IM 12B03D02-01E
9-3
9
.
Technical Information
In the equation, pH
i
is the pH buffer solution filled in the glass electrode so the pH
should be constant. Using a solution (pH standard solution) with known pH as pH
S
at
a certain temperature, the relationship between millivolt and pH can be determined,
thereby the pH can be directly derived from the membrane potential difference, as
shown in Figure 9.3.
Internal solution side
Sample solution side
Hydrated layers on glass
Boundary layers
i
e
S
e
H
+
H
+
F0902.ai
Figure 9.2 Diagram of Glass Membrane
-400
-500
pH
2
0
E (mV)
-300
-200
-100
0
100
200
300
400
500
4
6
8
10 12 14
F0903.ai
Alkaline error
Figure 9.3 Relationship between Glass Electrode Potential and pH
