What Is a pH Electrode?
A pH electrode is an electrode used to measure the pH of an aqueous solution. The pH value indicates the hydrogen ion activity in a solution, which approximates the negative of the logarithm of the hydrogen ion concentration.
The pH electrode is the measuring part of a pH meter. Due to the delicate nature of its glass and internal liquid, it is used with a defined expiration date.
Uses of pH Electrodes
Glass electrodes are commonly used in various fields such as pharmaceuticals, water quality control, industrial, and environmental sectors. Plastic electrodes are also available for situations where breakage is a concern. These electrodes are versatile, being used for measuring pH on surfaces, in gels, foods, and materials like cloth and paper.
Principle of pH Electrodes
1. Glass Electrodes
The glass electrode method measures pH by gauging the potential difference between a glass electrode and a reference electrode.
2. Reference Electrodes
A reference electrode with stable electromotive force is essential. The tip of the reference electrode maintains an electrical connection with the measuring instrument through a liquid junction. Potassium chloride solution is typically used as the internal liquid in these electrodes.
3. Temperature Sensor
A temperature sensor is crucial for pH electrodes as temperature variations can cause measurement errors.
4. Combined Electrodes
Composite electrodes combine a glass electrode, a reference electrode, and a temperature sensor. These are commonly used in pH meters due to their ease of use, maintenance, and cleaning.
Other Information on pH Electrodes
1. How to Use pH Electrodes
For accurate measurements, it’s important to properly prepare the electrode, check for damages, ensure the internal liquid is at the right level, and calibrate using pH standard solutions. Measurements should be taken with care, immersing the electrode correctly and allowing sufficient time for stabilization. Post-measurement, the electrode should be cleaned and stored with a moistened cap to maintain its condition.