An Efficient Electrochemical Sensing of Caffeic Acid at Thermolysis Prepared Urea-formaldehyde Resin Modified with Fe(III) and Ti(IV) Oxide Particles

Urea-formaldehyde resin (UF) is primarily used as an adhesive applied in the wood composites industry. In this work, we found that this resin modified with metal compounds could be a good starting point to produce high-performance electrode material applied for the construction of electrochemical sensor for important antioxidant, such as caffeic acids (CA). The conductivity of carbon paste electrodes (CPE) modified by materials produced by thermolysis of in situ synthesized urea formaldehyde resins with Fe(III) and Ti(IV) compounds (mixed metal compounds and individually) were examined. For comparison, pure CPE and CPE modified with material produced from the physical mixture of UF resins and metal compounds in the same combinations were also electrochemically characterized by impedance spectroscopy and cyclic voltammetry. The most conductive material, which consists of a combination of metal oxide particles in situ synthesized with UF (SynFe+Ti/UF-TP@CPE), was used as a CPE modifier and proved itself in sensitive differential pulse voltammetric determination of caffeic acid at a wide working range of 0.5-100 and limit of detection of 0.046 μM. The proposed electrode was successfully applied for the determination of the content of CA in spiked urine samples and the estimation of total phenol content, based on CA equivalents, of honey, liqueur and juice samples.