Sensores eletroquímicos baseados em biocarvão de moringa para a determinação simultânea de carbamatos

Abstract

The use of electrochemical sensors modified with biochar is a viable alternative for the determination of species as pesticides. In this context, Moringa oleifera Lamarck (moringa; MO) has physicochemical characteristics that enable its use in the detection of contaminants, with the husks of its pods being a material with highly adsorptive properties, which favors the interaction between the material and target compounds. In this work, MO pods husks were collected, processed, and subjected to pyrolysis (400 °C) to obtain biochar (MOB). MO and MOB samples were characterized by spectroscopic, morphological, electrochemical, titrimetric techniques, among others, observing the presence of functional groups and cavities on the MOB surface. Electrodes modified with MOB (MOB/E) were successfully obtained and applied in the simultaneous determination of carbendazim and carbaryl. After optimizing the electrochemical analysis parameters, increases of approximately 30 and 45 times were observed in the analytical signals of carbendazim and carbaryl, respectively. The studies of reproducibility and repeatability of the MOB/E indicated high stability and homogeneity in the composition of the electrodes, through values of relative standard deviation smaller than 6% between the intensities of currents obtained. An analytical curve was built through consecutive and simultaneous additions of the analytes, and limits of detection values equal to 0.08 μmol L-1 for carbendazim and 1.28 μmol L-1 for carbaryl were obtained by the developed method. The method proved to be selective for analytes in the presence of different organic and inorganic species and was successfully applied for direct quantification (without extraction or filtration) in river, sea, tap and mineral water samples, with recoveries between 86.8% and 110.9%. The developed method was evaluated comparatively with high performance liquid chromatography coupled to a diode array detector and mass spectrometer, which failed to determine carbendazim in the evaluated concentrations due to the high matrix effect, highlighting the efficiency and applicability of MOB/E.