Analytical Sciences

Gibbs Transfer Energies of Ions from a Mixed Solvent of 2H,3H-Decafluoropentane and 1,2-Dichloroethane to Water

Hajime KATANO,* Kohei UEMATSU,* Yasuhiro KURODA,* and Toshiyuki OSAKAI**

*Department of Bioscience and Biotechnology, Fukui Prefectural University, Eiheiji, Fukui 910-1195, Japan
**Department of Chemistry, Kobe University, Nada, Kobe 657-8501, Japan

The transfer of hydrophilic, lipophilic, and fluorophilic ions at the interface between water (W) and a mixed solvent (MIX) of 2H,3H-decafluoropentane (DFP) and 1,2-dichloroethane (DCE) was studied voltammetrically and potentiometrically, and the formal Gibbs transfer energies of the ions from MIX to W, ΔG⁰_tr,^′_MIX→W, were determined. The ΔG⁰_tr,^′_MIX→W values of all the ions tested were higher than those from DFP to W. Namely, the ions would exist more stably in MIX than DFP, even for fluorophilic ions. This is due to the addition of DCE, which has a higher dielectric constant. A comparison of ΔG⁰_tr,^′_MIX→W with that from DCE to W showed a superior affinity of fluorophilic ions to the fluorous solvent in spite of equivolume addition of DCE. Therefore, the mixed solvent would be a practically superior extraction medium for fluorophilic ions. In practice, the MIX | methylene blue⁺ (W) system showed higher extractability of a fluorophilic ion C₈F₁₇SO₃⁻ than the DFP | W and DCE | W systems.

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