Marisa C.F. Barros

Mass transport techniques as a tool for a better understanding of the structure of L-Dopa in aqueous solutions.

Mutual diffusion coefficients, D, densities, ρ, and viscosities, η, are reported for aqueous solutions of L-3,4-dihydroxyphenylalanine (L-Dopa) at 298.15K and 310.15K at concentrations from (0.00025 to 0.0075) moldm(-3). The aim of this study is to contribute to a better understanding of the structure of these systems and the thermodynamic behaviour of L-Dopa in solution. Thus, from these experimental data it was possible to estimate some parameters, such as the hydrodynamic radius, Rh, apparent molar volumes, ϕV, and diffusion coefficients at infinitesimal concentration, D(0), essential for a better understanding of disperse systems. From the measured diffusion coefficients, activity coefficients, γ, for aqueous L-Dopa solutions were also estimated by using Nernst-Hartley equation. The effect of the viscosity on the estimated hydrodynamic radius was also studied.

Limiting values of diffusion coefficients of glycine, alanine,

Abstract.The side chain effect on transport in ionic aqueous salt solutions was investigated for

\alpha

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-amino butyric acid, norvaline and norleucine in a relevant physiological aqueous medium

α-amino acids glycine, alanine,

Binary Diffusion Coefficients for Aqueous Solutions of Lactic Acid

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Diffusion coefficients of paracetamol in aqueous solutions

α-amino butyric acid, norvaline, and norleucine --that together define a chemical homologous series based on the length of the characteristic side chain which increases from zero to four carbons, respectively. Binary mutual diffusion coefficients at infinitesimal concentration in aqueous solutions of NaCl (0.15 mol kg-1) are measured by means of Taylor dispersion technique for this series and significant differences were found against previous published results for identical systems in pure water. In this way, NaCl effect on the transport of each amino acid is thus assessed and discussed in terms of salting-out effects. Also, solvated Stokes hydrodynamic radii were computed for the series showing comparable results in water and NaCl solution. The new information should prove useful in the design and characterization of transport-controlled systems in physiological and pharmacological studies.Graphical abstract