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Results for “Volatile Organic Compounds”

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PubMed2006

Testing VOC emission measurement techniques in wood-coating industrial processes and developing a cost-effective measurement methodology.

Availability of reliable emission measurements of concentrated volatile organic compounds (VOCs) bear great significance in facilitating the selection of a feasible emission abatement technique. There are numerous methods, which can be used to measure VOC emissions, however, there is no single method that would allow sampling of the whole range of volatile organics. In addition, research efforts are usually directed to the development of measuring VOCs in diluted concentrations. Therefore, there is a need for a novel measurement method, which can give reliable results while entailing simple operations and low costs. This paper represents a development effort of finding a reliable measurement procedure. A methodology is proposed and used to measure solvent emissions from coating processes.

Air Pollutants↗

PubMed1983

A simple dynamic flow-through exposure system for assessment of biological activity of complex organic mixtures to mammalian cells in vitro.

A system for in vitro exposure of lung epithelial cells and Chinese hamster ovary cells maintained at an air-medium interface to volatile organic compounds has been developed. The system has been used for exposure of cells to phenol (vapor pressure at 40 degrees C = 1.6 mm Hg) and to a complex mixture of organic compounds (vapor pressure range at 32 degrees C = 0.17 to 269 mm Hg). A linear relationship was found between vapor generator air flow rate (0.25 to 1.0 L/min at 39 degrees C) and exposure chamber phenol concentration. The relationship between generator air flow rate (0.5 to 1.0 L/min at 39 degrees C) and concentration of the complex mixture in the exposure chamber was also linear. Gas chromatographic analyses of chamber exhaust indicated that a majority of the compounds present in the crude mixture had been volatilized and made available to the cells in the chamber. This exposure system appears suitable for screening of complex mixtures of volatile organic pollutants for biological activity in mammalian cells in culture.

Air Movements↗

PubMed1992

[The two ozone problems: too much in the troposphere, too little in the stratosphere].

Trends analysis based on the long-term Swiss ozone measurements from Arosa and Payerne operationally performed by the Swiss Meteorological Institute are presented. These measurement include stratospheric ozone (approximately 90% of total ozone) and tropospheric ozone. The total ozone measurements from Arosa, the world longest series started at 1926, indicate, that total ozone has declined since about 1970 by approximately 5%. The ozone balloon soundings, operationally performed at Payerne since 1969 (2-3 ascents per week) show, that stratospheric ozone has decreased strongly in the last 20 years, whereas tropospheric ozone, remarkably has increased during this period. The relative change was strongest in the troposphere (more than 10% per decade, 3-4% increase per year during 1982-1988). However, on an absolute scale, changes in the stratosphere were strongest (relative decrease: 6 to 7% per decade at 20-22 km). The present scientific theories of the two ozone problems are reviewed: stratospheric ozone decrease was caused by the anthropogenic emissions of fluorochlorocarbons and other compounds mainly released from the earth surface. Tropospheric ozone has increased due to photochemical production of mainly anthropogenically emitted nitrogen oxides, volatile organic compounds and CO.

Atmosphere↗

PubMed2005

Experimental determination and calculation of distribution coefficients between air and fiber with polydimethylsiloxane coating for some groups of organic compounds.

This paper reports the results of experimental determination of distribution coefficients K(fa) for five terpene hydrocarbons and five aliphatic ketones between air and polydimethylsiloxane (PDMS) coating for solid-phase microextraction. To estimate the values of K(fa) for compounds of the same classes, which did not undergo experiments, it is proposed to use an empirical two-parameter equation in which various physicochemical and structural characteristics weakly correlated with each other are used as descriptors. It is also shown that for these purposes it is possible to use distribution coefficients of compounds in any other two-phase heterogeneous system, e.g. octanol-water or hexane-acetonitrile. This approach was applied to estimate K(fa) values of 92 volatile organic compounds.

Air↗

PubMed2005

On-line multi-bed sorption trap for VOC analysis of large-volume vapor samples: injection plug width, effects of water vapor and sample decomposition.

A multibed on-line sorption trap is used to preconcentrate organic vapors from air samples and inject the analytes into a GC separation column. Injection plug widths depend on the boiling point for the lipophilic compounds and on the polarity and boiling point for the polar compounds. Injection plug widths are sufficiently small (0.7-0.8 s) as to allow the direct injection of the most volatile compounds into the GC column without the need for a second focusing device. The presence of water in the samples has an effect on the retention of polar compounds by the trap. However, this effect is reproducible for a fixed water content and so can be overcome by using calibration standards under the same conditions of humidity as the samples. The thermal decomposition of many volatile organic compounds in an on-line sorption trap during the GC analysis of air samples is examined. The results show that degradation of unstable compounds is governed by the amount of heat transferred to the compounds during desorption (i.e., applied temperature and pulse duration). The use of an on-line trap results in the immediate transfer of desorbed compounds to the analytical column, which can reduce the formation of artifacts.

Journal Article↗

PubMed2000

Exposure to airborne fungi, MVOC and mycotoxins in biowaste-handling facilities.

Health impacts due to fungi in indoor air can only be estimated reliably, if both fungal propagules and fungal secondary metabolites are qualified and quantified. In the present study, the fungal species composition in a compost facility is compared to the spectrum of microbial metabolites in the air with regard to the physiological properties of different fungal species. A number of relevant fungi was tested for the production of both volatile and non-volatile metabolites on different substrata. The profiles of mycotoxins and microbial volatile organic compounds (MVOC) turned out to be specific for certain species in pure culture. Consequently, the fungi may have different toxicological health impacts, though information on the relevance of microbial volatiles is still limited.

Air Microbiology↗

PubMed2005

Identification of volatile basic components in tobacco by headspace liquid-phase microextraction coupled to matrix-assisted laser desorption/ionization with Fourier transform mass spectrometry.

A method incorporating headspace liquid-phase microextraction (HS-LPME) coupled to matrix-assisted laser desorption/ionization (MALDI) with Fourier transform mass spectrometry (FTMS) was established to analyze volatile basic components in tobacco. The sample preparation volume for MALDI-MS was compatible with the volume of the solvent microdrop in the HS-LPME procedure. The pH and the polarity of the solvent for HS-LPME were adjusted by choice of the MALDI matrix and matrix additive. Based on the elemental composition and tandem mass spectrometry information, 25 volatile nitrogenous compounds in tobacco were detected and identified. The approach is fast and sensitive, and has the potential for automation for high-throughput analysis. This approach offers an alternative method for analysis of trace volatile organic compounds in complex samples.

Gas Chromatography-Mass Spectrometry↗

PubMed2005

Nucleation particles in diesel exhaust: composition inferred from in situ mass spectrometric analysis.

Mass spectrometric measurements of size and composition of diesel exhaust particles have been performed under various conditions: chassis dynamometer tests, field measurements near a German motorway, and individual car chasing. Nucleation particles consisting of volatile sulfate and organic material could be detected both at the chassis dynamometer test facility and during individual car chasing. We found evidence that if nucleation occurs, sulfuric acid/water is the nucleating agent. Low-volatile organics species condense only on the preexisting sulfuric acid/water clusters. Nucleation was found to depend strongly on various parameters such as exhaust dilution conditions, fuel sulfur content, and engine load. The latter determines the fraction of the fuel sulfur that is converted to sulfuric acid. The organic compounds (volatile and low-volatile) condense only on preexisting particles, such as both sulfuric acid nucleation particles and larger accumulation mode soot particles. On the latter, sulfuric acid also condenses, if the conditions for nucleation are not given. The overall ratio of sulfate to organic (volatile and low-volatile) is also strongly dependent on the engine load. It was found that the production of nucleation particles even at high engine load can be suppressed by using low-sulfur fuel.

Air Pollutants↗

PubMed2004

Class separation of buildings with high and low prevalence of SBS by principal component analysis.

In this study, we were able to separate buildings with high and low prevalence of sick building syndrome (SBS) using principal component analysis. The prevalence of SBS was defined by the presence of at least one typical skin, mucosal and general (headache and fatigue) symptom. Data from the Swedish Office Illness Study describing the presence and level of chemical compounds in outdoor, supply, and room air, respectively, were evaluated together with information about the buildings in six models. When all data were included the most complex model was able to separate 71% of the high prevalence buildings from the low prevalence buildings. The most important variable that separates the high prevalence buildings from the low prevalence buildings was a more frequent occurrence or a higher concentration of compounds with shorter retention time in the high prevalence buildings. Elevated relative humidity in supply and room air and higher levels of total volatile organic compounds in outdoor and supply air were more common in high prevalence buildings. Ten building variables also contributed to the separation of the two classes of low and high prevalence buildings.

Air Pollutants↗

PubMed2005

Health complaints and annoyances after moving into a new office building: a multidisciplinary approach including analysis of questionnaires, air and house dust samples.

After moving into a new office building, employees complained about eye irritations, sore throats and unspecific symptoms. They were concerned about visible dust as a potential cause of adverse health effects. An external working group was appointed to investigate indoor air pollution and health complaints and to suggest measures to improve the situation. Air samples and floor dust samples for analysis of organic compounds were collected in three offices. Bimonthly during 8 months, measurement campaigns were conducted to assess the trend of air pollutants. A questionnaire was administered concerning environmental conditions at the work place and complaints before and after moving into the new office building. Overall the concentrations of volatile organic compounds (VOC) and formaldehyde were fairly low. However, initially high concentrations (4300-7800 mg/kg) of tris-(2-butoxyethyl)-phosphate (TBEP) and diethylhexylphthalate (DEHP: 980-3000 mg/kg) were found in dust samples. The coating of the rubber floor was identified as the source of TBEP, while no single predominant source of DEHP was found. Results of the questionnaire demonstrated an increased irritation of the mucous membranes and a reduction of well-being after the employees had moved into the new building. Perception of low relative humidity and high temperature as well as unpleasant odors were associated with respiratory complaints. After removal of the coating of the rubber floor throughout the whole building, a reduction up to 90% of TBEP in the dust samples was found. In spite of several attempts, no such marked reduction was achieved with the concentration of phthalates. Although there was no significant association between visible dust exposure and increase of complaints after moving in, room climate conditions that could increase the deposition of dust in the airways were associated with the complaints. Hence it cannot be ruled out that fine dust containing TBEP together with unfavorable indoor factors were responsible for the development of the complaints.

Air Pollutants↗

PubMed2004

Occurrence and abatement of volatile sulfur compounds during biogas production.

Volatile sulfur compounds (VSCs) in biogas originating from a biogas production plant and from a municipal sewage water treatment plant were identified. Samples were taken at various stages of the biogas-producing process, including upgrading the gas to vehicle-fuel quality. Solid-phase microextraction was used for preconcentration of the VSCs, which were subsequently analyzed using gas chromatography in combination with mass spectrometry. Other volatile organic compounds present also were identified. The most commonly occurring VSCs in the biogas were hydrogen sulfide, carbonyl sulfide, methanethiol, dimethyl sulfide, and dimethyl disulfide, and hydrogen sulfide was not always the most abundant sulfur (S) compound. Besides VSCs, oxygenated organic compounds were commonly present (e.g., ketones, alcohols, and esters). The effect of adding iron chloride to the biogas reactor on the occurrence of VSCs also was investigated. It was found that additions of 500-g/m3 substrate gave an optimal removal of VSCs. Also, the use of a prefermentation step could reduce the amount of VSCs formed in the biogas process. Moreover, in the carbon dioxide scrubber used for upgrading the gas, VSCs were removed efficiently, leaving traces (ppbv levels). The scrubber also removed other organic compounds.

Air Pollutants↗

PubMed2003

Positive and negative gas-phase ion chemistry of chlorofluorocarbons in air at atmospheric pressure.

This paper presents a report on the ionization/dissociation of some representative chlorofluorocarbons (CFCs) induced by corona discharges in air at atmospheric pressure. Both positive and negative ions formed from Freons 1,1,1-trichlorotrifluoroethane (CFC 113a), 1,1,2-trichlorotrifluoroethane (CFC 113), and 1,1,1,2-tetrachlorodifluoroethane (CFC 112a) were analyzed using an atmospheric pressure chemical ionization mass spectrometry (APCI-MS) instrument. Energy-resolved mass spectra were obtained by modulating the kinetic energy of the ions via adjustment of the sampling cone potential (V(cone)). Positive ion spectra of the CFCs (M) at low V(cone) show no signals due to either M(+)* or MH(+) but only those due to species [M - Cl](+) and CX(3)(+) (X = Cl, F), likely formed via C-Cl and C-C bond cleavages following ionization via charge exchange. Charge localization in the products of C-C bond cleavage in M(+)* is driven by the stability of the neutral fragment. At low V(cone) the hydrates [M - Cl](+)(H(2)O) are also observed. In the case of 1,1,2,-trichlorotrifluoroethane, [M - F](+) species also form as a result of ion-molecule reactions. As V(cone) is increased collision-induced dissociation of [M - Cl](+) and [M - F](+), i.e., the perhalogenated cations C(2)X(5)(+) (X = Cl, F), takes place via carbene elimination. In some cases such elimination is preceded or accompanied by rearrangements involving transfer of halogen from one carbon to the other. Evidence is also presented for the occurrence of a condensation reaction of C(2)Cl(3)F(2)(+) with water to form a C(2)Cl(2)F(2)HO(+) species via elimination of HCl. Negative ion spectra are dominated by Cl(-) and its ion-neutral complexes with M and with water. Additional components of the plasma include ion-neutral complexes O(3)(-)(M), the molecular anion M(-) (observed only with 1,1,2-trichlorotrifluoroethane), and an interesting species corresponding to [M - Cl + O](-). The origin and structure of these [M - Cl + O](-) species are discussed in terms of available thermochemical and reactivity data and current mechanistic views concerning reaction of O(2)(-) with halogenated compounds. The observation of both positive and negative ions containing oxygen is of special relevance to development of new processes for the treatment of volatile organic compounds (VOCs) based on oxidative decomposition induced by corona discharges in air at room temperature and pressure.

Journal Article↗

PubMed2006

Absolute configuration of volicitin from the regurgitant of lepidopteran caterpillars and biological activity of volicitin-related compounds.

Volicitin [N-(17-hydroxylinolenoyl)-L-glutamine] and N-linolenoyl-L-glutamine are known as insect-produced plant volatile elicitors. The absolute configuration of the hydroxylinolenoyl moiety of volicitin from three noctuid species, Helicoverpa armigera, Mythimna separata and Spodoptera litura, was determined to be all 17S in high enantiomeric excess. When treated with 30 pmol of (17S)- and (17R)-volicitin, corn seedlings were induced to release volatiles, there being no significant difference in the amount released between the two isomers. On the other hand, N-linolenoyl-L-glutamine was only about 30% as active as volicitin. Among several synthesized N-linolenoylamino acid conjugates, only the L-glutamine conjugate induced the emission of volatile organic compounds. These results show that the L-glutamine moiety of volicitin played a more critical role than the hydroxyl moiety, although both moieties affected the elicitor activity inducing the release of volatiles.

Animals↗

PubMed2001

Headspace solvent microextraction.

A hanging microliter drop of 1-octanol is shown to be an excellent preconcentration medium for headspace analysis of volatile compounds in an aqueous matrix by gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). Model compounds benzene, toluene, ethylbenzene, and o-xylene (BTEX) are conveniently and rapidly preconcentrated in the microdrop. An internal standard, decane, is present in the organic extracting solvent, and linear calibration curves of relative peak area versus aqueous concentration are obtained for the four model compounds. Detailed kinetic studies reveal that the overall rate of mass transfer is limited by both the aqueous-phase stirring rate and the degree of convection within the organic phase. The very low vapor pressure of 1-octanol results in minimal evaporation of the microdrop during the extraction time. This system represents an inexpensive, convenient, and precise sample cleanup and preconcentration method for the determination of volatile organic compounds at trace levels.

Journal Article↗

PubMed1988

Sampling and analysis techniques for trace volatile organic emissions from consumer products.

Comparisons are made of two techniques for the trace analysis of volatile organic compound (VOC) emissions from consumer products: direct on-line sampling and analysis and on-line solid sorbent collection followed by off-line analysis. Two types of direct analyses are examined. The first consists of direct injection of emissions from a sample loaded environmental chamber into a gas chromatograph equipped with a flame ionization detector (FID) for compound identification. Direct injection of headspace collected emissions into a gas chromatograph equipped with a mass selective detector is the second direct method scrutinized. The more traditional technique of solid sorbent collection of the volatile organic emissions followed by thermal desorption (TD)/gas chromatographic (GC)/mass spectrometric (MS) analysis is compared to both direct on-line methods.

Deodorants↗

PubMed2001

Preparation and applications of polypyrrole films in solid-phase microextraction.

Polypyrrole (PPY) and poly-N-phenylpyrrole (PPPY) films were prepared and applied for solid-phase microextraction (SPME). The extraction properties of the new films to volatile organic compounds were examined using an SPME device coupled with GC-flame ionization detection. A PPY-coated capillary was applied for in-tube SPME to evaluate its extraction efficiency towards less volatile compounds and ionic species. The porous surface structures of the films, revealed by scanning electron microscopy, provided high surface areas and allowed for high extraction efficiency. Compared with commercial SPME stationary phases, the new phases showed better selectivity and sensitivity toward polar, aromatic, basic and anionic compounds, due to their inherent multifunctional properties. In addition, PPY and PPPY films showed different selectivity to various groups of compounds studied, indicating that the selectivity of the films could be modified by introducing a new functional group (phenyl in PPPY) into the polymer. For in-tube SPME, the PPY-coated capillary showed superior extraction efficiency to commercial capillaries for a variety of compounds, demonstrating its potential applications for a wide range of analytes when coupled with HPLC. The sensitivity and selectivity of the films for SPME could be tuned by changing the film thickness. These results are in line with both the theoretical expectations and the results obtained by other methods, which indicate not only that PPY films can be used as new stationary phases for SPME. but also that SPME method may provide an alternative tool for studying materials like polypyrrole.

Capillary Action↗

PubMed2006

Practical approaches to plant volatile analysis.

Plants emit volatile organic compounds (VOCs) that play important roles in their interaction with the environment and have a major impact on atmospheric chemistry. The development of static and dynamic techniques for headspace collection of volatiles in combination with gas chromatography-mass spectrometry analysis has significantly improved our understanding of the biosynthesis and ecology of plant VOCs. Advances in automated analysis of VOCs have allowed the monitoring of fast changes in VOC emissions and facilitated in vivo studies of VOC biosynthesis. This review presents an overview of methods for the analysis of plant VOCs, including their advantages and disadvantages, with a focus on the latest technical developments. It provides guidance on how to select appropriate instrumentation and protocols for biochemical, physiological and ecologically relevant applications. These include headspace analyses of plant VOCs emitted by the whole organism, organs or enzymes as well as advanced on-line analysis methods for simultaneous measurements of VOC emissions with other physiological parameters.

Gas Chromatography-Mass Spectrometry↗

PubMed1998

Headspace solid-phase microextraction for the determination of volatile and semi-volatile pollutants in water and air.

In this work we report the use of solid-phase microextraction (SPME) to extract and concentrate water-soluble volatile as well as semi-volatile pollutants. Both methods of exposing the SPME fibre were utilised: immersion in the aqueous solution (SPME) and in the headspace over the solution (HSSPME). The proposed HSSPME procedure was compared to conventional static headspace (HS) analysis for artificially spiked water as well as real water samples, which had been, equilibrated with various oil and petroleum products. Both techniques gave similar results but HSSPME was much more sensitive and exhibited better precision. Detection limits were found to be in the sub-ng/ml level, with precision better than 5% R.S.D. in most cases. To evaluate the suitability of SPME for relatively high contamination level analysis, the proposed HSSPME method was applied to the screening of run-off water samples that had heavy oil suspended in them from a tire fire incident. HSSPME results were compared with liquid--liquid extraction. Library searches were conducted on the resulting GC-MS total ion chromatograms to determine the types of compounds found in such samples. Both techniques found similar composition in the water samples with the exception of alkylnaphthalenes that were detected only by HSSPME. A brief study was carried out to assess using SPME for air monitoring. By sampling and concentrating the volatile organic compounds in the coating of the SPME fibre without any other equipment, this new technique is useful as an alternative to active air monitoring by means of sampling pumps and sorbent tubes.

Air Pollutants↗