2002 Fiscal Year Final Research Report Summary
Development of a separation/determination method based on the quantitative controlled potential electrolysis at the aqueous/organic solution interface and its application to coulometry of ions
| Project/Area Number |
13554031
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
分離・精製・検出法
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| Research Institution | Kyoto Institute of Technology |
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Principal Investigator |
KIHARA Sorin Graduate School of Science and Technology, Kyoto Institute of Technology, Professor, 大学院・工芸科学研究科, 教授 (60161543)
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| Co-Investigator(Kenkyū-buntansha) |
HORI Kiichi Hokuto Denko Co. Ltd., Counselor (Researcher), 相談役(研究職)
YOSHIDA Yumi Graduate School of Science and Technology, Kyoto Institute of Technology, Research Associate, 大学院・工芸科学研究科, 助手 (40314306)
MAEDA Khoji Graduate School of Science and Technology, Kyoto Institute of Technology, Associate Professor, 大学院・工芸科学研究科, 助教授 (00229303)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Rapid coulometric electrolysis / Ion transfer / Aqueous / organic solution interface / Electrolytic cell with interfacial stirring / Electrolytic cell of flow type / Porous TeflonR tube / rapid electrolysis / high accuracy and precision |
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| Research Abstract |
The coulometric determination had been applied only to species which are easily reduced or oxidized before the present work. The purpose of the present work was to expand the field of coulometry to ionic species which are not easily reduced or oxidized by referring to the recently developed electrochemical method, voltammetry for ion transfer at the interface between aqueous (W) and organic (O) solutions.
(1) Theoretical consideration
The rapid electrolysis was considered to be essential for the precise and accurate coulometric electrolysis, since the inaccuracy due to the background current could be reduced when the electrolysis was rapid. Here, the rapid electrolysis is performed when the ratio of the area (A) of the W/O interface to the volume (V) of the sample solution (W and/or O) is large and the thickness (δ) of the diffusion layer at the interface is thin.
(2) Development of electrolytic cells
It was found that the ratio of A/V was extremely large and δ was considerably small when
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the W/O interface was stirred directly, and an "electrolytic cell with interfacial stirring (ECIS)" was developed. Another cell developed was a "electrolytic cell of flow type (ECFT)". The ETFC was composed of a porous Teflon【○R】 tube of 1 mm in inner diameter, 2 mm in outer diameter and 50 cm in length. A silver wire of 0.8 mm in outer diameter and 60 cm in length which was coated with silver chloride was inserted into Teflon^【○R】 tube. The silver wire worked as a working/reference electrode. The counter electrode was a silver wire wound around the tube. The electrolysis was carried out by dipping the tube with silver electrodes in an organic solution (O) and forcing an aqueous sample solution (W) to flow into the gap between the tube and the silver working/reference electrode. A tetraphenylborate ion selective electrode set in O near to the tube worked as a reference electrode in O. The V/A ratio is large with ECFT and δ 6 is thin since W flows in ECFT.
(3) Evaluation of capabilities of ECIS and ECFT
The capabilities were evaluated under various conditions by changing objective ions, organic solvents, supporting electrolytes, dimensions of cells, etc, and it was found that the coulometric transfer of not only hydrophobic ions but also hydrophilic ions from W to 0 could be attained when ionophors were added in O. When the concentration of an objective ion in W was 10^<-3> M, the quantitative electrolysis (the transfer of more than 99 % of the ion from W to O) could be attained with a precision of less than 1 % within 20 min by ECIS and within 1 min by ECFT. This result indicates that the field of coulometry has been expanded to the ion transfer at the W/O interface. Less
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