Microelectrochemical multitransistor devices based on the reversible electrostatic incorporation of electroactive anionic metal complexes, such as IrCl62-, Mo(CN)84-, and Fe(CN)64-, into protonated Poly(4-vinylpyridine) [(VPyH+)n] can detect and differentiate between these species. Arrays of closely spaced, individually addressable, band microelectrodes are connected by (VPyH+)n. Pairs of these microelectrodes are operated as independent microelectrochemical transistors. Each transistor shows high drain current only when its gate potential corresponds to the redox potential of a metal complex bound to the (VPyH+)n, and this serves as the means of detecting and identifying the metal complex. Binding of anionic metal complexes in (VPyH+)n is reversible, and therefore, the devices can be demonstrated to respond continuously to a flow of electrolyte in which the number and identity of the metal complexes is varied.