ABL800 FLEX Reference Manual 1. Potentiometric measuring principles
Electrolyte electrodes, Continued
The Ca electrode (E733) is an ion-
selective electrode whose sensing
element is a PVC membrane containing
a calcium-neutral ion carrier. The ion-
sensitive membrane is covered with a
cellophane membrane in order to
protect it from the samples.
The electrolyte has a constant and
known concentration of calcium ions.
When a sample is brought in contact
with the electrode, a potential develops
across the PVC and cellophane
membranes. The potential depends on
the difference between the calcium
(more precisely, activity) in the
electrolyte and the sample. If the
cCa
2+
in both solutions is the same, the
potential across the electrode tip will be
0 V.
The Cl electrode (E744) is an ion-
selective electrode whose sensing
element is a PVC membrane containing
a chloride ion carrier. The ion-sensitive
membrane is covered with a cellophane
membrane in order to protect it from the
samples.
The electrolyte has a constant and
known concentration of chloride ions.
When a sample is brought in contact
with the electrode, a potential develops
across the PVC and cellophane
membranes. The potential depends on
the difference between the chloride
(more precisely, activity) in the
electrolyte and the sample. If the
cCl
−
in
both solutions is the same, the potential
across the electrode tip will be 0 V.
Cellophane membrane
Electrode contact
Description
(continued)
Electrode jacket
Cellophane membrane
Electrode contact
Electrode jacket
Continued on next page
1-23
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