GE AKTA avant User Manual page 368

8 Troubleshooting
8.3 Troubleshooting: Monitors
Problem
Unstable signal
The UV curve shows a
gradient that is invert-
ed compared to the ex-
pected gradient
UV monitor U9-L
Problem
Autozero out of accept-
ed range
368
Possible cause and action
Bad pump function
•
Check that the pump is operating properly. See Exam-
ples of pump pressure curves, on page 400 for example
of pump pressure curves.
Poor mixing function
•
Check the mixer chamber size and change the
chamber if necessary. See Select Mixer chamber, on
page 157.
Check the function of the mixer. Place a stirrer bar in
the palm of your hand. Hold the hand above the mixer.
The stirrer should move when the mixer is activated.
Check that the mixer chamber is free from solids. To
open the mixer, see Section 7.3.2 Replace the inline
filter, on page 275.
Large difference in refractive index between buffer
•
A and buffer B
Due to light spreading effects in the UV cell, the buffer
with the highest UV absorption shows the lowest UV
absorption in the chromatogram, and the buffer with
the lowest UV absorption shows the highest UV ab-
sorption. This can occur if there is a large difference
in refractive index between buffer A and buffer B and
the UV is run at high sensitivity.
Possible cause and action
Wrong UV flow cell for current buffer
•
Change to a shorter UV flow cell or change buffer.
The UV flow cell is not correctly installed
•
Check that the UV flow cell is fitted correctly, see Sec-
tion 7.8.5 Replace UV monitor U9-L flow cell, on
page 345.
Broken UV flow cell
•
Replace the cell, see Section 7.8.5 Replace UV monitor
U9-L flow cell, on page 345.
ÄKTA avant User Manual 29035184 AE