Specifications

Rejuvenation and Reconditioning of Electrodes
As electrodes age, their efficiency is reduced. Symptoms include
sluggish or erratic readings. This aging is usually caused either by
contamination of the glass membrane, or by blockage of the liquid
junction reference. Below are a few remedial procedures to improve
the performance of such electrodes.
Unblocking Reference Junction
A blocked or clogged reference junction attributes to about 80 % of
all pH measurement difficulties; resulting in extremely slow response,
off-scale readings and electrically noisy measurements. Procedures
for unblocking the junction depend on the type of reference junction
electrode in use:
• Gel-Filled Electrodes
Soak the electrode in warm water (about 60 °C) for 5 to 10 minutes
to re-establish contact. Or place the electrode in warm saturated KCl
solution (60 °C) and allow both electrode and solution to cool down
to room temperature.
• Liquid-Filled Electrodes
Sleeve and Annular Junction – Drain the electrode, rinse the cavity
with distilled water and refill it with fresh electrolyte. For sleeve-type
electrodes, rotate the sleeve to re-establish flow if necessary.
• Ceramic Junction
For Silver/Silver Chloride Types Only – Soak the electrode in warm
saturated KCl solution (60 °C) for about 10 minutes, and check for
electrolyte flow. Alternatively, soak the electrode tip in concentrated
ammonium hydroxide for 5 to 10 minutes (use adequate ventilation
and precautionary measures when performing this task). Rinse the
electrode, then check for electrolyte flow.
For Ceramic Junctions Only – If the junction remains clogged, gently
sand the junction area (be careful not to touch the glass bulb), and
check for electrolyte flow.
Cleaning Glass pH Membrane
Dirty glass membranes are usually indicated by beads of water forming
on the bulb when rinsing with distilled water. The bulb can be cleaned
as follows:-
• For Protein – Soak in fresh protein removal solution ECDPCBT
for 30 minutes, rinse thoroughly before use.
• For Inorganic Deposits – Wash with EDTA, ammonia or acids
• For Grease and Similar Films – Wash with acetone,
methanol, etc.
Reconditioning Glass pH Membrane
Prolonged use, excessive alkaline immersion, or high temperature
operation will cause surface leaching of the membrane glass; resulting
in erratic or sluggish response which cannot be remedied by clearing
the electrode. Immerse the electrode tip into 0.1N HCl for less than 5
minutes, and rinse with water. Then immerse the electrode tip into 0.1N
KOH for 5 minutes, and rinse thoroughly with water. Check for electrode’s
performance. If the problem persists, repeat the steps but note that
frequent HCl/KOH treatment can shorten the electrode life.
Warranty
Eutech Instruments warrants its electrodes to be free from
manufacturing defects for 6 months (unless otherwise specified).
Electrodes
Electrode
Maintenance Guide
Use and Care of Electrodes
Maintenance and Storage of pH Electrodes
Electrodes are delicate measuring instruments that require proper
care and maintenance to produce accurate and reliable results, and
to prolong useful life.
Always keep the pH electrode moist when not in use for a period of
time, by using an electrode storage solution or a pH 7 buffer as storage
media to soak the electrode. DO NOT store the electrode in distilled or
deionised water as this will cause ions to leach out of the glass bulb and
reference electrolyte, causing slow and sluggish response.
Electrodes may be shipped with either protective caps or in electrode
soaking bottles to prevent cracking or scratching, and to keep the glass
bulbs moist. Remove the electrode gently from the storage bottle and
rinse it with distilled water before use. For long-term storage, always
keep the electrode in the bottle, filled with sufficient storage solution
to cover the bulb. Replenish the bottle as needed.
Handling
The electrode should be rinsed thoroughly between sample
measurements and calibrations with distilled or deionised water. Blot
the electrode dry to gently dislodge excess water. Use a lint-free wiping
paper as rubbing causes the electrode to be charged electrostatically.
Never use polymer or plastic body electrodes in samples containing
organic solvents.
Rellable Electrodes
The filling solution in refillable electrodes should be filled up to, but
not past, the refill hole. Make sure that the refill hole is open when
measuring to ensure that the fill solution flows properly through the
reference junction.
Electrode Maintenance Guide
page | 103
Electrode