PC850 Version 1.0
For calibration accuracy, the pH of the standard buffer solution must be reliable. The buffer solution
should be refreshed often, especially after heavy use.
4.5.3. Protect glass bulb
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 washed with pure water and dried. Do not clean the
glass bulb with a tissue for it will affect the stability of the electrode potential and increase the
response time. The electrode should be thoroughly cleaned if a sample sticks to the electrode. Use
a solvent if the solution does not appear clean after washing.
4.5.4. Renew glass bulb
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 wash the electrode in pure water, then
submerge it in soaking solution for 24 hours.
The method to prepare 0.1mol/L hydrochloric acid: dilute 9mL hydrochloric acid in pure water to
1000mL. For serious passivation, submerge the bulb in 4% HF (hydrofluoric acid) for 3-5 seconds,
and wash it in pure water, then submerge it in the soaking solution for 24 hours to renew it.
4.5.5. Clean contaminated glass bulb and junction (please refer to Chart-6)
Chart
– 6 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
Note: The electrode housing is polycarbonate. When use cleaning solutions, take cautions
on carbon tetrachloride, trichlorethylene, tetrahydrofuran, acetone, etc., which will dissolve
the housing and invalidate the electrode.
