of consumers. Herein, a non-target screening methodology was applied to the identification of volatile and semi-volatile compounds in a set of e-liquids from different suppliers, with different flavors, and containing different kinds of additives, such as nicotine or cannabidiol. To this end, samples were characterized by gas chromatography accurate mass spectrometry, using a time-of-flight mass analyzer. Combination of deconvoluted electronic ionization mass spectra with linear retention index values, obtained for two columns with different selectivity, permitted the identification of more than 250 chemicals with different confidence levels. Among them, respiratory pro-inflammatory compounds, acetals of propylene glycol and glycerin with aldehydes, nicotine-related and non-related alkaloids, and psychoactive cannabinoids were confirmed as concerning compounds in e-liquid samples. Concentration ratios between propylene glycol acetals and parent aldehydes varied in the range from 2% (ethyl vanillin) to more than 80% (case of benzaldehyde). The ratios between the concentrations of delta-9-tetrahydrocannabinol and cannabidiol in e-liquids stayed in the range from 0.02% to 0.3%.

Method Comparison of Sample Pretreatment and Discovery of Differential Compositions of Natural Flavors and Fragrances for Quality Analysis by Using Chemometric Tools

Natural flavors and fragrances or their extracts have been widely used in a large variety of areas, including food, cosmetic, and tobacco industrial processes, among others. The compositions and intrinsic attributes of flavors and fragrances were related to many factors, such as species, geographical origin, planting environment, storage condition, processing method, and so on. This not only increased the difficulty in analyzing the product quality of flavors and fragrances, but also challenged the idea of "quality-by-design (QbD)". This work proposed an integrated strategy for precise discovery of differential compounds among different classes and subsequent quality analysis of complex samples through flavors and fragrances used in tobacco industry as examples. Three pretreatment methods were first inspected to effectively characterize the sample compositions, including direct injection (DI), thermal desorption (TD), and stir bar sorptive extraction (SBSE)-TD, coupled with gas chromatography-mass spectrometry (GC-MS) analysis to obtain characteristic information of samples of flavors and fragrances. Then, principal component analysis (PCA) was applied to discover the relation and difference between chromatographic fingerprints and peak table data once significant components were recognized in a holistic manner. Model population analysis (MPA) was then used to quantitatively extract the characteristic chemicals representing the quality differences among different classes of samples. Some differential marker compounds were discovered for difference analysis, including benzyl alcohol, latin acid, l-menthol acid, decanoic acid ethyl ester, vanillin, trans-o-coumaric acid, benzyl benzoate, and so on. Furthermore, partial least squares-discriminant analysis (PLS-DA) and support vector machine (SVM) were respectively applied to construct multivariate models for evaluation of quality differences and variations. It was found that the accuracy attains to 100% for sample classification. With the help of optimal sample pretreatment technique and chemometric methods, the strategy for quality analysis and difference discovery proposed in this work can be widely delivered to more areas of complex plants with good interpretability and high accuracy.

Robust, comprehensive, sensitive analysis of flavour additives with carboxyl and hydroxyl groups in cigarette smoke combining silylation and gas chromatography-tandem mass spectrometry with an improved backflushing system

Flavour additives with carboxyl and hydroxyl groups (FACHs), the key ingredients in characteristic flavours, are frequently detected in cigarette smoke. They are attracting increasing attention in regulating the flavour additives used in tobacco to curb youth tobacco use and prevent the use of additives that are harmful. In this study, a highly robust, sensitive, and precise method based on silylation and GC-MS/MS with an improved backflushing system was developed for the simultaneous analysis of 171 FACHs in cigarette smoke. Silylation has been shown to have advantages in terms of high selectivity and sensitivity to chemicals with carboxyl and hydroxyl groups, especially when combined with GC-MS/MS. The extraction and silylation conditions were optimised. Dichloromethane was used as the extraction agent. BSTFA in combination with 1% TMCS and 0.2% TMSI was selected as silylating agent for high silylation efficiency, particularly for hindered analytes. The method has been validated. The limit of detection (LOD) ranged from 0.6 to 332.3 ng/mL. 91.1% out of the analytes in QC samples had precisions lower than 10% during one month run. The improved backflushing system with a fused silica splitter was shown to be crucial in the excellent long-term robustness of the method. The developed method was used to determine flavour additives in 270 practical cigarette smoke samples with reliable results. A total of 154 FACHs were identified with wide-range levels among different cigarette brands.

Menthol in Electronic Cigarettes Causes Biophysical Inhibition of Pulmonary Surfactant

With an increasing prevalence of electronic cigarette (e-cigarette) use, especially among youth, there is an urgent need to better understand the biological risks and pathophysiology of health conditions related to e-cigarettes. A majority of e-cigarette aerosols are in the submicron size and would deposit in the alveolar region of the lung, where they must first interact with the endogenous pulmonary surfactant. To date, little is known whether e-cigarette aerosols have an adverse impact on the pulmonary surfactant. We have systematically studied the effect of individual e-cigarette ingredients on an animal-derived clinical surfactant preparation, bovine lipid extract surfactant, using a combination of biophysical and analytical techniques, including in vitro biophysical simulations using constrained drop surfactometry, molecular imaging with atomic force microscopy, chemical assays using carbon nuclear magnetic resonance and circular dichroism, and in silico molecular dynamics simulations. All data collectively suggest that flavorings used in e-cigarettes, especially menthol, play a predominant role in inhibiting the biophysical function of the surfactant. The mechanism of biophysical inhibition appears to involve menthol interactions with both phospholipids and hydrophobic proteins of the natural surfactant. These results provide novel insights into the understanding of the health impact of e-cigarettes and may contribute to a better regulation of e-cigarette products.

Effects of tobacco smoke on indoor air quality: the use of mosses in biomonitoring

This research was carried out to assess the possibility of using Pleurozium schreberi mosses as bioindicators of atmospheric aerosol pollution in living quarters (kitchen and bedroom), with metals originating from tobacco smoke from various types of cigarettes: conventional cigarettes, e-cigarettes and heated tobacco products. The moss-bag method of active biomonitoring was used. The mosses were exposed in these indoor spaces for three months and, after the exposition period, their analytes - Ni, Cu, Zn, Cd and Pb - were determined using flame atomic absorption spectrometry (F-AAS). Results were interpreted using the relative accumulation factors (RAF), coefficients of variation (CV) and the Wilcoxon test. As a result of the research, it was found that there were statistically significant differences in Zn and Cd concentrations in tobacco smoke from different types of cigarettes. The analyses showed that heated tobacco products contaminate indoor air with metals, similar to conventional cigarettes and e-cigarettes. It was demonstrated that the reliability of biomonitoring results was affected, for example, by the method of preparation of bioindicator samples, such as mosses.

Optimization of Determination Method of Cooling Agents in Cigarette Tipping Paper by Gas Chromatography

Monitoring the characteristic components in tipping paper is important to ensure the quality of cigarette products. This study establishes a method based on gas chromatography (GC) for determining cooling agents in tipping paper. The tipping paper was cut into pieces and extracted by ethanol under specific temperatures in a shaker. Then, the characteristic cooling agents of (-)-menthone, L-menthol, and (-)-menthyl lactate in extract were determined using GC coupled with a flame ionization detector (GC-FID). The limits of detection (LODs) and limits of quantification (LOQs) for the three cooling agents ranged from 0.15~0.32 μg/mL and 0.49~1.06 μg/mL, respectively. Results demonstrated a good linear relationship with high correlation coefficients for the three tested cooling agents. The extraction conditions of the cooling agents were optimized through a single-factor experiment as well as an orthogonal experiment. The standard addition recovery experiment showed that the average recoveries range from 81.23 to 100.62%, and the relative standard deviations (RSDs) of the measured values (n = 5) ranged from 0.34 to 1.64%.

Flavor components in tobacco capsules identified through non-targeted quantitative analysis

Tobacco flavors increase the attractiveness of a tobacco brand and ultimately promote addiction. Information about what flavor and how much flavor is in flavor capsules can provide an effective way to regulate tobacco flavor. In this study, 128 flavor chemicals were identified and quantified by gas chromatography-mass spectrometry using libraries and authentic standards. Validation of the developed method was performed for interference, detection limits, calibration curves, accuracy, and precision. Menthol was the main ingredient in all capsules, and the carcinogenic pulegone was detected. Detected menthofuran, benzyl alcohol, geraniol, and eugenol cause toxic or severe irritation, and detected lactones can increase nicotine addiction by inhibiting nicotine metabolism in smokers. Margin of exposures for carcinogenic pulegone and non-carcinogenic menthol were well below safety thresholds, indicating a significant risk of inhalation exposure. It is desirable to prohibit the use of flavor capsules in consideration of human risk.

Qualitative and quantitative comparison of flavor chemicals in tobacco heating products, traditional tobacco products and flavoring capsules

A gas chromatography-mass spectrometric (GC-MS) method was developed for the qualitative and quantitative analysis of flavor chemicals in tobacco heating products (THPs), traditional tobacco products (TTPs) and their flavoring capsules. A total of 283 compounds were identified through non-target analysis, and the final 302 compounds were selected to develop an analytical method. The lower limits of detection (LOD) of analytes were 0.00074-12 mg/kg and their LOD range was wide depending on the presence or absence in the reference cigarette. The precision of the 302 compounds was less than 24.5%, and the accuracy ranged from 80.0% to 120%. A total of 190 flavors and 5 contaminants were determined in 21 THP, 10 TTP, 8 THP capsules and 11 TTP capsules. When comparing the total flavor content of flavors per cigarette, it was in the order of THP capsule> TTP capsule ≫ THP ≫ TTP. The correlations between the 53 cigarette products and 190 flavor chemicals were analyzed using PCA. It has been demonstrated that PCA results can be a useful tool in differentiating brands and manufacturers of tobacco products.

Urinary volatomic profile of traditional tobacco smokers and electronic cigarettes users as a strategy to unveil potential health issues

Many harmful and potentially harmful constituents are present in tobacco products. Cigarette smoke is known to cause different forms of cancer and trigger the development of chronic diseases. In the last decade, electronic cigarettes have emerged as a healthier alternative associated to less harmful effects in comparison to traditional tobacco. However, the lack of standardization of electronic cigarettes products makes it difficult to establish and compare the real effects on health of products from different manufacturers. To better understand the impact of smoking and vaping, the volatomic composition of urine samples from traditional tobacco smokers and electronic cigarette users was established and compared with nonsmokers (control group), using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry. A total of 45 urinary volatile organic metabolites belonging to different chemical families were identified in the urine of the studied groups. Benzene derivatives, terpenes, and aromatics were the chemical families that contributed the most to the urinary profile of smokers. The vapers urinary volatomic pattern was also dominated by terpenes and aromatics, in addition to alcohols. The orthogonal partial least squares-discriminant analysis of the data obtained indicated that the urinary profile of vapers is more closely related to the control group, reinforcing the hypothesis of the lowest harmfulness of electronic cigarettes. Further studies recruiting a higher number of subjects are therefore necessary to consolidate the data obtained.

The Chemical Complexity of e-Cigarette Aerosols Compared With the Smoke From a Tobacco Burning Cigarette

Background: As e-cigarette popularity has increased, there is growing evidence to suggest that while they are highly likely to be considerably less harmful than cigarettes, their use is not free of risk to the user. There is therefore an ongoing need to characterise the chemical composition of e-cigarette aerosols, as a starting point in characterising risks associated with their use. This study examined the chemical complexity of aerosols generated by an e-cigarette containing one unflavored and three flavored e-liquids. A combination of targeted and untargeted chemical analysis approaches was used to examine the number of compounds comprising the aerosol. Contributions of e-liquid flavors to aerosol complexity were investigated, and the sources of other aerosol constituents sought. Emissions of 98 aerosol toxicants were quantified and compared to those in smoke from a reference tobacco cigarette generated under two different smoking regimes. Results: Combined untargeted and targeted aerosol analyses identified between 94 and 139 compounds in the flavored aerosols, compared with an estimated 72-79 in the unflavored aerosol. This is significantly less complex (by 1-2 orders of magnitude) than the reported composition of cigarette smoke. Combining both types of analysis identified 5-12 compounds over and above those found by untargeted analysis alone. Gravimetrically, 89-99% of the e-cigarette aerosol composition was composed of glycerol, propylene glycol, water and nicotine, and around 3% comprised other, more minor, constituents. Comparable data for the Ky3R4F reference tobacco cigarette pointed to 58-76% of cigarette smoke "tar" being composed of minor constituents. Levels of the targeted toxicants in the e-cigarette aerosols were significantly lower than those in cigarette smoke, with 68.5->99% reductions under ISO 3308 puffing conditions and 88.4->99% reductions under ISO 20778 (intense) conditions; reductions against the WHO TobReg 9 priority list were around 99%. Conclusion: These analyses showed that the e-cigarette aerosols contain fewer compounds and at significantly lower concentrations than cigarette smoke. The chemical diversity of an e-cigarette aerosol is strongly impacted by the choice of e-liquid ingredients.

The chemistry and toxicology of vaping

Vaping is the process of inhaling and exhaling an aerosol produced by an e-cigarette, vape pen, or personal aerosolizer. When the device contains nicotine, the Food and Drug Administration (FDA) lists the product as an electronic nicotine delivery system or ENDS device. Similar electronic devices can be used to vape cannabis extracts. Over the past decade, the vaping market has increased exponentially, raising health concerns over the number of people exposed and a nationwide outbreak of cases of severe, sometimes fatal, lung dysfunction that arose suddenly in otherwise healthy individuals. In this review, we discuss the various vaping technologies, which are remarkably diverse, and summarize the use prevalence in the U.S. over time by youths and adults. We examine the complex chemistry of vape carrier solvents, flavoring chemicals, and transformation products. We review the health effects from epidemiological and laboratory studies and, finally, discuss the proposed mechanisms underlying some of these health effects. We conclude that since much of the research in this area is recent and vaping technologies are dynamic, our understanding of the health effects is insufficient. With the rapid growth of ENDS use, consumers and regulatory bodies need a better understanding of constituent-dependent toxicity to guide product use and regulatory decisions.

Jacek Namieśnik-Analytical Chemist and Dedicated Biker: From Wine Analysis to Toxic Compounds

Jacek Namieśnik, who died at the age of 69, was one of the most influential analytical chemists in Poland at the second half of the 20th century and the first two decades of the 21st century [...].

Development of a “Freeze-Pour” Sample Preparation Method for the GC Analysis of Semivolatile Flavouring Chemicals Present in E-cigarette Refill Liquids

During the past decade, e-cigarettes have become increasingly popular. To guarantee their safe use and to comply with the notification requirements of the EU Tobacco Product Directive, the EU member state regulatory authorities need information about the exact composition of the e-liquids and their emissions. However, one of the challenges encountered during the analysis of e-liquids is the presence of the highly abundant e-liquid matrix components propylene glycol and glycerol. In this study, headspace gas chromatography (HS-GC) analysis is presented as an excellent method for the analysis of high volatile components in e-liquids. For the analysis of semivolatile ingredients, an additional sample preparation step is proposed based on a liquid–liquid extraction (LLE) followed by a freeze-out of the matrix components. The developed method was successfully validated in accordance with the validation requirements of ICH guidelines for the quantification of four flavourings with a potential health concern for e-cigarette users.

Development and validation of a gas chromatography method coupled with flame ionization detector for quantitative analysis of fragrance allergens in aromas for e-cigarettes

Aromas can give smell and/or flavor to a variety of products in the cosmetic and food industry. They are also used as e-cigarette additives. Some of those substances are recognized as fragrance allergens and can cause allergic reactions so there is a need to control their use. Gas chromatography is the method of choice for analyzing fragrance allergens because of their low boiling points. This study aimed to develop and validate a robust and simple method for the analysis of fragrance allergens in aromas for e-cigarettes. A method using gas chromatography coupled with a flame ionization detector was developed for 25 fragrance allergens. Optimized parameters were sample diluent, internal standard, and carrier gas. The output method was the one previously developed and optimized. The linearity of the method was >0.994 over the range of 0.5-40 μg/mL. Accuracy and precision were within the acceptance range. Limits of detection and quantification were determined, and calibration curves were plotted. The method was applied to three real samples of aromas. Thirteen fragrance allergens were detected. Concentrations varied in the range of dozens to thousands of μg/mL showed that concentrations of fragrances in aromas for e-cigarettes can be high and varies among products.

Enabling the inclusion of non-hydrolysed sulfated long term anabolic steroid metabolites in a screening for doping substances by means of gas chromatography quadrupole time-of-flight mass spectrometry

The World Anti-Doping Agency (WADA) publishes yearly their prohibited list, and sets a minimum required performance limit for each substance. To comply with these stringent requirements, the anti-doping laboratories have at least two complementary methods for their initial testing procedure (ITP), one using gas chromatography - mass spectrometry (GC-MS) and the other using liquid chromatography-MS (LC-MS). Anabolic androgenic steroids (AAS) have in previous years consistently been listed as the most frequently detected class of compounds. Over the last decade, evidence has emerged where a longer detection time is attained by focusing on sulfated metabolites of AAS instead of the conventional gluco-conjugated metabolites. Despite a decade of research on sulphated AAS using LC-MS, no LC-MS ITP has been developed that combines this class of compounds with the other mandatory targets. Such combination is essential for economical purposes. Recently, it was demonstrated that the direct injection of non-hydrolysed sulfates is compatible with GC-MS. Using this approach and by taking full use of the open screening capabilities of the quadrupole time of flight MS (QTOF-MS), this work describes for the first time a validated ITP that allows the detection of non-hydrolysed sulfated metabolites of AAS while, simultaneously, remaining capable of detecting a vast range of other classes of compounds, as well as the quantification of endogenous steroids, as required for an ITP compliant with the applicable WADA regulations. The method contains 263 compounds from 9 categories, including stimulants, narcotics, anabolic androgenic steroids and beta-blockers. Additionally, the advantages of the new method were illustrated by analysing excretion samples of drostanolone, mesterolone and metenolone. No negative effects were observed for the conventional markers and the detection time for mesterolone and metenolone increased by up to 150% and 144%, respectively compared to conventional markers.

Serum Metabolomic Profiles of Paratuberculosis Infected and Infectious Dairy Cattle by Ambient Mass Spectrometry

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of paratuberculosis [Johne's disease (JD)], a chronic disease that causes substantial economic losses in the dairy cattle industry. The long incubation period means clinical signs are visible in animals only after years, and some cases remain undetected because of the subclinical manifestation of the disease. Considering the complexity of JD pathogenesis, animals can be classified as infected, infectious, or affected. The major limitation of currently available diagnostic tests is their failure in detecting infected non-infectious animals. The present study aimed to identify metabolic markers associated with infected and infectious stages of JD. Direct analysis in real time coupled with high resolution mass spectrometry (DART-HRMS) was, hence, applied in a prospective study where cohorts of heifers and cows were followed up annually for 2–4 years. The animals' infectious status was assigned based on a positive result of both serum ELISA and fecal PCR, or culture. The same animals were retrospectively assigned to the status of infected at the previous sampling for which all JD tests were negative. Stored sera from 10 infected animals and 17 infectious animals were compared with sera from 20 negative animals from the same herds. Two extraction protocols and two (-/+) ionization modes were tested. The three most informative datasets out of the four were merged by a mid-level data fusion approach and submitted to partial least squares discriminant analysis (PLS-DA). Compared to the MAP negative subjects, metabolomic analysis revealed the m/z signals of isobutyrate, dimethylethanolamine, palmitic acid, and rhamnitol were more intense in infected animals. Both infected and infectious animals showed higher relative intensities of tryptamine and creatine/creatinine as well as lower relative abundances of urea, glutamic acid and/or pyroglutamic acid. These metabolic differences could indicate altered fat metabolism and reduced energy intake in both infected and infectious cattle. In conclusion, DART-HRMS coupled to a mid-level data fusion approach allowed the molecular features that identified preclinical stages of JD to be teased out.

Both Nonsmoking Youth and Smoking Adults Like Sweet and Minty E-liquid Flavors More Than Tobacco Flavor

Smokers may reduce their health risk by switching to electronic cigarette (e-cigarette) use. As e-cigarettes are not harmless, concerns exist about e-cigarette use by nonsmokers and youth. E-liquids are available in many different flavors that increase sensory appeal. Flavor preferences may differ between user groups, which could open doors for product regulation. We investigated which e-liquid flavors are attractive to specific user groups by comparing liking between adolescent nonsmokers (n = 41; mean age 16.9 ± 0.8), young adult nonsmokers (n = 42; mean age 22.7 ± 1.7), and adult smokers (n = 56; mean age 39.7 ± 11.1). Participants smelled tobacco- (n = 6) and nontobacco (n = 24)-flavored e-liquids and rated liking on a 9-point labeled hedonic scale, and familiarity, overall intensity, perceived sweetness, perceived bitterness, and irritation of the odors on a 100-unit Visual Analog Scale. Mean liking ranged from 2.3 (whiskey) to 6.7 (peppermint). Within all groups, the typically sweet and minty flavors (e.g., wine gum, watermelon, peppermint, menthol) were liked significantly more than the tobacco-flavored e-liquids. The set of tobacco-flavored e-liquids was significantly, but slightly, less disliked by adult smokers (3.9 ± 0.2) than adolescent (3.1 ± 0.3) and young adult (3.4 ± 0.3) nonsmokers (P < 0.001). No between-group differences were observed for sweet and minty flavors. Liking correlated significantly positively with odor sweetness (R = 0.49) and familiarity (R = 0.48) and negatively with odor bitterness (R = -0.58), irritation (R = -0.47), and overall intensity (R = -0.27). Thus, sweet- and minty-flavored e-liquids are liked equally by young nonsmokers and adult smokers, and more than tobacco flavors. Banning all flavors except tobacco will likely reduce e-cigarette appeal; potentially more for young nonsmokers than adult smokers.

Electronic Cigarette Refill Fluids Sold Worldwide: Flavor Chemical Composition, Toxicity, and Hazard Analysis

Flavor chemicals in electronic cigarette (EC) fluids, which may negatively impact human health, have been studied in a limited number of countries/locations. To gain an understanding of how the composition and concentrations of flavor chemicals in ECs are influenced by product sale location, we evaluated refill fluids manufactured by one company (Ritchy LTD) and purchased worldwide. Flavor chemicals were identified and quantified using gas chromatography/mass spectrometry (GC/MS). We then screened the fluids for their effects on cytotoxicity (MTT assay) and proliferation (live-cell imaging) and tested authentic standards of specific flavor chemicals to identify those that were cytotoxic at concentrations found in refill fluids. A total of 126 flavor chemicals were detected in 103 bottles of refill fluid, and their number per/bottle ranged from 1-50 based on our target list. Two products had none of the flavor chemicals on our target list, nor did they have any nontargeted flavor chemicals. A total of 28 flavor chemicals were present at concentrations ≥1 mg/mL in at least one product, and 6 of these were present at concentrations ≥10 mg/mL. The total flavor chemical concentration was ≥1 mg/mL in 70% of the refill fluids and ≥10 mg/mL in 26%. For sub-brand duplicate bottles purchased in different countries, flavor chemical concentrations were similar and induced similar responses in the in vitro assays (cytotoxicity and cell growth inhibition). The levels of furaneol, benzyl alcohol, ethyl maltol, ethyl vanillin, corylone, and vanillin were significantly correlated with cytotoxicity. The margin of exposure calculations showed that pulegone and estragole levels were high enough in some products to present a nontrivial calculated risk for cancer. Flavor chemical concentrations in refill fluids often exceeded concentrations permitted in other consumer products. These data support the regulation of flavor chemicals in EC products to reduce their potential for producing both cancer and noncancer toxicological effects.

E-cigarettes and health risks: more to the flavor than just the name

The growing interest in regulating flavored E-liquids must incorporate understanding of the "flavoring profile" of each E-liquid-which flavorings (flavoring chemicals) are present and at what concentrations not just focusing on the flavor on the label. We investigated the flavoring profile of 10 different flavored E-liquids. We assessed bronchial epithelial cell viability and apoptosis, phagocytosis of bacteria and apoptotic cells by macrophages after exposure to E-cigarette vapor extract (EVE). We validated our data in normal human bronchial epithelial cells (NHBE) and alveolar macrophages (AM) from healthy donors. We also assessed cytokine release and validated in the saliva from E-cigarette users. Increased necrosis/apoptosis (16.1-64.5% apoptosis) in 16HBE cells was flavor dependent, and NHBEs showed an increased susceptibility to flavors. In THP-1 differentiated macrophages phagocytosis was also flavor dependent, with AM also showing increased susceptibility to flavors. Further, Banana and Chocolate were shown to reduce surface expression of phagocytic target recognition receptors on alveolar macrophages. Banana and Chocolate increased IL-8 secretion by NHBE, whereas all 4 flavors reduced AM IL-1β secretion, which was also reduced in the saliva of E-cigarette users compared with healthy controls. Flavorant profiles of E-liquids varied from simple 2 compound mixtures to complex mixtures containing over a dozen flavorants. E-liquids with high benzene content, complex flavoring profiles, high chemical concentration had the greatest impacts. The Flavorant profile of E-liquids is key to disruption of the airway status quo by increasing bronchial epithelial cell apoptosis, causing alveolar macrophage phagocytic dysfunction, and altering airway cytokines.

Determination of exogenous prohibited flavour compounds added in coffee using gas chromatography triple quadrupole tandem massspectrometry and gas chromatography/combustion/isotope ratio mass spectrometry

An analytical method based on gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-MS/MS) was developed for the simultaneous determination of exogenous prohibited flavour compounds in coffee samples. In addition, gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) was developed to determine the origin of the founded prohibited flavour compound, N-methylpyrrole-2-carboxaldehyde (NMPCA). The good selectivity and sensitivity achieved in multiple reactions monitoring (MRM) mode allowed satisfactory confirmation and quantitation for the flavour compounds. The limits of detection (LODs) and limits of quantitation (LOQs) of these compounds were in the range of 0.0005-5.0 µg/kg and 0.002-16.0 µg/kg, respectively. The coffee samples were extracted with simultaneous distillation extraction (SDE) and NMPCA was analysed on a GC/C/IRMS system. The δ¹³C values of endogenous NMPCA in coffee beans were within a range of -35.0‰ to -31.1‰, whereas exogenous NMPCA was the range from -27.9‰ to -23.9‰. The validation results revealed that the GC-MS/MS method was sensitive and reliable, and the origin of NMPCA can be distinguished by GC/C/IRMS. Finally, this method was successfully applied to coffee samples analysis and NMPCA was found in coffee samples.

Sensory Evaluation of E-Liquid Flavors by Smelling and Vaping Yields Similar Results

INTRODUCTION

Sensory research on e-liquid flavors can be performed by means of smelling and vaping. However, data comparing smelling versus vaping e-liquid flavors are lacking. This study aims to investigate if smelling could be an alternative to vaping experiments by determining the correlation for hedonic flavor assessment between orthonasal smelling and vaping of e-liquids, for smokers and nonsmokers.

METHODS

Twenty-four young adult smokers (mean age 24.8 ± 9.3) and 24 nonsmokers (mean age 24.9 ± 7.7) smelled and vaped 25 e-liquids in various flavors. Participants rated liking, intensity, familiarity, and irritation on a 100-mm Visual Analog Scale. Pearson correlations within and between smelling and vaping were calculated. Differences between user groups were calculated using t tests.

RESULTS

Correlation coefficients between smelling and vaping based on mean group ratings were 0.84 for liking, 0.82 for intensity, 0.84 for familiarity, and 0.73 for irritation. Means of the within-subjects correlation coefficients were, respectively, 0.51, 0.37, 0.47, and 0.25. Correlations between smelling and vaping varied across individuals (ranging from -0.27 to 0.87) and flavors (-0.33 to 0.81). Correlations and mean liking ratings did not differ between smokers and nonsmokers.

CONCLUSIONS

The strong group-level correlations between orthonasal smelling and vaping e-liquid flavors justify the use of smelling instead of vaping in future research. For example, smelling could be used to investigate differences in e-liquid flavor liking between (potential) user groups such as nicotine-naïve adolescents. The more modest within-subject correlations and variation across individuals and flavors merit caution in using smelling instead of vaping in other types of experiments.

IMPLICATIONS

This study supports the use of orthonasal smelling (instead of vaping) e-liquids to measure hedonic flavor perception in some studies where vaping would be inappropriate or not feasible. Examples of research situations where smelling e-liquids may be sufficient are (1) investigating nicotine-naïve individuals (ie, nonusers), (2) investigating individuals under legal age for e-cigarette use (ie, youth and adolescents), (3) investigating brain responses to exposure of e-liquid flavors using functional magnetic resonance imaging or electroencephalogram, and (4) comparing hedonic flavor assessment between adolescent nonusers and current smokers to provide support for future regulations on e-liquid flavors.

GC-MS analysis of e-cigarette refill solutions: A comparison of flavoring composition between flavor categories

OBJECTIVES

Electronic cigarette refill solutions (e-liquids) are available in various flavor descriptions that can be categorized as fruit, tobacco, and more. Flavors increase sensory appeal, thereby stimulating e-cigarette use, and flavoring ingredients can contribute to e-cigarette toxicity. We aim to inform toxicologists, sensory scientists, and regulators by determining flavoring compounds in e-liquids with various flavors, and compare results between flavor categories.

METHODS

Gas chromatography - mass spectrometry (GC-MS) was used to identify 79 flavorings in 320 e-liquids, classified in 15 flavor categories. Ten flavorings highly prevalent in e-liquids according to information from manufacturers were quantified. Flavoring prevalence was defined as the number of e-liquids with the flavoring as percentage of the total number of e-liquids. The method was validated in terms of specificity, linearity, repeatability, recovery, and sensitivity.

RESULTS

The mean number of flavorings per e-liquid was 6 ± 4. Flavoring prevalence was highest for vanillin (creamy/vanilla flavor), ethyl butyrate (ethereal/fruity), and cis-3-hexenol (fresh/green). Based on similarities in flavoring prevalence, four clusters of categories were distinguished: (1) fruit, candy, alcohol, beverages; (2) dessert, coffee/tea, nuts, sweets; (3) menthol/mint; and (4) spices, tobacco, and unflavored. Categories from cluster 4 generally had less flavorings per e-liquid than fruit, candy, alcohol, beverages (cluster 1) and dessert (cluster 2) (p < 0.05). Flavoring concentrations varied between e-liquids within the categories.

CONCLUSIONS

We evaluated flavoring compositions of 320 e-liquids using a simple GC-MS method. Flavoring prevalence was similar within four clusters of typically fresh/sweet, warm/sweet, fresh/cooling, and non-sweet flavor categories. To compare flavoring concentrations between individual flavor categories, additional research is needed.

Method Validation Approaches for Analysis of Constituents in ENDS

OBJECTIVE

We assessed how many peer-reviewed publications reporting chemical quantities and/or yields from electronic nicotine delivery systems (ENDS) have included adequate method validation characteristics in the publication for appropriate interpretation of data quality for informing tobacco regulatory science.

METHODS

We searched 5 databases (Web of Knowledge, PubMed, SciFinder, Embase, EBSCOhost) for ENDS publications between January 2007 and September 2018. Of the 283 publications screened, 173 publications were relevant for analysis. We identified the publications that report a certain degree of control in data quality, ie, the publications that report marginally validated methods (MVMs). MVMs refer to the methods that: (1) report 3 or more International Conference on Harmonisation (ICH) method validation characteristics, (2) state the method was validated, (3) cite their own previous publication(s) that report MVMs, or (4) use a method within the accreditation scope of an accredited laboratory.

RESULTS

Overall, 97 publications (56%) report MVMs in their studies. This percentage also reflects the publication distribution for the majority of the 28 chemicals measured by MVMs.

CONCLUSIONS

This study highlights the need for reporting sufficient validation characteristics following appropriate guidance to ensure the accuracy and reliability of the published analytical data for proper data interpretations that may support policy.

Chemical Characterization of Electronic Cigarette (e-cigs) Refill Liquids Prior to EU Tobacco Product Directive Adoption: Evaluation of BTEX Contamination by HS-SPME-GC-MS and Identification of Flavoring Additives by GC-MS-O

The present study focused on the determination of benzene, toluene, ethylbenzene and xylenes (BTEX) concentration levels in 97 refill liquids for e-cigs selected by the Italian National Institute of Health as representative of the EU market between 2013 and 2015 prior to the implementation of the European Union (EU) Tobacco Product Directive (TPD). Most of the e-liquids investigated (85/97) were affected by BTEX contamination, with few exceptions observed (levels below the limit of quantification (LOQ) of headspace-solid phase micro extraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) methodology). Across brands, concentration levels ranged from 2.7 to 30,200.0 µg/L for benzene, from 1.9 to 447.8 µg/L for ethylbenzene, from 1.9 to 1,648.4 µg/L for toluene and from 1.7 to 574.2 µg/L for m,p,o-xylenes. The variability observed in BTEX levels is likely to be related to the variability in contamination level of both propylene glycol and glycerol and flavoring additives included. No correlation was found with nicotine content. Moreover, on a limited number of e-liquids, gas chromatography-mass spectrometry-olfactometry (GC-MS-O) analysis was performed, allowing the identification of key flavoring additives responsible of specific flavor notes. Among them, diacetyl is a flavoring additive of concern for potential toxicity when directly inhaled into human airways. The data reported are eligible to be included in the pre-TPD database and may represent a reference for the ongoing evaluation on e-liquids safety and quality under the current EU Legislation.

Ultrasound-Assisted Solvent Extraction of a Porous Membrane Packed Sample for the Determination of Tobacco-Specific Nitrosamines in the Replacement Liquids for E-Cigarettes

The content of tobacco-specific nitrosamines (TSNAs) possessing carcinogenic properties has been an important area of research since replacement liquids were introduced for e-cigarettes. A method for determining N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N'-nitrosoanatabine (NAT), and N'-nitrosoanabasine (NAB) in replacement liquids for electronic cigarettes was developed using liquid chromatography-tandem mass spectrometry with electrospray ionisation (HPLC-ESI-MS/MS) in the multiple reaction monitoring mode. The sample preparation of replacement liquids was accomplished via the ultrasound-assisted solvent extraction of a porous membrane packed sample. The sample preparation proved to be successful in extracting the analytes, with recoveries from 87% to 105%, with coefficients of variation < 4.9%. Moreover, the linearity and limits of detection and quantitation (LOD, LOQ), together with repeatability and accuracy, were determined for the developed method. The proposed sample preparation and developed chromatographic method were successfully applied to the determination of TSNAs in 9 replacement liquid samples. The NNK and NNN were found to be most frequently detected (89 and 67%, respectively), with concentration ranges from 1.2-54.3 ng/mL and 4.1-30.2 ng/mL, respectively, while NAT was detected with frequency of 22% with range 1.7-2.5 ng/mL and NAB were found to be below the LOD in all samples.

Differences between selected volatile aromatic compound concentrations in sludge samples in various steps of wastewater treatment plant operations

Sewage sludge, one of the main wastes generated during wastewater treatment, constitutes an important source of emissions of volatile chemical compounds such as volatile aromatic compounds These substances may undergo various changes as a result of operations and unit processes, which affects their concentrations in sewage sludge. An important factor determining the potential hazardousness of volatile organic compounds is the quality of wastewater delivered to wastewater treatment plants and the technical and equipment solutions applied to wastewater. In this study, a rapid and sensitive headspace gas chromatography method, coupled with tandem mass spectrometry using the standard addition method, was developed for the determination of selected volatile aromatic compounds in sewage sludge samples collected at different stages from three wastewater treatment plants located in Poland. This study attempted to assess the relationship between differences in the emissions of representative VACs and the given stage of the technological process within three analysed wastewater treatment plants. Toluene was detected with the highest frequency in analysed samples, at concentrations varying from 0.234 ± 0.035 ng/g of sludge to 28.3*10²±3.2*10² ng/g of sludge. The highest concentration levels were determined for p-cresol, with concentrations ranging from 44.0*10¹±5.6*10¹ ng/g of sludge (sludge from aerobic chamber, wastewater treatment plant no.2) to 47.7*10²±6.9*10² ng/g of sludge (sludge from aerobic chamber, wastewater treatment plant no.1), while the lowest concentration levels were observed for chlorobenzene, with concentrations ranging from 0.1300 ± 0.0030 ng/g of sludge (sludge from anaerobic chamber, wastewater treatment plant no.2), to 0.2606 ± 0.0046 ng/g of sludge (primary sludge, wastewater treatment plant no.1). The repeatability of the method was better than 10%, with accuracy levels in the ranges 89%-108%.Wastewater treatment technologies and residual sludge management in the selected wastewater treatment plantsinfluenced volatile aromatic compounds emission. Furthermore, the diversity of the wastewater quality, depending on the catchment area, is also an important factor determining the differentiation in volatile aromatic compounds emission. The microbial composition of raw wastewater highly influenced not only the treatment effectiveness of wastewater treatment plants but also the production of intermediate products, such as volatile aromatic compounds, which may contribute to odour emissions.

Influence of the E-Cigarette Emission Profile by the Ratio of Glycerol to Propylene Glycol in E-Liquid Composition

The use of electronic cigarettes (E-cig) is popular because of the perception that they are less addictive and safer compared to the traditional cigarettes. Nevertheless, there are still harmful effects associated with chemicals emitted from E-cig. Identifying the sources of the emitted compounds can be challenging because of the differences in the design of E-cig devices and the variability in the composition of E-cig liquids used in these devices. In this study, the emission profiles from impurity-free E-liquids containing only propylene glycol and glycerol in various percentage ratios along with two commercially available E-liquids were evaluated using gas chromatography-mass spectrometry (GC-MS). This study approach allows the elucidation of the transformation pathways of the major emitted compounds without the confounding effects of existing impurities or flavor ingredients added to E-liquids. Analysis of the vapor phases of E-cig emissions detected toxicants such as acetaldehyde, acrolein, benzaldehyde, as well as benzene, toluene, ethylbenzene, and xylene (BTEX) compounds. The amount of glycerol in the E-liquids has a major effect on the concentration of these hazardous compounds emitted because the concentration of these chemicals increased with increasing glycerol percentage in the E-liquid. Acetaldehyde and acrolein increased by 175-fold and 28-fold, respectively, when the glycerol composition was increased from 0 to 80%. Benzaldehyde, naphthalene, diphenyl ether, and glycerol along with menthol and nicotine that were present in the commercial E-liquids were also detected in the aerosol condensates. The cascade impactor data on the distribution of the nicotine and menthol in different size fractions from >2.5 to <2.5 μm allow the estimates of the extent of toxicant deposition in different parts of the pulmonary system including the oropharynx region, the trachea as well as inside the alveoli and bronchioles. In summary, users of E-cig are exposed to harmful chemicals even if the E-liquids contain only propylene glycol and glycerol without flavorings, nicotine, or impurities. Furthermore, this study shows that E-liquids containing higher percentages of glycerol will produce higher levels of toxicants compared to E-liquids with similar percentages of propylene glycol. This finding has important implications to E-cigarette vendors and manufacturers, consumers, and regulatory agencies.

Why flavored vape products may be attractive: Green apple tobacco flavor elicits reward-related behavior, upregulates nAChRs on VTA dopamine neurons, and alters midbrain dopamine and GABA neuron function

While nicotine is the primary addictive component in tobacco products, additional flavors have become a concern with the growing popularity of electronic nicotine delivery systems (ENDS). For this reason, we have begun to investigate popular tobacco and ENDS flavors. Here, we examined farnesol, a chemical flavorant used in green apple and fruit flavors in ENDS e-liquids, for its ability to produce reward-related behavior. Using male and female 3-6 month old C57BL/6 J mice and farnesol doses of 0.1, 1, and 10 mg/kg we identified a sex-dependent effect in a conditioned place preference assay: farnesol-alone produces reward-related behavior in only male mice. Despite this sex-dependent effect, 1.0 mg/kg farnesol enhances locomotor activity in both male and female mice. To understand farnesol's effect on reward-related behavior, we used whole-cell patch-clamp electrophysiology and confocal microscopy to investigate changes in putative dopamine and GABA neurons. For these approaches, we utilized genetically modified mice that contain fluorescent nicotinic acetylcholine receptors (nAChRs). Our electrophysiological assays with male mice revealed that farnesol treatment increases ventral tegmental area (VTA) dopamine neuron firing frequency and this may be due to a decrease in inhibitory tone from GABA neurons. Our microscopy assays revealed that farnesol treatment produces a significant upregulation of α6* nAChRs in male mice but not female mice. This was supported by an observed increase in α6* nAChR function in additional electrophysiology assays. These data provide evidence that popular tobacco flavorants may alter smoking-related behavior and promote the need to examine additional ENDS flavors.

Main and side stream effects of electronic cigarettes

Over the last decade there has been a significant boost towards the use of electronic cigarettes (e-cigarettes), especially among youth. Different concentrations of propylene glycol (PG) or vegetable glycerin (VG), flavors and nicotine are mixed in plastic cartridges and commercially offered or privately produced by the vapers. During vaping, a mixture of air and vapors is inhaled to the lungs. Since the ingredients of the e-cigarettes are not burned but vaporized (heated), fewer chemicals are emitted. The levels of potentially toxic compounds (e.g. volatile organic compounds (VOCs), particulate matter (PM), metals, radicals, nitrosamines, etc.) emitted from vaping appear to be lower compared to that of tobacco smoking (from combustible cigarettes). Nevertheless, measurable toxic elements and VOCs are still released (e.g. acetaldehyde, formaldehyde, acrolein, benzene, etc.) along with other volatiles associated with e-liquid flavoring and device variability with PG and VG. The wide range of available flavors at various purities along with the heating temperature are important parameters affecting the evolution of VOCs and aerosols. There is lack of standardized short- and long-term epidemiological medical data (chronic exposure) on e-cigarettes effects to users, non-users and the human micro-environment (second- or third-hand exposure). Therefore, the potential health, safety and environmental effects of vaping are reviewed, examined and discussed.

New approach for e-cigarette aerosol collection by an original automatic aerosol generator utilizing melt-blown non-woven fabric

Currently, there is lack of standardized conditions for the collection and analysis of e-cigarette (EC) aerosol. Considering the urgent need for the development of these guidelines, a procedure for EC aerosol analysis was developed. A novel automatic e-cigarette aerosol generator was designed. For the first time, melt-blown non-woven fabric was applied for the effective uptake of compounds released from vaporized e-liquid. The extraction procedure was optimized in terms of type of extraction solvent, amount of sorbent and solvent volume. For optimization, a model e-liquid containing flavour additives belonging to various chemicals group with various chemical properties was investigated. The aerosol trapping efficiency was satisfactory and was equal to 92 ± 7%. Final determination was performed by GC-MS/MS. Quantitation was based on the mass change tracking approach (MCT), which assumes the monitoring of e-liquid mass changes before and after vaping. The combination of non-woven fabric and sampling approach (MCT) was proven to be effective in acquisition of reliable data. Thus, the concentrations in aerosol and emission factors were calculated for aerosols collected during the vaping of both model e-liquids and real samples. Validation was performed by evaluating key analytical parameters, such as linearity, accuracy, precision, limit of detection (LOD) and quantitation (LOQ). For all investigated compounds, recoveries from 70% to 118% together with precision and reproducibility below 12% were achieved. The applicability of the described approach was examined by analysing EC refill solutions commercially available on the Polish market.