Objective  To establish a rapid method for simultaneous determination of 27 antibiotics in tap water with ultra high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) combined with automatic solid phase extraction.

  Methods   After added internal standard solutions of 27 antibiotics within 24 hours, the tap water sample (200 mL) was filtered with glass fiber filters and adjusted for pH value of 7.5 – 8.5. The reference antibiotics in the tap water samples were concentrated with extraction column in the automated solid phase extraction instrument and then eluted with methanol solution. The reference antibiotics in the eluate was reconstituted into constant solution with 20% methanol and separated gradiently with T3 chromatography column using 40% acetonitrile methanol and 0.2% formic acid solution as mobile phase; and finally detected with UHPLC-MS/MS and quantified with internal standard method. Thereafter, 70 tap water samples were collected in rural areas of Zhejiang province and 27 antibiotics in the samples were detected simultaneously using the established method.

  Results  A good linearity was observed for detections of the 27 antibiotics at the concentration of 1 to 100 ng/mL, with the correlation coefficient ranging from 0.9963 to 1.0000. For the established method, the detection limits were between 0.004 – 0.296 ng/L; the quantification limits were from 0.013 to 0.998 ng/L; and the mean recoveries ranged from 70.0% – 120.8%. For the 70 rural tap water samples, only four macrolide antibiotics were detected, including roxithromycin, clarithromycin, erythromycin, and tilmicosin, with the concentration ranges (ng/L) of 0.162 – 2.858, 0.063 – 0.849, 0.100 – 1.804, and 0.100 – 1.804, respectively．

  Conclusion   The established method is simple to operate, time- and labor-saving; the method is also of high sensitivity, accuracy and reliability; and the method could be applied to rapid determination of 27 antibiotics in tap water．