Metrohm tiamo 2.3 (process analysis) - Manual (Page 1121)

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tiamo 2.3 (for Process Analysis) ￭￭￭￭￭￭￭￭ 1105
5.6.5.6 CAL LOOP Conc
5.6.5.6.1 CAL LOOP Conc - Overview
Dialog window: Method ▶ CAL LOOP Conc ▶ Properties.. ▶ CAL LOOP Conc -
'Command name'
Loop command for the calibration of ion-selective electrodes, which
is used together with the command CAL MEAS Conc.
Appearance
The command has the following appearance:
Parameters
The parameters for the command CAL LOOP Conc are configured in the
following dialog window:
￭ CAL LOOP Conc - Properties
Principle
For calibrating ion-selective electrodes (ISE), a linear correlation of the
measured potential U
i
and the logarithm of the sought ion concentration
c
i
cannot always be assumed. In ion measurements, interfering ions have
an influence on the measurement and that is why this effect is perceptible
by a flattening of the curve, especially in low concentration ranges.
The influence of interfering ions can be described by the Nikolski equa-
tion. This is an extended Nernst equation which considers the selectivity of
the ISE. For the ISE calibration with tiamo it is used in the following form: