ELECTROKINETIC BEHAVIOR OF SELECTED ALKALI AND ALKALINE-EARTH FLUORIDE SALTS IN ORGANIC-SOLVENTS

Electrophoretic mobility measurements by laser-Doppler electrophoresis are reported for selected alkali and alkaline-earth fluorides in diff erent organic solvents. These measurements coupled with FTIR/transmiss ion spectroscopy (FTIR/TS) studies allow for the sign of the surface c harge to be predicted for fluoride salts in organic solvents. On the b asis of this analysis, the electrokinetic behavior in both hydrogen an d non-hydrogen bonding liquids can now be explained. Analysis of these results show that the surface charge of fluorides in methanol (hydrog en bonding liquid) is positive as it is in water. Importantly, the sur face charge of fluoride salts in other organic solvents (nonhydrogen b onding liquids) can be either positive or negative depending on the na ture of the organic solvent. For example fluoride salts are negatively charged in acetone due to the strong solvation of the cation relative to the fluoride ion. The opposite is true for water and other protic solvents where the fluoride ion is more extensively solvated. (C) 1998 Elsevier Science B.V. All rights reserved.