uplc gradient baseline

[gooshi81]

I'm running a method which I am transfering from HPLC to UPLC and I have a wavy baseline during the end of the run (ACN increase) the thing is i don't get the same thing in HPLC, detector filtring didn't help and also not washing the system and the column.
what could be the reason for this and how can i get rid of it?

[Hfranz]

One explanation could be an insufficient mixing. With your HPLC system, this is probably better. However, it would be beneficial to know your gradient conditions to judge it better.

[adrien16]

Yeah that's true !

We must know your final conditions of your gradient. I suppose you observe it when the gradient is the most elutive. With my own experience in UPLC, you could see a wavy baseline dur to a mixer issue. UPLC is equiped with a 50µL mixer. Try to use a 100µL mixer for example.
Secondly, sometimes you could see noisy peaks due to solvent impurities that you 've never seen in HPLC.
Try to use advanced grade of solvents like in LC/MS.

Have fun !