Direct electrochemical response of Myoglobin using a room temperature ionic liquid, 1-(2-hydroxyethyl)-3-methyl imidazolium tetrafluoroborate, as supporting electrolyte

Direct electrochemical response of Myoglobin (Myb) at the basal plane graphite (BPG) electrode was observed when a room temperature ionic liquid (RTIL), 1-(2-hydroxyethyl)-3-methyl imidazolium tetrafluoroborate ([HEMIm][BF4]), was used as the supporting electrolyte. In a 0.17 M [HEMIm]BF4 aqueous solution, a couple of well-defined redox peaks of Myb could be obtained, whose anodic and cathodic peak potentials were at −0.158 and −0.224 V (vs. Ag/AgCl), respectively. Both anodic and cathodic peak currents increased linearly with the potential scan rate. Compared with the supporting electrolyte of phosphate buffer, [HEMIm][BF4] played an obvious promotion for the direct electron transfer between Myb and the BPG electrode. Further investigation suggested that Myb was adsorbed tightly on the surface of the BPG electrode in the presence of [HEMIm][BF4] to form a stable, approximate monolayer Myb film. Myb adsorbed on the BPG electrode surface showed a remarkable electrocatalytic activity for the reduction of oxygen in a [HEMIm][BF4] aqueous solution. Based on these, a third-generation biosensor could be constructed to directly detect the concentration of oxygen in aqueous solution with a limit of detection of 2.3 × 10−8 M.