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pH electrode 50 11
Introduction
The 50 11 is a pH low maintenance electrode, as it does not
require monitoring of electrolyte level.
The open diaphragm allows direct contact between the sample
and the reference electrolyte. This avoids the classical problem
of diaphragm clogging.
Electrode preparation
Remove the storage protector containing electrolyte by unscrew-
ing it
. Verify that there are not air bubbles inside the membrane
. They can be removed by shaking the electrode as a clinical
thermometer.
Calibration
See pH-meter instruction manual.
Measurements. Recommendations
• During calibration and measurement the buffers and the sam-
ples must be slightly stirred. The stirring speed should be iden-
tical in both cases.
• The sample must cover the electrode's diaphragm
• After measurement, rinse the electrode with distilled water. Dry
it with soft tissue, only by contact, without rubbing.
• Between measurements the electrode's membrane should be
immersed in aqueous solution. The most appropriate place is
the storage protector with some electrolyte.
Do not leave the electrode immersed in distilled water.
Do not leave the electrode immersed in solutions with pH < 2.
Maintenance
• Maintain the membrane's surface clean
tion or knocking.
• When an electrode gets contaminated, the simple rinsing with
distilled water is not sufficient. The most suitable cleaning
solution is one which acts in a more selective way over the
contamination.
Proteins: Immerse the electrode in 2% NaOH solution during ap-
prox. 20 min.
Fats, oils: Wash the electrode with ethanol or soapy tap water at
approx. 40ºC.
Afterwards, rinse the electrode with plenty of distilled water and
leave for rest in the reference electrolyte.
Troubleshooting
... the pH-meter always measures the same pH value.
Short circuit in the electrode or connector.
Substitute the electrode.
... unstable reading.
Air bubble in the membrane.
Shake the electrode as a thermometer.
... impossible to perform calibration.
... very slow response.
Dirt on the membrane.
De-hydrated membrane.
Electrode ageing or wear.
Clean, regenerate or substitute the electrode.
Storage
Place the electrode in the storage protector
glycerine.
10
.
. Protect it from fric-
with KCl with
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