EMF Research RbF / CsF Thermodynamic Properties Of The Amino Acid Aqueous Solution

The thermodynamic behavior of electrolyte in water or mixed solvents systems has become an important content of the solution chemical research due to their important roles in areas such as biology, chemistry, desalination, process engineering and atmospheric processes. As the basic constituent unit of peptides and proteins, the research for Amino acids and electrolyte system will give an insight on the structures and properties of the protein. Based on the reseach of the thermodynamic properties for rubidium and cesium salts in our group, this thesis focus on the thermodynamic properties of RbF/CsF in amino acids (Alanine, Glycine, Proline, Serine)+water systems. EMF method was utilized and the following galvanic cells without liquid junction were designed:Rb/Cs-ISE|RbF/CsF (m), Amino acids (mA), water|F-ISEThe electromotive force of RbF/CsF+Alanine/Glycine/Proline/Serine+water systems at298.15K were determined and modelled with the Pitzer, the modified Pitzer and the extended Debye-Huckel models. These three models could correlate the experimental data satisfactorily. The mean activity coefficients, osmotic coefficients, excess Gibbs free energy and Gibbs energies of transfer were obtained. The value of the mean activity coefficients γ±and excess Gibbs free energy GE decrease as the total ionic strength increase and the molalities of Amino acids decrease. This phenomenon may be explained by the electrostatic interactions model and the properties of mixed solvent. The ΔGt0are all negative obviously, indicating that the interactions are mainly controlled by zwitterion and ion attractions and the transference of RbF/CsF from water to the Amino acids+water mixed solvent is spontaneous. The ΔGt0are more negative with the increasing concentration of Amino acids since the stronger interaction between the electrolyte and zwitterion in amino acid solution.In all, this work provided the thermodynamic data to study the interactions of Amino acids and inorganic salts by using the experiments and the model fitting.