pH Electrode Frequently Asked Questions
1. What is the service life of a pH electrode?
The life of a properly used and maintained pH electrode is expected to be about one to three years. Factors that can shorten the life of an electrode include high temperatures and measurements at extreme pH conditions, which can shorten the life of even a properly maintained and stored electrode. If the performance of the electrode begins to deteriorate, the pH sensitive glass membrane can be regenerated and the electrode performance can be restored to its original level.
2. How do I choose the right pH electrode?
To ensure the best pH measurement, it is important to select the correct pH electrode for each application. The most important sample criteria are: chemical composition, homogeneity, temperature, process pressure, pH range and vessel size (length and width limitations). The choice of electrode is particularly important for non-aqueous, low conductivity, protein-rich and viscous measurement media, where general-purpose glass electrodes are susceptible to a number of different influences that can lead to measurement errors. The response time and accuracy of an electrode depends on a number of factors. Measurements at extreme pH values and temperatures or low conductivity have longer response times than measurements at room temperature for neutral pH values in aqueous solutions.
3. How do I maintain/clean the electrode?
Routine maintenance is important to extend the life of the pH electrode. Electrolyte-fillable electrodes need to be refilled with electrolyte when the level is likely to fall below the level of the sample solution. Maintenance prevents the sample from flowing back into the electrode. The entire reference electrolyte should also be changed at regular intervals (approximately once a month). This ensures that the electrolyte is fresh and does not crystallise during the measurement due to evaporation from the open filling port. It is important to ensure that air bubbles do not form inside the electrode, especially near the liquid complex. If this occurs, the measurement results will become unstable. To eliminate air bubbles, gently shake the electrode in a similar manner as you would a thermometer.
To clean the electrodes, rinse them with deionised water after each measurement, but do not wipe them with paper towels. The surface of the paper towel may scratch and damage the pH sensitive glass membrane, remove the gel layer, and create a static charge on the electrode. This electrostatic charge can cause the measurement signal to become very unstable. Special cleaning operations may be required after contamination of certain samples.
