Preparation of Melamine Molecularly Imprinted Polymeric Microspheres by Two-Step Seed Swelling Polymerization

Abstract

Melamine molecularly imprinted polymeric microsphere (MIPM) was initially prepared by two-step seed swelling polymerization methods. Factors affecting the particle morphologies including emulsifier, dispersant, the water-oil ratio, and etc were optimized in order to obtain the MIPMs with a final narrow particle diameter of 3-5 μm. Characterization of the resulted polymeric microspheres was investigated by scanning electron microscope (SEM), infrared absorption spectroscopy (IR), and mercury analyzer (MA), respectively. When the initial concentration of melamine was 1.0 mmol L-1, the affinity capacity of MIPMs was 2.0 times than that of NIPMs. Scatchard analysis suggested melamine were recognized by the prepared MIPMs with two classes of binding sites. The apparent maximum binding capacity and dissociation constant were calculated to be 43.2 μmol g-1 (Qmax1) and 2.2×10-4 mol L-1 (Kd1) for high affinity site, whilst to be 102.3 μmol g-1 (Qmax2) and 1.3×10-3 mol L-1 (Kd2) for low affinity site, respectively. Obvious molecular effects towards melamine were further confirmed by the comparative HPLC experiments using NIPMs and MIPMs as the stationary phases, respectively.