Preconcentration of Quinolones on Magnetic Hypercrosslinked Polystyrene before Their Determination by High-Performance Liquid Chromatography in Milk

Magnetic hypercrosslinked polystyrene (MHCPS) is proposed for the group adsorption and preconcentration of quinolones. The conditions for magnetic solid-phase extraction are selected as follows: 25 mL of solution (pH 6), sorbent mass 20 mg, and sorption time 20 min. The analytes have been desorbed with 2 mL of methanol. It is shown that the sorbent provides the quantitative extraction of all 23 studied compounds not only from aqueous solutions, but also from milk, bypassing the deproteinization stage. The determination is carried out by HPLC-tandem mass spectrometry using matrix calibration. The limits of detection and determination for quinolones are 0.012–0.12 and 0.04–0.4 μg/L, respectively, which are below their maximum residue levels in milk.