Preparation of 2,4-dichlorophenoxyacetic acid molecular-imprinted materials via surface-initiated atom transfer radical polymerization and its recognition character analysis

2,4-Dichlorophenoxyacetic acid imprinted materials (2,4-D MIPs) were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) method. With chloromethyl polystyrene resin (CMCPS) as carrier and macro-initiator, the imprinted polymers were synthesized by using 2,4-D as template, acrylic amide as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linker, and CuBr/2,2'-bipyridine (CuBr/Bpy) as the catalytic system. The influence of ratio of template and monomer on the adsorption capacity of 2,4-D MIPs was discussed in details. The binding properties of 2,4-D MIPs for 2,4-dichlorophenoxyacetic acid were studied with both static and dynamic experimental methods. The results showed that 2,4-D MIPs had specific recognition selectivity and excellent binding selectivity for the template molecule. In respect to 2,4- dichlorophenol and 2,4-dichlorobenzaldehyde, its selectivity coefficient to 2,4-D were 2.84 and 3.75, with relative selectivity coefficient 2.31 and 2.29. From the Scatchard analysis, Qmax (the apparent maximum binding amount) values were calculated to be 76.92 and 142.91 mg/g, respectively, and Kd(the dissociation constant) values were 632.91 and 2 309.47 mg/L. Using 2,4-D MIPs as solid phase materials, the fotified recoveries were among 86%-104%, with relative standard deviations (RSDs) of 1.9%-10%, and the limit of detection (LOD) in the bean sprout samples reached 20 ng/g. In conclusion, these imprinted materials can be used for enrichment or separation of trace amounts of 2,4-D, with merits of good stability, simple handling.