原理:离子选择电极与甘汞电极插入溶液中构成一组测量电池,在这一组测量电池中,电池电动势 Ex 和被测离子活度(ax)之间的关系符合 Nernst 能斯脱方程。Ex=E_0+(2.303RT/nF)logax式中:E_0——零电位或截距电位,包括内外参比电极电位、膜扩散电位、不对称电位等,在一定温度下可视为常数;2.303——自然对数换算为常用对数之系数; Principle: The ion-selective electrode and calomel electrode are inserted into the solution to form a set of measuring cells. In this set of measuring cells, the relationship between the battery electromotive force Ex and the measured ion activity (ax) is in accordance with the Nernst Nernst equation. Ex = E_0 + (2.303RT / nF) logax Where: E_0-- zero potential or intercept potential, including internal and external reference electrode potential, membrane diffusion potential, asymmetric potential, etc., at a certain temperature can be regarded as a constant; 2.303- - natural logarithm converted to common logarithm of the coefficient;