Sensitive detection of melamine by an electrochemiluminescence sensor based on tris(bipyridine)ruthenium(II)-functionalized metal-organic frameworks

Metal-organic frameworks (MOFs) are microporous materials that consist of metal ions or clusters and organic ligands. Their luminescence activities can be improved by functionalization, and the present work describes the synthesis of a luminescence-functionalized MOF in which tris(2,2′-bipyridyl) dichlororuthenium(II) hexahydrate (Ru(bpy)32+) was introduced into the MOF. The synthesized RuMOF was then fabricated as an ECL sensor that can be used for the rapid and sensitive detection of melamine in dairy products. The optimum detection conditions were established by single-factor analysis and surface response multivariate optimization. Under optimum conditions, the ECL intensity was proportional to log(melamine) concentration in the range 10−10-10−4 M with a detection limit of about 3.8 × 10−11 M (signal/noise = 3). In an application to the detection of melamine in milk and infant formula powder, recoveries in the range 98-104% and 95-103%, respectively were obtained from spiked samples. Thus this novel ECL sensor represents a potentially valuable product for the analysis of melamine food samples.