Classes Of Volatile Organic Compounds Research Articles

Active Atmosphere-Ecosystem Exchange of the Vast Majority of Detected Volatile Organic Compounds

Numerous volatile organic compounds (VOCs) exist in Earth's atmosphere, most of which originate from biogenic emissions. Despite VOCs' critical role in tropospheric chemistry, studies for evaluating their atmosphere-ecosystem exchange (emission and deposition) have been limited to a few dominant compounds owing to a lack of appropriate measurement techniques. Using a high-mass resolution proton transfer reaction-time of flight-mass spectrometer and an absolute value eddy-covariance method, we directly measured 186 organic ions with net deposition, and 494 that have bidirectional flux. This observation of active atmosphere-ecosystem exchange of the vast majority of detected VOCs poses a challenge to current emission, air quality, and global climate models, which do not account for this extremely large range of compounds. This observation also provides new insight for understanding the atmospheric VOC budget.

Different Reactions of Potato Varieties to Infection by Potato Leafroll Virus, and Associated Responses by its Vector, Myzus persicae (Sulzer)

Vector-dependent plant pathogens can alter their hosts such that vector behavior and pathogen spread are affected. For example, Potato leafroll virus (PLRV)-induces changes in volatiles emitted by potato plants (Solanum tuberosum L.) that influence settling behavior by Myzus persicae, a principal vector of the virus. Prior work in this pathosystem has utilized a single potato variety, Russet Burbank, but as is true for other plant responses to biotic stresses, responses may differ among plant genotypes. To examine this, PLRV-induced changes in headspace volatile organic compounds (VOCs) and associated aphid responses to these VOCs were compared among four potato varieties (Chipeta, Desiree, IdaRose, and Russet Burbank). Total headspace VOCs differed among the varieties and were differentially induced by PLRV infection such that the effect of variety, infection, and their interaction was significant; two of the varieties had increased concentrations of headspace VOCs, and two did not. MANOVA for the effect of infection and variety on total VOCs and major VOC classes also was significant. A principal component analysis (PCA) partially separated the VOC profiles from the four varieties. Aphid arrestment differed in response to the VOCs of the four varieties, and was greater on those that were more readily infected by PLRV (Desiree and Russet Burbank) as compared with those that were less readily infected (Chipeta and IdaRose). Aphid responses were not clearly related to specific characteristics of blends, such that total VOCs and composition appear to contribute. The four varieties used in this study have distinct pedigrees representative of different cultivated forms of S. tuberosum. Although cultivated potato varieties have been subjected to genetic manipulation by humans, the differences in PLRV induced changes in VOCs nonetheless indicate the potential for complex effects of PLRV infection on host plant VOC emissions, and vector responses in managed, and natural systems.

Field Effect Transistors Based on Polycyclic Aromatic Hydrocarbons for the Detection and Classification of Volatile Organic Compounds

We show that polycyclic aromatic hydrocarbon (PAH) based field effect transistor (FET) arrays can serve as excellent chemical sensors for the detection of volatile organic compounds (VOCs) under confounding humidity conditions. Using these sensors, w/o complementary pattern recognition methods, we study the ability of PAH-FET(s) to: (i) discriminate between aromatic and non-aromatic VOCs; (ii) distinguish polar and non-polar non-aromatic compounds; and to (iii) identify specific VOCs within the subgroups (i.e., aromatic compounds, polar non-aromatic compounds, non-polar non-aromatic compounds). We further study the effect of water vapor on the sensor array's discriminative ability and derive patterns that are stable when exposed to different constant values of background humidity. Patterns based on different independent electronic features from an array of PAH-FETs may bring us one step closer to creating a unique fingerprint for individual VOCs in real-world applications in atmospheres with varying levels of humidity.

VOCs classification based on the committee of classifiers coupled with single sensor signals

A gas classification method based on a Multiple Classifiers System (MCS) is presented in this paper. The novelty of the approach consists in utilizing a signal of one sensor as the information source of a single member of the classifier ensemble. The size of the committee is delimited by the number of sensors applied for solving gas identification problems. The following base classifiers were considered: Support Vector Machine (SVM), the k-Nearest Neighbor (k-NN) method and two kinds of decision trees — CART and C4.5. Additionally, three fusion strategies were examined: majority voting, weight assignment based on the individual accuracy of the committee member and optimal weights combination found by the genetic algorithm. The MCSs performance was compared with the effectiveness of single classifiers which operated on the data set containing the response of the entire sensor array. The sensor signal compression by means of granulation was applied as the data pre-processing step. The classification problem consisted in recognizing volatile organic compounds (VOCs) in air, based on measurements performed by the array composed of fifteen semiconductor gas sensors. These devices were operated in the stop flow mode. Thus their signals were affected by many factors associated with altering exposure conditions, which enhanced the discrimination abilities of the sensors.

Towards fully printed capacitive gas sensors on flexible PET substrates based on Ag interdigitated transducers with increased stability

Interdigitated capacitive transducers have been inkjet printed onto flexible substrates and optimized for gas sensing applications. Their characteristics have been improved by tuning the annealing/sintering conditions and making use of additional passivation procedures, such as Ag electroplating with Ni or Parylene-C coating of the whole device surface.The as-prepared transducers printed with Ag ink could be utilized in capacitive gas sensing structures up to 70% relative humidity only. Higher humidity levels irreversibly altered the nominal capacitance and conductance of the devices, limiting their practical application. This drawback could be eliminated through the upgrading routes specified above and stable operation over wide temperature ranges has been achieved.From the acquired data a quite accurate description of the sorption processes, involving the printed conducting layers and the supporting material, has been inferred.Furthermore the parasitic sensitivity to test vapours from the class of Volatile Organic Compounds in the concentration range of Threshold Limit Value - Time-Weighted Average as possible interfering analytes has been estimated.Test gas sensors obtained from the optimized transducers by additional coating with gas sensing films poly(ether urethane) successfully passed the laboratory evaluations and seem to be appropriate for use in real devices.

ChemInform Abstract: Kinetics, Products, and Mechanisms of Secondary Organic Aerosol Formation

AbstractReview: 200 refs.

Large-Scale Chemical Sensor Array Testing Biological Olfaction Concepts

Biological olfactory systems are characterized by a large number of sensors with broad overlapping specificities. The sensitivity and selectivity of the system may be enhanced by the huge redundancy of the olfactory receptor neurons (ORNs). A European project, NEUROCHEM, was devoted to test computational models of the olfactory system of vertebrates and insects. To test these models, a realistic artifact of the olfactory epithelium was developed as a large sensor array mimicking some features of biological ORNs, in particular, the broad and overlapping selectivity to many odors, the combinatorial response, the high level of redundancy, and the different dynamic ranges exhibited by same types of ORNs. The sensor array is composed of 16 384 elements arranged in four smaller arrays of 64 × 64 interdigitated electrodes deposited on a borosilicate substrate. To mimic the redundancy of the biological ORNs, tens of organic conductive polymers were chosen as active sensing materials because of their broad and diverse, but overlapping, specificity to different classes of volatile organic compounds. These sensors were characterized by their responses to varying concentrations of test analytes. The collected sensor data were processed with standard multivariate techniques and the results are reported in this paper.

Differential binding between volatile ligands and major urinary proteins due to genetic variation in mice

Two different structural classes of chemical signals in mouse urine, i.e., volatile organic compounds (VOCs) and the major urinary proteins (MUPs), interact closely because MUPs sequester VOCs. Although qualitative and/or quantitative differences in each chemical class have been reported, previous studies have examined only one of the classes at a time. No study has analyzed these two sets simultaneously, and consequently binding interactions between volatile ligands and proteins in urines of different strains have not been compared. Here, we compared the release of VOCs in male urines of three different inbred strains (C57BL/6J, BALB/b and AKR) before and after denaturation of urinary proteins, mainly MUPs. Both MUP and VOC profiles were distinctive in the intact urine of each strain. Upon denaturation, each of the VOC profiles changed due to the release of ligands previously bound to MUPs. The results indicate that large amounts of numerous ligands are bound to MUPs and that these ligands represent a variety of different structural classes of VOCs. Furthermore, the degree of release in each ligand was different in each strain, indicating that different ligands are differentially bound to proteins in the urines of different strains. Therefore, these data suggest that binding interactions in ligands and MUPs differ between strains, adding yet another layer of complexity to chemical communication in mice.

Simultaneous indoor and outdoor on-line hourly monitoring of atmospheric volatile organic compounds in an urban building. The role of inside and outside sources

Indoor air quality (IAQ) has become a very important issue in recent years. As in developed countries people spend more than 90% of their time indoors, besides outdoor pollution assessment, the indoor one is also required. IAQ is not only affected by indoor sources linked to indoor activities, outdoor sources such as road or street traffic and industrial and commercial activities have their role too. Volatile organic compounds (VOCs) frequently show higher indoor mixing ratios with respect to the outdoor ones, and monitoring is required to report their indoor mixing ratios.Many studies have reported average indoor VOCs' mixing ratios in different environments, but their temporal variability has not been well documented. The main objective of this work was to simultaneously measure VOCs' indoor and outdoor mixing ratios with high time-resolution in order to assess the effect of sources inside and outside the building upon indoor mixing ratios of individual VOCs. Simultaneous hourly, continuous, and on-line measurements of C2–C11 VOCs were performed inside and outside the School of Engineering of Bilbao (ETSI) building, located in the city center of Bilbao, an urban area in Northern Spain.The analysis of simultaneous data allowed the classification of VOCs based on their main sources. Some VOCs were mainly emitted by indoor sources (1-pentene, 2-methylpentane, n-hexane, methylcyclopentane, benzene, 1-heptene+2,2,4-trimethylbenzene, and tetrachloroethylene) or by outdoor sources (n-heptane, C8 alkanes except trimethylpentanes and C9 aromatics). Other VOCs, such as toluene, were emitted by both indoor and outdoor sources. The isoprene indoor pattern indicated that its main indoor source could be the air exhaled by people occupying the building. Some halocarbons, such as trichloroethylene, tetrachloroethylene, and carbon tetrachloride may be generated from the use inside the building of chlorine bleach containing products.

REMOVAL OF TOLUENE AND DICHLOROMETHANE FROM AQUEOUS PHASE BY GRANULAR ACTIVATED CARBON (GAC)

Chlorinated hydrocarbons and aromatics constitute the major class of volatile organic compounds that contaminate groundwater. In this study, the equilibrium uptake and column dynamics for the adsorption of dichloromethane (as a typical chlorinated hydrocarbon) and toluene (as a representative of aromatic compounds) from aqueous phase on coal-based granular activated carbon (GAC) were investigated. The adsorption isotherms were measured in a temperature range of 20–40°C. The experimental data obtained were correlated with several adsorption isotherm models. The Langmuir model was well adapted to describe the dichloromethane adsorption on GAC, while the adsorption of toluene on GAC was found to be well described by the Langmuir-BET hybrid model in the stated temperature range with R-squared value of about 0.99. The variations in adsorption breakthrough curves of toluene and dichloromethane with respect to operational parameters such as initial concentration, flow rate, column length, and temperature were investigated. The experimental breakthrough curves of both adsorbates are well fitted by Yan's model with high accuracy (R-squared value of 0.98–99) in most cases.

Kinetics, products, and mechanisms of secondary organic aerosol formation

Secondary organic aerosol (SOA) is formed in the atmosphere when volatile organic compounds (VOCs) emitted from anthropogenic and biogenic sources are oxidized by reactions with OH radicals, O(3), NO(3) radicals, or Cl atoms to form less volatile products that subsequently partition into aerosol particles. Once in particles, these organic compounds can undergo heterogenous/multiphase reactions to form more highly oxidized or oligomeric products. SOA comprises a large fraction of atmospheric aerosol mass and can have significant effects on atmospheric chemistry, visibility, human health, and climate. Previous articles have reviewed the kinetics, products, and mechanisms of atmospheric VOC reactions and the general chemistry and physics involved in SOA formation. In this article we present a detailed review of VOC and heterogeneous/multiphase chemistry as they apply to SOA formation, with a focus on the effects of VOC molecular structure on the kinetics of initial reactions with the major atmospheric oxidants, the subsequent reactions of alkyl, alkyl peroxy, and alkoxy radical intermediates, and the composition of the resulting products. Structural features of reactants and products discussed include compound carbon number; linear, branched, and cyclic configurations; the presence of C[double bond, length as m-dash]C bonds and aromatic rings; and functional groups such as carbonyl, hydroxyl, ester, hydroxperoxy, carboxyl, peroxycarboxyl, nitrate, and peroxynitrate. The intention of this review is to provide atmospheric chemists with sufficient information to understand the dominant pathways by which the major classes of atmospheric VOCs react to form SOA products, and the further reactions of these products in particles. This will allow reasonable predictions to be made, based on molecular structure, about the kinetics, products, and mechanisms of VOC and heterogeneous/multiphase reactions, including the effects of important variables such as VOC, oxidant, and NO(x) concentrations as well as temperature, humidity, and particle acidity. Such knowledge should be useful for interpreting the results of laboratory and field studies and for developing atmospheric chemistry models. A number of recommendations for future research are also presented.

Sensing of Vaporous Organic Compounds by TiO2 Porous Films Covered with Polythiophene Layers

AbstractThis paper describes the detection of volatile organic compounds (VOCs) through analyses of two output signals from integrated microcantilever sensor arrays coated with organic‐inorganic hybrid sensing layers. The surface of TiO2 porous films was modified by amphiphilic terthiophene monomers and the adsorbed monomers were polymerized at the surface of TiO2 nanoparticles. The TiO2 porous films covered with polythiophene layers worked as highly sensitive sensing interfaces to provide two output signals for weight and resistance changes during exposure to VOC vapor. When the TiO2 porous films onto the sensor arrays were dyed with various kinds of amphiphilic monomers with different substituents, the resulting films provide exact information on VOC concentration from the mass changes as well as VOC classification from the analyses of response patterns.

Fluorescent Gas Sensors Based on Nanoporous Optical Resonators (Microcavities) Infiltrated With Sensory Emissive Polymers

In this contribution, we report fluorescent gas chemosensors for detection of nitroaromatic vapors and other classes of volatile organic compounds based on porous silicon (PSi) microcavity (MC) infiltrated with sensory emissive polymers. Such hybrid functional sensors have several advantages over traditional fluorescent chemosensors, where the sensory polymers are deposited on flat substrate. This includes a high interfacial area of nanoporous Si (high sensitivity), narrow fluorescent band due to photon confinement, dependence of the spectral peak position on nature of analyte (enhanced selectivity), and fast recovery time. We demonstrated that deep and uniform polymer infiltration is critical for effective gas sensing and investigated the experimental conditions required for preparation of high-quality hybrid sensors. In the case of deep infiltration, the broad polymer fluorescence (FWHM ~100 nm) shows a narrowing to the resonance peak (FWHM ~10 nm) with narrow intensity angle diagram. In addition, the potential of the sensor array platform and sensor recovery under ultrasound power is discussed.

Characterizations of volatile organic compounds during high ozone episodes in Beijing, China

Air samples were collected in Beijing from June through August 2008, and concentrations of volatile organic compounds (VOCs) in those samples are here discussed. This sampling was performed to increase understanding of the distributions of their compositions, illustrate the overall characteristics of different classes of VOCs, assess the ages of air masses, and apportion sources of VOCs using principal compound analysis/absolute principal component scores (PCA/APCS). During the sampling periods, the relative abundance of the four classes of VOCs as determined by the concentration-based method was different from that determined by the reactivity approach. Alkanes were found to be most abundant (44.3-50.1%) by the concentration-based method, but aromatic compounds were most abundant (38.2-44.5%) by the reactivity approach. Aromatics and alkenes contributed most (73-84%) to the ozone formation potential. Toluene was the most abundant compound (11.8-12.7%) during every sampling period. When the maximum incremental reactivity approach was used, propene, toluene, m,p-xylene, 1-butene, and 1,2,4-trimethylbenzene were the five most abundant compounds during two sampling periods. X/B, T/B, and E/B ratios in this study were lower than those found in other cities, possibly due to the aging of the air mass at this site. Four components were extracted from application of PCA to the data. It was found that the contribution of vehicle exhaust to total VOCs accounted for 53% of VOCs, while emissions due to the solvent use contributed 33% of the total VOCs. Industrial sources contributed 3% and biogenic sources contributed 11%. The results showed that vehicle exhausts (i.e., unburned vehicle emissions+ vehicle internal engine combustion) were dominant in VOC emissions during the experimental period. The solvent use made the second most significant contribution to ambient VOCs.

Multi-day ozone production potential of volatile organic compounds calculated with a tagging approach

Calculation of the ozone production potential of Volatile Organic Compounds (VOC) has traditionally been performed using so-called incremental reactivity techniques, requiring multiple photochemical model runs in which the combined direct and indirect effects on ozone from slight perturbations to each VOC are investigated in turn. A new approach to this problem is presented here using an extensively tagged chemical mechanism, in which the direct effects of VOC on ozone are calculated using a single model run. The results of this approach are consistent with previous work, but deliver much more detailed information about the VOC intermediate oxidation products involved in the production of ozone. We show that different classes of VOC exhibit very different temporal evolution in their ozone production potential, with alkenes and reactive aromatic VOC producing ozone rapidly, while the ozone production potential of alkanes increases in the day after they are emitted. We suggest that this is related to the rate at which these different classes of compounds are able to produce very small oxidation fragments. This multi-day ozone production potential has implications for emission control strategies for the management of air quality in polluted regions. We also relate the ozone production potential of VOC to the OH reactivity of the VOC oxidation intermediates, and show that the early oxidation products of alkenes and reactive aromatics are more efficient at producing ozone in their subsequent reactions with OH than similarly reactive alkanes. While this study examines idealised chemical conditions in a box model, the techniques employed here could potentially be adapted to the study of a wider range of atmospheric conditions using three-dimensional air quality models.

Infinite-Dilution Activity Coefficients of Volatile Organic Compounds in Cyclic Olefin Copolymers

Infinite-dilution activity coefficients for nine classes of volatile organic compounds (paraffins, olefins, cycloparaffins, aromatics, ketones, nitriles, alcohols, esters, and chlorocompounds) in a series of four cyclic olefin copolymers were determined using an inverse gas chromatography technique with a packed column. Abraham’s equation of solvation was used for the evaluation of the different types of interactions between the solvents and polymers. The results are compared with the activity coefficients at infinite dilution obtained for other polymers of similar use.

Sources of Glycol Ether Exposure at Home

O-30A7-5 Background/Aims: Glycol ethers are a group of globally consumed high-production-volume chemicals with wide uses in consumer products and building materials. Despite their well-demonstrated endocrine disrupting properties in several animal species, possible human health effects remain mostly unknown. Furthermore, indoor sources and occupant behavior that modify emission and/or retention have never been examined. Thus, we investigated indoor sources and lifestyle practices that contribute to an elevated indoor level of glycol ethers within 390 homes of preschool age children in Sweden. Methods: In a case-control investigation of 198 cases with multiple allergic symptoms and 202 healthy controls, air samples were collected in the room where the child spent most time. The air samples were analyzed for the levels of 8 classes of volatile organic compounds. Six home environment inspectors visually examined each home for water damages, presence of mold odor, building's structural characteristics, indoor temperature, relative humidity, and air exchange rate. Results: Frequent use of water-based cleaning agent and recent history of repainting at least 1 of the rooms significantly contributed to an elevated glycol ether concentrations at home. When the subjects were restricted to those who live in concrete-based structure, self-reported dampness in the concrete-based homes were associated with an elevated mean GGE concentrations. The indoor concentration of glycol ethers were further elevated in homes with highest quartile relative humidity or temperature. Conclusion: Multiple sources and human behavior contribute to home glycol ethers levels. Intervention efforts targeting behavior change of residential occupants might reduce glycol ether concentrations in the indoor air.

Indoor air quality in elementary schools of Lisbon in spring

Analysis of indoor air quality (IAQ) in schools usually reveals higher levels of pollutants than in outdoor environments. The aims of this study are to measure indoor and outdoor concentrations of NO(2), speciated volatile organic compounds (VOCs) and carbonyls at 14 elementary schools in Lisbon, Portugal. The investigation was carried out in May-June 2009. Three of the schools were selected to also measure comfort parameters, such as temperature and relative humidity, carbon dioxide (CO(2)), carbon monoxide (CO), total VOCs, and bacterial and fungal colony-forming units per cubic metre. Indoor concentrations of CO(2) in the three main schools indicated inadequate classroom air exchange rates. The indoor/outdoor (I/O) NO(2) ratio ranged between 0.36 and 0.95. At the three main schools, the total bacterial and fungal colony-forming units (CFU) in both indoor and outdoor air were above the advised maximum value of 500CFU/m(3) defined by Portuguese legislation. The aromatic compounds benzene, toluene, ethylbenzene and xylenes, followed by ethers, alcohols and terpenes, were usually the most abundant classes of VOCs. In general, the indoor total VOC concentrations were markedly higher than those observed outdoors. At all locations, indoor aldehyde levels were higher than those observed outdoors, particularly for formaldehyde. The inadequate ventilation observed likely favours accumulation of pollutants with additional indoor sources.

Common Household Chemicals and the Allergy Risks in Pre-School Age Children

BackgroundThe risk of indoor exposure to volatile organic compounds (VOCs) on allergic airway diseases in children remains unknown.ObjectiveWe examined the residential concentrations of VOCs, emitted from building materials, paints, furniture, and other lifestyle practices and the risks of multiple allergic diseases as well as the IgE-sensitization in pre-school age children in Sweden.MethodsIn a case-control investigation (198 case children with asthma and allergy and 202 healthy controls), air samples were collected in the room where the child slept. The air samples were analyzed for the levels of eight classes of VOCs.ResultsA natural-log unit of summed propylene glycol and glycol ethers (PGEs) in bedroom air (equal to interquartile range, or 3.43 – 15.65 µg/m3) was associated with 1.5-fold greater likelihood of being a case (95% CI, 1.1 – 2.1), 1.5-fold greater likelihood of asthma (95% CI, 1.0 – 2.3), 2.8-fold greater likelihood of rhinitis (95% CI, 1.6 – 4.7), and 1.6-fold greater likelihood of eczema (95% CI, 1.1 – 2.3), accounting for gender, secondhand smoke, allergies in both parents, wet cleaning with chemical agents, construction period of the building, limonene, cat and dog allergens, butyl benzyl phthalate (BBzP), and di(2-ethylhexyl)phthalate (DEHP). When the analysis was restricted to the cases, the same unit concentration was associated with 1.8-fold greater likelihood of IgE-sensitization (95% CI, 1.1 – 2.8) compared to the non-IgE sensitized cases. No similar associations were found for the other classes of VOCs.ConclusionWe propose a novel hypothesis that PGEs in indoor air exacerbate and/or induce the multiple allergic symptoms, asthma, rhinitis and eczema, as well as IgE sensitization respectively.

Pattern Classification of Volatile Organic Compounds in Various Indoor Environments

The purpose of this study was to survey the distribution patterns of volatile organic compounds (VOCs) and formaldehyde in the various indoor environments using cluster analysis. We investigated VOCs and formaldehyde in subway stations, underground shopping areas, medical centers, maternity recuperation centers, public childcare centers, large stores, funeral homes, and indoor parking lots from June 2005 to May 2006 (9 p.m. to 6 a.m.). The concentration of total volatile compounds (TVOCs) in maternity recuperations was 2,605.7 μg/m3, which was higher than that stated in the guideline and other chosen facilities. TVOCs in public childcare centers were 1,951.6 μg/m3, which also exceeded the guideline. Moreover, the concentration of TVOCs in every facility exceeded the guideline of the Ministry of Environment, Korea. In the case of formaldehyde, the mean concentration of 336.5 μg/m3 found only in public childcare centers exceeded the 120 μg/m3 stated in the guideline. Finally, by applying cluster analysis, three patterns of the indoor air pollutions were distinguished. In the results of the analysis, concentrations of TVOCs and formaldehyde of cluster 3 were higher than clusters 1 and 2, which were 2,561.4 and 184.9 μg/m3, respectively.