We have immobilized biotinilated DNA in a neutravidin chip. We have problems of carryover and after different experiments we don´t know how to solve it. Even we don´t know if it can be a problem in the fluidic system.
You can test the carry-over by injecting a high salt solution followed by a flow buffer injection. In Biacore type of instruments there are several wash routines that you can use to wash needle and/or IFC between injections to minimize carry-over.
To test the fluidics: In a system with four channels start detection on all four channels and inject high salt (e.g. 0.5 M NaCl or the solution that gives you problems) over flow channel 1 followed by an injection with flow buffer. Then repeat for ch 2, 3 and four. You should only see the bulk salt response in one channel at the time. If the salt response appears in the other channels, the micro fluidics is leaking.
Thanks for the answer. However, I think I have not explained properly the problem. After the immobilization of the DNA we passed NaOH 2mM, as it is described in the literature, then the buffer PBS and we see these (attached document)