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Results for “ATMOSPHERIC PRESSURE”

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PubMed2001

Atmospheric pressure and sudden infant death syndrome in Cook County, Chicago.

We investigated daily deaths from sudden infant death syndrome (SIDS) in Cook County, Chicago, from 1 January 1986 to 31 December 1990. The daily SIDS rate was 0.54 deaths/day. Mean daily atmospheric pressure ranged from 952 to 1007 mb. We found a weak link with barometric pressure, whereby an increase of 10 mb was associated with an increased risk of 12% [95% CI 0.1%, 24%]. Cross-tabulation revealed that the highest SIDS rates were associated with a drop from high to low pressure. Possible reasons for this are discussed.

Atmospheric Pressure↗

PubMed2006

Ion-neutral potential models in atmospheric pressure ion mobility time-of-flight mass spectrometry IM(tof)MS.

The ion mobilities and their respective masses of several classes of amines (primary, secondary, and tertiary) were measured by electrospray ionization atmospheric pressure ion mobility time-of-flight mass spectrometry IM(tof)MS. The experimental data obtained were comparatively analyzed by the one-temperature kinetic theory of Chapman-Enskog. Several theoretical models were used to estimate the collision cross-sections; they include the rigid-sphere, polarization-limit, 12-6-4, and 12-4 potential models. These models were investigated to represent the interaction potentials contained within the collision integral that occurs between the polyatomic ions and the neutral drift gas molecules. The effectiveness of these collision cross-section models on predicting the mobility of these amine ions was explored. Moreover, the effects of drift gas selectivity on the reduced-mass term and in the collision cross-section term was examined. Use of a series of drift gases, namely, helium, neon, argon, nitrogen, and carbon dioxide, made it possible to distinguish between mass effects and polarizability effects. It was found that the modified 12-4 potential that compensates for the center of charge not being at the same location as the centers of mass showed improved agreement over the other collision cross-section models with respect to experimental data.

Amines↗

PubMed2000

Determination of patulin in apple juice by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

An HPLC-MS-MS method with selected reaction monitoring (SRM) for the determination of patulin in apple juice samples is described. Mass spectrometric detection was accomplished following atmospheric pressure chemical ionization (APCI) in both positive and negative ion modes. Collision induced dissociation (CID) of the protonated molecular ion led initially to the loss of H2O (fragment m/z 137). At higher energies CO is lost from both the protonated parent molecule (fragment m/z 127) and the dehydrated molecular ion (fragment m/z 109). In contrast, CID of the deprotonated molecular ion led initially to the fragment at m/z 109 corresponding to the loss of either CO2 or acetaldehyde, followed at higher CID energy by the loss of H2O (fragment m/z 135) and CO (fragment m/z 125) from the deprotonated molecular ion. Detection in the negative ion mode proved superior and a linear response was observed over the injected range from 6 to 200 ng patulin. Apple juice samples spiked with patulin between 10 and 135 microg/l were analyzed following liquid-liquid extraction with ethyl acetate and clean up with sodium carbonate. Utilizing reversed-phase HPLC with acetonitrile-water (10:90) at 0.5 ml/min, levels down to 10 microg/l were readily quantified and a detection limit of 4 microg/l was attainable at a signal-to-noise (SIN) ratio of 4. The MS data for the spiked samples compared well to the UV data and when plotted against each other displayed a correlation coefficient (R) of 0.99.

Atmospheric Pressure↗

PubMed2003

Identification of ubiquinones and menaquinones in activated sludge by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

A sensitive analytical method has been developed for identification of ubiquinones (UQ-n(Hx)) and menaquinones (MK-n(Hx)) in activated sludge by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry in negative mode (LC-NI-APCI-MS). Extraction and clean-up of samples were carried out on Sep-Pak Plus Silica solid-phase extraction cartridges. Complete separation of quinones was achieved with an ODS analytical column and using isopropyl ether-methanol (17:83, v/v) as the mobile phase. The compositions of ubiquinones and menaquinones were determined directly using combined information on retention time, the molecular ion mass and fragment ion masses. The lowest instrument quantitative detection limits (LODinst) for UQ-6, UQ-10, and Vitamin K1 were estimated to be 0.4, 4 and 0.12 ng (S/N = 10) using LC-NI-APCI-MS in SIM mode, and the lowest method detection limits (LODmeth) achieved by spiking experiment were estimated to be 0.2, 2 and 0.06 microg/g for UQ-6, UQ-10 and Vitamin K1, respectively. On the other hand, the LODinst for UQ-6, UQ-10, and Vitamin K1 were estimated to be 10, 100 and 2 ng (S/N = 10) using LC-NI-APCI-MS in full-scan mode, and the LODmeth were estimated to be 7, 60 and 1.2 microg/g for UQ-6, UQ-10, and Vitamin K1, respectively. Both LC-NI-APCI-MS and LC-UV/DAD were applied in the analysis of an activated sludge extract. UQ-n (n = 6-10), MK-n (n = 6-10), MK-n(H2) (n = 7-10), MK-n(H4) (n = 8-9) and MK-8(H6) were detected by LC-NI-APCI-MS, while UQ-6, UQ-7, MK-7(H), MK-9 and MK-10(H2) were not found by LC-UV/DAD. These results suggest that LC-NI-APCI-MS is more sensitive than LC-UV/DAD for the analysis of quinones in environmental samples such as sediment, activated sludge and bio-film in biological processes and other aquatic environments.

Atmospheric Pressure↗

PubMed2002

UV photochemistry of DNA in vitro and in Bacillus subtilis spores at earth-ambient and low atmospheric pressure: implications for spore survival on other planets or moons in the solar system.

Two major parameters influencing the survival of Bacillus subtilis spores in space and on bodies within the Solar System are UV radiation and vacuum, both of which induce inactivating damage to DNA. To date, however, spore survival and DNA photochemistry have been explored only at the extremes of Earth-normal atmospheric pressure (101.3 kPa) and at simulated space vacuum (10(-3)-10(-6) Pa). In this study, wild-type spores, mutant spores lacking alpha/beta-type small, acid-soluble spore proteins (SASP), naked DNA, and complexes between SASP SspC and DNA were exposed simultaneously to UV (254 nm) at intermediate pressure (1-2 Pa), and the UV photoproducts cis,syn-thymine-thymine cyclobutane dimer (c,sTT), trans,syn-thymine-thymine cyclobutane dimer (t,sTT), and "spore photoproduct" (SP) were quantified. At 101.3 kPa, UV-treated wild-type spores accumulated only SP, but spores treated with UV radiation at 1-2 Pa exhibited a spectrum of DNA damage similar to that of spores treated at 10(-6) Pa, with accumulation of SP, c,sTT, and t,sTT. The presence or absence of alpha/beta-type SASP in spores was partly responsible for the shift observed between levels of SP and c,sTT, but not t,sTT. The changes observed in spore DNA photochemistry at 1-2 Pa in vivo were not reproduced by irradiation of naked DNA or SspC:DNA complexes in vitro, suggesting that factors other than SASP are involved in spore DNA photochemistry at low pressure.

Atmospheric Pressure↗

PubMed1982

Natural tritiated moisture levels in air vary with atmospheric pressure.

Natural HTO levels in air at ground level were measured on 100 days during 1979-80. Levels of between 6-140 Bq m-3 of air were observed and found to have a correlation with atmospheric pressure. Lithium chloride was used to absorb moisture, which was then recovered by distillation with xylene prior to liquid scintillation counting using a Triton X-100 cocktail. HTO in the air of a reactor hall and HTO in seawater were also measured by this method.

Air Pollution, Radioactive↗

PubMed2000

Liquid chromatography-atmospheric pressure chemical ionization mass spectrometry as a tool for the characterization of anthraquinone derivatives from Chinese herbal medicine.

We have examined the anthraquinone derivatives of a Chinese herb medicine 'Rhubarb' by using HPLC/MS/MS, equipped with an atmospheric pressure chemical ionization source. The simultaneous determination of five ingredients in the sample extracts by HPLC/MS/MS was demonstrated. Product ion spectra of these components in the extracts were obtained and matched against known standards. Concentrations of these active ingredients were estimated by multiple reaction monitoring in the negative ion mode using a single HPLC run.

Anthraquinones↗

PubMed2000

[Expansion of intraocular gas due to reduced atmospheric pressure. Case report and review of the literature].

Since the advent of vitrectomy and the increased use of intraocular gases, there had been concern voiced about the safety of air travel for patients with intraocular gas. Anecdotal reports and experimental models verify the danger of acute glaucoma and central retinal artery occlusion following depressurization and expansion of intraocular gas. However, the amount of gas, that can be compensated for, is a matter of controversy. CASE REPORT I: A 58-year old man underwent vitrectomy with intraocular air tamponade as a primary procedure for retinal detachment. The patient went home by airplane with a residual gas volume of less than 30% of the volume of the eye. Before takeoff at 530 m (1739 ft) above sea level, the intraocular pressure was 12 mmHg. During the ascent, severe ocular pain and loss of vision occurred. CASE REPORT II: A 38-year old woman underwent vitrectomy for primary repair of retinal detachment. The eye was injected with a 15% mixture of perfluoroethan (C2F6). When traveling home to Italy by car, the eye contained a residual gas volume of 50% of the volume of the globe. Intraocular pressure was 17 mmHg. During the ascent to the "Brennerpass", 1375 m (4511 ft) above sea level, the eye became severely painful and vision was lost for approximately three minutes. Descending to a lower altitude relieved the symptoms. CONCLUSION: The expansion of intraocular gases depends on the atmospheric pressure and the mechanisms for compensation. Small volumes of intraocular gas or moderate traveling altitudes can cause a symptomatic rise in intraocular pressure.

Adult↗

PubMed2001

Application of sweeping to micellar electrokinetic chromatography-atmospheric pressure chemical ionization-mass spectrometric analysis of environmental pollutants.

An application study of sweeping, an on-line sample concentration technique, to micellar electrokinetic chromatography (MEKC) directly combined with mass spectrometry (MS) using an atmospheric pressure chemical ionization (APCI) interface, namely MEKC-APCI-MS, was investigated to enhance the concentration sensitivity for the analysis of environmental pollutants. Under a neutral condition, around 100-fold increase in the concentration sensitivity was achieved for several aromatic amines and alkyl phthalates as test samples by sweeping-MEKC-APCI-MS compared to conventional MEKC-APCI-MS, whereas under an acidic condition, 100 to 600-fold sensitivity enhancement was gained for similar solutes. Linearity of the corrected peak area obtained in the mass chromatogram against the sample concentration was examined for 3,4-dichloroaniline and diisopropyl phthalate (DIPP). The estimated limits of detection for 3,4-dichloroaniline and DIPP were 0.6 and 0.4 ppm, respectively, in terms of the injected sample concentration.

Amines↗

PubMed2003

Improved quantitative detection of 11 urinary phthalate metabolites in humans using liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry.

Phthalates are widely used as industrial solvents and plasticizers, with global use exceeding four million tons per year. We improved our previously developed high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometric (HPLC-APCI-MS/MS) method to measure urinary phthalate metabolites by increasing the selectivity and the sensitivity by better resolving them from the solvent front, adding three more phthalate metabolites, monomethyl phthalate (mMP), mono-(2-ethyl-5-oxohexyl)phthalate (mEOHP) and mono-(2-ethyl-5-hydroxyhexyl)phthalate (mEHHP); increasing the sample throughput; and reducing the solvent usage. Furthermore, this improved method enabled us to analyze free un-conjugated mono-2-ethylhexyl phthalate (mEHP) by eliminating interferences derived from coelution of the glucuronide-bound, or conjugated form, of the mEHP on measurements of the free mEHP. This method for measuring phthalate metabolites in urine involves solid-phase extraction followed by reversed-phase HPLC-APCI-MS/MS using isotope dilution with (13)C(4) internal standards. We further evaluated the ruggedness and the reliability of the method by comparing measurements made by multiple analysts at different extraction settings on multiple instruments. We observed mMP, monoethyl phthalate (mEP), mono-n-butyl phthalate (mBP), monobenzyl phthalate (mBzP), mEHP, mEHHP and mEOHP in the majority of urine specimens analyzed with DEHP-metabolites mEHHP and mEOHP present in significantly higher amounts than mEHP.

Atmospheric Pressure↗

PubMed2006

'On-the-fly' hydrogen/deuterium exchange liquid chromatography/mass spectrometry using a dual-sprayer atmospheric pressure ionisation source.

In-source 'on-the-fly' hydrogen/deuterium (H/D) exchange liquid chromatography mass spectrometry (LC/MS) has been investigated. The work was performed using a dual-sprayer source. The analyte was introduced through an electrospray ionisation sprayer and D2O was introduced through an atmospheric pressure chemical ionisation sprayer. To achieve H/D exchange sufficient to determine the number of exchangeable H atoms of a compound, a saturated 'steady-state' D2O atmosphere had to be created in the ion source by having a 2:1 or higher D2O-to-analyte flow rate ratio. Under these conditions H/D exchange levels of 32-90% were achieved. In most cases the H/D exchange was sufficient to measure the number of exchangeable H atoms in some antiulcerative and anthelmintic pharmaceuticals. The concept of in-source 'on-the-fly' H/D exchange by introducing the deuterating agent via a second sprayer has been shown. It allows the integrity of the chromatographic separation to be kept, since the H/D exchange takes place post-separation.

Atmospheric Pressure↗

PubMed2006

Steroid hormone profiles of urban and tidal rivers using LC/MS/MS equipped with electrospray ionization and atmospheric pressure photoionization sources.

A highly sensitive and uncomplicated method of analyzing steroidal hormones in river and estuarine water samples was developed using a liquid chromatography tandem mass spectrometer equipped with an electrospray ionization (ESI) source and atmospheric pressure photoionization (APPI) source. Steroidal hormones included not only estrogen but also androgen and conjugates of these two. APPI displayed greater sensitivity than ESI for most of the unconjugated steroids examined, with very high sensitivity for testosterone and 4-androstene-3,17-dione in particular. For conjugated hormones, in contrast, ESI was more effective. The method developed was applied to the determination of hormones in the rivers of Osaka City and their estuaries, where the hormones detected were affected by the effluent from municipal wastewater treatment plants (WWTPs), and hormone concentration values were comparable to those reported in previous studies of such effluent. Because of the two-way flow and stagnancy of streams and watercourses, continuous input of steroidal hormones from WWTPs seems to bring about local accumulation. Levels of androgen were 1 order of magnitude lower than those of estrogen. Estrone, estrone 3-sulfate, and 4-androstene-3,17-dione were detected in almost all water samples, with maxima of 51, 5.1, and 6.4 ng L(-1), respectively.

Atmospheric Pressure↗

PubMed2003

Ion suppression in the determination of clenbuterol in urine by solid-phase extraction atmospheric pressure chemical ionisation ion-trap mass spectrometry.

Ion suppression effects were observed during the determination of clenbuterol in urine with solid-phase extraction/multiple-stage ion-trap mass spectrometry (SPE/MS(3)), despite the use of atmospheric pressure chemical ionisation. During SPE, a polymeric stationary phase (polydivinylbenzene) was applied. Post-cartridge infusion of analyte to the SPE eluate after the extraction of blank urine was performed to obtain a profile of the suppression. Single and multiple-stage MS were performed to provide insight in the suppressing compounds. The ion suppression was mainly ascribed to two m/z values, but still no identification of the compounds was achieved from the multiple-stage MS data. No ionisable and non-ionisable complexes and/or precipitation of clenbuterol with matrix compounds were observed. A concentration dependence of the percentage of suppression was observed. Up to 70% of the signal was suppressed upon post-cartridge infusion of 0.22 microg/mL (at 5 microL/min) clenbuterol into the eluate, and this decreased to about 4% at infusion of 22 microg/mL clenbuterol. Molecularly imprinted polymers were used to enhance the selectivity of the extraction. Although matrix components were still present after extraction, no interference of these compounds with the analyte was observed. However, the bleeding of the imprint from the polymer (brombuterol) caused significant ion suppression.

Animals↗

PubMed2005

Determination of testosterone concentrations in rat plasma using liquid chromatography-atmospheric pressure chemical ionization mass spectrometry combined with ethyl oxime and acetyl ester derivatization.

A quantitative method for measuring testosterone (T) concentrations in rat plasma was developed using ethyl oxime and acetyl ester derivatization and liquid chromatography-atmosphere pressure chemical ionization tandem mass spectrometry (LC-APCI-MS/MS). The method utilizes a solid phase extraction with Varian Bond Elut C18, a derivatization process to form testosterone ethoxime acetate and LC-APCI-MS/MS with a reversed phase LC and a C8 column. This method is capable of detecting testosterone concentrations as low as 0.2 ng/ml in a 0.05 ml sample of rat plasma. This method can be used as a sensitive chromatography-based assay for small sample volumes of rat blood.

Animals↗

PubMed2006

Power ultrasound interaction with DC atmospheric pressure electrical discharge.

The effect of power ultrasound application on DC hollow needle to plate atmospheric pressure electrical discharge enhanced by the flow of air through the needle electrode was studied experimentally. It was found that applying ultrasound increases discharge volume. In this volume take place plasmachemical processes, used in important ecological applications such as the production of ozone, VOC decomposition and de-NOx processes enhancement. In our experiments we used a negatively biased needle electrode as a cathode and a perpendicularly placed surface of the ultrasonic resonator--horn--as an anode. To demonstrate the effect of ultrasound waves on electrical discharge photographs of the discharge for the needle to the ultrasonic resonator at distances of 4, 6 and 8mm are shown. By varying the distance between needle and the surface of the transducer, we were able to create the node or the antinode at the region around the tip of the needle, where the ionization processes are effective. In our experimental arrangement the amplitude of acoustic pressure at antinode exceeded 10(4) Pa. The photographs reveal that the diameter of the discharge on the surface of the ultrasonic horn is increased when ultrasound is applied. The increase of discharge volume caused by the application of ultrasound can be explained as a combined effect of the change of the reduced electric field E/n (E is electric field strength and n is the neutral particles density), strong turbulence of the particles in the discharge region caused by quick changes of amplitudes of the standing ultrasonic wave and finally by the boundary layer near the ultrasonic transducer perturbations due to vibrations of the transducer surface.

Journal Article↗

PubMed2006

Atmospheric pressure photoionization for ionization of both polar and nonpolar compounds in reversed-phase LC/MS.

Atmospheric pressure photoionization can provide high ionization efficiency simultaneously to both polar and nonpolar compounds delivered in reversed-phase solvent. The method to achieve this utilizes toluene as a dopant and simply requires that the solvent flow be limited so that reactions between toluene photoions and the organic component of the solvent are not driven to completion. Under these conditions, toluene photoions remain in the source for ionizing nonpolar compounds via charge exchange (electron transfer), while protonated solvent ions are available for proton-transfer reactions with polar molecules. The reagent ion mixture is then suitable for ionizing a wide range of both polar and nonpolar compounds. The critical effect of solvent flow rate is demonstrated here with results for a test analyte, 9-methylanthracene, which may be ionized by either charge exchange or proton transfer. For a solvent of 50:50 methanol/water (v/v), lowering the flow from 200 to 50 microL min-1 results in a 10x increase in charge exchange ionization efficiency--further flow reductions provide even greater enhancements. This method is compatible with sample delivery by direct infusion and micro- and narrow-bore LC, as well as conventional LC using a flow splitter.

Journal Article↗

PubMed2006

[Electron excitation temperature of hexagon pattern in argon discharge at atmospheric pressure].

The emission spectrum and the discharge current waveform of argon dielectric barrier discharge at atmospheric pressure were measured when the filaments self-organized in hexagon pattern by using a specially designed experimental setup. Electron excitation temperature of hexagon pattern was calculated using intensity ratio method. It was found that the electron excitation temperature is higher as the frequency of feeding voltage increases. And the temporal correlation among all micro-discharge channels also becomes higher as the frequency of feeding voltage increases. This work gives useful reference for studying pattern formation dynamics.

English Abstract↗

PubMed2004

Highly sensitive and rapid normal-phase chiral screen using high-performance liquid chromatography-atmospheric pressure ionization tandem mass spectrometry (HPLC/MS).

In the last years, there has been an increasing demand on the development of quantitative assays for determination of enantiopurity. Herein, we present a methodology based on a direct linking of an atmospheric pressure ionization mass spectrometer (MS-APCI) with a high-performance liquid chromatography HPLC (DAD) system, operated under normal-phase mode and without post-column addition of MS-compatible solvents, which provides the high specificity/selectivity (identification of isomers in complex mixtures) and accuracy (1-2% area level) required for daily chiral studies. As result of the success of our screen, the preparation of individual enantiomers or the racemic mixture in our Drug Discovery Research Laboratories at Lilly, Spain is usually not required. Therefore, additional non-valuable synthetic work is eliminated.

Atmospheric Pressure↗