高等学校化学学报 ›› 2000, Vol. 21 ›› Issue (2): 267.

• 论文 • 上一篇    下一篇

沉淀基离子选择电极对干扰离子的动力学响应研究

史生华, 王仲文, 索志荣, 于书平, 高鸿   

  1. 西北大学分析科学研究所, 西安 710069
  • 收稿日期:1999-03-31 出版日期:2000-02-24 发布日期:2000-02-24
  • 通讯作者: 史生华(1934年出生),男,教授,主要从事电分析化学研究.
  • 基金资助:

    国家自然科学基金(批准号:29775018);陕西省自然科学基金(批准号:98H07)资助

A Study on the Dynamic Response of Precipitate-based Ion-selective Electrodes to Interfering Ions

SHI Sheng-Hua, WANG Zhong-Wen, SUO Zhi-Rong, YU Shu-Ping, GAO Hong   

  1. Institute of Analytical Science, Northwest University, Xi′an 710069, China
  • Received:1999-03-31 Online:2000-02-24 Published:2000-02-24

摘要: 用活度阶梯法研究了AgI,AgBr,CuS,PbS和CdS电极对干扰离子的动力学响应.溶液中含一定浓度主要离子时上述电极对某些干扰离子响应非单一突跃型瞬时信号;溶液中不含主要离子时,除了AgBr电极响应Cl-外,其它都响应单一瞬时信号.离子交换产物的溶解度越小,离子的水合焓差越小,瞬时信号峰高度越大.离子水合焓差对瞬时信号峰高度的影响说明,试液高速喷向电极表面时由于扩散层厚度很薄,电极对干扰离子响应瞬时信号的峰电位不决定于离子扩散速度,而决定于离子交换速度.除CuS电极外,根据其它电极非单一突跃型瞬时信号所测定的平衡电位选择性系数Kxye与相应化合物溶度积比值是一致的.

关键词: 离子选择性电极, 电极动力学响应, 水合焓, 离子交换速度, 选择性系数

Abstract: The dynamic response of precipitate-based ion-selective electrodes to a sudden step change in the activity of interfering ions (Y±) is studied in this paper. In this case the responses of AgIelectrode to Cl-,Br-and SCN-, AgBr electrode to Cl-and SCN-, CuSelectrode to Pb2+, Zn2+, Cd2+, Co2+, Ni2+and Mn2+, PbSelectrode to Cd2+and CdSelectrode to Pb2+are all nonmonotonic overshoo-type transient signals in the presence of certain concentration of primary ion(X±) in the solution, while all the other transient signals in the absence of primary ion in the solution are monotonictype, except the response of AgBr electrode to Cl-. For the responses of a certain electrode to different interfering ions, the experiment discovers that both the smaller solubility product Ksp(MY) of ionexchange product (MY) and difference [ΔHh(X±)° -ΔHh(Y±)°] of hydration enthalpies of ions in ionexchange process, the larger the peak height ΔEPof transient signal responded to sudden increase in the activity of interfering ion by electrode, and the effect of [ΔHh(X)°-ΔHh(Y±) °] on ΔEPislarger than the KSP(MY). For the responses of AgIelectrode to Br-and SCN-, although pKsp(AgSCN)≈pKsp(AgBr), ΔEP(SCN-)>ΔEP(Br-). This is probably related to [ΔHh(I-)°-ΔH h(SCN-)°]<[ΔH h(I-)°-ΔHh(Br-)°]. For CuSelectrode, pKsp(PbS) <pKsp(CdS) , pKsp(MnS)<pKsp(CoS)and pKsp(NiS), but ΔEp(Pb2+)>ΔEp(Cd2+), ΔEp(Mn2+) >ΔEp(Co2+ )and ΔEp(Ni2+). These are the same due to [ΔHh(Cu2+)°-ΔHh(Pb2+)°]<[ΔHh(Cu2+)°-ΔHh(Cd2+)°], [ΔHh(Cu2+)°-ΔHh(Mn2+)°]<[ΔHh(Cu2+)°-ΔH(Co2+)°] and [ΔH(Cu2+)°-ΔHh(Ni2+)°]. The relative magnitudes of differences of hydration enthalpies in positive and reverse reactions in ionexchange can also be used to explain the relative magnitudes of peak heights ΔEpand ΔE of transient signals in the positive and negative activity steps. Therefore, on the basis of the above facts, we believe that the peak potential of the transient signal responded to the interfering ion by an electrode is determined not by the velocity of ion diffusion but by that of ionexchange because the thickness of diffusion layer is infinitely thin when the solution is sprayed on the surface of electrode at a high velocity .The smaller the difference in hydration enthalpies, the larger the velocity of ionexchange, then the larger the peak height of transient signal may be. Besides, for other electrodes, except Cu Selectrode, the selectivity coefficients Kxyedetermined on the basis of the equilibrium potentials in nonmonotonic overshoottype transient signals all conform to the Ksp(MX) /Ksp(MY) values.

Key words: Ion-selective electrode, Electrode dynamic response, Hydration enthalpy, Ion-exchange velocity, Selectivity coefficient

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