Standard Subtraction (Std Sub) - wtw inoLab Level 3 Operating Manual

Ion concentration
Measuring
122
7.4.4

Standard Subtraction (Std Sub)

In the "Standard Subtraction" procedure, a known amount of
standard solution is added to the sample (as complexing
agent or precipitating agent) and, thus, the ion concentration
lowered.
The ion concentration in the sample is calculated from the
change in potential.
1 Select the measuring method (see section 7.4.1).
2 Prepare two standard calibration solutions.
3 Perform a two-point calibration according to the user
guidance.
4 As soon as a stable value for the second standard
calibration solution is reached, the
display indicator
the electrode is displayed after the two-point
calibration. The probe symbol shows the electrode
evaluation after the two-point calibration.
5 Start the measurement with [Start].
A window for the entry of data opens.
h
stops flashing. The slope (mV) of