H24.0.01.6C-07 page 4 of 4
General maintenance and measuring instructions for pH combi-electrodes
(our standard type GE 014)
This pH electrode has been subjected to a series of tests demanding maximum quality standards in all stages of
manufacture.
Attached electrode can be used for 2 to 12 pH respectively at temperatures between 5 and 45°C and
conductivity > 200 µS/cm.
1.
Make sure to observe the following points to maintain optimum capacity and accuracy of electrode as long
as possible:
1.1. Remove storage-protection cap from pH-glass diaphragm and rinse glass body and pH-glass diaphragm with ordinary
tap water. Then dry glass body and pH-diaphragm with soft tissue.
1.2. Important! Make sure to always keep pH-glass diaphragm in a slightly moist condition. If electrode is not used, the pH-
glass diaphragm has to be immersed into a 3 mol/l KCl solution for storage.
Drying out of the pH-glass diaphragm will affect both its capacity and sensitivity. In order to wet it throughout, put glass
diaphragm in a 3 mol/l KCl solution for 24 hours.
1.3. Please avoid touching of the glass diaphragm as even the slightest damage to, or abrasion of its surface may
negatively affect the capacity of the electrode.
1.4. Make it a rule to always visually check pH-electrodes for any air bubbles that might be enclosed in the pH-glass
diaphragm and the external reference electrode cell. In case of air bubbles being apparent, these can be removed by
shaking the electrode (downwards as for a clinical mercury thermometer)
1.5. In order to avoid a pressure build-up or vacuum in the reference electrode cell, thus ensuring trouble-free penetration,
shift rubber closing collar covering the electrolyte filling hole. For storage, the closing collar has to be properly and
carefully replaced as otherwise the electrolyte will leak.
During measurements the lateral diaphragm should also come into contact with the material to be measured. Minimum
immersion depth for GE 014 is 20 mm, max. 50 mm
1.6. Electrode cable and plug should always be clean and dry as otherwise the electrical insulation may be damaged, this
resulting in incorrect measurements as well as other faults.
2.
Care and maintenance:
2.1. Check liquid level of reference electrolyte at regular intervals; if necessary top up with 3 mol/l KCl solution through filling
hole using a syringe or pipette.
2.2. Crystaization of the 3 mol/l KCl is not avoidable !
Crystalized KCl at protection cap or closing collar can easily be removed by fingernail or cloth and is no defect or
reason for reclamation.
2.3. Dirty electrodes have to be cleaned. You will find suitable cleaning agents for the pH-glass diaphragm in the following
table:
Contamination
Cleaning agent
Various deposits
Light cleaning agent
Inorganic coatings
Commercial liquids for cleaning of glass
Metal compounds
1 mol/l HCI solution
Oil, grease
Special cleaning agents or solvents
Biological coatings containing proteins
1 % pepsin enzyme in 0.1 molar HCI solution
Resin-lignines
Acetones
Highly resistant deposits
Hydrogen superoxide, sodium hypochloride
The distinct materials of the electrode have to be considered when choosing the cleaning agent.
E.g. electrodes with plastics shaft must not be cleaned with solvents. In case of doubt please contact the manufacturer for
further advice.
The same has to be considered when using aggressive or other, non water based agents!
6.
Cheese, fruit, meat
Insertion electrode (
Our type GE 101
).
When conducting measurements in cheese, milk and other products containing proteins, a special cleaning agent has
to be used for cleaning of the electrode (pepsin solution - can be ordered from us).
Normal cleaning: 0.1 molar HCI solution for at least 5 min. or protein cleaning agent.
Generally speaking, the service life of electrodes is 8 to 10 months; with proper care and maintenance their service life
may even be extended to over 2 years. The actual service life is, however, dependant on the individual application
If you can no longer set the pHX-value this could either be an indication that
a)
the electrode is worn out and needs to be replaced, or that
b)
the buffer solution is used up (prepare new solution). Even if treated very carefully during calibration (to avoid carrying
over of buffer solution residuals from one solution to another if electrode is not sufficiently cleaned and dried) buffer
solutions only keep for a certain period of time (approx. 1 month).
Buffer capsules can be kept for an unlimited period of time - we, therefore, recommend to keep a certain number on stock.
PH12-buffer-capsules (white) have to be stored in an exsiccator or stored together with drying agent.
We also recommend to keep a certain amount of 3 mol/l KCl on stock for re-filling.
