Extech Instruments PH210 User Manual page 8

Troubleshooting an Electrode
Symptom
Long response time or
reading drift
Dry Bulb
Static Charge
Same readings in
different buffers and
samples
Erratic LCD display
800.561.8187
Cause
Clogged Junction
Strong Alkaline
measurement
Deteriorated Gel layer
Protein coating on electrode
surface
Oil, paint, dyes, suspended
solids etc. are on sensor
Organic solvents are coating
the sensor
Dehydrated membrane
Long term storage without
wetting
Wiping electrodes
Cracked or broken bulb
Samples have low ionic
strength (lacks salt); e.g.
distilled, de‐ionized, boiled,
lake water (high pressure)
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Recommendation
Soak in 4.07 M Potassium Chloride (KCl)
o
@ 60 C for 30 minutes.
Soak in 0.1 M HCL overnight.
Replace electrode.
Soak in 1 gm Pepsin dissolved in 100ml
of 0.1 m HCL for 30 minutes or as
needed.
Rinse electrode alternately with a
materials solvent and a buffer 7.00.
Organic mole fraction has to be less
than 50% to assure reasonable readings.
Limit time of measurement. Keep probe
in the 7.0 buffer between readings.
Read solution for dry bulb below:
Soak electrode tip in wetting cap filled
with 1ml 7.00 buffer for 24 to 48 hours
Rinse electrode in 7.0 buffer and blot.
Do no wipe electrode.
Replace electrode. Use bulb guard.
Avoid plunging electrode to bottom of
container and spinning bars. Wetting
cap will protect bulb between tests.
For each 50 ml of sample add 1 drop
(50uL) of SAT. KCl (No alteration in pH
will occur using inert KCl).
8
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