Search results for "liquid"
showing 10 items of 4351 documents
Occurrence of fumonisins in organic and conventional cereal-based products commercialized in France, Germany and Spain
2013
A fast and effective method for quantitative determination of fumonisins B1 and B2 (FB1 and FB2) in different cereal-based products was developed. Fumonisins were extracted combining a solid liquid extraction (SLE) pre-treatment and immunoaffinity columns (IACs), which were applied for an effective clean-up. Consecutively, high pressure liquid chromatography (HPLC) coupled to hybrid triple quadrupole-linear ion trap mass spectrometer (QTrap®) was used for the separation, detection and quantification of targeted mycotoxins. The analytical method showed acceptable recoveries ranged from 89.7% to 99.1%, as well as a relative standard deviation (%, RSD) lower than 12%. A total of 1250 samples f…
Probing the low-temperature chemistry of ethanol via the addition of dimethyl ether
2018
Considering the importance of ethanol (EtOH) as an engine fuel and a key component of surrogate fuels, the further understanding of its auto-ignition and oxidation characteristics at engine-relevant conditions (high pressures and low temperatures) is still necessary. However, it remains difficult to measure ignition delay times for ethanol at temperatures below 850 K with currently available facilities including shock tube and rapid compression machine due to its low reactivity. Considering the success of our recent study of toluene oxidation under similar conditions [38], dimethyl ether (DME) has been selected as a radical initiator to explore the low-temperature reactivity of ethanol. In …
Liquid structure and dynamics in the choline acetate:urea 1:2 deep eutectic solvent
2021
We report on the thermodynamic, structural, and dynamic properties of a recently proposed deep eutectic solvent, formed by choline acetate (ChAc) and urea (U) at the stoichiometric ratio 1:2, hereinafter indicated as ChAc:U. Although the crystalline phase melts at 36-38 degrees C depending on the heating rate, ChAc:U can be easily supercooled at sub-ambient conditions, thus maintaining at the liquid state, with a glass-liquid transition at about -50 degrees C. Synchrotron high energy x-ray scattering experiments provide the experimental data for supporting a reverse Monte Carlo analysis to extract structural information at the atomistic level. This exploration of the liquid structure of ChA…
Experimental and theoretical studies on polar Diels–Alder reactions of 1-nitronaphathalene developed in ionic liquids
2013
The reactions between 1-nitronaphthalene 1 and two nucleophilic dienes, Danishefsky´s diene 2 and 1-trimethylsilyloxy-1,3-butadiene 3, to yield phenanthrenols 7 and 8 developed in protic and aprotic ionic liquids (ILs) with an imidazolium cation base permit to conclude that the reactions occur in better experimental conditions than in molecular solvents. The yields obtained with protic ILs are better than those observed with aprotic ILs. In this sense, the higher yields obtained with aprotic ILs, (working at 60ºC, 48 h) are comparable with the lower yields observed in protic ILs (60 ºC, 24 h). DFT calculations for the reaction of 1-nitronaphthalene 1 with diene 3, in the absence and in the …
Partitioning of Aerosol Particles in Mixed-phase Clouds at a High Alpine Site
2007
6 German Aerospace Centre, D-82234, Wessling, Germany * Now at Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland Abstract The partitioning of aerosol particles between the cloud and the interstitial phase (i.e., unactivated aerosol) has been investigated during several Cloud and Aerosol Characterization Experiments (CLACE) conducted in winter and summer 2004 and winter 2005 at the high alpine research station Jungfraujoch (3,580 m altitude, Switzerland). Ambient air was sampled using different inlets in order to determine the scavenged fraction of aerosol particles, F Scav , and of black carbon, F Scav,BC . They denote the fraction of the aerosol volume con…
Presence and coding properties of 2'-O-methyl-5-carbamoylmethyluridine (ncm5Um) in the wobble position of the anticodon of tRNA(Leu) (U*AA) from brew…
1992
AbstractThe unknown modified nucleoside U* has been isolated by enzymatic and HPLC protocols from tRNALeu(U*AA) recently discovered in brewer's yeast. The pure U* nucleoside has been characterized by electron impact mass spectroscopy, and comparison of its chromatographic and UV-absorption properties with those of appropriate synthetic compounds. The structure of U* was established as 2′-O-methyl-5-carbamoylmethyluridine (ncm5Um). The yeast tRNALeu (U*AA) is the only tRNA so far sequenced which has been shown to contain ncm5Um. The location of such a modified uridine at the first position of the anticodon restricts the decoding property to A of the leucine UUA codon.
Approaches to find complementary separation conditions for resolving complex mixtures by high-performance liquid chromatography
2012
Chromatographic problems are usually addressed trying to find out a single experimental condition aimed to resolve all compounds in the sample. However, very often, the chromatographic system is not able to provide full resolution. When a separation fails, the usual choice is introducing a drastic change in the chromatographic system (e.g. column, solvent, pH). There are, however, other possibilities that take advantage of the gathered information in the failed separation, without the need of new experiments, based on the concept of complementary separations (e.g. isocratic mobile phases, gradients, columns, chromatographic modes). One separation condition will focus on the resolution of so…
Automated Determination of Paroxetine and Its Main Metabolite by Column Switching and On-Line High-Performance Liquid Chromatography
1994
An automated column-switching method coupled to isocratic high-performance liquid chromatography has been developed for simultaneous determination of blood levels of paroxetine and its nonconjugated main metabolite BRL 36610. The lower limits of detection were 9-15 nmol/L (3-5 ng/ml) and linearity between drug concentration and detector response was found for 0-1,500 nmol/L (0-500 ng/ml). The method could be applied to the analysis of serum samples obtained from depressed patients who were treated with daily oral doses of 20 or 40 mg of paroxetine. After the 20-mg dose, the mean blood level of paroxetine was 69 nM (23 ng/ml), whereas the metabolite BRL 36610 was detectable in only one of 5 …
Novel Paraoxonase 2-Dependent Mechanism Mediating the Biological Effects of the Pseudomonas aeruginosa Quorum-Sensing Molecule N-(3-Oxo-Dodecanoyl)-l…
2015
ABSTRACT Pseudomonas aeruginosa produces N -(3-oxo-dodecanoyl)- l -homoserine lactone (3OC12), a crucial signaling molecule that elicits diverse biological responses in host cells thought to subvert immune defenses. The mechanism mediating many of these responses remains unknown. The intracellular lactonase paraoxonase 2 (PON2) hydrolyzes and inactivates 3OC12 and is therefore considered a component of host cells that attenuates 3OC12-mediated responses. Here, we demonstrate in cell lines and in primary human bronchial epithelial cells that 3OC12 is rapidly hydrolyzed intracellularly by PON2 to 3OC12 acid, which becomes trapped and accumulates within the cells. Subcellularly, 3OC12 acid acc…
Glucosylation of isatin-3-oxime followed by 2D in situ NMR in plant cells at highest magnetic field without labelling.
2001
The glucosylation of isatin-3-oxime (1) was monitored by in situ 2D 1H-13C inverse correlated gradient assisted NMR spectroscopy in plant cell suspension cultures of Rauvolfia serpentina without labelling. The applied high magnetic field of 800 MHz allowed measurements within 20 min at concentrations of 1 of 5.76 mM. Complete glucosylation of 1 occurs inside the cells within 72 hours. During this time isatin-3-oxime-glucoside (2) accumulates without further metabolism.