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.