MEDIATED BIOELECTROCATALYTIC DETERMINATION OF ORGANOPHOSPHORUS PESTICIDES WITH A TYROSINASE-BASED OXYGEN BIOSENSOR

An electrochemical biosensor for the detection of organophosphorus pes ticides 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 enzym atic reaction. Amperometric and coulometric techniques are used to stu dy inhibitory effects for pesticide determinations. This inhibition ap pears to be fully reversible, with full catalytic activity returning a fter removal of the pesticides. Detection limits are 5 mu M for diazin on and 75 nM for dichlorvos. Enzymatic inhibition of 50% occurs at sim ilar to 1000 and similar to 50 mu M, respectively.