1,721,004 research outputs found
Determination of Ciprofloxacin, Enrofloxacin, and Marbofloxacin in Bovine Urine, Serum, and Milk by Microextraction by a Packed Sorbent Coupled to Ultra-High Performance Liquid Chromatography
No full textThis article reports new, easy, and rapid microextraction by packed sorbent (MEPS)–ultra high performance liquid chromatography with photodiode array detection for the simultaneous determination in bovine urine, serum, and milk of three antibiotics belonging to the class of the fluoroquinolones, namely ciprofloxacin, enrofloxacin, and marbofloxacin, approved for veterinary and human use (ciprofloxacin). The chromatographic separation of the analytes and all aspects influencing the MEPS performance were optimized for the extraction from the considered biological samples. The optimized procedure required simple sample pretreatment, a short (<8 min) isocratic elution, and provided sufficient sensitivity for the determination of the analytes at trace levels in compliance with current legislation. Limits of quantitation were in the range from 0.002 (ciprofloxacin, urine) to 0.048 μg/mL (enrofloxacin, milk). Recoveries from 79% (enrofloxacin, milk) to 88% (ciprofloxacin, urine/serum) were obtained on spiked samples. The within-day (n = 6) and between-day (n = 6 over 3 days) relative standard deviation percentages in bovine urine, serum, and milk samples ranged from 2.2 (ciprofloxacin, urine) to 2.5 (enrofloxacin, serum) and from 3.1 (ciprofloxacin, urine) to 3.7 (enrofloxacin, milk), respectively, and were not concentration dependent. To the best of our knowledge, this is the first study describing a fast and simple method for the determination of fluoroquinolones in bovine biological samples
Palladium-catalysed cross-coupling of styrenes with aryl methyl ketones in ionic liquids: a straight route to cyclopropanes
No full textGreen production of biofuels from fish discards using supercritical Carbon Dioxide as the extraction solvent
No full textFishing discards and wastes have great potential as renewable energy sources of biofuel, biogas and bioactive molecules for a variety of applications. Fish oils have features resembling those of petroleum fuels, being a promising and eco-friendly alternative to fossil derivatives. Here we report a preliminary investigation of a green method of biofuel production from fishing discards, obtained by two trawl hauls in the South-Western Adriatic Sea. The method is based on the use of supercritical carbon dioxide (SC-CO2) as a green solvent for lipid oils extraction and subsequent conversion into fatty acid methyl esters (FAMEs) suitable as biodiesel. Experiments were carried out to optimize yields of lipid extracted oil by tuning SC-CO2 pressure, flow rates and temperature, with the best result of 10% (w/w) of fish oil extract recorded at 30 MPa, 50°C and 1 l/min SC-CO2 flow rat
Determination of Isoflavones in Soybean Flour by Matrix Solid-Phase Dispersion Extraction and Liquid Chromatography with UV-Diode Array Detection
Full text linkA new analytical method, based on liquid chromatography (LC) with UV-diode array detection, for the simultaneous determination of daidzein, genistein, and glycitein and their 7-O-β-D-glucopyranoside (daidzin, genistin, and glycitin, resp.) has been successfully developed. All the calibration curves showed good linearity within the concentration range 0.02–2 μg/ml. The limits of detection and quantitation were 0.057 (genistin and glycitein), 0.124 μg/ml (genistein), 0.190 μg/ml (genistin and glycitein), and 0.410 μg/ml (genistein), respectively. Within-day and between-days precision were found not to be significantly different according to an F-test; values (% RSD) ranged from 2.0 to 2.9%. Extraction and clean-up of soybean flour samples were carried out using matrix solid-phase dispersion extraction (MSPD). The main parameters affecting extraction yield, such as dispersant, type and amount of additives, cosorbent, and extractive solvent, were evaluated and optimized. The average recovery values were between 85.7 and 102.6%. The target isoflavone concentration levels estimated in this work fit existing literature data and were comprised between 39.3 and 345.3 μg/g. The whole procedure has proved to be simple, accurate, precise, and cheap
Determination of Trans-resveratrol in Wines, Spirits, and Grape Juices Using Solid-Phase Micro Extraction Coupled to Liquid Chromatography with UV Diode-Array Detection
Full text linkSolid phase microextraction (polyacrylate fiber), coupled to liquid chromatography with UV diode-array detection, has been optimized for the determination of trans-resveratrol in wines, spirits, and grape juices. The main aspects influencing fiber adsorption (fiber coating, extraction time, ethanol content, salt addition) and desorption (desorption and injection time, desorption solvent mixture composition, carryover) of the analyte have been investigated. The method permitted a fast and simple determination of free trans-resveratrol in commercial samples. It was found in all the analyzed samples at concentration levels ranging from 0.007 to 4.486 Î1⁄4g mLâ1. Total trans-resveratrol concentrations were also evaluated after enzymatic deconjugation of piceid
Ionic-Liquid-Assisted Metal-Free Oxidative Coupling of Amines To Give Imines
No full textAn oxidative coupling of amines to imines has been developed in ionic liquids (ILs) under metal-free aerobic conditions. The high efficiency achievable in ILs is mechanistically explained in terms of activation of the starting materials (benzylamine and molecular oxygen) by an initial electron transfer, which may be promoted by the ionic nature of the solvent. Reactivity data of variously para-substituted benzylamines show a general deactivating effect, which would imply a change in rate determining step within the same reaction mechanism
Infrared Irradiation‐Assisted Green Approach for Pd‐Catalyzed Buchwald–Hartwig Amination
No full textWe report a novel and green approach for Pd-catalyzed Buchwald–Hartwig amination, assisted by Infrared (IR) irradiation under quasi-solvent-free conditions, in a nonanhydrous environment, and without the exclusion of air. The C–N coupling reactions, performed with a stoichiometric amount of cyclopentyl methyl ether, proceed with moderate-to-good yields using aryl iodides and bromides bearing both electron-donating and electron-withdrawing groups, along with a variety of secondary and primary amines
Selective N-Alkylation of Arylamines with Alkyl Chloride in Ionic Liquids: Scope and Applications
No full textAn efficient N-selective alkylation of primary aromatic
amines in molten quaternary ammonium salts, as the solvent,
under relatively mild and base-free conditions is presented.
On the basis of the Kamlet–Taft parameters and the nucleophilicity
of the IL (ionic liquid) anions, the influence of the ionic liquid was evaluated. This protocol was validated on a
larger multigram scale and with the syntheses of bioactive
heterocycles (e.g., 1,4-benzothiazine and quinoxalines) and
new efficient MALDI matrixes
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