Abstract: We developed a method for simultaneous determination of tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC), doxycycline (DC) and their metabolites in soil by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) detection. The antibiotics were extracted using mixed solvent of acetonitrile and EDTA-Mcllvaine buffer solution and separated and purified by HLB solid phase extraction column. The purified antibiotics were detected by UPLC-MS/MS with ES(+) ionization and quantified in the multiple reaction monitoring (MRM) mode. Within 0.0010.5 mg·kg-1 range, we found a good linear relationship (R2>0.99) between the peak areas and concentrations of TCs and their metabolites, with limits of detection (LOD) and limits of quantification (LOQ) reaching 1.08515.780 and 3.61742.526 μg·kg-1, respectively. At the three addition levels of 0.05, 0.1 and 0.5 mg·kg-1, the average recovery rates for TCs and their metabolites in soil were 62.1%87.6%, with relative standard deviation (RSD) of 2.35%13.42%, except for ATC and EATC (<30%). This method is effective and meets the sensitivity, accuracy and precision demands for detecting residues of TCs and their metabolites in soil.

Key words:  tetracyclines, metabolites, soil, ultra-performance liquid chromatography-tandem mass spectrometry