Water Activity, pH and Density of Aqueous Amino Acids Solutions

Ninni, Luciana; Meirelles, Antônio J. A.

doi:10.1021/bp0100427

Cited by 52 publications

(32 citation statements)

References 24 publications

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“…Therefore, vapor-liquid equilibrium data and densities of the aqueous solutions were used to determine the amino acid parameters. [20][21][22][23][24] The purecomponent PC-SAFT parameters for the amino acids are summarized in Table 4:…”

Section: Resultsmentioning

confidence: 99%

Solubility of Amino Acids: Influence of the pH value and the Addition of Alcoholic Cosolvents on Aqueous Solubility

Fuchs

Fischer

Tumakaka

et al. 2006

Ind. Eng. Chem. Res.

189

176

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The solubility of DL-methionine in pure water has been measured in a temperature range of 293.15-353.15 K by means of on-line attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. These experimental data, as well as literature data for the solubility of glycine and DL-alanine in aqueous and alcohol solutions, were modeled using the PC-SAFT equation of state. Pure-component parameters for glycine, DL-alanine, and DL-methionine were fitted to the vapor pressures and to the densities of their aqueous solutions. Only one temperature-independent binary parameter is required for each system. The solubility of amino acids in water-alcohol mixtures (ternary systems) was then predicted without fitting any additional parameters. The results of the prediction correspond well to literature data. To retrieve the pH dependency, the solubility of DL-methionine in different HCl and NaOH solutions in the pH range of 1.5-9.5 was determined via gravimetric measurements. Using the knowledge of the acid-base behavior (pK a values) of the respective amino acids, the solubility of glycine, DL-alanine, and DL-methionine in aqueous electrolyte solutions can be predicted in good agreement with the experimental data.

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Section: Resultsmentioning

confidence: 99%

Solubility of Amino Acids: Influence of the pH value and the Addition of Alcoholic Cosolvents on Aqueous Solubility

Fuchs

Fischer

Tumakaka

et al. 2006

Ind. Eng. Chem. Res.

189

176

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“…For the three EPSR models, one model for each concentration, a box of molecules was constructed at the appropriate density for each measurement, 0.10408, 0.10518, and 0.10658 atoms Å -3 for 1:20, 1:15, and 1:10 proline/water concentrations, respectively. 32 Each EPSR model contained 1000 water molecules and varied with respect to the number of proline molecules present in the solution, 50 for the 1:20 concentration, 67 for the 1:15 concentration, and 100 for the 1:10 concentration. The intra-atomic distances and angles for the proline molecules were taken from the crystal structure determination of hydroxyl-L-proline.…”

Section: Methodsmentioning

confidence: 99%

Structure and Hydration of l-Proline in Aqueous Solutions

et al. 2007

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The structure and hydration of L-proline in aqueous solution have been investigated using a combination of neutron diffraction with isotopic substitution, empirical potential structure refinement modeling, and smallangle neutron scattering at three concentrations, 1:10, 1:15, and 1:20 proline/water mole ratios. In each solution the carboxylate oxygen atoms from proline accept less than two hydrogen bonds from the surrounding water solvent and the amine hydrogen atoms donate less than one hydrogen bond to the surrounding water molecules. The solute-solute radial distribution functions indicate relatively weak interactions between proline molecules, and significant clustering or aggregation of proline is absent at all these concentrations. The spatial density distributions for the hydration of the COO -group in proline show a similar shape to that found previously in L-glutamic acid in aqueous solution but with a reduced coordination number.

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“…The ebulliometer measurements remain, however, a difficult and very time consuming task so with aim at developing an experimental technique that would provide a fast, reliable and cheap scan of ionic liquids, and their interaction with water, the measurement of water activities using a hygrometer is proposed. This is a fast and reliable technique to assess the activity coefficients of water in systems with non volatile solutes [45,46], and it is here used, for the first time, for measurements of ionic liquid systems. The availability of water activity data for some quaternarium ammonium salts [47] that allows the validation of the technique for similar compounds was one of the reasons to study the cholinium-based ionic liquids.…”

Section: Introductionmentioning

confidence: 99%

Assessing the activity coefficients of water in cholinium-based ionic liquids: Experimental measurements and COSMO-RS modeling

Khan

Kurnia

Sintra

et al. 2014

Fluid Phase Equilibria

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a b s t r a c tThe vapor liquid-equilibrium of water + ionic liquids is relevant for a wide range of applications of these compounds. It is usually measured by ebulliometric techniques, but these are time consuming and expensive. In this work it is shown that the activity coefficients of water in a series of cholinium-based ionic liquids can be reliably and quickly estimated at 298.15 K using a humidity meter instrument. The cholinium based ionic liquids were chosen to test this experimental methodology since data for water activities of quaternary ammonium salts are available in the literature allowing the validation of the proposed technique.The COSMO-RS method provides a reliable description of the data and was also used to understand the molecular interactions occurring on these binary systems. The estimated excess enthalpies indicate that hydrogen bonding between water and ionic liquid anion is the dominant interaction that governs the behavior of water and cholinium-based ionic liquids systems, while the electrostatic-misfit and van der Walls forces have a minor contribution to the total excess enthalpies.The results here reported show that water activity measurements allow a quick scan for selecting ionic liquids according to their behavior in mixtures with water.

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Water Activity, pH and Density of Aqueous Amino Acids Solutions

Cited by 52 publications

References 24 publications

Solubility of Amino Acids: Influence of the pH value and the Addition of Alcoholic Cosolvents on Aqueous Solubility

Solubility of Amino Acids: Influence of the pH value and the Addition of Alcoholic Cosolvents on Aqueous Solubility

Structure and Hydration of l-Proline in Aqueous Solutions

Assessing the activity coefficients of water in cholinium-based ionic liquids: Experimental measurements and COSMO-RS modeling

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