UV baseline movement.
Hi,We have been observing some erratic baseline, I have attached some plots of the TUV and pump.The method we are using is being used on several UPLC, but for this one, baseline moves about resulting in failed %RSD of LOQ. It could be pump related, but we have carried out all the leak/pressure tests and which have passed and the valves/pistons and seals have been replaced.Despite the leak test/pressure tests the plots still show what I believe to be cyclic noise. This is the case if run on line A or B.Is there anything else I have missed that could link the two issues. If there is a issue with one of the pumps could it affect the other pump?ThanksDarren