Visual quantification of melamine using citrate-capped gold nanoparticles

N. Li
University of Miami, US

Keywords: melamine, gold nanoparticles, critical coagulation concentration

Summary:

Melamine is a nitrogen-rich compound widely used in plastics industry. Due to its high nitrogen content and low cost, it has been illegally added to food products to boost apparent protein content. Conventional methods to detect melamine(e.g. ELISA and chromatography/spectroscopy-based) usually require expensive instrumentation and/or labor-intensive procedures, thus limiting their use in resource-limited settings. We’ve previously developed a simple and rapid colorimetric method to detect melamine. This method utilizes the finding that melamine causes the unmodified, citrate-capped gold nanoparticles (AuNP) to aggregate, thus resulting in a red-to-blue color shift of AuNP. The melamine-concentration dependent gradual color shift could be observed with unassisted eyes; however, an absorbance reader would be still required for reliable quantification of melamine concentration. Herein, we present a novel strategy for reliable visual quantification of melamine without any equipment. First of all, we further explored the mechanism of the melamine-induced AuNP aggregation with various experimental techniques. Secondly,based on the findings from the mechanism studies, we’ve developed and demonstrated a critical coagulation concentration (CCC)-based salt titration as a reliable means to visually quantify the melamine. This has allowed us to accurate quantify melamine at a level as low as 30ppb without any equipment.