Care And Maintenance Of Ph Glass Electrodes - Metrohm 780 Manual

8.6 pH electrode test
Test criterion
pH 9: absolute drift in stirred
solution > 1 mV/min
pH 9:
-10 mV < U(unstirred) < 10 mV
AND
sum of abs. drift values after 1, 2,
3 and 4 min < 12 mV/min
2 slopes do not meet the
conditions for a passing
electrode
Electrode poor as streaming
potential dU is too high
All slopes meet conditions for
passing electrode
AND
Uoff outside the preset limit
All slopes do not meet conditions
for passing electrode
A response time does not meet
the criterion for passing electrode
8.6.5

Care and maintenance of pH glass electrodes

132
Message
problem
short circuit
check buffer/
electrode
bad diaphragm
reference not
matching
partial short
circuit
glass
membrane/
reference
General
• A combined pH electrode must be filled with the correct refer-
ence electrolyte, e.g. with c(KCl) = 3 mol/L.
• The reference electrolyte chamber should be completely filled
with clean electrolyte.
• The reference electrolyte filling opening must remain open during
the measurement and be closed during storage.
• There should be no air bubbles in the inner or reference electro-
lyte.
• All cable connections should be clean and dry.
Measure
Clean diaphragm and/or
regenerate the glass membrane.
Replace electrode (short circuit
or crack in glass membrane).
Repeat test using correct
buffers.
Clean diaphragm.
Repeat with suitable reference
system; replace contaminated
reference electrolyte. If
necessary select electrode type
' ' and adapt the Uoff limits.
own
Check temperature sensor or
enter correct temperature. If this
does not help then replace pH
electrode.
Regenerate glass membrane
and/or clean diaphragm.
780/781 pH/Ion Meter, Manual