Search results for " ionization"
showing 10 items of 621 documents
Analysis of β2-agonists in cattle hair samples using a rapid UHPLC–ESI–MS/MS method
2016
A simple and efficient method was developed for simultaneous analysis of five illegal residual β2-agonists in cattle hair. β2-Agonists were quantified by ultra high performance liquid chromatography coupled with electrospray ionisation tandem mass spectrometry operating in positive multiple-reaction monitoring mode. The method was validated as quantitative confirmatory method according to the EU Decision 2002/657/EC: instrumental linearity, specificity, precision, recovery, decision limit (CCα) and detection capability (CCβ) were evaluated. The recovery were greater than 90% and the method appeared suitable for the control of these β2-agonists in cattle hair samples with LOQ values between …
Occurrence of selected antibiotics and antiretroviral drugs in Nairobi River Basin, Kenya.
2015
In this paper, we investigated the occurrence of three antibiotics (sulfamethoxazole, trimethoprim and ciprofloxacin) and three antiretroviral (lamivudine, nevirapine and zidovudine) drugs in the Nairobi River Basin, Kenya. The analytical procedure involved extraction using solid phase extraction followed by liquid chromatography-electrospray ionization tandem mass spectrometry (SPE-LC-ESI-MS/MS). In this study, 40 sites were selected for sampling, including 38 sites along the rivers and 2 wastewater treatment effluent sites. All the studied compounds were detected with sulfamethoxazole having the highest detection frequency of 97.5% and ciprofloxacin had the lowest at 60%. The results show…
Non-Homogeneous Tension Profile
2013
In this chapter, we will look at the influence of a skewed tension profile on the divergence instability of a travelling, thin elastic plate. The travelling plate is subjected to axial tension at the supports, but the tension distribution along the supports is not uniform. For the nonuniformity, we will use a linear distribution. First, we will perform a dynamic analysis of small time-harmonic vibrations, after which we will concentrate on the divergence instability problem. We will see that a small inhomogeneity in the applied tension may have a large effect on the divergence modes, and that inhomogeneity in the tension profile may significantly decrease the critical velocity of the plate.
NovelAmycolatopsis balhimycinabiochemical abilities unveiled by proteomics
2014
Amycolatopsis balhimycina DSM5908 is an actinomycete producer of balhimycin, an analogue of vancomycin, the antibiotic of ‘last resort’ against multidrug-resistant Gram-positive pathogens. Most knowledge on glycopeptide biosynthetic pathways comes from studies on A. balhimycina as this strain, among glycopeptide producers, is genetically more amenable. The recent availability of its genome sequence allowed to perform differential proteomic analyses elucidating key metabolic pathways leading to antibiotic production in different growth conditions. To implement proteomic data on A. balhimycina derived from 2-DE approaches and to identify novel components, a combined approach based on protein …
Aroma characterization of freshly-distilled French brandies; their specificity and variability within a limited geographic area
2016
Freshly-distilled French wine brandies were evaluated by gas chromatography-olfactometry (GC-O). Six brandy samples were studied, coming from two growth areas, both belonging to the same limited geographic zone, which is a homogeneous vineyard area. The GC-O methodology, using detection frequency analysis, revealed 88 olfactive areas (OAs) for which the detection frequency was ≥ 25%. OAs were then identified using gas chromatography-mass spectrometry in electron and chemical ionization modes and semi-quantified by internal normalization using gas-chromatography with flame ionization detection. Co-eluting species were separated by multidimensional gas chromatography-mass spectrometry/olfacto…
Purification method for the isolation of monophosphate nucleotides from Champagne wine and their identification by mass spectrometry
2001
Monophosphate nucleotides are difficult to identify in Champagne wine because they are present in small concentrations in a complex mixture. A method for the isolation, separation and identification of reference compounds, which achieved on average 79% recovery (except for cytidine derivatives), was developed and applied to wine. Some monophosphate nucleotides were then isolated from a Champagne wine aged on lees for 8 years, by ultrafiltration followed by a semi-preparative HPLC step using a strong anion-exchange column. The fraction obtained was subjected to HPLC in a reversed-phase column to remove the salt previously introduced, before identification of compounds by HPLC coupled to a ma…
Pyrolysis-gas chromatography-mass spectrometry of cured phenolic resins.
2003
A previously described pyrolysis device with a movable reaction zone was used in the present work for thermal degradation of cured novolac and resol resins. After the pyrolysis the usual major components were identified, as well as relatively low-volatile aromatic compounds which were revealed after their separation in a capillary chromatographic column. Among the latter components, for both types of cured resins, xanthene and its methyl derivatives were found. The isomers of bis(hydroxyphenyl)methane were found in considerable quantities only in the case of partially cured novolac resins which contained any linear sequences in their structure.
Developments for resonance ionization laser spectroscopy of the heaviest elements at SHIP
2016
Abstract The experimental determination of atomic levels and the first ionization potential of the heaviest elements ( Z ⩾ 100 ) is key to challenge theoretical predictions and to reveal changes in the atomic shell structure. These elements are only artificially produced in complete-fusion evaporation reactions at on-line facilities such as the GSI in Darmstadt at a rate of, at most, a few atoms per second. Hence, highly sensitive spectroscopic methods are required. Laser spectroscopy is one of the most powerful and valuable tools to investigate atomic properties. In combination with a buffer-gas filled stopping cell, the Radiation Detected Resonance Ionization Spectroscopy (RADRIS) techniq…
In vivo aroma release by APCI-MS and PTR-MS: impact of water content of exhaled air and evidence for competition between aroma compounds
2013
Livre ISBN-13 : 978-3-902811-91-2; International audience; Atmospheric pressure chemical ionization mass spectrometry (APCI-MS) or proton transfer reaction mass spectrometry (PTR-MS) has been in use frequently for in vivo aroma release studies. In APCI-MS, protonated water clusters formed from moisture in the expired air are used as reagent ions. Yet the influence of a change in relative water content in the ionization gas on the data collected have been rarely studied and conflicting results were obtained. In this context our first objective was to study the impact of water content of the expired air on the level of aroma release measured by APCI-MS and to compare with the results obtained…
Effects of the net charge on abundance and stability of supramolecular surfactant aggregates in gas phase
2011
Self-assembling of amphiphilic molecules under electrospray ionization (ESI) conditions is characterized by quite unexpected phenomenology. The noticeable differences with respect to the condensed phase are attributable to the absence of the surfactant-solvent interactions, the presence of net charge in the aggregates, and the strong deviation from equilibrium conditions. Aiming to investigate the effects of the net charge on abundance and stability of supramolecular surfactant aggregates, positively and negatively charged aggregates of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and sodium methane sulfonate (MetS), butane sulfonate (ButS) and octane sulfonate (OctS) have been studied by E…