Experimental investigation of a mixed metal oxide (MMO)-based sensor for the detection of adulterants (urea and melamine) in milk at room temperature

Milk has high biological and nutritional value and is an essential component of a healthy diet for both children and adults. Despite the serious health risks, milk contamination with substances such as urea, melamine remains a widespread problem today. The consumption of adulterated milk causes severe health effects. The Mixed Metal Oxide (MMO)-based sensor, composed of Zinc Oxide (ZnO) and Nickel Oxide (NiO), was developed using the low-temperature hydrothermal method. The synthesized MMO nanostructure was coated over the surface of the Glassy Carbon Electrode (GCE). The fabricated MMO sensor material was characterized using XRD, FESEM, and EDX analysis to check its structural integrity, morphological features, and elemental composition. The developed MMO sensor is experimentally analysed for melamine and urea detection using a Cyclic Voltammetry (CV) setup at room temperature. The developed MMO sensor exhibited a maximum current of 0.010 µA, a high sensitivity of 0.1069 µAmM⁻¹ cm⁻² in which the melamine in milk is 10.6 times higher than urea and melamine, and a short response of 2 s when using melamine milk samples. The fabricated MMO sensor is capable of detecting adulterants in milk samples as evidenced by its linearity, response time, Limit of Detection (LOD) and quantification (LOQ), stability, and reproducibility.