Guanidinium Cation Effect on the Water Activity of Ternary (S)Aminopentanedioic Acid Sodium Salt Solutions at 298.15 and 310.15 K

Abstract

Vapor pressure measurements were applied to the systems guanidinium hydrochloride (methanamidine hydrochloride) + sodium l‑glutamate (S-aminopenthanedioic acid sodium salt) + water at varying concentrations of GndmCl and Na-l-Glu (m(NaGlu) = 0.1–1.6 mol/kg; m (GndmCl) = 0.104 mol/kg, 0.301 mol/kg, 0.684 mol/kg) for two temperatures, T = 298.15 and 310.15 K. From the experimental results, activities of water, activity coefficients of water, and the corresponding osmotic coefficients of the mixtures Na-l-Glu + GndmCl + water have been calculated, both being directly related to the chemical potentials of the different components and therefore to their Gibbs energy. The modeling of the components’ chemical potentials in ternary GndmCl + Na-l-Glu + water solutions was done with the equation of state ePC-SAFT. Osmotic coefficients, fugacity coefficients, and activity coefficients of the mixture components were modeled. Experimental osmotic coefficient values demonstrate nonlinear concentration dependences with several extremums at different NaGlu molalities. The theoretical ePC-SAFT approach correctly describes the experimental data. Negative values of binary interaction parameters between the guanidinium ion and the amino acid salt were required in order to model osmotic coefficients of ternary systems salt + amino acid salt + water in good agreement with the experimental data, which shows that the non-Coulomb short-range interactions between ion and amino acid salt are very strong.

Microfluidic lab-on-chip advances for liquid–liquid extraction process studies

“…Some of the modules developed in the framework of L/L extraction could also have a significant impact beyond this field as they give access to universal data in kinetics and thermodynamic. The most prominent example being the possibility to measure water or solvent chemical activity [72][73][74], for the study of the membranes [75] or to quantify mixing quality, especially when dealing with microfluidics. Indeed, mixing fluids down to the molecular level and its quantification is far from easy to perform when using microfluidics where creating turbulence or strong shearing can be challenging [76].…”