Hello

I have a Waters Acquity UPLC system coupled with premier XE. the Nitrogen that we were using was not complety good, it had traces of oil so the source got dirty. I cleaned the source and the ion guide but the system is unstable. I mean for short periods of time (1 min) the areas are below or above the expected value and after a minute or so the areas are back to normal. I checked the spary and it is fine and now Im using really pure nitrogen. Does anybody know what can be the problem?

thanks