Wavy baseline on agilent 1100 VWD

[semivoadude]

Column: C18 Varian
Flow 1ml/min
Gradient: First 5 minutes: 85% ACN and 15% water
next 25 minutes: 100% ACN

Everything was fine, UNTIL I switched mobile Phases from:
Water (MPA) and Acetonitrile (MPB)
To:
Water w/0.1% TFA (MPA) and Acetonitrile w/0.1% TFA (MPB)

I mixed them both well. I already replaced the lamp, that did not help.

Before I replace the pump seals, does anyone know what else I can try?

Should I flush the column with Methanol? Reverse flush the column to elute a late contaminant peak?

Thanks

[tom jupille]

TFA is notorious for baseline problems. See this thread, for example:
http://www.sepsci.com/chromforum/viewtopic.php?t=8447