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Possible cause and action Problem
• High pressure in the pH cell
Decrease the flow rate.
Bypass the pH electrode (see Ports and flow paths of the pH valve,
on page 62) and measure pH in fractions manually.
Alarm in UNICORN: (Alarm)
The pH cell can only be run
at pressures below 0.8 MPa.
Please check the tubing or
lower the flow through the
pH cell.
Note: The pressure limit 0.8
MPa is for the post column
pressure.
Pressure monitors
Possible cause and action Problem
• The monitors have lost their calibration
Calibrate the pressure monitors. See Section 7.7.2 Calibrate the
pressure monitors, on page 305.
• The temperature has changed
Wait until the temperature has stabilized and calibrate the pres-
sure monitors.
Pressure offset
• Unclean inline filter in the Mixer
Replace the inline filter in the Mixer. See Section 7.3.2 Replace the
inline filter, on page 266.
• Solids in the flow path
To use the predefined method System CIP to clean the flow path,
see Section 7.6.2 Perform System CIP, on page 278.
To clean the column, see Section 7.6.3 Perform Column CIP, on
page 284. If persistent, replace the column.
• 0.25 mm .i.d. tubing kit is mounted
A smaller tubing inner diameter gives higher back pressure. The
back pressure for the 0.25 mm i.d. tubing kit is normally 16 times
higher than for the 0.50 mm i.d. tubing kit used at the same run-
ning conditions.
Maximum system flow rate for 0.25 mm i.d. tubing is 10 ml/min
Excessively high pressure
values
• The cable between the Pressure monitors and the ICU is not
connected.
Remove the monitor and make sure that the cable is connected.
The pressure monitors are
not found by the instrument
372 ÄKTA pure User Manual 29119969 AB
8 Troubleshooting
8.3 Troubleshooting: Monitors