Preparation and application of surface molecularly imprinted silica gel for selective extraction of melamine from milk samples

Highly selective molecularly imprinted layer-coated silica gel (MIP@SiO2) for melamine (MEL) was prepared by the surface molecular imprinting technique on the supporter of silica gel. Non-imprinted polymer layer-coated silica gel (NIP@SiO2) and bulk molecularly imprinted polymer (MIP) were also prepared for comparison. Characterization and performance tests of the obtained products revealed that MIP@SiO2 not only had excellent selectivity to the target molecule MEL compared with NIP@SiO2, but also displayed absorption capacity superior to MIP due to the molecular recognition sites on the surface of silica gel. As the MIP@SiO2 were adopted as the adsorbents of solid-phase extraction for detecting MEL in milk samples, the recoveries of spiked samples ranged from 75.6% to 96.8% with the relative standard deviation of spiked samples less than 10%, which reveals that the MIP@SiO2 were efficient SPE adsorbents for melamine.