Negative peaks and disturbed baseline

<p>Hi!</p><p></p><p>We are having problems with the baseline; it started more or less fine and by the end of the run there is a lot of little negative peaks, like an upside down "saw". What could be the cause of that? I attached a copy of an overlay showing 3 std injections: the black line was at the beginning of the run, the blue line was from an injection about 4h later and the green line is the last injection, approx 10h later. </p><p></p><p>Thanks a lot!</p>