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At least 883 records · Page 49Linked to original sources
PubMed2000

Analytical method using gas chromatography and ion trap tandem mass spectrometry for the determination of S-triazines and their metabolites in the atmosphere.

Gas chromatography-ion trap detector (GC-ITD) was used to detect atmospheric triazines and their degradation products in the gaseous and particulate phases. Because triazines and their metabolites are expected to be present at very low concentrations and enclosed in the complex atmospheric matrix, the analytical method used was both highly selective and sensitive. These two properties were obtained by associating chromatography with ion trap tandem mass spectrometry (GC-ITD (MS/MS)). To develop this method, a comparison between the two ionization modes (electron impact and positive-chemical-ionisation) in single-MS was first conducted to choose the parent ions of the five target analytes, i.e. atrazine, desethylatrazine, deisopropylatrazine, terbuthylazine and desethylterbuthylazine. Then, a MS/MS method was optimised by parameters such as the radio frequency storage level and the collision-induced dissociation excitation voltage. Finally, a last step enabled the development of a calibrating program based on the quantification of daughter ions. With this analytical procedure, the detection limits varied between 0.8 and 15 pg m(-3) depending on the compounds under study. This method was tested with success for four atmospheric samples collected in Strasbourg (France) in which four of the five target compounds were detected.

Journal Article↗
PubMed2003

Interaction of a mixed yeast culture in an "autotroph-heterotroph" system with a closed atmosphere cycle and spatially separated components.

The study considers an experimental model of the "autotroph-heterotroph" system with a closed atmosphere cycle, in which the heterotrophic link is a mixed yeast population. The autotrophic link is represented by the algae Chlorella vulgaris and the heterotrophic link by the yeasts Candida utilis and Candida guilliermondii. The controls are populations of Chlorella and the same yeasts isolated from the atmosphere. It has been shown that the outcome of competition in the heterotrophic link depends on the strategy of the yeast population towards the substrate and oxygen. The C. utilis population quickly utilizes the substrate as it is an r-strategist and is less sensitive to oxygen deficiency. The C. guilliermondii population consumes low concentrations of the substrate because it is a K-strategist, but it is more sensitive to oxygen deficiency. That is why, in the "autotroph-heterotroph" system with a closed gas cycle, after a considerable amount of the substrate has been consumed, the C. guilliermondii population becomes more competitive that the C. utilis population. In the culture of yeasts, isolated from the atmosphere, the C. utilis population finds itself in more favorable conditions due to oxygen deficiency. The system with a complex heterotrophic component survive longer than a system whose heterotrophic component is represented by only one yeast species. This is explained for by the positive metabolite interaction of yeasts and a more complete utilization of the substrate by a mixed culture of yeasts featuring different strategies towards the substrate.

Anaerobiosis↗
PubMed2002

The effect of storage in an inert atmosphere on the release of inorganic constituents during intermittent wetting of a cement-based material.

Monolithic waste materials (e.g. Portland cement treated wastes) in many field scenarios do not remain continuously saturated, but experience intermittent wetting interspersed with periods of storage in an unsaturated environment. During storage, the matrix may loss moisture to the environment, promoting precipitation or redistribution of species. In addition, the matrix may react with the surrounding atmosphere through carbonation or oxidation. Upon subsequent leaching, changes in the chemical and physical composition incurred over the storage interval can influence the release of inorganic species. Current assessment approaches, which use continuous leaching data to project release over some assessment interval, do not allow for changes in leachability resulting from intermittent wetting and storage. Thus, this study evaluates the effect of storage intervals in an inert atmosphere on subsequent release of inorganic species from a synthetic Portland cement matrix. Tank leaching in deionized water was interspersed with storage at three relative humidity (RH) levels (nominally 0, 50 and 100% RH) in a 100% nitrogen atmosphere. Leaching data from the three intermittent wetting cases were compared to continuous leaching for the release of structural species (Ca, OH), highly soluble species (Na, K, Cl) and pH-dependent species (As, Cd, Pb). The RH of storage environment, which acted as a boundary condition for the drying process, influenced the precipitation of species within dried pores and relaxation of pH and concentration gradients within water-filled regions. Gradient relaxation resulted from continued mass transport within saturated pores over the storage interval and was most evident when storage was conducted at 98% RH. However, when storage RH promoted drying of the matrix, the effect of gradient relaxation was balanced by precipitation. When release was normalized to total leaching time, relaxation of concentration gradients of highly soluble species resulted in greater cumulative release for the intermittently wetted cases than in the case of continuous leaching. The release of pH-dependent constituents was controlled by relaxation of the pH gradient and species solubility as a function of local pore water pH. Application of a current assessment protocol to estimate intermittent wetting release resulted in either over or underestimation of actual cumulative release, depending on the nature of the constituent of interest. These results imply that long-term constituent release from Portland cement-based waste forms should not be made by simple correction of saturated release assessments because alterations to the matrix leachability induced by the storage environment need to be considered.

Chemical Phenomena↗
PubMed1998

On the physics, chemistry and toxicology of ultrafine anthropogenic, atmospheric aerosols (UAAA): new advances.

The existing data about the epidemiology, toxicology, physics and chemistry of atmospheric particulate pollutants were recently essentially completed and extended. They do support the hypothesis that the fine and very fine dispersed fraction of the atmospheric anthropogenic aerosols (UAAA) are responsible for the aggravation of the health risk potential of the polluted atmosphere during the last decade. The recently published data dealing primarily with the physics, chemistry, sampling and analysis of these highly dispersed particulate air pollutants are reviewed, summarized and critically evaluated.

Aerosols↗
PubMed2005

We reside in the sun's atmosphere.

The Sun is the origin of all activities of the Earth, including its solid, liquid and gas states, as well as life on the Earth surface. Life was created on this planet and was further evolved after long physical/chemical processes, so that life here matches with what this planet requires. This paper contends that the Earth is located within the solar atmosphere, but we do not feel it in a daily life because of the blocking effects of the Earth's magnetic field and atmosphere, preventing the entry of the solar atmosphere directly into the Earth's domain. This paper emphasizes that we should not attempt to change the quality of the natural environment that delicate interactions between the Sun and the Earth have established for us by taking a long time.

Earth, Planet↗
PubMed1999

Should severely disturbed psychiatric patients be distributed or concentrated in specialized wards? An empirical study on the effects of hospital organization on ward atmosphere, aggressive behavior, and sexual molestation.

This study examines whether ward atmosphere, aggressive behavior, and sexual molestation will change after severely disturbed patients have been distributed over several wards determined by their place of residence, instead of concentrating them in locked single-sex wards. Four wards for predominantly psychotic patients were investigated with the German version of the Ward Atmosphere Scale (WAS), and some further questions about the observation of aggressive behavior and sexual molestation once before and twice after internal sectorisation, partial ward opening, and mixing the sexes were asked. Questionnaires (345: 162 staff members, 183 patients) were evaluated. After the structural changes, a significant improvement of ward atmosphere and a reduction of aggressive behavior was found on average in all wards, whereas the impact on sexual molestation remained unclear. Internal sectorisation and sex integration policy, resulting in distributing rather than concentrating severely disturbed patients, have beneficial effects on the social climate of acute wards.

Adult↗
PubMed1999

Repeated 4-week inhalation exposure of rats: effect of low-, intermediate, and high-humidity chamber atmospheres.

A subacute nose-only inhalation study with low (approximately 3%), medium (approximately 40%), and high humidity (approximately 80%) has been performed on young adult Wistar rats. Exposure was 6-hr/day on 5 days/week for 4 consecutive weeks. Rats housed individually in the animal holding room, deprived of feed and water during exposure of the remaining groups, served as concurrent controls (sham controls). This study served the purpose to assess whether toxicologically significant effects occur when rats are repeatedly exposed to lower or higher humidity chamber atmospheres than proposed by current testing guidelines. For analysis, conventional end-points as required by common testing guidelines were considered, i.e., clinical observations before and after exposure, rectal temperatures, body weights, feed and water consumption. At the end of the 4-week exposure period, ophthalmological and gross pathological examinations were made and major organ weights determined. The histopathological examinations comprised the nasal cavities, larynx, trachea, and lungs. There was no apparent evidence of humidity-related effects on nose-only exposed rats. When compared with non-exposed sham controls, however, body weights, water and feed consumption were markedly reduced in all nose-only exposure groups. In summary, it can be concluded that rats tolerated either humidity atmosphere without any specific effects. As far as there were differences to sham controls they appear to be more controlled by the differences in the exposure patterns (nose-only versus normal housing) than differences in the humidity of chamber atmospheres. Thus, deviations of current testing guidelines for repeated exposure inhalation studies with regard to humidity, do not appear to have any appreciable impact on the study outcome.

Administration, Inhalation↗
PubMed2001

Effects of the type of sintering atmosphere on the chromium leachability of thermal-treated municipal solid waste incinerator fly ash.

The sintering process offers an opportunity to combine detoxification and resource recovery for the treatment of municipal solid waste (MSW) incinerator fly ash. However, the chromium (Cr) in the sintered fly ash becomes more readily leachable with increasing sintering time and temperature, thus posing severe threats to the environment and human health when the sintered ash is recycled or reused. This study investigated the enhanced leachability of fly ash containing Cr, by heating the chromium (III) oxide (Cr2O3)-spiked fly ash to 800 degrees C in atmospheres containing air, nitrogen gas (N2), and 5% H2 + 95% N2, respectively. The results indicated that trivalent chromium was converted to its soluble hexavalent form during sintering in the air atmosphere; whereas sintering in a nitrogen atmosphere significantly reduced the leachability of Cr due to lack of oxygen (O2) to oxidize. The effects of the sintering temperature on the total chromium content and the leaching concentration in the toxicity characteristic leaching procedure (TCLP) extract are also discussed.

Air Pollutants↗
PubMed2003

Radon, thoron and their progenies measured in different dwelling rooms and reference atmospheres by using CR-39 and LR-115 SSNTD.

Detection efficiencies of the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD) for alpha-particles emitted by radon, thoron and their decay products inside the air of different dwelling rooms and in various reference atmospheres were determined by using a Monte Carlo computer code. Alpha- and beta-activities per unit volume of air due to radon, thoron and their progenies were measured in the studied atmospheres by exploiting data obtained for the detection efficiencies of the SSNTD and measuring the resulting track density rates. Equilibrium factors between radon and its progeny and thoron and its daughters were evaluated in the studied atmospheres.

Air Movements↗
PubMed2002

Desorption/ionization of biomolecules from aqueous solutions at atmospheric pressure using an infrared laser at 3 microm.

A new atmospheric pressure (AP) infrared (IR) matrix-assisted laser desorption/ionization (MALDI) ion source was developed and interfaced with a Thermo Finnigan LCQ ion trap mass spectrometer. The source utilized a miniature all-solid-state optical parametric oscillator (OPO)-based IR laser system tunable in the lambda = 1.5-4 microm spectral range and a nitrogen ultraviolet (UV) laser (lambda = 337 nm) for use in comparative studies. The system demonstrated comparable performance at 3 microm and 337 nm wavelengths if UV matrices were used. However, AP IR-MALDI using a 3 microm wavelength showed good performance with a much broader choice of matrices including glycerol and liquid water. AP IR-MALDI mass spectra of peptides in the mass range up to 2000 Da were obtained directly from aqueous solutions at atmospheric conditions for the first time. A potential use of the new AP IR-MALDI ion source includes direct MS analysis of biological cells and tissues in a normal atmospheric environment as well as on-line coupling of mass spectrometers with liquid separation techniques.

Air Pressure↗
PubMed1997

Genotoxicity induced in human lymphoblasts by atmospheric reaction products of naphthalene and phenanthrene.

The genotoxic risks from exposure to polycyclic aromatic hydrocarbons (PAH) have long been recognized. Less well understood are the potential genotoxic risks of the atmospheric reaction products of this class of compounds. In this investigation, we have utilized several human cell genotoxicity assays to evaluate naphthalene, phenanthrene, and their atmospheric reaction products 1-nitronaphthalene, 2-nitronaphthalene, 1-hydroxy-2-nitronaphthalene, 2-hydroxy-1-nitronaphthalene, 1,4-naphthoquinone and 2-nitrodibenzopyranone. In addition, reaction products of naphthalene were generated in a 6700-1 Teflon environmental chamber, collected on a solid adsorbent, extracted and fractionated by normal-phase HPLC. Individual fractions were then analyzed using GC-MS, and tested for genotoxicity. Genotoxicity was determined using the human B-lymphoblastoid cell line, MCL-5, which expresses several transfected P450 and epoxide hydrolase genes. Mutagenicity was evaluated at both the heterozygous tk locus and the hemizygous hprt locus, permitting detection of both intragenic and chromosomal scale mutational events. Test compounds were also screened using the CREST modified micronucleus assay. Genotoxicity results indicate that 2-nitronaphthalene and 2-nitrodibenzopyranone possess greater mutagenic potency than their parent compounds, and interestingly, both compounds induced significant increases in mutation frequency at tk but not hprt. These results suggest a mechanistic difference in human cell response as compared to bacteria, where both compounds were previously shown to induce point mutations in the Salmonella reversion assay. The genotoxicity of 2-nitronaphthalene and 2-nitrodibenzopyranone in human cells, together with their high concentrations in ambient air relative to nitro-PAH directly emitted from combustion sources, emphasizes the need to consider atmospheric reaction products of PAH in genotoxicity assessments.

Air Pollutants↗
PubMed2003

Sleep quality responses to atmospheric variation: case studies of two elite female cyclists.

Strategies applied during sleep to potentially enhance athlete performance use different atmospheric conditions. High altitude conditions are known to affect sleep adversely but the effects of mild-moderate altitude and O2 enrichment at mild altitude are uncertain. We performed case studies using two elite female road cyclists (mass and maximal aerobic power of 62 kg, 65.8 ml x kg(-1) x min(-1); 57 kg, 62.7 ml x kg(-1) x min(-1)) to examine changes in sleep for different atmospheric conditions applied throughout the preparation for, and during, an International Stage race. Conditions were: i) normoxia (600 m), ii) simulated moderate altitude (2650 m), iii) natural mild altitude (1380 m) and iv) O2 enrichment at mild altitude (30% O2@ 1300-1500 m). We measured respiratory disturbances, arousals, number of awakenings, blood oxygen saturation (SpO2), heart rate (HR), rapid eye movement sleep (REM) and deep sleep. Respiratory disturbances, SpO2 and HR responses were similar for both cyclists for all conditions. Compared with normoxia, both cyclists had somewhat reduced REM at natural mild altitude and moderate simulated altitude but differed in their REM and deep sleep responses to O2 enrichment. Compared with mild altitude, both showed increased awakenings and deep sleep with O2 enrichment. Only one cyclist clearly increased her REM sleep with O2 enrichment compared to mild altitude. Our data highlight two different sleep quality responses to atmospheric variation.

Altitude↗
PubMed2000

Atmospheric pressure photoionization: an ionization method for liquid chromatography-mass spectrometry

Atmospheric pressure photoionization (APPI) has been successfully demonstrated to provide high sensitivity to LC-MS analysis. A vacuum-ultraviolet lamp designed for photoionization detection in gas chromatography is used as a source of 10-eV photons. The mixture of samples and solvent eluting from an HPLC is fully evaporated prior to introduction into the photoionization region. In the new method, large quantities of an ionizable dopant are added to the vapor generated from the LC eluant, allowing for a great abundance of dopant photoions to be produced. Because the ion source is at atmospheric pressure, and the collision rate is high, the dopant photoions react to completion with solvent and analyte molecules present in the ion source. Using APPI, at an LC flow rate of 200 microL/min, it is possible to obtain analyte signal intensities 8 times as high as those obtainable with a commercially available corona discharge-atmospheric pressure chemical ionization source.

Journal Article↗
PubMed2002

Monitoring atmospheric particulate matter through cavity ring-down spectroscopy.

Cavity ring-down spectroscopy was explored as a means to measure atmospheric optical extinction. Ambient air was sampled through a window on the campus of the University of Florida and transported to a ring-down cell fashioned from standard stainless steel vacuum components. When a copper vapor laser operating at 10 kHz is employed, this arrangement allowed for nearly continuous monitoring of atmospheric extinction at 510 and 578 nm. We have characterized the system performance in terms of detection limit and dynamic range and also monitored a change in atmospheric extinction during a nearby wildfire and fireworks exhibition. The sensitivity and compatibility with automation of the technique renders it useful as a laboratory-based measurement of airborne particulate matter.

Air Pollution↗
PubMed2002

Laser desorption-atmospheric pressure chemical ionization mass spectrometry for the analysis of peptides from aqueous solutions.

A recently reported ionization method, comprising an infrared (IR) laser pulse to desorb (LD) analyte species, followed by atmospheric pressure chemical ionization (APCI) with a corona discharge (LD-APCI) to effect ionization of the desorbed neutral analyte molecules, is described for the direct analysis of aqueous peptide solutions. The source employs a heated capillary atmospheric pressure (AP) inlet coupled to a quadrupole ion trap mass spectrometer and allows sampling under normal ambient air conditions. By use of the corona discharge, signals of the atmospheric pressure infrared matrix-assisted laser desorption/ionization (AP-IR-MALDI)-generated analyte protonated molecule were enhanced by factors as large as 1400. In addition, the acid modifier trifluoroacetic acid (TFA) was found to improve the AP-IR-MALDI-generated signal by a factor of approximately 10, whereas the LD-APCI generated signal yielded a 100-fold increase. In this study, the use of the corona discharge is described to enhance the analyte signal generated via AP-IR-MALDI and, as a tool, to probe the gas-phase neutral molecule population generated by the MALDI process. Finally, through the decoupling of desorption from ionization, implications regarding the application of LD-APCI for the direct analysis of numerous new analyte containing matrixes (e.g., polyacrylamide gel electrophoresis (PAGE), tissue, etc.) are discussed.

Peptides↗
PubMed2003

Direct quantitative analysis of organic compounds in the gas and particle phase using a modified atmospheric pressure chemical ionization source in combination with ion trap mass spectrometry.

A slightly modified atmospheric pressure chemical ionization source is employed for direct quantitative analysis of volatile or semivolatile organic compounds in air. The method described here is based on the direct introduction of an analyte in the gas or particle phase, or both, into the ion source of a commercial ion trap mass spectrometer. For quantitation, a standard solution is directly transferred into the vaporizer unit of the ion source via a deactivated fused-silica capillary by using the sheath liquid syringe pump, which is part of the mass spectrometer. The standard addition procedure is conducted by varying the pump rate of a diluted solution of the standard compound in methanol/water. A N2 sheath gas flow is applied for optimal vaporization and mixing with the analyte gas stream. By performing detailed reagent ion monitoring experiments, it is shown that the relative signal intensity of [M + H]+ ions is dependent on the relative humidity of the analyte gas stream as well as the composition and concentration of CI reagent ions. The method is validated by a comparison of the standard addition results with a calibration test gas of known concentration. To demonstrate the potential of atmospheric pressure chemical ionization mass spectrometry as a quantitative analytical technique for on-line investigations, a tropospherically relevant reaction is carried out in a 493-L reaction chamber at atmospheric pressure and 296 K in synthetic air at 50% relative humidity. Finally, the applicability of the technique to rapidly differentiate between analytes in the gas and particle phase is demonstrated.

Journal Article↗
PubMed2005

Atmospheric pressure ionization in a miniature mass spectrometer.

A miniature cylindrical ion trap mass spectrometer featuring an atmospheric pressure interface allowing atmospheric pressure chemical ionization and electrospray ionization is described together with its analytical performance characteristics. The vacuum system, ion optics, mass analyzer, control electronics system, and detection system have all been designed and built in-house. The design is based upon a three-stage, differentially pumped vacuum system with the instrument capable of being interfaced to many types of atmospheric pressure ionization sources. Ions are transferred through home-built ion optics, and instrument control is achieved through custom-designed electronics and LabView control software. Corona discharge ionization and electrospray ionization sources are implemented and used to allow the analysis of both gaseous- and solution-phase samples during the characterization of the instrument. An upper mass/charge limit of approximately 450 Th with unit resolution was achieved using a 2.5-mm-internal radius cylindrical ion trap as the mass analyzer. The specificity of the instrument can be increased by employing the MS/MS capabilities of the ion trap and has been demonstrated for nitrobenzene. Limits of detection for the trace analysis in air of the chemical warfare agent simulant methyl salicylate (1.24 ppb) and for nitrobenzene (629 pptr) are achieved. The dynamic range of the instrument is currently limited to approximately 2 orders of magnitude by saturation of the detection electronics. Isolation and collision-induced dissociation efficiencies in MS/MS experiments both greater than 50% are reported. Electrospray/nanospray data are presented on solutions including 100 microM (D,L)-arginine, 10 microM (-)-ephedrine, and 10 microM lomefloxacin.

Journal Article↗
PubMed2006

Isotopic analysis of atmospheric formaldehyde by gas chromatography isotope ratio mass spectrometry.

Little is known about the isotopic composition of formaldehyde in the atmosphere, a chemical intermediate in hydrocarbon oxidation. Here, we present a promising new method to analyze the carbon (delta 13C) and hydrogen (delta D) isotopic composition of atmospheric formaldehyde. The direct isotopic analytical technique described uses continuous-flow gas chromatography-isotope ratio mass spectrometry, which provides flexibility for either isotopic analysis without correction for derivative functional groups. Current levels of precision of measurement are +/-1.1 and +/-50 per thousand (1 sigma) for delta 13C and delta D analyses, respectively. Concentration of formaldehyde in ambient air is also determined, coincident with isotopic measurement, to a precision of +/-15%. The method has the required sensitivity for analyses of formaldehyde in urban air on relatively small volume grab samples of whole air (10-70L STP), potentially providing high temporal resolution. This is particularly advantageous for studying formaldehyde given its short lifetime and large variability in the atmosphere.

Journal Article↗