A reagentless nitrite biosensor based on direct electron transfer of hemoglobin on a room temperature ionic liquid/carbon nanotube-modified electrode

A novel amperometric biosensor for nitrite was developed by immobilization of hemoglobin (Hb) and a room temperature ionic liquid, 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIT), on a multi-walled carbon nanotubes (MWNTs) modified electrode. Compared with Hb/MWNTs modified electrode, the Hb/RTILs/MWNTs modified electrode showed better electrochemical response, indicating that EMIT can promote direct electron transfer of Hb. A pair of well-defined, quasi-reversible redox peaks of Hb with a formal potential of -0.315 V was observed. The immobilized Hb exhibited remarkable electrocatalytic activity for the reduction of nitrite. The linear response range was from 4.0 x 10(-6) to 3.2 x 10(-4) M with a detection limit of 8.1 x 10(-7) M at a signal-to-noise ratio of 3. The resulting biosensor has been successfully applied to the determination of nitrite in water samples.