13
Electrode Structure and Storage
G eneral pH Combination Electrode
1.
Reference Filling Hole ; hole filling electrode with the
filling solution
2.
Ag/AgCl or calomel electrode ; Reference Electrode
3.
pH mono electrode ; indicator electrode
4.
Temperature sensor
5. Reference Filling Solution ; Saturated KCl Solution
6. Glass Membrane ; membrane selectively responding
hydrogen ion
pH Electrode Storage
Electrodes are stored in the cap storage solution supplied by
istek
.
Membrane must be kept wet. If there is no storage solution, pH 4 buffer is best for the
single glass electrode and saturated KCl is preferred for a calomel and Ag/AgCl
reference electrode. Saturated KCl is the preferred solution for a combination electrode.
Electrodes are sometimes stored in distilled water, but this method causes electrode life
to decrease.
pH Electrode M aintenance (Electrode Cleaning)
If it takes long time to response or a stable data isn¡t obtained, can often be restored to
normal performance by one of the following procedures;
Glass electrodes fail because of scratches, deterioration or accumulation of debris on
the glass surface.
- Salt deposits
Recover electrode by alternately immersing it three
times each in 0.1N HCl and 0.1N NaOH for approx.
five minutes. If this fails, immerse tip in KCl
solution for 30s. After recovery, soak in pH 7.00
buffer overnight. Rinse and soak in pH 7.00 buffer.
Rinse again with distilled water before use.
- Oil/Grease films
Remove oil/Grease films with detergent, and then
rinse electrode with distilled water.
- Clogged Reference Junction
Heat diluted KCl solution to about 60 ~ 80
C.
The electrode must be stored in this solution for
approx. ten minutes, then cool electrode in not
heated KCl solution.
- Protein removal
Protein coatings can be removed by soaking glass
electrodes in a 10% pepsin solution adjusted to pH 1
to 2.
Chapter III General Functions
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