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At least 19 recordsLinked to original sources
PubMedDate not supplied

A dynamic two-dimensional system for measuring volatile organic compound volatilization and movement in soils.

There is an important need to develop instrumentation that allows better understanding of atmospheric emission of toxic volatile compounds associated with soil management. For this purpose, chemical movement and distribution in the soil profile should be simultaneously monitored with its volatilization. A two-dimensional rectangular soil column was constructed and a dynamic sequential volatilization flux chamber was attached to the top of the column. The flux chamber was connected through a manifold valve to a gas chromatograph (GC) for real-time concentration measurement. Gas distribution in the soil profile was sampled with gas-tight syringes at selected times and analyzed with a GC. A pressure transducer was connected to a scanivalve to automatically measure the pressure distribution in the gas phase of the soil profile. The system application was demonstrated by packing the column with a sandy loam in a symmetrical bed-furrow system. A 5-h furrow irrigation was started 24 h after the injection of a soil fumigant, propargyl bromide (3-bromo-1-propyne; 3BP). The experience showed the importance of measuring lateral volatilization variability, pressure distribution in the gas phase, chemical distribution between the different phases (liquid, gas, and sorbed), and the effect of irrigation on the volatilization. Gas movement, volatilization, water infiltration, and distribution of degradation product (Br-) were symmetric around the bed within 10%. The system saves labor cost and time. This versatile system can be modified and used to compare management practices, estimate concentration-time indexes for pest control, study chemical movement, degradation, and emissions, and test mathematical models.

Agriculture↗
PubMed1978

Comprehensive analytical procedures for the determination of volatile and non-volatile, polar and non-polar N-nitroso compounds.

The first comprehensive analytical procedures for the quantitative analysis of N-nitroso compounds are described. The scheme divides N-nitroso compounds into four major, overlapping categories: volatile (Class I), non-volatile, low polarity (Class II), non-volatile, non-ionic, high polarity (Class III) and non-volatile, ionic, high polarity (Class IV). Existing analytical techniques for each class of compound are integrated into an organized and logical sequence of analysis to allow all classes of compounds to be determined. TEA-GC is used for the volatile compounds and TEA-HPLC for the non-volatile. It is emphasized that the coincidence of retention time in either TEA-GC alone or TEA-HPLC alone cannot be taken as sufficient evidence for the identification of N-nitroso compounds, especially for samples from complex matrices. Independent techniques are required to confirm these results. The confirmatory techniques used frequently in our laboratory are: (1) spectroscopic analysis (IR, NMR, UV and MS), (2) formation and identification of derivatives, and (3) parallel TEA-GC/TEA-HPLC techniques. These procedures are now used at Thermo Electron for the comprehensive screening of environmental samples.

Chemical Phenomena↗
PubMed2004

Capillary gas chromatography-mass spectrometry of volatile and semi-volatile compounds of Salvia officinalis.

The essential oil and infusion of Salvia officinalis leaves have been widely applied in traditional medicine since ancient times and nowadays subjected to extensive research of their antibacterial, antiviral and cytotoxic properties. This paper shows chemical composition data of S. officinalis leaves essential oil isolated by steam distillation using a Clevenger-type apparatus. Also, the paper presents the chemical content of volatile and semi-volatile compounds of S. officinalis leaves infusion. The volatile and semi-volatile compounds of S. officinalis leaves infusion were isolated by solid-phase extraction (SPE) and liquid-liquid extraction with hexane and dichloromethane. SPE was carried out on 500 mg octadecylsilane (C18) cartridges and elution with dichloromethane. Liquid-liquid extraction was performed with hexane and dichloromethane. The essential oil in dichloromethane and infusion extracts in hexane and dichloromethane were analyzed by gas chromatography coupled with mass spectrometry. The quantitative results obtained by solid-phase extraction and liquid-liquid extraction showed that SPE on C18 performed the highest recovery of the volatile compounds from infusion sample.

Gas Chromatography-Mass Spectrometry↗
PubMed2005

Interactions between volatile and nonvolatile coffee components. 2. Mechanistic study focused on volatile thiols.

This study is the second of two publications that investigate the interactions between volatile and nonvolatile components in coffee brew. The purpose here was to shed some light into the chemical mechanisms responsible for the decrease of volatile thiols when in contact with coffee nonvolatiles. A mixture of volatile thiols covering a large range of physicochemical properties was monitored over time in the presence of a coffee brew model. The binding potential was estimated by SPME-GC-MS. Additives inhibiting specific reaction pathways were preincubated with the coffee brew 1 h prior to addition of the volatile compounds. Degradation kinetics of the volatile thiols were characterized by their rate constants k(obs). The effect of individual additives was shown by calculating k(rel), the relative rate constant as compared to the reference without additive. The conclusion was that thiols, mainly responsible for the "roasty" and "burnt" notes, disappear via two main chemical mechanisms. The results suggest that nucleophilic addition is the major pathway for thiol degradation. Addition occurs on oxidized species generated in the matrix in the presence of air. This mechanism prevails for aliphatic thiols (e.g., ethanethiol, methanethiol). Benzylic thiols (such as 2-furfurylthiol) can react in parallel via another pathway that is slowed in the absence of oxygen and in the presence of a radical scavenger. This points to a radical mechanism, but further work is needed to support this hypothesis. A direct correlation between thiol hydrophobicity and the magnitude of the interactions was shown as well. Therefore, weak physical interactions or hydrophobic assistance accelerating chemical reactions cannot be excluded at this point of the study.

Chemical Phenomena↗
PubMed2001

Volatile and non-volatile compounds in irradiated semi-rigid crystalline poly(ethylene terephthalate) polymers.

In this study two different semi-rigid crystalline and oriented polyethylene terephthalate materials were used and were irradiated at 25-kGy dose at room temperature by using a caesium137 radiator. Volatile and non-volatile compounds present in the irradiated materials were identified and quantified. The qualitative results obtained from HS/GC/TCD/FID analysis at room temperature showed volatiles could not be identified. The HS/GC/MSD analysis performed at 106 degrees C showed that the irradiation generated 668-742 micrograms/kg formic acid, 868-922 micrograms/kg acetic acid, 17-32 micrograms/kg 1,3-dioxolane, and 47-71 micrograms/kg 2-methyl-1, 3-dioxolane based on PET weight. The results obtained from the thermal desorption and GC/MSD performed at 200 degrees C showed that 10-12 mg/kg acetaldehyde, 479-975 micrograms/kg 1,3-dioxolane, and 6.6-11.2 mg/kg methyl-1, 3-dioxolane were detected after irradiation. The concentrations of the two dioxolanes found from thermal desorption were much higher than those observed in the HS, although formic and acetic acids were not detected. It is possible that the formic and acetic acids produced by irradiation underwent further reactions with ethylene glycol during thermal desorption to form the dioxolanes. The soluble solid extracted from various PET specimens before and after irradiation were in a range of 0.67-0.78%. PET cyclic trimer is the major component and is present at 0.41-0.50%, accounting for more than 50% of the percent total solid in PET. Statistically, irradiation did not increase the soluble solid and cyclic trimer. The overall results suggest that 25-kGy irradiation had a significant effect on increasing the volatile but not the non-volatile compounds detected in the PET specimens.

Analysis of Variance↗
PubMed2003

Comprehensive two-dimensional gas chromatography of volatile and semi-volatile components using a diaphragm valve-based instrument.

A high-temperature configuration for a diaphragm valve-based gas chromatography (GCXGC) instrument is demonstrated. GCxGC is a powerful instrumental tool often used to analyze complex mixtures. Previously, the temperature limitations of valve-based GCxGC instruments were set by the maximum operating temperature of the valve, typically 175 degrees C. Thus, valve-based GCxGC was constrained to the analysis of mainly volatile components; however, many complex mixtures contain semi-volatile components as well. A new configuration is described that extends the working temperature range of diaphragm valve-based GCxGC instruments to significantly higher temperatures, so both volatile and semi-volatile compounds can be readily separated. In the current investigation, separations at temperatures up to 250 degrees C are demonstrated. This new design features both chromatographic columns in the same oven with the valve interfacing the two columns mounted in the side of the oven wall so the valve is both partially inside as well as outside the oven. The diaphragm and the sample ports in the valve are located inside the oven while the temperature-restrictive portion of the valve (containing the O-rings) is outside the oven. Temperature measurements on the surface of the valve indicate that even after a sustained oven temperature of 240 degrees C, the portions of the valve directly involved with the sampling from the first column to the second column track the oven temperature to within 1.2% while the portions of the valve that are temperature-restrictive remain well below the maximum temperature of 175 degrees C. A 26-component mixture of alkanes, ketones, and alcohols whose boiling points range from 65 degrees C (n-hexane) to 270 degrees C (n-pentadecane) is used to test the new design. Peak shapes along the first column axis suggest that sample condensation or carry-over in the valve is not a problem. Chemometric data analysis is performed to demonstrate that the resulting data have a bilinear structure. After over 6 months of use and temperature conditions up to 265 degrees C, no deterioration of the valve or its performance has been observed.

Chromatography, Gas↗
PubMed1984

[Rumen fermentation with special reference to volatile fatty acid production during reproduction. 1. Methods and results of volatile fatty acid levels and production rates in vitro].

The target of the investigations was to register part of the synthesis performance in the rumen of ewes during the complete reproduction cycle. With the help of in-vitro experiments with artificial rumen the concentration and production rates of volatile fatty acids in the rumen fluid were measured. From the experiments the measured data of fertility-accentuated crossbreeding (experiment 1) and crossbreeding (experiment 2) ewes were contrasted. The average concentrations of volatile fatty acids in ewes are 95.4 m mol/l in experiment 1 and 109.2 m mol/l in experiment 2 during the early stage gestation, 121.4 m mol/l in experiment 1 and 99.8 m mol/l in experiment 2 in the last stage stage of gestation, 129.6 m mol/l in experiment 1 and 112.8 m mol/l in experiment 2 during lactation and 106.6 m mol/l in experiment 1 and 112.9 m mol/l in experiment 2 during the dry period. The production rates of volatile fatty acids calculated form their concentration amount to 4.8 m mol/l X h in experiment 1 and 2.6 m mol/l X h in experiment 2 in the early stage of gestation, 3.5 m mol/l X h in experiment 1 and 3.1 m mol/l X h in experiment 2 in the last stage of gestation, 3.2 m mol/l X h in experiment 1 and 2.7 m mol/l X h in experiment 2 during lactation and 3.7 m mol/l X h in experiment 1 and 2.9 m mol/l X h in experiment 2 in the dry period. The correlation between the concentration and the production rate of volatile fatty acids is not significantly negative in either of the ewe experiments. The scattering of the individual values is wide so that the individual influence of the test animals as well as the influence of the in-vitro method used permit the conclusion that a significant statement on the influence of the genotype and the stage of reproduction on the production rates cannot be made.

Animals↗
PubMed1976

Production of volatiles from decomposing plant tissues and effect of these volatiles on Rhizoctonia solani in culture.

Volatiles, of which NH3 is a major component, were evolved from decomposing immature corn tissue (c:n9) and affected R. solani in culture two ways: they supplied additional nitrogen to the growth medium so that fungal mycelial growth increased; and they raised substrate pH from 5.5 to 8.2 which induced melanization of mycelium. Volatiles increased fungus growth and pigmentation within 2 weeks of amendment addition to soil. Increases were concomitant with NH3 production from corn tissue. More NH3 evolved from decomposing corn tissues of C:N9 and 17 than from those of C-N 33 and 81. More growth and pigmentation occurred in flasks through which volatiles from decomposing corn (C:N9) were passed than in flasks through which volatiles from nonamended soil or decomposing corn (C:N81) were passed. Carbon dioxide from decomposing tissues did not affect growth or pigmentation. Twice as much NH3 evolved from corn tissue (C:N9) which decomposed in saturated soil than from tissue which decomposed in soil at 50% of its water-holding capacity. Pigment production doubled under saturated conditions.

Ammonia↗
PubMed1963

THE METABOLISM OF THE VOLATILE AMINES: VI. THE IDENTIFICATION OF THE VOLATILE BASE PRESENT IN BLOOD.

As part of a series of studies into the etiology of acute hepatic encephalopathy the identity of the volatile base, which had been extracted from blood and presumed to be ammonia, was investigated. In order to differentiate between ammonia and the other volatile bases with which it can be confused, a method of separating these compounds by the use of gas chromatography was developed. The technique is described in detail because it incorporates several novel ideas that can be applied to the isolation and identification of similar compounds in many biological systems. The volatile base extracted from blood was found to be ammonia, and no other volatile base was demonstrable in blood from both healthy subjects and patients suffering from acute hepatic encephalopathy.

Alkalies↗
PubMedDate not supplied

Emission of herbivore-induced volatiles in absence of a herbivore--response of Zea mays to green leaf volatiles and terpenoids.

Green leaf volatiles (GLV), a series of saturated and monounsaturated six-carbon aldehydes, alcohols, and esters are emitted by plants upon mechanical damage. Evidence is increasing that intact plants respond to GLV by activating their own defense mechanisms, thus suggesting that they function in plant-plant communication. The present paper demonstrates that exposure of maize plants to naturally occurring GLV, including (Z)-3-, (E)-2- and saturated derivatives, induce the emission of volatile blends typically associated with herbivory. Position or configuration of a double bond, but not the functional group of the GLV influenced the strength of the emissions. (Z)-3-Configured compounds elicited stronger responses than (E)-2- and saturated derivatives. The response to (Z)-3-hexen-1-ol increased linearly with the dose between 200 and 1000 nmol per plant. Not only the naturally occurring (E)-2-hexenal, but also (E)-2-pentenal and (E)-2-heptenal induced maize plants, although to a lesser extent. Externally applied terpenoids [(3E)-4,8-dimethyl-1,3,7-nonatriene, beta-caryophyllene, and (E)-beta-farnesene] did not significantly increase the total amount of inducible volatiles in maize. Of three tested maize cultivars Delprim and Pactol responded much stronger than Attribut. Recovery experiments in the presence and absence of maize plants demonstrated that large proportions of externally applied GLV were assimilated by the plants, whereas (3E)-4,8-dimethyl-1,3,7-nonatriene was recovered in much higher amounts. The results furthermore suggested that plants converted a part of the assimilated leaf aldehydes and alcohols to the respective acetates. We propose that GLV not only can alert neighboring plants, but may facilitate intra-plant information transfer and can help mediate the systemic defense response in a plant.

Animals↗
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↗
PubMed1985

[Studies on rumen fermentation with special reference to the volatile fatty acid production rate in ewes during reproduction. 2. Production rate of volatile fatty acids and rumen volume].

Methods and results of the measuring of the rumen volume and the passage rate as well as the dependence of the production of volatile fatty acids on the parameters mentioned are described. The correlative relations between rumen volume on the one hand and feed passage on the other hand to the production quotas are investigated. Passage rates and rumen volumes were determined with the help of the isotope dilution method. In the course of reproduction rumen volumes of 7.81, 6.41, 8.91, 7.11 in experiment 1 and 5.41, 5.81, 9.51 and 4.71 in experiment 2 were measured in the sequence early stage of gestation, late stage of gestation, lactation and the period between pregnancies. The average total production of volatile fatty acids within 12 hours amounted to 475 mmol, 265 mmol, 313 mmol and 351 mmol in experiment 1 and 155 mmol, 175 mmol, 271 mmol and 144 mmol in experiment 2 in the same sequence. The average passage duration of the feed through the digestive tract of the ewes was 32.4 h in experiment 1 and 33.6 h in experiment 2. The relatively high feed intake of the ewes resulted in a short passage duration and could be a cause of the low production quotas of the volatile fatty acids.

Animals↗
PubMed1983

Production and metabolism of volatile fatty acids, glucose and CO2 in steers and the effects of monensin on volatile fatty acid kinetics.

A study was conducted to determine effects of monensin supplementation on production and interconversion rates of rumen acetate, propionate, and butyrate and plasma acetate. Measurements were made by isotope dilution techniques in four Holstein steers fed a 70% alfalfa hay, 30% corn ration. In addition, a general kinetic method for solution of open systems has been applied to quantify metabolism of the rumen volatile fatty acids and glucose and the production of CO2. Dietary monensin increased rumen propionate production at the expense of rumen acetate production so that total volatile fatty acid production was unchanged. Butyrate production tended to increase, indicating that decreased acetate production may result in diversion of hexose to propionate and butyrate production and direction of reducing equivalents away from methane production. These changes were calculated to increase rumen fermentation efficiency by 6%. Oxidation of the rumen volatile fatty acids and systemic plasma glucose accounted for only 35% of CO2 production.

Acetates↗
PubMed2002

An essential role of s-adenosyl-L-methionine:L-methionine s-methyltransferase in selenium volatilization by plants. Methylation of selenomethionine to selenium-methyl-L-selenium- methionine, the precursor of volatile selenium.

Selenium (Se) phytovolatilization, the process by which plants metabolize various inorganic or organic species of Se (e.g. selenate, selenite, and Se-methionine [Met]) into gaseous Se forms (e.g. dimethylselenide), is a potentially important means of removing Se from contaminated environments. Before attempting to genetically enhance the efficiency of Se phytovolatilization, it is essential to elucidate the enzymatic pathway involved and to identify its rate-limiting steps. The present research tested the hypothesis that S-adenosyl-L-Met:L-Met S-methyltransferase (MMT) is the enzyme responsible for the methylation of Se-Met to Se-methyl Se-Met (SeMM). To this end, we identified and characterized an Arabidopsis T-DNA mutant knockout for MMT. The lack of MMT in the Arabidopsis T-DNA mutant plant resulted in an almost complete loss in its capacity for Se volatilization. Using chemical complementation with SeMM, the presumed enzymatic product of MMT, we restored the capacity of the MMT mutant to produce volatile Se. Overexpressing MMT from Arabidopsis in Escherichia coli, which is not known to have MMT activity, produced up to 10 times more volatile Se than the untransformed strain when both were supplied with Se-Met. Thus, our results provide in vivo evidence that MMT is the key enzyme catalyzing the methylation of Se-Met to SeMM.

Adaptation, Physiological↗
PubMed1991

Recent methods for the determination of volatile and non-volatile organic compounds in natural and purified drinking water.

Four analytical protocols for the extraction and preconcentration of organic residues in natural or purified drinking water were investigated and compared: closed loop stripping analysis; simultaneous extraction-distillation; purge and trap analysis; continuous liquid-liquid extraction. Organic extracts were submitted to a variety of separation and identification techniques. Volatiles were determined by conventional capillary column gas chromatography with tandem mass spectrometry, using triple-stage quadrupole instruments. Non-volatile and thermally labile molecules were investigated by several different techniques (high-temperature gas chromatography, capillary column supercritical fluid chromatography, pyrolysis gas chromatography-mass spectrometry, thermospray liquid chromatography with tandem mass spectrometry and conventional fast-atom bombardment with tandem mass spectrometry). Several samples recently examined in the laboratory provide examples of this multitechnique approach for a more complete knowledge of the organic carbon distribution in water-dissolved organic matter, taking into account organic substances with widely different volatilities, polarities and thermal stabilities.

Chlorides↗
PubMed1998

Volatile anesthetics and a volatile convulsant differentially affect GABA(A) receptor-chloride channel complex.

1. General anesthetics at clinical concentrations are known to affect neurotransmitter-gated ion channels in postsynaptic membranes. 2. Volatile anesthetics suppress excitatory transmissions, whereas they potentiate inhibitory chloride currents evoked by GABA or glycine. Hexafluorodiethyl ether (a volatile convulsant) markedly depresses the GABA(A) response but not the glycine-evoked chloride current or the glutamate-induced excitatory response. 3. Molecular biology has revealed that GABA(A) receptor is a heteromeric pentamer composed of alpha, beta, gamma, delta, and/or rho subunits. In baculovirus-Sf9 expression system, the gamma subunit was crucial for potentiation of the GABA-induced chloride current by volatile anesthetics. 4. Following sustained presence of GABA and high concentrations of isoflurane, simultaneous washout of both agents evoked a slowly decaying surge current, whose nature is controversial.

Anesthetics, Inhalation↗
PubMed2005

Simultaneous determination of volatile and semi-volatile aromatic hydrocarbons in virgin olive oil by headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry.

A reliable, simple and relatively fast method for the simultaneous determination of volatile and semi-volatile aromatic hydrocarbons in virgin olive oil was developed, based on headspace solid-phase microextraction (HS-SPME). The investigation regarded eco-contaminants such as alkylated monoaromatic hydrocarbons from C1- to C4-benzenes and light polyaromatic hydrocarbons up to four aromatic rings. Sampling and chromatographic conditions were optimized by using standard solutions in deodorized olive oil and the analytical performances of the method were determined. The proposed method was then applied to real samples of virgin olive oil were the target hydrocarbons could be identified and quantified. Several of them had not been previously quantified in virgin olive oil. Moreover, by the analysis of olive oil samples an additional number of C4-benzenes could be tentatively identified.

Chemical Fractionation↗