An electrochemical furosemide sensor based on pencil graphite surface modified with polymer film Ni-salen and Ni(OH)2/C nanoparticles

In this work, an advanced electrochemical sensor based on pencil graphite electrode modified via electropolymerization of the N,N′-bis(salicylidene) ethylenediaminonickel(II) monomer in the presence of carbon supported Ni(OH)2 nanoparticles (here called as poly[Ni(salen)] and Ni(OH)2/C) was developed and investigated for furosemide (FUR) quantification in alkaline medium. The electrochemical sensor and its components were extensively characterized by physico-chemical techniques, while the furosemide oxidation process was investigated by in situ Fourier transform infrared spectroscopy (in situ FTIR). These results indicate that the oxidation of furosemide leads to the formation of 2-amino-4-chloro-5-sulfamoylbenzoate and 5-hydroxy-furan-2-carboxylate in these conditions. The electrochemical response of the modified graphite electrode (MGE) for the determination of FUR was measured by cyclic voltammetry (CV). The calibration curve (change of voltammetric peak current vs. FUR concentration) presented a linear range from 2.5 × 10−10 M to 2.7 × 10−9 M with a calculated limit of detection as low as 1.4 × 10−10 M under the optimized conditions, which is lower than values reported in the literature. The ultra-low sensitivity obtained with the MGE sensor was attributed to an additiveeffect involving the poly[Ni(salen)] film and the high surface carbon-supported Ni(OH)2 nanoparticles.