Electroanalytical arrays of microwell with increased sensitivity and virtual immunity to interferents were reported previously by us. Such arrays were designed to be operated in a classical generator-collector mode but exhibited also similar properties when their common planar collector was left floating. This evidenced that the unbiased collector acted as a bipolar electrode. In this work a theory is elaborated to investigate in great details the generality of this phenomenon and its limit. This establishes that when the analyte pertains to a redox couple with relatively fast electron rate constants the bipolar collector results almost as efficient as when biased, thus suppressing the need for a bi-potentiostat with obvious gain for analytical applications. Conversely, when the analyte rate constant of electron transfer is small, efficient operation in a bipolar mode remains feasible but requires a drastic decrease of the microwells density in the array