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5.5.4. Always keep the meter clean and dry; especially around the socket connecting the meter and
electrode, otherwise it may lead to inaccurate measurements or a damaged probe/meter. To clean, dry
them with medical cotton and rubbing alcohol if the connectors appear dirty.
5.5.5. The sensitive glass bulb at the front of the combination electrode should not come in contact
with hard surfaces. Scratches or cracks on the electrode will cause inaccurate readings. Before and
after each measurement, the electrode should be rinsed with distilled water and dried. If a sample
sticks to the electrode or it’s contaminated, the electrode should be thoroughly cleaned using a soft
brush with soap water and then rinsed with distilledwater. After that, soak it in the KCL solution again
for 6 hours.
5.5.6. An electrode be used for a long time, or measured solution which contains a polluting solute
easily for the sensitive bulb, or a substance resulting in jam at the junction, the electrode will be
getting passivated, its sensitivity will decrease and its response is getting slow, the reading are not
correct. Users could adopt the following methods to clean in various cases:
(a) Electrodes that have been used over a long period of time will become aged. Submerge the
electrode in 0.1mol/L hydrochloric acid for 24 hours, then rinse the electrode in distilled water, then
submerge it in 3M KCL soaking solution for 24 hours.
(b) The method to prepare 0.1mol/L hydrochloric acid: dilute 9mL hydrochloric acid in distilled or
deionized water to 1000mL.
For serious passivation, submerge the bulb in 4% HF (hydrofluoric acid) for 3-5 seconds, and rinse it
in distilled water, then submerge it in the 3M KCL soaking solution for 24 hours to renew it.
Clean contaminated glass bulb and junction (please refer to Table-8)
Table-8 Clean contaminated glass bulb and junction
Contamination
Cleaning Solutions
Inorganic metal oxide
Dilute acid less than 1mol/L
Organic lipid
Dilute detergent (weak alkaline)
Resin macromolecule
Dilute alcohol, acetone, ether
Proteinic haematocyte sediment
Acidic enzymatic solution (saccharated yeast tablets)
Paints
Dilute bleacher, peroxide
