Melamine has been used as a non-protein nitrogenous additive in food products to artificially increase the apparent “false” protein content. Melamine is known as a dangerous and poisonous substance for human health and it causes diverse diseases. An electrochemical sensor for melamine detection has been developed by modification of a glassy carbon electrode using copolymer poly[DMAEMA-co-styrene], gold nanoparticles, and methylene blue. The characterization of the modified electrode was conducted using several analysis techniques including cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The electrochemical detection of melamine was performed by impedance spectroscopy. Obtained results revealed that the developed sensor has a large detection range from 5.0 × 10⁻¹³ to 3.8 × 10⁻⁸ M with a low detection limit of 1.8 × 10⁻¹² M (at S/N = 3). Various interfering species such as phenol, hydroquinone, and bisphenol A have been used and their behavior on modified electrode has been studied.

The free energy of adsorption is a parameter that describes the affinity between adsorbent and adsorbate; this affinity has a close relationship with the nature of the chemical or physical forces which can be formed, at the adsorbent-adsorbate interface. In the present work a polyvinyl chloride (PVC) based nanocomposite film containing poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) coated-iron oxide nanoparticles (IONPs) was prepared; this material was then used for methylene blue (MB) removal from water. The IONPs were synthesized by a co-precipitation method, coated with PDMAEMA using the emulsion approach, and then dispersed in a film of PVC. Ultraviolet-visible (UV-Vis) spectroscopy was used to study the MB adsorption process on the prepared nanocomposite; the obtained results showed that the adsorption process of MB onto the PVC-based nanocomposite film was linear as a function of initial MB concentrations in the range from 10⁻⁷ to 10⁻⁴mol/L; the free energy of adsorption was calculated using the Langmuir isotherm and found to be −46.82 kJ/mol with a high adsorption equilibrium constant of 2.93 × 10⁶ L/mol, indicating that the mechanism of the MB adsorption process was chemisorption. The synthesized PDMAEMA, coated IONPs, and uncoated IONPs were thoroughly characterized by Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance Spectroscopy (¹H NMR), and Scanning Electron Microscopy (SEM).