Troubleshooting - Metrohm ISE Handbuch

3.2 Troubleshooting

Ion-selective electrodes, Manual
The following problems may occur:
•
Measured signal is unstable
•
Sluggish response time ("running" measured value)
• Electrode slope too low
•
Electrode zero point (E(0)) not correct
•
Reduced linearity range
These problems can occur on account of the reference or the ion-
selective electrode.
Problems with the reference electrode
•
Is the quantity of the bridge electrolyte enough?
•
Are there air bubbles in the bridge electrolyte?
• Open and clean the ground-joint diaphragm. Is the flow through the
diaphragm OK after cleaning?
•
Is the electrode cable correctly plugged in?
•
Is the electrode cable defective?
Problems with the ion-selective crystal membrane electrode
•
Polish the sensor surface with the polishing set.
•
Exception: The sensor surface of the F
tooth paste or liquid soap.
•
Avoid electrode poisons, see also page 40. Electrode poisons must
be precipitated or masked.
• Is the electrode cable correctly plugged in?
•
Is the electrode cable defective?
•
The sensor surface may be destroyed. Use new electrode.
Problems with the ion-selective polymer membrane electrode
•
Don't use organic solvents!
•
Any other components which may destroy or contaminate the sen-
sor surface must be eliminated.
•
Avoid electrode poisons, see also page 40. Electrode poisons must
be precipitated or masked.
•
Is the electrode cable correctly plugged in?
•
Is the electrode cable defective?
•
The sensor surface may be destroyed. Use new electrode tip or
new electrode.
3 Maintenance
-
electrode is polished with
39