Raman probing trace melamine in milk by a functionalized test paper

The rapid sensing for melamine in milk products has been developed with a portable Raman system based on the facile synthesis of tri-sodium citrate and dodecasodium of phytic acid (IP6) dual-functionalized gold nanoparticles modified filter paper, shortly named IP6-TC@Au NPs test paper. The tri-sodium citrate improved the sensitivity of Raman probe and the later kept the shelf stability. The limit of detection for melamine in water is 5 μM (0.63 ppm) and it is 10 μM (1.26 ppm) for testing real milk sample, which is well below the FDA's tolerance level of 2.5 ppm in milk. The proposed easy assay of IP6-TC@Au NPs test paper combining with portable Raman system could be applied for on-site monitoring melamine in milk products.