21 of 21 INST.21
General (Unstable or Intermittent Readings)
- Check that all
connections between the electrode, temperature probe and pH meter
are clean and tightly fitting. Connections should be cleaned with a
small piece of cotton wool moistened with methylated spirits or
alcohol.
Noise (Readings Fluctuate Up and Down)
- Ensure the electrode is
clean. Rinse electrode tip thoroughly with distilled water.
Drift (Readings Constantly Move in One Direction)
- Soak the
electrode tip in warm 4M potassium chloride solution for one hour.
Then rinse tip of electrode with deionised water.
Low Slope (Electrode Will Not Calibrate/Meter Cannot be Adjusted to
Buffer Solution pH)
- Normally caused by hairline cracks in the glass
electrode. Replace electrode if this is suspected.
Slow Response (Long Time to Steady Readings/Excessive Drift)
-
Clean electrode thoroughly as described earlier. Allow the electrode
to stand for at least one hour in Palintest Electrode Storage Solution.
If no improvement in electrode performance is obtained, replace
electrode.
Sample Application (Steady Reading in Buffer Solution but Not in
Sample)
- Check that the sample has been correctly prepared and is
not subject to pH drift through continuing reaction, temperature
effects or interfering substances.
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