GENERAL OPERATIONS
17
For refillable electrodes:
y
Refill the electrode with fresh electrolyte solution (see the electrode’s specifications
to select the correct refilling solution).
y
Keep the electrode upright for 1 hour.
y
Follow the storage procedure above.
If electrodes are not maintained correctly, both accuracy and precision are affected. This
can be observed as a steady decrease in the slope of the electrode.
The slope (%) indicates the sensitivity of the glass membrane, the offset value (mV)
indicates the age of electrode and provides an estimation when the probe needs to be
changed. The slope percentage is referenced to the ideal slope value at 25 °C.
Milwaukee Instruments recommends that the offset does not exceed ±30 mV and that the
slope percentage is between 85–105%.
When the slope value drops below 50 mV per decade (85% slope efficiency) or the offset
at the zero point exceeds ±30 mV, reconditioning may improve performance, but a change
of electrode may be necessary to ensure accurate pH measurements.
