Modified Graphite Pencil Electrode Based on Graphene Oxide-Modified Fe(3)O(4) for Ferrocene-Mediated Electrochemical Detection of Hemoglobin

[Image: see text] This study describes the synthesis of graphene oxide-modified magnetite (rGO/Fe(3)O(4)) and its use as an electrochemical sensor for the quantitative detection of hemoglobin (Hb). rGO is characterized by a 2θ peak at 10.03° in its X-ray diffraction, 1353 and 1586 cm(–1) vibrations in Raman spectroscopy, while scanning electron microscopy coupled with energy-dispersive spectroscopy of rGO and rGO/Fe(3)O(4) revealed the presence of microplate structures in both materials and high presence of iron in rGO/Fe(3)O(4) with 50 wt %. The modified graphite pencil electrode, GPE/rGO/Fe(3)O(4), is characterized using cyclic voltammetry. Higher electrochemical surface area is obtained when the GPE is modified with rGO/Fe(3)O(4). Linear scan voltammetry is used to quantify Hb at the surface of the sensor using ferrocene (FC) as an electrochemical amplifier. Linear response for Hb is obtained in the 0.1–1.8 μM range with a regression coefficient of 0.995, a lower limit of detection of 0.090 μM, and a limit of quantitation of 0.28 μM. The sensor was free from interferents and successfully used to sense Hb in human urine. Due to the above-stated qualities, the GPE/rGO/Fe(3)O(4) electrode could be a potential competitive sensor for trace quantities of Hb in physiological media.