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

在本工作之前，库仑测定仅适用于易还原或易氧化的物种。本工作的目的是通过参考最近发展起来的电化学方法，即在水(W)和有机(O)溶液之间的离子转移伏安法，将库仑分析的范围扩大到不易还原或氧化的离子物种。(1)理论考虑快速电解被认为是精确和准确的库仑电解的关键，因为当电解速度很快时，由于背景电流的不准确性可以减少。这里，当W/O界面的面积(A)与样品溶液(W和/或O)的体积(V)之比较大，且界面处的扩散层厚度(δ)较薄时，进行快速电解。(2)电解槽的发展将W/O界面直接搅拌，研制成“界面搅拌电解槽(ECIS)”。另一种电池是“流动式电解槽(ECFT)”。ETFC由内径1 mm、外径2 mm、长50 cm的多孔特氟龙[0R]管组成。将一根外径0.8 mm、长60 cm的镀有氯化银的银丝插入聚四氟乙烯管内。银丝用作工作电极/参比电极。对电极是一根缠绕在管子上的银丝。通过在有机溶液(O)中将银电极浸泡在试管中并迫使水样溶液(W)流入试管与银工作电极/参比电极之间的间隙来进行电解。将四苯基硼酸根离子选择电极放置在靠近管子的O中，作为O中的参比电极。当W在ECFT中流动时，V/A值较大，δ6较薄。(3)ECIS和ECFT的性能评价通过改变目标离子、有机溶剂、支持电解质、电池尺寸等在不同条件下进行，发现当在O中加入离子载体时，不仅可以实现疏水离子的库仑转移，而且可以实现亲水离子从W到0的库仑转移。M，可实现定量电解(99%以上的离子从W向O的转移)，用ECIS和ECFT分别在20min和1min内达到小于1%的精度。这一结果表明，库仑场已扩展到W/O界面的离子转移。较少

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 considerationThe 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 cellsIt was found that the ratio of A/V was extremely large and δ was considerably small when … More 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 ECFTThe 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