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PubMed2004

Sonochemical decomposition of volatile and non-volatile organic compounds--a comparative study.

Sonochemical degradation which combines destruction of the target compounds by free radical reaction and thermal cleavage is one of the recent advanced oxidation processes (AOP) and proven to be effective for removing low concentration organic pollutants from aqueous streams. This work describes the degradation of several organic compounds of varying volatility in aqueous solution in two types of ultrasonic reactors. The process variables studied include initial concentration of the organics, temperature, and type of saturated gas. The effects of additional oxidant and electrolyte were also examined. A kinetic model was tested to determine its ability to predict the degradation rate constant of different volatile organic compounds at different initial conditions. A figure of merit for the electrical energy consumption for the two types of ultrasonic reactors is also presented.

Forecasting↗
PubMed2000

Time-weighted average sampling of volatile and semi-volatile airborne organic compounds by the solid-phase microextraction device.

The ultimate goal of the chemist is to perform sample preparation, and analysis, if possible at the place where a sample is located rather than moving the sample to laboratory, as is common practice in many cases at the present time. This approach eliminates errors and time associated with sample transport and storage and therefore it would result in more accurate, precise and faster analytical data. In addition to portability, two other important features of ideal field sample preparation technique are elimination of solvent use and integration with a sampling step. A method is developed which addresses these requirements for the determination of time-weighted average concentration of gas phase compounds using a solid-phase microextraction device. Quantification of target analytes in air using this method can be carried out without external calibration. The volatile and semi-volatile organic compounds in air diffuse into the fiber coating which is retracted a known distance into its needle housing during the sampling period. The coatings used are poly(dimethylsiloxane) and poly(dimethylsiloxane)-divinylbenzene. The sampling rate at which gas phase analytes load onto the fiber is determined for a wide range of hydrocarbons. There is a good agreement between the theoretical and experimental sampling rates. Sampling time ranges from 1 min to 24 h depending on the coating used and its retraction distance. Effect of the flow-rate on the uptake rate by the fiber is studied. The method is tested in the field and compared with National Institute of Occupational Health and Safety Method 1550. Good agreement between the results is obtained.

Chromatography↗
PubMed1999

Chemical uptake into human stratum corneum in vivo from volatile and non-volatile solvents.

PURPOSE: Simple, safe and quick in vivo methods for estimating chemical uptake into the stratum corneum (SC) from volatile and non-volatile solvents are invaluable to health risk assessors. This study compares the human in vivo SC uptake of a model compound (4-cyanophenol) from water and acetone using quantitative attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. METHODS: Small areas on the ventral forearms of human volunteers were treated with 4-cyanophenol (CP) dissolved either in water or acetone. After the skin was cleansed of remaining surface CP, SC samples were taken by a standard tape-stripping method. CP concentration profiles across the SC were quantitated by direct measurement of the permeant on the individual tape-strips using ATR-FTIR. RESULTS: Increasing the duration of exposure to CP aqueous solutions resulted in increasing CP uptake into the SC; the kinetics of uptake correlated well with predictive diffusion equations. Increasing the 'dose' of CP in acetone also resulted in increasing uptake into the SC, but uptake eventually plateaued at a maximum level. The amount of CP taken up into the SC from acetone was 2 to 8-fold greater than that from water following similar short-time exposures. CONCLUSIONS: These safe, simple experimental methods provide practical and predictive assessments of chemical uptake into human SC in vivo.

Adult↗
PubMed2002

Observation of volatile and semi-volatile carbonyls in an Algerian urban environment using dinitrophenylhydrazine/silica-HPLC and pentafluorophenylhydrazine/silica-GC-MS.

Lower carbonyls and n-alkanals from C5 to C10 were measured from late autumn 2000 to summer 2001 in two urban areas in the Algerian territory: Algiers and Ouargla. They were collected on silica cartridges coated with dinitrophenylhydrazine (DNPH) and pentafluorophenylhydrazine (PFPH), which were analysed by HPLC-UV and high-resolution GC-MS. respectively. The two methods were used in parallel samplings in a suburban Algiers site and provided consistent results for semi-volatile congeners, as differences in the concentration data did not exceed 21% on average for individual carbonyl levels ranging from 0.0 to 0.5-2.6 microg m(-3). Concentrations of formaldehyde up to 27 and 5 microg m(-3) were monitored during 10 h samplings in the daytime in Algiers and Ouargla, respectively; acetaldehyde reached values of 13 and 5 microg m(-3), whilst acetone was the most abundant ketone with peak levels of 14 and 4 microg m(-3), respectively. High night-time levels of lower carbonyls were also measured at both locations. Among the semi-volatile alkanals, the highest levels were observed in suburban Algiers for hexanal and nonanal (2.2 microg m(-3)) and in downtown Algiers for valeraldehyde (2.6 microg m(-3)), whilst in Ouargla only hexanal and nonanal levels within the C5-C10 fraction exceeded 1 microg m(-3). Moreover, benzaldehyde concentrations as high as 5 microg m(-3) were measured in the centre of Algiers. Algiers data are comparable with those found in photochemically polluted urban areas of Europe and the USA. Strong correlations between formaldehyde and acetaldehyde and between formaldehyde and benzaldehyde were observed; by contrast, acetone did not show any correlation with the lower aldehydes, suggesting the existence of carbonyl sources other than vehicular traffic. Diurnal variations of almost all carbonyls suggested that motor vehicles were the most important source in the winter, whereas photochemical production appeared to predominate during the summer.

Acetaldehyde↗
PubMed2001

[Reduction of the volatility of volatile organic compounds with cyclodextrins: application to their capture].

The interactions existing between beta-cyclodextrin, hydroxypropyl-beta-cyclodextrin and six volatile organic compounds (VOC) were studied and used for capture of such pollutants. The reduction of volatility for these VOC appeared to be equivalent for the two kinds of cyclodextrins at equal concentrations, while a higher solubility conferred higher efficiency to hydroxypropyl-beta-cyclodextrin. The use of such cyclodextrins in traps allowed a two-fold increase in VOC capture compared with genuine water. Application of this process to an industrial site showed its efficacity qualitatively while several optimization procedure are needed to achieve quantitative efficacy.

Cyclodextrins↗
PubMed2004

Surface microlayer enrichment of volatile organic compounds and semi-volatile organic compounds in drinking water source.

Enrichment of volatile organic compounds(VOC) and semi-volatility organic compounds(SVOC) in surface microlayer(SM) of three drinking water sources were studied. The enrichment factor(EFs) were 0.67 to 13.37 and 0.16 to 136, respectively. The results showed some VOC and most SVOC could enrich in SM. Some EFs of SVOC was quite high. Suspension and temperature could affect EFs of SVOC, slim wind and water movement do not destroy enrichment of organic in SM.

Gas Chromatography-Mass Spectrometry↗
PubMed1990

[Effects of processing methods on the amounts of volatile oil of nutmeg and on isolation and characterization of the volatile oil constituents].

In this paper, the authors investigated the effects of various processing methods, i.e., scalding in hot purified talc, simmering wrapped in flour in hot purified talc and stir-frying in smoking wheat bran, on nutmeg (Semen Myristicae) in terms of the quantities of the volatile oil. The experimental results revealed that the amounts of volatile oil contained in nutmeg vary remarkably with the lengths of cooking time and the fluctuation of temperature. Detected by GC-MS-computer, 32 compounds of nutmeg were characterized, and their contents were determined by GC respectively.

Allylbenzene Derivatives↗
PubMed1978

Recent studies in Canada on the analysis and occurrence of volatile and non-volatile N-nitroso compounds in foods.

The present paper briefly summarizes the research activities of the Food Research Laboratories, Canadian Health Protection Branch, during the past two years. Data presented indicate that traces of nitrosamines, mainly nitrosodimethylamine and nitrosodiethylamine, can occur in cheese. Several new analytical methods are presented for the determination of non-volatile nitroso compounds, such as nitrosohydroxypyrrolidine, nitrosodiethanolamine, nitrosoproline, nitrosohydroxyproline and nitrosoglyphosphate (a nitrosated herbicide). It is shown that all of the above compounds, even the very polar nitrosoglyphosphate, can be converted to volatile derivatives and then analysed by GLC-MS or by conventional GLC using a specific (such as P-photometric) detector. Traces of nitrosohydroxypyrrolidine have been detected in a few samples of cooked bacon. Contrary to previously reported findings, no significant levels of nitrosoproline were detected in the 6 samples of raw bacon analysed.

Animals↗
PubMed1982

A rapid and sensitive method for the determination of non-volatile n-nitroso compounds in foods and human urine: recent data concerning volatile N-nitrosamines in dried foods and malt-based beverages.

Methods are described for the rapid screening of various foods for the presence of nitrosamino acids (mainly NPRO and NSAR) and of hydroxylated nitrosamines (mainly BHBN, NHPYR and NDELA). Rapid screening methods (HPLC-TEA and GC-TEA) are also described for the determination of the above mentioned nitrosamines in human urine. Recent monitoring data indicate that, in Canada, the NDMA levels in both malt and beer have decreased significantly during the last two years. Contrary to published reports, no volatile nitrosamines could be detected in vegetable oils or pasteurized milk. A new method, based on oxidation of nitrosamines and nitramines and reanalysis by GC-TEA, is described for the confirmation of low microgram/kg levels of volatile nitrosamines in foods.

Beer↗
PubMed2006

A coaxially heated membrane introduction mass spectrometry interface for the rapid and sensitive on-line measurement of volatile and semi-volatile organic contaminants in air and water at parts-per-trillion levels.

A coaxially heated membrane introduction mass spectrometry (MIMS) sampling interface is presented that demonstrates improved on-line performance for the direct measurement of semi-volatile organic compounds (SVOCs) in air and water samples at parts-per-trillion levels. The device is based on a polydimethylsiloxane (PDMS) capillary hollow fibre membrane (HFM) in a pneumatically assisted "flow-over" configuration that is resistively heated on the membrane interior via a coaxial nichrome wire, establishing a thermal gradient counter to the analyte concentration gradient. This arrangement allows for continuous and/or pulsed heating modes, affording excellent sensitivity for the on-line measurement of SVOCs while retaining sensitivity for volatile organic compounds (VOCs). In addition, the signal response time for SVOCs is reduced substantially over conventional "flow-over" MIMS interfaces. Separation and quantitation of analytes are achieved using quadrupole ion trap tandem mass spectrometry.

Journal Article↗
PubMed1990

Infrared analysis of volatile anesthetics: impact of monitor agent setting, volatile mixtures, and alcohol.

Infrared analysis can determine exhaled concentrations of the three volatile anesthetics in common use because each absorbs infrared light. Many infrared analyzers use a single source of infrared light at a wavelength of 3.3 microns for measurements of all three agents but cannot identify which agent is in use. Organic gases such as ethanol also absorb infrared light. This study determined the effects on the accuracy of a single-wavelength infrared anesthetic monitor (Capnomac, Puritan-Bennett PB254) of (1) incorrect anesthetic agent setting, (2) mixtures of volatile anesthetics, and (3) ethanol vapor in the analyzed gas. Changing the agent setting on the monitor during steady-state delivery of an agent resulted in readings for the halothane setting five times higher than those for the enflurane setting, and six times higher than those for the isoflurane setting. These ratios reflect the monitor's fixed internal gain for each agent setting. Mixtures of anesthetics had a simple additive effect on the monitor's accuracy. With the monitor set for halothane, 0.2 vol% isoflurane mixed with halothane caused readings 1.2 vol% higher than the true halothane concentration. Conversely, with the monitor set for isoflurane, 1 vol% halothane mixed with isoflurane resulted in readings 0.2 vol% too high. In a model simulating alveolar gas, ethanol vapor corresponding to blood alcohol levels of 0.10, 0.30, and 0.50% had a slight but not clinically significant effect on readings for enflurane and isoflurane but increased readings with the halothane setting 3.5 times the corresponding level of blood alcohol. Clinicians can test for an interfering gas such as ethanol before induction by checking the reading in the halothane setting during preoxygenation.

Anesthesia, Inhalation↗
PubMed1990

Sonochemistry of volatile and non-volatile solutes in aqueous solutions: e.p.r. and spin trapping studies.

Recent spin trapping studies of the free radical intermediates generated by the sonolysis of aqueous solutions are reviewed. Studies of rare gas saturated solutions of volatile solutes (e.g., methanol and ethanol) and of non-volatile solutes (acetate, amino acids, sugars, pyrimidines, nucleotides and surfactants) are consistent with the theory of three reaction zones in aqueous sonochemistry. The very high temperatures and pressures induced by acoustic cavitation in collapsing gas bubbles in aqueous solutions lead to the thermal dissociation of water vapour into hydrogen atoms and hydroxyl radicals. Reactions take place in the gas phase (pyrolysis reactions), in the region of the gas-liquid interface, and in the bulk of the solution at ambient temperature (similar to radiation chemistry reactions). By use of the rare gases with different thermal conductivities, the contributions of individual reaction steps with widely different energies of activation can be evaluated.

Alcohols↗
PubMed2003

A universal temperature controlled membrane interface for the analysis of volatile and semi-volatile organic compounds.

A universal temperature controlled membrane interface (TCMI) has been constructed for hollow-fibre membranes. The membrane temperature is controllable in the range -70 to 250 degrees C using an electric heater and a flow of cooled nitrogen or helium gas. Volatile and semi-volatile organic compounds may be detected either by continuous diffusion across the membrane or by in-membrane pre-concentration followed by thermal desorption into the detector. The TCMI interface is demonstrated in combination with mass spectrometry and GC-MS, for the determination of VOCs and SVOCs in aqueous and air samples and for the on-line monitoring of a bioreactor.

Flow Injection Analysis↗
PubMed2005

Volatile and non-volatile radiolysis products in irradiated multilayer coextruded food-packaging films containing a buried layer of recycled low-density polyethylene.

The effects of gamma-irradiation (5-60 kGy) on radiolysis products and sensory changes of experimental five-layer food-packaging films were determined. Films contained a middle buried layer of recycled low-density polyethylene (LDPE) comprising 25-50% by weight (bw) of the multilayer structure. Respective films containing 100% virgin LDPE as the buried layer were used as controls. Under realistic polymer/food simulant contact conditions during irradiation, a large number of primary and secondary radiolysis products (hydrocarbons, aldehydes, ketones, alcohols, carboxylic acids) were produced. These compounds were detected in the food simulant after contact with all films tested, even at the lower absorbed doses of 5 and 10 kGy (approved doses for food preservation). The type and concentration of radiolysis products increased progressively with increasing dose. Generally, there were no significant differences in radiolysis products between samples containing a buried layer of recycled LDPE and those containing virgin LDPE (all absorbed doses), indicating the good barrier properties of external virgin polymer layers. Volatile and non-volatile compounds produced during irradiation affected the sensory properties of potable water after contact with packaging films. Taste transfer to water was observed mainly at higher doses and was more noticeable for multilayer structures containing recycled LDPE, even though differences were slight.

Color↗
PubMed1991

Effects of two volatile anesthetics and a volatile convulsant on the excitatory and inhibitory amino acid responses in dissociated CNS neurons of the rat.

1. Effects of two volatile anesthetics [halothane (Hal) and enflurane (Enf)] and a volatile convulsant [hexafluorodiethyl ether (HFE)] on amino acid-induced membrane currents in neurons dissociated from the nucleus tractus solitarius of the rat were examined. The dissociated neurons were voltage clamped in the whole-cell mode of the patch-clamp technique. All drugs were applied with a microperfusion system, termed the "Y-tube" method. 2. The glutamate (Glu)-induced excitatory response was slightly reduced by both the anesthetics. The responses to three agonists at Glu receptor were depressed by Hal (10(-3) M) in the rank order of quisqualate greater than N-methyl-D-aspartate greater than kainate. HFE slightly increased the Glu response at a high concentration of 2 x 10(-3) M. 3. The gamma-aminobutyric acid (GABA)-induced chloride current (ICl) was enhanced by both anesthetics. The dissociation constant (Kd) for the enhancement was 2.3 x 10(-4) M for Hal and 2.1 x 10(-4) M for Enf, and the Hill coefficient was 1.6 for Hal and 1.5 for Enf. HFE depressed the GABA response with a Kd of 8.7 x 10(-5) M and a Hill coefficient of 0.84. 4. Hal (10(-3) M) and Enf (10(-3) M) decreased the Kd of the GABA concentration-response curve from 3.5 x 10(-6) to 10(-6) and 1.9 x 10(-6) M, respectively, without changing the maximum response or the Hill coefficient (1.5). In the presence of HFE (10(-4) M), the Kd was increased to 1.4 x 10(-5) M and the Hill coefficient was slightly changed to 1.2.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed2007

An electrospray membrane probe for the analysis of volatile and semi-volatile organic compounds in water.

A new membrane probe incorporating electrospray ionization (ESI) was designed, built and coupled to an ion trap mass spectrometer to detect low levels of semi-volatile organic compounds (SVOCs) in water. Similar to other membrane introduction mass spectrometry (MIMS) systems, the probe contains a capillary polydimethylsiloxane (PDMS) membrane to allow for the preferential permeation of small molecules but, in contrast, the interface uses a liquid/membrane/liquid interface rather than liquid/membrane/gas. The ESI source allows the probe to be operated at atmospheric pressure in positive or negative ionization mode and the lack of fragmentation in ESI allows for the simultaneous screening of many analytes with high sensitivity. The interface allows for the addition of additives to both the external and the internal liquid mobile phases to selectively improve permeation and/or the ionization efficiency of various classes of compounds. Characterization of the probe with methanol as the internal mobile phase showed that the signal for aniline optimized at 60 degrees C and an internal flow rate between 2-5 microL/min. The transfer of analyte through the membrane from water to methanol ensures a strong signal and robust electrospray for both positive and negative ion mode which is not typical when spraying pure water. Detection limits for aniline, pyridine and pentachlorophenol, and for the herbicides alachlor, atrazine, butachlor, metolachlor and simazine, were in the ppb to pptr range.

Environmental Monitoring↗
PubMed1977

The adsorption of volatile aroma constituents by foods. VIII. Adsorption of volatile carbonyl compounds by amino acids.

The adsorption of some volatile aldehydes and ketones by 22 dry amino-acids was studied. The adsorbed amounts decreased approximately in the order: propanal, biacetyl, hexenal, hexanal, acetone, pentan-3-one, nonan-3-one, undecanal and nonan-5-one, but there were great differences in the adsorption capacity of the amino acids. Lys adsorbed best and often irreversible, arg, his, phe, trp, pro, and val (leu, ile) very good. With cys, thiazolidinecarboxylic acids were formed. In most cases of adsorption exceeding 100 mmol/mol, except for the monoketones, strong discoloration, probably of the maillard type, was observed. Propanal and hexanal were to a great extend converted to aldol addition and condensation products. Tyr and hyp adsorbed less than the corresponding amino-acids without hydroxyl groups. This is attributed to stronger crystal-lattice forces.

Adsorption↗