12
Introduction,
continued
4. Rinse the electrode with deionized water and blot dry with
a paper towel. Do not scrub the bulb.
5. To remove an empty cartridge, unscrew the dispenser unit
and rotate the cartridge counterclockwise while gently
pulling it out of the electrode.
1.3.2 Conditioning the Electrode
When a pH bulb is immersed in an aqueous solution, a hydrated
layer slowly forms at the glass/liquid interface. The formation
characteristics of this layer depend upon the type of glass, the
age of the glass, the previous usage history of the glass, the
temperature and ionic strength of the aqueous solution, etc.
This hydrated layer affects the sensing properties of the bulb
(charge transfer, and ion transport). A dry bulb will simply not
function.
To ensure the full development of the hydrated layer, electrodes
should be conditioned for several minutes in a solution
comparable to the sample in terms of pH and ionic strength.
Some samples may require special conditioning. See specific
applications for details.
1.3.2.1 Normal Conditioning
(For routine measurements in samples of moderate
to high conductivity, approximately 150 µS and
greater):
Initial use: During shipping, the electrode is kept hydrated by
a soaker bottle containing electrode solution. Remove the
bottle by loosening the cap. Save the bottle for reuse.
Between uses: Between sample measurements of medium to
high conductivity, store the electrode in Hach electrode storage
solution, a pH 6.35/1.7 M KCl buffer solution. The solution
keeps the bulb hydrated and prevents the reference gel from
solidifying in the reference junction. Hach electrode storage
solution is available in powder pillow form for dilution with
deionized water or as a prepared solution. The reusable soaker
bottle is convenient for field or laboratory use.
