Abstract: A method for the determination of 22 antibiotics in environmental water samples was developed by using high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI MS/MS). The target antibiotics in water samples were enriched and cleaned-up by HLB solid-phase extraction (SPE) cartridges, and then eluted with 6 mL ammonium hydroxide-methanol (5:95, v/v). The eluate was collected and concentrated to 1 mL under a gentle stream of nitrogen gas, and then analyzed by HPLC-ESI MS/MS in positive electrospray ionization and multiple reaction monitoring (MRM) mode. The separation was carried out on an XTerra MS C18 column with mobile phases of A, methanol-acetonitrile (1:1, v/v), and B, 0.3% formic acid/water (containing 0.1% ammonium formate, v/v, pH 2.9). The results showed that the average recoveries of antibiotics in tap water and wastewater were 54.9%~130% and 57.4%~138%, respectively, and the corresponding relative standard deviations (RSD, n=3) were 2.85%~28.6% and 2.02%~23.2%, respectively. The method detection limits were 0.05~0.5 ng/L. The developed method was applied to analyze the water samples of Gaobeidian Lake and Xiaoqinghe River in Beijing. The results showed that some antibiotics were detected both in the two samples.

Key words: antibiotics, environmental water samples , solid-phase extraction(SPE), high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI MS/MS)