ION-PAIR EXTRACTION BY USE OF LIQUID-CRYSTALS AS EXTRACTING SOLVENT

By using a liquid crystal, 4-cyano-4'-hexylbiphenyl (abbreviated as CHB), as an extracting solvent, the following ion-pair extraction reaction was investigated: [formula omitted] (Q+: cationic species such as Crystal Violet (CV+), Methylene Blue (MB+) and tetrabutylammonium (TBA+); Pi-: picrate anion; subscripts o and w denote organic and aqueous phases, respectively). The above extraction equilibrium was confirmed to hold in the case of a liquid crystal (CHB) solvent as well as in an ordinary solvent (hexylbenzene/cyanobenzene 1:1 mixture for comparison; abbreviated as MIX). The dependence of the extraction constant on the temperature was investigated. Only in the CV+-CHB system, the extraction constant discontinuously changed around a phase transition temperature of CHB (29°C; nematic/liquid). When an MIX solvent was used, such a phenomenon was not observed; the extraction constant gradually increased with an increase in temperature. The effect of the molecular orientation of the extracting solvent is discussed. © 1990, The Japan Society for Analytical Chemistry. All rights reserved.