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PubMed2001

Construction and validation of automated purge-and-trap-gas chromatography for the determination of volatile organic compounds.

An automated purge-and-trap chromatographic system for the determination of dissolved volatile organic compounds in aqueous samples was built in the laboratory with minimum cost both in the construction and routine operation. This system was built upon a commercial gas chromatograph with full automation capability using self-developed hardware and software. The use of a multi-sorbent bed quantitatively trapped a wide range of volatile organic compounds at ambient temperature, including the extremely volatile ones such as dichlorofluoromethane (CFC-12). Flash heating for rapid desorption and adequate plumbing for minimizing dead volume resulted in excellent chromatographic separation at above-ambient temperatures, which eliminated the need for cryogen for cooling at the head of the column, a second refocusing stage, or entire GC oven for refocusing. This cryogen-free system was tested with standard solutions and environmental samples for determining hydrocarbons with flame ionization detection, and halogenated compounds with electron-capture detection. An innovative method was also developed for validating the system's linearity for extremely volatile compounds. By introducing ambient air, which usually contains constant levels of anthropogenic halocarbons, e.g., CFC-12 and CFC-11 (CCl3F), the need to prepare aqueous standards containing extremely volatile compounds is avoided, hence providing a convenient method for evaluating a purge-and-trap system.

Automation↗

PubMed2003

Respiratory symptoms and peak expiratory flow in children with asthma in relation to volatile organic compounds in exhaled breath and ambient air.

Indoor volatile organic compounds (VOCs) have been associated with asthma, but there is little epidemiologic work on ambient exposures, and no data on relationships between respiratory health and exhaled breath VOCs, which is a biomarker of VOC exposure. We recruited 26 Hispanic children with mild asthma in a Los Angeles community with high VOC levels near major freeways and trucking routes. Two dropped out, three had invalid peak expiratory flow (PEF) or breath VOC data, leaving 21. Children filled out symptom diaries and performed PEF maneuvers daily, November 1999-January 2000. We aimed to collect breath VOC samples on asthma episode and baseline symptom-free days, but six subjects only gave samples on symptom-free days. We analyzed 106 breath samples by GC-MS. Eight VOCs were quantifiable in >75% of breath samples (benzene, methylene chloride, styrene, tetrachloroethylene, toluene, m,p-xylene, o-xylene, and p-dichlorobenzene). Generalized estimating equation and mixed linear regression models for VOC exposure-response relationships controlled for temperature and respiratory infections. We found marginally positive associations between bothersome or more severe asthma symptoms and same day breath concentrations of benzene [odds ratio (OR) 2.03, 95% confidence interval (CI) 0.80, 5.11] but not other breath VOCs. Ambient petroleum-related VOCs measured on the same person-days as breath VOCs showed notably stronger associations with symptoms, including toluene, m,p-xylene, o-xylene, and benzene (OR 5.93, 95% CI 1.64, 21.4). On breath sample days, symptoms were also associated with 1-h ambient NO(2), OR 8.13 (1.52, 43.4), and SO(2), OR 2.36 (1.16, 4.81). Consistent inverse relationships were found between evening PEF and the same ambient VOCs, NO(2), and SO(2). There were no associations with O(3). Given the high traffic density of the region, stronger associations for ambient than for breath VOCs suggest that ambient VOC measurements were better markers for daily exposure to combustion-related compounds thought to be causally related to acute asthma. Alternatively, the low sample size of symptom responses (15-21 responses per 108 breath samples) may have led to the nonsignificant results for breath VOCs.

Adolescent↗

PubMed2006

Occurrence, oral exposure and risk assessment of volatile organic compounds in drinking water for Izmir.

Concentrations of volatile organic compounds (VOCs) were measured in the drinking water in Province of Izmir, Turkey, and associated health risks due to ingestion of these compounds were investigated using population weighted random samples. A total of 100 houses were visited in different districts of Izmir and drinking water samples were collected from consumers' drinking water source. Questionnaires were administered to one participant in each house to determine demographics and drinking water consumption rates. Oral exposure and risks were estimated for each participant and Izmir population by deterministic and probabilistic approaches, respectively. The four trihalomethane (THM) species (i.e., chloroform, bromodichloromethane, dibromochloromethane, and bromoform), benzene, toluene, p-xylene, and naphthalene were the most frequently detected VOCs with concentrations ranging from below detection limit to 35 microg/l. The risk estimates were found to be less than the values reported in the literature with few exceptions. Noncarcinogenic risks attributable to ingestion of VOCs for Izmir population were negligible, whereas the mean carcinogenic risk estimates for bromodichloromethane and dibromochloromethane were above the de minimis level of one in a million (10(-6)). For all VOCs, the concentrations measured in metropolitan area were greater than those in other districts. All THM species were detected in higher concentrations in tap water, whereas nontap water contained more benzene, toluene, p-xylene, and naphthalene. Therefore, the concentrations of the latter four compounds and associated risks increased with increasing income and education level since bottled water was used in larger proportions within these subgroups. The results of this study showed that oral exposure to drinking water contaminants and associated risks may be higher than the acceptable levels even if the concentrations fall below the standards.

Administration, Oral↗

PubMedDate not supplied

Determination of trace volatile organic compounds in fish tissues by gas chromatography.

Several volatile organic compounds associated with petroleum fuels (mainly alkylated benzenes) were extracted from spiked fish tissue samples with a stream of air, trapped on charcoal, eluted with a solvent, and analyzed by gas chromatography. These volatile compounds are among the most water-soluble components of crude oils and petroleum products, and they have been associated with tainting in fish tissues. Recoveries for these compounds were about 90% when spiked directly either onto traps or into fish tissues although naphthalene desorbed poorly from the charcoal; recoveries of this compound were about 50%. Relative standard deviations (RSD) for most recoveries of spiked samples were in the 2-10% range based on 6 samples analyzed in duplicate. However, when live fish were contaminated experimentally by adding the aromatic compounds to the aquarium water, the RSDs were higher (10-30%).

Animals↗

PubMed2005

Comparison of the volatile organic compounds present in human odor using SPME-GC/MS.

We evaluated the volatile organic compounds (VOCs) present in human odor by using headspace solid phase microextraction gas chromatography-mass spectrometry for the extraction, separation, and analysis of the collected samples. Volatile organic compounds present in the headspace above axillary sweat samples collected from different individuals showed the presence of various types of compounds including organic fatty acids, ketones, aldehydes, esters, and alcohols. Qualitative differences and similarities noted between the males and females studied along with differences in chemical ratio patterns among the common compounds demonstrated the ability to differentiate between individuals through the examination of VOCs.

Adolescent↗

PubMed2005

In situ modification of herbivore-induced plant odors: a novel approach to study the attractiveness of volatile organic compounds to parasitic wasps.

Many parasitic wasps (parasitoids) exploit volatile organic compounds (VOCs) emitted by herbivore-infested plants in order to locate their hosts, but it remains largely unknown which specific compounds within the volatile blends elicit the attractiveness to parasitoids. One way of studying the importance of specific VOCs is to test the attractiveness of odor blends from which certain compounds have been emitted. We used this approach by testing the attraction of naive and experienced females of the two parasitoids Cotesia marginiventris and Microplitis rufiventris to partially altered volatile blends of maize seedlings (Zea mays var. Delprim) infested with Spodoptera littoralis larvae. Adsorbing filter tubes containing carbotrap-C or silica were installed in a four-arm olfactometer between the odor source vessels and the arms of the olfactometer. The blends breaking through were tested for chemical composition and attractiveness to the wasps. Carbotrap-C adsorbed most of the sesquiterpenes, but the breakthrough blend remained attractive to naive C. marginiventris females. Silica adsorbed only some of the more polar VOCs, but this essentially eliminated all attractiveness to naive C. marginiventris, implying that among the adsorbed compounds there are some that play key roles in the attraction. Unlike C. marginiventris, M. rufiventris was still attracted to the latter blend, showing that parasitoids with a comparable biology may employ different strategies in their use of plant-provided cues to locate hosts. Results from similar experiments with modified odor blends of caterpillar-infested cowpea (Vigna unguiculata) indicate that key VOCs in different plant species vary greatly in quality and/or quantity. Finally, experienced wasps were more strongly attracted to a specific blend after they perceived the blend while ovipositing in a host. Considering the high number of distinct adsorbing materials available today, this in situ modification of complex volatile blends provides a new and promising approach pinpointing on key attractants within these blends. Advantages and disadvantages compared to other approaches are discussed.

Adsorption↗

PubMed1998

Total volatile organic compounds in the urban environment of Delhi.

Total volatile organic compounds (TVOCs) in the urban ambient environment of Delhi were monitored from November 1994 to June 1995 at 13 sites using an inexpensive and a manual-labor-intensive sample collection procedure in want of sophisticated equipment. The results of the study show appreciable levels of TVOCs in the ambient environment of Delhi. The amount of TVOCs in the ambient environment was found to vary between 3 and 42 ppmv and exhibited wide temporal and seasonal variations. On a diurnal cycle, TVOC levels mostly peaked at 9:00 a.m., which coincided with the peak traffic hour. TVOC buildup in the urban atmosphere has serious implications for air quality through the formation of highly toxic oxidants. The results of this preliminary study make out a strong case for a regular monitoring of TVOCs in the urban environment of Delhi.

Air Pollution↗

PubMed2004

Source identification of volatile organic compounds in Houston, Texas.

The complexity of the volatile organic compound (VOC) mixture in the Houston area makes studies of the air quality in that area very challenging. In this paper, a novel factor analysis model, where the normal chemical mass balance model was augmented by a parallel equation that accounted for wind speed and direction, temperature, and weekend/weekday effects, was fitted with a multilinear engine (ME) to provide identification and apportionment of the VOC sources at the La Porte Municipal Airport site in Houston during the Texas Air Quality Study (TexAQS) 2000. The analysis determined the profiles and contributions of nine sources and the corresponding wind speed, wind direction, temperature, and weekend factors. The reasonableness of these results not only suggests the high resolving power of the expanded factor analysis model for source apportionment but also provides the novel and effective auxiliary information for more specific source identification. In addition, a new approach to estimate the measurement uncertainty and the details of determining the source number and dealing with missing values are also presented as important parts of the data analysis process. This study demonstrates the feasibility of the expanded model to identify sources in complex VOC systems and extract useful information for locating VOC emitters and controlling their emissions in the Houston area.

Air Pollutants↗

PubMed2004

Evaluation of dispersion methods for enumeration of microorganisms from peat and activated carbon biofilters treating volatile organic compounds.

To enumerate microorganisms having colonized biofilters treating volatile organic compounds, it is necessary firstly to evaluate dispersion methods. Crushing, shaking and sonication were then tested for the removal of microflora from biofilters packing materials (peat and activated carbon). Continuous or discontinuous procedures, and addition of glass beads had no effect on the number of microorganisms removed from peat particles. The duration of treatment also had no effect for shaking and crushing, but the number of microorganisms after 60 min of treatment with ultrasound was significantly higher than that obtained after 0.5 min. The comparison between these methods showed that crushing was the most efficient for the removal of microorganisms from both peat and activated carbon. The comparison between three chemical dispersion agents showed that 1% Na-pyrophosphate was less efficient, compared with 200 mM phosphate buffer or 1% Na-hexametaphosphate. To optimize the cultivation of microorganisms, three different agar media were compared. Tryptic soy agar tenfold diluted (TSA 1/10) was the most suitable medium for the culture of microflora from a peat biofilter. For the activated carbon biofilter, there was no significant difference between Luria Bertoni, TSA 1/10, and plate count agar. The optimized extraction and enumeration protocols were used to perform a quantitative characterization of microbial populations in an operating laboratory activated carbon biofilter and in two parallel peat biofilters.

Air Pollution↗

PubMed2004

Combining preconcentration of air samples with cavity ring-down spectroscopy for detection of trace volatile organic compounds in the atmosphere.

Quantitative detection of small volatile organic compounds in ambient air is demonstrated using a combination of continuous wave cavity ring-down spectroscopy (cw-CRDS) and the preconcentration of air samples with an adsorbent trap. The trap consists of a zeolite molecular sieve, selected for efficient trapping of the test compounds ethene (ethylene) and ethyne (acetylene). Upon heating of the trap, these organic compounds desorb into a small-volume ring-down cavity, and absolute concentrations are measured by CRDS at 6150.30 cm(-1) (ethene) and 6512.99 cm(-1) (ethyne) without the need for calibration. The efficiency of the trapping and desorption was tested using commercial standard gas mixtures and shown to be 100% in the case of ethene, whereas some ethyne is retained under the current operating conditions. Samples of indoor and outdoor air were analyzed for ethene content, and measurements were made of mixing ratios as low as 6 ppbv. Removal of water vapor and CO(2) from the air samples prior to trapping was unnecessary, and the selectivity of the trapping, desorption, and spectroscopic detection steps eliminates the need for gas chromatographic separation prior to analysis. With anticipated improvements to the design, measurements of these and other trace atmospheric constituents should be possible on time scales of a few minutes.

Journal Article↗

PubMed2001

Evaluation of tetraglyme for the enrichment and analysis of volatile organic compounds in air.

A recently developed method for the sampling and analysis of volatile organic compounds in air has been evaluated. The system is based on the enrichment of analytes in tetraethylene glycol dimethyl ether or tetraglyme, a water-soluble organic liquid. The subsequent analysis consists of dispersion of a sample aliquot in water followed by purge-and-trap and gas chromatographic separation. Physico-chemical data were investigated for 10 volatile organic compounds, providing information on the possibilities and limitations of the tetraglyme method. The target analytes included chlorinated alkanes and alkenes, and monocyclic aromatic hydrocarbons. Air/tetraglyme partition coefficients Kat were determined over an environmental relevant temperature range of 2-25 degrees C to evaluate sorption efficiencies and estimate breakthrough volumes at the sampling stage. At 2 degrees C breakthrough volumes (allowing 5% of breakthrough) ranged from 5.8 (1,1-dichloroethane) to 312 l (1,1,2-trichloroethane) for 20 ml of tetraglyme. With regard to the desorption stage, the effect of tetraglyme on the air/water partition of organic compounds was investigated through the measurement of air/tetraglyme-water partition coefficients Kat-w for 2-31% (v/v) tetraglyme in water. Finally a clean-up procedure for tetraglyme was evaluated. Analysis of a blank tetraglyme-water (17:83, v:v) mixture by gas chromatography-flame ionization detection/mass spectrometry showed minor background signals. None of the target compounds were detected.

Air↗

PubMed1993

Respiratory and irritant health effects of ambient volatile organic compounds. The Kanawha County Health Study.

Kanawha County, West Virginia, is one of the largest chemical manufacturing centers in the United States. In 1988, a survey of respiratory and irritant symptoms was administered to all third grade to fifth grade children attending 74 elementary schools in Kanawha County, and concentrations of 15 volatile organic compounds were measured at each school. Exposures were characterized by school location, by the sum of the concentrations of five petroleum-related compounds, and by the sum of the concentrations of 10 compounds more specific to industrial processes. Children enrolled in schools within the valley had higher rates of doctor-diagnosed asthma (odds ratio (OR) = 1.27, 95% confidence interval (CI) 1.09-1.48) and a higher score on a composite indicator of five chronic lower respiratory symptoms (OR = 1.13, 95% CI 1.02-1.26) than children who were enrolled in schools outside of the valley. The incidence of chronic respiratory symptoms was also positively associated with the concentrations of volatile organic compounds. The estimated change in the odds ratio for chronic lower respiratory symptoms associated with a 2-micrograms/m3 change in process-related compounds was 1.08 (95% CI 1.02-1.14). No consistent pattern was found between acute irritant symptoms in the 2 weeks preceding questionnaire administration and either proximity to industry or exposure to volatile organic compounds. The authors conclude that exposure to volatile organic compounds, including emissions from chemical manufacturing plants, is associated with increased rates of chronic respiratory symptoms characteristic of reactive airways.

Air Pollutants↗

PubMed2005

Fungal infections of fresh-cut fruit can be detected by the gas chromatography-mass spectrometric identification of microbial volatile organic compounds.

There is a large and rapidly growing market for fresh-cut fruit. Microbial volatile organic compounds indicate the presence of fungal or bacterial contamination in fruit. In order to determine whether microbial volatile organic compounds can be used to detect contamination before fruit becomes unmarketable, pieces of cantaloupe, apple, pineapple, and orange were inoculated with a variety of fungal species, incubated at 25 degrees C, then sealed in glass vials. The volatiles were extracted by headspace solid-phase microextraction and analyzed by gas chromatography-mass spectrometry. Forty-five compounds were identified that might serve as unique identifiers of fungal contamination. Fungal contamination can be detected as early as 24 h after inoculation.

Consumer Product Safety↗

PubMed1987

Capillary chromatographic analysis of volatile organic compounds in the indoor environment.

The wide variety of volatile organic compounds found in the indoor environment can present a difficult chromatographic problem for the analyst. Capillary-column gas chromatography is required to achieve adequate separation. Thermal desorption/capillary gas chromatography/mass spectrometry is usually the preferred method for broad spectrum analysis of the volatile organics detected indoors. Cryogenic trapping is required for capillary gas chromatographic analysis of the more volatile components.

Air Pollutants↗

PubMed2003

[The emission flux of volatile organic compounds in the Inner Mongolia Grassland].

During the summer season of 2002, emissions of volatile organic compounds were firstly measured by a static enclosure technique at a grassland site in the Inner Mongolia grassland. The parameters including solar radiation, air temperature and relative humidity were also measured in the same time period. The results showed that isoprene was the main component of volatile organic compounds emitted from the grassland. Isoprene exhibited an evident diurnal, daily and seasonal variation. Solar visible radiation, air temperature and water vapor content were the main factors to affect isoprene emission, and solar visible radiation was the most important factor to control the isoprene emission. Base on the correlation analysis, when considering the affecting factors of isoprene emission, it is not only to consider solar visible radiation, temperature, but also the water vapor. It is impossible to avoid the changes of solar radiation, temperature and humidity between inside and outside the chamber by using the enclosure technique. So, it is necessary to take these effects into the considerations and modify isoprene emission. In summer 2002, the maximum emission flux (C) of isoprene was 1649.3 micrograms/(m2.h), and monthly averaged emission flux (C) in June, August and September were 886.6, 707.0 and 427.2 micrograms/(m2.h), respectively.

Air↗

PubMed2000

Sorbent trapping of volatile organic compounds from air.

The use of sorbents in trapping volatile organic compounds in air for subsequent analysis is reviewed. Sorbents are classified in accordance with the mechanism used to recover the trapped compounds, either solvent or thermal desorption. The use of sorbents is contrasted with other sampling procedures, such as collecting whole air samples using canisters. New developments such as solid-phase microextraction are described. In particular, emphasis is placed on a holistic approach to sampling and analysis, and communication is encouraged between those who take samples in the field, and those who perform the analysis.

Adsorption↗

PubMed2003

Modification of the equilibrium partitioning approach for volatile organic compounds in sediment.

Although weakly hydrophobic chemicals such as volatile organic compounds (VOCs) tend not to persist in sediments, they may nevertheless be present in some sediments because of recent or ongoing releases. Standard methods are not available for assessing risks to benthic invertebrates due to VOCs in sediment. More strongly hydrophobic organic chemicals are frequently assessed by using the equilibrium partitioning (EqP) approach, which predicts the bioavailable fraction of chemical (the concentration dissolved in pore water) from the sediment-sorbed fraction, assuming that partitioning is at equilibrium. As typically applied, the EqP approach is ineffective for assessing VOCs in sediment, because the standard EqP equation fails to account for the contribution of dissolved chemical to the total chemical concentration in sediment. For chemicals with low organic carbon-water partition coefficients (Kocs), this results in nonsensical sediment-quality benchmarks that are more conservative (i.e., lower) than benchmarks calculated by assuming 100% bioavailability. A modified EqP equation is presented that accounts for the dissolved fraction of total chemical concentrations in sediment. Results of the standard and modified EqP equations converge with increasing Koc and are essentially identical at log Koc values exceeding approximately 3.5.

Benchmarking↗

PubMed2005

Distributions and source apportionment of ambient volatile organic compounds in Beijing city, China.

Ambient measurements of 108 volatile organic compounds (VOCs), including alkanes, alkenes, aromatics, and halogenated hydrocarbons, were conducted from 2002 to 2003 at six sites in Beijing city. The mean mass concentration of total VOCs was 132.6 +/- 52.2 microg/m3, with alkanes, aromatics, and alkenes accounting for 35%, 22%, and 17%, respectively. The concentrations of most VOC species showed a seasonal pattern, with higher values in November, mildly lower in March, and much lower in July. In winter and spring, apparent diurnal variations of reactive compounds such as 1,3-butadiene and isoprene were observed, whereas those were not distinct in summer. The propylene equivalent concentration was used to evaluate the contribution of individual VOCs in ozone formation. Reactive olefins from anthropogenic emissions dominated the reactions with OH at each season. In summer, isoprene became the largest contributor, followed by 1-butene and propene. The source profiles in Beijing, including vehicle exhaust, gasoline vapor, painting operations, and asphalt pavement, were investigated. Based on the measurement of source profiles and ambient concentrations of VOCs in Beijing, chemical mass balance receptor model was applied to estimate contributions of several potential VOCs sources in Beijing. The results indicated that vehicle exhaust contributed on average 57.7%, followed by painting operations, gasoline vapor, and liquefied petroleum gas (LPG) at 12.4%, 11.3%, and 5.8%, respectively.

Air Pollutants↗