Analytical Sciences

Formation of Minimal Third Phase in Ionic Liquid Extraction System with Trioctylphosphine Oxide and Its Possible Application to Extraction Concentration

Mizuki TOITA, Kotaro MORITA, and Naoki HIRAYAMA

Department of Chemistry, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi 274-8510, Japan

The third-phase formation behavior in ionic liquid (IL) extraction system using trioctylphosphine oxide (TOPO) was investigated. In the use of a relatively less-lipophilic IL, such as 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C₄mimTf₂N), the third phase was formed between the aqueous phase and the IL phase. The third phase seems to have a relatively high lipophilicity compared to the IL phase. The main components of the third phase were suggested as being (H₃O)TOPO⁺, IL anion (Tf₂N⁻), IL cation (C₄mim⁺) and free TOPO. In addition, the third phase showed an extraction concentration ability for the Fe(III)-thiocyanato complex.

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