I have an antibody - antigen couple. I am trying to measure the antibody from PBS solution. So, I immobilize the antigen on Screen Printed Electrode surface, as a capture probe. I use 11-MUA to generate self assambled monolayer on the surface. Followed by immobilization of antigen using EDC/NHS. Later I block the surface with BSA solution and Ethanolamine solution. I take my measurements after blocking. Later after antigen (target analyte) incubation.
However, I get weird DPV graphs the first time (sometimes the second time as well) I do the measurement after blocking (Figure1 and 2). When I repeat the measurement for a second or third time I get a normal graph.
Again after antigen (sample) binding, my initial measurement peaks (1st measurement and sometime 2nd measurement too) are exactly the same with the peaks I got following blocking step. But If I get additional measurement is drops to where it theoretically should be. In fact, if I discard the initial weird measurements (doesn't matter if I use any of the following measurements or average of the following measurements) I get an expected calibration curve.
Can you help me understand why this initial graphs might have happened?
Measurements are done in either 5 or 10 mM Ferrocyanide solution
You may be getting a peak for Ag/Ag+ from the reference electrode. This is a common and under-discussed "feature" of many commercial reference electrodes.
Danny O'Hare So, is Ag depositing on the surface of my electrode? Would it have a detrimental effect on my measurements. Or can I just ignore it and get the next reading (and that reading will not be affected by the Ag). Because the following measurements I get are stable and in line with what is expected. Thanks for the answer.
Whether or not the Ag matters will depend on your chemistry- it can form complexes with proteins and with nucleic acids and in any case there will be considerable uncertainty about the potential of the reference electrode as the Ag erodes in small lumps or dissolves, or both. Some sort of polymer coating may help reduce this effect.
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