(1) Powdered infant formula, milk-containing products, and pet food from China are some examples of melamine contamination incident recorded previously. It is a nitrogen-rich synthetic molecule (66.6% by weight) used in for-profit milk adulteration as the fake protein source and cannot be identified by indirect protein assays based on the total nitrogen content. Melamine (1,3,5-triazine-2,4,6-triamine) is a weak base, nonedible, nonhygroscopic, white crystalline solid, melts with decomposition above 347 ☌, sublimes at temperatures below its melting point, and slightly soluble in water (0.38 or 3.7 g/mL of water at 20 or 90 ☌, respectively). The results showed that the developed sensor using the new composite polymer receptor is promising for the online monitoring of melamine in the food industries in the future. Melamine-spiked infant formula and raw milk were analyzed by the developed sensor, and the recovery range of 95.87–105.63% with a relative standard deviation of 1.11–2.23% was obtained. The sensitivity of the sensor was attributed to the synergistic effects of amine from aniline and the carboxylic group from acrylic acid to form multiple noncovalent interactions with the template. Electrochemical measurements were performed to achieve the linear range, the limit of quantification, and limit of detection of 0.1–180, 0.0573, and 0.0172 nM, respectively. The optimization of important parameters and removal of melamine generated the binding sites in the polymer matrix, which can recognize melamine specifically. The prepolymerization complex formation was studied by using Fourier transform infrared (FTIR) spectrophotometry, while the film formation was performed and characterized by cyclic voltammetry, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). Simple, fast, and sensitive molecularly imprinted composite thin-film-based electrochemical sensor developed by using in situ co-electropolymerization of aniline and acrylic acid in the presence of melamine as a template is described here.
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