Vernier Tech Info Library TIL #706

Question

What is the best way to clean the glass bulb of the pH electrode?

Answer

Generally, rinsing the electrode with distilled water after using should suffice. If the glass bulb looks dirty, you can rinse the electrode with warm water and a mild household dish washing detergent (not Alconox detergent). In biological labs where proteins are used, the glass bulb can get fairly dirty. In this case, do the following:

1) Soak the electrode for 10-15 minutes in an acidic pepsin mixture. Approximately 5% pepsin in a 0.001 M HCl solution should work (pepsin can be purchased through Flinn Scientific, order code P0006).
2) Rinse the bulb in warm tap water.
3) Place the electrode back in the storage bottle which contains a pH 4 buffer/KCl storage solution. If the solution is looking dirty or moldy, replace with fresh buffer solution. Refer to the booklet which came with the pH Sensor for information on preparing new buffer solution.

If the electrode and bottle appear to have mold growing in or on them, you can clean with bleach to remove the mold.

1)Soak the electrode and fill the storage bottle with a mixture of 1 part chlorine bleach to 3 or 4 parts water (careful! such a mixture is hazardous to your skin and eyes!) for 8 minutes.
2)Vigorously rinse both in cold or lukewarm water.
3)Next, soak for 20 minutes in a good volume of distilled water. This procedure should remove any mold deposits and slow future growth.

Created by: dholmquist on August 30 2000
Last updated by: kredding on May 18 2005