Electrical mobility and diffusion in aqueous supercooled solutions

LONGINOTTI M.P; QUINTEIRO G; FRANK G; MARCONI M

Foz do Iguazú. Brasil.

Conferencia; VI Iberoamerican Conference on Phase Equilibria and Fluid Properties for Process Design; 2002

The microscopic features of the mobility of ionic (charged) and neutral species in aqueous supercooled systems is not well known. Therefore, it is difficult to predict the effect of composition and temperature on the cryoprotectant properties. In this work an experimental study has been performed on the electrical mobility of simple salts and the diffusion of non-ionic solutes in aqueous solutions containing disaccharides. The electrical conductivities of supercooled trehalose and sucrose aqueous solutions containing NaCl, MgCl2 or sodium borate were measured. over a wide range of disaccharide concentration and temperature, covering various orders of magnitude in viscosity. The results confirm that for small ions the transport is dominated by structural inhomogeneities at molecular level, which in turn leads to large deviation from the behavior predicted by the hydrodynamic model. On the other hand, the electrical mobility of the trehalose- and sucrose-borate ions seems to follow the Walden’s law. The FRAP method (fluorescence recovery after photobleaching) has been used to determine the diffusion coefficient of fluoresceine and some preliminary results are summarized, which indicate that the transport of this neutral solute obeys the hydrodynamic model.