An amperometric horseradish peroxidase inhibition biosensor based on a cysteamine self-assembled monolayer for the determination of sulfides

An amperometric horseradish peroxidase (HRP) inhibition biosensor based on a thiolate self-assembled monolayer (SAM) has been developed for the determination of sulfides (HS−, H2S and small amount S2−). Cysteamine SAM was applied to the gold electrode surface and HRP was then immobilized on the electrode by cross-linking with glutaraldehyde. The measurement was performed in the presence of an electron mediator hydroquinone and 0.067 M phosphate buffer of pH 6.5 at an applied potential of −150 mV versus SCE. The determination of sulfides can be achieved in the range of 0.5–12.7 μM with a detection limit of 0.3 μM. The kinetic parameters Michaelis–Menten constant (Kmapp) and maximum current (Imax) with and without inhibitor have also been calculated and possible mechanism has been deduced according to the variation of Kmapp.