Ammonium ion electrodeIt has the ability to convert the activity of a specific ion in a solution into a certain potential, and its potential is linearly related to the logarithm of the given ion activity in the solution. The ammonium ion electrode is a membrane electrode, and its core component is the sensing membrane of the electrode. According to their construction, they can be divided into solid membrane electrodes, liquid membrane electrodes, and membrane electrodes. The ammonium ion electrode is a branch of potentiometric analysis, generally used for direct potentiometry and can also be used for potentiometric titration.
Ammonium ion electrodeThe characteristics are:
① It measures the activity of specific ions in the solution rather than the total concentration;
② Easy and fast to use, with a wide range of applications, especially suitable for the determination of alkali metals, nitrate ions, etc;
③ Not affected by the color or turbidity of the test solution, it is particularly suitable for continuous automatic monitoring and on-site analysis of water quality.
Ammonium ion electrodeThe response mechanism
Ammonium ion electrodes typically use thin films of insoluble salts such as silver salts and rare earth fluoride metals, or liquid ion exchange films as sensing membranes.
The materials and preparation methods of electrode films are different, and their properties (such as stability, selectivity, and sensitivity) are also different. There are different theories for the membrane potential of different types of thin arms, some of which are still under investigation, but most of them are based on ion exchange reactions at the interface between the membrane and the solution.
When a membrane containing a substance that can exchange ions with the solution is placed in the solution, an ion exchange reaction occurs at the interface between the membrane and the solution, changing the original charge distribution between the two phases, forming a double layer, and generating a potential difference. The relationship between the membrane potential and the corresponding ion activity in the solution conforms to the Nernst equation. This is the basis for measuring ion activity in a solution using an ammonium ion electrode.