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PubMed2001

Volatile organic compound measurements in the California/Mexico border region during SCOS97.

Measurements of volatile organic compounds (VOC) were carried out in the California/Mexico border region during the Southern California Ozone Study in the summer of 1997 (SCOS97). Integrated 3-h samples were collected in Rosarito (south of Tijuana, Mexico) and in Mexicali during intensive operational periods (IOP), twice per IOP day. VOC were collected using stainless-steel 6-1 canisters; carbonyl compounds were collected using 2,4-dinitrophenyl-hydrazine (DNPH) impregnated C18 SepPak cartridges. The canister samples were analyzed for speciated volatile hydrocarbons (C2-C12), CO, CO2, CH4, methyl t-butyl ether (MTBE), and halogenated hydrocarbons. DNPH-impregnated cartridges were analyzed for 14 C1-C7 carbonyl compounds. The concentrations of all species were higher at Mexicali than in Rosarito. A good correlation between total non-methane hydrocarbons (TNMHC), CO, and other pollutants associated with motor vehicle emissions observed for Mexicali indicates that the main source of TNMHC at this site is vehicular traffic.

Air Pollution↗
PubMed2002

Fly-attracting volatiles produced by Rhodococcus fascians and Mycobacterium aurum isolated from myiatic lesions of sheep.

Bacterial strains isolated from the healthy breech mucosa and myiatic wounds of ewes were tested for their volatile production as fly attractants towards Wohlfahrtia magnifica (Diptera: Sarcophagidae). Cultures were studied as fly baits in field experiments, and strains performing with the best chemotropic effect were selected for further analysis. Static and dynamic headspace samples from shaken cultures were examined by gas chromatography-mass spectrometry (GC-MS). Strains identified as Rhodococcus fascians and Mycobacterium aurum produced various volatile sulfur compounds and benzene, and proved to be the best fly attractants.

Animals↗
PubMed2003

Effects of fermentation temperature and Saccharomyces species on the cell fatty acid composition and presence of volatile compounds in wine.

Low temperature alcoholic fermentations are becoming more frequent due to the wish to produce wines with more pronounced aromatic profiles. However, their biggest drawback is the high risk of stuck and sluggish fermentations. Changes in the plasma membrane composition may be an adaptive response to low temperature fermentations. The production of volatile compounds and the changes in the membrane fatty acids were determined by GC to show the degree of cell adaptation and performance at low temperatures (13 degrees C) taking 25 degrees C as reference. The tests were done in two strains of Saccharomyces cerevisiae and one strain of Saccharomyces bayanus. Low temperatures restricted yeast growth and lengthened the fermentations. The analysis of plasma membrane fatty acids showed that dry yeasts had similar levels of unsaturation, between 70% and 80%, with no medium-chain fatty acids (MCFA). Long-chain saturated fatty acids (SFA) were the most frequent membrane fatty acids throughout the fermentations. Lipid composition changed with the growth temperature. The optimal membrane fluidity at low temperatures was modulated by changes in the unsaturation degree in S. cerevisiae strains. In S. bayanus, however, this change in the unsaturated fatty acid (UFA) percentage was not observed at different growth temperatures but the concentration of MCFA at low fermentation temperatures was higher. Concentrations of volatile compounds were higher in wines produced at lower temperatures and depended on the strain.

Chromatography, Gas↗
PubMed2001

Removal of volatile and semivolatile organic contamination from soil by air and steam flushing.

A soil core, obtained from a contaminated field site, contaminated with a mixture of volatile and semivolatile organic compounds (VOC and SVOC) was subjected to air and steam flushing. Removal rates of volatile and semivolatile organic compounds were monitored during flushing. Air flushing removed a significant portion of the VOC present in the soil, but a significant decline in removal rate occurred due to decreasing VOC concentrations in the soil gas phase. Application of steam flushing after air flushing produced a significant increase in contaminant removal rate for the first 4 to 5 pore volumes of steam condensate. Subsequently, contaminant concentrations decreased slowly with additional pore volumes of steam flushing. The passage of a steam volume corresponding to 11 pore volumes of steam condensate reduced the total VOC concentration in the soil gas (at 20 degrees C) by a factor of 20 to 0.07 mg/l. The corresponding total SVOC concentration in the condensate declined from 11 to 3 mg/l. Declines in contaminant removal rates during both air and steam flushing indicated rate-limited removal consistent with the persistence of a residual organic phase, rate-limited desorption, or channeling. Pressure gradients were much higher for steam flushing than for air flushing. The magnitude of the pressure gradients encountered during steam flushing for this soil indicates that, in addition to rate-limited contaminant removal, the soil permeability (2.1 x 10(-9) cm2) would be a limiting factor in the effectiveness of steam flushing.

Air Movements↗
PubMed1999

Toxicity of selected plant volatiles in microbial and mammalian short-term assays.

In this study, several short-term microbial and mammalian in vitro assays were used to evaluate cytotoxicity and genotoxicity of four plant volatiles showing antifungal activity: cinnamaldehyde, carvacrol, thymol and S(+)-carvone. All inhibited viability and proliferation of Hep-2 cells in a dose-dependent manner. IC50 ranged from 0.3 mM (cinnamaldehyde) to 0.7 mM (thymol) in viability tests and from 0.2 mM (carvacrol) to 0.9 mM (carvone) in the proliferation test. The morphological analysis suggested an involvement of apoptosis in the cases of carvone, carvacrol and cinnamaldehyde. At nontoxic doses, carvacrol and thymol increased the number of revertants in the Ames test by 1.5-1.7 times, regardless of metabolic activation. In the SOS-chromotest, none of the four plant volatiles caused DNA damage at non-toxic doses. In the DNA repair test, a marked dose-dependent differential toxicity was observed with carvone and, to a lesser extent, with cinnamaldehyde, while with thymol and carvacrol, this effect was less pronounced. In conclusion, the considered in vitro cytotoxicity assays have shown to be sensitive enough to highlight a variety of toxic effects at the cellular level, which can be rather different between chemically closely related compounds, such as isomers.

Acrolein↗
PubMed2001

Air sparging effectiveness: laboratory characterization of air-channel mass transfer zone for VOC volatilization.

Air sparging in conjunction with soil vapor extraction is one of many technologies currently being applied for the remediation of groundwater contaminated with volatile organic compounds (VOCs). Mass transfer at the air-water interface during air sparging is affected by various soil and VOC properties. In this study with a single air-channel apparatus, mass transfer of VOCs was shown to occur within a thin layer of saturated porous media next to the air channel. In this zone, the VOCs were found to rapidly deplete during air sparging resulting in a steep concentration gradient while the VOC concentration outside the zone remained fairly constant. The sizes of the mass transfer zone were found to range from 17 to 41 mm or 70d(50) and 215d(50) (d(50)=mean particle size) for low organic carbon content media (<0.01% OC). The size of the mass transfer zone was found to be proportional to the square root of the aqueous diffusivity of the VOC, and was affected by the mean particle size, and the uniformity coefficient. Effects of the volatility of the VOCs as represented by the Henry's law constants and the airflow rates on the mass transfer zone were found to be negligible but VOC mass transfer from air-water interface to bulk air phase seems to play a role. A general correlation for predicting the size of the mass transfer zone was developed. The model was developed using data from nine different VOCs and verified by two other VOCs. The existence of the mass transfer zone provides an explanation for the tailing effect of the air phase concentration under prolonged air sparging and the rebound in the VOC air phase concentration after the sparging system is turned off.

Air Movements↗
PubMed1999

Transport and fate of volatile organic chemicals in unsaturated, nonisothermal, salty porous media: 1. Theoretical development.

A wide variety of volatile organic chemicals (VOC) have been applied to agricultural land or buried in chemical waste sites. The fate of these chemicals depends upon several mechanisms such as sorption, degradation, and transport in liquid and gaseous phases. Understanding the transport mechanisms affecting the volatile chemicals can lead to better management strategies. A theory describing inorganic solute transport, water and heat transfer, and the fate and transport of VOC in porous media has been developed. This theory includes matric water pressure head, solution osmotic pressure head, gravity pressure head, temperature, inorganic solute concentration, and VOC concentration gradients as driving forces for heat and mass transfer. The effect of surface tension, as a function of VOC concentration and temperature, on the matric water pressure head is included. The VOC can be associated with gas, liquid, and solid phases of the porous media. The gas and liquid phases are mobile, but the solid phase is immobile. The transfer of VOC across the gas/liquid, liquid/solid, and gas/solid interfaces is included using sorption-equilibrium assumptions at the interfaces. The VOC can degrade. This degradation is described by a first-order decay rate. The theory can be used to predict spatial and temporal variations of water content, temperature, inorganic concentration and the total concentration of VOC within a porous medium. The concentration of VOC in each phase can be predicted also.

Hot Temperature↗
PubMed2000

Partitioning behavior of amino acids in aqueous two-phase systems with recyclable volatile salts.

As part of an ongoing research effort on aqueous two-phase systems (ATPSs) with volatile salts, this work describes the partitioning behavior of a series of amino acids, namely L-serine, glycine, L-alanine, L-valine, L-methionine, L-isoleucine, and L-phenylalanine, in these systems. The results show that amino acids partition in a similar way in polymer-volatile salt ATPSs and in traditional polymer-salt ATPSs. Increasing amino acid hydrophobicities lead to increasing partition coefficients. Moreover, the common linear relationship between the logarithm of the partition coefficient and the tie line length is observed here as well. Furthermore, the relation between relative partition coefficients and relative hydrophobicities of amino acids in the extraction systems investigated in this work is comparable to that in other extraction systems.

Amino Acids↗
PubMed2000

Isoelectric precipitation of soybean protein using carbon dioxide as a volatile acid.

A novel process is presented for the isoelectric precipitation of soy protein, using carbon dioxide as a volatile acid. By contacting a soy meal extract with pressurized carbon dioxide, the solution pH was decreased to the isoelectric region of the soy proteins. Complete precipitation of the precipitable soy proteins could be achieved for protein concentrations up to 40 g/l at pressures less than 50 bar. Isoelectric precipitation with a volatile acid enabled accurate control of the solution pH by pressure and eliminated the local pH overshoot, usual in conventional precipitation techniques. The advantage of the improved precipitation control was reflected by the morphology of the precipitate particles. Protein aggregates formed by CO2 were perfectly spherical whereas protein precipitated by sulfuric acid had an irregular morphology. The influence of process variables to control particle size is discussed.

Carbon Dioxide↗
PubMed2000

Headspace solid-phase microextraction and gas chromatographic-mass spectrometric screening for volatile hydrocarbons in blood.

Optimization for headspace solid-phase microextraction (SPME) was studied with a view to performing gas chromatographic-mass spectrometric (GC-MS) screening of volatile hydrocarbons (VHCs) in blood. Twenty hydrocarbons comprising aliphatic hydrocarbons ranging from n-hexane to n-tridecane, and aromatic hydrocarbons ranging from benzene to trimethylbenzenes were used in this study. This method can be used for examining a burned body to ascertain whether the victim had been alive or not when the burning incident took place. n-Hexane, n-heptane and benzene, the main indicators of gasoline components, were found as detectable peaks through the use of cryogenic oven trapping upon SPME injection into a GC-MS instrument. The optimal screening procedure was performed as follows. The analytes in the headspace of 0.2 g of blood mixed with 0.8 ml of water plus 0.2 microg of toluene-d8 at -5 degrees C were adsorbed to a 100-microm polydimethylsiloxane (PDMS) fiber for 30 min, and measured using the full-mass-scanning GC-MS method. The lower detection limits of all the compounds were 0.01 microg per 1 g of blood. Linearities (r2) within the range 0.01 to 4 microg per 1 g of blood were only obtained for the aromatic hydrocarbons at between 0.9638 (pseudocumene) and 0.9994 (toluene), but not for aliphatic hydrocarbons at between 0.9392 (n-tridecane) and 0.9935 (n-hexane). The coefficients of variation at 0.2 microg/g were less than 8.6% (n-undecane). In conclusion, this method is feasible for the screening of volatile hydrocarbons from blood in forensic medicine.

Burns↗
PubMed1978

Routine direct injection gas--liquid chromatographic procedure for the analysis of volatile halogenated anaesthetics in whole blood using a new external injection port.

This communication describes the design and construction of a new external injection port for the direct gas--liquid chromatographic analysis of volatile compounds in whole blood. Aliquots (4--40 microliter) of EDTA anti-coagulated blood containing the volatile compound and a weighed quantity of the internal standard, isobutanol, were injected into the disposable glass wool filter of the carrier gas stream directly onto the chromatographic column. Typical data are presented from chromatography performed with dual 6 ft. x 2 mm I.D. glass columns containing Chromosorb 101 programmed from 110--180 degrees at 6 degrees/min and the external injection port maintained at 180 degrees. The method eliminated the problems usually associated with direct injection methods and permitted the accurate analysis of halothane, methoxyflurane, diethyl ether and ethanol over the approximate range 1--100 mg%. Using this analytical procedure the distribution of halothane between the cells and plasma of human blood at 4 degrees was found to be 2.0 +/- 0.2.

Anesthetics↗
PubMed1997

In situ derivatisation and extraction of volatile fatty acids entrapped on anion-exchange resin from aqueous solutions and urine as a test matrix using pentafluorobenzyl bromide in supercritical carbon dioxide.

The simultaneous extraction and derivatisation of anion-exchange resin-trapped volatile fatty acids (C2-C5) as their pentafluorobenzyl esters has successfully been performed under CO2 supercritical fluid extraction conditions. Volatile fatty acid standards of acetic, propionic and n-butyric acids (at 20 and 100 ppm) as their ester derivatives were recovered at 78.0-101.5% (C.V. 3.5-7.5%, n=6 and 7). Likewise, acrylic acid recoveries were 57.0-61.0% (C.V. 5.5-5.6%, n=6 and 7). This methodology was applied to the quantitation of acetic, propionic, n-butyric and n-valeric acids in spiked urine as a test matrix. Initial clean-up of phosphate and sulfate in the urine was required prior to anion-exchange application and this was achieved by barium salt precipitation. Recoveries ranged from 36 to 66.5% (C.V. 5.9-14.4%, n=9 and 6).

Anion Exchange Resins↗
PubMed1999

Role of residual solvents in the formation of volatile compounds after radiosterilisation of cefotaxime.

Radiation sterilisation is a promising method to sterilise pharmaceutical products. However, this process is accompanied by a modification of odour due to volatile compounds formation. The origin of malodorous compounds produced during solid cefotaxime radiosterilisation has been investigated and several mechanisms are proposed to explain their appearance. Moreover, some quantitative data are given. Analysis of the degradation products was performed using a GC-ITD system with an injection by the static headspace technique. It appeared that some of the radio-induced compounds (such as carbon oxide sulfide and carbon disulfide) came from the degradation of the drug itself, whereas the formation of others required the presence of residual solvents which are volatile impurities already present before irradiation. Acetaldehyde directly came from impurities but the appearance of esters and acetaldehyde O-methyloxime was due to the presence of both cefotaxime and residual solvents together. Thus, the residual solvents play a key role in the radiolysis compounds formation (six of eight require the presence of them) and consequently in the modification of odour as well.

Cefotaxime↗
PubMed2002

Volatiles with antimicrobial activity from the roots of Greek Paeonia taxa.

The traditional uses of the roots of Paeonia taxa are described. The volatile constituents, obtained by steam distillation of the roots of Paeonia clusii Stern subsp. clusii, Paeonia mascula L. subsp. hellenica and Paeonia parnassica, were studied by GC/MS. Salicylaldehyde, paeonol, methyl salicylate and benzoic acid were found to be the major components among the twelve constituents identified. The evaluation of the in vitro antimicrobial activity of the volatile compounds against six bacteria and three fungi is also reported.

Anti-Bacterial Agents↗
PubMed2003

Real time breath and headspace analysis of flavour volatiles.

An overview is presented of the principle, scope and major applications to date of the use of atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) for monitoring the kinetics of release of flavour volatiles in real time, principally from breath during eating. The technique is rapid, quantitative, sensitive to the ppb level and can be used to monitor the vast majority of flavour volatiles. Advances made during the last 5 years in our understanding of factors affecting flavour release, particularly when conducted simultaneously with sensory evaluation, are contributing increasingly to more efficient product development in the food and flavour industry and to the design of flavour systems with desired dynamic flavour characteristics. Real time APCI-MS headspace data may be used to validate mathematical modelling of flavour release. It is proposed that these advances may be applied with similar benefits in the pharmaceutical industry, particularly in the improvement of the flavour acceptability of orally administered drugs.

Animals↗
PubMed2001

Development and evaluation of a mass spectrometer-based continuous emission monitor for volatile organic compound emissions from combustion devices.

A mass spectrometer-based continuous emission monitor (MS-CEM) for organic compound emissions from combustion devices was developed and evaluated at the Louisiana State University (LSU) pilot-scale rotary kiln incinerator (RKI). The MS-CEM consists of a stack probe, heat-traced sampling line, vacuum pump, particulate filter, Nafion@ dryer and mass spectrometer. The mass spectrometer includes a computer that controls and optimizes the operation of the unit. The MS-CEM is capable of continuously analyzing up to 40 different volatile organic compounds on a real-time basis. The MS-CEM is capable of analyzing, computing and recording the analytical results for each and up to 40 different organic compounds in less than 0.3 s. Four different volatile organic compounds were mixed together and injected into the baghouse inlet while simultaneously analyzing each organic component exiting the RKI stack gas. The results obtained from MS-CEM were compared with the material balance values. The system response time (including the MS-CEM) varies from 1.1 to 1.5 min.

Air Pollutants↗
PubMed2001

Removal of an airborne low volatility metal under fuel-rich and fuel lean conditions through condensation onto soot and/or sorbent particles.

The removal by a sorbent of a low volatility heavy metal, barium, from a combustor exhaust stream was investigated experimentally. The barium was introduced into the gas phase through a combustion process simulating incineration of waste materials. Sorbent- and metal-feed-rate, temperature and air intake were varied to study the impact on the gas-to-particle conversion and the metal condensation process. Peak temperature and subsequent temperature drop were found to be the dominant factors affecting the condensation process. Fuel-rich and fuel-lean conditions result in lower peak temperatures and a more rapid temperature drop relative to stoichiometric conditions. Since the metal vapor saturation pressure falls exponentially with temperature a larger condensation rate was observed, as long as nucleation was suppressed. Fuel-rich conditions promote the formation of soot particles. These particles function as sites for subsequent metal-species condensation. Chlorine was injected into the flow, to study the effect on metal vaporization. Chlorine promoted the volatilization of barium and therefore the subsequent condensation capture was made more effective.

Adsorption↗
PubMed2001

Insecticidal properties of volatile extracts of orange peels.

Statistical studies using the randomised complete block design with four replicates showed that volatile extracts of two species of orange peel--Citrus sinensis (sweet orange) and Citrus aurantifolia (lime) had insecticidal activity against mosquito, cockroach and housefly. Insecticidal activity was better after 60 min than at 30 min spraying of rooms. Volatile extracts of C. sinensis showed greater insecticidal potency, while the cockroach was the most susceptible to the orange peels among the three insects studied.

Animals↗