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Rapidlab 1200 Operator's Guide: System Overview and Intended Use
During analysis, a membrane potential develops as a result of the interaction of
the analyte (ion) at the membrane. The membrane potential is related to the
amount of substance being measured in the sample. The half-cell potential in the
sensor consists of the inner reference element potential plus the membrane
potential.
1
2
3
4
5
6
7
Figure 1-28
The equation for calculating electrochemical cell potential can be expanded to
include the inner reference element and the membrane potential of the ISE.
E
= (E
cell
where
E
= electrochemical cell potential
cell
E
ref elmt
E
memb
E
= reference electrode half-cell potential
ref
E
= liquid junction potential
lj
Voltmeter
Potassium chloride solution
Inner element of the reference electrode
Liquid junction potential develops
Ion-selective membrane
ISE inner reference element
A fixed electrolyte solution
Electrode Elements
+ E
) - (E
ref elmt
memb
= potential of the ISE inner reference element
= potential of the ISE membrane
+ E
)
ref
lj
1-29
02087462 Rev. V
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