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William E Acree - One of the best experts on this subject based on the ideXlab platform.
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characterization of the solubilizing ability of tetraalkylammonium ionic liquids containing a pendant alkyl chain bearing a basic n n dimethylamino or n n dimethylaminoethoxy functionality
Journal of Molecular Liquids, 2019Co-Authors: Fadhila Rabhi, Fabrice Mutelet, Hocine Sifaoui, Durgesh V Wagle, Gary A Baker, Brittani Churchill, William E AcreeAbstract:Abstract Infinite dilution activity coefficients and gas-to-ionic liquid partition coefficients are reported for >40 different organic compounds dissolved in N-[2-(N′,N′-dimethylamino)ethyl]-N,N-(dimethyl)-1-propanaminium bis(trifluoromethylsufonyl)imide, N-[2-(N′,N′-dimethyl-amino)ethyl]-N,N-(dimethyl)-1-butanaminium bis(trifluoromethylsufonyl)imide, N-[2-(N′,N′-dimethylamino)ethoxyethyl]-N,N-(dimethyl)-1-propanaminium bis(trifluoromethylsufonyl)imide, and N-[2-(N′,N′-dimethylamino)ethoxyethyl]-N,N-(dimethyl)-1-butanaminium bis(trifluoromethylsufonyl)imide in the temperature range from 323.15 K to 373.15 K. Partial molar excess enthalpies and partial molar excess entropies of solution were calculated from the temperature dependence of the infinite dilution activity coefficient assuming a van't Hoff Relationship. Abraham model ionic liquid-specific correlations were determined from the measured partition coefficients. The derived mathematical expressions described the observed partition coefficients to within a standard deviation of 0.14 log units (or less).
Fadhila Rabhi - One of the best experts on this subject based on the ideXlab platform.
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characterization of the solubilizing ability of tetraalkylammonium ionic liquids containing a pendant alkyl chain bearing a basic n n dimethylamino or n n dimethylaminoethoxy functionality
Journal of Molecular Liquids, 2019Co-Authors: Fadhila Rabhi, Fabrice Mutelet, Hocine Sifaoui, Durgesh V Wagle, Gary A Baker, Brittani Churchill, William E AcreeAbstract:Abstract Infinite dilution activity coefficients and gas-to-ionic liquid partition coefficients are reported for >40 different organic compounds dissolved in N-[2-(N′,N′-dimethylamino)ethyl]-N,N-(dimethyl)-1-propanaminium bis(trifluoromethylsufonyl)imide, N-[2-(N′,N′-dimethyl-amino)ethyl]-N,N-(dimethyl)-1-butanaminium bis(trifluoromethylsufonyl)imide, N-[2-(N′,N′-dimethylamino)ethoxyethyl]-N,N-(dimethyl)-1-propanaminium bis(trifluoromethylsufonyl)imide, and N-[2-(N′,N′-dimethylamino)ethoxyethyl]-N,N-(dimethyl)-1-butanaminium bis(trifluoromethylsufonyl)imide in the temperature range from 323.15 K to 373.15 K. Partial molar excess enthalpies and partial molar excess entropies of solution were calculated from the temperature dependence of the infinite dilution activity coefficient assuming a van't Hoff Relationship. Abraham model ionic liquid-specific correlations were determined from the measured partition coefficients. The derived mathematical expressions described the observed partition coefficients to within a standard deviation of 0.14 log units (or less).
Sh Hooshmand - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic study of the dimerization equilibrium of methylene blue methylene green and thiazole orange at various surfactant concentrations and different ionic strengths and in mixed solvents by spectral titration and chemometric analysis
Dyes and Pigments, 2012Co-Authors: O Yazdani, Mohsen Irandoust, Jahan B Ghasemi, Sh HooshmandAbstract:Abstract The monomer–dimer equilibrium and thermodynamics of ionic dyes were investigated by spectrophotometric and chemometric methods. The dimerization constants of methylene blue, methylene green and thiazole orange have been determined by studying the dependence of their absorption spectra at different concentrations of surfactants, ionic strengths and mixed solvents by means of UV–visible spectroscopy in aqueous solutions. The processing of the data, performed for the quantitative analysis of pure spectral profiles, was based on the simultaneous resolution of the overlapping bands in the whole set of absorption spectra. Utilizing the van’t Hoff Relationship, which describes the dependence of the equilibrium constant on temperature, as a constraint we determined the spectral responses of the monomer and dimer species as well as the enthalpy and entropy of the dimerization equilibrium. The exciton theory was used for the elucidation of the angle between the monomer units and the interaction energy between the molecules of the dimers.
Lateefa A. Al-khateeb - One of the best experts on this subject based on the ideXlab platform.
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High temperature separations on hybrid stationary phases
2007Co-Authors: Lateefa A. Al-khateebAbstract:This project has focused on the study of hybrid phases at low percentage of organic modifier and pure water using high temperature in liquid chromatography (HTLC). It examined the effect of temperature on the retention of a range of test solutes and phenol homologues. The hybrid columns all showed linear van't Hoff Relationship at low percentages of methanol but at higher temperature non linear van't Hoff curves were observed. Non·linear van't Hoff curves were observed with pure water on hybrid phases. This was thought to be because the retention mechanism changed at a discontinuity point above 100 ·C due to change in the properties of the mobile phase as well as changes in the entropy. The methylene selectivity decreased with temperature and increase with increasing pressure. XTerra phenyl and XBridge phenyl columns were stable up to 200 ·C and also in different flow rates without distortion in peaks. The efficiency of both columns was significantly decreased at low linear velocities due the domination of the B-term but at higher linear velocities the C-term dominated the separation. XBridge phenyl showed a flattened van Deemter curve indicates that high flow rate enabled a better separation. The application of high temperature on hybrid phases was studied for the separation of the selected steroids on XTerra MS C18 at low percentages methanol and pure water. A high flow rate was used to decrease the retention on XTerra MS C18 column at low percentage of methanol. In this project, variable back-pressure was used as an external parameter at constant flow rate and temperature to study the effect of pressure on retention in liquid chromatography. Hydrophobicity and shape selectivity, which depend on retention factor, increased due to increases in the pressure
Al-khateeb, Lateefa A - One of the best experts on this subject based on the ideXlab platform.
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High temperature separations on hybrid stationary phases
2007Co-Authors: Al-khateeb, Lateefa AAbstract:This project has focused on the study of hybrid phases at low percentage of organic modifier and pure water using high temperature in liquid chromatography (HTLC). It examined the effect of temperature on the retention of a range of test solutes and phenol homologues. The hybrid columns all showed linear van't Hoff Relationship at low percentages of methanol but at higher temperature non linear van't Hoff curves were observed. Non·linear van't Hoff curves were observed with pure water on hybrid phases. This was thought to be because the retention mechanism changed at a discontinuity point above 100 ·C due to change in the properties of the mobile phase as well as changes in the entropy. The methylene selectivity decreased with temperature and increase with increasing pressure. XTerra phenyl and XBridge phenyl columns were stable up to 200 ·C and also in different flow rates without distortion in peaks. The efficiency of both columns was significantly decreased at low linear velocities due the domination of the B-term but at higher linear velocities the C-term dominated the separation. XBridge phenyl showed a flattened van Deemter curve indicates that high flow rate enabled a better separation. The application of high temperature on hybrid phases was studied for the separation of the selected steroids on XTerra MS C18 at low percentages methanol and pure water. A high flow rate was used to decrease the retention on XTerra MS C18 column at low percentage of methanol. In this project, variable back-pressure was used as an external parameter at constant flow rate and temperature to study the effect of pressure on retention in liquid chromatography. Hydrophobicity and shape selectivity, which depend on retention factor, increased due to increases in the pressure.EThOS - Electronic Theses Online ServiceGBUnited Kingdo