Article

Formation of polycyclic aromatic hydrocarbons from tobacco: The link between low temperature residual solid (char) and PAH formation

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  • Aerochemia Technologies LLC
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Abstract

The formation of condensed ring polycyclic aromatic hydrocarbons (PAHs) from the pyrolysis of ground tobacco in helium over the temperature range of 350-600 degrees C was investigated. PAH yields in the ng/g range were detected and the maximum yields of all PAHs studied including benzo[a]pyrene (B[a]P) and benzo[a]anthracene (B[a]A) occurred between 500 and 550 degrees C. The pathway to PAH formation in the 350-600 degrees C temperature range is believed to proceed via a carbonization process where the residual solid (char) undergoes a chemical transformation and rearrangement to give a more condensed polycyclic aromatic structure that upon further heating evolves PAH moieties. Extraction of tobacco with water led to a two fold increase in the yields of most PAHs studied. The extraction process removed low temperature non-PAH-forming components, such as alkaloids, organic acids and inorganic salts, and concentrated instead (on a per unit weight basis) tobacco components such as cell wall bio-polymers and lipids. Hexane extraction of the tobacco removed lipophilic components, previously identified as the main source of PAH precursors, but no change in PAH yields was observed from the hexane-extracted tobacco. Tobacco cell wall components such as cellulose, hemicellulose, and lignin are identified as major low temperature PAH precursors. A link between the formation of a low temperature char that evolves PAHs upon heating is established and the observed ng/g yields of PAHs from tobacco highlights a low temperature solid phase formation mechanism that may be operable in a burning cigarette.

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... High temperature is more beneficial for the formation and release of middle-molecular-weight components (Zhao et al. 2020). These observations are also in accordance with the evolution profiles of PAHs from McGrath et al. (2007), in which the PAHs in tar reached the highest value at the temperature between 500 and 550 °C, and then decreased sharply (McGrath et al. 2007). ...
... High temperature is more beneficial for the formation and release of middle-molecular-weight components (Zhao et al. 2020). These observations are also in accordance with the evolution profiles of PAHs from McGrath et al. (2007), in which the PAHs in tar reached the highest value at the temperature between 500 and 550 °C, and then decreased sharply (McGrath et al. 2007). ...
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Article
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... They are solid substances with high melting and boiling points, low aqueous solubility and vapor pressure (Masih et al., 2012). They are a group of over 100 chemicals originating from the incomplete combustion of oil, coal, plant materials and other organic substances (McGrath et al., 2007;Dhananjayan et al., 2012). PAHs causing the largest contamination to estuarine and marine environments are sourced to petrogenic (fossil fuel), pyrogenic (combustion of carbon, wood, and fossil fuels) related anthropogenic activities (Stout et al., 2004;Chen et al., 2013;Abdel-Shafy and Mansour, 2016) and incomplete combustion, either naturally or anthropogenically formed. ...
... On the other hand, researchers mentioned that adding 40 mL of oil into basic marination increased the PAH content of grilled beef meat (98.9-109 µg/kg). Similarly, it has been shown in some studies that oil and fatty components are major precursors of PAHs and that cooking oils can be contaminated with PAHs during various preparation processes [57,58]. In a study examining the level of PAH in grilled chicken, the ∑PAH16 amount of unmarinated, palm oil-marinated and sunflower oil-marinated samples was determined as 190.1µg/kg, 457.6 µg/kg and 376.6 µg/kg, respectively. ...
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... PAHs are carcinogens, in high concentrations they can be a major hazard to aquatic life in areas close to human activities [2,3]. Aromatic organic carbon compounds are abundant in aquatic environments, consist of many different chemical compounds, and are formed during the use of fossil fuels, incineration of waste, burning of wood, and the degradation of organic matter [4]. The formation of organic carbon compounds in nature generally has two origins, natural sources and anthropogenic sources that influence human activities. ...
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... At 300-600 °C, low PAH content biochar was produced, and it was dominated by alkylated PAHs with low toxicity. In another study by McGrath et al. [38] , a lower toxicity of 2-4 ring PAHs was observed at and above 400 °C. Benzo[a]pyrene and Benz[a]anthracene, which are highly toxic, were observed at and above 500 °C [12] . ...
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Biochar application for soil and agro-environmental development has attracted great attention due to its numerous advantages: improving the soil, mitigating greenhouse gas emissions, increasing crop productivity, and augmenting soil carbon storage. However, during the pyrolytic conversion of waste biomass, polycyclic aromatic hydrocarbons (PAHs), a category of toxic organic pollutants, are inescapably generated and linger on the residual solid coproduct called biochar. Therefore, it is crucial to assess the environmental persistence, bioavailability, effects of biochar-borne PAHs on plant growth and soil microbial community dynamics, food safety, and human health after application into soils. This review highlights the basic need to unravel critical mechanisms driving PAH formation in biochar and the dynamics between the sorbent (biochar) and soil microbes, along with the possible mitigation strategies. Current research gaps, including the influence of biochar application on the short and long-term fate of PAHs, as well as the proper control measures for biochar quality and associated risks, will be discussed herein. The key research findings from this script will lead to proposals in technological and quality control measures during biochar production to ensure they are clean and safe.
... Polynuclear Aromatic Hydrocarbons (PAHs) also referred to as Polycyclic Aromatic Hydrocarbons (PAHs), are a group of chemicals that are formed during the incomplete burning of coal, oil, gas, garbage and other organic substances (McGrath et al.,2007). They are a ubiquitous group of several hundred chemically related compounds, environmentally persistent with various structures and varied toxicity (Armstrong et al., 2004). ...
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Generally, Polynuclear Aromatic Hydrocarbons (PAHs) enter the environment through various routes and are usually found as a mixture containing two or more compounds formed during the incomplete burning of coal, oil and gas, and other organic substances. 11 Polynuclear Aromatic Hydrocarbons (PAHs) levels in commonly consumed roasted plantain food delicacy in Owerri Municipal, a southeastern city in Nigeria were assessed to evaluate possible human health risks associated with its consumption. Freshly roasted plantain samples were purchased from 3 roadside fast-food vendors in the Municipality, preserved in labeled sterile amber bottles with benzene, and taken to the laboratory in an iced-chest. The PAHs concentrations were determined using Gas Chromatography coupled with Flame Ionization Detector (GC-FID) in the analysis of samples. The single factor ANOVA and means plots were used to detect homogeneity in mean-variance and structure of group means of the PAHs determined in the foods, respectively. From the analysis, Phenanthrene and Anthracene comparatively recorded the highest concentrations of (0.169mg/kg) and (0.165mg/kg) respectively while pyrene recorded the lowest concentrations of PAHs. The high concentrations of combined PAHs recorded in roasted plantain could be due to the close proximity of the plantain samples and the source of the heat and the higher temperature required for roasting the plantains. The least concentrations (0.000mg/kg) of pyrene, chrysene, and benzo(a)anthracene in the samples indicate that these PAHs were not abundant in the woods (charcoal) used for their roasting. The study reveals high concentrations of the PAHs in the plantain food sampled. This, therefore, places consumers at great health risk if proper care is not taken.
... They are pervasive environmental pollutants that are characterized by their hazardous carcinogenic and mutagenic potential (Carreras et al., 2013;McGrath et al., 2007). PAHs have received increased attention in recent years due to their diverse sources and their ubiquitous presence in all the environmental components (air, soil, and water) not only in developing but also in developed countries. ...
Preprint
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In this study we aim to assess 16 priority PAHs enlisted by the US Environmental Protection Agency in PM 2.5 and PM 10 for the first time from industrial areas of Odisha State in India. During 2017–2018, bimonthly sampling of PM 10 and PM 2.5 were carried out for 24 hours by respirable dust sampler and PM 2.5 sampler respectively, in the industrial and mining areas of Jharsuguda (n = 2) and Angul (n = 4) during the pre-monsoon, monsoon and post monsoonal seasons. Highest average concentration of ∑ 16 PAHs in PM 2.5 was observed during post monsoon (170 ng/m ³ ) followed by pre-monsoon (17–89 ng/m ³ ; avg, 48 ng/m ³ ) and monsoonal season (2–40 ng/m ³ ; avg, 16 ng/m ³ ), respectively. Similar trend of ∑ 16 PAHs levels in PM 10 was seen with higher levels during post monsoon (116–471 ng/m ³ ; avg, 286 ng/m ³ ) followed by pre-monsoon (avg, 81 ng/m ³ ) and monsoon seasons (27 ng/m ³ . Diagnostic ratios BaA/(BaA + Chry), Phe/(Phe + Ant) and Flt/(Flt + Pyr) and principal component analysis (PCA) suggest diesel, gasoline and coal combustion are the major contributors for atmospheric PAHs pollution in Odisha. Back trajectories analysis revealed that PAHs concentration was affected majorly by air masses originating from the northwest direction traversing through central India. Toxic equivalents (TEQs) ranged between 0.24 to 94.13 ng TEQ/m ³ . In our study incremental lifetime cancer risk (ILCR) ranged between 10 − 5 and 10 − 3 representing potential cancer risk.
... PAHs are ubiquitous environmental pollutants that are generated primarily during the incomplete combustion of organic materials (e.g. coal, oil, petrol, wood, etc.) (McGrath et al., 2007;Vane et al., 2013). PAHs are highly lipid soluble and thus readily absorbed from the gastrointestinal tract of mammals. ...
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A range of polycyclic aromatic hydrocarbons has been identified, and regularities of their vertical distribution in the peatland of hummock-hollow complexes in the southern tundra – forest tundra and northern tundra – southern tundra ecotones of the European Arctic zone have been determined. Benzo[ghi]perylene, naphthalene, pyrene, fluorene, phenanthrene, benzo[b]fluoranthene and benzo[a]pyrene are displayed most in the peatlands under study. Regarding the peatland profile the vertical polyarene distribution is similar – in 150–175 cm permafrost layers (site 1) and 50(70)–210(250) cm layers (site 2), and on the border between the active layer and permafrost 35–50(60) cm (site 1) and 30(42) – 50 cm (site 2) a significant increase of HCO-accumulated PAHs weight fraction is observed. PAHs content maximums in tundra peatland horizons are associated both with 4-, 5- and 6-nuclear structures at both sites under the analysis, and with a larger amount of 2- and 3-nuclear polyarenes in the peatlands on the northern tundra-southern tundra ecotone. Aeration-exposed seasonally thawing peatland layers are subject to continuous formation of primarily light 2- and 3-nuclear PAHs of natural origin resulting from microbiological decomposition of plant residues, which are subsequently involved in equilibrium cycles of chemical and biochemical transformation, with their total capacity remaining almost unchanged and constituting ⁓200–500 ng/g. Owing to low productivity of plant communities and absence of tree vegetation in the seasonally thawed layer, accumulation of the sum of 4-, 5- and 6-nuclear PAHs weakens significantly. One can detect dependencies between individual PAHs and the botanic composition of peat through higher weight fraction of 4-, 5- and 6-nuclear polyarenes being lignin transformation products generated more as the share of tree vegetation grows. The PAHs composition is a paleoclimatic marker reflecting adequately both changing paleovegetation stages and the degree of peat decomposition.
... Moreover, a low heating process could increase the residence time of volatiles, enhancing the secondary reactions among these compounds. In contrast, a fast heating rate was supposed to attenuate secondary reaction, with some nitrogen compounds decomposed [21,22]. Consequently, selecting suitable heat treatment conditions was of high significance for the effective extraction of nitrogen compounds from tobacco waste. ...
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Alkaloids, typical nitrogen compounds, were found to be abundant in tobacco waste. The recovery of alkaloids from tobacco waste for biological pesticides could reduce the use of traditional chemical pesticides and avoid the pollution of farmland by the leaching of alkaloids from tobacco waste. Considering the fact that alkaloids can easily volatilize, thermal treatment is expected to be a potential technology to achieve the release and recovery of alkaloids from tobacco waste. For better understanding of conversion behavior of nitrogen-containing compounds in tobacco waste during thermal treatment, purge/trap-GC/MS (gas chromatography mass spectrometry), PY-GC/MS (pyrolysis-gas chromatography mass spectrometry), and fixed-bed/ATD-GC/MS (auto-thermal desorption gas chromatography mass spectrometry) were adopted to detect the ingredients and concentration of nitrogen-containing compounds in tobacco waste and/or volatiles. The results of purge/trap-GC/MS showed that nitrogen-containing compounds in tobacco waste could be effectively evaporated at 180 °C in the forms of N-benzyl-N-ethyl-P-isopropyl benzamide, 2-Amino-4-methylphenol, or N-butyl-tert-butylamine. Specifically, N-benzyl-N-ethyl-P-isopropyl benzamide was the main nitrogenous compound in the volatiles of tobacco wastes accordingly. (S)-3-(1-Methyl-2-pyrrolidinyl) pyridine was dominant in N-compounds in pyrolysis condition according to the results of Py-GC/MS. In air atmosphere, with the heating temperature increasing, the concentration of main (S)-3-(1-Methyl-2-pyrrolidinyl) pyridine was firstly increased and then decreased. Besides, the interactions between the released volatiles could be accelerated at a high temperature. Accordingly, these findings suggested that pyrolysis under proper conditions could effectively promote the extraction of alkaloids from tobacco waste.
... PAH merupakan senyawa organik yang keberadaanya tersebar luas di alam, terbentuk dari beberapa rantai siklik aromatik, serta terdiri dari lebih dari 100 senyawa kimia yang berbeda, yang terbentuk selama pembakaran yang tidak sempurna dari senyawa organik seperti batubara, minyak dan gas, sampah, dan zat organik lainnya (McGrath et al., 2007). Keberadaan PAH di alam dapat berasal dari dua sumber, yakni sumber alami dan sumber antropogenik (Xu et al., 2018). ...
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Polycyclic Aromatic Hydrocarbons (PAH) are polycyclic aromatic organic compounds that are toxic to humans and aquatic organisms. This research aims to determine the level of pollution of PAH compounds in seawater and sediments in Lampung Bay, Lampung. This research was conducted by survey method in November 2018. Sediments and seawater samples were taken using water and sediment sampling equipment. Sediment and seawater samples were taken at three and two research stations. The levels and types of PAH compounds were determined by using Gas Mass Spectrometry Chromatography and their sources using individual ratio diagnostic methods. The results showed that the levels of PAH total in seawater ranged 295,587-331,133 ppb, this level is relatively high and has passed the threshold values set by the Decision Letter of the Office of the State Minister of Environment No 51, 2004 for marine biota protection, while in the sediments range 51.481-62.448 ppb, this level is relatively small and still in accordance with the criteria for marine life. The results of individual ratios diagnosis analysis indicate that PAHs in seawater and sediment come from various sources, namely petroleum, burning of petroleum and burning of organic matter.
... Mezi významné faktory ovlivňující vznik PAU patří teplota spalování a obsah kyslíku ve spalovacím zařízení (Chagger et al., 2000;McGrath et al., 2007). V mnoha studiích byly publikovány rozdílné obsahy PAU v popelu vzniklé během různých teplot spalování. ...
... The occurrence of PAHs detected and distributed in both aquatic and terrestrial environment, and both of low solubility and hydrophobic nature PAHs are most found bind to soil and sediment (73). The PAHs in aquatic environment were originate from two sources the first one was pyrogenic which are produced from incomplete combustion of coal, oil, and gas, garbage, or other organic substances like tobacco or charbroiled meat (32,34,58). The second origin was petrogenic which produced from anthropogenic sources that are from the accidental leak out of fossil fuels include crude oil refinery oil (e.g. ...
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The objective of this study was to investigate concentrations, compositions of PAHs and to study physical and chemical water characteristic in Tigris River. This study was conducted during July 2017 to April 2018. The results showed that twelve PAHs compounds were detected in water and sediment of the river and the highest concentrations of these compounds were founded in sediment samples. Concentrations of PAHs in water samples have a ranged between (0.36µg. l-1) in wet season to (0.53µg.l-1) in dry season, while the sediment sample have a ranged between (633.23µg.kg-1) in wet season to (778.28µg.kg-1) in dry season. The origin of PAHs in water and sediment were pyrogenic depending on the ratios of Phenanthene/Anthracene, Anthacene/ (Anthacene + Phenanthene), low molecular weight/high molecular weight. According of these results, it can be concluded that the Tigris River is polluted with the PAHs, and anthropogenic activities with the largest impact on the water health and quality of the river.
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Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants known to have toxic properties, carcinogenic and mutagenic potential, cereals and derivative products being the most important sources of PAH exposure to humans as a result of the high intake of this kind of products. The aim of this study was to investigate the occurrence of PAH in cereals and cereal-based products and the effect of different factors on the content of these compounds. The factors that influence the PAH content of cereal-based products were the raw material used in the recipe, the category of processed product, the baking parameters (time and temperature), the type of fuel used. The maximum level for benzo(a)pyrene (BaP) and sum of BaP, benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF), and chrysene (ChR) in processed cereal-based food and baby foods for infants and young children was established by regulation no. 835/2011. This study can provide an overview of the PAH content of different cereal-based products commercialized on the market.
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Environmental exposure to ambient polycyclic aromatic hydrocarbons (PAHs) can disturb the immune response. However, the evidence on adverse health effects caused by exposure to PAHs emitted from specific sources among different vulnerable subpopulations is limited. In this cross‐sectional study, we aimed to evaluate whether exposure to source‐specific PAHs could increase systemic inflammation in older adults. The present study included community‐dwelling older adults and collected filter samples of personal exposure to PM2.5 during the winter of 2011. Blood samples were collected after the PM2.5 sample collection. We analyzed PM2.5 bound PAHs and serum inflammatory cytokines (interleukin (IL)1β, IL6, and tumor necrosis factor alpha levels. The Positive Matrix Factorization model was used to identify PAH sources. We used a linear regression model to assess the relative effects of source‐specific PM2.5 bound PAHs on the levels of measured inflammatory cytokines. After controlling for confounders, exposure to PAHs emitted from biomass burning or diesel vehicle emission was significantly associated with increased serum inflammatory cytokines and systemic inflammation. These findings highlight the importance of considering exposure sources in epidemiological studies and controlling exposures to organic materials from specific sources.
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This study’s goals were to look into PAH concentrations and compositions as well as chemical and physical water characteristics. In Al –Rumaytha river. This study was conducted out during from November 2021 to October 2022. According to the results, sixteen PAHs compounds were found in the water, including According to the results, water contained sixteen different PAHs components including Acenaphthene and Acenaphthylene ranged between (47.1-91.5, 24.9-55.7) ppm, The values Anthracene, Naphthalene, phenanthene and fluorine results ranged (14.9-48.9 ppm,18.9 -68.7ppm,8.9-41.7 ppm,8.5-41 ppm) respectively, the minimum and maximum concentrations of Benzo[A]anthracen, Benzo[B]fluoranthene, Benzo [K] fluorantyene, Benz [G,H] perylen, Benz [A] Pryene, Chrysene, Dibenzo [A,H] Anthracene, Anthracene, Fluoranthene, Indeno and Pryene was 4.1-20.6 ppm, 20.1-69.7ppm, 30.1-97.4 ppm,4.1-36.9 ppm,0.29-1.6ppm 10.5-40.8 ppm, 8.9-36.9 ppm, 6.5-33.4 ppm,2.5-10.2 ppm,1.3-10.4 ppm. The results show that the Al-Rumaytha River is PAH-polluted, with human activities having the greatest negative effects on the river’s water quality and health.
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Environmental exposure to atmospheric polycyclic aromatic hydrocarbons (PAHs) can disturb the immune response. However, the evidence on adverse health effects caused by exposing to PAHs emitted from various sources among different vulnerable subpopulation is limited. In this study, we aimed to evaluate whether exposure to source-specific PAHs could increase the level of systemic inflammation in older adults. The present study included 101 community-dwelling older adults and collected filter samples personal exposure to PM 2.5 during the winter of 2011 in Tianjin, China. We collected blood samples after the PM 2.5 sample collection, and analyzed PM 2.5 bound PAHs and serum inflammatory cytokines (interleukin (IL)1β, IL6, and tumor necrosis factor alpha) levels. The Positive Matrix Factorization model was applied to distinguish PAHs sources. We used a linear regression model to assess the relative effects of source-specific PM 2.5 bound PAHs on the levels of measured inflammatory cytokines. The key finding lies on that after controlling for confounders, the levels of systemic inflammation were adversely affected by exposing to most PAHs sources, especially the biomass burning or diesel vehicle emission. An interquartile range (IQR) increase in the concentration of PAHs originated from biomass burning could significantly increase the level of IL1β (16.3%, 95% confidence interval [CI]: 0.7%, 29.8%) and IL6 (13.0%, 95% CI: 0.3%, 27.3%), and an IQR increase in PAHs contributed by diesel vehicle emission was significantly associated with the increase of IL6 levels (12.7%, 95% CI: 0.1%, 26.9%). The stratified analysis revealed that non-smokers were more susceptible to the PAHs emitted from biomass burning and diesel emission. In summary, exposure to PAHs from certain specific sources of PAHs may significantly enhance systemic inflammation in the elderly. These findings highlight the importance of considering exposure sources in epidemiological studies and that of controlling exposures to organic materials from specific sources.
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The measurement of polynuclear aromatic hydrocarbons (PAHs) was conducted with respect to Gobiformes oxudecidae (mudskipper) specimens collected from Jones creek, Delta State. They were analyzed for 16 priority PAHs spanning through a total duration of eighteen months which adequately captured both wet and dry seasons. The ΣPAHs varied from 0.000 to 0.106 mg/kg for mud skipper samples within the aforesaid duration of the research. The most dominant PAH observed were chrysene and benzo(a)anthracene with amounts of 0.106 ± 0.095 mg/kg and 0.042 ± 0.030 mg/kg. The most abundant PAH in terms of its detection is chrysene accounting for 20.63% of the 16 PAHs while the least was dibenzo(a,h) anthracene with relative abundance of 0.37%. The individual component ratio revealed that refining operations, domestic and industrial discharges and possible storm runoff could Detection of Polynuclear aromatic hydrocarbons in mud skippers (Gobiformes oxudecidae) from Jones Creek, Delta State, Southern Nigeria. C. Ejeomo et al., DUJOPAS 9 (2b): 30-40, 2023 31 likely be the source of contamination. The total amounts of PAHs in the rainy season were comparatively higher than values obtained in the dry season. Distribution patterns revealed that PAHs possessing 3 and 4 rings were dominant which confirmed the pyrogenic source of the detected PAH. The dominance of the low molecular weight PAHs across the sampling stations was indicative of their bioavailability for uptake by biota. Diagnostic ratio among others employed included phenanthrene/anthracene and benzo(a)anthracene/chrysene. Calculation based on these ratios to determine the PAHs emission origins suggested pyrolytic origin of the sediment associated PAHs coupled with a pyrolytic or pyrogenic source of PAHs present in the mudskipper specimens.
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Cigarettes, despite being economically important legal consumer products, are highly addictive and harmful, particularly to the respiratory system. Tobacco smoke is a complex mixture containing over 7000 chemical compounds, 86 of which are identified to have “sufficient evidence of carcinogenicity” in either animal or human tests. Thus, tobacco smoke poses a significant health risk to humans. This article focuses on materials that help reduce the levels of major carcinogens in cigarette smoke; these include nicotine, polycyclic aromatic hydrocarbons, tobacco‐specific nitrosamines, hydrogen cyanide, carbon monoxide, and formaldehyde. Specifically, the research progress on adsorption effects and mechanisms of advanced materials such as cellulose, zeolite, activated carbon, graphene, and molecularly imprinted polymers are highlighted. The future trends and prospects in this field are also discussed. Notably, with advancements in supramolecular chemistry and materials engineering, the design of functionally oriented materials has become increasingly multidisciplinary. Certainly, several advanced materials can play a critical role in reducing the harmful effects of cigarette smoke. This review aims to serve as an insightful reference for the design of hybrid and functionally oriented advanced materials.
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Cigarette smoking is a major risk factor for the development of cardiovascular disease (CVD). Cigarette smoke contains toxicants that cross the alveolar barrier into the blood stream and elicit systemic oxidative stress and inflammatory responses, which can lead to an abnormal lipid profile and affect normal vascular functions. These changes predispose smokers to the development and progression of atherosclerosis, leading to various types of CVDs, such as ischaemic heart disease, cerebrovascular disease, peripheral artery disease, and aortic aneurysm. While the best choice a smoker can make is to stop smoking altogether, unfortunately not all smokers make that choice. In recent years, alternative products to cigarettes have been developed to offer a better alternative to continuing to smoke. However, new products representing a better alternative must be scientifically substantiated to understand how they present less risk to users compared with cigarettes. This literature review summarises the results of in vitro, in vivo, and clinical studies that, taken together, show the CVD risk reduction potential of switching from cigarette smoking to these smoke-free products.
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The chemical evidence that IQOS emissions fit the definition of both an aerosol and smoke, and that IQOS and potentially other heated tobacco products (HTPs) pose some harmful health threats from the range of compounds released even at somewhat lower concentrations is reviewed. Further, we address the yields of harmful and potentially harmful compounds (HPHCs), including polycyclic aromatic hydrocarbons (PAHs), and the constituents of IQOS emission that are diagnostic of pyrolysis to provide information on the temperatures reached in IQOS tobacco sticks. The HPHCs present in IQOS emissions are the same as in conventional cigarette smoke (CCs), analogous to emissions from earlier generation of HTPs classed as smoke. However, Philip Morris International (PMI) studies have to some degree underestimated IQOS aerosol HPHC yields, which are a factor of between 3.2 and 3.6 higher when expressed on a tobacco rather than an IQOS stick basis compared to the reference 3R4F cigarette. Further, IQOS emissions contain carbon particles, which fit definition of both aerosol and smoke. Continual reheating of deposited tar in the IQOS device will occur with real-life use, likely leading to generation of even higher concentrations of HPHCs and particulate matter. Despite IQOS not exceeding 350 °C, local hot spots could exist, causing formation of species (phenol/cresols, PAHs). It is recommended that the impact of repeated use to determine the levels of black carbon (insoluble organic matter) in the particulate matter, and the extent to which compounds in IQOS emissions are formed by pyrolysis need to be assessed rigorously. To address whether uneven temperature profiles in heat sticks can lead to potential hot spots that could, for example, lead to PAH formation, it is recommended that pyrolysis studies on tobacco and other constituents of HTPs are required in conjunction with more effort on heating tobacco blends under controlled temperature/time conditions.
Thesis
Le tabagisme est responsable de 8 millions de morts par an dans le monde. Le sevrage tabagique est actuellement la seule solution pour endiguer cette mortalité mais il est rendu difficile du fait de l’addiction à la nicotine. Depuis quelques années, de nouveaux dispositifs de délivrance de nicotine sont arrivés sur le marché : la cigarette électronique (e-cig) et le tabac chauffé. ien qu’ils soient généralement perçus comme des alternatives plus saines à la cigarette, leur impact précis sur la santé humaine reste à déterminer.Le premier objectif de cette thèse était d’analyser la composition chimique et la toxicité in vitro des émissions d’e-cig de différentes puissances (un modèle de deuxième génération et un modèle de troisième génération (Modbox) réglé à une puissance faible, Mb18W, ou forte, Mb30W) et du tabac chauffé et de les comparer à la fumée de cigarette. Nous avons pu montrer que le tabac chauffé génère beaucoup moins de composés carbonylés et de HAP que la cigarette, mais bien plus que l’e-cig, quel que soit le modèle. e manière concordante, l’exposition de cellules épithéliales bronchiques humaines (BEAS-2 ) cultivées à l’interface air-liquide aux émissions des différents dispositifs a permis de mettre en évidence que les émissions de tabac chauffé induisent une cytotoxicité réduite par rapport à la fumée de cigarette, mais bien plus élevée que les émissions d’e-cig. De plus, des expositions à 12 bouffées de tabac chauffé ou à 120 bouffées d’e-cig induisent un stress oxydant et la sécrétion de certaines cytokines pro-inflammatoires. Des effets similaires sont observés pour la fumée de cigarette mais seulement après 1 bouffée. e manière intéressante, en ce qui concerne l’e-cig, nous avons pu démontrer que la quantité de composés carbonylés émis et le stress oxydant augmentent avec la puissance du dispositif.Le deuxième objectif de mon projet doctoral consistait à évaluer sur un modèle murin la toxicité respiratoire sur le long terme des émissions d’e-cig de troisième génération. Des souris BALB/c ont été exposées exclusivement par voie nasale pendant 4 jours, 3 mois ou 6 mois aux aérosols de Mb18W ou de Mb30W, ou à la fumée de cigarette. Nos expérimentations in vivo ont montré que, d’une part, les émissions d’e-cig générées à 18 W et 30 W sont responsables de modifications épigénétiques induisant sur le long terme une hyper méthylation de l’ N et la dérégulation de certains mi RN à tous les temps d’exposition, mais que, d’autre part, seules celles générées à 30 W sont capables de provoquer des lésions oxydatives de l’ N, sans pour autant aboutir à des aberrations chromosomiques ou des mutations géniques. Les données transcriptomiques obtenues après 6 mois d’exposition aux aérosols d’e-cig ont mis en évidence la dérégulation de plusieurs voies de signalisation impliquées notamment dans la réponse inflammatoire, le stress oxydant et le métabolisme de composés carbonylés et, en particulier, des métabolites du propylène glycol. Cependant, le faible nombre de gènes impactés dans chacune de ces voies ne garantit pas que les dérégulations observées aient un réel impact biologique. Par comparaison, la fumée de cigarette a induit, dans les mêmes conditions d’exposition, la dérégulation d’un nombre plus important de voies de signalisation, notamment en lien avec l’inflammation et le métabolisme des H P, et impliquant chacune un nombre de gènes plus conséquent.Globalement, nos analyses chimiques et in vitro suggèrent que les émissions de tabac chauffé sont moins toxiques que la fumée de cigarette conventionnelle mais bien plus nocives que celles des e-cig, quelle que soit leur puissance. Par ailleurs, les expérimentations in vivo décrites dans ce travail n’ont pas permis de mettre en évidence une toxicité avérée des émissions d’e-cig sur le long terme [...]
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The aim of this study was to scientifically investigate the impact of optimal-water boiling cooking on the volatile profile of 26 japonica rice varieties. A modified direct solvent extraction combined with gas chromatography-mass spectrometry was applied to analyze the volatiles in raw and cooked samples. 2-Acetyl-1-pyrroline (2AP) was only detected in aromatic varieties and decreased after cooking (-81.94% – -43.97%). Great losses of esters and long-chain ketones were exhibited after cooking. Cooking accelerated lipid oxidation and degradation of phenolic acids, thus volatiles originate from lipid oxidation and several benzenoid compounds showed increase trends in majority of the samples. Increases of 3 saturated aldehydes including hexanal (48.01% – 306.02%), octanal and nonanal (67.03% – 544.15%) could be observed in all samples. Acetophenone, 2-methoxy-4-vinylphenol (11.95% – 297.61%) and vanillin (14.29% – 319.25%) were also enhanced upon cooking. Correlations existed in volatiles with common precursors or involved in same pathways. According to multivariate and univariate statistical analysis, 18 volatiles most greatly influenced by cooking were selected. This study will facilitate the aroma improvement of cooked rice in the future.
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This work provides insights on waterpipe tobacco and waterpipe charcoal as potential sources of environmental toxicants. Selected harmful and potentially harmful constituents (HPHCs) from ten U.S. commercial waterpipe tobacco filler products (before and after electric heating) and five waterpipe charcoal products (before and after burning) were investigated. The differences in quantities of HPHCs between the evaluated products appear to be affected by raw material properties and/or the manufacturing processes involved in product production. Trace metal quantities in waterpipe tobacco and charcoal products were observed after heating or burning conditions compared to unheated or unburned conditions, which could impact the environment through the generation of toxic tobacco product waste. This study demonstrates that waterpipe tobacco and waterpipe charcoal contain substantial quantities of benzo[a]pyrene (B[a]P) and trace metals (i.e., selenium, arsenic, cadmium, chromium, cobalt, lead, nickel) before use and that extensive and varied changes in trace metal quantities take place as a result of heating, and more studies are needed to estimate the magnitude of the environmental impact of waterpipe tobacco use.
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Araştırmada mangalda pişirilmiş sebzelerin (domates, sarımsak, soğan, patlıcan, sivri biber, yeşil biber, kapya biber) polisiklik aromatik hidrokarbon (PAH) içeriğinin belirlenmesi amaçlanmıştır. PAH bileşikleri QuEChERS yöntemi ile ekstrakte edilmiş ve PAH seviyesi HPLC-FLD ile analiz edilmiştir. BaP seviyesinin patlıcan ve sivri biber örneklerinde sırasıyla 1.5 ve 2.48 ng/g düzeyinde olduğu belirlenmiştir. Sarımsak ve yeşil biber örneklerinde BaP miktarının kantitatif ölçme sınırının altında kaldığı gözlenmiştir. BaA (0.33-2.30 ng/g) ve Chry (nq-3.69 ng/g) tüm sebzelerde tespit edilmiştir. Domates, soğan ve kapya biberin diğer sebzelere kıyasla daha düşük seviyelerde PAH içerdiği, patlıcan ve sivri biberin ise incelenen tüm genotoksik PAH bileşiklerini içerdiği belirlenmiştir.
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In the present study, volatile compounds from 15 yellow tea samples were extracted and examined using stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS), and the key odorants were identified by gas chromatography-olfactometry (GC-O) analysis. Results revealed 74 volatile compounds in these yellow teas, geraniol (3.89 μg/g) being the most abundant aroma compound. Alcohols and esters were the dominant volatiles, accounting for approximately 52.44% of the total volatiles in content. Moreover, 25 key odorants were identified by GC-O method, and were considered to be responsible for the unique aroma quality of yellow tea. Major key odorants included (E, E)-3,5-octadien-2-one, (Z)-linalool oxide (furanoid), (E)-2-heptanal, naphthalene, geraniol, (E)-linalool oxide (furanoid), styrene, linalool, α-ionone, 1-octen-3-ol, trans-β-ionone, and (E, Z)-3,5-octadien-2-one. In addition, huge differences were observed among the content levels of key odorants in three types of yellow tea samples, namely MengDingHuangYa (MDHY), WeiShanHuangCha (WSHC), and PingYangHuangTang (PYHT). This is an important study describing the characterization of aroma and key odorants in yellow tea. The results obtained from this study advance our understanding of the aroma quality of yellow tea, thereby providing a theoretical basis for the processing and quality control of yellow tea aroma quality.
Chapter
This chapter provides a short overview of the main consumer products that deliver nicotine and their design principles. These products can be classified by the technology used to deliver nicotine, the route of nicotine administration, and the substrate from which nicotine is extracted and aerosolized. This chapter also provides the rationale for development of electronic nicotine delivery products in the context of tobacco harm reduction. A brief historical overview of the development of these products concludes this overview.
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Epidemiological evidence shows that the body burden of polycyclic aromatic hydrocarbons (PAHs) is related to the disruption of glucose homeostasis. However, the contribution of PAHs to the development of diabetes remains poorly documented. In the current work, male Kunming mice received phenanthrene (Phe) (5, 50, and 500 ng/kg) by gavage administration once every 2 days for 28 weeks. The significant elevation of homeostasis model assessment-insulin resistance (HOMA-IR) and HOMA-β cell, accompanied by hyperinsulinemia, indicated the occurrence of insulin resistance. The suppression of the insulin receptor signaling pathway in skeletal muscle might be responsible for glucose intolerance. Under the nonobese state, the serum levels of resistin, tumor necrosis factor-α, and interleukin-6 were elevated, whereas the levels of adiponectin were reduced. These changes in adipocytokine levels were consistent with their transcription in white adipose tissue. The promoter methylation levels of Retn (encoding resistin) and Adipoq (encoding adiponectin) were inversely correlated with their mRNA levels, indicating that Phe exposure could cause the disruption of adipocytokine secretion via epigenetic modification. The results would be helpful for understanding the pathogenesis in the development of T2DM caused by nonobesogenic pollutants.
Book
Am 4. Februar 2020 hat die Europäische Kommission die erste öffentliche Anhörung zum Entwurf des Europäischen Plans zur Krebsbekämpfung („EU Cancer Plan“) gestartet. Dies vor dem Hintergrund dass etwa 40% der Europäer*innen im Laufe ihres Lebens von einer Krebserkrankung betroffen sind - mit bedeutsamen gesundheitlichen, familiären, sozialen und wirtschaftlichen Konsequenzen. Der WHO (2016) zufolge ist der Tabakgebrauch verantwortlich für etwa 25% aller krebsbedingten Todesfälle. Der Konsum von Verbrennungszigaretten ist in den Industrieländern das bedeutendste einzelne und vermeidbare Gesundheitsrisiko und die führende Ursache frühzeitiger Sterblichkeit. „Sowohl die Krankheitsbelastung durch Zigarettenkonsum als auch dessen Einfluss auf die Gesamtsterblichkeit sind in ihrem Ausmaß historisch beispiellos. Nach Schätzungen der Weltgesundheitsorganisation (WHO) sterben weltweit jährlich acht Millionen Menschen vorzeitig an den Folgen des Zigarettenkonsums.“ (DKFZ ). In Deutschland allein sind es jährlich ca. 110.000 tabak-bedingte vorzeitige Sterbefälle. Tabakrauch ist ein Gemisch aus über 5.300 Substanzen, darunter zahlreiche giftige und 90 krebserzeugende oder möglicherweise krebserzeugende Stoffe. Rauchen schädigt nahezu jedes Organ des Körpers (DKFZ 2015). Deutschland ist immer noch ein Hochkonsumland für Tabak. Die Zahl der Rauchenden in der Erwachsenenbevölkerung geht nur langsam zurück; aktuell liegt sie in der deutschen Gesamtbevölkerung (ab 14 Jahren) im Jahre 2020 bei 26,5% (Kotz 2018). Es ist also dringend geboten, den bestehenden Präventions- und Regulierungsbemühungen das Instrumentarium der Tobacco Harm Reduction an die Seite zu stellen. Diese Daten sind bereits alarmierend und sollten dazu einladen, einerseits mehr Menschen früher in den Kontakt mit (Nichtraucher*innen-)Beratungs- und Behandlungseinrichtungen zu bringen, und andererseits Rahmenbedingungen der Tabakkontrolle zu schaffen, die adäquate Antworten auf die Gesundheitsrisiken geben und Menschen motivieren das Rauchen aufzugeben. Umso erstaunlicher – aus verhaltenspräventiver Sicht - ist, dass in Deutschland die leitliniengemäßen Tabakentwöhnung (Verhaltenstherapie plus medikamentöse Unterstützung etc.) nur von verhältnismäßig wenigen Raucher*innen in Anspruch genommen wird: Über 80% der Raucher*innen in Deutschland probieren den Rauchstopp nicht, und sind im Schnitt nur bei jedem vierten erfolgreich (Andreas 2014; AWMF 2015; Fiore 2008). Aus verhältnispräventiver Sicht kommt dazu, dass die Rahmenbedingungen der Tabakkontrolle in Deutschland denkbar schlecht sind: Deutschland hat zwar die globale „Framework Convention on Tobacco Control (FCTC)“ am 16. Dezember 2003 ratifiziert, sie allerdings nicht annähernd vollständig umgesetzt. Deutschland steht daher im europäischen Vergleich aktuell in Bezug auf die Tabakkontrolle (Tobacco Control Scale) an letzter Stelle von 36 einbezogenen Ländern (Joossens 2020). In Deutschland bewegt sich auf dem Gebiet der Tabakkonbtrolle nicht viel und vieles nur sehr langsam: So wurde erst kürzlich ein Gesetz zum Werbeverbot für Zigaretten im Bundestag verabschiedet, welches sich zunächst auf Verbrennungszigaretten bezieht, in den nächsten zwei Jahren aber auch auf Tabakerhitzer und E-Zigaretten ausgedehnt werden soll. So begrüßenswert das längst überfällige Werbeverbot für Verbrennungszigaretten ist, so dringend ist es jedoch, Alternativprodukte nicht nur zu regulieren, sondern als Hilfsmittel zur Senkung der Raucher*innenzahlen anzuerkennen. So verpflichten sich die Unterzeichner*innen im FCTC auch auf „Strategien zur Verminderung […] des Schadens mit dem Ziel der Verbesserung der Gesundheit einer Bevölkerung durch Unterbindung oder Verminderung des Konsums an Tabakerzeugnissen“ (FCTC, Art. 1d; WHO 2003). Abhängige Raucher*innen sind in der gegebenen Situation auf Alternativen zu den sehr begrenzten Möglichkeiten der Hilfe im Rahmen der gesetzlichen Krankenversicherung angewiesen. Tatsächlich wird die Option der Angebote der Tabakentwöhnung im Rahmen der gesetzlichen Krankenversicherung gemäß Paragraf 20 SGB V (Prävention) nicht zuletzt aufgrund beträchtlicher Antragsbarrieren und Patient*innen teils zur Last gelegten Kosten nur im sehr begrenzten Rahmen (9.360 Fälle 2018) Deutschland umgesetzt (Bauer 2019). Entwöhnungswillige Raucher*innen weichen in großer Zahl auf die E-Zigarette, Tabakerhitzer oder andere Formen der Nikotinaufnahme aus, um ihre Gesundheit zu schützen. E-Zigaretten und Tabakerhitzer sind nach aktueller Risikoeinschätzung erheblich weniger schädlich als fortgesetztes Rauchen und daher schon jetzt geeignet, einen Beitrag zur Risikoreduktion beim Rauchen zu leisten. So schätzt Public Health England, dass E-Zigaretten 95% sicherer sind als gerauchter Tabak und beim Rauchstopp helfen können (Pieper 2018; Mallock et al. 2019, p.287). Doch die Information der Bevölkerung bezüglich dieser erheblichen Risikoreduktion durch alternativen Formen der Nikotinaufnahme, bzw. des Dampfens ist mangelhaft, insbesondere unter den Rauchenden. (BfR 2019). Wenn die Mehrheit der Rauchenden (aber auch der Ärzt*innen) immer noch denkt, die E-Zigarette sei genauso schädlich wie die Verbrennungszigarette (oder sogar schädlicher), dann lohnt sich ein Umstieg für sie nicht. Aufklärung über die Vorteile alternativer Produkte tut dringend not – v.a. von den dafür verantwortlichen Gesundheitsagenturen (vgl. Stöver, Jamin, Eisenbeil 2020; Stöver 2019). Der Aufklärung über differenzierte und diversifizierte Rauchentwöhnungsprogramme und – instrumente fühlen sie die Autor*innen des vorliegenden Bandes verpflichtet. Sie machen deutlich, dass es auch eine absolute ethische Notwendigkeit ist, differenzierte Risikokommunikation zu betreiben. D.h. ganz klar zu formulieren, dass die E-Zigarette und Tabakerhitzer nicht harmlos sind, aber eine weniger schädliche Alternative zum Weiterrauchen darstellen, wenn anders der Verzicht auf die weit gefährlichere Tabakzigarette nicht gelingt. Frankfurt am Main, im November 2020 Prof. Dr. Heino Stöver
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Longjing tea is the most famous premium green tea, and is regarded as the national tea in China, with its attractive aroma contributing as a prime factor for its general acceptability; however, its key aroma compounds are essentially unknown. In the present study, volatile compounds from Longjing tea were extracted and examined using stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS). Data obtained from the present study revealed that 151 volatile compounds from 16 different chemical classes were identified by GC-MS analysis. Enols (8096 µg/kg), alkanes (6744 µg/kg), aldehydes (6442 µg/kg), and esters (6161 µg/kg) were the four major chemical classes and accounted for 54% of the total content of volatile compounds. Geraniol (6736 µg/kg) was the most abundant volatile compound in Longjing tea, followed by hexanal (1876 µg/kg) and β-ionone (1837 µg/kg). Moreover, 14 volatile compounds were distinguished as the key aroma compounds of Longjing tea based on gas chromatography-olfactometry (GC-O) analysis, odor activity value (OAV) calculations, and a preliminary aroma recombination experiment, including 2-methyl butyraldehyde, dimethyl sulfoxide, heptanal, benzaldehyde, 1-octen-3-ol, (E, E)-2,4-heptadienal, benzeneacetaldehyde, linalool oxide I, (E, E)-3,5-octadien-2-one, linalool, nonanal, methyl salicylate, geraniol, and β-ionone. This is the first comprehensive report describing the aroma characterizations and the key aroma compounds in Longjing tea using SBSE/GC-MS. The findings from this study contribute to the scientific elucidation of the chemical basis for the aromatic qualities of Longjing tea.
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The effects of grilling on health risks posed by polycyclic aromatic hydrocarbons (PAHs) in food remain poorly understood. The changes of concentrations, distributions, and risks of PAHs in vegetables and animal-based foods before and after grilling were investigated in this study. The sum of 16 (∑16) PAH concentrations in grilled vegetables and grilled animal-based foods were 60.4–1936 and 69.1–4668 ng/g, respectively. Grilling markedly increased the ∑16 PAH concentrations in most foods analyzed. Grilling clearly increased the low-molecular-weight PAH contributions to the ∑16 PAH concentrations in vegetables but increased the heavier PAH contributions to the ∑16 PAH concentrations in some animal-based foods. With the grilling, the total benzo[a]pyrene-equivalent concentrations of the 16 PAHs in Chinese chives and enoki mushrooms and most animal-based foods were improved significantly. Source assessments indicated that environmental sources contributed PAHs to the raw foods and high-temperature pyrolysis during grilling contributed large proportions of the PAHs in the grilled foods. The carcinogenic risks to humans from the exposure of PAHs in vegetables and animal-based foods were estimated. Grilling increased the total risks of PAHs in vegetables and animal-based foods by factors of 3.12 and 5.49, respectively. Total risks of PAHs in the 11 foods were 3.43 times higher when the foods were grilled than when raw. The results suggested that the negative effects of grilling on human health should be of great concern.
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The effects of roasting, boiling, and freeze-drying after boiling on volatile aroma compounds in three varieties of Chinese foxtail millet (Setaria italica), namely, Jingu 21, Fenghonggu and Dongfangliang were determined. During boiling significant (p < 0.05) increases in the contents of several unsaturated aldehydes, alcohols, and benzene derivatives were observed, unlike roasting that mainly increased in the contents of pyrazines. Freeze-drying after boiling decreased complexity of flavors, with a reduction in the contents of volatile compounds. Descriptive sensory analysis showed that the maximum intensity of ‘popcorn-like’ and ‘smoky’ odors was observed for roasted samples, whereas boiled and pre-boiled-freeze-dried samples were characterized by ‘boiled rice’ and ‘boiled potatoes’ odors, respectively. A correlation of odor-active profile data with descriptive sensory analysis clearly established the role of pyrazines such as 2-ethyl-3,5-dimethylpyrazine in contributing to the ‘popcorn-like’ ‘boiled beans’ and ‘smoky’ odors, whereas dienals such as (E,E)-2,4-decadienal were responsible for the ‘boiled rice’ aroma.
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A rapid pyrolysis technique, combined with gas chromatographic separation and interpretation of mass spectra obtained from the resulting pyrolysispyrosynthesis products, has been used in the study of three different compounds present in processed tobacco: n-C25 alkane, neophytadiene and phytol. The compounds are representative for a homologous series of n-alkanes and for a series of branched-chain compounds including neophytadiene, phytol, solanesol and esters of solanesol (tobacco constituents). At temperatures below 600°C the pyrolysis in the absence of oxygen, but in a helium flow gives only slight aromatisation when n-alkanes are treated. For the isoprenoid compounds neophytadiene and phytol aromatisation starts between 500 and 600°C. The products formed tend to develop more-condensed ring structures at increasing temperature, although benzene and toluene are dominating even at temperatures as high as 800 to 900°C. Aromatisation leading to relatively less methyl substitution results with increasing temperature. Previous pyrolysis work and recent interpretations point to the formation of structures such as acenaphthylene, acenaphthene, cyclopenta[cd]pyrene, 3,4-dihydrocyclopenta[cd]pyrene and probably similar structures derived from three and four-membered condensed ring structures produced.
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The purpose of this study was to learn how cellulose pyrolysis was affected by changes in atmospheres, by varied pyrolysis temperatures, by the addition of inorganic materials, and by chemical modifications of the cellulose molecule. These studies have led to the hypothesis that cellulose can pyrolyse by two different modes to form B(a)P. Large quantities of B(a)P can be formed by high temperature (850°C) isothermal pyrolysis of cellulose via a very efficient gaseous reaction route. In this reaction the B(a)P yield decreased in the presence of iron, cobalt, and nickel while the yield increased with increasing temperatures and with the introduction of oxygen into the system. In contrast, graduated heating experiments demonstrated that B(a)P began to form at 450°C. This reaction was inefficient with respect to B(a)P yield and was unaffected by the presence of metals. The B(a)P precursors were hypothesized to be nonvolatile, being formed via a solid state decomposition of cellulose and involving the generation of free radicals. This reaction was inhibited by the presence of nitric oxide or salts generating nitric oxide. Additionally, oxidation of the cellulose molecule at the C6 position produced a decreased B(a)P yield.
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During the period of tobacco smoke research from the early 1950s to the mid-1960s it was repeatedly asserted that a) tobacco and many tobacco components were involved in the pyrogenesis of polycyclic aromatic hydrocarbons (PAHs), several of which were reported to initiate tumors on the skin of laboratory animals and b) tobacco additives (flavorants, casing materials, humectants) were highly likely to be similarly involved in PAH pyrogenesis. Extensive knowledge on PAHs was deemed highly necessary because of their claimed importance in the smoking-health issue. The numerous assertions about the generation of PAHs in cigarette mainstream smoke (MSS) triggered extensive and intensive research both within and outside the Tobacco Industry to define the nature of the PAHs, their per cigarette MSS delivery amounts, their precursors, etc. It was not until 1960 that VAN DUUREN et al. (1) reported three specific aza-arenes in cigarette MSS that were asserted to be involved in smokers’ respiratory tract cancer. As noted in a recent Letter to the Editors (2), the presence of these three aza-arenes in tobacco smoke has never been confirmed. Between 1960 and 1965, other MSS components (phenols as promoters, polonium-210
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One sample each of aged uncased, cured bright lamina, bright stems, Burley lamina and Burley stems were examined by a variety of general analytical methods and then characterized by our standard fractionation procedure. These tobacco samples were chosen to be reasonably representative of the tobaccos used in current commercial cigarette products. Although for a given variety of tobacco the concentrations of chemical constituents may vary as a function of stalk position, cultural management, geographic origin or crop year, we believe that the following conclusions based on these samples are generally valid: [1] levels of ethanol solubles, total reducing sugars and starch are much higher in bright than in Burley, [2] concentrations of soluble ammonia and nitrate are greater in Burley than in bright, [3] total alkaloid and protein concentrations are higher in lamina than in stems, [4] cellulose, potassium and chloride concentrations are much greater in stems than in lamina, [5] concentrations of pectin, lignin and soluble hemicellulose do not vary greatly from one type of tobacco to another, [6] Burley lamina has greater concentrations of protein and acid detergent solubles than do the other types of tobaccos, and [7] bright lamina has a much lower level of total ash than do the other types of tobaccos. An examination of some of the components in ash led to the following conclusions: [1] total ash values are reasonable relative indicators of the level of non-nitrate inorganics, [2] a good estimate of the total contents of potassium, calcium, chloride, sulfate, phosphorus, silicon and magnesium may be obtained by multiplying the total ash value by 0.612, and [3] it is likely that most of the potassium and calcium in total ash is actually present as carbonates rather than oxides. The significantly higher levels of both protein and acid detergent solubles found in Burley lamina are thought to indicate that this protein may be unique in terms of its carbohydrate content or in terms of the nature or extent of its cross linkage.
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The hexane soluble fraction of flue-cured tobacco has been pyrolyzed to reevaluate the importance of its contribution to the formation of aromatic compounds, especially polynuclear aromatic hydrocarbons (PAH), present in cigarette smoke. The pyrolyses were performed at 860° AA± 5°C under nitrogen. In general, the studies indicate that the hexane-solubles contribute significantly more to the aromatic hydrocarbon levels of tobacco pyrolysate than would be predicted on the basis of percent of dry leaf weight alone. Estimates of benzo[a]pyrene levels in pyrolysates indicate that nearly two-thirds of the amount produced during tobacco pyrolysis may be attributed to the hexane soluble components of leaf.
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In continued studies to reevaluate the contribution of the hexane-soluble fraction of flue-cured tobacco to the formation of aromatic compounds, especially polynuclear aromatic hydrocarbons, present in cigarette smoke, some compounds representative of that fraction have been pyrolyzed (860°C, N2). The straight chain saturated compounds, n-hexane, stearic acid, and dotriacontane, produced pyrolysates distinguished by relatively low yields of total neutrals and the absence of any significant quantities of aromatic products with alkyl side chains. Compounds containing double bonds, such as the unsaturated fatty acid, linolenic acid and its methyl ester, and the polyene squalene, which like phytol is also characterized by methyl groups on the chain, produced relatively higher yields of neutral products, including alkyl-substituted aromatic hydrocarbons. Phytol, of course, also exhibited this tendency. Pyrolysis of the plant sterol, b-sitosterol, produced the greatest amounts of phenanthrene and BaP. Estimates of BaP levels in pyrolysates indicate that phytol, in addition to the above mentioned sterol, is a relatively effective high temperature precursor of this important carcinogen. The hexane solubles of flue-cured tobacco were shown to produce BaP in levels intermediate to the least effective (stearic acid) and most effective (b-sitosterol) precursor examined.
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In an attempt to stud) the mode of formation of polycyclic aromatic hydrocarbons in cigarette tar, pyrolyses of dotriacontane (C32H66) and of stigmasterol at 700° have been undertaken. Both compounds gave complex tars containing many aromatic hydrocarbons. Mechanisms for the formation of some of these are discussed, and the relative concentrations of some of the polynuclear hydrocarbons present 1n both tars are compared with those in cigarette tar.
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The differential thermal analysis of reconstituted tobacco sheet heated at rates of 0.1°C/s to 500°C/s in an inert atmosphere is reported. As the heating rate is increased, the characteristic temperature of each global process observed is increased. Using a non-isothermal first-order kinetic equation, the activation energies and frequency factors are obtained for these bulk decomposition processes
Chapter
Developers of microbiological processes to convert biomass into chemicals and fuels recognized long ago that pretreatments were needed prior to fermentation or enzyme reactions, if high rates and yields are to be achieved.1,2 Microorganisms and enzymes have difficulty in depolymerizing crystalline polymers, such as cellulose, and hydrophobic molecules, such as lignin and triglycerides. Furthermore, biomass constituents frequently conspire to form complexes that are difficult for microbes or enzymes to break apart. Because of these problems, numerous pretreatment methods have been developed to aid in microbiological processing by disrupting the lignocellulose complex, facilitating the depolymerization of polymers, and removing protective extractives.
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The complex polyphenolic pigments of Turkish tobacco have been pyrolyzed to determine their possible contribution to the formation of aromatic compounds, especially polynuclear aromatic hydrocarbons (PAH), of smoke. The dark brown pigments were initially obtained by a basic aqueous extraction of tobacco. Various hydrolytic procedures showed the presence of rutin, chlorogenic acid, and a series of amino acids; some information on the structure of these pigments is presented. The pyrolysis of the pigments was carried out at 850°C and the products were fractionated to reveal the presence of more than a dozen PAH. Addition of pigments to cigarettes gave an increase in the level of benzo[a]pyrene in the smoke. The possible role of the polyphenolic pigments as a source of PAH in smoke is discussed
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The authors investigated the dependence upon temperature of the formation of benzo[a]pyrene and benzo[e]pyrene from tobacco pyrolyzed in a thermostatic oven in atmospheres of nitrogen or air. The heating of tobacco to temperatures between 400° and 1000°C was found to result in a marked increase of the benzopyrene yield in the volatile parts. In this temperature range the quantity of benzo[a]pyrene formed from 100 g of tobacco augments from 4.4 µg to 18 350.0 µg (N2). At comparable temperatures measured in the combustion material by a thermocouple, the amounts of benzopyrenes formed respectively in nitrogen and air atmospheres were almost identical. With the introduction of air into the system the combustion enthalpy causes, under the same experimental conditions, a heating of the tobacco and, therefore, an increase in temperature which is considerably raised above that of the thermostatic oven. The formation of benzopyrenes was found to depend very much upon the flow rate. Moisture content, packing density and other geometrical factors have also a strong effect on the amount of polycyclic hydrocarbons formed during combustion. The quantities of benzopyrenes produced under equal experimental conditions by pyrolysis of other organic materials such as glucose and paraffin wax have been found to vary markedly (1:100 proportion). The yields of benzopyrenes produced by pyrolysis of tobacco (preheated combustion material) with the introduction of air into the system do exceed considerably the corresponding amounts obtained by the smoking of cigarettes
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Simple correlation and multiple regressions among 160 variables of leaf characteristics and smoke constituents were calculated, based on experimental cigarettes made from 4 cultivars of bright-type tobacco, each from 8 stalk positions. Smoke composition is a function of the botanical, physical, and chemical properties of leaf tobacco used to make the cigarette. Detailed simple correlation data, multiple-regression equations, and expressions of variety and stalk position as factors of TPM and BaP formation are presented.
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Tobacco, its petroleum ether (PE) extract, and the residual extracted tobacco (marc) were pyrolyzed at 650-750°C, 650-850°C, and 700°C, respectively. Analyses of the polynuclear aromatic hydrocarbons (PAH) produced showed that the pyrolysis of the tobacco and the PE extract at 700°C produced PAH profiles comparable to those found in cigarette smoke condensate (CSC). The data indicated that most of the alkyl PAH and the major PAH in cigarette smoke are derived from the PE extractables of tobacco. The constituents of the marc were the major precursors for phenols, oxygenated PAH, and Iow molecular weight acids; and those of PE extract were the major producers of high molecular weight acids.
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Recent studies on the pyrogenesis of tobacco smoke constituents have been reviewed. Where appropriate, representative studies on pyrolyses of compounds reportedly present in tobacco leaf have been included. Various experimental conditions such as temperature, gaseous environment, and thermal stability of precursor were considered in light of current understanding of the smoking process. Attempts to alter the chemical constituents of smoke by use of additives have been discussed. Finally, various smoke constituents have been correlated with pyrolyses of leaf constituents in further hopes of better understanding the complex processes that produce tobacco smoke
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In 1954, a paper listing 79 substances in cigarette smoke was first published. Since then 4800 individual chemicals, most of them carcinogenic, have been identified in tobacco smoke. The earliest substances identified, were benzopyrene and polynuclear aromatic hydrocarbons (PAH), that were known to produce tumours in animal experiments. A burning cigarette was found to be a complex system in which many types of chemical reactions and physical processes occurred in parallel.
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Analyses of the smoke from cigarettes made from borate-treated tobacco have shown a significant increase in the levels of phenol, o-cresol, m-, p-cresol, and benzo[a]pyrene. To determine the temperature range at which this additive is operative temperature-yield profiles from tube pyrolyses have been obtained for both untreated and borate-treated tobacco. The profile for untreated tobacco indicates that there are two distinct modes of phenol formation. Addition of borate to the tobacco suppresses phenol formation at lower temperatures and greatly enhances its formation at higher temperatures. The modes of formation of the cresols do not appear to be markedly altered by the addition of borate to tobacco.
Article
In order to better understand the formation of polycyclic aromatic hydrocarbons (PAH) from complex fuels, we have performed pyrolysis experiments in a laminar-flow reactor, using the model fuel catechol (ortho-dihydroxybenzene), a phenol-type compound representative of structural entities in tobacco, coal, and wood. Employing high pressure liquid chromatography with diode-array ultraviolet–visible (UV) detection, we have unequivocally identified 59 individual species among the condensed-phase products of catechol pyrolysis at a temperature of 1000°C and a residence time of 0.4 s. Also identified are two oxygen-containing compounds that are produced only at pyrolysis temperatures lower than 900°C. Of the total 61 species, fifty have never before been identified as pyrolysis products of any pure phenol-type compound. Two of the catechol pyrolysis products, 5-ethynylacenaphthylene and 3-ethynylphenanthrene, have never before been identified as products of any fuel. Ranging in size from one to eight fused aromatic rings, the catechol pyrolysis products comprise several compound classes: bi-aryls, indene benzologues, benzenoid PAH, alkylated aromatics, fluoranthene benzologues, cyclopenta-fused PAH, ethynyl-substituted aromatics, polyacetylenes, and oxygen-containing aromatics. The catechol pyrolysis products bear remarkable compositional similarity to the products of bituminous coal volatiles pyrolyzed at the same temperature – demonstrating the relevance of these catechol model compound experiments to the study of complex fuels such as coal, wood, and tobacco. The UV spectra, establishing compound identity, are presented for several of the identified catechol product components.
Article
When tobacco is pyrolysed under non-isothermal flow conditions in an inert atmosphere, variation of the inert gas or its space velocity has only a minor effect on the profiles of formation rate versus temperature for seven product gases. Thus, mass transfer processes between the tobacco surface and the gas phase are very rapid, and the products are formed at an overall rate which is determined entirely by that of the chemical reactions.The effect of radical chain inhibitors (nitrogen oxides) on the pyrolysis is complex because of the resultant oxidation. Nevertheless, no evidence was found for the occurrence of radical chain reactions in the gas phase. A small proportion (less than 10%) of all the gases monitored are formed by homogeneous decomposition of volatile and semi-volatile intermediate products, in the furnace used.At temperatures above about 600°C the reduction of carbon dioxide to carbon monoxide by the carbonaceous tobacco residue becomes increasingly important. However, when tobacco is pyrolysed in an inert atmosphere, only a small amount of carbon dioxide is produced above 600°C and consequently its reduction to carbon monoxide contributes only a small proportion to the total carbon monoxide formed above that temperature. The rate of the tobacco/carbon dioxide reaction is controlled by chemical kinetic rather than mass transfer effects. Carbon monoxide reacts with tobacco to a small extent.When the tobacco is pyrolysed in an atmosphere containing oxygen (9–21% v/v), some oxidation occurs at 200°C. At 250°C the combustion rate is controlled jointly by both kinetic and mass transfer processes, but mass transfer of oxygen in the gas phase becomes increasingly important as the temperature is increased, and it is dominant above 400°C. About 8% of the total carbon monoxide formed by combustion is lost by its further oxidation.The results imply that inside the combustion coal of a burning cigarette the actual reactions occurring are of secondary importance, the rate of supply of oxygen being the dominant factor in determining the combustion rate and heat generation. In contrast, in the region immediately behind the coal, where a large proportion of the products which enter mainstream smoke are formed by thermal decomposition of tobacco constituents, the chemistry of the tobacco substrate is critical, since the decomposition kinetics are controlled by chemical rather than mass transfer effects. tobacco substrate is critical. In addition, the heat release or absorption due to the pyrolytic reactions occurring behind the coal will depend on the chemical composition of the substrate. Thus, together with the differing thermal properties of the tobacco, the temperature gradient behind the coal should depend on the nature of the tobacco.
Article
A single puff polycyclic aromatic hydrocarbon (PAH) analysis technique was developed in our laboratory and applied to study PAH formation in each puff during the cigarette smoking process. An impaction trap was used to collect the total particulate matter (TPM) from a single puff of smoke. The TPM was then weighed and dissolved in a 5:5:1 mixture of toluene, hexane, and isopropanol. Five PAHs, including naphthalene, phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene were analyzed by gas chromatography–mass spectrometry (MS) using selective ion monitoring mode. This technique offers the capability to analyze trace amounts of PAHs in a single puff of mainstream cigarette smoke and provides information on PAH formation from each puff. Comparison of relative PAH levels in the lighting puff of mainstream cigarette smoke using different types of lighters is presented to illustrate the importance of applying the single puff analysis technique in understanding smoke chemistry.
Article
Laser-induced fluorescence (LIF) spectroscopy can serve as a rapid analytical method for the quantitative analysis of polycyclic aromatic hydrocarbons (PAHs). The high quantum yields of this class of compounds, along with large absorption cross-sections, make fluorescence a very attractive technique for trace analysis determination of PAHs. Furthermore, fluorescence can provide in situ and online information regarding the composition and concentration of PAHs formed during combustion or pyrolysis processes. In this paper, we utilize a fiber-optic probe coupled to a spectrometer to collect fluorescence spectra of several PAH vapors at elevated temperatures using excitation at 337 nm. We have collected the fluorescence of standards as well as complex mixtures of PAHs at 300°C. The expected band broadening induced by temperature effects was observed, but did not compromise the spectrum signature for each PAH studied. We have measured fluorescence spectra of benzo[a]pyrene, pyrene, anthracene, and phenanthrene vapors. Determination of trace amounts of the toxicologically important benzo[a]pyrene has been shown to be feasible. Experimental results show that at 337 nm, benzo[a]pyrene is the most quantum efficient fluorophore among the PAHs studied. Furthermore, fluorescence lifetime measurements were found to be helpful in the characterization of PAH mixtures.
Article
It is well known that polycyclic aromatic hydrocarbons (PAHs) are formed from the pyrolysis of biomass, but the precursors and pathways that lead to PAHs are not well characterized. In this investigation, the flash vacuum pyrolysis (FVP) and the atmospheric pressure flow pyrolysis of a series of structurally different plant steroids, including stigmasterol, stigmasteryl acetate, (beta-sitosterol, stigmasta-3,5-diene, cholesterol, cholesteryl acetate, dihydrocholesterol, and ergosterol was investigated at 700 degreesC to determine the impact of steroid structure on the formation of three, four, and five ring PAHs. FVP of the steroids revealed that PAHs, such as phenanthrene, anthracene, pyrene, chrysene, benz[a]anthracene and their monomethylated derivatives, were formed by a series of unimolecular reactions, and the PAH yields were dependent upon the steroid structure. PAH yields were most sensitive to the number of double bonds in the steroid B-ring. Ergosterol (two double bonds) produced 13-fold more PAHs than dihydrocholesterol (no double bonds) in FVP experiments and 4-fold more PAHs in the flow pyrolysis experiments. Increasing the temperature from 700 to 800 degreesC in the FVP experiments only slightly increased the PAH yields for dihydrocholesterol relative to cholesterol, but the yield of small aromatic hydrocarbons, such as benzene and toluene, increased approximately 2-fold. Small increases in PAH yields (10-40%) were found in the FVP experiments if a double bond was placed in the steroid A-ring by 1,2-elimination of an ester (as for cholesteryl acetate), but this trend was not observed in the flow pyrolysis experiments. Insight into the structural origins of the PAHs was gained by FVP of [4-C-13]cholesterol, in which the C-13 content of the products was determined by mass spectrometry. The PAH yields from the flow pyrolysis of steroids.
Article
The chemical constituents of tobacco smoke are generated in the burning zone of the cigarette where the processes of combustion, pyrolysis, distillation and aerosol formation occur. Tobacco itself consists of many different chemical components and consequently a large number of reactions occur in parallel as the cigarette burns.Relationships between tobacco components and smoke products are complex and difficult to unravel. Pyrolysis experiments have commonly been used to establish such relationships. However, unless they are performed under dynamic conditions that are relevant to those that occur during tobacco burning, results can be obtained which have little resemblance to those obtained during cigarette smoking.Bearing in mind this limitation, a variety of pyrolysis studies are reviewed which give insights into the mechanisms and reaction pathways occurring in the cigarette. The oxides of carbon are formed by thermal decomposition and combustion of tobacco constituents, and carbon dioxide is further converted to carbon monoxide by carbonaceous reduction. Pyrolysis studies used to elucidate these three processes are discussed.Pyrolysis results are presented which indicate that the majority of the so-called semi-volatile components of cigarette smoke are formed from tobacco at temperatures below 600° C. A literature survey of the tobacco component-semi-volatile product routes has been summarised. It indicates that their formation is complex and only partially understood. A few components (e.g. nicotine and other alkaloids) are transferred directlyfrom the tobacco; most are formed principally as a result of pyrolytic decomposition of many tobacco components in parallel.
Article
Cellulosic chars prepared at HTTs ranging up to 500°C contain aromatic structures as evidenced by the production of benzene polycarboxylic acid derivatives on permanganate oxidation. Analysis of these products indicates the concentration of the aromatic units and the degree of substitution of benzene polycarboxylic acids represents the extent of condensation or crosslinking of the structures. Further information on this subject is obtained by elemental composition of the char and the ratio. These studies indicate a rapid weight loss and development of aromatic structures between 350 and 400°C, as the ratio is gradually reduced from 1.5 to 0.7 and the aromatic carbon of the benzene polycarboxylic acids formed is increased to 2.5% of the carbon content of the original cellulose. Above 400°C the rate of weight loss is reduced with the formation of the “stable” char and the yield of the aromatic carbon remains constant. However, the aromatization process continues with rapid reduction in ratio, due to the condensation and growth of the aromatic clusters as evidenced by the increased formation of the highly substituted benzene polycarboxylic acids. The presence of inorganic additives, representing flame retardants results in increased charring and enhancement of aromaticity and condensation.
Article
There have been many studies on the pyrolysis of biomass model compounds but most have not been performed under the high heating rate, short residence time conditions currently used in the thermochemical conversion of biomass. In this investigation, the pyrolysis of plant steroids is investigated by flash vacuum pyrolysis (FVP) and flow pyrolysis at residence times of 0.1–2.0s and temperatures of 550–800°C to determine if the native cyclic ring structure in the steroid leads to the formation of polycyclic aromatic hydrocarbons (PAHs) or whether PAHs are formed by pyrosynthesis. FVP of stigmasterol, stigmasterol acetate, β-sitosterol, and stigmasta-3,5-diene at 700°C showed that PAHs, such as acenaphthylene, phenanthrene, anthracene, pyrene, chyrsene, benz[a]anthracene, and their monomethylated derivatives were formed in the absence of bimolecular reactions, and the yield of PAHs was dependent of the structure of the steroid. Similar products were found in the flow pyrolysis of stigmasterol, and the yields of PAHs were found to increase with increasing temperature and residence time. Thermochemical kinetic estimates were used to postulate pathways for the formation of the primary pyrolysis products.
Article
The pyrolysis of biomass is receiving increasing attention since potentially all of the product streams have a valuable end use. The derived pyrolytic oils are chemically very complex and require detailed analysis involving several analytical steps. The analysis of biomass derived pyrolysis oils and catalytically upgraded biomass oils for aromatic, polycyclic aromatic hydrocarbons (PAH) and oxygenated aromatic compounds is described. The oils were fractionated into their chemical classes using mini-column liquid chromatography. The fractions were analysed by gas chromatography/mass spectrometry and using relative retention indices for indentification and quantification. The relative retention indices are compared with those in the literature. Relative retention indices and compound concentrations are presented for 161 compounds found in biomass oils. The catalytically upgraded biomass oils are shown to contain significant concentrations of PAH, some of which have been shown to be mutagenic and/or carcinogenic.
Article
A rapid, economical method was developed for the evaluation of the potential of different tobacco varieties to produce possibly hazardous smoke compounds. This controlled pyrolysis method produces pyrolyzate fractions very nearly identical with corresponding cigarette smoke fractions, as determined by analyses of their polynuclear aromatic hydrocarbons, neutral constituents, and phenolic contents.
Article
1H and 13C NMR have been used to detect solanesol directly in tobacco without destroying or modifying the sample. Magic angle sample spinning was employed to remove the resonance line broadening due to variations of magnetic susceptibility within the sample. 13C line widths of ca. 10 Hz were obtained. The 1H MAS spectrum of tobacco allows the solanesol signals to be resolved from the broad signal of exchangeable protons. 13C spin-lattice relaxation times (T1) and nuclear Overhauser enhancements (NOE) of solanesol in chloroform solution, in intact tobacco, and as neat oil indicate that the polyisoprene chain motion in tobacco is restricted relative to the motion in solution but still sufficient to average out the dipolar couplings between protons and carbons.
Article
13C CPMAS NMR spectra were obtained of the leaf laminae and stems of cured bright and burley tobaccos. The solid phase NMR spectra of some of the most abundant tobacco components were also obtained, including cellulose, hemicellulose, and pectin (each isolated from tobacco), calcium and potassium salts of malic and citric acid, calcium oxalate, rutin, chlorogenic acid, and nicotine (in the form of a crystalline ditartrate salt). The tobacco spectra have been interpreted in light of these reference materials, as well as the chemical analyses of similar samples. Multiple cross-polarization contact times, interrupted decoupling, and single-pulse excitation were employed to improve the discrimination between overlapping resonances, to reveal new spectral features, and to detect tobacco components obscured by the complexity of the spectra. These alternative pulse experiments permitted the selective detection of microscopic calcium oxalate crystals, solanesol and other mobile waxes, nicotine, citrate, and fructose.
Article
The composition of char from heated Avicel cellulose was monitored as a function of heating time and temperature, using 13C cross-polarization magic-angle spinning (CPMAS) NMR. Complex NMR line shapes observed in the carbohydrate region of the spectra are indicative of the presence of multiple carbohydrate forms. By successive spectral subtractions of the 300 °C pyrolysis char, the complex line shapes were separated into three distinct carbohydrate components that correspond to the crystalline cellulose starting material (SM), an intermediate cellulose (IC) that resembles a low degree-of-polymerization (low-DP) amorphous cellulose, and a disordered final carbohydrate (FC) that is characterized by a very broad 13C line width. Curve fitting was used to monitor the changes in the approximate abundance of these different carbohydrate forms relative to the aliphatic, aromatic, carboxyl, and ketone clusters of compounds of the char. The time evolution of the IC, together with its spectral line shapes, associate this component with the “active cellulose” intermediate that has long been postulated in many kinetic mechanisms for cellulose pyrolysis. After a heating period of 30 min, FC was the only remaining carbohydrate component. When subjected to prolonged heating, FC converted to aromatic carbons but not to aliphatic carbons, with little or no loss in char mass. This property distinguishes the FC as a char component that has not previously been recognized. Pyrolyses of cellulose with 1% K+ as KCl, and of pectin at 300 °C and cellulose at 350 °C were also performed. Evaluation of the combined data led to a new model for low-temperature cellulose pyrolysis. In this model, all char products are formed from IC, with FC being capable of forming aromatic carbon.
Article
Vacuum pyrolysis of aspen poplar wood chips was performed in a multiple hearth furnace process development uint. Various pyrolysis oils were collected in a series of cooling traps installed in parallel at the reactor outlets (primary condensing unit, H-I to H-VI). An aqueous phase containing about 45% water (96% of the total pyrolysis water) was collected separately in a secondary condensing unit (C-1 to C-3) which contained high-volatile and partially water soluble organic mater. Liguid-liquid and liquid-solid chromatographic techniques were developed to separate aliphatic and aromatic hydrocarbons. Preliminary characterization of the aliphatic and aromatic hydrocarbons was performed by gas chromatography and mass spectrometry (GC/MS). Aliphatic hydrocarbons represented between 0.08 and 0.44% of the oil phase and 0.01 and 0.02% of the aqueous phase. The aliphatic hydrocarbon fraction of the H-VI oil was dominated by n-alkanes in the range of n-C{sub 19} to n-C{sub 26}. Aromatic hydrocarbons contributed between 0.06 and 0.24% of the oil phase and were detected only in trace amounts in the aqueous phase. FTNMR and FTIR spectroscopic analyses of the aromatic fractions showed a complex mixture of highly branched aromatic hydrocarbons. Due to the highly branched nature of their aromatic fractions, neither phase is believed to have significant environmental and toxicological impact. The efficiency of the hydrocarbon separation technique was also tested on a tar sample from a 10 t/h wood gasifier which contained over 50% polycyclic aromatic hydrocarbons. Of this tar sample 85% was characterized by GC/MS.
Article
A great need exists for comprehensive biomass-pyrolysis models that could predict yields and evolution patterns of selected volatile products as a function of feedstock characteristics and process conditions. Low heating rate data obtained from a thermogravimetric analyzer (TGA), coupled with Fourier transform infrared analysis of evolving products (TG-FTIR), were used to perform kinetic analysis of tobacco pyrolysis. The results were utilized to create input to a biomass-pyrolysis model based on first-order kinetic expressions with a Gaussian distribution of activation energies. Pyrolysis simulations were carried out for high heating rate conditions, and predicted product yields were compared with literature data.
Article
The major chemical pathways for production of aromatic hydrocarbons in the pyrolysis and subsequent flaming combustion of biomass materials are high temperature secondary reactions of the primary pyrolysis products. The second and less explored route is the evolution of aromatics from the solid substrate in the temperature range of 400–600°C. Primary chars that form around 300–400°C, depending on the starting material, continue to undergo pyrolysis up to temperatures of 600°C and higher. In this work, the formation of aromatic hydrocarbons from the second route was investigated for cellulosic materials. Experimental work was performed primarily using TG/DSC/MS. In order to reduce the formation of hydrocarbons from secondary reactions of the primary pyrolysis products, small sample size, i.e., 2 –10 mg, and a high helium flow rate of 150 ml/min, were used. Heating rates of less than 60°C /Min were used to ensure uniform sample temperature. Py/GC/MS confirmed the identities and relative quantities of masses detected by TG/DSC/MS. Under slow heating conditions, which are typical of thermogravimetric analyzers, simple hydrocarbon products begin to evolve above 350°C, where the primary decomposition of cellulosic materials has completed and the remaining char has begun the carbonization/aromatization process. Most aromatic products such as benzene, toluene, naphthalene, anthracene are detected between 400 to 600°C. Detectable products formed at temperatures above 600°C are methane, benzene, and hydrogen, and carbon monoxide. Some kinetic parameters for the formation of hydrocarbon products are deduced from the experimental findings and discussed in this presentation.
Article
The formation of pyrolysis products, including polycyclic aromatic compounds (PACs), of three α-amino acids acids (asparagine, proline, and tryptophan) was studied in inert atmosphere. The PACs included polycyclic aromatic hydrocarbons (PAHs) and nitrogen-containing polycyclic aromatic compounds (N-PACs). A number of low temperature pyrolysis products, primarily single ring heterocyclic compounds, were also identified. The reactor consisted of a quartz tube with two-zones, each heated and controlled separately. The amino acids were pyrolyzed at 300 °C to obtain a low temperature tar (LTT) and a low temperature char (LTC). The LTC was then pyrolyzed at 625 °C to obtain a high temperature tar (HTT) and a high temperature char (HTC). In some cases, the LTT and HTT were subjected to higher temperatures in the range 700–920 °C to force secondary reactions. The various tars were analyzed by gas chromatography/mass spectrometry (GC/MS). In the absence of secondary reactions, asparagine and proline did not form any PACs. Tryptophan formed harman and norharman. After the secondary pyrolysis, all three amino acids formed three- and four-ring N-PACs and the yields generally increased with temperature. Asparagine and proline also formed PAHs in low yields, especially above 820 °C. The results suggest different decomposition pathways such as decarboxylation and deammoniation for the three amino acids leading to the formation of various PACs under different pyrolysis conditions.
Article
The formation of polycyclic aromatic hydrocarbons (PAHs) from the pyrolysis of cellulose over the temperature range of 300–650 °C has been investigated. Detectable amounts (microgram per gram) of 2–4 ring PAHs were observed at and above 400 °C. Benzo[a]pyrene and benz[a]anthracene were observed at and above 500 °C. Changing the gas phase residence time from 2 to 18 s and the sample size from 200 to 500 mg did not significantly affect the yields of PAHs formed over this low temperature range. The addition of oxygen to the carrier gas stream significantly reduced the yields of PAHs. The pathway to PAH formation in the 300–650 °C temperature range is believed to proceed via the carbonization process where the solid residue undergoes a chemical transformation and rearrangement to give a more condensed polycyclic aromatic structure. The evolution profiles of PAHs from the solid residue suggests that smaller 2–3 ring PAHs evolve first and pass through a maximum at a slightly lower temperature than the larger 4–5 ring PAHs. The yields of PAHs obtained from the pyrolysis of d-glucose and sucrose are comparable to those obtained from cellulose.
Article
The formation of polycyclic-aromatic hydrocarbons (PAH) from the pyrolysis of cellulose, pectin, and chlorogenic acid was studied. The primary product, mostly primary volatile tar, was exposed to a higher thermal severity, i.e. high temperatures and long residence times. The reactor setup consisted of a quartz tube with two zones, zone I and II, each heated and controlled separately. Zone I was used to first pyrolyze the substrate at 300°C to produce a low temperature tar (LTT) as well as to pyrolyze the product char at 600°C to produce a high temperature tar (HTT). The LTT and HTT were then subjected to a high thermal severity in the second zone (zone II) where the temperature was varied between 700 and 850°C. The residence time of the volatiles in zone II was varied between ca. 90 and 1400 ms (calculated at 800°C). The results showed that the yield of most PAHs increased with temperature, except in a few cases where the yield of two- and three-ring PAHs exhibited a maximum. PAHs yields also generally increased as the residence time was increased from 90 to 1400 ms at 800°C.
Article
The effect of pyrolysis conditions on the yield and composition of char from pectin was studied. Pectin is a component of the carbohydrate fraction of biomass-derived materials. The pyrolysis was done at atmospheric pressure under oxidative and non-oxidative (inert) atmospheres and at temperatures ranging from 150 to 550°C. The volatile product was analyzed by gas chromatography/mass spectrometry (GC/MS). The solid product, i.e. char, was characterized by solid-state 13C nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy. The char was also analyzed for its elemental composition and surface area. The surface morphology of char was studied by scanning electron microscopy (SEM). The results were compared to those from chlorogenic acid (CA), a component of the phenolic fraction of biomass-derived materials. The behavior of pectin was similar to that of CA. For both pectin and CA, the char yield decreased with increasing temperature before leveling-off at ca. 20% of the starting substrate in non-oxidative runs. In oxidative runs, the char yields from both substrates became negligible at 550°C. NMR analysis indicated that the aromatic character of char increased as the pyrolysis temperature increased. The oxygen functionality was progressively lost and the resonance bands corresponding to carbonyl groups mostly disappeared above 350°C. FTIR analysis also suggested the loss of hydroxyl and carbonyl groups from chars at high temperatures. The H/C and O/C ratios of chars decreased continuously with increasing temperature. The oxidative chars showed characteristics essentially similar to those of the non-oxidative chars. The surface area of char was negligible at low temperatures, but increased dramatically to a maximum of 70 m2 g−1 at 450°C before decreasing at 550°C. SEM analysis indicated that the pyrolysis of pectin occurred via softening and melting of the substrate followed by bubble formation. At high temperatures, surface etching followed by the appearance of crystal deposition on the char surfaces were also observed. The results are consistent with the analysis of the evolved gases
Article
The real time evolution kinetics of formaldehyde, hydroxyacetaldehyde, CO and CO2 during the pyrolysis of cellulose, Whatman 41, were studied in a fast evolved gas-FTIR apparatus (EGA). The samples were subjected to rapid exponential temperature increases ranging from 400 to 800°C within about one minute. A total of ten compounds were simultaneously detected in the gas phase by FTIR. Four of these: formaldehyde, hydroxyacetaldehyde, CO, and CO2, were studied in detail as a function of time.The yields of formaldehyde, hydroxyacetaldehyde and CO were found to approximately double with heating rate over the range of the experimental temperature profiles while that of CO2 decreased slightly. The kinetics of formaldehyde and CO formation were analyzed in terms of two competing first order reactions. The rate constants for the formation of formaldehyde and CO were found to have activation energies of 47 kcal/mole each while the competing reactions had activation energies of 35 kcal/mole in both cases. The case of hydroxyacetaldehyde was found to be more complex, with the same initial reactions as were found for formaldehyde and CO but requiring a third reaction step subsequent to the 47 kcal/mole reaction. The kinetics for CO2 were consistent with a single first order reaction with an activation energy of 35 kcal/mole. The results indicate that the formation reactions of formaldehyde, hydroxyacetaldehyde, CO and CO2 exhibit identical rate limiting steps that involve the major pyrolytic pathways of cellulose.
Article
Effect of pyrolysis conditions, such as temperature and substrate composition, i.e. inorganics, on the formation of polycyclic aromatic hydrocarbons (PAHs) from polyphenolic compounds, chlorogenic acid (CA) and lignin, was studied under inert atmosphere. Two routes for the PAH formation were investigated: primary volatile tar and the solid residue, i.e. char. The reactor consisted of a quartz tube with two zones. Zone 1 was used to first pyrolyze the substrate at 250–400 °C to produce a low temperature tar (LTT) and then to pyrolyze the char at 625 °C to produce a high temperature tar (HTT), The LTT and HTT were then passed through zone 2 maintained at temperatures between 700 and 920 °C. Yields of most PAHs increased with temperature, except in a few cases where the yields of two- and three-ring PAHs exhibited a maximum at 870 °C. The maximum may be due to the growth of these PAHs into heavier PAHs. The partial removal of sodium and potassium from lignin decreased the formation of char and PAHs, co-pyrolysis of CA and lignin also altered the PAH distribution. Preliminary analysis of the data from CA gave high activation energies for the PAH formation, with activation energy generally increasing with the PAH size.