文档介绍：Potentiometric Methods
These methods rely on the measurement of Ecell for quantification.
A number mon reference and ion selective electrodes are reviewed along with general calculations and analytical approaches
§4 Potentiometry
本章主要内容
电位分析法基本原理
离子选择性电极与膜电位
离子选择性电极的选择性
离子选择性电极的种类与性能
测定离子活(浓)度的方法
电位滴定法
重点掌握电位分析法的基本原理,掌握溶液pH值的计算方法、运用工作曲线法和标准加入法进行离子活度的计算。
Classification of electroanalytical methods
Based on the quantitative relationship between some physical chemical properties of the chemical cell and concentration of the solute
Use the mutation of the physical chemical properties as indicating method of a titration reaction end-point, that is, electrical volumetry
Transfer the analyte into solid state (metal or oxide), then weigh mass of these metal or oxide deposited to ascertain amount of the analyte, that is electro-gravimetry.
Classification of electroanalytical methods
§4-2 Principle of potentiometry
电位分析法的实质是通过在零电流条件下测定两电极间的电位差(即所构成原电他的电动势) 进行分析测定。包括电位测定法和电位滴定法。
Theoretical basis of potentiometric analysis is Nernst equation:
E = EOx/Red + ln
RT
nF
aOx
aRed
For metal base electrode, aRed = 1, hence,
E = EM n+/M + ln
RT
nF
aM n+
实际测量时,都是通过测定由 indicating electrode 和 reference electrode 组成的Cell 的电动势(electromotive force)来完成的。
Reference electrodes 通常由以下几种电极来充当,它们的电位在一定条件下是恒定的,与待测离子浓度无关。
甘汞电极
Ag/AgCl电极
氢电极
pH玻璃电极
Setup of potentiometric methods
Frame of reference electrodes mon use
(滞后作用,磁滞现象))