Electrochemical modification of electrodes with polymers derived from of hydroxybenzoic acid isomers: Optimized platforms for an alkaline phosphatase biosensor for pesticide detection

This work reports the electropolymerization of the three hydroxybenzoic acid isomers over pencil carbon graphite electrodes, and their characterization followed by further application in biosensors. Scanning electron microscopy images were obtained proving the electrodes modifications with homogeneous material and infrared spectra showed that the polymers present the unchanged carboxyl group suggesting that the polymerization begins through the phenol oxygen atom. pH and scan rate studies revealed that one electron and one proton are involved at the beginning of the polymerization in all of the isomers. A mechanism was proposed for all three structures based on these data. Alkaline phosphatase (ALP) enzyme was immobilized over the platforms through physical adsorption and covalent binding. Differential pulse voltammograms of 4-nitrophenol (4NP), the enzymatic product from the reaction between the ALP and 4-nitrophenylphosphate were recorded. The response with poly(2HB) and poly(4HB) was greater using the covalent binding than using physical adsorption technique, while poly(3HB) responses were lower than unmodified electrodes. Further studies using poly(2HB) and poly (4HB) platforms provided a low limit of detection of 20.0 mu M, and 18.0 mu M, respectively. The use of ALP allied with polymer platforms is an excellent choice for the determination of 4NP-generating organophosphorus pesticides, with low-cost and sensitive systems.