Biochemical and Rapid Paper Sensory Detection of Heavy Metals in Milk Based on Biosynthesized Silver Nanoparticles

Milk is an emulsion of proteins and fats in water that contributes to a nutritious diet and enhances our immune system. However, contamination of heavy metals in milk due to an increase in industrialization and urbanization can be a serious threat to human health. This study focused on the rapid detection of heavy metals particularly lead and mercury in milk using biochemical assays as well as paper-based colorimetric sensor based on green synthesized silver nanoparticles (AgNPs) from leaf extract of Hemigraphis colorata. Biochemical assays such as the lead chromate test and sodium hydroxide test were employed to detect lead and mercury in milk samples. The biogenic AgNPs were characterized by UV–Vis spectroscopy, scanning electron microscope, Fourier transform infrared spectroscopy, energy dispersive X-ray analysis (EDX) and X-ray diffraction. The unique properties of silver nanoparticles (AgNPs) like surface plasma resonance (SPR), large surface area and visible colour change upon aggregation when metal ions interact, enable them to detect heavy metals. This is a portable and affordable method of detection that ensures safer milk consumption and sustainable environmental practices.