I'm sorry we cannot help diagnose under the covers for safety reasons. Have you run DAD tests from lab advisor? Is the temperature in the lab stable? what happens to the baseline if you stop the flow?
You may want to cal your local Agilent office
Depends on the amplitude of the drift. Some drift is expected, the specification lists < 0.5 × 10-3 AU/hr at 230 nm for the 4nm slit.
Drift can be caused by changing thermal conditions
- AC cycling
- Changing sunlight through a window
- Changing airflow due to open doors / weather outside
- Changing temperature of solvents due to pump head warmup after start of flow
There is a test called "ASTM Drift and Noise Test" in Lab Advisor which checks if the drift is in normal limits.
You can get the latest version of Lab Advisor here: http://labadvisor.pl29.agilent.com/latest