Search results for "liquid"
showing 10 items of 4351 documents
Graphene and ionic liquids new gel paste electrodes for caffeic acid quantification
2015
Abstract Graphene/ionic liquids nanocomposite gels were synthesized by an electrochemical etching approach and fully characterized under a morphological and structural point of view. For this purpose, several analytical techniques were applied, as HR-TEM/EDX (High Resolution-Transmission Electron Microscopy/Energy Dispersive X-Ray Analysis); FE-SEM/EDX (Field Emission-Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis); XPS (X-Ray Photoelectron Spectroscopy); FT-IR (Fourier Transform-Infrared Spectroscopy) and electrochemical techniques. After the characterization study, nanocomposite-gel paste electrodes were assembled, exhibiting a selective and specific detection toward the ca…
Ultra high performance liquid chromatography-time-of-flight high resolution mass spectrometry in the analysis of hexabromocyclododecane diastereomers…
2014
An efficient ultra high performance liquid chromatography (UHPLC)-time-of-flight high resolution mass spectrometry (TOF-HRMS) method was elaborated for the determination of hexabromocyclododecane (HBCD) diastereomers in fish samples and compared against UHPLC-Orbitrap-HRMS and UHPLC-triple quadrupole (QqQ) tandem MS (MS/MS) techniques. The TOF-HRMS analyzer was operated at high resolution (>10000 full width at half maximum (FWHM)) with scanning the m/z range from 600 to 700, to achieve picogram quantitation limits. The effects of various operational parameters on the instrumental response were systematically investigated. Evaluation of the influence of sample clean-up procedure steps on sig…
Development and validation of a liquid chromatography tandem mass spectrometry method for the analysis of beta-agonists in animal feed and drinking w…
2010
A reproducible, sensitive and selective multiresidue analytical method for seven beta-agonists: clenbuterol (CBT), clenpenterol (CPT), ractopamine (RTP), brombuterol (BBT), mabuterol (MBT), mapenterol (MPT), and hydroxymethylclenbuterol (HMCBT) was developed and validated by using liquid chromatography tandem mass spectrometry (LC-MS/MS) in feed and drinking water samples. The validation was achieved according to the criteria laid down in the Commission Decision 2002/657/EC, however it was necessary to use minimum required performance limits (MRPLs) proposed by the Community Reference Laboratories (CRLs) due to the lack of maximum residue limits (MRLs) for beta-agonists. By setting up these…
A preliminary study in Wistar rats with enniatin : A contaminated feed
2014
A 28-day repeated dose preliminary assay, using enniatin A naturally contaminated feed through microbial fermentation by a Fusarium tricinctum strain, was carried out employing two months-old female Wistar rats as in vivo experimental model. In order to simulate a physiological test of a toxic compound naturally produced by fungi, five treated animals were fed during twenty-eight days with fermented feed. As control group, five rats were fed with standard feed. At the 28th day, blood samples were collected for biochemical analysis and the gastrointestinal tract, liver and kidneys were removed from each rat for enniatin A detection and quantitation. Digesta were collected from stomach, duode…
Liquid structure of a water-in-salt electrolyte with a remarkably asymmetric anion
2021
Water-in-salt systems, i.e., super-concentrated aqueous electrolytes, such as lithium bis(trifluoromethanesulfonyl)imide (21 mol/kgwater), have been recently discovered to exhibit unexpectedly large electrochemical windows and high lithium transference numbers, thus paving the way to safe and sustainable charge storage devices. The peculiar transport features in these electrolytes are influenced by their intrinsically nanoseparated morphology, stemming from the anion hydrophobic nature and manifesting as nanosegregation between anions and water domains. The underlying mechanism behind this structure-dynamics correlation is, however, still a matter of strong debate. Here, we enhance the apol…
Determination of fatty alcohol ethoxylates and alkylether sulfates by anionic exchange separation, derivatization with a cyclic anhydride and liquid …
2011
A method for the separation, characterization and determination of fatty alcohol ethoxylates (FAE) and alkylether sulfates (AES) in industrial and environmental samples is described. Separation of the two surfactant classes was achieved in a 50:50 methanol-water medium by retaining AES on a strong anionic exchanger (SAX) whereas most FAE were eluted. After washing the SAX cartridges to remove cations, the residual hydrophobic FAE were eluted by increasing methanol to 80%. Finally, AES were eluted using 80:20 and 95:5 methanol-concentrated aqueous HCl mixtures. Methanol and water were removed from the FAE and AES fractions, and the residues were dissolved in 1,4-dioxane. In this medium, este…
Chiral Monofluorobenzyl Carbanions: Synthesis of Enantiopure β‐Fluorinated β‐Phenylethylamines
2011
The preparation of a stabilized monofluorobenzyl carbanion by means of a remote homochiral sulfinyl group and its completely stereoselective reactions with N-p-tolylsulfinylimines are described. The use of these reactions followed by the simultaneous removal of both chiral auxiliaries with tBuLi, which occurs without epimerization at the benzylic position, provides the quickest entry to enantiomerically pure β-fluorinated β-phenylethylamines.
Micro magnetofluidics: droplet manipulation of double emulsions based on paramagnetic ionic liquids
2013
The ability to control and manipulate discrete fluid droplets by magnetic fields offers new opportunities in microfluidics. A surfactant-free and easy to realize technique for the continuous generation of double emulsion droplets, composed of an organic solvent and a paramagnetic ionic liquid, is applied. The inner phase of the emulsion droplet consists of imidazolium-based ionic liquids with either iron, manganese, nickel or dysprosium containing anions which provide paramagnetic behaviour. The double emulsion droplets are dispersed in a continuous phase of FC-40. All substances - the organic phase, the paramagnetic ionic liquid and the continuous phase -are immiscible. The magnetic proper…
Surface-anchored counterions on weak chiral anion-exchangers accelerate separations and improve their compatibility for mass-spectrometry-hyphenation
2017
In the present work we propose new variants of chiral stationary phases (CSP) with tert-butylcarbamoylquinine (tBuCQN) as chiral selector molecule. Four tBuCQN-CSPs with distinct bonding chemistries are compared in terms of their pH-dependent surface charge by ζ-potential determinations, by achiral and chiral liquid chromatographic tests and LC-ESI-MS hyphenation. In one embodiment tBuCQN was immobilized on 3-mercaptopropylmethylsilyl-modified silica by thiol-ene click reaction (brush type CSP with selector coverage of 0.38mmol/g). In another embodiment, poly-(3-mercaptopropyl)-methylsiloxane was coated onto vinylized silica particles in presence of tBuCQN and radical initiator. The tBuCQN …
Determination of low-molecular-mass aliphatic carboxylic acids and inorganic anions from kraft black liquors by ion chromatography.
2007
An ion chromatographic (IC) method with suppressed conductivity detection (CD) was developed and validated for the quantitative determination of several low-molecular-mass aliphatic mono- and dicarboxylic acids as their carboxylate anions together with some inorganic anions (chloride, sulfate, and thiosulfate) from kraft black liquors. To confirm the identification of some carboxylate anions which lack commercial model substances, a qualitative IC method with suppressed electrospray ionization mass spectrometry (ESI-MS) was also developed. The separations were performed on an IonPac AS 11-HC anion-exchange column operated at 25 degrees C within 25 min by a gradient elution with aqueous pota…