Visual and Sensitive Detection of Milk Adulterant Melamine by Localized Surface Plasmon Resonance Optical Characteristics of Ag-MOF@Fe/SnO2 Nanocomposite

Abstract

Melamine is being added in pet food, milk and infant formula to enhance its “false” apparent protein contents but when it is present in milk beyond its allowed limit, it causes serious health problems which leads to renal failure and kidney stones. In this work a highly selective, sensitive and rapid method has been developed for determination of melamine as potential milk adulterant. Ag-MOFs doped with magnetic nanocatalyst were synthesized by using chemical reduction method and characterized through UV-Vis spectroscopy, Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). The strong SPR peak of Ag-MOFs was observed at 400–500 nm and Fe-SnO₂ was observed at 250–300 nm. The absorption band of Ag-MOF@Fe/SnO₂ was found at 250–350 nm with energy band gap of 2.78. The average particle size of nanocomposite was found to be 54.11 nm having uniform and crystalline shape. Different factors i.e. adsorbent dose, adsorbate dose, pH, temperature and time were optimized for maximum sensing of melamine. Prepared nanocomposite showed 97% detection efficiency for melamine at pH = 8 and 45 °C temperature in time limit of 25 min. Feasibility of prepared nanocomposite was also checked by standard melamine samples and pre-treated spiked milk sample. Prepared nanocomposite gave a rapid sensitive detection of melamine with limit of detection 1.8 ppm and 77% recovery from spiked raw milk without using any costly instrument.

Graphical Abstract