Mediated Bioelectrocatalytic Determination of Organophosphorus Pesticides with a Tyrosinase-Based Oxygen Biosensor

An electrochemical biosensor for the detection of organophosphorus pesticides is described. A tyrosinase-based oxygen sensor is constructed where enzymatic oxygen consumption is monitored electrochemically with the mediator 1,2-naphthoquinone-4-sulfonate. This bioelectrocatalytic system allows electrochemical initiation and termination of the enzymatic reaction. Amperometric and coulometric techniques are used to study inhibitory effects for pesticide determinations. This inhibition appears to be fully reversible, with full catalytic activity returning after removal of the pesticides. Detection limits are 5 μM for diazinon and 75 nM for dichlorvos. Enzymatic inhibition of 50% occurs at ∼1000 and ∼50 μM, respectively.