The pH electrodes are a staple in laboratories and industries where pH measurement is integral to their operations. They consist of a glass electrode that responds to changes in the hydrogen ion concentration of the solution and a reference electrode that provides a stable and constant reference potential.

They are so often used in the laboratories that their maintenance becomes almost a routine necessity to keep the measurements as accurate and correct as possible. By conducting routine maintenance, you can ensure that your pH measurements are consistently reliable and free from any potential errors.

For example, if the electrolyte level is too low, or if there are bubbles inside the electrode, the measurements will become unstable, leading to inaccurate readings. Similarly, if the reference electrolyte is not replaced regularly, crystallization can occur, further affecting the accuracy of the measurements. By properly maintaining the electrode, you can prolong its lifespan and ensure that your pH measurements are consistent and reliable.

Here are some quick tips for your electrode maintenance:

Calibration

Calibration is a key step in electrode maintenance. The glass pH electrode measures the hydrogen ion concentration and needs to be calibrated regularly against the reference electrode to ensure that the system is operating correctly. There are three most common buffer solutions to conduct a three-point calibration — pH 7.00 (neutral), pH 4.01 (acidic), and pH 9.21 (alkaline). Even though a one-point calibration can also ensure accurate measurement results, to get the most reliable results, a two-point or three-point calibration is recommended.

Cleaning and storage

Proper cleaning and storage can prolong the life of the electrode significantly. The electrodes must be stored in storage solutions (3M KCI — if not available, then pH of 4.01 or 7.00 buffer solution) that keep the electrodes hydrated and prevent them from drying out. What is most important is that the pH electrodes should never be stored dry. If they are to be stored for the long term (more than a week), they should be ideally placed into a protective cap or storage bottle with the specific storage solution. The electrode must be rinsed well before putting in the wetting cap, to avoid contaminating the storage solution.

For a good cleaning practice, the pH electrode should be rinsed between measurements with distilled water and tap dry.

There are many more best practices to maintain and store the pH electrodes. To learn more, download METTLER TOLEDO’s pH Electrode Maintenance Poster. Also, to find the right sensor for your applications, visit: www.mt.com