Storing your pH Sensor in storage solution is important for preventing the reference electrolyte from leaching out, keeping the junction clear, and keeping the glass tip hydrated. If you’re out of pH storage solution, Vernier sells premade pH storage solution. As an alternative, you can prepare your own storage solution using a pH 4 buffer. It is recommended that you replace the pH Sensor storage solution annually.
If your pH Sensor was stored dry, immerse the tip in the pH storage solution for a minimum of 8 hours prior to use and then check the response in known buffer solutions. If the reading is close to the known pH of the buffer solution, recalibrating the sensor is recommended. If the readings are off by several pH values, the pH readings do not change when moved from one buffer solution to another different buffer, or the sensor response seems extremely slow, the problem may be more serious. Sometimes a method called “shocking” is used to revive pH electrodes.
Tip #2: Clean Your pH Sensor
Generally, rinsing the tip with DI water should suffice. If the glass tip looks dirty, you can rinse the tip with warm water and a mild household dishwashing detergent (not Alconox detergent). If the tip and bottle appear to have mold growing in or on them, you can clean it with a dilute bleach solution to remove the mold.
Fill the storage bottle with a mixture of 1 part chlorine bleach to 3 or 4 parts water and soak the electrode for 8 minutes.
Thoroughly rinse both in cold or lukewarm water.
Refill the bottle with pH Storage Solution and return the sensor to the bottle.
In biological labs where proteins are used, the glass tip can get fairly dirty. In this case, do the following:
Soak the tip for 10–15 minutes in an acidic pepsin mixture. Approximately 5% pepsin in a 0.001 M HCl solution should work.
Thoroughly rinse the tip in warm tap water.
Refill the storage bottle with pH Storage Solution and return the sensor to the bottle.
Tip #3: Maintain Your pH Calibration Solutions
A new pH Sensor is shipped with a default calibration, but as the sensor ages, it may need to be recalibrated. It is important to use good buffer solutions for calibrating.
To prevent contamination of your buffer solutions, never submerge your sensor right into the bottle. Pour out just what is needed into a container that has been rinsed with DI water and use that for your calibration. Never pour used buffer back into the bottle.
Vernier Tip: Instead of purchasing premade buffer solutions, consider buying buffer capsules. The buffer capsules have a longer shelf life than premade solutions.