GE AKTA avant User Manual page 378

8 Troubleshooting
8.3 Troubleshooting: Monitors
Problem
Drift of pH signal when
the pH electrode has
been removed from
storage solution
Temperature reading
error
It is not possible to in-
ject calibration solu-
tion
Alarm in UNICORN:
(Alarm) The pH cell can
only be run at pres-
sures 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.
378
Possible cause and action
Decreasing salt concentration in the electrode
•
membrane due to osmosis to buffer
Regenerate the pH electrode. Place the electrode in
deionized water for 30 minutes followed by 30 minutes
in a buffer with pH 4.
The temperature compensation of the pH monitor
•
is turned off
Contact Service.
Waste tubing is twisted or blocked
•
Untwist the tubing.
Perform System CIP to clean waste tubing. See Sec-
tion 7.6.2 Perform System CIP, on page 289.
Change the tubing.
High pressure in the pH cell
•
Decrease the flow rate.
By-pass the pH electrode (see Ports and flow paths of
the pH valve, on page 81) and measure pH in fractions
manually.
If ÄKTA avant 25 is used: Replace tubing between
Column valve and Outlet valve by tubing with i.d. 0.75
mm (tubing: 6, 7, 8, 9, 1R and 2R).
ÄKTA avant User Manual 29035184 AE