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Section 4
Maintenance
4.1 General
The Model 3520 is designed to give optimum performance with minimum maintenance. It is only
necessary to keep the external surfaces clean and free from dust. To give added protection when
not in use the unit should be switched off and covered with the optional dust cover.
4.2 Cleaning/Re-conditioning of Combination Electrodes
For general purpose use, combination electrodes can be cleaned with a mild detergent solution or a
commercial glass cleaning solution (provided these are not strongly acidic). The electrode surface
should be wiped with a clean cloth soaked in the cleaning agent, and/or allow the membrane to
stand in the solution until clean. Rinse and repeat as necessary. Electrodes which have been
allowed to dry out should be soaked overnight in warm distilled water.
Table of Cleaning Agents for Glass Electrodes
Deposit
General deposits
Inorganic coatings
Metal compounds
Oil/Grease
Resins/Lignins
Proteins (blood, etc)
Stubborn deposits
Cleaning Agent
Genklene or mild detergent solution
Commercial glass cleaning solution (not strongly acidic)
Acid solution, not stronger than 1M
Complexing agent (EDTA) or suitable solvent
Acetone, alcohol or detergent (not strongly acidic)
Enzyme solutions (e.g; pepsin in 0.1M HCl)
Hydrogen peroxide, sodium hypochlorite or domestic bleach
Note: Solvents such as carbon tetrachloride, trichloroethylene, petroleum, ether, etc,
MUST NOT be used for cleaning electrodes that have a plastic body or a plastic protective
skirt.
352 050/REV A/03-03
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