Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 303)

5 Troubleshooting – Maintenance
PC Control / Touch Control
291
Problem Possible cause Remedy
Does your sample evolve
water extremely sluggishly?
Adjust the method, add solubilizer,
work at increased temperature
(poss. use KF oven), see technical
literature.
Are acids esterified in your
sample?
Change the solution more
frequently and increase the buffer
capacity of the solvent.
Does your sample contain
ketones or aldehydes?
Use special reagents suitable for
ketones and aldehydes.
The drift increases
with every titration.
The pH value is no more in
the optimal range.
Add buffer solution, see technical
literature.
The endpoint is
reached "too
rapidly".
Reduce the Max. rate under
Control parameters/User-def.
parameters.
The buffer capacity of the
solvent can be depleted with
two-component reagents.
Change the solution. The titration times
become longer and
longer.
If the drift increases at the same
time, see there.
5.1.6 STAT titrations
Problem Possible cause Remedy
The titration is not controlled
properly.
Rule of thumb for the
minimum rate: expected rate
of reaction in μL/min / 10
- Reduce the Min. rate under
Control parameters/User-def.
Parameters, possibly the Max.
rate as well.
- Increase the Dynamics under
Control parameters/User-def.
parameters.
Insufficient stirring. Increase the stirring rate.
Improper assembly of
electrode and buret tip.
Make sure that the assembly of
electrode and buret tip is correct
(see Installation Instructions for the
Titrando).
The control point is
not kept constant
(The controller
oscillates).
Tubes are kinked. Use new tubes.