Development of a novel magnetic molecularly imprinted polymer coating using porous zeolite imidazolate framework-8 coated magnetic iron oxide as carrier for automated solid phase microextraction of estrogens in fish and pork samples

A high-performance magnetic molecularly imprinted polymer (MIP) coating using zeolite imidazolate framework-8 coated magnetic iron oxide (Fe3O4@ZIF-8) as a carrier was developed for simultaneous automated solid phase microextraction of four estrogens in 24 food samples. The coating material, abbreviated as MZMIP, was synthesized through time-efficient layer-by-layer assembling of ZIF-8 and MIP film on Fe3O4 particles. It was characterized and automatically coated on the surface of SPME fibers by electromagnetic bonding. The extraction performance, reusability, repeatability, and validity of the MZMIP-SPME system was evaluated for high-throughput analysis of estrone (E1), estradiol (E2), estriol (E3), and ethinylestradiol (EE2). Various factors affecting the quality of MZMIP coating were optimized. Compared with traditional magnetic MIP coating based on Fe3O4@SiO2 carrier, the MZMIP coating exhibited high extraction capacity and quick adsorption and desorption kinetics to E1, E2, E3, and EE2 owing to the larger amount of imprinting sites in MZMIP. Under optimum conditions, the proposed system requires only 25min for pretreatment of all 24 samples (62.5s per sample). The limits of detection and quantitation of the proposed automated system for analysis were found to range from 0.4 to 1.7 and 1.1 to 6.2ngg(-1), respectively. During analysis of spiked fish and pork, the new coating showed better recovery and selectivity compared with Fe3O4@SiO2@MIP (MMIP) and commercially available SPME. The results indicated that the MZMIP coating could be effectively employed for pretreatment of ultra-trace level of estrogens in food.