What are the requirements of users for pH glass electrodes?

What requirements do users have for pH glass electrodes? 1. Low impedance glass film 2. Chemical corrosion resistance in the range of 0--14 pH 3. Not easy to break 4. High thermal stability 5. Good reproducibility 6. Not easy to hydrolyze 7. No alkali error 8. 0-- 14 Good linearity in the pH range When the surface of the thin film glass is wetted by water, the alkali ions on the surface will dissolve, that is to say, the surface of the thin film glass is hydrolyzed. Depending on the type of glass, this hydrolysis can form a 0.3-0.6 nm thick swelling layer on the glass surface. For H+ ions, the swelling layer acts much like an ion exchanger. As the pH value of the measured medium changes, H+ ions will diffuse into or out of the swelling layer. For the inner side of the film glass, the whole process is the same as above, except that because the inner solution is fixed (such as the inner buffer solution with a pH of 7), only a constant H+ ion activity is formed. The inner and outer swelling layers are separated by the glass tissue, and a potential difference is established across the glass membrane due to the different surface potentials on the inner and outer sides of the glass membrane. This potential difference can be measured by the zero current method with a mV meter with a pH scale and displayed as a pH value. The potential follows the Nernst equation. Under the condition of 25 ℃, when the proton activity changes by one level (one pH), the potential changes by 59.16mV. The concept of an electrode with excellent performance should be as follows: 1. Reference system Ag/AgCL2, stable half-cell potential and anti-pollution reference system 3. Anti-pollution TEFLON annular diaphragm 4. Maintenance-free reference system capable of 10bar pressure, All of the above characteristics of polymer filling are reflected in our electrodes. 1. The circular Teflon diaphragm surrounds the pH glass film, forming a centrally symmetrical area of ​​high ion activity, which makes it have the advantages of a tapered gap diaphragm and avoids its shortcomings, such as: due to eddy currents, scaling and thermal load Shock causes diaphragm blockage and large KCL consumption. The electrodes are maintenance-free and the reference system is not prone to clogging. It can also be measured well in pure water with low conductivity by taking saline reserves. 2. There is no need to fill holes with electrolyte solution, so the glass tube is sealed, and the incompressibility of electrolyte solution makes it applicable to occasions where the pressure is 6 bar (special measures can reach 10 bar). 3. Unlike the traditional diaphragm, it is not sensitive to dirt. 4. The Ag/AgCL half-cell has an independent reference tube, that is, the stable half-cell potential is in contact with the measured medium through the salt bridge. This keeps the half-cell potential stable for a relatively long period of time. 5. The gel does not contain silver ions, so it does not react to the measured medium containing sulfur and other serious pollution. 6. When subjected to thermal shock and cooling in the air, it does not produce continuous bubbles like ceramic diaphragms. These air bubbles behind the porous ceramic diaphragm cause electrical insulation of the reference system. 7. Compared with ceramic diaphragms, there will be no gel extrusion under thermal shock.