Dispersive Magnetic Solid-Phase Extraction of Magnetic Hypercrosslinked Polystyrene with Carbon Dioxide for the Multicomponent Extraction of Residues of 55 Veterinary Drugs from River Waters Before Their Determination by HPLC–MS/MS

Magnetic effervescent tablets consisting of magnetic hypercrosslinked polystyrene, sodium bicarbonate, citric acid and EDTA are proposed for multicomponent isolation of residues of 55 veterinary drugs of various classes (sulfonamides and trimethoprim, amphenicols, nitroimidazoles, β-lactams, quinolones, macrolides, pleuromutilins and lincosamides) from river waters by magnetic solid-phase extraction prior to their HPLC–MS/MS determination. Due to the intensive release of carbon dioxide during tablet dissolution, this process was conducted without using stirring devices, and the magnetic properties of the sorbent ensures its separation without centrifugation and filtration; as a result, the sample preparation procedure (solid-phase extraction) took less than 3 min. The method ensures recoveries from 79 to 122% and good reproducibility (RSD ≤ 12%). Drugs were identified by the exact masses of analyte ions formed during polarity-switching electrospray ionization. The matrix effect for all drugs was below 20%. The determination was carried out using the matrix calibration method; the limits of detection and quantification are 0.012 and 0.04 μg/L for most sulfonamides, trimethoprim, amphenicols, nitroimidazoles, macrolides, pleuromutilins and lincosamides, and 0.06 and 0.2 μg/L for β-lactams and quinolones, respectively.