8 Troubleshooting
K-375 / K-376 / K-377
Operation Manual, Version E
148
Problem
Cause
Corrective measure
Poor repeatability
∙ Air bubbles in titration system,
buret, tubes
∙ Aspiration not working prop-
erly
∙ pH electrode incorrectly cali-
brated or not calibrated (only
in the case of potentiometric
determination)
∙ Setpoint determination out
of the specific range (only for
colorimetric determination)
∙ Sample inhomogeneous
∙ Sample weighing problems
∙ Incomplete digestion, diges-
tion time too short
∙ Suction capacity during
digestion is too strong
∙ Stirrer is not working
∙ Dip tube blocked, loose, too
short or defective
∙ Air bubbles disturb the colori-
metric titration
∙ Incorrect positioning of the
titration dosing tip
∙ Indicator aging
∙ Incorrect ratio of indicator to
boric acid, or incompatible
indicator used
∙ Loose contact of the sensor
cables
∙ Fix tubing and refill buret
∙ Check for leaks and fix
∙ Calibrate electrode with fresh
buffer
∙ Perform Setpoint determina-
tion
∙ Homogenize sample
∙ Use weighing boats to
improve procedure
∙ Check color of samples
during digestion and choose
digestion time accordingly
∙ Reduce suction power at the
Scrubber with the bypass
valve
∙ Clean the stirrer, replace if
necessary
∙ Check and collect dip tube
∙ Clean the sensor surface,
place the sensor in cleaning
solution during idle periods
∙ Check and correct position
∙ Exchange boric acid with
indicator by fresh solutions
∙ Check and correct according
to the BUCHI application
notes
∙ Check cables and correct