3.11 GOOD PRACTICE GUIDELINES
The following information contained within Section 3.1 is given as a general guide only. For more specific
detail regarding the pH electrode(s) you may be dealing with, please refer to the Technical Data Sheet
supplied with the electrode(s).
pH ELECTRODES
The types of electrodes are many and various. For the majority of tests carried out on aqueous solutions with
a reasonable ionic strength, at ambient temperatures and with limited use in stongly acidic or alkaline solutions,
the standard glass or epoxy bodied electrode is ideal. For other applications a more suitable pH/reference
electrode pair may be required, details or advice available on request.
The following general guidelines indicate the care and maintenance required for the three main groups of
electrodes, i.e. combination, reference and pH.
1)
After Use
Rinse thoroughly with distilled water
Short Term Storage
Immerse in pH4 buffer
Long Term Storage
Fit wetting cap with pH7 buffer (combination)
Fit wetting cap with pH4 buffer (Reference/pH)
2)
Electrodes should be stored:
a) away from direct sunlight
b) in a vertical position
c) within their specified temperature range
3) Always ensure the electrode is used within its specified temperature range. Ageing of electrodes used
above their specified temperature is rapid and irreversible.
4) Ensure the level of the fill solution is above the internal elements in the electrode and that this level remains
above the sample level in use.
5) DO NOT touch the sensitive glass pH membrane or reference junction during use. Excess droplets of
solution may be removed by gently blotting with filter paper or tissue. DO NOT rub the electrode as this may
induce an electrostatic charge.
6) Ensure no air bubbles are trapped at the bottom of the electrode. Removal of the air bubbles is possible by
holding the electrode vertically and gently tapping the electrode body. Larger bubbles may be removed by
shaking the electrode in a downward direction.
7. During use ensure the electrode is rinsed between each measurement to eliminate contamination of solutions.
8. Ensure that the side port/inlet is uncovered, especially during a long run of tests.
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