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PubMed2001

Potential of solid-phase microextraction fibers for the analysis of volatile organic compounds in air.

This work presents the usefulness of five different solid-phase microextraction fibers in the screening of volatile organic compound (VOC) traces in air samples. The performances of these fibers are compared by studying the sorption kinetics in an equimolar gaseous mixture of eleven VOCs. For each fiber, static and dynamic sampling are compared. It is shown that repeatability is better for the dynamic mode (less than 6% for dynamic sampling and 10% for static sampling). The equilibrium time and the sensitivity vary considerably from one fiber type to another. As an example, the classical polydimethylsiloxane (PDMS) coating presented the shortest equilibration time (5 min) but also the poorest sensitivity, whereas the PDMS-Carboxen showed the longest extraction time but the greatest sensitivity. The estimation of the quantity of VOCs fixed on the target fiber allows for the determination of the different affinities of the compounds with the involved sorbent and relates them with physicochemical properties of the molecules. Competitive sorption is observed for the fibers involved with the adsorption process (i.e., PDMS-divinylbenzene and PDMS-Carboxen fibers). These competitions can lead to SPME calibration problems and thus bad quantitative analysis.

Journal Article↗

PubMed1999

Species-specific production of microbial volatile organic compounds (MVOC) by airborne fungi from a compost facility.

Thirteen airborne fungal species frequently isolated in composting plants were screened for microbial volatile organic compounds (MVOC), i.e., Aspergillus candidus, A. fumigatus, A. versicolor, Emericella nidulans, Paecilomyces variotii, Penicillium brevicompactum, Penicillium clavigerum, Penicillium crustosum, Penicillium cyclopium, Penicillium expansum, Penicillium glabrum, Penicillium verruculosum, and Tritirachium oryzae. Air samples from pure cultures were sorbed on Tenax GR and analyzed by thermal desorption in combination with GC/MS. Various hydrocarbons of different chemical groups and a large number of terpenes were identified. Some compounds such as 3-methyl-1-butanol and 1-octen-3-ol were produced by a number of species, whereas some volatiles were specific for single species. An inventory of microbial metabolites will allow identification of potential health hazards due to an exposure to fungal propagules and metabolites in the workplace. Moreover, species-specific volatiles may serve as marker compounds for the selective detection of fungal species in indoor domestic and working environments.

Air Microbiology↗

PubMed2002

Ambient level volatile organic compound (VOC) monitoring using solid adsorbents--recent US EPA studies.

Ambient air spiked with 1-10 ppbv concentrations of 41 toxic volatile organic compounds (VOCs) listed in US Environmental Protection Agency (EPA) Compendium Method TO-14A was monitored using solid sorbents for sample collection and a Varian Saturn 2000 ion trap mass spectrometer for analysis. The adsorbent was a combination of graphitic carbon and a Carboxen-type carbon molecular sieve. The method detection limits (MDLs) for 11 samples were typically 0.5 parts per billion by volume (ppbv) and lower except for bromomethane and chloromethane, both of which exhibited breakthrough. Thirty-day sample storage on the sorbents resulted in less than a 20% change for most compounds, and water management was required for humid samples to avoid major anomalous decreases in response during analyses. The adsorbent-based system, a system using canister-based monitoring, and a semi-continuous automated GC/MS (autoGC) monitoring system with a Tenax GR/Carbotrap B/Carbosieve S-III adsorbent preconcentrator were compared using spiked ozone concentrations as a variable. In this comparison, the target compounds included a number of n-aldehydes as well as those listed in TO-14A. The effects of ozone on the TO-14A compounds were relatively minor with the exception of negative artifacts noted for styrene and 1,1,2,2-tetrachloroethane. However, a small, systematic decrease in response was evident for a number of aromatic VOCs and 1,1,2,2-tetrachloroethane when ozone was increased from 50 to 300 ppbv. Method averages for multiple runs under the same conditions were typically within +0.25 ppbv of their mean for most compounds. For n-aldehydes, strong positive artifacts using the autoGC preconcentrator and strong negative artifacts for the canister-based and carbon sorbent approaches caused major disagreement among methods. These artifacts were mostly eliminated by using MnO2 ozone scrubbers, although loss of the n-aldehydes for all methods occurred after a single sample collection of 1 h duration, apparently due to the interaction of the n-aldehydes and products of the O3, MnO2 reaction on the scrubber.

Adsorption↗

PubMed1997

Destruction of low levels of volatile organic compounds in dry air streams by an electron-beam generated plasma.

The destruction of parts per million (ppm) levels of volatile organic compounds in a dry air stream by high-energy electron-beam irradiation has been investigated in a pilot plant at the University of Tennessee Space Institute, Tullahoma, Tennessee. In a series of experiments, dry air contaminated with various VOCs in the concentration range of 50-1000 ppm were treated in the UTSI pilot plant to determine the extent of destruction at various electron-beam dose levels. The destruction removal efficiency was determined as a function of the electron beam irradiation dose. The results suggest a charge transfer reaction as the major decomposition mechanism. A theoretical foundation of the process, along with a simple first-generation reaction kinetics model, a summary of the results from the pilot plant flow reactor, and a preliminary cost analysis for a full-scale detoxification plant using currently available electron-beam gum technology are presented in this paper.

Air Pollutants↗

PubMed2005

Miniaturized membrane-assisted solvent extraction combined with gas chromatography/electron-capture detection applied to the analysis of volatile organic compounds.

A new module of membrane-assisted solvent extraction (MASE) with miniaturized membrane bags was applied to the determination of seven volatile organic compounds (VOCs): chloroform, 1,1,1-trichloroethane, trichloroethylene, 1,1,2-trichloroethane, tetrachloroethene, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane with boiling points between 61 and 147 degrees C in aqueous samples. Different from the known procedure the new, shortened membrane bags were filled with 100 microl of an organic solvent. The membrane bags were placed in a 20 ml headspace vial and filled with 15 ml of the aqueous sample. The vial was transferred into an autosampler where it was stirred for a definite time at elevated temperature. After the extraction, 1 microl of the organic extract was transferred into the spilt/splitless injector of a GC system equipped with an electron-capture detector. This work included optimization of the membrane device, the determination of the optimized extraction conditions such as stirring rate, extraction time and the impact of salt addition. The validation of the method involved repeatability, recovery and detection limit studies, followed of its application towards real water samples. The repeatability, expressed as the relative standard deviation of the peak areas of six extractions was below 10%. The detection limits (LODs) were between 5 ng/l (tetrachloroethene) and 50 ng/l (chloroform). Calibration was performed in a range from 5 ng/l to 150 microg/l, since the concentration in the aqueous samples was expected quite various in this concentration range. Five river water samples of Bitterfeld, Saxony-Anhalt, Germany were analyzed with miniaturized-MASE and the results were compared with those obtained with Headspace-Analysis. The method can be fully automated and moreover, it allows the simultaneous determination of volatile and semi volatile compounds.

Chromatography, Gas↗

PubMed2002

Hematological changes of children exposed to volatile organic compounds containing low levels of benzene.

We conducted a cohort study to evaluate the hematological changes of children environmentally exposed to volatile organic compounds (VOCs). The study subjects comprised 192 children who consisted of 97 children living near a petrochemical estate region and 95 children living in a suburban region of Ulsan, Korea. We executed the hematological examination three times, in April, July and October. A generalized linear model analysis was used to test for changes over time in the complete blood count (CBC) values of each study group. All CBC values of children showed differences between regions in accordance with the survey month. In the model, region was a significant independent variable for the total white blood cell, red blood cell, and platelet. This suggests that the amounts of exposure to VOCs are different between study groups in different months, and environmental exposure to VOCs is associated with a higher prevalence of hematological abnormalities. Hematological abnormalities in children exposed to VOCs containing low levels of benzene could serve as a biological marker of atmospheric VOCs.

Benzene↗

PubMed2006

Development of a portable instrument for the continuous analysis of volatile organic compounds (VOCs) and its application to environmental monitoring.

A small, time efficient and sensitive instrument for the continuous analysis of very volatile organic compounds (VOCs) with a boiling point lower than 100 degrees C in addition to the analysis of VOCs with a boiling point in the range of 100-150 degrees C was developed and applied to the measurement of VOCs in the course of university research and environmental monitoring. VOCs, such as n-hexane, acetone, ethyl acetate, alcohols, benzene, toluene and xylene, were continuously measured once every 30 min. The detection limits of hexane, ethyl acetate, benzene and toluene at a preconcentration time of 10 min were 0.41 microg/m(3) (0.12 ppb), 0.67 microg/m(3) (0.19 ppb), 0.22 microg/m(3) (0.07 ppb) and 0.22 microg/m(3) (0.06 ppb), respectively. The relative standard deviations of VOCs were less than 5%. The sensitivities of the present method VOCs were higher than those of the conventional method. The temporal changes in VOC concentrations in several laboratories and at a plant for the disposal of organic liquid wastes were measured, and the behavior of VOCs was analyzed. All the VOC concentrations, except that of ethyl acetate, determined using the portable instrument were slightly lower than those determined using a passive sampler. The portable instrument developed in the course of this study can be used for the risk assessment and management of chemicals.

Air Pollutants↗

PubMed2003

Kinetics and mechanisms of the sonolytic destruction of non-volatile organic compounds: investigation of the sonochemical reaction zone using several OH* monitoring techniques.

This study investigates the sonolytic degradation mechanism of non-volatile organic compounds and reaction sites for its degradation using various tools that allow OH* to be monitored, such as: the spin-trapping method of OH* detection using non-volatile nitrone trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the hydrogen peroxide analytical methods and the p-chlorobenzoic acid (pCBA)-probe method. These methods can successfully monitor OH* produced during sonochemical processes, and identify the major reaction sites involving OH* of the three proposed reaction zones--within the cavity, in the bulk solution, and at the gas-liquid interfacial (shell) region. The patterns of hydrogen peroxide accumulation under the various conditions suggest that peroxides pre-form at the interfacial region, but the self-scavenging reaction by hydrogen peroxide simultaneously takes place in the same region. The simultaneously measured peroxide concentration, in the absence and presence of DMPO, and that of the DMPO-OH adduct indicated the peroxide production and DMPO-OH adduct formation reaction occur at the shell region. The sonolytic destruction efficiency of ultrasound coupled with Fe(II) has been also investigated. The coupled Fe(II)/ultrasound process was found to enhance the OH* production rate by 70% compared to the ultrasound process alone due to the reaction of Fe(II) with sonochemically produced hydrogen peroxide (Fenton's reaction). This accelerated reaction was also found to occur at the shell region rather than in the bulk solution. The enhancement effect of Fe(II)/ultrasound was also examined using pCBA as a probe. 2.8-fold and 3.6-fold increases of the pCBA degradation rate were observed at Fe(II) concentrations of 10 and 20 microM, respectively.

Journal Article↗

PubMed2004

Construction and validation of an automated spray-and-trap gas chromatograph for the determination of volatile organic compounds in aqueous samples.

An automated spray-and-trap (ST) chromatographic system was constructed for fast and efficient extraction of volatile organic compounds (VOCs) in aqueous samples with the capability to be deployed in the field for unattended continuous monitoring of surface or ground water. This system was built upon a commercial gas chromatograph with full automation capability using self-developed hardware and software. For sample analysis, fine droplets of the aqueous solution were generated in the extraction chamber by pressure expansion of a clean air stream through a spray nozzle. A portion of the VOCs distributed into the gas phase was retained by a multi-sorbent micro-trap kept at ambient temperature. Flash heating of the sorbent trap desorbed the enriched VOCs onto the gas chromatography (GC) with flame ionization detection (FID) for hydrocarbons or electron-capture detection (ECD) for halocarbons. In order to validate the performance of the ST method. it was compared with a more conventional method, i.e., a purge-and-trap (PT), by analyzing a serious of standard solutions containing benzene, toluene, ethylene. and o-, m-xylenes. Using a purge-and-trap method as a reference for complete extraction, the ST method showed less sensitivity. Extraction recoveries are in consistent with Henry's law constants. To test response time the ST-GC-ECD was periodically switched between tap and underground waters. Negligible carry-over of halogenated species and reproducibility better than 2% relative standard deviation (R.S.D.) can be achieved regardless of large concentration difference between the two sources, thus demonstrating applicability of the ST system for on-site monitoring.

Automation↗

PubMed2005

Quantitative determination of volatile organic compounds in indoor dust using gas chromatography-UV spectrometry.

A novel technique, gas chromatography-UV spectrometry (GC-UV), was used to quantify volatile organic compounds (VOCs) in settled dust from 389 residences in Sweden. The dust samples were thermally desorbed in an inert atmosphere and evaporated compounds were concentrated by solid phase micro extraction and separated by capillary GC. Eluting compounds were then detected, identified, and quantified using a diode array UV spectrophotometer. Altogether, 28 compounds were quantified in each sample; 24 of these were found in more than 50% of the samples. The compounds found in highest concentrations were saturated aldehydes (C5-C10), furfuryl alcohol, 2,6-di-tert-butyl-4-methylphenol (BHT), 2-furaldehyde, and benzaldehyde. Alkenals were also found, notably 2-butenal (crotonaldehyde), 2-methyl-propenal (methacrolein), hexenal, heptenal, octenal, and nonenal. The concentrations of each of the 28 compounds ranged between two to three orders of magnitude, or even more. These results demonstrate the presence of a number of VOCs in indoor dust, and provide, for the first time, a quantitative determination of these compounds in a larger number of dust samples from residents. The findings also illustrate the potential use of GC-UV for analysing volatile compounds in indoor dust, some of which are potential irritants (to the skin, eyes or respiratory system) if present at higher concentrations. The potential use of GC-UV for improving survey and control of the human exposure to particle-bound irritants and other chemicals is inferred.

Air Pollution, Indoor↗

PubMed2005

Determinants for nasal trigeminal detection of volatile organic compounds.

We explored the influence of methodological and chemical parameters on the detection of nasal chemesthesis (i.e., trigeminal stimulation) evoked by volatile organic compounds (VOCs). To avoid odor biases, chemesthesis was probed via nasal pungency detection in anosmics and via nasal localization (i.e., lateralization) in normosmics, in both cases using forced-choice procedures. In the experiments with anosmics, 12 neat VOCs were selected based on previous reports of lack of chemesthetic response. Although none of the VOCs reached 100% detection, detectability and confidence of detection were higher when using a glass vessel system adapted with nosepieces to fit the nostrils tightly than when using wide-mouth glass jars. Half the stimuli were detected well above chance and half were not. When the latter were tested again after being heated to 37 degrees C, that is, body temperature (from room temperature, 23 degrees C), to increase their vapor concentration, only one, octane, significantly increased its detectability. Chemesthesis gauged with normosmics mirrored that with anosmics. Gas chromatography measurements showed that, even at 23 degrees C, the saturated vapor concentrations of the undetected stimuli, except vanillin, were well above the respective calculated nasal pungency threshold (NPT) from an equation that, in the past, had accurately described and predicted NPTs. We conclude that, except for octane and perhaps vanillin, the failure of the other four VOCs to precipitate nasal chemesthesis rests on a chemical-structural limitation, for example, the molecules lack a key property to fit a receptor pocket, rather than on a concentration limitation, for example, the vapor concentration is too low to reach a threshold value.

Adult↗

PubMed2001

Treatment of volatile organic compounds in a biotrickling filter under thermophilic conditions.

The objectives of this research were to investigate the potential to biologically treat volatile organic compounds emitted by the forest products industry at thermophilic conditions and to examine the microbial community developed at high temperatures. Three biotrickling filters were run in parallel at temperatures ranging from 40 degrees C (mesophilic control) to 70 degrees C. The first phase involved treatment of methanol, for a 3-month run, and the second phase involved a 260-day run on the treatment of alpha-pinene. Methanol removal rates over 100 g m(-3) h(-1) where achieved at temperatures up to 70 degrees C. Alpha-pinene removal was achieved at temperatures up to 60 degrees C with optimal treatment occurring at 55 degrees C at rates up to 60 g m(-3) h(-1). The time for acclimation increased with increasing temperature and was longer for pinene than for methanol. Filter performance was also able to quickly recover from a shutdown period of up to 2 weeks due to the robustness of the microbial communities as determined by DNA fingerprinting analysis. The high-temperature communities treating methanol or pinene were more similar to each other than the mesophilic communities (i.e., 40 degrees C). The mesophilic methanol community had a high degree of functional redundancy, while the mesophilic pinene community was more unique and very distinct from the others. These results show that biofiltration at high temperatures is achievable and opens up a range of possibilities for applying biofiltration to hot gas streams.

Acclimatization↗

PubMed2004

Volatile organic compounds inhibit human and rat neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes.

The relative sensitivity of rats and humans to volatile organic compounds (VOCs) such as toluene (TOL) and perchloroethylene (PERC) is unknown and adds to uncertainty in assessing risks for human exposures to VOCs. Recent studies have suggested that ion channels, including nicotinic acetylcholine receptors (nAChRs), are targets of TOL effects. However, studies comparing TOL effects on human and rat ligand-gated ion channels have not been conducted. To examine potential toxicodynamic differences between these species, the sensitivity of human and rat nAChRs to TOL was assessed. Since PERC has similar effects, in vivo, to TOL, effects of PERC on nAChR function were also examined. Two-electrode voltage-clamp techniques were utilized to measure acetylcholine-induced currents in neuronal nAChRs (alpha4beta2, alpha3beta2, and alpha7) expressed in Xenopus oocytes. PERC (0.065 mM) inhibited alpha7 nAChR currents by 60.1 +/- 4.0% (human, n = 7) and 40 +/- 3.5% (rat, n = 5), and inhibited alpha4beta2 nAChR currents by 42.0 +/- 5.2% (human, n = 6) and 52.2 +/- 5.5% (rat, n = 8). Likewise, alpha3beta2 nAChRs were significantly inhibited by 62.2 +/- 3.8% (human, n = 7) and 62.4 +/- 4.3% (rat, n = 8) in the presence of 0.065 mM PERC. TOL also inhibited both rat and human alpha7, alpha4beta2, and alpha3beta2 nAChRs. Statistical analysis indicated that although there was not a species (human vs. rat) difference with PERC (0.0015-0.065 mM) or TOL (0.03-0.9 mM) inhibition of alpha7, alpha4beta2, or alpha3beta2 nAChRs, all receptor types were more sensitive to PERC than TOL. These results demonstrate that human and rat nACh receptors represent a sensitive target for VOCs. This toxicodynamic information will help decrease the uncertainty associated with animal to human extrapolations in the risk assessment of VOCs.

Action Potentials↗

PubMed1990

Comparison of quarter-hourly on-line dynamic headspace analysis to purge-and-trap analysis of varying volatile organic compounds in drinking water sources.

On-line dynamic headspace analysis was refined for the quarter-hourly monitoring of select volatile organic compounds (VOCs) in ground and surface waters, for extended periods of time. Hourly comparisons were made to on-line purge-and-trap analysis, and to purge-and-trap analysis after sample preservation and storage. Variations in VOC concentrations of 6047% biweekly, 222% daily, 97% hourly, and 35% quarter-hourly were observable, with the 15-min cycle of the dynamic headspace analysis. The headspace analyzer had superior retention time stability, required less maintenance, and had 1/4 the analysis time as a typical purge-and-trap-gas chromatograph system used for hourly comparisons.

Calibration↗

PubMed2000

Near surface soil vapor clusters for monitoring emissions of volatile organic compounds from soils.

The overall objective of this research was to develop and test a method of determining emission rates of volatile organic compounds (VOCs) and other gases from soil surfaces. Soil vapor clusters (SVCs) were designed as a low dead volume, robust sampling system to obtain vertically resolved profiles of soil gas contaminant concentrations in the near surface zone. The concentration profiles, when combined with a mathematical model of porous media mass transport, were used to calculate the contaminant flux from the soil surface. Initial experiments were conducted using a mesoscale soil remediation system under a range of experimental conditions. Helium was used as a tracer and trichloroethene was used as a model VOC. Flux estimations using the SVCs were within 25% of independent surface flux estimates and were comparable to measurements made using a surface isolation flux chamber (SIFC). In addition, method detection limits for the SVC were an order of magnitude lower than detection limits with the SIFC. Field trials, conducted with the SVCs at a bioventing site, indicated that the SVC method could be easily used in the field to estimate fugitive VOC emission rates. Major advantages of the SVC method were its low detection limits, lack of required auxiliary equipment, and ability to obtain real-time estimates of fugitive VOC emission rates.

Air Pollutants↗

PubMed1993

Emissions of volatile organic compounds from new carpets measured in a large-scale environmental chamber.

This study was undertaken to quantify the emissions of volatile organic compounds (VOCs) released by new carpets. Samples of four typical carpets, including two with styrene-butadiene rubber (SBR) latex adhesive and two with different backings, were collected from the finish lines at manufacturers' mills. Individual VOCs released from these samples were identified, and their concentrations, emission rates and mass emissions were measured under simulated indoor conditions in a 20 m3 environmental chamber over one week periods. Concentrations and emission rates of VOCs emitted by a new SBR carpet were also measured in a house. The carpets emitted a variety of VOCs. The two SBR carpets primarily emitted 4-phenylcyclohexene (4-PCH), the source of "new carpet" odor, and styrene. The concentrations and emission rates of 4-PCH were similar for the two carpets, while the styrene values varied significantly. The carpet with a polyvinyl chloride backing emitted formaldehyde, vinyl acetate, isooctane, 1,2-propanediol, and 2-ethyl-1-hexanol. Of these, vinyl acetate and propanediol had the highest concentrations and emission rates. The carpet with a polyurethane backing primarily emitted butylated hydroxytoluene. With the exception of formaldehyde, little is known about the health effects of these VOCs at low concentrations.

Air Pollutants↗

PubMed2001

Frequently co-occurring pesticides and volatile organic compounds in public supply and monitoring wells, southern New Jersey, USA.

One or more pesticides were detected with one or more volatile organic compounds (VOCs) in more than 95% of samples collected from 30 public supply and 95 monitoring wells screened in the unconsolidated surficial aquifer system of southern New Jersey, USA. Overall, more than 140,000 and more than 3,000 unique combinations of pesticides with VOCs were detected in two or more samples from the supply and monitoring wells, respectively. More than 400 of these combinations were detected in 20% or more of the samples from the supply wells, whereas only 17 were detected in 20% or more of the samples from the monitoring wells. Although many constituent combinations detected in water from the supply and monitoring wells are similar, differences in constituent combinations also were found and can be attributed, in part, to differences in the characteristics of these two well types. The monitoring wells sampled during this study yield water that typically was recharged beneath a single land-use setting during a recent, discrete time interval and that flowed along relatively short paths to the wells. Public supply wells, in contrast, yield large volumes of water and typically have contributing areas that are orders of magnitude larger than those of the monitoring wells. These large contributing areas generally encompass multiple land uses; moreover, because flow paths that originate in these areas vary in length, these wells typically yield water that was recharged over a large temporal interval. Water withdrawn from public supply wells, therefore, contains a mixture of waters of different ages that were recharged beneath various land-use settings. Because public supply wells intercept water flowing along longer paths with longer residence times and integrate waters from a larger source area than those associated with monitoring wells, they are more likely to yield water that contains constituents that were used in greater quantities in the past, that were introduced from point sources, and/or that are derived from the degradation of parent compounds along extended flow paths.

Environmental Monitoring↗

PubMed2002

Evolution and kinetics of volatile organic compounds generated during low-temperature polymer degradation.

A method using direct flame ionization detector (FID) measurement was developed to study total volatile organic compound (VOC) emissions during thermal degradation of polymers. This method was used to estimate organic emissions from different polymers, such as low-density polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and commingled postconsumer streams, such as recycled carpet residue and auto shredder residue (ASR). The effects of process parameters, such as temperature, heating rate, and residence time, were also studied. Significant VOC emissions were observed at normal processing temperatures, particularly from recycled polymers. Each polymer showed a distinct evolution pattern during its thermal degradation. The kinetics of VOC emissions were also studied using a nonisothermal technique. The kinetic parameters were in agreement with data from the literature.

Air Pollutants↗