Hi Papillon,
From the figure I see that you use a ProteOn.
It strikes me that the PBS injections go up at the same point in each figure but that the effect seems to be bigger from L1 --> L6. Not exactly at the same point but also the DNA injection seems to deviate at the same moment of injection.
For me it seems that it could be something with the injection system but since I am not famillair with the workings of the ProteOn i suggest you send a mail to the Bio-rad technical department.
Kind regards
Arnoud