Introduction to the selection of pH meter electrodes
A, Electrode shell material
1. The glass shell is suitable for temperatures ranging from 0-150oC and is generally not corroded except by hydrofluoric acid solution, but it is prone to collision damage.
2. Polycarbonate shell is susceptible to corrosion in high alkaline solutions and some media, but resistant to collision and impact, suitable for temperatures below 80oC.
B, reference
Selection of electrodes
Ag/AgCl reference electrodes are commonly used, but general Ag/AgCl reference electrodes are prone to dissolution at high temperatures and have unstable potentials. On the other hand, capillary structured Ag/AgCl reference electrodes have very stable reference potentials and are suitable for use under high temperature and long-term continuous testing conditions.
C, Selection of liquid interface
The liquid interface is a connecting component that communicates the external reference solution and the measured solution, requiring stable and reproducible potential;
1. General liquid interface materials include fiber materials, ceramic cores, glass grinding ports, and other media. Fiber materials are generally used in plastic shell electrodes, and their solution leakage rate is fast and not easily blocked;
2. The glass grinding interface has a large contact area and leakage rate with the solution, making it suitable for the determination of weak ionic strength, high viscosity, turbid liquids or colloidal solutions.
3. Ceramic cores have good corrosion resistance, and the stability and reproducibility of the liquid interface potential are also good. They can be used in high-temperature media and are widely used as liquid interface materials;
D, Selection of electrode sockets
The commonly used socket for pH electrodes is BNC type (also known as Q9 type), and there are various other forms depending on the matching of the corresponding instrument. The last letter of this electrode model indicates the socket type.
