Search results for "SOLVENT"

Recent advances on ionic liquid uses in separation techniques

2018

International audience; The molten organic salts with melting point below 100°C, commonly called ionic liquids (ILs) have found numerous uses in separation sciences due to their exceptional properties as non molecular solvents, namely, a negligible vapor pressure, a high thermal stability, and unique solvating properties due to polarity and their ionic character of molten salts. Other properties, such as viscosity, boiling point, water solubility, and electrochemical window, are adjustable playing with which anion is associated with which cation. This review focuses on recent development of the uses of ILs in separation techniques actualizing our 2008 article (same authors, J. Chromatogr. A…

Conversion of carbohydrates into 5-HMF in Deep Eutectic Solvents under mild reaction conditions

Influence of solvents on conformation of dehydropeptides

2013

Abstract Structural investigations of dehydropeptides containing (Z)-dehydrophenylalanine in solvents characterized by different polarity are discussed. The conformational analysis are based on spectroscopic methods (NMR, CD), molecular modeling techniques and in case of the tripeptide, ab initio methods. The results of temperature experiment indicate, that the only conformation of the investigated hexapeptide 3 is stabilized by intramolecular hydrogen bonds. Depending on the length of the peptide chain, the polarity of solvent influences on arrangement of the side chain of the amino acids or of the main chain of the peptide.

Inverted molecular cups: 1-D and 2-D Ag(I) coordination polymers from resorcinarene bis-thiacrowns

2016

Resorcinarene bis-thiacrown hosts 1–3 were prepared and crystallized with silver trifluoroacetate yielding one and two dimensional Ag coordination polymers. The complexation of silver in exo-cavity fashion folds the thiacrown bridges inwards transforming the resorcinarene hosts into inverted molecular cups. The silver cations were coordinated to the resorcinarene ligands and trifluoroacetate anions, which act as monodentate or bidendate bridging ligands between the metal ions. Argentophilic Ag⋯Ag (2.93–3.38 A) interactions supported by two bridging carboxylate anions were found in two of the structures, whereas longer Ag⋯Ag distances were observed if only one anion connected the silver cati…

Solvent-driven dimensionality control in molecular systems containing CuII, 2,2′-bipyridine and an oxamato-based ligand

2013

A discrete dicopper(II) system, [Cu(bipy)(H2mpba)]2·2H2O (1), and its isomeric chain, [Cu(bipy)(H2mpba)]·dmso (2) [bipy = 2,2′-bipyridine and H4mpba = N,N′-1,3-phenylenebis(oxamic acid)], were obtained by modifying the ratio of the H2O–dmso solvent mixture, and their interconversion was also monitored by changing the solvents during the synthesis. The solvents play an essential role in the formation and crystallization of these complexes, presenting different dimensionalities and connectivities. The double deprotonated H2mpba2− adopts the bidentate/monodentate (1) and bis-bidentate (2) bridging modes toward the (2,2′-bipyridyl)copper(II) units affording a dinuclear compound (1) and a linear…

Hard-sphere fluids in annular wedges: density distributions and depletion potentials.

2009

We analyze the density distribution and the adsorption of solvent hard spheres in an annular slit formed by two large solute spheres or a large solute and a wall at close distances by means of fundamental measure density functional theory, anisotropic integral equations and simulations. We find that the main features of the density distribution in the slit are described by an effective, two--dimensional system of disks in the vicinity of a central obstacle. For large solute--solvent size ratios, the resulting depletion force has a straightforward geometrical interpretation which gives a precise "colloidal" limit for the depletion interaction. For intermediate size ratios 5...10 and high sol…

First‐Derivative Fourier‐Transform Infrared Determination of Oxadiazon in Commercial Herbicide Formulations

2008

Abstract A Fourier‐transform infrared (FTIR) method has been developed for the quantification of oxadiazon in herbicide formulations. The method involves the extraction of the active ingredient by sonication of the samples with CHCl3 and direct measurement of the peak area values in first‐order derivate spectra from 1770 cm−1 to 1774 cm−1 corrected with a baseline point located at 1950 cm−1 and after a 5‐point smoothing. A limit of detection (3 s) of 0.03 mg g−1 and a typical relative standard deviation (RSD) of 1.3% were found. Results obtained were comparable with those found by liquid chromatography with UV detection. The proposed method involves a 7‐times reduction in solvent consumptio…

Green determination of eight water-soluble B vitamins in cosmetic products by liquid chromatography with ultraviolet detection.

2021

Abstract B vitamins are a group of compounds with beneficious properties for dermatologic care, and therefore they are included in the cosmetic formulations as high added-value ingredients. In this paper, an analytical method for the simultaneous determination of eight water-soluble B vitamins in cosmetic products is reported for the first time. This method is based on liquid chromatography with ultraviolet detection (LC-UV) analysis after simple water leaching of the analytes from the cosmetic matrix. No organic solvents are required, beyond the ethanol used in the chromatographic mobile phase. The proposed method has been successfully validated showing good linearity, limits of detection …

Determination of UV filters in both soluble and particulate fractions of seawaters by dispersive liquid–liquid microextraction followed by gas chroma…

2014

An analytical method to determine the total content (i.e., not only in the soluble fraction but also in the particulate one) of eight commonly used UV filters in seawater samples is presented for the first time. Dispersive liquid-liquid microextraction (DLLME) is used as microextraction technique to pre-concentrate the target analytes before their determination by gas chromatography-mass spectrometry (GC-MS). In order to release the UV filters from the suspended particles an ultrasound treatment is performed before DLLME. The ultrasound treatment time was studied in order to achieve a quantitative lixiviation of the target analytes. The type and volume of both disperser and extraction solve…

Flow-injection determination of water in organic solvents by near-infrared spectrometry

1993

Abstract A flow-injection (FI) procedure was developed for the direct determination of water in organic solvents by using the O-H stretch absorbance band of water in the near-infrared (NIR) region. Dichloromethane was employed as a test solvent to study the influence of the flow parameters (carrier flow and sample injection volume) and time interval on the sensitivity and repeatability of the FI-NIR measurements. The developed procedure permits the determination of water in dichloromethane and isobutyl methyl ketone samples with limits of detection of 0.01 and 0.005% (v/v), respectively. Real and spiked samples of solvents were analysed by FI-NIR and accurate results were found. The method …