A halloysite nanotubes-based hybrid fluorous monolith as the mixed-mode sorbent for hydrophilic and hydrophobic interactions and its application for analysis of antibiotics from milk powder and milk samples

Determining the hydrophilic and hydrophobic antibiotics in milk and related products poses significant challenges due to their polarity differences and trace levels. Herein, we proposed a halloysite nanotubes-based hybrid fluorous monolith (HNTs-PFOTS monolith) as a sorbent for spin-tip solid-phase extraction (SPE). Leveraging the perfluorooctyl groups of the HNTs-PFOTS monolith, antibiotics can be adsorbed through hydrophilic and hydrophobic interactions. An analytical method was developed by combining the HNTs-PFOTS monolith-based spin-tip SPE method with liquid chromatography-tandem mass spectrometry. Under optimized conditions, the method exhibited excellent purification capabilities, low detection limits (0.01-0.03 μg/kg), high recoveries (80.0-112.3 %), and satisfactory reproducibility (intra-day RSDs of 0.4-8.8 % and inter-day RSDs of 1.0-10.9 %) for hydrophilic and hydrophobic antibiotics in milk and milk product samples. This study offers a novel approach for developing sorbents targeting antibiotics and provides a new analytical method for determining hydrophilic and hydrophobic antibiotics in food products.