In this paper it is presented the synthesis and characterization of magnetite nanoparticles coated with polyethylene glycol (PEG) and functionalized with cyanuryl chloride. The synthesis of magnetic core through modified Massart method, starts from high stability materials and it uses polyethylenglycols with variable molecular weight (300, 600, 1000, 2000, 4000 and 10,000 D). The obtained nanoparticles were structurally and morphologically analyzed by help of SEM, TEM, FT-IR spectroscopy and EDAX. The chemical responsiveness of the obtained nanoparticles was evaluated by help of FTIR spectrometry, titration and electrochemical evaluation.