Metrohm 917 - Page 306

30.7 Coulometric Karl Fischer titration
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917 Coulometer
Problem Cause Remedy
The diaphragm of the gen-
erator electrode is contam-
inated.
￭ Clean the diaphragm (in accordance with
directions in the leaflet for the generator
electrode).
A side reaction is taking
place.
￭ Consider using a KF oven.
￭ See technical literature.
The molecular sieve on the
KF oven has reached its
capacity limit.
￭ Replace the molecular sieve.
The gas flow from the KF
oven into the titration cell
is too high.
￭ Reduce the gas flow (if you are working
with the oven method with sample vials,
set the gas flow between 40 and 60
mL/min).
The drift becomes
greater after each
titration.
The sample releases water
very slowly.
￭ Consider using a KF oven.
￭ See technical literature.
The drift is fluctuat-
ing.
The sample solution is
poorly stirred.
￭ Set the stirring rate in such a way that the
sample solution will become very well
mixed.
The Control parameters
are set incorrectly.
￭ Reset the Control parameters to default
values.
The titration time is
too long.
The drift during condition-
ing is not stable.
￭ Wait before starting the titration until the
drift has become stable.
The parameter Start drift
is set too high.
￭ Set the Start drift lower.
￭ Adjust the Stop drift or use the Relative
stop drift.
The parameter Stop drift
is set too low.
￭ Set the Stop drift higher or use the Rela-
tive stop drift.
The water quantity is too
high.
￭ Observe the sample size and water con-
tents in accordance with .
The Control parameters
are set incorrectly.
￭ Set the parameter Dynamics lower and
the parameter Max. rate higher.
The result is too
high.
The titration cell is not yet
correctly conditioned.
￭ Shake the titration cell and wait until the
drift is stable.