[Prevention of atmospheric pressure hazards].
Explore the source record for details and available documents.
Atmospheric Pressure↗
SEARCH · PubMed Health
Results for “ATMOSPHERIC PRESSURE”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Effects of exercise on respiratory responses under high atmospheric pressure.
Explore the source record for details and available documents.
Adult↗
Influence of environmental factors on digestive enzymes. III. Atmospheric pressure.
Explore the source record for details and available documents.
Animals↗
Analysis of intact bacteriohopanepolyols from methanotrophic bacteria by reversed-phase high-performance liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry.
Direct detection of most intact biohopanoids is not possible using conventional GC-MS techniques due to their highly functionalised and amphiphilic nature. Here we report the application of a new reversed-phase high-performance liquid chromatography method for the direct analysis of acetylated, intact bacteriohopanepolyols in solvent extracts of methanotrophic bacteria. Atmospheric pressure chemical ionisation mass spectrometric detection provides structural information relating to the number and types of functional groups present in the four biohopanoids detected: bacteriohopanetetrol, aminobacteriohopanetriol, -tetrol and -pentol. The method should facilitate the assessment of hopanoid composition of both bacteria and environmental samples.
Atmospheric Pressure↗
Normal-phase high-performance liquid chromatographic separations using ethoxynonafluorobutane as hexane alternative. II. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry applications with methanol gradients.
We have reported recently that high-speed normal-phase (NP) HPLC separations of a broad range of organic compounds can be performed on cyano columns using gradients of methanol in hexane-like solvent-ethoxynonafluorobutane (ENFB), available commercially. In this communication, we demonstrate that atmospheric pressure chemical ionization (APCI) in combination with mass spectrometry (MS) can be effectively used for detection in such separations. The efficiency of APCI under conditions studied has also been compared to the efficiency of traditional electrospray ionization (ESI) in combination with MS for reversed-phase (RP) HPLC of the same compounds. The compounds included in this study were steroids, benzodiazepines, and other central nervous system-active substances, nonsteroidal anti-inflammatory drugs, tricyclic antidepressants, and beta-adrenergic blocking agents. Non-polar compounds were found to respond stronger when APCI-MS technique was used, whereas APCI and ESI ionization efficiencies were comparable when polar substances were studied. The combination of normal-phase HPLC separation conditions with mass spectral detection may expand the range of LC-MS applications traditionally associated with reversed-phase HPLC and ESI-MS detection.
Atmospheric Pressure↗
Identification of cyclic cystathionine sulfoxide and N-acetylcyclic cystathionine in the urine of a patient with cystathioninuria using liquid chromatography-mass spectrometry with an atmospheric pressure chemical ionization interface system.
Perhydro-1,4-thiazepine-4,5-dicarboxylic acid sulfoxide (cyclic cystathionine sulfoxide [cyclic cystaSO]) and N-acetylperhydro-1,4-thiazepine-3,5-dicarboxylic acid (NAc-cyclic cysta) have been identified in the urine of a patient with cystathioninuria as new metabolites of cystathionine for the first time using liquid chromatography-mass spectrometry with an atmospheric pressure chemical ionization interface system (LC/APCI-MS). The concentrations of cyclic cystaSO and NAc-cyclic cysta in the urine of a patient with cystathioninuria have also been determined for the first time using this method: 18.24 +/- 0.79 and 25.23 +/- 0.83 mg/g creatinine, respectively.
Atmospheric Pressure↗
[PSYCHOMETRIC FINDINGS IN HIGH ATMOSPHERIC PRESSURE].
Explore the source record for details and available documents.
Atmospheric Pressure↗
Analysis of bitter limonoids in citrus juices by atmospheric pressure chemical ionization and electrospray ionization liquid chromatography-mass spectrometry.
Improved analytical techniques for bitter limonoids in citrus and citrus juices can expedite the evaluation of freeze-induced citrus damage for citrus growers and juice quality for citrus juice producers. Microbore normal-phase and reverse-phase chromatography coupled to a mass spectrometer operating in a positive ion atmospheric pressure chemical ionization and electrospray ionization modes were found to be rapid, selective, and sensitive methods for the analysis of the bitter limonoids limonin and nomilin in citrus juices. Analysis was performed on a chloroform extract of citrus juice to which an internal standard was added. The methods are capable of detecting citrus limonoids in citrus juice in the 60-200 picogram range and quantifying citrus juice limonoids in concentrations as low as 120 picograms. An accurate "total limonoid bitterness" in citrus juice, as represented by the combined occurrence of limonin and nomilin, is easily determined by these methods.
Atmospheric Pressure↗
Determination of triacylglycerols in donkey milk by using high performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry.
The separation and determination of triacylglycerols (TAGs), which are the main components of naturally occurring fats and oils, in milk fat is a challenging task due to the very complex nature of this matrix. In the present study the TAG fraction of donkey milk lipids has been characterized by using high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (HPLC-APCI-MS). HPLC in reversed phase mode has been used for TAG separation and silver ion (Ag+) HPLC has been used as a second dimension to clarify and confirm the identification. The RP-HPLC eluate was fractionated and the fractions of interest were injected onto the Ag+-HPLC column. In both cases peak assignment was carried out by combining retention data with APCI-MS spectra information. In total, 55 TAGs in donkey milk fat were identified (without considering the positional isomers) and quantified on the basis of percentage peak areas in the RP-HPLC chromatogram (without the use of correction factors). Amongst the identified triacylglycerols, POLn, POO, PPO, CaPO, POL, and PPoO proved to be the main components of the TAG fraction of donkey milk.
Animals↗
Direct combination of immersed single-drop microextraction with atmospheric pressure matrix-assisted laser desorption/ionization tandem mass spectrometry for rapid analysis of a hydrophilic drug via hydrogen-bonding interaction and comparison with liquid-liquid extraction and liquid-phase microextraction using a dual gauge microsyringe with a hollow fiber.
This study presents the feasibility of direct coupling of the immersed single-drop microextraction (SDME) technique with atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry (AP-MALDI-MS) for the rapid analysis of a hydrophilic drug (dopamine) from aqueous solution and human urine in an ion trap tandem mass spectrometer through hydrogen-bonding interaction of dopamine with the extraction solvent (octanol). The optimum conditions for the SDME experiments coupled to AP-MALDI/MS were: stirring rate, 240 rpm; extraction time, 5 min; sample pH value, 8; and matrix concentration, 2000 ppm, using alpha-cyano-4-hydroxycinnamic acid (alpha-CHCA) as matrix. The limits of detection (LODs) for the SDME/AP-MALDI-MS experiments were 25 and 40 ppm in water and human urine, respectively. In a comparison of this method with the traditional liquid-liquid extraction (LLE), the SDME method shows better LODs than the LLE (40 ppm) and the same LODs (25 ppm) as the liquid-phase microextraction using a dual gauge microsyringe with a hollow fiber (LPME/DGM-HF). However, the SDME method is more convenient than the LPME/DGM-HF method.
Atmospheric Pressure↗
Determination of fungicide residues in fruits and vegetables by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.
A liquid chromatography (LC) method for the quantitative determination of five fungicide residues (dichloran, flutriafol, o-phenylphenol, prochloraz and tolclofos methyl) in oranges, lemons, bananas, peppers, chards and onions is described. The residues were extracted by matrix solid-phase dispersion (MSPD) using C8. Quantitative analysis was performed by isocratic LC coupled to quadrupole mass spectrometer using atmospheric pressure chemical ionization in the negative ionization mode. The limit of quantification was 0.01 mg kgmicro for flutriafol, o-phenylphenol and dichloran, and 0.1 mg kg(-1) for prochloraz and tolclofos methyl. The MSPD method is also suitable for LC-UV analysis but higher limits of quantification (between 1 and 5 mg kg(-1)) were obtained. Validation of the method was performed between 0.01 and 25 mg kg(-1). Recoveries for fungicides ranged from 52.5 to 91.1% with relative standard deviations between 6.1 and 11.9%. The method was applied to the determination of residues in samples taken from agricultural cooperatives. The fungicides most often detected were o-phenylphenol and prochloraz.
Atmospheric Pressure↗
Evaluation of different quantitative approaches for the determination of noneasily ionizable molecules by different atmospheric pressure interfaces used in liquid chromatography tandem mass spectrometry: abamectin as case of study.
The liquid chromatography tandem mass spectroscopy residue determination of compounds without any acidic or basic centers such as abamectin has been investigated. Several approaches regarding the interface used and adduct formation have been compared. The low acidity of the hydroxyl groups only made deprotonation feasible using the atmospheric pressure chemical ionization (APCI) interface. To obtain sufficient sensitivity for residue analysis, the Ion Sabre APCI interface was necessary. However, the sensitivity attained was lower than for monitoring adducts in positive ion mode. Using electrospray ionization, different adducts with Na+, NH4+, and Li+ were tested and compared. The best results were obtained for the ammoniated adduct in electrospray ionization (ESI) because of its high sensitivity and the presence of several product ions with similar abundance. The highest sensitivity was reached using an in-source fragment as precursor ion, leading to a limit of detection (LOD) of 2 microg/L with low relative standard deviation. The relatively high abundance of other transitions allowed abamectin confirmation at concentrations close to the LOD (6 microg/L). Alkali ions were found to be a suitable alternative to determine and confirm abamectin at residue levels. The [M + Na]+ also presented various product ions with similar abundance, which allowed confirmation at LOD levels. However, this LOD was found to be almost four times higher than with [M + NH4]+ because of the poor sensitivity of the transitions obtained. Although the use of Li+ facilitated the fragmentation of the adduct [M + Li]+, with similar sensitivity to [M + NH4]+, this fragmentation preferentially generated only one product ion, which did not allow confirmation at concentration levels lower than 15 microg/L. The use of APCI for monitoring adducts was also feasible, but with less sensitivity. The sensitivity increased with the Ion Sabre APCI, although it was still five times lower than with ESI. Other adduct formers such as Co2+ and Ni2+ also were tested with unsatisfactory results.
Algorithms↗
Improved method for the determination of zinc pyrithione in environmental water samples incorporating on-line extraction and preconcentration coupled with liquid chromatography atmospheric pressure chemical ionisation mass spectrometry.
A method has been developed for the determination of zinc pyrithione (ZnPT) in environmental water samples using monolithic reversed-phase silica columns for rapid on-line large volume solid phase extraction in tandem with on-line matrix removal using sacrificial strong anion exchange (SAX) columns. This is coupled with reversed-phase liquid chromatography with atmospheric pressure chemical ionisation mass spectrometric detection. Limits of detection in spiked river water samples, using a 200 mL preconcentration volume, were determined as 18 ng L(-1), with a limit of quantitation of 62 ng L(-1). The percentage recovery from spiked river water was found to be 72+/-9 (n=3 extractions), whilst overall method precision, following 10 repeat complete analyses was found to be 27% RSD at 1 microg L(-1). Linearity was determined over the concentration range of 0.25-10 microg L(-1) and the calculated regression coefficient was R(2)=0.9802. The method was used to investigate the environmental fate of zinc pyrithione in waters and its partition coefficient between sediment and water phases.
Atmospheric Pressure↗
Atmospheric pressure ionization time-of-flight mass spectrometry coupled with fast liquid chromatography for quantitation and accurate mass measurement of five pharmaceutical drugs in human plasma.
The quantitative determination and accurate mass measurement of five tricyclic amine pharmaceutical drugs (doxepin, desipramine, imipramine, amitriptyline and trimipramine) fortified in human plasma within a per sample run time of 18 s was accomplished by atmospheric pressure ionization (API) time-of-flight (TOF) mass spectrometry using a turboIonspray liquid chromatography/mass spectrometry (LC/MS) interface coupled with high-performance liquid chromatography (HPLC). The relatively short HPLC separation (18 s) was achieved using a short C18 column (15 x 2.1 mm i.d.) with a high aqueous mobile phase maintained at a flow-rate of 1.4 ml min(-1). An acquisition speed of 0.2 s per spectrum accommodates these fast separation conditions. This method employs a one-step liquid-liquid extraction procedure to isolate the five tricyclic amines from biological matrix components The overall extraction recovery was 75% for desipramine and >90% for the other four tricyclic amines. The lower level of quantitation was 1-2 ng ml(-1) for each compound. The calibration curve was linear from 2 to 100 ng ml(-1) for desipramine and from 1 to 50 ng ml(-1) for the other four tricyclic amines. A deuterated internal standard, imipramine-d3, was used for all five tricyclic amines. Acceptable intra- and inter-assay precision (1.0-17.7%) and accuracy (0.2-14.5%) were obtained. The linear dynamic range was extended to 200 based on a software upgrade for correcting ion current detection saturation. The accurate masses of the five tricyclic amines were determined by on-line LC/TOFMS analyses of biological extracts using two-point internal mass calibration. This was done by infusing a reference standard, Jeffamine D230, post-column into the HPLC effluent. All results showed a mass error not greater than 9 ppm for all the target compounds. These results were obtained from both synthetic mixtures when as little as 100 pg were injected or extracts of spiked human plasma samples with analytical concentration as low as 5 ng ml(-1). The factors influencing accurate mass measurements are discussed.
Antidepressive Agents, Tricyclic↗
Determination of aldicarb, aldicarb sulfoxide and aldicarb sulfone in some fruits and vegetables using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.
An analytical method for the determination of aldicarb, and its two major metabolites, aldicarb sulfoxide and aldicarb sulfone in fruits and vegetables is described. Briefly the method consisted of the use of a methanolic extraction, liquid-liquid extraction followed by solid-phase extraction clean-up. Afterwards, the final extract is analyzed by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). The specific fragment ion corresponding to [M-74]+ and the protonated molecular [M+H]+ ion were used for the unequivocal determination of aldicarb and its two major metabolites. The analytical performance of the proposed method and the results achieved were compared with those obtained using the common analytical method involving LC with post-column fluorescence detection (FL). The limits of detection varied between 0.2 and 1.3 ng but under LC-FL were slightly lower than when using LC-APCI-MS. However both methods permitted one to achieve the desired sensitivity for analyzing aldicarb and its metabolites in vegetables. The method developed in this work was applied to the trace determination of aldicarb and its metabolites in crop and orange extracts.
Aldicarb↗
Characteristics of mass fragmentation of steroids by atmospheric pressure chemical ionization-mass spectrometry.
The characteristics of the mass spectra of sixty steroids were investigated using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). In APCI-MS, the drift voltage and nebulizer temperature affected the appearance of molecular ions. Solvent adducted ions [M+H+CH3CN]+ and [M+H+H2O]+ were decreased with an increase in drift voltage. The optimum drift voltage differed slightly for each steroid. These sixty steroids were divided into two groups according to their mass spectra profiles: one having a carbonyl group at position 3 together with a double bond at position 4 (group A) and the other bearing a hydroxyl group at the 3 position (group B). In group A, the predominant peak observed corresponded to the protonated molecular ion [M+H]+. The fragment ion corresponding to the elimination of CH2OH, COCH3 and/or COCH2OH from the steroid skeleton appeared as a base peak in some steroids of group A. In group B, predominantly [M+H-H2O]+ and/or [M+H-2H2O]+ ion(s), originating from the loss of water molecules, were observed. Other major ions in this group were the protonated molecular ions. Like other chemical ionization mass spectrometry, the mass spectrum of each steroid was very simple. These results suggest that APCI-MS is a suitable tool for the determination of the mass number of polar, nonvolatile and thermolabile steroids without derivatization.
Chromatography, High Pressure Liquid↗
Application of liquid chromatography-atmospheric pressure chemical ionization mass spectrometry to the differentiation of stereoisomeric diterpenoid alkaloids.
High-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (HPLC-APCI-MS) was successfully applied to seven stereoisomeric diterpenoid alkaloids at position 1 or 12. Comparison of the breakdown curves, observed by changing the potential difference between the first electrode and the second electrode of the APCI ion source, revealed stereochemical dependence of different fragmentations. The APCI spectra of alkaloids were predominantly the [M+H]+ ion and the major fragment ion, corresponding to the [M+H-H2O]+ ion or the [M+H-CH3COOH]+ ion, and comparison of the APCI spectra showed that the abundance of fragment ions was significantly higher for C-1 beta-form alkaloids than for C-1 alpha-form alkaloids, and for C-12 beta-form alkaloids than for C-12 alpha-form alkaloids. The characteristic fragment ions were formed due to the loss of an acetic acid or a water molecule at position 12. The fragmentation mechanisms depending on the stereochemistry of the precursor ion could be discerned by recording the spectra in a deuterated solvent system of 0.05 M ammonium acetate in D2O-acetonitrile-tetrahydrofuran. Loss of CH3COOD or D2O from the precursor ion gave the fragment ion. This result indicated that the proton of protonation was included in the leaving acetic acid and water molecule, respectively. The peak intensity ratio for R=[M+H]+/[M+ H-H2O]+ + [M + H-CH3COOH] + manifested the stereochemical differentiation of alkaloids at position 1 or 12.
Alkaloids↗
An atmospheric-pressure plasma process for C2F6 removal.
Perfluorocompounds (PFCs) are widely used in the semiconductor industry for plasma etching and chemical vapor deposition (CVD). They are relatively inert gases that intensely absorb infrared radiation and, therefore, aggravate the greenhouse effect. A bench-scale experimental system was designed and constructed to evaluate the effectiveness of C2F6 conversion by using dielectric barrier discharges (DBD) with atmospheric-pressure plasma processing. Experimental results indicated that the removal efficiency of C2F6 increased with applications of higher voltage and frequency. Combined plasma catalysis (CPC) is an innovative way for abatement of PFCs, and experimental results revealed that combining plasma generation with catalysts could effectively enhance C2F6 removal efficiency achieved with DBD. The major products of C2F6 with DBD processing include CO2, COF2, and CO, when O2 was included in the discharge process. Experimental results indicated that as high as 94.5% of C2F6 were removed via CPC at applied voltage of 15 kV, frequency of 240 Hz in the gas stream of N2:Ar:O2:C2F6 = 50:40:10:0.03.
Atmospheric Pressure↗