I have encountered the same problem. If the "wavy" baseline you see is
inconsistent ... not a distinguishable pattern ... then it can be noise
from the electrical circuit. I have seen this when someone else who is
using the same circuit in the building is running very power-intense
equipment. When this is the case, it is impossible to get a clean baseline
and since I cannot move the equipment to a different circuit I must simply
wait for the line noise to disappear.
It sounds like you have a bubble in your detector though. This would
display a pattern of waves, coinciding with the bubble moving back and
forth in front of the lamp. They can be very hard to get rid of, but the
best way I've found is:
1) disconnect the end of the column which is attached to the line going
into the detector
2) disconnect the waste line from the end going out of the connector.
3) fill a syringe (usually the one you use to purge the pump lines will
fit) with whatever solvent you're using and push it through the detector
backwards (from the waste line end to the column end). You may have to do
this several times, but it has always worked for me eventually.
Good luck!
