Novel Electrochemical Microsensor for Hydrogen Peroxide based on Iron-Ruthenium Hexacyanoferrate Modified Carbon Fiber Electrode

Nonenzymatic sensing of hydrogen peroxide using a glassy carbon electrode modified with graphene oxide, a polyamidoamine dendrimer, and with polyaniline deposited by the Fenton reaction

A highly sensitive electrochemical sensor is described for the determination of H₂O₂. It is based on based on the use of polyaniline that was generated in-situ and within 1 min on a glassy carbon electrode (GCE) with the aid of the Fe(II)/H₂O₂ system. Initially, a 2-dimensional composite was prepared from graphene oxide and polyamidoamine dendrimer through covalent interaction. It was employed as a carrier for Fe(II) ions. Then, the nanocomposite was drop-coated onto the surface of the GCE. When exposed to H₂O₂, the Fe(II) on the GCE is converted to Fe(III), and free hydroxy radicals are formed. The Fe(III) ions and the hydroxy radicals catalyze the oxidation of aniline to produce electroactive polyaniline on the GCE. The resulting sensor, best operated at a working potential as low as 50 mV (vs. SCE) which excludes interference by dissolved oxygen, has a linear response in the 500 nM to 2 mM H₂O₂ concentration range, and the detection limit is 180 nM. The sensor was successfully applied to the determination of H₂O₂ in spiked milk and fetal bovine serum samples. Graphical abstract Schematic presentation of a sensitive electrochemical sensor employed for detection of H₂O₂ in sophisticated matrices by using graphene oxide-PAMAM dendrimer as initiator container and Fe²⁺/H₂O₂ system as signal enhancer.

Hydrodynamic chronoamperometric method for the determination of H₂O₂ using MnO₂-based carbon paste electrodes in groundwater treated by Fenton and Fenton-like reagents for natural organic matter removal

A simple hydrodynamic chronoamperometric method based on the application of an unmodified carbon paste electrode (CPE) and bulk-modified with different contents of MnO2 was investigated for the determination of H2O2. The optimized method involving the CPE with 5% of MnO2 was applied for the determination of the H2O2 consumption in samples of groundwater from the Central Banat region (Province of Vojvodina, Serbia) treated by the Fenton (Fe(2+) and H2O2) and Fenton-like (Fe(3+) and H2O2) reagents to remove natural organic matter at different initial concentrations of iron species, and of their ratios to the initial concentration of H2O2. Under optimized conditions, with a working potential of 0.40V vs. the saturated calomel electrode and a phosphate buffer solution (pH 7.5) as supporting electrolyte, the method enabled the quantitation of H2O2 in the concentration interval from 1.4 to 65 μg mL(-1) with a relative standard deviation of less than 10%. The results obtained for the H2O2 consumption are in good agreement with those obtained by parallel measurements related to the efficiency of organic matter removal.