Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 302)

5.1 Troubleshooting
290
PC Control / Touch Control
5.1.5 KF titrations
Problem Possible cause Remedy
Inappropriate solvent, pH
value suboptimal (side
reactions)
Change the solvent with
problematic samples e. g. 2-
methoxyethanol for ketones or
aldehydes or a mixture of
methanol/glacial acetic acid for
amines, see technical literature.
Leaking titration cell Check the sealings and the septum
and replace them if necessary.
Replace the desiccant.
Min. increment too low Increase the Min. increment under
Control parameters/User-def.
parameters.
Dosing at the end
takes too long and
the increments are
too small or the
conditioning takes
very long, high drift.
Unfavorable Stop
criterion.
Try increasing the Stop drift or
select a shorter Delay time.
"Overshoot" The increments at the end of
the titration are too large.
- Reduce the Max. rate under
Control parameters/User-def.
parameters. The following
experiment gives you a clue for
the optimum max. rate: Display
the drift throughout conditioning
and add sample without starting
the titration. Select a value below
the maximum drift as max. rate.
- Optimize the assembly of
electrode and buret tip and
improve stirring (see Installation
Instructions for the Titrando).
The methanol fraction in the
solvent is too low.
Replace the solvent. Solution becomes
too brown at the end
of the titration.
The electrode may be
covered.
Wipe off the electrode with
acetone.
Replace the solvent.
The electrode may be
covered.
Wipe off the electrode with
acetone.
Solution becomes
darker with every
titration.
The electrode has a short
circuit.
Check the Pt wires and switch on
the electrode test.