Facile synthesis of magnetic molecularly imprinted polymers and its application in magnetic solid phase extraction for fluoroquinolones in milk samples

In this work, we proposed a simple co-mixing method to fabricate magnetic molecularly imprinted polymers (magnetic MIPs). MIPs were commercial products while magnetic nanoparticles (MNPs) were prepared by chemical oxidation and solvothermal methods. When MNPs and MIPs (with mass ratio 1:1) were co-mixed and vortexed evenly in methanol, they could assemble into magnetic composites spontaneously and thus be magnetically separable. To testify the feasibility of the magnetic composites in sample preparation, the resultant magnetic MIPs were applied as sorbents for magnetic solid-phase extraction (MSPE) of fluoroquinolones (FQs) in milk samples. Under optimized conditions, a rapid, convenient, and efficient method for the determination of three FQs in milk samples was established by magnetic MIPs based MSPE coupling with high performance liquid chromatography with ultraviolet detector (HPLC-UV). The limits of detection (LODs) for three FQs were found to be 1.8-3.2 ng/g. The intra- and inter-day relative standard deviations (RSDs) were less than 9.5% and 12.5%, respectively. The recoveries of FQs for two spiked milk samples were in the range from 94.0% to 124.4% with the RSDs less than 11.6%.