GE Monitor UPC-900 Operating Instructions Manual page 99

Component Problem
pH measure- Incorrect/unstable pH
ment reading
Monitor UPC-900 Operating Instructions 29-0567-16 AB
Corrective action
Check that the electrode cable is connected prop-
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erly to the rear of the module.
Check that the pump operates correctly.
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Check that the electrode is correctly inserted in the
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flow cell and, if necessary, hand-tighten the nut.
If air in the flow cell is suspected, tap the flow cell
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carefully or tilt it to remove the air. Alternatively,
flush the flow cell with buffer at 20 ml/min for 1/2
min. Use a flow restrictor after the pH electrode.
Check that the pH electrode is not broken.
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Check that the pH electrode is calibrated.
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Check the slope (see Section 5.6 Calibrate the pH
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electrode, on page 60). If it is outside the range 80
to 105% or if the asymmetry potential deviates
more than ±60 mV from 0 mV, clean the pH elec-
trode. Recalibrate. If the problem persists, replace
the pH electrode.
Clean the pH electrode if required, see Section 6.3.4
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Clean the pH electrode, on page 89.
Compare the response of the pH electrode with
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that of another pH electrode. If the response differs
greatly, the electrode may require cleaning or re-
placement.
There may be interference from static fields. Con-
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nect the pH flow cell and the rear panel of the
monitor using a standard laboratory 4 mm banana
connector cable.
Check that the pH electrode has been calibrated
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at the correct temperature.
In organic solvents such as ethanol, methanol and
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acetonitrile, stable pH measurements are not pos-
sible since dehydration of the membrane will occur.
We recommend that the pH electrode is not used
in applications using organic solvents. Mount the
dummy electrode instead.
Clogged liquid junction. Refer to Section 6.3.4 Clean
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the pH electrode, on page 89.
7 Troubleshooting
7.1 Fault actions
99