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In this work, an innovative nanocomposite modified electrode for ultrasensitive Hg(II) determination (limit of detection of 0.30 ± 0.034 pmol L-1, limit of quantification of 1.0 ± 0.11 pmol L-1) is presented, based on polyethylene glycol coated Fe3O4 magnetic nanoparticles (PEG-Fe3O4), multiwalled carbon nanotubes (MWCNTs), and in situ plated antimony-cadmium film (Sb&CdF). The application of the MWCNTs@PEG-Fe3O4/Sb&CdF as a glassy carbon electrode (GCE) surface modifier improves the electrochemical properties of the sensors and provides adsorption sites to expand the deposition of Hg(II), which was confirmed using scanning electron microscopy (SEM), optical profilometry, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential-pulse anodic stripping voltammetry (DPASV). The developed MWCNTs@PEG-Fe3O4/Sb&CdF nanocomposite is characterized by a low charge transfer resistance, and fast electron transfer kinetics. The DPASV procedure was validated using standard reference material and applied practically for the determination of total Hg in river and tap water samples after mineralization, with the results compared to those obtained by inductively coupled plasma mass spectrometry (ICP-MS/MS).
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