Mercury–enzyme inhibition assays with an amperometric sucrose biosensor based on a trienzymatic-clay matrix

The feasibility of amperometric sucrose and mercury biosensors based on the immobilization of invertase, glucose oxidase and mutarotase entrapped in a clay matrix (laponite) was investigated. The enzyme clay gel was deposited onto platinum electrodes and cross-linked with glutaraldehyde. The response of the biosensors to sucrose was measured by potentiostating the modified electrodes at +0.60 V versus Ag/AgCl in order to oxidize the enzymatically generated hydrogen peroxide. Mercury concentration was measured by inhibiting the invertase activity. The effect of different parameters, such as pH of the analyte solution, enzyme ratio, mercury incubation time, on the biosensor performance towards sucrose and mercury determinations was studied. The biosensor inhibition by inorganic and organic mercury was evaluated and the study of interference from other metal ions revealed a good selectivity towards mercury. Under optimized conditions, sucrose was determined from 3.3 × 10 −7 to 5.1 × 10 −3 M and mercury(II) in the concentration range of 1 × 10 −8 to 1 × 10 −6 M.