- Wiping the Sensing Glass
Your meter receives a voltage from an electrode that is determined by the pH of the sample it is immersed in. A static charge created by wiping the pH glass may obstruct the electrode’s voltage readout. Just use distilled or deionized water to cleanse the electrode rather than wiping the electrode sensing glass. Blotting the electrode with a lint-free paper towel (like Kimwipes) to remove additional moisture is an option if needed, but take great care not to rub the glass’s surface.
- Storing the Electrode in Deionized Water
Both the filling solution and the hydrated section of the pH sensor glass, the pH electrode is teeming with ions, but deionized water has almost no ions. When an electrode is immersed in an ion-free solution, the ions within the electrode will try to form an equilibrium by moving out into the solution. The electrode will become ineffective as the majority of the ions eventually depart. Additionally, glass will break down far more quickly, resulting in shorter electrode lifespans. Utilize electrode storage solution instead.
- Inadequate Probe Submersion
The pH sensing portion and reference junction needs to be completely immersed in order to properly function. A pH sensor works because the sensing glass interacts with the sample and produces a voltage that gets compared with the reference electrode (which is stable in all samples). Without one of these portions in complete contact with the sample, the measuring system is incomplete, leading to erroneous values. Submersion problems are easily corrected by adding enough sample to submerge both the junction and sensing glass.
- Low Electrolyte Fill Level
Refillable electrodes allow you to replenish the electrolyte in the reference compartment once it begins to run low. However, if you do not replenish the electrolyte from time to time, your pH measurements can be impacted. Erratic electrode response is the most common problem with inadequate electrolyte levels.
- Not Cleaning the Electrode
When it comes to achieving precise pH readings, cleaning is equally crucial as calibration. The detecting glass is coated with deposits that develop on the electrode. As a result, you will not only be measuring the sample but also the deposits. Unclean electrodes might also result in a delayed reaction time. When it seems stable, you may even record the value; nevertheless, in practice, it is drifting very slowly toward the true value. There may be a very small layer of oil or scale on the electrode, even if it looks clean. The most effective method of cleaning the electrode is to use a pH electrode cleaning solution that has been carefully made. The best way to clean the electrode is to use a specially formulated cleaning solution for pH electrodes.
- Using an Old or Expired Electrode
As electrodes age, the sensing portion of the glass will break down and become less responsive than it was when it was new. Eventually, your electrode will stop responding adequately to changes in pH.
These diagnostics will alert you to any possible errors associated with dirty electrodes and contaminated buffers, as well as determine overall electrode condition after each calibration. CAL Check takes the guess work out of pH calibration, allowing you to be confident that your electrode is in good working condition and ready to take accurate measurements.
Reference: Hanna Instrument blog post
Article by
Emmanuel Popoola
Emmanuel@aasnig.com