BENZOIC-ACID DETERMINATION THROUGH COMPETITIVE-INHIBITION OF MEDIATEDBIOELECTROCATALYSIS

A bioelectrochemical system for the sensing of benzoic acid is describ ed. An enzyme-based oxygen electrode is constructed where the enzymati c consumption of oxygen by tyrosinase is monitored electrochemically t hrough the mediator 1,2 naphthoquinone, 4-sulfonate' (NQS). The bioele ctrocatalysis of oxygen can be electrochemically initiated and termina ted and is sensitive to inhibition by benzoic acid in a concentration- dependent manner. Inhibition of catalytic current results from a compe titive interaction of benzoic acid at the enzymatic docking site of NQ S. This inhibition of catalytic activity is reversible, and full catal ytic activity can be reinstated following the removal of benzoic acid from solution. The sensing of benzoic acid is dependent on the nature of the mediator used, occurring with NQS but not with ferricyanide. Th ese studies provide support for the possibility that analytes can be t argeted for detection in such inhibition-based sensing through the pro per selection of mediator.