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)loC1]Cl; abbreviated 0s-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 150 mV (vs. Ag/ AgCI) and cyanide could be determined amperometrically with good sensitivity at OmV (vs. Ag/AgCI). The concentration range of linear response, apparent inhibition constant (K;), and detection limit were 0.004-0.04mM, 0.0637 mM, and 0.5 pM, 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.
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