Abstract:

Objective To establish an ultra-high performance liquid chromatography-tandem triple quadrupole mass spectrometry（UHPLC-MS/MS） method for the simultaneous determination of 10 tetracycline antibiotics and their metabolites（including minocycline， oxytetracycline，tetracycline，etc.） in breast milk. Methods Breast milk samples were extracted with Na₂EDTA-Mcllvaine buffer（pH 4.0±0.5），purified using HLB solid-phase extraction（SPE） cartridges，and then reconstituted in mobile phase after nitrogen drying. Separation was performed on an Acquity UPLC BEH C₁₈ column，followed by detection in electrospray positive ionization mode（ESI⁺） with multiple reaction monitoring（MRM）. Quantification was achieved using matrix-matched calibration curves. Results The method demonstrated a good linearity for all 10 tetracyclines and their metabolites in the range of LOQ-22.5 μg/kg，with correlation coefficients（r）≥0.998. The limits of detection（LODs） ranged from 0.011 to 0.210 μg/kg，and the limits of quantification（LOQs） ranged from 0.036 to 0.700 μg/kg. The recoveries at spiked levels were 70.7%-118.0%，with precision between 2.01% and 11.70%. Conclusion This method is sensitive，rapid，and accurate，suitable for detecting of tetracycline antibiotics and their metabolites in breast milk samples of large-scale.

Key words: Ultra performance liquid chromatography-tandem mass spectrometry, Solid phase extraction, Breast milk, Tetracycline, Metabolites