Determination of 23 antibiotics and 3 beta-agonists in livestock drinking water by ultra performance liquid chromatography-tandem mass spectrometry coupled with solid-phase extraction

A method has been developed for the simultaneous determination of 23 antibiotics (four categories) and 3 beta-agonists in livestock drinking water using solid. phase extraction and ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI MS/MS). The samples were adjusted pH to 5.0, added Na(2)EDTA, enriched and cleaned. up by an HLB solid. phase extraction cartridge. The target compounds were confirmed and quantified by UPLC. ESI MS/MS with external standard method for the anti. biotics and internal standard method for the beta-agonists. The recoveries were assessed by using lab tap water as matrix. The average recoveries of the 23 antibiotics and the 3 beta-agonists were in the range of 50.7% - 104.6% and the relative standard deviations (RSDs) were 2.6% - 8.8% (n = 3). Under the optimal conditions, the calibration curves of the 23 antibiotics and the 3 beta-agonists showed good linearity with the correlation coefficients better than 0.994. The limits of detection (LODs, S/N >= 3) ranged from 0.01-0.20 ng/L. The developed method was applied to analyze the livestock drinking waters in 36 Beijing intensive livestock farms. The results showed that some antibiotics were detected.