Effects of solvation on the ion-pair extraction of 8-quinolinol-5-sulfonic acid with tetrabutylammonium cation using the 1-nonanol/octane mixed solvents

Chlorinated hydrocarbons represented by chloroform and aromatic solvents, such as benzene and toluene, should be voluntarily refrained from use as much as possible, while taking account of the preserving the natural environment and carcinogenic activity. From these points of view, in order to develop a less toxic solvent which can be a useful substitute solvent for chloroform, benzene, toluene, etc., we took notice of mixed solvents consisting a solvating solvent, alcohols and a non-solvating solvent, alkanes, as a less toxic solvent. The ion-pair extraction of the 8-quinolinol-5-sulfonate anion with a tetrabutylammonium cation was carried out using 1-nonanol/octane mixed solvents with a variety of mixing ratios. The formation, partition and extraction constants of the ion-pair of the 8-quinolinol-5-sulfonate anion with a tetrabutylammonium cation were estimated by a slope analysis and a curve-fitting method. The ion-pair formation constant in the aqueous phase was found to be dependent on the mixing ratio of the solvents. The sulfonate group can be expected to be solvated by three l-nonanol molecules in the aqueous phase. The present results suggest that the 1-nonanol/octane mixed solvents are also useful not only for ion-pair extraction, but for analyzing the mechanism of ion-pair extraction.