New type of electrode material based on magnetic nanoparticles with high potential applicability in electrochemical sensors for nitrite detection

•A sensor for nitrite detection based on magnetic electrode material is described.•The electrode material, use Fe3O4 embedded in SiO2 matrix.•Toluidine Blue (TBO) was used as redox mediator for nitrite detection.•The new materials have good electrocatalytic effect towards nitrite oxidation. The development of a magnetic nanocomposites modified electrode materials, using iron oxide nanoparticles with superparamagnetic behaviour and high saturation magnetization which are embedded in silica matrix, with excellent adsorption capability is described, in order to prepare an electrochemical sensor for nitrite detection. SEM and TEM confirm the formation of magnetic nanocomposites (NP-SiO2). The structure of magnetic nanoparticles (MNPs) and magnetic nanocomposites (NP-SiO2) were confirmed by FTIR analysis. The magnetic properties were analyzed with a vibrating sample magnetometer (VSM) and the values of saturation magnetization are 81 emu/g for magnetic nanoparticles and 43 and 33 emu/g for the two different samples of magnetic nanocomposites NP-SiO2 prepared with different concentration of SiO2 precursor. The removal efficiency of magnetic nanoparticles (MNPs) and magnetic nanocomposites (NP-SiO2) for TBO was investigated in correlation with different parameters, such as pH, initial dye concentration, and absorbent material concentration and the optimum conditions of TBO adsorption on magnetic nanocomposites (NP-SiO2) were established to be: 50 mg of magnetic nanocomposites (NP-SiO2) and initial TBO solution 15 mg /ml concentration at pH = 7. The electrocatalytic effect towards nitrite oxidation was studied for two samples NP-SiO2-1 and NP-SiO2-2. A good electrocatalytic effect towards nitrite oxidation was observed for both electrodes. It can be concluded that these new modified electrodes can be used in the future as amperometric sensors for nitrite detection in environmental samples.