Magnetic molecular imprinting polymers based on three-dimensional (3D) graphene-carbon nanotube hybrid composites for analysis of melamine in milk powder

A novel analytical method for melamine in milk powder has been developed and exploited with three-dimensional (3D) magnetic molecularly imprinted polymers (MMIPs) combining with liquid chromatography-tandem mass spectrometry. The 3D MMIPs were synthesized with graphene-carbon nanotube hybrid composite as carrier which can increase the accessible surface area. The products were characterized, and the binding affinity was investigated by isothermal absorption, kinetic adsorption and selective adsorption. The results showed that the 3D MMIPs exhibited high adsorption capacity with maximum adsorption capacity of 123.1 mg g−1, fast adsorption rate (10 min) and high selectivity toward melamine. Various affecting extraction parameters were evaluated. The limit of detection was 0.00045 mg kg−1 and the recoveries were ranged from 90.3% to 95.7%. The precisions (RSDs) were lower than 4.7%. This method was applied for analyzing six milk powder samples. The result was in agreement with that obtained by the state standard method used in China.