wtw pH/Oxi 340i Operating Manual page 64

What to do if...
No stable measured
Obviously incorrect
measured values
64
Buffer solutions
– Incorrect buffer solutions
– Buffer solutions too old
– Buffer solutions depleted
Cause
value
pH electrode:
– Diaphragm contaminated
– Membrane contaminated
Test sample:
– pH value not stable
– Temperature not stable
Electrode + test sample:
– Conductivity too low
– Temperature too high
– Organic liquids
Cause
pH electrode:
– pH electrode unsuitable
– Temperature difference
between buffer and test
sample too high
– Measurement procedure not
suitable
– Change calibration procedure
– Use only once.
Note the shelf life
– Change solutions
Remedy
– Clean diaphragm
– Clean membrane
– Measure with air excluded if
necessary
– Adjust temperature if
necessary
– Use suitable electrode
– Use suitable electrode
– Use suitable electrode
Remedy
– Use suitable electrode
– Adjust temperature of buffers
or test samples
– Follow special procedure
pH/Oxi 340i