Roche 9180 - Page 55

Roche Diagnostics
Instructions for Use · Version 10.0 55
9180 Electrolyte Analyzer 4 Theoretical foundation
Principles of operation
Figure 4-2 Physical principle
If the ion concentration of one measuring solution is known, the ion concentration of
the sample can be determined on the basis of the difference of two measured
potentials.
Equation 4-4
Equation 4-5
Equation 4-6
The unknown ion concentration in the sample can now be determined by:
Equation 4-7
A Glass capillary G K
+
electrode M Chloride-selective membrane
B Reference electrode H Amplifier N Sample
C Reference solution (KCl) I Display O Potassium-selective membrane
D Reference electrode housing J Cl
-
electrode P Sodium-selective membrane
E Ground K Inner electrode
F Na
+
electrode L Inner electrolyte
A
B
C
D F G H I
J
K
L
MNO
E
P
ΔE
the difference between the measured potentials of the sample and the
standard
S
the potential difference of the electrode, determined from the potential
difference of two measured standard solutions
c
i,sample
concentration of the measured ions in the sample
c
i,standard
concentration of the measured ions in the standard solutions
E
sample
E Sf
i
c
isample
log+=
E
sdardtan
E Sf
i
c
istandard
log+=

EE
sample
E
sdardtan
– S
c
isample
c
istandard
------------------------ -
log==
c
isample
c
is dardtan
10
ES
=