Silver nanoparticles for melamine detection in milk based on transmitted light intensity

Melamine (C 3 H 6 N 6 ) is a commercially synthesised organic compound which is illegally added to milk during processing to boost the apparent protein content. Melamine cannot be metabolised by the body and forms insoluble crystals which causes tissue damage and renal dysfunction. Hence, there is a need to develop a rapid and reliable method for melamine detection. Attempted here is to develop a simple procedure to detect melamine in milk using silver nanoparticles (AgNPs). Borohydride‐reduced AgNPs, citrate‐capped AgNPs and polyvinyl pyrrolidone‐capped AgNPs are synthesised and characterised for their size, composition, structure etc. and studied for the suitability in this application. The first two NPs are determined to be suitable for this detection and exhibit a colour change from pale yellow to red at different concentration of melamine. To measure the melamine concentration, quantification of colour change and the transmitted light intensity is done using a colour sensor when the mixture is exposed to standard light source. Compared with visual observation in colour change, the transmitted light intensity provides more information to quantify melamine, more specifically citrate‐capped AgNPs are found to provide better results than borohydride‐reduced AgNPs. The results of this study are much agreeable to that obtained through standard laboratory experiment. Hence, this proposed method would be useful in developing an electronic‐based melamine testing instrument that can be used rapidly at home.