cytiva pH/C-902 Manual de instrucciones - Página 6

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Changing conductivity flow cells
The flow cells can be changed when required. Make sure that the
system is disconnected from the mains power and de-pressurized
before disconnecting/ connecting the flow cells.
If the cell is replaced with a new flow cell, the monitor must be
calibrated with the new cell constant value which is written on the
flow cell package. See Section

Troubleshooting

General
When contacting Cytiva for support, access the UNICORN
Maintenance Manager in the System Control module to display the
instrument information, e.g. version number, for reference.
Step
Action
Select System:Maintenance.
1
Select the Info tab.
2
3
Click the pH/Cond icon.
4
Click General.
WARNING
The electronics cabinet may only be opened by
Cytiva authorized personnel.
Faults and actions
If the suggested actions do not correct the fault, call Cytiva.
pH measurement
Fault
Action
No response to pH
1. Check that the electrode cable is
changes
2. The electrode glass membrane may be
Small response to pH
1. Clean the pH electrode.
changes
2. If the problem remains, replace the pH
Slow pH response or
1. Check the pH electrode tip. If it is
Calibration impossible
2. If the membrane has dried out, the
3. Clean the liquid junction.
Incorrect / unstable pH
1.
reading
2.
3.
6
Calibrating the conductivity cell,
connected properly to the electrode.
cracked.
Replace the electrode.
electrode.
contaminated, clean the electrode.
electrode may be restored by soaking it
in buffer overnight.
Check that the electrode cable is
connected properly to the electrode.
Check that the pump(s) and valves
operates correctly.
Check that the electrode is correctly
inserted in the flow cell and, if
necessary, hand-tighten the nut.
Fault
.
pH values vary with
varying back-pressure

Conductivity measurement

Fault
Incorrect or unstable
reading
Baseline drift or noisy
signal
Action
4.
If air in the flow cell is suspected, tap
the flow cell or tilt it to remove the air.
Alternatively flush the flow cell with
buffer at 8 ml/min for 1/2 min.
5.
Check that the pH electrode is not
broken.
6.
Check that the pH electrode is
calibrated.
7.
Check the slope. If it is outside the
range 80 – 105% or the asymmetry
potential deviates more than 60 mV
from 0mV, clean the pH electrode.
Recalibrate and if the problem
persists, replace the pH electrode.
8.
Clean the pH electrode if required.
9.
Compare the response of the pH
electrode with that of another pH
electrode. If the response differ
greatly, the electrode may require
cleaning or replacement.
10. Check that the pH electrode has been
calibrated at the correct temperature.
11. In organic solvents such as ethanol,
methanol and acetonitrile, stable pH
measurements are not possible since
dehydration of the membrane will
occur. It is recommended that the pH
electrode is not used in applications
using organic solvents. Replace the
electrode with the pH plug.
12. Clean the liquid junction.
Replace the pH electrode.
Action
1. Check that the conductivity flow cell
cable is connected properly.
2. Check that the pump(s) and valves
operate correctly.
3. If temperature compensation is being
used, check that the correct
temperature compensation factor is in
use.
4. Check that the column is equilibrated. If
necessary, clean the column.
1. There may be air in the flow cell. Use a
flow restrictor after the flow cell.
2. Check for leaking tubing connections.
3. Check that the column is equilibrated. If
necessary, clean the column.
4. Check the operation of the pump(s).
5. Clean the flow cell.
pH/C-902 Instruction 14003958 AB