Development of a sol-gel enzyme inhibition-based amperometric biosensor for cyanide

An amperometric sol-gel-based enzyme inhibition electrode for the detection of low levels of cyanide was constructed by immobilizing horseradish peroxidase (HRP) and an osmium redox polymer ([Os(bpy)(2)(PVP)(10)Cl]Cl; abbreviated Os-polymer) as mediator. Upon addition of hydrogen peroxide to the solution, a bioelectrocatalytic reduction wave was observed, which was diffusion controlled. This reduction current is subsequently inhibited by cyanide. The steady-state hydrogen peroxide catalytic reduction current reached a plateau at 150mV (vs. Ag/AgCl) and cyanide could be determined amperometrically with good sensitivity at OmV (vs. Ag/AgCl). The concentration range of linear response, apparent inhibition constant (K-i'), and detection limit were 0.004-0.04 mM, 0.0637 mM, and 0.5 mu M, respectively. Sodium azide, potassium thiocyanide and thiourea were all found not to interfere at this potential. The biosensor was found to be stable for over 1 week on storage at room temperature.