I am trying to develop a sandwich immunosensor in which a peroxidase mimicking N.P is conjugated to secondary antibody will be used to catalyse the HQ/H2O2 reaction. I have consistently observed one weird thing which I have never been able to understand. Sometimes when I start the reaction with 1mM HQ alone on the SPE surface, the current seems unstable. Ideally what I expect is a slight decrease and stabilization within a few seconds (50-100 seconds) until I inject H2O2 at that point. Mos of the successful runs I observe the same (as picture attached) but in some cases the current actually starts to increase.
Also, is it OK if the current at the start is in negative as I have observed in some cases. Mostly it starts in the positive.
I would appreciate if someone could explain what's going on here, what's normal and if something is wrong how can I avoid it
Pardon my ignorance but my basic training is as a biologist and I am new to all this analytical and electrochemistry things