User manual

7
An important condition for satisfactory operation of the glass electrode is the
presence of a water-containing layer a so-called soak layer, on the surface of
the glass membrane. If the electrode has been stored dry for a longer period
it is necessary to condition it before use. For this purpose it is immersed for
about 24 hours in a 3 M KCl solution.
The internal buffer has to cover the internal surface of the glass membrane.
Air bubbles in the membrane chamber have to be removed by gently shaking
down the electrode in the vertical position (similar to a clinical thermometer).
Electrodes have to be installed vertically downwards. The angle to the verti-
cal must not exceed 80°.
Any contamination deposited on the surface of the glass membrane has to be
removed. If Careful dabbing with a moist soft paper tissue is not successful,
various chemical cleaning methods may be used depending on the type of
contamination (gentle glass cleaning agents, laboratory detergents, acetone,
alcohol, acid solutions of low strength such as 10% hydrochloric acid). Spe-
cial cleaning solutions are available for removing protein-containing deposits
which may be present after measurement in dairy products such as milk, yo-
gurt, cheese etc.; they contain pepsin in dilute hydrochloric acid. The memb-
rane must never be treated with abrasive cleaners (Ata, Vim etc.).
If the electrode is used for pH measurement in non-aqueous media it should
be soaked in water between tests in order to regenerate the soak layer of the
glass membrane.
Warranty
The usefulness of measurement electrodes depends on their maintenance
and on the conditions of use. The period until an electrode has to be replaced
can vary between a few weeks and several years depending on the particular
application.
In case of any complaint please return the faulty electrode which must still
carry the serial number (label on the electrode head). In addition we require
details for the fault.