Determination of 26 veterinary antibiotics residues in water matrices by lyophilization in combination with LC–MS/MS

A sensitive, simple and reliable multi-residue method was developed for the determination of 26 widely used veterinary antibiotics including 6 macrolides, 2 pleuromutilins, 4 tetracyclines, 2 lincosamides, 6 fluoroquinolones and 6 sulfonamides in different water matrices using liquid chromatography–tandem mass spectrometry (LC–MS/MS). Water samples were lyophilized to dryness. Target compounds were separated on Zorbax SB-Aq column (150 mm × 2.1 mm i.d., 3.5 μm) and determined by LC–MS/MS operating in positive electrospray ionization mode. Spiked at concentration levels of 0.02, 0.4 and 4 μg L−1, recoveries of all target compounds were over 70% except sulfaquinoxaline (59.0% at 0.02 μg L−1) with relative standard deviations below 20%. Limits of detection (LOD) and limits of quantification (LOQ) of 26 drugs ranged from 0.1 to 6.5 ng L−1 and from 0.3 to 19 ng L−1, respectively. The developed method was successfully applied to the analysis of 26 antibiotics residues in fish pond water, groundwater, biogas digester water, and lagoon wastewater samples collected from local pig farms.