The lifespan of the probe is typically between 3 months and 2 years, depending on where and how often it is deployed, storage conditions, and the particular electrode performance. It is a good idea to periodically check the storage solution to make sure that it is still full, and you can use Parafilm on the bottle cap and store the sensor vertically for best results. Routine checks on performance can help prevent premature sensor drift.
Some indications that we use to evaluate if the electrode needs replacement:
– Physical condition – Sometimes the probe will crystalize and you can see large gaps (air pockets) in the reference electrode, whereas a good probe will be more uniform.
– Slow response time – Another symptom that a probe is going bad. For example, if it takes more than 10-15 minutes to reach a stable pH value, or it might not stabilize at all.
– Poor readings, such as high pH residuals or big changes in raw voltage output. For example, if it reads < 1.7 VDC in pH 4 solution. We look at all of the indications above to make the best determination about whether an electrode needs to be replaced. Generally, the best way to evaluate your pH probe is to calibrate your sensor frequently (such as once a month) using consistent and fresh buffer solutions, and track the change in response time, raw voltage output and pH residuals over time.