Determination of cyanide using a tyrosinase amperometric biosensor with catechol as substrate

Abstract

Low cyanide concentrations are determined with a tyrosinase amperometric biosensor using enzyme immobilized on a preactivated polyamide membrane that is closely attached to the end of a wax-impregnated graphite electrode. The test is performed in the presence of the catechol substrate at –0.200 V versus SCE in 0.1 mol l^–1 phosphate buffer (pH 7.5)(the reduction current results from o-benzoquinone, derived from the tyrosinase driving the oxidation of catechol, which is being measured). The decrease in substrate response within the linear range 2.0 × 10^–7–;4.0 × 10^–5 mol l^–1 is proportional to the square-root of cyanide concentration. This method is characterized by high selectivity and reproducibility.