Roche Diagnostics
Operator’s Manual · Version 3.4 C-33
Cedex Bio analyzer 8 Data analysis methods
ISE measurements
Calibration
To calibrate the electrodes the slope of the measurement system must be calculated.
Slope calculation (2-point calibration)
This calculation is performed for sodium and potassium. The slope of the electrodes
is determined by measuring two different standard solutions. It is calculated with the
following equation (based on the Nernst equation):
Slope out of Range check
This check is used in a calibration to determine if the slope lies within the defined
range.
The slope must fulfill the following conditions:
The Out of Rng flag is displayed if the check criteria are not fulfilled.
Slope in mV/dec.
Electrode potential of ISE Solution 1 in mV.
Electrode potential of ISE Solution 2 in mV.
Known concentration of ISE Solution 1.
Known concentration of ISE Solution 2.
S
E
sol 1
E
sol 2
–
C
sol 1
C
sol 2
-------------
log
------------------------------ -
=
Lower limit of slope range in mV/dec.
Slope in mV/dec.
Upper limit of slope range in mV/dec.
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